Patent ID: 7443557

Claim:
An optical beam scanning apparatus comprising: a light source for emitting one or plural luminous fluxes, a pre-deflection optical system for forming a luminous flux emitted from the light source to image the luminous flux as a line image in a direction corresponding to a main scanning direction, a scanning unit configured to scan the imaged luminous flux by the pre-deflection optical system against a scanning subject, and a post-deflection optical system for imaging the luminous flux scanned by the scanning unit on the scanning subject, wherein at least one optical parts for imaging the luminous flux scanned from the scanning unit on the scanning subject is provided in the post-deflection optical system; at least one projection on a vertical surface to a sub-scanning direction axis formed by an effective region through which the luminous flux passes is provided in the optical parts; and at least one positioning member having an engaging groove into which the projection is interfitted and which is engaged in a concave-convex shape in the main scanning direction against a housing unit is provided while being made opposing to the projection in the housing unit of the optical beam scanning apparatus.