Imaging device

Abstract

[Problem] To speed up AD conversion and frame rate and to reduce power consumption by reducing the load of signal wiring for reference signals. [Solution] This imaging device comprises: a plurality of photoelectric conversion elements that are arranged in a first direction and a second direction, which intersect each other, each of the plurality of photoelectric conversion elements accumulating a charge corresponding to the amount of incident light; a plurality of pixel circuits that respectively output pixel signals corresponding to the charges accumulated in the plurality of photoelectric conversion elements; a plurality of comparators that compare each of the plurality of pixel signals outputted from the plurality of pixel circuits with a reference signal; a digital signal generator that, on the basis of comparison results from the plurality of comparators, generates a digital signal in which the plurality of pixel signals are converted from analog to digital; and a plurality of switches that switch whether the reference signal is inputted to the plurality of comparators.

Description

Imaging device

[0001] The present disclosure relates to an imaging device.

[0002] In imaging devices, a vertical signal line is generally provided for each pixel column, and the pixel signals of each pixel in the pixel column are transmitted via the vertical signal line to a column signal processing circuit, where signal processing such as analog-to-digital conversion (hereinafter referred to as AD conversion) is performed.

[0003] However, as the number of pixels in an imaging device increases, the distance to the column signal processing circuit varies depending on the pixel position, which causes a delay in the propagation of pixel signals on the vertical signal lines and changes in signal level. To solve these problems, a technology has been proposed in which the vertical signal lines are divided into multiple lines and AD conversion is performed for each divided vertical signal line (see Patent Document 1).

[0004] International Publication No. 2023 / 058720A1

[0005] To perform AD conversion on a pixel signal, it is necessary to compare the pixel signal with a reference signal, generally called a ramp signal. In Patent Document 1, a separate AD converter is provided for each of the multiple divided vertical signal lines. This requires that the reference signal be distributed to multiple AD converters, which increases the load on the signal wiring that transmits the reference signal and takes time for AD conversion, potentially hindering efforts to increase frame rates and reduce power consumption.

[0006] Therefore, the present disclosure provides an imaging device that can achieve faster AD conversion and frame rate and lower power consumption by reducing the load on the signal wiring of the reference signal.

[0007] In order to solve the above problems, according to the present disclosure, there is provided an imaging device comprising: a plurality of photoelectric conversion elements arranged in a first direction and a second direction that intersect with each other, each accumulating an electric charge corresponding to the amount of incident light; a plurality of pixel circuits that output pixel signals corresponding to the electric charges accumulated in the plurality of photoelectric conversion elements; a plurality of comparators that compare each of the plurality of pixel signals output from the plurality of pixel circuits with a reference signal; a digital signal generator that generates digital signals by analog-to-digital conversion of the plurality of pixel signals based on the comparison results of the plurality of comparators; and a plurality of switchers that switch whether or not to input the reference signal to the plurality of comparators.

[0008] The plurality of switches may sequentially select one of the plurality of comparators to input the reference signal so that the reference signal is not input to two or more of the comparators at the same time.

[0009] The image sensor may include: signal lines that transmit the plurality of pixel signals output from two or more of the pixel circuits arranged in the second direction; and a conversion circuit that performs analog-to-digital conversion of the plurality of pixel signals transmitted on the signal lines, wherein the conversion circuit may have the comparator and the digital signal generator.

[0010] The image display device may include: a plurality of the signal lines arranged in the first direction; and a plurality of the conversion circuits connected to the plurality of signal lines.

[0011] The signal line may include a plurality of split signal lines split along the second direction, each of the plurality of split signal lines transmitting the pixel signals output from two or more of the pixel circuits arranged along the second direction, and one or more of the comparators may be provided for each of the plurality of split signal lines.

[0012] Each of the plurality of comparators may be provided for each of the plurality of pixel circuits.

[0013] The plurality of switches may switch, for each pixel group including two or more of the pixel circuits arranged in the first direction or the second direction, whether or not to input the reference signal to the corresponding two or more comparators.

[0014] The plurality of switchers may sequentially switch and select one of a plurality of pixel groups corresponding to a pixel region of interest from a plurality of pixel groups each including two or more of the pixel circuits arranged in the first direction or the second direction.

[0015] The plurality of switches may sequentially switch and select one of two or more pixel groups adjacent to each other in the first direction or the second direction out of a plurality of pixel groups each including two or more of the pixel circuits arranged in the first direction or the second direction.

[0016] The digital signal generator may include a counter that outputs, as the digital signal, a count value corresponding to a timing at which the pixel signal and the reference signal match in each of the plurality of comparators.

[0017] At least one of the plurality of switches may include: a first transistor of a first conductivity type that switches between making the first node and the second node conductive or cut off in response to a switch control signal; and a second transistor of a second conductivity type that switches between making the first node and the second node conductive or cut off in response to an inverted switch control signal having an inverse logic to the switch control signal.

[0018] At least one of the plurality of switchers may include: a third transistor of a first conductivity type having a source and a drain connected to the first node and a gate to which the inverted switch control signal is input; a fourth transistor of a first conductivity type having a source and a drain connected to the second node and a gate to which the inverted switch control signal is input; a fifth transistor of a second conductivity type having a source and a drain connected to the first node and a gate to which the switch control signal is input; and a sixth transistor of a second conductivity type having a source and a drain connected to the second node and a gate to which the switch control signal is input.

[0019] The amplifier may further include a capacitor disposed between the second node and a reference voltage node, and the second node may be connected to input nodes of the plurality of comparators.

[0020] at least one of the plurality of switches includes: a first transistor that switches whether to connect or disconnect the first node and the second node in response to a switch control signal; a voltage source that outputs a bias voltage between the third node and a fourth node; a first switch, a second switch, and a third switch that are connected in series between the third node and a reference voltage node; a fourth switch and a fifth switch that are connected in series between the fourth node and the first node; a first capacitor that is connected between a connection node of the first switch and the second switch and a connection node of the fourth switch and the fifth switch; and a second capacitor that is connected between the second node and the reference voltage node; and the switch control signal output from the connection node of the second switch and the third switch is input to a gate of the first transistor; and when the first node and the second node are connected, the first switch, the third switch, and the fourth switch are disconnected and the second switch and the fifth switch are connected; When the first node and the second node are cut off, the first switch, the third switch, and the fourth switch may be made conductive, and the second switch and the fifth switch may be made conductive.

[0021] At least one of the plurality of switches includes: a first transistor that switches whether to connect or disconnect the first node and the second node in response to a switch control signal; a first switch, a second switch, and a third switch connected in series between a first reference voltage node and a second reference voltage node; a fourth switch and a fifth switch connected in series between the second reference voltage node and the first node; a first capacitor connected between a connection node of the first switch and the second switch and a connection node of the fourth switch and the fifth switch; and a second capacitor connected between the second node and the second reference voltage node, wherein the switch control signal output from the connection node of the second switch and the third switch is input to a gate of the first transistor; and when the first node and the second node are to be connected, the first switch, the third switch, and the fourth switch are disconnected and the second switch and the fifth switch are connected; When the first node and the second node are cut off, the first switch, the third switch, and the fourth switch may be made conductive, and the second switch and the fifth switch may be made conductive.

[0022] The present invention may include a plurality of preamplifiers arranged between the plurality of switches and the plurality of comparators, each having a plurality of source follower circuits that converts impedance of the reference signals output from the plurality of switches, wherein each of the plurality of source follower circuits includes: a first transistor having a gate to which the reference signal output from the corresponding switch is input; a second transistor of a first conductivity type connected to the drain side of the first transistor, which is turned on when the corresponding switch outputs the reference signal and is turned off when the corresponding switch does not output the reference signal; and a third transistor of a second conductivity type connected to the source side of the first transistor, which is turned on when the corresponding switch outputs the reference signal and is turned off when the corresponding switch does not output the reference signal.

[0023] Each of the plurality of source follower circuits has a fourth transistor that functions as a current source and a fifth transistor that adjusts the voltage of the corresponding input node of the comparator, and may be connected between a first reference voltage node and a second reference voltage node in the order of the fourth transistor, the third transistor, the fifth transistor, the first transistor, and the second transistor, or in the order of the fourth transistor, the fifth transistor, the third transistor, the first transistor, and the second transistor.

[0024] the plurality of preamplifiers may include a plurality of preamplifiers arranged between the plurality of switches and the plurality of comparators, the preamplifier having a plurality of source follower circuits that convert impedances of the reference signals output from the plurality of switches, wherein each of the plurality of source follower circuits may include: a first transistor having a gate to which the reference signal output from the corresponding switch is input; a second transistor of a first conductivity type connected to a drain side of the first transistor and turned on when the corresponding switch outputs the reference signal and turned off when the corresponding switch does not output the reference signal; a third transistor connected to a source side of the first transistor and functioning as a current source; a fourth transistor that adjusts a voltage of an input node of the corresponding comparator; a fifth transistor connected to a gate of the fourth transistor and turned on when the corresponding switch outputs the reference signal to turn on the fourth transistor; and a sixth transistor connected to the gate of the fourth transistor and turned on when the corresponding switch does not output the reference signal to turn off the fourth transistor.

[0025] The circuit may further include a precharge circuit that supplies a precharge signal to the source of the first transistor in a source follower circuit that does not output the reference signal from the source of the first transistor, among the plurality of source follower circuits.

[0026] The precharge circuit may further include a replica circuit having the same circuit configuration as the plurality of source follower circuits and generating, as the precharge signal, a reference voltage of the reference signal when the plurality of comparators start a comparison operation, and the precharge circuit may supply the reference voltage generated by the replica circuit to the source of the first transistor in a source follower circuit among the plurality of source follower circuits that does not input the reference signal to the corresponding comparator.

[0027] 12A and 12B are graphs showing the relationship between the settling time of a reference signal on a reference signal line and the signal bandwidth of a reference signal line. 12B is a timing chart showing the relationship between the settling time of a reference signal on a reference signal line and the signal bandwidth of a reference signal line. 12C is a timing chart showing the relationship between the settling time of a reference signal on a reference signal line and the signal bandwidth of a reference signal line. 12D is a timing chart showing the relationship between the settling time of a reference signal on a reference signal line and the signal bandwidth of a reference signal line. 12E is a timing chart showing the relationship between the settling time of a reference signal on a reference signal line and the signal bandwidth of a reference signal line. 12F is a timing chart showing the relationship between the settling time of a reference signal on a reference signal line and the signal bandwidth of a reference signal line. 12G ... 28A and 28B. 28B is a circuit diagram showing a first example of a reference signal switch. 28C is a circuit diagram showing a second example of a reference signal switch. 28D is a circuit diagram showing a third example of a reference signal switch. 28E is a circuit diagram showing a fourth example of a reference signal switch. 28F is a circuit diagram showing a fifth example of a reference signal switch. 28G is a block diagram of a column readout unit and its periphery in an imaging device according to a second embodiment. 28H is a block diagram of a column readout unit and its periphery in an imaging device according to a second embodiment. 28I is a circuit diagram showing a first example of the internal configuration of a preamplifier. 28I is a circuit diagram showing a second example of the internal configuration of a preamplifier. 28I is a circuit diagram showing a third example of the internal configuration of a preamplifier. 28I is a circuit diagram showing a fourth example of the internal configuration of a preamplifier. 28I is a graph showing the settling time of a reference signal input to a column readout unit when the output node of a source follower circuit is precharged and when it is not precharged. 28I is a circuit diagram of a column readout unit 17 and its periphery in an imaging device according to a third embodiment. 28I is a diagram explaining the precharge operation of an imaging device according to a third embodiment. 28I is a diagram explaining the precharge operation of an imaging device according to a third embodiment. 28I is a timing chart corresponding to the explanations of FIGS. 26A and 26B. 28I is a block diagram of an imaging device according to a fourth embodiment. 28I is a diagram showing an example of the arrangement of two column readout units in FIG. 28. 30 is a block diagram of an imaging device according to a modification of the fourth embodiment. FIG. 31 is a diagram showing the locations of two column readout units in FIG.10 is a timing chart of an imaging device according to a fourth embodiment. FIG. 11 is a timing chart of an imaging device according to a modified example of the fourth embodiment. FIG. 12 is a diagram for explaining an imaging device according to a fifth embodiment. FIG. 13 is a diagram for explaining an imaging device according to a modified example of the fifth embodiment. FIG. 14 is a diagram for explaining an imaging device according to a sixth embodiment. A block diagram showing an example of a schematic configuration of a vehicle control system. An explanatory diagram showing an example of installation positions of an outside vehicle information detection unit and an imaging unit.

