Illumination systems utilizing highly reflective light emitting diodes and light recycling to enhance brightness

• US 6,869,206 B2
• Filed: 05/23/2003
• Issued: 03/22/2005
• Est. Priority Date: 05/23/2003
• Status: Active Grant

• Current Assignee: Karl Wayne Beeson, Scott Moore Zimmerman
• Original Assignee: Karl Wayne Beeson, Scott Moore Zimmerman
• Inventors: Beeson, Karl Wayne, Zimmerman, Scott Moore
• Primary Examiner(s): Sember, Thomas M.
• Assistant Examiner(s): Truong, Bao Q
• Application Number:
  US10/445,136
• Publication Number:
  US 20040233655A1
• Time in Patent Office: 669 Days
• Field of Search: 362/19, 362/242, 362/243, 362/245, 362/800, 362/240, 362/247, 362/310, 362/297, 362/298, 362/304, 362/300, 362/301, 362/307, 362/555, 362/545, 362/544, 362/329, 362/231, 362/11, 362/257, 362/296, 362/342, 362/516, 362/299, 362/308, 362/328
• US Class Current: 362/310
• CPC Class Codes: G02B 17/0668 having non-imaging properties
• CPC Class Codes: G02B 19/00 Condensers, e.g. light collectors or similar non-imaging opticsfor microscopes G02B21/08
• CPC Class Codes: G02B 19/0019 having reflective surfaces only (e.g. louvre systems, systems with multiple planar reflectors)
• CPC Class Codes: G02B 19/0066 in the form of an LED array
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

An illumination system that has an output luminance (brightness) L_O that is greater than the intrinsic output luminance (brightness) L_I of the light emitting diodes used within the system. The system utilizes one or more light emitting diodes having highly reflective surfaces and recycles a portion of the light generated by the light emitting diodes back to the light emitting diodes in order to enhance the effective luminance. The illumination system includes a light-reflecting cavity and one or more highly reflective light emitting diodes having total surface area A_S mounted inside the cavity, either on the interior surfaces of the cavity or within the cavity volume. The cavity has a light output aperture of area A_O. The light emitting diodes have reflectivity R_S. The exposed inside surfaces of the light-reflecting cavity have reflectivity R_C. In order to achieve enhanced brightness, it is required that the area of the light output aperture A_O be less than the total area A_S of the light emitting diodes. It is preferred that reflectivity R_C and reflectivity R_S each be at least 50%, more preferably 75% and most preferably 90%. Illumination systems with enhanced luminance resulting from light recycling may be used in projection displays, flat-panel displays, avionics displays, automotive lighting, residential lighting, commercial lighting and industrial lighting applications.

Claims

1. An optical illumination system comprising:

a) A light source for generating light, wherein said light source is at least one light emitting diode having a reflecting surface with reflectivity R_S greater than or equal to 50 percent, wherein the maximum intrinsic luminance of said light source is L_I and wherein the total light emitting area of said light source is area A_S;

b) A light-reflecting cavity enclosing said light source, wherein the inside surfaces of said light-reflecting cavity have reflectivity R_C greater than or equal to 50 percent, aid wherein the inside surfaces of said light-reflecting cavity can reflect and recycle a portion of the light generated by said light source back to said light source; and

c) At least one light output aperture in a surface of said light-reflecting cavity, wherein the area of said light output aperture is area A_O and wherein said area A_O is less than said area A_S.

2. An optical illumination system of claim 1, wherein the light output from said light output aperture has luminance L_O that is greater than L_I.

3. An optical illumination system of claim 1, wherein said light source is a plurality of light emitting diodes.

4. An optical illumination system of claim 3, wherein said light source is a plurality of green and blue light emitting diodes.

5. An optical illumination system of claim 3, wherein said light source is a plurality of red, green and blue light emitting diodes.

6. An optical illumination system of claim 5, wherein said plurality of red, green and blue light emitting diodes are illuminated in a color sequential fashion.

