LCD backlighting method and apparatus using a xenon flash tube including drive circuit

• US 5,673,999 A
• Filed: 06/05/1995
• Issued: 10/07/1997
• Est. Priority Date: 12/12/1994
• Status: Expired due to Fees

• Current Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Original Assignee: Norand Corporation (Baker Hughes Company)
• Inventors: Koenck, Steven E.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US08/464,536
• Time in Patent Office: 855 Days
• Field of Search: 362/26, 362/29, 362/30, 362/31, 362/263, 362/265, 362/330, 362/255, 362/84, 359/48, 359/49, 349/64, 349/61
• US Class Current: 362/263
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: H05B 41/34 to provide a sequence of flashes

Abstract

An liquid-crystal display panel is illuminated by one or more xenon flash tubes as a backlighting source. The LCD backlight includes a back reflector, a reflecting cavity, and a light diffuser. The LCD panel is illuminated by triggering a flash of light from the xenon flash tube at a given frequency, reflecting the flash of light off of a back reflector, and diffusing the flash of light through a light diffuser. Flash lamp drive circuitry controls the triggering of a flash of light from a xenon flash lamp.

Claims

1. An apparatus for backlighting and illuminating a flat panel display having a planar surface wherein said flat panel display is utilized as a means for displaying data in a hand-held portable data terminal, said apparatus comprising:

(a) a flashtube for providing a light output to the flat panel display generally across the planar surface thereof, said flashtube containing primarily an inert gas and providing a nearly continuous white, incoherent light output;

(b) means interposed between said flashtube and the flat panel display for evenly distributing and diffusing the light output of said flashtube across the planar surface of the flat panel display such that the light output of said flashtube illuminates the flat panel display with a substantially even flux density distribution; and

(c) means, operatively connected to said flashtube, for electrically driving said flashtube wherein the light output of said flashtube is operatively controlled therewith.

2. The apparatus of claim 1 further comprising reflecting means disposed adjacent to the flat panel display for redirecting the light output of said flashtube through said light distributing and diffusing means and through the flat panel display.

3. The apparatus of claim 1 wherein the inert gas is xenon.

4. The apparatus of claim 1 wherein said light distributing and diffusing means comprises a flexible diffuser material.

5. The apparatus of claim 1 wherein said light distributing and diffusing means comprises a geometric diffuser material.

6. The apparatus of claim 1 wherein said light distributing and diffusing means comprises a woven fiber optic diffuser material.

7. The apparatus of claim 1 wherein said light distributing and diffusing means comprises a fluorescent material.

8. The apparatus of claim 1 wherein said light distributing and diffusing means comprises a phosphorescent material.

9. The apparatus of claim 1 further comprising light filtering means disposed upon the flat display panel for spectrally altering of the light output of said flashtube.

10. The apparatus of claim 1 further comprising a digitizing screen layer disposed upon the flat display panel.

11. The apparatus of claim 1 wherein said means for electrically driving said flashtube comprises:

(a) a DC--DC converter means having an output for providing an output voltage to said flashtube in response to an input voltage from a direct current voltage source, the output voltage being greater than the input voltage;

(b) a resistor having first and second ends, said resistor being electrically connected in series with said DC--DC converter means and said flashtube;

(c) a first capacitor shunting the output of said DC--DC converter means at the first end of said resistor;

(d) a second capacitor shunting the output of said DC--DC converter at the second end of said resistor;

(e) a drive circuit means for providing an impulse voltage to the trigger electrode of said flashtube wherein said flashtube produces light when triggered by said drive circuit means; and

(f) a transformer means electrically connected between said drive circuit means and said flashtube.

12. The apparatus of claim 11 wherein the direct current voltage source is a battery.

13. The apparatus of claim 1 further comprising a shrink sleeve encompassing said flashtube, said shrink sleeve having a reflective inner surface for directing the light output of said flashtube into said light distributing and diffusing means.

14. The apparatus of claim 1 wherein said light distributing and diffusing means includes a fiber optic bundle for transferring the light output from said flashtube to the flat panel display.

15. The apparatus of claim 1 wherein said light distributing and diffusing means includes a plurality of quadratically shaped surfaces for distributing and diffusing light across the flat panel display.

16. The apparatus of claim 1 further comprising means disposed upon the flat panel display for polarizing the light output of said flashtube.

17. The apparatus of claim 1 further comprising means for synchronizing said flashtube at the same rate at which said flat panel display is refreshed.

18. An apparatus for backlighting an LCD panel, said apparatus comprising:

(a) a liquid-crystal display panel;

(b) at least one flashlamp for producing light, said at least one flashlamp being disposed adjacent to said liquid-crystal display panel for providing illumination thereof, wherein said flashlamp contains xenon;

(c) a diffuser means for altering the flux density of the light produced by said at least one flashlamp such that the light diffused therefrom is evenly distributed across said liquid-crystal display panel, said diffuser means being disposed between said liquid-crystal display panel and said at least one flashlamp;

(d) a reflector means for altering the direction of light produced by said at least one flashlamp, said reflector means being disposed adjacent to said at least one flashlamp such that the light reflected therefrom is directed toward said liquid-crystal display panel; and

(e) a circuit means electrically connected to said at least one flashlamp for triggering flashes of light from said at least one flashlamp such that light is thereby produced.

19. The apparatus of claim 18 wherein said at least one flashlamp is a U-shaped tube.

20. The apparatus of claim 18 wherein said at least one flashlamp is a straight light capillary tube.

21. The apparatus of claim 18 wherein said reflector means is a metallic reflector.

22. The apparatus of claim 18 wherein said reflector means is a mirror.

23. The apparatus of claim 18 wherein said reflector means is a light-reflective plastic.

24. The apparatus of claim 18 wherein the light reflected from said reflector means is directed toward said liquid-crystal display panel at an angle generally normal to said liquid-crystal display.

