Patent ID: 8693096

Claim:
A diffractive optical element comprising: multiple diffraction gratings that are laminated, wherein the multiple diffraction gratings include: a first combination defined by a combination of two diffraction gratings, among the multiple diffraction gratings, with grating side surfaces thereof contacting each other or disposed close to each other in a grating pitch direction; and a second combination defined by a combination of two diffraction gratings, among the multiple diffraction gratings, wherein at least one of the two diffraction gratings of the second combination is made of a material that is different from the materials of the two diffraction gratings of the first combination, wherein the following equation and conditional expressions are satisfied for a wavelength w (nm) in a range of 370 (nm)<w<730 (nm): N 1 Aw−N 1 Bw= 0; 16<( v 1 A−v 1 B )<75; 0.03 <|N 2 Ad−N 2 Bd|< 0.5; and 16<( v 2 A−v 2 B )<75, where N1Aw and N1Bw respectively denote refractive indices of the two diffraction gratings of the first combination at the wavelength w, v1A and v1B respectively denote Abbe numbers of the two diffraction gratings of the first combination, N2Ad and N2Bd respectively denote refractive indices of the two diffraction gratings of the second combination for a d-line, and v2A and v2B respectively denote Abbe numbers of the two diffraction gratings of the second combination.