Laser irradiation apparatus and method using a beam expander with two lenses, the position of the latter with respect to the laser oscillator governed by an equation

摘要

The present invention provides a laser irradiation apparatus and a laser irradiation method which can reduce displacement of entrance point of laser light (105) into a diffractive optical element (103), when laser light (105) enters the diffractive optical element (103) through a beam expander optical system (102). When the scale of laser light (105) emitted from a laser oscillator (101) is enlarged through a beam expander optical system (102) including two lenses (102a,102b), and the laser light (105) enters the diffractive optical element (103), the emission point of the laser light (105) and the first and second lenses (102a,102b) are arranged such that the positions of the emission point of the laser light (105) and the second lens (102b) are conjugate to each other by the first lens (102a).