Patent ID: 7589756

Claim:
An optical scanning device for an image forming apparatus that forms a color image by combining a plurality of single color images formed on a plurality of photosensitive elements, the optical scanning device comprising: a plurality of light sources each of which emits an optical beam; a deflecting unit that deflects the optical beams from the light sources; a plurality of optical elements provided for each of the optical beams, sequentially arranged between the deflecting unit and the photosensitive elements, to guide the optical beams deflected by the deflecting unit to the photosensitive elements; a pair of beam detecting units provided for each of the optical beams for detecting at least one of a position of the optical beam in a sub scanning direction and a position of the optical beam in a main scanning direction, the pair of beam detecting units including a first beam detecting unit and a second beam detecting unit; and a color-misalignment correcting unit provided for each of the optical beams for changing an optical-beam irradiating position on each of the corresponding photosensitive elements based on a result of detection by the corresponding pair of beam detecting units, wherein the pair of beam detecting units being, arranged between the optical element that is closest to the corresponding photosensitive element and the corresponding photosensitive element, integrally fitted to a housing of the optical scanning device, fixed between holding members that hold the optical scanning device and a dustproof glass through which the corresponding optical beam is transmitted, and arranged on a scanning line of the corresponding optical beam so that the corresponding optical beam outside an effective image area enters the pair of beam detecting units, and each first beam detecting unit being placed at a position on one of the holding members and each second beam detecting unit being placed at a position on another of the holding members.