Device and method for measuring distance and / or speed of object

Abstract

To enable measurement of distance or speed in a wider distance range.SOLUTION: A measuring device includes: a light source for emitting light in which frequency has been modulated; an interference optical system for separating the light emitted from the light source into reference light and output light, and for generating interference light of reflection light which is generated by the emission light being reflected by an object and the reference light; light detector for receiving the interference light and outputting a detection signal according to the intensity of the interference light; a storage device for storing a plurality of pieces of correction data used for correction of the detection signal; and a processing circuit. Each of the plurality of pieces of correction data is associated with one corresponding to a plurality of different distance ranges. The processing circuit modulates the frequency of the light from the light source at a predetermined cycle, and generates a correction detection signal by correcting the detection signal based on at least one of the plurality of pieces of correction data, and generates measurement data regarding distance and / or speed of the object based on the correction detection signal.SELECTED DRAWING: Figure 2

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] Distance or speed measurement devices that use the FMCW (Frequency Modulated Continuous Wave) method send out frequency-modulated electromagnetic waves and measure 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 measurement device is called an FMCW radar. When the electromagnetic waves used are light such as visible light or infrared light, the FMCW measurement 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, and generates interference light by interfering the reflected light from the target with a reference light from the light source. The interference light is detected by a photodetector and converted into an electrical signal. This electrical signal is hereinafter referred to as the "detection signal." The detection 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," and the frequency of the beat signal is called the "beat frequency." Because there is a correlation between the beat frequency and the distance from the measurement device to the target (also referred to simply as the "distance to the target" or "distance to the target" in this specification), the distance to the target can be calculated based on the beat frequency. Furthermore, the Doppler shift of the reflected light 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 between the beat frequency during the up-chirp period, in which the frequency of the light emitted from the light source increases, and the beat frequency during the down-chirp period, in which the frequency decreases.

[0004] Unlike ToF (Time of Flight) lidars, FMCW lidars detect the frequency of the detection signal output from a photodetector, which means that the distance measurement results are less susceptible to the influence of ambient light. On the other hand, it has been thought that the accuracy of FMCW lidar distance measurements depends on how linearly the optical frequency can be modulated with respect to time.

[0005] Patent Document 1 discloses a distance measuring device that can suppress degradation of distance measurement performance even when the frequency of laser light from a light source changes nonlinearly with time. The distance measuring device in Patent Document 1 includes a laser light source that generates a frequency-swept laser light, a measurement interferometer that causes interference between one of two laser light beams branched from the laser light and the other laser light beam, resulting from reflection of the other laser light beam by an object, and outputs a measurement interference signal, a photodetector that outputs a measurement detection signal indicating the intensity of the incident measurement interference signal, an auxiliary interferometer that applies different delay times to the other two laser light beams branched from the laser light, causes interference, and outputs an auxiliary interference signal, and a signal processing unit. The signal processing unit includes a photodetector that outputs an auxiliary detection signal indicating the intensity of the incident auxiliary interference signal, and calculates distance by dividing a value based on the beat frequency of the measurement detection signal by a value based on the beat frequency of the auxiliary detection signal.

[0006] Patent Document 2 discloses a technique for suppressing degradation of distance or velocity measurement performance caused by differences in the nonlinearity of frequency change between up-chirp and down-chirp periods. The technique in Patent Document 2 uses different correction data for the up-chirp and down-chirp periods, and corrects the interference wave detection signal during measurement using the correction data. This allows for more accurate measurement of distance or velocity.

[0007] Patent Document 3 discloses a technique for suppressing degradation of distance or speed measurement performance caused by differences in nonlinearity of frequency change depending on the operating state of a light source (for example, the amplitude of the voltage of a control signal input to the light source, the temperature of the light source, etc.). In the technique of Patent Document 3, multiple correction data corresponding to multiple different operating states of the light source are prepared in advance, and during measurement, the detection signal output from the photodetector is corrected based on the correction data corresponding to the operating state of the light source. This mitigates the effects of nonlinear frequency modulation that occurs differently depending on the operating state, making it possible to measure the distance or speed of an object more accurately. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2024-007750 [Patent Document 2] International Publication No. 2022 / 209367 [Patent Document 3] International Publication No. 2022 / 209309 Summary of the Invention [Problem to be solved by the invention]

[0009] The present disclosure provides a measurement device and a measurement method that can mitigate the effects of nonlinearity in beat signals that can vary depending on the distance to an object, and that can measure distance and / or velocity over a wider distance range. [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 memory device that stores a plurality of correction data used to correct the detection signal, each of the plurality of correction data being associated with a corresponding one of a plurality of different distance ranges; and a processing circuit that modulates the frequency of the light from the light source at a predetermined period, corrects the detection signal based on at least one of the plurality of correction data to generate a corrected detection signal, and generates measurement data regarding the distance and / or speed of the object based on the corrected detection signal.

[0011] A measurement device according to another 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 generated when the output light is reflected by an object, an optical branching device that separates the output light into multiple output light and emits the multiple output light in multiple different directions, a photodetector that receives the interference light and outputs a detection signal corresponding to the intensity of the interference light, a memory device that stores multiple correction data used to correct the detection signal, each of the multiple correction data being associated with a corresponding one of the multiple output lights, and a processing circuit that modulates the frequency of the light from the light source at a predetermined period, corrects the detection signal based on at least one of the multiple correction data, to generate a corrected detection signal, and generates measurement data related to the distance and / or speed of the object based on the corrected detection signal.

[0012] A comprehensive 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]

[0013] According to the embodiments of the present disclosure, the influence of nonlinearity of the beat signal, which may vary depending on the distance to the object, is mitigated, enabling precise measurements over a wider distance range. [Brief explanation of the drawings]

[0014] [Figure 1A] FIG. 1A is a graph showing an example of the change over time in the frequency of light emitted from a measurement device and the frequency of light reflected from two objects located at different distances from the measurement device. [Figure 1B] FIG. 1B is a graph showing an example of the time variation of the frequencies of two beat signals corresponding to the two waveforms shown in FIG. 1A. [Figure 1C] FIG. 1C is a graph showing the experimental results. [Figure 2] FIG. 2 is a block diagram showing a schematic configuration of a system including the measurement device according to the first embodiment. [Figure 3] FIG. 3 is a block diagram showing an example of a specific 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. [Figure 8] FIG. 8 is a flowchart showing an example of an operation for generating correction data. [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 showing an example of the relationship between the voltage and the period of the control signal. [Figure 11] FIG. 11 is a diagram illustrating an example of the correction data. [Figure 12] FIG. 12 is a diagram showing an example of the waveform of the detection signal before and after correction. [Figure 13] FIG. 13 is a diagram showing an example of correction data including information on a correction value for changing the sampling timing of the detection signal. [Figure 14] FIG. 14 is a diagram showing another example of the correction table. [Figure 15] FIG. 15 is a diagram showing yet another example of the correction table. [Figure 16] FIG. 16 is a diagram showing an example of data defining the relationship between the beat frequency and the distance. [Figure 17] FIG. 17 is a flowchart showing an example of a distance measurement operation by the measurement device. [Figure 18] FIG. 18 is a diagram illustrating an example of the configuration of a measurement system according to the second embodiment. [Figure 19]FIG. 19 is a flowchart showing the operation of the measurement device in the second embodiment. [Figure 20] FIG. 20 is a diagram illustrating an example of the configuration of a measurement system including an input device. [Figure 21] FIG. 21 is a flowchart showing the measurement operation in the third embodiment. [Figure 22] FIG. 22 is a flowchart showing another example of the measurement operation in the third embodiment. [Figure 23] FIG. 23 is a flowchart showing yet another example of the measurement operation in the third embodiment. [Figure 24] FIG. 24 is a flowchart showing an example of a measurement operation in the fourth embodiment. [Figure 25] FIG. 25 is a flowchart showing another example of the measurement operation in the fourth embodiment. [Figure 26] FIG. 26 is a flowchart showing yet another example of the measurement operation in the fourth embodiment. [Figure 27] FIG. 27 is a block diagram showing an example of the configuration of a measurement device according to the fifth embodiment. [Figure 28] FIG. 28 is a flowchart showing an outline of the operation of the measurement device in the fifth embodiment. [Figure 29] FIG. 29 is a diagram showing an example of correspondence data between irradiation directions and approximate distances stored in a storage device. [Figure 30A] FIG. 30A is a diagram schematically showing the rough scan in step S510. [Figure 30B] FIG. 30B is a diagram showing an example of the result of the region division process in step S530. [Figure 30C] FIG. 30C is a diagram schematically showing the detailed scan in step S550. [Figure 31] FIG. 31 is a flowchart showing a specific example of the outline scan process of step S510. [Figure 32] FIG. 32 is a flowchart showing a specific example of the region division process in step S530. [Figure 33] FIG. 33 is a flowchart showing a specific example of the detailed scan process in step S550. [Figure 34] FIG. 34 is a block diagram showing an example of the configuration of a measurement device according to the sixth embodiment. [Figure 35] FIG. 35 is a flowchart showing an example of the operation of the measurement apparatus according to the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Findings that formed the basis of this disclosure) Before describing the embodiments of the present disclosure, the findings of the present inventors will be described.

[0016] 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 due to a delay in the response of the light frequency to changes in the control voltage. Due to this nonlinearity, the beat frequency does not remain constant even when the target is stationary, but rather changes nonlinearly with time. Furthermore, the nonlinearity of the time variation of the beat frequency can change due to various factors, such as changes in the operating state of the light source, changes in the operating environment, and the passage of time. Therefore, to accurately determine the distance or velocity to the target, it is effective to correct the detection signal using appropriate correction data according to the operating state or sweep conditions of the light source, and then calculate the beat frequency based on the corrected detection signal. Examples of such methods are disclosed in Patent Documents 2 and 3.

[0017] However, according to the inventors' research, the nonlinearity of the time change in the beat frequency can change depending on the distance from the measurement device to the target object. Therefore, even if the detection signal is corrected using correction data suitable for a specific distance range, errors can become large in distance measurements for other distance ranges. This issue will be explained below with reference to Figures 1A to 1C.

[0018] FIG. 1A is a graph showing an example of the time variation of the frequency of light emitted from a measurement device and the frequency of light reflected from two objects located at different distances from the measurement device. FIG. 1A illustrates waveform 10, which shows the time variation of the frequency of the emitted light, and waveforms 12 and 14, which show the reflected light from the two objects due to the emitted light. Waveform 12 shows the time variation of the frequency of reflected light reflected from a first object located at a first distance from the measurement device and returning to the measurement device. Waveform 14 shows the time variation of the frequency of reflected light reflected from a second object located at a second distance, which is longer than the first distance, and returning to the measurement device. Waveform 12 lags waveform 10 by a time Δt1, which corresponds to the time it takes for light to travel a round trip over the first distance. Waveform 14 lags waveform 10 by a time Δt2, which corresponds to the time it takes for light to travel a round trip over the second distance.

[0019] FIG. 1B is a graph showing an example of the time variation of the frequencies (i.e., beat frequencies) of two beat signals corresponding to the two waveforms 12 and 14 shown in FIG. 1A. Waveform 32 in FIG. 1B shows the time variation of the beat frequency corresponding to waveform 12 shown in FIG. 1A. Waveform 34 in FIG. 1B shows the time variation of the beat frequency corresponding to waveform 14 shown in FIG. 1A. The beat frequency shown by waveform 32 corresponds to the difference Δf1 between the frequency shown by waveform 10 and the frequency shown by waveform 12, and the beat frequency shown by waveform 34 corresponds to the difference Δf2 between the frequency shown by waveform 10 and the frequency shown by waveform 14. If the time variation of the frequency of the emitted light were linear, the beat frequencies Δf1 and Δf2 should not change over time. However, in reality, the frequency of the emitted light changes nonlinearly, so the beat frequencies Δf1 and Δf2 change over time, and the change is nonlinear. Furthermore, the nonlinearities of the time variations of the beat frequencies Δf1 and Δf2 are different from each other.

[0020] As described above, the beat frequency changes over time due to the nonlinearity of the frequency change of the emitted light, and the nonlinearity of the time change of the beat frequency differs depending on the distance to the object or the propagation distance of the light, making it difficult to accurately determine the distance to the object from the beat frequency.

[0021] To prevent the beat frequency from changing over time, it is conceivable to employ a method of adjusting the sampling timing or period of the detection signal output from the photodetector based on prepared correction data, as disclosed in, for example, Patent Documents 2 and 3. This method makes it possible to correct the detection signal so that the frequency of the beat signal component contained in the detection signal becomes approximately constant, thereby improving the accuracy of distance or velocity measurement.

