JP2017116509A - Confocal displacement meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a confocal displacement meter that is resistant to an influence of a surrounding environment, and can suppress reduction in measurement accuracy arising from a temperature rising of a projection light source.SOLUTION: A confocal displacement meter comprises: a projection light source that generates detection light composed of light having a plurality of wavelengths; a confocal optical system that includes an objective lens ejecting the detection light toward a detection object, and generates a longitudinal chromatic aberration in the detection light; a spectrometer that spectroscopically splits reflection light passing through the confocal optical system after reflected by the detection object; an image sensor 26 that receives spectroscopically split reflection light to generate a light reception signal; received light waveform acquisition means 101 that acquires a received light waveform composed of a distribution of light reception intensity regarding a distance; a characteristic part position acquisition means 108 that specifies a peak position of a characteristic part on the basis of the received light waveform; correction-amount calculation means 110 that compares the specified peak position with a reference position to obtain an amount of correction; and distance calculation means 104 that obtains a distance to the detection object on the basis of the received light waveform and the amount of correction.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a confocal displacement meter, and more particularly, to an improvement of a confocal displacement meter that measures a distance to a detection target using longitudinal chromatic aberration by a confocal optical system.

  The confocal displacement meter has a confocal principle in which the light received by the reflected light from the imaging surface on which the image of the light source for projection is focused, and a color shift in the optical axis direction occurs in the image of the light source for projection. This is an optical distance measuring device that measures the distance to the workpiece using the phenomenon of axial chromatic aberration (for example, Patent Documents 1 to 3). For example, the confocal displacement meter includes a light source for projection, a confocal optical system, a spectroscope, and an image sensor.

  The light source for projection generates detection light composed of light having a plurality of wavelengths. The confocal optical system includes an objective lens that emits detection light toward the workpiece, and causes axial chromatic aberration in an image of the light source for projection by the detection light. The spectroscope splits the reflected light that has been reflected by the workpiece and then passed through the confocal optical system. The image sensor includes a plurality of light receiving elements that receive the reflected reflected light to generate a light reception signal, and a plurality of capacitance elements that accumulate charges according to the amount of light received based on the light reception signal. Each light receiving element is arranged in a straight line.

  The position of the image plane varies depending on the wavelength due to axial chromatic aberration. For this reason, the reflected light received by the image sensor is narrowed down to the wavelength component reflected and imaged on the workpiece. The distance to the workpiece is measured by acquiring a received light waveform including a distribution of received light intensity with respect to the distance based on the received light signal, and specifying the peak position. By this distance measurement, it is possible to detect the amount of movement of the workpiece, the height of the workpiece, and the like. Moreover, the thickness of a transparent body etc. can also be detected only by acquiring one light reception waveform. According to such a confocal displacement meter, it is difficult to be affected by the material, color, and tilt of the workpiece during distance measurement.

  The conventional confocal displacement meter has a problem that the light quantity of the light source for projection is small and the work that can be measured is limited. For example, when a workpiece with a low surface reflectance or a workpiece with a mirror surface is detected from an oblique direction, if the amount of light emitted is small, sufficient light reception intensity cannot be obtained, and the signal waveform is buried in noise. It becomes difficult to specify the peak position.

JP 2013-130580 A JP 2014-115242 A JP 2005-322996 A

  As described above, the conventional confocal displacement meter has a small amount of light from the light source for projection. In view of this, it is conceivable to increase the output of the light source for projection so as to cope with various works. However, if the output of the light source for projection is increased, there is a problem that the temperature rise of the light source for projection causes a shift in the positional relationship between the spectroscope and the image sensor. In particular, in a confocal displacement meter in which the spectroscope and the image sensor are arranged in a common housing, the relative positional relationship between the spectroscope and the image sensor is shifted due to expansion of the housing due to conduction heat from the light source for projection. May occur, and the measurement accuracy of the distance may be reduced.

  In order to suppress the decrease in accuracy due to such high output of the light source for projection, for example, a temperature sensor is arranged around the light source for projection and the spectroscope, and the correspondence between the ambient temperature and the positional deviation It is conceivable that a temperature correction table indicating the above is created in advance and the measured value is corrected according to the ambient temperature measured by the temperature sensor. However, there is a problem that the actual positional deviation between the spectroscope and the image sensor greatly differs from the value specified in the temperature correction table due to the influence of the environment around the place where the housing is installed.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a confocal displacement meter that can cope with various detection objects and can suppress a decrease in measurement accuracy. In particular, it is an object of the present invention to provide a confocal displacement meter that is hardly affected by the surrounding environment and can suppress a decrease in measurement accuracy caused by a temperature rise of a light source for light projection.

  A confocal displacement meter according to a first aspect of the present invention has a light source for projection that generates detection light composed of light having a plurality of wavelengths, and an objective lens that emits the detection light toward a detection target. A confocal optical system that causes axial chromatic aberration in the detection light, a spectroscope that separates the reflected light that has been reflected by the detection object and then passed through the confocal optical system, and two or more light receiving elements An image sensor that receives the reflected reflected light and generates a light reception signal, a light reception waveform acquisition unit that acquires a light reception waveform including a distribution of light reception intensity with respect to a distance based on the light reception signal, and the light reception Based on the waveform, the characteristic portion position acquisition means for specifying the peak position of the characteristic portion, the reference position storage means for holding the peak position of the characteristic portion obtained from the light reception waveform acquired in advance as the reference position, and the specified Up The peak position is compared with the reference position, comprising a correction amount calculating means for calculating a correction amount, based on the receiver frequency and the correction amount, and a distance calculation means for calculating a distance to the detection object.

  According to such a configuration, since the correction amount is determined by comparing the peak position of the characteristic portion with the reference position obtained from the received light waveform obtained in advance, the temperature of the light source for light projection is hardly affected by the surrounding environment. A decrease in measurement accuracy due to an increase can be suppressed.

  In the confocal displacement meter according to the second aspect of the present invention, in addition to the above configuration, the light source for projection is excited by the excitation light generating means for generating excitation light and the excitation light, and is different from the excitation light. A phosphor that emits fluorescence of a wavelength, and the detection light is a mixed light of the excitation light transmitted through the phosphor and the fluorescence emitted from the phosphor; The peak position is specified using the waveform region corresponding to the excitation light as a characteristic part, and the distance calculation means obtains the distance to the detection object based on the peak position of the waveform region corresponding to the fluorescence. Composed. According to such a configuration, since the waveform region corresponding to the excitation light is formed apart from the fluorescence waveform region used for distance measurement, it is easy to specify the peak position.

  The confocal displacement meter according to the third aspect of the present invention is configured such that, in addition to the above configuration, the excitation light generation means is a laser light source that generates laser light as the excitation light. According to such a configuration, since the laser light is monochromatic light and forms a sharp light receiving waveform, it is easy to specify the peak position of the waveform region corresponding to the excitation light.

  In the confocal displacement meter according to the fourth aspect of the present invention, in addition to the above configuration, the spectroscope uses a diffraction grating, and the image sensor uses zero-order diffraction light and first-order diffraction by the diffraction grating. The light receiving signal is simultaneously received to generate the light reception signal, the characteristic part position acquisition unit specifies a peak position with the waveform region corresponding to the 0th-order diffracted light as a characteristic part, and the distance calculation unit includes the 1 Based on the peak position of the waveform region corresponding to the next diffracted light, the distance to the detection target is obtained.

