LED array systems

• US 7,997,771 B2
• Filed: 06/01/2004
• Issued: 08/16/2011
• Est. Priority Date: 06/01/2004
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Epstein, Kenneth A., Emmons, Robert M., Tran, Hung T., Schultz, John C.
• Primary Examiner(s): Ward; John A
• Application Number:
  US10/858,539
• Publication Number:
  US 20050265029A1
• Time in Patent Office: 2,632 Days
• Field of Search: 362/330, 362/339, 362/231, 362/241, 362/19, 362/246, 362/632, 362/619, 362/625, 385/901, 385/125, 385/31
• US Class Current: 362/339
• CPC Class Codes: G02B 3/0056 arranged along two different directions in a plane, e.g. honeycomb arrangement of lenses G02B3/0043 takes precedence; miniaturised objectives for electronic devices employing wafer level optics G02B13/0085
• 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 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• 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: G09F 9/3026 Video wall, i.e. stackable semiconductor matrix display modules video wall control systems G06F3/1446, G09G2300/026
• CPC Class Codes: G09F 9/33 being semiconductor devices, e.g. diodes
• CPC Class Codes: G09F 9/35 being liquid crystals G09F9/302 takes precedence; liquid crystal materials C09K19/00; liquid crystal panels comprising a number of electrodes in a single cell per se G02F1/13

Abstract

A light emitting diode (LED) array comprises an array of LEDs mounted to a substrate. The LEDs emit light in a direction generally perpendicular to the substrate. An optical sheet is disposed over the LEDs. At least a portion of light entering one side of the optical sheet from the LEDs is guided within the optical sheet in a direction generally parallel to the substrate. Light extraction features direct light from the optical sheet in a generally forward direction. Such an array is useful for several applications, including space lighting, direct information display and backlighting of liquid crystal displays. The light spreading effect of the optical sheet reduces the amount of black space between LED pixels.

Claims

1. An optical assembly for emitting light, comprising:

an array of inorganic light emitting diodes (LEDs) mounted to a substrate, the LEDs emitting light in a direction generally perpendicular to the substrate; and

an optical sheet disposed over the LEDs, at least a portion of light entering one surface the optical sheet from the LEDs being guided within the optical sheet in a direction generally parallel to the substrate, wherein the optical sheet comprises a first light reflecting surface facing towards the substrate and a second light transmitting surface facing away from the substrate, at least one light extraction feature being provided with the optical sheet to extract light, that has been guided along the optical sheet from the LEDs, and wherein the extraction feature comprises a portion of the optical sheet where at least one of the first surface and the second surface of the optical sheet has a surface non-parallel to the substrate.

2. An assembly as recited in claim 1, wherein the light extraction feature comprises one or more light extraction prisms having prism bases disposed on the second side of the optical sheet.

3. An assembly as recited in claim 2, wherein the light extraction prisms are arranged on the second side of the optical sheet as one or more Fresnel lenses.

4. An assembly as recited in claim 2, wherein the light extraction prisms on the second side are substantially linear.

5. An assembly as recited in claim 2, wherein the light extraction prisms on the second side are curved.

6. An assembly as recited in claim 1, wherein the light extraction feature comprises one or more diffractive structures on at least one of the first and second sides of the optical sheet.

7. An assembly as recited in claim 1, wherein the light extraction feature comprises one or more patches of diffusely reflecting material on at least one of the first and second sides of the optical sheet.

8. An assembly as recited in claim 1, wherein the light extraction feature comprises one or more indentations on one of the sides of the optical sheet.

9. An assembly as recited in claim 1, wherein the light extraction feature comprises one or more grooves on the second side, light guided within the optical sheet being directed by the one or more grooves to the first side of the optical sheet.

10. An assembly as recited in claim 1, further comprising a reflecting layer disposed between the optical sheet and the substrate so that light, directed to the reflecting layer by the extraction feature, is reflected by the reflecting layer out of the optical sheet.

11. An assembly as recited in claim 1, wherein the extraction feature comprises an array of light extraction prisms disposed with respective prism apexes directed towards the optical sheet.

12. An assembly as recited in claim 11, further comprising a coupling layer on the second side of the optical sheet, wherein the guided light passes into the coupling layer and the prism apexes extend into the coupling layer.

13. An assembly as recited in claim 11, wherein light that has coupled from the optical sheet into the light extraction prisms is totally internally reflected by the prisms in a direction away from the optical sheet.

14. An assembly as recited in claim 11, further comprising an optical diffuser, light that has passed through the light extraction prisms from the optical sheet being passed through the optical diffuser.

15. An assembly as recited in claim 11, further comprising a filter, light that has passed through the light extraction prisms from the optical sheet being passed through the filter.

16. An assembly as recited in claim 15, wherein the filter comprises a projection screen.

17. An assembly as recited in claim 15, wherein the filter comprises a polarizer.

18. An assembly as recited in claim 11, wherein the light extraction prisms are substantially linear.

19. An assembly as recited in claim 11, wherein the light extraction prisms are curved.

20. An assembly as recited in claim 19, wherein the curved light extraction prisms are curved in patterns centered on respective LEDs.

21. An assembly as recited in claim 1, wherein the extraction feature comprises a portion of at least one of the sides of the optical sheet that lies nonparallel to the substrate.

22. An assembly as recited in claim 1, wherein the light internally reflects at the surface non-parallel to the substrate.

