Versatile optical techniques for non-destructive testing

These techniques encode information of the measurand in phase characteristics of a two-dimensional fringe pattern. The piecewise polynomial phase approximation approach that we introduced has enabled simultaneous and direct estimation of the phase and its first- and second-order derivatives from a single fringe pattern. This approach allows for the simultaneous measurement of displacement, strain, and curvature of a deformed object, and thus avoids the necessity of using filtering and unwrapping procedures, multiple analysis techniques, and multiple interferometric configurations. Moreover, its high computational efficiency has opened up avenues for rapidly obtaining measurements such as the evolution of full-field deformation and strain at standard video frame rates.