JP2019090840A - Distance measuring device and distance measuring method - Google Patents

Abstract

To provide a distance measuring device and a distance measuring method with which it is possible to measure the distance to an object in a liquid with high accuracy.SOLUTION: Provided is a distance measuring device comprising: an acquisition unit for acquiring a first signal based on first reflected light when first light is reflected on a measurement object in a medium, a second signal based on second reflected light when second light is reflected on the measurement object, and a third signal based on third reflected light when third light is reflected on the medium; and a calculation unit for calculating the distance from the reflection surface of the medium to the reflection surface of the measurement object in an environment formed by the medium on the basis of the first, second and third signals acquired by the acquisition unit.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a distance measuring device and a distance measuring method.

  As a device for measuring an object in a liquid, a measurement device using ultrasonic waves or light has been developed and proposed. As an apparatus using ultrasonic waves, ultrasonic waves of pulse signals are emitted into water, and the sound (echo) of the emitted ultrasonic waves reflected on the object is detected to measure the distance in the depth direction of the object in water. An apparatus is known (see Patent Document 1). In addition, as an apparatus using light, an apparatus that irradiates laser light to an object in a liquid and measures the surface shape of the object in the liquid from the reflected light reflected from the object (see Patent Document 2), low coherence An apparatus for irradiating light into a liquid and measuring the particle size and distribution of particles in the liquid (see Patent Document 3) is known.

JP 2002-341028 A JP 2012-2574 A JP, 2013-205145, A

  However, since the technique described in Patent Document 1 is a measurement device using ultrasonic waves, the distance to an object in the liquid may not be accurately measured due to the wavelength of ultrasonic waves used. Further, the techniques described in Patent Documents 2 and 3 are measurement devices using light, and there are cases where the distance to an object in the liquid can not be accurately measured by the absorption of light in the liquid. As a result, the measurement range may be limited to a small range.

  The problem to be solved by the present invention is to provide a distance measuring device capable of accurately measuring the distance to an object in a liquid, and a distance measuring method.

  In the distance measuring device according to the embodiment, the first reflected light when the first light whose wavelength is changed in the first wavelength band irradiated from the outside of the medium to the object to be measured in the medium is reflected by the object to be measured A second signal based on the second light emitted from the outside of the medium with respect to the object to be measured in the medium, wherein the wavelength changes in a second wavelength band different from the first wavelength band A second signal based on a second reflected light when light is reflected by the measurement object, and a third light emitted from the outside of the medium to the measurement object in the medium, the first light An acquisition unit for acquiring a third signal based on a third reflected light when the third light of a wavelength different from the second light is reflected by the medium, and the first signal acquired by the acquisition unit; Based on the second signal and the third signal, the medium is reflected by the medium from the reflective surface And a calculator for calculating the distance to the reflecting surface of the made measurement object in the environment.

  According to the present invention, it is possible to provide a distance measuring device and a distance measuring method capable of accurately measuring the distance to an object in liquid.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows an example of the distance measurement apparatus 10 which concerns on 1st Embodiment. FIG. 2 is a diagram showing an example of the functional configuration of the distance measurement device 10. The graph which shows an example of a mode of the time change of each wavelength of the 1st light emitted from the 1st wavelength sweep light source 12A, and the 2nd light emitted from the 2nd wavelength sweep light source 12B. The figure of an example showing the relation between the wavelength of light, and the transmissivity of light. The graph which shows an example of a mode of the time change of the wavelength of the 3rd measurement light generated in optical coupler 22. The figure which showed an example of the relationship between the wavelength of light, and the refractive index in air. The figure which showed an example of the relationship between the wave number of light, and the transmittance | permeability of light. FIG. 7 is a view exemplifying a part of first interference light detected by the first interference light detection unit 32A. FIG. 2 is a diagram showing an example of a functional configuration of a control device 50. The graph which shows an example of the 1st frequency spectrum obtained by Fourier-transforming 1st interference light. The graph which shows an example of the 2nd frequency spectrum obtained by Fourier-transforming 2nd interference light. The graph which shows an example of the 3rd frequency spectrum obtained by Fourier-transforming 3rd interference light. 5 is a flowchart showing an example of the flow of processing executed by the control device 50. The graph which shows correlation with a known 1st peak frequency and a known 2nd peak frequency, and a known distance (L1-L2). The graph which shows correlation with known 3rd peak frequency and known distance (L0-L2). The block diagram which shows an example of the distance measuring device 10 which concerns on 2nd Embodiment.

  Hereinafter, the distance measurement device and the distance measurement method of the embodiment will be described with reference to the drawings.

First Embodiment
FIG. 1: is a block diagram which shows an example of the distance measuring device 10 which concerns on 1st Embodiment. The distance measuring device 10 according to the present embodiment irradiates light from the outside of the liquid LM with respect to the measurement object SM installed in the liquid LM, and reflects the light from the reflection surface LM # of the liquid LM to the reflection surface SM of the measurement object SM. Measure the distance D to #. For example, the liquid LM is water, but may be ethanol, acetic acid, hydrochloric acid, ammonia, sodium hydroxide or the like instead.

  Here, the liquid LM is an example of a medium. The object to be measured SM is, for example, a silicon wafer, but instead, it may be an industrial product such as a multilayer film, a living body or the like, and is an opaque material that reflects almost all the irradiated light. It may be an object made of a transparent or translucent material that transmits a part of light.

  In the case where the measurement object SM is an object of a transparent or translucent material, the liquid LM may have a refractive index different from that of the measurement object SM and be transparent to light. In the present embodiment, the measurement object SM is in the liquid LM, but instead of this, for example, a transparent or translucent solid such as magnesium fluoride, silicon rubber, glass, acrylic resin, etc. It may be a configuration installed inside.

  The distance measuring device 10 includes a first wavelength swept light source 12A, a second wavelength swept light source 12B, an interferometer 20, a first interference light detection unit 32A, a second interference light detection unit 32B, and a third interference light detection. A unit 32C and a control device 50 are provided. Here, the control device 50 is an example of a calculation unit.

  The distance measurement device 10 guides, for example, the first light emitted from the first wavelength swept light source 12A and the second light emitted from the second wavelength swept light source 12B to the interferometer 20 and is guided. The first light and the second light are irradiated from the interferometer 20 to the measurement object SM described above. In addition, the distance measurement device 10 irradiates the measurement target SM described above from the interferometer 20 with the third light generated by the first light and the second light guided to the interferometer 20. Then, in the distance measuring device 10, among the first light, second light and third light irradiated to the measurement object SM, the first light and the second light are reflected on the reflection surface SM # of the measurement object SM The light is reflected and enters the interferometer 20 again, and the third light is reflected by the reflection surface LM # of the liquid LM and enters the interferometer 20 again. The distance measuring device 10 is reflected by the reflecting surface SM # of the measuring object SM, and is reflected by the reflecting surface LM # of the liquid LM and the first light and the second light incident on the interferometer 20 again, and again the interferometer 20 The distance D from the reflective surface LM # of the liquid LM to the reflective surface SM # of the object to be measured SM is measured based on the third light incident on the light source.

  The first wavelength swept light source 12A emits, to the interferometer 20, the first light whose wavelength changes at a predetermined cycle in a wavelength band where the light transmittance with respect to the liquid LM is high. The wavelength of the first light emitted from the first wavelength swept light source 12A changes sinusoidally in a wavelength band of 1550 ± 100 [nm] (first wavelength band) every 1 [kHz] period, for example.

  The second wavelength swept light source 12B is a second wavelength band in which the light transmittance with respect to the liquid LM is high, and the wavelength changes at a predetermined cycle in a second wavelength band different from the first wavelength band. Light is emitted to the interferometer 20 via an optical fiber. For example, the wavelength of the second light emitted from the second wavelength swept light source 12B changes sinusoidally in a wavelength band of 1310 ± 100 [nm] (second wavelength band) every 1 [kHz] period.

