Light guide illumination device appearing uniform in brightness along its length

• US 6,863,428 B2
• Filed: 01/10/2000
• Issued: 03/08/2005
• Est. Priority Date: 10/24/1997
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Lundin, David J.
• Primary Examiner(s): CARIASO, ALAN B
• Application Number:
  US09/479,795
• Publication Number:
  US 20020030999A1
• Time in Patent Office: 1,884 Days
• Field of Search: 362/31, 362/551, 362/558, 362/560, 385/31, 385/123, 385/146, 385/901, 349/64, 349/65
• US Class Current: 362/551
• CPC Class Codes: G02B 6/001 the light being emitted along at least a portion of the lateral surface of the fibre
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects
• CPC Class Codes: Y10S 385/901 Illuminating or display apparatus

Abstract

An illumination device that is relatively bright and uniform in appearance includes a light guide, which has a light guide core having an optically smooth surface for propagating light therethrough. A light emitting region, which extends along a portion of the core, includes at least one light extraction structure located along the optically smooth surface of the light guide core. The light extraction structure, which includes an optically reflective surface extending into the light guide core, is oriented to reflect light at an angle less than a critical angle necessary for light to propagate through the light guide core. A diffuse reflective material is disposed around at least a portion of the light guide. The diffuse reflective material directs at least a portion of the light reflected by the light extraction structure back through the light guide so that light is emitted through the light emitting region of the optically smooth surface.

Claims

1. An illumination device comprising:

a light guide including a light guide core having an optically smooth surface for propagating light therethrough and a light emitting region extending along a portion of the core wherein said light guide is a light fiber, the light emitting region including;

at least one light extraction structure located along the optically smooth surface of the light guide core, said light extraction structure including an optically reflective surface extending into the light guide core and oriented to reflect light at an angle less than a critical angle necessary for light to propagate through the light guide core; and

a diffuse reflective material disposed around at least a portion of the light guide to direct at least a portion of the light reflected by the light extraction structure back through the light guide core so that light is emitted through the light emitting region of the optically smooth surface.

2. The device of claim 1 wherein said light guide has a circular cross-sectional shape.

3. The device of claim 1 further comprising a plurality of light extraction structures distributed along the optically smooth surface of the light guide core.

4. The device of claim 3 wherein the plurality of light extraction structures are equally spaced apart from one another along the optically smooth surface.

5. The device of claim 3 wherein the plurality of light extraction structures are unequally spaced apart from one another along the optically smooth surface.

6. The device of claim 1 wherein said light guide is formed from a polymerizable material.

7. The device of claim 6 wherein said polymerizable material is an acrylate material.

8. The device of claim 7 wherein said polymerizable material is a urethane material.

9. The device of claim 1 further comprising a cladding material surrounding the light guide core.

10. The device of claim 9 wherein the diffuse reflective sheet material is disposed around a portion of the cladding.

11. The device of claim 1 wherein the diffuse reflective sheet material comprises a polymeric material.

12. The device of claim 1 wherein the diffuse reflective sheet material comprises a microvoided material.

13. The device of claim 1 wherein the diffuse reflective sheet material is a material formed by thermally induced phase separation.

14. The device of claim 1 wherein the diffuse reflective material comprises a microporous material.

15. The device of claim 14 wherein the microporous material comprises polytetrafluoroethylene.

16. An illumination device comprising:

a light guide including a light guide core having an optically smooth surface for propagating light therethrough, a cladding surrounding said core, and a light emitting region extending along a portion of the core, the light emitting region including;

at least one light extraction structure located along the optically smooth surface of the light guide core, said light extraction structure including an optically reflective surface extending into the light guide core and oriented to reflect light at an angle less than a critical angle necessary for light to propagate through the light guide core; and

a diffuse reflective material disposed around at least a portion of the light guide to direct at least a portion of the light reflected by the light extraction structure back through the light guide core so that light is emitted through the light emitting region of the optically smooth surface.

17. The device of claim 16 wherein said light guide is a light fiber.

18. The device of claim 16 wherein said light guide has a circular cross-sectional shape.

19. The device of claim 16 wherein said light guide is a planar light guide.

20. The device of claim 16 further comprising a plurality of light extraction structures distributed along the optically smooth surface of the light guide core.

21. The device of claim 20 wherein the plurality of light extraction structures are equally spaced apart from one another along the optically smooth surface.

22. The device of claim 20 wherein the plurality of light extraction structures are unequally spaced apart from one another along the optically smooth surface.

23. The device of claim 16 wherein said light guide is formed from a polymerizable material.

24. The device of claim 23 wherein said polymerizable material is an acrylate material.

25. The device of claim 24 wherein said polymerizable material is a urethane material.

26. The device of claim 16 wherein the diffuse reflective sheet material is disposed around a portion of the cladding.

27. The device of claim 16 wherein the diffuse reflective sheet material comprises a polymeric material.

28. The device of claim 16 wherein the diffuse reflective sheet material comprises a microvoided material.

29. The device of claim 16 wherein the diffuse reflective sheet material is a material formed by thermally induced phase separation.

30. The device of claim 16 wherein the diffuse reflective material comprises a microporous material.

31. The device of claim 30 wherein the microporous material comprises polytetrafluoroethylene.