Direct determination of derivatives of holographically recorded displacement by an optical diffraction technique

Abstract

This paper presents a novel technique for direct determination of derivatives of the displacement recorded by holographic interferometry. In the recording of a double exposure hologram, a set of relatively high frequency carrier fringes is coherently superimposed upon the displacement fringes by slightly changing the object beam direction, in addition to deforming the object. The resultant fringe pattern is a perturbed carrier fringe pattern, and the local fringe spacing directly determines displacement derivatives. Fringe spacing is accurately determined by measuring the separation of a pair of diffracted orders produced by a laser beam diffracted by the local carrier fringes.