Photoelectric conversion device and driving method of them

Abstract

To provide a photoelectric conversion device and a driving method of them, capable of correctly counting the number of periods where an avalanche multiplication occurs in a plurality of periods of which an APD is controlled in a standby state.SOLUTION: A photoelectric conversion device includes: an APD; and first and second input nodes, and includes: a signal processing circuit of which one of the nodes of the APD is connected to the first input node, and a periodic first control signal is input to a second input node; and a recharge circuit that is connected to one node of the APD, and controls a recharge operation of the APD in accordance with a periodic second control signal. The signal processing circuit can switch a first mode that an output voltage is changed in accordance with a signal of the first input node in accordance with the first control signal and a second mode that a fixing value is output independence of the first input node. The signal processing circuit outputs a first value in the first mode at only one time in the case where an avalanche multiplication occurs in the APD at two times during one period of the second control signal.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present invention relates to a photoelectric conversion device and a driving method thereof. [Background technology]

[0002] Known photoelectric conversion elements include APDs (Avalanche Photo Diodes) and SPADs (Single Photon Avalanche Diodes), which multiply charges generated by the incidence of photons through avalanche breakdown. These photoelectric conversion elements are used in photoelectric conversion devices equipped with a function for counting the number of detected photons. Patent Document 1 describes a photoelectric conversion device that alternately controls an APD between a standby state in which avalanche multiplication is possible and a recharge state in which avalanche multiplication is restored to a state in which avalanche multiplication is possible again, and counts the number of periods in which avalanche multiplication occurs among multiple periods controlled to the standby state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-123847 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technique described in the cited document 1, it was sometimes impossible to accurately count the number of periods in which avalanche multiplication occurred among a plurality of periods in which the APD is controlled to be in a standby state.

[0005] An object of the present invention is to provide a photoelectric conversion device and a driving method thereof that can accurately count the number of periods in which avalanche multiplication occurs among a plurality of periods in which an APD is controlled to be in a standby state. [Means for solving the problem]

[0006] According to one disclosure of the present specification, there is provided a photoelectric conversion device comprising: an avalanche photodiode; a first signal processing circuit having a first input node and a second input node, one node of the avalanche photodiode connected to the first input node and a periodic first control signal input to the second input node; and a recharge circuit connected to the one node of the avalanche photodiode and controlling a recharge operation of the avalanche photodiode in response to a periodic second control signal, wherein the first signal processing circuit is switchable between a first mode in which an output value changes in response to a signal at the first input node and a second mode in which a fixed value is output regardless of the signal at the first input node in response to the first control signal, and the first signal processing circuit outputs a first value only once in the first mode when avalanche multiplication occurs in the avalanche photodiode two or more times during one period of the second control signal.

[0007] According to another disclosure of the present specification, there is provided a first signal processing circuit having an avalanche photodiode, a first input node and a second input node, one node of the avalanche photodiode is connected to the first input node and a periodic first control signal is input to the second input node, and a recharge circuit connected to the one node of the avalanche photodiode and controlled by a periodic second control signal, wherein the first signal processing circuit has a first mode in which an output value changes in response to a signal at the first input node in response to the first control signal, and and a second mode in which a fixed value is output regardless of a signal from a first control signal, and the recharge circuit is controlled to a recharge operation mode in which a recharge operation in the avalanche photodiode is permitted and a quench operation mode in which a quench operation in the avalanche photodiode is permitted in response to the second control signal, and a period in which the recharge circuit is controlled to the recharge operation mode overlaps with a period in which the first signal processing circuit is controlled to the second mode and does not overlap with a period in which the first signal processing circuit is controlled to the first mode.

[0008] According to still another disclosure of the present specification, there is provided a first signal processing circuit having an avalanche photodiode, a first input node and a second input node, one node of the avalanche photodiode is connected to the first input node, and a periodic first control signal is input to the second input node, and a recharge circuit connected to the one node of the avalanche photodiode and controlled by a periodic second control signal, the recharge circuit allowing a recharge operation in the avalanche photodiode in response to the second control signal. and a quench operation mode that allows quench operation in the avalanche photodiode, wherein the first signal processing circuit outputs a second value when the first control signal is at a first level, outputs a first value when the first control signal is at a second level different from the first level and the avalanche photodiode is in a discharge state in which avalanche multiplication does not occur, and holds an output value when the first control signal is at the second level and the avalanche photodiode is in a standby state in which avalanche multiplication is possible.

[0009] According to yet another disclosure of the present specification, there is provided a method for driving a photoelectric conversion device having an avalanche photodiode, a first signal processing circuit having a first input node and a second input node, one node of the avalanche photodiode connected to the first input node and a periodic first control signal input to the second input node, and a recharge circuit connected to the one node of the avalanche photodiode and controlled by a periodic second control signal, the method including: controlling the first signal processing circuit to a first mode in which an output value changes in response to a signal at the first input node in response to the first control signal; and a second mode in which a fixed value is output regardless of a signal at an output node, and the recharge circuit is controlled to a recharge operation mode in which a recharge operation in the avalanche photodiode is permitted and a quench operation mode in which a quench operation in the avalanche photodiode is permitted in response to the second control signal, such that a period in which the recharge circuit is controlled to the recharge operation mode overlaps with a period in which the first signal processing circuit is controlled to the second mode and does not overlap with a period in which the first signal processing circuit is controlled to the first mode. Effect of the Invention

[0010] According to the present invention, in a photoelectric conversion device that counts the number of periods in which avalanche multiplication occurs among multiple periods in which an APD is controlled to a standby state in which avalanche multiplication is possible, the number of periods in which avalanche multiplication occurs can be accurately counted. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram (part 1) showing a schematic configuration of a photoelectric conversion device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram (part 2) showing a schematic configuration of the photoelectric conversion device according to the first embodiment of the present invention. [Diagram 3] 1 is a block diagram showing an example of the configuration of a pixel of a photoelectric conversion device according to a first embodiment of the present invention. [Figure 4] 1 is a perspective view showing an example of the configuration of a photoelectric conversion device according to a first embodiment of the present invention. [Diagram 5] FIG. 2 is a diagram illustrating a basic operation of a photoelectric conversion unit in the photoelectric conversion device according to the first embodiment of the present invention. [Figure 6] 1 is a circuit diagram showing an example of the configuration of a pixel in a photoelectric conversion device according to a first embodiment of the present invention. [Figure 7] 7 is a timing chart (part 1) showing a general operation of the pixel circuit shown in FIG. 6. [Figure 8] 7 is a timing chart (part 2) showing a general operation of the pixel circuit shown in FIG. 6. [Figure 9] FIG. 2 is a timing chart showing a method for driving the photoelectric conversion device according to the first embodiment of the present invention. [Figure 10] FIG. 11 is a circuit diagram showing an example of the configuration of a pixel in a photoelectric conversion device according to a second embodiment of the present invention. [Figure 11] 7 is a timing diagram (part 3) showing a general operation of the pixel circuit shown in FIG. 6. [Figure 12] FIG. 11 is a timing chart showing a method for driving a photoelectric conversion device according to a second embodiment of the present invention. [Figure 13] FIG. 11 is a circuit diagram showing an example of the configuration of a pixel in a photoelectric conversion device according to a third embodiment of the present invention. [Figure 14] FIG. 11 is a timing chart (part 1) showing a method of driving a photoelectric conversion device according to a third embodiment of the present invention. [Figure 15] FIG. 11 is a timing chart (part 2) showing a method of driving a photoelectric conversion device according to a third embodiment of the present invention. [Figure 16] FIG. 11 is a timing chart (part 3) showing a method of driving a photoelectric conversion device according to a third embodiment of the present invention. [Figure 17] FIG. 13 is a block diagram showing a schematic configuration of a light detection system according to a fourth embodiment of the present invention. [Figure 18] FIG. 13 is a block diagram showing a schematic configuration of a range image sensor according to a fifth embodiment of the present invention. [Figure 19]FIG. 13 is a schematic diagram showing an example of the configuration of an endoscopic surgery system according to a sixth embodiment of the present invention. [Figure 20] FIG. 13 is a schematic diagram showing a configuration example of a moving body according to a seventh embodiment of the present invention. [Figure 21] FIG. 13 is a block diagram showing a schematic configuration of a light detection system according to a seventh embodiment of the present invention. [Figure 22] FIG. 13 is a flow chart showing the operation of the light detection system according to the seventh embodiment of the present invention. [Figure 23] FIG. 13 is a schematic diagram showing a schematic configuration of a light detection system according to an eighth embodiment of the present invention. [Figure 24] FIG. 13 is a block diagram showing a schematic configuration of an apparatus according to a ninth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The following embodiments are intended to embody the technical ideas of the present invention, and are not intended to limit the present invention. The sizes and positional relationships of the components shown in the drawings may be exaggerated to clarify the description. In the following description, the same components may be designated by the same reference numerals, and the description may be omitted.

[0013] [First embodiment] A schematic configuration of a photoelectric conversion device according to a first embodiment of the present invention will be described with reference to Fig. 1 to Fig. 4. Fig. 1 and Fig. 2 are block diagrams showing a schematic configuration of a photoelectric conversion device according to this embodiment. Fig. 3 is a block diagram showing a configuration example of a pixel of the photoelectric conversion device according to this embodiment. Fig. 4 is a perspective view showing a configuration example of a photoelectric conversion device according to this embodiment.

[0014] The photoelectric conversion device 100 according to this embodiment includes a pixel section 10, a vertical scanning circuit section 40, a readout circuit section 50, a horizontal scanning circuit section 60, an output circuit section 70, and a control pulse generating section 80, as shown in FIG.

[0015] The pixel unit 10 includes a plurality of pixels 12 arranged in an array having a plurality of rows and a plurality of columns. As described later, each pixel 12 may be composed of a photoelectric conversion unit including a photoelectric conversion element and a pixel signal processing unit that processes a signal output from the photoelectric conversion unit. The number of pixels 12 constituting the pixel unit 10 is not particularly limited. For example, the pixel unit 10 may be composed of a plurality of pixels 12 arranged in an array of several thousand rows and several thousand columns, as in a general digital camera. Alternatively, the pixel unit 10 may be composed of a plurality of pixels 12 arranged in one row or one column. Alternatively, the pixel unit 10 may be composed of one pixel 12.

[0016] In each row of the pixel array of the pixel unit 10, a control line 14 is arranged extending in a first direction (horizontal direction in FIG. 1). The control line 14 is connected to each of the pixels 12 arranged in the first direction, and serves as a signal line common to these pixels 12. The first direction in which the control lines 14 extend may be called the row direction or horizontal direction. Each of the control lines 14 may include a plurality of signal lines for supplying a plurality of types of control signals to the pixels 12. The control lines 14 in each row are connected to a vertical scanning circuit unit 40.

[0017] Further, in each column of the pixel array of the pixel unit 10, a data line 16 is arranged extending in a second direction (vertical direction in FIG. 1) intersecting the first direction. The data line 16 is connected to each of the pixels 12 aligned in the second direction, and serves as a signal line common to these pixels 12. The second direction in which the data lines 16 extend may be referred to as the column direction or vertical direction. Each of the data lines 16 may include a plurality of signal lines for transferring a multi-bit digital signal output from the pixel 12 on a bit-by-bit basis.

[0018] The control lines 14 of each row are connected to a vertical scanning circuit section 40. The vertical scanning circuit section 40 is a control section that receives a control signal output from a control pulse generating section 80, generates a control signal for driving the pixels 12, and supplies the control signal to the pixels 12 via the control line 14. The vertical scanning circuit section 40 may include logic circuits such as a shift register and an address decoder. The vertical scanning circuit section 40 sequentially scans the pixels 12 in the pixel section 10 on a row-by-row basis, and outputs pixel signals of each pixel 12 to the readout circuit section 50 via the data line 16.

[0019] The data lines 16 of each column are connected to a readout circuit unit 50. The readout circuit unit 50 includes a plurality of holding units (not shown) provided corresponding to each column of the pixel array of the pixel unit 10, and has a function of holding, in the holding unit of the corresponding column, pixel signals of the pixels 12 of each column that are output row by row from the pixel unit 10 via the data lines 16.

[0020] The horizontal scanning circuit unit 60 is a control unit that receives a control signal output from the control pulse generation unit 80, generates a control signal for reading out pixel signals from the holding units of each column of the readout circuit unit 50, and supplies the control signal to the readout circuit unit 50. The horizontal scanning circuit unit 60 may include logic circuits such as a shift register and an address decoder. The horizontal scanning circuit unit 60 sequentially scans the holding units of each column of the readout circuit unit 50, and sequentially outputs the pixel signals held in each of them to the output circuit unit 70.

[0021] The output circuit unit 70 has an external interface circuit, and is a circuit unit for outputting the pixel signals output from the readout circuit unit 50 to the outside of the photoelectric conversion device 100. The external interface circuit included in the output circuit unit 70 is not particularly limited. For example, a SerDes (SERializer / DESerializer) transmission circuit such as an LVDS (Low Voltage Differential Signaling) circuit or an SLVS (Scalable Low Voltage Signaling) circuit can be used as the external interface circuit.

