Patent Description:
In a conventional imaging device, synchronous imaging elements that capture image data (frames) in synchronization with a synchronization signal such as a vertical synchronization signal are generally used. This type of synchronous imaging element can only acquire image data in one cycle time (for example, <NUM>/<NUM> seconds) of the synchronization signal, and thus is not suitable for use in acquiring image data at a higher speed. Therefore, asynchronous imaging elements have been proposed in which an event detection circuit that detects, for each pixel address, the fact that a light amount of the pixel exceeds a threshold value as an event in real time is provided for each pixel (see, for example, Patent Document <NUM>). In these imaging elements, a photodiode and a plurality of transistors for detecting an event are disposed for each pixel.

Patent Document <NUM>: Published <CIT> International Publication.

<CIT> relates to a solid-state imaging element with a plurality of photoelectric conversion elements, a signal supply unit, and a detection unit.

<CIT> relates to a power supply method for generating and supplying a local voltage different from the normal operating voltage supplied to most of other members to a predetermined terminal of various members constituting a unit component in an imaging device.

<CIT> relates to a solid-state imaging apparatus including a pixel array in which a plurality of unit pixels are arranged two-dimensionally.

<CIT> relates to a solid-state image pickup element including: a photodiode configured to convert incident light into a photocurrent; an amplification transistor configured to amplify a voltage between a gate having a potential depending on the photocurrent and a source having a predetermined reference potential and output the amplified voltage from a drain; and a potential supply section configured to supply an anode of the photodiode and a back-gate of the amplification transistor with a negative potential.

In the above-described asynchronous imaging elements, data can be generated and output at a much higher speed than in synchronous imaging elements. For this reason, for example, in the traffic field, it is possible to improve safety by executing processing of recognizing an image of a person or an obstacle at high speed. However, when a reverse bias of a photodiode decreases due to voltage fluctuation such as a decrease in power supply voltage or an increase in ground voltage, the sensitivity of the photodiode may decrease, and the dark current may increase. Therefore, there is a problem that the signal quality is deteriorated due to the insufficient sensitivity and the dark current. Increasing the area of the photodiode can improve the sensitivity and reduce the dark current, but this is not desirable because it reduces the number of pixels per unit area. Furthermore, the sensitivity can be improved and the dark current can be reduced by sufficiently increasing the power supply voltage, but the power consumption is thus increased, which is not preferable.

The present disclosure provides an imaging device, an electronic apparatus, and an imaging method capable of improving the sensitivity, reducing the dark current, and reducing the power consumption.

The following aspects may include some but not all features as literally defined in the claims and are present for illustration purposes only.

In order to solve the above problems, according to the present disclosure, there is provided an imaging device including a photoelectric conversion unit including a plurality of photoelectric conversion elements each of which photoelectrically converts incident light to generate an electric signal, a detector configured to output a detection signal indicating whether or not an amount of change in the electric signal of each of the plurality of photoelectric conversion elements exceeds a predetermined threshold value, a pixel signal generation unit configured to generate a pixel signal on the basis of the electric signal, a transfer controller configured to perform control to transfer the electric signal to the pixel signal generation unit, and an analog-to-digital converter configured to convert the pixel signal into a digital signal, in which a low-potential-side reference potential of the photoelectric conversion unit, a low-potential-side reference potential of the detector, a low-potential-side reference potential of the pixel signal generation unit, a low-potential-side reference potential of the analog-to-digital converter, and an off-potential of the transfer controller include three potentials having different potential levels.

A potential level of the low-potential-side reference potential of the photoelectric conversion unit may be lower than a potential level of the low-potential-side reference potential of the detector.

A potential level of the low-potential-side reference potential of the photoelectric conversion unit may be higher than a potential level of the off-potential of the transfer controller.

The potential level of the low-potential-side reference potential of the photoelectric conversion unit may be lower than the potential level of the low-potential-side reference potential of at least one of the pixel signal generation unit and the analog-to-digital converter.

At least one of the low-potential-side reference potential of the photoelectric conversion unit, the low-potential-side reference potential of the detector, the low-potential-side reference potential of the pixel signal generation unit, the low-potential-side reference potential of the analog-to-digital converter, and the off-potential of the transfer controller may be a ground potential, at least one of the others may be a first reference potential having a potential level lower than the ground potential, and at least one of the others may be a second reference potential having a potential level lower than the first reference potential.

The low-potential-side reference potential of the photoelectric conversion unit may be the second reference potential, the low-potential-side reference potentials of the detector, the pixel signal generation unit, and the analog-to-digital converter may be the ground potential, and the off-potential of the transfer controller may be the second reference potential.

The ground potential may be <NUM> V, the first reference potential may be a negative potential, and the second reference potential may be a negative potential having a potential level lower than that of the first reference potential.

The low-potential-side reference potentials of the photoelectric conversion unit, the pixel signal generation unit, and the analog-to-digital converter may be substantially equal.

At least one of the low-potential-side reference potential of the photoelectric conversion unit, the low-potential-side reference potential of the detector, the low-potential-side reference potential of the pixel signal generation unit, the low-potential-side reference potential of the analog-to-digital converter, and the off-potential of the transfer controller may be a ground potential, at least one of the others may be a first reference potential having a potential level lower than the ground potential, and at least one of the others may be a second reference potential having a potential level higher than the ground potential.

The low-potential-side reference potentials of the photoelectric conversion unit, the pixel signal generation unit, and the analog-to-digital converter may be the ground potential, the low-potential-side reference potential of the detector may be the first reference potential, and the off-potential of the transfer controller may be the second reference potential.

The ground potential may be <NUM> V, the first reference potential may be a positive potential, and the second reference potential may be a negative potential.

According to the present disclosure, there is provided an imaging device including a photoelectric conversion unit including a plurality of photoelectric conversion elements each of which photoelectrically converts incident light to generate an electric signal, a detector configured to output a detection signal indicating whether or not an amount of change in the electric signal of each of the plurality of photoelectric conversion elements exceeds a predetermined threshold value, a pixel signal generation unit configured to generate a pixel signal on the basis of the electric signal, a transfer controller configured to perform control to transfer the electric signal to the pixel signal generation unit, an analog-to-digital converter configured to convert the pixel signal into a digital signal, and a potential selection unit configured to switch a low-potential-side reference potential of the photoelectric conversion unit.

The analog-to-digital converter may convert the pixel signal into the digital signal when the detector detects that the amount of change exceeds the predetermined threshold value, and the potential selection unit may select a first reference potential within a period in which the detector detects whether or not the amount of change exceeds the predetermined threshold value, and select a second reference potential having a higher potential level than that of the first reference potential within a period in which the analog-to-digital converter converts the pixel signal into the digital signal.

The first reference potential may be a negative potential, and the second reference potential may be a ground potential.

The low-potential-side reference potential of the photoelectric conversion unit, the low-potential-side reference potential of the detector, the low-potential-side reference potential of the pixel signal generation unit, the low-potential-side reference potential of the analog-to-digital converter, and the off-potential of the transfer controller may include two or more potentials having different potential levels.

The low-potential-side reference potential of the detector, the low-potential-side reference potential of the pixel signal generation unit, and the low-potential-side reference potential of the analog-to-digital converter may be the ground potentials, and the off-potential of the transfer controller may be a negative potential.

A potential generation unit configured to generate at least one of the first reference potential and the second reference potential may be included.

At least the detector may be disposed on the second substrate stacked on a first substrate on which the photoelectric conversion unit is disposed.

A back gate of a transistor in the transfer controller may be set to a potential at a same potential level as the low-potential-side reference potential of the photoelectric conversion unit.

According to another aspect of the present disclosure, there is provided an electronic apparatus including an imaging device configured to output captured image data, and.

According to another aspect of the present disclosure, there is provided an imaging method including a step of photoelectrically converting incident light with a plurality of photoelectric conversion elements to generate an electric signal, a step of outputting a detection signal indicating whether or not an amount of change in the electric signal of each of the plurality of photoelectric conversion elements exceeds a predetermined threshold value, a step of transferring the electric signal, a step of generating a pixel signal on the basis of the transferred electric signal, and a step of converting the pixel signal into a digital signal, in which a low-potential-side reference potential at the time of the photoelectric conversion, a low-potential-side reference potential at the time of outputting the detection signal, a low-potential-side reference potential at the time of generating the pixel signal, a low-potential-side reference potential at the time of converting the pixel signal into a digital signal, and an off-potential at the time of transferring the electric signal include three potentials having different potential levels, and
using these potentials, the step of generating the electric signal, the step of outputting the detection signal, the step of transferring the electric signal, the step of generating the pixel signal, and the step of converting the detection signal into the digital signal are performed.

The first embodiment includes some but not all features of the independent claims and is an illustrative example considered useful for understanding the invention.

Hereinafter, embodiments of an imaging device, an electronic apparatus, and an imaging method will be described with reference to the drawings. Although main configuration components of the imaging device and the electronic apparatus will be mainly described below, the imaging device and the electronic apparatus may have components and functions that are not illustrated or described. The following description does not exclude configuration components and functions that are not illustrated or described.

