Photoelectric conversion device and driving method thereof

Abstract

To provide a technique to advance an exposure control function in a photoelectric conversion device including a function to count the number of incident photons.SOLUTION: A photoelectric conversion device has a photoelectric conversion unit that outputs pulse signals in response to incidence of photons, a signal processing unit that is connected with the photoelectric conversion unit and counts the number of pulse signals, and a control unit that controls the signal processing unit. The signal processing unit has a first count processing unit and a second count processing unit arranged parallel to each other. The control unit is configured to set an active period and a non-active period to each of the first count processing unit and the second count processing unit. A period during which the first count processing unit is active includes a first period during which the second count processing unit is active and a second period during which the second count processing unit is not active.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Single photon avalanche diodes (SPADs) are known as detectors capable of detecting weak light at the single photon level. SPADs amplify signal charges excited by photons several to several million times by using the avalanche multiplication phenomenon that occurs due to a strong electric field induced in a pn junction of a semiconductor. The number of incident photons can be directly measured by converting the current generated by the avalanche multiplication phenomenon into a pulse signal and counting the number of the pulse signals. Patent Document 1 discloses an example in which a method for counting the number of pulse signals output from a sensor unit is devised to provide an additional function to a sensing device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-140537 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional technology, sufficient consideration has not been given to exposure control of the photoelectric conversion device, and appropriate exposure control has not always been possible in accordance with the occurrence pattern of events on which photons are incident.

[0005] An object of the present invention is to provide a technique for achieving high-performance exposure control in a photoelectric conversion device having a function of counting incident photons. [Means for solving the problem]

[0006] According to one aspect of the present invention, a photoelectric conversion unit that outputs a pulse signal in response to incidence of a photon is provided. ,before a signal processing unit connected to the photoelectric conversion unit and configured to count the pulse signals; A plurality of pixels each having a A control unit that controls the signal processing unit, Each of the plurality of pixels The signal processing unit has a first counting processing unit and a second counting processing unit connected in parallel, and the control unit A plurality of control signals are supplied to the signal processing unit, The device is configured to set an active period and an inactive period for each of the first counting processing unit and the second counting processing unit, and the active period of the first counting processing unit includes a first period in which the second counting processing unit is active and a second period in which the second counting processing unit is inactive. a set of control signals supplied to the first counting processing unit and the second counting processing unit of a first pixel among the plurality of pixels is different from a set of control signals supplied to the first counting processing unit and the second counting processing unit of a second pixel among the plurality of pixels. A photoelectric conversion device is provided. According to another aspect of the present invention, there is provided a photoelectric conversion device comprising: a plurality of pixels, each of which has a photoelectric conversion unit that outputs a pulse signal in response to incidence of photons; and a signal processing unit connected to the photoelectric conversion unit and counting the pulse signal; and a control unit that controls the signal processing units of the plurality of pixels, wherein the signal processing unit of each of the plurality of pixels has a first counting processing unit and a second counting processing unit connected in parallel, and the control unit is configured to set an active period and an inactive period for each of the first counting processing unit and the second counting processing unit by a plurality of control signals supplied to the signal processing unit, the period in which the first counting processing unit is active includes a first period in which the second counting processing unit is active and a second period in which the second counting processing unit is inactive, and at least one pixel of the plurality of pixels has a set of control signals supplied to the first counting processing unit and the second counting processing unit in one frame that is different from a set of control signals supplied to the first counting processing unit and the second counting processing unit in another frame.

[0007] In addition, the present invention Furthermore According to another aspect, A method for driving a photoelectric conversion device having a plurality of pixels each having a photoelectric conversion unit that outputs a pulse signal in response to incidence of photons, and a signal processing unit connected to the photoelectric conversion unit and counting the pulse signal, wherein the signal processing unit of each of the plurality of pixels has a first counting processing unit and a second counting processing unit connected in parallel, wherein when an active period and an inactive period are set for each of the first counting processing unit and the second counting processing unit by a plurality of control signals supplied to the signal processing unit in each of the plurality of pixels, the active period of the first counting processing unit in each of the plurality of pixels includes a first period in which the second counting processing unit is active and a second period in which the second counting processing unit is inactive, and a set of control signals supplied to the first counting processing unit and the second counting processing unit of a first pixel of the plurality of pixels is different from a set of control signals supplied to the first counting processing unit and the second counting processing unit of a second pixel of the plurality of pixels. Photoelectric conversion device How to drive is provided.

[0008] According to yet another aspect of the present invention, a photoelectric conversion unit that outputs a pulse signal in response to incidence of a photon, and a signal processing unit that is connected to the photoelectric conversion unit and counts the pulse signal. Each of the pixels has Has Each of the plurality of pixels The signal processing unit is connected in parallel No. 1 Counting processing unit and a second counting processing unit A method for driving a photoelectric conversion device having the following features: When setting active periods and inactive periods for each of the first counting processing unit and the second counting processing unit by a plurality of control signals supplied to the signal processing unit in each of the plurality of pixels, the period in which the first counting processing unit is active in each of the plurality of pixels includes a first period in which the second counting processing unit is active and a second period in which the second counting processing unit is inactive, and in at least one pixel of the plurality of pixels, a set of control signals supplied to the first counting processing unit and the second counting processing unit in one frame is controlled to be different from a set of control signals supplied to the first counting processing unit and the second counting processing unit in another frame. A method for driving a photoelectric conversion device is provided. Effect of the Invention

[0009] According to the present invention, it is possible to realize high-performance exposure control in a photoelectric conversion device having a function of counting incident photons. [Brief description of the drawings]

[0010] [Figure 1]1 is a block diagram showing a schematic configuration of a photoelectric conversion device according to a first embodiment of the present invention. [Diagram 2] 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. [Diagram 3] FIG. 2 is a diagram illustrating a basic operation of a photoelectric conversion unit of the photoelectric conversion device according to the first embodiment of the present invention. [Figure 4] 2 is a diagram illustrating an example of the configuration of a counting processing unit of the photoelectric conversion device according to the first embodiment of the present invention. FIG. [Diagram 5] 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. [Figure 6] 4 is a timing chart showing an example of a method for driving the photoelectric conversion device according to the first embodiment of the present invention. [Figure 7] 10 is a timing chart showing an example of a method for driving the photoelectric conversion device according to the second embodiment of the present invention. [Figure 8] 13 is a timing chart showing an example of a method for driving a photoelectric conversion device according to a third embodiment of the present invention. [Figure 9] 13 is a timing chart showing an example of a method for driving a photoelectric conversion device according to a fourth embodiment of the present invention. [Figure 10] FIG. 13 is a block diagram showing an example of the configuration of a pixel in a photoelectric conversion device according to a modified example of the fourth embodiment of the present invention. [Figure 11] FIG. 13 is a block diagram showing an example of the configuration of a pixel in a photoelectric conversion device according to a modified example of the fifth embodiment of the present invention. [Figure 12] 13 is a timing chart showing an example of a method for driving a photoelectric conversion device according to a fifth embodiment of the present invention. [Figure 13] FIG. 13 is a block diagram showing a schematic configuration of an imaging system according to a sixth embodiment of the present invention. [Figure 14] FIG. 13 is a diagram showing an example of the configuration of an imaging system and a moving object according to a seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [First embodiment] A photoelectric conversion device and a driving method thereof according to a first embodiment of the present invention will be described with reference to Figs. 1 to 6. Fig. 1 is a block diagram showing a schematic configuration of a photoelectric conversion device according to this embodiment. Fig. 2 is a block diagram showing an example of the configuration of a pixel of the photoelectric conversion device according to this embodiment. Fig. 3 is a diagram explaining the basic operation of a photoelectric conversion section of the photoelectric conversion device according to this embodiment. Fig. 4 is a diagram showing an example of the configuration of a counting processing section of the photoelectric conversion device according to this embodiment. Fig. 5 is a perspective view showing an example of the configuration of the photoelectric conversion device according to this embodiment. Fig. 6 is a timing chart showing an example of a driving method of the photoelectric conversion device according to this embodiment.

