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2 March 1993 Strain measurement using heterodyne holographic interferometry
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Proceedings Volume 1732, Holographics International '92; (1993)
Event: Holographics International '92, 1992, London, United Kingdom
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.
© (1993) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
David G. H. Andrews, Ronald C. Spooncer, Barry E. Jones, and David C. Williams "Strain measurement using heterodyne holographic interferometry", Proc. SPIE 1732, Holographics International '92, (2 March 1993);

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