Generating artificial reference images for open loop correlation wavefront sensors

doi:10.1093/mnras/sty1362

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Generating artificial reference images for open loop correlation wavefront sensors

2018-05-25

Matthew J. Townson *

Gordon D. Love

DOI：10.1093/mnras/sty1362

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Abstract

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Shack-Hartmann wavefront sensors for both solar and laser guide star adaptive optics (with elongated spots) need to observe extended objects. Correlation techniques have been successfully employed to measure the wavefront gradient in solar adaptive optics systems and have been proposed for laser guide star systems. In this paper, we describe a method for synthesizing reference images for correlation Shack-Hartmann wavefront sensors with a larger field of view than individual sub-apertures. We then show how these supersized reference images can increase the performance of correlation wavefront sensors in regimes where large relative shifts are induced between sub-apertures, such as those observed in open-loop wavefront sensors. The technique we describe requires no external knowledge outside of the wavefront-sensor images, making it available as an entirely 'software' upgrade to an existing adaptive optics system. For solar adaptive optics we show the supersized reference images extend the magnitude of shifts, which can be accurately measured from 12 per cent to 50 per cent of the field of view of a sub-aperture and in laser guide star wavefront sensors the magnitude of centroids that can be accurately measured is increased from 12 per cent to 25 per cent of the total field of view of the sub-aperture.

Keywords:

atmospheric effects

instrumentation: adaptive optics

Sun: granulation

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