Error compensation by model-based interferometry

One of the main problems in interferometric form testing is to distinguish form defects of the tested mirror from wavefront aberrations due to bad adjustment of the experimental set-up (Tutsch R 1994). When testing planar and spherical mirrors, an interpretation of the result is achieved using Zernike polynominals, for example, and fitting them to the measured wavefront. With increasing complexity of the measuring task (for example the interferometrical examination of hyperbolic or parabolic mirrors) it becomes more complicated to differentiate between defects of the mirror and those of the interferometer. This paper presents research work concerning the application of computer-based adjustments to various complex types of interferometers with the objective of increasing the reliability and, finally, the accuracy of interferometric measurements.