Research on New Shearing Speckle Interferometry System

Abstract

Shearing speckle interferometry is a well known optical tool for qualitative as well as quantitative measurements of displacement components′ derivatives of engineering structures subjected either static or dynamic load. Shearing speckle interferometry, based on Mach-Zehnder interferometer, suffers from the disadvantage of low light efficiency due to the structure. A novel digital shearography setup with two fold which can improve light efficiency for the measurement of first order derivative of out-of-plane displacement (slope) is demonstrated. There is a double aperture mask in front of the imaging lens for spatial phase shifting. Independent control of the shear and the frequency of the spatial carrier can be attained with this setup. A shear is introduced between the two scattered fields. The double aperture which can introduce spatial carrier fringes within the speckle for spatial phase shifting is employed in this system. Phase extraction is obtained through advanced sinusoidal-fitting method, which is applied to interference patterns with a spatial carrier in the primary fringes. The experimental implementation of the setup and the results obtained with it are presented and discussed.