Imaging device, imaging system, and mobile object

Abstract

To improve the characteristics of an imaging device such as power consumption and readout speed in a photon counting type imaging device using an avalanche diode.SOLUTION: An imaging device includes a plurality of photoelectric conversion elements each including an avalanche diode and a counter. First selection means is provided corresponding to a first reading area 10a of a pixel area 10 of the photoelectric conversion element, and second selection means is provided corresponding to a second reading area 10b. In a first mode of the imaging device, a signal from the first reading area 10a is read, and the signal from the second reading area 10b is not read. In a second mode, a signal is read from the second reading area 10b.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an imaging device, an imaging system, and a moving object. [Background technology]

[0002] Photon-counting imaging devices using avalanche diodes are known. Patent Document 1 discloses an imaging device in which a plurality of photoelectric conversion elements, including avalanche diodes, are arranged in a matrix. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2015 / 0115131 Summary of the Invention [Problem to be solved by the invention]

[0004] The imaging device described in Patent Document 1 has room for improvement in characteristics such as power consumption and readout speed. In the imaging device described in Patent Document 1, if an attempt is made to constantly cause avalanche multiplication in each photoelectric conversion element to read out signals from the photoelectric conversion elements, power consumption increases and it takes time to finish reading out signals from all the photoelectric conversion elements. [Means for solving the problem]

[0005] An imaging device according to one aspect of the present invention includes a plurality of photoelectric conversion elements, each including an avalanche diode and a counter that counts a signal based on light incident on the avalanche diode, a first selection means provided corresponding to a first photoelectric conversion element of the plurality of photoelectric conversion elements, and a second selection means provided corresponding to a second photoelectric conversion element of the plurality of photoelectric conversion elements, wherein in a first mode, the first selection means controls the counter of the first photoelectric conversion element to a state in which a signal is read out, and the second selection means controls the counter of the second photoelectric conversion element to a state in which a signal is not read out, and in a second mode which is set for a period different from a period in which the first mode is set, In the first mode The second selection means controls the second photoelectric conversion element, which has been controlled to a state in which the signal is not read out, to a state in which the signal is read out; The first photoelectric conversion element, which has been controlled to a state in which the signal is read out in the first mode, is controlled to a state in which the signal is not read out by the first selection means. . [Effects of the Invention]

[0006] In a photon-counting imaging device using an avalanche diode, the characteristics of the imaging device, such as power consumption and readout speed, can be improved. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of an example of a photon-counting imaging device using an avalanche diode. [Figure 2] 1 is an equivalent circuit diagram of a photoelectric conversion element 11 according to a first embodiment. [Figure 3] 5A and 5B are diagrams illustrating an example of a photon detection operation of the photoelectric conversion element 11 according to the first embodiment. [Figure 4] FIG. 2 is a conceptual diagram of a readout region of the pixel region 10 according to the first embodiment. [Figure 5] FIG. 10 is a diagram showing an equivalent circuit diagram of a photoelectric conversion element 11 according to a second embodiment. [Figure 6] FIG. 10 is a diagram showing another example of an equivalent circuit diagram of the photoelectric conversion element 11 according to the second embodiment. [Figure 7]FIG. 10 is a diagram showing an equivalent circuit diagram of a photoelectric conversion element 11 according to a third embodiment. [Figure 8] FIG. 10 is a block diagram showing a part of a photoelectric conversion element 11 according to a third embodiment. [Figure 9] FIG. 10 is a schematic diagram illustrating the structure of an imaging device according to a fourth embodiment. [Figure 10] FIG. 10 is a block diagram showing the configuration of an imaging system according to a fifth embodiment. [Figure 11] FIG. 13 is a schematic diagram showing an example of the configuration of an imaging system and a moving body according to a sixth embodiment. [Figure 12] FIG. 13 is a flowchart showing the operation of the imaging system according to the seventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] (First embodiment) An imaging device according to a first embodiment will be described with reference to Figs. 1 to 4. Fig. 1 is a block diagram showing a schematic configuration of an imaging device according to this embodiment. Fig. 2 is a circuit diagram showing an example configuration of a photoelectric conversion element 11 of an imaging device according to this embodiment. In the following, a case where one photoelectric conversion element constitutes one pixel will be described, but cases where multiple photoelectric conversion elements constitute one pixel are also included in the present invention.

[0009] 1, the imaging device includes a pixel region 10, a vertical scanning circuit 20, a horizontal scanning circuit 30, an output circuit 40, and a control circuit 50. The pixel region 10 is provided with a plurality of photoelectric conversion elements 11 arranged in a matrix across a plurality of rows and a plurality of columns. Note that it is not necessary for all components of the photoelectric conversion elements 11 to be arranged across a plurality of rows and a plurality of columns. It is sufficient that at least the avalanche diodes included in the photoelectric conversion elements 11 are arranged across a plurality of rows and a plurality of columns.

[0010] A control line 12 is arranged in each row of the pixel region 10, extending in a first direction (the horizontal direction in FIG. 1 ). The control line 12 is connected to each of the photoelectric conversion elements 11 arranged in the first direction, and serves as a signal line common to these photoelectric conversion elements 11. The first direction in which the control lines 12 extend may be referred to as the row direction or the horizontal direction. Each of the control lines 12 may include a plurality of signal lines for supplying a plurality of types of control signals to the photoelectric conversion elements 11.

[0011] Furthermore, in the pixel region 10, a control line VSEL is arranged, extending in the first direction and connected to the selection means included in the photoelectric conversion element 11. In Figures 1 and 2, each photoelectric conversion element 11 includes the selection means, and therefore a control line VSEL is arranged for each row. However, this is not limiting, and in cases where the selection means is shared by multiple photoelectric conversion elements, the control line VSEL may be arranged corresponding to the photoelectric conversion element 11 to which the selection means is arranged.

