Optical detection device and optical detection system

Abstract

A photo-detection device according to the present disclosure is provided with: a light receiving unit that has a light receiving element and that generates a pulsed signal including pulses according to light receiving results of the light receiving element; a plurality of switches that are turned on / off on the basis of a plurality of respective control signals and that each transmit a pulsed signal as a result of being brought into an on state in a pulse period of the corresponding control signal of the plurality of control signals; a plurality of counters that are provided so as to correspond to the plurality of switches and that each generate a first count value as a result of performing count processing on the basis of the pulsed signal supplied via the corresponding switch of the plurality of switches; and a signal generation unit that generates the plurality of control signals in a detection period so as to successively shift the pulse period in each of the plurality of control signals by a unit period having a time duration shorter than the pulse period.

Description

[Technical Field]

[0001] The present disclosure relates to a light detection device and a light detection system for detecting light. [Background technology]

[0002] The TOF (Time Of Flight) method is often used to measure the distance to a detection target. In this TOF method, light is emitted and the light reflected by the detection target is detected. The TOF method measures the distance to the detection target by measuring the time difference between the timing at which the light is emitted and the timing at which the reflected light is detected. For example, Patent Document 1 discloses a distance measuring device that selectively accumulates electric charges generated by a light receiving element in one of two charge accumulation units. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-77143 Summary of the Invention

[0004] In the photodetector, Light detection timing It is desirable to improve detection accuracy, and further improvements in detection accuracy are expected.

[0005] Light detection timing It is desirable to provide a light detection device and a light detection system that can increase detection accuracy.

[0006] A photodetector according to an embodiment of the present disclosure includes a light receiving unit, a plurality of switches, a plurality of counters, a signal generating unit, and a processing unit. Able to detect light pulsesThe device has a light-receiving element and is configured to generate a pulse signal including a pulse corresponding to the light-receiving result of the light-receiving element. The multiple switches are respectively turned on and off based on multiple control signals, and each is configured to transmit a pulse signal by being on during the pulse period of a corresponding one of the multiple control signals. The multiple counters are provided corresponding to the multiple switches, and each is configured to generate a first count value by performing counting processing based on the pulse signal supplied via the corresponding one of the multiple switches. The signal generating unit is configured to generate the multiple control signals so that the pulse period of each of the multiple control signals is sequentially shifted by a unit period having a time length shorter than the pulse period during the detection period. The processing unit calculates a second count value for each of the multiple unit periods based on the first count values ​​of each of the multiple counters. and determining a component of the optical pulse based on two second count values ​​including the optical pulse component among the plurality of second count values. The optical timing sensor is configured to calculate the light detection timing.

[0007] An optical detection system according to an embodiment of the present disclosure includes a light emitting unit and an optical detecting unit. The light emitting unit is configured to emit light. The optical detecting unit is configured to detect light reflected by a detection target from the light emitting unit. The optical detecting unit includes: Able to detect light pulsesThe detector includes a light receiving unit, a plurality of switches, a plurality of counters, a signal generating unit, and a processing unit. The light receiving unit has a light receiving element and is configured to generate a pulse signal including a pulse corresponding to the light receiving result of the light receiving element. The plurality of switches are respectively turned on and off based on a plurality of control signals, and each is configured to transmit a pulse signal by being in an on state during a pulse period of a corresponding one of the plurality of control signals. The plurality of counters are provided corresponding to the plurality of switches, and each is configured to generate a first count value by performing count processing based on a pulse signal supplied via a corresponding one of the plurality of switches. The signal generating unit is configured to generate a plurality of control signals so as to sequentially shift the pulse period of each of the plurality of control signals by a unit period having a time length shorter than the pulse period during the detection period. The processing unit calculates a second count value for each of the plurality of unit periods based on the first count values ​​of each of the plurality of counters. and determining a component of the optical pulse based on two second count values ​​including the optical pulse component among the plurality of second count values. The optical timing sensor is configured to calculate the light detection timing.

[0008] In a photodetector and a photodetection system according to an embodiment of the present disclosure, a pulse signal including a pulse corresponding to a light receiving result of a light receiving element is generated. The pulse signal is supplied to a plurality of counters by a plurality of switches being turned on and off based on a plurality of control signals. Each of the plurality of switches is turned on during a pulse period of the control signal, thereby supplying the pulse signal to the counter. Each of the plurality of counters performs a counting process based on the pulse signal supplied from the switch, and generates a first count value. The plurality of control signals are generated such that the pulse period of each of the plurality of control signals is sequentially shifted by a unit period having a time length shorter than the pulse period. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a block diagram illustrating an example configuration of a light detection system according to an embodiment of the present disclosure. [Figure 2]2 is a block diagram illustrating an example of the configuration of a light detection unit illustrated in FIG. 1. FIG. [Figure 3] 3 is a circuit diagram illustrating an example of the configuration of the photodetection unit illustrated in FIG. 2. FIG. [Figure 4A] 4 is a circuit diagram illustrating an example of the configuration of the light receiving section illustrated in FIG. 3. [Figure 4B] 4 is a circuit diagram illustrating another example of the configuration of the light receiving section shown in FIG. 3. [Figure 5] 3 is a block diagram illustrating an example of the configuration of a signal generating unit illustrated in FIG. 2. FIG. [Figure 6] 2 is a timing waveform diagram illustrating an example of the operation of the photodetection system shown in FIG. 1. [Figure 7] 3 is an explanatory diagram illustrating an example of an operation of the signal processing unit illustrated in FIG. 2. [Figure 8] 3 is another explanatory diagram illustrating an example of the operation of the signal processing unit illustrated in FIG. 2.

[0023] FIG [Figure 9] FIG. 10 is a circuit diagram illustrating a configuration example of a light detection unit according to a comparative example. [Figure 10] FIG. 10 is a timing waveform diagram illustrating an example of operation of a photodetection system according to a comparative example. [Figure 11] FIG. 10 is an explanatory diagram illustrating an example of an operation of a signal processing unit according to a comparative example. [Figure 12] FIG. 10 is an explanatory diagram illustrating an example of a characteristic of a distance measurement error. [Figure 13] FIG. 10 is an explanatory diagram illustrating another example of characteristics of distance measurement errors. [Figure 14] FIG. 10 is a block diagram illustrating an example of the configuration of a signal generating unit according to a modified example. [Figure 15] FIG. 10 is a block diagram illustrating an example of the configuration of a light detection unit according to a modified example. [Figure 16] FIG. 10 is a block diagram illustrating an example of the configuration of a light detection unit according to another modified example. [Figure 17] FIG. 10 is a timing waveform diagram illustrating an example of an operation of a light detection system according to another modified example. [Figure 18] FIG. 10 is a block diagram illustrating an example of the configuration of a light detection unit according to another modified example. [Figure 19]FIG. 10 is a timing waveform diagram illustrating an example of an operation of a light detection system according to another modified example. [Figure 20] FIG. 10 is an explanatory diagram illustrating an example of an operation of a signal processing unit according to another modified example. [Figure 21] FIG. 10 is an explanatory diagram illustrating an example of an operation of a signal processing unit according to another modified example. [Figure 22] FIG. 10 is an explanatory diagram illustrating an example of an operation of a signal processing unit according to another modified example. [Figure 23] FIG. 10 is an explanatory diagram illustrating an example of an operation of a signal processing unit according to another modified example. [Figure 24] FIG. 10 is a block diagram illustrating an example of the configuration of a light detection unit according to another modified example. [Figure 25] FIG. 10 is a timing waveform diagram illustrating an example of an operation of a light detection system according to another modified example. [Figure 26] FIG. 10 is a block diagram illustrating an example of the configuration of a light detection unit according to another modified example. [Figure 27] FIG. 10 is a timing waveform diagram illustrating an example of an operation of a light detection system according to another modified example. [Figure 28] FIG. 10 is an explanatory diagram illustrating an example of an operation of a signal processing unit according to another modified example. [Figure 29] FIG. 10 is an explanatory diagram illustrating an example of an operation of a signal processing unit according to another modified example. [Figure 30A] FIG. 10 is a circuit diagram illustrating an example of the configuration of a light receiving section according to another modified example. [Figure 30B] FIG. 10 is a circuit diagram illustrating an example of the configuration of a light receiving section according to another modified example. [Figure 31] FIG. 10 is a block diagram illustrating an example of the configuration of a light detection unit according to another modified example. [Figure 32] 10A and 10B are explanatory diagrams illustrating an example of an implementation of a light detection unit according to another modified example. [Figure 33] FIG. 10 is a circuit diagram illustrating an example of the configuration of a light receiving section according to another modified example. [Figure 34] 10A and 10B are explanatory diagrams illustrating an example of an implementation of a light detection unit according to another modified example. [Figure 35] 10A and 10B are explanatory diagrams illustrating an example of an implementation of a light detection unit according to another modified example. [Figure 36]1 is a block diagram showing an example of a schematic configuration of a vehicle control system; [Figure 37] FIG. 2 is an explanatory diagram showing an example of the installation positions of an outside-vehicle information detection unit and an imaging unit. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be made in the following order. 1. Embodiment 2. Mobile application examples

[0011] <1. Embodiment> [Configuration example] 1 shows an example of the configuration of a light detection system (light detection system 1) according to one embodiment. The light detection system 1 is a ToF sensor configured to emit light and detect light reflected by a detection target object OBJ. The light detection system 1 includes a light emitter 11, an optical system 12, a light detector 20, and a controller 14.

[0012] The light emitting unit 11 is configured to emit a light pulse L0 toward the detection object OBJ based on an instruction from the control unit 14. The light emitting unit 11 emits the light pulse L0 by performing a light emitting operation that alternately repeats light emission and non-emission based on an instruction from the control unit 14. The light emitting unit 11 has a light source that emits, for example, infrared light. This light source is configured using, for example, a laser light source or an LED (Light Emitting Diode).

[0013] The optical system 12 includes a lens that forms an image on the light receiving surface S of the light detection unit 20. A light pulse (reflected light pulse L1) that is emitted from the light emitting unit 11 and reflected by the detection object OBJ is incident on this optical system 12.

[0014] The light detection unit 20 is configured to detect the reflected light pulse L1 based on instructions from the control unit 14. The light detection unit 20 then generates a distance image based on the detection result, and outputs image data of the generated distance image as data DT.

[0015] The control unit 14 is configured to control the operation of the light detection system 1 by supplying control signals to the light emitting unit 11 and the light detecting unit 20 and controlling their operations.

[0016] 2 shows an example of the configuration of the photodetector 20. The photodetector 20 includes a photodetector array 21, a signal generator 30, a readout controller 23, a signal processor 24, and a photodetection controller 25.

[0017] The photodetector array 21 has a plurality of photodetector units U arranged in a matrix. The photodetector units U are configured to detect reflected light pulses L1 and count the number of times they are detected.

[0018] 3 shows an example of the configuration of the light detection unit U. The light detection unit U has a light receiving unit DET, a plurality of switches SW (eight switches SW1 to SW8 in this example), and a plurality of counters CNT (eight counters CNT1 to CNT8 in this example).

[0019] The light receiving unit DET is configured to detect light and thereby generate a pulse signal PLS having pulses according to the detected light.

[0020] 4A shows an example of the configuration of the light receiving unit DET. In this example, the light receiving unit DET has a photodiode PD, a resistor R1, and an inverter IV1.

