Apparatus and method for measuring distance and / or velocity of an object

Abstract

This measurement apparatus comprises a light source, an interference optical system, a photodetector, a processing circuit, and a storage device. The interference optical system divides light emitted from the light source into reference light and output light, and generates interference light between the reference light and reflection light generated when the output light has been reflected by a target object. The photodetector outputs a detection signal according to the intensity of the interference light. The processing circuit modulates the frequency of the light emitted from the light source in a cycle including an up-chirp period during which the frequency increases and a down-chirp period during which the frequency decreases. The storage device has stored therein first correction data for the up-chirp period and second correction data for the down-chirp period. The processing circuit determines a distance or a speed, on the basis of a signal obtained by correcting the detection signal on the basis of the first correction data or the second correction data.

Description

[Technical Field]

[0001] The present disclosure relates to an apparatus and method for measuring the distance and / or velocity of an object. [Background technology]

[0002] A ranging device using the FMCW (Frequency Modulated Continuous Wave) method sends out frequency-modulated electromagnetic waves and measures distance based on the difference in frequency between the transmitted and reflected waves. When the electromagnetic waves used are radio waves such as millimeter waves, the FMCW ranging device is called an FMCW radar. In FMCW radar, a voltage-controlled oscillator (VCO), for example, is used as the radio wave oscillation source. When the electromagnetic waves are light such as visible light or infrared light, the FMCW ranging device is called an FMCW lidar (LiDAR). In FMCW lidar, a laser light source, for example, is used as the light source.

[0003] FMCW lidar emits periodically frequency-modulated light from a light source toward a target. The light reflected from the target interferes with a reference light from the light source to produce an interference light. The interference light is detected by a photodetector and converted into an electrical signal. This electrical signal contains a signal component with a frequency corresponding to the difference between the frequency of the reflected light and the frequency of the reference light. This signal component is called the "beat signal." The frequency of the beat signal is called the "beat frequency." There is a correlation between the beat frequency and the distance to the target. Therefore, the distance to the target can be calculated based on the beat frequency. Furthermore, the Doppler shift of the light reflected from a moving target can be used to calculate the target's velocity. For example, the velocity of the target can be calculated based on the difference in the frequency of the beat signal during the up-chirp period, when the frequency of the light emitted from the light source increases, and during the down-chirp period, when the frequency decreases.

[0004] Unlike ToF (Time of Flight) lidars, FMCW lidars detect the frequency of the electrical signal output from a photodetector, which means that their ranging results are less susceptible to the effects of ambient light.However, it has been thought that the accuracy of FMCW lidar ranging depends on how linearly the optical frequency can be modulated with respect to time.

[0005] Patent Document 1 describes that even if the voltage-controlled oscillator of an FMCW radar sweeps the voltage linearly with time, the frequency changes nonlinearly, resulting in a degradation of ranging performance. To solve this problem, Patent Document 1 discloses a method for dynamically changing the sampling timing of the interference signal based on the sweep signal obtained from an artificial target. It describes how this makes it possible to compensate for the nonlinearity of the frequency sweep.

[0006] Patent Document 2 discloses an FMCW radar device that corrects the frequency of an interference signal using correction data corresponding to a plurality of distances and a plurality of ambient temperatures, thereby improving detection accuracy.

[0007] Patent Document 3 discloses an example of an FMCW lidar device that continuously measures the frequency of a beat signal and calculates the distance to an object based on the average value of the measured frequency. It describes how this eliminates the effects of nonlinear laser chirp, enabling accurate distance measurement. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2006 / 035199 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-185973 [Patent Document 3] JP 2019-45200 A Summary of the Invention [Problem to be solved by the invention]

[0009] The present disclosure provides a novel technique for suppressing degradation of distance and / or velocity measurement performance caused by the nonlinearity of frequency changes that differ between up-chirp and down-chirp. [Means for solving the problem]

[0010] A measurement device according to one aspect of the present disclosure includes a light source that emits frequency-modulated light, an interference optical system that separates the light emitted from the light source into reference light and output light and generates interference light between the reference light and reflected light resulting from the output light being reflected by an object, a photodetector that receives the interference light and outputs a detection signal corresponding to the intensity of the interference light, a processing circuit that modulates the frequency of the light emitted from the light source with a period that includes an up-chirp period in which the frequency increases and a down-chirp period in which the frequency decreases, and generates and outputs measurement data related to the distance and / or velocity of the object based on the detection signal, and a storage device that stores first correction data for the up-chirp period and second correction data for the down-chirp period. Part of a first corrected signal obtained by correcting the signal based on the first correction data, and / or the detection signal corresponding to the down-chirp period. Part of The measurement data is generated based on a second corrected signal obtained by correcting the measured value based on the second correction data.

[0011] A general or specific aspect of the present disclosure may be realized by a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium such as a computer-readable recording disk, or by any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. The computer-readable recording medium may include a volatile recording medium or a non-volatile recording medium such as a CD-ROM (Compact Disc-Read Only Memory). An apparatus may be composed of one or more devices. When an apparatus is composed of two or more devices, the two or more devices may be located in a single device or may be located separately in two or more separate devices. In this specification and claims, the term "apparatus" may refer not only to a single device but also to a system consisting of multiple devices. [Effects of the Invention]

[0012] According to one aspect of the present disclosure, the performance of measuring distance and / or velocity can be improved by performing appropriate signal correction on one or both of the up-chirp period and the down-chirp period. [Brief explanation of the drawings]

[0013] [Figure 1A] FIG. 1A is a graph showing an example of the change over time of a control voltage applied to a light source. [Figure 1B] FIG. 1B is a graph showing the change over time in the electrical signal obtained by detecting the interference light. [Figure 1C] FIG. 1C is a graph showing the change over time in the instantaneous frequency of the interference wave signal shown in FIG. 1B. [Figure 2] FIG. 2 is a block diagram showing a schematic configuration of the measurement device 100 according to the first embodiment. [Figure 3] FIG. 3 is a block diagram showing an example of the configuration of the light source and the interference optical system. [Figure 4] FIG. 4 is a diagram showing an example of a control signal output from a processing circuit and a drive current signal output from a drive circuit. [Figure 5] FIG. 5 is a block diagram showing an example of the configuration of a measurement device in which the interference optical system is a fiber optical system. [Figure 6] FIG. 6 is a block diagram showing an example of a measurement device equipped with an optical deflector. [Figure 7A] FIG. 7A is a diagram schematically illustrating an example of temporal changes in the frequencies of the reference light and the reflected light when the object is stationary. [Figure 7B] FIG. 7B is a diagram schematically showing the change over time in the frequencies of the reference light and the reflected light when the object approaches the measurement device 100. [Figure 8] FIG. 8 is a flowchart showing the calibration operation performed by the measurement device. [Figure 9] FIG. 9 is a graph showing an example of the analysis results of the period of the detection signal. [Figure 10] FIG. 10 is a diagram illustrating an example of period data stored in the primary storage device. [Figure 11A] FIG. 11A is a diagram showing an example of a display screen. [Figure 11B] FIG. 11B is a diagram showing another example of the display screen. [Figure 12] FIG. 12 is a diagram illustrating an example of the correction table. [Figure 13] FIG. 13 is a diagram for explaining an example of a process for estimating a peak point. [Figure 14] FIG. 14 is a diagram showing yet another example of the display screen. [Figure 15] FIG. 15 is a diagram showing yet another example of the display screen. [Figure 16] FIG. 16 is a flowchart showing an example of the distance and speed measurement operation by the measurement device. [Figure 17] FIG. 17 is a diagram showing an example of a screen displayed on the display device during measurement. [Figure 18] FIG. 18 is a diagram showing an example of the waveform of the detection signal before and after correction. [Figure 19] FIG. 19 is a diagram showing an example of a conversion table that defines the relationship between the beat frequency and the distance. [Figure 20A] FIG. 20A is a diagram showing an example of a conversion table for up-chirp that defines the relationship between beat frequency and distance. [Figure 20B] FIG. 20B is a diagram showing an example of a conversion table for down-chirp that defines the relationship between beat frequency and distance. [Figure 21] FIG. 21 is a diagram showing an example of a conversion table that defines the relationship between the frequency difference and the speed. [Figure 22A] FIG. 22A shows an example of a screen showing the distance measurement results when the object is stationary. [Figure 22B] FIG. 22B shows an example of a screen showing distance and speed measurement results when the target object is moving. [Figure 23A] FIG. 23A is a diagram showing another example of the correction table. [Figure 23B] FIG. 23B is a diagram showing yet another example of the correction table. [Figure 23C] FIG. 23C is a diagram showing yet another example of the correction table. [Figure 24] FIG. 24 is a diagram for explaining the operation in the first modification of the first embodiment. [Figure 25] FIG. 25 is a block diagram showing a schematic configuration of a measurement device according to the third modification of the first embodiment. [Figure 26A] FIG. 26A is a diagram showing an example of an up-chirp correction table and a down-chirp correction table according to the third modification of the first embodiment. [Figure 26B] FIG. 26B is a diagram showing another example of the up-chirp correction table and the down-chirp correction table in the third modification of the first embodiment. [Figure 27] FIG. 27 is a block diagram showing the configuration of a measurement device in an experimental example for verifying the effects of an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] (Findings that formed the basis of this disclosure) The inventors discovered the following phenomenon regarding interference light in FMCW lidar. Even if the control voltage of the light source is swept linearly to linearly modulate the light frequency, the frequency changes nonlinearly, but the nonlinearity differs between up-chirp, which is the process of increasing the frequency, and down-chirp, which is the process of decreasing the frequency. This phenomenon will be explained below with reference to Figures 1A to 1C.

[0015] 1A to 1C show examples of data obtained from an experiment conducted by the present inventors. In this experiment, a semiconductor laser light source placed at a stationary point emitted laser light toward a stationary target, a reflector. The voltage of a control signal (hereinafter also referred to as "control voltage") input to the light source was linearly swept over a predetermined voltage range and at a predetermined cycle, causing the light source to emit laser light whose frequency was periodically modulated. An interference optical system was used to cause interference between the reflected light from the reflector and the emitted light from the light source, and the interference light was detected by a photodetector, and the acquired signal was recorded.

