Voltage detection circuit and light detection device

Abstract

A voltage detection circuit according to one embodiment of the present disclosure comprises a first light reception element, a connection circuit that is connected between the first light reception element and a first potential line, an amplification circuit into which the voltage of the first light reception element is inputted, and a clamp circuit that can limit the voltage amplitude at the amplification circuit.

Description

Voltage detection circuit and photodetector

[0001] The present disclosure relates to a voltage detection circuit and a photodetection device.

[0002] A circuit has been proposed that includes a monitor SPAD (Single Photon Avalanche Diode) and a current source that supplies a constant current to the monitor SPAD so that the monitor SPAD always operates in Geiger mode (Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2019-219345

[0004] In circuits that perform voltage detection, it is desirable to be able to improve detection performance.

[0005] It is desirable to provide a voltage detection circuit that can improve detection performance.

[0006] A voltage detection circuit according to an embodiment of the present disclosure includes a first light receiving element, a connection circuit connected between the first light receiving element and a first potential line, an amplifier circuit to which the voltage of the first light receiving element is input, and a clamp circuit capable of limiting the voltage amplitude in the amplifier circuit.A photodetector according to an embodiment of the present disclosure includes a voltage detection circuit having the first light receiving element, a second light receiving element capable of receiving light and outputting a current, and a readout circuit capable of outputting a signal based on the current of the second light receiving element.The voltage detection circuit includes a connection circuit connected between the first light receiving element and the first potential line, the amplifier circuit to which the voltage of the first light receiving element is input, and a clamp circuit capable of limiting the voltage amplitude in the amplifier circuit.

[0007] FIG. 1 is a block diagram illustrating an example of a schematic configuration of a photodetection system according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of a configuration of a photodetection device according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating an example of a signal generated by a voltage detection circuit according to an embodiment of the present disclosure. FIG. 4 is a diagram illustrating an example of a configuration of a voltage detection circuit according to an embodiment of the present disclosure. FIG. 5 is a diagram illustrating an example of a signal generated by a voltage detection circuit according to an embodiment of the present disclosure. FIG. 6 is a diagram illustrating an example of a configuration of a voltage detection circuit according to a comparative example. FIG. 7 is a diagram illustrating an example of a signal generated by a voltage detection circuit according to a comparative example. FIG. 8 is a diagram illustrating an example of a signal generated by a voltage detection circuit according to an embodiment of the present disclosure. FIG. 9 is a diagram illustrating an example of a configuration of a photodetection device according to an embodiment of the present disclosure. FIG. 10 is a diagram illustrating another example of a configuration of a photodetection device according to an embodiment of the present disclosure. FIG. 11 is a diagram illustrating another example of a configuration of a photodetection device according to an embodiment of the present disclosure. FIG. 12 is a diagram illustrating another example of a configuration of a voltage detection circuit according to an embodiment of the present disclosure. FIG. 13 is a timing chart illustrating an example of operation of a voltage detection circuit according to an embodiment of the present disclosure. Fig. 14 is a diagram for explaining a configuration example of a photodetector according to an embodiment of the present disclosure. Fig. 15 is a diagram for explaining a configuration example of a voltage detection circuit according to Modification 1 of the present disclosure. Fig. 16 is a diagram for explaining a configuration example of a voltage detection circuit according to Modification 2 of the present disclosure. Fig. 17 is a diagram for explaining a configuration example of a voltage detection circuit according to Modification 2 of the present disclosure. Fig. 18 is a diagram for explaining a configuration example of a voltage detection circuit according to Modification 3 of the present disclosure. Fig. 19 is a block diagram showing an example of a schematic configuration of a vehicle control system. Fig. 20 is an explanatory diagram showing an example of installation positions of an outside vehicle information detection unit and an imaging unit.

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be made in the following order: 1. Embodiment 2. Modification 3. Usage example 4. Application example

[0009] 1 is a block diagram showing an example of a schematic configuration of a light detection system according to an embodiment of the present disclosure. The light detection system 200 includes a light detection device 1, a light source control unit 210, and a light source 220. The light detection device 1 is a device capable of detecting incident light. The light detection device 1 has a plurality of pixels P including light receiving elements, and is configured to receive incident light and generate a signal.

[0010] The pixels P of the photodetector 1 include, for example, an avalanche photodiode (APD) as a light-receiving element and are configured to receive light and output a current. The light-receiving element (light-receiving unit) of each pixel P can be configured to generate a signal in response to receiving photons. The photodetector 1 generates a signal by receiving light that has passed through an optical system (not shown) including, for example, an optical lens.

[0011] The photodetector 1 is configured using, for example, a semiconductor substrate (e.g., a silicon substrate) on which light-receiving elements of each pixel P are provided. The photodetector 1 has a region (pixel section 100) in which a plurality of pixels P are provided. As shown in the example of FIG. 1 , the photodetector 1 is provided with the pixel section 100 in which a plurality of pixels P are two-dimensionally arranged in a matrix. The pixel section 100 can also be said to be a pixel array in which a plurality of pixels P are arranged.

[0012] The light-receiving element of each pixel P may be configured as a single-photon avalanche diode (SPAD). The photodetector 1 captures incident light from a measurement object via an optical system including an optical lens. The light-receiving element receives light from the measurement object (e.g., infrared light, visible light, etc.) and generates charges through photoelectric conversion, thereby generating a photocurrent.

[0013] The light detection device 1 can be configured as a distance measurement sensor, an image sensor, etc. The light detection device 1 is a device capable of performing distance measurement, and is configured to be able to perform distance measurement using a time-of-flight (TOF) method, for example. The light detection device 1 is applied, for example, as a distance measurement sensor capable of measuring distance using the TOF method.

[0014] The light source 220 is configured to be capable of generating light (optical signals). The light source 220 has, for example, one or more light-emitting elements and is configured to be capable of irradiating the measurement object with light. The light-emitting element is an LD (Laser Diode), an LED (Light Emitting Diode), or the like, and can output light (infrared light, visible light, etc.) to the outside.

[0015] The light source 220 (light source unit) may generate laser light and emit the laser light to the outside. The light source 220 may be configured using a semiconductor laser element, for example, a vertical cavity surface emitting laser (VCSEL).

[0016] The light source control unit 210 is configured to be able to control the light source 220. The light source control unit 210 is a drive unit (drive circuit) configured to drive the light source 220. The light source control unit 210 is configured by a plurality of circuits including, for example, a digital-to-analog converter (DAC), an amplifier circuit, etc., and can control the operation of the light source 220.

[0017] The light source control unit 210 is configured to be able to control, for example, the current and voltage to the light emitting elements of the light source 220. The light source control unit 210 supplies the light source 220 with the current and voltage for driving the light emitting elements of the light source 220, and can control the light emission by the light source 220 (for example, the light emission timing, the light emission duration, etc.).

[0018] The light source control unit 210 can also be said to be a light source driving unit configured to be able to drive the light source 220 (or the light emitting element of the light source 220). Note that the light source 220 and the light source control unit 210 may be partially or entirely configured as an integrated unit. For example, the light source 220 and the light source control unit 210 may be partially or entirely configured as a light source device (light source unit).

[0019] The light detection system 200 can irradiate a measurement object with light (e.g., laser light) using a light source 220 and receive the light reflected by the measurement object. In the light detection device 1, for example, reflected light (returned light) reflected by the measurement object is incident on the pixel unit 100, and an electrical signal corresponding to the reception of the reflected light is detected. The electrical signal generated by receiving the reflected light from the measurement object is a signal corresponding to the distance to the measurement object.

[0020] The light detection system 200 including the light detection device 1 can transmit and receive light and measure the distance to a measurement target. As an example, the light detection device 1 is configured to detect the distance to the object (subject) that is the measurement target for each pixel P and generate image data (distance image data) related to the distance to the object. The light detection device 1 can generate, for example, a depth map.

[0021] The light detection device 1 can also be applied as a sensor capable of detecting an event, for example, an event-driven sensor (also called an EVS (Event Vision Sensor), an EDS (Event Driven Sensor), or a DVS (Dynamic Vision Sensor)). The light detection device 1 and the light detection system 200 can be applied to various electronic devices.