[0021] The photodiode PD is a photoelectric conversion element that converts light into an electric charge. The power supply voltage VSS is supplied to the anode of the photodiode PD, and the cathode is connected to the node N1. The photodiode PD can be, for example, an avalanche photodiode (APD) or a single photon avalanche diode (SPAD).

[0022] The power supply voltage VDD is supplied to one end of the resistor element R1, and the other end is connected to a node N1.

[0023] The inverter IV1 is configured to generate the pulse signal PLS by outputting a low level when the voltage at the node N1 is higher than the logic threshold and outputting a high level when the voltage at the node N1 is lower than the logic threshold.

[0024] With this configuration, in the light-receiving unit DET, when the photodiode PD detects light, avalanche amplification occurs, causing the voltage at node N1 to drop. When the voltage at node N1 drops below the logic threshold of inverter IV1, the pulse signal PLS changes from low to high. Thereafter, current flows to node N1 via resistor R1, causing the voltage at node N1 to rise. When the voltage at node N1 rises above the logic threshold of inverter IV1, the pulse signal PLS changes from high to low. In this way, the light-receiving unit DET generates a pulse signal PLS having a pulse corresponding to the detected light.

[0025] 4B shows another example of the configuration of the light receiving unit DET. In this example, the light receiving unit DET has a photodiode PD, a transistor MP1, an inverter IV1, and a control circuit CKT1.

[0026] The transistor MP1 is a P-type MOS (Metal Oxide Semiconductor) transistor, with its gate connected to the output terminal of the control circuit CKT1, its source supplied with the power supply voltage VDD, and its drain connected to the node N1.

[0027] The control circuit CKT1 is configured to control the operation of the transistor MP1 based on the pulse signal PLS, specifically, the control circuit CKT1 sets the voltage of the gate of the transistor MP1 to a low level after the pulse signal PLS changes from a low level to a high level, and sets the voltage of the gate of the transistor MP1 to a high level after the pulse signal PLS changes from a high level to a low level.

[0028] With this configuration, in the light-receiving unit DET, when the photodiode PD detects light, the voltage at node N1 drops. When the voltage at node N1 drops below the logic threshold of the inverter IV1, the pulse signal PLS changes from low to high. After this change in pulse signal PLS, the control circuit CKT1 sets the voltage at the gate of transistor MP1 to low. This turns on the transistor MP1, causing current to flow to node N1 via the transistor MP1, increasing the voltage at node N1. When the voltage at node N1 rises above the logic threshold of the inverter IV1, the pulse signal PLS changes from high to low. After this change in pulse signal PLS, the control circuit CKT1 sets the voltage at the gate of transistor MP1 to high. This turns off the transistor MP1. In this way, the light-receiving unit DET generates a pulse signal PLS having a pulse corresponding to the detected light.

[0029] The switch SW1 (FIG. 3) is configured to turn on and off the supply of the pulse signal PLS to the counter CNT1 based on the control signal EN1. Specifically, the switch SW1 supplies the signal portion included in the pulse signal PLS to the counter CNT1 during a period (pulse period P1C) when the control signal EN1 is active (high level in this example), and supplies a low-level signal to the counter CNT1 during a period when the control signal EN1 is inactive (low level in this example). The switch SW1 is configured using, for example, a logical product (AND) circuit or a logical sum (OR) circuit.

[0030] Similarly, the switch SW2 is configured to turn on and off the supply of the pulse signal PLS to the counter CNT2 based on a control signal EN2. The switch SW3 is configured to turn on and off the supply of the pulse signal PLS to the counter CNT3 based on a control signal EN3. The switch SW4 is configured to turn on and off the supply of the pulse signal PLS to the counter CNT4 based on a control signal EN4. The switch SW5 is configured to turn on and off the supply of the pulse signal PLS to the counter CNT5 based on a control signal EN5. The switch SW6 is configured to turn on and off the supply of the pulse signal PLS to the counter CNT6 based on a control signal EN6. The switch SW7 is configured to turn on and off the supply of the pulse signal PLS to the counter CNT7 based on a control signal EN7. The switch SW8 is configured to turn on and off the supply of the pulse signal PLS to the counter CNT8 based on a control signal EN8.

[0031] Counter CNT1 is configured to increment a count value CO1 by performing a counting process based on the rising edge of the pulse signal PLS supplied from switch SW1. Similarly, counter CNT2 is configured to increment a count value CO2 by performing a counting process based on the rising edge of the pulse signal PLS supplied from switch SW2. Counter CNT3 is configured to increment a count value CO3 by performing a counting process based on the rising edge of the pulse signal PLS supplied from switch SW3. Counter CNT4 is configured to increment a count value CO4 by performing a counting process based on the rising edge of the pulse signal PLS supplied from switch SW4. Counter CNT5 is configured to increment a count value CO5 by performing a counting process based on the rising edge of the pulse signal PLS supplied from switch SW5. Counter CNT6 is configured to increment a count value CO6 by performing a counting process based on the rising edge of the pulse signal PLS supplied from switch SW6. Counter CNT7 is configured to increment a count value CO7 by performing a counting process based on the rising edge of the pulse signal PLS supplied from switch SW7. The counter CNT8 is configured to increment a count value CO8 by performing counting processing based on the rising edge of the pulse signal PLS supplied from the switch SW8.

[0032] The signal generating section 30 (FIG. 2) is configured to generate control signals EN1 to EN8 based on instructions from the light detection control section 25, and to supply the generated control signals EN1 to EN8 to the plurality of light detection units U in the light detection array .

[0033] 5 shows an example of the configuration of the signal generating unit 30. The signal generating unit 30 has a control signal generating unit 31, a clock signal generating unit 32, flip-flops (F / F) 33 to 39, and drivers DRV1 to DRV8.

[0034] The control signal generating unit 31 is configured to generate a signal EN1A synchronized with the clock signal CLK. The clock signal generating unit 32 is configured to generate the clock signal CLK.

[0035] Each of the flip-flops 33 to 39 is a D-type flip-flop configured to sample a signal input to a data terminal D based on the rising edge of a clock signal CLK supplied to a clock terminal CK and output the sampled signal from an output terminal Q. The flip-flops 33 to 39 form a shift register, with the flip-flops 33, 34, 35, 36, 37, 38, and 39 connected in this order. A signal EN1A generated by the control signal generator 31 is supplied to the data terminal D of the flip-flop 33, which is the first-stage circuit of the shift register. The flip-flops 33 to 39 then generate signals EN2A to EN8A, respectively. The waveform of the signal EN2A is delayed by one cycle of the clock signal CLK from the waveform of the signal EN1A. The waveform of the signal EN3A is delayed by one cycle of the clock signal CLK from the waveform of the signal EN2A. The waveform of signal EN4A is obtained by delaying the waveform of signal EN3A by one cycle of the clock signal CLK. The waveform of signal EN5A is obtained by delaying the waveform of signal EN4A by one cycle of the clock signal CLK. The waveform of signal EN6A is obtained by delaying the waveform of signal EN5A by one cycle of the clock signal CLK. The waveform of signal EN7A is obtained by delaying the waveform of signal EN6A by one cycle of the clock signal CLK. The waveform of signal EN8A is obtained by delaying the waveform of signal EN7A by one cycle of the clock signal CLK.

[0036] The drivers DRV1 to DRV8 are configured to supply control signals EN1 to EN8 to the plurality of photodetector units U in the photodetector array 21. The driver DRV1 is configured to generate a control signal EN1 based on a signal EN1A. The driver DRV2 is configured to generate a control signal EN2 based on a signal EN2A. The driver DRV3 is configured to generate a control signal EN3 based on a signal EN3A. The driver DRV4 is configured to generate a control signal EN4 based on a signal EN4A. The driver DRV5 is configured to generate a control signal EN5 based on a signal EN5A. The driver DRV6 is configured to generate a control signal EN6 based on a signal EN6A. The driver DRV7 is configured to generate a control signal EN7 based on a signal EN7A. The driver DRV8 is configured to generate a control signal EN8 based on a signal EN8A.

[0037] The readout control unit 23 (FIG. 2) is configured to control the operation of supplying the count values ​​CO1 to CO8 generated in each of the multiple photodetection units U in the photodetection array 21 to the signal processing unit 24 based on instructions from the photodetection control unit 25. The readout control unit 23 is configured to sequentially select, for example, one row of photodetection units U on a row-by-row basis and control the operation of the multiple photodetection units U so that the selected photodetection units U supply the count values ​​CO1 to CO8 to the signal processing unit 24.

[0038] Signal processing unit 24 is configured to generate a distance image based on instructions from light detection control unit 25. Specifically, signal processing unit 24 detects the timing at which reflected light pulse L1 is received by each of multiple light detection units U in light detection array 21, based on count values ​​CO1 to CO8 supplied from that light detection unit U. Signal processing unit 24 generates the distance image by measuring the time (TOF value) from when light emitter 11 emits light pulse L0 to when light detection unit U detects reflected light pulse L1. Signal processing unit 24 then outputs image data of the generated distance image as data DT.

[0039] The light detection control unit 25 is configured to control the operation of the light detection unit 20 by supplying control signals to the signal generation unit 30, the readout control unit 23, and the signal processing unit 24 based on instructions from the control unit 14 (Figure 1) and controlling their operations.

[0040] Here, the light receiving unit DET corresponds to a specific example of a "light receiving unit" in the present disclosure. The photodiode PD corresponds to a specific example of a "light receiving element" in the present disclosure. The pulse signal PLS corresponds to a specific example of a "pulse signal" in the present disclosure. The switches SW1 to SW8 correspond to a specific example of a "plurality of switches" in the present disclosure. The control signals EN1 to EN8 correspond to a specific example of a "plurality of control signals" in the present disclosure. The counters CNT1 to CNT8 correspond to a specific example of a "plurality of counters" in the present disclosure. The signal generating unit 30 corresponds to a specific example of a "signal generating unit" in the present disclosure. The signal processing unit 24 corresponds to a specific example of a "processing unit" in the present disclosure.

[0041] [Actions and Actions] Next, the operation and function of the light detection system 1 according to this embodiment will be described.

[0042] (Overview of overall operation) First, an overview of the overall operation of the light detection system 1 will be described with reference to Figures 1 and 2. The light emitter 11 emits a light pulse L0 toward the detection object OBJ. The optical system 12 forms an image on the light-receiving surface S of the light detector 20. The light detector 20 detects the reflected light pulse L1. The controller 14 supplies control signals to the light emitter 11 and the light detector 20 and controls their operations, thereby controlling the distance measurement operation of the light detection system 1.

[0043] In the photodetector 20, the photodetector units U of the photodetector array 21 detect the reflected light pulse L1 and generate count values ​​CO1-CO8. The signal generator 30 generates control signals EN1-EN8 and supplies these control signals EN1-EN8 to the multiple photodetector units U. The readout controller 23 controls the operation of supplying the count values ​​CO1-CO8 generated by each of the multiple photodetector units U in the photodetector array 21 to the signal processor 24. The signal processor 24 generates a distance image based on the count values ​​CO1-CO8 supplied from the multiple photodetector units U in the photodetector array 21 and outputs image data of the generated distance image as data DT. The photodetector controller 25 supplies control signals to the signal generator 30, the readout controller 23, and the signal processor 24 based on instructions from the controller 14, and controls the operation of these components, thereby controlling the operation of the photodetector 20.

