WO2022209206A1

WO2022209206A1 - Imaging element and imaging device

Info

Publication number: WO2022209206A1
Application number: PCT/JP2022/002339
Authority: WO
Inventors: 祐士田仲
Original assignee: ソニーセミコンダクタソリューションズ株式会社
Priority date: 2021-03-31
Filing date: 2022-01-24
Publication date: 2022-10-06
Also published as: JP2022156089A

Abstract

In an imaging element that detects movements of a target as an event, detection of events that are based on flickering of a light source is reduced. This imaging element has a brightness change detection unit and a request generation unit. On the basis of multiple threshold values, the brightness change detection unit of the imaging element detects change in the same direction as the brightness of the incident light. The request generation unit of the imaging element generates a request for requesting transfer of the results of the detection in the brightness change detection unit of the imaging element.

Description

Imaging element and imaging device

The present disclosure relates to imaging elements and imaging devices.

In an imaging device having a pixel array section in which pixels having photoelectric conversion sections that perform photoelectric conversion of incident light are arranged in a two-dimensional matrix, only pixels that have detected a predetermined change in brightness are selected and a signal of the change in brightness is generated. An imaging device that performs readout is used. Such changes in brightness are caused by the motion of the object, and by selecting and reading out only pixels in which changes in brightness are detected, a moving object can be detected at a high frame rate. Such an imaging device is called an EVS (Event-based Vision Sensor).

A pixel in this EVS detects a change in luminance of incident light as an event and transmits a signal indicating the occurrence of the event to the control circuit. This control circuit, called an arbitration circuit, arbitrates signals output from a plurality of pixels and determines a pixel from which an event is read. However, when capturing an image of a flickering light source such as an LED or a fluorescent lamp, the flickering of the lighting device generates an excessive number of events. Since this event is not an event associated with the movement of the light source, it interferes with the readout of the event associated with the movement of the subject.

An imaging device has been proposed that detects pixels that generate such unnecessary events as abnormal pixels and sets them to invalid (see, for example, Patent Document 1). This prior art has a detection mode for detecting the presence or absence of an event for each pixel and an abnormality determination mode for determining whether or not there is an abnormality for each pixel. In this abnormality determination mode, pixels that receive incident light from the flicker light source and detect unnecessary events are determined and recorded as abnormal pixels. Detection of events at this abnormal pixel is stopped.

JP 2020-088723 A

However, with the above-described conventional technology, pixel events are detected until they are determined to be abnormal, so there is a problem that it is difficult to detect events due to flicker.

Therefore, the present disclosure proposes an imaging device and an imaging device that reduce detection of events based on flickering of a light source.

The imaging device of the present disclosure has a luminance change detection unit and a request generation unit. The luminance change detector detects a change in luminance of incident light in the same direction based on a plurality of thresholds. A request generation unit generates a request requesting transfer of the detection result of the luminance change detection unit.

1 is a block diagram showing a configuration example of an imaging device according to an embodiment of the present disclosure; FIG. 1 is a block diagram showing a configuration example of an imaging device according to an embodiment of the present disclosure; FIG. FIG. 3 is a diagram showing a configuration example of a pixel according to the first embodiment of the present disclosure; FIG. 1 is a diagram illustrating a configuration example of a signal generation circuit according to an embodiment of the present disclosure; FIG. 3 is a diagram illustrating a configuration example of a luminance change detection unit according to the first embodiment of the present disclosure; FIG. 4 is a diagram illustrating a configuration example of a request generation unit according to the first embodiment of the present disclosure; FIG. FIG. 4 is a diagram illustrating an example of request generation according to the first embodiment of the present disclosure; FIG. FIG. 4 is a diagram illustrating an example of arbitration by an arbiter according to the first embodiment of the present disclosure; FIG. FIG. 7 is a diagram illustrating an example of request generation according to the second embodiment of the present disclosure; FIG. 11 is a diagram illustrating a configuration example of a luminance change detection unit according to a third embodiment of the present disclosure; FIG. 11 is a diagram illustrating a configuration example of a luminance change detection unit according to a fourth embodiment of the present disclosure; FIG. 11 is a diagram illustrating a configuration example of a pixel according to a fifth embodiment of the present disclosure; FIG. FIG. 11 is a diagram showing a configuration example of a pixel array unit according to a fifth embodiment of the present disclosure; FIG. 11 is a diagram showing a configuration example of a pixel array unit according to a fifth embodiment of the present disclosure; FIG. 11 is a diagram showing a configuration example of a threshold voltage generator 50 according to a sixth embodiment of the present disclosure; FIG. FIG. 11 is a diagram showing a configuration example of a threshold voltage generator 50 according to a sixth embodiment of the present disclosure; FIG.

Embodiments of the present disclosure will be described in detail below with reference to the drawings. The explanation is given in the following order. In addition, in each of the following embodiments, the same parts are denoted by the same reference numerals, thereby omitting redundant explanations.
1. First Embodiment 2. Second Embodiment 3. Third Embodiment 4. Fourth Embodiment 5. Fifth embodiment6. Sixth embodiment

(1. First embodiment)
[Configuration of imaging device]
FIG. 1 is a block diagram showing a configuration example of an imaging device according to an embodiment of the present disclosure. FIG. 1 is a diagram showing a configuration example of the imaging device 1. As shown in FIG.

