SYSTEM FOR DETERMINING A VIDEO OFFSET FROM DARK PHOT0SENSORS IN AN IMAGE SENSOR ARRAY

In a photosensitive device wherein voltages are read sequentially from a dark, or dummy, photosensor and a plurality of active photosensors with each of a series of scans, a circuit downstream of the photosensors resets the offset value of the voltage signals, based on successive voltage readings from the dark photosensor. An RC circuit in parallel with the video line maintains a running average of readings from the dark photosensor over a large number of scans. This averaging of many dark-pixel readings averages out short-term thermal noise on the dark photosensor, for a truer offset value.