Fast phase-map recovery from large shears in an electronic speckle-shearing pattern interferometer using a Fourier least-squares estimation

Electronic speckle-shearing pattern interferometry offers the possibility of analyzing out-of-plane and in-plane deformations in experimental mechanics. However, to obtain high-contrast fringes this technique must introduce large shears into the speckle patterns. Several techniques have recently been proposed to recover the phase from these data, but they all suffer limitations due to the slow convergence of the proposed algorithms or to the low precision of the recovered phase. This paper presents a least-squares estimation method in the frequency domain that allows wavefront recovery from two orthogonal shearing fringe patterns when a large shear is applied. This method is based on the application of a single Fourier filter using the fast Fourier transform process. The experimental results obtained by using electronic speckle-shearing pattern interferometry for the analysis of a finite circular plate deformed at the center illustrate the advantages of the proposed technique. (C) 2000 society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)00309-3].