Interferometry for Ellipso-Height-Topometry part 3: Correction of the aspect errors and reduction of the dispersion of the ellipsometric parameters

Ellipso-Height-Topometry, EHT, is an extended optical topometry, where both the topographies of the surface height H(x,y) and the ellipsometric local parameters Ψ(x,y) and Δ(x,y) of surfaces with locally changing materials are measured on the same pixel raster with high resolution and using the same data sets. Further quantities can be calculated from these measurements on the base of locally confined surface models: the local refractive index, the thickness t(x,y) of overlayers or films, or other parameters of layered systems.In part 1 of this work a z-scanning interferometric scheme with oblique incidence over the entire object field and very useful coherence properties for practical coherence-scanning have been introduced.In part 2, the theory of the ellipsometric parameter acquisition in this interferometer has been developed for isotropic surfaces and the theory for the local segmentation of different materials or such materials covered with films was introduced. The results were verified by two sets of topographies for two different kinds of objects: a grid of gold strips on a substrate of quartz glass and an engine cylinder surface featuring silicon crystals in an aluminium matrix.In this part we deal with the aspect error of the measured profile due to an oblique incidence of the light and the dispersion of the ellipsometric parameters due to the surface roughness and its reduction. The new results are verified by two EHT-sets of topographies for a cast iron surface with graphite laminas.