<FIG> is a block diagram illustrating a configuration example of an imaging device <NUM> according to a first embodiment of the present disclosure. The imaging device <NUM> includes an imaging lens <NUM>, a solid-state image sensing device <NUM>, a recording unit <NUM>, and a controller <NUM>. As the imaging device <NUM>, a camera mounted on an industrial robot, an in-vehicle camera, or the like is assumed.

The imaging lens <NUM> condenses incident light and guides the light to the solid-state image sensing device <NUM>. The solid-state image sensing device <NUM> photoelectrically converts the incident light to capture image data. The solid-state image sensing device <NUM> performs predetermined signal processing such as image recognition processing on the captured image data, and outputs data indicating the processing result and the detection signal of the address event to the recording unit <NUM> via a signal line <NUM>. A method of generating the detection signal will be described later.

The recording unit <NUM> records data from the solid-state image sensing device <NUM>. The controller <NUM> controls the solid-state image sensing device <NUM> to capture the image data.

<FIG> is a diagram illustrating an example of a laminated structure of a solid-state image sensing device <NUM> according to the present disclosure. The solid-state image sensing device <NUM> includes a detection chip <NUM> and a light receiving chip <NUM> stacked on the detection chip <NUM>. These chips are electrically connected via a connection portion such as a via. Note that, in addition to the via, connection can also be made by Cu-Cu bonding or a bump.

<FIG> is a block diagram illustrating a configuration example of the solid-state image sensing device <NUM> in the first embodiment of the present disclosure. The solid-state image sensing device <NUM> includes a drive circuit <NUM>, a signal processing unit <NUM>, an arbiter <NUM>, a column ADC <NUM>, and a pixel array unit <NUM>.

In the pixel array unit <NUM>, a plurality of pixels is arranged in a two-dimensional lattice pattern. Furthermore, the pixel array unit <NUM> is divided into a plurality of pixel blocks each including a predetermined number of pixels. Hereinafter, a set of pixels or pixel blocks arrayed in the horizontal direction is referred to as a "row", and a set of pixels or pixel blocks arrayed in a direction perpendicular to the row is referred to as a "column".

Each of the pixels generates an analog signal of a voltage corresponding to a photovoltaic current as a pixel signal. Furthermore, each of the pixel blocks detects the presence or absence of an address event on the basis of whether or not the amount of change in the photovoltaic current exceeds a predetermined threshold value. Then, when an address event occurs, the pixel block outputs a request to the arbiter <NUM>.

The drive circuit <NUM> drives each of the pixels to output a pixel signal to the column ADC <NUM>.

The arbiter <NUM> arbitrates the request from each pixel block and transmits a response to the pixel block on the basis of an arbitration result. The pixel block that has received the response supplies a detection signal indicating the detection result to the drive circuit <NUM> and the signal processing unit <NUM>.

The column ADC <NUM> converts an analog pixel signal from the column into a digital signal for each column of the pixel block. The column ADC <NUM> supplies the digital signal to the signal processing unit <NUM>.

The signal processing unit <NUM> performs predetermined signal processing such as correlated double sampling (CDS) processing or image recognition processing on the digital signal from the column ADC <NUM>. The signal processing unit <NUM> supplies data indicating the processing result and the detection signal to the recording unit <NUM> via the signal line <NUM>.

<FIG> is a block diagram illustrating a configuration example of a pixel array unit <NUM> according to the first embodiment of the present disclosure. The pixel array unit <NUM> is divided into a plurality of pixel blocks <NUM>. In each of the pixel blocks <NUM>, a plurality of pixels is arranged in I-rows x J-columns (I and J are integers).

Furthermore, the pixel block <NUM> includes a pixel signal generation unit <NUM>, a plurality of light receiving units <NUM> of I-rows x J-columns, and an address event detector <NUM>. The plurality of light receiving units <NUM> in the pixel block <NUM> shares the pixel signal generation unit <NUM> and the address event detector <NUM>. Then, a circuit including the light receiving unit <NUM>, the pixel signal generation unit <NUM>, and the address event detector <NUM> at certain coordinates functions as a pixel at the coordinates. Furthermore, a vertical signal line VSL is wired for each column of the pixel block <NUM>. When the number of columns of the pixel block <NUM> is m (m is an integer), m vertical signal lines VSL are disposed.

The light receiving unit <NUM> photoelectrically converts incident light to generate the photovoltaic current. The light receiving unit <NUM> supplies a photovoltaic current to either the pixel signal generation unit <NUM> or the address event detector <NUM> under the control of the drive circuit <NUM>.

The pixel signal generation unit <NUM> generates a signal of a voltage corresponding to the photovoltaic current as the pixel signal SIG. The pixel signal generation unit <NUM> supplies the generated pixel signal SIG to the column ADC <NUM> via the vertical signal line VSL.

The address event detector <NUM> detects the presence or absence of an address event on the basis of whether or not the amount of change in the photovoltaic current from each of the light receiving units <NUM> exceeds a predetermined threshold value. The address event includes, for example, an on-event indicating that the amount of change exceeds the upper limit threshold value and an off-event indicating that the amount of change falls below the lower limit threshold value. Furthermore, the detection signal of the address event includes, for example, <NUM>-bit indicating the detection result of the on-event and <NUM>-bit indicating the detection result of the off-event. Note that the address event detector <NUM> can also detect only the on-event.

When an address event occurs, the address event detector <NUM> supplies a request for requesting transmission of a detection signal to the arbiter <NUM>. Then, when a response to the request is received from the arbiter <NUM>, the address event detector <NUM> supplies a detection signal to the drive circuit <NUM> and the signal processing unit <NUM>. Note that the address event detector <NUM> is an example of a detector described in the claims.

<FIG> is a circuit diagram illustrating a configuration example of the pixel block <NUM> according to the first embodiment of the present disclosure. In the pixel block <NUM>, the pixel signal generation unit <NUM> includes a reset transistor <NUM>, an amplification transistor <NUM>, a selection transistor <NUM>, and a floating diffusion layer <NUM>. The plurality of light receiving units <NUM> in the pixel block <NUM> is commonly connected to the address event detector <NUM> via a connection node <NUM>.

Furthermore, each of the light receiving units <NUM> includes a transfer transistor <NUM>, an over flow gate (OFG) transistor <NUM>, and a photoelectric conversion element <NUM>. Assuming that the number of pixels in the pixel block <NUM> is N (N is an integer), N transfer transistors <NUM>, N OFG transistors <NUM>, and N photoelectric conversion elements <NUM> are disposed. A transfer signal TRGn is supplied to the gate of the n-th (n is an integer from <NUM> to N) transfer transistor <NUM> in the pixel block <NUM> by the drive circuit <NUM>. A control signal OFGn is supplied to the gate of the n-th OFG transistor <NUM> by the drive circuit <NUM>. In the present specification, the transfer transistor <NUM> and the OFG transistor <NUM> are collectively referred to as a transfer controller <NUM>, and the photoelectric conversion element is referred to as a photoelectric conversion unit <NUM>.

Furthermore, for example, an N-type metal-oxide-semiconductor (MOS) transistor is used as the reset transistor <NUM>, the amplification transistor <NUM>, and the selection transistor <NUM>. Similarly, an N-type MOS transistor is used for the transfer transistor <NUM> and the OFG transistor <NUM>.

Furthermore, each of the photoelectric conversion elements <NUM> is disposed on the light receiving chip <NUM>. All the elements other than the photoelectric conversion element <NUM> are disposed on the detection chip <NUM>. Note that a modification example in which a part of elements other than the photoelectric conversion element <NUM> is disposed on the light receiving chip <NUM> is also conceivable.

The photoelectric conversion element <NUM> photoelectrically converts the incident light to generate a charge. The transfer transistor <NUM> transfers a charge from the corresponding photoelectric conversion element <NUM> to the floating diffusion layer <NUM> according to the transfer signal TRGn. The OFG transistor <NUM> supplies an electric signal generated by the corresponding photoelectric conversion element <NUM> to the connection node <NUM> according to the control signal OFGn. Here, the supplied electric signal is a photovoltaic current including charges.

The floating diffusion layer <NUM> accumulates charge and generates a voltage corresponding to the amount of accumulated charge. The reset transistor <NUM> initializes the charge amount of the floating diffusion layer <NUM> according to a reset signal from the drive circuit <NUM>. The amplification transistor <NUM> amplifies the voltage of the floating diffusion layer <NUM>. The selection transistor <NUM> outputs an amplified voltage signal as a pixel signal SIG to the column ADC <NUM> via the vertical signal line VSL according to a selection signal SEL from the drive circuit <NUM>.

When the controller <NUM> instructs to start detecting an address event, the drive circuit <NUM> drives the OFG transistors <NUM> of all the pixels by the control signal OFGn to supply the photovoltaic current to the connection node <NUM>. Therefore, the current of the sum of the photovoltaic current of all the light receiving units <NUM> in the pixel block <NUM> is supplied to the address event detector <NUM>.

Then, when an address event is detected in a certain pixel block <NUM>, the drive circuit <NUM> turns off all the OFG transistors <NUM> of the block and stops supplying the photovoltaic current to the address event detector <NUM>. Next, the drive circuit <NUM> sequentially drives each transfer transistor <NUM> by the transfer signal TRGn to transfer the charge to the floating diffusion layer <NUM>. Therefore, the pixel signal of each of the plurality of pixels in the pixel block <NUM> is sequentially output.

