LED backlight for display systems

• US 8,100,544 B2
• Filed: 11/29/2010
• Issued: 01/24/2012
• Est. Priority Date: 10/10/2007
• Status: Expired due to Fees

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Chen, Wei, Qi, Jun, Yin, Victor, Zhong, John
• Primary Examiner(s): TSO, LAURA K
• Application Number:
  US12/955,813
• Publication Number:
  US 20110069511A1
• Time in Patent Office: 421 Days
• Field of Search: 362611-613, 362/800
• US Class Current: 362/6
• 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 for display systems comprising receiving a plurality of light emitting diodes categorized into a plurality of bins, wherein each bin references a separate range of white point colors, and determining an optimal order for mounting the plurality of light emitting diodes at spatially distributed positions, the plurality of light emitting diodes comprising white point colors associated with separate bins, wherein the optimal order of the plurality of light emitting diodes produces a light of a desired white point color when the light outputs of the plurality of light emitting diodes are mixed.

Claims

1. An LED backlight method for display systems comprising:

mounting a plurality of light emitting diodes at spatially distributed positions in a predetermined order, wherein each of the plurality of light emitting diodes outputs a white point color falling within one of a plurality of predetermined white point color ranges, and wherein the predetermined order of the plurality of light emitting diodes produces a light of a desired white point color when the light outputs of the plurality of light emitting diodes are mixed.

2. The method of claim 1, further comprising mounting the plurality of light emitting diodes on a display panel in the predetermined order.

3. The method of claim 2, further comprising mounting the plurality of light emitting diodes along an edge of the display panel spaced from an active area of the display panel.

4. The method of claim 3, wherein the plurality of light emitting diodes are spaced from each other by a distance similar to their distance from the active area of the display panel.

5. The method of claim 3, wherein the plurality of light emitting diodes are spaced from each other by a distance less than their distance from the active area of the display panel.

6. The method of claim 3, wherein the plurality of light emitting diodes are spaced from each other by a distance greater than their distance from the active area of the display panel.

7. The method of claim 1, wherein

the plurality of predetermined white point color ranges are categorized within a plurality of zones, each zone having multiple predetermined white point color ranges associated therewith, and wherein

the plurality of light emitting diodes output white point color ranges associated with separate zones.

8. The method of claim 1, further comprising minimizing near field and far field color differences.

9. The method of claim 1, wherein the predetermined order minimizes the distance from a center point of the mounted plurality of light emitting diodes.

10. The method of claim 1, the predetermined order minimizes the distance from a shifted Black-Body curve of the mounted plurality of light emitting diodes.

11. The method of claim 1, wherein mounting the predetermined order of the plurality of light emitting further comprises:

initiating an order of N predetermined white point color ranges;

then calculating the near field and far field color difference of the order of N predetermined white point color ranges;

then randomly permutating two of the predetermined white point color ranges;

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 predetermined white point color ranges;

then, if the color difference is reduced, accepting the permutation and returning to the step of randomly permutating two of the predetermined white point color range;

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 desired specifications;

then, if the near field and far field desired color specifications are met, outputting the plurality of predetermined white point color ranges, the near field color, and the far field color; and

then, if the near field and far field desired color specifications are not met, outputting that there is no plurality of predetermined white point color ranges for this predetermined white point color range of color bins and optionally repeating the method with a smaller value of N.

12. A portable computing device comprising:

a display panel;

a central processing unit coupled to the display panel; and

an LED backlight, the LED backlight comprising;

at least two light emitting diodes associated with different white point color ranges, wherein the at least two light emitting diodes are mounted on the display panel in a predetermined order at spatially distributed positions, and wherein the predetermined order produces light of a desired white point color when the light outputs of the at least two light emitting diodes are mixed.

13. The backlight of claim 12, wherein the at least two light emitting diodes are mounted along an edge of the display panel spaced from an active area of the display panel.

14. The backlight of claim 13, wherein the at least two light emitting diodes are spaced from each other by a distance similar to their distance from the active area of the display panel.

15. The backlight of claim 13, wherein the at least two light emitting diodes are spaced from each other by a distance less than their distance from the active area of the display panel.

16. The backlight of claim 13, wherein the at least two light emitting diodes are spaced from each other by a distance greater than their distance from the active area of the display panel.

17. The backlight of claim 12, wherein the different white point ranges are associated with different zones, each zone comprising multiple white point ranges.

18. The backlight of claim 12, wherein the predetermined order minimizes near field and far field color differences.

19. The backlight of claim 12, wherein the predetermined order minimizes the distance from a center point.

20. The backlight of claim 12, wherein the predetermined order minimizes the distance from a shifted Black-Body curve.

21. The backlight of claim 12, wherein the predetermined order comprises:

initiating an order of N predetermined white point color ranges;

then calculating the near field and far field color difference of the order of N predetermined white point color ranges;

then randomly permutating two of the predetermined white point color ranges;

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 predetermined white point color ranges;

then, if the color difference is reduced, accepting the permutation and returning to the step of randomly permutating two of the predetermined white point color ranges;

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 desired specifications;

then, if the near field and far field desired color specifications are met, outputting the plurality of predetermined white point color ranges, the near field color, and the far field color; and

then, if the near field and far field desired color specifications are not met, outputting that there is no plurality of predetermined white point color ranges for this range of predetermined white point color ranges.

22. A method for providing a desired white point color from an LED backlight, the method comprising:

generating light from a plurality of light emitting diodes, each light emitting diode outputting white point colors falling within one of a plurality of predetermined white point color ranges, wherein the light emitting diodes are spatially distributed in a predetermined order so as to produce a mixed light of the desired white point color.

23. The method of claim 22, wherein the plurality of light emitting diodes are mounted on a display panel in the predetermined order.

24. The method of claim 23, wherein the plurality of light emitting diodes are mounted along an edge of the display panel.

25. The method of claim 24, wherein the plurality of light emitting diodes are spaced from each other by a distance equal to, less than, or greater than their distance from an active area of the display panel.

26. The method of claim 22, wherein the plurality of predetermined white point color ranges are categorized within a plurality of zones, each zone having multiple predetermined white point color ranges associated therewith, and wherein

the plurality of light emitting diodes comprise white point color ranges associated with separate zones.

27. The method of claim 22, further comprising minimizing near field and far field color differences.

28. The method of claim 22, wherein the predetermined order minimizes the distance from a center point of the mounted plurality of light emitting diodes.

29. The method of claim 22, wherein the predetermined order minimizes the distance from a shifted Black-Body curve of the mounted plurality of light emitting diodes.

30. The method of claim 22, wherein the predetermined order for the plurality of light emitting diodes further comprises:

initiating an order of N predetermined white point color ranges;

then calculating the near field and far field color difference of the order of N predetermined white point color ranges;

then randomly permutating two of the predetermined color ranges;

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 predetermined white point color ranges;

then, if the color difference is reduced, accepting the permutation and returning to the step of randomly permutating two of the predetermined white point color ranges;

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 desired specifications;

then, if the near field and far field desired color specifications are met, outputting the predetermined plurality of white point color ranges, the near field color, and the far field color; and

then, if the near field and far field desired color specifications are not met, outputting that there is no predetermined plurality of white point color ranges for this range of predetermined color ranges and optionally repeating the method with a smaller value of N.