Abstract: A method of using the classic principles of moire patterns and holography to provide defect analysis of variable sensitivity on structures of various sizes, including large aircraft. By taking several holograms (usually a series of four) of the structure which has been illuminated with dual (or multiple) beams of coherent illumination (e.g. laser), each hologram will record an image of the test object which includes an interferometric fringe pattern on the surface. The spacing and orientation of the fringe pattern can be varied by the arrangement and nature of the dual illumination beams.