The energy distribution of the beam spot on the irradiated surface changes due to the change in the oscillation condition of the laser or before and after the maintenance. The present invention provides an optical system for forming a rectangular beam spot on an irradiated surface including a beam homogenizer...http://www.google.ca/patents/US20050079645?utm_source=gb-gplus-sharePatent US20050079645 - Beam homogenizer, laser irradiation apparatus, and method for manufacturing semiconductor device
