Distance measuring 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 rangefinder known as LiDAR (Light Detection and Ranging) is a well-known distance measuring device. LiDAR emits laser light towards a rangefinder target. The emitted laser light is reflected by the rangefinder target and detected by the LiDAR's optical sensor. The LiDAR then calculates the time of flight (ToF) of the laser light based on the time the laser light was emitted and the time the reflected laser light from the rangefinder target was detected. This allows the LiDAR to measure the distance between the LiDAR and the rangefinder target based on the ToF and the speed of the laser light. Thus, for LiDAR to perform range measurement, the optical sensor must be able to detect the laser light reflected by the rangefinder target. For example, the emitted laser light attenuates significantly as the visibility decreases, making it more difficult for the optical sensor to detect the laser light as the visibility decreases. Therefore, the range measurement performance of LiDAR tends to deteriorate as the visibility decreases. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 5832067 [Overview of the project] [Problems that the invention aims to solve]

[0004] The challenge is to provide a distance measuring device that can suppress the deterioration of distance measuring performance in response to visibility. [Means for solving the problem]

[0005] The distance measuring device of the embodiment includes a light source, a light sensor, a measurement circuit, and a control circuit. The light source is configured to emit a first laser beam. The light sensor is configured to detect a second laser beam corresponding to the first laser beam reflected by an external object. The measurement circuit is configured to measure the distance to the object based on the timing when the light source emits the first laser beam and the timing when the light sensor detects the second laser beam. The control circuit is configured to measure the amount of reflection from the object based on the distance measurement result and to change the distance measurement parameters according to the information using the measured amount of reflection. The control circuit is further configured to acquire multiple distance measurement results for the same subject with relative velocity, calculate visibility using the least squares method based on a linear equation of the distance (X) from the multiple distance measurement results and the logarithm of the product of the amount of light received (Y) and the square of the distance (X) (log(Y*X^2)), and change the distance measurement parameters according to the information including the calculated visibility. [Brief explanation of the drawing]

[0006] [Figure 1] A schematic diagram showing an example of the configuration of a distance measuring system according to the first embodiment. [Figure 2] 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. [Figure 3] A block diagram showing an example of the configuration of a distance measuring device according to the first embodiment. [Figure 4] A schematic diagram showing an example of the configuration of the optical system included in the distance measuring device according to the first embodiment. [Figure 5] A schematic diagram showing an example of the configuration of the scan area scanned by the distance measuring device according to the first embodiment. [Figure 6] 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] A schematic diagram showing an example of the configuration of an image representing the distance measurement result obtained by the distance measurement operation of the distance measuring device according to the first embodiment. [Figure 8] A schematic diagram showing an example of a scanning method based on the first setting of the distance measuring device according to the first embodiment. [Figure 9] A schematic diagram showing an example of a configuration based on the first setting of the optical sensor and measuring device included in the distance measuring device according to the first embodiment. [Figure 10] A schematic diagram showing an example of a scanning method based on the second setting of the distance measuring device according to the first embodiment. [Figure 11] Schematic diagram showing an example of a scanning method based on the third setting of the distance measuring device according to the first embodiment. [Figure 12] Schematic diagram showing an example of a configuration based on the fourth setting of the optical sensor and the measuring device included in the distance measuring device according to the first embodiment. [Figure 13] Schematic diagram showing an example of a scanning method based on the fifth setting of the distance measuring device according to the first embodiment. [Figure 14] Schematic diagram showing an example of a method for processing the light reception result based on the fifth setting of the distance measuring device according to the first embodiment. [Figure 15] Schematic diagram showing an example of a configuration based on the sixth setting of the optical sensor and the measuring device included in the distance measuring device according to the first embodiment. [Figure 16] Schematic diagram showing an example of a configuration based on the seventh setting of the optical sensor and the measuring device included in the distance measuring device according to the first embodiment. [Figure 17] Schematic diagram showing an example of a method for processing the light reception result based on the eighth setting of the distance measuring device according to the first embodiment. [Figure 18] Flowchart showing an example of the setting change operation of the distance measuring system according to the first embodiment. [Figure 19] Graph showing an example of the difference in light reception characteristics between the first comparative example and the first embodiment. [Figure 20] Schematic diagram showing an example of the configuration of the optical sensor and the measuring device included in the distance measuring device according to the second embodiment. [Figure 21] Schematic diagram showing an example of a method for processing the light reception result of the distance measuring device according to the second embodiment. [Figure 22] Schematic diagram showing an example of the configuration of the optical sensor and the measuring device included in the distance measuring device according to the third embodiment. [Figure 23] Schematic diagram showing an example of a method for processing the light reception result of the distance measuring device according to the third embodiment. [Figure 24] Schematic diagram showing an example of the configuration of the optical sensor and the measuring device included in the distance measuring device according to the fourth embodiment. [Figure 25] Schematic diagram showing an example of a method for processing the light reception result of the distance measuring device according to the fourth embodiment. [Figure 26]A schematic diagram showing an example of a distance measurement target of the distance measurement system according to the fifth embodiment. [Figure 27] A schematic diagram showing an example of the configuration of landmarks used in the distance measuring system according to the fifth embodiment. [Figure 28] A schematic diagram illustrating the general method for measuring visibility. [Figure 29] A schematic diagram illustrating an example of a method for measuring visibility. [Figure 30] A flowchart showing an example of the line of sight calculation operation of the distance measuring system according to the fifth embodiment. [Figure 31] This is a schematic diagram showing an example of a method for processing the light reception results of a distance measuring device according to the fifth embodiment. [Figure 32] A table showing a first example of measurement results to which the subject-based visibility calculation method is applied in the distance measuring system according to the fifth embodiment. [Figure 33] A table showing a second example of measurement results to which the subject-based visibility calculation method is applied in the distance measuring system according to the fifth embodiment. [Figure 34] A schematic diagram showing an example of the relationship between the location of landmark LM and the number of pixels. [Figure 35] A schematic diagram showing an example of the relationship between the amount of light received and the distance when measuring the distance of the landmark's measurement area RG1 under four different visibility conditions. [Figure 36] A schematic diagram showing an example of the relationship between the amount of light received and the distance when measuring the distance of the landmark's measurement area RG2 under four different visibility conditions. [Figure 37] A table showing an example of measurement results in the second comparative example. [Figure 38] A table showing an example of measurement results in the fifth embodiment. [Modes for carrying out the invention]

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

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

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

[0010] <1-1-1>Configuration of the distance measuring system 1 Figure 1 is a schematic diagram showing an example of the configuration of the distance measuring system 1 according to the first embodiment. Figure 1 shows a situation in which a transport device VE equipped with the distance measuring system 1 is moving along a predetermined route. As shown in Figure 1, the distance measuring system 1 includes an information processing device 10 and a distance measuring device 20. The transport device VE is, for example, a railway vehicle. However, the transport device VE equipped with the distance measuring system 1 may also be an automobile, aircraft, ship, etc. If the transport device VE is a railway vehicle, the predetermined route is a railway track. If the transport device VE is an automobile, the predetermined route is, for example, a road whose area of ​​travel is defined by lane markings, etc.

[0011] The information processing device 10 is a device that collects information such as distance measurement results obtained from the distance measuring device 20, the status of the transport equipment VE, the current position of the transport equipment VE, and the surrounding environment. The information processing device 10 may be configured to control the distance measuring device 20 based on the collected information, or to control the acceleration, deceleration, and direction of travel of the transport equipment VE. In other words, the information processing device 10 may have a function to support the autonomous driving of the transport equipment VE.

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

[0013] The distance measuring system 1 may acquire visibility information from an external source, or it may acquire it by measuring the visibility of the surrounding environment of the transport equipment VE itself. A method for 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 acquires distance information of a predetermined field of view in the direction of travel of the transport equipment VE. In this specification, the field of view of the distance measuring device 20, that is, 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 the information processing device 10 Figure 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. Figure 2 also shows a distance measuring device 20. As shown in Figure 2, the information processing device 10 includes, for example, an information collection device 11, a storage device 12, a transport equipment control device 13, a speed control device 14, and an image processing device 15.

