Multipoint vibration measurement device

Abstract

To precisely conduct a multipoint vibration measurement by a multipoint vibration measurement device.SOLUTION: In a multipoint vibration measurement device 100, an optical multiplexing / demultiplexing head 130 includes: an optical multiplexing / demultiplexing optical system 131 having an optical demultiplexer element 131A and an optical multiplexer element 131B, the optical demultiplexer element being connected to an interference optical system 120 in which measurement light LS is input from a light source 110, and the optical multiplexer element being connected to the interference optical system 120; a projection optical system 133 for radiating the frequency component of each optical comb of measurement light LS demultiplexed by the optical demultiplexing wave element 131A to plural points of a measurement surface 5 of the measurement target; and a coupling optical system 132 for inputting the frequency component of each light comb in the measurement light LS demultiplexed by the optical demultiplexer element 131A into the projection optical system 133 and inputting the frequency component of each light comb of the measurement light LS reflected by the measurement surface 5 and returned into the optical multiplexer element 131B.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a multi-point vibration measurement device that simultaneously measures vibration information of a measurement target at a plurality of points using light.

Background Art

[0002] In order to investigate the cause of vibration and the load due to vibration, measurement of the vibration distribution in the plane of the measurement target is required. For example, in the case of steady vibration, the vibration distribution in the plane can be measured by performing vibration measurement while shifting the location in accordance with the period of the vibration.

[0003] However, when it is desired to measure transiently changing vibrations in real time, when the vibration frequency components are not known in advance, or when vibration information at several points is required simultaneously, a vibration measurement device that can simultaneously measure vibration information at several points is needed.

[0004] In addition, conventional laser Doppler vibrometers can generally measure the amplitude of vibrations with a speed range of about 10 m per second, but cannot obtain the height of the stationary state. Also, it is not possible to synchronously measure the vibration distribution at multiple points.

[0005] The applicant of the present application has proposed a vibration measurement device and a vibration measurement method that can simultaneously measure vibration information at a plurality of points on a measurement surface of a measurement target by using an optical multiplexing / demultiplexing head that divides measurement light into frequency components and irradiates a plurality of points on the measurement surface of the measurement target, in a vibration meter that analyzes vibration information of the measurement surface of the measurement target by detecting interference light between coherent reference light and measurement light and obtaining the phase difference between the reference light and the measurement light (see, for example, Patent Documents 1-3).

[0006] Also, without using a frequency shifter, an optical comb with a center frequency f0 (Hz) and a frequency interval f m is generated as probe light, and a center frequency f0 (Hz) and a frequency interval f m +Δf mA vibrometer capable of multi-point measurement with a simplified device configuration has been proposed by generating an optical comb as a reference light (see, for example, Patent Document 4).

[0007] Furthermore, a multi-point measurement type laser Doppler vibrometer has been proposed that uses an optical comb generator that makes it possible to generate a wideband optical comb with multiple modes using a single modulator (Patent Document 5). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 5336921 [Patent Document 2] JP 2010-203860 A [Patent Document 3] Patent No. 5363231 [Patent Document 4] Patent No. 7276051 [Patent Document 5] JP 2022-47249 A [Patent Document 6] JP 2015-072136 A Summary of the Invention [Problem to be solved by the invention]

[0009] In a multi-point vibration measurement device using an optical comb, various optical elements are provided in the optical system that propagates the reference light and measurement light through space, such as an interference optical system into which reference light and measurement light are input, an optical multiplexer that splits the measurement light to be irradiated onto the measurement surface into each frequency component of the optical comb, and an optical element that irradiates the measurement surface with measurement light of each frequency component wavelength split by the optical multiplexer that irradiates the measurement surface with measurement light of each frequency component wavelength split by the optical multiplexer and returns the reflected light (scattered light) from the measurement surface to the optical multiplexer.However, there is a risk that unnecessary reflected components will be generated in the various optical elements and mixed into the interference light required for multi-point vibration measurement, resulting in measurement errors.

[0010] Here, like the multi-point vibration measurement device 10 shown in FIG. 1, by modularizing the input and output of the interference optical system 2 to be optical fibers and enabling the transmission of reference light and measurement light, optical elements with each function can be modularized elements, making the assembly and repair of the device easier. Further, by using a spatial optical system and optical fibers to form some functional element into an optical integrated circuit, the device can be miniaturized.

[0011] This multi-point vibration measurement device 10 includes an interference optical system 2 into which the coherent measurement light L S and reference light L R are input. The frequency components of each optical comb included in the measurement light L S input through this interference optical system 2 are split by an optical multiplexer / demultiplexer 3 into, for example, m×n (m and n are arbitrary positive integers) types of frequency components, and each frequency component of the measurement light L S is irradiated through a projection optical system 4 onto a plurality of points (for example, m×n measurement points arranged two-dimensionally in a matrix) on the measurement surface 5 of the measurement object. The reflected light of each frequency component of the measurement light S1 that is reflected at the m×n measurement points on the measurement surface 5 of the measurement object and returns through the projection optical system 4 is combined by the optical multiplexer / demultiplexer 3, and the measurement light L S ' consisting of the reflected light of each frequency component reflected at the m×n measurement points on the measurement surface 5 is input into the interference optical system 2.

[0012] The light source 1 consists of a first optical comb generator (COMB1) 1A and a second optical comb generator (COMB2) 1B that output linearly polarized measurement light L S and reference light L R respectively. They are connected to the interference optical system 2 through FBs 12A , FBs 12B using polarization maintaining fibers (PMF). The first optical comb generator (COMB1) 1A and the second optical comb generator (COMB2) 1B output the measurement light L S and reference light L RAs such, two types of optical combs are generated, each with its intensity or phase periodically modulated and with different modulation frequencies from each other. A polarization (PZ) fiber that can propagate only one polarization instead of a PMF may also be used.

[0013] Here, the PMF is an optical fiber that utilizes the photoelastic effect and structural changes to produce birefringence with different effective refractive indices in the longitudinal and transverse directions of the core, enhancing the polarization-maintaining characteristics of the transmitted light.

[0014] In the interference optical system 2, measurement light L 12A is input from the first optical comb generator (COMB1) 1A via an optical fiber FB S and reference light L 12B is input from the second optical comb generator (COMB2) 1B via an optical fiber FB R .

[0015] The interference optical system 2 consists of five optical couplers OC 2A1 , FB 2A2 , FB 2B1 , FB 2B2 , FB 2C connected by PMF-based optical fibers FB A , OC B , OC C , OC D , OC E . Measurement light L A is input from the first optical comb generator (COMB1) 1A via an optical fiber FB 12A externally connected to the optical coupler OC S , and reference light L B is input from the second optical comb generator (COMB2) 1B via an optical fiber FB 12B externally connected to the optical coupler OC R .

[0016] In this interference optical system 2, two optical fibers FB A are internally connected to the optical coupler OC 2A1 to two optical couplers OC 2A2 , FB D , OC E , and the optical coupler OCB There are two optical fibers FB 2B1 , FB 2B2 Internally connected to two optical couplers OC C , OC D through, and the optical coupler OC E has an optical fiber FB 2C Internally connected to the optical coupler OC through C .

[0017] And the measurement light L input to this interference optical system 2 S is the optical fiber FB using the PMF externally connected to the above optical coupler OC E and is input to the optical multiplexer / demultiplexer 3 through 23 .

[0018] The measurement light L input to the above optical multiplexer / demultiplexer 3 S is split in the optical multiplexer / demultiplexer 3 into a plurality of frequency components of the optical comb contained in the measurement light L S , and a plurality (m×n) of optical fibers FB using the PMF for each frequency component 341 , FB 342 , FB 343 , ···FB 34n , ··· are input to a plurality (m×n) of condenser lenses 4 of the projection optical system 4 A1 , 4 A2 , 4 A3 , ···, 4 An , ···, and a plurality (m×n) of frequency components are condensed by a plurality (m×n) of condenser lenses 4 A1 , 4 A2 , 4 A3 , ···, 4 An , ··· and are irradiated to a plurality of points on the measurement surface 5 of the object to be measured through the quarter-wave plates 4 B1 , 4 B2 , 4 B3 , ···, 4 Bn , ··· respectively.

[0019] And reflected from a plurality of points on the measurement surface 5 of the object to be measured and from the above projection optical system 4 to the optical fibers FB 341 , FB 342 , FB 343 , ···FB34n The measurement light L that returns through ··· S The reflected lights of the respective frequency components of the optical comb are multiplexed by the optical multiplexer / demultiplexer 3, and the optical multiplexer / demultiplexer 3 outputs the reflected light composed of the respective frequency components reflected at a plurality of points on the measurement surface 5 to the optical fiber FB 23 through the above-mentioned optical coupler OC of the interference optical system 2 E is inputted.

[0020] Here, the measurement light L E composed of the reflected lights of the respective frequency components of the optical comb reflected at a plurality of points on the measurement surface 5 inputted to the above-mentioned optical coupler OC S ’ is the measurement light L E outputted from the above-mentioned optical coupler OC S whose respective frequency components pass through the quarter-wave plates 4B1, 4B2, 4B3, ··· 4B n ··· twice, so that the polarization of the measurement light L S ’ is orthogonal to Ls, and since the above-mentioned optical coupler OC E is a polarization beam combiner / splitter (PBC / PBS, hereinafter, a module that can be inputted / outputted with an optical fiber is called a PBC module), the measurement light L S ’ composed of the reflected lights of the respective frequency components reflected at a plurality of points on the measurement surface 5, which is a component orthogonal to Ls in polarization, is inputted from the optical coupler OC E to the optical coupler OC 2C through the optical fiber FB C is inputted.

[0021] In the interference optical system 2, the measurement light L S ’ composed of the reflected lights of the frequency components of the respective optical combs reflected at a plurality of points on the measurement surface 5 and the reference light L R inputted from the light source 1 are outputted from the optical coupler OC C as the measurement interference light, and the interference light between the measurement light L S inputted from the light source 1 and the reference light L R is outputted from the optical coupler OC D as the reference interference light.

[0022] The interference light detection unit 6 into which the measurement interference light and the reference interference light obtained by the interference optical system 2 are input includes a measurement interference light detector 6A and a reference interference light detector 6B each composed of a balanced photodetector, and the optical coupler OC of the interference optical system 2 C is externally connected to two optical fibers FB 26A1 , FB 26A2 through which the measurement interference light input from the optical coupler OC C is received by the measurement interference light detector 6A, and the measurement interference signal S S obtained by detecting the measurement interference light and converting it into an electrical signal is output. At the same time, two optical fibers FB D externally connected to the optical coupler C of the interference optical system 2 26B1 , FB 26B2 through which the reference interference light input from the optical coupler OC D is received by the reference interference light detector 6B, and the reference interference signal S R obtained by detecting the reference interference light and converting it into an electrical signal is output.

