SCANNING IMAGE-FORMATION LENS, OPTICAL SCANNER AND IMAGE FORMING DEVICE

摘要

PROBLEM TO BE SOLVED: To realize high-density and excellent optical scanning by a small- diameter stable excellent light spot by excellently compensating wave front aberration on a pupil as well as the curvature of field and optical magnification in a scanning image-formation optical system. SOLUTION: This scanning image-formation lens condensing luminous flux deflected by a deflector 4 as the light spot on a surface to be scanned 7 is constituted of two or more lenses L1 and L2. As for the shape on a main scanning cross section, both surfaces of the lens L1 on the deflector side are convex and at least one surface is a non circular-arc, and the 1st surface of the lens L2 on the surface to be scanned side is convex and at least one surface is the non circular-arc, and the lens L2 has at least two special toroidal surfaces whose curvature on a subscanning cross section is changed in a main scanning direction.