Optical detection device and ranging system

Abstract

The present disclosure provides a light detection device capable of reducing an influence of disturbance light while suppressing a decrease in measurement accuracy on a short distance side.　According to the present disclosure, provided is an optical detection device (20) that detects laser light for measurement reflected from an object (50), the device comprising: a pixel (1000) that generates, in accordance with a received photon, a plurality of types of pulse signals (PLS1, PLS2) in which the pulse width increases with the elapse of time from the time at which the laser light is irradiated; a time information generation unit (111) that generates information on a first time range (tPLS1, tPLS2) that is a range corresponding to the pulse width and indicates an elapsed time; a histogram generation unit (112) that, on the basis of the information in the first time range, adds a prescribed number of frequencies in a range corresponding to the first time range to generate a histogram indicating the frequency value; and a signal processing unit (113) that generates a distance value (D) to the object (50) on the basis of the frequency value of the histogram.

Description

Optical detection device and ranging system

[0001] The present disclosure relates to a light detection device and a ranging system.

[0002] A distance measurement system that measures the distance to an object (target) based on the time of flight (ToF) is generally known. In the TOF system, laser light from a laser light source is emitted multiple times as pulsed light through a lens, and photons of the light reflected from the object irradiated with each pulsed light are detected by a light receiving element called a single photon avalanche diode (SPAD).

[0003] The carriers generated by this are converted into a pulse signal using avalanche multiplication, and this is input into a TDC (Time to Digital Converter) to measure the arrival time of the reflected light and calculate the distance to the object.

[0004] Furthermore, the arrival time of the reflected light for each of the laser beams emitted multiple times is measured using a histogram.

[0005] Japanese Patent Application Laid-Open No. 2021-1764

[0006] However, reflected light measurement is affected by ambient light. Particularly at medium and long distances, measurements are more affected by ambient light because reflected light is reduced. On the other hand, if you try to suppress the effects of ambient light, there is a risk that measurement accuracy will decrease at short distances, where higher measurement accuracy is required.

[0007] Therefore, the present disclosure provides a light detection device and a distance measurement system that can reduce the influence of ambient light while suppressing a decrease in measurement accuracy at short distances.

[0008] In order to solve the above problems, according to the present disclosure, there is provided a photodetection device that detects reflected light of a measurement laser light from an object, the photodetection device comprising: a pixel that generates, in response to received photons, multiple types of pulse signals whose pulse widths increase according to the elapsed time from the time when the laser light was irradiated; a time information generation unit that generates information on a first time range that is a range corresponding to the pulse widths and indicates the elapsed time; a histogram generation unit that adds up a predetermined number of frequencies in a range corresponding to the first time range based on the information on the first time range, to generate a histogram indicating frequency values; and a signal processing unit that generates a distance value to the object based on the frequency values ​​of the histogram.

[0009] The pixel may generate, as the plurality of types of pulse signals, a second pulse signal in accordance with the elapsed time, and then generate a first pulse signal having a pulse width wider than that of the second pulse signal.

[0010] The pixel may have a photoelectric conversion unit that generates an electrical signal whose value fluctuates in response to received photons; a pulse generation unit that is capable of generating the first pulse signal, the range of which is the pulse width of the first signal fluctuates in response to the time during which the electrical signal fluctuates within a predetermined value range; and a second pulse signal that is generated based on the start of fluctuation of the electrical signal and has a fixed range of the first signal.

[0011] The first signal range of the first pulse signal may be a second time range corresponding to a time during which the electrical signal exceeds a predetermined threshold, and the first signal range of the second pulse signal may be a fixed third time range based on a timing at which the first pulse signal is generated.

[0012] The pulse generating section may output one of the first pulse signal and the second pulse signal.

[0013] The pulse generating section may output the first pulse signal after outputting the second pulse signal up to a threshold value at a predetermined time elapsed from the time when the laser light was irradiated.

[0014] The pulse generating section may change the threshold value in accordance with the amount of ambient light received by the pixel.

[0015] The amount of the disturbance light may be measured before the measurement using the laser light is started.

[0016] The optical fiber may further include a disturbance light measurement unit that drives the pixels, the time information generation unit, and the histogram generation unit to generate a histogram during a disturbance light measurement time for measuring disturbance light before measurement using the laser light is started, and generates an evaluation value indicating the amount of disturbance light.

[0017] The image capturing device may further include a threshold value generating unit that generates a threshold value that shortens the elapsed time as the amount of disturbance light increases, based on the evaluation value.

[0018] The ambient light measurement section may cause the pixel to output the first pulse signal during the ambient light measurement time.

[0019] The measurement laser light may be pulsed light, and the measurement device may further include a generation instruction unit that repeatedly emits the pulsed light at a predetermined time interval, causes the pixel to output one of the first pulse signal and the second pulse signal based on the threshold during a reflected light measurement period within the time interval, causes the time information generation unit to generate information on the first time range of one of the first pulse signal and the second pulse signal, and causes the histogram generation unit to generate a histogram indicating frequency values ​​by adding up frequencies in a range corresponding to the first time range during the measurement period during which the pulsed light is repeatedly emitted.

[0020] The photoelectric conversion unit may be a single photon avalanche diode (SPAD), and the second time range may be longer as a dead period until a recharge operation of the SPAD is completed becomes longer.

[0021] The first signal may be a high-level signal, and the pulse generating unit may include: an inverter circuit that outputs the first pulse signal in response to the electrical signal; a pulse generating circuit that outputs the second pulse signal having a high-level signal in the third time range from an edge of the first pulse signal; and a multiplexer that selects and outputs the first pulse signal or the second pulse signal in response to a selection signal based on the threshold value.

[0022] In order to solve the above problem, according to the present disclosure, there may be provided a ranging system including: an emitting device that irradiates an object with measurement laser light; and an optical detection device that receives reflected light from the object, wherein the optical detection device has: pixels that generate, in response to received photons, multiple types of pulse signals whose pulse width increases according to the elapsed time since the laser light was irradiated; a time information generation unit that generates information on a first time range that corresponds to the pulse width and indicates the elapsed time; a histogram generation unit that adds up a predetermined number of frequencies in a range corresponding to the first time range based on the information on the first time range to generate a histogram indicating frequency values; and a signal processing unit that generates a distance value to the object based on the frequency value of the histogram.

[0023] The light detection device may further include an output unit that outputs information related to the histogram, a main control unit that visualizes the histogram based on the information related to the histogram, and a display / operation unit that displays the visualized histogram.

[0024] The pixel may have: a photoelectric conversion unit that generates an electrical signal whose value fluctuates in response to received photons; a pulse generation unit that is capable of generating a first pulse signal whose pulse width, or the range of the first signal, fluctuates in response to the time during which the electrical signal fluctuates within a predetermined value range; and a second pulse signal that is generated based on the start of fluctuation of the electrical signal and whose range of the first signal is fixed.

[0025] The pulse generating unit outputs the first pulse signal after outputting the second pulse signal up to a threshold value at a predetermined time elapsed from the time when the laser light was irradiated, the main control unit associates the threshold value with a histogram and images it, the display operation device has an operation unit that changes the position of an image of the second threshold value that indicates the position of the imaged threshold value, and the light detection device may be able to change the threshold value of the pulse generating unit using information on the threshold value corresponding to the position of the second threshold value input from the display operation device.

[0026] In the case of a preliminary measurement in which an image is generated by associating the threshold value with a histogram, the pulse generating section may output only the first pulse signal or only the second pulse signal.

[0027] The photodetector may have a pixel array in which a plurality of the pixels are arranged in a matrix, and the time information generating unit, the histogram generating unit, and the signal processing unit may process the first pulse signal and the second pulse signal output for each of the plurality of pixels.

[0028] 1 is a block diagram showing an example of a schematic configuration of a distance measuring system according to an embodiment of the present disclosure. FIG. 2 is a diagram showing an example of a light emission cycle and a measurement period of a light emitting device. FIG. 3 is a diagram showing a schematic configuration of an optical system of a distance measuring system according to the present embodiment. FIG. 4 is a diagram showing an example of a flash-type optical system. FIG. 5 is a diagram showing a schematic example of the pixel shown in FIG. 1. FIG. 6 is a diagram showing an example of a cathode potential of a photoelectric conversion unit and a pulse signal. FIG. 7 is a diagram showing an example of the configuration of a readout circuit. FIG. 8 is a diagram explaining the operation of a TDC with respect to a pulse signal. FIG. 9 is a diagram explaining the operation of a TDC with respect to a pulse signal when multiple photons are input. FIG. 10 is a diagram explaining the operation of a TDC with respect to a second pulse signal. FIG. 11 is a diagram explaining the operation of a TDC with respect to a pulse signal when multiple photons are input. FIG. 12 is a diagram showing an example of a histogram in a first mode (level detection mode). FIG. 13 is a diagram showing an example of a histogram in a second mode (edge ​​detection mode). FIG. 14 is a diagram showing count values ​​in a histogram generating unit for the same object. FIG. 15 is a diagram showing a schematic diagram of count values ​​in a histogram generating unit. FIG. 16 is a diagram showing a more detailed configuration example of a control unit. FIG. 17 is a diagram showing an example of control by the control unit when there is less ambient light. A diagram showing an example of control by the control unit when there is more ambient light. A diagram showing an example of an image displayed on the display operation unit. A diagram showing another example of an image displayed on the display operation unit. A diagram showing yet another example of an image displayed on the display operation unit. A flowchart showing an example of operation of the control unit. A block diagram showing an example of the schematic configuration of a vehicle control system. An explanatory diagram showing an example of installation positions of an outside vehicle information detection unit and an imaging unit.

