Common-path spatial phase-shift speckle shearography using a glass plate

Abstract

In this paper, a spatial phase shifting digital speckle pattern shearography setup based on a common path interferometer and modest components is proposed for direct measurement of dynamical deformation gradient of objects. The simplicity, stability, and efficiency of the setup are provided by employing a plane parallel glass plate as a shearing device. The desired field of view can easily be achieved by employing two lenses. Moreover, adjustable spatial carrier frequencies within the speckle pattern which is needed to evaluate the phase difference before and after deformation by Fourier transformation can easily be produced. Ultimately, the slope of the deformations on the test surface can be obtained with tunable sensitivity. To demonstrate our technique, the proposed setup is used to evaluate the phase change in a center-loaded aluminum plate. Experimental results for out of plane deformation gradient are presented and discussed.