Uncertainty estimation in a non-null metrology system

A method to characterize the uncertainties in an optical system for the measurement of aspheric and freeform surfaces without dedicated null optics in a non-null measurement fashion is presented. Even though non-null test arrangements allow for increased measurement flexibility the evaluation of the measurement results becomes much more complex than in the null test variant. The problem becomes then the identification of small phase deviations caused by the test surface in the presence of systematic system aberrations several orders of magnitude larger. The characterization of the interferometer aberrations plays hereby a central role in the measurement process for an accurate assessment of the test surface. In this work we present an approach to estimate the measurement uncertainties of the setup.