  According to such a configuration, since the waveform region corresponding to the 0th-order diffracted light is formed apart from the waveform region of the 1st-order diffracted light used for distance measurement, it is easy to specify the peak position. Further, since the 0th-order diffracted light has a larger amount of light than other orders of diffracted light, the peak position can be specified without being affected by noise.

  In the confocal displacement meter according to the fifth aspect of the present invention, in addition to the above configuration, the spectroscope uses a diffraction grating, and the image sensor includes first-order diffracted light and second-order or higher-order light by the diffraction grating. The diffracted light is simultaneously received to generate the received light signal, and the feature portion position acquisition unit specifies a peak position using the waveform regions corresponding to the first-order diffracted light and the second-order or higher-order diffracted light as feature portions. The distance calculating means is configured to determine the distance to the detection object based on the peak position of the waveform region corresponding to the first-order diffracted light.

  A confocal displacement meter according to a sixth aspect of the present invention, in addition to the above configuration, the received light waveform includes two or more received light intensity data each associated with a pixel position on the image sensor, and calculates the correction amount. Of the first-order diffracted light, the means is a peak position of the waveform region corresponding to the excitation light and a peak position of the waveform region corresponding to the zero-order diffracted light or a waveform region corresponding to second-order or higher-order diffracted light. By comparing each peak position with a corresponding reference position, an offset or span correction amount of a linear function used when converting the pixel position on the image sensor into the distance to the detection target is obtained. Composed.

  When the spectroscope and the image sensor are relatively displaced in the optical axis direction, the span and offset of the linear function used when converting the pixel position on the image sensor into the distance to the detection target changes. Further, if the spectroscope and the image sensor are relatively displaced in a direction crossing the optical axis, the offset of the linear function changes. It is possible to suppress a decrease in measurement accuracy due to such a positional relationship shift.

  A confocal displacement meter according to a seventh aspect of the present invention includes, in addition to the above configuration, a monitor light receiving element that receives a part of the reflected light and generates a monitor signal, and the image sensor based on the monitor signal. And a received light amount control means for controlling the received light amount. According to such a configuration, even when the light source for projecting light has a high output, saturation of the received light amount in the image sensor can be suppressed by automatically adjusting the received light amount.

  A confocal displacement meter according to an eighth aspect of the present invention includes a head housing in which the confocal optical system is arranged, a light source for projection, the spectroscope, and the image sensor in addition to the above configuration. A housing and an optical fiber cable that transmits the detection light and the reflected light between the head housing and the controller housing are configured. According to such a configuration, even if the relative positional relationship between the spectroscope and the image sensor is shifted due to the expansion of the controller housing due to the conduction heat from the light source for light projection, the measurement accuracy decreases. Can be suppressed.

  A confocal displacement meter according to a ninth aspect of the present invention is configured such that, in addition to the above configuration, the characteristic portion position acquisition unit specifies the pixel position having the maximum received light intensity or the barycentric position of the received light waveform as the peak position. Is done.

  ADVANTAGE OF THE INVENTION According to this invention, the confocal displacement meter which can respond to various detection target objects and can suppress the fall of a measurement precision can be provided. In particular, since the correction amount is determined by comparing the peak position of the characteristic part with the reference position acquired in advance, it is difficult to be affected by the surrounding environment and suppresses the decrease in measurement accuracy caused by the temperature rise of the light source for projection Can provide a confocal displacement meter.

It is the system figure which showed one structural example of the confocal displacement meter 1 by embodiment of this invention. It is sectional drawing which showed typically the structural example of the head unit 10 of FIG. FIG. 2 is a block diagram illustrating a configuration example of a controller 20 in FIG. 1. It is the figure which showed the structural example of the light source unit 21 for light projection of FIG. FIG. 4 is a diagram illustrating a configuration example of an image sensor 26 in FIG. 3. FIG. 4 is a diagram illustrating an example of the operation of the measurement control unit 27 in FIG. 3, in which received light waveforms 4 and 5 are illustrated. FIG. 4 is a block diagram illustrating a configuration example of a measurement control unit 27 in FIG. 3. It is an explanatory view schematically showing that span a _SP and the offset b _OS conversion formula is changed by relative displacement Δy of the spectroscope 24 and the image sensor 26. It is sectional drawing which showed typically the other structural example of the light source unit 21 for light projection. FIG. 6 is a cross-sectional view showing another configuration example of the head unit 10. It is the figure which showed the other structural example of the controller 20, and the transmissive | pervious spectroscopic optical system is shown. It is the figure which showed the other structural example of the confocal displacement meter.

  Embodiments of the present invention will be described below with reference to the drawings. In this specification, for the sake of convenience, the direction of the optical axis of the detection light DL is described as the vertical direction, but the posture of the confocal displacement meter 1 and the head unit 10 according to the present invention is not limited.

<Confocal displacement meter 1>
FIG. 1 is a system diagram showing a configuration example of a confocal displacement meter 1 according to an embodiment of the present invention. The confocal displacement meter 1 includes an optical fiber cable 2, a head unit 10 and a controller 20. The confocal displacement meter 1 receives reflected light from the work W when the detection light DL is emitted from the head unit 10 and is a distance to the work W. Is an optical distance measuring device for measuring

  The workpiece W is a detection target. The workpiece W is a sheet-like member in which a high reflectance area HA having a high reflectance and a low reflectance area LA having a low reflectance are alternately and repeatedly formed. To do. For example, the workpiece W has a glass plate as a base material, and a metal film such as chromium is formed in a slit shape on the surface of the glass plate.

  The head unit 10 and the controller 20 are connected via an optical fiber cable 2 that transmits the detection light DL. A PC (personal computer) 3 is connected to the controller 20. The PC 3 sets measurement conditions and the like for the controller 20, acquires measurement results and the like from the controller 20, and displays them on the screen.

  The head unit 10 is a light projecting / receiving unit that emits the detection light DL made of white light toward the work W and the reflected light from the work W enters. The optical fiber cable 2 is a transmission medium that transmits the detection light DL, and includes a thin wire core extending in the longitudinal direction and a clad surrounding the core. The controller 20 is a control unit that controls light projection and reception and calculates the distance to the workpiece W based on the reflected light from the workpiece W.

  Since the detection light DL and the reflected light are transmitted between the controller 20 and the head unit 10 via the optical fiber cable 2, the head unit 10 can be reduced in size. Further, the head unit 10 can be easily installed even at a location away from the controller 20.

<Head unit 10>
FIG. 2 is a cross-sectional view schematically showing a configuration example of the head unit 10 of FIG. 1, and shows a cut surface when the head unit 10 is cut by a vertical plane including the optical axis of the detection light DL. . The head unit 10 includes a confocal optical system 11 including a fiber end 2a, a collimating lens 13, and an objective lens 14, and a head housing 12 in which the confocal optical system 11 is disposed. The head housing 12 is a covered cylindrical barrel.

  The fiber end 2 a is an end of the optical fiber cable 2 on the head unit side, and functions as a pinhole of the confocal optical system 11. Specifically, the clad of the optical fiber cable 2 acts as a light shielding member that shields the return light to the optical fiber cable 2, and the end face of the core acts as an opening of a pinhole. The confocal effect is obtained by blocking the return light. In addition, the structure which arrange | positions the light-shielding plate which has a micro opening (through-hole) as a pinhole between the fiber end 2a and the collimating lens 13 may be sufficient.