In this manner, the solid-state image sensing device <NUM> outputs only the pixel signal of the pixel block <NUM> in which the address event has been detected to the column ADC <NUM>. Therefore, regardless of the presence or absence of the address event, the power consumption of the solid-state image sensing device <NUM> and the processing amount of image processing can be reduced as compared with the case of outputting the pixel signals of all the pixels.

Furthermore, since the plurality of pixels shares the address event detector <NUM>, the circuit scale of the solid-state image sensing device <NUM> can be reduced as compared with a case where the address event detector <NUM> is disposed for each pixel.

<FIG> is a block diagram illustrating a first configuration example of the address event detector <NUM> according to the present disclosure. The address event detector <NUM> includes a current-voltage converter <NUM>, a buffer <NUM>, a subtractor <NUM>, a quantizer <NUM>, and a transfer unit <NUM>.

The current-voltage converter <NUM> converts the photovoltaic current from the corresponding light receiving unit <NUM> into a logarithmic voltage signal. The current-voltage converter <NUM> supplies the voltage signal to the buffer <NUM>.

The buffer <NUM> corrects the voltage signal from the current-voltage converter <NUM>. The buffer <NUM> outputs the corrected voltage signal to the subtractor <NUM>.

The subtractor <NUM> lowers the level of the voltage signal from the buffer <NUM> in accordance with the row drive signal from the drive circuit <NUM>. The subtractor <NUM> supplies the reduced voltage signal to the quantizer <NUM>.

The quantizer <NUM> quantizes the voltage signal from the subtractor <NUM> into a digital signal and outputs the digital signal to the transfer unit <NUM> as a detection signal.

The transfer unit <NUM> transfers the detection signal from the quantizer <NUM> to the signal processing unit <NUM> and the like. When an address event is detected, the transfer unit <NUM> supplies a request for requesting transmission of a detection signal to the arbiter <NUM>. Then, when the response to the request is received from the arbiter <NUM>, the transfer unit <NUM> supplies the detection signal to the drive circuit <NUM> and the signal processing unit <NUM>.

<FIG> is a circuit diagram illustrating a configuration example of the current-voltage converter <NUM> according to the present disclosure. The current-voltage converter <NUM> includes N-type transistors <NUM> and <NUM> and a P-type transistor <NUM>. As these transistors, for example, MOS transistors are used.

A source of the N-type transistor <NUM> is connected to the light receiving unit <NUM>, and a drain thereof is connected to a power supply terminal. The P-type transistor <NUM> and the N-type transistor <NUM> are connected in series between the power supply terminal and the ground terminal. Furthermore, the connection node of the P-type transistor <NUM> and the N-type transistor <NUM> is connected to the gate of the N-type transistor <NUM> and the input terminal of the buffer <NUM>. Furthermore, a predetermined bias voltage Vbias is applied to the gate of the P-type transistor <NUM>.

Drains of the N-type transistors <NUM> and <NUM> are connected to a power supply side, and such a circuit is called a source follower. The photovoltaic current from the light receiving unit <NUM> is converted into the logarithmic voltage signal by the two source followers connected in the loop shape. Furthermore, the P-type transistor <NUM> supplies a constant current to the N-type transistor <NUM>.

<FIG> is a circuit diagram illustrating a configuration example of the subtractor <NUM> and the quantizer <NUM> according to the present disclosure. The subtractor <NUM> includes capacitors <NUM> and <NUM>, an inverter <NUM>, and a switch <NUM>. Furthermore, the quantizer <NUM> includes a comparator <NUM>.

One end of the capacitor <NUM> is connected to the output terminal of the buffer <NUM>, and the other end is connected to the input terminal of the inverter <NUM>. The capacitor <NUM> is connected in parallel to the inverter <NUM>. The switch <NUM> opens and closes a path connecting both ends of the capacitor <NUM> according to the row drive signal.

The inverter <NUM> inverts a voltage signal input via the capacitor <NUM>. The inverter <NUM> outputs the inverted signal to a non-inverting input terminal (+) of the comparator <NUM>.

When the switch <NUM> is turned on, a voltage signal Vinit is input to the buffer <NUM> side of the capacitor <NUM>, and the opposite side becomes a virtual ground terminal. The potential of the virtual ground terminal is set to zero for convenience. At this time, a potential Qinit accumulated in the capacitor <NUM> is expressed by the following equation, where the capacitance of the capacitor <NUM> is C1. On the other hand, since both ends of the capacitor <NUM> are short-circuited, the accumulated charge becomes zero.

Next, considering a case where the switch <NUM> is turned off and the voltage on the buffer <NUM> side of the capacitor <NUM> changes to Vafter, a charge Qafter accumulated in the capacitor <NUM> is expressed by the following equation.

On the other hand, when the output voltage is Vout, a charge Q2 accumulated in the capacitor <NUM> is expressed by the following equation.

At this time, since the total charge amounts of the capacitors <NUM> and <NUM> do not change, the following equation holds.

When Equations (<NUM>) to (<NUM>) are substituted into Equation (<NUM>) and deformed, the following equation is obtained.

Equation (<NUM>) represents the subtraction operation of the voltage signal, and the gain of the subtraction result is C1/C2. Normally, since it is desired to maximize the gain, it is preferable to design the capacitance C1 of the capacitor <NUM> to be large and the capacitance C2 of the capacitor <NUM> to be small. On the other hand, when C2 is too small, kTC noise increases, and noise characteristics may deteriorate. Therefore, capacity reduction of C2 is limited to a range in which noise can be tolerated. Furthermore, since the address event detector <NUM> including the subtractor <NUM> is mounted for each pixel block, the capacitances C1 and C2 have area restrictions. In consideration of these, the values of the capacitances C1 and C2 are determined.

The comparator <NUM> compares the voltage signal from the subtractor <NUM> with a predetermined threshold value voltage Vth applied to an inverting input terminal (-). The comparator <NUM> outputs a signal indicating the comparison result to the transfer unit <NUM> as a detection signal.

Furthermore, when the conversion gain of the current-voltage converter <NUM> is CGlog and the gain of the buffer <NUM> is "<NUM>", a gain A of the entire address event detector <NUM> is expressed by the following equation. [Formula <NUM>] <MAT>.

In the above equation, iphoto_n is the photovoltaic current of the n-th pixel, and the unit is, for example, ampere (A). N is the number of pixels in the pixel block <NUM>.

<FIG> is a block diagram illustrating a configuration example of the column ADC <NUM> according to the present disclosure. The column ADC <NUM> includes an ADC <NUM> for each column of the pixel blocks <NUM>. Furthermore, the column ADC <NUM> includes a reference signal generation unit <NUM> and an output unit <NUM>. The reference signal generation unit <NUM> generates a reference signal such as a ramp signal and supplies the reference signal to each of the ADCs <NUM>. A digital-to-analog converter (DAC) or the like is used as the reference signal generation unit <NUM>. The output unit <NUM> supplies the digital signal from the ADC <NUM> to the signal processing unit <NUM>.

The ADC <NUM> converts the analog pixel signal SIG supplied via the vertical signal line VSL into a digital signal. The ADC <NUM> includes a comparator <NUM>, a counter <NUM>, a switch <NUM>, and a memory <NUM>. The comparator <NUM> compares the reference signal with the pixel signal SIG, and the counter <NUM> counts the count value over a period until the comparison result is inverted. The switch <NUM> supplies and holds the count value in the memory <NUM> under the control of a timing control circuit (not illustrated) or the like. The memory <NUM> supplies a digital signal indicating the count value to the output unit <NUM> under the control of a horizontal drive unit (not illustrated) or the like. With this configuration, the pixel signal SIG is converted into a digital signal having a larger bit depth than the detection signal. For example, when the detection signal is <NUM>-bits, the pixel signal is converted into a digital signal of <NUM>-bits or more (<NUM> bits or the like). Note that the ADC <NUM> is an example of an analog-to-digital converter described in the claims.

<FIG> is a timing chart illustrating an example of operation of the solid-state image sensing device <NUM> according to the present disclosure. At timing T0, when the controller <NUM> issues an instruction to start detection of an address event, the drive circuit <NUM> sets all the control signals OFGn to the high level and turns on the OFG transistors <NUM> of all the pixels. Therefore, the sum of the photovoltaic currents of all the pixels is supplied to the address event detector <NUM>. On the other hand, the transfer signals TRGn are all at a low level, and the transfer transistors <NUM> of all the pixels are in an off state.

Then, it is assumed that the address event detector <NUM> detects an address event and outputs a high-level detection signal at timing T1. Here, the detection signal is assumed to be a <NUM>-bit signal indicating the detection result of the on-event.

When the detection signal is received, the drive circuit <NUM> sets all the control signals OFGn to the low level at timing T2 to stop the supply of the photovoltaic current to the address event detector <NUM>. Furthermore, the drive circuit <NUM> sets the selection signal SEL to the high level and sets a reset signal RST to the high level over a certain pulse period to initialize the floating diffusion layer <NUM>. The pixel signal generation unit <NUM> outputs the voltage at the time of initialization as a reset level, and the ADC <NUM> converts the reset level into a digital signal.

