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OPTODYNE

OPTODYNE. OPTODYNE. 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

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OPTODYNE

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  1. OPTODYNE OPTODYNE 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@attglobal.net http://www.optodyne.com/

  2. 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

  3. 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:Dftotal = 2p N + f , (1) where N is the number of half-wavelengths, and f is the phase angle less than 2p.

  4. 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.

  5. 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.

  6. Multiple-reflection optics for the laser Doppler displacement meter (LDDM)

  7. 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.

  8. 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.

  9. Calibration for a High-stiffness Weak-link Linear Motion Reduction Mechanism

  10. Prototype of a laser Doppler linear actuator system (LDLA) with sub-angstrom sensor resolution and positioning resolution over a 50-mm travel range.

  11. Prototype of a laser Doppler linear actuator system (LDLA) with sub-angstrom sensor resolution and positioning resolution over a 50-mm travel range.

  12. Setup for Large Field Atomic Probe Microscope Test with LDLA

  13. Test of a LDLA closed-loop feedback system

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

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

  16. MULTIPLE PASS ADAPTER A 6-pass optical arrangement achieved by an optical adapter and a 25mm diameter retroreflector .

  17. 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

  18. Laser Measuring System LDDM • Includes: • Retroreflector • Processor box • Laser Head • Performances • Resolution 1.2nm • Speed 5m/s

  19. 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.

  20. 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.

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