Basic TFT LCD ELOP

1. Basic TFT LCD ELOP Judy Chu Display Dpt. 2012/11/06

2. What is light • "Visible light" redirects here. For light that cannot be seen with human eye, see Electromagnetic radiation. For other uses, see Light (disambiguation) and Visible light (disambiguation). E: 電場方向

3. Visible light

4. Polarization Vertical linear polarized Circular polarized Horizontal linear polarized

5. Polarizer • A polarizer is an optical filter that passes light of a specific polarization and blocks waves of other polarizations. It can convert a beam of light of undefined or mixed polarization into a beam with well-defined polarization Polarizer

6. What is polarizer

7. Polarizer – surface treatment

8. LCD Module Structure Polarizer CF (Color Filter) LC Cell (Panel) Module Array Polarizer Back Light + PCB

10. Introduction of polarizer

11. LC property

12. TN

13. Upper Lower Glass substrate LC director Glass substrate ψ= 90o ψ= 0o ψ= 180o ψ= 270o Grey Scale Inversion TN-GSI (Gray Scale Inversion)

14. VA

15. VA-Color washout

16. IPS

17. IPS—wide viewing

18. Display Characteristic and Measurement • Luminance • Contrast Ratio • Viewing Angle • Chromaticity • Response Time • Gamma curve • Flicker

19. Luminance 定義為當顯示全白畫面下，垂直顯示器方向所得到光的亮度。單位為cd/cm2，有時也會使用nit的單位。

20. Luminance—T%

21. L(White) CR= L(Black) Contrast ratio • 一個顯示畫面的內容，是由畫素與畫素之間的差別來表現。這個差別可以用最亮的亮度與最暗的亮度之比率，作為量化的指標，此比例即為對比

22. Viewing angle

23. Viewing angle-Iso-contour White Black CR

24. Response time What doesResponse time means : Where tr is the total on time, td is the total off time, d is the cell gap, Vapp is LC applied voltage, K is the elastic constants of the liquid crystal mixture and h is the viscosity of the liquid crystal mixture

25. Response time Faster response Slower response

26. Chromaticity -- Structure of Human Eye • The retina is a mosaic of two types of photoreceptors, rods and cones. • Rods are sensitive to blue-green light with peak sensitivity at a wavelength of 498 nm, and are used for vision under dark or dim condition

27. Spectrum x = x

28. Color Representation

29. X Y Z x = y = z = X+Y+Z X+Y+Z X+Y+Z Chromaticity—CIE1931 color coordinate • Tri-stimulus values X =k∫ P(λ) ρ(λ) x(λ)d λ Y =k∫ P(λ) ρ(λ) y(λ)dλ Z =k∫ P(λ) ρ(λ) z(λ)d λ *x(λ) , y(λ) , z(λ) :color matching function • Chromaticity coordinates(x,y) CIE 1931(x,y) chromaticity coordinates

30. EBU: European Broadcasting Union Color saturation index RGB NTSC ratio=  100 % NTSC color gamut 1931 CIE Chart showing the color gamut of an RGB display Chromaticity--NTSC • NTSC ratio (National Television System Committee

31. Chromaticity--NTSC Lower NTSC% Higher NTSC%

32. Gamma Picture by different gamma setting Gamma =3 Gamma =2 Gamma =1

33. Gamma

34. Gamma

35. Gamma—V-T curve

36. Gamma—measurement

37. Gamma- Vdata setting

38. + - - - - VExt VInt + + + + - VLC = VExt - VInt Image retention( sticking)

39. Flicker—Polarity inversion • Liquid crystal must be driven with an alternating current to prevent any deterioration of image quality resulting from dc stress. This is usually implemented with a frame-reversal drive method, in which the voltage applied to each pixel varies from frame to frame. If the LC voltage changes unevenly between frames, the result would be a 30-Hz flicker.(One frame period is normally 1/60 of a second.)

40. Flicker—image sticking

41. Flicker—Driving method of LCDs

42. T% Vlc N+2 N+3 N+1 frame N V+ V- 1/30 S Time Flicker—measurement Vlc+= V+-VcomVlc-= Vcom-V- The optimized Vom Vlc+=Vlc- Vcom Vlc+ ≠Vlc = flicker ~ L186 (sharp area)luminance is depends on Vlc Measurement : light  voltage Luminance level Time

43. Flicker (dB) Optimum Common Electrode Voltage Common Electrode Voltage（Vcom）V Flicker—measurement Flicker= AC component/ DC component (%) Digital Fourier transfer

44. Flicker-improvement • Adjust Vcom to make LC applied voltage symmetrically • Reduce current leakage from TFT and LC • Increase frame rate • Changing driving scheme.

45. Reference

46. thanks for attention