Distance measurement device

Abstract

To provide a distance measurement device for suppressing deterioration of distance measurement performance corresponding to visibility.SOLUTION: A distance measurement device includes a light source, an optical sensor, a measurement circuit, and a control circuit. The light source emits a first laser beam. The optical sensor detects a second laser beam corresponding to the first laser beam reflected against a subject on an outer side. The measurement circuit measures a distance to the subject based on timing when the light source emits the first laser light and timing when the optical sensor detects the second laser beam. The control circuit measures a reflection amount of the subject based on a distance measurement result, so as to change a distance measurement parameter according to information using the measured reflection amount.SELECTED DRAWING: Figure 18

Description

[Technical field]

[0001] The embodiment relates to a distance measuring device. [Background technology]

[0002] A distance measuring device called LiDAR (Light Detection and Ranging) is known. The LiDAR emits laser light toward a distance measuring target. The emitted laser light is reflected by the distance measuring target and detected by the optical sensor of the LiDAR. The LiDAR calculates the time of flight (ToF) of the laser light based on the time when the laser light is emitted and the time when the laser light reflected by the distance measuring target is detected. This allows the LiDAR to measure (range) the distance between the LiDAR and the distance measuring target based on the ToF and the speed of the laser light. In this way, in order for the LiDAR to realize distance measuring, the optical sensor needs to be able to detect the laser light reflected by the distance measuring target. For example, the emitted laser light is attenuated more as the visibility becomes shorter, so that the detection of the laser light by the optical sensor becomes more difficult as the visibility becomes shorter. Therefore, the distance measuring performance of the LiDAR tends to deteriorate as the visibility becomes shorter. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5832067 Summary of the Invention [Problem to be solved by the invention]

[0004] The objective is to provide a distance measuring device capable of suppressing degradation of distance measuring performance according to visibility. [Means for solving the problem]

[0005] A distance measuring device according to an embodiment includes a light source, an optical sensor, a measurement circuit, and a control circuit. The light source is configured to emit a first laser light. The optical sensor is configured to detect a second laser light corresponding to the first laser light reflected by an external object. The measurement circuit is configured to measure the distance to the object based on the timing at which the light source emits the first laser light and the timing at which the optical sensor detects the second laser light. The control circuit is configured to measure the amount of reflection from the object based on the distance measurement result, and to change distance measurement parameters according to information using the measured amount of reflection. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a distance measuring system according to a first embodiment. [Diagram 2] FIG. 2 is a block diagram showing an example of the configuration of an information processing device included in the distance measuring system according to the first embodiment. [Diagram 3] FIG. 1 is a block diagram showing an example of the configuration of a distance measuring device according to a first embodiment. [Figure 4] FIG. 2 is a schematic diagram showing an example of the configuration of an optical system included in the distance measuring device according to the first embodiment. [Diagram 5] 2 is a schematic diagram showing an example of the configuration of a scan area scanned by the distance measuring device according to the first embodiment. [Figure 6] FIG. 2 is a schematic diagram showing an example of the configuration of an optical sensor included in the distance measuring device according to the first embodiment. [Figure 7] 3 is a schematic diagram showing an example of the configuration of an image showing a distance measurement result obtained by a distance measurement operation of the distance measuring device according to the first embodiment. [Figure 8] 3A and 3B are schematic diagrams showing an example of a scanning method based on a first setting of the distance measuring device according to the first embodiment. [Figure 9] 2 is a schematic diagram showing an example of a configuration based on a first setting of an optical sensor and a measurement device included in the distance measuring device according to the first embodiment. [Figure 10] 5 is a schematic diagram showing an example of a scanning method based on a second setting of the distance measuring device according to the first embodiment. [Figure 11]5 is a schematic diagram showing an example of a scanning method based on a third setting of the distance measuring device according to the first embodiment. [Figure 12] 4 is a schematic diagram showing an example of a configuration based on a fourth setting of the optical sensor and the measurement device included in the distance measuring device according to the first embodiment. FIG. [Figure 13] 5 is a schematic diagram showing an example of a scanning method based on a fifth setting of the distance measuring device according to the first embodiment. FIG. [Figure 14] 8A and 8B are schematic diagrams showing an example of a method for processing a light reception result based on a fifth setting of the distance measuring device according to the first embodiment. [Figure 15] 11 is a schematic diagram showing an example of a configuration based on a sixth setting of the optical sensor and the measurement device included in the distance measuring device according to the first embodiment. FIG. [Figure 16] 13 is a schematic diagram showing an example of a configuration based on a seventh setting of the optical sensor and the measurement device included in the distance measuring device according to the first embodiment. FIG. [Figure 17] 8 is a schematic diagram showing an example of a method for processing a light reception result based on an eighth setting of the distance measuring device according to the first embodiment. FIG. [Figure 18] 5 is a flowchart showing an example of a setting change operation of the distance measuring system according to the first embodiment. [Figure 19] 6 is a graph showing an example of a difference in light receiving characteristics between the first comparative example and the first embodiment. [Figure 20] FIG. 11 is a schematic diagram showing an example of the configuration of an optical sensor and a measurement device included in a distance measuring device according to a second embodiment. [Figure 21] 13 is a schematic diagram showing an example of a method for processing a light reception result of the distance measuring device according to the second embodiment. [Figure 22] FIG. 11 is a schematic diagram showing an example of the configuration of an optical sensor and a measurement device included in a distance measuring device according to a third embodiment. [Figure 23] 13 is a schematic diagram showing an example of a method for processing a light reception result of the distance measuring device according to the third embodiment. [Figure 24] FIG. 13 is a schematic diagram showing an example of the configuration of an optical sensor and a measurement device included in a distance measuring device according to a fourth embodiment. [Diagram 25] 13 is a schematic diagram showing an example of a method for processing a light reception result of a distance measuring device according to a fourth embodiment. [Figure 26]FIG. 13 is a schematic diagram showing an example of a distance measurement target of a distance measurement system according to a fifth embodiment. [Figure 27] FIG. 13 is a schematic diagram showing an example of the configuration of a landmark used in the distance measuring system according to the fifth embodiment. [Figure 28] Schematic diagram showing an overview of a method for measuring visibility. [Figure 29] FIG. 1 is a schematic diagram showing an example of a method for measuring visibility. [Diagram 30] 13 is a flowchart showing an example of a visibility calculation operation of the distance measuring system according to the fifth embodiment. [Diagram 31] 13 is a schematic diagram showing an example of a method for processing a light reception result of the distance measuring device according to the fifth embodiment. FIG. [Diagram 32] 13 is a table showing a first example of a measurement result to which a visibility calculation method using an object is applied in the distance measuring system according to the fifth embodiment. [Diagram 33] 13 is a table showing a second example of the measurement result when the subject-using visibility calculation method is applied in the distance measuring system according to the fifth embodiment. [Diagram 34] FIG. 4 is a schematic diagram showing an example of the relationship between the position of a landmark LM and the number of pixels. [Diagram 35] 1 is a schematic diagram showing an example of the relationship between the amount of received light and distance when measuring the distance to a measurement area RG1 of a landmark under four conditions with different visibility. [Diagram 36] 11 is a schematic diagram showing an example of the relationship between the amount of received light and distance when measuring the distance to the measurement area RG2 of a landmark under four conditions with different visibility. [Figure 37] 11 is a table showing an example of measurement results in the second comparative example. [Figure 38] 13 is a table showing an example of a measurement result in the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Each embodiment will be described below with reference to the drawings. Each embodiment illustrates an apparatus or method for embodying the technical idea of ​​the invention. The drawings are schematic or conceptual. The dimensions and ratios of each drawing are not necessarily the same as those in reality. In the following description, the same reference numerals are used to designate components having substantially the same functions and configurations.

[0008] <1> First embodiment The first embodiment relates to a distance measuring system 1 configured to change distance measuring parameters depending on visibility. Details of the distance measuring system 1 according to the first embodiment will be described below.

[0009] <1-1> Configuration First, the configuration of a distance measuring system 1 according to the first embodiment will be described.

[0010] <1-1-1> Configuration of distance measurement system 1 FIG. 1 is a schematic diagram showing an example of the configuration of a ranging system 1 according to the first embodiment. FIG. 1 shows a situation in which a transport equipment VE equipped with the ranging system 1 is moving along a predetermined route. As shown in FIG. 1, the ranging system 1 includes an information processing device 10 and a ranging device 20. The transport equipment VE is, for example, a railroad vehicle. Note that the transport equipment VE equipped with the ranging system 1 may be an automobile, an aircraft, a ship, etc. When the transport equipment VE is a railroad vehicle, the predetermined route is a railroad track. When the transport equipment VE is an automobile, the predetermined route is, for example, a road whose travel area is defined by dividing lines or the like.

[0011] The information processing device 10 is a device that collects information such as the distance measurement result obtained from the distance measurement device 20, the state of the transportation equipment VE, the current position of the transportation equipment VE, and the surrounding environment. The information processing device 10 may be configured to be able to control the distance measurement device 20 based on the collected information, and may be configured to be able to control the acceleration / deceleration and traveling direction of the transportation equipment VE. In other words, the information processing device 10 may have a function of supporting the autonomous driving of the transportation equipment VE.

[0012] The distance measuring device 20 is a type of LiDAR. The distance measuring device 20 emits laser light and detects the laser light reflected by a subject (a distance measuring target). The distance measuring device 20 then measures (measures distance) the distance between the distance measuring device 20 and the subject based on the flight time and speed of the laser light. The distance measuring parameters of the distance measuring device 20 can be changed based on visibility information. The visibility information includes information on visibility in the surrounding environment of the transportation equipment VE.

[0013] The distance measuring system 1 may obtain visibility information from an external source, or may obtain the visibility by measuring the visibility of the surrounding environment of the transport equipment VE by itself. A method of measuring visibility using the distance measuring device 20 will be described in the fifth embodiment. The distance measuring device 20 is installed, for example, in front of the transport equipment VE. In this case, the distance measuring device 20 obtains distance information of a predetermined angle of view in the traveling direction of the transport equipment VE. In this specification, the angle of view of the distance measuring device 20, i.e., the range that can be measured by the distance measuring device 20, is also called "FOV (Field Of View)".

[0014] <1-1-2> Configuration of information processing device 10 Fig. 2 is a block diagram showing an example of the configuration of an information processing device 10 included in the distance measuring system 1 according to the first embodiment. Fig. 2 also shows a distance measuring device 20. As shown in Fig. 2, the information processing device 10 includes, for example, an information collection device 11, a storage device 12, a transportation equipment control device 13, a speed control device 14, and an image processing device 15.

[0015] The information collection device 11 is a device that collects information such as the current position, state, and surrounding environment of the transportation equipment VE. The information collection device 11 includes, for example, a speed sensor 31, a GNSS (Global Navigation Satellite System) device 32, and a camera 33. The speed sensor 31, the GNSS device 32, and the camera 33 are a group of devices for collecting information such as the current position, state, and surrounding environment of the transportation equipment VE. The speed sensor 31 is a sensor that detects the current speed of the transportation equipment VE. The GNSS device 32 is a positioning device that receives radio waves emitted from multiple artificial satellites and identifies the current position of the transportation equipment VE based on the received radio waves. The camera 33 is an optical device that can capture images of the surroundings of the transportation equipment VE.

[0016] The storage device 12 is a storage medium used to store data, programs, and the like. The storage device 12 stores, for example, a route information database 34. The route information database 34 may include information on routes that the transport equipment VE can travel (hereinafter referred to as "route information"), information on the operation of the transport equipment VE (hereinafter referred to as "operation information"), visibility information, and the like. The route information may include, for example, the distance from a starting point on the route, and information on landmarks arranged on the travel route of the transport equipment VE. The operation information is set, for example, according to the distance from a starting point on the travel route or the current position of the transport equipment VE. The information stored in the storage device 12 may be downloaded via a server on the network.

[0017] The transportation equipment control device 13 is, for example, a computer configured to be able to communicate with the image processing device 15. The transportation equipment control device 13 generates a control signal related to acceleration / deceleration of the transportation equipment VE based on, for example, the speed obtained from the speed sensor 31, instructions from the image processing device 15, information obtained from the image processing device 15, operation information acquired from the route information database 34, and the like. The information obtained from the image processing device 15 includes, for example, position information of the railcar RV. The transportation equipment control device 13 can then control the traveling of the transportation equipment VE by transmitting the generated control signal to the speed control device 14.