[0012] First, the structure of the photoelectric conversion device according to the present embodiment will be described with reference to FIGS.

[0013] 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.

[0014] The pixel unit 10 includes a plurality of pixels 12 arranged in an array having a plurality of rows and a plurality of columns. Each pixel 12 may be composed of a photoelectric conversion unit 20 including a photon detection element and a pixel signal processing unit 30. 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.

[0015] A control line 14 is arranged in each row of the pixel array of the pixel unit 10, extending in a first direction (the 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 referred to as the row direction or the 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.

[0016] 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 a column direction or a 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.

[0017] 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 lines 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 lines 16.

[0018] 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.

[0019] The horizontal scanning circuit unit 60 is a control unit that supplies the readout circuit unit 50 with a control signal for reading out pixel signals from the holding units of each column of 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.

[0020] 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.

[0021] 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.

[0022] 2, each pixel 12 has a photoelectric conversion unit 20 and a pixel signal processing unit 30. The photoelectric conversion unit 20 has a photon detecting element 22, a quenching element 24, and a waveform shaping unit 26. The pixel signal processing unit 30 has count processing units 32A and 32B, and a selection circuit 38.

[0023] The photon detecting element 22 may be an avalanche photodiode (hereinafter, referred to as "APD"). The anode of the APD constituting the photon detecting element 22 is connected to a node to which a voltage VL is supplied. The cathode of the APD constituting the photon detecting element 22 is connected to one terminal of the quench element 24. 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.

[0024] An input node of the waveform shaping unit 26 is connected to a connection node between the photon detecting element 22 and the quenching element 24. An output node of the waveform shaping unit 26 is connected to an input node of the counting processing unit 32A and an input node of the counting processing unit 32B. An output node of the counting processing unit 32A and an output node of the counting processing unit 32B are connected to input nodes of the selection circuit 38. An output node of the selection circuit 38 is connected to the data line 16. Note that the data line 16 may include a signal line for outputting a signal from the counting processing unit 32A and a signal line for outputting a signal from the counting processing unit 32B.

[0025] The control lines 14 include a signal line through which the control signal pACT_A is supplied, a signal line through which the control signal pACT_B is supplied, a signal line through which the control signal pRES is supplied, and a signal line through which the control signal pSEL is supplied. The two control nodes of the counting processing unit 32A are connected to the signal line through which the control signal pACT_A is supplied and the signal line through which the control signal pRES is supplied, respectively. The two control nodes of the counting processing unit 32B are connected to the signal line through which the control signal pACT_B is supplied and the signal line through which the control signal pRES is supplied, respectively. The control node of the selection circuit 38 is connected to the signal line through which the control signal pSEL is supplied.

[0026] The photon detection 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 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 cathode is a reverse bias voltage close to or less than the breakdown voltage of the APD. An APD operated in Geiger mode is called a SPAD (Single Photon Avalanche Diode).

[0027] The quench element 24 has a function of converting a change in avalanche current occurring in the photon detecting 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 suppressing avalanche multiplication by reducing the voltage applied to the photon detecting element 22. The operation of the quench element 24 to suppress avalanche multiplication is called a quench operation. The quench element 24 can be composed of a resistor element, a MOS transistor, or the like.

[0028] The waveform shaping unit 26 is a pulse generating unit that converts an analog signal (potential change at the cathode of the photon detecting element 22) output from the photon detecting element 22 when a photon is detected into a photon detection pulse signal, and may be configured, for example, by an inverter circuit. Note that, although Fig. 2 shows an example in which one inverter circuit is used as the waveform shaping unit 26, the waveform shaping unit 26 is not limited to this, and may be configured, for example, by a circuit in which a plurality of inverter circuits are connected in series, or by another circuit having a waveform shaping effect.

[0029] Each of the count processing units 32A and 32B has a function of counting the number of pulses output from the waveform shaping unit 26 and holding a count value that is the result of the counting. The count processing unit 32A counts the number of pulses output from the waveform shaping unit 26 during a period in which a control signal pACT_A supplied from the vertical scanning circuit unit 40 via the control line 14 is active. Similarly, the count processing unit 32B counts the number of pulses output from the waveform shaping unit 26 during a period in which a control signal pACT_B supplied from the vertical scanning circuit unit 40 via the control line 14 is active. The control signals pACT_A and pACT_B are, so to speak, control signals for setting an exposure period. In addition, the count processing units 32A and 32B reset the count values ​​that they hold when the control signal pRES supplied from the vertical scanning circuit unit 40 via the control line 14 becomes active. Although FIG. 2 shows an example in which the count processing units 32A and 32B are reset by a common control signal pRES, the control signal for resetting the count processing unit 32A and the control signal for resetting the count processing unit 32B may be different control signals.

[0030] The selection circuit 38 has a function of switching the electrical connection state (connected or disconnected) between the count processing units 32A, 32B and the data lines 16. The selection circuit 38 switches the connection state between the count processing units 32A, 32B and the data lines 16 in response to a control signal pSEL supplied from the vertical scanning circuit unit 40 via the control line 14. The selection circuit 38 may include a buffer circuit for outputting a signal.

[0031] Fig. 3 is a diagram for explaining the operation of the photoelectric conversion unit 20. Fig. 3(a) is a circuit diagram of the photoelectric conversion unit 20, Fig. 3(b) shows the waveform of a signal at an input node (node ​​A) of the waveform shaping unit 26, and Fig. 3(c) shows the waveform of a signal at an output node (node ​​B) of the waveform shaping unit 26.

[0032] At time t0, a reverse bias voltage with a potential difference equivalent to (VH-VL) is applied to the photon detecting element 22. A reverse bias voltage sufficient to cause avalanche multiplication is applied between the anode and cathode of the APD constituting the photon detecting element 22, but there are no carriers to serve as the seeds of avalanche multiplication when no photons are incident on the photon detecting element 22. Therefore, avalanche multiplication does not occur in the photon detecting element 22, and no current flows through the photon detecting element 22.

[0033] At the next time t1, a photon is assumed to be incident on the photon detecting element 22 ("Photon Incidence" in FIG. 3). When a photon is incident on the photon detecting 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 photon detecting 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. The amount of voltage drop at node A becomes large, and when the avalanche multiplication stops at time t3, the voltage level at node A no longer drops.

