Sensitivity increase in digital holographic interferometry

Abstract

When using the interferometric techniques, the optical path changes induce the wavefront deformations that in turn cause the appearance of fringes. One general characteristic of such an approach is the measurement sensitivity. The actual sensitivity of a holographic interferometer is a function of, on one hand, the parameters of the measuring system (such as the wavelength of the light used) and, on the other hand, the environmental conditions in which the measurements are being made. The later depend predominately on statistical fluctuations inherent to the particular laboratory conditions. In many applications the sensitivity is near the limits of the deformation detectability. In such cases, it is of vital interest to increase the number of interferometric fringes thus improving the quality of the acquired data. In this paper, we give an overview of the sensitivity increase through various experimental and numerical approaches. We also present a new numerical iterative method in which every cycle doubles the number of interferometric fringes. The method has shown to be especially useful in applications with sub-wavelength wavefront deformations.