Measurement device and measurement method

Abstract

A measurement device is provided with: a first light source that repeatedly emits first pulsed light; a first photodetector that detects reflected pulsed light generated by reflection of the first pulsed light by the object, and outputs a first electric signal corresponding to a detection result of the reflected pulsed light; a signal processing circuit that calculates the distance from the measurement device to the object on the basis of the first electric signal during the sampling period; and a control circuit that controls a drive unit that varies the length of an optical path from the first light source to the first photodetector via the object. The control circuit controls the drive unit so as to change the position of the peak of the reflected pulsed light in the first electrical signal during the sampling period. The sampling period is synchronized with the timing at which the first light source emits the first pulsed light.

Description

Technical Field

[0001] The present disclosure relates to a measuring device and a measuring method. Background Art

[0002] An optical frequency comb laser is a laser source that emits laser light with pulse waveforms arranged at equal intervals on the time axis and spectra arranged at equal intervals on the frequency axis. Hereinafter, an optical frequency comb laser will be referred to as an optical comb laser.

[0003] In optical comb lasers, two parameters are important. One is the "repetition frequency" (f) which represents the spectral spacing. rep The other is the "carrier envelope offset frequency" (f CEO These parameters vary slightly due to disturbances such as vibration and temperature. By incorporating modulation devices such as Peltier elements and piezoelectric elements into the optical comb laser, these parameters can be stabilized, enabling precise measurement.

[0004] A method of preparing two such optical comb lasers and interfering and measuring light with slightly shifted repetition frequencies is called dual-comb.

[0005] In the double comb, the repetition frequency is f rep 、f rep +δf rep The two lasers interfere with each other, thus generating a beat. As a result, a time interval of δf can be obtained. rep What is important here is that the spectrum of the laser light before the interference is in the THz region, which is the frequency of light, while the spectrum of the laser light after the interference is in the MHz region, which is the radio frequency.

[0006] Conventional detectors, with their response frequencies below GHz, are physically unable to detect signals from light in the THz region. Consequently, detectors cannot be used directly to detect light wavelengths. Instead, spectrometers are used to separate the light by wavelength. This results in a time-consuming wavelength scan, making it difficult to quickly measure spectra.

[0007] However, dual-comb systems can downconvert light into the MHz range. This eliminates the need for an intervening spectrometer, allowing for faster spectrum measurement than ever before. Furthermore, since optical information can be directly measured, high-sensitivity and high-precision measurements are possible. Consequently, dual-comb systems are increasingly being used in a variety of measurement applications, including spectrometry, distance measurement, and frequency measurement (see, for example, Non-Patent Document 1).

[0008] Prior art literature

[0009] Non-patent literature

[0010] Non-Patent Literature 1: Zebin Zhu, Wu Guanhao, "Dual-comb ranging" Engineering, Vol. 4, Issue 6, December 2018, pp. 772-778 Summary of the Invention

[0011] Problems to be solved by the present invention

[0012] Improved accuracy is required not only in dual-comb distance measurement but also in distance measurement using pulsed light such as TOF (Time of Flight).

[0013] Therefore, the present disclosure provides a measuring device and a measuring method capable of measuring distance with high accuracy.

[0014] Means for solving problems

[0015] A measuring device according to one embodiment of the present disclosure includes: a first light source that repeatedly emits a first pulsed light; a first light detector that detects reflected pulsed light generated by reflection of the first pulsed light by an object and outputs a first electrical signal corresponding to the detection result of the reflected pulsed light; a signal processing circuit that calculates the distance from the measuring device to the object based on the first electrical signal during a sampling period; and a control circuit that controls a drive unit that varies the length of the optical path from the first light source through the object to the first light detector. The control circuit controls the drive unit so as to vary the position of the peak of the reflected pulsed light in the first electrical signal during the sampling period. The sampling period is synchronized with the timing at which the first light source emits the first pulsed light.

[0016] A measurement method according to one embodiment of the present disclosure includes: repeatedly emitting pulsed light from a light source; detecting reflected pulsed light generated by reflection of the pulsed light from an object by a photodetector, and outputting an electrical signal corresponding to the detection result of the reflected pulsed light; calculating the distance from the light source to the object based on the electrical signal during a sampling period by a signal processing circuit; and controlling a drive unit to vary the optical path length from the light source through the object to the photodetector. During the control, the drive unit is controlled so as to vary the position of a peak of the reflected pulsed light in the electrical signal during the sampling period. The sampling period is synchronized with the timing at which the first light source emits the first pulsed light.

[0017] Furthermore, one aspect of the present disclosure can be implemented as a program that causes a computer to execute the above-described measurement method. Alternatively, one aspect of the present disclosure can be implemented as a computer-readable nonvolatile recording medium storing the program.

[0018] Effects of the Invention

[0019] According to the present disclosure, distance can be measured with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1A This is a diagram schematically showing an example of temporal changes in the electric field of comb laser light.

[0021] Figure 1B FIG2 is a diagram schematically showing an example of a spectrum of comb laser light.

[0022] Figure 2 Schematic diagram showing an example of the spectrum of the first comb laser light and the spectrum of the second comb laser light in a dual-comb system.

[0023] Figure 3 This figure schematically shows the temporal waveforms of the reference light and the object light in the dual-comb system, respectively, obtained as a result of interference of the comb laser beams.

[0024] Figure 4 Schematically shows the phase spectrum after interference in a dual-comb system.

[0025] Figure 5 This is a diagram schematically showing the relationship between the position of the pulse waveform after interference and the measurement result during the sampling period.

[0026] Figure 6A This is a diagram schematically showing the measuring device according to the first embodiment.

[0027] Figure 6B This is a diagram schematically showing a measuring device according to the second embodiment.

[0028] Figure 6C This is a diagram schematically showing a measuring device according to the third embodiment.

[0029] Figure 7 This is a flowchart showing a first example of the operation of the measuring device according to each embodiment.

[0030] Figure 8 This is a flowchart showing a second example of the operation of the measuring device according to each embodiment.

[0031] Figure 9A This is a flowchart showing an example of pre-measurement in the third example of the measuring device according to each embodiment.

[0032] Figure 9B This is a flowchart showing an example of the actual measurement in the third example of the measuring device according to each embodiment.

[0033] Figure 10This is a flowchart showing an example of one-point measurement in the fourth example of the measuring device according to each embodiment. DETAILED DESCRIPTION

[0034] (Knowledge serving as the basis of this disclosure)

[0035] The present inventors have discovered that the following problems occur with respect to the conventional technology described in the "Background Art" section.

[0036] When using pulsed light for measurement, the sampling period used to process the signal corresponds to the pulse period. Therefore, the temporal waveform of the acquired signal corresponding to the pulsed light is distorted depending on the detection timing of the pulsed light—that is, the position of the pulsed light within the sampling period. This results in reduced measurement accuracy.

[0037] Furthermore, a technique using a phase spectrum instead of a time waveform is disclosed in Non-Patent Document 1. However, even when the phase spectrum is used for measurement, the accuracy of the measurement result is reduced depending on the position of the pulse light within the sampling period.

[0038] Therefore, an object of the present disclosure is to provide a measuring device and a measuring method capable of measuring distance with high accuracy.

[0039] The first embodiment of the present disclosure includes a measuring device comprising: a first light source that repeatedly emits a first pulsed light; a first light detector that detects reflected pulsed light generated by reflection of the first pulsed light by an object and outputs a first electrical signal corresponding to the detection result of the reflected pulsed light; a signal processing circuit that calculates the distance from the measuring device to the object based on the first electrical signal during a sampling period; and a control circuit that controls a drive unit that varies the length of the optical path from the first light source through the object to the first light detector. The control circuit controls the drive unit so as to vary the position of the peak of the reflected pulsed light in the first electrical signal during the sampling period. The sampling period is synchronized with the timing at which the first light source emits the first pulsed light.

[0040] By controlling the drive unit, the peak position of the reflected pulse light can be varied within the sampling period. This allows the timing for detecting the reflected pulse light to avoid a range within the sampling period that could potentially reduce measurement accuracy. Therefore, the measuring device of this embodiment can measure distance with high accuracy.

[0041] Furthermore, in the measuring device according to the second aspect of the present disclosure, for example, in the measuring device according to the first aspect, the first light source may be a comb laser.

[0042] This can improve the accuracy of distance measurement and shorten the time required for measurement.