[0015] The information gathering device 11 is a device that collects information such as the current location, status, and surrounding environment of the transport equipment VE. The information gathering 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, GNSS device 32, and camera 33 are a group of devices for collecting information such as the current location, status, and surrounding environment of the transport equipment VE. The speed sensor 31 is a sensor that detects the current speed of the transport equipment VE. The GNSS device 32 is a positioning device that receives radio waves emitted from multiple artificial satellites and determines the current location of the transport equipment VE based on the received radio waves. The camera 33 is an optical device capable of capturing images of the area around the transport 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"), and visibility information. The route information may include, for example, the distance from the starting point on the route and information on landmarks placed on the travel route of the transport equipment VE. The operation information is set, for example, according to the distance from the 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 transport equipment control device 13 is, for example, a computer configured to communicate with the image processing device 15. The transport equipment control device 13 generates control signals for acceleration and deceleration of the transport 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, and operational information acquired from the route information database 34. The information obtained from the image processing device 15 includes, for example, the position information of the railway vehicle RV. The transport equipment control device 13 can then control the movement of the transport equipment VE by transmitting the generated control signals to the speed control device 14.

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

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

[0020] The connections between devices within the information processing device 10 may be, for example, wired or wireless. The information acquisition 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), ROM (Read Only Memory), and RAM (Random Access Memory), etc. The CPU of the information processing device 10 may execute the processing of the transport equipment control device 13 and the processing of the image processing device 15, respectively. 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 communicate with the distance measuring device 20 via a communication interface (not shown). That is, the information processing device 10 can control the distance measuring device 20 via the communication interface.

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

[0022] The distance measuring control device 21 controls the overall operation of the distance measuring device 20. The distance measuring control device 21 includes, for example, a CPU, ROM, RAM, and an oscillator (not shown). The ROM of the distance measuring control device 21 stores the control program for the distance measuring device 20, etc. The CPU of the distance measuring control device 21 controls the laser driver 22, mirror control device 24, optical sensor 26, and measuring device 27 according to the control program. The RAM of the distance measuring control device 21 is used as the CPU's workspace. The oscillator of the distance measuring control device 21 is used to generate intermittent pulse signals. The distance measuring control device 21 may be configured to perform 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 source for the laser diode 23. The laser diode 23 emits laser light based on the drive current supplied by the laser driver 22. The laser light emitted by the laser diode 23 is incident on the optical system 25. The distance measuring device 21 controls the laser driver 22 so that the laser diode 23 emits laser light intermittently. Hereafter, the laser light generated based on the pulse signal will also be called a "pulsed laser". In the distance measuring device 20, the pulsed 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 for a motor that rotates the rotating mirror 251. The rotating mirror 251 is driven (rotates) 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 rotate around one axis, for example. The rotating mirror 251 may be a double-sided mirror or a polygon mirror having three or more reflective surfaces (mirror surfaces). The rotation speed of the rotating mirror 251 can be changed based on the instructions of the distance measuring device 21. The rotating mirror 251 may be a two-axis MEMS (Micro Electro Mechanical Systems) mirror. A combination of a rotating mirror and a one-axis MEMS mirror may be used as the rotating mirror 251. The rotating mirror 251 may also be called a “movable mirror”.

[0025] The optical sensor 26 is a collection of multiple light-receiving elements (pixels) that detect light incident on the distance measuring device 20. The optical sensor 26 is arranged so that laser light emitted from the laser diode 23 and reflected by an object outside the distance measuring device 20 is incident on it via the optical system 25. The optical sensor 26 then converts the laser light incident on the distance measuring device 20 into an electrical signal. This conversion to an electrical signal is performed using circuits such as an ADC (Analog-to-Digital Converter) or a TDC (Time-to-Digital Converter). The optical sensor 26 then adjusts the output level of the converted electrical signal and outputs it to the measuring device 27. Hereafter, the electrical signal generated by the optical sensor 26 based on the incident light will also be referred to as the light reception result.

[0026] The measuring device 27 measures the time when the optical sensor 26 detected the laser light based on the light reception result transmitted from the optical sensor 26. For example, the measuring device 27 determines the peak portion of the signal corresponding to the light reception result as the time when the laser light was detected. 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 emitted the laser light and the time when the laser light reflected by the subject was detected. Then, the measuring device 27 measures (measures 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 laser light, for example, by notification from the distance measurement control device 21. The time when the laser light is emitted may also 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 a single distance measurement result based on a signal obtained by adding the reception results of multiple pixels. The measuring device 27 may be configured to output a single distance measurement result based on a signal obtained by integrating the reception results of multiple distance measurement points.

[0028] The distance measuring device 20 according to the first embodiment can coordinately change the settings of the laser driver 22, mirror control device 24, and measuring device 27 based on visibility information. For example, the distance measuring device 21 can change the period and timing of emitting a pulsed laser from the laser diode 23, the rotation speed of the rotating mirror 251, and the integration setting of the received light result, according to the visibility information. The distance measuring device 21 may also change the settings of the distance measuring parameters based on instructions 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 may change according to the distance measuring parameters of the distance measuring device 20. Note that "resolution" corresponds to the density or number of pixels included in one frame.

[0029] (1:25 optical system configuration) Figure 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. Figure 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 reflected by the object OB (emitted light LE) will also be referred to as "reflected light LR".

[0030] As shown in Figure 4, the optical system 25 further includes optical elements depending on the arrangement of the laser diode 23 and the light sensor 26. Specifically, the optical system 25 further includes, for example, optical elements 252, 253, and 254. Optical elements 252 and 254 are, for example, lenses or mirrors. Optical element 253 is, for example, a half-mirror or a perforated mirror. Note that optical elements 252 and 254 may each be composed of a combination of multiple lenses and multiple mirrors.

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

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

[0033] This specification exemplifies a case where the rotating mirror 251 is a polygonal mirror having six reflective surfaces S1 to S6 with different tilt angles. The distance measuring device 21 controls the rotating mirror 251 to rotate at a rotational speed based on the frame rate. The distance measuring device 20 can scan the location to be measured in two dimensions using intermittently emitted 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 measurement results for multiple points corresponding to one scan is called a "frame". An image for one frame is generated, for example, corresponding to one rotation of the rotating mirror 251. The number of pixels in the image showing the distance measurement results corresponds to the number of pixels included in one frame. By continuously performing scans, the distance measuring device 20 can sequentially acquire distance information to an object OB in front of the device 20. The optical system 25 only needs to have a configuration that allows scanning using laser light, and other configurations are also acceptable.

[0035] (2: Configuration of scan area SA) Figure 5 is a schematic diagram showing an example of the configuration of a scan area SA scanned by the distance measuring device 20 according to the first embodiment. Figure 5 shows an example of the emission direction of the emitted light LE for one frame in the scan area SA. As shown in Figure 5, the emitted light LE is irradiated into the PQR space. The R axis is the 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 perpendicular to the R axis and extends concentrically from the emission port of the emitted light LE. The P axis and Q axis are mutually orthogonal axes within the PQ plane. 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 can map the distance data to an object in the spatial PQR to the FOV in the scan area SA and recognize the distance to an object in the FOV.

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

[0037] The distance measuring device 20 can generate multiple pixels (distance data) arranged in one dimension based on a single emitted light LE. The distance measuring device 20 repeatedly performs the processing of the measurement cycle related to the measurement associated with a single emitted light LE, shifting it one-dimensionally along the P-axis for 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. This type of scanning method is also called a "multi-channel raster scan." As a means of realizing a multi-channel raster scan, an emitted light LE having a vertically elongated illumination surface is used. The number of rows and scanning direction in a single scan by the distance measuring device 20 may be set to other settings.

