In publication 20110069511, we find a technique for separating LEDs based upon their white points, then ordering them during assembly such that the overall backlighting for the display produces a desirable average white point.
The end result? Apple can presumably maintain a tighter tolerance on overall display white point while accepting a lower tolerance on the individual LED backlights. The looser tolerance would likely lower the cost of the component LEDs.
1. An LED backlight method for display systems comprising:
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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
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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,
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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.