[0023] Here, in the balanced photodetector used as the measurement interference light detector 6A and the reference interference light detector 6B, the beats having frequencies corresponding to the frequency differences of the optical combs of the respective frequency components of the input measurement light and reference light are combined into one, converted into an electrical signal, and output. The frequency differences of the frequency components of the optical combs of the measurement light and the reference light described here are sufficiently small compared to the intervals of the respective frequency components of the optical combs, and are not split by the optical multiplexing element and the optical demultiplexing element described below. Also, the bandwidth of the balanced photodetector is sufficiently smaller than the intervals of the respective frequency components of the optical combs, and is sufficiently large to detect the frequency differences of the frequency components of the optical combs of the measurement light and the reference light.

[0024] And in this multi-point vibration measurement device 10, in the signal processing unit 7, the measurement interference signal S S obtained by the interference light detection unit 6 and the reference interference signal S RBy calculating the phase difference of each beat having a frequency corresponding to the frequency difference between the measurement light and the reference light of each optical comb input in the analysis of the discrete Fourier transform (DFT: discrete Fourier transform) (including the fast Fourier transform (FFT: fast Fourier transform)), the vibration information at a plurality of points on the measurement surface 5 is analyzed to measure the vibration distribution on the measurement surface 5.

[0025] As in this multi-point vibration measuring device 10, by configuring the input and output of the interference optical system 2 with optical fibers and sending the reference light and the measurement light through the optical fibers, it is possible to use modularized elements of optical elements having each function, and the assembly and repair of the device are facilitated. However, from the interference optical system 2 to the optical fiber FB 23 The measurement light L input to the optical multiplexer / demultiplexer 3 through S A part of it is reflected by the optical multiplexer / demultiplexer 3 and returns to the interference optical system 2, which causes a measurement error by mixing into the interference light necessary for multi-point vibration measurement.

[0026] For example, when an arrayed waveguide grating (AWG) is used for the optical multiplexer / demultiplexer 3, it is small in size and high in resolution, but the return loss (RL) is about 40 dB. This reflection occurs inside the optical multiplexer / demultiplexer 3 and at the connection part between the optical fiber and the optical multiplexer / demultiplexer 3. Also, when the optical path from the interference optical system 2 to the optical multiplexer / demultiplexer is an optical fiber, the reflection from the connector of the optical fiber cannot be ignored.

[0027] That is, as the optical multiplexer / demultiplexer 3, a triangular prism, a plurality of wavelength division multiplexing filters, a diffraction grating, etc. are used, but the problem was that the RL was small.

[0028] On the other hand, the amount of reflected light returning from the measurement surface 5 to the optical multiplexer / demultiplexer 3 depends on the surface properties and shape of the measurement surface 5 and greatly attenuates.

[0029] Furthermore, the insertion loss (IL) of the optical multiplexer / demultiplexer 3 is large, for example, about 6.5 dB for an AWG with 25 GHz spacing, and when used in a round trip, the loss becomes about 13 dB, so the effect of RL becomes relatively large.

[0030] If the reflection from the measurement surface 5 is not large enough, the measurement light (first optical comb) L S It is difficult to distinguish between the reflections from the measurement surface 5 and the reflections from the measurement surface 5.

[0031] In such a case, there is a problem that the vibration information calculated by the signal processing unit 7 becomes erroneous.

[0032] The present invention has been devised in view of the above-mentioned problems, and has as its object to provide a multi-point vibration measuring device, comprising an optical multiplexer and splitter provided in an optical path through which measurement light passes to irradiate a measurement surface via an interference optical system, The present invention aims to eliminate measurement errors caused by unwanted reflection components from various optical elements such as optical elements being mixed into interference light required for multi-point vibration measurement, thereby enabling highly accurate multi-point vibration measurement.

[0033] Other objects of the present invention and specific advantages obtained by the present invention will become more apparent from the following description of the embodiments. [Means for solving the problem]

[0034] In the present invention, in a multi-point vibration measurement device, two optical splitter-multiplexer elements are provided, and the functions of the optical splitter element and the optical multiplexer element are operated separately, and an optical path is separated into one that splits the measurement light output from the light source through an interference optical system into multiple frequency components of an optical comb contained in the measurement light and irradiates multiple points on the measurement surface of the object to be measured, and another optical path that combines the multiple frequency components reflected and returned from multiple points on the measurement surface and inputs them to the interference optical system, thereby preventing unnecessary reflected components by the optical splitter element that splits the multiple frequency components from being mixed into the interference light required for multi-point vibration measurement.

[0035] That is, the present invention is a multi-point vibration measurement device, which is a spectrum with a predetermined frequency interval, and includes a light source that outputs measurement light and reference light with interference, and divides the measurement light output from the light source into each frequency component of an optical comb and irradiates a plurality of points on the measurement surface of the measurement object as each frequency component of the optical comb. A light multiplexing / demultiplexing head, the measurement light and the reference light output from the light source are respectively input, the measurement light input from the light source is input to the light multiplexing / demultiplexing head, and the measurement light reflected by the measurement surface and returning through the light multiplexing / demultiplexing head. An interference optical system that interferes with the measurement light including each frequency component and the reference light output from the light source to output measurement interference light, and a measurement light detection unit that receives the measurement interference light obtained by the interference optical system and converts it into an electrical signal to obtain a measurement interference signal, and based on the measurement interference signal obtained by the measurement light detection unit, a signal processing unit that analyzes vibration information at a plurality of points on the measurement surface. The light multiplexing / demultiplexing head includes a demultiplexing element that demultiplexes each frequency component included in the measurement light input from the interference optical system, a projection optical system that irradiates each frequency component demultiplexed by the demultiplexing element to a plurality of points on the measurement surface of the measurement object, and a multiplexing element that multiplexes each frequency component of the measurement light reflected by the measurement surface and returning and inputs it to the interference optical system, and a coupling optical system that inputs each frequency component included in the measurement light demultiplexed by the demultiplexing element to the projection optical system and inputs each frequency component of the measurement light reflected by the measurement surface and returning to the multiplexing element. It is characterized by comprising.

[0036] In the multi-point vibration measurement device according to the present invention, the interference optical system outputs the measurement interference light, interferes the measurement light and the reference light input from the light source to output reference interference light, and receives the reference interference light obtained by the interference optical system and converts it into an electrical signal. A reference light detection unit that obtains a reference interference signal, and the signal processing unit can analyze vibration information at a plurality of points on the measurement surface based on the measurement interference signal obtained by the measurement light detection unit and the reference interference signal obtained by the reference light detection unit.

[0037] Further, in the multi-point vibration measurement device according to the present invention, the optical multiplexer / demultiplexer head splits each frequency component of the optical comb included in the measurement light into each frequency component for each frequency component of the optical comb by the optical demultiplexing element, and irradiates a plurality of points on the measurement surface of the measurement object through the projection optical system, and each frequency component for each frequency component of the measurement light reflected and returned from the measurement surface can be multiplexed by the optical multiplexing element.

[0038] Further, in the multi-point vibration measurement device according to the present invention, the optical multiplexer / demultiplexer head splits each frequency component of the optical comb included in the measurement light into each frequency component for each of a plurality of frequency components of the optical comb by the optical demultiplexing element, and irradiates a plurality of points on the measurement surface of the measurement object through the projection optical system, and each frequency component for each of the plurality of frequency components of the measurement light reflected and returned from the measurement surface can be multiplexed by the optical multiplexing element.

[0039] Further, the multi-point vibration measurement device according to the present invention can have the coupling optical system incorporated in the projection optical system.

[0040] Further, in the multi-point vibration measurement device according to the present invention, the optical demultiplexing element splits each frequency component of the optical comb included in the measurement light input through one optical fiber from the interference optical system, and outputs it through a plurality of optical fibers, and the optical multiplexing element multiplexes each frequency component input through a plurality of optical fibers and outputs it through one optical fiber, and the coupling optical system can include a coupling optical element that aligns the optical axes of two light beams with orthogonal polarization directions output from two optical fibers.

[0041] Further, in the multi-point vibration measurement device according to the present invention, the coupling optical element can be made of a birefringent crystal.

[0042] Further, in the multi-point vibration measurement device according to the present invention, the coupling optical element can be a Wollaston prism.

[0043] Further, in the multi-point vibration measurement device according to the present invention, the coupling optical system is composed of a coupling optical element array in which the optical elements are two-dimensionally arranged, and each frequency component of the optical comb of the measurement light input through the coupling optical element array is collected by a condenser optical element and output toward the measurement surface of the measurement target, and each frequency component of the optical comb of the measurement light reflected and returned by the measurement surface is collected by the condenser optical element and input to the coupling optical element array.

[0044] Furthermore, in the multi-point vibration measurement device according to the present invention, a delay optical system is provided in the optical path through which the reference light passes between the measurement light output from the light source and the reference light and the measurement light including each frequency component reflected by the measurement surface and returned through the coupling optical system until they are interfered with in the interference optical system and output as measurement interference light, so that the optical path length of the optical path through which the measurement light and the measurement light including each frequency component reflected by the measurement surface pass is made equal to the optical path length of the optical path through which the reference light passes.

Advantages of the Invention

[0045] In the multi-point vibration measurement device according to the present invention, two optical multiplexers / demultiplexers are provided, and the functions of the optical demultiplexer and the optical multiplexer are made to function individually. The measurement light output from the light source through the interference optical system is split into a plurality of frequency components of the optical comb included in the measurement light and irradiated to a plurality of points on the measurement surface of the measurement target, and the optical path for splitting the measurement light into the plurality of frequency components and the optical path for combining the plurality of frequency components reflected and returned at the plurality of points on the measurement surface and inputting them to the interference optical system are separated, so that unnecessary reflection components by the optical demultiplexer for splitting into the plurality of frequency components do not mix into the interference light necessary for multi-point vibration measurement.

[0046] Therefore, according to the present invention, measurement errors caused by unnecessary reflection components by various optical elements such as optical multiplexers / demultiplexers provided in the optical path through which the measurement light irradiating the measurement surface passes through the interference optical system from mixing into the interference light necessary for multi-point vibration measurement are eliminated, and multi-point vibration measurement can be performed with high precision.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0048] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. For common components, common reference numerals will be given in the drawings for explanation. It goes without saying that the present invention is not limited to the following examples and can be arbitrarily changed without departing from the gist of the present invention.

