Patent ID: 6870652

Claim:
An optical scanning lens which is used in a scanning and image forming optical system which gathers a light flux deflected by a light deflector in the vicinity of a surface to be scanned, wherein: said lens is formed by a resin having the following properties: photoelasticity constant≦8(10 −13 cm 2 /dyne); saturation moisture absorption≦0.5(%); and mold shrinkage coefficient≧20.7(%), and the following condition is satisfied: 0 <|Δn ( x )−min[Δ n ( x )]|<34×10 −5 (A) wherein: Δn(x) denotes a refractive-index distribution existing inside said lens, in a range which the light flux passes through, in said lens; and min [Δn(x)] denotes the minimum value of said Δn(x).