[0043] In addition, the measuring device involved in the third embodiment of the present invention, for example, in the measuring device involved in the second embodiment, may also further include: a second light source, which is a light comb laser, repeatedly emitting a second pulse light; and a second light detector, which causes a part of the first pulse light to interfere with and detect the first part of the second pulse light, and outputs a second electrical signal corresponding to the detection result of the part of the first pulse light. The repetition frequency of the second light source may also be different from the repetition frequency of the first light source, and the first light detector may also cause the reflected pulse light to interfere with and detect the second part of the second pulse light that is different from the first part, and the signal processing circuit may also calculate the distance based on the first electrical signal and the second electrical signal.

[0044] This allows measurement using a dual comb, and thus allows detection of reflected pulse light by a general-purpose photodetector, thereby reducing the cost of the measurement device and simplifying its configuration.

[0045] In addition, in the measuring device involved in the fourth embodiment of the present disclosure, for example, in the measuring device involved in any one of the first to third embodiments, the signal processing circuit can also calculate the distance based on the time waveform corresponding to the reflected pulse light during the sampling period, and the control circuit can also control the driving unit so that the position of the peak is close to the center of the sampling period.

[0046] When measuring using time information, measurement accuracy tends to decrease near the start and end of a sampling period. According to this aspect, the peak position of the reflected pulse is brought closer to the center of the sampling period, thereby suppressing a decrease in measurement accuracy.

[0047] In addition, in the measuring device involved in the 5th embodiment of the present disclosure, for example, in the measuring device involved in any one of the 1st to 3rd embodiments, the signal processing circuit can also calculate the distance based on the phase spectrum corresponding to the reflected pulse light during the sampling period, and the control circuit controls the driving unit so that the position of the peak moves away from the center of the sampling period.

[0048] When measuring using phase information, measurement accuracy tends to decrease near the center of the sampling period. According to this aspect, the peak position of the reflected pulse is shifted away from the center of the sampling period, thereby suppressing a decrease in measurement accuracy.

[0049] In addition, in the measuring device involved in the 6th embodiment of the present invention, for example, in the measuring device involved in any one of the 1st to 5th embodiments, the control circuit may also determine whether the optical path length needs to be changed each time the irradiation point, which is the position in the object irradiated with the first pulse light, moves, and when it is determined that the change is necessary, the control circuit may also control the driving unit to change the optical path length.

[0050] This allows the optical path length to be varied for each irradiation point, thereby suppressing a decrease in measurement accuracy.

[0051] In addition, in the measuring device involved in the 7th embodiment of the present disclosure, for example, in the measuring device involved in any one of the 1st to 6th embodiments, the signal processing circuit can also correct the distance based on the change in the optical path length when the driving unit causes the optical path length to change.

[0052] This allows correction to be performed to reduce the amount of offset added to the measurement result due to, for example, a change in the optical path length, thereby improving measurement accuracy.

[0053] In addition, in the measuring device involved in the 8th embodiment of the present disclosure, for example, in the measuring device involved in the 7th embodiment, the signal processing circuit may also record, for each of a plurality of irradiation points serving as positions in the object irradiated with the first pulse light, the amount of change in the optical path length when the driving unit causes the optical path length to change, and the signal processing circuit may also correct the distance for each of the plurality of irradiation points based on the amount of change recorded by the signal processing circuit.

[0054] Thus, by recording the amount of variation in advance for each irradiation point, the distance of each irradiation point can be corrected.

[0055] In addition, the measuring device involved in the 9th embodiment of the present disclosure, for example, in the measuring device involved in any one of the 1st to 8th embodiments, the measuring device can also be configured to perform a formal measurement of the distance after performing a preliminary measurement, and the control circuit can also determine the variation of the optical path length at each of the multiple irradiation points based on the first electrical signal obtained for each of the multiple irradiation points as the position of the object irradiated with the first pulse light in the preliminary measurement, and in the formal measurement, the driving unit can also be controlled according to the variation at each of the multiple irradiation points.

[0056] This allows, for example, pre-measurement information on the optical path length fluctuations at all points to be measured. This allows, for example, to suppress large variations in the amount of fluctuation when sequentially measuring multiple irradiation points, thereby improving measurement accuracy.

[0057] In addition, in the measuring device involved in the tenth embodiment of the present disclosure, for example, in the measuring device involved in any one of the first to ninth embodiments, the control circuit may also determine the amount of change in the optical path length at each of a plurality of irradiation points including the at least one irradiation point based on the first electrical signal obtained regarding at least one irradiation point as a position in the object irradiated with the first pulse light, and information related to the shape of the object, and may also control the driving unit according to the amount of change at each of the plurality of irradiation points.

[0058] Thus, by utilizing the design data, information on the amount of variation in the optical path length at all points scheduled to be measured can be acquired in advance in a short time and with a small amount of calculation.

[0059] Furthermore, the measuring device according to the eleventh aspect of the present disclosure may be the measuring device according to any one of the first to tenth aspects, for example, and may further include the driving unit.

[0060] This makes it possible to realize an integrated measuring device including a driving unit. Since the variation in optical path length can be controlled with high precision, measurement accuracy can be improved.

[0061] Furthermore, the measurement method according to the twelfth aspect of the present disclosure includes, for example, the following steps: a light source repeatedly emits pulsed light; a photodetector detects reflected pulsed light generated by reflection of the pulsed light by an object and outputs an electrical signal corresponding to the detection result of the reflected pulsed light; a signal processing circuit calculates the distance from the light source to the object based on the electrical signal during a sampling period; and a drive unit controls the drive unit to vary the length of the optical path from the light source through the object to the photodetector. During the control, the drive unit is controlled so as to vary the position of the peak of the reflected pulsed light in the electrical signal during the sampling period. The sampling period is synchronized with the timing at which the first light source emits the first pulsed light.

[0062] Thus, similar to the above-mentioned measuring device, it is possible to measure the distance with high accuracy.

[0063] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.

[0064] In addition, the embodiments described below are all general or specific examples. The numerical values, shapes, materials, components, configuration positions and connection methods of components, steps, and the order of steps shown in the following embodiments are examples and are not intended to limit the present disclosure. In addition, among the components in the following embodiments, components not listed in the independent claims are described as arbitrary components.

[0065] In addition, each figure is a schematic diagram and does not necessarily illustrate the figure strictly. Therefore, for example, the scales in each figure are not necessarily the same. In addition, in each figure, the same reference numerals are given to substantially the same components, and repeated descriptions are omitted or simplified.

[0066] In addition, in this specification, the numerical range is not intended to express only a strict meaning, but is intended to include a substantially equivalent range, for example, an expression with a difference of several %.

[0067] In this specification, ordinal numbers such as “first” and “second” do not indicate the number or order of components unless otherwise specified, but are used to distinguish components to avoid confusion between the same components.

[0068] [Optical comb laser]

[0069] Before describing the embodiments of the present disclosure, the basic principle of an optical comb laser will be briefly described.

[0070] First, refer to Figure 1A and Figure 1B , illustrating the temporal variation and spectrum of the electric field of the optical comb laser.

[0071] Figure 1A This is a diagram schematically showing an example of the temporal variation of the electric field of the comb laser. Figure 1A In the figure, the horizontal axis represents time, and the vertical axis represents the electric field of the optical comb laser. An optical comb laser is also called an optical frequency comb laser. In this specification, it is sometimes simply referred to as a laser.

[0072] like Figure 1A As shown, the optical comb laser is composed of a repetitive period T rep The generated optical pulse train is formed. The repetition period T rep For example, it is 100 ps or more and 100 ns or less. The full width at half maximum of each optical pulse is represented by Δt. The full width at half maximum of each optical pulse Δt is, for example, 10 fs or more and 100 ps or less.

[0073] In a laser resonator, the group velocity v at which the envelope of a light pulse propagates is g The phase velocity v of the wave propagating within the light pulse p The value becomes different due to the dispersion in the resonator, etc.g With phase velocity v p If two adjacent light pulses are overlapped so that their envelopes are consistent, the phases of the waves in these light pulses will be Offset. Takes a value between 0 and 2π. When the round-trip length of the laser resonator is L, the repetition period of the optical pulse train is given by T rep =L / v g Performance.

[0074] Figure 1B This is a diagram schematically showing an example of the spectrum of a comb laser. Figure 1B In the figure, the horizontal axis represents the frequency and the vertical axis represents the intensity of the comb laser.

