Data rate control for event-based vision sensor
In dynamic vision sensor (DVS) or change detection sensors, the chip or sensor is configured to control or modulate the event rate. For example, this control can be used to keep the event rate close to a desired rate or within desired bounds. Adapting the configuration of the sensor to the scene by changing the ON-event and/or the OFF-event thresholds, allows having necessary amount of data, but not much more than necessary, such that the overall system gets as much information about its state as possible.
1. A change detection sensor, comprising:
a pixel array comprising pixels that detect light, wherein the pixels comprise photosensors and photoreceptor circuits that output first signals based on the response of the photosensors;
event detectors for detecting events associated with light received by the pixels by comparing the first signals and a first reference voltage;
an event rate detector for counting the events with a counter; and
a controller for changing how the pixels detect the events based on the event rate detector by changing the first reference voltage;
wherein the controller compares an event rate provided by the event rate detector to a maximum event rate, if the event rate is larger than the maximum event rate the controller changes a time resolution of the sensor.
2. The sensor as claimed in claim 1 , further comprising a threshold generation circuit for setting thresholds applied by the event detectors by providing the first reference voltage.
3. The sensor as claimed in claim 1 , wherein the controller changes the first reference voltage in response to the assessment provided by the event rate detector.
4. The sensor as claimed in claim 1 , wherein the controller sets thresholds for ON events based on ON events in the pixel array based on the counter.
5. The sensor as claimed in claim 1 , wherein each of the pixels comprises a memory capacitor of one of the event detectors for storing a charge corresponding to received light when the pixel was reset.
6. The sensor as claimed in claim 1 , wherein each of the pixels comprises one or more comparators of one of the event detectors for comparing the changes in received light to the first reference voltage and a second reference voltage to detect the events.
7. The sensor as claimed in claim 1 , further comprising comparators of the event detectors for comparing changes in received light to the first reference voltage to detect the events, the comparators being located in a readout circuit.
8. The sensor as claimed in claim 1 , wherein the counter is incremented based on the events read out by a readout circuit.
9. The sensor as claimed in claim 1 , wherein the counter is reset by the controller when a new count is required.
10. The sensor as claimed in claim 1 , wherein the controller reduces the number of events during a sleep cycle and then increases the number of events during normal operating mode.
11. The sensor as claimed in claim 1 , wherein the controller sets thresholds for ON events and OFF events based on ON events and OFF events in the pixel array based on the counter.
12. A method of operation of a change detection sensor, the method comprising:
detecting light with pixels of a pixel array, wherein the pixels comprise circuits that output first signals based on the response of photosensors of the pixels;
detecting events associated with light received by the pixels by comparing the first signals and a first reference voltage;
counting the events with a counter with an event rate detector;
changing how the pixels detect the events based on the event rate detector by changing the first reference voltage;
comparing an event rate provided by the event rate detector to a maximum event rate; and
if the event rate is larger than the maximum event rate, changing a time resolution of the sensor.
13. The method as claimed in claim 12 , further comprising changing the first reference voltage in response to the assessment provided by the event rate detector.
14. The method as claimed in claim 12 , further comprising setting thresholds for ON events based on ON events in the pixel array based.
15. The method as claimed in claim 12 , wherein each of the pixels comprises a memory capacitor for storing a charge corresponding to received light when the pixel was reset.
16. The method as claimed in claim 12 , wherein each of the pixels comprises one or more comparators for comparing the changes in received light to the first reference voltage and a second reference voltage to detect the events.
17. The method as claimed in claim 12 , further comprising comparing changes in received light to the first reference voltage to detect the events using comparators located in a readout circuit.