[0022] However, because the nonlinearity of the time change in the beat frequency varies depending on the distance to the target object, even if the detection signal is corrected using correction data that is suited to a specific distance range, there is a possibility that the error will be large for other distance ranges and accurate distance measurement will not be possible.

[0023] Figure 1C is a graph showing the results of an experiment conducted by the inventors. The horizontal axis of the graph represents the true value of the distance to the object, and the vertical axis represents the difference between the measured distance and the true value. In this experiment, distance measurements were performed by varying the distance from the measurement device to the object from 1 m to 16.8 m. Measurements were performed using a measurement device similar to that described in Patent Documents 2 and 3. The measured distance was calculated based on the beat frequency obtained by performing frequency analysis such as fast Fourier transform on the detection signal corrected using correction data corresponding to a distance range of 1-2 meters (m). As shown in the graph in Figure 1C, when measuring the distance to the object using correction data for a distance range of 1-2 m, the difference between the measured distance and the true value increases as the actual distance deviates from the 1-2 m range. The difference between the measured distance and the true value is neither uniform nor linear with respect to the distance to the object. One of the reasons for this is that, as shown in Figure 1B, the pattern of nonlinear time changes in the beat frequency depends on the time between when light is emitted from the measurement device and when the reflected light from the target is received, or on the distance between the measurement device and the target.

[0024] Another example of a method for suppressing degradation of distance measurement performance due to nonlinear time-dependent changes in the frequency of light from a light source is disclosed in Patent Document 1. In the method of Patent Document 1, a more accurate distance is calculated by dividing a value based on the beat frequency of a measurement detection signal from a measurement interferometer by a value based on the beat frequency of an auxiliary detection signal from an auxiliary interferometer that has the same nonlinearity as the measurement signal. However, in the method of Patent Document 1, an auxiliary interferometer suitable for a certain distance range (e.g., around 10 m) is not compatible with distance measurement in other distance ranges (e.g., around 40 m), resulting in measurement errors. To perform accurate distance measurement over a wide distance range, multiple auxiliary interferometers, each corresponding to a different distance range, must be used interchangeably, which can lead to a complex configuration and high costs.

[0025] The present inventors have found the above problems and have come up with the configurations of the embodiments of the present disclosure described below in order to solve the problems. An outline of the embodiments of the present disclosure will be described below.

[0026] (overview) A measurement device according to one aspect of the present disclosure includes the following components: 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 storage device that stores a plurality of correction data used to correct the detection signal, each of the plurality of correction data being associated with a corresponding one of a plurality of different distance ranges; a processing circuit that modulates the frequency of the light from the light source at a predetermined cycle, corrects the detection signal based on at least one of the plurality of correction data to generate a corrected detection signal, and generates and outputs measurement data related to the distance and / or speed of the object based on the corrected detection signal.

[0027] According to the above configuration, corresponding correction data for each of a plurality of distance ranges is stored in advance in the storage device. The processing circuit generates a corrected detection signal by correcting the detection signal acquired from the photodetector based on at least one of the plurality of correction data, and calculates the distance and / or velocity of the object based on the corrected detection signal. This enables more accurate distance or velocity measurement over a wider distance range using appropriate correction data according to the distance to the object. Note that in this specification, "distance and / or velocity of the object" means the distance from the measurement device to the object and / or the velocity of the object.

[0028] The processing circuit may acquire information indicating an approximate distance to the object and generate a corrected detection signal based on correction data corresponding to the approximate distance from among the plurality of correction data. The information indicating the approximate distance may be generated by the processing circuit itself or may be input from an external device. For example, the processing circuit may generate a standard corrected detection signal by correcting the detection signal based on standard correction data included in the plurality of correction data, and calculate the approximate distance based on the standard corrected detection signal. Alternatively, the processing circuit may acquire information indicating the approximate distance measured by a sensing device with a distance measurement function (e.g., a stereo camera, radar, ultrasonic sensor, ToF distance sensor, etc.). Alternatively, the approximate distance may be input via an input device from a user or an external device.

[0029] The measurement device may further include an optical deflector that changes the direction of the output light. In this case, the processing circuit may be configured to perform the following operations (S1) to (S3). (S1) The optical deflector is controlled to change the direction of the output light within the target area, and a rough scanning operation is performed to calculate an approximate distance for each direction of the output light based on the detection signal output from the photodetector. (S2) Based on the approximate distance for each direction of the output light, the target area is divided into a plurality of partial areas, and suitable correction data is determined for each of the plurality of partial areas. (S3) For at least one of the plurality of partial regions, a detailed scan operation is performed in which the direction of the output light is changed within the partial region by controlling the optical deflector, a detection signal output from the photodetector is acquired for each direction of the output light, the detection signal is corrected based on correction data suitable for that partial region to generate a corrected detection signal, and the distance to an object present in that direction is calculated based on the corrected detection signal.

[0030] According to the above configuration, after obtaining approximate distance information in each direction within the target area through a rough scan operation, the target area can be divided into multiple partial areas based on that information, and high-precision distance measurement can be performed for each partial area through a detailed scan operation. This makes it possible to obtain distance information for multiple objects located in different directions from the measurement device.

[0031] In the rough scanning operation, the processing circuit may generate a standard corrected detection signal by correcting the detection signal based on standard correction data included in the plurality of correction data, and calculate the approximate distance based on the standard corrected detection signal.

[0032] The processing circuitry may increase the density of measurement points by the output light in the detailed scan operation compared to the density of measurement points by the output light in the rough scan operation, thereby enabling, for example, a quick rough scan to be performed, followed by a more precise detailed scan of a specific partial area.

[0033] The processing circuit may generate multiple corrected detection signals by correcting the detection signal based on each of the multiple correction data, calculate multiple distances based on each of the multiple corrected detection signals, and determine one distance selected from the multiple distances as the distance to the object. For example, the processing circuit may select one distance from the multiple distances that is included in or closest to the distance range associated with the correction data used to calculate the distance, and determine the selected distance as the distance to the object. This operation enables high-precision measurement without obtaining approximate distance information.

[0034] The processing circuit may generate a plurality of corrected detection signals by correcting the detection signal based on each of the plurality of correction data, calculate a plurality of beat frequencies based on each of the plurality of corrected detection signals, and calculate the distance to the object based on one beat frequency selected from the plurality of beat frequencies. For example, the processing circuit may select one beat frequency from the plurality of beat frequencies that is included in or closest to a frequency range corresponding to a distance range associated with the correction data used to calculate the beat frequency, and calculate the distance to the object based on the selected beat frequency.

[0035] The processing circuit may acquire information indicating an approximate distance to the object, select two or more correction data from the plurality of correction data sets associated with a distance range relatively close to the approximate distance, generate composite correction data based on the selected two or more correction data sets, and correct the detection signal based on the composite correction data to generate a corrected detection signal. This configuration may be effective, for example, when there are gaps or overlaps among the distance ranges associated with the plurality of correction data sets and it is not possible to identify a single correction data set that best matches the approximate distance. Even in such cases, measurement performance can be improved by synthesizing optimal correction data based on two or more correction data sets.

[0036] The measurement apparatus may further include an optical branching device that splits the output light from the interference optical system into multiple output light beams and outputs the multiple output light beams. In this case, the interference optical system sends interference light between multiple reflected light beams resulting from the multiple output light beams and the reference light beam to the photodetector. Each of the multiple output light beams may be associated with a corresponding one of multiple distance ranges. Accordingly, each of the multiple correction data may be associated with a corresponding one of the multiple output light beams. The processing circuit may generate a corrected detection signal for each of the multiple output light beams by correcting the detection signal based on the correction data associated with that output light, and generate measurement data regarding the distance and / or velocity of an object illuminated by the output light based on the corrected detection signal. This configuration enables more accurate measurement of the distance and / or velocity of multiple objects located at different positions.

[0037] The optical branching device may emit a plurality of output beams in a plurality of different directions. In this case, each of the plurality of correction data may be associated with a corresponding one of the plurality of directions. Alternatively, the optical branching device may emit a plurality of output beams in the same direction. For example, the optical branching unit may include a plurality of light emitting units arranged one-dimensionally or two-dimensionally and configured to emit a plurality of output beams in the same direction.

[0038] The processing circuit may generate a frequency spectrum for each of the multiple emitted lights based on the corrected detection signal, extract a spectral peak from the frequency spectrum that falls within a frequency range corresponding to a distance range associated with the emitted light, and calculate the distance to the object onto which the emitted light is irradiated based on the frequency of the spectral peak.

[0039] The processing circuit may generate a frequency spectrum based on the corrected detection signal for each of the plurality of emitted lights, extract a spectral peak from the frequency spectrum, calculate a distance based on the frequency of the spectral peak, and determine the distance as the distance to the object in the direction if the distance is within a distance range associated with that emitted light.

[0040] Each of the plurality of correction data may include information defining sampling timing of the detection signal. The processing circuit may generate the corrected detection signal by sampling the detection signal at irregular intervals based on at least one of the plurality of correction data.

[0041] A measurement device according to another aspect of the present disclosure includes the following components: A light source that emits frequency-modulated light according to the present disclosure 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. an optical branching device that splits the output light into a plurality of output light beams and emits the plurality of output light beams; a photodetector that receives interference light between a plurality of reflected lights resulting from the plurality of output lights and the reference light from the interference optical system and outputs a detection signal according to the intensity of the interference light; a storage device that stores a plurality of correction data used to correct the detection signal, each of the plurality of correction data being associated with a corresponding one of the plurality of output lights; a processing circuit that modulates the frequency of the light from the light source at a predetermined period, corrects the detection signal based on at least one of the plurality of correction data to generate a corrected detection signal, and generates measurement data related to the distance and / or speed of the object based on the corrected detection signal.

[0042] According to the above configuration, corresponding correction data for each of the multiple output beams is stored in advance in the storage device. The processing circuit generates a corrected detection signal by correcting the detection signal acquired from the photodetector based on at least one of the multiple correction data, and calculates the distance and / or speed of the object based on the corrected detection signal. This enables more accurate measurement of distance or speed using appropriate correction data corresponding to each output beam. The optical branching device may emit the multiple output beams in multiple different directions or in the same direction. In this configuration, the multiple output beams may be irradiated onto the same object. The propagation distance of light within the measurement device may be different for each output beam to enable simultaneous measurement.

[0043] 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 into a single chip or may be configured by combining multiple chips. For example, functional blocks other than memory elements may be integrated into 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). Field programmable gate arrays (FPGAs), which are programmable after LSI fabrication, or reconfigurable logic devices (RLDs), which can reconfigure connections within an LSI or set up circuit partitions within an LSI, can also be used for the same purpose.

[0044] 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.

[0045] 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 arrangements and connection forms, steps, and step orders 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, substantially identical components are assigned the same reference numerals, and duplicated descriptions may be omitted or simplified.

[0046] (Embodiment 1) A measurement device according to a first exemplary embodiment of the present disclosure will be described. The measurement device of this embodiment 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 used to acquire distance information of various objects, such as structures at a construction site or products manufactured in a factory. Alternatively, the measurement device may be mounted on a mobile object, such as an autonomous vehicle, an automated guided vehicle (AGV), an unmanned aerial vehicle (UAV), or a mobile robot, and used to acquire distance or speed information of objects around the mobile object.

[0047] <Configuration> Fig. 2 is a block diagram showing a schematic configuration of a measurement system including 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 a structure such as a pillar or a building, a product, an obstacle, a person, or a moving body (e.g., an automobile, a motorcycle, a mobile robot, or a drone).

[0048] 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 a reference light and an 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.

[0049] The photodetector 130 receives the interference light and generates and outputs an electrical signal, i.e., a detection signal, corresponding to the intensity of the interference light. 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 including multiple light-receiving elements, such as an image sensor.

[0050] 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 a plurality of correction data used in the detection signal correction process executed by the processing circuit 140. Each of the plurality of correction data is recorded in association with a corresponding one of a plurality of distance ranges (hereinafter also referred to as "ranges"). FIG. 2 illustrates N correction data for the first range to the Nth range (N is an integer equal to or greater than 2). N may be, for example, a value between 2 and 10, in one example, between 5 and 50, and in another example, between 10 and 100. Each correction data may be data in any format, such as a table or function that defines the correspondence between the distance range and the correction value of the detection signal. Specific examples of the correction data will be described later. The storage device 150 may also store a computer program executed by the processing circuit 140 and various data generated by the processing circuit 140 during processing.

[0051] 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 or current 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, and calculates the distance to the target 300 based on the detection signal. Specifically, the processing circuit 140 acquires information indicating the approximate distance to the object 300, corrects the detection signal based on the correction data corresponding to the approximate distance among the multiple correction data, and generates and outputs measurement data regarding the distance and / or speed of the object 300 based on the corrected detection signal.