[0044] (Detailed operation) Figure 6 shows an example of the operation of the light detection system 1, where (A) shows the waveform of light emitted from the light emitting unit 11, (B) shows the waveform of light reflected by the object to be detected OBJ and incident on a certain light detection unit U, (C) to (J) show the waveforms of the control signals EN1 to EN8, respectively, (K) to (R) show the waveforms of the count values ​​CO1 to CO8, respectively, and (S) shows the operation of the read control unit 23.

[0045] During the period from timing t11 to t22 (exposure period P1), the light detection system 1 repeatedly emits a light pulse L0 and repeatedly detects a reflected light pulse L1 reflected by the detection object OBJ.

[0046] Specifically, during the period from timing t11 to t12, the light emitting unit 11 emits a light pulse L0 (FIG. 6(A)).

[0047] The signal generating unit 30 sets the control signal EN1 to a high level during the period from timing t11 to t14 (FIG. 6(C)). The length of the period (pulse period P1C) during which the control signal EN1 is at a high level corresponds to three unit periods P1A. Similarly, the signal generating unit 30 sets the control signal EN2 to a high level during the period from timing t12 to t15, the control signal EN3 to a high level during the period from timing t13 to t16, the control signal EN4 to a high level during the period from timing t14 to t17, the control signal EN5 to a high level during the period from timing t15 to t18, the control signal EN6 to a high level during the period from timing t16 to t19, the control signal EN7 to a high level during the period from timing t17 to t20, and the control signal EN8 to a high level during the period from timing t18 to t21 (FIGS. 6(D) to 6(J)). In this way, the signal generating section 30 generates the control signals EN1 to EN8 so that the periods (pulse periods P1C) during which the control signals EN1 to EN8 are at high level are sequentially shifted by the unit period P1A.

[0048] In this example, the reflected light pulse L1 occurs at a position that straddles the timing t16 (FIG. 6(B)).

[0049] Based on the control signal EN1, the switch SW1 is turned on during the period from timing t11 to t14, and supplies a pulse signal PLS to the counter CNT1. During this period from timing t11 to t14, the counter CNT1 performs counting based on the rising edges of the pulse signal PLS supplied from the switch SW1, thereby incrementing the count value CO1 (FIGS. 6(C) and 6(K)). Note that, although the figure shows the count value CO1 changing at timing t11, it may change during the period when the control signal EN1 is at a high level.

[0050] Similarly, the switch SW2 is turned on based on the control signal EN2 from timing t12 to t15 and supplies the pulse signal PLS to the counter CNT2. During this period from timing t12 to t15, the counter CNT2 performs counting based on the rising edges of the pulse signal PLS supplied from the switch SW2, thereby incrementing the count value CO2 (FIGS. 6(D) and (L)).

[0051] The switch SW3 is turned on based on the control signal EN3 during the period from timing t13 to t16, and supplies the pulse signal PLS to the counter CNT3. During this period from timing t13 to t16, the counter CNT3 performs counting based on the rising edges of the pulse signal PLS supplied from the switch SW3, thereby incrementing the count value CO3 (FIGS. 6(E) and 6(M)).

[0052] The switch SW4 is turned on based on the control signal EN4 during the period from timing t14 to t17, and supplies the pulse signal PLS to the counter CNT4. During this period from timing t14 to t17, the counter CNT4 performs counting based on the rising edges of the pulse signal PLS supplied from the switch SW4, thereby incrementing the count value CO4 (FIGS. 6(F) and (N)).

[0053] The switch SW5 is turned on during the period from timing t15 to t18 based on the control signal EN5, and supplies the pulse signal PLS to the counter CNT5. During this period from timing t15 to t18, the counter CNT5 performs counting based on the rising edges of the pulse signal PLS supplied from the switch SW5, thereby incrementing the count value CO5 (FIGS. 6(G) and 6(O)).

[0054] The switch SW6 is turned on based on the control signal EN6 during the period from timing t16 to t19, and supplies the pulse signal PLS to the counter CNT6. During this period from timing t16 to t19, the counter CNT6 performs counting based on the rising edges of the pulse signal PLS supplied from the switch SW6, thereby incrementing the count value CO6 (FIGS. 6(H) and 6(P)).

[0055] The switch SW7 is turned on based on the control signal EN7 during the period from timing t17 to t20, and supplies the pulse signal PLS to the counter CNT7. During this period from timing t17 to t20, the counter CNT7 performs counting based on the rising edges of the pulse signal PLS supplied from the switch SW7, thereby incrementing the count value CO7 (FIGS. 6(I) and 6(Q)).

[0056] Switch SW8 is turned on based on control signal EN8 during the period from timing t18 to t21, and supplies pulse signal PLS to counter CNT8. During this period from timing t18 to t21, counter CNT8 performs counting based on the rising edges of pulse signal PLS supplied from switch SW8, thereby incrementing count value CO8 (FIGS. 6(J) and (R)).

[0057] For example, during the period from timing t12 to t13, two switches SW1 and SW2 are turned on, and counters CNT1 and CNT2 perform counting. Also, during the period from timing t13 to t14, three switches SW1 to SW3 are turned on, and counters CNT1 to CNT3 perform counting. In this way, in the light detection system 1, two or more of the switches SW1 to SW8 are turned on, and two or more counters CNT connected to the two or more switches SW that are turned on perform counting.

[0058] The light detection unit U repeats this operation during the period from timing t11 to t19 (detection period P1B). As a result, the counter CNT1 generates a count value CO1 by performing counting during multiple periods when the control signal EN1 is at a high level (for example, the period from timing t11 to t14, the period from timing t19 to t22, etc.). The same is true for the counters CNT2 to CNT8.

[0059] Then, during the period from timing t24 to t25 (readout period P2), the readout control unit 23 performs readout control CR to control the operations of the multiple light detection units U so as to supply the count values ​​CO1 to CO8 generated in the multiple light detection units U, respectively, to the signal processing unit 24 (FIG. 6(S)). After that, the count values ​​CO1 to CO8 in the counters CNT1 to CNT8 are reset.

[0060] The signal processing unit 24 calculates the timing of receiving the reflected light pulse L1 at the light detection unit U based on the count values ​​CO1 to CO8 supplied from the light detection unit U. Specifically, the signal processing unit 24 calculates the timing of receiving the reflected light pulse L1 by calculating the count values ​​CN (count values ​​CN1 to CN8) for each of the plurality of unit periods P1A in the detection period P1B based on the count values ​​CO1 to CO8.

[0061] FIG. 7 shows the relationship between the count values ​​CO1 to CO8 and the count values ​​CN1 to CN8.

[0062] The count value CO1 is an accumulation of the count values ​​in the first unit period P1A, the second unit period P1A, and the third unit period P1A in the detection period P1B. The count value CO2 is an accumulation of the count values ​​in the second unit period P1A, the third unit period P1A, and the fourth unit period P1A in the detection period P1B. The same is true for the count values ​​CO3 to CO8. In this way, each of the count values ​​CO1 to CO8 is an accumulation of the count values ​​in three unit periods P1A.

[0063] The count value CN1 is an accumulation of the count values ​​in the first unit period P1A in the detection period P1B. The count value CN2 is an accumulation of the count values ​​in the second unit period P1A in the detection period P1B. The same is true for the count values ​​CN3 to CN8. In this way, the count values ​​CN1 to CN8 are an accumulation of the count values ​​in one unit period P1A.

[0064] The count values ​​CO1 to CO8 can be expressed as follows using the count values ​​CN1 to CN8. CO1=CN1+CN2+CN3 CO2=CN2+CN3+CN4 CO3=CN3+CN4+CN5 CO4=CN4+CN5+CN6 CO5=CN5+CN6+CN7 CO6=CN6+CN7+CN8 CO7=CN7+CN8+CN1 CO8=CN8+CN1+CN2 By solving these eight equations simultaneously, the count values ​​CN1 to CN8 can be expressed using the count values ​​CO1 to CO8. In this way, the signal processing unit 24 can calculate the timing of receiving the reflected light pulse L1 by calculating the count values ​​CN1 to CN8.

[0065] 8 shows a more specific example of the operation of the light detection system 1. In this example, during the period from timing t31 to t32, the light emitter 11 emits a light pulse L0, and during the period from timing t36 to t38, a reflected light pulse L1 is incident on the light detection unit U. Furthermore, ambient light LA ​​is incident on the light detection unit U throughout the entire period.

[0066] During the period from timing t36 to t38, when the reflected light pulse L1 is incident on the photodiode PD of the light-receiving unit DET, avalanche amplification occurs in the photodiode PD with a certain probability. As a result, the light-receiving unit DET generates a pulse by changing the pulse signal PLS from low to high at a certain timing between timings t36 and t38. If the rising edge of this pulse signal PLS occurs before timing t37, the counters CNT3, CNT4, and CNT5 perform counting, thereby incrementing the count values ​​CO3, CO4, and CO5. If the rising edge of the pulse signal PLS occurs after timing t37, the counters CNT4, CNT5, and CNT6 perform counting, thereby incrementing the count values ​​CO4, CO5, and CO6.

[0067] Furthermore, avalanche amplification occurs in the photodiode PD even when ambient light is incident on it. Therefore, the counters CNT1 to CNT8 increment the count values ​​CO1 to CO8, respectively, based on the ambient light.

[0068] As a result, in this example, the count values ​​CO3 to CO6 include both a reflected light component and an ambient light component, and the count values ​​CO1 to CO3, CO7, and CO8 include only the ambient light component.

[0069] Based on these count values ​​CO1-CO8, the signal processing unit 24 calculates count values ​​CN1-CN8 for each of the plurality of unit periods P1A in the detection period P1B. In this example, the count values ​​CN5 and CN6 include both reflected light components and ambient light components, and the count values ​​CN1-CO4, CO7, and CO8 include only the ambient light component. Based on the count values ​​CN5 and CN6 that include the reflected light component, the signal processing unit 24 can calculate the timing of receiving the reflected light pulse L1.

[0070] Here, unit period P1A corresponds to a specific example of a "unit period" in the present disclosure. Pulse period P1C corresponds to a specific example of a "pulse period" in the present disclosure. Detection period P1B corresponds to a specific example of a "detection period" in the present disclosure. Each of count values ​​CO1 to CO8 corresponds to a specific example of a "first count value" in the present disclosure. Each of count values ​​CN1 to CN8 corresponds to a specific example of a "second count value" in the present disclosure.

[0071] In this way, the light detection system 1 calculates the timing of receiving the reflected light pulse L1 based on two count values ​​CN (count values ​​CN5 and CN6 in this example) that include a reflected light component. These two count values ​​CN include a reflected light component and an ambient light component in two unit periods P1A of the detection period P1B. This allows the light detection system 1 to improve the S / N (Signal / Noise) ratio.

[0072] (Comparative Example) Next, the effects of this embodiment will be described in comparison with a light detection system 1 according to a comparative example. This comparative example is a so-called indirect ToF sensor in which charges generated by a light receiving element are selectively accumulated in one of two floating diffusions.

[0073] 9 shows an example of a light detection unit UR in a light detection system 1R according to a comparative example. This light detection unit UR has a photodiode PD, transistors MN1 and MN2, and floating diffusions FD1 and FD2.

[0074] The photodiode PD has an anode supplied with the power supply voltage VSS, and a cathode connected to the sources of the transistors MN1 and MN2.

