Rock probe deformation measured by holographic interferometry

Mechanical pressure-induced deformations of cylindrical rock probes were measured by holographic time-lapse interferometry. As it was generally impossible to find any zeroth-order fringes, a moving-fringe evaluation method as first given by Bonch-Bruevich was used. Small displacements parallel to the hologram plane could thus be measured with very high accuracy. The method is applicable to any type of local displacement of surface elements, limited only by the solid angle subtended at the hologram by the object.