Solid-state image sensor and imaging device
In a solid-state image sensor that detects presence or absence of an address event, erroneous detection of the address event is suppressed. Each of a plurality of pixels executes detection processing for detecting whether or not a change amount of an incident light amount exceeds a predetermined threshold, and outputting a detection result. An abnormal pixel determination unit determines whether or not each of the plurality of pixels has an abnormality, and enables a pixel without an abnormality and disables a pixel with an abnormality. A control unit performs control for causing the enabled pixel to execute detection processing and control for fixing the detection result of the disabled pixel to a specific value.
1. A solid-state image sensor comprising:
a plurality of pixel circuits each configured to execute detection processing of detecting whether or not a change amount of an incident light amount exceeds a predetermined threshold and to output a detection result;
an abnormal pixel determination circuit configured to determine whether or not each of the plurality of pixel circuits has an abnormality, and set a pixel circuit without the abnormality to be enabled and set a pixel circuit with the abnormality to be disabled; and
a controller configured to perform control of causing the pixel circuit set to be enabled to execute the detection processing and control of fixing the detection result of the pixel circuit set to be disabled to a specific value, wherein
each of the plurality of pixel circuits includes
a logarithmic response circuit in which a photoelectric conversion element configured to generate a photocurrent by photoelectric conversion and a current-voltage conversion circuit configured to convert the photocurrent into a voltage are arranged,
a buffer configured to receive the voltage and then output the voltage as an output voltage,
a differentiator circuit configured to receive the output voltage and to generate a differential signal indicating a change amount of the output voltage by differential operation,
a comparator configured to compare the differential signal with the threshold, and
a transfer circuit configured to transfer a comparison result of the comparator as the detection result, and
at least one of the logarithmic response circuit, the buffer, the differentiator circuit, or the comparator includes a switch that opens or closes a predetermined path according to control of the controller.
2. The solid-state image sensor according to claim 1 , wherein
the controller controls the switch of the pixel circuit set to be disabled to be in an open state.
3. The solid-state image sensor according to claim 2 , wherein
the switch is inserted between the photoelectric conversion element and the current-voltage conversion circuit.
4. The solid-state image sensor according to claim 2 , wherein
the current-voltage conversion circuit includes a transistor and a switch connected in series to the photoelectric conversion element, and
the switch is inserted in at least one of a path between the photoelectric conversion element and the transistor or a path between the transistor and a power supply terminal.
5. The solid-state image sensor according to claim 2 , wherein
the buffer includes first and second transistors connected in series, and
the switch is inserted at least one of between the first and second transistors or between a connection point of the first and second transistors and the differentiator circuit.
6. The solid-state image sensor according to claim 2 , wherein
the differentiator circuit includes
a capacitance configured to output a charge according to the change amount of the output voltage to a predetermined input terminal, and
an inverting circuit configured to output a signal of an inverted voltage of the input terminal as the differential signal, and
the switch is inserted between the capacitance and the input terminal.
7. The solid-state image sensor according to claim 2 , wherein
the switch is inserted between an output node of the comparator and the transfer unit circuit.
8. The solid-state image sensor according to claim 1 , wherein the switch controls the switch of the pixel circuit set to be disabled to be in a close state.
9. The solid-state image sensor according to claim 8 , wherein the switch is inserted between a connection point of the current-voltage conversion circuit and the photoelectric conversion element and a predetermined reference terminal.
10. The solid-state image sensor according to claim 8 , wherein the switch is inserted between a connection point of the current-voltage conversion circuit and the buffer and a predetermined reference terminal.
11. The solid-state image sensor according to claim 8 , wherein
the switch is inserted between a connection point of the buffer and the differentiator circuit and a predetermined reference terminal.
12. The solid-state image sensor according to claim 8 ,
wherein
the differentiator circuit includes
a capacitance configured to output a charge according to the change amount of the output voltage to a predetermined input terminal, and
an inverting circuit configured to output a signal of an inverted voltage of the input terminal as the differential signal, and
the switch is inserted between the input terminal and an output terminal of the inverting circuit.
13. The solid-state image sensor according to claim 8 ,
wherein
the differentiator circuit includes
a capacitance configured to output a charge according to the change amount of the output voltage to a predetermined input terminal,
an inverting circuit configured to output a signal of an inverted voltage of the input terminal as the differential signal, and
a short-circuit transistor configured to short-circuit the input terminal and an output terminal of the inverting circuit according to an auto-zero signal from the transfer circuit, the auto-zero signal instructing initialization, and
the switch is inserted between a gate of the short-circuit transistor and the transfer circuit.
14. The solid-state image sensor according to claim 8 , wherein
the switch is inserted between an output terminal of the comparator and a predetermined terminal.
15. The solid-state image sensor according to claim 1 ,
wherein
the abnormal pixel determination circuit determines whether or not each of the plurality of pixel circuits has an abnormality before execution of the detection processing.
16. The solid-state image sensor according to claim 1 ,
wherein
the abnormal pixel determination circuit determines whether or not each of the plurality of pixel circuits has an abnormality during execution of the detection processing.
17. The solid-state image sensor according to claim 1 ,
wherein
the abnormal pixel determination circuit is one of a plurality of abnormal pixel determination circuits,
the plurality of abnormal pixel determination circuits is arranged in the pixels different from one another, and
the plurality of pixel circuits is arranged in pixels different from one another.
18. The solid-state image sensor according to claim 1 , wherein
the specific value is a value indicating that the change amount does not exceed the threshold.
19. An imaging device comprising the solid-state image sensor according to claim 1 .