Solid-state imaging device and electronic apparatus

Abstract

The present application relates to a solid-state imaging device and an electronic apparatus. Specifically, the present application makes an excessive bias an appropriate value in a device for detecting light. The solid-state imaging device is equipped with a photodiode, a resistor, and a control circuit. In the solid-state imaging device, the photodiode photoelectrically converts incident light and outputs a photoelectric current. Furthermore, in the solid-state imaging device, the resistor is connected to a cathode of the photodiode. In addition, in the solid-state imaging device, the higher the potential of the cathode when the photoelectric current flows into the resistor, the lower the potential that the control circuit provides to an anode of the photodiode.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201880062362.X entitled "Solid-State Imaging Element and Electronic Device" filed on August 24, 2018. Technical Field

[0002] This technology relates to a solid-state image sensor and an electronic device. Specifically, this technology relates to a solid-state image sensor that uses a photodiode to detect light. Background Technology

[0003] Traditionally, distance measurement methods known as the Time-of-Flight (ToF) method are known in electronic devices with distance measurement capabilities. The ToF method measures distance by illuminating an object with illumination light from the electronic device and obtaining the round-trip time until the illumination light is reflected and returns to the electronic device. For example, ToF-type cameras using single-photon avalanche diodes (SPADs) to detect reflected light have been proposed (see, for example, Non-Patent Literature 1). A SPAD is a photodiode in which sensitivity is enhanced by amplifying the photocurrent.

[0004] Here, the SPAD is used in Geiger mode, applying a reverse bias to a voltage of one or higher. In Geiger mode, control is executed to maintain a pull-up, applying a constant potential through the power supply on the anode side and a resistance or constant current on the cathode side. Then, when light is detected, the anode-cathode voltage drops to the breakdown voltage due to impact ionization, and the SPAD transitions from a high-impedance state to a low-impedance state. The solid-state image sensor can generate Time-of-Flight (ToF) data by detecting the change in the cathode potential at that time. When the anode-cathode voltage drops to the breakdown voltage, the SPAD becomes high-impedance again, and when the SPAD becomes high-impedance, it transitions back to Geiger mode through a pull-up. In this solid-state image sensor, pixel characteristics are determined by over-bias. Here, the over-bias is a value obtained by subtracting the breakdown voltage from the anode-cathode voltage in Geiger mode.

[0005] Reference List

[0006] Non-patent literature

[0007] Non-Patent Document 1: Larry Li, “Time-of-Flight Camera - An Introduction”, Texas Instruments, Technical White Paper SLOA190B, January 2014, revised May 2014. Summary of the Invention

[0008] The problem to be solved by the present invention

[0009] In the aforementioned conventional technology, highly sensitive avalanche photodiodes are used, allowing even the detection of faint reflected light. However, over-bias can fluctuate due to variations in breakdown voltage and temperature. Consequently, the over-bias may become too small, reducing the photodiode's sensitivity; conversely, the over-bias may become too large, increasing dark current noise. To suppress over-bias fluctuations caused by changes in breakdown voltage, the operator can adjust each product, but this increases workload. Therefore, in the aforementioned conventional technology, it is difficult to suppress over-bias fluctuations caused by changes in breakdown voltage, etc.

[0010] This technology is proposed in view of this situation, and the purpose of this technology is to control the excessive bias in the optical detection device to an appropriate value.

[0011] Solution to the problem

[0012] The present invention addresses the aforementioned problems, and a first aspect of the present invention is a solid-state image sensor comprising: a photodiode configured to photoelectrically convert incident light and output a photocurrent; a resistor connected to the cathode of the photodiode; and a control circuit configured to provide a lower potential to the anode of the photodiode as the photocurrent flows through the resistor, given a higher potential at the cathode. This configuration achieves the effect of providing a lower potential to the anode of the photodiode as the photocurrent flows through the resistor, thereby controlling excessive bias to an appropriate value.

[0013] Furthermore, in the first aspect, a detection circuit may also be included, configured to detect the cathode potential when photocurrent flows through the resistor, and to provide the detected potential to the control circuit. This configuration effectively detects the cathode potential when photocurrent flows.

[0014] Furthermore, in the first aspect, the resistor and photodiode can be disposed in each of a plurality of pixel circuits, the cathodes of the plurality of pixel circuits can be commonly connected to a detection circuit, and the detection circuit can detect the minimum potential of each cathode when the photocurrent flows through the resistor. This configuration achieves the effect of providing a potential to the anode based on the minimum potential of the corresponding cathode of the photodiode.

[0015] Furthermore, in the first aspect, a variable capacitor may also be included, which is connected to the cathode. The above configuration achieves the effect of reducing cathode potential error through the variable capacitor.

[0016] Furthermore, in the first aspect, a transistor may also be included, configured to short-circuit the resistor terminals according to an update pulse signal, wherein the control circuit may also provide the update pulse signal to the transistor just before the incident light is about to strike. This configuration achieves the effect of short-circuiting the resistor terminals via an update pulse signal just before the incident light is about to strike.

[0017] Furthermore, in the first aspect, the resistance value of the resistor can be a value to which the cathode potential is fixed. This configuration achieves the effect of providing a potential to the anode based on the fixed potential of the photodiode's cathode.

[0018] Furthermore, in the first aspect, a comparator may be included, configured to compare the potential of the cathode with a predetermined potential and output a comparison result. The control circuit may, based on the comparison result, provide a potential to the anode that is lower than the potential provided when the cathode potential is lower than the predetermined potential, if the cathode potential is higher than the predetermined potential. This configuration effectively provides a potential to the anode based on a comparison between the cathode potential of the photodiode and the predetermined potential.

[0019] Furthermore, in the first aspect, the control circuit can count the number of times the cathode potential falls below a predetermined threshold within a predetermined period, and if the number of times is less than a predetermined number, provide a potential to the anode that is lower than the potential provided if the number of times is greater than the predetermined number. This configuration achieves the effect of providing a potential to the anode of the photodiode based on the number of times the cathode potential falls below the predetermined threshold.

[0020] Furthermore, in the first aspect, an inverter may also be included, configured to invert the potential signal of the cathode and output the signal as a pulse signal, wherein the control circuit can provide a lower potential to the anode of the photodiode when the pulse width of the pulse signal is shorter. This configuration achieves the effect of providing a potential to the anode of the photodiode according to the pulse width of the pulse signal.

[0021] Furthermore, in the first aspect, one end of the resistor can be connected to the cathode, and the other end of the resistor can be connected to a terminal at a predetermined potential. The control circuit can measure the voltage between the cathode potential and the predetermined potential, and when the voltage is higher, a lower potential can be provided to the anode of the photodiode. This configuration achieves the effect of providing a potential to the anode based on the voltage between the cathode potential and the predetermined potential of the photodiode.

[0022] Furthermore, in the first aspect, the resistor and photodiode can be disposed in each of the plurality of pixel circuits, and the control circuit can enable any one of the plurality of pixel circuits and measure the voltage between the cathode potential of the disposed pixel circuit and a predetermined potential. This configuration achieves the effect of providing a potential to the anode of the photodiode based on the potential of the cathode of the pixel circuit group.

[0023] Furthermore, a second aspect of this technology is a solid-state image sensor comprising: a photodiode configured to photoelectrically convert incident light and output a photocurrent; a resistor connected to the cathode of the photodiode; and a control circuit configured to measure temperature and, as the temperature decreases, to provide a lower potential to the anode of the photodiode. This configuration achieves the effect of providing a lower potential to the anode of the photodiode as the temperature decreases.

[0024] Furthermore, a third aspect of this technology is an electronic device comprising: a light-emitting unit configured to provide illumination light; a photodiode configured to photoelectrically convert reflected light relative to the illumination light and output a photocurrent; a resistor connected to the cathode of the photodiode; and a control circuit configured to provide a lower potential to the anode of the photodiode when the photocurrent flows through the resistor. This configuration achieves the effect that a higher potential at the cathode when the photocurrent obtained through photoelectric conversion of reflected light flows through the resistor corresponds to a lower potential at the anode of the photodiode.

[0025] Effects of the present invention

[0026] According to this technology, excellent effects can be achieved in photodetectors by suppressing fluctuations in the appropriate value of the anode potential of a photodiode. Note that the effects described herein are not necessarily limited and may represent any of the effects described in this disclosure. Attached Figure Description

[0027] Figure 1 This is a block diagram illustrating a configuration example of a distance measurement module according to a first embodiment of the present technology;

[0028] Figure 2 This is a block diagram illustrating a configuration example of a solid-state image sensor according to a first embodiment of the present technology;

[0029] Figure 3 This is an example of a plan view of a pixel array unit according to a first embodiment of the present technology;

[0030] Figure 4 This is an example of a circuit diagram of a control circuit, a light-shielding pixel circuit, and a monitoring pixel circuit according to a first embodiment of the present technology;

[0031] Figure 5This is an example of a circuit diagram of a non-monitoring pixel circuit according to a first embodiment of the present technology;

[0032] Figure 6 This is a graph illustrating an example of the voltage-current characteristics of a photodiode according to a first embodiment of the present technology;

[0033] Figure 7 This is a block diagram illustrating an example configuration of a signal processing unit according to a first embodiment of the present technology;

[0034] Figure 8 This is a timing diagram illustrating an example of fluctuations in the cathode potential and bottom potential according to a first embodiment of the present technology;

[0035] Figure 9 This is a timing diagram illustrating an example of fluctuations in cathode potential, anode potential, and pulse signal when the bottom potential is high, according to a first embodiment of the present technology.