[0018] The speed control device 14 is a device that controls the speed of the transportation equipment VE. The speed control device 14 includes, for example, an acceleration means and a deceleration means for adjusting the speed of the transportation equipment VE. The speed control device 14 controls the stopping and acceleration / deceleration of the transportation equipment VE based on a control signal received from the transportation equipment control device 13. For example, the speed control device 14 controls a motor or an engine connected to the wheels of the transportation equipment VE, and a brake.

[0019] The image processing device 15 is, for example, a computer configured to be able to communicate with the transportation equipment control device 13. The image processing device 15 generates an image based on, for example, distance measurement information obtained from the distance measurement device 20. The image includes, for example, information on the distance from the distance measurement device 20 to a subject present in front of the transportation equipment VE. The image processing device 15 may instruct the transportation equipment control device 13 to accelerate, decelerate, or stop the transportation equipment VE based on the image obtained from the camera 33, the distance measurement information, and the like. The image processing device 15 may be configured to be able to measure the visibility based on the distance measurement information. Furthermore, the image processing device 15 may instruct the distance measurement device 20 to change the distance measurement parameters based on the visibility information. The distance measurement device 20 may change the angle of view, the frame rate, the number of integrations, the amount of light of the laser light, and the like based on the instruction from the image processing device 15.

[0020] The connection between the devices in the information processing device 10 may be, for example, wired or wireless. The information collection device 11 and the storage device 12 may be externally connected to the information processing device 10. The information processing device 10 may include a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The CPU of the information processing device 10 may execute each of the processing of the transportation equipment control device 13 and the processing of the image processing device 15. The information processing device 10 may be a system constructed of multiple devices connected via a network. The information processing device 10 is configured to be able to communicate with the distance measuring device 20 via a communication interface not shown. That is, the information processing device 10 may control the distance measuring device 20 via the communication interface.

[0021] <1-1-3> Configuration of distance measuring device 20 Fig. 3 is a block diagram showing an example of the configuration of the distance measuring device 20 according to the first embodiment. As shown in Fig. 3, the distance measuring device 20 includes, for example, a distance measurement control device 21, a laser driver 22, a laser diode 23, a mirror control device 24, an optical system 25, an optical sensor 26, and a measurement device 27. The optical system 25 includes, for example, a rotating mirror 251.

[0022] The distance measurement control device 21 controls the overall operation of the distance measurement device 20. The distance measurement control device 21 includes, for example, a CPU, a ROM, a RAM, and an oscillator (not shown). The ROM of the distance measurement control device 21 stores a control program for the distance measurement device 20, etc. The CPU of the distance measurement control device 21 controls the laser driver 22, the mirror control device 24, the optical sensor 26, and the measurement device 27 in accordance with the control program. The RAM of the distance measurement control device 21 is used as a working area for the CPU. The oscillator of the distance measurement control device 21 is used to generate an intermittent pulse signal. The distance measurement control device 21 may be configured to be able to execute various data processing and arithmetic processing.

[0023] The laser driver 22 drives the laser diode 23. That is, the laser driver 22 functions as a current supply source for the laser diode 23. The laser diode 23 emits a laser beam based on the drive current supplied by the laser driver 22. The laser beam emitted by the laser diode 23 enters an optical system 25. The distance measurement control device 21 controls the laser driver 22 so that the laser diode 23 emits the laser beam intermittently. Hereinafter, the laser beam generated based on the pulse signal is also referred to as a "pulse laser." In the distance measurement device 20, the pulse laser is emitted with a predetermined pulse width and period.

[0024] The mirror control device 24 drives the rotating mirror 251 included in the optical system 25. That is, the mirror control device 24 functions as a power supply circuit of a motor for rotating the rotating mirror 251. The rotating mirror 251 is driven (rotated) based on the drive current supplied by the mirror control device 24, and reflects the incident laser light. The rotating mirror 251 is configured to be rotatable around one axis, for example. The rotating mirror 251 may be a double-sided mirror or a polygon mirror having three or more reflecting surfaces (mirror surfaces). The number of rotations of the rotating mirror 251 may be changed based on an instruction from the distance measurement control device 21. The rotating mirror 251 may be a two-axis MEMS (Micro Electro Mechanical Systems) mirror. As the rotating mirror 251, a combination of a rotating mirror and a one-axis MEMS mirror may be used. The rotating mirror 251 may be called a "movable mirror."

[0025] The optical sensor 26 is a set of a plurality of light receiving elements (pixels) that detect light incident on the distance measuring device 20. The optical sensor 26 is arranged so that the laser light emitted from the laser diode 23 and reflected by an object outside the distance measuring device 20 enters the optical sensor 26 via the optical system 25. The optical sensor 26 converts the laser light incident on the distance measuring device 20 into an electric signal. The conversion into the electric signal is performed using a circuit such as an analog-to-digital converter (ADC) or a time-to-digital converter (TDC). The optical sensor 26 then adjusts the output level of the converted electric signal and outputs it to the measuring device 27. Hereinafter, the electric signal generated by the optical sensor 26 based on the incident light is also referred to as a light receiving result.

[0026] The measuring device 27 measures the time when the optical sensor 26 detects the laser light based on the light reception result transferred from the optical sensor 26. For example, the measuring device 27 determines the peak part of the signal corresponding to the light reception result as the detection time of the laser light. Then, the measuring device 27 calculates the flight time of the laser light based on the difference between the time when the laser diode 23 emits the laser light and the time when the laser light reflected by the subject is detected. Then, the measuring device 27 measures (distances) the distance between the distance measuring device 20 and the subject based on the flight time of the laser light and the speed of the laser light. The measuring device 27 outputs the distance measurement result to the information processing device 10 for each laser light (distance measurement point) emitted by the distance measuring device 20.

[0027] The measuring device 27 acquires the time when the laser diode 23 emits the laser light, for example, by a notification from the distance measurement control device 21. The time when the laser light is emitted may be measured by the optical sensor 26 detecting the laser light emitted from the laser diode 23. The measuring device 27 may be configured to output one distance measurement result based on a signal in which the light reception results of a plurality of pixels are added together. The measuring device 27 may be configured to output one distance measurement result based on a signal in which the light reception results of a plurality of distance measurement points are integrated together.

[0028] The distance measuring device 20 according to the first embodiment can change the settings of the laser driver 22, the mirror control device 24, and the measurement device 27 in a coordinated manner based on the visibility information. For example, the distance measuring control device 21 can change the cycle and timing of emitting a pulsed laser from the laser diode 23, the rotation speed of the rotating mirror 251, the integration setting of the light reception result, etc., based on the visibility information. The distance measuring control device 21 may change the settings of distance measuring parameters based on an instruction from the information processing device 10 (image processing device 15). The frame rate and resolution of the image generated by the image processing device 15 can change depending on the distance measuring parameters of the distance measuring device 20. Note that the "resolution" corresponds to the density or number of pixels included in one frame.

[0029] (1: Structure of optical system 25) Fig. 4 is a schematic diagram showing an example of the configuration of the optical system 25 included in the distance measuring device 20 according to the first embodiment. Fig. 4 also shows the laser diode 23, the optical sensor 26, and the object OB. Hereinafter, the pulsed laser emitted by the laser diode 23 will be referred to as "emitted light LE." The pulsed laser (emitted light LE) reflected by the object OB will also be referred to as "reflected light LR."

[0030] 4, the optical system 25 further includes optical elements corresponding to the arrangement of the laser diode 23 and the optical sensor 26. Specifically, the optical system 25 further includes, for example, optical elements 252, 253, and 254. Each of the optical elements 252 and 254 is, for example, a lens or a mirror. The optical element 253 is, for example, a half mirror or a perforated mirror. Each of the optical elements 252 and 254 may be configured by a combination of a plurality of lenses and a plurality of mirrors.

[0031] The optical element 252 guides the outgoing light LE emitted from the laser diode 23 to the optical element 253. The outgoing light LE guided by the optical element 252 is transmitted through or passes through the optical element 253 and is irradiated onto the rotating mirror 251. The rotating mirror 251 reflects the irradiated outgoing light LE in a direction according to the incident angle of the outgoing light LE with respect to the irradiation surface. The reflected outgoing light LE is reflected by an object OB located outside the distance measuring device 20 in the traveling direction of the outgoing light LE.

[0032] The reflected light LR from the object OB is reflected by the rotating mirror 251 and is irradiated onto the optical element 253. The optical element 253 reflects the reflected light LR reflected by the rotating mirror 251 toward the optical element 254. The optical element 254 guides the reflected light LR reflected by the optical element 253 to the optical sensor 26. The optical sensor 26 converts the reflected light LR guided by the optical element 254 into an electrical signal and outputs it to the measurement device 27.

[0033] In this specification, the rotating mirror 251 is a polygon mirror having six reflecting surfaces S1 to S6 with different tilt angles. The distance measurement control device 21 controls the rotating mirror 251 to rotate at a rotation speed based on the frame rate. The distance measurement device 20 can two-dimensionally scan a place to be measured by using the intermittently emitted emission light LE and the rotating mirror 251.

[0034] Hereinafter, the area that can be scanned by the distance measuring device 20 is referred to as the "scan area SA". A set of distance measuring results of a plurality of points corresponding to one scan is referred to as a "frame". An image of one frame is generated corresponding to one rotation of the rotating mirror 251, for example. The number of pixels of an image showing the distance measuring results corresponds to the number of pixels contained in one frame. The distance measuring device 20 can sequentially obtain information on the distance to an object OB in front of the distance measuring device 20 by continuously executing scans. Note that the optical system 25 may have another configuration as long as it has a configuration capable of scanning using laser light.

[0035] (2: Configuration of scan area SA) FIG. 5 is a schematic diagram showing an example of the configuration of the scan area SA scanned by the distance measuring device 20 according to the first embodiment. FIG. 5 shows an example of the emission direction of the emitted light LE for one frame in the scan area SA. As shown in FIG. 5, the emitted light LE is irradiated into the PQR space. The R axis is an axis from the distance measuring device 20 toward the subject, and is, for example, along the center of the emission direction of the emitted light LE. The PQ plane is a curved surface that is orthogonal to the R axis and spreads concentrically from the exit port of the emitted light LE. The P axis and the Q axis are axes that are orthogonal to each other in the PQ plane. The distance data measured based on each emitted light LE is generated, for example, as a mapping onto the PQ plane. The distance measuring system 1 maps the distance data to an object present in the space PQR in correspondence with the FOV in the scan area SA, and can recognize the distance to the object present in the FOV.

[0036] The distance measurement control device 21 realizes scanning in the P direction (horizontal direction) by controlling the laser driver 22, the mirror control device 24, etc. to intermittently emit the emitted light LE at a timing based on the distance measurement parameters. When a rotating mirror 251 having six reflecting surfaces S1 to S6 is used, the scan area SA includes a first row SS1 to a sixth row SS6. The scan positions of the first row SS1 to the sixth row SS6 are based on the tilt angles of the reflecting surfaces S1 to S6, respectively. That is, the distance measurement device 20 realizes scanning of multiple rows shifted in the Q direction (vertical direction) by irradiating the emitted light LE to different reflecting surfaces by the rotation of the rotating mirror 251. In addition, the distance measurement device 20 can change the scan speed and the emission timing of the emitted light LE according to the distance measurement parameters.

[0037] The distance measuring device 20 may generate a plurality of pixels (distance data) arranged one-dimensionally based on one emitted light LE. The distance measuring device 20 repeatedly executes a measurement cycle process related to a measurement associated with one emitted light LE while shifting one-dimensionally along the P axis in each of the first row SS1 to the sixth row SS6. This allows the distance measuring device 20 to generate distance data in a set FOV. Such a scanning method is also called "multi-channel raster scanning". As a means for realizing the multi-channel raster scanning, an emitted light LE having an irradiation surface elongated in the vertical direction is used. The number of rows and the scanning direction in one scan of the distance measuring device 20 may be set to other settings.