[0028] Hereinafter, an embodiment of an imaging device will be described with reference to the drawings. The following description will focus on the main components of the imaging device, but the imaging device may include components and functions that are not shown or described. The following description does not exclude components and functions that are not shown or described.

[0029] (Electronic Device Applicable to All Embodiments) FIG. 1 is a block diagram showing the configuration of an example of an electronic device applicable to all embodiments. In FIG. 1, electronic device 1000 includes an optical system 1002, a control unit 1003, an imaging device 1004, an image processing unit 1005, a memory 1006, a storage unit 1007, a display unit 1008, an interface (I / F) unit 1009, and an input device 1012. Here, a digital still camera, a digital video camera, a mobile phone or smartphone with an imaging function, or the like can be used as electronic device 1000. Furthermore, a surveillance camera, an in-vehicle camera, a medical camera, or the like can also be used as electronic device 1000.

[0030] The imaging device 1004 includes a plurality of photoelectric conversion elements arranged in, for example, a matrix. The photoelectric conversion elements convert received light into electric charges through photoelectric conversion. The imaging device 1004 includes a drive circuit that drives the plurality of photoelectric conversion elements, a signal processing circuit that reads electric charges from each of the plurality of photoelectric conversion elements and generates image data based on the read electric charges, and a power supply circuit that supplies power to the drive circuit.

[0031] The optical system 1002 includes a main lens formed by a combination of one or more lenses and a mechanism for driving the main lens, and forms an image of image light (incident light) from a subject on the light receiving surface of the imaging device 1004 via the main lens. The optical system 1002 also includes an autofocus mechanism that adjusts the focus in accordance with a control signal and a zoom mechanism that changes the zoom ratio in accordance with a control signal. The electronic device 1000 may also have a detachable optical system 1002 that can be replaced with another optical system 1002.

[0032] The image processing unit 1005 performs predetermined image processing on the pixel data output from the imaging device 1004. For example, the image processing unit 1005 is connected to a memory 1006 such as a frame memory, and writes the image data output from the imaging device 1004 to the memory 1006. The image processing unit 1005 performs predetermined image processing on the pixel data written to the memory 1006, and writes the processed pixel data back to the memory 1006. The memory 1006 can store one frame's worth of pixel data as image data.

[0033] The storage unit 1007 is a non-volatile memory such as a flash memory or a hard disk drive, and stores image data output from the image processing unit 1005 in a non-volatile manner. The display unit 1008 includes a display device such as an LCD (Liquid Crystal Display) and a drive circuit for driving the display device, and can display an image based on the image data output from the image processing unit 1005. The I / F unit 1009 is an interface for transmitting the image data output from the image processing unit 1005 to an external device. For example, a USB (Universal Serial Bus) can be used as the I / F unit 1009. However, the I / F unit 1009 is not limited to this, and may also be an interface that can be connected to a network via wired or wireless communication.

[0034] The input device 1012 includes an operator for accepting user input, etc. If the electronic device 1000 is, for example, a digital still camera, a digital video camera, a mobile phone with an imaging function, or a smartphone, the input device 1012 may include a shutter button for instructing the imaging device 1004 to capture an image, or an operator for realizing the function of the shutter button.

[0035] The control unit 1003 includes a processor such as a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), and controls the overall operation of the electronic device 1000 in accordance with a program pre-stored in the ROM, using the RAM as a work memory. For example, the control unit 1003 can control the operation of the electronic device 1000 in response to a user input received by the input device 1012. The control unit 1003 can also control an autofocus mechanism in the optical system 1002 based on the image processing results of the image processing unit 1005.

[0036] First Embodiment Fig. 2 is a block diagram of an imaging device 1004 according to a first embodiment of the present disclosure. In Fig. 2, the imaging device 1004 includes a pixel array unit 11, a vertical drive unit 12, a system control unit 13, a DAC (Digital to Analog Converter) 14, a column control unit 15, a plurality of reference signal switchers (switchers) 16, a plurality of column readout units 17, a column signal processing unit 18, and a horizontal drive unit 19. The imaging device 1004 can be configured as a CMOS image sensor (CIS) in which each of these units is integrally formed using CMOS (Complementary Metal Oxide Semiconductor).

[0037] The pixel array unit 11 includes a plurality of pixels 10 arranged in a first direction (for example, horizontal direction or row direction) X and a second direction (for example, vertical direction or column direction) Y.

[0038] In the pixel array unit 11, each pixel 10 includes a photoelectric conversion element that generates an electric charge in response to received light, and a pixel circuit that outputs a pixel signal based on the electric charge generated by the photoelectric conversion element. The vertical drive unit 12 drives each pixel 10 included in the pixel array unit 11 row by row, causing each pixel 10 to output a pixel signal. At this time, the vertical drive unit 12 sequentially drives each pixel 10 in row order, causing each pixel 10 to output a pixel signal. In other words, the vertical drive unit 12 functions as a read control circuit that controls the reading of electric charges from the photoelectric conversion elements and the output of pixel signals.

[0039] The system control unit 13 synchronizes with the vertical synchronization signal VSYNC to control the operation timing of each of the vertical drive unit 12, the DAC 14, the column control unit 15, the plurality of column readout units 17, the column signal processing unit 18, and the horizontal drive unit 19. The vertical synchronization signal VSYNC is a periodic signal of a predetermined frequency (for example, 60 Hz) that indicates the imaging timing.

[0040] The DAC 14 generates a predetermined reference signal by DA (Digital to Analog) conversion. For example, a sawtooth reference (RAMP) signal is used as the reference signal. The DAC 14 supplies the reference signal to the column signal processing unit 18.

[0041] In the imaging device 1004 according to the first embodiment, each of the multiple vertical signal lines VSL extending in the second direction (column direction) Y of the pixel array section 11 is divided into multiple parts, and multiple column control sections 15 are provided corresponding to the multiple divided signal lines.

[0042] The column control units 15 perform switching control of the reference signal switchers 16 in response to an instruction from the system control unit 13. The reference signal switchers 16 switch whether or not to input the reference signal generated by the DAC 14 to the column readout units 17.

[0043] Each of the plurality of column readout units 17 has a plurality of analog-to-digital converters (hereinafter referred to as ADCs), and each ADC converts a pixel signal into a digital signal. As will be described later, the ADC has a comparator (also called a comparator) 20 and a counter 30 (digital signal generator). The plurality of reference signal switches 16 described above are provided corresponding to the plurality of column readout units 17. The plurality of reference signal switches 16 sequentially select one of the plurality of column readout units 17 to input a reference signal to, so that a reference signal is not input to two or more column readout units 17 simultaneously.

[0044] The column signal processing unit 18 performs signal processing such as CDS (Correlated Double Sampling) processing on the digital pixel signals converted by the multiple column readout units 17 for each column. The column signal processing unit 18 outputs digital pixel signals (pixel data) after the signal processing. The pixel data output from the column signal processing unit 18 is supplied to the image processing unit 1005.

[0045] The horizontal driving unit 19 has a shift register, an address decoder, etc., and causes the column signal processing unit 18 to sequentially output pixel data that has been subjected to signal processing for each column.

[0046] (Processing Flow in Existing Technology) Next, signal processing of pixel signals in existing technology will be explained in brief. Fig. 3 is a schematic diagram showing signal processing of pixel signals in existing technology. In Fig. 3, a comparator 20 and a counter 30 are included in, for example, the column readout unit 17 in Fig. 2, and a logic circuit is included in, for example, the column signal processing unit 18 in Fig. 2.

[0047] The analog pixel signal output from the pixel 10 is supplied to the comparator 20. The comparator 20 is further supplied with a reference signal RAMP as a reference signal from the DAC 14. The reference signal RAMP is a signal whose level (voltage value) decreases stepwise over time in accordance with, for example, a predetermined clock pulse. The comparator 20 compares the pixel signal with the reference signal RAMP and supplies the comparison result to the counter 30. For example, if the level of the reference signal RAMP is higher than the level of the pixel signal, the comparator 20 outputs a High difference signal to the counter 30. On the other hand, if the level of the reference signal RAMP is equal to or lower than the level of the pixel signal, the comparator 20 inverts its output and outputs a Low difference signal to the counter 30.

[0048] The counter 30 counts the time from when the reference signal RAMP starts to drop in voltage until it reaches a level equal to or lower than that of the pixel signal in each of a P-phase (Preset Phase) period and a D-phase (Data Phase) period, in accordance with the difference signal input from the comparator 20, and outputs each count result to the logic circuit 40. The P-phase period is a period in which the reset level of the pixel signal is detected in CDS processing, and the D-phase period is a detection period in which the signal level of the pixel signal is detected in CDS processing.

[0049] The logic circuit 40 performs CDS processing and AD conversion processing based on the count result of the P-phase period and the count result of the D-phase period input from the counter 30, and generates and outputs a digital pixel signal (pixel data).

[0050] (Structure of Image Capturing Device 1004 Applicable to Each Embodiment) Next, a structure of the image capturing device 1004 applicable to each embodiment will be described in brief. The image capturing device 1004 according to the embodiment can be formed by a stacked structure in which multiple semiconductor chips are stacked.

[0051] As an example, the imaging device 1004 can be formed with a two-layer structure in which semiconductor chips are stacked in two layers. Fig. 4A is a diagram showing an example in which the imaging device 1004 according to each embodiment is formed with a two-layer stacked CIS. In the structure of Fig. 4A, a pixel section 2010 is formed in a first layer of semiconductor chips, and a memory + logic section 2011 is formed in a second layer of semiconductor chips.

[0052] The pixel unit 2010 includes at least a pixel array unit 11. The memory + logic unit 2011 can include, for example, a vertical drive unit 12, a system control unit 13, a DAC 14, a column signal processing unit 18, a horizontal drive unit 19, and an interface for communicating between the imaging device 1004 and the outside. The memory + logic unit 2011 can also include, for example, a memory that stores pixel data output from the column signal processing unit 18.

[0053] As shown on the right side of FIG. 4A, the imaging device 1004 is configured as a single solid-state imaging element 2000a by bonding the semiconductor chip of the first layer and the semiconductor chip of the second layer together while making electrical contact with each other.

[0054] As another example, the imaging device 1004 can be formed with a three-layer structure in which semiconductor chips are stacked in three layers. FIG. 4B is a diagram showing an example in which the imaging device 1004 according to each embodiment is formed using a three-layer stacked CIS. In the structure of FIG. 4B , a pixel unit 2010 is formed in a first layer of semiconductor chips, a memory unit 2012 is formed in a second layer of semiconductor chips, and a logic unit 2011′ is formed in a third layer of semiconductor chips. In this case, the logic unit 2011′ can include a vertical driver 12, a system controller 13, a DAC 14, a column signal processor 18, a horizontal driver 19, and an interface for communication between the imaging device 1004 and the outside. The memory unit 2012 can also include a memory for storing pixel data output from, for example, the column signal processor 18.

