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Wavefront-based active alignment of multi-element optical systems

: Krappig, R.; Schmitt, R.

Dirckx, J.:
6th International Conference on Optical Measurement Techniques for Structures & Systems III, OPTIMESS 2015. Proceedings : Antwerp, Belgium, 8-9 April 2015
Maastricht: Shaker Publishing, 2016
ISBN: 978-90-423-0439-0
ISBN: 90-423-0439-1
International Conference on Optical Measurement Techniques for Structures and Systems (OPTIMESS) <6, 2015, Antwerp>
Conference Paper
Fraunhofer IPT ()

Besides the demanding specifications in the manufacturing of single optical components, the complexity of multi-element systems is strongly increased due to positioning aspects of the several elements to each other. This positioning requires to be highly precise in order to ensure the best optical functionality possible. Conventional methods of alignment via respective marks or geometrical features on the elements offer only a limited accuracy and are simply not practicable for cases in which restrictions to the aperture sizes or other optical constraints apply. On the contrary active alignment methods provide an elegant approach to this challenge, since they rely only on the optical function itself to deviate suitable correction actions for the system. Among others, the investigation of the wavefront-shaping properties of the system indicates multiple possibilities to optimize the wavefront by correcting the adequate element position(s). However, the individual procedure as well as the attainable accuracy of the process is dependent on the optical properties of the involved elements. The complexity of the problem follows out of the extensive interdependencies of all the coefficients, since improving one coefficient may result in the degradation of many others. Once calculated the implementation into real applications poses an as demanding task. Based on explanations to the mathematical background of general alignment methods a specific procedure is used for a simple demonstrator system in order to transfer the alignment calculation to a smaller scale. It is shown which magnitude of sensor specification can be derived for the necessary measurement technology.