The imaging device 1 according to the embodiment includes an imaging lens 5 , an imaging element 2 , a recording section 3 and a control section 4 . As the imaging device 1, a camera mounted on a wearable device, an in-vehicle camera, or the like is assumed.

The imaging lens 5 is an example of an optical system, and captures incident light from a subject and forms an image on the imaging surface of the imaging device 2 .

The imaging device 2 is also called an EVS (Event-based Vision Sensor), and detects as an address event that the absolute value of the amount of luminance change exceeds a threshold for each of a plurality of pixels. This event includes, for example, an on-event indicating that the amount of increase in luminance has exceeded the threshold in the increasing direction, and an off-event indicating that the amount of decrease in luminance has fallen below the threshold in the decreasing direction.

Then, the imaging device 2 generates a detection signal indicating the event detection result for each pixel. Each detection signal includes a detection signal indicating presence/absence of an on-event and a detection signal indicating presence/absence of an off-event.

The imaging device 2 performs predetermined signal processing such as image recognition processing on image data consisting of detection signals, and outputs the processed data to the recording unit 3 via the signal line 6 .

The recording unit 3 records data from the imaging device 2 . The control unit 4 controls the image sensor 2 to capture image data with the image sensor 2 .

[Configuration of imaging device]
FIG. 2 is a block diagram showing a configuration example of an imaging device according to an embodiment of the present disclosure. This figure is a block diagram showing a configuration example of the imaging element 2. As shown in FIG. The imaging device 2 in FIG.

The pixel array section 10 is configured by arranging a plurality of pixels 100 . A pixel array section 10 in the figure represents an example in which pixels 100 are arranged in a two-dimensional matrix. The pixel 100 includes a photoelectric conversion unit that photoelectrically converts incident light, and detects an event based on the amount of change in photocurrent based on the photoelectric conversion.

The pixel 100 that has detected an event outputs an event detection signal to the control circuit 20 and the signal processing unit 40, which will be described later. The control circuit 20 outputs a control signal to the pixel 100 that has output the detection signal, and resets the event detected in the pixel 100 . Further, the signal processing unit 40 performs predetermined signal processing on the detection signal.

Prior to outputting this detection signal, the pixel 100 sends a request for outputting the detection signal to the arbiter 30, which will be described later. The arbiter 30 selects the pixel 100 that sent the request and outputs a response to the request. This response permits output of the detection signal.

The control circuit 20 is a circuit that controls resetting of pixel address events in each pixel 100 of the pixel array section 10 . This control circuit 20 outputs a control signal for resetting a differentiating circuit 130 arranged in a pixel 100, which will be described later. A signal line 11 connects between the pixel 100 and the control circuit 20 . An event detection signal from the pixel 100 and a control signal from the control circuit 20 are transmitted through the signal line 11 .

The arbiter 30 selects the pixel 100 that sent the request. As described above, the pixel 100 that has detected an address event outputs a detection signal to the control circuit 20 and the signal processing section 40 . This control signal must be supplied exclusively to one pixel 100 . This is to prevent collisions when outputting detection signals from the plurality of pixels 100 . Therefore, the arbiter 30 arbitrates the plurality of pixels 100 for which the pixel address event has been detected. Specifically, the arbiter 30 selects one of the pixels 100 that sent the request and returns a response to this selected pixel 100 . This response represents the result of the selection. A signal line 12 connects between the pixel 100 and the arbiter 30 . Requests from pixels 100 and responses from arbiter 30 are conveyed by signal line 12 .

When requests are sent from a plurality of pixels 100, the arbiter 30 can select the pixels 100 in the order in which the requests are sent. At this time, the arbiter 30 can preferentially select a specific pixel 100 . For example, the arbiter 30 can preferentially select a pixel 100 that has transmitted a request with a high priority, which will be described later.

The signal processing unit 40 performs predetermined signal processing on detection signals from the pixels 100 . For example, the signal processing unit 40 can arrange such detection signals as image signals in a two-dimensional matrix to generate image data having 2-bit information for each pixel 100 . Further, the signal processing unit 40 can perform signal processing such as image recognition processing on the generated image data. A signal line 13 connects between the pixel 100 and the signal processing unit 40 . A detection signal from the pixel 100 is transmitted through the signal line 13 .

The threshold voltage generation unit 50 generates a threshold voltage, which is a voltage corresponding to the above threshold. The threshold voltage generator 50 supplies the generated threshold voltage to the pixels 100 .

[Pixel configuration]
FIG. 3 is a diagram illustrating a configuration example of a pixel according to the first embodiment of the present disclosure; This figure is a diagram showing a configuration example of the pixel 100 . A pixel 100 shown in FIG.

The photoelectric conversion unit 110 performs photoelectric conversion of incident light. This photoelectric conversion unit 110 can be configured by a photodiode. This photoelectric conversion generates an electric charge corresponding to the luminance of the incident light. By applying a voltage to the photoelectric conversion unit 110, photocurrent, which is a current corresponding to the generated charge, can be supplied to an external circuit.

The current-voltage conversion circuit 120 converts the photocurrent from the photoelectric conversion section 110 into a voltage signal. During this conversion, the current-voltage conversion circuit 120 also performs logarithmic compression of the voltage signal. The converted voltage signal is output to the differentiating circuit 130 . The details of the configuration of the current-voltage conversion circuit 120 will be described later.

