WO2024209800A1 - Photodetection element and electronic device - Google Patents

Abstract

[Problem] To provide a photodetection element with which the detection cycle of an event signal can be shortened, and an electronic device. [Solution] A photodetection element according to one aspect of the present disclosure comprises: a light receiving unit that photoelectrically converts incident light to generate an electric signal; a comparison unit that outputs an event signal when the amount of change in the electric signal exceeds or falls below a threshold; a first recording unit that is connected to an output terminal of the comparison unit, records the event signal, and outputs the event signal; and a second recording unit that is connected to the first recording unit, records the event signal from the first recording unit, and outputs the event signal.

Description

Photodetector and electronic device

This disclosure relates to a photodetector element and an electronic device.

A photodetector has been developed that can detect an event signal in real time when the amount of light from a pixel exceeds a threshold. This type of photodetector that detects event signals is called an Event Vision Sensor (EVS).

JP 2021-048554 A

In such photodetection elements, a detection cycle is repeatedly executed, which consists of a detection period for detecting an event signal, a read period for reading out the recorded event signal, and a reset period for resetting the threshold for detecting the event signal. It is desirable to shorten this detection cycle so that the photodetection element can operate at high speed.

This technology was developed in consideration of these issues, and provides a photodetector element and electronic device that can shorten the detection period of an event signal.

The photodetector element of one aspect of the present disclosure includes a light receiving unit that performs photoelectric conversion on incident light to generate an electrical signal, a comparison unit that outputs an event signal when the amount of change in the electrical signal exceeds or falls below a threshold, a first recording unit that is connected to the output terminal of the comparison unit and records the event signal and outputs the event signal, and a second recording unit that is connected to the first recording unit and records the event signal from the first recording unit and outputs the event signal.

During the read period in which the event signal recorded in the second recording unit is being read, the first recording unit records the next event signal from the comparison unit.

The light detection element further includes a first switching element connected between the input terminal of the comparison unit and the output terminal of the comparison unit, a control unit provided between the output terminal of the first recording unit and the first switching element, which controls the first switching element based on an event signal output from the first recording unit, and a first readout wiring connected to the output terminal of the second recording unit, and when the first switching element is in a conductive state, the second recording unit outputs an event signal to the first readout wiring.

The light detection element further includes a third recording unit connected to the output terminal of the comparison unit and recording the event signal, and a fourth recording unit connected to the third recording unit and recording the event signal from the third recording unit.

During the read period in which the event signal recorded in the fourth recording unit is being read, the third recording unit records the next event signal from the comparison unit.

The light detection element further includes a first switching element connected between the input terminal of the comparison unit and the output terminal of the comparison unit, a control unit provided between the output terminals of the first and third recording units and the first switching element, and controlling the first switching element based on the event signals output from the first and third recording units, a first readout wiring connected to the output terminal of the second recording unit, and a second readout wiring connected to the output terminal of the fourth recording unit, and when the first switching element is in a conductive state, the event signal recorded in the second recording unit is read out to the first readout wiring, and the event signal recorded in the fourth recording unit is read out to the second readout wiring.

The comparison unit compares the amount of change with a first threshold during a first period and outputs a first event signal, and compares the amount of change with a second threshold different from the first threshold during a second period following the first period and outputs a second event signal, the first recording unit records the first event signal during the first period, the third recording unit records the second event signal during the second period, and when the first switching element is in a conductive state, the second recording unit records the first event signal from the first recording unit and outputs the first event signal to the first readout wiring, and the fourth recording unit records the second event signal from the third recording unit and outputs the second event signal to the second readout wiring.

The control unit resets the voltages of the input terminal and output terminal of the comparison unit to a voltage between the first threshold value and the second threshold value by turning on the first switching element.

The control unit controls the first switching element based on the event signals recorded in the first and third recording units.

The light detection element further includes an inverter connected to one of the output terminals of the first and second recording units, and a first logic gate that outputs the logical product of the other output signal of the first and second recording units and the output signal of the inverter to the first readout wiring.

The light detection element further includes an inverter connected to one of the output terminals of the first and second recording units, a first logic gate that outputs a logical product of the other output signal of the first and second recording units and the output signal of the inverter to a first readout wiring, an inverter connected to one of the output terminals of the third and fourth recording units, and a second logic gate that outputs a logical product of the other output signal of the third and fourth recording units and the output signal of the inverter to a second readout wiring.

The light detection element further includes a third logic gate that outputs the logical product of the output signals of the first and second recording units to the control unit, and the control unit controls the first switching element based on the output signal of the third logic gate.

The light detection element further includes a third logic gate that outputs the logical product of the output signals of the first and second recording units to the control unit, and a fourth logic gate that outputs the logical product of the output signals of the third and fourth recording units to the control unit, and the control unit controls the first switching element based on the output signals of the third and fourth logic gates.

The comparison unit compares the amount of change with a first threshold during a first period and outputs a first event signal, and compares the amount of change with a second threshold different from the first threshold during a second period following the first period and outputs a second event signal, the first recording unit alternately records the first event signal and the second event signal, and when the first switching element is in a conductive state, the second recording unit records the first event signal from the first recording unit and outputs the first event signal to the first readout wiring, or records the second event signal from the first recording unit and outputs the second event signal to the first readout wiring.

The light detection element further includes a first switching element connected between the input terminal of the comparison unit and the output terminal of the comparison unit, a control unit provided between the output terminals of the first and third recording units and the first switching element, which controls the first switching element based on the event signals output from the first and third recording units, a first switch circuit connected to the output terminals of the second and fourth recording units, and a first readout wiring connected to the output terminal of the first switch circuit, and the first switch circuit selectively connects the output terminal of either the second or fourth recording unit to the first readout wiring.

The light detection element further includes a plurality of light receiving sections, a plurality of comparison sections provided corresponding to the plurality of light receiving sections, a first recording section, a plurality of second recording sections provided corresponding to the plurality of first recording sections, a buffer provided between the plurality of comparison sections and the plurality of first recording sections, a second switch circuit provided between an input terminal of the buffer and the plurality of comparison sections, which connects a selective comparison section selected from the plurality of comparison sections to an input terminal of the buffer, and a third switch circuit provided between an output terminal of the buffer and the plurality of first recording sections, which connects a selective first recording section selected from the plurality of first recording sections to an output terminal of the buffer.

The photodetector element of another aspect of the present disclosure includes a light receiving unit that performs photoelectric conversion on incident light to generate an electrical signal, a comparison unit that compares the amount of change in the electrical signal generated by the light receiving unit with a threshold value and outputs an event signal, and first and second recording units connected in parallel to the output terminal of the comparison unit, and when one of the first and second recording units is recording an event signal, the other of the first and second recording units outputs the event signal.

The light detection element further includes a second switching element connected between the output terminal of the comparison unit and the first recording unit, a third switching element connected between the output terminal of the comparison unit and the second recording unit, a fourth switching element connected between the first recording unit and the first readout wiring, a fifth switching element connected between the second recording unit and the first readout wiring, a sixth switching element connected between the first recording unit and the control unit, and a seventh switching element connected between the second recording unit and the control unit, and when the first recording unit records an event signal and the second recording unit outputs an event signal, the second, fifth, and sixth switching elements are in a conductive state and the third, fourth, and seventh switching elements are in a non-conductive state, and when the second recording unit records an event signal and the first recording unit outputs an event signal, the third, fourth, and seventh switching elements are in a conductive state and the second, fifth, and sixth switching elements are in a non-conductive state.

In one aspect of the electronic device disclosed herein, the photodetector element includes a light receiving unit that performs photoelectric conversion on incident light to generate an electrical signal, a comparison unit that outputs an event signal when the amount of change in the electrical signal exceeds or falls below a threshold, a first recording unit that is connected to the output terminal of the comparison unit and records the event signal and outputs the event signal, and a second recording unit that is connected to the first recording unit and records the event signal from the first recording unit and outputs the event signal.

An electronic device according to another aspect of the present disclosure has a light-receiving unit that performs photoelectric conversion on incident light to generate an electrical signal, a comparison unit that compares the amount of change in the electrical signal generated by the light-receiving unit with a threshold value to output an event signal, and first and second recording units connected in parallel to the output terminal of the comparison unit, and has a light detection element in which, when one of the first and second recording units is recording an event signal, the other of the first and second recording units outputs the event signal.

FIG. 2 is a block diagram showing a configuration example of a light detection element according to the first embodiment. 1 is a diagram showing an example of a layered structure of a solid-state imaging element according to a first embodiment. FIG. 1 is a plan view of a light-receiving chip. FIG. 2 is an example of a plan view of a pixel array portion. FIG. 2 is a plan view of an example of a detection chip. FIG. 4 is a plan view of a detection unit. FIG. 2 is a block diagram showing an example of the configuration of an event detection circuit. FIG. 4 is a circuit diagram showing an example of the configuration of an event detection circuit, a recording area, and a control unit. 5 is a timing chart showing an example of the operation of the photodetector according to the first embodiment. FIG. FIG. 11 is a timing chart showing an example of the operation of the photodetector element according to the second embodiment. FIG. 13 is a circuit diagram showing an example of the configuration of an event detection circuit, a recording area, and a control unit according to a third embodiment. FIG. 11 is a timing chart showing an example of the operation of the photodetector element according to the third embodiment. FIG. 11 is a timing chart showing an example of the operation of the photodetector element according to the third embodiment. FIG. 13 is a circuit diagram showing an example of the configuration of an event detection circuit, a recording area, and a control unit according to a fourth embodiment. FIG. 13 is a timing chart showing an example of the operation of the photodetector according to the fourth embodiment. FIG. 13 is a timing chart showing an example of the operation of the photodetector according to the fourth embodiment. FIG. 13 is a circuit diagram showing an example of the configuration of an event detection circuit, a recording area, and a control unit according to a fifth embodiment. FIG. 13 is a timing chart showing an example of the operation of the photodetector element according to the fifth embodiment. FIG. 13 is a circuit diagram showing an example of the configuration of an event detection circuit, a recording area, and a control unit according to a sixth embodiment. FIG. 13 is a timing chart showing an example of the operation of the photodetector according to the sixth embodiment. FIG. 23 is a circuit diagram showing an example of the configuration of an event detection circuit, a recording area, and a control unit according to a seventh embodiment. FIG. 23 is a circuit diagram showing an example of the configuration of an event detection circuit, a recording area, and a control unit according to the eighth embodiment. FIG. 23 is a timing chart showing an example of the operation of the photodetector according to the eighth embodiment. FIG. 1 is a block diagram showing an example of a schematic configuration of a vehicle control system. FIG. 4 is an explanatory diagram showing an example of the installation positions of an outside-vehicle information detection unit and an imaging unit.

