A new set-up for pulsed digital shearography applied to defect detection in composite structures

An optical set-up based on the combination of new CCD technology, a ruby laser and a Mach-Zehnder shear interferometer is presented for defect detection in composites. Transient loads are used to excite defects in a sandwich structure and image-processing routines allow improving the detection resolution. Phase calculation is obtained by FFT algorithms applied to interference patterns with a spatial carrier in the primary fringes. Independent control of the shear and the frequency of the spatial carrier can be obtained with this set-up. The experimental implementation of the set-up and the results obtained with it are presented and discussed.

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