The Fast-DRGB method was implemented on hardware and displayed the FSC images and videos in a real-time process. The displayed FSC images and videos had less CBU artifact during human eyes movement. However, because the LC used in 15.4” panel is TN mode. The response time of LC might be not fast enough for 240Hz field frequency. After temporal color mixing in 1/60 second, human eyes perceived incorrect color of the displayed images compared with the original images. The other reason was color dependence occurs between different fields, this caused the color additive color mixing failed.
So we will build a color correction model to adjust the modified data stream from the Fast-DRGB algorithm and are shown in Fig. 6-1. The algorithm will output LC signal and transmit into color correction model to derive the modified LC signal.
The 15.4” panel will receive the modified LC signal and original backlight signal, and then display the correct FSC images.
Input
Fig. 6-1 Concept of color correction model adds into the FPGA
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The color correction model will be built using colorimeter, KONICA MINOLTA CA-210 to measure the CIEXYZ coordinates on the panel. The sRGB color checker will input into the algorithm and output signal transmit into 15.4” panel and measure the CIE XYZ color coordinates of each color and obtain Data Original. And then measuring color checker on the input source (notebook) panel to obtain Data Target, as shown in Fig. 6-2.
Input Source
CPT Panel
FPGA Modules
sRGB
Standard color checker
CA-210 colorimeter
Data Target Data Original
Fig. 6-2 Measurement of standard color checker using CA-210 colorimeter
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Data Original Matrix1 Digital Signal Value
CIE XYZ In CPT panel
(a) Step one
Data Target Inverse
Matrix1 New Digital Signal Value CIE XYZ
In NB panel
(b) Step two
Matrix2 Digital Signal Value
New Digital Signal Value (c) Step three
Fig. 6-3 Transformation between each data values in color correction model (a) Relationship between Data Original and digital signal value in CPT panel.
(b) Inverse the relationship in (a) to derive new digital signal value.
(c) Relationship between digital signal value and new digital signal value.
After deriving the CIE XYZ data from two panels, we build the color correction model in the procedure as shown in Fig. 6-3. In step one, finding the relationship between digital signal value and Data Original from CPT panel. Then, inverse the relationship and find new digital signal value from Data Target from source panel.
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Finally, find the relationship between digital signal value and new digital signal value.
Therefore, in the color correction model the modified LC signal transmits into the 15.4” panel. The coordinates of colors shows in panel would match the target color coordinates.
After inserting the color correction model into Fast-DRGB module, the 15.4”
panel will display the image with correct color. And the color correction model is not only used in FSC LCDs, but also used in different kinds of displays. If color distortion happens, building the color correction model in the procedure and will adjust the correct color.
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Program of Fast-DRGB
Simplified Matlab Code
%---%
% 3 approaches, a1(I,:) a2(I,:) a3(I,:),
% for red, green, blue B/L values, and sum of pixel difference (simplified delta E)
% B/L values 1->128, 2->160, 3->192, 4->224, 5->256,
% Shih-Hsun Chien
%---%
input_image=im2double(imresize(read_image,[1280,800],'bicubic'));
[X,Y,Z]=size(input_image);
region_part = 300;
%--- 1st approach: from 1 to 300 ---%
i = 1;
a1 = zeros(8,4);
for a, b, c = 0:1
a1(i,1)=a*4+1; a1(i,2)=b*4+1; a1(i,3)=c*4+1;
blr=(a1(i,1)-1)*32+128; blg=(a1(i,2)-1)*32+128; blb=(a1(i,3)-1)*32+128;
rp(1:region_part,:,1)=input_image(1:region_part,:,1);
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%--- 3rd approach: from 601~800 ---%
i=1;
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cc3=a3(:,4) [cc3,I]=min(cc3);
% choose adaptive backlight color for i=1:length(a3(I,:))
switch a3(I,i)
case 1 a(1,i)=128;
case 2 a(1,i)=160;
case 3 a(1,i)=192;
case 4 a(1,i)=224;
case 5 a(1,i)=256;
otherwise end
end
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