| 摘要 |
PROBLEM TO BE SOLVED: To effectively correct the deformation of a spot shape generated in a sub-scanning oblique incident optical system by most adequately setting the shapes, arrangement, etc., of respective elements constituting an optical scanning optical system and to enable an fθcharacteristic and a curvature of field to be well corrected compatibly. SOLUTION: The luminous flux to be made incident on a polygon mirror 6 is made incident from below at a prescribed angle with a main scanning plane in order to make the luminous flux to be made incident on the polygon mirror 6 from the approximate center of an operating range in a main scanning direction. A scanning lens 7 which is a second optical system L2 is arranged in a position nearer to the polygon mirror 6 side than the intermediate position of a distance from the polygon mirror 6 to a plane 9 to be scanned in order to prevent the aberration generated by skew-incidence on the scanning lens 7. The optical axis of the scanning lens 7 is so set as to be paralleled with the main scanning plane and is set by shifting the optical axis to the prescribed extent in the subscanning direction from the main scanning plane.
|
