Visualizing structural vibrations using laser speckleThomas R. Moore
Scientists have been seeking new ways of imaging small vibrations since Chladni first placed sand on a vibrating plate in the 18th century. For the 200 years following Chladnis discovery there were few other methods available for imaging vibrations; however, in the latter half of the 20th century the invention of the laser spurred the development of several different methods to optically image sub-micrometer vibrations. Of the optical methods available today for visualizing vibrations, the broad class of imaging techniques that rely on the phenomenon of laser speckle has become particularly useful. An overview of some of these speckle imaging techniques will be presented, with an emphasis on visualizing the vibrations of musical instruments. Several examples will be discussed, and ideas for the inexpensive construction of the necessary apparatus will be reviewed.