[0036] Figure 10 This is a timing diagram illustrating an example of fluctuations in cathode potential, anode potential, and pulse signal when the bottom potential is low, according to a first embodiment of the present technology.

[0037] Figure 11 This is a timing diagram illustrating an example of fluctuations in the light emission control signal and pulse signal according to a first embodiment of the present technology;

[0038] Figure 12 This is a flowchart illustrating an operational example of a distance measurement module according to a first embodiment of the present technology;

[0039] Figure 13 This is an example of a plan view of a pixel array unit according to the second embodiment of the present technology;

[0040] Figure 14 This is an example of a circuit diagram of a light-shielding pixel circuit and a monitoring pixel circuit according to a second embodiment of the present technology;

[0041] Figure 15 This is an example of a circuit diagram of a control circuit and a monitoring pixel circuit according to a third embodiment of the present technology;

[0042] Figure 16 This is an example of a circuit diagram of a monitoring pixel circuit according to the fourth embodiment of the present technology;

[0043] Figure 17 This is a block diagram illustrating an example configuration of a control circuit according to a fourth embodiment of the present technology;

[0044] Figure 18 This is a graph illustrating an example of the relationship between the cathode potential and the anode potential according to a fourth embodiment of the present technology;

[0045] Figure 19 This is an example of a circuit diagram of a monitoring pixel circuit according to the fifth embodiment of the present technology;

[0046] Figure 20 This is a block diagram illustrating an example configuration of the control circuit according to a fifth embodiment of the present technology;

[0047] Figure 21 This is a graph illustrating an example of the relationship between the count value and the anode potential according to the fifth embodiment of the present technology;

[0048] Figure 22 This is a block diagram illustrating an example configuration of a control circuit according to a sixth embodiment of the present technology;

[0049] Figure 23 This is a timing diagram illustrating an operational example of the control circuit and the monitoring pixel circuit according to the sixth embodiment of the present technology;

[0050] Figure 24 This is a block diagram illustrating an example configuration of the control circuit according to a seventh embodiment of the present technology;

[0051] Figure 25 This is an example of a circuit diagram of a monitoring pixel circuit according to the eighth embodiment of the present technology;

[0052] Figure 26 This is an example of a circuit diagram of a monitoring pixel circuit according to the ninth embodiment of the present technology;

[0053] Figure 27 This is a timing diagram illustrating an example of the bottom potential according to the ninth embodiment of the present technology;

[0054] Figure 28 This is an example of a circuit diagram of a monitoring pixel circuit according to the tenth embodiment of the present technology;

[0055] Figure 29 This is a block diagram illustrating an example configuration of the control circuit according to the tenth embodiment of the present technology;

[0056] Figure 30 This is a timing diagram illustrating an example of fluctuations in the light emission control signal, update pulse signal, and bottom potential according to the tenth embodiment of the present technology;

[0057] Figure 31 This is an example of a plan view of a pixel array unit according to the eleventh embodiment of the present technology;

[0058] Figure 32 This is a block diagram illustrating an example configuration of the control circuit according to the eleventh embodiment of the present technology;

[0059] Figure 33 This is a graph illustrating an example of the relationship between temperature and anode potential according to the eleventh embodiment of the present technology;

[0060] Figure 34 This is a block diagram illustrating a schematic configuration example of a vehicle control system;

[0061] Figure 35 This is an explanatory diagram showing an example of the mounting location of the imaging unit. Detailed Implementation

[0062] The following describes the modes (hereinafter referred to as implementation methods) used to implement this technology. The descriptions will be given in the following order.

[0063] 1. First Embodiment (Example of controlling anode potential based on cathode potential)

[0064] 2. Second Implementation (Example of controlling the anode potential based on the minimum value of the cathode potential of multiple monitoring pixels)

[0065] 3. Third Implementation (Example of controlling the anode potential based on the fixed cathode potential output by the monitoring pixel)

[0066] 4. Fourth Embodiment (Example of controlling the anode potential based on a comparison between the cathode potential and a predetermined potential)

[0067] 5. Fifth Implementation (Example of Controlling Anode Potential Based on a Count Value Related to Cathode Potential)

[0068] 6. Sixth Embodiment (Example of controlling anode potential based on pulse width related to cathode potential)

[0069] 7. Seventh Embodiment (Example of controlling anode potential based on over-biasing related to cathode potential)

[0070] 8. Eighth Embodiment (Example of controlling the anode potential based on the cathode potential of an enabled monitoring pixel)

[0071] 9. Ninth Embodiment (Example of controlling the anode potential based on the cathode potential of a monitoring pixel with an added variable capacitor)

[0072] 10. Tenth Embodiment (Example of controlling the anode potential based on the cathode potential of a monitoring pixel that provides a pulse signal)

[0073] 11. Eleventh Embodiment (Example of Controlling Anode Potential Based on Temperature)

[0074] 12. Application of moving bodies

[0075] <1. First Implementation Method>

[0076] [Configuration example of the distance measurement module]

[0077] Figure 1 This is a block diagram illustrating a configuration example of a distance measurement module 100 according to a first embodiment of the present technology. The distance measurement module 100 measures the distance to an object and includes a light-emitting unit 110, a synchronization control unit 120, and a solid-state image sensor 200. The distance measurement module 100 is installed in a smartphone, personal computer, vehicle-mounted device, etc., and is used for measuring distance.

[0078] The synchronization control unit 120 operates the light-emitting unit 110 and the solid-state image sensor 200 synchronously. The synchronization control unit 120 provides the light-emitting unit 110 and the solid-state image sensor 200 with a clock signal of a predetermined frequency (e.g., 10 to 20 MHz) via signal lines 128 and 129 as the light-emitting control signal CLKp.

[0079] The light-emitting unit 110 provides intermittent light in sync with the light-emitting control signal CLKp from the synchronization control unit 120, serving as illumination light. For example, near-infrared light or the like is used as illumination light.

[0080] The solid-state image sensor 200 receives reflected light relative to the illumination light and measures the round-trip time from the emission time indicated by the emission control signal CLKp to the time of receiving the reflected light. The solid-state image sensor 200 calculates the distance to the object from the round-trip time and generates and outputs distance data indicating the distance.

[0081] [Configuration example of a solid-state image sensor]

[0082] Figure 2 This is a block diagram illustrating a configuration example of a solid-state image sensor 200 according to a first embodiment of the present technology. The solid-state image sensor 200 includes a control circuit 210, a pixel array unit 240, and a signal processing unit 230. In the pixel array unit 240, a plurality of pixel circuits are arranged in a two-dimensional grid.

[0083] The control circuit 210 controls each potential of the pixel circuit in the pixel array unit 240. Details of the control will be described below.

[0084] The signal processing unit 230 measures the round-trip time of each pixel circuit based on signals from the pixel circuits and the light emission control signal CLKp from the synchronization control unit 120, and calculates the distance. The signal processing unit 230 generates distance data indicating the distance of each pixel circuit and outputs the distance data to the outside.

[0085] Figure 3This is an example of a plan view of a pixel array unit 240 according to a first embodiment of the present technology. A portion of the pixel array unit 240 is light-shielded, light-shielding pixel circuits 250 are arranged in the light-shielded portion, and monitoring pixel circuits 260 and non-monitoring pixel circuits 280 are arranged in the unshielded portion. Figure 3 In the diagram, the shaded portion is part of the pixel array unit 240 that arranges the light-shielding pixel circuits 250. Furthermore, the total number of monitoring pixel circuits 260 and non-monitoring pixel circuits 280 is N (N is an integer of 2 or greater), and the monitoring pixel circuits 260 and non-monitoring pixel circuits 280 are arranged in a two-dimensional grid. Additionally, one of the N circuits is a monitoring pixel circuit 260, and the rest are non-monitoring pixel circuits 280.

[0086] In the following text, a group of pixel circuits arranged horizontally is called a "row", and a group of pixel circuits arranged perpendicular to the row is called a "column".

[0087] [Pixel circuit configuration example]

[0088] Figure 4 This is an example of a circuit diagram of the control circuit 210, the light-shielding pixel circuit 250, and the monitoring pixel circuit 260 according to the first embodiment of the present technology.

[0089] The monitoring pixel circuit 260 includes a resistor 261, a photodiode 262, an inverter 263, and a transistor 264.

[0090] One end of resistor 261 is connected to the cathode of photodiode 262, and the other end of resistor 261 is connected to a terminal with potential VE. Transistor 264 is, for example, an N-type metal-oxide-semiconductor (MOS) transistor. A gate signal GAT with a predetermined potential is applied to the gate of transistor 264, the source of transistor 264 is connected to the back gate and ground, and the drain of transistor 264 is connected to the cathode of photodiode 262 and the input of inverter 263. For example, a low level is set as the gate signal GAT during a row read cycle.