  The interferometer 20 splits and combines the first light and the second light emitted from the first wavelength swept light source 12A and the second wavelength swept light source 12B, and irradiates them toward the measurement object SM. The light irradiated to the measurement object SM and reflected by the measurement object SM and the liquid LM is incident on the interferometer 20 again. The interferometer 20 generates a plurality of interference lights based on the reflected light.

The first interference light detection unit 32A detects the first interference light of the plurality of interference lights generated by the interferometer 20, converts the detected first interference light into an interference signal, and converts the converted interference signal. It outputs to the control device 50.
The second interference light detection unit 32B detects the second interference light of the plurality of interference lights generated by the interferometer 20, converts the detected second interference light into an interference signal, and converts the converted interference signal. It outputs to the control device 50.
The third interference light detection unit 32C detects the third interference light of the plurality of interference lights generated by the interferometer 20, converts the detected third interference light into an interference signal, and converts the converted interference signal. It outputs to the control device 50.

  The control device 50 calculates the distance from the reflective surface LM # of the liquid LM to the reflective surface SM # of the measurement object SM based on the interference signals output from the interference light detectors 32A, 32B, 32C. Hereinafter, when the first wavelength swept light source 12A and the second wavelength swept light source 12B are not distinguished from one another, they are collectively referred to as the wavelength swept light source 12 and will be described. When the first interference light detection unit 32A, the second interference light detection unit 32B, and the third interference light detection unit 32C are not distinguished from one another, they will be collectively referred to as the interference light detection unit 32.

  FIG. 2 is a diagram showing an example of a functional configuration of the distance measuring device 10. As shown in FIG. The distance measurement device 10 according to the present embodiment includes, for example, a first wavelength swept light source 12A, a second wavelength swept light source 12B, an optical coupler 22, a first collimator 24A, a second collimator 24B, and a reflector RM. A first interference light detection unit 32A, a second interference light detection unit 32B, a third interference light detection unit 32C, a control device 50, and optical fibers F1 to F7 are provided. Among them, one including the optical coupler 22, the first collimator 24 A, the second collimator 24 B, the optical fiber F 3, and the optical fiber F 4 corresponds to the interferometer 20. The interferometer 20 may be configured to include any combination of the optical coupler 22, the first collimator 24A, the second collimator 24B, the optical fiber F3, and the optical fiber F4, and further, a reflector. The configuration may include RM.

  In the distance measuring device 10, the first wavelength swept light source 12A and the optical coupler 22 are connected by the optical fiber F1, and the second wavelength swept light source 12B and the optical coupler 22 are connected by the optical fiber F2. In the distance measuring device 10, the optical coupler 22 and the first interference light detection unit 32A are connected by the optical fiber F5, and the optical coupler 22 and the second interference light detection unit 32B are connected by the optical fiber F6, The optical coupler 22 and the third interference light detection unit 32C are connected by an optical fiber F7. Further, the wavelength sweeping light source 12 and the interference light detection unit 32 are connected via an electric cable or the like so that communication with the control device 50 can be performed.

The first wavelength swept light source 12A emits the first light to the optical fiber F1. The optical fiber F1 guides the first light emitted by the first wavelength swept light source 12A to the optical coupler 22 of the interferometer 20.
The second wavelength swept light source 12B emits the second light to the optical fiber F2. The optical fiber F2 guides the second light emitted by the second wavelength swept light source 12B to the optical coupler 22 of the interferometer 20.

  Here, with reference to FIG. 3, the temporal change of the respective wavelengths of the first light emitted from the first wavelength swept light source 12A and the second light emitted from the second wavelength swept light source 12B will be described. . FIG. 3 is a graph showing an example of the time change of the respective wavelengths of the first light emitted from the first wavelength swept light source 12A and the second light emitted from the second wavelength swept light source 12B.

  The horizontal axis of the graph G1 represents an elapsed time Time (in units of [msec]). Further, the vertical axis of the graph G1 represents the wavelength λ (unit: [nm]) of light. In the graph G1, the curve LN1 represents the time change of the wavelength of the first light, and the curve LN2 represents the time change of the wavelength of the second light. As shown in FIG. 3, the first wavelength band (1550 ± 100 [nm]) in which the wavelength of the first light changes is the second wavelength band (1310 ± 100 [nm]) in which the wavelength of the second light changes. It is different from Further, in FIG. 3, the phase of the first light matches the phase of the second light, but the phases of these may be different.

  The interferometer 20 includes, for example, an optical coupler 22, an optical fiber F3, an optical fiber F4, a first collimator 24A, and a second collimator 24B. In the interferometer 20, as shown in FIG. 2, the optical coupler 22 is connected to the first collimator 24A via the optical fiber F3. In the interferometer 20, the optical coupler 22 is connected to the second collimator 24B via the optical fiber F4. The optical coupler 22 of the interferometer 20 is connected to the first interference light detection unit 32A by the optical fiber F5, to the second interference light detection unit 32B by the optical fiber F6, and to the third interference light detection unit 32C by the optical fiber F7. It is connected.

  The characteristics of the first light and the second light will be described with reference to FIG. FIG. 4 is a diagram of an example showing the relationship between the wavelength of light and the transmittance of light. The horizontal axis in FIG. 4 represents the wavelength of light (in [μm]). Further, the vertical axis in FIG. 4 represents the light transmittance (unit: [%]). In FIG. 4, a curve LN3 represents a change in light transmittance with respect to the wavelength of the irradiated light when the light is irradiated to water. As shown in FIG. 4, the first light having a wavelength band of 1550 ± 100 [nm] and the second light having a wavelength band of 1310 ± 100 [nm] are easily transmitted through a liquid such as water. Thereby, the distance measuring device 10 irradiates light from outside the liquid LM with respect to the measurement object SM installed in the liquid LM, and measures the distance L1 to the reflection surface SM # of the measurement object SM. Can.

  The optical fibers F1 and F2 are fibers having a transmission band including the wavelength of light guided by the wavelength swept light source 12. The optical fibers F1 and F2 are, for example, multimode optical fibers or single mode optical fibers. The optical fiber F1 guides the first light, and the optical fiber F2 guides the second light. The optical fibers F1 and F2 guide the first light and the second light to the optical coupler 22 of the interferometer 20 while maintaining mutual coherence.

  The optical coupler 22 is an example of a combining unit and an example of an interference unit. The optical coupler 22 has, for example, connection ports P1 to P7 (not shown) for connecting the optical fibers F1 to F7, respectively, and an optical fiber connector (not shown) for connecting the connection ports. The optical coupler 22 is, for example, a 5-to-2 fiber-optic coupler or the like in which the connection ports P1, P2, P5, P6, and P7 are primary ports and the connection ports P3 and P4 are secondary ports. The primary port and the secondary port are connected by, for example, one optical fiber connector.

  The first light guided from the optical fiber F1 to the connection port P1 is branched into the connection port P3 and the connection port P4 based on a predetermined branching ratio. The predetermined branching ratio is preset, for example, such that the ratio of the intensities of the light branched to the connection port P3 and the light branched to the connection port P4 is 1: 1. The branched first light (hereinafter referred to as “first measurement light”) is guided to the optical fiber F3 through the connection port P3, and is guided to the optical fiber F4 through the connection port P4. In addition, the second light guided from the optical fiber F2 to the connection port P2 is branched into the connection port P3 and the connection port P4 based on the above-described predetermined branching ratio. The branched second light (hereinafter referred to as “second measurement light”) is guided to the optical fiber F3 through the connection port P3, and is guided to the optical fiber F4 through the connection port P4.

  The first light and the second light guided to the optical coupler 22 interfere and combine in the optical fiber connector of the optical coupler 22. The combined first and second lights generate third light whose frequency is the difference between the frequencies of the first and second lights. The generated third light is branched into the connection port P3 and the connection port P4 based on the predetermined branching ratio described above. The branched third light (hereinafter, referred to as “third measurement light”) is guided to the optical fiber F3 through the connection port P3, and is guided to the optical fiber F4 through the connection port P4. The optical coupler 22 has, for example, a transmission band including the wavelengths of the first light, the second light, and the third light.

