Method and system for programming, calibrating and/or compensating, and driving an LED display
A method and system for programming, calibrating and driving a light emitting device display, and for operating a display at a constant luminance even as some of the pixels in the display are degraded over time. The system may include extracting a time dependent parameter of a pixel for calibration. Each pixel in the display is configured to emit light when a voltage is supplied to the pixel's driving circuit, which causes a current to flow through a light emitting element. Degraded pixels are compensated by supplying their respective driving circuits with greater voltages. The display data is scaled by a compression factor less than one to reserve some voltage levels for compensating degraded pixels. As pixels become more degraded, and require additional compensation, the compression factor is decreased to reserve additional voltage levels for use in compensation.
1. A method of operating a display having a plurality of pixels to compensate for a degradation of the plurality of pixels, wherein the plurality of pixels have driving circuits for driving currents through light emitting devices based on inputs, the method comprising:
receiving a video signal having a set of grayscale values for the plurality of pixels;
dynamically adjusting a grayscale compression factor according to at least one input received after usage of the display, the grayscale compression factor greater than zero and less than one;
compressing the video signal using the grayscale compression factor to produce compressed grayscale values so as to use fewer luminance values than in the original video signal and reserving a remaining amount of grayscale values for future adjustments associated with aging;
compensating said compressed grayscale values for degradation of said display, using at least a portion of said reserved grayscale values; and
outputting the compensated compressed grayscale values to a display driver for programming the driving circuits of the plurality of pixels.
2. The method of claim 1 , wherein the set of grayscale values is eight-bit data, and wherein the compressing is carried out according to a grayscale compression algorithm that translates the set of compressed grayscale values having a range of 200 values.
3. The method of claim 1 , wherein the remaining amount of grayscale values are reserved at a high end of the available range to provide adjustments that increase the luminosity of adjusted pixels.
4. The method of claim 1 , wherein the remaining amount of grayscale values are reserved at a low end of the available range to provide adjustments that decrease the luminosity of adjusted pixels.
5. The method of claim 1 , further comprising:
adjusting a value in the set of grayscale values corresponding to at least one of the plurality of pixels according to a decreasing brightness algorithm.
6. The method of claim 1 , further comprising:
adjusting a value in the set of grayscale values corresponding to at least one of the plurality of pixels according to a constant brightness algorithm.
7. The method of claim 1 , wherein said compensating said compressed grayscale values for degradation of said display includes compensating at least one of said compressed grayscale values for degradation of at least one of the plurality of pixels of the display, each one of the at least one of said compressed grayscale values compensated for degradation of an associated respective one of the at least one of the plurality of pixels of the display.