Use of a Faro Arm for optical alignment

Lisa A. Crause; Darragh E. O'Donoghue; James E. O'Connor; Francois Strümpfer

doi:10.1117/12.856810

22 July 2010 Use of a Faro Arm for optical alignment

Lisa A. Crause, Darragh E. O'Donoghue, James E. O'Connor, Francois Strümpfer

Proceedings Volume 7739, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation; 77392S (2010) https://doi.org/10.1117/12.856810
Event: SPIE Astronomical Telescopes + Instrumentation, 2010, San Diego, California, United States

Abstract

We discuss the use of a Faro Arm - a portable coordinate measuring machine - in the re-alignment and testing of the Southern African Large Telescope's Spherical Aberration Corrector. In pushing this versatile tool to its limits, we have arrived at a better understanding of its true capabilities and developed ways to compensate for some of its weaknesses. It is possible to achieve excellent results (~5 microns) when making relative measurements and keeping the Arm's orientation relatively constant. The Faro is also extremely useful in providing live feedback while making fine adjustments. However, single measurements of the same position are considerably less reliable (~50 microns) when the Arm is operated in widely different orientations. If the latter is unavoidable, one may largely counteract this by taking continuous streams of measurements (1000 readings) for a given point while exercising the Arm as much as possible in order to average the encoder errors. Various other techniques and accessories that we have found useful, as well as some painful lessons, are described here and a few examples are given to demonstrate how we have used a Faro Arm in our challenging optical alignment project.

Citation Download Citation

Lisa A. Crause, Darragh E. O'Donoghue, James E. O'Connor, and Francois Strümpfer "Use of a Faro Arm for optical alignment", Proc. SPIE 7739, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation, 77392S (22 July 2010); https://doi.org/10.1117/12.856810

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