[0052] 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 and / or perform signal processing based on the detection signal output from the photodetector 130 via a wired or wireless communication network.

[0053] When measuring the distance to the object 300, the processing circuit 140 performs the following operations. A control signal is sent to the light source 110, causing the light source 110 to emit light whose frequency changes periodically within a predetermined range. Obtain information indicating the approximate distance to the object 300. From the plurality of correction data stored in the storage device 150, one or more correction data corresponding to the approximate distance are selected. Corrects the waveform of the detection signal based on the selected correction data. - Calculate the beat frequency by frequency analysis based on the corrected waveform. The calculated beat frequency is converted into a distance value, and measurement data including the distance value is output externally.

[0054] The measurement data may be output to, for example, a display device 210. The display device 210 may be configured to display information related to the measured distance or speed. When the measurement device 100 is mounted on a moving object, the measurement data may be output to a control device 220 that controls the operation of the moving object. Such a control device 220 may be configured to control the operation (e.g., steering, speed, etc.) of the moving object based on the measured distance or speed of the object. Note that the display device 210 and the control device 220 are provided as needed and may be omitted if not required. The measurement data may be recorded in the storage device 150 or an external storage device.

[0055] 3 is a block diagram showing an example of a more specific 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.

[0056] 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.

[0057] 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 sweep of the light frequency is not completely linear. The amplitude of the modulation waveform of the 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.

[0058] 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).

[0059] 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.

[0060] 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.

[0061] The measurement device 100 may further include an optical deflector that changes the direction of the output light. FIG. 6 is a block diagram illustrating an example of the measurement device 100 including the optical deflector 170. The optical deflector 170 may include, for example, a MEMS (Micro-Electro-Mechanical Systems) mirror or a galvanometer mirror. The optical deflector 170 can change the output direction of the output light 22 by changing the angle of the mirror according to a command from the processing circuit 140. This enables beam scanning. The configuration is not limited to including a mirror or a galvanometer mirror. For example, a beam scanning device that changes the output direction of light using an optical phased array and a slow-light waveguide, as described in International Publication No. WO 2019 / 130720, may also be used.

[0062] Next, the FMCW-LiDAR technology used in this embodiment will be briefly described with reference to FIGS. 7A and 7B.

[0063] FIG. 7A is a schematic diagram illustrating an example of temporal changes in the frequencies of the reference light and the reflected light when the object 300 is stationary. Here, we explain an ideal case in which the frequencies of the reference light and the reflected light change in a triangular wave pattern. 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 detection signal indicating the intensity of the interference light. The frequency of the beat signal included in the detection 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.

[0064] FIG. 7B is a diagram showing the time change in the frequency of the reference light and the reflected light as the object 300 approaches the measurement device 100. As the object 300 approaches, the frequency of the reflected light shifts in an 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 depending on whether the frequencies of the reference light and the reflected light increase or decrease linearly. In the example shown in FIG. 7B, the beat frequency during the down-chirp period, in which both frequencies decrease linearly, is higher than the beat frequency during the up-chirp period, in which both frequencies increase linearly. The processing circuit 140 can calculate the velocity of the object 300 based on the difference between these beat frequencies. As the object 300 moves away from the measurement device 100, the frequency of the reflected light shifts in a 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.

[0065] 7A and 7B show an example of an ideal case in which the frequency of light emitted from light source 110 repeatedly increases and decreases linearly with time. However, in reality, as described above, the frequency of light changes nonlinearly, and therefore the beat frequency also changes nonlinearly. Furthermore, since this nonlinearity depends on the distance to the target, it is necessary to appropriately correct the detection signal according to the expected distance to the target. Therefore, in this embodiment, correction data corresponding to each of multiple distance ranges is prepared in advance, and the detection signal is corrected based on the correction data selected according to the expected distance. This can improve the accuracy of distance or speed measurement.

[0066] <Operation> An example of the operation of the measurement device 100 of this embodiment will be described below.

[0067] The operation of the measurement device 100 of this embodiment can be broadly divided into two steps: (1) generating correction data corresponding to each of a plurality of distance ranges, and (2) measuring distances. The generation of correction data can be performed, for example, by a person in charge at the manufacturer (hereinafter referred to as an "operator") before shipping the measurement device 100. The measuring distances can be mainly performed by a user of the measurement device 100.

[0068] <Correction data generation operation> Fig. 8 is a flowchart showing an example of an operation for generating correction data. The operation for generating correction data includes the operations of steps S101 to S108 shown in Fig. 8. The operations of steps S101 to S108 can be repeated multiple times by changing the distance from the measurement device to the reference object. The operation of each step will be described below.

[0069] (Step S101) The operator places a stationary reference object at a specific distance from the measurement device 100 while the measurement device 100 is stationary. The specific distance can be set, for example, to the median of the minimum or maximum distance range among multiple predetermined distance ranges. For example, if 20 distance ranges with a width of 1 m are set, such as 0-1 m, 1-2 m, and 19-20 m, the median of the minimum distance range is 0.5 m, and the median of the maximum distance range is 19.5 m. Here, "distance" refers to the distance from the light output unit of the measurement device to the surface of the object. The light output unit is the part or component of the measurement device from which light is emitted. In the examples of FIGS. 3 and 5, the collimator 123 corresponds to the light output unit, and in the example of FIG. 6, the optical deflector 170 corresponds to the light output unit. The reference object can be, for example, a mirror, a diffuse reflector, or an actual object to be measured.

[0070] (Step S102) The processing circuitry 140 sends a control signal to the light source 110, causing the light source 110 to emit frequency-modulated light. This operation may be performed according to instructions from an operator.

[0071] (Step S103) The processing circuit 140 acquires a detection signal from the photodetector 130. While light is being emitted from the light source 110, the photodetector 130 outputs a detection signal corresponding to the intensity of the interference light. The time length of the detection signal acquired by the processing circuit 140 may be, for example, approximately 1 to 50 times the modulation period. The detection signal may be averaged to improve the S / N ratio of the detection signal. In this case, the processing circuit 140 acquires the detection signal for a relatively long time and repeats the process of averaging the detection signal over a predetermined period of time that is sufficiently shorter than the modulation period. The processing circuit 140 includes, for example, an analog-to-digital (A / D) converter and a memory. The processing circuit 140 digitizes the detection signal waveform using, for example, the A / D converter and stores the digitized signal in memory.

[0072] (Step S104) The processing circuit 140 stops the emission of light from the light source 110 by stopping the transmission of the control signal. This step can be performed in accordance with an instruction from an operator. Alternatively, the processing circuit 140 may automatically stop the emission in accordance with a predetermined program. Note that, if the operation of generating correction data is to be continuously repeated, the light may continue to be emitted.

[0073] (Step S105) The processing circuit 140 analyzes the period of the detection signal. The period analysis method may, for example, extract the maximum value of an upwardly convex portion or the minimum value of a downwardly convex portion in the waveform of the detection signal, and define one period as the period from the maximum value to the next maximum value, or the period from the minimum value to the next minimum value. Alternatively, the period analysis method may extract zero-crossing points (i.e., points where the value of the detection signal changes from positive to negative or negative to positive), 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.

[0074] FIG. 9 is a graph showing an example of the analysis results of the period of the detection signal. In FIG. 9, 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 V i , V i+1 , V i+2 , , and the period when i , P i+1 , P i+2 ,... In this example, the control signal voltage is V i From the point of V i+1 The time length up to this point is the period P i It is defined as follows.

[0075] Next, the processing circuit 140 calculates the control signal voltage V i , V i+1 , V i+2 , and period P i , P i+1 , P i+2 , ... is plotted, and an approximate equation is found for the plotted points. The approximate equation is, for example, a polynomial of degree two or higher, and can be found using, for example, the least squares method. Figure 10 shows an example of a correction curve indicated by the approximate equation.

[0076] (Step S106) The processing circuit 140 generates correction data indicating the relationship between the voltage of the control signal and the period correction ratio based on the generated approximation formula, and records the generated correction data in the storage device 150. FIG. 11 shows an example of the correction data. The correction data is generated for each of a plurality of distance ranges. FIG. 11 shows N tables corresponding to N ranges, from the first range to the Nth range, as an example of the correction data. The correction data shown in FIG. 11 holds information on the value of the control voltage applied to the light source 110 and the period correction ratio, which is a numerical value for correcting the period of the detection signal. The format of the correction data is not limited to a table, and other data formats, such as a function, may also be used. Regardless of the format, the correction table may include information on correction values ​​for adjusting the period of the detection signal if it is too long or too short.

[0077] The period correction ratio may be, for example, a value by which the period before correction is multiplied 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. Figure 12 shows an example of the waveform of the detection signal before and after correction. The period correction ratio may be set to a value such that the beat frequency of the waveform of the detection signal after correction becomes a constant value 1 / Pm.

[0078] The correction data is not limited to a correction table or correction function that defines the correspondence between the control voltage and the period correction value. The correction data 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 within the modulation period and the period correction value may be used as the correction data.

[0079] Furthermore, instead of data for correcting the period of the detection signal, data for changing the sampling timing of the detection signal may be generated as correction data. Based on such correction data, the digitization timing, which would normally be sampled at equal time intervals, can be appropriately changed in accordance with the control voltage, drive current, or phase, thereby correcting the detection signal.

[0080] 13 is a diagram showing an example of correction data including information on correction values ​​for changing the sampling timing of the detection signal. In this example, each correction data includes information on the sampling interval corresponding to each value of the drive voltage. By referring to this correction data, the processing circuit 140 can correct the detection signal to a signal with a substantially constant period by changing the sampling intervals, which would normally be equal, to uneven sampling intervals.

[0081] FIG. 14 shows another example of a correction table. The correction table in this example includes information on the phase within one cycle of the frequency modulation of the laser beam and the cycle 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 cycle is constant and the same control signal is repeated, the same effect as described above can be achieved by using correction data that defines the phase of the sweep cycle and the cycle correction ratio, as shown in FIG. 14 . Alternatively, as shown in FIG. 15 , correction data that defines the phase within one cycle and the sampling interval may be used. The processing circuit 140 can correct the detection signal to a signal with a substantially constant cycle by referring to such correction data and changing the sampling timing of the detection signal.

[0082] Data defining the relationship between beat frequency and distance may also be recorded in the memory of the storage device 150 or the processing circuit 140. FIG. 16 shows an example of data defining the relationship between beat frequency and distance. Such data may be referenced when the processing circuit 140 calculates a distance value based on the beat frequency during a distance measurement operation. Note that the distance value may be calculated from the beat frequency based on data in the form of a function, not limited to the table shown in FIG. 16.

[0083] (Steps S107 and S108) The processing circuit 140 determines whether correction data has been generated for all distance ranges required for actual use of the measurement device 100. If correction data has been generated for all distance ranges, the process ends. If correction data generation for all distance ranges has not yet been completed, the distance between the measurement device and the reference object is changed, and the process returns to step S102. The distance change may be performed manually by an operator or automatically by the system using a device to move the object. For example, if 20 distance ranges, each with a width of 1 m, are set, such as 0-1 m, 1-2 m, and 19-20 m, the distance can be changed so that the reference object moves 1 m away from or closer to the measurement device. Note that each of the multiple distance ranges does not necessarily have to have the same width, and the intervals between the multiple distance ranges do not necessarily have to be equal. The multiple distance ranges can be set arbitrarily depending on the purpose and application.

[0084] The processing circuit 140 repeats the operations of steps S102 to S108 until correction data for all distance ranges is generated and recorded. Through the above operations, the processing circuit 140 can generate correction data corresponding to each of the multiple distance ranges and store it in the storage device 150.

[0085] In addition to the distance, the operating state of the light source 110 may also be changed in a similar manner, and correction data may be generated for each combination of distance and operating state of the light source 110. The operating state of the light source 110 depends on various parameters, such as the modulation voltage amplitude of the control signal, the bias voltage of the control signal, or the temperature of the light source 110. As described in Patent Document 3, the nonlinearity of the beat frequency may change depending on these parameters, so it may be effective to generate correction data associated with not only the distance but also these parameters. Furthermore, different correction data may be generated for the up-chirp period and down-chirp period of the frequency modulation for each distance range. As described in Patent Document 2, the nonlinearity of the beat frequency may change depending on the up-chirp period and down-chirp period, so it may be effective to generate separate correction data not only for the distance but also for the up-chirp period and down-chirp period.