[0055] As shown on the right side of Figure 4B, the imaging device 1004 is constructed as a single solid-state imaging element 2000b by bonding the first layer semiconductor chip, the second layer semiconductor chip, and the third layer semiconductor chip together while maintaining electrical contact.

[0056] (Stacked Structure) As shown in FIGS. 4A and 4B , the imaging device 1004 according to the first embodiment can be configured by stacking multiple semiconductor substrates. The number of layers can be any number. FIG. 5 is a schematic diagram showing the stacked structure of the imaging device 1004 according to the first embodiment. In the example of FIG. 5 , the imaging device 1004 employs the two-layer solid-state imaging element 2000a described with reference to FIG. 4A . In the case of a back-illuminated image sensor, photoelectric conversion elements are formed on a first layer 2010a of a substrate, and pixel circuits that convert charges generated by the photoelectric conversion elements into pixel signals and output the signals are formed on a second layer 2010b of the substrate. The first layer 2010a and the second layer 2010b form the pixel section 2010.

[0057] 5 , photoelectric conversion units 100, each including a photoelectric conversion element and a transistor for controlling readout of electric charges from the photoelectric conversion element, are arranged in a matrix on the first layer 2010a. Circuit units 101, each including a pixel circuit for converting electric charges readout from the photoelectric conversion units 100 into pixel signals, are arranged in a matrix on the second layer 2010b in correspondence with the photoelectric conversion units 100 on the first layer 2010a. More specifically, the circuit units 101 are arranged in electrical contact between the first layer 2010a and the second layer 2010b in a one-to-one relationship with the photoelectric conversion units 100 that correspond to their positions on the first layer 2010a.

[0058] In each embodiment, the circuit unit 101 (denoted as Pixel-CMP(1) in the drawings) further includes a portion of the comparator 20. That is, in each embodiment, the comparator 20 is configured by being divided into at least two portions: a first circuit (denoted as CMP(1)) to which a pixel signal is directly supplied from the pixel circuit, and a second circuit and a third circuit (denoted as CMP(2) and (3)) to which the output of the first circuit is supplied. The first circuit includes, for example, a circuit that compares the pixel signal output from the pixel circuit with a reference signal RAMP supplied from the DAC 14.

[0059] In FIG. 5, a vertical drive unit 12, a counter 30, a logic circuit 40, a peripheral circuit 50, and an interface circuit 60 (also referred to as an IF circuit in the drawing) are arranged for a memory+logic unit 2011.

[0060] The peripheral circuit 50 includes a DAC 14. The interface circuit 60 is an interface for transmitting and receiving signals between the imaging device 1004 as the solid-state imaging element 2000a and the outside.

[0061] 5, the vertical drive unit 12 is arranged along the column direction of the pixel array unit 11, at one end in the row direction of the memory+logic unit 2011 (the right end in the example shown in the figure). The interface circuit 60 is arranged along the column direction of the pixel array unit 11, at the other end in the row direction of the memory+logic unit 2011 (the left end in the example shown in the figure).

[0062] Further, a second circuit 210 obtained by dividing the comparator 20 is disposed for the memory+logic unit 2011. In the example of Fig. 5 , the second circuit 210 is disposed along the row direction of the memory+logic unit 2011, at one end and the other end in the column direction (top and bottom ends in the example of Fig. 5 ). The second circuit 210 is provided for each column in the pixel array unit 11. In the example of Fig. 5 , the second circuit 210 is provided along the row direction of the pixel array unit 11, at both ends in the column direction of the memory+logic unit 2011.

[0063] The second circuits 210 are shared by a plurality of circuit units 101 arranged along a column in the second layer 2010b. For example, each second circuit 210 arranged at one end of the column direction of the memory+logic unit 2011 (e.g., the upper end in the figure) is shared by each circuit unit 101 arranged in the half of the column side (the upper half in the example of FIG. 5 ) of the circuit units 101 arranged on the second layer 2010b. Similarly, each second circuit 210 arranged at the other end of the column direction of the memory+logic unit 2011 (e.g., the lower end in FIG. 5 ) is shared by each circuit unit 101 arranged in the half of the column side (the lower half in the example of FIG. 5 ) of the circuit units 101 arranged on the second layer 2010b.

[0064] Each pixel 10 (each photoelectric conversion unit 100 and each circuit unit 101) is scanned in the column direction, i.e., the vertical direction, as indicated by the arrow. The output from each pixel 10 (each circuit unit 101) is transferred to the memory+logic unit 2011 row by row.

[0065] FIG. 6 is a schematic diagram illustrating signal processing for a pixel signal according to the present disclosure. The comparator 20 according to the present disclosure can be configured by being divided into multiple circuits. In the example of FIG. 6, the comparator 20 is divided into three circuits: a first-stage comparator 201, a middle-stage comparator 202, and a latter-stage comparator 203. The first-stage comparator 201 corresponds to the first circuit described with reference to FIG. 5 and includes, for example, a circuit that compares a pixel signal output from the pixel 10 with a reference signal RAMP supplied from the DAC 14. The middle-stage comparator 202 and the latter-stage comparator 203 correspond to the second circuit described with reference to FIG. 5 and compare the output of the first circuit with a threshold value. The middle-stage comparator 202 and the latter-stage comparator 203 can also be configured as a single circuit.

[0066] (Example of dividing the pixel array unit 11 into regions) By dividing the pixel array unit 11 into multiple regions in the vertical direction and transferring pixel signals for each divided region, it is possible to shorten the transmission distance of pixel signals. Fig. 7 is a schematic diagram showing an example in which the pixel array unit 11 is divided into multiple regions in the vertical direction.

[0067] 7, in the pixel unit 2010, the pixel array unit 11 is divided vertically into four regions: pixel regions 11Up1 and 11Up2, and pixel regions 11Dwn1 and 11Dwn2. Of these, the pixel regions 11Up1 and 11Up2 are the first and second upper pixel regions, respectively, and the pixel regions 11Dwn1 and 11Dwn2 are the first and second lower pixel regions, respectively.

[0068] In the memory+logic section 2011, an analog circuit 80Up1 and a logic circuit 40Up1 are arranged in a position corresponding to the pixel region 11Up1, and an analog circuit 80Up2 and a logic circuit 40Up2 are arranged in a position corresponding to the pixel region 11Up2. Similarly, an analog circuit 80Dwn1 and a logic circuit 40Dwn1 are arranged in a position corresponding to the pixel region 11Dwn1, and an analog circuit 80Up2 and a logic circuit 40Dwn2 are arranged in a position corresponding to the pixel region 11Up2.

[0069] Each of the analog circuits 80Up1, 80Up2, 80Dwn1, and 80Dwn2 includes, for example, a pixel circuit, a comparator 20, and a counter 30.

[0070] The pixel signals output from each pixel in the pixel region 11Up1 are input to the pixel region 11Up １ through the vertical signal line VSL in the pixel area 11Up １ The signal is transferred from the end of the analog circuit 80Up1 to the memory+logic unit 2011 and input to the analog circuit 80Up1. The output of the analog circuit 80Up1 is input to the logic circuit 40Up1. The same applies to the pixel regions 11Up2, 11Dwn1, and 11Dwn2.

[0071] 7, pixel signals output from each pixel are transferred over a distance of at most ¼ of the distance between both ends of the pixel array unit 11 in the column direction. However, the pixel signals are transmitted via the vertical signal lines VSL, which is the same as in the existing configuration. Therefore, the parasitic capacitance of the shortened vertical signal lines VSL only affects settling in the pixels 10 and is unlikely to lead to improvements in characteristics such as the effect of noise.

[0072] In contrast to this, in each embodiment of the present disclosure, the distance over which a pixel signal corresponding to charge generated in the pixel 10 is transmitted to the first-stage comparator 201 is extremely short, which shortens the settling time in the pixel 10 and thereby speeds up the readout time of charge from the pixel 10. Furthermore, because the vertical signal line VSL, which is a large load, is connected to the output side of the first-stage comparator 201, it is possible to narrow the bandwidth of the signal transferred to the vertical signal line VSL, thereby enabling noise reduction.

[0073] In the above description, the vertical signal line VSL is divided in the vertical direction to reduce the load on the vertical signal line VSL. However, even if the number of divisions of the vertical signal line VSL is increased, it is necessary to route wiring to the input terminal of the ADC provided in the column signal processing unit 18, making it difficult to increase the processing speed and achieve a high frame rate. For example, in a two-layer stacked structure, the number of divisions of the vertical signal line VSL is limited to about two. Furthermore, since one ADC corresponds to multiple pixels, the load at the pixel switching point becomes heavy.

[0074] For this reason, in the imaging device 1004 according to the present disclosure, one first-stage comparator 201 is arranged for each divided region of the vertical signal line VSL in an intermediate layer (second layer of the first substrate) of a three-layer configuration consisting of the first and second layers of the first substrate and the second substrate, and the output of the first-stage comparator 201 is switched by a select switch and input to the intermediate-stage comparator 202. By adopting such a configuration, the load on the VSL is reduced by the amount that the number of divisions of the vertical signal line VSL is increased, enabling faster processing and a higher frame rate.

[0075] Furthermore, in the imaging device 1004 according to the present disclosure, multiple pixels (photoelectric conversion units 100) are connected to one first-stage comparator 201. That is, in the imaging device 1004 according to the present disclosure, the connection is switched at two points: between the pixel and the first-stage comparator 201, and between the first-stage comparator 201 and the middle-stage comparator 202. This reduces the load at the pixel switching points (i.e., the VSL wiring).

[0076] FIG. 8 is a schematic diagram illustrating signal processing for pixel signals in the imaging device 1004 according to the present disclosure.

[0077] 8, similarly to the above-described Fig. 6, the comparator 20 includes a first-stage comparator 201, a middle-stage comparator 202, and a second-stage comparator 203, and the output of the second-stage comparator 203 is input to a counter 30, and the output of the counter 30 is input to a logic circuit 40. In addition, a reference signal RAMP output from the DAC 14 is supplied to the first-stage comparator 201.

[0078] In the configuration shown in FIG. 8, the first-stage comparator 201 has N (N≧1) pixels 101, 102, . . . , 10 N The pixel signals from the first stage comparator 201 and the pixels 101, 102, ..., 10 N M (M≧2) pixel / first stage comparator units 250 1 , 250 2 , . . . , 250 M The output of is input to the middle comparator 202.

[0079] Among these, pixel / first stage comparator units 2501, 2502, ..., 250 M Each pixel 101, 102, ..., 10 N are arranged on a first layer 2010a of the pixel section 2010, and the initial-stage comparators 201 are arranged on a second layer 2010b of the pixel section 2010. The configuration from the middle-stage comparator 202 onwards is arranged in a memory+logic section 2011.

[0080] 9 is a schematic diagram for explaining division of the VSL in the imaging device 1004 according to the present disclosure. In FIG. 9, the first-stage comparators 201 to 201 M are also shown as first circuits CMP(1), respectively. The subsequent circuit 251 includes a middle stage comparator 202 and a subsequent stage comparator 203 (second and third circuits CMP(2), (3)), and a counter 30.

[0081] As shown in FIG. 9, VSL is a voltage signal from pixel / first stage comparator units 250 1 , 250 2 , . . . , 250 M In each of the above, each pixel 101 to 10N and the corresponding first stage comparators 2011 to 201 M That is, in the imaging device 1004 according to the present disclosure, the VSL is connected to the first-stage comparators 201 to 201. M It is divided into each.

[0082] In this way, in the imaging device 1004 according to the present disclosure, each of the pixels 101 to 10 N and the first-stage comparator 201, and each pixel / first-stage comparator unit 2501 to 2502 M Therefore, VSL is connected to the first stage comparators 201 to 201. M The load on the VSL wiring is reduced.

