Selvan Viswanathan, a MicroVision principal engineer, presented on Laser Beam Scanning Short Throw Displays & Laser-Based Virtual Touchscreens at LDC 2017.

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

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PicoP Scanning
Technology Platform

3. Laser Beam Scanning Displays

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

7. Resolution
1280×720
Refresh rate
60Hz
PicoP® Scanning Technology - Projection Display
Raster Scan

8. 8
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500mm Laser spot size grows
proportionally to the
image size
PicoP® Scanning Technology – Always in Focus

9. Short Throw Challenges

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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.

12. Short Throw Interactivity

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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
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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

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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

20. DON’T JUST THINK OUTSIDE THE BOX.
SEE OUTSIDE THE BOX.
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