Comparison of alignment errors in asphere metrology between an interferometric null-test measurement and a non-null measurement with the tilted-wave-interferometer

Abstract

In interferometric testing of surfaces a major task is to avoid the introduction of aberrations due to misalignment of the surface under test (SUT). An automated method for the positioning of aspheric and free-form surfaces in a non-null test interferometer, as well as a method for the distinction between alignment introduced aberrations and surface errors is presented. A combination of both methods allows for a fully automated alignment with low accuracy requirements concerning the positioning stage. In this work the method for the alignment as well as the alignment error correction is presented and the misalignment introduced measurement uncertainties are estimated. Simulation results as well as experimental results showing the feasibility of the method are presented.