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6 September 2011 Arago spot and turbulent distortions
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Arago spot is a small bright spot that is formed in the shadow of the circular obscurer. The coherent nature of the Arago spot makes it susceptible to the turbulence-induced distortions of the incident wave. We describe the formation of the Arago spot for the using the narrow-angle Fresnel optics diffraction, and develop a simple equation for the field and irradiance distributions in the center of the shadow area behind an obscurer. We calculate the average irradiance distribution, random wander variance and scintillation index of the Arago spot using the Markov approximation for optical propagation in turbulence. Using the same technique we extend the single obscurer results to the Arago spot observed in the image of the annular aperture typical for the Cassegrain-type telescopes. The statistics of the Arago spot distortions can be used for the estimation of the turbulence strength on the propagation path. We suggest an optical design of a build-in sensor that allows monitoring of the turbulent conditions without interfering with the principal function of the optical system.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Mikhail Charnotskii "Arago spot and turbulent distortions", Proc. SPIE 8161, Atmospheric Optics IV: Turbulence and Propagation, 816103 (6 September 2011);

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