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Full-Text Articles in Physics
Evaluation Of Performance Of A Maximum Likelihood Estimator For Tracking Purposes In The Presence Of Speckle Noise, Adrian Brett Monz
Evaluation Of Performance Of A Maximum Likelihood Estimator For Tracking Purposes In The Presence Of Speckle Noise, Adrian Brett Monz
Theses and Dissertations
In many cases, optical tracking systems do not have cooperative beacons avail- able. This is particularly true for the case involving tracking a laser illuminated target such as a missile seeker head, where the object of interest is an extended source. Furthermore the extended source is often observed in the presence of noise such as shot and speckle noise as well as atmospheric turbulence which further degrades the signal. This research effort presents the evaluation of an existing algorithm based on the maximum-likelihood technique for tilt estimation in the presence of extended sources and speckle noise, with particular application to …
Maximum Likelihood Estimation Of Wave Front Slopes Using A Hartmann-Type Sensor, Scott A. Sallberg
Maximum Likelihood Estimation Of Wave Front Slopes Using A Hartmann-Type Sensor, Scott A. Sallberg
Theses and Dissertations
Current methods for estimating the wave front slope at the pupil of a telescope equipped with a Hartmann-type wave front sensor (H-WFS) are based on a simple centroid calculation of the intensity distributions (spots) recorded in each subaperture of the H-WFS. The centroid method does not include any knowledge concerning correlation properties of the slopes over the subapertures or the amount of light collected by the telescope and diverted to the H-WFS for wave front reconstruction purposes. This thesis devises a maximum likelihood (ML) estimation of the spot centroids by incorporating statistical knowledge of the spot shifts. The light level …
Flow Visualization Of A Turbulent Shear Flow Using An Optical Wavefront Sensor, Daniel W. Jewell
Flow Visualization Of A Turbulent Shear Flow Using An Optical Wavefront Sensor, Daniel W. Jewell
Theses and Dissertations
The research reported here investigated the use of a shearing interferometer (SI) wavefront sensor to determine the effects of shear-layer turbulence on an optical wavefront. A collimated helium-neon laser beam was propagated through a plane shear-layer produced by mixing helium and nitrogen at different velocities. Since the gases have different indices of refraction, the optical wavefront was distorted by different amounts by each gas. The SI measured the wavefront slope across the sampled area of the wavefront. The shear-layer was viewed from two orthogonal directions. This document contains shadow graphs, interference patterns imaged by each of the SI's six cameras, …
Remote Sensing Of Turbulence And Transverse Atmospheric Wind Profiles Using Optical Reference Sources, Steven C. Koeffler
Remote Sensing Of Turbulence And Transverse Atmospheric Wind Profiles Using Optical Reference Sources, Steven C. Koeffler
Theses and Dissertations
This thesis examines a remote sensing technique for measuring the atmospheric structure constant and the transverse atmospheric wind velocity as a function of altitude by performing temporal and spatial correlations of band pass filtered wave front slope sensor measurements. Two point sources are used to illuminate two pairs-of cc>-located wave front slope sensors. The sources and sensors are arranged to give rise to crossed optical paths. For each pair of wave front slope sensors, the output of the larger sensor is subtracted from the output of the smaller sensor. This band pass filters the smaller sensor's output. The filtered …