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Proceedings Paper

Optical ultrasonic sensors for monitoring from industrial surfaces
Author(s): Richard J. Dewhurst
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Paper Abstract

An overview is presented of recent developments in the use of laser-generated ultrasound. Until the late 1980s, implementation of laser-ultrasound instruments in industry was impeded by a lack of detection sensitivity. Various optical detection schemes were investigated, including the Michelson interferometer, interferometers incorporating phase conjugation, techniques based on heterodyne holographic interferometry and lasers using two-wave mixing in photorefractive crystals. These detectors remain within research laboratories. The first interferometers to be developed for industrial applications have been those based on the confocal Fabry-Perot interferometer (CFPI). These are capable of analyzing the frequency shift of light imposed by ultrasound when light is back-scattered from a rough surface. A description of their properties is presented, showing how their frequency response to ultrasound may be modified. Typical signals recorded for thickness measurement or for defect imaging are presented, together with ultrasonic images acquired of defects in materials such as carbon fiber composite. They have now demonstrated their relevance to industrial applications, the challenge for the future being to reduce their overall costs.

Paper Details

Date Published: 15 November 1994
PDF: 10 pages
Proc. SPIE 2248, Optical Measurements and Sensors for the Process Industries, (15 November 1994); doi: 10.1117/12.194309
Show Author Affiliations
Richard J. Dewhurst, Univ. of Manchester Institute of Science and Technology (United Kingdom)

Published in SPIE Proceedings Vol. 2248:
Optical Measurements and Sensors for the Process Industries
Christophe Gorecki; Richard W. T. Preater, Editor(s)

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