Camera system and associated method for removing reset noise and fixed

Abstract

A low noise operation method for a camera system having an image sensing active pixel array, the method comprising the steps of: (a) providing an optical shutter in front of an image sensing pixel array of a camera system, said image sensing pixel array having an image sensing face defined by a series of active pixels arranged in rows and columns; (b) while said shutter is closed, resetting each said pixel and then reading a first output from each said pixel; (c) opening said optical shutter for a predetermined exposure period so as to allow light to be incident upon said image sensing face of said pixel array; (d) closing said optical shutter and then reading a second output from each said pixel, without resetting said pixels; and (e) subtracting one of said first and second outputs from the other of said first and second outputs for each said pixel, so as to obtain a first difference signal for each said pixel, which first difference signal is substantially free of reset and fixed offset noise components. The first and second pixel outputs are preferably subtracted on-the-fly. The method may also include additional steps for estimating dark current fixed pattern noise and producing a modified pixel output signal which is substantially free of reset noise, fixed offset noise and dark current fixed pattern noise.