Quantitative measurement of dynamic deformations using pulsed holographic interferometry

Abstract

Full field, quantitative measurements of dynamic object motions are performed using double-pulsed holographic interferometry with a custom built Nd:YAG laser. The double pulsed holographic technique measures dynamic object motions by creating two pulsed holograms at distinct times. Quantitative displacement information, with an accuracy of 10 nm and at a spatial content of over ten thousand points, is obtained with phase shifting interferometry. For sinusoidal vibration analysis, the in-phase and quadrature components of the operating mode shapes of a test structure are extracted by performing measurements with the laser pulsed at specific times in the vibration cycle. By combining the high spatial content of the holographic measurements acquired at a few frequencies with high spectral content measurements acquired at a few points, the potential exists for performing modal analysis with advantages over the conventional approach. Video animation methods are used to display the response of a test structure at several excitation frequencies.