[0075] The transistors MN1 and MN2 are N-type MOS transistors. A control signal CTL1 is supplied to the gate of the transistor MN1, its source is connected to the cathode of the photodiode PD, and its drain is connected to the floating diffusion FD1. A control signal CTL2 is supplied to the gate of the transistor MN2, its source is connected to the cathode of the photodiode PD, and its drain is connected to the floating diffusion FD2. The control signals CTL1 and CTL2 are supplied by a signal generating unit 30R (not shown).

[0076] The floating diffusion FD1 is configured to accumulate charge transferred from the photodiode PD via the transistor MN1. The floating diffusion FD2 is configured to accumulate charge transferred from the photodiode PD via the transistor MN2. The floating diffusions FD1 and FD2 are configured using, for example, diffusion layers formed on the surface of a semiconductor substrate. In FIG. 9, the floating diffusions FD1 and FD2 are represented by symbols representing capacitive elements.

[0077] 10 shows an example of operation of the photodetection system 1R, where (A) shows the waveform of light emitted from the light-emitting unit 11, (B) shows the waveform of light reflected by the object OBJ and incident on a photodetection unit U, (C), (E), (G), and (I) show the waveform of the control signal CTL1, and (D), (F), (H), and (J) show the waveform of the control signal CTL2. In the photodetection system 1R, the exposure period P1 includes four subframe periods PS (subframe periods PS1 to PS4). The control signals CTL1 and CTL2 shown in (C) and (D) are used in subframe period PS1, the control signals CTL1 and CTL2 shown in (E) and (F) are used in subframe period PS2, the control signals CTL1 and CTL2 shown in (G) and (H) are used in subframe period PS3, and the control signals CTL1 and CTL2 shown in (I) and (J) are used in subframe period PS4.

[0078] During the exposure period P1, the light detection system 1R repeatedly emits a light pulse L0 and repeatedly detects a reflected light pulse L1 reflected by the detection object OBJ.

[0079] Specifically, during the period from timing t41 to timing t42, the light emitting unit 11 emits a light pulse L0 (FIG. 10(A)).

[0080] During subframe period PS1, at timing t41, the signal generating unit 30R changes the control signal CTL1 from low to high and the control signal CTL2 from high to low, and at timing t45, changes the control signal CTL1 from high to low and the control signal CTL2 from low to high. Based on the control signal CTL1, transistor MN1 is turned on from timing t41 to t45, and charge generated by photodiode PD is accumulated in floating diffusion FD1. Based on the control signal CTL2, transistor MN2 is turned on from timing t45 to t49, and charge generated by photodiode PD is accumulated in floating diffusion FD2.

[0081] During subframe period PS2, at timing t42, the signal generating unit 30R changes the control signal CTL1 from low to high and the control signal CTL2 from high to low, and at timing t46, changes the control signal CTL1 from high to low and the control signal CTL2 from low to high. Transistor MN1 is turned on based on the control signal CTL1 from timing t42 to t46, and charge generated by photodiode PD is accumulated in floating diffusion FD1. Transistor MN2 is turned on based on the control signal CTL2 from timing t46 to t50, and charge generated by photodiode PD is accumulated in floating diffusion FD2.

[0082] During subframe period PS3, at timing t43, the signal generation unit 30R changes the control signal CTL1 from low to high and the control signal CTL2 from high to low, and at timing t47, changes the control signal CTL1 from high to low and the control signal CTL2 from low to high. Based on the control signal CTL1, transistor MN1 is turned on from timing t43 to t47, and charge generated by photodiode PD is accumulated in floating diffusion FD1. Based on the control signal CTL2, transistor MN2 is turned on from timing t47 to t51, and charge generated by photodiode PD is accumulated in floating diffusion FD2.

[0083] During subframe period PS4, at timing t44, the signal generation unit 30R changes the control signal CTL1 from low to high and the control signal CTL2 from high to low, and at timing t48, changes the control signal CTL1 from high to low and the control signal CTL2 from low to high. Based on the control signal CTL1, transistor MN1 is turned on from timing t44 to t48, and charge generated by photodiode PD is accumulated in floating diffusion FD1. Based on the control signal CTL2, transistor MN2 is turned on from timing t48 to t52, and charge generated by photodiode PD is accumulated in floating diffusion FD2.

[0084] In this way, in the photodetection system 1R, only one of the two transistors MN1 and MN2 is turned on in each of the subframe periods PS1 to PS4.

[0085] 11 shows a more specific example of the operation of the light detection system 1R. In this example, the light emitter 11 emits a light pulse L0 during the period from timing t51 to t52, and a reflected light pulse L1 is incident on the light detection unit UR during the period from timing t56 to t58. Furthermore, ambient light LA ​​is incident on the light detection unit UR throughout the entire period.

[0086] In the sub-frame period PS1, the charge CH1 accumulated in the floating diffusion FD1 contains only the ambient light component, and the charge CH2 accumulated in the floating diffusion FD2 contains both the reflected light component and the ambient light component.

[0087] During subframe period PS2, the charge CH1 accumulated in floating diffusion FD1 includes a component of reflected light and a component of ambient light, and the charge CH2 accumulated in floating diffusion FD2 includes both a component of reflected light and a component of ambient light. The component of reflected light in charge CH2 is greater than the component of reflected light in charge CH1.

[0088] In the sub-frame period PS3, the charge CH1 accumulated in the floating diffusion FD1 includes a component of reflected light and a component of ambient light, and the charge CH2 accumulated in the floating diffusion FD2 includes only a component of ambient light.

[0089] In the sub-frame period PS4, the charge CH1 accumulated in the floating diffusion FD1 includes a component of reflected light and a component of ambient light, and the charge CH2 accumulated in the floating diffusion FD2 includes only a component of ambient light.

[0090] The signal processing unit 24R of the light detection system 1R can calculate the timing of receiving the reflected light pulse L1 based on the total amount of charge CH1 and the total amount of charge CH2 in the four subframe periods PS1 to PS4. The charges CH1 and CH2 contain a reflected light component and an ambient light component in the detection period P1B. Therefore, the S / N ratio of the light detection system 1R deteriorates.

[0091] On the other hand, the light detection system 1 according to this embodiment calculates the timing of receiving the reflected light pulse L1 based on two count values ​​CN (count values ​​CN5 and CN6 in the example of FIG. 8) that include a reflected light component. These two count values ​​CN include a reflected light component and an ambient light component in two unit periods P1A of the detection period P1B. Therefore, the light detection system 1 can improve the S / N ratio.

[0092] 12 and 13 show an example of characteristics of the distance measurement error in the light detection system 1 according to the present embodiment and the light detection system 1R according to the comparative example, where Fig. 12 shows a case where there is no ambient light, and Fig. 13 shows a case where the ambient light is strong. The horizontal axis represents the distance to the detection object OBJ, and the vertical axis represents the distance measurement error.

[0093] When there is no ambient light, the ranging error in the optical detection system 1 is lower than the ranging error in the optical detection system 1R, as shown in Fig. 12. Specifically, the ranging error in the optical detection system 1 is reduced to approximately 1 / √8 of the ranging error in the optical detection system 1R.

[0094] Even when the ambient light is strong, the ranging error in the light detection system 1 is lower than the ranging error in the light detection system 1R, as shown in Fig. 13. Specifically, the ranging error in the light detection system 1 is reduced to about ¼ of the ranging error in the light detection system 1R.

[0095] In this way, the light detection system 1 according to this embodiment can increase the S / N ratio, and therefore can reduce measurement errors more than the light detection system 1R according to the comparative example.

[0096] In the photodetection system 1R (FIGS. 9 and 10) according to this comparative example, for example, one method would be to increase the frequencies of the control signals CTL1 and CTL2 to improve ranging accuracy. However, semiconductor circuits generally have an upper limit on the operating frequency, which limits how much ranging accuracy can be improved. In addition, increasing the frequencies of the control signals CTL1 and CTL2 in this way narrows the ranging range. Specifically, doubling the frequencies of the control signals CTL1 and CTL2 halves the ranging range. Another method would be to reduce the phase difference between the control signals CTL1 and CTL2 in multiple subframe periods PS to improve ranging accuracy. However, this would increase the number of subframe periods PS. Specifically, for example, halving the phase difference would double the number of subframe periods PS. As a result, the ranging time would be longer.

[0097] On the other hand, in the optical detection system 1 according to this embodiment (FIGS. 3 and 6), the phase difference between the multiple control signals EN can be reduced to improve ranging accuracy. For example, to double the ranging accuracy, the phase difference between the multiple control signals EN can be halved and the number of switches SW and counters CNT can be doubled. In this case, unlike the comparative example, the optical detection system 1 maintains the operating frequency, ranging range, and ranging time. This allows the optical detection system 1 to improve ranging accuracy relatively easily.

[0098] Thus, the light detection system 1 is provided with eight switches SW1 to SW8 that are turned on and off based on eight control signals EN1 to EN8 and transmit a pulse signal PLS by turning on during a pulse period P1C of a corresponding one of the control signals EN1 to EN8. Eight counters CNT1 to CNT8 are also provided corresponding to the eight switches SW1 to SW8, and each counter performs a count process based on the pulse signal PLS supplied via a corresponding one of the switches SW1 to SW8 to generate a count value CO. A signal generator 30 is provided to generate the eight control signals EN1 to EN8 so that the pulse periods P1C of the eight control signals EN1 to EN8 are sequentially shifted by a unit period P1A having a time length shorter than the pulse periods P1C during the detection period P1B. As a result, in the light detection system 1, for example, two or more of the switches SW1 to SW8 are turned on, and two or more counters CNT connected to the two or more switches SW that are on perform count processes. For example, the light detection system 1 can calculate count values ​​CN1 to CN8 for each of the plurality of unit periods P1A based on the count values ​​CO1 to CO8 of the eight counters CNT1 to CNT8. This allows the light detection system 1 to calculate the timing of receiving the reflected light pulse L1 based on the two count values ​​CN that include a reflected light component, thereby improving the distance measurement accuracy.

[0099] [effect] As described above, in this embodiment, eight switches are provided that are turned on and off based on eight control signals and transmit pulse signals by being turned on during the pulse period of a corresponding one of these control signals. Eight counters are also provided corresponding to the eight switches, each performing count processing based on the pulse signal supplied via the corresponding one of these switches to generate a count value. A signal generator is provided that generates the eight control signals so that the pulse period of each of the eight control signals is sequentially shifted by a unit period shorter than the pulse period during the detection period. This improves detection accuracy.

[0100] [Variation 1] In the above embodiment, the signal generating unit 30 generates eight control signals EN1 to EN8, but this is not limited to this. Alternatively, for example, the signal generating unit may generate some of the eight control signals EN1 to EN8, and the light detection unit may generate the remaining control signal EN. This modification will be described in detail below.

[0101] The photodetection system 1A according to this modification includes a photodetector 20A, similar to the photodetector system 1 (FIG. 1) according to the above embodiment. The photodetector 20A includes a signal generator 30A and a photodetector array 21A, similar to the photodetector 20 (FIG. 2) according to the above embodiment.

[0102] The signal generating section 30A is configured to generate five control signals EN1 to EN5 out of the eight control signals EN1 to EN8, and to supply the generated control signals EN1 to EN5 to the photodetector array 21A.

