SOLID-STATE IMAGING ELEMENT AND IMAGING DEVICE

Abstract

Solid-state imaging element comprising: a photodiode configured to convert incident light into a photocurrent; an amplifying transistor configured to amplify a voltage between a gate having a potential dependent on the photocurrent and a source having a predetermined reference potential and outputting the amplified voltage from a drain; and a potential supply section configured to supply an anode of the photodiode and a back gate of the amplifying transistor with a predetermined potential lower than the reference potential, and wherein the solid-state image pickup element further comprises: a conversion transistor configured to convert the photocurrent into a voltage between a gate and a source, wherein the conversion transistor includes a source connected to a cathode of the photodiode and the gate of the amplifying transistor, and the drain of the amplification transistor is connected to the gate of the conversion transistor.

Description

[Technical field]

[0001] The present technology relates to a solid-state imaging element and an image pickup device. More particularly, the present technology relates to a solid-state imaging element and an image pickup device that detect that the amount of light of a pixel exceeds a threshold. [State of the art]

[0002] Historically, a synchronous solid-state image pickup element that captures image data (frames) in synchronization with a synchronization signal, such as a vertical synchronization signal, has been used in an image pickup device or the like. With this general synchronous solid-state image pickup element, image data can be captured only every cycle (e.g., 1 / 60 second) of the synchronization signal. Therefore, if higher-speed processing is required in fields related to traffic, robots, and the like, it is difficult to cope with this. In view of this, a non-synchronous solid-state image pickup element has been proposed (see, for example, JP 6 415 572 B2).

[0003] The non-synchronous solid-state imaging element includes an address event detection circuit that detects, in real time, for each pixel address as an address event when the light amount of that pixel exceeds the threshold. The address event detection circuit is provided in each pixel. This solid-state imaging element includes a photodiode and multiple transistors for detecting the address event for each pixel. [Citation list][Patent literature]

[0004] Exemplary solid-state imaging elements are known from the documents JP 6 415 572 B2 and US 2009 / 0 251 576 A1. [Summary][Technical Problem]

[0005] With such a non-synchronous solid-state imaging element, data can be generated and output at a much higher speed than the synchronous solid-state imaging element. Therefore, in traffic areas, for example, safety can be improved by performing image recognition processing for a person or obstacle at high speed. However, if the reverse bias of the photodiode is reduced due to voltage fluctuations such as a drop in a power supply voltage and a rise in a ground voltage, the sensitivity of this photodiode may be reduced and the dark current may increase. Therefore, there is a problem that the signal quality is reduced due to insufficient sensitivity and dark current. The sensitivity can be improved and the dark current can be reduced by increasing the area of ​​the photodiode.However, the number of pixels per unit area decreases in this case, and therefore, it is undesirable. Furthermore, sensitivity can be improved and dark current reduced by sufficiently increasing the power supply voltage. However, in this case, power consumption increases, and therefore, it is undesirable.

[0006] The present technology has been produced in consideration of such circumstances, and it is an object to improve the signal quality of the detection signal in the solid-state image pickup element that detects the address event. [Solution to the problem]

[0007] The invention is defined in the independent claims. Further developments are subject to the dependent claims. According to a first aspect of the present technology, a solid-state imaging element is provided, including: a photodiode configured to convert incident light into a photocurrent; an amplifying transistor configured to amplify a voltage between a gate having a potential dependent on the photocurrent and a source having a predetermined reference potential and outputting the amplified voltage from a drain; and a potential supply section configured to supply an anode of the photodiode and a back gate of the amplifying transistor with a predetermined potential lower than the reference potential.This configuration provides an effect of increasing the reverse bias voltage of the photodiode and the threshold voltage of the amplifying transistor.

[0008] Furthermore, the solid-state imaging element in this first aspect includes a conversion transistor configured to convert the photocurrent into a voltage between a gate and a source, wherein the conversion transistor includes a source connected to a cathode of the photodiode and the gate of the amplification transistor, and the drain of the amplification transistor is connected to the gate of the conversion transistor. This configuration provides an effect of converting the photocurrent into the voltage.

[0009] Furthermore, in this first aspect, the photodiode and the amplification transistor can be arranged in both an effective pixel where light is not shielded and a light-shielding pixel where light is shielded, and the potential supply section can supply the anode of the photodiode corresponding to the effective pixel with the predetermined potential and supply the anode of the photodiode corresponding to the light-shielding pixel with the reference potential. This configuration provides an effect of supplying a negative potential only to the effective pixel.

[0010] Furthermore, in this first aspect, the photodiode, the conversion transistor, and the amplification transistor may be arranged on a predetermined light-receiving board, and the potential supply section may supply the light-receiving board with the negative potential. This configuration provides an effect of increasing the reverse bias voltage of the photodiode and the threshold voltage of the amplification transistor.

[0011] Furthermore, the solid-state imaging element in this first aspect may further include: a buffer configured to output a voltage signal output from the amplification transistor; a subtractor configured to reduce a level of the voltage signal from the buffer; and a comparator configured to compare the reduced voltage signal with a predetermined threshold. This configuration provides an effect of detecting an address event.

[0012] Furthermore, in this first aspect, the conversion transistor and the amplification transistor may be arranged in a current-to-voltage conversion circuit configured to convert the photocurrent into the voltage signal, and the current-to-voltage conversion circuit may have a power supply voltage different from a power supply voltage of the buffer, the subtractor, and the comparator. This configuration provides an effect of performing current-to-voltage conversion with a power supply voltage lower than the power supply voltage of the buffer and the like.

