Patent ID: 7997739
Filing Date: 2011-08-16
Classification: G02B,H04N

Abstract:
1. An optical beam scanning device that is capable of causing light from a light source to scan in a main scanning direction on photoconductive surfaces of respective plural photoconductive members, the optical beam scanning device comprising: a rotating deflector that reflects and deflects an incident light beam with plural reflecting surfaces arrayed in association with the respective plural photoconductive members in a rotating direction to thereby cause the incident light beam to scan in the main scanning direction, tilt angles with respect to a rotation axis of the rotating deflector of the respective plural reflecting surfaces being set to angles corresponding to the photoconductive members associated with the respective reflecting surfaces; a post-deflection optical system that guides light beams reflected and deflected by the respective plural reflecting surfaces in the rotating deflector to the photoconductive surfaces of the photoconductive members corresponding to the respective reflecting surfaces, wherein the post-deflection optical system includes a shared optical element that gives, according to positions of incidence of the light beams, power to light beams, which should be reflected and deflected by the rotating deflector and guided to the respective plural photoconductive members, such that light beams guided to the photoconductive surfaces by the post-deflection optical system have a predetermined optical characteristic on the photoconductive surfaces, the post-deflection optical system guides, after principal rays of light beams located at both ends in the sub-scanning direction among plural light beams guided by the post-deflection optical system pass the shared optical element, light beams reflected and deflected by the respective plural reflecting surfaces in the rotating deflector to the photoconductive surfaces of the photoconductive member corresponding to the respective reflecting surfaces through optical paths that pass an upper side and a lower side of an optical axis of the shared optical element in the sub-scanning direction, all the respective light beams which should be reflected and deflected by the rotating deflector and guided to the respective plural photoconductive members, pass the shared optical element; and a pre-deflection optical system that shapes the light from the light source to be a light beam of a predetermined sectional shape and guides the light beam to the rotating deflector, the pre-deflection optical system guiding the light from the light source to the rotating deflector through an optical path that passes, in the sub-scanning direction, a position further apart from the optical axis of the post-deflection optical system than all light beams after reflection and deflection guided by the post-deflection optical system.