  Here, the generation principle of the third light generated by the optical coupler 22 will be described with reference to equations. The wave function of the light emitted from the first collimator 24A described later is expressed by the following equation (1). In the formulas described later, E represents amplitude, ω represents angular frequency, f represents frequency, λ represents wavelength, k represents wave number, n represents refractive index, and t represents time. . Further, subscripts in the formula described later indicate the central wavelength of the light emitted from the wavelength swept light source 12.

  Here, the first measurement light of a sine wave having a frequency of 1 [kHz] in a wavelength band of 1550 ± 100 [nm] and the first measurement light of a sine wave having a frequency of 1 [kHz] in a wavelength band of 1310 ± 100 [nm] When the two measurement lights are simultaneously guided to the optical coupler 22, the wave function of the first measurement light emitted from the first collimator 24A is expressed by the following equation (2), and is emitted from the first collimator 24A. The wave function of the second measurement light to be obtained is expressed by the following equation (3). In the following formula, the formula is applied using only the main wavelengths (1550 [nm] and 1310 [nm]) excluding the swept wavelength band (± 100 [nm]) of the first measurement light and the second measurement light. Represents

  The third measurement light which is a combined light of the first measurement light and the second measurement light is expressed by the following equation (4).

Here, the frequency f _sw (t) of the third measurement light is expressed by the following equations (5) and (6) showing the difference between the frequencies of the first measurement light and the second measurement light.

The wavelength f _sw (t) of the third measurement light is expressed by the following equation (7).

  Therefore, in the optical coupler 22, third measurement light is generated in which the wavelength is periodically changed in the 8460 ± 596 [nm] wavelength band (infrared light).

  Here, with reference to FIG. 5, an aspect of the time change of the wavelength of the third measurement light generated in the optical coupler 22 will be described. FIG. 5 is a graph showing an example of how the wavelength of the third measurement light generated in the optical coupler 22 changes with time.

  The horizontal axis of the graph G2 represents an elapsed time Time (in units of [msec]). Further, the vertical axis of the graph G2 represents the wavelength λ (unit: [nm]) of light. In the graph G2, the curve LN4 represents the time change of the wavelength of the third light. As shown in FIG. 5, the third light may change in wavelength in the third wavelength band (8460 ± 596 [nm]) or may be a single wavelength.

  The characteristics of the third measurement light generated in the optical coupler 22 will be described with reference to FIGS. 6 and 7. FIG. 6 is a diagram showing an example of the relationship between the wavelength of light and the refractive index in air. FIG. 7 is a diagram showing an example of the relationship between the wave number of light and the transmittance of light. As shown in FIG. 6, the third measurement light (infrared light) whose wavelength changes in the 8460 ± 596 [nm] wavelength band generated in the optical coupler 22 is visible light, the first measurement light, (2) Due to the large wavelength compared with the measurement light, it is not easily affected by the refractive index of the atmosphere. Thereby, when the third measurement light (infrared light) is used for distance measurement, the influence of measurement error of atmospheric disturbance can be reduced. As a result, the distance measuring device 10 can accurately measure the distance L0 from the interferometer 20 to the reflection surface LM # of the liquid LM.

  Further, as shown in FIG. 7, as the liquid layer of the liquid (water) becomes thicker, the light transmittance decreases, so the distance measuring device 10 is compared with the first measurement light and the second measurement light. The third measurement light which does not easily pass through the liquid LM can be used as the measurement light for measuring the distance L0 from the interferometer 20 to the reflection surface LM # of the liquid LM. Thereby, the distance measuring device 10 measures the object to be measured from the interferometer 20 by the two lights (the first measurement light and the second measurement light) that transmit the liquid LM of the first wavelength swept light source 12A and the second wavelength swept light source 12B. The distance L1 to the reflecting surface SM # of the object SM can be calculated. In addition, the distance measurement device 10 can calculate the distance L0 by the third measurement light generated by the first measurement light and the second measurement light. Further, the distance measuring device 10 does not need to separately provide a light source for emitting the third light (third measurement light) necessary to calculate the distance L0. As a result, the size and cost of the device can be reduced.

  The optical fibers F3 and F4 are fibers having a transmission band including the wavelengths of the first measurement light, the second measurement light, and the third measurement light. The optical fiber F3 is an example of a light guide. The optical fiber F3 has, for example, a hollow optical fiber or a core to which a Ge-As-Se-based and Ge-Se-Te-based chalcogen compound is added.

  The first collimator 24A changes the guided light into parallel light or condenses it at a certain focal point. Here, the first collimator 24A is an example of the irradiation unit. The first collimator 24A transmits part or all of the first measurement light, the second measurement light, and the third measurement light guided through the optical fiber F3. Then, the first collimator 24A changes part or all of the transmitted first measurement light, second measurement light and third measurement light into parallel light or condensed light. A part or all of the first measurement light, the second measurement light, and the third measurement light, which are collimated light or condensed light, is emitted from the first collimator 24A toward the measurement object SM. Here, the first collimator 24A is separated from the reflection surface LM # of the liquid LM by an arbitrary distance L0, and installed at a position separated from the reflection surface SM # of the measurement object SM by an arbitrary distance L1.

  The first measurement light irradiated by the first collimator 24A is reflected by the measurement object SM and is incident on the first collimator 24A as a first reflected light. Further, the second measurement light irradiated by the first collimator 24A is reflected by the measurement object SM and is incident on the first collimator 24A as a second reflected light. In addition, the third measurement light irradiated by the first collimator 24A is reflected by the liquid LM and is incident on the first collimator 24A as a third reflected light. The first reflected light, the second reflected light, and the third reflected light incident on the first collimator 24A are guided to the optical coupler 22 via the optical fiber F3.

  The second collimator 24B changes the guided light into parallel light or condenses it at a certain focal point. Here, the second collimator 24B is an example of a reference light irradiation unit. The second collimator 24B transmits part or all of the first measurement light, the second measurement light, and the third measurement light guided through the optical fiber F4. Then, the second collimator 24B changes part or all of the transmitted first measurement light, second measurement light and third measurement light into parallel light or condensed light. A part or all of the first measurement light, the second measurement light, and the third measurement light, which are collimated light or condensed light, are emitted from the second collimator 24B toward the reflector RM.

  The first measurement light irradiated by the second collimator 24B is reflected by the reflector RM and is incident on the second collimator 24B as a first reference light. Further, the second measurement light irradiated by the second collimator 24B is reflected by the reflector RM and is incident on the second collimator 24B as a second reference light. In addition, the third measurement light irradiated by the second collimator 24B is reflected by the reflector RM and is incident on the second collimator 24B as a third reference light. The first reference light, the second reference light, and the third reference light incident on the second collimator 24B are guided to the optical coupler 22 via the optical fiber F4.

  The reflector RM reflects light (reference light) in parallel to the light emitted from the second collimator 24B toward the second collimator 24B. The reflector RM is, for example, an object having high light reflection characteristics such as an optical mirror and a corner cube prism, and is installed at a position separated by a predetermined distance L2 from the second collimator 24B.

  Here, the first reflected light guided to the optical coupler 22 via the optical fiber F3, the second reflected light and the third reflected light, and the first reference light guided to the optical coupler 22 via the optical fiber F4. The second reference light and the third reference light generate a plurality of interference lights which are interfered and combined in the optical coupler 22. The plurality of generated interference lights are guided to the first interference light detection unit 32A through the optical fiber F5, are guided to the second interference light detection unit 32B through the optical fiber F6, and the third interference light is transmitted through the optical fiber F7. The light is guided to the interference light detection unit 32C.