Below, specific embodiments to which this technology is applied will be described in detail with reference to the drawings. The drawings are schematic or conceptual, and the proportions of each part are not necessarily the same as those in reality. In the specification and drawings, elements similar to those described above with reference to the previous drawings will be given the same reference numerals, and detailed descriptions will be omitted as appropriate.

First Embodiment
1 is a block diagram showing an example of a configuration of a light detection element 1 according to the first embodiment. The light detection element 1 is, for example, an EVS or a DVS (Dynamic Vision Sensor). The light detection element 1 includes an imaging lens 10, a solid-state imaging element 20, a recording area 30, and a control unit 40. Assumed examples of the light detection element 1 include electronic devices such as a camera mounted on an industrial robot, an in-vehicle camera, and a surveillance camera.

The imaging lens 10 collects the incident light and guides it to the solid-state imaging element 20. The solid-state imaging element 20 photoelectrically converts the incident light to generate a voltage signal according to the amount of light received, and detects the change in the amount of light received as an event signal based on the amount of change in the voltage signal. The detected event signal is output to the recording area 30.

The recording area 30 records the event signal from the solid-state imaging element 20. The recording area 30 may be, for example, a latch circuit, a DRAM (Dynamic Random Access Memory), a flash memory, or other semiconductor memory. The internal structure of the recording area 30 will be described in more detail later.

The control unit 40 is configured with a microcomputer equipped with, for example, a CPU (Central Processing Unit), ROM (Read Only Memory), RAM, etc., and the CPU controls the operation of the light detection element 1 by executing processing according to a program. In particular, the control unit 40 controls the solid-state imaging element 20 to perform the above-mentioned event signal detection operation, controls the recording area 30 to record the event signal, and executes processing to read the event signal from the recording area 30.

FIG. 2 is a diagram showing an example of a stacked structure of the solid-state imaging element 20 according to the first embodiment. The solid-state imaging element 20 includes a detection chip 202 and a light-receiving chip 201 stacked on the detection chip 202. In this stacked structure, the light-receiving chip 201 and the detection chip 202 are electrically connected through a connection such as a via. Note that in addition to vias, they can also be connected by Cu-Cu bonding or bumps.

FIG. 3 is an example of a plan view of the light-receiving chip 201. The light-receiving chip 201 is provided with a pixel array section 220 and via arrangement sections 211, 212, and 213. Vias that are connected to the detection chip 202 are arranged in the via arrangement sections 211, 212, and 213.

FIG. 4 is an example of a plan view of the pixel array section 220. In the pixel array section 220, a plurality of light receiving sections 221 are arranged in a two-dimensional lattice. The light receiving sections 221 are, for example, photodiodes. The light receiving sections 221 perform photoelectric conversion of incident light to generate a photocurrent. Each of the light receiving sections 221 is assigned a pixel address consisting of a row address and a column address.

FIG. 5 is an example of a plan view of the detection chip 202. The detection chip 202 is provided with via arrangement sections 231, 232, and 233, a signal processing circuit 240, a row driving circuit 251, a column driving circuit 252, and a detection section 260. Vias that are connected to the light receiving chip 201 are arranged in the via arrangement sections 231, 232, and 233.

The row drive circuit 251 selects a row address of the pixel array section 220 and outputs a photocurrent corresponding to the row address to the detection section 260. The column drive circuit 252 selects a column address of the pixel array section 220 and outputs a photocurrent corresponding to the column address to the detection section 260.

The detection unit 260 detects an event signal by quantizing a voltage signal obtained by logarithmically converting the input photocurrent, and outputs the detected event signal to the signal processing circuit 240. An event indicates that the amount of change in the voltage signal obtained by logarithmically converting the photocurrent has exceeded or fallen below a predetermined threshold. The event signal is activated (e.g., raised) when an event occurs. The event signal is a signal that has been quantized (binarized) by the quantizer 330. The signal processing circuit 240 performs a predetermined signal processing on the event signal output from the detection unit 260, and outputs the signal to the recording area 30.

FIG. 6 is an example of a plan view of the detection unit 260. In the detection unit 260, a plurality of event detection circuits 300 are arranged in a two-dimensional grid. A pixel address is assigned to each event detection circuit 300, and each event detection circuit 300 is connected to a light receiving unit 221 with the same address. The event detection circuit 300 quantizes a voltage signal corresponding to the photocurrent from the corresponding light receiving unit 221, and outputs the quantized voltage signal as an event signal.

FIG. 7 is a block diagram showing an example of the configuration of the event detection circuit 300. The event detection circuit 300 includes a logarithmic conversion circuit 310, a buffer 320, and a quantizer 330.

The logarithmic conversion circuit 310 converts the photocurrent from the corresponding light receiving unit 221 into a logarithmically converted voltage signal. The logarithmic conversion circuit 310 supplies the converted voltage signal to the buffer 320.

Buffer 320 corrects the voltage signal from logarithmic conversion circuit 310. Buffer 320 outputs the corrected voltage signal to quantizer 330.

The quantizer 330 compares the amount of change in the input voltage signal with a predetermined threshold (comparison reference voltage) and detects an event signal indicating that the threshold has been exceeded or fallen below. The quantizer 330 quantizes the voltage signal after the drop into a digital signal and outputs it to the recording area 30 as an event signal.

The control unit 40 controls the operation of the quantizer 330 and controls the reading of the detection signal recorded in the recording area 30.

FIG. 8 is a circuit diagram showing an example of the configuration of the event detection circuit 300, the recording area 30, and the control unit 40. The logarithmic conversion circuit 310 includes N-type transistors 311 and 313 and a P-type transistor 312. For example, MOS (Metal-Oxide-Semiconductor) transistors are used as these transistors.

The source of N-type transistor 311 is connected to the cathode of light receiving section 221, and the drain is connected to the power supply line. P-type transistor 312 and N-type transistor 313 are connected in series between the power supply line and ground. The connection point of P-type transistor 312 and N-type transistor 313 is connected to the gate of N-type transistor 311 and the input terminal of buffer 320. A predetermined bias voltage Vbias1 is applied to the gate of P-type transistor 312.

The drains of N-type transistors 311 and 313 are connected to the power supply, and this type of circuit is called a source follower. These two source followers connected in a loop convert the photocurrent from the light receiving section 221 into a logarithmic voltage signal. In addition, P-type transistor 312 supplies a constant current to N-type transistor 313.

The logarithmic conversion circuit 310 described above converts the light intensity received by the light receiving unit 221 into a logarithmic converted voltage signal.

The ground of the light receiving chip 201 and the ground of the detection chip 202 are separated from each other to prevent interference. The light receiving chip 201 is provided with the light receiving unit 221 and the N-type transistors 311 and 313 of the event detection circuit 300, while the detection chip 202 is provided with the event detection circuit 300 other than the N-type transistors 311 and 313.

Quantizer 330 includes capacitor 331, switching elements 332, 333, 334, and 335, and comparator 336. Each switching element is turned on in response to an operation control signal from control unit 40. Switching elements 332, 333, 334, and 335 are, for example, MOS transistors.

One end of the capacitor 331 is connected to the output terminal of the buffer 320, and the other end is connected to the inverting input terminal of the comparator 336. Therefore, the voltage representing the amount of change in the voltage signal from the buffer 320 becomes the voltage signal input to the comparator 336. In other words, a voltage signal corresponding to the amount of change in luminance detected by photoelectric conversion is input to the inverting input terminal of the comparator 336. A comparison reference voltage (Von, Vreset, or Voff) is input to the non-inverting input terminal of the comparator 336 as a threshold voltage.

Switching element 332 is connected between the output terminal and the inverting input terminal of comparator 336. Switching element 332 is turned on/off in response to an operation control signal from control unit 40. Control unit 40 performs a reset operation by turning on switching element 332 and switching element 334 based on an event signal from recording area 30.

Switching elements 333, 334, and 335 conduct the three paths connected to the non-inverting input terminal of comparator 336 in response to operation control signals Son, Srs, and Soff from control unit 40. Either of switching elements 333, 334, and 335 corresponding to each operation control signal is made conductive by operation control signals (ON control signal Son, reset control signal Srs, OFF control signal Soff) from control unit 40. As a result, a comparison reference voltage (Von, Vreset, or Voff) corresponding to the operation control signal is selectively input to the non-inverting input terminal of comparator 336.

Comparator 336 compares the voltage signal input to the inverting input terminal with the comparison reference voltage input to the non-inverting input terminal, and outputs an event signal according to the detection result. The event signal is output from comparator 336 and recorded in recording area 30.

The control unit 40 controls the operation of the event detection circuit 300 in a time-division manner using the ON control signal Son, the reset control signal Srs, and the OFF control signal Soff. The control unit 40 turns on the switching element 333 using the ON control signal Son. This causes the positive comparison reference voltage Von to be input to the non-inverting input terminal of the comparator 336. The comparator 336 compares the amount of change in the input voltage signal with the comparison reference voltage Von, and outputs an ON event signal when the voltage signal exceeds the comparison reference voltage Von as a threshold value. The ON event signal output from the comparator 336 is recorded in the recording area 30.

The control unit 40 also executes a process to read the recorded on-event signal from the recording area 30.

The control unit 40 turns on the switching element 335 using the OFF control signal Soff. This causes the negative comparison reference voltage Voff to be input to the non-inverting input terminal of the comparator 336. The comparator 336 compares the amount of change in the input voltage signal with the comparison reference voltage Voff, and outputs an off event signal when the voltage signal falls below the comparison reference voltage Voff, which serves as a threshold value. The off event signal output from the comparator 336 is recorded in the recording area 30.

The control unit 40 also executes a process to read the recorded off-event signal from the recording area 30.

The control unit 40 turns on the switching elements 332 and 334 using the reset control signal Srs. This resets the comparison reference voltage that has fluctuated in the event detection circuit 300 due to the ON control signal Son and the OFF control signal Soff to Vreset.

The recording area 30 includes recording units 31a, 32a, 31b, and 32b. Each of the recording units 31a, 32a, 31b, and 32b is, for example, a latch circuit that records (holds) an event signal from the comparator 336 and outputs the recorded event signal. The recording units 31a, 32a, 31b, and 32b may be a latch circuit or a semiconductor memory such as an SRAM, a DRAM, or a flash memory.

