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19 August 2005 Fabrication and metrology of freeform aluminum mirrors for the SCUBA-2 instrument
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TNO Science and Industry was contracted by the UK Astronomy Technology Center to deliver nine aluminum freeform mirrors for a new sub-millimeter instrument called SCUBA-2. With a much larger field-of-view and sky-background limited sensitivity, SCUBA-2 will map large areas of sky up to 1000 times faster than the original SCUBA camera. The requirement for freeform optics on SCUBA-2 is due to the fact that conventional spherical optic systems do not fit into the allotted space. TNO, who has developed a number of enabling technologies for freeform fabrication and metrology, applied its skills to the mechanical design and analysis of the mirrors. Due to the diverging requirements of the nine mirrors in size, form, and accuracy, TNO needed to spread the fabrication and metrology over additional organizations. The National Aerospace Laboratory of the Netherlands machined and hand polished the five largest mirrors (dimensions exceeding 1 meter and mass exceeding 150kg). They obtained form accuracies between 10 and 15μm peak to valley and roughness down to 40nm RMS. TNO fabricated the smaller and more accurate mirrors (dimensions between 300 and 700mm) on a Precitech Nanoform 350 with a slow tool servo. Measurements by the Dutch National Metrology Institute indicated form accuracies between 4 and 6μm peak to valley and roughness below 20nm RMS for the smaller mirrors.
© (2005) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ian J. Saunders, Leo Ploeg, Michiel Dorrepaal, and Bart van Venrooij "Fabrication and metrology of freeform aluminum mirrors for the SCUBA-2 instrument", Proc. SPIE 5869, Optical Manufacturing and Testing VI, 586905 (19 August 2005);


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