7. An optical illumination system of claim 1, wherein said light-reflecting cavity is hollow.

8. An optical illumination system of claim 1, wherein said light-reflecting cavity is filled or partially filled with a transparent material.

9. An optical illumination system of claim 8, wherein said transparent material is a glass.

10. An optical illumination system of claim 8, wherein said transparent material is a plastic.

11. An optical illumination system of claim 8, wherein said transparent material is a liquid.

12. An optical illumination system of claim 1, wherein said reflectivity R_S is at least 75%.

13. An optical illumination system of claim 1, wherein said reflectivity R_S is at least 90%.

14. An optical illumination system of claim 1, wherein said reflectivity R_C is at least 75%.

15. An optical illumination system of claim 1, wherein said reflectivity R_C is at least 90%.

16. An optical illumination system of claim 1, wherein said surface of said light-reflecting cavity contains a plurality of said light output apertures with total output aperture area of A_O.

17. An optical illumination system of claim 1, wherein said area A_O is less than or equal to 50% of said area A_S.

18. An optical illumination system of claim 1, wherein said area A_O is less than or equal to 25% of said area A_S.

19. An optical illumination system of claim 1, wherein said area A_O is less than or equal to 10% of said area A_S.

20. An optical illumination system of claim 1, wherein said area A_O is less than 25 square millimeters.

21. An optical illumination system of claim 1, wherein said area A_O is less than 10 square millimeters.

22. An optical illumination system of claim 1, wherein said light-reflecting cavity has a polygonal cross-section.

23. An optical illumination system of claim 22, wherein said polygonal cross-section is a square.

24. An optical illumination system of claim 1, wherein said light-reflecting cavity has an elliptical cross-section.

25. An optical illumination system of claim 24, wherein said elliptical cross-section is a circle.

26. An optical illumination system of claim 1, wherein said light-reflecting cavity has a uniform cross-section along an axis of said light-reflecting cavity that passes through the center of said light output aperture and that is perpendicular to the plane of said light output aperture.

27. An optical illumination system of claim 1, wherein said light-reflecting cavity has a tapered cross-section along an axis of said light-reflecting cavity that passes through the center of said light output aperture and that is perpendicular to the plane of said light output aperture.

28. An optical illumination system comprising:

a) A light source for generating light, wherein said light source is at least one light emitting diode having a reflecting surface with reflectivity R_S greater than or equal to 50 percent, wherein the maximum intrinsic luminance of said light source is L_I and wherein the total light emitting area of said light source is area A_S;

b) A light-reflecting cavity enclosing said light source, wherein the inside surfaces of said light-reflecting cavity have reflectivity R_C greater than or equal to 50 percent, and wherein the inside surfaces of said light-reflecting cavity can reflect and recycle a portion of the light generated by said light source back to said light source;

c) At least one light output aperture in a surface of said light-reflecting cavity, wherein the area of said light output aperture is area A_O and wherein said area A_O is less than said area A_S; and

d) At least one partially reflecting optical element located in the light output optical path and located adjacent to said light output aperture of said light-reflecting cavity, wherein said partially reflecting optical element passes a first portion of the light transmitted by said light output aperture and reflects and recycles a second portion of the light transmitted by said light output aperture back into said light-reflecting cavity.

29. An optical illumination system of claim 28, wherein the light output from said light output aperture has luminance L_O that is greater than L_I.

30. An optical illumination system of claim 28, wherein said light source is a plurality of light emitting diodes.

31. An optical illumination system of claim 28, wherein said partially reflecting optical element is a reflective polarizer.

32. An optical illumination system of claim 28, wherein said partially reflecting optical element is a variable aperture with a reflective coating.