[0013] Furthermore, in this first aspect, the buffer, the subtractor, and the comparator may include at least one part disposed on a predetermined circuit board stacked on the light-receiving board. This configuration provides an effect of increasing a reverse bias voltage of a photodiode and a threshold voltage of an amplification transistor in a solid-state imaging element having a stacked structure.

[0014] Furthermore, according to a second aspect of the present technology, there is provided an image pickup device including: a photodiode configured to convert incident light into a photocurrent; an amplifying transistor configured to amplify a voltage between a gate having a potential dependent on the photocurrent and a source having a predetermined reference potential and outputting the amplified voltage from a drain; a potential supply section configured to supply an anode of the photodiode and a back gate of the amplifying transistor with a predetermined potential lower than the reference potential; and a signal processing circuit configured to process a signal output from the amplifying transistor.This configuration provides an effect that the signal is processed by the circuit in which the reverse bias voltage of the photodiode and the threshold voltage of the amplifying transistor are increased. [Advantageous effects of the invention]

[0015] According to the present technology, an excellent effect of improving the signal quality of a detection signal in a solid-state imaging element that detects an address event can be provided. It should be noted that the effect described here is not necessarily limiting, and any effect described in the present disclosure can be provided. [Brief description of the drawings] [ Fig. 1] Fig. 1 is a block diagram illustrating a configuration example of an image pickup device according to an embodiment of the present technology. [ Fig. 2] Fig. 2 is a diagram for describing a stacking structure of the solid-state imaging element according to the embodiment of the present technology. [ Fig. 3] Fig. 3 is an example of a plan view of a light receiving board according to the embodiment of the present technology. [ Fig. 4] Fig. 4 is an example of a plan view of a printed circuit board according to the embodiment of the present technology. [ Fig. 5] Fig. 5 is a block diagram illustrating a configuration example of an address event detection section according to the embodiment of the present technology. [ Fig. 6] Fig. 6 is a diagram for describing a configuration of an effective pixel according to the embodiment of the present technology. [ Fig. 7] Fig. 7 is a circuit diagram illustrating a configuration example of the effective pixel according to the embodiment of the present technology. [ Fig. 8] Fig. 8 is an example of a cross-sectional view of effective pixels according to the embodiment of the present technology. [ Fig. 9] Fig. 9 is an example of a plan view of a pixel array portion in a modified example of the embodiment of the present technology. [ Fig. 10] Fig. 10 is an example of a plan view of a pixel array portion obtained by changing the arrangement of the light-shielding pixel region in the modified example of the embodiment of the present technology. [ Fig. 11] Fig. 11 is a block diagram showing an example of a schematic configuration of a vehicle control system. [ Fig. 12] Fig. 12 is a diagram of assistance in explaining an example of installation positions of an external vehicle information acquiring section and an imaging section. [Description of the embodiments]

[0016] A manner of carrying out the present technology (hereinafter referred to as an embodiment) will be described below. Descriptions will be given in the following order. 1. Embodiment (example where a negative potential is supplied to an anode of the photodiode) 2. Application example on a moving object <Embodiment 1>[Configuration example of the image pickup device]

[0017] Fig. Figure 1 is a block diagram illustrating a configuration example of an image pickup device 100 according to the embodiment of the present technology. This image pickup device 100 includes an image pickup lens 110, a solid-state image pickup element 200, a storage unit 120, and a control unit 130. Examples provided in Figure 1 may include a camera provided in a wearable device, a vehicle-mounted camera, and the like.

[0018] The image pickup lens 110 condenses incident light and introduces the condensed incident light into the solid-state image pickup element 200.

[0019] The solid-state imaging element 200 detects that an absolute value of a change in luminance exceeds a threshold for each of a plurality of pixels as an address event. This address event includes, for example, an on event indicating that an amount of luminance increase exceeds an upper limit threshold, and an off event indicating that an amount of luminance decrease becomes lower than a lower limit threshold that is lower than the upper limit threshold. Then, the solid-state imaging element 200 generates a detection signal indicating the detection result of the address event for each pixel. Each detection signal includes an on event detection signal VCH indicating the presence / absence of the on event, and an off event detection signal VCL indicating the presence / absence of the off event.It should be noted that although the solid-state imaging element 200 detects the presence / absence of both the on event and the off event, the solid-state imaging element 200 may detect the presence / absence of only one of the on event and the off event.

[0020] The solid-state image pickup element 200 performs predetermined signal processing, such as image recognition processing, on the image data including the detection signal and outputs the processed data to the storage unit 120 via a signal line 209.

[0021] The storage unit 120 stores data from the solid-state image pickup element 200. The control unit 130 controls the solid-state image pickup element 200 to capture the image data. [Configuration example of the solid-state image pickup element]

[0022] Fig. Figure 2 is a diagram illustrating an example of a stacking structure of the solid-state imaging element 200 according to the embodiment of the present technology. This solid-state imaging element 200 includes a circuit board 202 and a light-receiving board 201 stacked on the circuit board 202. These boards are electrically connected to each other via an interconnection such as a via hole. Note that, other than the via hole, these boards may be connected to each other by a Cu-Cu bond or a bump.

[0023] Fig. Figure 3 is an example of a top view of the light receiving board 201 according to the embodiment of the present technology. The light receiving board 201 includes a light receiving section 220 and via hole arrangement sections 211, 212, and 213.

[0024] Via holes to be connected to the circuit board 202 are arranged in the via-hole arrangement sections 211, 212, and 213. Furthermore, a plurality of light-receiving circuits 221 are arranged in a matrix form in the light-receiving section 220. The light-receiving circuits 221 photoelectrically convert incident light to generate a photocurrent, perform current-to-voltage conversion on this photocurrent, and output the resulting voltage signal. A pixel address, including a row address and a column address, is assigned to each of these light-receiving circuits 221.

