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1. WO2020229980 - EVENT-BASED VISION SENSOR USING ON/OFF EVENT AND GRAYSCALE DETECTION RAMPS

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[ EN ]

CLAIMS

What is claimed is:

1. An optical sensor, wherein each pixel comprises:

a photoreceptor for detecting received light;

an analog comparator for comparing signal from the photoreceptor to voltage ramps;

a memory for storing a previous illumination value;

a digital comparator for comparing a current count to the previous illumination value; and

control logic for determining whether event has occurred based on the digital comparator and the analog comparator.

2. The sensor of claim 1, wherein the control logic determines whether an ON event or OFF event occurred.

3. The sensor of any of claims 1-2, wherein the photoreceptor and at least part of the analog comparator are implemented in a different wafer from the memory and the digital comparator.

4. The sensor of any of claims 1-3, wherein the analog comparator compares the signal from the photoreceptor to a registration ramp and the control logic stores the count as a new illumination value in the memory based on the comparison by the analog comparator.

5. The sensor of any of claims 1-4, further comprising a controller and counter that generates an ON event ramp for determining ON events, an OFF event ramp for determining OFF events, and a registration ramp for determining a current illumination of the photoreceptor.

6. The sensor of any of claims 1-5, wherein the output of the digital comparator determines when the output of the analog comparator is analyzed to determine if an event has occurred.

7. The sensor of any of claims 1-6, wherein the digital comparator is shared with another pixel.

8. The sensor of any of claims 1-8, wherein ramp voltage varies exponentially over time.

9. An optical sensing method, comprising:

generating a digital comparison of a count and a previous illumination value; generating an analog comparison between a signal from a photoreceptor and voltage ramps; and

determining whether an event has occurred based on the digital comparison and the analog comparison.

10. The method of claim 9, further comprising determining whether an ON event or OFF event occurred based on the digital comparison and the analog comparison.

11. The method of any of claims 9-10, wherein photoreceptor and at least part of an analog comparator are implemented in a different wafer from a memory and a digital comparator.

12. The method of any of claims 9-11, further comprising performing an analog comparison between the signal from the photoreceptor and a registration ramp and storing a new illumination value based on the analog comparison.

13. The method of any of claims 9-12, further comprising generating an ON event ramp for determining ON events, an OFF event ramp for determining OFF events, and a registration ramp for determining a current illumination of the photoreceptor.

14. The method of any of claims 9-13, further comprising sharing a digital comparator between pixels.

15. The method of any of claims 9-14, wherein ramp voltages vary exponentially over time.

16. The method of any of claims 9-15, wherein determining whether an event has occurred based on the digital comparison and the analog comparison comprises checking an output of an analog comparator producing the analog comparison at a time when the digital comparison performed by a digital comparator is based on a count and content of a memory.