Patent ID: 8736651

Claim:
An optical scanning apparatus comprising: a light source configured to emit a plurality of laser beams; a deflector configured to deflect the laser beam so that the laser beam emitted from said light source scans a photoconductor; a beam splitter configured to separate the laser beam emitted from said light source toward said deflector, said beam splitter being arranged between said light source and said deflector on an optical path of the laser beam; a first detection unit configured to detect a laser beam separated from the laser beam emitted from said light source toward said deflector; an optical element configured to guide the laser beam deflected by said deflector to the photoconductor; a second detection unit configured to detect the laser beam deflected by said deflector in order to detect defocus amount of the laser beam guided to the photoconductor, said second detection unit being arranged at a position corresponding to a non-image forming area outside an image forming area of the photoconductor; a focusing unit configured to focus the scanning laser beam onto the photoconductor based on a detection result of said second detection unit; and a control unit configured to control said light source, wherein said control unit controls said light source so that the respective laser beams impinge on said first detection unit at different timings and controls the light amount of the respective laser beams based on detection results of said first detection unit, and wherein said control unit controls said light source so that a laser beam, which is used for correcting defocus thereof, among the plurality of laser beams impinges on said second detection unit and controls the light amount of the laser beam used for correcting defocus thereof based on detection result of said first detection unit of a laser beam separated from the laser beam used for correcting defocus thereof by said beam splitter when the laser beam used for correcting defocus thereof beams impinges on said second detection unit.