[0029] Hereinafter, embodiments of a light detection device and a distance measurement system will be described with reference to the drawings. The following description will focus on the main components of the light detection device and the distance measurement system, but the light detection device and the distance measurement system may include components and functions that are not shown or described. The following description does not exclude components and functions that are not shown or described.

[0030] First Embodiment Fig. 1 is a block diagram showing an example of a schematic configuration of a distance measuring system 1 according to an embodiment of the present disclosure. As shown in Fig. 1, the distance measuring system 1 includes a light emitting device 10, a light detecting device 20, an overall control unit 30, a light receiving optical system 40, a main control unit 60, and a display operation device 70. The distance measuring system 1 is a sensor system including a light source and a ToF sensor, and is configured to emit light and detect reflected light reflected by an object 50. Here, the object 50 may be one or more objects present within the angle of view of the distance measuring system 1.

[0031] 2A and 2B are diagrams showing an example of the light emission period and measurement period of the light emitting device 10. FIG. 2A shows the irradiation timing and period S0 of the laser light L0, and FIG. 2B shows the ambient light measurement period T1 and the reflected light measurement period T2. The horizontal axis represents time.

[0032] 2, light-emitting device 10 is configured to emit laser light (irradiation light) L0, which is pulsed light, toward target 50 based on instructions from overall control unit 30. Light-emitting device 10 performs an emission operation that alternates between emission and non-emission based on instructions from overall control unit 30, thereby emitting laser light L0 at emission timing TL0 that matches a predetermined emission cycle S0. In this case, there is a disturbance light measurement period T1 in which disturbance light is measured without emitting laser light L0, and a reflected light measurement period T2 in which reflected light of laser light L0 is measured in accordance with the emission cycle S0. In this way, during the measurement time of target 50, laser light L0 is repeatedly irradiated with the emission cycle S0.

[0033] 1 again, the light receiving optical system 40 is configured to include a lens that forms an image on the light receiving surface of the light detection device 20. Light L1 emitted from the light emitting device 10 and reflected by the object 50 is incident on this light receiving optical system 40. The reflected light L1 is received as photons by each pixel 1000, which will be described later, via the light receiving optical system 40. In the following description, the reflected light L1 may also be referred to as photon L1.

[0034] The photodetector 20 includes a pixel array 100, a ranging processing unit 110, a ranging control unit 120, a drive circuit 130, a light emission timing control unit 140, a control unit 150, a clock generation unit 160, and an output unit 170. The overall control unit 30 is configured to control the operation of the ranging system 1 by supplying control signals to the light emitting device 10 and the photodetector 20 and controlling their operations.

[0035] Photodetector 20 is configured to detect photon L1 based on instructions from overall control unit 30. Photodetector 20 then generates a distance image based on the detection result, and outputs image data of the generated distance image from output unit 170 as distance information D1.

[0036] The pixel array 100, ranging processing unit 110, ranging control unit 120, drive circuit 130, light emission timing control unit 140, control unit 150, clock generation unit 160, and output unit 170 can be arranged on a single semiconductor chip. On the other hand, the photodetector 20 may be configured by stacking a first semiconductor chip and a second semiconductor chip. In this case, for example, a configuration is conceivable in which a part of the pixel array 100 (the photoelectric conversion unit 1001) is arranged on the first semiconductor chip, and the other parts included in the ranging device are arranged on the second semiconductor chip.

[0037] 1, the overall control unit 30 controls the overall operation of the distance measuring system 1 in accordance with, for example, a pre-installed program. The overall control unit 30 can also execute control in response to an external control signal supplied from the outside. Meanwhile, the control unit 150 controls the overall operation of the photodetector device 20 in accordance with instructions from the overall control unit 30. The control unit 150 can also execute control to change the drive mode of the pixel array 100 between a first mode, which is a level detection mode, and a second mode, which is an edge detection mode. Details of the control unit 150 will be described later.

[0038] The clock generating unit 160 generates one or more clock signals used in the photodetector 20 based on a reference clock signal supplied from the outside. For example, the clock generating unit 160 generates a TDC clock, which will be described later. The light emission timing control unit 140 generates a light emission control signal indicating light emission timing TL0 (see FIG. 2) in accordance with a light emission trigger signal supplied from the overall control unit 30. The light emission control signal is supplied to the light emitting device 10 and also to the distance measurement processing unit 110. That is, the light emitting device 10 emits laser light L0 at light emission timing TL0 (see FIG. 2) in accordance with the light emission control signal.

[0039] The ranging control unit 120 controls the operation of the ranging processing unit 110 based on instructions from the control unit 150, thereby causing the ranging processing unit 110 to generate distance information based on the pulse signals PLS1, PLS2 (see Figures 5 and 6) output from each pixel 1000 of the pixel array 100.

[0040] The pixel array 100 includes a plurality of pixels 1000 arranged in a matrix. Each pixel 1000 is configured to detect a photon L1 and generate a pulse signal corresponding to the detected photon L1. The pixel 1000 can generate a plurality of pulse signals PLS1, PLS2 (see FIGS. 5 and 6 ) with different high-level signal ranges in response to the received photons. That is, the pixel 1000 generates a plurality of types of pulse signals PLS1, PLS2 whose pulse widths increase as time elapses from the time TL0 at which the laser light L0 is irradiated in response to the received photons. Details will be described later with reference to FIG. 5 . Note that in this embodiment, an example of the operation of the pixel 1000 will be described using one pixel as an example. However, the other pixels 1000 in the pixel array 100 have an equivalent configuration and can operate in a similar manner. That is, the photodetector 20 can generate distance information corresponding to each pixel 1000.

[0041] A pixel drive line LD (vertical direction in the drawing) is connected to the pixels 1000 for each column, and one end of the pixel drive line LD is connected to an output terminal of the drive circuit 130 corresponding to each column.

[0042] In this embodiment, photons L1 are detected using all or a part of the pixel array 100. The region to be used in the pixel array 100 may be a rectangle that is long in a direction perpendicular to the scanning direction (the up-and-down direction in the drawings; hereinafter, also referred to as the vertical direction), which is the same as the image of photons L1 that is formed on the pixel array 100 when the entire laser light L0 is reflected as photons L1. However, the region to be used is not limited to this, and may be variously modified, such as being larger or smaller than the image of photons L1 that is formed on the pixel array 100.

[0043] The drive circuit 130 includes a shift register, an address decoder, etc., and drives each pixel 1000 of the pixel array 1000 simultaneously, column by column, etc. Therefore, the drive circuit 130 includes at least a circuit that applies a quench voltage V_QCH (described later) to each pixel 1000 in a selected column in the pixel array 100, and a circuit that applies a selection control voltage V_SEL (described later) to each pixel 1000 in the selected column. The drive circuit 130 then applies the selection control voltage V_SEL to a pixel drive line LD corresponding to a column to be read out, thereby selecting, column by column, the pixels 1000 to be used for detecting incident photons.

[0044] The pulse signal output from the pixel array 100 is supplied to a ranging processing unit 110. The ranging processing unit 110 includes a TDC unit 111, a histogram generating unit 112, and a signal processing unit 113.

[0045] The pulse signals PLS1 and PLS2 read out from each pixel 1000 are supplied to the TDC unit 111. Here, the first pulse signal PLS1 is a pulse signal in the first mode, and the second pulse signal PLS2 is a pulse signal in the second mode. The pulse signals PLS1 and PLS2 are read out at a predetermined sampling period for each pixel column in the pixel array 100, for example, and supplied to the TDC unit 111. Details of the pulse signals PLS1 and PLS2 will be described later.

[0046] The TDC unit 111 measures the time difference between a reference timing (e.g., the timing at which a light-emission control signal is input from the light-emission timing control unit 140) and the input of the pulse signals PLS1 and PLS2 supplied from the pixel array 100, and generates digital information indicating the measured time difference. That is, based on the light-emission control signal and the pulse signals PLS1 and PLS2, the TDC unit 111 generates time information indicating the time of flight from when light is emitted from the light-emitting device 10, when the light is reflected by the object 50, and when the light is incident on each pixel 1000. That is, based on the range of the high-level signals (first signals) of the pulse signals PLS1 and PLS2, the TDC unit 111 generates information on a first time range (tPLS1, tPLS2) indicating the elapsed time from the time TL0 at which the laser light was irradiated. The TDC unit 111 according to this embodiment corresponds to a time information generating unit. Details of the operation of the TDC unit 111 will be described later with reference to FIGS. 8 to 10 .

[0047] The histogram generating unit 112 generates a histogram based on the time information generated by the TDC unit 111. Here, the histogram generating unit 112 counts the time information based on a unit time d set by the ranging control unit 120 to generate a histogram. The unit time d is, for example, a TDC clock, which is a periodic signal used by the TDC unit 111. This TDC clock is generated by the clock generating unit 160. The period of this TDC clock may be the time width assigned to one bin in the histogram. Furthermore, the unit time d may be, for example, the same time width as the sampling period for reading out pulse signals from each pixel 1000 in the pixel array 100.

[0048] The signal processing unit 113 performs predetermined arithmetic processing based on the histogram data generated by the histogram generation unit 112, and calculates, for example, distance information. For example, the signal processing unit 113 creates a curve approximation of the histogram based on the histogram data. The signal processing unit 113 detects peaks in the curve obtained by approximating the histogram, and can calculate the distance D to the object 50 based on the detected peaks.