[0022] 1 , the photodetector 1 includes a pixel unit 100, a pixel control unit 110, a signal processing unit 112, and a control unit 113. The photodetector 1 may also include a light source control unit 210. The light source 220 may be mounted on the photodetector 1 or may be provided outside the photodetector 1.

[0023] The pixel control unit 110 is configured to be able to control each pixel P of the pixel unit 100. The pixel control unit 110 is a control circuit and is configured by a plurality of circuits including, for example, a buffer, a shift register, an address decoder, etc. The pixel control unit 110 generates signals for controlling the pixels P and outputs them to each pixel P of the pixel unit 100. The pixel control unit 110 is controlled by the control unit 113 and controls the pixels P of the pixel unit 100.

[0024] The pixel control unit 110 generates signals for controlling the pixels P, such as signals for controlling a readout circuit of the pixels P, and supplies the signals to each pixel P. The pixel control unit 110 can control the reading out of pixel signals from each pixel P. The pixel control unit 110 can also be called a pixel driving unit (pixel driving circuit) configured to be able to drive each pixel P. The pixel control unit 110 and the control unit 113 can also be called a pixel control unit collectively.

[0025] The control unit 113 is configured to be able to control each unit of the photodetector 1. The control unit 113 receives an externally provided clock, data instructing an operation mode, and the like, and can also output data such as internal information of the photodetector 1. The control unit 113 is a control circuit, and has, for example, a timing generator configured to be able to generate various timing signals.

[0026] The control unit 113 controls the driving of the pixel control unit 110, the signal processing unit 112, etc. based on various timing signals (pulse signals, clock signals, etc.) generated by the timing generator. The control unit 113 may include circuits such as a PLL (Phase Locked Loop) and a DAC (Digital to Analog Converter).

[0027] The control unit 113 is also configured to supply a signal for controlling the light source control unit 210 to the light source control unit 210 and control the operation of the light source control unit 210. The control unit 113 can be configured to be able to control the generation process of pixel signals by the pixels P of the pixel unit 100, the timing of light irradiation by the light source 220, etc.

[0028] The signal processing unit 112 is a signal processing circuit configured to be able to perform signal processing. The signal processing unit 112 is configured with circuits that perform various types of signal processing on signals output from each pixel P. The signal processing unit 112 is configured to include an arithmetic circuit, a memory circuit, etc., and can perform various types of signal processing such as noise reduction processing, TD (Time to Digital) conversion processing, and counting (accumulation) processing.

[0029] The signal processing unit 112 is configured to, for example, acquire a signal from each pixel P and generate a signal related to the distance to the measurement target. The signal processing unit 112 can perform various signal processing on the signal from each pixel P and generate and output distance image data representing the distance to the measurement target. The signal processing unit 112 and the control unit 113 may be configured integrally. The signal processing unit 112 and the control unit 113 may include a processor and a memory.

[0030] The signal processing unit 112 generates a signal (distance signal) indicating the distance to the measurement object based on the pixel signal. For example, in the light detection system 200, the light source 220 repeatedly starts and stops emitting light, and the pixel P repeatedly detects reflected light (returned light). The signal processing unit 112 analyzes the pixel signals sequentially output from each pixel P through multiple distance measurements, and can generate and output image data (distance image data) including a distance signal for each pixel P.

[0031] The signal processing unit 112 has, for example, a histogram generating unit configured to generate a histogram of pixel signals. The histogram generating unit (histogram generating circuit) is configured to generate, for each pixel P, a histogram of count values ​​corresponding to the signal values ​​of the pixel signals, i.e., the round-trip time of light.

[0032] The histogram generator generates histogram data that shows the relationship between count values ​​corresponding to the round-trip time of light and the frequency (number) of count values. For example, the histogram generator classifies the count values ​​into predetermined intervals (ranges), i.e., into bins (BINs), and generates histogram data that shows the distribution of count values ​​according to the distance to the measurement target.

[0033] The signal processing unit 112 is configured to be able to calculate the distance to the measurement target based on a peak value (maximum value) in a histogram of pixel signal values. For example, the signal processing unit 112 calculates (estimates) the difference between the start time of light irradiation and the time of arrival of reflected light, i.e., the round-trip time (time of flight) of light, based on the pixel signal value (count value) whose frequency in the histogram indicates a peak value.

[0034] The signal processing unit 112 is configured to calculate the distance between the light detection device 1 and the measurement object using, for example, the calculated round-trip time. The signal processing unit 112 calculates the distance to the object for each pixel P and generates a distance signal related to the distance to the object. The distance to the measurement object is determined based on the time it takes for light irradiated from the light source 220 to be reflected by the measurement object and reach the light detection device 1. The signal processing unit 112 can generate distance image data including the distance signal for each pixel P and output it to the outside of the light detection device 1.

[0035] The pixel unit 100, pixel control unit 110, signal processing unit 112, control unit 113, etc. may be provided on a single substrate or may be provided separately on multiple substrates. For example, the photodetector 1 may have a structure (a stacked structure) formed by stacking multiple semiconductor layers. Some or all of the pixel control unit 110, signal processing unit 112, and control unit 113 may be integrally configured.

[0036] 2 is a diagram illustrating an example of the configuration of a photodetector according to an embodiment. As described above, the photodetector 1 has a plurality of pixels P provided in the pixel section 100. As shown in the example of FIG. 2, the photodetector 1 also has a voltage detection circuit 120, a control circuit 130, and a power supply circuit 140.

[0037] The voltage detection circuit 120, which will be described later, has, for example, a light-receiving element for monitoring and is configured to be able to detect a signal corresponding to the breakdown voltage of the light-receiving element. The voltage detection circuit 120 can also be called a monitor circuit (or a voltage monitor circuit). The voltage detection circuit 120 may include part or all of the control circuit 130.

[0038] Each pixel P of the photodetector 1 has a light receiving element 10 and a readout circuit 20. For example, a readout circuit 20 is provided for each light receiving element 10. Note that the readout circuit 20 may be provided for a plurality of light receiving elements 10. The photodetector 1 may have a configuration in which a plurality of pixels P share one readout circuit 20.

[0039] The light receiving element 10 is configured to receive light and generate a signal. The light receiving element 10 is, for example, a single photon avalanche diode (SPAD) and has a multiplication region (multiplication section) capable of avalanche multiplication. The light receiving element 10 can convert incident photons into electric charges and output a signal (e.g., signal S1a) that is an electrical signal corresponding to the incident photons. The light receiving element 10 can also be referred to as a photoelectric conversion element (photoelectric conversion section) configured to be capable of photoelectrically converting light.

[0040] The light receiving element 10 (also referred to as light receiving element 10a) of the pixel P is electrically connected to, for example, a supply circuit 21 and an output circuit 25. In the example shown in Fig. 2, one electrode of the light receiving element 10a, that is, a cathode, is electrically connected to a node N1 that is connected to the supply circuit 21 and the output circuit 25. The other electrode of the light receiving element 10a, that is, an anode, is electrically connected to, for example, a wiring, an electrode, or the like to which a relatively low voltage is supplied.

[0041] 2, the anode of the light receiving element 10a is electrically connected to a potential line L2 serving as a power supply line. A voltage VRLD is applied to the anode of the light receiving element 10a via the potential line L2 from a power supply circuit (power supply circuit 140 in FIG. 2) capable of supplying a voltage. The voltage VRLD is, for example, a negative voltage.

[0042] The readout circuit 20 is configured to be able to output a signal based on the current of the light receiving element 10 a. The readout circuit 20 includes circuits for reading out a signal based on the photocurrent flowing through the light receiving element 10 a, such as a supply circuit 21 and an output circuit 25. The configuration of the readout circuit 20 is not limited to the example shown in the figure and can be changed as appropriate.

[0043] The supply circuit 21 is configured to be able to supply current and voltage to the light receiving element 10a. The supply circuit 21 (supply unit) is electrically connected to the potential line L1 and is able to supply current and voltage to the light receiving element 10a. The supply circuit 21 is configured, for example, by a current source that is able to supply current to the light receiving element 10a. The potential line L1 is a wiring to which a predetermined potential (voltage) is applied. In the example shown in FIG. 2 , the potential line L1 is a power supply line to which a power supply voltage VDDH is applied.