[0012] In each column of the pixel region 10, a data line 13 is arranged, extending in a second direction (vertical direction in FIG. 1 ) intersecting the first direction. The data line 13 is connected to each of the photoelectric conversion elements 11 arranged in the second direction, and serves as a signal line common to these photoelectric conversion elements 11. The second direction in which the data lines 13 extend may be referred to as the column direction or vertical direction. Each of the data lines 13 may include a plurality of signal lines for transferring digital signals output from the photoelectric conversion elements 11 bit by bit.

[0013] Furthermore, in the pixel region 10, HSELs are arranged extending in the second direction and connected to the selection means included in the photoelectric conversion elements 11. In Figures 1 and 2, each photoelectric conversion element 11 includes the selection means, and therefore a control line HSEL is arranged for each column. However, if the selection means is shared by a plurality of photoelectric conversion elements, the control line HSEL may be arranged corresponding to the photoelectric conversion element 11 in which the selection means is arranged.

[0014] The control lines 12 and control lines VSEL of each row are connected to a vertical scanning circuit 20. The vertical scanning circuit 20 is a circuit section that supplies control signals for reading out signals from the photoelectric conversion elements 11 to the photoelectric conversion elements 11 via the control lines 12.

[0015] The control line 12 is a control line that controls, for example, a signal processing circuit SP included in the photoelectric conversion element 11. The vertical scanning circuit 20 sequentially scans the photoelectric conversion elements 11 in the pixel region 10 row by row, and outputs a signal from each photoelectric conversion element 11 to the output circuit 40 via the data line 13. The control line VSEL is a line that controls a selection means included in the photoelectric conversion element 11.

[0016] The data line 13 of each column is connected to a horizontal scanning circuit 30. The control line HSEL of each column is also connected to the horizontal scanning circuit 30. The horizontal scanning circuit 30 is a circuit section that selects signals of the photoelectric conversion elements 11 of each column that are output row by row from the pixel region 10 and sequentially outputs the signals to an output circuit 40. The horizontal scanning circuit 30 has a plurality of holding units corresponding to the plurality of columns of the pixel region 10, and holds the signals of the photoelectric conversion elements 11 of each column that are output row by row from the pixel region 10 in the holding unit of the corresponding column. The horizontal scanning circuit 30 sequentially scans the holding units of each column and sequentially outputs the signals from the photoelectric conversion elements held in the holding units of each column to the output circuit 40.

[0017] The output circuit 40 has a transmitter circuit 41, and is a circuit unit that outputs signals from the photoelectric conversion element 11, which are output from the horizontal scanning circuit 30, to the outside of the imaging device. The transmitter circuit 41 can be configured, for example, by a SerDes (SERializer / DESerializer) transmission circuit. The SerDes transmission circuit is, for example, an LVDS (Low Voltage Differential Signaling) circuit or an SLVS (Scalable Low Voltage Signaling) circuit. Note that the external interface circuit that configures the output circuit 40 is not particularly limited.

[0018] The control circuit 50 is a circuit section for supplying control signals that control the operations and timings of the vertical scanning circuit 20 and the horizontal scanning circuit 30. Note that at least some of the control signals that control the operations and timings of the vertical scanning circuit 20 and the horizontal scanning circuit 30 may be supplied from outside the imaging device.

[0019] As shown in FIG. 2, each photoelectric conversion element 11 includes an avalanche diode D, a quench element Rq, a waveform shaping unit INV, and a signal processing circuit SP including a counter. The avalanche diode D may be a photodiode that multiplies the charge generated by incident photons through avalanche breakdown. Specifically, such photodiodes are APDs (Avalanche Photo Diodes) and SPADs (Single Photon Avalanche Diodes). SPADs generate avalanche multiplication in Geiger mode, where they are operated at a bias voltage higher than the breakdown voltage. APDs generate avalanche multiplication in linear mode, where they are operated at a bias voltage slightly higher than the breakdown voltage. The following description will be given using a SPAD as an example. The avalanche diode D is connected to a counter included in the signal processing circuit SP, and the counter counts a signal based on the photons incident on the avalanche diode D. The quench element Rq may be, for example, a P-type MOS transistor. The waveform shaping unit INV can be configured with, for example, an inverter circuit, and is connected to the counter.

[0020] The anode of the photodiode that constitutes the avalanche diode D is supplied with a voltage Vss, and the cathode is connected to one end of the quench element Rq and the input terminal of the waveform shaping unit INV. The other end of the quench element Rq is supplied with a voltage Vdd. The output terminal of the waveform shaping unit INV is connected to the input terminal of the counter of the signal processing circuit SP. The output terminal of the signal processing circuit SP is connected to the data line 13.

[0021] The voltages Vss and Vdd are set so that a reverse bias voltage sufficient to operate the avalanche diode D in Geiger mode can be applied to the avalanche diode D. In one example, a negative high voltage is applied as the voltage Vss, and a positive voltage approximately equal to the power supply voltage is applied as the voltage Vdd. In this embodiment, the photodiode constituting the avalanche diode D is used as a single-photon avalanche diode (SPAD) capable of operating in Geiger mode. In this specification, a state in which a reverse bias voltage capable of avalanche multiplication is applied is also referred to as an active state, and a state in which a reverse bias voltage capable of avalanche multiplication is not applied is also referred to as an inactive state.

[0022] A reverse bias voltage equivalent to the potential difference between voltages Vdd and Vss is applied to the avalanche diode D. This reverse bias voltage is higher than the breakdown voltage of the avalanche diode D and is sufficient to cause avalanche multiplication (Geiger mode). However, when no photons are incident on the avalanche diode D, there are no seed carriers, so avalanche multiplication does not occur and no current flows through the avalanche diode D (standby state).