[0034] When the avalanche multiplication in the photon detecting element 22 stops, a current that compensates for the voltage drop flows from the node to which the voltage VL is supplied to the node A via the photon detecting element 22, and the voltage of the node A gradually increases. After that, at time t5, the node A stabilizes to the original voltage level.

[0035] The waveform shaping unit 26 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 unit 26 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 unit 26 outputs a high-level signal from node B. For example, as shown in FIG. 3(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. 3(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.

[0036] In this way, the analog signal input from node A is shaped into a digital signal by the waveform shaping section 26. The pulse signal output from the waveform shaping section 26 in response to a photon being incident on the photon detecting element 22 is a photon detection pulse signal.

[0037] Fig. 4 is a schematic diagram showing a configuration example of the count processing unit 32. Since the count processing unit 32A and the count processing unit 32B have the same structure, Fig. 4 shows only one count processing unit 32, and the reference characters A and B that distinguish the count processing unit 32A from the count processing unit 32B are omitted.

[0038] As shown in Fig. 4, the counting processing section 32 has a switch SW1 and a counter 34. One node of the switch SW1 is also an input node of the counting processing section 32, and is connected to an output node of the waveform shaping section 26 (see Fig. 2). The other node of the switch SW1 is connected to an input node of the counter 34. The output node of the counter 34 is also an output node of the counting processing section 32, and is connected to an input node of the selection circuit 38. A control signal pACT is supplied to the control node of the switch SW1 from the vertical scanning circuit section 40 via the control line 14. A control signal pRES is supplied to the control node of the counter 34 from the vertical scanning circuit section 40 via the control line 14.

[0039] The counter 34 has a function of counting the pulse signals output from the waveform shaping unit 26 and holding the count value that is the result of the counting. For example, if the counter 34 is a 10-bit binary counter, it can count and hold a maximum of 1023 pulses from when the control signal pRES supplied from the vertical scanning circuit unit 40 becomes inactive until when it next becomes active. Note that the counter 34 may be a counting means other than a binary counter, and the number of bits is not limited to 10 bits.

[0040] The switch SW1 has a function of switching whether to input or block the pulse signal output from the waveform shaping unit 26 to the counter 34 in response to a control signal pACT supplied from the vertical scanning circuit unit 40. The switch SW1 can be realized by, for example, a CMOS switch circuit, but may also be configured by a logic circuit such as a decoder or other selection means.

[0041] By providing the switch SW1 in front of the counter 34, the pulse signals output from the waveform shaping unit 26 can be input to the counter 34 only during the period when the control signal pACT is active, and the number of pulse signals can be counted. In other words, by setting the period during which the control signal pACT is active, the period during which the counter 34 counts the pulse signals output from the waveform shaping unit 26 can be set.

[0042] By arranging a plurality of counting processing units 32 having such functions in parallel, it becomes possible for the plurality of counting processing units 32 to count in parallel the photon detection pulse signals output from one photoelectric conversion unit 20. The counting period in each of the plurality of counting processing units 32 can be controlled by a control signal pACT.

[0043] In this embodiment, the switch SW1 is used to switch whether the pulse signal output from the waveform shaping unit 26 is input to or blocked from the counter 34, but the counter 34 may also have a function for selecting whether to enable or disable the counting operation.

[0044] 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. 5, it is possible to configure a stacked photoelectric conversion device in which a sensor substrate 110 and a circuit substrate 120 are stacked and electrically connected. At least the photon detection element 22, which is one of the components of the pixel 12, can be arranged on the sensor substrate 110. In addition, the pixel signal processing unit 30, which is one of the components of the pixel 12, can be arranged on the circuit substrate 120. 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 may be further arranged on the circuit substrate 120. By configuring a stacked photoelectric conversion device, it is possible to increase the integration degree of elements and achieve high functionality. The photoelectric conversion device 100 may be configured by stacking three or more substrates.

[0045] Next, a method for driving the photoelectric conversion device according to this embodiment will be described with reference to FIG. 6. The timing chart in FIG. 6 shows a pulse signal pEP, control signals pRES, pACT_A, and pACT_B, count values ​​Count_A and Count_B, and exposure periods A and B. The pulse signal pEP is a photon detection pulse signal that is output from node B of the waveform shaping unit 26 in response to the incidence of photons. The count value Count_A is the count value of the counter 34 in the count processing unit 32A. The count value Count_B is the count value of the counter 34 in the count processing unit 32B. B The exposure period A is a period during which the counting operation is performed in the counting processing unit 32A corresponding to the period during which the control signal pACT_A is active. The exposure period B is a period during which the counting operation is performed in the counting processing unit 32B corresponding to the period during which the control signal pACT_B is active.

[0046] 6, it is assumed, as an example, that 1200 photons are incident on a pixel 12 at equal intervals without overlapping during a given exposure period T. The counter 34 is capable of counting a maximum of 1023 pulses and holding the count value.

[0047] First, the operation of the count processing unit 32A will be described. At time t0, the control signal pRES becomes active (high level), and the count value Count_A of the counter 34 of the count processing unit 32A is reset to zero.

[0048] At the following time t1, the control signal pACT_A becomes active (high level), and the counter 34 of the count processing unit 32A starts counting the pulse signal pEP. The time t1 when the control signal pACT_A becomes active is the start timing of the exposure period A.

[0049] At the next time t2, the pulse signal pEP becomes active (high level) in response to the incidence of a photon. The counter 34 of the count processing unit 32A counts this pulse signal pEP, causing the count value Count_A of the counter 34 to transition from 0 to 1.

[0050] After that, the count value Count_A is incremented every time the pulse signal pEP becomes active. However, since the count value Count_A reaches 1023, which is the upper limit of the count value that can be held by the counter 34, at time t6, the count value Count_A is not incremented even when the pulse signal pEP rises at time t6.

[0051] At the next time t7, the control signal pACT_A becomes inactive (low level), and the count processing unit 32A ends counting the pulse signal pEP. The time t7 when the control signal pACT_A becomes inactive is the end timing of the exposure period A.

[0052] It is expected that the count value Count_A held by the counter 34 of the count processing unit 32A at time t7 is equal to the number of photons incident during the exposure period A (time T). However, if the count value Count_A reaches 1023, which is the maximum value that the counter 34 can hold, during the exposure period A, the only information that can be obtained is that 1023 or more photons have been incident.

[0053] Next, the operation of the count processing unit 32B will be described. At time t0, the control signal pRES becomes active, and the count value Count_B of the counter 34 in the count processing unit 32B is reset to zero.

[0054] At the next time t1, the control signal pACT_A becomes active and the exposure period A starts, but the control signal pACT_B is inactive (low level). At the next time t2, the pulse signal pEP becomes active, but the counter 34 of the counting processing unit 32B does not count this pulse signal pEP, and the count value Count_B of the counter 34 of the counting processing unit 32B remains at 0.

[0055] At the following time t3, the control signal pACT_B becomes active (High level), and the counter 34 of the count processing unit 32B starts counting the pulse signal pEP. The time t3 when the control signal pACT_B becomes active is the start timing of the exposure period B.

