Advanced Photon Source Nanomotion Diagnostic and Control

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Argonne National Laboratory
Applicazioni dell'interferometria laser ad alta
risoluzione
A linear actuator system with 1-angstrom
resolution and 50-millimeter travel
Applications of high-resolution laser
interferometry     Gianmarco Liotto  
Optodyne Laser Metrology srl Via Veneto,5
20044-Bernareggio (MI ) 39 039 6093618
optodyne_at_attglobal.net http//www.optodyne.com/
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• OUTLINE
• Introduction
• Laser Doppler Encoder with Sub-Angstrom
  Sensitivity
• High-Stiffness Weak-Link Linear Motion Reduction
  Mechanism
• One-dimensional Laser Doppler Linear Actuator
  Design
• One-dimensional Laser Doppler Linear Actuator
  Test
• Optics for Two-dimensional Laser Doppler Encoder
• Two-dimensional Laser Doppler Linear Actuator
  Design
• Discussion and Conclusions

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• A commercial Laser Doppler Displacement Meter
  (LDDM) system includes four components a laser
  head, a processor module, a display module, and a
  target reflector. The laser head houses a
  frequency-stabilized HeNe laser, an electro-optic
  assembly and a photodetector, which functions as
  a receiver. The laser light reflected by the
  target is frequency shifted by the motion of the
  target. The photodetector measures the phase
  variation caused by the frequency shift, which
  corresponds to the displacement of the target.
• When the displacement is larger than the
  half-wavelength, l/2, a counter records the total
  phase changes as Df
  total 2p N f , (1)
• where N is the number of half-wavelengths,
• 
  and f is the phase angle less than 2p.

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• The total target displacement, Dz, can be
  expressed as
• c
• Dz ------ (N f/2p)
  (2)
• 2f0
  ,
• where f0 is the frequency of the laser, and c is
  the speed of the light.
• If we make the laser light reflecting back and
  forth M times between the fixed base and the
  target before it finally reach the photodetector,
  then introducing equation (2) gives
• c
• Dz --------- (N f/2p)
  (3)
• 2f0 M ,
• which indicates that the multiple-reflection
  optics provides M-times resolution extension
  power for the system.

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Multiple-reflection optics for the laser Doppler
displacement meter (LDDM) The laser Doppler
displacement meter is based on the principles of
radar, the Doppler effect, and optical
heterodyning. We have chosen a LDDM as our basic
system, not only because of its high resolution
(2 nm typically) and high measuring speed (2 m/s)
but also because of its unique performance
independent of polarization, which provides the
convenience to create a novel multiple-reflection-
based optical design to attain sub-Angstrom
linear resolution extension.
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Multiple-reflection optics for the laser Doppler
displacement meter (LDDM)
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A prototype LDLE system having an extension with
optical resolution from twenty-four multiple
reflections has been developed and tested at the
Advanced Photon Source. A precision
stepping-motor-driven stage has been used to test
the LDLE over a 300-mm measuring range.
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• The resolution of the custom-made commercial
  LDDM system, which was used during this test, was
  2 nm (1 nm LSB), so that, theoretically, a 0.166
  nm resolution (0.083 nm LSB) was reached by the
  prototype LDLE system.

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Calibration for a High-stiffness Weak-link Linear
Motion Reduction Mechanism
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Prototype of a laser Doppler linear actuator
system (LDLA) with sub-angstrom sensor resolution
and positioning resolution over a 50-mm travel
range.
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Prototype of a laser Doppler linear actuator
system (LDLA) with sub-angstrom sensor resolution
and positioning resolution over a 50-mm travel
range.
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Setup for Large Field Atomic Probe Microscope
Test with LDLA
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• Test of a LDLA closed-loop feedback system

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• Prototype of a two-dimensional laser Doppler
  linear actuator system (LDLA) with subnanometer
  positioning resolution over a 50 mm x 50 mm
  travel range

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• Prototype of a two-dimensional laser Doppler
  linear actuator system (LDLA) with subnanometer
  positioning resolution over a 50 mm x 50 mm
  travel range

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MULTIPLE PASS
ADAPTER A 6-pass optical arrangement achieved by
an optical adapter and a 25mm diameter
retroreflector .
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MULTIPLE PASS
ADAPTER Effect of air circulation on a 6-pass
optical arrangement and on a single pass optical
arrangement.
6 - p a s s   v s   s in g le
0 10 20 30
40 50 60 t i m e , 
 s e c 0 -0,1?
-0,5?
Multi 6 Single
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• Laser Measuring System LDDM
• Includes
• Retroreflector
• Processor box
• Laser Head
• Performances
• Resolution 1.2nm
• Speed 5m/s

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• We have contributed to built a compact linear
  actuator system with 1-Angstrom closed-loop
  control resolution and 50-mm travel range.
• Two special techniques were developed for this
  ultraprecision motion control system. A laser
  Doppler encoder system with multiple-reflection
  optics has demonstrated its sub-Angstrom linear
  sensitivity. A specially designed high-stiffness
  weak-link linear motion reduction mechanism
  provided sub-Angstrom driving sensitivity with
  high stability.
• Further developments of the LDLA system are
  focused on the compactness of the two-dimensional
  system and optics for differential measurements
  for X-ray nanoprobe applications.

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References 1 Deming Shu, Yufeng Han, Thomas
S. Toellner, and Esen E. Alp A linear actuator
system with 1-angstrom closed-loop control
resolution and 50-millimeter travel range July
8, 2002 OPTOMECHANICS 2002, SPIE 2 D. Shu,
E. E. Alp, J. Barraza, and T. M. Kuzay, A Novel
Laser Doppler Linear Encoder Using
Multiple-Reflection Optical Design for High
Resolution Linear Actuator, Proceedings of SPIE,
Vol.3429 (1998)284-292. 3 D. Shu, T. S.
Toellner, and E. E. Alp, Ultraprecision Motion
Control Technique for High-Resolution X-ray
Instrumentation, Proceedings of the 1st
International Workshop on Mechanical Engineering
Design of Synchrotron Radiation Equipment and
Instrumentation, July 14, 2000, PSI-SLS,
Switzerland. 4 D. Shu, T. Toellner, and E.
E. Alp, Novel Miniature Multi-Axis Driving
Structure with Nanometer Sensitivity for
Artificial Channel-Cut Crystals, Synchrotron
Radiation Instrumentation Eleventh US National
Conference, ed. P. Pianetta, Am. Inst. Physics,
Conf. Proceedings vol 521 (2000) 219. 5 D.
Shu, T. S. Toellner, and E. E. Alp, Modular
Overconstrained Weak-Link Mechanism for
Ultraprecision Motion Control, Nucl. Instrum. and
Methods A 467-468, 771-774 (2001). 6  LDDM
is a trademark of the Optodyne Inc., 1180 Mahalo
Place, Compton, CA 90220, U.S.A. 7 Wang C.
P., (1987), Laser Optronics, Sept., p69-71.
8 Wang C. P., (1977), American Scientist, 65
(3), p289-293. 9 D. Shu, (2001), Patent
application in progress. 10 U.S. Patent
granted No. 5,896,200, Optical design for laser
encoder resolution extension and angular
measurement, D. Shu, 1999.