Patent ID: 6411366
Filing Date: 2002-06-25
Classification: G03F

Abstract:
A method of triggering an exposure device to expose a printing plate according to an electronically stored model, said exposure device comprising an exposure head (1) including a light source (3), a picture generating unit (8), a copying optical element (9), an electric linear drive (14) for moving the picture generating unit (8) and a device (19) for automatically measuring and regulating a distance of the picture generating unit (8) from a surface of the printing plate and for automatically correcting deviations of said distance from a set value, wherein said electric linear drive has a positioning precision of better than 2 &mgr;m and said picture generating unit (8) comprises movable electronically individually triggerable micro mirrors arranged in a grid, said method comprising the steps of:a) breaking down the electronically stored model electronically into two-dimensional partial images; b) moving said exposure head (1) with the coping optical element (9) and the picture generating unit (8) by means of the electric linear drive (14) between respective exposure positions and halting said exposure head (1) at each of said exposure positions to make successive corresponding partial exposures on the surface of said printing plate, so that individual copies of said partial images made at said exposure positions are combined into a total copy of the electronically stored model; and c) prior to making each of said partial exposures measuring the distance of the picture generating unit (8) from the surface of the printing plate and automatically correcting deviations from the set value by means of said device (19) for automatically measuring and regulating; whereby said copies of said partial images are positioned to an accuracy of better than 5 &mgr;m and exposure times are reduced while maintaining copy quality.