At timing T3 after the conversion of the reset level, the drive circuit <NUM> supplies the high-level transfer signal TRG1 over a certain pulse period, and causes the first pixel to output a voltage as a signal level. The ADC <NUM> converts the signal level into a digital signal. The signal processing unit <NUM> obtains a difference between the reset level and the signal level as a net pixel signal. This processing is called CDS processing.

At timing T4 after the conversion of the signal level, the drive circuit <NUM> supplies the high-level transfer signal TRG2 over a certain pulse period, and causes the second pixel to output the signal level. The signal processing unit <NUM> obtains a difference between the reset level and the signal level as a net pixel signal. Thereafter, similar processing is executed, and the pixel signals of the respective pixels in the pixel block <NUM> are sequentially output.

When all the pixel signals are output, the drive circuit <NUM> sets all the control signals OFGn to the high level and turns on the OFG transistors <NUM> of all the pixels.

<FIG> is a flowchart illustrating an example of the operation of the solid-state image sensing device <NUM> according to the present disclosure. This operation is started, for example, when a predetermined application for detecting an address event is executed.

Each of the pixel blocks <NUM> detects the presence or absence of an address event (step S901). The drive circuit <NUM> determines whether or not there is an address event in any pixel block <NUM> (step S902). In a case where there is an address event (step S902: Yes), the drive circuit <NUM> sequentially outputs the pixel signal of each pixel in the pixel block <NUM> in which the address event has occurred (step S903).

In a case where there is no address event (step S902: No), or after step S903, the solid-state image sensing device <NUM> repeats step S901 and the subsequent steps.

As described above, according to the present disclosure, since the address event detector <NUM> detects the amount of change in the photovoltaic current of each of the plurality (N) of photoelectric conversion elements <NUM> (pixels), the number of the arranged address event detectors <NUM> can be one for every N pixels. As the N pixels share one address event detector <NUM> in this manner, the circuit scale can be reduced as compared with a configuration in which the address event detector <NUM> is not shared and is provided for each pixel.

Note that the value of N described above is arbitrary. For example, in a case where it is not necessary to consider reduction in the circuit scale, the address event detector <NUM> may be provided for each pixel with N=<NUM>.

The low-potential-side reference potential and the off-potential used by each unit in the imaging device <NUM> include three types of potentials having different potential levels. The low-potential-side reference potential and the off-potential are typically the ground potential GND, but in the present example, it is assumed that a potential at a potential level other than the ground potential GND is used by each unit in the imaging device <NUM>.

More specifically, the low-potential-side reference potential of the photoelectric conversion unit <NUM>, the low-potential-side reference potential of the detector, the low-potential-side reference potential of the pixel signal generation unit <NUM>, the low-potential-side reference potential of the column ADC <NUM>, and the off-potential of the transfer controller <NUM> include three potentials having different potential levels.

For example, the potential level of the low-potential-side reference potential of the photoelectric conversion unit <NUM> may be lower than the potential level of the low-potential-side reference potential of the address event detector <NUM>. Furthermore, the potential level of the low-potential-side reference potential of the photoelectric conversion unit <NUM> may be higher than that of the off-potential of the transfer controller <NUM>. Furthermore, the potential level of the low-potential-side reference potential of the photoelectric conversion unit <NUM> may be lower than that of the low-potential-side reference potential of at least one of the pixel signal generation unit <NUM> and the column ADC <NUM>.

<FIG> is a diagram illustrating the low-potential-side reference potential and the off-potential used by each unit in the imaging device <NUM> according to an example. <FIG> illustrates an example in which the low-potential-side reference potential and the off-potential used by each unit in the imaging device <NUM> include three potentials having different potential levels. In the example of <FIG>, these three potentials are set as the ground potential, the first reference potential, and the second reference potential. The ground potential is, for example, <NUM> V, the first reference potential is a negative potential having a potential level lower than that of the ground potential GND, and the second reference potential is a negative potential having a potential level lower than that of the second reference potential.

The first reference potential and the second reference potential are supplied from the negative potential supply unit <NUM>. The negative potential supply unit <NUM> generates a first reference potential and a second reference potential lower than the ground potential GND using, for example, a charge pump.

In the example of <FIG>, the low-potential-side reference potential of the photoelectric conversion unit <NUM> is the first reference potential. Furthermore, the low-potential-side reference potentials of the address event detector <NUM>, the pixel signal generation unit <NUM>, and the column ADC <NUM> are the ground potential GND. The off-potential of the transfer controller <NUM> is the second reference potential. The transfer controller <NUM> includes the transfer transistor <NUM> and the OFG transistor <NUM>, and the off-potential of the transfer controller <NUM> refers to a potential for turning off the gates of the transfer transistor <NUM> and the OFG transistor <NUM>.

In <FIG>, by setting the low-potential-side reference potential of the photoelectric conversion unit <NUM> to the second reference potential that is a negative potential, the reverse bias of the photodiode (the photoelectric conversion element) in the photoelectric conversion unit <NUM> increases as compared with the case where the low-potential-side reference potential of the photoelectric conversion unit <NUM> is set to the ground potential GND. Therefore, the sensitivity of the photodiode <NUM> increases, and the dark current can be reduced.

Furthermore, the back gates of the transfer transistor <NUM> and the OFG transistor <NUM> in the transfer controller <NUM> may be set to the negative potential Vn. Therefore, it is possible to prevent the threshold value voltage of each transistor from becoming high and the gate-source voltage of each transistor from becoming zero or less due to the substrate bias effect as compared with the case where the potentials are set to the reference potential. When the gate-source voltage becomes zero or less, a normal output cannot be obtained due to the circuit configuration of the pixel signal generation unit <NUM>. Therefore, such a situation can be suppressed by supplying the negative potential Vn to the back gate. As described above, the signal quality of the detection signal can be improved by improving the sensitivity of the photodiode <NUM>, decreasing the dark current, and increasing the threshold value voltage.

In <FIG>, the low-potential-side reference potential (the first reference potential) of the address event detector <NUM> is set to a potential level higher than the low-potential-side reference potential (the first reference potential) of the photoelectric conversion unit <NUM>. If the low-potential-side reference potential of the address event detector <NUM> is set to be lower than the low-potential-side reference potential of the photoelectric conversion unit <NUM>, a sufficient reverse bias is not applied to the photodiode in the photoelectric conversion unit <NUM>, and there is a possibility that a response is delayed due to an increase in leakage current or an increase in noise. As illustrated in <FIG>, by setting the low-potential-side reference potential of the address event detector <NUM> to a potential level higher than the low-potential-side reference potential of the photoelectric conversion unit <NUM>, a sufficient reverse bias can be applied to the photodiode, and noise can be reduced and a response speed can be improved.

The OFG transistor <NUM> in the transfer controller <NUM> is turned on in a case where the address event detector <NUM> performs the address event detection process. At this time, the transfer transistor <NUM> needs to be turned off. Furthermore, when the address event is detected by the address event detector <NUM>, the OFG transistor <NUM> is turned off, and the transfer transistor <NUM> is turned on. When the transfer transistor <NUM> is turned on, an electric signal (the photovoltaic current) photoelectrically converted by the photodiode is sent to the pixel signal generation unit <NUM> via the transfer transistor <NUM> to generate a pixel signal, and then sent to the column ADC <NUM> to generate a digital signal.

In this manner, the OFG transistor <NUM> and the transfer transistor <NUM> are exclusively turned on/off. In order to reliably cause the OFG transistor <NUM> and the transfer transistor <NUM> to perform the exclusive operation, it is desirable to apply a positive potential to the gate of the transistor to be turned on and a negative potential to the gate of the transistor to be turned off. Therefore, in <FIG>, the off-potential of the transfer controller <NUM> is set to the second reference potential which is a negative potential.

<FIG> and <FIG> are examples of specific potential levels of the low-potential-side reference potential and the off-potential provided to each unit in the imaging device <NUM>. <FIG> illustrates the potential level in a case where the transfer transistor is turned off, and <FIG> illustrates the potential level in a case where the transfer transistor is turned on. In a case where the address event detection is performed, the potential level is set to the potential level in <FIG>. Note that the potential levels in <FIG> and <FIG> are examples, and various modification examples are conceivable.

As illustrated in <FIG>, in a case where the transfer transistor is turned off, an anode of the photodiode is set to a negative potential of -<NUM> V. Furthermore, the gate of the transfer transistor is set to a negative potential of -<NUM> V. Therefore, the transfer transistor is reliably turned off. The gate of the reset transistor in the pixel signal generation unit <NUM> is set to <NUM> V. Therefore, the reset transistor is turned on, and the charge amount of the floating diffusion layer <NUM> is initialized. The positive potential-side reference potential of the pixel signal generation unit <NUM> is set to <NUM> V.

Although not illustrated in <FIG>, in a case where the address event detection is performed, the gate of the OFG transistor is set to about <NUM> to <NUM> V. Furthermore, the low-potential-side reference potential of the address event detector <NUM> is set to a ground potential GND (<NUM> V) higher than the anode potential of the photodiode. The positive potential-side reference potential of the address event detector <NUM> is set to <NUM> V.

