Patent ID: 8077368

Claim:
An optical scanning apparatus comprising: a plurality of light sources each of which emits a light beam to scan a corresponding one of a plurality of scan target surfaces; an optical deflector having a plurality of deflecting-reflecting surfaces, the light beams from the light sources being reflected by different deflecting-reflecting surfaces; a plurality of scanning optical systems each of which focuses a corresponding one of the light beams onto a corresponding one of the scan target surfaces, the light sources being arranged on same side of optical axes of all the scanning optical systems; and a plurality of synchronization detecting units, each of which detects a synchronization signal regarding one of a start point and an end point of scanning with one of the light beams on one of the scan target surfaces, wherein one of the synchronization detecting units detects the synchronization signal by receiving a light beam that is deflected by the optical deflector toward a side, which is the same as the side on which a corresponding one of the light sources is arranged, of a corresponding one of optical axes of a corresponding one of the optical scanning systems, another of the synchronization detecting units detects the synchronization signal by receiving a light beam that is deflected by the optical deflector toward a side, which is opposite to the side on which a corresponding one of the light sources is arranged, of a corresponding one of the optical axes of a corresponding one of the scanning optical systems, and each of the synchronization detecting units includes a photodetector that detects the synchronization signal, each photodetector being arranged on a side, which is opposite to the side on which the light sources are arranged, of a corresponding one of the optical axes of a corresponding one of the scanning optical systems.