Digital Tolansky interferometer which is the conventional Tolansky interferometer interfaced to the personal computer through CCD TV-camera, is developed and applied to surface topography.
An dielectric coated, optically flat cover glass is made an slight edge with the aluminium overcoated specimen. The Tolansky fringe formed in the conventional Tolansky interferometer is imaged on CCD TV camera, and the intensity of the fringe is digitized by video digitizer, being stored into the memory of computer. The digitized interferogram is skeletonized and thinned to find its exact intensity valley points, and linear equations best fitting the valley points in the same order, seperately before and after the region where an apparently abrupt displacements of the valley points occur. The surface profile of the specimen in cross-sections orthogonal to the line joining the cover glass and the specimen is obtained from the spacings between the obtained valley lines.
By processing in this way two Tolansky fringes, each formed when the cover glass are wedged in one of two perpendicular directions with the specimen, it is shown that the three dimensional surface topography is possible. Actually, three dimensional surface profile of the specimen is constructed, with the standard deviation of 8A in heights of the surface profile.
Furthermore, comparing with the case of the ideal Tolansky interferometer, the resolution of the Tolansky system used in this experiment is determined.
