Download Mirasol Display technology

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
Hisense C108
Handset
Inventec V112
Smartphone
G-Core Mini Caddy
Erik Bettis
Mirasol Technology
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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
Interference
Josh Saylor
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 electromechanical 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 Dithering
Colors as Assigned
Color perceived
Josh Saylor
Proposal of New Design
Advantage: Analog mirror control allows for multiple
colors from a single unit
Blue: 450 nm
Green: 520 nm
Red: 675 nm
50 μm
Glass
Thin Film Electrode
Pull in distance
(450 nm)
Rigid SiO2 Support
Mirror
Analog operating
region (225 nm)
Spring
Si substrate
Side Profile
(not to scale)
Josh Saylor
Spring Fabrication
Spring can easily be machined by standard
surface micro-machining procedures
SiO2 Support
Spring Material
Compressible Design
0V
Josh Saylor
Pull In Voltage and Spacing
Values Used
Max Voltage = 5 V
Permittivity = ε0 = 8.85x10-12 F/m
Mirror will collapse
against thin film at
5 Volts
Area = (50 μm)2 = 2.5x10-9 m2
Initial spacing = 675 nm
Fpull-in =
= 1.4x10-6 N
k = Fpull-in / Δxspring = 6.1 N/m
Vpull-in =
=5V
Josh Saylor
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
Temporal and
Spatial
dithering still
possible
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
Questions