[0049] FIG. 2 is a schematic diagram showing the configuration of a multi-point vibration measurement device 100 to which the present invention is applied.

[0050] This multi-point vibration measurement device 100 has a spectrum at a predetermined frequency interval and outputs measurement light L S and reference light L R from a light source 110, and the measurement light L S and reference light L RAn interference optical system 120 into which [something] is input, and measurement light L that passes through the interference optical system 120 S An optical multiplexer / demultiplexer head 130 into which [something] is input, an interference light detection unit 140 into which measurement interference light and reference interference light output through the interference optical system 120 are input, and a measurement interference signal S S and a reference interference signal S R are input from a signal processing unit 150.

[0051] In this multi-point vibration measurement device 100, a light source 110 generates two types of optical combs in which the intensity or phase is periodically modulated as the measurement light (first optical comb) L S and the reference light (second optical comb) L R respectively, and the modulation frequencies are different from each other.

[0052] Also, the optical multiplexer / demultiplexer head 130 separates the measurement light L S output from the light source 110 through the interference optical system 120 for each frequency component of the optical comb and irradiates a plurality of points on the measurement surface 5 of the measurement object. The reflected light of the frequency components of the optical comb of the measurement light L S returning after being reflected by the measurement surface 5 is multiplexed, and the measurement light L S including each frequency component of the optical comb of the measurement light L S ' is input into the interference optical system 120.

[0053] The interference optical system 120 interferes the measurement light L S ' including each of the above frequency components returning through the optical multiplexer / demultiplexer head 130 and the reference light L R output from the light source 110, outputs the interference light as measurement interference light, and interferes the measurement light L S output from the light source 110 and the reference light L R and outputs the interference light as reference interference light.

[0054] The interference light detection unit 140 receives and detects the measurement interference light and the reference interference light output from the interference optical system 120, and thereby converts them into an electrical signal, obtaining a measurement interference signal S S and a reference interference signal S RIt is input to the signal processing unit 150.

[0055] Then, in the signal processing unit 150, based on the measurement interference signal S obtained by the interference light detection unit 140 and the reference interference signal S, the vibration information at a plurality of points on the measurement surface 5 is analyzed to measure the vibration distribution of the measurement surface 5. S and the reference interference signal S R Here, the multi-point vibration measurement device 100 applies the present invention to the multi-point vibration measurement device 10 shown in FIG. 1, provides two optical multiplexing / demultiplexing elements 3, functions the functions of the optical demultiplexing element and the optical multiplexing element individually, and separates the optical path for splitting the measurement light L output from the light source 110 through the interference optical system 120 into a plurality of frequency components of the optical comb included in the measurement light L and irradiating a plurality of points on the measurement surface 5 of the measurement object from the optical path for combining the plurality of frequency components of the optical comb reflected back from the plurality of points on the measurement surface 5 and inputting them to the interference optical system 120. In this multi-point vibration measurement device 100, the same components as those in the multi-point vibration measurement device 10 are denoted by the same reference numerals, and their detailed descriptions are omitted.

[0056] and irradiating a plurality of points on the measurement surface 5 of the measurement object, and the optical path for combining the plurality of frequency components of the optical comb reflected back from the plurality of points on the measurement surface 5 and inputting them to the interference optical system 120. In this multi-point vibration measurement device 100, the same components as those in the multi-point vibration measurement device 10 are denoted by the same reference numerals, and their detailed descriptions are omitted. S the measurement light L S Here, the multi-point vibration measurement device 100 applies the present invention to the multi-point vibration measurement device 10 shown in FIG. 1, provides two optical multiplexing / demultiplexing elements 3, functions the functions of the optical demultiplexing element and the optical multiplexing element individually, and separates the optical path for splitting the measurement light L output from the light source 110 through the interference optical system 120 into a plurality of frequency components of the optical comb included in the measurement light L and irradiating a plurality of points on the measurement surface 5 of the measurement object from the optical path for combining the plurality of frequency components of the optical comb reflected back from the plurality of points on the measurement surface 5 and inputting them to the interference optical system 120. In this multi-point vibration measurement device 100, the same components as those in the multi-point vibration measurement device 10 are denoted by the same reference numerals, and their detailed descriptions are omitted.

[0057] In this multi-point vibration measurement device 100, the light source 110 includes a first optical comb generator (COMB1) 1A and a second optical comb generator (COMB2) 1B that output measurement light (first optical comb) L S and reference light (second optical comb) L R respectively, and are connected to the interference optical system 120 through optical fibers FB 12A and FB 12B The first optical comb generator (COMB1) 1A and the second optical comb generator (COMB2) 1B generate two types of optical combs whose intensities or phases are periodically modulated and whose modulation frequencies are different from each other as the measurement light (first optical comb) L S and the reference light (second optical comb) L R respectively.

[0058] The interference optical system 120 includes optical fibers FB 2A2 and FB 2B1, FB 2B2 Four optical couplers OC connected by A , OC B , OC C , OC D and an optical fiber FB externally connected to the optical coupler OC A Measured light L is input from the light source 110 through 12A the optical fiber FB, and reference light L is input from the light source 110 through the optical fiber FB S externally connected to the optical coupler OC B externally connected to the optical coupler OC 12B through the optical fiber FB R is input.

[0059] In this interference optical system 120, an optical coupler OC A has an optical coupler OC internally connected through an optical fiber FB 2A2 through the optical fiber FB D , and an optical coupler OC A has an optical demultiplexing element 131A provided in the optical multiplexing / demultiplexing optical system 131 of the optical multiplexing / demultiplexing head 130 externally connected through an optical fiber FB 23 . Also, two optical fibers FB B are connected to an optical coupler OC 2B1 , FB 2B2 internally connect two optical couplers OC C , OC D , and an optical coupler OC C has a multiplexing element 131B provided in the optical multiplexing / demultiplexing optical system 131 of the optical multiplexing / demultiplexing head 130 externally connected through an optical fiber FB 32 .

[0060] Here, in the interference optical system 120, by making the lengths of the two optical fibers FB A , OC B , OC D connecting between the three optical couplers OC the same, the measured light L 2A2 , FB 2B2 output from the first optical comb generator (COMB1) 1A of the light source 110 passes through the optical fiber FB S and is input to the optical coupler OC 2A2 until the measured light L D enters the optical coupler OC SThe optical path length through which the reference light L output from the second optical comb generator (COMB2) 1B passes R is the same as the optical path length through which the reference light L 2B2 passes until it is input into the optical coupler OCD through the optical fiber FB R .

[0061] And the measurement light L input into this interference optical system 120 S is input into the optical demultiplexing element 131A through the optical fiber FB using the PMF externally connected to the optical coupler OC A . 23

[0062] The optical multiplexing / demultiplexing head 130 includes an optical multiplexing / demultiplexing optical system 131 including an optical demultiplexing element 131A and an optical multiplexing element 131B individually externally connected to two optical couplers OC 23 , FB 32 of the interference optical system 120 through two optical fibers FB A , OC C , and a coupling optical system 132 including a plurality (m×n) of optical couplers OC C1 , OC C2 , OC C3 , ···, OC Cn , ···, and a projection optical system 133 including a plurality (m×n) of projection optical elements 441, 442, 443, ···, 44 n , ··· connected to this coupling optical system 132. The optical couplers OC C1 , OC C2 , OC C3 , ···, OC Cn , ··· function as PBC modules in the same manner as the optical coupler OC E shown in FIG. 1.

[0063] The optical demultiplexing element 131A of the optical multiplexing / demultiplexing optical system 131 is connected to a plurality (m×n) of optical couplers OC of the coupling optical system 132 through a plurality (m×n) of optical fibers FB 341 , FB 342 , FB 343 , ···, FB 34n , ··· C1 , OC​C2 、OC C3 、···、OC Cn are connected to ···, and the multiplexing element 131B of the optical multiplexing / demultiplexing optical system 131 is connected to a plurality (m×n) of optical fibers FB 431 、FB 432 、FB 433 、···、FB 43n 、··· through a plurality (m×n) of optical couplers OC of the coupling optical system 132 C1 、OC C2 、OC C3 、···、OC Cn 、··· are connected.

[0064] The plurality (m×n) of projection optical elements 441, 442, 443, ···, 44 of the projection optical system 133 are respectively condenser lenses 4 n 、···, and quarter-wave plates 4 A1 、4 A2 、4 A3 、···、4 An 、··· and are composed of a plurality (m×n) of optical fibers FB B1 、4 B2 、4 B3 、···、4 Bn 、··· and are connected to the coupling optical system 132 through a plurality (m×n) of optical fibers FB 441 、FB 442 、FB 443 、···、FB 44n 、···.

[0065] The measurement light L input into the optical demultiplexing element 131A of the optical multiplexing / demultiplexing optical system 131 through the optical fiber FB 23 is demultiplexed in the optical demultiplexing element 131A into a plurality of frequency components of the optical comb included in the measurement light L, and for each frequency component of the optical comb, a plurality (m×n) of optical fibers FB S are connected to a plurality (m×n) of optical couplers OC of the coupling optical system 132 through S 、FB 341 、FB 342 、FB 343 、···、FB 34n 、··· C1 、OC C2 、OC C3 、···、OC Cnis input into ···, and respectively into the optical coupler OC C1 OC C2 OC C3 ···, OC Cn From ···, a plurality (m×n) of optical fibers FB 441 FB 442 FB 443 ···, FB 44n are input into a plurality (m×n) of condenser lenses 4 of the projection optical system 133 through ··· A1 4 A2 4 A3 ···, 4 An are input into ···, and a plurality (m×n) of frequency components are condensed by the condenser lenses 4 A1 4 A2 4 A3 ···, 4 An ··· and are irradiated onto a plurality of points (for example, m×n measurement points two-dimensionally arranged in a matrix) on the measurement surface 5 of the object to be measured through the quarter-wave plates 4 B1 4 B2 4 B3 ···, 4 Bn ···

[0066] Then, the measurement light L that is reflected at each measurement point on the measurement surface 5 of the object to be measured and returns from the projection optical system 133 through the optical fibers FB 441 FB 442 FB 443 FB 44n ··· returns to the optical coupler OC of the coupling optical system 132 C1 OC C2 OC C3 ···, OC Cn ··· The reflected light of each frequency component of ··· returns to the optical fibers FB from ··· S of the measurement light L C1 OC C2 OC C3 ···, OC Cn ··· and returns to the optical fibers FB from ··· 431 FB 432 FB 433 ···, FB 43nis input into the multiplexing element 131B of the optical multiplexing / demultiplexing optical system 131 through..., multiplexed by the multiplexing element 131B, and becomes the measurement light L composed of the reflected light of each frequency component reflected at each measurement point on the measurement surface 5 S as the optical fiber FB from the multiplexing element 131B 32 is input into the optical coupler OC of the interference optical system 120 through... C to be input.