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

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

[0040] Although Figure 6 shows the case where the optical sensor 26 is a one-dimensional sensor, it is not limited to this. The optical sensor 26 may also be a two-dimensional sensor having a configuration in which multiple light-receiving regions DR, as shown in Figure 6, are arranged in both the vertical and horizontal directions. The optical sensor 26 may be configured so that, in accordance with the control of the distance measuring control device 21, for example, the conversion of irradiated light into an electrical signal can be enabled or disabled for each light-receiving element PXL.

[0041] <1-1-4> Composition of distance measurement results Figure 7 is a schematic diagram showing an example of the configuration of an image representing 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 Figure 7, the two-dimensional image representing 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 contains multiple pixel groups PG(0) to PG(n) (n is an integer of 1 or more) aligned in the first direction D1. Each pixel group PG contains multiple pixels PX0 to PXm (m is an integer of 1 or more) aligned in the second direction intersecting the first direction D1. Specifically, pixel group PG(0) contains multiple pixels PX0(0) to PXm(0) aligned in the second direction D2. Pixel group PG(n) contains multiple pixels PX0(0) to PXm(n) aligned in the second direction D2.

[0043] Multiple pixels PX0 to PXm included in a single 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 contains (m+1) × (n+1) pixels PX. The number of scan result groups SRG included in the 2D image can be appropriately changed depending on the design of the optical system 25. Furthermore, the number of pixels PX included in each pixel group PG can be appropriately changed depending on the design of the optical sensor 26 and the measurement device 27, as well as the distance measurement parameters.

[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 to eighth settings as distance measuring parameters. The following describes in order the cases in which the first to eighth settings are applied as distance measuring operations of the distance measuring device 20.

[0046] (1: First setting) Figure 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. Figure 8(A) illustrates the emission position of the emitted light LE in the scan region SA when the first setting is applied. Figure 8(B) illustrates the waveform of the control signal for controlling the emission timing and light intensity of the emitted light LE(N), LE(N+1), and LE(N+2) (N is an integer greater than or equal to 0) shown in Figure 8(A).

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

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

[0049] Each of the photodetectors PXL0 to PXLm included in the light sensor 26 converts the irradiated reflected light LR(N) into an electrical signal and outputs it. The ADCs 271-0 to 271-m each convert the output signals of the photodetectors 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 each 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 pixels PX0(N) to PXm(N), respectively.

[0050] Thus, in the first setting, each pixel PX is generated based on the light detection result of a single photodetector PXL, corresponding to each distance measurement point. The first setting is used, for example, when visibility in the surrounding environment of a transport equipment VE is sufficiently large.

[0051] (2: Second setting) Figure 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. Figure 10(A) illustrates the emission timing of the emitted light LE in the scan region SA when the second setting is applied. Figure 10(B) illustrates the waveform of the control signal for controlling the emission timing and light intensity of the emitted light LE(N) and LE(N+2) shown in Figure 10(A).

[0052] The emission position of the emitted light LE shown in Figure 10(A) is the same as when one of the two consecutive emitted light LEs (for example, emitted light LE(N+1)) is omitted for the scan region SA shown in Figure 5. In other words, the emission position of the emitted light LE in the second setting is the same as when the emission of the emitted light LE is omitted every other time in the first setting.

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

[0054] In the second setting, the emitted light LE is generated with a period T2 that is longer than the period T1, resulting in fewer measurement points in each row SS than in the first setting. In other words, in the second setting, there are fewer pixels PX aligned in the first direction D1 than in the first setting. Instead, in the second setting, it is possible to increase the laser energy of each emitted light LE compared to the first setting, allowing the laser light to irradiate further than in the first setting. The second setting is used, for example, when the visibility in the surrounding environment of a transport equipment VE is below a certain length.

[0055] In the above explanation, we have provided an example of a case where the emission of the emitted light LE is omitted so that the number of pixels is halved compared to the first setting, but we are 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 in the first setting. In other words, the distance measuring control device 21 to which the second setting is applied should reduce the number of times the emitted light LE is emitted per frame during the distance measuring operation and increase the energy of the emitted light LE, according to the visibility information.

[0056] (3: Third setting) Figure 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. Figure 11(A) illustrates the emission timing of the emitted light LE in the scan region SA when the third setting is applied. Figure 11(B) illustrates the waveform of the control signal for controlling the emission timing and light intensity of the emitted light LE(N) and LE(N+1) shown in Figure 11(A).

[0057] The emission position of the emitted light LE shown in Figure 11(A) is the same as that of the scan region SA shown in Figure 5. As shown in Figure 11(B), the distance measuring control device 21 generates a pulse signal with voltage V2 at a period T3 and supplies it to the laser driver 22. 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 at a longer period than in the first setting, and the emission position of the emitted light LE is the same as in the first setting. In other words, in the third setting, the number of pixels PX is the same as in the first setting, but the frame rate is lower than in the first setting. Instead, in the third setting, it is possible to increase the laser energy of each emitted light LE compared to the first setting, and the laser light can be irradiated further than in the first setting. Thus, in the third setting, the laser energy per pixel PX is increased in exchange for a lower frame rate compared to the first setting. In other words, the distance measuring control device 21 to which the third setting is applied only needs to reduce the frame rate in the distance measuring operation and increase the energy of the emitted light LE according to the visibility information. The third setting is used, for example, when the visibility in the surrounding environment of the transport equipment VE is below a predetermined length.

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

[0059] Each of the photodetectors PXL(3k), PXL(3k+1), and PXL(3k+2) included in the light sensor 26 converts the irradiated reflected light LR(N) into an electrical signal and outputs it. The output signals of the photodetectors PXL(3k), PXL(3k+1), and PXL(3k+2) are then added together and input to the ADC271-k. The ADC271-k converts the added output signals into a digital signal and inputs it to the distance measuring circuit 272-k. The distance measuring circuit 272-k generates distance data based on the peak position of the digital signal input from the ADC272-k and transmits the generated distance data to the image processing device 15. The distance data generated by the distance measuring circuit 272-k corresponds to pixel PXk(N).

[0060] Thus, in the fourth setting, each pixel PX is generated based on the light detection results of three photodetectors PXL, corresponding to each distance measurement point. Furthermore, in the fourth setting, the number of pixels PX generated based on one emitted light LE(N) is less than in the first setting. That is, in the fourth setting, the number of pixels PX aligned in the second direction D2 in the pixel group PG is less than in the first setting. The connection between multiple photodetectors PXL and one ADC271 can be realized, for example, by a switch circuit provided in the light sensor 26 or the measuring device 27.

[0061] In this example, the case where the output signals of three photodetectors PXL are added together and input to one ADC272 is illustrated, but the system is not limited to this. In the fourth setting, it is sufficient that the output signals of at least two or more photodetectors PXL are added together and input to one ADC272. Therefore, in the fourth setting, the number of pixels PX output may vary depending on the number of photodetectors PXL associated with one ADC272. For example, when the output signals of three photodetectors PXL are added together and input to one ADC272, (m / 3) pixels PX are generated aligned in the second direction D2 based on one emitted light LE(N).

[0062] (5: Fifth setting) Figure 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. Figure 13(A) illustrates the emission timing of the emitted light LE in the scan region SA when the fifth setting is applied. Figure 13(B) illustrates the waveforms of control signals for controlling the emission timing and light intensity of the emitted light LE(2N), LE(2N+1), LE(2N+2), LE(2N+3), LE(2N+4), and LE(2N+5) shown in Figure 13(A).

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

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

[0065] As shown in Figure 14, in the fifth setting, the reception results of the two emitted light beams LE(2N) and LE(2N+1) are integrated, and the peak position corresponding to the reflected light LR is detected based on the integrated reception results. Then, distance data for 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 in the first setting. In the fifth setting, the laser energy of each emitted light beam LE is reduced compared to the first setting, and the reception results of multiple measurement points are integrated and used. In other words, in the fifth setting, the laser energy per measurement is reduced, but the number of measurements per pixel PX is increased. To put it another way, the distance measuring control device 21 to which the fifth setting is applied only needs to increase the number of emitted light beams LE emitted per unit time during the distance measuring operation and reduce the energy of the emitted light beams LE, according to the visibility information.

