Optical filter and optical device

• US 7,130,125 B2
• Filed: 10/08/2004
• Issued: 10/31/2006
• Est. Priority Date: 10/14/2003
• Status: Active Grant

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Corporation
• Inventors: Shinta, Yoshiki, Wada, Yorio
• Primary Examiner(s): Assaf, Fayez G.
• Application Number:
  US10/960,499
• Publication Number:
  US 20050111103A1
• Time in Patent Office: 753 Days
• Field of Search: 359/586, 359/587, 359/588, 359/589, 359/590, 359/580
• US Class Current: 359/586
• CPC Class Codes: G02B 21/16 adapted for ultraviolet illumination ; Fluorescence microscopes G02B21/0076 takes precedence
• CPC Class Codes: G02B 5/285 comprising deposited thin solid films G02B5/281 - G02B5/289 take precedence; multilayered film filters for fibre optic multiplexing G02B6/29361
• CPC Class Codes: G02B 5/289 Rugate filters

Abstract

This optical filter provides a substrate and thin films. The thin films comprise an outermost layer portion and a refractive index varying portion. The refractive index varying portion is formed by laminating alternately towards the substrate a low refractive index layer having a refractive index that is higher than that of air and a high refractive index layer having a refractive index that is higher than the low refractive index layer. The outermost layer portion comprises an outermost low refractive index layer having a refractive index that is higher than that of air, a first outermost high refractive index layer having a refractive index that is higher than that of the outermost low refractive index layer, and a second outermost high refractive index layer having a refractive index that is higher than that of the first outermost high refractive index layer.

Claims

1. An optical filter comprising a substrate and thin films formed on the substrate, wherein:

the thin films comprise an outermost layer portion and a refractive index varying portion;

the outermost layer portion contacts an optical medium whose refractive index is lower than the refractive index of the substrate, and comprises an outermost low refractive index layer, a first outermost high refractive index layer, and a second outermost high refractive index layer;

the outermost low refractive index layer is provided at a position in contact with the optical medium and has a refractive index that is higher than the refractive index of the optical medium;

the first outermost high refractive index layer is provided at a position in contact with the outermost low refractive index layer and has a refractive index that is higher than the refractive index of the outermost low refractive index layer;

the second outermost high refractive index layer is provided at a position in contact with the first outermost high refractive index layer and has a refractive index that is higher than the refractive index of the first outermost high refractive index layer;

the refractive index varying portion comprises low refractive index layers whose refractive index are higher than the refractive index of the optical medium, and high refractive index layers whose refractive index are higher than the refractive index of the low refractive index layer, the low refractive index layer and the high refractive index layer are alternately stacked towards the substrate side;

the refractive index varying portion is divided into a first stacked portion, a second stacked portion, and a third stacked portion;

the low refractive index layer which forms the first stacked portion is provided at a position in contact with the outermost layer portion, the refractive index of the high refractive index layer which is adjacent to the outermost layer portion by interposing between the outermost layer portion and itself among the high refractive index layers which form the first stacked portion is higher than the refractive index of the second outermost high refractive index layer, the refractive indices of other the high refractive index layers which form the first stacked portion, is as high as the high refractive index layer near the substrate;

the second stacked portion is provided at a position in contact with the substrate side of the first stacked portion, and the refractive indices of the high refractive index layers which form the second stacked portion, is as low as the high refractive index layer near the substrate; and

the third stacked portion is provided between the first stacked portion and the second stacked portion, and the refractive index of the high refractive index layer is substantially identical to that of the high refractive index layer which has the highest refractive index among the high refractive index layers which form the first stacked portion.

2. The optical filter according to claim 1, wherein:

the refractive index varying portion is provided in plurality, and the refractive index varying portions are stacked towards the substrate side; and

when one of the refractive index varying portions serves as a first refractive index varying portion and another one of the refractive index varying portions serves as a second refractive index varying portion, among the following refractive index layers, the film thickness of at least one of the refractive index layers differs from the film thickness of the other refractive index layers;

the high refractive index layer in the first refractive index varying portion;

the low refractive index layer in the first refractive index varying portion;

the high refractive index layer in the second refractive index varying portion;

the low refractive index layer in the second refractive index varying portion.

3. The optical filter according to claim 2, wherein:

the refractive index of the low refractive index layer in the first stacked portion and the third stacked portion is substantially identical to the refractive index of the outermost low refractive index layer; and

the refractive index of the low refractive index layer in the second stacked portion is as high as the low refractive index layer near the substrate.

4. An optical device comprising the optical filter according to claim 3.

5. An optical device comprising the optical filter according to claim 2.

6. The optical filter according to claim 1, wherein:

the refractive index of the low refractive index layer in the first stacked portion and the third stacked portion is substantially identical to the refractive index of the outermost low refractive index layer; and

the refractive index of the low refractive index layer in the second stacked portion is as high as the low refractive index layer near the substrate.

7. An optical device comprising the optical filter according to claim 6.

8. An optical device comprising the optical filter according to claim 1.