The recording unit 31a is connected between the output terminal of the comparator 336 and the recording unit 32a. The recording unit 31a receives the on-event signal Eon output from the comparator 336 and records the on-event signal Eon. The recording unit 31a also outputs the on-event signal Eon that it holds to the recording unit 32a.

The recording unit 32a is connected between the output terminal of the recording unit 31a and the readout wiring VSLa. The recording unit 32a receives the on-event signal Eon output from the recording unit 31a and records the on-event signal Eon. The recording unit 32a also outputs the on-event signal Eon that it holds to the readout wiring VSLa.

In this way, the multiple recording units 31a, 32a are connected in series between the output terminal of the comparator 336 and the readout wiring VSLa. The recording units 31a, 32a are provided to read out the on-event signal Eon to the readout wiring VSLa.

The recording unit 31b is connected between the output terminal of the comparator 336 and the recording unit 32b. The recording unit 31b receives the off-event signal Eoff output from the comparator 336 and records the off-event signal Eoff. The recording unit 31b also outputs the held off-event signal Eoff to the recording unit 32b.

The recording unit 32b is connected between the output terminal of the recording unit 31b and the readout wiring VSLb. The recording unit 32b receives the off-event signal Eoff output from the recording unit 31b and records the off-event signal Eoff. The recording unit 32b also outputs the held off-event signal Eoff to the readout wiring VSLb.

In this way, the multiple recording units 31b, 32b are connected in series between the output terminal of the comparator 336 and the readout wiring VSLb. The recording units 31b, 32b are provided to read out the off-event signal Eoff to the readout wiring VSLb.

The control unit 40 is connected between the output terminals of the recording units 31a and 31b and the switching element 332. The control unit 40 receives the event signals Eon and Eoff stored and output in the recording units 31a and 31b, and controls the switching element 332 to turn on and off according to the logic of the event signals Eon and Eoff. The control unit 40 also reads out the event signals Eon and Eoff from the recording units 32a and 32b to the read wiring VSLa and VSLb.

The readout wirings VSLa and VSLb are connected to the output terminals of the recording units 32a and 32b, respectively. The readout wirings VSLa and VSLb transmit the event signals Eon and Eoff read out from the recording units 32a and 32b, respectively, to the signal processing circuit 240 in FIG. 5.

Next, the operation of the photodetector element 1 according to this embodiment will be described.

FIG. 9 is a timing diagram showing an example of the operation of the photodetector 1 according to the first embodiment.

In one frame, an event signal detection operation and a reset operation are performed. In the event signal detection operation, the control unit 40 performs a detection operation of an on-event signal Eon with a comparison reference voltage of Von, and a detection operation of an off-event signal Eoff with a comparison reference voltage of Voff. In the reset operation, the control unit 40 turns on the switching elements 332 and 334 to return the comparison reference voltage to Vreset and equalize the potentials of the inverting input terminal and output terminal of the comparator 336.

First, from t1 to t2, an operation for detecting the on-event signal Eon is performed. In the operation for detecting the on-event signal Eon, the control unit 40 turns on the switching element 333 in FIG. 8 and inputs the comparison reference voltage Von as a threshold value to the non-inverting input terminal of the comparator 336. The comparator 336 compares the voltage signal input to the inverting input terminal with the comparison reference voltage Von.

If the voltage signal exceeds the comparison reference voltage Von, the comparator 336 raises (activates) the on-event signal Eon to a high-level voltage. If the voltage signal does not exceed the comparison reference voltage Von, the comparator 336 maintains (does not activate) the on-event signal Eon at a low-level voltage. This on-event signal Eon is recorded in the recording unit 31a. The on-event signal recorded at this time is referred to as Eon_1.

Next, from t2 to t3, an operation to detect the off-event signal Eoff is performed. In the operation to detect the off-event signal Eoff, the control unit 40 turns on the switching element 335 in FIG. 8 and inputs the comparison reference voltage Voff as a threshold value to the non-inverting input terminal of the comparator 336. The comparator 336 compares the voltage signal input to the inverting input terminal with the comparison reference voltage Voff.

If the voltage signal is below the comparison reference voltage Voff, the comparator 336 raises (activates) the off-event signal Eoff to a high-level voltage. If the voltage signal is not below the comparison reference voltage Voff, the comparator 336 maintains (does not activate) the off-event signal Eoff at a low-level voltage. This off-event signal Eoff is recorded in the recording unit 31b. The off-event signal recorded at this time is designated as Eoff_1.

Next, at t3 to t4, a reset operation is performed. In the reset operation, the control unit 40 turns on the switching elements 332 and 334 in FIG. 8 or maintains them off based on the logic of the on-event signal Eon_1 and the off-event signal Eoff_1 recorded in the recording units 31a and 31b. For example, when either the on-event signal Eon_1 or the off-event signal Eoff_1 is activated and rises to a high-level voltage, the control unit 40 turns on the switching elements 332 and 334 of that pixel. As a result, the comparison reference voltage Vreset is input to the non-inverting input terminal of the comparator 336, and the inverting input terminal and output terminal of the comparator 336 are short-circuited via the switching element 332. As a result, the inverting input terminal and output terminal of the comparator 336 are reset to the comparison reference voltage Vreset. The comparison reference voltage Vreset is a voltage between the comparison reference voltage Von and the comparison reference voltage Voff, and is preferably an intermediate voltage between them. On the other hand, for example, when neither the on-event signal Eon_1 nor the off-event signal Eoff_1 is activated and is at a low-level voltage, the control unit 40 maintains the switching elements 332 and 334 of that pixel in the off state. This is because no event has occurred in that pixel (i.e., the change in the amount of received light is small), and the signal voltage from the light receiving unit 221 does not exceed the comparison reference voltage Von and does not fall below the comparison reference voltage Voff, so no reset operation is required.

In addition, during the reset operation period from t3 to t4, the on-event signal Eon_1 recorded in the recording unit 31a is transferred to the recording unit 32a and recorded in the recording unit 32a. The recording unit 32a records the on-event signal Eon_1 from the recording unit 31a.

On the other hand, during the reset operation period from t3 to t4, the off-event signal Eoff_1 recorded in the recording unit 31b is transferred to the recording unit 32b and recorded in the recording unit 32b. The recording unit 32b records the off-event signal Eoff_1 from the recording unit 31b.

Furthermore, during the reset operation, the recording unit 32a starts outputting the on-event signal Eon_1 to the readout wiring VSLa. The recording unit 32b starts outputting the off-event signal Eoff_1 to the readout wiring VSLb. That is, during the reset operation, the on-event signal Eon_1 is temporarily transferred from the recording unit 31a to the recording unit 32a, and is sequentially read out from the recording unit 32a to the readout wiring VSLa. During the reset operation, the off-event signal Eoff_1 is temporarily transferred from the recording unit 31b to the recording unit 32b, and is sequentially read out from the recording unit 32b to the readout wiring VSLb. The on-event signal Eon_1 and the off-event signal Eoff_1 are read out, for example, in the order of row addresses ADD0 to ADDn (n is a positive integer). The read-out on-event signal Eon_1 and off-event signal Eoff_1 are transmitted to the signal processing circuit 240 via the read-out wiring VSLa and VSLb.

If the voltage signal exceeds the comparison reference voltage Von, during the reset period, the control unit 40 increases the comparison reference voltage Von by a predetermined value for the next frame. If the voltage signal does not exceed the comparison reference voltage Von, the control unit 40 does not change the comparison reference voltage Von. If the voltage signal is below the comparison reference voltage Voff, during the reset period, the control unit 40 decreases the comparison reference voltage Voff by a predetermined value for the next frame. If the voltage signal is not below the comparison reference voltage Voff, the control unit 40 does not change the comparison reference voltage Voff.

At t4, the next frame begins. From t4 to t5, the detection operation of the on-event signal Eon is performed in the same manner as from t1 to t2, and from t5 to t6, the detection operation of the off-event signal Eoff is performed in the same manner as from t2 to t3. As a result, the recording unit 31a records the on-event signal Eon_2, and the recording unit 31b records the off-event signal Eoff_2. At this time, the on-event signal Eon_1 and the off-event signal Eoff_1 are being read out from the recording units 32a and 32b to the readout wirings VSLa and VSLb, respectively. However, the on-event signal Eon_1 is recorded and held in the recording unit 32a, and the off-event signal Eoff_1 is recorded and held in the recording unit 32b. Therefore, even if the recording unit 31a is updated with the on-event signal Eon_2 and the recording unit 31b is updated with the off-event signal Eoff_2, there is no problem with the read operation of the on-event signal Eon_1 and the off-event signal Eoff_1.

In this way, the read operation of the event signals Eon and Eoff from the recording units 32a and 32b to the read wirings VSLa and VSLb takes a certain amount of time because it is performed for each row address. However, the photodetector element 1 according to this embodiment not only has recording units 31a and 31b, but also has recording units 32a and 32b provided after recording units 31a and 31b in correspondence with recording units 31a and 31b, respectively. Therefore, the event signals Eon_1 and Eoff_1 recorded in recording units 31a and 31b can be transferred in advance to recording units 32a and 32b, and the reset operation and the next frame can be performed while reading out the event signals Eon_1 and Eoff_1 from recording units 32a and 32b. This allows the reset operation to be performed even while the event signals Eon_1 and Eoff_1 are being read, and the next event signals Eon_2 and Eoff_2 can be recorded in the recording units 31a and 31b, respectively.

Note that the read operation of the event signals Eon_1 and Eoff_1 overlaps with the reset operation, so it must be completed before the reset operation of the next frame begins. This is because the read operation of the event signals Eon_2 and Eoff_2 begins during the reset operation of the next frame.

That is, from t6 to t7, the reset operation is performed in the same manner as the operation from t3 to t4. At this time, the event signals Eon_2 and Eoff_2 are read out from the recording units 32a and 32b to the read lines VSLa and VSLb, respectively.

Then, at t7 onwards, the next frame begins.

The photodetector element 1 according to this embodiment is provided with a plurality of 31a, 32a for recording the on-event signal Eon, and a plurality of 31b, 32b for recording the off-event signal Eoff. This allows the event signals Eon, Eoff recorded in the recording units 31a, 31b to be transferred in advance to the recording units 32a, 32b, and the reset operation and the next frame can be executed while the event signals Eon, Eoff are read from the recording units 32a, 32b. This allows the event signals Eon, Eoff to be read even during the reset operation. Furthermore, even during the readout period of the event signals Eon, Eoff, the next event signal can be recorded in the recording units 31a, 31b. As a result, the frame can be shortened, and the detection period of the event signal can be shortened.