[0083] (Detailed Description of First Embodiment) As shown in FIG. 2 , the imaging device 1004 according to the first embodiment has a plurality of reference signal switches 16 corresponding to a plurality of column readout units 17. The plurality of reference signal switches 16 are switched on or off by the column control unit 15. When the plurality of reference signal switches 16 are turned on, they input reference signals to the corresponding column readout units 17. Two or more reference signal switches 16 are not turned on at the same time. The column control unit 15 sequentially turns on the plurality of reference signal switches 16 to sequentially input reference signals to the plurality of column readout units 17. This reduces the load on the reference signal line Sramp that transmits the reference signal, enabling faster AD conversion processing and frame rate.

[0084] 10A and 10B show an example in which four column readout units 17 and four reference signal switches 16 are provided corresponding to four divided signal lines obtained by dividing the vertical signal line VSL into four. Fig. 10A shows an example in which the topmost reference signal switch 16 of the four reference signal switches 16 is turned on, and Fig. 10B shows an example in which the second-highest reference signal switch 16 of the four reference signal switches 16 is turned on. When a reference signal switch 16 is turned on, a reference signal is input to the corresponding column readout unit 17, and AD conversion is performed.

[0085] The column control unit 15 sequentially turns on the four reference signal switches 16 while the imaging device 1004 according to the first embodiment generates one frame of captured image.

[0086] As described above, in the first embodiment, two or more of the multiple reference signal switches 16 are prevented from being turned on at the same time, thereby reducing the load on the reference signal line Sramp.

[0087] 11 is a graph showing the relationship between the number of reference signal switches 16 that are simultaneously turned on and the load on the reference signal line Sramp. The horizontal axis of FIG. 11 represents the number of reference signal switches that are simultaneously turned on, and the vertical axis represents the signal bandwidth ratio. A smaller signal bandwidth ratio indicates a larger load. As shown in FIG. 11, as the number of reference signal switches 16 that are simultaneously turned on increases, the signal bandwidth ratio decreases and the load on the reference signal line Sramp increases.

[0088] 12A and 12B are graphs showing the relationship between the settling time of the reference signal RAMP on the reference signal line Sramp and the signal bandwidth. Fig. 12A shows a graph in the case where only one reference signal switch 16 is turned on at the same time, and Fig. 12B shows a graph in the case where two or more reference signal switches 16 are turned on at the same time. The horizontal axis of Fig. 12A and Fig. 12B represents time, and the vertical axis represents signal level.

[0089] As can be seen from FIGS. 12A and 12B, when two or more reference signal switches 16 are turned on simultaneously, the load on the reference signal line Sramp increases, the settling time becomes longer, and the signal band becomes narrower.

[0090] 13 is a timing diagram of the imaging device 1004 according to the first embodiment. Fig. 13 illustrates the waveforms of the vertical synchronization signal XVS, the horizontal synchronization signal XHS, a plurality of switching control signals output by the column control unit 15, the reference signals output from the DAC 14 and input to the plurality of reference signal switchers 16, and the output signals of the plurality of reference signal switchers 16. In this specification, the plurality of reference signal switchers 16 are referred to as reference signal switchers 16a, 16b, 16c, and 16d. In Fig. 13, times t1 to t5 correspond to one frame period, and the vertical synchronization signal XVS is output at times t1 and t5.

[0091] The column control unit 15 shifts the phases of four switching control signals that turn on or off the four reference signal switches 16a to 16d. When each switching control signal is at a high level, the corresponding reference signal switch 16 is turned on. By shifting the phases of the four phase control signals, reference signals are input sequentially to the four column readout units 17 during one frame period. As a result, reference signals are input to different column readout units 17 at times t1 to t2, t2 to t3, t3 to t4, and t4 to t5, and AD conversion of pixel signals is performed in each column readout unit 17.

[0092] In this way, in this embodiment, instead of inputting reference signals to the four column readout units 17 simultaneously using a single reference signal line Sramp, the four reference signal switches 16a to 16d are turned on one by one at different times, and the reference signals are input to the four column readout units 17 at different times. This reduces the load on the input node of each column readout unit 17, speeds up AD conversion, and ultimately speeds up the frame rate.

[0093] 14 is a circuit diagram showing a first example of the reference signal switcher 16. The reference signal switcher 16 according to the first example has a PMOS transistor Q1 connected between a first node n1 and a second node n2, and an NMOS transistor Q2 connected between the first node n1 and the second node n2. Switching control signals Φ1 and Φ2 having opposite logic values ​​are input to the gates of the PMOS transistor Q1 and NMOS transistor Q2.

[0094] In this way, by connecting a PMOS transistor and an NMOS transistor in parallel between the first node n1 and the second node n2, the reference signal input to the first node n1 can be output from the second node n2 without attenuating the signal level.

[0095] 15 is a circuit diagram showing a second example of the reference signal switcher 16. In addition to the circuit configuration of the first example, the reference signal switcher 16 according to the second example includes a capacitor C1 connected between the second node n2 and a reference voltage node (e.g., a ground node). This capacitor C1 functions as a hold capacitance, and can hold the reference signal for a long period of time even if the switch control signal outputs a pulse for only a short time, turning on the reference signal switcher 16 for only a short time.

[0096] FIG. 16 is a circuit diagram showing a third example of the reference signal switch 16. The reference signal switch 16 according to the third example has a circuit configuration that takes measures against injection current. Injection current is an electric charge that flows from the gate into the signal wiring when the switch is switched, and can cause fluctuations in the voltage level of the signal wiring. The reference signal switch 16 according to the third example includes a PMOS transistor Q1 and an NMOS transistor Q2 connected in parallel between a first node n1 and a second node n2, PMOS transistors Q3 and Q4, NMOS transistors Q5 and Q6, and a capacitor C1. The source and drain of the transistor Q3 are connected to the first node n1. The source and drain of the transistor Q4 are connected to the second node n2. An inverted switching control signal having the opposite logic to the switching control signal input to the gate of the transistor Q1 is input to the gates of the transistors Q3 and Q4. The source and drain of the transistor Q5 are connected to the first node n1. The source and drain of the transistor Q6 are connected to the second node n2. A switching control signal having the same logic as the switching control signal input to the gate of the transistor Q1 is input to the gates of the transistors Q5 and Q6.

[0097] By reversing the logic of the switching control signals applied to the gates of transistors Q1 and Q3, the injection current can be released from the gate of transistor Q1 to the gate of transistor Q3, as indicated by the arrow y1. Similarly, by reversing the logic of the switching control signals applied to the gates of transistors Q1 and Q4, the injection current can be released from the gate of transistor Q1 to the gate of transistor Q3, as indicated by the arrow y2. Similarly, by reversing the logic of the switching control signals applied to the gates of transistors Q2 and Q5, the injection current can be released from the gate of transistor Q2 to the gate of transistor Q5, as indicated by the arrow y3. Similarly, by reversing the logic of the switching control signals applied to the gates of transistors Q2 and Q6, the injection current can be released from the gate of transistor Q2 to the gate of transistor Q6, as indicated by the arrow y4.

[0098] In this way, the reference signal switcher 16 according to the third example shown in FIG. 16 reverses the logic of the switching control signal input to the gate of transistor Q1 and the gates of transistors Q3 and Q4, and reverses the logic of the switching control signal input to the gate of transistor Q2 and the gates of transistors Q5 and Q6, thereby allowing the injection current to escape and suppressing fluctuations in the voltage level of the second node n2.

[0099] 17 is a circuit diagram showing a fourth example of the reference signal switch 16. The reference signal switch 16 according to the fourth example has a circuit configuration that maintains a constant gate-source voltage of the main switch. As shown in FIG. 17 , the reference signal switch 16 according to the fourth example includes an NMOS transistor Q1 that serves as a main switch and is connected between a first node n1 and a second node n2, a voltage source 21 that outputs a bias voltage between a third node n3 and a fourth node n4, a first switch 22, a second switch 23, and a third switch 24 that are connected in series between the third node n3 and a reference voltage (e.g., ground voltage) node, a fourth switch 25 and a fifth switch 26 that are connected in series between the fourth node n4 and the first node n1, a first capacitor C1 that is connected between the connection node of the first switch 22 and the second switch 23 and the connection node of the fourth switch 25 and the fifth switch 26, and a second capacitor C2 that is connected between the second node n2 and the reference voltage (e.g., ground voltage) node.

[0100] A switching control signal output from the connection node between the second switch 23 and the third switch 24 is input to the gate of the transistor Q1. When the first node n1 and the second node n2 are made conductive, the first switch 22, the third switch 24, and the fourth switch 25 are made disconnected, and the second switch 23 and the fifth switch 26 are made conductive. When the first node n1 and the second node n2 are made disconnected, the first switch 22, the third switch 24, and the fourth switch 25 are made conductive, and the second switch 23 and the fifth switch 26 are made disconnected.

[0101] The first capacitor C1 accumulates a charge according to the bias voltage Vb. The gate-source voltage Vgs of the transistor Q1, which is the main switch, is a fixed value expressed using the bias voltage Vb, the capacitance Cb of the first capacitor C1, and the gate capacitance Cg of the transistor Q1, as shown in the following equation (1).

[0102] Vgs=(Cb×Vb) / Cg (1) The column control unit 15 outputs a switching control signal φ1 that controls switching of the first switch 22, the third switch 24, and the fourth switch 25, and a switching control signal φ2 that controls switching of the second switch 23 and the fifth switch 26. The switching control signals φ1 and φ2 have opposite logics to each other.

[0103] When the switching control signal φ1 is at a high level and the switching control signal φ2 is at a low level, the first switch 22, the third switch 24, and the fourth switch 25 are conductive, and the second switch 23 and the fifth switch 26 are cut off. At this time, the first capacitor C1 performs a sampling operation to accumulate a charge corresponding to the bias voltage Vb. Also, the transistor Q1 is turned off.

[0104] When the switching control signal φ1 is at a low level and the switching control signal φ2 is at a high level, the first switch 22, the third switch 24, and the fourth switch 25 are turned off, and the second switch 23 and the fifth switch 26 are turned on. At this time, the first capacitor C1 holds the accumulated charge, and the transistor Q1 is turned on.

[0105] In the reference signal switcher 16 according to the fourth example, the gate-source voltage Vgs of the transistor Q1 is constant, which makes it possible to maintain a constant on-resistance of the reference signal switcher 16. Therefore, even if the signal level of the reference signal changes, the signal quality (linearity, etc.) of the second node n2, which is the output node of the reference signal switcher 16, can be maintained.

[0106] Furthermore, by maintaining a high gate-source voltage Vgs of the transistor Q1, which is the main switch, the on-resistance can be reduced, and signal quality such as signal bandwidth and noise can be improved. Normally, to improve signal quality, it is necessary to increase the aspect ratio of the main switch, which allows the areas of the transistor Q1 and the first capacitor C1 to be reduced.

[0107] If the voltage level of the bias voltage Vb is increased, it becomes necessary to take into consideration the withstand voltage margin of the gate of the transistor Q1.

[0108] 18 is a circuit diagram showing a fifth example of the reference signal switch 16. As shown in Fig. 18, the reference signal switch 16 according to the fifth example includes an NMOS transistor Q1 serving as a main switch connected between a first node n1 and a second node n2, a first switch 22, a second switch 23, and a third switch 24 connected in series between a first reference voltage (e.g., power supply voltage) node and a second reference voltage (e.g., ground voltage) node, a fourth switch 25 and a fifth switch 26 connected in series between the second reference voltage (e.g., ground voltage) node and the first node n1, a first capacitor C1 connected between a connection node of the fourth switch 25 and the fifth switch 26, and a second capacitor C2 connected between the second node n2 and the reference voltage (e.g., ground voltage) node.