[0038] (3: Configuration of optical sensor 26) Fig. 6 is a schematic diagram showing an example of the configuration of the optical sensor 26 included in the distance measuring device 20 according to the first embodiment. In Fig. 6, reflected light LR that may be irradiated to the optical sensor 26 is indicated by a dashed line. As shown in Fig. 6, the optical sensor 26 has a light receiving region DR including P (P is an integer equal to or greater than 2) light receiving elements PXL0 to PXL(P-1) arranged one-dimensionally. The shape of the light receiving region DR is designed based on the shape of the output light LE output from the distance measuring device 20. Each light receiving element PXL may be called a pixel.

[0039] The reflected light LR incident on the optical sensor 26 is irradiated onto each light receiving element PXL in the light receiving region DR. Each light receiving element PXL is configured to convert the amount of reflected light LR incident on the light receiving region DR into a current or voltage and output it. One light receiving element PXL includes, for example, at least one photomultiplier element as an element that converts light into an electrical signal. As the photomultiplier element, for example, a single-photon avalanche diode (SPAD), which is a type of avalanche photodiode, is used.

[0040] 6 shows a case where the optical sensor 26 is a one-dimensional sensor, but is not limited thereto. The optical sensor 26 may be a two-dimensional sensor having a configuration in which a plurality of light receiving regions DR shown in FIG. 6 are arranged vertically and horizontally. The optical sensor 26 may be configured so that, for example, conversion of irradiated light into an electrical signal can be set to be enabled or disabled for each light receiving element PXL according to the control of the distance measurement control device 21.

[0041] <1-1-4> Structure of distance measurement results Fig. 7 is a schematic diagram showing an example of the configuration of an image showing the distance measurement result obtained by the distance measurement operation of the distance measuring device 20 according to the first embodiment. The image processing device 15 can generate an image on a frame-by-frame basis based on the distance data received from the measuring device 27. As shown in Fig. 7, the two-dimensional image showing the distance measurement result obtained by the distance measurement operation of the distance measuring system 1 includes six scan result groups SRG1 to SRG6.

[0042] The scan result groups SRG1 to SRG6 correspond to the distance measurement results of the first row SS1 to the sixth row SS6 of the scan area SA, respectively. Each scan result group SRG includes a plurality of pixel groups PG(0) to PG(n) (n is an integer equal to or greater than 1) aligned in a first direction D1. Each pixel group PG includes a plurality of pixels PX0 to PXm (m is an integer equal to or greater than 1) aligned in a second direction intersecting with the first direction D1. Specifically, the pixel group PG(0) includes a plurality of pixels PX0(0) to PXm(0) aligned in the second direction D2. The pixel group PG(n) includes a plurality of pixels PX0(0) to PXm(n) aligned in the second direction D2.

[0043] The pixels PX0 to PXm included in one pixel group PG are based on the distance measurement result of at least one distance measurement point. Each pixel group PG may be generated based on the distance measurement results of multiple distance measurement points. In this example, each scan result group SRG includes (m+1)×(n+1) pixels PX. The number of scan result groups SRG included in the two-dimensional image may be changed as appropriate depending on the design of the optical system 25. The number of pixels PX included in each pixel group PG may be changed as appropriate depending on the design of the optical sensor 26 and the measuring device 27, distance measurement parameters, etc.

[0044] <1-2> Operation Next, the operation of the distance measuring system according to the first embodiment will be described.

[0045] <1-2-1> Distance measurement operation In the distance measuring system 1 according to the first embodiment, the distance measuring device 20 is configured to be able to use at least one of the first setting to the eighth setting as a distance measuring parameter. The following describes the distance measuring operation of the distance measuring device 20 in order of the first setting to the eighth setting.

[0046] (1: First setting) Fig. 8 is a schematic diagram showing an example of a scanning method based on the first setting of the distance measuring device 20 according to the first embodiment. Fig. 8(A) illustrates an example of the emission position of the emission light LE in the scan area SA when the first setting is applied. Fig. 8(B) illustrates an example of the waveform of a control signal for controlling the emission timing and light intensity of the emission light LE(N), LE(N+1) and LE(N+2) (N is an integer equal to or greater than 0) shown in Fig. 8(A).

[0047] The emission position of the emitted light LE shown in (A) of FIG. 8 is the same as the scan area SA shown in FIG. 5. As shown in (B) of FIG. 8, the distance measurement control device 21 generates a pulse signal of voltage V1 with a period T1 and supplies it to the laser driver 22. Then, the laser driver 22 generates a drive current for the laser diode 23 based on the supplied pulse signal. Then, the laser diode 23 emits a laser light (emitted light LE) with a light intensity based on the voltage V1. Thus, in the first setting, the laser diode 23 generates the emitted light LE with a period T1. The measurement device 27 generates a pixel group PG(N) based on the emitted light LE(N), generates a pixel group PG(N+1) based on the emitted light LE(N+1), and generates a pixel group PG(N+2) based on the emitted light LE(N+2).

[0048] Fig. 9 is a schematic diagram showing an example of a configuration based on a first setting of the optical sensor 26 and the measurement device 27 included in the distance measuring device 20 according to the first embodiment. As shown in Fig. 9, the measurement device 27 in the first setting includes ADCs (Analog-to-Digital Converters) 271-0 to 271-m and distance measuring circuits 272-0 to 272-m.

[0049] Each of the light receiving elements PXL0 to PXLm included in the optical sensor 26 converts the irradiated reflected light LR(N) into an electric signal and outputs it. The ADCs 271-0 to 271-m convert the output signals of the light receiving elements PXL0 to PXLm into digital signals. The digital signals converted by the ADCs 271-0 to 271-m are input to the distance measuring circuits 272-0 to 272-m, respectively. The distance measuring circuits 272-0 to 272-m generate distance data based on the peak positions of the digital signals input from the ADCs 272-0 to 272-m, respectively, and transmit the generated distance data to the image processing device 15. The distance data generated by the distance measuring circuits 272-0 to 272-m corresponds to the pixels PX0(N) to PXm(N), respectively.

[0050] In this way, in the first setting, each pixel PX is generated based on the light detection result by one light receiving element PXL corresponding to each distance measurement point. The first setting is used, for example, when the visibility in the surrounding environment of the transportation vehicle VE is sufficiently large.

[0051] (2: Second setting) Fig. 10 is a schematic diagram showing an example of a scanning method based on the second setting of the distance measuring device 20 according to the first embodiment. Fig. 10(A) illustrates the emission timing of the emission light LE in the scan area SA when the second setting is applied. Fig. 10(B) illustrates the waveform of a control signal for controlling the emission timing and light intensity of the emission light LE(N) and LE(N+2) shown in Fig. 10(A).

[0052] The emission position of the emitted light LE shown in (A) of Fig. 10 is similar to that in which one of two consecutive emitted lights LE (e.g., the emitted light LE(N+1)) is omitted from the scan area SA shown in Fig. 5. In other words, the emission position of the emitted light LE in the second setting is similar to that in which every other emission of the emitted light LE is omitted in the first setting.

[0053] 10B, the distance measurement control device 21 generates a pulse signal of voltage V2 with a period T2 and supplies it to the laser driver 22. The period T2 is, for example, twice the period T1. The voltage V2 is higher than the voltage V1. The laser diode 23 then emits a laser beam (emitted beam LE) with a light intensity based on the voltage V2. The light intensity of the laser beam based on the voltage V2 is higher than the light intensity of the laser beam based on the voltage V1.

[0054] In the second setting, the emitted light LE is generated at a period T2 longer than the period T1, so that the number of measurement points in each row SS is fewer than in the first setting. That is, in the second setting, the number of pixels PX aligned in the first direction D1 is fewer than in the first setting. Instead, in the second setting, it is possible to increase the laser energy of each emitted light LE more than in the first setting, and the laser light can be irradiated farther than in the first setting. The second setting is used, for example, when the visibility in the surrounding environment of the transportation equipment VE is shorter than a predetermined length.

[0055] In the above description, the case where the emission of the emitted light LE is omitted so that the number of pixels is half that of the first setting is illustrated, but the present invention is not limited to this. In the second setting, it is sufficient that the number of times the emitted light LE is emitted is reduced compared to the first setting, and the light intensity of the laser light is set to be higher than that of the first setting. In other words, the distance measurement control device 21 to which the second setting is applied only needs to reduce the number of times the emitted light LE is emitted per frame in the distance measurement operation and increase the energy of the emitted light LE in accordance with the visibility information.

[0056] (3: Third setting) Fig. 11 is a schematic diagram showing an example of a scanning method based on the third setting of the distance measuring device 20 according to the first embodiment. Fig. 11(A) illustrates the emission timing of the emission light LE in the scan area SA when the third setting is applied. Fig. 11(B) illustrates the waveform of a control signal for controlling the emission timing and light intensity of the emission light LE(N) and LE(N+1) shown in Fig. 11(A).

[0057] The emission position of the emitted light LE shown in (A) of FIG. 11 is the same as the scan area SA shown in FIG. 5. As shown in (B) of FIG. 11, the distance measurement control device 21 generates a pulse signal of voltage V2 with a period T3 and supplies it to the laser driver 22. The period T3 is, for example, twice the period T1. The frame rate of the image generated in the third setting is lower than that of the first setting because the emitted light LE is emitted with a period longer than that of the first setting and the emission position of the emitted light LE is the same as that of the first setting. In other words, in the third setting, while the number of pixels PX is the same as that of the first setting, the frame rate is lower than that of the first setting. Instead, in the third setting, the laser energy of each emitted light LE can be increased more than that of the first setting, and the laser light can be irradiated farther than that of the first setting. In this way, in the third setting, the laser energy per pixel PX is increased instead of lowering the frame rate compared to the first setting. In other words, the distance measurement control device 21 to which the third setting is applied may reduce the frame rate in the distance measurement operation and increase the energy of the emitted light LE in accordance with the visibility information. The third setting is used, for example, when the visibility in the surrounding environment of the transportation equipment VE is shorter than a predetermined length.

[0058] (4: 4th setting) 12 is a schematic diagram showing an example of a configuration based on a fourth setting of the optical sensor 26 and the measurement device 27 included in the distance measuring device 20 according to the first embodiment. As shown in FIG 12, the measurement device 27 in the fourth setting includes an ADC 271-k and a distance measuring circuit 272-k (k is an integer equal to or greater than 0).

[0059] Each of the light receiving elements PXL(3k), PXL(3k+1), and PXL(3k+2) included in the optical sensor 26 converts the irradiated reflected light LR(N) into an electric signal and outputs it. The output signals of the light receiving elements PXL(3k), PXL(3k+1), and PXL(3k+2) are added and input to the ADC 271-k. The ADC 271-k converts the added output signal into a digital signal and inputs it to the distance measurement circuit 272-k. The distance measurement circuit 272-k generates distance data based on the peak position of the digital signal input from the ADC 272-k, and transmits the generated distance data to the image processing device 15. The distance data generated by the distance measurement circuit 272-k corresponds to the pixel PXk(N).

[0060] In this way, in the fourth setting, each pixel PX is generated based on the light detection results by the three light receiving elements PXL corresponding to each distance measurement point. In the fourth setting, the number of pixels PX generated based on one output light LE(N) is smaller than that in the first setting. That is, in the fourth setting, the number of pixels PX arranged in the pixel group PG in the second direction D2 is smaller than that in the first setting. The connection between the multiple light receiving elements PXL and one ADC 271 can be realized by, for example, a switch circuit provided in the optical sensor 26 or the measurement device 27.

[0061] In this example, the output signals of three light receiving elements PXL are added together and input to one ADC 272, but the present invention is not limited to this. In the fourth setting, it is sufficient that the output signals of at least two or more light receiving elements PXL are added together and input to one ADC 272. Therefore, in the fourth setting, the number of pixels PX to be output may change depending on the number of light receiving elements PXL associated with one ADC 272. For example, when the output signals of three light receiving elements PXL are added together and input to one ADC 272, (m / 3) pixels PX arranged in the second direction D2 are generated based on one output light LE(N).

[0062] (5: 5th setting) Fig. 13 is a schematic diagram showing an example of a scanning method based on the fifth setting of the distance measuring device 20 according to the first embodiment. Fig. 13(A) illustrates the emission timing of the emission light LE in the scan area SA when the fifth setting is applied. Fig. 13(B) illustrates the waveforms of control signals for controlling the emission timing and light intensity of the emission light LE(2N), LE(2N+1), LE(2N+2), LE(2N+3), LE(2N+4), and LE(2N+5) shown in Fig. 13(A).

