1. 1 Display technologies Lin Zhong ELEC424, Fall 2010

2. 2 Outline Liquid crystal displays (LCD) Organic light-emitting diode (OLED) display Flexible display Administration

3. 3 Mobile displays: Trend Brighter, clearer with probably the same size CIF: Common Intermediate Format Chung & Lee, 2005 iPhone 4: 326 ppi 960x640 Human retina has a resolution of 477ppi

4. Trend 2005 4

5. 5 Display power

6. 6 Display power (Contd.) iPAQ 4350, 2004

7. 7 Display power (Contd.) Audiovox 5600, 2004

8. 8 LCD principle Luminance controller Dot addressing Lighting Dot Electrode: indium tin oxide (ITO) Color filter

9. 9 Light and light guide MicroLen TM white LED light guide for cell phones

10. Lighting Cavity/direct backlight Edge-lit light-guide backlight 10 Abileah’08, Information Display

11. Laptop backlighting Cold cathode fluorescent tube (CCFL) LED (better white and brighter) 11

12. Edge-lit light-guide backlight Reflector Guide Diffuser 12 Abileah’08, Information Display

13. Edge-lit backlight (Contd.) 13

14. 14 Addressing Direct addressing – Numeric LED display Dot matrix: passive – Slow response, poor contrast – Low-cost, low-power, small displays Dot matrix: active – Higher power consumption Common electrode Switch for each pixel

15. Passive matrix addressing Cross talk between neighboring pixels Long latency due to scanning 15 http://www.hitachi-displays-eu.com/doc/AN-002_Passive_and_Active_Matrix.pdf

16. Active matrix addressing More expensive 16

17. 17 Thin-film transistor (TFT) LCD Cross-sectional diagram of an active-matrix LCD. The LC cell modulates light intensity according to the driving voltages. ITO = indium tin oxide Flynn et al, 1999 Switch Storage capacitor TFT ≈ Active Matrix

18. 18 LCD power consumption Liquid crystal cell requires polarization TFT panel must be on – DRAM – Refreshing at 60Hz

19. 19 Bistable display (Zero power) Cholesteric liquid crystal cell stays polarized without voltage Long response time – Fine for ebook, bulletin board, light interaction – Impossible for video Kent display Passive or Active addressing?

20. 20 OLED display LCD: filter white external light for colors OLED: generate different colors – Potential lower power Luminance for each pixel can be changed – Much larger view angle – Bright & high contrast – Broad color gamut (better colors) – Thin & light – Faster response – Flexible display

21. Commercial product Sony OLED TV – XEL-1, 11”, $2,500, 3mm-think Panel – http://www.youtube.com/watch?v=FTEt5o_jt30 http://www.youtube.com/watch?v=FTEt5o_jt30 21

22. Commercial products (Contd.) Samsung 12.1’’ OLED for laptops 22

23. 23 Power efficiency Green is the most efficient

24. Our measurement 24 http://www.4dsystems.com.auhttp://www.4dsystems.com.au: uOLED-3208-PMD3T

25. 25 OLED display power management Darken unused areas 2.5 times power reduction HP Labs, MobileHCI 2004

26. 26 OLED display power management Luminance inversion HP Labs, MobileHCI 2004 5 times power reduction

27. 27 Flexible display LCD impossible Organic electronics (TFT) Lighting? Color filter panel?

28. 28 OLED-based flexible display Organic electronics (TFF) on plastic or foil No need for color filter panel No need for back lighting Sony Flexible OLED display http://www.youtube.com/watch?v=9OvTLg4i2_U

29. 29 E-Ink: Electrophoretic ink TFT on 75um-thick steel-foil substrate Nature, 2003 L.G. Philips---E-Ink http://www.eink.com/

30. 30 E-Ink product: Sony Reader No back light Paper quality – High contrast – High resolution

31. E-Ink product: Amazon Kindle 31

32. 3D Displays Autostereoscopic 3D – Sony RayModeler http://www.youtube.com/watch?v=h5QSclrIdlE Virtual reality 3D http://www.youtube.com/watch?v=h5QSclrIdlE 32

33. Autostereoscopic 3D Lenticular display Parallax barrier display N. Dodgson, “Autostereoscopic 3D displays,” IEEE Computer Magazine, August 2005

34. Challenges

35. Head tracking