Speckle photography offers a technique for measuring small strains on an object in the presence of large displacements. An analysis is presented of this technique, which accounts for the phenomena observed and predicts its capabilities and limitations. The analysis is sufficiently general to describe either of two related techniques, one that permits measurement of strains in the absence of large displacements and one that permits measurement of large displacements alone.
Karl A. Stetson, "Analysis of double-exposure speckle photography with two-beam illumination," J. Opt. Soc. Am. 64, 857-861 (1974)