Light receiving device, distance measuring device and light receiving circuit

Abstract

[Problem] Provided are a light receiving device, a light receiving circuit, and a distance measuring device capable of minimizing dead time. [Solution] According to the present disclosure, a light receiving device may include: a light receiving circuit including a light receiving element; a power supply circuit configured to supply a power supply potential to the light receiving circuit; and a control circuit configured to control the power supply potential supplied by the power supply circuit based on a signal output from the light receiving circuit in response to photons.

Description

Technical Field

[0001] The present disclosure relates to a light receiving device, a distance measuring device, and a light receiving circuit. Background Art

[0002] In many fields such as vehicle-mounted devices and mobile devices, technical applications for measuring the distance to an object based on the time of flight (ToF) until the irradiated light from a light-emitting element is reflected by the object and returns to a light-receiving element have been proposed. An avalanche photodiode (APD) is known as a light-receiving element. In a Geiger mode APD, a voltage equal to or higher than a breakdown voltage is applied across the terminals, and an avalanche phenomenon occurs due to the incidence of a single photon. An APD that multiplies single photons by an avalanche phenomenon is called a single-photon avalanche diode (SPAD).

[0003] In SPAD, avalanche phenomenon can be stopped by reducing the voltage across the terminals to the breakdown voltage. Reducing the voltage across the terminals and stopping the avalanche phenomenon is called quenching. Then, when the voltage across the terminals of the SPAD is charged to a bias voltage equal to or higher than the breakdown voltage, the photons can be detected again.

[0004] Reference List

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2010-091377

[0007] Patent Document 2: Japanese Patent Application Publication No. 2014-081254

[0008] Patent Document 3: Japanese Patent Application Publication No. 2018-179732

[0009] Patent document 4: Japanese Patent Application National Publication (Tokkai) No. 2008-542706. Summary of the invention

[0010] Problems to be solved by the present invention

[0011] Before starting to measure distance by ToF, it is desirable to make settings to shorten the dead time when no photons can be detected.

[0012] Therefore, the present disclosure provides a light receiving device, a light receiving circuit, and a distance measuring device capable of minimizing a dead time.

[0013] Solution to the problem

[0014] According to one aspect of the present disclosure, an optical receiving device includes: an optical receiving circuit including an optical receiving element; a power supply circuit configured to supply a power supply potential to the optical receiving circuit; and a control circuit configured to control the power supply potential supplied by the power supply circuit based on a signal output from the optical receiving circuit that acts on photons.

[0015] The light receiving device may further include a load circuit connected to the light receiving circuit and supplying a charging current to the light receiving element, and the control circuit may be configured to change a parameter including at least one of a charging current of the load circuit and a resistance value of the load circuit based on the signal.

[0016] The light receiving device may include a plurality of light receiving circuits, and the control circuit may be configured to change at least one of a power supply potential of the power supply circuit and a parameter of a load circuit connected to at least one of the light receiving circuits based on signals output from the plurality of light receiving circuits.

[0017] The optical receiving device may further include an error detector configured to perform error determination based on a waveform of a signal output from the optical receiving circuit, and the control circuit may be configured to change at least one of a power supply potential of the power supply circuit and a parameter of a load circuit connected to at least one optical receiving circuit based on the number of error determinations of the signals output from the plurality of optical receiving circuits.

[0018] The at least one light receiving circuit may be configured to perform passive charging, and the control circuit may be configured to adjust a charging current of the light receiving circuit such that the amount of error determination is less than a first threshold.

[0019] At least one light receiving circuit may be configured to perform active charging, and the control circuit may be configured to adjust a time delay in generating a pulse for active charging in the light receiving circuit based on the amount of error determination.

[0020] The error detector may be configured to perform error determination on at least one of a signal having a pulse width exceeding a second threshold and a signal having an interval between pulses less than a third threshold.

[0021] The optical receiving device may further include an error correction circuit configured to perform error determination based on a waveform of a signal output from the optical receiving circuit and correct the waveform of the signal for which the error determination has been performed.

[0022] The error correction circuit may be configured to perform error determination on at least one of a signal having a pulse width exceeding a second threshold and a signal having an interval between pulses less than a third threshold.

[0023] The control circuit may be configured to change at least one of a power supply potential of the power supply circuit and a parameter of a load circuit connected to at least one of the light receiving circuits based on the number of error determinations for signals output from the plurality of light receiving circuits.

[0024] At least one of the light receiving circuits may be configured to perform passive charging, and the control circuit may be configured to adjust a charging current of the light receiving circuit so that the amount of error determination is less than a first threshold.

[0025] At least one light receiving circuit may be configured to perform active charging, and the control circuit may be configured to adjust a time delay in generating a pulse for active charging in the light receiving circuit based on the amount of error determination.

[0026] The light receiving element may be an avalanche photodiode.

[0027] According to one aspect of the present disclosure, a distance measuring device may include: a light-emitting element; a plurality of light-receiving circuits including the light-receiving element; a power supply circuit configured to provide a power supply potential to the plurality of light-receiving circuits; and a control circuit configured to control the power supply potential based on a signal output from the plurality of light-receiving circuits that reacts to photons during a period in which the light-emitting element does not emit light.

[0028] The light receiving device may further include a plurality of load circuits connected to each light receiving circuit and supplying a charging current to the light receiving element, and the control circuit may be configured to control at least one of a resistance value and a charging current of the plurality of load circuits based on the signal.

[0029] The control circuit may be configured to adjust a time delay of generating a pulse for active charging in the at least one light receiving circuit based on the signal.

[0030] According to one aspect of the present disclosure, a light receiving circuit may include: a light receiving element; a current source; a switch capable of turning on a first contact side connected to a reference potential or a second contact side connected to the light receiving element; a current mirror circuit configured to supply a second current obtained by mirroring a first current flowing between a reference potential and the current source from an output side; and a transistor having a first signal electrode connected to the reference potential, a second signal electrode connected to the light receiving element and the output side of the current mirror circuit, and a control electrode connected to the switch.

[0031] The light receiving circuit may include a plurality of switches and transistors, and may be configured such that a third current obtained by multiplying the first current by N (N is a positive integer) is supplied to the light receiving element in response to switching of the switch.

[0032] The light receiving circuit may further include a reading circuit configured to generate a pulse when the light receiving element interacts with a photon.

[0033] According to one aspect of the present disclosure, a light receiving circuit may include: a light receiving element; a plurality of resistors connected in parallel between a reference potential and the light receiving element; a plurality of switches, each switch being connected in series with a resistor; and a reading circuit configured to generate a pulse when the light receiving element interacts with a photon, and may be configured to adjust a current supplied to the light receiving element according to switching of the switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a block diagram showing an example of a light receiving device.

[0035] Figure 2 is a diagram schematically showing an example of distance measurement using a light receiving device.

[0036] Figure 3 is a circuit diagram showing an example of a light receiving circuit that performs passive charging.

[0037] Figure 4 It is shown Figure 3 A graph of an example of a voltage waveform in a light receiving circuit.

[0038] Figure 5 is a circuit diagram showing an example of a light receiving circuit that performs active charging.

[0039] Figure 6 It is shown Figure 5 A graph of an example of a voltage waveform in a light receiving circuit.

[0040] Figure 7 is a circuit diagram showing an example of the configuration of a pulse generator.

[0041] Figure 8 is a diagram schematically showing an example of a light receiving device according to the present disclosure.

[0042] Fig. 9 is a graph illustrating an example of error determination by an error detector.

[0043] Fig.10 is a flowchart showing an example of processing in the light receiving device or the distance measuring device according to the present disclosure.

[0044] Fig.11 is a table showing examples of settings and amounts of error determination in a light receiving device or a distance measuring device.

[0045] Fig.12 is a circuit diagram showing an example of a load circuit whose resistance value can be adjusted.

[0046] Fig.13is a circuit diagram showing an example of a load circuit in which a current value can be adjusted.

[0047] Fig.14 is a flowchart illustrating an example of a process of determining settings of a load circuit.

[0048] Fig.15 is a flowchart illustrating an example of a process of determining settings of a power supply circuit.

[0049] Fig.16 is a table showing examples of power supply potentials and quantities of error determination.

[0050] Fig.17 : is a block diagram showing an example of a distance measurement device according to Modification 2.

[0051] Fig.18 It shows Fig.17 A graph showing an example of a correction process of a voltage waveform in a distance measuring device.

[0052] Fig.19 It is shown Fig.17 A graph showing an example of a correction process of a voltage waveform in a distance measuring device.

[0053] Fig. 20 : is a block diagram showing an example of a distance measurement device according to Modification 3.

[0054] Fig.21 : is a block diagram showing an example of a light receiving device according to Modification 4.

[0055] Fig. 22 is a circuit diagram showing an example of a circuit according to Modification 5.

[0056] Fig.23 is a circuit diagram showing an example of a circuit according to Modification 6.

[0057] Fig.24 is a block diagram showing an example of a schematic configuration of a vehicle control system.

[0058] Fig.25 1 is an explanatory diagram showing an example of the installation positions of the vehicle exterior information detection portion and the imaging unit. DETAILED DESCRIPTION

[0059] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Note that in this specification and the drawings, the same reference numerals are given to constituent elements having substantially the same functional configuration, and redundant descriptions are omitted.

[0060] Figure 1 The block diagram shows an example of a light receiving device. In addition, Figure 2An example of distance measurement using a light receiving device is schematically shown. Figure 1 The optical receiving device 200 includes a communication circuit 210, a control circuit 220, a SPAD controller 221, a SPAD array 240, a circuit block 241, a processing circuit 230, a transmission circuit 211, a PLL 250, a clock generator 251, a current source 252, a temperature sensor 253, a trigger circuit 254, and a power supply circuit 256. The processing circuit 230 includes a histogram generator 232 and a distance calculation unit 233 as internal components. In addition, the optical receiving device 200 is connected to the transmission circuit 211 via a terminal T_OUT. Figure 2 The light emitting element 255 is included in the embodiment of the present invention.

[0061] The communication circuit 210 and the transmission circuit 211 communicate with the external circuit. The control circuit 220 controls each component of the optical receiving device 200. The SPAD array 240 corresponds to Figure 2 Detection unit 1 in. For example, in the SPAD array 240, a plurality of SPADs and a light receiving circuit corresponding to each SPAD are installed. The SPAD array includes a plurality of single photon avalanche diodes (SPADs). The light receiving circuit is configured to output a pulse to a subsequent circuit when the SPAD acts on a photon. In addition, the light receiving circuit includes a circuit that quenches the SPAD and performs charging. The SPAD controller 221 controls the light receiving circuit. For example, the SPAD controller 221 performs switching of switches in the light receiving circuit, control of current values, and control of pulse generation timing.

[0062] The circuit block 241 includes, for example, a sampler connected to the rear stage of each light receiving circuit. The sampler is also called a buffer, and digitizes the signal input from the light receiving circuit. In addition, the circuit block 241 may include an error detector and an error correction circuit. The details of the error detector and the error correction circuit will be described later. The trigger circuit 254 controls the light emission timing of the light emitting element 255.

[0063] The histogram generator 232 samples the voltage level of the digitized output signal of each light receiving circuit and generates a histogram. The histogram generator 232 can repeat the sampling operation multiple times to generate a histogram. By performing the sampling operation multiple times, the reflected light rl of the light emitted from the light emitting element can be distinguished from other light. The histogram generator 232 can perform operations such as averaging multiple measurement results when generating a histogram. The distance calculation unit 233 calculates the distance between the light receiving device 200 and the object based on information related to the irradiation time t0 of the light transmitted from the trigger circuit 254 and the peak time t1 of the histogram. For example, when the speed of light is c, the distance between the light receiving device 200 and the object OBJ can be obtained by the equation of L=c / 2(t1-t0). In this equation, t1-t0 corresponds to the flight time. The transmission circuit 211 can be used to transmit information including the calculated distance to an external circuit. A device having a function of calculating the distance to an object, such as the light receiving device 200, is called a distance measuring device.

[0064] The power supply circuit 256 is a circuit that supplies the power supply potential Vdd to the light receiving circuit installed as a pixel in the SPAD array 240. Each circuit described in the above circuit diagram can be used as the light receiving circuit in the SPAD array 240. That is, the power supply circuit 256 is electrically connected to the signal line of the power supply potential Vdd in the circuit diagram described later. In addition, the power supply circuit 256 is connected to the SPAD controller 221 via a control signal line. The SPAD controller 221 can change the value of the power supply potential Vdd by transmitting a control signal to the power supply circuit 256.

