Distance measuring device

Abstract

The present invention relates to a distance measuring device. The distance measuring device (10, 10a) comprises: a light emitting unit (40), a light receiving unit (60), a calculation unit (200) for calculating the distance to a reflecting object (OBJ), and a control unit (270). The calculation unit comprises a light receiving intensity determination unit (210), a peak detection unit (240), a distance calculation unit (250), and a distance determination unit (510). The control unit controls at least one of the intensity of pulsed light, the light receiving sensitivity in the light receiving unit, and the position of a region of interest, so that a first light receiving intensity is determined at least once as each light receiving intensity in a plurality of flight times, and a second light receiving intensity with a higher SN ratio is determined at least once as each light receiving intensity in a plurality of flight times. The distance determination unit determines the distance of the measurement object using a first distance based on the first light receiving intensity and a second distance based on the second light receiving intensity.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on Japanese application No. 2020-53118 filed on March 24, 2020 and Japanese application No. 2021-43155 filed on March 17, 2021, and the contents thereof are cited herein. Technical Field

[0003] The present disclosure relates to a distance measuring device. Background Art

[0004] A distance measuring device is known (see Patent Document 1 below), which emits pulsed light such as laser from a light emitting unit, detects reflected light from an object by a light receiving unit, and detects the presence of an object or the distance to the object by measuring the flight time (TOF: Time Of Flight) of light from irradiation to light reception. In the distance measuring device, pulsed light is emitted in various directions (azimuths) and the flight time of the reflected light is measured to measure the distance to the object, and a distance image consisting of the position and distance of the object is generated. Such a distance image is used, for example, to detect the position and speed of obstacles during automatic driving of a vehicle.

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-176721

[0006] Generally, in a distance measuring device, the emission of pulsed light and the reception of reflected light are performed via a window having the transmittance of these lights. A part of the pulsed light is also reflected in the window, and the reflected light is received in the light receiving section. Therefore, after the pulsed light is emitted, when the reflected light from the object located near the distance measuring device and the reflected light reflected by the window (so-called clutter) are received, the flight time of these lights is close, and the measurement accuracy of the distance to the object may be reduced. Such a problem may also be caused by other factors other than clutter. Specifically, in the case where the object has a part with a high reflectivity, the intensity of the reflected light from the part is very large, so there is a situation where a reflected light with an intensity greater than the actual reflection is measured at a position near the part, that is, the so-called flare. In such a case, the distance to the object corresponding to the position of the flare may be erroneously measured. Due to such a situation, a technology is desired that can suppress the reduction in measurement accuracy caused by reflected light (noise) different from the assumed reflected light, such as clutter and flare. Summary of the invention

[0007] As one aspect of the present disclosure, a distance measuring device is provided. The distance measuring device comprises: a light emitting unit that emits pulse light and emits the pulse light at multiple emission times for each emission direction; a light receiving unit that receives reflected light of the pulse light; a calculation unit that calculates a measurement object distance using a flight time of the reflected light received by the light receiving unit, wherein the measurement object distance is a distance to a reflecting object that reflects the pulse light and outputs the reflected light; and a control unit that controls at least one of the intensity of the pulse light emitted from the light emitting unit, the light receiving sensitivity of the reflected light in the light receiving unit, and the position of a focus area for determining the light receiving intensity in the light receiving unit, wherein the calculation unit comprises: a light receiving intensity determination unit that determines each light receiving intensity in a plurality of flight times; a peak detection unit that detects the flight time of a peak in each light receiving intensity in the plurality of flight times; a distance calculation unit that calculates the distance based on the detected flight time of the peak; and The distance determination unit determines the measurement object distance using the distance calculated by the distance calculation unit, and the control unit controls at least one of the intensity of the pulse light emitted from the light emitting unit, the light receiving sensitivity of the reflected light in the light receiving unit, and the position of the interest area, so that at least once in the multiple emission times, the light receiving intensity determination unit determines a first light receiving intensity as each light receiving intensity in the multiple flight times, and at least once in the multiple emission times, the light receiving intensity determination unit determines a second light receiving intensity with a higher SN ratio than the first light receiving intensity as each light receiving intensity in the multiple flight times. The distance determination unit determines the measurement object distance using the first distance and the second distance, wherein the first distance is the distance calculated based on the first light receiving intensity, and the second distance is the distance calculated based on the second light receiving intensity.

[0008] According to the distance measuring device of this mode, at least once among the multiple emission times, the light intensity determination unit determines the first light intensity as the light intensity for each of the multiple flight times, and at least once among the multiple emission times, the light intensity determination unit determines the second light intensity with a higher SN ratio than the first light intensity as the light intensity for each of the multiple flight times, and the measurement target distance is determined using the first distance calculated based on the first light intensity and the second distance calculated based on the second light intensity, so that the reduction in measurement accuracy caused by reflected light (noise) different from the assumed reflected light such as clutter and flare can be suppressed. Generally, clutter is detected as light with a smaller intensity than the reflected light from the reflector (object), and the reflected light existing in the area blocked by the flare can be detected as light with a smaller intensity than the reflected light from the high reflectivity portion under the condition that the light intensity (second light intensity) with a lower SN ratio is determined. Therefore, a distance that does not include noise such as clutter and flare can be generated as the first distance, and the reduction in accuracy of the measurement target distance determined using the first distance and the second distance can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above-mentioned objects and other objects, features and advantages of the present disclosure will become more apparent through the following detailed description with reference to the accompanying drawings. In the accompanying drawings:

[0010] Figure 1 is a schematic structural diagram of a distance measuring device as one embodiment of the present disclosure,

[0011] Figure 2 is an explanatory diagram schematically showing the structure of a light receiving array.

[0012] Figure 3 is a circuit diagram schematically showing the configuration of a SPAD circuit.

[0013] Figure 4 is a block diagram showing the functional configuration of the distance measuring device according to the first embodiment.

[0014] Figure 5 is a flowchart showing the sequence of the distance measurement process of the first embodiment.

[0015] Figure 6 is an explanatory diagram showing an example of changes in the histogram in the first embodiment,

[0016] Figure 7 is an explanatory diagram showing an example of changes in the histogram in the first embodiment,

[0017] Figure 8 is a flowchart showing the procedure of the range image generation process according to the first embodiment.

[0018] Fig. 9 is an explanatory diagram schematically showing how a comprehensive distance image is generated.

[0019] Fig.10 is a flowchart showing the procedure of the distance measurement process of the second embodiment.

[0020] Fig.11 is an explanatory diagram showing an example of changes in a histogram in the second embodiment.

[0021] Fig.12 is an explanatory diagram showing an example of changes in a histogram in the second embodiment.

[0022] Fig.13 is a block diagram showing the functional configuration of a distance measuring device according to a second embodiment.

[0023] Fig.14 is a flowchart showing the procedure of the distance measurement process of the third embodiment.

[0024] Fig.15 is a flowchart showing the procedure of the range image generation process according to the fourth embodiment.

[0025] Fig.16 is an explanatory diagram showing an example of an image in which flare occurs.

[0026] Fig.17 is an explanatory diagram showing an example of changes in a histogram in the fourth embodiment.

[0027] Fig.18 is an explanatory diagram showing an example of changes in a histogram in the fourth embodiment.

[0028] Fig.19 is an explanatory diagram showing a first distance image in the fourth embodiment,

[0029] Fig. 20 is an explanatory diagram schematically showing the structure of a light receiving array in the fifth embodiment,

[0030] Fig.21 is a flowchart showing the sequence of distance measurement processing according to the fifth embodiment.

[0031] Fig. 22 is a flowchart showing the sequence of distance measurement processing according to the sixth embodiment.

[0032] Fig.23 is an explanatory diagram showing an example of changes in the histogram of the high reflection direction in the sixth embodiment,

[0033] Fig.24 is an explanatory diagram schematically showing how a comprehensive distance image is generated in the seventh embodiment.

[0034] Fig.25 is a flowchart showing the detailed procedure of step S225 in the seventh embodiment.

[0035] Fig.26 is a schematic structural diagram of a distance measuring device in an eighth embodiment,

[0036] Fig. 27 is a block diagram showing an example of a connection structure between a light emitting element and a driving circuit in another embodiment.

[0037] Fig.28 is a block diagram showing an example of a connection structure between a light emitting element and a driving circuit in another embodiment.

[0038] Fig.29 is a block diagram showing an example of a connection structure between a light emitting element and a driving circuit in another embodiment.

[0039] Fig.30 is a block diagram showing an example of a connection structure between a light emitting element and a driving circuit in another embodiment.

[0040] Fig.31 It is an explanatory diagram schematically showing the structure of a light receiving array in another embodiment. DETAILED DESCRIPTION

[0041] A. First Implementation Method:

[0042] A1.Device composition:

[0043] Figure 1 The distance measuring device 10 shown includes: an optical system 30 that emits pulse light for distance measurement and receives reflected light from an external object, a calculation and determination unit 20 that processes a signal obtained from the optical system 30, and an ECU 500. The external object is also referred to as a "reflection object". The optical system 30 includes: a light emitting unit 40 that emits laser light as pulse light, a scanning unit 50 that scans the laser light within a predetermined field of view 80, and a light receiving unit 60 for receiving incident light including reflected light and interference light from an external object. The distance measuring device 10 is housed in a housing 90 having a window 92 on the front. The window 92 transmits most of the pulse light emitted from the light emitting unit 40 and reflects a portion.

[0044] The distance measuring device 10 is, for example, a vehicle-mounted LiDAR (Laser Imaging Detection and Ranging) mounted on a vehicle such as a car. When the vehicle is traveling on a horizontal road, the lateral direction of the field of view 80 coincides with the horizontal direction X, and the longitudinal direction coincides with the vertical direction Y.

[0045] The light emitting unit 40 includes: a semiconductor laser element (hereinafter, also simply referred to as a laser element) 41 that emits laser light including pulse light, a circuit substrate 43 provided with a driving circuit of the laser element 41, and a collimating lens 45 that makes the laser light emitted from the laser element 41 parallel light. The laser element 41 is a laser diode that can oscillate so-called short-pulse laser light. In the present embodiment, the laser element 41 forms a rectangular laser light emitting area by arranging a plurality of laser diodes in a vertical direction. The structure is such that the intensity of the laser light output by the laser element 41 can be adjusted according to the voltage supplied to the laser element 41.

[0046] The scanning unit 50 is composed of a so-called one-dimensional scanner. The scanning unit 50 is composed of a reflector 54, a rotary solenoid 58, and a rotating unit 56. The reflector 54 reflects the laser light that is parallelized by the collimating lens 45. The rotary solenoid 58 receives a control signal from the calculation and determination unit 20 and repeatedly rotates forward and reverse within a predetermined angle range. The rotating unit 56 is driven by the rotary solenoid 58 to repeatedly rotate forward and reverse with the vertical direction as the axial rotation axis, so that the reflector 54 scans in one direction along the horizontal direction. The laser light emitted from the laser element 41 via the collimating lens 45 is reflected by the reflector 54 and scanned in the horizontal direction by the rotation of the reflector 54. Figure 1 The field of view 80 shown is equivalent to the full scanning range of the laser. Since the light intensity is obtained at each pixel position within the field of view 80, the distribution of the light intensity within the field of view 80 constitutes an image. Therefore, the field of view 80 can also be referred to as an "image area". In the present embodiment, each position within the scanning range, in other words, each pixel position within the field of view 80 is irradiated with four pulses of light. If the pulse light is irradiated four times, the laser is scanned, and the irradiation position of the laser is moved to an adjacent pixel position within the field of view 80. Then, the position is irradiated with four pulses of light. In addition, the scanning unit 50 may be omitted, and pulse light may be emitted from the light emitting unit 40 throughout the entire field of view 80, and the reflected light throughout the entire field of view 80 may be received by the light receiving unit 60.