The differentiating circuit 130 extracts the amount of change in the voltage signal output from the current-voltage conversion circuit 120 and integrates the amount of change to generate a signal corresponding to the amount of change in the voltage signal. This signal corresponds to a signal corresponding to a change in luminance of incident light. This signal is called an optical signal. Differentiating circuit 130 outputs the generated optical signal to luminance change detecting section 140 via signal line 101 . Also, the differentiating circuit 130 receives a control signal from the control circuit 20 . This control signal is a signal for resetting the circuit that detects the amount of change in the voltage signal. The details of the configuration of the differentiating circuit 130 will be described later. Note that the current-voltage conversion circuit 120 and the differentiating circuit 130 are examples of the signal generation circuit described in the claims.

The brightness change detection unit 140 detects changes in brightness of incident light. A luminance change detector 140 in FIG. 1 detects a change in the optical signal output from the differentiating circuit 130 based on the threshold voltage supplied from the threshold voltage generator 50 . A detection result is output to the request generation unit 160 . The details of the configuration of luminance change detection section 140 will be described later.

The request generation unit 160 generates a request requesting transfer of the luminance change detection result in the luminance change detection unit 140 and outputs the request to the arbiter 30 . Further, when a response to the request is output from the arbiter 30 , the request generator 160 outputs a luminance change detection signal to the signal processor 40 and the control circuit 20 .

[Configuration of Signal Generation Circuit]
FIG. 4 is a diagram illustrating a configuration example of a signal generation circuit according to an embodiment of the present disclosure; This figure is a circuit diagram showing a configuration example of the current-voltage conversion circuit 120 and the differentiating circuit 130 . In addition, the photoelectric conversion unit 110 is further illustrated in FIG.

A current-voltage conversion circuit 120 in the figure includes MOS transistors 121 to 123 . In the figure, Vdd represents a power line Vdd for supplying power. Vb1 represents a signal line Vb1 that supplies a bias voltage.

MOS transistors

121 and 123 can be n-channel MOS transistors. A p-channel MOS transistor can be used for the MOS transistor 122 .

The photoelectric conversion unit 110 has an anode grounded and a cathode connected to the source of the MOS transistor 121 and the gate of the MOS transistor 123 . The drains of the

MOS transistors

121 and 122 are connected to the power supply line Vdd, and the gate of the MOS transistor 122 is connected to the signal line Vb1. The source of MOS transistor 123 is grounded, and the drain is connected to the gate of MOS transistor 121 , the drain of MOS transistor 122 and the output signal line of current-voltage conversion circuit 120 . One end of the capacitor of the differentiating circuit 130 is connected to this output signal line.

The MOS transistor 121 is a MOS transistor that supplies current to the photoelectric conversion section 110 . A sink current (photocurrent) corresponding to incident light flows through the photoelectric conversion unit 110 . MOS transistor 121 supplies this sink current. At this time, the gate of the MOS transistor 121 is driven by the output voltage of the MOS transistor 123 which will be described later, and outputs a source current equal to the sink current of the photoelectric conversion section 110 . Since the gate-source voltage Vgs of the MOS transistor is a voltage corresponding to the source current, the source voltage of the MOS transistor 121 is a voltage corresponding to the current of the photoelectric conversion section 110 . Thereby, the photocurrent of the photoelectric conversion unit 110 is converted into a voltage signal.

The MOS transistor 123 is a MOS transistor that amplifies the source voltage of the MOS transistor 121 . Also, the MOS transistor 122 constitutes a constant current load for the MOS transistor 123 . An amplified voltage signal is output to the drain of the MOS transistor 123 . This voltage signal is output to signal line 129 and fed back to the gate of MOS transistor 121 . When Vgs of MOS transistor 121 is equal to or lower than the threshold voltage, the source current changes exponentially with respect to changes in Vgs. Therefore, the output voltage of the MOS transistor 123 fed back to the gate of the MOS transistor 121 is a voltage signal obtained by logarithmically compressing the photocurrent of the photoelectric conversion unit 110 equal to the source current of the MOS transistor 121 .

[Configuration of differentiating circuit]
A differentiating circuit 130 in the figure includes

capacitors

131 and 132 ,

MOS transistors

133 and 134 , and a constant current circuit 135 .

MOS transistors

133 and 134 can be p-channel MOS transistors.

As described above, one end of the capacitor 131 is connected to the output of the current-voltage conversion circuit 120 , and the other end of the capacitor 131 is connected to the gate of the MOS transistor 133 , the drain of the MOS transistor 134 and one end of the capacitor 132 . The other end of the capacitor 132 is connected to the drain of the MOS transistor 133 , the drain of the MOS transistor 134 , the sink side terminal of the constant current circuit 135 and the signal line 101 . The source of MOS transistor 133 is connected to power supply line Vdd, and the gate of MOS transistor 134 is connected to signal line 11 . A sink side terminal of the constant current circuit 135 is grounded.

The capacitor 131 corresponds to a coupling capacitor. This capacitor 131 blocks the DC component of the output voltage of the current-voltage conversion circuit 120 and allows only the AC component to pass. Also, a current based on the change in the output voltage of the current-voltage conversion circuit 120 is supplied to the gate of the MOS transistor 133 via the capacitor 131 . The AC component of the output voltage of the current-voltage conversion circuit 120 corresponds to the variation of the photocurrent. The MOS transistor 133 and constant current circuit 135 constitute an inverting amplifier circuit. MOS transistor 522 constitutes a constant current load. A change in the output voltage of the current-voltage conversion circuit 120 is input to the gate of the MOS transistor 133 via the capacitor 131, inverted and amplified by the MOS transistor 133, and output to the drain. Therefore, a current based on the change in the output voltage of the current-voltage conversion circuit 120 flows through the capacitor 132, and the capacitor 132 is charged and discharged. That is, the amount of change in the output voltage of the current-voltage conversion circuit 120 is accumulated (integrated). An optical signal, which is a signal corresponding to the amount of change in the voltage signal output from the current-voltage conversion circuit 120 , is output to the signal line 101 .