[0049] The distance information and histogram data output from the distance measurement processing unit 110 are supplied to the output unit 170. The output unit 170 is also called an interface unit, and outputs the distance information and histogram data supplied from the distance measurement processing unit to the outside as output data. As the output unit 170, for example, a Mobile Industry Processor Interface (MIPI) can be applied.

[0050] Main control device 60 generates a two-dimensional distance image using the output data output from output unit 170. Main control device 60 also generates histogram data as image data.

[0051] The display operation device 70 is, for example, a liquid crystal touch panel, and is capable of displaying a two-dimensional distance image and a histogram image. The display operation device 70 also allows input of an adjustment value for a threshold value for switching between Mode 1 and Mode 2.

[0052] [Optical System] Fig. 3 is a diagram showing a schematic configuration of the optical system of the distance measuring system 1 according to this embodiment. Fig. 2 shows an example of a so-called scanning type optical system that scans the angle of view of the photodetector 20 in the horizontal direction.

[0053] 3, the distance measuring system 1 includes an optical system including a light source 11, a lens 12, a half mirror 13, a polygon mirror 14, a light-receiving lens 15, and a pixel array 100. The light source 11, the lens 12, the half mirror 13, and the polygon mirror 14 are included in, for example, the light-emitting device 10 in FIG. 1. The light-receiving lens 15 is included in the light-receiving optical system 40 in FIG. 1. The half mirror 13 and the polygon mirror 14 may be shared by the light-emitting device 10 and the light-receiving optical system 40.

[0054] In the configuration shown in FIG. 3 , laser light L0 emitted from light source 11 is converted by lens 12 into a rectangular parallel beam B10 whose cross-sectional intensity spectrum is elongated in the vertical direction, and then enters half mirror 13. Half mirror 13 reflects a portion of the incident laser light L0. The laser light L0 reflected by half mirror 13 enters polygon mirror 14. Polygon mirror 14 is oscillated in the horizontal direction around a predetermined rotation axis by driver 16, which operates, for example, under control of overall control unit 30. This causes horizontal scanning of laser light L0 such that the angle of view SR of laser light L0 reflected by polygon mirror 14 reciprocates horizontally across a distance measurement range AR. Note that a MEMS (Micro Electro Mechanical System), a micromotor, or the like can be used as driver 16.

[0055] The laser light L0 reflected by the polygon mirror 14 is reflected by an object 50 present within the distance measurement range AR and is incident on the polygon mirror 14 as photons L1. A portion of the photons L1 incident on the polygon mirror 14 passes through the half mirror 13 and enters the light receiving lens 15, whereby an image is formed on a specific region of the pixel array 100. Note that the specific region may be the entire pixel array 100 or a part of it. Furthermore, the specific region may be, for example, a region corresponding to the first region in the claims.

[0056] FIG. 4 is a diagram showing an example of a flash-type optical system. While FIG. 3 illustrates a scan-type optical system, the present invention is not limited thereto. For example, as shown in FIG. 4, a so-called flash-type optical system in which the angle of view of the ranging system 1 is fixed is also possible. In this case, as shown in FIG. 4, the system includes a light source 11, a lens 17, a condenser lens 18, and a pixel array 100. The laser light emitted from the light source 11 is converted into a light beam B10 with a necessary and sufficient divergence angle via the lens 17 and irradiated over the entire ranging range AR. The laser light L0 reflected by an object 50 present within the ranging range AR is incident on the pixel array 100 as photons L1 via the condenser lens 18. In this way, the flash-type ranging system 1, which can measure the entire ranging range AR with a single light emission, does not require a driver 16, a half mirror 13, or a polygon mirror 14 for scanning the ranging range AR. Therefore, compared to the scan-type ranging system 1, the flash-type ranging system 1 has the advantage of being smaller in size.

[0057] [Pixel configuration]

[0058] Fig. 5 is a diagram showing a schematic example of the pixel 1000 shown in Fig. 1. As shown in Fig. 5, the pixel array 100 has a plurality of pixels 1000 arranged in rows and columns, and each pixel 1000 includes a photoelectric conversion unit 1001, a quenching resistor 1002, a selection transistor 1003, and a pulse generation unit 1004. For example, the quenching resistor 1002 is configured with a PMOS transistor. The pulse generation unit 1004 includes an inverter 1004a and a readout circuit 1004b.

[0059] The photoelectric conversion unit 1001 converts incident light into an electrical signal by photoelectric conversion and outputs the signal. The photoelectric conversion unit 1001 converts incident photons into an electrical signal by photoelectric conversion and outputs a pulse corresponding to the incident photons. For example, a single photon avalanche diode (SPAD) is used as the photoelectric conversion unit 1001. A SPAD has the property that, when a large negative voltage that generates avalanche multiplication is applied to the cathode, electrons generated in response to the incidence of a single photon undergo avalanche multiplication, resulting in a large current flow. Utilizing this property of the SPAD, the incidence of a single photon can be detected with high sensitivity.

[0060] In FIG. 5 , the cathode of the photoelectric conversion unit 1001 is connected to the drain of the quench resistor 1002, and the anode is connected to a voltage source of a negative voltage (−Vop) corresponding to the voltage Vbd, which is the breakdown voltage of the photoelectric conversion unit 1001. The source of the quench resistor 1002 is connected to a power supply voltage Ve. A quench voltage V_QCH is input to the gate of the quench resistor 1002. The quench resistor 1002 is a current source that outputs a current corresponding to the power supply voltage Ve and the quench voltage V_QCH from its drain. With this configuration, a reverse bias is applied to the photoelectric conversion unit 1001. Furthermore, photocurrent flows in a direction from the cathode of the photoelectric conversion unit 1001 toward the anode.

[0061] The output state of the pixel 1000 operates, for example, as follows. During the period when the selection transistor 1003 is in the off state (disconnected period), a power supply voltage Ve is supplied to the cathode of the photoelectric conversion unit 1001. Therefore, when a photon is incident on the photoelectric conversion unit 1001, a voltage drop occurs, as described above, and an output pulse is output from the pixel 1000. A pixel 1000 in this state may be referred to as an active pixel hereinafter. On the other hand, during the period when the selection transistor 1003 is on (connected period), a voltage Vg is applied to the cathode of the photoelectric conversion unit 1001. In other words, a voltage exceeding the breakdown voltage is not applied to the photoelectric conversion unit 1001, and even if a photon is incident on the photoelectric conversion unit 1001, an output pulse is not output from the pixel 1000. A pixel 1000 in this state may be referred to as an inactive pixel hereinafter.

[0062] 6A and 6B are diagrams showing an example of the cathode potential Vca of the photoelectric conversion unit 1001 and examples of the pulse signals PLS1 and PLS2. FIG. 6A is a diagram showing the cathode potential Vca of the photoelectric conversion unit 1001. The horizontal axis represents time, and the vertical axis represents voltage. FIG. 6B is a diagram showing the first pulse signal PLS1, and FIG. 6C is a diagram showing the second pulse signal PLS2. The horizontal axis represents time, and the vertical axis represents the voltage V2 of the pulse signal.

[0063] When the pixel 1000 is an active pixel, the switch 1003 is set to OFF as described above. More specifically, as shown in FIG. 6A (also referring to FIG. 5 ), when a photon is incident on the photoelectric conversion unit 1001 at time t0 while a power supply voltage Ve is applied to the cathode and the voltage between the cathode and anode is Ve+Vop, avalanche multiplication begins, causing a current to flow from the cathode to the anode, resulting in a voltage drop of Vca in the photoelectric conversion unit 1001. This voltage drop causes the voltage between the cathode and anode of the photoelectric conversion unit 1001 to drop to Vbd at time t1, and the avalanche multiplication is stopped (quenching operation). The photoelectric conversion unit 1001 is then charged by a current (recharge current) from the quench resistor 1002, which serves as a current source, and the state of the photoelectric conversion unit 1001 returns to the state it was in before the photon was incident at time t2 (recharge operation). The period from time t0 to time t2 is a dead time DT. That is, the dead time DT is the period from when a photon is incident on the SPAD until the recharge operation is completed. When a photon is incident again, the recharge time to return to the state before the photon incidence becomes longer, and the dead time DT from time t0 to time t2 becomes longer.

[0064] A voltage Vca extracted from the connection point between the drain of the quench resistor 1002 and the cathode of the photoelectric conversion unit 1001 is input to the inverter 1004a. The inverter 1004a performs threshold determination on the input voltage Vca based on a threshold voltage Vth, and inverts the level of the first pulse signal PLS1 every time the voltage Vca exceeds the threshold voltage Vth in the positive or negative direction. The high-level period tPLS1 of this first pulse signal PLS1 becomes longer, for example, when a photon is input again.

[0065] More specifically, as shown in FIG. 6B , the inverter 1004a inverts the first pulse signal PLS1 from low to high at a first timing when the voltage Vca crosses the threshold voltage Vth due to avalanche multiplication in response to the incidence of photons on the photoelectric conversion unit 1001. Next, the photoelectric conversion unit 1001 is charged by a recharge operation, causing the voltage Vca to rise. The inverter 1004a inverts the first pulse signal PLS1 from high to low at a second timing when the rising voltage Vca crosses the threshold voltage Vth. This first pulse signal PLS1 has a high-level signal with a time width tPLAS1 between the first timing and the second timing. The high-level signal according to this embodiment corresponds to the first signal. Note that the first signal will be described as a high-level signal, but this is not limiting. For example, the first pulse signal PLS1 may be negative-positive inverted, and a low-level signal may be used as the first signal.

