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 TimeTypical UseMulti Media Use 4.5 Hours206 min160 min 3.3 Hours70 min24 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 Dithering Color perceived Colors as Assigned Josh Saylor

Interference Josh Saylor

Side Profile Thin Film Electrode Glass Spring Analog operating region (225 nm) Rigid SiO 2 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 nm Green: 520 nm Red: 675 nm Proposal of New Design Josh Saylor

Spring Material Spring can easily be machined by standard surface micro-machining procedures SiO 2 Support Compressible Design 0 V Spring Fabrication Josh Saylor

Values Used Max Voltage = 5 V Permittivity = ε 0 = 8.85x F/m Area = (50 μm) 2 = 2.5x10 -9 m 2 Initial spacing = 675 nm k = F pull-in / Δx spring = 6.1 N/m F pull-in = = 1.4x10 -6 N V pull-in = = 5 V Mirror will collapse against thin film at 5 Volts Pull In Voltage and Spacing Josh Saylor

Current Design 42 units per pixel One color per unit New Design 4 units per pixel 350 μm 100 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