[0023] When a photon strikes avalanche diode D in standby mode, it is excited by the incident photon and generates carriers within the diode. The carriers generated within the diode D are accelerated by the high electric field within the diode, causing avalanche multiplication and generating a large avalanche current (Geiger mode operation). This avalanche current flows through the quench element Rq. The voltage drop caused by this current reduces the potential at the cathode of the diode D, reducing the potential difference between the terminals of the diode D. This causes the diode D to exit Geiger mode (non-Geiger mode), and avalanche multiplication stops. The carriers on the cathode side of the diode D are gradually drained via the quench element Rq connected as a load. In other words, the potential Vdd is supplied to the cathode of the diode D via the quench element Rq, and the potential supplied to the cathode of the diode D returns to Vdd. As a result, the potential difference between the terminals of the avalanche diode D returns to the initial voltage, that is, the avalanche diode D returns to the Geiger mode or standby state.

[0024] This series of operations will be explained using Fig. 3. Fig. 3 is a timing chart showing a method for driving an imaging device according to this embodiment. The timing chart in Fig. 3 shows the timing at which photons are incident on the avalanche diode D, and the signal Sig_A input to the waveform shaping unit INV. The timing chart in Fig. 3 also shows the signal Sig_D, which is obtained by shaping the waveform of the signal Sig_A into a pulse-like signal and output to the signal processing circuit SP, and the count value (DOUT) of the signal Sig_D by the signal processing circuit SP.

[0025] In the initial state, no photons are incident on the avalanche diode D, the signal Sig_A is at a predetermined potential indicating a standby state, the signal Sig_D is at a low level, and the count value of the signal processing circuit SP is 0.

[0026] When a photon is incident on avalanche diode D, avalanche multiplication occurs using carriers excited by the incident photon as seeds, and an avalanche current flows, causing the potential of signal Sig_A to decrease. When signal Sig_A falls below a predetermined threshold, the potential of signal Sig_D transitions from low to high.

[0027] Thereafter, the potential of the signal Sig_A gradually increases via the quench element Rq. When the signal Sig_A exceeds a predetermined threshold, the potential of the signal Sig_D transitions from high to low.

[0028] The counter included in the signal processing circuit SP increments the count value by 1 in accordance with the number of pulses of the signal Sig_D.

[0029] As described above, the waveform shaping unit INV generates pulses based on the presence or absence of avalanche current generated by avalanche multiplication. The counter included in the signal processing circuit SP counts the number of pulses based on the presence or absence of avalanche current. In addition to the counting operation, the signal processing circuit SP may also perform predetermined signal processing on the signal Sig_D.

[0030] The signal processing circuit SP outputs an output signal DOUT, which is a signal after signal processing, to a data line 13 in response to a control signal 12 output from the vertical scanning circuit 20 and a control signal from a selection means 14, which will be described later.

[0031] In this embodiment, a selection means 14 switches whether or not a signal is output from the signal processing circuit SP. The control lines 12, HSEL, and VSEL are input to the signal processing circuit SP via the selection means 14. When the control lines 12, HSEL, and VSEL are all active, a signal is read from the signal processing circuit SP, and when at least one of them is inactive, a signal is not read from the signal processing circuit SP. The selection means 14 can be realized by a combinational circuit such as an AND circuit as shown in FIG. 2, but the realization method is not limited to this.

[0032] In this embodiment as well, it is possible to read out signals only from a desired region.

[0033] In Figure 2, the signal processing circuit SP is switched between active and inactive states. Specifically, a switch is placed at a node between the signal processing circuit SP and the data line 13 to control the reading of signals from the signal processing circuit SP to the data line. In this specification, an active signal processing circuit SP refers to a state in which a signal is read out from the signal processing circuit SP. Also, an inactive signal processing circuit SP refers to a state in which a signal is not read out from the signal processing circuit SP.

[0034] Fig. 4 is a diagram showing an image of a readout region 10a and a non-readout region 10b of the pixel region 10. Fig. 4 shows the region 10a that reads out signals from photoelectric conversion elements (first photoelectric conversion elements) and the region 10b that does not read out signals from photoelectric conversion elements (second photoelectric conversion elements). The region 10b shown in Fig. 4 may not always output signals, or may not output signals in a first mode and output signals in a second mode that is set for a period different from the period in which the first mode is set.

[0035] In this embodiment, photoelectric conversion is performed in the regions 10a and 10b. That is, light is also irradiated to the region 10b. In this embodiment, photoelectric conversion is also performed in the region 10b, but the region 10b is not read out from the region 10b to improve the signal readout speed. In other words, although the region 10b is not a defective pixel, whether or not to read out the signal is controlled depending on the mode. Here, the mode refers to, for example, the period during which the vertical scanning circuit 20 vertically scans the multiple photoelectric conversion elements arranged in the pixel region 10a. In FIG. 2, the period from top to bottom in the first vertical scan until the end of scanning from top to bottom and then back to top is the first vertical scan period. The period from top to bottom after scanning from top to bottom is the second vertical scan period. This will be explained using FIG. 4(a). In this explanation, it is assumed that signals are read out from the region 10a in both the first mode and the second mode. The first vertical scan period refers to the period from scanning the photoelectric conversion elements located at the top end of the region 10a until scanning the photoelectric conversion elements located at the bottom end of the region 10a until the end of scanning the photoelectric conversion elements located at the bottom end of the region 10a. The second vertical scan refers to the period from scanning the photoelectric conversion elements located at the top of the region 10a to completing scanning the photoelectric conversion elements located at the bottom of the region 10a. In this embodiment, if reading is not performed for all the photoelectric conversion elements arranged in the row or column direction, vertical or horizontal scanning is not performed either. This allows the signal readout time to be shorter than when signals are read out from all the photoelectric conversion elements.