[0066] Next, the first pulse signal PLS1 is input to a read circuit 1004b. Fig. 7 is a diagram showing an example of the configuration of the read circuit 1004b. As shown in Fig. 7, the read circuit 1004b includes a pulse generating circuit 1006 and a selection circuit 1007.

[0067] 6(c), the edge detection circuit outputs a high-level signal at a point corresponding to an edge of the first pulse signal PLS1, i.e., at a first timing when the voltage Vca crosses the threshold voltage Vth. When the high-level signal is input, the pulse generation circuit outputs a high-level signal of a predetermined duration tPLAS2 as the second pulse signal PLS2.

[0068] The selection circuit 1007 is, for example, a multiplexer, and outputs a first pulse signal PLS1 or a second pulse signal PLS2 in accordance with a mode signal Smode supplied from the control unit 150. That is, the selection circuit 1007 outputs the first pulse signal PLS1 if the mode signal Smode has information indicating the first mode (level detection mode), and outputs the second pulse signal PLS2 if the mode signal Smode has information indicating the second mode (edge ​​detection mode). The control unit 150 generates the mode signal Smode, for example, based on a threshold value described below.

[0069] When the pixel 1000 is set to an inactive pixel, a high-level gating signal V_SE1 is supplied to the switch 1003, turning on the switch 1003. When the switch 1003 is turned on, the cathode voltage Vca of the SPAD 1001 becomes 0 V. As a result, the anode-cathode voltage of the SPAD 1001 becomes equal to or lower than the breakdown voltage, and the SPAD 1001 does not react even if a photon enters it.

[0070] Fig. 8 is a diagram illustrating the operation of the TDC 111 in response to the first pulse signal PLS1. Fig. 9 is a diagram illustrating the operation of the TDC 111 in response to the first pulse signal PLS1 when multiple photons are input during an active period of the pixel 1000. From the top, the diagram illustrates the first pulse signal PLS1 and the TDC clock of the TDC 111, with the horizontal axis representing time.

[0071] 8, a first pulse signal PLS1 is generated in response to the input of photons, with the emission timing T0 of the pulsed light L0 set to 0. This first pulse signal PLS1 is input to the readout circuit 1004b (see FIG. 5) and is selectively output when in the first mode (level detection mode).

[0072] The first pulse signal PLS1 output from the read circuit 1004b is input to the TDC 111 (see FIG. 1). The TDC 111 counts up the TDC code based on the TDC clock signal. In this case, the TDC 111 outputs a TDC clock signal for the period during which the first pulse signal PLS1 is at a high level. For example, the TDC code is a signal such as [bs1-be1] that contains information about the period during which the first pulse signal PLS1 is at a high level. bs1 corresponds to the TDC clock indicating the time when the high-level period of the signal PLS1 started. Similarly, be1 corresponds to the TDC clock indicating the time when the high-level period of the signal PLS1 ended. The TDC code is output to the histogram generator 112 (see FIG. 1).

[0073] Similarly, as shown in Fig. 9, the emission timing T0 of the pulsed light L0 is set to 0, and a first pulse signal PLS1 is generated in response to the input of photons. In Fig. 9, multiple photons are input, and the range of [bs2-be2] of the TDC code is longer than [bs1-be1]. Thus, in the first mode (level detection mode), the range of [bs2-be2] of the TDC code correlates with the dead period DT.

[0074] Fig. 10 is a diagram illustrating the operation of the TDC 111 in response to the second pulse signal PLS2. Fig. 11 is a diagram illustrating the operation of the TDC 111 in response to the second pulse signal PLS2 when multiple photons are input during an active period of the pixel 1000. From the top, the diagram illustrates the first pulse signal PLS1, the second pulse signal PLS2, and the TDC clock of the TDC 111, with the horizontal axis representing time.

[0075] 10, the emission timing T0 of the pulsed light L0 is set to 0, and a first pulse signal PLS1 is generated in response to the input of photons. This first pulse signal PLS1 is input to the readout circuit 1004b (see FIG. 5). In the second mode (edge ​​detection mode), the second pulse signal PLS2 is selected and output.

[0076] The second pulse signal PLS2 output from the read circuit 1004b is input to the TDC 111 (see FIG. 1). The TDC 111 counts up the TDC code based on the TDC clock signal. In this case, the TDC 111 outputs a TDC clock signal during the period when the second pulse signal PLS2 is at a high level. For example, the TDC code is a signal such as [bs3-be4] that includes information about the period when the first pulse signal PLS1 is at a high level. The TDC code is output to the histogram generator 112 (see FIG. 1).

[0077] 11, a first pulse signal PLS1 is generated in response to the input of photons, with the emission timing T0 of the pulsed light L0 set to 0. In Fig. 11, a plurality of photons are input, and the dead period DT is longer than in the example of Fig. 10.

[0078] On the other hand, the length of the second pulse signal PLS2 is fixed at the period tPLS2 and is therefore not correlated with the dead period DT. Therefore, the range of [bs4-be4] of the TDC code is the same length as [bs3-be3]. Thus, in the second mode (edge ​​detection mode), the range of [bs4-be4] of the TDC code is not correlated with the dead period DT and is a fixed value.

[0079] The histogram generator 112 adds 1 to the frequency value of the bin of the histogram corresponding to the TDC code of the final state of the TDC 111. After the light source 32 emits light and receives the reflected light from the light source 32 a predetermined number of times (for example, several thousand to several tens of thousands of times), the histogram generator 112 completes a histogram indicating a frequency distribution according to the TDC code, as shown in FIGS.

[0080] FIG. 12 is a diagram showing an example histogram in the first mode (level detection mode). FIG. 13 is a diagram showing an example histogram in the second mode (edge ​​detection mode). The horizontal axis represents time, and the vertical axis represents count values ​​(frequency values). FIGS. 11 and 12 show examples of the same object 50 generated under the same ambient light. The half-width hw1 of the histogram in the first mode (level detection mode) is wider than the half-width hw2 of the histogram in the second mode (edge ​​detection mode). Note that the time on the horizontal axis corresponds to the number of periods of the TDC clock signal, and is sometimes referred to as a bin.

[0081] FIG. 14 is a diagram showing count values ​​in the histogram generator 112 for the same object. The horizontal axis represents the amount of ambient light, and the vertical axis represents the count values ​​in the histogram generator 112. In the first mode (level detection mode), as the amount of light increases, the count values ​​tend to increase in proportion to the amount of light. That is, in the first mode (level detection mode), as the amount of light increases, the time width tPLS1 of the first pulse signal PLS1 becomes longer in correlation with the increase in the amount of light. On the other hand, in the second mode (edge ​​detection mode), the time width tPLS2 of the second pulse signal PLS2 is a fixed value, so when the amount of light exceeds a predetermined value, the dead period DT increases and the count values ​​decrease.

[0082] 1 , the signal processing unit 113 performs predetermined arithmetic processing based on the histogram data generated by the histogram generation unit 112, to calculate, for example, distance information. For example, the signal processing unit 113 creates a curve approximation of the histogram based on the histogram data. The signal processing unit 113 detects peaks in the curve obtained by approximating the histogram, and generates a distance D value to the object 50 for each pixel 1000 based on the detected peaks.

[0083] When performing curve approximation of a histogram, the signal processing unit 113 can perform filtering on the curve obtained by approximating the histogram. For example, the signal processing unit 113 can suppress noise components by performing low-pass filtering on the curve obtained by approximating the histogram.

[0084] FIG. 15 is a diagram schematically illustrating count values ​​in the histogram generator 112. The horizontal axis represents time, and the vertical axis represents count values ​​(frequency values). FIG. 15 also schematically illustrates portions of peaks P1 and P2 of the histogram. The signal processor 113 generates the distance D value based on the premise that the peak of the histogram is detected. Therefore, the signal processor 113 can generate the distance D value when peak P1 of the histogram for the disturbance light level nL is not hidden. On the other hand, the signal processor 113 has difficulty measuring when peak P2 is hidden by the disturbance light level nL. In this embodiment, the ratio of the standard deviation of the count during the reflected light measurement period T2 (see FIG. 2) to the value of peak P1 of the histogram is sometimes referred to as SN. In other words, as SN increases, the likelihood of measuring the distance D increases.

[0085] 16 is a diagram schematically illustrating the count values ​​in the histogram generation unit 112. The horizontal axis represents time, and the vertical axis represents the count values ​​(frequency values). In FIG. 16, parts of peaks P3, P4, and P5 of the histogram are schematically illustrated.

[0086] On the other hand, if the SNR at peak P1 of the histogram is ensured, measurement accuracy becomes important. For example, if the half-width widens as in peak P3', the deviation from the true distance value D increases. Also, as shown in peaks P4 and P5, it is required that the true distance value D does not deviate from peaks P4 and P5 of the histogram. For example, by bringing the generation timing of the second pulse signal PLS2 closer to the reception timing of the photon, it is possible to bring the position closer to the true position. Conversely, by moving the generation timing of the second pulse signal PLS2 away from the reception timing of the photon, the position will move away from the true position.

[0087] 11 to 16, the histogram generated in the first mode (level detection mode) can maintain a measurable S / N value even when the amount of ambient light increases. On the other hand, the peaks of the histogram generated in the first mode (level detection mode) tend to have wider half-value widths than those in the second mode (edge ​​detection mode).