  Of the interference light guided from the optical coupler 22 via the optical fiber F5, the first interference light detection unit 32A generates interference light generated by interference between the first reflected light and the first reference light (hereinafter referred to as “second interference light”). 1) to detect interference light. The first interference light detection unit 32A includes, for example, a first band pass filter that allows only light of a wavelength included in a wavelength band of 1550 ± 100 [nm] to pass, and the interference light guided from the optical coupler 22 The first interference light is extracted. Then, the first interference light detection unit 32A detects (receives) the extracted first interference light, and converts the detected first interference light into an electric signal (hereinafter, referred to as "first interference signal"). The first interference light detection unit 32A outputs the first interference signal to the control device 50. Here, since the first interference light detection unit 32A detects the first interference light through the first band pass filter, the first interference light detection unit 32A is optimized to have the highest sensitivity to the frequency band of the first interference light. Good. In addition, the first interference light detection unit 32A may have a response speed of a frequency higher than the period of the wavelength swept light source 12 based on the sampling theorem.

  The second interference light detection unit 32B generates interference light (hereinafter referred to as “second interference light”) generated by interference between the second reflected light and the second reference light among the interference light guided from the optical coupler 22 via the optical fiber F6. 2) to detect interference light. The second interference light detection unit 32B includes, for example, a second band pass filter that allows only light of a wavelength included in a wavelength band of 1310 ± 100 [nm] to pass, and the interference light guided from the optical coupler 22 The second interference light is extracted. Then, the second interference light detection unit 32B detects (receives) the extracted second interference light, and converts the detected second interference light into an electric signal (hereinafter, referred to as "second interference signal"). The second interference light detection unit 32B outputs the second interference signal to the control device 50. Here, since the second interference light detection unit 32B detects the second interference light through the second band pass filter, the second interference light detection unit 32B is optimized to have the highest sensitivity to the frequency band of the second interference light. Good. In addition, the second interference light detection unit 32B may have a response speed of a frequency higher than the period of the wavelength swept light source 12 based on the sampling theorem.

  The third interference light detection unit 32C generates interference light (hereinafter referred to as “third interference light”) generated by the interference of the third reflected light and the third reference light among the interference light guided from the optical coupler 22 via the optical fiber F7. 3) to detect interference light. The third interference light detection unit 32C includes, for example, a third band pass filter that allows only light of a wavelength included in a wavelength band of 8460 ± 596 [nm] to pass, and the interference light guided from the optical coupler 22 And extract the third interference light. Then, the third interference light detection unit 32C detects (receives) the extracted third interference light, and converts the detected third interference light into an electric signal (hereinafter, referred to as "third interference signal"). The third interference light detection unit 32C outputs the third interference signal to the control device 50. Here, since the third interference light detection unit 32C detects the third interference light through the third band pass filter, the third interference light detection unit 32C is optimized to have the highest sensitivity to the frequency band of the third interference light. Good. In addition, the third interference light detection unit 32C may have a response speed of a frequency higher than the period of the wavelength swept light source 12 based on the sampling theorem.

  The optical fibers F5 to F7 have a transmission band including the wavelength of light guided by the optical coupler 22. The optical fiber F5 may be an optical fiber having only the wavelength of the first interference light of the interference light guided by the optical coupler 22 in the transmission band. The optical fiber F6 may be an optical fiber having only the wavelength of the second interference light in the transmission band among the interference light guided by the optical coupler 22. The optical fiber F7 may be an optical fiber having only the wavelength of the third interference light in the transmission band among the interference light guided by the optical coupler 22.

  Here, the first interference light detected by the first interference light detection unit 32A will be described with reference to FIG. FIG. 8 is a diagram illustrating a portion of the first interference light detected by the first interference light detection unit 32A. The horizontal axis in FIG. 8 represents an elapsed time Time (in units of [msec]). The vertical axis in FIG. 8 represents the amplitude of the interference light (the unit is, for example, a current value [mA] or the like). Signal LN5 is a difference between a distance L1 from first collimator 24A to reflective surface SM # of measurement object SM shown in FIG. 8 and a distance L2 from second collimator 24B to reflective surface RM # of reflector RM (FIG. The first interference light obtained when L1−L2) is 5 mm is shown. The second interference light and the third interference light detected by the second interference light detection unit 32B are similar to the first interference light detected by the first interference light detection unit 32A. I omit it.

  The control device 50 may be, for example, a processor such as a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), a hard disk drive (HDD), an electrically erasable programmable read only memory (EEPROM), or a flash. A storage device such as a memory, a communication interface for communicating with other devices, and the like are computer devices connected by an internal bus.

  The control device 50 acquires the first interference signal from the first interference light detection unit 32A, acquires the second interference signal from the second interference light detection unit 32B, and outputs the third interference signal from the third interference light detection unit 32C. get. The control device 50 calculates the distance from the reflective surface LM # of the liquid LM to the reflective surface SM # of the measurement object SM based on the acquired first interference signal, second interference signal, and third interference signal.

  Next, the functional configuration of the control device 50 will be described with reference to FIG. FIG. 9 is a diagram showing an example of a functional configuration of the control device 50. As shown in FIG. The control device 50 includes, for example, a device control unit 52, a first interference signal acquisition unit 54, a second interference signal acquisition unit 56, a third interference signal acquisition unit 58, an optical path length calculation unit 60, and a distance derivation unit 62 and a storage unit 64. Among them, the apparatus control unit 52, the first interference signal acquisition unit 54, the second interference signal acquisition unit 56, the third interference signal acquisition unit 58, the optical path length calculation unit 60, and the distance derivation unit 62 What is included corresponds to the control unit 51.

  The apparatus control unit 52 controls the first wavelength sweep light source 12A so that the first wavelength sweep light source 12A emits the first light, and the second wavelength sweep light so that the second wavelength sweep light source 12B emits the second light. The light source 12B is controlled. In addition, the device control unit 52 controls the first interference light detection unit 32A to output a first interference signal to the device control unit 52 with respect to the first interference light detection unit 32A that has detected the first interference light. . In addition, the device control unit 52 controls the second interference light detection unit 32B to output a second interference signal to the device control unit 52 with respect to the second interference light detection unit 32B that has detected the second interference light. . Further, the device control unit 52 controls the third interference light detection unit 32C to output the third interference signal to the device control unit 52 with respect to the third interference light detection unit 32C that has detected the third interference light. . Further, the device control unit 52 includes a timer unit (not shown), and the detection of the first interference light by the first interference light detection unit 32A, the detection of the second interference light by the second interference light detection unit 32B, and the second The detection time with the detection of the third interference light by the interference light detection unit 32C is synchronized. That is, the control device 50 acquires the first interference signal, the second interference signal, and the third interference signal at the same timing. The control unit 51 stores the acquired first interference signal, second interference signal, and third interference signal in the storage unit 64 in association with information indicating the time counted by the clock unit.

The first interference signal acquisition unit 54 acquires the first interference signal output from the first interference light detection unit 32A.
The second interference signal acquisition unit 56 acquires the second interference signal output from the second interference light detection unit 32B.
The third interference signal acquisition unit 58 acquires the third interference signal output from the third interference light detection unit 32C.

The optical path length calculation unit 60 calculates a first optical path length L ₁₅₅₀ based on the first interference signal acquired by the first interference signal acquisition unit 54. The first optical path length L ₁₅₅₀ is an optical distance when the first measurement light irradiated by the first collimator 24A propagates the distances L1 and L2. Further, the optical path length calculation unit 60 calculates a second optical path length L ₁₃₁₀ based on the second interference signal acquired by the second interference signal acquisition unit 56. The second optical path length L ₁₃₁₀ is an optical distance when the second measurement light irradiated by the first collimator 24A propagates the distances L1 and L2. Further, the optical path length calculation unit 60 calculates the third optical path length based on the third interference signal acquired by the third interference signal acquisition unit 58. The third optical path length is an optical distance when the third measurement light irradiated by the first collimator 24A propagates the distances L0 and L2. The optical path length calculation unit 60 acquires various types of information from the storage unit 64 when calculating the first optical path length, the second optical path length, and the third optical path length. The various information is, for example, parameters necessary to calculate the first optical path length such as the light velocity and the distance L2, the second optical path length, and the third optical path length.