[0063] The emission position of the emitted light LE shown in FIG. 13A is the same as that of the emitted light arranged in the P direction in the scan area SA shown in FIG. 5 with doubled arrangement density. As shown in FIG. 13B, the distance measurement control device 21 generates a pulse signal of voltage V3 with a period T4 and supplies it to the laser driver 22. The period T4 is, for example, half of the period T1. In this case, the pulse signals corresponding to the emitted light LE(2N), the emitted light LE(2N+2), the emitted light LE(2N+4), ... are generated with a period T1. The voltage V3 is, for example, half of the voltage V1. In the fifth setting, the laser diode 23 emits a laser light (emitted light LE) with a light intensity based on the voltage V3. The light intensity of the laser light based on the voltage V3 is weaker than the light intensity of the laser light based on the voltage V1. Then, in the fifth setting, the light reception result corresponding to the outgoing light LE(2N) and the light reception result corresponding to the outgoing light LE(2N+1) are integrated to generate distance measurement data for one pixel group PG(N).

[0064] Fig. 14 is a schematic diagram showing an example of a method for processing the light reception results based on the fifth setting of the distance measuring device 20 according to the first embodiment. Fig. 14(A) corresponds to the emission timing and light intensity of the emitted light LE(2N) and LE(2N+1) shown in Fig. 13(B). Fig. 14(B) shows the time change (light reception results) of two types of received light amounts ALR corresponding to the emitted light LE(2N) and LE(2N+1) shown in Fig. 14(A). Fig. 14(C) shows a waveform obtained by accumulating the time change (light reception results) of two types of received light amounts ALR corresponding to the emitted light LE(2N) and LE(2N+1) shown in Fig. 14(B).

[0065] As shown in FIG. 14, in the fifth setting, the light reception results of the two emitted lights LE(2N) and LE(2N+1) are accumulated, and a peak position corresponding to the reflected light LR is detected based on the accumulated light reception results. Then, distance data of the pixel group PG(N) is generated based on the peak position. The frame rate and resolution of the image generated in the fifth setting are, for example, the same as those in the first setting. In the fifth setting, the laser energy of each emitted light LE is reduced compared to the first setting, and the light reception results of multiple measurement points are accumulated and used. That is, in the fifth setting, the laser energy per measurement is reduced, but the number of measurements per pixel PX is increased. In other words, the distance measurement control device 21 to which the fifth setting is applied may increase the number of times the emitted light LE is emitted per unit time in the distance measurement operation and reduce the energy of the emitted light LE according to the visibility information.

[0066] For example, if the light receiving component due to scattering of fog (water) near the LiDAR is too large, the amount of light received by the background noise BGN may exceed the dynamic range. In such a case, the fifth setting is applied, and the laser power is reduced to convert the light into an electrical signal within the dynamic range. That is, the fifth setting can suppress saturation of the background noise BGN of the light receiving result at each ranging point, and can reduce the influence of scattering of fog near the LiDAR. On the other hand, the amount of light received based on the reflected light LR from the subject can be made equivalent to that of the first setting by integrating twice, even if the laser energy per time is 1 / 2. The fifth setting is used, for example, when the visibility in the surrounding environment of the transportation equipment VE is below a predetermined length and there is a risk of the background noise BGN being saturated.

[0067] (6: 6th setting) 15 is a schematic diagram showing an example of a configuration based on a sixth setting of the optical sensor 26 and the measurement device 27 included in the distance measuring device 20 according to the first embodiment. As shown in FIG 15, the measurement device 27 in the sixth setting includes ADCs 271-(3k), 271-(3k+1), and 271-(3k+2), and a distance measuring circuit 272-k.

[0068] Each of the light receiving elements PXL(3k), PXL(3k+1), and PXL(3k+2) included in the optical sensor 26 converts the irradiated reflected light LR(N) into an electrical signal and outputs it. The output signals of the light receiving elements PXL(3k), PXL(3k+1), and PXL(3k+2) are input to the ADCs 271-(3k), 271-(3k+1), and 271-(3k+2), respectively. Each of the ADCs 271-(3k), 271-(3k+1), and 271-(3k+2) converts the input signals into digital signals and inputs them to the distance measurement circuit 272-k. The output signals of the ADCs 271-(3k), 271-(3k+1), and 271-(3k+2) are added together and input to the distance measurement circuit 272-k. The distance measurement circuit 272-k generates distance data based on the peak position of the added digital signal, and transmits the generated distance data to the image processing device 15. The distance data generated by the distance measurement circuit 272-k corresponds to pixel PXk(N).

[0069] In this way, in the sixth setting, each pixel PX is generated based on the light detection results by the three light receiving elements PXL corresponding to each distance measurement point. In the sixth setting, the number of pixels PX generated based on one output light LE(N) is smaller than that in the first setting. That is, in the sixth setting, the number of pixels PX arranged in the second direction D2 in the pixel group PG is smaller than that in the first setting. The input of digital signals from the multiple ADCs 271 to one distance measurement circuit 272 can be realized by a logic circuit or the like provided in the measurement device 27. That is, in the sixth setting, in a system in which ADC sampling is performed in the measurement device 27, the light reception results are added by a logic circuit and input to the distance measurement circuit 272.

[0070] In this example, the output signals of the three ADCs 271 are added together and input to one distance measuring circuit 272, but the present invention is not limited thereto. In the sixth setting, it is sufficient that the output signals of at least two or more ADCs 271 are added together and input to one distance measuring circuit 272. Therefore, in the sixth setting, the number of pixels PX to be output may change depending on the number of pairs of the light receiving element PXL and the ADC 271 associated with one distance measuring circuit 272. For example, when the output signals of the three ADCs 271 are added together and input to one distance measuring circuit 272, (m / 3) pixels PX arranged in the second direction D2 are generated based on one output light LE(N). The sixth setting is used, for example, when the visibility in the surrounding environment of the transport equipment VE is less than a predetermined length.

[0071] (7: 7th setting) Fig. 16 is a schematic diagram showing an example of a configuration based on a seventh setting of the optical sensor 26 and the measurement device 27 included in the distance measuring device 20 according to the first embodiment. As shown in Fig. 16, in the seventh setting, each of the light receiving elements PXL0 to PXLm included in the optical sensor 26 converts the irradiated reflected light LR(N) into an electrical signal and outputs it. Then, the output signals of the light receiving elements PXL0 to PXLm are input to the ADCs 271-0 to 271-m, respectively.

[0072] Each of the ADCs 271-0 and 271-1 converts the input signal into a digital signal and inputs it to the distance measurement circuit 272-0. Each of the ADCs 271-1 and 271-2 converts the input signal into a digital signal and inputs it to the distance measurement circuit 272-1. Similarly, each of the ADCs 271-(k) and 271-(k+1) converts the input signal into a digital signal and inputs it to the distance measurement circuit 272-k. The output signals of the ADCs 271-k and 271-(k+1) are added together and input to the distance measurement circuit 272-k. The distance measurement circuit 272-k generates distance data based on the peak position of the added digital signal and transmits the generated distance data to the image processing device 15. The distance data generated by the distance measurement circuit 272-k corresponds to the pixel PXk(N).

[0073] In this way, in the seventh setting, each pixel PX is generated based on the light detection results by two adjacent light receiving elements PXL corresponding to each distance measurement point. In the seventh setting, at least one light receiving element PXL used to generate two adjacent pixels PX overlaps. In the seventh setting, unlike the sixth setting, the number of pixels PX generated based on one output light LE(N) is the same as that in the first setting. That is, in the seventh setting, the number of pixels PX arranged in the pixel group PG in the second direction D2 is the same as that in the first setting. The input of digital signals from the multiple ADCs 271 to one distance measurement circuit 272 can be realized by a logic circuit or the like provided in the measurement device 27. That is, in the seventh setting, in a system in which ADC sampling is performed in the measurement device 27, the light reception results are added by a logic circuit and input to the distance measurement circuit 272.

[0074] In this example, the output signals of two ADCs 271 are added together and input to one distance measuring circuit 272, but the present invention is not limited to this. In the seventh setting, it is sufficient that the output signals of at least two or more ADCs 271 are added together and input to one distance measuring circuit 272. The number of ADCs 271 used in the seventh setting is approximately equal to the number of distance measuring results (i.e., pixels PX) output by the measuring device 27 based on one emitted light LE. In addition, it is sufficient that two adjacent pixels PX share the light receiving result of at least one light receiving element PXL. The seventh setting is used, for example, when the visibility in the surrounding environment of the transport equipment VE is shorter than a predetermined length.

[0075] (8: 8th setting) Fig. 17 is a schematic diagram showing an example of a method for processing a light reception result based on the eighth setting of the distance measuring device 20 according to the first embodiment. Fig. 17(A) illustrates an example of a waveform of a control signal for controlling the emission timing of the emitted lights LE(N), LE(N+1), and LE(N+2) shown in Fig. 8(A). Fig. 17(B) shows the time change (light reception result) of three types of received light amount ALR corresponding to the emitted lights LE(N), LE(N+1), and LE(N+2) shown in Fig. 17(A). Fig. 17(C) is a table showing further detailed settings of the eighth setting.

[0076] As shown in (A) of FIG. 17, the waveform of the control signal for controlling the emission timing of the emitted light LE(N), LE(N+1), and LE(N+2) in the eighth setting is the same as that in the first setting. The light reception results corresponding to each emitted light LE shown in (B) of FIG. 17 are stored, for example, in a predetermined storage area of ​​the measurement device 27 for the integration process described later. As shown in (C) of FIG. 17, in the eighth setting, the integration process is executed, and in the integration process, for example, the first integration setting and the second integration setting may be used. The default setting corresponds to the case where the integration of the light reception results is not used. For example, in the default setting, the pixels PX(N), PX(N+1), PX(N+2), and PX(N+3) are calculated based on the light reception results D(N), D(N+1), D(N+2), and D(N+3), respectively.

[0077] In the first accumulation setting, pixels PX(N) and PX(N+2) are not calculated (no distance measurement data), the distance data of pixel PX(N+1) is calculated based on the result of accumulating the light reception results D(N) and D(N+1), and the distance data of pixel PX(N+3) is calculated based on the result of accumulating the light reception results D(N+2) and D(N+3). Therefore, in the first accumulation setting, the number of pixels PX arranged in the first direction D1 is reduced.

[0078] In the second accumulation setting, pixel PX(N) is calculated based on the result of accumulating light reception results D(N-1) and D(N), pixel PX(N+1) is calculated based on the result of accumulating light reception results D(N) and D(N+1), pixel PX(N+2) is calculated based on the result of accumulating light reception results D(N+1) and D(N+2), and pixel PX(N+3) is calculated based on the result of accumulating light reception results D(N+2) and D(N+3). That is, in the second accumulation setting, the number of pixels arranged in the first direction D1 is the same as in the default setting.

[0079] In this example, the light reception results corresponding to two ranging points (emitted light LE) are added to calculate distance data constituting one pixel group PG, but the present invention is not limited to this. In the eighth setting, it is sufficient that light reception results corresponding to at least two ranging points are added to generate distance data corresponding to one pixel PX. In other words, the distance measurement control device 21 to which the eighth setting is applied changes the number of integrated light reception results of the reflected light LR used for distance measurement by the measuring device 27 in the ranging operation according to the visibility information. The eighth setting is used, for example, when the visibility in the surrounding environment of the transport equipment VE is shorter than a predetermined length.

[0080] <1-2-2> Setting change operation 18 is a flowchart showing an example of the setting change operation of the distance measuring system 1 according to the first embodiment. The setting change operation of the distance measuring system 1 according to the first embodiment will be described below with reference to FIG.