[0036] For example, in FIG. 4(a), thinning readout is performed to read out only signals from an m×n pixel region (m and n are natural numbers) in the pixel region 10. Regions 10a and 10b can be controlled as shown in FIGS. 4(b) to 4(d). FIG. 4(b) shows an example of row thinning readout. Specifically, signals are read out from photoelectric conversion elements arranged in a predetermined number of rows, while signals from photoelectric conversion elements arranged in other rows are not read out. FIG. 4(c) shows an example of column thinning readout. Specifically, signals are read out from photoelectric conversion elements arranged in a predetermined number of columns, while signals from photoelectric conversion elements arranged in other columns are not read out. FIG. 4(d) shows an example of row / column thinning readout. Specifically, signals are read out from photoelectric conversion elements arranged in a predetermined position, while signals are not read out from rows or columns. Thinning may be performed pixel by pixel, rather than matrix by matrix as shown in FIGS. 4(a) to 4(d). For example, as shown in FIG. 6, the selection means 14 includes a memory MEM, and by using the memory MEM, it is possible to perform ROI (Region of Interest) readout as shown in FIG. 4(e). Specifically, a signal indicating whether to perform readout or not is written to the memory MEM included in each photoelectric conversion element via a signal line WRITE. Based on this signal, it is possible to control whether to supply a potential to turn on or off the switch. In this way, designers may implement the selection means 14 in various configurations to achieve the effects of the present invention.

[0037] The region 10a from which signals are read out may be different between the first mode and the second mode. For example, in the first mode, signals are read out from the photoelectric conversion elements arranged in the region 10a shown in FIGS. 4(a) to 4(d). In the second mode, signals may be read out from the photoelectric conversion elements arranged in the region 10b shown in FIGS. 4(a) to 4(d), and signals may also be read out from the photoelectric conversion elements arranged in the region 10a. In addition, in the first mode, signals may be read out from the region 10a but not from the region 10b, and in the second mode, signals may be read out from both the region 10a and the region 10b. In other words, in the second mode, the selection means (second selection means) controls the photoelectric conversion elements that have been controlled to a state in which signals are not read out to a state in which signals are read out. Then, the photoelectric conversion elements that have been controlled to a state in which signals are read out are maintained in a state in which signals are read out. This type of readout method is effective, for example, when the imaging device captures images in a first mode until an object such as a suspicious person appears in the imaging area, and then switches from the first mode to the second mode once the object appears in the imaging area. Priority is given to the signal readout speed until the object appears, and priority is given to image quality after the object appears. As described above, it is possible to switch modes depending on the purpose of imaging.

[0038] 4(e), when capturing an image of a moving object, it is possible to switch whether or not to read out a signal depending on the position of the moving object. Specifically, in a first mode in which the moving object is located in a first portion of the region to be captured, only the first portion is read out, and in a second mode in which the moving object is located in a second portion different from the first portion, only the second portion is read out.

[0039] 2, the selection means 14 is connected to the signal processing circuit SP, but it may also be connected to the input of the waveform shaping unit INV or to a node between the waveform shaping unit INV and the signal processing circuit SP. Even in this case, the counter included in the signal processing circuit SP will no longer count, and it is possible to prevent the signal from being output from the photoelectric conversion element.

[0040] In this embodiment, the signal processing circuit SP of the photoelectric conversion elements included in region 10a is controlled to be active, and therefore a signal is output from the signal processing circuit SP. The signal processing circuit SP of the photoelectric conversion elements included in region 10b is controlled to be inactive, and therefore no signal is output from the signal processing circuit SP. In this way, according to this embodiment, it is possible to select photoelectric conversion elements 11 in region 10b that do not require reading. This allows the signal readout speed of the imaging device to be shorter than when all photoelectric conversion elements are readout.

[0041] (Second embodiment) A photoelectric conversion element 11 according to the second embodiment will be described with reference to Fig. 5. The photoelectric conversion element 11 according to the second embodiment differs from the first embodiment in that the selection means 14 is connected to the quench element Rq. Other than the matters described below, the second embodiment is the same as the first embodiment.

[0042] In this embodiment, the quench element Rq is configured as a MOS transistor, and the gate terminal of the quench element Rq is connected to the output terminal of a selection means 14 that controls the on / off of the quench element Rq. The selection means 14 receives inputs from a control line VSEL arranged for each row and a control line HSEL arranged for each column. In this embodiment, the avalanche diode D is switched between active and inactive by controlling the on / off of the quench element Rq using the signals VSEL and HSEL. When both the signals VSEL and HSEL are active, the selection means 14 controls the quench element Rq so that the avalanche diode D is active. In other words, the selection means 14 controls the quench element Rq so that a reverse bias voltage that can cause avalanche multiplication in the avalanche diode D is applied. In FIG. 5, since the quench element Rq is configured as a PMOS transistor, for example, a ground voltage is applied to the gate terminal of the PMOS transistor. Furthermore, when at least one of the signals VSEL and HSEL is inactive, the selection means 14 controls the quench element Rq so that the avalanche diode D is inactive. In other words, it controls the avalanche diode D to a potential at which avalanche multiplication does not occur. In FIG. 4, a potential higher than Vdd, for example, is applied to the gate terminal to turn off the PMOS transistor. As a result, no potential is supplied to the cathode Vdd, and avalanche multiplication does not occur in the avalanche diode D.

