A novel approach for measuring nanometric displacements by correlating speckle interferograms

Recently, two phase evaluation methods were proposed to measure nanometric displacements by means of digital speckle pattern interferometry when the phase changes introduced by the deformation are in the range [0, π) rad. However, one of these techniques requires separate recording of the intensities of the object and the reference beams which correspond to both the initial and the deformed interferograms. The other technique only works to measure out-of-plane displacements. In this paper, we present a novel approach that overcomes these limitations. The performance of the proposed method is analyzed using computer-simulated speckle interferograms and it is also compared with the results obtained with a phase-shifting technique. Finally, an application of the proposed phase method used to process experimental data is illustrated.