Novel contour-mapping methods

Abstract

Three optical methods for contourmapping of phase objects are introduced. They are based on the partially coherent diffraction effect the joint Talbot effect and logic operated moire phenomenon and the Fourier filtering. 1. PARTIALLY COHERENT DIFFRACTION EFFEOS The Lau effect and the Talbot effect are interference phenomena relating to the selfimaging of periodic objects. It is known that the same specific distanceis needed for the both effects but the two effects differ in their modes of illumination spatially incoherentorcoherent. It is thus of great interest to look for new spatially partially coherent diffraction effects. 1. 1. Partially coherent effect between Lau and Talbot effects'' The observation of partially coherent effect can be achieved by illuminating the conventional Lau setup with a source slit of changable width. The spatially coherent state of illumination on the first grating can be varied continuously by the adjustment of the slit width. If the slit width is controlled to approach zero illumination is approximately coherent and the Talbot effect can be seen. If the slit is opened wide enough the illumination is incoherent resulting the Lau effect. A general formula is achieved as a joint correlation among the three functions of the source slit and the two gratings for an exact description of the fringes yielded by any state of illumination coherence. It is concluded that the fringe pattern changes in its profile not only as