Vibration mode separation of transient phenomena using multi-pulse digital holography

TLDR: In this article, a flat metal plate is made to randomly vibrate when excited by a shaker, and a digital holographic interferometry out-of-plane optical system is used to investigate the temporal development of the induced transient deformations.

Abstract: 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 deformations. The system relies on two and four laser pulses emitted within a single envelope of the flashlamp contained in the oscillator cavity of a ruby laser, and also on three CCD cameras used to record two or four digital images resulting from the same number of holographic interferograms. Hologram data reconstruction is per- formed digitally and Fourier evaluated to obtain quantitative deformation data for each of the formed interferograms. The deformation data is bro- ken down into resonant mode components, sums of which are used to computer reconstruct the experimental deformation data. The error pro- duced when using a finite sum of resonant mode components is consid- ered. Experimental and computer reconstruction results for the transient vibration deformation of the plate are presented and compared. © 1999 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(99)01712-2)