Agfa-Gevaert Ag

Hans Krenn

Hans J Vedder

A computer-controlled laser imaging system for switching on a laser imaging beam at the beginning of a line of an image surface has a laser and lens for emitting a laser-light beam, an acoustic/optical modulator for receiving and modulating the beam into a primary beam of first-order diffraction corresponding to the desired image and for separating in a y-direction transverse to the x-direction from the laser-light beam an unmodulated O.sup.th -order secondary beam for use in determining line start, and a first telescopic lens system and a rotary polygonal mirror for deflecting the modulated beam in the x-direction of the line to be written. The secondary beam is focussed through the first lens system on the mirror in registration with the primary modulated beam so that the primary and secondary beams cross on the mirror. A second telescopic lens system and a projecting lens receive the deflected main beam and cast it on the image surface. A photodetector in the second lens system is positioned in the secondary beam and is also positioned to intercept the primary beam generally at the beginning of a line. An electronic circuit is connected between the photodetector and the modulator for initiating modulation when the photodetector is impinged by the beams.

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Grasbrunn, Germany

Hans Krenn