[0091] When reflected light enters photodiode 262, photodiode 262 photoelectrically converts the incident light and outputs a photocurrent Im. For example, a SPAD is used as photodiode 262. Furthermore, the anode potential VSPAD of photodiode 262 is controlled by control circuit 210.

[0092] Inverter 263 inverts the signal of the cathode potential Vs of photodiode 262 and outputs the inverted signal as a pulse signal OUT to signal processing unit 230. Inverter 263 outputs a low-level pulse signal OUT when the cathode potential Vs is higher than a predetermined threshold, and outputs a high-level pulse signal OUT when the cathode potential Vs is equal to or lower than the threshold.

[0093] When reflected light is incident, the photocurrent Im from photodiode 262 flows through resistor 261, and the cathode potential Vs decreases according to the current value of photocurrent Im. When the cathode potential Vs at the point of decrease is equal to or below a threshold, inverter 263 outputs a high-level pulse signal OUT. Therefore, signal processing unit 230 can detect the rise time of pulse signal OUT as the light reception time. Furthermore, the cathode potential Vs of monitoring pixel circuit 260 is monitored by light-shielding pixel circuit 250.

[0094] Furthermore, the light-shielding pixel circuit 250 includes a resistor 251, a diode 252, and a capacitor 253. Resistor 251 and capacitor 253 are connected in series between the terminal at potential VE and the ground terminal. Additionally, the cathode of diode 252 is connected to the cathode of photodiode 262, and the anode of diode 252 is connected to the junction of resistor 251 and capacitor 253.

[0095] Using the above configuration, the light-shielding pixel circuit 250 detects the cathode potential when incident light is incident, which is taken as the bottom potential Vbtm. Note that the light-shielding pixel circuit 250 is an example of the detection circuit described in the claims.

[0096] Furthermore, the control circuit 210 includes a comparator 211 and a correction diode 212. The inverting input (-) of the comparator 211 is connected to the junction of the resistor 251 and the capacitor 253, and the non-inverting input (+) of the comparator 211 is connected to the anode of the correction diode 212. A predetermined power supply is connected to the cathode of the correction diode 212. The temperature characteristics of the correction diode 212 are the same as those of the diode 252. The error in the bottom potential Vtm caused by the temperature characteristics of the diode 252 can be corrected by inserting the correction diode 212.

[0097] When the bottom potential Vbtm is high, comparator 211 generates a lower potential as VSPAD and provides VSPAD to the anode of photodiode 262 according to the following expression.

[0098] VSPAD = Av(VDD - Vbtm)

[0099] In the above expression, Av represents the gain of comparator 211, and VDD represents the power supply potential.

[0100] Figure 5This is an example of a circuit diagram of a non-monitoring pixel circuit 280 according to a first embodiment of the present technology. The non-monitoring pixel circuit 280 includes a resistor 281, a photodiode 282, an inverter 283, and a transistor 284. The connection configuration of these components is similar to that of the monitoring pixel circuit 260. However, in the non-monitoring pixel circuit 280, the cathode of the photodiode 282 is not connected to the light-shielding pixel circuit 250, and the potential of the cathode is not monitored.

[0101] Figure 6 This is a graph illustrating an example of the voltage-current characteristics of a photodiode 262 according to a first embodiment of the present technology. Figure 6 The horizontal axis in the figure represents the voltage applied between the anode and cathode of the photodiode 262. Figure 6 The vertical axis represents the photocurrent from photodiode 262. When photodiode 262 is operated in Geiger mode, a negative value (i.e., reverse bias) is applied to the anode-cathode voltage of photodiode 262. When using the aforementioned SPAD as photodiode 262, avalanche breakdown occurs in photodiode 262 if the reverse bias is lower than the predetermined breakdown voltage, and the photocurrent is amplified. When a voltage a few volts lower than the breakdown voltage is applied between the anode and cathode, the amplification gain becomes essentially infinite, and a single photon can be detected.

[0102] [Signal processing unit configuration example]

[0103] Figure 7 This is a block diagram illustrating a configuration example of a signal processing unit 230 according to a first embodiment of the present technology. The signal processing unit 230 includes a time-to-digital converter (TDC) 231 for each column and a distance data generation unit 232.

[0104] TDC 231 measures the time from the emission control signal CLKp indicating the emission time to the rising edge of the pulse signal OUT from the corresponding column (i.e., the light reception time). TDC 231 provides a digital signal indicating the measurement time to the distance data generation unit 232.

[0105] The distance data generation unit 232 calculates the distance D to the object. The distance data generation unit 232 calculates the mode value of the time measured by the TDC 231 within each cycle of the vertical synchronization signal VSYNC, as the round-trip time dt. The vertical synchronization signal VSYNC has a frequency lower than the emission control signal CLKp (e.g., 30 Hz). Then, the distance data generation unit 232 calculates the distance D using the following expression and outputs distance data indicating the distance D.

[0106] D = c × dt / 2

[0107] In the expression above, c is the speed of light, measured in meters per second (m / s). Furthermore, the distance D is measured in meters (m), and the round-trip time dt is measured in seconds (s), for example.

[0108] Figure 8 This is a timing diagram illustrating an example of fluctuations in the cathode potential Vs and the bottom potential Vbtm according to a first embodiment of the present technology.

[0109] When reflected light is incident at a specific time T0, the photocurrent from photodiode 262 flows through resistor 261, causing a voltage drop and a decrease in the cathode potential Vs. The light-shielding pixel circuit 250 then outputs this potential as the bottom potential Vbtm to the control circuit 210.

[0110] Then, after a certain recharge time from time T0, the cathode potential Vs returns to its previous value. When the reflected light is incident at a subsequent time T2, the cathode potential Vs decreases again. This process is repeated thereafter.

[0111] Furthermore, depending on the capacitance of capacitor 253, the bottom potential Vbtm increases slightly between time T0 and time T2. Here, assuming the actual minimum value of the cathode potential Vs is the true value, the bottom potential Vbtm has a slight error relative to the true value, but by sufficiently increasing the capacitance of capacitor 253, a value close to the true value can be output.

[0112] Figure 9 This is a timing diagram illustrating an example of fluctuations in the cathode potential, anode potential, and pulse signal when the bottom potential is high according to a first embodiment of the present technology. When reflected light is incident at a specific time T0, the cathode potential Vs drops to a bottom potential Vbtm above a threshold VT, and returns to the original potential VE through recharging. Here, the threshold VT is the voltage used to determine whether incident light has been incident. When the cathode potential Vs is below the threshold VT, the inverter 263 outputs a high-level pulse signal OUT.

[0113] Then, assuming the voltage difference (breakdown voltage) between the bottom potential Vbtm and the anode potential VSPAD is VBD, the overbiasing fluctuates according to the breakdown voltage VBD and temperature. The higher the breakdown voltage VBD, the greater the overbiasing. Typically, overbiasing occurs when the bottom potential Vbtm becomes less than the threshold value VT.

[0114] However, in some cases, the over-biasing fluctuates due to variations in voltage VBD and temperature, and the bottom potential Vbtm does not fall below the threshold VT. In this situation, despite light incidence, the pulse signal OUT does not go high, and the subsequent signal processing unit 230 may become unable to detect the incident light. Therefore, if the anode potential is set to a fixed value, the photon detection efficiency (PDE) may decrease. Here, photon detection efficiency represents the ratio of the number of photons counted to the number of incident photons when incident light is emitted and photon counting is performed. As the photon detection efficiency increases, the sensitivity of the photodiode 262 becomes higher.

[0115] Therefore, when the bottom potential Vbtm is high, the control circuit 210 lowers the anode potential VSPAD. Consequently, the voltage VBD increases, the photocurrent increases, and the over-bias becomes larger. Therefore, when light is incident again at time T1, the cathode potential Vs becomes lower than the threshold VT at time T2. Then, when the cathode potential Vs reaches the bottom potential, it rises through recharging and becomes equal to or higher than the threshold VT at time T3. Furthermore, the inverter 263 outputs a high-level pulse signal OUT between time T2 and time T3. As described above, by controlling the anode potential VSPAD to be high, the pulse signal OUT rises when light is incident. Therefore, the signal processing unit 230 can detect light, and the photon detection efficiency (PDE) is sufficiently high.

[0116] Figure 10 This is a timing diagram illustrating an example of fluctuations in the cathode potential, anode potential, and pulse signal when the bottom potential is low, according to a first embodiment of the present technology. When reflected light is incident at a specific time T0, the cathode potential Vs decreases and becomes below the threshold VT at time T1. Then, the cathode potential Vs decreases to a bottom potential Vbtm below 0 volts, then rises through recharging, and becomes above the threshold VT at time T2. Furthermore, the inverter 263 outputs a high-level pulse signal OUT between time T1 and time T2.

[0117] When the voltage VBD is sufficiently high, the bottom potential Vbtm becomes below the threshold VT, allowing incident light to be detected, as described above. However, if the voltage VBD becomes too high due to factors such as temperature, the detection of incident light becomes susceptible to dark current noise. As a result, if the anode potential is set to a fixed value, the dark count rate (DCR), which indicates the false count rate due to dark current noise, may increase. Furthermore, there is a high probability of latch-up and failure of the photodiode 262.