  The fiber end 2 a is disposed so as to protrude downward from the canopy portion of the head housing 12. The collimating lens 13 is a condensing lens that condenses the detection light DL emitted from the fiber end 2a into parallel light. The collimating lens 13 is disposed so as to face the end face of the fiber end 2a and to coincide with the optical axis of the fiber end 2a.

  The objective lens 14 is a condenser lens that emits the detection light DL toward the workpiece W. The objective lens 14 is disposed so as to oppose the collimating lens 13 and the optical axis thereof coincides with the collimating lens 13. The collimating lens 13 and the objective lens 14 cause axial chromatic aberration in the detection light DL. The axial chromatic aberration is a color shift of the image in the optical axis direction due to dispersion.

  The optical system in the head unit 10 is not limited to the configuration shown in FIG. 2, but may have a configuration as shown in FIG. Further, a configuration using a diffractive lens instead of the collimating lens 13 or a configuration using a diffractive lens as the objective lens 14 may be used. That is, the optical system in the head unit 10 is subjected to axial chromatic aberration in the head unit 10 with respect to white light having a multi-wavelength component emitted from the fiber end 2a, and the axis from the head unit 10 toward the workpiece W Any light that emits light having upper chromatic aberration may be used.

  The confocal optical system 11 uses the confocal principle to narrow down the received light, and causes axial chromatic aberration in the detection light DL. The detection light DL emitted from the fiber end 2a and transmitted through the collimating lens 13 and the objective lens 14 forms an image at different positions in the vertical direction according to the wavelength. Among the wavelength components included in the detection light DL, a specific wavelength component imaged on the workpiece W is reflected by the workpiece W, and the reflected light passes through the objective lens 14 and the collimator lens 13 to be the end surface of the fiber end 2a. Image on top. On the other hand, the reflected light corresponding to wavelength components other than the specific wavelength component does not form an image on the end face of the fiber end 2a, but is blocked by the fiber end 2a.

  For example, the diameter of the core of the fiber end 2a is preferably 200 μm or less, and more preferably 50 μm or less. Further, the distance from the objective lens 14 to the workpiece W is about 20 mm to 70 mm, and the measurement range MR is about ± 1 mm to ± 20 mm.

<Controller 20>
FIG. 3 is a block diagram showing a configuration example of the controller 20 of FIG. The controller 20 includes a controller housing 20a, a light projecting light source unit 21, a splitter 22, a concave mirror 23, a spectroscope 24, an imaging lens 25, an image sensor 26, a measurement control unit 27, a display unit 28, and a monitor light receiving element 29. And a beam splitter 30.

  The fiber end 2b, the concave mirror 23, the spectroscope 24, the imaging lens 25, and the image sensor 26 constitute a reflection type spectroscopic optical system. The optical fiber cable 2 transmits the detection light DL between the head housing 12 and the controller housing 20a and the reflected light that has been reflected by the work W and then passed through the confocal optical system 11.

  The controller housing 20a houses the light source unit 21 for projection, the concave mirror 23, the spectroscope 24, the imaging lens 25, the image sensor 26, the measurement control unit 27, the light receiving element 29 for monitoring, and the beam splitter 30. The fiber end 2b, the light projecting light source unit 21, the splitter 22, the concave mirror 23, the spectroscope 24, the imaging lens 25, the image sensor 26, the monitor light receiving element 29, and the beam splitter 30 are directly or It is fixed indirectly.

  The light projecting light source unit 21 generates the detection light DL composed of white light including two or more wavelength components. The splitter 22 transmits the detection light DL incident from the light projecting light source unit 21 via the optical fiber cable 2 toward the head unit 10, while reflecting the incident light DL from the head unit 10 via the optical fiber cable 2. It is an optical member that transmits light toward the spectroscopic optical system. For example, the splitter 22 is a fiber coupler that branches or demultiplexes an optical signal.

  The fiber end 2b is the end of the optical fiber cable 2 on the spectroscopic optical system side. The concave mirror 23 is a mirror that reflects the light emitted from the fiber end 2b toward the spectroscope 24, and the reflection surface is formed of a concave surface. The concave mirror 23 condenses the light emitted from the fiber end 2b into substantially parallel light.

  The spectroscope 24 is an optical member that splits the reflected light that has been reflected by the workpiece W and then passed through the confocal optical system 11. The spectroscope 24 is a reflective spectroscope that splits incident light into different wavelength components according to the reflection angle, and is composed of a flat diffraction grating. The diffraction grating is an optical member that splits incident light using a light diffraction phenomenon, and a fine grating pattern is formed on an incident surface or an output surface of reflected light from the workpiece W. The imaging lens 25 is a condensing lens that forms an image of the reflected reflected light on the image sensor 26.

  The image sensor 26 is an image sensor that receives light that has been spectrally separated by the spectroscope 24 and transmitted through the imaging lens 25, and is based on two or more light receiving elements that generate a light reception signal corresponding to the light reception intensity, and the light reception signal. And two or more capacitive elements for accumulating charges according to the amount of received light. For example, the image sensor 26 is a CMOS (complementary metal oxide semiconductor) linear image sensor, and each light receiving element is arranged in a straight line. The image sensor 26 may be a CCD (charge coupled device) image sensor.

  The measurement control unit 27 reads the accumulated charge from the image sensor 26 to acquire a received light waveform, calculates the distance to the workpiece W, and displays it on the display unit 28 as a measurement result. Further, the measurement control unit 27 outputs the waveform data to the PC 3. The display unit 28 includes a 7-segment display provided on the housing 20a of the controller 20, and displays a distance measurement value, a determination threshold value, and the like.

  The monitor light receiving element 29 receives a part of the reflected light that has been reflected by the workpiece W and then passed through the confocal optical system 11, generates a monitor signal, and outputs the monitor signal to the measurement control unit 27. For example, the monitor light receiving element 29 is configured by one or more PDs (photodiodes) that generate a monitor signal corresponding to the received light intensity. The measurement control unit 27 controls the amount of light received by the image sensor 26 based on the monitor signal from the monitor light receiving element 29.

  The diffraction grating divides incident light into zero-order diffracted light, ± first-order diffracted light, ± second-order diffracted light,. The 0th-order diffracted light is diffracted light having a diffraction order of 0, and is composed of light that reinforces by interference without causing a shift in the emission direction according to the wavelength. The 0th-order diffracted light is white light and is composed of all the wavelength components included in the incident light, so that the amount of light per unit area is larger than other orders of diffracted light. Assuming that the order of diffraction is m = ± 1, ± 2,..., The m-th order diffracted light has different emission directions depending on the wavelength.

  In the controller 20, the image sensor 26 simultaneously receives the 0th-order diffracted light and the 1st-order diffracted light from the diffraction grating (spectrometer 24) to generate a light reception signal. That is, the image sensor 26 is disposed at a position where it can receive the 0th-order diffracted light and the 1st-order diffracted light by the diffraction grating (spectrometer 24). The zero-order diffracted light and the first-order diffracted light from the spectroscope 24 are received by the light receiving element provided on the common wiring board in the image sensor 26. The imaging lens 25 has a size capable of imaging the 0th-order diffracted light and the 1st-order diffracted light on the image sensor 26 by the diffraction grating (spectrometer 24). The image sensor 26 may be configured to simultaneously receive the first-order diffracted light and the second-order diffracted light from the diffraction grating.