[0075] like Figure 1B As shown, the optical comb laser has a comb-shaped spectrum formed by multiple discrete equally spaced lines. The frequency of the multiple discrete equally spaced lines corresponds to the resonant frequency of the longitudinal mode in the laser resonator. It corresponds to the repetition frequency f of the interval between two adjacent equally spaced lines in the optical comb laser. rep By f rep =1 / T rep Performance. Repetition frequency f rep For example, it is 10 MHz or more and 1 THz or less. When the round trip length L of the laser resonator is 30 cm and the group velocity v g The speed of light in vacuum (=3×10 8 m / s) are roughly equal, the repetition period T rep is 1ns, and the repetition frequency f rep is 1GHz.

[0076] When the full width at half maximum of the comb laser is set to Δf, Δf = 1 / Δt. The full width at half maximum of the comb laser Δf is, for example, greater than 10 GHz and less than 100 THz. Assuming that there are equally spaced lines up to near zero frequency, the frequency of the equally spaced line closest to zero frequency is called the carrier envelope offset frequency. Carrier envelope offset frequency f CEO Depend on Performance. Carrier envelope offset frequency f CEO Take 0 to repetition frequency f rep If the carrier envelope offset frequency f CEO Assuming it is the 0th mode, the nth mode frequency f in the optical comb laser is n By f n =f CEO +nf rep Performance. Figure 1A The electric field E(t) of the comb laser shown uses the nth mode frequency f nThe amplitude E of the electric field at n and phase Depend on Performance.

[0077] [Double Comb]

[0078] Next, refer to Figure 2 Briefly explain the principle of double combing.

[0079] Figure 2 : is a diagram showing an example of the spectrum of the first comb laser and the spectrum of the second comb laser in a dual comb. Figure 2 In the figure, the horizontal axis represents the frequency and the vertical axis represents the intensity of the comb laser.

[0080] In the first comb laser, the nth mode frequency f 1n By f 1n =f CEO1 +nf rep1 In addition, in the second optical comb laser, the nth mode frequency f 2n By f 2n =f CEO2 +nf rep2 v performance. f CEO1 and f CEO2 are the carrier envelope bias frequencies of the first and second optical comb lasers, respectively. rep1 and f rep2 are the repetition frequencies of the first and second comb lasers, respectively. rep1 and f rep2 are slightly different from each other. Specifically, f rep2 =f rep1 +δf rep Here, δf rep Larger than 0, but much smaller than f rep1 δf rep For example, it is 1 Hz or more and 10 MHz or less.

[0081] Here, let the i-th mode of the first comb laser be f 1i In the case of 1i =f CEO1 +if rep1 In contrast, assuming that the frequency axis is located at mode f 1i The nearest mode is the i-th mode f of the second optical comb laser. 2i At this time, f 2i =f CEO2 +if rep2 If these two patterns f 1i and f 2i Interference, then the generated 3i Here, f3i =f 2i -f 1i =(f CEO2 -f CEO1 )+(if rep2 -if rep1 )=δf CEO +iδf rep In addition, it is considered that δf CEO =f CEO2 -f CEO1 . It is described by the same formula as that of a single comb laser, so the waveform obtained by the interference of the first comb laser and the second comb laser is the same pulse waveform as that of a single comb laser. If δT rep =1 / δf rep , then the pulse period on the time axis is δT rep .

[0082] [Principle of Distance Measurement]

[0083] Next, use Figure 3 and Figure 4 , explaining the principle of distance measurement using a double comb.

[0084] Figure 3 This figure schematically shows the time waveforms of the reference light and the object light obtained as a result of the interference of the comb laser light in the dual comb. Figure 3 In the figure, the horizontal axis represents time and the vertical axis represents the electric field of the comb laser.

[0085] When performing distance measurement, for example, light emitted from a light source is split into two beams: one beam is directed away from the object, while the other beam is directed toward the object. The light that is not directed toward the object and the light reflected by the object are each received by a detector. Hereinafter, the light that is not directed toward the object is referred to as the reference-side light, and the light that is directed toward the object is referred to as the target-side light.

[0086] In this case, if Figure 3 As shown, the resulting signal waveforms are identical for both the reference and target light. However, due to differences in optical path length depending on whether or not the light passes through the target, the timing of pulse light detection, i.e., the position of the pulse light peak on the time axis, varies. Furthermore, the signal processing unit acquires signals during a predetermined sampling period, calculates the amount of deviation in the peak position of the pulse light, and converts this deviation into distance, thereby measuring the distance from the light source to the target object.

[0087] In addition, the sampling period is synchronized with the timing of the light source emitting pulse light. For example, the length of the sampling period is generally the same as the pulse period. In the case of a dual comb, the pulse period δT included in the signal after interference can berep Set to the length of the sampling period.

[0088] In addition to using the peak position of pulse light on the time axis, there is also a method that uses the phase spectrum in distance measurement. In other words, distance measurement can be performed using not only the time information of pulse light but also the phase information.

[0089] Figure 4 This is a diagram schematically showing the phase spectrum after interference in a dual comb. Figure 4 In the figure, the horizontal axis represents frequency and the vertical axis represents phase.

[0090] The phase spectrum is obtained by Fourier transforming the pulse waveform after interference. Figure 4 As shown, the phase spectrum can be fitted with a straight line with a certain slope. Furthermore, this slope varies proportionally with the optical path length. Therefore, the difference in slope between the reference and target comb lasers allows the distance from the light source to the object to be measured. This allows distance to be measured not only from the deviation in the peak position of the pulsed light but also from phase information.

[0091] Here, regarding the issue of the positional relationship between the sampling period and the pulse waveform, we use Figure 5 Provide explanation.

[0092] Figure 5 This diagram schematically illustrates the relationship between the position of the interfering pulse waveform during the sampling period and the measurement results. Here, the start of the sampling period is set to 0, and the end is set to T. Furthermore, the associated measurement distance is set to L. Here, L corresponds to the round-trip length of the pulse of the laser resonator described above. Therefore, L corresponds to the round-trip distance to the object, and the measurement value output by the measurement device is a value equivalent to L / 2.

[0093] When measuring distance based on the peak position of pulsed light in a temporal waveform, if a pulse occurs at the beginning or end of a sampling period, the distance measurement value may approach 0 or L for each measurement due to the timing jitter of the light source and the resolution of the measuring device. This results in a decrease in the accuracy of the measured value.

[0094] On the other hand, when measuring distance using a phase spectrum, if a pulse occurs at the center of the sampling period, the distance measurement result for each pulse will be close to -0.5L or 0.5L for the same reason. Consequently, the accuracy of the measured value decreases.

[0095] Therefore, the accuracy of the measurement results decreases depending on the peak position of the pulse light within the sampling period. The present inventors have discovered the above problems and have devised a new measurement device and measurement method to solve the problems. The following describes embodiments of the present disclosure.

[0096] [Implementation Method]

[0097] (Implementation 1)

[0098] First, refer to Figure 6A The basic configuration example of the measuring device according to Embodiment 1 is described below. The measuring device according to this embodiment is a device that performs off-axis distance measurement. Specifically, the axis of light irradiating an object is different from the axis of light receiving reflected light from the object.

[0099] Figure 6A It is a diagram schematically showing the measuring device 100 according to this embodiment. Figure 6A The measuring device 100 shown measures the distance from the measuring device 100 to the object 40. For example, the measuring device 100 measures the distance from the measuring device 100 to each measurement point on the surface of the object 40. This allows the measuring device 100 to obtain the surface shape of the object 40. The measurement point is the point where the pulsed light is irradiated.

[0100] Object 40 is, for example, a product such as a screw manufactured based on design data, but is not limited thereto. Object 40 may also be an industrial product or agricultural product. By measuring the surface shape using measuring device 100, object 40 can be inspected. Alternatively, measuring device 100 may be an animal such as a human. Furthermore, object 40 is not limited to a solid; it may also be a liquid as long as it can reflect pulsed light.

[0101] like Figure 6A As shown, the measuring device 100 includes a pulse light source 10, a coupler 20, optical heads 30 and 31, detectors 50 and 51, a signal processing circuit 60, a control circuit 70, and a drive unit 80. The various components of the measuring device 100 are connected via optical fibers (illustrated by dashed lines) or cables (illustrated by solid lines). For example, optical components such as the coupler 20, optical heads 30 and 31, and detectors 50 and 51 are arranged along the path of the optical fiber. The pulse light source 10 is connected to the end of the optical fiber. Furthermore, the detectors 50 and 51, the signal processing circuit 60, the control circuit 70, and the drive unit 80 are arranged along the path of the cable.