Second Embodiment
10 is a timing chart showing an example of the operation of the photodetector 1 according to the second embodiment. The configuration of the photodetector 1 according to the second embodiment may be the same as that of the first embodiment. The second embodiment differs from the first embodiment in that the transfer operations of the event signals Eon and Eoff from the recording units 31a and 31b to the recording units 32a and 32b are started from the next frame.

First, the operation from t1 to t3 is the same as the operation from t1 to t3 in FIG. 9. This executes the detection operation of the on-event signal Eon and the off-event signal Eoff. The on-event signal Eon_1 is recorded in the recording unit 31a. The off-event signal Eoff_1 is recorded in the recording unit 31b.

Next, the reset operation from t3 to t4 is the same as the reset operation from t3 to t4 in FIG. 9. However, during the reset operation from t3 to t4, the on-event signal Eon_1 recorded in recording unit 31a has not yet been transferred to recording unit 32a. The off-event signal Eoff_1 recorded in recording unit 31b has not yet been transferred to recording unit 32b. Therefore, during the reset operation, the read operation of the on-event signal Eon_1 and the off-event signal Eoff_1 has not yet started.

The next frame is executed from t4 to t7. At this time, the on-event signal Eon_1 recorded in the recording unit 31a is transferred to the recording unit 32a, and the off-event signal Eoff_1 recorded in the recording unit 31b is transferred to the recording unit 32b. The recording unit 32a also starts outputting the on-event signal Eon_1 to the readout wiring VSLa. The recording unit 32b starts outputting the off-event signal Eoff_1 to the readout wiring VSLb. That is, in the next frame, the on-event signal Eon_1 is temporarily transferred from the recording unit 31a to the recording unit 32a, and is sequentially read out from the recording unit 32a to the readout wiring VSLa. In the next frame, the off-event signal Eoff_1 is temporarily transferred from the recording unit 31b to the recording unit 32b, and is sequentially read out from the recording unit 32b to the readout wiring VSLb.

When the next frame starts, from t4 to t5, the detection operation of the on-event signal Eon is performed in the same manner as the operation from t1 to t2, and from t5 to t6, the detection operation of the off-event signal Eoff is performed in the same manner as the operation from t2 to t3. As a result, the recording unit 31a records the on-event signal Eon_2, and the recording unit 31b records the off-event signal Eoff_2. At this time, the on-event signal Eon_1 and the off-event signal Eoff_1 are being read out from the recording units 32a and 32b to the readout wirings VSLa and VSLb, respectively. However, the on-event signal Eon_1 is recorded and held in the recording unit 32a, and the off-event signal Eoff_1 is recorded and held in the recording unit 32b. Therefore, even if the recording unit 31a is updated with the on-event signal Eon_2 and the recording unit 31b is updated with the off-event signal Eoff_2, there is no problem with the read operation of the on-event signal Eon_1 and the off-event signal Eoff_1.

In the second embodiment, the read operation of the event signals Eon_1 and Eoff_1 must be completed before the detection operation of the next frame starts. This is because the read operation of the event signals Eon_2 and Eoff_2 starts during the detection operation of the next frame.

In other words, from t7 to t9, the detection operation is performed in the same manner as the operation from t4 to t6. At this time, the event signals Eon_2 and Eoff_2 are read out from the recording units 32a and 32b to the read lines VSLa and VSLb, respectively.

Then, from t9 onwards, the reset operation for the next frame begins.

Even in the operation of the second embodiment, the event signals Eon and Eoff recorded in the recording units 31a and 31b can be transferred to the recording units 32a and 32b in advance, and the next frame can be executed while the event signals Eon and Eoff are read from the recording units 32a and 32b. This makes it possible to shorten the frame and the detection period of the event signal.

Third Embodiment
11 is a circuit diagram showing an example of the configuration of an event detection circuit 300, a recording area 30, and a control unit 40 according to the third embodiment. The recording area 30 of the third embodiment includes inverters INV1a and INVb, and logic gates G1a and G1b.

The inverter INV1a is connected between the output terminal of the recording unit 32a and the logic gate G1a. The inverter INV1a outputs an inverted signal of the output signal of the recording unit 32a to the logic gate G1a.

The two input terminals of the logic gate G1a are connected to the output terminal of the inverter INV1a and the output terminal of the recording unit 31a, respectively. The output terminal of the logic gate G1a is connected to the read wiring VSLa. The logic gate G1a outputs the logical product of the output signal of the recording unit 31a and the output signal of the inverter INV1a to the read wiring VSL1a.

Inverter INV1b is connected between the output terminal of recording unit 32b and logic gate G1b. Inverter INV1b outputs an inverted signal of the output signal of recording unit 32b to logic gate G1b.

The two input terminals of the logic gate G1b are connected to the output terminal of the inverter INV1b and the output terminal of the recording unit 31b, respectively. The output terminal of the logic gate G1b is connected to the read wiring VSLb. The logic gate G1b outputs the logical product of the output signal of the recording unit 31b and the output signal of the inverter INV1b to the read wiring VSL1b.

The other configurations of the third embodiment may be similar to the corresponding configurations of the first embodiment.

In the third embodiment, the inverters INV1a and INV1b are connected to the output terminals of the recording units 32a and 32b. However, the inverters INV1a and INV1b may be connected to the output terminals of the recording units 31a and 31b, respectively, instead of the output terminals of the recording units 32a and 32b. In this case, the logic gate G1a outputs the logical product of the inverted signal of the output signal of the recording unit 31a and the output signal of the recording unit 32a to the read wiring VSL1a. The logic gate G1b outputs the logical product of the inverted signal of the output signal of the recording unit 31b and the output signal of the recording unit 32b to the read wiring VSL1b.

Next, the operation of the light detection element 1 according to the third embodiment will be described.

FIGS. 12 and 13 are timing diagrams showing an example of the operation of the photodetector 1 according to the third embodiment. The detection operation, reset operation, and read operation of the photodetector 1 according to the third embodiment may be basically the same as the respective operations shown in FIG. 10. However, in the third embodiment, the detection operation, reset operation, and read operation are each performed within one frame, and the read operation does not overlap with the detection operation or reset operation.

The read signals read out to the read lines VSLa and VSLb are the output signals of the logic gates G1a and G1b, respectively. Therefore, the read signal read out to the read line VSLa is the result of a logical operation between the output signals of the recording units 1a and 2a, and the read signal read out to the read line VSLb is the result of a logical operation between the output signals of the recording units 1b and 2b.

In this case, for example, when the light receiving unit 221 in FIG. 8 detects a change in the amount of received light, the output voltage of the logarithmic conversion circuit 310 may change gradually and significantly over multiple frames f1 to f6. In such a case, multiple event signals may be detected for one event. Such multiple event signals detected for one event are called tail events. In order to detect such tail events as one event signal, the light detection element 1 according to the third embodiment has logic gates G1a and G1b in the recording area 30.

In the following, it is assumed that when the on-event signal or off-event signal is not rising, the recording units 31a, 32a, 31b, and 32b record a logic "0," and when the on-event signal or off-event signal rises, the recording units 31a, 32a, 31b, and 32b record a logic "1."

For example, as shown in FIG. 12, the output of the light receiving unit 221 rises and the output of the logarithmic conversion circuit 310 gradually increases.

In the first frame f1, when the voltage signal input to the comparator 336 exceeds the comparison reference voltage Von, the output (on-event signal) of the comparator 336 rises, and the recording unit 31a records "1" as shown in FIG. 13. That is, the event signal Eon_1 in FIG. 10 becomes "1". At this time, as shown in FIG. 13, the recording unit 32a is still at "0", so the logic gate G1a outputs "1".

In the next frame f2, the comparison reference voltage Von is updated to a higher threshold voltage than the comparison reference voltage in frame f1. Also, as shown in FIG. 13, the on-event signal "1" of recording unit 31a is transferred to recording unit 32a, which records "1". Then, when the voltage signal input to comparator 336 exceeds the updated comparison reference voltage Von, the output (on-event signal) of comparator 336 rises, and recording unit 31a records "1" as shown in FIG. 13. Therefore, both recording units 31a and 32a output "1", and logic gate G1a outputs "0".

Frames f3 to f6 repeat the same operation as frame f2. Therefore, in frames f3 to f6, logic gate G1a outputs "0." At this time, the comparison reference voltage Von is updated to a threshold voltage higher than the comparison reference voltage in the previous frame.

In frame f7, the comparison reference voltage Von no longer exceeds the comparison reference voltage. Therefore, as shown in FIG. 13, the recording unit 32a records "0". Therefore, the recording units 31a and 32a output "0" and "1", respectively, and the logic gate G1a outputs "0". Thereafter, as long as the signal voltage does not exceed the comparison reference voltage Von, the logic gate G1a outputs "0".

In other words, in frames f1 to f7, logic gate G1a outputs "1", "0", "0", "0", "0", "0", "0", "0", "0"... respectively.

In this way, the photodetector element 1 according to the third embodiment can detect an event as a single event signal even if the event includes a tail event that spans multiple frames, as long as the voltage signal continuously exceeds the updated comparison reference voltage Von.

The above specific example describes an on-event signal. However, the same applies to an off-event signal. In this case, when the voltage signal input to comparator 336 falls below the comparison reference voltage Voff, the output of comparator 336 (off-event signal) rises and recording unit 31b records "1". At this time, recording unit 32b is still at "0", so logic gate G1b outputs "1".

In the next frame, the comparison reference voltage Voff is updated to a threshold voltage lower than the comparison reference voltage in the previous frame. In addition, the off event signal "1" of recording unit 31b is transferred to recording unit 32b, which records "1". Then, when the voltage signal input to comparator 336 falls below the updated comparison reference voltage Voff, the output (off event signal) of comparator 336 rises, and recording unit 31b records "1". Therefore, recording units 31b and 32b both output "1", and logic gate G1b outputs "0".

In the subsequent frames, as long as the voltage signal continues to fall below the updated comparison reference voltage Voff, the logic gate G1b outputs "0." At this time, the comparison reference voltage Voff has been updated to a threshold voltage lower than the comparison reference voltage in the previous frame.