  The monitor light receiving element 29 receives the light reflected by the beam splitter 30 disposed between the concave mirror 23 and the spectroscope 24 and generates a monitor signal. The beam splitter 30 reflects the concave mirror 23 and then reflects part of the light incident on the spectroscope 24 toward the monitor light receiving element 29 while transmitting the other part of the light. It is a member. According to such a configuration, it is possible to monitor the amount of light received by the image sensor 26 without increasing the size of the monitor light receiving element 29 by receiving the light before spectral separation.

  By using a reflective optical element, that is, the concave mirror 23 and the spectroscope 24, in the spectroscopic optical system of the controller 20, the controller 20 can be downsized as compared with the case where a transmissive optical element is used.

<Light Source Unit 21 for Projection>
FIG. 4 is a diagram illustrating a configuration example of the light source unit 21 for light projection in FIG. 3, (a) in the figure shows a side surface of the light source unit 21 for light projection, and (b) in FIG. The cut surface when the light source unit for projection 21 is cut along the line AA is shown. The light source unit 21 for light projection includes a light emitting element 211, a wiring board 212, an element holder 213, a condenser lens 214, a lens holder 215, a ferrule 216, a ferrule holder 217, a phosphor 220, a frame body 221, and a reflective filter 222. Composed.

  The light emitting element 211 is a laser light source for phosphor excitation that generates laser light having a single wavelength. The light emitting element 211 is disposed on the wiring board 212 with the light emitting portion facing forward in the horizontal direction. For example, the light emitting element 211 generates blue light or ultraviolet light having a wavelength of 450 nm or less. The element holder 213 is a member that holds the wiring board 212 and is inserted into the lens holder 215 from the back side.

  The condensing lens 214 is an optical member that condenses the laser light emitted from the light emitting element 211 on the fiber end of the optical fiber cable 2 on the light projecting light source unit side, and is disposed to face the light emitting element 211. . The lens holder 215 is a lens barrel that holds the condenser lens 214 and has a reduced diameter in front of the condenser lens 214. The ferrule 216 is a cylindrical connecting member in which a fiber end of the optical fiber cable 2 on the light source unit side for light projection is incorporated and extends in the front-rear direction. The ferrule retainer 217 is a bottomed cylindrical member for fixing the ferrule 216 inserted from the front side to the reduced diameter portion of the lens holder 215, and the cylindrical portion is covered with the outer peripheral surface of the reduced diameter portion. A lens holder 215 is attached.

  The phosphor 220 is a light emitter that is excited by laser light from the light emitting element 211 and emits fluorescence having a wavelength different from that of the laser light. The fluorescent body 220 is disposed in the lens holder 215 in a state where the outer peripheral surface thereof is held by the frame body 221 and is in contact with the end face of the fiber end of the optical fiber cable 2. For example, the phosphor 220 emits yellow fluorescence when irradiated with blue laser light. The phosphor 220 may be formed of two or more types of fluorescent materials. For example, the phosphor 220 is formed of a fluorescent material that emits green fluorescence and a fluorescent material that emits red fluorescence when irradiated with blue laser light.

  The reflective filter 222 is an optical member that transmits the laser light from the light emitting element 211 and reflects the light from the phosphor 220, and is disposed so as to cover the surface of the frame 221 on the light emitting element side. On the fiber end of the optical fiber cable 2, mixed light having a plurality of wavelengths in which laser light that has passed through the phosphor 220 and fluorescence emitted from the phosphor 220 are mixed is incident as detection light DL.

  The light projecting light source unit 21 has a configuration in which light mixed with laser light from the light emitting element 211 and fluorescence from the phosphor 220 is directly incident on the fiber end of the optical fiber cable 2. By using such a fiber type light source, the connection between the head unit 10 and the controller 20 with the optical fiber cable 2 can be simplified.

<Image sensor 26>
FIG. 5 is a diagram showing a configuration example of the image sensor 26 of FIG. 3, and shows a CMOS linear image sensor. The image sensor 26 includes a large number of pixel units PU ₀ , PU ₁ ,..., And a DC power supply Vcc and an output buffer BF ₂ that are common to these pixel units PU ₀ , PU ₁ ,. . The CMOS linear image sensor is a one-dimensional image sensor in which two or more pixels including a light receiving element are arranged in one row.

Each of the pixel units PU ₀ , PU ₁ ,... Is a pixel configuration unit that constitutes a pixel. The pixel unit PU ₀ includes a photodiode PD ₀ , a capacitor C ₀ , transistors TR _{10 to} TR _30, and a buffer BF ₁₀ .

Photodiode PD ₀ is a light receiving element for generating a light receiving signal corresponding to the received light intensity. The capacitor C ₀ is a capacitive element that accumulates electric charges according to the amount of light received based on the light reception signal from the photodiode PD ₀ . Transistor TR ₁₀ is switched by the reset signal, in the on state, a control device for adding a reverse bias due to the DC power source Vcc to the PD _0.

The transistor TR ₂₀ is a control element that is switched by a GS (global shutter) signal and accumulates electric charge in the capacitor C ₀ by a light receiving signal from the PD ₀ in the on state. The reset signal and the GS signal are exposure control signals for adjusting the exposure time of the image sensor 26 and are generated by the measurement control unit 27.

The transistor TR ₃₀ is a control element for switching in response to the read signal at address 0 and outputting a signal corresponding to the accumulated charge in the capacitor C ₀ in the on state. The read signal is a control signal for reading the accumulated charge from the image sensor 26 and is generated by the measurement control unit 27. A signal indicating the accumulated charge of the capacitor C ₀ is input to the output buffer BF ₂ via the buffers BF ₁₀ and TR ₃₀ .

The pixel unit PU ₁ includes a photodiode PD ₁ , a capacitor C ₁ , transistors TR _{11 to} TR _31, and a buffer BF ₁₁ , and these devices function in the same manner as each device of the pixel unit PU ₀ . The other pixel units PU ₂ , PU ₃ ,... Are configured in the same manner as PU ₀ and PU ₁ .

The operation of the image sensor 26 when measuring the distance is as follows. First, in the initialization step, the read signal is switched to the H level for all addresses 0, 1,..., And TR ₃₀ , TR ₃₁ ,. Further, both the reset signal and the GS signal are switched to the L level, TR ₁₀ , TR ₁₁ ,... Are simultaneously turned off, and TR ₂₀ , TR ₂₁ ,. . At this time, charges according to the power supply voltage of Vcc are accumulated in the capacitors C ₀ , C ₁ ,.

Next, in the exposure step, when the reset signal is switched to the H level and TR ₁₀ , TR ₁₁ ,... Are simultaneously turned on, exposure is started, and PD ₀ , PD ₁ ,. A light reception signal corresponding to the light reception intensity is generated, and the capacitors C ₀ , C ₁ ,... Start charge accumulation corresponding to the light reception amount. Next, when the GS signal is switched to the H level and TR ₂₀ , TR ₂₁ ,... Are simultaneously turned off, the exposure is terminated and charge accumulation for the capacitors C ₀ , C ₁ ,. To do.

