Multi-Colored LED Backlight with Color-Compensated Clusters Near Edge
First Claim
1. A light emitting device comprising:
- an arrangement of light emitting diodes (LEDs) for a backlight, the backlight having at least a first backlight edge and an opposite second backlight edge, the LEDs being grouped in an array of clusters, each cluster being formed of a plurality of colors of LEDs whose combined light has a white point, each cluster having the same number of LEDs, the arrangement comprising;
a first cluster configured to be adjacent the first backlight edge, the first cluster having a first white point;
a plurality of second clusters configured to be not adjacent to either one of the first backlight edge or the second backlight edge, the plurality of second clusters having an average white point different from the first white point; and
at least one LED of a first color in the first cluster having a light output characteristic that is different from a light output characteristic of LEDs of the first color in the plurality of second clusters so that the first white point of the first cluster is color shifted with respect to the average white point of the second clusters to at least partially offset an effect of the first cluster being along an edge of the backlight.
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Accused Products
Abstract
Various techniques are described for improving the color uniformity across a backlight for backlighting an LCD. In one embodiment, the backlight uses rows of red, green, and blue LEDs in a mixing chamber. The LEDs are arranged in clusters, such as GRBG or GBRG, each cluster having an associated white point. In order to achieve color uniformity along the left and right edges of the backlight, the LEDs in those edge clusters are specially selected to compensate for the color imbalance in the white point relative to the dimensions of the cluster. For example, a non-compensated cluster of GRBG along the left edge will produce a reddish tint along the left edge since the red peak intensity is to the left of the center of the cluster. To offset this reddish tint along the left side, the cluster'"'"'s overall white point is blue-cyan shifted. As a result, the left edge of the backlight has the same white point as near the middle of the backlight, where the white point imbalance of a single cluster is offset by the white point imbalance of the surrounding clusters. Similarly, a GBRG cluster along the left edge will have its white point red-yellow shifted.
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Citations
31 Claims
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1. A light emitting device comprising:
an arrangement of light emitting diodes (LEDs) for a backlight, the backlight having at least a first backlight edge and an opposite second backlight edge, the LEDs being grouped in an array of clusters, each cluster being formed of a plurality of colors of LEDs whose combined light has a white point, each cluster having the same number of LEDs, the arrangement comprising; a first cluster configured to be adjacent the first backlight edge, the first cluster having a first white point; a plurality of second clusters configured to be not adjacent to either one of the first backlight edge or the second backlight edge, the plurality of second clusters having an average white point different from the first white point; and at least one LED of a first color in the first cluster having a light output characteristic that is different from a light output characteristic of LEDs of the first color in the plurality of second clusters so that the first white point of the first cluster is color shifted with respect to the average white point of the second clusters to at least partially offset an effect of the first cluster being along an edge of the backlight. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A method of backlighting a display comprising:
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providing an arrangement of light emitting diodes (LEDs) in a mixing cavity of a backlight, the backlight having at least a first backlight edge and an opposite second backlight edge, the LEDs being grouped in an array of clusters, each cluster being formed of a plurality of colors of LEDs whose combined light has a white point, the plurality of colors comprising a first color, a second color, and a third color, each cluster having the same number of LEDs; energizing a first cluster adjacent the first backlight edge, so that the first cluster has a first white point; energizing a plurality of second clusters that are not adjacent to either one of the first backlight edge or the second backlight edge, so that the plurality of second clusters has an average white point different from the first white point, the first white point being color shifted relative to the average white point to at least partially offset an effect of the first cluster being along an edge of the backlight; mixing the light emitted from all the clusters in the mixing cavity; providing at least one liquid crystal layer over the mixing cavity; and controlling the at least one liquid crystal layer to control the brightness of red, green, and blue display pixels. - View Dependent Claims (29, 30, 31)
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Specification