When the signal voltage does not fall below the comparison reference voltage Voff, the recording unit 32b records "0". Therefore, the recording units 31a and 32a output "0" and "1", respectively, and the logic gate G1a outputs "0". Thereafter, as long as the signal voltage does not fall below the comparison reference voltage Voff, the logic gate G1b outputs "0".

In this way, even if a single event includes a tail event that spans multiple frames, it can be detected as a single event signal.

Other operations of the third embodiment may be similar to those of the second embodiment. Therefore, the third embodiment can achieve the same effects as the second embodiment.

Fourth Embodiment
14 is a circuit diagram showing an example of the configuration of an event detection circuit 300, a recording area 30, and a control unit 40 according to the fourth embodiment. The recording area 30 of the fourth embodiment includes logic gates G2a and G2b.

The two input terminals of logic gate G2a are connected to the output terminal of recording unit 31a and the output terminal of recording unit 32a, respectively. The output terminal of logic gate G2a is connected to read wiring VSLa. Logic gate G2a outputs the logical product of the output signal of recording unit 31a and the output signal of recording unit 32a to read wiring VSL1a and control unit 40.

The two input terminals of logic gate G2b are connected to the output terminal of recording unit 31b and the output terminal of recording unit 32b, respectively. The output terminal of logic gate G2b is connected to read wiring VSLb. Logic gate G2b outputs the logical product of the output signal of recording unit 31b and the output signal of recording unit 32b to read wiring VSL1b and control unit 40.

The output terminals of the logic gates G2a and G2b are connected to the control unit 40. The control unit 40 controls the switching element 332 based on the output signals of the logic gates G2a and G2b. Thus, the control unit 40 executes a reset operation when the on-event signal rises two consecutive times. Alternatively, the control unit 40 executes a reset operation when the off-event signal rises two consecutive times.

The other configurations of the fourth embodiment may be similar to the corresponding configurations of the first embodiment.

Next, the operation of the photodetector element 1 according to the fourth embodiment will be described.

FIGS. 15 and 16 are timing diagrams showing an example of the operation of the photodetector 1 according to the fourth embodiment. The detection operation, reset operation, and read operation of the photodetector 1 according to the fourth embodiment may basically be the same as the respective operations shown in FIG. 10. However, in the fourth embodiment, the detection operation, reset operation, and read operation are each performed within one frame, and the read operation does not overlap with the detection operation or reset operation.

The signal output to the control unit 40 is the output signal of logic gates G2a and G2b. Therefore, the control unit 40 executes a reset operation using the logical product of the output signals of recording unit 1a and recording unit 2a or the logical product of the output signals of recording unit 1b and recording unit 2b as a reset signal. In other words, when events occur consecutively, the control unit 40 executes a reset operation.

In the following, it is assumed that when the on-event signal or off-event signal is not rising, the recording units 31a, 32a, 31b, and 32b record a logic "0," and when the on-event signal or off-event signal rises consecutively, the recording units 31a, 32a, 31b, and 32b record a logic "1."

For example, in FIG. 15, if the output voltage of the logarithmic conversion circuit 310 is V310, the comparison reference voltage Von is higher than the output voltage V310 by the threshold voltage when there is no event.

Here, if noise N occurs in frame f1, the output voltage V310 may momentarily exceed the comparison reference voltage Von. In this case, since the output voltage V310 exceeds the comparison reference voltage Von, the recording unit 31a records "1". However, in the next frame f2, the output voltage V310 does not exceed the comparison reference voltage Von. Therefore, although the "1" of the recording unit 31a is transferred to the recording unit 32a, a "0" is recorded in the recording unit 31a. Since both recording units 31a and 32a are not "1", the logic gate G2a maintains "0". In this case, the control unit 40 does not execute a reset operation during the reset period. In this way, even if the output voltage V310 exceeds the comparison reference voltage Von in only one frame, the control unit 40 does not execute a reset operation during the reset period.

In frames f3 and f4, no noise or event occurs, and the output voltage V310 does not exceed the comparison reference voltage Von. Therefore, the recording units 31a and 32a record "0", and the logic gate G2a outputs "0".

For example, in FIG. 16, if an event occurs in frame f1, the output voltage V310 exceeds the comparison reference voltage Von. In this case, since the output voltage V310 exceeds the comparison reference voltage Von, the recording unit 31a records "1". However, since the logic gate G2a still maintains "0" in frame f1, the control unit 40 does not perform a reset operation during the reset period of frame f1.

In the next frame f2, an event occurs and the output voltage V310 remains above the comparison reference voltage Von. Therefore, the "1" in the recording unit 31a is transferred to the recording unit 32a, and a "1" is recorded in the recording unit 31a. Since both recording units 31a and 32a are "1", the logic gate G2a outputs "1". In this case, the control unit 40 executes a reset operation during the reset period, and the comparison reference voltage Von is updated. In this way, if the output voltage V310 exceeds the comparison reference voltage Von in two consecutive frames, the control unit 40 executes a reset operation during the reset period.

In frames f3 and f4, no event occurs, and the output voltage V310 does not exceed the comparison reference voltage Von. Therefore, the recording unit 31a records "0", and the logic gate G2a outputs "0".

The above specific example describes an on-event signal. However, the same applies to an off-event signal. Detection of an off-event signal can be easily understood from the above explanation of an on-event signal. Therefore, a description of the off-event signal according to the fourth embodiment will be omitted here.

If logic gates G2a and G2b were not provided, a momentary noise that occurs within one frame would be judged to be the occurrence of an event, and the control unit 40 would execute a reset operation, updating the comparison reference voltage Von or Voff.

In contrast, the photodetector element 1 according to the fourth embodiment includes logic gates G2a and G2b, which output the logical product of the output signals of the recording units 31a and 32a, or the logical product of the output signals of the recording units 31b and 32b. As a result, when an on-event signal or an off-event signal is detected in two or more consecutive frames, the logic gates G2a and G2b raise their output signals, and the control unit 40 can perform a reset operation. As a result, the photodetector element 1 is able to suppress erroneous determination of noise as an event and reliably detect events.

Other operations of the fourth embodiment may be similar to those of the second embodiment. Therefore, the fourth embodiment can achieve the same effects as the second embodiment.

Fifth Embodiment
17 is a circuit diagram showing an example of the configuration of the event detection circuit 300, the recording area 30, and the control unit 40 according to the fifth embodiment. The recording area 30 of the fifth embodiment includes two recording units 31a and 32a connected in series between the output terminal of the comparator 336 and the readout wiring VSLa. However, the recording units 31b and 32b and the readout wiring VSLb are omitted.

In this case, the recording units 31a and 32a alternately record the on-event signal Eon and the off-event signal Eoff. The recording units 31a and 32a also alternately read out the on-event signal Eon and the off-event signal Eoff via the readout wiring VSLa. Therefore, the readout operation for each pixel is performed twice for each frame.

FIG. 18 is a timing diagram showing an example of the operation of the photodetector 1 according to the fifth embodiment. The detection operation and reset operation are basically the same as those in the first embodiment. However, in the photodetector 1 according to the fifth embodiment, the recording units 31a and 32a alternately detect the on-event signal Eon and the off-event signal Eoff.

For example, in the detection operation of frame f1, the control unit 40 turns on the switching element 333. In the detection operation of frame f1, the event detection circuit 300 detects the on-event signal Eon using the comparison reference voltage Von, and the recording unit 31a records the on-event signal Eon. The on-event signal Eon of the recording unit 31a is transferred to the recording unit 32a. In the reset operation of frame f1 and the detection operation of the next frame f2, the on-event signal Eon of the recording unit 32a is read out to the read wiring VSLa.

In the detection operation of the next frame f2, the control unit 40 turns on the switching element 335. In the detection operation of frame f2, the event detection circuit 300 detects the off event signal Eoff using the comparison reference voltage Voff, and the recording units 31a and 32a record the off event signal Eoff. The off event signal Eoff of the recording unit 31a is transferred to the recording unit 32a. In the reset operation of frame f2 and the detection operation of the next frame f3, the off event signal Eoff of the recording unit 32a is read out to the read wiring VSLa.

In this way, the recording units 31a and 32a alternately record and alternately read out the on-event signal Eon and the off-event signal Eoff. That is, during the reset operation or the detection operation of the next frame, the recording unit 32a alternately records the event signal Eon or Eoff from the recording unit 31a, and alternately outputs this event signal Eon or Eoff to the readout wiring VSLa.

Other operations of the fifth embodiment may be similar to those of the first embodiment.

According to the fifth embodiment, the recording units 31b, 32b and the readout wiring VSLb are omitted, so that the circuit scale and layout area of the light detection element 1 are reduced. Furthermore, according to the fifth embodiment, the readout operation of the event signal Eon or Eoff can be executed in a redundant manner in the reset operation and the detection operation. Therefore, the fifth embodiment can obtain the same effect as the first embodiment.

Sixth Embodiment
19 is a circuit diagram showing an example of the configuration of an event detection circuit 300, a recording area 30, and a control unit 40 according to the sixth embodiment. The recording area 30 of the sixth embodiment includes a multiplexer MUX1 connected between the output terminals of the recording units 32a and 32b and a readout wiring VSLa. The readout wiring VSLa is connected to the output terminal of the multiplexer MUX1. The readout wiring VSLb is omitted.

The multiplexer MUX1 is composed of switching elements such as MOS transistors, and is configured to selectively connect one of the output terminals of the recording units 32a and 32b to the readout wiring VSLa. The control unit 40 controls the switching elements of the multiplexer MUX1.

In this case, the multiplexer MUX1 alternately reads out the event signals Eon and Eoff recorded in the recording units 32a and 32b to the readout wiring VSLa. Therefore, the readout operation for each pixel is performed twice for each address per frame.

FIG. 20 is a timing diagram showing an example of the operation of the photodetector 1 according to the sixth embodiment. The detection operation and reset operation are basically the same as those in the first embodiment. However, according to the sixth embodiment, the multiplexer MUX1 alternately reads out the on-event signal Eon of the recording unit 32a and the off-event signal Eoff of the recording unit 32b to the readout wiring VSLa.

For example, in the detection operation of frame f1, the event detection circuit 300 executes the detection operation and the reset operation in the same manner as in the first embodiment. The recording units 31a and 31b record the detected event signals Eon_1 and Eoff_1, respectively, and transfer the event signals Eon_1 and Eoff_1 to the recording units 32a and 32b, respectively, at the start of the reset operation.

