Disclosed is an
optical scanning system and an image forming apparatus using the same, which is designed to reduce the overall size of the
system and to make uniform the
light spot diameter in a sub-scan direction, inside an effective scan region, as well as to ensure high-speed production of high-quality images, wherein the
optical scanning system includes a
light source, a condensing optical system, a deflector and an imaging optical system having one or more optical elements, wherein, in at least one optical element of the optical elements, the curvature of the opposite surfaces thereof changes continuously, inside an effective region, from the
optical axis toward the
peripheral portion thereof so that the sign of the curvature is reversed at the middle, and wherein, when the curvature
radius of the surface of that optical element facing the deflector side, at the
optical axis and in the sub-scan
sectional plane, is denoted by r10 while the least quantity of an absolute value of the curvature
radius of the surface facing the scan surface side in an effective region of the portion where the sign of the curvature
radius is reversed is denoted by |r2|min, the optical element satisfies a specific relation for them.