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Proceedings Paper

Strain measurement using heterodyne holographic interferometry
Author(s): David G. H. Andrews; Ronald C. Spooncer; Barry E. Jones; David C. Williams
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Paper Abstract

The technique of heterodyne holographic interferometry for the accurate measurement of small displacements is well established. In this paper a new detection method is employed which allows the direct measurement of strain components. This potentially offers an optical, non-contact replacement for the strain gauge, with a resolution of better than one microstrain. In double exposure heterodyne holographic interferometry, a separate reference beam is used for each exposure, and during reconstruction a phase shift (10 kHz in this case) is applied to one of the reference beams. The phase of the beats between the two images is proportional to the displacement between the images. In the technique described in this paper, light from a small region on the two superimposed images is focused onto closely spaced photodetectors. The phase difference between the two signals is directly proportional to a component of the strain at that point. The instrument is insensitive to small translational movements of the surface in any direction. The method has been applied to both double exposure and real-time holographic interferometry, and it has been tested against a strain gauge. The results obtained so far show that the technique is a reliable method for measuring strain, with several advantages over alternative methods.

Paper Details

Date Published: 2 March 1993
PDF: 5 pages
Proc. SPIE 1732, Holographics International '92, (2 March 1993); doi: 10.1117/12.140442
Show Author Affiliations
David G. H. Andrews, Brunel Univ. (United Kingdom)
Ronald C. Spooncer, Brunel Univ. (United Kingdom)
Barry E. Jones, Brunel Univ. (United Kingdom)
David C. Williams, National Physical Lab. (United Kingdom)

Published in SPIE Proceedings Vol. 1732:
Holographics International '92
Yuri N. Denisyuk; Frank Wyrowski, Editor(s)

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