Patent ID: 8194319

Claim:
An optical system comprising a diffractive optical element and a refractive optical element on at least one of an object side and an image side of an aperture stop, wherein the following conditions are satisfied: |Δθ gd |>0.038 0.003<|δθ dC |<0.038 (Φ R ×ν d ×δθ dC )×(−Φ D )<0 where ν d represents an Abbe number of the refractive optical element, θ gd represents a partial dispersion ratio for a g-line and a d-line, θ dC represents a partial dispersion ratio for the d-line and a C-line, Φ R represents an optical power provided when light incident and exit surfaces of the refractive optical element are both in contact with air, and Φ D represents an optical power of the diffractive optical element, and wherein Δθ gd =θ gd −(−1.687×10 −7 ·ν d 3 +5.702×10 −5 ν d 2 −6.603×10 −3 ·ν d +1.462), and δθ dC =θ dC −(−0.1968θ gd +0.5480).