[0044] The supply circuit 21 is, for example, configured with a transistor M1. The transistor M1 is, for example, a MOS transistor (MOSFET) having terminals of a gate, a source, and a drain. In the example shown in Fig. 2, the transistor M1 is a P-type transistor (for example, a PMOS transistor). One of the source and drain of the transistor M1, which serves as a current source, is electrically connected to a potential line L1 to which a power supply voltage VDDH is applied, and the other of the source and drain of the transistor M1 is electrically connected to the light receiving element 10a.

[0045] The transistor M1 of the supply circuit 21 generates a current corresponding to the signal level of a signal input to its gate and supplies the generated current to the light receiving element 10a. The supply circuit 21 may be configured using a resistive element. The supply circuit 21 may also be configured by a switch that electrically connects or disconnects the potential line L1 and the light receiving element 10a.

[0046] A voltage that results in a potential difference greater than the breakdown voltage of the light receiving element 10 a can be applied between the cathode and anode of the light receiving element 10 a by the voltage supplied via the supply circuit 21 and the voltage VRLD supplied by the potential line L2. That is, the potential difference across the light receiving element 10 a can be set to a potential difference greater than the breakdown voltage.

[0047] When a reverse bias voltage greater than the breakdown voltage is applied to the light-receiving element 10a, the element 10a enters a state in which it can operate in Geiger mode. In Geiger mode, the light-receiving element 10a may undergo avalanche multiplication in response to incident photons, generating a pulsed current. In the pixel P, a signal S1a corresponding to the photocurrent flowing through the light-receiving element 10a due to the incident photons is output to the output circuit 25.

[0048] For example, when avalanche multiplication occurs and the potential difference between the electrodes of the light-receiving element 10a is small, the supply circuit 21 supplies current to the light-receiving element 10a. The supply circuit 21 recharges the light-receiving element 10a, making it possible for the light-receiving element 10a to operate in Geiger mode again. The supply circuit 21 can recharge the light-receiving element 10a with electric charge and recharge the voltage of the light-receiving element 10a.

[0049] The output circuit 25 is configured to generate a signal S2a based on the signal S1a generated by the light receiving element 10a. The output circuit 25 can output the signal S2a as a voltage signal based on the current of the light receiving element 10a. The output circuit 25 is configured, for example, by an inverter (INV).

[0050] The output circuit 25 has, for example, an input section 26 and an output section 27, and can output an inverted signal of an input signal. In the example shown in Fig. 2, the output circuit 25 is configured with an INV circuit (inverter circuit). The INV circuit is configured with, for example, a PMOS transistor and an NMOS transistor connected in series between the potential line L1 and a reference potential line. As an example, the reference potential line is a wiring to which a voltage VSSL (for example, 0 V) ​​is applied, i.e., a ground line (earth line).

[0051] The input section 26 of the output circuit 25 is electrically connected to, for example, the cathode of the light receiving element 10a and the supply circuit 21. In the example shown in Figure 2, the input section 26 of the output circuit 25 (i.e., the INV circuit) is electrically connected to a node N1 that connects the light receiving element 10a and the supply circuit 21.

[0052] The output circuit 25 receives a signal S1a from the light-receiving element 10a. The signal level of the signal S1a, i.e., the voltage (potential) of the signal S1a, varies depending on the current flowing through the light-receiving element 10a. For example, when the voltage of the signal S1a is higher than a threshold, the output circuit 25 outputs a low-level signal S2a. When the voltage of the signal S1a is lower than the threshold, the output circuit 25 outputs a high-level signal S2a.

[0053] 2, when the voltage of signal S1a becomes smaller than the threshold voltage of the INV circuit due to the reception of photons by light receiving element 10a, output circuit 25, which is an INV circuit, transitions the voltage of signal S2a from low to high. Furthermore, when the voltage of signal S1a becomes larger than the threshold voltage of the INV circuit due to recharging of light receiving element 10a by supply circuit 21, output circuit 25 transitions the voltage of signal S2a from high to low.

[0054] The output circuit 25 can output the signal S2a, which becomes a pulse signal, as a pixel signal to the signal processing unit 112 (see FIG. 1 ). In the photodetector 1, for example, the signal S2a, which becomes a pulse signal based on the voltage of the signal S1a, is output to the signal processing unit 112 as a pixel signal.

[0055] The output circuit 25 may be configured with a buffer circuit, an AND circuit, a NAND circuit, an OR circuit, a NOR circuit, etc. The readout circuit 20 or the output circuit 25 may be configured to include a counter circuit, a TDC (Time to Digital Converter) circuit, etc. The readout circuit 20 may include a circuit that controls the supply circuit 21.

[0056] The voltage detection circuit 120 has, for example, a light receiving element 10 similar to the pixel P and a readout circuit 30 including an amplifier circuit 50, and is configured to be able to output a voltage signal corresponding to the breakdown voltage of the light receiving element 10. The voltage detection circuit 120 is a circuit configured to measure (observe) the breakdown voltage, and can also be called a measurement circuit or an observation circuit.

[0057] The voltage detection circuit 120 includes, for example, one or more light receiving elements 10 as light receiving elements for monitoring. The light receiving elements 10 (also referred to as light receiving elements 10b) of the voltage detection circuit 120 are, for example, SPADs, and can generate pulsed currents by avalanche multiplication. The light receiving elements 10b may be shielded from light by a light shielding member (light shielding film).

[0058] The readout circuit 30 of the voltage detection circuit 120 is configured to be able to output a signal based on the voltage of the electrode (terminal) of the light receiving element 10 b. The readout circuit 30 is configured to output a voltage signal corresponding to the voltage (quench voltage) when the avalanche multiplication of the light receiving element 10 b stops, i.e., when the light receiving element 10 b is quenched.

[0059] The readout circuit 30 is configured to measure (monitor) the voltage after avalanche multiplication occurs in the light-receiving element 10 b, i.e., the voltage after the reaction of the light-receiving element 10 b. The readout circuit 30 can output a voltage signal corresponding to the quench voltage of the light-receiving element 10 b, i.e., a voltage signal based on the breakdown voltage.

[0060] 2, the readout circuit 30 includes a connection circuit 40 and an amplifier circuit 50. For example, the readout circuit 30 is provided for each light-receiving element 10b to be monitored. Note that the readout circuit 30 may be provided for a plurality of light-receiving elements 10b. The connection circuit 40 is connected between the light-receiving element 10b and the potential line L1.

[0061] The connection circuit 40 is controlled by a signal input from, for example, a control circuit (for example, the control circuit 130, the pixel control unit 110, or the control unit 113) that controls the connection circuit 40. The connection circuit 40 is controlled to a low resistance state (i.e., a low impedance state) or a high resistance state (i.e., a high impedance state) according to, for example, a signal voltage input from the control circuit.

[0062] The connection circuit 40 is configured using, for example, a transistor M2 as a switch, and is electrically connected in series between the light receiving element 10b and the potential line L1. The transistor M2 is, for example, configured by a P-type transistor (for example, a PMOS transistor).

[0063] One of the source and drain of the transistor M2 is electrically connected to, for example, the potential line L1. The other of the source and drain of the transistor M2 is electrically connected to the light receiving element 10b. The connection circuit 40 is controlled to be in an on state (conductive state) or an off state (non-conductive state) by the pixel control unit 110, the control circuit 130, or the like.

[0064] 2, the connection circuit 40 is configured to electrically connect or disconnect the potential line L1 and the light receiving element 10b based on the input signal RP. The connection circuit 40 is controlled by the signal RP, which is a pulse signal, and is configured to be able to recharge the light receiving element 10b.

[0065] The connection circuit 40 is electrically connected to the potential line L1 (power line) to which the power supply voltage VDDH is supplied, and can supply current and voltage to the light receiving element 10b. The connection circuit 40 is a charging circuit (charging unit) and is configured to be able to intermittently charge the light receiving element 10b, for example. The connection circuit 40 can also be called a recharge circuit (recharge unit).

[0066] In the photodetector 1, for example, a signal RP that controls the transistor M2 is input to the connection circuit 40, and the recharging of the light receiving element 10b is controlled. The signal RP, which is a pulse signal, controls the on / off of the transistor M2, and the timing of the recharging of the light receiving element 10b is controlled.

