Patent ID: 6954296

Claim:
A scanning optical system for emitting at least one beam scanning in a main scanning direction, comprising: a light source that emits at least one beam; a polygonal mirror that rotates and deflects the at least one beam to scan in the main scanning direction within a predetermined scanning range; and an imaging optical system that converges the at least one beam deflected by said polygonal mirror to form at least one beam spot on a surface to be scanned, the at least one beam spot scanning in the main scanning direction on the surface to be scanned, wherein said imaging optical system has: a scanning lens; and a compensation lens provided on the surface side with respect to said scanning lens, said compensation lens compensating for curvature of field, wherein said light source is arranged such that the at least one beam emitted by said light source is incident on the polygonal mirror from outside of the predetermined scanning range in the main scanning direction and is incident on the polygonal mirror with the at least one beam being inclined in an auxiliary scanning direction with respect to a plane perpendicular to a rotational axis of said polygonal mirror, wherein at least one surface of said scanning lens has a first anamorphic surface, power of said first anamorphic surface in the auxiliary scanning direction is distributed asymmetrically in the main scanning direction with respect to an optical axis of said scanning lens, wherein power of each surface of said compensation lens in the auxiliary scanning direction is distributed symmetrically with respect to a center position of said each surface.