[0016] Figure 1A is a graph showing an example of the change in the control voltage applied to the light source over time per cycle. In this experiment, the control signal was swept so that the voltage varied in a triangular waveform as shown in Figure 1A. This control signal included an up-chirp, in which the voltage increased from a lower limit to an upper limit, and a down-chirp, in which the voltage decreased from the upper limit to the lower limit. The period in which the control voltage increased is called the "up-chirp period," and the period in which the control voltage decreased is called the "down-chirp period."

[0017] 1B is a graph showing the time variation of the electrical signal obtained by detecting the interference light (hereinafter also referred to as the "detection signal" or "interference wave signal"). The graph shown in FIG. 1B shows the potential fluctuation of the interference wave signal, which reflects the time variation of the intensity of the interference wave.

[0018] Figure 1C shows the time variation of the instantaneous frequency of the interference signal shown in Figure 1B. The instantaneous frequency can be obtained by frequency analysis of the waveform shown in Figure 1B. This frequency is called the "beat frequency."

[0019] 1A to 1C, the horizontal axis represents time. All graphs show signal changes over one control voltage period. Hereinafter, the control voltage period may be referred to as the "modulation period."

[0020] In this experiment, light was projected from a stationary point onto a stationary target. If the optical frequency were swept linearly in response to the linear sweep of the control voltage, the frequency of the interference signal (i.e., the beat frequency) should be constant except for the brief period between the up-chirp and down-chirp periods. However, the experimental results showed that the beat frequency was not constant during either the up-chirp or down-chirp periods. Furthermore, the beat frequency showed different trends in change between the up-chirp and down-chirp periods. As shown in Figure 1C, during the up-chirp period, the frequency of the interference signal gradually increased, and then repeated increases and decreases above a certain frequency. On the other hand, during the down-chirp period, the frequency of the interference signal increased sharply, but remained at a lower frequency than during the up-chirp period. After repeated increases and decreases, it then rapidly decreased. Thus, the interference signal exhibited nonlinear fluctuations with respect to both the control voltage and time in both the up-chirp and down-chirp periods. Furthermore, the nonlinearity of the frequency of the interference wave with respect to the control voltage and time differs depending on the laser element used as the light source and its operating state. The reason for this phenomenon is thought to be as follows: The way in which the heat imparted to the laser element by the current driving the laser element changes over time varies depending on the manner in which the control voltage changes. This difference in the way of change affects the time-dependent changes in the cavity length, gain curve, and oscillation mode of the laser element, and is thought to result in differences in the fluctuations in the laser oscillation frequency.

[0021] If the beat frequency varies with respect to the control voltage or time, and the nonlinearity of the frequency modulation differs between up-chirp and down-chirp, the distance and velocity of the target cannot be uniquely determined. To stabilize the beat frequency fluctuations, it is possible to integrate (i.e., average) the spectrum obtained by frequency analysis with respect to the control voltage or time. However, such integration increases the spectral linewidth of the beat signal, making it difficult to determine the peak frequency of the beat signal, and reducing the accuracy of distance and velocity measurements.

[0022] As described above, it has been found that the above-mentioned problems occur in FMCW LIDAR. To solve the above problems, the inventors have conceived the configuration of the embodiment of the present disclosure described below. The inventors have conceived the idea that by preparing different correction data for the up-chirp period and the down-chirp period and correcting the detected signal of the interference wave using the correction data during measurement, the accuracy of distance and / or velocity measurement can be improved. Exemplary embodiments of the present disclosure will be described below.

[0023] A measurement device according to an embodiment of the present disclosure includes a light source, an interference optical system, a photodetector, a processing circuit, and a storage device. The light source emits frequency-modulated light. The interference optical system separates the light emitted from the light source into reference light and output light, and generates interference light between the reference light and reflected light resulting from reflection of the output light by an object. The photodetector receives the interference light and outputs a detection signal corresponding to the intensity of the interference light. The processing circuit modulates the frequency of the light emitted from the light source with a cycle including an up-chirp period in which the frequency increases and a down-chirp period in which the frequency decreases, and generates and outputs measurement data related to the distance and / or velocity of the object based on the detection signal. The storage device stores first correction data for the up-chirp period and second correction data for the down-chirp period. The processing circuit calculates the detection signal corresponding to the up-chirp period. Part ofa first corrected signal obtained by correcting the signal based on the first correction data, and / or the detection signal corresponding to the down-chirp period. Part of The measurement data is generated based on a second corrected signal obtained by correcting the measured value based on the second correction data.

[0024] According to the above configuration, the detection signal is corrected based on different correction data during the up-chirp and down-chirp periods, thereby suppressing degradation of measurement performance due to the different nonlinearities of frequency changes during the up-chirp and down-chirp periods.

[0025] The processing circuit may determine the frequency of the first correction signal and the frequency of the second correction signal, determine the distance from the measurement device to the object based on the frequency of the first correction signal and the frequency of the second correction signal, and generate the measurement data including information about the distance. For example, the processing circuit may calculate an average value of the frequency of the first correction signal and the frequency of the second correction signal and determine the distance to the object from the average value. Such an operation allows for more accurate measurement of the distance. Note that data such as a table or function defining the correspondence between frequency and distance may be pre-recorded in a storage device. The processing circuit can determine the distance from the frequency based on the data.

[0026] The processing circuit may determine the frequency of the first correction signal and the frequency of the second correction signal, determine the velocity of the object based on the difference between the frequency of the first correction signal and the frequency of the second correction signal, and generate the measurement data including information about the velocity. Such an operation allows the velocity of the object to be measured more accurately. Note that data such as a table or function defining the correspondence between the difference between the frequency of the first correction signal and the frequency of the second correction signal and the velocity may be stored in advance in a storage device. The processing circuit can determine the velocity from the frequency difference based on the data.

[0027] The processing circuit may change the frequency of the light emitted from the light source by changing a control voltage applied to the light source. The first correction data and the second correction data may be table or function data that define a correspondence relationship between the control voltage and a correction value. The processing circuit may correct the detection signal based on the correction value corresponding to the control voltage. Such an operation can mitigate the effect of nonlinearity of frequency modulation that changes depending on the value of the control voltage, thereby improving distance and / or speed measurement performance.

[0028] The correction value may be, for example, a coefficient for correcting the period of the detection signal. In this case, the processing circuit can determine the period from the detection signal and correct the period by multiplying the period by the correction value. Using the detection signal corrected in this way can improve the performance of measuring distance and / or velocity.

[0029] The first correction data may be data of a table or function defining the correspondence between the control voltage and the correction value during a first period that is part of the up-chirp period. The second correction data may be data of a table or function defining the correspondence between the control voltage and the correction value during a second period that is part of the down-chirp period. The processing circuit may extract a first signal corresponding to the first period and a second signal corresponding to the second period from the detection signal, correct the first signal based on the correction value in the first correction data to generate the first correction signal, and correct the second signal based on the correction value in the second correction data to generate the second correction signal. For example, periods during which signal fluctuations are relatively stable may be selected as the first and second periods. By extracting only a portion of the up-chirp period and down-chirp period during which signal fluctuations are relatively stable and correcting the signal in this manner, more accurate measurements are possible.

[0030] The interference optical system may be configured to separate the light emitted from the light source into the output light, a first reference light serving as the reference light, and a second reference light. The measurement device may further include a measuring instrument for measuring the wavelength or frequency of the second reference light. The first correction data and the second correction data may be table or function data defining a correspondence relationship between the wavelength or frequency of the second reference light and a correction value. Because there is a correlation between the control voltage and the frequency and wavelength of the light emitted from the light source, the correction value can be determined based on the frequency or wavelength of the emitted light instead of the control voltage. Such an operation can achieve the same effect as determining the correction value based on the control voltage.

[0031] The first correction data may be data of a table or function specifying the correspondence between the wavelength or frequency of the second reference beam and the correction value during a first period that is part of the up-chirp period. The second correction data may be data of a table or function specifying the correspondence between the wavelength or frequency of the second reference beam and the correction value during a second period that is part of the down-chirp period. The processing circuit may extract a first signal corresponding to the first period and a second signal corresponding to the second period from the detection signal, correct the first signal based on the correction value in the first correction data to generate the first correction signal, and correct the second signal based on the correction value in the second correction data to generate the second correction signal. For example, periods in which signal fluctuations are relatively stable may be selected as the first and second periods. By extracting only a portion of the up-chirp period and down-chirp period in which signal fluctuations are relatively stable and correcting the signal in this manner, more accurate measurements are possible.

[0032] The processing circuit may cause the light source to emit light having a constant frequency modulation period. The first correction data and the second correction data may be table or function data that defines a correspondence relationship between a phase within each period in the frequency modulation and a correction value. Alternatively, the first correction data and the second correction data may be table or function data that defines a correspondence relationship between a time from a reference time point in the frequency modulation of the light source and a correction value.

[0033] The first correction data and the second correction data may be table or function data including information on correction values ​​for changing the sampling timing of the detection signal, and the processing circuit can correct the detection signal by determining the sampling timing of the detection signal in accordance with the correction values.

[0034] According to another embodiment of the present disclosure, a method is executed by a computer in a system including a measurement device. The measurement device includes a light source that emits light whose frequency is modulated in a cycle including an up-chirp period in which the frequency increases and a down-chirp period in which the frequency decreases, an interference optical system that separates the light emitted from the light source into reference light and output light and generates interference light between the reference light and reflected light generated when the output light is reflected by an object, a photodetector that receives the interference light and outputs a detection signal corresponding to the intensity of the interference light, and a storage device that stores first correction data for the up-chirp period and second correction data for the down-chirp period. The method includes: Part of a first corrected signal obtained by correcting the first signal based on the first correction data, and / or the detection signal corresponding to the down-chirp period. Part of generating a second correction signal by correcting the first correction signal based on the second correction data, and generating and outputting measurement data regarding the distance and / or speed based on the first correction signal and / or the second correction signal.

