Patent ID: 7525710

Claim:
A scanning and imaging optical system that condenses beams of light deflected by an optical deflector toward a surface to be scanned, to form a light spot for optical scanning on the surface, comprising: a plurality of scanning lenses, wherein at least two of the scanning lenses are resin lenses that are formed by plastic molding and signs of a refractive index distribution Δn(X) at least in a vertical scanning direction of the two resin lenses are opposite to each other, a position coordinate in a horizontal scanning direction or in the vertical scanning direction is X, the refractive index distribution in a cross-section with respect to the position coordinate X is Δn(X), the refractive index distribution is in a cross-section in the horizontal scanning direction that includes an optical axis or in the vertical scanning direction of the resin lenses, and signs of the refractive index distribution Δn(X) at least in the vertical scanning direction are not identical for all of the resin lenses, one of the resin lenses has a thickness in a direction of the optical axis that is larger than an effective width in the vertical scanning direction and has a sectional shape in which the refractive index distribution, at least in the vertical scanning direction, increases toward a rim from a portion near the optical axis, the sectional shape being a shape of a cross-section in the vertical scanning direction, and another one of the resin lenses has a thickness in the direction of the optical axis that is smaller than an effective width in the vertical scanning direction and has a sectional shape in which the refractive index distribution, at least in the vertical scanning direction, decreases toward a rim from a portion near the optical axis, the sectional shape being a shape of a cross-section in the vertical scanning direction.