[0067] FIGS. 3(A) and 3(B) are diagrams for explaining the functions of the optical demultiplexing element 131A and the optical multiplexing element 131B provided in the optical multiplexing / demultiplexing head 130 in the multi-point vibration measuring device 100. The optical demultiplexing element 131A has a function of demultiplexing each frequency component of the optical comb included in the measurement light L into each frequency component of the optical comb one by one as shown in FIG. 3(A). Also, as shown in FIG. 3(B), the optical demultiplexing element 131A has a function of multiplexing each frequency component demultiplexed for each frequency component of the optical comb into the measurement light L S to be '. S

[0068] Here, in this multi-point vibration measuring device 100, an optical fiber using PMF is used as the optical path, and in the optical demultiplexing element 131A, each frequency component of the linearly polarized optical comb in which a plurality of frequency components of the optical comb included in the measurement light L are demultiplexed is, in the projection optical system 133, each condenser lens 4 S where the measurement light L is included in the measurement light L S is condensed by each of the condenser lenses 4 A1 4 A2 4 A3 4 An ... and irradiated onto the measurement surface 5 as each frequency component of circularly polarized light through each quarter-wave plate 4 B1 4 B2 4 B3 4 Bn ... Then, the reflected light of each circularly polarized light component reflected by the measurement surface 5 becomes each frequency component of linearly polarized light through each quarter-wave plate 4 B1 4 B2 4 B3 4 Bn ... and is condensed by each condenser lens 4 A1 4 A2 4A3 ,..., 4 An ,... is returned to

[0069] That is, in this multi-point vibration measurement device 100, in the projection optical system 133, the condenser lens 4 A1 , 4 A2 , 4 A3 ,..., 4 An ,... passes through the quarter-wave plate 4 B1 , 4 B2 , 4 B3 ,..., 4 Bn ,... The frequency components of the optical comb of the measurement light L output from S become circularly polarized light and irradiate the target, and the reflected light returning from the target passes through the above quarter-wave plate 4 B1 , 4 B2 , 4 B3 ,..., 4 Bn ,... passes through the condenser lens 4 A1 , 4 A2 , 4 A3 ,..., 4 An The frequency components of the optical comb of the reflected light input to A1 , 4 A2 , 4 A3 ,..., 4 An ,... with respect to the output light of A1 , 4 A2 , 4 A3 ,..., 4 An ,... The frequency components of the optical comb of the reflected light input to

[0070] The frequency components of the optical comb of the reflected light returning from the projection optical system 133 to the optical fiber FB 441 , FB 442 , FB 443 ,..., FB 44n ,... pass through the optical coupler OC of the coupling optical system 132 via C1 , OC C2 , OC C3 ,..., OC Cn ,... The frequency components of the optical comb of the reflected light returning to 341 , FB 342 , FB 343, ···, FB 34n , ··· are input into the optical coupler OC C1 , OC C2 , OC C3 , ···, OC Cn , the measurement light L input into ··· S has a polarization plane orthogonal to the polarization plane of each frequency component of the measurement light L, and the optical coupler OC C1 , OC C2 , OC C3 , ···, OC Cn , ··· are input into the multiplexing element 131B of the optical multiplexing / demultiplexing optical system 131 via the optical fiber FB 431 , FB 432 , FB 433 , ···, FB 43n , ··· are input into the multiplexing element 131B of the optical multiplexing / demultiplexing optical system 131 via ···

[0071] Thus, the optical coupler OC of the coupling optical system 132 C1 , OC C2 , OC C3 , ···, OC Cn , ··· are directional couplers in which each frequency component of the measurement light L, which is linearly polarized light with polarization planes orthogonal to each other, and each frequency component of the reflected light reflected back at the measurement surface 5 are input from opposite directions and output in opposite directions, and may be a PBC module or a circulator. In the coupling optical system 132, instead of the optical coupler OC S , OC C1 , OC C2 , OC C3 , ···, OC Cn , ···, for example, a fused PBC module that multiplexes two orthogonal polarization beams and outputs them to one fiber, a fused PBC module that branches the input light into linearly polarized light that is orthogonal and outputs it to two PMFs, a PBC module using a birefringent crystal, etc. can be used

[0072] Then, the reflected light of each frequency component of the measurement light L reflected at a plurality of points on the measurement surface 5 of the measurement object and returned via the projection optical system 133 is multiplexed by the multiplexing element 131B, and the measurement light L composed of the reflected light of each frequency component reflected at a plurality of points on the measurement surface 5 S is multiplexed by the multiplexing element 131B, and the measurement light L composed of the reflected light of each frequency component reflected at a plurality of points on the measurement surface 5S ' is transmitted from the above-mentioned optical multiplexing element 131B to the optical fiber FB 32 and input to the optical coupler OC of the above-mentioned interference optical system 120 through C it.

[0073] Here, each frequency component reflected at a plurality of points on the measurement surface 5 has a phase fluctuation caused by the Doppler shift due to the vibration at the plurality of points on the measurement surface 5. The measurement light L S The reflected light of each frequency component of is multiplexed by the above-mentioned optical multiplexing element 131B to form the measurement light L S ' has a phase fluctuation caused by the Doppler shift.

[0074] The above-mentioned optical coupler OC C is the optical coupler OC of the above-mentioned interference optical system 120 B The reference light L input from the optical fiber FB 2B1 to the above-mentioned optical coupler OC through C and the measurement light L R input to the above-mentioned optical coupler OC C are multiplexed with the same polarization plane to output the interference light between the reference light L S and the measurement light L R ' as the measurement interference light. S '

[0075] Also, the optical coupler OC of the above-mentioned interference optical system 120 D is the optical coupler OC A The measurement light L input from the optical fiber FB 2A2 to it and the reference light L S input from the optical fiber FB B to the optical coupler OC 2B2 are multiplexed with the same polarization plane to output the interference light between the reference light L R and the measurement light L R as the reference interference light. S '

[0076] That is, in the above-mentioned interference optical system 120, the measurement light L with a phase fluctuation caused by the Doppler shift consisting of the reflected light of each frequency component reflected at a plurality of points on the measurement surface 5 S' and the reference light L input from the light source 110 to the optical coupler OC B The interference light with the reference light L input to the optical coupler OC R is output from the optical coupler OC as the measurement interference light, and the measurement light L input from the light source 110 to the optical coupler OC C is output from the optical coupler OC as the reference interference light, together with the interference light between the measurement light L and the reference light L input to the optical coupler OC A S and the optical coupler OC B R is output from the optical coupler OC as the reference interference light. D

[0077] The interference light detection unit 140, which receives the measurement interference light and the reference interference light obtained by the interference optical system 120, includes a measurement interference light detector 6A and a reference light detector 6B, each of which is a balanced photodetector. Two optical fibers FB C externally connected to the optical coupler OC of the interference optical system 120 26A1 FB 26A2 receive the measurement interference light input from the optical coupler OC through the optical fibers FB C The measurement interference light detector 6A outputs a measurement interference signal S S obtained by detecting the measurement interference light and converting it into an electrical signal. At the same time, two optical fibers FB D externally connected to the optical coupler OC of the interference optical system 120 26B1 FB 26B2 receive the reference interference light input from the optical coupler OC through the optical fibers FB D and output a reference interference signal S R obtained by detecting the reference interference light and converting it into an electrical signal.

[0078] Then, in the signal processing unit 150, for the measurement interference signal S S and the reference interference signal S R obtained by the interference light detection unit 140, the phase difference for each frequency component of the measurement light and the reference light, which are optical comms, is calculated by DFT analysis. The measurement interference signal S S and the reference interference signal S R ​​​By obtaining the phase difference for each frequency component of the interference signal resulting from the Doppler shift due to vibrations at multiple points on the measurement surface 5, vibration information such as vibration velocity, moving distance, acceleration, etc. at multiple points on the measurement surface 5 is analyzed to measure the vibration distribution on the measurement surface 5.

[0079] Thus, in this multi-point vibration measurement device 100, the measurement light L S from the interference optical system 120 provided with the optical demultiplexing element 131A that demultiplexes a plurality of frequency components of the optical comb included in S The optical path through which the measurement light L passes and the measurement light L provided with the optical multiplexing element 131B that multiplexes the reflected lights of the respective frequency components reflected at multiple points on the measurement surface 5 of the object S ' are separated, and a part of the measurement light L output from the interference optical system 120 S is reflected by the optical demultiplexing element 131A to generate unnecessary reflection components. However, these reflection components are transmitted through the optical fiber FB 23 and return to the optical coupler OC A of the interference optical system 120, and from this branched optical coupler OC A return to the first optical comb generator (COMB1) 1A of the light source 110 through the optical fiber FB 12A and are absorbed by the isolator built into the light source unit. Therefore, even if unnecessary reflection components are generated by reflection in the optical demultiplexing element 131A, these reflection components do not affect the interference light of the reference light L C output from the optical coupler OC R of the interference optical system 120 and the measurement light L S ', that is, the measurement interference light, or the interference light of the reference light L D output from the optical coupler OC R of the interference optical system 120 and the measurement light L S ', that is, the reference interference light.

[0080] Therefore, in this multi-point vibration measurement device 100, the optical demultiplexing element 131A provided in the optical path through which the measurement light L irradiates the measurement surface 5 via the interference optical system 120, and the optical coupler OC of the coupling optical system 132 S C1 ​, OC C2 , OC C3 , ···, OC Cn By eliminating the measurement errors caused by the unnecessary reflection components of various optical elements such as ··· from mixing into the interference light required for multi-point vibration measurement, multi-point vibration measurement can be performed with high precision.

