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Proceedings Paper

Qualification of HEIDENHAIN linear encoders for picometer resolution metrology in VTF Etalons
Author(s): Clemens Halbgewachs; Thomas J. Kentischer; Karsten Sändig; Joerg Baumgartner; Alexander Bell; Andreas Fischer; Stefan Funk; Frank Heidecke; Thomas Scheiffelen; Wolfgang Schmidt; Erwin Spanner; Peter Speckbacher; Oskar F. von der Lühe
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Paper Abstract

The Visible Tunable Filter (VTF) is a narrowband tunable instrument for imaging spectropolarimetry in the wavelength range between 520 and 870 nm. It is based on large-format Fabry Perots with a free aperture of 250 mm. The instrument will be one of the first-light instruments of the 4 m aperture Daniel K. Inoue Solar Telescope (DKIST) that is currently under construction on Maui (Hawaii). To provide stable and repeatable spectral scanning by tuning the air gap distance of the Etalons, a metrology system with 20 pm resolution and drift stability of better 100 pm per hour is needed. The integration of the metrology system must preserve the tight optical specifications of the Etalon plates. The HEIDENHAIN LIP 382 linear encoder system has a selected linear scale for low noise high signal interpolation. The signal period is 128nm and the interpolated signal from the sensor can be read out at 128 nm/ 14 bit = 7.8125 pm. To qualify the LIP 382 system for the VTF, we investigated the resolution and stability under nominal VTF operation conditions and verified a mounting concept for the sensor heads. We present results that demonstrate that the LIP 382 system fulfills the requirements for the VTF Etalons. We also present a design for the sensor head mounts.

Paper Details

Date Published: 9 August 2016
PDF: 19 pages
Proc. SPIE 9908, Ground-based and Airborne Instrumentation for Astronomy VI, 99084H (9 August 2016); doi: 10.1117/12.2232297
Show Author Affiliations
Clemens Halbgewachs, Kiepenheuer-Institut für Sonnenphysik (Germany)
Thomas J. Kentischer, Kiepenheuer-Institut für Sonnenphysik (Germany)
Karsten Sändig, DR. JOHANNES HEIDENHAIN GmbH (Germany)
Joerg Baumgartner, Kiepenheuer-Institut für Sonnenphysik (Germany)
Alexander Bell, Kiepenheuer-Institut für Sonnenphysik (Germany)
Andreas Fischer, Kiepenheuer-Institut für Sonnenphysik (Germany)
Stefan Funk, DR. JOHANNES HEIDENHAIN GmbH (Germany)
Frank Heidecke, Kiepenheuer-Institut für Sonnenphysik (Germany)
Thomas Scheiffelen, Kiepenheuer-Institut für Sonnenphysik (Germany)
Wolfgang Schmidt, Kiepenheuer-Institut für Sonnenphysik (Germany)
Erwin Spanner, DR. JOHANNES HEIDENHAIN GmbH (Germany)
Peter Speckbacher, DR. JOHANNES HEIDENHAIN GmbH (Germany)
Oskar F. von der Lühe, Kiepenheuer-Institut für Sonnenphysik (Germany)

Published in SPIE Proceedings Vol. 9908:
Ground-based and Airborne Instrumentation for Astronomy VI
Christopher J. Evans; Luc Simard; Hideki Takami, Editor(s)

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