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Optical Engineering

High-speed FM demodulator of a homodyne laser interferometer for measuring mechanical vibration
Author(s): Jongpil La; Semyung Wang; Koungsuk Kim; Kyihwan Park
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Paper Abstract

A high-speed FM demodulation method for measuring mechanical vibration using a homodyne laser interferometer is presented. The Doppler frequency, which represents the surface velocity of a vibrating object, is obtained by using the homodyne laser interferometer, and converted to a voltage signal by using the proposed analogue FM demodulation circuit. The dc offsets of the interference signals obtained from the homodyne laser interferometer are eliminated by using simple subtraction. The new method for compensation of the asymmetry of each interference signal is presented. The laser power variation of the interferometer is normalized by using an auto-gain controller (AGC). The performance of the proposed FM demodulation algorithm is proved by using theoretical methods, and validated by using experimental results. In the experiments, the proposed FM demodulation algorithm is compared with a conventional demodulation method.

Paper Details

Date Published: 1 June 2004
PDF: 9 pages
Opt. Eng. 43(6) doi: 10.1117/1.1715097
Published in: Optical Engineering Volume 43, Issue 6
Show Author Affiliations
Jongpil La, Kwangju Institute of Science and Technology (South Korea)
Semyung Wang, Kwangju Institute of Science and Technology (South Korea)
Koungsuk Kim, Chosun Univ. (South Korea)
Kyihwan Park, Kwangju Institute of Science and Technology (South Korea)

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