[0103] 14 shows an example of the configuration of a signal generating unit 30A. The signal generating unit 30A has a control signal generating unit 31, a clock signal generating unit 32, flip-flops (F / F) 33-36, and drivers DRV1-DRV5. That is, while the signal generating unit 30 (FIG. 5) according to the above embodiment is provided with seven flip-flops 33-39 and eight drivers DRV1-DRV8 to generate eight control signals EN1-EN8, the signal generating unit 30A according to this modification is provided with four flip-flops 33-36 and five drivers DRV1-DRV5 to generate five control signals EN1-EN5.

[0104] The photodetector array 21A has a plurality of photodetector units UA arranged in a matrix. Each photodetector unit UA is configured to detect a reflected light pulse L1 and count the number of times it is detected. Each photodetector unit UA also has the function of generating control signals EN6 to EN8 based on the control signals EN1 to EN5.

[0105] 15 shows an example of the configuration of the light detection unit UA. The light detection unit UA has negative OR (NOR) circuits NR1 to NR3. The NOR circuit NR1 is configured to generate a control signal EN6 by taking the NOR of the control signals EN1 and EN3. The NOR circuit NR2 is configured to generate a control signal EN7 by taking the NOR of the control signals EN2 and EN4. The NOR circuit NR3 is configured to generate a control signal EN8 by taking the NOR of the control signals EN3 and EN5.

[0106] With this configuration, in the photodetector system 1A, for example, the number of wirings for the control signal EN in the photodetector array 21A can be reduced.

[0107] [Variation 2] In the above embodiment, as shown in Fig. 3, eight counters CNT are provided in the light detection unit U, but this is not limited to this, and seven or fewer counters CNT may be provided, or nine or more counters CNT may be provided. An example in which five counters CNT are provided will be described in detail below.

[0108] The photodetection system 1B according to this modification includes a photodetector 20B, similar to the photodetector system 1 (FIG. 1) according to the above embodiment. The photodetector 20B includes a signal generator 30B, a photodetector array 21B, a readout controller 23B, and a signal processor 24B, similar to the photodetector 20 (FIG. 2) according to the above embodiment.

[0109] The signal generating section 30B is configured to generate five control signals EN1 to EN5 and supply the generated control signals EN1 to EN5 to the photodetector array 21B.

[0110] The photodetector array 21B has a plurality of photodetector units UB arranged in a matrix.

[0111] 16 shows an example of the configuration of the light detection unit UB. The light detection unit UB has a light receiving part DET, five switches SW (switches SW1 to SW5), and five counters CNT (counters CNT1 to CNT5).

[0112] The switch SW1 is configured to turn on and off the supply of the pulse signal PLS to the counter CNT1 based on a control signal EN1, as are the switches SW2 to SW5.

[0113] The counter CNT1 is configured to increment the count value CO1 by performing counting processing based on the rising edge of the pulse signal PLS supplied from the switch SW1, as is the case with the counters CNT2 to CNT5.

[0114] The readout control unit 23B is configured to control, based on instructions from the light detection control unit 25, the operation of supplying the count values ​​CO1 to CO5 generated in each of the multiple light detection units UB in the light detection array 21B to the signal processing unit 24B.

[0115] The signal processing unit 24B detects the timing of reception of the reflected light pulse L1 by the light detection unit UB based on the count values ​​CO1 to CO5 supplied from each of the multiple light detection units UB in the light detection array 21B. The signal processing unit 24B then generates a distance image by measuring the time (TOF value) from when the light emitter 11 emits the light pulse L0 until when the light detection unit UB detects the reflected light pulse L1.

[0116] Figure 17 shows an example of the operation of the light detection system 1B, where (A) shows the waveform of light emitted from the light emitting unit 11, (B) shows the waveform of light reflected by the object to be detected OBJ and incident on a certain light detection unit U, (C) to (G) show the waveforms of the control signals EN1 to EN5, respectively, (H) to (L) show the waveforms of the count values ​​CO1 to CO5, respectively, and (M) shows the operation of the read control unit 23B.

[0117] During the period from timing t71 to t79 (exposure period P1), the light detection system 1 repeatedly emits a light pulse L0 and repeatedly detects a reflected light pulse L1 reflected by the detection object OBJ.

[0118] Specifically, in the period from timing t71 to timing t72, the light emitting unit 11 emits a light pulse L0 (FIG. 17(A)).

[0119] The signal generating unit 30B sets the control signal EN1 to a high level during the period from timing t71 to t73 (FIG. 17(C)). The length of the period (pulse period P1C) during which the control signal EN1 is at a high level corresponds to two unit periods P1A. Similarly, the signal generating unit 30B sets the control signal EN2 to a high level during the period from timing t72 to t74, sets the control signal EN3 to a high level during the period from timing t73 to t75, sets the control signal EN4 to a high level during the period from timing t74 to t76, and sets the control signal EN5 to a high level during the period from timing t75 to t77 (FIGS. 17(D) to 17(G)). In this way, the signal generating unit 30B generates the control signals EN1 to EN5 so that the periods (pulse periods P1C) during which the control signals EN1 to EN5 are at a high level are sequentially shifted by the unit periods P1A.

[0120] In this example, the reflected light pulse L1 occurs at a position that straddles the timing t73 (FIG. 17(B)).

[0121] Switch SW1 is turned on based on control signal EN1 from timing t71 to t73 and supplies pulse signal PLS to counter CNT1. During this period from timing t71 to t73, counter CNT1 performs counting based on the rising edge of the pulse signal PLS supplied from switch SW1, thereby incrementing count value CO1 (FIGS. 17(C) and (H)). The same applies to switches SW2 to SW5 and counters CNT2 to CNT5.

[0122] The light detection unit UB repeats this operation during the period from timing t71 to t75 (detection period P1B). As a result, the counter CNT1 generates a count value CO1 by performing counting during multiple periods when the control signal EN1 is at a high level (for example, the period from timing t71 to t73, the period from timing t76 to t78, etc.). The same is true for the counters CNT2 to CNT5.

[0123] Then, during the period from timing t80 to t81 (readout period P2), the readout control unit 23B performs readout control CR to control the operations of the multiple light detection units UB so as to supply the count values ​​CO1 to CO5 generated in the multiple light detection units UB, respectively, to the signal processing unit 24B (FIG. 17(M)). After that, the count values ​​CO1 to CO5 in the counters CNT1 to CNT5 are reset.

[0124] The signal processing unit 24B calculates the count value CN for each of the plurality of unit periods P1A in the detection period P1B based on the count values ​​CO1 to CO5, thereby calculating the timing of receiving the reflected light pulse L1.

[0125] [Variation 3] In the above embodiment, as shown in Fig. 6, the operation in the detection period P1B is repeated continuously, but this is not limited to this, and for example, the operation in the detection period P1B may be performed individually multiple times. Below, a light detection system 1C according to this modified example will be described in detail.

[0126] The photodetection system 1C according to this modification includes a photodetector 20C, similar to the photodetector system 1 (FIG. 1) according to the above embodiment. The photodetector 20C includes a signal generator 30C, a photodetector array 21C, a readout controller 23C, and a signal processor 24C, similar to the photodetector 20 (FIG. 2) according to the above embodiment.

[0127] The signal generating section 30C is configured to generate 14 control signals EN1 to EN14 and supply the generated control signals EN1 to EN14 to the photodetector array 21C.

[0128] The photodetector array 21C has a plurality of photodetector units UC arranged in a matrix.

[0129] 18 shows an example of the configuration of the light detection unit UC. The light detection unit UC has a light receiving part DET, 14 switches SW (switches SW1 to SW14), and 14 counters CNT (counters CNT1 to CNT14).

[0130] The switch SW1 is configured to turn on and off the supply of the pulse signal PLS to the counter CNT1 based on a control signal EN1, as are the switches SW2 to SW14.

[0131] The counter CNT1 is configured to increment the count value CO1 by performing counting processing based on the rising edge of the pulse signal PLS supplied from the switch SW1, as in the counters CNT2 to CNT14.

[0132] The readout control unit 23C is configured to control, based on an instruction from the light detection control unit 25, an operation of supplying the count values ​​CO1 to CO14 generated in each of the plurality of light detection units UC in the light detection array 21C to the signal processing unit 24C.

[0133] The signal processing unit 24C detects the timing of reception of the reflected light pulse L1 by the light detection unit UC based on the count values ​​CO1 to CO14 supplied from each of the multiple light detection units UC in the light detection array 21C. The signal processing unit 24C then generates a distance image by measuring the time (TOF value) from when the light emitter 11 emits the light pulse L0 until when the light detection unit UC detects the reflected light pulse L1.

[0134] Figure 19 shows an example of the operation of the light detection system 1C, where (A) shows the waveform of light emitted from the light emitting unit 11, (B) shows the waveform of light reflected by the object to be detected OBJ and incident on a certain light detection unit U, (C) to (P) show the waveforms of the control signals EN1 to EN14, respectively, and (Q) shows the operation of the read control unit 23C.

[0135] In each of the plurality of detection periods P1B in the exposure period P1, the light detection system 1 emits a light pulse L0 and detects a reflected light pulse L1 reflected by the detection object OBJ.

[0136] Specifically, during the period from timing t91 to t92, the light emitting unit 11 emits a light pulse L0 (FIG. 19(A)).

[0137] The signal generating unit 30C sets the control signal EN1 to a high level during the period from timing t91 to t94 (FIG. 19(C)). The length of the period (pulse period P1C) during which the control signal EN1 is at a high level corresponds to three unit periods P1A. Similarly, the signal generating unit 30C sets the control signal EN2 to a high level during the period from timing t92 to t95, sets the control signal EN3 to a high level during the period from timing t93 to t96, sets the control signal EN4 to a high level during the period from timing t94 to t97, sets the control signal EN5 to a high level during the period from timing t95 to t98, sets the control signal EN6 to a high level during the period from timing t96 to t99, sets the control signal EN6 to a high level during the period from timing t97 to t100, and sets the control signal EN7 to a high level during the period from timing t98 to t101. 19(D)-19(P)). In this manner, the signal generating unit 30C generates the control signals EN1-EN14 so that the periods (pulse periods P1C) during which the control signals EN1-EN14 are at a high level are sequentially shifted by the unit period P1A.

[0138] In this example, the reflected light pulse L1 occurs at a position that straddles timing t96 (FIG. 19(B)).

[0139] Switch SW1 is turned on based on control signal EN1 during the period from timing t91 to t94, and supplies pulse signal PLS to counter CNT1. During this period from timing t91 to t94, counter CNT1 performs counting based on the rising edge of pulse signal PLS supplied from switch SW1, thereby incrementing count value CO1 (FIG. 19(C)). The same applies to switches SW2 to SW14 and counters CNT2 to CNT14.

[0140] During the exposure period P1, the light detection units UC individually repeat the operation from timings t91 to t107 (detection period P1B) with a short interval between them. As a result, the counter CNT1 generates the count value CO1 by performing counting during multiple periods when the control signal EN1 is at a high level. The same applies to the counters CNT2 to CNT14.

[0141] Then, during the period from timing t108 to t109 (readout period P2), the readout control unit 23C performs readout control CR to control the operations of the multiple light detection units UC so as to supply the count values ​​CO1 to CO14 generated in the multiple light detection units UC to the signal processing unit 24C (FIG. 19(Q)). After that, the count values ​​CO1 to CO14 in the counters CNT1 to CNT14 are reset.

[0142] The signal processing unit 24C calculates estimated count values ​​CR1 to CR16 for each of the plurality of unit periods P1A in the detection period P1B based on the count values ​​CO1 to CO14, thereby calculating the timing of receiving the reflected light pulse L1.

