Wavelength dispersion compensation device, optical distance measurement device, and wavelength dispersion compensation method

Abstract

The wavelength dispersion compensation device (6) includes a wavelength dispersion compensation unit (61) that compensates for the difference in wavelength dispersion between the measurement interference signal and the reference interference signal in the reference interference signal based on the set wavelength dispersion compensation amount, and a wavelength dispersion amount adjustment unit (62) that adjusts the wavelength dispersion compensation amount set in the wavelength dispersion compensation unit 61 based on a compensation index corresponding to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal.

Description

Technical Field

[0001] The present disclosure relates to a wavelength dispersion compensation device, an optical distance measurement device, and a wavelength dispersion compensation method.

Background Art

[0002] There is an optical distance measurement method for measuring the distance to an object based on the peak position in the spectrum of a measurement interference signal obtained from an optical signal in a path not passing through the object and an optical signal in a path passing through the object. For example, Patent Document 1 describes an optical tomography imaging method for generating a tomographic image based on the distance in the depth direction of a measurement object. In this method, light emitted from a light source unit is split into measurement light and reference light, the measurement light is irradiated onto a biological measurement object, the reflected light from the measurement object and the reference light are combined, the interference light of the combined reflected light and reference light is detected, and a tomographic image of the measurement object is acquired from the detected interference light. In the above optical distance measurement method, when the measurement interference signal changes non-linearly with time, the shape of the spectrum obtained by Fourier-transforming the measurement interference signal spreads, and the accuracy of distance measurement based on the peak position decreases.

[0003] On the other hand, an optical distance measurement device including a reference interference system and a measurement interference system has been proposed. The reference interference system generates a reference interference signal obtained by combining wavelength-swept light that has passed through two optical paths having different optical path lengths. The measurement interference system generates a measurement interference signal obtained by combining wavelength-swept light that has passed through an optical path passing through the object and an optical path not passing through the object. By inputting the same wavelength-swept light into the reference interference system and the measurement interference system respectively, the reference interference signal and the measurement interference signal become signals with the same non-linear change with respect to time. Therefore, it is possible to compensate for the non-linearity of the measurement interference signal using the reference interference signal.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] However, in a conventional optical distance measuring device, the reference interference system is a path that does not pass through the object and is composed of an optical fiber, while the measurement interference system is a path that passes through the object via an air layer. For this reason, there may be a difference in wavelength dispersion, which is the dependence of the refractive index on the wavelength, between the reference interference signal and the measurement interference signal. In this case, distortion occurs in the frequency spectrum obtained from these signals, so there is a problem that the accuracy of distance measurement based on the peak position decreases.

[0006] The present disclosure solves the above problems, and an object thereof is to obtain a wavelength dispersion compensation device capable of reducing the influence on measurement accuracy due to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal.

MEANS FOR SOLVING THE PROBLEMS

[0007] The wavelength dispersion compensation device according to the present disclosure includes a wavelength-sweeping light source that outputs wavelength-sweeping light, and two optical paths having different optical path lengths. By photoelectrically converting the reference interference light obtained by combining the wavelength-sweeping light that has passed through the two optical paths, a reference interference system that generates a reference interference signal, and an optical path that passes through the object and an optical path that does not pass through the object, and photoelectrically converting the measurement interference light obtained by combining the wavelength-sweeping light that has passed through the two optical paths, a wavelength dispersion compensation device that compensates for the difference in wavelength dispersion between the reference interference signal and the measurement interference signal in an optical distance measuring device including a measurement interference system that generates a measurement interference signal, Provided in one of the two optical paths of the reference interference system, a compensation unit that compensates for the difference in wavelength dispersion between the measurement interference signal in the reference interference signal based on the set wavelength dispersion compensation amount, and an adjustment unit that adjusts the wavelength dispersion compensation amount set in the compensation unit based on a compensation index corresponding to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal.

EFFECTS OF THE INVENTION

[0008] According to the present disclosure, the wavelength dispersion compensation amount is adjusted based on a compensation index according to the difference in wavelength dispersion between a reference interference signal and a measurement interference signal, and based on the adjusted wavelength dispersion compensation amount, the difference in wavelength dispersion between the measurement interference signal and the reference interference signal in the reference interference signal is compensated. Thereby, the wavelength dispersion compensation apparatus according to the present disclosure can reduce the influence on the measurement accuracy due to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal.

Brief Description of Drawings

[0009]

Figure 1

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Embodiments for Carrying Out the Invention

[0010] Embodiment 1. The optical distance measurement device according to Embodiment 1 measures the distance to an object using a measurement interference signal generated by a measurement interference system. Further, the optical distance measurement device according to Embodiment 1 uses a reference interference signal generated by a reference interference system to compensate for a non-linear change (non-linearity) with respect to time in the measurement interference signal.

[0011] FIG. 1A is a diagram showing reflected light A1, reference light B1, beat signal AB1, and spectrum C1 in which wavelength sweep changes linearly with time. The upper diagram of FIG. 1A is a diagram showing the time change of the reflected light A1 and the reference light B1. As shown in this diagram, the reflected light A1 and the reference light B1 have linearity in wavelength sweep with respect to time. The reflected light A1 is the reflected light obtained by reflecting the wavelength-swept light irradiated from the optical distance measurement device to the object by the object. The reference light B1 is a reference for the wavelength change of the reflected light A1 with respect to time, and like the reflected light A1, it changes linearly with respect to time.

[0012] The beat signal AB1 is a signal obtained by interfering the reflected light A1 and the reference light B1 by combining them. The beat frequency fb of the beat signal AB1 is proportional to the wavelength difference between the reflected light A1 and the reference light B1. The middle diagram of FIG. 1A is a diagram showing the time change of the beat signal AB1. As shown in this diagram, when the wavelength sweeps of the reflected light A1 and the reference light B1 have linearity with respect to time, the beat signal AB1 becomes constant.

[0013] By performing Fourier transform (FT) on the beat signal AB1, the frequency spectrum C1 shown in the lower part of FIG. 1A is obtained. The frequency spectrum C1 is proportional to the position of the object. The frequency corresponding to the peak position of the frequency spectrum C1 represents the distance to the object. The optical distance measurement device has calibrated the relationship between the frequency of the beat signal AB1 and the distance in advance, and uses this relationship to calculate the distance.

[0014] FIG. 1B is a diagram showing reflected light A2, reference light B2, beat signal AB2, and frequency spectrum C2 in which wavelength sweep changes non-linearly with respect to time. The upper diagram of FIG. 1B is a diagram showing the time change of the reflected light A2 and the reference light B2. As shown in this diagram, the reflected light A2 and the reference light B2 have non-linearity in wavelength sweep with respect to time. The reflected light A2 is the reflected light obtained by reflecting the wavelength-swept light irradiated from the optical distance measuring device onto the object. The reference light B2 is a reference for the wavelength change of the reflected light A2 with respect to time and changes non-linearly with respect to time by the second order or higher.

