Heterodyne interferometer with frequency-modulated laser diode for in- and out-of-plane measurements of vibrations

Pawel Drabarek; Michael van Keulen; Siegbert Steinlechner

doi:10.1117/12.312946

30 June 1998 Heterodyne interferometer with frequency-modulated laser diode for in- and out-of-plane measurements of vibrations

Pawel Drabarek, Michael van Keulen, Siegbert Steinlechner

Author Affiliations +

Proceedings Volume 3478, Laser Interferometry IX: Techniques and Analysis; (1998) https://doi.org/10.1117/12.312946
Event: SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, 1998, San Diego, CA, United States

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.

Citation Download Citation

Pawel Drabarek, Michael van Keulen, and Siegbert Steinlechner "Heterodyne interferometer with frequency-modulated laser diode for in- and out-of-plane measurements of vibrations", Proc. SPIE 3478, Laser Interferometry IX: Techniques and Analysis, (30 June 1998); https://doi.org/10.1117/12.312946

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