Patent ID: 7643046

Claim:
A laser beam scanning device which scans a surface to be scanned by using a laser beam, comprising: a light source which emits the laser beam; a laser beam deflecting unit which deflects the laser beam emitted from the light source; a scanning optical system which condenses the laser beam deflected by the laser beam deflecting unit onto the surface to be scanned; a diffraction optical element which forms a pattern of a diffraction image by dividing the laser beam deflected by the laser beam deflecting unit into a plurality of laser beams; and a light detector which detects the pattern of the diffraction image, wherein, the pattern of the diffraction image at the light detector includes a plurality of images where intervals between the plural images are different in a first direction corresponding to the main scanning direction at a position in a second direction corresponding to the sub scanning direction at least at a part of the plural images.