[0065] The power supply circuit 256 may be controlled by components other than the SPAD controller 221. For example, the control circuit 220 that determines the charging method in the light receiving circuit may directly control the power supply circuit 256.

[0066] For example, the components of the processing circuit 230 (including the histogram generator 232 and the distance calculation unit 233) can be implemented by a hardware circuit (such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC)). However, the functions of the processing circuit 230 can be implemented by a central processing unit (CPU) and a program executed on the CPU. In this case, the processing circuit 230 may include a memory or a memory that stores the program and the data necessary for executing the program.

[0067] It should be noted that Figure 1The optical receiving device 200 in the embodiment is merely an example of the configuration of the optical receiving device. Therefore, the configuration of the optical receiving device according to the present disclosure may be different from the configuration of the optical receiving device 200. The optical receiving device may not include all components of the optical receiving device 200. For example, in the optical receiving device, at least one of the PLL 250, the clock generator 251, the current source 252, the temperature sensor 253, the trigger circuit 254, and the communication circuit 210 may be omitted. In addition, other components may be added, or other components may be omitted.

[0068] Figure 3 The circuit diagram shows an example of a light receiving circuit for photon detection. In addition, Figure 4 The graph shows an example of a voltage waveform in the light receiving circuit. Figure 3 The light receiving circuit 13 in includes a photodiode PD, a transistor TR0 and an inverter INV. The transistor TR0 is a PMOS transistor. For example, a SPAD can be used as a photodiode PD. The source of the transistor TR0 is connected to the power supply potential Vdd. The drain of the transistor TR0 is connected to the cathode of the photodiode PD. A voltage Van is applied to the anode of the photodiode PD. At both ends of the photodiode PD, a reverse voltage above the breakdown voltage is applied using the voltage Van. The input side of the inverter INV is connected to the drain of the transistor TR0 and the cathode of the photodiode PD. In addition, a post-stage circuit such as a buffer is connected to the output side of the inverter INV.

[0069] Transistor TR0 is an example of a load element 90 of the light receiving circuit 13. However, the configuration of the load element may be different from this. For example, a resistor may be used as a load element, or a combination of a transistor and a resistor may be used. In addition, a load circuit including a plurality of elements may be connected to the position of the load element.

[0070] When a photon enters the photodiode PD and the current flowing through the terminals of the photodiode PD increases due to avalanche multiplication, the cathode potential Vca decreases according to the voltage drop in the load element 90. When the voltage between the two ends of the photodiode PD is reduced to the breakdown voltage, the avalanche phenomenon stops and the current flowing through the terminals of the photodiode PD decreases. As a result, the voltage between the two ends of the photodiode PD becomes a value equal to or higher than the breakdown voltage, and the photon can be detected again (Vca of the graph 60). On the other hand, the inverter INV outputs a HIGH (positive polarity) pulse in a period when the positive electrode potential Vca is equal to or less than the threshold value thi (Vp of the graph 60). Since the light receiving circuit 13 outputs a pulse when a photon is detected, various processes such as photon counting, histogram generation, and flight time calculation can be performed in subsequent circuits.

[0071] It should be noted that a circuit that performs the operation shown in the graph 60 is called a passive charging circuit. The above-mentioned light receiving circuit 13 is an example of a passive charging circuit. As a passive charging circuit, a circuit having a configuration different from that of the light receiving circuit 13 may be used. For example, a circuit with polarity inversion may be used. In addition, a circuit in which other elements are added to the light receiving circuit 13 may be used. When a passive charging circuit is used, power consumption can be suppressed.

[0072] During the period from when the photodiode PD acts on the photon until the avalanche phenomenon stops (quenches) and the voltage across the photodiode PD is charged to a voltage equal to or higher than the breakdown voltage, the photodiode PD cannot detect the photon. This period is called the dead time. When the current supplied from the load element 90 is insufficient, the time tup until the voltage Vca shown in the graph 60 rises becomes longer, so the dead time becomes longer. The current supplied from the load element or the load circuit for resetting the voltage level of the terminal of the light receiving element (e.g., the photodiode PD) is called the charging current. In the case where a passive charging circuit is used as a light receiving circuit, it is preferred to set the charging current of the light receiving circuit so as to minimize the dead time before starting a process such as ranging. For example, in a calibration process performed at factory shipment, initial startup of a distance measuring device, or initialization operation, the charging current in the light receiving circuit (pixel) in the SPAD array 240 can be determined, the dead time can be minimized, and the distance measurement performance can be improved.

[0073] It should be noted that in the passive charging circuit, if the charging current is too large, the voltage across the terminals of the photodiode PD does not drop to the breakdown voltage, so that quenching cannot be performed (Vca in the curve graph 61). At this time, since the output voltage of the inverter INV is stable (stick), it is difficult to detect photons. Therefore, in order to enhance the ranging performance, it is desirable to suppress the probability of output voltage deadlock without providing an excessive charging current to the light receiving element.

[0074] Figure 5 The circuit diagram of shows an example of a circuit according to the present disclosure. Figure 5 The light receiving circuit 10 in FIG. 1 includes a photodiode PD, a switch SW1, a transistor TR0, a transistor TR1, a switch SW2, a transistor TR2, a switch SW3, an inverter INV, and a pulse generator PG. The transistor TR0, the transistor TR1, and the transistor TR2 are all PMOS transistors. For example, a SPAD can be used as the photodiode PD.

[0075] The switches SW1, SW2, and SW3 are implemented, for example, by MOS transistors. For example, the gate of each MOS transistor may be connected to the SPAD controller 221. In this case, the SPAD controller 221 turns the switch on / off by controlling the voltage applied to the gate of each MOS transistor. It should be noted that the gate of the transistor TR0 may be connected to the SPAD controller 221. In this case, the SPAD controller 221 may control the voltage applied to the gate of the transistor TR0 to adjust the resistance value between the source and the drain of the transistor TR0. Note that the control circuit 220 may perform the above control instead of the SPAD controller 221.

[0076] The source of transistor TR0 is connected to the power supply potential Vdd. Switch SW1 is connected between the drain of transistor TR0 and the cathode of photodiode PD. Voltage Van is applied to the anode of photodiode PD. The value of voltage Van can be determined so that a reverse voltage equal to or higher than the breakdown voltage is applied across the photodiode PD. The input terminal of inverter INV is connected to the cathode of photodiode PD and switch SW1 via signal line Lin.

[0077] The source of transistor TR1 and the source of transistor TR2 are both connected to the power supply potential Vdd. Switch SW2 is connected between the drain of transistor TR1 and the signal line Lin. On the other hand, switch SW3 is connected between the drain of transistor TR2 and the signal line Lin. The output end of inverter INV is connected to the gate of transistor TR2 and the input end of pulse generator PG via signal line Lout. The output end of pulse generator PG is connected to the gate of transistor TR1.

[0078] In the light receiving circuit 10, the method of charging the photodiode PD can be switched according to the switch setting. When the switch SW1 is turned off and the switch SW2 and the switch SW3 are turned on, the light receiving circuit 10 can be made to perform active charging. Figure 5 In the optical receiving circuit 10 shown in FIG. 1 , a switch for performing active charging is provided. In addition, when the switch SW1 is turned on and the switches SW2 and SW3 are turned off, the optical receiving circuit 10 can perform passive charging. In this case, the optical receiving circuit 10 and the Figure 3 The light receiving circuit 13 (passive charging circuit) in FIG. 1 operates similarly. In addition, when the switch SW1 and the switch SW2 are turned on, the light receiving circuit 10 can be made to perform both active charging and passive charging. In this case, the switch SW3 can be turned on or off.

[0079] Figure 6 The graph of φ shows an example of a voltage waveform in the light receiving circuit 10 . Figure 6The graph 63 in FIG. 6 corresponds to a voltage waveform in the case where active charging is performed by the light receiving circuit 10. It should be noted that Vg in the graph 63 represents the gate voltage of the transistor TR1. In each graph, the horizontal axis represents time.

[0080] The operation when the light receiving circuit 10 is made to perform active charging (when the switch is set to st1) will be described. When photons enter the photodiode PD and the current flowing through the terminals of the photodiode PD increases due to avalanche multiplication, the cathode potential Vca decreases according to the voltage drop across the source / drain of the transistor TR1 and the transistor TR2. When the voltage across the photodiode PD decreases to the breakdown voltage, the avalanche phenomenon stops (quenches), similar to the case of performing passive charging.

[0081] The inverter INV outputs a HIGH (positive polarity) pulse in a period when the voltage of the signal line Lin is equal to or less than the threshold value thi (Vp of the graph 64). The measurement circuit 30 in the subsequent stage can perform various types of processing based on the pulse. Since the voltage of the signal line Lin becomes LOW, the voltage of the signal line Lout on the output side of the inverter INV becomes HIGH. When a HIGH signal is input, the pulse generator PG outputs a LOW (negative polarity) pulse with a time delay td. Therefore, a LOW voltage is applied to the gate of the transistor TR1, and the source / drain of the transistor TR1 is turned on. In Vg of the graph 64, a LOW pulse is output in the period tr. As a result, the cathode potential Vca is raised by the power supply potential Vdd, and the photon can be detected by the photodiode PD again.

[0082] When the voltage of the signal line Lin becomes HIGH due to charging, the voltage of the signal line Lout on the output side of the inverter INV becomes LOW. At this time, the voltage of LOW is applied to the gate of the transistor TR2, and the source / drain of the transistor TR2 is turned on. In this way, the transistor TR2 latches the state of the transistor TR1. The transistor TR2 can suppress the generation of the through current and prevent the cathode potential Vca from being uncertain.

[0083] It should be noted that when not only switches SW2 and SW3 but also switch SW1 are turned on (switch setting st3), the voltage drop across the source and drain of transistor TR0 further contributes to the quenching of photodiode PD. When the current flowing between the terminals of photodiode PD decreases due to quenching, the voltage across photodiode PD decreases with Figure 3 The light receiving circuit 13 in is similarly increased.

[0084] like Figure 6As shown in the graph 63, in order to perform active charging and shorten the dead time of the photodiode PD, it is necessary to adjust the value of the time delay td. Here, the time delay td refers to the time difference from when the cathode potential Vca of the photodiode PD becomes equal to or less than the threshold value thi to when the pulse generator PG outputs a LOW pulse. Figure 6 Graph 64 shows a voltage waveform when the time delay td is set too short. If the time delay is set to td too short, the cathode potential Vca will decrease again even if a reset pulse is output from the pulse generator PG. The cathode potential Vca is lower than the threshold value thi, and the pulse generator PG generates multiple pulses in a short period of time. Therefore, hunting occurs at the cathode potential Vca, and photon detection cannot be performed using the optical receiving circuit 10. In order to improve the ranging performance, it is desirable to ensure a sufficient value of the time delay td for generating an active charging pulse in the optical receiving circuit and prevent voltage fluctuations.

[0085] In the case of using an active charging circuit as a light receiving circuit, it is preferable to set the time delay td of generating an active charging pulse of the light receiving circuit so as to minimize the dead time before starting a process such as distance measurement. For example, in a calibration process performed at the time of factory shipment, initial startup of the distance measuring device, or initialization operation, the time delay td of generating an active charging pulse in the light receiving circuit (pixel) in the SPAD array 240 can be determined, the dead time can be minimized, and the distance measurement performance can be improved.

[0086] In the light receiving circuit 10, a portion including the transistor TR1, the transistor TR2, the switch SW2, the switch SW3, and the pulse generator PG corresponds to the active charging circuit 91. In addition, in the light receiving circuit 10, a portion including the transistor TR0 (load element 90) and the switch SW1 corresponds to the passive charging circuit. The light receiving circuit 10 is an example of a light receiving circuit including a passive charging circuit and an active charging circuit.

[0087] Note that it is possible to use a device having the same configuration as the light receiving circuit 10 ( Figure 5 ) is a circuit having a configuration different from the configuration of the light receiving circuit 10. For example, a circuit in which an element is added to the light receiving circuit 10 can be used. In addition, a circuit obtained by reversing the polarity of the light receiving circuit 10 can be used. In the case of using a circuit with polarity reversal, an NMOS transistor is used instead of a PMOS transistor. In addition, in the case of polarity reversal of the light receiving circuit 10, a positive bias voltage is applied to the cathode of the photodiode PD. Thus, the cathode potential of the above-mentioned photodiode PD is replaced by the anode potential. Note that not only the light receiving circuit 10 but also other circuits described in this specification can adopt a configuration with polarity reversal.

[0088] Figure 7The circuit diagram shows an example of the configuration of the pulse generator. Figure 7 The pulse generator PG includes a flip-flop FP and an inverter INV2. The flip-flop FP is a D flip-flop. The signal line Lout is connected to the D terminal of the flip-flop F1. The signal line dctr is connected to the clock terminal of the flip-flop F1. The inverter INV2 is connected between the Q terminal of the flip-flop F1 and the gate of the transistor TR1.

[0089] exist Figure 7 In the pulse generator PG of the embodiment, by controlling the clock signal supplied to the signal line dctr, the time delay td from when the voltage of the signal line Lout becomes HIGH level to when the voltage Vg becomes LOW level can be changed. For example, when the interval between pulses in the clock signal is increased, the time delay td can be increased. In addition, when the interval between pulses in the clock signal is decreased, the time delay td can be decreased. When using Figure 7 When the pulse generator PG is used, it is easy to control the time delay by a clock signal provided from the outside. For example, the SPAD controller 221 or the clock generator 251 can supply the clock signal to the signal line dctr.

[0090] It should be noted that Figure 7 The circuit is only an example of the pulse generator PG. Thus, a pulse generator having a different configuration may be used. For example, the pulse generator may be implemented by an inverter chain. In addition, the pulse generator may be implemented by combining a delay unit and a logic operation element. That is, a pulse generator having any circuit configuration may be used as long as the pulse can be output to the gate of the transistor TR1 with a time delay after the level of the input voltage is changed.

[0091] Figure 8 An example of a light receiving device according to the present disclosure is schematically shown. Figure 8 The optical receiving device 101 includes a plurality of optical receiving circuits 11, a plurality of samplers 20, a plurality of error detectors 21, a measuring circuit 30 and a control circuit 40. The optical receiving circuit 11 includes a SPAD and an optical receiving circuit. The measuring circuit 30 includes a histogram generator 31 as an internal component.

[0092] The plurality of light receiving circuits 11 correspond to, for example, the light receiving device 200 ( Figure 1 ) of the SPAD array 240. For example, a plurality of samplers 20 and a plurality of error detectors 21 are arranged in a circuit block 241. The measurement circuit 30 corresponds to, for example, the processing circuit 230. The control circuit 40 corresponds to, for example, the control circuit 220 and the SPAD controller 221.

[0093] Each light receiving circuit 11 is connected to a sampler 20 at a subsequent stage via a signal line l_rd. The sampler is also called a buffer, and digitizes the signal input from the light receiving circuit. The output side of each sampler 20 is connected to an error detector 21. Then, a measurement circuit 30 is connected to the subsequent stage of each error detector 21. The measurement circuit 30 is connected to a control circuit 40. The control circuit 40 is connected to each light receiving circuit 11 via a signal line l_ct. Note that although Figure 8 , but the number of signal lines for control is not limited. For example, the control circuit 40 can control multiple light receiving circuits 11 using one signal line. Note that the configuration of the light receiving circuit 11 is not limited. For example, Figure 3 and Figure 5 The light receiving circuit shown in can be used as the light receiving circuit 11. The light receiving circuit 11 may be a charging circuit or an active charging circuit. In addition, circuits having different configurations may be mixed in a plurality of light receiving circuits 11.

[0094] When the SPAD acts on photons, the light receiving circuit 11 outputs a voltage signal to the signal line l_rd. The error detector 21 is configured to perform error detection based on the voltage signal output from the light receiving circuit 11. In addition, the sampler 20 digitizes the voltage signal output from the light receiving circuit 11. The histogram generator 31 generates a histogram based on the pulses included in the signal input from each sampler.

[0095] It should be noted that in Figure 8 The configuration of the light receiving device shown in is only an example. For example, the error detector 21 may be connected between the light receiving circuit 11 and the sampler 20. In addition, a circuit in which the function of the sampler 20 and the function of the error detector 21 are integrated may be connected between each light receiving circuit 11 and the input terminal of the measuring circuit 30. In addition, a plurality of signal lines l_rd may be connected to a common error detector without preparing an error detector 21 for each signal line l_rd. In this case, one error detector must perform error determination of a plurality of signal lines l_rd, but the necessary circuit area can be reduced. In addition, the function corresponding to the error detector 21 may be installed on the measuring circuit 30 side. In this case, it can be said that the measuring circuit 30 has the function of the error detector 21.

[0096] Fig. 9 The graph of φ shows an example of error detection by the error detector 21. The error detector 21 may perform error determination, for example, by the method described below. Fig. 9 Graphs 65 to 67 show waveforms of the cathode potential Vca of the photodiode PD and the output voltage Vp (inverter INV) of the light receiving circuit 11. In each graph, the horizontal axis represents time.

[0097] Graph 65 shows a situation where the photodiode PD interacts with photons again before the cathode potential Vca rises to a voltage higher than the threshold of the inverter INV, and the pulse width output from the inverter INV becomes too large. For example, the error detector 21 detects the rising of the pulse in the voltage signal output from the light receiving circuit 11. Then, the error detector 21 monitors the pulse width. The error detector 21 makes an error determination when the pulse width exceeds the threshold t_h. For example, the error detector 21 samples the voltage of the signal in the period t_s, and the error determination can be performed continuously when the sampled voltage becomes HIGH n_h times continuously. In this case, the values ​​of t_s and n_h can be set to satisfy the relationship of t_h=t_s×n_h. However, the error determination can be performed by a method different from this method.

[0098] In the graph 66, since the charging current in the light receiving circuit 11 is too large, the voltage across the photodiode PD does not drop to the breakdown voltage, and quenching cannot be performed. Therefore, the output voltage of the light receiving circuit 11 is stable. For example, the error detector 21 detects the rise of the pulse in the voltage signal output from the light receiving circuit 11. Then, the error detector 21 measures the time period during which the output voltage of the light receiving circuit 11 is HIGH. The error detector 21 performs error determination when the time period during which the output voltage of the light receiving circuit 11 is HIGH exceeds the threshold value t_h. In the example of the graph 66, the error determination can be performed by a method similar to the case of the graph 65.

[0099] In the curve graph 67, after the interaction with the photon, a residual charge is generated in the photodiode PD. Therefore, even if the light receiving circuit 11 performs quenching and charging operations, the photodiode PD interacts with the photon again. The oscillation (hunting) of the cathode potential Vca occurs due to the re-interaction with the photon. For example, after the pulse in the voltage signal of the light receiving circuit 11 drops, when the period during which the output voltage of the light receiving circuit 11 is LOW is shorter than the threshold t_l, the error detector 21 performs error determination. For example, the error detector 21 samples the voltage of the signal in the period t_s, and performs error determination when the number of times the sampled voltage continuously becomes LOW is less than n_l. In this case, the values ​​of t_s and n_l can be set so as to satisfy the relationship of t_l=t_s×n_l. In addition, error determination can be performed by a method different from this method.

[0100] Here, the error determination in the case where the light receiving circuit 11 outputs a pulse of a HIGH level (positive polarity) at the time of photon detection has been described. The error detector 21 can also perform error determination in the case where the light receiving circuit 11 outputs a pulse of a LOW level (negative polarity). In this case, in the above description, it is sufficient that the error detector 21 performs the following operations: HIGH is replaced by LOW, LOW is replaced by HIGH, the fall of the pulse is replaced by the rise of the pulse, and the rise of the pulse is replaced by the fall of the pulse.

[0101] In the case of error determination, the error detector 21 outputs an error signal to the measurement circuit 30. For example, the error signal may be transmitted using a signal line separate from a signal line through which a pulse is transmitted upon photon detection. In addition, the error signal may be transmitted by superimposing on a signal line to which a pulse is transmitted upon photon detection. The error detector 21 may output an error signal including an error code indicating the type of error detected. The error code may include, for example, information indicating (1) a charging current that is too small, (2) a charging current that is too large, (3) a time delay td that is too short, and (4) a time delay td that is too long. In addition, the error signal may include information specifying the type of the above-mentioned error waveform or information about the detected waveform.

[0102] Next, an example of a process of searching for a setting that minimizes the dead time through error determination based on voltage signals output from a plurality of pixels (light receiving circuits) in the SPAD array 240 will be described.

[0103] Fig.10 The flowchart of FIG. 1 shows an example of processing in the light receiving device or the distance measuring device according to the present disclosure. Fig.10 The flowchart describes the process.

[0104] First, the SPAD array 240 is activated (step S101). Then, the measurement circuit 30 counts errors in a plurality of light receiving circuits in the SPAD array 240 (step S102). The error determination and detection in step S102 are performed by, for example, the above-mentioned error detector 21 or the measurement circuit 30. In the case where the error detector 21 detects an error, the measurement circuit 30 at the subsequent stage can obtain information about the number of error determinations in the SPAD array 240 through the error signal. Here, the measurement circuit 30 can count the number of error determinations for each error code.

[0105] For example, information including at least one of the number of error determinations in the SPAD array 240 and the number of error determinations for each error code is referred to as error information. The error information obtained by the measurement circuit 30 is transmitted to the control circuit 40 (control circuit 220). In the case of using a distance measurement device including a light emitting element, the light emission of the light emitting element is stopped during the execution cycle of step S102, and the influence from the light emitting element can be eliminated.

[0106] The control circuit 40 determines whether the error count is within the reference range (step S103). For example, the control circuit 40 may determine whether the number of error determinations in the SPAD array 240 is less than a threshold value. In addition, the control circuit 40 may compare the number of error determinations for each error code with a threshold value and determine whether the error count falls within the reference range. Thus, it is possible to specify the content of the adjustment to be performed next.

[0107] The processing to be performed is branched according to the determination result in step S103. In the case where the control circuit 40 determines that the error count is within the reference range (step S103 is "yes"), the adjustment processing is completed (step S105). After step S105, the distance measurement device can start the distance measurement processing by irradiating the object OBJ with light from the light emitting element.

[0108] In the case where the control circuit 40 determines that the error count is outside the reference range (step S103 is no), the control circuit 40 changes at least one of the charging current and / or the time delay of the pulse generated by the pulse generator PG (step S104). Examples of the case where the determination in step S103 is negative include a case where the number of error determinations is greater than a threshold value or a case where the number of error determinations of a specific error code is greater than a threshold value. The adjustment content in step S104 depends on the type of light receiving circuit in the SPAD array 240. For example, in the case where the light receiving circuit is a passive charging circuit, the charging current is adjusted. In addition, in the case where the light receiving circuit is a passive charging circuit, the time delay td of the pulse generated by the pulse generator PG is adjusted. The SPAD controller 221 can change the setting of each light receiving circuit in the SPAD array 240. In this case, the control circuit 40 can notify the SPAD controller 221 to set the address of the pixel (light receiving circuit) to be changed and the setting content.

[0109] For example, in the case where it is determined that the size of the charging current is insufficient, the control circuit 40 may adjust the charging current in the light receiving circuit to be larger. In this case, the control circuit 40 may adjust the resistance value in the load element or the load circuit to be smaller. In addition, in the case where it is determined that the charging current is too large, the control circuit 40 may adjust the charging current in the light receiving circuit to be smaller. In this case, the control circuit 40 may adjust the resistance value in the load element or the load circuit to be smaller.

[0110] In addition, if the time delay td of the pulse generated by the pulse generator PG is determined to be too short, the control circuit 40 can adjust the time delay td to be longer. In the case of determining that the time delay td of the pulse generated in the pulse generator PG is too long, the control circuit 40 can adjust the time delay td to be shorter.

[0111] When the processing in step S104 is completed, the processing in steps S102 and S103 is performed again. That is, the errors of the plurality of light receiving circuits are counted again to determine whether the error count is within the reference range. When the error count is within the reference range (yes in step S103), the adjustment processing is completed (step S105). After step S105, the distance measuring device can start the distance measurement processing by irradiating the object OBJ with light from the light emitting element.

