Backlight assembly for collimated illumination

• US 6,697,042 B1
• Filed: 11/27/2000
• Issued: 02/24/2004
• Est. Priority Date: 11/27/2000
• Status: Active Grant

• Current Assignee: Display Vectors LLC (Jeffrey M. Gross)
• Original Assignee: Rainbow Displays, Inc.
• Inventors: Greene, Raymond G., Cohen, Jennifer M., Strope, Douglas H., Skinner, Dean W.
• Primary Examiner(s): AWAD, AMR A
• Application Number:
  US09/721,819
• Time in Patent Office: 1,184 Days
• Field of Search: 345/102, 345/87, 345/6, 349/5, 349/61, 349/62, 349/64, 349/65, 349/66, 349/67, 349/113, 362/31, 362/558, 362/561, 359/613-614
• US Class Current: 345/102
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02F 1/133602 Direct backlight
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses

Abstract

A large, efficient, high power collimated backlight assembly has a highly reflective, substantially closed, thin rectangular light cavity containing highly reflective surfaces and one or more light sources. One of the large faces of the cavity is a light exit plate which contains a transmissive, light collimating structure. The cavity side of the collimating structure includes a highly reflective white planar structure containing an array of circular apertures with minimal sidewall absorption. The apertures are centered on the optical axis and located near the focal distance of a closely packed array of hemispherical or spherical lenses located on the outer surface of the collimating structure. Light rays are trapped between the highly reflective surfaces of the cavity, light sources, and aperture walls, until they enter the lenses, which output the majority of rays that enter in a collimated beam. The backlight assembly is advantageously used for transmissive type electro-optical displays, especially those whose performance is enhanced by efficient collimated light, such as seamless tiled liquid crystal displays.

Claims

1. A cavity exit plate light collimating structure comprising:

a) a single, substantially planar, composite substrate comprising a highly reflective layer and an optically absorptive layer disposed substantially parallel to one another, said composite substrate having two major, diametrically opposed exterior surfaces;

said optically absorptive layer defining an optical output surface and said highly reflective layer defining an optical input surface;

b) a plurality of spaced apart apertures disposed in said single composite substrate; and

c) a plurality of lenses for transmitting light, each of said lenses being associated with one of said apertures and disposed proximately thereto on said optical output surface of said single composite substrate.

2. The cavity exit plate light collimating structure in accordance with claim 1, wherein said apertures comprise physical openings.

3. The cavity exit plate light collimating structure in accordance with claim 2, wherein said physical openings each comprise substantially optically non-absorbing sidewalls.

4. The cavity exit plate light collimating structure in accordance with claim 2, wherein each aperture of said plurality of apertures comprises one of the configurations:

simple straight holes;

a tapered hole with large side at said optical input side and small end forming a lens entrance pupil;

a ball cut shape from said optical output side; and

an irregular, hour glass shape with narrowest diameter between said optical input side and a lens entrance pupil.

5. The cavity exit plate light collimating structure in accordance with claim 1, wherein said apertures comprise non-perforated annuli.

6. The cavity exit plate light collimating structure in accordance with claim 1, wherein said lenses are shaped substantially spherically.

7. The cavity exit plate light collimating structure in accordance with claim 6, wherein each of said lenses has a predetermined radius and said reflective layer has a predetermined thickness, said lens radius being no less than said predetermined thickness of said reflective layer.

8. The cavity exit plate light collimating structure in accordance with claim 1, wherein each of said lenses is a hybrid lens.

9. The cavity exit plate light collimating structure in accordance with claim 8, wherein said lenses have a convex surface and a hemispherical surface.

10. The cavity exit plate light collimating structure in accordance with claim 1, wherein said lenses are shaped substantially irregularly to conform to the function of said apertures.

11. The cavity exit plate light collimating structure in accordance with claim 10, wherein each of said lenses has a predetermined radius and said reflective structure has a predetermined thickness, said lens radius being no less than said reflective structure thickness.

12. The cavity exit plate light collimating structure in accordance with claim 1, wherein said reflective layer comprises one from the group of PTFE-coated aluminum, multi-layer polymer films, and phosphor mixtures coated over aluminum.