[0043] When the avalanche diode D is active, an avalanche current flows every time a photon is incident, but when the avalanche diode D is inactive, no avalanche current is generated even when a photon is incident. Therefore, when the avalanche diode D is inactive, the counter in the signal processing circuit SP cannot count the signal, and no signal is read out from the photoelectric conversion element 11.

[0044] 5 may be replaced with the selection circuit 14 shown in FIG. 6. In this case, the signal line WRITE is required, so the number of signal lines increases compared to the first embodiment. In this way, the selection means 14 may be configured with a combinational circuit and a memory MEM, and the activation / deactivation of the avalanche diode D may be controlled based on the signal input to the memory MEM.

[0045] In this embodiment, the photoelectric conversion elements located in the region 10b may be scanned. Even if scanning is performed, the counter value will be 0 because no avalanche current is generated. Note that if all of the photoelectric conversion elements located in the row or column direction among the photoelectric conversion elements located in the region 10b are photoelectric conversion elements that do not read out signals, it is preferable not to perform vertical or horizontal scanning. In other words, it is preferable to perform thinning-out scanning. This can improve the signal readout speed.

[0046] If the avalanche diodes D of all the photoelectric conversion elements in the pixel region 10 are active, an avalanche current flows in all the photoelectric conversion elements every time a photon is incident, and counting is performed. In other words, unnecessary power consumption occurs in the photoelectric conversion elements 11 in the region 10b where no photons are to be read. On the other hand, according to this embodiment, the avalanche diodes D of the photoelectric conversion elements 11 in the region 10b are inactive, so even if a photon is incident, no avalanche current is generated and no counting is performed. Therefore, unnecessary power consumption does not occur in the photoelectric conversion elements 11 in the region 10b, and power consumption can be reduced compared to when signals are read out from all the photoelectric conversion elements. In other words, according to this embodiment, in addition to the effects described in the first embodiment, the power consumption of the imaging device can be reduced. Furthermore, when vertical scanning is not performed, the signal readout speed can also be improved.

[0047] (Third embodiment) A photoelectric conversion element 11 according to the third embodiment will be described with reference to FIG.

[0048] In this embodiment, switching means 15 is connected to a node different from the anode of the avalanche diode D or the node to which the avalanche diode D of the quench element Rq is connected. The present embodiment differs from the second embodiment in that selection means 14 controls switching means 15. The present embodiment is similar to the second embodiment except for the matters described below.

[0049] 7, when both the signals VSEL and HSEL are active, the selection means 14 controls the switching means 15 so that the quench element Rq is connected to the voltage Vdd, and at this time the avalanche diode D is active. When at least one of the signals VSEL and HSEL is inactive, the selection means 14 controls the switching means 15 so that the quench element Rq is connected to the voltage VL, and at this time the avalanche diode D is inactive. At this time, the voltage VL is set to an arbitrary voltage that does not cause avalanche multiplication in the avalanche diode D.

[0050] Similarly, in Fig. 8, switching means 15 is provided at the anode of avalanche diode D. When the avalanche diode D is controlled to be active, the anode is connected to voltage Vss. When the avalanche diode D is controlled to be inactive, the anode is connected to voltage VH. In this case, voltage VH is set to an arbitrary voltage that does not cause avalanche amplification in the avalanche diode D.

[0051] In this embodiment, the switching means 15 selects, via the selection means 14, the voltage line connected to the avalanche diode D between the voltage line VL that supplies a potential that activates the avalanche diode D and the voltage line VL that supplies a potential that deactivates the avalanche diode D. This controls the activation / deactivation of the avalanche diode D.

[0052] According to this embodiment, although the number of voltage lines VL or VH is increased compared to the first embodiment, it is possible to read out signals only from a desired region, as in the first embodiment. Furthermore, as in the first embodiment, the activation / deactivation of the avalanche diode D is controlled, so that the power consumption of the imaging device can be reduced.

[0053] (Fourth embodiment) An imaging device according to a fourth embodiment will be described with reference to FIG. 9. FIG. 9 is a schematic diagram showing the structure of the imaging device according to the fourth embodiment. The imaging device according to this embodiment is formed by stacking a first substrate 60b and a second substrate 60a. The first substrate 60b has a plurality of photoelectric conversion element cells (hereinafter referred to as "cells") 11d, each having a signal processing circuit SP. The second substrate 60a has a plurality of cells 11c, each having an avalanche diode D. The cells 11c and 11d are connected to each other. In other words, one cell 11c and one cell 11d are connected to form one photoelectric conversion element 11.

[0054] Here, the quench element Rq, the selection means 14, and the waveform shaping unit INV may be placed in either cell 11c or cell 11d. For example, the following arrangements are possible, each of which is expected to have its own unique effect, so designers can adopt various arrangement positions depending on their purpose.

[0055] (Layout example 1) Only the avalanche diode D can be arranged in cell 11c, and all other components can be arranged in cell 11d. In this case, the area of ​​the avalanche diode D is maximized, thereby increasing the aperture ratio of the photoelectric conversion element 11. Furthermore, the second substrate 60b can be manufactured using a process specialized for the avalanche diode D, which also improves pixel characteristics.

[0056] (Layout example 2) When the components of the photoelectric conversion element include transistors with different breakdown voltages, only the components with low breakdown voltages can be arranged in cell 11d.

[0057] For example, if the quench element Rq is composed of high-voltage transistors and the other transistors are composed of low-voltage transistors, the avalanche diode D and the quench element Rq are arranged in cell 11c, and the other transistors are arranged in cell 11d. Alternatively, if the quench element Rq is composed of high-voltage transistors and the output stage of the selection means 14 is also composed of high-voltage transistors, the avalanche diode D, the quench element Rq, and the output stage of the selection means 14 are arranged in cell 11c. In this way, cell 11d can be composed only of low-voltage transistors. Therefore, the integration density of the first substrate 60b can be increased, and the first substrate 60a can be fabricated using a process specialized for low-voltage transistors, resulting in excellent circuit characteristics.

