Fringe analysis and enhanced characterization of sub-surface defects using fringe-shifted shearograms

A technique for fringe analysis using variance of directly fringe-shifted shearograms is demonstrated experimentally. Statistical variations in each of the fringe-shifted shearograms are calculated to obtain a contrast map which is then used to characterize sub-surface defects and mechanical loading points. The technique offers reduced computational load compared to Fourier transform-based fringe processing algorithms. The technique is implemented using both phase difference maps and interferograms. The latter allows the extension of the technique to physical (i.e., non-reconstructed) interferograms for the analysis of dynamic systems.