Method and apparatus for compensating image data for LED display
An LED display system has an LED display panel coupled to a driver circuitry. The driver circuitry includes a scrambled PWM generator, a register, and a memory. The driver circuit receives an image data from an external source and, after certain compensations, the compensated data is sent to the scrambled PWM generator to be distributed according to a new set of rules. Compared with existing technologies, this LED display has a host of benefits, including having a uniform optical energy output at low brightness.
1. An LED display system, comprising:
an LED display panel; and
a driver circuitry that drives the LED display panel,
wherein the driver circuitry comprises a scrambled PWM generator, a register, and a memory,
wherein the scrambled PWM generator receives a compensated image data of a grayscale value (X+K), X being a grayscale value of a data from an external image source and K being a compensation value generated by the driver circuitry,
wherein the scrambled PWM generator distributes the grayscale value (X+K) into a plurality of segments according the following set of rules:
when (X+K) equals or is smaller than G0*S0, S=ceil((X+K)/G0) and R=mod(X+K, G0),
wherein G0 is a grouping number and S0 is a preset segment number stored in the driver circuitry, S is the number of output segments, among which S−1 segments has a pulse width of G0 GCLKs and one segment has a pulse width of R; and
when (X+K) is larger than G0*S0, M=floor((X+K)/S0) and L=mod(X+K, S0),
wherein L is the number of segments that each receives a pulse width of M+1, while the remaining S0−L segments each receives a pulse width of M.
2. The LED display system according to claim 1 , wherein the compensation value K is predetermined or is obtained through measuring one or more performance characteristics of the LED display panel.
3. The LED display system according to claim 2 , wherein the one performance characteristic of the LED display panel is a brightness uniformity.
4. The LED display system according to claim 1 , wherein the grouping number is predetermined or is obtained by measuring one or more performance characteristics of the LED display.
5. The LED display system according to claim 3 , wherein the one performance characteristic is flickering of the LED display panel.
6. The LED display system according to claim 1 , wherein the LED display panel comprises an LED array of RGB LED pixels, wherein the LED array has a plurality of common anode nodes, each of the plurality common anode nodes operably connects anodes of LEDs of a same color in a row to a corresponding scan switch, and cathodes of LED pixels in the same column are operably connected to a power source.
7. The LED display system according to claim 1 , wherein the LED display panel comprises an LED array of RGB LED pixels, wherein the LED array has a plurality of common cathode nodes, each of the plurality of common cathode nodes operably connects cathodes of LED pixels in a row to a corresponding scan switch, and anodes of LEDs of a same color in a column of LED pixels are operably connected to a current source.
8. A method for operating an LED display system, comprising:
connecting an LED display panel to a driver circuitry comprising a scrambled PWM generator;
sending an image data to the driver circuitry, wherein the image data has a value of X;
adding a compensation value K to the value of the image data X to form a compensated image data having a grayscale value of (X+K);
sending the compensated image data into the scrambled PWM generator, wherein the scrambled PWM generator scrambles the compensated image data into a number of segments according to the following rules:
when (X+K) equals or is smaller than G0*S0, S=ceil((X+K)/G0) and R=mod(X+K, G0),
wherein G0 is a grouping number and S0 is a preset segment number stored in the driver circuitry, S is the number of output segments, among which S−1 segments has a pulse width of G0 GCLKs and one segment has a pulse width of R; and
when (X+K) is larger than G0*S0, M=floor((X+K)/S0) and L=mod(X+K, S0),
wherein L is the number of segments that each receives a pulse width of M+1, while the remaining S0−L segments each receives a pulse width of M; and
sending the PWM pulses from the scrambled PWM generator to a plurality of power sources or a plurality of current sources.
9. The method according to claim 8 , further comprising calibrating the LED display to obtain a value of the group number G0 by measuring flickering of the LED display.
10. The method according to claim 9 , further comprising storing a preset value of the group number G0 in a memory in the driver circuitry.
11. The method according to claim 8 , further comprising calibrating the LED display for brightness uniformity at a high brightness level to obtain a first set of calibration data.
12. The method according to claim 11 , further comprising calibrating the LED display for brightness uniformity at a low brightness level to obtain a second set of calibration data.
13. The method for operating an LED display according to claim 12 , further comprising determining the compensation value K using the first set of calibration data and the second set of calibration data.
14. The method according to claim 9 , wherein the compensation value K is predetermined.