Patent ID: 7489351

Claim:
An optical sensor covering an extended range of optical input intensity, comprising in combination: a photo detector for generating a photo-current at a rate that is a function of the optical input intensity; a first integrating well capacitor; a switch periodically connecting said photo detector to said integrating well capacitor for a predetermined time interval; a second integrating capacitor; a source of current; a second switch for connecting said source of current to said second integrating capacitor at the start of the predetermined time interval; a reference voltage; a comparator for comparing said reference voltage to a voltage on said integrating well capacitor during the predetermined time interval, said comparator generating an output signal when said voltage on said integrating capacitor reaches said reference voltage; said output signal causing said second switch to disconnect said source of current from said second integrating capacitor; and means for outputting the voltage on said first integrating well capacitor if it does not reach said reference voltage during said integrating interval and outputting the voltage on the second integrating capacitor when it is disconnected from said source of current if the voltage on said first integrating well capacitor does reach said reference voltage.