[0102] The pulse light source 10 is an example of a light source that repeatedly emits pulsed light. The pulse light source 10 is, for example, a light comb laser including a laser resonator. The pulse light source 10 outputs light 10L as output light. The light 10L has a repetition frequency of, for example, f rep And the carrier envelope offset frequency is fCEO Comb laser. Figure 1A As shown, the comb laser light includes a plurality of pulse lights at equal time intervals. That is, the pulse light source 10 repeatedly emits pulse lights by outputting the comb laser light.

[0103] The coupler 20 is an optical element that demultiplexes light. Specifically, the coupler 20 demultiplexes the light 10L into signal light 10Lt and reference light 10Lr.

[0104] The optical head 30 is an optical element such as a collimator that collimates light and emits it. Specifically, the optical head 30 converts the signal light 10Lt transmitted through the optical fiber into parallel light and emits it toward the object 40. The optical head 30 may also include an optical element such as a lens connected after the collimator to focus the light.

[0105] The optical head 31 is an optical element that receives light and guides it into an optical fiber. Specifically, the optical head 31 receives reflected light 10R, generated when emitted signal light 10Lt is reflected by an object 40, and guides it into the optical fiber. Like the signal light 10Lt, the reflected light 10R includes multiple light pulses. These multiple light pulses are generated by reflections of the light pulses included in the signal light 10Lt from the object 40.

[0106] Detectors 50 and 51 are optical elements that generate and output electrical signals by photoelectrically converting incident light. The signal level of the electrical signal corresponds to the intensity of the incident light. Detectors 50 and 51 are photoelectric conversion elements such as photodiodes and phototransistors, for example.

[0107] The detector 50 is an example of a first photodetector, detects a plurality of reflected pulsed lights, and outputs a first electrical signal corresponding to the detection result. Specifically, the detector 50 performs photoelectric conversion on the reflected light 10R incident via the optical head 31 and the optical fiber, and outputs the first electrical signal.

[0108] Detector 51 is an example of a second photodetector that detects a portion of the pulsed light emitted by pulse light source 10 and outputs a second electrical signal corresponding to the detection result. Specifically, detector 51 performs photoelectric conversion on reference light 10Lr demultiplexed by coupler 20 to output the second electrical signal.

[0109] The signal processing circuit 60 calculates the distance from the measuring device 100 to the object 40 based on the first electrical signal. Specifically, the signal processing circuit 60 calculates the distance based on the first electrical signal and the second electrical signal. Specific calculation methods include a method utilizing time information and a method utilizing phase information. For example, the signal processing circuit 60 calculates the distance based on the time waveform corresponding to the reflected pulse light during the sampling period. Alternatively, the signal processing circuit 60 may calculate the distance based on the phase spectrum corresponding to the reflected pulse light during the sampling period. Whether to use time information or phase information can be pre-set or switched based on instructions from a user or the like.

[0110] Control circuit 70 controls drive unit 80. Specifically, control circuit 70 controls drive unit 80 based on the timing of detecting reflected pulse light within the sampling period. The timing of detecting reflected pulse light is the position of the peak of the reflected pulse light on the time axis. Hereinafter, the timing of detecting reflected pulse light may be referred to as "pulse position."

[0111] In this embodiment, the control circuit 70 changes the control content of the drive unit 80 according to the method by which the signal processing circuit 60 calculates the distance. For example, when the signal processing circuit 60 uses time information, the control circuit 70 controls the drive unit 80 so that the position of the peak of the pulse light, that is, the pulse position, is close to the center of the sampling period. Specifically, when using time information, the control circuit 70 controls the drive unit 80 so that the pulse position does not become the end of the sampling period, for example, it does not become any of the ranges of greater than 0 and less than 0.05T and greater than 0.95T and less than T. In other words, the control circuit 70 controls the drive unit 80 so that the pulse position enters the range of greater than 0.05T and less than 0.95T. Here, T is as Figure 5 Shown is the length of the sampling period.

[0112] Furthermore, when the signal processing circuit 60 utilizes phase information, the control circuit 70 controls the driver 80 so that the pulse position is shifted away from the center of the sampling period. Specifically, when utilizing phase information, the control circuit 70 controls the driver 80 so that the pulse position does not fall within the center range of the sampling period, for example, within a range greater than 0.45T and less than 0.55T. In other words, the control circuit 70 controls the driver 80 so that the pulse position falls within a range of greater than 0 and less than 0.45T, or within a range of greater than 0.55T and less than T.

[0113] The signal processing circuit 60 and the control circuit 70 are each implemented, for example, by an LSI (Large Scale Integration) which is an integrated circuit (IC). In addition, the integrated circuit is not limited to LSI, and may also be a dedicated circuit or a general-purpose processor. For example, the signal processing circuit 60 and the control circuit 70 may also be a microcontroller. The microcontroller includes, for example: a non-volatile memory storing a program, a volatile memory as a temporary storage area for executing the program, input and output ports, and a processor for executing the program. In addition, the signal processing circuit 60 and the control circuit 70 may also be a programmable FPGA (Field Programmable Gate Array) or a reconfigurable processor capable of reconfiguring the connections and settings of the circuit units within the LSI. The functions performed by the signal processing circuit 60 and the control circuit 70 may be implemented by software or by hardware. The signal processing circuit 60 and the control circuit 70 may also be implemented by a common hardware configuration.

[0114] The driving unit 80 is an element that changes the optical path length on the object side. The optical path length on the object side is the optical path length from the pulse light source 10 through the object 40 to the detector 50. In the present embodiment, the driving unit 80 physically changes the position of the object 40. For example, the driving unit 80 is a movable moving stage that supports the object 40, but is not limited to this. The driving unit 80 can also be a conveyor belt or a robot arm, etc. As long as the physical position, posture, inclination, etc. of the object 40 can be changed, the type of the driving unit 80 is not particularly limited.

[0115] In the measurement device 100 configured as described above, when measuring the distance of an object 40, the pulse light source 10 outputs light 10L. The output light 10L is split by the coupler 20 into two beams: signal light 10Lt and reference light 10Lr. Signal light 10Lt is emitted from the optical head 30 and incident on the object 40, where it is reflected. Reflected light 10R, after being incident on the optical head 31, travels toward the detector 50. Reference light 10Lr travels toward the detector 51.

[0116] Reflected light 10R and reference light 10Lr are converted into electrical signals by detectors 50 and 51, respectively. The signal from detector 50 is used as the target signal, and the signal from detector 51 is used as the reference signal. Signal processing circuit 60 performs computational processing using time information or phase information to calculate the distance from measurement device 100 to the measurement point on object 40.

[0117] When measuring at a certain measurement point, the control circuit 70 activates the driver 80 based on the electrical signal output from the detector 50 to adjust the optical path length on the object side. Specifically, if the pulse position is within a range that could potentially reduce measurement accuracy, the control circuit 70 controls the driver 80 to shift the position of the object 40 so that the pulse position falls outside this range. After shifting the position of the object 40, measurement is then performed at the same measurement point. This allows the measuring device 100 to suppress any reduction in measurement accuracy and measure distance with high accuracy. Specific operational examples are described later.

[0118] As described in Embodiment 2 below, the drive unit 80 may move the optical head 30 or 31 instead of moving the object 40. In this case, as in the case of moving the object 40, the optical path length on the object side can be changed, and thus the distance can be measured with high accuracy.

[0119] (Implementation Method 2)

[0120] Next, refer to Figure 6B A basic configuration example of a measuring device according to the second embodiment will be described.

[0121] In Embodiment 2, unlike Embodiment 1, the axis of light irradiating the object coincides with the axis of light received by the reflected light from the object. In other words, the measuring device of Embodiment 2 performs coaxial distance measurement. Furthermore, unlike Embodiment 1, the drive unit for adjusting the optical path length is incorporated into the optical head. The following description focuses on the differences from Embodiment 1, and the description of common points will be omitted or simplified.

[0122] Figure 6B Schematically shows the measuring device 110 according to this embodiment. Figure 6B As shown, the measuring device 110 is different from the measuring device 100 according to the first embodiment in that a circulator 90 is provided instead of the optical head 31. In addition, in the measuring device 110, the driving unit 80 changes the position of the optical head 30.

[0123] The circulator 90 is an optical element that controls the traveling direction of light. As long as the traveling direction of light can be controlled, an element such as a beam splitter may be used instead of the circulator 90 .

[0124] In the measurement device 110 according to this embodiment, when measuring the distance of an object 40, the pulse light source 10 outputs light 10L. The output light 10L is split by the coupler 20 into two lights: signal light 10Lt and reference light 10Lr. The signal light 10Lt passes through the circulator 90, exits the optical head 30, and enters the object 40, where it is reflected. After entering the optical head 30, the reflected light 10R passes through the circulator 90 and travels toward the detector 50. Meanwhile, the reference light 10Lr travels toward the detector 51.

