Fringe compensation in speckle interferometry: application to nondestructive testing

Speckle interferometry when used for NDT suffers from overcrowding of fringes even for small loads, thereby making defect detection impossible. A fringe compensation technique is presented in this paper. The technique employs two objects, identical except for the defect in one, that are loaded in the same way resulting in full compensation except in the neighborhood of the defect. Theory and experimental results are presented.