Mirasol Displays

1
Mirasol Displays

• MAE 268
• Erik Bettis
• Josh Saylor

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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
3
Current Products
Hisense C108 Handset
Inventec V112 Smartphone
G-Core Mini Caddy
Erik Bettis
4
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
5
Interfermetric Modulation(IMOD)

• Enables reflective, direct view and flat panel
  displays
• Refresh rates on the order of microseconds
• Video-rate capable
• Contrast Ratio gt151
• Reflectivity 50
• Wall Street Journal
• Contrast Ratio 41
• Reflectivity 60

Erik Bettis
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Interference
Josh Saylor
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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
LCD
Erik Bettis
8
Increased Readabilty
Erik Bettis
9
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
10
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
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Bistability and Hysteresis in Mirasol
Erik Bettis
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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 ? 675 nm
• Green ? 520 nm
• Blue ? 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
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Examples of Spatial Dithering
Color perceived
Colors as Assigned
Josh Saylor
14
Proposal of New Design
Blue 450 nm Green 520 nm Red 675 nm
Advantage Analog mirror control allows for
multiple colors from a single unit
50 µm
Glass
Thin Film Electrode
Rigid SiO2 Support
Pull in distance (450 nm)
Mirror
Analog operating region (225 nm)
Spring
Si substrate
Side Profile
(not to scale)
Josh Saylor
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Spring Fabrication
Spring can easily be machined by standard surface
micro-machining procedures
SiO2 Support
Spring Material
Compressible Design
0 V
Josh Saylor
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Pull In Voltage and Spacing
Values Used Max Voltage 5 V Permittivity e0
8.85x10-12 F/m Area (50 µm)2 2.5x10-9
m2 Initial spacing 675 nm
Mirror will collapse against thin film at 5 Volts
k Fpull-in / ?xspring 6.1 N/m
Josh Saylor
17
Pixel Design of New Layout
100 µm
350 µm
New Design 4 units per pixel
Current Design 42 units per pixel One color per
unit
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
Josh Saylor
18
Questions