[0025] Fig. 4 is an example of a top view of the circuit board 202 according to the embodiment of the present technology. This circuit board 202 includes a negative potential supply section 230, via-hole arrangement sections 231, 232, and 233, a signal processing circuit 240, a row drive circuit 251, a column drive circuit 252, and an address event detection section 260. Via holes to be connected to the light-receiving board 201 are arranged in the via-hole arrangement sections 231, 232, and 233.

[0026] The negative potential supply section 230 supplies the light receiving board 201 with a predetermined potential that is lower than a predetermined reference potential (e.g., ground potential). The predetermined potential is provided as a negative potential.

[0027] For example, a charge pump circuit is used as the negative potential supply section 230. Effects provided by supplying the negative potential will be described later. Note that the negative potential supply section 230 is an example of a potential supply section defined in the scope of the claims.

[0028] The address event detection section 260 generates a detection signal from a voltage signal of each of the plurality of light receiving circuits 221 and outputs the generated detection signal to the signal processing circuit 240.

[0029] The row drive circuit 251 selects a row address and causes the address event detection section 260 to output a detection signal corresponding to this row address.

[0030] The column drive circuit 252 selects a column address and causes the address event detection section 260 to output a detection signal corresponding to that column address.

[0031] The signal processing circuit 240 performs predetermined signal processing on detection signals from the address event detection section 260. This signal processing circuit 240 arranges detection signals as pixel signals in a matrix form and acquires image data including two-bit information for each pixel. The signal processing circuit 240 then performs signal processing, such as image recognition processing, on this image data.

[0032] Fig. 5 is an example of a top view of the address event detection section 260 according to the embodiment of the present technology. In this address event detection section 260, a plurality of address event detection circuits 261 are arranged in a matrix form. A pixel address is assigned to each of the address event detection circuits 261. Each of the address event detection circuits 261 is connected to each of the light receiving circuits 221 having the same address as the corresponding address event detection circuit 261.

[0033] The address event detection circuit 261 quantizes a voltage signal from the corresponding light receiving circuit 221 and outputs the quantized voltage signal as a detection signal. [Configuration example of an effective pixel]

[0034] Fig. 6 is a diagram for describing a configuration of an effective pixel 310 according to the embodiment of the present technology. The effective pixel 310 includes the light-receiving circuit 221 within the light-receiving board 201 and the address event detection circuit 261 within the circuit board 202, to which the same pixel address is assigned. As described above, in each of the boards, the plurality of light-receiving circuits 221 and the plurality of address event detection circuits 261 are arranged in a matrix form. Therefore, a plurality of effective pixels 310, each including the light-receiving circuit 221 and the address event detection circuit 261, are arranged in a matrix form in the solid-state imaging element 200.

[0035] Fig. 7 is a circuit diagram illustrating a configuration example of the effective pixel 310 according to the embodiment of the present technology. The effective pixel 310 includes a photodiode 311, a current-to-voltage conversion circuit 320, a buffer 330, a subtractor 340, a quantizer 350, and a transfer circuit 360.

[0036] Photodiode 311 photoelectrically converts incident light to generate a photocurrent. This photodiode 311 supplies the generated photocurrent to current-to-voltage conversion circuit 320.

[0037] Current-to-voltage conversion circuit 320 converts the photocurrent from photodiode 311 into a voltage signal corresponding to the photocurrent. This current-to-voltage conversion circuit 320 inputs the voltage signal to buffer 330.

[0038] Buffer 330 outputs the input voltage signal to subtractor 340. This buffer 330 can be used to increase the driving force for driving a secondary stage. Furthermore, buffer 330 can ensure isolation from noise due to switching in the secondary stage.

[0039] Subtractor 340 determines the change amount of a correction signal by subtraction. This subtractor 340 supplies the change amount as a differential signal to quantizer 350.

[0040] The quantizer 350 converts (in other words, quantizes) an analog differential signal into a digital detection signal by comparing the differential signal with a predetermined threshold. This quantizer 350 compares the differential signal with both the upper and lower thresholds and supplies the transfer circuit 360 with two-bit detection signals as the comparison result. Note that the quantizer 350 is an example of a comparator defined within the scope of the claims.

[0041] The transfer circuit 360 transfers the detection signal to the signal processing circuit 240 according to a column drive signal from the column drive circuit 252.

[0042] Further, the current-to-voltage conversion circuit 320 includes n-type transistors 321 and 322 and a p-type transistor 323. A metal-oxide-semiconductor (MOS) transistor, for example, is used as those transistors.

[0043] A source of the n-type transistor 321 is connected to a cathode of the photodiode 311, and a drain of the n-type transistor 321 is connected to a terminal with a power supply voltage VDD1. The p-type transistor 323 and the n-type transistor 322 are connected in series between a terminal with a power supply voltage VDD2 and a terminal with a reference potential (e.g., a ground potential GND). Further, a connection point between the p-type transistor 323 and the n-type transistor 322 is connected to a gate of the n-type transistor 321 and an input terminal of the buffer 330. Further, a predetermined bias voltage Vblog is applied to a gate of the p-type transistor 323.

[0044] The drain of n-type transistor 321 and a drain of n-type transistor 322 are connected to one side of a power supply, and such a circuit is called a source follower. The n-type transistor 321 of these transistors converts a photocurrent into a voltage between the gate and the source. The n-type transistor 322 amplifies a voltage between a gate with a potential dependent on the photocurrent and a source with the reference potential (e.g., ground potential GND) and outputs the amplified voltage from the drain. Furthermore, the p-type transistor 323 supplies a constant current to the n-type transistor 322. With such a configuration, the photocurrent from the photodiode 311 is converted into the voltage signal.

