JP5363231B2 - Vibration measuring apparatus and vibration measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To concurrently measure vibration information and height information of an object to be measured at a plurality of points. <P>SOLUTION: Reference light L<SB>R</SB>and measuring light L<SB>M</SB>which are emitted from a light source part 110 and have phase synchronization and coherence between each other are divided by an interference optical system 140 and are made incident into a reference optical system 120 and a measuring optical system 130. The measuring light L<SB>M</SB>is separated into measuring light L<SB>CH1</SB>-L<SB>CHn</SB>of a plurality of channels including two or more frequency components for each channel by an optical multiplexer 131, with which a plurality of measuring points in the measuring surface 10 are irradiated. The measuring light L<SB>CH1</SB>'-L<SB>CHn</SB>' of the plurality of channels reflected and returned on the measuring surface 10 are returned to an interference optical system 140 from the measuring optical system 130 as measuring light L<SB>M</SB>'. An optical spectrum included in interference light L<SB>X</SB>of the reference light L<SB>R</SB>' and the measuring light L<SB>M</SB>' returned from the reference optical system 120 and the measuring optical system 130 is detected by a detection part 150. Subsequently, each spectrum component is analyzed by a signal processing portion 160, thereby to obtain vibration information and height information at the plurality of measuring points in the measuring surface 10. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a vibration measuring apparatus and a vibration measuring method for simultaneously measuring a plurality of pieces of vibration information and height information of a measurement object using light.

  A vibrometer is used as a measuring instrument that detects vibration and converts it into an electrical signal to measure vibration. There are two types of vibration meters: contact type and non-contact type. A contact-type vibrometer measures the acceleration of vibration by connecting a sensor to an object to be measured. Non-contact vibrometers are used when the vibration state changes due to sensor mounting, when the object to be measured is a rotating body and it is difficult to read out the signal, or when it is difficult to mount the sensor due to size or material. It is done.

  Non-contact type vibrometers include eddy current type, capacitance type, laser type, laser Doppler type and the like. For example, a laser Doppler vibrometer measures vibration by irradiating a vibrating body with laser light and observing a frequency change (Doppler shift) of reflected light due to the Doppler effect.

  Conventional vibration measurement devices measure vibration at one location for one head, regardless of contact type or non-contact type, and depending on the device, it is possible to measure vibration at multiple points by adding more heads. Some can be done.

JP 2008-101963 A

  In order to investigate the cause of vibration and the load caused by vibration, it is necessary to measure the vibration distribution within the measurement target surface. For example, in the case of steady vibration, the vibration distribution in the surface can be measured by performing vibration measurement while shifting the location according to the vibration period.

  However, if you want to measure vibrations that change transiently in real time, or if you do not know in advance what kind of frequency component vibrations are included, if you need several pieces of vibration information at the same time, A vibration measuring device capable of simultaneously measuring the vibration information is required.

  For example, even in a conventional apparatus such as a laser Doppler vibrometer, many heads and interferometers are used, and measurement is performed while synchronizing the apparatuses. It is not easy to adjust the optical axis of the laser beam and synchronize the measurement time.

  In addition, the conventional laser Doppler vibrometer can measure the amplitude of vibration, but cannot obtain the height of the stationary state, and the speed range that can be generally measured is only about 10 m per second. Absent.

  In view of the conventional problems as described above, the applicant of the present invention emits reference light and measurement light having a predetermined frequency interval, phase-synchronized and coherent from the light source, and emitted from the light source. The measurement light incident on the spectroscopic head is reflected on the measurement surface by irradiating the measurement light incident on the spectroscopic head for each frequency component and irradiating a plurality of measurement points on the measurement target surface. The measurement light incident via the spectroscopic head and the reference light emitted from the light source are caused to interfere with each other by an interference optical system, and the optical spectral component contained in the interference light is separated by a diffraction grating. By detecting vibration information at a plurality of measurement points on the measurement surface using a signal processing unit based on each detected spectral component, Without having to adjust the multipoint simultaneously measurable and the vibration measuring device and vibration measuring method vibration information of the measurement object is proposed as Japanese Patent Application No. 2009-048392.

  An object of the present invention is to improve the vibration measuring apparatus and the vibration measuring method previously proposed by the applicant of the present application, and to measure the vibration information and the height information of the measurement object simultaneously at a plurality of points simultaneously. It is to provide a method.

  Other objects of the present invention and specific advantages obtained by the present invention will become more apparent from the description of embodiments described below.

  In the present invention, the optical frequency comb is separated into measurement light of a plurality of channels including two or more frequency components for different channels, the measurement light of the plurality of channels is irradiated to the measurement object, and the measurement light reflected by the measurement object The interference optical system interferes with the reference light to obtain interference light, separates the optical spectrum components included in the interference light, and detects each of the separated spectral components by a plurality of photodetectors. Based on the spectral components, the vibration information at the plurality of measurement points on the measurement surface is analyzed by the signal processing unit, whereby the vibration information and the height information of the measurement target are simultaneously measured.

  That is, the vibration measuring apparatus according to the present invention has a spectrum of predetermined frequency intervals, a light source unit that emits reference light and measurement light that are phase-synchronized with each other, and reference light that is emitted from the light source unit. And an interference optical system that splits the measurement light and enters the reference optical system and the measurement optical system, and generates interference light of the reference light and the measurement light returning from the reference optical system and the measurement optical system, and the interference optical system The reference light split in step S is incident, the reference optical system that returns the incident reference light to the interference optical system, and the measurement light split in the interference optical system is incident. A plurality of channels of measurement light that are separated into a plurality of channels of measurement light containing two or more frequency components, irradiate the plurality of channels of measurement light onto a plurality of measurement points on the measurement surface, and are reflected back from the measurement surface. Into one A measurement optical system that returns the measurement light reflected at a plurality of measurement points on the measurement surface to the interference optical system via the optical multiplexer, and the interference optical system. An optical spectrum separation unit that separates an optical spectrum included in the generated interference light, a light detection unit that includes a plurality of photodetectors that detect each optical spectrum separated by the optical spectrum separation unit, and the detection unit. Analyzing each detected spectral component, obtaining vibration information at a plurality of measurement points on the measurement surface from the phase information of the frequency component of each channel, and obtaining a plurality of measurement surfaces from the relative phase information of each frequency component in each channel. And a signal processing unit for obtaining height information at the measurement points.

  In addition, the vibration measuring apparatus according to the present invention has a spectrum with a predetermined frequency interval, the modulation frequency and the center frequency are different from each other, the light source that emits the reference light and the measurement light that are phase-synchronized with each other, Interference that splits the reference light and measurement light emitted from the light source unit, enters the reference optical system and the measurement optical system, and generates interference light between the reference light and the measurement optical system that returns from the reference optical system and the measurement optical system. An optical system, a reference light split in the interference optical system is incident, a reference optical system that returns the incident reference light to the interference optical system, and a measurement light split in the interference optical system is incident and incident The measured measurement light is separated into a plurality of channels of measurement light including two or more frequency components for each channel, and the measurement light of the plurality of channels is irradiated to a plurality of measurement points on the measurement surface and reflected by the measurement surface. Back An optical multiplexer / demultiplexer for combining the measurement light of a plurality of channels into one, and returning the measurement light reflected at a plurality of measurement points on the measurement surface to the interference optical system via the optical multiplexer / demultiplexer An optical system, a detection unit that detects interference light generated by the interference optical system, and phase information of frequency components of each channel at a plurality of measurement points on the measurement surface based on the interference light detected by the detection unit And a signal processing unit that obtains vibration information and obtains height information at a plurality of measurement points on the measurement surface from relative phase information of each frequency component in each channel.