[0088] The peak of the histogram generated in the second mode (edge ​​detection mode) has a narrower half-width, which improves measurement accuracy. Note that the generation timing of the second pulse signal PLS2 almost coincides with the reception timing of the photon, so the narrower the half-width, the closer the high-level signal period of the two-pulse signal PLS2 approaches the true position described above.

[0089] On the other hand, as the amount of ambient light increases, the S / N ratio decreases, and the measurement accuracy tends to be lower than in the first mode (level detection mode). Thus, the peaks of the histogram generated in the first mode (level detection mode) and the peaks of the histogram generated in the second mode (edge ​​detection mode) have a complementary relationship.

[0090] 17 is a diagram showing a more detailed example of the configuration of the control unit 150 (see FIG. 1). As shown in FIG. 17, the control unit 150 has an execution control unit 150a, an ambient light measurement unit 150b, a threshold setting unit 150c, and a generation instruction unit 150d. As described above, the execution control unit 150a controls the operation of the entire photodetector 20 in accordance with instructions from the overall control unit 30.

[0091] The disturbance light measuring unit 150b measures disturbance light during a disturbance light measurement period T1 (see FIG. 2). More specifically, during the disturbance light measurement period T1, the pixel array 100, the TDC 111, and the histogram generating unit 112 perform measurement in the first mode (level detection mode) without irradiating the laser light L0. This generates a histogram without irradiating the laser light L0.

[0092] The disturbance light measuring unit 150b calculates a statistical value such as the standard deviation of the count values ​​from the histogram when the laser light L0 is not irradiated as an evaluation value indicating the magnitude of the disturbance light. For example, in this embodiment, the standard deviation is used as the evaluation value, but this is not limiting. The evaluation value may be any numerical value that is added to the magnitude of the disturbance light, and for example, the average value of the count values ​​may also be used as the evaluation value.

[0093] The threshold setting unit 150c sets a threshold based on the evaluation value measured by the ambient light measuring unit 150b. This threshold is the elapsed time from the light emission timing TL0 (see FIG. 2). The threshold setting unit 150c decreases the threshold as the evaluation value increases.

[0094] The generation instruction unit 150d causes the pixel array 100, the TDC 111, and the histogram generation unit 112 to perform measurements using the thresholds set by the threshold setting unit 150c. That is, the generation instruction unit 150d sets the mode signal Smode for the pixel array 100 to the second mode (edge ​​detection mode) from light timing TL0 (see FIG. 2) until the light timing is less than the threshold, and to the first mode (level detection mode) when the light timing is equal to or greater than the threshold.

[0095] FIG. 18 is a diagram showing an example of control by the control unit 150 when there is less ambient light. FIG. 19 is a diagram showing an example of control by the control unit 150 when there is more ambient light. In FIGS. 18 and 19, (a) shows a histogram generated by the ambient light measurement unit 150b by having the pixel array 100, the TDC 111, and the histogram generation unit 112 perform measurement in the first mode (level detection mode) without irradiating the laser light L0 during the ambient light measurement period T1. The ambient light measurement unit 150b uses this histogram to generate an evaluation value. Note that the ambient light measurement period T1 can also be repeated in the same way as the measurement period.

[0096] 1B shows the threshold value th1 set by the threshold value setting unit 150c and the histogram generated by the generation instruction unit 150d. As shown in FIG. 1B, the generation instruction unit 150d generates a histogram in the second mode (edge ​​detection mode) in a time range in which the elapsed period from the light emission timing TL0 is shorter than the threshold value th1, and generates a histogram in the first mode (level detection mode) in a range in which the elapsed period is equal to or greater than the threshold value th1. More specifically, in a time range in which the elapsed period from the light emission timing TL0 is shorter than the threshold value th1, the generation instruction unit 150d causes each pixel 1000 to output a second pulse signal PLS2, and in a range in which the elapsed period is equal to or greater than the threshold value th1, the generation instruction unit 150d causes each pixel 1000 to output a first pulse signal PLS1.

[0097] This improves measurement accuracy in measurements at short distances. On the other hand, the S / N ratio improves in measurements at long distances. As the photons L1 return from longer distances depending on the time elapsed from the light emission timing TL0, the number of returning photons L1 decreases. Therefore, as the distance increases, the number of photons returning from the laser light L0 tends to decrease, and increasing the S / N ratio makes it possible to detect peaks.

[0098] On the other hand, as the distance to the object 50 decreases, the relative error to the measurement distance increases even if the deviation in the measurement value is the same. For this reason, higher measurement accuracy is required at close distances, and generating a histogram in the second mode (edge ​​detection mode) makes it possible to further improve measurement accuracy.

[0099] 19, when the evaluation value increases, the measurement range in the first mode (level detection mode) can be expanded by setting the threshold value th2 to a shorter time, thereby ensuring a sufficient S / N ratio. In this way, by determining the threshold values ​​th1 and th2 using an evaluation value indicating the magnitude of ambient light, it is possible to maintain an S / N ratio at which peaks can be detected throughout the entire measurement period. Furthermore, since a histogram is generated in the second mode (edge ​​detection mode) on the condition that an S / N ratio at which peaks can be detected can be maintained, higher measurement accuracy can be achieved at close ranges. As can be seen from these results, determining the threshold values ​​th1 and th2 using an evaluation value indicating the magnitude of ambient light reduces the influence of ambient light while suppressing a decrease in measurement accuracy at close ranges.

[0100] 20 is a diagram showing an example of an image displayed on the display operation device 70. Image 72 shows an example in which a threshold value and edge detection ranges and level detection ranges are superimposed on image data of a histogram generated by the main control device 60. The input operation unit 74a of the input unit 74 of the display operation device 70 is linked to the threshold value, and the threshold value can be set by the operator operating the input operation unit 74a. For example, when the operator operates the input operation unit 74a, the threshold value is transmitted to the threshold setting unit 150c, and is set as the threshold value for pixel 1000.

[0101] 21 is a diagram showing another example of an image displayed on the display / operation device 70. FIG. 21 shows an example of a preliminary measurement in which the entire range of the reflected light measurement period T2 is measured in the second mode. In this way, when the entire range is measured in the second mode, it becomes possible to set a threshold value for the measurable range more efficiently when measurement accuracy is important.

[0102] 22 is a diagram showing yet another example of an image displayed on the display / operation device 70. FIG. 22 shows an example of a preliminary measurement in which the entire range of the reflected light measurement period T2 is measured in the first mode. In this way, when the entire range is measured in the first mode, it becomes possible to set a threshold value for the measurable range more efficiently when prioritizing S / N.

[0103] Fig. 23 is a flowchart showing an example of the operation of the control unit 150. As shown in Fig. 22, the disturbance light measuring unit 150b measures the disturbance light during the disturbance light measurement period T1 (see Fig. 2) (step S100) and generates an evaluation value.

[0104] Next, the threshold setting unit 150c sets a threshold for the evaluation value measured by the ambient light measurement unit 150b (step S101). Subsequently, the generation instruction unit 150d causes the pixel array 100, the TDC 111, and the histogram generation unit 112 to perform measurements using the threshold set by the threshold setting unit 150c a predetermined number of times during the reflected light measurement period T2 (step S102).

[0105] Next, the histogram generation unit 112 outputs information about the finally generated histogram to the signal processing unit 113 (step S103). Then, the signal processing unit 113 generates a distance value from the finally generated histogram for each pixel 1000, and outputs the distance value to the main control device 60 via the output unit 170 (step S104), thereby completing the process.

[0106] As described above, in the distance measuring system 1 of this embodiment, multiple types of pulse signals PLAS1 and PLAS2 whose pulse widths increase as time passes from the time TL0 when the pixel 1000 is irradiated with the laser light L0 are generated in response to received photons. This makes it possible to reduce the influence of photon promiscuity by increasing the S / N ratio of the pulse signal PLAS1 on the long distance side while suppressing a decrease in measurement accuracy on the short distance side from the object 50.

[0107] <<Application Examples>> The technology according to the present disclosure can be applied to various products. For example, the technology according to the present disclosure may be realized as a unit mounted on any type of moving body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, a robot, construction machinery, or agricultural machinery (tractor).

[0108] 24 is a block diagram showing a schematic configuration example of a vehicle control system 7000, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied. The vehicle control system 7000 includes a plurality of electronic control units connected via a communication network 7010. In the example shown in FIG. 24 , the vehicle control system 7000 includes a drive system control unit 7100, a body system control unit 7200, a battery control unit 7300, an outside-vehicle information detection unit 7400, an inside-vehicle information detection unit 7500, and an integrated control unit 7600. The communication network 7010 connecting these multiple control units may be an in-vehicle communication network conforming to any standard, such as a Controller Area Network (CAN), a Local Interconnect Network (LIN), a Local Area Network (LAN), or FlexRay (registered trademark).

[0109] Each control unit includes a microcomputer that performs arithmetic processing according to various programs, a memory unit that stores the programs executed by the microcomputer or parameters used in various calculations, and a drive circuit that drives various control target components. Each control unit includes a network I / F for communicating with other control units via a communication network 7010, and a communication I / F for communicating with components or sensors inside and outside the vehicle via wired or wireless communication. Figure 24 illustrates the functional configuration of the integrated control unit 7600, including a microcomputer 7610, a general-purpose communication I / F 7620, a dedicated communication I / F 7630, a positioning unit 7640, a beacon receiving unit 7650, an in-vehicle device I / F 7660, an audio / video output unit 7670, an in-vehicle network I / F 7680, and a memory unit 7690. Other control units also include a microcomputer, a communication I / F, a memory unit, and the like.