[0086] As shown in FIGS. 11 and 13-15, the storage device 150 stores multiple correction data. Each correction data is associated with a corresponding one of multiple different distance ranges. In the examples of FIGS. 11 and 13-15, one corresponding table is associated as correction data with each of N distance ranges. The width of each distance range is arbitrary, and a single distance value may be associated with the correction data as a "distance range." Furthermore, since the distance range correlates with the beat frequency range, a frequency range may be associated with the correction data. Even when a frequency range (or a single value) is associated with the correction data, it is interpreted that the "distance range" is associated with the correction data. Therefore, in the present disclosure, "each correction data is associated with a corresponding one of multiple different distance ranges" is synonymous with "each correction data is associated with a corresponding one of multiple different frequency ranges."

[0087] <Distance measurement operation> Next, an example of a distance measurement operation by the measurement device 100 will be described.

[0088] FIG. 17 is a flowchart showing an example of a distance measurement operation by the measurement device 100. In the example shown in FIG. 17, the processing circuit 140 first corrects the detection signal using one piece of correction data (hereinafter referred to as "standard correction data") corresponding to a specific distance range that serves as a reference from among the multiple correction data, and calculates an approximate value of the distance to the object based on the corrected detection signal. This approximate value of the distance is referred to as the "approximate distance." The processing circuit 140 selects one piece of correction data corresponding to the approximate distance from among the multiple correction data, corrects the detection signal based on the selected correction data, and calculates the distance to the object based on the corrected detection signal. The operation of each step shown in FIG. 17 will be described below.

[0089] (Step S201) The processing circuitry 140 sends a control signal to the light source 110, causing the light source 110 to emit frequency-modulated light. This operation may be performed, for example, in accordance with instructions from a user.

[0090] (Step S202) The processing circuit 140 acquires the detection signal output from the photodetector 130. The acquisition of the detection signal is performed over a certain period of time. As in step S103 shown in FIG. 8, the signal may be averaged over time to improve the S / N ratio of the signal. In this case, the processing circuit 140 may acquire the detection signal for a relatively long period of time, and repeat the process of averaging the detection signal over a predetermined period of time that is sufficiently shorter than the modulation period for each time step.

[0091] (Step S203) The processing circuit 140 acquires the standard correction data from the storage device 150. The standard correction data may be, for example, correction data corresponding to a range near the center of the entire distance range that can be measured by the measurement device 100. Alternatively, the standard correction data may be correction data corresponding to the shortest distance range or the longest distance range of the entire distance range.

[0092] (Step S204) The processing circuit 140 corrects the detection signal based on the standard correction data. The corrected detection signal is called the "standard corrected detection signal." This correction suppresses fluctuations in the period of the beat signal, as shown in FIG. 12, for example. However, if the standard correction data does not correspond to the actual distance to the target object, suppression of fluctuations in the period of the beat signal may be insufficient.

[0093] (Step S205) The processing circuit 140 performs a frequency analysis of the waveform of the standard corrected detection signal. In this step, the processing circuit 140 performs processing such as a fast Fourier transform on the waveform of the standard corrected detection signal to generate a frequency spectrum of the standard corrected detection signal.

[0094] (Step S206) The processing circuit 140 extracts the frequency at which the maximum peak of the frequency spectrum is obtained (hereinafter also referred to as the "spectral peak"), and sets this frequency as the beat frequency.

[0095] (Step S207) The processing circuit 140 calculates the approximate distance to the target object by converting the beat frequency into a distance value. In this conversion process, the processing circuit 140 reads and uses a conversion table such as that shown in FIG.

[0096] (Step S208) The processing circuit 140 determines whether the calculated approximate distance is within the distance range corresponding to the standard correction data. If the approximate distance is within the distance range corresponding to the standard correction data, the process proceeds to step S220. If the approximate distance is not within the distance range corresponding to the standard correction data, the process proceeds to step S211.

[0097] (Step S211) The processing circuit 140 selects correction data based on the approximate distance. Specifically, the processing circuit 140 selects correction data associated with a distance range including the approximate distance from among a plurality of correction data stored in the storage device 150. If there is no correction data associated with a distance range including the approximate distance, for example, correction data associated with a distance range closest to the approximate distance may be selected.

[0098] (Step S212) The processing circuit 140 corrects the waveform of the detection signal based on the selected correction data. This correction provides a corrected detection signal in which fluctuations in the period of the beat signal are suppressed, as shown in FIG.

[0099] (Step S213) The processing circuit 140 performs a frequency analysis of the waveform of the corrected detection signal. In this step, for example, the processing circuit 140 performs processing such as a fast Fourier transform on the waveform of the corrected detection signal to generate a frequency spectrum of the corrected detection signal.

[0100] (Step S214) The processing circuit 140 extracts the frequency at which the maximum peak of the frequency spectrum is obtained (i.e., the spectrum peak), and sets this frequency as the beat frequency.

[0101] (Step S215) The processing circuit 140 calculates the distance to the object by converting the beat frequency into a distance value. In this conversion process, the processing circuit 140 reads and uses a conversion table such as that shown in FIG.

[0102] (Step S220) The processing circuit 140 generates and outputs measurement data including information on the calculated distance.

[0103] Through the above operations, processing circuitry 140 can generate distance data for object 300. When measuring distance continuously, the operations from steps S201 to S220 are repeated continuously. Processing circuitry 140 may measure the speed of object 300 in addition to or instead of the distance. When measuring the speed, the speed can be calculated using the method described with reference to FIGS. 7A and 7B.

[0104] As described above, in this embodiment, the processing circuit 140 generates a standard corrected detection signal by correcting the detection signal based on standard correction data associated with a specific distance range, and calculates an approximate distance to the object based on the standard corrected detection signal. The processing circuit 140 generates a corrected detection signal by correcting the detection signal using correction data corresponding to the approximate distance. The processing circuit 140 calculates a beat frequency by performing frequency analysis on the corrected detection signal, and calculates the distance to the object based on the beat frequency. This operation reduces fluctuations in the frequency of the beat signal included in the detection signal, enabling more accurate measurement of the distance to the object.

[0105] (Embodiment 2) Next, a measurement system according to a second exemplary embodiment of the present disclosure will be described.

[0106] FIG. 18 is a diagram illustrating an example of the configuration of a measurement system according to the second embodiment. In this embodiment, a sensing device 230 different from the measurement device 100 is used. The sensing device 230 is a device with a distance measurement function, such as a camera, radar, ultrasonic sensor, or ToF ranging sensor. The sensing device 230 is, for example, a device that measures distance with lower accuracy than the measurement device 100. In the example of FIG. 18, the sensing device 230 is connected to the measurement device 100 for use, but it may also be included in the measurement device 100. The sensing device 230 measures an approximate distance to the object 300 and sends information indicating the approximate distance to the measurement device 100. The processing circuit 140 acquires the information indicating the approximate distance and, based on the approximate distance, selects correction data corresponding to the approximate distance from among multiple correction data. The subsequent processing is the same as in the first embodiment. The operation of this embodiment will be described in more detail below. Descriptions of operations similar to those in the first embodiment will be omitted.

[0107] FIG. 19 is a flowchart showing the operation of the measurement apparatus 100 in this embodiment. In FIG. 19, the same steps as in FIG. 17 are denoted by the same reference numerals. In the example shown in FIG. 19, step S210 is executed instead of steps S203-S208 in FIG. 17. That is, instead of acquiring approximate distance information by a preliminary distance measurement operation using standard correction data, the processing circuit 140 acquires approximate distance information from the external sensing device 230. The operations of steps S201-S202 and S211-S220 are the same as the corresponding operations shown in FIG. 17.

[0108] In step S210, the processing circuit 140 acquires information indicating the approximate distance to the object 300 measured by the sensing device 230. The processing circuit 140 sends a measurement command to the sensing device 230, and the sensing device 230 measures the approximate distance to the object 300 in response to the command. Note that the measurement of the approximate distance may be performed at any time before step S211. For example, the approximate distance may be measured before steps S201 and S202.

[0109] After step S210, processing circuit 140 executes steps S211 to S220, thereby enabling more accurate calculation of the distance to the object based on the correction data corresponding to the approximate distance.

[0110] The measuring device 100 in this embodiment acquires approximate distance information from the sensing device 230, but may be configured to acquire approximate distance information from another device (hereinafter collectively referred to as "input device").

[0111] FIG. 20 is a diagram showing an example of the configuration of a measurement system including an input device 240. The input device 240 may be, for example, a device or computer configured to receive input of an approximate distance from a user or an external device (e.g., a computer in a higher-level system). In the example of FIG. 20, the processing circuit 140 acquires approximate distance information from the input device 240 and selects optimal correction data based on the approximate distance. Operations other than the method of acquiring the approximate distance information are the same as those shown in FIG. 19. In the example of FIG. 20, the input device 240 is used by being connected to the measurement device 100, but the input device 240 may also be included in the measurement device 100. The input device 240 may be, for example, an interface that communicates with an external device.

[0112] Note that instead of the information indicating the "approximate distance," the input device 240 may input information specifying correction data, such as a "correction data number," to the processing circuit 140. In that case, the processing circuit 140 selects correction data based on the input information specifying the correction data, instead of the operations of steps S210 and S211 in FIG.

[0113] (Embodiment 3) Next, a measurement device according to a third exemplary embodiment of the present disclosure will be described.

[0114] The configuration of the measurement device in this embodiment is the same as that in embodiment 1, but the processing executed by the processing circuitry 140 differs from that in embodiment 1. The differences from embodiment 1 will be described below.

[0115] FIG. 21 is a flowchart showing the measurement operation in the third embodiment. In this embodiment, the processing circuit 140 generates multiple corrected detection signals by correcting the detection signal based on each of multiple pieces of correction data, calculates multiple distances based on each of the multiple corrected detection signals, and determines one distance selected from the multiple distances as the distance to the object. This makes it possible to accurately measure the distance to the object without obtaining information indicating the approximate distance. The operation of each step shown in FIG. 21 will be described below.

[0116] (Step S301) The processing circuit 140 sends a control signal to the light source 110, causing the light source 110 to emit frequency-modulated light. Step S301 is the same as the operation of step S201 shown in FIG.

[0117] (Step S302) The processing circuit 140 acquires the detection signal output from the photodetector 130. The acquisition of the detection signal is performed over a certain period of time. Step S302 is the same as the operation of step S202 shown in FIG.

[0118] (Step S303) The processing circuit 140 acquires a plurality of (for example, all) correction data from the storage device 150.

[0119] (Step S304) The processing circuit 140 corrects the detection signal based on each of the acquired correction data. The method of correcting the detection signal based on each correction data is the same as the method in step S204 or S212 shown in FIG. 17. This results in multiple corrected detection signals. Each of the multiple corrected detection signals is obtained by correcting the detection signal using a corresponding one of the correction data.

[0120] (Step S305) The processing circuit 140 performs frequency analysis on each of the plurality of corrected detection signals. The method of frequency analysis is the same as the method in step S205 or S213 in Fig. 17. The processing circuit 140 generates a frequency spectrum for each of the plurality of corrected detection signals through frequency analysis.

[0121] (Step S306) The processing circuit 140 extracts a spectral peak from the frequency spectrum of each of the corrected detection signals in the same manner as in step S206 or S214 shown in FIG.

[0122] (Step S307) The processing circuit 140 calculates the distance from each spectral peak extracted for each corrected detection signal. The distance calculation method is the same as the method in step S207 or S215 shown in Fig. 17. In step S307, multiple distances are calculated.

[0123] (Step S308) Processing circuitry 140 selects, from the distances calculated in step S307, the distance that best matches the distance range of the corresponding correction data. For example, processing circuitry 140 may select, from the calculated distances, one distance that is included in the distance range associated with the correction data used to calculate that distance, or one distance that is closest to that distance range.

[0124] (Step S309) The processing circuit 140 generates and outputs measurement data including information on the distance selected in step S308. Step S309 is the same as the operation in step S220 shown in FIG.

[0125] As described above, in this embodiment, the detection signal is corrected based on each of the multiple correction data to generate multiple corrected detection signals. Then, multiple distances are calculated based on each of the multiple corrected detection signals. From these distances, one distance estimated to be closest to the actual distance is selected as the distance to the object. This makes it possible to perform highly accurate measurements over a wide range without obtaining approximate distance information, unlike in the first and second embodiments.

[0126] In this embodiment, the distance ranges of the multiple correction data do not overlap, but the distance ranges may overlap. For example, two adjacent distance ranges may overlap, such as a first range of 0-12 m, a second range of 10 m-24 m, and a third range of 20 m-36 m. In such a case, two or more of the calculated distances may be included in the distance range associated with the corresponding correction data used to calculate each distance. In such a case, in step S308, processing circuit 140 may select, for example, one of the following distances: The distance whose difference between the median of the corresponding distance range and the calculated distance is smaller Distance calculated using correction data with a narrower distance range Distance calculated using correction data with a smaller distance range (i.e., corresponding to a shorter distance)

[0127] In the example shown in Fig. 21, in each of steps S304-S307, the process proceeds to the next step only after the process for all correction data is completed. Instead of such an operation, the process corresponding to steps S304-S307 may be executed in parallel for each correction data. An example of such a process will be described below.

