Fizeau type polarization electronic speckle pattern interferometry for deformation studies

Electronic Speckle Pattern Interferometry (ESPI) can provide on-site quantitative data for deformation field change in objects subjected to tensile stress. In this work, we propose a real-time polarization ESPI system based on a pixelated polarization camera with quantitative phase analysis of ESPI data. The optical configuration is a Fizeau type interferometer where the reference field is generated from the rough surface of a ground glass. The reference beam and the object beam are circularly polarized fields orthogonal to each other. The pixelated polarization camera captures simultaneously the four phase-shifted ESPI interferograms that have phase steps of 0, /2, , 3/2, which permits the implementation of the well-established phase shifting algorithm. Both temporal and spatial interference signals are used in the analysis, where the four-frame phase shifting algorithm in space is carried out to determine the phase, while the data in the time domain are used for unwrapping of the phase at each pixel. Simultaneous acquisition of the four-phase shifted interferograms on a single frame allows us to study dynamic processes. We performed numerical simulations for the proposed optical set-up taking into consideration different temporal correlation intervals for the dynamic speckle pattern formed on the sample surface during deformation. In the experiment, we use a Plexiglass (Polymethyl methacrylate - PMMA) object with introduced defects that was subjected to thermal expansion.