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 Luminance controller ID: 769044
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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 Luminance controller Dot addressing Lighting Dot Electrode: indium tin oxide (ITO) Color filter
Lighting Cavity/direct backlight Edge-lit light-guide backlight 6 Abileah’08, Information Display
Edge-lit light-guide backlight ReflectorGuideDiffuser 7 Abileah’08, Information Display
Edge-lit backlight (Contd.) 8
Backlighting Cold cathode fluorescent tube (CCFL)LED (better white and brighter) 9
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 Common electrode Switch for each pixel
Passive matrix addressing Cross talk between neighboring pixels Long latency due to scanning 11 http://www.hitachi-displays-eu.com/doc/AN-002_Passive_and_Active_Matrix.pdf
Active matrix addressing More expensive 12
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 Flynn et al, 1999 Switch Storage capacitor TFT ≈ Active Matrix
14 LCD power consumption Liquid crystal cell requires polarization TFT panel must be on DRAM Refreshing at 60Hz
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 TFT on 75 u m-thick steel-foil substrate Nature, 2003 L.G. Philips---E-Ink http://www.eink.com/
17 E-Ink product No back light Paper quality High contrast High resolution
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
Commercial product Sony OLED TVXEL-1, 11”, $2,500, 3mm-think Panel http://www.youtube.com/watch?v=FTEt5o_jt30 19
Commercial products (Contd.) Samsung 12.1’’ OLED for laptops 20
21 Power efficiency Green is the most efficient
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 HP Labs, MobileHCI 2004 5 times power reduction
Dark R’ = λ R G’ = λ G B’ = λ B ↓25% Green R’ = λ R R G’ = λ G G B’ = λ B B ↓34% Arbitrary R’ = R* G’ = G* B’ = B* ↓72% Inversion R’= λ (1-R) G’= λ (1-G) B’= λ (1-B) ↓66% Original
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
Color sensitivity Single color sensitivity diagram of the human eye.