Liquid crystal display illumination system

• US 4,915,479 A
• Filed: 12/08/1987
• Issued: 04/10/1990
• Est. Priority Date: 12/17/1986
• Status: Expired due to Term

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Clarke, John A.
• Primary Examiner(s): James, Andrew J.
• Assistant Examiner(s): GROSS, ANITA P
• Application Number:
  US07/130,365
• Time in Patent Office: 854 Days
• Field of Search: 350/345, 350/96.1, 350/96.18, 362/32
• US Class Current: 349/62
• CPC Class Codes: G02F 1/133524 Light-guides, e.g. fibre-optic bundles, louvered or jalousie light-guides

Abstract

An illumination system is provided for a liquid crystal display panel. The panel 1 is placed to transmit light 2 from a light source 3 to a viewing location, the light source being an extended area source of omnidirectional light of high efficiency, such as a fluorescent tube. A light guide 6 is placed between the source and the panel, the light guide comprising a transparent input face 7 adjacent the source, a transparent output face 10 adjacent the panel, and reflective side walls 11 transverse to the input and output faces. The light guide is tapered, the input face being smaller in area than the output face. The divergence of light from the source is thereby reduced as it passes through the panel. The LCD panel then functions with an improved contrast range.

Claims

1. An illumination system for a liquid crystal display panel comprising

a liquid crystalline display panel,

an extended area source of omnidirectional light,

light conducting means for conducting said extended area of omnidirectional light from said source to said display panel, said light conducting means including

an extended transparent input face adjacent said source of omnidirectional light,

an extended transparent output face directly adjacent to said display panel, said output face being larger in area than said input face, and said output face being convex toward said display panel, and

tapered reflective side walls extending from said input face to said output face, said side walls being at an angle to said input face and said output face,

wherein said output face passes collimated light directly into said liquid crystal display panel at smaller angles of divergence than light entering said input face from said source.

2. An illumination system according to claim 1, wherein said light conducting means includes a transparent material having a refractive index higher than that of surrounding space, and wherein said side walls are totally internally reflecting.

3. An illumination system according to claim 1, wherein said output face includes a positive lens.

4. An illumination system according to claim 3, wherein said light conducting means includes a transparent material having a refractive index higher than that of surrounding space, and wherein said side walls are totally internally reflecting.

5. An illumination system according to claim 1 or claim 3 or claim 4, wherein said side walls are curved in planes transverse to said input face and said output face.

6. An illumination system according to claim 5, wherein a plurality of said light conducting means are disposed between said extended area source and said display panel, said output face of each of said plurality being adjacent to one another to cover the entire area of said display panel.

7. An illumination system according to claim 6, wherein said output face of each of said plurality are identical to one another, and wherein said output faces of said plurality are arranged in rows and columns to cover said entire area of said display panel.

8. An illumination system according to claim 7, wherein each of said plurality of output faces and each of the plurality of input faces of said light conducting means are rectangular.

9. An illumination system for a liquid crystal display panel comprising

a liquid crystalline display panel,

an extended area source of omnidirectional light,

light conducting means for conducting said extended area of omnidirectional light from said source to said display panel, said light conducting means including

an extended transparent input face adjacent said source of omnidirectional light,

an extended transparent output face directly adjacent to said display panel, said output face being larger in area than said input face, and

tapered reflective side walls extending from said input face to said output face, said side walls being at an angle to said input face and said output face,

wherein said output face passes collimated light directly into said liquid crystal display panel at smaller angles of divergence than light entering said input face from said source,

wherein said side walls are curved in planes transverse to said input face and said output face,

wherein a plurality of said light conducting means are disposed between said extended area source and said display panel, said output face of each of said plurality being adjacent to one another to cover the entire area of said display panel, and

wherein a plurality of feeder light guides are disposed between said source and said light conducting means, each of said plurality of feeder light guides extending between different areas of said extended area source and said input face of each of said plurality of light conducting means.

10. An illumination system according to claim 9, wherein said source of light includes a phosphor layer energized to produce light.

11. An illumination system according to claim 10, wherein said phosphor layer is energized by ultra-violet radiation from a gas discharge in a fluorescent tube.

12. An illumination system according to claim 11, wherein a part of said phosphor layer is disposed in said fluorescent tube free of said plurality of feeder light guides, and wherein light excited from said part is reflected back into said fluorescent tube onto other parts of said phosphor layer coupled to said feeder light guides.

13. An illumination system according to claim 12, wherein a light diffusing screen is disposed adjacent to a side of said liquid crystal display panel opposite to said light conducting means.

14. An illumination system according to claim 13, wherein said light diffusing screen includes a cylindrical lens array.

15. An illumination system according to claim 11, further comprising an envelope of a material transparent to said ultra-violet radiation, said envelope surrounding a portion of said fluorescent tube free of said feeder light guides, wherein said phosphor layer is disposed only at an inner area of said fluorescent tube facing said feeder light guides, and wherein other inner areas of said fluorescent tube are reflective to direct said ultra-violet radiation back onto said phosphor layer.

16. An illumination system according to claim 15 wherein a light diffusing screen is disposed adjacent to a side of said liquid crystal display panel opposite to said light conducting means.

