Display panel compensation methods
What is disclosed are methods of non-uniformity compensation for active matrix light emitting diode device (AMOLED) and other emissive displays. For each pixel, greyscale level offsets for a number of predetermined greyscale drive levels which produce a uniform flat field are determined and used to generate a correction function for the pixel.
1. A method of compensating for non-uniformity of an emissive display panel having pixels, each pixel having a light-emitting device, the method comprising:
selecting a plurality of greyscale drive levels representing a significant portion of a usable greyscale drive level range for the display panel, the plurality of greyscale drive levels being only a subset of the operational greyscale drive levels of the emissive display panel;
for each pixel,
measuring the pixel at each predetermined greyscale drive level;
for each predetermined greyscale drive level determining an offset value from the predetermined greyscale drive level for the pixel which creates a uniform flat field with use of said measurements and storing said offset value in an array in a memory of said emissive display device, each offset value stored in said array using a bit depth less than the bit depth of the predetermined greyscale drive level;
determining a uniformity correction function with use of said determined offset values; and
correcting an input drive level for the pixel with use of the uniformity correction function to compensate for said non-uniformity.
2. The method of claim 1 , wherein measuring the pixel comprises taking optical measurements of luminosity with use of at least one of an external optical measurement system and an integrated optical measurement device.
3. The method of claim 2 , wherein the uniform flat field which is created with the determined offset value for each predetermined greyscale drive level comprises a uniform luminosity produced by each of the pixels of the emissive display panel.
4. The method of claim 1 , wherein measuring the pixel comprises taking electrical measurement of the output current of the pixel with use of a monitoring system of the emissive display panel.
5. The method of claim 4 , wherein the uniform flat field which is created with the determined offset value for each predetermined greyscale drive level comprises a uniform current output by each of the pixels of the emissive display panel.
6. The method of claim 1 , wherein determining said offset value with use of said measurements comprises determining said offset value with use of measurements made previously.
7. The method of claim 1 , wherein determining said offset value with use of said measurements comprises iteratively adjusting an initial offset value from said predetermined greyscale drive level and repeatedly measuring the pixel until reaching the offset value which creates said uniform flat field.
8. The method of claim 1 , wherein the number of selected predetermined greyscale drive levels is two and wherein the uniformity correction function is a linear uniformity correction function generated from the offset values for each predetermined greyscale drive level.
9. The method of claim 8 , wherein said linear uniformity correction function is a function of said input drive level and the offset values for each predetermined greyscale drive level.
10. The method of claim 1 , wherein the number of selected predetermined greyscale drive levels N is greater than two and wherein the uniformity correction function is a piecewise linear uniformity correction function generated from the offset values for each predetermined greyscale drive level.
11. The method of claim 10 , wherein said piecewise linear uniformity correction function is a function of said input drive level and the offset values for each predetermined greyscale drive level.
12. The method of claim 1 , wherein the number of selected predetermined greyscale drive levels N is greater than two and wherein the uniformity correction function is a curve fit polynomial uniformity correction function of order N- 1 or lower generated from the offset values for each predetermined greyscale drive level.
13. The method of claim 12 , wherein said polynomial uniformity correction function of order N- 1 or lower is a function of said input drive level and said offset values for each predetermined greyscale drive level.
14. The method of claim 1 , wherein each light-emitting device comprises an organic light emitting devices (OLED).