[0067] In the voltage detection circuit 120, for example, a signal RP, which is a pulse signal, is repeatedly input to the connection circuit 40, causing the connection circuit 40 to be intermittently turned on. The voltage detection circuit 120 can perform intermittent recharging of the light receiving element 10b by controlling the connection circuit 40. The connection circuit 40 may be turned on at predetermined cycles (time intervals) to periodically recharge the light receiving element 10b.

[0068] In the voltage detection circuit 120, the voltage of the electrode of the light receiving element 10b is output to the amplifier circuit 50. In the example shown in Fig. 2, the cathode voltage of the light receiving element 10b is applied to a node N2 where the connection circuit 40 and the amplifier circuit 50 are connected. A signal S1b having the cathode voltage of the light receiving element 10b is input to the amplifier circuit 50.

[0069] 3 is a diagram illustrating an example of a signal generated by the voltage detection circuit according to the embodiment. In FIG. 3, the vertical axis represents the signal level of signal S1b, and the horizontal axis represents time t. During the period from time t1 to time t2, when a photon is incident on light-receiving element 10b and avalanche multiplication occurs, the current flowing through light-receiving element 10b increases, and the potential difference between the cathode and anode of light-receiving element 10b decreases.

[0070] 2 and 3, the cathode voltage of the light receiving element 10b, i.e., the voltage of the signal S1b, decreases. Then, the potential difference between the electrodes of the light receiving element 10b decreases, causing avalanche multiplication to stop (quench). The difference between the voltage of the signal S1b (i.e., the quench voltage) during quenching and the voltage VRLD supplied by the potential line L2 has a magnitude (value) equivalent to the breakdown voltage VBD of the light receiving element 10b. That is, the potential difference between the electrodes of the light receiving element 10b during quenching is equivalent to the breakdown voltage of the light receiving element 10b.

[0071] During the period from time t3 to time t4, transistor M2 of connection circuit 40 is turned on. As a result, a current (recharge current) is supplied from connection circuit 40 to light receiving element 10b, and the potential difference between the electrodes of light receiving element 10b increases. In the example shown in Figures 2 and 3, the cathode voltage of light receiving element 10b, i.e., the voltage of signal S1b, increases.

[0072] The recharge operation sets the voltage between the electrodes of the light-receiving element 10b to a value greater than the breakdown voltage VBD by the voltage VEX, and the light-receiving element 10b is again able to operate in Geiger mode. The voltage VEX is a bias voltage that exceeds the breakdown voltage VBD and is also called an excess bias voltage or excess voltage.

[0073] 2 is configured to be able to output a signal based on the voltage of the light receiving element 10b. The amplifier circuit 50 is, for example, electrically connected to the electrode of the light receiving element 10b and configured to be able to output a voltage signal based on the voltage of the light receiving element 10b. The amplifier circuit 50 is configured by a source follower circuit, a differential amplifier circuit, etc.

[0074] 2, the amplifier circuit 50 is electrically connected to a node N2 that connects the light receiving element 10b and the connection circuit 40. The amplifier circuit 50 can output a signal S2b, which is a voltage signal corresponding to the cathode voltage of the light receiving element 10b, to the control circuit 130. The signal S2b is a signal that indicates a voltage level corresponding to the quench voltage of the light receiving element 10b, for example.

[0075] The control circuit 130 is configured to include, for example, an AD conversion circuit 131 and an arithmetic circuit 132. As an example, the control circuit 130 is configured to control the power supply circuit 140 based on the output voltage of the amplifier circuit 50, i.e., the voltage of the signal S2b, and to control the voltage supplied by the power supply circuit 140 to the light receiving elements 10 (light receiving elements 10a and 10b in FIG. 2).

[0076] The AD conversion circuit 131 is configured to be capable of AD (Analog-to-Digital) conversion and converts an input analog signal into a digital signal. The AD conversion circuit 131 is an ADC (Analog-to-Digital Converter). A signal S2b corresponding to the quench voltage is input to the AD conversion circuit 131 from, for example, the amplifier circuit 50.

[0077] The AD conversion circuit 131 performs AD conversion processing on the signal S2b, which is an analog signal input from the amplifier circuit 50. The AD conversion circuit 131 (AD conversion unit) may, for example, sample the signal S2b and convert the analog signal S2b into a digital signal. The AD conversion circuit 131 outputs the digitally converted signal S2b to the arithmetic circuit 132.

[0078] The arithmetic circuit 132 is configured to acquire the signal S2b converted into a digital signal and perform arithmetic processing. The arithmetic circuit 132 (arithmetic unit) is configured, for example, with a logic circuit, a memory, etc. The arithmetic circuit 132 is configured, for example, to change the voltage supplied to the light receiving element 10 (light receiving elements 10a and 10b in FIG. 2) based on the signal S2b indicating the quench voltage.

[0079] The arithmetic circuit 132 is configured to grasp the magnitude of the breakdown voltage using the signal S2b obtained by the monitor light-receiving element 10b and to correct (adjust) the voltage supplied to the light-receiving element 10. As an example, the arithmetic circuit 132 is configured to control the power supply circuit 140 so that the voltage VEX supplied to the light-receiving element 10 is constant.

[0080] The power supply circuit 140 is configured to be able to supply voltage and current to the light receiving element 10. The power supply circuit 140 includes, for example, a voltage generation circuit (a step-down circuit, a step-up circuit, etc.) and is configured to generate a voltage by stepping down or stepping up an input voltage. In the example shown in FIG. 2 , the power supply circuit 140 generates a voltage VRLD and can supply it to the light receiving element 10 a of each pixel P and the light receiving element 10 b of the voltage detection circuit 120.

[0081] The arithmetic circuit 132 calculates a correction amount (correction value) of the voltage VRLD supplied to the light receiving element 10 (light receiving elements 10a and 10b) based on, for example, the signal S2b, and controls the power supply circuit 140. The arithmetic circuit 132 controls the power supply circuit 140 based on the correction amount that takes into account the breakdown voltage VBD and the voltage VEX, and can set and update the voltage VRLD supplied to the light receiving element 10.

[0082] 4 is a diagram illustrating an example of the configuration of a voltage detection circuit according to an embodiment. As shown in the example of FIG. 4, the readout circuit 30 of the voltage detection circuit 120 includes an amplifier circuit 50 including a transistor M3 and a current source 51, and a clamp circuit 60. The transistor M3 is, for example, a P-type transistor (e.g., a PMOS transistor), and is configured to generate and output a signal S2b based on the voltage of the light receiving element 10b.

[0083] The gate of the transistor M3 is electrically connected to, for example, the cathode of the light receiving element 10b and the connection circuit 40. In the example shown in Fig. 4, the gate of the transistor M3 is electrically connected to a node N2 that connects the light receiving element 10b and the connection circuit 40, and a signal S1b having the cathode voltage of the light receiving element 10b is input to the node N2.

[0084] The drain of the transistor M3 is electrically connected to, for example, a potential line L3. In the example shown in Fig. 4, the potential line L3 is a wiring to which a voltage VSSL (for example, 0 V) ​​is applied, i.e., a ground line (earth line). The source of the transistor M3 is electrically connected to a current source 51. The transistor M3 and the current source 51 form a source follower circuit.

[0085] The current source 51 is electrically connected to the transistor M3 and the clamp circuit 60 and is configured to be able to supply current. In the example shown in Fig. 4, the current source 51 is connected between the transistor M3 and a potential line L1 to which a power supply voltage VDDH is applied. The current source 51 is electrically connected in series to the transistor M3 and is able to supply current to the transistor M3. The current source 51 may be configured using a PMOS transistor, for example.

[0086] The amplifier circuit 50 outputs a signal S2b based on the voltage of the light receiving element 10b to a node N3 to which the transistor M3 and the current source 51 are connected. The amplifier circuit 50 may generate a signal S2b that is a voltage signal corresponding to the cathode voltage of the light receiving element 10b, for example, and output the signal S2b to the control circuit 130 via the node N3 (see also FIG. 2).

[0087] The clamp circuit 60 is electrically connected to the amplifier circuit 50 and configured to be able to limit the voltage amplitude. The clamp circuit 60 is configured, for example, by a transistor M4. The transistor M4 is electrically connected in series between a node N3, to which the current source 51 and the transistor M3 are connected, and the potential line L3. The transistor M4 is configured, for example, by a P-type transistor (for example, a PMOS transistor).

