Phosphor based illumination system having a short pass reflector and method of making same

• US 20060002141A1
• 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., Watson, James E.
• Granted Patent: US 7,213,958 B2
• Time in Patent Office: Days
• US Class Current: 362/609
• CPC Class Codes: G02B 6/0001 specially adapted for lighting devices or systems lighting or signalling on vehicles using light guides B60Q1/00; lighting devices for vehicle dashboards B60Q3/10; lighting devices for vehicle interior using light guides B60Q3/62; lighting devices mounted on the vehicle rear part using light guides F21S43/235; measuring arrangements having light conducting pointers G01D13/265; illumination of liquid crystal displays G02F1/1336; illuminated signs G09F13/00
• 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: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 1/133617 Illumination with ultraviolet light; Luminescent elements or materials associated to the cell

Abstract

An illumination system including a light source, a light guide including an output surface, emissive material positioned to receive light from the output surface of the light guide, and a first interference reflector positioned between the output surface of the light guide and the emissive material 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 light guide comprising an output surface, wherein the light guide is configured to direct at least a portion of the light emitted by the light source through the output surface;

emissive material positioned to receive light from 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

a first interference reflector positioned between the output surface of the light guide and the emissive material, 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 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 is a plurality of lines of emissive material.

11. The system of claim 9, wherein the discontinuous emissive material is 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 12, wherein the first interference reflector comprises a major surface comprising a plurality of indentations, wherein the plurality of phosphor dots are located in one or more of the plurality of indentations.

17. The system of claim 1, wherein the system comprises an optical cavity optically coupled to the light source, wherein the optical cavity is configured to direct light comprising at least one of the first optical characteristic and second optical characteristic toward an input surface of the light guide.

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

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

20. 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.

21. The system of claim 20, 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.

22. The system of claim 2 l, wherein the TIR promoting layer comprises an air gap.

23. The system of claim 21, wherein the TIR promoting layer comprises a microstructured layer.

24. The system of claim 20, 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.

25. The system of claim 24, wherein the system further comprises a TIR promoting layer in contact with the emissive material between 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.

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 1, further comprising at least one optical element positioned to receive the light emitted by the emissive material.

29. The system of claim 28, wherein the at least one optical element comprises a reflective polarizer.

30. The system of claim 29, wherein the reflective polarizer comprises cholesteric material.

31. The system of claim 29, wherein the reflective polarizer comprises multilayer polymeric material.

32. The system of claim 31, wherein the reflective polarizer comprises multilayer birefringent polymeric material.

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

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

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

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

positioning a light guide to receive light emitted by the light source, wherein the light guide directs at least a portion of light emitted by the light source through an output surface of the light guide;

positioning emissive material to receive light from 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

positioning a first interference reflector between the output surface of the light guide and the emissive material, wherein the first interference reflector substantially transmits light comprising the first optical characteristic and substantially reflects light comprising the second optical characteristic.

36. 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, wherein the light guide is configured to direct at least a portion of the light emitted by the light source through the output surface of the light guide;

emissive material positioned to receive light from 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;

a first interference reflector positioned between the emissive material and the output surface of the light guide, 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.

37. The display of claim 36, 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.

38. The display of claim 36, wherein the plurality of controllable elements of the spatial light modulator comprises variable-transmissivity display elements.

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

illuminating a light guide with light comprising a first optical characteristic, wherein the light guide directs the light through an output surface;

illuminating a first interference reflector with light from the output surface of the 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.