[0128] FIG. 22 is a flowchart showing an example of an operation in which processing corresponding to steps S304-S307 shown in FIG. 21 is performed in parallel for each correction data. The operations of steps S301-S303 and S308-S309 in the example of FIG. 22 are the same as the operations of the corresponding steps shown in FIG. 21. In the example of FIG. 22, after step S303, steps S300a, S300b, ..., S300n are performed in parallel. Steps S300a, S300b, ..., S300n represent processing using correction data for the first range, the second range, ..., the Nth range, respectively. For each correction data, detection signal correction, frequency analysis, spectral peak extraction, and distance calculation are performed in parallel. When all of steps S300a, S300b, ..., S300n are completed, the process proceeds to step S308, where the optimal distance is selected.

[0129] The processes of steps S300a, S300b, ..., S300n may be performed serially, for example, in the order of steps S300a, S300b, ..., S300n.

[0130] 21 and 22, an optimal distance is selected from multiple distances calculated from multiple corrected detection signals corrected using each of multiple correction data. However, the operation is not limited to this. An optimal spectral peak may be selected based on the multiple spectral peaks calculated in step S306 or steps S306a, ..., S306n, and the distance to the target object may be calculated based on the selected spectral peak. In this case, each correction data is recorded in association with a range of spectral peak positions (i.e., beat frequencies). Note that, since there is a correlation between beat frequencies and distances, it can be said that correction data associated with a range of beat frequencies is also associated with a distance range.

[0131] Fig. 23 is a flowchart showing an example of an operation for selecting an optimal spectral peak based on a plurality of calculated spectral peaks and calculating the distance to the object based on the selected spectral peak. In the flowchart shown in Fig. 23, steps S307 and S308 shown in Fig. 21 are replaced with steps S317 and S318. Other points are the same as those in the flowchart shown in Fig. 21.

[0132] In step S317, processing circuit 140 selects, from the extracted multiple spectral peaks, the spectral peak that best matches the distance range (or beat frequency range) of the corresponding correction data. In step S318, processing circuit 140 calculates the distance from the selected spectral peak (i.e., beat frequency). The distance calculation method is the same as in step S307. The calculated distance is output as the distance to the object in step S220.

[0133] In the example of FIG. 23, similarly to the example of FIG. 22, the processes of steps S304 to S306 may be executed in parallel for each piece of correction data.

[0134] 23, the processing circuit 140 calculates multiple beat signals based on the multiple corrected detection signals, and calculates the distance to the target based on one beat signal selected from the multiple beat signals. Specifically, the processing circuit 140 selects one beat signal from the multiple beat signals that corresponds to the correction data used to calculate the beat signal, and calculates the distance to the target based on that beat signal. This operation also makes it possible to expand the range of distances that can be measured with high accuracy.

[0135] (Embodiment 4) Next, a measurement device according to a fourth exemplary embodiment of the present disclosure will be described.

[0136] The configuration of the measurement device in this embodiment is the same as that in the first embodiment, but the processing executed by the processing circuitry 140 is different from that in the first embodiment.

[0137] Fig. 24 is a flowchart showing the measurement operation in the fourth embodiment. The operations of steps S201-S207 and S211-S220 shown in Fig. 24 are the same as the operations of the corresponding steps shown in Fig. 17. In this embodiment, steps S209, S216, and S217 are added instead of step S208 in Fig. 17. The operations of these steps will be described below.

[0138] (Step S209) Processing circuit 140 determines whether or not there is correction data corresponding to the approximate distance calculated in step S207 among the multiple correction data stored in storage device 150. If there is correction data corresponding to the approximate distance, the process proceeds to step S211, and similar to the example in Fig. 17, the processes of steps S212-S220 are executed and the distance is output. On the other hand, if there is no correction data corresponding to the approximate distance, the process proceeds to step S216.

[0139] (Step S216) The processing circuit 140 selects, from the plurality of correction data, two or more correction data associated with distance ranges relatively close to the approximate distance. For example, from the plurality of correction data, the processing circuit 140 may select, from the plurality of correction data, correction data associated with the distance range closest to the approximate distance and correction data associated with the distance range next closest to the approximate distance.

[0140] (Step S217) The processing circuit 140 combines the two or more selected correction data to generate new correction data (hereinafter referred to as "composite correction data"). For example, the processing circuit 140 may generate the composite correction data by averaging corresponding values ​​in the two or more correction data. Alternatively, the processing circuit 140 may generate the composite correction data by mixing the two or more correction data at a ratio based on the difference between the median of the distance range of each correction data and the approximate distance, and interpolating the values. The processing circuit 140 corrects the detection signal in step S212 using the generated composite correction data. The processing from step S212 onwards is the same as the example in FIG. 17.

[0141] As described above, in this embodiment, the processing circuit 140 acquires information about the approximate distance and then generates composite correction data by combining two or more correction data pieces that are close to the approximate distance. The processing circuit 140 corrects the detection signal based on the composite correction data. This allows the detection signal to be appropriately corrected by combining the correction data pieces even if there is no correction data piece corresponding to the approximate distance. For example, if the correction data pieces are associated with specific distances such as 1 m, 5 m, 10 m, etc., or if there are gaps in the distance ranges of the correction data pieces such as 0-5 m, 8-12 m, 15-20 m, etc., even if the approximate distance does not fall within the distance range of any of the correction data pieces, the correction data pieces can be appropriately combined. The processing circuit 140 corrects the detection signal using the combined correction data and calculates the distance based on the corrected detection signal. This enables ranging over a wider distance range.

[0142] In the example of Fig. 24, the approximate distance is calculated based on the detection signal corrected using the standard correction data, as in the example of Fig. 17, but the approximate distance information may be obtained by other methods. For example, the approximate distance information may be input from a sensing device or another input device, as in the example of Fig. 19.

[0143] Furthermore, instead of obtaining approximate distance information, it is also possible to combine the process of correcting the detection data using each of a plurality of correction data to calculate the beat frequency or distance, and then selecting the optimal result from among these calculation results, with the process of synthesizing the correction data in this embodiment, as shown in the examples of Figures 21, 22, and 23. Such an example will be described below.

[0144] Fig. 25 is a flowchart showing an example of an operation that combines a process for selecting an optimal result from calculation results using a plurality of correction data with a process for synthesizing correction data. The flowchart shown in Fig. 25 is obtained by adding steps S310-S316 to the flowchart shown in Fig. 21. In the example of Fig. 25, after step S307, the process proceeds to step S310.

[0145] In step S310, processing circuit 140 determines whether the multiple calculated distances include a distance that matches the distance range of the corresponding correction data. Here, "the distance range of the corresponding correction data" means the distance range (which may be a single value) associated with the correction data used to calculate that distance. If the multiple distances include a distance that falls within the distance range of the corresponding correction data, processing proceeds to step S308. The processing of step S308 is the same as the processing of step S308 in FIG. 21. If the multiple distances include a distance that falls within the distance range of the corresponding correction data, processing proceeds to step S311.

[0146] In step S311, the processing circuitry 140 selects, from among the plurality of correction data, two or more pieces of correction data whose distances calculated based on the correction data are relatively close to the distance range associated with the correction data. For example, from among the plurality of correction data, the processing circuitry 140 may select two pieces of correction data whose distances calculated based on the correction data are closest to the distance range associated with the correction data.

[0147] In step S312, the processing circuit 140 combines the two or more selected correction data. The combining process is similar to the process in step S217 in FIG. As a result, composite correction data is generated in which each value is interpolated based on two or more correction data.

[0148] In step S313, the processing circuit 140 corrects the detection signal based on the combined correction data. This process is similar to step S212 in FIG.

[0149] Subsequently, frequency analysis is performed based on the corrected detection signal (step S314), spectral peaks are extracted (step S315), and distances are calculated based on the spectral peaks (step S316). The processes in steps S314, S315, and S316 are similar to the processes in steps S213, S214, and S215 shown in FIG. 24, respectively.

[0150] In the example of Fig. 25, the processes of steps S310-S316 are added to the operation shown in Fig. 21, but the processes of steps S310-S316 may also be added to the operation shown in Fig. 22. Also, similar processes may be added to the operation shown in Fig. 23.

[0151] Fig. 26 shows an example of such an operation. In the example of Fig. 26, step S320 is added between step S306 and step S317, and if the determination in step S320 is No, the processes of steps S321-S326 are executed. In this example, in steps S320 and S321, the processes are executed based on the value of the extracted spectral peak (i.e., the beat frequency) rather than the calculated distance. The processes of steps S322-S326 are similar to the processes of steps S312-S316 shown in Fig. 25, respectively.

[0152] (Embodiment 5) Next, a measurement device according to a fifth exemplary embodiment of the present disclosure will be described.

[0153] FIG. 27 is a block diagram showing an example of the configuration of a measurement apparatus 100 according to a fifth embodiment. The measurement apparatus 100 in this embodiment includes an optical deflector 170 (also referred to as a "beam scanner") that changes the direction of output light from the interference optical system 120. As described with reference to FIG. 6, the optical deflector 170 may include, for example, a MEMS mirror or a galvanometer mirror. The optical deflector 170 can change the emission direction of the output light 22 by changing the angle of the mirror in accordance with a command from the processing circuit 140. The optical deflector 170 is not limited to one that includes a MEMS mirror or a galvanometer mirror, and may be another type of beam scanning device.

[0154] In this embodiment, the processing circuit 140 controls the optical deflector 170 to perform a scanning operation in which the direction of the output light (i.e., the light beam) is changed within the target region while the photodetector 130 generates a detection signal. The processing circuit 140 calculates an approximate distance for each direction of the output light based on the detection signal output from the photodetector 130 during the scanning operation. The processing circuit 140 stores the approximate distance in the storage device 150 in association with the direction of the output light. The processing circuit 140 classifies (also referred to as "dividing") the target region into multiple partial regions based on the approximate distances associated with each of the multiple directions of the output light. The processing circuit 140 determines appropriate correction data for each partial region. The processing circuit 140 performs a more detailed scan of at least one of the multiple partial regions. Specifically, the processing circuit 140 controls the optical deflector 170 to change the direction of the output light within the partial region and acquires a detection signal output from the photodetector 130 for each direction of the output light. The processing circuit 140 selects correction data suitable for the partial region from the plurality of correction data, corrects the detection signal based on the selected correction data to generate a corrected detection signal, and calculates the distance to the object 300 based on the corrected detection signal.

[0155] Fig. 28 is a flowchart showing an outline of the operation of the measuring apparatus 100 in this embodiment. The measuring apparatus 100 in this embodiment executes the operations of steps S510, S530, and S550 shown in Fig. 28. The operation of each step will be described below.

[0156] (Step S510) In step S510, the measurement device 100 performs a rough scan to measure the entire target area at a relatively high speed, calculates the rough distance for each direction of emitted light (hereinafter also referred to as the “irradiation direction”), and records the calculated rough distance in the storage device 150.

[0157] 29 is a diagram showing an example of correspondence data between irradiation directions and approximate distances recorded in storage device 150. In this example, the irradiation direction is specified by a combination of x and y coordinates, and the measured approximate distances for each of a plurality of irradiation directions are recorded in the form of a table in storage device 150. Note that the approximate distance data for each irradiation direction may be recorded in a storage device different from storage device 150 that stores correction data. Instead of the approximate distances, information such as a number that identifies a correction table corresponding to the approximate distances may be recorded for each irradiation direction.

[0158] (Step S530) The measurement device 100 divides the target area into multiple partial areas according to distance. For each partial area, the processing circuitry 140 determines a representative value of the approximate distance or correction data to be used in the subsequent detailed scan.

[0159] (Step S550) The measurement device 100 performs a detailed scan of each partial region, which is more dense than a rough scan. In the detailed scan, a correction process is performed on the detection signal using correction data that differs for each partial region. This allows for precise distance measurement for each partial region. Note that the detailed scan may be performed on only some of the partial regions.

[0160] 30A to 30C show an example of a scene in which the measurement device 100 of this embodiment is used. In this example, the measurement target area includes a road intersection where vehicles and pedestrians are passing by. Note that the measurement is not limited to such a busy environment, and may also be performed in an environment with few moving objects, such as a construction site.