The multiplexer MUX1 connects the output terminal of the recording unit 32a to the readout wiring VSLa, and reads out the on-event signal Eon_1 of the recording unit 32a to the readout wiring VSLa. Next, the multiplexer MUX1 connects the output terminal of the recording unit 32b to the readout wiring VSLa, and reads out the off-event signal Eoff_1 of the recording unit 32b to the readout wiring VSLa.

The read operation of the on-event signal Eon_1 is executed overlapping with the reset operation of frame f1, and the read operation of the off-event signal Eoff_1 is executed overlapping with the detection operation of frame f2.

In the detection operation of the next frame f2, after the detection operation and the reset operation are performed, the recording units 31a and 31b record the detected on-event signals Eon_2 and Eoff_2, respectively, and transfer the on-event signals Eon_2 and Eoff_2 to the recording units 32a and 32b, respectively, at the start of the reset operation.

The multiplexer MUX1 connects the output terminal of the recording unit 32a to the readout wiring VSLa, and reads out the on-event signal Eon_2 of the recording unit 32a to the readout wiring VSLa. Next, the multiplexer MUX1 connects the output terminal of the recording unit 32b to the readout wiring VSLa, and reads out the off-event signal Eoff_2 of the recording unit 32b to the readout wiring VSLa.

The read operation of the on-event signal Eon_2 is executed overlapping with the reset operation of frame f2, and the read operation of the off-event signal Eoff_2 is executed overlapping with the detection operation of frame f3.

In this way, the control unit 40 controls the multiplexer MUX1 to alternately read out the on-event signal Eon and the off-event signal Eoff.

Other operations of the sixth embodiment may be similar to those of the first embodiment.

According to the sixth embodiment, although a multiplexer MUX1 is added to each pixel, the readout wiring VSLb is omitted, so that the circuit scale and layout area of the photodetection element 1 can be reduced. Also, according to the sixth embodiment, the readout operation of the event signal Eon or Eoff can be executed in a redundant manner in the reset operation and the detection operation. Therefore, the sixth embodiment can obtain the same effect as the first embodiment.

Seventh Embodiment
21 is a circuit diagram showing an example of the configuration of an event detection circuit 300, a recording area 30, and a control unit 40 according to the seventh embodiment. A buffer BUF1 and multiplexers MUX2 and MUX3 are provided in common between a plurality of event detection circuits 300 and a plurality of recording areas 30 of the seventh embodiment.

The buffer BUF1 is provided between the output terminals of the comparators 336 of the multiple event detection circuits 300 and the multiple recording areas 30, and transfers the on-event signal Eon or the off-event signal Eoff from the event detection circuits 300 to the recording areas 30.

The multiplexer MUX2 is provided between the input terminal of the buffer BUF1 and the output terminals of the multiple comparators 336, and connects the output terminal of a selection comparator 336 arbitrarily selected from the multiple comparators 336 to the input terminal of the buffer BUF1.

The multiplexer MUX3 is provided between the output terminal of the buffer BUF1 and the input terminals of the multiple recording areas 30, and connects the input terminal of a selected recording area 30 arbitrarily selected from the multiple recording areas 30 to the output terminal of the buffer BUF1.

The configuration of each event detection circuit 300 and each recording area 30 may be the same as that of the first embodiment. The control unit 40 may be provided in common to multiple event detection circuits 300 and multiple recording areas 30, similar to the buffer BUF1. The control unit 40 controls the multiplexers MUX2, MUX3 and the buffer BUF1.

The configuration of the recording area 30 may be any of the configurations in the first to sixth embodiments.

In the seventh embodiment, the multiplexer MUX2 connects the selection comparator 336 to the buffer BUF1 and transfers the on-event signal Eon or the off-event signal Eoff from the selection comparator 336 to the buffer BUF1.

Buffer BUF1 amplifies the on-event signal Eon or off-event signal Eoff from selection comparator 336 and transfers it to multiplexer MUX3.

The multiplexer MUX3 connects the selected recording area 30 to the buffer BUF1 and transfers the on-event signal Eon or the off-event signal Eoff from the selection comparator 336 to the selected recording area 30. This allows the recording units 31a and 32a of the selected recording area 30 to record the on-event signal Eon, or the recording units 31b and 32b of the selected recording area 30 to record the off-event signal Eoff.

If the wiring distance between the event detection circuit 300 and the recording area 30 is long, the buffer BUF1 is required. If a buffer BUF1 is provided between each of a plurality of event detection circuits 300 and a plurality of recording areas 30, the circuit scale of the light detection element 1 will become large.

In contrast, in the seventh embodiment, one buffer BUF1 is provided in common for multiple event detection circuits 300 and multiple recording areas 30. This makes it possible to suppress an increase in the circuit size of the light detection element 1. Note that in FIG. 22, one buffer BUF1 is provided in common for two event detection circuits 300 and two recording areas 30. However, one buffer BUF1 may be provided in common for three or more event detection circuits 300 and three or more recording areas 30.

Other configurations and operations of the seventh embodiment may be the same as those of any of the first to sixth embodiments. Therefore, the seventh embodiment can also obtain the effects of any of the first to sixth embodiments.

Eighth embodiment
22 is a circuit diagram showing an example of the configuration of the event detection circuit 300, the recording area 30, and the control unit 40 according to the eighth embodiment. In the recording area 30 according to the eighth embodiment, the recording units 31a and 32a are connected in parallel to the output terminal of the comparator 336. The recording units 31b and 32b are connected in parallel to the output terminal of the comparator 336.

When one of the recording units 31a and 32a is recording an on-event signal Eon, the other of the recording units 31a and 32a outputs the immediately preceding on-event signal Eon to the readout wiring VSLa. When one of the recording units 31b and 32b is recording an off-event signal Eoff, the other of the recording units 31b and 32b outputs the immediately preceding off-event signal Eoff to the readout wiring VSLb. In this way, the recording units 31a and 32a are used by alternately switching between the recording operation and the readout operation of the on-event signal Eon over time. The recording units 31b and 32b are used by alternately switching between the recording operation and the readout operation of the off-event signal Eoff over time. Thus, the recording units 31a and 32a alternately record and output consecutive different on-event signals Eon. The recording units 31b and 32b alternately record and output consecutive different off-event signals Eoff.

To achieve this operation, the recording area 30 is equipped with switching elements 301a to 306a and 301b to 306b. For example, MOS transistors are used for the switching elements 301a to 306a and 301b to 306b.

Switching element 301a is connected between the output terminal of comparator 336 and the input terminal of recording unit 31a. Switching element 302a is connected between the output terminal of comparator 336 and the input terminal of recording unit 32a.

The switching element 303a is connected between the output terminal of the recording unit 31a and the readout wiring VSLa. The switching element 304a is connected between the output terminal of the recording unit 31a and the control unit 40. The switching element 305a is connected between the output terminal of the recording unit 32a and the readout wiring VSLa. The switching element 306a is connected between the output terminal of the recording unit 32a and the control unit 40.

Switching element 301b is connected between the output terminal of comparator 336 and the input terminal of recording unit 31b. Switching element 302b is connected between the output terminal of comparator 336 and the input terminal of recording unit 32b.

Switching element 303b is connected between the output terminal of recording unit 31b and the readout wiring VSLb. Switching element 304b is connected between the output terminal of recording unit 31b and the control unit 40. Switching element 305b is connected between the output terminal of recording unit 32b and the readout wiring VSLb. Switching element 306b is connected between the output terminal of recording unit 32b and the control unit 40.

When switching elements 301a, 304a, and 305a are on (conductive state) and switching elements 302a, 303a, and 306a are off (non-conductive state), recording unit 31a records on-event signal Eon, and recording unit 32a outputs the immediately preceding on-event signal Eon to readout wiring VSLa. Also, control unit 40 determines whether or not to perform a reset operation depending on the on-event signal Eon recorded in recording unit 31a.

When switching elements 302a, 303a, and 306a are on and switching elements 301a, 304a, and 305a are off, recording unit 32a records on-event signal Eon, and recording unit 31a outputs the immediately preceding on-event signal Eon to read wiring VSLa. In addition, control unit 40 determines whether or not to perform a reset operation depending on the on-event signal Eon recorded in recording unit 32a.

When switching elements 301b, 304b, and 305b are on and switching elements 302b, 303b, and 306b are off, recording unit 31b records off-event signal Eoff, and recording unit 32b reads out the immediately preceding off-event signal Eoff and outputs it to read wiring VSLb. Also, control unit 40 determines whether or not to perform a reset operation depending on the off-event signal Eoff recorded in recording unit 31b.

When switching elements 302b, 303b, and 306b are on and switching elements 301b, 304b, and 305b are off, recording unit 32b records off-event signal Eoff, and recording unit 31b reads out the immediately preceding off-event signal Eoff and outputs it to read wiring VSLb. Also, control unit 40 determines whether or not to perform a reset operation depending on the off-event signal Eoff recorded in recording unit 32b.

FIG. 23 is a timing diagram showing an example of the operation of the photodetector 1 according to the eighth embodiment. The detection operation and reset operation are basically the same as those in the first embodiment. However, according to the eighth embodiment, the switching elements 301a to 306a alternately switch the operation of the recording unit 31a and the operation of the recording unit 32a between the recording operation of the on-event signal Eon and the read operation of the on-event signal Eon. The switching elements 301b to 306b alternately switch the operation of the recording unit 31b and the operation of the recording unit 32b between the recording operation of the off-event signal Eoff and the read operation of the off-event signal Eoff.

Signal Φ1 is a control signal for switching elements 301a, 304a, and 305a, and switching elements 301b, 304b, and 305b.

Signal Φ2 is a control signal for switching elements 302a, 303a, and 306a, and switching elements 302b, 303b, and 306b.

In frame f1, signal Φ1 is activated and signal Φ2 is in an inactive state. Therefore, switching elements 301a, 304a, and 305a are turned on, and switching elements 302a, 303a, and 306a are turned off. This causes recording unit 31a to record on-event signal Eon_2. Recording unit 32a outputs on-event signal Eon_1, which was recorded immediately before on-event signal Eon_2, to read wiring VSLa. Furthermore, control unit 40 performs or does not perform a reset operation depending on on-event signal Eon_2 recorded in recording unit 31a.

Furthermore, switching elements 301b, 304b, and 305b are turned on, and switching elements 302b, 303b, and 306b are turned off. As a result, recording unit 31b records off-event signal Eoff_2. Recording unit 32b reads out off-event signal Eoff_1 recorded immediately before off-event signal Eoff_2 and outputs it to read wiring VSLb. Furthermore, control unit 40 performs or does not perform a reset operation according to off-event signal Eoff_2 recorded in recording unit 31b.