The MOS transistor 134 resets the differentiating circuit 130 . By making the MOS transistor 134 conductive, both ends of the capacitor 132 are short-circuited. The accumulated change in the output voltage of the current-voltage conversion circuit 120 is discharged and reset. With this reset, the output voltage of the differentiating circuit 130 becomes, for example, the voltage at the middle point between the power supply line Vdd and the ground line.

[Configuration of Luminance Change Detector]
FIG. 5 is a diagram illustrating a configuration example of a luminance change detection unit according to the first embodiment of the present disclosure; This figure is a circuit diagram showing a configuration example of the luminance change detection unit 140. As shown in FIG. A luminance change detection unit 140 in FIG. In addition, the request generating unit 160 is also shown in the figure.

Also, the signal line 14 from the threshold voltage generator 50 is connected to the luminance change detector 140 . The signal lines 14 in the figure include a signal line VbhA, a signal line VbhB and a signal line Vbl. These signal lines are signal lines for transmitting the threshold voltages generated by the threshold voltage generator 50 . The threshold voltages supplied by signal line VbhA, signal line VbhB and signal line Vbl are denoted as VbhA, VbhB and Vbl, respectively.

VbhA and VbhB are threshold voltages higher than the output voltage of the differentiating circuit 130 at reset. Therefore, VbhA and VbhB are rising threshold voltages for the output voltage of the differentiating circuit 130 . That is, VbhA and VbhB constitute thresholds in the direction in which the luminance of incident light increases. VbhB is assumed to be a threshold voltage higher than VbhA.

On the other hand, Vbl is a threshold voltage lower than the output voltage of the differentiating circuit 130 at reset. Therefore, Vbl becomes a decreasing threshold voltage with respect to the output voltage of the differentiating circuit 130 . That is, Vbl constitutes a threshold in the direction in which the luminance of incident light decreases.

The determination circuit 141 includes a MOS transistor 150 and a MOS transistor 153 .

MOS transistors

150 and 153 can be p-channel MOS transistors and n-channel MOS transistors, respectively. The MOS transistor 150 has a source connected to the power supply line Vdd and a gate connected to the signal line 101 . MOS transistor 153 has a source grounded and a gate connected to signal line VbhA. The drain of the MOS transistor 153 is connected to the drain of the MOS transistor 150 and the signal line VinA. A signal line VinA is an output signal line of the determination circuit 141 .

The determination circuit 141 constitutes a comparator. Specifically, the determination circuit 141 connects the drain of the MOS transistor 153 to the gate of which the threshold voltage VbhA is applied and the drain of the MOS transistor 150 to the gate of which the output voltage of the differentiating circuit 130 is applied. The output of determination circuit 141 changes according to the magnitude relationship between the drain current on the sink side of MOS transistor 153 and the drain current on the source side of MOS transistor 150 .

When the output voltage of the differentiation circuit 130 is lower than VbhA, specifically, the voltage obtained by subtracting VbhA from the power supply voltage Vdd, the source current of the MOS transistor 150 is smaller than the sink current of the MOS transistor 153 . Therefore, the output voltage (the voltage of the signal line VinA) becomes L level. On the other hand, when the output voltage of differentiating circuit 130 becomes higher than VbhA (the voltage obtained by subtracting VbhA from power supply voltage Vdd), the sink current of MOS transistor 153 becomes smaller than the source current of MOS transistor 150 . Therefore, the output voltage shifts to H level. Thus, the determination circuit 141 compares the output voltage of the differentiating circuit 130 and the threshold voltage VbhA, and detects a change in the direction in which the luminance of incident light increases.

The determination circuit 142 includes

MOS transistors

151 and 154 . A signal line VbhB is connected to the gate of the MOS transistor 154, and a signal line VinB is connected as an output signal line. Since the configuration other than this is the same as that of the determination circuit 141, description thereof is omitted. The determination circuit 142 compares the output voltage of the differentiating circuit 130 and the threshold voltage VbhB. Since VbhB is a voltage higher than VbhA, the determination circuit 142 detects a larger luminance change amount than the determination circuit 141 does.

The determination circuit 143 includes

MOS transistors

152 and 155, the signal line Vbl is connected to the gate of the MOS transistor 155, and the signal line VinD is connected as an output signal line. be done. Since the configuration other than this is the same as that of the determination circuit 141, description thereof is omitted. The determination circuit 143 compares the output voltage of the differentiating circuit 130 and the threshold voltage Vbl. When the output voltage of the differentiating circuit 130 is higher than Vbl, specifically, the voltage obtained by subtracting Vbl from the power supply line Vdd, the output voltage (the voltage of the signal line VinD) becomes H level. On the other hand, when the output voltage of the differentiating circuit 130 becomes lower than Vbl (the voltage obtained by subtracting Vbl from the power supply voltage Vdd), the output voltage shifts to L level. Thus, the determination circuit 143 compares the output voltage of the differentiating circuit 130 and the threshold voltage Vbl, and detects a change in the direction in which the luminance of incident light decreases.

