Phosphor based illumination system having a plurality of light guides and a display using same

• US 20060001037A1
• Filed: 06/30/2004
• Published: 01/05/2006
• Est. Priority Date: 06/30/2004
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Wheatley, John A., Weber, Michael F., Ouderkirk, Andrew J., Epstein, Kenneth A., Schardt, Craig R., Schultz, John C., Watson, James E.
• Granted Patent: US 7,204,630 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: G02B 6/0008 the light being emitted at the end of the fibre
• CPC Class Codes: G02B 6/0018 Redirecting means on the surface of the light guide
• CPC Class Codes: G02B 6/0021 for housing at least a part of the light source, e.g. by forming holes or recesses
• CPC Class Codes: G02B 6/0026 Wavelength selective element, sheet or layer, e.g. filter or grating
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources

Abstract

An illumination system including a light source, light guides coupled to the light source, each including an input surface and an output surface, emissive material positioned to receive light from at least one light guide, and a first interference reflector positioned between the emissive material and the output surfaces of the light guides is disclosed. The light source emits light having a first optical characteristic. The emissive material emits light having a second optical characteristic when illuminated with light having the first optical characteristic. The first interference reflector substantially transmits light having the first optical characteristic and substantially reflects light having the second optical characteristic.

Claims

1. An illumination system, comprising:

a light source that emits light comprising a first optical characteristic;

a plurality of light guides optically coupled to the light source, wherein each light guide comprises an input surface and an output surface;

emissive material positioned to receive light from at least one light guide of the plurality of light guides, wherein the emissive material emits light comprising a second optical characteristic when illuminated with light comprising the first optical characteristic; and

a first interference reflector positioned between the emissive material and the output surfaces of the plurality of light guides, wherein the first interference reflector substantially transmits light comprising the first optical characteristic and substantially reflects light comprising the second optical characteristic.

2. The system of claim 1, wherein the first optical characteristic comprises a first wavelength region and the second optical characteristic comprises a second wavelength region different than the first wavelength region.

3. The system of claim 2, wherein the first wavelength region comprises UV light.

4. The system of claim 2, wherein the first wavelength region comprises blue light.

5. The system of claim 2, wherein the second wavelength region comprises visible light.

6. The system of claim 1, wherein the light source comprises at least one solid state light source.

7. The system of claim 6, wherein the at least one solid state light source comprises at least one LED.

8. The system of claim 1, wherein the emissive material comprises phosphor material.

9. The system of claim 1, wherein the emissive material is discontinuous.

10. The system of claim 9, wherein the discontinuous emissive material comprises a plurality of lines of emissive material.

11. The system of claim 9, wherein the discontinuous emissive material comprises a pattern of emissive material.

12. The system of claim 9, wherein the discontinuous emissive material comprises a plurality of dots of emissive material.

13. The system of claim 12, wherein each dot of the plurality of dots of emissive material has an area of less than 10000 μ

m².

14. The system of claim 12, wherein at least one dot of the plurality of dots of emissive material comprises a first emissive material and at least one other dot of the plurality of dots of emissive material comprises a second emissive material.

15. The system of claim 12, wherein the first optical characteristic comprises a first wavelength region and the second optical characteristic comprises a second wavelength region different than the first wavelength region, wherein at least a first phosphor dot emits light having a first peak wavelength within the second wavelength region and at least a second phosphor dot emits light having a second peak wavelength within the second wavelength region different than the first peak wavelength.

16. The system of claim 1, wherein the first interference reflector comprises a non-planar interference reflector.

17. The system of claim 16, wherein the first interference reflector is a concave interference reflector.

18. The system of claim 17, wherein the output ends of the plurality of light guides form a non-planar surface.

19. The system of claim 1, further comprising at least one optical element positioned to receive at least a portion of light emitted by the emissive material.