[0118] Therefore, when the bottom potential Vbtm is low, the control circuit 210 increases the anode potential VSPAD. Consequently, the voltage VBD decreases, the over-biasing decreases, and the bottom potential Vbtm increases. As a result, adverse effects, such as an increase in the error count rate (DCR), are suppressed.

[0119] However, the bottom potential Vbtm is controlled to be below the threshold VT. Therefore, when light re-incident at time T3, the cathode potential Vs becomes below the threshold VT at time T4. Then, when the cathode potential Vs reaches the bottom potential, it rises through recharging and becomes equal to or above the threshold VT at time T5. Furthermore, the inverter 263 outputs a high-level pulse signal OUT between time T4 and time T5. Therefore, the photon detection efficiency is maintained at a sufficiently high value.

[0120] Figure 11 This is a timing diagram illustrating an example of fluctuations in the light emission control signal and pulse signal according to a first embodiment of the present technology. The light emission unit 110 emits light synchronously with the light emission control signal CLKp, and the solid-state image sensor 200 receives the reflected light and generates a pulse signal OUT. The time from the rise time Ts of the light emission control signal CLKp to the rise time Te of the pulse signal is a value corresponding to distance. The solid-state image sensor 200 calculates the distance to the object based on time statistics (mode values, etc.).

[0121] [Operational Example of Distance Measurement Module]

[0122] Figure 12 This is a flowchart illustrating an operational example of the distance measurement module 100 according to a first embodiment of the present technology. For example, the operation begins when a predetermined application for measuring distance is executed.

[0123] The light-emitting unit 110 begins to emit light, and the pixel circuit in the solid-state image sensor 200 begins to receive reflected light (step S901). Furthermore, the control circuit 210 controls the anode potential VSPAD based on the bottom potential Vbtm (step S902). Additionally, the signal processing unit 230 measures the round-trip time (step S903) and calculates distance data using the round-trip time (step S904). After step S904, the solid-state image sensor 200 terminates the distance measurement operation. In the case of multiple distance measurements, steps S901 to S904 are repeated synchronously with the vertical synchronization signal VSYNC.

[0124] As described above, in the first embodiment of this technology, when the bottom potential Vbtm is high, the solid-state image sensor 200 provides a lower anode potential VSPAD, thereby increasing the photocurrent from the photodiode 262 when the bottom potential Vbtm is high. Therefore, fluctuations in excessive bias caused by changes in breakdown voltage (VBD) and temperature can be suppressed.

[0125] <2. Second Implementation Method>

[0126] In the first embodiment described above, the solid-state image sensor 200 has only one monitoring pixel circuit 260 disposed in the pixel array unit 240. However, there is a possibility that the monitoring pixel circuit 260 may fail due to, for example, degradation over time, and the pixel may become a defective pixel. The pixel array unit 240 of the second embodiment differs from the pixel array unit of the first embodiment when multiple monitoring pixel circuits 260 are disposed.

[0127] Figure 13 This is an example of a plan view of a pixel array unit 240 according to a second embodiment of the present technology. The pixel array unit 240 differs from the pixel array unit of the first embodiment when two or more monitoring pixel circuits 260 are provided.

[0128] For example, one row of pixel array unit 240 includes M (M is an integer from 2 to N, excluding N) monitoring pixel circuits 260, and non-monitoring pixel circuits 280 are arranged in the remaining rows.

[0129] Figure 14 This is an example of a circuit diagram of a light-shielding pixel circuit 250 and a monitoring pixel circuit 260 according to a second embodiment of the present technology. The monitoring pixel circuit 260 is typically connected to the light-shielding pixel circuit 250. The light-shielding pixel circuit 250 provides a diode 252 for each monitoring pixel circuit 260.

[0130] The corresponding cathode of diode 252 is connected to the corresponding monitoring pixel circuit 260, and the anode of diode 252 is typically connected to the junction of resistor 251 and capacitor 253.

[0131] Using the above configuration, the light-shielding pixel circuit 250 can detect the minimum value of the cathode potential of each of the plurality of monitoring pixel circuits 260 as the bottom potential Vbtm.

[0132] As described above, according to the second embodiment of the present technology, the solid-state image sensor 200 detects the minimum value of the cathode potential of each of the plurality of monitoring pixel circuits 260, so that even if a fault occurs in any monitoring pixel circuit 260, the over-bias will be controlled to an appropriate value.

[0133] <3. Third Implementation Method>

[0134] In the first embodiment described above, the solid-state image sensor 200 uses a light-shielding pixel circuit 250, which includes a capacitor 253 and a diode 252, to detect the bottom potential Vbtm. However, due to the addition of circuitry such as the capacitor 253, the circuit size may increase. From the perspective of reducing the mounting area of ​​the solid-state image sensor 200, a small circuit size is desirable. The pixel array unit 240 of the third embodiment differs from the first embodiment in that a monitoring pixel circuit 260 replaces the light-shielding pixel circuit 250 in detecting the bottom potential Vbtm.

[0135] Figure 15 This is an example of a circuit diagram of the control circuit 210 and the monitoring pixel circuit 260 according to a third embodiment of the present technology. The monitoring pixel circuit 260 of the third embodiment differs from that of the first embodiment in that a resistor 265 is provided instead of a resistor 261. Furthermore, the cathode of the photodiode 262 is connected to the inverting input (-) of the comparator 211. Additionally, the control circuit 210 does not include a correction diode 212, and the light-shielding pixel circuit 250 does not include a capacitor 253 and a diode 252.

[0136] The resistance value of resistor 265 is less than that of resistor 281 in the non-monitoring pixel circuit 280, and is set to a value that causes avalanche breakdown even in darkness when no light enters photodiode 262. Therefore, even in darkness, the photocurrent I... L The value is fixed (in other words, latched) to a value similar to that at the time of light incidence. Therefore, the cathode potential is fixed to the bottom potential Vbtm, and the control circuit 210 can control the anode potential VSPAD according to the potential.

[0137] As described above, according to the third embodiment of this technology, the monitoring pixel circuit 260 detects the bottom potential Vbtm, thus reducing the size of capacitor 253 and diode 252. Consequently, the circuit size of the pixel array unit 240 can be reduced.

[0138] <4. Fourth Implementation Method>

[0139] In the first embodiment described above, the solid-state image sensor 200 uses a light-shielding pixel circuit 250 equipped with a capacitor 253 and a diode 252 to detect the bottom potential Vbtm. However, due to the addition of circuitry such as the capacitor 253, the circuit size may increase. From the viewpoint of reducing the mounting area of ​​the solid-state image sensor 200, a small circuit size is desirable. The solid-state image sensor 200 of the fourth embodiment differs from that of the first embodiment in that the control circuit 210 estimates the bottom potential Vbtm based on the output value of the monitoring pixel circuit 260.

[0140] Figure 16 This is an example of a circuit diagram of a monitoring pixel circuit 260 according to a fourth embodiment of the present technology. The monitoring pixel circuit 260 of the fourth embodiment differs from that of the first embodiment in that a comparator 266 is included instead of an inverter 263. Furthermore, the cathode of the photodiode 262 is not connected to the light-shielding pixel circuit 250, and the light-shielding pixel circuit 250 does not include a capacitor 253 and a diode 252.

[0141] The non-inverting input (+) of comparator 266 is connected to the cathode of photodiode 262, and the inverting input (-) of comparator 266 is connected to a power supply with a predetermined potential (e.g., 0.1 volts). Comparator 266 compares the cathode potential with the predetermined potential and provides the comparison result as a switching signal SW to control circuit 210. When the cathode potential Vs is higher than the predetermined potential, the switching signal SW goes high; when the cathode potential Vs is equal to or lower than the predetermined potential, the switching signal SW goes low.

[0142] Figure 17 This is a block diagram illustrating an example configuration of a control circuit 210 according to a fourth embodiment of the present technology. The control circuit 210 includes a controller 213 and a power integrated circuit (IC) 214, replacing the comparator 211 and the correction diode 212.

[0143] The controller 213 controls the potential provided by the power IC 214 according to the switching signal SW. Details of the control are described below. The power IC 214 provides the anode potential VSPAD according to the control of the controller 213.

[0144] Figure 18 This is a graph illustrating an example of the relationship between the cathode potential and the anode potential according to a fourth embodiment of the present technology. Figure 18 In the diagram, the vertical axis represents the cathode potential Vs, and the horizontal axis represents the anode potential VSPAD.

[0145] When the switch signal SW is high (i.e., the cathode potential Vs is higher than a predetermined potential), the estimated bottom potential Vbtm is not less than the threshold VT. At this time, the controller 213 causes the power IC 214 to provide the target value VL. Conversely, when the switch signal SW is low (i.e., the cathode potential Vs is equal to or lower than a predetermined potential), the estimated bottom potential Vbtm is less than the threshold VT. At this time, the controller 213 causes the power IC 214 to provide the target value VH. This target value VH is set to a value higher than the target value VL. By controlling the switch signal SW, when the bottom potential Vbtm is high, a lower anode potential VSPAD is provided.

[0146] As described above, according to the fourth embodiment of this technology, the control circuit 210 estimates the bottom potential Vbtm based on a comparison between the cathode potential Vs and a predetermined potential, thereby reducing the size of the capacitor 253 and the diode 252. This reduces the circuit size of the pixel array unit 240.