[0081] The distance measuring system 1 starts a setting change operation based on a user's operation, a predetermined schedule, or the like (START). First, the distance measuring system 1 acquires visibility information (S11). As the visibility information, visibility information calculated based on the measurement of the distance measuring device 20 may be used, or visibility information received from the outside may be used. Next, the distance measuring system 1 changes the distance measuring setting according to the visibility information (S12). This distance measuring setting corresponds to, for example, any of the first to eighth settings described above. For example, the distance measuring system 1 uses the first setting when the visibility is sufficiently long. On the other hand, the distance measuring system 1 uses any of the second to eighth settings when the visibility is shorter than a predetermined value. The ideas of the second to eighth settings described above may be combined to the extent possible. When the distance measuring system 1 reflects the distance measuring setting based on the visibility information in the distance measuring parameters, the series of processes in FIG. 18 ends (END).

[0082] <1-3> Effects of the first embodiment According to the distance measuring system 1 according to the first embodiment described above, it is possible to suppress the deterioration of distance measuring performance according to visibility. The effects of the first embodiment will be described in detail below.

[0083] For example, when fog occurs, visibility is significantly shortened and the laser light is greatly attenuated. When fog occurs, visibility is shortened and the amount of reflected light LR is reduced, making long-distance measurement by LiDAR impossible. It is preferable that the LiDAR mounted on the transportation equipment VE can measure long distances as much as possible even in such an environment. It is also possible to give up long-distance measurement by LiDAR from the beginning depending on visibility.

[0084] Therefore, the ranging system according to the first embodiment uses ranging parameters that emphasize short-distance ranging when the visibility is short and the environment is difficult to measure long distances. Specifically, the ranging system 1 according to the first embodiment changes ranging parameters, such as changing the number of pixels integrated or the laser energy, instead of lowering the number of pixels or the frame rate when the visibility is short. For example, when the measurable distance of a LiDAR is 400 m and the measurable distance is only 200 m, it is possible to reduce the number of pixels to 1 / 4. This value corresponds to a value where the number of pixels detected for a subject located 400 m away from the LiDAR is the same as the number of pixels for the same subject located 200 m away from the LiDAR.

[0085] FIG. 19 is a graph showing an example of the difference in light receiving characteristics between the first comparative example and the first embodiment. In FIG. 19, the vertical axis indicates the amount of received light, and the horizontal axis indicates the maximum distance that can be measured. The numbers 40 and 300 shown in the figure indicate the corresponding visibility values. The results of the first comparative example shown in FIG. 19 correspond to the case where the first setting described in the first embodiment is used. The results of the first embodiment shown in FIG. 19 correspond to the case where the setting change operation is used. It is shown that the longer the maximum distance that can be measured, the higher the distance measurement performance.

[0086] As shown in FIG. 19, in the first embodiment, when the visibility is 300 m, the number of pixels is set to 1 / 4 and the frame rate is set to 1 / √2 based on at least one of the second to eighth settings. Also, in the first embodiment, when the visibility is 40 m, the number of pixels is set to 1 / 16 and the frame rate is set to 1 / 2 based on at least one of the second to eighth settings. This makes the distance measurement performance in the first embodiment higher than that in the first comparative example when the visibility is 300 m and when the visibility is 40 m. Specifically, when the visibility is 40 m, the measurable distance in the first comparative example is about 30 m, whereas the measurable distance in the first embodiment is as long as 50 m.

[0087] As described above, the distance measuring system 1 according to the first embodiment can measure a longer distance when the visibility is short than when the distance measuring parameters are fixed, although this depends on the configuration of the distance measuring device 20. Therefore, the distance measuring system 1 according to the first embodiment can suppress the deterioration of the distance measuring performance according to the visibility.

[0088] <2> Second embodiment The second embodiment relates to a distance measuring device 20 configured to remove noise components in a waveform of a light receiving result of a distance measuring object based on a previous light receiving result. Details of the distance measuring device 20 according to the second embodiment will be described below, focusing on differences from the first embodiment.

[0089] <2-1> Configuration Fig. 20 is a schematic diagram showing an example of the configuration of the optical sensor 26 and the measurement device 27a included in the distance measuring device 20 according to the second embodiment. Fig. 20 shows a detailed configuration of the measurement device 27a associated with one light receiving element PXL onto which the reflected light LR(N) is irradiated. As shown in Fig. 20, the measurement device 27a includes, for example, an ADC 271, a distance measuring circuit 272, a noise value holding unit 273, and a difference calculator 274 corresponding to each light receiving element PXL of the optical sensor 26.

[0090] The ADC 271 converts the output signal (amount of received light) of the light receiving element PXL irradiated with the reflected light LR(N) into a digital signal D(N) and outputs it. The digital signal D(N) is time-series data having a value that changes with time. The digital signal D(N) is sent to a difference calculator 274 and is held in a buffer circuit (not shown). The noise value holding unit 273 reads out a digital signal D(N-1) of the previous reflected light LR(N) from the buffer circuit. Then, the noise value holding unit 273 sends the digital signal D(N-1) to the difference calculator 274 in synchronization with the digital signal D(N) output from the ADC 271.

[0091] The difference calculator 274 performs a difference calculation between the digital signal D(N) transmitted from the ADC 271 and the digital signal D(N-1) transmitted from the noise value holding unit 273. Specifically, in the difference calculation, the difference calculator 274 subtracts the numerical value of the digital signal D(N-1) from the numerical value of the digital signal D(N) at the same time up to the fixed time tA, starting from the emission time of each emitted light LE as time 0. Then, the difference calculator 274 transmits the digital signal obtained by the difference calculation to the distance measurement circuit 272.

[0092] The distance measurement circuit 272 generates distance data based on the peak position of the digital signal obtained by the difference calculation by the difference calculator 274, and transmits the generated distance data to the image processing device 15. As described above, in the second embodiment, a difference calculation is performed using the digital signal D(N-1) of the previous pixel between the output of the ADC 271 and the distance measurement calculation by the distance measurement circuit 272. The other configurations of the distance measurement system 1 according to the second embodiment are similar to those of the first embodiment.

[0093] <2-2> How to process the light reception results Fig. 21 is a schematic diagram showing an example of a method for processing the light reception results of the distance measuring device 20 according to the second embodiment. Fig. 21(A) shows the change in the amount of light received by the optical sensor 26 corresponding to the emitted light LE(N-1). Fig. 21(B) shows a case where a difference calculation is performed on the change in the amount of light received by the optical sensor 26 corresponding to the emitted light LE(N). In this example, it is assumed that fog is occurring in the surrounding environment of the distance measuring system 1.

[0094] As shown in (A) of FIG. 21, when the emitted light LE(N-1) is emitted at time t0, background noise influenced by fog is detected immediately after emission. In this example, the reflected light LR is detected after time tA. If the detection threshold TH is set as shown in the figure, a false detection occurs between times t0 and tA before the reflected light LR is detected. For example, if the detection threshold is assumed to be the maximum value of the subject, the amount of received light is greater for a time shorter than the "false detection" in red text, and this will be mistaken for the false detection.

[0095] 21B, in the second embodiment, a difference calculation is performed using the light reception results between times t0 and tA. Between times t0 and tA, large background noise is detected before the difference calculation, whereas after the difference calculation, the background noise in the period from immediately after emission to time tA is suppressed.

[0096] As described above, in the second embodiment, the measuring device 27 corrects the light reception results of the optical sensor 26 from the emission time of the emitted light LE to time tA based on the light reception results of the previous pixel PX, and measures the distance to the subject OB based on the corrected light reception results. Other operations of the distance measuring device 20 according to the second embodiment are similar to those of the first embodiment.

[0097] <2-3> Effects of the second embodiment The fog signal, which is one of the factors that reduces visibility, is relatively stable, so LiDAR can estimate the fog-related signal in the current signal by using the previous signal.

[0098] Therefore, the distance measuring device 20 according to the second embodiment executes a difference calculation based on the actual measurement value of the amount of received light of the previous pixel. As a result, in the second embodiment, the effect of short-distance water scattering due to fog or the like can be canceled by the difference calculation. Therefore, the distance measuring device 20 according to the second embodiment can suppress deterioration of distance measuring performance even when background noise at short distances increases due to a shortened visibility caused by fog or the like.

[0099] In the second embodiment, the value used by the difference calculator 274 for the difference calculation is not limited to the value of the previous pixel (i.e., the digital signal D(N-1)), and the value of the previous frame may be used. In this case, the noise value holding unit 273 calculates a calculation value such as an average or a median for each time from time 0 to a fixed time tA of the digital signal D acquired in the previous frame instead of the digital signal D(N-1), and transmits the calculated value to the difference calculator 274. Then, the difference calculator 274 executes a calculation process between the digital signal D(N) transmitted from the ADC 271 and the calculation value transmitted from the noise value holding unit 273 for each time.

[0100] In this example, the timing of transmitting digital signals between the ADC 271 and the noise value holding unit 273 is synchronized, but the present invention is not limited to this. It is sufficient that the difference calculation unit 274 can perform the difference calculation of the digital signals D(N) and D(N-1), and the difference calculation unit 274 may have a buffer circuit capable of temporarily holding the data of the digital signals D(N) and D(N-1) that are the subject of the difference calculation.

[0101] <3> Third embodiment The third embodiment relates to a distance measuring device 20 configured to remove noise components in a waveform of a light receiving result of a distance measuring object based on a combination of data of one point of the previous light receiving result and a predetermined function. Details of the distance measuring device 20 according to the third embodiment will be described below, focusing on differences from the first and second embodiments.

[0102] <3-1> Configuration Fig. 22 is a schematic diagram showing an example of the configuration of the optical sensor 26 and the measurement device 27b included in the distance measuring device 20 according to the third embodiment. Fig. 22 shows a detailed configuration of the measurement device 27b associated with one light receiving element PXL onto which the reflected light LR(N) is irradiated. As shown in Fig. 22, the measurement device 27b includes an ADC 171, a distance measuring circuit 272, a difference calculator 274, and a noise value calculator 275 corresponding to each light receiving element PXL of the optical sensor 26.

[0103] The ADC 271 converts the output signal (amount of received light) of the light receiving element PXL irradiated with the reflected light LR(N) into a digital signal D(N) and outputs it. The digital signal D(N) includes point data PD(N) corresponding to the digital value of the amount of received light at a predetermined time. This predetermined time is set, for example, near time t0. The point data PD(N) is held in a buffer circuit not shown. The noise value calculation unit 275 reads out point data PD(N-1) of the previous reflected light LR(N) from the buffer circuit. Then, the noise value calculation unit 275 calculates time-series noise value data for a predetermined period based on the point data PD(N-1) and a predetermined function. Then, the noise value calculation unit 275 transmits the calculated time-series noise value data to the difference calculator 274.

[0104] The difference calculator 274 performs a difference calculation between the digital signal D(N) transmitted from the ADC 271 and the time-series noise value data transmitted from the noise value calculation unit 275. Specifically, in the difference calculation, the difference calculator 274 subtracts data associated with the same time between the digital signal D(N) and the time-series noise value data. Then, the difference calculator 274 transmits the digital signal obtained by the difference calculation to the distance measurement circuit 272.

[0105] The distance measurement circuit 272 generates distance data based on the peak position of the digital signal obtained by the difference calculation by the difference calculator 274, and transmits the generated distance data to the image processing device 15. As described above, in the third embodiment, similar to the second embodiment, a difference calculation is performed between the output of the ADC 271 and the distance measurement calculation by the distance measurement circuit 272, using the point data PD(N-1) of the previous pixel and noise value data based on a predetermined function. The other configurations of the distance measurement system 1 according to the third embodiment are similar to those of the second embodiment.

[0106] <3-2> How to process the light reception results Fig. 23 is a schematic diagram showing an example of a method for processing the light reception results of the distance measuring device 20 according to the third embodiment. Fig. 23(A) shows a change in the amount of light received by the optical sensor 26 corresponding to the emitted light LE(N-1). Fig. 23(B) shows a case where a difference calculation is performed on the change in the amount of light received by the optical sensor 26 corresponding to the emitted light LE(N). In this example, it is assumed that fog is occurring in the surrounding environment of the distance measuring system 1.

[0107] As shown in (A) of Fig. 23, when the emitted light LE(N-1) is emitted at time t0, background noise influenced by fog is detected immediately after the emission. In this example, the reflected light LR is detected after time tA, and there is a risk of erroneous detection occurring as in the second embodiment. In contrast, in the third embodiment, point data PD(N-1) is acquired at time tB in response to the emitted light LE(N-1).

