Patent ID: 7116497

Claim:
An optical system comprising: a refractive optical element composed of a solid material that satisfies the following conditions: νd<30 θ gd <−3.333×10 −3 ·νd+ 1.40 θ gF <−2.615×10 −3 ·νd+ 0.67 where νd is the Abbe constant of the solid material, and θgd and θgF are partial dispersion ratios of the solid material, wherein, in the optical system, height from the optical axis of a point on the frontmost lens surface through which a paraxial marginal ray passes is smaller than the maximum value of heights from the optical axis of points on lens surfaces, on the rear side of an intersection P of the optical axis and a paraxial chief ray, through which the paraxial marginal ray passes, and in the case that the refractive optical element is disposed on the front side of the intersection P, the refractive optical element has a positive refractive power, and in the case that the refractive optical element is disposed on the rear side of the intersection P, the refractive optical element has a negative refractive power.