| 摘要 |
PROBLEM TO BE SOLVED: To provide a scanning optical system capable of restraining the curve of a scanning line on a surface to be scanned even when luminous flux is made incident on a polygon mirror at a certain angle in a subscanning direction. SOLUTION: This scanning optical system is equipped with a light source part 10 emitting two lines of luminous flux, a polygon mirror 20, a scanning lens 30 constituted of a 1st lens 31 and a 2nd lens 32, and a correction lens 50, and forms a beam spot on a photoreceptor drum 60. One convex surface of the scanning lens 30 is a toric surface and the surface of the correction lens 50 on the polygon mirror 20 side is an anamorphic aspherical surface. The surfaces satisfy a following condition. -1.1<rz2 /rz1 <-0.3 Provided that rz1 means the radius of curvature in the subscanning direction of the toric surface and rz2 means the radius of curvature in the subscanning direction of the anamorphic aspherical surface.
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