WO2024176635A1 - Ultrasonic inspection device and ultrasonic inspection method - Google Patents

Ultrasonic inspection device and ultrasonic inspection method Download PDF

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Publication number
WO2024176635A1
WO2024176635A1 PCT/JP2024/000169 JP2024000169W WO2024176635A1 WO 2024176635 A1 WO2024176635 A1 WO 2024176635A1 JP 2024000169 W JP2024000169 W JP 2024000169W WO 2024176635 A1 WO2024176635 A1 WO 2024176635A1
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Prior art keywords
frequency
probe
component
signal
ultrasonic
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PCT/JP2024/000169
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French (fr)
Japanese (ja)
Inventor
睦三 鈴木
友輔 高麗
茂 大野
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株式会社日立パワーソリューションズ
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Publication of WO2024176635A1 publication Critical patent/WO2024176635A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/12—Analysing solids by measuring frequency or resonance of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/36—Detecting the response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/42—Detecting the response signal, e.g. electronic circuits specially adapted therefor by frequency filtering or by tuning to resonant frequency
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/46—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by spectral analysis, e.g. Fourier analysis or wavelet analysis

Definitions

  • This disclosure relates to an ultrasonic inspection device and an ultrasonic inspection method.
  • a method of inspecting defective parts of an object to be inspected using an ultrasonic beam is known. For example, if there is a defective part (cavity, etc.) with a small acoustic impedance such as air inside the object to be inspected, a gap in acoustic impedance will occur inside the object to be inspected, and the amount of transmission of the ultrasonic beam will be small. Therefore, by measuring the amount of transmission of the ultrasonic beam, it is possible to detect defective parts inside the object to be inspected.
  • Patent Document 1 The technology described in Patent Document 1 is known for an ultrasonic inspection device.
  • a rectangular wave burst signal consisting of a predetermined number of consecutive negative rectangular waves is applied to a transmitting ultrasonic probe arranged opposite the test object through the air.
  • the ultrasonic waves propagated through the test object are converted into a transmitted wave signal by a receiving ultrasonic probe arranged opposite the test object through the air.
  • the presence or absence of a defect in the test object is determined based on the signal level of this transmitted wave signal.
  • the transmitting ultrasonic probe and receiving ultrasonic probe have a lower acoustic impedance of the transducer and the front panel attached to the ultrasonic transmission and reception side of the transducer compared to a contact type ultrasonic probe that is used by abutting the test object.
  • the ultrasonic inspection device described in Patent Document 1 has a problem in that it is difficult to detect a minute defect in an object to be inspected. In particular, when the size of the defect to be detected is smaller than the ultrasonic beam, it becomes difficult to detect the defect.
  • the problem to be solved by the present disclosure is to provide an ultrasonic inspection device and an ultrasonic inspection method that have high detection performance for defective parts, for example, a small detectable defect size, making it possible to detect even minute defects.
  • the ultrasonic inspection device disclosed herein is an ultrasonic inspection device that inspects an object to be inspected by irradiating the object with an ultrasonic beam through a gas, and includes a scanning and measuring device that scans and measures the ultrasonic beam on the object to be inspected, and a control device that controls the driving of the scanning and measuring device.
  • the scanning and measuring device includes a transmitting probe that emits the ultrasonic beam, and a receiving probe that receives the ultrasonic beam and is installed on the opposite side of the transmitting probe with respect to the object to be inspected.
  • the transmitting probe emits an ultrasonic beam by applying a voltage waveform of a repeating wave packet composed of a wave packet with a wave number of two or more, and drives the transmitting probe with an excitation frequency shifted from the resonant frequency of the transmitting probe.
  • the control device includes a signal processing unit, and the signal processing unit includes a filter unit that reduces at least the maximum intensity frequency component of the received signal of the receiving probe, and the filter unit detects the base components other than the maximum intensity frequency component of the fundamental wave band including the maximum intensity frequency component.
  • the present disclosure provides an ultrasonic inspection device and an ultrasonic inspection method that improve the detection performance of defective parts, for example, by making it possible to detect even minute defects with a small detectable size.
  • FIG. 1 is a diagram showing the configuration of an ultrasonic inspection apparatus according to a first embodiment
  • 3 is a schematic cross-sectional view showing a structure of a transmission probe.
  • FIG. FIG. 1 is a diagram showing a propagation path of an ultrasonic beam in a conventional ultrasonic inspection method, showing the time when the ultrasonic beam is incident on a healthy part.
  • FIG. 1 is a diagram showing a propagation path of an ultrasonic beam in a conventional ultrasonic inspection method, showing the time of incidence on a defect portion.
  • FIG. 2 is a diagram showing an interaction between an ultrasonic beam and a defect in an object to be inspected, showing how a direct ultrasonic beam is received.
  • FIG. 2 is a schematic diagram showing a scattered wave, which is an ultrasonic beam that has interacted with a defect.
  • FIG. 2 is a functional block diagram of a control device.
  • FIG. 2 is a diagram illustrating a schematic distribution of frequency components of a received signal. This shows the change in signal strength information depending on the position when the transmitting probe and the receiving probe are scanned so as to straddle the defective portion. This is the result of measuring signal strength information using a control device equipped with a filter section.
  • 1 shows a voltage waveform of a burst wave applied to a transmitting probe.
  • 10 shows a frequency component distribution of a received signal under the conditions shown in FIG. FIG.
  • FIG. 1 is a diagram comparing measured data of the frequency component distribution (frequency spectrum) of a received signal between a healthy portion (solid line) and a defective portion (dashed line). 4 shows the frequency spectrum of the transmitted ultrasound when the wave number is changed. These are frequency spectra when the number of waves is 3 (dashed line), 5 (solid line), and 10 (dotted line).
  • FIG. 2 is a diagram illustrating a frequency spectrum of a fundamental wave band.
  • FIG. 1 is a diagram showing the relationship between the full width at half maximum ratio (FWHM ratio) of the fundamental waveband and the wave number. 4 shows the frequency characteristics of the gain in a band-stop filter.
  • FIG. 10 is a diagram illustrating the frequency characteristics of a signal after processing by a band-stop filter.
  • FIG. 2 is a diagram illustrating a frequency characteristic of a signal after processing by a low-pass filter. This shows the frequency characteristics of the gain in a high-pass filter.
  • FIG. 10 is a diagram illustrating a frequency characteristic of a signal after processing by a high-pass filter.
  • FIG. 2 is a block diagram showing a digital filter section;
  • FIG. 13 is a block diagram showing a filter unit according to another embodiment.
  • 1 is a diagram illustrating a schematic diagram of a propagation path of an ultrasonic beam when the focal length of a transmitting probe and the focal length of a receiving probe are set equal to each other.
  • FIG. 10 is a diagram illustrating a schematic diagram of a propagation path of an ultrasonic beam when the focal length of a receiving probe is set longer than the focal length of a transmitting probe.
  • 4A and 4B are diagrams illustrating the relationship between a beam incident area in a transmitting probe and a beam incident area in a receiving probe.
  • FIG. 13 is a diagram showing the configuration of an ultrasonic inspection apparatus according to a second embodiment.
  • FIG. 2 is a diagram for explaining the transmission sound axis, the reception sound axis, and the eccentricity distance, in the case where the transmission sound axis and the reception sound axis extend in the vertical direction.
  • FIG. 1 is a diagram for explaining a transmission sound axis, a reception sound axis, and an eccentric distance, in which the transmission sound axis and the reception sound axis extend at an angle.
  • FIG. FIG. 13 is a diagram showing the configuration of an ultrasonic inspection apparatus according to a third embodiment. 13A to 13C are diagrams for explaining the reason why the third embodiment has an effect.
  • FIG. 13 is a functional block diagram of a control device 2 in an ultrasonic inspection device according to a fourth embodiment.
  • FIG. 13 is a functional block diagram of a control device 2 in an ultrasonic inspection device according to a fifth embodiment.
  • FIG. 13 is a functional block diagram of a control device 2 in an ultrasonic inspection device according to a sixth embodiment.
  • FIG. 2 is a diagram illustrating a hardware configuration of a control device. 4 is a flowchart showing an ultrasonic inspection method according to each of the above embodiments.
  • FIG. 13 is a diagram showing the configuration of an ultrasonic inspection apparatus according to a seventh embodiment.
  • FIG. 2 is a functional block diagram of a control device. This shows the change in signal strength information depending on the position when the transmitting probe and the receiving probe are scanned so as to straddle the defective portion.
  • the excitation frequency fex of the transmitting probe was set to 0.78 MHz, and the signal strength information was measured using a control device equipped with a filter section. 13 shows a frequency component distribution of a received signal under the conditions shown in the seventh embodiment.
  • FIG. 1 is a diagram comparing measured data of the frequency component distribution (frequency spectrum) of a received signal between a healthy portion (solid line) and a defective portion (dashed line).
  • 36B is a diagram showing how the full width at half maximum of the fundamental wave band of the spectrum shown in FIG. 36A changes with respect to the wave number N0 of the wave packet.
  • FIG. This shows the results of measuring the frequency spectrum of the received signal while changing the excitation frequency fex.
  • FIG. 1 shows the change in instantaneous frequency of a wave packet in the time domain.
  • FIG. 23 is a functional block diagram of a control device in an ultrasonic inspection device Z in the eighth embodiment.
  • FIG. 13 is a functional block diagram of a control device in an ultrasonic inspection device Z in the ninth embodiment.
  • FIG. 23 is a diagram showing the configuration of an ultrasonic inspection apparatus according to an eleventh embodiment.
  • FIG. 23 is a functional block diagram of the control device 2 of the thirteenth embodiment.
  • 1 is an example of a database.
  • FIG. 43B is a three-dimensional view of the database shown in FIG. 43A.
  • FIG. 2 is a diagram illustrating a configuration example of an operation screen of an ultrasonic inspection device according to an example of the present disclosure.
  • FIG. 23 is a functional block diagram of an ultrasonic inspection apparatus according to a sixteenth embodiment.
  • FIG. 2 is a diagram illustrating a hardware configuration of a control device.
  • 4 is a flowchart showing an ultrasonic inspection method according to each of the above embodiments.
  • Fig. 1 is a diagram showing the configuration of an ultrasonic inspection device Z according to a first embodiment.
  • a scanning measurement device 1 is shown in a schematic cross-sectional view.
  • Fig. 1 shows a coordinate system of three orthogonal axes including an x-axis as a left-right direction on the paper surface, a y-axis as a direction perpendicular to the paper surface, and a z-axis as a top-bottom direction on the paper surface.
  • the ultrasonic inspection device Z inspects the object E by irradiating an ultrasonic beam U (described later) onto the object E through a fluid F.
  • the fluid F is a gas G such as air.
  • the object E is present in the fluid F.
  • air an example of gas G
  • the inside of the housing 101 of the scanning measurement device 1 is a cavity filled with air.
  • the ultrasonic inspection device Z includes the scanning measurement device 1, a control device 2, and a display device 3.
  • the display device 3 is connected to the control device 2.
  • the scanning measurement device 1 scans and measures the object E with an ultrasonic beam U, and is provided with a sample stage 102 fixed to a housing 101, on which the object E is placed. It is more preferable that the object E is fixed to the sample stage 102 with a fixture so as not to move. If the object E is sufficiently heavy and does not move unintentionally, a fixture is not necessary.
  • the object E is made of any material.
  • the object E is, for example, a solid material, and more specifically, is, for example, a metal, glass, a resin material, or a composite material such as CFRP (Carbon-Fiber Reinforced Plastics).
  • CFRP Carbon-Fiber Reinforced Plastics
  • the object E has a defect D inside.
  • the defect D is a cavity, etc. Examples of the defect D are a cavity, a foreign material different from the material that should be there, etc.
  • the portion other than the defective portion D is called the healthy portion N.
  • the defective area D and the healthy area N are made of different materials, so the acoustic impedance differs between the two, and the propagation characteristics of the ultrasonic beam U change.
  • the ultrasonic inspection device Z observes this change to detect the defective area D.
  • the scanning measurement device 1 has a transmitting probe 110 that emits an ultrasonic beam U, and a receiving probe 121.
  • the transmitting probe 110 is installed in the housing 101 via the transmitting probe scanning unit 103, and emits an ultrasonic beam U.
  • the receiving probe 121 is installed on the opposite side of the transmitting probe 110 with respect to the subject E, and receives the ultrasonic beam U.
  • the receiving probe 121 is a receiving probe 140 (coaxially arranged receiving probe) that is arranged coaxially with the transmitting probe 110 (the eccentric distance L described below is zero).
  • the eccentric distance L (distance described below) between the transmitting sound axis AX1 (sound axis) of the transmitting probe 110 and the receiving sound axis AX2 (sound axis) of the receiving probe 140 is zero. This makes it easy to install the transmitting probe 110 and the receiving probe 140.
  • the opposite side of the transmitting probe 110 means, of the two spaces separated by the subject E, the space opposite the space in which the transmitting probe 110 is located (the opposite side in the z-axis direction), and does not mean the opposite side with the same x and y coordinates (i.e., a position that is symmetrical with respect to the xy plane).
  • the configuration in which the receiving probe 140 is arranged on the opposite side of the transmitting probe 110 with respect to the subject E corresponds to a transmission type arrangement.
  • a reflection type arrangement is also known in the ultrasound inspection device Z, in which the receiving probe is arranged on the same side as the transmitting probe with respect to the subject E.
  • the transmission type arrangement is also called the transmission method.
  • the transmission type arrangement an ultrasonic beam U that has passed through the object E to be inspected is received.
  • the presence of a defect D in the object E causes a change in the amount of transmission of the ultrasonic beam U, and the defect D is detected.
  • the reflection type arrangement is also called the reflection method, and the defect D is detected by detecting the ultrasonic beam U reflected by the defect D.
  • the transmitting probe 110 is installed so that the transmission sound axis AX1 of the transmitting probe 110 is perpendicular to the mounting surface 1021 of the sample stage 102.
  • the transmitting probe 110 is installed so that the transmission sound axis AX1 is normal to the mounting surface 1021 of the sample stage 102 for the object E to be inspected.
  • the transmission sound axis AX1 is arranged perpendicular to the surface of the object E to be inspected, which has the effect of making it easier to understand the correspondence between the scanning position and the position of the defect D.
  • the present disclosure is not limited to installing the transmission probe 110 so that the transmission sound axis AX1 is perpendicular to the mounting surface 1021 of the sample stage 102 for the object E to be inspected.
  • the present disclosure is effective even if the transmission sound axis AX1 is not perpendicular to the mounting surface 1021 of the sample stage 102 for the object E to be inspected.
  • the path of the transmission sound axis AX1 can be calculated according to the inclination of the transmission sound axis AX1 from the vertical direction.
  • the distance between the transmitting sound axis AX1 of the transmitting probe 110 and the receiving sound axis AX2 of the receiving probe 121 is defined as the eccentricity distance L (described below).
  • the eccentricity distance L is set to zero. That is, the receiving probe 121 is positioned so that the transmitting sound axis AX1 and the receiving sound axis AX2 are coaxial. This is called a coaxial arrangement. Note that in this disclosure, the eccentricity distance L is not limited to 0.
  • the arrangement of the receiving probe 121 in which the transmission sound axis AX1 and the reception sound axis AX2 are coaxially arranged is called a coaxial arrangement
  • the arrangement in which the two sound axes (the transmission sound axis AX1 and the reception sound axis AX2) are shifted (i.e., eccentrically arranged) is called an eccentric arrangement.
  • This disclosure is effective in both cases where the receiving probe 121 is coaxially arranged and where it is eccentrically arranged. Therefore, this disclosure includes both the coaxial arrangement and the eccentric arrangement as the arrangement of the receiving probe 121. Specific illustrations of the eccentric arrangement are provided below.
  • the coaxially arranged receiving probe 121 will be referred to as receiving probe 140 (coaxially arranged receiving probe), and the eccentrically arranged receiving probe 121 will be referred to as receiving probe 120 (eccentrically arranged receiving probe).
  • the sound axis is defined as the central axis of the ultrasonic beam U.
  • the transmission sound axis AX1 is defined as the sound axis of the propagation path of the ultrasonic beam U emitted by the transmitting probe 110.
  • the transmission sound axis AX1 is the central axis of the propagation path of the ultrasonic beam U emitted by the transmitting probe 110.
  • the transmission sound axis AX1 includes refraction due to the interface of the object E to be inspected, as described below.
  • the center (sound axis) of the propagation path of the ultrasonic beam U becomes the transmission sound axis AX1.
  • the receiving sound axis AX2 is defined as the sound axis of the propagation path of a virtual ultrasonic beam when it is assumed that the receiving probe 121 emits the ultrasonic beam U.
  • the receiving sound axis AX2 is the central axis of a virtual ultrasonic beam when it is assumed that the receiving probe 121 emits the ultrasonic beam U.
  • the direction of the receiving sound axis AX2 is the normal direction of the probe surface 114, and the axis passing through the center point of the probe surface 114 becomes the receiving sound axis AX2. If the probe surface 114 is rectangular, the center point is defined as the intersection of the diagonals of the rectangle.
  • the control device 2 is connected to the scanning measurement device 1.
  • the control device 2 controls the driving of the scanning measurement device 1, and controls the movement (scanning) of the transmitting probe 110 and the receiving probe 121 by instructing the transmitting probe scanning unit 103 and the receiving probe scanning unit 104.
  • the transmitting probe scanning unit 103 and the receiving probe scanning unit 104 move synchronously in the x-axis and y-axis directions, so that the transmitting probe 110 and the receiving probe 121 scan the subject E in the x-axis and y-axis directions.
  • the control device 2 emits an ultrasonic beam U from the transmitting probe 110, and performs waveform analysis based on the signal acquired from the receiving probe 121.
  • the plane formed by the two axes, the x-axis and y-axis directions, which are the scanning directions of the transmitting probe 110 is called the scanning plane.
  • the transmitting probe 110 and the receiving probe 121 are scanned in a state in which the test subject E is fixed to the housing 101 via the sample stage 102, that is, in a state in which the test subject E is fixed to the housing 101.
  • a configuration in which the transmitting probe 110 and the receiving probe 121 are fixed to the housing 101 and the position of the sample stage 102 is scanned in the x-axis and y-axis directions may also be used.
  • the test subject E placed on the sample stage 102 also moves, so that the relative position with the transmitting probe 110 is scanned in the x-axis and y-axis directions.
  • gas G is interposed between the transmitting probe 110 and the test subject E, and between the receiving probe 121 and the test subject E. Therefore, the transmitting probe 110 and the receiving probe 121 can test the test subject E without contacting it, so it is possible to change the relative positions in the xy plane smoothly and quickly. In other words, by interposing gas G between the transmitting probe 110 and the receiving probe 121 and the test subject E, smooth scanning is possible.
  • the localized ultrasonic beam U By emitting a localized ultrasonic beam U from the transmitting probe 110, the localized ultrasonic beam U is locally irradiated onto the object to be inspected E.
  • the position to which the localized ultrasonic beam U is irradiated is changed by scanning.
  • the ultrasonic beam U that reaches the receiving probe 121 changes depending on whether it is a defective part D or a healthy part N of the object to be inspected E, so this configuration makes it possible to detect the defective part D.
  • a convergent transmitting probe 110 can be used.
  • the specific configuration of the convergent transmitting probe 110 will be described later.
  • a configuration for generating a localized ultrasonic beam U may be used in which the area of a piezoelectric element (transducer 111 described later; the same applies below) that generates the ultrasonic beam U is reduced to reduce the beam diameter.
  • the convergent transmitting probe 110 is more preferable because it is possible to reduce the beam diameter while increasing the area of the piezoelectric element, thereby generating a localized ultrasonic beam U with high beam intensity and small beam diameter.
  • the transmitting probe 110 is a convergent type transmitting probe 110.
  • the receiving probe 121 is a probe with looser convergence than the transmitting probe 110.
  • a non-convergent type probe with a flat probe surface is used for the receiving probe 121.
  • FIG. 2 is a schematic cross-sectional view showing the structure of the transmitting probe 110.
  • FIG. 2 shows only the outer contour of the emitted ultrasonic beam U, but in reality, a large number of ultrasonic beams U are emitted in the normal vector direction of the probe surface 114 over the entire area of the probe surface 114.
  • the transmitting probe 110 is configured to focus the ultrasonic beam U. This allows for highly accurate detection of minute defects D in the object E to be inspected. The reason why minute defects D can be detected will be described later.
  • the transmitting probe 110 comprises a transmitting probe housing 115, which comprises a backing 112, a transducer 111, and a matching layer 113 inside the transmitting probe housing 115.
  • An electrode (not shown) is attached to the transducer 111, and the electrode is connected to a connector 116 by a lead wire 118. Furthermore, the connector 116 is connected to a power supply (not shown) and a control device 2 by a lead wire 117.
  • the probe surface 114 of the transmitting probe 110 or the receiving probe 121 is defined as the surface of the matching layer 113 if the matching layer 113 is provided, and as the surface of the transducer 111 if the matching layer 113 is not provided. That is, the probe surface 114 is the surface that emits the ultrasonic beam U in the case of the transmitting probe 110, and is the surface that receives the ultrasonic beam U in the case of the receiving probe 121.
  • FIG. 3A is a diagram showing the propagation path of an ultrasonic beam U in a conventional ultrasonic inspection method, showing the beam entering a healthy part N.
  • FIG. 3B is a diagram showing the propagation path of an ultrasonic beam U in a conventional ultrasonic inspection method, showing the beam entering a defective part D.
  • a transmitting probe 110 and a receiving probe 140 serving as a receiving probe 121 are positioned so that a transmitting sound axis AX1 and a receiving sound axis AX2 coincide with each other.
  • the method of detecting a defect D by blocking the transmission of an ultrasonic beam U at the defect D, thereby reducing the received signal is referred to here as the "blocking method.”
  • FIG. 4 is a diagram showing the interaction between a defect D and an ultrasonic beam U in an object E to be inspected, and shows how a direct ultrasonic beam U (hereinafter referred to as a "direct wave U3") is received.
  • the direct wave U3 will be described later.
  • the beam width BW here is the width of the ultrasonic beam U when it reaches the defect D.
  • FIG. 4 shows a schematic representation of the shape of the ultrasonic beam U in a minute area near the defect D
  • the ultrasonic beam U is drawn parallel, but in reality it is a converged ultrasonic beam U.
  • the position of the receiving probe 121 in FIG. 4 is a conceptual position shown for easy understanding, and the position and shape of the receiving probe 121 are not precisely scaled. In other words, when considering the enlarged scale of the shapes of the defect D and the ultrasonic beam U, the receiving probe 121 is located at a position further away in the vertical direction of the drawing than the position shown in FIG. 4.
  • Figure 4 shows the case of a blocking method in which the transmitting sound axis AX1 and the receiving sound axis AX2 are aligned. If the defect D is smaller than the beam width BW, part of the ultrasonic beam U is blocked, so the received signal decreases, but does not become zero. For example, if the cross-sectional area of the defect D is 5% of the beam cross-sectional area defined by the beam width BW, the received signal decreases by only about 5%, making it difficult to detect the defect D. In other words, in the case shown in Figure 4, where the defect D exists, the received signal decreases by only 5%. In this way, if the defect D is smaller than the beam width BW, many beams pass through without interacting with the defect D, making it difficult to detect the defect.
  • FIG. 5 is a schematic diagram showing a scattered wave U1, which is an ultrasonic beam U that has interacted with a defect D.
  • the ultrasonic beam U that has interacted with the defect D is called the scattered wave U1. Therefore, in this disclosure, the "scattered wave U1" refers to an ultrasonic wave that has interacted with the defect D.
  • Some of the scattered waves U1 change direction as shown in FIG. 5. Some of the scattered waves U1 change at least one of the phase or frequency of the wave due to the interaction with the defect D, but the direction of travel does not change.
  • An ultrasonic wave that passes through the defect D without interacting with it is called a direct wave U3. If only the scattered waves U1 can be detected, distinguishing them from the direct waves U3, it will be easier to detect small defects D. In this disclosure, the scattered waves U1 are efficiently detected by focusing on the difference in frequency.
  • a gas G such as air is used as the fluid F between the transmitting probe 110 and the test object E.
  • a gas G such as air is used as the fluid F between the transmitting probe 110 and the test object E.
  • ultrasonic waves are attenuated more in gas G. It is known that the attenuation of ultrasonic waves in gas G is proportional to the square of the frequency. For this reason, the upper limit for ultrasonic waves propagating in gas G is about 1 MHz. In liquids, ultrasonic waves of 5 MHz to several tens of MHz can also propagate, so the frequencies that can be used in gas G are smaller than those in liquids.
  • the 1 MHz ultrasonic beam U propagating through gas G has a larger beam diameter that can be converged compared to the ultrasonic beam U in liquid.
  • the blocking mode which is the conventional method, it is difficult to detect a defect D smaller than the beam size.
  • the proportion of the scattered wave U1 component is increased for detection, making it possible to detect a defect D smaller than the beam size.
  • FIG. 6 is a functional block diagram of the control device 2.
  • the control device 2 controls the driving of the scanning measurement device 1.
  • the control device 2 includes a transmission system 210, a reception system 220, a data processing unit 201, a scan controller 204, a driving unit 202, a position measurement unit 203, and a signal processing unit 250.
  • the reception system 220 and the data processing unit 201 are collectively referred to as the signal processing unit 250.
  • the signal processing unit 250 performs signal processing to extract significant information by amplifying and filtering the signal from the receiving probe 121.
  • the transmission system 210 is a system that generates a voltage to be applied to the transmission probe 110.
  • the transmission system 210 includes a waveform generator 211 and a signal amplifier 212.
  • a burst wave signal is generated by the waveform generator 211.
  • the generated burst wave signal is then amplified by the signal amplifier 212.
  • the voltage output from the signal amplifier 212 is applied to the transmission probe 110.
  • the transmission system 210 included in the control device 2 outputs a voltage waveform of a burst wave, and the outputted voltage waveform of the burst wave is applied to the transmission probe 110.
  • the burst wave is also referred to as a repeating wave packet. The waveform of the burst wave will be described later.
  • the signal processing unit 250 includes a receiving system 220.
  • the receiving system 220 is a system that detects the received signal output from the receiving probe 121.
  • the signal output from the receiving probe 121 is input to a signal amplifier 222 and amplified.
  • the amplified signal is input to a filter unit 240 (blocking filter).
  • the filter unit 240 reduces (blocks) components of a specific frequency range of the input signal.
  • the filter unit 240 will be described later.
  • the output signal from the filter unit 240 is input to the data processing unit 201.
  • the data processing unit 201 generates signal strength data from the signal input from the filter unit 240.
  • the peak-to-peak signal is used as a method for generating signal strength data. This is the difference between the maximum and minimum values of the signal.
  • Another method for generating signal strength data is to use the strength of frequency components in a specific frequency range by performing a Fourier transform.
  • the data processing unit 201 also receives scanning position information from the scan controller 204. In this way, the signal intensity data value at the current two-dimensional scanning position (x, y) is obtained. By plotting the signal intensity data value against the scanning position, an image (defect image) corresponding to at least one of the position and shape of the defect D is obtained. This defect image is output to the display device 3.
  • the filter unit 240 is defined as a control unit that performs signal processing to reduce the intensity of signal components in a predetermined frequency range. Filter processing is also defined as signal processing to reduce the intensity of signal components in a predetermined frequency range.
  • the maximum intensity frequency component is a frequency component at the maximum component frequency. In other words, the maximum component frequency is a frequency corresponding to the maximum intensity frequency component.
  • the filter unit 240 of the present disclosure reduces the intensity of the fundamental wave band including the maximum intensity frequency component, that is, the signal components in the frequency range including the maximum component frequency.
  • the distribution of component intensities for each frequency component is called a frequency spectrum.
  • FIG. 7 is a diagram showing a schematic distribution of frequency components (frequency spectrum) of a received signal.
  • the filter section 240 will be explained in more detail using FIG. 7.
  • the horizontal axis shows frequency
  • the vertical axis shows component strength (intensity).
  • the vertical axis is shown on a logarithmic scale, and a wide range of strength is shown.
  • the maximum component frequency at which the component strength is at its maximum is designated as fm.
  • the maximum component frequency fm is approximately equal to the fundamental frequency f0 of the burst wave transmitted from the transmitting probe 110.
  • the frequency components of the signal have a spread before and after the maximum component frequency fm, which is called the fundamental wave band W1.
  • the component with a frequency (N x fm) that is N times the maximum component frequency fm is a harmonic.
  • the component with a frequency (fm/N) that is 1/N times the maximum component frequency fm is a sub-harmonic.
  • Harmonics and sub-harmonics also have a spread. In this disclosure, when it is particularly emphasized that harmonics and sub-harmonics have a frequency spread, they are called harmonic bands and sub-harmonic bands, respectively. Therefore, even when simply written as "harmonic", it has a frequency spread. Harmonic bands and sub-harmonic bands are generated by nonlinear phenomena, and occur when the sound pressure of the ultrasonic beam U input to the test object E is extremely strong.
  • the fundamental wave band W1 has a wide frequency range.
  • the frequency components other than the maximum component frequency fm are referred to as "foot components W3."
  • the foot components W3 also include the side lobes of the fundamental wave.
  • the filter unit 240 reduces the component strength in the cutoff frequency range including the maximum component frequency fm. That is, the filter unit 240 reduces at least the maximum intensity frequency component (the component corresponding to the maximum component frequency fm) of the received signal of the receiving probe 121. The filter unit 240 then detects the skirt component W3 other than the maximum intensity frequency component of the fundamental wave band W1 including the maximum intensity frequency component. Because the filter unit 240 reduces the component strength in the cutoff frequency range, the proportion of the skirt component W3 in the fundamental wave band W1 increases in the signal after passing through the filter unit 240. In this way, the detection performance of the defect portion D can be improved, as described below.
  • Figure 8A shows the change in signal strength information depending on the position when the transmitting probe 110 and the receiving probe 121 are scanned across the defective area D.
  • Figure 8A shows the results of a measurement using a configuration in which the filter section 240 has been removed from the configuration in Figure 6 above.
  • the signal strength in the healthy area N is v0.
  • the rate of change in signal strength ( ⁇ v/v0) is small.
  • the rate of change in signal strength is defined as the amount of signal change ⁇ v in the defective area D divided by the signal strength v0 in the healthy area N.
  • Figure 8B shows the results of measuring signal strength information using a control device 2 ( Figure 6) equipped with a filter unit 240. It can be seen that the rate of change in signal strength ( ⁇ v/v0) at the location of defect D has increased, improving the detectability of defect D.
  • Figure 9 shows the voltage waveform of a burst wave applied to the transmitting probe 110.
  • the horizontal axis is time, and the vertical axis is voltage.
  • ten sine waves with a fundamental frequency f0 of 0.82 MHz are applied. These ten waves are called a wave packet.
  • the inverse of the fundamental frequency f0 is called the fundamental period T0.
  • the fundamental period T0 is the period of the waves that make up one wave packet.
  • each wave packet is a sine wave with a fundamental frequency of f0, but it may be a wave packet other than a sine wave.
  • the wave packet may be a wave packet composed of a rectangular wave with a wave number of N0.
  • the wave number N0 of a wave packet is the number of waves (number of cycles) of fundamental frequency f0 contained in one wave packet.
  • the wave number N0 of a wave packet is 2 or more, and it is preferable that the wave number N0 of a wave packet is 3 or more. Therefore, the transmitting probe 110 emits an ultrasonic beam U by applying a voltage waveform of a repeating wave packet composed of wave packets with a wave number N0 of 2 or more.
  • the wave number N0 is 10 waves, as described above.
  • a waveform of a repeating wave packet in which wave packets are repeated is called a burst wave.
  • Figure 10 shows the frequency component distribution of the received signal under the conditions shown in Figure 9.
  • the horizontal axis is frequency
  • the vertical axis plots the measured data of component strength at each frequency.
  • This graph shows the frequency component distribution of a signal not processed by the filter section 240.
  • 0.82 MHz where the component strength is at its maximum, is the maximum component frequency fm.
  • the fundamental wave band W1 extends from 0.74 MHz to 0.88 MHz, and the components excluding the maximum component frequency fm are the skirt components W3.
  • the maximum component frequency fm is equal to the fundamental frequency f0 of the ultrasound transmitted by the transmitting probe 110.
  • the maximum component frequency fm is roughly equal to the fundamental frequency f0 of the ultrasound transmitted.
  • the filter section 240 excludes the maximum component frequency fm. Specifically, in the illustrated example, the filter section 240 (Fig. 6) transmits the base component W3 below 0.78 MHz and blocks waves above 0.78 MHz, including 0.82 MHz.
  • the rate of change of the signal intensity at the defective section D increases, and it can be seen that the detectability of the defect is greatly improved.
  • Figure 11 is a diagram comparing the measured data of the frequency component distribution (frequency spectrum) of the received signal between a healthy part N (solid line) and a defective part D (dashed line).
  • the inventors have examined the frequency components of the received signal and found that the difference between the healthy part N and the defective part D is greater for the base component W3 than for the maximum component frequency fm. Based on this knowledge, they have found that the detectability of the defective part D can be improved by using a filter section 240 that reduces the frequency component of the maximum component frequency fm, which is the smallest difference between the healthy part N and the defective part D.
  • the present disclosure is based on the new knowledge found by the inventors that in the frequency component distribution of a received signal, the base component W3 of the fundamental wave band W1 has a greater signal change rate at the defect D than the signal component at the maximum component frequency fm.
  • the component at the maximum component frequency fm accounts for a large proportion of the received signal, but the signal change rate at the defect D is small, so by reducing this component, the proportion of the base component W3 increases.
  • the signal after processing by the filter unit 240 has an increased signal change rate at the defect D, improving the detectability of the defect D.
  • the effect of improving the detectability of the defect D by the filter unit 240 is clear.
  • burst wave effect In this disclosure, the effect of applying a burst wave, i.e., a repeating wave packet voltage waveform, to the transmitting probe 110 is described.
  • this disclosure is based on the new knowledge that the frequency component (foot component) that is shifted by ⁇ f from the maximum component frequency fm has a large signal change rate at the defect part D. Therefore, by narrowing the bandwidth of the fundamental wave band W1 to an appropriate width, the frequency range of the shifted component (fm ⁇ f) falls within a specific range, making it easier to detect the defect information contained in the shifted component (foot component W3).
  • the method of inspecting a defect D inside an object E by applying a single pulse or one cycle of a voltage waveform is known as the pulse-echo method.
  • the pulse-echo method By measuring the time from when the ultrasonic wave is transmitted to when it is received, the distance to the defect D can be determined.
  • Figure 12A shows the frequency spectrum of the transmitted ultrasound when the wave number N0 is changed.
  • the frequency spectrum was calculated by Fourier transforming the time waveform of the wave packet composed of wave number N0.
  • the fundamental frequency f0 of the waves that compose wave packet N0 is set to 0.82 MHz.
  • Figure 12A shows the spectrum when wave number N0 is 1 to 3. Note that when there is a wave number of 1, it does not become a wave packet, so it is not a repeating wave packet and is not a burst wave.
  • Figure 12B shows the frequency spectrum when the wave number N0 is 3 (dashed line), 5 (solid line), and 10 (dotted line). It can be seen that increasing the wave number N0 further narrows the width (bandwidth) of the fundamental wave band.
  • the bandwidth of the fundamental wave band W1 is defined as follows.
  • the spectrum intensity at the maximum component frequency fm of the fundamental wave band W1 is set to 1, and the frequency width at half the intensity is set to the full width at half maximum (FWHM).
  • the value obtained by normalizing the full width at half maximum by the maximum component frequency fm is defined as the full width at half maximum ratio (FWHM ratio). That is, the full width at half maximum ratio is expressed by the following formula.
  • Full width at half maximum ratio full width at half maximum/fm
  • FIG. 14 is a diagram showing the relationship between the full width at half maximum ratio (FWHM ratio) of the fundamental wave band W1 and the wave number N0.
  • the full width at half maximum ratio shown on the vertical axis was calculated from the frequency spectrum in FIG. 12A and FIG. 12B.
  • the wave number N0 is set to 2 or more, the effect of the present disclosure is large.
  • the width of the fundamental wave band W1 of the spectrum of the transmitted wave is narrower than this.
  • the full width at half maximum of the frequency spectrum of the fundamental wave band W1 is 50% or less of the maximum component frequency fm. This can improve the detection accuracy of the defect D.
  • the full width at half maximum ratio (FWHM ratio) of the fundamental waveband W1 can be reduced to 50% or less by setting the wave number N0 of the wave packet to 3 or more. Therefore, as described above, it is even more preferable to set the wave number N0 of the wave packet to 3 or more.
  • the frequencies detected by the filter section 240 include frequencies in the range of (fm ⁇ 0.25fm) with respect to the maximum component frequency fm.
  • 0.25fm means 0.25 times (i.e., 25%) the maximum component frequency fm.
  • the frequency detected by the filter section 240 includes a range of (fm ⁇ 0.15fm) with respect to the maximum component frequency fm.
  • the broadband probe has a full width at half maximum ratio of the fundamental wave band W1 of about 70% or more, and the narrowband probe has a full width at half maximum ratio of about 50% or less.
  • a broadband probe is often used to expand the frequency band of the transmitted wave.
  • narrowband probes are advantageous for detecting frequency components of specific frequencies because the ultrasonic energy is concentrated in a narrow frequency range.
  • the full width at half maximum ratio of the fundamental wave band W1 be 50% or less. From this point of view, it is even more preferable that the transmitting probe 110 is a narrowband probe in this disclosure.
  • the filter unit 240 preferably includes at least one of a band-blocking filter, a low-pass filter, or a high-pass filter. By including at least one of these, components in a frequency range including the maximum component frequency fm can be reduced. Among these, by including at least one of a low-pass filter or a high-pass filter, only one of the high frequency or low frequency is blocked, so that the program for blocking can be simplified. Furthermore, when the filter unit 240 is implemented by an electronic circuit, the circuit configuration for blocking can be simplified.
  • Fig. 15A shows the frequency characteristic of the gain in a band-stop filter.
  • the band-stop filter reduces the components in a frequency range W2 (Fig. 15B) that includes the maximum component frequency fm (maximum intensity frequency component) out of the fundamental wave band W1 (Fig. 15B) that includes the maximum component frequency fm.
  • the reduction rate x is the ratio G1/G0 of the gain G0 in the transmission region to the gain G1 in the blocking region. In the first embodiment, the reduction rate x is set to -20 dB (1/10) to -40 dB (1/100).
  • FIG. 15B is a diagram showing a schematic of the frequency characteristics of a signal after processing with a band-stop filter.
  • the waveform shown by the solid and dotted lines is the fundamental wave band W1.
  • the dotted lines show the signal components before processing, and the components in the frequency range W2 shown in the dotted line are reduced by the band-stop filter.
  • the base component W3 of the fundamental wave band W1, shown by the solid line can be detected.
  • Fig. 16A shows the frequency characteristics of the gain in a low-pass filter.
  • the cutoff frequency of a filter is the frequency at the boundary between the passband that passes the signal and the attenuation band that attenuates the signal.
  • the cutoff frequency is set to 0.78 MHz. In other words, it is set to a frequency 40 kHz lower than the maximum component frequency fm (0.82 MHz).
  • the reduction rate at the cutoff section is set to approximately -40 dB.
  • FIG. 16B is a diagram showing the frequency characteristics of a signal after processing with a low-pass filter.
  • the dotted and solid lines have the same meanings as in FIG. 15B.
  • Figure 17A shows the frequency characteristics of the gain in a high-pass filter.
  • FIG. 17B is a diagram showing the frequency characteristics of a signal after processing with a high-pass filter.
  • the dotted and solid lines have the same meanings as in FIG. 15B.
  • Method of mounting filter section 240 The following describes a typical configuration example of a method for implementing the filter section 240. Methods for implementing the filter section 240 are roughly divided into analog methods and digital methods.
  • the analog method uses an analog circuit to reduce signal components in a desired frequency range.
  • Typical examples of frequency characteristics of the filter section 240 include a band-blocking filter (Figs. 15A and 15B), a low-pass filter (Figs. 16A and 16B), and a high-pass filter (Figs. 17A and 17B).
  • Figs. 15A and 15B a band-blocking filter
  • Figs. 16A and 16B a low-pass filter
  • Figs. 17A and 17B high-pass filter
  • FIG. 18 is a block diagram showing a digital filter section 240.
  • the filter section 240 includes a frequency component conversion section 241, a frequency selection section 242, and a frequency component inverse conversion section 243.
  • the frequency component conversion section 241 converts the received signal of the receiving probe 121 input from the signal amplifier 222 into frequency components.
  • the frequency selection section 242 selects the foot component W3 by removing the frequency band including the maximum component frequency fm (maximum intensity frequency component).
  • the frequency component inverse conversion section 243 converts only the necessary frequency components back into a time domain signal. By including the frequency component conversion section 241 and the frequency selection section 242 among these, in particular, the digital filter section 240 can be configured.
  • Such a digital filter unit 240 can also reduce components in a frequency range including the maximum component frequency fm.
  • the processing performed by the frequency component conversion unit 241 is processing to convert the signal waveform in the time domain into frequency components, typically using a Fourier transform.
  • the processing performed by the frequency component inverse conversion unit 243 is processing to convert the frequency components (frequency spectrum) into a signal waveform in the time domain, typically using an inverse Fourier transform.
  • FIG. 19 is a block diagram showing a filter unit 240 according to another embodiment.
  • the filter unit 240 is provided in the signal processing unit 250.
  • the filter unit 240 includes a frequency component conversion unit 241 and a frequency selection unit 242.
  • the output of the frequency selection unit 242 is input to a signal strength calculation unit 231 in the data processing unit 201.
  • the signal strength calculation unit 231 calculates the signal strength based on the information of the frequency components.
  • the direct wave U3 which does not interact with the defective part D, does not change in wave propagation direction, phase, frequency, etc. Therefore, the signal component of the maximum component frequency fm is largely dominated by the direct wave U3. Therefore, the change between the defective part D and the healthy part N is small.
  • the scattered wave U1 that interacts with the defect D has components that change the propagation direction, and components that do not change the propagation direction but at least one of the phase or frequency changes. Furthermore, among the components that change the propagation direction, there are components whose frequency changes. Therefore, the proportion of the scattered wave U1 component, which is the ultrasonic beam U that interacts with the defect D, in the base component W3 of the fundamental wave band W1, which is a component shifted from the maximum frequency fm, increases. As a result, the change between the defect D and the healthy part N becomes greater. In this way, the detection performance of the defect D can be improved by reducing the component of the maximum component frequency fm and detecting the base component W3 of the fundamental wave band W1.
  • the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110. This is because, as described below, by doing so, it becomes possible to detect more components of the scattered wave U1.
  • the scattered wave U1 is an ultrasonic beam U that has interacted with the defect D, so the greater the proportion of the scattered wave U1 components, the easier it becomes to detect the defect D.
  • FIG. 20A is a schematic diagram showing the propagation path of an ultrasonic beam U when the focal length R1 of the transmitting probe 110 and the focal length R2 of the receiving probe 121 are equal.
  • the receiving probe 121 can detect an ultrasonic beam U within the range of a cone (shape) C2 of a virtual beam virtually emitted from the receiving probe 121.
  • the convergence point of the ultrasonic beam U transmitted from the transmitting probe 110 and the convergence point of the virtual beam virtually emitted from the receiving probe 121 are the same. Therefore, an ultrasonic beam U whose propagation direction does not change at the defect D can be efficiently received.
  • an ultrasonic beam U whose propagation direction changes at the defect D is difficult to detect.
  • FIG. 20B is a schematic diagram showing the propagation path of the ultrasonic beam U when the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110.
  • the receiving probe 121 can detect the ultrasonic beam U within the range of the cone (shape) C3 of the virtual beam virtually emitted from the receiving probe 121. Therefore, even if the scattered wave U1 has changed its propagation direction slightly at the defect D, it can be detected if it is within the range of the cone C3. In this way, by making the focal length R2 of the receiving probe 121 longer than the focal length R1 of the transmitting probe 110, the detectable scattered wave U1 can be increased. As described above, the scattered wave U1 is a wave that has interacted with the defect D, so this can further improve the detection performance of the defect D.
  • the magnitude relationship of the convergence is also defined by the magnitude relationship between the beam incident areas T1 and T2 on the surface of the object E to be inspected.
  • the beam incident areas T1 and T2 are explained below.
  • FIG. 21 is a diagram explaining the relationship between the beam incidence area T1 in the transmitting probe 110 and the beam incidence area T2 in the receiving probe 121.
  • the beam incidence area T1 in the subject E of the transmitting probe 110 is the intersection area of the ultrasonic beam U emitted from the transmitting probe 110 on the surface of the subject E.
  • the beam incidence area T2 in the receiving probe 121 is the intersection area of the virtual ultrasonic beam U2, which is assumed to be emitted from the receiving probe 121, on the surface of the subject E.
  • the path of the ultrasonic beam U is shown when there is no object under test E.
  • the ultrasonic beam U is refracted at the surface of the object under test E, and the ultrasonic beam U propagates along a path different from the path shown by the dashed line.
  • the beam incidence area T2 of the receiving probe 121 at the object under test E is larger than the beam incidence area T1 of the transmitting probe 110 at the object under test E. In this way, the convergence of the receiving probe 121 can be made looser than that of the transmitting probe 110.
  • the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110. In this way, the convergence of the receiving probe 121 can be made looser than the convergence of the transmitting probe 110. At this time, the distance from the subject E to the transmitting probe 110 and the receiving probe 121 is, for example, the same for both, but does not have to be the same.
  • the convergence of the receiving probe 121 is looser than that of the transmitting probe 110. That is, the focal length R2 of the receiving probe 121 is set longer than the focal length R1 of the transmitting probe 110. As a result, the beam incidence area T2 of the receiving probe 121 is wider, so that a wider range of scattered waves U1 can be detected. This makes it possible for the receiving probe 121 to detect the scattered waves U1 even if the propagation path of the scattered waves U1 changes slightly. As a result, a wider range of defective portions D can be detected.
  • the focus P1 of the receiving probe 121 is located closer to the transmitting probe 110 (above in the illustrated example) than the focus P2 of the transmitting probe 110. By shifting the foci P1 and P2 in this way, it becomes easier for the receiving probe 121 to receive the scattered wave U1, and easier to detect the scattered wave U1.
  • a non-converging probe may be used as the receiving probe 121 in a configuration in which the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110. That is, in another embodiment, the receiving probe 121 is a non-converging probe. In a non-converging probe, the focal length R2 is infinite, so it is longer than the focal length R1 of the transmitting probe 110. That is, even with a non-converging receiving probe 121, the convergence of the receiving probe 121 is weaker than the convergence of the transmitting probe 110.
  • Second Embodiment 22 is a diagram showing the configuration of an ultrasonic inspection device Z in the second embodiment.
  • the transmission sound axis AX1 of the transmitting probe 110 and the reception sound axis AX2 of the receiving probe 121 are arranged to be offset from each other. That is, the receiving probe 121 in the second embodiment is a receiving probe 120 (eccentrically arranged receiving probe) having a reception sound axis AX2 arranged at a position different from the transmission sound axis AX1 of the transmitting probe 110. Therefore, the eccentric distance L (distance) between the transmission sound axis AX1 (sound axis) of the transmitting probe 110 and the reception sound axis AX (sound axis) of the receiving probe 120 is greater than zero.
  • the receiving probe 120 is arranged offset by an eccentric distance L in the x-axis direction of FIG. 22 with respect to the transmitting probe 110, but the receiving probe 120 may be arranged offset in the y-axis direction of FIG. 22.
  • the receiving probe 120 may be arranged at L1 in the x-axis direction and L2 in the y-axis direction (i.e., if the position of the transmitting probe 110 on the xy plane is taken as the origin, then the position is (L1, L2)).
  • FIG. 23A is a diagram explaining the transmission sound axis AX1, reception sound axis AX2, and eccentricity distance L when the transmission sound axis AX1 and reception sound axis AX2 extend vertically.
  • FIG. 23B is a diagram explaining the transmission sound axis AX1, reception sound axis AX2, and eccentricity distance L when the transmission sound axis AX1 and reception sound axis AX2 extend at an angle.
  • FIGS. 23A and 23B also show the receiving probe 140 (coaxially arranged receiving probe) in dashed lines.
  • the sound axis is defined as the central axis of the ultrasonic beam U.
  • the transmission sound axis AX1 is defined as the sound axis of the propagation path of the ultrasonic beam U emitted by the transmitting probe 110.
  • the transmission sound axis AX1 is the central axis of the propagation path of the ultrasonic beam U emitted by the transmitting probe 110.
  • the transmission sound axis AX1 is intended to include refraction due to the interface of the object to be inspected E, as shown in FIG. 23B. In other words, as shown in FIG.
  • the receiving sound axis AX2 is defined as the sound axis of the propagation path of the virtual ultrasonic beam when it is assumed that the receiving probe 121 emits the ultrasonic beam U.
  • the receiving sound axis AX2 is the central axis of the virtual ultrasonic beam when it is assumed that the receiving probe 121 emits the ultrasonic beam U.
  • the direction of the receiving sound axis AX2 is the normal direction of the probe surface, and the axis passing through the center point of the probe surface becomes the receiving sound axis AX2. If the probe surface is rectangular, the center point is defined as the intersection of the diagonals of the rectangle.
  • the reason why the direction of the receiving sound axis AX2 is the normal direction to the probe surface is because the virtual ultrasonic beam U radiated from the receiving probe 121 is emitted in the normal direction to the probe surface.
  • the ultrasonic beam U incident in the normal direction to the probe surface can be received with good sensitivity.
  • the eccentricity distance L is defined as the deviation between the transmission sound axis AX1 and the reception sound axis AX2. Therefore, as shown in FIG. 23B, when the ultrasonic beam U emitted from the transmission probe 110 is refracted, the eccentricity distance L is defined as the deviation between the refracted transmission sound axis AX1 and the reception sound axis AX2.
  • the transmission probe 110 and the reception probe 120 are adjusted by the eccentricity distance adjustment unit 105 (FIG. 22) so that the eccentricity distance L defined in this way is greater than zero.
  • FIG. 23A shows the case where the transmitting probe 110 is arranged in the normal direction on the surface of the test object E.
  • the transmitting sound axis AX1 is indicated by a solid arrow.
  • the receiving sound axis AX2 is indicated by a dashed arrow. Note that in Figs. 23A and 23B, the position of the receiving probe 121 indicated by the dashed line is a position where the eccentricity distance L is zero, and the receiving probe 121 where the transmitting sound axis AX1 and the receiving sound axis AX2 coincide is the receiving probe 140 as a coaxially arranged receiving probe.
  • the receiving probe 121 indicated by the solid line is the receiving probe 120 (eccentrically arranged receiving probe) arranged at a position with an eccentricity distance L greater than zero.
  • the transmitting probe 110 is installed so that the transmitting sound axis AX1 is perpendicular to the horizontal plane (xy plane in Fig. 22), the propagation path of the ultrasonic beam U is not refracted. In other words, the transmitting sound axis AX1 is not refracted. This corresponds to the case where the transmission probe 110 is installed so that the transmission sound axis AX1 of the transmission probe 110 is perpendicular to the mounting surface 1021 of the sample stage 102.
  • the transmitting probe 110 is installed so that the transmission sound axis AX1 is normal to the mounting surface 1021 of the test object E on the sample stage 102. As described above, this has the effect of making it easier to understand the correspondence between the scanning position and the position of the defect D, since the transmission sound axis AX1 is arranged perpendicular to the surface of the test object E for a plate-shaped test object E.
  • FIG. 23B shows a case where the transmitting probe 110 is arranged at an angle ⁇ from the normal direction on the surface of the test object E.
  • the transmitting sound axis AX1 is indicated by a solid arrow
  • the receiving sound axis AX2 is indicated by a dashed arrow.
  • the propagation path of the ultrasonic beam U is refracted at a refraction angle ⁇ at the interface between the test object E and the fluid F. Therefore, the transmitting sound axis AX1 is bent (refracted) as shown by the solid arrow in FIG. 23B.
  • the position of the receiving probe 140 shown by the dashed line is located on the transmitting sound axis AX1, so that the eccentricity distance L is zero.
  • the receiving probe 120 is arranged so that the distance between the transmitting sound axis AX1 and the receiving sound axis AX2 is L.
  • the transmitting probe 110 is installed in the normal direction to the surface of the test object E, so the eccentricity distance L is as shown in FIG. 23A.
  • Third Embodiment 24 is a diagram showing the configuration of an ultrasonic inspection device Z in the third embodiment.
  • the scanning measurement device 1 includes an installation angle adjustment unit 106 that adjusts the inclination of the receiving probe 120. This makes it possible to increase the strength of the received signal and to increase the signal-to-noise ratio (SNR) of the signal.
  • the installation angle adjustment unit 106 is, for example, configured by an actuator, a motor, etc., neither of which are shown in the figure.
  • the angle ⁇ between the transmission sound axis AX1 and the reception sound axis AX2 is defined as the receiving probe installation angle.
  • the transmitting probe 110 is installed vertically, so the transmission sound axis AX1 is vertical, and the angle ⁇ , which is the receiving probe installation angle, is the angle between the transmission sound axis AX1 (i.e., the vertical direction) and the normal to the probe surface of the receiving probe 120.
  • the installation angle adjustment unit 106 tilts the angle ⁇ toward the side where the transmission sound axis AX1 exists, and sets the angle ⁇ to a value greater than zero. That is, the receiving probe 120 is tilted.
  • the receiving probe 120 is tilted so as to satisfy 0° ⁇ 90°
  • the angle ⁇ is, for example, 10°, but is not limited to this.
  • the eccentricity distance L when the receiving probe 120 is arranged at an angle is defined as follows.
  • An intersection P12 between the receiving sound axis AX2 and the probe surface of the receiving probe 120 is defined.
  • An intersection P11 between the transmitting sound axis AX1 and the probe surface of the transmitting probe 110 is defined.
  • the eccentricity distance L is defined as the distance between the coordinate position (x4, y4) (not shown) obtained by projecting the position of intersection P11 onto the xy plane, and the coordinate position (x5, y5) (not shown) obtained by projecting the position of intersection P12 onto the xy plane.
  • FIG. 25 is a diagram explaining why the effect of the third embodiment is produced.
  • the scattered wave U1 propagates in a direction deviating from the transmission sound axis AX1. Therefore, as shown in FIG. 25, when the scattered wave U1 reaches the outside of the test object E, it is incident on the interface between the test object E and the outside at a non-zero angle ⁇ 2 with the normal vector of the test object E's surface.
  • the angle of the scattered wave U1 emerging from the surface of the test object E has an angle ⁇ 2, which is a non-zero exit angle with respect to the normal direction of the test object E's surface.
  • the scattered wave U1 can be received most efficiently when the normal vector of the probe surface of the receiving probe 120 is aligned with the traveling direction of the scattered wave U1. In other words, the strength of the received signal can be increased by tilting the receiving probe 120.
  • the reception effect is highest when the angle ⁇ 2 of the ultrasonic beam U emitted from the subject E coincides with the angle ⁇ between the transmission sound axis AX1 and the reception sound axis AX2.
  • the angle ⁇ 2 and the angle ⁇ do not coincide perfectly, the effect of increasing the reception signal can be obtained, so as shown in Figure 25, the angle ⁇ 2 and the angle ⁇ do not have to coincide perfectly.
  • Fourth Embodiment 26 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the fourth embodiment.
  • the filter used in the filter section 240 is determined by irradiating an ultrasonic beam U onto a sample (not shown) having a known position of a defect D before inspection of the object to be inspected E. Then, the inspection of the object to be inspected E is performed using the filter determined before the inspection.
  • the filter unit 240 includes a detection unit 244 and a determination unit 245.
  • the detection unit 244 detects multiple different foot components W3 of the fundamental wave band W1 in the relationship between frequency and signal strength (component strength).
  • the relationship referred to here is, for example, the relationship shown in FIG. 11, which is obtained by irradiating an ultrasonic beam U to a healthy part N and a defective part D in a sample (not shown) in which the position of the defective part D is known.
  • the determination unit 245 determines which foot component W3 to use by comparing the multiple detected foot components W3. By configuring the filter unit 240 in this way, it is possible to use a foot component W3 that makes it easy to identify signal changes caused by the defective part D, and the detection accuracy of the defective part D can be improved.
  • the detection unit 244 includes, for example, a filter capable of detecting different foot components W3.
  • the filter here is, for example, at least two of the band-blocking filter (FIG. 15A), low-pass filter (FIG. 16A), and high-pass filter (FIG. 17A).
  • the detection unit 244 detects the foot components W3 shown in FIG. 15B, FIG. 16B, and FIG. 17B using the three filters in the relationship shown in FIG. 11.
  • the determination unit 245 then compares the three detected foot components W3 with each other, for example by selecting the foot component W3 with the largest difference between the healthy part N and the defective part D, and determines which foot component W3 to use.
  • the filter unit 240 uses the determined foot component W3 to inspect the test object E, thereby improving the detection accuracy of the defective part D.