[0161] FIG. 30A is a schematic diagram illustrating the rough scan performed in step S510. The rough scan is performed to obtain approximate distance information for each irradiation direction or for each subregion. A rough scan is a high-speed scan that is completed in a short time compared to the subsequent detailed scan. For example, a rough scan may be spatially coarse, may have a small number of signal averages when measuring in one irradiation direction, or may have a short frequency modulation period compared to a detailed scan. A short modulation period shortens the measurement time, enabling faster measurement. As shown in FIG. 30A, the measurement device 100 scans with a light beam within a certain range in each of the horizontal and vertical directions. The measurement device 100 measures distances by emitting a light beam in multiple directions, each indicated by a circle in FIG. 30A. This allows for approximate distance information to be obtained for each irradiation direction of the light beam. The approximate distances for each irradiation direction may be recorded in the form of a table, such as that shown in FIG. 29.

[0162] Fig. 30B is a diagram showing an example of the result of the region division process in step S530. By the region division process, the target region is divided into a plurality of partial regions based on the magnitude of the approximate distance. In the example of Fig. 30B, the target region is divided (i.e., classified) into partial region A corresponding to a relatively short distance, partial region B corresponding to a medium distance, and partial region C corresponding to a relatively long distance. In such a case, different correction data is associated with each of partial regions A, B, and C.

[0163] For example, assume that three types of correction data are used: for 0-7 m, for 7-27 m, and for 27 m or more. In this case, the target area can be divided into partial area A corresponding to the correction data for 0-7 m, partial area B corresponding to the correction data for 7-27 m, and partial area C corresponding to the correction data for 27 m or more. As an example, it is assumed that the approximate distances d00, dij, and dnm shown in FIG. 29 are respectively the following data. d00: corresponds to the location of the building wall beyond the road in the upper left of Figure 30B, and the value is 15m dij: corresponds to the sky position in Figure 30B, and the value indicates that it is not possible to measure dnm: corresponds to the position on the road arrow in Figure 30B, and the value is 3m In this case, the data of d00 is classified into the partial area B, the data of dij is classified into the partial area C, and the data of dnm is classified into the partial area C.

[0164] FIG. 30C is a diagram illustrating the detailed scan performed in step S550. In the detailed scan, more precise distance measurement is performed on some or all of the multiple partial regions. FIG. 30C illustrates a detailed scan being performed on partial region A. Similar detailed scans can be performed on the other partial regions B and C.

[0165] The distances measured in the detailed scan shown in Figure 30C are closer to each other than in the rough scan, i.e., the spatial density of the detailed scan is higher than that of the rough scan.

[0166] Next, more specific examples of the operations in steps S510, S530, and S550 will be described with reference to FIGS.

[0167] 31 is a flowchart showing a specific example of the operation of step S510. Step S510 includes the operations of steps S511 to S521. The operation of each step will be described below.

[0168] (Step S511) The processing circuit 140 performs a light beam irradiation plan for the rough scan. The irradiation plan determines the direction and order in which the light beam is to be emitted. The processing circuit 140 performs the light beam irradiation plan, for example, according to a predetermined setting. As illustrated in FIG. 30A, the processing circuit 140 determines multiple irradiation directions so as to cover a certain range of the measurement target. Measurement is performed in all of the directions determined here.

[0169] (Step S512) The processing circuit 140 acquires the standard correction data from the storage device 150. This operation is similar to step S203 shown in FIG.

[0170] (Step S513) The processing circuitry 140 selects an irradiation direction for which measurement has not yet been performed from the multiple irradiation directions determined in step S511. The processing circuitry 140 sets or switches the irradiation direction to a desired direction by sending a control signal to the optical deflector 170 (scanner).

[0171] (Step S514) The processing circuit 140 sends a control signal to the light source 110, causing the light source 110 to emit frequency-modulated light. This operation is similar to step S201 shown in FIG.

[0172] (Step S515) The processing circuit 140 acquires the detection signal output from the photodetector 130. The acquisition of the detection signal is carried out over a certain period of time. This operation is similar to step S202 shown in FIG.

[0173] (Step S516) The processing circuit 140 corrects the detection signal based on the standard correction data to generate a standard corrected detection signal. This operation is similar to step S204 shown in FIG.

[0174] (Step S517) The processing circuit 140 performs frequency analysis on the waveform of the standard corrected detection signal to generate a frequency spectrum of the standard corrected detection signal. This operation is similar to step S205 shown in FIG.

[0175] (Step S518) The processing circuit 140 extracts the frequency at which the maximum peak of the frequency spectrum is obtained (spectral peak) and sets this frequency as the beat frequency. This operation is the same as step S206 shown in FIG.

[0176] (Step S519) The processing circuit 140 converts the beat frequency into a distance value to calculate an approximate distance to the object. This operation is similar to step S207 shown in FIG.

[0177] (Step S520) The processing circuit 140 associates the calculated approximate distance with the irradiation direction and stores the association in the storage device 150. The processing circuit 140 stores the association between the irradiation direction and the approximate distance in the storage device 150 in a format such as that shown in FIG.

[0178] (Step S521) The processing circuit 140 determines whether measurement has been completed for all irradiation directions determined in step S511. If measurement has been completed for all irradiation directions, the process proceeds to step S530. If measurement has not been completed for all irradiation directions, the process returns to step S513, and the operations of steps S514-S520 are executed again for the next irradiation direction. The operations of steps S513-S521 are repeated until it is determined in step S521 that measurement has been completed for all irradiation directions.

[0179] When the above rough scan is completed, the processing circuit 140 executes the region division process in step S530.

[0180] 32 is a flowchart showing a specific example of the region division process in step S530. Step S530 includes steps S531, S532, and S533. The operation of each step will be described below.

[0181] (Step S531) The processing circuit 140 classifies the approximate distances calculated for each irradiation direction into distance ranges associated with multiple correction data. For example, if three types of correction data are used, for example, for 0-7 m, 7-27 m, and 27 m or more, the approximate distances for each irradiation direction are classified into 0-7 m, 7-27 m, or 27 m or more.

[0182] (Step S532) The processing circuit 140 groups all the irradiation points or irradiation directions for which approximate distances have been obtained into multiple groups based on the classification result in step S531. For example, the processing circuit 140 may group two or more irradiation points or two or more irradiation directions whose three-dimensional coordinates are close to each other into the same group based on the irradiation direction and the approximate distance.

[0183] (Step S533) Based on the grouping results, the processing circuitry 140 divides the target region into multiple partial regions. The processing circuitry 140 associates information identifying each partial region with a representative value (e.g., average value) of the approximate distance of that partial region or information identifying correction data (e.g., identification number) to be used in a subsequent detailed scan, and stores the information in the storage device 150.

[0184] Instead of the above operation, the processing circuit 140 may cluster the approximate distances for each irradiation direction, classify the irradiation directions according to the clusters, and generate correction data that matches the distances of the cluster centroids based on multiple existing correction data. The correction data may be generated by, for example, the correction data synthesis process described with reference to Figures 24 to 26.

[0185] When the above region division process is completed, the processing circuit 140 executes a detailed scan in step S550.

[0186] 33 is a flowchart showing a specific example of the detailed scan process of step S550. Step S550 includes the operations of steps S551 to S563. The operation of each step will be described below.

[0187] (Step S551) The processing circuit 140 performs a light beam irradiation plan for each partial region. That is, the processing circuit 140 determines the direction and order in which the light beam is to be emitted for each partial region. The processing circuit 140 determines multiple irradiation directions to cover the partial region, as illustrated in FIG. 30C, for example. Measurements are performed for all of the determined directions.

[0188] (Step S552) The processing circuit 140 selects a partial region that has not yet been measured from among the plurality of partial regions.

[0189] (Step S553) The processing circuit 140 obtains the correction data corresponding to the selected partial region from the storage device 150 .

[0190] (Step S554) The processing circuitry 140 selects an irradiation direction for which measurement has not yet been performed from among the plurality of irradiation directions included in the partial region determined in step S551.

[0191] (Step S555) The processing circuit 140 sends a control signal to the light source 110, causing the light source 110 to emit frequency-modulated light. This operation is similar to step S201 shown in FIG.

[0192] (Step S556) The processing circuit 140 acquires the detection signal output from the photodetector 130. The acquisition of the detection signal is carried out over a certain period of time. This operation is similar to step S202 shown in FIG.

[0193] (Step S557) The processing circuit 140 generates a corrected detection signal by correcting the detection signal based on the correction data. This operation is similar to step S212 shown in FIG.

[0194] (Step S558) The processing circuit 140 performs frequency analysis on the waveform of the corrected detection signal to generate a frequency spectrum of the corrected detection signal. This operation is similar to step S213 shown in FIG.

[0195] (Step S559) The processing circuit 140 extracts the frequency at which the maximum peak of the frequency spectrum is obtained (spectral peak) and sets this frequency as the beat frequency. This operation is the same as step S214 shown in FIG.

[0196] (Step S560) Processing circuitry 140 calculates the distance to the object by converting the beat frequency into a distance value. This operation is similar to step S215 shown in Fig. 17. Processing circuitry 140 stores the calculated distance in a storage device such as a memory of processing circuitry 140.

[0197] (Step S561) The processing circuit 140 determines whether or not measurements have been completed for all irradiation directions within the partial region. If measurements have been completed for all irradiation directions, the process proceeds to step S562. If measurements have not been completed for all irradiation directions, the process returns to step S554.

[0198] In step S561, the operations of steps S554 to S561 are repeated until it is determined that measurements have been completed for all irradiation directions within the partial region.

[0199] (Step S562) Processing circuit 140 determines whether measurement has been completed for all partial regions. If measurement has been completed for all partial regions, the process proceeds to step S563. If measurement has not been completed for any partial region, the process returns to step S552, and a detailed scan is performed on the partial regions for which measurement has not been completed.

[0200] (Step S563) The processing circuitry 140 generates and outputs measurement data including the distances of each point measured by the detailed scan.

[0201] Through the above operations, precise distance measurement is realized using appropriate correction data for each partial area included in the target area.

[0202] In the example of Figure 33, detailed scanning is performed on all partial regions, but detailed scanning may also be performed on only some partial regions. For example, detailed scanning may be performed on only one or more partial regions that fall within a specific distance range. Alternatively, detailed scanning may be performed on only one or more partial regions that include a specific type of object recognized by a separately provided image recognition device.

[0203] Furthermore, instead of performing a detailed scan for each partial region, a detailed scan may be performed for the entire target region. In this case, the correction data used to correct the detection signal may be switched depending on which partial region each irradiation direction belongs to.

[0204] In a detailed scan, the signal may be averaged more frequently during measurement at each irradiation point than in a rough scan. This allows for a signal with a high S / N ratio. The frequency modulation period in a detailed scan may be longer than that in a rough scan. By lengthening the modulation period (i.e., lowering the modulation frequency), the number of data points increases, thereby improving distance resolution and data stability. When the modulation period or modulation frequency is changed, correction data corresponding to each distance range for each modulation period or modulation frequency may be prepared in advance and stored in the storage device 150. For example, correction data (e.g., a table) in a format similar to that shown in any of Figures 11 and 13-15 may be prepared in advance for each modulation period or modulation frequency. The period or sampling interval of the detection signal can be appropriately corrected using the correction data corresponding to the modulation period or modulation frequency. In such a configuration, each of the multiple correction data is associated with a corresponding one of multiple different modulation frequencies.

[0205] (Embodiment 6) Next, a measurement device according to a sixth exemplary embodiment of the present disclosure will be described.

[0206] FIG. 34 is a block diagram showing an example of the configuration of a measurement apparatus 100 according to a sixth embodiment. The measurement apparatus 100 according to this embodiment includes a light branching device 180 that splits output light from an interference optical system 120 into multiple output light beams and emits the multiple output light beams in multiple different directions. The interference optical system 120 sends interference light between multiple reflected light beams resulting from the multiple output light beams and a reference light beam to a photodetector 130. Each of the multiple output light beams is associated with a corresponding one of multiple distance ranges. Therefore, each of the multiple correction data is associated with a corresponding one of the multiple output light beams. The processing circuitry 140 generates a corrected detection signal for each of the multiple output light beams by correcting the detection signal based on the correction data associated with that output light, and generates measurement data related to the distance and / or speed to an object in that direction based on the corrected detection signal.

[0207] An optical branching device 180 shown in Fig. 34 includes an optical branching device 181, two optical fibers 182, and two beam shapers 184. The ring-shaped thick line shown in Fig. 34 schematically indicates that the lengths of the two optical fibers 182 are different due to the winding of the optical fibers 182. The two beam shapers 184 can be disposed at different positions and in different orientations.