  The optical path length calculation unit 60 reads the first interference signal in the predetermined time range from the storage unit 64 using the time associated with the first interference signal, and Fourier-transforms the read first interference signal. Then, the optical path length calculation unit 60 detects the first peak frequency from the first interference signal subjected to Fourier transform. The first peak frequency is a frequency at which the first frequency spectrum obtained by Fourier transforming the first interference signal has a maximum value (peak).

  Here, the method of calculating the first peak frequency by the optical path length calculation unit 60 will be described with reference to FIG. FIG. 10 is a graph showing an example of a first frequency spectrum obtained by subjecting the first interference light to Fourier transform. The horizontal axis of the graph shown in FIG. 10 represents a frequency (unit is [kHz]). Also, the vertical axis of the graph represents the amplitude of the frequency spectrum (in units of, for example, [W / Hz]). FIG. 10 shows a frequency spectrum when the difference between the distance L1 and the distance L2 is 5 [mm].

  For example, in FIG. 10, the optical path length calculation unit 60 detects the first peak frequency 2000 [kHz] when the first frequency spectrum LN6 reaches the peak P1. The first peak frequency changes in accordance with the difference between the distance L1 and the distance L2.

  Also, the optical path length calculation unit 60 reads the second interference signal in the predetermined time range from the storage unit 64 using the time associated with the second interference signal, and performs Fourier transform on the read second interference signal. Do. Then, the optical path length calculation unit 60 detects the second peak frequency from the Fourier-transformed second interference signal. The second peak frequency is a frequency at which the second frequency spectrum obtained by Fourier transforming the second interference signal has a maximum value.

  Here, a method of calculating the second peak frequency by the optical path length calculation unit 60 will be described with reference to FIG. FIG. 11 is a graph showing an example of a second frequency spectrum obtained by subjecting the second interference light to Fourier transform. The horizontal axis of the graph shown in FIG. 11 represents a frequency (unit is [kHz]). Also, the vertical axis of the graph represents the amplitude of the frequency spectrum (in units of, for example, [W / Hz]). FIG. 11 shows a frequency spectrum when the difference between the distance L1 and the distance L2 is 5 [mm].

  The optical path length calculation unit 60 detects, for example, the value 1300 [kHz] of the second peak frequency when the second frequency spectrum LN7 reaches the peak P2 in FIG. The second peak frequency changes in accordance with the difference between the distance L1 and the distance L2.

  Further, the optical path length calculation unit 60 reads the third interference signal in the predetermined time range from the storage unit 64 using the time associated with the third interference signal, and performs Fourier transform on the read third interference signal. Do. Then, the optical path length calculation unit 60 detects the third peak frequency from the third interference signal subjected to the Fourier transform. The third peak frequency is a frequency at which the third frequency spectrum obtained by Fourier transforming the third interference signal has a maximum value.

  Here, a method of calculating the third peak frequency by the optical path length calculation unit 60 will be described with reference to FIG. FIG. 12 is a graph showing an example of a third frequency spectrum obtained by subjecting the third interference light to Fourier transform. The horizontal axis of the graph shown in FIG. 12 represents a frequency (in units of [Hz]). Also, the vertical axis of the graph represents the amplitude of the frequency spectrum (in units of, for example, [W / Hz]). FIG. 12 shows a frequency spectrum when the difference between the distance L0 and the distance L2 is 5 [mm].

  For example, in FIG. 12, the optical path length calculation unit 60 detects the value 500 [Hz] of the third peak frequency when the third frequency spectrum LN 8 becomes the peak P3. The third peak frequency changes in accordance with the difference between the distance L0 and the distance L2.

When detecting the first peak frequency, the optical path length calculation unit 60 reads first correspondence information in which the known first peak frequency stored in advance in the storage unit 64 is associated with the known optical path length. Then, the optical path length calculation unit 60 detects a first optical path length L ₁₅₅₀ associated with the detected first peak frequency from the read first correspondence information. Also, when detecting the second peak frequency, the optical path length calculation unit 60 reads second correspondence information in which the known second peak frequency stored in advance in the storage unit 64 is associated with the known optical path length. Then, the optical path length calculation unit 60 detects a second optical path length L ₁₃₁₀ associated with the detected second peak frequency from the read second correspondence information.
Further, when detecting the third peak frequency, the optical path length calculation unit 60 reads third correspondence information in which the known third peak frequency stored in advance in the storage unit 64 is associated with the known optical path length. Then, the optical path length calculation unit 60 detects the third optical path length L ₈₄₆₀ associated with the detected third peak frequency from the read third correspondence information. The first correspondence information, the second correspondence information, and the third correspondence information are stored in advance in the storage unit 64 by calibration or the like.

The distance deriving unit 62 receives the first optical path length L ₁₅₅₀ , the second optical path length L ₁₃₁₀ and the third optical path length L ₈₄₆₀ calculated by the optical path length calculating unit 60, and the reflecting surface of the measuring object SM from the interferometer 20 A distance D (= L1−L0) which is a difference between the distance L1 to SM # and the distance L0 from the interferometer 20 to the reflection surface LM # of the liquid LM is calculated.

  The storage unit 64 includes, for example, a Hard Disk Drive (HDD), a Solid State Drive (SSD), an Electrically Erasable Programmable Read-Only Memory (EEPROM), a Read-Only Memory (ROM), a Random Access Memory (RAM), etc. The control device 50 stores various information for calculating the distance L1. The storage unit 64 may be an external storage device instead of the one incorporated in the control device 50.

[Operation flow of control device 50]
Hereinafter, the processing performed by each functional unit of the control device 50 will be described with reference to FIG. FIG. 13 is a flowchart illustrating an example of the flow of processing executed by the control device 50. First, the apparatus control unit 52 causes the first wavelength swept light source 12A to emit the first light, and causes the second wavelength swept light source 12B to emit the second light (Step S100).

  Next, the first interference signal acquisition unit 54 acquires the first interference signal output from the first interference light detection unit 32A (step S102). Next, the second interference signal acquisition unit 56 acquires the second interference signal output from the second interference light detection unit 32B (step S104). Next, the third interference signal acquisition unit 58 acquires the third interference signal output from the third interference light detection unit 32C (step S106). Then, the control unit 51 associates the acquired first interference signal, the second interference signal, and the third interference signal with the information indicating the time measured by the timer unit (not shown) included in the device control unit 52 and stores the memory unit 64. Remember. Of the processes performed by the control device 50, steps S102 to S106 may be in any order, or some or all of them may be performed simultaneously.

Next, the optical path length calculation unit 60 calculates the first optical path length L ₁₅₅₀ based on the first interference signal acquired by the first interference signal acquisition unit 54, and is acquired by the second interference signal acquisition unit 56. The second optical path length L ₁₃₁₀ is calculated based on the second interference signal, and the third optical path length is calculated based on the third interference signal acquired by the third interference signal acquisition unit 58 (step S108). The optical path length calculation unit 60 acquires various types of information from the storage unit 64 when calculating the first optical path length, the second optical path length, and the third optical path length.

Next, based on the first optical path length L ₁₅₅₀ , the second optical path length L ₁₃₁₀ and the third optical path length L ₈₄₆₀ calculated by the optical path length calculator 60, the distance deriving unit 62 _{transmits the} measurement object SM from the interferometer 20. The distance D (= L1−L0) which is the difference between the distance L1 to the reflective surface SM # and the distance L0 from the interferometer 20 to the reflective surface LM # of the liquid LM is calculated (step S110).