  • Fifth Embodiment 27 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the fifth embodiment.
  • the ultrasonic beam U is irradiated onto a sample (not shown) whose position of the defect D is known, and the data obtained is presented to a user, who then decides which base component W3 to use, i.e., which filter to use.
  • the control device 2 includes a display unit 223 and a reception unit 224.
  • the display unit 223 and the reception unit 224 are provided in the data processing unit 201.
  • the display unit 223 displays the relationship between frequency and signal strength (component strength) on the display device 3.
  • the relationship is, for example, the relationship shown in FIG. 11, which is obtained by irradiating an ultrasonic beam U to a healthy part N and a defective part D in a sample (not shown) whose position of the defective part D is known.
  • the reception unit 224 receives information input by the user based on the relationship between frequency and signal strength, and represents the foot component W3 to be detected.
  • the input is performed through the input device 4, which is, for example, a keyboard, a mouse, a touch panel, etc.
  • the filter unit 240 detects the foot component W3 corresponding to the information based on the information received by the reception unit 224.
  • the base component W3 to be detected can be determined based on the user's subjective opinion. This allows the user to make a determination based on their experience, making it possible to perform an inspection that is suited to the actual inspection.
  • Sixth Embodiment 28 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the sixth embodiment.
  • the received signal is converted into frequency components by a frequency conversion unit 230 and stored, and after the measurement for the inspection, an image is generated using appropriate frequency components. This constitutes a filter unit 240.
  • the control device 2 controls the driving of the scanning measurement device 1.
  • the control device 2 includes a transmission system 210, a reception system 220, a data processing unit 201, a scan controller 204, a driving unit 202, a position measurement unit 203, and a signal processing unit 250.
  • the driving unit 202 changes the relative positions of the transmitting probe 110 and the receiving probe 121 with respect to the subject E, for example, by driving the transmitting probe 110 and the receiving probe 121.
  • the position measurement unit 203 measures the scanning position.
  • the scan controller 204 drives the transmitting probe 110 and the receiving probe 121 through the driving unit 202.
  • the scanning positions of the transmitting probe 110 and the receiving probe 121 are input to the scan controller 204 through the position measurement unit 203.
  • the receiving system 220 and the data processing unit 201 are collectively referred to as the signal processing unit 250.
  • the signal processing unit 250 performs signal processing on the signal from the receiving probe 121, such as amplification processing and frequency selection processing, to extract significant information.
  • the transmission system 210 is a system that generates a voltage to be applied to the transmission probe 110.
  • the configuration of the transmission system 210 is the same as in the first embodiment.
  • the voltage waveform applied to the transmitting probe 110 is a repeating wave packet waveform, as shown in FIG. 9 above.
  • the voltage waveform applied is the same as in the first embodiment.
  • the signal processing unit 250 includes a data processing unit 201 and a receiving system 220.
  • the receiving system 220 is a system that detects the received signal output from the receiving probe 121.
  • the signal output from the receiving probe 121 is input to a signal amplifier 222 and amplified.
  • the amplified signal is input to a frequency conversion unit 230.
  • the frequency conversion unit 230 is included in the signal processing unit 250 and converts the received signal of the receiving probe 121 into frequency components (signal processing).
  • the frequency conversion unit 230 converts the received signal, which is a time domain waveform, into frequency components.
  • the frequency components are the magnitude (spectrum) of each frequency component. Examples of frequency components include a method of expressing a combination of a real part and an imaginary part as a complex number, and a method of expressing an amplitude (absolute value) and a phase.
  • the conversion in the frequency conversion unit 230 can be performed, for example, by a Fourier transform. The conversion may also be performed along with the extraction of only frequency components in a pre-specified frequency range (frequency parameters).
  • the signal converted into frequency components by the frequency conversion unit 230 is input to the data processing unit 201.
  • the frequency conversion unit 230 may be provided inside the data processing unit 201. That is, the conversion into frequency components may be performed within the data processing unit.
  • the data processing unit 201 includes a storage unit 261, a frequency selection unit 242, an imaging unit 262, and a display unit 263. Therefore, the signal processing unit 250 includes a frequency conversion unit 230, an imaging unit 262, a frequency selection unit 242, and a display unit 263.
  • the frequency conversion unit 230 converts the time domain waveform into frequency component data and stores it together with the position information in the storage unit 261.
  • the imaging unit 262 then generates an image 273 (described below) indicating the defect position using a portion of the converted frequency components that is specified by the frequency parameters, as described in detail below. That is, the imaging unit 262 visualizes the signal features based on the input frequency parameters. That is, when the test object E is measured once, the conversion to frequency component data is performed only once, and the extraction of the signal features from the frequency component data is performed multiple times.
  • the conversion process to frequency component data in the frequency conversion unit 230 takes time.
  • a Fourier transform is used as described above, but even if a fast Fourier transform (FFT), known as a high-speed algorithm, is used, the processing time for this conversion is long.
  • FFT fast Fourier transform
  • the signal feature amount is calculated using equation (1) described later, and the calculation time required for this is short.
  • the process is completed in 0.2 seconds or less even for measurement points of 100 rows x 100 columns.
  • the signal waveform of the receiving probe 140 has about 100,000 points for one measurement position in the time domain waveform, whereas the frequency component data only requires complex numbers for 20 to 100 different frequencies. In other words, the amount of data for the subject E can be reduced to about 1/1000. This has the advantage of significantly reducing the amount of data stored in the memory unit 261.
  • the data processing unit 201 also receives information on the scanning position from the scan controller 204. In this way, data on the frequency components of the received signal at the current two-dimensional scanning position (x, y) (hereinafter referred to as frequency component data) is obtained.
  • the data processing unit 201 associates the scanning position (x, y) with the frequency component data at that position and stores them in the storage unit 261. Note that an image 273 of the defect D is created by determining the signal feature amount determined from the frequency component data for each scanning position.
  • the frequency component data is frequency components corresponding to multiple frequencies.
  • the frequency component data is a frequency spectrum obtained by Fourier transform of the received signal.
  • the frequency components it is more preferable for the frequency components to include phase information in addition to amplitude (absolute value). This is synonymous with treating the frequency components as complex numbers. As described below, by including phase information, it is possible to calculate signal features with higher performance.
  • the data processing unit 201 includes an imaging unit 262.
  • the imaging unit 262 is included in the signal processing unit 250, and generates an image 273 (described below) indicating the position (defect position) of the defect D using a portion of the converted frequency components that is specified by the frequency parameters.
  • the imaging unit 262 creates the image 273 based on the change (amount of change) in the signal caused by the defect D of the test object E in the frequency spectrum of the portion that corresponds to the appropriate frequency parameter out of the frequency spectrum that corresponds to the frequency components converted by the frequency conversion unit 230. In this way, the image 273 can be generated.
  • the signal change (change in the received signal) referred to here is a signal feature in the example of the present disclosure. Therefore, the imaging unit 262 first calculates the signal feature from the portion of the frequency spectrum corresponding to the converted frequency component that is the input frequency parameter.
  • the signal feature is, for example, a value that represents the signal change as described above, and is a value calculated from the frequency component data so as to appropriately include defect information (for example, the position of the defect D).
  • defect information for example, the position of the defect D.
  • the above procedure is performed while changing the scanning position (x, y) to scan the desired range.
  • frequency component data and signal features corresponding to the scanning position (x, y) are stored in the memory unit 261 in the data processing unit 201.
  • the signal features are calculated each time a signal is acquired at the scanning position.
  • the frequency component data may be stored in the memory unit 261, and the signal features may be calculated collectively to generate a defect image after measurement.
  • Equation (1) j is the imaginary unit
  • Re[ ] is the process of extracting the real part of a complex number.
  • the subscript ⁇ of the ⁇ symbol indicates the frequency set of the angular frequency components to be integrated.
  • the angular frequency components to be integrated are calculated for an appropriately set frequency set ⁇ , as described below.
  • the set of frequencies ⁇ to be included in the accumulation is called a frequency parameter.
  • the frequency parameter may be specified in the form of a frequency set ⁇ or in the form of a frequency range.
  • the frequency parameter may also be set in advance.
  • the frequency parameter may also be input by the user.
  • the h(t) obtained by equation (2) is a time domain signal waveform synthesized from a frequency set set by the frequency parameters.
  • the difference between the maximum and minimum values of this h(t) (Peak-to-Peak value) is used as the signal feature.
  • the difference between the maximum and minimum values (Peak-to-Peak value) is abbreviated as the PP value.
  • H( ⁇ ) and exp(j ⁇ t) are both complex numbers, and are calculated as complex numbers.
  • the signal feature is calculated taking into account the phase information of the frequency component H( ⁇ ). This is more preferable because it allows for a signal feature that accurately reflects the position information of the defect D.
  • the selection of the frequency parameters is important.
  • the maximum component frequency fm is excluded from the set of frequencies ⁇ to be included in the accumulation.
  • a filter section 240 can be configured that reduces at least the maximum intensity frequency component of the received signal of the receiving probe 120.
  • the frequencies to be included in the accumulation include the frequency of the base component W3 of the fundamental wave band W1. This can improve the detectability of the defective portion D in the inspected object E. Furthermore, it is even more effective to also exclude frequency components near the maximum component frequency fm.
  • the maximum component frequency fm is the frequency at which the spectrum of the fundamental wave band W1 of the received signal is at its maximum, but in this disclosure it is defined as the frequency at which it is approximately at its maximum.
  • the set of frequencies ⁇ to be included in the accumulation may include only frequencies lower than the maximum component frequency fm. This allows the filter section 240 to be configured with low-pass filter characteristics. Similarly, it may include only frequencies lower than the maximum component frequency fm.
  • the frequency parameters are appropriately set in the frequency selection unit 242 ( Figure 28). In this way, the frequency conversion unit 230 and the frequency selection unit 242 form the filter unit 240.
  • the frequency parameters may be set to appropriate parameters before the test, or may be changed after the measurement. They may also be set by the user.
  • the signal feature amount is not limited to the above calculation method, as long as it is a value calculated from frequency component data so as to appropriately include the position information of the defect D.
  • the PP value of the signal waveform h(t) in the time domain is used as the signal feature amount, but the absolute value of h(t) may be calculated, and the area of h(t) may be calculated as the signal feature amount.
  • the procedure for calculating the area is to sample h(t) at appropriate time intervals and calculate the sum of h(t) at the sampling points.
  • the squared value of h(t) may be used instead of using equations (1) and (2), the absolute values of the frequency components H( ⁇ ) may be summed for the input frequency set ⁇ and used as the signal feature amount.
  • FIG. 29 is a diagram showing the hardware configuration of the control device 2.
  • the above-mentioned configurations, functions, and each part constituting the block diagram may be realized in hardware by designing some or all of them as an integrated circuit, for example.
  • the above-mentioned configurations, functions, etc. may be realized in software by a processor such as a CPU 252 interpreting and executing a program that realizes each function.
  • the control device 2 includes, for example, a memory 251, a CPU 252, a storage device 253 (SSD, HDD, etc.), a communication device 254, and an I/F 255.
  • information such as programs, tables, and files that realize each function can be stored in a recording device such as a memory or SSD (Solid State Drive), or a recording medium such as an IC (Integrated Circuit) card, an SD (Secure Digital) card, or a DVD (Digital Versatile Disc).
  • a recording device such as a memory or SSD (Solid State Drive), or a recording medium such as an IC (Integrated Circuit) card, an SD (Secure Digital) card, or a DVD (Digital Versatile Disc).
  • FIG. 30 is a flow chart showing the ultrasonic inspection method of each of the above-mentioned embodiments.
  • the ultrasonic inspection method of the first embodiment can be performed by the above-mentioned ultrasonic inspection device Z, and will be described as an example with reference to FIG. 1 and FIG. 6 as appropriate.
  • the ultrasonic inspection method of the first embodiment inspects the object E (FIG. 1) by irradiating the object E (FIG. 1) with an ultrasonic beam U via a gas G (FIG. 1).
  • the ultrasonic inspection method disclosed herein includes steps S101 to S105, S111, and S112.
  • the transmitting probe 110 performs step S101 (emission step) of emitting an ultrasonic beam U from the transmitting probe 110.
  • step S101 an ultrasonic beam U of a repeating wave packet composed of a wave packet with a wave number of two or more is emitted from the transmitting probe 110.
  • step S102 reception step of receiving the ultrasonic beam U.
  • step S103 filter processing step of reducing a specific frequency range, specifically, a component (maximum intensity frequency component) in a frequency range including the maximum component frequency fm, based on the signal (e.g., waveform signal) of the ultrasonic beam U received by the receiving probe 121. That is, in step S103, the maximum intensity frequency component of the signal of the ultrasonic beam U received in step S102 is reduced.
  • step S104 signal intensity calculation step
  • step S104 the base component W3 of the fundamental wave band W1 of the signal of the ultrasonic beam U is detected.
  • a peak-to-peak signal is used as a method of generating the signal intensity data. This is the difference between the maximum value and the minimum value of the signal.
  • step S105 shape display step
  • Scanning position information of the transmitting probe 110 and the receiving probe 121 is sent from the position measurement unit 203 to the scan controller 204.
  • the data processing unit 201 plots the signal intensity data at each scanning position against the scanning position information of the transmitting probe 110 obtained from the scan controller 204. In this way, the signal intensity data is visualized. This is step S105.
  • FIG. 8B shows a case where the scanning position information is one-dimensional (one direction); when the scanning position information is two-dimensional (x, y), the signal intensity data is plotted to show the defect D as a two-dimensional image, which is then displayed on the display device 3.
  • the data processing unit 201 determines whether the scanning is complete (step S111). If the scanning is complete (Yes), the control device 2 ends the processing. If the scanning is not complete (No), the data processing unit 201 outputs a command to the driving unit 202 to move the transmitting probe 110 and the receiving probe 121 to the next scanning position (step S112), and the processing returns to step S101.
  • Fig. 31 is a diagram showing the configuration of an ultrasonic inspection device Z of the seventh embodiment.
  • a scanning measurement device 1 is shown in a schematic cross-sectional view.
  • Fig. 31 shows a coordinate system of three orthogonal axes including an x-axis as a left-right direction on the paper, a y-axis as a direction perpendicular to the paper, and a z-axis as a top-bottom direction on the paper.
  • the ultrasonic inspection device Z inspects the object E by irradiating an ultrasonic beam U (described later) to the object E through a fluid F.
  • the fluid F is a gas G such as air, and the object E is present in the fluid F.
  • air an example of gas G
  • the inside of the housing 101 of the scanning measurement device 1 is a cavity filled with air.
  • the ultrasonic inspection device Z includes the scanning measurement device 1, a control device 2, and a display device 3.
  • the display device 3 is connected to the control device 2.
  • the scanning measurement device 1 scans and measures the object E with an ultrasonic beam U, and includes a sample stage 102 fixed to a housing 101, on which the object E is placed. It is more preferable that the object E is fixed to the sample stage 102 with a fixture (not shown) so as not to move. If the object E is heavy enough not to move inadvertently, a fixture is not necessary.
  • the object E is made of any material.
  • the object E is, for example, a solid material, and more specifically, is, for example, a metal, glass, a resin material, or a composite material such as CFRP (Carbon-Fiber Reinforced Plastics).
  • CFRP Carbon-Fiber Reinforced Plastics
  • the object E has a defect D inside.
  • the defect D (defect) is a cavity, etc. Examples of the defect D are a cavity, a foreign material different from the material that should be there, etc.
  • the portion other than the defective portion D is called the healthy portion N.
  • the defective area D and the healthy area N are made of different materials, so the acoustic impedance differs between the two, and the propagation characteristics of the ultrasonic beam U change.
  • the ultrasonic inspection device Z observes this change to detect the defective area D.
  • the scanning measurement device 1 has a transmitting probe 110 that emits an ultrasonic beam U and a receiving probe 121 that receives the ultrasonic beam U.
  • the transmitting probe 110 is installed in the housing 101 via the transmitting probe scanning unit 103, and emits an ultrasonic beam U.
  • the receiving probe 121 is a receiving probe 140 (coaxially arranged receiving probe) that is installed on the opposite side of the transmitting probe 110 with respect to the subject E to receive the ultrasonic beam U and is arranged coaxially with the transmitting probe 110 (the eccentric distance L described below is zero).
  • the eccentric distance L (distance, described below) between the transmitting sound axis AX1 (sound axis) of the transmitting probe 110 and the receiving sound axis AX2 (sound axis) of the receiving probe 140 is zero. This makes it possible to easily install the transmitting probe 110 and the receiving probe 140.
  • the opposite side of the transmitting probe 110 means, of the two spaces separated by the subject E, the space opposite the space in which the transmitting probe 110 is located (the opposite side in the z-axis direction), and does not mean limited to the opposite side with the same x and y coordinates (i.e., a position that is symmetrical with respect to the xy plane).
  • the transmitting probe 110 is installed so that the transmission sound axis AX1 of the transmitting probe 110 is perpendicular to the mounting surface 1021 of the sample stage 102.
  • the transmitting probe 110 is installed so that the transmission sound axis AX1 is normal to the mounting surface 1021 of the sample stage 102 for the object E to be inspected.
  • the transmission sound axis AX1 is arranged perpendicular to the surface of the object E to be inspected, which has the effect of making it easier to understand the correspondence between the scanning position and the position of the defect D.
  • the control device 2 is connected to the scanning measurement device 1.
  • the control device 2 controls the driving of the scanning measurement device 1, and controls the movement (scanning) of the transmitting probe 110 and the receiving probe 121 by instructing the transmitting probe scanning unit 103 and the receiving probe scanning unit 104.
  • the transmitting probe scanning unit 103 and the receiving probe scanning unit 104 move in the x-axis and y-axis directions in sync, so that the transmitting probe 110 and the receiving probe 121 scan the subject E in the x-axis and y-axis directions.
  • the control device 2 emits an ultrasonic beam U from the transmitting probe 110, and performs waveform analysis based on the signal acquired from the receiving probe 121.
  • the plane formed by the two axes, the x-axis and y-axis directions, which are the scanning directions of the transmitting probe 110, is called the scanning plane.
  • gas G is interposed between the transmitting probe 110 and the test subject E, and between the receiving probe 121 and the test subject E. Therefore, the transmitting probe 110 and the receiving probe 121 can test the test subject E without contacting it, so that the relative positions in the xy plane can be changed smoothly and quickly. In other words, by interposing a fluid F (gas G) between the transmitting probe 110 and the receiving probe 121 and the test subject E, smooth scanning becomes possible.
  • the emitted ultrasonic beam U is locally irradiated onto the object E to be inspected.
  • the position to which the localized ultrasonic beam U is irradiated is changed by scanning.
  • the ultrasonic beam U that reaches the receiving probe 121 changes depending on whether it is a defective part D or a healthy part N of the object E to be inspected, so this configuration makes it possible to detect the defective part D.
  • a focused transmitting probe 110 is used to generate a localized ultrasonic beam U.
  • the transmitting probe 110 is a convergent type transmitting probe 110.
  • the receiving probe 121 uses a probe with looser convergence than the transmitting probe 110.
  • a non-convergent type probe with a flat probe surface is used for the receiving probe 121. Therefore, the receiving probe 121 is a non-convergent type receiving probe.
  • the scattered wave U1 is efficiently detected by focusing on the difference in frequency detected in the received signal. The details are as described with reference to FIG. 5.
  • FIG. 32 is a functional block diagram of the control device 2.
  • the control device 2 controls the driving of the scanning measurement device 1.
  • the control device 2 includes a transmission system 210, a reception system 220, a data processing unit 201, a scan controller 204, a driving unit 202, a position measurement unit 203, and a signal processing unit 250.
  • the driving unit 202 changes the relative positions of the transmitting probe 110 and the receiving probe 121 with respect to the test subject E, for example, by driving the transmitting probe 110 and the receiving probe 121.
  • the position measurement unit 203 measures the scanning position.
  • the scan controller 204 drives the transmitting probe 110 and the receiving probe 121 through the driving unit 202.
  • the scanning positions of the transmitting probe 110 and the receiving probe 121 are input to the scan controller 204 through the position measurement unit 203.
  • the receiving system 220 and the data processing unit 201 are collectively referred to as the signal processing unit 250.
  • the signal processing unit 250 performs signal processing on the signal from the receiving probe 121, such as amplification and filtering, to extract significant information.
  • the transmission system 210 is a system that generates a voltage to be applied to the transmission probe 110.
  • the transmission system 210 includes a waveform generator 211, a signal amplifier 212, and a transmission frequency setting unit 213.
  • a burst wave signal is generated by the waveform generator 211.
  • the generated burst wave signal is then amplified by the signal amplifier 212.
  • the voltage output from the signal amplifier 212 is applied to the transmission probe 110.
  • the waveform of the burst wave signal will be described later, but in brief, the waveform is a repeating wave packet waveform in which a wave packet of wave number N is repeated at fundamental frequency f0.
  • the transmission system 210 includes a transmission frequency setting unit 213.
  • the transmission frequency setting unit 213 can change the fundamental frequency f0. Since one of the features of this disclosure is the method of selecting the fundamental frequency f0, the changed fundamental frequency f0 is called the excitation frequency fex (excitation frequency) in the sense of the frequency that excites the transmission probe 110.
  • the performance of the ultrasonic inspection device Z of this embodiment can be improved by setting the excitation frequency fex to an appropriate value.
  • the transmitting probe 110 when the transmitting probe 110 is operated at a specific frequency determined for each probe, the amplitude intensity (sound pressure) of the generated ultrasound is maximized. This maximum frequency is called the natural frequency fres (resonance frequency) of the transmitting probe 110.
  • the reason that the sound pressure is maximized at the natural frequency is because the vibration of the built-in piezoelectric element resonates at the natural frequency fres. For this reason, the transmitting probe 100 is usually used with the excitation frequency set equal to the natural frequency.
  • the excitation frequency fex is set to a frequency that is shifted from the natural frequency fres of the transmitting probe 110. Therefore, the scanning measurement device 1 drives the transmitting probe 110 at the excitation frequency fex that is shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110.
  • the signal processing unit 250 includes a data processing unit 201 and a receiving system 220.
  • the receiving system 220 is a system that detects the received signal output from the receiving probe 121.
  • the receiving system 220 includes a signal amplifier 222 and a filter unit 240.
  • the signal processing unit 250 includes a filter unit 240.
  • the signal output from the receiving probe 121 is input to the signal amplifier 222 and amplified.
  • the amplified signal is input to the filter unit 240 (blocking filter).
  • the filter unit 240 reduces (blocks) components of a specific frequency range of the input signal.
  • the filter unit 240 will be described later.
  • the output signal from the filter unit 240 is input to the data processing unit 201.
  • the configuration of the data processing unit 201 is similar to that used in the first embodiment.
  • the configuration of the filter unit 240 is also similar to that used in the first embodiment.
  • the data processing unit 201 generates signal strength data from the signal input from the filter unit 240.
  • the peak-to-peak signal is used as a method for generating signal strength data.
  • the peak-to-peak signal is the difference between the maximum and minimum values of the signal.
  • Another method for generating signal strength data is to use the strength of frequency components in a specific frequency range by performing a Fourier transform.
  • the data processing unit 201 also receives scanning position information from the scan controller 204. In this way, the signal intensity data value at the current two-dimensional scanning position (x, y) is obtained. By plotting the signal intensity data value (peak-to-peak signal amount) against the scanning position, an image (defect image) corresponding to at least one of the position and shape of the defect D is obtained. This defect image is output to the display device 3.
  • Filter section 240 The configuration of the filter unit 240 used in this embodiment is the same as that of the filter unit 240 in the first embodiment, as described above.
  • the definition of the filter unit 240 is also as described above.
  • the filter unit 240 is defined as a control unit that performs signal processing to reduce the intensity of signal components in a specified frequency range.
  • Filter processing is also defined as signal processing that reduces the intensity of signal components in a specified frequency range.
  • the maximum component frequency is the frequency at which the component intensity is maximum.
  • the maximum intensity frequency component is the frequency component at the maximum component frequency.
  • the filter unit 240 of this disclosure reduces the intensity of the fundamental wave band that includes the maximum intensity frequency component, i.e., the signal components in the frequency range that includes the maximum component frequency.
  • the distribution of component intensities for each frequency component is called the frequency spectrum.
  • the filter unit 240 reduces the component strength in the cutoff frequency range including the maximum component frequency fm. That is, the filter unit 240 reduces at least the maximum intensity frequency component (the component corresponding to the maximum component frequency fm) of the received signal of the receiving probe 121. The filter unit 240 then detects the base component W3 other than the maximum intensity frequency component of the fundamental wave band W1 including the maximum intensity frequency component. Because the filter unit 240 reduces the component strength in the cutoff frequency range, the proportion of the base component W3 in the fundamental wave band W1 increases in the signal after passing through the filter unit 240. In this way, the detection performance of the defect portion D can be improved, as described below.
  • Figure 33A shows the change in signal strength information depending on the position when the transmitting probe 110 and the receiving probe 121 are scanned across the defective portion D.
  • Figure 33A shows the result of measurement using a configuration in which the filter unit 240 is removed from the configuration in Figure 32 above.
  • the signal strength in the healthy portion N is v0.
  • the rate of change in signal strength ( ⁇ v/v0) is small.
  • the rate of change in signal strength is defined as the signal change amount ⁇ v at the defective portion D divided by the signal strength v0 at the healthy portion N.
  • Figure 33B shows the result of measuring signal strength information using a control device 2 ( Figure 32) equipped with a filter unit 240, with the excitation frequency fex of the transmitting probe 110 set to 0.78 MHz. It can be seen that the rate of change in signal strength ( ⁇ v/v0) at the location of defect D has increased, improving the detectability of defect D.
  • FIG. 9 above shows the voltage waveform of the burst wave applied to the transmitting probe 110.
  • the horizontal axis is time, and the vertical axis is voltage.
  • ten sine waves with a fundamental frequency f0 of 0.78 MHz are applied in the waveform of FIG. 9. These ten waves are called a wave packet.
  • the inverse of the fundamental frequency f0 is called the fundamental period T0.
  • the fundamental period T0 is the period of the waves that make up one wave packet.
  • each wave packet is a sine wave with a fundamental frequency of f0, but it may be a wave packet other than a sine wave.
  • the wave packet may be a wave packet composed of a rectangular wave with a wave number of N0.
  • Figure 34 shows the frequency component distribution of the received signal when 10 sine waves with a fundamental frequency f0 of 0.78 MHz are applied to the waveform shown in Figure 9 above.
  • the horizontal axis is frequency
  • the vertical axis is measured data of component strength at each frequency.
  • This is the frequency component distribution of a signal not processed by the filter unit 240.
  • 0.82 MHz, where the component strength is maximum is the maximum component frequency fm ( Figure 7).
  • the fundamental wave band W1 ( Figure 7) extends from 0.72 MHz to 0.86 MHz, and the components excluding the maximum component frequency fm are the skirt components W3 ( Figure 7).
  • the maximum component frequency fm is equal to the fundamental frequency f0 ( Figure 9) of the ultrasound transmitted by the transmitting probe 110. In this way, in many cases, the maximum component frequency fm is roughly equal to the fundamental frequency f0 of the ultrasound transmitted.
  • the filter section 240 excludes the maximum component frequency fm. Specifically, in the illustrated example, the filter section 240 (Fig. 32) transmits the base component W3 below 0.78 MHz and blocks waves above 0.78 MHz, including 0.82 MHz.
  • the rate of change of the signal intensity at the defective section D increases, and it can be seen that the detectability of the defect is greatly improved.
  • Figure 35 is a diagram comparing the measured data of the frequency component distribution (frequency spectrum) of the received signal between a healthy part N (solid line) and a defective part D (dashed line).
  • the present disclosure is based on the new knowledge found by the inventors that in the frequency component distribution of a received signal, the base component W3 of the fundamental wave band W1 has a greater signal change rate at the defect D than the signal component at the maximum component frequency fm.
  • the component at the maximum component frequency fm accounts for a large proportion of the received signal, but the signal change rate at the defect D is small, so by reducing this component, the proportion of the base component W3 increases.
  • the signal after processing by the filter unit 240 has an increased signal change rate at the defect D, improving the detectability of the defect D.
  • the effect of improving the detectability of the defect D by the filter unit 240 is clear.
  • the filter section 240 preferably includes at least one of a band-blocking filter, a low-pass filter, or a high-pass filter. By including at least one of these, it is possible to reduce components in a frequency range that includes the maximum component frequency fm.
  • a representative configuration of the filter section 240 is similar to that described in the first embodiment.
  • the implementation method of the filter unit 240 is roughly divided into an analog type and a digital type. In this embodiment, the effect can be obtained regardless of whether the analog type or the digital type is used. The specific configurations of the analog type and the digital type are described in the first embodiment.
  • the direct wave U3 which does not interact with the defective part D, does not change in wave propagation direction, phase, frequency, etc. Therefore, the signal component of the maximum component frequency fm is largely dominated by the direct wave U3. Therefore, the change between the defective part D and the healthy part N is small.
  • the scattered wave U1 that interacts with the defect D has components that change the propagation direction, and components that do not change the propagation direction but at least one of the phase or frequency changes. Furthermore, among the components that change the propagation direction, there are components whose frequency changes. Therefore, the proportion of the scattered wave U1 component, which is the ultrasonic beam U that interacts with the defect D, in the base component W3 of the fundamental wave band W1, which is a component shifted from the maximum frequency fm, increases. As a result, the change between the defect D and the healthy part N becomes greater. In this way, the detection performance of the defect D can be improved by reducing the component of the maximum component frequency fm and detecting the base component W3 of the fundamental wave band W1.
  • the performance of detecting the defect D is improved by detecting the foot component W3 of the fundamental wave band W1. Therefore, increasing the foot component W3 of the fundamental wave band W1 further contributes to improving the detection performance. Therefore, the inventors have thoroughly studied the relationship of the transmitted ultrasonic waveform to increase the foot component W3 of the fundamental wave band W1.
  • the wave number of a wave packet is the number of waves of fundamental frequency f0 contained in one wave packet, as shown in FIG.
  • Figure 36A shows the frequency spectrum of the wave number N0 of the wave packet and the fundamental wave band W1 of the ultrasound.
  • the spectrum shown by the dashed dotted line is for a continuous wave. In the case of a continuous wave, it only has the component of the fundamental frequency f0, and the skirt component W3 is almost nonexistent.
  • Figure 36B shows how the full width at half maximum (FWHM) of the fundamental waveband of the spectrum shown in Figure 36A changes with respect to the wave number N0 of the wave packet.
  • FWHM full width at half maximum
  • the change due to the defect D is large in the base component W3 of the fundamental wave band W1, so it is preferable that the ultrasonic waves used in the present disclosure are ultrasonic waves composed of repeated wave packets rather than continuous waves.
  • the smaller the wave number N0 of each wave packet the more the base component W3 of the fundamental wave band W1 increases, so the smaller the wave number N0, the more preferable it is.
  • the wave number N0 of the wave packet is 30 or less.
  • the full width at half maximum (FWHM) of the fundamental wave band is too wide.
  • the wave number N0 of the wave packet is preferably 2 or more, and more preferably 3 or more. The reasons for this are as described in the first embodiment.
  • the wave number N0 of the wave packet is 2 or more and 30 or less.
  • the width of the fundamental wave band W1 of the spectrum of the transmitted wave is narrower than this.
  • the full width at half maximum of the frequency spectrum of the fundamental wave band W1 is 50% or less of the maximum component frequency fm. This can improve the detection accuracy of the defect D.
  • the frequency detected by the filter section 240 includes frequency components in the range of (fm ⁇ 0.25fm) with respect to the maximum component frequency fm.
  • 0.25fm means 0.25 times (i.e., 25%) the maximum component frequency fm.
  • the filter section 240 detects frequency components that include the range of (fm ⁇ 0.15fm) with respect to the maximum component frequency fm.
  • the excitation frequency fex is a frequency corresponding to the fundamental frequency f0 of the wave packet, and is a frequency applied to the transmission probe 110.
  • the excitation frequency fex is set in the frequency range of the fundamental wave band W1.
  • the transmitting probe 110 has a natural frequency fres (resonance frequency).
  • the natural frequency fres of the transmitting probe 110 is the frequency at which the piezoelectric element constituting the transmitting probe 110 is most likely to vibrate.
  • the intensity (acoustic energy) of the emitted ultrasonic waves is maximized, so the excitation frequency fex is usually set to be equal to the natural frequency fres of the transmitting probe 110.
  • the natural frequency fres is synonymous with the resonance frequency fres.
  • Figure 37 shows the results of measuring the frequency spectrum of the received signal by changing the excitation frequency fex.
  • the natural frequency fres of this transmitting probe 110 is 0.82 MHz.
  • the dashed line in Figure 37 shows the frequency spectrum when the excitation frequency fex is set equal to the natural frequency fres.
  • this is the normal usage method.
  • This measurement uses a repeating wave packet, and the wave number N0 of each wave packet is 10.
  • the fundamental wave band W1 has a certain degree of spread and a skirt component W3.
  • the frequency spectrum shown by the dotted line has a spectral shape that is roughly symmetrical around the natural frequency fres.
  • the solid line in Figure 37 is the frequency spectrum when the excitation frequency fex is set to 0.78 MHz, which is 40 kHz lower than the natural frequency fres.
  • the set value of the excitation frequency fex (0.78 MHz) is within the frequency range of the fundamental wave band W1, and is a value shifted from the natural frequency fres. It can be seen that the amount (component strength) of the base component W3 of the fundamental wave band W1 is increased in the solid line spectrum compared to the dashed line spectrum.
  • the excitation frequency fex is set to a value within the frequency range of the fundamental wave band W1 and shifted from the natural frequency fres, the amount of the base component W3 of the fundamental wave band W1 increases, improving the detection performance of the defect D. Therefore, it is preferable to set the excitation frequency fex within the frequency range of the fundamental wave band W1.
  • the full width at half maximum of the fundamental wave band W1 is 50% or less of the maximum component frequency fm. Therefore, it is preferable that the excitation frequency fex is set in the range of (fres ⁇ 0.25 fm), where fres is the natural frequency of the transmitting probe 110. In other words, it is preferable that the absolute value
  • Figure 38 shows the change in instantaneous frequency in the time domain of one wave packet.
  • the instantaneous frequency was found from the zero crossing points of the amplitude waveform.
  • the zero crossing points indicate the time when the signal crosses the zero point, and the period can be determined from the interval between the zero crossing points, so the instantaneous frequency can be calculated.
  • the wave number N0 of the wave packet was set to 10.
  • the dashed line shows the results when the excitation frequency fex was set to 0.82 MHz, which is equal to the natural frequency fres, and the solid line shows the results when the excitation frequency fex was set to 0.74 MHz.
  • the excitation frequency fex when the excitation frequency fex is set equal to the natural frequency fres, the instantaneous frequency becomes constant at the natural frequency fres of 0.82 MHz. This corresponds to the conventional setting conditions.
  • a localized ultrasonic beam U is irradiated onto the object E to be inspected, and a defect D at that position is detected. Therefore, the smaller the beam diameter of the localized ultrasonic beam U, the more preferable it is. For this reason, it is preferable to use a convergent probe for the transmitting probe 110.
  • the natural frequency fres of the transmitting probe 110 is 200 kHz or higher.
  • the natural frequency of the transmitting probe 110 is 0.82 MHz (820 kHz).
  • the scattered wave U1 is detected, so as shown in Figure 5 above, it is possible to detect a defect D that is smaller than the beam diameter.
  • each wave packet is a sine wave with a fundamental frequency of f0, but it may be a wave packet other than a sine wave.
  • it may be a wave packet composed of a rectangular wave with a wave number of N0.
  • the excitation frequency fex may be a wave having multiple excitation frequencies within one wave packet.
  • a chirp wave, whose frequency changes over time, is known as such a wave.
  • each excitation frequency is set within the frequency range of the fundamental wave band W1.
  • Eighth embodiment 39 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the eighth embodiment.
  • the filter used in the filter section 240 is determined by irradiating an ultrasonic beam U onto a sample (not shown) having a known position of a defect D before inspection of the object to be inspected E. Then, the inspection of the object to be inspected E is performed using the filter determined before the inspection.
  • the transmission system 210 is a system that generates a voltage to be applied to the transmission probe 110.
  • the transmission system 210 includes a waveform generator 211, a signal amplifier 212, and a transmission frequency setting unit 213.
  • a burst wave signal is generated by the waveform generator 211.
  • the generated burst wave signal is then amplified by the signal amplifier 212.
  • the voltage output from the signal amplifier 212 is applied to the transmission probe 110.
  • the transmitting probe 110 is driven by a burst wave.
  • the transmitting system 210 includes a transmitting frequency setting unit 213.
  • the transmitting frequency setting unit 213 can change the fundamental frequency f0 of the burst wave, and can set the fundamental frequency f0 to an appropriate excitation frequency fex.
  • the excitation frequency fex is set to a frequency shifted from the natural frequency fres of the transmitting probe 110. Therefore, the scanning measurement device 1 drives the transmitting probe 110 at the excitation frequency fex shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110.
  • the excitation frequency fex is set to an appropriate value, the performance of the ultrasonic inspection device Z of this embodiment can be improved.
  • the filter unit 240 includes a detection unit 244 and a determination unit 245.
  • the detection unit 244 detects multiple different foot components W3 of the fundamental wave band W1 in the relationship between frequency and signal strength (component strength).
  • the relationship referred to here is, for example, the relationship shown in FIG. 35 above, which is obtained by irradiating an ultrasonic beam U to a healthy part N and a defective part D in a sample (not shown) whose position of the defective part D is known.
  • the determination unit 245 determines which foot component W3 to use by comparing the multiple detected foot components W3. By configuring the filter unit 240 in this way, it is possible to use a foot component W3 that makes it easy to identify signal changes caused by the defective part D, and the detection accuracy of the defective part D can be improved.
  • the detection unit 244 includes, for example, a filter capable of detecting different foot components W3.
  • the filter here is, for example, at least two of the band-blocking filter (FIG. 15A), low-pass filter (FIG. 16A), and high-pass filter (FIG. 17A).
  • the detection unit 244 detects the foot components W3 shown in FIG. 15B, FIG. 16B, and FIG. 17B using the three filters, for example, in the relationship shown in FIG. 35.
  • the determination unit 245 then compares the three detected foot components W3 with each other to determine which foot component W3 to use, for example, by selecting the foot component W3 with the largest difference between the healthy part N and the defective part D.
  • the filter unit 240 uses the determined foot component W3 to inspect the test object E, thereby improving the detection accuracy of the defective part D.
  • Ninth embodiment 40 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the ninth embodiment.
  • data obtained by irradiating an ultrasonic beam U onto a sample (not shown) having a known position of a defect D is presented to a user, and the user decides which base component W3 to use, i.e., which filter to use.
  • the transmission system 210 is a system that generates a voltage to be applied to the transmission probe 110.
  • the transmission system 210 includes a waveform generator 211, a signal amplifier 212, and a transmission frequency setting unit 213.
  • a burst wave signal is generated by the waveform generator 211.
  • the generated burst wave signal is then amplified by the signal amplifier 212.
  • the voltage output from the signal amplifier 212 is applied to the transmission probe 110.
  • the transmitting probe 110 is driven by a burst wave.
  • the transmitting system 210 includes a transmitting frequency setting unit 213.
  • the transmitting frequency setting unit 213 can change the fundamental frequency f0 of the burst wave, and can set the fundamental frequency f0 to an appropriate excitation frequency fex.
  • the excitation frequency fex is set to a frequency shifted from the natural frequency fres of the transmitting probe 110. Therefore, the scanning measurement device 1 drives the transmitting probe 110 at the excitation frequency fex shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110.
  • the excitation frequency fex is set to an appropriate value, the performance of the ultrasonic inspection device Z of this embodiment can be improved.
  • the control device 2 includes a display unit 223 and a reception unit 224.
  • the display unit 223 and the reception unit 224 are provided in the data processing unit 201.
  • the display unit 223 displays the relationship between frequency and signal strength (component strength) on the display device 3.
  • the relationship referred to here is, for example, the relationship shown in FIG. 35 above, which is obtained by irradiating an ultrasonic beam U to a healthy part N and a defective part D in a sample (not shown) whose position of the defective part D is known.
  • the reception unit 224 receives information input by the user based on the relationship between frequency and signal strength, and which represents the foot component W3 to be detected. The input is performed through the input device 4, which is, for example, a keyboard, a mouse, a touch panel, etc. Then, the filter unit 240 detects the foot component W3 corresponding to the information based on the information received by the reception unit 224.
  • the base component W3 to be detected can be determined based on the user's subjective opinion. This allows the user to make a determination based on their experience, making it possible to perform an inspection that is suited to the actual inspection.
  • the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110. This is because, as described above, by doing so, it becomes possible to detect more components of the scattered wave U1.
  • the scattered wave U1 is an ultrasonic beam U that has interacted with the defect D, so the greater the proportion of the scattered wave U1 components, the easier it becomes to detect the defect D.
  • the reason why increasing the focal length of the receiving probe 121 allows more scattered wave components to be detected is as described in the first embodiment. That is, by making the focal length R2 of the receiving probe 121 longer than the focal length R1 of the transmitting probe 110, the detectable scattered waves U1 can be increased. As described above, the scattered waves U1 are waves that have interacted with the defect D, and this can further improve the detection performance of the defect D.
  • the convergence of the receiving probe 121 is looser than that of the transmitting probe 110. That is, the focal length R2 of the receiving probe 121 is set longer than the focal length R1 of the transmitting probe 110. As a result, the beam incidence area T2 of the receiving probe 121 is wider, so that a wider range of scattered waves U1 can be detected. This makes it possible for the receiving probe 121 to detect the scattered waves U1 even if the propagation path of the scattered waves U1 changes slightly. As a result, a wider range of defective parts D can be detected.
  • a non-convergent probe may be used as the receiving probe 121 in a configuration in which the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110.
  • the focal length R2 is infinite, so it is longer than the focal length R1 of the transmitting probe 110.
  • the convergence of the receiving probe 121 is weaker than the convergence of the transmitting probe 110.
  • Eleventh Embodiment 41 is a diagram showing the configuration of an ultrasonic inspection device Z in the eleventh embodiment.
  • the transmission sound axis AX1 of the transmitting probe 110 and the reception sound axis AX2 of the receiving probe 121 are arranged to be shifted from each other. That is, the receiving probe 121 in the eleventh embodiment is a receiving probe 120 (eccentrically arranged receiving probe) having a reception sound axis AX2 arranged at a position different from the transmission sound axis AX1 of the transmitting probe 110. Therefore, the eccentric distance L (distance) between the transmission sound axis AX1 (sound axis) of the transmitting probe 110 and the reception sound axis AX (sound axis) of the receiving probe 120 is greater than zero.
  • the receiving probe 120 is arranged offset by an eccentric distance L in the x-axis direction of FIG. 41 with respect to the transmitting probe 110, but the receiving probe 120 may be arranged offset in the y-axis direction of FIG. 41.
  • the receiving probe 120 may be arranged at L1 in the x-axis direction and L2 in the y-axis direction (i.e., if the position of the transmitting probe 110 on the xy plane is taken as the origin, then the position is (L1, L2)).
  • the transmitting probe 110 is installed so that the transmission sound axis AX1 is normal to the mounting surface 1021 of the test object E on the sample stage 102. As described above, this has the effect of making it easier to understand the correspondence between the scanning position and the position of the defect D, since the transmission sound axis AX1 is arranged perpendicular to the surface of the test object E for a plate-shaped test object E.
  • the scanning measurement device 1 includes an installation angle adjustment unit 106 that adjusts the inclination of the receiving probe 120. This makes it possible to increase the strength of the received signal and to increase the signal-to-noise ratio (SNR) of the signal.
  • SNR signal-to-noise ratio
  • the configuration of the ultrasonic inspection device Z in this embodiment is as shown in FIG. 24.
  • the angle ⁇ between the transmission sound axis AX1 and the reception sound axis AX2 is defined as the receiving probe installation angle.
  • the transmitting probe 110 is installed vertically, so the transmission sound axis AX1 is vertical, and the angle ⁇ , which is the receiving probe installation angle, is the angle between the transmission sound axis AX1 (i.e., the vertical direction) and the normal to the probe surface of the receiving probe 120.
  • the installation angle adjustment unit 106 tilts the angle ⁇ toward the side where the transmission sound axis AX1 exists, and sets the angle ⁇ to a value greater than zero. That is, the receiving probe 120 is tilted.
  • the receiving probe 120 is tilted so as to satisfy 0° ⁇ 90°
  • the angle ⁇ is, for example, 10°, but is not limited to this.
  • the control device 2 controls the driving of the scanning measurement device 1.
  • the control device 2 includes a transmission system 210, a reception system 220, a data processing unit 201, a scan controller 204, a driving unit 202, a position measurement unit 203, and a signal processing unit 250.
  • the driving unit 202 changes the relative positions of the transmitting probe 110 and the receiving probe 121 with respect to the test subject E, for example, by driving the transmitting probe 110 and the receiving probe 121.
  • the position measurement unit 203 measures the scanning position.
  • the scan controller 204 drives the transmitting probe 110 and the receiving probe 121 through the driving unit 202.
  • the scanning positions by the transmitting probe 110 and the receiving probe 121 are input to the scan controller 204 through the position measurement unit 203.
  • the receiving system 220 and the data processing unit 201 are collectively referred to as the signal processing unit 250.
  • the signal processing unit 250 performs signal processing on the signal from the receiving probe 121, such as amplification processing and frequency selection processing, to extract significant information.
  • the transmission system 210 is a system that generates a voltage to be applied to the transmission probe 110.
  • the transmission system 210 includes a waveform generator 211 and a signal amplifier 212.
  • a burst wave signal is generated by the waveform generator 211.
  • the generated burst wave signal is then amplified by the signal amplifier 212.
  • the voltage output from the signal amplifier 212 is applied to the transmission probe 110.
  • the voltage waveform applied to the transmitting probe 110 is a repeating wave packet waveform as shown in FIG. 9 above.
  • Each wave packet is composed of a finite number of wave numbers N0 of sine waves with a fundamental frequency f0.
  • the fundamental frequency f0 corresponds to the excitation frequency fex.
  • the excitation frequency fex is set to a frequency shifted from the natural frequency fres of the transmitting probe. Specifically, the excitation frequency fex is set to 0.78 MHz for the natural frequency fres of the transmitting probe of 0.82 MHz.
  • the wave number N0 of the wave packet is set to 10.
  • the signal processing unit 250 includes a data processing unit 201 and a receiving system 220.
  • the receiving system 220 is a system that detects the received signal output from the receiving probe 121.
  • the signal output from the receiving probe 121 is input to a signal amplifier 222 and amplified.
  • the amplified signal is input to a frequency conversion unit 230.
  • the frequency conversion unit 230 is included in the signal processing unit 250 and converts the received signal from the receiving probe 121 into frequency components (signal processing), and in the example of the present disclosure, converts the received signal, which is a time domain waveform, into frequency components.
  • the frequency components are the magnitude (spectrum) of the components at each frequency.
  • the configuration of the frequency conversion unit 230 is the same as that in the sixth embodiment.
  • the data processing unit 201 includes a storage unit 261, an imaging unit 262, and a display unit 263.
  • the storage unit 261 includes a database 261a. Therefore, the signal processing unit 250 includes a frequency conversion unit 230, an imaging unit 262, the database 261a, and a display unit 263.
  • the frequency conversion unit 230 converts the time domain waveform into frequency component data and stores it together with the position information in the storage unit 261.
  • the imaging unit 262 then generates an image 273 (described below) indicating the defect position using a portion of the converted frequency components that is specified by the frequency parameters, as described in detail below. That is, the imaging unit 262 visualizes the signal features based on the input frequency parameters. That is, when the test object E is measured once, the conversion to frequency component data is performed only once, and the extraction of the signal features from the frequency component data is performed multiple times.
  • this configuration has two favorable points: it requires less time to perform calculations and reduces the amount of data.
  • the data processing unit 201 also receives information on the scanning position from the scan controller 204. In this way, data on the frequency components of the received signal at the current two-dimensional scanning position (x, y) (hereinafter referred to as frequency component data) is obtained.
  • the data processing unit 201 associates the scanning position (x, y) with the frequency component data at that position and stores them in the storage unit 261. Note that an image 273 of the defect D is created by determining the signal feature amount determined from the frequency component data for each scanning position.
  • the frequency component data is frequency components corresponding to multiple frequencies.
  • the frequency component data is a frequency spectrum obtained by Fourier transform of the received signal.
  • the frequency components it is more preferable for the frequency components to include phase information in addition to amplitude (absolute value). This is synonymous with treating the frequency components as complex numbers. As described below, by including phase information, it is possible to calculate signal features with higher performance.
  • the control device 2 includes a database 261a in the storage unit 261 constituting the data processing unit 201 in the example of the present disclosure.
  • the database 261a associates information that affects the detection accuracy of the defective part D in the inspected object E (hereinafter referred to as "information about the inspected object E") with frequency parameters.
  • the information here includes, for example, the inspection conditions of the inspected object E.
  • the appropriate frequency parameters may differ depending on the inspection conditions.
  • the appropriate frequency parameters here are frequency parameters for increasing the difference between the frequency spectrum of the healthy part N and the frequency spectrum of the defective part D to a level that makes the defective part D detectable.
  • the frequency parameters indicate a frequency set ⁇ n ⁇ suitable for detecting the defective part D. Therefore, the user can specify the part of the frequency spectrum used to create an image 273 (described later) by inputting the inspection conditions into an input unit 272 (described later).
  • the excitation frequency fex used to the frequency parameters it is even more preferable to add the excitation frequency fex used to the frequency parameters and store it in the database 261a.
  • the detection performance of the defect D changes depending on how much the excitation frequency fex is shifted from the natural frequency fres of the transmission probe 110. Therefore, by also registering the excitation frequency fex (amount of shift) in the database 261a, it becomes possible to select an appropriate excitation frequency fex for the next and subsequent measurements.
  • the inspection conditions include, for example, at least one of the following: the material of the object E to be inspected, the thickness of the object E to be inspected, the structure of the object E to be inspected (e.g., whether it is a single-layer structure or a multi-layer structure), the position of the object E to be inspected relative to the receiving probe 121 and the transmitting probe 110 (e.g., the position in the z direction), and the type of fluid F. Since these are pieces of information that can affect the appropriate frequency parameters, the appropriate frequency parameters can be determined by the user inputting at least one of these pieces of information.
  • FIG. 43A is an example of database 261a.
  • the frequency parameters are a set of ratios f/f0 relative to the transmission frequency f0 (FIG. 9).
  • the preferred frequency parameters for information about the subject E are expressed as a certain range.
  • the information here is, for example, the thickness and material of the subject E, as an example for explanation.
  • FIG. 43B is a three-dimensional view of the database 261a shown in FIG. 43A.
  • It[1] is the thickness of the test object E
  • It[2] is the material of the test object E.
  • database 261a is a database that has test subject information, which is multidimensional information, as its axis.
  • the database 261a may be expressed in a tabular format. That is, a table may be created in which suitable frequency parameters are recorded as one record (row) for each piece of information relating to the multidimensional test subject E. Furthermore, when the database 261a is processed by a computer or the like, it may be expressed as a tabular database, or it may be expressed in a database format in which each piece of information relating to the multidimensional test subject E is a single record.
  • the data processing unit 201 includes an imaging unit 262.
  • the imaging unit 262 is included in the signal processing unit 250, and generates an image 273 (described below) indicating the position (defect position) of the defect D using a portion of the converted frequency components that is specified by the frequency parameters. Specifically, the imaging unit 262 creates the image 273 based on the change (amount of change) in the signal caused by the defect D of the test object E in the frequency spectrum of the portion that corresponds to the input frequency parameters out of the frequency spectrum that corresponds to the frequency components converted by the frequency conversion unit 230. In this way, the image 273 can be generated.
  • the signal change (change in the received signal) referred to here is a signal feature in the example of the present disclosure. Therefore, the imaging unit 262 first calculates the signal feature from the portion of the frequency spectrum corresponding to the converted frequency component that is the frequency parameter input by the user.
  • the signal feature is, for example, a value that represents the signal change as described above, and is a value calculated from frequency component data so as to appropriately include defect information (for example, the position of the defect D).
  • defect information for example, the position of the defect D.
  • the data processing unit 201 includes a display unit 263 that displays on the display device 3.
  • the display unit 263 outputs an image 273 to the display device 3 for display.
  • the display device 3 is, for example, a monitor, a display, or the like.
  • the display unit 263 displays, on the display device 3, a frequency spectrum 271 (described later) corresponding to the frequency components converted by the frequency conversion unit 230.
  • the display unit 263 displays, on the display device 3, an input unit 272 (described later) that accepts input of frequency parameters.
  • the input is performed, for example, by a user of the ultrasound inspection device Z, but may also be input from another device (not shown). In this disclosure, as an example, a case in which the user inputs frequency parameters will be described.
  • the above procedure is performed while changing the scanning position (x, y) to scan the desired range.
  • frequency component data and signal features corresponding to the scanning position (x, y) are stored in the memory unit 261 in the data processing unit 201.
  • the signal features are calculated each time a signal is acquired at the scanning position.
  • the frequency component data may be stored in the memory unit 261, and the signal features may be calculated collectively to generate a defect image after measurement.
  • the signal feature amount is not limited to the above calculation method, as long as it is a value calculated from frequency component data so as to appropriately include the position information of the defect D.
  • the PP value of the signal waveform h(t) in the time domain is used as the signal feature amount, but the absolute value of h(t) may be calculated, and the area of h(t) may be calculated as the signal feature amount.
  • the procedure for calculating the area is to sample h(t) at appropriate time intervals and calculate the sum of h(t) at the sampling points.
  • the squared value of h(t) may be used instead of using equations (1) and (2), the absolute values of the frequency components H( ⁇ ) may be summed for the input frequency set ⁇ and used as the signal feature amount.
  • FIG. 44 is a diagram illustrating a configuration example of the operation screen 270 of the ultrasonic inspection device Z in the example of the present disclosure.
  • the operation screen 270 is displayed on the display device 3 (FIG. 42) by the display unit 263 (FIG. 42).
  • the display unit 263 displays, on the display device 3, a frequency spectrum 271 corresponding to the frequency components converted by the frequency conversion unit 230 (FIG. 42) as described above, and an input unit 272 that accepts input of frequency parameters by the user.
  • the display unit 263 displays the operation screen 270 of the ultrasonic inspection device Z on the display device 3, and displays the frequency spectrum 271 and the input unit 272 on the operation screen 270. This allows the user to operate the input unit 272 while checking the operation screen 270 including the frequency spectrum 271.
  • an image 273 showing the position of the defective part D of the inspected object E is displayed on the left side.
  • a frequency spectrum 271 is displayed in the upper right side.
  • the frequency spectrum 271 includes a first frequency spectrum shown by a dashed line and a second frequency spectrum shown by a solid line.
  • the dashed and solid line graphs are the dashed and solid line graphs in FIG. 35 above. This allows the user to compare the frequency spectra with each other, and the user can input the appropriate frequency components.
  • the frequency spectrum 271 displayed may be either the first frequency spectrum or the second frequency spectrum. If the user has a certain amount of experience, he or she may be able to determine the appropriate frequency parameters based on only one of the frequency parameters.
  • the input unit 272 is where the user inputs frequency parameters.
  • the input unit 272 is a frequency selection unit configured with a slide bar whose length and position can be adjusted.
  • the user can input a frequency range (frequency set) for extracting signal features by adjusting the length and position of the slide bar using, for example, a mouse, keyboard, etc., to a position corresponding to the frequency position of the frequency spectrum.
  • the frequency range input here is the frequency parameter.
  • the frequency spectrum 271 is updated by pressing the update button 274.
  • the imaging unit 262 determines, as the initial frequency parameters, frequency parameters corresponding to the information on the object E received through the input unit 275 from the database 261a (FIG. 42).
  • the input unit 275 receives information that affects the detection accuracy of the defect D in the object E (the above-mentioned "information on the object E").
  • the above-mentioned display unit 263 displays the input unit 275 on the display device 3. If there is no corresponding frequency parameter, the frequency parameters corresponding to the information closest to that information are determined.
  • the determined frequency parameters are displayed on the display device 3.
  • the imaging unit 262 creates an image 273 (FIG. 44) based on the determined frequency parameters.
  • the fourteenth embodiment is configured to select an optimal excitation frequency f ex from a plurality of excitation frequencies f ex
  • the fourteenth embodiment uses the ultrasonic inspection device Z of FIG. 31 and the control device 2 of FIG.
  • FIG. 45 shows the steps for obtaining a defect image of the inspected object E in the 14th embodiment.
  • Step S100 image acquisition step of the 14th embodiment is broadly divided into two steps: step S1 for selecting an appropriate excitation frequency, and step S2 for acquiring a defect image of the object E to be inspected using the selected excitation frequency.
  • Step S1 includes steps S11, S12, and S13.
  • step S11 an excitation frequency fex[n] is set.
  • step S12 the signal strength is measured.
  • step S13 an optimal excitation frequency is selected.
