Bi-directional backlight assembly

• US 20080219025A1
• Filed: 03/07/2007
• Published: 09/11/2008
• Est. Priority Date: 03/07/2007
• Status: Abandoned Application

• Current Assignee: Google Inc. (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Spitzer, Mark B., Lincoln, Maureen A., Rensing, Noa M., Haghayegh, Arash
• Application Number:
  US11/715,289
• Publication Number:
  US 20080219025A1
• Time in Patent Office: Days
• US Class Current: 362/609
• CPC Class Codes: G02B 2027/0118 comprising devices for improving the contrast of the display / brillance control visibility
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/017 Head mounted
• 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 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0041 provided in the bulk of the light guide
• CPC Class Codes: G02B 6/0063 for extracting light out both the major surfaces of the light guide

Abstract

A backlight assembly emits light out of two light emitting faces using a light source such as side-emitting LEDs that send light into an optical guide or body of optical material that diffuses the light uniformly and emits bi-facially. In this way, two displays, such as LCDs, can be illuminated at the same time and the efficiency is increased. The backlight assembly can be incorporated into an eyewear system such as a binocular display system.

Claims

1. A backlight assembly comprising:

a circuit substrate comprising a first surface defining a first side and a second surface defining a second side, an opening formed through the circuit substrate from the first side to the second side;

a body of optical material disposed within the opening in the circuit substrate, the body comprising an edge disposed within the opening in the circuit substrate, a first light emitting face located on the first side of the circuit substrate, and a second light emitting face located on the second side of the circuit substrate; and

a light source disposed to direct light into a location along the edge of the optical material body, the light source in communication with circuitry on the circuit substrate.

2. The assembly of claim 1, wherein the optical material is physically coupled to the light source.

3. The assembly of claim 1, wherein the optical material encapsulates the light source.

4. The assembly of claim 1, wherein the first and second light emitting faces are flat.

5. The assembly of claim 1, wherein the first and second light emitting faces are curved.

6. The assembly of claim 1, wherein the first and second light emitting faces are shaped to provide a desired light emission pattern.

7. The assembly of claim 1, wherein the first and second light emitting faces are textured.

8. The assembly of claim 1, wherein the light source comprises one or more light emitting diodes.

9. The assembly of claim 1, wherein the light source comprises a plurality of light emitting diodes disposed to direct light into a plurality of locations along the edge of the optical material body.

10. The assembly of claim 1, wherein the light source comprises a plurality of side-emitting light emitting diode packages.

11. The assembly of claim 1, wherein the light source comprises a plurality of top-emitting light emitting diode packages.

12. The assembly of claim 1, wherein the light source comprises a plurality of unpackaged light emitting diodes.

13. The assembly of claim 1, further comprising a reflective surface adjacent the light source to direct emissions toward the optical material body.

14. The assembly of claim 1, wherein the optical material body further comprises corner regions, and the light source comprises a light emitting diode located generally at each corner region of the optical material body.

15. The assembly of claim 1, wherein the optical material body further comprises a generally rectangular shape having four sides, and the light source comprises a light emitting diode located generally along each of the four sides.

16. The assembly of claim 1, wherein the light source comprises a plurality of light emitting diodes located on one of the first and second sides of the circuit substrate.

17. The assembly of claim 1, wherein the light source comprises a plurality of light emitting diodes located on both of the first and second sides of the circuit substrate.

18. The assembly of claim 1, wherein the optical material is comprised of optical polymethylmethacrylate, polycarbonate, glass, urethane, or optical epoxy.

19. The assembly of claim 1, wherein the optical material has an index of refraction between 1.4 and 1.8.

20. The assembly of claim 1, wherein the optical material has a low optical absorption.

21. The assembly of claim 1, wherein the circuit substrate comprises a printed circuit board.

22. The assembly of claim 1, wherein the circuit substrate comprises a flexible printed circuit.

23. The assembly of claim 1, wherein the optical material extends to edges of the circuit substrate.

24. The assembly of claim 1, further comprising a diffusing sheet disposed on at least one of the first and second light emitting faces of the optical material body.

25. The assembly of claim 1, further comprising a brightness enhancing film disposed on at least one of the first and second light emitting faces.

26. The assembly of claim 1, further comprising laminar reflectors disposed within the optical material body.

27. The assembly of claim 26, wherein the laminar reflectors comprise a stack of optically clear plates interspersed with partially reflective dielectric coatings.

