Distance measuring device and distance measuring method

Abstract

This disclosure aims to compensate for the effects of fluctuations in the repetition frequency of a pulsed light source, which cause distance measurement errors, without using a continuous wave light source. [Solution] The present disclosure relates to a distance measuring device that irradiates an object to be measured with a test light pulse and measures the distance to the object using the interference waveform of the signal light pulse reflected by the object and a reference light pulse, wherein the test light pulse and the reference light pulse have a plurality of frequency components, and the distance measuring device includes a correction signal acquisition unit that detects the interference signal of the test light pulse and the reference light pulse of at least two of the plurality of frequency components contained in the test light pulse and the reference light pulse as a correction signal.

Description

[Technical Field]

[0001] This disclosure relates to an optical pulse distance measuring device and a distance measuring method. [Background technology]

[0002] Time-of-flight (ToF) LiDAR (Light Detection and Ranging), which measures the time from the emission of a light pulse to the detection of its reflection, is suitable for long-range distance measurement required for infrastructure inspection. However, in the general method of receiving light pulses with a width of ns-class by direct detection, the depth resolution is on the order of centimeters, making high-resolution measurements difficult. Therefore, research is being conducted to improve depth resolution and depth accuracy by projecting short test light pulses with a width of 1 ps or less onto the target object and detecting the signal light reflected from the object using the dual-comb interferometry (DCI) method [Non-patent documents 1, 2]. In the DCI method, two pulse light sources with slightly different repetition frequencies are used, but fluctuations in these repetition frequencies can lead to distance measurement errors, so it is desirable to phase-synchronize the two lasers [Non-patent documents 1, 2].

[0003] To eliminate the need for precise laser control, a technique has been proposed in which two pulsed light sources used in DCI are made to move autonomously, generate interference signals, and then compensate for fluctuations in the repetition frequencies of the two lasers through software processing [Non-Patent Literature 3]. In this method, a pair of continuous wave (CW) light sources are installed on the receiving side, and information necessary for compensation processing is obtained from four types of interference signals obtained by interfering them with the two autonomous pulsed light sources. However, this method requires two continuous wave lasers with stable frequencies and is costly. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] I. Coddington, WC Swann, L. Nenadovic, and NR Newbury, “Rapid and precise absolute distance measurements at long range,” Nature Photonics, vol. 3, no. 6, pp. 351-356, 2009. [Non-Patent Document 2] P. Trocha, M. Karpov, D. Ganin, MHP Pfeiffer, A. Kordts, S. Wolf, J. Krockenberger, P. Marin-Palomo, C. Weimann, S. Randel, W. Freude, TJ Kippenberg, and C. Koos, “Ultrafast optical ranging using microresonator soliton frequency combs,” Science, vol. 359, no. 6378, pp. 887-891, 2018. [Non-Patent Document 3] Takahiro Suyama, Akira Izumoto, Kyogo Osawa, Chao Zhang, Fumihiko Ito, Atsushi Nakamura, Yusuke Koshikiya, "Time-of-Flight Optical Distancing by Two-Comb Interferometry Using Continuous-Wave Reference Light," Japan Society of Applied Physics, Optical Wave Sensing Technology Workshop, LST70-09, Morito Memorial Hall, Tokyo University of Science, June 2024. [Overview of the project] [Problems that the invention aims to solve]

[0005] This disclosure aims to compensate for the effects of fluctuations in the repetition frequency of a pulsed light source, which cause distance measurement errors, without using a continuous wave light source. [Means for solving the problem]

[0006] In order to achieve the above object, the distance measuring device of the present disclosure irradiates a test light pulse onto a measurement object, and uses an interference waveform between a signal light pulse reflected by the measurement object and a reference light pulse of the test light pulse to measure the distance to the measurement object. In the distance measuring device, the test light pulse and the reference light pulse have a plurality of frequency components, and includes a correction signal acquisition unit that detects an interference signal of at least two frequency components among the plurality of frequency components included in the test light pulse and the reference light pulse as a correction signal.