  • Step S2 includes steps S21, S22, and S23.
  • step S21 the frequency of the ultrasonic beam U transmitted from the transmitting probe 110 is set to the selected excitation frequency.
  • step S22 measurement is performed by scanning the object E to be inspected.
  • step S23 an image 273 is displayed.
  • the signal amount of the defect portion D is measured using a standard test object (not shown).
  • the standard test object is an inspection object in which a simulated defect (a defect simulating the defect portion D) with a known shape, location, etc. is formed. It is preferable that the material constituting the standard test object is the same as that of the inspected object E to be inspected, or a material with similar characteristics.
  • the shape of the simulated defect can be 10 mm in length and 1 mm in width. It is more preferable to form simulated defects of multiple shapes and positions in terms of width, length, depth position, etc. of the simulated defect.
  • Figure 46 shows the results of transmitting an ultrasonic beam U while scanning a standard inspection object across a simulated defect, measuring the received signal, and then calculating the signal amount using appropriate signal processing of the received signal, then plotting the results.
  • Curve a in the figure is the result of measurement at excitation frequency fex1
  • curve b is the result of measurement at excitation frequency fex2 which is different from excitation frequency fex1.
  • ⁇ v and v0 are the same as in Figures 33A and 33B above.
  • Curve b has a larger ⁇ v than curve a. In this way, a simulated defect with a known position was measured using multiple excitation frequencies.
  • the excitation frequency fex may be changed to around 5 to 10 types, and the signal amount measured as in Figure 46.
  • the optimum excitation frequency fex can be selected from the results in FIG. 46.
  • the excitation frequency fex at which the rate of change of the signal strength ⁇ v/v0 is maximized can be selected.
  • the selection criterion is not limited to this, and the optimum value may be selected from two values, the rate of change of the signal strength ⁇ v/v0 and the signal strength v0.
  • control device 2 can automatically select the optimum excitation frequency fex based on the above-mentioned selection criteria.
  • the measurement results in FIG. 46 may be displayed on the operation screen 270, and the user may select the optimum excitation frequency fex.
  • the excitation frequency fex is set to the optimum frequency selected in this manner, and the test object E is measured, and the defective portion D is measured.
  • the optimum frequency is used as the excitation frequency fex, which has the effect of further improving the detection accuracy of the defective portion.
  • the fifteenth embodiment is configured to select an optimal excitation frequency fex from a plurality of excitation frequencies fex.
  • FIG. 47 shows the steps for obtaining a defect image of the inspected object E in the 15th embodiment.
  • step S14 is further executed between step S12 and step S13 in step S1 of the fourteenth embodiment.
  • Step S100 (image acquisition step) of the fifteenth embodiment is broadly divided into two steps: step S1 for selecting an appropriate excitation frequency, and step S2 for acquiring a defect image of the inspected object E using the selected excitation frequency.
  • the frequency spectrum is measured at a plurality of excitation frequencies fex using the test object E as the measurement object and displayed on the operation screen 270 (step S14).
  • the position at which the frequency spectrum is measured may be either a healthy part or a defective part D of the test object E.
  • Figure 48 shows the frequency spectrum displayed in step S14.
  • step S14 the frequency spectrum is calculated from the measured received signal, and the frequency spectrum corresponding to the excitation frequency fex[n] is displayed on the operation screen 270 as shown in Figure 48.
  • each spectrum is displayed corresponding to a different excitation frequency.
  • Figure 48 shows the result of measuring the frequency spectrum of the received signal by changing the excitation frequency fex.
  • the dashed line in Figure 48 shows the frequency spectrum when the excitation frequency fex is set equal to the natural frequency fres (0.82 MHz).
  • the solid line shows the frequency spectrum when the excitation frequency fex is set to 0.78 MHz, which is 40 kHz lower than the natural frequency fres.
  • the selection criterion for the excitation frequency is that the proportion of the base component W3 in the spectrum is large.
  • the selection criterion for the optimal excitation frequency may be something other than this.
  • the optimal excitation frequency may be selected based on two factors: the proportion of the base component W3 and the magnitude of the signal strength.
  • step S2 is executed to acquire a defect image.
  • the selected excitation frequency fex is set, and the inspected object E is scanned to acquire a received signal. Using the acquired received signal, a defect image is displayed on the operation screen 270.
  • the fifteenth embodiment since an optimal frequency is used as the excitation frequency fex, it is possible to further improve the detection accuracy of the defect portion D.
  • the fifteenth embodiment also has the advantage that it is possible to select the optimal excitation frequency fex without using a standard test piece.
  • the frequency range for calculating the signal features can be selected based on the spectrum displayed on the operation screen 270.
  • the control device 2 may select the optimal excitation frequency.
  • the algorithm for selecting the excitation frequency may calculate the intensity ratio of the tail components for each measured excitation frequency fex[n] based on the component intensity of the center frequency of the spectrum, and select the excitation frequency fex at which this ratio is maximized.
  • Sixteenth Embodiment 49 is a functional block diagram of an ultrasonic inspection device Z according to the sixteenth embodiment.
  • the input unit 275 (FIG. 44) does not necessarily have to be provided.
  • the signal processing unit 250 includes an update unit 291 (frequency parameter update unit).
  • the update unit 291 automatically updates the frequency parameters.
  • An example of a more specific process in the update unit 291 is shown below.
  • the imaging unit 262 calculates the above-mentioned signal feature amount while changing the frequency parameters for the received signals at two points, the defective part D and the healthy part N.
  • the update unit 291 searches for and determines the frequency parameters that maximize the difference between the signal feature amounts of the defective part D and the healthy part N. Using the frequency parameters thus updated by the update unit 291, the imaging unit 262 creates an image 273.
  • the frequency parameters thus updated are also registered in the database 261a, and the database 261a is updated.
  • the database 261a includes information on the excitation frequency fex. Since the detectability of defects changes depending on how much the excitation frequency fex is shifted from the natural frequency fres of the transmitting probe, by registering this in the database 261a as well, it becomes possible to select the appropriate excitation frequency fex for the next and subsequent measurements.
  • the determined frequency parameters may be displayed on the display device 3. Also, instead of automatically updating the frequency parameters by the update unit 291, the user may specify the frequency parameters through the input unit 272 while viewing the image 273. This also makes it possible to further improve the detection accuracy of the defective portion D.
  • FIG. 50 is a diagram showing the hardware configuration of the control device 2.
  • the above-mentioned configurations, functions, and each part constituting the block diagram may be realized in hardware by, for example, designing some or all of them as an integrated circuit.
  • the above-mentioned configurations, functions, etc. may be realized in software by a processor such as a CPU 252 interpreting and executing a program that realizes each function.
  • the control device 2 includes, for example, a memory 251, a CPU 252, a storage device 253 (SSD, HDD, etc.), a communication device 254, and an I/F 255.
  • information such as programs, tables, and files that realize each function can be stored in a recording device such as a memory or SSD (Solid State Drive), or a recording medium such as an IC (Integrated Circuit) card, an SD (Secure Digital) card, or a DVD (Digital Versatile Disc).
  • a recording device such as a memory or SSD (Solid State Drive), or a recording medium such as an IC (Integrated Circuit) card, an SD (Secure Digital) card, or a DVD (Digital Versatile Disc).
  • FIG. 51 is a flow chart showing the ultrasonic inspection method of each of the above-mentioned embodiments.
  • the ultrasonic inspection method disclosed herein can be executed by the control device 2 of the above-mentioned ultrasonic inspection device Z, and will be described as an example with reference to FIGS. 31 and 32 as appropriate.
  • the ultrasonic inspection method disclosed herein inspects the object E (FIG. 31) by irradiating the object E (FIG. 31) with an ultrasonic beam U via a gas G (FIG. 31).
  • the ultrasonic inspection method disclosed herein includes steps S101 to S105, S111, and S112. First, in response to a command from the control device 2, the transmitting probe 110 performs step S101 (emission step) of emitting an ultrasonic beam U from the transmitting probe 110.
  • step S101 the excitation frequency fex of the transmitting probe 110 is set to a frequency shifted from the natural frequency fres of the transmitting probe 110. Therefore, in step S101, the transmitting probe 110 is excited at the excitation frequency fex shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110 to emit an ultrasonic beam U.
  • step S102 reception step
  • the receiving probe 121 receives the ultrasound beam U.
  • step S103 filter processing step
  • components maximum intensity frequency components
  • a specific frequency range specifically, a frequency range including the maximum component frequency fm
  • the signal e.g., waveform signal
  • step S104 signal intensity calculation step of detecting the base component W3 of the fundamental wave band W1 from the filtered signal and generating signal intensity data. Therefore, in step S104, the base component W3 of the fundamental wave band W1 in the signal of the ultrasound beam U is detected.
  • the peak-to-peak signal is used as a method of generating signal intensity data. This is the difference between the maximum and minimum values of the signal.
  • step S105 shape display step
  • Scanning position information of the transmitting probe 110 and the receiving probe 121 is sent from the position measurement unit 203 to the scan controller 204.
  • the data processing unit 201 plots the signal intensity data at each scanning position against the scanning position information of the transmitting probe 110 obtained from the scan controller 204. In this way, the signal intensity data is visualized. This is step S105.
  • Figure 33B above shows a case where the scanning position information is one-dimensional (one direction); when the scanning position information is two-dimensional in x and y, the signal intensity data is plotted to show the defect D as a two-dimensional image, which is then displayed on the display device 3.
  • the data processing unit 201 determines whether the scanning is complete (step S111). If the scanning is complete (Yes), the control device 2 ends the processing. If the scanning is not complete (No), the data processing unit 201 outputs a command to the driving unit 202 to move the transmitting probe 110 and the receiving probe 121 to the next scanning position (step S112), and the processing returns to step S101.
  • the ultrasonic inspection device Z and ultrasonic inspection method described above can improve the detection performance of defective areas D, for example the performance of detecting minute defects.
  • the defect D is a cavity
  • the defect D may also be a foreign object containing a material different from the material of the object E to be inspected.
  • the ultrasonic inspection device Z according to each of the above embodiments is premised on an ultrasonic defect imaging device, but may also be applied to a non-contact in-line internal defect inspection device.
  • the present disclosure is not limited to the above-described embodiments, but includes various modified examples.
  • the above-described embodiments have been described in detail to clearly explain the present disclosure, and are not necessarily limited to those having all of the configurations described.
  • it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment and it is also possible to add the configuration of another embodiment to the configuration of one embodiment.
  • control lines and information lines shown are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it can be considered that almost all components are interconnected.

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Abstract

A scanning measurement device (1) of an ultrasonic inspection device (Z) comprises a transmitting probe (110) and a receiving probe (121) which is installed on the opposite side to the transmitting probe (110) with respect to an object to be inspected, wherein: the transmitting probe (110) emits an ultrasonic beam upon application thereto of a voltage waveform of a repeating wave packet composed of a wave packet having a wave number of two or more, and drives the transmitting probe (110) at an excitation frequency offset from a resonant frequency of the transmitting probe (110); a control device (2) includes a signal processing unit (250); the signal processing unit (250) includes a filter unit (240) that reduces at least a maximum intensity frequency component of a received signal of the receiving probe (121); and the filter unit (240) detects tail components, other than the maximum intensity frequency component, within a fundamental wave band including the maximum intensity frequency component.

Description

超音波検査装置及び超音波検査方法Ultrasonic inspection device and ultrasonic inspection method
　本開示は、超音波検査装置及び超音波検査方法に関する。 This disclosure relates to an ultrasonic inspection device and an ultrasonic inspection method.
　超音波ビームを用いた被検査体の欠陥部の検査方法が知られている。例えば、被検査体の内部に空気等の音響インピーダンスが小さな欠陥部（空洞等）がある場合、被検査体の内部で音響インピーダンスのギャップが生じるため、超音波ビームの透過量が小さくなる。従って、超音波ビームの透過量を計測することで、被検査体内部の欠陥部を検出できる。 　A method of inspecting defective parts of an object to be inspected using an ultrasonic beam is known. For example, if there is a defective part (cavity, etc.) with a small acoustic impedance such as air inside the object to be inspected, a gap in acoustic impedance will occur inside the object to be inspected, and the amount of transmission of the ultrasonic beam will be small. Therefore, by measuring the amount of transmission of the ultrasonic beam, it is possible to detect defective parts inside the object to be inspected.
　超音波検査装置について特許文献１に記載の技術が知られている。特許文献１に記載の超音波検査装置では、連続する所定個数の負の矩形波からなる矩形波バースト信号を被検体に空気を介して対向配設された送信超音波探触子に印加する。被検体に空気を介して対向配設され受信超音波探触子で被検体を伝搬した超音波を透過波信号に変換する。この透過波信号の信号レベルに基づき被検体の欠陥の有無を判定する。また、送信超音波探触子及び受信超音波探触子は、振動子及び当該振動子の超音波の送受信側に取付られた前面板の音響インピーダンスを、被検体に当接して使用する接触型超音波探触子に比較して低く設定している。 The technology described in Patent Document 1 is known for an ultrasonic inspection device. In the ultrasonic inspection device described in Patent Document 1, a rectangular wave burst signal consisting of a predetermined number of consecutive negative rectangular waves is applied to a transmitting ultrasonic probe arranged opposite the test object through the air. The ultrasonic waves propagated through the test object are converted into a transmitted wave signal by a receiving ultrasonic probe arranged opposite the test object through the air. The presence or absence of a defect in the test object is determined based on the signal level of this transmitted wave signal. In addition, the transmitting ultrasonic probe and receiving ultrasonic probe have a lower acoustic impedance of the transducer and the front panel attached to the ultrasonic transmission and reception side of the transducer compared to a contact type ultrasonic probe that is used by abutting the test object.
特開２００８－１２８９６５号公報JP 2008-128965 A
　特許文献１に記載の超音波検査装置では、被検査体中の微小な欠陥を検出することが困難であるという課題がある。特に、検出しようとする欠陥のサイズが、超音波ビームよりも小さい場合に、欠陥の検出が困難になる。
　本開示が解決しようとする課題は、欠陥部の検出性能、例えば検出可能な欠陥サイズが小さく、微小な欠陥でも検出可能にする超音波検査装置及び超音波検査方法の提供である。 The ultrasonic inspection device described in Patent Document 1 has a problem in that it is difficult to detect a minute defect in an object to be inspected. In particular, when the size of the defect to be detected is smaller than the ultrasonic beam, it becomes difficult to detect the defect.
The problem to be solved by the present disclosure is to provide an ultrasonic inspection device and an ultrasonic inspection method that have high detection performance for defective parts, for example, a small detectable defect size, making it possible to detect even minute defects.
　本開示の超音波検査装置は、気体を介して被検査体に超音波ビームを入射することにより前記被検査体の検査を行う超音波検査装置であって、前記被検査体への前記超音波ビームの走査及び計測を行う走査計測装置と、前記走査計測装置の駆動を制御する制御装置とを備え、前記走査計測装置は、前記超音波ビームを放出する送信プローブと、前記被検査体に関して前記送信プローブの反対側に設置された、前記超音波ビームを受信する受信プローブとを備え、前記送信プローブは、波数が２以上の波束で構成される繰り返し波束の電圧波形を印加されて超音波ビームを放出し、前記送信プローブの共振周波数からずらした励起周波数で前記送信プローブを駆動し、前記制御装置は信号処理部を備え、前記信号処理部は、前記受信プローブの受信信号のうちの少なくとも最大強度周波数成分を低減するフィルタ部を備え、前記フィルタ部は、前記最大強度周波数成分を含む基本波帯のうちの前記最大強度周波数成分以外の裾野成分を検出する。その他の解決手段は発明を実施するための形態において後記する。 The ultrasonic inspection device disclosed herein is an ultrasonic inspection device that inspects an object to be inspected by irradiating the object with an ultrasonic beam through a gas, and includes a scanning and measuring device that scans and measures the ultrasonic beam on the object to be inspected, and a control device that controls the driving of the scanning and measuring device. The scanning and measuring device includes a transmitting probe that emits the ultrasonic beam, and a receiving probe that receives the ultrasonic beam and is installed on the opposite side of the transmitting probe with respect to the object to be inspected. The transmitting probe emits an ultrasonic beam by applying a voltage waveform of a repeating wave packet composed of a wave packet with a wave number of two or more, and drives the transmitting probe with an excitation frequency shifted from the resonant frequency of the transmitting probe. The control device includes a signal processing unit, and the signal processing unit includes a filter unit that reduces at least the maximum intensity frequency component of the received signal of the receiving probe, and the filter unit detects the base components other than the maximum intensity frequency component of the fundamental wave band including the maximum intensity frequency component. Other solutions will be described later in the description for implementing the invention.
　本開示によれば、欠陥部の検出性能、例えば検出可能な欠陥サイズが小さく、微小な欠陥でも検出可能にする超音波検査装置及び超音波検査方法を提供できる。 The present disclosure provides an ultrasonic inspection device and an ultrasonic inspection method that improve the detection performance of defective parts, for example, by making it possible to detect even minute defects with a small detectable size.
第１実施形態の超音波検査装置の構成を示す図である。1 is a diagram showing the configuration of an ultrasonic inspection apparatus according to a first embodiment; 送信プローブの構造を示す断面模式図である。3 is a schematic cross-sectional view showing a structure of a transmission probe. FIG. 従来の超音波検査方法での超音波ビームの伝搬経路を示す図であり、健全部への入射時を示す図である。FIG. 1 is a diagram showing a propagation path of an ultrasonic beam in a conventional ultrasonic inspection method, showing the time when the ultrasonic beam is incident on a healthy part. 従来の超音波検査方法での超音波ビームの伝搬経路を示す図であり、欠陥部への入射時を示す図である。FIG. 1 is a diagram showing a propagation path of an ultrasonic beam in a conventional ultrasonic inspection method, showing the time of incidence on a defect portion. 被検査体内での欠陥部と超音波ビームとの相互作用を示す図であり、直達する超音波ビームを受信する様子を示す図である。FIG. 2 is a diagram showing an interaction between an ultrasonic beam and a defect in an object to be inspected, showing how a direct ultrasonic beam is received. 欠陥部と相互作用した超音波ビームである散乱波を模式的に示した図である。FIG. 2 is a schematic diagram showing a scattered wave, which is an ultrasonic beam that has interacted with a defect. 制御装置の機能ブロック図である。FIG. 2 is a functional block diagram of a control device. 受信信号の周波数成分の分布を模式的に示した図である。FIG. 2 is a diagram illustrating a schematic distribution of frequency components of a received signal. 欠陥部をまたがるように送信プローブ及び受信プローブを走査したときの信号強度情報の位置による変化を示したものである。This shows the change in signal strength information depending on the position when the transmitting probe and the receiving probe are scanned so as to straddle the defective portion. フィルタ部を備えた制御装置により、信号強度情報を測定した結果である。This is the result of measuring signal strength information using a control device equipped with a filter section. 送信プローブに印加するバースト波の電圧波形である。1 shows a voltage waveform of a burst wave applied to a transmitting probe. 図９に示す条件での受信信号の周波数成分分布を示したものである。10 shows a frequency component distribution of a received signal under the conditions shown in FIG. 受信信号の周波数成分分布（周波数スペクトル）の実測データを、健全部（実線）と欠陥部（破線）とで比較した図である。FIG. 1 is a diagram comparing measured data of the frequency component distribution (frequency spectrum) of a received signal between a healthy portion (solid line) and a defective portion (dashed line). 波数を変えた時の送信超音波の周波数スペクトルを示す。4 shows the frequency spectrum of the transmitted ultrasound when the wave number is changed. 波数が３個（破線）、５個（実線）、１０個（一点鎖線）の場合の周波数スペクトルである。These are frequency spectra when the number of waves is 3 (dashed line), 5 (solid line), and 10 (dotted line). 基本波帯の周波数スペクトルを模式的に示した図である。FIG. 2 is a diagram illustrating a frequency spectrum of a fundamental wave band. 基本波帯の半値全幅比（ＦＷＨＭ比）と波数との関係を示す図である。FIG. 1 is a diagram showing the relationship between the full width at half maximum ratio (FWHM ratio) of the fundamental waveband and the wave number. 帯域遮断フィルタでのゲイン（利得）の周波数特性を示す。4 shows the frequency characteristics of the gain in a band-stop filter. 帯域遮断フィルタで処理した後の信号の周波数特性を模式的に示した図である。FIG. 10 is a diagram illustrating the frequency characteristics of a signal after processing by a band-stop filter. 低域通過フィルタでのゲイン（利得）の周波数特性を示す。This shows the frequency characteristics of the gain in a low-pass filter. 低域通過フィルタで処理した後の信号の周波数特性を模式的に示した図である。FIG. 2 is a diagram illustrating a frequency characteristic of a signal after processing by a low-pass filter. 高域通過フィルタでのゲイン（利得）の周波数特性を示す。This shows the frequency characteristics of the gain in a high-pass filter. 高域通過フィルタで処理した後の信号の周波数特性を模式的に示した図である。FIG. 10 is a diagram illustrating a frequency characteristic of a signal after processing by a high-pass filter. デジタル方式のフィルタ部を示すブロック図である。FIG. 2 is a block diagram showing a digital filter section; 別の実施形態に係るフィルタ部を示すブロック図である。FIG. 13 is a block diagram showing a filter unit according to another embodiment. 送信プローブの焦点距離と受信プローブの焦点距離を等しくした場合の超音波ビームの伝播経路を模式的に示した図である。1 is a diagram illustrating a schematic diagram of a propagation path of an ultrasonic beam when the focal length of a transmitting probe and the focal length of a receiving probe are set equal to each other. 送信プローブの焦点距離よりも、受信プローブの焦点距離を長くした場合の超音波ビームの伝播経路を模式的に示した図である。10 is a diagram illustrating a schematic diagram of a propagation path of an ultrasonic beam when the focal length of a receiving probe is set longer than the focal length of a transmitting probe. 送信プローブにおけるビーム入射面積及び受信プローブにおけるビーム入射面積の関係を説明する図である。4A and 4B are diagrams illustrating the relationship between a beam incident area in a transmitting probe and a beam incident area in a receiving probe. 第２実施形態での超音波検査装置の構成を示す図である。FIG. 13 is a diagram showing the configuration of an ultrasonic inspection apparatus according to a second embodiment. 送信音軸、受信音軸及び偏心距離を説明する図であり、送信音軸及び受信音軸が鉛直方向に延びる場合である。FIG. 2 is a diagram for explaining the transmission sound axis, the reception sound axis, and the eccentricity distance, in the case where the transmission sound axis and the reception sound axis extend in the vertical direction. 送信音軸、受信音軸及び偏心距離を説明する図であり、送信音軸及び受信音軸が傾斜して延びる場合である。1 is a diagram for explaining a transmission sound axis, a reception sound axis, and an eccentric distance, in which the transmission sound axis and the reception sound axis extend at an angle. FIG. 第３実施形態での超音波検査装置の構成を示す図である。FIG. 13 is a diagram showing the configuration of an ultrasonic inspection apparatus according to a third embodiment. 第３実施形態による効果が生じる理由を説明する図である。13A to 13C are diagrams for explaining the reason why the third embodiment has an effect. 第４実施形態での超音波検査装置における制御装置２の機能ブロック図である。FIG. 13 is a functional block diagram of a control device 2 in an ultrasonic inspection device according to a fourth embodiment. 第５実施形態での超音波検査装置における制御装置２の機能ブロック図である。FIG. 13 is a functional block diagram of a control device 2 in an ultrasonic inspection device according to a fifth embodiment. 第６実施形態での超音波検査装置における制御装置２の機能ブロック図である。FIG. 13 is a functional block diagram of a control device 2 in an ultrasonic inspection device according to a sixth embodiment. 制御装置のハードウェア構成を示す図である。FIG. 2 is a diagram illustrating a hardware configuration of a control device. 上記各実施形態の超音波検査方法を示すフローチャートである。4 is a flowchart showing an ultrasonic inspection method according to each of the above embodiments. 第７実施形態の超音波検査装置の構成を示す図である。FIG. 13 is a diagram showing the configuration of an ultrasonic inspection apparatus according to a seventh embodiment. 制御装置の機能ブロック図である。FIG. 2 is a functional block diagram of a control device. 欠陥部をまたがるように送信プローブ及び受信プローブを走査したときの信号強度情報の位置による変化を示したものである。This shows the change in signal strength information depending on the position when the transmitting probe and the receiving probe are scanned so as to straddle the defective portion. 送信プローブの励起周波数ｆｅｘを０．７８ＭＨｚに設定するとともに、フィルタ部を備えた制御装置により、信号強度情報を測定した結果である。The excitation frequency fex of the transmitting probe was set to 0.78 MHz, and the signal strength information was measured using a control device equipped with a filter section. 第７実施形態に示す条件での受信信号の周波数成分分布を示したものである。13 shows a frequency component distribution of a received signal under the conditions shown in the seventh embodiment. 受信信号の周波数成分分布（周波数スペクトル）の実測データを、健全部（実線）と欠陥部（破線）とで比較した図である。FIG. 1 is a diagram comparing measured data of the frequency component distribution (frequency spectrum) of a received signal between a healthy portion (solid line) and a defective portion (dashed line). 波束の波数と、その超音波の基本波帯の周波数スペクトルである。The wave number of the wave packet and the frequency spectrum of the fundamental wave band of the ultrasound. 図３６Ａに示したスペクトルの基本波帯の半値全幅が波束の波数Ｎ０に対してどのように変化するかを示した図である。36B is a diagram showing how the full width at half maximum of the fundamental wave band of the spectrum shown in FIG. 36A changes with respect to the wave number N0 of the wave packet. FIG. 励起周波数ｆｅｘを変えて、受信信号の周波数スペクトルを測定した結果である。This shows the results of measuring the frequency spectrum of the received signal while changing the excitation frequency fex. １つの波束の時間領域において、瞬時周波数の変化を示す図である。FIG. 1 shows the change in instantaneous frequency of a wave packet in the time domain. 第８実施形態での超音波検査装置Ｚにおける制御装置の機能ブロック図である。FIG. 23 is a functional block diagram of a control device in an ultrasonic inspection device Z in the eighth embodiment. 第９実施形態での超音波検査装置Ｚにおける制御装置の機能ブロック図である。FIG. 13 is a functional block diagram of a control device in an ultrasonic inspection device Z in the ninth embodiment. 第１１実施形態での超音波検査装置の構成を示す図である。FIG. 23 is a diagram showing the configuration of an ultrasonic inspection apparatus according to an eleventh embodiment. 第１３実施形態の制御装置２の機能ブロック図である。FIG. 23 is a functional block diagram of the control device 2 of the thirteenth embodiment. データベースの一例である。1 is an example of a database. 図４３Ａに示すデータベースを立体的に示す図である。FIG. 43B is a three-dimensional view of the database shown in FIG. 43A. 本開示の例での超音波検査装置の操作画面の構成例を模式的に示す図である。FIG. 2 is a diagram illustrating a configuration example of an operation screen of an ultrasonic inspection device according to an example of the present disclosure. 第１４実施形態で被検査体Ｅの欠陥画像を得るステップを示す図である。A diagram showing steps for obtaining a defect image of an inspection object E in the fourteenth embodiment. 標準検査体を模擬欠陥を横切るように走査しながら、超音波ビームを送信して受信信号を計測し、受信信号を適切な信号処理により信号量を算出してプロットした結果である。The standard inspection object is scanned across the artificial defect, an ultrasonic beam is transmitted, the received signal is measured, and the received signal is subjected to appropriate signal processing to calculate the signal amount and plot the result. 第１５実施形態で被検査体の欠陥画像を得るステップを示す図である。A diagram showing steps for obtaining a defect image of an object to be inspected in the fifteenth embodiment. ステップで表示される周波数スペクトルである。This is a frequency spectrum displayed in steps. 第１６実施形態の超音波検査装置の機能ブロック図である。FIG. 23 is a functional block diagram of an ultrasonic inspection apparatus according to a sixteenth embodiment. 制御装置のハードウェア構成を示す図である。FIG. 2 is a diagram illustrating a hardware configuration of a control device. 上記各実施形態の超音波検査方法を示すフローチャートである。4 is a flowchart showing an ultrasonic inspection method according to each of the above embodiments.
　以下、図面を参照しながら本開示を実施するための形態（実施形態と称する）を説明する。ただし、本開示は以下の実施形態に限られず、例えば異なる実施形態同士を組み合わせたり、本開示の効果を著しく損なわない範囲で任意に変形したりできる。また、同じ部材については同じ符号を付すものとし、重複する説明は省略する。更に、同じ機能を有するものは同じ名称を付すものとする。図示の内容は、あくまで模式的なものであり、図示の都合上、本開示の効果を著しく損なわない範囲で実際の構成から変更することがある。 Below, a form for implementing the present disclosure (referred to as an embodiment) will be described with reference to the drawings. However, the present disclosure is not limited to the following embodiment, and for example, different embodiments can be combined, or modified as desired without significantly impairing the effects of the present disclosure. In addition, the same components will be given the same reference numerals, and duplicate descriptions will be omitted. Furthermore, components having the same functions will be given the same names. The contents shown are merely schematic, and for convenience of illustration, the actual configuration may be changed without significantly impairing the effects of the present disclosure.
（第１実施形態）
　図１は、第１実施形態の超音波検査装置Ｚの構成を示す図である。図１では、走査計測装置１は、断面模式図で示している。図１には、紙面左右方向としてのｘ軸、紙面直交方向としてのｙ軸、紙面上下方向としてのｚ軸を含む直交３軸の座標系が示される。 First Embodiment
Fig. 1 is a diagram showing the configuration of an ultrasonic inspection device Z according to a first embodiment. In Fig. 1, a scanning measurement device 1 is shown in a schematic cross-sectional view. Fig. 1 shows a coordinate system of three orthogonal axes including an x-axis as a left-right direction on the paper surface, a y-axis as a direction perpendicular to the paper surface, and a z-axis as a top-bottom direction on the paper surface.
　超音波検査装置Ｚは、流体Ｆを介して被検査体Ｅに超音波ビームＵ（後記する）を入射することにより被検査体Ｅの検査を行うものである。本実施形態では、流体Ｆは空気等の気体Ｇである。被検査体Ｅは流体Ｆ中に存在する。第１実施形態では、流体Ｆとして空気（気体Ｇの一例）が使用される。従って、走査計測装置１の筐体１０１の内部は空気で満たされた空洞となっている。図１に示すように、超音波検査装置Ｚは、走査計測装置１と、制御装置２と、表示装置３とを備える。表示装置３は制御装置２に接続される。 The ultrasonic inspection device Z inspects the object E by irradiating an ultrasonic beam U (described later) onto the object E through a fluid F. In this embodiment, the fluid F is a gas G such as air. The object E is present in the fluid F. In the first embodiment, air (an example of gas G) is used as the fluid F. Therefore, the inside of the housing 101 of the scanning measurement device 1 is a cavity filled with air. As shown in FIG. 1, the ultrasonic inspection device Z includes the scanning measurement device 1, a control device 2, and a display device 3. The display device 3 is connected to the control device 2.
　走査計測装置１は、被検査体Ｅへの超音波ビームＵの走査及び計測を行うものであり、筐体１０１に固定された試料台１０２を備え、試料台１０２には被検査体Ｅが載置される。被検査体Ｅは、動かないように固定具で試料台１０２に固定されるとなお好ましい。被検査体Ｅが充分に重く不用意に動かない場合などは、固定具が無くてもよい。被検査体Ｅは、任意の材料で構成されている。被検査体Ｅは例えば固体材料であり、より具体には例えば金属、ガラス、樹脂材料、あるいはＣＦＲＰ（炭素繊維強化プラスチック、Ｃａｒｂｏｎ－Ｆｉｂｅｒ　Ｒｅｉｎｆｏｒｃｅｄ　Ｐｌａｓｔｉｃｓ）等の複合材料等である。また、図１の例において、被検査体Ｅは内部に欠陥部Ｄを有している。欠陥部Ｄは、空洞等である。欠陥部Ｄの例は、空洞、本来あるべき材料と異なる異物材等である。被検査体Ｅにおいて、欠陥部Ｄ以外の部分を健全部Ｎと称する。 The scanning measurement device 1 scans and measures the object E with an ultrasonic beam U, and is provided with a sample stage 102 fixed to a housing 101, on which the object E is placed. It is more preferable that the object E is fixed to the sample stage 102 with a fixture so as not to move. If the object E is sufficiently heavy and does not move unintentionally, a fixture is not necessary. The object E is made of any material. The object E is, for example, a solid material, and more specifically, is, for example, a metal, glass, a resin material, or a composite material such as CFRP (Carbon-Fiber Reinforced Plastics). In addition, in the example of FIG. 1, the object E has a defect D inside. The defect D is a cavity, etc. Examples of the defect D are a cavity, a foreign material different from the material that should be there, etc. In the specimen E, the portion other than the defective portion D is called the healthy portion N.
　欠陥部Ｄと健全部Ｎとは、構成する材料が異なるため、両者の間では音響インピーダンスが異なり、超音波ビームＵの伝搬特性が変化する。超音波検査装置Ｚは、この変化を観測して、欠陥部Ｄを検出する。 The defective area D and the healthy area N are made of different materials, so the acoustic impedance differs between the two, and the propagation characteristics of the ultrasonic beam U change. The ultrasonic inspection device Z observes this change to detect the defective area D.
　走査計測装置１は、超音波ビームＵを放出する送信プローブ１１０と、受信プローブ１２１とを有する。送信プローブ１１０は、送信プローブ走査部１０３を介して筐体１０１に設置され、超音波ビームＵを放出する。受信プローブ１２１は、被検査体Ｅに関して送信プローブ１１０の反対側に設置された、超音波ビームＵを受信するものである。受信プローブ１２１は、送信プローブ１１０と同軸に配置された（後記する偏心距離Ｌがゼロ）の受信プローブ１４０（同軸配置受信プローブ）である。従って、第１実施形態では、送信プローブ１１０の送信音軸ＡＸ１（音軸）と受信プローブ１４０の受信音軸ＡＸ２（音軸）との間の偏心距離Ｌ（距離。後記する。）がゼロである。これにより、送信プローブ１１０及び受信プローブ１４０を容易に設置できる。 The scanning measurement device 1 has a transmitting probe 110 that emits an ultrasonic beam U, and a receiving probe 121. The transmitting probe 110 is installed in the housing 101 via the transmitting probe scanning unit 103, and emits an ultrasonic beam U. The receiving probe 121 is installed on the opposite side of the transmitting probe 110 with respect to the subject E, and receives the ultrasonic beam U. The receiving probe 121 is a receiving probe 140 (coaxially arranged receiving probe) that is arranged coaxially with the transmitting probe 110 (the eccentric distance L described below is zero). Therefore, in the first embodiment, the eccentric distance L (distance described below) between the transmitting sound axis AX1 (sound axis) of the transmitting probe 110 and the receiving sound axis AX2 (sound axis) of the receiving probe 140 is zero. This makes it easy to install the transmitting probe 110 and the receiving probe 140.
　ここで、「送信プローブ１１０の反対側」とは、被検査体Ｅにより区切られる２つの空間のうち、送信プローブ１１０が位置する空間と反対側（ｚ軸方向において反対側）の空間という意味であり、ｘ、ｙ座標が同一の反対側（つまり、ｘｙ平面に関して面対称の位置）という意味ではない。 Here, "the opposite side of the transmitting probe 110" means, of the two spaces separated by the subject E, the space opposite the space in which the transmitting probe 110 is located (the opposite side in the z-axis direction), and does not mean the opposite side with the same x and y coordinates (i.e., a position that is symmetrical with respect to the xy plane).
　本開示での、被検査体Ｅに関して送信プローブ１１０の反対側に受信プローブ１４０を配置する構成は、透過型配置に対応する。超音波検査装置Ｚでは、この他、被検査体Ｅに関して送信プローブと同じ側に受信プローブを配置する、反射型配置も知られている。 In this disclosure, the configuration in which the receiving probe 140 is arranged on the opposite side of the transmitting probe 110 with respect to the subject E corresponds to a transmission type arrangement. In addition, a reflection type arrangement is also known in the ultrasound inspection device Z, in which the receiving probe is arranged on the same side as the transmitting probe with respect to the subject E.
　透過型配置は、透過法とも呼ばれる。透過型配置では、被検査体Ｅを透過してきた超音波ビームＵが受信される。被検査体Ｅ内の欠陥部Ｄの存在による超音波ビームＵの透過量の変化により、欠陥部Ｄが検出される。これに対して、反射型配置は、反射法とも呼ばれ、欠陥部Ｄで反射された超音波ビームＵを検出することで、欠陥部Ｄが検出される。 The transmission type arrangement is also called the transmission method. In the transmission type arrangement, an ultrasonic beam U that has passed through the object E to be inspected is received. The presence of a defect D in the object E causes a change in the amount of transmission of the ultrasonic beam U, and the defect D is detected. In contrast, the reflection type arrangement is also called the reflection method, and the defect D is detected by detecting the ultrasonic beam U reflected by the defect D.
　本開示の例では、送信プローブ１１０の送信音軸ＡＸ１が、試料台１０２の載置面１０２１に対して垂直になるように、送信プローブ１１０が設置される。即ち、送信音軸ＡＸ１が試料台１０２の被検査体Ｅの載置面１０２１の法線方向になるように送信プローブ１１０が設置される。このようにすると、板状の被検査体Ｅにおいては、被検査体Ｅの表面に垂直に送信音軸ＡＸ１が配置されるので、走査位置と欠陥部Ｄの位置との対応関係がわかり易くなるという効果がある。 In the example disclosed herein, the transmitting probe 110 is installed so that the transmission sound axis AX1 of the transmitting probe 110 is perpendicular to the mounting surface 1021 of the sample stage 102. In other words, the transmitting probe 110 is installed so that the transmission sound axis AX1 is normal to the mounting surface 1021 of the sample stage 102 for the object E to be inspected. In this way, for a plate-shaped object E to be inspected, the transmission sound axis AX1 is arranged perpendicular to the surface of the object E to be inspected, which has the effect of making it easier to understand the correspondence between the scanning position and the position of the defect D.
　但し、送信音軸ＡＸ１が試料台１０２の被検査体Ｅの載置面１０２１に対して垂直になるように送信プローブ１１０を設置することに本開示が限定されるわけではない。送信音軸ＡＸ１が試料台１０２の被検査体Ｅの載置面１０２１に対して垂直でない場合でも、本開示の効果はある。後者の場合、欠陥部Ｄの位置を正確に知るには、垂直方向からの送信音軸ＡＸ１の傾きに応じて、送信音軸ＡＸ１の経路を計算すればよい。 However, the present disclosure is not limited to installing the transmission probe 110 so that the transmission sound axis AX1 is perpendicular to the mounting surface 1021 of the sample stage 102 for the object E to be inspected. The present disclosure is effective even if the transmission sound axis AX1 is not perpendicular to the mounting surface 1021 of the sample stage 102 for the object E to be inspected. In the latter case, to accurately determine the position of the defect D, the path of the transmission sound axis AX1 can be calculated according to the inclination of the transmission sound axis AX1 from the vertical direction.
　ここで、送信プローブ１１０と受信プローブ１２１との位置関係について述べる。送信プローブ１１０の送信音軸ＡＸ１と受信プローブ１２１の受信音軸ＡＸ２との距離を偏心距離Ｌ（後記）と定義する。第１実施形態では、上記のように、偏心距離Ｌがゼロに設定される。即ち、送信音軸ＡＸ１と受信音軸ＡＸ２とが同軸上になるような受信プローブ１２１が配置される。これを同軸配置と呼ぶ。なお、本開示では、偏心距離Ｌは０に限定されるものではない。 Here, the positional relationship between the transmitting probe 110 and the receiving probe 121 will be described. The distance between the transmitting sound axis AX1 of the transmitting probe 110 and the receiving sound axis AX2 of the receiving probe 121 is defined as the eccentricity distance L (described below). In the first embodiment, as described above, the eccentricity distance L is set to zero. That is, the receiving probe 121 is positioned so that the transmitting sound axis AX1 and the receiving sound axis AX2 are coaxial. This is called a coaxial arrangement. Note that in this disclosure, the eccentricity distance L is not limited to 0.
　本開示では、受信プローブ１２１の配置位置として、送信音軸ＡＸ１と受信音軸ＡＸ２とを同軸に配置したものを同軸配置と呼び、２つの音軸（送信音軸ＡＸ１及び受信音軸ＡＸ２）をずらしたもの（即ち、偏心させた配置）を偏心配置と呼ぶ。本開示は、受信プローブ１２１を同軸配置にした場合と、偏心配置にした場合とのいずれの場合でも効果を奏する。従って、本開示は、受信プローブ１２１の配置として、同軸配置及び偏心配置のいずれも含む。偏心配置の具体的な図示は後記する。 In this disclosure, the arrangement of the receiving probe 121 in which the transmission sound axis AX1 and the reception sound axis AX2 are coaxially arranged is called a coaxial arrangement, and the arrangement in which the two sound axes (the transmission sound axis AX1 and the reception sound axis AX2) are shifted (i.e., eccentrically arranged) is called an eccentric arrangement. This disclosure is effective in both cases where the receiving probe 121 is coaxially arranged and where it is eccentrically arranged. Therefore, this disclosure includes both the coaxial arrangement and the eccentric arrangement as the arrangement of the receiving probe 121. Specific illustrations of the eccentric arrangement are provided below.
　本開示において、特に、受信配置位置を指定する場合には、同軸配置された受信プローブ１２１を受信プローブ１４０（同軸配置受信プローブ）と記し、偏心配置された受信プローブ１２１を、受信プローブ１２０（偏心配置受信プローブ）と記すことにする。 In this disclosure, particularly when specifying the receiving arrangement position, the coaxially arranged receiving probe 121 will be referred to as receiving probe 140 (coaxially arranged receiving probe), and the eccentrically arranged receiving probe 121 will be referred to as receiving probe 120 (eccentrically arranged receiving probe).
　受信プローブ１２１と記した場合は、同軸配置か偏心配置かは特段に指定しない。 When referring to the receiving probe 121, there is no specific specification as to whether it is arranged coaxially or eccentrically.
　音軸とは、超音波ビームＵの中心軸と定義される。ここで、送信音軸ＡＸ１は、送信プローブ１１０が放出する超音波ビームＵの伝搬経路の音軸と定義される。言い換えると、送信音軸ＡＸ１は、送信プローブ１１０が放出する超音波ビームＵの伝搬経路の中心軸である。送信音軸ＡＸ１は、後記するように、被検査体Ｅの界面による屈折を含めることとする。つまり、送信プローブ１１０から放出された超音波ビームＵが、被検査体Ｅの界面で屈折する場合は、その超音波ビームＵの伝搬経路の中心（音軸）が送信音軸ＡＸ１となる。 The sound axis is defined as the central axis of the ultrasonic beam U. Here, the transmission sound axis AX1 is defined as the sound axis of the propagation path of the ultrasonic beam U emitted by the transmitting probe 110. In other words, the transmission sound axis AX1 is the central axis of the propagation path of the ultrasonic beam U emitted by the transmitting probe 110. The transmission sound axis AX1 includes refraction due to the interface of the object E to be inspected, as described below. In other words, when the ultrasonic beam U emitted from the transmitting probe 110 is refracted at the interface of the object E to be inspected, the center (sound axis) of the propagation path of the ultrasonic beam U becomes the transmission sound axis AX1.
　また、受信音軸ＡＸ２は、受信プローブ１２１が超音波ビームＵを放出すると想定した場合の仮想的な超音波ビームの伝搬経路の音軸と定義される。言い換えると、受信音軸ＡＸ２は、受信プローブ１２１が超音波ビームＵを放出すると想定した場合の仮想的な超音波ビームの中心軸である。 Furthermore, the receiving sound axis AX2 is defined as the sound axis of the propagation path of a virtual ultrasonic beam when it is assumed that the receiving probe 121 emits the ultrasonic beam U. In other words, the receiving sound axis AX2 is the central axis of a virtual ultrasonic beam when it is assumed that the receiving probe 121 emits the ultrasonic beam U.
　具体例として、探触子面１１４（後記）が平面状である非収束型の受信プローブ１２１の場合を述べる。この場合、受信音軸ＡＸ２の方向は探触子面１１４の法線方向であり、探触子面１１４の中心点を通る軸が受信音軸ＡＸ２になる。探触子面１１４が長方形の場合は、その中心点は長方形の対角線の交点と定義する。 As a specific example, we will consider the case of a non-converging receiving probe 121 with a planar probe surface 114 (described below). In this case, the direction of the receiving sound axis AX2 is the normal direction of the probe surface 114, and the axis passing through the center point of the probe surface 114 becomes the receiving sound axis AX2. If the probe surface 114 is rectangular, the center point is defined as the intersection of the diagonals of the rectangle.
　走査計測装置１には、制御装置２が接続されている。制御装置２は、走査計測装置１の駆動を制御するものであり、送信プローブ走査部１０３及び受信プローブ走査部１０４に指示することで、送信プローブ１１０及び受信プローブ１２１の移動（走査）を制御する。送信プローブ走査部１０３及び受信プローブ走査部１０４がｘ軸及びｙ軸方向に同期して移動することにより、送信プローブ１１０及び受信プローブ１２１は被検査体Ｅをｘ軸及びｙ軸方向に走査する。更に、制御装置２は、送信プローブ１１０から超音波ビームＵを放出し、受信プローブ１２１から取得した信号に基づいて波形解析を行う。なお、送信プローブ１１０の走査方向であるｘ軸及びｙ軸方向の２つの軸が作る平面を走査面と呼ぶことにする。 The control device 2 is connected to the scanning measurement device 1. The control device 2 controls the driving of the scanning measurement device 1, and controls the movement (scanning) of the transmitting probe 110 and the receiving probe 121 by instructing the transmitting probe scanning unit 103 and the receiving probe scanning unit 104. The transmitting probe scanning unit 103 and the receiving probe scanning unit 104 move synchronously in the x-axis and y-axis directions, so that the transmitting probe 110 and the receiving probe 121 scan the subject E in the x-axis and y-axis directions. Furthermore, the control device 2 emits an ultrasonic beam U from the transmitting probe 110, and performs waveform analysis based on the signal acquired from the receiving probe 121. Note that the plane formed by the two axes, the x-axis and y-axis directions, which are the scanning directions of the transmitting probe 110, is called the scanning plane.
　なお、第１実施形態では、被検査体Ｅが試料台１０２を介して筐体１０１に固定された状態、つまり、被検査体Ｅは筐体１０１に対し固定された状態で、送信プローブ１１０と受信プローブ１２１とを走査する例が示される。これとは逆に、送信プローブ１１０と受信プローブ１２１とが筐体１０１に対して固定され、試料台１０２の位置をｘ軸及びｙ軸方向に走査する構成としてもよい。この構成では、試料台１０２に載置された被検査体Ｅも移動するので、送信プローブ１１０との相対位置がｘ軸およびｙ軸方向に走査される。 In the first embodiment, an example is shown in which the transmitting probe 110 and the receiving probe 121 are scanned in a state in which the test subject E is fixed to the housing 101 via the sample stage 102, that is, in a state in which the test subject E is fixed to the housing 101. Conversely, a configuration in which the transmitting probe 110 and the receiving probe 121 are fixed to the housing 101 and the position of the sample stage 102 is scanned in the x-axis and y-axis directions may also be used. In this configuration, the test subject E placed on the sample stage 102 also moves, so that the relative position with the transmitting probe 110 is scanned in the x-axis and y-axis directions.
　送信プローブ１１０と被検査体Ｅとの間、及び受信プローブ１２１と被検査体Ｅとの間には、図示の例では気体Ｇが介在する。このため、送信プローブ１１０及び受信プローブ１２１を被検査体Ｅに非接触で検査できるため、ｘｙ面内方向の相対位置をスムーズかつ高速に変えることが可能である。即ち、送信プローブ１１０及び受信プローブ１２１と被検査体Ｅとの間に気体Ｇを介在させることにより、スムーズな走査が可能になる。 In the illustrated example, gas G is interposed between the transmitting probe 110 and the test subject E, and between the receiving probe 121 and the test subject E. Therefore, the transmitting probe 110 and the receiving probe 121 can test the test subject E without contacting it, so it is possible to change the relative positions in the xy plane smoothly and quickly. In other words, by interposing gas G between the transmitting probe 110 and the receiving probe 121 and the test subject E, smooth scanning is possible.
　送信プローブ１１０から局所的な超音波ビームＵを発することで、局所的な超音波ビームＵが被検査体Ｅに局所的に照射する。局所的な超音波ビームＵを照射する位置は走査して変える。前述の通り、被検査体Ｅの欠陥部Ｄと健全部Ｎとで受信プローブ１２１に到達する超音波ビームＵが変化するので、この構成により欠陥部Ｄを検出することができる。 By emitting a localized ultrasonic beam U from the transmitting probe 110, the localized ultrasonic beam U is locally irradiated onto the object to be inspected E. The position to which the localized ultrasonic beam U is irradiated is changed by scanning. As described above, the ultrasonic beam U that reaches the receiving probe 121 changes depending on whether it is a defective part D or a healthy part N of the object to be inspected E, so this configuration makes it possible to detect the defective part D.
　局所的な超音波ビームＵを生成するために、本実施形態では収束型の送信プローブ１１０を用いることができる。収束型の送信プローブ１１０の具体的な構成は後述する。局所的な超音波ビームＵを生成する構成としては、超音波ビームＵを発生する圧電素子（後記する振動子１１１。以下同じ）の面積を小さくすることでビーム径を小さくする構成を用いてもよい。収束型の送信プローブ１１０では、圧電素子の面積を大きくしながら、ビーム径を小さくできるので、ビーム強度が強くて、かつビーム径が小さい局所的な超音波ビームＵを発生できるのでより好ましい。 In order to generate a localized ultrasonic beam U, in this embodiment, a convergent transmitting probe 110 can be used. The specific configuration of the convergent transmitting probe 110 will be described later. A configuration for generating a localized ultrasonic beam U may be used in which the area of a piezoelectric element (transducer 111 described later; the same applies below) that generates the ultrasonic beam U is reduced to reduce the beam diameter. The convergent transmitting probe 110 is more preferable because it is possible to reduce the beam diameter while increasing the area of the piezoelectric element, thereby generating a localized ultrasonic beam U with high beam intensity and small beam diameter.
　送信プローブ１１０は、収束型の送信プローブ１１０である。一方で、受信プローブ１２１は、収束性が送信プローブ１１０よりも緩いプローブである。本実施形態では、受信プローブ１２１には探触子面が平面である非収束型のプローブが使用される。このような、非収束型の受信プローブ１２１を用いることで、幅広い範囲について欠陥部Ｄの情報を収集することができる。 The transmitting probe 110 is a convergent type transmitting probe 110. On the other hand, the receiving probe 121 is a probe with looser convergence than the transmitting probe 110. In this embodiment, a non-convergent type probe with a flat probe surface is used for the receiving probe 121. By using such a non-convergent type receiving probe 121, information on the defect portion D can be collected over a wide range.
　図２は、送信プローブ１１０の構造を示す断面模式図である。図２では、簡略化のために、放出される超音波ビームＵの外郭のみを図示しているが、実際には、探触子面１１４の全域にわたり、探触子面１１４の法線ベクトル方向に多数の超音波ビームＵが放出される。 FIG. 2 is a schematic cross-sectional view showing the structure of the transmitting probe 110. For simplicity, FIG. 2 shows only the outer contour of the emitted ultrasonic beam U, but in reality, a large number of ultrasonic beams U are emitted in the normal vector direction of the probe surface 114 over the entire area of the probe surface 114.
　送信プローブ１１０は、超音波ビームＵを収束するように構成される。これにより、被検査体Ｅ中の微小な欠陥部Ｄを高精度に検出できる。微小な欠陥部Ｄを検出できる理由は後記する。送信プローブ１１０は、送信プローブ筐体１１５を備え、送信プローブ筐体１１５の内部に、バッキング１１２と、振動子１１１と、整合層１１３とを備える。振動子１１１には電極（不図示）が取り付けられており、電極はリード線１１８により、コネクタ１１６に接続されている。さらに、コネクタ１１６はリード線１１７により電源装置（不図示）及び制御装置２に接続される。 The transmitting probe 110 is configured to focus the ultrasonic beam U. This allows for highly accurate detection of minute defects D in the object E to be inspected. The reason why minute defects D can be detected will be described later. The transmitting probe 110 comprises a transmitting probe housing 115, which comprises a backing 112, a transducer 111, and a matching layer 113 inside the transmitting probe housing 115. An electrode (not shown) is attached to the transducer 111, and the electrode is connected to a connector 116 by a lead wire 118. Furthermore, the connector 116 is connected to a power supply (not shown) and a control device 2 by a lead wire 117.
　本開示において、送信プローブ１１０又は受信プローブ１２１の探触子面１１４とは、整合層１１３を備える場合は整合層１１３の表面と定義し、整合層１１３を備えない場合は振動子１１１の表面と定義する。即ち、探触子面１１４は、送信プローブ１１０の場合は、超音波ビームＵを放出する面であり、受信プローブ１２１の場合は、超音波ビームＵを受信する面である。 In this disclosure, the probe surface 114 of the transmitting probe 110 or the receiving probe 121 is defined as the surface of the matching layer 113 if the matching layer 113 is provided, and as the surface of the transducer 111 if the matching layer 113 is not provided. That is, the probe surface 114 is the surface that emits the ultrasonic beam U in the case of the transmitting probe 110, and is the surface that receives the ultrasonic beam U in the case of the receiving probe 121.
　ここで、比較例として、従来の超音波検査の手法を説明する。 Here, we will explain a conventional ultrasonic inspection method as a comparative example.
　図３Ａは、従来の超音波検査方法での超音波ビームＵの伝搬経路を示す図であり、健全部Ｎへの入射時を示す図である。図３Ｂは、従来の超音波検査方法での超音波ビームＵの伝搬経路を示す図であり、欠陥部Ｄへの入射時を示す図である。従来の超音波検査方法では、例えば特許文献１に記載されているように、送信音軸ＡＸ１と受信音軸ＡＸ２とが一致するように、送信プローブ１１０及び受信プローブ１２１としての受信プローブ１４０が配置される。 FIG. 3A is a diagram showing the propagation path of an ultrasonic beam U in a conventional ultrasonic inspection method, showing the beam entering a healthy part N. FIG. 3B is a diagram showing the propagation path of an ultrasonic beam U in a conventional ultrasonic inspection method, showing the beam entering a defective part D. In a conventional ultrasonic inspection method, as described in Patent Document 1, for example, a transmitting probe 110 and a receiving probe 140 serving as a receiving probe 121 are positioned so that a transmitting sound axis AX1 and a receiving sound axis AX2 coincide with each other.
　図３Ａに示すように、被検査体Ｅの健全部Ｎに超音波ビームＵが入射された場合、超音波ビームＵが被検査体Ｅを通過して受信プローブ１４０に到達する。従って、受信信号が大きくなる。一方、図３Ｂに示すように、欠陥部Ｄに超音波ビームＵが入射された場合、欠陥部Ｄにより超音波ビームＵの透過が阻止されるために受信信号が減少する。このように受信信号の減少により欠陥部Ｄを検出する。これは、特許文献１に示されている通りである。 As shown in FIG. 3A, when an ultrasonic beam U is incident on a healthy portion N of an object to be inspected E, the ultrasonic beam U passes through the object to be inspected E and reaches the receiving probe 140. Therefore, the received signal becomes large. On the other hand, as shown in FIG. 3B, when an ultrasonic beam U is incident on a defective portion D, the defective portion D prevents the ultrasonic beam U from passing through, and the received signal decreases. In this way, the defective portion D is detected by the decrease in the received signal. This is as shown in Patent Document 1.
　ここで、図３Ａ及び図３Ｂに示すように、欠陥部Ｄにおいて超音波ビームＵの透過が阻止されることによって受信信号が減少し、欠陥部Ｄを検出する方法を、ここでは「阻止法」と呼ぶことにする。 As shown in Figures 3A and 3B, the method of detecting a defect D by blocking the transmission of an ultrasonic beam U at the defect D, thereby reducing the received signal, is referred to here as the "blocking method."
　従来技術の問題点は、欠陥サイズがビームサイズよりも小さくなると検出が困難になることである。この点を、図４を参照して説明する。 The problem with the conventional technology is that it becomes difficult to detect defects when the size of the defect becomes smaller than the beam size. This point will be explained with reference to Figure 4.
　図４は、被検査体Ｅ内での欠陥部Ｄと超音波ビームＵとの相互作用を示す図であり、直達する超音波ビームＵ（以下、「直達波Ｕ３」という）を受信する様子を示す図である。直達波Ｕ３については後記する。ここでは、欠陥部Ｄの大きさが超音波ビームＵの幅（以下、ビーム幅ＢＷと称する）よりも小さい場合を考察する。ここでのビーム幅ＢＷとは、欠陥部Ｄに到達した時の超音波ビームＵの幅である。 FIG. 4 is a diagram showing the interaction between a defect D and an ultrasonic beam U in an object E to be inspected, and shows how a direct ultrasonic beam U (hereinafter referred to as a "direct wave U3") is received. The direct wave U3 will be described later. Here, we consider the case where the size of the defect D is smaller than the width of the ultrasonic beam U (hereinafter referred to as the beam width BW). The beam width BW here is the width of the ultrasonic beam U when it reaches the defect D.