[0081] Here, in the optical multiplexing / demultiplexing head 130 of the multi-point vibration measurement device 100, as shown in Fig. 3(A), the measurement light L S The frequency components of the optical comb contained in are demultiplexed by the optical demultiplexing element 131A for each frequency component, and each frequency component is irradiated to a plurality of points on the measurement surface 5 of the measurement object through the projection optical system 133. As shown in Fig. 3(B), the measurement light L S ' composed of the reflected light of each frequency component for each of the above frequency components reflected and returned from the measurement surface 5 is multiplexed by the optical multiplexing element 131B. However, as shown in Fig. 4(A), the optical demultiplexing element 131A demultiplexes the frequency components contained in the measurement light L S into a plurality of frequency components for each frequency component, and as shown in Fig. 4(B), the measurement light L S ' composed of the reflected light of each frequency component demultiplexed for each of the plurality of frequency components reflected and returned from the measurement surface 5 may be multiplexed by the multiplexing element 131B.

[0082] Figs. 4(A) and (B) are diagrams for explaining the functions of the optical demultiplexing element 131A and the optical multiplexing element 131B provided in the optical multiplexing / demultiplexing head 130 of the multi-point vibration measurement device 100. As shown in Fig. 4(A), the optical demultiplexing element 131A has a function of demultiplexing each frequency component of the optical comb contained in the measurement light L S into a plurality of frequency components for each frequency component, and also, as shown in Fig. 4(B), the optical multiplexing element 131B has a function of multiplexing each frequency component demultiplexed for each of the plurality of frequency components to obtain the measurement light L S '.

[0083] In this way, the measurement light L SBy demultiplexing each frequency component of the optical comb contained in [the relevant object] for each of a plurality of frequency components, since the frequency components of each optical comb containing the demultiplexed plurality of frequency components are each reflected at a plurality of points on the measurement surface 5 and return through the same optical path, the measurement light L S ' can be used for distance measurement to a plurality of points on the measurement surface 5.

[0084] Measurement light L S When demultiplexing the frequency components of each optical comb contained in [the relevant object] for each of the frequency components of a plurality of optical combs by an optical multiplexer / demultiplexer, compared with the case of demultiplexing the frequency components of the optical comb in the frequency band of each channel for each of the frequency components of a plurality of optical combs for each frequency component of one optical comb and performing multi-point vibration measurement, the number of divisions of the measurement light L S becomes smaller, but displacement measurement and distance measurement of a plurality of points on the measurement surface 5 can be performed.

[0085] For example, in an optical multiplexer / demultiplexer for 100 GHz wavelength division multiplexing (WDM), when demultiplexing optical combs with a 25 GHz interval generated so as to overlap with the ITU grid, as shown in the measurement results by an optical spectrum analyzer in FIG. 5, optical combs with 25 GHz each can be demultiplexed for each of the frequency components of three optical combs in eight frequency bands (ch1 to ch8) centered on 192.4 THz, 192.5 THz, 192.6 THz, 192.7 THz, 192.9 THz, 193.0 THz, 193.1 THz, and 193.2 THz. Since this optical multiplexer / demultiplexer is dedicated to a frequency interval of 100 GHz, the frequency components of optical combs in the middle of channels separated by 100 GHz have a large loss, so they can be demultiplexed for each of the frequency components of three optical combs.

[0086] The multi-point vibration measurement device 100 can be compatible with both multi-point vibration measurement and multi-point distance measurement by adopting the 100 GHz WDM optical multiplexer / demultiplexer as the optical demultiplexing element 131A and the optical multiplexing element 131B of the optical multiplexing / demultiplexing head 130, respectively. Thus, the measurement light L SIn the multi-point vibration measurement device 100 configured to demultiplex each frequency component of the optical comb included therein for each of a plurality of components, whether to analyze the phase of any one frequency component or each frequency component included within the frequency band of the same channel is a component that has been reflected from the same optical path and the same point. Therefore, if phase information is obtained using a plurality of frequency components of each frequency component, it becomes a vibrometer that measures the same point, and thus the signal-to-noise ratio can be improved by performing processing such as averaging. Also, since each frequency component included within the frequency band of the same channel is a component that has been reflected from the same optical path and the same point, distance information can be obtained by utilizing the relative displacement difference of each frequency component.

[0087] That is, the multi-point vibration measurement device 100 can correspond to both multi-point vibration measurement and multi-point distance measurement by adopting the 100 GHz WDM optical multiplexer / demultiplexer as the optical demultiplexing element 131A and the optical multiplexing element 131B of the optical multiplexer / demultiplexer head 130, respectively.

[0088] Here, in the interference optical system 120 of this multi-point vibration measurement device 100, a delay optical system that gives a delay to the reference light L R so that the time required from when the reference light L is output from the second optical comb generator (COMB2) 1B of the light source 110 until it is input to the optical coupler OC C is equal to the time required from when the measurement light L is output from the first optical comb generator (COMB1) 1A of the light source 110 until the measurement light L S is input to the optical coupler OC S ' of the interference optical system 120 is the delay fiber FB C R 2B1 ' is provided in the optical fiber FB R which internally connects the optical coupler OC B to which the reference light L is input from the second optical comb generator (COMB2) 1B of the light source 110 and the optical coupler OC C that outputs the measurement interference light. 2B1 A B

[0089] That is, the four optical couplers OC A B OC B, OC C , OC D Three optical fibers FB with the same length between them 2A2 , FB 2B1 , FB 2B2 In the interference optical system 120 connected via the optical fibers FB, a delay fiber FB 2B1 which is a delay optical system is provided in the optical fiber FB 2B1 ', so that the measurement light L S output from the first optical comb generator (COMB1) 1A of the light source 110 and reflected by the reflection surface 5 of the measurement object S ' is input to the optical coupler OC C of the interference optical system 120 until the optical path length through which the measurement light L S , L S ' passes is made equal to the optical path length through which the reference light L R output from the second optical comb generator (COMB2) 1B of the light source 110 passes until it is input to the optical coupler OC C of the interference optical system 120. That is, the optical path length through which the measurement light L R output from the first optical comb generator (COMB1) 1A of the light source 110 passes until it is input to the optical coupler OC S of the interference optical system 120 is made equal to the optical path length through which the reference light L D output from the second optical comb generator (COMB2) 1B of the light source 110 passes until it is input to the optical coupler OC S of the interference optical system 120. R That is, the optical path length through which the measurement light L D output from the first optical comb generator (COMB1) 1A of the light source 110 passes until it is input to the optical coupler OC R of the interference optical system 120 is made equal to the optical path length through which the reference light L

[0090] In this way, until the measurement light L S and the reference light L R output from the light source 110 interfere with each other in the interference optical system 120 and are output as measurement interference light, the reference light L 32 passes through a delay fiber FB which is a delay optical system in the optical path through which the measurement light L S ' including each frequency component returning via the optical fiber FB R interferes with the reference light L R in the interference optical system 120.2B1 is provided, and the measurement light L S and the measurement light L S ' containing each frequency component reflected by the measurement surface 5, and the optical path length of the optical path through which the measurement light L R ' passes is made equal to the optical path length of the optical path through which the reference light L R passes, so that the reference interference signal S S output from the interference light detection unit 160 that detects the measurement interference light and the reference interference light obtained by the interference optical system 120, and the measurement interference signal S S in the measurement light L R and the reference light L S and the reference light L R can cancel the difference in phase noise between the measurement light L 2B1 ' and the reference light L

[0091] Here, on the premise that the optical combs are generated by electro-optic modulation in the first optical comb generator (COMB1) 1A and the second optical comb generator (COMB2) 1B of the light source 110, the effect of the delay optical system will be explained by mathematical formulas.

[0092] Let the phase noise of the laser, which is the seed light source of the light source 110, be Φ Laser (t), and the phase noises of the oscillators that modulate the first optical comb generator (COMB1) 1A and the second optical comb generator (COMB2) 1B be Φ fm1 (t) and Φ fm2 (t) respectively. Consider the vibration information component ΦBn(t) due to this phase noise component and the phase fluctuation caused by the Doppler shift.

[0093] The phase noise Φ S (t) of the optical comb component of index n based on the carrier of the optical comb of the measurement light L Sn output from the first optical comb generator (COMB1) 1A is

Equation

Number

[0094] The phase noise Φ of the optical communication component of the measurement light L S ’ returning through the target Sn ’(t) is the vibration information component due to the phase fluctuation caused by the Doppler shift due to vibration with the delay of the optical system as τ. When Φ Bn (t) is set,

Number

[0095] The noise due to the phase difference between the frequency components of the index n optical comb 1 and the frequency components of the index n optical comb 2 included in the signal interference light detection unit 6A is the measurement interference signal S S (t) obtained by FFT analysis of this, and when this is set as Φ Ssn (t), Equation (C) - Equation (B), that is,[[]]

Number

[0096] On the other hand, the noise due to the phase difference between the frequency components of the index n optical comb 1 and the frequency components of the index n optical comb 2 included in the reference interference light detection unit 6B is the reference interference signal S R (t) obtained by FFT analysis of this, and when this is set as Φ SRn (t), Equation (A) - Equation (B), that is,[[]]

Number

[0097] The measurement interference signal S shown in Equation (1) S (t) noise Φ Ssn (t) and the reference interference signal S shown in Equation (2) R (t) noise Φ SRn (t) difference (Equation (1) - Equation (2)) is calculated by the signal processing unit 150, [Number] It becomes

[0098] Here, Φ Sn ’(t) - Φ Sn (t) does not have simultaneity, so the noise component does not become 0.

[0099] However, although it cannot be applied to a rangefinder that requires a large dynamic range, as a means that can be applied when the distance to the target object is almost determined like a vibration meter, a delay fiber FB that imparts a delay corresponding to +τ in the optical path through which the reference light L R passes is inserted into the optical fiber FB 2B1 ’ through which the above reference light L R passes, then the above Equation (1) becomes 2B1 By inserting it into [Number] It becomes and the phase noise of the in-phase laser disappears. Since originally both optical comb 1 and optical comb 2 are made from the same laser, the phase noise of the laser is in-phase, and the in-phase noise is removed.

[0100] The difference (Equation (4) - Equation (2)) between the above Equation (4) and Equation (2) is calculated by the signal processing unit 150, [Number] It becomes. In this Equation (5), the phase noise of the laser is canceled, but the phase noise of the oscillator cannot be completely removed because it is uncorrelated.

[0101] Therefore, a time difference of τ is created between the reference interference signal SR and the measurement interference signal SS for comparing the phases. For example, the cable of the reference interference signal SR, or the optical fiber FB 26B1 and FB 26B2 or FB 2A2 and FB 2B2 If the length of FB is increased by the time τ to increase the delay of the reference interference signal SR, the above equation (2) is delayed by the time τ

Number

Number

[0102] Here, the cable of the reference interference signal SR, or the optical fiber FB 26B1 and FB 26B2 or FB 2A2 and FB 2B2 is used to adjust τ, but since the reference interference signal SR and the measurement interference signal SS are digitized by the signal processing unit 150, it is possible to digitally adjust by adding a time delay by shifting the calculation start point, and by making all other delays the same according to the component with the largest delay, the influence of the phase noise of the laser and the oscillator can be minimized.