[0047] If there is an external object (reflecting object) such as a person or a car, the laser light output from the light emitting unit 40 is diffusely reflected on its surface, and a part of it returns to the reflector 54 of the scanning unit 50 as reflected light. The reflected light is reflected by the reflector 54, and is incident on the light receiving lens 61 of the light receiving unit 60 together with the disturbance light as incident light, and is focused by the light receiving lens 61 and incident on the light receiving array 65. In addition, not limited to external objects, the laser light output from the distance measuring device 10 is also diffusely reflected by an object inside the distance measuring device 10, such as the window 92, and a part of its reflected light is incident on the light receiving array 65.

[0048] like Figure 2As shown, the light receiving array 65 is composed of a plurality of pixels 66 arranged in two dimensions. One pixel 66 is composed of a plurality of SPAD (Single Photon Avalanche Diode) circuits 68 arranged in H numbers in the horizontal direction and V numbers in the vertical direction. H and V are integers greater than 1, respectively. In the present embodiment, H=V=5, and it is composed of five SPAD circuits 68 in the horizontal direction and five in the vertical direction, respectively. However, the pixel 66 can be composed of any number of SPAD circuits 68, or it can be composed of one SPAD circuit 68. The light receiving result of one pixel 66 is the light receiving intensity at a pixel position within the field of view 80.

[0049] like Figure 3 As shown, the SPAD circuit 68 connects the avalanche diode Da and the quenching resistor Rq in series between the power supply Vcc and the ground line, and inputs the voltage at the connection point to the inversion element INV, which is one of the logic operation elements, and converts it into a digital signal with the voltage level inverted. The output signal Sout of the inversion element INV is output to the outside as it is. In this embodiment, the quenching resistor Rq is configured as a FET, and if the selection signal SC is activated, its on-state resistance acts as the quenching resistor Rq. If the selection signal SC is inactive, the quenching resistor Rq becomes a high impedance state, so even if light is incident on the avalanche diode Da, no quenching current flows, and as a result, the SPAD circuit 68 does not operate. The selection signal SC is output to the 5×5 SPAD circuits 68 in the pixel 66, which is used to specify whether to read out or read out the signal from each pixel 66. In this embodiment, the avalanche diode Da is operated in the Geiger mode, but the avalanche diode Da can also be used in the linear mode, and its output is directly regarded as an analog signal. In addition, a PIN photodiode can also be used instead of the avalanche diode Da.

[0050] If light is not incident on the SPAD circuit 68, the avalanche diode Da remains in a non-conducting state. Therefore, the input side of the inversion element INV remains in a state of being pulled up via the quenching resistor Rq, that is, a high level H. Therefore, the output of the inversion element INV remains at a low level L. If light is incident on each SPAD circuit 68 from the outside, the avalanche diode Da becomes energized due to the incident light (photon). As a result, a large current flows through the quenching resistor Rq, the input side of the inversion element INV temporarily becomes a low level L, and the output of the inversion element INV is reversed to a high level H. As a result of a large current flowing through the quenching resistor Rq, the voltage applied to the avalanche diode Da is reduced, so the power supply to the avalanche diode Da stops, and the avalanche diode Da returns to a non-conducting state. As a result, the output signal of the inversion element INV is also reversed and returned to a low level L. As a result, if light (photon) is incident on each SPAD circuit 68, the inversion element INV outputs a pulse signal that becomes a high level in a very short time. Therefore, if the selection signal SC is set to high level H in coordination with the timing of each SPAD circuit 68 receiving light, the output signal of the inversion element INV, that is, the output signal Sout from each SPAD circuit 68 becomes a digital signal reflecting the state of the avalanche diode Da. And, the output signal Sout is equivalent to a pulse signal generated by receiving incident light including reflected light and disturbance light that is reflected and returned by an external object or window 92 existing in the scanning range.

[0051] like Figure 4 As shown, the calculation and determination unit 20 includes: a calculation unit 200, a memory 260, a first distance image memory 261, a second distance image memory 262, and a control unit 270. The calculation unit 200 uses the flight time of the reflected light received by the light receiving unit 60 to calculate the distance to the reflecting object that reflects the pulse light and outputs the reflected light. The outline of the distance calculation method is as follows. Figure 4 As shown, the pulse light P1 emitted from the light emitting unit 40 is reflected by the reflector OBJ, which is an external object. In other words, the reflector OBJ outputs the reflected light P2 of the pulse light P1. In addition, the pulse light P1 is also reflected on the inner surface of the window 92, and the reflected light P3 is output. As a result, the reflected lights P2 and P3 reach the light receiving unit 60. At this time, the time from the emission of the pulse light P1 to the reception of the reflected lights P2 and P3 is determined as the flight time Tf of the light. The calculation unit 200 uses the flight time Tf to calculate the distance from the distance measuring device 10 (the light emitting unit 40 and the light receiving unit 60) to the reflector OJB.

[0052] The calculation unit 200 includes a received light intensity determination unit 210 , a peak detection unit 240 , and a distance calculation unit 250 .

[0053] The light intensity determination unit 210 determines the light intensity of each light receiving unit 60 in a plurality of flight times. In the light receiving unit 60, in addition to the reflected light of the pulse light emitted from the light emitting unit 40, various interference lights such as sunlight, reflected light of sunlight on external objects, and light from street lamps are also received. The timing of receiving these interference lights is various and is detected as different flight times. Therefore, the light intensity is determined at each flight time of the plurality of flight times. The light intensity determination unit 210 includes an adding unit 220 and a histogram generating unit 230.

[0054] The adding unit 220 adds the outputs of the SPAD circuits 68 included in the pixels 66 constituting the light receiving array 65. If an incident light pulse is incident on one pixel 66, the SPAD circuit 68 included in the pixel 66 operates. The SPAD circuit 68 can detect the photon even if only one photon is incident. However, in the SPAD circuit 68, the detection of the limited light output from the reflector OBJ is necessarily random. Therefore, the adding unit 220 is configured to more reliably detect the reflected light from the reflector OBJ in each pixel 66 by adding the output signal Sout from the SPAD circuit 68 that can only randomly detect the incident light to the amount of all the SPAD circuits 68 included in each pixel 66.

[0055] The histogram generation unit 230 generates a histogram of the light intensity by acquiring the addition result of the adder 220 in time series, and stores it in the memory 260, and outputs it to the peak detection unit 240. In addition, as described later, the histogram generation unit 230 generates a new histogram by accumulating the newly generated histogram with the histogram already stored in the memory 260. The histogram generated by the histogram generation unit 230 can be said to be a graph representing the light intensity at each flight time of multiple flight times. The light intensity is the total number of light-receiving SPAD circuits 68 within a pixel 66. Multiple flight times are set at constant time intervals. As described above, the light emitting unit 40 emits pulse light four times in succession. If the histogram generation unit 230 generates a histogram representing the received intensity within a specified time period including the flight time of the first pulse, the memory 260 is cleared by the control unit 270. After that, when a histogram showing the reception intensity within a predetermined time period including the flight time of the second to fourth pulsed light is generated and accumulated, the memory 260 is cleared by the control unit 270. Details of the accumulation and storage of the histogram and the clearing of the memory 260 will be described later.

[0056] The peak detection unit 240 detects the flight time of the peak of the histogram generated by the histogram generation unit 230. Specifically, the peak detection unit 240 analyzes the light intensity of the histogram input from the histogram generation unit 230 to detect the peak of the light intensity, and determines the flight time of the detected peak. The flight time of the detected peak is equivalent to the flight time Tf of the light reflected by the reflector OBJ, the window 92, etc.

[0057] The distance calculation unit 250 calculates the distance to the reflecting object OBJ based on the flight time Tf of the light determined by the peak detection unit 240 .

[0058] The memory 260 is used for the generation and accumulation of the histogram of the light intensity described later. The distance to the reflection object OBJ in each pixel calculated in step S135 of the distance measurement process described later is stored in the first distance image memory 261. The distance to the reflection object OBJ in each pixel calculated in step S170 of the distance measurement process described later is stored in the second distance image memory 262.

[0059] The control unit 270 controls the entire distance measuring device 10. For example, the control unit 270 controls the intensity of the pulse light by controlling the voltage supplied to the laser element 41 of the light emitting unit 40. In addition, the control unit 270 clears the memory 260, for example.

[0060] ECU500 is provided with an MPU (Micro Processor Unit) and a memory. By executing a control program pre-stored in the memory, the MPU functions as a distance determination unit 510 and a distance image generation unit 520. The distance image generation unit 520 determines the distance to the reflector OBJ in each pixel (hereinafter referred to as "measurement object distance") using the distance calculated by the distance calculation unit 250. The distance image generation unit 520 generates an image (hereinafter referred to as "distance image") representing the measurement object distance in each pixel using the measurement object distance determined by the distance determination unit 510. The position of each pixel means the position (orientation) of the reflector observed from the distance measuring device 10. Therefore, the distance image can be said to be an image representing the position of the reflector OBJ and the distance to the reflector OBJ. In the distance image generation process described later, the distance image generation unit 520 combines two distance images to generate one distance image (comprehensive distance image). For example, in a structure where the distance measuring device 10 is mounted on an autonomous driving vehicle, the comprehensive distance image generated in this way is used for detecting obstacles existing around the vehicle and driving control to avoid the detected obstacles.

[0061] As described above, the reflected light (clutter) from the window 92 is incident on the light receiving unit 60 in the same manner as the reflected light from the reflector OBJ. Therefore, generally speaking, due to the clutter, the measurement of the distance to the reflector OBJ present at a position close to the distance measuring device 10 may cause an error. However, in the distance measuring device 10, by performing the distance measurement process and the distance image generation process described later, the influence of clutter is suppressed, and the distance to the reflector OBJ present at a position close to the distance measuring device 10 (measurement target distance) is calculated with good accuracy, so that a comprehensive distance image with high accuracy can be generated.

[0062] A2. Ranging Processing:

[0063] Figure 5 The distance measurement process shown means a process for calculating the distance from the distance measuring device 10 to the reflecting object OBJ (measurement target distance). If the electric eye of the distance measuring device 10 is turned on, the distance measurement process is executed. And this distance measurement process is executed for each pixel position.

[0064] The control unit 270 clears the memory 260 (step S105). The histogram generation unit 230 accumulates the histogram (step S110). When step S110 is executed for the first time after the memory 260 is cleared, the histogram is not generated because the pulse light from the light emitting unit 40 and the reflected light from the light receiving unit 60 have not yet been emitted. Therefore, in this case, the histogram is not accumulated in the memory 260.

[0065] The control unit 270 determines the cumulative number n (step S115). In the present embodiment, when the histogram obtained by accumulating the emission of the pulse light and the reception of the reflected light is accumulated, the cumulative number n means the cumulative number (the number of times). When step S115 is executed for the first time after executing step S105, the cumulative number n is 1. As described above, pulse light is emitted four times at each pixel position at a predetermined time interval. Then, as described later, the histogram is accumulated each time (step S110).

[0066] When it is determined that the cumulative number of times is the first time, the control unit 270 controls the light emitting unit 40 to emit a pulse light with a relatively small intensity (hereinafter referred to as "first pulse light"), and then causes the light receiving unit 60 to receive light for a predetermined time including the assumed flight time of the pulse light (step S120). The intensity of the first pulse light is determined in advance by experiments and is set to a light intensity such that the SPAD circuits 68 constituting each pixel 66 are not operated in a predetermined amount due to the reflected light (clutter) generated by the reflection of the first pulse light by the window 92, and the SPAD circuits 68 constituting the pixel 66 are operated in a predetermined amount due to the reflected light from the reflection of the external object, and the intensity is such that the SPAD circuits 68 constituting the pixel 66 are operated in a predetermined amount. Since such a first pulse light is set to a smaller intensity at which noise cannot be detected in the light receiving unit 60, only the reflected light from the reflector within the threshold distance from the ranging device 10 is detected. On the other hand, the reflected light from the reflector located at a distance longer than the threshold distance from the ranging device 10 cannot be detected.