[0147] <5. Fifth Implementation Method>

[0148] In the first embodiment described above, the solid-state image sensor 200 uses a light-shielding pixel circuit 250 equipped with a capacitor 253 and a diode 252 to detect the bottom potential Vbtm. However, due to the addition of circuitry such as the capacitor 253, the circuit size may increase. From the viewpoint of reducing the mounting area of ​​the solid-state image sensor 200, a small circuit size is desirable. The solid-state image sensor 200 of the fifth embodiment differs from that of the first embodiment in that the control circuit 210 estimates the bottom potential Vbtm from the count value of the pulse signal OUT of the monitoring pixel circuit 260.

[0149] Figure 19 This is an example of a circuit diagram of a monitoring pixel circuit 260 according to a fifth embodiment of the present technology. The monitoring pixel circuit 260 in the fifth embodiment differs from that in the first embodiment in that a transistor 267 is provided instead of a resistor 261, and an inverter 263 provides a pulse signal OUT to the control circuit 210. Furthermore, the cathode of the photodiode 262 is not connected to the light-shielding pixel circuit 250, and the light-shielding pixel circuit 250 does not include a capacitor 253 and a diode 252.

[0150] For example, a pMOS transistor is used as transistor 267. Furthermore, a low-level bias voltage Vb is applied to the gate of transistor 267. Note that the on-resistance of transistor 267 is an example of the resistor described in the claims.

[0151] Figure 20 This is a block diagram illustrating an example configuration of the control circuit 210 according to a fifth embodiment of the present technology. The control circuit 210 of the fifth embodiment differs from that of the first embodiment in that it includes a controller 213, a power IC 214, a comparison unit 215, and a counter 216 in place of the comparator 211 and the correction diode 212.

[0152] Counter 216 counts the number of times the pulse signal OUT goes high within the period of the vertical synchronization signal VSYNC. Counter 216 provides the count value to the comparison unit 215.

[0153] The comparison unit 215 compares the count value with a predetermined fixed value. The comparison unit 215 provides the comparison result as a switch signal SW to the controller 213. For example, if the count value is greater than the fixed value, the switch signal SW goes high, and if the count value is equal to or less than the fixed value, the switch signal SW goes low.

[0154] The controller 213 controls the potential provided by the power IC 214 according to the switching signal SW. Details of the control are described below. The power IC 214 provides the anode potential VSPAD according to the control of the controller 213.

[0155] Figure 21 This is a graph illustrating an example of the relationship between the count value and the anode potential according to a fifth embodiment of the present technology. Figure 21 In the diagram, the vertical axis represents the count value, and the horizontal axis represents the anode potential VSPAD.

[0156] When the switch signal SW is low (i.e., the count value is fixed or less), it means that the bottom potential Vbtm falls below the threshold VT very rarely. In this case, the controller 213 causes the power IC 214 to provide the target value VL. Conversely, when the switch signal SW is high (i.e., the count value is greater than fixed), it means that the bottom potential Vbtm falls below the threshold VT very frequently. In this case, the controller 213 causes the power IC 214 to provide the target value VH. This target value VH is set to a value higher than the target value VL.

[0157] As described above, according to the fifth embodiment of this technology, the control circuit 210 controls the anode potential VSPAD based on a comparison between the count value and a fixed value of the bottom potential Vbtm, thereby reducing the size of the capacitor 253 and the diode 252. This reduces the circuit size of the pixel array unit 240.

[0158] <6. Sixth Implementation Method>

[0159] In the first embodiment described above, the solid-state image sensor 200 uses a light-shielding pixel circuit 250 equipped with a capacitor 253 and a diode 252 to detect the bottom potential Vbtm. However, due to the addition of circuitry such as the capacitor 253, the circuit size may increase. From the viewpoint of reducing the mounting area of ​​the solid-state image sensor 200, a small circuit size is desirable. The solid-state image sensor 200 of the sixth embodiment differs from that of the first embodiment in that the control circuit 210 estimates the bottom potential Vbtm based on the pulse width of the monitoring pixel circuit 260.

[0160] Figure 22This is a block diagram illustrating a configuration example of the control circuit 210 according to a sixth embodiment of the present technology. The control circuit 210 of the sixth embodiment differs from that of the first embodiment in that it includes a controller 213, a power IC 214, and a pulse width detection unit 217, replacing the comparator 211 and the correction diode 212. Furthermore, the cathode of the photodiode 262 is not connected to the light-shielding pixel circuit 250, and the light-shielding pixel circuit 250 does not include a capacitor 253 and a diode 252.

[0161] The pulse width detection unit 217 detects the pulse width of the pulse signal OUT from the monitoring pixel circuit 260. The pulse width detection unit 217 provides the detected pulse width to the controller 213.

[0162] The controller 213 controls the potential supplied from the power IC 214 based on pulse width modulation. Details of the control are described below. The power IC 214 provides the anode potential VSPAD according to the control of the controller 213.

[0163] Figure 23 This is a timing diagram illustrating an operational example of the control circuit 210 and the monitoring pixel circuit 260 according to a sixth embodiment of the present technology.

[0164] The pulse width detection unit 217 provides a high-level gate signal GAT during a predetermined pulse period at the start of distance measurement or before the start of distance measurement. At this time, the controller 213 maintains the pulse width detected by the pulse width detection unit 217 as a reference value.

[0165] Then, each time reflected light is received, the pulse width detection unit 217 detects the pulse width, and the controller 213 compares the pulse width with a reference value. When the bottom potential Vbtm is low, the pulse width tends to widen. Based on this trend, when the pulse width is wider than the reference value, the controller 213 causes the power IC 214 to provide a target value VL. On the other hand, when the pulse width is equal to or less than the reference value, the controller 213 causes the power IC 214 to provide a target value VH. This target value VH is set to a value higher than the target value VL.

[0166] As described above, according to the sixth embodiment of this technology, the control circuit 210 controls the anode potential VSPAD based on a comparison between the pulse width of the bottom potential Vbtm and a reference value, thereby reducing the size of the capacitor 253 and the diode 252. This reduces the circuit size of the pixel array unit 240.

[0167] <7. Seventh Implementation Method>

[0168] In the first embodiment described above, the control circuit 210 uses a comparator 211, which is an analog circuit, to control the anode potential VSPAD. However, since the circuit size of an analog circuit is generally larger than that of a digital circuit, the mounting area may increase. The control circuit 210 of the seventh embodiment differs from that of the first embodiment in that the anode potential VSPAD is controlled by a digital circuit.

[0169] Figure 24 This is a block diagram illustrating an example configuration of the control circuit 210 according to a seventh embodiment of the present technology. The control circuit 210 differs from the first embodiment in that it includes a controller 213, a power IC 214, and an analog-to-digital converter (ADC) 218 ​​in place of the comparator 211 and the correction diode 212.

[0170] ADC 218 receives an over-bias dV, which is the difference between the potential VE and the bottom potential Vbtm. ADC 218 performs analog-to-digital (AD) conversion on the over-bias dV and provides the digital signal to controller 213. Because the potential VE is constant, the over-bias dV takes a higher value when the bottom potential Vbtm is low.

[0171] Controller 213 controls the potential supplied from power IC 214 based on over-bias dV. Controller 213 causes power IC 214 to provide a lower anode potential VSPAD when the over-bias dV is low (i.e., the bottom potential Vbtm is high). Power IC 214 provides the anode potential VSPAD according to the control of controller 213.

[0172] As described above, in the seventh embodiment of this technology, the control circuit 210 controls the anode potential VSPAD via the controller 213 and the power IC 214. Therefore, the circuit size can be reduced compared to the case using analog circuits.

[0173] <8. Eighth Implementation>

[0174] In the seventh embodiment described above, the solid-state image sensor 200 has only one monitoring pixel circuit 260 disposed in the pixel array unit 240. However, there is a possibility that the monitoring pixel circuit 260 may fail due to, for example, degradation over time, and the pixel may become a defective pixel. The pixel array unit 240 of the eighth embodiment differs from that of the seventh embodiment in that multiple monitoring pixel circuits 260 are disposed and any one of the monitoring pixel circuits 260 is enabled.

[0175] In the pixel array unit 240 of the eighth embodiment, as Figure 13 Multiple monitoring pixel circuits 260 are arranged as shown in the second embodiment.

[0176] Figure 25 This is an example of a circuit diagram of a monitoring pixel circuit 260 according to the eighth embodiment of the present technology. The monitoring pixel circuit 260 of the eighth embodiment differs from that of the seventh embodiment in that it includes a transistor 267 instead of a resistor 261. Furthermore, the monitoring pixel circuit 260 of the eighth embodiment differs from that of the seventh embodiment in that it includes switches 268 and 270, an inverter 269, a diode 271, and a latch circuit 272 instead of a transistor 264.

[0177] For example, a pMOS transistor is used as transistor 267. Furthermore, a low-level bias voltage Vb is applied to the gate of transistor 267. Note that the on-resistance of transistor 267 is an example of the resistor described in the claims.

[0178] The latch circuit 272 holds the enable signal EN from the control circuit 210. The enable signal EN is a signal used to enable or disable the monitoring pixel circuit 260. For example, when the monitoring pixel circuit 260 is enabled, the enable signal EN is set to a high level, and when the monitoring pixel circuit 260 is disabled, it is set to a low level.

