MULTIBEAM INTERNAL DRUM SCANNING SYSTEM

摘要

An internal drum scanning system comprising a cylinder with an imaging surface, a laser source for generating a first and a second laser beam, a rotating deflector for deflecting the beams towards said imaging surface, a focussing lens for focussing the laser beams onto respective positions on said imaging surface, and a controllable optical elements which, during operation, is positioned such that its optical axis is displaced from the optical axis of the focussing lens, and which is adapted to direct the second laser beam onto said focussing leans at a varying incident angle causing the focussing lens to image the second laser beam onto the imaging surface such that, during relative rotation between the deflector and the cylinder, the focussing spot of the second laser beam is fixed relative to the optical axis.