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Proceedings Paper

Laboratory experiments on the 8-octant phase-mask coronagraph
Author(s): Naoshi Murakami; Ryosuke Uemura; Naoshi Baba; Hiroshi Shibuya; Jun Nishikawa; Lyu Abe; Motohide Tamura; Nobuyuki Hashimoto
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Paper Abstract

A four-quadrant phase-mask (FQPM) coronagraph can suppress perfectly stellar light when a star can be regarded as a point-like source. However, the FQPM coronagraph is highly sensitive to partially resolved stars, and shows second-order sensitivity to tip-tilt error leakage. Higher-order sensitivity is required for extremely high-contrast imaging of nearby stars. We propose an eight-octant phase-mask (EOPM) for achieving fourth-order sensitivity to tip-tilt errors. We manufactured the phase-mask utilizing a nematic liquid crystal (LC) device, which is composed of eight segments. A phase retardation of the LC can be adjustable by an applied voltage to the device. The LC phase-mask can be switched between FQPM-mode and EOPM-mode by applying appropriate voltages to the segments. We carry out experiments on the phase-mask coronagraph with various tip-tilt errors. The experimental results show the higher-order behavior of the EOPM compared to the FQPM. We present a current status of the laboratory experiments on the EOPM coronagraph, and also show coronagraphic performance of the EOPM derived from numerical simulations.

Paper Details

Date Published: 12 July 2008
PDF: 8 pages
Proc. SPIE 7010, Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter, 70101J (12 July 2008); doi: 10.1117/12.788145
Show Author Affiliations
Naoshi Murakami, National Astronomical Observatory of Japan (Japan)
Ryosuke Uemura, Hokkaido Univ. (Japan)
Naoshi Baba, Hokkaido Univ. (Japan)
Hiroshi Shibuya, Hokkaido Univ. (Japan)
Jun Nishikawa, National Astronomical Observatory of Japan (Japan)
Lyu Abe, National Astronomical Observatory of Japan (Japan)
Motohide Tamura, National Astronomical Observatory of Japan (Japan)
Nobuyuki Hashimoto, Citizen Technology Ctr. Co. (Japan)

Published in SPIE Proceedings Vol. 7010:
Space Telescopes and Instrumentation 2008: Optical, Infrared, and Millimeter
Jacobus M. Oschmann Jr.; Mattheus W. M. de Graauw; Howard A. MacEwen, Editor(s)

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