[0056] At the next time t4, the pulse signal pEP becomes active in response to the incidence of a photon. The counter 34 of the counting processing unit 32B counts this pulse signal pEP, causing the count value Count_B of the counter 34 to transition from 0 to 1.

[0057] Thereafter, the count value Count_B is incremented every time the pulse signal pEP becomes active.

[0058] At time t5, which is a time T / 2 after time t3, the control signal pACT_B becomes inactive (low level), and the count processing unit 32B ends counting the pulse signal pEP. Time t5, when the control signal pACT_B becomes inactive, is the end timing of the exposure period B. The count value Count_B held by the counter 34 of the count processing unit 32B at time t5 is 600, which is less than the maximum count value (1023) that the counter 34 can hold. Thereafter, the count value Count_B of the counter 34 of the count processing unit 32B is not incremented.

[0059] In this embodiment, the length of the period during which the count processing unit 32B is continuously active is the same as the length of the period during which both the count processing units 32A and 32B are active.

[0060] The count value Count_B held by the counter 34 of the count processing unit 32B at time t7 is equal to the number of photons incident during the exposure period B (time T / 2).

[0061] Here, if the frequency with which photons enter the pixel 12 during the exposure period A does not change significantly, it can be estimated that approximately twice as many as 600 photons enter the pixel 12 during the exposure period A (time T), which is twice as long as the exposure period B (time T / 2). In other words, by providing multiple counting processing units 32 with different exposure periods, even if the upper limit of the count value is exceeded in one counting processing unit 32, it is possible to obtain information on the number of incident photons from the count values ​​of the other counting processing units 32.

[0062] By using the configuration and driving method of this embodiment, an image with a wide dynamic range can be obtained in the photoelectric conversion device 100 having a plurality of pixels 12. That is, by driving each pixel 12 of the pixel unit 10 as described above, an image can be obtained with an appropriate exposure time while maintaining time synchronism for both a low-luminance region in which the appropriate exposure time is time T and a high-luminance region in which the appropriate exposure time is time T / 2.

[0063] In the driving method of the present embodiment, the period in which the count processing unit 32A is active includes a period in which the count processing unit 32B is active and a period in which the count processing unit 32B is inactive. Providing a period in which both the count processing unit 32A and the count processing unit 32B are active has an advantage in that it is possible to obtain information such as the optical flow of the subject.

[0064] In the description of this embodiment, the length of the period from time t1 to time t3 is T / 4, the length of the period from time t3 to time t5 is T / 2, and the length of the period from time t5 to time t7 is T / 4, but the length of each period may be greater than 0, and the total of the three periods may be T. By setting each period in this manner, information on the number of photons incident during each of a plurality of exposure periods can be obtained while maintaining time synchronism.

[0065] Furthermore, count processing units 32A and 32B do not necessarily have to have the same configuration. For example, the counter 34 of count processing unit 32B holds a smaller count value than the counter 34 of count processing unit 32A, so the maximum count value may be smaller. This allows the circuit scale of pixel signal processing unit 30 to be reduced.

[0066] As described above, according to this embodiment, in a photoelectric conversion device having a function of counting incident photons, it is possible to realize high-performance exposure control.

[0067] [Second embodiment] A method for driving a photoelectric conversion device according to a second embodiment of the present invention will be described with reference to Fig. 7. Components similar to those in the photoelectric conversion device according to the first embodiment are given the same reference numerals, and descriptions thereof will be omitted or simplified. In this embodiment, another method for driving the photoelectric conversion device according to the first embodiment will be described.

[0068] Fig. 7 is a timing chart showing an example of a method for driving a photoelectric conversion device according to this embodiment. The timing chart in Fig. 7 shows a pulse signal pEP, control signals pRES, pACT_A, and pACT_B, count values ​​Count_A and Count_B, and exposure periods A and B, similar to Fig. 6.

[0069] In the driving method of the present embodiment, the length of the period during which the count processing unit 32A is continuously active is the same as the length of the period during which the count processing unit 32B is continuously active.

[0070] First, at time t0, the control signal pRES becomes active, and the count value Count_A of the counter 34 in the count processing unit 32A and the count value Count_B of the counter 34 in the count processing unit 32B are reset to zero.

[0071] At the following time t1, the control signal pACT_A becomes active, and the counter 34 of the count processing unit 32A starts counting the pulse signal pEP. The time t1 when the control signal pACT_A becomes active is the start timing of the exposure period A.

[0072] Then, at time t2, which is a time T / 2 after time t1, the control signal pACT_B becomes active, and the counter 34 of the counting processing unit 32B starts counting the pulse signal pEP. The time t2 when the control signal pACT_B becomes active is the start timing of the exposure period B.

[0073] Thereafter, at time t3, which is a time T after time t0, the control signal pACT_A becomes inactive, and the counting processing unit 32A ends counting the pulse signal pEP. The time t3 at which the control signal pACT_A becomes inactive is the end timing of the exposure period A. After that, the count value Count_A of the counter 34 of the counting processing unit 32A is not incremented.

[0074] In the subsequent period from time t4 to time t5, it is assumed that an event (event A) occurs in which 500 photons are incident on the pixel 12. Then, 500 pulses are superimposed on the pulse signal pEP during the period from time t4 to time t5, and the count value Count_B of the counter 34 of the count processing unit 32B is incremented to 500.

[0075] Thereafter, at time t6, which is a time T after time t2, the control signal pACT_B becomes inactive, and the counting processing unit 32B ends counting the pulse signal pEP. The time t6 at which the control signal pACT_B becomes inactive is the end timing of the exposure period B. After that, the count value Count_B of the counter 34 of the counting processing unit 32B is not incremented.

[0076] As a result, at time t6, the count value Count_A held by the counter 34 of the count processing unit 32A becomes 0, and the count value Count_B held by the counter 34 of the count processing unit 32B becomes 500.

[0077] As an example, assume that event A occurs at a cycle of 3T / 2, but is not synchronized with exposure periods A and B, and occurs at a time shorter than T / 2. If the length of the exposure period is desired to be T, the counting processing unit 32A alone may not be able to count the number of photons generated in event A. For example, if event A occurs between time t3 and time t6 as shown in FIG. 7, the counting processing unit 32A alone may not be able to count the number of photons generated in event A.

[0078] In this regard, in the driving method of the present embodiment, the exposure period B of the counting processing unit 32B is set with a phase shift of T / 2 with respect to the exposure period A of the counting processing unit 32A. Therefore, regardless of the phase relationship between the event A and the exposure period, the number of incident photons in the event A can be acquired. By using this method, in the photoelectric conversion device 100 having a plurality of pixels 12, it is possible to stably capture an image of the illumination of a light source that is turned on for a time shorter than the length of the exposure period and then turned off without being synchronized with the exposure period.

[0079] Moreover, according to the driving method of the present embodiment, continuous imaging with high time resolution can be performed. For example, both an event occurring between time t1 and time t3 and an event occurring between time t2 and time t6 can be detected without resetting the count values ​​of the count processing units 32A and 32B midway or outputting them to the outside of the pixel 12. In this case, the length of the period from time t1 to time t2 does not necessarily have to be T / 2, but may be any value greater than 0 and smaller than T. Moreover, the period from time t1 to time t3 (exposure period A) and the period from time t2 to time t6 (exposure period B) do not necessarily have to be equal in length, and may be different in length.

