US Patent 11181419 Photon sensing with threshold detection using capacitor-based comparator

A threshold detection circuit includes a plurality of capacitors. A plurality of switching circuits is coupled to the capacitors such that a first end of each of the capacitors is coupled to a corresponding photon sensor during detection intervals, and the first end of each capacitor is coupled to a variable initialization value during reset intervals. A threshold number of the capacitors are initialized to a first value and the remaining capacitors are initialized to a second value during reset intervals. A comparator is coupled to a second of the capacitors to generate a detection event in response to the threshold number of photon sensors sensing one or more incident photons during detection intervals.