Selvan Viswanathan, a MicroVision principal engineer, presented on Laser Beam Scanning Short Throw Displays & Laser-Based Virtual Touchscreens at LDC 2017.
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Laser Beam Scanning Short Throw Displays & an Exploration of Laser-Based Virtual Touchscreens
1. Don’t just think outside the box.
See outside the box.
Laser Beam Scanning Short Throw Displays &
an Exploration of Laser-Based Virtual Touchscreens
Selvan Viswanathan [selvan@ieee.org]
LDC2-2, LDC 2017, Yokohama, Japan
2. 2 MICROVISION, INC. COPYRIGHT 2016. ALL RIGHTS RESERVED.5/2/2017
PicoP Scanning
Technology Platform
4. 4
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SLOW SCAN AXIS
(Vertical)
FAST SCAN AXIS
(Horizontal)
MEMS = Micro Electro Mechanical System
Coil
Mirror
Φ1.2mm
PicoP® Scanning Technology - MEMS
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Vertical Trajectory:
Drive vs. Time
Generation of Raster Pattern
Horizontal Trajectory: Drive vs. Time
Single drive input contains both
Slow Scan Ramp and Fast Scan
Sinusoidal drive signals
PicoP® Scanning Technology – MEMS Actuation
6. PicoP® Scanning Technology - Projection Display
Red laser
Green laserBlue laser
2D MEMS
Micro mirror
Raster Scan
8. 8
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500mm Laser spot size grows
proportionally to the
image size
PicoP® Scanning Technology – Always in Focus
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Distortions in Short Throw Configuration
Projection distal end
Projection proximal end
Spot-size bloom
Raster separation
Keystone distortion
Proximal End Distal End
Proximal End
Distal End
[SIDE VIEW]
[TOP VIEW]
Raw Display Simulated
Corrected Display
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MicroVision’s Distortion Correction Methods
Modulate horizontal
sine amplitude
(or modify horizontal
interpolation of laser pulsing)
Reduce vertical
scan amplitude
Non-linear vertical
ramp
Optional optical
correction
Keystoned image
showing raster
separation
Final image rendered
accurately. Image
expanded in short
throw application.
Correct image
aspect ratio
Apply keystone
correction
Correct raster
separation. Spot size
bloom might be
objectionable.
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Conventional Interactivity – IR Light Plane
An IR light sheet or light plane skims the surface
Intrusions into plane detected by IR camera
Offset camera and projection FOVs
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Conventional Interactivity – IR Camera
Structured light with conventional CMOS sensor
(or) Flash IR with CMOS ToF imager
Offset projection and detection fields-of-view
15. 15
MICROVISION, INC. PROPRIETARY AND CONFIDENTIAL
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5/2/2017
Red laser
Green laser
Blue laser
2D MEMS
Micro mirror
IR laser
IR Photodiode
👈
• X,Y location of object known because of
knowledge of MEMS pointing angle.
• Z determined by Time-of-Flight
Interactivity – The MicroVision Way
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Interactivity – The MicroVision Way (contd.)
Omni-directional IR receiver (photodiode)
Self-registering Projection and Detection Fields-of-View
Focus-free projection and detection
17. 17
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Demo Video Showing the MicroVision ToF
Time-of-flight amplitude
data visualized as a 2D
image
Unfiltered raw shape
classification processing
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Objective Technology Comparison (Interactivity)
Criteria IR Light Plane IR Camera
(Structured Light
or ToF Imager)
MicroVision
Flying-Spot ToF
Framerate Fast Medium Fast
Software Complexity Low High Medium
System Size Large Large Small
Works with arbitrary
product
configurations
No No Yes
Works on irregular
surfaces
No Yes Yes
Support both virtual
touch and in-air
gestures
No Yes Yes
19. 19 MICROVISION, INC. COPYRIGHT 2016. ALL RIGHTS RESERVED.5/2/2017
Conclusion
Laser beam scanning displays have inherent advantages when
considering short throw displays with interactivity
Reduced optics complexity by offloading distortion compensation to
the MEMS drive scheme
Highly integrated projection and detection components
Self-registering detection field-of-view allows freedom in various
consumer product designs