Digital Shearograph for Detecting Defect in Materials

Abstract

Currently, one of the rapidly developing optical methods is the digital version of shear interferometry (shearography). The advantages of the method are: contactless method of obtaining data; low dependence on the shape and surface of the material being studied; determination of gradients of movements of surface points, manifested in the form of anomalies in the pattern of interference fringes, which are associated with areas of deformation. Experiments were carried out to obtain shearograms using a Michelson interferometer. An optical scheme for forming an image shift was tested. A scheme of a compact speckle interferometer for digital shearography has been proposed and implemented. A software algorithm for obtaining shearograms has been implemented. The device was tested to determine out-of-plane deformations on samples such as a round thin membrane. Experiments were carried out to detect defects in welds as zones with nonuniform deformation.