Ultrahigh resolution sandwich holography

A modified method of fabrication of sandwich holographic interferograms coupled with a digital evaluation technique has yielded ultrahigh resolution of surface deformation. The computer processing technique permits both the subfringe resolution and automatic fringe order determination (i.e., discrimination between depression and elevation of the deformed object surface). The technique presented here requires neither the interactive processing nor the fringe interpolation required by other techniques. Such processes are inaccurate, especially when there is a small number of interference fringes. With this type of analysis, sandwich interferometry is capable of fast, simple, ultrahigh resolution of surface deformation.