[0143] 20 and 21 show the relationships between the count values ​​CO1 to CO14, the count values ​​CN1 to CN16, and the estimated count values ​​CR1 to CR16.

[0144] The estimated count values ​​CR1 to CR16 are the count values ​​for each unit period P1A when it is assumed that the count value CO14 includes only ambient light components. Like the count value CN1, the estimated count value CR1 is an accumulation of the count values ​​for the first unit period P1A in the detection period P1B. Like the count value CN2, the estimated count value CR2 is an accumulation of the count values ​​for the second unit period P1A in the detection period P1B. The same is true for the estimated count values ​​CR3 to CR16.

[0145] When count value CO14 contains only ambient light components, each of estimated count values ​​CR14 to CR16 is estimated to be 1 / 3 of count value CO14. Therefore, in Fig. 20, estimated count value α is estimated to be 1 / 3 of count value CO14, and estimated count value β is estimated to be 2 / 3 of count value CO14. Signal processing unit 24C can calculate estimated count values ​​CR1 to CR16 using estimated count values ​​α and β.

[0146] That is, for example, the estimated count value CR1 can be obtained by subtracting the sum of count values ​​CO2, CO5, CO8, CO11, and CO14 from the sum of count values ​​CO1, CO4, CO7, CO10, and CO13 and estimated count value α. Also, for example, the estimated count value CR2 can be obtained by subtracting the sum of count values ​​CO3, CO6, CO9, and CO12 and estimated count value β from the sum of count values ​​CO2, CO5, CO8, CO11, and CO14. Also, for example, the estimated count value CR3 can be obtained by subtracting the sum of count values ​​CO4, CO7, CO10, and CO13 and estimated count value α from the sum of count values ​​CO3, CO6, CO9, and CO12 and estimated count value β. The same applies to estimated count values ​​CR4 to CR13. In FIG. 21, the estimated count values ​​CR1 to CR6 are represented using count values ​​CO1 to CO14 and estimated count values ​​α and β, as well as count values ​​CN1 to CN16. Since it is assumed that the count value CO14 contains only the component of ambient light, the second term in the equation in which the estimated count values ​​CR1 to CR6 are expressed using the count values ​​CN1 to CN16 is expected to be zero.

[0147] In this way, when the count value CO14 includes only the ambient light component, the signal processing unit 24C can calculate the estimated count values ​​CR1 to CR16 based on the count values ​​CO1 to CO14 by such calculation. In Fig. 19, when the end timing of the reflected light pulse L1 is before the rising edge timing of the control signal EN14, the count value CO14 includes only the ambient light component. Therefore, for example, when the distance to the detection object OBJ can be estimated to some extent in advance and the end timing of the reflected light pulse L1 is before the rising edge timing of the control signal EN14, the signal processing unit 24C can calculate the estimated count values ​​CR1 to CR16 based on the count values ​​CO1 to CO14 by such calculation.

[0148] In this example, it is assumed that the count value CO14 includes only the ambient light component, but this is not limiting, and it may also be assumed that the count value CO1 includes only the ambient light component. In this case, each of the estimated count values ​​CR1 to CR3 is estimated to be 1 / 3 of the count value CO1. Therefore, as shown in FIG. 22, the estimated count value α is estimated to be 1 / 3 of the count value CO1, and the estimated count value β is estimated to be 2 / 3 of the count value CO1. The signal processing unit 24C can calculate the estimated count values ​​CR1 to CR16 using these estimated count values ​​α and β, as shown in FIG. 23. For example, if the distance to the detection object OBJ can be estimated to some extent in advance and the start timing of the reflected light pulse L1 is after the timing of the falling edge of the control signal EN1, the signal processing unit 24C can calculate the estimated count values ​​CR1 to CR16 based on the count values ​​CO1 to CO14 by such calculation.

[0149] Furthermore, the signal processing unit 24C may identify a count value CO that includes only an ambient light component among the count values ​​CO1 to CO14, for example, based on the count values ​​CO1 to CO14. For example, if the count value CO14 includes only an ambient light component, the signal processing unit 24C can calculate the estimated count values ​​CR1 to CR16 based on the count values ​​CO1 to CO14 using the method shown in Figures 20 and 21. For example, if the count value CO1 includes only an ambient light component, the signal processing unit 24C can calculate the estimated count values ​​CR1 to CR16 based on the count values ​​CO1 to CO14 using the method shown in Figures 22 and 23.

[0150] Furthermore, in the light detection system 1C according to this modified example, the operations in the detection period P1B are performed individually multiple times, but this is not limited to this, and the operations in the detection period P1B may be repeated continuously, as in the case of the above embodiment (FIG. 6).

[0151] [Variation 4] In the light detection system 1C according to the third modification, the estimated count values ​​α and β were calculated based on the count value CO14, assuming that the count value CO14 contains only the ambient light component. However, this is not limited to this, and a dedicated counter for detecting ambient light may be provided, and the estimated count values ​​α and β may be calculated based on the count value of this counter. The light detection system 1D according to this modification will be described in detail below.

[0152] The photodetection system 1D according to this modification includes a photodetector 20D, similar to the photodetector system 1 (FIG. 1) according to the above embodiment. The photodetector 20D includes a signal generator 30D, a photodetector array 21D, a readout controller 23D, and a signal processor 24D, similar to the photodetector 20 (FIG. 2) according to the above embodiment.

[0153] The signal generating section 30D is configured to generate 14 control signals EN1 to EN14 and a control signal ENB, and to supply the generated control signals EN1 to EN14 and ENB to the photodetector array 21D.

[0154] The photodetector array 21D has a plurality of photodetector units UD arranged in a matrix.

[0155] 24 shows an example of the configuration of the light detection unit UD. The light detection unit UD has a switch SWB and a counter CNTB.

[0156] The switch SWB is configured to turn on and off the supply of the pulse signal PLS to the counter CNTB based on the control signal ENB.

[0157] The counter CNTB is configured to increment the count value COB by performing counting processing based on the rising edge of the pulse signal PLS supplied from the switch SWB.

[0158] The read control unit 23D is configured to control, based on instructions from the light detection control unit 25, the operation of supplying the count values ​​CO1 to CO14, COB generated in each of the multiple light detection units UD in the light detection array 21D to the signal processing unit 24D.

[0159] The signal processing unit 24D detects the timing of reception of the reflected light pulse L1 by the light detection unit UD based on the count values ​​CO1 to CO14 and COB supplied from each of the multiple light detection units UD in the light detection array 21D. The signal processing unit 24D then generates a distance image by measuring the time (TOF value) from when the light emitter 11 emits the light pulse L0 until when the light detection unit UD detects the reflected light pulse L1.

[0160] Figure 25 shows an example of operation of the light detection system 1D, where (A) shows the waveform of light emitted from the light emitting unit 11, (B) shows the waveform of light reflected by the object to be detected OBJ and incident on a certain light detection unit U, (C) to (P) show the waveforms of the control signals EN1 to EN14, respectively, (Q) shows the waveform of the control signal ENB, and (R) shows the operation of the read control unit 23C.

[0161] The signal generating unit 30D sets the control signal ENB to high level during the period from timing t90 to t91 (ambient light detection period P1D) before the light emitting unit 11 emits the light pulse L0 (FIG. 25(Q)). In this example, the length of this ambient light detection period P1D corresponds to six unit periods P1A. Based on the control signal ENB, the switch SWB is turned on during the period from timing t90 to t91 and supplies a pulse signal PLS to the counter CNTB. During this period from timing t90 to t91, the counter CNTB performs counting based on the rising edge of the pulse signal PLS supplied from the switch SWB, thereby incrementing the count value COB.

[0162] Since this ambient light detection period P1D is a period before the light-emitting unit 11 emits the light pulse L0, the count value COB includes only the ambient light component. Therefore, the estimated count value α according to the third modification is estimated to be 1 / 6 of the count value COB, and the estimated count value β according to the third modification is estimated to be 1 / 3 of the count value COB. In this way, by increasing the length of the ambient light detection period P1D, the accuracy of the estimated count values ​​α and β can be improved.

[0163] During the exposure period P1, the light detection units UD individually repeat the operations of the period from timing t90 to t107 (ambient light detection period P1D and detection period P1B) with a short time interval between each operation, for example.

[0164] Then, during the period from timing t108 to t109 (readout period P2), the readout control unit 23D performs readout control CR to control the operations of the multiple light detection units UD so as to supply the count values ​​CO1 to CO14, COB generated in the multiple light detection units UD to the signal processing unit 24D (FIG. 25(R)). After that, the count values ​​CO1 to CO14, COB in the counters CNT1 to CNT14, CNTB are reset.

[0165] The signal processing unit 24D calculates estimated count values ​​α and β based on the count value COB, and similarly to the signal processing unit 24C, calculates estimated count values ​​CR1 to CR16 for each of the multiple unit periods P1A in the detection period P1B based on the count values ​​CO1 to CO14 and the estimated count values ​​α and β, thereby calculating the timing of receiving the reflected light pulse L1.

[0166] [Variation 5] In the light detection system 1C according to the third modification, the light detection unit UC is provided with 14 counters CNT, but this is not limited to this, and the light detection unit UC may be provided with 13 or less counters CNT, or may be provided with 15 or more counters CNT. An example in which four counters CNT are provided will be described in detail below.

[0167] The photodetection system 1E according to this modification includes a photodetector 20E, similar to the photodetector system 1 (FIG. 1) according to the above embodiment. The photodetector 20E includes a signal generator 30E, a photodetector array 21E, a readout controller 23E, and a signal processor 24E, similar to the photodetector 20 (FIG. 2) according to the above embodiment.

[0168] The signal generating section 30E is configured to generate four control signals EN1 to EN4 and supply the generated control signals EN1 to EN4 to the photodetector array 21E.

[0169] The photodetector array 21E has a plurality of photodetector units UE arranged in a matrix.

[0170] 26 shows an example of the configuration of the light detection unit UE. The light detection unit UB has a light receiving part DET, four switches SW (switches SW1 to SW4), and four counters CNT (counters CNT1 to CNT4).

[0171] The switch SW1 is configured to turn on and off the supply of the pulse signal PLS to the counter CNT1 based on a control signal EN1, as are the switches SW2 to SW4.

[0172] The counter CNT1 is configured to increment the count value CO1 by performing counting processing based on the rising edge of the pulse signal PLS supplied from the switch SW1, as is the case with the counters CNT2 to CNT4.

[0173] The readout control unit 23E is configured to control, based on an instruction from the light detection control unit 25, an operation of supplying the count values ​​CO1 to CO4 generated in each of the plurality of light detection units UE in the light detection array 21E to the signal processing unit 24E.

[0174] The signal processing unit 24E detects the timing of reception of the reflected light pulse L1 by the light detection unit UE based on the count values ​​CO1 to CO4 supplied from each of the multiple light detection units UE in the light detection array 21E. The signal processing unit 24E then generates a distance image by measuring the time (TOF value) from when the light emitter 11 emits the light pulse L0 to when the light detection unit UB detects the reflected light pulse L1.

[0175] Figure 27 shows an example of operation of the light detection system 1E, where (A) shows the waveform of light emitted from the light emitting unit 11, (B) shows the waveform of light reflected by the object to be detected OBJ and incident on a certain light detection unit U, (C) to (F) show the waveforms of the control signals EN1 to EN4, respectively, (G) to (J) show the waveforms of the count values ​​CO1 to CO4, respectively, and (K) shows the operation of the read control unit 23E.