[0080] As described above, according to this embodiment, in a photoelectric conversion device having a function of counting incident photons, it is possible to realize high-performance exposure control.

[0081] [Third embodiment] A method for driving a photoelectric conversion device according to a third embodiment of the present invention will be described with reference to Fig. 8. Components similar to those of the photoelectric conversion devices according to the first and second embodiments are given the same reference numerals, and descriptions thereof will be omitted or simplified. In this embodiment, another method for driving the photoelectric conversion device according to the first embodiment will be described.

[0082] 8 is a timing chart showing an example of a method for driving the photoelectric conversion device according to this embodiment. The timing chart in FIG. 8 shows a pulse signal pEP, control signals pRES, pACT_A, pACT_B, and exposure periods A and B.

[0083] In this embodiment, the number of times that the count processing unit 32A becomes active during a predetermined period (e.g., a frame period) is a first number of times (one time), and the number of times that the count processing unit 32B becomes active during the predetermined period is a second number of times (eight times) that is greater than the first number of times. The period during which the count processing unit 32B is active and the period during which the count processing unit 32B is inactive are repeated periodically. In addition, the total length of the period during which the count processing unit 32A is active during a predetermined period (e.g., a frame period) is equal to the total length of the period during which the count processing unit 32B is active during the predetermined period.

[0084] In this embodiment, it is assumed that an event (event B) occurs in which a photon is incident on the pixel 12 between time t1 and time t4. In this case, if one of the counting processing units 32A and 32B is always active while the event B occurs, the number of incident photons can be recorded in its entirety. However, if the size of the counting processing units 32A and 32B is limited due to the area constraint of the pixel 12, or if the bandwidth of the data line 16 is limited, it is necessary to reduce the amount of data held by the counting processing units 32A and 32B. In such a case, it is effective to shorten the length of the period during which the counting processing units 32A and 32B count photons relative to the length T of the period during which the event B occurs, and reduce the amount of data held by the counting processing units 32A and 32B.

[0085] The control signal pACT_A becomes active at time t2 after 3T / 8 time has elapsed since time t1 when event B starts, and becomes inactive at time t3 after T / 4 time has elapsed since time t2. That is, the period from time t2 to time t3 is exposure period A.

[0086] On the other hand, the control signal pACT_B periodically repeats active and inactive states so that the total active time during the period from time t1 to time t4 is T / 4. During the period from time t1 to time t4, the period during which the control signal pACT_B is active is the exposure period B.

[0087] In other words, the total length of the period during which the control signals pACT_A and pACT_B are active within the period (length T) from time t1 to time t4 is both T / 4, but the timing at which they become active is different.

[0088] By setting the exposure periods A and B in this way, the counting processing unit 32A can densely detect the incidence of photons in a period near the center of the period during which the event B occurs. B In the case of the counting processing unit 32A, it is not possible to detect the incidence of photons densely, but there are timings at which the incidence of photons can be detected over the entire period of the event B. Therefore, it is possible to obtain different information according to differences in the timings at which the incidence of photons is detected by the counting processing unit 32A and the counting processing unit 32B.

[0089] Therefore, by using the driving method of this embodiment, in a photoelectric conversion device 100 having a plurality of pixels 12, it is possible to record information on events having a long duration while suppressing the amount of data held in the count processing units 32A and 32B.

[0090] As described above, according to this embodiment, in a photoelectric conversion device having a function of counting incident photons, it is possible to realize high-performance exposure control.

[0091] [Fourth embodiment] A method for driving a photoelectric conversion device according to a fourth embodiment of the present invention will be described with reference to Fig. 9 and Fig. 10. The same components as those in the photoelectric conversion devices according to the first to third embodiments are given the same reference numerals, and the description will be omitted or simplified. In this embodiment, another method for driving the photoelectric conversion device according to the first embodiment will be described.

[0092] 9 is a timing chart showing an example of a method for driving the photoelectric conversion device according to the present embodiment. The timing chart in FIG. 9 shows a pulse signal pEP, control signals pRES, pACT_A, and pACT_B, and exposure periods A and B.

[0093] In this embodiment, it is assumed that an event (event C) occurs in which a photon is incident on the pixel 12 between time t1 and time t2.

[0094] The control signal pACT_A becomes active at time t1 when the event C starts, and becomes inactive at time t2 when the event C ends. That is, the period from time t1 to time t2 is the exposure period A.

[0095] On the other hand, the control signal pACT_B is a signal obtained by pulse density modulating a sine wave, and is supplied to the counting processing unit 32B during the period from time t1 to time t2. During the period from time t1 to time t2, the period during which the control signal pACT_B is active corresponds to the exposure period B.

[0096] The count value held by the counter 34 of the counting processing unit 32A at time t2 corresponds to the number of photons incident on the pixel 12 between time t1 and time t2. On the other hand, the count value held by the counter 34 of the counting processing unit 32B at time t2 corresponds to the number of photons incident on the pixel 12 between time t1 and time t2 digitally modulated by the exposure time. Modulating the number of incident photons by the exposure time has the effect of retaining information that would be lost if the number of incident photons were simply integrated over time.

[0097] According to the driving method of this embodiment, in a photoelectric conversion device 100 having a plurality of pixels 12, an image with sufficient exposure time can be obtained from the counting processing unit 32A of each pixel 12, and an image with a modulated exposure time can be obtained from the counting processing unit 32B of each pixel 12. By combining these two images in a signal processing unit at a subsequent stage, an image with low noise and from which motion blur and shaking have been removed can be obtained.

[0098] In this embodiment, a signal obtained by pulse density modulating a sine wave is applied as the control signal pACT_B, but the control signal pACT_B may be another pulse group. By changing the pulse group constituting the control signal pACT_B, the modulation method can be changed.

[0099] In addition, in the present embodiment, the pixel signal processing unit 30 of each pixel 12 has two count processing units 32A and 32B. However, the number of count processing units 32 of the pixel signal processing unit 30 is not limited to two, and may be three or more. Each pixel 12 may be configured to include three count processing units 32A, 32B, and 32C, as shown in FIG. 10, for example. By configuring the pixel signal processing unit 30 in this way, a photoelectric conversion device 100 having a plurality of pixels 12 can obtain a plurality of images in which the exposure time is modulated by a plurality of sine waves with different phases. By synthesizing these images in a signal processing unit at a later stage, information such as the optical flow of the subject can be obtained.

[0100] As described above, according to this embodiment, in a photoelectric conversion device having a function of counting incident photons, it is possible to realize high-performance exposure control.

[0101] [Fifth embodiment] A photoelectric conversion device and a driving method thereof according to a fifth embodiment of the present invention will be described with reference to Figs. 11 and 12. Components similar to those of the photoelectric conversion devices according to the first to fourth embodiments are given the same reference numerals, and descriptions thereof will be omitted or simplified. Fig. 11 is a block diagram showing an example of the configuration of a pixel of the photoelectric conversion device according to this embodiment. Fig. 12 is a timing chart showing an example of a driving method of the photoelectric conversion device according to this embodiment.

