Patent ID: 7245410

Claim:
An optical scanning device, comprising: a light source unit that emits a plurality of light beams; an optical deflector that deflects the light beams from the light source unit; and a scanning optical system that focuses the deflected light beams on different surfaces to be scanned, respectively, wherein each of the light beams is incident on a deflecting reflection surface of the optical deflector obliquely in a sub-scanning direction with respect to a line normal to the deflecting reflection surface, light beams that are deflected at a same deflecting reflection surface of the optical deflector are incident on the scanning optical system from both sides with respect to the line normal to the deflecting reflection surface in the sub-scanning direction, an even number of reflection mirrors reflecting the light beam in the sub-scanning direction are disposed on an optical path, from the deflecting reflection surface to a corresponding surface to be scanned, of a light beam having a largest incident angle that is incident on the deflecting reflection surface from one side of the line normal to the deflecting reflection surface in the sub-scanning direction, and an odd number of reflection mirrors reflecting the light beam in the sub-scanning direction are disposed on an optical path, from the deflecting reflection surface to a corresponding surface to be scanned, of a light beam having a largest incident angle that is incident on the deflecting reflection surface from an other side of the line normal to the deflecting reflection surface in the sub-scanning direction.