  Further, the vibration measuring method according to the present invention is a spectrum having a predetermined frequency interval, the modulation frequency and the center frequency are different from each other, and the reference light and the measurement light that are phase-synchronized and coherent are emitted from the light source unit. A process, an incident process for entering the measurement light emitted from the light source unit into the optical multiplexer / demultiplexer, and a plurality of the measurement light incident on the optical multiplexer / demultiplexer including two or more frequency components for each channel The measurement light of the channels is separated into a plurality of measurement points on the measurement surface to be measured, and the plurality of measurement lights reflected and returned from the measurement surface are returned to the optical multiplexer / demultiplexer. Irradiating the interference optical system together with the measurement light that is reflected by the measurement surface and incident through the optical multiplexer / demultiplexer and the reference light emitted from the light source unit Interference process for interference by optical system , Separating the optical spectrum included in the interference light generated by the interference optical system, detecting each optical spectrum, analyzing each spectral component detected in the detecting step, and analyzing the frequency component of each channel An analysis step of obtaining vibration information at a plurality of measurement points on the measurement surface from phase information and obtaining height information at a plurality of measurement points on the measurement surface from relative phase information of each frequency component in each channel. It is characterized by.

  Furthermore, the vibration measurement method according to the present invention includes an emission step of emitting a reference light and a measurement light, which are spectra having predetermined frequency intervals and are phase-synchronized with each other, from the light source unit, and a light source in the emission step. The measurement light emitted from the unit is separated into multiple channels of measurement light containing two or more frequency components for each channel by an optical multiplexer / demultiplexer, and the multiple channels of measurement light are measured on the measurement surface of the measurement target. Irradiating a point and irradiating a plurality of measurement lights reflected and returned from the measurement surface into one by the optical multiplexer / demultiplexer and entering the interference optical system, and via the optical multiplexer / demultiplexer An interference process for causing the measurement light incident on the light source unit and the reference light emitted from the light source unit to interfere with each other by the interference optical system, a detection process for detecting the interference light generated by the interference optical system, and the detection process Interference light Accordingly, vibration information at a plurality of measurement points on the measurement surface is obtained from the phase information of the frequency component of each channel, and heights at the plurality of measurement points on the measurement surface are obtained from the relative phase information of each frequency component in each channel. And an analysis step for obtaining information.

  According to the present invention, it is possible to simultaneously measure a plurality of vibration information and height information of a measurement target.

It is a block diagram which shows an example of the vibration measuring device to which this invention is applied. It is a figure which shows typically the optical frequency comb output from the generator of the optical frequency comb with which the said vibration measuring device was equipped on a frequency axis. It is a figure which shows typically the relationship between the frequency component of the optical frequency comb demultiplexed by the optical demultiplexer with which the said vibration measuring device was equipped, and each channel. It is a figure which shows typically the structural example of the said optical multiplexer / demultiplexer using a triangular prism. It is a figure which shows typically the structural example of the optical multiplexer / demultiplexer using an arrayed-waveguide grating | lattice. It is a figure which shows typically the structural example of the said optical multiplexer / demultiplexer using a some wavelength division multiplexing filter. It is a figure which shows typically the waveform and relative phase of the several interference signal detected in the detection part of the said vibration measuring device. In the above vibration measurement apparatus, a plurality of measurement lights positioned on a straight line along the longitudinal direction (x direction) of the measurement surface through the heads of the respective channels are separated from the measurement light of the plurality of channels demultiplexed by the optical multiplexer / demultiplexer. It is a figure which shows typically the state irradiated to a point. In the vibration measuring apparatus, in order to measure vibration information two-dimensionally on the measurement surface, a light separating element that separates light having a plurality of frequencies included in the measurement light of each channel so that one frequency corresponds to one measurement point. Is a diagram schematically showing a state in which the measurement light is radiated to the three measurement points in the y direction by the head portions of the respective channels. In the said vibration measuring device, in order to measure the twist of a measurement surface, it is a figure which shows typically the state which irradiates the measurement light of each channel via the head part of each channel arrange | positioned in 2 rows. It is a block diagram which shows the other structural example of the vibration measuring device to which this invention is applied. It is a figure which shows typically the measurement light and reference light which are returned to the interference optical system in the said vibration measuring device on a frequency axis. It is a block diagram which shows the further another structural example of the vibration measuring device to which this invention is applied. It is a figure which shows typically the optical frequency comb radiate | emitted as a reference light and measurement light from two optical frequency comb generation | occurrence | production emitted from a light source part in the said vibration measuring device on a frequency axis.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the invention will be described in detail with reference to the drawings.

  The present invention is applied to, for example, a vibration measuring apparatus 100 configured as shown in FIG.

The vibration measurement device 100 includes a light source unit 110 that emits the reference light L _R and the measurement light L _M, the reference optical system 120 in which the reference light L _R is incident, the measurement optical system in which the measurement light L _M enters 130, the reference above measurement interference optical system 140 via the optical system 130 the measurement light L _M is incident with through the optical system 120 is the reference light L _R is incident occurred in the interference optical system 140 The detection unit 150 detects the interference light L _X , the signal processing unit 160 analyzes the detection output of the interference light L _X detected by the detection unit 150, and the like.

In the vibration measuring apparatus 100, the light source unit 110 includes, for example, a laser light source 111 that emits laser light having a frequency ν, an optical frequency comb generator 112 that receives laser light from the laser light source 111, and the optical frequency. The reference signal L _R and the measurement light L _M are coherent with the optical frequency comb generated by the optical frequency comb generator 112. To be emitted.

The optical frequency comb generator 112 includes, for example, an electro-optic modulator (EOM) that modulates the intensity and phase of light outside the laser, and a reflecting mirror that is disposed so as to face the EOM. A Fabry-Perot type electro-optic modulation system in which an optical oscillator is constituted by an electro-optic modulator and a reflecting mirror is used. As the optical frequency comb generator 112, a phase modulator using an LiNbO ₃ crystal, an intensity modulator, a modulator using a semiconductor absorption or phase change, or the like may be used.
The optical frequency comb generator 112, by modulating the laser light emitted from the laser light source 111 in modulated signal of a frequency f _m supplied from the oscillator 113, generates an optical frequency comb. Optical frequency comb has, for example, as shown in FIG. 2, the microwave frequency around the optical frequency [nu (modulated signal frequency) sideband that is generated at equal frequency intervals that match the f _m (side band) It is light, and the center frequency of the optical frequency comb coincides with the optical frequency ν of the incident laser. Since the optical frequency ν is in the region of several hundred THz, it is difficult to directly handle the phase information of light. However, since f _m is a region of several tens of GHz even if it is high, phase information can be easily obtained by conventional electronic circuit technology. Can be handled. Therefore, by using the optical frequency comb, it becomes possible to electrically handle relative light frequency and phase information within a band in which the optical frequency comb exists.

  The light source unit 110 may be a single light source, such as a mode-locked laser, whose intensity or phase is periodically modulated and whose carrier frequency is stabilized. If the coherence is good, two independent light sources may be used.

In the vibration measurement device 100, the reference optical system 120, referring to the emitted light frequency comb as the reference light L _R and the measurement light L _M from the light source unit 110 is divided by the beam splitter 141 in the interference optical system 140 the reference surface 122 which light _{L R} is incident through the 1/8 wavelength (lambda / 8) plate 121, the 1/8 wavelength (lambda / 8) plate 121 reflects the reference light _{L R} incident Through the interference optical system 140.

Further, in the vibration measurement device 100, the measurement optical system 130, in the interference optical system 140 the measurement light L _M divided by the beam splitter 141 is incident, two for each channel the measurement light L _M incident A plurality of measurement light beams L _{CH1 to} L _CHn including the frequency components described above are separated into a plurality of measurement light beams L _{CH1 to} L _CHn and irradiated to a plurality of corresponding measurement points on the measurement surface 10, 10 includes an optical multiplexer / demultiplexer 131 that combines the measurement light beams L _CH1 ′ to L _CHn ′ reflected from the plurality of channels that have been reflected by the light source 10 and reflected at a plurality of measurement points on the measurement surface 10. the _{CH1 '~L CHn'} through the optical demultiplexer 131 is adapted to return to the interference optical system 140.

