| 摘要 |
PROBLEM TO BE SOLVED: To suppress changes in a spot form on a plane to be scanned at applying of an oblique incident optical system to cause a light beam to enter at a prescribed angle both in a main scanning direction and in the subscanning direction. SOLUTION: This device is composed of a light source 10, collimating lens 11, first imaging optical system 14 having a cylindrical lens 12, rotating polygon mirror 20, and second imaging optical system 34 having an fθlens so that a light beam P is made to enter the rotating polygon mirror 20 at a certain angle both in the main scanning direction and in the sub-scanning direction. By disposing the cylindrical lens 12 with a generating line of the cylindrical lens 12 parallel to a plane, which is perpendicular to a rotation axis T of the rotary polygonal mirror 20, changes in the spot form on a plane 40 so as to be scanned can be suppressed. |
