Determination of the absolute order of one component of the surface displacement due to the evaluation of two interferograms of the specimen recorded under different loads

摘要

Abstract: The holographic interferometry is a tool to detect internal defects of a specimen, due to the recording of the inhomogeneous surface deformation in the area of these defects. By means of a standard evaluation method, e.q. the phase-shifting, the Fourier-transformation or the heterodyning method, it is possible to determine the relative phase distribution of the interference pattern. However, for the quantitative evaluation it is necessary to evaluate the absolute fringe-order. A new method has been developed, which allows the determination of the absolute displacement, based on two interferograms of the specimen, recorded under different loads, provided that the dependence between the load and the displacement is linear.!5