　また、図４は、欠陥部Ｄ近傍の微小領域での超音波ビームＵの形状を模式的に示しているので超音波ビームＵを平行に描いてあるが、実際には収束させた超音波ビームＵである。さらに、図４での受信プローブ１２１の位置は、わかりやすく説明するために概念的な位置を記入したものであり、受信プローブ１２１の位置と形状は正確にスケールされていない。即ち、欠陥部Ｄと超音波ビームＵとの形状の拡大スケールで考えると、図４に示す位置よりも、図面上下方向で離れた位置に受信プローブ１２１は位置する。 In addition, since FIG. 4 shows a schematic representation of the shape of the ultrasonic beam U in a minute area near the defect D, the ultrasonic beam U is drawn parallel, but in reality it is a converged ultrasonic beam U. Furthermore, the position of the receiving probe 121 in FIG. 4 is a conceptual position shown for easy understanding, and the position and shape of the receiving probe 121 are not precisely scaled. In other words, when considering the enlarged scale of the shapes of the defect D and the ultrasonic beam U, the receiving probe 121 is located at a position further away in the vertical direction of the drawing than the position shown in FIG. 4.
　図４では、送信音軸ＡＸ１と受信音軸ＡＸ２とを一致させた阻止法の場合が示される。欠陥部Ｄがビーム幅ＢＷよりも小さい場合、一部の超音波ビームＵは阻止されるので受信信号は減少するが、ゼロにはならない。例えば、欠陥部Ｄの断面積がビーム幅ＢＷで規定されるビーム断面積の５％の場合、受信信号は概ね５％の減少に止まるので、欠陥部Ｄの検出が困難である。つまり、図４に示すような場合、欠陥部Ｄが存在する箇所では、受信信号が５％減少するにとどまる。このように、欠陥部Ｄがビーム幅ＢＷよりも小さい場合、欠陥部Ｄと相互作用することなく、素通りするビームが多くなるので、欠陥の検出が困難になる。 Figure 4 shows the case of a blocking method in which the transmitting sound axis AX1 and the receiving sound axis AX2 are aligned. If the defect D is smaller than the beam width BW, part of the ultrasonic beam U is blocked, so the received signal decreases, but does not become zero. For example, if the cross-sectional area of the defect D is 5% of the beam cross-sectional area defined by the beam width BW, the received signal decreases by only about 5%, making it difficult to detect the defect D. In other words, in the case shown in Figure 4, where the defect D exists, the received signal decreases by only 5%. In this way, if the defect D is smaller than the beam width BW, many beams pass through without interacting with the defect D, making it difficult to detect the defect.
　図５は、欠陥部Ｄと相互作用した超音波ビームＵである散乱波Ｕ１を模式的に示した図である。本開示では、欠陥部Ｄと相互作用した超音波ビームＵを散乱波Ｕ１と呼ぶ。従って、本開示での「散乱波Ｕ１」とは、欠陥部Ｄと相互作用した超音波を指す。散乱波Ｕ１には、図５のように方向を変える波もある。また、散乱波Ｕ１には、欠陥部Ｄとの相互作用により波の位相又は周波数の少なくとも一方が変化するが、進行方向は変わらない波もある。欠陥部Ｄと相互作用することなく、通過する超音波を直達波Ｕ３と呼ぶ。直達波Ｕ３と区別して、散乱波Ｕ１のみを検出できれば、小さな欠陥部Ｄを検出し易くできる。本開示では、周波数の違いに着目することで、散乱波Ｕ１が効率的に検出される。 FIG. 5 is a schematic diagram showing a scattered wave U1, which is an ultrasonic beam U that has interacted with a defect D. In this disclosure, the ultrasonic beam U that has interacted with the defect D is called the scattered wave U1. Therefore, in this disclosure, the "scattered wave U1" refers to an ultrasonic wave that has interacted with the defect D. Some of the scattered waves U1 change direction as shown in FIG. 5. Some of the scattered waves U1 change at least one of the phase or frequency of the wave due to the interaction with the defect D, but the direction of travel does not change. An ultrasonic wave that passes through the defect D without interacting with it is called a direct wave U3. If only the scattered waves U1 can be detected, distinguishing them from the direct waves U3, it will be easier to detect small defects D. In this disclosure, the scattered waves U1 are efficiently detected by focusing on the difference in frequency.
　本実施形態では、送信プローブ１１０と被検査体Ｅとの間の流体Ｆとして空気等の気体Ｇが使用される。この場合、以下に述べる理由から、従来法である阻止法では微小な欠陥部Ｄの検出がとりわけ困難になる。このため、散乱波Ｕ１を検出する本開示の効果が大きい。 In this embodiment, a gas G such as air is used as the fluid F between the transmitting probe 110 and the test object E. In this case, for the reasons described below, it becomes particularly difficult to detect minute defects D using the conventional blocking method. For this reason, the effect of the present disclosure in detecting the scattered wave U1 is significant.
　液体中と比較して、気体Ｇ中では超音波の減衰量が大きい。超音波の気体Ｇ中での減衰量は周波数の２乗に比例することが知られている。このため、気体Ｇ中で超音波を伝搬させるには１ＭＨｚ程度が上限となる。液体中の場合は、５ＭＨｚ～数１０ＭＨｚの超音波でも伝搬するので、気体Ｇ中で使用可能な周波数は、液体中のそれより小さいことになる。 Compared to liquids, ultrasonic waves are attenuated more in gas G. It is known that the attenuation of ultrasonic waves in gas G is proportional to the square of the frequency. For this reason, the upper limit for ultrasonic waves propagating in gas G is about 1 MHz. In liquids, ultrasonic waves of 5 MHz to several tens of MHz can also propagate, so the frequencies that can be used in gas G are smaller than those in liquids.
　一般に、超音波ビームＵの周波数が低くなると、超音波ビームＵの収束が困難になる。そのため、気体Ｇ中を伝搬させる１ＭＨｚの超音波ビームＵは、液体中の超音波ビームＵと比べて収束可能なビーム径が大きくなる。一方、上記図４に示したように、従来法である阻止モードでは、ビームサイズよりも小さな欠陥部Ｄを検出することが困難である。しかし、本開示によれば、上記図５に示したように、散乱波Ｕ１の成分の割合を増やして検出するため、ビームサイズよりも小さな欠陥部Ｄを検出することが可能である。 In general, as the frequency of the ultrasonic beam U decreases, it becomes more difficult to converge the ultrasonic beam U. Therefore, the 1 MHz ultrasonic beam U propagating through gas G has a larger beam diameter that can be converged compared to the ultrasonic beam U in liquid. On the other hand, as shown in Figure 4 above, in the blocking mode, which is the conventional method, it is difficult to detect a defect D smaller than the beam size. However, according to the present disclosure, as shown in Figure 5 above, the proportion of the scattered wave U1 component is increased for detection, making it possible to detect a defect D smaller than the beam size.
　図６は、制御装置２の機能ブロック図である。制御装置２は、走査計測装置１の駆動を制御するものである。制御装置２は、送信系統２１０と、受信系統２２０と、データ処理部２０１と、スキャンコントローラ２０４と、駆動部２０２と、位置計測部２０３と、信号処理部２５０とを備える。受信系統２２０とデータ処理部２０１とを合わせて、信号処理部２５０と呼ぶ。信号処理部２５０は、受信プローブ１２１からの信号を増幅処理、フィルタ処理等により、有意な情報を抽出する信号処理を行う。 FIG. 6 is a functional block diagram of the control device 2. The control device 2 controls the driving of the scanning measurement device 1. The control device 2 includes a transmission system 210, a reception system 220, a data processing unit 201, a scan controller 204, a driving unit 202, a position measurement unit 203, and a signal processing unit 250. The reception system 220 and the data processing unit 201 are collectively referred to as the signal processing unit 250. The signal processing unit 250 performs signal processing to extract significant information by amplifying and filtering the signal from the receiving probe 121.
　送信系統２１０は、送信プローブ１１０への印加電圧を生成する系統である。送信系統２１０は、波形発生器２１１及び信号アンプ２１２を備える。波形発生器２１１でバースト波信号が発生する。そして、発生したバースト波信号は信号アンプ２１２で増幅される。信号アンプ２１２から出力された電圧は送信プローブ１１０に印加される。 The transmission system 210 is a system that generates a voltage to be applied to the transmission probe 110. The transmission system 210 includes a waveform generator 211 and a signal amplifier 212. A burst wave signal is generated by the waveform generator 211. The generated burst wave signal is then amplified by the signal amplifier 212. The voltage output from the signal amplifier 212 is applied to the transmission probe 110.
　このようにして、制御装置２に含まれる送信系統２１０はバースト波の電圧波形を出力し、出力されたバースト波の電圧波形が送信プローブ１１０に印加される。本開示では、バースト波は繰り返し波束とも呼ぶ。バースト波の波形については後述する。 In this way, the transmission system 210 included in the control device 2 outputs a voltage waveform of a burst wave, and the outputted voltage waveform of the burst wave is applied to the transmission probe 110. In this disclosure, the burst wave is also referred to as a repeating wave packet. The waveform of the burst wave will be described later.
　信号処理部２５０は、受信系統２２０を備える。受信系統２２０は、受信プローブ１２１から出力される受信信号を検出する系統である。受信プローブ１２１から出力された信号は、信号アンプ２２２に入力されて増幅される。増幅された信号は、フィルタ部２４０（遮断フィルタ）に入力される。フィルタ部２４０は、入力信号の特定の周波数範囲の成分を低減する（遮断する）。フィルタ部２４０については後述する。フィルタ部２４０からの出力信号は、データ処理部２０１に入力される。 The signal processing unit 250 includes a receiving system 220. The receiving system 220 is a system that detects the received signal output from the receiving probe 121. The signal output from the receiving probe 121 is input to a signal amplifier 222 and amplified. The amplified signal is input to a filter unit 240 (blocking filter). The filter unit 240 reduces (blocks) components of a specific frequency range of the input signal. The filter unit 240 will be described later. The output signal from the filter unit 240 is input to the data processing unit 201.
　データ処理部２０１では、フィルタ部２４０から入力された信号から、信号強度データを生成する。信号強度データの生成方法として、本実施例ではピーク間信号量（Ｐｅａｋ－ｔｏ－Ｐｅａｋ　ｓｉｇｎａｌ）を用いた。これは信号のうち最大値と最小値との差である。信号強度データの生成方法には、この他、フーリエ変換をして特定周波数範囲の周波数成分の強度を用いてもよい。 The data processing unit 201 generates signal strength data from the signal input from the filter unit 240. In this embodiment, the peak-to-peak signal is used as a method for generating signal strength data. This is the difference between the maximum and minimum values of the signal. Another method for generating signal strength data is to use the strength of frequency components in a specific frequency range by performing a Fourier transform.
　データ処理部２０１は、スキャンコントローラ２０４から走査位置の情報も受け取る。このようにして、現在の２次元走査位置（ｘ、ｙ）における信号強度データの値が得られる。信号強度データの値を走査位置に対してプロットすると、欠陥部Ｄの位置又は形状の少なくとも一方に対応した画像（欠陥画像）が得られる。この欠陥画像は表示装置３に出力される。 The data processing unit 201 also receives scanning position information from the scan controller 204. In this way, the signal intensity data value at the current two-dimensional scanning position (x, y) is obtained. By plotting the signal intensity data value against the scanning position, an image (defect image) corresponding to at least one of the position and shape of the defect D is obtained. This defect image is output to the display device 3.
（フィルタ部２４０）
　本開示においてフィルタ部２４０は、所定の周波数範囲の信号成分の強度を低減させる信号処理を行う制御部と定義される。また、フィルタ処理は、所定の周波数範囲の信号成分の強度を低減させる信号処理と定義される。受信信号をフーリエ変換等で周波数成分毎の成分強度に分解した際、成分強度が最大になる周波数を最大成分周波数と呼ぶ。最大強度周波数成分は最大成分周波数における周波数成分である。即ち、最大成分周波数は、最大強度周波数成分に対応した周波数である。本開示のフィルタ部２４０は、最大強度周波数成分を含む基本波帯、即ち、最大成分周波数を含む周波数範囲の信号成分の強度を低減する。なお、周波数成分毎の成分強度の分布を周波数スペクトルと呼ぶ。 (Filter section 240)
In the present disclosure, the filter unit 240 is defined as a control unit that performs signal processing to reduce the intensity of signal components in a predetermined frequency range. Filter processing is also defined as signal processing to reduce the intensity of signal components in a predetermined frequency range. When a received signal is decomposed into component intensities for each frequency component by Fourier transform or the like, the frequency at which the component intensity is maximum is called the maximum component frequency. The maximum intensity frequency component is a frequency component at the maximum component frequency. In other words, the maximum component frequency is a frequency corresponding to the maximum intensity frequency component. The filter unit 240 of the present disclosure reduces the intensity of the fundamental wave band including the maximum intensity frequency component, that is, the signal components in the frequency range including the maximum component frequency. The distribution of component intensities for each frequency component is called a frequency spectrum.
　図７は、受信信号の周波数成分の分布（周波数スペクトル）を模式的に示した図である。図７を用いて、フィルタ部２４０をさらに具体的に説明する。同図において、横軸が周波数、縦軸は成分強度（強度）を示す。縦軸は、対数スケールで示してあり、幅広い強度範囲を模式的に示している。 FIG. 7 is a diagram showing a schematic distribution of frequency components (frequency spectrum) of a received signal. The filter section 240 will be explained in more detail using FIG. 7. In the figure, the horizontal axis shows frequency, and the vertical axis shows component strength (intensity). The vertical axis is shown on a logarithmic scale, and a wide range of strength is shown.
　成分強度が最大になる最大成分周波数をｆｍとする。最大成分周波数ｆｍは、送信プローブ１１０から送信したバースト波の基本周波数ｆ０にほぼ等しい。信号の周波数成分は、最大成分周波数ｆｍの前後に広がりを持ち、これを基本波帯Ｗ１と呼ぶ。 The maximum component frequency at which the component strength is at its maximum is designated as fm. The maximum component frequency fm is approximately equal to the fundamental frequency f0 of the burst wave transmitted from the transmitting probe 110. The frequency components of the signal have a spread before and after the maximum component frequency fm, which is called the fundamental wave band W1.
　最大成分周波数ｆｍのＮ倍の周波数（Ｎ×ｆｍ）の成分は、高調波である。最大成分周波数ｆｍの１／Ｎ倍の周波数（ｆｍ／Ｎ）の成分は、分調波である。ここで、Ｎは、Ｎ≧２の整数である。高調波、分調波もそれぞれ広がりをもつ。本開示では、高調波、分調波が周波数的な広がりを持つことを特に強調する場合に、それぞれ高調波帯、分調波帯と呼ぶ。従って、単に「高調波」と記した場合も、周波数的な広がりを持つ。高調波帯、分調波帯は、非線形現象で発生するものであり、被検査体Ｅに入力した超音波ビームＵの音圧が極めて強い場合に発生する。 The component with a frequency (N x fm) that is N times the maximum component frequency fm is a harmonic. The component with a frequency (fm/N) that is 1/N times the maximum component frequency fm is a sub-harmonic. Here, N is an integer N >= 2. Harmonics and sub-harmonics also have a spread. In this disclosure, when it is particularly emphasized that harmonics and sub-harmonics have a frequency spread, they are called harmonic bands and sub-harmonic bands, respectively. Therefore, even when simply written as "harmonic", it has a frequency spread. Harmonic bands and sub-harmonic bands are generated by nonlinear phenomena, and occur when the sound pressure of the ultrasonic beam U input to the test object E is extremely strong.
　第１実施形態のように、送信プローブ１１０と被検査体Ｅとの間に気体Ｇを介した場合には、被検査体Ｅの内部に音圧が強い超音波ビームＵを入れることは、一般的には困難なため、高調波帯又は分調波帯の少なくとも一方は観測されないことが多い。第１実施形態での条件でも、高調波帯及び分調波帯は検出限界以下であった。 When gas G is present between the transmitting probe 110 and the test object E as in the first embodiment, it is generally difficult to introduce an ultrasonic beam U with a high sound pressure into the test object E, so at least one of the harmonic bands or sub-harmonic bands is often not observed. Even under the conditions of the first embodiment, the harmonic bands and sub-harmonic bands were below the detection limit.
　図７に示すように、基本波帯Ｗ１は周波数的に広がりを持つ。基本波帯Ｗ１のうち、最大成分周波数ｆｍの成分以外の周波数成分を「裾野成分Ｗ３」と呼ぶことにする。裾野成分Ｗ３には、基本波のサイドローブも含まれる。 As shown in Figure 7, the fundamental wave band W1 has a wide frequency range. Within the fundamental wave band W1, the frequency components other than the maximum component frequency fm are referred to as "foot components W3." The foot components W3 also include the side lobes of the fundamental wave.
　第１実施形態では、フィルタ部２４０は、最大成分周波数ｆｍを含む遮断周波数範囲の成分強度を低減する。即ち、フィルタ部２４０は、受信プローブ１２１の受信信号のうちの少なくとも最大強度周波数成分（最大成分周波数ｆｍに対応する成分）を低減する。そして、フィルタ部２４０は、最大強度周波数成分を含む基本波帯Ｗ１のうちの最大強度周波数成分以外の裾野成分Ｗ３を検出する。フィルタ部２４０により、遮断周波数範囲の成分強度が低減するので、フィルタ部２４０を通過した後の信号では、基本波帯Ｗ１のうち裾野成分Ｗ３が占める割合が増加する。このようにすることで、後記のように、欠陥部Ｄの検出性能を向上できる。 In the first embodiment, the filter unit 240 reduces the component strength in the cutoff frequency range including the maximum component frequency fm. That is, the filter unit 240 reduces at least the maximum intensity frequency component (the component corresponding to the maximum component frequency fm) of the received signal of the receiving probe 121. The filter unit 240 then detects the skirt component W3 other than the maximum intensity frequency component of the fundamental wave band W1 including the maximum intensity frequency component. Because the filter unit 240 reduces the component strength in the cutoff frequency range, the proportion of the skirt component W3 in the fundamental wave band W1 increases in the signal after passing through the filter unit 240. In this way, the detection performance of the defect portion D can be improved, as described below.
　図８Ａは、欠陥部Ｄに跨るように送信プローブ１１０及び受信プローブ１２１を走査したときの信号強度情報の位置による変化を示したものである。図８Ａでは、上記図６の構成からフィルタ部２４０を除いた構成で測定した結果である。健全部Ｎでの信号強度はｖ０である。一方で、欠陥部Ｄに対応する位置（ｘ＝０）で、信号強度がΔｖだけ低下しており、欠陥部Ｄを検出できている。しかし、信号強度の変化率（Δｖ／ｖ０）は小さい。ここで信号強度の変化率とは、欠陥部Ｄでの信号変化量Δｖを健全部Ｎでの信号強度ｖ０で割った値と定義する。 Figure 8A shows the change in signal strength information depending on the position when the transmitting probe 110 and the receiving probe 121 are scanned across the defective area D. Figure 8A shows the results of a measurement using a configuration in which the filter section 240 has been removed from the configuration in Figure 6 above. The signal strength in the healthy area N is v0. On the other hand, at the position (x = 0) corresponding to the defective area D, the signal strength has decreased by Δv, and the defective area D has been detected. However, the rate of change in signal strength (Δv/v0) is small. Here, the rate of change in signal strength is defined as the amount of signal change Δv in the defective area D divided by the signal strength v0 in the healthy area N.
　図８Ｂは、フィルタ部２４０を備えた制御装置２（図６）により、信号強度情報を測定した結果である。欠陥部Ｄの場所での信号強度の変化率（Δｖ／ｖ０）が大きくなり、欠陥部Ｄの検出性が改善したことがわかる。 Figure 8B shows the results of measuring signal strength information using a control device 2 (Figure 6) equipped with a filter unit 240. It can be seen that the rate of change in signal strength (Δv/v0) at the location of defect D has increased, improving the detectability of defect D.
　図８Ａ及び図８Ｂの実験結果を取得した実験条件を説明する。 The experimental conditions under which the results shown in Figures 8A and 8B were obtained are explained below.
　図９は、送信プローブ１１０に印加するバースト波の電圧波形である。横軸は時間、縦軸は電圧である。図９の例では、基本周波数ｆ０が０．８２ＭＨｚの正弦波が１０波印加される。この１０波を波束と呼ぶ。なお、基本周波数ｆ０の逆数を基本周期Ｔ０と呼ぶ。基本周期Ｔ０は、同図に示した通り、１波束を構成する波の周期である。波束は繰り返し周期Ｔｒ＝５ｍｓで印加される。従って、送信プローブ１１０は、波数が２以上の波束で構成される繰り返し波束の電圧波形を印加されて超音波ビームＵを放出する。 Figure 9 shows the voltage waveform of a burst wave applied to the transmitting probe 110. The horizontal axis is time, and the vertical axis is voltage. In the example of Figure 9, ten sine waves with a fundamental frequency f0 of 0.82 MHz are applied. These ten waves are called a wave packet. The inverse of the fundamental frequency f0 is called the fundamental period T0. As shown in the figure, the fundamental period T0 is the period of the waves that make up one wave packet. The wave packet is applied with a repetition period Tr = 5 ms. Therefore, the transmitting probe 110 emits an ultrasonic beam U when a voltage waveform of a repeating wave packet made up of a wave packet with two or more waves is applied to it.
　なお、本実施形態では各々の波束は基本周波数ｆ０の正弦波を用いたが，正弦波以外でも良い。例えば、波束は、波数Ｎ０の矩形波で構成された波束であってもよい。 In this embodiment, each wave packet is a sine wave with a fundamental frequency of f0, but it may be a wave packet other than a sine wave. For example, the wave packet may be a wave packet composed of a rectangular wave with a wave number of N0.
　波束の波数Ｎ０とは、１つの波束に含まれる基本周波数ｆ０の波の個数（サイクル数）である。本開示では、波束の波数Ｎ０は２以上であり、波束の波数Ｎ０は３以上であることが好ましい。従って、送信プローブ１１０は、波数Ｎ０が２以上の波束で構成される繰り返し波束の電圧波形を印加されて超音波ビームＵを放出する。本実施形態の実験条件では、前述の通り波数Ｎ０は１０波である。波束を繰り返す、繰り返し波束の波形をバースト波と呼ぶ。 The wave number N0 of a wave packet is the number of waves (number of cycles) of fundamental frequency f0 contained in one wave packet. In the present disclosure, the wave number N0 of a wave packet is 2 or more, and it is preferable that the wave number N0 of a wave packet is 3 or more. Therefore, the transmitting probe 110 emits an ultrasonic beam U by applying a voltage waveform of a repeating wave packet composed of wave packets with a wave number N0 of 2 or more. Under the experimental conditions of this embodiment, the wave number N0 is 10 waves, as described above. A waveform of a repeating wave packet in which wave packets are repeated is called a burst wave.
　図１０は、図９に示す条件での受信信号の周波数成分分布を示したものである。同図は、横軸が周波数で、縦軸がそれぞれの周波数での成分強度の実測データをプロットしている。このグラフは、フィルタ部２４０で処理していない信号の周波数成分分布である。成分強度が最大になる０．８２ＭＨｚが最大成分周波数ｆｍである。基本波帯Ｗ１は、０．７４ＭＨｚから０．８８ＭＨｚに拡がっており、このうち最大成分周波数ｆｍを除いた成分が裾野成分Ｗ３である。本実施形態では、最大成分周波数ｆｍは、送信プローブ１１０が送信する超音波の基本周波数ｆ０と等しくなっている。このように、多くの場合、最大成分周波数ｆｍは送信する超音波の基本周波数ｆ０に概ね等しくなる。 Figure 10 shows the frequency component distribution of the received signal under the conditions shown in Figure 9. In this figure, the horizontal axis is frequency, and the vertical axis plots the measured data of component strength at each frequency. This graph shows the frequency component distribution of a signal not processed by the filter section 240. 0.82 MHz, where the component strength is at its maximum, is the maximum component frequency fm. The fundamental wave band W1 extends from 0.74 MHz to 0.88 MHz, and the components excluding the maximum component frequency fm are the skirt components W3. In this embodiment, the maximum component frequency fm is equal to the fundamental frequency f0 of the ultrasound transmitted by the transmitting probe 110. Thus, in many cases, the maximum component frequency fm is roughly equal to the fundamental frequency f0 of the ultrasound transmitted.
　フィルタ部２４０（図６）は、上記のように、最大成分周波数ｆｍを除く。具体的には、図示の例では、フィルタ部２４０（図６）は０．７８ＭＨｚ以下の裾野成分Ｗ３を透過させ、０．８２ＭＨｚを含む、０．７８ＭＨｚを超える波を遮断する。このようなフィルタ部２４０を用いると、上記図８Ｂのように、欠陥部Ｄでの信号強度の変化率が増大し、欠陥の検出性が大幅に改善することがわかる。 As described above, the filter section 240 (Fig. 6) excludes the maximum component frequency fm. Specifically, in the illustrated example, the filter section 240 (Fig. 6) transmits the base component W3 below 0.78 MHz and blocks waves above 0.78 MHz, including 0.82 MHz. When such a filter section 240 is used, as shown in Fig. 8B above, the rate of change of the signal intensity at the defective section D increases, and it can be seen that the detectability of the defect is greatly improved.
　図１１は、受信信号の周波数成分分布（周波数スペクトル）の実測データを、健全部Ｎ（実線）と欠陥部Ｄ（破線）とで比較した図である。フィルタ部２４０により欠陥部Ｄの検出性が改善するメカニズムは以下の通りである。最大成分周波数ｆｍ＝０．８２ＭＨｚでは、健全部Ｎと欠陥部Ｄとで成分強度（信号の大きさ）の違いは小さい。一方、最大成分周波数ｆｍ以外である裾野成分Ｗ３、特に低域帯については、健全部Ｎと欠陥部Ｄとの差が大きくなっている。 Figure 11 is a diagram comparing the measured data of the frequency component distribution (frequency spectrum) of the received signal between a healthy part N (solid line) and a defective part D (dashed line). The mechanism by which the filter section 240 improves the detectability of the defective part D is as follows. At the maximum component frequency fm = 0.82 MHz, the difference in component strength (signal magnitude) between the healthy part N and the defective part D is small. On the other hand, for the base component W3 other than the maximum component frequency fm, especially in the low frequency band, the difference between the healthy part N and the defective part D is large.
　このように、受信信号の周波数成分を調べ、最大成分周波数ｆｍよりも、裾野成分Ｗ３の方が健全部Ｎと欠陥部Ｄとの差が大きい、ことを発明者らは見出した。この知見に基づき、健全部Ｎと欠陥部Ｄとの差が小さい最大成分周波数ｆｍの周波数成分を低減するようなフィルタ部２４０を用いることにより、欠陥部Ｄの検出性を改善できることを見出した。 In this way, the inventors have examined the frequency components of the received signal and found that the difference between the healthy part N and the defective part D is greater for the base component W3 than for the maximum component frequency fm. Based on this knowledge, they have found that the detectability of the defective part D can be improved by using a filter section 240 that reduces the frequency component of the maximum component frequency fm, which is the smallest difference between the healthy part N and the defective part D.
　このように、本開示は受信信号の周波数成分分布において、最大成分周波数ｆｍでの信号成分よりも、基本波帯Ｗ１の裾野成分Ｗ３の方が欠陥部Ｄでの信号変化率が大きいという、発明者らが見出した新しい知見に基づくものである。最大成分周波数ｆｍの成分は、受信信号の中で大きな割合を占めるが、欠陥部Ｄでの信号変化率が小さいので、この成分を低減することで、その結果、裾野成分Ｗ３が占める割合が増大する。このようにすることで、フィルタ部２４０で処理後の信号は、欠陥部Ｄでの信号変化率が増大するために、欠陥部Ｄの検出性を改善できる。そして、図８Ａ及び図８Ｂに示した実測データを比較しても、フィルタ部２４０による欠陥部Ｄの検出性が改善する効果は明らかである。 In this way, the present disclosure is based on the new knowledge found by the inventors that in the frequency component distribution of a received signal, the base component W3 of the fundamental wave band W1 has a greater signal change rate at the defect D than the signal component at the maximum component frequency fm. The component at the maximum component frequency fm accounts for a large proportion of the received signal, but the signal change rate at the defect D is small, so by reducing this component, the proportion of the base component W3 increases. In this way, the signal after processing by the filter unit 240 has an increased signal change rate at the defect D, improving the detectability of the defect D. And even when comparing the actual measurement data shown in Figures 8A and 8B, the effect of improving the detectability of the defect D by the filter unit 240 is clear.
（バースト波の効果）
　本開示において、送信プローブ１１０に、バースト波、即ち繰り返し波束の電圧波形を印加する効果を述べる。 (Burst wave effect)
In this disclosure, the effect of applying a burst wave, i.e., a repeating wave packet voltage waveform, to the transmitting probe 110 is described.
　前記した通り、本開示では最大成分周波数ｆｍからΔｆだけずれた周波数成分（裾野成分）が欠陥部Ｄでの信号変化率が大きいという新しい知見に基づいている。そのため、基本波帯Ｗ１の帯域を適正な幅に狭めることにより、ずれた成分（ｆｍ±Δｆ）の周波数領域が特定の領域に入るので、ずれた成分（裾野成分Ｗ３）に含まれる欠陥情報を検出し易くなる。 As mentioned above, this disclosure is based on the new knowledge that the frequency component (foot component) that is shifted by Δf from the maximum component frequency fm has a large signal change rate at the defect part D. Therefore, by narrowing the bandwidth of the fundamental wave band W1 to an appropriate width, the frequency range of the shifted component (fm±Δf) falls within a specific range, making it easier to detect the defect information contained in the shifted component (foot component W3).
　これに対し、単一パルス又は１周期の電圧波形を印加すると、後述するように、送信波の周波数帯域自体が広帯域に拡がるため、ずれた成分（ｆｍ±Δｆ）も広い周波数範囲に拡がってしまう。このため、本開示のように、Δｆだけずれた周波数成分を抽出して検出することが困難である。 In contrast, when a single pulse or one-cycle voltage waveform is applied, as described below, the frequency band of the transmission wave itself spreads over a wide band, and the shifted component (fm±Δf) also spreads over a wide frequency range. For this reason, it is difficult to extract and detect the frequency component shifted by Δf, as in the present disclosure.
　単一パルス又は１周期の電圧波形を印加して、被検査体Ｅの内部の欠陥部Ｄを検査する方法はパルスエコー法として知られている。超音波の送信時刻から受信までの時間を計ることで、欠陥部Ｄまでの距離を知ることが出来る。 The method of inspecting a defect D inside an object E by applying a single pulse or one cycle of a voltage waveform is known as the pulse-echo method. By measuring the time from when the ultrasonic wave is transmitted to when it is received, the distance to the defect D can be determined.
　次に、送信プローブ１１０に印加する波束の波数Ｎ０と送信される超音波の周波数帯域との関係を述べる。 Next, we will describe the relationship between the wave number N0 of the wave packet applied to the transmitting probe 110 and the frequency band of the transmitted ultrasound.
　図１２Ａは、波数Ｎ０を変えた時の送信超音波の周波数スペクトルを示す。ここでは、波数Ｎ０で構成する波束の時間波形をフーリエ変換することで、周波数スペクトルを算出した。波束Ｎ０を構成する波の基本周波数ｆ０は０．８２ＭＨｚとしている。図１２Ａは波数Ｎ０が１～３個の場合のスペクトルを示した。なお、波数１個の場合は、波束にならないので繰り返し波束にならず、バースト波ではない。 Figure 12A shows the frequency spectrum of the transmitted ultrasound when the wave number N0 is changed. Here, the frequency spectrum was calculated by Fourier transforming the time waveform of the wave packet composed of wave number N0. The fundamental frequency f0 of the waves that compose wave packet N0 is set to 0.82 MHz. Figure 12A shows the spectrum when wave number N0 is 1 to 3. Note that when there is a wave number of 1, it does not become a wave packet, so it is not a repeating wave packet and is not a burst wave.
　破線で示す波数Ｎ０＝１の場合、０～１．６ＭＨｚの周波数範囲に基本波帯Ｗ１の周波数成分が拡がっていることがわかる。これは０～２ｆｍに対応する。従って、前述の通り、本開示のような最大成分周波数ｆｍからずれた信号成分を優先的に抽出することは困難である。なお、波数Ｎ０＝１の周波数スペクトルは、パルスエコー法の典型的なスペクトル形状である。 When wave number N0=1, as indicated by the dashed line, it can be seen that the frequency components of the fundamental wave band W1 are spread over a frequency range of 0 to 1.6 MHz. This corresponds to 0 to 2 fm. Therefore, as mentioned above, it is difficult to preferentially extract signal components that deviate from the maximum component frequency fm as in this disclosure. The frequency spectrum for wave number N0=1 has a typical spectral shape for the pulse-echo method.
　図１２Ａからわかるように、実線で示す波数Ｎ０が２個の場合、基本波帯Ｗ１の幅（帯域）はＮ０＝１の場合の１／２に狭まる。更に、一点鎖線で示す波数Ｎ０が３個の場合、基本波帯Ｗ１の幅（帯域）はＮ０＝１の場合の１／３に狭まる。このため、本開示のように最大成分周波数ｆｍからずれた信号成分を抽出することが可能になる。 As can be seen from FIG. 12A, when the wave number N0 shown by the solid line is 2, the width (bandwidth) of the fundamental wave band W1 is narrowed to 1/2 of when N0=1. Furthermore, when the wave number N0 shown by the dashed and dotted line is 3, the width (bandwidth) of the fundamental wave band W1 is narrowed to 1/3 of when N0=1. This makes it possible to extract signal components that are shifted from the maximum component frequency fm, as disclosed herein.
　図１２Ｂは、波数Ｎ０が３個（破線）、５個（実線）、１０個（一点鎖線）の場合の周波数スペクトルである。波数Ｎ０を増やすと、基本波帯の幅（帯域）がさらに狭くなることがわかる。 Figure 12B shows the frequency spectrum when the wave number N0 is 3 (dashed line), 5 (solid line), and 10 (dotted line). It can be seen that increasing the wave number N0 further narrows the width (bandwidth) of the fundamental wave band.
　図１３は、基本波帯Ｗ１の周波数スペクトルを模式的に示した図である。ここで、基本波帯Ｗ１の帯域幅を以下のように定義する。基本波帯Ｗ１の最大成分周波数ｆｍでのスペクトル強度を１として、その１／２の強度での周波数幅を半値全幅ＦＷＨＭ（Ｆｕｌｌ－Ｗｉｄｔｈ　ｏｆ　Ｈａｌｆ　Ｍａｘｉｍｕｍ）とする。そして、半値全幅を最大成分周波数ｆｍで規格化した値を半値全幅比（ＦＷＨＭ比）と定義する。即ち、半値全幅比は、次式で表される。
　　半値全幅比＝半値全幅／ｆｍ 13 is a diagram showing a schematic diagram of the frequency spectrum of the fundamental wave band W1. Here, the bandwidth of the fundamental wave band W1 is defined as follows. The spectrum intensity at the maximum component frequency fm of the fundamental wave band W1 is set to 1, and the frequency width at half the intensity is set to the full width at half maximum (FWHM). The value obtained by normalizing the full width at half maximum by the maximum component frequency fm is defined as the full width at half maximum ratio (FWHM ratio). That is, the full width at half maximum ratio is expressed by the following formula.
Full width at half maximum ratio = full width at half maximum/fm
　図１４は、基本波帯Ｗ１の半値全幅比（ＦＷＨＭ比）と波数Ｎ０との関係を示す図である。縦軸に示す半値全幅比は、図１２Ａ及び図１２Ｂの周波数スペクトルから算出した。波数Ｎ０＝１の場合、半値全幅比は１２０％にまで拡がる。波数Ｎ０＝２の場合は、半値全幅比は６０％にまで狭まる。前述した通り、Ｎ０＝１の場合は、送信波の周波数スペクトルが０～２ｆｍの範囲に拡がる。一方、波数Ｎ０を２以上にすると、本開示の効果が大きい。 FIG. 14 is a diagram showing the relationship between the full width at half maximum ratio (FWHM ratio) of the fundamental wave band W1 and the wave number N0. The full width at half maximum ratio shown on the vertical axis was calculated from the frequency spectrum in FIG. 12A and FIG. 12B. When the wave number N0=1, the full width at half maximum ratio expands to 120%. When the wave number N0=2, the full width at half maximum ratio narrows to 60%. As mentioned above, when N0=1, the frequency spectrum of the transmitted wave expands to the range of 0 to 2 fm. On the other hand, when the wave number N0 is set to 2 or more, the effect of the present disclosure is large.
　なお、欠陥部Ｄの情報を含む信号成分は、ｆｍ±０．２５ｆｍの周波数範囲に現れるので、送信波のスペクトルの基本波帯Ｗ１の幅はこれより狭いとさらに好ましい。即ち、基本波帯Ｗ１の周波数スペクトルの半値全幅は最大成分周波数ｆｍの５０％以下であることが好ましい。これにより、欠陥部Ｄの検出精度を向上できる。 Incidentally, since the signal components containing information about the defect D appear in the frequency range of fm ±0.25 fm, it is even more preferable that the width of the fundamental wave band W1 of the spectrum of the transmitted wave is narrower than this. In other words, it is preferable that the full width at half maximum of the frequency spectrum of the fundamental wave band W1 is 50% or less of the maximum component frequency fm. This can improve the detection accuracy of the defect D.
　基本波帯Ｗ１の半値全幅比（ＦＷＨＭ比）を５０％以下にするには、図１４からわかるように、波束の波数Ｎ０を３以上にすることで達成できる。従って、上記のように、波束の波数Ｎ０を３以上にすると、さらに好ましい。 As can be seen from FIG. 14, the full width at half maximum ratio (FWHM ratio) of the fundamental waveband W1 can be reduced to 50% or less by setting the wave number N0 of the wave packet to 3 or more. Therefore, as described above, it is even more preferable to set the wave number N0 of the wave packet to 3 or more.
　基本波帯Ｗ１の裾野成分Ｗ３を検出することで欠陥検出性が向上するのであるから、フィルタ部２４０が検出する周波数は、最大成分周波数ｆｍに対して、（ｆｍ±０．２５ｆｍ）の範囲を含む周波数を含むことが好ましい。ここで、「０．２５ｆｍ」は最大成分周波数ｆｍの０．２５倍（即ち２５％）を意味する。例として、ｆｍ＝１ＭＨｚの場合は、（１±０．２５）ＭＨｚの範囲、即ち（０．７５～１．２５）ＭＨｚの範囲を指す。これは半値全幅比を５０％以下にすることに対応する。 Since defect detectability is improved by detecting the base component W3 of the fundamental wave band W1, it is preferable that the frequencies detected by the filter section 240 include frequencies in the range of (fm±0.25fm) with respect to the maximum component frequency fm. Here, "0.25fm" means 0.25 times (i.e., 25%) the maximum component frequency fm. As an example, when fm=1 MHz, this refers to a range of (1±0.25) MHz, that is, a range of (0.75 to 1.25) MHz. This corresponds to a full width at half maximum ratio of 50% or less.
　図１４からわかるように、波数Ｎ０を５にすると、基本波帯Ｗ１の半値全幅比は３０％以下になる。これに対応して、フィルタ部２４０が検出する周波数は、最大成分周波数ｆｍに対して、（ｆｍ±０．１５ｆｍ）の範囲を含むとさらに好ましい。 As can be seen from FIG. 14, when the wave number N0 is set to 5, the full width at half maximum ratio of the fundamental wave band W1 is 30% or less. Correspondingly, it is even more preferable that the frequency detected by the filter section 240 includes a range of (fm±0.15fm) with respect to the maximum component frequency fm.
（狭帯域のプローブ）
　よく知られているように、送信プローブ１１０には広帯域型のプローブと狭帯域型のプローブとが存在する。一般的には、広帯域型のプローブは基本波帯Ｗ１の半値全幅比が７０％程度以上であり、狭帯域型のプローブは半値全幅比が５０％程度以下である。 (Narrowband probe)
As is well known, there are broadband and narrowband probes in the transmitting probe 110. In general, the broadband probe has a full width at half maximum ratio of the fundamental wave band W1 of about 70% or more, and the narrowband probe has a full width at half maximum ratio of about 50% or less.
　パルスエコー法では、送信波の周波数帯域を拡げるために、広帯域型のプローブを用いることが多い。 In the pulse-echo method, a broadband probe is often used to expand the frequency band of the transmitted wave.
　一方、狭帯域型のプローブは、狭い周波数範囲に超音波のエネルギが集中するため、特定周波数の周波数成分を検出するのに有利である。 On the other hand, narrowband probes are advantageous for detecting frequency components of specific frequencies because the ultrasonic energy is concentrated in a narrow frequency range.
　前述の通り、本開示では基本波帯Ｗ１の半値全幅比を５０％以下にすることが好ましい。この点からも、本開示においては、送信プローブ１１０は、狭帯域のプローブであることが更に好ましい。 As mentioned above, in this disclosure, it is preferable that the full width at half maximum ratio of the fundamental wave band W1 be 50% or less. From this point of view, it is even more preferable that the transmitting probe 110 is a narrowband probe in this disclosure.
（フィルタ部２４０の構成の具体例）
　本開示の効果を奏するためのフィルタ部２４０の周波数特性の代表的な例を以下に示す。フィルタ部２４０は、帯域遮断フィルタ、低域通過フィルタ、又は、高域通過フィルタの少なくとも１つを含むことが好ましい。これらの少なくとも１つを含むことで、最大成分周波数ｆｍを含む周波数範囲の成分を低減できる。中でも、低域通過フィルタ、又は、高域通過フィルタの少なくとも１つを含むことで、高域又は低域の一方のみが遮断されるため、遮断のためのプログラムを簡便にできる。また、フィルタ部２４０を電子回路で実装する場合は、遮断のための回路構成を簡便にできる。 (Specific example of the configuration of the filter unit 240)
Representative examples of frequency characteristics of the filter unit 240 for achieving the effects of the present disclosure are shown below. The filter unit 240 preferably includes at least one of a band-blocking filter, a low-pass filter, or a high-pass filter. By including at least one of these, components in a frequency range including the maximum component frequency fm can be reduced. Among these, by including at least one of a low-pass filter or a high-pass filter, only one of the high frequency or low frequency is blocked, so that the program for blocking can be simplified. Furthermore, when the filter unit 240 is implemented by an electronic circuit, the circuit configuration for blocking can be simplified.
　図１５Ａは、帯域遮断フィルタでのゲイン（利得）の周波数特性を示す。帯域遮断フィルタは、最大成分周波数ｆｍ（最大強度周波数成分）を含む基本波帯Ｗ１（図１５Ｂ）のうち、最大成分周波数ｆｍを含む周波数範囲Ｗ２（図１５Ｂ）の成分を低減する。低減率ｘは、透過領域でのゲインＧ０と遮断領域でのゲインＧ１との比Ｇ１／Ｇ０である。第１実施形態では、低減率ｘを－２０ｄＢ（１／１０）～－４０ｄＢ（１／１００）にした。 Fig. 15A shows the frequency characteristic of the gain in a band-stop filter. The band-stop filter reduces the components in a frequency range W2 (Fig. 15B) that includes the maximum component frequency fm (maximum intensity frequency component) out of the fundamental wave band W1 (Fig. 15B) that includes the maximum component frequency fm. The reduction rate x is the ratio G1/G0 of the gain G0 in the transmission region to the gain G1 in the blocking region. In the first embodiment, the reduction rate x is set to -20 dB (1/10) to -40 dB (1/100).
　図１５Ｂは、帯域遮断フィルタで処理した後の信号の周波数特性を模式的に示した図である。実線及び点線で示される波形が基本波帯Ｗ１である。点線は処理前の信号成分であり、点線の部分に示す周波数範囲Ｗ２の成分が帯域遮断フィルタで低減される。この結果、実線で示した、基本波帯Ｗ１の裾野成分Ｗ３を検出できる。 FIG. 15B is a diagram showing a schematic of the frequency characteristics of a signal after processing with a band-stop filter. The waveform shown by the solid and dotted lines is the fundamental wave band W1. The dotted lines show the signal components before processing, and the components in the frequency range W2 shown in the dotted line are reduced by the band-stop filter. As a result, the base component W3 of the fundamental wave band W1, shown by the solid line, can be detected.
　図１６Ａは、低域通過フィルタでのゲイン（利得）の周波数特性を示す。低域通過フィルタの遮断周波数（カットオフ周波数）を最大成分周波数ｆｍよりも小さな周波数に設定することで、最大成分周波数ｆｍでの信号成分を低減できる。ここで、フィルタの遮断周波数（カットオフ周波数）とは、信号を通過させる通過域と減衰させる減衰域との境界の周波数である。第１実施形態では、遮断周波数を０．７８ＭＨｚとした。即ち、最大成分周波数ｆｍ（０．８２ＭＨｚ）よりも４０ｋＨｚ小さな周波数に設定した。遮断部での低減率は－４０ｄＢ程度にした。 Fig. 16A shows the frequency characteristics of the gain in a low-pass filter. By setting the cutoff frequency of the low-pass filter to a frequency lower than the maximum component frequency fm, the signal components at the maximum component frequency fm can be reduced. Here, the cutoff frequency of a filter is the frequency at the boundary between the passband that passes the signal and the attenuation band that attenuates the signal. In the first embodiment, the cutoff frequency is set to 0.78 MHz. In other words, it is set to a frequency 40 kHz lower than the maximum component frequency fm (0.82 MHz). The reduction rate at the cutoff section is set to approximately -40 dB.
　図１６Ｂは、低域通過フィルタで処理した後の信号の周波数特性を模式的に示した図である。点線及び実線の意味は、図１５Ｂと同じである。低域通過フィルタを用いると、裾野成分Ｗ３のうち、実線で示すように、最大成分周波数ｆｍよりも小さな周波数成分を検出できる。 FIG. 16B is a diagram showing the frequency characteristics of a signal after processing with a low-pass filter. The dotted and solid lines have the same meanings as in FIG. 15B. By using a low-pass filter, it is possible to detect frequency components of the base component W3 that are smaller than the maximum component frequency fm, as shown by the solid line.
　図１７Ａは、高域通過フィルタでのゲイン（利得）の周波数特性を示す。高域通過フィルタの遮断周波数（カットオフ周波数）を最大成分周波数ｆｍよりも大きな周波数に設定することで、最大成分周波数ｆｍでの信号成分を低減できる。 Figure 17A shows the frequency characteristics of the gain in a high-pass filter. By setting the cutoff frequency of the high-pass filter to a frequency higher than the maximum component frequency fm, the signal components at the maximum component frequency fm can be reduced.
　図１７Ｂは、高域通過フィルタで処理した後の信号の周波数特性を模式的に示した図である。点線及び実線の意味は、図１５Ｂと同じである。高域通過フィルタを用いると、裾野成分Ｗ３のうち、実線で示すように、最大成分周波数ｆｍよりも大きな周波数成分を検出できる。 FIG. 17B is a diagram showing the frequency characteristics of a signal after processing with a high-pass filter. The dotted and solid lines have the same meanings as in FIG. 15B. By using a high-pass filter, it is possible to detect frequency components of the base component W3 that are greater than the maximum component frequency fm, as shown by the solid line.
（フィルタ部２４０の実装方法）
　フィルタ部２４０の実装方法の代表的な構成例を以下に述べる。フィルタ部２４０の実装方法は、アナログ方式及びデジタル方式に大別される。 (Method of mounting filter section 240)
The following describes a typical configuration example of a method for implementing the filter section 240. Methods for implementing the filter section 240 are roughly divided into analog methods and digital methods.
　アナログ方式は、アナログ回路により所望の周波数範囲の信号成分を低減するものである。フィルタ部２４０の周波数特性としては、帯域遮断フィルタ（図１５Ａ及び図１５Ｂ）、低域通過フィルタ（図１６Ａ及び図１６Ｂ）、高域通過フィルタ（図１７Ａ及び図１７Ｂ）が代表的な例である。このような周波数特性を持つアナログ回路の実現方式は種々の既知のものが知られている。 The analog method uses an analog circuit to reduce signal components in a desired frequency range. Typical examples of frequency characteristics of the filter section 240 include a band-blocking filter (Figs. 15A and 15B), a low-pass filter (Figs. 16A and 16B), and a high-pass filter (Figs. 17A and 17B). There are various known methods for realizing analog circuits with such frequency characteristics.
　図１８は、デジタル方式のフィルタ部２４０を示すブロック図である。フィルタ部２４０は、周波数成分変換部２４１と、周波数選択部２４２と、周波数成分逆変換部２４３とを備える。周波数成分変換部２４１は、信号アンプ２２２から入力される受信プローブ１２１の受信信号を周波数成分に変換するものである。周波数選択部２４２は、最大成分周波数ｆｍ（最大強度周波数成分）を含む周波数帯の除去により上記裾野成分Ｗ３を選択するものである。周波数成分逆変換部２４３は、必要な周波数成分のみを、時間領域信号に戻すものである。これらのうち、特に、周波数成分変換部２４１及び周波数選択部２４２を備えることで、デジタル方式のフィルタ部２４０を構成できる。 FIG. 18 is a block diagram showing a digital filter section 240. The filter section 240 includes a frequency component conversion section 241, a frequency selection section 242, and a frequency component inverse conversion section 243. The frequency component conversion section 241 converts the received signal of the receiving probe 121 input from the signal amplifier 222 into frequency components. The frequency selection section 242 selects the foot component W3 by removing the frequency band including the maximum component frequency fm (maximum intensity frequency component). The frequency component inverse conversion section 243 converts only the necessary frequency components back into a time domain signal. By including the frequency component conversion section 241 and the frequency selection section 242 among these, in particular, the digital filter section 240 can be configured.
　このようなデジタル方式のフィルタ部２４０によっても、最大成分周波数ｆｍを含む周波数範囲の成分を低減できる。周波数成分変換部２４１で行う処理は、時間領域の信号波形を周波数成分に変換する処理であり、典型的にはフーリエ変換を用いる。周波数成分逆変換部２４３で行う処理は、周波数成分（周波数スペクトル）から時間領域の信号波形に変換する処理であり、典型的にはフーリエ逆変換を用いる。 Such a digital filter unit 240 can also reduce components in a frequency range including the maximum component frequency fm. The processing performed by the frequency component conversion unit 241 is processing to convert the signal waveform in the time domain into frequency components, typically using a Fourier transform. The processing performed by the frequency component inverse conversion unit 243 is processing to convert the frequency components (frequency spectrum) into a signal waveform in the time domain, typically using an inverse Fourier transform.
　図１９は、別の実施形態に係るフィルタ部２４０を示すブロック図である。フィルタ部２４０は、信号処理部２５０の中に設けられている。フィルタ部２４０は、周波数成分変換部２４１及び周波数選択部２４２を備える。周波数選択部２４２の出力は、データ処理部２０１内の信号強度算出部２３１に入力される。信号強度算出部２３１は、周波数成分の情報に基づいて信号強度を算出する。 FIG. 19 is a block diagram showing a filter unit 240 according to another embodiment. The filter unit 240 is provided in the signal processing unit 250. The filter unit 240 includes a frequency component conversion unit 241 and a frequency selection unit 242. The output of the frequency selection unit 242 is input to a signal strength calculation unit 231 in the data processing unit 201. The signal strength calculation unit 231 calculates the signal strength based on the information of the frequency components.
　上記図１１の周波数スペクトルに示したように、基本波帯Ｗ１の裾野成分Ｗ３が欠陥部Ｄに敏感に変化する理由は以下のように考えられる。 As shown in the frequency spectrum of Figure 11 above, the reason why the base component W3 of the fundamental wave band W1 changes sensitively to the defect D is thought to be as follows.
　欠陥部Ｄと相互作用しない直達波Ｕ３は、波の伝播方向、位相、周波数等が変化しない。従って、最大成分周波数ｆｍの信号成分は、直達波Ｕ３が占める割合が多い。そのため、欠陥部Ｄと健全部Ｎとの変化が小さい。 The direct wave U3, which does not interact with the defective part D, does not change in wave propagation direction, phase, frequency, etc. Therefore, the signal component of the maximum component frequency fm is largely dominated by the direct wave U3. Therefore, the change between the defective part D and the healthy part N is small.
　上記図５に示したように、欠陥部Ｄと相互作用する散乱波Ｕ１は、伝播方向を変える成分もあり、また、伝播方向は変わらないが位相又は周波数の少なくとも一方が変化する成分もある。また、伝播方向を変える成分の中にも、周波数が変化する成分がある。従って、最大周波数ｆｍからずれた成分である基本波帯Ｗ１の裾野成分Ｗ３には、欠陥部Ｄと相互作用した超音波ビームＵである散乱波Ｕ１の成分が占める割合が増える。このため、欠陥部Ｄと健全部Ｎとの変化が大きくなる。このようにして、最大成分周波数ｆｍの成分を低減して、かつ基本波帯Ｗ１の裾野成分Ｗ３を検出することで、欠陥部Ｄの検出性能を向上できる。 As shown in Figure 5 above, the scattered wave U1 that interacts with the defect D has components that change the propagation direction, and components that do not change the propagation direction but at least one of the phase or frequency changes. Furthermore, among the components that change the propagation direction, there are components whose frequency changes. Therefore, the proportion of the scattered wave U1 component, which is the ultrasonic beam U that interacts with the defect D, in the base component W3 of the fundamental wave band W1, which is a component shifted from the maximum frequency fm, increases. As a result, the change between the defect D and the healthy part N becomes greater. In this way, the detection performance of the defect D can be improved by reducing the component of the maximum component frequency fm and detecting the base component W3 of the fundamental wave band W1.
（受信プローブの焦点距離）
　受信プローブ１２１の焦点距離Ｒ２は、送信プローブ１１０の焦点距離Ｒ１よりも長いことがさらに好ましい。このようにすると、後述の通り、散乱波Ｕ１の成分をより多く検出できるようになるためである。前述の通り、散乱波Ｕ１は、欠陥部Ｄと相互作用した超音波ビームＵであるから、散乱波Ｕ１の成分の割合が増えるほど、欠陥部Ｄを検出し易くできる。 (Focal length of receiving probe)
It is more preferable that the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110. This is because, as described below, by doing so, it becomes possible to detect more components of the scattered wave U1. As described above, the scattered wave U1 is an ultrasonic beam U that has interacted with the defect D, so the greater the proportion of the scattered wave U1 components, the easier it becomes to detect the defect D.
　受信プローブ１２１の焦点距離を長くすると散乱波の成分を多く検出できる理由を図２０Ａ及び図２０Ｂを用いて述べる。 The reason why more scattered wave components can be detected by increasing the focal length of the receiving probe 121 will be explained using Figures 20A and 20B.
　図２０Ａは、送信プローブ１１０の焦点距離Ｒ１と受信プローブ１２１の焦点距離Ｒ２を等しくした場合の超音波ビームＵの伝播経路を模式的に示した図である。受信プローブ１２１は、受信プローブ１２１から仮想的に放出される仮想ビームのコーン（形状）Ｃ２の範囲内の超音波ビームＵを検出可能である。図２０Ａに示す例では、送信プローブ１１０から送信された超音波ビームＵの収束点と、受信プローブ１２１から仮想的に放出される仮想ビームの収束点が同じである。従って、欠陥部Ｄにおいて伝播方向が変化しない超音波ビームＵを効率的に受信できる。一方、欠陥部Ｄで伝播方向が変化した超音波ビームＵは、検出が困難になる。 FIG. 20A is a schematic diagram showing the propagation path of an ultrasonic beam U when the focal length R1 of the transmitting probe 110 and the focal length R2 of the receiving probe 121 are equal. The receiving probe 121 can detect an ultrasonic beam U within the range of a cone (shape) C2 of a virtual beam virtually emitted from the receiving probe 121. In the example shown in FIG. 20A, the convergence point of the ultrasonic beam U transmitted from the transmitting probe 110 and the convergence point of the virtual beam virtually emitted from the receiving probe 121 are the same. Therefore, an ultrasonic beam U whose propagation direction does not change at the defect D can be efficiently received. On the other hand, an ultrasonic beam U whose propagation direction changes at the defect D is difficult to detect.
　図２０Ｂは、送信プローブ１１０の焦点距離Ｒ１よりも、受信プローブ１２１の焦点距離Ｒ２を長くした場合の超音波ビームＵの伝播経路を模式的に示した図である。受信プローブ１２１から仮想的に放出される仮想ビームのコーン（形状）Ｃ３の範囲内の超音波ビームＵを受信プローブ１２１は検出可能である。そのため、欠陥部Ｄで伝播方向が少し変化した散乱波Ｕ１であっても、コーンＣ３の範囲に入っていれば検出できる。このように、受信プローブ１２１の焦点距離Ｒ２を送信プローブ１１０の焦点距離Ｒ１よりも長くすることにより、検出可能な散乱波Ｕ１を増加できる。前述の通り、散乱波Ｕ１は欠陥部Ｄと相互作用した波であるから、これにより欠陥部Ｄの検出性能をさらに向上できる。 FIG. 20B is a schematic diagram showing the propagation path of the ultrasonic beam U when the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110. The receiving probe 121 can detect the ultrasonic beam U within the range of the cone (shape) C3 of the virtual beam virtually emitted from the receiving probe 121. Therefore, even if the scattered wave U1 has changed its propagation direction slightly at the defect D, it can be detected if it is within the range of the cone C3. In this way, by making the focal length R2 of the receiving probe 121 longer than the focal length R1 of the transmitting probe 110, the detectable scattered wave U1 can be increased. As described above, the scattered wave U1 is a wave that has interacted with the defect D, so this can further improve the detection performance of the defect D.
　図５においては、比較的大きな角度で散乱した散乱波Ｕ１を示したので、受信プローブ１２０の位置をずらして描いている。一方、微小な角度で散乱した散乱波Ｕ１は、受信プローブ１２１の焦点距離を長くすることで検出可能になる。これにより欠陥部Ｄの検出性能が向上する。 In Figure 5, the position of the receiving probe 120 is shifted because the scattered wave U1 scattered at a relatively large angle is shown. On the other hand, the scattered wave U1 scattered at a small angle can be detected by increasing the focal length of the receiving probe 121. This improves the detection performance of the defect D.
　収束性の大小関係は、被検査体Ｅの表面におけるビーム入射面積Ｔ１、Ｔ２の大小関係でも定義される。ビーム入射面積Ｔ１、Ｔ２について説明する。 The magnitude relationship of the convergence is also defined by the magnitude relationship between the beam incident areas T1 and T2 on the surface of the object E to be inspected. The beam incident areas T1 and T2 are explained below.
　図２１は、送信プローブ１１０におけるビーム入射面積Ｔ１及び受信プローブ１２１におけるビーム入射面積Ｔ２の関係を説明する図である。送信プローブ１１０の被検査体Ｅでのビーム入射面積Ｔ１は、送信プローブ１１０から放出された超音波ビームＵの被検査体Ｅ表面での交差面積である。また、受信プローブ１２１のビーム入射面積Ｔ２は、受信プローブ１２１から超音波ビームＵが放出された場合を想定した仮想的な超音波ビームＵ２と被検査体Ｅ表面での交差面積である。 FIG. 21 is a diagram explaining the relationship between the beam incidence area T1 in the transmitting probe 110 and the beam incidence area T2 in the receiving probe 121. The beam incidence area T1 in the subject E of the transmitting probe 110 is the intersection area of the ultrasonic beam U emitted from the transmitting probe 110 on the surface of the subject E. The beam incidence area T2 in the receiving probe 121 is the intersection area of the virtual ultrasonic beam U2, which is assumed to be emitted from the receiving probe 121, on the surface of the subject E.
　なお、図２１において、超音波ビームＵの経路は、被検査体Ｅがない場合における経路を示したものである。被検査体Ｅがある場合は、被検査体Ｅ表面で超音波ビームＵが屈折するため、超音波ビームＵは破線で示した経路とは異なる経路を伝搬する。ここで、図２１に示すように、受信プローブ１２１の被検査体Ｅでのビーム入射面積Ｔ２は、送信プローブ１１０の被検査体Ｅでのビーム入射面積Ｔ１よりも大きい。このようにすることで、受信プローブ１２１の収束性を、送信プローブ１１０の収束性よりも緩くできる。 In FIG. 21, the path of the ultrasonic beam U is shown when there is no object under test E. When there is an object under test E, the ultrasonic beam U is refracted at the surface of the object under test E, and the ultrasonic beam U propagates along a path different from the path shown by the dashed line. Here, as shown in FIG. 21, the beam incidence area T2 of the receiving probe 121 at the object under test E is larger than the beam incidence area T1 of the transmitting probe 110 at the object under test E. In this way, the convergence of the receiving probe 121 can be made looser than that of the transmitting probe 110.
　さらに、受信プローブ１２１の焦点距離Ｒ２は、送信プローブ１１０の焦点距離Ｒ１よりも長い。このようにしても、受信プローブ１２１の収束性を、送信プローブ１１０の収束性よりも緩くできる。このとき、被検査体Ｅから送信プローブ１１０及び受信プローブ１２１までの距離は例えば何れも同じであるが、同じでなくてもよい。 Furthermore, the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110. In this way, the convergence of the receiving probe 121 can be made looser than the convergence of the transmitting probe 110. At this time, the distance from the subject E to the transmitting probe 110 and the receiving probe 121 is, for example, the same for both, but does not have to be the same.
　このように、本実施形態では、受信プローブ１２１の収束性を送信プローブ１１０の収束性よりも緩くしている。即ち、受信プローブ１２１の焦点距離Ｒ２は、送信プローブ１１０の焦点距離Ｒ１よりも長く設定されている。この結果、受信プローブ１２１のビーム入射面積Ｔ２が広くなるため、広い範囲の散乱波Ｕ１を検出できる。これにより、散乱波Ｕ１の伝搬経路が多少変化しても、受信プローブ１２１で散乱波Ｕ１を検出可能になる。その結果、広い範囲の欠陥部Ｄを検出できる。 In this manner, in this embodiment, the convergence of the receiving probe 121 is looser than that of the transmitting probe 110. That is, the focal length R2 of the receiving probe 121 is set longer than the focal length R1 of the transmitting probe 110. As a result, the beam incidence area T2 of the receiving probe 121 is wider, so that a wider range of scattered waves U1 can be detected. This makes it possible for the receiving probe 121 to detect the scattered waves U1 even if the propagation path of the scattered waves U1 changes slightly. As a result, a wider range of defective portions D can be detected.
　また、受信プローブ１２１の焦点Ｐ１は、送信プローブ１１０の焦点Ｐ２よりも、送信プローブ１１０の側（図示の例では上方）に存在する。このように焦点Ｐ１，Ｐ２をずらすことで、受信プローブ１２１で散乱波Ｕ１を受信し易くでき、散乱波Ｕ１を検出し易くできる。 Furthermore, the focus P1 of the receiving probe 121 is located closer to the transmitting probe 110 (above in the illustrated example) than the focus P2 of the transmitting probe 110. By shifting the foci P1 and P2 in this way, it becomes easier for the receiving probe 121 to receive the scattered wave U1, and easier to detect the scattered wave U1.
　なお、送信プローブ１１０の焦点距離Ｒ１よりも受信プローブ１２１の焦点距離Ｒ２を長くする構成として、受信プローブ１２１として、非収束型のプローブ（不図示）が用いられてもよい。即ち、別の実施形態では、受信プローブ１２１は、非収束型のプローブである。非収束型のプローブでは焦点距離Ｒ２が無限大なので、送信プローブ１１０の焦点距離Ｒ１よりも長くなる。即ち、非収束型の受信プローブ１２１でも、受信プローブ１２１の収束性は送信プローブ１１０の収束性よりも緩くなる。 Note that a non-converging probe (not shown) may be used as the receiving probe 121 in a configuration in which the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110. That is, in another embodiment, the receiving probe 121 is a non-converging probe. In a non-converging probe, the focal length R2 is infinite, so it is longer than the focal length R1 of the transmitting probe 110. That is, even with a non-converging receiving probe 121, the convergence of the receiving probe 121 is weaker than the convergence of the transmitting probe 110.
（第２実施形態）
　図２２は、第２実施形態での超音波検査装置Ｚの構成を示す図である。第２実施形態では、送信プローブ１１０の送信音軸ＡＸ１と受信プローブ１２１の受信音軸ＡＸ２とがずらして配置される。即ち、第２実施形態での受信プローブ１２１は、送信プローブ１１０の送信音軸ＡＸ１とは異なる位置に配置された受信音軸ＡＸ２を有する受信プローブ１２０（偏心配置受信プローブ）である。従って、送信プローブ１１０の送信音軸ＡＸ１（音軸）と受信プローブ１２０の受信音軸ＡＸ（音軸）との間の偏心距離Ｌ（距離）がゼロより大きい。 Second Embodiment
22 is a diagram showing the configuration of an ultrasonic inspection device Z in the second embodiment. In the second embodiment, the transmission sound axis AX1 of the transmitting probe 110 and the reception sound axis AX2 of the receiving probe 121 are arranged to be offset from each other. That is, the receiving probe 121 in the second embodiment is a receiving probe 120 (eccentrically arranged receiving probe) having a reception sound axis AX2 arranged at a position different from the transmission sound axis AX1 of the transmitting probe 110. Therefore, the eccentric distance L (distance) between the transmission sound axis AX1 (sound axis) of the transmitting probe 110 and the reception sound axis AX (sound axis) of the receiving probe 120 is greater than zero.
　このような配置にすることで、散乱波Ｕ１のうち空間的な方向が変わった波を検出できる。フィルタ部２４０（図６）による周波数的な散乱波Ｕ１の抽出原理と、偏心配置による空間的な散乱波Ｕ１の抽出原理とを組み合わせることで、欠陥部Ｄの検出性をさらに向上できる。 By using such an arrangement, it is possible to detect scattered waves U1 whose spatial direction has changed. By combining the principle of extracting frequency-based scattered waves U1 using the filter unit 240 (Figure 6) with the principle of extracting spatial scattered waves U1 using an eccentric arrangement, it is possible to further improve the detectability of the defect D.
　第２実施形態では、送信プローブ１１０に対して、図２２のｘ軸方向に偏心距離Ｌだけ受信プローブ１２０がずらされて配置されているが、図２２のｙ軸方向にずらされた状態で受信プローブ１２０が配置されてもよい。又は、ｘ軸方向にＬ１、ｙ軸方向にＬ２（即ち、送信プローブ１１０のｘｙ平面での位置を原点とすると、（Ｌ１、Ｌ２）の位置）に受信プローブ１２０が配置されてもよい。 In the second embodiment, the receiving probe 120 is arranged offset by an eccentric distance L in the x-axis direction of FIG. 22 with respect to the transmitting probe 110, but the receiving probe 120 may be arranged offset in the y-axis direction of FIG. 22. Alternatively, the receiving probe 120 may be arranged at L1 in the x-axis direction and L2 in the y-axis direction (i.e., if the position of the transmitting probe 110 on the xy plane is taken as the origin, then the position is (L1, L2)).
　図２３Ａは、送信音軸ＡＸ１、受信音軸ＡＸ２及び偏心距離Ｌを説明する図であり、送信音軸ＡＸ１及び受信音軸ＡＸ２が鉛直方向に延びる場合である。図２３Ｂは、送信音軸ＡＸ１、受信音軸ＡＸ２及び偏心距離Ｌを説明する図であり、送信音軸ＡＸ１及び受信音軸ＡＸ２が傾斜して延びる場合である。図２３Ａ及び図２３Ｂには、参考として、破線で受信プローブ１４０（同軸配置受信プローブ）も図示される。 FIG. 23A is a diagram explaining the transmission sound axis AX1, reception sound axis AX2, and eccentricity distance L when the transmission sound axis AX1 and reception sound axis AX2 extend vertically. FIG. 23B is a diagram explaining the transmission sound axis AX1, reception sound axis AX2, and eccentricity distance L when the transmission sound axis AX1 and reception sound axis AX2 extend at an angle. For reference, FIGS. 23A and 23B also show the receiving probe 140 (coaxially arranged receiving probe) in dashed lines.
　音軸とは、超音波ビームＵの中心軸と定義される。ここで、送信音軸ＡＸ１は、送信プローブ１１０が放出する超音波ビームＵの伝搬経路の音軸と定義される。言い換えると、送信音軸ＡＸ１は、送信プローブ１１０が放出する超音波ビームＵの伝搬経路の中心軸である。送信音軸ＡＸ１は、図２３Ｂに示すように、被検査体Ｅの界面による屈折を含めることとする。つまり、図２３Ｂに示すように、送信プローブ１１０から放出された超音波ビームＵが、被検査体Ｅの界面で屈折する場合は、その超音波ビームＵの伝搬経路の中心（音軸）が送信音軸ＡＸ１となる。 The sound axis is defined as the central axis of the ultrasonic beam U. Here, the transmission sound axis AX1 is defined as the sound axis of the propagation path of the ultrasonic beam U emitted by the transmitting probe 110. In other words, the transmission sound axis AX1 is the central axis of the propagation path of the ultrasonic beam U emitted by the transmitting probe 110. The transmission sound axis AX1 is intended to include refraction due to the interface of the object to be inspected E, as shown in FIG. 23B. In other words, as shown in FIG. 23B, when the ultrasonic beam U emitted from the transmitting probe 110 is refracted at the interface of the object to be inspected E, the center (sound axis) of the propagation path of the ultrasonic beam U becomes the transmission sound axis AX1.
　また、受信音軸ＡＸ２は、受信プローブ１２１が超音波ビームＵを放出すると想定した場合の仮想超音波ビームの伝搬経路の音軸と定義される。言い換えると、受信音軸ＡＸ２は、受信プローブ１２１が超音波ビームＵを放出すると想定した場合の仮想超音波ビームの中心軸である。 Furthermore, the receiving sound axis AX2 is defined as the sound axis of the propagation path of the virtual ultrasonic beam when it is assumed that the receiving probe 121 emits the ultrasonic beam U. In other words, the receiving sound axis AX2 is the central axis of the virtual ultrasonic beam when it is assumed that the receiving probe 121 emits the ultrasonic beam U.
　具体例として、探触子面が平面状である非収束型のプローブ（不図示）の場合を述べる。この場合、受信音軸ＡＸ２の方向は探触子面の法線方向であり、探触子面の中心点を通る軸が受信音軸ＡＸ２になる。探触子面が長方形の場合は、その中心点は長方形の対角線の交点と定義する。 As a specific example, we will consider a non-focused probe (not shown) with a planar probe surface. In this case, the direction of the receiving sound axis AX2 is the normal direction of the probe surface, and the axis passing through the center point of the probe surface becomes the receiving sound axis AX2. If the probe surface is rectangular, the center point is defined as the intersection of the diagonals of the rectangle.
　受信音軸ＡＸ２の方向が探触子面の法線方向である理由は、その受信プローブ１２１から放射する仮想的な超音波ビームＵが探触子面の法線方向に出射するからである。超音波ビームＵを受信する場合も、探触子面の法線方向で入射する超音波ビームＵを感度よく受信できる。 The reason why the direction of the receiving sound axis AX2 is the normal direction to the probe surface is because the virtual ultrasonic beam U radiated from the receiving probe 121 is emitted in the normal direction to the probe surface. When receiving the ultrasonic beam U, the ultrasonic beam U incident in the normal direction to the probe surface can be received with good sensitivity.
　偏心距離Ｌとは、送信音軸ＡＸ１と、受信音軸ＡＸ２とのずれの距離で定義される。従って、図２３Ｂに示すように、送信プローブ１１０から放出された超音波ビームＵが屈折する場合、偏心距離Ｌは、屈折している送信音軸ＡＸ１と、受信音軸ＡＸ２とのずれの距離で定義される。第２実施形態の超音波検査装置Ｚは、このように定義される偏心距離Ｌが、ゼロより大きな距離となるよう、偏心距離調整部１０５（図２２）によって送信プローブ１１０及び受信プローブ１２０が調整される。 The eccentricity distance L is defined as the deviation between the transmission sound axis AX1 and the reception sound axis AX2. Therefore, as shown in FIG. 23B, when the ultrasonic beam U emitted from the transmission probe 110 is refracted, the eccentricity distance L is defined as the deviation between the refracted transmission sound axis AX1 and the reception sound axis AX2. In the ultrasonic inspection device Z of the second embodiment, the transmission probe 110 and the reception probe 120 are adjusted by the eccentricity distance adjustment unit 105 (FIG. 22) so that the eccentricity distance L defined in this way is greater than zero.
　図２３Ａでは、送信プローブ１１０を被検査体Ｅの表面における法線方向に配置した場合が示される。図２３Ａ及び図２３Ｂにおいて、送信音軸ＡＸ１を実線の矢印で示している。また、受信音軸ＡＸ２を一点鎖線の矢印で示している。なお、図２３Ａ及び図２３Ｂにおいて、破線で示す受信プローブ１２１の位置が偏心距離Ｌがゼロの位置であり、送信音軸ＡＸ１と受信音軸ＡＸ２とが一致する受信プローブ１２１は同軸配置受信プローブとしての受信プローブ１４０である。また、実線で示す受信プローブ１２１はゼロより大きな偏心距離Ｌの位置に配置されている受信プローブ１２０（偏心配置受信プローブ）である。送信音軸ＡＸ１が水平面（図２２のｘｙ平面）に対して垂直になるように送信プローブ１１０が設置される場合、超音波ビームＵの伝搬経路は屈折しない。つまり、送信音軸ＡＸ１は屈折しない。これは、送信プローブ１１０の送信音軸ＡＸ１が試料台１０２の載置面１０２１に対して垂直になるように、送信プローブ１１０を設置した場合に対応する。 23A shows the case where the transmitting probe 110 is arranged in the normal direction on the surface of the test object E. In Figs. 23A and 23B, the transmitting sound axis AX1 is indicated by a solid arrow. Also, the receiving sound axis AX2 is indicated by a dashed arrow. Note that in Figs. 23A and 23B, the position of the receiving probe 121 indicated by the dashed line is a position where the eccentricity distance L is zero, and the receiving probe 121 where the transmitting sound axis AX1 and the receiving sound axis AX2 coincide is the receiving probe 140 as a coaxially arranged receiving probe. Also, the receiving probe 121 indicated by the solid line is the receiving probe 120 (eccentrically arranged receiving probe) arranged at a position with an eccentricity distance L greater than zero. When the transmitting probe 110 is installed so that the transmitting sound axis AX1 is perpendicular to the horizontal plane (xy plane in Fig. 22), the propagation path of the ultrasonic beam U is not refracted. In other words, the transmitting sound axis AX1 is not refracted. This corresponds to the case where the transmission probe 110 is installed so that the transmission sound axis AX1 of the transmission probe 110 is perpendicular to the mounting surface 1021 of the sample stage 102.
　本実施形態では、送信音軸ＡＸ１が試料台１０２の被検査体Ｅの載置面１０２１の法線方向になるように送信プローブ１１０が設置される。前述の通り、このようにすると、板状の被検査体Ｅにおいては、被検査体Ｅの表面に垂直に送信音軸ＡＸ１が配置されるので、走査位置と欠陥部Ｄの位置との対応関係がわかり易くなるという効果がある。 In this embodiment, the transmitting probe 110 is installed so that the transmission sound axis AX1 is normal to the mounting surface 1021 of the test object E on the sample stage 102. As described above, this has the effect of making it easier to understand the correspondence between the scanning position and the position of the defect D, since the transmission sound axis AX1 is arranged perpendicular to the surface of the test object E for a plate-shaped test object E.
　図２３Ｂでは、送信プローブ１１０を被検査体Ｅの表面における法線方向から角度αだけ傾けて配置した場合が示される。図２３Ｂでも図２３Ａと同様、送信音軸ＡＸ１を実線の矢印で示し、受信音軸ＡＸ２を一点鎖線の矢印で示している。図２３Ｂに示す例の場合、前記したように、被検査体Ｅと流体Ｆとの界面で、超音波ビームＵの伝搬経路が屈折角βで屈折する。そのため、送信音軸ＡＸ１は、図２３Ｂの実線矢印で示すように折れ曲がる（屈折する）。この場合、破線で示した受信プローブ１４０の位置は、送信音軸ＡＸ１上に位置するため偏心距離Ｌがゼロの位置である。そして、前記したように、超音波ビームＵが屈折する場合であっても、受信プローブ１２０は、送信音軸ＡＸ１と受信音軸ＡＸ２との距離がＬになるように、配置される。なお、図２２に示す例では、送信プローブ１１０を被検査体Ｅの表面における法線方向に設置しているので、偏心距離Ｌは、図２３Ａに示すようなものとなる。 23B shows a case where the transmitting probe 110 is arranged at an angle α from the normal direction on the surface of the test object E. In FIG. 23B, as in FIG. 23A, the transmitting sound axis AX1 is indicated by a solid arrow, and the receiving sound axis AX2 is indicated by a dashed arrow. In the example shown in FIG. 23B, as described above, the propagation path of the ultrasonic beam U is refracted at a refraction angle β at the interface between the test object E and the fluid F. Therefore, the transmitting sound axis AX1 is bent (refracted) as shown by the solid arrow in FIG. 23B. In this case, the position of the receiving probe 140 shown by the dashed line is located on the transmitting sound axis AX1, so that the eccentricity distance L is zero. And, as described above, even when the ultrasonic beam U is refracted, the receiving probe 120 is arranged so that the distance between the transmitting sound axis AX1 and the receiving sound axis AX2 is L. In the example shown in FIG. 22, the transmitting probe 110 is installed in the normal direction to the surface of the test object E, so the eccentricity distance L is as shown in FIG. 23A.
　偏心距離Ｌは、被検査体Ｅの健全部Ｎでの受信信号よりも、欠陥部Ｄでの信号強度の方が大きくなるような位置に設定するとさらに好ましい。 It is even more preferable to set the eccentricity distance L at a position where the signal strength at the defective portion D is greater than the signal strength at the healthy portion N of the test object E.
（第３実施形態）
　図２４は、第３実施形態での超音波検査装置Ｚの構成を示す図である。第３実施形態では、走査計測装置１は、受信プローブ１２０の傾きを調整する設置角度調整部１０６を備える。これにより、受信信号の強度を増大でき、信号のＳＮ比（Ｓｉｇｎａｌ　ｔｏ　Ｎｏｉｓｅ比、信号雑音比）を大きくできる。設置角度調整部１０６は、例えば、いずれも図示しないが、アクチュエータ、モータ等により構成される。 Third Embodiment
24 is a diagram showing the configuration of an ultrasonic inspection device Z in the third embodiment. In the third embodiment, the scanning measurement device 1 includes an installation angle adjustment unit 106 that adjusts the inclination of the receiving probe 120. This makes it possible to increase the strength of the received signal and to increase the signal-to-noise ratio (SNR) of the signal. The installation angle adjustment unit 106 is, for example, configured by an actuator, a motor, etc., neither of which are shown in the figure.
　ここで、送信音軸ＡＸ１と受信音軸ＡＸ２とが為す角度θを受信プローブ設置角度と定義する。図２４の場合、送信プローブ１１０は鉛直方向に設置されているので送信音軸ＡＸ１は鉛直方向であるため、受信プローブ設置角度である角度θは、送信音軸ＡＸ１（即ち鉛直方向）と受信プローブ１２０の探触子面の法線との為す角度である。そして、設置角度調整部１０６により、角度θを送信音軸ＡＸ１が存在する側に傾け、角度θをゼロより大きな値に設定する。即ち、受信プローブ１２０が傾斜配置される。具体的には、受信プローブ１２０は、０°＜θ＜９０°を満たすように傾斜配置され、角度θは例えば１０°であるがこれに限られない。 Here, the angle θ between the transmission sound axis AX1 and the reception sound axis AX2 is defined as the receiving probe installation angle. In the case of FIG. 24, the transmitting probe 110 is installed vertically, so the transmission sound axis AX1 is vertical, and the angle θ, which is the receiving probe installation angle, is the angle between the transmission sound axis AX1 (i.e., the vertical direction) and the normal to the probe surface of the receiving probe 120. Then, the installation angle adjustment unit 106 tilts the angle θ toward the side where the transmission sound axis AX1 exists, and sets the angle θ to a value greater than zero. That is, the receiving probe 120 is tilted. Specifically, the receiving probe 120 is tilted so as to satisfy 0°<θ<90°, and the angle θ is, for example, 10°, but is not limited to this.
　また、受信プローブ１２０を傾斜配置する場合の偏心距離Ｌは以下のように定義される。受信音軸ＡＸ２と、受信プローブ１２０の探触子面との交点Ｐ１２を定義する。また、送信音軸ＡＸ１と、送信プローブ１１０の探触子面との交点Ｐ１１を定義する。交点Ｐ１１の位置をｘｙ平面に投影した座標位置（ｘ４、ｙ４）（図示せず）と、交点Ｐ１２の位置をｘｙ平面に投影した座標位置（ｘ５、ｙ５）（図示せず）との距離を偏心距離Ｌと定義する。 The eccentricity distance L when the receiving probe 120 is arranged at an angle is defined as follows. An intersection P12 between the receiving sound axis AX2 and the probe surface of the receiving probe 120 is defined. An intersection P11 between the transmitting sound axis AX1 and the probe surface of the transmitting probe 110 is defined. The eccentricity distance L is defined as the distance between the coordinate position (x4, y4) (not shown) obtained by projecting the position of intersection P11 onto the xy plane, and the coordinate position (x5, y5) (not shown) obtained by projecting the position of intersection P12 onto the xy plane.
　このように受信プローブ１２０を傾斜配置して、本発明者が実際に欠陥部Ｄの検出を行ったところ、受信信号の信号強度がθ＝０の場合と比較して３倍に増加した。 When the inventor actually tried to detect defect D by positioning the receiving probe 120 at an angle in this way, the signal strength of the received signal increased three times compared to when θ = 0.
　図２５は、第３実施形態による効果が生じる理由を説明する図である。散乱波Ｕ１は送信音軸ＡＸ１から外れた方向に伝搬する。従って、図２５に示すように、散乱波Ｕ１は被検査体Ｅの外側に到達した際、被検査体Ｅ表面の法線ベクトルとは非ゼロの角度α２をもって被検査体Ｅと外部との界面に入射する。そして、被検査体Ｅの表面から出る散乱波Ｕ１の角度は被検査体Ｅ表面の法線方向に対して非ゼロの出射角である角度β２を有する。散乱波Ｕ１は、受信プローブ１２０の探触子面の法線ベクトルを散乱波Ｕ１の進行方向と一致させたときに、最も効率よく受信できる。つまり、受信プローブ１２０を傾斜配置することで受信信号強度を増大できる。 FIG. 25 is a diagram explaining why the effect of the third embodiment is produced. The scattered wave U1 propagates in a direction deviating from the transmission sound axis AX1. Therefore, as shown in FIG. 25, when the scattered wave U1 reaches the outside of the test object E, it is incident on the interface between the test object E and the outside at a non-zero angle α2 with the normal vector of the test object E's surface. The angle of the scattered wave U1 emerging from the surface of the test object E has an angle β2, which is a non-zero exit angle with respect to the normal direction of the test object E's surface. The scattered wave U1 can be received most efficiently when the normal vector of the probe surface of the receiving probe 120 is aligned with the traveling direction of the scattered wave U1. In other words, the strength of the received signal can be increased by tilting the receiving probe 120.
　なお、被検査体Ｅから出射する超音波ビームＵの角度β２と、送信音軸ＡＸ１と受信音軸ＡＸ２との為す角度θとが一致すると、最も受信効果が高くなる。しかしながら、角度β２と角度θとが完全に一致しない場合であっても、受信信号増大の効果が得られるので、図２５に示しているように、角度β２と角度θとが完全に一致しなくてもよい。 The reception effect is highest when the angle β2 of the ultrasonic beam U emitted from the subject E coincides with the angle θ between the transmission sound axis AX1 and the reception sound axis AX2. However, even if the angle β2 and the angle θ do not coincide perfectly, the effect of increasing the reception signal can be obtained, so as shown in Figure 25, the angle β2 and the angle θ do not have to coincide perfectly.
（第４実施形態）
　図２６は、第４実施形態での超音波検査装置Ｚにおける制御装置２の機能ブロック図である。第４実施形態では、フィルタ部２４０で使用されるフィルタが、被検査体Ｅの検査前に、欠陥部Ｄの位置が既知の試料（不図示）に対して超音波ビームＵを照射することにより決定される。そして、被検査体Ｅの検査は、検査前に決定されたフィルタを使用して行われる。 Fourth Embodiment
26 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the fourth embodiment. In the fourth embodiment, the filter used in the filter section 240 is determined by irradiating an ultrasonic beam U onto a sample (not shown) having a known position of a defect D before inspection of the object to be inspected E. Then, the inspection of the object to be inspected E is performed using the filter determined before the inspection.
　フィルタ部２４０は、検出部２４４及び決定部２４５を備える。検出部２４４は、周波数と信号強度（成分強度）との関係において、基本波帯Ｗ１のうちの異なる複数の裾野成分Ｗ３を検出するものである。ここでいう関係は、例えば図１１に示した関係であり、欠陥部Ｄの位置が既知の試料（不図示）での健全部Ｎ及び欠陥部Ｄに超音波ビームＵを照射することで得られたものである。決定部２４５は、検出した複数の裾野成分Ｗ３同士の比較により、どの裾野成分Ｗ３を使用するかを決定するものである。フィルタ部２４０をこのように構成することで、欠陥部Ｄに起因する信号変化を識別し易い裾野成分Ｗ３を使用でき、欠陥部Ｄの検出精度を向上できる。 The filter unit 240 includes a detection unit 244 and a determination unit 245. The detection unit 244 detects multiple different foot components W3 of the fundamental wave band W1 in the relationship between frequency and signal strength (component strength). The relationship referred to here is, for example, the relationship shown in FIG. 11, which is obtained by irradiating an ultrasonic beam U to a healthy part N and a defective part D in a sample (not shown) in which the position of the defective part D is known. The determination unit 245 determines which foot component W3 to use by comparing the multiple detected foot components W3. By configuring the filter unit 240 in this way, it is possible to use a foot component W3 that makes it easy to identify signal changes caused by the defective part D, and the detection accuracy of the defective part D can be improved.
　検出部２４４は、例えば、異なる裾野成分Ｗ３を検出可能なフィルタを備える。ここでいうフィルタは、例えば、上記の帯域遮断フィルタ（図１５Ａ）、低域通過フィルタ（図１６Ａ）、高域通過フィルタ（図１７Ａ）のうちの少なくとも２つである。例えば、検出部２４４がこれら３つのフィルタを備える場合、検出部２４４は、例えば図１１に示す関係において、３つのフィルタを用いて、図１５Ｂに示す裾野成分Ｗ３、図１６Ｂに示す裾野成分Ｗ３、及び、図１７Ｂに示す裾野成分Ｗ３を検出する。そして、決定部２４５は、検出した３つの裾野成分Ｗ３同士の比較により、例えば健全部Ｎと欠陥部Ｄとの差分が最も大きくなる裾野成分Ｗ３の選択等により、どの裾野成分Ｗ３を使用するかを決定する。フィルタ部２４０は、決定した裾野成分Ｗ３を使用して、被検査体Ｅの検査を行うことで、欠陥部Ｄの検出精度を向上できる。 The detection unit 244 includes, for example, a filter capable of detecting different foot components W3. The filter here is, for example, at least two of the band-blocking filter (FIG. 15A), low-pass filter (FIG. 16A), and high-pass filter (FIG. 17A). For example, if the detection unit 244 includes these three filters, the detection unit 244 detects the foot components W3 shown in FIG. 15B, FIG. 16B, and FIG. 17B using the three filters in the relationship shown in FIG. 11. The determination unit 245 then compares the three detected foot components W3 with each other, for example by selecting the foot component W3 with the largest difference between the healthy part N and the defective part D, and determines which foot component W3 to use. The filter unit 240 uses the determined foot component W3 to inspect the test object E, thereby improving the detection accuracy of the defective part D.
（第５実施形態）
　図２７は、第５実施形態での超音波検査装置Ｚにおける制御装置２の機能ブロック図である。第５実施形態では、被検査体Ｅの検査前、欠陥部Ｄの位置が既知の試料（不図示）に対して超音波ビームＵを照射することにより得られたデータを使用者に提示し、使用者が、どの裾野成分Ｗ３を使用するか、即ち、どのフィルタを使用するのかを決定する。 Fifth Embodiment
27 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the fifth embodiment. In the fifth embodiment, before the inspection of the object E to be inspected, the ultrasonic beam U is irradiated onto a sample (not shown) whose position of the defect D is known, and the data obtained is presented to a user, who then decides which base component W3 to use, i.e., which filter to use.
　制御装置２は、表示部２２３及び受付部２２４を備える。表示部２２３及び受付部２２４は、図示の例ではデータ処理部２０１に備えられる。表示部２２３は、周波数と信号強度（成分強度）との関係を表示装置３に表示させるものである。ここでいう関係は、例えば図１１に示す関係であり、欠陥部Ｄの位置が既知の試料（不図示）での健全部Ｎ及び欠陥部Ｄに超音波ビームＵを照射することで得られたものである。受付部２２４は、周波数と信号強度との関係に基づいて使用者によって入力され、検出すべき裾野成分Ｗ３を表す情報を受け付けるものである。入力は、例えばキーボード、マウス、タッチパネル等である入力装置４を通じて行われる。そして、フィルタ部２４０は、受付部２２４が受け付けた情報に基づいて、当該情報に対応する裾野成分Ｗ３を検出する。 The control device 2 includes a display unit 223 and a reception unit 224. In the illustrated example, the display unit 223 and the reception unit 224 are provided in the data processing unit 201. The display unit 223 displays the relationship between frequency and signal strength (component strength) on the display device 3. The relationship here is, for example, the relationship shown in FIG. 11, which is obtained by irradiating an ultrasonic beam U to a healthy part N and a defective part D in a sample (not shown) whose position of the defective part D is known. The reception unit 224 receives information input by the user based on the relationship between frequency and signal strength, and represents the foot component W3 to be detected. The input is performed through the input device 4, which is, for example, a keyboard, a mouse, a touch panel, etc. Then, the filter unit 240 detects the foot component W3 corresponding to the information based on the information received by the reception unit 224.
　制御装置２をこのように構成することで、使用者の主観に基づいて検出すべき裾野成分Ｗ３を判断できる。これにより、使用者の経験に基づき判断ができるため、検査実体に即した検査を実行できる。 By configuring the control device 2 in this way, the base component W3 to be detected can be determined based on the user's subjective opinion. This allows the user to make a determination based on their experience, making it possible to perform an inspection that is suited to the actual inspection.
（第６実施形態）
　図２８は、第６実施形態での超音波検査装置Ｚにおける制御装置２の機能ブロック図である。第６実施形態では、受信信号を周波数変換部２３０で周波数成分に変換して記憶し、検査の測定後に、適切な周波数成分を用いて画像化する構成である。これによりフィルタ部２４０が構成される。 Sixth Embodiment
28 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the sixth embodiment. In the sixth embodiment, the received signal is converted into frequency components by a frequency conversion unit 230 and stored, and after the measurement for the inspection, an image is generated using appropriate frequency components. This constitutes a filter unit 240.
　制御装置２は、走査計測装置１の駆動を制御するものである。制御装置２は、送信系統２１０と、受信系統２２０と、データ処理部２０１と、スキャンコントローラ２０４と、駆動部２０２と、位置計測部２０３と、信号処理部２５０とを備える。駆動部２０２は、例えば、送信プローブ１１０及び受信プローブ１２１を駆動させることで、被検査体Ｅに対する送信プローブ１１０及び受信プローブ１２１の相対的な位置を変更するものである。位置計測部２０３は、走査位置を計測するものである。スキャンコントローラ２０４は、駆動部２０２を通じて、送信プローブ１１０及び受信プローブ１２１を駆動させる。送信プローブ１１０及び受信プローブ１２１による走査位置は、位置計測部２０３を通じて、スキャンコントローラ２０４に入力される。 The control device 2 controls the driving of the scanning measurement device 1. The control device 2 includes a transmission system 210, a reception system 220, a data processing unit 201, a scan controller 204, a driving unit 202, a position measurement unit 203, and a signal processing unit 250. The driving unit 202 changes the relative positions of the transmitting probe 110 and the receiving probe 121 with respect to the subject E, for example, by driving the transmitting probe 110 and the receiving probe 121. The position measurement unit 203 measures the scanning position. The scan controller 204 drives the transmitting probe 110 and the receiving probe 121 through the driving unit 202. The scanning positions of the transmitting probe 110 and the receiving probe 121 are input to the scan controller 204 through the position measurement unit 203.
　受信系統２２０とデータ処理部２０１とを合わせて、信号処理部２５０と呼ぶ。信号処理部２５０は、受信プローブ１２１からの信号を増幅処理、周波数選択処理等により、有意な情報を抽出する信号処理を行う。 The receiving system 220 and the data processing unit 201 are collectively referred to as the signal processing unit 250. The signal processing unit 250 performs signal processing on the signal from the receiving probe 121, such as amplification processing and frequency selection processing, to extract significant information.
　送信系統２１０は、送信プローブ１１０への印加電圧を生成する系統である。送信系統２１０の構成は、第１実施形態と同様である。 The transmission system 210 is a system that generates a voltage to be applied to the transmission probe 110. The configuration of the transmission system 210 is the same as in the first embodiment.
　送信プローブ１１０へ印加する電圧波形は、上記図９に示す通り、繰り返し波束の波形である。印加する電圧波形は、第１実施形態と同様である。 The voltage waveform applied to the transmitting probe 110 is a repeating wave packet waveform, as shown in FIG. 9 above. The voltage waveform applied is the same as in the first embodiment.
　信号処理部２５０は、データ処理部２０１と、受信系統２２０とを備える。受信系統２２０は、受信プローブ１２１から出力される受信信号を検出する系統である。受信プローブ１２１から出力された信号は、信号アンプ２２２に入力されて増幅される。増幅された信号は、周波数変換部２３０に入力される。周波数変換部２３０は、信号処理部２５０に備えられ、受信プローブ１２１の受信信号を周波数成分に変換（信号処理）するものであり、本開示の例では、時間領域波形である受信信号を周波数成分に変換する。周波数成分は、夫々の周波数の成分の大きさ（スペクトル）である。周波数成分としては、例えば複素数で表現され実部と虚部との組合せで表す方法、振幅（絶対値）と位相とにより表す方法等が挙げられる。 The signal processing unit 250 includes a data processing unit 201 and a receiving system 220. The receiving system 220 is a system that detects the received signal output from the receiving probe 121. The signal output from the receiving probe 121 is input to a signal amplifier 222 and amplified. The amplified signal is input to a frequency conversion unit 230. The frequency conversion unit 230 is included in the signal processing unit 250 and converts the received signal of the receiving probe 121 into frequency components (signal processing). In the example of the present disclosure, the frequency conversion unit 230 converts the received signal, which is a time domain waveform, into frequency components. The frequency components are the magnitude (spectrum) of each frequency component. Examples of frequency components include a method of expressing a combination of a real part and an imaginary part as a complex number, and a method of expressing an amplitude (absolute value) and a phase.
　周波数変換部２３０での変換は、例えばフーリエ変換により実行できる。また、変換は、予め指定した周波数範囲（周波数パラメータ）の周波数成分のみの抽出とともに実行されてもよい。周波数変換部２３０で周波数成分に変換された信号は、データ処理部２０１に入力される。なお、周波数変換部２３０は、データ処理部２０１の内部に設けられてもよい。即ち、データ処理部の中で周波数成分に変換されてもよい。 The conversion in the frequency conversion unit 230 can be performed, for example, by a Fourier transform. The conversion may also be performed along with the extraction of only frequency components in a pre-specified frequency range (frequency parameters). The signal converted into frequency components by the frequency conversion unit 230 is input to the data processing unit 201. The frequency conversion unit 230 may be provided inside the data processing unit 201. That is, the conversion into frequency components may be performed within the data processing unit.
（周波数成分データの蓄積）
　データ処理部２０１は、記憶部２６１と、周波数選択部２４２と、画像化部２６２と、表示部２６３とを備える。従って、信号処理部２５０は、周波数変換部２３０と、画像化部２６２と、周波数選択部２４２と、表示部２６３とを備える。 (Accumulation of frequency component data)
The data processing unit 201 includes a storage unit 261, a frequency selection unit 242, an imaging unit 262, and a display unit 263. Therefore, the signal processing unit 250 includes a frequency conversion unit 230, an imaging unit 262, a frequency selection unit 242, and a display unit 263.
　本開示の例では、周波数変換部２３０は、時間領域波形を周波数成分データに変換して位置情報と合わせて記憶部２６１に保存する。そして、画像化部２６２は、詳細は後記するが、変換された周波数成分のうち、周波数パラメータにより指定された周波数成分の部分を用いて、欠陥位置を示す画像２７３（後記）を生成する。即ち、画像化部２６２は、入力された周波数パラメータに基づき、信号特徴量を画像化する。即ち、被検査体Ｅを１回測定する場合に、周波数成分データへの変換は１回で済み、周波数成分データから信号特徴量の抽出は複数回行われる。 In the example of the present disclosure, the frequency conversion unit 230 converts the time domain waveform into frequency component data and stores it together with the position information in the storage unit 261. The imaging unit 262 then generates an image 273 (described below) indicating the defect position using a portion of the converted frequency components that is specified by the frequency parameters, as described in detail below. That is, the imaging unit 262 visualizes the signal features based on the input frequency parameters. That is, when the test object E is measured once, the conversion to frequency component data is performed only once, and the extraction of the signal features from the frequency component data is performed multiple times.
　この構成は、以下の２つの点で好ましい。
　第１は、計算所要時間である。周波数変換部２３０での周波数成分データへの変換処理には時間がかかる。典型的には、上記のようにフーリエ変換が用いられが、高速なアルゴリズムとして知られる高速フーリエ変換（ＦＦＴ）を用いても、この変換の処理時間は長い。一方、信号特徴量の算出は、後記する式（１）を用いて行われるが、この計算所要時間は短い。典型例として１００行×１００列の測定点に対しても、０．２秒以下で処理が終わる。 This configuration is preferable for the following two reasons.
The first is the time required for calculation. The conversion process to frequency component data in the frequency conversion unit 230 takes time. Typically, a Fourier transform is used as described above, but even if a fast Fourier transform (FFT), known as a high-speed algorithm, is used, the processing time for this conversion is long. On the other hand, the signal feature amount is calculated using equation (1) described later, and the calculation time required for this is short. As a typical example, the process is completed in 0.2 seconds or less even for measurement points of 100 rows x 100 columns.
　このため、本開示の例によれば、詳細は後記するが、周波数パラメータを「更新」すると、瞬時に更新された画像２７３（後記）を得ることが可能である。このように、周波数成分データを記憶部２６１に保存することにより、欠陥検出性を向上させるのに好適な周波数集合を選択するのを短時間で行える。 Thus, according to an example of the present disclosure, as described in detail below, when the frequency parameters are "updated," it is possible to obtain an instantly updated image 273 (described below). In this way, by storing the frequency component data in the memory unit 261, it is possible to quickly select a frequency set suitable for improving defect detectability.
　第２に、データ量の低減である。受信プローブ１４０の信号波形は、１測定位置に対して、時間領域波形では１０万点程度あるのに対し、周波数成分データでは、２０～１００種類の周波数に対する複素数があればよい。即ち、被検査体Ｅに対するデータ量を１／１０００程度に削減できる。このように記憶部２６１に保存するデータ量を大幅に削減できるという利点もある。 Secondly, the amount of data is reduced. The signal waveform of the receiving probe 140 has about 100,000 points for one measurement position in the time domain waveform, whereas the frequency component data only requires complex numbers for 20 to 100 different frequencies. In other words, the amount of data for the subject E can be reduced to about 1/1000. This has the advantage of significantly reducing the amount of data stored in the memory unit 261.
　データ処理部２０１は、スキャンコントローラ２０４から走査位置の情報も受け取る。このようにして、現在の２次元走査位置（ｘ、ｙ）における受信信号の周波数成分に関するデータ（以下、周波数成分データという）が得られる。データ処理部２０１は、走査位置（ｘ、ｙ）と、その位置での周波数成分データとを対応づけて記憶部２６１に保存する。なお、周波数成分データから決定される信号特徴量を、走査位置毎に決定することで、欠陥部Ｄに関する画像２７３が作成される。 The data processing unit 201 also receives information on the scanning position from the scan controller 204. In this way, data on the frequency components of the received signal at the current two-dimensional scanning position (x, y) (hereinafter referred to as frequency component data) is obtained. The data processing unit 201 associates the scanning position (x, y) with the frequency component data at that position and stores them in the storage unit 261. Note that an image 273 of the defect D is created by determining the signal feature amount determined from the frequency component data for each scanning position.
　周波数成分データは、複数の周波数に対応する周波数成分である。典型的な例では、周波数成分データは、受信信号のフーリエ変換で得られる周波数スペクトルである。上記のように、周波数成分は振幅（絶対値）に加えて位相情報も含むことがより好ましい。これは、周波数成分を複素数として扱うことと同義である。後記のように、位相情報も含めることで、より高性能な信号特徴量を算出できる。 The frequency component data is frequency components corresponding to multiple frequencies. In a typical example, the frequency component data is a frequency spectrum obtained by Fourier transform of the received signal. As described above, it is more preferable for the frequency components to include phase information in addition to amplitude (absolute value). This is synonymous with treating the frequency components as complex numbers. As described below, by including phase information, it is possible to calculate signal features with higher performance.
　図２８において、データ処理部２０１は、画像化部２６２を備える。画像化部２６２は、信号処理部２５０に備えられ、変換された周波数成分のうち、周波数パラメータにより指定された周波数成分の部分を用いて、欠陥部Ｄの位置（欠陥位置）を示す画像２７３（後記）を生成する。画像化部２６２は、具体的には、周波数変換部２３０により変換された周波数成分に対応する周波数スペクトルのうち、適切な周波数パラメータに対応する部分の周波数スペクトルにおいて、被検査体Ｅの欠陥部Ｄに起因する信号の変化（変化量）に基づき、画像２７３を作成する。このようにすることで、画像２７３を生成できる。 In FIG. 28, the data processing unit 201 includes an imaging unit 262. The imaging unit 262 is included in the signal processing unit 250, and generates an image 273 (described below) indicating the position (defect position) of the defect D using a portion of the converted frequency components that is specified by the frequency parameters. Specifically, the imaging unit 262 creates the image 273 based on the change (amount of change) in the signal caused by the defect D of the test object E in the frequency spectrum of the portion that corresponds to the appropriate frequency parameter out of the frequency spectrum that corresponds to the frequency components converted by the frequency conversion unit 230. In this way, the image 273 can be generated.
　ここでいう信号の変化（受信信号の変化）は、本開示の例では、信号特徴量である。従って、画像化部２６２は、まず、変換された周波数成分に対応する周波数スペクトルのうち、入力された周波数パラメータの部分から、信号特徴量を算出する。信号特徴量は、上記のように信号の変化を表す例えば値であり、欠陥情報（例えば欠陥部Ｄの位置）を適切に含むように周波数成分データから算出した値である。信号特徴量の具体的な算出方法の例は後記する。このようにして得られた信号特徴量を走査位置（ｘ、ｙ）に対してプロットすることで、被検査体Ｅの内部に存在する欠陥部Ｄの２次元画像（欠陥画像）が生成する。 The signal change (change in the received signal) referred to here is a signal feature in the example of the present disclosure. Therefore, the imaging unit 262 first calculates the signal feature from the portion of the frequency spectrum corresponding to the converted frequency component that is the input frequency parameter. The signal feature is, for example, a value that represents the signal change as described above, and is a value calculated from the frequency component data so as to appropriately include defect information (for example, the position of the defect D). A specific example of a method for calculating the signal feature will be described later. By plotting the signal feature thus obtained against the scanning position (x, y), a two-dimensional image (defect image) of the defect D present inside the inspected object E is generated.
　以上の手順を走査位置（ｘ，ｙ）を変えながら行うことで、所望の範囲が走査される。走査完了すると、走査位置（ｘ，ｙ）に対応した周波数成分データ及び信号特徴量がデータ処理部２０１内の記憶部２６１に保存される。本開示では、走査位置で信号を取得する毎に信号特徴量が算出される。ただし、測定中、周波数成分データが記憶部２６１に保存され、測定後に信号特徴量が纏めて算出されることで欠陥画像を生成してもよい。 The above procedure is performed while changing the scanning position (x, y) to scan the desired range. When scanning is completed, frequency component data and signal features corresponding to the scanning position (x, y) are stored in the memory unit 261 in the data processing unit 201. In this disclosure, the signal features are calculated each time a signal is acquired at the scanning position. However, during measurement, the frequency component data may be stored in the memory unit 261, and the signal features may be calculated collectively to generate a defect image after measurement.
（信号特徴量の算出）
　本開示の例で用いた、周波数成分データから信号特徴量の算出方法を述べる。
　ここでは数式を見やすくするため、周波数ｆを角周波数ωで表す。角周波数ωは周波数ｆに２πを乗じたものである。複素数で表した周波数成分がＨ（ω）で表される。次式（１）に従ってｈ（ｔ）が算出される。 (Calculation of signal features)
A method for calculating signal features from frequency component data used in the examples of the present disclosure will be described.
Here, to make the formula easier to understand, the frequency f is expressed as an angular frequency ω. The angular frequency ω is obtained by multiplying the frequency f by 2π. The frequency component expressed as a complex number is represented as H(ω). h(t) is calculated according to the following formula (1).
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000002
Figure JPOXMLDOC01-appb-M000002
　ここで、式（１）においてｊは虚数単位であり、式（２）においてＲｅ［　］は複素数の実部を取り出す処理である。式（１）において、Σ記号の添え字ωは、積算する角周波数成分の周波数集合を示す。式（１）において、積算する角周波数成分は、後記のように、適切に設定された周波数集合｛ω｝について行う。 Here, in equation (1), j is the imaginary unit, and in equation (2), Re[ ] is the process of extracting the real part of a complex number. In equation (1), the subscript ω of the Σ symbol indicates the frequency set of the angular frequency components to be integrated. In equation (1), the angular frequency components to be integrated are calculated for an appropriately set frequency set {ω}, as described below.
　式（１）において、積算に含める周波数の集合｛ω｝を周波数パラメータと呼ぶ。周波数パラメータは、周波数集合｛ω｝の形で指定してもよいし、周波数範囲の形で指定しても良い。また、周波数パラメータは、あらかじめ設定しておいてもよい。また、周波数パラメータは、使用者により入力されてもよい。 In formula (1), the set of frequencies {ω} to be included in the accumulation is called a frequency parameter. The frequency parameter may be specified in the form of a frequency set {ω} or in the form of a frequency range. The frequency parameter may also be set in advance. The frequency parameter may also be input by the user.
　式（２）で得られるｈ（ｔ）は、周波数パラメータにより設定された周波数集合から合成した時間領域の信号波形である。このｈ（ｔ）の最大値と最小値との差（Ｐｅａｋ－ｔｏ－Ｐｅａｋ値）を本開示の例では信号特徴量とした。本開示の例においては、最大値と最小値との差（Ｐｅａｋ－ｔｏ－Ｐｅａｋ値）をＰＰ値と略記する。 The h(t) obtained by equation (2) is a time domain signal waveform synthesized from a frequency set set by the frequency parameters. In the example of this disclosure, the difference between the maximum and minimum values of this h(t) (Peak-to-Peak value) is used as the signal feature. In the example of this disclosure, the difference between the maximum and minimum values (Peak-to-Peak value) is abbreviated as the PP value.
　式（１）において、Ｈ（ω）及びｅｘｐ（ｊωｔ）はいずれも複素数であり、複素数として計算している。即ち、周波数成分Ｈ（ω）の位相情報も考慮して信号特徴量を算出している。これにより、欠陥部Ｄの位置情報が正確に反映した信号特徴量が得られるので、より好ましい。 In formula (1), H(ω) and exp(jωt) are both complex numbers, and are calculated as complex numbers. In other words, the signal feature is calculated taking into account the phase information of the frequency component H(ω). This is more preferable because it allows for a signal feature that accurately reflects the position information of the defect D.
　周波数パラメータ、即ち、式（１）において積算に含める周波数の集合｛ω｝の選択が重要になる。積算に含める周波数の集合｛ω｝からは、最大成分周波数ｆｍが除かれる。このようにすることで、受信プローブ１２０の受信信号のうちの少なくとも最大強度周波数成分を低減するフィルタ部２４０を構成できる。また、積算に含める周波数には、基本波帯Ｗ１の裾野成分Ｗ３の周波数を含める。これにより、被検査体Ｅ内の欠陥部Ｄの検出性を向上できる。また、最大成分周波数ｆｍの近傍の周波数成分も除くとさらに効果がある。 The selection of the frequency parameters, i.e., the set of frequencies {ω} to be included in the accumulation in equation (1), is important. The maximum component frequency fm is excluded from the set of frequencies {ω} to be included in the accumulation. In this way, a filter section 240 can be configured that reduces at least the maximum intensity frequency component of the received signal of the receiving probe 120. Furthermore, the frequencies to be included in the accumulation include the frequency of the base component W3 of the fundamental wave band W1. This can improve the detectability of the defective portion D in the inspected object E. Furthermore, it is even more effective to also exclude frequency components near the maximum component frequency fm.
　角周波数ωが周波数ｆは、ω＝２πｆの関係で換算できるので、適宜換算して解釈することとする。例えば、「周波数の集合｛ω｝から最大成分周波数ｆｍを除く」と記載した場合は、「ωｍ＝２πｆｍを除く」ということを意味する。 Since angular frequency ω can be converted to frequency f using the relationship ω = 2πf, we will make appropriate conversions and interpretations. For example, if we write "excluding the maximum component frequency fm from the frequency set {ω}," this means "excluding ωm = 2πfm."
　最大成分周波数ｆｍとは、受信信号の基本波帯Ｗ１のスペクトルが最大になる周波数であるが、本開示においては概ね最大になる周波数とする。 The maximum component frequency fm is the frequency at which the spectrum of the fundamental wave band W1 of the received signal is at its maximum, but in this disclosure it is defined as the frequency at which it is approximately at its maximum.
　また、式（１）において、積算に含める周波数の集合｛ω｝に、最大成分周波数ｆｍよりも低い周波数のみを含むようにしてもよい。これにより、低域通過フィルタの特性を有するフィルタ部２４０を構成できる。同様にして、最大成分周波数ｆｍよりも低い周波数のみを含むようにしてもよい。 Furthermore, in equation (1), the set of frequencies {ω} to be included in the accumulation may include only frequencies lower than the maximum component frequency fm. This allows the filter section 240 to be configured with low-pass filter characteristics. Similarly, it may include only frequencies lower than the maximum component frequency fm.
　周波数パラメータを適正に設定することは、周波数選択部２４２（図２８）においてなされる。このようにして、周波数変換部２３０と周波数選択部２４２とにより、フィルタ部２４０が構成される。 The frequency parameters are appropriately set in the frequency selection unit 242 (Figure 28). In this way, the frequency conversion unit 230 and the frequency selection unit 242 form the filter unit 240.
　周波数パラメータは、検査に先立ち予め適正なパラメータを設定しておいてもよいし、測定後に変更してもよい。また、ユーザが設定してもよい。 The frequency parameters may be set to appropriate parameters before the test, or may be changed after the measurement. They may also be set by the user.
　なお、信号特徴量は、欠陥部Ｄの位置情報を適切に含むように周波数成分データから算出した値であればよく、上記の算出方法に限定されるものではない。上記の例では、時間領域の信号波形ｈ（ｔ）のＰＰ値を信号特徴量としたが、ｈ（ｔ）の絶対値を算出し、ｈ（ｔ）の面積を算出して信号特徴量としてもよい。ここで面積の算出手順は、ｈ（ｔ）を適切な時間間隔でサンプリングして、サンプリング点でのｈ（ｔ）の総和を算出すればよい。また、ｈ（ｔ）の絶対値の代わりに、ｈ（ｔ）の２乗値を用いてもよい。更に、式（１）及び式（２）を用いる代わりに、周波数成分Ｈ（ω）の絶対値を、入力された周波数集合｛ω｝について合計した値を信号特徴量として用いてもよい。 Note that the signal feature amount is not limited to the above calculation method, as long as it is a value calculated from frequency component data so as to appropriately include the position information of the defect D. In the above example, the PP value of the signal waveform h(t) in the time domain is used as the signal feature amount, but the absolute value of h(t) may be calculated, and the area of h(t) may be calculated as the signal feature amount. Here, the procedure for calculating the area is to sample h(t) at appropriate time intervals and calculate the sum of h(t) at the sampling points. Also, instead of the absolute value of h(t), the squared value of h(t) may be used. Furthermore, instead of using equations (1) and (2), the absolute values of the frequency components H(ω) may be summed for the input frequency set {ω} and used as the signal feature amount.
