Patent ID: 7609430
Filing Date: 2009-10-27
Classification: G02B

Abstract:
1. An optical beam scanning device that shapes a diverging ray from a light source to be a light beam having a predetermined sectional shape in a pre-deflection optical system including plural optical elements and deflects the light beam shaped by the pre-deflection optical system with a rotating deflector to cause the light beam to scan in a main scanning direction, wherein the pre-deflection optical system has optical elements arranged between the light source and reflecting surfaces of the rotating deflector in a light beam traveling direction and having negative power, among the plural optical elements forming the pre-deflection optical system, in at least one optical element in which a principal ray of the light beam from the light source is made incident on a position of incidence different from an optical path of an optical axis of the pre-deflection optical system in a sub-scanning direction orthogonal to the main scanning direction, a diffraction grating is formed on at least one of a plane of beam incidence and a plane of beam exit in the optical element, and the optical element having the diffraction grating formed therein has a plane of incidence formed as a convex surface and a plane of exit formed as a concave surface.