A software configurable optical test system (SCOTS) based on fringe reflection was implemented for measuring the primary mirror segments of the Giant Magellan Telescope (GMT). The system uses modulated fringe patterns on an LCD monitor as the source, and captures data with a CCD camera and calibrated imaging optics. The large dynamic range of SCOTS provides good measurement of regions with large slopes that cannot be captured reliably with interferometry. So the principal value of the SCOTS test for GMT is to provide accurate measurements that extend clear to the edge of the glass, even while the figure is in a rough state of figure, where the slopes are still high. Accurate calibration of the geometry and the mapping also enable the SCOTS test to achieve accuracy that is comparable measurement accuracy to the interferometric null test for the small- and middle- spatial scale errors in the GMT mirror.

Date Published: 13 September 2012
PDF: 9 pages
Proc. SPIE 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II, 84500W (13 September 2012); doi: 10.1117/12.926719

Published in SPIE Proceedings Vol. 8450:
Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II
Ramón Navarro; Colin R. Cunningham; Eric Prieto, Editor(s)