Antireflection film, and optical element and optical device including same
AssigneeCanon Kabushiki Kaisha
InventorKAZUE UCHIDA
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Abstract
An antireflection film that is formed on an optical surface of a base material includes first to fourth layers disposed in order from a side of the base material. The fourth layer has a refractive index that decreases as the fourth layer is away from the base material. The following inequalities are satisfied: n1>n2, n2<n3, and n3>n4, where n1, n2, and n3 are refractive indices of the first to third layers respectively at a wavelength of 550 nm, and n4 is a maximum value of the refractive index of the fourth layer at a wavelength of 550 nm.
Claims20
An antireflection film that is formed on an optical surface of a base material, the antireflection film comprising:
- first to fourth layers disposed in order from a side of the base material, wherein the fourth layer has a refractive index that decreases as the fourth layer is away from the base material, and
- wherein the following inequalities are satisfied:
- n
- 1
- >
- n
- 2
- ,
- n
- 2
- <
- n
- 3
- ,
- and
- n
- 3
- >
- n
- 4
- where n1, n2, and n3 are refractive indices of the first to third layers respectively at a wavelength of 550 nm, and
- n4 is a maximum value of the refractive index of the fourth layer at a wavelength of 550 nm.
An antireflection film that is formed on an optical surface of a base material, the antireflection film comprising:
- first to fourth layers disposed in order from a side of the base material,
- wherein the fourth layer has a refractive index that decreases as the fourth layer is away from the base material,
- wherein the first layer is in contact with the optical surface and contains an organic compound having at least one of an aromatic ring and an imide ring,
- wherein the second layer contains an organic compound, and
- wherein the third layer and the fourth layer each contain aluminum oxide.
Dependencies are inferred from the claim text.