Anti-reflection structure with graded refractive index layer and optical apparatus including same

Patent metadata

Field	Value
Publication number	US-9291748-B2
Application number	US-201113078231-A
Country	US
Kind code	B2
Filing date	Apr 1, 2011
Priority date	Apr 1, 2010
Publication date	Mar 22, 2016
Grant date	Mar 22, 2016

Abstract

The anti-reflection structure includes a graded refractive index layer that is disposed on a substrate and whose refractive index decreases as a distance from the substrate increases, and a homogeneous layer that is disposed on the graded refractive index layer and whose refractive index is homogeneous. The structure satisfies a condition of nb−na>0.10 where na represents the refractive index of the homogenous layer, and nb represents a homogenous layer side effective refractive index of the graded index refractive index layer.

First claim

What is claimed is:

1. An anti-reflection structure comprising:
a first layer that is a graded refractive index layer which is disposed on a substrate and whose refractive index decreases as a distance from the substrate increases;
a second layer that is disposed on the first layer and whose refractive index is homogeneous, wherein refractive index of the second layer is na and 1.10<na<1.35, and
an interface between the first layer and the second layer, wherein the following condition is satisfied at the interface:
nb−na> 0.10

where nb represents refractive index of the first layer at the interface between the first layer and the second layer.

2. An anti-reflection structure according to claim 1 , wherein the second layer is a porous layer.

3. An anti-reflection structure according to claim 2 , wherein the second layer contains silica or magnesium fluoride.

4. An anti-reflection structure according to claim 2 , wherein the second layer is a mesoporous layer.

5. An anti-reflection structure according to claim 1 , wherein the following condition is satisfied:
| ns−nc|< 0.10
where ns represents a refractive index of the substrate, and nc represents refractive index of a part of the first layer that is adjacent to the substrate.

6. An anti-reflection structure according to claim 1 , further comprising:
a third layer that is disposed between the first layer and the substrate and whose refractive index is homogeneous.

7. An anti-reflection structure according to claim 1 , wherein the first layer is constituted by (a) a base layer having roughness including convex portions whose pitch is equal to or smaller than a wavelength of light entering the anti-reflection structure, and (b) a first medium with which a concave area around the convex portions in the base layer is filled and whose refractive index is lower than the base layer,
wherein a filling rate of the first medium increases as a distance from the substrate increases.

8. An anti-reflection structure according to claim 7 , wherein the base layer is formed of a same medium as that of the substrate.

9. An anti-reflection structure according to claim 7 , wherein the first medium is a same medium as that of the second layer.

10. An anti-reflection structure according to claim 1 , wherein the following condition is satisfied:
0.1< na·Da/λo< 0.5
where Da represents a thickness of the second layer, and λo is 550 nm.

11. An anti-reflection structure according to claim 1 , wherein the following condition is satisfied:
nb−na> 0.17.

12. An anti-refection structure according to claim 1 , wherein the interface is configured so that light reflected by the interface and light reflected by an interface between the second layer and air cancel each other.

13. An anti-reflection structure according to claim 1 , wherein nb is the minimum effective refractive index in the first layer.

14. An optical element comprising:
a substrate;
a first layer that is a graded refractive index layer which is disposed on a substrate and whose refractive index decreases as a distance from the substrate increases;
a second layer that is disposed on the first layer and whose refractive index is homogeneous, wherein refractive index of the second layer is na and 1.10<na<1.35, and
an interface between the first layer and the second layer, wherein the following condition is satisfied at the interface:
nb−na> 0.10

where nb represents refractive index of the first layer at the interface between the first layer and the second layer.

15. An optical apparatus comprising:
an optical element; and
an image pickup element
wherein the optical element comprises:
a substrate;
a first layer that is a graded refractive index layer which is disposed on a substrate and whose refractive index decreases as a distance from the substrate increases;
a second layer that is disposed on the first layer and whose refractive index is homogeneous, wherein refractive index of the second layer is na and 1.10<na<1.35, and
an interface between the first layer and the second layer, wherein the following condition is satisfied at the interface:
nb−na> 0.10

where nb represents refractive index of the first layer at the interface between the first layer and the second layer.

Assignees

• Momoki Kazuhiko
• Miyata Hirokatsu
• Takahashi Masahiko
• Sano Daisuke
• Canon Kk

Inventors

• Momoki Kazuhiko
• Miyata Hirokatsu
• Takahashi Masahiko
• Sano Daisuke

Classifications

• B29L2011/0016

  Lenses · CPC title

• G02B1/118 Primary

  having sub-optical wavelength surface structures designed to provide an enhanced transmittance, e.g. moth-eye structures · CPC title