1 Flat Panel Display System Lab Human Visual perception for Color Breakup Artifact Evaluation 量化色分離現象之人眼視覺指標 Speaker: Chen Sheng-Chang ( 陳勝昌 ) Advisors: Prof. Han-Ping D.Shieh ( 謝漢萍 教授 ) Prof. Yi-Pai Huang ( 黃乙白 助理教授 ) 2008/03/04

2 Flat Panel Display System Lab Outline Introduction –Conventional & Field-sequential Color Display –Color Breakup Evaluation Index –Color Breakup Angle (CBUA) –Color Difference (ΔE) –Combination of CBUA & ΔE Conclusions & Future works

3 Flat Panel Display System Lab Conventional Display Backlight (CCFL) LC layer TFT matrix Color filter Polarizer R G B R G B sub-pixel one-pixel Disadvantage: Higher power consumption Lower optical efficiency Lower NTSC

4 Flat Panel Display System Lab Field Sequential Color Display time I Backlight LC layer TFT matrix Polarizer Full color image Advantage: Lower power consumption Higher optical efficiency Higher NTSC

5 Flat Panel Display System Lab What’s Color Breakup ? Definition: Color breakuprainbow effect Color breakup (CBU), or the rainbow effect, is an artifact in FSC Displays. Where the different color fields are observed separately. Original CBU Focus on pursuit eye movement

6 Flat Panel Display System Lab Color Breakup_ moving object Time Position Visual system Pursuit movement Eye-Trace Integration

7 Flat Panel Display System Lab Outline Introduction Evaluation Index –Prior Color Breakup Angle (CBUA) Color Difference (ΔE) –Propose Combination of CBUA & ΔE Conclusions & Future works

8 Flat Panel Display System Lab Unit : Degree T : Target Width (mm) D : Viewing Distance (mm) V : Eye Moving Velocity (mm/s) F : Frame Rate (Hz) Unit : mm L T : Target Luminous (nits) V : Eye Moving Velocity (mm/s) L S : Surrounding Luminous (nits) K, a, b, c,i : Constant value Color Breakup Angle (CBUA) Color Breakup Angle (CBUA), SID’07, Yan SP, et al. Viewing distance D ind D T V/F CBUA  Spatial sensitivity  Color information

9 Flat Panel Display System Lab Color Difference (ΔE) ΔE, IDMC’06, J. Lee, et al, samsung. Reference FSC CIE1976L * u * v * ΔEΔEΔEΔE  Color information  Spatial sensitivity

10 Flat Panel Display System Lab Evaluation concept Evaluation index Physical Exp. Psychophysical Exp. CBU Score CBU# = ΔE & CBUA Nonlinear regression Spatial Sensitivity Color Information

11 Flat Panel Display System Lab Experiment flow chart –Explanation the ΔE calculation. How to calculate the typical color difference? –Color difference calculation in our experiment. Assume human visual will more sensitive to difference color in the near point. The minimum spatial sensitivity = 0.016° will be considered. –Psychophysical Experiments. How many kinds of test patterns are there in the experiment? What is the CBU# ? –Summary

12 Flat Panel Display System Lab How to calculate ΔE – Typical color difference calculation: CIEL*a*b* (1976) Test image 1 2 Color difference L*a*b* ΔEΔE Lab ΔE calculation XYZ GL R GL G GL B

13 Flat Panel Display System Lab Proposedmethod (ΔE) Proposed method (ΔE) –ΔE calculation in our experiment. Calculate difference color in near points. ΔE BK ΔE CW ΔE BC ΔE BK = ΔE B 1 K +ΔE B 2 K … ΔE B n K ΔE CW =ΔE C 1 W +ΔE C 2 W … ΔE C n W ΔE BC = ΔE B 1 C +ΔE B 2 C … ΔE B n C +ΔE C 1 B +ΔE C 2 B … ΔE C n B, n= CBUA / CBU image CBUA D Human eye The minimum human visual spatial sensitivity =0.016° ΔE YW ΔE RK ΔE YR

14 Flat Panel Display System Lab Psychophysical Experiments ” x x 1˚1˚ D Test pattern  Panel specification: 32” TV OCB mode 180Hz, 1366x768  Parameters: Velocity:60,120,180,240,300,360 mm/s. Brightness:350, 300, 250, 150 nits. Viewing distance:80, 120, 160 cm. 2˚ is more sensitive for color perception 80cm x x 160 cm 2x

