A new analog computer has been constructed and used for the practical evaluation of hologram interference fringes. Stretched strings represent the pathlength of the light rays that travel from the light source to the observer via the object. The method can be used in a very general way, and it is only concerned with the number of fringes, not with the type of fringe pattern. Therefore, the calculation of the displacement is independent of the actual type of motion, e.g., rotation, translation, deformation, or extension. Very little mathematical, optical, or linguistic preknowledge is needed for the use of the method.
N. Abramson, "The Holo-Diagram. V: A Device for Practical Interpreting of Hologram Interference Fringes," Appl. Opt. 11, 1143-1147 (1972)