[0022] The control pulse generating unit 80 is a control circuit for generating control signals for controlling the operations and timings of the vertical scanning circuit unit 40, the readout circuit unit 50, and the horizontal scanning circuit unit 60, and supplying them to each functional block. Note that at least some of the control signals for controlling the operations and timings of the vertical scanning circuit unit 40, the readout circuit unit 50, and the horizontal scanning circuit unit 60 may be supplied from outside the photoelectric conversion device 100.

[0023] The connection of each functional block of the photoelectric conversion device 100 is not limited to the example configuration shown in FIG. 1, and may be configured as shown in FIG. 2, for example.

[0024] In the configuration example of Fig. 2, data lines 16 extending in a first direction are arranged in each row of the pixel array of the pixel section 10. The data lines 16 are connected to the pixels 12 arranged in the first direction, respectively, and form a common signal line for these pixels 12. Furthermore, control lines 18 extending in a second direction are arranged in each column of the pixel array of the pixel section 10. The control lines 18 are connected to the pixels 12 arranged in the second direction, respectively, and form a common signal line for these pixels 12.

[0025] The control line 18 of each column is connected to a horizontal scanning circuit section 60. The horizontal scanning circuit section 60 receives a control signal output from the control pulse generating section 80, generates a control signal for reading out a pixel signal from the pixel 12, and supplies the control signal to the pixel 12 via the control line 18. Specifically, the horizontal scanning circuit section 60 sequentially scans the pixels 12 of the pixel section 10 on a column-by-column basis, and outputs pixel signals of the pixels 12 of each row belonging to the selected column to the data line 16.

[0026] The data lines 16 of each row are connected to a readout circuit unit 50. The readout circuit unit 50 includes a plurality of holding units (not shown) provided corresponding to each row of the pixel array of the pixel unit 10, and has a function of holding, in the holding unit of the corresponding row, pixel signals of the pixels 12 of each row that are output on a column-by-column basis from the pixel unit 10 via the data lines 16.

[0027] The readout circuit section 50 receives a control signal output from a control pulse generating section 80, and outputs the pixel signals held in the holding sections of each row to the output circuit section 70 in sequence. Other configurations in the configuration example of FIG. 2 may be similar to the configuration example of FIG.

[0028] 3, each pixel 12 has a photoelectric conversion unit 20 and a pixel signal processing unit 30. The photoelectric conversion unit 20 has a photoelectric conversion element 22 and a quenching element 24. The pixel signal processing unit 30 is a signal processing circuit that processes a signal output from the photoelectric conversion unit 20, and has, for example, a waveform shaping circuit 32, a counter circuit 34, and a selection circuit 36. It is sufficient that the pixel signal processing unit 30 has at least the waveform shaping circuit 32. The pixel signal processing unit 30 may further have a counter saturation detection circuit that detects saturation of the count value in the counter circuit 34.

[0029] The photoelectric conversion element 22 may be an avalanche photodiode (hereinafter, referred to as "APD"). The anode of the APD constituting the photoelectric conversion element 22 is connected to a node to which a voltage VL is supplied. The cathode of the APD constituting the photoelectric conversion element 22 is connected to one terminal of the quench element 24. The connection node between the photoelectric conversion element 22 and the quench element 24 is the output node of the photoelectric conversion unit 20. The other terminal of the quench element 24 is connected to a node to which a voltage VH higher than the voltage VL is supplied. The voltages VL and VH are set so that a reverse bias voltage sufficient for the APD to perform an avalanche multiplication operation is applied. In one example, a negative high voltage is applied as the voltage VL, and a positive voltage approximately equal to the power supply voltage is applied as the voltage VH. For example, the voltage VL is -30V, and the voltage VH is 1V.

[0030] The photoelectric conversion element 22 may be constituted by an APD as described above. By supplying the APD with a reverse bias voltage sufficient for avalanche multiplication, the charge generated by the incidence of light on the APD undergoes avalanche multiplication, generating an avalanche current. There are two operation modes when the APD is supplied with a reverse bias voltage: Geiger mode and linear mode. The Geiger mode is an operation mode in which the voltage applied between the anode and the cathode is a reverse bias voltage greater than the breakdown voltage of the APD. The linear mode is an operation mode in which the voltage applied between the anode and the cathode is a reverse bias voltage close to or less than the breakdown voltage of the APD. An APD operated in the Geiger mode is called a SPAD (Single Photon Avalanche Diode). The APD constituting the photoelectric conversion element 22 may be operated in either the linear mode or the Geiger mode.

[0031] In this embodiment, the anode of the APD is set to a fixed potential, and a signal is taken out from the cathode side. Therefore, the first conductive type semiconductor region having charges of the same polarity as the signal charge as the majority carriers is an N-type semiconductor region, and the second conductive type semiconductor region having charges of a polarity opposite to the signal charge as the majority carriers is a P-type semiconductor region. The first conductive type carriers are electrons, and the second conductive type carriers are holes. The present invention is also valid when the cathode of the APD is set to a fixed potential, and a signal is taken out from the anode side. In this case, the first conductive type semiconductor region having charges of the same polarity as the signal charge as the majority carriers is a P-type semiconductor region, and the second conductive type semiconductor region having charges of a polarity opposite to the signal charge as the majority carriers is an N-type semiconductor region. In the following, a case where one node of the APD is set to a fixed potential will be described, but the potentials of both nodes may fluctuate.

[0032] The quench element 24 has a function of converting a change in avalanche current generated in the photoelectric conversion element 22 into a voltage signal. The quench element 24 also functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication, and has a function of reducing the voltage applied to the photoelectric conversion element 22 to suppress avalanche multiplication. The operation of the quench element 24 to suppress avalanche multiplication is called a quench operation. The quench element 24 also has a function of returning the voltage supplied to the photoelectric conversion element 22 to the voltage VH by flowing a current equivalent to the voltage drop caused by the quench operation. The operation of the quench element 24 to return the voltage supplied to the photoelectric conversion element 22 to the voltage VH is called a recharge operation. The quench element 24 may be configured of a resistor element, a MOS transistor, or the like. In this specification, the quench element 24 may also be called a recharge circuit.

[0033] The waveform shaping circuit 32 has an input node to which the output signal of the photoelectric conversion unit 20 is supplied, and an output node. The waveform shaping circuit 32 has a function of converting the analog signal supplied from the photoelectric conversion unit 20 into a pulse signal. The waveform shaping circuit 32 can be configured with logic circuits including a NOT circuit (inverter circuit), a NOR circuit, a NAND circuit, etc. The output node of the waveform shaping circuit 32 is connected to a counter circuit 34.

[0034] The counter circuit 34 has an input node to which the output signal of the waveform shaping circuit 32 is supplied, an input node connected to the control line 14, and an output node. The counter circuit 34 has a function of counting the pulses superimposed on the signal output from the waveform shaping circuit 32 and holding a count value that is the counting result. The signal supplied to the counter circuit 34 from the vertical scanning circuit section 40 via the control line 14 may include an enable signal for controlling the pulse count period (exposure period) and a reset signal for resetting the count value held by the counter circuit 34. The output node of the counter circuit 34 is connected to the data line 16 via the selection circuit 36.

[0035] The selection circuit 36 ​​has a function of switching an electrical connection state (connected or unconnected) between the counter circuit 34 and the data line 16. The selection circuit 36 ​​switches the connection state between the counter circuit 34 and the data line 16 in response to a control signal supplied from the vertical scanning circuit unit 40 via the control line 14 (in the configuration example of FIG. 2, a control signal supplied from the horizontal scanning circuit unit 60 via the control line 18). The selection circuit 36 ​​may include a buffer circuit for outputting a signal.

[0036] The pixel 12 is typically a unit structure that outputs a pixel signal for forming an image. However, in cases where the purpose is distance measurement using a TOF (Time of Flight) method, the pixel 12 does not necessarily have to be a unit structure that outputs a pixel signal for forming an image. In other words, the pixel 12 can also be a unit structure that outputs a signal for measuring the time when light arrives and the amount of light.

[0037] It is not necessary that one pixel signal processing unit 30 is provided for each pixel 12, but one pixel signal processing unit 30 may be provided for multiple pixels 12. In this case, the single pixel signal processing unit 30 can be used to sequentially execute signal processing for the multiple pixels 12.

[0038] The photoelectric conversion device 100 according to the present embodiment may be formed on a single substrate, or may be configured as a stacked photoelectric conversion device in which a plurality of substrates are stacked. In the latter case, for example, as shown in FIG. 4, it is possible to configure a stacked photoelectric conversion device in which a sensor substrate 110 and a circuit substrate 180 are stacked and electrically connected. At least the photoelectric conversion element 22, which is one of the components of the pixel 12, can be arranged on the sensor substrate 110. Furthermore, among the components of the pixel 12, the quench element 24 and the pixel signal processing unit 30 can be arranged on the circuit substrate 180. The photoelectric conversion element 22, the quench element 24, and the pixel signal processing unit 30 are electrically connected via connection wiring provided for each pixel 12. Furthermore, the vertical scanning circuit unit 40, the readout circuit unit 50, the horizontal scanning circuit unit 60, the output circuit unit 70, the control pulse generating unit 80, and the like can be further arranged on the circuit substrate 180.

[0039] The photoelectric conversion element 22, quench element 24, and pixel signal processing unit 30 of each pixel 12 may be provided on the sensor substrate 110 and the circuit substrate 180 so as to overlap in a plan view. The vertical scanning circuit unit 40, readout circuit unit 50, horizontal scanning circuit unit 60, output circuit unit 70, and control pulse generating unit 80 may be disposed around the pixel unit 10 composed of a plurality of pixels 12. Note that "plan view" here refers to a view from a direction perpendicular to the surface of the sensor substrate 110.

[0040] By configuring the stacked photoelectric conversion device 100, it is possible to increase the integration density of elements and achieve high performance. In particular, by arranging the photoelectric conversion elements 22, the quenching elements 24, and the pixel signal processing unit 30 on separate substrates, it is possible to arrange the photoelectric conversion elements 22 at a high density without sacrificing the light receiving area of ​​the photoelectric conversion elements 22, and it is possible to improve the photon detection efficiency.

[0041] The number of substrates constituting the photoelectric conversion device 100 is not limited to two, and the photoelectric conversion device 100 may be formed by stacking three or more substrates.

[0042] 4, it is assumed that the sensor substrate 110 and the circuit substrate 180 are diced chips, but the sensor substrate 110 and the circuit substrate 180 are not limited to chips. For example, the sensor substrate 110 and the circuit substrate 180 may each be a wafer. The sensor substrate 110 and the circuit substrate 180 may be stacked in the wafer state and then diced, or may be stacked and bonded after being formed into chips.

[0043] Next, the basic operation of the photoelectric conversion unit 20 in the photoelectric conversion device according to this embodiment will be described with reference to Fig. 5. Fig. 5 is a diagram for explaining the basic operation of the photoelectric conversion unit in the photoelectric conversion device according to this embodiment. Fig. 5(a) is a circuit diagram of the photoelectric conversion unit 20 and the waveform shaping circuit 32, Fig. 5(b) shows the waveform of a signal at the input node (node ​​A) of the waveform shaping circuit 32, and Fig. 5(c) shows the waveform of a signal at the output node (node ​​B) of the waveform shaping circuit 32. Note that, for simplicity of explanation, it is assumed here that the waveform shaping circuit 32 is configured with an inverter circuit.

[0044] At time t0, a reverse bias voltage with a potential difference equivalent to (VH-VL) is applied to the photoelectric conversion element 22. A reverse bias voltage sufficient to cause avalanche multiplication is applied between the anode and cathode of the APD constituting the photoelectric conversion element 22, but there are no carriers to serve as the seeds of avalanche multiplication when no photons are incident on the photoelectric conversion element 22. Therefore, avalanche multiplication does not occur in the photoelectric conversion element 22, and no current flows through the photoelectric conversion element 22.

[0045] At the next time t1, a photon is incident on the photoelectric conversion element 22. When a photon is incident on the photoelectric conversion element 22, electron-hole pairs are generated by photoelectric conversion, and avalanche multiplication occurs with these carriers as seeds, causing an avalanche multiplication current to flow through the photoelectric conversion element 22. This avalanche multiplication current flows through the quench element 24, causing a voltage drop across the quench element 24, and the voltage at node A begins to drop. When the amount of voltage drop at node A becomes large and the avalanche multiplication stops at time t3, the voltage level at node A no longer drops.

[0046] When the avalanche multiplication in the photoelectric conversion element 22 stops, a current compensating for the voltage drop flows from the node to which the voltage VL is supplied to the node A via the photoelectric conversion element 22, and the voltage of the node A gradually increases. After that, at time t5, the node A is stabilized to the original voltage level.

