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30 September 2011 Adaptive null test system using a ferrofluid deformable mirror
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With the growing number of complex-shaped lenses, aspheric and freeform surfaces, the demand for an appropriate and cost effective measurement technique to test these high quality components is still very high. Ferrofluid deformable mirrors (FDMs) offer a promising alternative. However, high accuracy profiles produced by FDMs have only been demonstrated in a closed-loop system which is inappropriate for metrology applications as it requires an additional measurement instrument and complicates the setup. Consequently, a FDM open-loop driving technique which maintains good precision while being simple, robust and stable, is required. In the following paper, we present a new active null test system based on a FDM for the testing of deep aspheric surfaces. We show a new driving method which provides an accurate open-loop operation mode of a FDM. We demonstrate that the method gives a significant improvement in comparison with the normalized influence function method. The results are promising enough to consider an active null test configuration for measuring optical components having high sag departures or complicated continuous profiles.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Daniel B. Landry, Denis Brousseau, Simon Thibault, and Ermanno F. Borra "Adaptive null test system using a ferrofluid deformable mirror", Proc. SPIE 8169, Optical Fabrication, Testing, and Metrology IV, 81690Z (30 September 2011);


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