　図２９は、制御装置２のハードウェア構成を示す図である。前記した各構成、機能、ブロック図を構成する各部等は、それらの一部又はすべてを、例えば集積回路で設計すること等によりハードウェアで実現してもよい。また、図２９に示すように、前記した各構成、機能等は、ＣＰＵ２５２等のプロセッサがそれぞれの機能を実現するプログラムを解釈し、実行することによりソフトウェアで実現してもよい。制御装置２は、例えば、メモリ２５１、ＣＰＵ２５２、記憶装置２５３（ＳＳＤ，ＨＤＤ等）、通信装置２５４及びＩ／Ｆ２５５を備える。各機能を実現するプログラム、テーブル、ファイル等の情報は、ＨＤＤに格納すること以外に、メモリ、ＳＳＤ（Ｓｏｌｉｄ　Ｓｔａｔｅ　Ｄｒｉｖｅ）等の記録装置、又は、ＩＣ（Ｉｎｔｅｇｒａｔｅｄ　Ｃｉｒｃｕｉｔ）カード、ＳＤ（Ｓｅｃｕｒｅ　Ｄｉｇｉｔａｌ）カード、ＤＶＤ（Ｄｉｇｉｔａｌ　Ｖｅｒｓａｔｉｌｅ　Ｄｉｓｃ）等の記録媒体に格納することができる。 FIG. 29 is a diagram showing the hardware configuration of the control device 2. The above-mentioned configurations, functions, and each part constituting the block diagram may be realized in hardware by designing some or all of them as an integrated circuit, for example. Also, as shown in FIG. 29, the above-mentioned configurations, functions, etc. may be realized in software by a processor such as a CPU 252 interpreting and executing a program that realizes each function. The control device 2 includes, for example, a memory 251, a CPU 252, a storage device 253 (SSD, HDD, etc.), a communication device 254, and an I/F 255. In addition to being stored in the HDD, information such as programs, tables, and files that realize each function can be stored in a recording device such as a memory or SSD (Solid State Drive), or a recording medium such as an IC (Integrated Circuit) card, an SD (Secure Digital) card, or a DVD (Digital Versatile Disc).
　図３０は、上記各実施形態の超音波検査方法を示すフローチャートである。第１実施形態の超音波検査方法は上記の超音波検査装置Ｚにより実行でき、一例として適宜、図１及び図６を参照して説明する。第１実施形態の超音波検査方法は、気体Ｇ（図１）を介して被検査体Ｅ（図１）に超音波ビームＵを入射することにより被検査体Ｅの検査を行うものである。 FIG. 30 is a flow chart showing the ultrasonic inspection method of each of the above-mentioned embodiments. The ultrasonic inspection method of the first embodiment can be performed by the above-mentioned ultrasonic inspection device Z, and will be described as an example with reference to FIG. 1 and FIG. 6 as appropriate. The ultrasonic inspection method of the first embodiment inspects the object E (FIG. 1) by irradiating the object E (FIG. 1) with an ultrasonic beam U via a gas G (FIG. 1).
　本開示の超音波検査方法は、ステップＳ１０１～Ｓ１０５，Ｓ１１１，Ｓ１１２を含む。まず、制御装置２の指令により、送信プローブ１１０が、送信プローブ１１０から超音波ビームＵを放出するステップＳ１０１（放出ステップ）を行う。ステップＳ１０１では、送信プローブ１１０から波数が２以上の波束で構成される繰り返し波束の超音波ビームＵが放出される。続いて、受信プローブ１２１が、超音波ビームＵを受信するステップＳ１０２（受信ステップ）を行う。 The ultrasonic inspection method disclosed herein includes steps S101 to S105, S111, and S112. First, in response to a command from the control device 2, the transmitting probe 110 performs step S101 (emission step) of emitting an ultrasonic beam U from the transmitting probe 110. In step S101, an ultrasonic beam U of a repeating wave packet composed of a wave packet with a wave number of two or more is emitted from the transmitting probe 110. Next, the receiving probe 121 performs step S102 (reception step) of receiving the ultrasonic beam U.
　その後、フィルタ部２４０は、受信プローブ１２１が受信した超音波ビームＵの信号（例えば波形信号）を基に、特定の周波数範囲、具体的には、最大成分周波数ｆｍを含む周波数範囲の成分（最大強度周波数成分）を低減するステップＳ１０３（フィルタ処理ステップ）を行う。即ち、ステップＳ１０３では、ステップＳ１０２で受信した超音波ビームＵの信号の最大強度周波数成分が低減される。そして、データ処理部２０１は、フィルタ処理を行った信号から、基本波帯Ｗ１の裾野成分Ｗ３を検出して信号強度データを生成するステップＳ１０４（信号強度算出ステップ）を行う。即ち、ステップＳ１０４では、超音波ビームＵの信号の基本波帯Ｗ１の裾野成分Ｗ３が検出される。信号強度データの生成方法として、本実施例ではピーク間信号量(Peak-to-Peak signal)が使用される。これは
信号のうち最大値と最小値との差である。 Thereafter, the filter unit 240 performs step S103 (filter processing step) of reducing a specific frequency range, specifically, a component (maximum intensity frequency component) in a frequency range including the maximum component frequency fm, based on the signal (e.g., waveform signal) of the ultrasonic beam U received by the receiving probe 121. That is, in step S103, the maximum intensity frequency component of the signal of the ultrasonic beam U received in step S102 is reduced. Then, the data processing unit 201 performs step S104 (signal intensity calculation step) of detecting the base component W3 of the fundamental wave band W1 from the signal subjected to the filter processing and generating signal intensity data. That is, in step S104, the base component W3 of the fundamental wave band W1 of the signal of the ultrasonic beam U is detected. In this embodiment, a peak-to-peak signal is used as a method of generating the signal intensity data. This is the difference between the maximum value and the minimum value of the signal.
　この次に、ステップＳ１０５（形状表示ステップ）が行われる。送信プローブ１１０及び受信プローブ１２１の走査位置情報は、位置計測部２０３からスキャンコントローラ２０４に送信される。データ処理部２０１は、スキャンコントローラ２０４から取得した送信プローブ１１０の走査位置情報に対して、それぞれの走査位置での信号強度データをプロットする。このようにして、信号強度データが画像化される。これがステップＳ１０５である。 Next, step S105 (shape display step) is performed. Scanning position information of the transmitting probe 110 and the receiving probe 121 is sent from the position measurement unit 203 to the scan controller 204. The data processing unit 201 plots the signal intensity data at each scanning position against the scanning position information of the transmitting probe 110 obtained from the scan controller 204. In this way, the signal intensity data is visualized. This is step S105.
　なお、図８Ｂは走査位置情報が１次元（１方向）の場合であり、走査位置情報がｘ、ｙの２次元の場合については、信号強度データをプロットすることで、欠陥部Ｄが２次元画像として示され、それが表示装置３に表示される。 Note that FIG. 8B shows a case where the scanning position information is one-dimensional (one direction); when the scanning position information is two-dimensional (x, y), the signal intensity data is plotted to show the defect D as a two-dimensional image, which is then displayed on the display device 3.
　データ処理部２０１は、走査が完了したか否かを判定する（ステップＳ１１１）。走査が完了している場合（Ｙｅｓ）、制御装置２は処理を終了する。走査が完了していない場合（Ｎｏ）、データ処理部２０１は駆動部２０２に指令を出力することによって、次の走査位置まで送信プローブ１１０及び受信プローブ１２１を移動させ（ステップＳ１１２）、ステップＳ１０１へ処理を戻す。 The data processing unit 201 determines whether the scanning is complete (step S111). If the scanning is complete (Yes), the control device 2 ends the processing. If the scanning is not complete (No), the data processing unit 201 outputs a command to the driving unit 202 to move the transmitting probe 110 and the receiving probe 121 to the next scanning position (step S112), and the processing returns to step S101.
（第７実施形態）
　図３１は、第７実施形態の超音波検査装置Ｚの構成を示す図である。図３１では、走査計測装置１は、断面模式図で示している。図３１には、紙面左右方向としてのｘ軸、紙面直交方向としてのｙ軸、紙面上下方向としてのｚ軸を含む直交３軸の座標系が示される。 Seventh Embodiment
Fig. 31 is a diagram showing the configuration of an ultrasonic inspection device Z of the seventh embodiment. In Fig. 31, a scanning measurement device 1 is shown in a schematic cross-sectional view. Fig. 31 shows a coordinate system of three orthogonal axes including an x-axis as a left-right direction on the paper, a y-axis as a direction perpendicular to the paper, and a z-axis as a top-bottom direction on the paper.
　超音波検査装置Ｚは、流体Ｆを介して被検査体Ｅに超音波ビームＵ（後記する）を入射することにより被検査体Ｅの検査を行うものである。流体Ｆは、空気等の気体Ｇであり、被検査体Ｅは流体Ｆ中に存在する。第７実施形態では、流体Ｆとして空気（気体Ｇの一例）が使用される。従って、走査計測装置１の筐体１０１の内部は空気で満たされた空洞となっている。図３１に示すように、超音波検査装置Ｚは、走査計測装置１と、制御装置２と、表示装置３とを備える。表示装置３は制御装置２に接続される。 The ultrasonic inspection device Z inspects the object E by irradiating an ultrasonic beam U (described later) to the object E through a fluid F. The fluid F is a gas G such as air, and the object E is present in the fluid F. In the seventh embodiment, air (an example of gas G) is used as the fluid F. Therefore, the inside of the housing 101 of the scanning measurement device 1 is a cavity filled with air. As shown in FIG. 31, the ultrasonic inspection device Z includes the scanning measurement device 1, a control device 2, and a display device 3. The display device 3 is connected to the control device 2.
　走査計測装置１は、被検査体Ｅへの超音波ビームＵの走査及び計測を行うものであり、筐体１０１に固定された試料台１０２を備え、試料台１０２には被検査体Ｅが載置される。被検査体Ｅは、動かないように固定具（不図示）で試料台１０２に固定されるとなお好ましい。被検査体Ｅが充分に重く不用意に動かない場合等は、固定具が無くてもよい。被検査体Ｅは、任意の材料で構成されている。被検査体Ｅは例えば固体材料であり、より具体的には例えば金属、ガラス、樹脂材料、あるいはＣＦＲＰ（炭素繊維強化プラスチック、Ｃａｒｂｏｎ－Ｆｉｂｅｒ　Ｒｅｉｎｆｏｒｃｅｄ　Ｐｌａｓｔｉｃｓ）等の複合材料等である。また、図３１の例において、被検査体Ｅは内部に欠陥部Ｄを有している。欠陥部Ｄ（欠陥）は、空洞等である。欠陥部Ｄの例は、空洞、本来あるべき材料と異なる異物材等である。被検査体Ｅにおいて、欠陥部Ｄ以外の部分を健全部Ｎと称する。 The scanning measurement device 1 scans and measures the object E with an ultrasonic beam U, and includes a sample stage 102 fixed to a housing 101, on which the object E is placed. It is more preferable that the object E is fixed to the sample stage 102 with a fixture (not shown) so as not to move. If the object E is heavy enough not to move inadvertently, a fixture is not necessary. The object E is made of any material. The object E is, for example, a solid material, and more specifically, is, for example, a metal, glass, a resin material, or a composite material such as CFRP (Carbon-Fiber Reinforced Plastics). In the example of FIG. 31, the object E has a defect D inside. The defect D (defect) is a cavity, etc. Examples of the defect D are a cavity, a foreign material different from the material that should be there, etc. In the specimen E, the portion other than the defective portion D is called the healthy portion N.
　欠陥部Ｄと健全部Ｎとは、構成する材料が異なるため、両者の間では音響インピーダンスが異なり、超音波ビームＵの伝搬特性が変化する。超音波検査装置Ｚは、この変化を観測して、欠陥部Ｄを検出する。 The defective area D and the healthy area N are made of different materials, so the acoustic impedance differs between the two, and the propagation characteristics of the ultrasonic beam U change. The ultrasonic inspection device Z observes this change to detect the defective area D.
　走査計測装置１は、超音波ビームＵを放出する送信プローブ１１０と、超音波ビームＵを受信する受信プローブ１２１とを有する。送信プローブ１１０は、送信プローブ走査部１０３を介して筐体１０１に設置され、超音波ビームＵを放出する。受信プローブ１２１は、被検査体Ｅに関して送信プローブ１１０の反対側に設置されて超音波ビームＵを受信し、送信プローブ１１０と同軸に配置された（後記する偏心距離Ｌがゼロ）、受信プローブ１４０（同軸配置受信プローブ）である。従って、本開示では、送信プローブ１１０の送信音軸ＡＸ１（音軸）と受信プローブ１４０の受信音軸ＡＸ２（音軸）との間の偏心距離Ｌ（距離。後記する）がゼロである。これにより、送信プローブ１１０及び受信プローブ１４０を容易に設置できる。 The scanning measurement device 1 has a transmitting probe 110 that emits an ultrasonic beam U and a receiving probe 121 that receives the ultrasonic beam U. The transmitting probe 110 is installed in the housing 101 via the transmitting probe scanning unit 103, and emits an ultrasonic beam U. The receiving probe 121 is a receiving probe 140 (coaxially arranged receiving probe) that is installed on the opposite side of the transmitting probe 110 with respect to the subject E to receive the ultrasonic beam U and is arranged coaxially with the transmitting probe 110 (the eccentric distance L described below is zero). Therefore, in this disclosure, the eccentric distance L (distance, described below) between the transmitting sound axis AX1 (sound axis) of the transmitting probe 110 and the receiving sound axis AX2 (sound axis) of the receiving probe 140 is zero. This makes it possible to easily install the transmitting probe 110 and the receiving probe 140.
　ここで、「送信プローブ１１０の反対側」とは、被検査体Ｅにより区切られる２つの空間のうち、送信プローブ１１０が位置する空間と反対側（ｚ軸方向において反対側）の空間という意味であり、ｘ、ｙ座標が同一の反対側（つまり、ｘｙ平面に関して面対称の位置）に限定される意味ではない。 Here, "the opposite side of the transmitting probe 110" means, of the two spaces separated by the subject E, the space opposite the space in which the transmitting probe 110 is located (the opposite side in the z-axis direction), and does not mean limited to the opposite side with the same x and y coordinates (i.e., a position that is symmetrical with respect to the xy plane).
　本開示の例では、送信プローブ１１０の送信音軸ＡＸ１が、試料台１０２の載置面１０２１に対して垂直になるように、送信プローブ１１０が設置される。即ち、送信音軸ＡＸ１が試料台１０２の被検査体Ｅの載置面１０２１の法線方向になるように送信プローブ１１０が設置される。このようにすると、板状の被検査体Ｅにおいては、被検査体Ｅの表面に垂直に送信音軸ＡＸ１が配置されるので、走査位置と欠陥部Ｄの位置との対応関係がわかり易くなるという効果がある。 In the example disclosed herein, the transmitting probe 110 is installed so that the transmission sound axis AX1 of the transmitting probe 110 is perpendicular to the mounting surface 1021 of the sample stage 102. In other words, the transmitting probe 110 is installed so that the transmission sound axis AX1 is normal to the mounting surface 1021 of the sample stage 102 for the object E to be inspected. In this way, for a plate-shaped object E to be inspected, the transmission sound axis AX1 is arranged perpendicular to the surface of the object E to be inspected, which has the effect of making it easier to understand the correspondence between the scanning position and the position of the defect D.
　走査計測装置１には、制御装置２が接続されている。制御装置２は、走査計測装置１の駆動を制御するものであり、送信プローブ走査部１０３及び受信プローブ走査部１０４に指示することで、送信プローブ１１０及び受信プローブ１２１の移動（走査）を制御する。送信プローブ走査部１０３及び受信プローブ走査部１０４が同期して、ｘ軸及びｙ軸方向に移動することにより、送信プローブ１１０及び受信プローブ１２１は被検査体Ｅをｘ軸及びｙ軸方向に走査する。更に、制御装置２は、送信プローブ１１０から超音波ビームＵを放出し、受信プローブ１２１から取得した信号に基づいて波形解析を行う。なお、送信プローブ１１０の走査方向であるｘ軸及びｙ軸方向の２つの軸が作る平面を走査面と呼ぶことにする。 The control device 2 is connected to the scanning measurement device 1. The control device 2 controls the driving of the scanning measurement device 1, and controls the movement (scanning) of the transmitting probe 110 and the receiving probe 121 by instructing the transmitting probe scanning unit 103 and the receiving probe scanning unit 104. The transmitting probe scanning unit 103 and the receiving probe scanning unit 104 move in the x-axis and y-axis directions in sync, so that the transmitting probe 110 and the receiving probe 121 scan the subject E in the x-axis and y-axis directions. Furthermore, the control device 2 emits an ultrasonic beam U from the transmitting probe 110, and performs waveform analysis based on the signal acquired from the receiving probe 121. The plane formed by the two axes, the x-axis and y-axis directions, which are the scanning directions of the transmitting probe 110, is called the scanning plane.
　送信プローブ１１０と被検査体Ｅとの間、及び受信プローブ１２１と被検査体Ｅとの間には、図示の例では気体Ｇが介在する。このため、送信プローブ１１０及び受信プローブ１２１を被検査体Ｅに非接触で検査できるため、ｘｙ面内方向の相対位置をスムーズかつ高速に変えることが可能である。即ち、送信プローブ１１０及び受信プローブ１２１と被検査体Ｅとの間に流体Ｆ（気体Ｇ）を介在させることにより、スムーズな走査が可能になる。 In the illustrated example, gas G is interposed between the transmitting probe 110 and the test subject E, and between the receiving probe 121 and the test subject E. Therefore, the transmitting probe 110 and the receiving probe 121 can test the test subject E without contacting it, so that the relative positions in the xy plane can be changed smoothly and quickly. In other words, by interposing a fluid F (gas G) between the transmitting probe 110 and the receiving probe 121 and the test subject E, smooth scanning becomes possible.
　送信プローブ１１０から局所的な超音波ビームＵを発すると、発された超音波ビームＵは、被検査体Ｅに局所的に照射する。局所的な超音波ビームＵを照射する位置は走査して変える。前述の通り、被検査体Ｅの欠陥部Ｄと健全部Ｎとで受信プローブ１２１に到達する超音波ビームＵが変化するので、この構成により欠陥部Ｄを検出することができる。 When a localized ultrasonic beam U is emitted from the transmitting probe 110, the emitted ultrasonic beam U is locally irradiated onto the object E to be inspected. The position to which the localized ultrasonic beam U is irradiated is changed by scanning. As described above, the ultrasonic beam U that reaches the receiving probe 121 changes depending on whether it is a defective part D or a healthy part N of the object E to be inspected, so this configuration makes it possible to detect the defective part D.
　局所的な超音波ビームＵを生成するために、本実施形態では収束型の送信プローブ１１０を用いた。 In this embodiment, a focused transmitting probe 110 is used to generate a localized ultrasonic beam U.
　送信プローブ１１０は、収束型の送信プローブ１１０である。一方で、受信プローブ１２１は、収束性が送信プローブ１１０よりも緩いプローブを用いる。本開示では、受信プローブ１２１には探触子面が平面である非収束型のプローブが使用される。従って、受信プローブ１２１は非収束型の受信プローブである。このような、非収束型の受信プローブ１２１を用いることで、幅広い範囲について欠陥部Ｄの情報を収集することができる。 The transmitting probe 110 is a convergent type transmitting probe 110. On the other hand, the receiving probe 121 uses a probe with looser convergence than the transmitting probe 110. In this disclosure, a non-convergent type probe with a flat probe surface is used for the receiving probe 121. Therefore, the receiving probe 121 is a non-convergent type receiving probe. By using such a non-convergent type receiving probe 121, information on the defect portion D can be collected over a wide range.
　第１実施形態において図５に即して述べた通り、本開示では、受信信号で検出する周波数の違いに着目することで、散乱波Ｕ１が効率的に検出される。この詳細は、図５に即して述べた通りである。 As described in the first embodiment with reference to FIG. 5, in this disclosure, the scattered wave U1 is efficiently detected by focusing on the difference in frequency detected in the received signal. The details are as described with reference to FIG. 5.
　図３２は、制御装置２の機能ブロック図である。制御装置２は、走査計測装置１の駆動を制御するものである。制御装置２は、送信系統２１０と、受信系統２２０と、データ処理部２０１と、スキャンコントローラ２０４と、駆動部２０２と、位置計測部２０３と、信号処理部２５０とを備える。駆動部２０２は、例えば、送信プローブ１１０及び受信プローブ１２１を駆動させることで、被検査体Ｅに対する送信プローブ１１０及び受信プローブ１２１の相対的な位置を変更するものである。位置計測部２０３は、走査位置を計測するものである。スキャンコントローラ２０４は、駆動部２０２を通じて、送信プローブ１１０及び受信プローブ１２１を駆動させる。送信プローブ１１０及び受信プローブ１２１による走査位置は、位置計測部２０３を通じて、スキャンコントローラ２０４に入力される。 FIG. 32 is a functional block diagram of the control device 2. The control device 2 controls the driving of the scanning measurement device 1. The control device 2 includes a transmission system 210, a reception system 220, a data processing unit 201, a scan controller 204, a driving unit 202, a position measurement unit 203, and a signal processing unit 250. The driving unit 202 changes the relative positions of the transmitting probe 110 and the receiving probe 121 with respect to the test subject E, for example, by driving the transmitting probe 110 and the receiving probe 121. The position measurement unit 203 measures the scanning position. The scan controller 204 drives the transmitting probe 110 and the receiving probe 121 through the driving unit 202. The scanning positions of the transmitting probe 110 and the receiving probe 121 are input to the scan controller 204 through the position measurement unit 203.
　受信系統２２０とデータ処理部２０１とを合わせて、信号処理部２５０と呼ぶ。信号処理部２５０は、受信プローブ１２１からの信号を増幅処理、フィルタ処理等により、有意な情報を抽出する信号処理を行う。 The receiving system 220 and the data processing unit 201 are collectively referred to as the signal processing unit 250. The signal processing unit 250 performs signal processing on the signal from the receiving probe 121, such as amplification and filtering, to extract significant information.
（送信プローブの固有周波数ｆｒｅｓと励起周波数ｆｅｘ）
　送信系統２１０は、送信プローブ１１０への印加電圧を生成する系統である。送信系統２１０は、波形発生器２１１、信号アンプ２１２及び送信周波数設定部２１３を備える。波形発生器２１１でバースト波信号が発生する。そして、発生したバースト波信号は信号アンプ２１２で増幅される。信号アンプ２１２から出力された電圧は送信プローブ１１０に印加される。 (The natural frequency of the transmitting probe fres and the excitation frequency fex)
The transmission system 210 is a system that generates a voltage to be applied to the transmission probe 110. The transmission system 210 includes a waveform generator 211, a signal amplifier 212, and a transmission frequency setting unit 213. A burst wave signal is generated by the waveform generator 211. The generated burst wave signal is then amplified by the signal amplifier 212. The voltage output from the signal amplifier 212 is applied to the transmission probe 110.
　バースト波信号の波形は後述するが、概略を述べると、当該波形は、基本周波数ｆ０で波数Ｎの波束を繰り返えす、繰り返し波束の波形である。送信系統２１０は、送信周波数設定部２１３を備える。送信周波数設定部２１３により、基本周波数ｆ０を変更することができる。本開示は、基本周波数ｆ０の選定方法を特徴の１つとするので、変更後の基本周波数ｆ０を、送信プローブ１１０を励起する周波数という意味から励起周波数ｆｅｘ（ｅｘｃｉｔａｔｉｏｎ　ｆｒｅｑｕｅｎｃｙ）と呼ぶ。 The waveform of the burst wave signal will be described later, but in brief, the waveform is a repeating wave packet waveform in which a wave packet of wave number N is repeated at fundamental frequency f0. The transmission system 210 includes a transmission frequency setting unit 213. The transmission frequency setting unit 213 can change the fundamental frequency f0. Since one of the features of this disclosure is the method of selecting the fundamental frequency f0, the changed fundamental frequency f0 is called the excitation frequency fex (excitation frequency) in the sense of the frequency that excites the transmission probe 110.
　後述するように、励起周波数ｆｅｘを適正な値に設定することにより、本実施形態の超音波検査装置Ｚの性能を高めることができる。 As described below, the performance of the ultrasonic inspection device Z of this embodiment can be improved by setting the excitation frequency fex to an appropriate value.
　一般に、送信プローブ１１０は、プローブ毎に定まる特定の周波数で動作させると、発生する超音波の振幅強度（音圧）が最大になる。この最大になる周波数をその送信プローブ１１０の固有周波数ｆｒｅｓ（ｒｅｓｏｎａｎｃｅ　ｆｒｅｑｕｅｎｃｙ）と呼ぶことにする。固有周波数で音圧が最大になる理由は、固有周波数ｆｒｅｓにおいて、内蔵する圧電素子の振動が共振するためである。このため、通常は励起周波数を固有周波数に等しく設定して、送信プローブ１００が利用される。 Generally, when the transmitting probe 110 is operated at a specific frequency determined for each probe, the amplitude intensity (sound pressure) of the generated ultrasound is maximized. This maximum frequency is called the natural frequency fres (resonance frequency) of the transmitting probe 110. The reason that the sound pressure is maximized at the natural frequency is because the vibration of the built-in piezoelectric element resonates at the natural frequency fres. For this reason, the transmitting probe 100 is usually used with the excitation frequency set equal to the natural frequency.
　本実施形態では、励起周波数ｆｅｘが、送信プローブ１１０の固有周波数ｆｒｅｓからずらした周波数に設定される。従って、走査計測装置１は、送信プローブ１１０の固有周波数ｆｒｅｓ（共振周波数と同義）からずらした励起周波数ｆｅｘで送信プローブ１１０を駆動する。 In this embodiment, the excitation frequency fex is set to a frequency that is shifted from the natural frequency fres of the transmitting probe 110. Therefore, the scanning measurement device 1 drives the transmitting probe 110 at the excitation frequency fex that is shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110.
　信号処理部２５０は、データ処理部２０１と、受信系統２２０とを備える。受信系統２２０は、受信プローブ１２１から出力される受信信号を検出する系統である。受信系統２２０は、信号アンプ２２２と、フィルタ部２４０とを備える。従って、信号処理部２５０はフィルタ部２４０を備える。受信プローブ１２１から出力された信号は、信号アンプ２２２に入力されて増幅される。増幅された信号は、フィルタ部２４０（遮断フィルタ）に入力される。フィルタ部２４０は、入力信号の特定の周波数範囲の成分を低減する（遮断する）。フィルタ部２４０については後述する。フィルタ部２４０からの出力信号は、データ処理部２０１に入力される。 The signal processing unit 250 includes a data processing unit 201 and a receiving system 220. The receiving system 220 is a system that detects the received signal output from the receiving probe 121. The receiving system 220 includes a signal amplifier 222 and a filter unit 240. Thus, the signal processing unit 250 includes a filter unit 240. The signal output from the receiving probe 121 is input to the signal amplifier 222 and amplified. The amplified signal is input to the filter unit 240 (blocking filter). The filter unit 240 reduces (blocks) components of a specific frequency range of the input signal. The filter unit 240 will be described later. The output signal from the filter unit 240 is input to the data processing unit 201.
　データ処理２０１の構成は、第１実施形態で用いた構成と同様である。また、フィルタ部２４０の構成も、第１実施形態で用いた構成と同様である。 The configuration of the data processing unit 201 is similar to that used in the first embodiment. The configuration of the filter unit 240 is also similar to that used in the first embodiment.
　データ処理部２０１では、フィルタ部２４０から入力された信号から、信号強度データを生成する。信号強度データの生成方法として、本実施形態ではピーク間信号量（Ｐｅａｋ－ｔｏ－Ｐｅａｋ　ｓｉｇｎａｌ）を用いた。ピーク間信号量は信号のうち最大値と最小値との差である。信号強度データの生成方法には、この他、フーリエ変換をして特定周波数範囲の周波数成分の強度を用いてもよい。 The data processing unit 201 generates signal strength data from the signal input from the filter unit 240. In this embodiment, the peak-to-peak signal is used as a method for generating signal strength data. The peak-to-peak signal is the difference between the maximum and minimum values of the signal. Another method for generating signal strength data is to use the strength of frequency components in a specific frequency range by performing a Fourier transform.
　データ処理部２０１は、スキャンコントローラ２０４から走査位置の情報も受け取る。このようにして、現在の２次元走査位置（ｘ，ｙ）における信号強度データの値が得られる。信号強度データの値（ピーク間信号量）を走査位置に対してプロットすると、欠陥部Ｄの位置又は形状の少なくとも一方に対応した画像（欠陥画像）が得られる。この欠陥画像は表示装置３に出力される。 The data processing unit 201 also receives scanning position information from the scan controller 204. In this way, the signal intensity data value at the current two-dimensional scanning position (x, y) is obtained. By plotting the signal intensity data value (peak-to-peak signal amount) against the scanning position, an image (defect image) corresponding to at least one of the position and shape of the defect D is obtained. This defect image is output to the display device 3.
（フィルタ部２４０）
　本実施形態で用いるフィルタ部２４０の構成は、第１実施形態でのフィルタ部２４０と同様であり、前述した通りである。フィルタ部２４０の定義も前述の通りである。 (Filter section 240)
The configuration of the filter unit 240 used in this embodiment is the same as that of the filter unit 240 in the first embodiment, as described above. The definition of the filter unit 240 is also as described above.
　本開示においてフィルタ部２４０は、所定の周波数範囲の信号成分の強度を低減させる信号処理を行う制御部と定義される。また、フィルタ処理は、所定の周波数範囲の信号成分の強度を低減させる信号処理と定義される。受信信号をフーリエ変換等で周波数成分毎の成分強度に分解した際、成分強度が最大になる周波数を最大成分周波数と呼ぶ。最大強度周波数成分は最大成分周波数における周波数成分である。本開示のフィルタ部２４０は、最大強度周波数成分を含む基本波帯、即ち、最大成分周波数を含む周波数範囲の信号成分の強度を低減する。なお、周波数成分毎の成分強度の分布を周波数スペクトルと呼ぶ。 In this disclosure, the filter unit 240 is defined as a control unit that performs signal processing to reduce the intensity of signal components in a specified frequency range. Filter processing is also defined as signal processing that reduces the intensity of signal components in a specified frequency range. When a received signal is decomposed into component intensities for each frequency component using a Fourier transform or the like, the frequency at which the component intensity is maximum is called the maximum component frequency. The maximum intensity frequency component is the frequency component at the maximum component frequency. The filter unit 240 of this disclosure reduces the intensity of the fundamental wave band that includes the maximum intensity frequency component, i.e., the signal components in the frequency range that includes the maximum component frequency. The distribution of component intensities for each frequency component is called the frequency spectrum.
　第７実施形態では、フィルタ部２４０は、最大成分周波数ｆｍを含む遮断周波数範囲の成分強度を低減する。即ち、フィルタ部２４０は、受信プローブ１２１の受信信号のうちの少なくとも最大強度周波数成分（最大成分周波数ｆｍに対応する成分）を低減する。そして、フィルタ部２４０は、最大強度周波数成分を含む基本波帯Ｗ１のうちの最大強度周波数成分以外の裾野成分Ｗ３を検出する。フィルタ部２４０により、遮断周波数範囲の成分強度が低減するので、フィルタ部２４０を通過した後の信号では、基本波帯Ｗ１のうち裾野成分Ｗ３が占める割合が増加する。このようにすることで、後記のように、欠陥部Ｄの検出性能を向上できる。 In the seventh embodiment, the filter unit 240 reduces the component strength in the cutoff frequency range including the maximum component frequency fm. That is, the filter unit 240 reduces at least the maximum intensity frequency component (the component corresponding to the maximum component frequency fm) of the received signal of the receiving probe 121. The filter unit 240 then detects the base component W3 other than the maximum intensity frequency component of the fundamental wave band W1 including the maximum intensity frequency component. Because the filter unit 240 reduces the component strength in the cutoff frequency range, the proportion of the base component W3 in the fundamental wave band W1 increases in the signal after passing through the filter unit 240. In this way, the detection performance of the defect portion D can be improved, as described below.
　図３３Ａは、欠陥部Ｄにまたがるように送信プローブ１１０及び受信プローブ１２１を走査したときの信号強度情報の位置による変化を示したものである。図３３Ａでは、上記図３２の構成からフィルタ部２４０を除いた構成で測定した結果である。送信プローブ１１０の励起周波数ｆｅｘは、送信プローブ１１０の固有周波数ｆｒｅｓ＝０．８２ＭＨｚと等しく設定している。健全部Ｎでの信号強度はｖ０である。一方で、欠陥部Ｄに対応する位置（ｘ＝０）で、信号強度がΔｖだけ低下しており、欠陥部Ｄを検出できている。しかし、信号強度の変化率（Δｖ／ｖ０）は小さい。ここで信号強度の変化率は、欠陥部Ｄでの信号変化量Δｖを健全部Ｎでの信号強度ｖ０で割った値と定義される。 Figure 33A shows the change in signal strength information depending on the position when the transmitting probe 110 and the receiving probe 121 are scanned across the defective portion D. Figure 33A shows the result of measurement using a configuration in which the filter unit 240 is removed from the configuration in Figure 32 above. The excitation frequency fex of the transmitting probe 110 is set equal to the natural frequency fres = 0.82 MHz of the transmitting probe 110. The signal strength in the healthy portion N is v0. On the other hand, at the position (x = 0) corresponding to the defective portion D, the signal strength is reduced by Δv, and the defective portion D can be detected. However, the rate of change in signal strength (Δv/v0) is small. Here, the rate of change in signal strength is defined as the signal change amount Δv at the defective portion D divided by the signal strength v0 at the healthy portion N.
　図３３Ｂは、送信プローブ１１０の励起周波数ｆｅｘを０．７８ＭＨｚに設定するとともに、フィルタ部２４０を備えた制御装置２（図３２）により、信号強度情報を測定した結果である。欠陥部Ｄの場所での信号強度の変化率（Δｖ／ｖ０）が大きくなり、欠陥部Ｄの検出性が改善したことがわかる。 Figure 33B shows the result of measuring signal strength information using a control device 2 (Figure 32) equipped with a filter unit 240, with the excitation frequency fex of the transmitting probe 110 set to 0.78 MHz. It can be seen that the rate of change in signal strength (Δv/v0) at the location of defect D has increased, improving the detectability of defect D.
　図３３Ａ及び図３３Ｂの実験結果を取得した実験条件を説明する。 The experimental conditions under which the results shown in Figures 33A and 33B were obtained are explained below.
　上記の図９は、上記のように、送信プローブ１１０に印加するバースト波の電圧波形である。横軸は時間、縦軸は電圧である。本実施形態では、図９の波形で、基本周波数ｆ０が０．７８ＭＨｚの正弦波が１０波印加される。この１０波を波束と呼ぶ。なお、基本周波数ｆ０の逆数を基本周期Ｔ０と呼ぶ。基本周期Ｔ０は、同図に示した通り、１波束を構成する波の周期である。波束は繰り返し周期Ｔｒ＝５ｍｓで印加される。従って、送信プローブ１１０は、波数が２以上の波束で構成される繰り返し波束の電圧波形を印加されて超音波ビームＵを放出する。 As described above, FIG. 9 above shows the voltage waveform of the burst wave applied to the transmitting probe 110. The horizontal axis is time, and the vertical axis is voltage. In this embodiment, ten sine waves with a fundamental frequency f0 of 0.78 MHz are applied in the waveform of FIG. 9. These ten waves are called a wave packet. The inverse of the fundamental frequency f0 is called the fundamental period T0. As shown in the figure, the fundamental period T0 is the period of the waves that make up one wave packet. The wave packet is applied with a repetition period Tr = 5 ms. Therefore, the transmitting probe 110 emits an ultrasonic beam U when a voltage waveform of a repeating wave packet made up of a wave packet with two or more waves is applied to it.
　なお、本実施形態では各々の波束は基本周波数ｆ０の正弦波を用いたが，正弦波以外でも良い。例えば、波束は、波数Ｎ０の矩形波で構成された波束であってもよい。 In this embodiment, each wave packet is a sine wave with a fundamental frequency of f0, but it may be a wave packet other than a sine wave. For example, the wave packet may be a wave packet composed of a rectangular wave with a wave number of N0.
　図３４は、上記図９に示す波形で、基本周波数ｆ０が０．７８ＭＨｚの正弦波を波数１０波を印加した時の、受信信号の周波数成分分布を示したものである。同図は、横軸が周波数で、縦軸がそれぞれの周波数での成分強度の実測データをプロットしている。これは、フィルタ部２４０で処理していない信号の周波数成分分布である。成分強度が最大になる０．８２ＭＨｚが最大成分周波数ｆｍ（図７）である。基本波帯Ｗ１（図７）は、０．７２ＭＨｚから０．８６ＭＨｚに拡がっており、このうち最大成分周波数ｆｍを除いた成分が裾野成分Ｗ３（図７）である。本実施形態では、最大成分周波数ｆｍは、送信プローブ１１０が送信する超音波の基本周波数ｆ０（図９）と等しくなっている。このように、多くの場合、最大成分周波数ｆｍは送信する超音波の基本周波数ｆ０に概ね等しくなる。 Figure 34 shows the frequency component distribution of the received signal when 10 sine waves with a fundamental frequency f0 of 0.78 MHz are applied to the waveform shown in Figure 9 above. In this figure, the horizontal axis is frequency, and the vertical axis is measured data of component strength at each frequency. This is the frequency component distribution of a signal not processed by the filter unit 240. 0.82 MHz, where the component strength is maximum, is the maximum component frequency fm (Figure 7). The fundamental wave band W1 (Figure 7) extends from 0.72 MHz to 0.86 MHz, and the components excluding the maximum component frequency fm are the skirt components W3 (Figure 7). In this embodiment, the maximum component frequency fm is equal to the fundamental frequency f0 (Figure 9) of the ultrasound transmitted by the transmitting probe 110. In this way, in many cases, the maximum component frequency fm is roughly equal to the fundamental frequency f0 of the ultrasound transmitted.
　フィルタ部２４０（図３２）は、上記のように、最大成分周波数ｆｍを除く。具体的には、図示の例では、フィルタ部２４０（図３２）は０．７８ＭＨｚ以下の裾野成分Ｗ３を透過させ、０．８２ＭＨｚを含む、０．７８ＭＨｚを超える波を遮断した。このようなフィルタ部２４０を用いると、上記図８Ｂのように、欠陥部Ｄでの信号強度の変化率が増大し、欠陥の検出性が大幅に改善することがわかる。 As described above, the filter section 240 (Fig. 32) excludes the maximum component frequency fm. Specifically, in the illustrated example, the filter section 240 (Fig. 32) transmits the base component W3 below 0.78 MHz and blocks waves above 0.78 MHz, including 0.82 MHz. When such a filter section 240 is used, as shown in Fig. 8B above, the rate of change of the signal intensity at the defective section D increases, and it can be seen that the detectability of the defect is greatly improved.
　図３５は、受信信号の周波数成分分布（周波数スペクトル）の実測データを、健全部Ｎ（実線）と欠陥部Ｄ（破線）とで比較した図である。フィルタ部２４０により欠陥部Ｄの検出性が改善するメカニズムは以下の通りである。最大成分周波数ｆｍ＝０．８２ＭＨｚでは、健全部Ｎと欠陥部Ｄとで成分強度（信号の大きさ）の違いは小さい。一方、最大成分周波数ｆｍ以外である裾野成分Ｗ３、特に低域帯については、健全部Ｎと欠陥部Ｄとの差が大きくなっている。 Figure 35 is a diagram comparing the measured data of the frequency component distribution (frequency spectrum) of the received signal between a healthy part N (solid line) and a defective part D (dashed line). The mechanism by which the filter section 240 improves the detectability of the defective part D is as follows. At the maximum component frequency fm = 0.82 MHz, the difference in component strength (signal magnitude) between the healthy part N and the defective part D is small. On the other hand, for the base component W3 other than the maximum component frequency fm, especially in the low frequency band, the difference between the healthy part N and the defective part D is large.
　このように、本開示は受信信号の周波数成分分布において、最大成分周波数ｆｍでの信号成分よりも、基本波帯Ｗ１の裾野成分Ｗ３の方が欠陥部Ｄでの信号変化率が大きいという、発明者らが見出した新しい知見に基づくものである。最大成分周波数ｆｍの成分は、受信信号の中で大きな割合を占めるが、欠陥部Ｄでの信号変化率が小さいので、この成分を低減することで、その結果、裾野成分Ｗ３が占める割合が増大する。このようにすることで、フィルタ部２４０で処理後の信号は、欠陥部Ｄでの信号変化率が増大するために、欠陥部Ｄの検出性を改善できる。そして、図３３Ａ及び図３３Ｂに示した実測データを比較しても、フィルタ部２４０による欠陥部Ｄの検出性が改善する効果は明らかである。 In this way, the present disclosure is based on the new knowledge found by the inventors that in the frequency component distribution of a received signal, the base component W3 of the fundamental wave band W1 has a greater signal change rate at the defect D than the signal component at the maximum component frequency fm. The component at the maximum component frequency fm accounts for a large proportion of the received signal, but the signal change rate at the defect D is small, so by reducing this component, the proportion of the base component W3 increases. In this way, the signal after processing by the filter unit 240 has an increased signal change rate at the defect D, improving the detectability of the defect D. And even when comparing the actual measurement data shown in Figures 33A and 33B, the effect of improving the detectability of the defect D by the filter unit 240 is clear.
　本開示の効果を奏するためのフィルタ部２４０の周波数特性の代表的な例を以下に示す。フィルタ部２４０は、帯域遮断フィルタ、低域通過フィルタ、又は、高域通過フィルタの少なくとも１つを含むことが好ましい。これらの少なくとも１つを含むことで、最大成分周波数ｆｍを含む周波数範囲の成分を低減できる。フィルタ部２４０の代表的な構成は、第１実施形態で述べたものと同様である。 A representative example of the frequency characteristics of the filter section 240 for achieving the effects of the present disclosure is shown below. The filter section 240 preferably includes at least one of a band-blocking filter, a low-pass filter, or a high-pass filter. By including at least one of these, it is possible to reduce components in a frequency range that includes the maximum component frequency fm. A representative configuration of the filter section 240 is similar to that described in the first embodiment.
（フィルタ部２４０の実装方法）
　第１実施形態で述べたように、フィルタ部２４０の実装方法は、アナログ方式及びデジタル方式に大別される。本実施形態においては、アナログ方式、デジタル方式のいずれを用いても効果が奏される。アナログ方式、デジタル方式の具体的な構成については、第１実施形態において述べた。 (Method of Implementing Filter Unit 240)
As described in the first embodiment, the implementation method of the filter unit 240 is roughly divided into an analog type and a digital type. In this embodiment, the effect can be obtained regardless of whether the analog type or the digital type is used. The specific configurations of the analog type and the digital type are described in the first embodiment.
　基本波帯Ｗ１の裾野成分Ｗ３が欠陥部Ｄに敏感に変化する理由は以下のように考えられる。 The reason why the base component W3 of the fundamental wave band W1 changes sensitively to the defect D is thought to be as follows.
　欠陥部Ｄと相互作用しない直達波Ｕ３は、波の伝播方向、位相、周波数等が変化しない。従って、最大成分周波数ｆｍの信号成分は、直達波Ｕ３が占める割合が多い。そのため、欠陥部Ｄと健全部Ｎとの変化が小さい。 The direct wave U3, which does not interact with the defective part D, does not change in wave propagation direction, phase, frequency, etc. Therefore, the signal component of the maximum component frequency fm is largely dominated by the direct wave U3. Therefore, the change between the defective part D and the healthy part N is small.
　上記図５に示したように、欠陥部Ｄと相互作用する散乱波Ｕ１は、伝播方向を変える成分もあり、また、伝播方向は変わらないが位相又は周波数の少なくとも一方が変化する成分もある。また、伝播方向を変える成分の中にも、周波数が変化する成分がある。従って、最大周波数ｆｍからずれた成分である基本波帯Ｗ１の裾野成分Ｗ３には、欠陥部Ｄと相互作用した超音波ビームＵである散乱波Ｕ１の成分が占める割合が増える。このため、欠陥部Ｄと健全部Ｎとの変化が大きくなる。このようにして、最大成分周波数ｆｍの成分を低減して、かつ基本波帯Ｗ１の裾野成分Ｗ３を検出することで、欠陥部Ｄの検出性能を向上できる。 As shown in Figure 5 above, the scattered wave U1 that interacts with the defect D has components that change the propagation direction, and components that do not change the propagation direction but at least one of the phase or frequency changes. Furthermore, among the components that change the propagation direction, there are components whose frequency changes. Therefore, the proportion of the scattered wave U1 component, which is the ultrasonic beam U that interacts with the defect D, in the base component W3 of the fundamental wave band W1, which is a component shifted from the maximum frequency fm, increases. As a result, the change between the defect D and the healthy part N becomes greater. In this way, the detection performance of the defect D can be improved by reducing the component of the maximum component frequency fm and detecting the base component W3 of the fundamental wave band W1.
（基本周波数の裾野成分）
　前述の通り、本開示では基本波帯Ｗ１の裾野成分Ｗ３を検出することで欠陥部Ｄの検出性能を向上するものである。そのため、基本波帯Ｗ１の裾野成分Ｗ３を増やすことがさらに検出性能の向上に寄与する。そこで、発明者らは、基本波帯Ｗ１の裾野成分Ｗ３を増やすための、送信する超音波波形の関係を鋭意検討した。 (Fundamental frequency tail components)
As described above, in the present disclosure, the performance of detecting the defect D is improved by detecting the foot component W3 of the fundamental wave band W1. Therefore, increasing the foot component W3 of the fundamental wave band W1 further contributes to improving the detection performance. Therefore, the inventors have thoroughly studied the relationship of the transmitted ultrasonic waveform to increase the foot component W3 of the fundamental wave band W1.
　基本波帯Ｗ１の裾野成分Ｗ３の量を増やす効果があるものは、繰り返し波束を構成する個々の波束の波数、及び、励起周波数の選択の２つである。 There are two things that have the effect of increasing the amount of the base component W3 of the fundamental wave band W1: the wave number of each wave packet that makes up the repeating wave packet, and the selection of the excitation frequency.
（波束の波数）
　始めに、繰り返し波束を構成する波束の波数と裾野成分との関係を示す。波束の波数とは、上記図９に示す通り、１つの波束に含まれる基本周波数ｆ０の波の個数である。 (Wave number of the wave packet)
First, the relationship between the wave number of a wave packet constituting a repeating wave packet and the tail component will be shown. The wave number of a wave packet is the number of waves of fundamental frequency f0 contained in one wave packet, as shown in FIG.
　図３６Ａは、波束の波数Ｎ０と、その超音波の基本波帯Ｗ１の周波数スペクトルである。ここでは基本周波数ｆ０＝０．８２ＭＨｚの超音波を例とした。波数Ｎ０＝１０（破線）、Ｎ０＝２０（実線）の種類の波束について、それぞれの周波数スペクトルを示した。一点鎖線で示したスペクトルは連続波の場合である。連続波の場合は、基本周波数ｆ０の成分のみを有し、裾野成分Ｗ３は殆ど存在しない。これに対して、Ｎ０＝２０、１０でのスペクトルからわかるように、波数Ｎ０が少なくするほど、基本波帯Ｗ１の幅が拡がり裾野成分Ｗ３が増加する。 Figure 36A shows the frequency spectrum of the wave number N0 of the wave packet and the fundamental wave band W1 of the ultrasound. Here, we use an example of ultrasound with a fundamental frequency f0 = 0.82 MHz. The frequency spectra are shown for wave packets of wave numbers N0 = 10 (dashed line) and N0 = 20 (solid line). The spectrum shown by the dashed dotted line is for a continuous wave. In the case of a continuous wave, it only has the component of the fundamental frequency f0, and the skirt component W3 is almost nonexistent. In contrast, as can be seen from the spectra for N0 = 20 and 10, the lower the wave number N0, the wider the width of the fundamental wave band W1 and the larger the skirt component W3.
　図３６Ｂは、図３６Ａに示したスペクトルの基本波帯の半値全幅（ＦＷＨＭ）が波束の波数Ｎ０に対してどのように変化するかを示した図である。 Figure 36B shows how the full width at half maximum (FWHM) of the fundamental waveband of the spectrum shown in Figure 36A changes with respect to the wave number N0 of the wave packet.
　本開示によれば、基本波帯Ｗ１の裾野成分Ｗ３では、欠陥部Ｄによる変化が大きいのであるから、本開示に用いる超音波は、連続波ではなく、繰り返し波束で構成される超音波が好ましいことがわかる。さらに、図３６Ｂに示す通り、各々の波束の波数Ｎ０は少ないほど基本波帯Ｗ１の裾野成分Ｗ３が増えるので、波数Ｎ０は少ないほど好ましい。図３６Ｂに示すように、Ｎ０≦３０では半値全幅は３０ｋＨｚ（０．０３ＭＨｚ）以上に拡がるので、波束の波数Ｎ０は３０以下であることが好ましい。 According to the present disclosure, the change due to the defect D is large in the base component W3 of the fundamental wave band W1, so it is preferable that the ultrasonic waves used in the present disclosure are ultrasonic waves composed of repeated wave packets rather than continuous waves. Furthermore, as shown in Figure 36B, the smaller the wave number N0 of each wave packet, the more the base component W3 of the fundamental wave band W1 increases, so the smaller the wave number N0, the more preferable it is. As shown in Figure 36B, when N0≦30, the full width at half maximum spreads to 30 kHz (0.03 MHz) or more, so it is preferable that the wave number N0 of the wave packet is 30 or less.
　なお、基本波帯の半値全幅（ＦＷＨＭ)は広すぎても好ましくなく、最大成分周波数ｆ
ｍの５０％以下が好ましい。基本波帯Ｗ１の半値全幅を、最大成分周波数ｆｍの５０％以下にするために、波束の波数Ｎ０は２つ以上が好ましく、また、Ｎ０が３以上だとさらに好ましい。これらの理由は、第１実施例において述べた通りである。 In addition, it is not preferable that the full width at half maximum (FWHM) of the fundamental wave band is too wide.
In order to set the full width at half maximum of the fundamental waveband W1 to 50% or less of the maximum component frequency fm, the wave number N0 of the wave packet is preferably 2 or more, and more preferably 3 or more. The reasons for this are as described in the first embodiment.
　従って、波束の波数Ｎ０は、２つ以上、かつ３０以下が好ましい。 Therefore, it is preferable that the wave number N0 of the wave packet is 2 or more and 30 or less.
　なお、欠陥部Ｄの情報を含む信号成分は、ｆｍ±０．２５ｆｍの周波数範囲に現れるので、送信波のスペクトルの基本波帯Ｗ１の幅はこれより狭いとさらに好ましい。即ち、基本波帯Ｗ１の周波数スペクトルの半値全幅は最大成分周波数ｆｍの５０％以下であることが好ましい。これにより、欠陥部Ｄの検出精度を向上できる。 Incidentally, since the signal components containing information about the defect D appear in the frequency range of fm ±0.25 fm, it is even more preferable that the width of the fundamental wave band W1 of the spectrum of the transmitted wave is narrower than this. In other words, it is preferable that the full width at half maximum of the frequency spectrum of the fundamental wave band W1 is 50% or less of the maximum component frequency fm. This can improve the detection accuracy of the defect D.
　基本波帯Ｗ１の半値全幅を最大成分周波数ｆｍの５０％以下にするには、上記図１４からわかるように、波束の波数Ｎ０を３以上にすることで達成できる。従って、上記のように、波束の波数Ｎ０を３以上にすると、さらに好ましい。 As can be seen from FIG. 14 above, in order to make the full width at half maximum of the fundamental wave band W1 50% or less of the maximum component frequency fm, this can be achieved by making the wave number N0 of the wave packet 3 or more. Therefore, as described above, it is even more preferable to make the wave number N0 of the wave packet 3 or more.
　基本波帯Ｗ１の裾野成分Ｗ３を検出することで欠陥検出性が向上するのであるから、フィルタ部２４０が検出する周波数は、最大成分周波数ｆｍに対して、（ｆｍ±０．２５ｆｍ）の範囲を含む周波数成分を検出することが好ましい。ここで、「０．２５ｆｍ」は最大成分周波数ｆｍの０．２５倍（即ち２５％）を意味する。例として、ｆｍ＝１ＭＨｚの場合は、（１±０．２５）ＭＨｚの範囲、即ち（０．７５～１．２５）ＭＨｚの範囲を指す。これは半値全幅比を５０％以下にすることに対応する。 Since defect detectability is improved by detecting the base component W3 of the fundamental wave band W1, it is preferable that the frequency detected by the filter section 240 includes frequency components in the range of (fm±0.25fm) with respect to the maximum component frequency fm. Here, "0.25fm" means 0.25 times (i.e., 25%) the maximum component frequency fm. For example, when fm=1 MHz, this refers to the range of (1±0.25) MHz, that is, the range of (0.75 to 1.25) MHz. This corresponds to a full width at half maximum ratio of 50% or less.
　上記図１４からわかるように、波数Ｎ０を５以上にすると、基本波帯Ｗ１の半値全幅比は３０％以下になる。これに対応して、フィルタ部２４０は、最大成分周波数ｆｍに対して、（ｆｍ±０．１５ｆｍ）の範囲を含む周波数成分を検出すると更に好ましい。 As can be seen from FIG. 14 above, when the wave number N0 is set to 5 or more, the full width at half maximum ratio of the fundamental wave band W1 is 30% or less. Accordingly, it is more preferable that the filter section 240 detects frequency components that include the range of (fm±0.15fm) with respect to the maximum component frequency fm.
（励起周波数）
　次に、励起周波数ｆｅｘと裾野成分Ｗ３との関係を示す。励起周波数ｆｅｘは波束の基本周波数ｆ０に対応する周波数であり、送信プローブ１１０に印加される周波数である。励起周波数ｆｅｘは、基本波帯Ｗ１の周波数範囲に設定される。 (excitation frequency)
Next, the relationship between the excitation frequency fex and the base component W3 will be shown. The excitation frequency fex is a frequency corresponding to the fundamental frequency f0 of the wave packet, and is a frequency applied to the transmission probe 110. The excitation frequency fex is set in the frequency range of the fundamental wave band W1.
　一般に送信プローブ１１０は固有周波数ｆｒｅｓ（ｒｅｓｏｎａｎｃｅ　ｆｒｅｑｕｅｎｃｙ）を持つ。送信プローブ１１０の固有周波数ｆｒｅｓは、送信プローブ１１０を構成する圧電素子が最も振動し易い周波数である。固有周波数ｆｒｅｓの電圧を印加すると、放出される超音波の強度（音響エネルギ）が最大になるので、通常は、励起周波数ｆｅｘは送信プローブ１１０の固有周波数ｆｒｅｓに等しくなるようにされる。なお、本開示において、固有周波数ｆｒｅｓは、共振周波数ｆｒｅｓと同義である。 Generally, the transmitting probe 110 has a natural frequency fres (resonance frequency). The natural frequency fres of the transmitting probe 110 is the frequency at which the piezoelectric element constituting the transmitting probe 110 is most likely to vibrate. When a voltage of the natural frequency fres is applied, the intensity (acoustic energy) of the emitted ultrasonic waves is maximized, so the excitation frequency fex is usually set to be equal to the natural frequency fres of the transmitting probe 110. Note that in this disclosure, the natural frequency fres is synonymous with the resonance frequency fres.
　図３７は、励起周波数ｆｅｘを変えて、受信信号の周波数スペクトルを測定した結果である。この送信プローブ１１０の固有周波数ｆｒｅｓは０．８２ＭＨｚである。図３７の破線は、固有周波数ｆｒｅｓと等しく励起周波数ｆｅｘを設定した時の周波数スペクトルである。前述の通り、これが通常の使用方法である。この測定では繰り返し波束を用いており、各波束の波数Ｎ０は１０個である。このため、基本波帯Ｗ１はある程度の拡がりを持ち、裾野成分Ｗ３を有する。点線で示す周波数スペクトルは、固有周波数ｆｒｅｓを中心として概ね対称なスペクトル形状である。 Figure 37 shows the results of measuring the frequency spectrum of the received signal by changing the excitation frequency fex. The natural frequency fres of this transmitting probe 110 is 0.82 MHz. The dashed line in Figure 37 shows the frequency spectrum when the excitation frequency fex is set equal to the natural frequency fres. As mentioned above, this is the normal usage method. This measurement uses a repeating wave packet, and the wave number N0 of each wave packet is 10. For this reason, the fundamental wave band W1 has a certain degree of spread and a skirt component W3. The frequency spectrum shown by the dotted line has a spectral shape that is roughly symmetrical around the natural frequency fres.
　これに対して、図３７の実線は、励起周波数ｆｅｘを固有周波数ｆｒｅｓよりも４０ｋＨｚ小さい０．７８ＭＨｚに設定した時の周波数スペクトルである。ここで、励起周波数ｆｅｘの設定値（０．７８ＭＨｚ）は、基本波帯Ｗ１の周波数範囲内であり、かつ固有周波数ｆｒｅｓからずらした値にしている。破線のスペクトルと比べて実線のスペクトルでは、基本波帯Ｗ１の裾野成分Ｗ３の量（成分強度）が増えていることがわかる。 In contrast, the solid line in Figure 37 is the frequency spectrum when the excitation frequency fex is set to 0.78 MHz, which is 40 kHz lower than the natural frequency fres. Here, the set value of the excitation frequency fex (0.78 MHz) is within the frequency range of the fundamental wave band W1, and is a value shifted from the natural frequency fres. It can be seen that the amount (component strength) of the base component W3 of the fundamental wave band W1 is increased in the solid line spectrum compared to the dashed line spectrum.
　このように、励起周波数ｆｅｘを、基本波帯Ｗ１の周波数範囲内であり、かつ固有周波数ｆｒｅｓからずらした値に設定することにより、基本波帯Ｗ１の裾野成分Ｗ３の量が増加し、欠陥部Ｄの検出性能が向上する。従って、励起周波数ｆｅｘは、基本波帯Ｗ１の周波数範囲に設定されることが好ましい。 In this way, by setting the excitation frequency fex to a value within the frequency range of the fundamental wave band W1 and shifted from the natural frequency fres, the amount of the base component W3 of the fundamental wave band W1 increases, improving the detection performance of the defect D. Therefore, it is preferable to set the excitation frequency fex within the frequency range of the fundamental wave band W1.
　前述の通り、基本波帯Ｗ１の半値全幅は最大成分周波数ｆｍの５０％以下にすることが好ましい。従って、励起周波数ｆｅｘは（ｆｒｅｓ±０．２５ｆｍ）の範囲に設定することが好ましい。ここで、ｆｒｅｓは送信プローブ１１０の固有周波数である。即ち、励起周波数ｆｅｘと固有周波数ｆｒｅｓ（共振周波数）との差の絶対値｜ｆｅｘ－ｆｒｅｓ｜は最大成分周波数ｆｍの２５％以下にすることが好ましい。なお、本開示において、固有周波数ｆｒｅｓは、共振周波数ｆｒｅｓと同義である。 As mentioned above, it is preferable that the full width at half maximum of the fundamental wave band W1 is 50% or less of the maximum component frequency fm. Therefore, it is preferable that the excitation frequency fex is set in the range of (fres ± 0.25 fm), where fres is the natural frequency of the transmitting probe 110. In other words, it is preferable that the absolute value |fex-fres| of the difference between the excitation frequency fex and the natural frequency fres (resonant frequency) is 25% or less of the maximum component frequency fm. Note that in this disclosure, the natural frequency fres is synonymous with the resonant frequency fres.
　また、送信プローブ１１０は固有振動数ｆｒｅｓで駆動すると、最も強い超音ビームＵ波が放出されることが知られている。励起周波数ｆｅｘの固有周波数ｆｒｅｓからのずれが大きいほど超音波ビームＵの放出効率が低下する。このため、励起周波数ｆｅｘと固有周波数ｆｒｅｓ（共振周波数）との差の絶対値｜ｆｅｘ－ｆｒｅｓ｜は最大成分周波数ｆｍの１５％以下にすると更に好ましい。 It is also known that when the transmitting probe 110 is driven at the natural frequency fres, the strongest ultrasonic beam U wave is emitted. The greater the deviation of the excitation frequency fex from the natural frequency fres, the lower the emission efficiency of the ultrasonic beam U. For this reason, it is more preferable that the absolute value |fex-fres| of the difference between the excitation frequency fex and the natural frequency fres (resonance frequency) is 15% or less of the maximum component frequency fm.
（瞬時周波数）
　励起周波数ｆｅｘを送信プローブ１１０の固有周波数ｆｒｅｓからずらすことにより基本波帯Ｗ１の裾野成分Ｗ３を増えることを述べた。このように裾野成分Ｗ３が増加するメカニズムを述べる。 (instantaneous frequency)
It has been described that the foot component W3 of the fundamental wave band W1 increases by shifting the excitation frequency fex from the natural frequency fres of the transmission probe 110. The mechanism by which the foot component W3 increases in this manner will be described.
　図３８は、１つの波束の時間領域において、瞬時周波数の変化を示す図である。ここでは、固有周波数ｆｒｅｓ＝０．８２ＭＨｚの圧電素子を励起周波数ｆｅｘで駆動した時の振幅波形を振動体モデルで計算した。瞬時周波数は、振幅波形のゼロクロス点から求めた。ゼロクロス点とは、信号がゼロ点を横切る時間を表し、ゼロクロス点の間隔からが周期が分かるので、瞬時周波数が算出できる。図３８の計算では、波束の波数Ｎ０を１０個とした。破線は、励起周波数ｆｅｘを固有周波数ｆｒｅｓに等しい０．８２ＭＨｚに設定した場合の結果であり、実線は励起周波数ｆｅｘを０．７４ＭＨｚに設定した場合の結果である。 Figure 38 shows the change in instantaneous frequency in the time domain of one wave packet. Here, the amplitude waveform was calculated using a vibrating body model when a piezoelectric element with a natural frequency fres = 0.82 MHz was driven at an excitation frequency fex. The instantaneous frequency was found from the zero crossing points of the amplitude waveform. The zero crossing points indicate the time when the signal crosses the zero point, and the period can be determined from the interval between the zero crossing points, so the instantaneous frequency can be calculated. In the calculations of Figure 38, the wave number N0 of the wave packet was set to 10. The dashed line shows the results when the excitation frequency fex was set to 0.82 MHz, which is equal to the natural frequency fres, and the solid line shows the results when the excitation frequency fex was set to 0.74 MHz.
　図３８の破線を見ると、励起周波数ｆｅｘを固有周波数ｆｒｅｓに等しくすると、瞬時周波数は固有周波数ｆｒｅｓである０．８２ＭＨｚで一定になる。これが従来の設定条件に対応する。これに対して、実線を見ると、励起周波数ｆｅｘを０．７４ＭＨｚにした場合は、瞬時周波数が時間とともに変化する。即ち、横軸に示す時刻ｔ＝０で励起周波数ｆｅｘを印加すると、固有周波数ｆｒｅｓに近い周波数で振動を開始し、その後だんだんと励起周波数ｆｅｘに近づいていく。そして、Ｎ０＝１０個を過ぎて励起電圧の印加が終了すると、縦軸に示す瞬時周波数は固有周波数ｆｒｅｓ＝０．８２ＭＨｚに戻る。 Looking at the dashed line in Figure 38, when the excitation frequency fex is set equal to the natural frequency fres, the instantaneous frequency becomes constant at the natural frequency fres of 0.82 MHz. This corresponds to the conventional setting conditions. In contrast, looking at the solid line, when the excitation frequency fex is set to 0.74 MHz, the instantaneous frequency changes over time. That is, when the excitation frequency fex is applied at time t = 0 shown on the horizontal axis, vibration begins at a frequency close to the natural frequency fres, and then gradually approaches the excitation frequency fex. Then, when N0 = 10 has passed and the application of the excitation voltage has ended, the instantaneous frequency shown on the vertical axis returns to the natural frequency fres = 0.82 MHz.
　このように、励起周波数ｆｅｘから固有周波数ｆｒｅｓの間の広い範囲の超音波が発生するため、受信信号には基本波帯Ｗ１の裾野成分Ｗ３の量が増えるわけである。 In this way, ultrasonic waves are generated over a wide range between the excitation frequency fex and the natural frequency fres, so the amount of the base component W3 of the fundamental wave band W1 increases in the received signal.
（送信プローブ１１０の固有周波数の範囲）
　本開示に用いる送信プローブ１１０の固有周波数ｆｒｅｓの好ましい範囲を述べる。 (Range of Natural Frequency of Transmitting Probe 110)
A preferred range of the natural frequency fres of the transmitting probe 110 used in this disclosure will now be described.
　本開示では局所的な超音波ビームＵを被検査体Ｅに照射して、その位置にある欠陥部Ｄが検知される。従って、局所的な超音波ビームＵのビーム径は小さいほど好ましい。そのため、送信プローブ１１０には収束型プローブを用いることが好ましい。 In this disclosure, a localized ultrasonic beam U is irradiated onto the object E to be inspected, and a defect D at that position is detected. Therefore, the smaller the beam diameter of the localized ultrasonic beam U, the more preferable it is. For this reason, it is preferable to use a convergent probe for the transmitting probe 110.
　超音波は波動であるから、音響レンズ等を用いて収束させても波長の程度以下に収束させることは難しいことが知られている。これは、波動の回折の効果が現れるためである。 Because ultrasound is a wave, it is known that it is difficult to converge it to less than the wavelength, even if it is focused using an acoustic lens or the like. This is because of the effect of wave diffraction.
　周波数ｆ０の超音波は、音速ｃの媒質中での波長λは、λ＝ｃ／ｆ０で表される。被検査体Ｅとしてアクリルを例にとると、音速ｃは２７３０（ｍ／ｓ）であるから、周波数ｆ０＝５０ＫＨｚでは超音波の波長λ＝５４ｍｍになる。即ち、周波数ｆ０＝５０ｋＨｚの超音波は収束型プローブを用いても５０ｍｍ程度までしか収束できず、充分に収束させることが困難である。 The wavelength λ of an ultrasonic wave with frequency f0 in a medium with sound speed c is expressed as λ = c/f0. If we take acrylic as an example of the test object E, the sound speed c is 2730 (m/s), so the wavelength λ of the ultrasonic wave at frequency f0 = 50 kHz is 54 mm. In other words, even with a focusing probe, ultrasonic waves with frequency f0 = 50 kHz can only be focused to about 50 mm, making it difficult to focus sufficiently.
　周波数ｆ０＝２００ｋＨｚの場合は、波長λ＝１４ｍｍとなるので、収束した超音波ビームＵを実現できる。このため、送信プローブ１１０の固有周波数ｆｒｅｓは２００ｋＨｚ以上にすることが好ましい。本実施形態では、送信プローブ１１０の固有周波数は０．８２ＭＨｚ（８２０ｋＨｚ）にしている。 When the frequency f0 = 200 kHz, the wavelength λ = 14 mm, so a focused ultrasonic beam U can be realized. For this reason, it is preferable that the natural frequency fres of the transmitting probe 110 is 200 kHz or higher. In this embodiment, the natural frequency of the transmitting probe 110 is 0.82 MHz (820 kHz).
　なお、本開示では散乱波Ｕ１を検出するため、上記図５に示した通り、ビーム径よりも小さな欠陥部Ｄを検出することができる。 In addition, in this disclosure, the scattered wave U1 is detected, so as shown in Figure 5 above, it is possible to detect a defect D that is smaller than the beam diameter.
　なお、本実施形態では各々の波束は基本周波数ｆ０の正弦波を用いたが、正弦波以外でも良い。例えば、波数Ｎ０の矩形波で構成された波束であってもよい。 In this embodiment, each wave packet is a sine wave with a fundamental frequency of f0, but it may be a wave packet other than a sine wave. For example, it may be a wave packet composed of a rectangular wave with a wave number of N0.
　また、励起周波数ｆｅｘが１つの波束の中で複数の励起周波数を持つ波であってもよい。このような波としては、周波数が時間とともに変化するチャープ波が知られている。複数の励起周波数を持つ波を用いる場合も、各励起周波数が基本波帯Ｗ１の周波数範囲に設定されることが好ましい。 Furthermore, the excitation frequency fex may be a wave having multiple excitation frequencies within one wave packet. A chirp wave, whose frequency changes over time, is known as such a wave. Even when using a wave having multiple excitation frequencies, it is preferable that each excitation frequency is set within the frequency range of the fundamental wave band W1.
（第８実施形態）
　図３９は、第８実施形態での超音波検査装置Ｚにおける制御装置２の機能ブロック図である。第８実施形態では、フィルタ部２４０で使用されるフィルタが、被検査体Ｅの検査前に、欠陥部Ｄの位置が既知の試料（不図示）に対して超音波ビームＵを照射することにより決定される。そして、被検査体Ｅの検査は、検査前に決定されたフィルタを使用して行われる。 Eighth embodiment
39 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the eighth embodiment. In the eighth embodiment, the filter used in the filter section 240 is determined by irradiating an ultrasonic beam U onto a sample (not shown) having a known position of a defect D before inspection of the object to be inspected E. Then, the inspection of the object to be inspected E is performed using the filter determined before the inspection.
　送信系統２１０は、送信プローブ１１０への印加電圧を生成する系統である。送信系統２１０は、波形発生器２１１、信号アンプ２１２及び送信周波数設定部２１３を備える。波形発生器２１１でバースト波信号が発生する。そして、発生したバースト波信号は信号アンプ２１２で増幅される。信号アンプ２１２から出力された電圧は送信プローブ１１０に印加される。 The transmission system 210 is a system that generates a voltage to be applied to the transmission probe 110. The transmission system 210 includes a waveform generator 211, a signal amplifier 212, and a transmission frequency setting unit 213. A burst wave signal is generated by the waveform generator 211. The generated burst wave signal is then amplified by the signal amplifier 212. The voltage output from the signal amplifier 212 is applied to the transmission probe 110.
　本実施形態では、第７実施形態と同様に、バースト波により送信プローブ１１０を駆動する。送信系統２１０は、送信周波数設定部２１３を備える。送信周波数設定部２１３により、バースト波の基本周波数ｆ０を変更することができ、基本周波数ｆ０を適切な励起周波数ｆｅｘに設定できる。 In this embodiment, as in the seventh embodiment, the transmitting probe 110 is driven by a burst wave. The transmitting system 210 includes a transmitting frequency setting unit 213. The transmitting frequency setting unit 213 can change the fundamental frequency f0 of the burst wave, and can set the fundamental frequency f0 to an appropriate excitation frequency fex.
　第７実施形態と同様に、本実施形態では、励起周波数ｆｅｘが、送信プローブ１１０の固有周波数ｆｒｅｓからずらした周波数に設定される。従って、走査計測装置１は、送信プローブ１１０の固有周波数ｆｒｅｓ（共振周波数と同義）からずらした励起周波数ｆｅｘで送信プローブ１１０を駆動する。励起周波数ｆｅｘを適正な値に設定することにより、本実施形態の超音波検査装置Ｚの性能を高めることができる。 As in the seventh embodiment, in this embodiment, the excitation frequency fex is set to a frequency shifted from the natural frequency fres of the transmitting probe 110. Therefore, the scanning measurement device 1 drives the transmitting probe 110 at the excitation frequency fex shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110. By setting the excitation frequency fex to an appropriate value, the performance of the ultrasonic inspection device Z of this embodiment can be improved.
　フィルタ部２４０は、検出部２４４及び決定部２４５を備える。検出部２４４は、周波数と信号強度（成分強度）との関係において、基本波帯Ｗ１のうちの異なる複数の裾野成分Ｗ３を検出するものである。ここでいう関係は、例えば上記図３５に示した関係であり、欠陥部Ｄの位置が既知の試料（不図示）での健全部Ｎ及び欠陥部Ｄに超音波ビームＵを照射することで得られたものである。決定部２４５は、検出した複数の裾野成分Ｗ３同士の比較により、どの裾野成分Ｗ３を使用するかを決定するものである。フィルタ部２４０をこのように構成することで、欠陥部Ｄに起因する信号変化を識別し易い裾野成分Ｗ３を使用でき、欠陥部Ｄの検出精度を向上できる。 The filter unit 240 includes a detection unit 244 and a determination unit 245. The detection unit 244 detects multiple different foot components W3 of the fundamental wave band W1 in the relationship between frequency and signal strength (component strength). The relationship referred to here is, for example, the relationship shown in FIG. 35 above, which is obtained by irradiating an ultrasonic beam U to a healthy part N and a defective part D in a sample (not shown) whose position of the defective part D is known. The determination unit 245 determines which foot component W3 to use by comparing the multiple detected foot components W3. By configuring the filter unit 240 in this way, it is possible to use a foot component W3 that makes it easy to identify signal changes caused by the defective part D, and the detection accuracy of the defective part D can be improved.
　検出部２４４は、例えば、異なる裾野成分Ｗ３を検出可能なフィルタを備える。ここでいうフィルタは、例えば、上記の帯域遮断フィルタ（図１５Ａ）、低域通過フィルタ（図１６Ａ）、高域通過フィルタ（図１７Ａ）のうちの少なくとも２つである。例えば、検出部２４４がこれら３つのフィルタを備える場合、検出部２４４は、例えば上記図３５に示す関係において、３つのフィルタを用いて、図１５Ｂに示す裾野成分Ｗ３、図１６Ｂに示す裾野成分Ｗ３、及び、図１７Ｂに示す裾野成分Ｗ３を検出する。そして、決定部２４５は、検出した３つの裾野成分Ｗ３同士の比較により、例えば健全部Ｎと欠陥部Ｄとの差分が最も大きくなる裾野成分Ｗ３の選択等により、どの裾野成分Ｗ３を使用するかを決定する。フィルタ部２４０は、決定した裾野成分Ｗ３を使用して、被検査体Ｅの検査を行うことで、欠陥部Ｄの検出精度を向上できる。 The detection unit 244 includes, for example, a filter capable of detecting different foot components W3. The filter here is, for example, at least two of the band-blocking filter (FIG. 15A), low-pass filter (FIG. 16A), and high-pass filter (FIG. 17A). For example, if the detection unit 244 includes these three filters, the detection unit 244 detects the foot components W3 shown in FIG. 15B, FIG. 16B, and FIG. 17B using the three filters, for example, in the relationship shown in FIG. 35. The determination unit 245 then compares the three detected foot components W3 with each other to determine which foot component W3 to use, for example, by selecting the foot component W3 with the largest difference between the healthy part N and the defective part D. The filter unit 240 uses the determined foot component W3 to inspect the test object E, thereby improving the detection accuracy of the defective part D.
（第９実施形態）
　図４０は、第９実施形態での超音波検査装置Ｚにおける制御装置２の機能ブロック図である。第９実施形態では、被検査体Ｅの検査前、欠陥部Ｄの位置が既知の試料（不図示）に対して超音波ビームＵを照射することにより得られたデータを使用者に提示し、使用者が、どの裾野成分Ｗ３を使用するか、即ち、どのフィルタを使用するのかが決定される。 Ninth embodiment
40 is a functional block diagram of the control device 2 in the ultrasonic inspection device Z in the ninth embodiment. In the ninth embodiment, before the inspection of the object E to be inspected, data obtained by irradiating an ultrasonic beam U onto a sample (not shown) having a known position of a defect D is presented to a user, and the user decides which base component W3 to use, i.e., which filter to use.
　送信系統２１０は、送信プローブ１１０への印加電圧を生成する系統である。送信系統２１０は、波形発生器２１１、信号アンプ２１２及び送信周波数設定部２１３を備える。波形発生器２１１でバースト波信号が発生する。そして、発生したバースト波信号は信号アンプ２１２で増幅される。信号アンプ２１２から出力された電圧は送信プローブ１１０に印加される。 The transmission system 210 is a system that generates a voltage to be applied to the transmission probe 110. The transmission system 210 includes a waveform generator 211, a signal amplifier 212, and a transmission frequency setting unit 213. A burst wave signal is generated by the waveform generator 211. The generated burst wave signal is then amplified by the signal amplifier 212. The voltage output from the signal amplifier 212 is applied to the transmission probe 110.
　本実施形態では、上記第７実施形態と同様に、バースト波により送信プローブ１１０を駆動する。送信系統２１０は、送信周波数設定部２１３を備える。送信周波数設定部２１３により、バースト波の基本周波数ｆ０を変更することができ、基本周波数ｆ０を適切な励起周波数ｆｅｘに設定できる。 In this embodiment, as in the seventh embodiment, the transmitting probe 110 is driven by a burst wave. The transmitting system 210 includes a transmitting frequency setting unit 213. The transmitting frequency setting unit 213 can change the fundamental frequency f0 of the burst wave, and can set the fundamental frequency f0 to an appropriate excitation frequency fex.
　上記第７実施形態と同様に、本実施形態では、励起周波数ｆｅｘが、送信プローブ１１０の固有周波数ｆｒｅｓからずらした周波数に設定される。従って、走査計測装置１は、送信プローブ１１０の固有周波数ｆｒｅｓ（共振周波数と同義）からずらした励起周波数ｆｅｘで送信プローブ１１０を駆動する。励起周波数ｆｅｘを適正な値に設定することにより、本実施形態の超音波検査装置Ｚの性能を高めることができる。 Similar to the seventh embodiment, in this embodiment, the excitation frequency fex is set to a frequency shifted from the natural frequency fres of the transmitting probe 110. Therefore, the scanning measurement device 1 drives the transmitting probe 110 at the excitation frequency fex shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110. By setting the excitation frequency fex to an appropriate value, the performance of the ultrasonic inspection device Z of this embodiment can be improved.
　制御装置２は、表示部２２３及び受付部２２４を備える。表示部２２３及び受付部２２４は、図示の例ではデータ処理部２０１に備えられる。表示部２２３は、周波数と信号強度（成分強度）との関係を表示装置３に表示させるものである。ここでいう関係は、例えば上記図３５に示す関係であり、欠陥部Ｄの位置が既知の試料（不図示）での健全部Ｎ及び欠陥部Ｄに超音波ビームＵを照射することで得られたものである。受付部２２４は、周波数と信号強度との関係に基づいて使用者によって入力され、検出すべき裾野成分Ｗ３を表す情報を受け付けるものである。入力は、例えばキーボード、マウス、タッチパネル等である入力装置４を通じて行われる。そして、フィルタ部２４０は、受付部２２４が受け付けた情報に基づいて、当該情報に対応する裾野成分Ｗ３を検出する。 The control device 2 includes a display unit 223 and a reception unit 224. In the illustrated example, the display unit 223 and the reception unit 224 are provided in the data processing unit 201. The display unit 223 displays the relationship between frequency and signal strength (component strength) on the display device 3. The relationship referred to here is, for example, the relationship shown in FIG. 35 above, which is obtained by irradiating an ultrasonic beam U to a healthy part N and a defective part D in a sample (not shown) whose position of the defective part D is known. The reception unit 224 receives information input by the user based on the relationship between frequency and signal strength, and which represents the foot component W3 to be detected. The input is performed through the input device 4, which is, for example, a keyboard, a mouse, a touch panel, etc. Then, the filter unit 240 detects the foot component W3 corresponding to the information based on the information received by the reception unit 224.
　制御装置２をこのように構成することで、使用者の主観に基づいて検出すべき裾野成分Ｗ３を判断できる。これにより、使用者の経験に基づき判断ができるため、検査実体に即した検査を実行できる。 By configuring the control device 2 in this way, the base component W3 to be detected can be determined based on the user's subjective opinion. This allows the user to make a determination based on their experience, making it possible to perform an inspection that is suited to the actual inspection.
（第１０実施形態。受信プローブ１２１の焦点距離）
　第１０実施形態では、受信プローブ１２１の焦点距離Ｒ２は、送信プローブ１１０の焦点距離Ｒ１よりも長いと、さらに好ましい。このようにすると、前記の通り、散乱波Ｕ１の成分をより多く検出できるようになるためである。前記の通り、散乱波Ｕ１は、欠陥部Ｄと相互作用した超音波ビームＵであるから、散乱波Ｕ１の成分の割合が増えるほど、欠陥部Ｄを検出し易くできる。 (Tenth embodiment. Focal length of the receiving probe 121)
In the tenth embodiment, it is more preferable that the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110. This is because, as described above, by doing so, it becomes possible to detect more components of the scattered wave U1. As described above, the scattered wave U1 is an ultrasonic beam U that has interacted with the defect D, so the greater the proportion of the scattered wave U1 components, the easier it becomes to detect the defect D.
　受信プローブ１２１の焦点距離を長くすると散乱波の成分を多く検出できる理由は、第１実施形態において述べた通りである。即ち、受信プローブ１２１の焦点距離Ｒ２を送信プローブ１１０の焦点距離Ｒ１よりも長くすることにより、検出可能な散乱波Ｕ１を増加できる。前記の通り、散乱波Ｕ１は欠陥部Ｄと相互作用した波であるから、これにより欠陥部Ｄの検出性能をさらに向上できる。 The reason why increasing the focal length of the receiving probe 121 allows more scattered wave components to be detected is as described in the first embodiment. That is, by making the focal length R2 of the receiving probe 121 longer than the focal length R1 of the transmitting probe 110, the detectable scattered waves U1 can be increased. As described above, the scattered waves U1 are waves that have interacted with the defect D, and this can further improve the detection performance of the defect D.
　本開示の例では、受信プローブ１２１の収束性を送信プローブ１１０の収束性よりも緩くしている。即ち、受信プローブ１２１の焦点距離Ｒ２は、送信プローブ１１０の焦点距離Ｒ１よりも長く設定されている。この結果、受信プローブ１２１のビーム入射面積Ｔ２が広くなるため、広い範囲の散乱波Ｕ１を検出できる。これにより、散乱波Ｕ１の伝搬経路が多少変化しても、受信プローブ１２１で散乱波Ｕ１を検出可能になる。その結果、広い範囲の欠陥部Ｄを検出できる。 In the example disclosed herein, the convergence of the receiving probe 121 is looser than that of the transmitting probe 110. That is, the focal length R2 of the receiving probe 121 is set longer than the focal length R1 of the transmitting probe 110. As a result, the beam incidence area T2 of the receiving probe 121 is wider, so that a wider range of scattered waves U1 can be detected. This makes it possible for the receiving probe 121 to detect the scattered waves U1 even if the propagation path of the scattered waves U1 changes slightly. As a result, a wider range of defective parts D can be detected.
　なお、送信プローブ１１０の焦点距離Ｒ１よりも受信プローブ１２１の焦点距離Ｒ２を長くする構成として、受信プローブ１２１として、非収束型のプローブ（不図示）が用いられてもよい。非収束型のプローブでは焦点距離Ｒ２が無限大なので、送信プローブ１１０の焦点距離Ｒ１よりも長くなる。即ち、非収束型の受信プローブ１２１でも、受信プローブ１２１の収束性は送信プローブ１１０の収束性よりも緩くなる。 Note that a non-convergent probe (not shown) may be used as the receiving probe 121 in a configuration in which the focal length R2 of the receiving probe 121 is longer than the focal length R1 of the transmitting probe 110. In a non-convergent probe, the focal length R2 is infinite, so it is longer than the focal length R1 of the transmitting probe 110. In other words, even with a non-convergent receiving probe 121, the convergence of the receiving probe 121 is weaker than the convergence of the transmitting probe 110.
（第１１実施形態）
　図４１は、第１１実施形態での超音波検査装置Ｚの構成を示す図である。第１１実施形態では、送信プローブ１１０の送信音軸ＡＸ１と受信プローブ１２１の受信音軸ＡＸ２とがずらして配置される。即ち、第１１実施形態での受信プローブ１２１は、送信プローブ１１０の送信音軸ＡＸ１とは異なる位置に配置された受信音軸ＡＸ２を有する受信プローブ１２０（偏心配置受信プローブ）である。従って、送信プローブ１１０の送信音軸ＡＸ１（音軸）と受信プローブ１２０の受信音軸ＡＸ（音軸）との間の偏心距離Ｌ（距離）がゼロより大きい。 Eleventh Embodiment
41 is a diagram showing the configuration of an ultrasonic inspection device Z in the eleventh embodiment. In the eleventh embodiment, the transmission sound axis AX1 of the transmitting probe 110 and the reception sound axis AX2 of the receiving probe 121 are arranged to be shifted from each other. That is, the receiving probe 121 in the eleventh embodiment is a receiving probe 120 (eccentrically arranged receiving probe) having a reception sound axis AX2 arranged at a position different from the transmission sound axis AX1 of the transmitting probe 110. Therefore, the eccentric distance L (distance) between the transmission sound axis AX1 (sound axis) of the transmitting probe 110 and the reception sound axis AX (sound axis) of the receiving probe 120 is greater than zero.
　このような配置にすることで、散乱波Ｕ１のうち空間的な方向が変わった波を検出できる。受信信号の周波数スペクトル（図７）に基づく周波数的な散乱波Ｕ１の抽出原理と、偏心配置による空間的な散乱波Ｕ１の抽出原理とを組み合わせることで、欠陥部Ｄの検出性をさらに向上できる。 By using this type of arrangement, it is possible to detect scattered waves U1 whose spatial direction has changed. By combining the principle of extracting frequency-wise scattered waves U1 based on the frequency spectrum of the received signal (Figure 7) with the principle of extracting spatially scattered waves U1 using an eccentric arrangement, it is possible to further improve the detectability of the defect D.
　第１１実施形態では、送信プローブ１１０に対して、図４１のｘ軸方向に偏心距離Ｌだけ受信プローブ１２０がずらされて配置されているが、図４１のｙ軸方向にずらされた状態で受信プローブ１２０が配置されてもよい。又は、ｘ軸方向にＬ１、ｙ軸方向にＬ２（即ち、送信プローブ１１０のｘｙ平面での位置を原点とすると、（Ｌ１、Ｌ２）の位置）に受信プローブ１２０が配置されてもよい。 In the eleventh embodiment, the receiving probe 120 is arranged offset by an eccentric distance L in the x-axis direction of FIG. 41 with respect to the transmitting probe 110, but the receiving probe 120 may be arranged offset in the y-axis direction of FIG. 41. Alternatively, the receiving probe 120 may be arranged at L1 in the x-axis direction and L2 in the y-axis direction (i.e., if the position of the transmitting probe 110 on the xy plane is taken as the origin, then the position is (L1, L2)).
　送信音軸ＡＸ１、受信音軸ＡＸ２及び偏心距離Ｌの定義及び説明は、前述の通りである。 The definitions and explanations of the transmitting sound axis AX1, the receiving sound axis AX2, and the eccentricity distance L are as described above.
　本実施形態では、送信音軸ＡＸ１が試料台１０２の被検査体Ｅの載置面１０２１の法線方向になるように送信プローブ１１０が設置される。前述の通り、このようにすると、板状の被検査体Ｅにおいては、被検査体Ｅの表面に垂直に送信音軸ＡＸ１が配置されるので、走査位置と欠陥部Ｄの位置との対応関係がわかり易くなるという効果がある。 In this embodiment, the transmitting probe 110 is installed so that the transmission sound axis AX1 is normal to the mounting surface 1021 of the test object E on the sample stage 102. As described above, this has the effect of making it easier to understand the correspondence between the scanning position and the position of the defect D, since the transmission sound axis AX1 is arranged perpendicular to the surface of the test object E for a plate-shaped test object E.
　偏心距離Ｌは、被検査体Ｅの健全部Ｎでの受信信号よりも、欠陥部Ｄでの信号強度の方が大きくなるような位置に設定するとさらに好ましい。 It is even more preferable to set the eccentricity distance L at a position where the signal strength at the defective part D is greater than the signal strength at the healthy part N of the test object E.
（第１２実施形態）
　第１２実施形態では、走査計測装置１は、受信プローブ１２０の傾きを調整する設置角度調整部１０６を備える。これにより、受信信号の強度を増大でき、信号のＳＮ比（Ｓｉｇｎａｌ　ｔｏ　Ｎｏｉｓｅ比、信号雑音比）を大きくできる。本実施形態での超音波検査装置Ｚの構成は、図２４に示した通りである。 Twelfth Embodiment
In the twelfth embodiment, the scanning measurement device 1 includes an installation angle adjustment unit 106 that adjusts the inclination of the receiving probe 120. This makes it possible to increase the strength of the received signal and to increase the signal-to-noise ratio (SNR) of the signal. The configuration of the ultrasonic inspection device Z in this embodiment is as shown in FIG. 24.
　ここで、送信音軸ＡＸ１と受信音軸ＡＸ２とが為す角度θを受信プローブ設置角度と定義する。上記図２４の場合、送信プローブ１１０は鉛直方向に設置されているので送信音軸ＡＸ１は鉛直方向であるため、受信プローブ設置角度である角度θは、送信音軸ＡＸ１（即ち鉛直方向）と受信プローブ１２０の探触子面の法線との為す角度である。そして、設置角度調整部１０６により、角度θを送信音軸ＡＸ１が存在する側に傾け、角度θをゼロより大きな値に設定する。即ち、受信プローブ１２０が傾斜配置される。具体的には、受信プローブ１２０は、０°＜θ＜９０°を満たすように傾斜配置され、角度θは例えば１０°であるがこれに限られない。 Here, the angle θ between the transmission sound axis AX1 and the reception sound axis AX2 is defined as the receiving probe installation angle. In the case of FIG. 24 above, the transmitting probe 110 is installed vertically, so the transmission sound axis AX1 is vertical, and the angle θ, which is the receiving probe installation angle, is the angle between the transmission sound axis AX1 (i.e., the vertical direction) and the normal to the probe surface of the receiving probe 120. Then, the installation angle adjustment unit 106 tilts the angle θ toward the side where the transmission sound axis AX1 exists, and sets the angle θ to a value greater than zero. That is, the receiving probe 120 is tilted. Specifically, the receiving probe 120 is tilted so as to satisfy 0°<θ<90°, and the angle θ is, for example, 10°, but is not limited to this.
　このように受信プローブ１２０を傾斜配置して、本発明者が実際に欠陥部Ｄの検出を行ったところ、受信信号の信号強度がθ＝０の場合と比較して３倍に増加した。 When the inventor actually tried to detect defect D by positioning the receiving probe 120 at an angle in this way, the signal strength of the received signal increased three times compared to when θ = 0.
（第１３実施形態）
　図４２は、第１３実施形態の制御装置２の機能ブロック図である。制御装置２は、走査計測装置１の駆動を制御するものである。制御装置２は、送信系統２１０と、受信系統２２０と、データ処理部２０１と、スキャンコントローラ２０４と、駆動部２０２と、位置計測部２０３と、信号処理部２５０とを備える。駆動部２０２は、例えば、送信プローブ１１０及び受信プローブ１２１を駆動させることで、被検査体Ｅに対する送信プローブ１１０及び受信プローブ１２１の相対的な位置を変更するものである。位置計測部２０３は、走査位置を計測するものである。スキャンコントローラ２０４は、駆動部２０２を通じて、送信プローブ１１０及び受信プローブ１２１を駆動させる。送信プローブ１１０及び受信プローブ１２１による走査位置は、位置計測部２０３を通じて、スキャンコントローラ２０４に入力される。 Thirteenth Embodiment
42 is a functional block diagram of the control device 2 of the thirteenth embodiment. The control device 2 controls the driving of the scanning measurement device 1. The control device 2 includes a transmission system 210, a reception system 220, a data processing unit 201, a scan controller 204, a driving unit 202, a position measurement unit 203, and a signal processing unit 250. The driving unit 202 changes the relative positions of the transmitting probe 110 and the receiving probe 121 with respect to the test subject E, for example, by driving the transmitting probe 110 and the receiving probe 121. The position measurement unit 203 measures the scanning position. The scan controller 204 drives the transmitting probe 110 and the receiving probe 121 through the driving unit 202. The scanning positions by the transmitting probe 110 and the receiving probe 121 are input to the scan controller 204 through the position measurement unit 203.
　受信系統２２０とデータ処理部２０１とを合わせて、信号処理部２５０と呼ぶ。信号処理部２５０は、受信プローブ１２１からの信号を増幅処理、周波数選択処理等により、有意な情報を抽出する信号処理を行う。 The receiving system 220 and the data processing unit 201 are collectively referred to as the signal processing unit 250. The signal processing unit 250 performs signal processing on the signal from the receiving probe 121, such as amplification processing and frequency selection processing, to extract significant information.
　送信系統２１０は、送信プローブ１１０への印加電圧を生成する系統である。送信系統２１０は、波形発生器２１１及び信号アンプ２１２を備える。波形発生器２１１でバースト波信号が発生する。そして、発生したバースト波信号は信号アンプ２１２で増幅される。信号アンプ２１２から出力された電圧は送信プローブ１１０に印加される。 The transmission system 210 is a system that generates a voltage to be applied to the transmission probe 110. The transmission system 210 includes a waveform generator 211 and a signal amplifier 212. A burst wave signal is generated by the waveform generator 211. The generated burst wave signal is then amplified by the signal amplifier 212. The voltage output from the signal amplifier 212 is applied to the transmission probe 110.
　送信プローブ１１０へ印加する電圧波形は、上記図９に示す通り、繰り返し波束の波形である。各々の波束は、基本周波数ｆ０の正弦波を有限個の波数Ｎ０で構成される。基本周波数ｆ０は、励起周波数ｆｅｘに対応する。本実施形態では、励起周波数ｆｅｘを、送信プローブの固有周波数ｆｒｅｓからずらした周波数に設定している。具体的には、送信プローブの固有周波数ｆｒｅｓ＝０．８２ＭＨｚに対して、励起周波数ｆｅｘ＝０．７８ＭＨｚに設定した。なお、波束の波数Ｎ０は１０に設定した。 The voltage waveform applied to the transmitting probe 110 is a repeating wave packet waveform as shown in FIG. 9 above. Each wave packet is composed of a finite number of wave numbers N0 of sine waves with a fundamental frequency f0. The fundamental frequency f0 corresponds to the excitation frequency fex. In this embodiment, the excitation frequency fex is set to a frequency shifted from the natural frequency fres of the transmitting probe. Specifically, the excitation frequency fex is set to 0.78 MHz for the natural frequency fres of the transmitting probe of 0.82 MHz. The wave number N0 of the wave packet is set to 10.
　信号処理部２５０は、データ処理部２０１と、受信系統２２０とを備える。受信系統２２０は、受信プローブ１２１から出力される受信信号を検出する系統である。受信プローブ１２１から出力された信号は、信号アンプ２２２に入力されて増幅される。増幅された信号は、周波数変換部２３０に入力される。周波数変換部２３０は、信号処理部２５０に備えられ、受信プローブ１２１の受信信号を周波数成分に変換（信号処理）するものであり、本開示の例では、時間領域波形である受信信号を周波数成分に変換する。周波数成分は、夫々の周波数の成分の大きさ（スペクトル）である。 The signal processing unit 250 includes a data processing unit 201 and a receiving system 220. The receiving system 220 is a system that detects the received signal output from the receiving probe 121. The signal output from the receiving probe 121 is input to a signal amplifier 222 and amplified. The amplified signal is input to a frequency conversion unit 230. The frequency conversion unit 230 is included in the signal processing unit 250 and converts the received signal from the receiving probe 121 into frequency components (signal processing), and in the example of the present disclosure, converts the received signal, which is a time domain waveform, into frequency components. The frequency components are the magnitude (spectrum) of the components at each frequency.
　周波数変換部２３０の構成は第６実施形態での構成と同様である。 The configuration of the frequency conversion unit 230 is the same as that in the sixth embodiment.
（周波数成分データの蓄積）
　データ処理部２０１は、記憶部２６１と、画像化部２６２と、表示部２６３とを備える。記憶部２６１は、データベース２６１ａを備える。従って、信号処理部２５０は、周波数変換部２３０と、画像化部２６２と、データベース２６１ａと、表示部２６３とを備える。 (Accumulation of frequency component data)
The data processing unit 201 includes a storage unit 261, an imaging unit 262, and a display unit 263. The storage unit 261 includes a database 261a. Therefore, the signal processing unit 250 includes a frequency conversion unit 230, an imaging unit 262, the database 261a, and a display unit 263.
　本開示の例では、周波数変換部２３０は、時間領域波形を周波数成分データに変換して位置情報と合わせて記憶部２６１に保存する。そして、画像化部２６２は、詳細は後記するが、変換された周波数成分のうち、周波数パラメータにより指定された周波数成分の部分を用いて、欠陥位置を示す画像２７３（後記）を生成する。即ち、画像化部２６２は、入力された周波数パラメータに基づき、信号特徴量を画像化する。即ち、被検査体Ｅを１回測定する場合に、周波数成分データへの変換は１回で済み、周波数成分データから信号特徴量の抽出は複数回行われる。 In the example of the present disclosure, the frequency conversion unit 230 converts the time domain waveform into frequency component data and stores it together with the position information in the storage unit 261. The imaging unit 262 then generates an image 273 (described below) indicating the defect position using a portion of the converted frequency components that is specified by the frequency parameters, as described in detail below. That is, the imaging unit 262 visualizes the signal features based on the input frequency parameters. That is, when the test object E is measured once, the conversion to frequency component data is performed only once, and the extraction of the signal features from the frequency component data is performed multiple times.
　この構成の好ましい点は、第６実施形態で述べた通り、計算所要時間が短くなることと、データ量の低減の２つある。 As described in the sixth embodiment, this configuration has two favorable points: it requires less time to perform calculations and reduces the amount of data.
　データ処理部２０１は、スキャンコントローラ２０４から走査位置の情報も受け取る。このようにして、現在の２次元走査位置（ｘ、ｙ）における受信信号の周波数成分に関するデータ（以下、周波数成分データという）が得られる。データ処理部２０１は、走査位置（ｘ、ｙ）と、その位置での周波数成分データとを対応づけて記憶部２６１に保存する。なお、周波数成分データから決定される信号特徴量を、走査位置毎に決定することで、欠陥部Ｄに関する画像２７３が作成される。 The data processing unit 201 also receives information on the scanning position from the scan controller 204. In this way, data on the frequency components of the received signal at the current two-dimensional scanning position (x, y) (hereinafter referred to as frequency component data) is obtained. The data processing unit 201 associates the scanning position (x, y) with the frequency component data at that position and stores them in the storage unit 261. Note that an image 273 of the defect D is created by determining the signal feature amount determined from the frequency component data for each scanning position.
　周波数成分データは、複数の周波数に対応する周波数成分である。典型的な例では、周波数成分データは、受信信号のフーリエ変換で得られる周波数スペクトルである。上記のように、周波数成分は振幅（絶対値）に加えて位相情報も含むことがより好ましい。これは、周波数成分を複素数として扱うことと同義である。後記のように、位相情報も含めることで、より高性能な信号特徴量を算出できる。 The frequency component data is frequency components corresponding to multiple frequencies. In a typical example, the frequency component data is a frequency spectrum obtained by Fourier transform of the received signal. As described above, it is more preferable for the frequency components to include phase information in addition to amplitude (absolute value). This is synonymous with treating the frequency components as complex numbers. As described below, by including phase information, it is possible to calculate signal features with higher performance.
　図４２に示すように、制御装置２は、本開示の例ではデータ処理部２０１を構成する記憶部２６１に、データベース２６１ａを備える。データベース２６１ａは、被検査体Ｅにおける欠陥部Ｄの検出精度に影響を与える情報（以下、「被検査体Ｅに関する情報」という）と、周波数パラメータとを対応付けたものである。ここでいう情報は、例えば、被検査体Ｅの検査条件を含む。検査条件によっては、適正な周波数パラメータが異なり得る。ここでいう適正な周波数パラメータは、健全部Ｎの周波数スペクトルと欠陥部Ｄの周波数スペクトルとの差分を、欠陥部Ｄを検出可能な程度に大きくするための周波数パラメータである。周波数パラメータは、欠陥部Ｄの検出に好適な周波数集合｛ωｎ｝を示すものである。そこで、使用者が検査条件を入力部２７２（後記）に入力することで、画像２７３（後記）の作成に使用される周波数スペクトルの部分を指定できる。 As shown in FIG. 42, the control device 2 includes a database 261a in the storage unit 261 constituting the data processing unit 201 in the example of the present disclosure. The database 261a associates information that affects the detection accuracy of the defective part D in the inspected object E (hereinafter referred to as "information about the inspected object E") with frequency parameters. The information here includes, for example, the inspection conditions of the inspected object E. The appropriate frequency parameters may differ depending on the inspection conditions. The appropriate frequency parameters here are frequency parameters for increasing the difference between the frequency spectrum of the healthy part N and the frequency spectrum of the defective part D to a level that makes the defective part D detectable. The frequency parameters indicate a frequency set {ωn} suitable for detecting the defective part D. Therefore, the user can specify the part of the frequency spectrum used to create an image 273 (described later) by inputting the inspection conditions into an input unit 272 (described later).
　なお、本実施形態においては、周波数パラメータに使用した励起周波数ｆｅｘを追加してデータベース２６１ａに保存するとさらに好ましい。励起周波数ｆｅｘを送信プローブ１１０の固有周波数ｆｒｅｓからどれだけずらすかにより、欠陥部Ｄの検出性能が変わる。このため、励起周波数ｆｅｘ（ずらした量）もデータベース２６１ａに登録することで、次回以降の測定時に適正な励起周波数ｆｅｘを選択することが可能になる。 In this embodiment, it is even more preferable to add the excitation frequency fex used to the frequency parameters and store it in the database 261a. The detection performance of the defect D changes depending on how much the excitation frequency fex is shifted from the natural frequency fres of the transmission probe 110. Therefore, by also registering the excitation frequency fex (amount of shift) in the database 261a, it becomes possible to select an appropriate excitation frequency fex for the next and subsequent measurements.
　なお、使用した励起周波数ｆｅｘを周波数パラメータとして登録する際には、固有周波数ｆｒｅｓからのシフト量が重要なので、差分量Δｆｅｘ＝ｆｅｘ－ｆｒｅｓの形式で登録すると好ましい。さらに、差分量Δｆｅｘと固有周波数ｆｒｅｓとの比（Δｆｅｘ／ｆｒｅｓ）を登録すると好ましい。 When registering the used excitation frequency fex as a frequency parameter, since the amount of shift from the natural frequency fres is important, it is preferable to register it in the form of the difference amount Δfex = fex - fres. Furthermore, it is preferable to register the ratio of the difference amount Δfex to the natural frequency fres (Δfex/fres).
　検査条件は、例えば、被検査体Ｅの材料、被検査体Ｅの厚さ、被検査体Ｅの構造（例えば単層構造又は多層構造の別）、受信プローブ１２１及び送信プローブ１１０に対する被検査体Ｅの位置（例えばｚ方向の位置）、流体Ｆの種類、の少なくとも１つを含む。これらは適正な周波数パラメータに影響を与え得る情報のため、これらの少なくとも１つを使用者が入力することで、適正な周波数パラメータを決定できる。 The inspection conditions include, for example, at least one of the following: the material of the object E to be inspected, the thickness of the object E to be inspected, the structure of the object E to be inspected (e.g., whether it is a single-layer structure or a multi-layer structure), the position of the object E to be inspected relative to the receiving probe 121 and the transmitting probe 110 (e.g., the position in the z direction), and the type of fluid F. Since these are pieces of information that can affect the appropriate frequency parameters, the appropriate frequency parameters can be determined by the user inputting at least one of these pieces of information.
　図４３Ａは、データベース２６１ａの一例である。周波数パラメータは、本開示の例では、送信周波数ｆ０（図９）に対する比率ｆ／ｆ０の集合である。図４３Ａに示す例では、被検査体Ｅに関する情報に対する好適な周波数パラメータが、ある範囲として表現される。ここでいう情報は、説明のための一例として、例えば被検査体Ｅの厚さ及び材料である。上記図３１に示す超音波検査装置Ｚで測定を行い、好適な周波数パラメータが繰り返し登録、即ち更新されると、データベース２６１ａに情報が蓄積されていく。 FIG. 43A is an example of database 261a. In the example disclosed herein, the frequency parameters are a set of ratios f/f0 relative to the transmission frequency f0 (FIG. 9). In the example shown in FIG. 43A, the preferred frequency parameters for information about the subject E are expressed as a certain range. The information here is, for example, the thickness and material of the subject E, as an example for explanation. When measurements are performed with ultrasonic inspection device Z shown in FIG. 31 above and the preferred frequency parameters are repeatedly registered, i.e., updated, information is accumulated in database 261a.
　図４３Ｂは、図４３Ａに示すデータベース２６１ａを立体的に示す図である。被検査体Ｅに関する情報は、複数の軸を持つ多次元情報である。即ち、被検査体Ｅに関する情報を各成分Ｉｔ［ｋ］（ｋは１以上の整数）に分けて表記すると、ｋ＝１、２、．．．が多次元情報の各軸に対応する。図４３Ｂに示す例では、説明のための一例として、Ｉｔ［１］が被検査体Ｅの厚さ、Ｉｔ［２］が被検査体Ｅの材料である。 FIG. 43B is a three-dimensional view of the database 261a shown in FIG. 43A. The information about the test object E is multidimensional information having multiple axes. That is, if the information about the test object E is expressed by dividing it into components It[k] (k is an integer equal to or greater than 1), then k=1, 2, ... corresponds to each axis of the multidimensional information. In the example shown in FIG. 43B, as an example for explanation, It[1] is the thickness of the test object E, and It[2] is the material of the test object E.
　図４３Ａでは、多次元情報である被検査体Ｅに関する情報を１つの軸として抽象化して示している。具体的に記すと、図４３Ｂに示すように、被検査体Ｅに関する情報は複数の軸で構成される。従って、データベース２６１ａは、本開示の例では、このように多次元情報である検査体情報を軸とするデータベースである。 In Figure 43A, information about the test subject E, which is multidimensional information, is abstracted and shown as one axis. More specifically, as shown in Figure 43B, information about the test subject E is composed of multiple axes. Therefore, in the example of the present disclosure, database 261a is a database that has test subject information, which is multidimensional information, as its axis.
　データベース２６１ａは、表形式で表してもよい。即ち、多次元の被検査体Ｅに関する情報ごとに１つのレコード（行）として、好適な周波数パラメータを記した表を作成してもよい。また、データベース２６１ａをコンピュータ等で処理する場合には、表形式のデータベースで表現してもよいし、多次元の被検査体Ｅに関する情報ごとに１つのレコードにしたデータベース形式で表現してもよい。 The database 261a may be expressed in a tabular format. That is, a table may be created in which suitable frequency parameters are recorded as one record (row) for each piece of information relating to the multidimensional test subject E. Furthermore, when the database 261a is processed by a computer or the like, it may be expressed as a tabular database, or it may be expressed in a database format in which each piece of information relating to the multidimensional test subject E is a single record.
　図４２に戻って、データ処理部２０１は、画像化部２６２を備える。画像化部２６２は、信号処理部２５０に備えられ、変換された周波数成分のうち、周波数パラメータにより指定された周波数成分の部分を用いて、欠陥部Ｄの位置（欠陥位置）を示す画像２７３（後記）を生成する。画像化部２６２は、具体的には、周波数変換部２３０により変換された周波数成分に対応する周波数スペクトルのうち、入力された周波数パラメータに対応する部分の周波数スペクトルにおいて、被検査体Ｅの欠陥部Ｄに起因する信号の変化（変化量）に基づき、画像２７３を作成する。このようにすることで、画像２７３を生成できる。 Returning to FIG. 42, the data processing unit 201 includes an imaging unit 262. The imaging unit 262 is included in the signal processing unit 250, and generates an image 273 (described below) indicating the position (defect position) of the defect D using a portion of the converted frequency components that is specified by the frequency parameters. Specifically, the imaging unit 262 creates the image 273 based on the change (amount of change) in the signal caused by the defect D of the test object E in the frequency spectrum of the portion that corresponds to the input frequency parameters out of the frequency spectrum that corresponds to the frequency components converted by the frequency conversion unit 230. In this way, the image 273 can be generated.
　ここでいう信号の変化（受信信号の変化）は、本開示の例では、信号特徴量である。従って、画像化部２６２は、まず、変換された周波数成分に対応する周波数スペクトルのうち、使用者によって入力された周波数パラメータの部分から、信号特徴量を算出する。信号特徴量は、上記のように信号の変化を表す例えば値であり、欠陥情報（例えば欠陥部Ｄの位置）を適切に含むように周波数成分データから算出した値である。信号特徴量の具体的な算出方法の例は後記する。このようにして得られた信号特徴量を走査位置（ｘ、ｙ）に対してプロットすることで、被検査体Ｅの内部に存在する欠陥部Ｄの２次元画像（欠陥画像）が生成する。 The signal change (change in the received signal) referred to here is a signal feature in the example of the present disclosure. Therefore, the imaging unit 262 first calculates the signal feature from the portion of the frequency spectrum corresponding to the converted frequency component that is the frequency parameter input by the user. The signal feature is, for example, a value that represents the signal change as described above, and is a value calculated from frequency component data so as to appropriately include defect information (for example, the position of the defect D). A specific example of a method for calculating the signal feature will be described later. By plotting the signal feature thus obtained against the scanning position (x, y), a two-dimensional image (defect image) of the defect D present inside the inspected object E is generated.
　データ処理部２０１（信号処理部２５０）は、表示装置３への表示を行う表示部２６３を備える。表示部２６３は、画像２７３を表示装置３に出力して表示する。表示装置３は、例えばモニタ、ディスプレイ等である。詳細は後記するが、表示部２６３は、表示装置３に、周波数変換部２３０により変換された周波数成分に対応する周波数スペクトル２７１（後記）を表示する。これとともに、表示部２６３は、表示装置３に、周波数パラメータの入力を受け付ける入力部２７２（後記）を表示する。入力は、例えば、超音波検査装置Ｚの使用者によって行われるが、別の装置（不図示）からの入力でもよい。本開示では、一例として、使用者が周波数パラメータを入力する場合を説明する。 The data processing unit 201 (signal processing unit 250) includes a display unit 263 that displays on the display device 3. The display unit 263 outputs an image 273 to the display device 3 for display. The display device 3 is, for example, a monitor, a display, or the like. Although details will be described later, the display unit 263 displays, on the display device 3, a frequency spectrum 271 (described later) corresponding to the frequency components converted by the frequency conversion unit 230. In addition, the display unit 263 displays, on the display device 3, an input unit 272 (described later) that accepts input of frequency parameters. The input is performed, for example, by a user of the ultrasound inspection device Z, but may also be input from another device (not shown). In this disclosure, as an example, a case in which the user inputs frequency parameters will be described.
　以上の手順を走査位置（ｘ，ｙ）を変えながら行うことで、所望の範囲が走査される。走査完了すると、走査位置（ｘ，ｙ）に対応した周波数成分データ及び信号特徴量がデータ処理部２０１内の記憶部２６１に保存される。本開示では、走査位置で信号を取得する毎に信号特徴量が算出される。ただし、測定中、周波数成分データが記憶部２６１に保存され、測定後に信号特徴量が纏めて算出されることで欠陥画像を生成してもよい。 The above procedure is performed while changing the scanning position (x, y) to scan the desired range. When scanning is completed, frequency component data and signal features corresponding to the scanning position (x, y) are stored in the memory unit 261 in the data processing unit 201. In this disclosure, the signal features are calculated each time a signal is acquired at the scanning position. However, during measurement, the frequency component data may be stored in the memory unit 261, and the signal features may be calculated collectively to generate a defect image after measurement.
（信号特徴量の算出）
　本開示の例で用いた、周波数成分データから信号特徴量の算出方法については、上記第６実施形態で述べた通りである。 (Calculation of signal features)
The method of calculating signal features from frequency component data used in the examples of the present disclosure is as described in the sixth embodiment above.
　上記第６実施形態で記載した、上記式（１）において、積算に含める周波数の集合｛ω｝の選択が重要になる。選択は、例えば、使用者によって実行される。上記周波数スペクトルからわかるように、基本波帯Ｗ１（図７）のうち、健全部Ｎと欠陥部Ｄとの差が大きい部分の周波数範囲を選択すると、欠陥部Ｄの画像をより明瞭に得ることが出来る。従って、使用者は、健全部Ｎと欠陥部Ｄとの差が大きい部分の周波数範囲（周波数パラメータ）を入力することが好ましい。ここでいう「大きい」は、例えば、使用者が２つの周波数スペクトルの違いを明瞭の認識できる程度の違い、又は、予め決定された所定の閾値以上等を採用できる。 In the above formula (1) described in the sixth embodiment, it is important to select the set of frequencies {ω} to be included in the accumulation. The selection is performed, for example, by the user. As can be seen from the above frequency spectrum, by selecting a frequency range in the fundamental wave band W1 (FIG. 7) where the difference between the healthy part N and the defective part D is large, an image of the defective part D can be obtained more clearly. Therefore, it is preferable for the user to input a frequency range (frequency parameter) where the difference between the healthy part N and the defective part D is large. Here, "large" can mean, for example, a difference that allows the user to clearly recognize the difference between the two frequency spectra, or a difference equal to or greater than a predetermined threshold value.
　なお、信号特徴量は、欠陥部Ｄの位置情報を適切に含むように周波数成分データから算出した値であればよく、上記の算出方法に限定されるものではない。上記の例では、時間領域の信号波形ｈ（ｔ）のＰＰ値を信号特徴量としたが、ｈ（ｔ）の絶対値を算出し、ｈ（ｔ）の面積を算出して信号特徴量としてもよい。ここで面積の算出手順は、ｈ（ｔ）を適切な時間間隔でサンプリングして、サンプリング点でのｈ（ｔ）の総和を算出すればよい。また、ｈ（ｔ）の絶対値の代わりに、ｈ（ｔ）の２乗値を用いてもよい。更に、式（１）及び式（２）を用いる代わりに、周波数成分Ｈ（ω）の絶対値を、入力された周波数集合｛ω｝について合計した値を信号特徴量として用いてもよい。 Note that the signal feature amount is not limited to the above calculation method, as long as it is a value calculated from frequency component data so as to appropriately include the position information of the defect D. In the above example, the PP value of the signal waveform h(t) in the time domain is used as the signal feature amount, but the absolute value of h(t) may be calculated, and the area of h(t) may be calculated as the signal feature amount. Here, the procedure for calculating the area is to sample h(t) at appropriate time intervals and calculate the sum of h(t) at the sampling points. Also, instead of the absolute value of h(t), the squared value of h(t) may be used. Furthermore, instead of using equations (1) and (2), the absolute values of the frequency components H(ω) may be summed for the input frequency set {ω} and used as the signal feature amount.
