Diffractive optical element and optical system having the same
First Claim
1. A diffractive optical element having a first diffraction grating surface formed at a boundary between first and second layers made of materials of different dispersions and a second diffraction grating surface formed at a boundary between the second layer and air to enhance diffraction efficiency of a design order over a wavelength region,wherein at least one of the layers is made of a plastic resin material, wherein, rates of change in refractive index due to temperature variation of the materials of the first and second layers are dn1/dt, respectively, a thickness of a first diffraction grating formed by the first layer is d1, a thickness of a second diffraction grating formed by the second layer having the first and second diffraction grating surfaces is d2, and wherein said diffractive optical element satisfies the following conditions:
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Abstract
In a diffractive optical element having a diffraction grating formed at an interface between different substances, a total sum of values obtained by multiplying rates of change in refractive index due to temperature variations of the substances by a grating thickness of the diffraction grating is smaller than a useful wavelength.
30 Citations
11 Claims
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1. A diffractive optical element having a first diffraction grating surface formed at a boundary between first and second layers made of materials of different dispersions and a second diffraction grating surface formed at a boundary between the second layer and air to enhance diffraction efficiency of a design order over a wavelength region,
wherein at least one of the layers is made of a plastic resin material, wherein, rates of change in refractive index due to temperature variation of the materials of the first and second layers are dn1/dt, respectively, a thickness of a first diffraction grating formed by the first layer is d1, a thickness of a second diffraction grating formed by the second layer having the first and second diffraction grating surfaces is d2, and wherein said diffractive optical element satisfies the following conditions:
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2. A diffractive optical element having diffraction gratings formed by a plurality of layers made of at least two kinds of materials of different dispersions to enhance diffraction efficiency of a design order over a wavelength region,
wherein at least one of the plurality of layers is made of a plastic resin material, wherein, a rate of change in refractive index due to temperature variation of the material of the L-th layer is dnoL/dt, a thickness of the diffraction grating formed by the L-th layer is dL, and wherein said diffractive optical element satisfies the following conditions:
Specification