Patent ID: 6930833

Claim:
A diffractive optical element comprising: a plurality of diffraction gratings including at least two materials with different Abbe numbers ν d , wherein the plurality of diffraction gratings are layered with each other; wherein a partial dispersion ratio θ g, F with respect to a g-line and a F-line of the material constituting at least one of the plurality of diffraction gratings satisfies the following condition: θ g,F <(− 1/600)ν d +0.55 where θ g,F =( n g −n F )/( n F −n C ) ν d =( n d −1)/( n F −n C ) and n g , n F , n d and n C are the refractive indices at the g-line, the F-line, a d-line and a C-line, respectively, and wherein each of the plurality of diffraction gratings satisfies the following condition: d/P<⅙ where P is grating pitch and d is grating thickness.