[0035] According to yet another embodiment of the present disclosure, there is provided a computer program executed by a computer in a system including a measurement device. The measurement device includes a light source that emits light whose frequency is modulated in a cycle including an up-chirp period in which the frequency increases and a down-chirp period in which the frequency decreases, an interference optical system that separates the light emitted from the light source into reference light and output light and generates interference light between the reference light and reflected light generated when the output light is reflected by an object, a photodetector that receives the interference light and outputs a detection signal corresponding to the intensity of the interference light, and a storage device that stores first correction data for the up-chirp period and second correction data for the down-chirp period. The computer program causes the computer to generate the detection signal corresponding to the up-chirp period. Part of a first corrected signal obtained by correcting the first signal based on the first correction data, and / or the detection signal corresponding to the down-chirp period. Part of generating a second correction signal by correcting the first correction signal based on the second correction data, and generating and outputting measurement data regarding the distance and / or speed based on the first correction signal and / or the second correction signal.

[0036] In this disclosure, all or part of a circuit, unit, device, component, or part, or all or part of a functional block in a block diagram, may be implemented by one or more electronic circuits, including, for example, a semiconductor device, a semiconductor integrated circuit (IC), or an LSI (large scale integration). An LSI or IC may be integrated on a single chip or may be configured by combining multiple chips. For example, functional blocks other than memory elements may be integrated on a single chip. While the terms LSI and IC are used here, the term may be changed depending on the degree of integration, and may be referred to as a system LSI, a VLSI (very large scale integration), or an ULSI (ultra large scale integration). A field programmable gate array (FPGA), which is programmable after LSI fabrication, or a reconfigurable logic device, which can reconfigure connections within an LSI or set up circuit partitions within an LSI, may also be used for the same purpose.

[0037] Furthermore, all or part of the functions or operations of a circuit, unit, device, component, or section can be implemented by software processing. In this case, the software is recorded on one or more non-transitory recording media such as ROMs, optical disks, hard disk drives, etc., and when the software is executed by a processor, the functions specified in the software are performed by the processor and peripheral devices. A system or device may include one or more non-transitory recording media on which software is recorded, a processor, and necessary hardware devices, such as interfaces.

[0038] Exemplary embodiments of the present disclosure will be described in detail below. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, components, component placement and connection configurations, steps, step order, display screen layout, and the like shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not recited in the independent claims that represent the highest concepts will be described as optional components. Furthermore, each figure is a schematic diagram and is not necessarily an exact illustration. Furthermore, in each figure, the same or similar components are designated by the same reference numerals. Duplicate descriptions may be omitted or simplified.

[0039] (Embodiment 1) A measurement device according to a first exemplary embodiment of the present disclosure will be described. The measurement device of this embodiment is a distance measuring device that measures the distance to an object using FMCW-LiDAR technology. The measurement device may measure the speed of the object in addition to or instead of the distance. The measurement device may be mounted on a moving object such as an autonomous vehicle, an automated guided vehicle (AGV), an unmanned aerial vehicle (UAV), or a mobile robot. The measurement device may be mounted on any device and used, not limited to moving objects.

[0040] [composition] Fig. 2 is a block diagram showing a schematic configuration of the measurement device 100 according to this embodiment. In Fig. 2, thick arrows represent the flow of light, and thin arrows represent the flow of signals or data. Fig. 2 also shows an object 300, the object of which distance and / or speed is to be measured, and a display device 210 and a control device 220 connected to the measurement device 100. The object 300 may be any object, such as an obstacle, a person, or a moving body (e.g., an automobile, a motorcycle, a mobile robot, or a drone).

[0041] The measurement device 100 shown in Fig. 2 includes a light source 110, an interference optical system 120, a photodetector 130, a processing circuit 140, and a storage device 150. The light source 110 can change the frequency of the emitted light in response to a control signal output from the processing circuit 140. The interference optical system 120 separates the light emitted from the light source 110 into reference light and output light, and generates interference light by causing the reference light to interfere with the reflected light generated when the output light is reflected by the object 300. The interference light is incident on the photodetector 130. The detailed configurations of the light source 110 and the interference optical system 120 will be described later.

[0042] The photodetector 130 receives the interference light and generates and outputs an electrical signal corresponding to the intensity of the interference light. This electrical signal will be referred to hereinafter as a "detection signal" or an "interference wave signal." The photodetector 130 includes one or more light-receiving elements. The light-receiving elements include photoelectric conversion elements such as photodiodes. The photodetector 130 may also be a sensor, such as an image sensor, that includes multiple light-receiving elements.

[0043] The processing circuit 140 is an electronic circuit that controls the light source 110 and performs processing based on the detection signal output from the photodetector 130. The processing circuit 140 may include a control circuit that controls the light source 110 and a signal processing circuit that performs signal processing based on the detection signal. The processing circuit 140 may be configured as a single circuit, or may be a collection of multiple separate circuits. The processing circuit 140 sends a control signal to the light source 110. The control signal causes the light source 110 to periodically change the frequency of the light emitted within a predetermined range. In other words, the control signal is a signal that sweeps the frequency of the light emitted from the light source 110. The control signal is a signal that inputs a voltage that periodically fluctuates with a certain amplitude to the light source 110. The processing circuit 140 acquires the detection signal output from the photodetector 130 while the light source 110 is emitting frequency-modulated light. The processing circuit 140 outputs the acquired detection signal Part ofis corrected based on the correction data stored in the storage device 150. The processing circuit 140 determines the distance to the object 300 and / or the speed of the object 300 based on the corrected detection signal. The processing circuit 140 generates and outputs data indicating the distance and / or speed. This data will be referred to as "measurement data" hereinafter.

[0044] The storage device 150 includes any storage medium, such as a semiconductor memory, a magnetic disk, or an optical disk. The storage device 150 stores correction data used in the correction process executed by the processing circuit 140. In this embodiment, the correction data includes a first correction table for the up-chirp period and a second correction table for the down-chirp period. The up-chirp period is a period during which the voltage of the control signal monotonically increases and the frequency of the light emitted from the light source 110 increases. The down-chirp period is a period during which the voltage of the control signal monotonically decreases and the frequency of the light emitted from the light source 110 decreases. The first correction table is used to correct the detection signal of the interference light based on the light emitted during the up-chirp period. The second correction table is used to correct the detection signal of the interference light based on the light emitted during the down-chirp period. Each correction table defines, for example, the correspondence between the operating state of the light source 110 and a correction value. Details of these correction tables will be described later. Each correction table is an example of correction data. The correction data is not limited to a correction table, but may be data in any format, such as a function that defines the correspondence between the operating state and the correction value of the detection signal. The storage device 150 also stores a computer program executed by the processing circuit 140.

[0045] The processing circuit 140 and the memory device 150 may be integrated on a single circuit board or may be provided on separate circuit boards. The functions of the processing circuit 140 may be distributed across multiple circuits. At least a portion of the functions of the processing circuit 140 may be realized by an external computer installed in a location remote from the other components. Such an external computer may control the operations of the light source 110 and the photodetector 130 or perform signal processing based on the detection signal output from the photodetector 130 via a wired or wireless communication network.

[0046] Processing circuitry 140 performs the following operations when making distance and / or velocity measurements of object 300. A control signal is sent to the light source 110, causing the light source 110 to emit light whose frequency is modulated in a cycle including an up-chirp period in which the frequency increases and a down-chirp period in which the frequency decreases. The waveform of the detection signal is corrected based on the first correction table for up-chirp and the second correction table for down-chirp stored in the storage device 150. · The beat frequency is determined for each of the up-chirp and down-chirp periods by frequency analysis based on the corrected waveform. Determine the distance to the object 300 based on the beat frequency in at least one of the up-chirp period and the down-chirp period. Determine the velocity of the object 300 based on the difference in beat frequency during the up-chirp and down-chirp periods. Outputs measurement data including distance and speed information.

[0047] The measurement data is output to, for example, a display device 210. When the measurement device 100 is mounted on a moving body, the measurement data may be output to a control device 220 that controls the operation (e.g., steering, speed, etc.) of the moving body. The measurement data may be recorded in the storage device 150 or an external storage device.

[0048] The display device 210 displays the distance and / or speed based on the measurement data. The display device 210 is, for example, a display that displays numerical values ​​or graphs. Instead of or in addition to the display device 210, the measurement data may be output to an output device such as a speaker that outputs audio that reads out numerical values, or a printer that prints out numerical values ​​or graphs.

[0049] Next, a more detailed configuration example of the light source 110 and the interference optical system 120 will be described.

[0050] 3 is a block diagram showing an example configuration of the light source 110 and the interference optical system 120. In this example, the light source 110 includes a drive circuit 111 and a light-emitting element 112. The drive circuit 111 receives a control signal output from the processing circuit 140, generates a drive current signal corresponding to the control signal, and inputs the drive current signal to the light-emitting element 112. The light-emitting element 112 may be an element that emits laser light with high coherence, such as a semiconductor laser element. The light-emitting element 112 emits laser light whose frequency is modulated in response to the drive current signal.

[0051] The frequency of the laser light emitted from the light emitting element 112 is modulated at a constant period. The frequency modulation period may be, for example, 1 microsecond (μs) or more and 10 milliseconds (ms) or less. The frequency modulation amplitude may be, for example, 100 MHz or more and 1 THz or less. The wavelength of the laser light may be, for example, in the near-infrared wavelength range of 700 nm or more and 2000 nm or less. In sunlight, the amount of near-infrared light is less than the amount of visible light. Therefore, by using near-infrared light as the laser light, the influence of sunlight can be reduced. Depending on the application, the wavelength of the laser light may be in the visible light wavelength range of 400 nm or more and 700 nm or less, or in the ultraviolet light wavelength range.