[0066] For example, if the light-receiving component due to scattering from fog (water) near the LiDAR is too large, the amount of background noise (BGN) received may exceed the dynamic range. In such cases, the fifth setting is applied, and the laser power is reduced, allowing the light to be converted into an electrical signal within the dynamic range. In other words, the fifth setting can suppress the saturation of background noise (BGN) in the light-receiving results at each distance measurement point, and can reduce the effect of fog scattering near the LiDAR. On the other hand, the amount of light received based on reflected light (LR) from the subject can be made equivalent to the first setting by integrating two laser energy readings, even if the laser energy per reading is halved. The fifth setting is used, for example, when the visibility in the surrounding environment of a transport equipment VE falls below a predetermined length and there is a risk of background noise (BGN) saturation.

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

[0068] Each of the light-receiving elements PXL(3k), PXL(3k+1), and PXL(3k+2) included in the light 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 then 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 signal into a digital signal and inputs it to the distance measuring circuit 272-k. The output signals of ADCs 271-(3k), 271-(3k+1), and 271-(3k+2) are added together and input to the distance measuring circuit 272-k. The distance measuring circuit 272-k generates distance data based on the peak position of the added digital signals and transmits the generated distance data to the image processing device 15. The distance data generated by the distance measuring circuit 272-k corresponds to pixel PXk(N).

[0069] Thus, in the sixth setting, each pixel PX corresponding to each distance measurement point is generated based on the light detection results of the three photodetectors PXL. Furthermore, in the sixth setting, the number of pixels PX generated based on one emitted light LE(N) is less than in the first setting. That is, in the sixth setting, the number of pixels PX aligned in the second direction D2 in the pixel group PG is less than in the first setting. The input of digital signals from multiple ADCs 271 to one distance measuring circuit 272 can be realized by logic circuits provided in the measuring device 27. That is, in the sixth setting, in the system of the measuring device 27 where ADC sampling is performed, the light reception results are added by the logic circuit and input to the distance measuring circuit 272.

[0070] In this example, the case where the output signals of three ADC271 are added together and input to one distance measuring circuit 272 is illustrated, but the example is not limited to this. In the sixth setting, it is sufficient that the output signals of at least two or more ADC271 are added together and input to one distance measuring circuit 272. Therefore, in the sixth setting, the number of pixels PX output may change depending on the number of sets of photodetectors PXL and ADC271 associated with one distance measuring circuit 272. For example, when the output signals of three ADC271 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 emitted light LE(N). The sixth setting is used, for example, when the visibility in the surrounding environment of a transport equipment VE is below a predetermined length.

[0071] (7: Setting 7) Figure 16 is a schematic diagram showing an example of the configuration of the optical sensor 26 and measuring device 27 included in the distance measuring device 20 according to the first embodiment, based on the seventh setting. As shown in Figure 16, in the seventh setting, each of the photodetectors PXL0 to PXLm 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 photodetectors PXL0 to PXLm are then input to ADC271-0 to 271-m, respectively.

[0072] Each of the ADCs, ADC271-0 and ADC271-1, converts the input signal into a digital signal and inputs it to the distance measuring circuit 272-0. Each of the ADCs, ADC271-1 and ADC271-2, converts the input signal into a digital signal and inputs it to the distance measuring circuit 272-1. Similarly, each of the ADCs, ADC271-(k) and ADC271-(k+1), converts the input signal into a digital signal and inputs it to the distance measuring circuit 272-k. The output signals of ADC271-k and ADC271-(k+1) are added together and input to the distance measuring circuit 272-k. The distance measuring 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 measuring circuit 272-k corresponds to pixel PXk(N).

[0073] Thus, in the seventh setting, each pixel PX corresponding to each distance measurement point is generated based on the light detection results of two adjacent photodetectors PXL. In the seventh setting, at least one of the photodetectors PXL used to generate two adjacent pixel PXs is duplicated. In the seventh setting, unlike the sixth setting, the number of pixels PX generated based on one emitted light LE(N) is the same as in the first setting. That is, in the seventh setting, the number of pixels PX aligned in the second direction D2 in the pixel group PG is the same as in the first setting. The input of digital signals from multiple ADCs 271 to one distance measuring circuit 272 can be realized by logic circuits provided in the measuring device 27. That is, in the seventh setting, in the system of the measuring device 27 where ADC sampling is performed, the light detection results are added by the logic circuit and input to the distance measuring circuit 272.

[0074] In this example, the case where the output signals of two ADC271 are added together and input to one distance measuring circuit 272 is illustrated, but the example is not limited to this. In the seventh setting, it is sufficient that the output signals of at least two ADC271 are added together and input to one distance measuring circuit 272. The number of ADC271 used in the seventh setting is approximately equal to the number of distance measurement results (i.e., pixels PX) output by the measuring device 27 based on one emitted light LE. Furthermore, it is sufficient that two adjacent pixels PX share the light reception result of at least one photodetector PXL. The seventh setting is used, for example, when the visibility in the surrounding environment of the transport equipment VE is below a predetermined length.

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

[0076] As shown in Figure 17(A), the waveforms of the control signals for controlling the emission timing of the emitted light LE(N), LE(N+1), and LE(N+2) in the eighth setting are the same as in the first setting. The received light results corresponding to each emitted light LE shown in Figure 17(B) are stored, for example, in a predetermined memory area of ​​the measuring device 27 for the integration process described later. As shown in Figure 17(C), the integration process is performed in the eighth setting, 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 integration of the received light results is not used. For example, in the default setting, pixels PX(N), PX(N+1), PX(N+2), and PX(N+3) are calculated based on the received light results D(N), D(N+1), D(N+2), and D(N+3), respectively.

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

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

[0079] In this example, we have illustrated a case where the received light results corresponding to two distance measurement points (outgoing light LE) are added together to calculate distance data that constitutes one pixel group PG, but we are not limited to this. In the eighth setting, it is sufficient that the received light results corresponding to at least two distance measurement points are added together 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 should change the number of accumulated received light results of reflected light LR used for distance measurement by the measuring device 27 in the distance measurement 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 below a predetermined length.

[0080] <1-2-2> Configuration change operation Figure 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 Figure 18.

[0081] The distance measuring system 1 starts a setting change operation based on user operation or a predetermined schedule (start). First, the distance measuring system 1 acquires visibility information (S11). The visibility information may be visibility information calculated based on measurements by the distance measuring device 20, or visibility information received from an external source. Next, the distance measuring system 1 changes the distance measuring settings according to the visibility information (S12). This distance measuring setting corresponds to, for example, one of the first to eighth settings described above. For example, the distance measuring system 1 uses the first setting when visibility is sufficiently long. On the other hand, the distance measuring system 1 uses one of the second to eighth settings when visibility is shorter than a predetermined value. The concepts of the second to eighth settings described above may be combined to the extent possible. Once the distance measuring system 1 reflects the distance measuring setting based on the visibility information in the distance measuring parameters, it terminates the series of processes shown in Figure 18 (end).

[0082] <1-3> Effects of the First Embodiment The distance measuring system 1 according to the first embodiment described above can suppress the deterioration of distance measuring performance in response to visibility. The effects of the first embodiment will be described in detail below.

[0083] For example, when fog occurs, visibility is significantly reduced, and laser light is greatly attenuated. Long-range distance measurement using LiDAR may become impossible when fog occurs because visibility is reduced and the amount of reflected light (LR) decreases. It is preferable that LiDAR mounted on VE (Value Engineering) equipment for transportation can measure long distances as much as possible even in such environments. It is also possible to consider giving up on long-range distance measurement using LiDAR from the outset depending on the visibility.