The outputs of the

determination circuits

141 and 142 correspond to the on-event detection signal, and the output of the determination circuit 143 corresponds to the off-event detection signal. Note that the determination circuit 143 is an example of a second luminance change detection unit described in the claims.

The request generation unit 160 in the figure includes a first request generation unit 161 and a second request generation unit 162. Signal lines VinA and VinB from the brightness change detection unit 140 are connected to the first request generation unit 161, and the results of brightness change detection by the

determination circuits

141 and 142 are input. The first request generator 161 generates a request based on the change in the direction in which the luminance of incident light increases, and outputs the request to the arbiter 30 .

A signal line VinD from the brightness change detection unit 140 is connected to the second request generation unit 162, and the brightness change detection result of the determination circuit 143 is input. The second request generation unit 162 generates a request based on the change in the direction of decrease in luminance of incident light, and outputs the request to the arbiter 30 .

[Configuration of request generator]
6A is a diagram illustrating a configuration example of a request generation unit according to the first embodiment of the present disclosure; FIG. This figure is a diagram showing a configuration example of the first request generation unit 161 . A first request generation unit 161 shown in the figure receives the results of luminance change detection by

determination circuits

141 and 142 supplied via signal lines VinA and VinB. The first request generator 161 also generates two types of requests based on these detection results, and outputs them to the arbiter 30 via the signal lines REQstrength and REQweak.

FIG. 6B is a diagram illustrating an example of request generation according to the first embodiment of the present disclosure. This figure is a diagram showing an example of request generation in the first request generation unit 161, and is a truth table showing an example of request generation based on the detection result of luminance change.

"Luminance change" in the figure represents the detection result of the luminance change in the luminance change detection unit 140. “Determination circuit 141” and “determination circuit 142” represent outputs of the luminance change detection unit 140 corresponding to this luminance change. "Request" represents the strength of the request determined based on the detection result of luminance change. "REQstrength" and "REQweak" represent requests generated based on the strength of the request.

When the outputs of the

determination circuits

141 and 142 are both at L level, it corresponds to the case where no luminance change is detected. In this case, the first request generator 161 does not generate a request.

When the output of the determination circuit 141 is at H level and the output of the determination circuit 142 is at L level, it corresponds to the case where the change in detected brightness is relatively small. In this case, the first request generation unit 161 determines that the change in luminance is caused by the movement of the object, and generates a strong request (strong request). The first request generator 161 outputs an H level signal to the signal line REQstrength. This signal represents a strong request.

When both the outputs of the determination circuit 141 and the determination circuit 142 are at H level, it corresponds to the detection of a large change in luminance. In this case, the first request generation unit 161 determines that the change in brightness is caused by flicker, and generates a weak request (weak request). The first request generator 161 outputs an H level signal to the signal line REQweak. This signal represents a weak request.

In this way, the luminance change detection unit 140 generates different requests according to the luminance change of incident light. A strong request corresponds to a high priority request and a weak request corresponds to a low priority request.

[arbitration of arbiter]
FIG. 7 is a diagram illustrating an example of arbitration by an arbiter according to the first embodiment of the present disclosure; This figure is a flow chart showing an example of request arbitration by the arbiter 30 . First, the arbiter 30 determines whether or not there is a pixel 100 that outputs a strong request (step S101). As a result, if there is a pixel 100 that outputs a strong request (step S101, Yes), the arbiter 30 sends a response to the target pixel 100 (step S102), and returns to step S101.

On the other hand, if there is no pixel 100 outputting a strong request (step S101, No), the arbiter 30 determines whether there is a pixel 100 outputting a weak request (step S103). As a result, if there is a pixel 100 that outputs a weak request (step S103, Yes), the arbiter 30 sends a response to the target pixel 100 (step S104), and returns to step S101. On the other hand, if there is no pixel 100 outputting a weak request (step S103, No), the arbiter 30 terminates the process.

In this way, the arbiter 30 performs arbitration giving priority to pixels 100 that generate strong requests. As a result, the pixel 100 that has generated a strong request can preferentially output the luminance change detection signal to the signal processing unit 40 and the control circuit 20 .

In this way, the imaging device 2 of the first embodiment of the present disclosure detects changes in luminance of incident light based on a plurality of thresholds. This makes it possible to determine whether the change in brightness of the incident light is a change in brightness accompanying the movement of the object or a change in brightness due to flicker. It is possible to lower the priority of the event based on the change in luminance due to flicker, and reduce the detection of unnecessary events.

(2. Second embodiment)
The imaging device 2 of the first embodiment described above detects changes in brightness due to flicker. On the other hand, the imaging device 2 of the second embodiment of the present disclosure is different from the above-described first embodiment in that it detects changes in luminance due to noise.

FIG. 8 is a diagram showing an example of request generation according to the second embodiment of the present disclosure. This figure, like FIG. 6B, is a diagram showing an example of request generation in the first request generation unit 161. In FIG. The request generation in FIG. 6 differs from that in FIG. 6B in the setting of the request strength.

When the detected luminance change is relatively small, that is, when the output of the determination circuit 141 is at the H level and the output of the determination circuit 142 is at the L level, the first request generation unit 161 detects the luminance change due to noise. judge and generate a weak request (weak request). The first request generator 161 outputs an H level signal to the signal line REQweak.

