GB1444099A - Electrophotographic copier - Google Patents

Abstract

1444099 Projection printing OCE-VAN DER GRINTEN NV 24 June 1974 [25 June 1973] 30128/73 Heading G2A A projection printer, for the copying of different size originals placed against fixed mutually perpendicular guide means, has (a) two alternative optical systems (corresponding to originals of two different sizes) of different focal length and having spaced optical axes, (b) a fixed illuminating system capable of providing an illumination zone of increasing brightness from centre to periphery (to counteract vignetting) and providing symmetrical illumination for one optical system and asymmetrical illumination for the other, and (c) an asymmetrical mask associated with the optical system having asymmetrical illumination. When the former optical system (with symmetrical illumination) corresponds to the original of smaller size, Fig. 3, one mask only is necessary. When, however, the former optical system corresponds to the original of larger size, Fig. 1, a symmetrical mask is necessary for this optical system. The separate optical systems may be formed by parate movable lenses, a compound lens of variable focal length or a single lens with movable mirrors. The asymmetrical mask may have an asymmetrical orifice or an asymmetrically situated circular orifice; and may be planar or tubular.