[0084] Therefore, the ranging system according to the first embodiment utilizes ranging parameters that prioritize short-distance ranging when visibility is short and long-distance ranging is difficult. Specifically, when visibility is short, the ranging system 1 according to the first embodiment changes the ranging parameters, such as changing the number of integrated pixels or the laser energy, instead of reducing the number of pixels or the frame rate. For example, if a LiDAR has a measurable distance of 400m but can only measure 200m, it is conceivable to reduce the number of pixels to 1 / 4. This value corresponds to the number of pixels detected by an object located 400m away from the LiDAR being the same as the number of pixels detected by the same object located 200m away from the LiDAR.

[0085] Figure 19 is a graph showing an example of the difference in light reception characteristics between the first comparative example and the first embodiment. In Figure 19, the vertical axis represents the amount of light received, and the horizontal axis represents the maximum distance that can be measured. The numbers 40 and 300 shown represent the corresponding visibility values. The results for the first comparative example shown in Figure 19 correspond to the case where the first setting described in the first embodiment was used. The results for the first embodiment shown in Figure 19 correspond to the case where the setting change operation was used. Measuring performance is higher when the maximum distance that can be measured is longer.

[0086] As shown in Figure 19, in the first embodiment, when the visibility is 300m, 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 40m, 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. As a result, the distance measurement performance in the first embodiment is higher than that of the first comparative example in both the case of visibility of 300m and visibility of 40m. Specifically, when the visibility is 40m, the distance that can be measured is about 30m in the first comparative example, whereas in the first embodiment, the distance that can be measured is longer at 50m.

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

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

[0089] <2-1> Composition Figure 20 is a schematic diagram showing an example of the configuration of the optical sensor 26 and measuring device 27a included in the distance measuring device 20 according to the second embodiment. Figure 20 shows a detailed configuration of the measuring device 27a associated with one photodetector PXL to which reflected light LR(N) is irradiated. As shown in Figure 20, the measuring 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 photodetector PXL of the optical sensor 26.

[0090] The ADC271 converts the output signal (amount of light received) of the photodetector PXL, which is irradiated with reflected light LR(N), into a digital signal D(N) and outputs it. The digital signal D(N) is time-series data with a value that changes with time. The digital signal D(N) is transmitted to the difference calculator 274 and is also held in a buffer circuit (not shown in the figure). The noise value holding unit 273 reads the digital signal D(N-1) of the previous reflected light LR(N) from the buffer circuit. Then, the noise value holding unit 273 transmits the digital signal D(N-1) to the difference calculator 274 in synchronization with the digital signal D(N) output from the ADC271.

[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 takes the emission time of each emitted light LE as the starting time 0 and subtracts the value of the digital signal D(N-1) from the value of the digital signal D(N) at the same time until the fixed time tA. Then, the difference calculator 274 transmits the digital signal calculated by the difference calculation to the distance measuring circuit 272.

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

[0093] <2-2> Processing method of light reception results Figure 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. Figure 21(A) shows the change in the amount of light received by the light sensor 26 corresponding to the emitted light LE(N-1). Figure 21(B) shows the case when a difference calculation is performed on the change in the amount of light received by the light sensor 26 corresponding to the emitted light LE(N). In this example, it is assumed that fog is present in the surrounding environment of the distance measuring system 1.

[0094] As shown in Figure 21(A), when the outgoing light LE(N-1) is emitted at time t0, background noise affected by fog is detected immediately after emission. Then, 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 will occur 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 light received will be greater in a shorter time than the "false detection" indicated in red, leading to a mistaken detection of that.

[0095] On the other hand, as shown in Figure 21(B), 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 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 result of the light sensor 26 from the emission time of the emitted light LE to time tA based on the light reception result of the previous pixel PX, 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 second embodiment are the same as in 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. Therefore, LiDAR can use data from previous light reception results to infer the signal corresponding to fog in the current light reception results.

[0098] Therefore, in the distance measuring device 20 according to the second embodiment, a difference calculation is performed based on the measured value of the amount of light received by the previous pixel. As a result, in the second embodiment, the effect of short-range water scattering due to fog, etc., can be canceled by the difference calculation. Accordingly, the distance measuring device 20 according to the second embodiment can suppress deterioration of distance measuring performance even when short-range background noise increases due to reduced visibility caused by fog, etc.

[0099] In the second embodiment, the value used by the difference calculator 274 for difference calculation is not limited to the value of the previous pixel (i.e., the digital signal D(N-1)), but the value of the previous frame may be used. In this case, the noise value holding unit 273 calculates an average or median value for each time interval from time 0 to fixed time tA of the digital signal D acquired in the previous frame, instead of the digital signal D(N-1), and transmits it to the difference calculator 274. The difference calculator 274 then performs calculation processing between the digital signal D(N) transmitted from the ADC 271 and the time interval calculation values ​​transmitted from the noise value holding unit 273.

[0100] Furthermore, although this example describes the case where the timing of digital signal transmission between the ADC271 and the noise value holding unit273 is synchronized, it is not limited to this. It is sufficient that it is possible to perform difference calculations of digital signals D(N) and D(N-1), and the difference calculator 274 may have a buffer circuit that can temporarily hold 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 the waveform of the light reception result of the object to be measured based on a combination of data from a single point in the previous light reception result and a predetermined function. The details of the distance measuring device 20 according to the third embodiment will be described below, mainly focusing on the differences from the first and second embodiments.

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

[0103] The ADC271 converts the output signal (amount of light received) of the photodetector PXL, which is irradiated with 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 light received at a predetermined time. This predetermined time is set, for example, around time t0. The point data PD(N) is held in a buffer circuit (not shown in the figure). The noise value calculation unit 275 reads the 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 the data associated with the same time between the digital signal D(N) and the time-series noise value data. The difference calculator 274 then transmits the digital signal calculated by the difference calculation to the distance measuring circuit 272.

[0105] The distance measuring circuit 272 generates distance data based on the peak position of the digital signal calculated by the difference calculator 274, and transmits the generated distance data to the image processing device 15. Thus, in the third embodiment, similar to the second embodiment, a difference calculation is performed between the output of the ADC 271 and the distance measuring calculation by the distance measuring 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 measuring system 1 according to the third embodiment are the same as in the second embodiment.

[0106] <3-2> Processing method of light reception results Figure 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. Figure 23(A) shows the change in the amount of light received by the light sensor 26 corresponding to the emitted light LE(N-1). Figure 23(B) shows the case when a difference calculation is performed on the change in the amount of light received by the light sensor 26 corresponding to the emitted light LE(N). In this example, it is assumed that fog is present in the surrounding environment of the distance measuring system 1.

[0107] As shown in Figure 23(A), when the emitted light LE(N-1) is emitted at time t0, background noise affected by fog is detected immediately after emission. In this example, the reflected light LR is detected after time tA, and there is a risk of false detection, similar to 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 Figure 21(B), in the third embodiment, a difference calculation is performed using the calculation result of point data PD(N-1) with a predetermined function. Between times t0 and tA, large background noise is detected before the difference calculation, whereas after the difference calculation, the background noise can be suppressed. The range to which the difference calculation is applied may be from time t0 to time tA, or from time tB to time tA.

[0109] As described above, in the third embodiment, when the measuring device 27 measures distance associated with the emitted light LE, it uses noise value data for a predetermined period calculated based on the light reception result of the previous pixel (photodetector PXL) at time tB to correct the portion of the light reception result of the light sensor 26 that corresponds to the predetermined period, 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 the same as in the first embodiment.

[0110] <3-3> Effects of the Third Embodiment In the distance measuring device 20 according to the third embodiment, a difference calculation similar to that in the second embodiment is performed using a predetermined function and point data PD(N-1) from the light reception result of the previous pixel. As a result, in the third embodiment, the effect of short-range water scattering due to fog, etc., 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 short-range background noise increases due to reduced visibility caused by fog, etc.

[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)), but the value of the same pixel may be used. Alternatively, the average value over a predetermined period may be used instead of the point data PD(N-1). The noise value calculation unit 275 may also 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 uses a calculated value such as the average or median of multiple pixels acquired in the previous frame at a predetermined time, instead of the point data PD(N-1), to calculate time-series noise value data and transmits the calculation result to the difference calculator 274. The difference calculator 274 then performs calculation processing between the digital signal D(N) transmitted from the ADC 271 and the time-series calculated value transmitted from the noise value calculation unit 275.

