7 September 2013 Advanced surface metrology for meter-class optics
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Abstract
Refinements in computer controlled optical surfacing allow efficient grinding and polishing of meterclass optics to accuracy limited only by the surface metrology. We present a categorization of metrology methods and their implementation for meter-class optical components. Interferometry with computer generated holograms provides nanometer accuracy for full surface measurements of a wide range of convex and concave aspheric surfaces. For measuring off-axis and freeform aspheric surfaces, the holograms include features that provide references for alignment. Very high spatial resolution is achieved with subaperture interferometric measurements which can be stitched together to provide a full-aperture map. Scanning systems complement the capabilities of interferometry by achieving larger dynamic range and providing independent corroboration. Optical coordinate measurement machines (CMMs) provide non-contact measurements of surfaces in their ground state to guide figuring, as well as highly accurate measurements of finished optics. Scanning systems for measuring flat mirrors provide excellent resolution and absolute accuracy. The performance and practical issues for this full array of measurement techniques are presented to show the relative strengths of each method.
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M. Valente, M. Valente, B. Lewis, B. Lewis, N. Melena, N. Melena, M. Smith, M. Smith, J. H. Burge, J. H. Burge, C. Zhao, C. Zhao, } "Advanced surface metrology for meter-class optics", Proc. SPIE 8838, Optical Manufacturing and Testing X, 88380F (7 September 2013); doi: 10.1117/12.2035141; https://doi.org/10.1117/12.2035141
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