Quantitative measurement of dynamic deformations using pulsed holographic interferometry

Full field, quantitative measurements of dynamic object motions are performed using double-pulsed holographic interferometry with a custom built Nd 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.