| 摘要 |
A diffractive optical element having plural diffraction grating surfaces accumulated, wherein a pair of diffraction grating surfaces are positioned so that a protrusion and/or a recess formed on an outside of one diffraction grating surface engages with a recess and/or a protrusion formed on an outside of the other diffraction grating surface, and wherein the pair of diffraction grating surfaces are defined on materials having different refractive indices and different dispersions and being formed into a kinoform, or a shape and a height of blazed or binary, close to it, such that a largest optical path difference to be applied to light rays passing through the diffraction grating surfaces with respect to plural wavelengths becomes equal to a multiple, by an integral number, of the wavelength.
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