[0103] Here, in the above multi-point vibration measuring device 100, the reference light L R and the measurement light L S L S ' are sent through an optical fiber, and an interference optical system 120 is adopted which is modularized so that the reference light L R and the measurement light L S L Sis sending , the interference optical system 120 may be configured with an optical element that propagates in space, for example, a spatial optical system using a trapezoidal prism disclosed in Patent Document 6, and the input and output may be optical fibers. Alternatively, without using optical fibers, the reference light L R and the measurement light L S , L S ’ may be sent.

[0104] Next, FIG. 6 is a schematic diagram showing the configuration of a multi-point vibration measurement device 100A including a projection optical system 133A with a built-in coupling optical element to which the present invention is applied in an optical multiplexing / demultiplexing head 130A.

[0105] This multi-point vibration measurement device 100A replaces the coupling optical system 132 and the projection optical system 133 in the optical multiplexing / demultiplexing head 130 of the multi-point vibration measurement device 100 with a projection optical system 133A with a built-in coupling optical element having the function of the coupling optical system 132. In this multi-point vibration measurement device 100A, the same components as those in the multi-point vibration measurement device 100 are denoted by the same reference numerals in the figure, and detailed descriptions thereof are omitted.

[0106] This multi-point vibration measurement device 100A is connected to a plurality of optical fibers FB 341 , FB 342 , FB 343 , ···, FB 34n , ··· via the optical demultiplexing element 131A of the optical multiplexing / demultiplexing optical system 131, and a plurality of projection optical elements 44 431 , FB 432 , FB 433 , ···, FB 43n , ··· are connected to the optical demultiplexing element 131A of the optical multiplexing / demultiplexing optical system 131 via the plurality of projection optical elements 44 A1 , 44 A2 , 44 A3 , ···, 44 An , ··· that constitute a projection optical system 133A with a built-in coupling optical element provided in the optical multiplexing / demultiplexing head 130A.

[0107] The plurality of projection optical elements 44 A1, 44 A2 , 44 A3 , ···, 44 An , ···, for example, a projection optical element 44A having a configuration as shown in FIGS. 7(A) and 7(B) is used respectively.

[0108] FIGS. 7(A) and 7(B) are diagrams showing a configuration example of the projection optical element 44A used in the combined optical element built-in projection optical system 133A. (A) is a schematic diagram showing the configuration of the projection optical element 44A, and (B) is a front view of the two-core capillary 4C1 provided in the projection optical element 44A.

[0109] This projection optical element 44A includes a two-core capillary 4C1 and a coupling optical unit 4C composed of a coupling optical element 4C2 having an optical characteristic of making the axes of light beams with orthogonal polarization directions output from the tips of the two-core optical fibers inserted into the two-core capillary 4C1 coincide. A is provided with an input-side optical fiber FB 34 and an output-side optical fiber FB 43 being led out to the outside.

[0110] The stress application parts of the polarization maintaining fibers inserted into the two-core capillary 4C1 provided in the coupling optical unit 4C A are arranged orthogonally as shown in FIG. 7(B). In this text, all optical module elements connected to the optical fibers so that the stress application part direction becomes the polarization plane are manufactured with a unified standard.

[0111] The input-side optical fiber FB 34 led out to the outside from the two-core capillary 4C1 is connected to the optical splitting element 131A of the optical multiplexing / demultiplexing optical system 131, and the output-side optical fiber FB 43 led out to the outside from the two-core capillary 4C1 is connected to the optical multiplexing element 131B of the optical multiplexing / demultiplexing optical system 131.

[0112] And in this projection optical element 44A, from the optical splitting element 131A to the input-side optical fiber FB 34The measurement light L input through S frequency component l S is input into the condenser lens 4A through the coupling optical element 4C2. The frequency component l condensed by this condenser lens 4A S is irradiated onto the measurement surface 5 of the measurement object through the quarter-wave plate 4B. The reflected light reflected by the measurement surface 5 passes through the quarter-wave plate 4B and the frequency component l S and the frequency component l of the polarization plane whose polarization direction is orthogonal to S is returned to the condenser lens 4A as l'.

[0113] The frequency component l S and the frequency component l of the polarization plane whose polarization direction is orthogonal to S l' is condensed by the condenser lens 4A and reaches the optical fiber FB on the output side through the coupling optical element 4C2 of the coupling optical unit 4C A and is input into the multiplexing element 131B of the optical multiplexing / demultiplexing optical system 131 through the optical fiber FB on the output side 43 through this optical fiber FB on the output side. 43

[0114] For the coupling optical element 4C2, for example, a birefringent crystal can be used to separate light rays by utilizing walk-off.

[0115] Also, in the projection optical system 133A incorporating the coupling optical element, instead of the coupling optical element 4C2 using the birefringent crystal, a projection optical element 44B using a coupling optical element 4C2' composed of a Wollaston prism 4C as shown in FIGS. 8(A) and 8(B) b etc. can also be employed.

[0116] FIGS. 8(A) and 8(B) are diagrams showing a configuration example of the projection optical element 44B used in the projection optical system 133A incorporating the coupling optical element. (A) is a schematic diagram showing the configuration of the projection optical element 44B, and (B) is a front view of the two-core capillary 4C1 provided in the projection optical element 44B.

[0117] This projection optical element 44B consists of a two-core capillary 4C1 and a coupling optical element 4C2' having optical characteristics for aligning the axes of optical beams with orthogonal polarization directions output from the tips of two optical fibers inserted into the two-core capillary 4C1, forming a coupling optical unit 4C. B It includes an input-side optical fiber FB 34 and an output-side optical fiber FB 43 which are led out to the outside.

[0118] The polarization-maintaining fiber inserted into the stress-applying portion of the two-core capillary 4C1 provided in the coupling optical unit 4C B is arranged orthogonally as shown in Fig. 8(B).

[0119] The coupling optical element 4C2' is formed by arranging a Wollaston prism 4C a , 4C c between two collimator lenses 4C b .

[0120] Also in this projection optical element 44B, the frequency component l 34 of the measurement light L S input from the optical demultiplexing element 131A through the input-side optical fiber FB S is input into the condenser lens 4A through the coupling optical element 4C2', and the frequency component l S condensed by this condenser lens 4A is irradiated onto the measurement surface 5 of the measurement object through the quarter-wave plate 4B. The reflected light reflected by the measurement surface 5 passes through the quarter-wave plate 4B and becomes a frequency component l S with a polarization plane orthogonal to the polarization direction of the frequency component l S ' and is returned to the condenser lens 4A.

[0121] The frequency component l S and the frequency component l S ' with a polarization plane orthogonal to the polarization direction are condensed by the condenser lens 4A, input into the output-side optical fiber FB 43 through the coupling optical element 4C2', and input into this output-side optical fiber FB 43It is input to the multiplexing element 131B of the optical multiplexing / demultiplexing optical system 131 via the above.

[0122] In the projection optical elements 44A and 44B, as shown in (B) of FIG. 7 and (B) of FIG. 8, for the light input from the fiber end faces Port1 and Port2 in the two-core capillary 4C1 where the stress applying portions are arranged orthogonally to the polarization plane in the direction of the stress applying portion, the optical axis becomes coaxial and is output in the same direction by passing through the coupling optical elements 4C2 and 4C2'. The measurement light L S frequency component l S with the polarization plane in the same direction as the stress applying portion of Port1 is input from Port1 (input-side optical fiber FB 34 ), and the frequency component l S ' reflected by the measurement surface 5 with the polarization plane in the same direction as the stress applying portion of Port2 can be received by Port2 (output-side optical fiber FB 43 ).

[0123] Here, in the optical multiplexing / demultiplexing head 130 in the multi-point vibration measuring device 100 described above, the optical multiplexing / demultiplexing optical system 131 is connected to the projection optical system 133 via the coupling optical system 132. However, in the multi-point vibration measuring device 100A, the coupling optical system 132 and the projection optical system 133 in the multi-point vibration measuring device 100 are replaced with a projection optical system 133A with a built-in coupling optical element having the function of the coupling optical system 132. As a result, the optical fibers FB 441 , FB 442 , FB 443 , ···, FB 44n , ··· that connect the coupling optical system 132 and the projection optical system 133 are no longer necessary, and the optical multiplexing / demultiplexing head 130A can be composed of two optical systems, the optical multiplexing / demultiplexing optical system 131 and the projection optical system 133A with a built-in coupling optical element. Not only is the configuration simplified, but also there is no generation of unnecessary reflected light due to the end faces of the optical fibers FB 441 , FB 442 , FB 443 , ···, FB 44n , ···.

[0124] That is, using an element such as a PBC module as the coupling optical system 132, like the optical multiplexing / demultiplexing head 130 in the above multi-point vibration measurement device 100, complicates the optical system and has problems such as reflections inside the PBC module and the extinction ratio of the PM fiber. Also, using a PBC module or the like increases the number of components. Reflections due to a plurality of lenses and fiber end faces inside the PBC module also pose problems. However, in this multi-point vibration measurement device 100A, by providing the optical multiplexing / demultiplexing head 130A with the coupling optical element built-in projection optical system 133A, there is no need to separately use the above PBC module or the like, and a configuration with a larger directional coupling loss from Port1 to Port2 can be achieved, thus eliminating such problems.

[0125] In the Wollaston prism type coupling optical element built-in projection optical system 133A provided in the optical multiplexing / demultiplexing head 130A, as measured, a directional coupling loss of 80 dB to 90 dB from Port1 to Port2 is obtained.

[0126] And in the multiplexing element 131B of the above optical multiplexing optical system 131, the measurement light L S reflected at a plurality of points on the measurement surface 5 of the object to be measured and returning through the above projection optical system 133B S has each frequency component of the optical comb multiplexed, and the measurement light L 32 ' consisting of the reflected light of each frequency component of the optical comb reflected at a plurality of points on the measurement surface 5 C is input from the multiplexing element 131B to the optical coupler OC

[0127] of the interference optical system 120 through the optical fiber FB C The optical coupler OC S of the interference optical system 120 receives the measurement light L 32 ' consisting of the reflected light of each frequency component of the optical comb reflected at a plurality of points on the measurement surface 5 through the optical fiber FB 12B and also receives the reference light L B input from the second optical comb generator (COMB2) 1B of the light source 110 to the optical coupler OC R through the optical fiber FB 2B1is input via the above, and the measurement light L S ’ and the reference light L R are output as measurement interference light for measuring the interference light therebetween. Further, the optical coupler OC D of the interference optical system 120 is such that the measurement light L 12A input from the first optical comb generator (COMB1) 1A of the light source 110 via the optical fiber FB A to the optical coupler OC S is input via the optical fiber FB 2A2 and the reference light L 12B input from the second optical comb generator (COMB2) 1B of the light source 110 via the optical fiber FB B to the optical coupler OC R is input via the optical fiber FB 2B2 and the interference light between the measurement light L S and the reference light L R is output as reference interference light.