The optical demultiplexer 131 separates the measurement light L _M incident on each channel to a plurality of channels of the measurement light L _CH1 ~L _CHn comprising two or more frequency components, the measuring light L of the plurality of channels bundling a demultiplexing function for irradiating the _CH1 ~L _CHn the plurality of measurement points on the measurement surface 10, a plurality of channels that have reflected back by the measuring surface 10 of the measuring light _{L CH1 '~L CHn'} one In this case, the measurement light L _M ′ reflected and returned from the measurement surface 10 has a multiplexing function to be incident on the interference optical system 140. As components for multiplexing and demultiplexing light, prisms, A spectral element such as an interference film filter or a diffraction grating is used.

  In the optical multiplexer / demultiplexer 131, as shown in FIG. 3, the output bandwidth and center frequency of each channel are set so that two or more frequency components of the optical frequency comb are included for each channel.

The optical demultiplexer 131, for example, as shown in FIG. 4, a condenser lens 131A, the measurement light _{L M} consists triangular prism 131B which is input and output via 131C, by the triangular prism 131B, incident The measurement light L _M is demultiplexed into a plurality of channels of measurement light L _{CH1 to} L _CHn including two or more frequency components for each channel, and the plurality of channels of the measurement light L reflected by the measurement surface 10 and returned. it can be bundled into one by multiplexing _{CH1 '~L CHn'.}

  Further, as the optical multiplexer / demultiplexer 131, for example, as shown in FIG. 5, an arrayed waveguide grating 131D (AWG: Arrayed Waveguide Grating) having an optical waveguide functioning as the triangular prism is used. it can.

  Further, for example, as shown in FIG. 6, the optical multiplexer / demultiplexer 131 can be configured by vertically connecting a plurality of wavelength division multiplex filters having slightly different division wavelengths.

The optical multiplexer / demultiplexer 131 shown in FIG. 6 is formed by vertically connecting nine wavelength division multiplexing filters 131a to 131i. The nine wavelength division multiplexing filters 131a to 131i have wavelengths λ _−n , λ _{−n + 1} , each spectrum of the incident measurement light L _M , that is, the optical frequency comb of a predetermined frequency interval emitted from the light source 110, _{··· λ -5, λ -4, λ} -3, λ -2, λ -1, λ 0, λ 1, λ 2, λ 3, λ 4, λ 5 ··· λ n-1, λ n On the other hand, as an integer of m = −4, −3, −2, −1, 0, 1, 2, 3, 4, light having a wavelength of λ _{3m + 1} or less is transmitted and light having a wavelength of λ _{3m + 2} or more is transmitted. It has the optical property to do.

  The optical multiplexer / demultiplexer 131 performs wavelength division as follows using nine wavelength division multiplexing filters 131a to 131i.

The first wavelength division multiplexing filter 131a is a wavelength lambda _-13 included in the measurement light _{L M} incident, lambda _-12, light lambda _-11 emits a measurement light _{L CH1} of the first channel by transmitting, Light having a wavelength of λ ₋₁₀ or less is reflected and enters the second wavelength division multiplexing filter 131b.

The second wavelength division multiplexing filter 131b, the wavelength lambda _-10 included in the measurement light _{L M} incident, lambda _-9, light lambda _-8 is emitted as measuring light _{L CH2} of the second channel is transmitted through Then, light having a wavelength of λ ₋₇ or less is reflected and enters the third wavelength division multiplexing filter 131c.

The third wavelength division multiplex filter 131c transmits light of wavelengths λ ₋₇ , λ ₋₆ , and λ ₋₅ and emits it as measurement light L _CH3 of the third channel, and light having a wavelength of λ ₋₄ or less. Then, the light enters the fourth wavelength division multiplex filter 131d.

The fourth wavelength division multiplex filter 131d transmits light having wavelengths λ ₋₄ , λ ₋₃ , and λ ₋₂ and emits it as measurement light L _CH4 of the fourth channel, and light having a wavelength of λ ₋₁ or less. Is reflected and enters the fifth wavelength division multiplex filter 131e.

The fifth wavelength division multiplex filter 131e transmits light of wavelengths λ ₋₁ , λ ₋₀ , λ ₁ and emits it as measurement light L _CH5 of the fifth channel, and reflects light having a wavelength of λ ₂ or less. Then, the light enters the sixth wavelength division multiplex filter 131f.

The sixth wavelength division multiplex filter 131f transmits light of wavelengths λ ₂ , λ ₃ , and λ ₄ and emits it as measurement light L _CH6 of the sixth channel, and reflects light having a wavelength of λ ₅ or less. The light enters the seventh wavelength division multiplexing filter 131g.

The seventh wavelength division multiplex filter 131g transmits light of wavelengths λ ₅ , λ ₆ , and λ ₇ and emits it as measurement light L _CH7 of the seventh channel, and reflects light having a wavelength of λ ₈ or less. The light enters the eighth wavelength division multiplexing filter 131h.

The eighth wavelength division multiplex filter 131h transmits light having wavelengths λ ₈ , λ ₉ , and λ ₁₀ and emits it as measurement light L _CH8 of the eighth channel, and reflects light having a wavelength of λ ₁₁ or less. The light enters the ninth wavelength division multiplexing filter 131i.

Further, the ninth wavelength division multiplexing filter 131i transmits the light of the wavelengths λ ₁₁ , λ ₁₂ , and λ ₁₃ and emits it as the measurement light L _CH9 of the ninth channel.

That is, the optical demultiplexer 131 may measure the measurement light _{L M} that enters the 9 channels including three frequency components for each channel by the nine WDM filter 131a~131i light _L CH1 _{~L CH9} The 9-channel measurement lights L _{CH1 to} L _CH19 are irradiated to a plurality of measurement points on the measurement surface 10.

The optical multiplexer / demultiplexer 131 multiplexes the nine channels of measurement light L _CH1 ′ to L _CH9 ′ reflected and returned from the measurement surface 10 by the nine wavelength division multiplexing filters 131a to 131i. .

That is, the nine channels of measurement light L _CH1 ′ to L _CH9 ′ reflected and returned from the measurement surface 10 have wavelengths λ ₋₁₃ , λ ₋₁₂ , and λ ₋ included in the first channel measurement light L _CH1 ′. ₁₁ light passes through the first wavelength division multiplexing filter 131a, and the light of wavelengths λ ₋₁₀ , λ ₋₉ , and λ ₋₈ included in the measurement light L _CH2 ′ of the second channel is the second wavelength division multiplexing filter. The light of wavelengths λ ₋₇ , λ ₋₆ , and λ ₋₅ that passes through 131 b and is included in the measurement light L _CH3 ′ of the third channel passes through the third wavelength division multiplexing filter 131 c, and so on. The light beams of wavelengths λ _{−4 to} λ ₁₃ included in the measurement light beams L _CH4 ′ to L _CH9 ′ are combined by passing through the wavelength division multiplexing filters 131 d to 131 i and bundled together.

That is, the nine wavelength division multiplexing filter 131a~131i is multiplexes the light having a wavelength of lambda _-13 to [lambda] ₁₃ contained in the nine channels of the measuring light that has reflected back by the measuring surface 10 1 Bundled together, the measurement light L _M ′ reflected and returned from the measurement surface 10 is returned to the interference optical system 140.

  Here, the number of wavelengths of light and the number of channels included in one channel can be set arbitrarily according to the measurement target.