[0088] One of the source and drain of the transistor M4, for example, the source of the transistor M4, is electrically connected to the current source 51 and the transistor M3. The other of the source and drain of the transistor M4, for example, the drain of the transistor M4, is electrically connected to the potential line L3. A predetermined bias voltage is applied to the gate of the transistor M4.

[0089] For example, a constant voltage Vclamp is applied to the gate of transistor M4. Transistor M4 can be used as a voltage limiting transistor and can also be called a clamp transistor. Transistor M4 can be controlled by the voltage Vclamp input to its gate, for example, to limit the voltage at node N3.

[0090] In the voltage detection circuit 120, for example, during a period when the light receiving element 10b is not receiving photons (i.e., a standby period), the voltage of the node N3, i.e., the voltage of the signal S2b, is fixed (clamped) to a voltage based on the voltage Vclamp by the clamp circuit 60. The clamp circuit 60 (transistor M4) may be configured as a part of the amplifier circuit 50.

[0091] 5 is a diagram illustrating an example of signals generated by a voltage detection circuit according to an embodiment. In FIG. 5, signals S1b and S2b are illustrated on the same time axis. Also, in FIG. 5, the timing of incidence of photons on light receiving element 10b is schematically indicated by outline arrows on the same time axis.

[0092] At time t11, a photon is incident on the light-receiving element 10b, causing avalanche multiplication. Time t11 is the timing at which light is received by the light-receiving element 10b. When avalanche multiplication occurs in the light-receiving element 10b between time t11 and time t12, the cathode voltage of the light-receiving element 10b, i.e., the voltage of the signal S1b, drops, and the avalanche multiplication is stopped (quenched). Furthermore, as the voltage of the signal S1b drops, the voltage of the signal S2b drops.

[0093] In this embodiment, the provision of clamp circuit 60 limits the voltage amplitude of signal S2b, making it possible to properly read out signal S2b corresponding to the quench voltage of light receiving element 10b. As shown in the example of FIG. 5, signal S2b can be obtained that properly follows signal S1b indicating the cathode voltage of light receiving element 10b. The voltage detection circuit according to this embodiment will be further described below in comparison with a comparative example.

[0094] Fig. 6 is a diagram showing an example of the configuration of a voltage detection circuit according to a comparative example. The comparative example is a case in which the voltage detection circuit 120 does not include a clamp circuit 60. The capacitance Cgs shown by the dotted line in Fig. 6 is the capacitance between the gate and source of transistor M4. Fig. 7 is a diagram showing an example of a signal generated by the voltage detection circuit according to the comparative example.

[0095] In the comparative example, as shown in Fig. 7, the voltage amplitude of signal S2b generated by avalanche multiplication is large, and the voltage of signal S1b may fluctuate due to capacitance Cgs. When node N2 is in a high impedance (HiZ) state after avalanche breakdown stops (time t12 in Fig. 7), capacitive coupling due to capacitance Cgs may cause the voltage of signal S1b to drop by ΔV, as schematically indicated by the arrow in Fig. 7. Furthermore, as the voltage of signal S1b drops, the voltage of signal S2b tends to drop below its original value.

[0096] As described above, the voltage detection circuit 120 according to this embodiment is provided with the clamp circuit 60. This reduces the amount of voltage fluctuation in the signal S1b caused by capacitive coupling. As shown by the solid line in FIG. 8, the voltage fluctuation in the signal S1b can be suppressed, and the tracking of the signal S2b can be accelerated. This makes it possible to prevent the voltage of the signal S2b from dropping below its original value.

[0097] In this embodiment, the error in signal S2b can be reduced, making it possible to accurately detect a voltage corresponding to the quench voltage. The magnitude of the breakdown voltage can be estimated (detected) with high accuracy. Furthermore, signal S2b can be used to appropriately control the voltage supplied to light receiving element 10, making it possible to prevent the characteristics of light receiving element 10 from deteriorating. This makes it possible to improve distance measurement accuracy.

[0098] 9 is a diagram illustrating an example of the configuration of a photodetector according to an embodiment. The photodetector 1 may include a voltage generation circuit 150, for example, as shown in the example of FIG. 9. The voltage generation circuit 150 is configured to output a predetermined voltage (potential) to the voltage detection circuit 120 (see FIG. 4, etc.). The voltage detection circuit 120 may be configured to include the voltage generation circuit 150.

[0099] The voltage generation circuit 150 is configured to generate, for example, a voltage Vclamp that is a bias voltage and to supply the generated voltage Vclamp to the clamp circuit 60 of the voltage detection circuit 120. As an example, the voltage generation circuit 150 (voltage generation unit) may be configured by a resistive voltage divider circuit as shown in FIG.

[0100] 9, the voltage generating circuit 150 has resistor elements R1 and R2 electrically connected in series between a power supply line and a reference potential line. The voltage generating circuit 150 can generate a voltage Vclamp by dividing the power supply voltage using the resistor elements R1 and R2, and output the voltage Vclamp to the clamp circuit 60. Note that the configuration of the voltage generating circuit 150 is not limited to the example shown in the figure and can be modified as appropriate.

[0101] 10 , the voltage generating circuit 150 may be configured using a bandgap circuit 151 and a resistive element R3. The voltage generating circuit 150 may generate a voltage Vclamp by supplying the output current Iref of the bandgap circuit 151 to the resistive element R3, and output the voltage Vclamp to the clamp circuit 60. By using the same type of resistive element as the resistive element used in the bandgap circuit 151 as the resistive element R3, it is possible to reduce variations in the voltage Vclamp.

[0102] 11 , the voltage generation circuit 150 may be configured by a circuit (replica circuit) including circuit elements (e.g., transistors M3 and M4, current source 51, etc.) similar to those of the readout circuit 30. In the example shown in FIG. 11 , the voltage generation circuit 150 has an amplifier circuit 152 to which a reference voltage Vref is input, and can output a voltage Vclamp generated by the amplifier circuit 152 to the clamp circuit 60.

[0103] 12 is a diagram illustrating another example of the configuration of a voltage detection circuit according to an embodiment. The voltage detection circuit 120 may include a capacitive element capable of holding a voltage. For example, as shown in FIG. 12, the voltage detection circuit 120 includes a capacitive element C1 and is configured to be able to hold the signal voltage of the signal S2b.

[0104] 12, the voltage detection circuit 120 has a sample-and-hold circuit 70 including a capacitive element C1 and a pulse generating circuit 72. The sample-and-hold circuit 70 is configured to be able to hold a voltage corresponding to the quench voltage (i.e., breakdown voltage) of the light receiving element 10b. The sample-and-hold circuit 70, for example, has an INV circuit 71 (inverter circuit), a pulse generating circuit 72, a switch 73, and the capacitive element C1.

[0105] The switch 73 is configured to be able to electrically connect the amplifier circuit 50 and the capacitive element C1. The switch 73 is configured using, for example, a transistor, and is on / off controlled by a signal SP that is an output signal of the pulse generating circuit 72. In the example shown in Fig. 12, the switch 73 electrically connects or disconnects the capacitive element C1 to or from a node N3 to which the transistor M3 and the current source 51 are connected.

[0106] The capacitance element C1 has a predetermined capacitance value and is configured to hold a voltage. One electrode of the capacitance element C1 is connected to the switch 73 and the amplifier circuit 55, and the other electrode of the capacitance element C1 is connected to the potential line L3. The capacitance element C1 is configured, for example, by a MOS capacitance, an MIM (Metal-Insulator-Metal) capacitance, or the like. The capacitance element C1 can hold the voltage of the signal S2b input via the switch 73.

[0107] The INV circuit 71 is electrically connected to the node N2 and outputs an inverted signal of the input signal S1b to the pulse generation circuit 72. The pulse generation circuit 72 is configured to be able to generate a signal SP that becomes a pulse signal based on the signal input from the INV circuit 71. The pulse generation circuit 72 is configured using logic circuits such as a NAND circuit and a NOR circuit, and can generate the signal SP and supply it to the switch 73.

