High-speed digital in-line holography as multipoint vibrometry to analyze vibrations of structures

Abstract

Structural vibrations can be measured with optical digital holography. Such a method provides measurements with a very high spatial resolution and is a nonintrusive technique. This method is based on the interference between a reference laser beam and the field diffracted by the studied object. Using a high speed camera, it can also be implemented in the time domain to investigate non-stationary problems. In this paper, we present a recent investigation which shows that the high-speed digital holography is comparable with classical laser vibrometry. Furthermore, an experimental investigation of the vibratory field inside the Acoustic Black Hole is discussed. The principle of digital holography is explained and it is used here to provide a full field measurement of the velocity field at the extremity of the structure.