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Proceedings Paper

Optical design of MOIRCS
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Paper Abstract

We describe an optical design process and image performance evaluations for Multi-Object near-InfraRed Camera and Spectrograph (MOIRCS). MOIRCS is a near-infrared imager and multi-object spectrograph under construction for the Subaru Telescope. MOIRCS provides direct imaging of 4' x 7' F.O.V. with a pixel scale of 0.12". MOIRCS also provides low-resolution multi-object spectroscopy with grisms and cooled multi-slit masks on the Cassegrain focal plane. CaF2, BaF2, ZnSe, and Fused Silica are used as the lens materials. They have high transmission in the near-infrared wavelength. During the design process, we find that a triplet with an achromatic doublet and a ZnSe singlet shows good performance for chromatic aberration. Therefore, we design our optics on the basis of the triplet with ZnSe. The designed optics shows good performances. Ensquared energy within 2 pixel square is more than 85% over the entire wavelength range and F.O.V. We do not need refocusing with the change of observed wavelengths because chromatic aberration is as small as 100 μm by the triplet with ZnSe over the entire wavelength range from 0.85 to 2.5 μm. Lateral chromatic aberration of 15 μm is less than 1 pixel size. Detailed tolerance analysis is done with possible manufacturing and aligning errors considered. The result shows that designed performances will be kept with a probability of 80% with reasonable tolerances. Ghost analysis is also done over entire F.O.V. and we find a ghost image of 13 magnitude fainter than original image that is not significant for our purpose. Therefore, we conclude that we can obtain enough performances with designed optics.

Paper Details

Date Published: 7 March 2003
PDF: 12 pages
Proc. SPIE 4841, Instrument Design and Performance for Optical/Infrared Ground-based Telescopes, (7 March 2003); doi: 10.1117/12.461446
Show Author Affiliations
Ryuji Suzuki, Astronomical Institute/Tohoku Univ. (Japan)
Subaru Telescope/NAOJ (United States)
Chihiro Tokoku, Subaru Telescope/NAOJ (United States)
Astronomical Institute/Tohoku Univ. (Japan)
Takashi Ichikawa, Astronomical Institute/Tohoku Univ. (Japan)
Tetsuo Nishimura, Subaru Telescope/NAOJ (United States)

Published in SPIE Proceedings Vol. 4841:
Instrument Design and Performance for Optical/Infrared Ground-based Telescopes
Masanori Iye; Alan F. M. Moorwood, Editor(s)

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