As illustrated in <FIG>, in a case where the transfer transistor is turned on, the anode of the photodiode is also set to -<NUM> V. Furthermore, the gate of the transfer transistor is set to <NUM> V. The gate of the reset transistor in the pixel signal generation unit <NUM> is set to a negative potential of -<NUM> V. The drain of the reset transistor is set to <NUM> V. The drain of the amplification transistor <NUM> in the pixel signal generation unit <NUM> is set to <NUM> V.

Although not illustrated in <FIG>, the gate of the OFG transistor is set to -<NUM> V. The low-potential-side reference potential of the address event detector <NUM> is the ground potential GND (<NUM> V) as in <FIG>.

As described above, in the first embodiment, the low-potential-side reference potential and the off-potential used by each unit in the imaging device <NUM> include three types of potentials having different potential levels. Therefore, the operation of each unit in the imaging device <NUM> can be optimized. For example, since the low-potential-side reference potential of the photoelectric conversion unit <NUM> is set to the reference potential, the sensitivity of the photodiode can be improved, and the dark current can be reduced. Furthermore, by setting the low-potential-side reference potential of the address event detector <NUM> higher than the low-potential-side reference potential of the photoelectric conversion unit <NUM>, a sufficient reverse bias is applied to the photodiode, so that noise reduction and an improvement in response speed can be achieved. Moreover, by setting the off-potential of the transfer controller <NUM> to a negative potential, the transfer transistor and the OFG transistor can be reliably operated exclusively.

<FIG> is a diagram illustrating the low-potential-side reference potential and the off-potential used by each unit in the imaging device <NUM> according to the second example. Also in the example of <FIG>, three types of reference potentials having different potential levels are used as the low-potential-side reference potential and the off-potential used by each unit in the imaging device <NUM>, but the potential levels of these three types of reference potentials are different from those in <FIG>. More specifically, the first reference potential in <FIG> is at a potential level higher than the ground potential GND, and the second reference potential is at a potential level lower than the ground potential GND.

The second reference potential is supplied from the negative potential supply unit <NUM>. The first reference potential is supplied from a power supply unit (not illustrated).

In the example of <FIG>, the low-potential-side reference potentials of the photoelectric conversion unit <NUM>, the pixel signal generation unit <NUM>, and the column ADC <NUM> are the ground potential GND (<NUM> V). Furthermore, the low-potential-side reference potential of the address event detector <NUM> is the first reference potential that is a positive potential. Furthermore, the off-potential of the transfer controller <NUM> is the second reference potential that is a negative potential lower than the first reference potential.

In the case of <FIG>, since the low-potential-side reference potential of the photoelectric conversion unit <NUM> is set to lower than the low-potential-side reference potential of the address event detector <NUM>, the reverse bias of the photodiode in the photoelectric conversion unit <NUM> can be sufficiently increased, and noise reduction and an improvement in response speed can be achieved. In addition, since the off-potential of the transfer controller <NUM> is set to the second reference potential that is a negative potential lower than the first reference potential, the transfer transistor and the OFG transistor can be reliably operated exclusively.

<FIG> and <FIG> are examples of specific potential levels of the low-potential-side reference potential and the off-potential provided to each unit in the imaging device <NUM> according to the second embodiment. <FIG> illustrates the potential level in a case where the transfer transistor is turned off, and <FIG> illustrates the potential level in a case where the transfer transistor is turned on.

As illustrated in <FIG>, in a case where the transfer transistor is turned off, the anode of the photodiode is set to a ground potential GND (<NUM> V) that is a negative potential. Furthermore, the gate of the transfer transistor is set to a negative potential of -<NUM> V. Therefore, the transfer transistor is reliably turned off. The gate of the reset transistor in the pixel signal generation unit <NUM> is set to <NUM> V. Therefore, the reset transistor is turned on, and the charge amount of the floating diffusion layer <NUM> is initialized. The positive potential-side reference potential of the pixel signal generation unit <NUM> is set to <NUM> V. The low-potential-side reference potential of the address event detector <NUM> is set to <NUM> V higher than the anode potential of the photodiode. The positive potential-side reference potential of the address event detector <NUM> is set to <NUM> V.

As illustrated in <FIG>, in a case where the transfer transistor is turned on, the anode of the photodiode is also set to the ground potential GND (<NUM> V). Furthermore, the gate of the transfer transistor is set to <NUM> V. The gate of the reset transistor in the pixel signal generation unit <NUM> is set to the ground potential GND (<NUM> V). The drain of the reset transistor is set to <NUM> V. The drain of the amplification transistor <NUM> in the pixel signal generation unit <NUM> is set to <NUM> V.

In <FIG>, <FIG>, <FIG>, and <FIG>, <NUM> V and <NUM> V are mixed as the positive potential-side reference potential, but these are examples, and the positive potential-side reference potential may be set to a specific potential.

As described above, in the second example, since the first reference potential of the positive potential and the second reference potential of the negative potential are provided as the low-potential-side reference potential and the off-potential in the imaging device <NUM> in addition to the ground potential GND, it is possible to set the low-potential-side reference potential of the optimum voltage level in each unit in the imaging device <NUM> and to optimize the operation of each unit. In particular, by setting the low-potential-side reference potential of the address event detector <NUM> higher than the low-potential-side reference potential of the photoelectric conversion unit <NUM>, a sufficient reverse bias is applied to the photodiode, so that noise reduction and an improvement in response speed can be achieved. Moreover, by setting the off-potential of the transfer controller <NUM> to a negative potential, the transfer transistor and the OFG transistor can be reliably operated exclusively.

Furthermore, in the second example, since only one type of negative potential is used as the low-potential-side reference potential and the off-potential, the circuit configuration of the negative potential supply unit <NUM> can be simplified.

<FIG> is a diagram illustrating the low-potential-side reference potential and the off-potential used by each unit in the imaging device <NUM> according to a third example.

As illustrated in <FIG>, the imaging device <NUM> according to the third example includes a potential selection unit <NUM> that switches a low-potential-side reference potential of a photoelectric conversion unit <NUM>. The potential selection unit <NUM> selects the first reference potential during a period in which the address event detector <NUM> detects whether or not the amount of change in the electric signal (the photovoltaic current) photoelectrically converted by the photodiode in the address event detector <NUM> exceeds a predetermined threshold value, and selects the second reference potential having a potential level higher than the first reference potential during a period in which the analog-to-digital converter converts the pixel signal into a digital signal.

The low-potential-side reference potential and the off-potential used by each unit of the imaging device <NUM> according to the third example are the first reference potential and the second reference potential having different potential levels, respectively. That is, the third example has one less number of reference potentials than the first and second embodiments.

The second reference potential in the third example is, for example, a ground potential GND (<NUM> V), and the first reference potential is a negative potential having a potential level lower than that of the ground potential GND. The first reference potential is supplied from the negative potential supply unit <NUM>.

In the imaging device <NUM> of <FIG>, the low-potential-side reference potential of the address event detector <NUM>, the pixel signal generation unit <NUM>, and the column ADC <NUM> is the ground potential GND (the second reference potential). The off-potential of the transfer controller <NUM> is a negative potential (the first reference potential).

The address event detector <NUM> needs to quickly detect an address event on the basis of an electric signal photoelectrically converted by a photodiode in the photoelectric conversion unit <NUM>. Therefore, during the period in which the address event detector <NUM> performs the address event detection operation, the low-potential-side reference potential of the photoelectric conversion unit <NUM> is lowered to the negative potential to improve the sensitivity of the photodiode and reduce the dark current. On the other hand, when the address event is detected by the address event detector <NUM>, the operation of generating the pixel signal is performed by the pixel signal generation unit <NUM>, but since it is not necessary to improve the sensitivity of the photodiode within this period, the low-potential-side reference potential of the receiving unit is set to the ground potential GND, and the power consumption is reduced.

As described above, in the third example, since the low-potential-side reference potential of the photoelectric conversion unit <NUM> is switched between the case of performing the address event detection and the case of generating the pixel signal, the sensitivity of the photodiode at the time of address event detection can be improved and the dark current can be reduced, and the power consumption at the time of generating the pixel signal can be reduced.

In the examples described above, the imaging device <NUM> including the address event detector <NUM> in <FIG> has been described, but an internal configuration of the address event detector <NUM> is not necessarily limited to <FIG>. <FIG> is a block diagram illustrating a second configuration example of the address event detector <NUM>. As illustrated in <FIG>, the address event detector <NUM> according to the present configuration example includes a storage unit <NUM> and a controller <NUM> in addition to the current-voltage converter <NUM>, the buffer <NUM>, the subtractor <NUM>, the quantizer <NUM>, and the transfer unit <NUM>.

The storage unit <NUM> is provided between the quantizer <NUM> and the transfer unit <NUM>, and accumulates the output of the quantizer <NUM>, that is, the comparison result of the comparator <NUM> in the quantizer <NUM> on the basis of the sample signal supplied from the controller <NUM>. The storage unit <NUM> may be a sampling circuit such as a switch, plastic, or a capacitor, or may be a digital memory circuit such as a latch or a flip-flop.

