Correlation of holograms for surface characterization of diffuse objects

Abstract

In our previous work, digital holographic topography has been used to investigate the depth pattern of different surfaces. Two-wavelength digital holography has been used to resolve depth variations on surfaces, which are in the order of several microns to centimeters. These holograms are reconstructed numerically by Fresnel diffraction to retrieve phase and intensity information, which reveals the three-dimensional topographic surface details. To determine the similarity/difference between two 3D objects, we have recently proposed a novel technique involving 2D correlation of holograms, where holograms constructed from sets of point sources in 3D space were simulated to demonstrate the feasibility of this method. Crosscorrelation of holograms can also be used to authenticate the quality of holograms, and for 3D image encryption. In this work, correlation of holograms, both computer-generated, as well as optically recorded from diffuse objects, will be investigated. Computer generated holograms are also created to mimic surface roughness of real 3D objects. Correlation can be used to evaluate the quality of the surfaces, such as objects fabricated by 3D manufacturing techniques.