Speckle interferometry for highly localized displacement fields

A method of obtaining phase fringe patterns of improved quality using electronic speckle pattern interferometry (ESPI) is complemented by new equations governing the displacement sensitivity if asymmetric illumination is used. The techniques are experimentally verified. The accuracy of the method for determination of highly localized strain fields is demonstrated by comparing the measurements with the results of a finite-element model. The potential of the improved method in the field of fracture mechanics is outlined.