[0045] It should be noted that the n-type transistor 321 is an example of a conversion transistor defined in the scope of the claims, and the n-type transistor 322 is an example of an amplification transistor defined in the scope of the claims.

[0046] Furthermore, the photodiode 311 and the n-type transistors 321 and 322 are arranged on the light receiving board 201, and the circuits following the p-type transistor 323 are arranged in the circuit board 202.

[0047] Then, the negative potential supply section 230 supplies a negative potential Vn lower than the reference potential (e.g., ground potential GND) to a p-well region of the light receiving board 201. The photodiode 311 is embedded in this p-well region. Furthermore, back gates (bulks) of the n-type transistors 321 and 322 are formed in this region. Therefore, by supplying the negative potential Vn to the p-well region, the negative potential Vn can be supplied to an anode of the photodiode 311 and the respective back gates of the n-type transistors 321 and 322.

[0048] By setting the anode of photodiode 311 to the negative potential Vn, the reverse bias of photodiode 311 becomes larger compared to the case where this potential is set to the reference potential. With this setting, the sensitivity of photodiode 311 is increased and the dark current can be reduced. Furthermore, by setting the back gates of n-type transistors 321 and 322 to the negative potential Vn, a threshold voltage of each transistor is higher due to a board bias effect compared to the case where these potentials are set to the reference potential. With this setting, it is possible to prevent the voltages between the gates and sources of those transistors from being equal to or lower than zero.When the voltages between the gates and sources are equal to or less than zero, it may be impossible to obtain a normal output due to the circuit configuration of the current-to-voltage conversion circuit 320. Therefore, such a situation can be suppressed by providing the negative potential Vn. In this way, the signal quality of the detection signal can be improved due to the increased sensitivity of the photodiode 311, the reduced dark current, and the higher threshold voltage.

[0049] The n-type transistors included in the circuits at the post-stage following the buffer 330 may also be arranged in the p-well region having the negative potential Vn. Even if such a configuration is employed, it is difficult to obtain the effect regarding the characteristics described in the context of the current-to-voltage conversion process. Furthermore, it is typically desirable for the current-to-voltage conversion circuit 320 to be isolated while the circuits at the post-stage are operated at a large amplitude or high logic level. Accordingly, it is generally preferable to provide a configuration in which the p-well region on the light-receiving side is separated from the circuits at the post-stage.

[0050] Furthermore, the buffer 330 includes p-type transistors 331 and 332. MOS transistors are used, for example, as those transistors.

[0051] P-type transistors 331 and 332 are connected in series between a terminal connected to the power supply voltage VDD2 and a terminal connected to the reference potential (e.g., GND). Furthermore, a predetermined bias voltage Vbsf is applied to a gate of p-type transistor 331. A gate of p-type transistor 332 is connected to an output terminal of current-to-voltage conversion circuit 320. Then, the voltage signal from a connection point between p-type transistors 331 and 332 is output to subtractor 340.

[0052] The subtractor 340 includes capacitors 341 and 343, p-type transistors 342 and 344, and an n-type transistor 345.

[0053] P-type transistor 344 and n-type transistor 345 are connected in series between a terminal connected to the power supply voltage VDD2 and a terminal connected to the reference potential. By setting a gate of p-type transistor 344 as an input terminal and a connection point between p-type transistor 344 and n-type transistor 345 as an output terminal, p-type transistor 344 and n-type transistor 345 function as an inverter that inverts an input signal.

[0054] One end of capacitor 341 is connected to an output terminal of buffer 330, and the other end of capacitor 341 is connected to an input terminal of the inverter (i.e., the gate of p-type transistor 344). Capacitor 343 is connected in parallel with the inverter. P-type transistor 342 opens / closes a path connecting both ends of capacitor 343 to each other according to a row drive signal.

[0055] When the p-type transistor 342 is turned on, a voltage signal V Anf is input to a side of the capacitor 341 that is closer to the buffer 330, and an opposite side thereof is a virtual ground terminal. For simplicity, the potential of the virtual ground terminal is set to zero. At this time, assuming that the capacitance of the capacitor 341 is C1, a potential Q accumulated in the capacitor 341 Anf expressed as an expression below. On the other hand, both ends of capacitor 343 are short-circuited, and accordingly, the accumulated electric charge is zero. [Math. 1] QAnf=C1×VAnf

[0056] Next, assuming a case where the p-type transistor 342 is turned off and a voltage on the side of the capacitor 341 closer to the buffer 330 changes and V Danachthe electric charge Q accumulated in the capacitor 341 Danach expressed as an expression below. [Math. 2] QAfter=C1×VDaisy

[0057] On the other hand, assuming that an output voltage V Out is, the electric charge Q2 accumulated in the capacitor 343 is expressed as an expression below. [Math. 3] Q2=−C2×VOut

[0058] At this time, a total electric charge amount of the capacitors 341 and 343 does not change and accordingly an expression is established below. [Math. 4] QAnf=QDanach+Q2

[0059] When expression 4 is modified by substituting expressions 1 to 3 into expression 4, an expression below is obtained. [Math. 5] VOut=−(C1 / C2)×(VAfter−VAnf)

[0060] Expression 5 expresses a subtraction operation of the voltage signal, and the gain, which is a subtraction result, is C1 / C2. It is typically desirable to maximize the gain. Therefore, it is preferable to set C1 large and C2 small. However, if C2 is too small, the kTC noise increases and a noise characteristic may be deteriorated. Therefore, a reduction in the capacitance of C2 is limited to a range for which the noise can be tolerated. Further, the subtractor 340 is provided in each effective pixel 310. Therefore, the area for the capacitance C1 and C2 is limited. In consideration of these circumstances, C1 is set, for example, to a value of 20 to 200 femtofarads (fF), and C2 is set to a value of 1 to 20 femtofarads (fF).

