OPTICAL SYSTEM FOR UNIFORMLY IRRADIATING LASER BEAM

摘要

PROBLEM TO BE SOLVED: To provide an optical system for forming an irradiation beam which brings about uniform intensity distribution on a face to be irradiated by superposing split beams obtained by splitting a laser beam while reducing an interference between the beams. SOLUTION: The optical system consists of a waveguide or a cylindrical lens array for splitting as a laser beam splitting means to split the laser beam from a laser beam source into beams spatially split in a beam cross section, and a lens for superposition which superposes the split beams on a face to be irradiated and irradiates the face with the superposed beam. The waveguide makes the width of the split beams into 1/2 times or more than a spatial coherence distance in the direction of a cross section in the laser beam cross section. A superposition irradiation means shifts and transfers each split laser beam on the face to be irradiated to each other to form the irradiation beam. A retarder plate is inserted between the laser beam splitting means and the lens for superposition, and delays one of the split beams adjacent to each other relative to the other by a long period compared to a time coherence distance, thereby reduces the interference of the split beams on the face to be irradiated. COPYRIGHT: (C)2004,JPO