[0112] Fig.10 The execution timing of the above-mentioned processing is not limited to the calibration time of the device. Fig.10 The processing may be performed at a timing other than the calibration time of the device. For example, after starting the operation of the device, the processing may be performed Fig.10 processing.

[0113] Fig.11 Table T1 shows the number of error determinations when a charging current of each value is used in the light receiving circuit in the SPAD array 240. For example, the measurement circuit 30 or the control circuit 40 uses different charging currents to measure the number of error determinations and generates Table T1. Fig.11 , when the charging current is suppressed, the number of error determinations is reduced. For example, the control circuit 40 may adjust the charging current based on a threshold value of the error determination number. In this case, the control circuit 40 will adjust the charging current based on the threshold value of the error determination number. c1 The error in determining the quantity e c1 With the threshold th e For comparison. c1 >th e In the case of c2 (ic1≠ic2). The control circuit 40 can determine whether to use the ratio i according to the information of the error code. c1 Big i c2Still better than i c1 Small i c2 Then, when the control circuit 40 determines that the number of error determinations is less than the threshold value, the distance measurement may be performed using the charging current at that time.

[0114] For example, in the case where the data of table T1 is obtained in the adjustment process, the error determination number 3 may be used as the threshold value th e However, the threshold value may be different from this. It should be noted that Fig.11 The current values ​​in the table are merely examples and are not intended to limit the values ​​of the charging current used in the light receiving circuit.

[0115] Note that in the case of using a different charge current measurement error determination number, the maximum value i of the charge current that can be set in the light receiving circuit can be obtained from max The measurement of the error determination quantity can be started, or the minimum value i of the charging current that can be set in the light receiving circuit can be obtained. min In addition, it is possible to measure the number of errors determined by the max and i min The charging current starts measuring the value between the values ​​determined by the amount of error. That is, the charging current at the start of the adjustment process is not limited.

[0116] The control circuit 40 may determine that the amount of error becomes smaller than the threshold value th e For example, in the case where it is desired to use a charging current as large as possible to shorten the dead time, the number of error determinations can be counted using a larger charging current, and the number of error determinations can be compared with the threshold value th. e Even if the amount of error determination after changing the charging current is less than the threshold value th e In the case of , the distance measurement can also be performed using a larger charging current. In addition, in the case where it is desired to use a smaller charging current to suppress power consumption, the number of error determinations can be counted using a smaller charging current, and the number of error determinations can be compared with a threshold value. Even if the number of error determinations is less than the threshold value th after the charging current is changed e In this case, distance measurement can also be performed using a smaller charging current.

[0117] Fig.11 Table T2 shows the number of error determinations when the charging current of each value is used in the light receiving circuit in the SPAD array 240. For example, the measurement circuit 30 or the control circuit 40 measures the number of error determinations using different time delays td and generates Table T2. Fig.11, in the case where the pulse generator PG generates a pulse with a shorter time delay td, the number of error determinations is reduced. For example, the control circuit 40 may be based on the threshold value th of the number of error determinations. e Adjust the time delay td. In this case, the control circuit 40 will use the time delay td 1 The error in determining the quantity e d1 With the threshold th e For comparison. d1 >th e In the case of 2 (td 1 ≠td 2 ). The control circuit 40 may determine whether to use a value greater than td based on information about the error code. 1 td 2 Or use less than td 1 td 2 Then, when the control circuit 40 determines that the number of error determinations is less than the threshold, an active charging pulse may be generated at the time delay at that time and a distance measurement performed.

[0118] For example, in the case where the data of table T2 is obtained in the adjustment process, the error determination number 3 may be used as the threshold value th e However, the threshold can be different from this. Note that Fig.11 The values ​​of the time delays in the table are merely provided as an example and are not intended to limit the values ​​of the time delays for generating pulses.

[0119] Note that in the case of measuring the amount of error determination using different charging currents, the measurement of the amount of error determination can be performed from the minimum value td of the time delay that can be set in the pulse generator PG. min To begin with, or measure the error determination quantity, the maximum value td of the time delay that can be set in the pulse generator PG can be used. max In addition, the error determination quantity can be measured from td min and td max That is, the time delay at the start of the adjustment process is not limited.

[0120] The control circuit 40 may determine that the amount of error becomes smaller than the threshold value th e For example, in the case where it is desired to use the shortest possible time delay to shorten the dead time, the number of error determinations may be counted using a shorter time delay, and the number of error determinations may be compared with the threshold value th. e Even after changing to a shorter time delay, the number of error determinations is less than the threshold value th eIn the case of , a smaller time delay can also be used to perform distance measurement. In addition, in the case of desiring to use as long a time delay as possible to suppress power consumption, the number of error determinations can be counted using a longer time delay, and the number of error determinations can be compared with the threshold value th e Even if the number of errors determined after the time delay change is less than the threshold value th e In this case, longer time delays can also be used to perform distance measurements.

[0121] Next, an example of a load circuit that can be used for the light receiving device, the distance measuring device, and the light receiving circuit according to the present disclosure will be described.

[0122] Figure 3 and Figure 5 An example of a light receiving circuit is shown in which a transistor TR0 is used as a load element 90 for controlling a charging current. However, in order to control the charging current with higher accuracy, a load circuit including a plurality of elements may be used instead of the load element 90. An example of a load circuit capable of controlling a resistance value or a charging current will be described below.

[0123] Fig.12 The circuit diagram shows an example of a load circuit in which the resistance value can be adjusted. Fig.12 A load circuit 90A connected to the light receiving circuit is shown. The load circuit 90A is connected to the cathode of the photodiode PD and the signal line Lin via a switch SW1. For example, Figure 3 and Figure 5 The transistor TR0 in the circuit diagram of can be replaced with the load circuit 90A. The switch SW1 is a switch for switching the enable / disable of the passive charging. In the case where the passive charging is not disabled in the light receiving circuit, the switch SW1 can be omitted, and the load circuit 90A can be directly connected to the cathode of the photodiode PD and the signal line Lin.

[0124] The load circuit 90A includes a plurality of pairs of resistors and switches connected in series. The resistor R1 is connected in series with the pair of switches s1. In addition, the resistor R2 is connected in series with the pair of switches S2. The resistor R3 is connected in series with the pair of switches s3. The resistor R4 is similarly connected in series with the pair of switches s4. Fig.12 The load circuit 90A includes four pairs of resistors and switches. However, the number of pairs of resistors and switches included in the load circuit may be different from this. For example, a load circuit may be used in which the number of resistor-switch pairs is any integer equal to or greater than 2. In addition, the paired resistors and switches are connected in parallel to each other. A power supply potential Vdd is applied to an endpoint opposite to the photodiode PD of each pair.

[0125] It is assumed that switches s1 to s4 in the load circuit 90A are switched by a circuit that controls the SPAD array 240. For example, the switches s1 to s4 are turned on / off by at least one of the control circuit 40, the control circuit 220, the SPAD controller 221, and the external processing circuit 300. The switches s1 to s4 are implemented by MOS transistors, for example. However, the installation method of the switches s1 to s4 is not limited.

[0126] In the load circuit 90A, the resistance value can be adjusted according to the number of switches to be turned on. When the number of switches to be turned on increases, the number of resistors connected in parallel increases, so that the resistance value of the load circuit 90A decreases. For example, it is assumed that the resistance values ​​of the resistors R1 to R4 are equal. In this case, when two switches are turned on, the resistance value of the load circuit 90A becomes 1 / 2 compared to the case where one switch is turned on. Similarly, when three switches are turned on, the resistance value of the load circuit 90A becomes 1 / 3 compared to the case where one switch is turned on. In addition, when four switches are turned on, the resistance value of the load circuit 90A becomes 1 / 4 compared to when one switch is turned on.

[0127] Note that the resistance values ​​of the plurality of resistors of the load circuit may not necessarily be equal to each other. Therefore, the load circuit may include resistors having different resistance values.

[0128] In the case of using the same power supply potential Vdd, increasing the resistance value of the load circuit 90A reduces the charging current. In addition, when the resistance value of the load circuit 90A decreases, the charging current can be increased. As described above, in the light receiving device, light receiving circuit, and distance measuring device according to the present disclosure, the charging current can be adjusted by changing the number of switches to be turned on in the load circuit 90A. When the load circuit 90A is used, the charging current can be adjusted with high precision.

[0129] like Fig.12 As shown in the example, the light receiving circuit according to the present disclosure may include: a light receiving element; a plurality of resistors connected in parallel between a reference potential and the light receiving element; a plurality of switches, each switch being connected in series with the resistor; and a reading circuit configured to generate a pulse when the light receiving element interacts with a photon. The light receiving circuit according to the present disclosure may be configured so that the current supplied to the light receiving element is adjusted according to the switching of the switch. The above-mentioned power supply potential Vdd is an example of a reference potential. The above-mentioned photodiode PD is an example of a light receiving element. The reading circuit corresponds to, for example, Figure 3 and Figure 5 The portion of the circuit shown in excluding transistor TR0, switch SW1 and photodiode PD.

[0130] Fig.13 The circuit diagram shows an example of a load circuit in which the current value can be adjusted. Fig.13A load circuit 90B connected to the light receiving circuit is shown. The load circuit 90B is connected to the cathode of the photodiode PD and the signal line Lin via a switch SW1. For example, Figure 3 and Figure 5 The transistor TR0 in the circuit diagram of can be replaced with a load circuit 90B. The switch SW1 is a switch for switching the enable / disable of passive charging. In the case where passive charging is not disabled in the light receiving circuit, the switch SW1 can be omitted, and the load circuit 90B can be directly connected to the cathode of the photodiode PD and the signal line Lin. The load circuit 90B will be described below assuming that the switch SW1 is turned on.

[0131] The load circuit 90B includes a current source CS, a transistor tr0, a transistor tr1, a transistor tr3, a transistor tr4, a switch sec2, a switch sec3, and a switch sec4. As the current source CS, a current source transistor can be used. As the current source transistor, a MOS transistor can be used. However, the installation method of the current source CS is not limited. The current source CS can be a constant current source. Transistors tr0 to tr4 are PMOS transistors. Switches se2 to se4 are switches capable of switching the electrical connection destination between contact c0 and contact c1.

[0132] Each of the sources of transistors tr0 to tr4 is connected to the power supply potential Vdd. In addition, the drains of transistors tr2 to tr4 are connected to the photodiode PD and the signal line Ln via the switch SW1. Transistors tr0 and tr1 form a current mirror circuit that mirrors the current Is between the power supply potential Vdd and the current source CS. Therefore, the gate and drain of transistor Tr0 are short-circuited. In addition, the gate of transistor Tr0 is connected to the gate of transistor tr1 via the signal line Lc.

[0133] The switch se2 is connected to the gate of the transistor tr2. In addition, the switch se3 is connected to the gate of the transistor tr3. In addition, the switch se4 is connected to the gate of the transistor tr4. The contacts c0 of the switches se2 to se4 are all connected to the power supply potential Vdd. In addition, the contacts cl of the switches se2-se4 are all connected to the signal line Lc.

[0134] It is assumed that switches se2 to se4 in the load circuit 90B can be switched by a circuit controlling the SPAD array 240. For example, the switches se2 to se4 are switched by at least one of the control circuit 40, the control circuit 220, the SPAD controller 221, and the external processing circuit 300.

[0135] Fig.13The load circuit 90B includes three pairs of transistors and switches connected to the gates of the transistors. However, the number of pairs of transistors and switches may be different from this. For example, the load circuit may include any number of transistor and switch pairs, such as one or more transistors and switches. Fig.13 In the case of a circuit of , the wiring of the additional transistor and switch follows the existing transistor and switch wiring method. In the case of adding a switch, the contact c0 is connected to the power supply potential Vdd, and the contact c1 is connected to the signal line Lc. In addition, in the case of adding a transistor, the gate is connected to the switch, the source is connected to the power supply potential Vdd, and the drain is connected to the drain of another transistor.