[0061] The quantizer 350 includes p-type transistors 351 and 353 and n-type transistors 352 and 354. MOS transistors are used, for example, as those transistors.

[0062] The p-type transistor 351 and the n-type transistor 352 are connected in series between a terminal of the power supply voltage VDD2 and a terminal of the reference potential. The p-type transistor 353 and the n-type transistor 354 are also connected in series between a terminal of the power supply voltage VDD2 and a terminal of the reference potential. Furthermore, gates of the p-type transistors 351 and 353 are connected to an output terminal of the subtractor 340. A bias voltage Vbon indicating an upper limit threshold is applied to a gate of the n-type transistor 352. A bias voltage Vboff indicating a lower limit threshold is applied to a gate of the n-type transistor 354.

[0063] A junction point between the p-type transistor 351 and the n-type transistor 352 is connected to the transfer circuit 360, and a voltage of this junction point is output as the on-event detection signal VCH. A junction point between the p-type transistor 353 and the n-type transistor 354 is also connected to the transfer circuit 360, and a voltage of this junction point is output as the off-event detection signal VCL. With such a connection, the quantizer 350 outputs the on-event detection signal VCH at a high level if the differential signal exceeds the upper limit threshold and outputs the off-event detection signal VCL at a low level if the differential signal becomes lower than the lower limit threshold.

[0064] It should be noted that although the photodiode 311 and part of the current-to-voltage conversion circuit 320 are arranged in the light-receiving board 201, and the downstream circuits thereof are arranged in the circuit board 202, the circuits arranged in the respective chips are not limited to this configuration. For example, the photodiode 311 and the entire current-to-voltage conversion circuit 320 may be arranged in the light-receiving board 201, and other circuits may be arranged in the circuit board 202. Furthermore, the photodiode 311, the current-to-voltage conversion circuit 320, and the buffer 330 may be arranged in the light-receiving board 201, and other circuits may be arranged in the circuit board 202.Furthermore, the photodiode 311, the current-to-voltage conversion circuit 320, the buffer 330, and the capacitor 341 may be arranged in the light-receiving board 201, and other circuits may be arranged in the circuit board 202. Furthermore, the photodiode 311, the current-to-voltage conversion circuit 320, the buffer 330, the subtractor 340, and the quantizer 350 may be arranged in the light-receiving board 201, and other circuits may be arranged in the circuit board 202.

[0065] Fig. 8 is an example of a cross-sectional view of the effective pixels 310 according to the embodiment of the present technology. Photodiode 311 is embedded in each p-well region of the light-receiving board 201, and the backgates of n-type transistors 321 and 322 are formed. The drain of n-type transistor 321 is supplied with the power supply voltage VDD1, and the source potential of n-type transistor 322 is the reference potential (e.g., GND). Furthermore, the p-well regions of adjacent effective pixels 310 are separated from each other by the long-short-dashed line.

[0066] By supplying the back gate (bulk) of the n-type transistor 321 with the negative potential Vn, a high voltage is applied between the drain and the back gate compared to a case where the reference potential is applied. Typically, with regard to the output of the current-to-voltage conversion circuit 320, it is desirable to achieve large-amplitude operation to expand the dynamic range, and it is difficult to reduce the power supply voltage VDD2 at the post-stage. However, the dynamic range is not greatly affected with regard to the power supply voltage VDD1. Therefore, it is desirable to set the power supply voltage VDD1 lower than the power supply voltage VDD2.

[0067] The photocurrent from all effective pixels 310 flows into the negative potential supply section 230. If an IR drop causes a potential gradient in the pixel plane, the pixel characteristics themselves can also be varied in the plane in a manner that depends on the IR drop. Therefore, it is preferable to eliminate the negative potential gradient in the pixel plane by arranging via holes at multiple positions on the light-receiving board 201 and the printed circuit board 202.

[0068] As described above, according to the embodiment of the present technology, the reverse bias voltage of the photodiode 311 and the threshold voltage can be increased by supplying the negative potential Vn to the anode of the photodiode 311 and the back gate of the n-type transistor 321, or the like. With the increased reverse bias voltage, the sensitivity of the photodiode 311 can be improved and the dark current can be reduced. Furthermore, with the increased threshold voltage, a situation in which it may be impossible to obtain a normal output can be suppressed. Therefore, the signal quality of the detection signal can be improved. [Modified example]

[0069] In the above-mentioned embodiment, the negative potential supply section 230 supplies the negative potential Vn to all pixels. However, power consumption may increase as the number of pixels increases. A solid-state imaging element 200 according to this modified example differs from the above-mentioned embodiment in that the light-shielding pixel is not supplied with the negative potential Vn.

[0070] Fig. 9 is an example of a top view of a pixel array section 300 in the modified example of the embodiment of the present technology. This pixel array section 300 includes a light receiving section 220 and an address event detection section 260 stacked on top of each other. The pixel array section 300 includes horizontal light-shielding pixel regions 301 and 303 and an effective pixel region 302.

[0071] The plurality of effective pixels 310 are arranged in a matrix form in the effective pixel region 302. Light is not shielded in those pixels.

[0072] On the other hand, a plurality of light-shielding pixels 315 are arranged in a matrix form in each of the horizontal light-shielding pixel regions 301 and 303. Light is shielded in those pixels. Furthermore, the light-shielding pixels 315 within the horizontal light-shielding pixel regions 301 and 303 are assigned column addresses different from those of the effective pixels 310. Furthermore, a circuit configuration of the light-shielding pixels 315 is similar to the effective pixels 310.

[0073] The negative potential supply section 230 supplies a negative potential Vn1 to the p-well region of the effective pixel 310. On the other hand, the negative potential supply section 230 supplies a potential Vn2, such as the reference potential (GND), to the p-well regions of the light-shielding pixels 315.

[0074] The signal processing circuit 240 and the circuits at the post-stage thereof determine a dark current amount based on pixel signals from the light-shielding pixels 315 and remove the dark current in pixel signals from the effective pixels 310.

[0075] It should be noted that although the horizontal light-shielding pixel regions 301 and 303 are arranged, a vertical light-shielding pixel region 304 may be arranged instead of the horizontal light-shielding pixel regions 301 and 303, as shown in Fig. 10. The light-shielding pixels 315 within this vertical light-shielding pixel region 304 are assigned row addresses different from those of the effective pixels 310. Furthermore, both the horizontal light-shielding pixel regions 301 and 303 and the vertical light-shielding pixel region 304 can be arranged.

[0076] As described above, according to the modified example of the embodiment of the present technology, the negative potential supply section 230 supplies the negative potential Vn1 only to the effective pixels 310 of all pixels. Accordingly, power consumption can be reduced compared to the case where the negative potential Vn1 is supplied to all pixels. <Anwendungsbeispiel auf ein bewegliches Objekt>

[0077] The technology (present technology) according to the present disclosure can be applied to various products. For example, the technology according to the present disclosure can be implemented as a device mounted on any type of moving object, such as a car, an electric car, a hybrid electric car, a motorcycle, a bicycle, a personal mobility device, an aircraft, a drone, a ship, and a robot.

[0078] Fig. 11 is a block diagram illustrating an example of a schematic configuration of a vehicle control system as an example of a mobile body control system to which the technology according to an embodiment of the present disclosure can be applied.

[0079] The vehicle control system 12000 includes several electronic control units that are interconnected via a communication network 12001. In the Fig. In the example shown in Fig. 11, the vehicle control system 12000 includes a driving system control unit 12010, a body system control unit 12020, a vehicle exterior information detection unit 12030, a vehicle interior information detection unit 12040, and an integrated control unit 12050. In addition, a microcomputer 12051, a sound / image output section 12052, and a vehicle-mounted network interface (SST) 12053 are illustrated as a functional configuration of the integrated control unit 12050.

[0080] The driving system control unit 12010 controls the operation of devices related to the vehicle's drive system according to various types of programs. For example, the driving system control unit 12010 functions as a control device for a driving force generating device for generating the vehicle's driving force, such as an internal combustion engine, a drive motor, or the like, a driving force transmitting mechanism for transmitting the driving force to wheels, a steering mechanism for adjusting the vehicle's steering angle, a braking device for generating the vehicle's braking force, and the like.

[0081] The body system control unit 12020 controls the operation of various types of devices provided on a vehicle body according to various types of programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various types of lamps such as a headlight, a taillight, a brake light, a turn signal, a fog light, or the like. In this case, radio waves transmitted from a mobile device can be input to the body system control unit 12020 as an alternative to a key or signals from various types of switches.The body system control unit 12020 receives these input radio waves or signals and controls a door locking device, the power window device, the lamps or the like of the vehicle.

[0082] The vehicle exterior information detection unit 12030 detects information about the exterior of the vehicle including the vehicle control system 12000. For example, the vehicle exterior information detection unit 12030 is connected to an imaging section 12031. The vehicle exterior information detection unit 12030 causes the imaging section 12031 to image an image of the exterior of the vehicle and receives the imaged image. Based on the received image, the vehicle exterior information detection unit 12030 can perform processing for detecting an object such as a person, a vehicle, an obstacle, a sign, a symbol on a road surface, or the like, or processing for detecting a distance thereto.

[0083] The imaging section 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging section 12031 can output the electrical signal as an image or can output the electrical signal as information about a measured distance. Furthermore, the light received by the imaging section 12031 can be visible light or can be non-visible light, such as infrared rays or the like.

[0084] The vehicle interior information detection unit 12040 detects information about the interior of the vehicle. The vehicle interior information detection unit 12040 is connected, for example, to a driver state detection section 12041 that detects the state of a driver. The driver state detection section 12041 includes, for example, a camera that captures an image of the driver. Based on detection information input from the driver state detection section 12041, the vehicle interior information detection unit 12040 can calculate a driver's fatigue level or a driver's concentration level, or can determine whether the driver is dozing.

[0085] The microcomputer 12051 can calculate a control target value for the driving force generating device, the steering mechanism, or the braking device based on the information about the interior or exterior of the vehicle, which information is acquired by the vehicle exterior information detection unit 12030 or the vehicle interior information detection unit 12040, and output a control command to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control intended to implement functions of a driving assistance system (ADAS), the functions of which include collision avoidance or shock mitigation for the vehicle, following distance-based travel, speed maintenance travel, vehicle collision warning, vehicle lane departure warning, or the like.

[0086] In addition, the microcomputer 12051 can perform cooperative control provided for automatic driving, which causes the vehicle to drive autonomously without depending on the driver's operation, or the like, by controlling the driving force generating device, the steering mechanism, the braking device, or the like based on the information about the exterior or interior of the vehicle, the information obtained by the vehicle exterior information detection unit 12030 or the vehicle interior information detection unit 12040.

[0087] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information about the exterior of the vehicle, which information is obtained by the vehicle exterior information detection unit 12030. For example, the microcomputer 12051 can perform cooperative control aimed at preventing glare by controlling the headlight to switch from, for example, a high beam to a low beam according to the position of a preceding vehicle or an oncoming vehicle detected by the vehicle exterior information detection unit 12030.