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

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

[0114] TIA276 amplifies and outputs the output signal (amount of light received) of the photodetector PXL, which is illuminated by reflected light LR(N). The signal amplified by TIA276 is transmitted to ADC277 and comparator 279, respectively. ADC277 converts the signal amplified by TIA276 into a digital signal D(N) and outputs it. The digital signal D(N) is held in a buffer circuit (not shown in the figure).

[0115] The threshold determination unit 278 reads the digital signal D(N-1) of the previous reflected light LR(N) from the buffer circuit. The threshold determination unit 278 then 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 set variably according to time (subject distance). The comparator 279 determines whether or not reflected light LR has been received at each time interval based on the output of the TIA 276 and the detection threshold received from the threshold determination unit 278. The other configurations of the distance measuring device 20 according to the fourth embodiment are the same as those of the first embodiment.

[0116] <4-2> Processing method of light reception results Figure 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. Figure 25(A) shows the change in the amount of light received by the light sensor 26 corresponding to the emitted light LE(N-1). Figure 25(B) shows the case when a difference calculation is performed on the change in the amount of light received by the light sensor 26 corresponding to the emitted light LE(N). In this example, it is assumed that fog is present in the surrounding environment of the distance measuring system 1.

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

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

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

[0120] As described above, in the fourth embodiment, when measuring distance associated with the emitted light LE, the measuring device 27 calculates detection thresholds for determining the distance in multiple periods based on the light reception result of the previous pixel (photoreceiving element PXL), and measures the distance to the subject OB using the detection thresholds for each of the multiple periods. Other operations of the distance measuring device 20 according to the fourth embodiment are the same as in the first embodiment.

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

[0122] In this example, the threshold determination unit 278 has illustrated the case where it determines the detection threshold based on the digital signal D(N), but it is not limited to this. The threshold determination unit 278 may also determine the detection threshold based on the digital data of the digital signal D(N-1) at a predetermined time, 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)), but the value of the previous frame may be used. In this case, instead of the digital signal D(N-1), the threshold determination unit 278 calculates the detection threshold based on calculated values ​​such as the average or median of the digital signal D acquired in the previous frame for each time interval from time 0 to a fixed time tA.

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

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

[0125] <5-2-1> Distance measurement target of distance measurement system 1 Figure 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 Figure 26, landmark LMs are placed along the travel path of a transport device VE equipped with the distance measurement system 1. A landmark LM is a marker provided to indicate the stopping position of the transport device VE, for example, when the transport device VE is a railway vehicle. In this case, the transport device VE can control its stopping position by measuring its relative position to the landmark LM using the distance measurement system 1. Note that the landmark LM may be a utility pole or another transport device VE. The information processing device 10 may determine the placement of the landmark LMs based on information stored in the route information database 34.

[0126] <5-2-2> Landmark LM Configuration Figure 27 is a schematic diagram showing an example of the configuration of a landmark LM used in the distance measuring system 1 according to the fifth embodiment. As shown in Figure 27, the landmark LM may have two types of measurement areas RG. The first measurement area RG1 and the second measurement area RG2 are areas with different reflectances to the laser light (emitted light LE) emitted from the distance measuring device 20. In this embodiment, the case in which the reflectance to the emitted light LE is lower in the second measurement area RG2 than in the first measurement area RG1 will be described. The first measurement area RG1 and the second measurement area RG2 only need to be arranged and configured on the landmark LM so that they can be distinguished by the distance measuring system 1. The other configurations of the distance measuring system 1 according to the fifth embodiment are the same as in 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> Regarding fog detection Figure 28 is a schematic diagram showing an example of light reception results depending on the presence or absence of fog. In Figure 28, the time-series data of the light reception results 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 results of the distance measuring device 20 when there is fog is shown by a dashed line. Time t0 indicates the time of emission of the emitted light LE by the distance measuring device 20.

[0129] As shown in Figure 28, the change in the amount of light received when there is no fog shows a large peak at the time of detection of reflected light LR. On the other hand, the change in the amount of light received when there is fog shows a smaller peak than when there is no fog. Furthermore, when there is fog, light based on water scattering is detected near time t0, i.e., at short distances. Such background noise BGN can be a cause of mismeasurement. Also, as the fog becomes denser and the amount of reflected light LR decreases, the amount of reflected light LR received by the distance measuring device 20 decreases, degrading the measurable distance or making distance measurement difficult. The amount of light received can be calculated by the following equation (1).

[0130]

number

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

[0132] Equation (1) shows that if the subject distance, subject reflectivity, and LiDAR's ranging parameters are known, visibility can be measured by measuring the amount of light received at one point. According to equation (1), for example, the amount of light received when visibility is infinite and the subject distance is 400m is approximately the same as the amount of light received when visibility is 40m and the subject distance is 33m. In other words, in this example, even a LiDAR that can normally measure distances up to 400m can only measure distances up to 33m in fog. For this reason, it is desirable for LiDARs to have improved ranging performance even in foggy environments, i.e., environments with short visibility.

[0133] Figure 29 is a schematic diagram showing an example of a visibility measurement method. Examples of visibility calculation methods include the backscattering type shown in Figure 29(A) and the subject-based method shown in Figure 29(B). In the backscattering type, the visibility meter emits outgoing light, receives scattered light from the water component of the fog, and calculates the visibility of the surrounding environment based on the received scattered light. In the backscattering type, it is necessary that the portion of the received light used for visibility calculation does not include any objects that reflect the outgoing light. On the other hand, in the subject-based method, the visibility meter emits outgoing light, receives reflected light from an object, and calculates the visibility of the surrounding environment based on the received reflected light. In the subject-based method, if the fog is too thick, i.e., the visibility is too short, it may not be possible to detect the object, and visibility may not be calculated. In other words, when calculating visibility, different visibility calculation methods are appropriate depending on the length of visibility. Therefore, the distance measuring system 1 according to the fifth embodiment is configured to be able to use multiple types of visibility calculation methods in its visibility calculation operation.

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

[0135] The distance measuring system 1 starts the visibility calculation operation based on user operation or a predetermined schedule (start). In the visibility calculation operation, the distance measuring system 1 first checks whether the landmark LM has been measured (S21). If the landmark LM has been measured (S21: YES), the distance measuring system 1 calculates the visibility using the subject (S22). On the other hand, if the landmark LM has not been measured (S21: NO), the distance measuring system 1 calculates the visibility using the backscatter type (S23). Once processing S22 or S23 is completed, the distance measuring system 1 terminates the series of processes shown in Figure 30 (end).

[0136] Furthermore, the landmark LM does not necessarily have to be a stationary object placed near the path as shown in Figures 26 and 27. The distance measuring system 1 may use a moving subject in its vicinity as the subject used for calculating visibility. For example, if the transport equipment VE is an automobile, another automobile traveling ahead may be used as the subject used for calculating visibility instead of the landmark LM.

[0137] <5-2-3> Method for calculating visibility in the backscatter type Next, we will explain the method for calculating visibility using backscatter.

[0138] Figure 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. Figure 31 shows time-series data of the light reception results of the distance measuring device 20 in the case of fog. Time t0 indicates the time of emission of the emitted light LE by the distance measuring device 20. Times tA and tB indicate the period of the light reception results used for calculating visibility. "LUMI" indicates the brightness detected by the reflected light LR. "DIST" indicates the distance measurement result.

[0139] When calculating visibility using the backscatter method, in addition to the landmark LM, it is necessary that no other objects have been detected during the period from time tA to time tB. For example, if the distance measurement result DIST corresponding to a specific pixel PX is greater than or equal to the sum of the distance corresponding to time tB and a fixed value α, it is proven that no object was detected during the period from time tA to time tB. In this case, the distance measuring device 20 calculates the integral (average) or median value of the amount of light received during the period from time tA to time tB. The distance measuring device 20 can then estimate visibility by referring to a table that associates the calculated value with 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 in which the distance measuring device calculates visibility based on the light reception result has been described, but visibility may also be calculated by the information processing device 10.

