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Proceedings Paper

Heterodyne interferometry for real-time displacement measurement by phase-to-amplitude conversion technique
Author(s): Hui-Kang Teng; Kuo-Chen Lang
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Paper Abstract

The high precision measurement of displacement in nanoscale is crucial to nowadays many applications. We present a heterodyne interferoemtry with external modulation configuration for nanoscale displacement measurement. In the proposed method, the differential phase introduced by the displacement is converted into the amplitudes of quadrature heterodyne signals, so that the displacement can be determined from the amplitude ratio of the quadrature signals. The phase to amplitude conversion is achieved through the optical addition and subtraction by polarization tuning, which results in two phase quadrature signals in amplitude quadrature. Therefore, the proposed method also benefits from the feature of differential detection with common noise rejection. The nonlinearity of measurement due to polarization coupling is reduced by the conversion and the frequency coupling is eliminated by the external modulation approach. With proper phase bias to keep the interferometer in dark fringe operation, the shot-noise-limited performance is possible to realize. To demonstrate the capability of proposed method in real-time displacement measurement, we measure the dynamics of a commercially available PZT pusher and found close agreement between the experiment and the theory. The experimental evidence is also found with spectral distribution measurements, which demonstrates the minimum detectable phase and noise suppression capability of this approach.

Paper Details

Date Published: 17 January 2008
PDF: 10 pages
Proc. SPIE 6723, 3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment, 67230J (17 January 2008); doi: 10.1117/12.782909
Show Author Affiliations
Hui-Kang Teng, Nan-Kai Institute of Technology (Taiwan)
Kuo-Chen Lang, Nan-Kai Institute of Technology (Taiwan)


Published in SPIE Proceedings Vol. 6723:
3rd International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optical Test and Measurement Technology and Equipment
Junhua Pan; James C. Wyant; Hexin Wang, Editor(s)

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