Next, in the readout step, the stored charge is read out from the capacitors C ₀ , C ₁ ,... In time series by sequentially switching the readout signal to the L level for the addresses 0, 1,. The accumulated charges in the capacitors C ₀ , C ₁ ,... Are output to the measurement control unit 27 as the voltage signal Vout. At the time of distance measurement, such initialization step, exposure step, and readout step are repeated for each exposure cycle.

  FIG. 6 is a diagram illustrating an example of the operation of the measurement control unit 27 in FIG. 3, and the received light waveforms 4 and 5 are illustrated. In this figure, received light waveforms 4 and 5 are drawn with the horizontal axis as the pixel position x and the vertical axis as the received light intensity.

  The received light waveform 4 is a characteristic curve representing the relationship between the pixel position on the image sensor 26 and the received light intensity, and is generated based on the accumulated charge read from the image sensor 26. In the received light waveform 4, sharp peaks are formed on the short wavelength side and the long wavelength side, and one peak in which the received light intensity gradually changes is formed between these peaks.

Peak waveform of the short wavelength side, which is a light receiving waveform corrugated region WA ₁ corresponding to the laser light for the phosphor excitation. Peak position x ₁ of the short wavelength side, corresponding to the wavelength of the laser beam. On the other hand, the peak waveform that changes gradually and peak waveform of the long-wavelength side, which is a light receiving waveform corrugated region WA ₂ corresponding to the fluorescence. The waveform areas WA ₁ and WA ₂ are waveform areas corresponding to the first-order diffracted light by the spectroscope 24.

Peak waveform of the long-wavelength side is a signal waveform corresponding to the reflected light from the work W, the peak position x ₂ corresponds to the wavelength of the reflected light from the work W. By identifying the peak position x _2, the distance to the workpiece W is obtained. On the other hand, the peak waveform on the short wavelength side and the slowly changing peak waveform are light reception waveforms corresponding to reflected light from members other than the workpiece W.

Receiving waveform 5 is a receiver frequency corresponding to the wavelength of the laser light receiving waveform or second- or higher-order diffracted light are formed in the waveform area WA ₃ corresponding to the zero-order diffracted light by the spectroscope 24. One sharp peak is formed in the received light waveform 5. The peak position x ₁ and the peak position x ₃ of the received light waveform 5 are parameters specific to the controller 20.

By using a laser light source as a light source for projection and using mixed light of fluorescence emitted from the phosphor 220 excited by the laser light and laser light transmitted through the phosphor 220 as the detection light DL, the amount of light of the detection light DL Can be made extremely large. Therefore, even when the reflectance of the surface is measured with low low-reflectance region LA, since sufficient light intensity can be obtained, rather than the signal waveform buried in noise, accurately identify the peak position x ₂ can do.

  In the confocal displacement meter 1 according to the present embodiment, the relative positions between the spectroscope 24 and the image sensor 26 due to the change in the temperature environment are compared by comparing the peak position with the reference position for the characteristic portions of the light reception waveforms 4 and 5. A temperature correction process is performed to detect a typical misalignment and correct the waveform data and measurement values.

<Measurement control unit 27>
FIG. 7 is a block diagram showing a configuration example of the measurement control unit 27 of FIG. The measurement control unit 27 includes a received light waveform acquisition unit 101, a base waveform estimation unit 102, a signal waveform calculation unit 103, a distance calculation unit 104, a conversion formula storage unit 105, a reference range reception unit 106, a received light amount control unit 107, a characteristic portion. The position acquisition unit 108, the reference position storage unit 109, and the correction amount calculation unit 110 are configured.

  The received light waveform acquisition unit 101 sequentially reads accumulated charges from the image sensor 26 to acquire received light waveforms 4 and 5 that are distributions of received light intensity with respect to the distance, and obtains a base waveform estimation unit 102, a signal waveform calculation unit 103, and a feature. The data is output to the partial position acquisition unit 108.

  Since a large number of light receiving elements are linearly arranged in the image sensor 26, the received light intensity data indicating the amount of light received for each light receiving element is managed in association with the position in the arrangement direction. The received light waveforms 4 and 5 are each composed of a large number of received light intensity data associated with pixel positions on the image sensor 26 if the positions of the light receiving elements in the arrangement direction are called pixel positions.

  The base waveform estimation unit 102 estimates the base waveform based on the shape of the light reception waveform 4 acquired by the light reception waveform acquisition unit 101. The base waveform is a light reception waveform indicating a noise component, and corresponds to the detection light DL that has not been emitted from the objective lens 14 of the head unit 10.

  For example, the base waveform estimation unit 102 includes a representative point sequence generation unit, an intensity difference calculation unit, a weight coefficient calculation unit, and a representative point sequence update unit. The representative point sequence generation means fits to the data point sequence in the reference range RR every time the reference range RR is moved by a certain distance with respect to the data point sequence composed of two or more data points DP constituting the light reception waveform 4. By obtaining a regression curve and determining a representative point RP, a representative point sequence including two or more representative points RP is generated. The intensity difference calculation means obtains a difference in received light intensity between the data point DP and the representative point RP. The weighting factor calculating means obtains the weighting factor w based on the difference. The representative point sequence updating means assigns a weighting coefficient w to the data point sequence, and obtains a regression curve that fits the data point sequence within the reference range RR with weight each time the reference range RR is moved by a certain distance. The representative point sequence is updated by newly determining RP. The base waveform is composed of the updated representative point sequence.

  The signal waveform calculation unit 103 obtains a signal waveform based on the received light waveform 4 and the base waveform, and outputs the signal waveform to the distance calculation unit 104. The signal waveform is a light reception waveform corresponding to the detection light DL emitted from the objective lens 14 and reflected by the workpiece W, and is obtained from the difference between the light reception waveform 4 and the base waveform.

The distance calculation unit 104 obtains a distance WD to the workpiece W based on the signal waveform obtained by the signal waveform calculation unit 103 and outputs the distance WD to the display unit 28. Pixel position on receiver frequency corresponds to a wavelength of light imaged on the corresponding position on the image sensor 26, since the wavelength corresponding to the distance WD, the distance WD is identify the peak position x ₂ of the signal waveform It is required by doing.

For example, if there is a data point sequence whose received light intensity is greater than or equal to the determination threshold for the data point sequence constituting the signal waveform, it is determined that the reflected light component from the workpiece W corresponds, and the received light intensity is maximum in the data point sequence. pixel position of the data points is specified as the peak position x _2. Alternatively, it obtains a curve received light intensity is fit to the data point sequence over determination threshold may be a pixel position of the maximum point of the curve as the peak position x _2. Alternatively, the received light intensity is on the data point sequence over determination threshold may be the position of the center of gravity as the peak position x _2.

  The distance calculation unit 104 obtains a displacement amount by comparing the calculated distance WD with a reference value, and outputs the displacement amount to the display unit 28. The conversion formula storage unit 105 holds a conversion formula or table for associating pixel positions, wavelengths, and distances WD with each other.

  In addition, the distance calculation unit 104 outputs waveform data for displaying the signal waveform obtained by the signal waveform calculation unit 103 on the screen to the PC 3. The reference range receiving unit 106 receives the reference range RR from the PC 3. The reference range RR is a processing unit when analyzing the data point sequence constituting the light reception waveform 4, and the base waveform is estimated based on the reference range RR.

  The received light amount control unit 107 controls the received light amount of the image sensor 26 based on the monitor signal from the monitor light receiving element 29. This received light amount control is performed by adjusting the exposure time by the light receiving element in the image sensor 26.