[0179] Inverter 269 inverts the enable signal EN held in latch circuit 272 and outputs the inverted enable signal EN as an inverted signal to switch 268.

[0180] Switch 268 opens and closes the path between the cathode and ground of photodiode 262 based on the inverted signal from inverter 269. For example, when the inverted signal is high, switch 268 switches to the closed state, and when the inverted signal is low, switch 268 switches to the open state.

[0181] Switch 270 opens and closes the path between the cathode of photodiode 262 and the cathode of diode 271 based on the enable signal EN held in latch circuit 272. For example, when the enable signal EN is high, switch 270 switches to the closed state, and when the enable signal EN is low, switch 270 switches to the open state. The anode of diode 271 is connected to the light-shielding pixel circuit 250.

[0182] In the eighth embodiment, the controller 213 selects and enables any one of the plurality of monitoring pixel circuits 260 via the enable signal EN, and disables the remaining monitoring pixel circuits 260. The enabled monitoring pixel circuit 260 provides a cathode potential Vs to the light-shielding pixel circuit 250, the cathode potential Vs having a potential that decreases due to incident light. Meanwhile, the disabled monitoring pixel circuit 260, in the off state, will not experience avalanche breakdown in the photodiode 262 due to discharge of the switch 268, and in the on state, will not output the cathode potential Vs through the switch 270.

[0183] Furthermore, the controller 213 periodically switches the enabled monitoring pixel circuits 260. For example, it switches the enabled monitoring pixel circuits 260 in each cycle of the vertical synchronization signal VSYNC. Since avalanche breakdown does not occur in the photodiodes 262 of the disabled monitoring pixel circuits 260, degradation of the photodiodes 262 can be suppressed by periodically enabling only one monitoring pixel circuit 260, compared to always enabling all monitoring pixel circuits 260.

[0184] As described above, in the eighth embodiment of this technology, the control circuit 210 enables any one of the plurality of monitoring pixel circuits 260 and controls the anode potential VSPAD. Therefore, compared to the case where all monitoring pixel circuits 260 are enabled, the degradation of the photodiode 262 can be suppressed.

[0185] <9. Ninth Implementation Method>

[0186] In the first embodiment described above, the light-shielding pixel circuit 250 has detected the bottom potential Vbtm. However, as... Figure 8 As shown, the value of the bottom potential Vbtm may be inaccurate. The difference between the monitoring pixel circuit 260 of the ninth embodiment and the monitoring pixel circuit 260 of the first embodiment is that a variable capacitor is added to reduce the error of the bottom potential Vbtm.

[0187] Figure 26 This is an example of a circuit diagram of a monitoring pixel circuit 260 according to a ninth embodiment of the present technology. The monitoring pixel circuit 260 of the ninth embodiment differs from that of the first embodiment in that it includes a transistor 267 instead of a resistor 261, and also includes a variable capacitor 273.

[0188] For example, a pMOS transistor is used as transistor 267. Furthermore, a low-level bias voltage Vb is applied to the gate of transistor 267. Note that the on-resistance of transistor 267 is an example of the resistor described in the claims.

[0189] The variable capacitor 273 is a capacitor with a variable capacitance value. One end of the variable capacitor 273 is connected to the cathode of the photodiode 262, and the other end of the variable capacitor 273 is connected to the ground terminal.

[0190] Because the variable capacitor 273 is connected in parallel with the capacitor 253 in the light-shielding pixel circuit 250, their combined capacitance is greater than that of the individual capacitor 253. Therefore, the addition of the variable capacitor 273 can reduce the error in the bottom potential Vbtm. The capacitance value of the variable capacitor 273 is adjusted by the user or others before distance measurement.

[0191] Figure 27 This is a timing diagram illustrating an example of the bottom potential according to the ninth embodiment of the present technology. Figure 27 Figure 'a' shows a timing diagram illustrating an example of the bottom potential detected in a comparative example without the variable capacitor 273. Figure 27 b in the figure shows a timing diagram that illustrates an example of the bottom potential detected in the ninth embodiment.

[0192] In the comparative example, the bottom potential Vbtm detected by the light-shielding pixel circuit 250 is inconsistent with the actual minimum value (i.e., the true value) of the cathode potential Vs, and an error occurs. Meanwhile, in the ninth embodiment, the bottom potential Vbtm is substantially consistent with the true value, and the error is reduced.

[0193] As described above, in the ninth embodiment of this technology, the variable capacitor 273 is connected in parallel with the capacitor 253, thus increasing the circuit capacitance compared to using only capacitor 253. Therefore, the error in the bottom potential Vbtm can be reduced.

[0194] <10. Tenth Implementation Method>

[0195] In the first embodiment described above, the light-shielding pixel circuit 250 has detected the bottom potential Vbtm. However, as... Figure 8 As shown, the value of the bottom potential Vbtm may be inaccurate. The difference between the monitoring pixel circuit 260 of the tenth embodiment and the first embodiment is that the error of the bottom potential Vbtm is reduced by applying an update pulse signal.

[0196] Figure 28 This is an example of a circuit diagram of a monitoring pixel circuit 260 according to a tenth embodiment of the present technology. The tenth monitoring pixel circuit 260 differs from the first embodiment in that it also includes a transistor 274.

[0197] For example, a pMOS transistor is used as transistor 274. Transistor 274 short-circuits the two ends of resistor 261 according to the update pulse signal REF.

[0198] Figure 29 This is an example of a circuit diagram of a control circuit 210 according to the tenth embodiment of the present technology. The control circuit 210 of the tenth embodiment differs from that of the first embodiment in that it further includes a refresh pulse supply unit 219.

[0199] The update pulse supply unit 219 supplies the update pulse signal REF to the monitoring pixel circuit 260 synchronously with the light emission control signal CLKp.

[0200] Figure 30 This is a timing diagram illustrating an example of fluctuations in the light emission control signal CLKp, the update pulse signal REF, and the bottom potential Vbtm according to the tenth embodiment of the present technology.

[0201] Immediately before the rise time Tp of the light emission control signal CLKp, the update pulse supply unit 219 supplies a low-level update pulse signal REF within a specific pulse period. Except for the pulse period, the update pulse signal REF is set to a high level. Through the low-level update pulse signal REF, the bottom potential Vbtm rises to potential VE, and capacitor 253 is charged. Because the discharge time of capacitor 253 shortens the time period from time Tr to Tp, the fluctuation of the bottom potential Vbtm due to discharge is reduced, and the error of the bottom potential Vbtm is decreased.

[0202] As described above, in the tenth embodiment of this technology, the control circuit 210 provides an update pulse signal REF to charge the capacitor 253. Therefore, the discharge time of the capacitor 253 can be shortened accordingly. Thus, the error in the bottom potential Vbtm can be reduced.

[0203] <11. Eleventh Implementation Method>

[0204] In the first embodiment described above, the control circuit 210 has controlled the anode potential VSPAD based on the bottom potential Vbtm. However, the sensitivity of the photodiode 262 may fluctuate due to temperature changes. This fluctuation in sensitivity may reduce the detection efficiency of the incident light. The control circuit 210 of the eleventh embodiment differs from the control circuit of the first embodiment in controlling the anode potential VSPAD based on temperature.

[0205] Figure 31 This is an example of a plan view of a pixel array unit 240 according to the eleventh embodiment of the present technology. The pixel array unit 240 of the eleventh embodiment differs from that of the first embodiment in that the monitoring pixel circuit 260 is not arranged therein.

[0206] Figure 32This is a block diagram illustrating a configuration example of the control circuit 210 according to the eleventh embodiment of the present technology. The control circuit 210 of the eleventh embodiment includes a controller 213, a power IC 214, a comparison unit 215, a temperature sensor 220, and a reverse bias setpoint storage unit 221.

[0207] Temperature sensor 220 measures the temperature in distance measurement module 100. Temperature sensor 220 provides the measured value to comparison unit 215. Comparison unit 215 compares the measured value with a predetermined fixed value and provides the comparison result as a switch signal SW to controller 213. For example, when the temperature is higher than the fixed value, the switch signal SW is set to a high level, and when the temperature is equal to or lower than the fixed value, the switch signal SW is set to a low level.

[0208] The reverse bias setting value storage unit 221 stores the pre-measured breakdown voltage as the setting value VBD.

[0209] Controller 213 controls the potential provided by power IC 214 based on temperature and setpoint VBD. Details of the control are described below. Power IC 214 provides the anode potential VSPAD according to the control of controller 213.

[0210] Figure 33 This is a graph illustrating an example of the relationship between temperature and anodic potential according to the eleventh embodiment of the present technology. Figure 33 In the diagram, the vertical axis represents the measured temperature, and the horizontal axis represents the anode potential VSPAD.

[0211] When the switch signal SW is high (i.e., the temperature is higher than a fixed value), the controller 213 sets the target value VL by the following expression and provides the target value VL to the power IC 214.

[0212] VL = VE - (VBD + dVH)

[0213] In the above expression, dVH represents the over-bias at relatively high temperatures.

