Patent ID: 7616364

Claim:
A scanning-optical system that converges, with a single lens, a divergent luminous flux, which is deflected in a main scanning direction by an optical deflector, on a surface of a scan target, the scanning optical system comprising: a lens configured to have two surfaces in a biconvex shape in both the main scanning direction and a sub-scanning direction, wherein the surfaces are anamorphic surfaces, at least one of the surfaces of the lens configured to have two surfaces in a biconvex shape in both the main scanning direction and a sub-scanning direction is a toric surface in which a line that connects, on a cross section in the main scanning direction, centers of curvature in a cross section in the sub-scanning direction is nonlinear, and a change of the curvature of the toric surface in the cross section in the sub-scanning direction along the main scanning direction is asymmetric with an optical axis of the lens.