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Lawrence Livermore
CfAO Video Conference - March 29, 2001
Emily CarrDepartment of Electrical and Computer Engineering
University of California, Davis 95616
Lawrence Livermore National Laboratory
Livermore, CA 94550
Scot Olivier, Peter KrulevitchLawrence Livermore National Laboratory
Livermore, CA 94550
Olav SolgaardE. L. Ginzton Laboratory
Stanford University, Stanford, CA 94305-4085
Micro-Deformable Mirrors for Adaptive Optics
Lawrence Livermore
CfAO Video Conference - March 29, 2001
Outline
• Why use micromirrors in an AO system?• Current Research
– Boston University’s Deformable Mirror • Characterization of Mirror Surface• Voltage vs. Displacement Results
– AO Testbed Results with BU Mirror• Far-field spot
– Airforce/Cowan/Sandia Mirror• Characterization of Mirror Surface• Voltage vs. Displacement Results
• Future Research– New mirror design
Lawrence Livermore
CfAO Video Conference - March 29, 2001
Conventional Deformable MirrorConventional Deformable Mirror
http://www2.keck.hawaii.edu:3636/realpublic/inst/ao/about/slides/dmirror.html
Lawrence Livermore
CfAO Video Conference - March 29, 2001http://www.bostonmicromachines.com
Boston Micromachines Corporation Mirror
Lawrence Livermore
CfAO Video Conference - March 29, 2001
Optical Characterization of BU Micromirror
3.3mm
3.3mm
300m
Electrostatically actuated diaphragm
Attachment post
Membrane mirror
Continuous mirror
• 2 m deflection achieved with 240 V applied to each individual actuator.
Lawrence Livermore
CfAO Video Conference - March 29, 2001
Line Scan ~ 8 actuators
Static Mirror Surface - No Voltage Applied
rms: 35.84 nm
•Mosaic of 4 images taken with a Zygo white light interferometer.
Lawrence Livermore
CfAO Video Conference - March 29, 2001
Influence Function of BU Mirror
• 100 V applied to one central actuator on the BU mirror
Lawrence Livermore
CfAO Video Conference - March 29, 2001
Boston Micromachines 140 Actuator DM - Voltage vs. Displacement Curve
-200
0
200
400
600
800
1000
1200
1400
1600
0 50 100 150 200
Voltage (Volts)
Dis
pla
cem
en
t (n
m)
•Pink data points - measured data•Blue data points - curve fit: y=0.02028 x2.2105
Lawrence Livermore
CfAO Video Conference - March 29, 2001Good Mirror - W25C27
Flattening the Good Mirror
• Zero Voltage applied to all the actuators• Best Flat with an 8x10 array of actuators
Lawrence Livermore
CfAO Video Conference - March 29, 2001
Flattening different areas of the mirror
This is the flat being used in the AOtestbed.
Flattest 8x8 elements - central actuators Flattest 10x10 elements
Lawrence Livermore
CfAO Video Conference - March 29, 2001
Zero Volts on MEMS – Far-field Spot in AO Testbed
• This is the far-field spot we obtain when we put the mirror on the left in the AO testbed.
Zero Volts on all the actuators
Lawrence Livermore
CfAO Video Conference - March 29, 2001
Far-Field Spot with Flat Voltages Applied
• Far-field spot with the mirror at left in the AO testbed.
Flattest 10x10 array
Lawrence Livermore
CfAO Video Conference - March 29, 2001
MEMS Mirror Far Field
Row and column slices: red is measured, black is perfect beam. Strehl~0.43
Lawrence Livermore
CfAO Video Conference - March 29, 2001
Reconstructed Waveforms from DM
Big Checkerboard – 125V appliedTo sets of 4 actuators.
Small Checkerboard – 125VApplied to every other actuator
• Reconstructed waveforms from the Shack-Hartman wavefrontsensor.
Bad Actuator CoupledActuators
Lawrence Livermore
CfAO Video Conference - March 29, 2001
Airforce/Cowan/Sandia 256 Actuator Segmented Mirror
•256 Active Actuators•Segmented Mirror•Maximum voltage needed 20V•0.65 microns of stroke
Lawrence Livermore
CfAO Video Conference - March 29, 2001
Actuator Structures
Airforce Mirror - Voltage vs. Displacement Curve
-100
0
100
200
300
400
500
600
700
0 5 10 15 20 25
Voltage (Volts)
•Light blue data points - measured data•Red data points - curve fit: y=0.39789 x2.3676
200 m
Airforce/Cowan/Sandia Mirror Voltage vs. Displacement Curve
Lawrence Livermore
CfAO Video Conference - March 29, 2001
“New” Mirror Design
Lawrence Livermore
CfAO Video Conference - March 29, 2001
Conclusion
• The Deformable Mirror (DM) is a crucial part of an AO system.• MEMS based DM’s are cheaper, faster, and have the potential
to have more stroke then conventional DM’s.• Boston Micromachines Corporation has a commercially
available continuous face-sheet MEMS DM with 2m of stroke, 7kHz resonance frequency, and an rms surface error of 30nm. 240 V needed to get maximum deflection.
• The Airforce mirror designed by William Cowan has a better surface quality, but only 0.65m of stroke, and it is segmented. 20 V needed to get maximum deflection.
• Will continue to work on new high-stroke design based on the Justin Mansell’s deformable mirror architecture.
