Image conversion apparatus with gas discharge switching

Abstract

An image conversion apparatus has a line array of light responsive circuits connected in parallel across a voltage source. Each circuit comprises the capacitance of an elemental area of a photoconductive insulating layer arranged in series with a capacitor which is shunted by a normally open switch. The levels to which charge is distributed in the capcitance of the photoconductive insulating layer and in its associated capacitor is related to the quantity of light incident on the elemental area of the photoconductive insulating layer over intervals an associated switch is open. Closure of a switch serves to discharge its associated capacitor and to cause the capacitance of the photoconductive insulating layer to charge to the voltage of a source from a lower level obtained during open switch intervals. The magnitude of the charging current is related to the quantity of light incident on the elemental area of the photoconductive insulating layer. The switches take the form of gas spaces which are ignitable in turn by read pulses whereby a signal train of individual pulses of magnitudes corresponding to light incident on discrete circuits in the array is generated.