[0015] The beat signal AB2 is a signal obtained by combining the reflected light A2 and the reference light B2 and causing them to interfere with each other. The beat frequency fb of the beat signal AB2 is proportional to the wavelength difference between the reflected light A2 and the reference light B2. The middle diagram of FIG. 1B is a diagram showing the time change of the beat signal AB2. As shown in this diagram, since the wavelength sweeps of the reflected light A2 and the reference light B2 have non-linearity with respect to time, the beat signal AB2 is not constant with respect to time.

[0016] By performing Fourier transform (FT) on the beat signal AB2, the frequency spectrum C2 shown in the lower part of FIG. 1B is obtained. The frequency spectrum C2 is distorted as shown in the lower part of FIG. 1B, and the peak position cannot be accurately extracted. Although the optical distance measuring device has calibrated the relationship between the frequency of the beat signal AB2 and the distance in advance, since the peak position cannot be accurately extracted, the distance cannot be accurately calculated using this relationship.

[0017] On the other hand, the optical distance measuring device according to Embodiment 1 compensates for the non-linearity of the wavelength sweep in the measurement interference signal corresponding to the beat signal AB2 shown in FIG. 1B using a reference interference signal having the same non-linearity of the wavelength sweep as the measurement interference signal. As a result, the distortion of the spectrum obtained by Fourier-transforming the measurement interference signal disappears, and it is possible to accurately measure the distance to the object based on the peak position of the spectrum.

[0018] FIG. 2 is a diagram showing an overview of wavelength dispersion compensation using a reference interference signal. In FIG. 2, the upper left diagram shows the temporal change of the reference interference signal D, the middle left diagram shows the temporal change of the measurement interference signal E, and the lower left diagram shows the waveform F of the measurement interference signal resampled based on the reference interference signal D. As shown in FIG. 2, the waveform F of the measurement interference signal is obtained by so-called resampling, in which the measurement interference signal E is sampled at the point where the rising edge of the reference interference signal D crosses zero.

[0019] In FIG. 2, the upper right diagram is a waveform G showing the temporal change of the beat frequency fb of the reference interference signal D. Also, the beat frequency fb of the reference interference signal D is proportional to the optical path length difference in the reference interference system. Further, the middle right diagram is a waveform H showing the temporal change of the beat frequency fb of the measurement interference signal E. The lower right diagram is a waveform I showing the relationship between the wavenumber and the distance obtained based on the measurement interference signal F.

[0020] The waveforms G and H are calculated based on the reference interference signal D and the measurement interference signal E, which have the same non-linear change with respect to the wavelength sweep time. Therefore, the waveforms G and H have similar non-linearities. As a result, the waveform I becomes a waveform in which the distance is almost constant with respect to the wavenumber. By performing a Fourier transform on this waveform I, a spectrum J is obtained. The spectrum J shows a reflection peak at the frequency position corresponding to the distance to the reflection point of the object. For example, when an object is placed at a position at a distance L from the interference origin, a reflection peak at the object appears at the frequency position corresponding to the distance L.

[0021] However, as will be described later with reference to FIG. 3, the reference interference system is a path that does not pass through the object, while the measurement interference system is a path that passes through the object via an air layer. In this case, since there is a difference in wavelength dispersion between the reference interference signal and the measurement interference signal, as shown in FIG. 2, some distortion occurs in the waveform I, and distortion also occurs in the spectrum J. Therefore, the ranging accuracy based on the peak position of the spectrum J decreases.

[0022] (Basic Configuration of Optical Ranging Device) Therefore, the optical distance measuring device according to Embodiment 1 adjusts the amount of wavelength dispersion compensation based on a compensation index corresponding to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal, and compensates for the difference in wavelength dispersion between the measurement interference signal and the reference interference signal in the reference interference signal based on the adjusted amount of wavelength dispersion compensation. FIG. 3 is a block diagram showing the configuration of the optical distance measuring device 1 according to Embodiment 1. As shown in FIG. 3, the optical distance measuring device 1 includes a wavelength-sweeping light source 2, a reference interference system 3, a measurement interference system 4, a signal processing unit 5, a wavelength dispersion compensation device 6, an optical coupler 7, and a lens barrel 8, and measures the distance to the object TG.

[0023] (Wavelength-sweeping light source) The wavelength-sweeping light source 2 outputs wavelength-sweeping light based on a sweeping signal. The wavelength-sweeping light source 2 includes an electrical unit 21 and a light source 22. The electrical unit 21 generates a sweeping signal of potential and outputs the generated sweeping signal to the light source 22. The light source 22 generates wavelength-sweeping light whose wavelength changes in synchronization with the potential of the sweeping signal and outputs the wavelength-sweeping light. The wavelength-sweeping light output from the wavelength-sweeping light source 2 is output to the optical coupler 7 via an optical fiber. The optical coupler 7 branches the wavelength-sweeping light to the reference interference system 3 and the measurement interference system 4 via optical fibers.

[0024] (Reference interference system) The reference interference system 3 has two optical paths with different optical path lengths, and generates a reference interference signal by photoelectrically converting the reference interference light obtained by combining the wavelength-sweeping light that has passed through the two optical paths. For example, as shown in FIG. 3, the reference interference system 3 is connected to an optical coupler 31, an optical coupler 32, a photoelectric conversion unit 33, and an AD conversion unit 34 via optical fibers. Two optical paths constituted by optical fibers are connected to the optical coupler 31, and these optical paths have different optical path lengths from each other.

[0025] The optical coupler 31 inputs the wavelength-swept light from the wavelength-swept light source 2 via the optical coupler 7, and branches and outputs the input wavelength-swept light to two optical paths respectively. The two optical paths are composed of optical fibers. The wavelength dispersion compensation unit 61 is provided in the optical fiber of one of the two optical paths. The optical coupler 32 outputs the wavelength-swept light that has passed through the two optical paths to the photoelectric conversion unit 33.

[0026] The photoelectric conversion unit 33 combines the input wavelength-swept light and performs photoelectric conversion on the combined light to generate a reference interference signal of an electrical signal. The AD conversion unit 34 performs analog-to-digital conversion on the reference interference signal of the electrical signal generated by the photoelectric conversion unit 33 to generate a reference interference signal of a digital signal. The reference interference signal converted into a digital signal by the AD conversion unit 34 is output to the signal processing unit 5.

[0027] (Measurement interference system) The measurement interference system 4 has an optical path passing through the object TG and an optical path not passing through the object TG, and generates a measurement interference signal by photoelectrically converting the measurement interference light obtained by combining the wavelength-swept light that has passed through the two optical paths respectively. For example, as shown in FIG. 3, the measurement interference system 4 is connected with an optical coupler 41, a circulator 42, an optical coupler 43, a photoelectric conversion unit 44, and an AD conversion unit 45 via an optical fiber. Two optical paths composed of optical fibers are connected to the optical coupler 41.