13. The cavity exit plate light collimating structure in accordance with claim 12, wherein said reflective layer exhibits a total diffuse plus specular reflectivity in the range of approximately 90-99%.

14. The cavity exit plate light collimating structure in accordance with claim 1, further comprising an adhesive layer disposed adjacent said optical output surface and said plurality of lenses.

15. The cavity exit plate light collimating structure in accordance with claim 14, wherein said adhesive layer is optically absorptive.

16. In a flat panel display having a display panel and a backlight cavity associated therewith, the improvement comprising an exit plate collimating structure disposed in said backlight cavity, said exit plate collimating structure comprising:

a) a single, substantially planar, composite substrate comprising a highly reflective layer and an optically absorptive layer disposed substantially parallel to one another, said composite substrate having two major, diametrically opposed exterior surfaces;

said optically absorptive layer defining an optical output surface and said highly reflective layer defining an optical input surface;

b) a plurality of spaced apart apertures disposed in said single composite substrate; and

c) a plurality of lenses for transmitting light, each of said lenses being associated with one of said apertures and disposed proximately thereto on said optical output surface of said single composite substrate.

17. The flat panel display in accordance with claim 16, said structure further comprising:

d) a light source disposed in said backlight cavity for providing light to said optical input surface of said exit plate collimating structure and to said display panel.

18. The flat panel display in accordance with claim 16, wherein said flat panel display comprises a monolithic or a monolithic-like display.

19. The flat panel display in accordance with claim 17, wherein said light source comprises at least one of the light sources:

at least one fluorescent lamp, and light emitting devices.

20. The cavity exit plate light collimating structure in accordance with claim 17, wherein said apertures comprise physical openings.

21. The cavity exit plate light collimating structure in accordance with claim 17, wherein said apertures comprise non-perforated annuli.

22. The cavity exit plate light collimating structure in accordance with claim 17, wherein said lenses are shaped substantially spherically.

23. The cavity exit plate light collimating structure in accordance with claim 22, wherein each of said lenses has a predetermined radius and said reflective structure has a predetermined thickness, said lens radius being no less than said reflective structure thickness.

24. The cavity exit plate light collimating structure in accordance with claim 17, wherein each of said lenses is a hybrid lens.

25. The cavity exit plate light collimating structure in accordance with claim 24, wherein said lenses have a convex surface and a hemispherical surface.

26. The cavity exit plate light collimating structure in accordance with claim 17, wherein said lenses are shaped substantially irregularly to conform to the function of said apertures.

27. The cavity exit plate light collimating structure in accordance with claim 26, wherein each of said lenses has a predetermined radius and said reflective structure has a predetermined thickness, said lens radius being no less than said reflective structure thickness.

28. The cavity exit plate light collimating structure in accordance with claim 17, wherein said reflective structure comprises one from the group of PTFE-coated aluminum, multi-layer polymer films, and phosphor mixtures coated over aluminum.

29. The flat panel display in accordance with claim 17, further comprising:

e) a black, light absorbing surface disposed beneath said plurality of lenses on said optical output side of said substrate.

30. A cavity exit plate light collimating structure comprising:

a) a single, solid, optically transparent substantially planar substrate having a first surface defining an optical input surface and a second surface substantially planar to said first surface defining an optical output surface;

b) a reflective composite layer having a plurality of spaced apart apertures therein adhered to and substantially covering said optical output surface, said reflective composite layer having an outward facing surface;

c) adhesive applied to said outward facing surface; and

d) a plurality of lenses adhered to said outward facing surface of said reflective composite layer, each of said plurality of lenses being substantially centered on a respective one of said plurality of apertures.

31. The cavity exit plate light collimating structure as recited in claim 30, further comprising:

e) a layer of reflective tape applied to said outward facing surface of said reflective composite layer.

32. The cavity exit plate light collimating structure as recited in claim 30, wherein said optical input surface of said single, solid, optically transparent substantially planar substrate comprises an absorptive coating.

33. The cavity exit plate light collimating structure as recited in claim 30, wherein said adhesive layer is substantially absorptive.