[0176] In this example, during the period from timing t111 to t123 (exposure period P1), the light detection system 1E repeatedly emits a light pulse L0 and repeatedly detects a reflected light pulse L1 reflected by the detection object OBJ.

[0177] Specifically, in the period from timing t111 to t112, the light emitting unit 11 emits a light pulse L0 (FIG. 27(A)).

[0178] The signal generating unit 30E sets the control signal EN1 to a high level during the period from timing t111 to t113 (FIG. 27(C)). The length of the period (pulse period P1C) during which the control signal EN1 is at a high level corresponds to two unit periods P1A. Similarly, the signal generating unit 30E sets the control signal EN2 to a high level during the period from timing t112 to t114, sets the control signal EN3 to a high level during the period from timing t113 to t115, and sets the control signal EN4 to a high level during the period from timing t114 to t116 (FIGS. 27(D) to 27(F)). In this way, the signal generating unit 30E generates the control signals EN1 to EN4 so that the periods (pulse periods P1C) during which the control signals EN1 to EN4 are at a high level are sequentially shifted by the unit periods P1A.

[0179] In this example, the reflected light pulse L1 occurs at a position that straddles the timing t73 (FIG. 27(B)).

[0180] Switch SW1 is turned on from timing t111 to t113 based on control signal EN1 and supplies pulse signal PLS to counter CNT1. During this period from timing t111 to t113, counter CNT1 performs counting based on the rising edge of pulse signal PLS supplied from switch SW1, thereby incrementing count value CO1 (FIGS. 27(C) and (G)). The same applies to switches SW2 to SW4 and counters CNT2 to CNT4.

[0181] The light detection unit UE repeats this operation during the period from timing t111 to t115 (detection period P1B). As a result, the counter CNT1 generates a count value CO1 by performing counting during multiple periods when the control signal EN1 is at a high level (for example, the period from timing t111 to t113, the period from timing t115 to t117, the period from timing t119 to t121, etc.). The same is true for the counters CNT2 to CNT4.

[0182] Then, during the period from timing t124 to t125 (readout period P2), the readout control unit 23E performs readout control CR to control the operation of the plurality of light detection units UE so as to supply the count values ​​CO1 to CO4 generated in the plurality of light detection units UE to the signal processing unit 24E (FIG. 27(K)). After that, the count values ​​CO1 to CO4 in the counters CNT1 to CNT4 are reset.

[0183] The signal processing unit 24E calculates estimated count values ​​CR1 to CR4 for each of the plurality of unit periods P1A in the detection period P1B based on the count values ​​CO1 to CO4, thereby calculating the timing of receiving the reflected light pulse L1.

[0184] 28 and 29 show the relationships between the count values ​​CO1 to CO4, the count values ​​CN1 to CN4, and the estimated count values ​​CR1 to CR4.

[0185] The estimated count values ​​CR1 to CR4 are the count values ​​in each unit period P1A when it is assumed that the count value CO4 includes only the ambient light component.

[0186] When count value CO4 contains only ambient light components, each of estimated count values ​​CR14 to CR1, CR4 is estimated to be 1 / 2 of count value CO4. Therefore, estimated count value α in FIG. 28 is estimated to be 1 / 2 of count value CO4. The signal processing unit 24E can calculate estimated count values ​​CR1 to CR4 using this estimated count value α. For example, if the distance to the detection object OBJ can be estimated to some extent in advance, and the start timing of reflected light pulse L1 is after the timing of the falling edge of control signal EN4 and the end timing of reflected light pulse L1 is before the timing of the rising edge of control signal EN4, the signal processing unit 24E can calculate estimated count values ​​CR1 to CR4 based on count values ​​CO1 to CO4 by such calculation.

[0187] [Variation 6] In the above embodiment, as shown in FIGS. 4A and 4B, the light receiving unit DET has one photodiode PD, but this is not limited thereto. Instead, for example, as shown in FIGS. 30A and 30B, the light receiving unit DET may have a plurality of photodiodes PD (four photodiodes PD1 to PD4 in this example). The photodiodes PD1 to PD4 are connected in parallel with each other, and the anodes of the photodiodes PD1 to PD4 are supplied with the power supply voltage VSS, and the cathodes are connected to the node N1. Note that in this example, a photodiode PD is provided, but this is not limited thereto. For example, three or less or five or more photodiodes PD may be provided. This can increase, for example, the light receiving sensitivity of the light receiving unit DET.

[0188] [Variation 7] In the above embodiment, as shown in FIG. 3, the light detection unit UF has one light receiving element DET. However, this is not limited thereto. Instead, for example, as shown in FIG. 31, multiple light receiving elements DET may be included. This light detection unit UF has multiple light receiving elements DET (four light receiving elements DET1 to DET4 in this example) and a logical OR circuit OR1. The light receiving elements DET1 to DET4 each generate a pulse signal. Each of the multiple light receiving elements DET has, for example, the circuit configuration shown in FIG. 4A or 4B. Note that in this example, four light receiving elements DET are provided, but this is not limited thereto. For example, three or less or five or more light receiving elements DET may be provided. The logical OR circuit OR1 is configured to generate a pulse signal PLS by calculating the logical OR of the pulse signals generated by the four light receiving elements DET1 to DET4. This can increase, for example, the light receiving sensitivity of the light detection unit UF.

[0189] [Variation 8] The photodetector 20 according to the above embodiment may be formed on one semiconductor substrate or on multiple semiconductor substrates. This modification will be described in detail below using an example in which the photodetector 20 is formed on two semiconductor substrates.

[0190] FIG. 32 shows an example of an implementation of the photodetector 20. In this example, the photodetector 20 is formed on two semiconductor substrates 101 and 102. The semiconductor substrate 101 is disposed on the light-receiving surface S side of the photodetector 20, and the semiconductor substrate 102 is disposed on the opposite side of the light-receiving surface S side of the photodetector 20. The semiconductor substrates 101 and 102 are superimposed on each other. The wiring of the semiconductor substrate 101 and the wiring of the semiconductor substrate 102 are connected by wiring 103. For example, metal bonding such as Cu-Cu bonding or bump bonding can be used for the wiring 103. The photodetector unit U is disposed across these two semiconductor substrates 101 and 102, for example.

[0191] FIG. 33 shows an example of the configuration of the light receiving unit DET in the light detection unit U. This light receiving unit DET has the same circuit configuration as the light receiving unit DET shown in FIG. 4A. In this example, this light receiving unit DET is arranged across two semiconductor substrates 101 and 102. Specifically, the photodiode PD is arranged on the semiconductor substrate 101, and the resistor R1 and inverter IV1 are arranged on the semiconductor substrate 102. The cathode of the photodiode PD is connected to the other end of the resistor R1 and the input terminal of the inverter IV1 via wiring 103. Note that in this example, this modification is applied to the light detecting unit 20 having the light receiving unit DET shown in FIG. 4A. However, this modification may also be applied to the light detecting unit 20 having the light receiving unit DET shown in FIG. 4B.

[0192] The switches SW1 to SW8 and counters CNT1 to CNT8 in the light detection unit U are arranged, for example, on the semiconductor substrate 102. The region on the semiconductor substrate 102 where the switches SW1 to SW8 and counters CNT1 to CNT8 are formed is an area arranged at a position corresponding to the region on the semiconductor substrate 101 where the photodiodes PD are formed. Specifically, the region on the semiconductor substrate 102 where the switches SW1 to SW8 and counters CNT1 to CNT8 are formed is arranged directly below the region on the semiconductor substrate 101 where the photodiodes PD are formed.

[0193] For example, when four photodiodes PD are provided in the light-detecting unit U, such as when four photodiodes PD are provided in the light-receiving unit DET as shown in Figures 30A and 30D, or when four light-receiving units DET are provided as shown in Figure 31, these four photodiodes PD are arranged, for example, on a semiconductor substrate 101, and the switches SW1 to SW8 and counters CNT1 to CNT8 are arranged, for example, on a semiconductor substrate 102, as shown in Figure 34. Similarly, when nine photodiodes PD are provided in the light-detecting unit U, these nine photodiodes PD are arranged, for example, on a semiconductor substrate 101, and the switches SW1 to SW8 and counters CNT1 to CNT8 are arranged, for example, on a semiconductor substrate 102, as shown in Figure 35.

[0194] [Other variations] Two or more of these variations may be combined.

[0195] <2. Application examples for mobile devices> The technology according to the present disclosure (the present technology) can be applied to various products. For example, the technology according to the present disclosure may be realized as a device 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, or a robot.

[0196] FIG. 36 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied.

[0197] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 36, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside-vehicle information detection unit 12030, an inside-vehicle information detection unit 12040, and an integrated control unit 12050. Also shown as functional components of the integrated control unit 12050 are a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (interface) 12053.

[0198] The drivetrain control unit 12010 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a drive force generating device for generating a drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, a braking device for generating a braking force of the vehicle, etc.

[0199] The body system control unit 12020 controls the operation of various devices equipped in the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as headlamps, 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 12020. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0200] The outside-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the outside-vehicle information detection unit 12030. The outside-vehicle information detection unit 12030 causes the imaging unit 12031 to capture images outside the vehicle and receives the captured images. The outside-vehicle information detection unit 12030 may perform object detection processing or distance detection processing for people, cars, obstacles, signs, characters on the road surface, etc., based on the received images.

[0201] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal according to the amount of light received. The imaging unit 12031 can output the electrical signal as an image, or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0202] The in-vehicle information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041 that detects the state of the driver is connected to the in-vehicle information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that captures an image of the driver, and the in-vehicle information detection unit 12040 may calculate the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

[0203] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, steering mechanism, or braking device based on the information inside and outside the vehicle acquired by the outside-vehicle information detection unit 12030 or the inside-vehicle information detection unit 12040, and output control commands to the drivetrain control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including avoiding or mitigating collisions between vehicles, following based on the distance between vehicles, maintaining vehicle speed, warning of vehicle collisions, or warning of vehicle lane departure.

[0204] In addition, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation, by controlling the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle obtained by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040.

[0205] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information about the outside of the vehicle acquired by the outside information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the outside information detection unit 12030, and perform cooperative control for the purpose of preventing glare, such as switching from high beams to low beams.

[0206] The audio / video output unit 12052 transmits at least one of audio and video output signals to an output device capable of visually or audibly notifying information to vehicle occupants or the outside of the vehicle. In the example of Fig. 36, an audio speaker 12061, a display unit 12062, and an instrument panel 12063 are exemplified as output devices. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0207] FIG. 37 is a diagram showing an example of the installation position of the imaging unit 12031.

[0208] In FIG. 37, a vehicle 12100 has imaging units 12101, 12102, 12103, 12104, and 12105 as the imaging unit 12031.

[0209] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided, for example, at positions such as the front nose, side mirrors, rear bumper, back door, and the top of the windshield inside the vehicle cabin of the vehicle 12100. The imaging unit 12101 provided at the front nose and the imaging unit 12105 provided at the top of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided at the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided at the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The forward images acquired by the imaging units 12101 and 12105 are mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0210] 37 shows an example of the imaging ranges of the imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 12101 to 12104, a bird's-eye view image of the vehicle 12100 viewed from above can be obtained.