[0007] The distance measurement method of the present disclosure is a distance measurement method executed by the distance measurement device of the present disclosure. The test light pulse and the reference light pulse have a plurality of frequency components, and an interference signal of at least two frequency components among the plurality of frequency components included in the test light pulse and the reference light pulse is detected as a correction signal.

[0008] The distance measuring device of the present disclosure may include a signal processing circuit that obtains the distance to the measurement object using the interference waveform. The signal processing circuit corrects the fluctuation of the repetition frequency of the signal light pulse and the reference light pulse in the interference waveform using the correction signal detected by the correction signal acquisition unit.

[0009] The repetition frequency of the reference light pulse is different from the repetition frequency of the test light pulse within the time width range of the test light pulse. The signal processing circuit configures the interference waveform by rearranging the instantaneous values obtained by the coherent correlation detection of the signal light pulse and the reference light pulse on the time axis.

[0010] The signal processing circuit may calculate a phase term associated with the fluctuation and correct the interference waveform so that the increment of the phase term is constant.

[0011] The correction signal acquisition unit may include a plurality of optical filters that transmit any of the plurality of frequency components contained in the test light pulse and the reference light pulse. Alternatively, the correction signal acquisition unit may transmit a frequency filter with a narrower bandwidth than the plurality of optical filters to the signal light pulse and the reference light pulse. Furthermore, the correction signal acquisition unit may use a 90-degree optical hybrid to detect the interference signal of the signal light pulse and the reference light pulse.

[0012] Furthermore, the above disclosures can be combined as much as possible. [Effects of the Invention]

[0013] According to this disclosure, it is possible to compensate for the effects of fluctuations in the repetition frequency of a pulsed light source, which causes distance measurement errors, without using a continuous wave light source. Therefore, this disclosure enables high-precision measurement with an inexpensive device configuration. [Brief explanation of the drawing]

[0014] [Figure 1] This is an explanatory diagram illustrating the principle of ultrafast complex electric field amplitude measurement using linear optical sampling. [Figure 2] An example of the system configuration described in Non-Patent Document 3 is shown. [Figure 3] An example of the interference signal generated in Non-Patent Document 3 is shown below. [Figure 4] An example of the optical frequency of the interference signal in Non-Patent Document 3 is shown. [Figure 5] An example of the system configuration described herein is shown. [Figure 6] An example of optical frequency components f1 and f2 is shown. [Figure 7] An example of the connection configuration for the correction signal acquisition unit is shown. [Figure 8] An example of the wavelength characteristics of the first embodiment is shown. [Figure 9] An example of the connection configuration of the correction signal acquisition unit in the second embodiment is shown. [Figure 10] An example of the wavelength characteristics of the second embodiment is shown. [Figure 11] An example of the system configuration of the second embodiment is shown. [Figure 12] An example of the connection configuration of the correction signal acquisition unit in the third embodiment is shown. [Figure 13] An example of the wavelength characteristics of the third embodiment is shown. [Figure 14] An example of the system configuration of the third embodiment is shown. [Figure 15] An example of the connection configuration of the correction signal acquisition unit in the fourth embodiment is shown. [Figure 16] An example of the system configuration of the fifth embodiment is shown. [Modes for carrying out the invention]

[0015] Embodiments of this disclosure will be described in detail below with reference to the drawings. However, this disclosure is not limited to the embodiments shown below. These examples are illustrative, and this disclosure can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. In this specification and in the drawings, components with the same reference numerals refer to the same components.

[0016] (Linear sampling method) Figure 1 shows an explanatory diagram of the principle described in Non-Patent Document 3. In the linear sampling method (two-comb interferometry) used in Non-Patent Document 3, a short pulse of light with a width of 1 ps or less is used as the reference light, and the test light pulse is irradiated onto the object to be measured. Sampling is performed by detecting the coherent correlation between the signal light pulse reflected by the object to be measured and the reference light pulse, and the instantaneous complex amplitude of the signal light pulse is measured. Then, by rearranging the instantaneous values ​​obtained from the coherent correlation detection of the signal light pulse and the reference light pulse on the time axis, an interference waveform of the signal light pulse and the reference light pulse is constructed. This gives a measurement signal. Using this measurement signal, the distance can be measured by converting the time difference from the input to the reception of the light pulse into distance.