[0102] In the photoelectric conversion device according to the present embodiment, as shown in FIG. 11, the pixel signal processing unit 30 of the pixel 12 further includes a control signal selection circuit 36. The control line 14 further includes a signal line to which a control signal pACT_C is supplied and a signal line to which a control signal pACT_D is supplied. The four input nodes of the control signal selection circuit 36 ​​are respectively connected to a signal line to which a control signal pACT_A is supplied, a signal line to which a control signal pACT_B is supplied, a signal line to which a control signal pACT_C is supplied, and a signal line to which a control signal pACT_D is supplied. The two output nodes of the control signal selection circuit 36 ​​are respectively connected to one control node of the count processing unit 32A and one control node of the count processing unit 32B. The other points are the same as those of the photoelectric conversion device according to the first embodiment.

[0103] The control signal selection circuit 36 ​​has a function of supplying a control signal selected from the control signals pACT_A, pACT_B, pACT_C, and pACT_D to the count processing unit 32A and the count processing unit 32B. The combination of control signals supplied to the count processing unit 32A and the count processing unit 32B may be the same or different for all the pixels 12 constituting the pixel unit 10. Also, the circuit may be configured to supply a randomly selected control signal to each of the multiple pixels 12, on the condition that the same control signal is not input to the count processing unit 32A and the count processing unit 32B of one pixel 12.

[0104] The active and inactive periods in the count processing sections 32A and 32B are defined by the control signals selected by the control signal selection circuit 36, respectively.

[0105] Next, a method for driving the photoelectric conversion device according to the present embodiment will be described with reference to Fig. 12. The timing chart of Fig. 12 shows a pulse signal pEP, control signals pRES, pSEL, pACT_A, pACT_B, pACT_C, and pACT_D, exposure periods A and B of the pixel 12A, and an exposure period A, 3B. The pixel 12A and the pixel 12B are any of the pixels 12 constituting the pixel section 10.

[0106] Here, the first time when any of the control signals pACT_A, pACT_B, pACT_C, and pACT_D changes from inactive to active after the control signal pRES changes from active to inactive is defined as a first time. The last time when any of the control signals pACT_A, pACT_B, pACT_C, and pACT_D changes from active to inactive after the first time and before the control signal pRES next changes from inactive to active is defined as a second time. The period between the first time and the second time is called a frame.

[0107] 12, the first time which is the start timing of one frame (first frame) is time t1, and the second time which is the end timing of the frame is time t2. The first time which is the start timing of the next frame (second frame) is time t5, and the second time which is the end timing of the frame is time t6.

[0108] As an example, the control signal pACT_A is assumed to be a control signal that is always active during a frame period. The control signals pACT_B, pACT_C, and pACT_D are assumed to be control signals that alternate between active and inactive during a frame period. The control signal pACT_B is assumed to be a control signal that becomes active twice during a frame period. The control signals pACT_C and pACT_D are assumed to be control signals that become active four times during a frame period. The control signals pACT_C and pACT_D have different phases from each other.

[0109] First, at time t0, the control signal pRES becomes active (high level), and the count value of the counter 34 of the count processing unit 32A and the count value of the counter 34 of the count processing unit 32B of each pixel 12 are reset to zero.

[0110] The control signal pRES NonAt time t1 after becoming active (Low level), the first frame starts. In the pixel 12A, the control signal selection circuit 36 ​​selects the control signal pACT_A as the control signal to be supplied to the count processing unit 32A, and selects the control signal pACT_B as the control signal to be supplied to the count processing unit 32B. In the pixel 12B, the control signal selection circuit 36 ​​selects the control signal pACT_A as the control signal to be supplied to the count processing unit 32A, and selects the control signal pACT_C as the control signal to be supplied to the count processing unit 32B.

[0111] As a result, the counting processing unit 32A of pixel 12A counts the number of incident photons during exposure period A corresponding to the control signal pACT_A. Also, the counting processing unit 32B of pixel 12A counts the number of incident photons during exposure period B corresponding to the control signal pACT_B. Similarly, the counting processing unit 32A of pixel 12B counts the number of incident photons during exposure period A corresponding to the control signal pACT_A. Also, the counting processing unit 32B of pixel 12B counts the number of incident photons during exposure period B corresponding to the control signal pACT_C. The counting process in each pixel 12 is performed until time t2.

[0112] In this way, in the first frame, the set of control signals pACT supplied to the count processing unit 32A and the count processing unit 32B of the pixel 12A is different from the set of control signals pACT supplied to the count processing unit 32A and the count processing unit 32B of the pixel 12B.

[0113] At the following time t3, the control signal pSEL becomes active (high level), and the count values ​​held by the counters 34 of the count processing units 32A and 32B of each pixel 12 are output to the readout circuit unit 50 via the data line 16.

[0114] At the following time t4, the control signal pRES becomes active, and the count value of the counter 34 in the count processing unit 32A and the count value of the counter 34 in the count processing unit 32B of each pixel 12 are reset to zero.

[0115] The control signal pRES Non At time t5 after becoming active, the second frame starts. In the pixel 12A, the control signal selection circuit 36 ​​selects the control signal pACT_A as the control signal to be supplied to the count processing unit 32A, and selects the control signal pACT_C as the control signal to be supplied to the count processing unit 32B. In the pixel 12B, the control signal selection circuit 36 ​​selects the control signal pACT_A as the control signal to be supplied to the count processing unit 32A, and selects the control signal pACT_D as the control signal to be supplied to the count processing unit 32B.

[0116] As a result, the counting processing unit 32A of pixel 12A counts the number of incident photons during exposure period A corresponding to the control signal pACT_A. Also, the counting processing unit 32B of pixel 12A counts the number of incident photons during exposure period B corresponding to the control signal pACT_C. Similarly, the counting processing unit 32A of pixel 12B counts the number of incident photons during exposure period A corresponding to the control signal pACT_A. Also, the counting processing unit 32B of pixel 12B counts the number of incident photons during exposure period B corresponding to the control signal pACT_D. The counting process in each pixel 12 is performed until time t6.

[0117] In this way, in the second frame, the set of control signals pACT supplied to the count processing unit 32A and count processing unit 32B of the pixel 12A is different from the set of control signals pACT supplied to the count processing unit 32A and count processing unit 32B of the pixel 12B. Also, in the first frame, the set of control signals pACT supplied to the count processing unit 32A and count processing unit 32B of the pixel 12A is different from the set of control signals pACT supplied to the count processing unit 32A and count processing unit 32B of the pixel 12A in the second frame. Similarly, the set of control signals pACT supplied to the count processing unit 32A and count processing unit 32B of the pixel 12B in the first frame is different from the set of control signals pACT supplied to the count processing unit 32A and count processing unit 32B of the pixel 12B in the second frame.

[0118] Thereafter, in the same manner as in the first frame, the count values ​​held by the counters 34 of the count processing units 32A and 32B of each pixel 12 are output to the readout circuit unit 50 via the data line 16.

[0119] According to the driving method of the present embodiment, it is possible to obtain images in which the pattern of the exposure period is changed for each pixel 12 or for each frame in a photoelectric conversion device 100 having a plurality of pixels 12. By synthesizing these images in a downstream signal processing unit, it is possible to reconstruct an image with high temporal and spatial resolution.

