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Proceedings Paper

Design of the optics for an imaging classic mount multi-etalon spectro-polarimeter for the next generation of ground-based solar telescopes
Author(s): V. Greco; F. Cavallini
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Paper Abstract

In designing the optics of an imaging classic mount multi-étalon spectro-polarimeter as a post-focus instrument for the next generation of ground-based solar telescopes (Advanced Technology Solar Telescope, European Solar Telescope), many constraints must be considered. The large entrance pupil diameter of the telescope (4 m), the demanded large field of view (≥ 90 arcsec), high spectral resolving power (≥ 200000), and limited field-dependent blue-shift of the instrumental profile (≤ 3 FWHM) require Fabry-Pérot interferometers of large diameter (≥ 200 mm), lighted by highly collimated beams. This implies large optical elements and long optical paths. Moreover, to use interference pre-filters, placed between the interferometers to reduce the inter-reflections in axial-mount, with a relatively small diameter (≤ 70 mm), a "pupil adapter" should be included, with a further increase of the optical path length. Although a multi-étalon spectro-polarimeter works in quasi-monochromatic light, the Fraunhofer lines of interest cover a wide range of wavelengths (850 nm - 1650 nm), demanding a good chromatic aberration control. Finally, a low instrumental polarization (≤ 0.5 %) is required to allow a high polarimetric precision. In this paper a diffraction limited optical solution is described, fulfilling all the above requirements in a relative small volume.

Paper Details

Date Published: 30 September 2011
PDF: 10 pages
Proc. SPIE 8172, Optical Complex Systems: OCS11, 817219 (30 September 2011); doi: 10.1117/12.896824
Show Author Affiliations
V. Greco, Istituto Nazionale di Ottica, CNR (Italy)
F. Cavallini, INAF - Osservatorio Astrofisico di Arcetri (Italy)

Published in SPIE Proceedings Vol. 8172:
Optical Complex Systems: OCS11
Gérard Berginc, Editor(s)

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