Chroma compensated backlit display
First Claim
1. An electro-optical apparatus, comprising:
- a first group of LEDs configured to emit light of a first color, a second group of LEDs configured to emit light of a second color, and a third group of LEDs configured to emit light of a third color;
one or more sensors optically coupled to the LEDs and configured to measure quantities S1, S2 and S3 proportional to the intensities of light emitted from the first, second, and third groups of LEDs respectively;
electronic circuitry coupled to the one or more sensors and the groups of LEDs for receiving S1, S2 and S3, K1, K2, and K3, and LC, and determining
D1=LC−
K1*S1,
D2=LC−
K2*S2, and
D3=LC−
K3*S3,where D1, D2, and D3 determine current drive levels for the first, second, and third group of LEDs respectively, LC is a commanded luminance signal determining overall luminance produced by the LEDs and K1, K2, and K3 are chrominance parameters for determining the relative light output from the first, second, and third group of LEDs respectively.
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Abstract
Methods and apparatus are provided for a backlit display with variable luminance and chrominance. The apparatus comprises i groups of LEDs of different colors and one or more sensors optically coupled to the LEDs. The combined light produced by the LEDs is directed to a transmissive liquid crystal display, preferably through a diffusing layer. The sensors monitor the output Si of each group of LEDs. Si for each group of LEDs is multiplied by a chrominance determining parameter Ki to obtain Ki*Si which is then compared to a commanded luminance signal LC to obtain LC−Ki*Si, which difference is used to adjust the drive current to each group of LEDs to achieve LC with the desired chrominance set by Ki. By changing Ki and LC the chrominance and luminescence of the display may be varied and aging effects compensated.
37 Citations
9 Claims
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1. An electro-optical apparatus, comprising:
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a first group of LEDs configured to emit light of a first color, a second group of LEDs configured to emit light of a second color, and a third group of LEDs configured to emit light of a third color; one or more sensors optically coupled to the LEDs and configured to measure quantities S1, S2 and S3 proportional to the intensities of light emitted from the first, second, and third groups of LEDs respectively; electronic circuitry coupled to the one or more sensors and the groups of LEDs for receiving S1, S2 and S3, K1, K2, and K3, and LC, and determining
D1=LC−
K1*S1,
D2=LC−
K2*S2, and
D3=LC−
K3*S3,where D1, D2, and D3 determine current drive levels for the first, second, and third group of LEDs respectively, LC is a commanded luminance signal determining overall luminance produced by the LEDs and K1, K2, and K3 are chrominance parameters for determining the relative light output from the first, second, and third group of LEDs respectively. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for operating a backlit display with variable luminance and chrominance using i groups of LEDs of different colors and one or more sensors optically coupled to the LEDs and electrically coupled through a feedback controller and current drivers to the LEDs, comprising:
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obtaining from the one or more sensors values Si proportional to the intensity of light emitted by each group of LEDs; determining Ki*Si for each group of LEDs where Ki is a chrominance adjustment parameter for each group of LEDs; comparing Ki*Si to a luminance command signal LC where LC determines the overall luminance; and adjusting current drive to each group of LEDs so that LC−
Ki*Si˜
0. - View Dependent Claims (8, 9)
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Specification