  For example, the received light amount control unit 107 compares the received light amount of the monitor light receiving element 29 with the determination threshold value DT, and when the received light amount is equal to or greater than the determination threshold value DT, charge accumulation in the capacitive element in the image sensor 26 is performed. By stopping, the exposure time is shortened. On the other hand, if the amount of received light does not exceed the determination threshold value DT during the exposure of the image sensor 26, the charge accumulation in the capacitive element is continued until a predetermined exposure time elapses.

  By controlling the amount of light received by the image sensor 26 in this way, saturation of the image sensor 26 can be suppressed. In particular, since it is not necessary to read out the accumulated charges for all the light receiving elements from the image sensor 26, the followability of the received light amount control is improved, and the work W whose reflectance changes greatly with each exposure cycle is measured. Even if it exists, saturation of the image sensor 26 can be suppressed.

The characteristic part position acquisition unit 108 specifies the peak position of the characteristic part based on the light reception waveforms 4 and 5 acquired by the light reception waveform acquisition unit 101. For example, the characteristic part position acquisition unit 108 specifies the peak position x ₁ using the waveform area WA ₁ corresponding to the excitation light of the first-order diffracted light as a characteristic part. In addition, the characteristic part position acquisition unit 108 specifies the peak position x ₃ using the waveform area WA ₃ corresponding to the 0th-order diffracted light as a characteristic part.

Since the waveform area WA ₁ corresponding to the excitation light is formed apart from the fluorescence waveform area WA ₂ used for distance measurement, the peak position x ₁ can be easily identified. Further, since the waveform area WA ₃ corresponding to the 0th-order diffracted light is formed apart from the waveform areas WA ₁ and WA _{2 of the} 1st-order diffracted light used for distance measurement, the peak position x ₃ can be easily identified. It is. In particular, zero order diffracted light for the light amount is larger than the other order diffracted light, without being affected by noise, it is possible to identify the peak position x _3.

For example, if there is a data point sequence whose received light intensity is equal to or greater than the determination threshold for the data point sequence constituting the received light waveform, the pixel position of the data point having the maximum received light intensity in the data point sequence is the peak position x ₁ , x Specified as ₃ . Alternatively, a curve that fits a data point sequence whose received light intensity is greater than or equal to the determination threshold may be obtained, and the pixel position of the maximum point of the curve may be set as the peak positions x ₁ and x ₃ . Alternatively, the position of the center of gravity may be set as the peak positions x ₁ and x ₃ for a data point sequence whose received light intensity is greater than or equal to the determination threshold.

  In the reference position storage unit 109, the peak position of the characteristic portion obtained from the received light waveform acquired in advance is held as the reference position. For example, the reference position is acquired when the confocal displacement meter 1 is manufactured. Alternatively, the reference position is acquired at a timing arbitrarily designated by the user.

The correction amount calculation unit 110 compares the peak positions x ₁ and x ₃ specified by the feature portion position acquisition unit 108 with the corresponding reference positions, thereby corresponding to the positional deviation between the spectroscope 24 and the image sensor 26. A correction amount for correcting an error in the measured value is obtained.

For example, the correction amount calculation unit 110 calculates the correction amount of the offset b _OS or the span a _SP of the linear function (conversion formula) used when the pixel position x on the image sensor 26 is converted into the distance z _WD to the workpiece W. Ask. If the pixel position of the first pixel in the waveform area WA ₂ and _{x f,} conversion formula _is represented by _{z WD = a SP (x-} x f) + b OS.

The offset b _OS is a distance z _{WD associated} with the pixel position x _f of the first pixel in the waveform area WA ₂ . The span a _Sp is a rate of change of the distance z _{WD associated with} the pixel arrangement pitch. a _SP , b _OS and x _f are known parameters. The distance _{z WD} associating with the reference position of the peak position _{x 1} and _{x 3} are also known.

Assuming that the correction amount of the offset b _OS is Δb and the correction amount of the span a _SP is Δa, the conversion formula considering the positional deviation between the spectroscope 24 and the image sensor 26 is z _WD = (a _SP + Δa) (x _{-x f) + (b OS +} Δb) represented by (1).

If the peak positions x ₁ and x ₃ are acquired, the correction amount calculation unit 110 _assumes that the distance z _{WD associated} with these peak positions x ₁ and x ₃ is the same as that in the case of the reference position. The correction amounts Δa and Δb are calculated according to 1).

The distance calculation unit 104 obtains the distance WD based on the received light waveform 4 and the correction amounts Δa and Δb. That is, the distance calculation unit 104 specifies the peak position x ₂ for the waveform area WA ₂ corresponding to the fluorescence of the first-order diffracted light, and calculates the distance z _WD using the above equation (1). According to such a configuration, even if the relative positional relationship between the spectroscope 24 and the image sensor 26 is deviated due to expansion of the controller housing 20a due to conduction heat from the light source unit 21 for projection. , A decrease in measurement accuracy can be suppressed.

FIG. 8 is an explanatory diagram schematically showing that the span a _SP and the offset b _{OS in the} conversion formula are changed by the relative positional deviation Δy between the spectroscope 24 and the image sensor 26. In (a) of the figure, when the image sensor 26 is shifted by Δy in the optical axis direction, the wavelength associated with the first pixel and the wavelength increment Δλ associated with the pixel arrangement pitch Δx change. The situation is shown.

The reflection angle of the first-order diffracted light by the spectroscope 24 continuously changes according to the wavelength component. For this reason, if the image sensor 26 moves relative to the spectroscope 24 by Δy in the optical axis direction, the wavelength associated with the first pixel (pixel position x _f ), that is, the offset b _OS changes. Further, the wavelength increment Δλ associated with the pixel arrangement pitch Δx, that is, the span a _SP also changes.

(B) in the figure shows a graph 6 representing a first-order conversion formula with the horizontal axis as the pixel position x and the vertical axis as the distance _zWD . The graph 6 is a straight line represented by the above formula (1), and its slope is the span a _SP . Since the offset b _OS and the span a _SP change due to the relative positional deviation Δy between the spectroscope 24 and the image sensor 26 in this way, the correction amount Δa and Δb are obtained and the conversion formula is calibrated to thereby eliminate the positional deviation. The measurement error of the resulting distance WD can be reduced.

According to this embodiment, for determining the correction amount as compared to the previously acquired reference position peak positions x ₁ and x ₃ of the characteristic part, hardly influenced by the surrounding environment, the Light source unit 21 A decrease in measurement accuracy due to a temperature rise can be suppressed. In particular, if the spectroscope 24 and the image sensor 26 are relatively displaced in the optical axis direction, the span a _{SP of} a linear function used when converting the pixel position x on the image sensor 26 to the distance z _WD to the workpiece W. And the offset b _OS changes. Further, if the spectroscope 24 and the image sensor 26 are relatively displaced in the x-axis direction intersecting the optical axis, the linear function offset b _OS changes. It is possible to suppress a decrease in measurement accuracy due to such a positional relationship shift.

In this embodiment, if the peak position is specified and a waveform area WA ₃ corresponding to the waveform area WA ₁ corresponding to the excitation light of first-order diffracted light and 0-order diffracted light as the characteristic part However, the present invention does not limit the selection of the feature portion. For example, the configuration may be such that the peak position is specified using only _{one of} the waveform areas WA ₁ and WA ₃ as a characteristic part. Alternatively, the waveform area WA ₂ corresponding to the fluorescence of the first-order diffracted light, the base waveform is estimated, may be configured to identify a location from its shape the base waveform as the feature portion. Or the structure which uses the waveform area | region corresponding to a higher order diffracted light as a characteristic part may be sufficient.

