System for determining a video offset from dark photosensors in an image sensor array

Claim 1

A photosensitive device, comprising: a set of active photosensors, each active photosensor outputting a voltage signal representative of light intensity thereon; a dark photosensor, the dark photosensor being adapted to receive no light thereon; a video line, adapted to receive voltage signals in a readout sequence from the dark photosensor and each active photosensor of the set of photosensors; a correction capacitor directly connected to the video line, the correction capacitor adapted to retain a correction charge thereon to influence the voltage signals from the active photosensors; and means for determining the correction charge on the correction capacitor, said determining means including means for sampling a voltage signal from the dark photosensor over at least three readout sequences and deriving the correction charge based on a plurality of sampled voltage signals from the dark photosensor, the determining means including means for applying a reference voltage to the correction capacitor when the voltage related to a plurality of voltage signals from the dark photosensor is applied to the correction capacitor.