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 compensating for a degradation of a pixel having a driving circuit for driving current through a light emitting device based on an input, the method comprising:
receiving luminosity data;
determining a compensation headroom for compensating for the degradation of the pixel;
determining a compression factor with use of said compensation headroom;
scaling the luminosity data by the compression factor to create compressed data;
compensating for the degradation of the pixel by adjusting the compressed data to create compensated data; and
supplying the driving circuit based on the compensated data.
2. The method of claim 1 , wherein the compensation headroom is determined based on a user selected profile and a usage time of the pixel.
3. The method of claim 1 , wherein the compression factor is determined based on an estimation of degradation of the pixel and on a display requirement, and wherein the estimation is based on a design of hardware aspects of the pixel and of the driving circuit.
4. The method of claim 1 , wherein the scaling is carried out by multiplying the luminosity data by a constant integer to create resulting data with a greater number of bits, and multiplying the resulting data by the compression factor.
5. The method of claim 4 , wherein the luminosity data is an eight-bit integer and the compressed data is a ten-bit integer.
6. The method of claim 1 , wherein the driving circuit includes at least one thin film transistor (TFT).
7. The method of claim 6 , wherein the at least one TFT is an n-type TFT.
8. The method of claim 6 , wherein the at least one TFT is used to drive current through the light emitting device, and wherein the degradation is due to a voltage threshold of the at least one TFT or due to a shift in the voltage threshold of the at least one TFT.
9. The method of claim 1 , wherein the light emitting device is an organic light emitting diode (OLEO).
10. The method of claim 9 , wherein the degradation is due to a bias voltage of the OLED or due to a shift in the bias voltage of the OLED.
11. The method of claim 9 , wherein the degradation is due to a voltage required to compensate for an inefficiency of the OLED or due to a shift in the voltage required to compensate for the inefficiency of the OLED.
12. A method of compensating for a degradation of a pixel in a display having a plurality of pixels said pixel having a driving circuit for driving a current through a light emitting device based on an input, the input being supplied to the driving circuit by a display driver, the method comprising:
receiving luminosity data;
determining a compensation headroom for compensating for the degradation of the pixel;
determining a compression factor with use of the compensation headroom;
scaling the luminosity data by the compression factor to create compressed data;
compensating for a degradation of a pixel in the display by adjusting the compressed data based on the degradation to create compensated data; and
sending the compensated data to the display driver.
13. The method of claim 12 , wherein the luminosity data includes eight-bit integers and wherein the scaling is carried out by: multiplying the luminosity data by a constant integer to create resulting data with a greater number of bits, and multiplying the resulting data by the compression factor.
14. The method of claim 12 , further comprising compensating for degradations of the plurality of pixels in the display by adjusting the compressed data based on the degradations to create compensated data.
15. The method of claim 12 , wherein the compensation headroom is determined based on a user selected profile and a usage time of the display.
16. The method of claim 12 , wherein the compression factor is determined based on an estimation of the degradation of the display and based on display requirements and the design of hardware aspects within the display.
17. The method of claim 12 , further comprising:
ascertaining a maximum compensation applied to the plurality of pixels; and
adjusting the compensation headroom based on the ascertained maximum compensation.
18. The method of claim 17 , wherein the determining the compression factor comprises computing the ratio of the compensation headroom to a maximum assignable value of the inputs and updating the compression factor to be one minus the computed ratio.
19. The method of claim 12 , wherein at least one of the driving circuits includes at least one thin film transistor (TFT).
20. The method of claim 19 , wherein the at least one TFT is used to drive current through at least one of the light emitting devices, and wherein the degradation is due to a voltage threshold of the at least one TFT or due to a shift in the voltage threshold of the at least one TFT.
21. The method of claim 12 , wherein at least one of the light emitting devices is an organic light emitting diode (OLED).
22. The method of claim 21 , wherein the degradation is due to a bias voltage of the OLED or due to a shift in the bias voltage of the OLED.
23. The method of claim 21 , wherein the degradation is due to a voltage required to compensate for an inefficiency of the OLED or due to a shift in the voltage required to compensate for the inefficiency of the OLED.