Here, a method of calculating the distance D using the first optical path length L ₁₅₅₀ and the second optical path length L ₁₃₁₀ calculated by the optical path length calculation unit 60 and the refractive index depending on the liquid LM with reference to the following equation Will be explained. In the following formulas (8) and (9), the first optical path length L ₁₅₅₀ and the second optical path length L ₁₃₁₀ are values obtained by subtracting the third optical path length L ₈₄₆₀ .

First, the refractive index depending on the liquid LM when the first measurement light propagates in the liquid LM is taken as a first refractive index n _1550, and the refractive index depends on the liquid LM when the second measurement light propagates in the liquid LM When the second refractive index n ₁₃₁₀ is the refractive index, the following relational expression holds between the distance D to be calculated.

Based on the above equation (10), the distance D can be calculated using numerical calculation such as Monte Carlo simulation. For example, there is a method in which the value of the first refractive index n _{1550 and} the value of the second refractive index n ₁₃₁₀ in the above equation (10) are randomly allocated using Monte Carlo simulation or the like. In this method, when the value obtained by dividing the first optical path length L ₁₅₅₀ ^* by the first refractive index n ₁₅₅₀ and the value obtained by dividing the second optical path length L ₁₃₁₀ ^* by the second refractive index n ₁₃₁₀ become the same value. , And the distance D to be calculated. However, in this method, by randomly allocating two parameters (the first refractive index n ₁₅₅₀ and the second refractive index n ₁₃₁₀ ), the calculation time is longer than when one parameter is randomly allocated. Therefore, the distance D is calculated more quickly than when the distance D is calculated by randomly allocating two parameters by the following method.

Further, when the difference between the first optical path length and the second optical path length (L ₁₅₅₀ ^* −L ₁₃₁₀ ^* ) is ΔL, the following formula (11) is established.

  Moreover, Formula (11) is deform | transformed and represented like the following Formula (12).

Here, based on Formula (11) and Formula (12), the ratio of the first refractive index n ₁₅₅₀ and the second refractive index n ₁₃₁₀ is expressed as the following Formula (13).

  On the other hand, the square of the distance D is expressed by the following equation (14) by the equation (10).

  Here, equation (14) is expressed as equation (15) below by equation (13).

Next, from equation (15) representing the square of the distance D, the distance D is represented as the following equation (16) using the first refractive index n ₁₅₅₀ .

Further, from the equation (15) expressing the square of the distance D, the distance D is represented as the following equation (17) using the second refractive index n ₁₃₁₀ .

  Moreover, Formula (17) is represented like a following formula (18) using Formula (13).

The above equation (16) and equation (18) are a table showing the distance D by the first optical path length L ₁₅₅₀ ^* and the second optical path length L ₁₃₁₀ ^* , which are measured values, and the first refractive index n ₁₅₅₀ , which is unknown. It is an expression that Further, as described above, according to the equation (12), the unknowns of the equations (16) and (18) are only the first refractive index n ₁₅₅₀ which is one parameter. The distance deriving unit 62 calculates the distance D by solving the simultaneous equations of Equation (16) and Equation (18). Further, the distance deriving unit 62 calculates the first refractive index n ₁₅₅₀ , which is an unknown number, by solving the simultaneous equations of Equation (13), Equation (16), and Equation (18).

As an example of a method of solving this simultaneous equation, the distance deriving unit 62 changes, for example, the value of the first refractive index n ₁₅₅₀ within a predetermined range (for example, ± 0.001), and the distance D in Expression (16) And the distance D in equation (18) agree with each other.

At this time, the distance deriving unit 62 may randomly change the value of the first refractive index n ₁₅₅₀ within a predetermined range (for example, ± 0.001) by Monte Carlo simulation or the like. For example, the value of the first refractive index n ₁₅₅₀ may be changed continuously at ± 0.001). Further, the distance deriving unit 62 may make a total use of the value of the first refractive index n ₁₅₅₀ within a predetermined range (for example, ± 0.001).

When the first refractive index n ₁₅₅₀ is changed in a predetermined range, the distance deriving unit 62 calculates a value when the equation (16) matches the equation (18) as the distance D. Thus, the distance D can be calculated with high accuracy as compared to the case where the distance D is calculated without using the two optical path lengths of the first optical path length L ₁₅₅₀ ^* and the second optical path length L ₁₃₁₀ ^* . As a result, the distance D from the reflective surface LM # of the liquid LM to the reflective surface SM # of the measurement object SM can be measured with high accuracy. Further, the distance deriving unit 62 may calculate the first refractive index n ₁₅₅₀ and the second refractive index n ₁₃₁₀ using Expression (10). Thus, the component of the liquid LM can be analyzed based on one or both of the calculated first refractive index n ₁₅₅₀ and the second refractive index n ₁₃₁₀ while measuring the distance D. As a result, the distance measuring device 10 can identify the liquid LM without contacting the liquid LM.

  Further, another method for the distance deriving unit 62 to calculate the distance (L1-L2) and the distance (L0-L2) will be described here with reference to FIGS. 14 and 15. FIG. 14 is a graph showing the correlation between the known first peak frequency and the known second peak frequency and the known distance (L1-L2). The horizontal axis of the graph shown in FIG. 14 represents a distance (unit is [mm]). Further, the vertical axis of the graph represents the frequency (in units of, for example, [MHz]) of the first interference signal and the second interference signal.

  FIG. 15 is a graph showing the correlation between the known third peak frequency and the known distance (L0-L2). The horizontal axis of the graph shown in FIG. 15 represents a distance (unit is [mm]). The vertical axis of the graph represents the frequency of the third interference signal (in units of, for example, [kHz]).

  The distance deriving unit 62 determines, based on the first peak frequency and the second peak frequency detected by the optical path length calculating unit 60, a known first peak frequency and a known second peak frequency and a known distance (L1-L2). The distance (L1-L2) is calculated with reference to the data (FIG. 14) indicating the correlation with. For example, when the value of the detected first peak frequency is 2 [MHz], the optical path length calculation unit 60 reads the value 5 [mm] of the distance (L1-L2) corresponding to the detected frequency. In addition, for example, when the value of the detected second peak frequency is 1.3 [MHz], the optical path length calculation unit 60 reads the value 5 [mm] of the distance (L1-L2) corresponding to the detected frequency. Data indicating the correlation between the known first peak frequency and the known second peak frequency shown in FIG. 14 and the known distance (L1-L2) is acquired in advance by control device 50 and stored in storage unit 64. It shall be done.

  Further, the distance deriving unit 62 is data indicating the correlation between the known third peak frequency and the known distance (L0−L2) based on the third peak frequency detected by the optical path length calculating unit 60 (FIG. 15). To calculate the third optical path length to be obtained. For example, when the value of the detected third peak frequency is 0.5 [kHz], the optical path length calculation unit 60 reads the value 2 [mm] of the third optical path length corresponding to the detected frequency. It is assumed that data indicating the correlation between the known third peak frequency and the known distance (L0-L2) shown in FIG. 15 is acquired in advance by control device 50 and stored in storage unit 64.

  The distance deriving unit 62 calculates the distance D from the read distances (L1-L2) and the distances (L0-L2). Further, the distance deriving unit 62 outputs, for example, one of the distance D calculated with reference to the data shown in FIGS. 14 and 15 and the distance D calculated by numerical calculation such as Monte Carlo simulation as a measurement result. Or the average value of both may be output as the measurement result. This makes it possible to reduce the influence of an error included in the measured distance D. By this, the processing of this flowchart ends.