[0067] If the reflected light is received in the light receiving unit 60, the adding unit 220 adds the outputs of the SPAD circuits 68 included in each pixel 66, and the histogram generating unit 230 generates a histogram of each pixel and stores it in the memory 260, and outputs it to the peak detecting unit 240 (step S125). In addition, in the present embodiment, storing the histogram corresponding to the first pulse light in the memory 260 is referred to as the accumulation of the first histogram. In the present embodiment, the first histogram (the light receiving intensity of each flight time) is equivalent to the first light receiving intensity in the present disclosure.

[0068] The peak detection unit 240 detects the peak in the input histogram and determines its flight time (step S130). The distance calculation unit 250 calculates the distance based on the flight time of the peak determined in step S130 (step S135). The calculated distance is stored in the first distance image memory 261 in correspondence with each pixel position. After step S135 is completed, the process returns to step S105. Therefore, in this case, the data of the first histogram stored in the memory 260 is eliminated by step S105.

[0069] When the distance measurement process is started and step S110 is executed for the second time, the histogram accumulation is not performed because the data of the first histogram is deleted. In addition, in step S115 executed later, it is determined that the cumulative number is 2. In this case, the control unit 270 controls the light emitting unit 40 to emit a pulse light with a relatively large intensity (hereinafter referred to as the "second pulse light"), and then causes the light receiving unit 60 to receive light within a specified time including the assumed flight time of the pulse light (step S140). The intensity of the second pulse light is obtained in advance through experiments and is set to an intensity that is greater than the specified light receiving intensity due to the reflected light from the reflector (external object) present within a specified distance from the distance measuring device 10, so that the SPAD circuit 68 constituting each pixel 66 operates at a specified amount or more. The above-mentioned "prescribed distance" is greater than the "threshold distance" previously described for the first pulse light. The second pulse light is also reflected by any of the external object and the window 92 present within the specified distance, and light is detected in the light receiving unit 60.

[0070] After step S140 is completed, the adding section 220 adds the outputs of the SPAD circuits 68 included in each pixel 66, and the histogram generating section 230 generates a histogram for each pixel (step S145). After step S145 is completed, the process returns to step S110. Therefore, in this case, in step S110, the histogram generated in step S145 is accumulated in the memory 260 and stored. In step S115 executed thereafter, it is determined that the cumulative number of times is 3. In this case, the above-mentioned steps S140 and S145 are executed, and the process returns to step S110. In this case, in step S110, the histogram corresponding to the third pulse light is accumulated in the memory 260 and stored. In other words, the histogram corresponding to the second pulse light is accumulated with the histogram corresponding to the third pulse light.

[0071] In the next executed step S115, it is determined that the cumulative number is 4. In this case, the control unit 270 controls the light emitting unit 40 to emit the second pulse light, and then causes the light receiving unit 60 to receive light within a specified time including the assumed flight time of the pulse light (step S150). The adding unit 220 generates a histogram of each pixel by the output of the SPAD circuit 68 included in each pixel 66, and the histogram generating unit 230 accumulates the histogram corresponding to the fourth pulse light into the memory 260 and stores it (step S160). In this case, the histogram corresponding to the fourth pulse light is accumulated in the histogram corresponding to the second and third pulse lights. The histogram obtained by accumulating the second to fourth histograms (the light receiving intensity at each flight time) is equivalent to the second light receiving intensity in the present disclosure.

[0072] The peak detection unit 240 detects the peak in the histogram stored in the memory 260 and determines its flight time (step S165). The distance calculation unit 250 calculates the distance based on the flight time of the peak determined in step S165 (step S170). The calculated distance is stored in the second distance image memory 262 in correspondence with each pixel position. After step S170 is completed, the distance measurement process for the pixel position is completed. After that, the laser is scanned at the adjacent pixel position, and the distance measurement process is performed at other pixel positions.

[0073] use Figure 6 as well as Figure 7 An example of a histogram stored in the memory 260 as a result of the above-mentioned distance measurement process will be described. Figure 6 In FIG. 1 , an example of a histogram is shown when a reflector exists within a range within a threshold distance (hereinafter referred to as a “short distance range”). Figure 7 , an example of a histogram is shown when a reflective object exists in a range farther than a threshold distance (hereinafter referred to as a “long-distance range”).

[0074] At a certain pixel position, when there is a reflector different from the window 92, that is, an external object, in a close range, after the first pulse light emission and the reflected light reception are performed, as shown in FIG. Figure 6 As shown, in the first histogram H1, a peak appears at a flight time t2 that is shorter than the flight time ta. The flight time ta is the flight time corresponding to the above-mentioned threshold distance. This peak is based on the peak of the reflected light output from the reflector. On the other hand, the reflected light output from the window 92 may appear as a peak at a flight time t1 that is shorter than the flight time t2. However, as mentioned above, since the intensity of the first pulse light is an intensity that cannot detect clutter by the light receiving unit 60, no peak corresponding to clutter appears. Therefore, there are no other peaks near the flight time t2, so the flight time t2 can be detected with good accuracy. Specifically, the range of flight times where the light receiving intensity is greater than the first threshold intensity Ith1 is determined, and the flight time t2, which is the peak value of the median, is detected.

[0075] In this embodiment, after calculating the flight time of the peak corresponding to the first pulse light, the memory 260 is cleared, and the histogram is accumulated and stored in the memory 260 again. Then, in the emission of the second and subsequent pulse light, the second pulse light is emitted, so that Figure 6As shown, in the second histogram H2, in addition to the flight time t2, there is also a peak at the flight time t1 which corresponds to the flight time of the clutter. The flight time t1 is close to the flight time t2. Since the histograms H3 and H4 generated corresponding to the emission and reception of the third and fourth second pulse light are accumulated, the intensity of the received light at each flight time increases. By accumulating the histograms in this way, the ratio of reflected light to interference light, that is, the S / N ratio, is increased, and the peak of the reflected light from the reflector can be detected with good accuracy. Figure 6 In the example, the peak of the flight time t1 and the peak of the flight time t2 can be distinguished, in which case two peaks and two flight times t1 and t2 are detected. In addition, in the fourth histogram H4, a range larger than the second threshold intensity Ith2 is determined, from which the above-mentioned two peaks and flight times t1 and t2 are determined.

[0076] like Figure 7 As shown in FIG. 1 , at a certain pixel position, when an external object exists in a long distance range, when the first pulse light is emitted and its reflected wave is received, Figure 6 As in the example, the peak of the flight time t1 does not appear in the first histogram H1a. In addition, since the reflector exists in a long distance range, the reflected light of the first pulse light cannot be detected in the light receiving unit 60, and therefore, the peak corresponding to the reflector does not appear in the first histogram H1a. On the other hand, the peak of the flight time t1 and the peak of the flight time t3 appear in the second histogram H2a, the third histogram H3a, and the fourth histogram H4a. The peak of the flight time t3 corresponds to the reflected light output from the reflector. Moreover, the result of accumulating the second to fourth histograms H2a to H4a is that the light receiving intensities of the two peaks of the flight times t1 and t3 exceed the second threshold intensity Ith2, and the two peaks and the two flight times t1 and t3 are detected.

[0077] A3. Range image generation process:

[0078] Figure 8 The distance image generation process shown means a process for generating a distance image. If the above-mentioned distance measurement process is performed at all pixel positions in the field of view range 80, the distance determination unit 510 and the distance image generation unit 520 perform the distance image generation process.

[0079] The distance determination unit 510 obtains the first distance image data from the first distance image memory 261 (step S205). The first distance image refers to an image composed of distances calculated for each pixel based on the flight time of the peak value obtained from the histogram corresponding to the emission of the first pulse light. In other words, it refers to the distance data about each pixel stored in the first distance image memory 261. The distance determination unit 510 uses the first distance image data obtained in step S205 to cut out the short-distance area from the first distance image to obtain a first partial image (step S210). The short-distance area refers to an area within the above-mentioned threshold distance from the distance measuring device 10. This step S210 is equivalent to the process of determining the distance represented by the first distance image data as the distance of the measured object in the short-distance area. The distance image generation unit 520 performs the steps S215 and S220 described later in parallel with the above-mentioned steps S205 and S210.

[0080] The distance determination unit 510 obtains the second distance image data from the second distance image memory 262 (step S215). The second distance image refers to an image composed of distances calculated for each pixel based on the flight time of the peak obtained from the histogram of the result of accumulating the histogram corresponding to the emission of the second pulse light. In other words, it means the distance data about each pixel stored in the second distance image memory 262. The distance determination unit 510 uses the second distance image data obtained in step S215 to cut out the long-distance area from the second distance image to obtain a second partial image (step S220). The long-distance area means an area that is farther from the distance measuring device 10 than the above-mentioned threshold distance. This step S220 is equivalent to the process of determining the distance represented by the second distance image data as the distance of the measured object in the long-distance area.

[0081] After the above steps S210 and S220 are completed, the distance image generation unit 520 combines the first partial image obtained in step S210 with the second partial image obtained in step S220 to generate a comprehensive distance image (step S225), and the distance image generation process ends. Fig. 9 , the first and second range images and the integrated range image generated in the above-mentioned range image generation process are described in detail.

[0082] exist Fig. 9 In FIG. 1 , the uppermost row shows an image I1 showing an example of the positional relationship between two reflective objects OJBJ1 and OBJ2 and the window 92. Fig. 9 In FIG. 1 , the middle section shows the first distance image IL1 and the second distance image IL2. Fig. 9 In FIG. 1 , the bottom row shows the integrated distance image I10 . Fig. 9Each image shows a state of looking down in the vertical direction. In addition, the first partial image Ip1 is surrounded by a thick solid line in the first distance image IL1. Similarly, the second partial image Ip2 is surrounded by a thick solid line in the second distance image IL2. Fig. 9 The X-axis and the Y-axis are axes that are parallel to the horizontal direction and have the center of gravity of the distance measuring device 10 as the origin O.

[0083] like Fig. 9 As shown in the image I1, in the region R1 within the threshold distance La from the distance measuring device 10, there is a reflector OBJ1 as an external object in addition to the window 92. In addition, there is a reflector OBJ2 at a position farther from the distance measuring device 10 than the threshold distance La. In such a situation, Fig. 9 As shown in the middle left of FIG. 1 , in the first partial image Ip1 cut from the first distance image IL1 , only the distance data about the reflector OBJ1 existing in the region R1 exists, and no distance data about other objects such as the window 92 (clutter) exists. Fig. 9 As shown in the middle right of FIG. 1 , in the second partial image Ip2 cut from the second range image IL2, only the distance data about the reflector OBJ2 existing in the area outside the area R1 exists, and there is no distance data about other objects such as the reflector OBJ1 and the window 92. By integrating such two partial images Ip1 and Ip2, as shown in FIG. Fig. 9 As shown in the bottom row of FIG. 1 , in the integrated distance image I10 , only the distance data of the reflection objects OBJ1 and OBJ2 do not include the window 92 (clutter). Therefore, for example, it is possible to avoid an emergency avoidance action of the vehicle due to the presence of the window 92 (clutter).

[0084] According to the distance measuring device 10 of the first embodiment described above, at each pixel position, one of the four pulses of light emitted is set as the first pulse of light with a smaller intensity, so the first distance (first distance image) obtained in this case can exclude the distance to the window 92 obtained based on the reflected light (clutter) from the window 92. Therefore, the influence of clutter can be suppressed and the peak of the reflector located at a position close to the distance measuring device 10 can be detected with good accuracy, and the distance to the reflector (measurement object distance) can be measured with good accuracy. In addition, three of the four pulses of light emitted are set as the second pulse of light with a larger intensity. In this case, the peak value is detected by accumulating the obtained histogram, so the peak value can be determined in a state where the S / N ratio is increased. Therefore, the distance of each pixel of the second distance image (second distance) can be obtained with good accuracy.

[0085] In addition, a comprehensive distance image is generated by merging a first partial image of a reflector within a threshold distance from the ranging device and a second partial image of a reflector located at a distance longer than the threshold distance from the ranging device in the second distance image. Therefore, a distance image (comprehensive distance image) can be generated in which the positions and distances of the reflector within the threshold distance from the ranging device and the reflector located at a distance longer than the threshold distance are accurately determined, respectively.

