Pulsed holography in non-destructive testing

The current use and potential of holographic pulsed ruby laser equipment in nondestructive testing (NDT) of large objects are described. Major topics include: the limitations on the size of holographic objects (pulse energy and coherence length); recent improvements in the coherence of pulsed lasers; the amount of laser energy required for holography of specific object sizes; and current holocamera designs and holographic NDT techniques. Several examples are considered of industrial NDT application of pulsed holography, including surface vibration analysis, debond detection in epoxied panels, delamination detection in layered materials, and airfoil dynamic testing. Photographs of holograms taken with a 7-meter coherence length ruby laser are shown to demonstrate the present object size capability of pulsed holography.