[0058] The arrangement of the components of the photoelectric conversion element 11 in the cells 11c and 11d in this embodiment is not limited to the above example, and any arrangement may be used.

[0059] According to this embodiment, in addition to the effects described in the first to third embodiments, it is possible to reduce the chip size of the imaging device while suppressing degradation of pixel characteristics.

[0060] (Fifth embodiment) FIG. 10 is a block diagram showing the configuration of an imaging system 200 according to this embodiment. The imaging system 200 of this embodiment includes an imaging device 204. Here, any of the imaging devices described in the above embodiments can be used as the imaging device 204. Specific examples of imaging systems include a digital still camera, a digital camcorder, and a surveillance camera. FIG. 10 shows an example of a digital still camera as the imaging system 200.

[0061] 10 includes an imaging device 204, a lens 202 that forms an optical image of a subject on the imaging device 204, an aperture 203 that adjusts the amount of light passing through the lens 202, and a barrier 201 that protects the lens 202. The lens 202 and the aperture 203 form an optical system that focuses light on the imaging device 204.

[0062] The imaging system 200 includes a signal processing unit 205 that processes an output signal output from an imaging device 204. The signal processing unit 205 performs signal processing operations, performing various corrections and compression on an input signal as necessary and outputting the signal. The imaging system 200 also includes a buffer memory unit 206 for temporarily storing image data and an external interface unit (external I / F unit) 209 for communicating with an external computer or the like. The imaging system 200 also includes a recording medium 211 such as a semiconductor memory for recording or reading imaging data, and a recording medium control interface unit (recording medium control I / F unit) 210 for recording or reading data from the recording medium 211. The recording medium 211 may be built into the imaging system 200 or may be removable. Communication between the recording medium control I / F unit 210 and the recording medium 211 and communication from the external I / F unit 209 may be performed wirelessly.

[0063] The imaging system 200 further includes an overall control and calculation unit 208 that performs various calculations and controls the entire digital still camera, and a timing generation unit 207 that outputs various timing signals to the imaging device 204 and the signal processing unit 205. Here, timing signals and the like may be input from an external source, and the imaging system 200 only needs to include at least the imaging device 204 and the signal processing unit 205 that processes the output signal from the imaging device 204. As described above, the control circuit 50 may control all of the operations and timings of the vertical scanning circuit and the horizontal scanning circuit, or at least some of these may be supplied from the timing generation unit 207. The overall control and calculation unit 208 and the timing generation unit 207 may be configured to perform some or all of the control functions of the imaging device 204.

[0064] The imaging device 204 outputs an image signal to the signal processing unit 205. The signal processing unit 205 performs predetermined signal processing on the image signal output from the imaging device 204 and outputs image data. The signal processing unit 205 also generates an image using the image signal. The signal processing unit 205 may also perform distance measurement calculations on the signal output from the imaging device 204. The signal processing unit 205 and the timing generating unit 207 may be mounted on the imaging device. The signal processing unit 205 and the timing generating unit 207 may be provided on a board on which a photoelectric conversion element is arranged, or may be provided on a separate board as described in the fourth embodiment. By configuring an imaging system using the imaging devices of each of the above-mentioned embodiments, an imaging system that can acquire higher quality images can be realized.

[0065] (Sixth embodiment) The imaging system and moving body of this embodiment will be described with reference to Fig. 11 and Fig. 12. Fig. 11 is a schematic diagram showing an example of the configuration of the imaging system and moving body according to this embodiment. Fig. 12 is a flow diagram showing the operation of the imaging system according to this embodiment. In this embodiment, an example of an in-vehicle camera is shown as the imaging system.

[0066] FIG. 11 shows an example of a vehicle system and an imaging system installed therein. The imaging system 1301 includes an imaging device 1302, an image pre-processing unit 1315, an integrated circuit 1303, and an optical system 1314. The optical system 1314 forms an optical image of a subject on the imaging device 1302. The imaging device 1302 converts the optical image of the subject formed by the optical system 1314 into an electrical signal. The imaging device 1302 is one of the imaging devices according to the above-mentioned embodiments. The image pre-processing unit 1315 performs predetermined signal processing on a signal output from the imaging device 1302. The function of the image pre-processing unit 1315 may be incorporated into the imaging device 1302. The imaging system 1301 includes at least two sets of the optical system 1314, the imaging device 1302, and the image pre-processing unit 1315, and the output from each set of the image pre-processing unit 1315 is input to the integrated circuit 1303.

[0067] The integrated circuit 1303 is an integrated circuit for use in an imaging system, and includes an image processing unit 1304 including a memory 1305, an optical distance measurement unit 1306, a parallax calculation unit 1307, an object recognition unit 1308, and an abnormality detection unit 1309. The image processing unit 1304 performs image processing such as development and defect correction on the output signal of the image pre-processing unit 1315. The memory 1305 temporarily stores captured images and stores the positions of defects in the captured pixels. The optical distance measurement unit 1306 focuses on the object and measures the distance. The parallax calculation unit 1307 calculates parallax information (phase difference between parallax images) from multiple image data acquired by multiple image capture devices 1302. The object recognition unit 1308 recognizes objects such as cars, roads, signs, and people. If the abnormality detection unit 1309 detects an abnormality in the image capture device 1302, it notifies the main control unit 1313 of the abnormality.