[0086] In the histogram, the peak detection unit 240 identifies the range of flight time where the received light intensity is higher than the intensity thresholds Ith1 and Ith2 and detects the flight time of the peak of the received light intensity in the identified range, so that the peak flight time can be detected with high accuracy.

[0087] B. Second Implementation Method:

[0088] The device configuration of the distance measuring device 10 of the second embodiment is the same as that of the first embodiment, and therefore the same components are denoted by the same reference numerals and their detailed descriptions are omitted. Fig.10 The distance measurement process of the second embodiment shown is different from the distance measurement process of the first embodiment in that step S108 is additionally executed and step S112 is executed instead of step S115. The other procedures of the distance measurement process and the distance image generation process of the second embodiment are the same as those of the first embodiment, so the same reference numerals are attached to the same procedures and their detailed descriptions are omitted.

[0089] like Fig.10 As shown, after step S105 is completed, the control unit 270 determines whether the cumulative number is the first time (step S108). If it is determined to be the first time (step S108: Yes), the above-mentioned steps S120 to S135 are executed. Therefore, when the distance measurement process is started at a certain pixel position and step S108 is executed for the first time, it is determined that the cumulative number is the first time, and steps S120 to S135 are executed. After step S135 is completed, the process returns to step S108. Therefore, in this embodiment, step S105 is not executed in this case.

[0090] If it is determined that it is not the first time (step S108: No), the above-mentioned step S110 is executed, and the histogram is accumulated and stored in the memory 260. After step S110 is completed, the control unit 270 determines the cumulative number of times n (step S112). In this step S112, as the cumulative number of times, it is determined (determined) to be any one of 2, 3, and 4, which is different from step S115 of the first embodiment in that it is not determined to be 1.

[0091] When the cumulative number is the second or third time, the above steps S140 to S145 are executed. After step S145 is completed, the process returns to step S110 as in the first embodiment. Here, in the second embodiment, after the first histogram is stored in the memory 260, the memory 260 is not cleared. Therefore, the histogram corresponding to the second light emission is accumulated with the first histogram already stored in the memory 260 and stored in the memory 260.

[0092] When the cumulative number is the fourth time, the above steps S150 to S170 are executed. Here, the histogram obtained after step S160 is completed is a histogram obtained by accumulating all histograms from the first to fourth times. After step S170 is completed, the distance measurement process of the pixel position is completed.

[0093] like Fig.11 As shown, in the case where there is a reflector at a close range, as in the first embodiment, only the peak of the flight time t2 representing the reflector appears in the first histogram H1b, and the peak of the flight time t1 caused by clutter does not appear. Afterwards, the peak of the flight time t1 appears in the histogram H2b obtained by accumulating the second histogram. In the order of the histogram H3b obtained by accumulating the third histogram and the histogram H4b obtained by accumulating the fourth histogram, the light intensity increases at any flight time. Moreover, in the finally obtained histogram H4b, two peaks in the range above the threshold intensity Ith2 are detected.

[0094] like Fig.12 As shown, in the case where there is a reflector at a long distance, similar to the first embodiment, no peak appears in the first histogram H1c. Then, the peak of the flight time t1 and the peak of the flight time t3 appear in the histogram H2c obtained by accumulating the second histogram. In the order of the histogram H3c obtained by accumulating the third histogram and the histogram H4c obtained by accumulating the fourth histogram, the light intensity increases at any flight time. Moreover, in the finally obtained histogram H4c, two peaks in the range above the threshold intensity Ith2 are detected.

[0095] The distance measuring device 10 of the second embodiment described above has the same effect as the distance measuring device 10 of the first embodiment. In addition, the histograms from the first to the fourth times are accumulated, and the peak value is detected based on the obtained histogram, so the S / N ratio is further improved, and the detection accuracy of the peak value and the detection accuracy of the position of the reflector and the distance to the reflector can be further improved.

[0096] C. Third Implementation Method:

[0097] Fig.13The distance measuring device 10a of the third embodiment shown is different from the distance measuring device 10 of the first embodiment in that the calculation and determination unit 20 includes two memories 263 and 264 instead of the memory 260, and the other structures are the same. Therefore, the same reference numerals are attached to the same structures, and the detailed description thereof is omitted.

[0098] The memories 263 and 264 can be accessed from the control unit 270, the histogram generation unit 230, and the peak detection unit 240. The memory 263 only stores the light intensity within a specified time and the flight time recording the light intensity. The memory 264 does not accumulate and store the histogram generated by the histogram generation unit 230 each time. The memory 263 is equivalent to the first storage unit of the present disclosure. In addition, the memory 264 is equivalent to the second storage unit of the present disclosure.

[0099] Fig.14 The distance measurement process of the third embodiment shown in the figure is different from the embodiment shown in that step S110 is omitted, step S115a is executed instead of step S115, step S125a is executed instead of step S125, steps S130 and S135 are omitted, step S165a is executed instead of step S165, and step S170a is executed instead of step S170. Figure 5 The distance measurement process of the first embodiment shown is different. The other procedures of the distance measurement process of the third embodiment are the same as those of the first embodiment, so the same reference numerals are attached to the same procedures and their detailed descriptions are omitted.

[0100] After step S105 is completed, the control unit 270 determines the number of times the pulse light at the pixel position emits light (step S115a). When it is determined that the number of times the light is emitted is the first time, the control unit 270 executes the above-mentioned step S120 to emit and receive the first pulse light. After step S120 is completed, the histogram generation unit 230 stores the added light intensity in the memory 263 in sequence according to each flight time within the specified time. At this time, when the light intensity (the output addition number of the SPAD circuit 68) is larger, the information stored in the memory 263 is overwritten with the light intensity and the flight time at this time and stored. In other words, when the light intensity of a certain flight time is greater than the light intensity already stored in the memory 263, the flight time and its light intensity are overwritten and stored in the memory 263. After step S125a is completed, the process returns to step S115a.

[0101] In step S115a, when it is determined that the number of times of light emission is the second or third time, the above-mentioned steps S140 and S145 are executed as in the first embodiment. In step S145, the histograms generated for each time are stored in the memory 264 as they are. After step S145 is completed, the process returns to step S115a. At this time, unlike the first embodiment, the histograms are not accumulated.

[0102] If it is determined in step S115a that the number of light emission is the fourth time, steps S150 to S160 are executed as in the first embodiment. Here, in step S160 of the third embodiment, the second to fourth histograms independently stored in the memory 264 are accumulated.

[0103] The peak detection unit 240 detects the peak in the accumulated histogram obtained in step S160 to identify the flight time thereof, and reads the flight time stored in the memory 263 to identify the flight time of the peak (step S165a).

[0104] The distance calculation unit 250 calculates the distance to the reflector based on the flight time of the two peaks determined in step S165a (step S170a). In step S170a, the position and distance of the reflector determined by the emission of the first pulse light are determined, and the position and distance of the reflector determined by the emission of the second pulse light three times and the reception of its reflected light are determined. Then, they are stored as distance images in the first distance image memory 261 and the second distance image memory 262, respectively.

[0105] The distance measuring device 10a of the third embodiment described above has the same effect as the distance measuring device 10 of the first embodiment. In addition, when the first pulse light is emitted, when each light receiving intensity in a plurality of flight times is determined in sequence, the flight time corresponding to the greater light receiving intensity is updated and stored in the memory 263, and the flight time stored in the memory 263 is detected as the peak flight time, so that the storage area for detecting the peak flight time, that is, the storage area of ​​the memory 263 can be suppressed from being too large.

[0106] D. Fourth Implementation Method:

[0107] The device configuration of the distance measuring device 10 of the fourth embodiment is the same as that of the first embodiment, so the same figure marks are attached to the same components and their detailed descriptions are omitted. The distance measuring device 10 of the fourth embodiment is different from the distance measuring device 10 of the first embodiment in the detailed sequence of the distance image generation process. The distance measuring process of the fourth embodiment is the same as that of the first embodiment, so the same figure marks are attached to the same sequence and the detailed sequence descriptions are omitted. However, in this embodiment, in step S135, in addition to the calculated distance, the peak light intensity is also stored in the first distance image memory 261. In addition, in step S170, in addition to the calculated distance, the peak light intensity is also stored in the second distance image memory 262. The distance image (comprehensive distance image) obtained by the distance image generation process of the fourth embodiment is an image in which the influence of flare is suppressed. Use Fig.16 This flare will be described.

[0108] exist Fig.16 The image I2 shows that flares FL1 and FL2 represented by thick solid lines are respectively generated on the left and right sides of the lower rear part of the vehicle C1. These flares FL1 and FL2 are generated with the reflectors Rf1 and Rf2 having very high reflectivity as the center. Since the reflectivity of the reflectors Rf1 and Rf2 is very high, if the pulse light or sunlight emitted from the distance measuring device 10 is irradiated to the reflectors Rf1 and Rf2, reflected light with very high intensity is output. If such reflected light with very high intensity is received by the light receiving unit 60, light is also incident on the pixels 66 near the pixels 66 that receive the reflected light from the reflectors Rf1 and Rf2 in the light receiving unit 60, and the received light is counted. As a result, the distance to a location that would have been determined to be the correct distance if there were no flares, such as a location near the rear tire of the vehicle C1, may be calculated incorrectly. However, in the distance measuring device 10 of the fourth embodiment, the influence of flare is suppressed by executing the distance image generation process described later, and the distance to the reflecting object OBJ can be calculated with high accuracy.

[0109] In the fourth embodiment, the intensity of the first pulse light used in the distance measurement process is determined in advance by experiments and is set to an intensity that does not generate flare when the light receiving unit 60 receives the reflected light when an external object with a reflectivity greater than a specified value within a specified distance from the distance measuring device 10 reflects the first pulse light. Fig.16 When a vehicle C1 as shown in FIG. 1 is present in the visual range 80, a distance measurement is generated. Fig.17 as well as Fig.18 A histogram as shown.

[0110] exist Fig.17In FIG. 1 , a histogram obtained at the pixel position of an area containing an object having a very high reflectivity such as reflectors Rf1 and Rf2 (hereinafter referred to as a "high reflectivity area") is shown. When the first pulse light is emitted, reflected light is generated in the high reflectivity area, and reflected light is not generated in other areas. Therefore, in the first histogram H1d, a peak is generated at the flight time t4 corresponding to the high reflectivity area (the area where reflectors Rf1 and Rf2 exist). Moreover, the peak exceeds the first threshold intensity Ith1, so the peak is detected. Afterwards, similar to the first embodiment, a peak of the flight time t4 also appears in the second histogram H2d, and the light intensity increases at any flight time in the order of the histogram H3d obtained by accumulating the third histogram and the histogram H4d obtained by accumulating the fourth histogram. In the final histogram H4d, the peak of the flight time t4 is detected as the peak of the range above the second threshold intensity Ith2.

[0111] exist Fig.18 In FIG. 6 , there is shown a histogram obtained at the pixel position of the area including the vicinity of the reflectors Rf1 and Rf2 and the area where the flare occurs (hereinafter referred to as the "flare area"), in other words, the area blocked by the flare when the flare occurs. When the first pulse of light is emitted, since the reflectivity of the flare area itself is not high, the reflected light of the first pulse of light cannot be detected in the light receiving unit 60. Therefore, no peak is detected in the first histogram H1e. In contrast, when the second pulse of light is irradiated, the light intensity is very high due to the flare. Therefore, in the second histogram H2e, a peak representing the flare area, that is, a peak of the flight time t5, appears. Similarly, in either the histogram H3e obtained by accumulating the third histogram or the histogram H4e obtained by accumulating the fourth histogram, a peak of the flight time t5 appears.

[0112] like Fig.19 As shown, in the distance images shown by the distances calculated from these histograms, for the first distance image, an image I3 is generated in which the distances (reflectors) exist only in the two areas A1 and A2 corresponding to the two reflectors Rf1 and Rf2. In addition, for the second distance image, an image I3 is generated. Fig.16 A range image including two flares FL1 and FL2, such as the image I2 shown.

