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Proceedings Paper

Sparse-array phasing algorithm based on recursive estimation of fringe contrast
Author(s): Karl N. Schrader; Robert H. Fetner; Mark J. Balas; Richard Scott Erwin
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Paper Abstract

This paper describes a novel real-time algorithm for optically phasing sub-apertures of a sparse-array telescope system based on recursive estimation of the sub-aperture placement that maximizes a fringe-contrast metric. The sub-apertures are phased in pairs using broad spectral band flood-illumination of the sparse-array, while blocking reflections from all but two sub-apertures. The resulting Young’s geometry at the pupil produces an interference pattern that is characterized to determine spatial-frequency filters that are utilized to generate a contrast metric from the fringe patterns. This contrast metric is shown to generate a near-Gaussian variation as a function of optical path-length difference (OPD), with the maximum contrast occurring at zero OPD. The functional relationship between fringe contrast and sub-aperture position based on a common-path, laser-based relative-piston measurement system is developed into an estimator for maximization of fringe contrast (and therefore phasing of sub-apertures). The recursive algorithm produces real-time estimates of the zero OPD value of the relative position that improves as additional data is acquired.

Paper Details

Date Published: 18 December 2002
PDF: 12 pages
Proc. SPIE 4849, Highly Innovative Space Telescope Concepts, (18 December 2002); doi: 10.1117/12.460570
Show Author Affiliations
Karl N. Schrader, Boeing-SVS, Inc. (United States)
Robert H. Fetner, Boeing-SVS, Inc. (United States)
Mark J. Balas, Univ. of Colorado/Boulder (United States)
Richard Scott Erwin, Air Force Research Lab. (United States)

Published in SPIE Proceedings Vol. 4849:
Highly Innovative Space Telescope Concepts
Howard A. MacEwen, Editor(s)

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