In the next frame f2, signal Φ2 is activated and signal Φ1 is inactive. Therefore, switching elements 301a, 304a, and 305a are turned off, and switching elements 302a, 303a, and 306a are turned on. This causes recording unit 31a to output on-event signal Eon_2 to read wiring VSLa. Recording unit 32a records on-event signal Eon_3. Furthermore, control unit 40 performs or does not perform a reset operation depending on on-event signal Eon_3 recorded in recording unit 32a.

Furthermore, switching elements 301b, 304b, and 305b are turned off, and switching elements 302b, 303b, and 306b are turned on. This causes recording unit 31b to output off-event signal Eoff_2 to read wiring VSLb. Recording unit 32b records off-event signal Eoff_3. Furthermore, control unit 40 performs or does not perform a reset operation depending on off-event signal Eoff_3 recorded in recording unit 32b.

In the next frame f3, signal Φ1 is activated again, and signal Φ2 is inactivated again. Therefore, switching elements 301a, 304a, and 305a are turned on, and switching elements 302a, 303a, and 306a are turned off. This causes recording unit 31a to record on-event signal Eon_4. Recording unit 32a outputs on-event signal Eon_3 to read wiring VSLa. Furthermore, control unit 40 performs or does not perform a reset operation depending on on-event signal Eon_4 recorded in recording unit 31a.

Furthermore, switching elements 301b, 304b, and 305b are turned on, and switching elements 302b, 303b, and 306b are turned off. As a result, recording unit 31b records off-event signal Eoff_4. Recording unit 32b outputs off-event signal Eoff_3 to read wiring VSLb. Furthermore, control unit 40 performs or does not perform a reset operation according to off-event signal Eoff_4 recorded in recording unit 31b.

In this way, the recording units 31a and 32a according to the eighth embodiment are connected in parallel between the comparator 336 and the readout wiring VSLa. The recording units 31b and 32b are connected in parallel between the comparator 336 and the readout wiring VSLb. In addition, switching elements 301a to 306a and 301b to 306b are provided. As a result, the recording units 31a and 32a alternately record the on-event signal Eon, and alternately read out the recorded on-event signal Eon to the readout wiring VSLa. The recording units 31b and 32b alternately record the off-event signal Eoff, and alternately read out the recorded off-event signal Eoff to the readout wiring VSLb.

Other configurations and operations of the eighth embodiment may be similar to those of the first embodiment. According to the eighth embodiment, the read operation of the event signal Eon or Eoff can be executed in a redundant manner during the reset operation and the detection operation. Therefore, the eighth embodiment can also achieve the same effects as the first embodiment.

(Example of application to moving objects)
The technology according to the present disclosure (the present technology) can be applied to various electronic devices. For example, the technology according to the present disclosure may be realized as a device mounted on any type of moving object, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility device, an airplane, a drone, a ship, a robot, or the like.

FIG. 24 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile object control system to which the technology disclosed herein can be applied.

The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in FIG. 24, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside vehicle information detection unit 12030, an inside vehicle information detection unit 12040, and an integrated control unit 12050. Also shown as functional components of the integrated control unit 12050 are a microcomputer 12051, an audio/video output unit 12052, and an in-vehicle network I/F (Interface) 12053.

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

The body system control unit 12020 controls the operation of various devices installed in the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as headlamps, tail lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves or signals from various switches transmitted from a portable device that replaces a key can be input to the body system control unit 12020. The body system control unit 12020 accepts the input of these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

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

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

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

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

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

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

The audio/image output unit 12052 transmits at least one output signal of audio and image to an output device capable of visually or audibly notifying the occupants of the vehicle or the outside of the vehicle of information. In the example of FIG. 24, an audio speaker 12061, a display unit 12062, and an instrument panel 12063 are exemplified as output devices. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

FIG. 25 shows an example of the installation position of the imaging unit 12031.

In FIG. 25, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

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

Note that FIG. 25 shows an example of the imaging ranges of the imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, an overhead image of the vehicle 12100 viewed from above is obtained by superimposing the image data captured by the imaging units 12101 to 12104.

At least one of the imaging units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the imaging units 12101 to 12104 may be a stereo camera consisting of multiple imaging elements, or an imaging element having pixels for phase difference detection.

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

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

At least one of the imaging units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether or not a pedestrian is present in the captured image of the imaging units 12101 to 12104. The recognition of such a pedestrian is performed, for example, by a procedure of extracting feature points in the captured image of the imaging units 12101 to 12104 as infrared cameras, and a procedure of performing pattern matching processing on a series of feature points that indicate the contour of an object to determine whether or not it is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the captured image of the imaging units 12101 to 12104 and recognizes a pedestrian, the audio/image output unit 12052 controls the display unit 12062 to superimpose a rectangular contour line for emphasis on the recognized pedestrian. The audio/image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating a pedestrian at a desired position.

The above describes an example of a vehicle control system to which the technology disclosed herein can be applied. The technology disclosed herein can be applied to, for example, the imaging unit 12031, etc., of the configurations described above.

This technology can be configured as follows:

(1)
a light receiving unit that performs photoelectric conversion on incident light to generate an electrical signal;
a comparison unit that outputs an event signal when the amount of change in the electrical signal exceeds or falls below a threshold;
a first recording unit connected to an output terminal of the comparison unit, for recording the event signal, and outputting the event signal;
a second recording unit connected to the first recording unit, for recording the event signal from the first recording unit, and for outputting the event signal.

(2)
The photodetector element according to (1), wherein the first recording section records a next event signal from the comparison section during a readout period in which the event signal recorded in the second recording section is being read out.

(3)
a first switching element connected between an input terminal of the comparison unit and an output terminal of the comparison unit;
a control unit provided between an output terminal of the first recording unit and the first switching element, the control unit controlling the first switching element based on the event signal output from the first recording unit;
a first read wiring connected to an output terminal of the second recording unit;
The photodetector element according to (1) or (2), wherein when the first switching element is in a conductive state, the second recording unit outputs the event signal to the first readout wiring.

(4)
a third recording unit connected to an output terminal of the comparison unit and configured to record the event signal;
The light detection element according to any one of (1) to (3), further comprising: a fourth recording unit connected to the third recording unit and configured to record the event signal from the third recording unit.

(5)
The photodetector element according to (4), wherein the third recording section records a next event signal from the comparison section during a readout period in which the event signal recorded in the fourth recording section is being read out.

(6)
a first switching element connected between the input terminal of the comparison unit and the output terminal of the comparison unit;
a control unit provided between output terminals of the first and third recording units and the first switching element, the control unit controlling the first switching element based on the event signals output from the first and third recording units;
a first read wiring connected to an output terminal of the second recording unit;
A second readout wiring connected to an output terminal of the fourth recording unit,
A photodetector element according to (4) or (5), wherein, when the first switching element is in a conductive state, the event signal recorded in the second recording section is read out to the first readout wiring, and the event signal recorded in the fourth recording section is read out to the second readout wiring.

(7)
the comparison unit compares the amount of change with a first threshold during a first period to output a first event signal, and compares the amount of change with a second threshold different from the first threshold during a second period following the first period to output a second event signal;
the first recording unit records the first event signal during the first period;
the third recording unit records the second event signal during the second period;
The photodetector element of claim 6, wherein, when the first switching element is in a conductive state, the second recording unit records the first event signal from the first recording unit and outputs the first event signal to the first readout wiring, and the fourth recording unit records the second event signal from the third recording unit and outputs the second event signal to the second readout wiring.

(8)
The photodetector element of (7), wherein the control unit resets the voltages of the input terminal and output terminal of the comparison unit to a voltage between the first threshold value and the second threshold value by turning on the first switching element.

(9)
The light detection element according to (6), wherein the control unit controls the first switching element based on the event signals recorded in the first and third recording units.

(10)
an inverter connected to one output terminal of the first and second recording units;
The light detection element according to (3), further comprising a first logic gate that outputs a logical product of the output signal of the other of the first and second recording units and the output signal of the inverter to the first read wiring.

(11)
an inverter connected to one output terminal of the first and second recording units;
a first logic gate that outputs a logical product of the other output signal of the first and second recording units and an output signal of the inverter to the first read wiring;
an inverter connected to one output terminal of the third and fourth recording units;
The light detection element according to (6), further comprising a second logic gate that outputs a logical product of the other output signal of the third and fourth recording units and an output signal of the inverter to the second read wiring.

(12)
a third logic gate that outputs a logical product of the output signals of the first and second recording units to the control unit;
The light detection element according to (3), wherein the control unit controls the first switching element based on an output signal of the third logic gate.

(13)
a third logic gate that outputs a logical product of the output signals of the first and second recording units to the control unit;
a fourth logic gate that outputs a logical product of the output signals of the third and fourth recording units to the control unit;
The light detection element according to (6), wherein the control unit controls the first switching element based on output signals of the third and fourth logic gates.

(14)
the comparison unit compares the amount of change with a first threshold during a first period to output a first event signal, and compares the amount of change with a second threshold during a second period following the first period, the second threshold being different from the first threshold, to output a second event signal;
the first recording unit alternately records the first event signal and the second event signal;
The photodetector element of claim 3, wherein, when the first switching element is in a conductive state, the second recording unit records the first event signal from the first recording unit and outputs the first event signal to the first readout wiring, or records the second event signal from the first recording unit and outputs the second event signal to the first readout wiring.

(15)
a first switching element connected between an input terminal of the comparison unit and an output terminal of the comparison unit;
a control unit provided between output terminals of the first and third recording units and the first switching element, the control unit controlling the first switching element based on the event signals output from the first and third recording units;
a first switch circuit connected to the output terminals of the second and fourth recording units;
a first read wiring connected to an output terminal of the first switch circuit;
The photodetector element according to any one of (4), (5), (12), or (13), wherein the first switch circuit selectively connects an output terminal of either the second or fourth recording unit to the first read wiring.

