Table of Contents
Advances in Optics
Volume 2014 (2014), Article ID 576380, 7 pages
http://dx.doi.org/10.1155/2014/576380
Research Article

Submicron Surface Vibration Profiling Using Doppler Self-Mixing Techniques

1Instrumentation Centre, Physics Department, University of Coimbra, Rua Larga, 3004-516 Coimbra, Portugal
2Instituto Pedro Nunes, Rua Pedro Nunes-Edifício D, 3030-199 Coimbra, Portugal

Received 23 April 2014; Revised 9 July 2014; Accepted 10 July 2014; Published 23 July 2014

Academic Editor: Chi-Wai Chow

Copyright © 2014 Tânia Pereira et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Doppler self-mixing laser probing techniques are often used for vibration measurement with very high accuracy. A novel optoelectronic probe solution is proposed, based on off-the-shelf components, with a direct reflection optical scheme for contactless characterization of the target’s movement. This probe was tested with two test bench apparatus that enhance its precision performance, with a linear actuator at low frequency (35 µm, 5–60 Hz), and its dynamics, with disc shaped transducers for small amplitude and high frequency (0.6 µm, 100–2500 Hz). The results, obtained from well-established signal processing methods for self-mixing Doppler signals, allowed the evaluation of vibration velocity and amplitudes with an average error of less than 10%. The impedance spectrum of piezoelectric (PZ) disc target revealed a maximum of impedance (around 1 kHz) for minimal Doppler shift. A bidimensional scan over the PZ disc surface allowed the categorization of the vibration mode (0, 1) and explained its deflection directions. The feasibility of a laser vibrometer based on self-mixing principles and supported by tailored electronics able to accurately measure submicron displacements was, thus, successfully demonstrated.