[0208] In the example of FIG. 34 , light from the interference optical system 120 is split by an optical splitter 181 and input into two optical fibers 182 of different lengths. The light propagating through the two optical fibers 182 is collimated by respective beam shapers 184 and output as two output beams, i.e., a first beam 201 and a second beam 202. The first beam 201 and the second beam 202 are output toward different objects 301 and 302, respectively. The reflected light of the first beam 201 and the reflected light of the second beam 202 are each incident on the corresponding optical fiber 182, pass through the interference optical system 120, and are input into the photodetector 130. The photodetector 130 detects the interference light obtained by combining the interference light between the reference light and the reflected light of the first beam 201 and the interference light between the reference light and the reflected light of the second beam, and outputs a detection signal including a beat signal corresponding to the first beam 201 and a beat signal corresponding to the second beam 202. Because the lengths of the two optical fibers 182 are different, a frequency difference occurs between the beat signal corresponding to the first beam 201 and the beat signal corresponding to the second beam 202, even if the distances from the measurement device 100 to the two objects 301 and 302 are the same. The processing circuit 140 detects the respective beat frequencies by performing processing such as fast Fourier transform on the detection signals output from the photodetector 130. The processing circuit 140 can calculate the distance to the object 301 irradiated with the first beam 201 and the distance to the object 302 irradiated with the second beam 202 based on the respective beat frequencies.

[0209] The objects 301 and 302 may be structures such as pillars or buildings installed at a construction site, for example. The measurement device 100 may be used, for example, to precisely measure the distances to multiple objects 301 and 302 whose distances from the measurement device 100 do not change. The estimated distance from the measurement device 100 to the object 301 and the estimated distance from the measurement device 100 to the object 302 may be approximately the same, or these distances may be significantly different. When the two distances are significantly different, the lengths of the two optical fibers 182 may be the same because the frequencies of the interference light due to the reflected light from each direction do not overlap. Furthermore, multiple light beams emitted from the optical branching device 180 may be irradiated at different positions on the same object.

[0210] In this embodiment, the storage device 150 stores correction data for each of the separated output beams. Since the length of the waveguide and / or the expected range of the distance to the target differs for each output beam, correction data corresponding to the propagation length of the beam is stored in the storage device 150 for each of the separated output beams.

[0211] 34, correction data for the first beam and correction data for the second beam are stored in the storage device 150. In the example of Fig. 34, the optical branching device 180 branches the output light from the interference optical system 120 into two light beams, and therefore two pieces of correction data corresponding to the propagation lengths of these two light beams are stored in the storage device 150. When the optical branching device 180 branches the output light from the interference optical system 120 into three or more light beams, three or more pieces of correction data can be stored in the storage device 150, the same number as the number of branched light beams.

[0212] Fig. 35 is a flowchart showing an example of the operation of the measurement apparatus 100 in this embodiment. In the example of Fig. 35, the processing circuitry 140 generates a frequency spectrum for each of the multiple light beams based on the corrected detection signal, extracts from the frequency spectrum a spectral peak that falls within a frequency range corresponding to the distance range associated with that light beam, and calculates the distance to an object irradiated with the light beam based on the frequency of that spectral peak. The operation of each step will be described below.

[0213] (Step S601) The processing circuit 140 sends a control signal to the light source 110, causing the light source 110 to emit frequency-modulated light. This operation is similar to the operation of step S201 shown in FIG.

[0214] (Step S602) The processing circuit 140 acquires the detection signal output from the photodetector 130. The acquisition of the detection signal is carried out over a certain period of time. This operation is similar to the operation of step S202 shown in FIG.

[0215] (Step S603) The processing circuitry 140 acquires a plurality of correction data from the storage device 150. In the examples of Figures 34 and 35, correction data for the first beam and correction data for the second beam are acquired.

[0216] (Steps S604a and S604b) The processing circuitry 140 executes distance calculation processing for the first beam (step S604a) and distance calculation processing for the second beam (step S604b) in parallel. Step S604a includes steps S605a to S609a. Step S604b includes steps S605b to S609b.

[0217] (Steps S605a and S605b) The processing circuitry 140 generates a first corrected detection signal by correcting the detection signal based on the correction data for the first beam (step S605a). Similarly, the processing circuitry 140 generates a second corrected detection signal by correcting the detection signal based on the correction data for the second beam (step S605b). The process of correcting the detection signal is similar to the processes in steps S204 and S212 in FIG. 17.

[0218] (Steps S606a and S606b) The processing circuit 140 performs frequency analysis on the waveform of the first corrected detection signal to generate a frequency spectrum of the first corrected detection signal (step S606a). Similarly, the processing circuit 140 performs frequency analysis on the waveform of the second corrected detection signal to generate a frequency spectrum of the second corrected detection signal (step S606b). The frequency analysis process is similar to the processes of steps S205 and S213 in FIG. 17.

[0219] (Steps S607a and S607b) The processing circuit 140 determines whether or not there is a spectral peak within a frequency range corresponding to the first beam in the frequency spectrum of the first corrected detection signal (step S607a). If the result of this determination is Yes, the process proceeds to step S608a, and if the result of the determination is No, the process of step S604a ends. Similarly, the processing circuit 140 determines whether or not there is a spectral peak within a frequency range corresponding to the second beam in the frequency spectrum of the second corrected detection signal (step S607b). If the result of this determination is Yes, the process proceeds to step S608b, and if the result of the determination is No, the process of step S604b ends.

[0220] (Steps S608a and S608b) The processing circuit 140 extracts a spectral peak within a frequency range corresponding to the first beam from the frequency spectrum of the first corrected detection signal, and sets the frequency as a first beat frequency (step S608a).Similarly, the processing circuit 140 extracts a spectral peak within a frequency range corresponding to the second beam from the frequency spectrum of the second corrected detection signal, and sets the frequency as a second beat frequency (step S608b).

[0221] (Steps S609a and S609b) Processing circuitry 140 calculates the distance to first object 601 by converting the first beat frequency into a distance value (step S609a). Similarly, processing circuitry 140 calculates the distance to second object 602 by converting the second beat frequency into a distance value (step S609b).

[0222] (Step S610) The processing circuit 140 generates and outputs measurement data including information on the distances calculated in steps S609a and S609b.

[0223] Through the above operations, the distances from the measurement device 100 to two objects located in different directions can be measured with high accuracy.

[0224] The processing circuitry 140 may execute the processes of steps S604a and S604b serially rather than in parallel. Also, when the optical branching device 180 branches the output light from the interference optical system 120 into three or more output lights (i.e., three or more light beams), the same processes as steps S604a and S604b shown in FIG. 35 may be executed in parallel or serially for each of the three or more light beams.

[0225] As described above, the processing circuit 140 in this embodiment generates multiple corrected detection signals by applying multiple correction data to the detection signals output from the photodetector 130. The correction can be performed, for example, by changing the sampling timing of the detection signals. The processing circuit 140 generates a frequency spectrum of the corrected detection signal for each light beam by performing frequency analysis such as Fourier transform processing on each corrected detection signal. When the processing circuit 140 detects a spectral peak within a predetermined frequency range for each light beam in each frequency spectrum, it calculates the distance based on the frequency of the spectral peak. Through the above operations, the distance to multiple objects in different directions from the measurement device 100 can be measured with high accuracy.

[0226] Instead of determining whether a spectral peak exists in steps S607a and S607b, processing circuitry 140 may determine whether the distance calculated in steps S609a and S609b falls within a distance range preset for each light beam. In this case, processing circuitry 140 may be configured to output the distance if the calculated distance falls within the distance range preset for each light beam, and not output the distance if not. That is, processing circuitry 140 may generate a frequency spectrum for each of a plurality of directions based on the corrected detection signal, extract a spectral peak from the frequency spectrum, calculate a distance based on the frequency of the spectral peak, and determine the distance as the distance to the object in that direction if the distance falls within the distance range associated with that direction.

[0227] 34, the optical branching device 180 is configured to emit a plurality of optical beams in different directions. The optical branching device 180 is not limited to this configuration, and may emit a plurality of optical beams in the same direction. For example, the optical branching device 180 may include a plurality of optical emitting units (e.g., beam shapers 184) that are arranged one-dimensionally or two-dimensionally and oriented in the same direction.

[0228] In the example of FIG. 34 , the range of distances measured for each light beam is substantially fixed, and therefore each light beam is associated with one correction data set. This configuration is not limited to this, and the range of distances that each light beam can measure does not have to be fixed. In this case, multiple correction data sets may be prepared in advance for each light beam. That is, multiple correction data sets corresponding to multiple distance ranges may be stored in advance in the storage device 150 for each of the multiple branched light beams. More specifically, correction data sets such as those illustrated in any of FIGS. 11 and 13-15 may be generated in advance for each light beam and stored in the storage device 150. In such a configuration, selection of correction data sets may be performed first in steps S604a and S604b shown in FIG. 35 . For example, the processing circuitry 140 may select optimal correction data sets for each of the multiple branched light beams by performing steps S203 to S208 and S211 shown in FIG. 17 . In this case, the processing circuitry 140 performs steps S604a and S604b using the selected correction data sets. In addition, if it is determined in step S208 that the approximate distance is within the distance range corresponding to the standard correction data, the subsequent processing can be omitted and the processing of step S610 can be performed with the approximate distance being the distance measured by the light beam.

[0229] [Note] The above description of the embodiments discloses the following techniques.

[0230] (Technology 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 storage device that stores a plurality of correction data used to correct the detection signal, each of the plurality of correction data being associated with a corresponding one of a plurality of different distance ranges; a processing circuit that modulates the frequency of the light from the light source at a predetermined period, corrects the detection signal based on at least one of the plurality of correction data to generate a corrected detection signal, and generates measurement data related to the distance and / or speed of the object based on the corrected detection signal; A measuring device comprising:

[0231] (Technology 2) The measurement device described in Technology 1, wherein the processing circuit acquires information indicating an approximate distance to the object, and generates the corrected detection signal based on correction data corresponding to the approximate distance among the plurality of correction data.

[0232] (Technology 3) the processing circuit corrects the detection signal based on standard correction data included in the plurality of correction data to generate a standard corrected detection signal, and calculates the approximate distance based on the standard corrected detection signal. The measurement device described in Technology 2.

[0233] (Technology 4) The measuring device according to technology 2 further comprises a sensing device that measures the approximate distance.

[0234] (Technology 5) The measuring device according to Art 2 further comprises an input device for receiving input of the approximate distance from a user or an external device.

[0235] (Technology 6) further comprising an optical deflector that changes the direction of the output light; The processing circuitry a rough scanning operation for controlling the optical deflector to change the direction of the output light within a target area, and calculating the rough distance for each direction of the output light based on the detection signal output from the photodetector; classifying the target area into a plurality of partial areas based on the approximate distance for each direction of the output light, and determining appropriate correction data for each of the plurality of partial areas; For at least one of the plurality of partial regions, controlling the optical deflector to change the direction of the output light within the sub-region; For each direction of the output light, acquiring the detection signal output from the photodetector; generating a corrected detection signal by correcting the detection signal based on the correction data that matches the partial region; Calculating the distance to an object present in the direction based on the corrected detection signal, and performing a detailed scan operation. The measurement device described in Technology 2.

[0236] (Technology 7) The measurement device described in Technology 6, wherein the processing circuit generates a standard corrected detection signal by correcting the detection signal based on standard correction data included in the plurality of correction data during the rough scanning operation, and calculates the approximate distance based on the standard corrected detection signal.

[0237] (Technology 8) The measurement device according to technique 6 or 7, wherein the processing circuit increases the density of measurement points by the output light in the detailed scanning operation compared to the density of measurement points by the output light in the rough scanning operation.

[0238] (Technology 9) The processing circuitry generating a plurality of corrected detection signals by correcting the detection signal based on each of the plurality of correction data; calculating a plurality of distances based on the plurality of corrected detection signals, determining one distance selected from the plurality of distances as the distance to the object; The measurement device described in Technology 1.

[0239] (Technology 10) The measurement device described in Technology 9, wherein the processing circuit selects one distance from the plurality of distances that is included in a distance range associated with the correction data used to calculate the distance or that is closest to the distance range, and determines the distance as the distance to the object.

[0240] (Technology 11) The processing circuitry generating a plurality of corrected detection signals by correcting the detection signal based on each of the plurality of correction data; calculating a plurality of beat frequencies based on the plurality of corrected detection signals, calculating a distance to the object based on one beat frequency selected from the plurality of beat frequencies; The measurement device described in Technology 1.

[0241] (Technology 12) The measurement device described in Technology 11, wherein the processing circuit selects one beat frequency from the plurality of beat frequencies that is included in a frequency range corresponding to a distance range associated with the correction data used to calculate the beat frequency or that is closest to the frequency range, and calculates the distance to the object based on the beat frequency.