[0028] The optical coupler 41 inputs the wavelength-swept light from the wavelength-swept light source 2 via the optical coupler 7, and branches and outputs the input wavelength-swept light to two optical paths respectively. The two optical paths are composed of optical fibers. The circulator 42 is provided in the optical fiber of one of the two optical paths. The circulator 42 outputs the wavelength-swept light from the optical coupler 41 to the lens barrel 8, and outputs the light returned from the lens barrel 8 to the optical coupler 43.

[0029] The lens barrel 8 is an optical system that irradiates the object TG with the light output from the circulator 42 through the air layer, and returns the reflected light reflected by the object TG through the air layer to the circulator 42. The optical coupler 43 outputs the wavelength-swept light that has passed through the optical path passing through the object TG by the lens barrel 8 and the wavelength-swept light that has passed through the optical path not passing through the object TG to the photoelectric conversion unit 44.

[0030] The photoelectric conversion unit 44 combines the input wavelength-swept light and photoelectrically converts the combined light to generate a measurement interference signal of an electrical signal. The AD conversion unit 45 generates a measurement interference signal of a digital signal by performing analog-to-digital conversion on the measurement interference signal of the electrical signal generated by the photoelectric conversion unit 44. The measurement interference signal converted into a digital signal by the AD conversion unit 45 is output to the signal processing unit 5.

[0031] The signal processing unit 5 resamples the measurement interference signal based on the reference interference signal, performs Fourier transform on the resampled measurement interference signal, and measures the distance to the object TG based on the optical path length difference of the measurement interference system calculated based on the peak position of the spectrum obtained by the Fourier transform. Further, the signal processing unit 5 calculates a compensation index corresponding to the difference in wavelength dispersion between the two based on the phase difference between the reference interference signal and the measurement interference signal. As shown in FIG. 3, the signal processing unit 5 includes a resampling unit 51, a Fourier transform unit 52 (hereinafter referred to as the FFT unit 52), a distance measurement unit 53, and a feedback unit 54 (hereinafter referred to as the FB unit 54).

[0032] (Resampling Unit) The resampling unit 51 inputs the reference interference signal from the reference interference system 3 and the measurement interference signal from the measurement interference system 4, and resamples the measurement interference signal based on the reference interference signal. For example, the resampling unit 51 samples the measurement interference signal using the reference interference signal as a clock signal. For example, the resampling unit 51 may sequentially sample the measurement interference signal at the time when the rising edge crosses zero in the reference interference signal. The measurement interference signal sampled by the resampling unit 51 is output to the FFT unit 52.

[0033] (FFT section) The FFT section 52 Fourier-transforms the measured interference signal resampled by the resampling section 51. For example, the FFT section 52 obtains a spectrum by performing a fast Fourier transform on the measured interference signal. In this spectrum, a reflection peak appears at a frequency position corresponding to the distance to the reflection point of the object TG.

[0034] (Distance measurement section) The distance measurement section 53 calculates the optical path length difference of the measurement interference system 4 based on the peak position of the spectrum obtained by Fourier transform, and measures the distance to the object TG based on the calculated optical path length difference. In the spectrum, a peak corresponding to the wave number appears, and the peak position corresponds to the optical path length difference of the measurement interference system 4. The distance measurement section 53 converts the optical path length difference in the measurement interference system 4 into a distance based on the relationship between the speed of light and the wave number.

[0035] (FB section) The FB section 54 calculates a compensation index corresponding to the difference in wavelength dispersion between the two based on the phase difference between the reference interference signal and the measurement interference signal. Thereby, the wavelength dispersion compensation device 6 can obtain a compensation index for compensating the difference in wavelength dispersion between the reference interference system 3 and the measurement interference system 4. The FB section 54 calculates a wavelength dispersion compensation index based on the signals obtained by the reference interference system 3 and the measurement interference system 4, and feeds back the calculated compensation index to the wavelength dispersion compensation device 6. As shown in FIG. 3, the FB section 54 includes a Hilbert transform section 541, an unwrapping section 542, and a difference acquisition section 543.

[0036] The Hilbert transform section 541 Hilbert-transforms the reference interference signal and the measurement interference signal. The Hilbert transform is one of the conversion methods for converting a signal in the time domain into the frequency domain. By the Hilbert transform, an analytic signal composed of the real part and the imaginary part of the original signal is obtained. This analytic signal has the same amplitude as the original signal and contains information regarding the phase.

[0037] The unwrapping unit 542 unwraps the Hilbert-transformed reference interference signal and the measurement interference signal. For example, the phase information of the Hilbert-transformed signal is expressed in the range from -π to π. Phase unwrapping is a process of detecting discontinuous jumps in the phase and continuously connecting them to the accurately estimated phase. Thereby, the continuity of the phase is ensured. The unwrapping unit 542, for example, detects 2π jumps and corrects them to a continuous phase, or calculates the difference in phase and continuously integrates it to estimate the phase.

[0038] The difference acquisition unit 543 calculates a correction term for wavelength dispersion as a compensation index based on the phase difference between the unwrapped reference interference signal and the measurement interference signal. The correction term for wavelength dispersion may be, for example, a phase difference corresponding to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal. The correction term calculated by the difference acquisition unit 543 is fed back from the signal processing unit 5 to the wavelength dispersion amount adjustment unit 62.

[0039] (Wavelength dispersion compensation device) The wavelength dispersion compensation device 6 is a device that compensates for the difference in wavelength dispersion between the reference interference signal and the measurement interference signal in the optical distance measurement device 1. As shown in FIG. 3, the wavelength dispersion compensation device 6 includes a wavelength dispersion compensation unit 61 and a wavelength dispersion amount adjustment unit 62.

[0040] (Wavelength dispersion compensation unit) The wavelength dispersion compensation unit 61 is a compensation unit that compensates for the difference in wavelength dispersion between the measurement interference signal and the reference interference signal in the reference interference signal based on the set wavelength dispersion compensation amount. For example, the wavelength dispersion compensation unit 61 is configured to include a wavelength dispersion member having the same or a similar wavelength dispersion amount as the measurement interference system. By having the wavelength dispersion member, the wavelength dispersion compensation unit 61 can compensate for the difference in wavelength dispersion between the measurement interference signal and the reference interference signal in the reference interference signal.

[0041] The wavelength dispersion member is a member used to compensate or control wavelength dispersion. Examples of the wavelength dispersion member include a holey fiber, a dispersion fiber, a dispersion compensation module, or a dispersion compensation film. By having a holey fiber or a dispersion fiber, etc., the wavelength dispersion compensation unit 61 can compensate for the difference in wavelength dispersion between the measurement interference signal and the reference interference signal.

