Mirasol Displays MAE 268 Erik Bettis Josh Saylor.
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Transcript of Mirasol Displays MAE 268 Erik Bettis Josh Saylor.
Mirasol Displays
MAE 268
Erik Bettis
Josh Saylor
Introduction
• MEMS device developed by Qualcomm– Low power display
• Uses ambient light as source• Operation requires very low voltages
– Replacement for current LCD screens• Cell phones and other small devices
– Enhance viewability in direct light• Brightness of display increases as ambient light
intensifies• Light reflection of up to 50%
Erik Bettis
Current Products
Inventec V112 Smartphone
G-Core Mini Caddy
Hisense C108 Handset
Erik Bettis
Mirasol Technology
• Interferometric Modulation (IMOD)• Low power consumption• Increased readability in direct light• Bistability
– Hysteresis– Built in Memory
• Pixels– Color Generation
• Interference• Spatial Dithering
Erik Bettis
Interfermetric Modulation(IMOD)• Enables reflective, direct view and flat panel
displays• Refresh rates on the order of microseconds
– Video-rate capable• Contrast Ratio: >15:1• Reflectivity: ~ 50%• Wall Street Journal
– Contrast Ratio: 4:1– Reflectivity: ~ 60%
Erik Bettis
Power Metrics
• Mirasol IMOD Display vs. TFT LCD Displays
Video Time Typical Use Multi Media Use
4.5 Hours 206 min 160 min
3.3 Hours 70 min 24 min
Erik Bettis
Increased Readabilty
Erik Bettis
What is Bistability?
• Main feature of Mirasol devices that allows for low power consumption.
• Allows for pixels to be left on or off with near-zero power drain.– Uses imbalance between electro-mechanical
forces and mechanical forces to hold membrane in place with very low power.
• Provides built in memory for pixel placement
Erik Bettis
Hysteresis
• Stage 1– Constant bias voltage holds membrane in open state
• Stage 2– Positive pulse applied to drive membrane into
collapsed state• Stage 3
– Constant bias voltage holds membrane in collapsed state
• State 4– Negative pulse applied to snap membrane back to
open position
Erik Bettis
Bistability and Hysteresis in Mirasol
Erik Bettis
Pixel Design and Color Generation• Pixels create patterns of Red, Green and Blue to create 256k
color range– Interference
• Reflects different wavelengths to create different colors– Red: λ = 675 nm– Green: λ = 520 nm– Blue: λ = 450 nm
– Dithering• Meshes different amounts of Red, Green and Blue to create
new colors– Similar to mixing paint colors on the nano-scale
Josh Saylor
Examples of Spatial DitheringColor perceivedColors as Assigned
Josh Saylor
Interference
Josh Saylor
Side Profile
Thin Film ElectrodeGlass
Spring Analog operating region (225 nm)
Rigid SiO2 Support
Mirror
50 μm
(not to scale)
Pull in distance (450 nm)
Si substrate
Advantage: Analog mirror control allows for multiple colors from a single unit
Blue: 450 nmGreen: 520 nmRed: 675 nm
Proposal of New Design
Josh Saylor
Spring Material
Spring can easily be machined by standard surface micro-machining procedures
SiO2 Support
Compressible Design
0 V
Spring Fabrication
Josh Saylor
Values Used
Max Voltage = 5 V
Permittivity = ε0 = 8.85x10-12 F/m
Area = (50 μm)2 = 2.5x10-9 m2
Initial spacing = 675 nm
k = Fpull-in / Δxspring = 6.1 N/m
Fpull-in = = 1.4x10-6 N
Vpull-in = = 5 V
Mirror will collapse against thin film at
5 Volts
Pull In Voltage and Spacing
Josh Saylor
Current Design42 units per pixelOne color per unit
New Design4 units per pixel
350 μm100 μm
Resolution Scaling Factor of 10
The old 1.4 inch display with 176 x 144 resolution
would increase to 1760 x 1440 pixels with new design
Temporal and Spatial
dithering still possible
Pixel Design of New Layout
Josh Saylor
Questions