[0108] The voltage detection circuit 120 may also include an amplifier circuit 55. The amplifier circuit 55 is, for example, configured as a source follower circuit and includes circuit elements similar to those of the amplifier circuit 50. A transistor M3′ of the amplifier circuit 55 corresponds to the transistor M3 of the amplifier circuit 50. A current source 51′ of the amplifier circuit 55 corresponds to the current source 51 of the amplifier circuit 50.

[0109] The amplifier circuit 55 is configured to generate a signal S3b based on the voltage held in the capacitance element C1, i.e., the voltage of the signal S2b, and output the signal S3b to an external circuit (e.g., the control circuit 130). As an example, the signal S3b has a voltage equivalent to the signal S2b, and is a signal indicating the quench voltage, i.e., the breakdown voltage, of the light receiving element 10b.

[0110] The control circuit 130 is configured to control the power supply circuit 140 based on the output voltage of the amplifier circuit 55, i.e., the voltage of the signal S3b, and to be able to control the voltage supplied to the light receiving elements 10a and 10b by the power supply circuit 140. The control circuit 130 can control the power supply circuit 140 in accordance with the signal S3b, for example, so that the voltage VEX applied to the light receiving elements 10a and 10b is constant.

[0111] 13 is a timing chart illustrating an example of the operation of the voltage detection circuit according to the embodiment. In FIG. 13, signals RP, S1b, S2b, SP, and S3b are shown on the same time axis. Also in FIG. 13, the timing of photon incidence on light receiving element 10b is schematically indicated by an outline arrow on the same time axis.

[0112] When avalanche breakdown occurs in the light-receiving element 10b between time t21 and time t22, the cathode voltage of the light-receiving element 10b, i.e., the voltage of the signal S1b, drops, and the light-receiving element 10b enters a quenched state. In addition, as the voltage of the signal S1b drops, the voltage of the signal S2b drops.

[0113] Furthermore, as the voltage of signal S1b decreases due to the avalanche breakdown, pulse generating circuit 72 transitions the voltage of signal SP from high to low between time t22 and time t23. Between time t22 and time t23, low-level signal SP is input to switch 73, turning switch 73 on.

[0114] When the switch 73 is turned on, the node N3 and the capacitive element C1 are electrically connected, and a signal S2b having a voltage level corresponding to the quench voltage is supplied to the capacitive element C1 and the amplifier circuit 55. The amplifier circuit 55 outputs a signal S3b, which is a voltage signal corresponding to the signal S2b, to the control circuit 130.

[0115] During the period from time t24 to time t25, signal RP goes low, turning on transistor M2 of connection circuit 40. This causes connection circuit 40 to supply a recharge current to light receiving element 10b. Charging (i.e., recharging) light receiving element 10b increases the cathode voltage of light receiving element 10b, i.e., the voltage of signal S1b. Light receiving element 10b is again ready to operate in Geiger mode.

[0116] Although the configuration example of the voltage detection circuit 120 has been described above, the configuration of the voltage detection circuit 120 is not limited to the above example. The light receiving element 10b, readout circuit 30, etc. of the voltage detection circuit 120 may be provided separately on multiple substrates (or semiconductor layers). For example, the photodetector 1 may have a layered structure formed by stacking multiple substrates.

[0117] As an example, the photodetector 1 may be configured by stacking a substrate 101 and a substrate 102. For example, the light receiving element 10a of each pixel P may be arranged on the substrate 101, and the readout circuit 20 of each pixel P may be arranged on the substrate 102. The pixel control unit 110, the signal processing unit 112, the control unit 113, and the like described above may be provided on the substrate 102, for example.

[0118] 14, the light receiving element 10b of the voltage detection circuit 120 may be arranged on the substrate 101, and the readout circuit 30 (connection circuit 40, amplifier circuit 50, clamp circuit 60, etc.) of the voltage detection circuit 120 may be arranged on the substrate 102. This configuration makes it possible to reduce the capacitance added to the electrode (e.g., cathode) of the light receiving element 10b. The control circuit 130, power supply circuit 140, etc. described above may be provided on the substrate 102, for example.

[0119] By disposing the light receiving element 10b and the readout circuit 30 on separate substrates, the parasitic capacitance added to the light receiving element 10b can be reduced, and for example, the cathode voltage of the light receiving element 10b, i.e., the voltage fluctuation of the signal S1b, can be suppressed. Furthermore, by providing the clamp circuit 60, voltage fluctuation of the signals S1b and S2b can be effectively suppressed, thereby improving the degree of freedom in layout.

[0120] [Functions and Effects] The voltage detection circuit according to this embodiment includes a first light receiving element (light receiving element 10b), a connection circuit (connection circuit 40) connected between the first light receiving element and a first potential line (e.g., potential line L1), an amplifier circuit (amplifier circuit 50) to which the voltage of the first light receiving element is input, and a clamp circuit (clamp circuit 60) capable of limiting the voltage amplitude in the amplifier circuit.

[0121] The voltage detection circuit 120 according to this embodiment includes a clamp circuit 60 that can limit the voltage amplitude of the signal S2b from the amplifier circuit 50. By providing the clamp circuit 60, voltage fluctuations can be suppressed. This makes it possible to realize a voltage detection circuit that can improve detection performance.

[0122] Next, a modified example of the present disclosure will be described. In the following, the same components as those in the above embodiment will be denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0123] 2. Modifications (2-1. Modification 1) FIG. 15 is a diagram illustrating a configuration example of a voltage detection circuit according to Modification 1 of the present disclosure. In a voltage detection circuit 120 according to this modification, the cathode of the light receiving element 10b is electrically connected to the potential line L4. In the example shown in FIG. 15, the potential line L4 is a power supply line to which a power supply voltage VSPAD is applied. The anode of the light receiving element 10b is electrically connected to the connection circuit 40 and the amplifier circuit 50.

[0124] The connection circuit 40 is, for example, configured with an N-type transistor (NMOS transistor) and is electrically connected in series between the light receiving element 10b and the potential line L3. The transistor M3 of the amplifier circuit 50 and the transistor M4 of the clamp circuit 60 are, for example, each configured with an NMOS transistor. In this modified example, the same effects as those of the above-described embodiment can be obtained.

[0125] 16 and 17 are diagrams illustrating a configuration example of a voltage detection circuit according to Modification 2. The amplifier circuit 50 of the voltage detection circuit 120 may be configured using a differential amplifier circuit (differential amplifier). The amplifier circuit 50 may be configured, for example, by a voltage follower, as in the examples shown in FIGS. 16 and 17 .

[0126] The amplifier circuit 50 has a differential amplifier including, for example, transistors M3a and M3b that form a differential pair, transistors M5a and M5b that form a current mirror, and a current source 51. The clamp circuit 60 may be configured integrally with the amplifier circuit 50. In the example shown in FIG. 17 , the transistor M4 of the clamp circuit 60 is provided within the amplifier circuit 50 and can be considered a part of the amplifier circuit 50.

[0127] 17, the transistor M4 is electrically connected to a node N4 to which the current source 51 and the transistors M3a and M3b are connected. The transistor M4 is controlled by a voltage Vclamp applied to its gate, and can limit the voltage at the node N4.

[0128] In the voltage detection circuit 120, for example, during a period (a standby period) when the light receiving element 10b is not receiving photons, the clamp circuit 60 limits the voltage at the node N4. This limits the voltage amplitude at the node N4, making it possible to reduce fluctuations in the signal voltage. This modification also provides the same effects as the above-described embodiment.

[0129] (2-3. Modification 3) FIG. 18 is a diagram illustrating a configuration example of a voltage detection circuit according to Modification 3. The clamp circuit 60 may be configured to be able to supply a predetermined voltage to the node N3. In the example shown in FIG. 18, the transistor M4 of the clamp circuit 60 is electrically connected to a potential line L5 (wiring) to which the voltage Vclamp is applied.

[0130] One of the source and drain of the transistor M4 serving as the clamp circuit 60 is electrically connected to the potential line L5, and the other of the source and drain of the transistor M4 is electrically connected to the transistor M3 and the current source 51. The transistor M4 is, for example, configured by a PMOS transistor.