  According to the distance measurement device 10 of the present embodiment described above, the wavelength of the first collimator 24A changes in the first wavelength range where the wavelength changes in the first wavelength range, and in the second wavelength range different from the first wavelength range. Of the second measurement light and the third measurement light of a wavelength different from the first measurement light and the second measurement light were emitted to the measurement object SM in the liquid LM and reflected by the measurement object SM The first reflected light, the second reflected light, and the third reflected light reflected by the liquid LM are received, and the reflection of the liquid LM is received based on the received first reflected light, the second reflected light, and the third reflected light. By calculating the distance D from the surface LM # to the reflection surface SM # of the measurement object SM, the error included in the distance L1 from the interferometer 20 to the reflection surface SM # of the measurement object SM is reduced while the interference is reduced. Errors included in the distance L0 from the total 20 to the reflection surface LM # of the liquid LM Can be reduced, the distance D is the difference between the distance L1 and the distance L0 can be calculated more accurately with respect to the true value. As a result, the distance measuring device 10 can accurately measure the distance to the object in the liquid.

  Moreover, according to the distance measurement device 10 of the present embodiment, the wavelength is obtained by using the third light generated by the interference of the first light and the second light for measuring the shape of the measurement object SM in the liquid LM. The refractive index of the liquid can be calculated from the difference in the measurement distance for each. As a result, the liquid LM can be identified without contacting the liquid LM.

Second Embodiment
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. The distance measuring device 10 according to the second embodiment is configured to reflect the first reflected light and the second reflected light reflected by the measurement object SM, the third reflected light reflected by the liquid LM, and the reflector RM. The first reflected light and the second reflected light reflected by the object to be measured SM instead of the configuration in which the six lights of the first reference light, the second reference light and the third reference light interfere with each other The third reflection light reflected by the LM, the first reference light reflection of the first measurement light by the liquid LM, the second reference light reflection of the second measurement light by the liquid LM, and the third reference light The measurement light interferes with the third reference light that is end-face reflected by the first collimator 24A. Description of functions and the like common to the first embodiment will be omitted.

  FIG. 16 is a block diagram showing an example of the distance measuring device 10 according to the second embodiment. Some configurations are described with reference to FIG. 2 and FIG. 9 and the same functional parts are given the same reference numerals. For example, the distance measurement device 10 includes a first wavelength swept light source 12A, a second wavelength swept light source 12B, an interferometer 20-1, a first interference light detection unit 32A, a second interference light detection unit 32B, A three-interference light detection unit 32C and a control device 50 are provided.

  The interferometer 20-1 includes, for example, an optical coupler 22-1, a first collimator 24A, and an optical fiber F3.

  The optical coupler 22-1 is connected to the first collimator 24A via the optical fiber F3. The optical coupler 22-1 includes, for example, a connection port P1 (not shown) for connecting the optical fiber F1, a connection port P2 (not shown) for connecting the optical fiber F2, and a connection port P3 (not shown) for connecting the optical fiber F3. A connection port P5 (not shown) for connecting the optical fiber F5, a connection port P6 (not shown) for connecting the optical fiber F6, a connection port P7 (not shown) for connecting the optical fiber F7, and an optical fiber connector for connecting each connection port And (not shown). The optical coupler 22 is, for example, a 5-to-1 optical fiber coupler or the like in which the connection ports P1, P2, P5, P6, and P7 are primary ports and the connection port P3 is a secondary port.

  The first light guided from the optical fiber F1 to the connection port P1 is guided as the first measurement light to the optical fiber F3 via the connection port P3. In addition, the second light guided from the optical fiber F2 to the connection port P2 is guided as the second measurement light to the optical fiber F3 via the connection port P3. In addition, the third light generated in the optical coupler 22-1 is guided as the third measurement light to the optical fiber F3 through the connection port P3.

  The first collimator 24A changes the guided light into parallel light or condenses it at a certain focal point. The first collimator 24A transmits part or all of the first measurement light, the second measurement light, and the third measurement light guided through the optical fiber F3. Then, the first collimator 24A changes part or all of the transmitted first measurement light, second measurement light and third measurement light into parallel light or condensed light. A part or all of the first measurement light, the second measurement light, and the third measurement light, which are collimated light or condensed light, are emitted from the first collimator 24A toward the measurement object SM.

  The first measurement light irradiated by the first collimator 24A is reflected by the measurement object SM and is incident on the first collimator 24A as a first reflected light. In addition, a part of the first measurement light irradiated by the first collimator 24A is reflected by the liquid LM and is incident on the first collimator 24A as a first reference light. Further, the second measurement light irradiated by the first collimator 24A is reflected by the measurement object SM and is incident on the first collimator 24A as a second reflected light. In addition, a part of the second measurement light irradiated by the first collimator 24A is reflected by the liquid LM and is incident on the first collimator 24A as a second reference light. In addition, the third measurement light irradiated by the first collimator 24A is reflected by the liquid LM and is incident on the first collimator 24A as a third reflected light. In addition, a part of the third measurement light irradiated by the first collimator 24A is reflected on the end face by the first collimator 24A, and is incident on the first collimator 24A as a third reference light. The first reflected light, the second reflected light, the third reflected light, the first reference light, the second reference light, and the third reference light incident on the first collimator 24A are guided to the optical coupler 22 via the optical fiber F3. Ru.

  Here, the first reflected light, the second reflected light, the third reflected light, the first reference light, the second reference light, and the third reference light guided to the optical coupler 22 via the optical fiber F3 are the optical coupler 22. And generate a plurality of interference lights that are interfered and combined. The plurality of generated interference lights are guided to the first interference light detection unit 32A through the optical fiber F5, are guided to the second interference light detection unit 32B through the optical fiber F6, and the third interference light is transmitted through the optical fiber F7. The light is guided to the interference light detection unit 32C.

  As described above, the distance measurement device 10 in the present embodiment uses the liquid LM instead of the configuration in which the interference light is generated by using the light reflected by the reflector RM as the first reference light, the second reference light, and the third reference light. Since the reflected light is used as the first reference light and the second reference light, and the light reflected on the end face by the first collimator 24A is used as the third reference light to generate interference light, the same effects as in the first embodiment are obtained. Be Further, in addition to the same effects as those of the first embodiment, the distance measuring device 10 has the length of the optical fiber F3 between the optical coupler 22 and the first collimator 24A in the first embodiment, and the first embodiment. It is possible to suppress the occurrence of the difference in the optical path length due to the expansion and contraction of the length of the optical fiber F4 from the optical coupler 22 to the second collimator 24B due to the air temperature or the like. Further, the distance measuring device 10 can reduce the equipment cost as compared with the configuration shown in FIG.

  In the description of the first and second embodiments above, the interferometer 20 comprises optical fibers F3 and F4, an optical coupler 22, a first collimator 24A, a second collimator 24B, and a reflector RM However, the present invention is not limited to this. For example, the interferometer 20 may be configured to include some or all of the optical fibers F1, F2, F7, F8, and F9. In addition, the interferometer 20 further includes a first wavelength sweep light source 12A, a second wavelength sweep light source 12B, a first interference light detection unit 32A, a second interference light detection unit 32B, and a third interference light detection unit 32C. It may be configured to include some or all of the above.

  Further, in the distance measurement device 10, the first interference light detection unit 32A detects the first interference light using the first band pass filter, and the second interference light detection unit 32B uses the second band pass filter to perform the second operation. Although the configuration is such that the interference light is detected, and the third interference light detection unit 32C detects the third interference light using the third band pass filter, instead of this, the first reflected light and the second reflected light from the optical coupler 22 are used. One interference light in which the reflected light, the third reflected light, the first reference light, the second reference light, and the third reference light cause interference is guided to one interference light detection unit via one optical fiber, It may be configured to be detected by the interference light detection unit. In this case, the control device 50 detects three peaks P1, P2 and P3 from the frequency spectrum obtained by Fourier transforming one interference light, and the first peak frequency and the second peak frequency corresponding to the respective peaks. And the third peak frequency is detected based on the peaks corresponding to the first wavelength band, the second wavelength band and the third wavelength band. The first interference light detection unit 32A, the second interference light detection unit 32B, and the third interference light detection unit 32C are examples of light receiving units.

  In addition, although the control unit 51 stores the acquired first interference light, second interference light, and third interference light in the storage unit 64 in association with the time counted by the clock unit, instead of this, The acquired first interference light, second interference light, and third interference light may be stored in the storage unit 64 in association with an interval of time elapsed until acquisition of the interference light.