25. The apparatus of claim 18 wherein said diffuser means comprises a flexible light diffuser material.

26. The apparatus of claim 18 wherein said diffuser means comprises a plastic geometric diffuser material.

27. The apparatus of claim 18 wherein said diffuser means comprises a woven fiber optic diffuser material.

28. The apparatus of claim 18 wherein said diffuser means comprises a fluorescent material.

29. The apparatus of claim 18 wherein said diffuser means comprises a phosphorescent material.

30. The apparatus of claim 18 further comprising a light filtering means disposed upon said liquid-crystal display for providing color balance to the light produced by said at least one flashlamp.

31. The apparatus of claim 18 further comprising a digitizing screen layer disposed upon said liquid-crystal display.

32. The apparatus of claim 18 wherein said at least one flashlamp includes a trigger electrode.

33. The apparatus of claim 32 wherein said circuit means comprises:

(a) a DC--DC converter means having an output for providing an output voltage to said at least one flashlamp in response to an input voltage from a direct current voltage source, the output voltage being greater than the input voltage;

(b) a resistor having first and second ends, said resistor being electrically connected in series with said DC--DC converter means and said at least one flashlamp;

(c) a first capacitor shunting the output of said DC--DC converter means at the first end of said resistor;

(d) a second capacitor shunting the output of said DC--DC converter means at the second end of said resistor;

(e) a drive circuit means for providing an impulse voltage to the trigger electrode of said at least one flashlamp wherein said at least one flashlamp produces light when triggered by said drive circuit means; and

(f) a transformer means electrically connected between said drive circuit means and said at least one flashlamp.

34. The apparatus of claim 33 wherein the direct current voltage source is a battery.

35. A method of backlighting an LCD panel comprising:

(a) triggering a flash of light from a xenon light source at a given frequency;

(b) reflecting said flash of light off of a reflector disposed adjacent to the xenon light source;

(c) diffusing said flash of light through a light diffuser, the light diffuser receiving light directly incident from the xenon light source and light reflected off of the reflector; and

(d) illuminating a liquid-crystal display, the liquid-crystal display being adjacent to the light diffuser and receiving the light diffused therefrom.

36. The method according to claim 35 wherein said flash of light is triggered from the xenon light source at a frequency of 60 to 70 Hz.

37. An apparatus for backlighting an LCD panel, said apparatus comprising:

(a) a liquid-crystal display panel;

(b) at least one flashlamp for producing light, said at least one flashlamp being disposed adjacent to said liquid-crystal display panel for providing illumination thereof, wherein said flashlamp contains xenon;

(c) a diffuser for altering the flux density of the light produced by said at least one flashlamp such that the light diffused therefrom is evenly distributed across said liquid-crystal display panel, said diffuser being disposed between said liquid-crystal display panel and said at least one flashlamp;

(d) a reflector for altering the direction of light produced by said at least one flashlamp, said reflector being disposed adjacent to said at least one flashlamp such that the light reflected therefrom is directed toward said liquid-crystal display panel; and

(e) a circuit electrically connected to said at least one flashlamp for triggering flashes of light from said at least one flashlamp such that light is thereby produced.

38. The apparatus of claim 37 wherein said at least one flashlamp is a U-shaped tube.

39. The apparatus of claim 37 wherein said at least one flashlamp is a straight light capillary tube.

40. The apparatus of claim 37 wherein said reflector is a metallic reflector.

41. The apparatus of claim 37 wherein said reflector is a mirror.

42. The apparatus of claim 37 wherein said reflector is a light-reflective plastic.

43. The apparatus of claim 37 wherein the light reflected from said reflector is directed toward said liquid-crystal display panel at an angle generally normal to said liquid-crystal display.

44. The apparatus of claim 37 wherein said diffuser comprises a flexible light diffuser material.

45. The apparatus of claim 37 wherein said diffuser comprises a plastic geometric diffuser material.

46. The apparatus of claim 37 wherein said diffuser comprises a woven fiber optic diffuser material.

47. The apparatus of claim 37 wherein said diffuser comprises a fluorescent material.

48. The apparatus of claim 37 wherein said diffuser comprises a phosphorescent material.

49. The apparatus of claim 37 further comprising a light filtering disposed upon said liquid-crystal display for providing color balance to the light produced by said at least one flashlamp.

50. The apparatus of claim 37 further comprising a digitizing screen layer disposed upon said liquid-crystal display.

51. The apparatus of claim 37 wherein said at least one flashlamp includes a trigger electrode.

52. The apparatus of claim 51 wherein said circuit comprises:

(a) a DC--DC converter having an output for providing an output voltage to said at least one flashlamp in response to an input voltage from a direct current voltage source, the output voltage being greater than the input voltage;

(b) a resistor having first and second ends, said resistor being electrically connected in series with said DC--DC converter and said at least one flashlamp;

c) a first capacitor shunting the output of said DC--DC converter at the first end of said resistor;

(d) a second capacitor shunting the output of said DC--DC converter at the second end of said resistor;

(e) a drive circuit for providing an impulse voltage to the trigger electrode of said at least one flashlamp wherein said at least one flashlamp produces light when triggered by said drive circuit; and

(f) a transformer electrically connected between said drive circuit and said at least one flashlamp.

53. The apparatus of claim 52 wherein the direct current voltage source is a battery.

54. In combination, an apparatus comprising:

(a) a hand-held portable data terminal having a flat panel display; and

(b) means disposed within said hand-held portable data terminal for illuminating the flat panel display of said hand-held portable data terminal wherein said illuminating means includes a flashtube, said flashtube containing primarily xenon gas and providing a nearly continuous white, actinic, incoherent light output.