Optical scanning apparatus and an image forming apparatus using the same which is capable of reducing pitch unevenness in wave optics and sub-scanning field curvature

摘要

An optical scanning apparatus, including: a light source unit; a deflection unit; an incident optical system; and an imaging optical system, wherein at least one optical surface of a plurality of imaging lenses included in an imaging optical system has a non-circular shape in a sub-scanning section perpendicular to a main scanning direction, and a non-circular amount of the non-circular shape changes along the main scanning direction, and wherein the followings are satisfied: ds(Y=0)<0; and ds(Y=Ymax)>0, where ds(Y=0) and ds(Y=Ymax) respectively represent a paraxial field curvature at a center position in a sub-scanning direction perpendicular to the main scanning direction and a paraxial field curvature in the sub-scanning direction at a maximum image height in an effective scanning range of the surface to be scanned by the beam from the light source unit in the main scanning direction, among field curvatures at a center position in the effective scanning range.

主权项

1. An optical scanning apparatus, comprising:
a light source unit emitting beam from an emitting point; a deflection unit which deflects a beam from the light source unit for scanning a surface to be scanned in a main scanning direction; an incident optical system which forms a focal line image of the emitting point; and an imaging optical system including a plurality of optical surfaces for forming an image of the emitting point by using the beam deflected by the deflection surface on the surface to be scanned or a vicinity thereof, wherein at least one of the plurality of optical surfaces has a non-circular shape in a sub-scanning section perpendicular to the main scanning direction, and a non-circular amount of the non-circular shape changes along the main scanning direction, and wherein the following conditions are satisfied:
ds(Y=0)<0;andds(Y=Ymax)>0,where ds(Y=0) represents a paraxial field curvature in the sub-scanning section at a center position within an effective scanning range of the surface to be scanned in the main scanning direction and ds(Y=Ymax) represents a paraxial field curvature in the sub-scanning section at a maximum image height within the effective scanning range.