Date of Award

3-2000

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Electrical and Computer Engineering

First Advisor

Steven C. Gustafson, PhD

Abstract

Two deformable mirrors (DMs) with finite conjugate ranges are investigated for compensating amplitude and phase distortions due to laser propagation through turbulent atmospheres. Simulations are performed based on Adaptive Optics (AO) for an Airborne Laser-type scenario. The Strehl ratio, the number of branch points in DM controls, and the number of iterations to convergence are used as figures of merit to evaluate performance of the Sequential Generalized Projection Algorithm that generates mirror commands. The results are ensemble averages over 32 realizations of the scintillated test fields for each value of the Rytov parameter within the test scenario. The Gaussian beam shape that optimizes the Strehl ratio is determined. The least squares two-DM Strehl, phase-only Strehl, least squares phase-only Strehl, and uncompensated Strehl are also determined for comparison. Finally, for the Strehl ratio versus Rytov parameter analysis the Strehl is also calculated beyond the telescope by propagating the pre-compensated laser wavefront back through the phase screens of the modeled atmosphere. Results from the more critical beyond-telescope Strehl analysis indicate that a two-DM AO system provides an increase in performance of approximately 0.1 in Strehl as compared to the phase-only system for the most severe simulated turbulence (theoretical log-amlitude variance of 1.0)

AFIT Designator

AFIT-GEO-ENG-00M-01

DTIC Accession Number

ADA380597

Comments

The author's Vita page is omitted.

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