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US 6,650,477 B2Granted
Diffractive optical element and optical apparatus having the same
AssigneeCanon Kabushiki Kaisha
InventorTakehiko Nakai
Life of this patent
Estimating the term…
Abstract
A diffractive optical element includes a diffraction optical part provided with a phase-type diffraction grating. The diffraction grating of the diffraction optical part has on the surface thereof minute uneven structure of which the period is substantially constant. The period is smaller than a wavelength used.
Claims8
A laminated-type diffractive optical element comprising:
- a first diffraction optical part provided with a phase-type diffraction grating;
- and
- a second diffraction optical part provided with a phase-type diffraction grating;
- wherein said laminated-type diffractive optical element has high diffraction efficiency in a desired used wavelength region by making a material forming the phase-type diffraction grating of said first diffraction optical part different from a material forming the phase-type diffraction grating of said second diffraction optical part,
- at least one of the diffraction gratings of said first diffraction optical part and said second diffraction optical part has on the surface thereof minute uneven structure smaller than a predetermined wavelength in the used wavelength region, and
- said first diffraction optical part and said second diffraction optical part are disposed in proximity to each other with an air layer interposed therebetween.
3 more elements
Dependencies are inferred from the claim text.