(16)
A plurality of the light receiving units;
A plurality of the comparison units provided corresponding to the plurality of light receiving units;
A plurality of the first recording units;
a plurality of the second recording sections provided corresponding to the plurality of the first recording sections;
a buffer provided between the plurality of comparison units and the plurality of first recording units;
a second switch circuit provided between an input terminal of the buffer and the plurality of comparison units, the second switch circuit connecting a selection comparison unit selected from the plurality of comparison units to the input terminal of the buffer;
The light detection element described in any one of (1) to (16), further comprising: a third switch circuit provided between an output terminal of the buffer and the plurality of first recording units, the third switch circuit connecting a selected first recording unit selected from the plurality of first recording units to the output terminal of the buffer.

(17)
a light receiving unit that performs photoelectric conversion on incident light to generate an electrical signal;
a comparison unit that compares an amount of change in the electrical signal generated by the light receiving unit with a threshold value and outputs an event signal;
a first and a second recording unit connected in parallel to an output terminal of the comparison unit;
A photodetector element, wherein when one of the first and second recording sections is recording the event signal, the other of the first and second recording sections outputs the event signal.

(18)
a second switching element connected between an output terminal of the comparison unit and the first recording unit; a third switching element connected between an output terminal of the comparison unit and the second recording unit; and a fourth switching element connected between the first recording unit and the first read wiring.
a fifth switching element connected between the second recording unit and the first read wiring;
a sixth switching element connected between the first recording unit and the control unit;
a seventh switching element connected between the second recording unit and the control unit,
when the first recording unit records the event signal and the second recording unit outputs the event signal, the second, fifth and sixth switching elements are in a conductive state and the third, fourth and seventh switching elements are in a non-conductive state;
When the second recording unit records the event signal and the first recording unit outputs the event signal, the third, fourth, and seventh switching elements are in a conductive state, and the second, fifth, and sixth switching elements are in a non-conductive state.

(19)
a light receiving unit that performs photoelectric conversion on incident light to generate an electrical signal;
a comparison unit that outputs an event signal when the amount of change in the electrical signal exceeds or falls below a threshold;
a first recording unit connected to an output terminal of the comparison unit, for recording the event signal, and outputting the event signal;
and a second recording unit connected to the first recording unit, for recording the event signal from the first recording unit, and for outputting the event signal.

(20)
a light receiving unit that performs photoelectric conversion on incident light to generate an electrical signal;
a comparison unit that compares an amount of change in the electrical signal generated by the light receiving unit with a threshold value and outputs an event signal;
a first and a second recording unit connected in parallel to an output terminal of the comparison unit;
An electronic device having a photodetector, wherein, when one of the first and second recording units is recording the event signal, the other of the first and second recording units outputs the event signal.

Note that this disclosure is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of this disclosure. Furthermore, the effects described in this specification are merely examples and are not limiting, and other effects may also be present.

30 Recording area 40 Control unit 221 Light receiving unit 300 Event detection circuit 310 Logarithmic conversion circuit 320 Buffer 330 Quantizer 331 Capacitors 332, 333, 334, 335 Switching element 336 Comparators 31a, 32a, 31b, 32b Recording unit

Claims (20)

a light receiving unit that performs photoelectric conversion on incident light to generate an electrical signal;
a comparison unit that outputs an event signal when the amount of change in the electrical signal exceeds or falls below a threshold;
a first recording unit connected to an output terminal of the comparison unit, for recording the event signal, and outputting the event signal;
a second recording unit connected to the first recording unit, for recording the event signal from the first recording unit, and for outputting the event signal. The photodetector element of claim 1, wherein the first recording section records the next event signal from the comparison section during a read period in which the event signal recorded in the second recording section is being read. a first switching element connected between an input terminal of the comparison unit and an output terminal of the comparison unit;
a control unit provided between an output terminal of the first recording unit and the first switching element, the control unit controlling the first switching element based on the event signal output from the first recording unit;
a first read wiring connected to an output terminal of the second recording unit;
The photodetector element according to claim 1 , wherein the second recording section outputs the event signal to the first readout wiring when the first switching element is in a conductive state. a third recording unit connected to an output terminal of the comparison unit and configured to record the event signal;
The light detection element according to claim 1 , further comprising: a fourth recording section connected to the third recording section and configured to record the event signal from the third recording section. The photodetector element according to claim 4, wherein during a read period in which the event signal recorded in the fourth recording section is being read, the third recording section records the next event signal from the comparison section. a first switching element connected between an input terminal of the comparison unit and an output terminal of the comparison unit;
a control unit provided between output terminals of the first and third recording units and the first switching element, the control unit controlling the first switching element based on the event signals output from the first and third recording units;
a first read wiring connected to an output terminal of the second recording unit;
A second readout wiring connected to an output terminal of the fourth recording unit,
5. The photodetector element of claim 4, wherein when the first switching element is in a conductive state, the event signal recorded in the second recording section is read out to the first readout wiring, and the event signal recorded in the fourth recording section is read out to the second readout wiring. the comparison unit compares the amount of change with a first threshold during a first period to output a first event signal, and compares the amount of change with a second threshold during a second period following the first period, the second threshold being different from the first threshold, to output a second event signal;
the first recording unit records the first event signal during the first period;
the third recording unit records the second event signal during the second period;
7. The photodetector element of claim 6, wherein when the first switching element is in a conductive state, the second recording unit records the first event signal from the first recording unit and outputs the first event signal to the first readout wiring, and the fourth recording unit records the second event signal from the third recording unit and outputs the second event signal to the second readout wiring. The light detection element according to claim 7, wherein the control unit resets the voltages of the input terminal and output terminal of the comparison unit to a voltage between the first threshold value and the second threshold value by turning on the first switching element. The light detection element according to claim 6, wherein the control unit controls the first switching element based on the event signal recorded in each of the first and third recording units. an inverter connected to one output terminal of the first and second recording units;
4. The light detection element according to claim 3, further comprising a first logic gate that outputs a logical product of the output signal of the other of said first and second recording units and an output signal of said inverter to said first read wiring. an inverter connected to one output terminal of the first and second recording units;
a first logic gate that outputs a logical product of the other output signal of the first and second recording units and an output signal of the inverter to the first read wiring;
an inverter connected to one output terminal of the third and fourth recording units;
7. The light detection element according to claim 6, further comprising a second logic gate that outputs a logical product of the other output signal of said third and fourth recording units and an output signal of said inverter to said second read wiring. a third logic gate that outputs a logical product of the output signals of the first and second recording units to the control unit;
The light detection element according to claim 3 , wherein the control unit controls the first switching element based on an output signal of the third logic gate. a third logic gate that outputs a logical product of the output signals of the first and second recording units to the control unit;
a fourth logic gate that outputs a logical product of the output signals of the third and fourth recording units to the control unit;
The light detection element according to claim 6 , wherein the control unit controls the first switching element based on output signals of the third and fourth logic gates. the comparison unit compares the amount of change with a first threshold during a first period to output a first event signal, and compares the amount of change with a second threshold during a second period following the first period, the second threshold being different from the first threshold, to output a second event signal;
the first recording unit alternately records the first event signal and the second event signal;
4. The photodetector element according to claim 3, wherein, when the first switching element is in a conductive state, the second recording unit records the first event signal from the first recording unit and outputs the first event signal to the first readout wiring, or records the second event signal from the first recording unit and outputs the second event signal to the first readout wiring. a first switching element connected between an input terminal of the comparison unit and an output terminal of the comparison unit;
a control unit provided between output terminals of the first and third recording units and the first switching element, the control unit controlling the first switching element based on the event signals output from the first and third recording units;
a first switch circuit connected to the output terminals of the second and fourth recording units;
a first read wiring connected to an output terminal of the first switch circuit;
5. The light detection element according to claim 4, wherein the first switch circuit selectively connects an output terminal of either the second or fourth recording portion to the first read wiring. A plurality of the light receiving units;
A plurality of the comparison units provided corresponding to the plurality of light receiving units;
A plurality of the first recording units;
a plurality of the second recording sections provided corresponding to the plurality of the first recording sections;
a buffer provided between the plurality of comparison units and the plurality of first recording units;
a second switch circuit provided between an input terminal of the buffer and the plurality of comparison units, the second switch circuit connecting a selection comparison unit selected from the plurality of comparison units to the input terminal of the buffer;
2. The light detection element according to claim 1, further comprising: a third switch circuit provided between an output terminal of the buffer and the plurality of first recording units, the third switch circuit connecting a selected first recording unit selected from the plurality of first recording units to the output terminal of the buffer. a light receiving unit that performs photoelectric conversion on incident light to generate an electrical signal;
a comparison unit that compares an amount of change in the electrical signal generated by the light receiving unit with a threshold value and outputs an event signal;
a first and a second recording unit connected in parallel to an output terminal of the comparison unit;
A photodetector element, wherein when one of the first and second recording units is recording the event signal, the other of the first and second recording units outputs the event signal. a first switching element connected between an input terminal of the comparison unit and an output terminal of the comparison unit;
a control unit provided between output terminals of the first and second recording units and the first switching element, the control unit controlling the first switching element based on the event signal output from the first or second recording unit;
a first read wiring provided on the output terminal side of the first and second recording units;
a second switching element connected between an output terminal of the comparison unit and the first recording unit;
a third switching element connected between an output terminal of the comparison unit and the second recording unit;
a fourth switching element connected between the first recording unit and the first read wiring;
a fifth switching element connected between the second recording unit and the first read wiring;
a sixth switching element connected between the first recording unit and the control unit;
a seventh switching element connected between the second recording unit and the control unit,
when the first recording unit records the event signal and the second recording unit outputs the event signal, the second, fifth and sixth switching elements are in a conductive state and the third, fourth and seventh switching elements are in a non-conductive state;
18. The photodetector element of claim 17, wherein when the second recording unit records the event signal and the first recording unit outputs the event signal, the third, fourth and seventh switching elements are in a conductive state and the second, fifth and sixth switching elements are in a non-conductive state. a light receiving unit that performs photoelectric conversion on incident light to generate an electrical signal;
a comparison unit that outputs an event signal when the amount of change in the electrical signal exceeds or falls below a threshold;
a first recording unit connected to an output terminal of the comparison unit, for recording the event signal, and outputting the event signal;
and a second recording unit connected to the first recording unit, for recording the event signal from the first recording unit, and for outputting the event signal. a light receiving unit that performs photoelectric conversion on incident light to generate an electrical signal;
a comparison unit that compares an amount of change in the electrical signal generated by the light receiving unit with a threshold value and outputs an event signal;
a first and a second recording unit connected in parallel to an output terminal of the comparison unit;
An electronic device having a photodetector, wherein, when one of the first and second recording units is recording the event signal, the other of the first and second recording units outputs the event signal.