[0068] The integrated circuit 1303 may be realized by dedicated hardware, a software module, or a combination thereof. It may also be realized by an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or the like, or a combination thereof.

[0069] The main control unit 1313 supervises and controls the operations of the imaging system 1301, vehicle sensor 1310, control unit 1320, etc. It is also possible to adopt a method in which the main control unit 1313 is not provided, and the imaging system 1301, vehicle sensor 1310, and control unit 1320 each have their own communication interface and each transmits and receives control signals via a communication network (for example, CAN standard).

[0070] The integrated circuit 1303 has a function of receiving a control signal from the main control unit 1313 or transmitting a control signal or a set value to the imaging device 1302 by its own control unit.

[0071] The imaging system 1301 is connected to a vehicle sensor 1310 and can detect the vehicle's driving conditions, such as vehicle speed, yaw rate, and steering angle, as well as the conditions of the environment outside the vehicle and other vehicles and obstacles. The vehicle sensor 1310 also serves as a distance information acquisition means for acquiring distance measurement information to an object from a parallax image. The imaging system 1301 is also connected to a driving assistance control unit 1311 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 imaging system 1301 and the vehicle sensor 1310. This allows for avoidance control when a collision is predicted, and activation of safety devices in the event of a collision.

[0072] The imaging system 1301 is also connected to an alarm device 1312 that issues an alarm to the driver based on the determination result of 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 1313 performs vehicle control to avoid the collision and mitigate damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 1312 warns the user by sounding an alarm or the like, displaying alarm information on a display screen of a car navigation system or meter panel, vibrating the seat belt or steering wheel, etc.

[0073] In this embodiment, the surroundings of the vehicle, for example, the front or rear of the vehicle, are photographed by the imaging system 1301. Fig. 12(b) shows an example of the arrangement when the imaging system 1301 photographs the area in front of the vehicle.

[0074] The two image capturing devices 1302 are arranged in front of the vehicle 1300. Specifically, if the center line of the vehicle 1300's heading or outer shape (for example, vehicle width) is regarded as an axis of symmetry, and the two image capturing devices 1302 are arranged symmetrically about the axis of symmetry, this is preferable for obtaining distance information between the vehicle 1300 and an object to be photographed and determining the possibility of a collision. Furthermore, the image capturing devices 1302 are preferably arranged so as not to obstruct the driver's field of vision when the driver visually checks the situation outside the vehicle 1300 from the driver's seat. The warning device 1312 is preferably arranged so as to be easily within the driver's field of vision.

[0075] Next, the operation of detecting a fault in the image capturing device 1302 in the image capturing system 1301 will be described with reference to Fig. 12. The operation of detecting a fault in the image capturing device 1302 is performed in accordance with steps S1410 to S1480 shown in Fig. 12.

[0076] Step S1410 is a step for performing startup settings for the imaging device 1302. That is, settings for the operation of the imaging device 1302 are transmitted from outside the imaging system 1301 (for example, from the main control unit 1313) or from inside the imaging system 1301, and the imaging operation and fault detection operation of the imaging device 1302 are started.

[0077] Next, in step S1420, pixel signals are acquired from the effective pixels. Furthermore, in step S1430, output values ​​are acquired from failure detection pixels provided for failure detection. These failure detection pixels, like the effective pixels, have avalanche diodes that function as photoelectric conversion units. A predetermined voltage is written to these photoelectric conversion units. The failure detection pixels output signals corresponding to the voltages written to these photoelectric conversion units. Note that steps S1420 and S1430 may be reversed.

[0078] Next, in step S1440, a correspondence between the expected output value of the fault detection pixel and the actual output value from the fault detection pixel is determined. If the result of the correspondence determination in step S1440 indicates that the expected output value and the actual output value match, the process proceeds to step S1450, where it is determined that the imaging operation is being performed normally, and the process proceeds to step S1460. In step S1460, the pixel signals of the scanning row are sent to the memory 1305 and temporarily stored. Thereafter, the process returns to step S1420, where the fault detection operation continues. On the other hand, if the result of the correspondence determination in step S1440 indicates that the expected output value and the actual output value do not match, the process proceeds to step S1470. In step S1470, it is determined that an abnormality exists in the imaging operation, and an alarm is issued to the main control unit 1313 or the alarm device 1312. The alarm device 1312 displays on the display unit that an abnormality has been detected. Thereafter, in step S1480, the image capturing device 1302 is stopped, and the operation of the image capturing system 1301 is terminated.

[0079] 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 S1470 may be notified to the outside of the vehicle via a wireless network.

[0080] In addition, although the present embodiment has been described as a control for preventing collisions with other vehicles, the present invention is also applicable to control for automatic driving by following other vehicles, control for automatic driving so as not to deviate from a lane, etc. Furthermore, the imaging system 1301 is not limited to vehicles such as the subject vehicle, but can be applied to moving bodies (moving devices) such as ships, aircraft, and industrial robots. In addition, the imaging system 1301 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).

[0081] The imaging device of the present invention may further include a color filter and a microlens, and may be configured to be able to acquire various types of information such as distance information.

