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1998

Theses/Dissertations

Theses and Dissertations

Articles 1 - 6 of 6

Full-Text Articles in Physics

Collisional Effects In The Absorption Spectra Of The Oxygen A Band And Nitric Oxide Fundamental Band, Robert S. Pope Dec 1998

Collisional Effects In The Absorption Spectra Of The Oxygen A Band And Nitric Oxide Fundamental Band, Robert S. Pope

Theses and Dissertations

Fourier transform spectroscopy was used to measure pressure broadening coefficients in the absorption spectra of both the oxygen A band and the nitric oxide fundamental band. Oxygen spectra were recorded with O2, N2, CO, CO2, SF6 and noble gas collision partners, while nitric oxide spectra were recorded using noble gas collision partners. Pressure broadening coefficients were determined in the P and R branches for every resolved line for each of the fifteen collision pairs studied. In addition, broadening coefficients and qualitative evidence of line coupling were found for the Q branch of NO …

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Optimal Atmospheric Compensation For Anisoplanatism In Adaptive-Optical Systems, Matthew R. Whiteley Sep 1998

Optimal Atmospheric Compensation For Anisoplanatism In Adaptive-Optical Systems, Matthew R. Whiteley

Theses and Dissertations

Anisoplanatism in adaptive optics (AO) systems is a performance-degrading effect that arises whenever light from the wave-front sensor beacon and light from the object of interest sample different volumes of optical turbulence. This effect occurs if there is either a spatial separation between the object and the beacon, or a spatial separation between the wave-front sensor and phase-compensation aperture, or if both types of separation are present in the AO system. Anisoplanatism results in an increased value of the aperture-averaged residual phase variance after AO compensation, which causes an exponential decrease in system performance. This dissertation offers a theoretical framework …

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Regression Analysis Of Radar Measured Optical Turbulence With Synoptic Scale Meteorological Variables, Diana L. Hajek Mar 1998

Regression Analysis Of Radar Measured Optical Turbulence With Synoptic Scale Meteorological Variables, Diana L. Hajek

Theses and Dissertations

A key issue to the USAF's Airborne Laser (ABL) program is the ability to accurately predict the level of optical turbulence that the ABL will encounter at its flight levels. The optical turbulence must be characterized so that the range and range variation of the ABL can be determined. Gravity wave spectra resulting from frontal or jet stream passage are presumed to cause layers of optical turbulence; however, exact relationships between optical turbulence and synoptic scale meteorological phenomena are unclear. This study assesses the statistical relationship between optical turbulence and synoptic scale variables through multiple linear regression. The optical turbulence …

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Linear Reconstruction Of Non-Stationary Image Ensembles Incorporating Blur And Noise Models, Stephen D. Ford Mar 1998

Linear Reconstruction Of Non-Stationary Image Ensembles Incorporating Blur And Noise Models, Stephen D. Ford

Theses and Dissertations

Two new linear reconstruction techniques are developed to improve the resolution of images collected by ground-based telescopes imaging through atmospheric turbulence. The classical approach involves the application of constrained least squares (CLS) to the deconvolution from wavefront sensing (DWFS) technique. The new algorithm incorporates blur and noise models to select the appropriate regularization constant automatically. In all cases examined, the Newton-Raphson minimization converged to a solution in less than 10 iterations. The non-iterative Bayesian approach involves the development of a new vector Wiener filter which is optimal with respect to mean square error (MSE) for a non-stationary object class degraded …

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Optical Physics Of Microcavity Surface Emitting Lasers, Michael J. Noble Mar 1998

Optical Physics Of Microcavity Surface Emitting Lasers, Michael J. Noble

Theses and Dissertations

This dissertation consists of an in-depth theoretical analysis of the optical impact of transverse index confinement on the lasing modes of microcavity surface emitting lasers. Two different variational techniques were employed to calculate the relevant optical laser parameters: (1) modal resonance, field profile, (2) confinement factor, and (3) threshold gain. Through a semianalytic field analysis, two new confinement related effects were discovered: (1) a polarization dependent change in mirror reflectance with aperture radius, and (2) a mode dependent blueshift. Through a numerical field analysis, the physical mechanisms governing diffraction were ascertained. These are: (1) the transverse confinement of the optical …

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Performance Of Imaging Laser Radar In Rain And Fog, Kathleen M. Campbell Mar 1998

Performance Of Imaging Laser Radar In Rain And Fog, Kathleen M. Campbell

Theses and Dissertations

The Air Force is currently developing imaging laser radar systems (ladar) for use on precision guided munitions and other imaging systems. Scientists at Eglin Air Force Base, in conjunction with Wright Laboratories, are testing a 1.06-um wavelength ladar system and need to understand the weather effects on the ladar images. As the laser beam propagates through the atmosphere, fog droplets and raindrops can cause image degradation, and these image degradations are manifested as either dropouts or false returns. An analysis of the dropouts and false returns helped to quantify the performance of the system in adverse weather conditions. Statistical analysis …

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