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Outline
• Liquid crystal displays (LCD)• Organic light-emitting diode (OLED) display• Flexible display• Administration
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Mobile displays: Trend
• Brighter, clearer with probably the same size
CIF: Common Intermediate Format
Chung & Lee, 2005
iPhone 4: 326 ppi960x640
Human retina has a resolution of 477ppi
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Display power (Contd.)
Basic idle; 244; 12%
Computing; 383; 19%
LCD; 82; 4%
Lighting; 444; 22%
Speaker; 367; 18%
Earphone; 65; 3%
Bluetooth; 470; 23%
Power profile of HP iPAQ 4350 (mW)
iPAQ 4350, 2004
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Display power (Contd.)
Lighting: Keyboard; 72.937037227937; 3%
Lighting: Display I; 147.835647317401; 5%
Lighting: Display II; 61.2835089189648; 2%
LCD; 12.8726439856928; 0%
Speaker; 45; 2%
Bluetooth; 440; 16%
GPRS; 1600; 58%
Compute; 370; 13%
Cellular network; 17; 1%
Flight mode: Sleep; 3; 0%
Audiovox 5600, 2004
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LCD principle
Luminance controller
Dot addressing
Lighting
DotElectrode: indium tin oxide (ITO)
Color filter
Lighting
• Cavity/direct backlight
• Edge-lit light-guide backlight10Abileah’08, Information Display
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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
15http://www.hitachi-displays-eu.com/doc/AN-002_Passive_and_Active_Matrix.pdf
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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, 1999Switch
Storage capacitor
TFT ≈ Active Matrix
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LCD power consumption• Liquid crystal cell
requires polarization• TFT panel must be on
– DRAM– Refreshing at 60Hz
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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?
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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
Commercial product
• Sony OLED TV– XEL-1, 11”, $2,500, 3mm-think Panel
– http://www.youtube.com/watch?v=FTEt5o_jt30
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Our measurement
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0 10 20 30 40 50 60 700.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Red Green
Blue
Intensity level
Pow
er (m
W)
http://www.4dsystems.com.au: uOLED-3208-PMD3T
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OLED display power management
• Darken unused areas
2.5 times power reduction
HP Labs, MobileHCI 2004
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OLED display power management
• Luminance inversion
HP Labs, MobileHCI 2004
5 times power reduction
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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 displayhttp://www.youtube.com/watch?v=9OvTLg4i2_U
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E-Ink: Electrophoretic ink
TFT on 75um-thick steel-foil substrateNature, 2003
L.G. Philips---E-Ink
http://www.eink.com/
3D Displays
• Autostereoscopic 3D– Sony RayModeler
• http://www.youtube.com/watch?v=h5QSclrIdlE
• Virtual reality 3D• http://www.youtube.com/watch?v=h5QSclrIdlE
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Autostereoscopic 3D
Lenticular display
Parallax barrier display
N. Dodgson, “Autostereoscopic 3D displays,” IEEE Computer Magazine, August 2005