[0047] The waveform shaping circuit 32 binarizes the signal input from node A according to a predetermined judgment threshold and outputs it from node B. Specifically, when the voltage level of node A exceeds the judgment threshold, the waveform shaping circuit 32 outputs a low-level signal from node B, and when the voltage level of node A is equal to or lower than the judgment threshold, the waveform shaping circuit 32 outputs a high-level signal from node B. For example, as shown in FIG. 5(b), it is assumed that the voltage of node A is equal to or lower than the judgment threshold during the period from time t2 to time t4. In this case, as shown in FIG. 5(c), the signal level at node B is low during the period from time t0 to time t2 and the period from time t4 to time t5, and is high during the period from time t2 to time t4.

[0048] In this way, the analog signal input from node A is waveform-shaped into a digital signal by the waveform shaping circuit 32. The pulse signal output from the waveform shaping circuit 32 in response to a photon being incident on the photoelectric conversion element 22 is a photon detection pulse signal.

[0049] Next, the circuit configuration of the pixel 12 in the photoelectric conversion device according to the present embodiment will be described with reference to Fig. 6. Fig. 6 is a circuit diagram showing an example of the configuration of a pixel in the photoelectric conversion device according to the present embodiment. Fig. 6 shows, among the components of the pixel 12, the photoelectric conversion element 22, the quench element 24, and the waveform shaping circuit 32. The other components of the pixel 12 are the same as those in Fig. 3.

[0050] As shown in FIG. 6, in the pixel 12 of the photoelectric conversion device according to the present embodiment, the quench element 24 is composed of a P-type MOS transistor Mq, and the waveform shaping circuit 32 is composed of a two-input NOR circuit LC1. The source of the P-type MOS transistor Mq is connected to a node to which a voltage VH is supplied. The drain of the P-type MOS transistor Mq is connected to a cathode of an APD constituting the photoelectric conversion element 22. A connection node between the photoelectric conversion element 22 and the P-type MOS transistor Mq is an output node of the photoelectric conversion unit 20. The anode of the APD is connected to a node to which a voltage VL is supplied. A control signal P2 is supplied to the gate of the P-type MOS transistor Mq from the vertical scanning circuit unit 40 (or the horizontal scanning circuit unit 60). The output node of the photoelectric conversion unit 20 is connected to one input node of the NOR circuit LC1. The other input node of the NOR circuit LC1 is supplied with a control signal P1 from the vertical scanning circuit unit 40 (or the horizontal scanning circuit unit 60). The output node of the NOR circuit LC1 is connected to an input node of a counter circuit 34 not shown in FIG. 6. The control signals P1 and P2 are periodic signals that repeat a high level and a low level at a constant cycle, and can be generated from, for example, a clock signal.

[0051] The P-type MOS transistor Mq serves as a recharge circuit that controls the recharge operation of the APD in response to a periodic control signal P2. For example, the P-type MOS transistor Mq can be controlled to a recharge operation mode that allows the recharge operation in the APD and a quench operation mode that allows the quench operation in the APD in response to the control signal P2. During the period when the P-type MOS transistor Mq operates in the recharge operation mode, the APD can be in a recharge state. Also, during the period when the P-type MOS transistor Mq operates in the quench operation mode, the APD can be in a standby state. The waveform shaping circuit 32 can be switched between a first mode in which the output value changes in response to the cathode voltage Vcath of the APD and a second mode in which a fixed value is output regardless of the cathode voltage Vcath of the APD in response to the control signal P1.

[0052] Next, the operation of the photoelectric conversion device according to the present embodiment will be described with reference to Fig. 7 to Fig. 9. Fig. 7 and Fig. 8 are timing charts showing a general operation of the pixel circuit shown in Fig. 6. Fig. 9 is a timing chart showing a method of driving the photoelectric conversion device according to the present embodiment.

[0053] First, a general operation of the pixel circuit shown in FIG. 6 will be described with reference to FIG. 7 and FIG. 8. FIG. 7 is a timing diagram of an ideal state in which there is no phase difference between the control signal P1 and the control signal P2. FIG. 8 is a timing diagram in which there is a phase difference between the control signal P1 and the control signal P2. In either case, in the initial state before time t0, the control signal P1 is at a low level, and the control signal P2 is at a high level. The P-type MOS transistor Mq is turned off in response to the high-level control signal P2, and is operating in a quench operation mode. In addition, the waveform shaping circuit 32 receives the low-level control signal P1, and is in a state in which the value of the output OUT changes according to the cathode voltage Vcath of the APD.

[0054] First, the operation in an ideal state in which no phase difference occurs between the control signal P1 and the control signal P2 will be described with reference to FIG.

[0055] At time t10, a photon is incident on pixel 12 in the initial state described above. When a photon is incident on photoelectric conversion element 22, avalanche multiplication occurs in the APD using electron-hole pairs generated by photoelectric conversion as seeds, and the cathode voltage Vcath of the APD drops. As a result, the signal level of the output OUT of waveform shaping circuit 32 transitions from a low level to a high level. The downstream counter circuit 34 counts the state transitions of the output OUT from a low level to a high level, and increments the count value by one.

[0056] At the next time t11, the control signal P1 transitions from a low level to a high level. This transition causes the signal level of the output OUT of the waveform shaping circuit 32 to transition from a high level to a low level. Also, at the same time t11, the control signal P2 transitions from a high level to a low level. This transition causes the P-type MOS transistor Mq to turn on in response to the low-level control signal P2 and transition to the recharge operation mode. This transition causes the APD to enter a recharge state, and the cathode voltage Vcath returns to the voltage VH. As the cathode voltage Vcath returns to the voltage VH, the APD enters a standby state in which avalanche multiplication is possible. In the recharge operation mode, the APD is always in a state in which recharge is possible, and even if avalanche multiplication occurs in the APD and the cathode voltage Vcath drops, the cathode voltage Vcath returns to the voltage VH when the avalanche multiplication stops.

[0057] During the period when the control signal P1 is at a high level and the control signal P2 is at a low level, the signal level of the output OUT of the waveform shaping circuit 32 is maintained at a low level even if a photon is incident. For example, if a photon is incident at time t12, the cathode voltage Vcath drops due to avalanche multiplication caused by the incident photon, but is immediately recharged and returns to the voltage VH when the avalanche multiplication stops. In addition, the output OUT of the waveform shaping circuit 32 is maintained at a low level regardless of changes in the cathode voltage Vcath because the control signal P1 at a high level is input to the NOR circuit LC1. In other words, the waveform shaping circuit 32 outputs a fixed value regardless of the cathode voltage Vcath.

[0058] At the next time t13, the control signal P1 transitions from High to Low, and the control signal P2 transitions from Low to High, causing the P-type MOS transistor Mq to enter the quench operation mode again, and the waveform shaping circuit 32 returns to a state in which the output value changes according to the cathode voltage Vcath.

[0059] When a photon is incident on the photoelectric conversion element 22 at the next time t16, the cathode voltage Vcath falls due to avalanche multiplication in the APD, and the output OUT of the waveform shaping circuit 32 transitions from a low level to a high level. The downstream counter circuit 34 counts the state transitions of the output OUT from a low level to a high level, and increments the count value by one.

[0060] During the period when the control signal P1 is at a low level and the control signal P2 is at a high level, that is, after a photon is detected once in the quench operation mode, even if a photon is again incident, the signal level of the output OUT of the waveform shaping circuit 32 is maintained at a high level. For example, even if a photon is incident at time t17, the APD is not recharged and avalanche multiplication does not occur. Therefore, the output OUT of the waveform shaping circuit 32 is maintained at a high level. In other words, the period from time t11 to time t16 in this operation example can be said to be a period during which the APD is controlled to a standby state in which avalanche multiplication is possible.

[0061] In this way, in an ideal state where there is no phase difference between the control signal P1 and the control signal P2, avalanche multiplication occurring during one period of the control signals P1 and P2 can be counted only once. In other words, when avalanche multiplication occurs in the APD two or more times during one period of the control signals P1 and P2, the pixel signal processor 30 outputs the first value only once in the first mode. Here, the first value is 1.

[0062] The timing of the start of one cycle of the control signals P1 and P2 can be determined arbitrarily. For example, the length of one cycle of the control signals P1 and P2 can be defined as the length of the period from the timing when the control signals P1 and P2 transition from a low level to a high level to the timing when the control signals P1 and P2 next transition from a low level to a high level. In the driving example of FIG. 7, for example, the length of the period from time t11 to time t18 corresponds to the length of one cycle of the control signals P1 and P2.

[0063] Next, the operation when a phase difference occurs between the control signal P1 and the control signal P2 will be described with reference to Fig. 8. Here, a case will be considered where the control signal P2 is delayed with respect to the control signal P1.

[0064] At time t10, a photon is incident on pixel 12, which is in the initial state described above. When a photon is incident on photoelectric conversion element 22, avalanche multiplication occurs in the APD using electron-hole pairs generated by photoelectric conversion as seeds, and the cathode voltage Vcath of the APD drops. As a result, the signal level of output OUT of waveform shaping circuit 32 transitions from low level to high level. The downstream counter circuit 34 counts state transitions of output OUT from low level to high level, and increments the count value by one.

[0065] At the following time t11a, the control signal P1 transitions from the low level to the high level, and the signal level of the output OUT of the waveform shaping circuit 32 transitions from the high level to the low level.

[0066] At the next time t11b, the control signal P2 transitions from high to low after the transition of the control signal P1. As a result, the P-type MOS transistor Mq receives the low-level control signal P2 and turns on, transitioning to the recharge operation mode. As a result, the APD is recharged, and the cathode voltage Vcath returns to the voltage VH.

[0067] At the next time t13a, the control signal P1 transitions from a High level to a Low level. As a result, even though the control signal P2 is in the recharge period at a Low level, the waveform shaping circuit 32 is in a state in which the value of the output OUT can be changed according to the cathode voltage Vcath. As a result, for example, when a photon is incident on the pixel 12 at the next time t14, the cathode voltage Vcath drops due to avalanche multiplication in the APD, but is recharged as soon as the avalanche multiplication stops. The output OUT of the waveform shaping circuit 32 transitions to a High level in response to the drop in the cathode voltage Vcath, and transitions to a Low level immediately upon completion of recharge. The counter circuit 34 at the rear stage counts the state transitions of the output OUT from a Low level to a High level, and increments the count value by one.

[0068] At the next time t13b, when the control signal P2 transitions from the low level to the high level, the P-type MOS transistor Mq receives the high level control signal P2 and turns off, returning to the quench operation mode.

[0069] When a photon is incident on the photoelectric conversion element 22 at the next time t16, the cathode voltage Vcath falls due to avalanche multiplication in the APD, and the output OUT of the waveform shaping circuit 32 transitions from a low level to a high level. The downstream counter circuit 34 counts the state transitions of the output OUT from a low level to a high level, and increments the count value by one.

[0070] In this way, when the length of the period when the control signal P1 is at a high level is the same as the length of the period when the control signal P2 is at a low level, if a phase shift occurs between them, photons may be detected two or more times during one period of the control signals P1 and P2. In the driving example of Fig. 8, the length of one period of the control signal P1 corresponds to the length of the period from time t11a to time t18a, for example. The length of one period of the control signal P2 corresponds to the length of the period from time t11b to time t18b, for example.

[0071] If a photon is detected two or more times during one period of the control signals P1 and P2, an accurate count value cannot be obtained in the downstream counter circuit 34. Furthermore, if the pixel signal processing unit 30 has a counter saturation detection circuit (not shown), it may not be possible to detect saturation of the count value at the correct timing, and the count value may return to the initial value.

[0072] Next, a method for driving the photoelectric conversion device according to this embodiment will be described with reference to Fig. 9. In the driving method of this embodiment, the control signals P1 and P2 are set so that the period when the control signal P2 is at a low level coincides with the period when the control signal P1 is at a high level, so that a photon can be detected only once during one cycle of the control signals P1 and P2. In other words, the period when the P-type MOS transistor Mq is controlled to the recharge operation mode overlaps with the period when the waveform shaping circuit 32 is controlled to the second mode, but does not overlap with the period when the waveform shaping circuit 32 is controlled to the first mode.

[0073] At time t10, a photon is incident on pixel 12, which is in the initial state described above. When a photon is incident on photoelectric conversion element 22, avalanche multiplication occurs in the APD using electron-hole pairs generated by photoelectric conversion as seeds, and the cathode voltage Vcath of the APD drops. As a result, the signal level of output OUT of waveform shaping circuit 32 transitions from low level to high level. The downstream counter circuit 34 counts state transitions of output OUT from low level to high level, and the count value increases by one.

[0074] At the following time t11a, the control signal P1 transitions from the low level to the high level, and the signal level of the output OUT of the waveform shaping circuit 32 transitions from the high level to the low level.

[0075] At the next time t11b, the control signal P2 transitions from High to Low with a delay from the transition of the control signal P1. As a result, the P-type MOS transistor Mq receives the Low-level control signal P2 and turns on, transitioning to the recharge operation mode. As a result, the APD is recharged, and the cathode voltage Vcath returns to the voltage VH.