[0136] In the load circuit 90B, the current value can be adjusted according to the number of switches connected on the contact c1 side. For example, in the case where the number of switches connected on the contact c1 side is zero, a charging current equal to the current ic of the current source CS is supplied to the light receiving circuit. In the case where there is one switch connected on the contact c1 side, a charging current of twice (2×ics) the current of the current source CS is supplied to the light receiving circuit. In addition, in the case where there are two switches connected on the contact c1 side, a charging current of three times (3×ics) the current of the current source CS is supplied to the light receiving circuit. In addition, in the case where there are three switches connected on the contact c2 side, a charging current of four times (4×ics) the current of the current source CS is supplied to the light receiving circuit. As described above, in the light receiving device, the light receiving circuit and the distance measuring device according to the present disclosure, the charging current can be adjusted by changing the number of switches connected on the contact c1 side in the load circuit 90B. When the load circuit 90B is used, the charging current can be adjusted with high precision.

[0137] Note that in the case of performing photon detection using a circuit in which the polarity of the light receiving circuit is reversed, the polarity of the load circuit 90B may be reversed. Fig.13 The PMOS transistor in can reverse the polarity of the load circuit 90B.

[0138] like Fig.13 As shown in the example of, the light receiving circuit according to the present disclosure may include a light receiving element, a current source, a switch, a current mirror circuit and a transistor. The switch can be connected to the first contact side connected to the reference potential or the second contact side connected to the light receiving element. The current mirror circuit is configured to supply a second current obtained by mirroring the first current flowing between the reference potential and the current source from the output side. In the transistor, the first signal electrode is connected to the reference potential, the second signal electrode is connected to the output side of the light receiving element and the current mirror circuit, and the control electrode is connected to the switch.

[0139] Here, for example, the first contact corresponds to the contact c0 in the above-mentioned switches se2 to se4. The second contact corresponds to the contact c1 in the above-mentioned switches se2 to se4, for example. The current mirror circuit is, for example, a current mirror circuit formed by the above-mentioned transistor tr0 and transistor tr1. The output side of the current mirror circuit corresponds to, for example, the drain of transistor tr1. The first signal electrode is, for example, the source of a MOS transistor. The second signal electrode is, for example, the drain of a MOS transistor. However, the correspondence between the first signal electrode, the second signal electrode, and the electrodes of the MOS transistor may be reversed. The control electrode is, for example, the gate of a MOS transistor.

[0140] In addition, if Fig.13 As shown in the example of , the light receiving circuit according to the present disclosure may include a plurality of switches and transistors. The light receiving circuit according to the present disclosure may be configured so that in response to the switching of the switch, a third current obtained by multiplying the first current by N (N is a positive integer) is supplied to the light receiving element. In addition, the light receiving circuit according to the present disclosure may further include a reading circuit configured to generate a pulse when the light receiving element acts on a photon.

[0141] When controlling the SPAD charging method, the power supply potential Vdd used in the light receiving circuit can be changed. The charging current during passive charging can be adjusted by changing the power supply potential Vdd. In the case of supplying a common power supply potential to the pixels in the SPAD array, the setting of the charging current of all pixels in the SPAD array can be changed in a short time. However, a light receiving device and a distance measuring device having a configuration in which a common power supply potential is not supplied to the pixels in the SPAD array can be used. For example, multiple power supply circuits can be used to supply the power supply potential to the pixels in the SPAD array.

[0142] In the optical receiving device and the distance measuring device according to the present disclosure, a power supply circuit capable of adjusting the value of the power supply potential Vdd and the above-mentioned load circuit 90A or 90B can be used in combination. By using a combination of multiple components, the charging current value can be set in a wide range in the optical receiving circuit.

[0143] By optimizing the setting of the load circuit and the setting of the power circuit, the dead time in the light receiving device or the distance measuring device can be minimized. Hereinafter, an example of a process of determining the setting of the load circuit and the setting of the power circuit will be described.

[0144] Fig.14 The flowchart of FIG. 1 shows an example of a process for determining the setting of a load circuit. Fig.14 The flowchart describes the process.

[0145] First, the SPAD array 240 is activated (step S201). Then, the measurement circuit 30 counts the errors in the plurality of light receiving circuits in the SPAD array 240 (step S202). For example, the error determination and detection in step S202 are performed by the above-mentioned error detector 21 or the measurement circuit 30. In the case where the error detector 21 detects an error, the measurement circuit 30 at the subsequent stage can obtain information about the number of error determinations in the SPAD array 240 through the error signal. Here, the measurement circuit 30 can count the number of error determinations for each error code of a specified error type.

[0146] For example, information including at least one of the number of error determinations in the SPAD array 240 and the number of error determinations for each error code is referred to as error information. The error information obtained by the measurement circuit 30 is transmitted to the control circuit 40 (control circuit 220). In the case of using a distance measurement device including a light-emitting element, the light emission of the light-emitting element is stopped during the execution cycle of step S202. This makes it possible to eliminate the influence of the light-emitting element.

[0147] The control circuit 40 determines whether the error count is within the reference range (step S203). For example, the control circuit 40 may determine whether the number of error determinations in the SPAD array 240 is less than a threshold value. In addition, the control circuit 40 may compare the number of error determinations for each error code with a threshold value and determine whether the error count falls within the reference range. For example, in step S203, the control circuit 40 may estimate whether the charging current is too small or the charging current is too large based on the number of error determinations and the error code.

[0148] The processing to be performed branches according to the determination result in step S203. In the case where the control circuit 40 determines that the error count is within the reference range ("Yes" in step S203), the adjustment processing is completed (step S205). After step S205, the distance measurement device can start the distance measurement processing by irradiating the object OBJ with light from the light emitting element.

[0149] In the case where the control circuit 40 determines that the error count is outside the reference range ("No" in step S203), the control circuit 40 changes at least one of the charging current and the resistance value of the load circuit (step S204). Examples of the case where the determination in step S203 is negative include a case where the number of error determinations is greater than a threshold value or a case where the number of error determinations of a specific error code is greater than a threshold value. As described above, the SPAD controller 221 can change the setting of each light receiving circuit in the SPAD array 240. In this case, the control circuit 40 can notify the SPAD controller 221 to set the address of the pixel (light receiving circuit) to be changed and the setting content.

[0150] For example, in the case where it is determined that the magnitude of the charging current is insufficient, the control circuit 40 may change the charging current in the light receiving circuit to be larger. In this case, the control circuit 40 may change the resistance value in the load circuit to be smaller. As the load circuit, for example, Fig.12 The load circuit 90A or Fig.13 In addition, the light receiving circuit in the SPAD array 240 detects Figure 4 When the phenomenon shown in the graph 62 of FIG. 64 is observed and it is determined that the charging current is too large, the control circuit 40 may change the charging current in the light receiving circuit to be smaller. In this case, the control circuit 40 may change the resistance value in the load circuit to be larger.

[0151] When the processing in step S204 is completed, the processing in steps S202 and S203 is performed again. That is, the errors of the plurality of light receiving circuits are counted again to determine whether the error count is within the reference range. When the error count is within the reference range ("Yes" in step S203), the calibration process is completed (step S205). After step S205, the distance measuring device can start the distance measurement process by irradiating the object OBJ with light from the light emitting element.

[0152] Fig.14 The execution timing of the above-mentioned processing is not limited to the calibration time of the device. Fig.14 The processing can be performed at a timing other than the calibration time of the device. For example, after the operation of the device starts, the Fig.12 The resistance value in the load circuit 90A.

[0153] Fig.15 The flowchart of FIG. 1 shows an example of a process for determining the setting of a power supply circuit. Fig.15 The flowchart describes the process.

[0154] First, the SPAD array 240 is activated (step S211). Then, the measurement circuit 30 counts the errors in the plurality of light receiving circuits in the SPAD array 240 (step S212). The error determination and detection in step S212 are performed by, for example, the error detector 21 or the measurement circuit 30 described above. In the case where the error detector 21 detects an error, the measurement circuit 30 in the subsequent stage can obtain the error information in the SPAD array 240 through the error signal.

[0155] The error information obtained by the measurement circuit 30 is transmitted to the control circuit 40 (control circuit 220). In the case of using a distance measurement device including a light emitting element, the light emission of the light emitting element is stopped in step S202. This makes it possible to eliminate the influence of the light emitting element.

[0156] The control circuit 40 determines whether the error count is within the reference range (step S213). The detailed determination method in step S213 may be any determination method as long as determination based on error information is performed.

[0157] The processing to be performed is branched according to the determination result in step S213. In the case where the control circuit 40 determines that the error count is within the reference range (step S213 is "yes"), the adjustment processing is completed (step S215). After step S215, the distance measurement device can start the distance measurement processing by irradiating the object OBJ with light from the light emitting element.

[0158] In the case where the control circuit 40 determines that the error count is outside the reference range ("No" in step S213), the control circuit 40 controls the power supply circuit and changes the power supply voltage of the SPAD array 240 (step S214). Examples of cases where the determination in step S213 is negative include a case where the number of error determinations is greater than a threshold value or a case where the number of error determinations for a specific error code is greater than a threshold value. Instead of the control circuit 40, the SPAD controller 221 or the external processing circuit 300 may change the setting of the power supply circuit. In addition, in the case where a plurality of power supply circuits are connected to the SPAD array 240, in step S214, the setting of at least one of the power supply circuits may be changed.

[0159] For example, in the case where it is determined that the magnitude of the charging current is insufficient, the control circuit 40 may control the power supply circuit to change the power supply potential Vdd used in the SPAD array 240 to a higher value. As a result, the charging current in each light receiving circuit may be increased. In addition, the light receiving circuit in the SPAD array 240 may detect Figure 4 When the control circuit 40 detects the phenomenon shown in the graph 62 and determines that the charging current is too large, the control circuit 40 can control the power supply circuit to change the power supply potential Vdd used in the SPAD array 240 to a lower level. Therefore, the charging current in the light receiving circuit in the SPAD array 240 can be reduced.

[0160] When the processing in step S214 is completed, the processing in steps S212 and S213 is performed again. That is, the errors of the plurality of light receiving circuits are counted again to determine whether the error count is within the reference range. When the error count is within the reference range ("Yes" in step S213), the adjustment processing is completed (step S215). After step S215, the distance measuring device can start the distance measurement processing by irradiating the object OBJ with light from the light emitting element.

[0161] Fig.15 The execution timing of the above-mentioned processing is not limited to the calibration time of the device. Fig.15The processing can be performed at a timing other than the calibration time of the device. For example, after starting the operation of the device, the value of the power supply potential Vdd provided by the power supply circuit can be adjusted.

[0162] Fig.16 Table T3 in FIG. 2 indicates the number of error determinations when a plurality of values ​​of the power supply potential Vdd are used in the SPAD array 240. For example, the measurement circuit 30 or the control circuit 40 measures the number of error determinations using different power supply potentials Vdd and generates Table T3. Fig.16 , when a higher power supply potential Vdd is set, the number of error determinations decreases. For example, the control circuit 40 may be based on a threshold value th of the number of error determinations. e In this case, the control circuit 40 will use the power supply potential Vdd 1 The error in determining the quantity e d1 With the threshold th e For comparison. d1 >th e In the case of 2 (Vdd 1 ≠Vdd 2 ). The control circuit 40 can determine whether to use a voltage greater than Vdd based on the information of the error code. 1 Vdd 2 Or use a voltage less than Vdd 1 Vdd 2 Then, when the control circuit 40 determines that the number of error determinations is smaller than the threshold value, the distance measurement can be performed using the power supply potential at that time.

[0163] For example, in the case where the data of table T3 is obtained in the adjustment process, the number of error determinations 3 may be used as the threshold value th e However, the threshold can be different from this. Note that Fig.16 The values ​​of the power supply potential in the table are merely examples and are not intended to limit the values ​​of the power supply potential used in the light receiving circuit.

[0164] Note that in the case of using a plurality of power supply potentials to measure the number of error determinations, the highest power supply potential Vdd available in the light receiving circuit can be selected. max Start the measurement of the error determination quantity, or the lowest power supply potential Vdd available from the optical receiving circuit min Start the measurement of the error determination quantity. In addition, it is possible to max with Vdd min The power supply potential between the values ​​at which the error is determined is measured. That is, the power supply potential at the start of the adjustment process is not limited.