  The measurement light of each channel spatially separated by the optical multiplexer / demultiplexer 131 has an optical frequency comb in a shape corresponding to the spread of the frequency spectrum, for example, a sheet shape, and each measurement point on the measurement surface 10 to be measured. , Reflected at each measurement point on the measurement surface 10, returned to the optical multiplexer / demultiplexer 131, and bundled again into one beam. The phase of the return light that returns from the measurement point on the measurement surface 10 to the optical multiplexer / demultiplexer 131 undergoes a phase shift according to the position of the measurement surface 10. For example, when the measurement surface 10 is moving, the frequency of the return light undergoes a Doppler shift that is proportional to the speed of the measurement surface 10. Doppler shift is a phenomenon in which when a sound wave, radio wave, or light wave having a certain frequency component is applied to an object moving at a certain speed, the frequency changes in proportion to the velocity component of the moving object. Note that the measurement target is not limited to a smoothly connected surface, and for example, it is possible to irradiate an object that vibrates independently in each mode of the optical frequency comb.

  In the interference optical system 140, in the measurement optical system 130, the measurement light of each channel irradiated on the measurement surface 10 is reflected at each measurement point, and returns to the optical multiplexer / demultiplexer 131. It is bundled and incident.

The interference optical system 140 reflects the measurement light measurement lights L _{CH1 to} L _{CHn of} each channel irradiated on the measurement surface 10 at each measurement point, and returns to the optical multiplexer / demultiplexer 131 to form one beam again. The bundled measurement light L _M ′ is incident from the measurement optical system 130, and the reference light L _R ′ incident on the reference optical system 120 and the measurement light L _M ′ incident from the measurement optical system 130 are changed to the above. By superimposing the beams on the beam splitter 141, the reference light L _R ′ and the measurement light L _M ′ are caused to interfere with each other, and the interference light L _X is incident on the detection unit 150.

In the vibration measuring apparatus 100, the detection unit 150 includes the polarization beam splitter 151 that separates the interference light L _X incident from the interference optical system 140 into light L _X1 and L _X2 having two orthogonal polarization components, and the polarization The beam splitter 151 includes two light detection units 152A and 152B on which light L _X1 and L _X2 having two orthogonal polarization components are incident. The two light detection units 152A and 52B include spectroscopic elements 152A1 and 152B1 such as diffraction gratings, and light detector arrays 52A2 and 52B2, respectively.

In the detection unit 150, the interference light L _X incident from the interference optical system 140 is separated into two polarized light components L _X1 and L _X2 by the polarization beam splitter 151. In the light detection unit 152A, Each light spectrum component included in the light L _X1 of the polarization component is separated by the spectroscopic element 152A1 and detected by the photodetector array 152A2, and each light component LX2 included in the light L _X2 of the other polarization component is detected by the light detection unit 152B. The optical spectral components are separated by the spectroscopic element 52B1 and detected by the photodetector array 152B2.

  Each light spectrum component decomposed by the spectroscopic elements 152A1 and 152B1 is incident on one sideband for each element of the photodetector arrays 152A2 and 152B2. The photodetector arrays 152A2 and 152B2 are a series of many detectors, and the diffraction angles of the diffraction gratings used as the spectroscopic elements 152A1 and 152B1 so that a plurality of frequency components of interference light do not enter one detector. Adjust the arrangement of the optical system.

Here, since the vibration measuring apparatus 100 uses a quadrature homodyne interferometer, the polarization of the light emitted from the light source unit 110 is changed to the output polarization of the polarization beam splitter (PBS) 151 provided in the detection unit 150. With respect to the reference optical system 120, the reference light _LR is reflected by the reference surface 122 and returned to the interference optical system 140 in the reference optical system 120. The wavelength is 1/8 wavelength (λ / 8). By inserting the plate 121 and passing it through the 1/8 wavelength (λ / 8) plate 121 twice in a reciprocating manner, the incident linearly polarized reference light _LR is used as the circularly polarized reference light _LR ′. Return to 140.

The frequency of the interference light L _X generated by the interference optical system 140 is equal to the frequency of the difference between the reference light L _R ′ and the measurement light L _M ′. In the detection unit 150, the intensity of the interference light L _X is obtained. Is detected. As described above, the detection unit 150 separates the optical spectral components included in the interference light L _X generated by the interference optical system 140 and detects the separated spectral components, thereby detecting a plurality of spectral components on the measurement surface 10. The vibrations at the measurement points can be separated and measured.

In the vibration measuring apparatus 100, the signal processing unit 150 analyzes vibration information at a plurality of measurement points on the measurement surface 10 based on each spectral component of the interference light L _X detected by the detection unit 150. The principle of vibration measurement for each point on the measurement surface 10 is the same as that of a conventional laser Doppler vibrometer. Specifically, the velocity component of the measurement surface 10 is measured using the frequency shift in the measurement light reflected by the measurement surface 10 described above, that is, the Doppler shift. For example, when the wavelength of light is λ, the relationship of the following equation (1) is established between the frequency change f _{d corresponding} to the Doppler shift and the vibration velocity V of the measurement surface 10.

f _d = 2V / λ (1)
Accordingly, in the vibration measurement device 100, a frequency change f _d of the Doppler shift component, the vibration information of the measurement surface 10, for example, can be analyzed vibration speed, travel distance, acceleration, and the like.

Then, in the vibration measurement device 100, the signal processing unit 160, the comb mode order of the optical frequency comb emitted from the light source unit 110 is n, the amplitude of a _n of the interference _signal, the phase of the interference signal as theta _n, for example, on the basis of the detection output of the photodetector array 152A2 by the first light detector 152A which detects the intensity of the light spectrum components contained in the light L _X1 of one polarization component of the interference light L _X, the interference signals It calculates a voltage value of a _n cos [theta] _n component of the light detected by the second light detector 152B for detecting the intensity of the light spectrum components contained in the light L _X2 of the other polarized light component of the interference light L _X The voltage value of the an _n sin θ _n component of the interference signal is calculated based on the detection output of the detector array 152B2, and the sin component and the cos component of the calculated interference signal are calculated. From the voltage value, it obtains a distance D _R of the measuring surface 10 from the beam splitter 41 constituting the interferometer optics 140.

Here, in the vibration measuring apparatus 100, a plurality of channels of measurement light including two or more frequency components for each channel are irradiated to a plurality of measurement points on the measurement surface 10 via the optical multiplexer / demultiplexer 131, Since the measurement light beams of a plurality of channels reflected and returned from the measurement surface 10 are bundled and incident on the interference optical system 140, as shown in FIGS. 7A and 7B, the frequency component of the interference signal is obtained. The relative phase changes at a rate of 2π per distance λ _m = c / Δν. Since Δν is the frequency interval of the optical frequency comb, it is about several tens of GHz and is much lower than the frequency of light. When Δν = 1GHz~30GHz, distance lambda _m is much longer 300mm~10mm compared to the wavelength of light. Therefore, it is possible to obtain stationary height information by measuring the relative phase. Also in vibration measurement, an interference signal of one frequency has a periodicity that is half the optical wavelength (several hundreds of nanometers), so the sensitivity is high, and if it is displaced more than half a wavelength within the sampling period, it cannot be measured correctly. Since the relative phase is low in sensitivity to displacement, it can be measured correctly if the displacement is within λ _m / 2 within one measurement time.

That is, in the vibration measuring device 100, the spectrum is a predetermined frequency interval emitted from the light source unit 110, and the reference light and the measuring light that are phase-synchronized with each other and are coherent are divided by the interference optical system 140 and divided. The reference light is incident on the reference optical system 120 and the divided measurement light is incident on the measurement optical system 130, and the incident measurement light is separated into multiple channels of measurement light including two or more frequency components for each channel. Measurement optics including an optical multiplexer / demultiplexer 131 for irradiating a plurality of measurement points of the measurement surface 10 with a plurality of channels and measuring the plurality of channels of measurement light reflected and returned from the measurement surface 10 into one. The measurement light reflected at the plurality of measurement points on the measurement surface 10 is returned to the interference optical system 140 via the optical multiplexer / demultiplexer 131 by the system 130, and the interference optical system 140. In this case, the measurement light reflected by the measurement surface 10 and incident via the optical multiplexer / demultiplexer 131 interferes with the reference light incident from the reference optical system 1, and interference generated by the interference optical system 140. by detecting the light detecting unit 150 comprising a plurality of photodetector light spectrum contained in the light L _X separated by the light spectral separation unit, the signal processing unit 160, the spectral component detected by the detection unit 150 And obtaining vibration information at a plurality of measurement points on the measurement surface 10 from the phase information of the frequency component of each channel, and a plurality of measurement points on the measurement surface 10 from the relative phase information of each frequency component in each channel. Get height information at.

