Sharon Hornstein, PhD
1
Optical Engineering Conf.
February 26th, 2014
Outline
 About Maradin
 MEMS Mirror - motion definition
 Problem definition:
Why are image corrections needed
when a scanning mirror is used for
projection?
 The algorithm for image correction,
using laser modulation.
 Summary
2
About Maradin
 Fabless MEMS company (Founded in 2007)
 Develop innovative MEMS Scanning Mirror solutions for
laser projection and laser scanning applications
 Experienced and committed Team, in MEMS,
Semiconductors, and System
– Electronics, Mechanics, Dynamics, Control, Material
Science, Semi-conductor’s processing
 Privately held, backed by solid investors and industry
veterans
3
The Core of Laser Steering Systems
Laser Diodes +
Optics
Laser Driver
4
Maradin 2D
MEMS Scanning
Mirror
Maradin Laser
Timing Algorithm
Video Data
Maradin MEMS
Drive & Control
Maradin Chipset
Markets and Applications
Pico Projectors
Automotive HUD
Medical
Eyewear Displays
Large Displays
More to
emerge…
Industrial
5
Gesture Sensing
2D MEMS Mirror
• Horizontal Axis:
•
Electro-static actuator built into Silicon
•
Operation at resonance (~10KHz)
•
Capacitive sensing and resonance lock
control
• Vertical Axis:
•
Hybrid Electro-magnetic actuator (“DC”
motor)
•
Step function scanning
•
Modulated capacitance sensing and position
control
6
MEMS Mirror - motion definition
Horizontal Axis – Sinusoidal Motion
(~10KHz])
Vertical Axis – Saw Tooth Pattern
(60Hz])
Reference signal
1
Sensor
measurement
7
V [V]
0.5
0
-0.5
-1
0
0.005
0.01
0.015
t [sec]
0.02
0.025
Projection – System Sketch
Spherical (3D)
Projected Surface
Planar (2D) image
Mirror position
8
Projection – 3D Surface and Projections
Front View
X-Y Plane
Side View
X-Z Plane
Optical Distortions
9
Problem Definition
 The mirror is resonating in a
sinusoidal profile.
𝜃𝑥 𝑡 = 𝜃𝑥 𝑂𝑝 ∙ 𝑐𝑜𝑠 𝜔𝑛 𝑡
Its non-constant velocity implies a
non-uniform distribution of pixels
along the lines.
Y direction
15
10
Y
Differences in mirror velocity
create non-uniform brightness
along the lines
Y direction [m]
5
0
X
-5
-10
-15
-45
-40
-35
-30
-25
-20
-15
X direction, in X' coordinate system [m]
-10
-5
0
X direction
 The scanning mirror creates
a 3D surface. The image is
created by intersection of
light onto a 2D plane.
10
Pincushion distortion (e.g. bowed
boundaries) due to geometry.
Solution Method – Laser Modulation
 Avoid edge-effects – only 70% of the mirror’s period is
used for projection
0.2
EFFECTIVE SCAN = 70%
90%(T/2)
(T/2)
0.15
Amplitude [rad]
0.1
0.05
0
-0.05
-0.1
-0.15
-0.2
0
11
1
2
3
time [sec]
4
5
-5
x 10
Algorithm – Eliminate Distortions
 Eliminate geometrical (Pincushion, Barrel) distortions
by defining a different initial projection time for each row
t2
12
t1
Algorithm – Uniform Distribution of Pixels
1 2 3 4 5 6 7 8 9 10 11 12 13 14
5
8
10
Result: uniform distribution
13
12
14
15
17
19
1 2 3 4
21
Nh
Results
“Target Resolution“:
• Linearly distributed pixels
along the x axis
• Vertical lines are one-pixel
width
• Fine Forward\backward
alignment
• Diagonal lines are sharp
(not bowed)
14
Maradin Ltd.
P.O. Box 56 Yokneam Industrial Park, South Yokneam 20692, Israel
Tel. +972 (4) 627 3653 | Fax. +972 (4) 959 0327
www.maradin.co.il
15