Although shearography was originally developed for strain measurements, it is more readily accepted by industry for discontinuity detection than for strain measurement. This is because in the determination of strain, identification of fringe order is needed. There is also an ambiguity in fringe order determination (Hung, 1982). In inspection for discontinuities, however, identification of fringe orders is generally not required. Shearography detects discontinuities in materials by looking for discontinuity induced fringe anomalies which are identifiable without knowing fringe orders.
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