EXPOSURE OPTICAL DEVICE FOR PLATE MAKING MACHINE

摘要

PROBLEM TO BE SOLVED: To obtain the exposure optical device of a plate making machine by which density unevenness on a master paper surface caused by direct light and reflected light from an illuminating lamp is eliminated. SOLUTION: As for the exposure optical device of the plate making machine where plural illuminating lamps 13A-13D are positioned at four corners of an original cover glass on which an original is positioned so as to illuminate the original and an image is formed of the reflected light of an objective mirror opposed to the original cover glass on the master paper surface on an exposure stage by a projection lens, a frame-like exposure part mask 16 that does not disturb incident light from the original is positioned between the original cover glass and the objective mirror 8, and the direct light from the illuminating lamps 13B and 13D to the projection lens and the objective mirror 8 is prevented from being made incident by plural skirt walls 16a integrally formed at an exposure part mask 16.