23. An assembly as recited in claim 1, wherein the surface non-parallel to the substrate is provided with a surface structure that directs light incident thereon towards an opposing side of the optical sheet.

24. An assembly as recited in claim 23, wherein the surface structure comprises one or more turning prisms.

25. An assembly as recited in claim 23, wherein the surface structure comprises one or more surface steps.

26. An assembly as recited in claim 1, wherein the second side of the optical sheet contains one or more indented surfaces disposed above respective LEDs, so that light from the LEDs that passes through the optical sheet from the LEDs in a direction substantially normal to the optical sheet is internally reflected at the one or more indented surfaces.

27. An assembly as recited in claim 1, wherein the extraction feature comprises one or more surface structures disposed on the first side of the optical sheet.

28. An assembly as recited in claim 27, wherein the one or more surface structures on the first side of the optical sheet comprise angled reflective faces so that light, that has been guided within the optical sheet, is directed by the angled reflective faces to be incident on the second side of the optical sheet at an angle that permits transmission of the light through the second side.

29. An assembly as recited in claim 27, wherein the one or more surface structures on the first side of the optical sheet comprise diffusive elements that diffusely reflect light incident thereon.

30. An assembly as recited in claim 1, wherein the extraction feature comprises at least one continuous light extraction feature surrounding a respective LED.

31. An assembly as recited in claim 1, wherein the extraction feature comprises at least one light extraction feature that does not continuously surround its respective LED.

32. An assembly as recited in claim 1, wherein the extraction features comprise areas of diffusely reflecting material.

33. An assembly as recited in claim 32, wherein the diffusely reflecting material is arranged so as to provide a greater degree of diffuse reflection at positions illuminated by relatively more intense light from the LEDs than for positions illuminated by relatively less intense light from the LEDs.

34. An assembly as recited in claim 1, further comprising one or more light management films to direct light extracted from the optical sheet.

35. An assembly as recited in claim 34, wherein the one or more light management films comprise at least a first brightness enhancing prismatic film having an array of prisms arranged to direct light extracted from the optical sheet in a direction more parallel to an axis normal to the optical sheet.

36. An assembly as recited in claim 34, wherein the one or more light management films further comprises a second brightness enhancing optical film having an array of prisms arranged to direct light extracted from the optical sheet in a direction more parallel to the axis normal to the optical sheet, the prisms of the second brightness enhancing optical film extending in a direction perpendicular to an extension direction of the prisms of the first brightness enhancing sheet.

37. An assembly as recited in claim 1, further comprising a projection screen disposed over the optical sheet so that light extracted from the optical sheet passes through the projection screen.

38. An assembly as recited in claim 1, wherein the optical sheet comprises one or more elements to deflect some of the light from the LEDs, that would otherwise pass through the optical sheet, within the optical sheet.

39. An assembly as recited in claim 38, wherein the one or more elements comprise indented surfaces disposed above respective LEDs, so that some of the light from the LEDs that passes through the optical sheet from the LEDs in a direction substantially normal to the optical sheet is internally reflected within the optical sheet at the one or more indented surfaces.

40. An assembly as recited in claim 1, wherein the optical sheet generally lies parallel to the substrate.

41. An assembly as recited in claim 1, wherein the LEDs are disposed on the substrate as LED dies.

42. An assembly as recited in claim 1, further comprising an intermediate layer disposed between the optical sheet and the substrate.

43. An assembly as recited in claim 42, wherein the intermediate layer is reflective.

44. An assembly as recited in claim 42, wherein the intermediate layer is provided with at least one light extraction feature to extract light that has been guided along the optical sheet from the LEDs.

45. An assembly as recited in claim 44, wherein the light extraction feature comprises one or more angled surfaces non-parallel to the substrate.

46. An assembly as recited in claim 44, wherein the light extraction feature comprises one or more patches of diffusely reflective material.

47. An assembly as recited in claim 42, further comprising an arrangement of areas of diffusely reflecting material disposed to diffusely reflect at least some of the light that has passed out of the optical sheet.

48. An assembly as recited in claim 47, wherein the intermediate layer is reflective, and some of the light diffusely reflected by the areas of diffusely reflecting material is reflected by the reflective intermediate layer so as to pass between the areas of diffusely reflecting material.

49. An assembly as recited in claim 48, further comprising a diffuser disposed to diffuse light that has passed between the areas of diffusely reflecting material.

50. An assembly as recited in claim 1, wherein the substrate is reflective.

51. An assembly as recited in claim 1, wherein the optical sheet comprises electrical conductors disposed on a side of the optical sheet facing the LEDs, the electrical conductors connecting to emitting sides of respective LEDs.

52. An assembly as recited in claim 1, wherein the substrate comprises electrical conductors connecting to base sides of respective LEDs.

53. An assembly as recited in claim 1, further comprising an intermediate layer between the optical sheet and the substrate, and electrical conductors on the intermediate layer connecting to respective LEDs.

54. An assembly as recited in claim 1, wherein the assembly is flexible so as to be formable into a non-planar shape.

55. The optical assembly of claim 1, wherein the first light reflecting side comprises a light reflecting coating.

56. The optical assembly of claim 1, wherein the first light reflecting side comprises one or more steps to totally internally reflect light.

57. The optical assembly of claim 1, wherein the first light reflecting side comprises an element for reflecting light by a combination of refraction and total internal reflection.