  Accordingly, it is not necessary to perform complicated optical axis adjustment in individual vibration measurement devices, and vibration information of the measurement surface 10 to be measured that requires multipoint synchronization without considering time synchronization between measurement points. And height information at a plurality of measurement points on the measurement surface 10 can be obtained from the relative phase information of each frequency component in each channel.

Here, in the vibration measuring apparatus 100, when the measurement surface 10 is irradiated with the measurement light of a plurality of channels demultiplexed by the optical multiplexer / demultiplexer 131, as shown in FIG. by irradiating the measurement light _L CH1 _{~L CHn} of the channel through the head portion _H 1 to H _n of each channel arranged on a straight line along the direction (x direction), is positioned on a straight line of the measurement surface 10 Vibration information and height information at a plurality of measurement points can be measured simultaneously. Further, measurement is performed by providing scanning means for moving the head portions H _{1 to} H _n of the respective channels arranged on a straight line along the longitudinal direction (x direction) of the measurement surface 10 in the y direction orthogonal to the x direction. Vibration information and height information can also be measured in two dimensions for the surface 10.

Incidentally, resulting in the height information is lost. For example, as shown in FIG. 9 (A), the first measurement point 1 frequency light of a plurality of frequencies included in the measurement light L _CH1 ~L _CHn in each channel The light dispersion elements 135 that are separated so as to correspond to each other are provided in each of the head portions H _{CH1 to} H _CHn . As shown in FIG. 9B, the three head portions H _{CH1 to} H _CHn of each channel have three points in the y direction. By irradiating the measurement point with measurement light, the vibration information can be measured two-dimensionally on the measurement surface 10.

Further, in the vibration measurement device 100, for example, as shown in FIG. 10, by irradiating the measurement light _L CH1 _{~L CHn} of the channel through the head portion _H CH1 _{to H CHn} of each channel arranged in two rows Thus, the twist of the measurement surface 10 can also be measured.

In the embodiment described above, the detection unit 150 separates the interference light L _X incident from the interference optical system 140 into two light components L _X1 and L _X2 having two polarization components orthogonal to each other by the polarization beam splitter 151. Although the present invention is applied to the vibration measuring apparatus 100 configured to perform wavelength division quadrature phase shift homodyne detection detected by the two light detection units 152A and 152B, the present invention is applied to the detection unit 250 as shown in FIG. The present invention can also be applied to the vibration measuring apparatus 200 that performs wavelength division heterodyne detection.

  In the vibration measuring apparatus 200, the detailed description of components common to the vibration measuring apparatus 100 is omitted.

The vibration measurement device 200 includes a light source unit 210 that emits the reference light L _R and the measurement light L _M, the reference optical system 220 to the reference light L _R is incident, the measurement optical system in which the measurement light L _M enters measurement optical system 230, the supra measured through the optical system 230 the measurement light L _M interference optical system 240 is incident with through the optical system 220 is the reference light L _R is incident, the interference optical system 240 in detector 250 for detecting the generated interference light L _X, and the like signal processing unit 260 for analyzing the detection output of the interference light L _X detected by the detection unit 250.

In the vibration measurement device 200, the reference optical system 220, the reference light L _R separated by the beam splitter 241 constituting the interference optical system 240 is incident on the reference surface 222 through a frequency shifter 121, the reference surface The reference light L _R ′ reflected by 222 is returned to the interference optical system 240 via the frequency shifter 222.

The frequency shifter 222 operates by the output of the oscillator 223, the frequency of the reference light L _R incident from the interference optical system 240 is shifted by f _a, emits reference light is shifted to the frequency. The frequency shifter 222 includes, for example, an acoustooptic modulator (AOM) that changes the phase of the reference light by acoustooptic interaction using ultrasonic waves generated inside.

Further, in the interference optical system 240, the detection unit 250 causes the reference light L _R ′ and the measurement light L _M ′ returned from the reference optical system 220 and the measurement optical system 230 to overlap and interfere with each other with the beam splitter 241. and it detects the light detector array 252 is decomposed into each light spectral component by the interference light L _X a spectral element 251 that is generated by the.

In the vibration measurement device 200, the frequency of the laser beam emitted from the laser light source 211 of the light source unit 210 [nu, and the frequency of a given modulated signal from the optical frequency comb generator 212 to the oscillator 213 and f _m, in FIG. 12 as (a), in the center (0-order) frequency [nu, the measurement light L _M of n-th order comb mode frequency ν + nf _{m 'is} returned to the interference optical system 240 through the measurement optical system 230, as shown in FIG. 12 (B), the center (0-order) at frequency [nu + _{f a,} the reference beam n-th order comb mode frequency _{ν + f a + nf m L} R ' is through the reference system 230 the interference optical system Returned to 240.

Accordingly, the beat frequency of the interference light _{L X} generated in the interference optical system 240 is a 0-order frequency _{(ν + f a) -ν =} f a, n order frequency is _{{ν + f a + nf m} } - (ν + nf m ) = _{f a} (here, n = 0, ± 1, ± 2, ... ..), that is, to become an _{all-f a.}

In other words, each element of the photodetector array 252 of the detection unit 250 detects each optical spectrum component having _a beat frequency fa.

  Here, the electric field en (t) of the interference wave in the nth order mode is expressed by the following equation (2).

In this equation (2), ν is a laser frequency, f _a is a shift frequency, n is a comb mode order, f _m is a modulation frequency, ET _n is an electric field of measurement light, and ER _n is an electric field of reference light. Furthermore, θ _n is the relative phase of the measurement light pulse with respect to the phase of the n-th mode of the reference light pulse.

  The detection output current in (t) by the photodetector array 252 is expressed by the following equation (3).

  In the formula (3), a is a proportionality constant.

  Therefore, the signal processing unit 260 can know the relative phase / amplitude between the sidebands in real time by comparing the phase and amplitude of the AC signals in (t) simultaneously detected by the photodetector array 252.

When measuring the DC component of the interference signal L _X, but it is not easy to determine the phase difference between the measured voltage and the amplitude of the measurement light from the values adjacent sidebands, the reference light L _R as the vibration measurement device 200 by inserting the frequency shifter 222 to a path, the signal observed at the photodetector array 252 is shifted frequency f _a, easily performed the phase comparison by signal processing in the signal processing unit 260, also the AC component Since it is observing, the phase and amplitude of the interference signal can be known with one detector per mode.

