Modeling Optical Turbulence Effects on Centrally Obscured Aperture Systems

Report No. ARL-TR-6273
Authors: David H. Tofsted
Date/Pages: December 2012; 34 pages
Abstract: Recent studies of the effect of optical turbulence on short-exposure imaging focused on circular aperture receivers. However, a critical class of optical systems - telescopic optics containing a central, axially symmetric secondary mirror obscuration - has been omitted. The current study addresses this sub-class, considering two elements needed to describe short-exposure turbulence effects: angle-of-arrival variance and tilt-phase correlation. These effects are modeled relative to a dimensionless variable, C = D1/D2, the ratio of D1, the diameter of the inner obscuring disk, and D2, the outer diameter of the full aperture. Expressions are developed to model these effects relative to C, along with diffraction effects modeled using the dimensionless Q = D2/P, where P is the Fresnel zone, and turbulence strength modeled using the dimensionless X = D2/ro, using ro, the turbulent coherence diameter. A follow-on report will fully describe the modeled tilt-phase effect.
Distribution: Approved for public release
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Last Update / Reviewed: December 1, 2012