[0110] The drivetrain control unit 7100 controls the operation of parts related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 7100 functions as a control unit for a drive force generating unit for generating drive force for the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking unit for generating braking force for the vehicle. The drivetrain control unit 7100 may also function as a control unit for an ABS (Antilock Brake System) or an ESC (Electronic Stability Control), etc.

[0111] A vehicle state detection unit 7110 is connected to the drivetrain control unit 7100. The vehicle state detection unit 7110 includes at least one of a gyro sensor that detects the angular velocity of the axial rotational motion of the vehicle body, an acceleration sensor that detects the acceleration of the vehicle, or a sensor that detects the amount of operation of the accelerator pedal, the amount of operation of the brake pedal, the steering angle of the steering wheel, the engine rotation speed, the rotation speed of the wheels, etc. The drivetrain control unit 7100 performs arithmetic processing using signals input from the vehicle state detection unit 7110, and controls the internal combustion engine, the drive motor, the electric power steering unit, the brake unit, etc.

[0112] The body system control unit 7200 controls the operation of various parts equipped in the vehicle body according to various programs. For example, the body system control unit 7200 functions as a control unit for a keyless entry system, a smart key system, a power window unit, or various lamps such as headlights, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches may be input to the body system control unit 7200. The body system control unit 7200 receives these radio waves or signals and controls the door lock unit, power window unit, lamps, etc. of the vehicle.

[0113] The battery control unit 7300 controls the secondary battery 7310, which is the power supply source for the drive motor, in accordance with various programs. For example, information such as battery temperature, battery output voltage, or remaining battery capacity is input to the battery control unit 7300 from a battery section equipped with the secondary battery 7310. The battery control unit 7300 performs arithmetic processing using these signals, and controls the temperature regulation of the secondary battery 7310 or a cooling section or the like equipped in the battery section.

[0114] The outside vehicle information detection unit 7400 detects information outside the vehicle equipped with the vehicle control system 7000. For example, at least one of an imaging unit 7410 and an outside vehicle information detection unit 7420 is connected to the outside vehicle information detection unit 7400. The imaging unit 7410 includes at least one of a ToF (Time Of Flight) camera, a stereo camera, a monocular camera, an infrared camera, and other cameras. The outside vehicle information detection unit 7420 includes at least one of an environmental sensor for detecting the current weather or climate, or a surrounding information detection sensor for detecting other vehicles, obstacles, pedestrians, etc. around the vehicle equipped with the vehicle control system 7000.

[0115] The environmental sensor may be, for example, at least one of a raindrop sensor that detects rain, a fog sensor that detects fog, a sunshine sensor that detects the degree of sunshine, and a snow sensor that detects snowfall. The surrounding information detection sensor may be at least one of an ultrasonic sensor, a radar unit, and a LIDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging) unit. The imaging unit 7410 and the outside vehicle information detection unit 7420 may each be provided as an independent sensor or unit, or may be provided as a unit in which multiple sensors or units are integrated.

[0116] 25 shows an example of the installation positions of the imaging unit 7410 and the vehicle exterior information detection unit 7420. The imaging units 7910, 7912, 7914, 7916, and 7918 are provided, for example, at least one of the front nose, side mirrors, rear bumper, back door, and upper part of the windshield inside the vehicle cabin of the vehicle 7900. The imaging unit 7910 provided on the front nose and the imaging unit 7918 provided on the upper part of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 7900. The imaging units 7912 and 7914 provided on the side mirrors mainly acquire images of the sides of the vehicle 7900. The imaging unit 7916 provided on the rear bumper or back door mainly acquires images of the rear of the vehicle 7900. The imaging unit 7918 provided on the upper part of the windshield inside the vehicle cabin is mainly used to detect leading vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0117] 25 shows an example of the imaging ranges of the imaging units 7910, 7912, 7914, and 7916. Imaging range a indicates the imaging range of the imaging unit 7910 provided on the front nose, imaging ranges b and c indicate the imaging ranges of the imaging units 7912 and 7914 provided on the side mirrors, respectively, and imaging range d indicates the imaging range of the imaging unit 7916 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 7910, 7912, 7914, and 7916, a bird's-eye view image of the vehicle 7900 viewed from above can be obtained.

[0118] The outside vehicle information detection units 7920, 7922, 7924, 7926, 7928, and 7930 provided on the front, rear, sides, corners, and above the windshield inside the vehicle cabin of the vehicle 7900 may be, for example, ultrasonic sensors or radar units. The outside vehicle information detection units 7920, 7926, and 7930 provided on the front nose, rear bumper, back door, and above the windshield inside the vehicle cabin of the vehicle 7900 may be, for example, LIDAR units. These outside vehicle information detection units 7920 to 7930 are mainly used to detect preceding vehicles, pedestrians, obstacles, etc.

[0119] Returning to FIG. 24 , the explanation will be continued. The outside-vehicle information detection unit 7400 causes the imaging unit 7410 to capture an image outside the vehicle and receives the captured image data. The outside-vehicle information detection unit 7400 also receives detection information from the connected outside-vehicle information detection unit 7420. If the outside-vehicle information detection unit 7420 is an ultrasonic sensor, a radar unit, or a LIDAR unit, the outside-vehicle information detection unit 7400 emits ultrasonic waves or electromagnetic waves and receives information on the received reflected waves. Based on the received information, the outside-vehicle information detection unit 7400 may perform object detection processing or distance detection processing for people, vehicles, obstacles, signs, text on the road, etc. Based on the received information, the outside-vehicle information detection unit 7400 may also perform environment recognition processing for recognizing rainfall, fog, road conditions, etc. Based on the received information, the outside-vehicle information detection unit 7400 may also calculate the distance to an object outside the vehicle.

[0120] The outside vehicle information detection unit 7400 may also perform image recognition processing or distance detection processing to recognize people, vehicles, obstacles, signs, or characters on the road surface based on the received image data. The outside vehicle information detection unit 7400 may perform processing such as distortion correction or alignment on the received image data, and may also generate an overhead image or a panoramic image by combining image data captured by different image capturing units 7410. The outside vehicle information detection unit 7400 may also perform viewpoint conversion processing using image data captured by different image capturing units 7410.

[0121] The interior information detection unit 7500 detects information inside the vehicle. A driver state detection unit 7510 that detects the driver's state is connected to the interior information detection unit 7500, for example. The driver state detection unit 7510 may include a camera that captures an image of the driver, a biosensor that detects the driver's biometric information, or a microphone that collects sound from within the vehicle cabin. The biosensor is provided, for example, on the seat or steering wheel, and detects the biometric information of a passenger sitting in the seat or the driver gripping the steering wheel. The interior information detection unit 7500 may calculate the driver's level of fatigue or concentration based on the detection information input from the driver state detection unit 7510, or may determine whether the driver is dozing off. The interior information detection unit 7500 may perform processing such as noise canceling on the collected audio signal.

[0122] The integrated control unit 7600 controls the overall operation of the vehicle control system 7000 in accordance with various programs. An input unit 7800 is connected to the integrated control unit 7600. The input unit 7800 is realized by a unit that can be operated by a passenger, such as a touch panel, a button, a microphone, a switch, or a lever. Data obtained by voice recognition of voice input through a microphone may be input to the integrated control unit 7600. The input unit 7800 may be, for example, a remote control unit that uses infrared or other radio waves, or an externally connected device such as a mobile phone or a personal digital assistant (PDA) that is compatible with the operation of the vehicle control system 7000. The input unit 7800 may be, for example, a camera, in which case the passenger can input information using gestures. Alternatively, data obtained by detecting the movement of a wearable unit worn by the passenger may be input. Furthermore, the input unit 7800 may include, for example, an input control circuit that generates an input signal based on information input by a passenger or the like using the input unit 7800 and outputs the signal to the integrated control unit 7600. The passenger or the like operates the input unit 7800 to input various data to the vehicle control system 7000 and to instruct processing operations.

[0123] The storage unit 7690 may include a ROM (Read Only Memory) that stores various programs executed by the microcomputer, and a RAM (Random Access Memory) that stores various parameters, calculation results, sensor values, etc. The storage unit 7690 may also be realized by a magnetic storage device such as a HDD (Hard Disc Drive), a semiconductor storage device, an optical storage device, a magneto-optical storage device, or the like.

[0124] The general-purpose communication I / F 7620 is a general-purpose communication I / F that mediates communication with various devices present in the external environment 7750. The general-purpose communication I / F 7620 may implement a cellular communication protocol such as GSM (registered trademark) (Global System of Mobile communications), WiMAX (registered trademark), LTE (registered trademark) (Long Term Evolution), or LTE-A (LTE-Advanced), or other wireless communication protocols such as a wireless LAN (also referred to as Wi-Fi (registered trademark)) or Bluetooth (registered trademark). The general-purpose communication I / F 7620 may connect to a device (e.g., an application server or a control server) present on an external network (e.g., the Internet, a cloud network, or an operator-specific network) via, for example, a base station or an access point. In addition, the general-purpose communication I / F 7620 may connect to a terminal located near the vehicle (for example, a terminal of a driver, a pedestrian, or a store, or an MTC (Machine Type Communication) terminal) using, for example, P2P (Peer To Peer) technology.

