New method for phase analysis in speckle shearing interferometer

Abstract

A new method for generating a phase map in digital speckle shearing pattern interferometry (DSSPI) is proposed. In DSSPI, a subtraction procedure is generally used to obtain a fringe pattern which is subsequently used in generating a phase map. In the proposed method, unlike previous methods the current phases of a correlation speckle pattern of an object at an initial state are first obtained using a phase-shifting technique. The phase map containing the deformation of the object due to any incremental loading is subsequently generated by subtracting the corresponding phases of the two states. The procedure simplifies the computational process and hence results in a reduction in computing time. To decrease the effect of speckle noises, the phase map is transformed into two parts consisting of sine and cosine functions. Digital image processing algorithms are then applied on the two functions to eliminate random noises and subsequently, a phase map with significant improvement in image quality is obtained. Theory of the method and some experimental results are presented.