When the outputs of the determination circuit 141 and the determination circuit 142 are both at the H level, the first request generation unit 161 determines that the change in brightness is caused by the movement of the object and generates a strong request (strong request). The first request generator 161 outputs an H level signal to the signal line REQstrength.

Based on the requests generated in this way, the arbiter 30 arbitrates the requests. A low priority is set for requests that are determined to be luminance due to noise.

The configuration of the image pickup device 2 other than this is the same as the configuration of the image pickup device 2 in the first embodiment of the present disclosure, so the description is omitted.

In this way, the imaging device 2 of the second embodiment of the present disclosure detects changes in luminance of incident light based on a plurality of thresholds. This makes it possible to determine whether the change in luminance of incident light is due to noise. It is possible to lower the priority of the event based on the luminance change due to this noise, and reduce the detection of unnecessary events.

(3. Third Embodiment)
The imaging device 2 of the first embodiment described above detects changes in the direction of increase in luminance of incident light based on a plurality of thresholds. On the other hand, the imaging device 2 of the third embodiment of the present disclosure is different from the above-described first embodiment in that the change in the decreasing direction of the luminance of incident light is also determined based on a plurality of thresholds.

[Configuration of Luminance Change Detector]
FIG. 9 is a diagram illustrating a configuration example of a luminance change detection unit according to the third embodiment of the present disclosure; This figure, like FIG. 5, is a circuit diagram showing a configuration example of the luminance change detection section 140. As shown in FIG. The brightness change detection section 140 in FIG. 5 is different from the brightness change detection section 140 in FIG. 5 in that it further includes a determination circuit 144 and the signal lines 14 include the signal lines VblA and VblB.

The threshold voltages supplied by the signal line VblA, the signal line VblB, and the signal line Vbl are denoted as VblA and VblB, respectively. These are threshold voltages generated by the threshold voltage generator 50 . VblA and VblB are threshold voltages lower than the output voltage of the differentiating circuit 130 at reset. Therefore, VblA and VblB are threshold voltages that decrease with respect to the output voltage of the differentiating circuit 130 . That is, VblA and VblB constitute thresholds in the direction in which the luminance of incident light decreases. Note that VblB is a threshold voltage lower than VblA. A signal line VblA is connected to the determination circuit 143 in the figure, and the threshold voltage VblA is supplied.

The determination circuit 144 includes

MOS transistors

156 and 157 . A signal line VblB is connected to the gate of the MOS transistor 157, and a signal line VinE is connected as an output signal line. Since the configuration other than this is the same as that of the determination circuit 141, description thereof is omitted. The determination circuit 144 compares the output voltage of the differentiating circuit 130 and the threshold voltage VblB. Since VblB is a voltage lower than VblA, the determination circuit 144 detects a greater amount of change in luminance in the direction of decrease than the determination circuit 143 does.

The signal lines VinD and VinE from the brightness change detection unit 140 are connected to the second request generation unit 162 in FIG. The second request generation unit 162 generates a request based on the change in the direction of decrease in luminance of incident light, and outputs the request to the arbiter 30 .

In this way, the imaging device 2 of the third embodiment of the present disclosure detects changes in the direction of increase and decrease in luminance of incident light based on a plurality of thresholds. Accordingly, noise can be detected based on changes in the direction of increase and decrease in the luminance of incident light.

(4. Fourth Embodiment)
The imaging device 2 of the first embodiment described above detects changes in the direction in which the luminance of incident light increases based on two types of threshold values. On the other hand, the imaging device 2 of the fourth embodiment of the present disclosure is different from the above-described first embodiment in that the change in the increasing direction of the luminance of incident light is detected based on three or more thresholds. .

[Configuration of Luminance Change Detector]
FIG. 10 is a diagram illustrating a configuration example of a luminance change detection unit according to the fourth embodiment of the present disclosure; This figure, like FIG. 5, is a circuit diagram showing a configuration example of the luminance change detection section 140. As shown in FIG. The brightness change detection unit 140 in FIG. 5 is different from the brightness change detection unit 140 in FIG. 5 in that it further includes a determination circuit 145 and the signal line 14 includes the signal line VbhC.

The threshold voltage supplied by the signal line VbhC is denoted as VbhC. VbhC is the threshold voltage generated by the threshold voltage generator 50 . VbhC is a threshold voltage higher than the output voltage of the differentiating circuit 130 at reset. Therefore, VbhC becomes a rising threshold voltage with respect to the output voltage of the differentiating circuit 130 . That is, VblC constitutes a threshold in the direction in which the luminance of incident light increases. Note that VbhC is a threshold voltage lower than VbhB. A signal line VbhC is connected to the determination circuit 145 in the figure, and the threshold voltage VbhC is supplied.

The determination circuit 145 includes

MOS transistors

158 and 159 . A signal line VbhC is connected to the gate of the MOS transistor 159, and a signal line VinC is connected as an output signal line. Since the configuration other than this is the same as that of the determination circuit 141, description thereof is omitted. The determination circuit 145 compares the output voltage of the differentiating circuit 130 and the threshold voltage VbhC. Since VbhC is a voltage lower than VbhB, the determination circuit 145 detects a smaller amount of change in the upward direction of luminance than the determination circuit 142 does.

