LED backlight system for LCD displays

• US 20070274093A1
• Filed: 05/25/2006
• Published: 11/29/2007
• Est. Priority Date: 05/25/2006
• Status: Abandoned Application

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Haim, Victoria, Davey, Dennis, Haim, Elias, Larson, Brent
• Application Number:
  US11/440,487
• Publication Number:
  US 20070274093A1
• Time in Patent Office: Days
• US Class Current: 362/561
• CPC Class Codes: G02B 6/0028 Light guide, e.g. taper
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133609 including means for improving the color mixing, e.g. white

Abstract

A LCD display comprises a backlight assembly that includes a backlight substrate, one or more first white LEDs coupled to the backlight substrate and configured to produce a first light output, and one or more second white LEDs coupled to the backlight substrate and configured to produce a second light output. A light integration unit is coupled to the backlight assembly and configured to produce a combined output from the first light output and the second light output, the combined output having a desired luminance and chrominance. A LCD assembly is coupled to the light integration unit.

Claims

1. A backlight assembly for a LCD display comprising:

one or more first white LEDs having a first color temperature and producing a first light output;

one or more second white LEDs having a second color temperature other than the first color temperature and producing a second light output;

a backlight substrate coupled to the one or more first white LEDs and the one or more second white LEDs; and

wherein the first light output and the second light output optically mix to produce a combined backlight output having a desired luminance and chrominance.

2. The backlight assembly of claim 1 wherein the ratio of the one or more first white LEDs to the one or more second white LEDs is selected to produce a combined backlight output having a desired luminance and chrominance.

3. The backlight assembly of claim 1 wherein an intensity of the one or more first white LEDs and the one or more second white LEDs are adjusted to produce a combined backlight output having a desired luminance and chrominance.

4. The backlight assembly of claim 1 further comprising a controller coupled to the one or more first white LEDs and the one or more second white LEDs, the controller configured to vary a first current through the one or more first white LEDs independently of a second current through the one or more second white LEDs.

5. The backlight assembly of claim 4 wherein the first current and the second current can be varied to vary the first light output and the second light output to produce a combined backlight output having a desired luminance and chrominance.

6. The backlight assembly of claim 1 wherein the backlight substrate includes part of an edge illumination unit.

7. The backlight assembly of claim 1 wherein the backlight substrate includes part of a direct view illumination unit.

8. The backlight assembly of claim 1 wherein the desired luminance and chrominance is selected to enhance the readability of symbology in an avionics display.

9. A LCD display comprising:

a backlight assembly comprising;

a plurality of first white LEDs coupled to a backlight substrate and configured to produce a first light output comprising a first color temperature; and

a plurality of second white LEDs coupled to the backlight substrate and configured to produce a second light output comprising a second color temperature;

a light integration unit coupled to the backlight assembly and configured to produce a combined output from the first light output and the second light output; and

a LCD assembly coupled to the light integration unit.

10. The LCD display of claim 9 wherein the ratio of the plurality of the first white LEDs to the plurality of second white LEDs is selected to produce the combined output having a desired luminance and chrominance.

11. The LCD display of claim 9 wherein an intensity of the plurality of the first white LEDs and the plurality of the second white LEDs are adjusted to produce the combined output having a desired luminance and chrominance.

12. The LCD display of claim 9 further comprising a controller coupled to the plurality of the first white LEDs and the plurality of the second white LEDs, the controller configured to vary a first current through the first white LEDs independently of a second current through the plurality of the second white LEDs.

13. The LCD display of claim 9 wherein the backlight assembly is part of an edge illumination unit.

14. The LCD display of claim 9 wherein the backlight assembly is a direct view illumination unit.

15. The LCD display of claim 9 further comprising a sensor mounted in the light integration unit, the sensor configured to send data to the controller to provide adjustment of a combined optical output of the plurality of first white LEDs and the plurality of second white LEDs.

16. The LCD display of claim 9 wherein the light integration unit comprises an illumination cavity and a diffuser.

17. The LCD display of claim 9 wherein the first color temperature is in the range of 20,000 to 5,000 Kelvin and the second color temperature is in the range of 5,000 to 2,000 Kelvin to produce a combined output in the range of 10,000 to 4,000 Kelvin.

18. The LCD display of claim 9 wherein the backlight assembly is part of an edge illumination unit and a direct view illumination unit.

19. A method for illuminating a LCD display comprising:

generating a first output from a first white LED, the first output having a color temperature;

generating a second output from a second white LED, the second output having a color temperature that is different than the color temperature of the first output;

optically mixing the first output and the second output in a backlight cavity to produce a combined output having a desired chrominance and luminance; and

directing the combined output through an LCD assembly.

20. The method of claim 19 wherein the step of generating a first output from a first white LED further comprises providing a first current through the first white LED to produce the first output and wherein the step of generating a second output from a second white LED further comprises providing a second current through the second white LED to produce the second output.