[0113] like Fig.15 As shown, the distance image generating unit 520 obtains the first distance image data (step S305). Step S305 and Figure 8The fourth embodiment is the same as step S205 shown in the figure, so the detailed description is omitted. However, in addition to the distance of each pixel position, the light intensity is also obtained as the first distance image data. The distance image generation unit 520 determines the area where the light intensity is above the threshold intensity in the first distance image obtained in step S305 (hereinafter referred to as the "high intensity area") (step S310). In addition, the high intensity area determined in step S310 is referred to as the first high intensity area. In addition, the threshold intensity used when determining the first high intensity area is also referred to as the first threshold intensity. After obtaining Fig.19 In the case of the first range image shown in FIG. 1 , two areas A1 and A2 are determined as first high-intensity areas. Fig.15 In order to facilitate understanding, one first high-intensity region A1 of the two determined first high-intensity regions A1 and A2 is shown. The distance image generation unit 520 performs steps S315 and S320 described later in parallel with steps S305 and S310.

[0114] The distance image generation unit 520 obtains the second distance data (step S315). Step S315 and Figure 8 The fourth embodiment is the same as step S215 shown in the figure, so the detailed description is omitted. However, in addition to the distance of each pixel position, the light intensity is also obtained as the second distance image data. The distance image generation unit 520 determines the high-intensity area in the second distance image obtained in step S315 (step S320). In addition, the high-intensity area determined in step S320 is referred to as the second high-intensity area. In addition, the threshold intensity used when determining the second high-intensity area is also referred to as the second threshold intensity. For example, when obtaining Fig.16 When an image such as the image I2 shown in the figure is used as the second range image, two areas corresponding to the two reflectors Rf1 and Rf2 and the two flares FL1 and FL2 are determined as the second high intensity areas. Fig.15 In FIG. 1 , in order to help understanding, a second high intensity region A10 corresponding to the reflector Rf1 and the flare FL1 is shown among two regions corresponding to the two reflectors Rf1 , Rf2 and the two flares FL1 , FL2 .

[0115] The distance image generation unit 520 uses the first high intensity region determined in step S310 and the second high intensity region determined in step S330 to determine a region of an object with a very high reflectivity (hereinafter referred to as a "strong reflector region") in the second distance image (step S325). Specifically, the region in the second high intensity region determined in step S320 at the same position as the first high intensity region determined in step S310 is determined as a strong reflector region. Fig.15In order to facilitate understanding, a strong reflector region Ar1 is shown. The strong reflector region Ar1 is a strong reflector region in the high-intensity region A10 that is determined to be at the same position as the high-intensity region A1.

[0116] In parallel with the above-mentioned step S325, the distance image generation unit 520 uses the first high intensity region determined in step S310 and the second high intensity region determined in step S320 to determine the region corresponding to the flare (hereinafter referred to as the "flare region") in the second distance image (step S330). Specifically, the other regions of the second high intensity region determined in step S320 except the first high intensity region determined in step S310 are determined as the flare region. Fig.15 In order to help understanding, the flare region Af1 is shown. The flare region Af1 is a flare region determined as a region other than the high-intensity region A1 in the high-intensity region A10.

[0117] The distance image generation unit 520 generates a comprehensive distance image by deleting the data of the flare region in the second distance image data (step S335). By deleting the data of the flare region, i.e., the distance of the pixel position of the flare region and the data of the light intensity, the data of the portion where the distance is calculated with low accuracy due to the influence of the flares FL1 and FL2 is deleted, so that the low-precision distance data can be suppressed from remaining in the distance image.

[0118] The distance measuring device 10 of the fourth embodiment described above has the same effect as the distance measuring device 10 of the first embodiment. In addition, the other regions except the region corresponding to the first high-intensity region in the second high-intensity region in the second range image are determined as flare regions, and the image except the flare region in the second range image is generated as the integrated range image, so it is possible to suppress the region (pixel) whose position and distance are determined with low accuracy due to flare from being included in the integrated range image.

[0119] E. Fifth Implementation Method:

[0120] The distance measuring device 10 of the fifth embodiment is configured such that the light receiving unit 60 includes a Fig. 20 The light receiving array 65a shown is different from the device configuration of the distance measuring device 10 of the first embodiment. The other configurations of the distance measuring device 10 of the fifth embodiment are the same as those of the distance measuring device 10 of the first embodiment, so the same components are denoted by the same reference numerals and their detailed descriptions are omitted.

[0121] like Fig. 20 As shown, the light receiving array 65a of the fifth embodiment is Figure 2Compared with the light receiving array 65 of the first embodiment shown in FIG. 1 , the number of pixels 66 in the lateral direction (horizontal direction) is larger. Fig. 20 The lower section shows an example of the light intensity at each lateral position (horizontal position) of the pixel 66 constituting the light receiving array 65a. In this embodiment, by controlling the angle of the reflector 54 of the scanning unit 50, the light intensity is set to be greater as the lateral position in the light receiving array 65a is closer to the center.

[0122] In the fifth embodiment, when generating a histogram, not all pixels 66 of the light receiving array 65a are taken as objects, but only a part of the pixel group is taken as an object for generating a histogram. In other words, in the fifth embodiment, the light intensity is determined only in a part of the area of ​​the light receiving unit 60. The area where the light intensity is determined in the light receiving unit 60 is called a "region of interest (ROI)". In the fifth embodiment, it is possible to set Fig. 20 The two regions (first region of interest ROI1 and second region of interest ROI2) shown are regions of interest. The first region of interest ROI1 is a region including a pixel column composed of a plurality of pixels 66 that are located at a position offset from the center of the lateral position of the light receiving array 65a to the end side and are adjacent in the longitudinal direction (vertical direction). On the other hand, the second region of interest ROI2 is a region including a pixel column composed of a plurality of pixels 66 that are located at the center of the lateral position of the light receiving array 65a and are adjacent in the longitudinal direction (vertical direction). The numbers of pixels 66 included in the two regions of interest ROI1 and ROI2 are equal to each other. However, due to the difference in the lateral position mentioned above, even if the reflected light of the same pulse light is received, the light intensity determined in the second region of interest ROI2 is greater than the light intensity determined in the first region of interest ROI1.

[0123] Fig.21 The distance measurement process of the fifth embodiment shown in the figure is different from the embodiment shown in that step S120b is executed instead of step S120, step S145b is executed instead of step S145, and step S150b is executed instead of step S150. Figure 5 The distance measurement process of the first embodiment shown is different. The other procedures of the distance measurement process of the fifth embodiment are the same as those of the first embodiment, so the same reference numerals are attached to the same procedures and their detailed descriptions are omitted.

[0124] In step S115, when it is determined that the cumulative number of times is the first time, the control unit 270 controls the light emitting unit 40 to emit the second pulse light, and then causes the light receiving unit 60 to receive light (step S120b). In step S120 of the first embodiment, the first pulse light is emitted, but in step S120b of the fifth embodiment, the second pulse light is emitted instead of the first pulse light, in other words, a pulse light with a larger intensity is emitted. In this way, in the fifth embodiment, the second pulse light is emitted regardless of the cumulative number of times. After step S120b is completed, if the reflected light is received in the light receiving unit 60, the adding unit 220 adds the output of the SPAD circuit 68 included in the first region of interest ROI1, and the histogram generating unit 230 generates a histogram of each pixel in the first region of interest ROI1 and stores it in the memory 260, and outputs it to the peak detecting unit 240 (step S125b). As described above, the light intensity determined in the first region of interest ROI1 is small. Therefore, similarly to the first embodiment, the peak corresponding to the reflected light (clutter) from the window 92 does not appear in the histogram generated in step S125 b .

[0125] In step S115, when it is determined that the cumulative number of times is the second or third time, the above-mentioned step S140 is executed, and then a histogram of the second region of interest ROI2 is generated (step S145b). As described above, the light intensity determined in the second region of interest ROI2 is large. Therefore, similar to the first embodiment, a peak value corresponding to the reflected light (clutter) of the window 92 appears in the histogram generated by step S145b.

[0126] In step S115, if it is determined that the cumulative number of times is the fourth time, the above-mentioned step S150 is executed, and then a histogram of the second region of interest ROI2 is generated (step S155b). In the histogram generated at this time, a peak value corresponding to the reflected light (clutter) of the window 92 appears, similarly to the histogram generated by the above-mentioned step S145b. After step S155b is completed, the above-mentioned step S160 is executed.

[0127] The distance measuring device 10 of the fifth embodiment described above has the same effect as the distance measuring device 10 of the first embodiment. In addition, by changing the area to be generated as the histogram according to the cumulative number of times, that is, the area to determine the light intensity, the intensity of the pulse light is not changed, so that the aging of the light emitting unit 40 caused by frequently changing the light emission intensity or the complicated processing in the control unit 270 is suppressed.

[0128] F. Sixth Implementation Method:

[0129] The device configuration of the distance measuring device 10 of the sixth embodiment is the same as that of the first embodiment, so the same reference numerals are attached to the same components and their detailed descriptions are omitted. Fig. 22 In the distance measurement process of the sixth embodiment shown in FIG. Figure 5 The same steps in the distance measurement process in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0130] like Fig. 22 As shown, in the distance measurement process of the sixth embodiment, first, the above-mentioned steps S120 to S135 are executed. That is, the emission of the first pulse light and the reception of its reflected light, histogram generation, peak detection, and distance calculation are performed. After the completion of step S135, the control unit 270 determines the high reflection direction. "High reflection direction" means the direction of an area of ​​a predetermined size containing an object with a reflectivity higher than a predetermined value (hereinafter referred to as "high reflectivity object"), and the direction based on the distance measuring device 10. It is estimated that the high reflectivity object exists at the position where the flight time Tf with a light intensity greater than a predetermined value is recorded in the histogram generated by step S125. Then, in step S136, the direction where the area of ​​a predetermined size containing the high reflectivity object exists is determined. Specifically, in the example of the fourth embodiment, the direction of the flares FL1 and FL2 generated as a result of the reflection of the pulse light in the reflectors Rf1 and Rf2 is determined. The size of the flare generated around the high reflectivity object is determined in advance by experiments, simulations, etc. in relation to the size of the high reflectivity object, and in step S135, the high reflectivity direction is determined as the direction of the area corresponding to the size of the flare. After step S136 is completed, the control unit 270 clears the memory 260 (step S137).

[0131] The control unit 270 determines whether the emission direction of the second pulse light to be emitted later is in the high reflection direction (step S138). As described above, the laser is scanned, and the control unit 270 determines whether the emission direction at the irradiation timing of the next pulse light (second pulse light) is in the high reflection direction determined in step S136.

[0132] When it is determined that the emission direction of the second pulse light does not conform to the high reflection direction (step S138: No), the histogram generation unit 230 generates a histogram of each pixel and stores it in the memory 260, and outputs it to the peak detection unit 240 (step S110d). The order of step S110d is the same as the order of step S110 described above. The control unit 270 determines whether the cumulative number of histograms has reached N (step S180d). "N" in step S180d is a positive integer, which is a number larger than "M" described later. In the present embodiment, N is "3". That is, in step S180d, it is determined whether the cumulative number of histograms has reached three times.

[0133] When it is determined that the cumulative number of histograms has not reached N(3) (step S180d: No), the emission of the second pulse light and the reception of its reflected light (step S140d) and the generation of the histogram (step S145d) are performed. The order of these steps S140d and S145d is the same as the order of the above-mentioned steps S140 and S145. After step S145d is completed, the process returns to step S110d.

[0134] On the other hand, when it is determined that the cumulative number of histograms has reached N(3) (step S180d: yes), the above steps S165 and S170 are executed and the processing ends. That is, the peak is detected based on the histogram obtained by adding up the cumulative number of times three times, and the distance is calculated. Therefore, when the above steps S110d, S180d, S140d, and S145d are executed, the second pulse light is irradiated three times in total, as in the first embodiment, and the distance is calculated based on the histogram accumulated by the light received corresponding to the three times of irradiation.

