Driving system for active-matrix displays

1. A method of using raw grayscale image data representing images to be displayed in a plurality of successive frames, to drive a display having a plurality of pixels that include a drive transistor and an organic light emitting device, said method comprising:

dividing each frame into at least a long sub-frame and a short sub-frame, a time period of the long sub-frame being greater than a time period of the short sub-frame; and

for each pixel of the plurality of pixels and for each frame of the plurality of frames

supplying the pixel with drive currents during each of said long sub-frame and said short sub-frame based upon a raw grayscale value for the pixel during the frame, such that

the drive current supplied to the pixel during the long sub-frame is greater than the drive current supplied to the pixel during the short sub-frame for raw grayscale values in a preselected high range of grayscale values, and

the drive current supplied to the pixel during the long sub-frame is less than the drive current supplied to the pixel during the short sub-frame for raw grayscale values in a preselected low range of grayscale values less than the grayscale values of the preselected high range of grayscale values.

2. The method of claim 1 wherein the drive current supplied to the pixel during the long sub-frame for raw grayscale values in the preselected low range of grayscale values is a drive current corresponding to a black grayscale value.

3. The method of claim 2 wherein the grayscale values in the preselected low range of grayscale values include compensation for the pixel.

4. The method of claim 1 wherein the drive current supplied to the pixel during the short sub-frame for raw grayscale values in the preselected high range of grayscale values is a drive current less than a drive current corresponding to a full brightness grayscale value.

5. The method of claim 4 wherein the grayscale values in the preselected high range of grayscale values includes compensation for the pixel.

6. The method of claim 1 wherein the drive currents for the long and short sub-frames are preselected to produce a pixel luminance during that frame that has a predetermined gamma relationship to said raw grayscale value for that frame.

7. The method of claim 6 wherein the drive currents for the long and short sub-frames are preselected with use of a look-up table (LUT) and wherein the predetermined gamma relationship is a mapping to produce a pixel luminance according to a gamma 2.2 curve.

8. The method of claim 1 in which said display is an active matrix display and said plurality of pixels in said active matrix display are OLED pixels.

9. An apparatus for using raw grayscale image data representing images to be displayed in a plurality of successive frames, to drive a display having a plurality of pixels that each include a drive transistor and an organic light emitting device, multiple select lines coupled to said array for delivering signals that select when each pixel is to be driven, and multiple data lines for delivering drive signals to the selected pixels, said apparatus comprising:

a source driver coupled to said data lines and including a processing circuit for receiving said raw grayscale image data and adapted to, for each pixel of the plurality of pixels and for each frame of the plurality of frames:

divide the frame into at least a long sub-frame and a short sub-frame, a time period of the long sub-frame being greater than a time period of the short sub-frame; and

program the pixel for each of said long sub-frame and said short sub-frame for supplying the pixel with drive currents based upon a grayscale value for the pixel during the frame, such that

the drive current supplied to the pixel during the long sub-frame is greater than the drive current supplied to the pixel during the short sub-frame for raw grayscale values in a preselected high range of grayscale values, and

the drive current supplied to the pixel during the long sub-frame is less than the drive current supplied to the pixel during the short sub-frame for raw grayscale values in a preselected low range of grayscale values less than the grayscale values of the preselected high range of grayscale values.

10. The apparatus of claim 9 wherein the drive current supplied to the pixel during the long sub-frame for raw grayscale values in the preselected low range of grayscale values is a drive current corresponding to a black grayscale value.

11. The apparatus of claim 10 further comprising:

a controller coupled to the source driver for controlling the source driver to program the pixel including compensation for the pixel during the short sub-frame for raw grayscale values in the preselected low range of grayscale values.

12. The apparatus of claim 9 wherein the drive current supplied to the pixel during the short sub-frame for raw grayscale values in the preselected high range of grayscale values is a drive current less than a drive current corresponding to a full brightness grayscale value.

13. The apparatus of claim 12 further comprising:

a controller coupled to the source driver for controlling the source driver to program the pixel including compensation for the pixel during the long sub-frame for raw grayscale values in the preselected high range of grayscale values.

14. The apparatus of claim 9 wherein the drive currents for the long and short sub-frames are preselected to produce a pixel luminance during that frame that has a predetermined gamma relationship to said raw grayscale value for that frame.

15. The apparatus of claim 14 wherein the drive currents for the long and short sub-frames are preselected with use of a look-up table (LUT) and wherein the predetermined gamma relationship is a mapping to produce a pixel luminance according to a gamma 2.2 curve.

16. The apparatus of claim 9 in which said display is an active matrix display and said plurality of pixels in said active matrix display are OLED pixels.