22 July 2010 A very accurate filter wheel for a large field IR imager
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Abstract
HAWK-I is a near-infrared imager with a relatively large field of view. Two filter wheels with 6 positions each offer a choice of 10 filters. The filters are directly in front of the detector, a mosaic of 2 × 2HAWAII 2RG 2048×2048 pixels detectors. A rather high positioning reproducibility (< 6 arc sec) is required in order to avoid any disagreement caused by subtraction of eventual fix pattern on the filters. The document describes various drive systems which have been tested in order to reach the specified positioning reproducibility. This includes an interesting dissipation free locking system combining electro magnet and permanent magnet. Every solution is discussed and the performances measured in the laboratory during a long campaign of test are exposed. We also address the choice of other critical components like the ball bearings, mounting of the filters and cooling of the wheels.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
J. L. Lizon, J. L. Lizon, "A very accurate filter wheel for a large field IR imager", Proc. SPIE 7739, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation, 77393G (22 July 2010); doi: 10.1117/12.856093; https://doi.org/10.1117/12.856093
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