  In addition, the wavelength band of the first light swept by the first wavelength swept light source 12A is not limited to the first wavelength band (1550 ± 100 [nm]), and may be swept in another wavelength band. Further, the wavelength band of the second light swept by the second wavelength swept light source 12B is not limited to the second wavelength band (1310 ± 100 [nm]), and may be swept in another wavelength band. The wavelength band of the first light and the wavelength band of the second light are different from each other. Further, the wavelength band of the first light and the wavelength band of the second light are swept so that the third light generated by the first light and the second light becomes infrared light.

  The first wavelength swept light source 12A and the controller 50, the second wavelength swept light source 12B and the controller 50, the first interference light detector 32A and the controller 50, and the second interference light detector 32B and the controller 50, the third The interference light detection unit 32C and a part or all of the control device 50 may be communicably connected by wireless.

Further, in the distance measuring device 10, in order to acquire the light in which the first reflected light and the first reference light interfere with each other as the first interference light, it is possible to split the first light emitted from the first wavelength swept light source 12A. The interference distance should be longer than the difference between the distance L1 and the distance L2 shown in FIG.
Further, in the distance measurement device 10, the coherent distance of the second light emitted from the second wavelength swept light source 12B is obtained in order to acquire the light in which the second measurement light and the second reference light interfere as the second interference light. It has to be longer than the difference between the distance L1 and the distance L2 shown in FIG.

  In the above embodiment, as a preferable example of the interferometer 20, the optical path length from the optical coupler 22 to the first collimator 24A and the optical path length from the optical coupler 22 to the second collimator 24B are the same distance. However, instead of this, for example, depending on the distance L1 from the first collimator 24A to the reflection surface SM # of the measurement object SM and the coherence length of the wavelength swept light source 12, the optical path length difference is the optical fiber F3 and the optical fiber You may adjust by changing the length of F4.

  When there are a plurality of points where it is desired to measure the distance L1 in the measurement object SM, the series of processes shown in FIG. 15 may be repeated for the number of points to be measured. In that case, the distance measuring device 10 can change the irradiation direction of the measurement light toward a point to be measured, and also stores information indicating the measurement direction in the storage unit 64 in association.

  Further, the interferometer 20 is configured such that the first reflected light and the second reflected light reflected by the measurement object SM, the third reflected light reflected by the liquid LM, and the first reflected by the reflector RM. The configuration for generating interference light by causing the reference light, the second reference light, and the third reference light to interfere with each other may be replaced with another configuration. For example, the first reference light, the second reference light, and the third reference light that are connected to the optical coupler 22 so that the optical fiber F6 forms a loop-like path, and pass through the loop-like path and return to the optical coupler 22 The interference light may be generated by causing the first measurement light and the second measurement light reflected by the measurement object SM to interfere with the third reflection light reflected by the liquid LM. This looped path may be adjusted according to the distance L1 to the reflection surface SM # of the measurement object SM and the coherence length of the wavelength swept light source 12.

  A program for realizing the function of the control device 50 in the device (for example, the distance measurement device 10) described above is recorded in a computer readable recording medium, and the program is read and executed by a computer system. You may do so. Note that the “computer system” referred to here includes hardware such as an operating system (OS) and peripheral devices.

  The computer readable recording medium refers to a flexible disk, a magneto-optical disk, a ROM, a portable medium such as a CD (Compact Disk) -ROM, and a storage device such as a hard disk built in a computer system. Furthermore, "computer-readable recording medium" refers to volatile memory (RAM) in a computer system serving as a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those that hold the program for a certain period of time are also included.

  Also, the above program may be transmitted from a computer system in which the program is stored in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program is a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.

  In addition, the above program may be for realizing a part of the functions described above. Furthermore, the program described above may be a so-called difference file (difference program) that can realize the functions described above in combination with the program already recorded in the computer system.

  While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and the equivalents thereof as well as included in the scope and the gist of the invention.

DESCRIPTION OF SYMBOLS 10 ... Distance measuring apparatus, 12A ... 1st wavelength sweep light source, 12B ... 2nd wavelength sweep light source, 20, 20-1 ... Interferometer, 22, 22-1 ... Optical coupler, 24A ... 1st collimator, 24B ... 2nd Collimator, 32A: first interference light detection unit, 32B: second interference light detection unit, 32C: third interference light detection unit, 50: control device, 51: control unit, 52: device control unit, 54: first interference Signal acquisition unit 56 Second interference signal acquisition unit 58 Third interference signal acquisition unit 60 Optical path length calculation unit 62 Distance derivation unit 64 Storage unit LM Liquid, SM Measurement object RM ... reflector

Claims (8)

A first signal based on a first reflected light when a first light whose wavelength changes in a first wavelength band irradiated from the outside of the medium with respect to the object to be measured in the medium is reflected by the object to be measured; The second light emitted from the outside of the medium to the object to be measured in the medium, the second light whose wavelength changes in a second wavelength band different from the first wavelength band is reflected by the object to be measured A second signal based on the second reflected light at the same time and the third light irradiated from the outside of the medium to the object to be measured in the medium, the first light and the second light being different An acquisition unit configured to acquire a third signal based on a third reflected light when the third light of the wavelength is reflected by the medium;
Based on the first signal, the second signal, and the third signal acquired by the acquisition unit, the distance from the reflection surface of the medium to the reflection surface of the measurement target in the environment formed by the medium is A calculation unit to calculate
Distance measuring device comprising The first light has a wavelength with high transmittance to the medium, the second light has a high transmittance to the medium, and a wavelength different from that of the first light, and the third light has a wavelength to the medium Low transmission wavelength,
The distance measuring device according to claim 1. The first wavelength band in which the wavelength of the first light changes and the second wavelength band in which the wavelength of the second light changes are:
When the first light and the second light are guided by the light guiding unit, the wavelength band does not break the coherence of each other.
The distance measuring device according to claim 1. The third light has a frequency difference between the frequency of the first light and the frequency of the second light,
The distance measuring device according to any one of claims 1 to 3. The calculation unit calculates the refractive index of the medium based on the first reflected light, the second reflected light, and the third reflected light.
The distance measuring device according to any one of claims 1 to 4. A reference light irradiator configured to irradiate the first light, the second light and the third light to a reflector provided outside the medium;
A reference light receiving unit that receives the reference light that is emitted by the reference light irradiation unit and reflected by the reflector;
And an interference unit that causes the first reflected light, the second reflected light, and the third reflected light to interfere with the reference light to generate interference light.
The calculation unit is an object to be measured in the medium based on interference light generated by the first reflection light, the second reflection light, and the third reflection light being interfered with the reference light by the interference unit. Calculate the position of,
The distance measuring device according to any one of claims 1 to 5. An irradiation unit that irradiates the first light, the second light, and the third light from outside the medium to the measurement object;
And a combining unit configured to combine the first light and the second light to generate the third light.
The combining unit and the irradiating unit are connected by a light guiding unit that simultaneously guides the first reflected light, the second reflected light, and the third reflected light.
The distance measuring device according to any one of claims 1 to 6. The computer is
A first signal based on a first reflected light when a first light whose wavelength changes in a first wavelength band irradiated from the outside of the medium with respect to the object to be measured in the medium is reflected by the object to be measured; The second light emitted from the outside of the medium to the object to be measured in the medium, the second light whose wavelength changes in a second wavelength band different from the first wavelength band is reflected by the object to be measured A second signal based on the second reflected light at the same time and the third light irradiated from the outside of the medium to the object to be measured in the medium, the first light and the second light being different Acquiring a third signal based on the third reflected light when the third light of the wavelength is reflected by the medium,
The distance from the reflective surface of the medium to the reflective surface of the measurement target in the environment formed by the medium is calculated based on the acquired first signal, the second signal, and the third signal.
How to measure distance.

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