A fringe-compensation technique for stress analysis by reflection holographic interferometry

Stress analysis of nontransparent objects using holographic interferometry is limited by rigid-body displacements of the object which alter the fringe patterns and often cause the fringes to disappear completely. A method for compensating for this fringe deterioration for real-time holographic interferometry is described. The fringe compensation is to be effected by optical modifications of the holographic system and involves compensation for translations and rotations. The method is shown to be effective for the case when the rigid-body displacement is unknown. The fringe compensation method is especially designed for the measurement of the out-of-plane strain near regions of stress concentration in plates subjected to in-plane loading.