Antireflection coating and optical element using the same

An antireflection coating comprising at least a first layer constituted by a coating with refractivity of n1 and optical thickness of d1 which is provided on a substantially transparent substrate with refractivity of n0, and a second layer constituted by a MgF2 coating with optical thickness of d2 which is provided on the first layer,

• wherein said n0, n1, d1 and d2 satisfy the following conditions:
• 1.42≦n0≦1.53,
• 1.95≦n1≦2.35, 0.42λ≦d1≦0.46λ, and
• 0.17λ≦d2≦0.19λ,
• wherein the central wavelength of light to be prevented from being reflected is λ.

An antireflection coating comprising at least a first layer constituted by a SiO2 coating with optical thickness of d1 which is provided on a substantially transparent substrate with refractivity of n0, a second layer constituted by a coating with refractivity of n2 and optical thickness of d2 which is provided on the first layer, and a third layer constituted by a SiO2 coating with optical thickness of d3 which is provided on the second layer,

• wherein said n0, d1, n2, d2 and d3 satisfy the following conditions:
• 1.42≦n0≦1.53,
• 0.06≦d1≦0.07λ,
• 1.95≦n2≦2.35, 0.41λ≦d2≦0.45λ, and
• 0.16λ≦d3≦0.18λ,
• wherein the central wavelength of light to be prevented from being reflected is λ.

An antireflection coating comprising at least a first layer constituted by a MgF2 coating with optical thickness of d1 which is provided on a substantially transparent substrate with refractivity of n0, a second layer constituted by a coating with refractivity of n2 and optical thickness of d2 which is provided on the first layer, and a third layer constituted by a MgF2 coating with optical thickness of d3 which is provided on the second layer,

• wherein said n0, d1, n2, d2 and d3 satisfy the following conditions:
• 1.42≦n0≦1.53,
• 0.05λ≦d1≦0.07λ,
• 1.95≦n2≦2.35, 0.43λ≦d2≦0.46λ, and
• 0.16λ≦d3≦0.19λ,
• wherein the central wavelength of light to be prevented from being reflected is λ.

An antireflection coating comprising at least a first layer constituted by a coating with refractivity of n1 and optical thickness of d1 which is provided on a substantially transparent substrate with refractivity of n0, a second layer constituted by a SiO2 coating with optical thickness of d2 which is provided on the first layer, third layer constituted by a coating with refractivity of n3 and optical thickness of d3 which is provided on the second layer, and a fourth layer constituted by a SiO2 coating with optical thickness of d4 which is provided on the third layer,

• wherein said n0, n1, d1, d2, n3, d3 and d4 satisfy the following conditions:
• 1.42≦n0≦1.53,
• 1.95≦n1≦2.35, 0.08λ≦d1≦0.11λ,
• 0.06λ≦d2≦0.07λ,
• 1.95≦n3≦2.35, 0.24λ≦d3≦0.26λ, and
• 0.24λ≦d4≦0.26λ,
• wherein the central wavelength of light to be prevented from being reflected is λ.

An antireflection coating comprising at least a first layer constituted by a coating with refractivity of n1 and optical thickness of d1 which is provided on a substantially transparent substrate with refractivity of n0, a second layer constituted by a MgF2 coating with optical thickness of d2 which is provided on the first layer, third layer constituted by a coating with refractivity of n3 and optical thickness of d3 which is provided on the second layer, and a fourth layer constituted by a MgF2 coating with optical thickness of d4 which is provided on the third layer,

• wherein said n0, n1, d1, d2, n3, d3 and d4 satisfy the following conditions:
• 1.42≦n0≦1.53,
• 1.95≦n1<2.35, 0.11λ≦d1≦0.13λ,
• 0.05λ≦d2≦0.06λ,
• 1.95≦n3≦2.35, 0.23λ≦d3≦0.25λ, and
• 0.25λ≦d4≦0.27λ,
• wherein the central wavelength of light to be prevented from being reflected is λ.