[0109] The first switch 22, second switch 23, third switch 24, fourth switch 25, and fifth switch 26 in the reference signal switch 16 of the fifth example are controlled to switch by switching control signals φ1 and φ2, similar to the first switch 22 to fifth switch 26 in the reference signal switch 16 of the fourth example.

[0110] The reference signal switch 16 according to the fifth example is characterized in that it omits the voltage source 21 of the reference signal switch 16 according to the fourth example and sets the bias voltage Vb to the differential voltage between the power supply voltage VDD and the ground voltage VSS. In this way, the imaging device 1004 according to the first embodiment sequentially shifts the timing at which the multiple reference signal switches 16 are turned on, thereby inputting reference signals to the multiple column readout units 17 one by one at different times. This reduces the load on the reference signal line Sramp, speeds up the AD conversion and frame rate in each column readout unit 17, and reduces power consumption.

[0111] (Second embodiment) In the first embodiment, one of the multiple reference signal switches 16 is sequentially turned on to sequentially input the reference signal RAMP to the corresponding column readout unit 17, but a configuration can also be considered in which a preamplifier is placed in front of each column readout unit 17 to improve the drive capability of the reference signal.

[0112] 19A and 19B are block diagrams of the periphery of a column readout unit 17 of an imaging device 1004 according to the second embodiment. The imaging device 1004 according to the second embodiment has a preamplifier 31 arranged in front of each of the multiple column readout units 17. Except for the preamplifier 31 being arranged in front of each column readout unit 17, the imaging device 1004 has the same configuration as in FIGS. 10A and 10B.

[0113] 19A shows an example in which the top reference signal switch 16 of the four reference signal switches 16 is turned on, and the reference signal RAMP is input to the column readout unit 17 via the top preamplifier 31. Fig. 19B shows an example in which the second reference signal switch 16 of the four reference signal switches 16 is turned on, and the reference signal RAMP is input to the column readout unit 17 via the second preamplifier 31.

[0114] The preamplifier 31 has a source follower circuit 32. The preamplifier 31 performs impedance conversion of the reference signal using the source follower circuit 32, thereby lowering the output impedance and outputting a reference signal RAMP that changes faithfully in accordance with changes in the signal level of the input reference signal RAMP.

[0115] 20 is a circuit diagram showing a first example of the internal configuration of a preamplifier 31. The preamplifier 31 according to the first example is a source follower circuit 32 having a current source transistor Q11, a first current cut transistor Q12, a cascode transistor Q13, an input transistor Q14, and a second current cut transistor Q15, which are connected in series between a first reference voltage (e.g., power supply voltage) node and a second reference voltage (e.g., ground voltage) node. Only the second current cut transistor Q15 in the source follower circuit 32 is an NMOS transistor, and the other transistors are PMOS transistors.

[0116] The current source transistor Q11 functions as a current source, and a predetermined voltage is input to its gate. The first current cut transistor Q12 and the second current cut transistor Q15 are used to prevent current from flowing between the source and drain of the input transistor Q14 when the input transistor Q14 is turned on. A reference signal RAMP is input to the gate of the input transistor Q14.

[0117] The source of the input transistor Q14 and the drain of the cascode transistor Q13 are connected to the output node of the preamplifier 31. An impedance-converted reference signal RAMP is output from the output node of the preamplifier 31. The reference signal RAMP output from the output node of the preamplifier 31 is input to the corresponding column readout unit 17, where it is subjected to AD conversion processing.

[0118] The first current cut transistor Q12 and the second current cut transistor Q15 in the source follower circuit 32 connected in the upstream stage of the column readout unit 17 to which the reference signal RAMP is not input are set to OFF. This allows the input node of the corresponding column readout unit 17 to have a high impedance, and prevents unnecessary current from flowing through the source follower circuit 32, thereby reducing power consumption. On the other hand, the first current cut transistor Q12 and the second current cut transistor Q15 in the source follower circuit 32 connected in the upstream stage of the column readout unit 17 to which the reference signal RAMP is input are set to ON. This causes the reference signal RAMP with low output impedance to be output from the output node of the source follower circuit 32 and input to the corresponding column readout unit 17.

[0119] Various modifications can be made to the internal configuration of the source follower circuit 32 that constitutes the preamplifier 31. Fig. 21 is a circuit diagram showing a second example of the internal configuration of the preamplifier 31. In the preamplifier 31 of the second example, the connection order of the first current cut transistor Q12 and the cascode transistor Q13 in the preamplifier 31 of the first example is reversed, but the rest of the circuit configuration is the same.

[0120] In FIG. 21, when the first current cut transistor Q12 is turned off, the drain side of the first current cut transistor Q12 becomes high impedance, resulting in the same circuit operation as when the cascode transistor Q13 is turned off, and therefore the connection order of the first current cut transistor Q12 and the cascode transistor Q13 can be reversed.

[0121] 22 is a circuit diagram showing a third example of the internal configuration of the preamplifier 31. The preamplifier 31 according to the third example omits the first current cut transistor Q12 shown in FIG. 20 and connects a current cut switch 39 having the same function as the first current cut transistor Q12 to its gate. This effectively allows the cascode transistor Q13 to double as the first current cut transistor Q12. The current cut switch 39 includes a PMOS transistor Q16 connected between the gate of the cascode transistor Q13 and a first reference voltage (e.g., power supply voltage) node, and a PMOS transistor Q17 connected between the gate of the cascode transistor Q13 and a second reference voltage (e.g., ground voltage) node.

[0122] Switching control signals of opposite logic are input to the gates of PMOS transistors Q16 and Q17. When PMOS transistor Q16 is turned on, PMOS transistor Q17 is turned off and cascode transistor Q13 is turned off. When PMOS transistor Q16 is turned off, PMOS transistor Q17 is turned on and cascode transistor Q13 is turned on. In this way, by using current cut switch 39, cascode transistor Q13 can be reliably turned off.

[0123] Fig. 23 is a circuit diagram showing a fourth example of the internal configuration of preamplifier 31. Preamplifier 31 according to the fourth example includes a precharge circuit 33 connected to the output node of preamplifier 31 according to any of the first to third examples. Fig. 23 shows a configuration in which precharge circuit 33 is connected to the output node of preamplifier 31 according to the first example, but precharge circuit 33 may also be connected to the output node of preamplifier 31 shown in Fig. 21 or 22.

[0124] The precharge circuit 33 has a precharge switch 34 connected to the output node of the preamplifier 31. The precharge switch 34 switches whether or not to supply a precharge signal to the output node of the preamplifier 31. As will be described later, the precharge signal is, for example, a signal at the reference voltage level of the reference signal RAMP.

[0125] Of the multiple column readout units 17, only one receives the reference signal RAMP via the multiple reference signal switches 16 and multiple preamplifiers 31, and the column readout unit 17 to which the reference signal RAMP is input is switched sequentially. The input node of the column readout unit 17 to which the reference signal RAMP is not input may have a signal level that is significantly different from the signal level of the reference signal RAMP, which increases the settling time when the reference signal RAMP is input. Therefore, by precharging the signal level of the input node of the column readout unit 17 to which the reference signal RAMP is not input with a precharge signal, the settling time when the reference signal RAMP is input can be shortened.

[0126] As described above, in the second embodiment, a preamplifier 31 is arranged in front of each column readout unit 17, and the first current cut transistor Q12 and the second current cut transistor Q15 of the source follower circuit 32 in the preamplifier 31 are turned on / off in synchronization with the on / off of the plurality of reference signal switches 16. This prevents unnecessary current from flowing in the source follower circuit 32 when the reference signal RAMP is not input to the column readout unit 17, thereby reducing power consumption.

[0127] Furthermore, by connecting a precharge circuit 33 to the output node of the preamplifier 31, the output node of the preamplifier 31 to which the reference signal RAMP is not input can be precharged, and when the reference signal RAMP is subsequently input, the output node of the preamplifier 31 can be quickly set to the desired voltage level, thereby shortening the settling time.

[0128] Third Embodiment The third embodiment relates to a circuit that generates a precharge signal for precharging the output node of the source follower circuit 32 in the preamplifier 31 in the second embodiment.

[0129] 24 is a graph showing the settling time of the reference signal input to the column readout unit 17 when the output node of the source follower circuit 32 is precharged and when it is not precharged. The horizontal axis of Fig. 24 represents time, and the vertical axis represents the voltage level of the input node of the column readout unit 17. The upper waveform shows the voltage waveform of the input node of the column readout unit 17 when the output node of the source follower circuit 32 is not precharged, and the lower waveform shows the voltage waveform of the input node of the column readout unit 17 when the output node of the source follower circuit 32 is precharged.

[0130] 24, the settling time is longer when the output node of the source follower circuit 32 is not precharged than when it is precharged. In the example of FIG. 24, the settling time is reduced to almost zero by precharging the output node of the source follower circuit 32. The AZ level is the reference level of the comparator 20 in the column readout unit 17.

[0131] As described in the second embodiment, when the first current cut transistor Q12 and the second current cut transistor Q15 in the source follower circuit 32 are turned off, the output node of the source follower circuit 32 enters a high impedance state, and the voltage level becomes undefined. Therefore, as shown in FIG. 23 , when the first current cut transistor Q12 and the second current cut transistor Q15 are turned off, it is desirable to precharge the output node of the source follower circuit 32 with a precharge signal. The voltage level of the precharge signal may be the same as the power supply voltage or the ground voltage, and the circuit that inputs the precharge signal may be a simple circuit such as a pull-up resistor or a pull-down resistor. However, if the voltage level of the precharge signal is inappropriate, the settling time when the reference signal is input will be long, and the AD time in the column readout unit 17 will be long.

[0132] The third embodiment is characterized in that the output node of the source follower circuit 32 is precharged to the reference voltage level (AZ level) of the reference signal RAMP used when performing AD conversion in the column readout unit 17, thereby shortening the settling time when the reference signal RAMP is input to the column readout unit 17.

[0133] 25 is a circuit diagram of the periphery of a column readout unit 17 of an imaging device 1004 according to the third embodiment. The imaging device 1004 according to the third embodiment includes a plurality of reference signal switches 16, a plurality of preamplifiers 31, a plurality of column readout units 17, and a precharge circuit 33.

[0134] The precharge circuit 33 has a replica circuit 36 ​​having substantially the same circuit configuration as the source follower circuit 32 in the preamplifier 31. The replica circuit 36 ​​has, for example, a current source transistor Q11, a first current cut transistor Q12, a cascode transistor Q13, an input transistor Q14, and a second current cut transistor Q15.

[0135] The plurality of reference signal switches 16 have, for example, any of the circuit configurations shown in Figures 14 to 18. The plurality of reference signal switches 16 are provided corresponding to the plurality of preamplifiers 31. In addition, a reference signal switch 16 for the precharge circuit 33 is newly provided.

[0136] A replica circuit 36 ​​constituting the precharge circuit 33 outputs a signal at a reference voltage level of the reference signal. A plurality of precharge switches 34 are connected between the output node of the replica circuit 36 ​​and the output nodes of a plurality of source follower circuits 32 in a plurality of preamplifiers 31. Of the plurality of precharge switches 34, the precharge switches 34 connected to the output nodes of the source follower circuits 32 upstream of all column readout units 17 except for the column readout unit 17 to which the reference signal is input are turned on, and the output nodes of the source follower circuits 32 are precharged. On the other hand, the precharge switches 34 connected to the output nodes of the source follower circuits 32 upstream of the column readout unit 17 to which the reference signal is input are turned off, and the reference signal RAMP output from the source follower circuits 32 is input to the column readout unit 17.