[0042] A holey fiber is a special optical fiber having a periodic structure, and its structure can control wavelength dispersion. For example, a holey fiber can adjust the propagation characteristics of an optical fiber and compensate for dispersion in a specific wavelength range. A dispersion fiber is an optical fiber designed to compensate for wavelength dispersion in a specific wavelength range. In the dispersion fiber, the refractive index profile inside the fiber is set to cancel out the dispersion characteristics at a specific wavelength. A dispersion compensation module is an example of a wavelength dispersion compensation device including a dispersion fiber. For example, the dispersion compensation module includes optical elements or pipes connected via a dispersion fiber to compensate for the difference in wavelength dispersion. A dispersion compensation film is a wavelength dispersion member provided in the form of an optical film. For example, the dispersion compensation film is used to compensate for wavelength dispersion in a specific wavelength range and is provided on the surface of an optical element or device.

[0043] The wavelength dispersion compensation unit 61 minimizes the influence of wavelength dispersion, for example, by using a temperature control device to control the temperature of the optical fiber constituting the optical path of the reference interference system 3 and applying a set amount of wavelength dispersion. For example, the characteristics of a holey fiber or a dispersion fiber are affected by temperature changes. In particular, the refractive index or dispersion characteristics of an optical fiber tend to change with temperature. Generally, when the temperature of an optical fiber rises, its refractive index decreases and the wavelength dispersion characteristics change. For example, the wavelength dispersion compensation unit 61 uses a temperature control device that controls the temperature of the optical fiber of the reference interference system 3 to keep the temperature of the optical fiber constant and eliminates the difference in wavelength dispersion between the reference interference system 3 and the measurement interference system 4.

[0044] Further, the wavelength dispersion compensation unit 61 may compensate for the difference in wavelength dispersion between the reference interference system 3 and the measurement interference system 4 using pressure. The refractive index or propagation speed of an optical fiber or an optical element may change due to pressure. By utilizing this change, it is possible to compensate for the difference in wavelength dispersion. For example, the wavelength dispersion compensation unit 61 uses a pressure control device that applies pressure to an optical fiber or an optical element. The wavelength dispersion compensation unit 61 changes the refractive index of the optical fiber or the optical element and changes the wavelength dispersion characteristics by applying pressure to the optical fiber or the optical element of the reference interference system 3 using the pressure control device. Due to this change, the wavelength dispersion compensation unit 61 corrects the difference in wavelength dispersion between the reference interference system 3 and the measurement interference system 4.

[0045] Note that the wavelength dispersion compensation unit 61 can be used as an object for correcting the difference in wavelength dispersion as long as it is a physical quantity other than temperature and pressure and can change the wavelength dispersion characteristics of the optical path of the reference interference system 3.

[0046] (Wavelength dispersion amount adjustment unit) The wavelength dispersion amount adjustment unit 62 is an adjustment unit that adjusts the wavelength dispersion compensation amount set for the wavelength dispersion compensation unit 61 based on the compensation index acquired from the FB unit 54. For example, the wavelength dispersion compensation amount is calculated based on the phase difference corresponding to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal. The wavelength dispersion amount adjustment unit 62 calculates the wavelength dispersion compensation amount using calibration data or a calibration model regarding the temperature dependence of the optical fiber set in advance. The wavelength dispersion amount adjustment unit 62 adjusts the wavelength dispersion compensation amount as the temperature of the optical fiber in the reference interference system 3 changes to correspond to the temperature dependence.

[0047] The influence of the difference in wavelength dispersion between the reference interference signal and the measurement interference signal is determined by the length of the air layer between the object TG. The length of the air layer also changes due to the temperature change of the lens barrel 8, that is, the change in the expansion and contraction amount of the lens barrel 8 caused by the temperature change. However, while the general measurement cycle is about 1000 times / second, the temperature change speed of the lens barrel 8 is assumed to be about 0.1 degree / second. Therefore, the wavelength dispersion adjustment unit 62 may periodically acquire a compensation index and adjust the wavelength dispersion compensation amount set in the wavelength dispersion compensation unit 61 based on the acquired compensation index. For example, the compensation index may be acquired during a periodic calibration process of the optical distance measurement device 1. Thereby, the wavelength dispersion compensation device 6 can perform wavelength dispersion compensation with simple signal processing for acquiring the compensation index without frequently acquiring the compensation index.

[0048] Next, the operation of the optical distance measurement device 1 according to the first embodiment will be described. FIG. 4 is a flowchart showing the operation of the optical distance measurement device 1 according to the first embodiment. The wavelength-swept light output from the wavelength-swept light source 2 is branched into a reference interference system 3 and a measurement interference system 4. The reference interference system 3 generates a reference interference signal from the wavelength-swept light, and the measurement interference system 4 generates a measurement interference signal from the wavelength-swept light (step ST1). The reference interference signal and the measurement interference signal are output to the signal processing unit 5.

[0049] Next, in the signal processing unit 5, the FB unit 54 calculates a correction term for the difference in wavelength dispersion between the two based on the phase difference between the reference interference signal and the measurement interference signal, and feeds back the calculated correction term to the wavelength dispersion adjustment unit 62 (step ST2). The wavelength dispersion compensation device 6 compensates for the difference in wavelength dispersion between the reference interference signal and the measurement interference signal based on the correction term fed back from the FB unit 54 (step ST3). Thereby, the reference interference system 3 and the measurement interference system 4 generate a reference interference signal and a measurement interference signal in which the difference in wavelength dispersion is compensated. The reference interference signal and the measurement interference signal are output to the signal processing unit 5.

[0050] The resampling unit 51 resamples the measurement interference signal based on the reference interference signal and outputs the resampled measurement interference signal to the FFT unit 52 (step ST4). The FFT unit 52 performs a Fourier transform on the resampled measured interference signal (step ST5). The spectrum obtained by the Fourier transform is output from the FFT unit 52 to the distance measurement unit 53. The distance measurement unit 53 calculates the optical path length difference of the measurement interference system based on the peak position of the spectrum generated by the FFT unit 52, and measures the distance to the object TG based on the calculated optical path length difference of the measurement interference system (step ST6).

[0051] FIG. 5 is a flowchart showing the calculation process of the compensation index and shows the operation of the FFT unit 52. The Hilbert transform unit 541 performs a Hilbert transform on the reference interference signal and the measured interference signal (step ST1A). The signals obtained by performing a Hilbert transform on the reference interference signal and the measured interference signal respectively are output to the unwrapping unit 542.

[0052] The unwrapping unit 542 unwraps the Hilbert-transformed reference interference signal and measured interference signal (step ST2A). For example, the unwrapping unit 542 generates a signal indicating the phase change with respect to time for the reference interference signal by unwrapping the Hilbert-transformed reference interference signal, and generates a signal indicating the phase change with respect to time for the measured interference signal by unwrapping the Hilbert-transformed measured interference signal. There is an optical path length difference determined by the optical path composed of optical fibers between the measurement interference system 4 and the reference interference system 3. Therefore, the peak height in the waveform of the signal indicating the phase change with respect to time for the measured interference signal is lower than that of the reference interference signal. Therefore, the unwrapping unit 542 doubles the signal indicating the phase change with respect to time for the measured interference signal at a ratio corresponding to the optical path length difference between the two interference systems.

