Abstract
Propagation of uniform and Gaussian profiled beams without and with images through random phase turbulence is investigated in the Fraunhofer regimes. To set the tone for the subsequent image transmission, beam propagation through conventional planar apertures is first examined using a split-step approach. The numerical approach is then extended to examine the effects of isoplanatic propagation through turbulence on lens-based imaging of a 2D transparency, as well as time signals derived via PCM-type digitization of the image propagated along arbitrary turbulence regimes. Simulation results based on the split-step method whereby the phase screen is placed at specific (including multiple) locations along the propagation path, and the Fresnel-Kirchhoff diffraction integral is invoked, are presented. The modified von Karman spectrum (MVKS) power spectrum model is used to describe a random phase distribution over narrow and extended turbulent regions. Simulation results are limited to the transverse-plane intensity of the diffracted field in the Fraunhofer regimes and the cross-correlation between the received profiles (beam and image) without and with turbulence. We focus specifically on the process of modeling turbulent effects in imagery by developing a workable space-time phase model for random phase changes in the transverse field profile based on von Karman turbulence. Cross-correlation as a performance measure is preferred in this work (instead of the bit error rate or BER approach) because it may be applied readily to both the case of lens-based imaging (in analog fashion) and the case of PCM-type digitization.
Published Version
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