Measurement errors in speckle interferometry: numerical simulation and experimental testing

The aim of the paper is to provide some tools for defining the actual operative conditions of a speckle interferometer. Two sources of error are investigated: the digitalization process of the interferograms and the decorrelation of the speckle pattern. For the first source of error a heuristic model was defined by analyzing the speckle patterns acquired in several experimental configurations, then the model was verified by simulating the actual operating conditions. The effect of the decorrelation at the pupil plane was evaluated by simulating the diffraction of the speckle pattern and subsequently including the error due to the digitalization process; the numerical results were compared with the experimental results obtained by a shearometer measuring out-ofplane displacements.