Measurement of transient deformations by double-pulsed video speckle interferometry. Recent developments

The analysis of high speed transient phenomena caused by impact loading and wave propagation is very important to improve the design of mechanical, components. In previous years, this analysis has been limited to temporal domain using accelerometers and laser vibrometers. As the generation of a whole-field mesh of data requires many transducers operating simultaneously, there exists a requirement to develop a practical technique for the analysis of transient events. Video speckle interferometry is a non-contact whole-field optical technique which can be used for measuring static and dynamic deformations [1]. Fringe patterns are obtained by digitally correlating video images of two speckle interferograms recorded before and after deformation, and displacement fields can be determined using various methods based on the evaluation of the optical phase distribution. The aim of this paper is to present the main developments that have been taken place in the field of transient phenomena analysis using double-pulsed video speckle interferometry during the last years. Currently, the field is growing rapidly, partly as a result of the recent development of new CCD cameras and more flexible lasers which periodically emit pulses of about 20 ns duration.