[0053] The difference acquisition unit 543 calculates a phase difference corresponding to the difference in wavelength dispersion between the reference interference signal and the measured interference signal as a correction term for correcting the difference in wavelength dispersion based on the phase difference between the unwrapped reference interference signal and the measured interference signal (step ST3A). For example, the difference acquisition unit 543 calculates the difference between a signal indicating the phase change with respect to time for the reference interference signal generated by the unwrapping unit 542 and a signal indicating the phase change with respect to time for the measurement interference signal that has been doubled at a ratio corresponding to the optical path length difference between the two interference systems, as the phase difference corresponding to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal. The correction term calculated by the difference acquisition unit 543 is fed back from the signal processing unit 5 to the wavelength dispersion amount adjustment unit 62.

[0054] Next, the operation of the wavelength dispersion compensation device 6 according to Embodiment 1 will be described. FIG. 6 is a flowchart showing the wavelength dispersion compensation method according to Embodiment 1. The wavelength dispersion amount adjustment unit 62 adjusts the wavelength dispersion compensation amount to be set in the wavelength dispersion compensation unit 61 based on a compensation index corresponding to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal (step ST1B). Next, the wavelength dispersion compensation unit 61 compensates for the difference in wavelength dispersion between the measurement interference signal and the reference interference signal based on the wavelength dispersion compensation amount set from the wavelength dispersion amount adjustment unit 62 (step ST2B). By the wavelength dispersion compensation device 6 executing the above method, the influence on the measurement accuracy due to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal can be reduced.

[0055] (Outline of Wavelength Dispersion Compensation) FIG. 7 is a diagram showing the outline of the wavelength dispersion compensation process in Embodiment 1. The diagram surrounded by the left dashed line in FIG. 7 shows the outline of the process by the FB unit 54, and the series of processes shown on the right shows the processes by the components other than the FB unit 54 of the signal processing unit 5. The Hilbert transform unit 541 performs a Hilbert transform on the reference interference signal D and the measurement interference signal E. The unwrapping unit 542 generates a signal G indicating the change in phase Φ with respect to time for the reference interference signal D and a signal H indicating the change in phase Φ with respect to time for the measurement interference signal E by unwrapping the Hilbert-transformed reference interference signal D and measurement interference signal E, respectively. As shown in FIG. 7, the peak height in the waveform of signal H is lower than that of signal G. Therefore, the unwrapping unit 542 generates a signal K by doubling the waveform of signal H at a ratio corresponding to the optical path length difference between the reference interference system 3 and the measurement interference system 4.

[0056] The difference acquisition unit 543 calculates the difference L between the waveform of signal G and the waveform of signal K as a phase difference corresponding to the difference in wavelength dispersion between the reference interference signal D and the measurement interference signal E. The phase difference can be represented by Ae -iΔφ(t) where A is the amplitude of waveform L and Δφ(t) is the phase difference at time t. The correction term Ae -iΔφ(t) calculated by the difference acquisition unit 543 is fed back to the wavelength dispersion adjustment unit 62.

[0057] In the wavelength dispersion adjustment unit 62, a relationship of correction terms corresponding to the temperature T at a certain time t as shown in the upper right of FIG. 7 is set in advance. The wavelength dispersion adjustment unit 62, for example, at the time of measurement, when the phase difference Ae dis e -iΔφdis(t,T) is obtained as waveform L, adjusts the wavelength dispersion compensation amount using the relationship of correction terms corresponding to the temperature T set in advance.

[0058] When the difference in wavelength dispersion between the reference interference signal D and the measurement interference signal E is compensated, the resampling unit 51 resamples the measurement interference signal E based on the reference interference signal D and outputs the resampled measurement interference signal to the FFT unit 52 (step ST4). The FFT unit 52 obtains a spectrum J by performing a Fourier transform on the resampled measurement interference signal I. The distance measurement unit 53 calculates the optical path length difference between the reference interference system 3 and the measurement interference system 4 based on the peak position of the spectrum J generated by the FFT unit 52, and measures the distance to the object TG based on the calculated optical path length difference.

[0059] (Modified Example) FIG. 8 is a block diagram showing the configuration of a wavelength dispersion compensator 6A which is a modified example of the wavelength dispersion compensator 6. In FIG. 8, the wavelength dispersion compensator 6A is a device that compensates for the difference in wavelength dispersion between the reference interference signal and the measurement interference signal in the optical distance measuring device 1. As shown in FIG. 8, the wavelength dispersion compensator 6A includes a Hilbert transform unit 611, an unwrapping unit 612, a difference acquisition unit 613, a wavelength dispersion amount adjustment unit 614, and a wavelength dispersion compensation unit 615. For example, the wavelength dispersion compensator 6A is implemented by a computer. In the memory included in the computer, a program that constitutes an information processing application for realizing the functions of the Hilbert transform unit 611, the unwrapping unit 612, the difference acquisition unit 613, the wavelength dispersion amount adjustment unit 614, and the wavelength dispersion compensation unit 615 is stored. By executing the information processing application read by the processor included in the computer from the memory, the functions of the Hilbert transform unit 611, the unwrapping unit 612, the difference acquisition unit 613, the wavelength dispersion amount adjustment unit 614, and the wavelength dispersion compensation unit 615 are realized.

[0060] The Hilbert transform unit 611 performs a Hilbert transform on the reference interference signal and the measurement interference signal. The signals obtained by performing a Hilbert transform on the reference interference signal and the measurement interference signal respectively are output from the Hilbert transform unit 611 to the unwrapping unit 612. The unwrapping unit 612 unwraps the Hilbert-transformed reference interference signal and measurement interference signal. The unwrapped signals are output from the unwrapping unit 612 to the difference acquisition unit 613. The difference acquisition unit 613 calculates a correction term for wavelength dispersion as a compensation index based on the phase difference between the unwrapped reference interference signal and the measurement interference signal. The correction term calculated by the difference acquisition unit 613 is output to the wavelength dispersion amount adjustment unit 614.

[0061] The wavelength dispersion amount adjustment unit 614 is an adjustment unit that adjusts the wavelength dispersion compensation amount set in the wavelength dispersion compensation unit 615 based on the compensation index acquired from the difference acquisition unit 613. For example, the wavelength dispersion adjustment unit 614 calculates the wavelength dispersion compensation amount using calibration data or a calibration model regarding the temperature dependency of a pre-set optical fiber.