[0017] Non-patent document 3 describes how to observe interference waveforms with sub-picosecond time resolution by slightly detuning the repetition period T of the signal light pulse and the repetition period T+ΔT of the reference light pulse, and detecting the instantaneous amplitude while shifting the interference point.

[0018] The repetition frequency of the reference light pulse differs from that of the test light pulse, within the time width range of the test light pulse. For example, if the repetition frequency of the signal light pulse is F, the repetition frequency of the reference light pulse is expressed as 1 / (F-ΔF). The speed of the observable signal is determined solely by the sampling pulse width, and it can handle ultrafast signals. The electronics used only need to be able to keep up with the sampling pulse period, and those with a bandwidth of a few MHz can be used.

[0019] The effective time interval between interference points is called the effective sampling interval ΔT, and can be expressed as follows.

number

[0020] Figure 2 shows an example of the system configuration of Non-Patent Document 3. The system of Non-Patent Document 3 has two pulsed light sources, two continuous wave light sources, and an optical receiver. The two pulsed light sources are optical frequency comb light sources, which repeatedly output a test light pulse and a reference light pulse, respectively. CW1 and CW2 shown in the figure are the two continuous wave light sources. The figure shows an optical receiver using an optical 90-degree hybrid (hereinafter sometimes abbreviated as "90H"), a BPD, and an ADC. CW is a CW laser, BPD is a balanced photodetector, ADC is an analog-to-digital converter, CP is an optical coupler, Cir is a circulator, ADC is an AD converter, and PC (Personal Computer) is a signal processing circuit that performs arbitrary processing of the digital signal obtained by the optical receiver. Hereafter, the signal processing circuit will be referred to as "PC".

[0021] Two pulsed light sources are operated autonomously at slightly different repetition frequencies, and the distance between the measuring device and the object under measurement is obtained from the interference signal of the signal light pulse and the reference light pulse. From the four types of interference signals obtained using pulsed and continuous wave light sources, the "repetition frequency fluctuations" that cause distance measurement errors are acquired, and their effects are compensated for by digital signal processing.

[0022] The optical frequency of the continuous laser beam is set to different optical frequencies within the bandwidths of the test light pulse and the reference light pulse. Under these conditions, as shown in Figure 3, four types of interference signals α1, β1, α2, and β2 are generated using CW1 and the signal light pulse, CW1 and the reference light pulse, CW2 and the signal light pulse, and CW2 and the reference light pulse. These signals are converted into digital data by an ADC and stored in the PC's memory.

[0023] Figure 4 shows an example of the optical frequencies of the interference signals α1, β1, α2, and β2. The interference signals α1, β1, α2, and β2 are expressed by the following equations.

number

[0024] In the linear sampling method, the above equation is subjected to phase conjugation and multiplication so that only terms with ΔF remain, as shown below.

number

[0025] From Equation (1), ΔT≒ΔF / F 2 Therefore, since this is the case, the change in the phase 2πnΔFt in Equation (8) is proportional to ΔT. Thus, this phase fluctuation corresponds to the fluctuation of ΔT. And α1β * 1(α2β * 2) * By resampling the measurement signal every time the phase 2πnΔFt of α1β1(α2β2) increases by a constant value, an interference signal on the correct time axis can be obtained.

[0026] In the linear sampling method, by compensating for the fluctuation in the repetition period of two self-running pulse light sources and obtaining an interference signal on the correct time axis, high-precision distance measurement can be realized. However, the conventional method requires two stable continuous light lasers, which is costly.

[0027] (Summary of the Present Disclosure) The present disclosure aims to obtain the same effect using a lower-cost and simpler configuration in a distance measurement device using the linear sampling method. That is, by compensating for the fluctuation in the repetition period of two self-running pulse light sources and obtaining an interference waveform on the correct time axis, high-precision distance measurement is realized. For this purpose, a new method for detecting the fluctuation in the repetition frequency of the pulse light source is disclosed.