[0076] In this driving example, even if a photon is incident in this state, the signal level of the output OUT of the waveform shaping circuit 32 is maintained at a low level. For example, if a photon is incident at time t12, the cathode voltage Vcath drops due to avalanche multiplication caused by the incident photon, but is immediately recharged and returns to the voltage VH when the avalanche multiplication stops. In addition, the output OUT of the waveform shaping circuit 32 receives a high-level control signal P1 and is maintained at a low level regardless of changes in the cathode voltage Vcath.

[0077] At the next time t13b, when the control signal P2 transitions from the low level to the high level, the P-type MOS transistor Mq receives the high level control signal P2 and turns off, returning to the quench operation mode.

[0078] At the following time t13a, the control signal P1 transitions from the high level to the low level, and the waveform shaping circuit 32 returns to a state in which the value of the output OUT changes according to the cathode voltage Vcath.

[0079] When a photon is incident on the photoelectric conversion element 22 at the next time t16, the cathode voltage Vcath falls due to avalanche multiplication in the APD, and the output OUT of the waveform shaping circuit 32 transitions from a low level to a high level. The downstream counter circuit 34 counts the state transitions of the output OUT from a low level to a high level, and increments the count value by one.

[0080] After a photon is detected once during the period when the control signal P1 is at a low level and the control signal P2 is at a high level, even if a photon is again incident, the signal level of the output OUT of the waveform shaping circuit 32 is maintained at a high level. For example, even if a photon is incident at time t17, avalanche multiplication does not occur because the APD is not recharged. Therefore, the output OUT of the waveform shaping circuit 32 is maintained at a high level.

[0081] In this way, by setting the low level period of the control signal P2 to be included in the high level period of the control signal P1, the difficulty of phase management of the control signals P1 and P2 is eased, and avalanche multiplication can be detected only once during one period of the control signals P1 and P2. In the driving example of FIG. 9, the length of one period of the control signal P1 corresponds to the length of the period from time t11a to time t18a, for example. The length of one period of the control signal P2 corresponds to the length of the period from time t11b to time t18b, for example.

[0082] Thus, according to this embodiment, when counting the number of periods in which avalanche multiplication occurs among multiple periods in which the APD is controlled to a standby state in which avalanche multiplication is possible, the number of periods in which avalanche multiplication occurs can be accurately counted.

[0083] [Second embodiment] A photoelectric conversion device and a driving method thereof according to a second embodiment of the present invention will be described with reference to FIGS.

[0084] The photoelectric conversion device according to the present embodiment is basically the same as the photoelectric conversion device according to the first embodiment, except for the configuration of the waveform shaping circuit 32 of the pixel 12. In this embodiment, the differences between the waveform shaping circuit 32 of this embodiment and the waveform shaping circuit 32 of the first embodiment will be mainly described, and descriptions of parts common to the waveform shaping circuit 32 of this embodiment and the waveform shaping circuit 32 of the first embodiment will be omitted as appropriate.

[0085] First, the circuit configuration of the pixel 12 in the photoelectric conversion device according to this embodiment will be described with reference to Fig. 10. Fig. 10 is a circuit diagram showing an example of the configuration of a pixel in the photoelectric conversion device according to this embodiment. Fig. 10 shows, among the components of the pixel 12, the photoelectric conversion element 22, the quench element 24, and the waveform shaping circuit 32. The other components of the pixel 12 are the same as those in Fig. 3.

[0086] As shown in Fig. 10, the waveform shaping circuit 32 in the pixel 12 of the photoelectric conversion device according to this embodiment further includes a Schmitt trigger circuit SC in addition to the NOR circuit LC1. The output node of the photoelectric conversion unit 20 is connected to the input node of the Schmitt trigger circuit SC. The output node of the Schmitt trigger circuit SC is connected to one input node of the NOR circuit LC1. A control signal P1 is supplied to the other input node of the NOR circuit LC1 from the vertical scanning circuit unit 40 (or the horizontal scanning circuit unit 60). The output node of the NOR circuit LC1 is connected to an input node of a counter circuit 34 not shown in Fig. 10.

[0087] Next, the operation of the photoelectric conversion device according to the present embodiment will be described with reference to Fig. 11 and Fig. 12. Fig. 11 is a timing chart showing a general operation of the pixel circuit shown in Fig. 6. Fig. 12 is a timing chart showing a method of driving the photoelectric conversion device according to the present embodiment.

[0088] First, another problem that may occur in the pixel circuit shown in FIG. 6 will be described with reference to FIG.

[0089] In the initial state before time t10, the P-type MOS transistor Mq is turned off in response to a high-level control signal P2 and operates in a quench operation mode. The waveform shaping circuit 32 receives a low-level control signal P1 and is in a state in which the value of the output OUT changes according to the cathode voltage Vcath of the APD.

[0090] At time t10, a photon is incident on pixel 12, which is in the initial state described above. When a photon is incident on photoelectric conversion element 22, avalanche multiplication occurs in the APD using electron-hole pairs generated by photoelectric conversion as seeds, and the cathode voltage Vcath of the APD drops. As a result, the signal level of output OUT of waveform shaping circuit 32 transitions from low level to high level. The downstream counter circuit 34 counts state transitions of output OUT from low level to high level, and the count value increases by one.

[0091] At the next time t11, the control signal P1 transitions from a low level to a high level, and the signal level of the output OUT of the waveform shaping circuit 32 transitions from a high level to a low level. Also at the same time t11, the control signal P2 transitions from a high level to a low level. As a result, the P-type MOS transistor Mq receives the low-level control signal P2 and turns on, transitioning to the recharge operation mode. As a result, the APD is recharged, and the cathode voltage Vcath returns to the voltage VH.

[0092] During the period when the control signal P1 is at a high level and the control signal P2 is at a low level, the signal level of the output OUT of the waveform shaping circuit 32 is maintained at a low level even if a photon is incident. For example, if a photon is incident at time t12, the cathode voltage Vcath decreases due to avalanche multiplication caused by the incident photon, but when the avalanche multiplication stops, recharging of the APD begins. In addition, the output OUT of the waveform shaping circuit 32 is maintained at a low level regardless of changes in the cathode voltage Vcath because the control signal P1 at a high level is input to the NOR circuit LC1.

[0093] At the next time t13, the control signal P1 transitions from High to Low, and the control signal P2 transitions from Low to High, causing the P-type MOS transistor Mq to enter the quench operation mode again, and the waveform shaping circuit 32 returns to the state in which the value of the output OUT changes according to the cathode voltage Vcath.

[0094] However, if the timing of the incidence of photons (time t12) is near the end of the recharge period (the period from time t11 to time t13), the recharge period of the APD cannot be sufficiently secured, and the cathode voltage Vcath may not return to the voltage VH. In this case, the recharge operation of the cathode voltage Vcath stops at an intermediate potential between the voltages VL and VH. If the increase in the cathode voltage Vcath stops near the logical threshold of the waveform shaping circuit 32, when the cathode voltage Vcath fluctuates due to a disturbance, the cathode voltage Vcath may vary across the logical threshold. For example, when a disturbance is applied to the cathode terminal of the APD at time t15 and the cathode voltage Vcath fluctuates, chattering occurs in the output OUT of the waveform shaping circuit 32 according to the fluctuation of the cathode voltage Vcath. As a result, the waveform shaping circuit 32 continues to output a false signal to the subsequent stage until the cathode voltage Vcath settles to a voltage away from the vicinity of the logical threshold. Each time the subsequent counter circuit 34 receives a false signal, it increments its count value by 1. The chattering appearing in the output OUT continues until a photon is incident at time t16 and the cathode voltage Vcath settles down.

[0095] Next, a method for driving the photoelectric conversion device according to the present embodiment will be described with reference to FIG. The operation of the pixel 12 in this embodiment from time t20 to time t23 is the same as the operation from time t10 to time t13 in Fig. 11. However, the waveform shaping circuit 32 in this embodiment is composed of a Schmitt trigger circuit SC and a NOR circuit LC1, and chattering can be suppressed by the effect of hysteresis of the Schmitt trigger circuit SC.

[0096] For example, even if a disturbance occurs at the cathode terminal of the APD at time t25, causing a change in the cathode voltage Vcath, the output OUT of the waveform shaping circuit 32 does not transition in response to the change in the cathode voltage Vcath. After that, at time t26, a photon is incident and the cathode voltage Vcath transitions significantly, causing the output OUT to transition from a low level to a high level. The downstream counter circuit 34 counts the state transitions of the output OUT from a low level to a high level, and increments the count value by one.

[0097] After a photon is detected once during the period when the control signal P1 is at a low level and the control signal P2 is at a high level, even if a photon is again incident, the signal level of the output OUT of the waveform shaping circuit 32 is maintained at a high level. For example, even if a photon is incident at time t27, avalanche multiplication does not occur because the APD has not been recharged. Therefore, the output OUT of the waveform shaping circuit 32 is maintained at a high level.

[0098] In this way, by connecting the Schmitt trigger circuit SC between the output node of the photoelectric conversion unit 20 and the input node of the NOR circuit LC1, chattering appearing in the output OUT can be suppressed. In addition, the pixel 12 of this embodiment can also be combined with the driving method of the first embodiment. That is, by setting the period of the low level of the control signal P2 to be included in the period of the high level of the control signal P1, avalanche multiplication can be detected only once during one period of the control signals P1 and P2. In the driving example of FIG. 12, the length of one period of the control signals P1 and P2 corresponds to the length of the period from time t21 to time t28, for example.

[0099] Thus, according to this embodiment, when counting the number of periods in which avalanche multiplication occurs among multiple periods in which the APD is controlled to a standby state in which avalanche multiplication is possible, the number of periods in which avalanche multiplication occurs can be accurately counted.

[0100] [Third embodiment] A photoelectric conversion device and a driving method thereof according to a third embodiment of the present invention will be described with reference to FIGS.

[0101] The photoelectric conversion device according to the present embodiment is basically the same as the photoelectric conversion device according to the first embodiment, except for the configuration of the waveform shaping circuit 32 of the pixel 12. In this embodiment, the differences between the waveform shaping circuit 32 of this embodiment and the waveform shaping circuit 32 of the first embodiment will be mainly described, and descriptions of parts common to the waveform shaping circuit 32 of this embodiment and the waveform shaping circuit 32 of the first embodiment will be omitted as appropriate.

[0102] First, the circuit configuration of the pixel 12 in the photoelectric conversion device according to this embodiment will be described with reference to Fig. 13. Fig. 13 is a circuit diagram showing an example of the configuration of a pixel in the photoelectric conversion device according to this embodiment. Fig. 13 shows, among the components of the pixel 12, the photoelectric conversion element 22, the quench element 24, and the waveform shaping circuit 32. The other components of the pixel 12 are the same as those in Fig. 3.

[0103] As shown in FIG. 13, the waveform shaping circuit 32 in the pixel 12 of the photoelectric conversion device according to this embodiment is composed of two NAND circuits LC2 and LC3 forming a NAND type SR latch. The output node of the photoelectric conversion unit 20 is connected to one input node of the NAND circuit LC3. The output node of the NAND circuit LC3, which also serves as the output node of the waveform shaping circuit 32, is connected to one input node of the NAND circuit LC2. The output node of the NAND circuit LC2 is connected to the other input node of the NAND circuit LC3. A control signal P1 is supplied to the other input node of the NAND circuit LC2 from the vertical scanning circuit unit 40 (or the horizontal scanning circuit unit 60). The output node of the NAND circuit LC3 is connected to an input node of a counter circuit 34 not shown in FIG. 13.

[0104] The waveform shaping circuit 32 outputs a second value when the control signal P1 is at a first level, and outputs the first value when the control signal P1 is at a second level different from the first level and the APD is in a discharge state in which avalanche multiplication does not occur. The waveform shaping circuit 32 holds the output value when the control signal P1 is at the second level and the APD is in a standby state in which avalanche multiplication is possible. The first level is, for example, a low level, and the second level is, for example, a high level. The first value is, for example, 1 (high level), and the second value is, for example, 0 (low level).

[0105] Next, the operation of the photoelectric conversion device according to this embodiment will be described with reference to Figs. 14 to 16. Fig. 14 is a timing diagram of an ideal state in which there is no phase difference between the control signal P1 and the control signal P2. Fig. 15 is a timing diagram in the case where there is a phase difference between the control signal P1 and the control signal P2. Fig. 16 is a timing diagram in the case where the cathode voltage Vcath is affected by a disturbance. In either case, in the initial state before time t0, the control signals P1, P2 and the cathode voltage Vcath are at a high level, and the output OUT is at a low level. The P-type MOS transistor Mq is turned off in response to the high-level control signal P2 and operates in a quench operation mode. In addition, the waveform shaping circuit 32 receives a high-level control signal P1 and is in a standby state in which the value of the output OUT changes according to the cathode voltage Vcath of the APD.