[0052] FIG. 4 shows examples of the control signal output from the processing circuit 140 and the drive current signal output from the drive circuit 111. Parts (a) and (b) of FIG. 4 show examples of the waveforms of the control signal and the drive current signal, respectively. The control signal applies a voltage that fluctuates with a predetermined period and a predetermined amplitude to the drive circuit 111 of the light source 110. For example, as shown in part (a) of FIG. 4, the voltage of the control signal can be modulated into a triangular waveform. The voltage of the control signal is not limited to a triangular waveform, but may also be modulated into a sawtooth waveform. A control signal whose voltage repeatedly changes linearly, such as a triangular or sawtooth waveform, can sweep the frequency of the light emitted from the light-emitting element 112 in a manner that is close to linear. However, as mentioned above, the frequency sweep is not completely linear. The amplitude of the modulation waveform of such a control signal is called the modulation voltage amplitude, and the voltage at the center of the modulation range is called the bias voltage. The control signal applies a voltage that fluctuates around the bias voltage to the drive circuit 111 of the light source 110.

[0053] The drive circuit 111 converts the control signal into a drive current signal and drives the light-emitting element 112 with the drive current signal. As shown in part (b) of Figure 4, the drive current signal changes with a waveform corresponding to the control signal. The modulation range, i.e., amplitude, of the drive current signal is called the modulation current amplitude, and the current in the center of the modulation range is called the bias current. When the voltage of the control signal increases, the drive current signal increases, and the frequency of the laser light emitted from the light-emitting element 112 increases (i.e., the wavelength becomes shorter). Conversely, when the voltage of the control signal decreases, the drive current signal decreases, and the frequency of the laser light emitted from the light-emitting element 112 decreases (i.e., the wavelength becomes longer).

[0054] The interference optical system 120 in the example shown in FIG. 3 includes a splitter 121, a mirror 122, and a collimator 123. The splitter 121 splits the laser light emitted from the light emitting element 112 of the light source 110 into reference light and output light, and combines the light reflected from the object 300 with the reference light to generate interference light. The mirror 122 reflects the reference light back to the splitter 121. The collimator 123 includes a collimating lens and irradiates the output light with a nearly parallel divergence angle onto the object 300. Note that the interference optical system 120 is not limited to the configuration shown in FIG. 3 and may be, for example, a fiber optical system. In this case, a fiber coupler may be used as the splitter 121. The reference light does not necessarily need to be reflected by the mirror 122; for example, the reference light may be returned to the splitter 121 by routing an optical fiber.

[0055] 5 is a block diagram showing a configuration example of a measurement apparatus 100 in which the interference optical system 120 is a fiber optical system. In the example shown in FIG. 5, the interference optical system 120 includes a first fiber splitter 125, a second fiber splitter 126, and an optical circulator 127. The first fiber splitter 125 splits the laser light 20 emitted from the light source 110 into a reference light 21 and an output light 22. The first fiber splitter 125 inputs the reference light 21 to the second fiber splitter 126 and inputs the output light 22 to the optical circulator 127. The optical circulator 127 inputs the output light 22 to a collimator 123. The optical circulator 127 also inputs reflected light 23, which is generated when the output light 22 is irradiated onto the object 300, into the second fiber splitter 126. The second fiber splitter 126 causes the interference light 24 between the reference light 21 and the reflected light 23 to enter the photodetector 130. The collimator 123 shapes the beam shape of the output light 22 and outputs the output light 22 towards the object 300.

[0056] The measurement device 100 may further include an optical deflector that changes the direction of the emitted light. FIG. 6 is a block diagram showing an example of the measurement device 100 that includes an optical deflector 170. The optical deflector 170 may be, for example, a MEMS ( microelectromechanical systemThe optical deflector 170 may include a gyro mirror or a galvanometer mirror. The optical deflector 170 can change the direction of output light 22 by changing the angle of the mirror according to commands from the processing circuit 140. This enables wide-range ranging by beam scanning. The optical deflector 170 is not limited to the above configuration and may be, for example, a beam scanning device using an optical phased array and a slow-light waveguide, as described in International Publication No. WO 2019 / 130720.

[0057] Next, the FMCW-LiDAR technology used in this embodiment will be briefly described with reference to FIGS. 7A and 7B.

[0058] FIG. 7A is a schematic diagram illustrating an example of the temporal change in the frequency of the reference light and the reflected light when the object 300 is stationary. Here, we will explain an example in which the frequency changes in a triangular waveform. In FIG. 7A, the solid line represents the reference light, and the dashed line represents the reflected light. The frequency of the reference light shown in FIG. 7A increases linearly over one period and then decreases linearly by the same amount. The frequency of the reflected light is shifted along the time axis compared to the frequency of the reference light by the amount of time it takes for the output light to be emitted from the measurement device 100, reflected by the object 300, and returned. Therefore, the interference light between the reference light and the reflected light has a frequency corresponding to the difference between the frequency of the reflected light and the frequency of the reference light. The double arrow in FIG. 7A represents the difference between the two frequencies. The photodetector 130 outputs a signal indicating the intensity of the interference light. This signal is called a beat signal. The frequency of the beat signal, i.e., the beat frequency, is equal to the above-mentioned frequency difference. The processing circuit 140 can calculate the distance from the measurement device 100 to the object 300 based on the beat frequency.

[0059] FIG. 7B is a diagram illustrating the temporal change in the frequency of the reference light and the reflected light when the object 300 approaches the measurement device 100. When the object 300 approaches, the frequency of the reflected light shifts in the increasing direction along the frequency axis due to Doppler shift compared to when the object 300 is stationary. The amount of frequency shift of the reflected light depends on the magnitude of the component of the velocity vector at a certain part of the object 300 projected onto the direction of the reflected light. The beat frequency differs when the frequencies of the reference light and the reflected light increase linearly and when they decrease linearly. In the example shown in FIG. 7B, the beat frequency when both frequencies decrease linearly is higher than the beat frequency when both frequencies increase linearly. The processing circuit 140 can calculate the velocity of the object 300 based on the difference between these beat frequencies. When the object 300 moves away from the measurement device 100, the frequency of the reflected light shifts in the decreasing direction along the frequency axis compared to when the object 300 is stationary. In this case as well, the velocity of the object 300 can be calculated based on the difference in beat frequency between when the frequencies of the reference light and the reflected light increase linearly and when they decrease linearly.

[0060] [Operation] The operation of the measurement device 100 of this embodiment will be described below.

[0061] The operation of the measurement device 100 of this embodiment can be broadly divided into two processes: (1) calibration and (2) measurement. Calibration is performed, for example, by a person in charge at the manufacturer (hereinafter referred to as the "operator") before shipping the measurement device 100. Distance measurement is mainly performed by the user of the measurement device 100.

[0062] In the calibration, a correction table for up-chirp and a correction table for down-chirp are generated and stored in the storage device 150. The operation of the calibration is outlined below. While the measurement device 100 is stationary, the light source 110 emits a laser beam toward a stationary object. The laser beam is controlled by a triangular waveform control voltage, for example, as shown in FIG. The photodetector 130 detects the interference light between the reflected light from the object and the reference light, and outputs a detection signal. Based on the detection signal, the processing circuit 140 generates a correction table for correcting the detection signal so that the frequency of the spectral peak of the interference light corresponding to the up-chirp period and the frequency of the spectral peak of the interference light corresponding to the down-chirp period correspond to the distance to the target regardless of the magnitude of the control voltage, and stores the correction table in the memory device 150.

[0063] In the measurement operation, the distance to the object and / or the speed of the object are measured from the detection signal corrected based on the correction table generated by calibration. The outline of the operation in the measurement process is as follows. The light source 110 emits a laser beam toward an object. The laser beam is controlled by a control voltage having a triangular waveform, for example, as shown in FIG. The photodetector 130 detects the interference light between the reflected light from the object and the reference light, and outputs a detection signal. Processing circuit 140 corrects the detection signal according to the control voltage based on a correction table for at least one of the up-chirp period and the down-chirp period, and determines the distance from measurement device 100 to the object based on the spectral peak of the corrected detection signal. Furthermore, processing circuit 140 determines the relative velocity between the object and measurement device 100 from the difference between the spectral peak in the up-chirp period and the spectral peak in the down-chirp period.

[0064] Each operation will be explained in more detail below.

[0065] [Calibration operation] Fig. 8 is a flowchart showing the calibration operation by the measurement device 100. In the calibration, the measurement device 100 executes the operations of steps S1110 to S1230 shown in Fig. 8. The operation of each step will be described below.

[0066] The measuring device 100 starts the calibration operation in response to input of a calibration operation start command via an input means (not shown).

[0067] <Step S1110> The processing circuit 140 causes the light source 110 to start emitting laser light. The processing circuit 140 applies a control voltage that periodically fluctuates at a predetermined amplitude, thereby emitting laser light whose frequency periodically fluctuates within a certain range. The laser light is separated into output light and reference light by the interference optical system 120. The output light irradiates a stationary object (e.g., a reflector). The interference optical system 120 causes the interference light between the reflected light from the object and the reference light to enter the photodetector 130. The photodetector 130 receives the interference light and outputs a detection signal according to the intensity of the interference light.

[0068] <Step S1120> The processing circuit 140 determines whether an end command for data processing has been input. The processing circuit 140 determines, for example, whether an end command has been input by the user. The end command can be input, for example, by the user pressing a specific button on a screen displayed on the display device 210. Details of the screen displayed on the display device 210 will be described later. If a data end command has not been input, the process proceeds to step S1130. If a data end command has been input, the process proceeds to step S1190.

[0069] <Step S1130> The processing circuit 140 acquires the detection signal output from the photodetector 130. The processing circuit 140 stores the detection signal in a primary storage device such as a memory within the processing circuit 140.

[0070] <Step S1140> Processing circuit 140 determines whether detection signals with a data length equal to or greater than one cycle of frequency modulation of the laser light output by light source 110, i.e., one cycle of rise and fall of the control voltage, have been accumulated. If the data length of the accumulated detection signals is equal to or greater than one cycle of frequency modulation, processing proceeds to step S1150. If the data length of the accumulated detection signals is less than one cycle of frequency modulation, processing returns to step S1130.