[0088] The sound / image output section 12052 transmits an output signal of a sound and / or an image to an output device capable of visually or acoustically communicating information to an occupant of the vehicle or the exterior of the vehicle. In the example of Fig. 11 illustrates an audio speaker 12061, a display section 12062, and an instrument panel 12063 as the output device. The display section 12062 may include, for example, an on-board display and / or a head-up display.

[0089] Fig. 12 is a diagram showing an example of the installation position of the imaging section 12031.

[0090] In Fig. 12, the imaging section 12031 includes imaging sections 12101, 12102, 12103, 12104 and 12105.

[0091] The imaging sections 12101, 12102, 12103, 12104, and 12105 are arranged, for example, at positions on a front end, side mirrors, a rear bumper, and a rear door of the vehicle 12100, and a position on an upper part of a windshield inside the vehicle. The imaging section 12101 provided at the front end and the imaging section 12105 provided at the upper part of the windshield inside the vehicle mainly obtain an image of the front of the vehicle 12100. The imaging sections 12102 and 12103 provided at the side mirrors mainly obtain an image of the sides of the vehicle 12100. The imaging section 12104 provided at the rear bumper or the tailgate mainly obtains an image of the rear of the vehicle 12100.The imaging section 12105 provided at the upper part of the windshield inside the vehicle is mainly used to detect a preceding vehicle, a pedestrian, an obstacle, a signal, a traffic sign, a roadway, or the like.

[0092] By the way, Fig. 12 illustrates an example of photographing areas of the imaging sections 12101 to 12104. An imaging area 12111 represents the imaging area of ​​the imaging section 12101 provided at the front end. The imaging areas 12112 and 12113 respectively represent the imaging areas of the imaging sections 12102 and 12103 provided at the side mirrors. An imaging area 12114 represents the imaging area of ​​the imaging section 12104 provided at the rear bumper or the tailgate. A bird's-eye view image of the vehicle 12100 as seen from above is obtained, for example, by superimposing image data imaged by the imaging sections 12101 to 12104.

[0093] At least one of the imaging sections 12101 to 12104 may have a function of obtaining distance information. For example, at least one of the imaging sections 12101 to 12104 may be a stereo camera consisting of multiple imaging elements, or may be an imaging element with pixels for phase difference detection.

[0094] For example, the microcomputer 12051 may determine a distance to each three-dimensional object within the imaging areas 12111 to 12114 and a temporal change of the distance (relative speed with respect to the vehicle 12100) based on the distance information obtained from the imaging sections 12101 to 12104, and thereby extract a nearest three-dimensional object that exists specifically on a moving path of the vehicle 12100 and that travels substantially in the same direction as the vehicle 12100 at a predetermined speed (e.g., equal to or greater than 0 km / h) as a preceding vehicle.Furthermore, the microcomputer 12051 can set a following distance to be maintained with the preceding vehicle in advance and can perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), or the like. Accordingly, it is possible to perform cooperative control aimed at automatic driving, which causes the vehicle to drive autonomously without depending on a driver's operation or the like.

[0095] For example, the microcomputer 12051 can classify three-dimensional object data about three-dimensional objects into three-dimensional object data of a two-wheeled vehicle, a standard-size vehicle, a large-size vehicle, a pedestrian, a utility pole, and other three-dimensional objects based on the distance information obtained from the imaging sections 12101 to 12104, extract the classified three-dimensional object data, and use the extracted three-dimensional object data for automatic obstacle avoidance. For example, the microcomputer 12051 identifies obstacles around the vehicle 12100 as obstacles that the driver of the vehicle 12100 can visually recognize and obstacles that the driver of the vehicle 12100 has difficulty visually recognizing. Then, the microcomputer 12051 determines a collision risk that indicates a risk of collision with each obstacle.In a situation where the collision risk is equal to or higher than a set value and there is a possibility of a collision, the microcomputer 12051 issues a warning to the driver through the audio speaker 12061 or the display section 12062 and performs forced deceleration or evasive steering through the drive system control unit 12010. The microcomputer 12051 can thereby assist in avoiding a collision during driving.

[0096] At least one of the imaging sections 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 may detect a pedestrian by determining whether there is a pedestrian in the captured images of the imaging sections 12101 to 12104. Such detection of a pedestrian is performed, for example, by a process for extracting characteristic points in the captured images of the imaging sections 12101 to 12104 as infrared cameras and a process for determining whether or not it is the pedestrian by performing pattern matching processing on a series of characteristic points representing the contour of the object.When the microcomputer 12051 determines that there is a pedestrian in the captured images of the image pickup sections 12101 to 12104 and accordingly detects the pedestrian, the audio / video output section 12052 controls the display section 12062 to display a square contour line for highlighting, superimposed on the detected pedestrian. The audio / video output section 12052 can also control the display section 12062 to display an icon or the like representing the pedestrian at a desired position.

[0097] The example of the vehicle control system to which the technology according to the present disclosure can be applied has been described above. The technology according to the present disclosure can be applied to the imaging section 12031 of the configurations described above. Specifically, the image pickup device 100 of Fig.1 can be applied to the imaging section 12031. By applying the technology according to the present disclosure to the imaging section 12031, the signal quality of the detection signal can be improved. Therefore, the accuracy of image recognition or the like using a detection signal can be improved.

[0098] It is noted that the above-mentioned embodiments provide examples for practicing the present technology, and the subject matter in the embodiments and the inventive subject matter within the scope of the claims are associated. Likewise, the inventive subject matter within the scope of the claims and the subject matter in the embodiments of the present technology, which are denoted by the identical names, have a correspondence. It is noted that the present technology is not limited to the embodiments and can be practiced by making various modifications to the embodiments without departing from its essence.

