LED BACKLIGHT FOR DISPLAY SYSTEMS

• US 20090097271A1
• Filed: 10/10/2007
• Published: 04/16/2009
• Est. Priority Date: 10/10/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Qi, Jun, Chen, Wei, Yin, Victor, Zhong, John
• Granted Patent: US 7,841,759 B2
• Time in Patent Office: Days
• US Class Current: 362/612
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133609 including means for improving the color mixing, e.g. white
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

An LED backlight method and apparatus for display systems provides a plurality of light emitting diodes having different white point colors. At least two of the light emitting diodes having different white point colors are selected to produce a light of a predetermined white point color when the light outputs of the selected light emitting diodes are mixed. The selected light emitting diodes are mounted on a display panel in a predetermined order at spatially distributed positions for mixing their light outputs to produce the light of the predetermined white point color to illuminate the display panel with the light of the predetermined white point color.

Claims

1. An LED backlight method for display systems, comprising:

providing a plurality of light emitting diodes having different white point colors;

selecting at least two of the light emitting diodes having different white point colors to produce a light of a predetermined white point color when the light outputs of the selected light emitting diodes are mixed; and

mounting the selected light emitting diodes on a display panel in a predetermined order at spatially distributed positions for mixing their light outputs to produce the light of the predetermined white point color to illuminate the display panel with the light of the predetermined white point color.

2. The method as claimed in claim 1 further comprising mounting the light emitting diodes along an edge of the display panel spaced from the active area of the display panel.

3. The method as claimed in claim 2 wherein the light emitting diodes are spaced from each other by a distance similar to their distance from the active area of the display panel.

4. The method as claimed in claim 2 wherein the light emitting diodes are spaced from each other by a distance generally less than their distance from the active area of the display panel.

5. The method as claimed in claim 2 wherein the light emitting diodes are spaced from each other by a distance generally greater than their distance from the active area of the display panel.

6. The method as claimed in claim 1:

wherein the light emitting diodes are binned according to their white point colors; and

further comprising selecting the light emitting diodes from at least two different bins.

7. The method as claimed in claim 1 further comprising selecting at least three of the light emitting diodes, each having a different white point color.

8. The method as claimed in claim 1 further comprising:

splitting the different white point diodes into zones having multiple bins in each zone, each bin having a different white point color; and

picking one color bin from each zone.

9. The method as claimed in claim 1 further comprising minimizing the near field and far field color differences.

10. The method as claimed in claim 1 further comprising optimizing the LED order to minimize the distance from the center point.

11. The method as claimed in claim 1 further comprising optimizing the LED order to minimize the distance from the shifted Black-Body curve.

12. The method as claimed in claim 1 wherein selecting at least two of the light emitting diodes having different white point colors further comprises:

initiating an order of N color bins;

then calculating the near field and far field color difference of the order of N color bins;

then randomly permutating two of the color bins;

then again calculating the near field and far field color difference;

then determining if the again-calculated near field and far field color difference is reduced from the near field and far field color difference of the order of N color bins;

then, if the color difference is reduced, accepting the permutation and returning to the step of randomly permutating two of the color bins;

otherwise rejecting the permutation;

then, based upon the rejection of the permutation, determining if the again-calculated near field and far field color difference is stabilized, and if not, returning to the step of again calculating the near field and far field color difference;

then determining if the near field and far field colors meet predetermined specifications;

then, if the near field and far field predetermined color specifications are met, outputting the optimal bin order, the near field color, and the far field color; and

then, if the near field and far field predetermined color specifications are not met, outputting that there is no optimal bin order for this range of color bins.

13. An LED backlight for display systems, comprising:

a plurality of light emitting diodes having different white point colors;

at least two of the light emitting diodes having different white point colors being selected to produce a light of a predetermined white point color when the light outputs of the selected light emitting diodes are mixed;

a display panel; and

the selected light emitting diodes being mounted on the display panel in a predetermined order at spatially distributed positions for mixing their light outputs to produce the light of the predetermined white point color to illuminate the display panel with the light of the predetermined white point color.

14. The backlight as claimed in claim 13 wherein the light emitting diodes are mounted along an edge of the display panel spaced from the active area of the display panel.

15. The backlight as claimed in claim 14 wherein the light emitting diodes are spaced from each other by a distance similar to their distance from the active area of the display panel.

16. The backlight as claimed in claim 14 wherein the light emitting diodes are spaced from each other by a distance generally less than their distance from the active area of the display panel.

17. The backlight as claimed in claim 14 wherein the light emitting diodes are spaced from each other by a distance generally greater than their distance from the active area of the display panel.

18. The backlight as claimed in claim 13:

further comprising light emitting diodes that are binned according to their white point colors; and

wherein the selected light emitting diodes have the characteristics of being selected from at least two different such bins.

19. The backlight as claimed in claim 13 further comprising at least three of the light emitting diodes, each having a different white point color.

20. The backlight as claimed in claim 13:

further comprising different white point diodes that are split into zones having multiple bins in each zone, each bin having a different white point color; and

wherein the selected light emitting diodes have the characteristics of being selected by picking one color bin from each zone.

21. The backlight as claimed in claim 13 wherein the selected light emitting diodes minimize the near field and far field color differences.

22. The backlight as claimed in claim 13 wherein the selected light emitting diodes optimize the LED order by minimizing the distance from the center point.

23. The backlight as claimed in claim 13 wherein the selected light emitting diodes optimize the LED order by minimizing the distance from the shifted Black-Body curve.

24. The backlight as claimed in claim 13 wherein at least two of the selected light emitting diodes having different white point colors have the characteristics of having been selected by:

initiating an order of N color bins;

then calculating the near field and far field color difference of the order of N color bins;

then randomly permutating two of the color bins;

then again calculating the near field and far field color difference;

then determining if the again-calculated near field and far field color difference is reduced from the near field and far field color difference of the order of N color bins;

then, if the color difference is reduced, accepting the permutation and returning to the step of randomly permutating two of the color bins;

otherwise rejecting the permutation;

then, based upon the rejection of the permutation, determining if the again-calculated near field and far field color difference is stabilized, and if not, returning to the step of again calculating the near field and far field color difference;

then determining if the near field and far field colors meet predetermined specifications;

then, if the near field and far field predetermined color specifications are met, outputting the optimal bin order, the near field color, and the far field color; and

then, if the near field and far field predetermined color specifications are not met, outputting that there is no optimal bin order for this range of color bins.