[0135] In the above-mentioned step S138, when it is determined that the emission direction of the second pulse light matches the high reflection direction (step S138: yes), the histogram generation unit 230 generates a histogram of each pixel and stores it in the memory 260, and outputs it to the peak detection unit 240 (step S110c). The order of this step S110c is the same as the order of the above-mentioned steps S110 and S110d. The control unit 270 determines whether the cumulative number of histograms has reached M (step S180c). "M" in step S180c is a positive integer, which is a number smaller than the above-mentioned "N". In the present embodiment, M is "2". That is, in step S180c, it is determined whether the cumulative number of histograms has reached twice.

[0136] When it is determined that the cumulative number of histograms has not reached N(2) (step S180c: No), the emission of the second pulse light and the reception of its reflected light (step S140c) and the generation of the histogram (step S145c) are performed. The order of these steps S140c and S145c is the same as the order of the above-mentioned steps S140 and S145. After step S145c is completed, the process returns to step S110c.

[0137] On the other hand, when it is determined that the cumulative number of histograms has reached N(2) (step S180c: Yes), the above steps S165 and S170 are executed. That is, the peak is detected based on the histogram obtained by adding up the cumulative number of times twice, and the distance is calculated. Therefore, when the above steps S110c, S180c, S140c, and S145c are executed, unlike the first embodiment, the second pulse light is irradiated twice in total, and the distance is calculated based on the histogram accumulated by the light received corresponding to the two irradiations.

[0138] use Fig.23 As described above, in the sixth embodiment, the reason why the number of integration of the histogram corresponding to the second pulse light is made different depending on whether or not the azimuth direction is highly reflective is described.

[0139] exist Fig.23 , the changes in the histogram are shown when the high reflection direction is irradiated with the first pulse light (first pulse light), the second and third pulse light (second pulse light), and the fourth pulse light (second pulse light).

[0140] As in the first embodiment, the light intensity increases in any flight time of the first histogram H1f, the second histogram H2f, and the third histogram H3f. Moreover, in the first to third histograms H1f to H3f, a peak of the flight time t6 appears. However, in the fourth histogram H4f, the light intensity increases excessively at the flight time near the flight time t6, and exceeds the upper limit UL of the measurable range of the light intensity in the light receiving unit 60. Therefore, there is a problem that the detection accuracy is reduced if the peak is detected based on the histogram H4f. However, in this embodiment, for the high reflection direction, the second pulse light is irradiated twice, that is, if the first pulse light is included, the pulse light is irradiated three times in total, and the peak is detected based on the cumulative result of the histogram corresponding to the second and third second pulse lights. Therefore, the peak is detected based on the histogram H3f where the light intensity is not saturated, so the reduction in the detection accuracy of the distance to the reflector can be suppressed.

[0141] According to the distance measuring device 10 of the sixth embodiment described above, the same effect as the distance measuring device 10 of the first embodiment is achieved. In addition, for the high reflection direction, the peak value is detected based on the histogram obtained by accumulating fewer times than other directions different from the high reflection direction, so the peak value can be detected based on the histogram of the state before the light intensity is saturated. Therefore, the reduction in the detection accuracy of the distance to the reflector can be suppressed. On the other hand, for other directions different from the high reflection direction, the peak value is detected based on the histogram obtained by accumulating more times than the high reflection direction, so the peak value can be detected based on the histogram of the state where the peak value is more obvious. In these cases, the reduction in the detection accuracy of the distance to the reflector can also be suppressed. In addition, the cumulative times M and N are not limited to 2 and 3, and can be any number that satisfies N>M. In addition, the sixth embodiment can also be applied to the second embodiment. That is, in the structure in which the light intensity of the reflected light of the first pulse light and the light intensity of the reflected light of the second pulse light are both accumulated, the cumulative times for the high reflection direction can also be reduced compared with other directions.

[0142] G. Seventh Implementation Method:

[0143] The device configuration of the distance measuring device 10 of the seventh embodiment is the same as that of the first embodiment, and therefore the same components are denoted by the same reference numerals and their detailed descriptions are omitted. Fig.24 The upper, middle, and lower sections of Fig. 9 In the first embodiment, the first partial image Ip1 and the second partial image Ip2 do not overlap with each other. In contrast, in the seventh embodiment, the first partial image Ip10 and the second partial image Ip20 overlap with each other. Fig.24 For reference, the dashed line is shown Fig. 9 In the seventh embodiment, each partial image includes information on the light intensity at each pixel position in addition to the distance.

[0144] like Fig.24 As shown in the middle left of FIG. 1 , in the seventh embodiment, the distance image of the area within the first threshold distance Lb from the distance measuring device 10 is cut out from the first distance image IL1 as the first partial image Ip10. Fig.24As shown in the middle right section of , the distance image of the area far away from the distance measuring device 10 and more than the second threshold distance Lc is cut from the second distance image IL2 as the second partial image Ip20. Then, the two partial images Ip10 and Ip20 are combined to generate a comprehensive distance image I30. Here, the above-mentioned first threshold distance Lb is longer than the threshold distance La in the first embodiment. On the other hand, the above-mentioned second threshold distance Lc is shorter than the threshold distance La. In other words, the first threshold distance Lb is longer than the second threshold distance Lc. As a result, the first partial image Ip10 and the second partial image Ip20 have an overlapping area (hereinafter referred to as the "overlapping area") MA.

[0145] like Fig.25 As shown, step S225 of the distance image generation process in the seventh embodiment includes two steps S226 and S227 in addition to combining the first partial image and the second partial image in the same manner as in the first embodiment. In step S226, for the overlap area MA, the distance image generation unit 520 calculates the light intensity of the corresponding area by weighted averaging the light intensity in the two partial images Ip10 and Ip20. Specifically, for each position (pixel) in the overlap area MA, the weight that the closer to the radial inner boundary B1 of the overlap area MA, the greater the influence of the light intensity of the first partial image Ip10, and the smaller the influence of the light intensity of the second partial image Ip20 is multiplied by the light intensity of each partial image, and the average value is calculated. In other words, the weight that the closer to the radial outer boundary B2 of the overlap area MA, the smaller the influence of the light intensity of the first partial image Ip10, and the larger the influence of the light intensity of the second partial image Ip20 is multiplied by the light intensity of each partial image, and the average value is calculated.

[0146] like Fig.25 As shown, in step S227 , the distance image generating unit 520 selectively uses and sets the light receiving intensity in the first partial image Ip10 or the second partial image Ip20 for each position (pixel) in the area other than the overlapping area MA.

[0147] According to the distance measuring device 10 of the seventh embodiment described above, the same effects as those of the distance measuring device 10 of the first embodiment are achieved. In addition, since the first threshold distance Lb is longer than the second threshold distance Lc, the first partial image Ip10 and the second partial image Ip20 can be overlapped to generate an overlap area MA. Therefore, it is possible to suppress the generation of an area that does not belong to any of the first partial image Ip10 and the second partial image Ip20, and it is possible to suppress the generation of a position (pixel) where the distance and the light intensity cannot be calculated. In addition, for each position (pixel) in the overlap area MA, a weight is multiplied by the light intensity of each partial image, and the closer to the radial inner boundary B1 of the overlap area MA, the greater the influence of the light intensity of the first partial image Ip10 and the smaller the influence of the light intensity of the second partial image Ip20. For example, in a situation where a single object gradually moves away from the overlap area MA, it is possible to suppress the distance and light intensity of the object from changing excessively, and it is possible to suppress the misrecognition of the object and the reduction in the detection accuracy of the distance to the object.

[0148] H. Eighth Implementation Method:

[0149] Fig.26 The distance measuring device 10b of the eighth embodiment shown in FIG. 1 includes a first light emitting unit 40 and a second light emitting unit 40a which correspond to the light emitting unit 40 of the first embodiment, and a light emitting unit 40b which is different from the light emitting unit 40b of the first embodiment. Figure 1 The distance measuring device 10 of the eighth embodiment is different from the distance measuring device 10 of the first embodiment shown. The other structures in the distance measuring device 10b of the eighth embodiment are the same as the distance measuring device 10 of the first embodiment, so the same reference numerals are added to the same components and their detailed descriptions are omitted. The structure of the first light emitting unit 40 is the same as the light emitting unit 40 of the first embodiment, so the same reference numerals are added and their detailed descriptions are omitted.

[0150] The second light emitting unit 40a irradiates the entire scanning range of the laser beam, that is, the field of view 80, once (surface irradiation). In this embodiment, the second light emitting unit 40a includes a VCEL (Vertical Cavity Surface Emitting LASER) and an optical system for diffusing the laser beam output from the VCEL.

[0151] The light-emitting unit 40b has an action mode in which pulse light is emitted from the first light-emitting unit 40 and scans in the same manner as in the first embodiment (hereinafter referred to as the "first irradiation mode"), and an action mode in which pulse light is emitted from the second light-emitting unit 40a to irradiate the entire field of view 80 at one time (hereinafter referred to as the "second irradiation mode") as action modes.

[0152] The control unit 270 irradiates the first pulse light in the second irradiation mode and irradiates the second pulse light in the first irradiation mode. Figure 5 In step S120 shown, the first pulse light is irradiated from the second light emitting unit 40 a , and in steps S140 and S150 , the second pulse light is irradiated from the first light emitting unit 40 .

[0153] The distance measuring device 10 according to the eighth embodiment described above has the same effect as the distance measuring device 10 of the first embodiment. In addition, since the second light emitting unit 40a irradiates the field of view 80 once (surface irradiation) with the first pulse light of relatively low intensity, the output light amount from the VCEL can be suppressed, which can be beneficial to power saving. In addition, the area 80a that the first light emitting unit 40 can irradiate once in the first irradiation mode is equivalent to the "first irradiation area" in the present disclosure. In addition, the area that the second light emitting unit 40a can irradiate once in the second irradiation mode, that is, the field of view 80, is equivalent to the "second irradiation area" in the present disclosure. The above-mentioned "relatively low intensity" is not the light emission intensity in the laser element 41, but means that the intensity of light per unit area on the light receiving surface is relatively low. Similarly, "relatively high intensity" means that the intensity of light per unit area on the light receiving surface is relatively high.

[0154] I. Other embodiments:

[0155] I1. Other implementations 1:

[0156] In the first to fourth embodiments, two types of pulsed light, a first pulsed light with a relatively small intensity and a second pulsed light with a relatively large intensity, are emitted, but the present disclosure is not limited to this. As in the fifth embodiment, the first pulsed light may be omitted and only four second pulsed lights may be emitted. However, in the above-described configuration, the light receiving sensitivity of the light receiving unit 60 may be reduced during a specified period of emitting the first pulsed light and receiving its reflected light, and the light receiving sensitivity of the light receiving unit 60 may be increased during a period of emitting the second to fourth pulsed light and receiving its reflected light, which is different from the fifth embodiment. The light receiving sensitivity of the light receiving unit 60 can be achieved, for example, by adjusting the voltage supplied to the avalanche diode Da. Specifically, the light receiving sensitivity can be increased by increasing the voltage of the power supply Vcc, and the light receiving sensitivity can be reduced by decreasing the voltage of the power supply Vcc. During the period corresponding to the emission of the first pulsed light, the light receiving sensitivity of the light receiving unit 60 is adjusted to a light receiving sensitivity to a degree that does not perceive clutter. In addition, during the period corresponding to the emission of the second to fourth pulsed light, the adjustment is made so that when the second pulsed light is emitted, the SPAD circuit 68 constituting each pixel 66 operates at a predetermined amount or more due to the reflected light from the reflector (external object) present within a predetermined distance from the distance measuring device 10, and the sensitivity becomes a predetermined light receiving intensity or more. Through such control, a histogram consisting of light receiving intensities with a relatively small S / N ratio at each flight time is determined by the emission of the first pulsed light, and a histogram consisting of light receiving intensities with a relatively large S / N ratio at each flight time is determined by the emission of the second to fourth pulsed light, so that the same effect as that of each embodiment can be achieved. In the above-mentioned configuration, the histogram determined by the emission of the first pulsed light is equivalent to the first light receiving intensity in the present disclosure. In addition, the histogram determined by the emission of the second to fourth pulsed light is equivalent to the second light receiving intensity in the present disclosure. In addition, the emission of the first and second pulsed light and the sensitivity adjustment of the light receiving unit 60 can also be performed together.