[0137] In this embodiment, for the sake of simplicity, an imaging device 1004 will be described that includes two reference signal switchers 16 (16a, 16b) (hereinafter referred to as the first reference signal switcher 16a and the second reference signal switcher 16b), a reference signal switcher 16 for a replica circuit 36 ​​(hereinafter referred to as the third reference signal switcher 16c), two source follower circuits 32 (the first source follower circuit 32a and the second source follower circuit 32b), and two column readout units 17 (the first column readout unit 17 and the second column readout unit 17). In this specification, the first source follower circuit 32a may be abbreviated as SF1, and the second source follower circuit 32b may be abbreviated as SF2.

[0138] 26A and 26B are diagrams for explaining the precharge operation of the imaging device 1004 according to the third embodiment, and Fig. 27 is a timing chart corresponding to the explanations of Fig. 26A and 26B. Fig. 27 shows waveforms of the reference signal RAMP, the gate voltage of the first current cut transistor Q12 in the first source follower circuit 32a, the gate voltage of the second current cut transistor Q15 in the first source follower circuit 32a, the switching control signal of the first reference signal switcher 16a, the output voltage of the first source follower circuit 32a, the gate voltage of the first current cut transistor Q12 in the second source follower circuit 32b, the gate voltage of the second current cut transistor Q15 in the second source follower circuit 32b, the switching control signal of the second reference signal switcher 16b, and the output voltage of the second source follower circuit 32b.

[0139] 26A shows the precharge operation when the first reference signal switch 16a is turned on and the second reference signal switch 16b is turned off, and FIG. 26B shows the precharge operation when the first reference signal switch 16a is turned off and the second reference signal switch 16b is turned on.

[0140] 27, the period from time t1 to time t2 corresponds to a vertical blanking (V-blank) period. During the vertical blanking period, the first reference signal switch 16a and the third reference signal switch 16c are temporarily turned on. As a result, the first reference signal switch 16a and the third reference signal switch 16c each sample and hold the reference signal RAMP.

[0141] During the period from time t2 to t6, the first reference signal switch 16a is turned on, and the reference signal RAMP that passes through the first reference signal switch 16a is input to the first source follower circuit 32a. During this period, the second reference signal switch 16b is turned off. At times t2, t3, t4, and t5, the third reference signal switch 16c is temporarily turned on, and the third reference signal switch 16c samples and holds the reference signal RAMP. This causes the voltage level of the output node of the replica circuit 36 ​​to rise stepwise. The output node of the replica circuit 36 ​​is connected to the output node of the second source follower circuit 32b via the precharge switch 34. Because the precharge switch 34 is on, the output node of the second source follower circuit 32b is precharged to the same voltage level as the output node of the replica circuit 36, as shown in FIG. 26A .

[0142] Therefore, when the first current cut transistor Q12 and the second current cut transistor Q15 in the second source follower circuit 32b are turned on at time t6, as shown in FIG. 26B, the second source follower circuit 32b can start outputting the reference signal RAMP at approximately the same voltage level as before time t6.

[0143] In this way, in the third embodiment, a replica circuit 36 ​​having the same circuit configuration as the source follower circuit 32 is provided to precharge the output nodes of all source follower circuits 32 connected to the column readout unit 17 to which the reference signal RAMP is not input, thereby shortening the settling time of the input node of the column readout unit 17 when the reference signal is input.

[0144] Fourth Embodiment In the first to third embodiments, an example has been described in which a column readout unit 17 is provided for each divided signal line obtained by dividing the vertical signal line VSL into a plurality of lines, but the present invention is also applicable to a configuration in which a plurality of column readout units 17 are provided without dividing the vertical signal line VSL into a plurality of lines. Below, an image pickup device 1004 in which two column readout units 17 are provided without dividing the vertical signal line VSL into a plurality of lines will be described.

[0145] Fig. 28 is a block diagram of an imaging device 1004 according to the fourth embodiment. As shown in Fig. 28, the imaging device 1004 according to the fourth embodiment includes a vertical driver 12, a system controller 13, a DAC 14, a column controller 15, two reference signal switches 16 (16a, 16b), a pixel array unit 11, and two column readout units 17. Note that the column signal processor 18 and horizontal driver 19 are omitted from Fig. 28.

[0146] Fig. 29 is a diagram showing an example of the locations of the two column readout units 17 in Fig. 28. As shown in Fig. 29, the two column readout units 17 are arranged close to each other near the bottom end in the second direction (vertical direction) Y. Two reference signal switches 16 (16a, 16b) are arranged between the two column readout units 17 and the DAC 14.

[0147] The two column readout units 17 may be arranged at an upper end and a lower end in the second direction (vertical direction) Y, spaced apart from each other.

[0148] Fig. 30 is a block diagram of an imaging device 1004 according to a modified example of the fourth embodiment. In Fig. 30, compared to Fig. 29, the column control unit 15 is divided into two and arranged at the upper end and the lower end, and two reference signal switches 16 (16a, 16b) and two column readout units 17 are arranged beside the column control units 15. In Fig. 30, two system control units 13 are provided corresponding to the two column control units 15, but one system control unit 13 may also control two column control units 15.

[0149] 31 is a diagram showing the locations of the two column readout units 17 in FIG. 30. The DAC 14 is disposed near the center of the pixel array unit 11 in the second direction (vertical direction) Y, two reference signal switches 16 (16a, 16b) are disposed at positions approximately equidistant from the DAC 14, and two column readout units 17 are disposed at positions approximately equidistant from the two reference signal switches 16 (16a, 16b). This makes the propagation delay and wiring load of the reference signal line Sramp equal.

[0150] In the following, the two reference signal switchers 16 (16a, 16b) shown in Figures 28 and 30 will be referred to as the first reference signal switcher 16a and the second reference signal switcher 16b, and the two column readout units 17 will be referred to as the first column readout unit 17 and the second column readout unit 17.

[0151] Fig. 32 is a timing diagram of the imaging device 1004 according to the fourth embodiment. Fig. 32 shows the timing when the reference signal input to one of the two column readout units 17 is switched on a frame-by-frame basis. Fig. 32 illustrates the waveforms of the vertical synchronization signal XVS, the horizontal synchronization signal XHS, the switching control signal of the first reference signal switch 16a, the switching control signal of the second reference signal switch 16b, the reference signals input to the first and second reference signal switchers 16b, the output signal of the first reference signal switch 16a, and the output signal of the second reference signal switch 16b.

[0152] During one frame period from time t1 to t2, the first reference signal switch 16a is turned on and the second reference signal switch 16b is turned off. Therefore, a reference signal is output from the first reference signal switch 16a and input to the first column readout unit 17. The output of the second reference signal switch 16b remains at a low level, and no reference signal is input to the second column readout unit 17.

[0153] Figure 32 shows an example in which the reference signal input to one of the two column readout units 17 is switched every frame, but the reference signals input to the two column readout units 17 may also be switched within the scanning period of each horizontal line.

[0154] Fig. 33 is a timing diagram of the imaging device 1004 according to a modified example of the fourth embodiment, showing waveforms of the horizontal synchronization signal XHS, the switching control signal of the first reference signal switch 16a, the switching control signal of the second reference signal switch 16b, the output signal of the first reference signal switch 16a, and the output signal of the second reference signal switch 16b.

[0155] Between times t1 and t2 and between times t3 and t4, the first reference signal switch 16a is on and the second reference signal switch 16b is off, and between times t2 and t3, the first reference signal switch 16a is off and the second reference signal switch 16b is on.

[0156] A reference signal for low conversion efficiency is generated from time t1 to t2 and from time t3 to t4, and a reference signal for high conversion efficiency is generated from time t2 to t3. Furthermore, AD conversion of the reset level is performed from time t1 to t2, and AD conversion of the pixel signal level is performed from time t3 to t4. AD conversion of the reset level and pixel signal level is performed continuously from time t1 to t2.

[0157] In this way, in the fourth embodiment, even if multiple column readout units 17 are provided without dividing the vertical signal line VSL, the load on the reference signal line Sramp can be reduced by sequentially supplying a reference signal to any one of the column readout units 17 using multiple reference signal switchers 16, thereby shortening the AD time and enabling a higher frame rate.

[0158] Fifth Embodiment In a fifth embodiment, an imaging device 1004 according to the present disclosure is applied to a pixel ADC or an area ADC.

[0159] Fig. 34 is a diagram illustrating an image pickup device 1004 according to the fifth embodiment. The image pickup device 1004 in Fig. 34 has an AD converter for each pixel, and a reference signal line Sramp that transmits a reference signal RAMP used in the AD converter of each pixel is provided for each pixel column.

[0160] These multiple reference signal lines Sramp are aligned in a first direction (horizontal direction) X, and the multiple reference signal lines Sramp are connected to multiple reference signal switches 16. When one of the multiple reference signal switches 16 is turned on, the reference signal RAMP output from the turned-on reference signal switch 16 is input to each AD converter of each pixel in the corresponding pixel column.

[0161] Fig. 35 is a diagram illustrating an image pickup device 1004 according to a modified example of the fifth embodiment. The image pickup device 1004 shown in Fig. 35 has an AD converter for each pixel, but can capture an image of only a pixel region of any size as an ROI (Region of Interest).

[0162] 35, only the reference signal switches 16 connected to pixel columns corresponding to the pixel region of the ROI are sequentially turned on, and the reference signal switches 16 connected to pixel columns corresponding to pixel regions other than the pixel region of the ROI are turned off, thereby making it possible to speed up the AD conversion time and frame rate.

[0163] As described above, in the fifth embodiment, when an AD converter is provided for each pixel and a reference signal line Sramp is provided for each pixel column, multiple reference signal switches 16 are connected to the multiple reference signal lines Sramp, and one of the multiple reference signal switches 16 is sequentially turned on to supply a reference signal to only one of the reference signal lines Sramp, thereby reducing the load on the reference signal line Sramp and enabling faster AD conversion and frame rate. Furthermore, even when imaging only the pixel region of the ROI, one of the multiple reference signal lines Sramp corresponding to the pixel region of the ROI is sequentially selected to supply a reference signal, thereby further increasing the AD conversion and frame rate.

[0164] Sixth Embodiment FIG. 36 is a diagram illustrating an image pickup device 1004 according to a sixth embodiment. The image pickup device 1004 according to the sixth embodiment is a so-called column ADC, and is provided with a column readout unit 17 that performs AD conversion for each vertical signal line VSL extending in the second direction (vertical direction) Y. A plurality of vertical signal lines VSL arranged in the first direction (horizontal direction) X are connected to the column readout unit 17. The column readout unit 17 has a plurality of AD converters that perform AD conversion of pixel signals transmitted through each vertical signal line VSL. In other words, the column readout unit 17 has the same number of AD converters as the number of vertical signal lines VSL.

[0165] In this embodiment, there is provided a first reference signal switch 16a that switches whether or not to input a reference signal to an AD converter to which pixel signals from odd-numbered vertical signal lines VSL among the multiple vertical signal lines VSL are input, and a second reference signal switch 16b that switches whether or not to input a reference signal to an AD converter to which pixel signals from even-numbered vertical signal lines VSL are input.

[0166] The first reference signal switch 16 a and the second reference signal switch 16 b are turned on / off exclusively, and when one of them is turned on, the other is turned off. This reduces the load on the reference signal line Sramp, which transmits the reference signal generated by the DAC 14.

[0167] As an application example of this embodiment, it is also possible to perform AD conversion by transmitting the result of adding pixel signals on two adjacent vertical signal lines VSL via any one of the vertical signal lines VSL. In this case, the reference signal switch 16 that inputs a reference signal to the AD converter to which the pixel signal on the vertical signal line VSL that transmits the addition result is input is turned on, and the reference signal switch 16 that inputs a reference signal to the AD converter connected to the vertical signal line VSL that does not transmit the addition result is turned off. This reduces the load on the reference signal line Sramp.

