Sparse-array phasing algorithm based on recursive estimation of fringe contrast

Karl N. Schrader; Robert H. Fetner; Mark J. Balas; Richard Scott Erwin

doi:10.1117/12.460570

18 December 2002 Sparse-array phasing algorithm based on recursive estimation of fringe contrast

Karl N. Schrader, Robert H. Fetner, Mark J. Balas, Richard Scott Erwin

Proceedings Volume 4849, Highly Innovative Space Telescope Concepts; (2002) https://doi.org/10.1117/12.460570
Event: Astronomical Telescopes and Instrumentation, 2002, Waikoloa, Hawai'i, United States

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.

Citation Download Citation

Karl N. Schrader, Robert H. Fetner, Mark J. Balas, and Richard Scott Erwin "Sparse-array phasing algorithm based on recursive estimation of fringe contrast", Proc. SPIE 4849, Highly Innovative Space Telescope Concepts, (18 December 2002); https://doi.org/10.1117/12.460570

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