Subpixel layouts for high brightness displays and systems
A display device comprises a display panel comprising high brightness subpixel repeating groups—for example, RGBW display panels. Displays comprise subpixel repeating groups that include first and second primary color stripes and third and fourth primary color subpixels that are disposed on a checkerboard pattern. A subpixel rendering operation includes, or is followed by, a white subpixel adjustment operation that adjusts the brightness of the white subpixels in the areas of the displayed image that contain high spatial frequency features such as lines and text, in order to improve image quality such as image contrast.
1. A display device comprising:
a display panel having a display area substantially populated by repetition of a subpixel repeating group;
said subpixel repeating group having first and second rows and plural columns defining a matrix of subpixels, with each subpixel defined as having a respective subpixel color and where the subpixel colors of the subpixels in the subpixel repeating group include first, second, third and fourth primary colors arranged in the first and second rows of the subpixel repeating group,
wherein one of said first, second, third and fourth primary colors is white and remaining primary colors of the subpixel repeating group are saturated non-white colors;
wherein the plural columns of said subpixel repeating group include a first column, a second column and a third column, the first column consisting of subpixels of said first primary color and the third column consisting of subpixels of said second primary color such that when copies of the subpixel repeating group are tiled vertically one above the next, the first column forms a vertical stripe of subpixels of its respective first primary color, the third column forms a vertical stripe of subpixels of its respective second primary color;
wherein the second column includes subpixels of both of the third and fourth primary colors disposed in an alternating pattern in the second column;
an input image data unit configured to receive source image data defining a plurality of source image pixels each with a same set and organization of primary source colors, the plurality of source image pixels defining an image; and
a subpixel rendering unit configured to subpixel render said received source image data for thereby substantially rendering the image defined by the source image data on said display panel in a form of generating signals representing firstly subpixel rendered luminance levels for corresponding subpixels of the subpixel repeating group;
wherein said subpixel rendering unit is further configured to perform a white subpixel adjustment operation for adjusting luminance levels of firstly subpixel rendered ones of said white subpixels using white data values of source image pixels in said source image data.
2. The display device of claim 1 wherein said source image data defines its plurality of source image pixels in terms of only three saturated primary colors; and
wherein said display device further comprises a gamut mapping unit for mapping said source image data into gamut mapped signals representing said first, second, third and fourth primary colors.
3. The display device of claim 1 wherein said white subpixel adjustment operation adjusts the brightness level of a white subpixel using a difference between white data values in adjacent source image data pixels.
4. The display device of claim 1 wherein said white subpixel adjustment operation adjusts the brightness level of a white subpixel using a maximum absolute value of a difference between white data values in adjacent source image data pixels.
5. The display device of claim 1 wherein said white subpixel adjustment operation adjusts the brightness level of a white subpixel using an absolute value of a difference between white data values in adjacent source image data pixels.
6. The display device of claim 1 wherein said white subpixel adjustment operation adjusts the brightness level of a white subpixel using a scaling factor.
7. The display device of claim 1 wherein said subpixel rendering unit performs area resampling of said source image data to produce luminance values for each of the subpixels of the display panel having said subpixel repeating group.
8. The display device of claim 1 wherein said source image data is specified in said three saturated primary colors of the subpixels;
wherein said display device further comprises a gamut mapping unit for mapping said source image data from a color gamut area whose bounds are defined by said three saturated primary colors to a color gamut area whose bounds are defined by said first, second, third and fourth primary colors such that each source image data pixel area is defined to include a white luminance data value; and
wherein said white subpixel adjustment operation adjusts the luminance data value of a respective white subpixel of the display area by:
(a) calculating an average of white luminance data values for two adjacent source image pixels to produce a respective white subpixel value, W;
(b) calculating a difference in luminance, ΔL, between said white luminance data values for two adjacent source image pixels;
(c) multiplying an absolute value of ΔL by a predetermined scaling factor, S1, to thereby produce a white adjustment quantity, W-adjust, and
subtracting W-adjust from W.