[0082] The present invention is not limited to the above-described embodiments and can be modified in various ways. For example, adding a portion of one of the embodiments to another embodiment or replacing a portion of the other embodiment with another embodiment is also an embodiment of the present invention. For example, as in the first embodiment, it is possible to control whether or not to output a signal from the signal processing circuit SP by controlling the activation / deactivation of the avalanche diode D. Furthermore, the above-described embodiments are merely examples of specific embodiments for carrying out the present invention, and the technical scope of the present invention should not be interpreted as being limited by these examples. In other words, the present invention can be embodied in various forms without departing from its technical concept or main features. [Explanation of symbols]

[0083] 10 pixel area 11 Photoelectric conversion element 14 Selection Method 15 Switching Method D Avalanche diode Vdd voltage Vss voltage VH voltage VL voltage

Claims

1. a plurality of photoelectric conversion elements each including an avalanche diode and a counter that counts a signal based on light incident on the avalanche diode; At least some of the plurality of photoelectric conversion elements are arranged side by side in a row direction, a first selection means is provided corresponding to a first photoelectric conversion element among the plurality of photoelectric conversion elements; a second selection means is provided corresponding to a second photoelectric conversion element among the plurality of photoelectric conversion elements; a first mode is a period during which a first vertical scan is being performed, and in the first mode, the first selection means controls the counter of the first photoelectric conversion element to a state in which a signal is read out, and the second selection means controls the counter of the second photoelectric conversion element to a state in which a signal is not read out; the first photoelectric conversion elements are arranged in a predetermined row, and the second photoelectric conversion elements are arranged in a row different from the predetermined row, An imaging device characterized in that a second mode, which is set during a period different from the period during which the first mode is set, is a period during which a second vertical scan is performed, and in the second mode, the second photoelectric conversion element, which was controlled to a state in which the signal is not read out in the first mode, is controlled by the second selection means to a state in which the signal is read out, and the first photoelectric conversion element, which was controlled to a state in which the signal is read out in the first mode, is controlled by the first selection means to a state in which the signal is not read out.

2. a third selection means is provided corresponding to the first photoelectric conversion element; a fourth selection means is provided corresponding to the second photoelectric conversion element; In the first mode, the third selection means controls the avalanche diode of the first photoelectric conversion element to be in a state in which a reverse bias voltage capable of avalanche multiplication is applied thereto, 2. The imaging device according to claim 1, wherein the fourth selection means controls the avalanche diode of the second photoelectric conversion element so that a reverse bias voltage capable of avalanche multiplication is not applied to the avalanche diode.

3. A vertical scanning circuit and a horizontal scanning circuit are provided, 3. The imaging device according to claim 1, wherein the first selection means and the second selection means are controlled by the vertical scanning circuit and the horizontal scanning circuit.

4. each of the plurality of photoelectric conversion elements includes a quench element connected to the avalanche diode; the third selection means controls the on / off of the quench element of the first photoelectric conversion element, 3. The imaging device according to claim 2, wherein the fourth selection means controls the on / off of the quench element of the second photoelectric conversion element.

5. a fifth selection means is provided corresponding to the first photoelectric conversion element; a sixth selection means is provided corresponding to the second photoelectric conversion element; each of the plurality of photoelectric conversion elements is connected to a control line that controls a potential applied to an anode or a cathode of the avalanche diode; the control line includes a first voltage line that supplies a potential that causes the avalanche diode to enter a state in which avalanche multiplication does not occur, and a second voltage line that supplies a potential that causes the avalanche diode to enter a state in which avalanche multiplication is possible, 2. The imaging device according to claim 1, wherein the fifth selection means and the sixth selection means select the control line connected to the avalanche diode from the first voltage line and the second voltage line.

6. 4. The imaging device according to claim 1, wherein in the first mode, the counter included in the second photoelectric conversion element is controlled by the second selection means not to perform counting.

7. 7. The imaging device according to claim 1, wherein the first selection means is configured by a combinational circuit.

8. 8. The imaging device according to claim 7, wherein the combinational circuit is an AND circuit.

9. The first mode and the second mode have different signal readout regions, In the first mode, signals are read out from photoelectric conversion elements arranged in predetermined rows among the plurality of photoelectric conversion elements, and signals are not read out from photoelectric conversion elements arranged in the remaining rows among the plurality of photoelectric conversion elements, 9. The imaging device according to claim 1, wherein in the second mode, signals are read out from photoelectric conversion elements arranged in the remaining rows of the plurality of photoelectric conversion elements, and signals are not read out from photoelectric conversion elements arranged in a predetermined plurality of rows of the plurality of photoelectric conversion elements.

10. 2. The imaging device according to claim 1, wherein in the first mode, photoelectric conversion is performed between the avalanche diode of the first photoelectric conversion element and the avalanche diode of the second photoelectric conversion element.

11. the plurality of photoelectric conversion elements include third and fourth photoelectric conversion elements arranged in a column different from a column in which the first photoelectric conversion elements are arranged, In the first mode, the counters of the third photoelectric conversion elements and the fourth photoelectric conversion elements are controlled to be in a state in which signals are not read out, 11. The imaging device according to claim 1, wherein in the second mode, the imaging device is controlled to a state in which signals are read out from the counter of the third photoelectric conversion element and the counter of the fourth photoelectric conversion element.

12. a first substrate and a second substrate laminated on the first substrate; the first substrate includes the counter; 12. The imaging device according to claim 1, wherein the second substrate includes the avalanche diode.

13. the photoelectric conversion element includes a waveform shaping unit, The imaging device according to claim 12 , wherein the second substrate includes the waveform shaping section.

14. the photoelectric conversion element includes a quenching element, The imaging device according to claim 13 , wherein the second substrate includes the quenching element.

15. 15. The imaging device according to claim 1, wherein, among the plurality of photoelectric conversion elements, the number of photoelectric conversion elements corresponding to the signals read out from the counter in the first mode is different from the number of photoelectric conversion elements corresponding to the signals read out from the counter in the second mode.

16. An imaging device according to any one of claims 1 to 15; a signal processing unit that processes a signal output by the imaging device.

17. An imaging device according to any one of claims 1 to 15; a distance information acquisition means for acquiring distance information to an object from information based on a signal from the imaging device, A moving body further comprising a control means for controlling the moving body based on the distance information.

Images