US 11,729,534 B1
Low power event driven pixels with passive difference detection circuitry, and reset control circuits for the same
Andreas Suess, San Jose, CA (US); and Shoushun Chen, Shanghai (CN)
Assigned to OmniVision Technologies, Inc., Santa Clara, CA (US)
Filed by OMNIVISION TECHNOLOGIES, INC., Santa Clara, CA (US)
Filed on Jul. 27, 2022, as Appl. No. 17/875,240.
Int. Cl. H04N 25/772 (2023.01); H04N 25/42 (2023.01); H04N 25/50 (2023.01); H04N 25/709 (2023.01); H03K 19/00 (2006.01); H03K 19/20 (2006.01); H03M 1/40 (2006.01); H03M 1/44 (2006.01)
CPC H04N 25/772 (2023.01) [H04N 25/42 (2023.01); H04N 25/50 (2023.01); H04N 25/709 (2023.01)] 30 Claims
OG exemplary drawing
 
1. An event driven pixel, comprising:
a photosensor configured to generate photocurrent in response to incident light received from an external scene;
a photocurrent-to-voltage converter coupled to the photosensor to convert the photocurrent to a first voltage; and
a difference circuit AC-coupled to the photocurrent-to-voltage converter,
wherein the difference circuit includes a source follower transistor and a switched-capacitor filter having an input coupled to the photocurrent-to-voltage converter and an output coupled to a gate of the source follower transistor,
wherein the switched-capacitor filter includes (a) a first capacitor coupled between the input and the output of the switched-capacitor filter, (b) a second capacitor having a first plate coupled to the output of the switched-capacitor filter, and (c) a reset transistor coupled between a reference voltage and the output of the switched-capacitor filter, and
wherein the difference circuit is configured to sample a reference light level based at least in part on the reference voltage and the first voltage at a first time, and to generate a difference signal based at least in part on a second voltage at the gate of the source follower transistor, wherein the second voltage is based at least in part on the reference light level and the first voltage at a second time, and wherein the difference signal is indicative of whether the event driven pixel has detected an event in the external scene.