Differential Interferometry or ''Shearography'': Use in Fluid Mechanica and in Solid Mechanics. A Long Story (Keynote Lecture)
by
Paul Smigielski
French-German ResearchInstitute of Saint-Louis, 68301 Saint-Louis, FRANCE

Differential interferometry in polarized light using Wollaston prismas is a wellknown technique used for a very long time for flow visualization either with light or with a laser source.

"Shearography" was used more recently but in solid mechanics mainly for non-destrutive testing. A laser source is necessary with this technique.

One argument for using ßhearography" on site for industrial application is its relative insensitivity to environmental industrial conditions, i-e vibrations and air convection. On the other side, ßhearography" is used to visualize vibrations and air flows! I shall comment upon that.

This talk will describe different set-up and applications in both fields of mechanics and will comment upon sensitivity, spatial and temporal coherence, and image processing.

An outlook on the future will be done including new developments on digital interferometry.

Date received: February 1, 1999