[0131] The clamp circuit 60 is controlled by a signal input from a control circuit (e.g., the control circuit 130, the pixel control unit 110, or the control unit 113) that controls the clamp circuit 60. The transistor M4 of the clamp circuit 60 is controlled by a signal TP, which is, for example, a pulse signal, and can output a voltage Vclamp to the node N3. In this modified example, fluctuations in the signal voltage can also be suppressed. The same effects as those of the above-described embodiment can be obtained.

[0132] 3. Usage Examples The above-described light detection device 1 and light detection system 200 can be used in various cases for sensing light such as visible light, infrared light, ultraviolet light, and X-rays, for example, as described below.・Devices for taking images for viewing purposes, such as digital cameras and mobile devices with camera functions. ・Devices for traffic purposes, such as in-vehicle sensors that take images of the front, rear, surroundings, and interior of a car for safe driving such as automatic stopping, and for recognizing the driver's state, surveillance cameras that monitor moving vehicles and roads, and distance measuring sensors that measure distances between vehicles. ・Devices for home appliances such as televisions, refrigerators, and air conditioners that take images of user gestures and operate the device according to those gestures. ・Devices for medical and healthcare purposes, such as endoscopes and devices that take images of blood vessels by receiving infrared light. ・Devices for security purposes, such as surveillance cameras for crime prevention and cameras for person authentication. ・Devices for beauty purposes, such as skin measuring devices that take images of the skin and microscopes that take images of the scalp. ・Devices for sports purposes, such as action cameras and wearable cameras for sports, etc. ・Devices for agricultural purposes, such as cameras to monitor the condition of fields and crops.

[0133] 4. Application Examples (Application Examples to Mobile Bodies) The technology according to the present disclosure (the present technology) can be applied to various products. For example, the technology according to the present disclosure may be realized as a device mounted on any type of mobile body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, or a robot.

[0134] FIG. 19 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied.

[0135] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 19, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside-vehicle information detection unit 12030, an inside-vehicle information detection unit 12040, and an integrated control unit 12050. Also shown as functional components of the integrated control unit 12050 are a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (interface) 12053.

[0136] The drivetrain control unit 12010 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a drive force generating device for generating a drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force of the vehicle.

[0137] The body system control unit 12020 controls the operation of various devices equipped in the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as headlamps, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches can be input to the body system control unit 12020. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0138] The outside-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the outside-vehicle information detection unit 12030. The outside-vehicle information detection unit 12030 causes the imaging unit 12031 to capture images outside the vehicle and receives the captured images. The outside-vehicle information detection unit 12030 may perform object detection processing or distance detection processing for people, cars, obstacles, signs, characters on the road surface, etc. based on the received images.

[0139] 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 as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0140] The in-vehicle information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041 that detects the state of the driver is connected to the in-vehicle information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that captures an image of the driver, and the in-vehicle information detection unit 12040 may calculate the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

[0141] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, steering mechanism, or braking device based on the information inside and outside the vehicle acquired by the outside-vehicle information detection unit 12030 or the inside-vehicle information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the inter-vehicle distance, vehicle speed maintenance driving, vehicle collision warning, vehicle lane departure warning, etc.

[0142] In addition, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation, by controlling the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle obtained by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040.

[0143] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information outside the vehicle acquired by the outside information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the outside information detection unit 12030, and perform cooperative control aimed at preventing glare, such as switching from high beams to low beams.

[0144] The audio / video output unit 12052 transmits at least one of audio and video output signals to an output device capable of visually or audibly notifying the passengers of the vehicle or the outside of the vehicle of information. In the example of Fig. 19, the output devices are exemplified by an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0145] FIG. 20 is a diagram showing an example of the installation position of the imaging unit 12031.

[0146] In FIG. 20 , a vehicle 12100 has imaging units 12101, 12102, 12103, 12104, and 12105 as an imaging unit 12031.

[0147] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided, for example, at positions such as the front nose, side mirrors, rear bumper, back door, and the top of the windshield inside the vehicle cabin of the vehicle 12100. The imaging unit 12101 provided on the front nose and the imaging unit 12105 provided on the top of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The forward images acquired by the imaging units 12101 and 12105 are mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0148] 20 shows an example of the imaging ranges of the imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 12101 to 12104, an overhead image of the vehicle 12100 viewed from above can be obtained.

[0149] At least one of the image capturing units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the image capturing units 12101 to 12104 may be a stereo camera made up of multiple image capturing elements, or may be an image capturing element having pixels for phase difference detection.

[0150] For example, based on the distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 can calculate the distance to each three-dimensional object within the imaging ranges 12111 to 12114 and the change in this distance over time (relative speed with respect to the vehicle 12100), thereby extracting as a preceding vehicle, in particular, the three-dimensional object that is the closest three-dimensional object on the path of the vehicle 12100 and traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or higher). Furthermore, the microcomputer 12051 can set a vehicle-to-vehicle distance to be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), etc. In this way, cooperative control can be performed for the purpose of autonomous driving, which runs autonomously without relying on driver operation.

[0151] For example, the microcomputer 12051 classifies and extracts three-dimensional object data regarding three-dimensional objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects based on distance information obtained from the imaging units 12101 to 12104, and can use the data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines a collision risk that indicates the risk of collision with each obstacle, and when the collision risk is equal to or greater than a set value and a collision is possible, the microcomputer 12051 can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drive system control unit 12010.

[0152] At least one of the image capturing units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether a pedestrian is present in the images captured by the image capturing units 12101 to 12104. Such pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104 as infrared cameras and performing pattern matching on a series of feature points that indicate the outline of an object to determine whether the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the image capturing units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular outline on the recognized pedestrian for emphasis. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating the pedestrian at a desired position.

[0153] An example of a mobile object 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, for example, the image capturing unit 12031 of the above-described configuration. Specifically, for example, the light detection device 1 can be applied to the image capturing unit 12031. By applying the technology according to the present disclosure to the image capturing unit 12031, a high-resolution captured image can be obtained, and high-precision control using the captured image can be performed in the mobile object control system.

[0154] Although the present disclosure has been described above by giving embodiments, modifications, use examples, and application examples, the present technology is not limited to the above-described embodiments, etc., and various modifications are possible. For example, although the modifications described above have been described as modifications of the above-described embodiments, the configurations of the modifications can be combined as appropriate.

[0155] According to an embodiment of the present disclosure, a voltage detection circuit includes a first light receiving element, a connection circuit connected between the first light receiving element and a first potential line, an amplifier circuit to which the voltage of the first light receiving element is input, and a clamp circuit capable of limiting the voltage amplitude in the amplifier circuit, thereby enabling the realization of a voltage detection circuit capable of improving detection performance.

[0156] According to one embodiment of the present disclosure, a photodetector includes a voltage detection circuit having a first photodetector, a second photodetector capable of receiving light and outputting a current, and a readout circuit capable of outputting a signal based on the current of the second photodetector. The voltage detection circuit includes a connection circuit connected between the first photodetector and a first potential line, an amplifier circuit to which the voltage of the first photodetector is input, and a clamp circuit capable of limiting the voltage amplitude of the amplifier circuit. This makes it possible to realize a photodetector capable of improving detection performance.

