SURFACE TILT CORRECTING OPTICAL SYSTEM

摘要

PROBLEM TO BE SOLVED: To correct a surface tilt with high precision by the surface tilt correcting optical system which is used for an optical scanning device. SOLUTION: A light beam L which is emitted from a laser light source 11 and deflected by a polygon mirror 13 rotating at a high speed is imaged on the surface of a photosensitive material 20 through an fθlens 15 to make a scan in a horizontal scanning direction X at an equal speed, and variation to a vertical scanning direction Y due to a surface tilt of the polygon mirror 13 is corrected by an in-mirror lens 18 which is arranged between the fθlens 15 and photosensitive material 20 and has a concave cylindrical refracting surface and a concave cylindrical reflecting surface.