[0125] The reflected light 10R and the reference light 10Lr are converted into electrical signals by the detectors 50 and 51, respectively. The distance can be calculated using the same method as that of the first embodiment.

[0126] In this way, signal light 10Lt and reflected light 10R are input and output via the same optical head 30. That is, the irradiation axis of signal light 10Lt on object 40 coincides with the light receiving axis of reflected light 10R from object 40. This allows for highly accurate distance measurement even when object 40 has a complex shape. For example, if object 40 has a structure such as a deep hole, the measurement device 100 can receive light reflected from the bottom surface of the hole by aligning the irradiation axis with the light receiving axis.

[0127] Furthermore, in this embodiment, the drive unit 80 moves the position of the optical head 30. Moving the optical head 30 also allows the optical path length on the object side to vary, similar to moving the object 40. Furthermore, in this embodiment, since the irradiation axis and the light receiving axis coincide with each other, it is easy to control the variation in the optical path length when the optical head 30 is moved.

[0128] Furthermore, as in Embodiment 1, the drive unit 80 may move the object 40 instead of moving the optical head 30. In this case, as in the case of moving the optical head 30, the optical path length on the object side can be changed, and thus the distance can be measured with high accuracy.

[0129] (Implementation 3)

[0130] Next, refer to Figure 6C A basic configuration example of a measuring device according to the third embodiment will be described.

[0131] Embodiment 3 differs from Embodiment 2 in that distance measurement is performed using a double comb. The following description will focus on the differences from Embodiments 1 and 2, and the description of the common points will be omitted or simplified.

[0132] In addition, when using multiple pulse light sources such as dual comb, Figure 6CAs shown, one pulse light source is set to a path where both the reference side and the target side do not irradiate the target object 40. This enables measurement with higher sensitivity.

[0133] Figure 6C Schematically shows the measuring device 120 according to this embodiment. Figure 6C As shown, the measuring device 120 is different from the measuring device 110 according to the second embodiment in that it includes optical comb lasers 11 and 12 instead of the pulse light source 10 . The measuring device 120 also includes couplers 21 , 22 , and 23 .

[0134] like Figure 6C As shown, the various components of measurement device 120 are connected via optical fibers (illustrated by dashed lines) or cables (illustrated by solid lines). For example, optical components such as couplers 20, 21, 22, and 23, a circulator 90, an optical head 30, and detectors 50 and 51 are arranged along the optical fiber path. Comb lasers 11 and 12 are connected to the ends of the optical fibers.

[0135] The optical comb laser 11 is an example of a first light source that repeatedly emits a first pulse light. The optical comb laser 11 is an optical comb laser including a laser resonator. The optical comb laser 11 outputs light 11L as output light. The light 11L is, for example, Figure 2 The upper part shows the repetition frequency f rep1 And the carrier envelope offset frequency is f CEO1 optical comb laser.

[0136] The optical comb laser 12 is an example of a second light source that repeatedly emits a second pulsed light. The optical comb laser 12 is an optical comb laser having a repetition frequency different from that of the optical comb laser 11. The optical comb laser 12 outputs light 12L as output light. The light 12L is, for example, Figure 2 The lower part shows the repetition frequency f rep2 And the carrier envelope offset frequency is f CEO2 optical comb laser.

[0137] Couplers 20, 21, 22, and 23 are optical elements that demultiplex or combine light. Coupler 20 demultiplexes light 11L into signal light 11Lt and reference light 11Lr. Coupler 21 demultiplexes light 12L into signal light 12Lt and reference light 12Lr. Coupler 22 combines reference light 11Lr with reference light 12Lr. Coupler 23 combines reflected light 11R with signal light 12Lt.

[0138] In the measurement device 120 according to this embodiment, when measuring the distance of an object 40, the optical comb lasers 11 and 12 respectively output light 11L and 12L. Light 11L is split by the coupler 20 into two beams: signal light 11Lt and reference light 11Lr. Signal light 11Lt passes through the circulator 90, exits the optical head 30, and enters the object 40, where it is reflected. Reflected light 11R, after entering the optical head 30, passes through the circulator 90 and travels toward the coupler 23. Reference light 11Lr travels from the coupler 20 toward the coupler 22.

[0139] Light 12L is split into signal light 12Lt and reference light 12Lr by coupler 21. Reference light 12Lr is combined with reference light 11Lr by coupler 22 and travels toward detector 50. Signal light 12Lt is combined with reflected light 11R by coupler 23 and travels toward detector 51.

[0140] In this embodiment, two optical comb lasers interfere with each other in each of the detectors 50 and 51. Specifically, the detector 51 interferes with the reflected light 11R and the signal light 12Lt and detects them, and outputs a first electrical signal corresponding to the detection result. The first electrical signal is, for example, Figure 3 In addition, the detector 50 makes the reference light 11Lr and the reference light 12Lr interfere and detect, and outputs a second electrical signal corresponding to the detection result. The second electrical signal is, for example, Figure 3 The signal processing circuit 60 calculates the distance from the measuring device 120 to the measurement point of the object 40 based on the first electric signal and the second electric signal.

[0141] In this embodiment, the drive unit 80 moves the position of the optical head 30. As in Embodiment 2, moving the optical head 30 can change the optical path length on the object side. Furthermore, as in Embodiment 1, the drive unit 80 can also move the object 40 instead of moving the optical head 30. In either case, the optical path length on the object side can be changed, enabling highly accurate distance measurement.

[0142] [Operation of the measuring device (measurement method)]

[0143] Next, the operations of the measuring devices 100, 110, and 120 according to the above-mentioned embodiments will be described. The operation of the measuring device 120 using a double comb will be described below as a representative example, but the operations of the measuring devices 100 and 110 are also similar.

[0144] [Example 1]

[0145] First, refer to Figure 7 A first example of the operation of the measuring device 120 will be described.

[0146] Figure 7 This is a flowchart showing a first example of the operation of the measuring device according to each embodiment. Figure 7 The example shown is an example of an operation for determining whether the optical path length needs to be changed during each measurement. If a change is determined to be necessary, the optical path length is changed so as not to reduce measurement accuracy. Furthermore, the measuring device 120 starts operation in response to a start signal from an input mechanism (not shown).

[0147] (Step S101)

[0148] like Figure 7 As shown, first, the signal processing circuit 60 obtains the electrical signals detected by the detectors 50 and 51. The electrical signals obtained by the signal processing circuit 60 include, for example Figure 3 In other words, the signal processing circuit 60 obtains the time information of the pulse train.

[0149] (Step S102)

[0150] Next, the signal processing circuit 60 or the control circuit 70 detects the largest peak based on the time information of the pulse train. Here, the peak may be a peak in the obtained electrical signal or a peak in the envelope of the pulse waveform.

[0151] (Step S103)

[0152] Next, the control circuit 70 obtains the position of the maximum peak in the sampling period (T Peak Here, the start of the sampling period is set to 0 and the end is set to T, so that 0≤T Peak ≤T.

[0153] (Step S104)

[0154] Next, the control circuit 70 determines the distance conversion calculation method. Specifically, the control circuit 70 determines whether to use phase information or time information. The information type to be used is preset. Alternatively, the information type to be used may be switched based on a user instruction. Furthermore, the determination in step S104 may be performed at the beginning of the measurement device 120's operation, i.e., before step S101.

[0155] When using phase information ("Phase" in S104), the measuring device 120 executes the processes shown in steps S105 to S107, and steps S111 and S112. When using time information ("Time" in S104), the measuring device 120 executes the processes shown in steps S108 to S111.

[0156] (Step S105)

[0157] When using phase information ("Phase" in S104), the control circuit 70 determines the position T of the maximum peak. Peak Specifically, the control circuit 70 determines whether T Peak ≤0.45T or 0.55T≤T Peak .

[0158] (Step S106)

[0159] In meeting T Peak ≤0.45T or 0.55T≤T Peak If (S105: Yes), the signal processing circuit 60 calculates the distance using the phase information. Specifically, the signal processing circuit 60 performs a Fourier transform on each of the acquired reference-side second electrical signal and the acquired target-side first electrical signal. The signal processing circuit 60 converts the slope of each phase spectrum obtained through the Fourier transform into a distance, and calculates the distance from the measurement device 120 to the irradiation point based on the difference between the two phase spectra.