[0028] The distance measuring device of this disclosure performs the distance measuring method of this disclosure. Specifically, in the distance measuring method of this disclosure, the distance measuring device measures the interference waveform of a signal light, which is the reflected light from a test light pulse train irradiated onto an object to be measured, and a reference light pulse train having a repetition frequency different from that of the test light pulse train, and determines the distance to the object to be measured based on the principle of linear optical sampling. The distance measuring device of this disclosure includes a first optical filter and a second optical filter that extract different optical frequencies from the interference signals of the test light pulse train and the reference light pulse train, and a signal processing unit that obtains a phase term associated with the difference in repetition frequencies between the test light pulse train and the reference light pulse train from a first beat signal obtained by receiving the interference signal extracted by the first optical filter and a second beat signal obtained by receiving the interference signal extracted by the second optical filter, and compensates for the influence of fluctuations in the repetition frequencies of the test light pulse train and the reference light pulse train on the distance measuring signal based on the time change of the phase term.

[0029] Figure 5 shows an example of the system configuration of this embodiment. The measuring device of this embodiment comprises a light generation unit 10, a distance measurement signal acquisition unit 20, and a correction signal acquisition unit 30. For the light generation unit 10 and the distance measurement signal acquisition unit 20, the same device configuration as the conventional technology that detects using the two-comb interferometry (DCI) method can be used.

[0030] For example, the light generation unit 10 of this embodiment includes a pulse light source 11 that generates test light pulses that repeat at regular time intervals, and a pulse light source 12 that generates reference light pulses that repeat at regular time intervals. The test light pulses and reference light pulses have multiple frequency components. The pulse light sources 11 and 12 are any light sources capable of generating pulsed light having multiple frequency components, and for example, optical frequency comb light sources with equal frequency intervals f can be used.

[0031] For example, the distance measurement signal acquisition unit 20 includes a circulator 21 that irradiates the object to be measured with a test light pulse and guides the signal light reflected from the object to the optical 90-degree hybrid 22, a CP 25 that branches the reference light pulse to the optical 90-degree hybrid 22, a BPD 223 that receives the output from the optical 90-degree hybrid 22, and an ADC 24 that converts the analog signal from the BPD 223 into a digital signal.

[0032] The correction signal acquisition unit 30 includes multiple optical filters that extract multiple different optical frequency components from the interference signal of the signal light pulse and the reference light pulse, and detects the interference signal of the signal light pulse and the reference light pulse extracted by the multiple optical filters. This interference signal is used as a correction signal.

[0033] Figure 6 shows an example of an optical frequency comb. Multiple optical filters transmit one of several frequency components contained in the test light pulse and the reference light pulse. In the following embodiment, an example is shown in which multiple optical filters extract two optical frequency components f1 and f2 from the teeth of the frequency comb used in the test light pulse and the reference light pulse. |f1-f2| is represented as Nf using a natural number N. In this disclosure, the natural number N can be any number greater than or equal to 1.

[0034] The signals obtained by the distance measurement signal acquisition unit 20 and the correction signal acquisition unit 30 are output to the PC 40. As shown in Figure 1, the PC 40 constructs an interference waveform of the signal light pulse and the reference light pulse by rearranging the instantaneous values ​​of the interference waveform of the signal light pulse and the reference light pulse obtained by the distance measurement signal acquisition unit 20 on the time axis. This gives rise to a measurement signal. The PC 40 uses the correction signal obtained by the correction signal acquisition unit 30 to correct fluctuations in the repetition frequency of the signal light pulse and the reference light pulse in the interference waveform.