[0214] Meanwhile, when the switching signal SW is at a low level (i.e., the temperature is equal to or lower than a fixed value), the controller 213 sets the target value VH by the following expression and provides the target value VH to the power IC 214.

[0215] VH = VE - (VBD + dVL)

[0216] In the above expression, dVL represents the over-bias at relatively low temperatures and is set to a value lower than dVH.

[0217] As described above, in the eleventh embodiment of this technology, the control circuit 210 controls the anode potential VSPAD according to the temperature. Therefore, even if the sensitivity of the photodiode 262 fluctuates due to temperature changes, the detection efficiency of the incident light can be maintained.

[0218] <12. Examples of applications involving moving objects>

[0219] The technology disclosed herein (the Technology) can be applied to a variety of products. For example, the Technology disclosed herein can be implemented as a device mounted on any type of mobile body, including automobiles, electric vehicles, hybrid electric vehicles, motorcycles, bicycles, personal mobility devices, airplanes, drones, ships, robots, etc.

[0220] Figure 34 This is a block diagram illustrating a schematic configuration example of a vehicle control system, which is an example of a mobile body control system to which the technology according to this disclosure can be applied.

[0221] The vehicle control system 12000 includes multiple electronic control units connected via a communication network 12001. Figure 34 In the example shown, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, a vehicle external information detection unit 12030, a vehicle internal information detection unit 12040, and an integrated control unit 12050. Furthermore, as part of the functional configuration of the integrated control unit 12050, a microcomputer 12051, an audio-visual output unit 12052, and an in-vehicle network interface (I / F) 12053 are shown.

[0222] The drive system control unit 12010 controls the operation of devices related to the vehicle drive system according to various programs. For example, the drive system control unit 12010 is used as a control device for a drive force generating device (e.g., an internal combustion engine or drive motor) for generating vehicle driving force, a drive force transmission mechanism for transmitting driving force to the wheels, a steering mechanism for adjusting the vehicle steering angle, a braking device for generating vehicle braking force, etc.

[0223] The body system control unit 12020 controls the operation of various devices installed in the vehicle body according to various programs. For example, the body system control unit 12020 serves as a control device for keyless entry systems, smart key systems, automatic windows, and various lights (e.g., headlights, taillights, brake lights, turn signals, and fog lights). In this case, radio waves transmitted from a mobile device can be input to the body system control unit 12020, replacing the keys or signals of various switches. The body system control unit 12020 receives the input radio waves or signals and controls the vehicle's door locking devices, automatic windows, lights, etc.

[0224] The vehicle exterior information detection unit 12030 detects information about the exterior of the vehicle on which the vehicle control system 12000 is installed. For example, an 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 images of the exterior of the vehicle and receives the captured images. The vehicle exterior information detection unit 12030 can perform object detection processing or distance detection processing on people, vehicles, obstacles, signs, letters on the road surface, etc., based on the received images.

[0225] Imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal based on the amount of light received. Imaging unit 12031 can output an electrical signal as an image, and can also output an electrical signal as distance measurement information. Furthermore, the light received by imaging unit 12031 can be visible light or invisible light such as infrared light.

[0226] The vehicle interior information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041, which detects the driver's state, is connected to the vehicle interior information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that captures the driver, and the vehicle interior information detection unit 12040 can calculate the driver's level of fatigue or concentration, or can determine whether the driver is asleep based on detection information input from the driver state detection unit 12041.

[0227] The microcomputer 12051 calculates control target values ​​for the drive force generating device, steering mechanism, or braking device based on external and internal vehicle information acquired in the vehicle external information detection unit 12030 or the vehicle internal information detection unit 12040, and can output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control to realize the functions of advanced driver assistance systems (ADAS), including vehicle collision avoidance or shock absorption, following based on vehicle distance, vehicle speed maintenance, vehicle collision warning, vehicle lane departure warning, etc.

[0228] Furthermore, the microcomputer 12051 controls the drive force generating device, steering mechanism, braking device, etc., based on information about the vicinity of the vehicle obtained in the vehicle external information detection unit 12030 or the vehicle internal information detection unit 12040, to perform cooperative control for autonomous driving without relying on the operation of the driver or others.

[0229] Furthermore, the microcomputer 12051 can output control commands to the body system control unit 12020 based on vehicle external information acquired in the vehicle external information detection unit 12030. For example, the microcomputer 12051 can perform cooperative control to achieve glare reduction, such as controlling the headlights and switching from high beam to low beam based on the position of the vehicle ahead or oncoming vehicle detected in the vehicle external information detection unit 12030.

[0230] The audio-visual output unit 12052 transmits an output signal of at least one of sound or image to an output device that can visually and audibly notify passengers of information or the exterior of the vehicle. Figure 34 In the example, an audio speaker 12061, a display unit 12062, and a dashboard 12063 are exemplary shown as output devices. The display unit 12062 may include at least one of, for example, an in-vehicle display or a head-up display.

[0231] Figure 35 This is a diagram showing an example of the mounting location of the imaging unit 12031.

[0232] exist Figure 35 The imaging unit includes imaging units 12101, 12102, 12103, 12104 and 12105, which together form imaging unit 12031.

[0233] Imaging units 12101, 12102, 12103, 12104, and 12105 are disposed in locations such as the front nose, side mirrors, rear bumper, rear door, and upper windshield inside the vehicle 12100. Imaging unit 12101 at the front nose and imaging unit 12105 at the upper windshield inside the vehicle primarily acquire images of the front of the vehicle 12100. Imaging units 12102 and 12103 at the side mirrors primarily acquire side images of the vehicle 12100. Imaging unit 12104 at the rear bumper or rear door primarily acquires rear images of the vehicle 12100. Imaging unit 12105 at the upper windshield inside the vehicle is primarily used to detect vehicles, pedestrians, obstacles, traffic signals, traffic signs, lanes, etc., ahead.

[0234] Notice, Figure 35An example of the imaging range of imaging units 12101 to 12104 is shown. Imaging range 12111 represents the imaging range of imaging unit 12101 located at the front nose, imaging ranges 12112 and 12113 represent the imaging ranges of imaging units 12102 and 12103 located at the side mirrors, respectively, and imaging range 12114 represents the imaging range of imaging unit 12104 located at the rear bumper or rear door. For example, a bird's-eye view of the vehicle 12100 viewed from above can be obtained by overlaying the image data captured by imaging units 12101 to 12104.

[0235] At least one of the imaging units 12101 to 12104 may have the 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.

[0236] For example, based on distance information obtained from imaging units 12101 to 12104, microcomputer 12051 obtains the distance to a three-dimensional object within imaging ranges 12111 to 12114 and the time variation of that distance (relative speed to vehicle 12100), thereby specifically extracting the three-dimensional object closest to vehicle 12100 on the driving road and traveling in substantially the same direction as vehicle 12100 at a predetermined speed (e.g., 0 km / h or higher), as the vehicle ahead. Furthermore, microcomputer 12051 can pre-set the appropriate vehicle-to-vehicle distance to ensure and execute automatic braking control (including follow-stop control) and automatic acceleration control (including follow-start control), etc. In this way, cooperative control can be performed for autonomous driving without relying on the operation of a driver or other personnel.

[0237] For example, based on distance information obtained from imaging units 12101 to 12104, microcomputer 12051 classifies three-dimensional object data about three-dimensional objects into two-wheeled vehicles, ordinary cars, large vehicles, pedestrians, and other three-dimensional objects, such as utility poles to be extracted, and can use this data to automatically avoid obstacles. For example, microcomputer 12051 distinguishes obstacles around vehicle 12100 into obstacles that are visually identifiable to the driver of vehicle 12100 and obstacles that are not visually identifiable to the driver. Then, microcomputer 12051 determines the collision risk indicating the risk of collision with each obstacle, and if the collision risk is a set value or greater and there is a possibility of collision, outputs a warning to the driver through audio speaker 12061 or display unit 12062, and performs forced deceleration or evasive steering through drive system control unit 12010, thus performing driving assistance for collision avoidance.

[0238] At least one of the imaging units 12101 to 12104 may be an infrared camera that detects infrared light. For example, the microcomputer 12051 determines whether a pedestrian is present in the imaging images of the imaging units 12101 to 12104, thereby identifying the pedestrian. Pedestrian identification is performed by extracting feature points from the imaging images of the imaging units 12101 to 12104 (e.g., as an infrared camera) and by performing pattern matching processing on a series of feature points indicating the outline of an object and identifying whether the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the imaging images of the imaging units 12101 to 12104 and identifies the pedestrian, the audio-visual output unit 12052 causes the display unit 12062 to overlay and display a rectangular outline to emphasize the identified pedestrian. Furthermore, the audio-visual output unit 12052 may cause the display unit 12062 to display an icon or the like representing a pedestrian at a desired location.

[0239] Examples of vehicle control systems to which the technology according to this disclosure can be applied have been described. The technology according to this disclosure can be applied to the vehicle external information detection unit 12030 configured as described above. Specifically, Figure 1 The distance measurement module 100 can be applied to the vehicle external information detection unit 12030. By applying the technology according to this disclosure to the vehicle external information detection unit 12030, the anode potential can be controlled to an appropriate value that reduces the error count rate and makes the photon detection efficiency sufficiently high, and accurate distance information can be obtained.

