Phosphor based illumination system having a light guide and an interference reflector

• US 7,255,469 B2
• Filed: 06/30/2004
• Issued: 08/14/2007
• 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., Watson, James E.
• Primary Examiner(s): O'Shea; Sandra
• Assistant Examiner(s): Cranson, Jr.; James W
• Application Number:
  US10/884,720
• Publication Number:
  US 20060002101A1
• Time in Patent Office: 1,140 Days
• Field of Search: 362/560, 362/612, 362/616, 362/617, 362/609
• US Class Current: 362/609
• CPC Class Codes: G02B 6/0003 the light guides being doped with fluorescent agents
• 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 6/0065 Manufacturing aspects; Material aspects
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/58 Optical field-shaping elements
• CPC Class Codes: H01L 33/60 Reflective elements

Abstract

An illumination system including a light source, a light guide including an output surface, emissive material positioned between the light source and the output surface of the light guide, and an interference reflector positioned between the emissive material and the output surface of the light guide 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 interference reflector substantially transmits light having the second optical characteristic and substantially reflects light having the first optical characteristic.

Claims

1. An illumination system, comprising:

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

a light guide comprising an output surface;

emissive material positioned between the light source and the output surface of the light guide, wherein the emissive material emits light comprising a second optical characteristic when illuminated with light comprising the first optical characteristic; and

an interference reflector positioned between the emissive material and the output surface of the light guide, wherein the interference reflector substantially transmits light comprising the second optical characteristic and substantially reflects light comprising the first 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 light guide further comprises an input surface, wherein the interference reflector is positioned adjacent the input surface of the light guide.

9. The system of claim 1, wherein the light source, the emissive material, and the interference reflector are positioned within the light guide.

10. The system of claim 9, wherein the interference reflector comprises a non-planar interference reflector.

11. The system of claim 10, wherein the interference reflector is a concave interference reflector.

12. The system of claim 1, wherein the system further comprises at least one optical element positioned between the interference reflector and an input surface of the light guide.

13. The system of claim 12, wherein the at least one optical element is configured to control the angle of light emitted by the emissive material and directed into the light guide.

14. The system of claim 1, wherein the system further comprises at least one optical element positioned between the light source and the interference reflector.

15. The system of claim 1, wherein the light guide comprises a wedge-shape.

16. The system of claim 1, wherein the emissive material is dispersed within the light guide.

17. The system of claim 1, wherein the emissive material comprises an adhesive.

18. The system of claim 1, wherein the interference reflector comprises a polymeric material that resists degradation when exposed to UV.

19. The system of claim 1, wherein the interference reflector comprises a polymeric material substantially free of inorganic materials.

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

21. The system of claim 20, wherein the discontinuous emissive material is a plurality of lines of emissive material.

22. The system of claim 20, wherein the discontinuous emissive material is a pattern of emissive material.

23. The system of claim 20, wherein the discontinuous emissive material comprises a plurality of dots of emissive material.

24. The system of claim 23, wherein each dot of the plurality of dots of emissive material has an area of less than 10000 μ

m².

25. The system of claim 23, 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.

26. The system of claim 23, 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.

27. The system of claim 1, wherein the interference reflector comprises alternating layers of a first and second thermoplastic polymer, and further wherein at least some of the layers are birefringent.

28. 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.

29. The system of claim 28, wherein the system further comprises a TIR promoting layer in contact with the emissive material between the 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.

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

33. A method of manufacturing an illumination system, comprising:

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

positioning emissive material to receive light emitted by the light source, wherein the emissive material emits light comprising a second optical characteristic when illuminated with light comprising the first optical characteristic;

positioning an interference reflector such that the emissive material is between the light source and the interference reflector, wherein the interference reflector substantially transmits light comprising the second optical characteristic and substantially reflects light comprising the first optical characteristic; and

positioning a light guide to receive light transmitted by the interference reflector, wherein the light guide directs at least a portion of light transmitted by the interference reflector through an output surface of the light guide.

34. A display, comprising:

an illumination system, wherein the illumination system comprises;

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

a light guide comprising an output surface;

an interference reflector positioned between the light source and the output surface of the light guide, wherein the interference reflector substantially transmits light comprising a second optical characteristic and substantially reflects light comprising the first optical characteristic; and

emissive material positioned between the light source and the interference reflector, wherein the emissive material emits light comprising the second optical characteristic when illuminated light comprising the first 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.