Use of sensitivity vector variations to determine absolute displacements in double exposure hologram interferometry

Two solutions are presented to the problem of unknown absolute fringe order in double exposure hologram interferometry, a problem that confronts systems that require a single view of an object. One solution determines the vectorial object displacements relative to one reference point on the object. The other employs variations of the sensitivity vectors to provide absolute displacement analysis. For absolute displacements, a minimum of four illuminations is required.