The manufacturing and metrology of off-axis mirrors

Karlheinz Penzkofer; Rolf Rascher; Lutz Küpper; Johannes Liebl

doi:10.1117/12.2195893

11 October 2015 The manufacturing and metrology of off-axis mirrors

Karlheinz Penzkofer, Rolf Rascher, Lutz Küpper, Johannes Liebl

Proceedings Volume 9633, Optifab 2015; 96330X (2015) https://doi.org/10.1117/12.2195893
Event: SPIE Optifab, 2015, Rochester, New York, United States

Abstract

Especially in the area of the large mirror manufacturing only a few manufacturers are capable to produce optical surfaces of high quality. Therefore a deterministic process should be developed in the project IFasO. In the field of telescope optics off-axis optical systems are becoming increasingly important. These systems try to avoid an obstructing of the incoming light by moving the secondary mirror out of the primary mirror's optical axis. This advantage leads to an increasing market for this type of optical surface.

Until now off-axis mirrors were difficult or almost impossible to produce. With the processes developed in IFasO, high quality mirrors become possible. For this reason, this paper describes the manufacturing of off-axis surfaces and its problems.

The mirror production used in the project IFasO is based on the specific design of the CNC center developed by the company Optotech. This center UPG2000 is capable of grinding, polishing, sagitta measurement and interferometric measurement in one mounting of the specimen. Usually a large optics has to be transported during their manufacturing after every individual process step. There is always a risk of damage of the specimen. The exact orientation of the surface relatively to the tool position is also required. This takes a huge amount of time and makes up most of the production time.

In this presentation the use of UPG2000 and the next steps within the process development are described. In the current status the manufacturing of large off-axis elements with a PV < λ/10 rms is reproducible.

Citation Download Citation

Karlheinz Penzkofer, Rolf Rascher, Lutz Küpper, and Johannes Liebl "The manufacturing and metrology of off-axis mirrors", Proc. SPIE 9633, Optifab 2015, 96330X (11 October 2015); https://doi.org/10.1117/12.2195893

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