[0106] First, the operation in an ideal state where no phase difference occurs between the control signal P1 and the control signal P2 will be described with reference to FIG.

[0107] At time t30, a photon is incident on pixel 12 in the initial state described above. When a photon is incident on photoelectric conversion element 22, avalanche multiplication occurs in the APD using electron-hole pairs generated by photoelectric conversion as seeds, and the cathode voltage Vcath of the APD drops. As a result, the signal level of output OUT of waveform shaping circuit 32 transitions from low level to high level. The downstream counter circuit 34 counts state transitions of output OUT from low level to high level, and the count value increases by 1.

[0108] At the next time t31, the control signal P1 transitions from High to Low, resetting the waveform shaping circuit 32 and causing the signal level of the output OUT to transition from High to Low. Also at time t31, the control signal P2 transitions from High to Low. As a result, the P-type MOS transistor Mq receives the Low-level control signal P2 and turns on, transitioning to the recharge operation mode. As a result, the APD is charged, and the cathode voltage Vcath returns to the voltage VH.

[0109] During the period when the control signals P1 and P2 are at a low level, even if a photon is incident, the signal level of the output OUT of the waveform shaping circuit 32 is maintained at a low level. For example, if a photon is incident at time t32, the cathode voltage Vcath drops due to avalanche multiplication caused by the incident photon, but is immediately recharged and returns to the voltage VH when the avalanche multiplication stops. In addition, the output OUT of the waveform shaping circuit 32 receives the control signal P1 at a low level and is maintained at a low level regardless of changes in the cathode voltage Vcath.

[0110] At the next time t33, the control signals P1 and P2 transition from the low level to the high level, causing the P-type MOS transistor Mq to enter the quench operation mode again, and the waveform shaping circuit 32 is released from the reset state and returns to the standby state.

[0111] Subsequently, at time t36, when a photon is incident on the photoelectric conversion element 22, the cathode voltage Vcath decreases due to avalanche multiplication in the APD, and the output OUT of the waveform shaping circuit 32 transitions from the low level to the high level.

[0112] After a photon is detected once during the period when the control signals P1 and P2 are at a high level, even if a photon is again incident, the signal level of the output OUT of the waveform shaping circuit 32 is maintained at a high level. For example, even if a photon is incident at time t37, avalanche multiplication does not occur because the APD is not recharged. Therefore, the output OUT of the waveform shaping circuit 32 is maintained at a high level.

[0113] In this way, in an ideal state where there is no phase difference between the control signals P1 and P2, the avalanche multiplication occurring during one period of the control signals P1 and P2 can be counted only once. In the driving example of Fig. 14, the length of one period of the control signals P1 and P2 corresponds to the length of the period from time t31 to time t38, for example.

[0114] Next, the operation when a phase difference occurs between the control signal P1 and the control signal P2 will be described with reference to Fig. 15. Here, a case will be considered where the control signal P2 is delayed with respect to the control signal P1.

[0115] At time t30, a photon is incident on pixel 12 in the initial state described above. When a photon is incident on photoelectric conversion element 22, avalanche multiplication occurs in the APD using electron-hole pairs generated by photoelectric conversion as seeds, and the cathode voltage Vcath of the APD drops. As a result, the signal level of output OUT of waveform shaping circuit 32 transitions from low level to high level. The downstream counter circuit 34 counts state transitions of output OUT from low level to high level, and the count value increases by 1.

[0116] At the next time t31a, the control signal P1 transitions from a high level to a low level, causing the waveform shaping circuit 32 to enter a reset state, and the signal level of the output OUT transitions from a high level to a low level.

[0117] At the next time t31b, the control signal P2 transitions from high to low after the transition of the control signal P1. As a result, the P-type MOS transistor Mq receives the low-level control signal P2 and turns on, transitioning to the recharge operation mode. As a result, the APD is recharged, and the cathode voltage Vcath returns to the voltage VH.

[0118] At the next time t33a, the control signal P1 transitions from a low level to a high level. This releases the reset state of the waveform shaping circuit 32 and returns it to a standby state, but since the control signal P2 is at a low level, the P-type MOS transistor Mq remains in the recharge operation mode. As a result, for example, when a photon is incident on the pixel 12 at the next time t34, the cathode voltage Vcath drops due to avalanche multiplication in the APD, the waveform shaping circuit 32 is in the set state, and the output OUT transitions from a low level to a high level. The counter circuit 34 at the rear stage counts the state transitions of the output OUT from a low level to a high level, and the count value is incremented by 1. After that, the cathode voltage Vcath is recharged, but the set state of the waveform shaping circuit 32 is maintained.

[0119] At the following time t33b, when the control signal P2 transitions from the low level to the high level, the P-type MOS transistor Mq returns to the quench operation mode.

[0120] At the next time t36, when a photon is incident on the photoelectric conversion element 22, the cathode voltage Vcath decreases due to avalanche multiplication in the APD. However, at this time, the waveform shaping circuit 32 is already in the set state, and the output OUT is maintained at the High level.

[0121] Even if a photon is again incident after time t36, the signal level of the output OUT of the waveform shaping circuit 32 is maintained at a high level. For example, even if a photon is incident at time t37, the APD is not recharged and no avalanche multiplication occurs. Therefore, the output OUT of the waveform shaping circuit 32 is maintained at a high level.

[0122] In this way, even when there is a phase difference between the control signal P1 and the control signal P2, it is possible to count avalanche multiplication occurring during one period of the control signals P1 and P2 only once. In the driving example of FIG. 15, the length of one period of the control signal P1 corresponds to, for example, the length of the period from time t31a to time t38a. Also, the length of one period of the control signal P2 corresponds to, for example, the length of the period from time t31b to time t38b.

[0123] Next, the operation when the cathode voltage Vcath is affected by a disturbance will be described with reference to FIG.

[0124] At time t30, a photon is incident on pixel 12 in the initial state described above. When a photon is incident on photoelectric conversion element 22, avalanche multiplication occurs in the APD using electron-hole pairs generated by photoelectric conversion as seeds, and the cathode voltage Vcath of the APD drops. As a result, the signal level of output OUT of waveform shaping circuit 32 transitions from low level to high level. The downstream counter circuit 34 counts state transitions of output OUT from low level to high level, and the count value increases by 1.

[0125] At the next time t31, the control signal P1 transitions from High to Low, resetting the waveform shaping circuit 32 and causing the signal level of the output OUT to transition from High to Low. Also at time t31, the control signal P2 transitions from High to Low. As a result, the P-type MOS transistor Mq receives a Low-level control signal and turns on, transitioning to the recharge operation mode. This recharges the APD, and the cathode voltage Vcath returns to the voltage VH.

[0126] During the period when the control signals P1 and P2 are at a low level, even if a photon is incident, the signal level of the output OUT of the waveform shaping circuit 32 is maintained at a low level. For example, if a photon is incident at time t32, the cathode voltage Vcath decreases due to avalanche multiplication caused by the incident photon, but when the avalanche multiplication stops, recharging of the APD begins. In addition, the output OUT of the waveform shaping circuit 32 receives the control signal P1 at a low level and is maintained at a low level regardless of changes in the cathode voltage Vcath.

[0127] At the next time t33, the control signal P1 transitions from a low level to a high level, and the control signal P2 transitions from a low level to a high level, causing the P-type MOS transistor Mq to enter the quench operation mode again, and the waveform shaping circuit 32 returns to the standby state in which the value of the output OUT changes according to the cathode voltage Vcath again.

[0128] If the timing of photon incidence (time t32) is near the end of the recharge period (the period from time t31 to time t33), the APD recharge period cannot be sufficiently secured, and the cathode voltage Vcath may not return to the voltage VH. In this case, the recharge operation of the cathode voltage Vcath stops at an intermediate potential between the voltages VL and VH. If the increase in the cathode voltage Vcath stops near the logic threshold of the waveform shaping circuit 32, when the cathode voltage Vcath fluctuates due to a disturbance, the cathode voltage Vcath may vary across the logic threshold. For example, if a disturbance occurs at the cathode terminal of the APD at time t35 and the cathode voltage Vcath fluctuates across the logic threshold, there is a concern that chattering may occur as described in the second embodiment.

[0129] However, once the cathode voltage Vcath exceeds the logic threshold and enters the set state, the waveform shaping circuit 32 maintains the set state regardless of the cathode voltage Vcath thereafter. Therefore, even if a disturbance occurs at the cathode terminal of the APD and the cathode voltage Vcath fluctuates, the effect of this disturbance is not transmitted to the output OUT of the waveform shaping circuit 32.

[0130] At the next time t36, when a photon is incident on the photoelectric conversion element 22, the cathode voltage Vcath decreases due to avalanche multiplication in the APD. However, at this time, the waveform shaping circuit 32 is already in the set state, and the output OUT is maintained at the High level.

[0131] Even if a photon is again incident after time t36, the signal level of the output OUT of the waveform shaping circuit 32 is maintained at a high level. For example, even if a photon is incident at time t37, the APD is not recharged and no avalanche multiplication occurs. Therefore, the output OUT of the waveform shaping circuit 32 is maintained at a high level.

[0132] In this way, even if the cathode voltage Vcath is affected by a disturbance, the avalanche multiplication occurring during one period of the control signals P1 and P2 can be counted only once. In the driving example of FIG. 16, the length of one period of the control signals P1 and P2 corresponds to the length of the period from time t31 to time t38, for example.

[0133] Thus, according to this embodiment, when counting the number of periods in which avalanche multiplication occurs among multiple periods in which the APD is controlled to a standby state in which avalanche multiplication is possible, the number of periods in which avalanche multiplication occurs can be accurately counted.

[0134] [Fourth embodiment] A light detection system according to a fourth embodiment of the present invention will be described with reference to Fig. 17. Fig. 17 is a block diagram showing a schematic configuration of the light detection system according to this embodiment. In this embodiment, a light detection sensor to which the photoelectric conversion device 100 according to the first to third embodiments is applied will be described.

[0135] The photoelectric conversion device 100 described in the first to third embodiments is applicable to various photodetection systems. Examples of the applicable photodetection systems include imaging systems such as digital still cameras, digital camcorders, security cameras, copiers, fax machines, mobile phones, vehicle-mounted cameras, and observation satellites. Camera modules equipped with an optical system such as a lens and an imaging device are also included in the photodetection system. FIG. 17 illustrates a block diagram of a digital still camera as an example of these.

[0136] 17 includes a photoelectric conversion device 201, a lens 202 that forms an optical image of a subject on the photoelectric conversion device 201, an aperture 204 that varies the amount of light passing through the lens 202, and a barrier 206 that protects the lens 202. The lens 202 and the aperture 204 form an optical system that focuses light on the photoelectric conversion device 201. The photoelectric conversion device 201 is the photoelectric conversion device 100 described in any one of the first to third embodiments, and converts the optical image formed by the lens 202 into image data.

[0137] The light detection system 200 also includes a signal processing unit 208 that processes an output signal output from the photoelectric conversion device 201. The signal processing unit 208 generates image data from a digital signal output from the photoelectric conversion device 201. The signal processing unit 208 also performs various corrections and compression as necessary to output image data. The photoelectric conversion device 201 may include an AD conversion unit that generates a digital signal to be processed by the signal processing unit 208. The AD conversion unit may be formed in a semiconductor layer (semiconductor substrate) in which the photon detection element of the photoelectric conversion device 201 is formed, or may be formed in a semiconductor layer different from the semiconductor layer in which the photon detection element of the photoelectric conversion device 201 is formed. The signal processing unit 208 may also be formed in the same semiconductor layer as the photoelectric conversion device 201.

[0138] The light detection system 200 further includes a memory unit 210 for temporarily storing image data, and an external interface unit (external I / F unit) 212 for communicating with an external computer or the like. The light detection system 200 further includes a recording medium 214 such as a semiconductor memory for recording or reading out imaging data, and a recording medium control interface unit (recording medium control I / F unit) 216 for recording or reading out the imaging data on the recording medium 214. The recording medium 214 may be built into the light detection system 200, or may be removable. Furthermore, communication between the recording medium control I / F unit 216 and the recording medium 214 and communication from the external I / F unit 212 may be performed wirelessly.

[0139] The light detection system 200 further includes an overall control / calculation unit 218 that performs various calculations and controls the entire digital still camera, and a timing generation unit 220 that outputs various timing signals to the photoelectric conversion device 201 and the signal processing unit 208. Here, the timing signals and the like may be input from outside, and the light detection system 200 only needs to include at least the photoelectric conversion device 201 and the signal processing unit 208 that processes the output signal output from the photoelectric conversion device 201. The timing generation unit 220 may be mounted on the photoelectric conversion device 201. Moreover, the overall control / calculation unit 218 and the timing generation unit 220 may be configured to implement a part or all of the control functions of the photoelectric conversion device 201.

[0140] The photoelectric conversion device 201 outputs an imaging signal to the signal processing unit 208. The signal processing unit 208 performs predetermined signal processing on the imaging signal output from the photoelectric conversion device 201 and outputs image data. The signal processing unit 208 generates an image using the imaging signal. The signal processing unit 208 may be configured to perform distance measurement calculation on the signal output from the photoelectric conversion device 201.