[0108] Then, as shown in (B) of Fig. 21, in the third embodiment, a difference calculation is performed using the calculation result using the point data PD(N-1) with a predetermined function. Between times t0 and tA, a large background noise is detected before the difference calculation, whereas the background noise can be suppressed after the difference calculation. Note that the range to which the difference calculation is applied may be the range from time t0 to time tA, or the range from time tB to time tA.

[0109] As described above, in the third embodiment, the measuring device 27, during distance measurement associated with the output light LE, corrects a portion of the light reception result of the optical sensor 26 that corresponds to the predetermined period using noise value data for the predetermined period calculated based on the light reception result of the previous pixel (light receiving element PXL) at time tB, and measures the distance to the subject OB based on the corrected light reception result. Other operations of the distance measuring device 20 according to the third embodiment are similar to those of the first embodiment.

[0110] <3-3> Effects of the third embodiment The distance measuring device 20 according to the third embodiment executes a difference calculation similar to that of the second embodiment, using a predetermined function and point data PD(N-1) from the light receiving result of the previous pixel. As a result, in the third embodiment, the effect of short-distance water scattering due to fog or the like can be canceled by the difference calculation. Therefore, the distance measuring device 20 according to the third embodiment can suppress deterioration of distance measuring performance even when background noise at short distances increases due to a shortened visibility caused by fog or the like.

[0111] In the third embodiment, the value used by the noise value calculation unit 275 to calculate the noise value data is not limited to the value of the previous pixel (i.e., the point data PD(N-1)), and the value of the same pixel may be used. Also, instead of the point data PD(N-1), an average value in a predetermined period may be used. Also, the noise value calculation unit 275 may use a value based on the value of the previous frame to calculate the noise value data. In this case, the noise value holding unit 273 calculates time-series noise value data using a calculated value such as an average or median value at a predetermined time of a plurality of pixels acquired in the previous frame instead of the point data PD(N-1), and transmits the calculation result to the difference calculator 274. Then, the difference calculator 274 executes a calculation process between the digital signal D(N) transmitted from the ADC 271 and the calculated value for each time transmitted from the noise value calculation unit 275.

[0112] <4> Fourth embodiment The fourth embodiment relates to a distance measuring device 20 configured to be able to change a determination threshold applied to a light receiving result of a distance measuring target based on a previous light receiving result. Details of the distance measuring device 20 according to the fourth embodiment will be described below, focusing on differences from the first to third embodiments.

[0113] <4-1> Configuration Fig. 24 is a schematic diagram showing an example of the configuration of the optical sensor 26 and the measurement device 27c included in the distance measuring device 20 according to the fourth embodiment. Fig. 24 shows a detailed configuration of the measurement device 27c associated with one light receiving element PXL onto which the reflected light LR(N) is irradiated. As shown in Fig. 24, the measurement device 27c includes, for example, a transimpedance amplifier (TIA) 276, an ADC 271, a threshold value determination unit 289, and a comparator 279 corresponding to each light receiving element PXL of the optical sensor 26.

[0114] The TIA 276 amplifies and outputs an output signal (amount of received light) of the light receiving element PXL illuminated with the reflected light LR(N). The signal amplified by the TIA 276 is transmitted to each of the ADC 277 and the comparator 279. The ADC 277 converts the signal amplified by the TIA 276 into a digital signal D(N) and outputs it. The digital signal D(N) is held in a buffer circuit not shown.

[0115] The threshold determination unit 278 reads out the digital signal D(N-1) of the previous reflected light LR(N) from the buffer circuit. Then, the threshold determination unit 278 calculates a detection threshold based on the digital signal D(N-1) and a predetermined function, and transmits it to the comparator 279. The detection threshold is variably set according to time (subject distance). The comparator 279 determines whether or not the reflected light LR has been received for each time based on the output of the TIA 276 and the detection threshold received from the threshold determination unit 278. Other configurations of the distance measuring device 20 according to the fourth embodiment are similar to those of the first embodiment.

[0116] <4-2> How to process the light reception results Fig. 25 is a schematic diagram showing an example of a method for processing the light reception results of the distance measuring device 20 according to the fourth embodiment. Fig. 25(A) shows a change in the amount of light received by the optical sensor 26 corresponding to the emitted light LE(N-1). Fig. 25(B) shows a case where a difference calculation is performed on the change in the amount of light received by the optical sensor 26 corresponding to the emitted light LE(N). In this example, it is assumed that fog is occurring in the surrounding environment of the distance measuring system 1.

[0117] 25A, when the emitted light LE(N-1) is emitted at time t0, background noise affected by fog is detected immediately after the emission. In this example, the threshold value determination unit 278 calculates a detection threshold value based on the light reception results for each of the periods from time t0 to t1, from time t1 to t2, and from time t2 to t3.

[0118] 21B, in the fourth embodiment, distance measurement is performed using a detection threshold for each period calculated based on the emitted light LE(N-1). Specifically, in this example, the threshold determination unit 278 sets a detection threshold TH1 from time t0 to t1, sets a detection threshold TH2 from time t1 to t2, and sets a detection threshold TH3 from time t2 to t3.

[0119] The detection thresholds TH1 to TH3 are different values ​​according to the magnitude of the background noise. For example, the detection threshold TH is set to a higher value as the background noise increases. This reduces the influence of background noise on the detection of the reflected light LR in each period with a different detection threshold TH. In the fourth embodiment, the unit length of the period during which the detection threshold TH is changed may be changed as appropriate.

[0120] As described above, in the fourth embodiment, the measuring device 27 calculates the detection threshold for determining the distance for a plurality of periods based on the light receiving result of the previous pixel (light receiving element PXL) during distance measurement associated with the output light LE, and measures the distance to the subject OB using the detection threshold for each of the plurality of periods. Other operations of the distance measuring device 20 according to the fourth embodiment are similar to those of the first embodiment.

[0121] <4-3> Effects of the fourth embodiment The distance measuring device 20 according to the fourth embodiment uses the light receiving result of the previous pixel to measure distance using a detection threshold TH that is variable according to time. As a result, the distance measuring device 20 according to the fourth embodiment can suppress deterioration of distance measuring performance even when background noise at short distances increases due to reduced visibility caused by fog or the like.

[0122] In this example, the threshold determination unit 278 determines the detection threshold based on the digital signal D(N), but the present invention is not limited to this. The threshold determination unit 278 may determine the detection threshold based on digital data at a predetermined time in the digital signal D(N-1) as in the third embodiment. In the fourth embodiment, the value used by the threshold determination unit 278 to calculate the detection threshold is not limited to the value of the previous pixel (i.e., the digital signal D(N-1)), and the value of the previous frame may be used. In this case, the threshold determination unit 278 calculates the detection threshold based on a calculated value such as the average or median of the digital signal D acquired in the previous frame for each time from time 0 to a fixed time tA, instead of the digital signal D(N-1).

[0123] <5> Fifth embodiment The fifth embodiment relates to a method for calculating visibility using a distance measuring device 20 (LiDAR). Details of a distance measuring system 1 according to the fifth embodiment will be described below, focusing on differences from the first to fourth embodiments.

[0124] <5-1> Configuration First, the configuration of a distance measuring system 1 according to the fifth embodiment will be described.

[0125] <5-2-1> Target of distance measurement by distance measurement system 1 FIG. 26 is a schematic diagram showing an example of a distance measurement target of the distance measurement system 1 according to the fifth embodiment. As shown in FIG. 26, a landmark LM is arranged on a moving route of a transport equipment VE equipped with the distance measurement system 1. The landmark LM is a sign provided to indicate a stopping position of the transport equipment VE when the transport equipment VE is, for example, a railroad vehicle. In this case, the transport equipment VE can control its own stopping position by measuring a relative position with respect to the landmark LM using the distance measurement system 1. The landmark LM may be a utility pole, another transport equipment VE, or the like. The information processing device 10 may grasp the arrangement of the landmark LM based on information stored in the route information database 34.

[0126] <5-2-2> Configuration of Landmark LM FIG. 27 is a schematic diagram showing an example of the configuration of a landmark LM used in the ranging system 1 according to the fifth embodiment. As shown in FIG. 27, the landmark LM may have two types of measurement regions RG. The first measurement region RG1 and the second measurement region RG2 are regions having different reflectances for the laser light (emitted light LE) emitted from the ranging device 20. In this embodiment, a case will be described in which the reflectance for the emitted light LE is lower in the second measurement region RG2 than in the first measurement region RG1. It is sufficient that the first measurement region RG1 and the second measurement region RG2 are arranged and configured on the landmark LM so as to be distinguishable by the ranging system 1. The other configurations of the ranging system 1 according to the fifth embodiment are the same as those of the first embodiment.

[0127] <5-2>Operation Next, the operation of the distance measuring system 1 according to the fifth embodiment will be described.

[0128] <5-2-1> Fog detection Fig. 28 is a schematic diagram showing an example of the light reception result depending on the presence or absence of fog. In Fig. 28, the time series data of the light reception result of the distance measuring device 20 when there is no fog is shown by a solid line, and the time series data of the light reception result of the distance measuring device 20 when there is fog is shown by a dashed line. Time t0 indicates the emission time of the emitted light LE by the distance measuring device 20.

[0129] As shown in FIG. 28, the change in the amount of received light when there is no fog forms a large peak at the detection time of the reflected light LR. On the other hand, the change in the amount of received light when there is fog has a smaller peak than when there is no fog. Furthermore, when there is fog, light due to scattering by water is detected near time t0, i.e., at a short distance. Such background noise BGN can cause erroneous distance measurement. Furthermore, when the fog becomes thicker and the amount of reflected light LR decreases, the amount of reflected light LR received by the distance measuring device 20 decreases, deteriorating the measurable distance or making distance measurement difficult. The amount of received light can be calculated by the following formula (1).

[0130]

number

[0131] In equation (1), Y represents the amount of received light. In equation (1), X represents the subject distance. In equation (1), A represents a variable. For example, A is the product of the amount of emitted light, the light receiving efficiency (including electricity), and the subject reflectance. In other words, A can change depending on the light intensity of the laser diode 23 and the reflectance of the subject onto which the emitted light LE is irradiated. In equation (1), B represents the visibility.

[0132] In formula (1), if the subject distance, subject reflectance, and distance measurement parameters of the LiDAR are known, the visibility can be measured by measuring the amount of light received at one point. According to formula (1), for example, the amount of light received when the visibility is infinite and the subject distance is 400 m is approximately the same as the amount of light received when the visibility is 40 m and the subject distance is 33. That is, in this example, even a LiDAR that can normally measure a distance of 400 m can only measure a distance of 33 m in fog. For this reason, it is preferable for the LiDAR to improve the distance measurement performance even a little in a foggy environment, i.e., an environment with short visibility.

[0133] FIG. 29 is a schematic diagram showing an example of a method for measuring visibility. Visibility calculation methods include, for example, a backscattering type as shown in FIG. 29(A) and an object use type as shown in FIG. 29(B). In the backscattering type, a visibility meter emits outgoing light, receives scattered light from the water component of fog, and calculates the visibility of the surrounding environment based on the result of receiving the scattered light. In the backscattering type, the part of the light reception result used for calculating the visibility must not include an object that reflects the outgoing light. On the other hand, in the object use type, a visibility meter emits outgoing light, receives reflected light from the object, and calculates the visibility of the surrounding environment based on the result of receiving the reflected light. In the object use type, if the fog is too deep, that is, if the visibility is too short, the object cannot be detected, and the visibility may not be calculated. In other words, when calculating the visibility, the appropriate visibility calculation method differs depending on the length of the visibility. Therefore, the distance measurement system 1 according to the fifth embodiment is configured to be able to use multiple types of visibility calculation methods in the visibility calculation operation.

[0134] <5-2-2> Visibility calculation operation 30 is a flowchart showing an example of the visibility calculation operation of the distance measuring system 1 according to the fifth embodiment. The visibility calculation operation of the distance measuring system 1 according to the fifth embodiment will be described below with reference to FIG.

[0135] The ranging system 1 starts the visibility calculation operation (START) based on a user's operation, a predetermined schedule, etc. In the visibility calculation operation, the ranging system 1 first checks whether the landmark LM has been measured (S21). If the landmark LM has been measured (S21: YES), the ranging system 1 calculates the visibility using the subject (S22). On the other hand, if the landmark LM has not been measured (S21: NO), the ranging system 1 calculates the visibility using the backscattering type (S23). When the process of S22 or S23 is completed, the ranging system 1 ends the series of processes in FIG. 30 (END).

