Theses and Dissertations at Montana State University (MSU)
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Item Characterization of a division-of-focal-plane polarization imager(Montana State University - Bozeman, College of Engineering, 2020) Syed, Musaddeque Anwar Al Abedin; Chairperson, Graduate Committee: Joseph A. ShawPolarization is a fundamental property of light that can be detected with polarization-sensitive instruments. Imaging polarimetry has an immensely wide range of applications, and while much has been accomplished in recent years, there is still a need for sensor systems with improved accuracy, precision, and stability. This paper presents the optical characterization of a commercial division-of-focal plane (DoFP) polarization imager, in an effort to evaluate its performance as a promising instrument in the application of ground-based cloud thermodynamic phase detection. Radiometric characterization values were well within the acceptable region, but the polarimetric contrast was in the range of 20-30, much lower than expected, which may be a result of the broadband measurements being impaired by poor polarizer performance at the blue end of the spectrum. Later, a narrowband polarimetric measurement at 532 + or - 5 nm produced a much enhanced result, with polarimetric contrast in the higher 300s, making the imager a viable option for many remote sensing applications. Also, all-sky imaging of clear daytime sky and its analysis of degree of linear polarization (DoLP) showed encouraging result.Item Combining spectral and polarimetric methods to classify cloud thermodynamic phase(Montana State University - Bozeman, College of Engineering, 2019) Tauc, Martin Jan; Chairperson, Graduate Committee: Joseph A. Shaw; David W. Riesland, Laura M. Eshelman, Wataru Nakagawa and Joseph A. Shaw were co-authors of the article, 'Radiance ratios for CTP discrimination' submitted to the journal 'Journal of applied remote sensing' which is contained within this thesis.; Wataru Nakagawa and Joseph A. Shaw were co-authors of the article, 'The SWIR three-channel polarimeter for cloud thermodynamic phase detection' in the journal 'Optical engineering' which is contained within this thesis.Cloud thermodynamic phase--whether a cloud is composed of spherical water droplets or polyhedral ice crystals--is an important parameter for optical communication with space-based instruments, remote sensing of the atmosphere, and, perhaps most importantly, understanding weather and climate. Although some methods exist to detect the phase of clouds, there is still a need for passive remote sensing of cloud thermodynamic phase due to its low-cost, scalability, and ease of use. Two methods for cloud thermodynamic phase classification employ spectral radiance ratios in the short-wave infrared, and the S 1 Stokes parameter, a polarimetric quantity. In this dissertation, the combination of the two methods is realized in an instrument called the short-wave infrared three-channel polarimeter. The coalescence of radiance ratios in the short-wave infrared and polarization channels oriented parallel and perpendicular to the scattering plane provides better classification of cloud phase than either method independently. Despite the improvement, the low-cost system suffered from hardware and software limitations, which caused an increase in noise and polarimetric artifacts. These errors are analyzed and a subset of low-noise data shows even better classification ability. All together, the results attained from the deployment of the polarimeter in early 2019 showed promise that the combination of the two methods is an improvement over past techniques.Item Real-time software-defined free-space optical communication system(Montana State University - Bozeman, College of Engineering, 2019) Sultana, Nishat; Chairperson, Graduate Committee: Ioannis RoudasNext-generation software-defined free-space optical (FSO) communication systems may substitute many conventional radio communication systems. The conventional single-purpose dedicated hardware resources in the telecommunication systems have significant limitations since they provide a single communication service using a specific standard at a time. It is also expensive to upgrade to the emerging new standards such as 5G New Radio (5GNR) by substituting the existing hardware resources. Reprogrammable FPGA-based Software Defined Radio (SDR) technology is deployed as a feasible solution to this problem since they can be reconfigured simultaneously realizing the user requirements. When integrated with the FSO system it opens a plethora of opportunities since the Visible Light Frequency Spectrum is barely occupied by the existing technologies and can be designed cost-effectively for the vast bandwidth it has to offer. In this thesis work, we implemented a real-time FSO communication system using an SDR platform. A fully-functional optical communication link has been accomplished using the Universal Software Radio Peripheral (USRP), MATLAB-Simulink communication toolbox and hardware support package, Laser diode, and a Photodetector. We demonstrate successful transmission and reception of baseband signals with very low bit error rate. Visually identical transmitted and received signals also validate the accuracy of the simulation results when compared to those obtained from the real-time FSO-SDR communication system.Item Weed and crop discrimination with hyperspectral imaging and machine learning(Montana State University - Bozeman, College of Engineering, 2019) Scherrer, Bryan Joseph; Chairperson, Graduate Committee: Joseph A. ShawHerbicide-resistant weed biotypes are spreading across crop fields nationally and internationally and mapping them with traditional crop science methods - cloning plants and testing their resistance levels in a lab - are costly and time consuming. A segment of the field of precision agriculture is being developed to accurately and quickly map the location of herbicide-resistant and herbicide-susceptible weeds using advanced optics and computer algorithms. In our study, we collected hundreds of thousands of spectra of herbicide-resistant and herbicide-susceptible biotypes of the weeds kochia, mare's tail and lamb's quarter and of crops including barley, corn, dry pea, garbanzo, lentils, pinto bean, safflower, sugar beet at the Southern Agricultural Research Center in Huntley, Montana using a hyperspectral imager. Plants were imaged in a controlled greenhouse setting as well as in crop fields using ground-based and drone-based imaging platforms. The spectra were differentiated from one another using a feedforward neural network machine learning algorithm. Classification accuracies depended on what plants were imaged, the age of the plants and lighting conditions of the experiment. They ranged from 77% to 99% for spectra acquired on our ground-based imaging platform and from 25% to 79% on our drone- based platform.Item A study of atmospheric polarization in unique scattering conditions at twilight, during a solar eclipse, and for cloud phase retrievals using all-sky polarization imaging(Montana State University - Bozeman, College of Engineering, 2018) Eschelman, Laura Marie; Chairperson, Graduate Committee: Joseph A. ShawPolarization is a fundamental property of light that can be detected with polarization-sensitive instruments for many remote sensing applications. To quantitatively interpret the remote sensing data, an understanding how naturally occurring polarization depends on wavelength and environmental parameters is needed. The most obvious source of naturally occurring polarization is atmospheric scattering. For a clear-sky environment, Rayleigh scattering dominates, resulting from scattering by atmospheric gas molecules that are much smaller than the optical wavelength, and a distinct all-sky polarization pattern exists. A band of maximum degree of linear polarization can be observed 90? from the sun with polarization vectors orientated perpendicular to the scattering plane (i.e. the plane containing the incident and scattered light). However, aerosols, clouds, and underlying surface reflectance can alter the observed sky polarization. Military, environmental, and navigational applications exploit the sky polarization pattern to detect objects, retrieve aerosol and cloud properties, and to find compass headings based on the sky polarization pattern. Sky polarization is also being used to calibrate the polarization response of large telescopes. It is important to understand how partially polarized skylight can vary with environmental factors, as well as with wavelength and solar position, so that polarization measurements can be interpreted correctly. The direction of polarization when aligned to a specific reference frame can provide additional information beyond the basic polarization pattern. This dissertation expands the current knowledge of skylight polarization by validating radiative transfer simulations in the shortwave infrared, by reporting the first-ever retrievals of cloud thermodynamic phase from all-sky polarization images using the Stokes S1 parameter referenced in the scattering plane, and by quantifying how partially polarized skylight varied under unique scattering conditions during the 2017 solar eclipse. In order to accurately predict cloud thermodynamic phase and to analyze the temporal distribution of skylight during a total solar eclipse, a physics-based understanding of the Stokes parameters and angle of polarization (AoP) with respect to the instrument, scattering, and solar principal planes was also developed. Through each experiment, two underlying threads were observed. First, in order to accurately interpret results, environmental parameters needed to be characterized. Second, when rotated into a specific reference frame, the Stokes parameters and AoP can be utilized differently and provide unique insights when analyzing all-sky polarization data.Item Coherent imaging via temporal heterodyne and spatial shearing methods(Montana State University - Bozeman, College of Letters & Science, 2018) Galloway, Ryan Moore; Chairperson, Graduate Committee: Wm. Randall BabbittAtmospheric turbulence rapidly decreases image quality at long ranges. Here multiple coherent imaging methods are discussed that lead to a new type of active imaging system, which may help mitigate the effects of atmospheric turbulence. This is accomplished via a self-referencing, linear frequency modulated laser signal, where the signal is both offset in transmitter location (spatial shearing), and is demultiplexed in the temporal frequency domain using unique time delays for each transmitter (temporal heterodyne). Spatial shearing allows one to capture a spatial derivative of the object's spatial frequency content, which if properly 'integrated' can be used to reconstruct an atmospheric phase-aberration-corrected image of the object. The system is illustrated from the starting point of temporal digital holography methods, and builds up to the self-referencing scheme. Various coherent imaging methods and situational parameters are compared.Item Synthesis of new electron donors and acceptors based on ethylenedioxythienylpolyenes(Montana State University - Bozeman, College of Letters & Science, 2002) Tarter, Edward ScottItem Synthesis of dendrons and dendrimers incorporating diphenylamino-N-ethyl-N-hydroxyethylaminodiphenylpolyenes for photonic applications(Montana State University - Bozeman, College of Letters & Science, 2000) Ashworth, Kimba Lee