Vibration mode separation of transient phenomena using multi-pulse digitalholography

A rectangular flat metal plate is made to randomly vibrate when excited by a shaker. A digital holographic interferometry out-of-plane optical system is used to investigate the temporal development of the induced transient de formations. The system relies on two and four laser pulses emitted within a single envelope of the flashlamp contained in the oscillator cavity of a r uby laser, and also on three CCD cameras used to record two or four digital images resulting from the same number of holographic interferograms. Holog ram data reconstruction is performed digitally and Fourier evaluated to obt ain quantitative deformation data for each of the formed interferograms. Th e deformation data is broken down into resonant mode components, sums of wh ich are used to computer reconstruct the experimental deformation data. The error produced when using a finite sum of resonant mode components is cons idered. Experimental and computer reconstruction results for the transient Vibration deformation of the plate are presented and compared. (C) 1999 Soc iety of Photo-Optical Instrumentation Engineers. [S0091-3286(99)01712-2].