Holographic interferometry with an injection seeded Nd:YAG laser and two reference beams

The performance of twin injection seeded Nd:YAG lasers is compared with the performance of an argon-ion laser for recording dual-reference-beam holograms in Agfa 8E56 emulsion. Optical heterodyning is used to measure interference and the results are expressed in terms of heterodyning signal level and intensity signal to noise. The Nd:YAG laser system is to be used for optical inspections of structures for cracks, defects, gas leaks, and structural changes.