Light scanning assembly for electrophotographic printing plate making

Abstract

A light scanning assembly for apparatus including a copyboard, an optical train and a carriage carrying charging, exposure and toning devices. The copyboard is movable from a horizontal disposition to a vertical disposition at which it is scanned in synchronism with simultaneous movement of the carriage horizontally. The light scanning assembly comprises a support bracket mounting a pair of illuminating lamps disposed each with an associated elliptically configured reflector. The support bracket is driven translating the lamp pair and their common intersection band across the face of the copyboard synchronously with the movement of the carriage. A third lamp is mounted (with reflector) on a second bracket to illuminate through the copyboard and is movable vertically with the first bracket. The third lamp is energized only when a transparent document is carried by the copyboard. The first pair of lamps are not energized at that occasion. The brackets are pivotable to rotate said respective lamps and associated reflectors along a predetermined arc during the vertical translation thereof so that the light emitted therefrom is focused along a straight line continuously directed to the center of the optical train along the line representing the shortest distance to the lens so that the image always is in focus. A cam wheel on the bracket follows a canted or tapered guide surface formed on a vertically arranged leg supporting said light scanning assembly to effect pivoting of the said bracket, return of the bracket being effected solely by gravity.