[0125] The dedicated communication I / F 7630 is a communication I / F that supports a communication protocol designed for use in a vehicle. The dedicated communication I / F 7630 may implement a standard protocol such as WAVE (Wireless Access in Vehicle Environment), which is a combination of IEEE 802.11p at a lower layer and IEEE 1609 at an upper layer, DSRC (Dedicated Short Range Communications), or a cellular communication protocol. The dedicated communication I / F 7630 performs V2X communication, which is a concept including one or more of, for example, vehicle-to-vehicle communication, vehicle-to-infrastructure communication, vehicle-to-home communication, and vehicle-to-pedestrian communication.

[0126] The positioning unit 7640 performs positioning by receiving, for example, GNSS signals from GNSS (Global Navigation Satellite System) satellites (for example, GPS signals from GPS (Global Positioning System) satellites) and generates position information including the latitude, longitude, and altitude of the vehicle. Note that the positioning unit 7640 may identify the current position by exchanging signals with a wireless access point, or may obtain position information from a terminal such as a mobile phone, PHS, or smartphone that has a positioning function.

[0127] The beacon receiving unit 7650 receives, for example, radio waves or electromagnetic waves transmitted from radio stations or the like installed on the road, and acquires information such as the current location, congestion, road closures, required travel time, etc. The function of the beacon receiving unit 7650 may be included in the dedicated communication I / F 7630 described above.

[0128] The in-vehicle device I / F 7660 is a communication interface that mediates connections between the microcomputer 7610 and various in-vehicle devices 7760 present in the vehicle. The in-vehicle device I / F 7660 may establish wireless connections using wireless communication protocols such as wireless LAN, Bluetooth (registered trademark), NFC (Near Field Communication), or WUSB (Wireless USB). The in-vehicle device I / F 7660 may also establish a wired connection such as USB (Universal Serial Bus), HDMI (registered trademark) (High-Definition Multimedia Interface), or MHL (Mobile High-Definition Link) via a connection terminal (and a cable, if necessary) not shown. The in-vehicle device 7760 may include, for example, at least one of a mobile device or a wearable device owned by a passenger, or an information device carried into or attached to the vehicle. The in-vehicle device 7760 may also include a navigation unit that searches for a route to an arbitrary destination. The in-vehicle device I / F 7660 exchanges control signals or data signals with these in-vehicle devices 7760.

[0129] The in-vehicle network I / F 7680 is an interface that mediates communication between the microcomputer 7610 and the communication network 7010. The in-vehicle network I / F 7680 transmits and receives signals in accordance with a predetermined protocol supported by the communication network 7010.

[0130] The microcomputer 7610 of the integrated control unit 7600 controls the vehicle control system 7000 according to various programs based on information acquired via at least one of the general-purpose communication I / F 7620, the dedicated communication I / F 7630, the positioning unit 7640, the beacon receiving unit 7650, the in-vehicle device I / F 7660, and the in-vehicle network I / F 7680. For example, the microcomputer 7610 may calculate control target values ​​for the driving force generating unit, the steering mechanism, or the braking unit based on the acquired information inside and outside the vehicle, and output control commands to the drivetrain control unit 7100. For example, the microcomputer 7610 may perform cooperative control aimed at realizing functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the following distance, vehicle speed maintenance driving, vehicle collision warning, vehicle lane departure warning, etc. In addition, the microcomputer 7610 may perform cooperative control for the purpose of autonomous driving, in which the vehicle travels autonomously without relying on driver operation, by controlling the driving force generating unit, steering mechanism, braking unit, etc. based on the information acquired about the vehicle's surroundings.

[0131] The microcomputer 7610 may generate three-dimensional distance information between the vehicle and objects such as surrounding structures and people, and may generate local map information including information about the vicinity of the vehicle's current location, based on information acquired via at least one of the general-purpose communication I / F 7620, the dedicated communication I / F 7630, the positioning unit 7640, the beacon receiving unit 7650, the in-vehicle device I / F 7660, and the in-vehicle network I / F 7680. Furthermore, the microcomputer 7610 may predict dangers, such as a vehicle collision, the approach of a pedestrian, or entry into a closed road, based on the acquired information, and generate a warning signal. The warning signal may be, for example, a signal for generating a warning sound or turning on a warning lamp.

[0132] The audio / video output unit 7670 transmits at least one audio and / or visual output signal to an output unit capable of visually or audibly notifying the vehicle occupants or the outside of the vehicle of information. In the example of FIG. 24 , an audio speaker 7710, a display unit 7720, and an instrument panel 7730 are illustrated as examples of the output units. The display unit 7720 may include, for example, at least one of an on-board display and a head-up display. The display unit 7720 may have an AR (Augmented Reality) display function. The output unit may be other units, such as headphones, a wearable device such as an eyeglass-type display worn by the occupant, a projector, or a lamp. When the output unit is a display unit, the display unit visually displays results obtained by various processes performed by the microcomputer 7610 or information received from other control units in various formats, such as text, images, tables, and graphs. Furthermore, when the output unit is an audio output unit, the audio output unit converts an audio signal consisting of reproduced audio data or acoustic data into an analog signal and outputs it audibly.

[0133] In the example shown in FIG. 24 , at least two control units connected via the communication network 7010 may be integrated into a single control unit. Alternatively, each control unit may be composed of multiple control units. Furthermore, the vehicle control system 7000 may include another control unit not shown. In the above description, some or all of the functions performed by one of the control units may be assigned to another control unit. In other words, as long as information is transmitted and received via the communication network 7010, predetermined arithmetic processing may be performed by one of the control units. Similarly, a sensor or unit connected to one of the control units may be connected to another control unit, and multiple control units may transmit and receive detection information to and from each other via the communication network 7010.

[0134] A computer program for realizing each function of the ranging system 1 according to this embodiment described with reference to FIG. 1 can be implemented in any control unit or the like. A computer-readable recording medium storing such a computer program can also be provided. Examples of the recording medium include a magnetic disk, an optical disk, a magneto-optical disk, and a flash memory. The computer program may also be distributed, for example, via a network without using a recording medium.

[0135] In the vehicle control system 7000 described above, the ranging system 1 according to the present embodiment described with reference to Fig. 1 can be applied to the integrated control unit 7600 of the application example shown in Fig. 24. For example, the ranging system 1 corresponds to the imaging unit 7410.

[0136] The present technology can be configured as follows:

[0137] (1) A photodetector that detects reflected light of a measurement laser beam from an object, comprising: a pixel that generates, in response to received photons, multiple types of pulse signals whose pulse widths increase according to the elapsed time from the time when the laser beam was irradiated; a time information generator that generates information on a first time range that corresponds to the pulse widths and indicates the elapsed time; a histogram generator that adds up a predetermined number of frequencies in a range corresponding to the first time range based on the information on the first time range, to generate a histogram indicating frequency values; and a signal processor that generates a distance value to the object based on the frequency values ​​of the histogram.

[0138] (2) The photodetector according to (1), wherein the pixel generates, as the plurality of types of pulse signals, a second pulse signal in accordance with the elapsed time, and then generates a first pulse signal having a pulse width wider than that of the second pulse signal.

[0139] (3) The photodetector according to (2), wherein the pixel includes a photoelectric conversion unit that generates an electrical signal whose value fluctuates in response to received photons; a pulse generation unit that can generate the first pulse signal, the pulse width of which is a range of the first signal, that fluctuates in response to a time during which the electrical signal fluctuates within a predetermined value range; and a second pulse signal that is generated based on the start of fluctuation of the electrical signal and in which the range of the first signal is fixed.

[0140] (4) The photodetector according to (3), wherein the first signal range of the first pulse signal is a second time range corresponding to a time during which the electrical signal exceeds a predetermined threshold, and the first signal range of the second pulse signal is a fixed third time range based on a timing at which the first pulse signal is generated.

[0141] (5) The photodetector according to (4), wherein the pulse generating unit outputs one of the first pulse signal and the second pulse signal.

[0142] (6) The photodetector according to (5), wherein the pulse generating unit outputs the first pulse signal after outputting the second pulse signal up to a threshold value that is a predetermined time elapsed from the time when the laser light is irradiated.

[0143] (7) The photodetection device according to (6), wherein the pulse generation unit changes the threshold value in accordance with the amount of ambient light received by the pixel.

[0144] (8) The light detection device according to (7), wherein the amount of the disturbance light is measured before measurement using the laser light is started.

[0145] (9) The light detection device according to (8), further comprising a disturbance light measurement unit that drives the pixels, the time information generation unit, and the histogram generation unit to generate a histogram during a disturbance light measurement time for measuring disturbance light before measurement using the laser light is started, and generates an evaluation value indicating the amount of disturbance light.

[0146] (10) The light detection device according to (9), further comprising: a threshold value generating unit that generates a threshold value that shortens the elapsed time as the amount of disturbance light increases, based on the evaluation value.

[0147] (11) The light detection device according to (10), wherein the ambient light measurement unit causes the pixel to output the first pulse signal during the ambient light measurement time.

[0148] (12) The photodetector according to (11), further comprising: a generation instruction unit that causes the measurement laser light to be pulsed light, repeatedly emits the pulsed light at a predetermined time interval, causes the pixel to output one of the first pulse signal and the second pulse signal based on the threshold during a reflected light measurement period within the time interval, causes the time information generation unit to generate information on the first time range of one of the first pulse signal and the second pulse signal, and causes the histogram generation unit to generate, during the measurement period during which the pulsed light is repeatedly emitted, a histogram indicating frequency values ​​by adding frequencies in a range corresponding to the first time range.

[0149] (13) The photodetector according to (12), wherein the photoelectric conversion unit is a single photon avalanche diode (SPAD), and the second time range is longer as a dead period until a recharge operation of the SPAD is completed is longer.

