Optical filter and optical apparatus

Patent metadata

Field	Value
Publication number	US-9513417-B2
Application number	US-201314443191-A
Country	US
Kind code	B2
Filing date	Nov 18, 2013
Priority date	Nov 16, 2012
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

Regarding an optical filter comprising a light-transmitting substrate, a gradient refractive index thin film with a refractive index change in the film thickness direction formed on the substrate and an anti-reflection structure formed on the gradient refractive index thin film, the gradient refractive index thin film is formed so as to have light absorbing characteristic and a refractive index characteristic such that the refractive index change comprising plural changing points with increases and decreases of the refractive index has a tendency to reduce from the side of the substrate toward the side of the anti-reflection structure. The optical filter has excellent environmental resistance and low reflection. The optical filter can be suitably used in an imaging optical system of an optical apparatus or a display of an electronic device.

First claim

The invention claimed is:

1. An optical filter comprising:
a light-transmitting substrate;
a gradient refractive index thin film with a refractive index change in the film thickness direction formed on the substrate; and
an anti-reflection structure formed on the gradient refractive index thin film,
wherein the gradient refractive index thin film has a light absorption property and a gradient refractive index property such that the refractive index change comprises plural changing points, each of which has an increase and a decrease of the refractive index,
wherein the gradient refractive index thin film has a gradient refractive index property comprising plural local maximum value points, at each of which the refractive index turns to reduction after increase, as the plural changing points in the refractive index change,
wherein the gradient refractive index thin film has a gradient refractive index property in that, of the plural local maximum value points, the local maximum value point nearest to the substrate is the global maximum value point of the refractive index change, and
wherein the gradient refractive index thin film comprises, in the film thickness direction thereof:
(a) a region where a spectral transmission characteristic of a visible wavelength region increases as approaching a long wavelength side; and
(b) a region where the spectral transmission characteristic of the visible wavelength region decreases as approaching the long wavelength side.

2. The optical filter according to claim 1 , wherein the anti-reflection structure comprises a multi-layer film.

3. The optical filter according to claim 1 , wherein the anti-reflection structure comprises a fine structure having a pitch shorter than a wavelength of visible light.

4. The optical filter according to claim 1 , wherein the substrate is a transparent resin substrate with transmittance of ray of light of 89%, or more than 89%.

5. An optical apparatus using an optical filter in an imaging optical system, wherein the optical filter is the optical filter according to claim 1 .

6. An optical filter comprising:
a light-transmitting substrate; and
a light-absorbing gradient refractive index thin film with a refractive index change in the film thickness direction formed on the substrate; and
an anti-reflection structure formed on the substrate,
wherein the refractive index change of the gradient refractive index thin film comprises (a) plural slope-changing regions of the refractive index, each of which has a portion where the slope of an increase rate of the refractive index changes from plus to minus as a local maximum value point, and (b) plural changing points with increase and decrease,
wherein the relation of the refractive index of the substrate, the refractive indexes of the local maximum value points corresponding to the plural slope-changing regions, and the refractive index of the anti-reflection structure comprises a change from a monotonous increase to a monotonous decrease from the side of the substrate toward the side of the anti-reflection structure,
wherein the gradient refractive index thin film has a gradient refractive index property comprising plural local maximum value points, at each of which the refractive index turns to reduction after increase, as the plural changing points in the refractive index change,
wherein the gradient refractive index thin film has a gradient refractive index property in that, of the plural local maximum value points, the local maximum value point nearest to the substrate is the global maximum of the refractive index change, and
wherein the gradient refractive index thin film comprises, in the film thickness direction thereof:
(a) a region where a spectral transmission characteristic of a visible wavelength region increases as approaching a long wavelength side; and
(b) a region where the spectral transmission characteristic of the visible wavelength region decreases as approaching the long wavelength side.

7. The optical filter according to claim 6 , wherein the anti-reflection structure comprises a multi-layer film.

8. The optical filter according to claim 6 , wherein the anti-reflection structure comprises a fine structure having a pitch shorter than a wavelength of visible light.

9. The optical filter according to claim 8 , further comprising a multi-function film having light-absorption property formed on the gradient refractive index thin film and consisting of a composition different from the gradient refractive index thin film,
wherein a fine structure is formed on the multi-function film.

10. The optical filter according to claim 9 , wherein the multi-function film comprises an oxide containing at least one of Al and Si.

11. The optical filter according to claim 10 , wherein the multi-function film comprises an oxide containing Al and Si.

12. The optical filter according to claim 9 , wherein the gradient refractive index thin film comprises an oxide of a metal or a metalloid, and wherein the multi-function film is formed by at least a saturated oxide of the oxide forming the gradient refractive index thin film.

13. The optical filter according to claim 6 , wherein the substrate is a transparent resin substrate with transmittance of ray of light of 89%, or more than 89%.

14. An optical apparatus using an optical filter in an imaging optical system, wherein the optical filter is the optical filter according to claim 6 .

15. An optical filter comprising:
a light-transmitting substrate;
a gradient refractive index thin film with a refractive index change in the film thickness direction formed on the substrate;
an anti-reflection structure formed on the gradient refractive index thin film,
wherein the gradient refractive index thin film has a light absorption property and a gradient refractive index property such that the refractive index change comprises plural changing points, each of which has an increase and a decrease of the refractive index,
wherein the gradient refractive index thin film has a gradient refractive index property comprising plural local maximum value points, at each of which the refractive index turns to reduction after increase, as the plural changing points in the refractive index change,
wherein the gradient refractive index thin film has a gradient refractive index property in that, of the plural local maximum value points, the local maximum value point nearest to the substrate is the global maximum value point of the refractive index change, and
wherein the gradient refractive index thin film comprises, in the film thickness direction thereof, a region changing from a region where a spectral transmission characteristic of a visible wavelength region increases as approaching a long wavelength side to a region where the spectral transmission characteristic of the visible wavelength region decreases as approaching the long wavelength side.

16. An optical apparatus using an optical filter in an imaging optical system, wherein the optical filter is the optical filter according to claim 15 .

17. An optical filter comprising:
a light-transmitting substrate;
a light-absorbing gradient refractive index thin film with a refractive index change in the film thickness direction formed on the substrate; and
an anti-reflection structure formed on the substrate,
wherein the refractive index change of the gradient refractive index thin film comprises (a) plural slope-changing regions of the refractive index, each of which has a portion where the slope of an increase rate of the refractive index changes from plus to minu

Assignees

• Canon Denshi Kk

Inventors

• Uchiyama Masayuki
• Yanagi Michio

Classifications

• G02B1/115

  Multilayers · CPC title

• G02B5/205

  Neutral density filters · CPC title

• G02B1/118

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

• G02B5/22 Primary

  Absorbing filters {(G02B5/201 - G02B5/208 take precedence)} · CPC title

• G03B11/00

  Filters or other obturators specially adapted for photographic purposes · CPC title