[0140] <5-2-4> Method for calculating visibility when using a subject Next, we will explain the method for calculating the visibility of the subject. Assuming that the same LiDAR (distance measuring device 20) is used to measure the distance of the same subject at multiple distances, the following equation (2) can be derived from equation (1).

[0141]

number

[0142] In equation (2), Y represents the amount of light received, similar to equation (1). In equation (2), X represents the distance to the subject, similar to equation (1). In equation (2), A represents a variable, similar to equation (1). In equation (2), B represents visibility, similar to equation (1). According to equation (2), similar to equation (1), visibility can be measured by measuring the amount of light received at one point, provided that the distance to the subject, the reflectivity of the subject, and the LiDAR's ranging parameters are known. Transforming equation (2) using the natural logarithm yields the following equation (3).

[0143]

number

[0144] Thus, equation (3) is log(Y*X 2 ) becomes a linear equation in X. Therefore, by measuring the distance of the subject at multiple distances, the least squares method calculation can be performed. This calculation is robust to changes in the subject, the LiDAR's distance measurement parameters, and the transmittance of the output window, and is therefore superior to calculating visibility based on distance measurement data at a single point. The distance measurement system 1 installed on the transport equipment VE can easily obtain multiple distance measurement results for the same subject with relative velocity, and can calculate visibility in the surrounding environment. In this specification, "relative velocity" corresponds to the difference between the velocity of the transport equipment VE and the velocity of the subject. In the fifth embodiment, an example was given in which visibility is calculated by moving the transport equipment VE to multiple distances relative to the subject and performing distance measurements at multiple distances to the same subject by the LiDAR mounted on the transport equipment VE. Not limited to this, the distance measurement system 1 according to the fifth embodiment can measure the distance of the same subject at multiple distances over time as the transport equipment VE and the subject do not have the same velocity, i.e., a relative velocity occurs between the transport equipment VE and the subject. Therefore, in the fifth embodiment, the visibility calculation operation is not limited to the case where the transport equipment VE is moving, but multiple distance measurements may be achieved by the movement of the subject.

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

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

[0147] (Method of using the landmark LM) Figure 34 is a schematic diagram showing an example of the relationship between the position of the landmark LM and the number of pixels. Figure 34 illustrates the position of the landmark LM arranged in the angular range scanned by the distance measurement device 20. As shown in Figure 34, the landmark LM1 located at a distance of 30 m from the distance measurement device 20 is detected, for example, with 30 pixels PX. On the other hand, the landmark LM2 located at a distance of 100 m from the distance measurement device 20 is detected, for example, with 10 pixels PX.

[0148] Thus, when the landmark LM (subject) is far from the rangefinder 20, the number of pixels corresponding to the landmark LM in the image decreases, making it difficult to detect the landmark LM. When detecting distant landmark LMs, it is preferable to design the landmark LM to be large. Also, if the landmark LM is extremely close to the rangefinder, it may not be within the field of view, or the amount of light received may become too large, making distance measurement difficult.

[0149] In the distance measuring 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 for measuring the landmark LM is predetermined according to the size of the landmark LM. Furthermore, from the viewpoint of ease of data collection, it is preferable to set the range for measuring the distance as narrow as possible.

[0150] The first condition shown in Figure 34 allows for the detection of both landmark LM1, located at 30m, and landmark LM2, located at 100m. However, in the first condition, the size of the landmark LM needs to be increased in order to detect the distant landmark LM. On the other hand, the second condition shown in Figure 34 is configured to measure the distance of the landmark LM within a narrower range than the first condition, including 30m. Thus, by changing the range for measuring the distance of the landmark LM from the first condition to the second condition, it may be permissible to design the landmark LM to be smaller.

[0151] Figure 35 is a schematic diagram showing an example of the relationship between the amount of light received and the distance when measuring the distance of the measurement area RG1 of the landmark LM under four different visibility conditions. Figure 36 is a schematic diagram showing an example of the relationship between the amount of light received and the distance when measuring the distance of the measurement area RG2 of the landmark LM under four different visibility conditions. Figures 35 and 36 show the relationship between the amount of light received and the measurable distance when the visibility is 40m, 100m, 300m, and 1000m, respectively. In Figures 35 and 36, the range where the amount of light received is 1 to 10 corresponds to the range of light received that can be used for distance measurement, and the visibility measurement range is assumed to be 40 to 1000m. It is also assumed that the reflectance of the measurement area RG1 to the emitted light LE is 10, and the reflectance of the measurement area RG2 is 1.

[0152] As shown in Figure 35, when distance measurement is performed to calculate visibility only within the measurement area RG1, for example, visibility from 40m to 1000m can be calculated by measuring distances within a range of 24m to 229m. On the other hand, under these conditions, the wide distance range requires that the size of the landmark LM be designed to be large.

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

[0154] Therefore, in the distance measuring system 1 according to the fifth embodiment, distance measurement data from both measurement areas RG1 and RG2 of the landmark LM is acquired, and the more preferable distance measurement data is used to calculate the visibility. For example, if both measurement area RG1 (reflectance = 10) and measurement area RG2 (reflectance = 1) can be used, the distance measuring device 20 can calculate visibility from 40m to 1000m in a distance range of 24m to 106m. As a result, in this example, the size of the landmark LM, that is, the area of ​​the portion of the landmark LM in which measurement areas RG1 and RG2 are located, can be designed to be smaller than when measuring distances in a distance range of 24m to 229m.

[0155] As described above, the distance measuring system 1 according to the fifth embodiment can acquire a first distance measurement result measured based on reflected light from a first measurement area RG1 of the same subject, and a second distance measurement 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 and second distance measurement results.

[0156] <5-3> Effects of the Fifth Embodiment In value engineering (VE) for transportation equipment such as railway vehicles, the ability to detect rain and fog is required. Backscatter-type visibility calculations require that the visibility meter is fixed in place and that no objects are present in the measurement area. However, conventional visibility meters do not incorporate the concept of time. Therefore, conventional visibility meters cannot guarantee that no objects are present in the measurement area. Furthermore, visibility calculations using transmittance require a certain distance, resulting in excessively large visibility meters.

[0157] Therefore, the distance measuring 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 the subject. The distance measuring system 1 calculates visibility by using both backscattering and subject-based methods. For example, since LiDAR measures distance using the concept of time, it can guarantee that no objects exist within a predetermined distance (short distance). Accordingly, the distance measuring system 1 can calculate visibility using the backscattering method after guaranteeing that there are no subjects.

[0158] Furthermore, the distance measuring system 1 calculates visibility using the least squares method with multiple distance measurement results based on the subject. This allows the distance measuring system 1 to calculate visibility with higher accuracy than when measuring distance at a single point. Since the transport equipment VE equipped with the distance measuring system 1 is a moving object, it is easy to secure a distance measuring range for calculating visibility using the subject. Moreover, the travel route of a railway vehicle is suitable for placing landmarks LM that can be used for visibility calculation. Since landmarks LM can be shared for other purposes, installation costs can also be kept down.

[0159] Furthermore, since the calculation of visibility using a subject in the fifth embodiment is not dependent on reflectivity, it can also be applied to unknown objects. When the subject is a known subject (e.g., a landmark LM), the distance measuring system 1 can also measure the amount of reflectivity of the subject, and thus can detect the subject's deterioration over time. In other words, by acquiring multiple distances, the distance measuring system 1 can reduce the influence of the subject's deterioration over time on the calculation of visibility. For example, the distance measuring system 1 can also be used to detect anomalies in landmark LMs.

[0160] As described above, the distance measuring system 1 according to the fifth embodiment can realize a LiDAR with a function to calculate visibility. The calculated visibility is referenced, 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 the deterioration of distance measuring performance according to visibility.