The signal lines VinAVinB and VinC from the brightness change detection unit 140 are connected to the first request generation unit 161 in FIG. The first request generator 161 can, for example, lower the priority of requests for changes in luminance due to flicker based on the detection results of the

determination circuits

141 and 142 . Also, the first request generation unit 161 can lower the priority of the request for luminance change due to noise based on the detection results of the

determination circuits

142 and 145 .

In this way, the imaging device 2 of the fourth embodiment of the present disclosure detects changes in the increasing direction of the luminance of incident light based on three or more thresholds.

(5. Fifth Embodiment)
The imaging device 2 of the first embodiment described above has a plurality of

determination circuits

141 and 142 for each pixel 100 . On the other hand, the imaging device 2 of the fifth embodiment of the present disclosure differs from the above-described first embodiment in that the

determination circuits

141 and 142 are distributed and arranged in the plurality of pixels 100 .

[Pixel configuration]
FIG. 11 is a diagram illustrating a configuration example of a pixel according to the fifth embodiment of the present disclosure; This figure, like FIG. 3, is a diagram showing a configuration example of pixels (

pixels

100a and 100b). A pixel 100a and a pixel 100b in FIG. 3 differ from the pixel 100 in FIG. 3 in that

determination circuits

141 and 142 are arranged in a distributed manner.

A determination circuit 141 is arranged in the brightness change detection section 140 of the pixel 100a in the same figure, and a determination circuit 142 is arranged in the brightness change detection section 140 of the pixel 100b in the same figure. Also, a request generation unit 160 is arranged to generate a request in common for the

pixels

100a and 100b. A signal line VinA from the pixel 100a and a signal line VinB from the pixel 100b are wired to the request generation unit 160 . The request generation unit 160 sets the priority of the flicker request based on the detection result based on the threshold voltage VbhA in the determination circuit 141 of the pixel 100a and the detection result based on the threshold voltage VbhB in the determination circuit 142 of the pixel 100b. can be done. In addition, the request generation unit 160 can generate a request based on the change in luminance based on the motion of the object based on the detection result of the pixel 100a.

[Configuration of Pixel Array Section]
12A and 12B are diagrams showing configuration examples of a pixel array unit according to the fifth embodiment of the present disclosure. This figure is a diagram showing an arrangement example of

pixels

100 a and 100 b in the pixel array section 10 .

FIG. 12A shows an example in which

pixels

100a and 100b are alternately arranged in row and column directions. Note that the dotted line in FIG. 2 represents the range of pixels connected to the common request generator 160 .

FIG. 12B shows an example in which three pixels 100a and one pixel 100b are arranged in four pixels of two rows and two columns. A request generator 160 can be arranged for each pixel in two rows and two columns.

In this way, the imaging device 2 of the fifth embodiment of the present disclosure can simplify the configuration of the pixels 100 by arranging the determination circuits 141 and the like in a plurality of pixels 100 in a distributed manner.

(6. Sixth Embodiment)
In the imaging device 2 of the first embodiment described above, the threshold voltage generator 50 generates the threshold voltage. On the other hand, the imaging device 2 of the sixth embodiment of the present disclosure differs from the above-described first embodiment in that the threshold voltage generator 50 adjusts the threshold rolling pressure.

[Configuration of Pixel Array Section]
13A and 13B are diagrams showing configuration examples of the threshold voltage generator 50 according to the sixth embodiment of the present disclosure.

FIG. 13A is a diagram showing an example of the threshold voltage generation unit 50 including the illuminance measurement unit 60. FIG. The illuminance measurement unit 60 measures the illuminance around the imaging element 2 and outputs the result to the threshold voltage generation unit 50 .

The threshold voltage generation unit 50 in FIG. 13A adjusts the threshold voltage based on the illuminance from the illuminance measurement unit 60. For example, the threshold voltage generator 50 can set thresholds for illuminance, for example, two illuminances, low illuminance (L1) and high illuminance (L2). Further, the threshold voltage generation unit 50 can adjust the values of VinA and VbhB for three cases: when the illuminance from the illuminance measurement unit 60 is less than L1, when it is greater than or equal to L1 and less than L2, and when it is greater than or equal to L2.

As a result, when using the camera outdoors or capturing images while moving, it is possible to distinguish between changes in brightness based on changes in brightness with respect to the target part and changes in brightness due to flicker from the illuminance information. By adjusting the threshold voltage based on the illuminance, changes in luminance due to flicker can be detected even when ambient light changes.

The threshold voltage generator 50 in FIG. 13B includes a strong request counter 51 , a weak request counter 52 , comparators 53 and 54 , and voltage generators 55 and 56 .

The strong request counting unit 51 counts the number of strong requests in a predetermined period and outputs the count to the comparing unit 53 . The weak request counting unit 52 counts the number of weak requests in a predetermined period and outputs the count to the comparing unit 54 .

The comparison unit 53 compares the target number of strong request events and the number of strong requests, and outputs the comparison result to the voltage generation unit 55 . The comparison unit 54 compares the target number of weak requests with the number of weak requests, and outputs the comparison result to the voltage generation unit 56 .

The voltage generating section 55 generates a threshold voltage according to the comparison result from the comparing section 53. Also, the voltage generator 56 generates a threshold voltage according to the comparison result from the comparator 54 .

The comparison unit 53 and the voltage generation unit 55 perform feedback control so that the number of strong requests converges to the target number of strong request events, and adjust the threshold voltage. Similarly, the comparison unit 54 and the voltage generation unit 56 perform feedback control so that the number of weak requests converges to the target number of weak request events, and adjust the threshold voltage.