[0035] PC40 calculates 2πNΔFt, which is a phase term associated with the fluctuations, and corrects the interference waveform so that the increment of the phase term becomes constant. This compensates for the effect of "fluctuations in the repetition frequency of the pulsed light source," which cause distance measurement errors, through digital signal processing, and the distance between the distance measurement signal acquisition unit 20 and the object to be measured 50 is obtained by calculating the distance corresponding to the time difference from the input to the reception of the optical pulse using the corrected interference waveform. This disclosure makes it possible to compensate for the effect of "fluctuations in the repetition frequency of the pulsed light source," which cause distance measurement errors, without using an expensive continuous wave light source. In other words, high-precision measurement becomes possible with an inexpensive device configuration. The detailed operation of the correction signal acquisition unit 30 will be described later.

[0036] (First embodiment) Figure 7 shows an example of the connection configuration of the correction signal acquisition unit 30. The correction signal acquisition unit 30 has two narrowband BPFs 32-1 and 32-2 with different optical frequencies. As shown in Figure 8, BPFs 32-1 and 32-2 extract components of different optical frequencies f1 and f2 from the optical frequencies of the frequency comb used in the test optical pulse and the reference optical pulse.

[0037] The correction signal acquisition unit 30 includes a CP31 that combines the signal light pulse and the reference light pulse. The light combined by the CP31 is split into two and incident on BPF32-1 and 32-2. PD33-1 receives the interference light after it has passed through BPF32-1. PD33-2 receives the interference light after it has passed through the narrowband filter 32-2. ADC34-1 and 34-2 convert the analog signals from PD33-1 and 33-2, respectively, into digital signals. PC40 calculates the correction signal using the digital signals from ADC34-1 and 34-2 and stores it in memory 40-1 and 40-2.

[0038] The calculation of the correction signal can be exemplified by, for example, phase conjugation and multiplication. Specifically, PC40 uses the interference signal detected by ADC34-1 to calculate a1b * Calculate 1 and use the interference signal detected by ADC34-2 to calculate a2b *Calculate 2. Here, a1 is the signal light pulse with optical frequency f1, b1 is the reference light pulse with optical frequency f1, a2 is the signal light pulse with optical frequency f2, b2 is the reference light pulse with optical frequency f2, and * indicates phase conjugate.

[0039] In this embodiment, a1b * 1 and a2b * 2 is represented as follows:

number

[0040] PC40 calculates the phase term associated with ΔF by the following calculation. (Math 11) a1 * 1(a2b * 2) * =exp(j2πNΔFt) (11)

[0041] The process from this point onward is the same as in the conventional technology. Specifically, PC40 corrects the interference waveform of the measurement signal so that the increment of the phase term is constant. More precisely, PC40 corrects the instantaneous complex amplitude of the interference waveform obtained by the distance measurement signal acquisition unit 20 so that the increment of the phase term 2πNΔFt obtained in the above equation is constant between consecutive samples. For example, PC40 resamples the interference waveform so that the increment of the phase 2πNΔFt obtained in the above equation is constant between consecutive samples. This allows for obtaining an interference waveform on the correct time axis, thereby compensating for the effects of fluctuations in the repetition frequency.

[0042] Here, the frequency bandwidth W of BPF32-1 and 32-2 BTherefore, the measurement distance range (delay time width) is 1 / W B It is constrained by this. In order to expand the measurement distance range, W B The narrower the bandwidth, the better. Ideally, W B It is desirable that the frequency interval of the optical frequency comb be less than or equal to f.

[0043] (Second embodiment) When different filters are applied to the signal light pulse and the reference light pulse, the narrower the bandwidth of the filters, the stronger the effect of filter mismatch becomes. Therefore, in this embodiment, filter mismatch is prevented by sharing a narrowband filter made of Fabry-pero-etalon (FP) for both the signal light pulse and the reference light pulse.

[0044] Figure 9 shows an example of the connection configuration of the correction signal acquisition unit 30. The correction signal acquisition unit 30 has FP41 inserted in the line connecting pulse light sources 11 and 12. A circulator 43-1 is inserted between pulse light source 11 and FP41, and a circulator 43-2 is inserted between light source 12 and FP41. Signal light pulses are incident on FP41 from CP43-1, and the signal light pulses that have passed through FP41 are incident on CP31 from CP43-2. ​​Reference light pulses are incident on FP41 from CP43-2, and the reference light pulses that have passed through FP41 are incident on CP31 from CP43-1. The light combined at CP31 is split into two and incident on optical bandpass filters (OBF) 42-1 and 42-2.