[0128] In the interference light detector 140 into which the measurement interference light and the reference interference light obtained by the interference optical system 120 are input, a measurement interference signal S C obtained by detecting the measurement interference light by a measurement interference light detector 6A that receives the measurement interference light via two optical fibers FB 26A1 , FB 26A2 externally connected to the optical coupler OC S of the interference optical system 120 is output after being converted into an electrical signal, and a reference interference signal S D obtained by detecting the reference interference light by an interference light detector 6B that receives the reference interference light via two optical fibers FB 26B1 , FB 26B2 externally connected to the optical coupler OC R of the interference optical system 120 is output after being converted into an electrical signal.

[0129] Then, in the signal processing unit 150, the measurement interference signal S S obtained by the interference light detector 140 and the reference interference signal S RRegarding the DFT analysis, the phase for each frequency component of the optical comb is calculated, and the phase difference for each frequency component due to the Doppler shift caused by the vibration at multiple points on the measurement surface 5 is obtained, thereby analyzing the vibration information at multiple points on the measurement surface 5 and measuring the distribution of the vibration on the measurement surface 5.

[0130] Also in this multi-point vibration measurement device 100A, the measurement light L S The measurement light L output from the interference optical system 120 provided with the optical demultiplexing element 131A that demultiplexes a plurality of frequency components of the optical comb included in S The optical path through which passes, and the measurement light L provided with the optical multiplexing element 131B that multiplexes the reflected lights of the respective frequency components of the optical comb reflected at multiple points on the measurement surface 5 of the object S ' is separated from the optical path for inputting into the interference optical system 120, so that unnecessary reflection components due to the optical demultiplexing element 131A provided in the optical path through which the measurement light L irradiating the measurement surface 5 passes through the interference optical system 120 are prevented from being mixed into the interference light necessary for multi-point vibration measurement, and multi-point vibration measurement can be performed with high precision. S And in the signal processing unit 150, regarding the measurement interference signal S

[0131] obtained by the interference light detection unit 140 and the reference interference signal S S and the reference interference signal S R For, the phase for each frequency component of the optical comb is calculated by DFT analysis, and between the measurement interference signal S S and the reference interference signal S R By obtaining the phase difference for each frequency component of the optical comb due to the Doppler shift caused by the vibration at multiple points on the measurement surface 5, vibration information at multiple points on the measurement surface 5, for example, vibration speed, moving distance, acceleration, etc. is analyzed, and the distribution of the vibration on the measurement surface 5 is measured.

[0132] Next, FIG. 9 is a schematic diagram showing the configuration of a multi-point vibration measurement device 100B including a combined optical element built-in projection optical system 133B having a combined optical element array formed by two-dimensionally arranging a plurality (m×n) of projection optical elements in the optical multiplexing / demultiplexing head 130B.

[0133] This multi-point vibration measurement device 100B is obtained by replacing the projection optical system 133A in the above multi-point vibration measurement device 100A with a projection optical system 133B incorporating coupling optical elements, and a plurality (m×n) of coupling optical elements 44 of the projection optical system 133A in the above multi-point vibration measurement device 100A A1 、44 A2 、44 A3 、···、44 An 、 n ···、44 Amn are modularized into a coupling optical element array 44, and the condenser lenses 4A1, 4A2, 4A3, ···, 4A of the projection optical system 4 n 、···, that is, the condenser optical element 4A that functions as a projection optical element a 、4A b consisting of a set of optical systems 4A ab and a projection optical system 133B incorporating coupling optical elements consisting of a quarter-wave plate 4B1, 4B2, 4B3, ···, 4B of the projection optical system 4 n 、···, and a single quarter-wave plate 4B that functions as such. Here, the illustrated set of optical systems 4A ab is a simplified bilateral telecentric optical system. Actually, it is composed of a large number of lenses. The bilateral telecentric optical system can project and condense the measurement light output vertically from the coupling optical element array 44 onto a horizontal target vertically. This is the most sensitive projection optical system. For a large target, a telecentric optical system on only one side may be adopted, and an fθ optical system may be adopted on the other side. Also, it is not necessary to use a telecentric optical system, and an optical system suitable for the size and shape of the target can be selected.

[0134] In this multi-point vibration measurement device 100B, the same components as those in the above multi-point vibration measurement device 100A are denoted by the same reference numerals in the figure, and their detailed descriptions are omitted.

[0135] FIGS. 10(A) and (B) are diagrams showing a configuration example of the coupling optical element array 44, where (A) is a longitudinal sectional view seen from the side of the coupling optical element array 44, and (B) is a longitudinal sectional view seen from the front of the coupling optical element array 44.

[0136] In the combined optical element built-in projection optical system 133B, as shown in FIGS. 10(A) and 10(B), a combined optical element array 44 is adopted in which a plurality (m×n) of combined optical elements 44 A1 , 44 A2 , 44 A3 , ···, 44 An , ··· are two-dimensionally arranged and modularized.

[0137] In the plurality (m×n) of combined optical elements 44 in the combined optical element array 44 A1 , 44 A2 , 44 A3 , ···, 44 An ···, 44 Amn are combined optical elements 4C2 made of birefringent crystals or combined optical elements 4C2' such as Wollaston prisms, which are used to separate light rays by utilizing the above-mentioned walk-off. The input-side optical fiber and the output-side optical fiber are each led out to the outside from a two-core capillary.

[0138] In this combined optical element array 44, the input-side FBs 341 , FB 342 , FB 343 , ···, FB 34n , ··· and the output-side optical fibers FB 431 , FB 432 , FB 433 , ···, FB 43n , ··· are each led out to the outside from a two-core capillary. However, without using a two-core capillary, for example, a structure in which a plurality of optical fibers are led out to the outside through a plurality of insertion holes provided in a substrate may be adopted, and a structure that can accurately install a plurality of optical fibers and control the direction of the PMF may be adopted.

[0139] In addition, in the combined optical element built-in projection optical system 133B, a plurality (m×n) of combined optical elements 44 are arranged so as to irradiate each frequency component of the optical communication of the measurement light to m×n measurement points arranged two-dimensionally in a matrix A1 , 44 A2 , 44 A3 , ···, 44 AnA combined optical element array 44 that is two-dimensionally arrayed and modularized is adopted. However, depending on the object to be measured, a plurality of combined optical elements 44 A1 、44 A2 、44 A3 、···、44 An 、··· may be two-dimensionally arrayed in a fine grid pattern (e.g., a hexagonal close-packed lattice pattern) and modularized to form a combined optical element array.

[0140] The plurality of modularized combined optical elements 44 A1 、44 A2 、44 A3 、···、44 An 、··· are connected to the optical splitting element 131A of the optical multiplexing / demultiplexing optical system 131 via a plurality of optical fibers FB 341 、FB 342 、FB 343 、···、FB 34n 、···, and are also connected to the optical multiplexing element 131B of the above optical multiplexing / demultiplexing optical system 131 via a plurality (m×n) of optical fibers FB 431 、FB 432 、FB 433 、···、FB 43n 、···.

[0141] In this multi-point vibration measurement device 100B, the combined optical element built-in projection optical system 133B adopts a modularized combined optical element array 44. As a result, a plurality of frequency components of the optical comb of the measurement light Ls input via a plurality of optical fibers FB 341 、FB 342 、FB 343 、···、FB 34n 、··· from the optical splitting element 131A of the optical multiplexing / demultiplexing optical system 131 are condensed by the set of optical elements 4A a 、4A b consisting of the set of optical elements 4A ab and can be irradiated onto a plurality of points on the measurement surface 5 of the object to be measured via a single quarter-wave plate 4B.

[0142] Then, the reflected light reflected at multiple points on the measurement surface 5 passes through the quarter-wave plate 4B and becomes a frequency component with a polarization plane orthogonal to the polarization direction of the irradiated optical comb as the optical system 4A of the set. ab is condensed by, and enters the multiplexer 131B of the optical multiplexing / demultiplexing optical system 131 from the plurality of optical fibers FB 431 , FB 432 , FB 433 , ···, FB 43n , ··· through.

[0143] In the multiplexer 131B of the optical multiplexing / demultiplexing optical system 131, the measurement light L S returning through the projection optical system 133B after being reflected at multiple points on the measurement surface 5 of the object to be measured is multiplexed, and the measurement light L S ' composed of the reflected light of each frequency component of the optical comb reflected at multiple points on the measurement surface 5 is input from the multiplexer 131B to the optical coupler OC 32 of the interference optical system 120 through the optical fiber FB. C

[0144] In the interference optical system 120, the measurement light L S ' composed of the reflected light of each frequency component of the optical comb reflected at multiple points on the measurement surface 5 and the reference light L 12B input from the second optical comb generator (COMB2) 1B of the light source 110 to the optical coupler OC B through the optical fiber FB are used as measurement interference light and output from the optical coupler OC R , and the measurement light L C input from the first optical comb generator (COMB1) 1A of the light source 110 to the optical coupler OC 12A through the optical fiber FB and the reference light L A input to the optical coupler OC S are used as reference interference light and output from the optical coupler OC B . R D

[0145] In an interference light detector 140 into which the measurement interference light and the reference interference light obtained by the interference optical system 120 are input, an optical coupler OC of the interference optical system 120 C is externally connected to two optical fibers FB 26A1 , FB 26A2 A measurement interference signal S obtained by detecting the measurement interference light with a measurement interference light detector 6A that receives the measurement interference light via the optical fibers and converting it into an electrical signal is output. At the same time, an optical coupler OC of the interference optical system 120 S is externally connected to two optical fibers FB D A reference interference signal S obtained by detecting the reference interference light with an interference light detector 6B that receives the reference interference light via the optical fibers and converting it into an electrical signal is output. 26B1 , FB 26B2 R

[0146] Then, in the signal processing unit 150, for the measurement interference signal S S and the reference interference signal S R obtained by the interference light detector 140, the phase for each frequency component of the optical comb is calculated by DFT analysis, and the phase difference for each frequency component caused by the Doppler shift due to the vibration at a plurality of points on the measurement surface 5 is obtained, thereby analyzing the vibration information at a plurality of points on the measurement surface 5 and measuring the vibration distribution on the measurement surface 5.