[0141] As described above, according to this embodiment, by configuring a light detection system using the photoelectric conversion devices according to the first to third embodiments, it is possible to realize a light detection system capable of acquiring images of higher quality.

[0142] [Fifth embodiment] A range image sensor according to a fifth embodiment of the present invention will be described with reference to Fig. 18. Fig. 18 is a block diagram showing a schematic configuration of the range image sensor according to this embodiment. In this embodiment, the range image sensor will be described as an example of a light detection system to which the photoelectric conversion device 100 of the first to third embodiments is applied.

[0143] 18, the range image sensor 300 according to this embodiment may include an optical system 302, a photoelectric conversion device 304, an image processing circuit 306, a monitor 308, and a memory 310. This range image sensor 300 receives light (modulated light or pulsed light) that is irradiated from a light source device 320 toward a subject 330 and reflected by the surface of the subject 330, and obtains a range image according to the distance to the subject 330.

[0144] The optical system 302 is composed of one or more lenses, and serves to focus image light (incident light) from a subject 330 on the light receiving surface (sensor section) of the photoelectric conversion device 304 .

[0145] The photoelectric conversion device 304 is the photoelectric conversion device 100 described in any of the first to third embodiments, and has the function of generating a distance signal indicating the distance to the subject 330 based on the image light from the subject 330, and supplying the generated distance signal to the image processing circuit 306.

[0146] The image processing circuit 306 has a function of performing image processing to construct a distance image based on the distance signal supplied from the photoelectric conversion device 304 .

[0147] The monitor 308 has a function of displaying a distance image (image data) obtained by image processing in the image processing circuit 306. In addition, the memory 310 has a function of storing (recording) the distance image (image data) obtained by image processing in the image processing circuit 306.

[0148] Thus, according to this embodiment, by constructing a distance image sensor using the photoelectric conversion devices of the first to third embodiments, it is possible to realize a distance image sensor that, in combination with improved characteristics of pixel 12, can acquire a distance image including more accurate distance information.

[0149] [Sixth embodiment] An endoscopic surgery system according to a sixth embodiment of the present invention will be described with reference to Fig. 19. Fig. 19 is a schematic diagram showing a configuration example of the endoscopic surgery system according to this embodiment. In this embodiment, the endoscopic surgery system will be described as an example of a light detection system to which the photoelectric conversion device 100 according to the first to third embodiments is applied.

[0150] FIG. 19 shows a state in which an operator (doctor) 460 is performing surgery on a patient 472 lying on a patient bed 470 using an endoscopic surgery system 400.

[0151] The endoscopic surgery system 400 of this embodiment may include an endoscope 410, a surgical tool 420, and a cart 430 on which various devices for endoscopic surgery are mounted, as shown in Fig. 16. The cart 430 may be mounted with a CCU (camera control unit) 432, a light source device 434, an input device 436, a treatment tool control device 438, a display device 440, and the like.

[0152] The endoscope 410 includes a lens barrel 412, a region of a predetermined length from the tip of which is inserted into a body cavity of a patient 472, and a camera head 414 connected to the base end of the lens barrel 412. Although Fig. 16 illustrates the endoscope 410 configured as a so-called rigid lens barrel having a rigid lens barrel 412, the endoscope 410 may be configured as a so-called flexible lens barrel having a flexible lens barrel. The endoscope 410 is held in a movable state by an arm 416.

[0153] An opening into which an objective lens is fitted is provided at the tip of the lens barrel 412. A light source device 434 is connected to the endoscope 410, and light generated by the light source device 434 is guided to the tip of the lens barrel by a light guide extending inside the lens barrel 412, and is irradiated via the objective lens toward an observation target in the body cavity of the patient 472. The endoscope 410 may be a direct-viewing endoscope, an oblique-viewing endoscope, or a side-viewing endoscope.

[0154] An optical system and a photoelectric conversion device (not shown) are provided inside the camera head 414, and reflected light (observation light) from an observation target is collected by the optical system onto the photoelectric conversion device. The photoelectric conversion device photoelectrically converts the observation light to generate an electrical signal corresponding to the observation light, i.e., an image signal corresponding to an observation image. The photoelectric conversion device may be the photoelectric conversion device 100 described in the first to third embodiments. The image signal is transmitted to the CCU 432 as RAW data.

[0155] The CCU 432 is configured with a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), etc., and performs overall control of the operations of the endoscope 410 and the display device 440. Furthermore, the CCU 432 receives an image signal from the camera head 414, and performs various types of image processing on the image signal, such as development processing (demosaic processing), for displaying an image based on the image signal.

[0156] Under the control of the CCU 432 , the display device 440 displays an image based on the image signal that has been subjected to image processing by the CCU 432 .

[0157] The light source device 434 is composed of a light source such as an LED (Light Emitting Diode), and supplies the endoscope 410 with irradiation light when photographing an operation site or the like.

[0158] The input device 436 is an input interface for the endoscopic surgery system 400. A user can input various information and instructions to the endoscopic surgery system 400 via the input device 436.

[0159] The treatment tool control device 438 controls the driving of an energy treatment tool 450 for cauterizing tissue, incising, sealing blood vessels, or the like.

[0160] The light source device 434 that supplies irradiation light to the endoscope 410 when photographing the surgical site can be composed of a white light source composed of, for example, an LED, a laser light source, or a combination of these. When the white light source is composed of a combination of RGB laser light sources, the output intensity and output timing of each color (each wavelength) can be controlled with high precision, so that the white balance of the captured image can be adjusted in the light source device 434. In this case, it is also possible to capture images corresponding to each of the RGB colors in a time-division manner by irradiating the observation target with laser light from each of the RGB laser light sources in a time-division manner and controlling the driving of the image sensor of the camera head 414 in synchronization with the irradiation timing. According to this method, a color image can be obtained without providing a color filter to the image sensor.

[0161] Furthermore, the light source device 434 may be controlled to change the intensity of the light it outputs at predetermined time intervals. By controlling the driving of the image sensor of the camera head 414 in synchronization with the timing of the change in the light intensity to obtain images in a time-division manner and synthesizing the images, it is possible to generate an image with a high dynamic range that is free of so-called blackout and whiteout.

[0162] The light source device 434 may be configured to supply light in a predetermined wavelength band corresponding to the special light observation. In the special light observation, for example, the wavelength dependency of light absorption in body tissue is utilized. Specifically, a predetermined tissue such as blood vessels on the mucous membrane surface is photographed with high contrast by irradiating light in a narrower band than the irradiation light (i.e., white light) in normal observation. Alternatively, the special light observation may be a fluorescent observation in which an image is obtained by fluorescence generated by irradiating excitation light. In the fluorescent observation, it is possible to irradiate excitation light to the body tissue and observe the fluorescence from the body tissue, or to locally inject a reagent such as indocyanine green (ICG) into the body tissue and irradiate the body tissue with excitation light corresponding to the fluorescent wavelength of the reagent to obtain a fluorescent image. The light source device 434 may be configured to supply narrow band light and / or excitation light corresponding to such special light observation.

[0163] Thus, according to this embodiment, by configuring an endoscopic surgery system using the photoelectric conversion devices of the first to third embodiments, it is possible to realize an endoscopic surgery system capable of acquiring higher quality images.

[0164] [Seventh embodiment] A light detection system and a moving body according to a seventh embodiment of the present invention will be described with reference to Figs. 20 to 22. Fig. 20 is a schematic diagram showing a configuration example of a moving body according to this embodiment. Fig. 21 is a block diagram showing a schematic configuration of a light detection system according to this embodiment. Fig. 22 is a flow diagram showing the operation of the light detection system according to this embodiment. In this embodiment, an application example to an in-vehicle camera is shown as a light detection system to which the photoelectric conversion device 100 according to the first to third embodiments is applied.

[0165] FIG. 20 is a schematic diagram showing a configuration example of a moving body (vehicle system) according to this embodiment. FIG. 20 shows the configuration of a vehicle 500 (automobile) as an example of a vehicle system incorporating a light detection system to which the photoelectric conversion device according to the first to third embodiments is applied. FIG. 20(a) is a schematic front view of the vehicle 500, FIG. 20(b) is a schematic plan view of the vehicle 500, and FIG. 20(c) is a schematic rear view of the vehicle 500. The vehicle 500 is provided with a pair of photoelectric conversion devices 502 on the front side. Here, the photoelectric conversion device 502 is the photoelectric conversion device 100 described in any one of the first to third embodiments. The vehicle 500 also includes an integrated circuit 503, an alarm device 512, and a main control unit 513.

[0166] FIG. 21 is a block diagram showing a configuration example of a light detection system 501 mounted on a vehicle 500. The light detection system 501 includes a photoelectric conversion device 502, an image preprocessing unit 515, an integrated circuit 503, and an optical system 514. The photoelectric conversion device 502 is the photoelectric conversion device 100 described in any one of the first to third embodiments. The optical system 514 forms an optical image of a subject on the photoelectric conversion device 502. The photoelectric conversion device 502 converts the optical image of the subject formed by the optical system 514 into an electric signal. The image preprocessing unit 515 performs a predetermined signal processing on the signal output from the photoelectric conversion device 502. The function of the image preprocessing unit 515 may be incorporated in the photoelectric conversion device 502. The light detection system 501 is provided with at least two sets of the optical system 514, the photoelectric conversion device 502, and the image preprocessing unit 515, and the output from each set of the image preprocessing unit 515 is input to the integrated circuit 503.

[0167] The integrated circuit 503 is an integrated circuit for use in an imaging system, and includes an image processing unit 504, an optical distance measuring unit 506, a parallax calculation unit 507, an object recognition unit 508, and an abnormality detection unit 509. The image processing unit 504 processes an image signal output from an image pre-processing unit 515. For example, the image processing unit 504 performs image processing such as development processing and defect correction on the output signal of the image pre-processing unit 515. The image processing unit 504 includes a memory 505 that temporarily stores the image signal. For example, the positions of known defective pixels in the photoelectric conversion device 502 can be stored in the memory 505.

[0168] The optical distance measuring unit 506 performs focusing and distance measurement of a subject. The parallax calculation unit 507 calculates distance measurement information (distance information) from a plurality of image data (parallax images) acquired by a plurality of photoelectric conversion devices 502. Each of the photoelectric conversion devices 502 may have a configuration capable of acquiring various information such as distance information. The object recognition unit 508 recognizes subjects such as cars, roads, signs, and people. When the abnormality detection unit 509 detects an abnormality in the photoelectric conversion device 502, it notifies the main control unit 513 of the abnormality.

[0169] The integrated circuit 503 may be realized by dedicated hardware, a software module, or a combination of these. It may also be realized by a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or the like, or a combination of these.

[0170] The main control unit 513 supervises and controls the operations of the light detection system 501, the vehicle sensor 510, the control unit 520, etc. The vehicle 500 does not necessarily have to include the main control unit 513. In this case, the photoelectric conversion device 502, the vehicle sensor 510, and the control unit 520 transmit and receive control signals via a communication network. For example, the CAN standard may be applied to the transmission and reception of these control signals.

[0171] The integrated circuit 503 has a function of receiving a control signal from the main control unit 513 or transmitting a control signal or a set value to the photoelectric conversion device 502 by its own control unit.

[0172] The optical detection system 501 is connected to a vehicle sensor 510, and can detect the vehicle's driving state, such as vehicle speed, yaw rate, and steering angle, as well as the state of the environment outside the vehicle and other vehicles and obstacles. The vehicle sensor 510 is also a distance information acquisition means for acquiring distance information to an object. The optical detection system 501 is also connected to a driving assistance control unit 511 that performs various driving assistance functions, such as automatic steering, automatic cruising, and collision prevention functions. In particular, the collision determination function determines whether or not a collision with another vehicle or obstacle has occurred based on the detection results of the optical detection system 501 and the vehicle sensor 510. This allows for avoidance control when a collision is estimated, and activation of a safety device in the event of a collision.

[0173] The light detection system 501 is also connected to an alarm device 512 that issues an alarm to the driver based on the result of the determination by the collision determination unit. For example, if the collision determination unit determines that there is a high possibility of a collision, the main control unit 513 performs vehicle control to avoid a collision and reduce damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 512 warns the user by sounding an alarm, displaying alarm information on a display screen such as a car navigation system or a meter panel, vibrating a seat belt or steering wheel, etc.

[0174] In this embodiment, the surroundings of the vehicle, for example, the front or rear, are photographed by the light detection system 501. Fig. 20(b) shows an example of the arrangement of the light detection system 501 when the light detection system 501 photographs the area in front of the vehicle.

