Diffractive optical element and optical system having the same
AssigneeCanon Kabushiki Kaisha
InventorTakehiko Nakai
Life of this patent
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Abstract
In a diffractive optical element, which is formed by laminating at least three layers of diffraction gratings made of at least three kinds of materials which differ in dispersion, at least three design wavelengths are set.
Claims17
A diffractive optical element formed by laminating at least three layers of diffraction gratings made of at least three kinds of materials which differ in dispersion,
- wherein thicknesses and materials of said diffraction gratings are determined in such a manner that diffraction efficiency for each of at least three wavelengths in an operable wavelength spectrum becomes 100%.
A diffractive optical element formed by laminating L diffraction gratings, L being three or more, including a first diffraction grating, a second diffraction grating, and up through an L-th diffraction grating, wherein, letting a grating thickness of said first diffraction grating be denoted by d1, a grating thickness of said second diffraction grating be denoted by d2, a grating thickness of said L-th diffraction grating be denoted by dL, a refractive index of said first diffraction grating at a wavelength .lambda. be denoted by n1(.lambda.), a refractive index of said second diffraction grating at the wavelength .lambda. be denoted by n2(.lambda.), a refractive index of said L-th diffraction grating at the wavelength .lambda. be denoted by nL(.lambda.), a wavelength within an operable wavelength spectrum be denoted by .lambda.0, and a design order of diffraction be denoted by m, the following condition is satisfied:
- ##EQU12## 10.
A diffractive optical element formed by laminating L diffraction gratings, L being three or more, including a first diffraction grating, a second diffraction grating, and up through an L-th diffraction grating, wherein, letting a grating thickness of said first diffraction grating be denoted by d1, a grating thickness of said second diffraction grating be denoted by d2, a grating thickness of said L-th diffraction grating be denoted by dL, a refractive index of said first diffraction grating at a wavelength .lambda. be denoted by n1(.lambda.), a refractive index of said second diffraction grating at the wavelength .lambda. be denoted by n2 (.lambda.), a refractive index of said L-th diffraction grating at the wavelength .lambda. be denoted by nL(.lambda.), a wavelength within an operable wavelength spectrum be denoted by .lambda.0, and a design order of diffraction be denoted by m, the following condition is satisfied:
- ##EQU13##
Dependencies are inferred from the claim text.