  In this embodiment, an example in which the conversion equation is calibrated by obtaining both span and offset correction amounts has been described, but the present invention provides a correction method for correcting the temperature characteristics of the spectroscopic optical system. It is not limited. For example, the configuration may be such that only one of the span and the offset is obtained and the conversion formula is calibrated. Alternatively, the pixel position may be corrected with respect to the data point sequence constituting the light reception waveform or the signal waveform.

  In the present embodiment, an example in which mixed light of excitation light and fluorescence is used as the detection light DL has been described. However, the present invention does not limit the configuration of the light source for projection. For example, a white light source that generates white light and a monochromatic light source that generates monochromatic light of a specific wavelength for forming a characteristic light-receiving waveform is used as a light source for projection, and mixed light of white light and monochromatic light is detected light. The structure used as DL may be sufficient.

  In the present embodiment, an example in which the light emitting element 211 and the fiber end of the optical fiber cable 2 are arranged coaxially has been described. However, the present invention limits the configuration of the light source unit 21 for projecting light to this. Not what you want. For example, the light projecting light source unit 21 includes a reflecting mirror that reflects laser light emitted from the light emitting element 211 toward the fiber end of the optical fiber cable 2.

  FIG. 9 is a cross-sectional view schematically showing another configuration example of the light source unit 21 for projecting light. The light source unit 21 for light projection includes a light emitting element 211, a condenser lens 214, a ferrule 216, a phosphor 220, a reflecting mirror 231, and a condenser lens 232.

  The laser light emitted from the light emitting element 211 is condensed on the reflecting mirror 231 via the condenser lens 214. The phosphor 220 is disposed on the reflecting surface of the reflecting mirror 231 and is excited by the laser light from the light emitting element 211 to generate fluorescence. The light in which the laser light reflected by the reflecting mirror 231 and the fluorescent light from the phosphor 220 are mixed is condensed on the fiber end of the optical fiber cable 2 in the ferrule 216 via the condenser lens 232, and the optical fiber cable. 2 enters as detection light DL.

  Further, in the present embodiment, an example in which the confocal optical system 11 of the head unit 10 is configured by the fiber end 2a, the collimating lens 13, and the objective lens 14 has been described. However, the configuration of 11 is not limited to this.

  FIG. 10 is a cross-sectional view showing another configuration example of the head unit 10. (A) in the figure shows a head unit 10 having a diffractive lens 15 and an objective lens 14 in a housing 12.

  The diffractive lens 15 is a relief-type diffractive lens, and is an optical member that collects or diffuses incident light by utilizing a light diffraction phenomenon. A fine relief (undulation) is formed on the incident surface or the exit surface of the detection light DL. ) Is formed. In the relief, the depth in the optical axis direction is about the wavelength of light, and a plurality of annular patterns centering on the optical axis are arranged coaxially.

  When the diffractive lens 15 is used in the confocal optical system 11 of the head unit 10, it is desirable to use a diffraction grating for the spectroscope 24 because the optical characteristics can be matched between the head unit 10 and the controller 20. .

  FIG. 2B shows the head unit 10 including the doublet lens 16 and the objective lens 14. The doublet lens 16 is an optical member that combines a concave lens and a convex lens.

  When the doublet lens 16 is used in the confocal optical system 11 of the head unit 10, it is desirable to use a prism for the spectroscope 24 because the optical characteristics can be matched between the head unit 10 and the controller 20.

  FIG. 2C shows the head unit 10 including the condenser lens 17 and the objective lens 14. The condensing lens 17 is an optical member that condenses the detection light DL emitted from the fiber end 2 a toward the objective lens 14. In the head unit 10, a doublet lens is used as the objective lens 14.

  (D) in the figure shows the head unit 10 including the condenser lens 17 and the objective lens 14. In the head unit 10, a diffractive lens is used as the objective lens 14. Even with such a combination of optical members, axial chromatic aberration can be generated in the detection light DL as the confocal optical system 11. For example, a prism and a cylindrical lens having a refractive index distribution in the radial direction can be used as the confocal optical system 11.

  In the present embodiment, an example in which the spectroscope 24 is a reflective diffraction grating has been described. However, the present invention does not limit the configuration of the spectroscope 24 to this. For example, a transmissive diffraction grating that splits incident light into different wavelength components according to the transmission angle may be used as the spectroscope 24.

  FIG. 11 is a diagram showing another configuration example of the controller 20 and shows a transmission type spectroscopic optical system. This spectroscopic optical system is different from the spectroscopic optical system of FIG. 3 in that the spectroscope 24 is a transmission type diffraction grating.

  Light emitted from the fiber end 2b of the optical fiber cable 2 and incident on the spectroscope 24 via the spectroscope lens 41 is split into different wavelength components according to the transmission angle. The spectroscope lens 41 is a condensing lens that condenses the light emitted from the fiber end 2b, and is disposed so as to face the end surface of the fiber end 2b and to coincide with the optical axis of the fiber end 2b. For example, the spectroscope lens 41 is a collimating lens that condenses the light emitted from the fiber end 2b into parallel light. The imaging lens 25 forms an image of the split transmitted light on the image sensor 26.

  The image sensor 26 simultaneously receives the 0th-order diffracted light and the 1st-order diffracted light from the spectroscope 24 via the imaging lens 25. According to such a configuration, since the image sensor 26 receives the diffracted light transmitted through the spectroscope 24, the positional deviation of the diffraction grating gives the received light waveform compared to the case where the diffracted light reflected by the diffraction grating is received. The influence can be suppressed.

  Further, in the present embodiment, the example of the confocal displacement meter 1 in which the head unit 10 and the controller 20 are connected via the optical fiber cable 2 has been described. It is not limited to. For example, the confocal displacement meter 1 guides the detection light DL emitted from the light source for light projection to the confocal optical system without using an optical fiber cable, and is reflected by the workpiece W to change the confocal optical system. A configuration in which the transmitted light is directly guided to the spectroscopic optical system may be employed.

  FIG. 12 is a diagram illustrating another configuration example of the confocal displacement meter 1. The confocal displacement meter 1 does not include an optical fiber cable, and includes a light source 31 for projection, condensing lenses 32 and 34, pinhole plates 33 and 37, an objective lens 35, a beam splitter 36, a concave mirror 23, a spectroscope 24, The imaging lens 25, the image sensor 26, the monitor light receiving element 29, and the beam splitter 30 are configured. The pinhole plate 37, the concave mirror 23, the spectroscope 24, the imaging lens 25, and the image sensor 26 are reflection type spectroscopic optical systems and are configured in the same manner as the spectroscopic optical system shown in FIG.

  The light source 31 for projection generates detection light DL. The condensing lens 32 is an optical member that condenses the detection light DL emitted from the light projecting light source 31 at the opening of the pinhole plate 33, and is disposed to face the light emitting surface of the light projecting light source 31. Yes. The pinhole plate 33 is a flat light shielding member having a minute opening.