[0165] The control circuit 40 may determine that the amount of error becomes smaller than the threshold value th e For example, in the case where it is desired to use as large a charging current as possible to shorten the dead time, the number of error determinations can be counted using a higher power supply potential, and the number of error determinations can be compared with the threshold value th. e Even if the number of errors determined after the power supply potential is changed is less than the threshold value th e In the case of , the distance measurement can also be performed using a higher power supply potential. In addition, in the case where it is desired to use the power supply potential as low as possible to suppress power consumption, the number of error determinations can be counted using a lower power supply potential, and the number of error determinations can be compared with the threshold value th e Even in the case where the number of error determinations after the power supply potential is changed is smaller than the threshold value, distance measurement can be performed using a lower power supply potential.

[0166] According to the present disclosure, the optical receiving device may include: an optical receiving circuit including an optical receiving element; a power supply circuit configured to supply a power supply potential to the optical receiving circuit; and a control circuit configured to control the power supply potential provided by the power supply circuit based on a signal output from the optical receiving circuit that acts on photons.

[0167] As described above, the optical receiving device according to the present disclosure may further include a load circuit connected to the optical receiving circuit and supplying a charging current to the optical receiving element. In this case, the control circuit may be configured to change a parameter including at least one of a charging current of the load circuit and a resistance value of the load circuit based on a signal output from the optical receiving circuit by the action of the optical receiving circuit with photons.

[0168] In addition, the optical receiving device according to the present disclosure may include a plurality of optical receiving circuits. In this case, the control circuit may be configured to change at least one of the power supply potential of the power supply circuit and the parameters of the load circuit connected to at least one of the optical receiving circuits based on the signals output from the plurality of optical receiving circuits.

[0169] In addition, the optical receiving device according to the present disclosure may further include an error detector configured to determine an error based on the waveform of a signal output from the optical receiving circuit. As the error detector, the above-mentioned error detector 21 or the measurement circuit 30 can be used. In this case, the control circuit is configured to change at least one of the power supply potential of the power supply circuit and the parameter of the load circuit connected to at least one optical receiving circuit based on the number of error determinations of the signals output from the plurality of optical receiving circuits.

[0170] In addition, in the optical receiving device of the present disclosure, at least one optical receiving circuit may be configured to perform passive charging. In this case, the control circuit is configured to adjust the charging current of the optical receiving circuit so that the number of error determinations is less than the first threshold.

[0171] In addition, in the optical receiving device of the present disclosure, at least one optical receiving circuit may be configured to perform active charging. In this case, the control circuit is configured to adjust the time delay of generating a pulse for active charging in the optical receiving circuit based on the amount of error determination.

[0172] The error detector may be configured to perform error determination on at least one of a signal having a pulse width exceeding a second threshold and a signal having an interval between pulses less than a third threshold. In addition, in the light receiving device according to the present disclosure, an avalanche photodiode may be used as the light receiving element.

[0173] Next, an example of a light receiving device having a function of correcting an output signal from a light receiving circuit in a case where the output signal is determined to be an error will be described.

[0174] Fig.17 The block diagram shows an example of a distance measuring device according to Modification 2. Fig.17 In the optical receiving device 102, the error correction circuit 22 is connected between the sampler 20 and each input terminal of the measuring circuit 30. The error correction circuit 22 is configured to correct the voltage signal determined to be in an error state among the voltage signals output from the sampler 20. The error correction circuit 22 corresponds to the error detector 21, to which the function of converting the voltage signal determined by the error into a voltage signal that is not in an error state is added. For example, the error correction circuit 22 is arranged in the circuit block 241 together with the sampler 20. The configuration and function of the optical receiving device 102 are similar to those of the above-mentioned optical receiving device 101, except that the error detector 21 is replaced by the error correction circuit 22.

[0175] It should be noted that in Fig.17The configuration of the optical receiving device shown in is only an example. For example, the error correction circuit 22 can be connected between the optical receiving circuit 11 and the sampler 20. In addition, a circuit in which the function of the sampler 20 and the function of the error correction circuit 22 are integrated can be connected between each optical receiving circuit 11 and the input terminal of the measuring circuit 30. In addition, a plurality of signal lines l_rd can be connected to a common error correction circuit without preparing an error correction circuit 22 for each signal line l_rd. In this case, one error correction circuit needs to perform error determination and signal correction of a plurality of signal lines l_rd, but the required circuit area can be reduced. It should be noted that the function of converting the error determination voltage signal into a voltage signal that is not in an error state can be implemented in the input stage of the measuring circuit 30. In this case, the measuring circuit 30 can correct the voltage signal output from the optical receiving circuit 11 based on the error signal received from the error detector 21. That is, a configuration in which the measuring circuit 30 includes the error correction circuit 22 can also be adopted.

[0176] Note that the configuration of the light receiving circuit 11 is not limited. For example, Figure 3 and Figure 5 The light receiving circuit shown in can be used as the light receiving circuit 11. The light receiving circuit 11 may be a charging circuit or an active charging circuit. In addition, circuits having different configurations may be mixed in a plurality of light receiving circuits 11.

[0177] Fig.18 and Fig.19 The curve graph shows Fig.17 FIG. 1 is an example of a correction process of a voltage waveform in the light receiving device 102. In each graph, the horizontal axis represents time.

[0178] Fig.18 Graph 73 shows the waveforms of the input voltage Vai of the error correction circuit 22, the output voltage Vao of the error correction circuit 22, and the error signal Ves. In graph 73, the light receiving circuit 11 performs passive charging, but the time required for charging is too long. Therefore, in graph 73, the pulse width output from the light receiving circuit 11 is too large. For example, the error correction circuit 22 detects the rise of the pulse in the voltage signal output from the light receiving circuit 11. Then, the error correction circuit 22 monitors the pulse width. The error correction circuit 22 outputs the input signal as is until error determination is performed. In the case where the pulse width exceeds the threshold value t_h, the error correction circuit 22 performs error determination. When error determination is performed during pulse detection, the error correction circuit 22 masks the portion of the pulse that exceeds the threshold value t_h.

[0179] In the example of the graph 73, the error correction circuit 22 outputs a HIGH voltage in the time period t_h from the rise of the pulse. Then, the error correction circuit 22 outputs a LOW voltage in a portion of the time period t_m1 corresponding to the pulse width exceeding t_h. As described above, even in the case where the light receiving circuit 11 outputs a pulse having a pulse width exceeding the threshold t_h, the error correction circuit 22 can correct the pulse to a pulse having a pulse width equal to the threshold t_h. In addition, in the example of the graph 73, during the period t_m1 during which the pulse is masked, the voltage of the error signal Ves is HIGH. As a result, the measurement circuit 30 of the subsequent stage can be notified that error determination has been performed. Note that the error correction circuit 22 can notify the measurement circuit 30 of the error code.

[0180] The error correction circuit 22 samples the input voltage Vai in the period t_s, and can perform error determination when the sampled voltage is continuously at the HIGH level n_h times. Here, the values ​​of t_s and n_h can be set to satisfy the relationship of t_h=t_s×n_h. For example, t_s=1 nanosecond, n_h=10, and t_h=10 nanoseconds can be set. However, error determination can be performed by a method different from this method.

[0181] Fig.19 The graph 74 of FIG. 74 shows the waveforms of the input voltage Vai of the error correction circuit 22, the output voltage Vao of the error correction circuit 22, and the error signal Ves. In the example of the graph 74, the light receiving circuit 11 performs active charging. In the example of the graph 74, the output voltage of the light receiving circuit 11 (i.e., the input voltage Vai of the error correction circuit 22) oscillates due to the phenomenon shown in the graph 64 or the graph 67. The error correction circuit 22 outputs the input signal as it is until the error determination is performed. For example, after the pulse of the input voltage Vai falls, when the input voltage Vai is in a period LOW shorter than the threshold value t_l, the error correction circuit 22 performs the error determination. When the error determination is performed, the error correction circuit 22 may output the high error signal Ves. In addition, it should be noted that the error correction circuit 22 may notify the measurement circuit 30 of the error code. The error correction circuit 22 masks the pulse within a predetermined period t_m2 after the error determination.

[0182] In the example of the graph 74, the error correction circuit 22 outputs a LOW level voltage in the period t_m2 after the error determination. This period t_m2 is called a masking period. When the masking period t_m2 has passed after the error determination, the error correction circuit 22 outputs the input signal again as it is. For example, in the graph 74, after the masking period t_m2 has passed, the error correction circuit 22 outputs a pulse again. For example, a value greater than the threshold value t_1 may be set as the masking period t_m2.

[0183] In addition, the error correction circuit 22 can adjust the masking period t_m2 according to the error determination under the input voltage Vai. For example, after the input voltage Vai in the curve graph 74 arrives at the first pulse, three pulses arrive at intervals shorter than the threshold t_l. Therefore, the error correction circuit 22 performs three consecutive error determinations at the timing indicated by the white arrow. However, the error correction circuit 22 can release the error state without performing the error determination during the period t_r after the last error determination. When the error state is released, the error correction circuit 22 outputs the re-input pulse as is. As in the example in Figure 74, when the error state is released, the error correction circuit 22 can set the error signal Ves to low. In addition, the error correction circuit 22 can also output the HIGH error signal Ves continuously during the period t_m2, but output a discontinuous HIGH error signal Ves each time the error determination is performed.

[0184] For example, the error correction circuit 22 samples the voltage of the signal in the period t_s, and can perform error determination when the number of times the sampled voltage continuously becomes LOW is less than n_l times. The values ​​of t_s and n_l can be set so as to satisfy the relationship of t_l=t_s×n_l. However, the error correction circuit 22 can perform error determination by a method different from this method.

[0185] Here, the error determination and error correction in the case where the light receiving circuit 11 outputs a pulse of a HIGH level (positive polarity) at the time of photon detection have been described. However, in the case where the light receiving circuit 11 outputs a pulse of a LOW level (negative polarity), the error correction circuit 22 can also perform error determination. In this case, as described above, it is sufficient for the error correction circuit 22 to perform the following operations: HIGH is replaced by LOW, LOW is replaced by HIGH, the fall of the pulse is replaced by the rise of the pulse, and the rise of the pulse is replaced by the fall of the pulse.

[0186] Even in the case of using the optical receiving device 102 including the error correction circuit 22, the adjustment process of the optical receiving circuit, the pulse generator, or the power supply circuit can be performed using the above-described flowchart or table.

[0187] As described above, the optical receiving device according to the present disclosure may further include an error correction circuit, which is configured to perform error determination based on the waveform of the signal output from the optical receiving circuit and correct the waveform of the signal for which the error determination has been performed. As the error correction circuit, for example, the above-mentioned error correction circuit 22 or the measurement circuit 30 can be used. In this case, the error correction circuit may be configured to perform error determination on at least one of a signal whose pulse width exceeds the second threshold and a signal whose interval between pulses is less than the third threshold. In the case where the optical receiving device includes an error correction circuit, the control circuit may be configured to change at least one of the power supply potential of the power supply circuit and the parameters of the load circuit connected to at least one of the optical receiving circuits based on the number of error determinations of the signals output from the plurality of optical receiving circuits.

[0188] Fig. 20 The block diagram shows an example of a distance measurement device according to Modification 3. Fig. 20 2 and an external processing circuit 300. The optical receiving device 202 corresponds to the optical receiving device 200 ( Figure 1 ) components omit the configuration of the control circuit 220 and the power supply circuit 256. The processing circuit 230 of the optical receiving device 202 is connected to the external processing circuit 300 via the transmission circuit 211 and the terminal S_OUT. In addition, the SPAD controller 221 of the optical receiving device 202 is connected to the external processing circuit 300 via the terminal S_IN and the communication circuit 210. Fig. 20 As shown, an external power supply circuit 257 can be used as a circuit for supplying power supply potential Vdd to the SPAD array 240. The power supply circuit 257 is connected to the SPAD array 240 in the distance measurement device 204 via a terminal PWR. In addition, the power supply circuit 257 is connected to the external processing circuit 300 via a control signal line. The external processing circuit 300 changes the value of the power supply potential Vdd by sending a control signal to the power supply circuit 257.

[0189] The external processing circuit 300 is, for example, a hardware circuit such as an ASIC or an FPGA. However, the external processing circuit 300 may be a computer including a central processing unit (CPU) and a memory. In this case, the external processing circuit 300 provides various functions by executing a program stored in the memory on the CPU.