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

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

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

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

[0165] Figure 38 is a table showing an example of measurement results in the fifth embodiment. Figures 38(A) and (B) correspond to measurement results under conditions where the amount of received light differs by a factor of 10, when the visibility calculation operation described in the fifth embodiment is applied.

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

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

[0168] <6> others The above 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 any of the distance measurement parameters of the second to fourth embodiments.

[0169] In the first embodiment, an example was given of a case where the distance measurement parameters are changed according to visibility, but the invention is not limited thereto. The distance measurement system 1 may control the distance measurement parameters according to the amount of reflectivity of a specific subject 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 amount of reflectivity (amount of light received) at a specific distance of a specific subject is associated with the distance measurement parameters. The information processing device 10 can then measure the reflectivity of a specific subject based on the distance measurement operation and change (control) the distance measurement parameters of the distance measurement device 20 by referring to the table using the measured reflectivity. Note that there may be multiple specific subjects. There may be multiple specific distances for specific subjects. Specific subjects may be identified based on the route information database 34, or based on information acquired by the information collection device 11. In this example, visibility may or may not be calculated.

[0170] If it is possible to realize the operations described in the above embodiments, some functions of the information processing device 10 may be implemented in 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 implemented by the distance measuring device 20. Some functions of the distance measuring control device 21 may be implemented in the optical sensor 26 or the measuring device 27. This allows the distance measuring device 20 to perform fine operations in a timely manner. The classification of the configurations described in each embodiment may be other classifications if it is possible to realize the operations described in each embodiment. The setting change operation described in the first embodiment and the visibility calculation operation described in the fifth embodiment may be implemented by an embedded computer having a CPU, memory, bus, and input / output circuitry (I / O).

[0171] The CPU included in the distance measuring system 1 may be any other circuit. For example, an MPU (Micro Processing Unit) may be used instead of a CPU. Each of the processes described in each embodiment may be implemented by dedicated hardware. In each embodiment, there may be a mixture of processes performed by software and processes performed by hardware, or only one or the other. The distance measuring control device 21 and the CPU may be called a “control circuit” or “processor”. The measuring device 27 may be called a “measuring 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, an example was given of a case where a multi-channel raster scan is performed by the distance measuring device 20, 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," or "OPA method (Optical Phased Array)." In other words, regardless of whether a mechanical method or an OPA method is used as the scanning method, the distance measuring device 20 only needs to be able to adjust the distance measuring direction (FOV position) by, for example, adjusting the emission timing of the pulsed laser.

[0173] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Explanation of symbols]

[0174] 1... Distance measuring 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... Distance measuring device, 21... Distance measuring control device, 22... Laser driver, 23... Laser diode, 24... Mirror control device, 25... Optical system, 26... Optical sensor, 27, 27a, 27b, 27c... Measurement device, 31... Speed ​​sensor, 32... GNSS device, 33... Camera, 34... Route information data Base, 251...Rotating mirror, 252,253,254...Optical elements, 272...Distance measuring circuit, 273...Noise value holding unit, 274...Difference calculator, 275...Noise value calculation unit, 276...Transimpedance amplifier, 278...Threshold determination unit, 279...Comparator, 289...Threshold determination unit, LM...Landmark, PG...Pixel group, PX...Pixel, PXL...Photodetector, RG1,RG2...Measurement area, S1~S6...Reflective surface, SA...Scan area, SRG...Scan result group

Claims

1. A light source configured to emit a first laser beam, A light sensor configured to detect a second laser beam corresponding to the first laser beam reflected by an external object, A measurement circuit configured to measure the distance to the subject based on the timing at which the light source emits the first laser beam and the timing at which the light sensor detects the second laser beam, The system includes a control circuit configured to measure the amount of reflectivity of the subject based on the distance measurement result, and to change the distance measurement parameters according to the information using the measured amount of reflectivity, The control circuit is further configured to acquire multiple distance measurement results for the same subject having a relative velocity, calculate the visibility in the surrounding environment using the least squares method based on a linear equation of the distance (X) from the multiple distance measurement results and the logarithm of the product of the amount of light received (Y) and the square of the distance (X) (log(Y*X^2)), and change the distance measurement parameters according to the information including the calculated visibility. Ranging device.

2. The control circuit is configured to calculate the visibility based on the measured amount of reflectance, The distance measuring device according to claim 1.

3. The aforementioned information is a table relating the amount of reflection of the subject to the distance measurement parameters. The control circuit modifies the distance measurement parameters by referring to the information based on the measured amount of reflection. The distance measuring device according to claim 1.

4. The control circuit, in accordance with the information, reduces the number of times the first laser beam is emitted per frame in the distance measurement and increases the energy of the first laser beam. The distance measuring device according to claim 1.

5. The control circuit reduces the frame rate in the distance measurement and increases the energy of the first laser beam according to the information. The distance measuring device according to claim 1.

6. The aforementioned light sensor includes a plurality of light-receiving elements configured to output a current based on the intensity of the irradiated light, The control circuit, in accordance with the information, adds the output signals of two or more sets of light-receiving elements from the plurality of light-receiving elements and outputs them to the measurement circuit. The distance measuring device according to claim 1 or claim 4.

7. The measurement circuit further includes an analog-to-digital converter, The output signals of the two or more photodetectors, which have been added together, are converted from analog to digital by the analog-to-digital converter and output to the measurement circuit. The distance measuring device according to claim 6.

8. The control circuit, in accordance with the information, increases the number of times the first laser beam is emitted per unit time in the distance measurement and decreases the energy of the first laser beam. The distance measuring device according to claim 1.

9. The optical sensor includes a plurality of light-receiving elements configured to output a current based on the intensity of the second laser light, The measurement circuit includes a plurality of analog-to-digital converters, each of which converts the output signals of the plurality of light-receiving elements into digital signals. The control circuit, in accordance with the information, causes the measurement circuit to measure the distance based on a signal obtained by adding the output signals of two or more pairs of analog-to-digital converters from the plurality of analog-to-digital converters. The distance measuring device according to claim 1.

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

11. The control circuit, in accordance with the information, changes the number of integrated values ​​of the reception results of the second laser light used for distance measurement by the measurement circuit in the distance measurement. The distance measuring device according to claim 1.

12. The measurement circuit corrects the light reception result of the light sensor from the emission time of the first laser beam to the first time, based on the light reception result of the previous pixel or previous frame, and measures the distance to the subject based on the corrected light reception result. The distance measuring device according to claim 1.

13. The measurement circuit, when measuring distance associated with the first laser beam, corrects the portion of the light sensor's light reception result corresponding to the first period using noise value data for the first period calculated based on the light reception result at a second time point of the same pixel, the previous pixel, or the previous frame, and measures the distance to the subject based on the corrected light reception result. The distance measuring device according to claim 1.

14. The measurement circuit, when measuring distance associated with the first laser beam, calculates detection thresholds for determining distance in multiple periods based on the light reception result of the previous pixel or previous frame, and measures the distance to the subject using the detection thresholds for each of the multiple periods. The distance measuring device according to claim 1.

15. The control circuit obtains a first distance measurement result obtained based on reflected light from a first region of the same subject and a second distance measurement result obtained based on reflected light from a second region of the same subject that is different from the first region, and calculates the visibility using both the first distance measurement result and the second distance measurement result. The distance measuring device according to claim 1.

16. If the control circuit determines that the second laser light could not be received by the light sensor, it calculates the visibility based on the light detection results of the portion where it is guaranteed that no object exists. The absence of the aforementioned subject is guaranteed by the fact that the distance measurement result corresponding to a specific pixel is greater than or equal to the sum of the distance corresponding to the time and a fixed value. The distance measuring device according to claim 1.

17. When the control circuit determines that the second laser beam has been received by the optical sensor, it calculates the visibility in the surrounding environment based on the results of multiple distance measurements taken for the same object having a relative velocity. The distance measuring device according to claim 16.

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