Patent ID: 8797649

Claim:
An achromatic lens system comprising, in order from an object: a resin lens having positive refractive power; a diffractive optical element; and a resin lens having negative refractive power; they being cemented with each other, and having positive refractive power as a whole, the diffractive optical element being constructed by cementing two diffractive element members made of different optical materials with each other, and the cemented surface thereof being a diffractive optical surface on which grooves of a diffraction grating are formed, wherein the following conditional expression is satisfied: 0.2 ≦|R/f|≦ 1.3 where R denotes a radius of curvature of the-resin-lens-having-negative-refractive-power side surface of the resin lens having positive refractive power, and f denotes a focal length of the achromatic lens system.