[0120] As described above, according to this embodiment, in a photoelectric conversion device having a function of counting incident photons, it is possible to realize high-performance exposure control.

[0121] [Sixth embodiment] An imaging system according to a sixth embodiment of the present invention will be described with reference to Fig. 13. Fig. 13 is a block diagram showing a schematic configuration of the imaging system according to this embodiment.

[0122] The photoelectric conversion device 100 described in the first to fifth embodiments is applicable to various imaging systems. Examples of applicable imaging systems include digital still cameras, digital camcorders, security cameras, copiers, fax machines, mobile phones, car-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 imaging system. FIG. 13 illustrates a block diagram of a digital still camera as an example of these.

[0123] 13 includes an imaging device 201, a lens 202 that forms an optical image of a subject on the imaging 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 imaging device 201. The imaging device 201 is the photoelectric conversion device 100 described in any one of the first to fifth embodiments, and converts the optical image formed by the lens 202 into image data.

[0124] The imaging system 200 also includes a signal processing unit 208 that processes an output signal output from the imaging device 201. The signal processing unit 208 generates image data from a digital signal output from the imaging device 201. The signal processing unit 208 also performs various corrections and compression as necessary to output image data. The imaging 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 a photoelectric conversion unit of the imaging device 201 is formed, or may be formed in a semiconductor substrate different from the semiconductor layer in which the photoelectric conversion unit of the imaging device 201 is formed. The signal processing unit 208 may also be formed in the same semiconductor substrate as the imaging device 201.

[0125] The imaging 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 imaging 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 on the recording medium 214. The recording medium 214 may be built into the imaging system 200, or may be removable.

[0126] Furthermore, the imaging system 200 has 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 imaging device 201 and the signal processing unit 208. Here, the timing signals and the like may be input from outside, and the imaging system 200 only needs to have at least the imaging device 201 and the signal processing unit 208 that processes the output signal output from the imaging device 201.

[0127] The imaging 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 imaging device 201, and outputs image data. The signal processing unit 208 generates an image using the imaging signal.

[0128] In this way, according to this embodiment, it is possible to realize an imaging system to which the photoelectric conversion device 100 according to the first to fifth embodiments is applied.

[0129] [Seventh embodiment] An imaging system and a moving object according to a seventh embodiment of the present invention will be described with reference to Fig. 14. Fig. 14 is a diagram showing the configuration of the imaging system and the moving object according to this embodiment.

[0130] FIG. 14(a) shows an example of an imaging system related to a vehicle-mounted camera. The imaging system 300 has an imaging device 310. The imaging device 310 is the photoelectric conversion device 100 described in any one of the first to fifth embodiments. The imaging system 300 includes an image processing unit 312 that performs image processing on a plurality of image data acquired by the imaging device 310, and an imaging equipment 310 The imaging system 300 has a parallax acquisition unit 314 that calculates parallax (phase difference of parallax images) from a plurality of image data acquired by the above. The imaging system 300 also has a distance acquisition unit 316 that calculates a distance to an object based on the calculated parallax, and a collision determination unit 318 that determines whether or not there is a possibility of collision based on the calculated distance. Here, the parallax acquisition unit 314 and the distance acquisition unit 316 are examples of distance information acquisition means that acquire distance information to an object. That is, the distance information is information on the parallax, the defocus amount, the distance to the object, and the like. The collision determination unit 318 may determine the possibility of collision using any of these pieces of distance information. The distance information acquisition means may be realized by dedicated hardware or may be realized by a software module. Also, it may be realized by an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated circuit), or the like, or may be realized by a combination of these.

[0131] The imaging system 300 is connected to a vehicle information acquisition device 320, and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The imaging system 300 is also connected to a control ECU 330, which is a control device that outputs a control signal to generate a braking force for the vehicle based on the judgment result of the collision judgment unit 318. The imaging system 300 is also connected to an alarm device 340 that issues an alarm to the driver based on the judgment result of the collision judgment unit 318. For example, when the judgment result of the collision judgment unit 318 indicates that there is a high possibility of a collision, the control ECU 330 performs vehicle control to avoid a collision and reduce damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 340 warns the user by sounding an alarm, displaying alarm information on the screen of a car navigation system, etc., and vibrating the seat belt or steering wheel.

[0132] In this embodiment, the surroundings of the vehicle, for example, the front or rear, are imaged by the imaging system 300. Fig. 14(b) shows an imaging system for imaging the area in front of the vehicle (imaging range 350). A vehicle information acquisition device 320 sends instructions to the imaging system 300 or imaging device 310. This configuration can further improve the accuracy of distance measurement.

[0133] Although the above describes an example of control to prevent collision with other vehicles, the present invention can also be applied to control of automatic driving by following other vehicles, control of automatic driving to prevent deviation from lanes, etc. Furthermore, the imaging system 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 present invention can be applied not only to moving bodies, but also to devices that use object recognition widely, such as intelligent transport systems (ITS).

[0134] [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.

[0135] In the first to fifth embodiments, the circuit configuration of the pixel 12 is not limited to that shown in FIG. 2. For example, in FIG. 2, the quench element 24 is connected to the cathode terminal side of the photon detection element 22, but the quench element 24 may be connected to the anode terminal side of the photon detection element 22. In this case, the waveform shaping unit 26 may be connected between the anode terminal of the photon detection element 22 and the quench element 24. In addition, a switch such as a transistor may be provided between the photon detection 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. In addition, a switch such as a transistor may be provided between the node to which the voltage VH is supplied and the quench element 24 and / or between the node to which the voltage VL is supplied and the photon detection element 22 to control the electrical connection state between them.

[0136] Moreover, the pixel signal processing unit 30 does not necessarily need to be provided in every pixel 12, and a plurality of pixels 12 may be configured to share one pixel signal processing unit 30. In this case, the single pixel signal processing unit 30 can be configured to sequentially process signals output from the photoelectric conversion units 20 of the plurality of pixels 12.

[0137] Furthermore, in the above first to fifth embodiments, a pixel signal processing unit 30 having count processing units 32A and 32B has been described, but the number of count processing units 32 that the pixel signal processing unit 30 has is not limited to two and may be three or more.

[0138] In addition, in the above first to fifth embodiments, the relationship between the signal levels of the control signals and the states of the counting processing unit 32, etc. is defined by positive logic in which each control signal is in an active state when it is at a high level, but it may also be defined by negative logic.

[0139] In the above fifth embodiment, an example was shown in which the control signals supplied to the count processing units 32A and 32B are selected from four types of control signals pACT_A, pACT_B, pACT_C, and pACT_D, but the number of types of control signals pACT is not limited to four. Also, the number of control signals pACT does not necessarily have to be the same in all the pixels 12 constituting the pixel unit 10.

[0140] Furthermore, the imaging systems shown in the sixth and seventh embodiments are examples of imaging systems to which the photoelectric conversion device of the present invention can be applied, and imaging systems to which the photoelectric conversion device of the present invention can be applied are not limited to the configurations shown in Figures 13 and 14.