[0071] <Step S1150> Processing circuit 140 extracts signals during the up-chirp period and signals during the down-chirp period from the detection signals stored in the temporary storage device, and performs the processes of steps S1160 and S1170 independently for the extracted signals during the up-chirp period and down-chirp period.

[0072] <Step S1160> The processing circuit 140 analyzes the period of the extracted detection signal. For example, one method of analyzing the period is to identify the maximum point of the upwardly convex portion of the detection signal waveform or the minimum point of the downwardly convex portion, and define the period from the maximum point to the next maximum point or the period from the minimum point to the next minimum point as one period. Alternatively, if the detection signal values ​​are uniformly distributed between positive and negative values, the period may be determined based on zero-crossing points. A zero-crossing point is a point where the signal value changes from positive to negative or from negative to positive. The processing circuit 140 may extract zero-crossing points from the detection signal and define one period as the period from a positive-to-negative zero-crossing point to the next positive-to-negative zero-crossing point or from a negative-to-positive zero-crossing point to the next negative-to-positive zero-crossing point.

[0073] FIG. 9 is a graph showing an example of the analysis results of the period of the detection signal. In this example, a waveform showing the relationship between the voltage of the control signal and the voltage of the detection signal is plotted. The control signal voltage at which the voltage of the detection signal reaches the peak of the upward convex part (i.e., the maximum value) is V i , V i+1 , V i+2,..., the period is P i , P i+1 , P i+2 In this example, the control signal voltage is V i From the time V i+1 The length of time up to the point is the period P i It is defined as follows.

[0074] <Step S1170> The processing circuit 140 stores the determined period in a primary storage device within the processing circuit 140. For example, the processing circuit 140 stores the determined period in the primary storage device in association with the value of the corresponding control voltage or the elapsed time from a reference point within one period.

[0075] 10 shows an example of period data stored in the primary storage device. In this example, the control voltage and period are associated and recorded for each of the up-chirp and down-chirp. Instead of the control voltage, the period may be associated and recorded with the time from a reference point.

[0076] <Step S1180> Processing circuitry 140 displays the results of the period analysis on display device 210. For example, processing circuitry 140 displays a graph of the relationship between the control voltages generated for each up-chirp and down-chirp and the period for each chirp. After step S1180, the process returns to step S1120, and the above-described operations are repeated.

[0077] FIG. 11A is a diagram showing an example of a display screen displayed by display device 210. In this example, the period of the interference wave in the up-chirp and the period of the interference wave in the down-chirp are plotted in correspondence with the control voltage. Other information that may be displayed on the display screen include the date, the distance to the object being calibrated, and the frequency sweep period or frequency. The display screen shown in FIG. 11A also displays a button 410 for determining the correction function and a button 420 for forcibly terminating the calibration. The button 410 for determining the correction function is used to terminate the operations from step S1130 to step S1170 and to proceed to step S1190 and beyond. The button 420 for forcibly terminating the operation is used to immediately terminate the operation. Pressing the button 420 for forcibly terminating the operation immediately terminates the operation at any point in the flowchart of FIG. 8. The flowchart of FIG. 8 does not show the forcible termination operation that occurs when the button 420 for forcibly terminating the operation shown in FIG. 11A is pressed.

[0078] <Step S1190> When button 410 for determining the correction function on the display screen is pressed, processing circuit 140 determines in step S1120 that a command to end data processing has been issued, and causes light source 110 to stop emitting laser light.

[0079] <Step S1200> The processing circuit 140 approximates a graph of the period of the interference wave versus the control voltage with a model function. The model function is, for example, a polynomial of degree two or higher, and can be determined using, for example, the least squares method. The processing circuit 140 displays the determined model function on the display device 210 as a correction function.

[0080] 11B is a diagram showing an example of the screen displayed in step S1200. In this example, graphs of approximate functions are displayed as dotted lines superimposed on the up-chirp graph and the down-chirp graph. Additionally, a button 430 for writing the table, a button 440 for redoing the calibration, and a button 420 for forcibly terminating the calibration are displayed.

[0081] <Step S1210> In step S1210, processing circuit 140 determines whether an instruction has been issued to generate a correction table using the correction function determined in step S1200 and write the table to storage device 150. The instruction to write the table is issued when "Write Table" button 430 shown in FIG. 11B is pressed. If button 430 is pressed, the process proceeds to step S1220. If button 430 is not pressed and a predetermined time has elapsed, or if "Recalibrate" button 440 is pressed, the process returns to step S1110, and calibration is resumed.

[0082] <Step S1220> Processing circuit 140 creates a correction table based on the function values ​​generated in step S1200. Specifically, processing circuit 140 calculates a correction value for each control voltage by dividing a value corresponding to the distance to the calibration target by the value of the correction function. If the control voltage is V and the correction function is f(V), the correction value corresponding to the control voltage V is a / f(V). Processing circuit 140 generates a correction table that specifies the correspondence between the control voltage and the correction value for each up-chirp and down-chirp. The correction table is used to correct the period or frequency of the detection signal when measuring distance or velocity.

[0083] <Step S1230> Processing circuit 140 outputs the up-chirp correction table and the down-chirp correction table generated in step S1220 to storage device 150. Storage device 150 stores these correction tables.

[0084] FIG. 12 shows an example of a correction table stored in storage device 150. In this example, the correction tables for up-chirp and down-chirp have the same data format. Each correction table holds information on the value of the control voltage applied to light source 110 and a period correction ratio, which is a numerical value for correcting the period of the detection signal. Note that the format of the correction table is not limited to the example shown in the figure. Regardless of the format, the correction table may include information on a correction value for adjusting a detection signal period that is too long or too short.

[0085] The period correction ratio may be, for example, a value obtained by normalizing the period by a predetermined constant so that the beat frequency after correcting the waveform of the detection signal becomes a value theoretically derived from the distance to the reference object, the modulation period, the modulation frequency range, and the speed of light. The constant may be set to a value such that the beat frequency of the waveform of the detection signal after correction matches the theoretical value.

[0086] The measurement apparatus 100 in this embodiment can accumulate sufficient data to determine the correction function by repeating steps S1120 to S1180. Furthermore, by repeating steps S1110 to S1210, if the data is unstable, the calibration operation can be performed again to create a preferable correction table.

[0087] In step S1160, the period may be determined to be, for example, the period from the maximum point of an upwardly convex portion to the maximum point of the next upwardly convex portion, or the period from the minimum point of a downwardly convex portion to the minimum point of the next downwardly convex portion, but the method for determining the period is not limited to such methods. If there are insufficient sampling points for the period in the digitized data, the maximum point of an upwardly convex portion or the minimum point of a downwardly convex portion formed by the data points may not coincide with the peak points of the actual signal. In such cases, the peak points of the signal may be estimated by fitting a model waveform.

[0088] FIG. 13 is a diagram illustrating an example of a process for estimating peak points. In the example of FIG. 13, the processing circuit 140 includes an analog-to-digital (A / D) converter and a primary storage device such as a memory. The processing circuit 140 digitizes the waveform of the detection signal using the A / D converter and stores the digitized waveform in the primary storage device. In FIG. 13, multiple digitized data points are indicated by circles. The horizontal axis in the diagram represents time. The processing circuit 140 uses a sine wave as a model wave and determines a model wave that minimizes the distance from the data points. FIG. 13 illustrates a sine wave that is minimally distant from the data points and a sine wave that is greater distant from the data points. The processing circuit 140 may determine the period of the detection signal based on the peak points (i.e., maximum points), minimum points, or zero-crossing points of the determined model wave. Note that the period and frequency are inversely related to each other, so determining the period is equivalent to determining the frequency.

[0089] 8, in step S1120, the user determines whether to end data accumulation, but processing circuitry 140 may automatically determine whether to end data accumulation. For example, data accumulation may be automatically terminated based on criteria such as when a predetermined number of data items have been accumulated or when the variation in variance of the accumulated data becomes smaller than a predetermined value. If the determination in step S1120 is made automatically, the display operation in step S1180 may be omitted.

[0090] Furthermore, when the determination of whether to terminate the process in step S1120 is made automatically, a user interface that allows the user to instruct correction of the automatically made termination determination may be displayed on the display device 210. FIG. 14 shows such a user interface. tough11 is a diagram showing an example of a calibration interface. In this example, the up-chirp and down-chirp data and correction functions are sequentially displayed on the display screen, and a button 440 for instructing recalibration is also displayed. The user monitors the displayed correction functions and presses the recalibration button 440 if they determine that the correction functions should be regenerated, or that there is too little data to determine the correction functions, or that the data is inappropriate. In response to this, the processing circuit 140 repeats the operations from step S1120 to step S1180. This allows further accumulation of data for generating the correction functions. As a result, an accurate correction function can be set even if a problem such as noise being mixed into the data occurs for some reason.

[0091] In the flowchart of Figure 8, the correction tables for up-chirp and down-chirp are created in parallel, and the steps for creating the correction tables proceed similarly, but they may also proceed at different times. That is, the determination of the end of data accumulation in step S1120 may be made separately for up-chirp and down-chirp. Also, the determination of whether to write period correction values ​​in step S1210 may be made separately for up-chirp and down-chirp.

[0092] FIG. 15 shows a user interface that allows the decision to write correction values ​​separately for up-chirp and down-chirp. tough1 is a diagram showing an example of an interface. In this example, buttons 450 for determining a correction function are provided for each of the up-chirp graph and the down-chirp graph. The user can press only the button 450 for either the up-chirp or down-chirp for which it is determined that sufficient data has been accumulated to determine the correction function. When one of the buttons 450 is pressed, the processing circuit 140 stops accumulating data for the pressed button and proceeds to determine the correction function. The processing circuit 140 repeats the operation of accumulating further data for the up-chirp or down-chirp for which the button 450 was not pressed. When the user determines to end data accumulation for both chirps and presses both correction function determination buttons 450, the processing circuit 140 causes the light source 110 to stop emitting laser light.

[0093] Regarding the determination of the end of data accumulation in step S1120, processing circuitry 140 may automatically determine the end based on the number of accumulated data or statistical criteria, etc. In this case, it may be possible to set the determination criteria for up-chirp and down-chirp separately.