[0211] At least one of the imaging units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the imaging units 12101 to 12104 may be a stereo camera made up of multiple imaging elements, or may be an imaging element having pixels for phase difference detection.

[0212] For example, the microcomputer 12051 can calculate the distance to each three-dimensional object within the imaging ranges 12111 to 12114 and the change in this distance over time (relative speed with respect to the vehicle 12100) based on the distance information obtained from the imaging units 12101 to 12104, thereby extracting as a preceding vehicle, in particular, the three-dimensional object that is the closest three-dimensional object on the path of the vehicle 12100 and traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (for example, 0 km / h or higher). Furthermore, the microcomputer 12051 can set a vehicle-to-vehicle distance to be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), etc. In this way, cooperative control can be performed for the purpose of automatic driving, which runs autonomously without relying on driver operation.

[0213] For example, the microcomputer 12051 classifies and extracts three-dimensional object data regarding three-dimensional objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects based on distance information obtained from the imaging units 12101 to 12104, and can use the data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines the collision risk, which indicates the degree of risk of collision with each obstacle, and when the collision risk is equal to or greater than a set value and a collision is possible, the microcomputer 12051 can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drivetrain control unit 12010.

[0214] At least one of the image capturing units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether or not a pedestrian is present in the images captured by the image capturing units 12101 to 12104. The pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104, which are infrared cameras, and then performing pattern matching on a series of feature points that indicate the outline of an object to determine whether or not the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the image capturing units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular outline on the recognized pedestrian for emphasis. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating the pedestrian at a desired position.

[0215] An example of a vehicle control system to which the technology according to the present disclosure can be applied has been described above. The technology according to the present disclosure can be applied to the imaging unit 12031 of the above-described configuration. This allows the vehicle control system 12000 to improve the accuracy of detecting time (TOF value) and distance. As a result, the vehicle control system 12000 can achieve, with high accuracy, functions such as a vehicle collision avoidance or collision mitigation function, a following driving function based on the inter-vehicle distance, a vehicle speed maintenance driving function, a vehicle collision warning function, and a vehicle lane departure warning function.

[0216] The present technology has been described above by giving several embodiments and modifications thereof, as well as specific application examples thereof, but the present technology is not limited to these embodiments and the like, and various modifications are possible.

[0217] For example, in each of the above-described embodiments, the light receiving unit DET is provided as shown in FIGS. 4A and 4B, but the circuit configuration of the light receiving unit DET is not limited to this, and various circuit configurations can be applied.

[0218] The effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0219] The present technology can be configured as follows: According to the present technology configured as follows, it is possible to improve detection accuracy.

[0220] (1) a light receiving unit having a light receiving element and generating a pulse signal including a pulse corresponding to a result of light reception by the light receiving element; a plurality of switches that are turned on and off based on a plurality of control signals, each of which transmits the pulse signal by being turned on during a pulse period of a corresponding control signal among the plurality of control signals; a plurality of counters provided corresponding to the plurality of switches, each of which performs counting based on the pulse signal supplied via a corresponding one of the plurality of switches to generate a first count value; a signal generating unit that generates the plurality of control signals so that the pulse periods in each of the plurality of control signals are sequentially shifted by a unit period having a time length shorter than the pulse periods during a detection period; A photodetector comprising: (2) The pulse durations of the respective control signals are equal to one another. The photodetector according to (1) above. (3) The time length of the pulse period is an integer multiple of the time length of the unit period. The photodetector according to (1) or (2) above. (4) In the detection period, the light receiving unit detects a light pulse in a period other than the first one or more unit periods. The photodetector according to any one of (1) to (3) above. (5) The light receiving unit detects a light pulse during a detection period excluding the last one or more unit periods. The photodetector according to any one of (1) to (4). (6) The apparatus further includes a processing unit that calculates a second count value in each of the plurality of unit periods based on the first count value of each of the plurality of counters, thereby calculating a light detection timing. The photodetector according to any one of (1) to (5) above. (7) a first switch among the plurality of switches is turned on based on a first control signal, among the plurality of control signals, for which the pulse period is set first, during a detection period; The processing unit divides the first count value of a first counter of the plurality of counters that corresponds to the first switch by the number of the unit periods included in the pulse period, and calculates the second count value based on the division result. The photodetector according to (6) above. (8) a second switch among the plurality of switches is turned on based on a second control signal, the second control signal having the pulse period set at the end of the plurality of control signals, during a detection period; The processing unit divides the first count value of a second counter of the plurality of counters that corresponds to the second switch by the number of the unit periods included in the pulse period, and calculates the second count value based on the division result. The photodetector according to (6) above. (9) a first switch among the plurality of switches is turned on based on a first control signal, among the plurality of control signals, for which the pulse period is set first during a detection period; a second switch among the plurality of switches is turned on based on a second control signal, the second control signal having the pulse period set at the end of the plurality of control signals, during a detection period; selecting, based on the first count values ​​of each of the plurality of counters, one of the first count value of a first counter corresponding to the first switch and the first count value of a second counter corresponding to the second switch, dividing the selected first count value by the number of unit periods included in the pulse period, and calculating the second count value based on the division result; The photodetector according to (6) above. (10) The light receiving element includes a single photon avalanche diode. The photodetector according to any one of (1) to (9) above. (11) The light receiving element includes an avalanche photodiode. The photodetector according to any one of (1) to (9) above. (12) A plurality of light detection units are provided, Each of the plurality of light detection units includes the light receiving portion, the plurality of switches, and the plurality of counters. The photodetector according to any one of (1) to (11) above. (13) the light receiving element is provided on a first semiconductor substrate, The light receiving unit, the plurality of switches, and the plurality of counters are provided on a second semiconductor substrate attached to the first semiconductor substrate. The photodetector according to (12) above. (14) the light receiving element is provided in a first region of the first semiconductor substrate; The light receiving unit, the plurality of switches, and the plurality of counters are provided in a second region arranged in a position corresponding to the first region on the second semiconductor substrate. The photodetector according to (13) above. (15) A light-emitting part that emits light; a light detection unit that detects light reflected by a detection target out of the light emitted from the light emitting unit; Equipped with The light detection unit a light receiving unit having a light receiving element and generating a pulse signal including a pulse corresponding to a result of light reception by the light receiving element; a plurality of switches that are turned on and off based on a plurality of control signals, each of which transmits the pulse signal by being turned on during a pulse period of a corresponding control signal among the plurality of control signals; a plurality of counters provided corresponding to the plurality of switches, each of which performs counting based on the pulse signal supplied via a corresponding one of the plurality of switches to generate a first count value; a signal generating unit that generates the plurality of control signals so that the pulse periods in each of the plurality of control signals are sequentially shifted by a unit period having a time length shorter than the pulse periods during a detection period; Contains Optical detection system.

[0221] This application claims priority based on Japanese Patent Application No. 2021-005817, filed on January 18, 2021, with the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0222] Those skilled in the art will recognize that various modifications, combinations, subcombinations, and variations may occur depending on design requirements and other factors, and are intended to be within the scope of the appended claims and their equivalents.

Claims

1. A light-receiving unit having a light-receiving element capable of detecting an optical pulse, and generating a pulse signal including a pulse corresponding to the light-receiving result of the light-receiving element; a plurality of switches that are turned on and off based on a plurality of control signals, each of which transmits the pulse signal by being turned on during a pulse period of a corresponding control signal among the plurality of control signals; a plurality of counters provided corresponding to the plurality of switches, each of which performs counting based on the pulse signal supplied via a corresponding one of the plurality of switches to generate a first count value; a signal generating unit that generates the plurality of control signals so that the pulse periods in each of the plurality of control signals are sequentially shifted by a unit period having a time length shorter than the pulse periods during a detection period; a processing unit that calculates a second count value for each of the plurality of unit periods based on the first count values ​​of the plurality of counters, and calculates a light detection timing of the light pulse based on two of the second count values ​​that include a component of the light pulse; A photodetector comprising:

2. The pulse durations of the respective control signals are equal to one another. The photodetector device according to claim 1 .

3. The time length of the pulse period is an integer multiple of the time length of the unit period. The photodetector device according to claim 1 .

4. The light receiving unit detects the light pulse during a period other than the first one or more unit periods in the detection period. The photodetector device according to claim 1 .

5. The light receiving unit detects the light pulse during a period other than the last one or more unit periods in the detection period. The photodetector device according to claim 1 .

6. a first switch among the plurality of switches is turned on based on a first control signal, among the plurality of control signals, for which the pulse period is set first during the detection period; The processing unit divides the first count value of a first counter of the plurality of counters that corresponds to the first switch by the number of the unit periods included in the pulse period, and calculates the second count value based on the division result. The photodetector device according to claim 1 .

7. a second switch among the plurality of switches is turned on based on a second control signal, the second control signal having the pulse period set at the end of the plurality of control signals, during the detection period; The processing unit divides the first count value of a second counter of the plurality of counters corresponding to the second switch by the number of the unit periods included in the pulse period, and calculates the second count value based on the division result. The photodetector device according to claim 1 .

8. a first switch among the plurality of switches is turned on based on a first control signal, among the plurality of control signals, for which the pulse period is set first during the detection period; a second switch among the plurality of switches is turned on based on a second control signal, the second control signal having the pulse period set at the end of the plurality of control signals, during the detection period; selecting one of the first count value of a first counter corresponding to the first switch and the first count value of a second counter corresponding to the second switch from among the plurality of counters based on the first count values ​​of each of the plurality of counters, dividing the selected first count value by the number of unit periods included in the pulse period, and calculating the second count value based on the division result; The photodetector device according to claim 1 .

9. The light receiving element includes a single photon avalanche diode. The photodetector device according to claim 1 .

10. The light receiving element includes an avalanche photodiode. The photodetector device according to claim 1 .

11. A plurality of light detection units are provided, Each of the plurality of light detection units includes the light receiving portion, the plurality of switches, and the plurality of counters. The photodetector device according to claim 1 .

12. the light receiving element is provided on a first semiconductor substrate, The light receiving unit, the plurality of switches, and the plurality of counters are provided on a second semiconductor substrate attached to the first semiconductor substrate. The optical detection device according to claim 11 .

13. the light receiving element is provided in a first region of the first semiconductor substrate, the light receiving unit, the plurality of switches, and the plurality of counters are provided in a second region arranged in a position corresponding to the first region on the second semiconductor substrate; The optical detection device according to claim 12.

14. A light-emitting part that emits light; a light detection unit that detects light reflected by a detection target out of the light emitted from the light emitting unit; Equipped with The light detection unit a light receiving unit having a light receiving element capable of detecting an optical pulse and generating a pulse signal including a pulse corresponding to the light receiving result of the light receiving element; a plurality of switches that are turned on and off based on a plurality of control signals, each of which transmits the pulse signal by being turned on during a pulse period of a corresponding control signal among the plurality of control signals; a plurality of counters provided corresponding to the plurality of switches, each of which performs counting based on the pulse signal supplied via a corresponding one of the plurality of switches to generate a first count value; a signal generating unit that generates the plurality of control signals so that the pulse periods in each of the plurality of control signals are sequentially shifted by a unit period having a time length shorter than the pulse periods during a detection period; a processing unit that calculates a second count value for each of the plurality of unit periods based on the first count values ​​of the plurality of counters, and calculates a light detection timing of the light pulse based on two of the second count values ​​that include a component of the light pulse; Contains Optical detection system.

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