Abstract:
A new approach to automate 2D interferometric flatness deviation (FD) measurements is developed. A Finite Element Method (FEM) technique allows height map estimations from phase reconstruction of digitized Fizeau type interferograms. An algorithm computes local phase values by a least-squares fit from preprocessed interferograms, partitioned by FEM into a small triangle elements pattern inside a circular mask. Those local linear phase variations are combined into a global map by phase unwrapping and tilt plane removal steps. Flatness deviation of optical surfaces is evaluated from height variations obtained by this final map, with reduced uncertainties in comparison with previous measurement methods.