[0094] [Distance and speed measurement operation] Next, an example of the distance and speed measurement operation by the measurement device 100 will be described.

[0095] Fig. 16 is a flowchart showing an example of the distance and speed measurement operation by the measuring device 100. When measuring distance and speed, the measuring device 100 executes the operations of steps S1110 to S2150 shown in Fig. 16. The operations of steps S1110 to S1150 and S1190 are the same as the operations of the corresponding steps shown in Fig. 8. The operation of each step will be described below.

[0096] The measuring device 100 starts a measuring operation in response to a command to start the measuring operation input by an input means (not shown).

[0097] <Step S1110> The processing circuit 140 causes the light source 110 to start emitting laser light. The processing circuit 140 applies a control voltage that periodically fluctuates at a predetermined amplitude, thereby causing the light source 110 to emit laser light whose frequency periodically fluctuates within a certain range. The laser light is split into output light and reference light by the interference optical system 120. The output light irradiates the object 300. The interference optical system 120 causes interference light between the reflected light from the object 300 and the reference light to enter the photodetector 130. The photodetector 130 receives the interference light and outputs a detection signal according to the intensity of the interference light.

[0098] <Step S1120> The processing circuit 140 determines whether a command to end measurement has been input. For example, the processing circuit 140 determines whether a command to end measurement has been input by a user. The command to end measurement can be input by the user pressing a specific button on a screen displayed on the display device 210, for example.

[0099] 17 is a diagram showing an example of a screen displayed by display device 210 during measurement. This screen includes an end button 520 for instructing the end of measurement. When the user presses this button 520, a command to end measurement is input. If an end command has not been input, processing circuit 140 proceeds to step S1130. If an end command has been input, processing circuit 140 proceeds to step S1190.

[0100] <Step S1130> The processing circuit 140 acquires the detection signal output from the photodetector 130. The processing circuit 140 stores the detection signal in a primary storage device such as a memory within the processing circuit 140.

[0101] <Step S1140> Processing circuit 140 determines whether detection signals with a data length equal to or greater than one cycle of the frequency modulation of the laser light output by light source 110 have been accumulated. If the data length of the accumulated detection signals is equal to or greater than one cycle of the frequency modulation, processing proceeds to step S1150. If the data length of the accumulated detection signals is less than one cycle of the frequency modulation, processing returns to step S1130.

[0102] <Step S1150> The processing circuit 140 extracts signals during the up-chirp period and signals during the down-chirp period from the detection signals stored in the temporary storage device.

[0103] <Step S2110> Processing circuit 140 corrects the signals during the up-chirp period and the down-chirp period extracted in step S1150 by referring to the correction table stored in storage device 150.

[0104] FIG. 18 shows an example of the waveform of the detection signal before and after correction. The solid line indicates the detection signal before correction, and the dashed line indicates the detection signal after correction. The horizontal axis represents the time corresponding to the detection signal before correction. The processing circuit 140 separates the detection signal into a signal for the up-chirp period and a signal for the down-chirp period, and corrects each signal using correction value information stored in a correction table. For example, the processing circuit 140 multiplies the instantaneous value of the period of each chirp signal by the correction value stored in the correction table, thereby shortening the portion of the signal with a longer period than the original period and lengthening the portion with a shorter period than the original period. This allows the signal of each chirp to be corrected so that it maintains a substantially constant period.

[0105] More specifically, processing circuit 140 first extracts one cycle from each chirp signal extracted in step S1150. Extraction of one cycle of the signal can be performed, as in calibration, by extracting the signal portion between two adjacent peaks or zero-crossing points (e.g., points where the signal changes from negative to positive) on the time axis. Next, processing circuit 140 determines the corresponding drive voltage using the starting point of the extracted one cycle of the signal as a reference point. Processing circuit 140 then references the correction table (see FIG. 12 ) stored in storage device 150 to obtain a correction value (i.e., a cycle correction ratio) corresponding to the determined drive voltage. Processing circuit 140 corrects the cycle of the detection signal by multiplying the obtained cycle correction ratio, thereby modifying the waveform of the detection signal. Processing circuit 140 performs the above operation for each cycle of the detection signal to obtain the corrected waveform of the detection signal. This process is performed independently for both the up-chirp period signal and the down-chirp period signal extracted in step S1150. The processing from step S2110 to step S2130 can be performed independently for both the up-chirp period signal and the down-chirp period signal.

[0106] <Step S2120> Processing circuit 140 multiplies each of the up-chirp and down-chirp detection signals corrected in step S2110 by a window function, for example, a Hanning window, to transform the waveform of each signal into a waveform suitable for frequency analysis.

[0107] <Step S2130> The processing circuit 140 performs Fourier transform processing on the detection signals in the up-chirp period and the down-chirp period to generate frequency spectra.

[0108] <Step S2140> Processing circuitry 140 determines the frequency of each chirp (i.e., beat frequency) by extracting the maximum spectral peak from each of the up-chirp and down-chirp frequency spectra generated in step S2130. Processing circuitry 140 then references a conversion table stored in storage device 150 to determine the distance value from the frequency of each chirp period.

[0109] Fig. 19 shows an example of a conversion table that defines the relationship between beat frequency and distance. Such a conversion table can be stored in advance in storage device 150. As shown in Figs. 20A and 20B, conversion tables corresponding to up-chirp and down-chirp respectively may be stored in storage device 150. Furthermore, instead of a conversion table, the relationship between beat frequency and distance may be recorded using data in another format, such as a function.

[0110] 20A and 20B, processing circuit 140 references the up-chirp conversion table to determine the distance from the beat frequency during the up-chirp period. Processing circuit 140 also references the down-chirp conversion table to determine the distance from the beat frequency during the down-chirp period.

[0111] For example, processing circuit 140 determines the final distance by averaging the distance obtained from the beat frequency during the up-chirp period and the distance obtained from the beat frequency during the down-chirp period. Note that processing circuit 140 may also use either the distance obtained from the beat frequency during the up-chirp period or the distance obtained from the beat frequency during the down-chirp period as the final distance.

[0112] Meanwhile, processing circuitry 140 determines the velocity of object 300 based on the difference between the beat frequency during the up-chirp period and the beat frequency during the down-chirp period (hereinafter also referred to as the "frequency difference"). If the beat frequency during the up-chirp period is greater than the beat frequency during the down-chirp period, this indicates that object 300 is moving away. If the beat frequency during the up-chirp period is smaller than the beat frequency during the down-chirp period, this indicates that object 300 is approaching.

[0113] 21 is a diagram showing an example of a conversion table that defines the relationship between frequency difference and speed. Such a conversion table can be generated in advance and stored in storage device 150. Processing circuit 140 can determine speed from the difference frequency by referring to such a conversion table. Note that the conversion table is not limited to this, and other types of data, such as a function that defines the relationship between frequency difference and speed, may also be used.

[0114] <Step S2150> Processing circuit 140 displays the distance and speed determined in step S2140 on display device 210. For example, the distance and speed measurements may be displayed as indicators and / or numerical values, as shown in Figure 17. After step S2150, processing returns to step S1120.

[0115] <Step S1190> If an end command is detected in step S1120, the processing circuitry 140 proceeds to step S1190, where it ends the irradiation of laser light by the light source 110, and ends the operation of the measuring device 100.

[0116] When the object 300 is moving, a difference occurs between the beat frequency during the up-chirp period and the beat frequency during the down-chirp period. Therefore, the processing circuit 140 may display the beat frequency during the up-chirp period and the beat frequency during the down-chirp period on the display device 210. Such a display allows the user to know that the object 300 is moving even when the velocity of the object 300 is not being measured.

[0117] 22A and 22B are diagrams showing examples of a screen displaying the beat frequency for each chirp period. Fig. 22A shows an example of a screen displaying the distance measurement results when the object 300 is stationary. Fig. 22B shows an example of a screen displaying the distance measurement results when the object 300 is moving. speed 22A shows an example of a measurement result screen. In this example, the display device 210 not only displays the distance and velocity measurement results, but also displays indicators indicating the magnitude of the beat frequency during the up-chirp period and the down-chirp period, and a velocity measurement button 530. The processing circuit 140 normally measures only the distance, not the velocity. When the velocity measurement button 530 is pressed by the user, the processing circuit 140 measures the velocity in addition to the distance, and displays the measurement results on the display device 210. The user can check the difference between the beat frequency during the up-chirp period and the beat frequency during the down-chirp period displayed on the screen using the indicator. If there is no difference between the two beat frequencies, as in the example of FIG. 22A, this means that the object 300 is stationary. On the other hand, if there is a difference between the beat frequencies during the up-chirp period and the down-chirp period, as in the example of FIG. 22B, this means that the object 300 is moving. In this case, when the user presses the velocity measurement button 530, the processing circuit 140 measures the velocity and displays the measurement results. In the display example of FIG. 22B, the user 0 It can be seen that the target object 300 is moving at 9 km / h in a direction away from the measurement device 100. This display allows the user to know whether the target object 300 is moving or stationary by looking at the display of the distance and the beat frequencies for the up-chirp period and the down-chirp period, making it possible to take measurements tailored to the target object 300.

[0118] In this embodiment, a correction table or correction function that defines the correspondence between the control voltage and the period correction value for each of the up-chirp and down-chirp is created as the correction data and stored in the storage device 150. The correction data is not limited to such data, and may be, for example, data such as a table or function that defines the drive current of the laser light source and the period correction value. Furthermore, when the frequency modulation of the laser light is performed periodically, data such as a table or function that defines the phase in the modulation period and the period correction value may be used as the correction data.

[0119] The processing circuit 140 in this embodiment corrects the detection signal by correcting the period of the detection signal, which varies nonlinearly with time, based on the correction data. Instead of this method, the same effect may be achieved, for example, by changing the sampling timing of the detection signal. That is, the detection signal may be corrected by appropriately changing the digitization timing, which would normally be sampled at equal time intervals, depending on the control voltage, drive current, or phase.

