71.2: Gray-Level Redistribution in Field-Sequential-Color LCD Technique for Color-Breakup Reduction 71.2: Gray-Level Redistribution in Field-Sequential-Color LCD Technique for Color-Breakup Reduction Chun-Ho Chen 1*, Ke-Horng Chen 2, Yi-Pai Huang 3, Han-Ping D. Shieh 3, and Ming-Tsung Ho 4 1 Dept. of Photonics & Inst. of Electro-Optical Eng. 2 Dept. of Electrical & Control Eng., 3 Dept. of Photonics & Display Inst. National Chiao Tung University, Hsinchu, Taiwan 4 Chunghwa Picture Tubes Ltd., Taoyuan, Taiwan * SID’08, Los Angeles, CA, USA, May 23, 2008

2/14 Outline Field-Sequential-Color & Color-Breakup Issue Proposed Gray-Level-Redistribution Method Experimental Results Adaptive Color Backlight Conclusions

3/14 FSC and CBU RGB Flashing Backlight Color Filter less High Transmittance Low Material Cost High Color Saturation Low Motion Blur Low Power Consumption Low Resource Utilization High Image Performance time location on retina color field offset Perceived Color Separation However, CBU degrades the image quality. *Ref: J.B. Eichenlaub, SID’94, 293 M.Mori, SID’99, 350 Y.T. Hsu, IDW’07, 59 Solutions: Field rate increasing Multi-primary color Color field arrangement* Remaining issues include LC response time and color intensity.

4/14 Discolored Primary Color Fields Concept: 1.To decrease the intensity of color separation 2.To determine color field sequence based on image content Viewpoint shift CBU Conventional RGB 3-fieldNovel Lightened 4-field time location ++ + = +

5/14 Gray Level Redistribution RGBY o gamma curve: T(i) transmittance gray level T(r) T(g) gr T(r)-T(g) r’ i g’ y=g none g r r ≥ g Rg_Count = Rg_count+1 g r r’ g’ y=r none r < g Rg_Count = Rg_count

6/14 Rg_Count > a half of # total pixels ? RGBC RGBY YES NO Time Exchange of RGBY and RGBC Color sequence was determined by image contents.

7/14 Experimental Photos Size32” OCB Resolution1366x768 Brightness400 nits at white Power Consumption 50W Color Gamut105% of NTSC Color Depth24 bits Field Frequency240 Hz DSC The camera-tracking setup simulates observer’s viewpoint shift Track Gradual change of color

8/14 Photos of Color Bars white yellow cyan strong red grass green sky blue still images moving images gray levels white yellow cyan strong red grass green sky blue w/o w/ w/o w/ Color bars’ margins were discolored by yellow or cyan fields. Lower values with modification

9/14  E Index Still CBU To sum up the color difference between Still and CBU image pixel by pixel as an index,  E, for the CBU evaluation* *Ref: J.Lee, IMID/IDMC’06, 92 Specific color bars range from 27% to 46%. White is improved to 56%. white yellow cyan strong red grass green sky blue CBU-  E (a.u.) 56% 100% 27% 43% 46% Suppression Ratio (%)

10/14 (a)KRGB  E=42.6 (c) DRGB  E=8.9 Adaptive LC/BL Determination This method can be extended for a suitable BL color besides C/Y. This concentrates image intensity in a dominate field (D). The lower index obtained, the less color separation observed. + + = + (b) C/YRGB  E=15.8

11/14 Space robotAirplaneTiffany typical CBU D-field CBU Normal and Optimized CBU Images Normal and Optimized CBU Images Optimized CBU reduction with min  E

12/14 CBU-  E (a.u.) Space Robot AirplaneBaboonLenaTiffanyAvg.  E Suppression Ratio (%)  E Comparison of Test Images *Ref.: L.Y. Liao, 51.1; G.Z. Wang, 51.2; F.C. Lin, 71.5, SID08’ Global Adaptation 240Hz (4.2ms) OCB Local Adaptation* 120Hz (8.3ms) TN baboon

13/14 With redistributing LC signals dynamically, our results demonstrated a practical way to suppress CBU. Conclusions  E 100% ~50% off ~70% off

14/14 This work was partially supported by : National Science Council, Taiwan, under Grant NSC E MY3. We would like to express appreciation to: Ching-Ming Wei, Jian-Lung Wu, Sheng-Chang Chen, Wuan-Zheng Yi, Ted Chiu, and Augus Wu, NCTU for valuable discussion and technical support. Acknowledgment Thank you for your kind attention!