[0062] The wavelength dispersion compensation unit 615 is a compensation unit that compensates for the difference in wavelength dispersion between the measurement interference signal and the reference interference signal based on the wavelength dispersion compensation amount set by the wavelength dispersion adjustment unit 614. For example, the wavelength dispersion compensation unit 615 is configured to include a wavelength dispersion member having the same or a similar wavelength dispersion amount as that of the measurement interference system. By having the wavelength dispersion member, the wavelength dispersion compensation unit 61 can compensate for the difference in wavelength dispersion between the measurement interference signal and the reference interference signal in the reference interference signal. Examples of the wavelength dispersion member include a holey fiber, a dispersion fiber, a dispersion compensation module, or a dispersion compensation film. By having a holey fiber or a dispersion fiber, etc., the wavelength dispersion compensation unit 615 can compensate for the difference in wavelength dispersion between the measurement interference signal and the reference interference signal in the reference interference signal.

[0063] Subsequently, a hardware configuration for realizing the functions of the wavelength dispersion compensation apparatus 6A according to the first embodiment will be described. FIG. 9 is a block diagram showing a hardware configuration for realizing the functions of the wavelength dispersion compensation apparatus 6A according to the first embodiment. Each function of the Hilbert transform unit 611, the unwrapping unit 612, the difference acquisition unit 613, the wavelength dispersion adjustment unit 614, and the wavelength dispersion compensation unit 615 included in the wavelength dispersion compensation apparatus 6A is realized by a processing circuit. That is, the wavelength dispersion compensation apparatus 6A includes a processing circuit for executing the processing of each step shown in FIGS. 5 and 6. The processing circuit may be a CPU (Central Processing Unit) that executes a program stored in a memory.

[0064] The Hilbert transform unit 611 acquires, for example, the digital signals output from the reference interference system 3 and the measurement interference system 4 via the input interface 100. Also, when the digital signals are stored in the storage unit included in the wavelength dispersion compensation device 6A, the Hilbert transform unit 611 may read and acquire the digital signals from the storage unit via the input interface 100. Further, the wavelength dispersion compensation unit 615 performs a compensation process on the wavelength dispersion member via, for example, the output interface 101.

[0065] The functions of the Hilbert transform unit 611, the unwrapping unit 612, the difference acquisition unit 613, the wavelength dispersion amount adjustment unit 614, and the wavelength dispersion compensation unit 615 included in the wavelength dispersion compensation device 6A are realized by software, firmware, or a combination of software and firmware. Note that the software or firmware is described as a program and stored in the memory 103.

[0066] The processor 102 reads and executes the program stored in the memory 103, thereby realizing the functions of the Hilbert transform unit 611, the unwrapping unit 612, the difference acquisition unit 613, the wavelength dispersion amount adjustment unit 614, and the wavelength dispersion compensation unit 615 included in the wavelength dispersion compensation device 6A. For example, the wavelength dispersion compensation device 6A includes a memory 103 for storing a program that, when executed by the processor 102, results in the execution of the processes of each step shown in FIGS. 5 and 6. These programs cause a computer to execute the procedures or methods of the processes performed by the Hilbert transform unit 611, the unwrapping unit 612, the difference acquisition unit 613, the wavelength dispersion amount adjustment unit 614, and the wavelength dispersion compensation unit 615. The memory 103 may be a computer-readable storage medium storing a program for causing a computer to function as the Hilbert transform unit 611, the unwrapping unit 612, the difference acquisition unit 613, the wavelength dispersion amount adjustment unit 614, and the wavelength dispersion compensation unit 615.

[0067] The memory 103 corresponds to, for example, non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically-EPROM) (registered trademark), magnetic disks, flexible disks, optical disks, compact disks, mini-disks, DVDs, and the like.

[0068] Part of the functions of the Hilbert transform unit 611, the unwrapping unit 612, the difference acquisition unit 613, the wavelength dispersion amount adjustment unit 614, and the wavelength dispersion compensation unit 615 included in the wavelength dispersion compensation device 6A may be realized by dedicated hardware, and the other part may be realized by software or firmware. For example, the function of the wavelength dispersion compensation unit 615 may be realized by a processing circuit that is dedicated hardware, and the functions of the Hilbert transform unit 611, the unwrapping unit 612, the difference acquisition unit 613, and the wavelength dispersion amount adjustment unit 614 may be realized by the processor 102 reading and executing a program stored in the memory 103. In this way, the processing circuit can realize the above functions by hardware, software, firmware, or a combination thereof.

[0069] As described above, the wavelength dispersion compensation device 6 according to Embodiment 1 is a wavelength dispersion compensation device 6 that compensates for the difference in wavelength dispersion between the reference interference signal and the measurement interference signal in the optical distance measurement device 1. Based on the set wavelength dispersion compensation amount, a wavelength dispersion compensation unit 61 that compensates for the difference in wavelength dispersion between the reference interference signal and the measurement interference signal, and a wavelength dispersion amount adjustment unit 62 that adjusts the wavelength dispersion compensation amount set in the wavelength dispersion compensation unit 61 based on a compensation index corresponding to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal. The wavelength dispersion compensation amount is adjusted based on a compensation index corresponding to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal, and based on the adjusted wavelength dispersion compensation amount, the difference in wavelength dispersion between the reference interference signal and the measurement interference signal is compensated. Thereby, the wavelength dispersion compensation device 6 can reduce the influence on the measurement accuracy due to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal.

[0070] The wavelength dispersion compensator 6A according to Embodiment 1 includes a Hilbert transform unit 611 that performs a Hilbert transform on a reference interference signal and a measurement interference signal, an unwrapping unit 612 that unwraps the Hilbert-transformed reference interference signal and measurement interference signal, and a difference acquisition unit 613 that calculates a correction term based on the phase difference between the unwrapped reference interference signal and measurement interference signal. Thereby, the wavelength dispersion compensator 6A can obtain a compensation index for compensating for the difference in wavelength dispersion between the reference interference system 3 and the measurement interference system 4.

[0071] In the wavelength dispersion compensator 6 according to Embodiment 1, the wavelength dispersion amount adjustment unit 62 periodically acquires the compensation index and adjusts the wavelength dispersion compensation amount set in the wavelength dispersion compensation unit 61 based on the acquired compensation index. Thereby, the wavelength dispersion compensator 6 can perform wavelength dispersion compensation by simple signal processing for acquiring the compensation index without frequently acquiring the compensation index.

[0072] In the wavelength dispersion compensators 6 and 6A according to Embodiment 1, the compensation index is a correction term representing the phase difference due to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal. By using this correction term, the wavelength dispersion compensators 6 and 6A can determine the wavelength dispersion compensation amount for compensating for the difference in wavelength dispersion between the reference interference signal and the measurement interference signal.

[0073] In the wavelength dispersion compensator 6 according to Embodiment 1, the wavelength dispersion compensation unit 61 includes a wavelength dispersion member having a wavelength dispersion amount the same as or similar to that of the measurement interference system. By having the wavelength dispersion member, the wavelength dispersion compensation unit 61 can compensate for the difference in wavelength dispersion between the reference interference signal and the measurement interference signal.