The controller <NUM> supplies a predetermined threshold value voltage Vth to an inverting (-) input terminal of the comparator <NUM>. The threshold value voltage Vth supplied from the controller <NUM> to the comparator <NUM> may have different voltage values in a time division manner. For example, the controller <NUM> supplies the threshold value voltage Vth1 corresponding to the on-event indicating that the amount of change in the photovoltaic current exceeds the upper limit threshold value and the threshold value voltage Vth2 corresponding to the off-event indicating that the amount of change falls below the lower limit threshold value at different timings, so that one comparator <NUM> can detect a plurality of types of address events.

For example, the storage unit <NUM> may accumulate the comparison result of the comparator <NUM> using the threshold value voltage Vth1 corresponding to the on-event in a period in which the threshold value voltage Vth2 corresponding to the off-event is supplied from the controller <NUM> to the inversion (-) input terminal of the comparator <NUM>. Note that the storage unit <NUM> may be inside the pixel <NUM> or may be outside the pixel <NUM>. Furthermore, the storage unit <NUM> is not an essential configuration element of the address event detector <NUM>. That is, the storage unit <NUM> may be omitted.

An imaging device <NUM> including the first configuration example of the address event detector <NUM> illustrated in <FIG> described above is an asynchronous imaging device <NUM> that reads an event by an asynchronous reading method. However, the event reading method is not limited to the asynchronous reading method, and may be a synchronous reading method. The imaging device <NUM> to which the synchronous readout method is applied is the same scanning type imaging device <NUM> as the normal imaging device <NUM> that performs imaging at a predetermined frame rate.

<FIG> is a block diagram illustrating an example of a configuration of the imaging device <NUM> according to the second configuration example, that is, the scanning type imaging device <NUM> used as the imaging device <NUM> in an imaging system <NUM> to which the technology according to the present disclosure is applied.

As illustrated in <FIG>, the imaging device <NUM> according to the second configuration example as the imaging device <NUM> of the present disclosure includes a pixel array unit <NUM>, a drive unit <NUM>, a signal processing unit <NUM>, a reading area selecting unit <NUM>, and a signal generation unit <NUM>.

The pixel array unit <NUM> includes a plurality of pixels <NUM>. The plurality of pixels <NUM> outputs an output signal in response to the selection signal of the reading area selecting unit <NUM>. Each of the plurality of pixels <NUM> may have a quantizer in the pixel as illustrated in <FIG>, for example. The plurality of pixels <NUM> outputs an output signal corresponding to the amount of change in the intensity of light. The plurality of pixels <NUM> may be two-dimensionally arranged in a matrix as illustrated in <FIG>.

The drive unit <NUM> drives each of the plurality of pixels <NUM> to output the pixel signal generated in each pixel <NUM> to the signal processing unit <NUM>. Note that the drive unit <NUM> and the signal processing unit <NUM> are circuit units for acquiring gradation information. Therefore, in a case where only the event information is acquired, the drive unit <NUM> and the signal processing unit <NUM> may not be provided.

The reading area selecting unit <NUM> selects some of the plurality of pixels <NUM> included in the pixel array unit <NUM>. For example, the reading area selecting unit <NUM> selects any one or a plurality of rows among the rows included in the structure of the two-dimensional matrix corresponding to the pixel array unit <NUM>. The reading area selecting unit <NUM> sequentially selects one or a plurality of rows according to a preset cycle. Furthermore, the reading area selecting unit <NUM> may determine the selected area in response to a request from each pixel <NUM> of the pixel array unit <NUM>.

The signal generation unit <NUM> generates an event signal corresponding to the active pixel in which the event has been detected among the selected pixels on the basis of the output signal of the pixel selected by the reading area selecting unit <NUM>. The event is an event in which the intensity of light changes. The active pixel is a pixel in which the amount of change in the intensity of light corresponding to the output signal exceeds or falls below a preset threshold value. For example, the signal generation unit <NUM> compares the output signal of the pixel with a reference signal, detects an active pixel that outputs the output signal in a case where the output signal is larger or smaller than the reference signal, and generates an event signal corresponding to the active pixel.

The signal generation unit <NUM> can include, for example, a column selection circuit that arbitrates a signal entering the signal generation unit <NUM>. Furthermore, the signal generation unit <NUM> can be configured to output not only the information of the active pixel that has detected the event but also the information of the inactive pixel that has not detected the event.

The address information and the time stamp information (for example, (X, Y, T)) of the active pixel in which the event has been detected are output from the signal generation unit <NUM> through an output line <NUM>. However, the data output from the signal generation unit <NUM> may be not only the address information and the time stamp information but also information in a frame format (for example, (<NUM>, <NUM>, <NUM>, <NUM>,.

As a chip (semiconductor integrated circuit) structure of the imaging device <NUM> according to the first configuration example or the second configuration example described above, a stacked chip structure can be adopted as illustrated in <FIG>. The stacked chip structure, that is, the stacked structure has a structure in which at least two chips of the light receiving chip <NUM> as a first chip and the detection chip <NUM> as a second chip are stacked. Then, in the circuit configuration of the pixel <NUM> illustrated in <FIG>, each of the light receiving units <NUM> is disposed on the light receiving chip <NUM>, and all elements other than the light receiving element <NUM>, elements of other circuit portions of the pixel <NUM>, and the like are disposed on the detection chip <NUM>. The light receiving chip <NUM> and the detection chip <NUM> are electrically connected via a connection portion such as a via (VIA), Cu-Cu bonding, or a bump.

Note that, here, a configuration example in which the light receiving element <NUM> is disposed on the light receiving chip <NUM>, and elements other than the light receiving element <NUM>, elements of other circuit portions of the pixel <NUM>, and the like are disposed on the detection chip <NUM> has been exemplified, but the present invention is not limited to this configuration example.

For example, in the circuit configuration of the pixel <NUM> illustrated in <FIG>, each element of the light receiving unit <NUM>, the reset transistor <NUM> of a pixel signal generation unit <NUM>, and the floating diffusion layer <NUM> may be arranged in the light receiving chip <NUM>, and the other elements may be arranged in the detection chip <NUM>. Alternatively, some of the elements configuring the address event detector <NUM> may be disposed on the light receiving chip <NUM> together with each element of the light receiving unit <NUM> and the like.

<FIG> illustrates a configuration example in which the analog-to-digital converter (ADC) <NUM> is disposed in the column ADC <NUM> in a one-to-one correspondence with the pixel column of the pixel array unit <NUM>, but the present invention is not limited to this configuration example. For example, the analog-to-digital converter (ADC) <NUM> may be disposed in units of a plurality of pixel columns, and the analog-to-digital converter (ADC) <NUM> may be used in a time division manner between the plurality of pixel columns.

The analog-to-digital converter (ADC) <NUM> converts the analog pixel signal SIG supplied via the vertical signal line VSL into a digital signal having a larger number of bits than the detection signal of the address event described above. For example, when the detection signal of the address event is <NUM>-bits, the pixel signal is converted into a digital signal of <NUM>-bits or more (<NUM> bits or the like). The analog-to-digital converter (ADC) <NUM> supplies the digital signal generated by the analog-digital conversion to the signal processing unit <NUM>.

By the way, the imaging device <NUM> according to the first configuration example is an asynchronous imaging device <NUM> called DVS including, for each pixel <NUM>, a detector (that is, the address event detector <NUM>) that detects, for each pixel address, that the light amount of the pixel exceeds a predetermined threshold value as an address event in real time.

In the imaging device <NUM> according to the asynchronous first configuration example, when some event (that is, a true event) originally occurs in the scene, data due to the occurrence of the true event is acquired. However, in the asynchronous imaging device <NUM>, there is a case where data is wastefully acquired due to a noise event (a false event) such as sensor noise even in a scene where no true event occurs. Therefore, not only the noise signal is read, but also the throughput of the signal output is reduced.

The technology according to the present disclosure can be applied to various products. Hereinafter, a more specific application example will be described. For example, the technology according to the present disclosure may be realized as a distance measuring device mounted on any type of mobile body such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility, an airplane, a drone, a ship, a robot, a construction machine, and an agricultural machine (tractor).

<FIG> is a block diagram illustrating a schematic configuration example of a vehicle control system <NUM> which is an example of a mobile body control system to which the technology according to the present disclosure can be applied. The vehicle control system <NUM> includes a plurality of electronic control units connected via a communication network <NUM>. In the example illustrated in <FIG>, the vehicle control system <NUM> includes a drive system control unit <NUM>, a body system control unit <NUM>, a battery control unit <NUM>, a vehicle exterior information detection unit <NUM>, a vehicle interior information detection unit <NUM>, and an integrated control unit <NUM>. The communication network <NUM> connecting the plurality of control units may be, for example, an in-vehicle communication network conforming to an arbitrary standard such as a controller area network (CAN), a local interconnect network (LIN), a local area network (LAN), or FlexRay (registered trademark).

Each control unit includes a microcomputer (processor) that performs arithmetic processing according to various programs, a storage unit that stores programs executed by the microcomputer, parameters used for various calculations, or the like, and a drive circuit that drives various devices to be controlled. Each control unit includes a network I/F for communicating with other control units via the communication network <NUM>, and a communication I/F for communicating with devices, sensors, or the like inside and outside the vehicle by wired communication or wireless communication. In <FIG>, as a functional configuration of the integrated control unit <NUM>, a microcomputer <NUM>, a general-purpose communication I/F <NUM>, a dedicated communication I/F <NUM>, a positioning unit <NUM>, a beacon receiving unit <NUM>, an in-vehicle device I/F <NUM>, an audio image output unit <NUM>, an in-vehicle network I/F <NUM>, and a storage unit <NUM> are illustrated. The other control units similarly include a microcomputer, a communication I/F, a storage unit, and the like.