[0045] Here, the bandwidth W of FP41 F This refers to the bandwidth W of OBF42-1 and 42-2. B It is narrower than that. Also, the bandwidth W of OBF42-1 and 42-2 B This is narrower than the free spectral range (FSR) of the shared FP41. PD33-1 receives the interference light after it has passed through OBF42-1, and PD33-2 receives the interference light after it has passed through OBF42-2. Similar to the first embodiment, a1b is obtained from the signal detected by PD33-1. * A value of 1, from the signal detected by PD33-2, is a2b. * The value 2 is calculated in PC40.

[0046] Figure 10 shows an example of the wavelength characteristics of this embodiment. FP41 is a frequency filter with a narrower bandwidth than OBF42-1 and 42-2. Also, the transmission bandwidth of OBF42-1 and 42-2 is narrower than the free spectral range (FSR) of FP41. By extracting the two wavelengths after transmission through OBF42-1 and 42-2, a1b * 1 and a2b * The value obtained is 2.

[0047] In this embodiment, a1b * 1 and a2b * 2 is represented as follows:

number

[0048] Figure 11 shows an example of the system configuration of this embodiment. PC40 calculates the phase term associated with ΔF by the calculation of equation (11) described above, and corrects the interference waveform, which is the measurement signal, so that the increment of the phase term is constant.

[0049] (Third embodiment) In this embodiment, an alternative configuration of the correction signal acquisition unit 30 in the second embodiment will be described. Figure 12 shows an example of the connection configuration of the correction signal acquisition unit 30. In this embodiment, CP54-1, 54-2, 55-1 and 55-2 are provided instead of CP31, and BPD53-1 and 53-2 are provided instead of PD33-1 and 33-2.

[0050] Figure 13 shows an example of the wavelength characteristics of this embodiment. The transmission bandwidths of OBF52-1 and 52-2 are made narrower than the free spectral range (FSR) of FP41. By extracting the two wavelengths after transmission through OBF52-1 and 52-2, a1b * 1 and a2b * The value obtained is 2.

[0051] In this embodiment, a1b * 1 and a2b *2 is expressed by equations (12) and (13) described above. Figure 14 shows an example of the system configuration of this embodiment. PC40 calculates the phase term to which ΔF is attached by the calculation of equation (11) described above, and corrects the interference waveform, which is the measurement signal, so that the increment of the phase term is constant.

[0052] In this embodiment, OBF52-1 transmits only the reference light pulse, and OBF52-2 transmits only the signal light pulse. Therefore, the transmission bandwidths of OBF52-1 and 52-2 can be made narrower.

[0053] (Fourth embodiment) In the first to third embodiments, a1b is obtained by numerically performing a Hilbert transform on the interference signal detected by the PD or BPD. * 1 and a2b * Although a value of 2 was obtained, by using a 90-degree optical hybrid, the correction signal can be obtained without using a Hilbert transform. This eliminates the polarity ambiguity that occurs during the Hilbert transform.

[0054] Figure 15 shows an example of the connection configuration of the correction signal acquisition unit 30. In this embodiment, optical 90-degree hybrid 56-1 and 56-2 are provided instead of CP55-1 and 55-2 in the third embodiment, BPD53-1I and 53-1Q are provided instead of BPD53-1, and BPD53-2I and 53-2Q are provided instead of BPD53-2. In BPD53-1I, interference signal a1b * I1, which is the I component of 1, is detected, and the interference signal a1b is detected in BPD53-1Q. * The Q component Q1 of 1 is detected. In BPD53-2I, the interference signal a2b * I2, which is the I component of 2, was detected, and the interference signal a2b was detected in BPD53-2Q. * The Q component of 2, Q2, is detected.

