Evaluation of interference fringe pattern on spatially curved objects

摘要

Abstract: This paper discusses methods to evaluate displacements of three-dimensional partially curved object surfaces taken by automatic digital image processing from multiple hologram analysis in order to determine the strain and stress state on the surface as well as inside the objects. The information is used to transform from the hologram plane, i.e., the image plane, into spatial object configurations. In doing that, the image scale, the perspective distortions, and the three- dimensional grid of the discrete evaluation algorithm, which is independent of the holographic set-up, must be considered. Having evaluated the holograms (at least three in order to determine the displacement vector u on the object surface) the order of the interference fringes in the nodes of the evaluation grid fixed in object space. Two different procedures are described to perform this transformation.!6