In the vibration measurement device 200, a spectrum of a predetermined frequency interval that is emitted from the light source unit 210, divides the reference light L _R and the measurement light L _M and the interference optical system 240 is phase synchronized with interference with each other, the measurement light L _M divided make incidence the divided reference light L _R to a reference optical system 220 is incident on the measuring optical system 230, a plurality comprises two or more frequency components of the measurement light L _M incident on each channel separating the channels of the measurement light _L CH1 _{~L CHn,} and irradiation of the plurality of channels the measurement light _L CH1 _{~L CHn} the plurality of measurement points of the measurement surface 20, a plurality of channels that have reflected back by the measurement surface 20 of the measurement light _{L CH1} by measuring optical system 230 includes an optical demultiplexer 231 to align _{'~L CHn'} into one, the measurement light L reflected by the plurality of measurement points of the measurement surface 20 The _{H1 '~L CHn'} back to the interference optical system 240 through the optical demultiplexer 231, in the interference optical system 240, is incident is reflected by the measurement surface 20 via the optical demultiplexer 231 The measurement light L _M ′ and the reference light L _R ′ incident from the reference optical system 220 are caused to interfere with each other, and the light spectrum included in the interference light L _X generated by the interference optical system 240 is separated by the spectroscopic element 251. The signal processing unit 260 analyzes each spectrum component detected by the detection unit 250 and detects the measurement surface from the phase information of the frequency component of each channel. Vibration information at a plurality of measurement points of 20 is obtained, and height information at a plurality of measurement points of the measurement surface 20 is obtained from relative phase information of each frequency component in each channel. Get.

  Accordingly, it is not necessary to perform complicated optical axis adjustment in individual vibration measurement devices, and vibration information of the measurement surface 20 of the measurement target that requires multipoint synchronization without considering time synchronization between measurement points. And height information at a plurality of measurement points on the measurement surface 20 can be obtained from the relative phase information of each frequency component in each channel.

Further, the vibration measurement device 100, 200 described above, by using the optical frequency comb generated by the respective one of the optical frequency comb generator 112, 212 in the light source units 110 and 210 and the reference light _{L R} as the measurement light _{L M} vibrations was to perform measurement, the present invention is, for example, as shown in FIG. 13, the reference light L _R and the measurement light L _M two optical frequency comb generator 313A, see optical frequency comb generated by 313B It can also be applied to the vibration measurement device 300 for vibration measurements using an optical L _R as the measurement light L _M.

The vibration measurement device 300 includes a light source unit 310 that emits the reference light L _R and the measurement light L _M, the reference optical system 320 to the reference light L _R is incident, the measurement optical system in which the measurement light L _M enters 330, the measurement through the optical system 330 the measurement light L _M interference optical system 340 is incident with through the reference optical system 320 is the reference light L _R is incident occurred in the interference optical system 340 The detection unit 350 detects the interference light L _X , the signal processing unit 360 analyzes the detection output of the interference light L _X detected by the detection unit 350, and the like.

  In the vibration measuring apparatus 300, the light source unit 310 uses two optical frequency comb generators 313A and 313B, the modulation frequency and the center frequency are different from each other, and the reference light and the measurement light that are phase-synchronized and coherent with each other. A laser light source 311 that emits a laser beam having a frequency ν, and two optical frequency comb generators 313A on which the laser light emitted from the laser light source 311 is split by a beam splitter 312 and incident. , 313B, and a polarization beam splitter (PBS) 318 that emits the optical frequency combs individually generated by the two optical frequency comb generators 313A and 313B as reference light and measurement light.

  In the light source unit 310, the laser light having a frequency ν emitted from the laser light source 311 is divided by the beam splitter 312, and one of the divided laser lights is directly incident on the optical frequency comb generator 313A and divided. The other laser beam is incident on an optical frequency comb generator 313B via a frequency shifter (AOFS) 314.

The frequency shifter 314 is driven by the oscillation signal given by the oscillator 315, and shifts the frequency of the laser light incident on the optical frequency comb generator 313B by f _aom . The frequency shifter 317 is composed of, for example, an acoustooptic modulator (AOM) that changes the phase of incident light by an acoustooptic interaction by an ultrasonic wave generated inside.

The optical frequency comb generator 313A is frequency given one of the laser beams divided by the beam splitter 312 by an oscillator 316A is by modulating a modulation signal of f _m, to generate an optical frequency comb. Optical frequency comb generated by the optical frequency comb generator 313A is incident on the polarization beam splitter 318 as the measurement light L _M.

The optical frequency comb generator 313B modulates the laser beam split by the beam splitter 312 and frequency-shifted by the frequency shifter 314 with a modulation signal whose frequency is provided by the oscillator 316B is f _m + Δf _m. to generate an optical frequency comb, an optical frequency comb generated by the optical frequency comb generator 313B is incident on the polarization beam splitter 318 as reference light L _R through a half wavelength (lambda / 2) plate 317 .

Here, the oscillators 316A and 316B that supply the modulation signals to the two optical frequency comb generators 313A and 313B are phase-synchronized by a common reference oscillator (not shown), so that the relationship between f _m + Δf _m and f _m The frequency is stabilized.

The optical frequency comb generators 313A and 313B include, for example, an electro-optic modulator (EOM) that modulates the intensity and phase of light outside the laser, and a reflector that is disposed so as to face the EOM. , Fabry-Perot type electro-optic modulation type comprising optical oscillator with electro-optic modulator and reflector, phase modulator using LiNbO ₃ crystal, intensity modulator, semiconductor absorption and phase change are utilized A modulator or the like is used.

The light source unit 310 as two optical frequency comb generator 313A, by using the 313B, it is possible to shift the frequency of the optical frequency comb each mode between the reference light L _R and the measurement light L _M. Thereby, since the frequency of the interference signal can be set to a different value depending on the mode, phase information of each mode can be separated by frequency analysis of the interference signal without performing wavelength division at the time of light detection.

The light source unit 310 emits optical frequency combs (OFC1, OFC2) having frequencies as shown in FIGS. 14A and 14B, for example, by optical frequency comb generators 313A and 313B. FIG. 14A shows an optical frequency comb (OFC1) as measurement light emitted from the optical frequency comb generator 313A. FIG. 14B shows an optical frequency comb (OFC2) as reference light whose frequency is shifted by the frequency shifter 314. The optical frequency comb shown in FIG. 14 has a comb-like mode that matches the repetition frequency of the optical pulse, and the mode interval of the measurement light shown in FIG. 14A is _fm , and FIG. mode spacing of the reference light indicated is _{f m} + △ _{f m.}

Examples of the optical frequency comb shown in FIG. 14, with the mode number around the spectral center mode, the frequency of the interference signal between the modes of N = 0 is assumed that f _a. In the example of the optical frequency comb shown in FIG. 14, when the number attached to the mode counted the center frequency components as 0-th and N, N-th beat frequency = f a _{+ N} △ f _m becomes, N-th beat frequency light Depending on the mode of the frequency comb, it appears at a different frequency.

The polarization beam splitter 318, and the reference light L _R emitted from the optical frequency comb generator 213B through the measurement light L _M and a half wavelength (lambda / 2) plate 317 which is incident from the optical frequency comb generator 313A mixed and emits light superposed with polarization perpendicular to the reference light L _R and the measurement light L _M.

  As described above, the light source unit 310 includes a plurality of optical frequency comb generators 313A and 313B having a single laser beam as input and different driving frequencies, so that a plurality of optical frequency combs can be generated at the same beat frequency. To avoid overlapping of information.

  The light source unit 310 may use two light sources, for example, mode-locked lasers, whose intensity or phase is periodically modulated and whose carrier frequency is stabilized.

In the vibration measurement device 300, the interference optical system 340, light superposed with polarization perpendicular to the reference light L _R and the measurement light L _M by the polarization beam splitter 318 to be emitted from the light source unit 310 is incident .

Interference optical system 340, light superposed with polarization perpendicular to the reference light L _R and the measurement light L _M from the light source unit 310 is incident, the beam splitter 341 for splitting the incident light by the beam splitter 341 The first polarizer 344A into which one of the divided lights is incident, the polarizing beam splitter 343 into which the other light divided by the beam splitter 341 enters through the optical fiber 342, and the polarizing beam splitter 343 The second polarizer 344 </ b> B into which the light returned through the optical fiber 243 is incident through the beam splitter 341 is provided.