[0175] As described above, the photoelectric conversion device 502 is disposed in front of the vehicle 500. Specifically, if the center line of the vehicle 500 with respect to its forward / backward direction or outer shape (for example, vehicle width) is regarded as an axis of symmetry, and the two photoelectric conversion devices 502 are disposed in line symmetry with respect to the axis of symmetry, this is preferable for obtaining distance information between the vehicle 500 and an object to be photographed and for determining the possibility of a collision. In addition, the photoelectric conversion device 502 is preferably disposed so as not to obstruct the driver's field of vision when the driver visually checks the situation outside the vehicle 500 from the driver's seat. The warning device 512 is preferably disposed so as to be easily within the driver's field of vision.

[0176] Next, a fault detection operation of the photoelectric conversion device 502 in the light detection system 501 will be described with reference to Fig. 22. The fault detection operation of the photoelectric conversion device 502 can be performed according to steps S110 to S180 shown in Fig. 22.

[0177] Step S110 is a step for performing startup settings of the photoelectric conversion device 502. That is, settings for the operation of the photoelectric conversion device 502 are transmitted from outside the photodetection system 501 (e.g., the main control unit 513) or from inside the photodetection system 501, and the image capturing operation and fault detection operation of the photoelectric conversion device 502 are started.

[0178] Next, in step S120, pixel signals are obtained from the valid pixels. In addition, in step S130, output values ​​are obtained from failure detection pixels provided for failure detection. The failure detection pixels have photoelectric conversion elements, just like the valid pixels. A predetermined voltage is written to the photoelectric conversion elements. The failure detection pixels output signals corresponding to the voltage written to the photoelectric conversion elements. Note that steps S120 and S130 may be reversed.

[0179] Next, in step S140, a judgment is made as to whether the output expected value of the fault detection pixel corresponds to the output value from the actual fault detection pixel. If the result of the judgment in step S140 indicates that the output expected value and the actual output value correspond to each other, the process proceeds to step S150, where it is judged that the imaging operation is performed normally, and the process proceeds to step S160. In step S160, the pixel signal of the scanning row is sent to the memory 505 and temporarily stored. Thereafter, the process returns to step S120, and the fault detection operation is continued. On the other hand, if the result of the judgment in step S140 indicates that the output expected value and the actual output value do not correspond to each other, the process proceeds to step S170. In step S170, it is judged that there is an abnormality in the imaging operation, and an alarm is notified to the main control unit 513 or the alarm device 512. The alarm device 512 displays the fact that an abnormality has been detected on the display unit. Thereafter, in step S180, the photoelectric conversion device 502 is stopped, and the operation of the light detection system 501 is terminated.

[0180] In this embodiment, the flowchart is looped for each line, but the flowchart may be looped for each set of lines, or the fault detection operation may be performed for each frame. The issuance of the alarm in step S170 may be notified to the outside of the vehicle via a wireless network.

[0181] In addition, in this embodiment, the control to prevent collision with other vehicles has been described, but the control can also be applied to automatic driving control to follow other vehicles, automatic driving control not to go out of the lane, etc. Furthermore, the light detection system 501 is not limited to vehicles such as the vehicle itself, but can be applied to moving bodies (moving devices) such as ships, aircraft, and industrial robots. In addition, the light detection system 501 is not limited to moving bodies, but can be applied to a wide range of devices that use object recognition, such as intelligent transport systems (ITS).

[0182] [Eighth embodiment] A light detection system according to an eighth embodiment of the present invention will be described with reference to Fig. 23. Fig. 23 is a schematic diagram showing a configuration example of the light detection system according to this embodiment. In this embodiment, an application example to glasses (smart glasses) will be described as a light detection system to which the photoelectric conversion device 100 according to the first to third embodiments is applied.

[0183] 23(a) shows glasses 600 (smart glasses) according to one application example. The glasses 600 include a lens 601, a photoelectric conversion device 602, and a control device 603.

[0184] The photoelectric conversion device 602 is the photoelectric conversion device 100 described in any one of the first to third embodiments, and is provided on the lens 601. The number of photoelectric conversion devices 602 may be one or more. When a plurality of photoelectric conversion devices 602 are used, a combination of a plurality of types of photoelectric conversion devices 602 may be used. The arrangement position of the photoelectric conversion device 602 is not limited to that shown in FIG. 20(a). A display device (not shown) including a light-emitting device such as an OLED or an LED may be provided on the back side of the lens 601.

[0185] The control device 603 functions as a power source that supplies power to the photoelectric conversion device 602 and the display device. The control device 603 also has a function of controlling the operations of the photoelectric conversion device 602 and the display device. The lens 601 is provided with an optical system for collecting light on the photoelectric conversion device 602.

[0186] 23(b) shows glasses 610 (smart glasses) according to another application example. The glasses 610 include lenses 611 and a control device 612. The control device 612 may be equipped with a photoelectric conversion device (not shown) corresponding to the photoelectric conversion device 602 and a display device.

[0187] The lens 611 is provided with a photoelectric conversion device in the control device 612 and an optical system for projecting light from the display device, and an image is projected. The control device 612 functions as a power source for supplying power to the photoelectric conversion device and the display device, and also has a function for controlling the operations of the photoelectric conversion device and the display device.

[0188] The control device 612 may further include a line-of-sight detection unit that detects the line of sight of the wearer. In this case, an infrared light emitting unit may be provided in the control device 612, and infrared light emitted from the infrared light emitting unit may be used to detect the line of sight. Specifically, the infrared light emitting unit emits infrared light toward the eyeball of the user gazing at the display image. An imaging unit having a light receiving element detects the reflected light of the emitted infrared light from the eyeball, thereby obtaining an image of the eyeball. By providing a reduction means for reducing the light from the infrared light emitting unit to the display unit in a planar view, it is possible to reduce degradation of image quality.

[0189] The user's line of sight with respect to the displayed image can be detected from a captured image of the eyeball obtained by capturing infrared light. Any known method can be applied to gaze detection using a captured image of the eyeball. As an example, a gaze detection method based on a Purkinje image formed by reflection of irradiated light on the cornea can be used. More specifically, a gaze detection process based on a pupil-corneal reflex method is performed. Using the pupil-corneal reflex method, a gaze vector representing the direction (rotation angle) of the eyeball is calculated based on the image of the pupil and the Purkinje image included in the captured image of the eyeball, thereby detecting the user's gaze.

[0190] The display device of this embodiment may be configured to include a photoelectric conversion device having a light receiving element, and to control a display image based on the user's line of sight information from the photoelectric conversion device. Specifically, the display device determines a first field of view area to which the user gazes and a second field of view area other than the first field of view area based on the line of sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be determined by an external control device. When determined by an external control device, they are communicated to the display device via communication. In the display area of ​​the display device, the display resolution of the first field of view area may be controlled to be higher than the display resolution of the second field of view area. In other words, the resolution of the second field of view area may be lower than the resolution of the first field of view area.

[0191] The display area may also be configured to have a first display area and a second display area different from the first display area, and to determine an area having a high priority from the first display area and the second display area based on line-of-sight information. The first display area and the second display area may be determined by a control device of the display device, or may be determined by an external control device. When determined by an external control device, the determination is communicated to the display device via communication. The resolution of the area having a high priority may be controlled to be higher than the resolution of areas other than the area having a high priority. In other words, the resolution of an area having a relatively low priority may be lowered.

[0192] AI may be used to determine the first field of view area and areas with high priority. The AI ​​may be a model configured to estimate the angle of the line of sight and the distance to an object at the end of the line of sight from the image of the eyeball, using as teacher data an image of the eyeball and the direction in which the eyeball in the image was actually looking. The AI ​​program may be included in the display device, the photoelectric conversion device, or an external device. If included in the external device, it is transmitted to the display device via communication.

[0193] When display control is performed based on visual recognition detection, the present invention is preferably applicable to smart glasses further including a photoelectric conversion device for capturing an image of the outside world. The smart glasses can display captured outside information in real time.

[0194] [Ninth embodiment] A device according to a ninth embodiment of the present invention will be described with reference to Fig. 24. Fig. 24 is a block diagram showing a schematic configuration of the device according to this embodiment.

[0195] FIG. 24 is a schematic diagram showing an apparatus EQP including a photoelectric conversion device APR. The photoelectric conversion device APR has the functions of the photoelectric conversion device 100 according to any one of the first to third embodiments. All or a part of the photoelectric conversion device APR is a semiconductor device IC. The photoelectric conversion device APR of this example can be used as, for example, an image sensor, an AF (Auto Focus) sensor, a photometry sensor, or a distance measurement sensor. The semiconductor device IC has a pixel area PX in which pixel circuits PXC including photoelectric conversion units are arranged in a matrix. The semiconductor device IC can have a peripheral area PR around the pixel area PX. Circuits other than pixel circuits can be arranged in the peripheral area PR.

[0196] The photoelectric conversion device APR may have a structure (a chip stacking structure) in which a first semiconductor chip provided with a plurality of photoelectric conversion units and a second semiconductor chip provided with peripheral circuits are stacked. The peripheral circuits in the second semiconductor chip may be column circuits corresponding to the pixel columns of the first semiconductor chip. The peripheral circuits in the second semiconductor chip may be matrix circuits corresponding to the pixels or pixel blocks of the first semiconductor chip. The first and second semiconductor chips may be connected to each other by through-hole vias (TSVs), inter-chip wiring by direct bonding of a conductor such as copper, connection by microbumps between chips, connection by wire bonding, or the like.

[0197] The photoelectric conversion device APR may include a package PKG that houses the semiconductor device IC in addition to the semiconductor device IC. The package PKG may include a base to which the semiconductor device IC is fixed, a cover such as glass that faces the semiconductor device IC, and connection members such as bonding wires and bumps that connect terminals provided on the base and terminals provided on the semiconductor device IC.

[0198] The equipment EQP may further include at least one of an optical device OPT, a control device CTRL, a processing device PRCS, a display device DSPL, a memory device MMRY, and a mechanical device MCHN. The optical device OPT corresponds to the photoelectric conversion device APR as a photoelectric conversion device, and is, for example, a lens, a shutter, or a mirror. The control device CTRL controls the photoelectric conversion device APR, and is, for example, a semiconductor device such as an ASIC. The processing device PRCS processes a signal output from the photoelectric conversion device APR, and constitutes an AFE (analog front end) or a DFE (digital front end). The processing device PRCS is a semiconductor device such as a CPU (central processing unit) or an ASIC (application specific integrated circuit). The display device DSPL is an EL display device or a liquid crystal display device that displays information (images) obtained by the photoelectric conversion device APR. The memory device MMRY is a magnetic device or a semiconductor device that stores information (images) obtained by the photoelectric conversion device APR. The memory device MMRY is a volatile memory such as an SRAM or a DRAM, or a non-volatile memory such as a flash memory or a hard disk drive. The mechanical device MCHN has a moving part or a propulsion part such as a motor or an engine. In the device EQP, the signal output from the photoelectric conversion device APR is displayed on the display device DSPL, and is transmitted to the outside by a communication device (not shown) provided in the device EQP. For this purpose, the device EQP preferably further includes a memory device MMRY and a processing device PRCS in addition to the memory circuit unit and the arithmetic circuit unit provided in the photoelectric conversion device APR.

[0199] The device EQP shown in FIG. 24 may be an electronic device such as an information terminal having a photographing function (e.g., a smartphone or a wearable device) or a camera (e.g., an interchangeable lens camera, a compact camera, a video camera, or a surveillance camera). The mechanical device MCHN in the camera can drive components of the optical device OPT for zooming, focusing, and shutter operation. The device EQP may also be a transportation device (moving object) such as a vehicle, a ship, or an aircraft. The device EQP may also be a medical device such as an endoscope or a CT scanner.

[0200] The mechanical device MCHN in the transportation equipment can be used as a moving device. The device EQP as a transportation equipment is suitable for transporting the photoelectric conversion device APR and for assisting and / or automating driving (operation) by using a photographing function. The processing device PRCS for assisting and / or automating driving (operation) can perform processing for operating the mechanical device MCHN as a moving device based on information obtained by the photoelectric conversion device APR.

[0201] The photoelectric conversion device APR according to this embodiment can provide high value to its designer, manufacturer, seller, purchaser and / or user. Therefore, if the photoelectric conversion device APR is installed in equipment EQP, the value of the equipment EQP can also be increased. Therefore, when manufacturing and selling equipment EQP, deciding to install the photoelectric conversion device APR of this embodiment in the equipment EQP is advantageous in increasing the value of the equipment EQP.

[0202] [Modified embodiment] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, an example in which part of the configuration of any one of the embodiments is added to another embodiment, or an example in which part of the configuration of another embodiment is substituted therefor, is also an embodiment of the present invention.

[0203] The circuit configuration of the pixel 12 is not limited to the above embodiment. For example, a switch such as a transistor may be provided between the photoelectric conversion element 22 and the quench element 24 or between the photoelectric conversion unit 20 and the pixel signal processing unit 30 to control the electrical connection state between them. A switch such as a transistor may be provided between a node to which the voltage VH is supplied and the quench element 24 and / or between a node to which the voltage VL is supplied and the photoelectric conversion element 22 to control the electrical connection state between them. A plurality of photoelectric conversion elements 22 may be provided for one pixel 12.