[0160] (Step S107)

[0161] If T is not satisfied Peak ≤0.45T or 0.55T≤T Peak In the case of (S105: No), the control circuit 70 controls the driving unit 80 so that the position of the maximum peak T Peak Be outside the range of greater than 0.45T and less than 0.55T, that is, satisfy T Peak ≤0.45T or 0.55T≤T Peak By controlling the driving unit 80, the optical path length on the object side changes, so the position of the maximum peak T Peak In this state, the process returns to step S101 again to obtain the electrical signal at the same irradiation point. Thereafter, the measuring device 120 executes the processes from step S102 onwards.

[0162] (Step S108)

[0163] When using time information ("time" in S104), the control circuit 70 determines the position T of the maximum peak. Peak Specifically, the control circuit 70 determines whether 0.05T≤T Peak ≤0.95T.

[0164] (Step S109)

[0165] When 0.05T≤T PeakIf ≤0.95T (S108: YES), the signal processing circuit 60 calculates the distance using the time information. Specifically, the signal processing circuit 60 converts the distance based on the positions of the respective maximum peaks of the acquired second electrical signal on the reference side and the first electrical signal on the target side, and calculates the distance from the measurement device 120 to the irradiation point based on the difference between the two.

[0166] (Step S110)

[0167] If 0.05T≤T is not satisfied Peak When ≤0.95T (S108: No), the control circuit 70 controls the driving unit 80 so that the position of the maximum peak T Peak Avoid the range of less than 0.05T and the range of greater than 0.95T, that is, satisfy 0.05T≤T Peak ≤0.95T. By controlling the driving unit 80, the optical path length on the object side changes, so the position of the maximum peak T Peak In this state, the process returns to step S101 again to obtain the electrical signal at the same measurement point. Thereafter, the measuring device 120 executes the processes from step S102 onwards.

[0168] (Step S111)

[0169] After calculating the distance from the measuring device 120 to the irradiation point in step S106 or S109, the control circuit 70 determines whether measurement has been completed at all points. Here, "all points" refers to, for example, all points on the surface of the object 40 that are scheduled for measurement, that is, all points that are scheduled to be irradiated with the irradiation signal light 11Lt. If measurement of all points has been completed (S111: Yes), the distance measurement operation performed by the measuring device 120 ends. On the other hand, if measurement of all points has not yet been completed (S111: No), the measuring device 120 executes the processing shown in step S112.

[0170] (Step S112)

[0171] If measurement of all points has not yet been completed, the measuring device 120 moves the irradiation point on the object 40. To move the irradiation point on the object 40, for example, a moving stage (not shown) supporting the object 40 is used. Other methods may also be used as long as the irradiation point can be changed. After the irradiation point has been moved, the process returns to step S101 to acquire the electrical signal at the new irradiation point. The measuring device 120 then performs the processing from step S102 onwards.

[0172] As above, in Figure 7In the example shown, the control circuit 70 determines whether the optical path length needs to be changed during each measurement, that is, at each irradiation point of the signal light 11Lt (step S105 or S108). If the control circuit 70 determines that a change is necessary, it controls the drive unit 80 to change the optical path length (step S107 or S110). This improves the measurement accuracy at each irradiation point.

[0173] [Example 2]

[0174] Next, refer to Figure 8 A second example of the operation of the measuring device 120 will be described.

[0175] Figure 8 This is a flowchart showing a second example of the operation of the measuring device according to each embodiment. Figure 8 The example shown differs from the first example in that distance correction is performed based on the variation in optical path length. The following description will focus on the differences from the first example, and the description of the common points will be omitted or simplified.

[0176] like Figure 8 As shown, each process of steps S101, S102, S103, S104, S105, S106, S107, S108, S109, S110, S111 and S112 is the same as Figure 7 Since the respective processes involved in the first example shown are the same, their description is omitted.

[0177] (Step S207)

[0178] The process shown in step S207 is performed after the process shown in step S107. Specifically, the control circuit 70 records the amount of change in the optical path length. The amount of change may be the amount of change in the optical path length on the object side itself, the amount of movement of the drive unit 80, or the amount of physical movement of the optical head 30 or the object 40.

[0179] The control circuit 70 stores the variation in a memory built into the control circuit 70 or the signal processing circuit 60. Alternatively, the variation may be recorded in another memory included in the measuring device 120 or in a memory included in a device different from the measuring device 120, as long as the variation can be recorded.

[0180] (Step S210)

[0181] The process shown in step S210 is executed after the process shown in step S110. Specifically, the control circuit 70 records the variation of the optical path length. The specific process is the same as that of step S207.

[0182] (Step S211)

[0183] exist Figure 8 In the example shown, after all points have been measured (S111: YES), the signal processing circuit 60 reads the variation stored in the memory and corrects the distance calculated in step S106 or S109. Distance correction is performed for one or more irradiation points after the drive unit 80 has been controlled in step S107 or S110.

[0184] In the measuring device 120, the optical path length is varied by controlling the drive unit 80. Therefore, the amount of variation in the optical path length is added as an offset to the calculated distance. For example, when measuring the surface shape of the object 40, the offset results may overlap at various locations, making it impossible to accurately determine the surface shape.

[0185] In contrast, Figure 8 As shown, when the optical path length is varied by the driver 80, the signal processing circuit 60 corrects the distance based on the variation in the optical path length. This allows the measurement results of all points on the object 40 to be appropriately corrected, enabling, for example, high-precision measurement of the surface shape of the object 40.

[0186] In addition, Figure 8 In the example shown, correction is performed after measuring all points, but the present invention is not limited thereto. The signal processing circuit 60 may correct the calculated distance each time the distance is calculated, that is, immediately after step S106 or S109.

[0187] [Example 3]

[0188] Next, refer to Figure 9A and Figure 9B A third example of the operation of the measuring device 120 will be described.

[0189] Figure 9A This is a flowchart showing an example of pre-measurement in the third example of the measuring device according to each embodiment. Figure 9B This is a flowchart showing an example of a formal measurement in the third example of the measuring device according to each embodiment. In the third example, the measuring device 120 performs Figure 9A After the pre-test shown, Figure 9B Formal measurement shown.

[0190] First, refer to Figure 9A The following describes the actions related to the pre-measurement. The following description focuses on the differences from the first example, and the description of the common points is omitted or simplified. Figure 9A As shown, each process of steps S101, S102 and S103 is the same as Figure 7 Each process involved in the first example shown is the same, so the description thereof is omitted.

[0191] (Step S303)

[0192] The process shown in step S303 is executed after the process shown in step S103. Specifically, the signal processing circuit 60 calculates the position of the maximum peak (T Peak ) is recorded to the memory.

[0193] (Step S304)

[0194] Next, the control circuit 70 determines whether to terminate the pre-measurement. Pre-measurement is performed, for example, on all points of the object 40. For example, these all points are all points on the surface of the object 40 that are scheduled for measurement, that is, all points that are scheduled to be irradiated with the signal light 11Lt. Furthermore, in the pre-measurement, only a portion of all points may be measured.

[0195] (Step S305)

[0196] If the pre-measurement is not complete (S304: No), that is, if measurement of all points has not yet been completed, the measuring device 120 moves the irradiation point on the object 40. To move the irradiation point on the object 40, for example, a moving stage (not shown) supporting the object 40 is used. Alternatively, other methods may be used as long as the irradiation point can be changed. After the irradiation point is moved, the process returns to step S101 to acquire the electrical signal at the new irradiation point. The measuring device 120 then executes the processing from step S102 onwards.

[0197] (Step S306)

[0198] When the estimated measurement is completed (S304: Yes), the control circuit 70 determines the distance conversion calculation method. Specifically, the control circuit 70 determines whether to use phase information or time information. The determination of step S306 is the same as Figure 7 or Figure 8 The determination of step S306 may be performed at the beginning of the operation of the measuring device 120, that is, before step S101.

[0199] (Step S307)

[0200] When phase information is used ("Phase" in S306), the control circuit 70 calculates the maximum peak position T based on the recorded value. Peak Specifically, the control circuit 70 determines the variation of the optical path length at all points to satisfy T Peak ≤0.45T or 0.55T≤T PeakThat is, the control circuit 70 determines the variation of the optical path length so that the position T of the maximum peak at each irradiation point is Peak Move away from the center of the sampling period. For example, at the location of the maximum peak recorded, T Peak When the T is greater than 0.45T and less than 0.55T, the control circuit 70 determines to set the T Peak The control circuit 70 avoids the fluctuation amount in this range. Peak Meet T Peak ≤0.45T or 0.55T≤T Peak In the case of , the change is considered to be 0.

