Short-exposure passive imaging through path-varying convective boundary layer turbulence

David H. Tofsted

doi:10.1117/12.920840

18 May 2012 Short-exposure passive imaging through path-varying convective boundary layer turbulence

David H. Tofsted

Proceedings Volume 8355, Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXIII; 83550J (2012) https://doi.org/10.1117/12.920840
Event: SPIE Defense, Security, and Sensing, 2012, Baltimore, Maryland, United States

Abstract

As is well known, the turbulent coherence diameter is evaluated via an integral over path varying turbulence. However, a recent analysis also suggests a system aperture size effect that interacts with the coherence diameter effect. This effect, due to the phase structure function, produces an altered behavior on the short-exposure atmospheric modulation transfer function (MTF). This behavior can be modeled as multiplicative adjustments to two dimensionless imaging scenario parameters. To illustrate these effects, path dependent turbulence effects are introduced through the context of a daytime convective boundary layer scenario featuring turbulence strength that varies as a function of height to the minus-four-thirds power. Two path geometry cases are studied: slant path propagation above flat terrain, where the object viewed and observer are at varying heights, and propagation between an object viewed and an observer at equal heights above the terrain situated on opposite sides of a valley. Results for both cases show the newly proposed atmospheric MTF is unaltered in form, but that path dependent scaling laws apply to the two governing dimensionless parameters. Scaling relations are plotted for each case studied, and the integral relations developed can be easily computed for further specific cases.

Citation Download Citation

David H. Tofsted "Short-exposure passive imaging through path-varying convective boundary layer turbulence", Proc. SPIE 8355, Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XXIII, 83550J (18 May 2012); https://doi.org/10.1117/12.920840

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