[0157] Note that the effects described in this specification are merely examples and are not limited to those described, and other effects may be present. The present disclosure may also have the following configurations: (1) A voltage detection circuit including: a first light-receiving element; a connection circuit connected between the first light-receiving element and a first potential line; an amplifier circuit to which the voltage of the first light-receiving element is input; and a clamp circuit capable of limiting the amplitude of the voltage generated in the amplifier circuit. (2) The voltage detection circuit described in (1), wherein the first light-receiving element is an avalanche photodiode. (3) The voltage detection circuit described in (1) or (2), wherein the connection circuit is capable of intermittently charging the first light-receiving element. (4) The voltage detection circuit described in any one of (1) to (3), wherein the amplifier circuit is capable of outputting a voltage corresponding to the breakdown voltage of the first light-receiving element. (5) The voltage detection circuit according to any one of (1) to (4), wherein the first light-receiving element has a first electrode and a second electrode, the first electrode of the first light-receiving element is electrically connected to the amplifier circuit and the connection circuit, the second electrode of the first light-receiving element is electrically connected to a second potential line, and a voltage of the first electrode of the first light-receiving element is input to the amplifier circuit. (6) The voltage detection circuit according to any one of (1) to (5), wherein the first potential line is a power supply line or a ground line, and the connection circuit has a first switch electrically connected in series between the first light-receiving element and the first potential line. (7) The voltage detection circuit according to any one of (1) to (6), wherein the connection circuit is controlled by a pulse signal and is capable of recharging the first light-receiving element. (8) The voltage detection circuit according to any one of (1) to (7), wherein the amplifier circuit includes a first transistor to which the voltage of the first light receiving element is input, and the clamp circuit is capable of limiting the amplitude of the voltage output by the first transistor. (9) The voltage detection circuit according to (8), wherein the first transistor has a gate to which the voltage of the first light receiving element is input.(10) The voltage detection circuit according to any one of (1) to (9), further comprising: a node at which the amplifier circuit and the clamp circuit are electrically connected, the clamp circuit including a second transistor having a gate electrically connected to the node and to which a predetermined voltage is applied. (11) The voltage detection circuit according to any one of (1) to (10), further comprising: a node at which the amplifier circuit and the clamp circuit are electrically connected, the clamp circuit including a second transistor electrically connected to the node and capable of supplying a predetermined voltage to the node. (12) The voltage detection circuit according to any one of (1) to (11), further comprising: a capacitive element capable of holding a voltage corresponding to a breakdown voltage of the first light-receiving element. (13) The voltage detection circuit according to (12), further comprising: a node at which the amplifier circuit and the clamp circuit are electrically connected; and a sample-and-hold circuit capable of holding a voltage corresponding to the breakdown voltage of the first light-receiving element, the sample-and-hold circuit having: a capacitive element capable of holding a voltage; and a second switch capable of electrically connecting the node and the capacitive element. (14) The voltage detection circuit according to any one of (1) to (13), wherein the amplifier circuit has a voltage follower circuit. (15) The voltage detection circuit according to any one of (1) to (14), further comprising: a first substrate having the first light receiving element; and a second substrate having the amplifier circuit and the clamp circuit and stacked on the first substrate. (16) The voltage detection circuit according to any one of (1) to (15), further comprising: a second light receiving element capable of receiving light and outputting a current; and a readout circuit capable of outputting a signal based on the current of the second light receiving element. (17) The voltage detection circuit according to (16), further comprising a control circuit capable of controlling a voltage supplied to the second light receiving element based on the output voltage of the amplifier circuit.(18) A photodetector comprising: a voltage detection circuit having a first photodetector; a second photodetector capable of receiving light and outputting a current; and a readout circuit capable of outputting a signal based on the current of the second photodetector, wherein the voltage detection circuit comprises: a connection circuit connected between the first photodetector and a first potential line; an amplifier circuit to which the voltage of the first photodetector is input; and a clamp circuit capable of limiting the voltage amplitude in the amplifier circuit. (19) The photodetector described in (18), further comprising a control circuit capable of controlling the voltage supplied to the second photodetector based on the output voltage of the amplifier circuit. (20) The photodetector described in (19), further comprising: a first electrode and a second electrode; the first electrode of the first photodetector electrically connected to the amplifier circuit and the connection circuit; and the control circuit capable of controlling the voltage supplied to the second electrode of the first photodetector based on the output voltage of the amplifier circuit. (21) A light detection system comprising: a light source capable of irradiating light onto an object; and a light detection device that receives light from the object, wherein the light detection device has: a voltage detection circuit having a first light receiving element; a second light receiving element that is capable of receiving light and outputting a current; and a readout circuit that is capable of outputting a signal based on the current of the second light receiving element, and the voltage detection circuit includes: a connection circuit connected between the first light receiving element and a first potential line; an amplifier circuit to which the voltage of the first light receiving element is input; and a clamp circuit that is capable of limiting the voltage amplitude in the amplifier circuit.

[0158] This application claims priority based on Japanese Patent Application No. 2024-098006, filed on June 18, 2024, in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0159] Those skilled in the art will recognize that various modifications, combinations, subcombinations, and variations may occur depending on design requirements and other factors, and are intended to be within the scope of the appended claims and their equivalents.

Claims

1. A voltage detection circuit comprising: a first light receiving element; a connection circuit connected between the first light receiving element and a first potential line; an amplifier circuit to which the voltage of the first light receiving element is input; and a clamp circuit capable of limiting the voltage amplitude in the amplifier circuit.

2. The voltage detection circuit according to claim 1, wherein the first light receiving element is an avalanche photodiode.

3. The voltage detection circuit according to claim 1, wherein the connection circuit is capable of intermittently charging the first light receiving element.

4. The voltage detection circuit according to claim 1, wherein the amplifier circuit is capable of outputting a voltage corresponding to the breakdown voltage of the first light receiving element.

5. The voltage detection circuit according to claim 1, wherein the first light receiving element has a first electrode and a second electrode, the first electrode of the first light receiving element is electrically connected to the amplifier circuit and the connection circuit, the second electrode of the first light receiving element is electrically connected to a second potential line, and the voltage of the first electrode of the first light receiving element is input to the amplifier circuit.

6. The voltage detection circuit according to claim 1, wherein the first potential line is a power supply line or a ground line, and the connection circuit has a first switch electrically connected in series between the first light receiving element and the first potential line.

7. The voltage detection circuit according to claim 1, wherein the connection circuit is controlled by a pulse signal and is capable of recharging the first light receiving element.

8. The voltage detection circuit according to claim 1, wherein the amplifier circuit includes a first transistor to which the voltage of the first light receiving element is input, and the clamp circuit is capable of limiting the amplitude of the voltage output by the first transistor.

9. The voltage detection circuit according to claim 8, wherein the first transistor has a gate to which the voltage of the first light receiving element is input.

10. The voltage detection circuit according to claim 1, further comprising a node at which the amplifier circuit and the clamp circuit are electrically connected, the clamp circuit including a second transistor electrically connected to the node and having a gate to which a predetermined voltage is applied.

11. The voltage detection circuit according to claim 1, further comprising a node at which the amplifier circuit and the clamp circuit are electrically connected, the clamp circuit including a second transistor electrically connected to the node and capable of supplying a predetermined voltage to the node.

12. The voltage detection circuit according to claim 1, further comprising a capacitance element capable of holding a voltage corresponding to the breakdown voltage of said first light receiving element.

13. A voltage detection circuit according to claim 12, further comprising: a node at which the amplifier circuit and the clamp circuit are electrically connected; and a sample-and-hold circuit capable of holding a voltage corresponding to the breakdown voltage of the first light-receiving element, wherein the sample-and-hold circuit has a capacitance element capable of holding a voltage; and a second switch capable of electrically connecting the node and the capacitance element.

14. The voltage detection circuit according to claim 1, wherein the amplifier circuit includes a voltage follower circuit.

15. The voltage detection circuit according to claim 1, further comprising: a first substrate having the first light receiving element; and a second substrate having the amplifier circuit and the clamp circuit, the second substrate being stacked on the first substrate.

16. The voltage detection circuit according to claim 1, further comprising: a second light receiving element capable of receiving light and outputting a current; and a readout circuit capable of outputting a signal based on the current of said second light receiving element.

17. The voltage detection circuit according to claim 16, further comprising a control circuit capable of controlling the voltage supplied to the second light receiving element based on the output voltage of the amplifier circuit.

18. A photodetector comprising: a voltage detection circuit having a first light-receiving element; a second light-receiving element capable of receiving light and outputting a current; and a readout circuit capable of outputting a signal based on the current of the second light-receiving element, wherein the voltage detection circuit has: a connection circuit connected between the first light-receiving element and a first potential line; an amplifier circuit to which the voltage of the first light-receiving element is input; and a clamp circuit capable of limiting the voltage amplitude in the amplifier circuit.

19. The photodetector according to claim 18, further comprising a control circuit capable of controlling the voltage supplied to the second light receiving element based on the output voltage of the amplifier circuit.

20. The photodetector device of claim 19, wherein the first light-receiving element has a first electrode and a second electrode, the first electrode of the first light-receiving element is electrically connected to the amplifier circuit and the connection circuit, and the control circuit is capable of controlling the voltage supplied to the second electrode of the first light-receiving element based on the output voltage of the amplifier circuit.

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