[0201] (Step S308)

[0202] When time information is used ("time" in S306), the control circuit 70 calculates the maximum peak position T based on the record. Peak Specifically, the control circuit 70 determines the variation of the optical path length at all points to satisfy 0.05T≤T Peak ≤0.95T. That is, the control circuit 70 determines the variation of the optical path length so that the position T of the maximum peak at each irradiation point is Peak Close to the center of the sampling period. For example, at the location of the maximum peak recorded T Peak When the temperature is less than 0.05T or greater than 0.95T, the control circuit 70 determines to set the T Peak Avoid any of the above ranges of fluctuation. The control circuit 70 records the maximum peak position T Peak Satisfy 0.05T≤T Peak When ≤0.95T, the variation is regarded as 0.

[0203] (Step S309)

[0204] After determining the variation in step S307 or S308, the control circuit 70 records the determined variation in memory. At this point, the control circuit 70 may also record the drive amount of the driver 80, specifically the physical movement of the optical head 30 or the object 40, as the variation. By recording the drive amount of the driver 80, the driver 80 can be controlled quickly at the corresponding irradiation point.

[0205] As described above, according to this example, the variation in optical path length when measuring each irradiation point is determined by pre-measurement. Therefore, during the actual measurement, the control circuit 70 can control the drive unit 80 based on the determined variation.

[0206] Below, refer to Figure 9BThe following describes the actions related to the actual measurement. The following description focuses on the differences from the first example, and the description of the common points is omitted or simplified. Figure 9B As shown, each process of steps S101, S102, S103 and S112 is the same as Figure 7 Since the respective processes involved in the first example shown are the same, their description is omitted.

[0207] (Step S310)

[0208] When the actual measurement starts, the control circuit 70 first obtains the amount of variation corresponding to the irradiation point. Specifically, the control circuit 70 reads the amount of variation recorded in the pre-measurement from the memory.

[0209] (Step S311)

[0210] Next, the control circuit 70 determines whether the optical path length needs to be changed. Specifically, if the change amount read is zero, the control circuit 70 determines that no change is necessary. Alternatively, if the change amount corresponding to the irradiation point is not recorded in the memory, the control circuit 70 also determines that no change is necessary. If no change in the optical path length is necessary (S311: No), the measurement device 120 executes the processing from step S101 onwards.

[0211] (Step S312)

[0212] If the optical path length needs to be changed (S311: YES), the control circuit 70 controls the driving unit 80 based on the read variation. The variation is determined based on the estimated value so that the position of the maximum peak T Peak Therefore, by controlling the driving unit 80 based on the variation, the position T of the maximum peak is set to Peak Since the value is within the appropriate range, high-precision measurement can be performed. After controlling the driving unit 80, the measuring device 120 executes the processing after step S101.

[0213] (Step S313)

[0214] The processing shown in step S313 is performed after the processing shown in step S103. Specifically, the signal processing circuit 60 uses phase information or time information to calculate the distance from the measuring device 120 to the irradiation point. At this time, the signal processing circuit 60 uses the information used in the pre-measurement. That is, when the signal processing circuit 60 uses phase information in the pre-measurement, the phase information is also used in the actual measurement. When the signal processing circuit 60 uses time information in the pre-measurement, the time information is also used in the actual measurement. The specific distance calculation method is the same as Figure 7 The processing shown in step S106 or S109 is the same.

[0215] (Step S314)

[0216] After calculating the distance from the measuring device 120 to the irradiation point in step S313, the control circuit 70 determines whether measurement has been completed at all points. Here, "all points" refers to, for example, all points on the surface of the object 40 that are scheduled for measurement, that is, all points that are scheduled to be irradiated with the irradiation signal light 11Lt. If measurement of all points has been completed (S314: Yes), the distance measurement operation performed by the measuring device 120 ends. On the other hand, if measurement of all points has not yet been completed (S313: No), the measuring device 120 executes the processing shown in step S112.

[0217] As above, in Figure 9A and Figure 9B In the example shown, the control circuit 70 performs a preliminary measurement at all irradiated points on the object 40. Based on the measurement results, the control circuit 70 determines the amount of change in the optical path length. The control circuit 70 then performs a final measurement at all points on the object 40, changing the optical path length based on the determined amount of change while maintaining measurement accuracy.

[0218] By pre-acquiring information about the optical path length fluctuation at all points, it is possible to suppress large changes in the fluctuation. For example, if the optical path length fluctuates at a certain measurement point, it is possible to avoid having to change the optical path length again at the next measurement point due to a large fluctuation, or conversely, a small fluctuation. This suppresses fluctuations in the optical path length and improves distance measurement accuracy.

[0219] [Example 4]

[0220] Next, refer to Figure 10 A fourth example of the operation of the measuring device 120 will be described.

[0221] Figure 10 This is a flowchart showing an example of one-point measurement in the fourth example of the measuring device according to each embodiment. Figure 10 The one-point measurement shown is equivalent to the estimated measurement of the third example. Figure 10 After measuring the one point shown, Figure 9B In the fourth example, the Figure 10 The one-point measurement shown in the fourth example determines the amount of change in the optical path length at each irradiation point.

[0222] The following describes the operation related to one-point measurement. The description focuses on the differences from the first example, and the description of the common points is omitted or simplified. Figure 10As shown, each process of steps S101, S102 and S103 is the same as Figure 7 Each process involved in the first example shown is the same, so the description thereof is omitted.

[0223] (Step S403)

[0224] The process shown in step S403 is executed after the process shown in step S103. Specifically, the signal processing circuit 60 calculates the position of the maximum peak (T Peak ) is recorded to the memory.

[0225] (Step S404)

[0226] Next, the control circuit 70 reads the design data of the object 40. For example, in the case of distance measurement, the design data of the object 40 may be 3D-CAD (Computer Aided Design) data. For example, if the object 40 is an industrial product and the measuring device 120 is used for inspection of the object 40, the design data used to manufacture the object 40 is stored in the memory. The control circuit 70 reads the design data from the memory to obtain the design data.

[0227] (Step S405)

[0228] Next, the control circuit 70 determines the distance conversion calculation method. Specifically, the control circuit 70 determines whether to use phase information or time information. The determination of step S405 is the same as Figure 7 or Figure 8 The determination of step S405 may be performed at the beginning of the operation of the measuring device 120, that is, before step S101.

[0229] (Step S406)

[0230] When phase information is used ("Phase" in S406), the control circuit 70 calculates the maximum peak position T based on the recorded value. Peak Specifically, the control circuit 70 determines the variation of the optical path length at all points to satisfy T Peak ≤0.45T or 0.55T≤T Peak That is, the control circuit 70 determines the variation of the optical path length so that the position T of the maximum peak at each irradiation point is Peak The control circuit 70 can refer to the design data and can adjust the maximum peak position T of a point according to the measurement result. Peak Estimate the maximum peak position T of all remaining points that have not been measured PeakTherefore, the control circuit 70 can determine the variation of the optical path length at all points by using the estimation result. Figure 9A The same is true for step S307 shown.

[0231] (Step S407)

[0232] When time information is used ("time" in S405), the control circuit 70 calculates the maximum peak position T based on the record. Peak Specifically, the control circuit 70 determines the variation of the optical path length at all points so as to satisfy 0.05T≤T Peak ≤0.95T. That is, the control circuit 70 determines the variation of the optical path length so that the position T of the maximum peak at each irradiation point is Peak As in step S406, the control circuit 70 can refer to the design data and calculate the maximum peak position T of a point according to the measurement result. Peak Estimate the maximum peak position T of all remaining points that have not been measured Peak Therefore, the control circuit 70 can determine the variation of the optical path length at all points by using the estimation result. Figure 9A The same is true for step S308 shown.

[0233] (Step S408)

[0234] After determining the variation in step S406 or S407, the control circuit 70 records the determined variation in memory. At this point, the control circuit 70 may also record the drive amount of the driver 80, specifically the physical movement of the optical head 30 or the object 40, as the variation. By recording the drive amount of the driver 80, the driver 80 can be controlled quickly at the corresponding irradiation point.

[0235] As described above, according to the fourth example, a measurement is performed at a single point on the object 40. The variation in optical path length when measuring each irradiation point is determined based on the measurement results and the design data of the object 40. Therefore, during the actual measurement, the control circuit 70 can control the drive unit 80 based on the determined variation. This can shorten the measurement time compared to pre-measurement.

