Patent ID: 7538310

Claim:
A beam irradiation device comprising: a light source that emits laser beams; a scan means for scanning a target region with the laser beams emitted from the light source; an irradiation position detection means for detecting irradiation positions of the laser beams on the target region; a beam receiving means for detecting amounts of the laser beams reflected from the target region; and an error position detection means for making correspondence between the irradiation positions detected by the irradiation position detection means and the amounts of the reflected laser beams detected by the beam receiving means, comparing the amounts of the reflected laser beams for the respective irradiation positions, and detecting an irradiation position at which an intensity of the laser beams is nonuniform in the target region; and a light source control means for controlling the light source to change the intensity of the laser beams to the irradiation position that has been detected by the error position detection means; wherein the scan means scans the target region with the laser beams in horizontal direction; the light source control means controls the light source to irradiate the target region with the laser beams in pulse shape intensity with a predetermined interval, while the target region is scanned with the laser beams in horizontal direction by the scan means; and the error position detection means compares a first amount of the reflected laser beams for a first irradiation position with a second amount of the reflected laser beams for a second irradiation position that is adjacent to the first irradiation position, detects if a ratio of the second amount of the reflected laser beams to the first amount of the reflected laser beams is less than a predetermined ratio of 1 or less, and determines the second irradiation position as the irradiation position at which the intensity of the laser beams is nonuniform in the target region in response to the detection.