17. An illumination system according to claim 16, wherein said light diffusing screen includes a cylindrical lens array.

18. An illumination system for a liquid crystal display panel comprising

a liquid crystalline display panel,

an extended area source of omnidirectional light,

light conducting means for conducting said extended area of omnidirectional light from said source to said display panel, said light conducting means including

an extended transparent input face adjacent said source of omnidirectional light,

an extended transparent output face directly adjacent to said display panel, said output face being larger in area than said input face, and

tapered reflective side walls extending from said input face to said output face, said side walls being at an angle to said input face and said output face,

wherein said output face passes collimated light directly into said liquid crystal display panel at smaller angles of divergence than light entering said input face from said source,

wherein said side walls are curved in planes transverse to said input face and said output face,

wherein a plurality of said light conducting means are disposed between said extended area source and said display panel, said output face of each of said plurality being adjacent to one another to cover the entire area of said display panel,

wherein said output face of each of said plurality are identical to one another, and wherein said output faces of said plurality are arranged in rows and columns to cover said entire area of said display panel, and

wherein a plurality of feeder light guides are disposed between said source and said light conducting means, each of said plurality of feeder light guides extending between different areas of said extended area source and said input face of each of said plurality of light conducting means.

19. An illumination system according to claim 18, wherein said source of light includes a phosphor layer energized to produce light.

20. An illumination system according to claim 19, wherein said phosphor layer is energized by ultra-violet radiation from a gas discharge in a fluorescent tube.

21. An illumination system according to claim 20 wherein a part of said phosphor layer is disposed in said fluorescent tube free of said plurality of feeder light guides, and wherein light excited from said part is reflected back into said fluorescent tube onto other parts of said phosphor layer coupled to said feeder light guides.

22. An illumination system according to claim 21, wherein a light diffusing screen is disposed adjacent to a side of said liquid crystal display panel opposite to said light conducting means.

23. An illumination system according to claim 22, wherein said light diffusing screen includes a cylindrical lens array.

24. An illumination system according to claim 20, further comprising an envelope of a material transparent to said ultra-violet radiation, said envelope surrounding a portion of said fluorescent tube free of said feeder light guides, wherein said phosphor layer is disposed only at an inner area of said fluorescent tube facing said feeder light guides, and wherein other inner areas of said fluorescent tube are reflective to direct said ultra-violet radiation back onto said phosphor layer.

25. An illumination system according to claim 24 wherein a light diffusing screen is disposed adjacent to a side of said liquid crystal display panel opposite to said light conducting means.

26. An illumination system according to claim 25, wherein said light diffusing screen includes a cylindrical lens array.

27. An illumination system for a liquid crystal display panel comprising

a liquid crystalline display panel,

an extended area source of omnidirectional light,

light conducting means for conducting said extended area of omnidirectional light from said source to said display panel, said light conducting means including

an extended transparent input face adjacent said source of omnidirectional light,

an extended transparent output face directly adjacent to said display panel, said output face being larger in area than said input face, and

tapered reflective side walls extending from said input face to said output face, said side walls being at an angle to said input face and said output face,

wherein said output face passes collimated light directly into said liquid crystal display panel at smaller angles of divergence than light entering said input face from said source,

wherein said side walls are curved in planes transverse to said input face and said output face,

wherein a plurality of said light conducting means are disposed between said extended area source and said display panel, said output face of each of said plurality being adjacent to one another to cover the entire area of said display panel,

wherein said output face of each of said plurality are identical to one another, and wherein said output faces of said plurality are arranged in rows and columns to cover said entire area of said display panel,

wherein each of said plurality of output faces and each of the plurality of input faces of said light conducting means are rectangular, and

wherein a plurality of feeder light guides are disposed between said source and said light conducting means, each of said plurality of feeder light guides extending between different areas of said extended area source and said input face of each of said plurality of light conducting means.

28. An illumination system according to claim 27, wherein said source of light includes a phosphor layer energized to produce light.

29. An illumination system according to claim 28, wherein said phosphor layer is energized by ultra-violet radiation from a gas discharge in a fluorescent tube.

30. An illumination system according to claim 29 wherein a part of said phosphor layer is disposed in said fluorescent tube free of said plurality of feeder light guides, and wherein light excited from said part is reflected back into said fluorescent tube onto other parts of said phosphor layer coupled to said feeder light guides.

31. An illumination system according to claim 30, wherein a light diffusing screen is disposed adjacent to a side of said liquid crystal display panel opposite to said light conducting means.

32. An illumination system according to claim 31, wherein said light diffusing screen includes a cylindrical lens array.

33. An illumination system according to claim 29, further comprising an envelope of a material transparent to said ultra-violet radiation, said envelope surrounding a portion of said fluorescent tube free of said feeder light guides, wherein said phosphor layer is disposed only at an inner area of said fluorescent tube facing said feeder light guides, and wherein other inner areas of said fluorescent tube are reflective to direct said ultra-violet radiation back onto said phosphor layer.

34. An illumination system according to claim 33 wherein a light diffusing screen is disposed adjacent to a side of said liquid crystal display panel opposite to said light conducting means.

35. An illumination system according to claim 34, wherein said light diffusing screen includes a cylindrical lens array.