Patent ID: 7507947

Claim:
A method to increase effective differential dynamic range and common mode rejection for a differential pixel detector responsive to optical energy having a common mode component, the differential pixel detector including a first photodetector and an associated first capacitor, and a second photodetector and an associated second capacitor, the method comprising: (a) within an interval preceding start of an integration time T, setting voltage on each said capacitor to a reference voltage whose amplitude is substantially constant during said interval, but which reference voltage can have a substantially constant but different amplitude during another proceeding said interval; (b) during said integration time T, integrating photocurrent generated by said first photodetector in said first capacitor, and integrating photocurrent generated by said second photodetector in said second capacitor; (c) within said integration time T, before voltage developed across either said first capacitor or said second capacitor attains a saturation voltage Vsat associated with said differential pixel detector, setting the developed voltage on each said capacitor such that differential pixel detector signal is still determinable; and (d) within said integration time T and prior to step (c), transferring and storing at least a fraction of charge differential between charge on said first capacitor and charge on said second capacitor so as to isolate and preserve magnitude of differential detection charge so transferred and stored from any subsequent resetting operation at step (c).