In the interference optical system 340, the beam splitter 341 splits light superposed with polarized light orthogonal to the measurement light L _M and the reference light L _R incident from the light source unit 310. One of the lights divided by the beam splitter 341 is incident on the first photodetector 351A of the detection unit 350 and the reference light L _R through the first polarizer 344A as interference light S1 of the measuring light L _M The The other light split by the beam splitter 341 enters the polarization beam splitter 343 via the optical fiber 342.

Further, the polarizing beam splitter 343, split the reference beam L _R contained in the light superimposed by the polarization orthogonal to the reference light L _R and the measurement light L _M which is incident through the optical fiber 342 the measurement light L _M To do. Then, the reference light L _R split by the polarization beam splitter 343 is incident on the reference optical system 320, also split the measurement light L _M is incident on the measuring optical system 330.

Further, in the polarization beam splitter 343, the reference light L _R coming back from the reference optical system 320 _'with is incident measuring light coming back from the measuring optical system 330 L _M' is incident . Then, the polarization beam splitter 343 superimposes the reference light L _R 'on the measurement light L _M '. It returns to the beam splitter 341 via the optical fiber 342. The light returned from the polarizing beam splitter 342 to the beam splitter 341 via the optical fiber 342 is converted from the beam splitter 341 via the second polarizer 344B to the reference light L _R ′ as the measurement light L _M. The interference light S <b> 2 enters the second photodetector 351 </ b> B of the detection unit 350.

Here, in the vibration measurement device 300, the light reference light L _R and the measurement light L _M are superimposed from the light source unit 310 is incident on the Symbol interference optical system 340, the reference light L _R and the measurement light L _M polarizations are orthogonal, it is not possible is a directly detected as interference light, in the Symbol interference optical system 340, the interference of the reference light L _R and the measurement light L _M as a transmission component of the first polarizer 344A light S1 emitted, also emits interference light S2 of the reference light L _{R 'and} the measurement light L _M' as a transmission component of the second polarizer 344B. The first polarizer 344A of the Symbol interference optical system 340 is adjusted to the direction of the polarization to be oblique with reference light L _R with respect to the polarization of the measuring light L _M. The second polarizer 344B of the Symbol interference optical system 340 is adjusted to the direction of the polarization to be oblique to the polarization of the _'measurement beam L _{M and'} the reference light L _R.

Further, in the vibration measurement device 300, the reference optical system 320 is provided with a reference surface 321 for reflecting the reference light _{L R} from the interference optical system 340 is incident through the polarizing beam splitter 343, by the reference surface 321 The reflected reference light L _R ′ is returned to the reference optical system 320.

Further, in the vibration measurement device 300, the measurement optical system 330, the interference optical system 340 measures light through the polarizing beam splitter 343 from is L _M incident, two for each channel the measurement light L _M incident A plurality of measurement light beams L _{CH1 to} L _CHn including the above frequency components are separated into a plurality of measurement light beams L _{CH1 to} L _CHn, and a plurality of corresponding measurement points on the measurement surface 30 are irradiated to the measurement surfaces. 30 includes an optical multiplexer / demultiplexer 331 that combines the measurement light beams L _CH1 ′ to L _CHn ′ reflected from the plurality of channels 30 into one, and the measurement light L reflected from the measurement surface 30 at a plurality of measurement points. the _{CH1 '~L CHn'} through the optical demultiplexer 331 is adapted to return to the interference optical system 340.

The optical demultiplexer 331 separates the measurement light L _M incident on each channel to a plurality of channels of the measurement light L _CH1 ~L _CHn comprising two or more frequency components, the measuring light L of the plurality of channels bundling a demultiplexing function for irradiating the _CH1 ~L _CHn the plurality of measurement points on the measurement surface 30, a plurality of channels that have reflected back by the measuring surface 30 of the measuring light _{L CH1 '~L CHn'} one In this case, the measurement light L _M ′ reflected and returned from the measurement surface 30 has a multiplexing function to be incident on the interference optical system 340. The components for multiplexing and demultiplexing the light include a prism, A spectral element such as an interference film filter or a diffraction grating is used.

Further, in the vibration measurement device 300, detector 350, and the light intensity of the interference light S1 of the reference light coming back through the Symbol interference optical system 340 L _R and the measurement light L _M, the Symbol Interference first photodetector 351A and the second light detector for detecting light intensity of the interference light L _X of the _'measurement beam L _{M and'} the reference light L _R coming back through the optical system 340 individually 351B.

The detection unit 350, the light intensity of the interference light S1 of the measurement light L _M and the reference light L _R as well as detected by the first photodetector 351A, the reference light L _{R 'and} the measurement light L _M' The second light detector 351B detects the light intensity of the interference light S2 with the first light detector 351B, and inputs the detection outputs of the first light detector 351A and the second light detector 351B to the signal processing unit 360. .

In the vibration measurement device 300, the light source unit 310, two optical frequency comb generator based on the laser light by the laser light source 311 is emitted 313A, individual optical frequency comb and the reference light _{L R} and the measurement light _{L M} by 313B In other words, there is a possibility that a difference in delay time may occur between the time when the beam splitter 312 branches and the time when the beam beam is overlapped with the polarization beam splitter 318. the light intensity of the interference light S1 and the reference light L _R that is incident through the polarizer 344A and the measurement light L _M detected by the first photodetector 351A, the interference due to the first photodetector 351A The signal processing unit 360 performs frequency analysis on the detection output of the light S1, and measures a time difference in the process of generating the optical frequency comb. Further, the light intensity of the interference light S2 of the reference beam incident from the Symbol interference optical system 340 through the second polarizer 344B L _{R 'and} the measurement light L _M' and the second light detector 351B The signal processing unit 360 performs frequency analysis on the detection output of the interference light S2 by the second photodetector 351B, and the reference light L _R ′ returned from the reference optical system 320 and the measurement. The time difference of the measurement light L _M ′ returned from the optical system 320 is measured.

Then, in the signal processing unit 360, from the time difference between the reference light L _R ′ and the measurement light L _M ′, which are measured by frequency analysis of the detection output of the second photodetector 351B, the first light the difference between the distance of the detection output of the photodetector 351A by subtracting the time difference of the reference light L _R and the measurement light L _M as measured by frequency analysis, and the measuring surface 30 distance to the reference surface 321 The absolute distance to the measurement surface 30 can be obtained by obtaining the time during which the light propagates and dividing the value obtained by multiplying the obtained time by the speed of light by the refractive index at the measurement wavelength.

In the vibration measurement device 300, a spectrum of a predetermined frequency interval, different modulation frequency and the center frequency with each other, a light source 310 for emitting the reference light L _R is phase locked to each other with a coherent measurement light L _M, a spectrum of a predetermined frequency interval that is emitted from the light source unit 310, divides the reference light L _R and the measurement light L _M and the interference optical system 340 is phase synchronized with interference with each other, the divided reference light L _R the measurement light L _M divided make incidence to the reference optical system 320 is incident on the measuring optical system 330, a plurality of channels including at least two frequency components the measurement light L _M incident on each channel measurement light L _CH1 ~ Separated into L _CHn , a plurality of channels of measurement light L _{CH1 to} L _CHn are irradiated to a plurality of measurement points on the measurement surface 30, and then reflected by the measurement surface 30 and returned. The measurement optical system 320 includes an optical demultiplexer 331 to align the measurement light _{L CH1 '~L CHn'} of several channels to one, the measurement light _{L CH1} is reflected at a plurality of measurement points of the measurement surface 30 '~ L _CHn ′ is returned to the interference optical system 340 via the optical multiplexer / demultiplexer 331, and the measurement light L reflected by the measurement surface 30 and incident via the optical multiplexer / demultiplexer 331 in the interference optical system 340. _M ′ and the reference light L _R ′ incident from the reference optical system 320 are interfered with each other, the light spectrum included in the interference light generated by the interference optical system 340 is separated by the light spectrum separation unit, and the light detection unit 350, and the signal processing unit 360 performs frequency analysis on the detection output from the detection unit 350, so that the phase information of the frequency component of each channel can be used at a plurality of measurement points on the measurement surface 30. Together to obtain vibration information may be obtained from the relative phase information of each frequency component in each channel to obtain height information at a plurality of measurement points of the measurement surface 30.

