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Display Power Characteristics

Display Power Characteristics. Lin Zhong ELEC518, Spring 2011. Display power. Display power (Contd.). iPAQ 4350, 2004. Display power (Contd.). Audiovox 5600, 2004. LCD principle. Lighting. Electrode: indium tin oxide (ITO). Dot. Dot addressing. Luminance controller. Color filter.

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Display Power Characteristics

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  1. Display Power Characteristics Lin Zhong ELEC518, Spring 2011

  2. Display power

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

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

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

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

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

  8. Edge-lit backlight (Contd.)

  9. Backlighting • Cold cathode fluorescent tube (CCFL) • LED (better white and brighter)

  10. 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 Switch for each pixel Common electrode

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

  12. Active matrix addressing • More expensive

  13. 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 Storage capacitor Switch Flynn et al, 1999 TFT ≈ Active Matrix

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

  15. 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?

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

  17. No back light Paper quality High contrast High resolution E-Ink product

  18. 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

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

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

  21. Power efficiency • Green is the most efficient

  22. Color Power Model of OLED uOLED N85

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

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

  25. Original • Dark • R’ = λR • G’ = λG • B’ = λB • ↓25% Green R’ = λRR G’ = λGG B’ = λBB ↓34% • Arbitrary • R’ = R* • G’ = G* • B’ = B* • ↓72% • Inversion • R’= λ(1-R) • G’= λ(1-G) • B’= λ(1-B) • ↓66%

  26. Human visual system Normalized response spectra of human cones, S, M, and L types, to monochromatic spectral stimuli, with wavelength given in nanometers. http://en.wikipedia.org/wiki/Color_vision

  27. Color sensitivity Single color sensitivity diagram of the human eye.

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