15 Flat Panel Display System Lab Color Breakup Scores (CBU#) Dark room D Scores Eyelink CBU# CBU# standard Scores Test pattern –17 observers: Age: 20~25 (14 males & 3 females ). Normal visual. Nonlinear regression

16 Flat Panel Display System Lab Result - I Same color, but in different brightness. R:218 G:218 B:218 R:209 G:209 B:209 R:197 G:197 B:197 R:179 G:179 B:179 CBU↑ Velocity ↑ & Brightness ↑ 350nits300nits 250nits 150nits

17 Flat Panel Display System Lab Result - II R:235 G:172 B:215 R:184 G:198 B:235 R:197 G:197 B:197 R:235 G:185 B:148 Same brightness, but in different color. 250nits White color has more serious CBU in the same Velocity, Brightness

18 Flat Panel Display System Lab Result - III Same brightness, but different distance. R:235 G:172 B:215 R:184 G:198 B:235 R:197 G:197 B:197 R:235 G:185 B:148 Brightness: 250nits Velocity: 300mm/s CBU↑ Viewing distance↓

19 Flat Panel Display System Lab Summary –Psychophysical Experiment –CBU phenomenon will increase with Faster velocity Higher brightness Shorter viewing distance –White color has more serious CBU compare to another color. D Scores

20 Flat Panel Display System Lab Color Breakup score ( CBU# ind ) –Indistinguishable Color Breakup score D NO CBU Record Velocity Calculate ΔE CBU# ≈ 0.4 Percept CBU NO CBU Brightness:400,300,200,100nits Viewing distance:120cm Only white test pattern OPT’07, Yi WZ, et al. Dark room

21 Flat Panel Display System Lab Application in 5.6” OCB panel –Replacing the human eye by pursuit camera. D Camera pursuit the target Velocity:360 mm/s, GL=255 (White) Exposure time:16.67ms (1 frame) Distance:120cm RGB RGBW min New Method Original method CBU# =17 CBU# =0.1 OPT’07, Wu JL, et al.

22 Flat Panel Display System Lab Compare 32” & 15.4” OBC panel 32 inch15.4 inch R: G: B: Test pattern 32” 15.4” Lab ΔE calculation XYZ NTSC: 93.8% NTSC: 88.4% V=360mm/s D=120cm

23 Flat Panel Display System Lab Compare 32” & 15.4” OBC panel R:235 G:172 B:215 R:184 G:198 B:235 R:197 G:197 B:197 R:235 G:185 B:148 R:154 G:203 B: ” better than 32” 32”15.4” Backlight modedirect-litLight guide NTSC93.8%88.4% color Saturation higherlower

24 Flat Panel Display System Lab Outline Introduction Evaluation Index Conclusions & Future works

25 Flat Panel Display System Lab Conclusions - I –A psychophysical experiment was be finished. 17 observers participated. The more CBU information had been verified. CBU ↑ –Brightness↑ Velocity↑ Viewing distance↓ –White color has more serious CBU. –A color difference (ΔE ) calculation with human visual was be found out. ΔE BK ΔE CW ΔE BC CBU image ΔE YW ΔE RK ΔE YR

26 Flat Panel Display System Lab Conclusions - II Percept CBU NO CBU –A Color Breakup evaluation with human visual perception was be established. CBU# = Color information & spatial sensitivity CBU# = 0.4 (NO CBU) –The evaluation index can apply successfully on FSC panel. –TV 32” –Notebook 15.4” –Mobile 5.6”

27 Flat Panel Display System Lab Future works –The CBU evaluation index will be modified by the Relative Contrast Sensitivity (RCS). The more psychophysical information will be considered. RCS was focused on instantaneous CBU flash.

28 Flat Panel Display System Lab 28

29 Flat Panel Display System Lab Eye’s resolution 0.07mm Eye’s best resolution= 8 lp/mm (line pairs/ mm), Normal vision:7 lp/mm Min distinguishable= 0.07mm (about= 1’) D=25cm 0.07mm 250mm Θ=0.016° (1°=60’, 1’=60”) 1967, "Vision and the Eye," Chapman and Hall, London, pp mm