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Full-Text Articles in Physics
High Energy Laser Pointing Through Extended Turbulence, Jason A. Tellez
High Energy Laser Pointing Through Extended Turbulence, Jason A. Tellez
Theses and Dissertations
The airborne laser (ABL) uses adaptive optics to compensate the atmospheric turbulence between the ABL and the target. The primary purpose of this compensation is to increase the energy density of the energy laser at the target. However, the specifics of the engagement scenario require the tracking point of reference and the adaptive optics point of reference to be located at different points on the target. This research considers the effects of tracking a target in one direction while compensating for atmospheric turbulence in a different directions. The target references used are a point source and a rectangle, while a …
Characterization Of Atmospheric Turbulence Over Long Horizontal Paths Using Optical Slope Measurements, Eric E. Silbaugh
Characterization Of Atmospheric Turbulence Over Long Horizontal Paths Using Optical Slope Measurements, Eric E. Silbaugh
Theses and Dissertations
Atmospheric turbulence has long been recognized as one of the fundamental factors affecting optical systems operating through the atmosphere. Turbulence over vertical paths has been well characterized, both theoretically and experimentally. Much less is known about turbulence over long, horizontal paths. Perturbations of the wave front phase can be measured using a Hartmann wave front sensor (H-WFS). Theoretical expressions for the tilt removed structure function of the H-WFS slope measurements were derived and evaluated using quadrature. These slope structure functions are functions of the phase structure function. The Kolmogorov turbulence model was assumed. Simulated H-WFS slope measurements were generated using …
Laser Beam Propagation In Non-Kolmogorov Atmospheric Turbulence, Bruce E. Stribling
Laser Beam Propagation In Non-Kolmogorov Atmospheric Turbulence, Bruce E. Stribling
Theses and Dissertations
Several observations of atmospheric turbulence statistics have been reported which do not obey Kolmogorov's power spectral density model. These observations have prompted the study of optical propagation through turbulence described by non-classical power spectra. This thesis presents an analysis of optical propagation through turbulence which causes index of refraction fluctuations to have spatial power spectra that obey arbitrary power laws. The spherical and plane wave structure functions are derived using Mellin transform techniques and are applied to the field mutual coherence function (MCF) using the extended Huygens-Fresnel principle. The MCF is used to compute the Strehl ratio of a focused, …
Performance Impacts For Actuator Misalignments And Failures In Large- Aperture Adaptive-Optic Telescopes, Timothy D. Hogan
Performance Impacts For Actuator Misalignments And Failures In Large- Aperture Adaptive-Optic Telescopes, Timothy D. Hogan
Theses and Dissertations
Large-aperture telescopes require adaptive optics in order to compensate for atmospheric turbulence which would otherwise negate the resolution advantages of using large apertures. This investigation analyzes the impacts of misalignments and failures, in the deformable mirror actuators, upon the performance of such systems. A numerical simulation of a standard adaptive optics system is used to generate characteristic optical transfer function OTF and signal-to-noise ratio SNR performance metrics. The performance impacts of the misalignments are shown to be dependent upon the Fried parameter effective telescope diameter, the source object brightness, and the control system time delay. The degree of performance degradation …
Characterization Of Laboratory Generated Turbulence By Optical Phase Measurements, Eric P. Magee
Characterization Of Laboratory Generated Turbulence By Optical Phase Measurements, Eric P. Magee
Theses and Dissertations
The resolution achieved by an optical imaging system in the presence of the random effects of the atmosphere is severely degraded from the theoretical diffraction limit. Techniques exist for recovering near diffraction limited performance of an imaging system in the presence of atmospheric turbulence. As opposed to laboratory testing, testing image enhancement techniques in the Earth's atmosphere imposes many limitations. Unfavorable weather conditions could result in the loss of time and money invested in conducting the experiments. With a properly characterized turbulence generator, with statistics that match those of the atmosphere, experimental testing of image enhancement techniques can be conducted …