Patent ID: 7466333

Claim:
An optical scanning apparatus comprising: a light source that emits a light beam; a deflecting unit having a deflecting surface that deflects and scans the light beam emitted from the light source; a light-power detector that detects the intensity of the light beam deflected and scanned by the deflecting surface of the deflecting unit; an imaging optical unit that focuses the light beam deflected and scanned by the deflecting surface of the deflecting unit on a surface to be scanned; a light-power-detection optical unit for guiding the light beam deflected and scanned by the deflecting surface of the deflecting unit toward the light-power detector; and an automatic power controller that controls the intensity of the light beam emitted from the light source on the basis of a signal obtained from the light-power detector, wherein the light-power-detection optical unit establishes an optically conjugate relationship between the deflecting surface of the deflecting unit and a light-receiving surface of the light-power detector in the main-scanning plane, and a scanning angular velocity Vapc on the light-receiving surface of the light-power detector satisfies the following expression: Vapc<f /10 where f is fθ coefficient of the optical scanning apparatus in the unit of mm/rad.