28. The assembly of claim 26, wherein the laminar reflectors comprise plates having textured surfaces.

29. The assembly of claim 26, wherein the laminar reflectors comprise plates separated by air gaps.

30. The assembly of claim 26, wherein the laminar reflectors comprise plates separated by plates or films of a different index of refraction.

31. The assembly of claim 1, further comprising scattering centers distributed within the optical material.

32. The assembly of claim 31, wherein the scattering centers comprise air-filled glass bubbles.

33. The assembly of claim 31, wherein the scattering centers comprise gas bubbles.

34. The assembly of claim 31, wherein the scattering centers comprise particles having a different index of refraction than the optical material.

35. The assembly of claim 31, wherein the scattering centers comprise white or metallic particles.

36. The assembly of claim 1, further comprising reflecting or refracting elements distributed within the optical material.

37. The assembly of claim 1, further comprising light emitting phosphors dispersed throughout the optical material.

38. The assembly of claim 1, further comprising light emitting phosphors coated on one or both of the first and second light emitting faces of the optical material.

39. The assembly of claim 1, further comprising an optical film disposed within the optical material.

40. The assembly of claim 1, further comprising a shaped diffusing element disposed with the optical material.

41. The assembly of claim 1, further comprising a shaped reflective element disposed with the optical material.

42. The assembly of claim 1, further comprising a reflective surface disposed on one or both of the first and second light emitting faces.

43. A backlight and display assembly comprising:

a backlight assembly according to claim 1;

a first display disposed on the first side of the circuit substrate to receive light emitted from the first light emitting face of the optical material body; and

a second display disposed on the second side of the circuit substrate to receive light emitted from the second light emitting face of the optical material body.

44. The assembly of claim 43, wherein the first display and the second display comprise liquid crystal displays.

45. The assembly of claim 43, wherein the first light emitting face has an area corresponding to an area of a pixel field of the first display, and the second light emitting face has an area corresponding to an area of a pixel field of the second display.

46. The assembly of claim 43, further comprising a spacer between the circuit substrate and at least one of the first and second displays, the optical material body filling a volume between the spacer and the first and second displays.

47. The assembly of claim 46, wherein the spacer masks areas outside an active matrix pixel area on the first display or the second display.

48. The assembly of claim 43, further comprising a mask disposed to mask areas outside an active matrix pixel area on the first display or the second display.

49. A binocular viewing device comprising:

a backlight assembly according to claim 1;

a first display disposed on the first side of the circuit substrate to receive light emitted from the first light emitting face of the optical material body; and

a second display disposed on the second side of the circuit substrate to receive light emitted from the second light emitting face of the optical material body;

a first optical assembly disposed to receive an image from the first display and relay the image to a user'"'"'s first eye;

a second optical assembly disposed to receive an image from the second display and relay an image to a user'"'"'s second eye; and

a frame or housing, the backlight assembly, the first display, and the second display supported by the frame or housing between the first optical assembly and the second optical assembly.

50. The binocular viewing device of claim 49, wherein a focal length and an image convergence distance are infinity or approximately infinity.

51. The binocular viewing device of claim 49, wherein a focal length and an image convergence distance are less than infinity.

52. The binocular viewing device of claim 49, wherein the optical material body is tapered so that the first light emitting face and the second light emitting face of the backlight assembly are not parallel.

53. The binocular viewing device of claim 52, wherein the taper imparts a curvature about a horizontal axis to the binocular viewer.

54. The binocular viewing device of claim 52, wherein the taper imparts a curvature about a vertical axis to the binocular viewer.

55. The binocular viewing device of claim 49, wherein the first optical assembly and the second optical assembly each comprise an objective lens in optical alignment with an associated one of the first display and the second display.

56. The binocular viewing device of claim 55, wherein the first optical assembly and the second optical assembly each further comprise a reflective surface to reflect an image from the objective lens to the user'"'"'s eyes.

57. The binocular viewing device of claim 49, wherein the first optical assembly and the second optical assembly further comprise an optical component to magnify an image.

58. The binocular viewing device of claim 49, wherein the frame or housing is head-mountable for wearing by the user.

59. The binocular viewing device of claim 58, wherein the frame or housing holds the backlight assembly, the first display, the second display, the first optical assembly, and the second optical assembly in optical alignment.

60. The binocular viewing device of claim 49, wherein the backlight assembly, the first display, and the second display are disposed generally midway between the first optical assembly and the second optical assembly.