[0168] As described above, in the sixth embodiment, two reference signal switches 16 (a first reference signal switch 16 a and a second reference signal switch 16 b) are connected to a column readout unit 17 having a plurality of AD converters connected to a plurality of vertical signal lines VSL, and the first reference signal switch 16 a switches whether or not a reference signal is input to odd-numbered AD converters, while the second reference signal switch 16 b switches whether or not a reference signal is input to even-numbered AD converters. By turning on either the first reference signal switch 16 a or the second reference signal switch 16 b and turning off the other, the load on the reference signal line Sramp can be reduced, thereby enabling faster AD conversion and frame rate.

[0169] Seventh Embodiment As a concept that encompasses the first to sixth embodiments described above, an imaging device 1004 according to the seventh embodiment includes a plurality of photoelectric conversion elements, a plurality of pixel circuits, a plurality of comparators, a digital signal generator, and a plurality of switches.

[0170] The photoelectric conversion elements are arranged in a first direction X and a second direction Y that intersect with each other, as shown in FIG. 2, for example, and each accumulates electric charges according to the amount of incident light.

[0171] The plurality of pixel circuits each output a pixel signal corresponding to the charge accumulated in the plurality of photoelectric conversion elements.

[0172] A plurality of comparators (comparators 20) compare each of a plurality of pixel signals output from a plurality of pixel circuits with a reference signal. The comparators are included in the column readout unit 17 shown in FIG.

[0173] The digital signal generator generates digital signals by analog-to-digital converting the pixel signals based on the comparison results of the comparators. The digital signal generator is, for example, the counter 30 shown in FIG.

[0174] The plurality of switches (reference signal switches 16) switch whether or not to input the reference signal to the plurality of comparators. In the imaging device 1004 according to the first embodiment, as shown in FIG. 2 , the plurality of switches are provided corresponding to the plurality of column readout units 17. In the imaging device 1004 according to the fifth embodiment, as shown in FIG. 34 , the plurality of switches are provided corresponding to the plurality of ADCs connected to the plurality of vertical signal lines VSL. The plurality of switches sequentially select one of the plurality of comparators to input the reference signal so that the reference signal is not input to two or more comparators simultaneously.

[0175] According to the seventh embodiment, the reference signal is not input to multiple comparators at the same time, so the load on the reference signal line can be reduced, and the AD conversion and frame rate of the ADC including the comparators can be increased.

[0176] <Application to a Mobile Body> The technology according to the present disclosure (the present technology) can be applied to various products. For example, the technology according to the present disclosure may be realized as a device mounted on any type of mobile body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, or a robot.

[0177] FIG. 37 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied.

[0178] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 37, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside-vehicle information detection unit 12030, an inside-vehicle information detection unit 12040, and an integrated control unit 12050. Also shown as functional components of the integrated control unit 12050 are a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (Interface) 12053.

[0179] The drivetrain control unit 12010 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a drive force generating device for generating a drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force of the vehicle.

[0180] The body system control unit 12020 controls the operation of various devices equipped in the vehicle body according to various 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 lamps such as headlamps, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches can be input to the body system control unit 12020. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0181] The outside-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the outside-vehicle information detection unit 12030. The outside-vehicle information detection unit 12030 causes the imaging unit 12031 to capture images outside the vehicle and receives the captured images. The outside-vehicle information detection unit 12030 may perform object detection processing or distance detection processing for people, cars, obstacles, signs, characters on the road surface, etc. based on the received images.

[0182] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0183] The in-vehicle information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041 that detects the state of the driver is connected to the in-vehicle information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that captures an image of the driver, and the in-vehicle information detection unit 12040 may calculate the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

[0184] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, steering mechanism, or braking device based on the information inside and outside the vehicle acquired by the outside-vehicle information detection unit 12030 or the inside-vehicle information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the distance between vehicles, maintaining vehicle speed, vehicle collision warning, vehicle lane departure warning, etc.

[0185] In addition, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation, by controlling the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle obtained by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040.

[0186] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12030 based on the information outside the vehicle acquired by the outside information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the outside information detection unit 12030, and perform cooperative control aimed at preventing glare, such as switching from high beams to low beams.

[0187] The audio / video output unit 12052 transmits at least one of audio and video output signals to an output device capable of visually or audibly notifying information to vehicle occupants or the outside of the vehicle. In the example of Fig. 37, the output devices are exemplified by an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0188] FIG. 38 is a diagram showing an example of the installation position of the imaging unit 12031.

[0189] In FIG. 38, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0190] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided, for example, at positions such as the front nose, side mirrors, rear bumper, back door, and the top of the windshield inside the vehicle cabin of the vehicle 12100. The imaging unit 12101 provided on the front nose and the imaging unit 12105 provided on the top of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The imaging unit 12105 provided on the top of the windshield inside the vehicle cabin is mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0191] 38 shows an example of the imaging ranges of the imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 12101 to 12104, an overhead image of the vehicle 12100 viewed from above can be obtained.

[0192] At least one of the image capturing units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the image capturing units 12101 to 12104 may be a stereo camera made up of multiple image capturing elements, or may be an image capturing element having pixels for phase difference detection.

[0193] For example, based on the distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 can calculate the distance to each three-dimensional object within the imaging ranges 12111 to 12114 and the change in this distance over time (relative speed with respect to the vehicle 12100), thereby extracting as a preceding vehicle, in particular, the three-dimensional object that is the closest three-dimensional object on the path of the vehicle 12100 and traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or higher). Furthermore, the microcomputer 12051 can set a vehicle-to-vehicle distance to be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), etc. In this way, cooperative control can be performed for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation.

[0194] For example, the microcomputer 12051 classifies and extracts three-dimensional object data regarding three-dimensional objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects based on distance information obtained from the imaging units 12101 to 12104, and can use the data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines a collision risk that indicates the risk of collision with each obstacle, and when the collision risk is equal to or greater than a set value and a collision is possible, the microcomputer 12051 can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drive system control unit 12010.

[0195] At least one of the image capturing units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether a pedestrian is present in the images captured by the image capturing units 12101 to 12104. Such pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104 as infrared cameras and performing pattern matching on a series of feature points that indicate the outline of an object to determine whether the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the image capturing units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular outline on the recognized pedestrian for emphasis. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating the pedestrian at a desired position.

[0196] An example of a 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 device 1004 among the configurations described above. By applying the technology according to the present disclosure, noise in the imaging device 1004 can be further reduced.

[0197] The present technology may have the following configuration: (1) An imaging device comprising: a plurality of photoelectric conversion elements arranged in a first direction and a second direction intersecting each other, each accumulating a charge corresponding to the amount of incident light; a plurality of pixel circuits each outputting a pixel signal corresponding to the charge accumulated in the plurality of photoelectric conversion elements; a plurality of comparators each comparing the plurality of pixel signals output from the plurality of pixel circuits with a reference signal; a digital signal generator generating digital signals obtained by analog-to-digital conversion of the plurality of pixel signals based on comparison results of the plurality of comparators; and a plurality of switchers switching whether to input the reference signal to the plurality of comparators. (2) The imaging device described in (1), wherein the plurality of switchers sequentially select one of the plurality of comparators to input the reference signal so that the reference signal is not input to two or more of the comparators simultaneously. (3) The imaging device according to (1) or (2), comprising: signal lines that transmit the plurality of pixel signals output from two or more of the pixel circuits arranged in the second direction; and a conversion circuit that performs analog-to-digital conversion of the plurality of pixel signals transmitted through the signal lines, the conversion circuit having the comparator and the digital signal generator. (4) The imaging device according to (3), comprising: a plurality of the signal lines arranged in the first direction; and a plurality of the conversion circuits connected to the plurality of signal lines. (5) The imaging device according to (3) or (4), wherein the signal lines have a plurality of divided signal lines divided along the second direction, each of the plurality of divided signal lines transmits the pixel signals output from two or more of the pixel circuits arranged along the second direction, and one or more of the comparators are provided for each of the plurality of divided signal lines. (6) The imaging device according to (1) or (2), wherein each of the plurality of comparators is provided for each of the plurality of pixel circuits. (7) The imaging device described in (6), wherein the plurality of switches switch whether or not to input the reference signal to the corresponding two or more comparators for each pixel group including two or more pixel circuits arranged in the first direction or the second direction.(8) The imaging device according to (6), wherein the plurality of switchers sequentially switch to select one of the plurality of pixel groups corresponding to a pixel region of interest from among a plurality of pixel groups each including two or more pixel circuits arranged in the first direction or the second direction. (9) The imaging device according to (6), wherein the plurality of switchers sequentially switch to select one of two or more pixel groups adjacent in the first direction or the second direction from among a plurality of pixel groups each including two or more pixel circuits arranged in the first direction or the second direction. (10) The imaging device according to any one of (1) to (9), wherein the digital signal generator has a counter that outputs, as the digital signal, a count value corresponding to a timing at which the pixel signal and the reference signal match in each of the plurality of comparators. (11) The imaging device described in any one of (1) to (10), wherein at least one of the plurality of switchers includes: a first transistor of a first conductivity type that switches between making the first node and the second node conductive or cut off in response to a switch control signal, and a second transistor of a second conductivity type that switches between making the first node and the second node conductive or cut off in response to an inverted switch control signal having an inverted logic of the switch control signal. (12) The imaging device described in (11), wherein at least one of the plurality of switchers includes: a third transistor of a first conductivity type having a source and a drain connected to the first node and a gate to which the inverted switch control signal is input, a fourth transistor of a first conductivity type having a source and a drain connected to the second node and a gate to which the inverted switch control signal is input, a fifth transistor of a second conductivity type having a source and a drain connected to the first node and a gate to which the switch control signal is input, and a sixth transistor of a second conductivity type having a source and a drain connected to the second node and a gate to which the switch control signal is input. (13) The imaging device according to (11) or (12), further comprising: a capacitor disposed between the second node and a reference voltage node, wherein the second node is connected to input nodes of the plurality of comparators.(14) At least one of the plurality of switches includes: a first transistor that switches whether to connect or disconnect the first node and the second node by a switch control signal; a voltage source that outputs a bias voltage between the third node and the fourth node; a first switch, a second switch, and a third switch that are connected in series between the third node and a reference voltage node; a fourth switch and a fifth switch that are connected in series between the fourth node and the first node; a first capacitor that is connected between a connection node of the first switch and the second switch and a connection node of the fourth switch and the fifth switch; and a second capacitor that is connected between the second node and the reference voltage node, wherein the switch control signal output from the connection node of the second switch and the third switch is input to a gate of the first transistor; and when the first node and the second node are connected, the first switch, the third switch, and the fourth switch are disconnected and the second switch and the fifth switch are connected. The imaging device according to any one of (1) to (10), wherein, when the first node and the second node are disconnected, the first switch, the third switch, and the fourth switch are made conductive, and the second switch and the fifth switch are disconnected.(15) At least one of the plurality of switches includes: a first transistor that switches whether to connect or disconnect the first node and the second node by a switching control signal; a first switch, a second switch, and a third switch that are connected in series between a first reference voltage node and a second reference voltage node; a fourth switch and a fifth switch that are connected in series between the second reference voltage node and the first node; a first capacitor that is connected between a connection node of the first switch and the second switch and a connection node of the fourth switch and the fifth switch; and a second capacitor that is connected between the second node and the second reference voltage node, wherein the switching control signal output from the connection node of the second switch and the third switch is input to a gate of the first transistor; and when the first node and the second node are connected, the first switch, the third switch, and the fourth switch are disconnected and the second switch and the fifth switch are connected; The imaging device according to any one of (1) to (10), wherein, when the first node and the second node are disconnected, the first switch, the third switch, and the fourth switch are made conductive, and the second switch and the fifth switch are disconnected. (16) The imaging device according to any one of (1) or (15), further comprising: a plurality of preamplifiers arranged between the plurality of switches and the plurality of comparators, each preamplifier having a plurality of source follower circuits that convert impedances of the reference signals output from the plurality of switches, wherein each of the plurality of source follower circuits comprises: a first transistor to whose gate the reference signal output from the corresponding switch is input; a second transistor of a first conductivity type connected to the drain side of the first transistor, which is turned on when the corresponding switch outputs the reference signal and is turned off when the corresponding switch does not output the reference signal; and a third transistor of a second conductivity type connected to the source side of the first transistor, which is turned on when the corresponding switch outputs the reference signal and is turned off when the corresponding switch does not output the reference signal.(17) The imaging device described in (16), wherein each of the plurality of source follower circuits has a fourth transistor that functions as a current source and a fifth transistor that adjusts the voltage of the corresponding input node of the comparator, and the fourth transistor, the third transistor, the fifth transistor, the first transistor, and the second transistor are connected in this order between a first reference voltage node and a second reference voltage node, or the fourth transistor, the fifth transistor, the third transistor, the first transistor, and the second transistor are connected in this order. (18) The imaging device according to any one of (1) to (15), further comprising: a plurality of preamplifiers arranged between the plurality of switches and the plurality of comparators, the preamplifiers having a plurality of source follower circuits that convert impedances of the reference signals output from the plurality of switches, wherein each of the plurality of source follower circuits comprises: a first transistor having a gate to which the reference signal output from the corresponding switch is input; a second transistor of a first conductivity type connected to a drain side of the first transistor, turning on when the corresponding switch outputs the reference signal and turning off when the corresponding switch does not output the reference signal; a third transistor connected to a source side of the first transistor and functioning as a current source; a fourth transistor that adjusts a voltage of an input node of the corresponding comparator; a fifth transistor connected to a gate of the fourth transistor, turning on when the corresponding switch outputs the reference signal to turn on the fourth transistor; and a sixth transistor connected to the gate of the fourth transistor, turning on when the corresponding switch does not output the reference signal to turn off the fourth transistor. (19) The imaging device according to any one of (16) to (18), further comprising a precharge circuit that supplies a precharge signal to the source of the first transistor in a source follower circuit that does not output the reference signal from the source of the first transistor, among the plurality of source follower circuits.(20) The imaging device described in (19), wherein the precharge circuit has the same circuit configuration as the plurality of source follower circuits and further includes a replica circuit that generates, as the precharge signal, a reference voltage of the reference signal when the plurality of comparators start a comparison operation, and the precharge circuit supplies the reference voltage generated by the replica circuit to the source of the first transistor in a source follower circuit among the plurality of source follower circuits that does not input the reference signal to the corresponding comparator.

