<title>Contributions Of Acoustical Holography To Mechanical Metrology</title>

Abstract

Holographic transposition of ultrasonic waves into light waves can be exploited not only qualitatively, as a technique for non-destructive testing of opaque materials, but also quantitatively. In fact, as a method of visualization, acoustical holography translates the variations of acoustical transparence of the object inspected into the form of variations of lighting. Generally, the non-linearities of this process limit the accessible information solely to the contour of the variations in transparence as well as their localization, which leads to a simple dimensional metrology. It is nonetheless possible to exploit the conservation of the phase to effect, by means of optical techniques, measurements on the parameters characterizing the inhomogeneous zones of a material. The conditions of linearity of the transfer of the information by holography are examined in the case of the surface relief method and some examples of the optical treatment of the acoustical information are presented.