The drive system control unit <NUM> controls the operation of devices related to the drive system of the vehicle according to various programs. For example, the drive system control unit <NUM> functions as a control device of a driving force generation device for generating a driving force of the vehicle such as an internal combustion engine or a driving motor, a driving force transmission mechanism for transmitting the driving force to wheels, a steering mechanism for adjusting a steering angle of the vehicle, a braking device for generating a braking force of the vehicle, and the like. The drive system control unit <NUM> may have a function as a control device such as an antilock brake system (ABS) or an electronic stability control (ESC).

A vehicle state detector <NUM> is connected to the drive system control unit <NUM>. The vehicle state detector <NUM> includes, for example, at least one of a gyro sensor that detects an angular velocity of axial rotational motion of a vehicle body, an acceleration sensor that detects acceleration of the vehicle, or a sensor for detecting an operation amount of an accelerator pedal, an operation amount of a brake pedal, a steering angle of a steering wheel, an engine speed, a wheel rotation speed, or the like. The drive system control unit <NUM> performs arithmetic processing using a signal input from the vehicle state detector <NUM>, and controls an internal combustion engine, a driving motor, an electric power steering device, a brake device, or the like.

The body system control unit <NUM> controls operations of various devices mounted on the vehicle body according to various programs. For example, the body system control unit <NUM> functions as a control device of a keyless entry system, a smart key system, a power window device, or various lamps such as a head lamp, a back lamp, a brake lamp, a blinker, or a fog lamp. In this case, radio waves transmitted from a portable device that substitutes for a key or signals of various switches can be input to the body system control unit <NUM>. The body system control unit <NUM> receives input of these radio waves or signals, and controls a door lock device, a power window device, a lamp, and the like of the vehicle.

The battery control unit <NUM> controls a secondary battery <NUM>, which is a power supply source of the driving motor, according to various programs. For example, information such as a battery temperature, a battery output voltage, or a remaining capacity of a battery is input to the battery control unit <NUM> from a battery device including the secondary battery <NUM>. The battery control unit <NUM> performs arithmetic processing using these signals, and performs temperature adjustment control of the secondary battery <NUM> or control of a cooling device or the like included in the battery device.

The vehicle exterior information detection unit <NUM> detects information outside the vehicle on which the vehicle control system <NUM> is mounted. For example, at least one of an imaging unit <NUM> or a vehicle exterior information detector <NUM> is connected to the vehicle exterior information detection unit <NUM>. The imaging unit <NUM> includes at least one of a time of flight (ToF) camera, a stereo camera, a monocular camera, an infrared camera, or other cameras. The vehicle exterior information detector <NUM> includes, for example, at least one of an environment sensor for detecting current climate or weather, or a surrounding information detection sensor for detecting another vehicle, an obstacle, a pedestrian, or the like around the vehicle on which the vehicle control system <NUM> is mounted.

The environment sensor may be, for example, at least one of a raindrop sensor that detects rainy weather, a fog sensor that detects fog, a sunshine sensor that detects a degree of sunshine, and a snow sensor that detects snowfall. The surrounding information detection sensor may be at least one of an ultrasonic sensor, a radar device, or a light detection and ranging, laser imaging detection and ranging (LIDAR) device. The imaging unit <NUM> and the vehicle exterior information detector <NUM> may be provided as independent sensors or devices, or may be provided as a device in which a plurality of sensors or devices is integrated.

Here, <FIG> is a diagram illustrating an example of installation positions of the imaging unit <NUM> and the vehicle exterior information detector <NUM>. The imaging units <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are provided, for example, at least one position of a front nose, a side mirror, a rear bumper, a back door, or an upper portion of a windshield in a vehicle interior of a vehicle <NUM>. The imaging unit <NUM> provided at the front nose and the imaging unit <NUM> provided at the upper portion of the windshield in the vehicle interior mainly acquire images in front of the vehicle <NUM>. The imaging units <NUM> and <NUM> provided at the side mirrors mainly acquire images of the sides of the vehicle <NUM>. The imaging unit <NUM> provided on the rear bumper or the back door mainly acquires an image behind the vehicle <NUM>. The imaging unit <NUM> provided at the upper portion of the windshield in the vehicle interior is mainly used to detect a preceding vehicle, a pedestrian, an obstacle, a traffic light, a traffic sign, a lane, or the like.

Note that <FIG> illustrates an example of imaging ranges of the respective imaging units <NUM>, <NUM>, <NUM>, and <NUM>. An imaging range a indicates an imaging range of the imaging unit <NUM> provided at the front nose, imaging ranges b and c indicate imaging ranges of the imaging units <NUM> and <NUM> provided at the side mirrors, respectively, and an imaging range d indicates an imaging range of the imaging unit <NUM> provided at the rear bumper or the back door. For example, by superimposing pieces of image data captured by the imaging units <NUM>, <NUM>, <NUM>, and <NUM>, an overhead view image of the vehicle <NUM> viewed from above can be obtained.

Vehicle exterior information detectors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> provided at the front, rear, sides, corners, and the upper portion of the windshield in the vehicle interior of the vehicle <NUM> may be, for example, ultrasonic sensors or radar devices. The vehicle exterior information detectors <NUM>, <NUM>, and <NUM> provided at the front nose, the rear bumper, the back door, and the upper portion of the windshield in the vehicle interior of the vehicle <NUM> may be, for example, LIDAR devices. These vehicle exterior information detectors <NUM> to <NUM> are mainly used for detecting a preceding vehicle, a pedestrian, an obstacle, or the like.

Returning to <FIG>, the description will be continued. The vehicle exterior information detection unit <NUM> causes the imaging unit <NUM> to capture an image outside the vehicle, and receives the captured image data. Furthermore, the vehicle exterior information detection unit <NUM> receives detection information from the connected vehicle exterior information detector <NUM>. In a case where the vehicle exterior information detector <NUM> is an ultrasonic sensor, a radar device, or a LIDAR device, the vehicle exterior information detection unit <NUM> transmits ultrasonic waves, electromagnetic waves, or the like, and receives information of received reflected waves. The vehicle exterior information detection unit <NUM> may perform object detection processing or distance detection processing of a person, a vehicle, an obstacle, a sign, a character on a road surface, or the like on the basis of the received information. The vehicle exterior information detection unit <NUM> may perform environment recognition processing of recognizing rainfall, fog, road surface conditions, or the like on the basis of the received information. The vehicle exterior information detection unit <NUM> may calculate a distance to an object outside the vehicle on the basis of the received information.

Furthermore, the vehicle exterior information detection unit <NUM> may perform image recognition processing or distance detection processing of recognizing a person, a car, an obstacle, a sign, a character on a road surface, or the like on the basis of the received image data. The vehicle exterior information detection unit <NUM> may perform processing such as distortion correction or alignment on the received image data, and combine image data captured by different imaging units <NUM> to generate a bird's-eye view image or a panoramic image. The vehicle exterior information detection unit <NUM> may perform viewpoint conversion processing using image data captured by different imaging units <NUM>.

The vehicle interior information detection unit <NUM> detects information inside the vehicle. For example, a driver state detector <NUM> that detects a state of a driver is connected to the vehicle interior information detection unit <NUM>. The driver state detector <NUM> may include a camera that captures the driver, a biological sensor that detects biological information of the driver, a microphone that collects audio in the vehicle interior, or the like. The biological sensor is provided, for example, on a seat surface, a steering wheel, or the like, and detects biological information of an occupant sitting on a seat or a driver holding the steering wheel. The vehicle interior information detection unit <NUM> may calculate the degree of fatigue or the degree of concentration of the driver or may determine whether or not the driver is dozing on the basis of the detection information input from the driver state detector <NUM>. The vehicle interior information detection unit <NUM> may perform processing such as noise canceling processing on the collected audio signal.

The integrated control unit <NUM> controls the overall operation in the vehicle control system <NUM> according to various programs. An input unit <NUM> is connected to the integrated control unit <NUM>. The input unit <NUM> is realized by, for example, a device such as a touch panel, a button, a microphone, a switch, or a lever that can be operated by an occupant for input. Data obtained by performing audio recognition on the audio input by the microphone may be input to the integrated control unit <NUM>. The input unit <NUM> may be, for example, a remote control device using infrared rays or other radio waves, or an external connection device such as a mobile phone or a personal digital assistant (PDA) corresponding to the operation of the vehicle control system <NUM>. The input unit <NUM> may be, for example, a camera, and in this case, the passenger can input information by gesture. Alternatively, data obtained by detecting the movement of the wearable device worn by the passenger may be input. Furthermore, the input unit <NUM> described above may include, for example, an input control circuit or the like that generates an input signal on the basis of information input by the occupant or the like using the input unit <NUM> and outputs the input signal to the integrated control unit <NUM>. By operating the input unit <NUM>, the occupant or the like inputs various data to the vehicle control system <NUM> or instructs a processing operation.

