Holographic interferometry - Principles

In 1965, a number of laboratories pioneered holographic interferometry and the real start of holography in industry. Researchers realized that excessive movement of the object (or any other element of the set-up) during hologram recording led to the appearance of spurious dark and light interference bangs on the rendered image, which could completely alter it. To obtain a good quality hologram, it was therefore necessary to eliminate these parasitic bangs, ensuring sufficient stability of the object and the various elements of the montage during the exposure time. But, on the other hand, these parasitic interference bangs could be exploited to provide valuable quantitative information on the displacements that gave rise to them. A major shortcoming for an image hologram was now of great interest for industrial applications.

Everything that deforms in nature is "a priori" amenable to analysis by holographic interferometry: from the deformation of an eardrum under the effect of a supersonic airplane bang, to the deformation of engine components in operation, via the growth of a crystal or variations in air density around an airplane wing profile.

In this article, we will cover both the physical and theoretical aspects of holographic interferometry, followed by an overview of applications.