19 August 2005 Design of a machine for the universal non-contact measurement of large free-form optics with 30 nm uncertainty
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Abstract
A new universal non-contact measurement machine design for measuring free-form optics with 30 nm expanded uncertainty is presented. In the cylindrical machine concept, an optical probe with 5 mm range is positioned over the surface by a motion system. Due to a 2nd order error effect when measuring smoothly curved surfaces, only 6 position measurement errors are critical (nanometer level). A separate metrology system directly measures these critical errors of the probe and the product relative to a metrology frame, circumventing most stage errors. An uncertainty estimation has been performed for the presented design, including a calibration uncertainty estimation and a dynamic analysis. Machine dynamics certainly cause relative motion between probe and product, but due to the non-contact nature of the measurement and the short metrology loop, these motions do not cause significant measurement errors. The resulting shape measurement error for aspheres up to medium free-forms is between 24 and 37 nm, and 30 - 85 nm for medium to heavily free-form surfaces. The suitability of the proposed design is herewith confirmed. A detailed design and a prototype of the machine are currently being developed.
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Rens Henselmans, Rens Henselmans, Nick Rosielle, Nick Rosielle, Maarten Steinbuch, Maarten Steinbuch, Ian Saunders, Ian Saunders, Rob Bergmans, Rob Bergmans, } "Design of a machine for the universal non-contact measurement of large free-form optics with 30 nm uncertainty", Proc. SPIE 5869, Optical Manufacturing and Testing VI, 586919 (19 August 2005); doi: 10.1117/12.613919; https://doi.org/10.1117/12.613919
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