Patent ID: 8184352

Claim:
An optical scanning device of opposed scanning type, comprising: a plurality of light sources corresponding to a plurality of photosensitive elements, the light sources being arranged substantially symmetrically about a rotating deflection unit that is located substantially in a center of an optical housing; a group of pre-deflection optical elements including at least one or a plurality of optical elements that shape divergent light from the light sources into light beams having a predetermined cross-sectional shape and make the light beams incident on the rotating deflection unit; and scanning optical systems which are provided to perform exposure scanning on the photosensitive elements with the respective corresponding light sources, each of which includes a reflecting optical element and at least one lens having power in a main-scanning direction and a sub-scanning direction, and which are distributed to right and left with the rotating deflection unit as an axis of symmetry, wherein optical elements of the respective scanning optical systems are arranged substantially symmetrically about the rotating deflection unit, and the optical elements are arranged in a same order of arrangement performing exposure scanning on the plurality of photosensitive elements simultaneously, wherein a plurality of rib structures are arranged on respective areas of an optical housing substrate where the group of pre-deflection optical elements are arranged, the areas extends from the respective light sources to a vicinity of the rotating deflection unit, and the plurality of rib structures are arranged asymmetrically in the right and left optical systems with the rotating deflection unit as the axis of symmetry, so as to suppress an amount of variation in positions of scanning lines of the light beams on the photosensitive elements when the areas are displaced by thermal expansion.