Holographic strain analysis: extension of fringe-vector method to include perspective

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Abstract
A method has been published recently that permits determination of complete strain and rotation tensors of homogeneously deformed objects directly from fringes that are observed on their surfaces. However, the illumination and observation directions had to be considered constant over the regions of interest to apply the technique. This paper presents an extension of that theory to include both observation and illumination perspectives. It is shown that bulk translations of an object combine with linear variations in the directions of observation and illumination to generate fringe vectors that add directly to those generated by the object’s homogeneous transformations. These linear variations are calculable from illumination and observation geometry.