[0055] In this embodiment, PC40 calculates a1b by the following equation. * 1 and a2b * The value obtained is 2. (Number 14) a1* 1 = I1 + jQ1 (14) a2b * 2 = I² + jQ² (15)

[0056] Figure 16 shows an example of the system configuration of this embodiment. PC40 calculates the phase term associated with ΔF by the calculation of equation (11) described above, and corrects the interference waveform, which is the measurement signal, so that the increment of the phase term is constant.

[0057] (Other embodiments) In the embodiments described above, an example was shown in which only two frequency components out of the multiple frequency components contained in the test light pulse and the reference light pulse are used, but the effects of this disclosure can be obtained even if three or more frequency components are used. Furthermore, the frequency filter in the correction signal acquisition unit 30 may be configured by hardware, or it may be configured by software such as a PC 40. The signal processing circuit of the distance measuring device of the present invention can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a network. [Explanation of Symbols]

[0058] 10:Light generation part 11, 12: Pulsed light source 13, 25, 31, 54-1, 54-2, 55-1, 55-2:CP 20: Ranging signal acquisition section 21, 43-1, 43-2: Circulator 22, 56-1, 56-2: 90-degree optical hybrid 23, 53-1, 53-2, 53-1I, 53-1Q, 53-2I, 53-2Q:BPD 24, 34, 34-1, 34-2: ADC 30: Correction signal acquisition unit 32, 32-1, 32-2: BPF 33, 33-1, 33-2: PD 40: PC 40-1, 40-2, 40-1I, 40-1Q, 40-2I, 40-2Q: Memory 41:FP 42-1, 42-2, 52-1, 52-2: OBF 50: Analyzed substance

Claims

1. In a distance measuring device that irradiates an object to be measured with a test light pulse and measures the distance to the object using the interference waveform of the signal light pulse reflected by the object and the reference light pulse, The test light pulse and the reference light pulse have multiple frequency components. The system includes a correction signal acquisition unit that detects the interference signal between the test light pulse and the reference light pulse, which is an interference signal of at least two frequency components from among the plurality of frequency components contained in the test light pulse and the reference light pulse, as a correction signal. Ranging device.

2. The correction signal acquisition unit includes a plurality of optical filters that transmit any of the frequency components among the plurality of frequency components included in the test light pulse and the reference light pulse. The distance measuring device according to claim 1.

3. The correction signal acquisition unit transmits a frequency filter with a narrower bandwidth than the plurality of optical filters to the signal light pulse and the reference light pulse. The distance measuring device according to claim 2.

4. The correction signal acquisition unit uses a 90-degree optical hybrid to detect the interference signal of the signal light pulse and the reference light pulse. The distance measuring device according to claim 1.

5. The system includes a signal processing circuit that uses the interference waveform to determine the distance to the object to be measured, The signal processing circuit uses the correction signal detected by the correction signal acquisition unit to correct fluctuations in the repetition frequency of the signal light pulse and the reference light pulse in the interference waveform. The distance measuring device according to claim 1.

6. The aforementioned signal processing circuit is The phase term associated with the aforementioned fluctuation is calculated, The interference waveform is corrected so that the increment of the phase term remains constant. The distance measuring device according to claim 5.

7. The repetition frequency of the reference light pulse is different from the repetition frequency of the test light pulse, within the time width range of the test light pulse. The signal processing circuit constructs the interference waveform by rearranging the instantaneous values ​​obtained by coherent correlation detection of the signal light pulse and the reference light pulse in the time axis. The distance measuring device according to claim 5.

8. A distance measuring method performed by a distance measuring device, which irradiates an object to be measured with a test light pulse and measures the distance to the object using the interference waveform of the signal light pulse reflected by the object and the reference light pulse, The test light pulse and the reference light pulse have multiple frequency components. The interference signal between the test light pulse and the reference light pulse, of at least two frequency components among the plurality of frequency components contained in the test light pulse and the reference light pulse, is detected as a correction signal. Distance measurement method.

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