25 March 1999 New shearing setup for simultaneous measurement of two shear directions
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Shearography is a full field interferometric technique for the measurement of small deformation gradients. The main fields of application are non-destructive testing in quality control and material inspection. In both cases the direction of the deformation gradient plays a major role. We present a new image shearing speckle pattern interferometer set-up for simultaneous measurement of two independent deformation gradients equivalent to two shear directions. Herein, we use the polarization effect to separate the two directions. Based on a Michelson interferometer, we placed in one arm an additional polarization beamsplitter (PBS) and an additional mirror. The two orthogonal polarized images can be separated by a further PBS and simultaneously captured by a second camera. Substituting the second PBS with a rotatable polarizator and using only one camera, both sheared images can be recorded in rapid succession. We make use of a liquid crystal cell as a fast rotating polarizator and demonstrate the utility of this new concept with measurements in an industrial environment on a tensile testing machine.
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Thorsten Siebert, Thorsten Siebert, Bernhard Schmitz, Bernhard Schmitz, } "New shearing setup for simultaneous measurement of two shear directions", Proc. SPIE 3637, Practical Holography XIII, (25 March 1999); doi: 10.1117/12.343778; https://doi.org/10.1117/12.343778

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