REFLECTION TYPE SCANNING OPTICAL SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a scanning optical system characterized by that the reflecting surface of a curved-surface reflecting mirror can be formed in a cuttable shape although the curvature of a scanning line on a scan object surface can be canceled. SOLUTION: The laser beam emitted by a laser light source 1 passes through a collimator lens 2 and a cylindrical lens 3 and is made incident on the respective reflecting surfaces of a polygon mirror 4 obliquely in the vertical scanning direction. The laser beam reflected by this polygon mirror 4 is reflected by the curved-surface reflecting mirror 5 obliquely in the vertical scanning direction and then converged on the scan object surface through a field curvature correcting lens 6. The reflecting surface of the curved-surface reflecting mirror 5 is machined into a rotationally symmetrical aspherical surface. The respective surfaces of the field curvature correcting lens 6 are machined into rotationally asymmetrical aspherical surfaces whose curvature in the vertical scanning direction and curvature center are set irrelevantly to the lens shape in the horizontal scanning direction.