[0136] Note that the landmark LM does not necessarily have to be a stationary object placed near the route as shown in Figures 26 and 27. The distance measurement system 1 may use a subject moving around the distance measurement system 1 as a subject used for calculating the visibility. For example, when the transportation equipment VE is an automobile, another automobile traveling ahead may be used as a subject used for calculating the visibility instead of the landmark LM.

[0137] <5-2-3> Calculation method for backscattering visibility Next, a method for calculating the visibility of the backscattering type will be described.

[0138] Fig. 31 is a schematic diagram showing an example of a method for processing the light reception results of the distance measuring device 20 according to the fifth embodiment. Fig. 31 shows time series data of the light reception results of the distance measuring device 20 when there is fog. Time t0 indicates the emission time of the emitted light LE by the distance measuring device 20. Times tA and tB indicate the period of the light reception results used to calculate the visibility. "LUMI" indicates the luminance at which the reflected light LR is detected. "DIST" indicates the distance measurement result.

[0139] When calculating visibility using the backscattering type, other than the landmark LM, it is necessary that no other object is detected during the period from time tA to time tB. For example, when the distance measurement result DIST corresponding to a specific pixel PX is equal to or greater than the distance corresponding to time tB plus a fixed value α, it is proven that no object is detected during the period from time tA to time tB. In this case, the distance measuring device 20 calculates the integral value (average) or median value of the amount of light received during the period from time tA to time tB. Then, the distance measuring device 20 can estimate the visibility by referring to a table that associates the calculated value with the visibility. Such a table is prepared in advance and stored in either the information processing device 10 or the distance measuring device 20. In this example, the case where the distance measuring device calculates the visibility based on the light receiving result has been described, but the visibility may be calculated by the information processing device 10.

[0140] <5-2-4> How to calculate visibility when using a subject Next, a method for calculating visibility using an object will be described. Assuming that the same object is measured at multiple distances using the same LiDAR (distance measuring device 20), the following equation (2) is derived from equation (1).

[0141]

number

[0142] Y in equation (2) indicates the amount of received light, as in equation (1). X in equation (2) indicates the subject distance, as in equation (1). A in equation (2) indicates a variable, as in equation (1). B in equation (2) indicates the visibility, as in equation (1). According to equation (2), as in equation (1), if the subject distance, subject reflectance, and LiDAR ranging parameters are known, the visibility can be measured by measuring the amount of received light at one point. Transforming equation (2) using natural logarithms yields the following equation (3).

[0143]

number

[0144] Thus, equation (3) becomes log(Y*X 2 ) and X. Therefore, the least squares method can be calculated by measuring the distance to the object at multiple distances. This calculation is robust against changes in the object, the distance measurement parameters of the LiDAR, the transmittance of the exit window, and the like, and is therefore more advantageous than calculating visibility based on distance measurement data at one point. The distance measurement system 1 provided in the transport equipment VE can easily obtain multiple distance measurement results for the same object having a relative speed, and can calculate visibility in the surrounding environment. In this specification, the "relative speed" corresponds to the difference between the speed of the transport equipment VE and the speed of the object. In the fifth embodiment, the transport equipment VE is moved to multiple distances from the object, and the LiDAR mounted on the transport equipment VE measures multiple distances for the same object, thereby calculating visibility. Not limited to this, the distance measurement system 1 according to the fifth embodiment can measure the distance to the same object at multiple distances over time as long as the transport equipment VE and the object are not at the same speed, that is, a relative speed occurs between the transport equipment VE and the object. Therefore, the visibility calculation operation in the fifth embodiment is not limited to the case where the transport equipment VE moves, and a plurality of distances may be measured by moving the subject.

[0145] FIG. 32 is a table showing a first example of a measurement result in which a method for calculating visibility using an object is applied in the distance measuring system 1 according to the fifth embodiment. In the first example shown in FIG. 32, at a distance of 20 m, the reflection amount is 24.4, and log(Y*X 2 ) is 9.186. At a distance of 22 m, the reflection is 20.1, and log(Y*X 2 ) is 9.184. At a distance of 24 m, the reflection is 16.9, and log(Y*X 2 ) is 9.182. At a distance of 26 m, the reflection is 14.3, and log(Y*X 2 ) is 9.179. At a distance of 28 m, the reflection is 12.3, and log(Y*X 2) is 9.177. At a distance of 30 m, the reflection is 10.7, and log(Y*X 2 ) is 9.174. Using the least squares method based on these calculation results, 2 / B*log(0.05)=-0.0012, and log(A)=9.21034. Therefore, the variable A=10000 and the visibility B=5000 are calculated.

[0146] FIG. 33 is a table showing a second example of a measurement result in which the object-based visibility calculation method is applied in the distance measuring system according to the fifth embodiment. In the second example shown in FIG. 33, the reflection amount is 1.3 at a distance of 20 m, and log(Y*X 2 ) is 6.215. At a distance of 22 m, the reflection is 0.8, and log(Y*X 2 ) is 5.915. At a distance of 24 m, the reflection is 0.5, and log(Y*X 2 ) is 5.615. At a distance of 26 m, the reflection is 0.3, and log(Y*X 2 ) is 5.316. At a distance of 28 m, the reflection is 0.2, and log(Y*X 2 ) is 5.016. At a distance of 30 m, the reflection is 0.1, and log(Y*X 2 ) is 4.717. Using the least squares method based on these calculation results, 2 / B*log(0.05)=-0.1498, and log(A)=9.21034. Therefore, the variable A=10000 and the visibility B=40 are calculated.

[0147] (How to use Landmark LM) Fig. 34 is a schematic diagram showing an example of the relationship between the position of the landmark LM and the number of pixels. Fig. 34 illustrates the positions of the landmarks LM arranged in the angle of view scanned by the distance measuring device 20. As shown in Fig. 34, a landmark LM1 located at a distance of 30 m from the distance measuring device 20 is detected by, for example, 30 pixels PX. On the other hand, a landmark LM2 located at a distance of 100 m from the distance measuring device 20 is detected by, for example, 10 pixels PX.

[0148] In this way, when the landmark LM (subject) is far from the distance measuring device 20, the number of pixels in the image corresponding to the landmark LM decreases, making it difficult to detect the landmark LM. When detecting a distant landmark LM, it is preferable to design the landmark LM to be large in size. Also, when the landmark LM is extremely close to the distance measuring device, it may not be included in the angle of view or the amount of light received may be too large, making distance measurement difficult.

[0149] In the distance measurement system 1, the same landmark LM may be measured at multiple distances in order to calculate visibility. For this reason, it is preferable that the range in which the distance to the landmark LM is measured is determined in advance according to the size of the landmark LM. Also, from the viewpoint of ease of data collection, it is preferable that the range in which the distance is measured is set as narrow as possible.

[0150] The first condition shown in Fig. 34 makes it possible to detect both the landmark LM1 located at 30 m and the landmark LM2 located at 100 m. However, under the first condition, it is necessary to increase the size of the landmark LM in order to detect the landmark LM at a long distance. On the other hand, the second condition shown in Fig. 34 is configured to be able to measure the distance to the landmark LM in a range that includes 30 m and is narrower than the first condition. In this way, by changing the range for measuring the distance to the landmark LM from the first condition to the second condition, it is possible to design the size of the landmark LM to be smaller.

[0151] FIG. 35 is a schematic diagram showing an example of the relationship between the amount of received light and the distance when measuring the measurement area RG1 of the landmark LM under four conditions with different visibility. FIG. 36 is a schematic diagram showing an example of the relationship between the amount of received light and the distance when measuring the measurement area RG2 of the landmark LM under four conditions with different visibility. Each of FIG. 35 and FIG. 36 shows the relationship between the amount of received light and the measurable distance when the visibility is 40 m, 100 m, 300 m, and 1000 m. In each of FIG. 35 and FIG. 36, the range of the amount of received light from 1 to 10 corresponds to the range of the amount of received light that can be used for distance measurement, and the visibility measurement range is assumed to be 40 to 1000 m. In addition, it is assumed that the reflectance of the measurement area RG1 with respect to the output light LE is 10, and the reflectance of the measurement area RG2 is 1.

[0152] 35, when distance measurement for calculating visibility is performed only for measurement region RG1, for example, by measuring a distance range of 24 m to 229 m, it is possible to calculate visibility from 40 m to 1000 m. On the other hand, under this condition, since the distance range is wide, it is required that the landmark LM be designed to be large in size.

[0153] 36, when distance measurement for calculating visibility is performed only for measurement region RG2, visibility from 100 m to 1000 m can be calculated by measuring the distance range of 24 m to 106 m. On the other hand, under these conditions, when the visibility is 40 m, the number of points that can be measured is reduced, making it difficult for the distance measuring device 20 to calculate the visibility.

[0154] Therefore, in the distance measuring system 1 according to the fifth embodiment, distance measurement data of both the two measurement regions RG1 and RG2 of the landmark LM is obtained, and the more preferable distance measurement data is used to calculate the visibility. For example, if both the measurement region RG1 (reflectance=10) and the measurement region RG2 (reflectance=1) can be used, the distance measuring device 20 can calculate the visibility of 40m to 1000m in the distance range of 24m to 106m. As a result, in this example, the size of the landmark LM, that is, the area of ​​the part of the landmark LM where the measurement regions RG1 and RG2 are arranged, can be designed to be smaller than the case of measuring the distance range of 24m to 229m.

[0155] As described above, the ranging system 1 of the fifth embodiment acquires a first ranging result measured based on reflected light from a first measurement area RG1 of the same subject, and a second ranging result measured based on reflected light from a second measurement area RG2 of the same subject, and can calculate visibility in the surrounding environment using both the first ranging result and the second ranging result.

[0156] <5-3> Effects of the fifth embodiment There is a demand for the ability to detect rain and fog in transportation vehicles such as railway vehicles. In backscattering visibility calculation, the prerequisites are that the visibility meter is operated in a fixed position and that no objects exist in the measurement area. However, conventional visibility meters do not have a concept of time. In other words, conventional visibility meters cannot guarantee that no objects exist in the measurement area. In addition, visibility calculation using transmittance requires a certain distance, which makes the size of the visibility meter too large.

[0157] Therefore, the ranging system 1 according to the fifth embodiment is configured to estimate visibility based on scattered light from water components in the air or reflected light from a subject. The ranging system 1 calculates visibility by selectively using both backscattering and subject utilization. For example, LiDAR measures distances using the concept of time, so it can ensure that no object exists within a specified distance (short distance). Therefore, the ranging system 1 can calculate visibility by backscattering after ensuring that there is no subject.

[0158] Furthermore, the distance measurement system 1 uses the object to calculate visibility by the least squares method using multiple distance measurement results. This allows the distance measurement system 1 to calculate visibility with higher accuracy than when measuring distance at one point. Since the transportation equipment VE equipped with the distance measurement system 1 is a moving body, it is easy to ensure a distance measurement range for calculating visibility by using the object. Furthermore, the travel route of the railway vehicle is suitable for placing landmarks LM that can be used to calculate visibility. Since the landmarks LM can be shared for other purposes, installation costs can also be reduced.

[0159] Furthermore, the calculation of visibility using an object in the fifth embodiment is not dependent on reflectance, and therefore can be applied to unknown objects. When the object is a known object (e.g., a landmark LM), the distance measurement system 1 can also measure the amount of reflection of the object, and therefore can detect deterioration of the object over time. That is, the distance measurement system 1 can reduce the effect of deterioration of the object over time on the calculation of visibility by acquiring multiple distances. For example, the distance measurement system 1 can also be used to detect abnormalities in a landmark LM.

[0160] As described above, the distance measuring system 1 according to the fifth embodiment can realize a LiDAR having a function of calculating visibility. The calculated visibility is referred to, for example, when changing the distance measuring parameters described in the first to fourth embodiments. Therefore, the distance measuring system 1 according to the fifth embodiment can also suppress deterioration of distance measuring performance according to the visibility.