[0242] (Technology 13) The measurement device described in Technology 1, wherein the processing circuit acquires information indicating an approximate distance to the object, selects two or more correction data from the plurality of correction data that are associated with a distance range relatively close to the approximate distance, generates composite correction data based on the two or more correction data, and corrects the detection signal based on the composite correction data, thereby generating the corrected detection signal.

[0243] (Technology 14) further comprising an optical branching device that separates the output light output from the interference optical system into a plurality of output light beams and emits the plurality of output light beams; the interference optical system sends interference light between the reference light and a plurality of reflected lights resulting from the plurality of output lights to the photodetector; each of the plurality of correction data is associated with a corresponding one of the plurality of output lights; the processing circuit generates a corrected detection signal for each of the plurality of output lights by correcting the detection signal based on correction data associated with the output light, and generates measurement data relating to a distance and / or a speed to an object irradiated with the output light based on the corrected detection signal. The measurement device described in Technology 1.

[0244] (Technology 15) The measurement device described in Technology 14, wherein the processing circuit generates a frequency spectrum for each of the plurality of output light beams based on the corrected detection signal, extracts spectral peaks from the frequency spectrum that are included in a frequency range corresponding to a distance range associated with the output light beam, and calculates a distance to the object irradiated with the output light beam based on the frequency of the spectral peaks.

[0245] (Technology 16) The measurement device described in Technology 14, wherein the processing circuit generates a frequency spectrum for each of the plurality of output lights based on the corrected detection signal, extracts a spectral peak from the frequency spectrum, calculates a distance based on the frequency of the spectral peak, and determines the distance as the distance to the object in the direction if the distance is included in a distance range associated with the output light.

[0246] (Technology 17) The measurement device according to technology 1, wherein each of the plurality of correction data is associated with a corresponding one of a plurality of different modulation frequencies.

[0247] (Technology 18) each of the plurality of correction data includes information defining a sampling timing of the detection signal; the processing circuit generates the corrected detection signal by sampling the detection signal at irregular intervals based on at least one of the plurality of correction data. A measuring device according to any one of techniques 1 to 17.

[0248] (Technology 19) 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; an optical branching device that splits the output light into a plurality of output light beams and emits the plurality of output light beams; a photodetector that receives interference light between a plurality of reflected lights resulting from the plurality of output lights and the reference light from the interference optical system, and outputs a detection signal corresponding to the intensity of the interference light; a storage device that stores a plurality of correction data used to correct the detection signal, each of the plurality of correction data being associated with a corresponding one of the plurality of output lights; a processing circuit that modulates the frequency of the light from the light source at a predetermined period, corrects the detection signal based on at least one of the plurality of correction data to generate a corrected detection signal, and generates measurement data related to the distance and / or speed of the object based on the corrected detection signal; A measuring device comprising:

[0249] (Technology 20) 1. A method implemented by one or more computers in a system including a metrology device, comprising: The measuring device is 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 storage device that stores a plurality of correction data used to correct the detection signal, each of the plurality of correction data being associated with a corresponding one of a plurality of different distance ranges; Equipped with The method comprises: modulating the frequency of the light from the light source at a predetermined period; correcting the detection signal based on at least one of the plurality of correction data to generate a corrected detection signal; generating measurement data relating to the distance and / or velocity of the object based on the corrected detection signal; A method comprising:

[0250] (Technology 21) A computer program executed by one or more computers in a system including a metrology device, The measuring device is 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 storage device that stores a plurality of correction data used to correct the detection signal, each of the plurality of correction data being associated with a corresponding one of a plurality of different distance ranges; Equipped with The computer program may be configured to: modulating the frequency of the light from the light source at a predetermined period; correcting the detection signal based on at least one of the plurality of correction data to generate a corrected detection signal; generating measurement data relating to the distance and / or velocity of the object based on the corrected detection signal; A computer program that executes the following:

[0251] (Technology 22) 1. A method implemented by one or more computers in a system including a metrology device, comprising: The measuring device is 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; an optical branching device that splits the output light into a plurality of output light beams and emits the plurality of output light beams; a photodetector that receives interference light between a plurality of reflected lights resulting from the plurality of output lights and the reference light from the interference optical system, and outputs a detection signal according to the intensity of the interference light; a storage device that stores a plurality of correction data used to correct the detection signal, each of the plurality of correction data being associated with a corresponding one of the plurality of output lights; Equipped with The method comprises: modulating the frequency of the light from the light source at a predetermined period; correcting the detection signal based on at least one of the plurality of correction data to generate a corrected detection signal; generating measurement data relating to the distance and / or velocity of the object based on the corrected detection signal; A method comprising:

[0252] (Technology 23) A computer program executed by one or more computers in a system including a metrology device, The measuring device is 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; an optical branching device that splits the output light into a plurality of output light beams and emits the plurality of output light beams; a photodetector that receives interference light between a plurality of reflected lights resulting from the plurality of output lights and the reference light from the interference optical system, and outputs a detection signal according to the intensity of the interference light; a storage device that stores a plurality of correction data used to correct the detection signal, each of the plurality of correction data being associated with a corresponding one of the plurality of output lights; Equipped with The computer program may be configured to: modulating the frequency of the light from the light source at a predetermined period; correcting the detection signal based on at least one of the plurality of correction data to generate a corrected detection signal; generating measurement data relating to the distance and / or velocity of the object based on the corrected detection signal; A computer program that executes the following:

[0253] The above description of the embodiments discloses the following techniques. [Industrial Applicability]

[0254] The technology of the present disclosure can be widely used in devices or systems that measure the distance to an object or the speed of an object, for example, in devices or systems that use FMCW-LiDAR. [Explanation of symbols]

[0255] 100 Measuring Equipment 110 Light source 120 Interference Optical System 130 Photodetector 140 Processing Circuit 150 Storage device 170 Optical deflector 180 Optical Branching Device 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 storage device that stores a plurality of correction data used to correct the detection signal, each of the plurality of correction data being associated with a corresponding one of a plurality of different distance ranges; a processing circuit that modulates the frequency of the light from the light source at a predetermined period, corrects the detection signal based on at least one of the plurality of correction data to generate a corrected detection signal, and generates measurement data related to the distance and / or speed of the object based on the corrected detection signal; A measuring device comprising:

2. 2. The measurement device according to claim 1, wherein the processing circuit acquires information indicating an approximate distance to the object, and generates the corrected detection signal based on correction data corresponding to the approximate distance among the plurality of correction data.

3. the processing circuit corrects the detection signal based on standard correction data included in the plurality of correction data to generate a standard corrected detection signal, and calculates the approximate distance based on the standard corrected detection signal. The measurement device according to claim 2 .

4. The measurement device according to claim 2 , further comprising a sensing device that measures the approximate distance.

5. The measurement device according to claim 2 , further comprising an input device that receives an input of the approximate distance from a user or an external device.

6. further comprising an optical deflector that changes the direction of the output light; The processing circuitry a rough scanning operation for controlling the optical deflector to change the direction of the output light within a target area, and calculating the rough distance for each direction of the output light based on the detection signal output from the photodetector; classifying the target area into a plurality of partial areas based on the approximate distance for each direction of the output light, and determining appropriate correction data for each of the plurality of partial areas; For at least one of the plurality of partial regions, controlling the optical deflector to change the direction of the output light within the sub-region; For each direction of the output light, acquiring the detection signal output from the photodetector; generating a corrected detection signal by correcting the detection signal based on the correction data that matches the partial region; Calculating the distance to an object present in the direction based on the corrected detection signal, and performing a detailed scan operation. The measurement device according to claim 2 .

7. 7. The measurement device according to claim 6, wherein the processing circuit, in the rough scanning operation, generates a standard corrected detection signal by correcting the detection signal based on standard correction data included in the plurality of correction data, and calculates the approximate distance based on the standard corrected detection signal.

8. The measurement device according to claim 6 , wherein the processing circuitry increases the density of measurement points by the output light in the detailed scan operation to a value higher than the density of measurement points by the output light in the rough scan operation.

9. The processing circuitry generating a plurality of corrected detection signals by correcting the detection signal based on each of the plurality of correction data; calculating a plurality of distances based on the plurality of corrected detection signals, determining one distance selected from the plurality of distances as the distance to the object; The measurement device according to claim 1 .

10. The measurement device according to claim 9, wherein the processing circuit selects one distance from the plurality of distances that is included in a distance range associated with the correction data used to calculate the distance or that is closest to the distance range, and determines the distance as the distance to the object.

11. The processing circuitry generating a plurality of corrected detection signals by correcting the detection signal based on each of the plurality of correction data; calculating a plurality of beat frequencies based on the plurality of corrected detection signals, calculating a distance to the object based on one beat frequency selected from the plurality of beat frequencies; The measurement device according to claim 1 .

12. 12. The measurement instrument according to claim 11, wherein the processing circuitry selects, from the plurality of beat frequencies, one beat frequency that is included in a frequency range corresponding to a distance range associated with correction data used to calculate the beat frequency or that is closest to the frequency range, and calculates the distance to the object based on the beat frequency.

13. 2. The measurement device according to claim 1, wherein the processing circuit acquires information indicating an approximate distance to the object, selects two or more correction data from the plurality of correction data that are associated with a distance range relatively close to the approximate distance, generates composite correction data based on the two or more correction data, and corrects the detection signal based on the composite correction data to generate the corrected detection signal.

14. further comprising an optical branching device that separates the output light output from the interference optical system into a plurality of output light beams and emits the plurality of output light beams; the interference optical system sends interference light between the reference light and a plurality of reflected lights resulting from the plurality of output lights to the photodetector; each of the plurality of correction data is associated with a corresponding one of the plurality of output lights; the processing circuit generates a corrected detection signal for each of the plurality of output lights by correcting the detection signal based on correction data associated with the output light, and generates measurement data relating to a distance and / or a speed to an object irradiated with the output light based on the corrected detection signal. The measurement device according to claim 1 .

15. 15. The measurement device of claim 14, wherein the processing circuit generates a frequency spectrum for each of the plurality of output beams based on the corrected detection signal, extracts a spectral peak from the frequency spectrum that is included in a frequency range corresponding to a distance range associated with the output beam, and calculates a distance to the object irradiated with the output beam based on the frequency of the spectral peak.

16. 15. The measurement device of claim 14, wherein the processing circuit generates a frequency spectrum for each of the plurality of output lights based on the corrected detection signal, extracts a spectral peak from the frequency spectrum, calculates a distance based on the frequency of the spectral peak, and determines the distance as the distance to the object in the direction if the distance is within a distance range associated with the output light.

17. The measurement device according to claim 1 , wherein each of the plurality of correction data is associated with a corresponding one of a plurality of different modulation frequencies.

18. each of the plurality of correction data includes information defining a sampling timing of the detection signal; the processing circuit generates the corrected detection signal by sampling the detection signal at irregular intervals based on at least one of the plurality of correction data.

18. The measuring device according to claim 1.

19. 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; an optical branching device that splits the output light into a plurality of output light beams and emits the plurality of output light beams; a photodetector that receives interference light between a plurality of reflected lights resulting from the plurality of output lights and the reference light from the interference optical system, and outputs a detection signal corresponding to the intensity of the interference light; a storage device that stores a plurality of correction data used to correct the detection signal, each of the plurality of correction data being associated with a corresponding one of the plurality of output lights; a processing circuit that modulates the frequency of the light from the light source at a predetermined period, corrects the detection signal based on at least one of the plurality of correction data to generate a corrected detection signal, and generates measurement data related to the distance and / or speed of the object based on the corrected detection signal; A measuring device comprising:

20. 1. A method implemented by one or more computers in a system including a metrology device, comprising: The measuring device is 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 storage device that stores a plurality of correction data used to correct the detection signal, each of the plurality of correction data being associated with a corresponding one of a plurality of different distance ranges; Equipped with The method comprises: modulating the frequency of the light from the light source at a predetermined period; generating a corrected detection signal by correcting the detection signal based on at least one of the plurality of correction data; generating measurement data relating to the distance and / or velocity of the object based on the corrected detection signal; A method comprising:

21. A computer program executed by one or more computers in a system including a metrology device, The measuring device is 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 storage device that stores a plurality of correction data used to correct the detection signal, each of the plurality of correction data being associated with a corresponding one of a plurality of different distance ranges; Equipped with The computer program may be configured to: modulating the frequency of the light from the light source at a predetermined period; generating a corrected detection signal by correcting the detection signal based on at least one of the plurality of correction data; generating measurement data relating to the distance and / or velocity of the object based on the corrected detection signal; A computer program that executes the following:

Images