[0190] The external processing circuit 300 performs the corresponding Figure 1 The control circuit 220 ( Figure 8 and Fig.17That is, the external processing circuit 300 separated from the optical receiving device 202 can perform the setting of each optical receiving circuit 11 and the setting of the power supply circuit. Note that the communication between the external processing circuit 300 and the optical receiving device 202 can be performed by wire or wirelessly.

[0191] Fig.21 The block diagram shows an example of a light receiving device according to Modification 4. Figure 1 and Fig. 20 In the device shown in , the light receiving device according to the present disclosure may be a distance measuring device including a light emitting element and a distance calculating unit. However, the light receiving device according to the present disclosure may not necessarily include a distance measuring function. For example, as in Fig.21 In the light receiving device 201 in the embodiment, a device in which the distance calculation unit 233 and the trigger circuit 254 are omitted may be used. The light receiving device 201 may detect photons through the SPAD array 240 and generate a histogram. The light receiving device 201 may be connected to another device, and functions corresponding to the distance calculation unit, the trigger circuit, and the light emitting element may be added. In addition, the light receiving device 201 may be used as a device for determining the settings and power supply potential of the SPAD array 240. In this case, another distance measuring device may perform distance measurement based on the settings and power supply potential of the SPAD array 240 determined by the light receiving device 201.

[0192] Hereinafter, an example of another light receiving circuit that can be used as a pixel in the SPAD array 240 will be described.

[0193] Fig. 22 The circuit diagram shows an example of a circuit according to Modification 5. Fig. 22 The light receiving circuit 12 in corresponds to a circuit in which the transistor TR2 and the switch SW3 of the light receiving circuit 10 are omitted. That is, in the light receiving circuit 12, a part of the light receiving circuit 10 that latches the state of the transistor TR1 is omitted. In the light receiving circuit 12, when SW1 is set to be on and SW2 is set to be off, passive charging is performed. In addition, in the light receiving circuit 12, when SW1 is set to be off and SW2 is set to be on, active charging is performed. It should be noted that in the light receiving circuit 12, when both SW1 and SW2 are set to be on, passive charging and active charging are performed. Note that the operation of the light receiving circuit 12 is similar to that of the light receiving circuit 10 described above, except that the operation of latching the state of the transistor TR1 is canceled.

[0194] Fig.23 The circuit diagram shows an example of a circuit according to Modification Example 6. Fig.23The light receiving circuit 14 in Table 70 corresponds to a circuit in which the load element 90 (transistor TR0) of the light receiving circuit 10 is omitted. That is, the light receiving circuit 14 is a circuit dedicated to active charging. The operation of the light receiving circuit 14 is similar to the case where the switch SW1 is set to OFF, the switch SW2 is set to ON, and the switch SW3 is set to ON in the light receiving circuit 10 (switch setting st1 of Table 70).

[0195] The distance measuring device according to the present disclosure may include: a light-emitting element; a plurality of light-receiving circuits; a power supply circuit configured to supply a power supply potential to the plurality of light-receiving circuits; and a control circuit configured to control the power supply potential based on a signal output from the plurality of light-receiving circuits acting on photons during a period when the light-emitting element does not emit light. In addition, the distance measuring device according to the present disclosure may further include a plurality of load circuits, each of which is connected to each light-receiving circuit and supplies a charging current to the light-receiving element in the light-receiving circuit. In this case, the control circuit may be configured to control at least one of the resistance value and the charging current of the plurality of load circuits based on the signal.

[0196] Furthermore, the control circuit of the distance measuring device according to the present disclosure may be configured to adjust a time delay of generating a pulse for active charging in at least one light receiving circuit based on the signal.

[0197] When using the optical receiving device, distance measuring device and optical receiving circuit according to the present disclosure, the distance measurement can be started after performing the setting for minimizing the dead time. Therefore, photon detection or distance measurement can be performed with high precision. In the optical receiving device, distance measuring device and optical receiving circuit according to the present disclosure, at least one of a plurality of methods can be selected to adjust the charging current. For example, the power supply circuit can adjust the power supply potential to be supplied to the plurality of optical receiving circuits according to the number of error determinations of the plurality of optical receiving circuits. In the case of supplying a common power supply potential in the SPAD array, the setting of the charging current of the entire SPAD array can be changed in a short time.

[0198] In addition, the SPAD array may include pixels in which a load circuit with an adjustable resistance value or a load circuit with an adjustable current value is connected to the light receiving circuit. Therefore, the value of the charging current can be adjusted with higher precision in units of a single pixel. For example, it is easy to adjust the charging current of each area in the SPAD array. This makes it possible to obtain high-quality distance images. In the case of using a light receiving device, a light receiving circuit, and a distance measuring device according to the present disclosure, the distance measurement performance can be improved while suppressing power consumption.

[0199] 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 can be implemented as a device installed on any type of mobile body (such as a car, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, or a robot).

[0200] Fig.24 : is a block diagram showing a schematic configuration example of a vehicle control system which is an example of a moving body control system to which the technology according to the present disclosure can be applied.

[0201] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. Fig.24 In the example shown, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an external information detection unit 12030, an internal information detection unit 12040, and an integrated control unit 12050. In addition, as a functional configuration of the integrated control unit 12050, a microcomputer 12051, a sound and image output unit 12052, and an in-vehicle network interface (I / F) 12053 are shown.

[0202] The drive system control unit 12010 controls the operation of devices related to the drive system of the vehicle according to various programs. For example, the drive system 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 wheels, a steering mechanism for adjusting the steering of the vehicle, a braking device for generating a braking force of the vehicle, and the like.

[0203] The body system control unit 12020 controls the operation of various devices equipped in the body according to various programs. For example, the body system control unit 12020 is used as a control device for a keyless entry system, a smart key system, a power window device, or various lights such as headlights, taillights, brake lights, turn indicators, or fog lights. In this case, radio waves emitted from a portable device instead of a key or signals of various switches may be input to the body system control unit 12020. The body system control unit 12020 receives input of these radio waves or signals and controls the door lock device, power window device, lights, etc. of the vehicle.

[0204] The vehicle exterior information detection unit 12030 detects information outside the vehicle in which the vehicle control system 12000 is installed. For example, the imaging unit 12031 is connected to the vehicle exterior information detection unit 12030. The vehicle exterior information detection unit 12030 causes the imaging unit 12031 to capture an image outside the vehicle and receive the captured image. The vehicle exterior information detection unit 12030 can perform object detection processing or distance detection processing on, for example, a person, a car, an obstacle, a sign, or a character on the road surface based on the received image.

[0205] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image, or output the electrical signal as distance measurement information. In addition, the light received by the imaging unit 12031 can be visible light or invisible light such as infrared light.

[0206] The vehicle interior 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 vehicle interior information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that photographs the driver, and the vehicle interior information detection unit 12040 can calculate the driver's fatigue or concentration based on the detection information input from the driver state detection unit 12041, or can determine whether the driver is dozing off.

[0207] The microcomputer 12051 can calculate the control target value of the driving force generating device, the steering mechanism or the braking device based on the information inside and outside the vehicle acquired by the vehicle outside information detection unit 12030 or the vehicle inside information detection unit 12040, and can output the control command to the driving system control unit 12010. For example, in order to realize the functions of the advanced driver assistance system (ADAS), the microcomputer 12051 can perform cooperative control, and the functions of the advanced driver assistance system include collision avoidance or impact mitigation of the vehicle, follow-up driving based on the vehicle-to-vehicle distance, speed maintenance driving, vehicle collision warning, vehicle lane departure warning, etc.

[0208] In addition, the microcomputer 12051 controls the driving force generating device, steering mechanism, braking device, etc. based on the information about the vehicle's surroundings obtained by the external information detection unit 12030 or the internal information detection unit 12040. Thus, the microcomputer 12051 can perform coordinated control for automatic driving for autonomous driving of the vehicle without relying on the driver's operation.

[0209] In addition, the microcomputer 12051 can output a control instruction to the body system control unit 12020 based on the vehicle exterior information acquired by the vehicle exterior information detection unit 12030. For example, the microcomputer 12051 can control the headlights according to the position of the preceding vehicle or the oncoming vehicle detected by the vehicle exterior information detection unit 12030, and perform cooperative control for the purpose of anti-glare (such as switching the high beam to the low beam).

[0210] The sound and image output unit 12052 sends at least one of a sound and an image output signal to an output device capable of visually or auditorily notifying the occupants of the vehicle or the outside of the vehicle of information. Fig.24 In the example of FIG. 1 , as output devices, an audio speaker 12061, a display unit 12062, and a dashboard 12063 are shown. For example, the display unit 12062 may include at least one of an on-board display or a head-up display.

[0211] Fig.25 12031 is a diagram showing an example of the setting position of the imaging unit 12031.

[0212] exist Fig.25 In the figure, vehicle 12100 includes imaging units 12101, 12102, 12103, 12104 and 12105 as imaging unit 12031.

[0213] For example, the imaging units 12101, 12102, 12103, 12104, 12105 are arranged at positions such as the front nose, side mirrors, rear bumper, rear door, and the upper part of the windshield in the compartment of the vehicle 12100. The imaging unit 12101 included in the front nose and the imaging unit 12105 included in the upper part of the windshield in the compartment mainly acquire images in front of the vehicle 12100. The imaging units 12102 and 12103 included in the side mirrors mainly acquire images on the sides of the vehicle 12100. The imaging unit 12104 included in the rear bumper or the rear door mainly acquires images of the rear of the vehicle 12100. The front images acquired by the imaging units 12101 and 12105 are mainly used for the detection of front vehicles, pedestrians, obstacles, traffic signals, traffic signs, lanes, etc.

[0214] Please note that Fig.25An example of the imaging ranges of the imaging units 12101 to 12104 is shown. The imaging range 12111 indicates the imaging range of the imaging unit 12101 provided in the front nose, the imaging ranges 12112 and 12113 respectively indicate the imaging ranges of the imaging units 12102 and 12103 provided in the side mirrors, and the imaging range 12114 indicates the imaging range of the imaging unit 12104 provided in the rear bumper or the rear door. For example, by overlapping the image data imaged by the imaging units 12101 to 12104, a top-view image of the vehicle 12100 viewed from above is obtained.

[0215] 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 including a plurality of imaging elements, or may be an imaging element having pixels for phase difference detection.

[0216] For example, the microcomputer 12051 obtains the distance to each three-dimensional object within the imaging range 12111 to 12114 and the time change of the distance (relative speed relative to the vehicle 12100) based on the distance information obtained from the imaging units 12101 to 12104, so that the microcomputer 12051 can extract the three-dimensional object that is closest on the travel path of the vehicle 12100 and travels in the same direction as the vehicle 12100 at a predetermined speed (for example, 0 km / h or more) as the front vehicle. In addition, the microcomputer 12051 can set the inter-vehicle distance to be ensured in front of the front vehicle, and can perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), etc. In this way, coordinated control can be performed for the purpose of automatic driving that operates autonomously without relying on the driver's operation, etc.

[0217] For example, the microcomputer 12051 can classify the three-dimensional object data about the three-dimensional object into other three-dimensional objects such as two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, telephone poles, etc. based on the distance information obtained from the imaging units 12101 to 12104, and extract the result to use the result to automatically avoid obstacles. For example, the microcomputer 12051 identifies obstacles near the vehicle 12100 as obstacles that can be seen by the driver of the vehicle 12100 and obstacles that are difficult to see. Then, the microcomputer 12051 determines the collision risk representing the risk of collision with each obstacle, and when the collision risk is equal to or higher than the operating parameter and there is a possibility of collision, the microcomputer 12051 can output an alarm to the driver via the audio speaker 12061 and the display unit 12062 or perform forced deceleration or avoid steering via the drive system control unit 12010 to perform driving assistance for collision prevention.

[0218] At least one of the imaging units 12101 to 12104 may be an infrared camera for detecting infrared rays. For example, the microcomputer 12051 may identify a pedestrian by determining whether there is a pedestrian in the captured images of the imaging units 12101 to 12104. For example, such identification of pedestrians is performed by a process of extracting feature points in the captured images of the imaging units 12101 to 12104 as infrared cameras and a process of performing pattern matching processing on a series of feature points representing the outline of an object and discerning whether it is a pedestrian. If the microcomputer 12051 determines that there is a pedestrian in the captured images of the imaging units 12101 to 12104 and identifies the pedestrian, the sound image output unit 12052 causes the display unit 12062 to overlap and display a rectangular contour line for emphasizing the recognized pedestrian. In addition, the sound image output unit 12052 may cause the display unit 12062 to display an icon indicating a pedestrian at a desired position, etc.

