A method for the isolation of two-dimensional (2D) displacement components by using one phase map obtained by phase-shifting electronic speckle pattern interferometry (ESPI) is presented. When the typical ESPI is used for displacement measurement, a mixed phase distribution of deformation is measured. If the deformation of the object is symmetrical, two components of deformation can be separated from each other by using the mixed phase distribution. We turn over the mixed phase map first to obtain the second phase map, and then overlap them. Two displacement components can be separated from each other by boundary alignment and algebraic calculation between the two phase maps. This method has been proved feasible by a typical three-point bending experiment. Some experimental results are offered and compared with the results obtained by a dual-beam symmetrical illuminations experiment. This technique presented provides an alternative approach to 2D deformation measurement.
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