[0120] 23A shows an example of a correction table containing information on correction values ​​for changing the sampling timing of the detection signal. In this example, the up-chirp correction table and the down-chirp correction table each contain information on the sampling interval corresponding to each value of the drive voltage. Processing circuit 140 may refer to such a table to correct the detection signal by correcting the sampling interval, which is normally equal.

[0121] FIG. 23B shows another example of a correction table. The correction table in this example includes information on the phase of the frequency modulation period of the laser beam and the period correction ratio corresponding to each phase. An FMCW-based lidar device repeatedly modulates the frequency of the laser beam to continuously measure distance and velocity. When the frequency modulation period is constant and the same control signal is repeated, a correction table that defines the phase of the sweep period and the period correction ratio, as shown in FIG. 23B, can be used to achieve the same effect as described above. Alternatively, a correction table that defines the phase of the sweep period and the sampling interval, as shown in FIG. 23C, can be used. The processing circuit 140 can achieve the same effect by correcting the sampling timing of the detection signal by referring to such a table. In the examples shown in FIGS. 23B and 23C, a single table includes correction data for the up-chirp period (i.e., the period when the phase is from 0 to π) and correction data for the down-chirp period (i.e., the period when the phase is from π to 2π). Instead of such a table, a correction table for the up-chirp and a correction table for the down-chirp may be recorded separately.

[0122] [effect] As described above, in this embodiment, the processing circuit 140 corrects the detection signal of the interference wave using correction data for the up-chirp period and correction data for the down-chirp period, which were generated by prior calibration. Each correction data may include, for example, information on a correction value for correcting the period of the detection signal or a correction value for correcting the sampling timing of the detection signal. The correction value may be recorded in association with, for example, a control voltage for sweeping the frequency of the laser light emitted from the light source 110, the value of the laser drive current, or the phase of the frequency modulation period. Based on this correction data, the processing circuit 140 corrects the detection signal in the time direction. The processing circuit 140 calculates the distance from the frequency of the spectral peak obtained by Fourier transforming the corrected detection signal. The processing circuit 140 can further determine the velocity of the object 300 based on the difference between the frequency of the spectral peak in the up-chirp period and the frequency of the spectral peak in the down-chirp period. In this way, the processing circuit 140 performs time correction of the detection signal for each of the up-chirp period and the down-chirp period before Fourier transform. This reduces distortion in the spectral pattern obtained by Fourier transform of the detection signal during each chirp period. As a result, the accuracy of the distance data obtained during each chirp period can be improved. The improved accuracy of the distance data obtained during each period also improves the accuracy of the velocity measurement calculated from the frequency difference between those periods.

[0123] (Variation 1) Fig. 24 is a diagram for explaining the operation of Modification 1 of Embodiment 1. In the FMCW system, the frequency modulation period may be longer than the observation period of the interference wave, i.e., the period during which the detection signal is acquired. For example, the detection signal may be acquired in a period shorter than the modulation period, such as a, b, c, and d, which are separated by dashed lines in Fig. 24. In such a case, the method of correcting the detection signal in the time direction and then performing a Fourier transform, as described above, is also effective.

[0124] For example, the table shown in FIG. 12, which records correction values ​​such as the period correction ratio of the interference signal corresponding to the voltage of the control signal, is Frequency Modulation In this case, the time length of the detection signal acquired for distance and speed measurement can be Frequency Modulation Even if the period is shorter than that of the first embodiment, the same correction process as in the first embodiment is possible.

[0125] (Variation 2) When measuring distance and velocity based on a short period of the detection signal, as in the example of FIG. 24, it is desirable to extract a signal within a range in which the behavior of the detection signal is stable with respect to the control voltage. In the example of FIG. 24, during periods b and d, the detection signal is in an unstable state, repeatedly rising and falling. On the other hand, during periods a and c, the detection signal rises uniformly with increasing control voltage. Although nonlinear, it is more stable than periods b and d. Therefore, the signal used to measure distance and velocity may be extracted from the detection signal within a certain control voltage range. In this case, the correction table may hold correction values ​​only within the control voltage range used for measurement, which are set separately for the up-chirp and down-chirp of the control voltage. In this modification, in step S1130 shown in FIG. 16, the processing circuit 140 acquires the detection signal when the control voltage is within a predetermined control voltage range.

[0126] In this way, the up-chirp correction data may be a table or function data specifying the correspondence between the control voltage and the correction value during a first period (e.g., period a in FIG. 24 ), which is a part of the up-chirp period. The down-chirp correction data may be a table or function data specifying the correspondence between the control voltage and the correction value during a second period (e.g., period c in FIG. 24 ), which is a part of the down-chirp period. In this case, processing circuit 140 extracts from the detection signal a first signal corresponding to the first period and a second signal corresponding to the second period. Processing circuit 140 generates a first correction signal by correcting the first signal based on the correction value in the up-chirp correction data. Processing circuit 140 also generates a second correction signal by correcting the second signal based on the correction value in the down-chirp correction data. Processing circuit 140 can determine at least one of the distance and velocity of object 300 based on the first correction signal and the second correction signal.

[0127] According to this modification, it is possible to perform stable measurements while reducing the amount of data stored in the storage device 150.

[0128] (Variation 3) 25 is a block diagram showing a schematic configuration of the measurement device 100 according to Modification 3 of Embodiment 1. In this modification, the measurement device 100 includes a measuring instrument 160 that measures the frequency or wavelength of light in addition to the components shown in FIG.

[0129] The interference optical system 120 in this modification separates the laser light emitted from the light source 110 into output light, a first reference light, and a second reference light. The output light is emitted toward the object 300. The first reference light corresponds to the reference light in the first embodiment, and interferes with the light reflected from the object 300 to enter the photodetector 130 as interference light. The second reference light enters the measuring instrument 160.

[0130] The wavelength measuring instrument 160 receives the second reference light, detects the wavelength or frequency of the second reference light, and sends a signal indicating the detection result to the processing circuit 140 .

[0131] The processing circuit 140 acquires a detection signal indicating the time variation in the intensity of the interference light output from the photodetector and a signal indicating the frequency of the second reference light output from the measuring instrument 160. The processing circuit 140 generates measurement data indicating the distance and / or velocity of the object 300 based on these signals and two correction tables stored in the storage device 150.

[0132] An outline of the operation during calibration in this modified example is as follows. With the measuring device 100 in a stationary state, the light source 110 emits frequency-modulated laser light toward a stationary object. The photodetector 130 detects the interference light between the reflected light from the object and the first reference light, and outputs a detection signal. The measuring instrument 160 measures the wavelength or frequency of the second reference light and outputs a signal indicating the measurement value. Based on the detection signal output from the photodetector 130 and the signal output from the measuring instrument 160, the processing circuit 140 generates a correction table for correcting the detection signal so that the frequency of the spectral peak of the interference light corresponding to the up-chirp period and the frequency of the spectral peak of the interference light corresponding to the down-chirp period correspond to the distance to the object regardless of the frequency of the second reference light, and stores the correction table in the memory device 150.

[0133] The outline of the distance and speed measurement operation in this modified example is as follows. The light source 110 emits frequency-modulated laser light toward the target. The photodetector 130 detects the interference light between the reflected light from the object and the reference light, and outputs a detection signal. The processing circuit 140 corrects the detection signal according to the frequency of the second reference light based on a correction table for at least one of the up-chirp period and the down-chirp period, and determines the distance from the measurement device 100 to the object based on the spectral peak of the corrected detection signal. Furthermore, the processing circuit 140 determines the relative velocity between the object and the measurement device 100 from the difference between the spectral peak in the up-chirp period and the spectral peak in the down-chirp period.

[0134] 26A and 26B are diagrams showing examples of an up-chirp correction table and a down-chirp correction table in this modification. Each correction table shown in FIG. 26A includes information on the frequency of the second reference light measured by measuring instrument 160 and the period correction ratio corresponding to each frequency. Each correction table shown in FIG. 26B includes information on the frequency of the second reference light measured by measuring instrument 160 and the sampling interval corresponding to each frequency. In this way, the correction table in this modification defines the correspondence relationship between the frequency of the second reference light and the correction value. Note that the correction table may also define the correspondence relationship between the wavelength of the second reference light and the correction value.

[0135] In this modification, instead of a correction table that defines the correspondence relationship between the drive voltage and the correction value, a correction table that defines the correspondence relationship between the frequency or wavelength of the light emitted from light source 110 and the correction value is used. Since there is a correlation between the drive voltage and the frequency and wavelength of the light emitted from light source 110, even if the frequency or wavelength of the emitted light is used instead of the drive voltage, the same effect as in the first embodiment can be obtained.

[0136] In this modification, the distance and velocity may also be measured based on a detection signal having a period shorter than one cycle of the frequency modulation, as shown in FIG. 24 . In this case, the first correction data may be table or function data specifying the correspondence between the wavelength or frequency of the second reference light and the correction value during a first period, which is part of the up-chirp period. Similarly, the second correction data may be table or function data specifying the correspondence between the wavelength or frequency of the second reference light and the correction value during a second period, which is part of the down-chirp period. The processing circuit 140 may extract a first signal corresponding to the first period and a second signal corresponding to the second period from the detection signal, correct the first signal based on the correction value in the first correction data, to generate a first correction signal, and the processing circuit 140 may correct the second signal based on the correction value in the second correction data, to generate a second correction signal. The processing circuit 140 may determine the beat frequency during each chirp period based on the first correction signal and the second correction signal, thereby determining the distance and / or velocity of the target 300.

[0137] <Experimental Examples for Explaining Effects of the Embodiments> FIG. 27 is a diagram illustrating a measurement device 2601 in an experimental example for verifying the effects of an embodiment of the present disclosure. Unlike the configuration of the measurement device 100 illustrated in FIG. 2, the measurement device 2601 receives a dummy detection signal output from an external signal generator 2602 as input to the processing circuit 140 instead of the detection signal from the photodetector 130. The signal generator 2602 acquires a control signal output from the processing circuit 140 to the light source 110 and generates a dummy detection signal synchronized with the frequency modulation of the laser light output from the light source 110. The dummy detection signal is a pseudo-sine wave with a fluctuating frequency, and its amplitude and center frequency are set to values ​​close to those of the original detection signal (e.g., 1 Vpp and 50 MHz). The dummy detection signal includes a detection signal synchronized with the up-chirp period of the frequency modulation of the laser light and a detection signal synchronized with the down-chirp period, and the frequency fluctuation width and timing differ between the up-chirp period and the down-chirp period.

