Image sensor

Abstract

A linear image sensor of a self-scanning type comprising a phototransistor array and a scanning circuit, whose circuit comprises decoders of current switches connected dendritically, input signal converter circuits generating input signals for driving the current switches, and a current switch array which turns on or off charging currents to the phototransistors according to whether or not an output current of decoder exists, so that video signals from the phototransistors, when the output currents of decoder flow, are obtainable from the phototransistors in the charge storage mode, all the transistors for scanning circuit being operated in nonsaturation condition for high-speed operation and the input signals being encoded so that the input signals to the decoder vary by one bit at each scanning step for noise reduction. The cancellation circuit of dark signal and noise signal is also provided.