Illumination devices and related systems and methods
First Claim
1. A method for controlling a color and an intensity of light produced by a group of emission LEDs comprising at least a first LED and a second LED, the method comprising:
- measuring light from the group of emission LEDs with a photodetector by detecting photocurrents separately induced on the photodetector by each LED in the group of emission LEDs;
comparing a ratio of the photocurrent induced by the first LED over the photocurrent induced by the second LED to a desired ratio of photocurrents, which was previously measured at a particular temperature and stored;
measuring a temperature of the photodetector;
using the measured temperature to scale the photocurrent induced by the second LED to the particular temperature; and
adjusting light produced by the group of emission LEDs based on a difference in the compared ratios of photocurrents and the temperature scaled photocurrent induced by the second LED.
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Accused Products
Abstract
Illumination devices and related systems and methods are disclosed that can be used for LCD (Liquid Crystal Display) backlights, LED lamps, or other applications. The illumination devices can include a photo detector, such as a photodiode or an LED or other light detecting device, and one or more LEDs of different colors. A related method can be implemented using these illumination devices to maintain precise color produced by the blended emissions from such LEDs. One application for the illumination devices is backlighting for FSC (Field Sequential Color) LCDs (Liquid Crystal Displays). FSC LCDs temporally mix the colors in an image by sequentially loading the red, green, and blue pixel data of an image in the panel and flashing the different colors of an RGB backlight. Precise and uniform color temperature across such a display can be advantageously maintained by continually monitoring ratios of photodiode currents induced by the different colored LEDs in each illumination device as each color is flashed.
279 Citations
22 Claims
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1. A method for controlling a color and an intensity of light produced by a group of emission LEDs comprising at least a first LED and a second LED, the method comprising:
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measuring light from the group of emission LEDs with a photodetector by detecting photocurrents separately induced on the photodetector by each LED in the group of emission LEDs; comparing a ratio of the photocurrent induced by the first LED over the photocurrent induced by the second LED to a desired ratio of photocurrents, which was previously measured at a particular temperature and stored; measuring a temperature of the photodetector; using the measured temperature to scale the photocurrent induced by the second LED to the particular temperature; and adjusting light produced by the group of emission LEDs based on a difference in the compared ratios of photocurrents and the temperature scaled photocurrent induced by the second LED. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A system for controlling a color and an intensity of light produced by a group of emission LEDs, the system comprising:
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a group of emission LEDs configured to produce light, wherein the group of emission LEDs comprise at least a first LED and a second LED; a first photodetector configured to receive light from the group of emission LEDs; and control circuitry configured to; detect photocurrents separately induced on the first photodetector by the light from each LED in the group of emission LEDs; compare a ratio of the photocurrent induced by the first LED over the pbotocurrent induced by the second LED to a desired ratio of photocurrents, which was previously measured at a particular temperature and stored; determine a temperature of the first photodetector; use the determined temperature to scale the photocurrent induced by the second LED to the particular temperature; adjust the light produced by the group emission LEDs based on a difference in the compared ratios of photocurrents and the temperature scaled photocurrent induced by the second LED. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification