Patent ID: 7262924

Claim:
An optical system comprising: a compound optical element including a lens element and a resin layer having optical characteristics different from optical characteristics of the lens element and provided on a surface of the lens element, wherein an interface between the lens element and the resin layer is aspherical, and wherein, when Rref is a reference radius of curvature of the interface within an effective diameter, L is a distance from a diaphragm, which determines an on-axis marginal ray, to the interface along an optical axis in a state in which a focal length of the overall optical system is at a minimum, ndg is a refractive index of a material of the lens element at the d-line, and ndj is a refractive index of a material of the resin layer at the d-line, the following expressions are satisfied: −1.5 <Rref/L<− 0.3 0.1 <|ndg−ndj|.