Diffractive optical element having high diffraction efficiency at plural wavelengths and image-pickup optical system using the same

摘要

A diffractive optical element in which the maximum optical path length of light is an integral multiple of each of a plurality of wavelengths includes a diffractive grating configured by combining a first member and a second member having a refractive index lower than a refractive index of the first member and having dispersion higher than a dispersion of the first member. At least one of the first member and the second member is made of a glass material, and the diffractive grating is formed by the glass material which is heated to be softened using a thermal press forming, and has a concave grating shape that has a grating height increasing from a central part toward a peripheral part.

主权项

1. A diffractive optical element comprising:
a first member and a second member in contact with each other, wherein the second member has a refractive index lower than a refractive index of the first member and has a dispersion higher than that of the first member, wherein the first member is made of a resin material and the second member is made of a glass material, wherein the second member includes a plurality of diffractive grating portions each having a grating wall surface and a grating surface that merge with each other, wherein each of the diffractive grating portions is configured so that a grating height thereof increases as a distance increases away from an optical axis, wherein the diffractive optical element has a positive power, and wherein the following expressions are met:
ngd