[0147] Also in this multi-point vibration measurement device 100B, the optical path through which the measurement light L S output from the interference optical system 120 provided with the optical demultiplexing element 131A that demultiplexes a plurality of frequency components of the optical comb included in the measurement light L S passes, and the optical path for inputting the measurement light L S ' that combines the reflected lights of each frequency component reflected at a plurality of points on the measurement surface 5 of the object into the interference optical system 120 are separated. Therefore, unnecessary reflection components due to the optical demultiplexing element 131A provided in the optical path through which the measurement light L S irradiating the measurement surface 5 via the interference optical system 120 are prevented from mixing into the interference light necessary for multi-point vibration measurement, eliminating measurement errors and enabling high-precision multi-point vibration measurement.​​

[0148] Here, in the interference optical system 120 of the multi-point vibration measuring devices 100, 100A, and 100B, the measurement light L output from the light source 110 S and the reference light L R are output as reference interference light, and the measurement light L output from the light source 110 S is irradiated from the interference optical system 120 to the measurement surface 5 of the measurement object through the optical multiplexer / demultiplexer heads 130, 130A, and 130B, and the measurement light L reflected by the measurement surface 5 and returned through the optical multiplexer / demultiplexer heads 130, 130A, and 130B S ’ and the reference light L R are output as measurement interference light, and in the interference light detection unit 140 including a measurement interference light detector 6A that receives the measurement interference light output from the interference optical system 120 and an interference light detector 6B that receives the reference interference light output from the interference optical system 120, the measurement interference signal S obtained by detecting the measurement interference light with the measurement interference light detector 6A and converting it into an electrical signal S is obtained, and the reference interference signal S obtained by detecting the reference interference light with the interference light detector 6B and converting it into an electrical signal R is obtained.

[0149] And in the multi-point vibration measuring devices 100, 100A, and 100B, in the signal processing unit 150, for the measurement interference signal S and the reference interference signal S S obtained by the interference light detection unit 140, the phase for each frequency component of the optical comb is calculated by DFT analysis, and the phase difference for each frequency component of the optical comb due to the Doppler shift caused by the vibration at a plurality of points on the measurement surface 5 is obtained, thereby analyzing the vibration information at the plurality of points on the measurement surface 5. However, since the measurement interference signal S R is an interference signal obtained by detecting the measurement interference light that is the interference light of the measurement light L S reflected by the measurement surface 5 and returned and the reference light L S ’, in the signal processing unit 150, the measurement interference signal S R SBy performing DFT analysis only, the phase for each frequency component of the optical comb can be calculated, and the phase difference for each frequency component of the optical comb caused by the Doppler shift due to vibration at a plurality of points on the measurement surface 5 can be obtained.

[0150] That is, the multi-point vibration measuring devices 100, 100A, and 100B are configured such that, like the multi-point vibration measuring device 100' shown in FIG. 11, the multi-point vibration measuring device 100A' shown in FIG. 12, and the multi-point vibration measuring device 100B' shown in FIG. 13, an interference optical system 120' that outputs only measurement interference light, an interference light detection unit 140' that receives only the measurement interference light, and a measurement interference signal S obtained by the interference light detection unit 140' S By performing DFT analysis only, the phase for each frequency component of the optical comb can be calculated, and a signal processing unit 150' that obtains the phase difference for each frequency component of the optical comb caused by the Doppler shift due to vibration at a plurality of points on the measurement surface 5 can be provided.

[0151] In these multi-point vibration measuring devices 100', 100A', and 100B', the same components as those in the multi-point vibration measuring devices 100, 100A, and 100B are denoted by the same reference numerals in the drawings, and detailed descriptions thereof are omitted.

Explanation of Reference Numerals

[0152] 1, 110 Light source, 1A First optical comb generator (COMB1), 1B Second optical comb generator (COMB1), 2, 120, 120' Interference optical system, 3 Optical multiplexer / demultiplexer, 4 Projection optical system, 4A a , 4A b Condensing optical element, 4A ab Set of optical systems, 4 A1 , 4 A2 , 4 A3 , ···, 4 An , ···, 4A Condensing lens, 4 B1 , 4 B2 , 4 B3 , ···, 4 Bn , ···, 4B Quarter-wave plate, 4C A , 4C B Coupling optical unit, 4C 12-core capillary, 4C2, 4C2' Coupling optical element, 4C a , 4Cc Collimator lens, 4C b Wollaston prism, 5 measurement surface, 6,140,140’ interference light detector, 6A interference light detector, 6B reference light detector, 7,150,150’ signal processing unit, 10,100,100’,100A,100A’,100B,100B’ multi-point vibration measurement device, 441,442,443,···,44 n ,44A,44B projection optical element, 130A,130B optical multiplexer / demultiplexer head, 131 optical multiplexer / demultiplexer optical system, 131A optical demultiplexing element, 131B optical multiplexing element, 132 coupling optical system, 133,133A,133A projection optical system, FB 12A ,FB 12B ,FB 2A1 ,FB 2A2 ,FB 2B1 ,FB 2B2 ,FB 2C ,FB 23 ,FB 32 ,FB 341 ,FB 342 ,FB 343 ,···FB 34n ,···,FB 26A1 ,FB 26A2 ,FB 431 ,FB 432 ,FB 433 ,···,FB 43n ,··· optical fiber, FB 2B1 ’ delay fiber, FB 34 Input-side optical fiber, FB 43 Output-side optical fiber, OC A ,OC B ,OC C ,OC D ,OC E ,OC C1 ,OC C2 ,OC C3 ,···,OC Cn 、··· optical coupler, L S Measurement light, L R Reference light, S S Measurement interference signal, S R Reference interference signal

Claims

1. A light source that outputs measurement light and reference light that are spectra at a predetermined frequency interval and have interference; An optical multiplexer / demultiplexer head that divides the measurement light output from the light source into each frequency component and irradiates a plurality of points on the measurement surface of the measurement object as each frequency component; An interference optical system that receives the measurement light and reference light output from the light source, inputs the measurement light input from the light source to the optical multiplexer / demultiplexer head, and reflects the measurement light reflected by the measurement surface and returned through the optical multiplexer / demultiplexer head. Interferes the measurement light including each frequency component with the reference light output from the light source to output measurement interference light; A measurement photodetector that receives the measurement interference light obtained by the interference optical system and converts it into an electrical signal to obtain a measurement interference signal; A signal processing unit that analyzes vibration information at a plurality of points on the measurement surface based on the measurement interference signal obtained by the measurement photodetector comprising: The optical multiplexer / demultiplexer head includes an optical demultiplexing element that demultiplexes each frequency component included in the measurement light input from the interference optical system, a projection optical system that irradiates each frequency component demultiplexed by the optical demultiplexing element onto a plurality of points on the measurement surface of the measurement object, and a measurement light that is reflected by the measurement surface and returned. A multiplexing optical element that multiplexes each frequency component of the light and inputs it to the interference optical system, and a coupling optical system that inputs each frequency component included in the measurement light demultiplexed by the optical demultiplexing element to the projection optical system and reflects the measurement light reflected by the measurement surface and returned. A multi-point vibration measurement device, characterized in that it includes a plurality of frequency components of the light input to the multiplexing optical element.

2. The interference optical system outputs the measurement interference light, and interferes the measurement light and the reference light input from the light source to output reference interference light, A reference photodetector that receives the reference interference light obtained by the interference optical system and converts it into an electrical signal to obtain a reference interference signal is provided, The signal processing unit analyzes vibration information at a plurality of points on the measurement surface based on the measurement interference signal obtained by the measurement photodetector and the reference interference signal obtained by the reference photodetector. The multi-point vibration measurement device according to claim 1.

3. The optical multiplexer / demultiplexer head splits each frequency component included in the measurement light into each frequency component for each single frequency component by the optical demultiplexing element, irradiates a plurality of points on the measurement surface of the measurement object through the projection optical system, and multiplexes each frequency component for each single frequency component of the measurement light reflected and returned from the measurement surface by the multiplexing element. The multi-point vibration measurement device according to claim 1 or claim 2, characterized in that.

4. The optical multiplexer / demultiplexer head splits each frequency component included in the measurement light into each frequency component for each plurality of frequency components by the optical demultiplexing element, irradiates a plurality of points on the measurement surface of the measurement object through the projection optical system, and multiplexes each frequency component for each plurality of frequency components of the measurement light reflected and returned from the measurement surface by the multiplexing element. The multi-point vibration measurement device according to claim 1 or claim 2, characterized in that.

5. The multi-point vibration measurement device according to claim 1 or claim 2, characterized in that the coupling optical system is incorporated in the projection optical system.

6. The optical demultiplexing element splits each frequency component included in the measurement light input from the interference optical system through one optical fiber and outputs it through a plurality of optical fibers. The optical multiplexing element multiplexes each frequency component input through a plurality of optical fibers and outputs it through one optical fiber. The multi-point vibration measurement device according to claim 5, characterized in that the coupling optical system includes a coupling optical element that aligns the optical axes of two light beams with orthogonal polarization directions output from two optical fibers.

7. The multi-point vibration measurement device according to claim 6, characterized in that the coupling optical element is made of a birefringent crystal.

8. The multi-point vibration measurement device according to claim 6, characterized in that the coupling optical element is a Wollaston prism.

9. The coupling optical system is composed of an array of coupling optical elements in which the coupling optical elements are arranged two-dimensionally. Each frequency component of the measurement light input through the array of coupling optical elements is condensed by a condensing optical element and output toward the measurement surface of the measurement object. At the same time, each frequency component of the measurement light reflected and returned from the measurement surface is condensed by the condensing optical element and input to the array of coupling optical elements. The multi-point vibration measurement device according to claim 6, characterized in that.

10. Before the measurement light and the reference light output from the light source are reflected by the measurement surface and return through the coupling optical system, and the measurement light and the reference light including each frequency component are interfered with in the interference optical system to be output as measurement interference light, a delay optical system is provided in the optical path through which the reference light passes, so that the optical path length of the optical path through which the measurement light and the measurement light including each frequency component reflected by the measurement surface pass is made equal to the optical path length of the optical path through which the reference light passes. The multi-point vibration measurement device according to claim 1 or claim 2, characterized in that.

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