Patent ID: 6872910

Claim:
A laser irradiation apparatus for irradiating a laser beam having a linear or rectangular shape on an irradiation surface, comprising: a laser oscillator; an optical system for transforming the shape of the laser beam on the irradiation surface into the linear or rectangular shape; and a stage moving in at least one direction; wherein the optical system includes, in a width direction of the laser beam, a first optical system serving to convert the laser beam into a parallel light with respect to a traveling direction of the laser beam, and a second optical system serving to divide the laser beam of the parallel light into plural beams, to unite them to make one beam at the irradiation surface, and to unify energy of the laser beam in which the shape on the irradiation surface becomes linear or rectangular, and in a longitudinal direction of the laser beam, a third optical system serving to divide the laser beam into plural beams in a direction perpendicular to the traveling direction of the laser beam, and a fourth optical system serving to unite the divided laser beams to make one beam at the irradiation surface, and to unify energy of the laser beam in which the shape on the irradiation surface becomes linear or rectangular, and means for making differences between optical paths from outlets of the respective laser beams divided by the second optical system to the irradiation surface longer than a coherent length of the laser beam.