[0074] In the wavelength dispersion compensator 6 according to Embodiment 1, the wavelength dispersion compensation unit 61 includes a hollow fiber or a dispersion fiber. By having the hollow fiber or the dispersion fiber, the wavelength dispersion compensation unit 61 can compensate for the difference in wavelength dispersion between the reference interference signal and the measurement interference signal.

[0075] The optical distance measuring device 1 according to Embodiment 1 includes a wavelength-sweeping light source 2 that outputs wavelength-sweeping light, has two optical paths with different optical path lengths, and combines the wavelength-sweeping light that has passed through the two optical paths respectively to photoelectrically convert the reference interference light to generate a reference interference signal, a reference interference system 3; a measurement interference system 4 that has an optical path passing through the object TG and an optical path not passing through the object TG, and combines the wavelength-sweeping light that has passed through the two optical paths respectively to photoelectrically convert the measurement interference light to generate a measurement interference signal; a resampling unit 51 that resamples the measurement interference signal based on the reference interference signal; an FFT unit 52 that performs Fourier transform on the resampled measurement interference signal; a distance measurement unit 53 that calculates the optical path length difference of the measurement interference system based on the peak position of the spectrum obtained by Fourier transform, and measures the distance to the object TG based on the calculated optical path length difference; an FB unit 54 that calculates a compensation index according to the difference in wavelength dispersion between the two based on the phase difference between the reference interference signal and the measurement interference signal; a wavelength dispersion compensation unit 61 that compensates for the difference in wavelength dispersion between the measurement interference signal in the reference interference signal based on the set wavelength dispersion compensation amount; and a wavelength dispersion amount adjustment unit 62 that adjusts the wavelength dispersion compensation amount set in the wavelength dispersion compensation unit 61 based on the compensation index obtained from the FB unit 54. Thereby, the optical distance measuring device 1 can reduce the influence on the measurement accuracy due to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal.

[0076] In the optical distance measuring device 1 according to Embodiment 1, the resampling unit 51 samples the measurement interference signal at the time when the rising edge crosses zero in the reference interference signal. Thereby, the optical distance measuring device 1 can resample the measurement interference signal in synchronization with the reference interference signal.

[0077] The wavelength dispersion compensation method according to Embodiment 1 includes a step ST1B in which a wavelength dispersion amount adjustment unit 62 adjusts a wavelength dispersion compensation amount set in a wavelength dispersion compensation unit 61 based on a compensation index corresponding to a difference in wavelength dispersion between a reference interference signal and a measurement interference signal, and a step ST2B in which the wavelength dispersion compensation unit 61 compensates for a difference in wavelength dispersion between the measurement interference signal and the reference interference signal in the reference interference signal based on the wavelength dispersion compensation amount set by the wavelength dispersion amount adjustment unit 62. By the wavelength dispersion compensation device 6 executing the above method, it is possible to reduce the influence on the measurement accuracy due to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal.

[0078] Hereinafter, aspects of the present disclosure will be collectively described as appendices.

[0079] (Appendix 1) A wavelength-sweeping light source that outputs wavelength-sweeping light, A reference interference system that has two optical paths with different optical path lengths and generates a reference interference signal by photoelectrically converting reference interference light obtained by combining the wavelength-sweeping light that has passed through the two optical paths, In an optical distance measurement device including a measurement interference system that has an optical path passing through an object and an optical path not passing through the object and generates a measurement interference signal by photoelectrically converting measurement interference light obtained by combining the wavelength-sweeping light that has passed through the two optical paths, a wavelength dispersion compensation device that compensates for a difference in wavelength dispersion between the reference interference signal and the measurement interference signal, A compensation unit that compensates for a difference in wavelength dispersion between the measurement interference signal and the reference interference signal in the reference interference signal based on a set wavelength dispersion compensation amount, An adjustment unit that adjusts the wavelength dispersion compensation amount set in the compensation unit based on a compensation index corresponding to a difference in wavelength dispersion between the reference interference signal and the measurement interference signal, A wavelength dispersion compensation device comprising:

[0080] (Appendix 2) A Hilbert transform unit that performs a Hilbert transform on the reference interference signal and the measurement interference signal, An unwrapping unit that unwraps the Hilbert-transformed reference interference signal and measurement interference signal, A difference acquisition unit that calculates the compensation index based on the phase difference between the unwrapped reference interference signal and the measurement interference signal, and The wavelength dispersion compensation device according to Supplementary Note 1, characterized in that

[0081] (Supplementary Note 3) The adjustment unit periodically acquires the compensation index and adjusts the wavelength dispersion compensation amount set in the compensation unit based on the acquired compensation index The wavelength dispersion compensation device according to Supplementary Note 1 or Supplementary Note 2, characterized in that

[0082] (Supplementary Note 4) The compensation index is a correction term representing the phase difference due to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal The wavelength dispersion compensation device according to any one of Supplementary Notes 1 to 3, characterized in that

[0083] (Supplementary Note 5) The compensation unit includes a wavelength dispersion member having a wavelength dispersion amount the same as or similar to that of the measurement interference system The wavelength dispersion compensation device according to any one of Supplementary Notes 1 to 4, characterized in that

[0084] (Supplementary Note 6) The compensation unit includes a holey fiber or a dispersion fiber The wavelength dispersion compensation device according to Supplementary Note 5, characterized in that

[0085] (Supplementary Note 7) A wavelength-sweeping light source that outputs wavelength-sweeping light, A reference interference system that has two optical paths with different optical path lengths, and generates a reference interference signal by photoelectrically converting the reference interference light obtained by combining the wavelength-sweeping light that has passed through the two optical paths respectively, A measurement interference system that has an optical path passing through an object and an optical path not passing through the object, and generates a measurement interference signal by photoelectrically converting the measurement interference light obtained by combining the wavelength-sweeping light that has passed through the two optical paths respectively, A resampling unit that resamples the measurement interference signal based on the reference interference signal; A Fourier transform unit that Fourier-transforms the resampled measurement interference signal; A distance measurement unit that calculates the optical path length difference of the measurement interference system based on the peak position of the spectrum obtained by Fourier transform, and measures the distance to the object based on the calculated optical path length difference; A feedback unit that calculates a compensation index according to the difference in wavelength dispersion between the two based on the phase difference between the reference interference signal and the measurement interference signal; A compensation unit that compensates for the difference in wavelength dispersion between the measurement interference signal and the reference interference signal based on the set wavelength dispersion compensation amount; An adjustment unit that adjusts the wavelength dispersion compensation amount set for the wavelength dispersion compensation unit based on the compensation index obtained from the feedback unit; An optical distance measurement device comprising the above.

[0086] (Appendix 8) The resampling unit samples the measurement interference signal at the time when the rising edge of the reference interference signal crosses zero. The optical distance measurement device according to Appendix 7, characterized in that.

