Date of Award

12-1997

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Electrical and Computer Engineering

First Advisor

Byron M. Welsh, PhD

Abstract

A new atmospheric turbulence screen generator is developed for use in performance calculations of adaptive optics systems valid over a wide range of atmospheric turbulence parameters. The screen generator accounts for diffraction effects caused by weak turbulence and incorporates the phase, amplitude, and cross statistics of the perturbed optical field. The wavefront's phase and amplitude perturbations are taken from the correlation functions developed by Lee and Harp and the cross correlation of the phase and amplitude derived in this thesis. The screen generator uses a modal representation to perform a Fourier series expansion of the wavefront phase and amplitude over a square area. The phase, amplitude, and cross power spectral densities determined from the correlation functions are used in the Fourier series expansion. The mean square value and the structure functions of the phase, amplitude, and cross terms are calculated to within 1% of the theoretical values in a Monte Carlo experiment using the screen generator. Monte Carlo experiments performed using the screen generator showed the amplitude perturbations can significantly reduce the accuracy of full-aperture tilt estimation using image centroid motion. However, since the amplitude perturbations affect the image centroid, the tilt estimate using the combined amplitude and phase screen allows for a higher Strehl ratio than using only the phase to estimate the correction.

AFIT Designator

AFIT-GE-ENG-97D-11

DTIC Accession Number

ADA336418

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