Adaptive Optics for Michelson Interferometry DIPLOMARBEIT

Precise distance measurement is crucial for the high-precision industry as the semiconductor manufacturing is one. Measurement devices based on the concept of a Michelson interferometer are widely used to implement a very accurate and non-contact distance measurement with nanometer resolution. Interferometers are often applied in environments where the optical path is uncovered and influenceable by air turbulences such as caused by fast moving targets. Air turbulences cause aberrations in the wavefront, deteriorate the interference pattern and lead to a smaller peak-to-valley intensity signal which cause problems in the determination of the traveling distance. To determine as well as to compensate for aberrated wavefronts this thesis investigates the integration of an adaptive optics system into a Michelson interferometer. The aberrated wavefront is measured with a Shack-Hartmann wavefront sensor and compensated by a deformable mirror. A feedback controller is implemented that computes the signals for the deformable mirror. The proposed setup comprises off-the-shelf products for the interferometer and the adaptive optics setup. The implemented system is capable of compensating low order aberrations, resulting in an average improvement of 5, 7 of the peak-to-valley signal.