[0157] As can be understood from such other embodiment 1 and each embodiment, the following structure can also be applied to the ranging device of the present disclosure, that is, controlling at least one of the intensity of the pulse light emitted from the light emitting unit 40, the light receiving sensitivity of the reflected light in the light receiving unit 60, and the position of the area of ​​interest in the light receiving unit 60, so that a light receiving intensity (first light receiving intensity) with a relatively small S / N ratio is determined as each light receiving intensity in a plurality of flight times corresponding to the emission of the first pulse light, and a light receiving intensity (second light receiving intensity) with a higher SN ratio than the first light receiving intensity is determined as each light receiving intensity in a plurality of flight times corresponding to the emission of the second to fourth pulse light.

[0158] I2. Other implementations 2:

[0159] In the first to third embodiments, the first pulse light is emitted for the first time, and the second pulse light is emitted for the second to fourth times, but the present disclosure is not limited to this. The first pulse light may be emitted only for the fourth time, and the second pulse light may be emitted for the first to third times. In addition, for example, the second pulse light may be emitted for the first, third, and fourth times, and the first pulse light may be emitted for the second time. Furthermore, the second pulse light may be emitted once, or any number of times more than three times. In addition, the first pulse light may be emitted multiple times. In the above configuration, the histograms obtained by emitting multiple first pulse lights may be accumulated to find the peak value (first distance image).

[0160] Similarly, in the above-mentioned other embodiment 1, the light receiving sensitivity may be increased during the period of emitting pulse light for the first to third times and receiving its reflected light, and the light receiving sensitivity may be reduced during the period of emitting pulse light for the fourth time and receiving its reflected light. In addition, the light receiving sensitivity may be increased during the period of emitting pulse light for the first, third, and fourth times and receiving its reflected light, and the light receiving sensitivity may be reduced during the period of emitting pulse light for the second time and receiving its reflected light. In addition, the number of times the light receiving sensitivity is increased may be once. In addition, the number of times the light receiving sensitivity is reduced may be multiple times.

[0161] As can be understood from such other embodiment 2 and each embodiment, the following structure can also be applied to the ranging device of the present disclosure, namely, controlling at least one of the intensity of the pulse light emitted from the light emitting unit 40 and the light receiving sensitivity of the reflected light in the light receiving unit 60, so that a light receiving intensity (first light receiving intensity) with a relatively small S / N ratio is determined as each of the light receiving intensities in the multiple flight times corresponding to at least one of the multiple emission times of the pulse light, and a light receiving intensity (second light receiving intensity) with a higher S / N ratio than the first light receiving intensity is determined as each of the light receiving intensities in the multiple flight times corresponding to at least one of the multiple emission times of the pulse light.

[0162] I3. Other implementation methods 3:

[0163] The configuration of the distance measuring device 10, 10a in each embodiment is only an example, and various changes can be made. For example, the distance image generating unit 520 is provided by an ECU500 different from the calculation and determination unit 20, but it can also be configured to be provided by the calculation and determination unit 20 instead of the ECU500. In addition, for example, in the fourth embodiment, in the configuration in which the distance measuring device 10 does not have a window, for example, in the configuration in which the shell only forms an opening to accommodate the calculation and determination unit 20, the optical system 30, etc., the prescribed effect can also be achieved. In addition, for example, although the distance measuring device 10, 10a is a vehicle-mounted LiDAR, it can also be used instead of a vehicle and mounted on any mobile body such as a ship or an airplane. Alternatively, it can also be used in a fixed setting for safety purposes.

[0164] I4. Other implementation methods 4:

[0165] In each embodiment, the distance image generation process may be omitted. In the above configuration, the measurement object distance of each pixel can also be determined by performing the distance measurement process. In addition, in the above configuration, in addition to determining the measurement object distance for all pixels in the field of view 80 as objects, it is also possible to determine only the measurement object distance for a single pixel. In the above configuration, as in each embodiment, any one of the first distance based on the first light receiving intensity and the second distance based on the second light receiving distance is determined as the measurement object distance of the pixel.

[0166] I5. Other implementations 5:

[0167] The control unit 270, the operation unit 200, the distance image generation unit 520 and their methods described in the present disclosure may also be implemented by a dedicated computer provided by a processor and a memory programmed to perform one or more functions embodied by a computer program. Alternatively, the control unit 270, the operation unit 200, the distance image generation unit 520 and their methods described in the present disclosure may also be implemented by a dedicated computer provided by a processor composed of one or more dedicated hardware logic circuits. Alternatively, the control unit 270, the operation unit 200, the distance image generation unit 520 and their methods described in the present disclosure may also be implemented by one or more dedicated computers composed of a combination of a processor and a memory programmed to perform one or more functions and a processor composed of one or more hardware logic circuits. In addition, the computer program may also be stored as an instruction executed by a computer in a non-transient tangible recording medium that can be read by a computer.

[0168] I6. Other implementations 6:

[0169] The configuration of the laser element and its driving circuit in each of the above-mentioned embodiments is merely an example and various modifications are possible. Fig. 27 In the example of the light emitting unit 40c shown, four laser elements 41a, 41b, 41c, and 41d and a drive circuit 46 are configured. The four laser elements 41a to 41d irradiate pulse light to different ranges within the field of view 80. Specifically, the laser element 41a irradiates pulse light to the range of the uppermost segment after the field of view 80 is divided into four equal parts in the vertical direction. The laser element 41b irradiates pulse light to the range of the second segment from the top. The laser element 41c irradiates pulse light to the range of the third segment from the top. The laser element 41d irradiates pulse light to the range of the fourth segment from the top. The drive circuit 46 is connected to the four laser elements 41a to 41d, and outputs the same signal to the four laser elements 41a to 41d at the same time. As a result, Fig. 27In the example shown in FIG. 1 , four laser elements 41 a to 41 d simultaneously irradiate pulse light in the same direction in the horizontal direction.

[0170] In addition, for example Fig.28 The light emitting unit 40d shown in the figure includes a weak light emitting unit 42a and a normal light emitting unit 42b. The weak light emitting unit 42a includes a laser element 41e and a driving element 46e thereof. The normal light emitting unit 42b includes a laser element 41f and a driving element 46f thereof. The weak light emitting unit 42a causes the first pulse light to scan the visual field 80 and illuminate the entire range. The normal light emitting unit 42b causes the second pulse light to scan the visual field 80 and illuminate the entire range.

[0171] In addition, for example Fig.29 The light emitting unit 40e shown in the figure includes a laser element 41, two drive circuits 46g and 46h, and a line selector 47. The drive circuit 46g is a drive circuit for irradiating the first pulse light. The drive circuit 46h is a drive circuit for irradiating the second pulse light. The line selector 47 selectively connects one of the two drive circuits 46g and 46h to the laser element 41. The line selector 47 switches the connection according to the instruction from the control unit 270.

[0172] In addition, for example Fig.30 The light emitting unit 40f shown in the figure has two laser elements 41i and 41j, a driving circuit 46 and a line selector 47i. The laser element 41i is a laser element for irradiating the first pulse light. The laser element 41j is a laser element for irradiating the second pulse light. The line selector 47i selectively connects one of the two laser elements 41i and 41j to the driving circuit 46. The line selector 47i switches the connection according to the instruction from the control unit 270. In each of the above-described structures, the same effects as those of the embodiments are also achieved.

[0173] I7. Other implementations 7:

[0174] In the fifth embodiment, when the region to be generated as the histogram, that is, the region to determine the light intensity, is changed according to the cumulative number of times, the center of the horizontal position of the region of interest and the position shifted horizontally from the center are selectively changed, but the present disclosure is not limited to this. Fig.31 In the example, four regions of interest ROI31, ROI32, ROI33, and ROI34 having the same longitudinal size are set at the center of the horizontal position of the light receiving array 65a. Fig. 27The light emitting unit is a light emitting unit having the same structure as the light emitting unit 40c shown in the figure. However, the four laser elements 41a~41d irradiate pulse light to ranges with different lateral positions at the same time. In addition, in this example, none of the four laser elements 41a~41d irradiates the first pulse light, and only irradiates the second pulse light. Moreover, for example, during the second to fourth pulse light irradiation in the first embodiment, only the pixel group of the area of ​​interest corresponding to the irradiation position of the pulse light among the four areas of interest POI31~POI34 is used as the object for generating a histogram. For example, in the case where pulse light is irradiated to the area corresponding to the area of ​​interest POI31, as shown in Fig.31 As shown, the peak of the light intensity at the longitudinal position becomes the position of the area of ​​interest POI31. In contrast, during the first pulse light irradiation in the first embodiment, only the pixel group of the area of ​​interest adjacent to the area of ​​interest corresponding to the irradiation position of the pulse light is used as the object for generating a histogram. For example, as described above, when the pulse light is irradiated to the area corresponding to the area of ​​interest POI31, only the pixel group of the area of ​​interest POI32 adjacent to the area of ​​interest POI31 is used as the object for generating a histogram. In the area of ​​interest adjacent to the area of ​​interest corresponding to the irradiation position of the pulse light, as Fig.31 As shown in FIG. 1 , the received light intensity deviates from the peak and decreases. Therefore, the same effect as the case of irradiating the above-mentioned first pulse light can be achieved.

[0175] I8. Other implementations 8:

[0176] In each embodiment, the entire range of the field of view 80 is used as an object for generating a comprehensive distance image, but the present disclosure is not limited to this. For example, a range of a specified angle in the horizontal direction (a specified azimuth range) may be used as a unit to generate a distance image. In addition, for example, in the fourth embodiment, the first high-intensity area, the second high-intensity area, the strong reflector area, and the flare area may also be determined in units of a specified angle range in the horizontal direction (a specified azimuth range).

[0177] I9. Other implementations 9:

[0178] In each embodiment, there are two types of pulsed light, namely, the first pulsed light and the second pulsed light having different irradiation intensities, but the present disclosure is not limited thereto. Three or more pulsed lights having different irradiation intensities may also be used. In the fourth embodiment, the distance from the distance measuring device 10 to the reflectors Rf1 and Rf2 may vary according to the position of the vehicle C1. In this way, if the distance from the distance measuring device 10 to the reflectors Rf1 and Rf2 changes, the intensity of the reflected light from the first high-intensity areas A1 and A2 may also change, so depending on the position of the vehicle C1, it is possible that the first high-intensity areas A1 and A2 cannot be determined in the first pulsed light. However, as described above, by irradiating three or more pulsed lights having different irradiation intensities, the possibility of determining the first high-intensity areas A1 and A2 regardless of the position of the vehicle C1 can be increased.

[0179] I10. Other embodiments 10:

[0180] In each embodiment, the ECU 500 is housed in the housing 90, but may be disposed outside the housing 90. In the above-described configuration, the same effects as those of the embodiments are achieved.

[0181] I11. Other implementations 11:

[0182] In the eighth embodiment, the first light emitting unit 40 may be omitted and only the second light emitting unit 40a may emit pulse light. In the above configuration, control is performed so that the intensity of the output laser light is adjusted so that the second light emitting unit 40a emits not only the first pulse light but also the second pulse light.

[0183] The present disclosure can be implemented in various forms, such as a distance measurement system, a mobile object equipped with a distance measurement device, a distance measurement method, a computer program for implementing these devices and methods, and a non-transitory recording medium recording such a computer program.

