Three layer anti-reflection film

• US 3,934,961 A
• Filed: 09/21/1973
• Issued: 01/27/1976
• Est. Priority Date: 10/29/1970
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Itoh, Susumu, Kamiya, Osamu, Sekimura, Nobuyuki, Nishida, Keijiro
• Primary Examiner(s): Kendall, Ralph S.
• Assistant Examiner(s): Smith, John D.
• Application Number:
  US05/399,612
• Time in Patent Office: 858 Days
• Field of Search: 350/164, 117/33.3, 117/169 R, 117/211, 117/69
• US Class Current: 359/586
• CPC Class Codes: G02B 1/115 Multilayers
• CPC Class Codes: Y10T 428/2495 Thickness [relative or absolute]

Abstract

Three-layer anti-reflection coatings consisting of first, second and third layers, respectively positioned from a glass base plate. The optical film thickness of the first layer and the second layer is one-half of a designed wavelength while that of the third layer is one-fourth of the same. And the relationship among the refractive index of each layer is second layer (n₂) glass (n_g) first layer (n₁) third layer (n₃). The first layer is made of a mixture of Al₂ O₃ and ZrO₂.

Claims

1. A three-layer anti-reflection coating deposited by vapor-deposition consisting of a first layer, a second layer and a third layer being positioned in the recited order from a glass base plate:

the first layer having an optical thickness of one-half the designed wavelength and being composed of aluminium oxide and zirconium oxide;

the second layer having an optical thickness of one-half the designed wavelength; and

the third layer having an optical thickness of one-fourth the designed wavelength,

wherein the relationship among the refractive indices of the glass base plate, the first layer, the second layer, and the third layer is

that the second layer >

the glass base plate >

the first layer >

the third layer.

2. A three-layer anti-reflection coating deposited by vapor deposition consisting of a first layer, a second layer and a third layer being positioned in the recited order from a glass base plate with a refractive index of from 1.65 to 1.775:

the first layer having an optical thickness of one-half the designed wavelength and a refractive index of 1.63, said first layer being composed of aluminium oxide and zirconium oxide;

the second layer having an optical thickness of one-half the designed wavelength and a refractive index of about 2.05; and

the third layer having an optical thickness of one-fourth of the designed wavelength and a refractive index of 1.38.

3. A three layer anti-reflection coating deposited by vapor deposition consisting of a first layer, a second layer and a third layer being positioned in the recited order from a glass base plate with a refractive index of from 1.775 to 1.825:

the first layer having an optical thickness of one-half the designed wavelength and a refractive index of 1.68, said first layer being composed of aluminium oxide and zirconium oxide;

the second layer having an optical thickness of one-half the designed wavelength and a refractive index of about 2.05; and

the third layer having an optical thickness of one-fourth the designed wavelength and a refractive index of 1.38.

4. A three layer anti-reflection coating deposited by vapor deposition consisting of a first layer, a second layer and a third layer being positioned in the recited order from a glass base plate with a refractive index of from 1.825 to 1.875:

the first layer having an optical thickness of one-half the designed wavelength and a refractive index of 1.72, being composed of aluminium oxide and zirconium oxide;

the second layer having an optical thickness of one-half the designed wavelength and a refractive index of about 2.05; and

the third layer having an optical thickness of one-fourth of the designed wavelength and a refractive index of about 1.38.

5. A three layer anti-reflection coating deposited by vapor deposition consisting of a first layer, a second layer and a third layer being positioned in the recited order from a glass base plate with a refractive index of from 1.875 to 1.925:

the first layer having an optical thickness of one-half the designed wavelength and a refractive index of 1.75, being composed of aluminium oxide and zirconium oxide;

the second layer having an optical thickness of one-half the designed wavelength and a refractive index of about 2.05; and

the third layer having an optical thickness of one-fourth the designed wavelength and a refractive index of about 1.38.