The storage unit <NUM> may include a read only memory (ROM) that stores various programs to be executed by the microcomputer, and a random access memory (RAM) that stores various parameters, calculation results, sensor values, or the like. Furthermore, the storage unit <NUM> may be realized by a magnetic storage device such as a hard disc drive (HDD), a semiconductor storage device, an optical storage device, a magneto-optical storage device, or the like.

The general-purpose communication I/F <NUM> is a general-purpose communication I/F that mediates communication with various devices existing in an external environment <NUM>. The general-purpose communication I/F <NUM> may implement a cellular communication protocol such as global system of mobile communications (GSM) (registered trademark), WiMAX, long term evolution (LTE), or LTE-advanced (LTE-A), or another wireless communication protocol such as wireless LAN (also referred to as Wi-Fi (registered trademark)) or Bluetooth (registered trademark). The general-purpose communication I/F <NUM> may be connected to a device (for example, an application server or a control server) existing on an external network (for example, the Internet, a cloud network, or a company-specific network) via, for example, a base station or an access point. Furthermore, the general-purpose communication I/F <NUM> may be connected to a terminal (for example, a terminal of a driver, a pedestrian, or a store, or a machine type communication (MTC) terminal) existing in the vicinity of the vehicle using, for example, a Peer to Peer (P2P) technology.

The dedicated communication I/F <NUM> is a communication I/F that supports a communication protocol formulated for use in a vehicle. For example, the dedicated communication I/F <NUM> may implement a standard protocol such as wireless access in vehicle environment (WAVE) which is a combination of IEEE <NUM>. 11p of the lower layer and IEEE <NUM> of the upper layer, dedicated short range communications (DSRC), or a cellular communication protocol. The dedicated communication I/F <NUM> typically performs V2X communication which is a concept including one or more of vehicle to vehicle communication, vehicle to infrastructure communication, vehicle to home communication, and vehicle to pedestrian communication.

The positioning unit <NUM> receives, for example, a global navigation satellite system (GNSS) signal from a GNSS satellite (for example, a global positioning system (GPS) signal from a GPS satellite), executes positioning, and generates position information including the latitude, longitude, and altitude of the vehicle. Note that the positioning unit <NUM> may specify the current position by exchanging signals with a wireless access point, or may acquire the position information from a terminal such as a mobile phone, a PHS, or a smartphone having a positioning function.

The beacon receiving unit <NUM> receives, for example, radio waves or electromagnetic waves transmitted from a wireless station or the like installed on a road, and acquires information such as a current position, a traffic jam, a closed road, a required time, or the like. Note that the function of the beacon receiving unit <NUM> may be included in the dedicated communication I/F <NUM> described above.

The in-vehicle device I/F <NUM> is a communication interface that mediates connection between the microcomputer <NUM> and various in-vehicle devices <NUM> existing in the vehicle. The in-vehicle device I/F <NUM> may establish wireless connection using a wireless communication protocol such as wireless LAN, Bluetooth (registered trademark), near field communication (NFC), or wireless USB (WUSB). Furthermore, the in-vehicle device I/F <NUM> may establish wired connection such as universal serial bus (USB), high-definition multimedia interface (HDMI) (registered trademark), or mobile high-definition link (MHL) via a connection terminal (and, if necessary, a cable. ) not illustrated. The in-vehicle device <NUM> may include, for example, at least one of a mobile device or a wearable device possessed by a passenger, or an information device carried in or attached to the vehicle. Furthermore, the in-vehicle device <NUM> may include a navigation device that searches for a route to an arbitrary destination. The in-vehicle device I/F <NUM> exchanges a control signal or a data signal with these in-vehicle devices <NUM>.

The in-vehicle network I/F <NUM> is an interface that mediates communication between the microcomputer <NUM> and the communication network <NUM>. The in-vehicle network I/F <NUM> transmits and receives signals and the like in accordance with a predetermined protocol supported by the communication network <NUM>.

The microcomputer <NUM> of the integrated control unit <NUM> controls the vehicle control system <NUM> according to various programs on the basis of information acquired via at least one of the general-purpose communication I/F <NUM>, the dedicated communication I/F <NUM>, the positioning unit <NUM>, the beacon receiving unit <NUM>, the in-vehicle device I/F <NUM>, or the in-vehicle network I/F <NUM>. For example, the microcomputer <NUM> may calculate a control target value of the driving force generation device, the steering mechanism, or the braking device on the basis of the acquired information regarding the inside and outside of the vehicle, and output a control command to the drive system control unit <NUM>. For example, the microcomputer <NUM> may perform cooperative control for the purpose of implementing functions of an advanced driver assistance system (ADAS) including collision avoidance or impact mitigation of the vehicle, follow-up traveling based on an inter-vehicle distance, vehicle speed maintenance traveling, vehicle collision warning, vehicle lane departure warning, or the like. Furthermore, the microcomputer <NUM> may perform cooperative control for the purpose of automatic driving or the like in which the vehicle autonomously travels without depending on the operation of the driver by controlling the driving force generation device, the steering mechanism, the braking device, or the like on the basis of the acquired information around the vehicle.

The microcomputer <NUM> may generate three-dimensional distance information between the vehicle and an object such as a surrounding structure or a person on the basis of information acquired via at least one of the general-purpose communication I/F <NUM>, the dedicated communication I/F <NUM>, the positioning unit <NUM>, the beacon receiving unit <NUM>, the in-vehicle device I/F <NUM>, or the in-vehicle network I/F <NUM>, and create local map information including surrounding information of the current position of the vehicle. Furthermore, the microcomputer <NUM> may predict danger such as collision of the vehicle, approach of a pedestrian or the like, or entry into a closed road on the basis of the acquired information, and generate a warning signal. The warning signal may be, for example, a signal for generating a warning sound or turning on a warning lamp.

The audio image output unit <NUM> transmits an output signal of at least one of an audio or an image to an output device capable of visually or audibly notifying an occupant of the vehicle or the outside of the vehicle of information. In the example of <FIG>, an audio speaker <NUM>, a display unit <NUM>, and an instrument panel <NUM> are illustrated as the output device. The display unit <NUM> may include, for example, at least one of an on-board display and a head-up display. The display unit <NUM> may have an augmented reality (AR) display function. The output device may be another device other than these devices, such as a wearable device such as a headphone or an eyeglass-type display worn by a passenger, a projector, or a lamp. In a case where the output device is a display device, the display device visually displays results obtained by various processes performed by the microcomputer <NUM> or information received from another control unit in various formats such as text, images, tables, and graphs. Furthermore, in a case where the output device is an audio output device, the audio output device converts an audio signal including reproduced audio data, audio data, or the like into an analog signal and aurally outputs the analog signal.

Note that, in the example illustrated in <FIG>, at least two control units connected via the communication network <NUM> may be integrated as one control unit. Alternatively, each control unit may include a plurality of control units. Further, the vehicle control system <NUM> may include another control unit (not illustrated). In addition, in the above description, some or all of the functions performed by any of the control units may be provided to another control unit. That is, as long as information is transmitted and received via the communication network <NUM>, predetermined arithmetic processing may be performed by any control unit. Similarly, a sensor or a device connected to any of the control units may be connected to another control unit, and a plurality of control units may mutually transmit and receive detection information via the communication network <NUM>.

An example of the vehicle control system to which the technology according to the present disclosure can be applied has been described above. The technology according to the present disclosure can be applied to, for example, the imaging units <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, the vehicle exterior information detectors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, the driver state detector <NUM>, and the like, among the above-described configurations. Specifically, the imaging system <NUM> in <FIG> including the imaging device <NUM> of the present disclosure can be applied to these imaging units and detectors. Then, by applying the technology according to the present disclosure, the influence of a noise event such as sensor noise can be mitigated, and the occurrence of a true event can be reliably and quickly sensed, so that safe vehicle traveling can be achieved.

Claim 1:
An imaging device (<NUM>, <NUM>) comprising:
a photoelectric conversion unit (<NUM>) including a plurality of photoelectric conversion elements (<NUM>) each of which photoelectrically converts incident light to generate an electric signal;
an address event detector (<NUM>) configured to output a detection signal indicating whether or not an amount of change in the electric signal of each of the plurality of photoelectric conversion elements (<NUM>) exceeds a predetermined threshold value;
a pixel signal generation unit (<NUM>) configured to generate a pixel signal on a basis of the electric signal;
a transfer controller (<NUM>, <NUM>, <NUM>) configured to perform control to transfer the electric signal to the pixel signal generation unit (<NUM>); and
an analog-to-digital converter (<NUM>, <NUM>) configured to convert the pixel signal into a digital signal,
characterised in that
a low-potential-side reference potential of the photoelectric conversion unit (<NUM>), a low-potential-side reference potential of the address event detector (<NUM>), a low-potential-side reference potential of the pixel signal generation unit (<NUM>), a low-potential-side reference potential of the analog-to-digital converter (<NUM>, <NUM>), and an off-potential of the transfer controller (<NUM>, <NUM>, <NUM>) include three potentials having different potential levels, and
the low-potential-side reference potentials of the photoelectric conversion unit (<NUM>), the pixel signal generation unit (<NUM>), and the analog-to-digital converter (<NUM>, <NUM>) are substantially equal.