[0240] Note that the above embodiments describe examples for implementing this technology, and the matters in the embodiments correspond to the matters in the claims that specify the invention. Similarly, the matters in the claims that specify the invention correspond to the matters with the same names in the embodiments of this technology. However, this technology is not limited to the embodiments and can be implemented by applying various modifications to the embodiments without departing from the spirit of this technology.

[0241] Furthermore, the processing described in the above embodiments can be considered as a method having these series of processes, and also as a program for causing a computer to execute these series of processes and a recording medium for storing the program. For example, optical discs (CDs), mini-CDs (MDs), digital versatile optical discs (DVDs), memory cards, Blu-ray discs (Blu-ray discs, a registered trademark), etc., can be used as such recording media.

[0242] Note that the effects described in this manual are merely examples and are not limited to any particular effect; other effects may be shown.

[0243] Note that this technology can also have the following configurations.

[0244] (1) A solid-state image sensor, comprising:

[0245] A photodiode is configured to convert incident light into photocurrent.

[0246] A resistor connected to the cathode of a photodiode; and

[0247] The control circuit is configured such that the higher the potential of the cathode when the photocurrent flows through the resistor, the lower the potential supplied to the anode of the photodiode.

[0248] (2) The solid-state image sensor according to (1) further includes:

[0249] The detection circuit is configured to detect the cathode potential when photocurrent flows through the resistor and provide the detected potential to the control circuit.

[0250] (3) The solid-state image sensor according to (2), wherein,

[0251] The resistors and photodiodes are disposed in each of the plurality of pixel circuits.

[0252] The cathodes of the multiple pixel circuits are all connected to the detection circuit, and

[0253] The detection circuit detects the minimum potential of the cathode when the photocurrent flows through the resistor.

[0254] (4) The solid-state image sensor according to (2) or (3) further includes:

[0255] A variable capacitor connected to the cathode.

[0256] (5) The solid-state image sensor according to any one of (2) to (4) further comprises:

[0257] A transistor, configured to short-circuit the two ends of a resistor according to an update pulse signal, wherein,

[0258] The control circuit also provides an update pulse signal to the transistor just before the incident light is about to strike.

[0259] (6) The solid-state image sensor according to (1), wherein,

[0260] The resistance value of the resistor is the value at which the cathode potential is fixed.

[0261] (7) The solid-state image sensor according to (1) further includes:

[0262] A comparator is configured to compare the potential of the cathode with a predetermined potential and output the comparison result, wherein...

[0263] Based on the comparison results, the control circuit provides a lower potential to the anode than would be provided if the cathode potential were lower than the predetermined potential, when the cathode potential is higher than the predetermined potential.

[0264] (8) The solid-state image sensor according to (1), wherein,

[0265] The control circuit counts the number of times the cathode potential falls below a predetermined threshold within a predetermined period, and if the number of times falls below a predetermined threshold, it supplies the anode with a potential lower than the potential if the number of times falls above a predetermined threshold.

[0266] (9) The solid-state image sensor according to (1) further includes:

[0267] An inverter, configured to invert the potential signal of the cathode and output the signal as a pulse signal, wherein...

[0268] The shorter the pulse width of the pulse signal, the lower the potential the control circuit provides to the anode of the photodiode.

[0269] (10) The solid-state image sensor according to (1), wherein,

[0270] One end of the resistor is connected to the cathode, and the other end of the resistor is connected to a terminal at a predetermined potential.

[0271] The control circuit measures the voltage between the cathode potential and a predetermined potential, and provides a lower potential to the anode of the photodiode when the voltage is higher.

[0272] (11) The solid-state image sensor according to (10), wherein,

[0273] The resistor and photodiode are disposed in each of the plurality of pixel circuits, and

[0274] The control circuit enables any one of the multiple pixel circuits and measures the voltage between the cathode potential and a predetermined potential of the configured pixel circuit.

[0275] (12) A solid-state image sensor, comprising:

[0276] A photodiode is configured to convert incident light into photocurrent.

[0277] A resistor connected to the cathode of a photodiode; and

[0278] The control circuit is configured to measure temperature and, as the temperature decreases, to provide a lower potential to the anode of the photodiode.

[0279] (13) An electronic device comprising:

[0280] A light-emitting unit configured to provide illumination light;

[0281] A photodiode is configured to perform photoelectric conversion on incident light relative to illumination light and output a photocurrent;

[0282] A resistor connected to the cathode of a photodiode; and

[0283] The control circuit is configured such that the higher the potential of the cathode when the photocurrent flows through the resistor, the lower the potential supplied to the anode of the photodiode.

[0284] List of reference numerals

[0285] 100 Distance Measurement Module

[0286] 110 light-emitting units

[0287] 120 Synchronous Control Unit

[0288] 200 solid-state image sensor

[0289] 210 control circuit

[0290] 211 and 266 comparators

[0291] 212 correction diode

[0292] 213 controller

[0293] 214 Power IC

[0294] 215 Comparison Units

[0295] 216 counter

[0296] 217 pulse width detection unit

[0297] 218ADC

[0298] 219 Updated Pulse Supply Unit

[0299] 220 temperature sensor

[0300] 221 Reverse Bias Setpoint Storage Unit

[0301] 230 signal processing unit

[0302] 231TDC

[0303] 232 Distance Data Generation Unit

[0304] 240 pixel array unit

[0305] 250 light-shielding pixel circuit

[0306] 251, 261, 265, 281 resistors

[0307] 252, 271 diodes

[0308] 253 capacitor

[0309] 260° monitoring pixel circuit

[0310] 262, 282 photodiodes

[0311] 263, 269, 283 inverters

[0312] 264, 267, 274, 284 transistors

[0313] 268, 270 switches

[0314] 272 latch circuit

[0315] 273 variable capacitor

[0316] 280 non-monitoring pixel circuit

[0317] 12030 Vehicle External Information Detection Unit

Claims

1. A light detection device, comprising: A first pixel circuit includes a first avalanche photodiode, the first pixel circuit being configured to output a first output signal from a first terminal of the first avalanche photodiode; The second pixel circuit includes a second avalanche photodiode, and the second pixel circuit is configured to output a second output signal from a first terminal of the second avalanche photodiode. A control circuit configured to receive the second output signal, wherein the output of the control circuit is coupled to a second terminal of the first avalanche photodiode and a second terminal of at least one second avalanche photodiode; as well as A resistor is connected to the cathode of the second avalanche photodiode; and The control circuit is configured to provide a lower potential to the anode of the first avalanche photodiode and the second avalanche photodiode as the potential of the cathode increases when the photocurrent flows through the resistor.

2. The optical detection device according to claim 1, wherein, The control circuit, including the comparator circuit, is configured to adjust the output based on the second output signal.

3. The optical detection device according to claim 1, wherein, The first terminal is the cathode, and the second terminal is the anode.

4. The optical detection device according to claim 3, further comprising: The second avalanche photodiode is one of a plurality of second avalanche photodiodes. At least one of the anodes of the second avalanche photodiode is one of a plurality of anodes, each of the plurality of anodes corresponding to one of the plurality of second avalanche photodiodes, and the output of the control circuit is coupled to the plurality of anodes.

5. The optical detection device according to claim 4, wherein, The plurality of second avalanche photodiodes are arranged in a row.

6. The optical detection device according to claim 1, wherein, The first pixel circuit and the second pixel circuit are arranged in an array, and a first portion of the array is shielded from light.

7. The optical detection device according to claim 6, wherein, The second portion of the array is not shaded, and the first avalanche photodiode and the second avalanche photodiode are located in the second portion of the array.

8. The optical detection device according to claim 1, wherein, in, The first pixel circuit also includes a transistor, one of the source or drain of the transistor being coupled to a first potential.

9. The optical detection device according to claim 8, wherein, The first pixel circuit also includes a first inverter coupled to the transistor.

10. The optical detection device according to claim 9, wherein, The first inverter and the other of the source or drain of the transistor are coupled to the first terminal of the first avalanche photodiode.

11. The optical detection device according to claim 1, wherein, in, The second pixel circuit includes a transistor, one of which is coupled to a first potential.

12. The optical detection device according to claim 11, wherein, The second pixel circuit also includes a second inverter coupled to the transistor.

13. The optical detection device according to claim 12, wherein, The inverter and the other of the source or drain of the transistor are coupled to the first terminal of the first avalanche photodiode.

14. The optical detection device according to claim 1, wherein, The first pixel circuit includes a first transistor, the source or drain of which is coupled to a first potential, and The second pixel circuit includes a second transistor, the source or drain of which is coupled to the first potential.

15. An electronic device comprising: The light-emitting unit is configured to provide illumination light; A light receiving device configured to receive reflected light relative to an illuminating light, the light receiving device comprising: A first pixel circuit includes a first avalanche photodiode, the first pixel circuit being configured to output a first output signal from a first terminal of the first avalanche photodiode; and The second pixel circuit includes a second avalanche photodiode, and the second pixel circuit is configured to output a second output signal from a first terminal of the second avalanche photodiode. A resistor connected to the cathode of the second avalanche photodiode; and The control circuit is configured to provide a lower potential to the anode of the first avalanche photodiode and the second avalanche photodiode as the potential of the cathode increases when the photocurrent flows through the resistor.

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