Illumination system and display device

• US 6,840,646 B2
• Filed: 02/15/2002
• Issued: 01/11/2005
• Est. Priority Date: 02/19/2001
• Status: Expired due to Fees

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Clarke, John Alfred, Cornelissen, Hugo Johan, Greiner, Horst
• Primary Examiner(s): CARIASO, ALAN B
• Application Number:
  US10/077,060
• Publication Number:
  US 20020126478A1
• Time in Patent Office: 1,061 Days
• Field of Search: 362/31, 362/228, 362/230, 362/231, 362/263, 362/295, 362/561, 362/583, 349/65, 349/68, 349/70, 40544-547
• US Class Current: 362/606
• CPC Class Codes: G02B 6/005 provided by one optical element, or plurality thereof, placed on the light output side of the light guide
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources

Abstract

A back lighting system for illuminating a display device comprises a light-emitting panel (1) and a light source (6) for coupling light into the light-emitting panel. The light source comprises a low-pressure discharge lamp (6; 7). The light source additionally comprises a plurality of LEDs (8, 8′, . . . ; 9, 9′, . . . ) for selectively setting the color temperature of the light emitted by the light source. Preferably, the LEDs increase the color temperature of the light emitted by the light source. Preferably, the light emitted by the back lighting system ranges from 6,000 to 10,500 K. Preferably, the LEDs are blue light emitting LEDs, each preferably having a luminous flux of at least 5 lm. The color point of an image to be displayed on a display screen of the display device is set by the back lighting system, thus enabling an optimum contrast to be achieved for the image to be displayed by the display device.

Claims

1. An illumination system for illuminating a display device, comprising:

a light-emitting panel and a light source for coupling light into the light-emitting panel, said light source including a low-pressure mercury-vapor discharge lamp having, in normal operation, a fixed electromagnetic spectrum, characterized in that the light source further comprises a plurality of light-emitting diodes, and means for selectively controlling, in operation, the color temperature of the light emitted by the light source.

2. An illumination system as claimed in claim 1, characterized in that one or more of the light-emitting diodes produce a light emission wavelength for selectively increasing the color temperature of the light emitted by the light source.

3. An illumination system as claimed in claim 2, characterized in that the color temperature of the light emitted by the light source can be set so as to range from 6,000 K to 11,000 K.

4. An illumination system as claimed in claim 1, characterized in that the light-emitting diodes produce a predominantly blue light emission wavelength.

5. An illumination system as claimed in claim 1, characterized in that each one of the light-emitting diodes and the low-pressure discharge lamp directly transmit their light, without substantial reflection to the light-emitting panel.

6. An illumination system as claimed in claim 1, characterized in that the controlling means comprises control electronics for changing the luminous flux of only the light-emitting diodes.

7. A display device comprising:

a liquid crystal display device optically coupled to an illumination system as claimed in claim 1.

15. The illumination system as claimed in claim 1 wherein the controlling means controls at least one of the light emitting diodes so as to adjust the color temperature of the light emitted by the light source to a color temperature different from that of the discharge lamp alone.

8. An illumination system for illuminating a display device, comprising:

a light-emitting panel, and

a light source arranged to couple light from the light source into the light-emitting panel, wherein the light source comprises;

at least one electric discharge lamp having, in normal operation, a fixed electromagnetic spectrum, and

at least one light emitting diode chosen so as to adjust the color temperature of the light emitted by the light source such that the color point of an image displayed by the display device is adjusted independently of the display device illuminated by the light source.

10. The illumination system as claimed in claim 8 wherein the at least one electric discharge lamp includes first and second electric discharge lamps physically separated from one another by the light-emitting panel.

11. The illumination system as claimed in claim 8 wherein the at least one light emitting diode provides light at a predominantly blue light emission wavelength.

12. The illumination system as claimed in claim 8 further comprising control electronics for selectively setting the luminous flux of the at least one light emitting diode under control of a user of the illumination system.

13. The illumination system as claimed in claim 8 wherein the at least one electric discharge lamp comprises first and second low pressure mercury vapor discharge lamps located at opposite sides of the light emitting panel and the at least one light emitting diode comprises at least first and second light emitting diodes also located at opposite sides of the light emitting panel.

14. The illumination system as claimed in claim 8 further comprising control electronics for selectively adjusting, during normal operation of the illumination system, the luminous flux of the at least one light emitting diode dependent upon the illumination level of an image displayed by the display device.

16. The illumination system as claimed in claim 8 wherein the light emitting panel includes a light-mixing chamber housing the at least one electric discharge lamp and a micro-grooved bar into which light from the at least one light emitting diode is coupled and in turn emitted by the micro-grooved bar into the light emitting panel.

17. The illumination system as claimed in claim 8 wherein the at least one electric discharge lamp includes first and second electric discharge lamps and the at least one light emitting diode comprises at least first and second light emitting diodes, and

the light emitting panel includes first and second light-mixing chambers housing the first and second electric discharge lamps, respectively, and

the first and second light emitting diodes contact the first and second light-mixing chambers, respectively, so as to project their light into the light-emitting panel.

18. The illumination system as claimed in claim 8 wherein the at least one electric discharge lamp includes only one single low pressure mercury vapor discharge lamp.

19. The illumination system as claimed in claim 8 further comprising control electronics for selectively adjusting the luminous flux of the at least one light emitting diode as determined by ambient light.

9. An illumination system for illuminating a display device, comprising:

a light-emitting panel, and

a light source arranged to couple light from the light source into the light-emitting panel, wherein the light source comprises;

at least one electric discharge lamp, and

at least one light emitting diode chosen so as to set the color temperature of the light emitted by the light source, wherein said at least one light emitting diode has a light emission wavelength relative to the light emission wavelength of the electric discharge lamp so as to set the color temperature of the light emitted by the light source to a level above that of the discharge lamp alone.