Patent ID: 9400396
Filing Date: 2016-07-26
CPC Classification: G02B

Claim Text:
1. A diffractive optical element comprising: a diffraction grating including a base surface, a plurality of grating surfaces, and a plurality of grating wall surfaces, the plurality of grating surfaces and the plurality of grating wall surfaces being arranged on the base surface, wherein the diffraction grating is made from a resin material containing inorganic nanoparticles that are dispersed unevenly to provide a refractive index distribution, wherein an inclination of each of the grating surfaces gradually gets smaller as a distance from the center of the base surface increases, wherein the refractive index distribution causes a rate of increase of a phase difference of light transmitting through the diffraction grating to increase as the distance from the center of the base surface increases, and wherein a height of each of the grating wall surfaces is determined based on the refractive index distribution to reduce the rate of increase of the phase difference.