Patent ID: 7443415
Filing Date: 2008-10-28
Classification: G02B

Abstract:
1. An optical beam scanning device, comprising: a light deflecting device, at least a polygon mirror portion of which is covered by a cover having a cover window portion for keeping a passage for an entering/emitting light; a pre-deflection optical system for entering an optical beam from a light source into said light deflecting device; and a post-deflection optical system for focusing a reflection light from said light deflecting device on a surface to be scanned, wherein constituent elements of said light deflecting device and said post-deflection optical system and said cover window portion are so disposed that the pretreated light-shielding reflection light from said cover window portion, avoids from striking upon a flange portion and an edge portion of one or a plurality of said optical element parts within said post-deflection optical system, with respect to said entering light, the optical systems do not match, with the optical axis of the post-deflection optical system, the direction when the optical axis of entering light is projected on a plane including a central optical axis of the post-deflection optical system and a main scanning direction axis, and the optical systems are configured to partially overlap an incident light and a reflection light in an effective area of a cover glass; wherein the constituent elements of said light deflecting device and said post-deflection optical system and said cover window portion are disposed, so that the pretreated light-shielding reflection light from said cover window portion passes through an outside of a certain optical element part; and wherein a light shielding structure is provided in vicinity of the certain optical element part, through which said reflection light passes in the outside thereof.