[0236] (Other embodiments)

[0237] While one or more embodiments of the laser device have been described above, the present disclosure is not limited to these embodiments. Any embodiment resulting from various modifications conceived by those skilled in the art to the present embodiment, or any embodiment resulting from combining components from different embodiments, is encompassed within the scope of the present disclosure, provided it does not depart from the spirit of the present disclosure.

[0238] For example, the pulse light source 10 may not be a comb laser. In other words, the pulse light source 10 may not include a resonator, and may be, for example, an LD (Laser Diode) or LED (Light Emitting Diode) that repeatedly emits pulsed light.

[0239] Furthermore, as an example of the drive unit 80 that changes the optical path length, the example of moving the object 40 or the optical head 30 is described, but the present invention is not limited to this. For example, the drive unit 80 may also utilize the expansion and contraction of the optical fiber to change the optical path length. For example, the drive unit 80 may also be a temperature adjustment element that heats or cools the optical fiber. Examples of temperature adjustment elements include a Peltier element, a blower, and a heater.

[0240] Furthermore, for example, the range of less than 0.05T or greater than 0.95T is cited as an example of the end of the sampling period, but the present invention is not limited thereto. For example, the upper limit value at the beginning of the sampling period may be a value greater than 0 and less than 0.10T. Alternatively, the lower limit value at the end of the sampling period may be a value greater than 0.90T and less than T.

[0241] Furthermore, while the central range of the sampling period is, for example, a range greater than 0.45T and less than 0.55T, this is not limiting. For example, the lower limit of the central range may be greater than 0.40T and less than 0.50T. The upper limit of the central range may be greater than 0.50T and less than 0.60T. For example, the upper and lower limits may be changed depending on the length of the sampling period.

[0242] Furthermore, for example, in the above-described embodiment, a process executed by a specific processing unit may be executed by another processing unit. Furthermore, the order of multiple processes may be changed, or multiple processes may be executed in parallel.

[0243] Furthermore, for example, the processing described in the above embodiments can be implemented by centralized processing using a single device (system) or distributed processing using multiple devices. Furthermore, the processors that execute the above programs can be either a single processor or multiple processors. That is, centralized processing or distributed processing is possible.

[0244] In addition, in the above-described embodiment, all or part of the components such as the signal processing circuit 60 and the control circuit 70 may be formed by dedicated hardware, or may be implemented by executing software programs suitable for each component. Each component may also be implemented by a program execution unit such as a CPU (Central Processing Unit) or a processor reading and executing a software program recorded on a recording medium such as an HDD (Hard Disk Drive) or a semiconductor memory.

[0245] Furthermore, components such as the signal processing circuit 60 and the control circuit 70 may be formed of one or more electronic circuits. Each of the one or more electronic circuits may be a general-purpose circuit or a dedicated circuit.

[0246] One or more electronic circuits may include, for example, semiconductor devices, ICs, or LSIs. ICs or LSIs can be integrated into one chip or multiple chips. Although referred to herein as ICs or LSIs, the term may vary depending on the degree of integration and may also be referred to as system LSIs, VLSIs (very large scale integration), or ULSIs (ultra large scale integration). In addition, FPGAs programmed after LSI manufacturing can also be used for the same purpose.

[0247] Furthermore, the present disclosure, in its entirety or in its specific aspects, may also be implemented by a system, apparatus, method, integrated circuit, or computer program. Alternatively, it may be implemented by a computer-readable non-volatile recording medium such as an optical disc, HDD, or semiconductor memory storing the computer program. Furthermore, it may be implemented by any combination of systems, apparatuses, methods, integrated circuits, computer programs, and recording media.

[0248] Furthermore, various changes, substitutions, additions, omissions, etc. can be made to the above-described embodiments within the scope of the claims or their equivalents.

[0249] Industrial Applicability

[0250] The present disclosure can be used for distance measurement and displacement measurement, for example. For example, the measuring device and measuring method of the present disclosure can be used for displacement meters and shape inspection devices.

[0251] Description of reference numerals:

[0252] 10 Pulsed light source

[0253] 10L, 11L, 12L light

[0254] 10Lr, 11Lr, 12Lr reference light

[0255] 10Lt, 11Lt, 12Lt signal light

[0256] 10R, 11R reflected light

[0257] 11, 12 optical comb lasers

[0258] 20, 21, 22, 23 couplers

[0259] 30, 31 Optical Head

[0260] 40 objects

[0261] 50, 51 detectors

[0262] 60 signal processing circuit

[0263] 70 Control Circuit

[0264] 80 drive unit

[0265] 90 Circulator

[0266] 100, 110, 120 measuring devices

Claims

1. A measuring device comprising: A first light source repeatedly emits a first pulse light; a first light detector for detecting a reflected pulse light generated by the first pulse light being reflected by an object and outputting a first electrical signal corresponding to a detection result of the reflected pulse light; a signal processing circuit that calculates the distance from the measuring device to the object based on the first electrical signal during a sampling period; as well as a control circuit that controls a drive unit that changes the length of an optical path from the first light source through the object to the first light detector; The control circuit controls the driving unit so as to change the peak position of the reflected pulse light in the first electrical signal during the sampling period. The sampling period is synchronized with the timing at which the first light source emits the first pulse light.

2. The measuring device according to claim 1, The first light source is a comb laser.

3. The measuring device according to claim 2, further comprising: The second light source is a comb laser that repeatedly emits a second pulse light; and a second light detector that causes a portion of the first light pulse to interfere with the first portion of the second light pulse to detect the interference, and outputs a second electrical signal corresponding to the detection result of the portion of the first light pulse; The repetition frequency of the second light source is different from the repetition frequency of the first light source, The first photodetector causes the reflected pulse light to interfere with a second portion of the second pulse light that is different from the first portion and detects the interference. The signal processing circuit calculates the distance based on the first electrical signal and the second electrical signal.

4. The measuring device according to any one of claims 1 to 3, The signal processing circuit calculates the distance based on the time waveform corresponding to the reflected pulse light during the sampling period. The control circuit controls the drive unit so that the position of the peak approaches the center of the sampling period.

5. The measuring device according to any one of claims 1 to 3, The signal processing circuit calculates the distance based on the phase spectrum corresponding to the reflected pulse light during the sampling period. The control circuit controls the drive unit so that the position of the peak is shifted from the center of the sampling period.

6. The measuring device according to any one of claims 1 to 3, The control circuit determines whether the optical path length needs to be changed each time the irradiation point, which is the position in the object irradiated with the first pulse light, moves. When it is determined that the change is necessary, the control circuit controls the drive unit to change the optical path length.

7. The measuring device according to any one of claims 1 to 3, When the driving unit changes the optical path length, the signal processing circuit corrects the distance based on the amount of change in the optical path length.

8. The measuring device according to claim 7, The signal processing circuit records, for each of a plurality of irradiation points serving as positions on the object irradiated with the first pulse light, an amount of change in the optical path length when the driving unit changes the optical path length. The signal processing circuit corrects the distance for each of the plurality of irradiation points based on the variation recorded by the signal processing circuit.

9. The measuring device according to any one of claims 1 to 3, The measuring device is configured to perform a main measurement of the distance after performing a preliminary measurement. The control circuit determines, in the pre-measurement, an amount of variation in the optical path length at each of the plurality of irradiation points, based on the first electrical signal obtained for each of the plurality of irradiation points as positions in the object irradiated with the first pulse light. The control circuit controls the drive unit according to the amount of variation at each of the plurality of irradiation points during the main measurement.

10. The measuring device according to any one of claims 1 to 3, The control circuit determines the amount of change in the optical path length at each of a plurality of irradiation points including the at least one irradiation point based on the first electrical signal obtained for at least one irradiation point as a position in the object irradiated with the first pulse light and information related to the shape of the object. The control circuit controls the driving unit according to the variation amount at each of the plurality of irradiation points.

11. The measuring device according to any one of claims 1 to 3, The measuring device further includes the driving unit.

12. A measurement method comprising: The light source repeatedly emits pulsed light; detecting, by a light detector, reflected pulse light generated by the pulse light being reflected by an object, and outputting an electrical signal corresponding to a detection result of the reflected pulse light; calculating, by a signal processing circuit, the distance from the light source to the object based on the electrical signal during a sampling period; as well as controlling a driving unit that changes the length of an optical path from the light source through the object to the light detector, When performing the control, the driving unit is controlled so that the position of the peak of the reflected pulse light in the electrical signal during the sampling period changes. The sampling period is synchronized with the timing at which the first light source emits the first pulse light.

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