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Proceedings Paper

Performance analysis of a Hartmann wavefront sensor used for sensing atmospheric turbulence statistics
Author(s): Byron M. Welsh; Toby D. Reeves; Michael C. Roggemann
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Paper Abstract

The ability to measure atmospheric turbulence characteristics such as Fried's coherence diameter, the outer scale of turbulence, and the turbulence power law are critical for the optimized operation of adaptive optical telescopes. One approach for sensing these turbulence parameters is to use a Hartmann wavefront sensor (H-WFS) array to measure the wavefront slope structure function (SSF) . The SSF is defined as the second moment of the wavefront slope difference between any two subapertures separated in time and/or space. Accurate knowledge of the SSF allows turbulence parameters to be estimated. The H-WFS slope measurements, composed of a true slope signal corrupted by noise, are used to estimate the SSF by computing a mean square difference of slope signals from different subapertures. This computation is typically performed over a large number of H-WFS measurement frames. The quality of the SSF estimate is quantified by the signal-to-noise ratio (SNR) of the estimator. The quality of the SSF estimate then can in turn be related to the quality of the atmospheric turbulence parameter estimates. This research develops a theoretical SNR expression for the SSF estimator. This SNR is a function of H-WFS geometry, the number of temporal measurement frames, the outer scale of turbulence, the turbulence spectrum power law, and the temporal properties of the turbulence. Results are presented for various H-WFS configurations and atmospheric turbulence properties.

Paper Details

Date Published: 23 September 1997
PDF: 12 pages
Proc. SPIE 3125, Propagation and Imaging through the Atmosphere, (23 September 1997); doi: 10.1117/12.279027
Show Author Affiliations
Byron M. Welsh, Air Force Institute of Technology (United States)
Toby D. Reeves, Air Force Institute of Technology (United States)
Michael C. Roggemann, Air Force Institute of Technology (United States)

Published in SPIE Proceedings Vol. 3125:
Propagation and Imaging through the Atmosphere
Luc R. Bissonnette; Christopher Dainty, Editor(s)

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