[0198] The aspects of the present disclosure are not limited to the individual embodiments described above, but include various modifications that may be conceived by those skilled in the art, and the effects of the present disclosure are not limited to the above-described contents. In other words, various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and intent of the present disclosure, which is derived from the contents defined in the claims and their equivalents.

[0199] 10 Pixel, 11 Pixel array section, 12 Vertical drive section, 13 System control section, 15 Column control section, 16 Reference signal switch, 16a First reference signal switch, 16b Second reference signal switch, 16c Third reference signal switch, 17 Column readout section, 18 Column signal processing section, 19 Horizontal drive section, 20 Comparator, 21 Voltage source, 22 First switch, 23 Second switch, 24 Third switch, 25 Fourth switch, 26 Fifth switch, 30 Counter, 31 Preamplifier, 32 Source follower circuit, 32a First source follower circuit, 32b Second source follower circuit, 33 Precharge circuit, 34 Precharge switch, 36 Replica circuit, 39 Current cut switch, 40 Logic circuit, 50 Peripheral circuit, 60 Interface circuit, 100 Photoelectric conversion section, 101 Pixel, 101 Circuit section, 102 pixel, 201 first stage comparator, 202 middle stage comparator, 203 last stage comparator

Claims

1. An imaging device comprising: a plurality of photoelectric conversion elements arranged in a first direction and a second direction that intersect with each other, each accumulating an electric charge corresponding to the amount of incident light; a plurality of pixel circuits that output pixel signals corresponding to the electric charges accumulated in the plurality of photoelectric conversion elements; a plurality of comparators that compare each of the plurality of pixel signals output from the plurality of pixel circuits with a reference signal; a digital signal generator that generates digital signals by analog-to-digital conversion of the plurality of pixel signals based on comparison results of the plurality of comparators; and a plurality of switches that switch whether or not the reference signal is input to the plurality of comparators.

2. The imaging device according to claim 1, wherein the plurality of switches sequentially select one of the plurality of comparators to input the reference signal so that the reference signal is not input to two or more of the comparators simultaneously.

3. The imaging device according to claim 1, further comprising: a signal line for transmitting the plurality of pixel signals output from two or more of the pixel circuits arranged in the second direction; and a conversion circuit for performing analog-to-digital conversion of the plurality of pixel signals transmitted on the signal line, the conversion circuit having the comparator and the digital signal generator.

4. The imaging device according to claim 3, comprising: a plurality of the signal lines arranged in the first direction; and a plurality of the conversion circuits connected to the plurality of signal lines.

5. The imaging device described in claim 3, wherein the signal line has a plurality of split signal lines split along the second direction, each of the plurality of split signal lines transmits the pixel signals output from two or more of the pixel circuits arranged along the second direction, and one or more of the comparators are provided for each of the plurality of split signal lines.

6. The imaging device according to claim 1, wherein each of the plurality of comparators is provided for each of the plurality of pixel circuits.

7. The imaging device according to claim 6, wherein the plurality of switches switch, for each pixel group including two or more pixel circuits arranged in the first direction or the second direction, whether or not to input the reference signal to the corresponding two or more comparators.

8. The imaging device according to claim 6, wherein the plurality of switches sequentially switch to select one of a plurality of pixel groups corresponding to a pixel region of interest from among a plurality of pixel groups each including two or more of the pixel circuits arranged in the first direction or the second direction.

9. The imaging device described in claim 6, wherein the plurality of switches sequentially switch to select one of two or more pixel groups adjacent in the first direction or the second direction among a plurality of pixel groups each including two or more pixel circuits arranged in the first direction or the second direction.

10. The imaging device according to claim 1, wherein the digital signal generator has a counter that outputs, as the digital signal, a count value corresponding to the timing at which the pixel signal and the reference signal match in each of the plurality of comparators.

11. The imaging device of claim 1, wherein at least one of the plurality of switches comprises: a first transistor of a first conductivity type that switches between making the first node and the second node conductive or cut off in response to a switching control signal; and a second transistor of a second conductivity type that switches between making the first node and the second node conductive or cut off in response to an inverted switching control signal having the opposite logic to the switching control signal.

12. The imaging device of claim 11, wherein at least one of the plurality of switches comprises: a third transistor of a first conductivity type having a source and a drain connected to the first node and a gate to which the inverted switching control signal is input; a fourth transistor of a first conductivity type having a source and a drain connected to the second node and a gate to which the inverted switching control signal is input; a fifth transistor of a second conductivity type having a source and a drain connected to the first node and a gate to which the switching control signal is input; and a sixth transistor of a second conductivity type having a source and a drain connected to the second node and a gate to which the switching control signal is input.

13. The imaging device according to claim 11, further comprising a capacitor disposed between the second node and a reference voltage node, the second node being connected to input nodes of the plurality of comparators.

14. At least one of the plurality of switches includes: a first transistor that switches whether the first node and the second node are conductive or cut off by a switching control signal; a voltage source that outputs a bias voltage between the third node and the fourth node; a first switch, a second switch, and a third switch that are connected in series between the third node and a reference voltage node; a fourth switch and a fifth switch that are connected in series between the fourth node and the first node; a first capacitor that is connected between a connection node of the first switch and the second switch and a connection node of the fourth switch and the fifth switch; and a second capacitor that is connected between the second node and the reference voltage node, wherein the switching control signal that is output from the connection node of the second switch and the third switch is input to a gate of the first transistor; and when the first node and the second node are conductive, the first switch, the third switch, and the fourth switch are cut off and the second switch and the fifth switch are made conductive; 2 . The imaging device according to claim 1 , wherein, when the first node and the second node are disconnected, the first switch, the third switch, and the fourth switch are made conductive, and the second switch and the fifth switch are made disconnected.

15. At least one of the plurality of switches includes: a first transistor that switches whether to make the first node and the second node conductive or cut off by a switching control signal; a first switch, a second switch, and a third switch that are connected in series between a first reference voltage node and a second reference voltage node; a fourth switch and a fifth switch that are connected in series between the second reference voltage node and the first node; a first capacitor that is connected between a connection node of the first switch and the second switch and a connection node of the fourth switch and the fifth switch; and a second capacitor that is connected between the second node and the second reference voltage node, wherein the switching control signal output from the connection node of the second switch and the third switch is input to a gate of the first transistor; and when the first node and the second node are to be made conductive, the first switch, the third switch, and the fourth switch are cut off and the second switch and the fifth switch are made conductive; 2 . The imaging device according to claim 1 , wherein, when the first node and the second node are disconnected, the first switch, the third switch, and the fourth switch are made conductive, and the second switch and the fifth switch are made disconnected.

16. The imaging device according to claim 1, further comprising: a plurality of preamplifiers arranged between the plurality of switches and the plurality of comparators, the preamplifiers having a plurality of source follower circuits for converting impedance of the reference signals output from the plurality of switches, each of the plurality of source follower circuits comprising: a first transistor having a gate to which the reference signal output from the corresponding switch is input; a second transistor of a first conductivity type connected to the drain side of the first transistor and turned on when the corresponding switch outputs the reference signal and turned off when the corresponding switch does not output the reference signal; and a third transistor of a second conductivity type connected to the source side of the first transistor and turned on when the corresponding switch outputs the reference signal and turned off when the corresponding switch does not output the reference signal.

17. The imaging device of claim 16, wherein each of the plurality of source follower circuits has a fourth transistor that functions as a current source and a fifth transistor that adjusts the voltage of the corresponding input node of the comparator, and is connected between a first reference voltage node and a second reference voltage node in the order of the fourth transistor, the third transistor, the fifth transistor, the first transistor, and the second transistor, or in the order of the fourth transistor, the fifth transistor, the third transistor, the first transistor, and the second transistor.

18. The imaging device according to claim 1, further comprising: a plurality of preamplifiers arranged between the plurality of switches and the plurality of comparators, the preamplifier having a plurality of source follower circuits for converting impedance of the reference signals output from the plurality of switches, each of the plurality of source follower circuits comprising: a first transistor having a gate to which the reference signal output from the corresponding switch is input; a second transistor of a first conductivity type connected to the drain side of the first transistor and turned on when the corresponding switch outputs the reference signal and turned off when the corresponding switch does not output the reference signal; a third transistor connected to the source side of the first transistor and functioning as a current source; a fourth transistor for adjusting a voltage of an input node of the corresponding comparator; a fifth transistor connected to the gate of the fourth transistor and turned on when the corresponding switch outputs the reference signal to turn on the fourth transistor; and a sixth transistor connected to the gate of the fourth transistor and turned on when the corresponding switch does not output the reference signal to turn off the fourth transistor.

19. The imaging device according to claim 16, further comprising a precharge circuit that supplies a precharge signal to the source of the first transistor in a source follower circuit that does not output the reference signal from the source of the first transistor, among the plurality of source follower circuits.

20. The imaging device described in claim 19, wherein the precharge circuit has the same circuit configuration as the multiple source follower circuits and further includes a replica circuit that generates, as the precharge signal, a reference voltage of the reference signal when the multiple comparators start a comparison operation, and the precharge circuit supplies the reference voltage generated by the replica circuit to the source of the first transistor in a source follower circuit among the multiple source follower circuits that does not input the reference signal to the corresponding comparator.

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