[0184] The present disclosure is not limited to the above-mentioned embodiments, and can be implemented in various configurations within the scope of the main purpose. For example, in order to solve part or all of the above-mentioned problems, or to achieve part or all of the above-mentioned effects, the technical features in each embodiment corresponding to the technical features in the method described in the invention content column can be appropriately replaced or combined. In addition, if the technical feature is not described as a necessary feature in this specification, it can be appropriately deleted.

Claims

1. A distance measuring device, comprising: The light emitting unit is a light emitting unit that emits pulse light and emits the pulse light in a plurality of emission times for each emission direction; A light receiving part, receiving the reflected light of the pulse light; The calculation unit calculates the distance to the measurement object using the flight time of the reflected light received by the light receiving unit, wherein: The measurement target distance is a distance to a reflecting object that reflects the pulse light and outputs the reflected light; and a control unit that controls at least one of the intensity of the pulse light emitted from the light emitting unit, the light receiving sensitivity of the reflected light in the light receiving unit, and the position of a focus area for determining the light receiving intensity in the light receiving unit, The computing unit has: a light receiving intensity determining unit that determines the light receiving intensity of each of the plurality of flight times; a peak detection unit for detecting a peak flight time in each of the plurality of flight times; a distance calculation unit for calculating the distance based on the detected flight time of the peak; and a distance determination unit that determines the measurement target distance using the distance calculated by the distance calculation unit; The control unit controls at least one of the intensity of the pulse light emitted from the light emitting unit, the light receiving sensitivity of the reflected light in the light receiving unit, and the position of the region of interest, so that at least once in the multiple emission times, the light receiving intensity determination unit determines a first light receiving intensity as each light receiving intensity in the multiple flight times, and at least once in the multiple emission times, the light receiving intensity determination unit determines a second light receiving intensity having a higher SN ratio than the first light receiving intensity as each light receiving intensity in the multiple flight times. The distance determination unit determines the measurement target distance using a first distance calculated based on the first received light intensity and a second distance calculated based on the second received light intensity.

2. The distance measuring device according to claim 1, wherein: The control unit causes the light intensity determination unit to determine the first light intensity by causing the first pulse light to be emitted from the light emitting unit, and causes the light intensity determination unit to determine the second light intensity by causing the second pulse light having a greater intensity than the first pulse light to be emitted from the light emitting unit.

3. The distance measuring device according to claim 2, wherein: It also includes a housing that accommodates the light emitting unit and the light receiving unit and has a window that allows the pulse light and the reflected light to pass through. The first pulse light is emitted as the reflected light of the first pulse light in the window, and has an intensity such that the light receiving section cannot recognize the light received.

4. The distance measuring device according to claim 1, wherein: The light receiving unit is configured to be able to adjust the light receiving sensitivity. The control unit causes the received light intensity determination unit to determine the first received light intensity by adjusting the received light sensitivity to be lower, and causes the received light intensity determination unit to determine the second received light intensity by adjusting the received light sensitivity to be higher.

5. The distance measuring device according to any one of claims 1, 2 and 4, wherein: further comprising a distance image generating unit for generating a distance image, wherein the distance image is an image indicating the position of the reflecting object and the distance to the measuring object, The distance image generating unit generates a comprehensive distance image by combining a first distance image including the first distances determined for each of the emission directions and a second distance image including the second distances determined for each of the emission directions.

6. The distance measuring device according to claim 3, wherein: further comprising a distance image generating unit for generating a distance image, wherein the distance image is an image indicating the position of the reflecting object and the distance to the measuring object, The distance image generating unit generates a comprehensive distance image by combining a first distance image including the first distances determined for each of the emission directions and a second distance image including the second distances determined for each of the emission directions.

7. The distance measuring device according to claim 5, wherein: The device further comprises: a first storage unit for storing a flight time corresponding to a maximum light receiving intensity; and a second storage unit for storing a histogram representing a light receiving intensity at each of a plurality of flight times. When the light receiving intensity determining unit sequentially determines each of the first light receiving intensities in the plurality of flight times, the flight time corresponding to the larger light receiving intensity is updated and stored in the first storage unit. The light receiving intensity determining unit sequentially determines each of the second light receiving intensities in the plurality of flight times, creates the histogram and stores them in the second storage unit respectively. The peak detection unit detects the flight time stored in the first storage unit as the flight time of the peak, i.e., the first flight time, and further detects the flight time of the peak, i.e., the second flight time, based on a histogram obtained by accumulating the histogram stored in the second storage unit. The range image generating unit generates the first range image using the first distance calculated based on the first flight time, and generates the second range image using the second distance calculated based on the second flight time.

8. The distance measuring device according to claim 6, wherein: The device further comprises: a first storage unit for storing a flight time corresponding to a maximum light receiving intensity; and a second storage unit for storing a histogram representing a light receiving intensity at each of a plurality of flight times. When the light receiving intensity determining unit sequentially determines each of the first light receiving intensities in the plurality of flight times, the flight time corresponding to the larger light receiving intensity is updated and stored in the first storage unit. The light receiving intensity determining unit sequentially determines each of the second light receiving intensities in the plurality of flight times, creates the histogram and stores them in the second storage unit respectively. The peak detection unit detects the flight time stored in the first storage unit as the flight time of the peak, i.e., the first flight time, and further detects the flight time of the peak, i.e., the second flight time, based on a histogram obtained by accumulating the histogram stored in the second storage unit. The range image generating unit generates the first range image using the first distance calculated based on the first flight time, and generates the second range image using the second distance calculated based on the second flight time.

9. The distance measuring device according to claim 6, wherein: The distance image generating unit generates the integrated distance image by combining a first partial image in the first distance image and a second partial image in the second distance image. The first part of the image represents the position of the reflector and the distance to the reflector whose distance to the reflector is within the threshold distance from the distance measuring device, The second partial image indicates the position of the reflector that exists at a position where the distance from the reflector to the distance measuring device is longer than the threshold distance and the distance to the reflector.

10. The distance measuring device according to claim 9, wherein: The light receiving intensity determining unit includes a histogram generating unit that creates a histogram representing the light receiving intensity at each of the plurality of flight times. The peak detection unit identifies a range of flight times in which the received light intensity is higher than an intensity threshold value in the histogram, and detects a flight time of a peak of the received light intensity in the identified range.

11. The distance measuring device according to claim 10, wherein: It also includes a storage unit for storing the light intensity at each of the plurality of flight times. The light emitting unit emits the first pulse light as the first emission of the pulse light, and emits the second pulse light as the second and subsequent emission of the pulse light. The histogram generating unit generates the histogram by storing the light intensity within a prescribed time including the flight time of the reflected light corresponding to the first pulse light for the first time in the storage unit. If the peak detecting unit detects the flight time of the peak value, i.e., the first flight time, using the histogram, the storage unit is cleared. The light intensity within the prescribed time including the flight time of the reflected light corresponding to the second pulse light from the second time to the last time is accumulated in sequence according to each emission and stored in the storage unit to generate the histogram. If the peak detection unit detects the flight time of the peak value, i.e., the second flight time, using the histogram, the storage unit is cleared. The range image generating unit generates the first range image using the first distance calculated based on the first flight time. The range image generating unit generates the second range image using the second distance calculated based on the second flight time.

12. The distance measuring device according to claim 10, wherein: It also includes a storage unit for storing the light intensity at each of the plurality of flight times. The light emitting unit emits the first pulse light as the first emission of the pulse light, and emits the second pulse light as the emission of the pulse light from the second time to the last time, The histogram generation unit generates the histogram by sequentially accumulating the light intensity within a predetermined time including the flight time of the reflected light corresponding to the pulse light emitted from the first to the last time according to each emission, and storing the accumulated light intensity in the storage unit. If the light intensity within the prescribed time including the flight time of the reflected light corresponding to the first pulse light is stored in the storage unit to generate the histogram, the peak detection unit detects the first flight time of the peak value using the histogram. If the light intensity within the prescribed time including the flight time of the reflected light corresponding to the first pulse light or the second pulse light from the first time to the last time is accumulated in sequence according to each emission and stored in the storage unit to generate the histogram, the peak detection unit uses the histogram to detect the second flight time of the peak value, The range image generating unit generates the first range image using the first distance calculated based on the first flight time, and generates the second range image using the second distance calculated based on the second flight time.

13. The distance measuring device according to claim 5, wherein: The distance image generating unit determines, in the first distance image, a first high intensity region where the received light intensity is greater than a first threshold intensity, Determine in the second range image a second high intensity region where the light intensity is above a second threshold intensity, The other regions in the second high-intensity region in the second range image except the region corresponding to the first high-intensity region are determined as regions representing flares, i.e., flare regions, and an image excluding the flare region in the second range image is acquired as the comprehensive range image.

14. The distance measuring device according to claim 6, wherein: The distance image generating unit determines, in the first distance image, a first high intensity region where the received light intensity is greater than a first threshold intensity, Determine in the second range image a second high intensity region where the light intensity is above a second threshold intensity, The other regions in the second high-intensity region in the second range image except the region corresponding to the first high-intensity region are determined as regions representing flares, i.e., flare regions, and an image excluding the flare region in the second range image is acquired as the comprehensive range image.

15. The distance measuring device according to claim 11, wherein: The control unit determines the direction of an area of ​​a predetermined size including a high-reflectivity object having a reflectivity higher than a predetermined value, i.e., a high-reflectivity direction, based on the distance measuring device, after the first emission of the first pulse light and before the second emission of the second pulse light, using the first distance calculated based on the first flight time. For other directions different from the high reflection direction, the histogram generation unit accumulates the light intensity within the prescribed time including the flight time of the reflected light corresponding to the second pulse light from the second time to the last time according to each emission and stores it in the storage unit to generate the histogram. For the high reflection direction, the histogram generating unit accumulates the light intensity within the prescribed time including the flight time of the reflected light corresponding to the second pulse light from the second time to the last time according to each emission and stores it in the storage unit to generate the histogram.

16. The distance measuring device according to claim 12, wherein: The control unit determines the direction of an area of ​​a predetermined size including a high-reflectivity object having a reflectivity higher than a predetermined value, i.e., a high-reflectivity direction, based on the distance measuring device, after the first emission of the first pulse light and before the second emission of the second pulse light, using the first distance calculated based on the first flight time. For other orientations different from the above-mentioned high reflection orientation, if the above-mentioned histogram generating unit accumulates the light intensity within the above-mentioned prescribed time including the flight time of the above-mentioned reflected light corresponding to the above-mentioned first pulse light or the above-mentioned second pulse light from the above-mentioned first time to the last time according to each emission and stores it in the above-mentioned storage unit to generate the above-mentioned histogram, then the histogram is used to detect the second flight time of the above-mentioned peak value. For the above-mentioned high reflection direction, if the above-mentioned histogram generating unit accumulates the light intensity within the above-mentioned prescribed time of the flight time of the above-mentioned reflected light corresponding to the above-mentioned first pulse light or the above-mentioned second pulse light from the first time to the last time according to each emission time and stores it in the above-mentioned storage unit to generate the above-mentioned histogram, the histogram is used to detect the second flight time of the above-mentioned peak value.

17. The distance measuring device according to claim 6, wherein: The distance image generating unit generates the integrated distance image by combining a first partial image in the first distance image and a second partial image in the second distance image. The first partial image represents the position of the reflector and the distance to the reflector, the distance to the reflector being within a first threshold distance from the distance measuring device, The second partial image represents the position of the reflector that is located at a distance from the reflector that is longer than a second threshold distance from the distance measuring device and the distance to the reflector, The first threshold distance is longer than the second threshold distance.

18. The distance measuring device according to claim 2, wherein: The light emitting unit has a first irradiation mode for irradiating the second pulse light to a first irradiation area of ​​a predetermined size and scanning the first irradiation area, and a second irradiation mode for irradiating the first pulse light to a second irradiation area corresponding to the scanning range in the first irradiation mode. The control unit causes the light emitting unit to operate in the second irradiation mode to irradiate the first pulse light, and causes the light emitting unit to operate in the first irradiation mode to irradiate the second pulse light.

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