[0087] (Appendix 9) A wavelength-swept light source that outputs wavelength-swept light; A reference interference system that has two optical paths with different optical path lengths, and generates a reference interference signal by photoelectrically converting the reference interference light obtained by combining the wavelength-swept light that has passed through the two optical paths; A wavelength dispersion compensation method for compensating for the difference in wavelength dispersion between the reference interference signal and the measurement interference signal in an optical distance measurement device including a measurement interference system that has an optical path passing through an object and an optical path not passing through the object, and generates a measurement interference signal by photoelectrically converting the measurement interference light obtained by combining the wavelength-swept light that has passed through the two optical paths, comprising: A step in which an adjustment unit adjusts the wavelength dispersion compensation amount based on a compensation index corresponding to the difference in wavelength dispersion between the reference interference signal and the measurement interference signal; The compensating unit compensates for the difference in wavelength dispersion between the measurement interference signal and the reference interference signal in the reference interference signal based on the wavelength dispersion compensation amount set by the adjusting unit. A wavelength dispersion compensation method comprising the above.

[0088] It should be noted that any component of the embodiment can be modified or any component of the embodiment can be omitted.

Industrial Applicability

[0089] The wavelength dispersion compensation device according to the present disclosure can be used, for example, in an optical distance measurement device.

Explanation of Signs

[0090] 1 Optical distance measurement device, 2 Wavelength sweeping light source, 3 Reference interference system, 4 Measurement interference system, 5 Signal processing unit, 6, 6A Wavelength dispersion compensation device, 7 Optical coupler, 8 Telescope barrel, 21 Electrical unit, 22 Light source, 31, 32, 41, 43 Optical coupler, 33, 44 Photoelectric conversion unit, 34, 45 AD conversion unit, 42 Circulator, 51 Resampling unit, 52 FFT unit, 53 Distance measurement unit, 54 FB unit, 61, 615 Wavelength dispersion compensation unit, 62, 614 Wavelength dispersion amount adjustment unit, 100 Input interface, 101 Output interface, 102 Processor, 103 Memory, 541, 611 Hilbert conversion unit, 542, 612 Unwrap unit, 543, 613 Difference acquisition unit.

Claims

1. A wavelength-swept light source that outputs wavelength-swept light, A reference interference system having two optical paths with different optical path lengths, which generates a reference interference signal by photoelectric conversion of the reference interference light obtained by combining the wavelength-swept light that has passed through each of the two optical paths, A wavelength dispersion compensation device for an optical ranging device comprising a measurement interference system having an optical path passing through an object and an optical path not passing through the object, and generating a measurement interference signal by photoelectric conversion of measurement interference light obtained by combining the wavelength-swept light that has passed through the two optical paths, wherein the wavelength dispersion compensation device compensates for the difference in wavelength dispersion between the reference interference signal and the measurement interference signal, A compensation unit is provided in one of the two optical paths of the reference interference system, and compensates for the difference in wavelength dispersion between the reference interference signal and the measured interference signal based on a set wavelength dispersion compensation amount. An adjustment unit adjusts the wavelength dispersion compensation amount set in the compensation unit based on a compensation index corresponding to the difference in wavelength dispersion between the reference interference signal and the measured interference signal. A wavelength dispersion compensation device equipped with the following features.

2. A Hilbert transformer unit that performs a Hilbert transform on the reference interference signal and the measured interference signal, An unwrapping unit that unwraps the Hilbert-transformed reference interference signal and the measured interference signal, The system includes a difference acquisition unit that calculates the compensation index based on the phase difference between the unwrapped reference interference signal and the measured interference signal. The wavelength dispersion compensation apparatus according to feature 1.

3. The adjustment unit periodically acquires the compensation index and adjusts the wavelength dispersion compensation amount set in the compensation unit based on the acquired compensation index. A wavelength dispersion compensation device according to claim 1 or 2.

4. The compensation index is a correction term that represents the phase difference due to the difference in wavelength dispersion between the reference interference signal and the measured interference signal. A wavelength dispersion compensation device according to claim 1 or 2.

5. The compensation unit includes a wavelength dispersion member having the same or similar wavelength dispersion amount as the measurement interference system. A wavelength dispersion compensation device according to claim 1 or 2.

6. The compensation unit includes a holy fiber or a dispersed fiber. The wavelength dispersion compensation apparatus according to feature 5.

7. A wavelength-swept light source that outputs wavelength-swept light, A reference interference system having two optical paths with different optical path lengths, which generates a reference interference signal by photoelectric conversion of the reference interference light obtained by combining the wavelength-swept light that has passed through each of the two optical paths, A measurement interference system having an optical path that passes through an object and an optical path that does not pass through the object, and generating a measurement interference signal by photoelectric conversion of the measurement interference light obtained by combining the wavelength-swept light that has passed through the two optical paths, respectively, A resampling unit that resamples the measured interference signal based on the reference interference signal, A Fourier transform unit that performs a Fourier transform on the resampled measurement interference signal, A distance measuring unit calculates the difference in optical path length of the measurement interferometer based on the peak position of the spectrum obtained by the Fourier transform, and measures the distance to the object based on the calculated difference in optical path length, A feedback unit calculates a compensation index corresponding to the difference in wavelength dispersion between the reference interference signal and the measured interference signal based on the phase difference between the two. A compensation unit is provided in one of the two optical paths of the reference interference system, and compensates for the difference in wavelength dispersion between the reference interference signal and the measured interference signal based on a set wavelength dispersion compensation amount. An adjustment unit that adjusts the wavelength dispersion compensation amount set in the compensation unit based on the compensation index obtained from the feedback unit, An optical distance measuring device equipped with the following features.

8. The resampling unit samples the measurement interference signal when the rising edge of the reference interference signal crosses zero. The optical distance measuring device according to feature 7.

9. A wavelength-swept light source that outputs wavelength-swept light, A reference interference system having two optical paths with different optical path lengths, which generates a reference interference signal by photoelectric conversion of the reference interference light obtained by combining the wavelength-swept light that has passed through each of the two optical paths, A wavelength dispersion compensation method for a light ranging device comprising a measurement interference system having an optical path passing through an object and an optical path not passing through the object, and generating a measurement interference signal by photoelectric conversion of measurement interference light obtained by combining the wavelength-swept light that has passed through the two optical paths, the method for compensating for the difference in wavelength dispersion between the reference interference signal and the measurement interference signal, The adjustment unit performs the steps of adjusting the wavelength dispersion compensation amount based on a compensation index corresponding to the difference in wavelength dispersion between the reference interference signal and the measured interference signal, The compensation unit provided in one of the two optical paths of the reference interference system compensates for the difference in wavelength dispersion between the reference interference signal and the measurement interference signal based on the wavelength dispersion compensation amount set by the adjustment unit. A wavelength dispersion compensation method comprising the following features.

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