33. An optical illumination system comprising:

a) A light source for generating light, wherein said light source is at least one light emitting diode having a reflecting surface with reflectivity R_S greater than or equal to 50 percent, wherein the maximum intrinsic luminance of said light source is L_I and wherein the total light emitting area of said light source is area A_S;

b) A light-reflecting cavity enclosing said light source, wherein the inside surfaces of said light-reflecting cavity have reflectivity R_C greater than or equal to 50 percent, and wherein the inside surfaces of said light-reflecting cavity can reflect and recycle a portion of the light generated by said light source back to said light source;

c) At least one light output aperture in a surface of said light-reflecting cavity, wherein the area of said light output aperture is area A_O and wherein said area A_O is less than said area A_S; and

d) At least one light collimating element located in the light output optical path and located adjacent to said light output aperture of the said light-reflecting cavity, wherein said light collimating element partially collimates the light passing through said light output aperture.

34. An optical illumination system of claim 33, wherein the light output from said light output aperture has luminance L_O that is greater than L_I.

35. An optical illumination system of claim 33, wherein said light collimating element is a refracting element.

36. An optical illumination system of claim 35, wherein said refracting element is a convex lens.

37. An optical illumination system of claim 33, wherein said light collimating element is a reflective element.

38. An optical illumination system of claim 37, wherein said reflective element is a compound parabolic reflector.

39. An optical illumination system of claim 33, wherein said optical illumination system includes a plurality of said light collimating elements.

40. An optical illumination system of claim 39, wherein said plurality of said light collimating elements includes a refractive element and a reflective element.

41. An optical illumination system comprising:

a) A light source for generating light, wherein said light source is at least one light emitting diode having a reflecting surface with reflectivity R_S greater than or equal to 50 percent, wherein the maximum intrinsic luminance of said light source is L_I and wherein the total light emitting area of said light source is area A_S;

b) A light-reflecting cavity enclosing said light source, wherein the inside surfaces of said light-reflecting cavity have reflectivity R_C greater than or equal to 50 percent, and wherein the inside surfaces of said light-reflecting cavity can reflect and recycle a portion of the light generated by said light source back to said light source;

c) At least one light output aperture in a surface of said light-reflecting cavity, wherein the area of said light output aperture is area A_O and wherein said area A_O is less than said area A_S;

d) At least one light collimating element located in the light output optical path and located adjacent to said light output aperture of the said light-reflecting cavity, wherein said light collimating element partially collimates the light passing through said light output aperture; and

e) At least one partially reflecting optical element located in the light output optical path and located adjacent to said light collimating element, wherein said partially reflecting optical element passes a first portion of the light transmitted by said light output aperture and reflects and recycles a second portion of the light transmitted by said light output aperture back into said light-reflecting cavity.

42. An optical illumination system of claim 41, wherein the light output from said light output aperture has luminance L_O that is greater than L_I.

43. An optical illumination system of claim 41, wherein said partially reflecting optical element is a reflective polarizer.

44. A first optical illumination system comprising:

a) A light source for generating light, wherein said light source is at least one light emitting diode having a reflecting surface with reflectivity R_S greater than or equal to 50 percent, wherein the maximum intrinsic luminance of said light source is L_I and wherein the total light emitting area of said light source is area A_S;

b) A light-reflecting cavity enclosing said light source, wherein the inside surfaces of said light-reflecting cavity have reflectivity R_C greater than or equal to 50 percent, and wherein the inside surfaces of said light-reflecting cavity can reflect and recycle a portion of the light generated by said light source back to said light source;

c) A light output aperture in a surface of said light-reflecting cavity, wherein the area of said light output aperture is area A_O and wherein said area A_O is less than said area A_S;

d) At least one light collimating element located in the light output optical path and located adjacent to said light output aperture of the said light-reflecting cavity, wherein said light collimating element partially collimates the light passing through said light output aperture; and

e) At least one partially reflecting optical element located in the light output optical path and located adjacent to said light collimating element, wherein said partially reflecting optical element passes a first portion of the light transmitted by said light output aperture and reflects and recycles a second portion of the light transmitted by said light output aperture into a second optical illumination system.

45. An optical illumination system of claim 44, wherein the light output from said light output aperture has luminance L_O that is greater than L_I.

46. An optical illumination system of claim 44, wherein said partially reflecting optical element is a reflective polarizer.