[0204] Furthermore, in the above embodiment, a configuration using the counter circuit 34 as the pixel signal processing unit 30 has been described, but a TDC (Time to Digital Converter) and a memory may be used instead of the counter circuit 34. In this case, the generation timing of the pulse signal output from the waveform shaping circuit 32 is converted into a digital signal by the TDC. When measuring the timing of the pulse signal, the TDC is supplied with a control pulse pREF (reference signal) from the vertical scanning circuit unit 40 via the control line 14. The TDC acquires, as a digital signal, a signal obtained when the input timing of the signal output from each pixel 12 is converted into a relative time based on the control pulse pREF.

[0205] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0206] It should be noted that the above-mentioned embodiments are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted as being limited by these embodiments. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features.

[0207] The disclosure of the above embodiment includes the following configurations and methods. (Configuration 1) an avalanche photodiode; a first signal processing circuit having a first input node and a second input node, one node of the avalanche photodiode being connected to the first input node and a periodic first control signal being input to the second input node; a recharge circuit connected to the one node of the avalanche photodiode and controlling a recharge operation of the avalanche photodiode in response to a periodic second control signal; the first signal processing circuit is switchable between a first mode in which an output value varies depending on a signal at the first input node and a second mode in which a fixed value is output regardless of the signal at the first input node, in response to the first control signal; The first signal processing circuit outputs a first value only once in the first mode when avalanche multiplication occurs in the avalanche photodiode two or more times during one period of the second control signal. A photoelectric conversion device comprising: (Configuration 2) an avalanche photodiode; a first signal processing circuit having a first input node and a second input node, one node of the avalanche photodiode being connected to the first input node and a periodic first control signal being input to the second input node; a recharge circuit connected to the one node of the avalanche photodiode and controlled by a periodic second control signal; the first signal processing circuit is controlled in accordance with the first control signal to a first mode in which an output value varies in accordance with a signal at the first input node, and a second mode in which a fixed value is output regardless of the signal at the first input node; the recharge circuit is controlled in response to the second control signal to a recharge operation mode that allows a recharge operation in the avalanche photodiode and a quench operation mode that allows a quench operation in the avalanche photodiode; A period during which the recharge circuit is controlled in the recharge operation mode overlaps with a period during which the first signal processing circuit is controlled in the second mode, and does not overlap with a period during which the first signal processing circuit is controlled in the first mode. A photoelectric conversion device comprising: (Configuration 3) The first signal processing circuit outputs a first value only once in the first mode when avalanche multiplication occurs in the avalanche photodiode two or more times during one period of the second control signal. 3. The photoelectric conversion device according to configuration 2. (Configuration 4) The first signal processing circuit has a NOR circuit to which signals are input from the first input node and the second input node. 4. The photoelectric conversion device according to any one of configurations 1 to 3. (Configuration 5) The first signal processing circuit further includes a Schmitt trigger circuit provided between the first input node and the NOR circuit. 5. The photoelectric conversion device according to configuration 4. (Configuration 6) an avalanche photodiode; a first signal processing circuit having a first input node and a second input node, one node of the avalanche photodiode being connected to the first input node and a periodic first control signal being input to the second input node; a recharge circuit connected to the one node of the avalanche photodiode and controlled by a periodic second control signal; the recharge circuit is controlled in response to the second control signal to a recharge operation mode that allows a recharge operation in the avalanche photodiode and a quench operation mode that allows a quench operation in the avalanche photodiode; The first signal processing circuit is outputting a second value when the first control signal is at a first level; outputting a first value when the first control signal is at a second level different from the first level and the avalanche photodiode is in a discharge state in which no avalanche multiplication occurs; When the first control signal is at the second level and the avalanche photodiode is in a standby state where avalanche multiplication is possible, the output value is held. A photoelectric conversion device comprising: (Configuration 7) The first signal processing circuit outputs the first value only once when avalanche multiplication occurs in the avalanche photodiode two or more times during one period of the second control signal. 7. The photoelectric conversion device according to configuration 6. (Configuration 8) The first signal processing circuit has an SR latch. 8. The photoelectric conversion device according to any one of configurations 1, 6 and 7, (Configuration 9) The SR latch is a NAND type SR latch. 9. The photoelectric conversion device according to configuration 8. (Configuration 10) The first signal processing circuit outputs a second value when avalanche multiplication does not occur during one period of the second control signal. 10. The photoelectric conversion device according to any one of configurations 1 to 9. (Configuration 11) Further comprising a second signal processing circuit connected to the first signal processing circuit. 11. The photoelectric conversion device according to any one of configurations 1 to 10. (Configuration 12) The second signal processing circuit is a counter circuit. 12. The photoelectric conversion device according to claim 11, (Configuration 13) The second signal processing circuit further includes a counter saturation detection circuit. 13. The photoelectric conversion device according to configuration 12. (Configuration 14) The first value is 1. 7. The photoelectric conversion device according to any one of configurations 1, 3 and 6. (Configuration 15) The second value is 0. 11. The photoelectric conversion device according to configuration 10. (Configuration 16) A photoelectric conversion device according to any one of structures 1 to 15, a signal processing device that processes a signal output from the photoelectric conversion device; 1. An optical detection system comprising: (Configuration 17) The signal processing device generates a distance image representing distance information to an object based on the signal. 17. The optical detection system of claim 16. (Configuration 18) A mobile object, A photoelectric conversion device according to any one of structures 1 to 15, a distance information acquisition unit that acquires distance information to an object from a parallax image based on a signal output from the photoelectric conversion device; a control means for controlling the moving object based on the distance information; A moving object comprising: (Configuration 19) A photoelectric conversion device according to any one of structures 1 to 17; an optical device corresponding to the photoelectric conversion device; A control device for controlling the photoelectric conversion device; a processing device that processes a signal output from the photoelectric conversion device; a mechanical device controlled based on information obtained by the photoelectric conversion device; A display device that displays information obtained by the photoelectric conversion device; and a storage device for storing information obtained by the photoelectric conversion device; An apparatus comprising: (Method 1) A method for driving a photoelectric conversion device having an avalanche photodiode, a first signal processing circuit having a first input node and a second input node, one node of the avalanche photodiode being connected to the first input node and a periodic first control signal being input to the second input node, and a recharge circuit connected to the one node of the avalanche photodiode and controlled by a periodic second control signal, The first signal processing circuit is controlled in accordance with the first control signal to have an output value that varies depending on a signal at the first input node, and a second mode that outputs a fixed value regardless of the signal at the first input node; When controlling the recharge circuit to a recharge operation mode that allows a recharge operation in the avalanche photodiode and a quench operation mode that allows a quench operation in the avalanche photodiode in response to the second control signal, A period during which the recharge circuit is controlled to the recharge operation mode is controlled so as to overlap a period during which the first signal processing circuit is controlled to the second mode and not to overlap a period during which the first signal processing circuit is controlled to the first mode. A method for driving a photoelectric conversion device comprising the steps of: [Explanation of symbols]

[0208] LC1...NOR circuit LC2, LC3...NAND circuit Mq...P-type MOS transistor SC...Schmitt trigger circuit 12…pixels 22...Photoelectric conversion element 24...Quench element 32...Waveform shaping circuit 34…Counter circuit 36...Selection circuit 100...Photoelectric conversion device

Claims

1. an avalanche photodiode; a first signal processing circuit having a first input node and a second input node, one node of the avalanche photodiode being connected to the first input node and a first periodic control signal being input to the second input node; a recharge circuit connected to the one node of the avalanche photodiode and controlling a recharge operation of the avalanche photodiode in response to a periodic second control signal; the first signal processing circuit is switchable between a first mode in which an output value varies depending on a signal at the first input node and a second mode in which a fixed value is output regardless of the signal at the first input node, in response to the first control signal; The first signal processing circuit outputs a first value only once in the first mode when avalanche multiplication occurs in the avalanche photodiode two or more times during one period of the second control signal. A photoelectric conversion device comprising:

2. an avalanche photodiode; a first signal processing circuit having a first input node and a second input node, one node of the avalanche photodiode being connected to the first input node and a first periodic control signal being input to the second input node; a recharge circuit connected to the one node of the avalanche photodiode and controlled by a periodic second control signal; the first signal processing circuit is controlled in accordance with the first control signal to a first mode in which an output value varies in accordance with a signal at the first input node, and a second mode in which a fixed value is output regardless of the signal at the first input node; the recharge circuit is controlled in response to the second control signal to a recharge operation mode that allows a recharge operation in the avalanche photodiode and a quench operation mode that allows a quench operation in the avalanche photodiode; A period during which the recharge circuit is controlled in the recharge operation mode overlaps with a period during which the first signal processing circuit is controlled in the second mode, and does not overlap with a period during which the first signal processing circuit is controlled in the first mode. A photoelectric conversion device comprising:

3. The first signal processing circuit outputs a first value only once in the first mode when avalanche multiplication occurs in the avalanche photodiode two or more times during one period of the second control signal.

3. The photoelectric conversion device according to claim 2.

4. The first signal processing circuit has a NOR circuit to which signals are input from the first input node and the second input node.

4. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

5. The first signal processing circuit further includes a Schmitt trigger circuit provided between the first input node and the NOR circuit.

5. The photoelectric conversion device according to claim 4.

6. an avalanche photodiode; a first signal processing circuit having a first input node and a second input node, one node of the avalanche photodiode being connected to the first input node and a first periodic control signal being input to the second input node; a recharge circuit connected to the one node of the avalanche photodiode and controlled by a periodic second control signal; the recharge circuit is controlled in response to the second control signal to a recharge operation mode that allows a recharge operation in the avalanche photodiode and a quench operation mode that allows a quench operation in the avalanche photodiode; The first signal processing circuit is outputting a second value when the first control signal is at a first level; a first value is output when the first control signal is at a second level different from the first level and the avalanche photodiode is in a discharge state in which no avalanche multiplication occurs; When the first control signal is at the second level and the avalanche photodiode is in a standby state where avalanche multiplication is possible, the output value is held. A photoelectric conversion device comprising:

7. The first signal processing circuit outputs the first value only once when avalanche multiplication occurs in the avalanche photodiode two or more times during one period of the second control signal.

7. The photoelectric conversion device according to claim 6.

8. The first signal processing circuit has an SR latch.

8. The photoelectric conversion device according to claim 1, 6 or 7.

9. The SR latch is a NAND type SR latch.

9. The photoelectric conversion device according to claim 8.

10. The first signal processing circuit outputs a second value when avalanche multiplication does not occur during one period of the second control signal.

8. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

11. The second signal processing circuit is connected to the first signal processing circuit.

8. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

12. The second signal processing circuit is a counter circuit.

12. The photoelectric conversion device according to claim 11.

13. The second signal processing circuit further includes a counter saturation detection circuit.

13. The photoelectric conversion device according to claim 12.

14. The first value is 1.

7. The photoelectric conversion device according to claim 1, 3 or 6.

15. The second value is 0.

11. The photoelectric conversion device according to claim 10.

16. The photoelectric conversion device according to any one of claims 1 to 3, 6 and 7, a signal processing device that processes a signal output from the photoelectric conversion device; 1. An optical detection system comprising:

17. The signal processing device generates a distance image representing distance information to an object based on the signal.

17. The optical detection system of claim 16.

18. A mobile object, The photoelectric conversion device according to any one of claims 1 to 3, 6 and 7, a distance information acquisition unit that acquires distance information to an object from a parallax image based on a signal output from the photoelectric conversion device; a control means for controlling the moving object based on the distance information; A moving object comprising:

19. The photoelectric conversion device according to any one of claims 1 to 3, 6 and 7, an optical device corresponding to the photoelectric conversion device; A control device for controlling the photoelectric conversion device; a processing device that processes a signal output from the photoelectric conversion device; a mechanical device controlled based on information obtained by the photoelectric conversion device; A display device that displays information obtained by the photoelectric conversion device; and a storage device for storing information obtained by the photoelectric conversion device; An apparatus comprising:

20. A method for driving a photoelectric conversion device having an avalanche photodiode, a first signal processing circuit having a first input node and a second input node, one node of the avalanche photodiode being connected to the first input node and a periodic first control signal being input to the second input node, and a recharge circuit connected to the one node of the avalanche photodiode and controlled by a periodic second control signal, the first signal processing circuit is controlled in response to the first control signal to a first mode in which an output value varies in response to a signal at the first input node, and a second mode in which a fixed value is output regardless of the signal at the first input node; when controlling the recharge circuit to a recharge operation mode that allows a recharge operation in the avalanche photodiode and a quench operation mode that allows a quench operation in the avalanche photodiode in response to the second control signal, A period during which the recharge circuit is controlled to the recharge operation mode is controlled so as to overlap a period during which the first signal processing circuit is controlled to the second mode and not to overlap a period during which the first signal processing circuit is controlled to the first mode. A method for driving a photoelectric conversion device comprising the steps of:

Images