Patent ID: 7750931

Claim:
An optical scanning apparatus comprising: a plurality of light sources; a deflecting unit having a deflecting surface, the deflecting surface configured to deflect a plurality of light beams emitted from the light sources; and a plurality of imaging optical systems provided in correspondence with the light beams deflected for scanning by the deflecting surface of the deflecting unit, wherein the imaging optical systems respectively form such corresponding light beams onto corresponding surfaces to be scanned, wherein the deflecting unit deflects the light beams so that the light beams scan the surfaces to be scanned in a uniform direction in the imaging optical systems, and wherein, defining an optical path length of an imaging optical system to be an optical distance from a deflection point of the deflecting unit to the corresponding surface to be scanned, an optical path length of an imaging optical system configured to form an image onto a surface to be scanned located physically closest to the deflecting unit is different from an optical path length of an imaging optical system configured to form an image onto a surface to be scanned located physically farthest from the deflecting unit, and the following condition is satisfied: 0.85 <K 1 /K 2 <0.98 where K 1 is a Kθ coefficient of an imaging optical system with a short optical path length from among the imaging optical systems, and K 2 is a Kθ coefficient of an imaging optical system with a long optical path length from among the imaging optical systems.