（周波数の選択）
　図４４は、本開示の例での超音波検査装置Ｚの操作画面２７０の構成例を模式的に示す図である。操作画面２７０は、表示部２６３（図４２）によって、表示装置３（図４２）に表示される。表示部２６３は、表示装置３に、上記のように、周波数変換部２３０（図４２）により変換された周波数成分に対応する周波数スペクトル２７１と、使用者による周波数パラメータの入力を受け付ける入力部２７２と、を表示する。本開示の例では、表示部２６３は、超音波検査装置Ｚの操作画面２７０を表示装置３に表示するとともに、周波数スペクトル２７１及び入力部２７２を操作画面２７０に表示する。これにより、周波数スペクトル２７１を含む操作画面２７０を確認しながら、使用者が入力部２７２を操作できる。 (Frequency Selection)
FIG. 44 is a diagram illustrating a configuration example of the operation screen 270 of the ultrasonic inspection device Z in the example of the present disclosure. The operation screen 270 is displayed on the display device 3 (FIG. 42) by the display unit 263 (FIG. 42). The display unit 263 displays, on the display device 3, a frequency spectrum 271 corresponding to the frequency components converted by the frequency conversion unit 230 (FIG. 42) as described above, and an input unit 272 that accepts input of frequency parameters by the user. In the example of the present disclosure, the display unit 263 displays the operation screen 270 of the ultrasonic inspection device Z on the display device 3, and displays the frequency spectrum 271 and the input unit 272 on the operation screen 270. This allows the user to operate the input unit 272 while checking the operation screen 270 including the frequency spectrum 271.
　図４４に示す構成例では、左側に被検査体Ｅの欠陥部Ｄの位置を示す画像２７３が表示される。右側の上部に周波数スペクトル２７１が表示される。ここでは、検査位置による複数箇所の周波数スペクトル２７１を表示できると比較ができるため好ましい。特に、周波数スペクトル２７１は、破線で示す第１周波数スペクトルと、実線で示す第２周波数スペクトルとを含む。破線及び実線の各グラフは、上記図３５における破線及び実線の各グラフである。これにより、周波数スペクトル同士を使用者が比較でき、適切な周波数成分を使用者が入力できる。ただし、表示される周波数スペクトル２７１は、第１周波数スペクトル又は第２周波数スペクトルのうちの何れか一方のみでよい。使用者がある程度の経験を有することで、何れか一方のみの周波数パラメータに基づいて、好適な周波数パラメータを決定でき得る。 In the configuration example shown in FIG. 44, an image 273 showing the position of the defective part D of the inspected object E is displayed on the left side. A frequency spectrum 271 is displayed in the upper right side. Here, it is preferable to display the frequency spectrum 271 at multiple locations depending on the inspection position, so that comparison can be made. In particular, the frequency spectrum 271 includes a first frequency spectrum shown by a dashed line and a second frequency spectrum shown by a solid line. The dashed and solid line graphs are the dashed and solid line graphs in FIG. 35 above. This allows the user to compare the frequency spectra with each other, and the user can input the appropriate frequency components. However, the frequency spectrum 271 displayed may be either the first frequency spectrum or the second frequency spectrum. If the user has a certain amount of experience, he or she may be able to determine the appropriate frequency parameters based on only one of the frequency parameters.
　入力部２７２は、使用者によって周波数パラメータが入力されるものである。本開示の例では、入力部２７２は、長さ及び位置を調整可能なスライドバーにより構成される周波数選択部である。使用者がスライドバーを例えばマウス、キーボード等を使用し、周波数スペクトルの周波数位置に対応した位置にスライドバーの長さ及び位置を調整することで、信号特徴量を抽出するための周波数範囲（周波数集合）を入力できる。ここで入力された周波数範囲が周波数パラメータである。入力後、更新ボタン２７４が押下されることで、周波数スペクトル２７１が更新される。 The input unit 272 is where the user inputs frequency parameters. In the example of the present disclosure, the input unit 272 is a frequency selection unit configured with a slide bar whose length and position can be adjusted. The user can input a frequency range (frequency set) for extracting signal features by adjusting the length and position of the slide bar using, for example, a mouse, keyboard, etc., to a position corresponding to the frequency position of the frequency spectrum. The frequency range input here is the frequency parameter. After input, the frequency spectrum 271 is updated by pressing the update button 274.
　周波数スペクトル２７１は、表示されることが好ましいものの、表示されなくてもよい。表示されない場合、例えば、画像化部２６２は、データベース２６１ａ（図４２）の中から、入力部２７５を通じ、受け付けた被検査体Ｅに関する情報に対応する周波数パラメータを初期の周波数パラメータとして決定する。入力部２７５は、被検査体Ｅにおける欠陥部Ｄの検出精度に影響を与える情報（上記の「被検査体Ｅに関する情報」）を受け付けるものである。上記表示部２６３は表示装置３に入力部２７５を表示する。該当する周波数パラメータが無い場合には、その情報に最も近い情報に対応する周波数パラメータが決定される。決定された周波数パラメータは、表示装置３に表示される。画像化部２６２は、決定した周波数パラメータに基づき、画像２７３（図４４）を作成する。データベース２６１ａの情報を利用することで、欠陥部Ｄの検出精度を向上できる。 Although it is preferable that the frequency spectrum 271 is displayed, it does not have to be displayed. In the case where it is not displayed, for example, the imaging unit 262 determines, as the initial frequency parameters, frequency parameters corresponding to the information on the object E received through the input unit 275 from the database 261a (FIG. 42). The input unit 275 receives information that affects the detection accuracy of the defect D in the object E (the above-mentioned "information on the object E"). The above-mentioned display unit 263 displays the input unit 275 on the display device 3. If there is no corresponding frequency parameter, the frequency parameters corresponding to the information closest to that information are determined. The determined frequency parameters are displayed on the display device 3. The imaging unit 262 creates an image 273 (FIG. 44) based on the determined frequency parameters. By using the information in the database 261a, the detection accuracy of the defect D can be improved.
（第１４実施形態）
　第１４実施形態は、複数の励起周波数ｆｅｘから最適な励起周波数ｆｅｘを選択する構成である。第１４実施形態は、上記図３１の超音波検査装置Ｚ、及び、上記図３２の制御装置２を用いた。 Fourteenth Embodiment
The fourteenth embodiment is configured to select an optimal excitation frequency f ex from a plurality of excitation frequencies f ex The fourteenth embodiment uses the ultrasonic inspection device Z of FIG. 31 and the control device 2 of FIG.
　図４５は、第１４実施形態で被検査体Ｅの欠陥画像を得るステップを示す図である。 FIG. 45 shows the steps for obtaining a defect image of the inspected object E in the 14th embodiment.
　第１４実施形態のステップＳ１００（画像取得ステップ）は、適切な励起周波数を選択するステップＳ１と、選択した励起周波数を用いて被検査体Ｅの欠陥画像を取得するステップＳ２と、の２段階に大別される。ステップＳ１は、ステップＳ１１，Ｓ１２，Ｓ１３を含む。ステップＳ１１では、励起周波数ｆｅｘ［ｎ］が設置される。ステップＳ１２では、信号強度が測定される。ステップＳ１３では、最適な励起周波数が選択される。ステップＳ２は、ステップＳ２１，Ｓ２２，Ｓ２３を含む。ステップＳ２１では、送信プローブ１１０から送信される超音波ビームＵの周波数が選択された励起周波数に設定される。ステップＳ２２では、被検査体Ｅを走査することで測定が実行される。ステップＳ２３では、画像２７３が表示される。 Step S100 (image acquisition step) of the 14th embodiment is broadly divided into two steps: step S1 for selecting an appropriate excitation frequency, and step S2 for acquiring a defect image of the object E to be inspected using the selected excitation frequency. Step S1 includes steps S11, S12, and S13. In step S11, an excitation frequency fex[n] is set. In step S12, the signal strength is measured. In step S13, an optimal excitation frequency is selected. Step S2 includes steps S21, S22, and S23. In step S21, the frequency of the ultrasonic beam U transmitted from the transmitting probe 110 is set to the selected excitation frequency. In step S22, measurement is performed by scanning the object E to be inspected. In step S23, an image 273 is displayed.
　第１４実施形態では、まず標準試験体（不図示）を用いて欠陥部Ｄの信号量が計測される。標準試験体は、形状、場所等が既知の模擬欠陥（欠陥部Ｄを模擬した欠陥）を形成した検査体である。標準試験体を構成する材料は、検査する被検査体Ｅと同じ材料、又は特性が近い材料で構成することが好ましい。 In the fourteenth embodiment, first, the signal amount of the defect portion D is measured using a standard test object (not shown). The standard test object is an inspection object in which a simulated defect (a defect simulating the defect portion D) with a known shape, location, etc. is formed. It is preferable that the material constituting the standard test object is the same as that of the inspected object E to be inspected, or a material with similar characteristics.
　第１４実施形態で用いる標準検査体では、模擬欠陥の形状は、長さ１０ｍｍ、幅１ｍｍとすることができる。幅、長さ、模擬欠陥の深さ位置等は、複数の形状、位置の模擬欠陥を形成するとさらに好ましい。 In the standard inspection object used in the 14th embodiment, the shape of the simulated defect can be 10 mm in length and 1 mm in width. It is more preferable to form simulated defects of multiple shapes and positions in terms of width, length, depth position, etc. of the simulated defect.
　図４６は、標準検査体を模擬欠陥を横切るように走査しながら、超音波ビームＵを送信して受信信号を計測し、受信信号を適切な信号処理により信号量を算出してプロットした結果である。図中の曲線ａは励起周波数ｆｅｘ１で測定した結果であり、曲線ｂは励起周波数ｆｅｘ１とは異なる励起周波数ｆｅｘ２で測定した結果である。Δｖ及びｖ０は、上記図３３Ａ及び図３３Ｂと同じである。曲線ｂは曲線ａよりΔｖが大きい。このように複数の励起周波数で位置が既知の模擬欠陥を計測した。励起周波数ｆｅｘは、５～１０種類程度に変更して、図４６のように信号量を計測しても良い。 Figure 46 shows the results of transmitting an ultrasonic beam U while scanning a standard inspection object across a simulated defect, measuring the received signal, and then calculating the signal amount using appropriate signal processing of the received signal, then plotting the results. Curve a in the figure is the result of measurement at excitation frequency fex1, and curve b is the result of measurement at excitation frequency fex2 which is different from excitation frequency fex1. Δv and v0 are the same as in Figures 33A and 33B above. Curve b has a larger Δv than curve a. In this way, a simulated defect with a known position was measured using multiple excitation frequencies. The excitation frequency fex may be changed to around 5 to 10 types, and the signal amount measured as in Figure 46.
　図４６の結果から最適な励起周波数ｆｅｘを選択できる。選択基準として、第１４実施形態では、信号強度の変化率Δｖ／ｖ０が最大になる励起周波数ｆｅｘを選択できる。選択基準はこれに限定されるわけでなく、信号強度の変化率Δｖ／ｖ０と信号強度ｖ０との２つの値から最適値を選択しても良い。 The optimum excitation frequency fex can be selected from the results in FIG. 46. In the fourteenth embodiment, as a selection criterion, the excitation frequency fex at which the rate of change of the signal strength Δv/v0 is maximized can be selected. The selection criterion is not limited to this, and the optimum value may be selected from two values, the rate of change of the signal strength Δv/v0 and the signal strength v0.
　第１４実施形態では、最適な励起周波数ｆｅｘの選択は、制御装置２が前述の選択基準に基づいて自動的に選択できる。この他、図４６の測定結果を操作画面２７０上に表示して、ユーザが最適な励起周波数ｆｅｘを選択する構成でもよい。 In the fourteenth embodiment, the control device 2 can automatically select the optimum excitation frequency fex based on the above-mentioned selection criteria. Alternatively, the measurement results in FIG. 46 may be displayed on the operation screen 270, and the user may select the optimum excitation frequency fex.
　次に、このように選択した最適な励起周波数ｆｅｘに設定して、被検査体Ｅを計測を行い、欠陥部Ｄの計測を行うことができる。第１４実施形態によれば、励起周波数ｆｅｘとして最適な周波数を用いるため、欠陥部の検出精度をさらに向上できるという効果がある。 Then, the excitation frequency fex is set to the optimum frequency selected in this manner, and the test object E is measured, and the defective portion D is measured. According to the fourteenth embodiment, the optimum frequency is used as the excitation frequency fex, which has the effect of further improving the detection accuracy of the defective portion.
（第１５実施形態）
　第１５実施形態は、複数の励起周波数ｆｅｘから最適な励起周波数ｆｅｘを選択する構成である。 Fifteenth embodiment
The fifteenth embodiment is configured to select an optimal excitation frequency fex from a plurality of excitation frequencies fex.
　図４７は、第１５実施形態で被検査体Ｅの欠陥画像を得るステップを示す図である。 FIG. 47 shows the steps for obtaining a defect image of the inspected object E in the 15th embodiment.
　第１５実施形態では、上記第１４実施形態のステップＳ１において、ステップＳ１２とステップＳ１３との間に、更にステップＳ１４が実行される。第１５実施形態のステップＳ１００（画像取得ステップ）は、適切な励起周波数を選択するステップＳ１と、選択した励起周波数を用いて被検査体Ｅの欠陥画像を取得するステップＳ２との２段階に大別される。 In the fifteenth embodiment, step S14 is further executed between step S12 and step S13 in step S1 of the fourteenth embodiment. Step S100 (image acquisition step) of the fifteenth embodiment is broadly divided into two steps: step S1 for selecting an appropriate excitation frequency, and step S2 for acquiring a defect image of the inspected object E using the selected excitation frequency.
　第１５実施形態では、被検査体Ｅを測定対象として複数の励起周波数ｆｅｘで周波数スペクトルが測定して操作画面２７０に表示される（ステップＳ１４）。周波数スペクトルを測定する位置は、被検査体Ｅの健全部でも欠陥部Ｄのいずれでも良い。 In the fifteenth embodiment, the frequency spectrum is measured at a plurality of excitation frequencies fex using the test object E as the measurement object and displayed on the operation screen 270 (step S14). The position at which the frequency spectrum is measured may be either a healthy part or a defective part D of the test object E.
　送信プローブ１１０の励起周波数をｆｅｘ［１］に設定して被検査体Ｅに超音波ビームを照射することで受信信号が測定する。次に、別の励起周波数ｆｅｘ［２］に設定して、同様に受信信号が測定される。このようにして、励起周波数ｆｅｘ［ｎ］（ｎ＝１、２、．．．．）と変えて受信信号が測定される。 The excitation frequency of the transmitting probe 110 is set to fex[1] and an ultrasonic beam is irradiated onto the subject E, and the received signal is measured. Next, it is set to another excitation frequency fex[2], and the received signal is measured in the same manner. In this way, the excitation frequency is changed to fex[n] (n = 1, 2, ...) and the received signal is measured.
　図４８は、ステップＳ１４で表示される周波数スペクトルである。ステップＳ１４では、測定された受信信号から周波数スペクトルを算出し、図４８に示すように、励起周波数ｆｅｘ［ｎ］に対応する周波数スペクトルが操作画面２７０上に表示される。このようにすると、図４８に示すように、異なる励起周波数に対応して、それぞれのスペクトルが表示される。なお、図４８は前述の通り、励起周波数ｆｅｘを変えて、受信信号の周波数スペクトルを測定した結果である。図４８の破線は、固有周波数ｆｒｅｓ（０．８２ＭＨｚ）と等しく励起周波数ｆｅｘを設定した時の周波数スペクトルである。実線は、励起周波数ｆｅｘを固有周波数ｆｒｅｓよりも４０ｋＨｚ小さい０．７８ＭＨｚに設定した時の周波数スペクトルである。 Figure 48 shows the frequency spectrum displayed in step S14. In step S14, the frequency spectrum is calculated from the measured received signal, and the frequency spectrum corresponding to the excitation frequency fex[n] is displayed on the operation screen 270 as shown in Figure 48. In this way, as shown in Figure 48, each spectrum is displayed corresponding to a different excitation frequency. As described above, Figure 48 shows the result of measuring the frequency spectrum of the received signal by changing the excitation frequency fex. The dashed line in Figure 48 shows the frequency spectrum when the excitation frequency fex is set equal to the natural frequency fres (0.82 MHz). The solid line shows the frequency spectrum when the excitation frequency fex is set to 0.78 MHz, which is 40 kHz lower than the natural frequency fres.
　ユーザは、これら複数のスペクトルを見て、適切な励起周波数ｆｅｘを選択する。励起周波数の選択基準は、第１５実施形態では、スペクトルのうち裾野成分Ｗ３の割合が大きくなるように励起周波数を選択できる。最適な励起周波数の選択基準は、これ以外であっても良い。例えば、裾野成分Ｗ３の割合と、信号強度の大きさとの２つの要素から最適な励起周波数を選択してもよい。 The user looks at these multiple spectra and selects an appropriate excitation frequency fex. In the fifteenth embodiment, the selection criterion for the excitation frequency is that the proportion of the base component W3 in the spectrum is large. The selection criterion for the optimal excitation frequency may be something other than this. For example, the optimal excitation frequency may be selected based on two factors: the proportion of the base component W3 and the magnitude of the signal strength.
　図４７に戻って、このようにして最適な励起周波数ｆｅｘを選択した後、欠陥画像を取得するステップＳ２が実行される。ステップＳ２では、選択された励起周波数ｆｅｘを設定して、被検査体Ｅを走査して受信信号が取得される。取得した受信信号を用いて、欠陥画像が操作画面２７０上に表示される。 Returning to FIG. 47, after the optimum excitation frequency fex is selected in this manner, step S2 is executed to acquire a defect image. In step S2, the selected excitation frequency fex is set, and the inspected object E is scanned to acquire a received signal. Using the acquired received signal, a defect image is displayed on the operation screen 270.
　第１５実施形態によれば、励起周波数ｆｅｘとして最適な周波数を用いるため、欠陥部Ｄの検出精度をさらに向上できるという効果がある。第１５実施形態では、標準試験体を用いることなく、最適な励起周波数ｆｅｘを選択できるという効果もある。 According to the fifteenth embodiment, since an optimal frequency is used as the excitation frequency fex, it is possible to further improve the detection accuracy of the defect portion D. The fifteenth embodiment also has the advantage that it is possible to select the optimal excitation frequency fex without using a standard test piece.
　また、第１５実施形態において、操作画面２７０上に表示されたスペクトルを基にして、信号特徴量を算出する周波数範囲を選定することができる。 In addition, in the fifteenth embodiment, the frequency range for calculating the signal features can be selected based on the spectrum displayed on the operation screen 270.
　複数の周波数スペクトルからユーザが最適な励起周波数を選択する代わりに、制御装置２が最適な励起周波数を選択してもよい。励起周波数を選択するアルゴリズムは、測定した励起周波数ｆｅｘ［ｎ］ごとに、スペクトルの中央周波数の成分強度を基準として裾野成分の強度比率を算出し、その比率が最大になる励起周波数ｆｅｘを選択すればよい。 Instead of the user selecting the optimal excitation frequency from multiple frequency spectra, the control device 2 may select the optimal excitation frequency. The algorithm for selecting the excitation frequency may calculate the intensity ratio of the tail components for each measured excitation frequency fex[n] based on the component intensity of the center frequency of the spectrum, and select the excitation frequency fex at which this ratio is maximized.
（第１６実施形態）
　図４９は、第１６実施形態の超音波検査装置Ｚの機能ブロック図である。本実施形態では、入力部２７５（図４４）を備えなくてもよい。 Sixteenth Embodiment
49 is a functional block diagram of an ultrasonic inspection device Z according to the sixteenth embodiment. In this embodiment, the input unit 275 (FIG. 44) does not necessarily have to be provided.
　信号処理部２５０は更新部２９１（周波数パラメータ更新部）を備える。更新部２９１は、周波数パラメータを自動的に更新する。更新部２９１でのより具体的な処理の一例を示す。画像化部２６２は、欠陥部Ｄ及び健全部Ｎの２点の受信信号について、周波数パラメータを変更しながら上記信号特徴量を算出する。そして、更新部２９１は、欠陥部Ｄ及び健全部Ｎの信号特徴量の差が最大になるような周波数パラメータを探索し、決定する。このようにして更新部２９１で更新された周波数パラメータを用いて、画像化部２６２は、画像２７３を作成する。また、このように更新された周波数パラメータがデータベース２６１ａに登録され、データベース２６１ａが更新される。 The signal processing unit 250 includes an update unit 291 (frequency parameter update unit). The update unit 291 automatically updates the frequency parameters. An example of a more specific process in the update unit 291 is shown below. The imaging unit 262 calculates the above-mentioned signal feature amount while changing the frequency parameters for the received signals at two points, the defective part D and the healthy part N. The update unit 291 then searches for and determines the frequency parameters that maximize the difference between the signal feature amounts of the defective part D and the healthy part N. Using the frequency parameters thus updated by the update unit 291, the imaging unit 262 creates an image 273. The frequency parameters thus updated are also registered in the database 261a, and the database 261a is updated.
　なお、周波数パラメータに使用した励起周波数ｆｅｘを追加してデータベース２６１ａに保存するとさらに好ましい。従って、データベース２６１ａは、励起周波数ｆｅｘの情報を含むことが好ましい。励起周波数ｆｅｘを送信プローブの固有周波数ｆｒｅｓからどれだけずらすかにより、欠陥の検出性が変わるので、これもデータベース２６１ａに登録することで、次回以降の測定時に適正な励起周波数ｆｅｘを選択することが可能になる。 It is more preferable to add the excitation frequency fex used to the frequency parameters and store it in the database 261a. Therefore, it is preferable that the database 261a includes information on the excitation frequency fex. Since the detectability of defects changes depending on how much the excitation frequency fex is shifted from the natural frequency fres of the transmitting probe, by registering this in the database 261a as well, it becomes possible to select the appropriate excitation frequency fex for the next and subsequent measurements.
　なお、使用した励起周波数ｆｅｘを周波数パラメータとして登録する際には、固有周波数ｆｒｅｓからのシフト量が重要なので、差分量Δｆｅｘ＝ｆｅｘ－ｆｒｅｓの形式で登録すると好ましい。さらに、差分量Δｆｅｘと固有周波数ｆｒｅｓとの比（Δｆｅｘ／ｆｒｅｓ）を登録すると好ましい。 When registering the used excitation frequency fex as a frequency parameter, since the amount of shift from the natural frequency fres is important, it is preferable to register it in the form of the difference amount Δfex = fex - fres. Furthermore, it is preferable to register the ratio of the difference amount Δfex to the natural frequency fres (Δfex/fres).
　なお、決定された周波数パラメータは、表示装置３に表示されてもよい。また、周波数パラメータを更新部２９１で自動的に更新するかわりに、使用者が、画像２７３を見ながら、入力部２７２を通じて、周波数パラメータを指定してもよい。このようにしても、欠陥部Ｄの検出精度をさらに向上できる。 The determined frequency parameters may be displayed on the display device 3. Also, instead of automatically updating the frequency parameters by the update unit 291, the user may specify the frequency parameters through the input unit 272 while viewing the image 273. This also makes it possible to further improve the detection accuracy of the defective portion D.
　図５０は、制御装置２のハードウェア構成を示す図である。前記した各構成、機能、ブロック図を構成する各部等は、それらの一部又はすべてを、例えば集積回路で設計すること等によりハードウェアで実現してもよい。また、図５０に示すように、前記した各構成、機能等は、ＣＰＵ２５２等のプロセッサがそれぞれの機能を実現するプログラムを解釈し、実行することによりソフトウェアで実現してもよい。制御装置２は、例えば、メモリ２５１、ＣＰＵ２５２、記憶装置２５３（ＳＳＤ，ＨＤＤ等）、通信装置２５４及びＩ／Ｆ２５５を備える。各機能を実現するプログラム、テーブル、ファイル等の情報は、ＨＤＤに格納すること以外に、メモリ、ＳＳＤ（Ｓｏｌｉｄ　Ｓｔａｔｅ　Ｄｒｉｖｅ）等の記録装置、又は、ＩＣ（Ｉｎｔｅｇｒａｔｅｄ　Ｃｉｒｃｕｉｔ）カード、ＳＤ（Ｓｅｃｕｒｅ　Ｄｉｇｉｔａｌ）カード、ＤＶＤ（Ｄｉｇｉｔａｌ　Ｖｅｒｓａｔｉｌｅ　Ｄｉｓｃ）等の記録媒体に格納することができる。 FIG. 50 is a diagram showing the hardware configuration of the control device 2. The above-mentioned configurations, functions, and each part constituting the block diagram may be realized in hardware by, for example, designing some or all of them as an integrated circuit. Also, as shown in FIG. 50, the above-mentioned configurations, functions, etc. may be realized in software by a processor such as a CPU 252 interpreting and executing a program that realizes each function. The control device 2 includes, for example, a memory 251, a CPU 252, a storage device 253 (SSD, HDD, etc.), a communication device 254, and an I/F 255. In addition to being stored in the HDD, information such as programs, tables, and files that realize each function can be stored in a recording device such as a memory or SSD (Solid State Drive), or a recording medium such as an IC (Integrated Circuit) card, an SD (Secure Digital) card, or a DVD (Digital Versatile Disc).
　図５１は、上記各実施形態の超音波検査方法を示すフローチャートである。本開示の超音波検査方法は上記の超音波検査装置Ｚの制御装置２により実行でき、一例として適宜、図３１及び図３２を参照して説明する。本開示の超音波検査方法は、気体Ｇ（図３１）を介して被検査体Ｅ（図３１）に超音波ビームＵを入射することにより被検査体Ｅの検査を行うものである。 FIG. 51 is a flow chart showing the ultrasonic inspection method of each of the above-mentioned embodiments. The ultrasonic inspection method disclosed herein can be executed by the control device 2 of the above-mentioned ultrasonic inspection device Z, and will be described as an example with reference to FIGS. 31 and 32 as appropriate. The ultrasonic inspection method disclosed herein inspects the object E (FIG. 31) by irradiating the object E (FIG. 31) with an ultrasonic beam U via a gas G (FIG. 31).
　本開示の超音波検査方法は、ステップＳ１０１～Ｓ１０５，Ｓ１１１，Ｓ１１２を含む。まず、制御装置２の指令により、送信プローブ１１０が、送信プローブ１１０から超音波ビームＵを放出するステップＳ１０１（放出ステップ）を行う。 The ultrasonic inspection method disclosed herein includes steps S101 to S105, S111, and S112. First, in response to a command from the control device 2, the transmitting probe 110 performs step S101 (emission step) of emitting an ultrasonic beam U from the transmitting probe 110.
　ステップＳ１０１においては、送信プローブ１１０の励起周波数ｆｅｘが送信プローブ１１０の固有周波数ｆｒｅｓからずらした周波数に設定される。従って、ステップＳ１０１では、送信プローブ１１０の固有周波数ｆｒｅｓ（共振周波数と同義）からずらした励起周波数ｆｅｘで、送信プローブ１１０を励起して超音波ビームＵが放出される。 In step S101, the excitation frequency fex of the transmitting probe 110 is set to a frequency shifted from the natural frequency fres of the transmitting probe 110. Therefore, in step S101, the transmitting probe 110 is excited at the excitation frequency fex shifted from the natural frequency fres (synonymous with the resonant frequency) of the transmitting probe 110 to emit an ultrasonic beam U.
　続いて、ステップＳ１０２（受信ステップ）では、受信プローブ１２１が、超音波ビームＵを受信する。 Next, in step S102 (reception step), the receiving probe 121 receives the ultrasound beam U.
　その後、フィルタ部２４０は、受信プローブ１２１が受信した超音波ビームＵの信号（例えば波形信号）を基に、特定の周波数範囲、具体的には、最大成分周波数ｆｍを含む周波数範囲の成分（最大強度周波数成分）を低減するステップＳ１０３（フィルタ処理ステップ）を行う。即ち、ステップＳ１０３では、ステップＳ１０２で受信した超音波ビームＵの信号の最大強度周波数成分が低減される。 Then, the filter unit 240 performs step S103 (filter processing step) to reduce components (maximum intensity frequency components) in a specific frequency range, specifically, a frequency range including the maximum component frequency fm, based on the signal (e.g., waveform signal) of the ultrasound beam U received by the receiving probe 121. That is, in step S103, the maximum intensity frequency component of the signal of the ultrasound beam U received in step S102 is reduced.
　そして、データ処理部２０１は、フィルタ処理を行った信号から、基本波帯Ｗ１の裾野成分Ｗ３を検出して信号強度データを生成するステップＳ１０４（信号強度算出ステップ）を行う。従って、ステップＳ１０４では、超音波ビームＵの信号における基本波帯Ｗ１の裾野成分Ｗ３が検出される。信号強度データの生成方法として、本実施形態ではピーク間信号量（Ｐｅａｋ－ｔｏ－Ｐｅａｋ　ｓｉｇｎａｌ）が使用される。これは信号のうち最大値と最小値との差である。 Then, the data processing unit 201 performs step S104 (signal intensity calculation step) of detecting the base component W3 of the fundamental wave band W1 from the filtered signal and generating signal intensity data. Therefore, in step S104, the base component W3 of the fundamental wave band W1 in the signal of the ultrasound beam U is detected. In this embodiment, the peak-to-peak signal is used as a method of generating signal intensity data. This is the difference between the maximum and minimum values of the signal.
　この次に、ステップＳ１０５（形状表示ステップ）が行われる。送信プローブ１１０及び受信プローブ１２１の走査位置情報は、位置計測部２０３からスキャンコントローラ２０４に送信される。データ処理部２０１は、スキャンコントローラ２０４から取得した送信プローブ１１０の走査位置情報に対して、それぞれの走査位置での信号強度データをプロットする。このようにして、信号強度データが画像化される。これがステップＳ１０５である。 Next, step S105 (shape display step) is performed. Scanning position information of the transmitting probe 110 and the receiving probe 121 is sent from the position measurement unit 203 to the scan controller 204. The data processing unit 201 plots the signal intensity data at each scanning position against the scanning position information of the transmitting probe 110 obtained from the scan controller 204. In this way, the signal intensity data is visualized. This is step S105.
　なお、上記図３３Ｂは走査位置情報が１次元（１方向）の場合であり、走査位置情報がｘ、ｙの２次元の場合については、信号強度データをプロットすることで、欠陥部Ｄが２次元画像として示され、それが表示装置３に表示される。 Note that Figure 33B above shows a case where the scanning position information is one-dimensional (one direction); when the scanning position information is two-dimensional in x and y, the signal intensity data is plotted to show the defect D as a two-dimensional image, which is then displayed on the display device 3.
　データ処理部２０１は、走査が完了したか否かを判定する（ステップＳ１１１）。走査が完了している場合（Ｙｅｓ）、制御装置２は処理を終了する。走査が完了していない場合（Ｎｏ）、データ処理部２０１は駆動部２０２に指令を出力することによって、次の走査位置まで送信プローブ１１０及び受信プローブ１２１を移動させ（ステップＳ１１２）、ステップＳ１０１へ処理を戻す。 The data processing unit 201 determines whether the scanning is complete (step S111). If the scanning is complete (Yes), the control device 2 ends the processing. If the scanning is not complete (No), the data processing unit 201 outputs a command to the driving unit 202 to move the transmitting probe 110 and the receiving probe 121 to the next scanning position (step S112), and the processing returns to step S101.
　以上の超音波検査装置Ｚ及び超音波検査方法によれば、欠陥部Ｄの検出性能、例えば微小欠陥を検出する性能を向上できる。 The ultrasonic inspection device Z and ultrasonic inspection method described above can improve the detection performance of defective areas D, for example the performance of detecting minute defects.
　以上の各実施形態では、欠陥部Ｄは空洞である例を記載しているが、欠陥部Ｄとして被検査体Ｅの材質とは異なる材質が混入している異物であってもよい。この場合も、異なる材料が接する界面で音響インピーダンスの差（Ｇａｐ）があるため、散乱波Ｕ１が発生するので、上記各実施形態の構成が有効である。上記各実施形態に係る超音波検査装置Ｚは、超音波欠陥映像装置を前提としているが、非接触インライン内部欠陥検査装置に適用されてもよい。 In each of the above embodiments, an example is described in which the defect D is a cavity, but the defect D may also be a foreign object containing a material different from the material of the object E to be inspected. In this case, too, there is a difference (Gap) in acoustic impedance at the interface where the different materials come into contact, so scattered waves U1 are generated, and the configurations of the above embodiments are effective. The ultrasonic inspection device Z according to each of the above embodiments is premised on an ultrasonic defect imaging device, but may also be applied to a non-contact in-line internal defect inspection device.
　本開示は前記した実施形態に限定されるものではなく、様々な変形例が含まれる。例えば、前記した実施形態は本開示を分かりやすく説明するために詳細に説明したものであり、必ずしも説明したすべての構成を有するものに限定されるものではない。また、ある実施形態の構成の一部を他の実施形態の構成に置き換えることが可能であり、ある実施形態の構成に他の実施形態の構成を加えることも可能である。また、各実施形態の構成の一部について、他の構成の追加・削除・置換をすることが可能である。 The present disclosure is not limited to the above-described embodiments, but includes various modified examples. For example, the above-described embodiments have been described in detail to clearly explain the present disclosure, and are not necessarily limited to those having all of the configurations described. In addition, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.
　また、各実施形態において、制御線及び情報線は説明上必要と考えられるものを示しており、製品上必ずしもすべての制御線及び情報線を示しているとは限らない。実際には、ほとんどすべての構成が相互に接続されていると考えてよい。 In addition, in each embodiment, the control lines and information lines shown are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it can be considered that almost all components are interconnected.
１　走査計測装置
１００　送信プローブ
１０１　筐体
１０２　試料台
１０２１　載置面
１０３　送信プローブ走査部
１０４　受信プローブ走査部
１０５　偏心距離調整部
１０６　設置角度調整部
１１０　送信プローブ
１１１　振動子
１１２　バッキング
１１３　整合層
１１４　探触子面
１１５　送信プローブ筐体
１１６　コネクタ
１１７　リード線
１１８　リード線
１２０　受信プローブ
１２１　受信プローブ
１４０　受信プローブ
２　制御装置
２０１　データ処理部
２０２　駆動部
２０３　位置計測部
２０４　スキャンコントローラ
２１０　送信系統
２１１　波形発生器
２１２　信号アンプ
２１３　送信周波数設定部
２２０　受信系統
２２２　信号アンプ
２２３　表示部
２２４　受付部
２３０　周波数変換部
２３１　信号強度算出部
２４０　フィルタ部
２４１　周波数成分変換部
２４２　周波数選択部
２４３　周波数成分逆変換部
２４４　検出部
２４５　決定部
２５０　信号処理部
２５１　メモリ
２５２　ＣＰＵ
２５３　記憶装置
２５４　通信装置
２５５　Ｉ／Ｆ
２６１　記憶部
２６１ａ　データベース
２６２　画像化部
２６３　表示部
２７０　操作画面
２７１　周波数スペクトル
２７２　入力部
２７３　画像
２７４　更新ボタン
２７５　入力部
２９１　更新部
３　表示装置
４　入力装置
ＡＸ　受信音軸
ＡＸ１　送信音軸
ＡＸ２　受信音軸
ＢＷ　ビーム幅
Ｃ２　コーン
Ｃ３　コーン
Ｄ　欠陥部
Ｅ　被検査体
Ｆ　流体
Ｇ　気体
Ｌ　偏心距離
Ｎ　健全部
Ｐ１　焦点
Ｐ１１　交点
Ｐ１２　交点
Ｐ２　焦点
Ｒ１　焦点距離
Ｒ２　焦点距離
Ｔ１　ビーム入射面積
Ｔ２　ビーム入射面積
Ｕ　超音波ビーム
Ｕ１　散乱波
Ｕ２　超音波ビーム
Ｕ３　直達波
Ｗ　液体
Ｗ１　基本波帯
Ｗ２　周波数範囲
Ｗ３　裾野成分
Ｚ　超音波検査装置 1 Scanning measurement device 100 Transmitting probe 101 Housing 102 Sample stage 1021 Mounting surface 103 Transmitting probe scanning section 104 Receiving probe scanning section 105 Eccentricity distance adjustment section 106 Installation angle adjustment section 110 Transmitting probe 111 Transducer 112 Backing 113 Matching layer 114 Probe surface 115 Transmitting probe housing 116 Connector 117 Lead wire 118 Lead wire 120 Receiving probe 121 Receiving probe 140 Receiving probe 2 Control device 201 Data processing section 202 Driving section 203 Position measurement section 204 Scan controller 210 Transmission system 211 Waveform generator 212 Signal amplifier 213 Transmission frequency setting section 220 Receiving system 222 Signal amplifier 223 Display section 224 Reception section 230 Frequency conversion section 231 Signal strength calculation section 240 Filter section 241 Frequency component transform unit 242 Frequency selection unit 243 Frequency component inverse transform unit 244 Detection unit 245 Determination unit 250 Signal processing unit 251 Memory 252 CPU
253 Storage device 254 Communication device 255 I/F
261 Storage unit 261a Database 262 Imaging unit 263 Display unit 270 Operation screen 271 Frequency spectrum 272 Input unit 273 Image 274 Update button 275 Input unit 291 Update unit 3 Display device 4 Input device AX Receiving sound axis AX1 Transmitting sound axis AX2 Receiving sound axis BW Beam width C2 Cone C3 Cone D Defective part E Inspected object F Fluid G Gas L Eccentricity distance N Healthy part P1 Focus P11 Intersection P12 Intersection P2 Focus R1 Focal length R2 Focal length T1 Beam incidence area T2 Beam incidence area U Ultrasonic beam U1 Scattered wave U2 Ultrasonic beam U3 Direct wave W Liquid W1 Fundamental wave band W2 Frequency range W3 Base component Z Ultrasonic inspection device

Claims (29)

  1. 　気体を介して被検査体に超音波ビームを入射することにより前記被検査体の検査を行う超音波検査装置であって、
    　前記被検査体への前記超音波ビームの走査及び計測を行う走査計測装置と、前記走査計測装置の駆動を制御する制御装置とを備え、
    　前記走査計測装置は、
    　前記超音波ビームを放出する送信プローブと、前記被検査体に関して前記送信プローブの反対側に設置された、前記超音波ビームを受信する受信プローブとを備え、
    　前記送信プローブは、波数が２以上の波束で構成される繰り返し波束の電圧波形を印加されて超音波ビームを放出し、
    　前記送信プローブの共振周波数からずらした励起周波数で前記送信プローブを駆動し、
    　前記制御装置は信号処理部を備え、
    　前記信号処理部は、前記受信プローブの受信信号のうちの少なくとも最大強度周波数成分を低減するフィルタ部を備え、
    　前記フィルタ部は、前記最大強度周波数成分を含む基本波帯のうちの前記最大強度周波数成分以外の裾野成分を検出する超音波検査装置。     1. An ultrasonic inspection apparatus for inspecting an object to be inspected by irradiating an ultrasonic beam onto the object to be inspected through a gas, comprising:
    a scanning and measuring device that scans and measures the object to be inspected with the ultrasonic beam; and a control device that controls the driving of the scanning and measuring device,
    The scanning measurement device is
    a transmitting probe that emits the ultrasonic beam, and a receiving probe that receives the ultrasonic beam and is disposed on the opposite side of the transmitting probe with respect to the object to be inspected,
    the transmitting probe emits an ultrasonic beam in response to a voltage waveform of a repeating wave packet having a wave packet with a wave number of two or more;
    Driving the transmitting probe at an excitation frequency shifted from a resonant frequency of the transmitting probe;
    The control device includes a signal processor.
    the signal processing unit includes a filter unit that reduces at least a maximum intensity frequency component of the reception signal of the receiving probe;
    The filter unit detects frequency components other than the maximum intensity frequency component in a fundamental wave band that includes the maximum intensity frequency component.
  2. 　前記受信プローブの焦点距離は、前記送信プローブの焦点距離よりも長いことを特徴とする請求項１に記載の超音波検査装置。 The ultrasonic inspection device according to claim 1, characterized in that the focal length of the receiving probe is longer than the focal length of the transmitting probe.
  3. 　前記受信プローブは、非収束型の受信プローブであることを特徴とする請求項１に記載の超音波検査装置。 The ultrasonic inspection device according to claim 1, characterized in that the receiving probe is a non-converged type receiving probe.
  4. 　前記基本波帯の周波数スペクトルの半値全幅は、前記最大強度周波数成分に対応した周波数である最大成分周波数の５０％以下であることを特徴とする請求項１に記載の超音波検査装置。 The ultrasonic inspection device of claim 1, characterized in that the full width at half maximum of the frequency spectrum of the fundamental wave band is 50% or less of the maximum component frequency, which is the frequency corresponding to the maximum intensity frequency component.
  5. 　前記フィルタ部は、
    　前記受信プローブの受信信号を周波数成分に変換する周波数成分変換部と、
    　前記最大強度周波数成分を含む周波数帯の除去により前記裾野成分を選択する周波数選択部と、
    　を備えることを特徴とする請求項１に記載の超音波検査装置。     The filter unit includes:
    a frequency component converter for converting a received signal of the receiving probe into a frequency component;
    a frequency selection unit that selects the base component by removing a frequency band including the maximum intensity frequency component;
    2. The ultrasonic inspection apparatus according to claim 1, further comprising:
  6. 　前記励起周波数は、前記基本波帯の周波数範囲に設定されることを特徴とする請求項１に記載の超音波検査装置。 The ultrasonic inspection device according to claim 1, characterized in that the excitation frequency is set within the frequency range of the fundamental wave band.
  7. 　前記波束の波数は３０以下であることを特徴とする請求項１に記載の超音波検査装置。 The ultrasonic inspection device according to claim 1, characterized in that the wave number of the wave packet is 30 or less.
  8. 　前記励起周波数と前記共振周波数との差の絶対値は、前記最大強度周波数成分に対応した周波数である最大成分周波数の２５％以下であることを特徴とする請求項１に記載の超音波検査装置。 The ultrasonic inspection device of claim 1, characterized in that the absolute value of the difference between the excitation frequency and the resonant frequency is 25% or less of the maximum component frequency, which is the frequency corresponding to the maximum intensity frequency component.
  9. 　前記励起周波数と前記共振周波数との差の絶対値は、前記最大強度周波数成分に対応した周波数である最大成分周波数の１５％以下であることを特徴とする請求項１に記載の超音波検査装置。 The ultrasonic inspection device of claim 1, characterized in that the absolute value of the difference between the excitation frequency and the resonant frequency is 15% or less of the maximum component frequency, which is the frequency corresponding to the maximum intensity frequency component.
  10. 　前記フィルタ部が検出する周波数は、前記最大強度周波数成分に対応した周波数である最大成分周波数をｆｍとすると、（ｆｍ±０．２５ｆｍ）の範囲の周波数を含むことを特徴とする請求項１に記載の超音波検査装置。 The ultrasonic inspection device of claim 1, characterized in that the frequencies detected by the filter unit include frequencies in the range of (fm ± 0.25 fm), where fm is the maximum component frequency, which is the frequency corresponding to the maximum intensity frequency component.
  11. 　気体を介して被検査体に超音波ビームを入射することにより前記被検査体の検査を行う超音波検査装置であって、
    　前記被検査体への前記超音波ビームの走査及び計測を行う走査計測装置と、前記走査計測装置の駆動を制御する制御装置とを備え、
    　前記走査計測装置は、
    　前記超音波ビームを放出する送信プローブと、前記超音波ビームを受信する受信プローブとを備え、
    　前記送信プローブの共振周波数からずらした励起周波数で前記送信プローブを駆動し、
    　前記制御装置は信号処理部を備え、
    　前記信号処理部は、
    　　前記受信プローブの受信信号を周波数成分に変換する周波数変換部と、
    　　変換された前記周波数成分のうち、周波数パラメータにより指定された周波数成分の部分を用いて、欠陥位置を示す画像を生成する画像化部と、
    　　前記被検査体における欠陥部の検出精度に影響を与える情報と、前記周波数パラメータとを対応付けたデータベースと、
    　　表示装置への表示を行う表示部と、
    　を備え、
    　前記表示部は、前記表示装置に、前記被検査体における欠陥部の検出精度に影響を与える情報を受け付ける入力部を表示する
    　超音波検査装置。     1. An ultrasonic inspection apparatus for inspecting an object to be inspected by irradiating an ultrasonic beam onto the object to be inspected through a gas, comprising:
    a scanning and measuring device that scans and measures the object to be inspected with the ultrasonic beam; and a control device that controls the driving of the scanning and measuring device,
    The scanning measurement device is
    a transmitting probe for emitting the ultrasonic beam and a receiving probe for receiving the ultrasonic beam,
    Driving the transmitting probe at an excitation frequency shifted from a resonant frequency of the transmitting probe;
    The control device includes a signal processor.
    The signal processing unit includes:
    a frequency conversion unit that converts a received signal of the receiving probe into a frequency component;
    an imaging unit that generates an image showing a defect position by using a portion of the converted frequency components that is designated by a frequency parameter;
    a database in which information that affects the accuracy of detecting defects in the object to be inspected is associated with the frequency parameters;
    A display unit that displays information on a display device;
    Equipped with
    The display unit displays, on the display device, an input unit that receives information that affects the accuracy of detecting a defect in the object to be inspected.
  12. 　前記データベースは、前記励起周波数の情報を含むことを特徴とする請求項１１に記載の超音波検査装置。 The ultrasonic inspection device according to claim 11, characterized in that the database includes information on the excitation frequency.
  13. 　気体を介して被検査体に超音波ビームを入射することにより前記被検査体の検査を行う超音波検査方法であって、
    　送信プローブの共振周波数からずらした励起周波数で、前記送信プローブを励起して超音波ビームを放出する放出ステップと、
    　前記超音波ビームを受信する受信ステップと、
    　前記受信ステップで受信した前記超音波ビームの信号の最大強度周波数成分を低減するフィルタ処理ステップと、
    　前記超音波ビームの信号における基本波帯の裾野成分を検出する信号強度算出ステップとを含む
    　ことを特徴とする超音波検査方法。     1. An ultrasonic inspection method for inspecting an object to be inspected by irradiating an ultrasonic beam onto the object to be inspected through a gas, comprising:
    an emission step of exciting the transmitting probe at an excitation frequency shifted from a resonant frequency of the transmitting probe to emit an ultrasonic beam;
    a receiving step of receiving the ultrasonic beam;
    a filtering step of reducing a maximum intensity frequency component of the signal of the ultrasonic beam received in the receiving step;
    and a signal intensity calculation step of detecting a base component of a fundamental wave band in the signal of the ultrasonic beam.
  14. 　気体を介して被検査体に超音波ビームを入射することにより前記被検査体の検査を行う超音波検査装置であって、
    　前記被検査体への前記超音波ビームの走査及び計測を行う走査計測装置と、前記走査計測装置の駆動を制御する制御装置とを備え、
    　前記走査計測装置は、
    　前記超音波ビームを放出する送信プローブと、前記被検査体に関して前記送信プローブの反対側に設置された、前記超音波ビームを受信する受信プローブとを備え、
    　前記送信プローブは、波数が２以上の波束で構成される繰り返し波束の電圧波形を印加されて超音波ビームを放出し、
    　前記制御装置は信号処理部を備え、
    　前記信号処理部は、前記受信プローブの受信信号のうちの少なくとも最大強度周波数成分を低減するフィルタ部を備え、
    　前記フィルタ部は、前記最大強度周波数成分を含む基本波帯のうちの前記最大強度周波数成分以外の裾野成分を検出する超音波検査装置。     1. An ultrasonic inspection apparatus for inspecting an object to be inspected by irradiating an ultrasonic beam onto the object to be inspected through a gas, comprising:
    a scanning and measuring device that scans and measures the object to be inspected with the ultrasonic beam; and a control device that controls the driving of the scanning and measuring device,
    The scanning measurement device is
    a transmitting probe that emits the ultrasonic beam, and a receiving probe that receives the ultrasonic beam and is disposed on the opposite side of the transmitting probe with respect to the object to be inspected,
    the transmitting probe emits an ultrasonic beam in response to a voltage waveform of a repeating wave packet having a wave packet with a wave number of two or more;
    The control device includes a signal processor.
    the signal processing unit includes a filter unit that reduces at least a maximum intensity frequency component of the reception signal of the receiving probe;
    The filter unit detects frequency components other than the maximum intensity frequency component in a fundamental wave band that includes the maximum intensity frequency component.
  15. 　前記受信プローブの焦点距離は、前記送信プローブの焦点距離よりも長いことを特徴とする請求項１４に記載の超音波検査装置。 The ultrasonic inspection device according to claim 14, characterized in that the focal length of the receiving probe is longer than the focal length of the transmitting probe.
  16. 　前記受信プローブは、非収束型のプローブであることを特徴とする請求項１４に記載の超音波検査装置。 The ultrasonic inspection device according to claim 14, characterized in that the receiving probe is a non-focused probe.
  17. 　前記波束の波数は３以上であることを特徴とする請求項１４に記載の超音波検査装置。 The ultrasonic inspection device according to claim 14, characterized in that the wave number of the wave packet is 3 or more.
  18. 　前記基本波帯の周波数スペクトルの半値全幅は、前記最大強度周波数成分に対応した周波数である最大成分周波数の５０％以下であることを特徴とする請求項１４に記載の超音波検査装置。 The ultrasonic inspection device of claim 14, characterized in that the full width at half maximum of the frequency spectrum of the fundamental wave band is 50% or less of the maximum component frequency, which is the frequency corresponding to the maximum intensity frequency component.
  19. 　前記送信プローブは、狭帯域のプローブであることを特徴とする請求項１４に記載の超音波検査装置。 The ultrasonic inspection device according to claim 14, characterized in that the transmitting probe is a narrowband probe.
  20. 　前記フィルタ部は、帯域遮断フィルタを含むことを特徴とする請求項１４に記載の超音波検査装置。 The ultrasonic inspection device according to claim 14, characterized in that the filter section includes a band-stop filter.
  21. 　前記フィルタ部は、低域通過フィルタを含むことを特徴とする請求項１４に記載の超音波検査装置。 The ultrasonic inspection device according to claim 14, characterized in that the filter section includes a low-pass filter.
  22. 　前記フィルタ部は、
    　前記受信プローブの受信信号を周波数成分に変換する周波数成分変換部と、
    　前記最大強度周波数成分を含む周波数帯の除去により前記裾野成分を選択する周波数選択部と、
    　を備えることを特徴とする請求項１４に記載の超音波検査装置。     The filter unit includes:
    a frequency component converter for converting a received signal of the receiving probe into a frequency component;
    a frequency selection unit that selects the base component by removing a frequency band including the maximum intensity frequency component;
    15. The ultrasonic inspection apparatus according to claim 14, further comprising:
  23. 　前記フィルタ部は、
    　　欠陥部の位置が既知の試料での健全部及び欠陥部に前記超音波ビームを照射することで得られた、周波数と信号強度との関係において、前記基本波帯のうちの異なる複数の前記裾野成分を検出する検出部と、
    　検出した複数の前記裾野成分同士の比較により、どの前記裾野成分を使用するかを決定する決定部とを備えることを特徴とする請求項１４に記載の超音波検査装置。     The filter unit includes:
    a detection unit that detects a plurality of different base components of the fundamental wave band in a relationship between frequency and signal intensity obtained by irradiating the ultrasonic beam to a healthy portion and a defective portion of a sample having a known position of the defective portion;
    15. The ultrasonic inspection device according to claim 14, further comprising a determination unit that determines which of the detected plurality of the footing components is to be used by comparing the detected plurality of footing components with each other.
  24. 　前記送信プローブの音軸と前記受信プローブの音軸との間の距離がゼロより大きいことを特徴とする請求項１４に記載の超音波検査装置。 The ultrasonic inspection device of claim 14, characterized in that the distance between the sound axis of the transmitting probe and the sound axis of the receiving probe is greater than zero.
  25. 　前記送信プローブの音軸と前記受信プローブの音軸との間の距離がゼロであることを特徴とする請求項１４に記載の超音波検査装置。 The ultrasonic inspection device according to claim 14, characterized in that the distance between the sound axis of the transmitting probe and the sound axis of the receiving probe is zero.
  26. 　気体を介して被検査体に超音波ビームを入射することにより前記被検査体の検査を行う超音波検査方法であって、
    　送信プローブから波数が２以上の波束で構成される繰り返し波束の超音波ビームを放出する放出ステップと、
    　前記超音波ビームを受信する受信ステップと、
    　前記受信ステップで受信した前記超音波ビームの信号の最大強度周波数成分を低減するフィルタ処理ステップと、
    　前記超音波ビームの信号の基本波帯の裾野成分を検出する信号強度算出ステップとを含む
    　ことを特徴とする超音波検査方法。     1. An ultrasonic inspection method for inspecting an object to be inspected by irradiating an ultrasonic beam onto the object to be inspected through a gas, comprising:
    An emission step of emitting an ultrasonic beam of a repetitive wave packet composed of a wave packet having a wave number of two or more from a transmission probe;
    a receiving step of receiving the ultrasonic beam;
    a filtering step of reducing a maximum intensity frequency component of the signal of the ultrasonic beam received in the receiving step;
    and a signal intensity calculation step of detecting a base component of a fundamental wave band of the ultrasonic beam signal.
  27. 　前記フィルタ部が検出する周波数は、前記最大強度周波数成分に対応した周波数である最大成分周波数をｆｍとすると、（ｆｍ±０．２５ｆｍ）の範囲の周波数を含むことを特徴とする請求項１４に記載の超音波検査装置。 The ultrasonic inspection device according to claim 14, characterized in that the frequencies detected by the filter unit include frequencies in the range of (fm ± 0.25 fm), where fm is the maximum component frequency, which is the frequency corresponding to the maximum intensity frequency component.
  28. 　前記フィルタ部が検出する周波数は、前記最大強度周波数成分に対応した周波数である最大成分周波数をｆｍとすると、（ｆｍ±０．１５ｆｍ）の範囲の周波数を含むことを特徴とする請求項１４に記載の超音波検査装置。 The ultrasonic inspection device according to claim 14, characterized in that the frequencies detected by the filter unit include frequencies in the range of (fm ± 0.15 fm), where fm is the maximum component frequency, which is the frequency corresponding to the maximum intensity frequency component.
  29. 　前記送信プローブの送信音軸が、前記被検査体を載置する試料台の載置面に対して垂直になるように、前記送信プローブが設置されたことを特徴とする請求項１４に記載の超音波検査装置。 The ultrasonic inspection device according to claim 14, characterized in that the transmitting probe is installed so that the transmission sound axis of the transmitting probe is perpendicular to the mounting surface of the sample stage on which the object to be inspected is placed.
PCT/JP2024/000169 2023-02-24 2024-01-09 Ultrasonic inspection device and ultrasonic inspection method WO2024176635A1 (en)

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JPH07190995A (en) * 1993-12-27 1995-07-28 Hitachi Constr Mach Co Ltd Method and device for detecting welding defect by ultrasonic wave
JPH10295694A (en) * 1996-12-30 1998-11-10 General Electric Co <Ge> Operation method for ultrasonic imaging system
JPH11183451A (en) * 1997-12-25 1999-07-09 Mitsubishi Heavy Ind Ltd Divided-spectrum processing method
JP2021032810A (en) * 2019-08-28 2021-03-01 株式会社日立パワーソリューションズ Ultrasonic inspection system and ultrasonic inspection method
JP2022000609A (en) * 2020-06-19 2022-01-04 株式会社日立パワーソリューションズ Ultrasonic inspection device and ultrasonic inspection method
JP2022038664A (en) * 2020-08-27 2022-03-10 株式会社日立パワーソリューションズ Ultrasonic inspection device and ultrasonic inspection method
WO2023058292A1 (en) * 2021-10-04 2023-04-13 株式会社日立パワーソリューションズ Ultrasonic inspection apparatus and ultrasonic inspection method
JP7355899B1 (en) * 2022-07-28 2023-10-03 株式会社日立パワーソリューションズ Ultrasonic inspection equipment and ultrasonic inspection method

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH07190995A (en) * 1993-12-27 1995-07-28 Hitachi Constr Mach Co Ltd Method and device for detecting welding defect by ultrasonic wave
JPH10295694A (en) * 1996-12-30 1998-11-10 General Electric Co <Ge> Operation method for ultrasonic imaging system
JPH11183451A (en) * 1997-12-25 1999-07-09 Mitsubishi Heavy Ind Ltd Divided-spectrum processing method
JP2021032810A (en) * 2019-08-28 2021-03-01 株式会社日立パワーソリューションズ Ultrasonic inspection system and ultrasonic inspection method
JP2022000609A (en) * 2020-06-19 2022-01-04 株式会社日立パワーソリューションズ Ultrasonic inspection device and ultrasonic inspection method
JP2022038664A (en) * 2020-08-27 2022-03-10 株式会社日立パワーソリューションズ Ultrasonic inspection device and ultrasonic inspection method
WO2023058292A1 (en) * 2021-10-04 2023-04-13 株式会社日立パワーソリューションズ Ultrasonic inspection apparatus and ultrasonic inspection method
JP7355899B1 (en) * 2022-07-28 2023-10-03 株式会社日立パワーソリューションズ Ultrasonic inspection equipment and ultrasonic inspection method

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