Multilayer antireflective coating with a graded base layer
First Claim
2. A low reflectance article comprising:
- a supporting surface having a refractive index, and a visible reflectance of a predetermined value;
a first film comprising a mixture of oxides, the first film having a first surface and a second surface opposite to the first surface with the second surface of the first film on the supporting surface, the first film at interface provided by the second surface of the first film and the supporting surface having a refractive index approximately equal to the refractive index of the supporting surface and between the first and second surfaces of the first film having a refractive index having a generally increasing value as the distance from the second surface of the film increases, anda second film having a first surface and a second surface opposite to the first surface with the second surface of the second film contacting the first surface of the first film, the second film having a substantially uniform refractive index throughout its thickness, with the refractive index substantially equal to the square root of the product of the refractive index of the first film at the first surface of the first film and refractive index of medium in contact with the first surface of the second film and an optical thickness approximately equal to one quarter of a selected design wavelength.
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Accused Products
Abstract
An antireflectance coating is disclosed comprising a first graded layer wherein the composition is varied throughout the thickness of the layer such that the refractive index of the graded layer varies from a low refractive index approximately matching the refractive index of the substrate at the interface of the graded layer and the substrate to a higher refractive index at the surface of the graded layer opposite the interface with the substrate, and a second substantially homogeneous layer of a composition selected to have a refractive index which is approximately the square root of the product of the higher refractive index of the graded layer and the refractive index of the incident medium at the surface of the second layer opposite the interface of the second layer with the graded layer, having an optical thickness of approximately at least one quarter of a selected design wavelength. The antireflectance properties of the coating of the present invention can be expanded to a broader range of reflected wavelengths by incorporating, between the graded layer and the second substantially homogeneous layer, an intermediate layer having a relatively high refractive index and an optical thickness of about half the design wavelength.
75 Citations
33 Claims
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2. A low reflectance article comprising:
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a supporting surface having a refractive index, and a visible reflectance of a predetermined value; a first film comprising a mixture of oxides, the first film having a first surface and a second surface opposite to the first surface with the second surface of the first film on the supporting surface, the first film at interface provided by the second surface of the first film and the supporting surface having a refractive index approximately equal to the refractive index of the supporting surface and between the first and second surfaces of the first film having a refractive index having a generally increasing value as the distance from the second surface of the film increases, and a second film having a first surface and a second surface opposite to the first surface with the second surface of the second film contacting the first surface of the first film, the second film having a substantially uniform refractive index throughout its thickness, with the refractive index substantially equal to the square root of the product of the refractive index of the first film at the first surface of the first film and refractive index of medium in contact with the first surface of the second film and an optical thickness approximately equal to one quarter of a selected design wavelength. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A low reflectance article comprising:
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a supporting surface having a refractive index, and a visible reflectance of a predetermined value; a first film comprising a mixture of oxides, the first film having a first surface and a second surface opposite to the first surface with the second surface of the first film on the supporting surface, the first film at interface provided by the second surface of the first film and the supporting surface having a refractive index approximately equal to the refractive index of the supporting surface and between the first and second surfaces of the first film having a refractive index having a generally increasing value as the distance from the second surface of the film increases; a second film having a first surface and a second surface opposite to the first surface with the second surface of the second film spaced from the first surface of the first film, the second film having a substantially uniform refractive index throughout its thickness, with the refractive index substantially equal to the square root of the product of the refractive index of the first film at the first surface of the first film and refractive index of medium in contact with the first surface of the second film and an optical thickness approximately equal to one quarter of a selected design wavelength, and a third film between the first and second films, the third film having an optical thickness of about one-half the selected design wavelength. - View Dependent Claims (1, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification