A fast method for measuring nanometric displacements by correlating speckle interferograms

A phase evaluation method was recently proposed to measure nanometric displacements by means of digital speckle pattern interferometry when the phase change introduced by the deformation is in the range [0,π)rad. To evaluate the phase change, however, it is necessary to record separately the intensities of the object and the reference beams corresponding to both the initial and the deformed interferograms. This paper presents a fast approach that overcomes this limitation. The rms phase errors introduced by the proposed method are determined using computer-simulated speckle interferograms and its performance is also compared with the results obtained with a phase-shifting technique. An application of the proposed phase retrieval method to process experimental data is finally illustrated.

► Nanometric displacements can be measured using digital speckle pattern interferometry.
► A fast phase retrieval method based on local correlation calculations is presented.
► The performance of the method is determined through a numerical analysis.
► Results are also compared with those obtained using a phase-shifting technique.
► Results obtained from the processing of experimental data are finally presented.