Signal Modeling of Turbulence-distorted Imagery

Report No. ARL-RP-0275
Authors: S. Susan Young, Ronald G. Driggers, Keith Krapels, Richard L. Espinola, Joseph P. Reynolds, and Jae Cha
Date/Pages: September 2009; 18 pages
Abstract: Understanding turbulence effects on wave propagation and imaging systems has been an active research area for more than 50 years. Conventional atmospheric optics methods use statistical models to analyze image degradation effects that are caused by turbulence. In this paper, we intend to understand atmospheric turbulence effects using a deterministic signal processing and imaging theory point of view and modeling. The model simulates the formed imagery by a lens by tracing the optical rays from the target through a band of turbulence. We examine the nature of the turbulence-degraded image, and identify its characteristics as the parameters of the band of turbulence, e.g., its width, angle, and index of refraction, are varied. Image degradation effects due to turbulence, such as image blurring and image dancing, are revealed by this signal modeling. We show that in fact these phenomena can be related not only to phase errors in the frequency domain of the image but also a 2D modulation effect in the image spectrum. Results with simulated and realistic data are provided.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2009