[0161] Conventional visibility meters can calculate visibility by measuring one point, for example. On the other hand, the distance measuring system 1 according to the fifth embodiment measures distances at multiple distances and calculates visibility. The difference between calculating visibility based on the measurement results of one point and calculating visibility based on the measurement results of multiple points will be described below with reference to FIG. 37.

[0162] Fig. 37 is a table showing an example of a measurement result in the second comparative example. (A) of Fig. 37 corresponds to a measurement result when the visibility calculation operation of the second comparative example is applied and the variable A = 10000. (B) of Fig. 37 corresponds to a measurement result when the visibility calculation operation of the second comparative example is applied and the variable A = 7000. In the second comparative example, the visibility is calculated based on the distance measurement result of one point using equation (1).

[0163] In the example shown in FIG. 37(A), at a distance of 20 m, the reflection amount is 7.5 and the calculated visibility is 100 m. At a distance of 22 m, the reflection amount is 5.5 and the calculated visibility is 100 m. At a distance of 24 m, the reflection amount is 4.1 and the calculated visibility is 100 m. At a distance of 26 m, the reflection amount is 3.1 and the calculated visibility is 100 m. At a distance of 28 m, the reflection amount is 2.4 and the calculated visibility is 100 m. At a distance of 30 m, the reflectivity is 1.8, and the calculated visibility is 100 m.

[0164] On the other hand, in the example shown in FIG. 37B, at a distance of 20 m, the reflection amount is 5.3, and the calculated visibility is 77 m. At a distance of 22 m, the reflection amount is 3.9, and the calculated visibility is 79 m. At a distance of 24 m, the reflection amount is 2.9, and the calculated visibility is 80 m. At a distance of 26 m, the reflection amount is 2.2, and the calculated visibility is 81 m. At a distance of 28 m, the reflection amount is 1.7, and the calculated visibility is 82 m. At a distance of 30 m, the reflection amount is 1.3, and the calculated visibility is 83 m. In other words, in the second comparative example, a 30% change in the amount of received light results in a measurement error of 20%.

[0165] Fig. 38 is a table showing an example of a measurement result in the fifth embodiment. (A) and (B) in Fig. 38 correspond to the measurement result under a condition where the amount of received light differs by 10 times when the visibility calculation operation described in the fifth embodiment is applied.

[0166] In the example shown in FIG. 38(A), the reflection amount is 7.5 at a distance of 20 m, and Log(Y*X 2 ) is 8.012. At a distance of 22 m, the reflection is 5.5, and Log(Y*X 2 ) is 7.892. At a distance of 24 m, the reflection amount is 4.1, and Log(Y*X 2 ) is 7.772. At a distance of 26 m, the reflection amount is 3.1, and Log(Y*X 2 ) is 7.653. At a distance of 28 m, the reflection amount is 2.4, and Log(Y*X 2 ) is 4.533. At a distance of 30 m, the reflection amount is 1.8, and Log(Y*X 2 ) is 7.413. Using the least squares method based on these calculation results, 2 / B*log(0.05)=-0.0599, and log(A)=9.21034. Therefore, the variable A=10000 and the visibility B=100 are calculated.

[0167] On the other hand, in the example shown in FIG. 38B, at a distance of 20 m, the reflection amount is 0.8, and Log(Y*X 2 ) is 5.709. At a distance of 22 m, the reflection amount is 0.6, and Log(Y*X 2 ) is 5.590. At a distance of 24 m, the reflection amount is 0.4, and Log(Y*X 2 ) is 5.470. At a distance of 26 m, the reflection amount is 0.3, and Log(Y*X 2 ) is 5.350. At a distance of 28 m, the reflection amount is 0.2, and Log(Y*X 2 ) is 5.230. At a distance of 30 m, the reflection amount is 0.2, and Log(Y*X 2) is 5.110. Using the least squares method based on these calculation results, 2 / B*log(0.05)=-0.0599, and log(A)=6.90776. Therefore, it is calculated that variable A=1000 and visibility B=100. In this way, in the fifth embodiment, even if the amount of received light is reduced to 1 / 10, the calculation accuracy of the visibility is the same. That is, the distance measuring system 1 according to the fifth embodiment can achieve a higher calculation accuracy of the visibility than conventional visibility meters.

[0168] <6> others The above-mentioned embodiments may be combined to the extent possible. For example, the fifth embodiment may be combined with any of the first to fourth embodiments. The setting change operation described in the first embodiment may apply the distance measurement parameters of any of the second to fourth embodiments.

[0169] In the first embodiment, the case where the distance measurement parameters are changed according to the visibility is illustrated, but the present invention is not limited thereto. The distance measurement system 1 may control the distance measurement parameters according to the reflection amount of a specific object measured based on the distance measurement result. In this case, for example, the storage device 12 of the information processing device 10 further stores a table in which the reflection amount (amount of received light) of a specific distance of a specific object is associated with the distance measurement parameters. Then, the information processing device 10 can change (control) the distance measurement parameters of the distance measurement device 20 by measuring the reflectance of the specific object based on the distance measurement operation and referring to the table using the measured reflectance. Note that the number of specific objects may be multiple. The specific distance of the specific object may be multiple. The specific object may be identified based on the route information database 34, or may be identified based on information acquired by the information collection device 11. In this example, the visibility may be calculated, or the visibility may not be calculated.

[0170] If the operations described in the above embodiments can be realized, some of the functions of the information processing device 10 may be mounted on the distance measuring device 20. For example, the functions of the information processing unit 101, the route information acquisition unit 104, the track detection unit 106, and the object recognition unit 107 may be realized by the distance measuring device 20. Some of the functions of the distance measuring control device 21 may be implemented in the optical sensor 26 or the measurement device 27. This allows the distance measuring device 20 to perform detailed operations in a timely manner. The classification of the configurations described in each embodiment may be other classifications as long as the operations described in each embodiment can be realized. The setting change operation described in the first embodiment and the visibility calculation operation described in the fifth embodiment may be realized by an embedded computer having a CPU, a memory, a bus, and an input / output circuit (I / O).

[0171] The CPU included in the distance measuring system 1 may be another circuit. For example, an MPU (Micro Processing Unit) or the like may be used instead of the CPU. Each of the processes described in each embodiment may be realized by dedicated hardware. In each embodiment, processes executed by software and processes executed by hardware may be mixed, or only one of them may be used. The distance measuring control device 21 and the CPU may be called a "control circuit" and a "processor". The measurement device 27 may be called a "measurement circuit". The image processing device 15 may be called an "image processing circuit". The laser diode 23 may be called a "light source".

[0172] In the above embodiment, the case where the distance measuring device 20 executes a multi-channel raster scan has been exemplified, but other scanning methods may be used. For example, the distance measuring device 20 may use other scanning methods such as "raster scan", "multi-channel scan", and "OPA (Optical Phased Array) method". In other words, regardless of whether the scanning method used is a mechanical method or an OPA method, the distance measuring device 20 may be capable of adjusting the distance measurement direction (the position of the FOV) by, for example, adjusting the emission timing of a pulsed laser.

[0173] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0174] 1... ranging system, 10... information processing device, 11... information collection device, 12... storage device, 13... transportation equipment control device, 14... speed control device, 15... image processing device, 20... ranging device, 21... ranging control device, 22... laser driver, 23... laser diode, 24... mirror control device, 25... optical system, 26... optical sensor, 27, 27a, 27b, 27c... measuring device, 31... speed sensor, 32... GNSS device, 33... camera, 34... route information data Base, 251... rotating mirror, 252, 253, 254... optical elements, 272... distance measurement circuit, 273... noise value holding unit, 274... difference calculator, 275... noise value calculator, 276... transimpedance amplifier, 278... threshold value determining unit, 279... comparator, 289... threshold value determining unit, LM... landmark, PG... pixel group, PX... pixel, PXL... light receiving element, RG1, RG2... measurement area, S1 to S6... reflecting surfaces, SA... scan area, SRG... scan result group

Claims

1. a light source configured to emit a first laser light; an optical sensor configured to detect a second laser light corresponding to the first laser light reflected by an external object; a measurement circuit configured to measure a distance to the subject based on a timing when the light source emits the first laser light and a timing when the optical sensor detects the second laser light; a control circuit configured to measure an amount of reflection from the object based on a distance measurement result, and to change distance measurement parameters in response to information utilizing the measured amount of reflection; Ranging device.

2. The information corresponds to information of visibility in a surrounding environment, and the control circuit is configured to calculate the visibility based on the measured amount of reflection.

2. A distance measuring device according to claim 1.

3. the information is a table in which the amount of reflection of the object is associated with the distance measurement parameters, the control circuit refers to the information based on the measured amount of reflection and changes the distance measurement parameters.

2. A distance measuring device according to claim 1.

4. the control circuit reduces the number of times the first laser light is emitted per frame in the distance measurement in response to the information, and increases energy of the first laser light.

2. A distance measuring device according to claim 1.

5. the control circuit reduces a frame rate in the distance measurement and increases energy of the first laser light in response to the information; 2. A distance measuring device according to claim 1.

6. The optical sensor includes a plurality of light receiving elements configured to be able to output a current based on the intensity of irradiated light, the control circuit adds output signals of a set of two or more light receiving elements among the plurality of light receiving elements in response to the information, and outputs the sum to the measurement circuit.

5. A distance measuring device according to claim 1 or 4.

7. the measurement circuit further includes an analog-to-digital converter; The output signal of the set of two or more light receiving elements that has been added is analog-to-digital converted by the analog-to-digital converter and output to the measurement circuit.

7. A distance measuring device according to claim 6.

8. the control circuit increases the number of times the first laser light is emitted per unit time and reduces energy of the first laser light in the distance measurement in response to the information.

2. A distance measuring device according to claim 1.

9. the optical sensor includes a plurality of light receiving elements configured to be able to output a current based on an intensity of the second laser light, the measurement circuit includes a plurality of analog-to-digital converters each converting an output signal of the plurality of light receiving elements into a digital signal; the control circuit causes the measurement circuit to measure the distance based on a signal obtained by adding up output signals of a set of two or more analog-to-digital converters among the plurality of analog-to-digital converters in response to the information; 2. A distance measuring device according to claim 1.

10. the number of the analog-to-digital converters is substantially equal to the number of distance measurement results output by the measurement circuit based on one of the first laser beams; 10. A distance measuring device according to claim 9.

11. the control circuit changes an integrated number of the light receiving results of the second laser light used for the distance measurement by the measurement circuit in response to the information, 2. A distance measuring device according to claim 1.

12. the measurement circuit corrects the light reception result of the optical sensor from the emission time of the first laser light to the first time based on the light reception result of a previous pixel or a previous frame, and measures the distance to the subject based on the corrected light reception result.

2. A distance measuring device according to claim 1.

13. the measurement circuit, during distance measurement associated with the first laser light, corrects a portion of the light reception result of the optical sensor corresponding to the first period using noise value data for a first period calculated based on the light reception result at a second time of the same pixel, a previous pixel, or a previous frame, and measures the distance to the subject based on the corrected light reception result.

2. A distance measuring device according to claim 1.

14. the measurement circuit calculates a detection threshold for determining a distance for a plurality of periods based on a light receiving result of a previous pixel or a previous frame during distance measurement associated with the first laser light, and measures the distance to the subject using the detection threshold for each of the plurality of periods.

2. A distance measuring device according to claim 1.

15. the control circuit calculates visibility in the surrounding environment based on multiple distance measurement results for the same object having a relative velocity; 2. A distance measuring device according to claim 1.

16. the control circuit acquires a first distance measurement result obtained by measuring the distance based on reflected light from a first area of ​​the same subject, and a second distance measurement result obtained by measuring the distance based on reflected light from a second area of ​​the same subject that is different from the first area, and calculates visibility in a surrounding environment using both the first distance measurement result and the second distance measurement result.

16. A distance measuring device according to claim 15.

17. When it is determined that the second laser light has not been received by the optical sensor, the control circuit calculates visibility in the surrounding environment based on the optical detection result of the portion where it is ensured that no subject is present.

2. A distance measuring device according to claim 1.

18. when it is determined that the second laser light has been received by the optical sensor, the control circuit calculates a visibility in the surrounding environment based on a plurality of distance measurement results for the same object having a relative speed.

18. A distance measuring device according to claim 17.

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