Loss enhanced reflective optical filters

• US 20020186474A1
• Filed: 06/28/2002
• Published: 12/12/2002
• Est. Priority Date: 08/21/2000
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Weber, Michael F., Ouderkirk, Andrew J., Strharsky, Roger J., Nevitt, Timothy J.
• Granted Patent: US 6,697,195 B2
• Time in Patent Office: Days
• US Class Current: 359/580
• CPC Class Codes: G02B 5/22 Absorbing filters G02B5/201 - G02B5/208 take precedence
• CPC Class Codes: G02B 5/26 Reflecting filters G02B5/28 takes precedence
• CPC Class Codes: G02B 5/287 comprising at least one layer of organic material
• CPC Class Codes: G02B 5/3025 Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state G02B5/3008, G02B5/3016 take precedence

Abstract

Optical filters and their manufacture, as well as the use of the optical filters in optical devices, such as polarizers and mirrors are described. The optical filters typically include a first reflective multilayer film, a second reflective multilayer film, and a lossy element disposed between the first and second reflective multilayer films.

Claims

1. An optical filter, comprising:

a first reflective element;

a second reflective element, wherein the second reflective element has a band edge within about 25 nm of a band edge of the first reflective element; and

a lossy element disposed between the first and second reflective elements, wherein the lossy element causes the loss of at least some light within the band edge of at least one of the first and second reflective elements.

2. The optical filter of claim 1, wherein a band edge of the lossy element is within 25 nm of the band edge of at least one of the first and second reflective elements.

3. The optical filter of claim 1, wherein the band edge of the first and second reflective elements extends from an optical density of 0.3 to an optical density of 2.

4. The optical filter of claim 1, wherein the band edges of the first and second reflective elements overlap.

5. The optical filter of claim 1, wherein a band edge of the lossy element overlaps with the band edges of at least one of the first and second reflective elements.

6. The optical filter of claim 1, wherein the lossy element is laminated to the first reflective element.

7. The optical filter of claim 6, wherein the second reflective element is laminated to the lossy element.

8. The optical filter of claim 1, wherein, over a wavelength range, the first and second multilayer reflective films substantially reflect light having a first polarization and substantially transmit light having a second polarization.

9. An optical filter comprising:

a first multilayer reflective film;

a second multilayer reflective film, wherein the first and second multilayer reflective films each have an optical density, for unpolarized light, of at least 1 over a same first wavelength range, the first wavelength range having a width of at least 50 nm; and

a lossy element disposed between the first and second multilayer reflective films, wherein the lossy element, in the absence of the first and second multilayer reflective films, causes the loss of, on average, at least 5% of light in the first wavelength range.

10. The optical filter of claim 9, wherein the first and second multilayer reflective films each comprise a polymeric multilayer optical film.

11. The optical filter of claim 10, wherein the polymeric multilayer optical films of the first and second multilayer reflective films are each a multiple pitch cholesteric liquid crystal film.

12. The optical filter of claim 9, wherein the first and second multilayer reflective films each comprise an inorganic multilayer optical film.

13. The optical filter of claim 9, wherein the first and second multilayer reflective films are substantially identical.

14. The optical filter of claim 13, wherein the first and second multilayer reflective films reflect on average at least 95% of light over the first wavelength range.

15. The optical filter of claim 13, wherein the lossy element is an absorptive element.

16. The optical filter of claim 15, wherein the absorptive element absorbs on average at least 20% of light over the first wavelength range.

17. The optical filter of claim 15, wherein the absorptive element has an absorptance of at least 0.2 over the first wavelength range.

18. The optical filter of claim 15, wherein the absorptive element has an absorptance of at least 0.5 over the first wavelength range.

19. The optical filter of claim 15, wherein the first and second multilayer reflective elements reflect infrared light and the absorptive element absorbs infrared light.

20. The optical filter of claim 15, wherein the first and second multilayer reflective elements reflect ultraviolet light and the absorptive element absorbs ultraviolet light.

21. An optical filter comprising:

a first multilayer reflective film;

a second multilayer reflective film; and

a lossy element disposed between the first and second multilayer reflective films;

wherein the first and second multilayer reflective films define a reflection wavelength range in which the first and second multilayer reflective films, in the absence of the lossy element, each have an optical density for unpolarized light of at least 1.5 and wherein the lossy element, in the absence of the first and second multilayer reflective films, has an optical density for unpolarized light of at least 0.1 over the reflection wavelength range.

22. An optical filter comprising:

a first multilayer reflective film;

a second multilayer reflective film; and

a lossy element disposed between the first and second multilayer reflective films;

wherein the optical film has an optical density of at least 2 over a first wavelength range of at least 50 nm and has an optical density of no more than 0.3 over a second wavelength range of at least 50 nm and wherein the lossy element, in the absence of the first and second multilayer reflective films, causes the loss of, on average, at least 5% of light in the first wavelength range.

24. The article of claim 23, wherein the at least one transparent substrate comprises at least one lens.

25. The article of claim 23, wherein the first and second multilayer reflective films reflect at least a portion of infrared light.

26. The article of claim 25, wherein the lossy element causes the loss of at least a portion of infrared light.

27. The article of claim 25, wherein the article has an optical density of at least 3 over a wavelength range from 700 to 1180 nm.

28. The article of claim 24, wherein the lens comprises an impact resistant plastic material.

23. An article, comprising:

at least one transparent substrate; and

an optical film disposed over a major surface of the at least one transparent substrate, the optical film comprising;

a first multilayer reflective film;

a second multilayer reflective film; and

a lossy element disposed between the first and second multilayer reflective films.

29. A method of filtering light, comprising:

filtering light through an optical filter comprising

a first multilayer reflective film;

a second multilayer reflective film, wherein the first and second multilayer reflective films each have an optical density, for unpolarized light, of at least 1 over a same first wavelength range, the first wavelength range having a width of at least 50 nm; and

a lossy element disposed between the first and second multilayer reflective films, wherein the lossy element, in the absence of the first and second multilayer reflective films, causes the loss of, on average, at least 5% of light in the first wavelength range.