This makes it possible to deal with unexpected flickering of light sources and other factors that lead to excess events.

It should be noted that the effects described in this specification are only examples and are not limited, and other effects may also occur.

Note that the present technology can also take the following configuration.
(1)
a luminance change detection unit that detects changes in the luminance of incident light in the same direction based on a plurality of thresholds;
and a request generation unit that generates a request to transfer the result of detection by the luminance change detection unit.
(2)
The imaging device according to (1), wherein the luminance change detection unit detects a change in a direction in which the luminance increases.
(3)
further comprising a second luminance change detection unit that detects a change in the direction in which the luminance of the incident light decreases;
The imaging device according to (2), wherein the request generating section requests transfer of the detection results of the luminance change detecting section and the second luminance change detecting section.
(4)
The imaging device according to (3), wherein the second brightness change detection unit detects the change based on a plurality of threshold values.
(5)
The imaging device according to any one of (1) to (4), wherein the request generation unit generates the requests with different priorities according to the detection result.
(6)
The imaging device according to (5), further comprising an arbiter that arbitrates the requests according to the priority.
(7)
a pixel further comprising a photoelectric conversion unit that photoelectrically converts the incident light and a signal generation circuit that generates an optical signal corresponding to a change in photocurrent based on the photoelectric conversion;
The imaging device according to any one of (1) to (6), wherein the luminance change detection section detects a change in luminance of the incident light based on the generated optical signal and the threshold.
(8)
The luminance change detection unit includes a plurality of determination circuits for detecting changes in the same direction of luminance of the incident light based on each of the plurality of thresholds,
the plurality of determination circuits detect a luminance change of the incident light based on optical signals generated by the signal generation circuits arranged in the different pixels;
The imaging device according to (7), wherein the request generation unit generates the request based on detection results of the plurality of determination circuits.
(9)
further comprising a threshold voltage generation unit that generates a threshold voltage that is a voltage corresponding to the threshold value and supplies the threshold voltage to the luminance change detection unit;
The imaging device according to any one of (1) to (8), wherein the luminance change detection section detects the luminance change of the incident light based on the generated threshold voltage.
(10)
The imaging device according to (9), wherein the threshold voltage generation unit adjusts the threshold voltage according to ambient illuminance.
(11)
The imaging device according to (9), wherein the threshold voltage generation unit adjusts the threshold voltage according to the number of generated requests.
(12)
a luminance change detection unit that detects changes in the luminance of incident light in the same direction based on a plurality of thresholds;
a request generating unit for generating a request requesting transfer of the detection result of the luminance change detecting unit;
and a signal processing unit that processes the result of the detection.

1 imaging device 2 imaging device 10 pixel array unit 20 control circuit 30 arbiter 40 signal processing unit 50 threshold

voltage generation unit

100, 100a, 100b pixel 110 photoelectric conversion unit 120 current-voltage conversion circuit 130 differentiation circuit 140 luminance change detection unit 141 to 145 Judgment circuit 160 request generator 161 first request generator 162 second request generator

Claims

a luminance change detection unit that detects changes in the luminance of incident light in the same direction based on a plurality of thresholds;
and a request generation unit that generates a request to transfer the result of detection by the luminance change detection unit.
2. The imaging device according to claim 1, wherein the luminance change detection section detects a change in the direction in which the luminance increases.
further comprising a second luminance change detection unit that detects a change in the direction in which the luminance of the incident light decreases;
3. The imaging device according to claim 2, wherein the request generating section requests transfer of the detection result in the luminance change detecting section and the second luminance change detecting section.
4. The imaging device according to claim 3, wherein the second luminance change detection section detects the change based on a plurality of thresholds.
The imaging device according to claim 1, wherein the request generation unit generates the requests with different priorities according to the detection result.
6. The imaging device according to claim 5, further comprising an arbiter that arbitrates the requests according to the priority.
a pixel further comprising a photoelectric conversion unit that photoelectrically converts the incident light and a signal generation circuit that generates an optical signal corresponding to a change in photocurrent based on the photoelectric conversion;
2. The imaging device according to claim 1, wherein the luminance change detection section detects a change in luminance of the incident light based on the generated optical signal and the threshold.
The luminance change detection unit includes a plurality of determination circuits for detecting changes in the same direction of luminance of the incident light based on each of the plurality of thresholds,
the plurality of determination circuits detect a luminance change of the incident light based on optical signals generated by the signal generation circuits arranged in the different pixels;
8. The imaging device according to claim 7, wherein the request generating section generates the request based on detection results of the plurality of determination circuits.
further comprising a threshold voltage generation unit that generates a threshold voltage that is a voltage corresponding to the threshold value and supplies the threshold voltage to the luminance change detection unit;
2. The imaging device according to claim 1, wherein the luminance change detection section detects the luminance change of the incident light based on the generated threshold voltage.
10. The imaging device according to claim 9, wherein the threshold voltage generator adjusts the threshold voltage according to ambient illuminance.
10. The imaging device according to claim 9, wherein the threshold voltage generator adjusts the threshold voltage according to the number of generated requests.
a luminance change detection unit that detects changes in the luminance of incident light in the same direction based on a plurality of thresholds;
a request generation unit for generating a request requesting transfer of the detection result of the luminance change detection unit;
and a signal processing unit that processes the result of the detection.