  10, 20, 30 Measuring surface, 100, 200, 300 Vibration measuring device, 110, 210, 310 Light source unit, 111, 211, 311 Laser light source, 112, 212, 313A, 313B Optical frequency comb generator, 113, 213 223, 315, 316A, 316B Oscillator, 120, 220, 320 Reference optical system, 121 1/8 wavelength (λ / 8) plate, 122, 222, 321 Reference plane, 130, 230, 330 Measurement optical system, 131, 231 331 Optical multiplexer / demultiplexer, 140, 240, 340 Interference optical system, 141, 241, 341, 312 Beam splitter, 150, 250, 350 detector, 151 Polarized beam splitter, 152A, 152B Photo detector, 160, 260 360 signal processor, 251, 152A1, 152B1 spectral element, 2A2, 152B2, 252 Photodetector array, 221, 314 Frequency shifter, 317 Half wavelength (λ / 2) plate, 318, 343 Polarizing beam splitter, 342 Optical fiber, 344A, 344B Polarizer, 351A, 351B First light Detector

Claims (7)

A light source unit that is a spectrum of a predetermined frequency interval and emits reference light and measurement light that are phase-synchronized with each other and coherent
The reference light and the measurement light emitted from the light source unit are divided and incident on the reference optical system and the measurement optical system, and interference light of the reference light and the measurement light returning from the reference optical system and the measurement optical system is generated. Interference optics,
A reference optical system that receives the reference light split in the interference optical system and returns the incident reference light to the interference optical system;
The measurement light divided by the interference optical system is incident, and the incident measurement light is separated into measurement light of a plurality of channels including two or more frequency components for each channel, and the measurement light of the plurality of channels is separated from the measurement surface. Measuring light reflected at a plurality of measurement points on the measurement surface, provided with an optical multiplexer / demultiplexer that irradiates a plurality of measurement points and combines the measurement light of a plurality of channels reflected and returned from the measurement surface. A measurement optical system that returns the interference optical system to the interference optical system via the optical multiplexer / demultiplexer;
An optical spectrum separating unit that separates an optical spectrum included in the interference light generated by the interference optical system, and a detection unit that includes a plurality of photodetectors that detect each optical spectrum separated by the optical spectrum separating unit;
Each spectral component detected by the detection unit is analyzed, and vibration information at a plurality of measurement points on the measurement surface is obtained from the phase information of the frequency component of each channel, and the relative phase information of each frequency component in each channel is used. A vibration measurement apparatus comprising: a signal processing unit that obtains height information at a plurality of measurement points on a measurement surface.   The vibration measurement apparatus according to claim 1, further comprising a frequency shifter that shifts a frequency of reference light or measurement light emitted from the light source unit. A reference optical system in which the reference light emitted from the light source unit is incident via the interference optical system, and the incident reference light is converted from linearly polarized light to circularly polarized light and returned to the interference optical system;
A polarization beam splitter that splits interference light between the reference light generated from the reference optical system generated by the interference optical system and the measurement light incident through the spectroscopic optical system into two orthogonal components; ,
The optical spectrum separation unit is included in a first spectral element that separates an optical spectrum component included in the first orthogonal component separated by the polarization beam splitter, and a second orthogonal component separated by the polarization beam splitter. A second spectroscopic element for separating the optical spectral components,
The detection unit includes a first plurality of photodetectors that respectively detect optical spectrum components included in the first orthogonal component separated by the first spectroscopic element, and a second that is separated by the second spectroscopic element. The vibration measuring device according to claim 1, further comprising a second plurality of photodetectors that respectively detect optical spectrum components included in the orthogonal components. A light source that emits a reference light and a measurement light that are spectra of a predetermined frequency interval, have different modulation frequencies and different center frequencies, are phase-synchronized with each other, and are coherent.
The reference light and the measurement light emitted from the light source unit are divided and incident on the reference optical system and the measurement optical system, and interference light of the reference light and the measurement light returning from the reference optical system and the measurement optical system is generated. Interference optics,
A reference optical system that receives the reference light split in the interference optical system and returns the incident reference light to the interference optical system;
The measurement light divided by the interference optical system is incident, and the incident measurement light is separated into measurement light of a plurality of channels including two or more frequency components for each channel, and the measurement light of the plurality of channels is separated from the measurement surface. Measuring light reflected at a plurality of measurement points on the measurement surface, provided with an optical multiplexer / demultiplexer that irradiates a plurality of measurement points and combines the measurement light of a plurality of channels reflected and returned from the measurement surface. A measurement optical system that returns the interference optical system to the interference optical system via the optical multiplexer / demultiplexer;
A detection unit for detecting interference light generated in the interference optical system;
Based on the interference light detected by the detection unit, vibration information at a plurality of measurement points on the measurement surface is obtained from the phase information of the frequency component of each channel, and the measurement is performed from the relative phase information of each frequency component in each channel. A vibration measurement apparatus comprising: a signal processing unit that obtains height information at a plurality of measurement points on a surface.   The light source unit includes a first optical frequency comb generator that generates a first optical frequency comb by modulating a laser beam with a modulation signal having a first modulation frequency by a first oscillator, and a second oscillator that generates the first optical frequency comb. A second optical frequency comb having a mode frequency interval different from that of the first optical frequency comb is generated by modulating the laser light with a modulation signal having a second modulation frequency different from the first modulation frequency. The vibration measuring apparatus according to claim 4, comprising two optical frequency comb generators. A spectrum of a predetermined frequency interval, the modulation frequency and the center frequency are different from each other, and an output step of emitting the reference light and the measurement light that are phase-synchronized and coherent from the light source unit,
An incident step of entering the measurement light emitted from the light source unit into the optical multiplexer / demultiplexer;
The measurement light incident on the optical multiplexer / demultiplexer is separated into a plurality of channels of measurement light including two or more frequency components for each channel, and the plurality of channels of measurement light are measured at a plurality of measurement points on the measurement surface to be measured. And irradiating a plurality of measurement lights reflected and returned from the measurement surface into one by the optical multiplexer / demultiplexer and entering the interference optical system,
An interference step in which the measurement light reflected by the measurement surface and incident via the optical multiplexer / demultiplexer interferes with the reference light emitted from the light source unit by an interference optical system;
A detection step of detecting each light spectrum by separating an optical spectrum included in the interference light generated by the interference optical system;
Each spectral component detected in the detection step is analyzed, and vibration information at a plurality of measurement points on the measurement surface is obtained from the phase information of the frequency component of each channel, and the relative phase information of each frequency component in each channel is obtained. And an analysis process for obtaining height information at a plurality of measurement points on the measurement surface. An emission step that is a spectrum of a predetermined frequency interval and emits reference light and measurement light that are phase-synchronized and coherent from the light source unit,
The measurement light emitted from the light source in the emission step is separated into measurement light of a plurality of channels including two or more frequency components for each channel by an optical multiplexer / demultiplexer, and the measurement light of the plurality of channels is measured on the measurement target An irradiation step of irradiating a plurality of measurement points on the surface and reflecting the plurality of measurement lights reflected and returned from the measurement surface into one by the optical multiplexer / demultiplexer;
An interference step of causing the measurement light incident through the optical multiplexer and the reference light emitted from the light source unit to interfere with each other by an interference optical system;
A detection step of detecting interference light generated in the interference optical system;
Based on the interference light detected in the detection step, vibration information at a plurality of measurement points on the measurement surface is obtained from the phase information of the frequency component of each channel, and the measurement is performed from the relative phase information of each frequency component in each channel. And an analysis step for obtaining height information at a plurality of measurement points on the surface.

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