20. The system of claim 19, wherein the at least one optical element comprises a reflective polarizer.

21. The system of claim 20, wherein the reflective polarizer comprises cholesteric material.

22. The system of claim 20, wherein the reflective polarizer comprises multilayer polymeric material.

23. The system of claim 22, wherein the reflective polarizer comprises multilayer birefringent polymeric material.

24. The system of claim 1, wherein the first optical characteristic comprises a first wavelength region and the second optical characteristic comprises a second wavelength region different than the first wavelength region, wherein the emissive material comprises a first index of refraction at the first wavelength region.

25. The system of claim 24, wherein the system further comprises a TIR promoting layer in contact with the emissive material between the first interference reflector and the emissive material, and further wherein the TIR promoting layer comprises a second index of refraction at the first wavelength region that is less than the first index of refraction.

26. The system of claim 25, wherein the TIR promoting layer comprises an air gap.

27. The system of claim 25, wherein the TIR promoting layer comprises a microstructured layer.

28. The system of claim 24, further comprising a second interference reflector positioned such that the emissive material is between the second interference reflector and the first interference reflector, wherein the second interference reflector substantially transmits light comprising the second optical characteristic and substantially reflects light comprising the first optical characteristic.

29. The system of claim 28, wherein the system further comprises a TIR promoting layer in contact with the emissive material between the second interference reflector and the emissive material, wherein the TIR promoting layer comprises a second index of refraction at the first wavelength region that is less than the first index of refraction.

30. The system of claim 29, wherein the TIR promoting layer comprises an air gap.

31. The system of claim 29, wherein the TIR promoting layer comprises a microstructured layer.

32. A vehicle headlight comprising the illumination system of claim 1.

33. A projection system comprising the illumination system of claim 1.

34. A light fixture comprising the illumination system of claim 1.

35. The system of claim 1, wherein the plurality of light guides comprises a plurality of optical fibers.

36. The system of claim 35, wherein the plurality of optical fibers comprises a plurality of polymer clad silica fibers, each having a core diameter of about 400 μ

m to about 1000 μ

m.

37. The system of claim 1, wherein the light source comprises a plurality of LEDs, wherein the system further comprises a controller in electrical communication with the plurality of LEDs, wherein the controller is operable to selectively activate one or more LEDs of the plurality of LEDs.

38. A sign comprising the illumination system of claim 1.

39. A display, comprising:

an illumination system, wherein the illumination system comprises;

a light source that emits light comprising a first optical characteristic;

a plurality of light guides optically coupled to the light source, wherein each light guide comprises an input surface and an output surface;

emissive material positioned to receive light from at least one light guide of the plurality of light guides, wherein the emissive material emits light comprising a second optical characteristic when illuminated with light comprising the first optical characteristic; and

a first interference reflector positioned between the emissive material and the output surfaces of the plurality of light guides, wherein the first interference reflector substantially transmits light comprising the first optical characteristic and substantially reflects light comprising the second optical characteristic; and

a spatial light modulator optically coupled to the illumination system, wherein the spatial light modulator comprises a plurality of controllable elements operable to modulate at least a portion of light from the illumination system.

40. The display of claim 39, wherein the illumination system further comprises a second interference reflector positioned such that the emissive material is between the second interference reflector and the first interference reflector, wherein the second interference reflector substantially transmits light comprising the second optical characteristic and substantially reflects light comprising the first optical characteristic.

41. The display of claim 39, wherein the plurality of controllable elements of the spatial light modulator comprises variable-transmissivity display elements.

42. The display of claim 40, wherein the variable-transmissivity display elements comprises liquid crystal display elements.

43. A method of providing illumination to a desired location, comprising:

illuminating at least one light guide of a plurality of light guides with light comprising a first optical characteristic, wherein the at least one light guide directs the light through an output surface;

illuminating a first interference reflector with light from the output surface of the at least one light guide, wherein the first interference reflector substantially transmits light comprising the first optical characteristic and substantially reflects light comprising a second optical characteristic;

illuminating emissive material with the light transmitted by the first interference reflector such that the emissive material emits light comprising the second optical characteristic; and

directing at least a portion of the light emitted by the emissive material to the desired location.