[0099] It should be noted that the effects described in the description are merely exemplary and not limiting, and other effects may be provided.

[0100] It should be noted that the present technology can take the following configurations. (1) A solid-state imaging element comprising: a photodiode configured to convert incident light into a photocurrent; an amplifying transistor configured to amplify a voltage between a gate having a potential dependent on the photocurrent and a source having a predetermined reference potential and outputting the amplified voltage from a drain; and a potential supply section configured to supply an anode of the photodiode and a back gate of the amplifying transistor with a predetermined potential lower than the reference potential. (2) The solid-state imaging element according to (1), further comprising: a conversion transistor configured to convert the photocurrent into a voltage between a gate and a source, wherein the conversion transistor includes a source connected to a cathode of the photodiode and the gate of the amplifying transistor, and the drain of the amplification transistor is connected to the gate of the conversion transistor. (3) The solid-state imaging element according to (2), wherein the photodiode and the amplifying transistor are arranged in both an effective pixel in which light is not shielded and a light-shielding pixel in which light is shielded, and the potential supply section supplies the anode of the photodiode corresponding to the effective pixel with the predetermined potential and supplies the anode of the photodiode corresponding to the light-shielding pixel with the reference potential. (4) The solid-state image pickup element according to (2) or (3), wherein the photodiode, the conversion transistor and the amplifying transistor are arranged on a predetermined light receiving board, and the potential supply section supplies the light receiving board with the predetermined voltage. (5) The solid-state imaging element according to (4), further comprising: a buffer configured to output a voltage signal output from the amplifying transistor; a subtractor configured to reduce a level of the voltage signal from the buffer; and a comparator configured to compare the reduced voltage signal with a predetermined threshold. (6) The solid-state image pickup element according to (5), wherein the conversion transistor and the amplification transistor are arranged in a current-to-voltage conversion circuit configured to convert the photocurrent into the voltage signal, and the current-to-voltage conversion circuit has a power supply voltage that is different from a power supply voltage of the buffer, the subtractor, and the comparator. (7) The solid-state image pickup element according to (5) or (6), wherein the buffer, the subtractor, and the comparator include at least a part disposed on a predetermined circuit board stacked on the light receiving board. (8) An image recording device comprising: a photodiode configured to convert incident light into a photocurrent; an amplifying transistor configured to amplify a voltage between a gate having a potential dependent on the photocurrent and a source having a predetermined reference potential and output the amplified voltage from a drain; a potential supply section configured to supply an anode of the photodiode and a back gate of the amplifying transistor with a predetermined potential lower than the reference potential; and a signal processing circuit configured to process a signal output from the amplifying transistor.

[0101] It will be understood by one skilled in the art that various modifications, combinations, sub-combinations and changes may occur depending on design requirements and other factors, insofar as they are within the scope of the appended claims or their equivalents. [List of reference symbols] 100 image recording device 110 Image pickup lens 120 storage units 130 Control unit 200 solid-state imaging elements 201 Light receiving board 202 circuit board 211, 212, 213, 231, 232, 233 via hole arrangement section 220 Light receiving section 221 Light receiving circuit 230 Negative potential supply section 240 signal processing circuit 251 Line control circuit 252 Column control circuit 260 Address event detection section 261 Address event detection circuit 300 pixel array section 310 Effective Pixels 311 photodiode 315 light shielding pixels 320 Current-to-voltage conversion circuit 321, 322, 345, 352, 354 n-type transistor 330 323, 331, 332, 342, 344, 351, 353 p-type transistor buffer 340 subtractors 341, 343 capacitor 350 quantizers 360 transfer circuit 12031 Imaging Section

Claims

[1] Solid-state imaging element comprising: a photodiode configured to convert incident light into a photocurrent; an amplifying transistor configured to amplify a voltage between a gate having a potential dependent on the photocurrent and a source having a predetermined reference potential and outputting the amplified voltage from a drain; and a potential supply section configured to supply an anode of the photodiode and a back gate of the amplifying transistor with a predetermined potential lower than the reference potential, and wherein the solid-state image pickup element further comprises: a conversion transistor configured to convert the photocurrent into a voltage between a gate and a source, wherein the conversion transistor includes a source connected to a cathode of the photodiode and the gate of the amplifying transistor, and the drain of the amplification transistor is connected to the gate of the conversion transistor. [2] A solid-state image pickup element according to claim 1, wherein the photodiode and the amplifying transistor are arranged in both an effective pixel in which light is not shielded and a light-shielding pixel in which light is shielded, and the potential supply section supplies the anode of the photodiode corresponding to the effective pixel with the predetermined potential and supplies the anode of the photodiode corresponding to the light-shielding pixel with the reference potential. [3] A solid-state imaging element according to claim 1, wherein the photodiode, the conversion transistor and the amplifying transistor are arranged on a predetermined light receiving board, and the potential supply section supplies the light receiving board with the predetermined voltage. [4] A solid-state imaging element according to claim 3, further comprising: a buffer configured to output a voltage signal output from the amplifying transistor; a subtractor configured to reduce a level of the voltage signal from the buffer; and a comparator configured to compare the reduced voltage signal with a predetermined threshold. [5] A solid-state image pickup element according to claim 4, wherein the conversion transistor and the amplification transistor are arranged in a current-to-voltage conversion circuit configured to convert the photocurrent into the voltage signal, and the current-to-voltage conversion circuit has a power supply voltage that is different from a power supply voltage of the buffer, the subtractor, and the comparator. [6] The solid-state imaging element according to claim 4, wherein the buffer, the subtractor, and the comparator include at least a part disposed on a predetermined circuit board stacked on the light receiving board. [7] An image pickup device comprising a solid-state image pickup element according to any one of the preceding claims.

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