Determining the optimum image recording conditions in shearography based on spatial frequency considerations

Abstract

The transmission function of a double-exposure shearing specklegram consists of fringe- bearing and non-fringe bearing components. To obtain interference fringes, spatial filtering is performed on the processed specklegram to allow only the fringe-bearing components to pass. The spatial frequency for filtering is often determined on a trial-and-error basis. In this paper, a technique is presented to obtain a spectral distribution from which the optimum spatial filtering frequency can be deduced. Knowledge of the optimum spatial filtering frequency to recording aperture relationship enables better selection of image recording conditions.