Patent ID: 7031078

Claim:
A diffractive optical element assembly comprising: a first diffractive optical element having a surface formed into a diffractive shape; and a second diffractive optical element having a surface formed into a diffractive shape, wherein the first diffractive optical element is made of an optical material in which n d >−6.667×10 −3 ν d +1.70 and θ g,F ≦−2×10 −3 ν d +0.59, where n d is a refractive index at d-line, ν d is an Abbe number at the d-line, and θ g,F is a second order dispersion at d-line, wherein the second diffractive optical element has an Abbe number greater than that of the first diffractive optical element, and wherein the diffracting surface of the first diffractive optical element and the diffracting surface of the second diffractive optical element are arranged opposite each other.