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Proceedings Paper

Heterodyne interferometer with frequency-modulated laser diode for in- and out-of-plane measurements of vibrations
Author(s): Pawel Drabarek; Michael van Keulen; Siegbert Steinlechner
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Paper Abstract

A prototype of a compact vibrometer which allows to measure both, in- and out-of-plane vibration components has been developed, built and tested. The vibration component to be measured was selected by switching the electronics and without moving the measuring head. The optical system is based on a heterodyne interferometer and contains two laser diodes. The heterodyne frequency shift of 7 MHz was realized by using laser diodes with frequency modulation by changing the injection current and using optical delay lines. Several low-cost laser diodes have been examined. The authors used a near IR, 10 mW laser diode for out-of-plane and a red, 10 mW laser diode for in-plane measurement channel, examining rectangle and triangle modulation of the injection current and found significant differences in the necessary length of delay lines. Shorter delay lines allow to reduce phase noise and yield a compact setup. The minimum resolvable velocity at 10 Hz measurement bandwidth was 1,8 10-6 m/s for out-of-plane and 1,4 10-5 for in-plane measurements. The maximum vibration frequency that can be measured is 100 kHz.

Paper Details

Date Published: 30 June 1998
PDF: 8 pages
Proc. SPIE 3478, Laser Interferometry IX: Techniques and Analysis, (30 June 1998); doi: 10.1117/12.312946
Show Author Affiliations
Pawel Drabarek, Robert Bosch GmbH (Germany)
Michael van Keulen, Robert Bosch GmbH (Germany)
Siegbert Steinlechner, Robert Bosch GmbH (Germany)


Published in SPIE Proceedings Vol. 3478:
Laser Interferometry IX: Techniques and Analysis
Malgorzata Kujawinska; Gordon M. Brown; Mitsuo Takeda, Editor(s)

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