[0138] In this experimental example, memory device 150 also stores different correction tables for up-chirp and down-chirp, as in the above-described embodiment. Assume that a dummy detection signal is input to processing circuit 140, and measurement operation by measurement device 2601 is performed with the up-chirp and down-chirp correction tables applied. The measured distance value is the average of the distance values ​​measured during the up-chirp period and the down-chirp period, so the variation in the distance value is the sum of the variation during the up-chirp period and the variation during the down-chirp period.

[0139] First, let us consider the case where the frequency fluctuation width of the dummy detection signal is set to zero during both the up-chirp and down-chirp periods, i.e., the dummy detection signal is a sinusoidal signal with a constant frequency. In this case, the dummy detection signal is corrected according to the up-chirp correction table and the down-chirp correction table, respectively, and therefore the distance value varies depending on the correction. In this case, the variation in the distance value obtained from multiple measurements is defined as σ 00 Let's say.

[0140] Next, let us consider a case where the frequency fluctuation during the up-chirp period of the dummy detection signal is different from the frequency fluctuation during the down-chirp period. When the frequency fluctuation width of the dummy detection signal only during the up-chirp period is set to a and the frequency fluctuation width during the down-chirp period is set to zero, the variation in distance values ​​obtained from multiple measurements is σ. a0 On the other hand, when the frequency fluctuation width of the dummy detection signal is set to a only during the down-chirp period and the frequency fluctuation width during the up-chirp period is set to zero, the variation in the distance values ​​obtained by multiple measurements is σ 0a Here, the frequency fluctuation pattern during the period when the frequency fluctuation width is a is set to be the same whether it is an up-chirp period or a down-chirp period.

[0141] When the above experiment was carried out, the variation in the distance values ​​was σ a0 ≠σ 0aThe reason for this is that when different correction tables are applied to dummy detection signals with the same frequency fluctuation width and fluctuation pattern, the spectral linewidth of the corrected detection signal changes, and the variation in distance values ​​also changes according to this change in linewidth. Comparing the cases where the two types of dummy detection signals mentioned above are input, the variation in distance values ​​that occurs during the up-chirp period is different from that of the down-chirp period, and therefore the variation in distance values ​​obtained by averaging the two also differs. On the other hand, in a conventional device that applies correction to the beat signal frequency after frequency analysis, even if different corrections are applied to the up-chirp period and the down-chirp period, the spectral linewidth of the original beat signal does not change, so the variation in distance values ​​is σ a0 =σ 0a It should be like this.

[0142] From the above experiments, it can be seen that in the measurement device of an embodiment of the present disclosure, the variation in distance values ​​is controlled by applying different correction tables to the up-chirp period and down-chirp period in the detection signal before frequency analysis.

[0143] In the above-described embodiment of the present disclosure, a correction is made to the detection signal before frequency analysis, thereby suppressing a decrease in measurement accuracy due to nonlinearity in the frequency modulation of laser light. A similar problem can be addressed by correcting the control signal itself for frequency modulation of laser light to eliminate nonlinearity. However, such a method requires nonlinear correction of the control signal to the light source. While generating a nonlinear control signal and controlling the current or voltage using that control signal are difficult, the correction of the detection signal before frequency analysis is performed at the signal processing level, making it simple and highly accurate. Therefore, the embodiment of the present disclosure enables measurements to be performed more easily and accurately than conventional methods. [Industrial Applicability]

[0144] The measurement device disclosed herein can be used in applications such as FMCW lidar systems mounted on mobile objects such as automated guided vehicles (AGVs), automobiles, unmanned aerial vehicles, or industrial robots, or on monitoring devices. [Explanation of symbols]

[0145] 100 Rangefinder 110 Light source 111 Drive circuit 112 Light-emitting element 120 Interference Optical System 121 Switch 122 Mirror 123 Collimator 124 Collimating Lens 125 1st Fiber Splitter 126 Second Fiber Splitter 127 Optical Circulator 130 Photodetector 140 Processing Circuit 150 Storage device 160 Measuring Instruments 170 Optical deflector 210 Display device 220 Control device 300 Objects

Claims

1. a light source that emits frequency-modulated light; an interference optical system that separates the light emitted from the light source into reference light and output light, and generates interference light between the reference light and reflected light generated when the output light is reflected by an object; a photodetector that receives the interference light and outputs a detection signal corresponding to the intensity of the interference light; a processing circuit that modulates the frequency of the light emitted from the light source with a period including an up-chirp period in which the frequency increases and a down-chirp period in which the frequency decreases, and generates and outputs measurement data related to the distance and / or velocity of the object based on the detection signal; a storage device that stores first correction data for the up-chirp period and second correction data for the down-chirp period; Equipped with the processing circuit generates the measurement data based on a first corrected signal obtained by correcting a portion of the detection signal corresponding to the up-chirp period based on the first correction data, and / or a second corrected signal obtained by correcting a portion of the detection signal corresponding to the down-chirp period based on the second correction data. Measuring equipment.

2. 2. The measurement device according to claim 1, wherein the processing circuit determines a frequency of the first correction signal and a frequency of the second correction signal, determines a distance from the measurement device to the object based on the frequency of the first correction signal and the frequency of the second correction signal, and generates the measurement data including information about the distance.

3. the processing circuit determines a frequency of the first correction signal and a frequency of the second correction signal; determining a velocity of the object based on a difference between the frequency of the first correction signal and the frequency of the second correction signal, and generating the measurement data including information about the velocity; The measuring device according to claim 1 or 2.

4. the processing circuitry varies a frequency of the light emitted from the light source by varying a control voltage applied to the light source; the first correction data and the second correction data are table or function data that define a correspondence relationship between the control voltage and a correction value, the processing circuit corrects the detection signal based on the correction value corresponding to the control voltage. The measuring device according to any one of claims 1 to 3.

5. the first correction data is table or function data that defines a correspondence relationship between the control voltage and the correction value in a first period that is a part of the up-chirp period, the second correction data is table or function data that defines a correspondence relationship between the control voltage and the correction value during a second period that is a part of the down-chirp period, The processing circuitry extracting a first signal corresponding to the first period and a second signal corresponding to the second period from the detection signal; generating the first correction signal by correcting the first signal based on the correction value in the first correction data; generating the second corrected signal by correcting the second signal based on the correction value in the second correction data; The measuring device according to claim 4.

6. the interference optical system separates the light emitted from the light source into the output light, a first reference light that is the reference light, and a second reference light; the measurement device further includes a measuring instrument that measures a wavelength or a frequency of the second reference light, the first correction data and the second correction data are table or function data that define a correspondence relationship between a wavelength or a frequency of the second reference light and a correction value; The measuring device according to any one of claims 1 to 3.

7. the first correction data is data of a table or function that defines a correspondence relationship between the wavelength or frequency of the second reference light and the correction value in a first period that is a part of the up-chirp period, the second correction data is data of a table or function that defines a correspondence relationship between the wavelength or frequency of the second reference light and the correction value in a second period that is a part of the down-chirp period, The processing circuitry extracting a first signal corresponding to the first period and a second signal corresponding to the second period from the detection signal; generating the first correction signal by correcting the first signal based on the correction value in the first correction data; generating the second corrected signal by correcting the second signal based on the correction value in the second correction data; The measurement device according to claim 6.

8. the processing circuit causes the light source to emit the light having a constant frequency modulation period; the first correction data and the second correction data are table or function data that define a correspondence relationship between a phase within each period of the frequency modulation and a correction value; The measuring device according to any one of claims 1 to 3.

9. the first correction data and the second correction data are table or function data that define a correspondence relationship between a time from a reference time point and a correction value in the frequency modulation of the light source, The measuring device according to any one of claims 1 to 3.

10. 10. The measurement device according to claim 1, wherein the first correction data and the second correction data are table or function data including information on correction values ​​for changing the sampling timing of the detection signal.

11. 1. A computer-implemented method in a system including a metrology device, comprising: The measuring device is a light source that emits light whose frequency is modulated in a cycle including an up-chirp period in which the frequency increases and a down-chirp period in which the frequency decreases; an interference optical system that separates the light emitted from the light source into reference light and output light, and generates interference light between the reference light and reflected light generated when the output light is reflected by an object; a photodetector that receives the interference light and outputs a detection signal corresponding to the intensity of the interference light; a storage device that stores first correction data for the up-chirp period and second correction data for the down-chirp period; Equipped with The method comprises: generating a first correction signal by correcting a portion of the detection signal corresponding to the up-chirp period based on the first correction data, and / or generating a second correction signal by correcting a portion of the detection signal corresponding to the down-chirp period based on the second correction data; generating and outputting measurement data relating to distance and / or speed based on the first correction signal and / or the second correction signal; A method comprising:

12. A computer program executed by a computer in a system including a measurement device, The measuring device is a light source that emits light whose frequency is modulated in a cycle including an up-chirp period in which the frequency increases and a down-chirp period in which the frequency decreases; an interference optical system that separates the light emitted from the light source into reference light and output light, and generates interference light between the reference light and reflected light generated when the output light is reflected by an object; a photodetector that receives the interference light and outputs a detection signal corresponding to the intensity of the interference light; a storage device that stores first correction data for the up-chirp period and second correction data for the down-chirp period; Equipped with The computer program causes the computer to: generating a first correction signal by correcting a portion of the detection signal corresponding to the up-chirp period based on the first correction data, and / or generating a second correction signal by correcting a portion of the detection signal corresponding to the down-chirp period based on the second correction data; generating and outputting measurement data relating to distance and / or speed based on the first correction signal and / or the second correction signal; A computer program that executes

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