  The condensing lens 34 condenses the detection light DL emitted from the opening of the pinhole plate 33 toward the objective lens 35. The objective lens 35 emits the detection light DL toward the workpiece W. The condenser lenses 32 and 34, the pinhole plate 33, and the objective lens 35 are arranged coaxially.

  The beam splitter 36 is an optical member that transmits light from the pinhole plate 33 and reflects light reflected by the work W and transmitted through the objective lens 35 and the condenser lens 34 toward the pinhole plate 37. The pinhole plates 33 and 37, the condenser lens 34, the objective lens 35, and the beam splitter 36 are confocal optical systems.

  The concave mirror 23 reflects the light emitted from the opening of the pinhole plate 37 toward the spectroscope 24. The spectroscope 24 is a reflection type diffraction grating that splits light reflected by the workpiece W and passed through the confocal optical system 11, and splits incident light into different wavelength components according to the reflection angle.

  In this embodiment, an example in which the amount of light received by the image sensor 26 is controlled by adjusting the exposure time by the light receiving element has been described. However, the present invention limits the method of controlling the amount of received light to this. It is not a thing. For example, the light receiving amount of the image sensor 26 may be controlled by adjusting the light amount of the detection light DL based on the monitor signal from the monitoring light receiving element 29.

  In the present embodiment, an example in which a laser light source that generates laser light is used as a light source for projection has been described. You may use LED (light emitting diode) for the light source for light projection. Further, an SC light source that generates SC (super continuum) light may be used as the laser light source. The SC light source generates continuous and broadband laser light by the nonlinear optical effect by the pulse laser.

  Further, the correction amount calculation processing for obtaining the correction amount by comparing the specified peak position with the reference position does not always have to be performed during the operation of the confocal displacement meter 1. For example, correction amount calculation processing is performed when the confocal displacement meter 1 is activated (when the power is turned on), or the activation time of the confocal displacement meter 1 (elapsed time since the power is turned on) exceeds a certain threshold. The correction amount calculation process may be performed as a trigger. Further, after the confocal displacement meter 1 is measured a certain number of times, the correction amount calculation process may be performed by using the measurement count exceeding a threshold value as a trigger.

  Further, when the confocal displacement meter 1 is activated, the activation time of the confocal displacement meter 1 exceeds a certain threshold value, or the confocal displacement meter 1 is measured a certain number of times and then the number of measurements is determined. The configuration may be such that, when the correction amount is obtained by using a trigger exceeding the threshold, the correction amount is obtained by increasing the gain of the light reception signal and the light reception intensity. The measurement conditions may be changed so that the correction amount can be easily calculated by increasing the received light intensity.

DESCRIPTION OF SYMBOLS 1 Confocal displacement meter 10 Head unit 11 Confocal optical system 12 Head housing 13 Collimating lens 14 Objective lens 15 Diffraction lens 16 Doublet lens 20 Controller 20a Controller housing 21 Projection light source unit 22 Splitter 23 Concave mirror 24 Spectroscope 25 Image lens 26 Image sensor 27 Measurement control unit 28 Display unit 29 Monitor light receiving element 30 Beam splitter 31 Light source 32, 34 Condensing lens 33, 37 Pinhole plate 35 Objective lens 36 Beam splitter 41 Spectroscope lens 101 Light receiving waveform Acquisition unit 102 Base waveform estimation unit 103 Signal waveform calculation unit 104 Distance calculation unit 105 Conversion formula storage unit 106 Reference range reception unit 107 Light reception amount control unit 108 Characteristic part position acquisition unit 109 Reference position storage unit 110 Correction amount calculation unit 211 Light emitting element 220 Phosphor 2 Optical fiber cable 2a, 2b Fiber end 3 PC
4,5 Light reception waveform

Claims (9)

A light source for projection that generates detection light composed of light having a plurality of wavelengths;
A confocal optical system having an objective lens that emits the detection light toward a detection target, and causing axial chromatic aberration in the detection light;
A spectroscope for spectroscopically reflecting the reflected light that has passed through the confocal optical system after being reflected by the detection object;
An image sensor having two or more light receiving elements and receiving the reflected reflected light to generate a light receiving signal;
Based on the received light signal, received light waveform acquisition means for acquiring a received light waveform consisting of a distribution of received light intensity with respect to distance,
Based on the received light waveform, feature part position acquisition means for specifying the peak position of the feature part;
Reference position storage means for holding the peak position of the characteristic portion obtained from the previously received light-receiving waveform as a reference position;
A correction amount calculating means for comparing the identified peak position with the reference position and obtaining a correction amount;
A confocal displacement meter comprising: distance calculation means for obtaining a distance to the detection object based on the light reception waveform and the correction amount. The light source for projection includes excitation light generation means for generating excitation light, and a phosphor that is excited by the excitation light and emits fluorescence having a wavelength different from that of the excitation light, and the detection light is the fluorescence. Mixed light of the excitation light transmitted through the body and the fluorescence emitted from the phosphor,
The feature portion position acquisition means specifies a peak position with a waveform region corresponding to the excitation light as a feature portion,
The confocal displacement meter according to claim 1, wherein the distance calculation unit obtains a distance to the detection target based on a peak position of a waveform region corresponding to the fluorescence.   3. The confocal displacement meter according to claim 2, wherein the excitation light generation means is a laser light source that generates laser light as the excitation light. The spectroscope uses a diffraction grating,
The image sensor simultaneously receives the 0th-order diffracted light and the 1st-order diffracted light from the diffraction grating, and generates the received light signal.
The feature portion position acquisition means specifies a peak position using the waveform region corresponding to the 0th-order diffracted light as a feature portion,
The confocal displacement meter according to claim 2, wherein the distance calculation unit obtains a distance to the detection target based on a peak position of a waveform region corresponding to the first-order diffracted light. The spectroscope uses a diffraction grating,
The image sensor simultaneously receives a first-order diffracted light and a second-order or higher-order diffracted light from the diffraction grating, and generates the light reception signal.
The characteristic part position acquisition means specifies a peak position using a waveform region corresponding to the first-order diffracted light and the second-order or higher-order diffracted light as a characteristic part,
The confocal displacement meter according to claim 2, wherein the distance calculation unit obtains a distance to the detection target based on a peak position of a waveform region corresponding to the first-order diffracted light. The received light waveform is composed of two or more received light intensity data each associated with a pixel position on the image sensor,
The correction amount calculating means applies the peak position of the waveform region corresponding to the excitation light and the peak position of the waveform region corresponding to the 0th order diffracted light or the second or higher order diffracted light of the first order diffracted light. Compensation amount of offset or span of a linear function used when converting the pixel position on the image sensor into the distance to the detection target by comparing the peak position of the corresponding waveform region with the corresponding reference position. The confocal displacement meter according to claim 4 or 5, wherein: A light receiving element for monitoring that receives a part of the reflected light and generates a monitor signal;
The confocal displacement meter according to claim 1, further comprising a received light amount control unit that controls a received light amount of the image sensor based on the monitor signal. A head housing in which the confocal optical system is disposed;
A controller housing that houses the light source for projection, the spectroscope, and the image sensor;
The confocal displacement meter according to claim 1, further comprising an optical fiber cable that transmits the detection light and the reflected light between the head housing and the controller housing.   9. The confocal displacement meter according to claim 1, wherein the characteristic portion position acquisition unit specifies a pixel position having a maximum light reception intensity or a barycentric position of a light reception waveform as the peak position.

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