| 摘要 |
PROBLEM TO BE SOLVED: To correct an asymmetry component of scanning line bend with a simple structure by use of a common lens, without depending on a layout.SOLUTION: An optical scanner includes a plurality of light source devices 1, and deflects light beams from the light source devices 1 by means of a common optical deflector 5, to be condensed on different scanning surfaces 11a by means of an optical-scanning optical system, for scanning in a main scanning direction. The optical-scanning optical system includes a common lens 7 to be used for the light beams to be scanned on the same deflection/reflection surface, and individual lenses 8 arranged for each of the light beams and each having a surface shape symmetrical in the main scanning direction. In the optical scanner, a scanning lens satisfying a predetermined condition and having a power in a sub-scanning direction is arranged so that an optical axis is inclined with respect to a normal of a scanned surface under a predetermined condition. An asymmetry component (waviness component) of scanning line bend which is caused by polygon sag can be reduced, accordingly. An image forming apparatus including the optical scanner eliminates color misregistration and ensures high-quality image reproducibility. |