[0150] (14) The photodetector according to (13), wherein the first signal is a high-level signal, and the pulse generating unit includes: an inverter circuit that outputs the first pulse signal in response to the electrical signal; a pulse generating circuit that outputs the second pulse signal having a high-level signal in the third time range from an edge of the first pulse signal; and a multiplexer that selects and outputs the first pulse signal or the second pulse signal in response to a selection signal based on the threshold value.

[0151] (15) A ranging system comprising: an emitting device that irradiates an object with measurement laser light; and an optical detection device that receives reflected light from the object, wherein the optical detection device has: pixels that generate, in response to received photons, multiple types of pulse signals whose pulse width increases according to the elapsed time since the laser light was irradiated; a time information generation unit that generates information on a first time range that corresponds to the pulse width and indicates the elapsed time; a histogram generation unit that adds up a predetermined number of frequencies in a range corresponding to the first time range based on the information on the first time range to generate a histogram indicating frequency values; and a signal processing unit that generates a distance value to the object based on the frequency values ​​of the histogram.

[0152] (16) The ranging system according to (15), wherein the light detection device further has an output unit that outputs information about the histogram, a main control device that visualizes the histogram based on the information about the histogram, and a display operation device that displays the visualized histogram.

[0153] (17) The ranging system described in (16), wherein the pixel has: a photoelectric conversion unit that generates an electrical signal whose value fluctuates according to received photons; a pulse generation unit that is capable of generating a first pulse signal whose pulse width, that is, the range of the first signal, fluctuates according to the time during which the electrical signal fluctuates within a predetermined value range; and a second pulse signal that is generated based on the start of fluctuation of the electrical signal and in which the range of the first signal is fixed.

[0154] (18) The ranging system described in (17), wherein the pulse generating unit outputs the first pulse signal after outputting the second pulse signal up to a threshold value that is a predetermined elapsed time from the time the laser light is irradiated, the main control unit associates the threshold value with a histogram and images it, the display operation device has an operation unit that changes the position of an image of the second threshold value that indicates the position of the imaged threshold value, and the light detection device is capable of changing the threshold value of the pulse generating unit using information on the threshold value corresponding to the position of the second threshold value input from the display operation device.

[0155] (19) The ranging system according to (18), wherein in the case of a preliminary measurement in which the threshold value and a histogram are associated with each other to generate an image, the pulse generating unit outputs only the first pulse signal or only the second pulse signal.

[0156] (20) The ranging system described in (19), wherein the photodetector has a pixel array in which a plurality of the pixels are arranged in a matrix, and the time information generating unit, the histogram generating unit, and the signal processing unit process the first pulse signal and the second pulse signal output for each of the plurality of pixels.

[0157] The aspects of the present disclosure are not limited to the individual embodiments described above, but include various modifications that may be conceived by those skilled in the art, and the effects of the present disclosure are not limited to the above-described contents. In other words, various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and spirit of the present disclosure, which is derived from the contents defined in the claims and their equivalents.

[0158] 1: ranging system, 10: light emitting device, 20: light detection device, 50: object, 60: main control device, 70: display operation device, 100: pixel array, 111: TDC unit, 112: histogram generation unit, 113: signal processing unit, 170: output unit, 1000: pixel, 1001: electrical conversion unit, 1004: pulse generation unit, 1004a: inverter, 1004b: readout circuit, 1006: pulse generation circuit, 1007: selection circuit, L0: laser light, L1: photon, PLS1: first pulse signal, PLS2: second pulse signal, tPLS1, tPLS2: first time range (period), TL0: light emission timing, th1, th2: threshold, Vca: voltage (electrical signal), Vth: threshold voltage.

Claims

1. A photodetection device that detects reflected light of a measurement laser light from an object, comprising: pixels that generate, in response to received photons, multiple types of pulse signals whose pulse widths increase according to the elapsed time from the time when the laser light was irradiated; a time information generation unit that generates information of a first time range that corresponds to the pulse width and indicates the elapsed time; a histogram generation unit that generates a histogram indicating frequency values ​​by adding up a predetermined number of frequencies in a range corresponding to the first time range based on the information of the first time range; and a signal processing unit that generates a distance value to the object based on the frequency value of the histogram.

2. The photodetection device of claim 1, wherein the pixel generates, as the multiple types of pulse signals, a second pulse signal in accordance with the elapsed time, and then generates a first pulse signal having a wider pulse width than the second pulse signal.

3. The photodetection device of claim 2, wherein the pixel has: a photoelectric conversion unit that generates an electrical signal whose value varies according to received photons; and a pulse generation unit that is capable of generating: a first pulse signal whose first signal range corresponding to the pulse width varies according to the time during which the electrical signal varies within a predetermined value range; and a second pulse signal that is generated based on the start of the fluctuation of the electrical signal and whose first signal range is fixed.

4. The optical detection device of claim 3, wherein the first signal range of the first pulse signal is a second time range corresponding to the time during which the electrical signal exceeds a predetermined threshold, and the first signal range of the second pulse signal is a fixed third time range based on the timing at which the first pulse signal is generated.

5. The photodetection device according to claim 4, wherein the pulse generating section outputs one of the first pulse signal and the second pulse signal.

6. The optical detection device of claim 5, wherein the pulse generating unit outputs the second pulse signal up to a threshold value that is a predetermined elapsed time from the time when the laser light is irradiated, and then outputs the first pulse signal.

7. The light detection device according to claim 6, wherein the pulse generating section changes the threshold value in accordance with the amount of disturbance light received by the pixel.

8. The light detection device according to claim 7, wherein the amount of the disturbance light is measured before measurement using the laser light is started.

9. The optical detection device described in claim 8, further comprising a disturbance light measurement unit that drives the pixels, the time information generation unit, and the histogram generation unit to generate a histogram during a disturbance light measurement time for measuring disturbance light before measurement using the laser light is started, and generates an evaluation value indicating the amount of disturbance light.

10. The light detection device according to claim 9, further comprising a threshold generation section that generates a threshold that shortens the elapsed time as the amount of disturbance light increases based on the evaluation value.

11. The light detection device according to claim 10, wherein the disturbance light measurement section causes the pixel to output the first pulse signal during the disturbance light measurement time.

12. The optical detection device of claim 11, further comprising a generation instruction unit that causes the measurement laser light to be pulsed light, repeatedly emits the pulsed light at a predetermined time interval, outputs one of the first pulse signal and the second pulse signal to the pixel based on the threshold during a reflected light measurement period within the time interval, causes the time information generating unit to generate information of the first time range of one of the first pulse signal and the second pulse signal, and causes the histogram generating unit to generate a histogram indicating a frequency value by adding up frequencies of a range corresponding to the first time range during the measurement period during which the pulsed light is repeatedly emitted.

13. The photodetector according to claim 12, wherein the photoelectric conversion unit is a SPAD (Single Photon Avalanche Diode), and the second time range is longer as a dead period until a recharge operation of the SPAD is completed is longer.

14. The photodetection device of claim 13, wherein the first signal is a high-level signal, and the pulse generating section comprises: an inverter circuit that outputs the first pulse signal in response to the electrical signal; a pulse generating circuit that outputs the second pulse signal having a high-level signal in the third time range from an edge of the first pulse signal; and a multiplexer that selects and outputs the first pulse signal or the second pulse signal in response to a selection signal based on the threshold value.

15. A distance measuring system comprising: an emitting device which irradiates an object with a measurement laser light; and an optical detection device which receives reflected light from the object, wherein the optical detection device has: pixels which generate, in response to the received photons, multiple types of pulse signals whose pulse width increases according to the time elapsed since the laser light was irradiated; a time information generating unit which generates information of a first time range which corresponds to the pulse width and indicates the elapsed time; a histogram generating unit which generates a histogram indicating frequency values ​​by adding up a predetermined number of frequencies in a range corresponding to the first time range based on the information of the first time range; and a signal processing unit which generates a distance value to the object based on the frequency value of the histogram.

16. The ranging system of claim 15, further comprising: an output section for outputting information regarding the histogram; a main control device for imaging the histogram based on the information regarding the histogram; and a display operation device for displaying the imaged histogram.

17. A ranging system as described in claim 16, wherein the pixel has: a photoelectric conversion unit that generates an electrical signal whose value changes according to received photons; and a pulse generation unit capable of generating a first pulse signal whose range of the first signal, which is the pulse width, changes according to the time during which the electrical signal changes within a predetermined value range; and a second pulse signal that is generated based on the start of the fluctuation of the electrical signal and whose range of the first signal is fixed.

18. The ranging system described in claim 17, wherein the pulse generating unit outputs the first pulse signal after outputting the second pulse signal up to a threshold value that is a predetermined elapsed time from the time when the laser light was irradiated, the main control unit associates the threshold value with a histogram and images it, the display operation device has an operation unit that changes the position of an image of the second threshold value that indicates the position of the imaged threshold value, and the light detection device is capable of changing the threshold value of the pulse generating unit using information on the threshold value corresponding to the position of the second threshold value input from the display operation device.

19. The distance measuring system according to claim 18, wherein in the case of a preliminary measurement in which the threshold value is associated with a histogram and an image is generated, the pulse generating unit outputs only the first pulse signal or only the second pulse signal.

20. The ranging system of claim 19, wherein the optical detection device has a pixel array in which a plurality of the pixels are arranged in a matrix, and the time information generating unit, the histogram generating unit, and the signal processing unit process the first pulse signal and the second pulse signal output for each of the plurality of the pixels.

Images