[0141] 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.

[0142] 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. [Explanation of symbols]

[0143] 12…pixels 20...Photoelectric conversion section 22...Photon detector 24...Quench element 26…Waveform shaping section 30...Pixel signal processing unit 32A, 32B: Counting processing section 34…Counter 36...Control signal selection circuit 38...Selection circuit 40...Vertical scanning circuit section 80...Control pulse generating unit 100...Photoelectric conversion device 200,300...imaging system

Claims

1. A plurality of pixels each including a photoelectric conversion unit that outputs a pulse signal in response to incidence of a photon, and a signal processing unit that is connected to the photoelectric conversion unit and that counts the pulse signal; A control unit that controls the signal processing unit of each of the plurality of pixels, the signal processing unit of each of the plurality of pixels includes a first counting processing unit and a second counting processing unit connected in parallel, the control unit is configured to set active periods and inactive periods for each of the first counting processing unit and the second counting processing unit by a plurality of control signals supplied to the signal processing unit, a period during which the first counting processing unit is active includes a first period during which the second counting processing unit is active and a second period during which the second counting processing unit is inactive; A set of control signals supplied to the first counting processing unit and the second counting processing unit of a first pixel of the plurality of pixels is different from a set of control signals supplied to the first counting processing unit and the second counting processing unit of a second pixel of the plurality of pixels. A photoelectric conversion device comprising:

2. A plurality of pixels, each of which has a photoelectric conversion unit that outputs a pulse signal in response to incidence of a photon, and a signal processing unit that is connected to the photoelectric conversion unit and counts the pulse signal; A control unit that controls the signal processing units of the plurality of pixels, the signal processing unit of each of the plurality of pixels includes a first counting processing unit and a second counting processing unit connected in parallel, the control unit is configured to set active periods and inactive periods for each of the first counting processing unit and the second counting processing unit by a plurality of control signals supplied to the signal processing unit, a period during which the first counting processing unit is active includes a first period during which the second counting processing unit is active and a second period during which the second counting processing unit is inactive; At least one pixel among the plurality of pixels has a set of control signals supplied to the first counting processing unit and the second counting processing unit in one frame different from a set of control signals supplied to the first counting processing unit and the second counting processing unit in another frame. A photoelectric conversion device comprising:

3. The length of the period during which the second counting processing unit is continuously active is equal to the length of the first period.

3. The photoelectric conversion device according to claim 1 or 2.

4. The length of a period during which the first counting processing unit is continuously active is equal to the length of a period during which the second counting processing unit is continuously active.

3. The photoelectric conversion device according to claim 1 or 2.

5. the number of times that the first counting processing unit becomes active during a predetermined period is a first number of times; The number of times that the second counting processing unit becomes active during the predetermined period is a second number of times that is greater than the first number of times.

3. The photoelectric conversion device according to claim 1 or 2.

6. The first counting processing unit is activated once during a period including the center of the predetermined period.

6. The photoelectric conversion device according to claim 5.

7. During the predetermined period, a period in which the second counting processing unit is active and a period in which the second counting processing unit is inactive are repeated cyclically.

7. The photoelectric conversion device according to claim 5 or 6.

8. The total length of the period during which the first counting processing unit is active during the predetermined period is equal to the total length of the period during which the second counting processing unit is active during the predetermined period.

7. The photoelectric conversion device according to claim 5 or 6.

9. the signal processing unit further includes a third counting processing unit connected in parallel to the first counting processing unit and the second counting processing unit, The control unit is further configured to set an active period and an inactive period for the third counting processing unit, the third counting processing unit is activated a third number of times during the predetermined period, the third number of times being greater than the first number of times; At least a part of a period during which the second counting processing unit is active and a part of a period during which the third counting processing unit is active are different from each other.

8. The photoelectric conversion device according to claim 5, wherein the first and second electrodes are arranged in a first direction.

10. The predetermined period is a frame period.

8. The photoelectric conversion device according to claim 5, wherein the first and second electrodes are arranged in a first direction.

11. Each of the plurality of pixels further includes a control signal selection circuit that selects a control signal to be supplied to each of the first count processing unit and the second count processing unit from the plurality of control signals supplied from the control unit, The active and inactive periods of the first and second counting processing units are defined by the control signals selected by the control signal selection circuit.

11. The photoelectric conversion device according to claim 1,

12. The photoelectric conversion unit includes an avalanche photodiode, a quench element connected to the avalanche photodiode, and a waveform shaping unit having an input node connected to a connection node between the avalanche photodiode and the quench element.

12. The photoelectric conversion device according to claim 1,

13. A first substrate on which the photoelectric conversion unit is provided and a second substrate on which the signal processing unit is provided are laminated.

13. The photoelectric conversion device according to claim 1,

14. The signal processing unit includes the first counting processing unit and the second counting processing unit arranged in parallel.

14. The photoelectric conversion device according to claim 1,

15. the photoelectric conversion unit is electrically connected to the first counting processing unit, The photoelectric conversion unit is electrically connected to the second counting processing unit.

15. The photoelectric conversion device according to claim 1,

16. A method for driving a photoelectric conversion device having a plurality of pixels each having a photoelectric conversion unit that outputs a pulse signal in response to incidence of a photon, and a signal processing unit that is connected to the photoelectric conversion unit and counts the pulse signal, wherein the signal processing unit of each of the plurality of pixels has a first counting processing unit and a second counting processing unit connected in parallel, In each of the plurality of pixels, when an active period and an inactive period are set for each of the first counting processing unit and the second counting processing unit by a plurality of control signals supplied to the signal processing unit, In each of the plurality of pixels, a period during which the first counting processing unit is active includes a first period during which the second counting processing unit is active and a second period during which the second counting processing unit is inactive; A set of control signals supplied to the first counting processing unit and the second counting processing unit of a first pixel among the plurality of pixels is controlled to be different from a set of control signals supplied to the first counting processing unit and the second counting processing unit of a second pixel among the plurality of pixels. A method for driving a photoelectric conversion device comprising the steps of:

17. A method for driving a photoelectric conversion device having a plurality of pixels each having a photoelectric conversion unit that outputs a pulse signal in response to incidence of a photon, and a signal processing unit connected to the photoelectric conversion unit and counting the pulse signal, wherein the signal processing unit of each of the plurality of pixels has a first counting processing unit and a second counting processing unit connected in parallel, In each of the plurality of pixels, when an active period and an inactive period are set for each of the first counting processing unit and the second counting processing unit by a plurality of control signals supplied to the signal processing unit, In each of the plurality of pixels, a period during which the first counting processing unit is active includes a first period during which the second counting processing unit is active and a second period during which the second counting processing unit is inactive; In at least one pixel among the plurality of pixels, a set of control signals supplied to the first counting processing unit and the second counting processing unit in one frame is controlled so as to be different from a set of control signals supplied to the first counting processing unit and the second counting processing unit in another frame. A method for driving a photoelectric conversion device comprising the steps of:

18. The photoelectric conversion device according to any one of claims 1 to 15, a signal processing device that processes a signal output from the photoelectric conversion device; An imaging system comprising:

19. A mobile object, The photoelectric conversion device according to any one of claims 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:

Images