21 September 1999 Shearography for determination of 2D strain distributions
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Proceedings Volume 3824, Optical Measurement Systems for Industrial Inspection; (1999); doi: 10.1117/12.364286
Event: Industrial Lasers and Inspection (EUROPTO Series), 1999, Munich, Germany
Abstract
We report on a novel set-up using image shearing speckle pattern interferometry for the determination of 2D strain distributions of an object surface. This system is based on simultaneous illumination of the object with three diode lasers that emit at different wavelengths between 810 nm and 850 nm. Their speckle images are separated within the shearographic set-up, consisting of a special color separation optics and 3 b/w CCD cameras, in such a way that each camera records the speckle image corresponding to one laser source only. Two methods are presented which allow to switch between the two directions of image shear. The shearographic camera in combination with the appropriate illumination geometry allowed us to determine and isolate all six displacement derivatives from phase stepped fringe patterns. The good suitability and accuracy of the system for the determination of 2D strain distributions are demonstrated on the basis of shearographic measurements during tensile testing and comparison with strain gage measurements.
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Ralf Kaestle, Erwin K. Hack, Urs J. Sennhauser, "Shearography for determination of 2D strain distributions", Proc. SPIE 3824, Optical Measurement Systems for Industrial Inspection, (21 September 1999); doi: 10.1117/12.364286; https://doi.org/10.1117/12.364286
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KEYWORDS
Cameras

CCD cameras

Fringe analysis

LCDs

Shearography

Speckle

Charge-coupled devices

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