Illumination system and display device

• US 20020126478A1
• Filed: 02/15/2002
• Published: 09/12/2002
• Est. Priority Date: 02/19/2001
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Cornelissen, Hugo Johan, Greiner, Horst, Clarke, John Alfred
• Granted Patent: US 6,840,646 B2
• Time in Patent Office: Days
• US Class Current: 362/228
• 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 (1). The light source comprises a low-pressure discharge lamp (6; 7). According to the invention, 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 (8, 8′, . . . ; 9, 9′, . . . ) 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 (8, 8′, . . . ; 9, 9′, . . . ) 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 (1) and a light source for coupling light into the light-emitting panel (1), said light source including a low-pressure mercury-vapor discharge lamp (6;

7), characterized in that the light source further comprises a plurality of light-emitting diodes (8, 8′

, . . . ;

9, 9′

, . . . ) for selectively setting the color temperature of the light emitted by the light source.

2. An illumination system as claimed in claim 1, characterized in that the light-emitting diodes (8, 8′

, . . . ;

9, 9′

, . . . ) comprise 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 (8, 8′

, . . . ;

9, 9′

,. . . ) comprise predominantly a blue light emission wavelength.

5. An illumination system as claimed in claim 1 or 2, characterized in that each one of the light-emitting diodes (8, 8′

, . . . ;

9, 9′

, . . . ) comprises a luminous flux of at least 5 lm.

6. An illumination system as claimed in claim 1 or 2, characterized in that the illumination system comprises control electronics for changing the luminous flux of the light-emitting diodes (8, 8′

, . . . ;

9, 9′

, . . . ).

7. A display device comprising an illumination system as claimed in claim 1 or 2.