[0219] 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 device 12031. For example, Figure 1 The light receiving device 200 and Figure 2 The light emitting element 255 may be mounted on the imaging unit 12031. In addition, at least one of the light receiving devices 200 to 202 may be mounted on the imaging unit 12031. By applying the technology according to the present disclosure to the imaging device 12031, distance measurement can be performed with higher accuracy. As a result, the safety of the vehicle 12100 can be improved.

[0220] It should be noted that the present technology can also adopt the following configurations.

[0221] (1) A light receiving device comprising:

[0222] A light receiving circuit, comprising a light receiving element;

[0223] a power supply circuit configured to supply a power supply potential to the light receiving circuit; and

[0224] The control circuit is configured to control a power supply potential supplied by the power supply circuit based on a signal output from the light receiving circuit that acts on the photons.

[0225] (2) The optical receiving device according to (1), further comprising:

[0226] a load circuit connected to the light receiving circuit and supplying a charging current to the light receiving element;

[0227] The control circuit is configured to change a parameter including at least one of a charging current of the load circuit and a resistance value of the load circuit based on the signal.

[0228] (3) The optical receiving device according to (2), further comprising:

[0229] Multiple optical receiving circuits,

[0230] The control circuit is configured to change at least one of a power supply potential of the power supply circuit and a parameter of a load circuit connected to at least one of the light receiving circuits based on signals output from the plurality of light receiving circuits.

[0231] (4) The optical receiving device according to (3), further comprising:

[0232] an error detector configured to perform error determination based on a waveform of a signal output from the light receiving circuit;

[0233] The control circuit is configured to change at least one of a power supply potential of a power supply circuit and a parameter of a load circuit connected to at least one of the light receiving circuits based on the amount of error determination of signals output from the plurality of light receiving circuits.

[0234] (5) The light receiving device according to (4),

[0235] wherein at least one light receiving circuit is configured to perform passive charging; and

[0236] The control circuit is configured to adjust a charging current of the light receiving circuit so that the amount of error determination is less than a first threshold.

[0237] (6) The light receiving device according to (4) or (5),

[0238] wherein at least one light receiving circuit is configured to perform active charging; and

[0239] The control circuit is configured to adjust a time delay in generating a pulse for active charging in the light receiving circuit based on the amount of error determination.

[0240] (7) The light receiving device according to any one of (4) to (6),

[0241] The error detector is configured to perform error determination on at least one of a signal having a pulse width exceeding a second threshold and a signal having an interval between pulses less than a third threshold.

[0242] (8) The optical receiving device according to any one of (3) to (7), further comprising:

[0243] The error correction circuit is configured to perform error determination based on the waveform of the signal output from the light receiving circuit and correct the waveform of the signal for which the error determination has been performed.

[0244] (9) The light receiving device according to (8),

[0245] The error correction circuit is configured to perform error determination on at least one of a signal having a pulse width exceeding a second threshold and a signal having an interval between pulses less than a third threshold.

[0246] (10) The light receiving device according to (8),

[0247] The control circuit is configured to change at least one of a power supply potential of a power supply circuit and a parameter of a load circuit connected to at least one of the light receiving circuits based on the amount of error determination of signals output from the plurality of light receiving circuits.

[0248] (11) The light receiving device according to (10),

[0249] wherein at least one light receiving circuit is configured to perform passive charging; and

[0250] The control circuit is configured to adjust a charging current of the light receiving circuit so that the amount of error determination is less than a first threshold.

[0251] (12) The light receiving device according to (10) or (11),

[0252] wherein at least one light receiving circuit is configured to perform active charging; and

[0253] The control circuit is configured to adjust a time delay in generating pulses for active charging in the light receiving circuit based on the amount of error determination.

[0254] (13) The light receiving device according to any one of (1) to (12),

[0255] Among them, the light receiving element is an avalanche photodiode.

[0256] (14) A distance measuring device comprising:

[0257] Light emitting element;

[0258] a plurality of light receiving circuits including light receiving elements;

[0259] a power supply circuit configured to supply a power supply potential to the plurality of light receiving circuits; and

[0260] A control circuit is configured to control the power supply potential based on signals output from a plurality of light receiving circuits in response to photons during a period in which the light emitting element does not emit light.

[0261] (15) The distance measuring device according to (14), further comprising:

[0262] a plurality of load circuits connected to each light receiving circuit and supplying a charging current to the light receiving element;

[0263] The control circuit is configured to control at least one of the resistance values ​​and the charging currents of the plurality of load circuits based on the signal.

[0264] (16) The distance measuring device according to (14) or (15),

[0265] The control circuit is configured to adjust a time delay of generating a pulse for active charging in at least one light receiving circuit based on the signal.

[0266] (17) An optical receiving circuit comprising:

[0267] A light receiving element;

[0268] Current source;

[0269] a switch capable of conducting a first contact side connected to a reference potential or a second contact side connected to the light receiving element;

[0270] a current mirror circuit configured to supply, from an output side, a second current obtained by mirroring a first current flowing between a reference potential and a current source; and

[0271] The transistor has a first signal electrode, a second signal electrode and a control electrode, the first signal electrode is connected to a reference potential, the second signal electrode is connected to a light receiving element and an output side of a current mirror circuit, and the control electrode is connected to a switch.

[0272] (18) The optical receiving circuit according to (17), further comprising:

[0273] Multiple switches and transistors,

[0274] The light receiving circuit is configured so that a third current obtained by multiplying the first current by N (N is a positive integer) is supplied to the light receiving element in response to switching of the switch.

[0275] (19) The optical receiving circuit according to (17) or (18), further comprising:

[0276] The readout circuit is configured to generate a pulse when the light receiving element interacts with a photon.

[0277] (20) An optical receiving circuit comprising:

[0278] A light receiving element;

[0279] A plurality of resistors connected in parallel between the reference potential and the light receiving element;

[0280] a plurality of switches, each switch being connected in series with a resistor; and

[0281] a readout circuit configured to generate a pulse when the light receiving element interacts with a photon;

[0282] The light receiving circuit is configured such that a current supplied to the light receiving element is adjusted according to switching of the switch.

[0283] The various aspects of the present disclosure are not limited to the above-mentioned embodiments, but include various modifications that can be thought of by those skilled in the art, and the effects of the present disclosure are not limited to the above-mentioned contents. That is, various additions, modifications, and partial deletions may be made without departing from the conceptual concept and spirit of the present disclosure obtained from the contents defined in the claims and their equivalents.

[0284] List of reference numbers

[0285] OBJ object

[0286] 1 Detection unit

[0287] 10, 12, 13 Optical receiving circuit

[0288] 11. Optical receiving circuit

[0289] 20 Sampler

[0290] 21 Error detector

[0291] 22 Error Correction Circuit

[0292] 30 Measurement circuit

[0293] 40 Control circuit

[0294] 50, 51, 52, 53, 54, 55, 56 pixels

[0295] 75, 76 Shading part

[0296] 80, 81 Opening surface

[0297] 90 Load Cell

[0298] 91, 91, 92 Active charging circuit

[0299] 100, 101, 102 optical receiving device

[0300] 200 Distance measuring device

[0301] 255 light emitting elements

[0302] 256 power supply circuit.

Claims

1. A light receiving device, comprising: A light receiving circuit, comprising a light receiving element; a power supply circuit configured to supply a power supply potential to the light receiving circuit; a control circuit configured to control the power supply potential supplied by the power supply circuit based on a signal output from the light receiving circuit that acts on the photon; a load circuit connected to the light receiving circuit and supplying a charging current to the light receiving element; a plurality of said light receiving circuits; as well as an error detector configured to perform error determination based on a waveform of the signal output from the light receiving circuit, wherein the control circuit is configured to change a parameter including at least one of a charging current of the load circuit and a resistance value of the load circuit based on the signal, wherein the control circuit is configured to change at least one of the power supply potential of the power supply circuit and a parameter of a load circuit connected to at least one of the light receiving circuits based on signals output from the plurality of light receiving circuits, wherein the control circuit is configured to change at least one of the power supply potential of the power supply circuit and a parameter of a load circuit connected to at least one of the light receiving circuits based on an amount of error determination of signals output from the plurality of light receiving circuits.

2. The light receiving device according to claim 1, in, at least one of the light receiving circuits is configured to perform passive charging; and The control circuit is configured to adjust the charging current of the light receiving circuit so that the error determination amount is less than a first threshold.

3. The light receiving device according to claim 1, in, at least one of the light receiving circuits is configured to perform active charging; and The control circuit is configured to adjust a time delay of generating pulses for the active charging in the light receiving circuit based on the error determined amount.

4. The light receiving device according to claim 1, in, The error detector is configured to perform error determination on at least one of a signal having a pulse width exceeding a second threshold and a signal having an interval between pulses less than a third threshold.

5. A light receiving device, comprising: A light receiving circuit, comprising a light receiving element; a power supply circuit configured to supply a power supply potential to the light receiving circuit; a control circuit configured to control the power supply potential supplied by the power supply circuit based on a signal output from the light receiving circuit that acts on the photon; a load circuit connected to the light receiving circuit and supplying a charging current to the light receiving element; as well as a plurality of said light receiving circuits; as well as an error correction circuit configured to perform error determination based on the waveform of the signal output from the light receiving circuit and correct the waveform of the signal on which the error determination has been performed, wherein the control circuit is configured to change a parameter including at least one of a charging current of the load circuit and a resistance value of the load circuit based on the signal, wherein the control circuit is configured to change at least one of the power supply potential of the power supply circuit and a parameter of a load circuit connected to at least one of the light receiving circuits based on signals output from the plurality of light receiving circuits, The error correction circuit is configured to perform error determination on at least one of a signal having a pulse width exceeding a second threshold and a signal having an interval between pulses less than a third threshold.

6. The light receiving device according to claim 5, in, The control circuit is configured to change at least one of the power supply potential of the power supply circuit and a parameter of a load circuit connected to at least one of the light receiving circuits based on a number of error determinations of signals output from the plurality of light receiving circuits.

7. The light receiving device according to claim 6, in, at least one of the light receiving circuits is configured to perform passive charging; and The control circuit is configured to adjust the charging current in the passive charging of the light receiving circuit based on the error determined amount.

8. The light receiving device according to claim 6, in, At least one of the light receiving circuits is configured to perform active charging; and The control circuit is configured to adjust a time delay of generating pulses for the active charging in the light receiving circuit based on the error determined amount.

9. The light receiving device according to claim 5, in, The light receiving element is an avalanche photodiode.

10. A distance measuring device, comprising: Light emitting element; a plurality of light receiving circuits including light receiving elements; a power supply circuit configured to supply a power supply potential to the plurality of light receiving circuits; as well as a control circuit configured to control the power supply potential based on signals output from the plurality of light receiving circuits that react to photons during a period in which the light emitting element does not emit light, The control circuit is configured to adjust a time delay of generating a pulse for active charging in at least one of the light receiving circuits based on the signal.

11. The distance measuring device according to claim 10, further comprising: a plurality of load circuits connected to each of the light receiving circuits and supplying a charging current to the light receiving element; The control circuit is configured to control at least one of the resistance values ​​of the plurality of load circuits and the charging current based on the signal.

12. An optical receiving circuit, comprising: A light receiving element; Current source; a switch capable of conducting a first contact side connected to a reference potential or a second contact side connected to the light receiving element; a current mirror circuit configured to supply, from an output side, a second current obtained by mirroring a first current flowing between the reference potential and the current source; as well as A transistor has a first signal electrode, a second signal electrode and a control electrode, the first signal electrode is connected to the reference potential, the second signal electrode is connected to the light receiving element and the output side of the current mirror circuit, and the control electrode is connected to the switch.

13. The optical receiving circuit according to claim 12, further comprising: Multiple switches and transistors, The light receiving circuit is configured so that a third current obtained by multiplying the first current by N is supplied to the light receiving element in response to switching of the switch, where N is a positive integer.

14. The optical receiving circuit according to claim 13, further comprising: The reading circuit is configured to generate a pulse when the light receiving element interacts with a photon.

Images