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Articles 751 - 780 of 3057

Full-Text Articles in Physical Sciences and Mathematics

The Design Of A Continuous Wave Molecular Nitrogen Stimulated Raman Laser In The Visible Spectrum, Timothy J. Bate Mar 2020

The Design Of A Continuous Wave Molecular Nitrogen Stimulated Raman Laser In The Visible Spectrum, Timothy J. Bate

Theses and Dissertations

Hollow-core photonic crystal fibers (HCPCFs) shows promise as a hybrid laser with higher nonlinear process limits and small beam size over long gain lengths. This work focuses on the design of a CW molecular nitrogen (N2) stimulated Raman laser. N2 offers Raman gains scaling up to 900 amg, scaling higher than H2. The cavity experiment showed the need to include Rayleigh scattering in the high pressure required for N2 Raman lasing. Even at relatively low pressure ssuch as 1,500 psi, high conversion percentages should be found if the fiber length is chosen based on …

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Cn And C2 Spectroscopy On The Pulsed Ablation Of Graphite In The Visible Spectrum, Brandon A. Pierce Mar 2020

Cn And C2 Spectroscopy On The Pulsed Ablation Of Graphite In The Visible Spectrum, Brandon A. Pierce

Theses and Dissertations

An experimental study was conducted on the nanosecond pulsed laser ablation of graphite using a KrF laser at a fluence of 3.8 J/cm2 in Air, Ar, He, and N2. Optical emissions spectroscopy revealed the C2 Swan sequences and the CN Violet sequences. A spectroscopic model was developed to extract the molecular rotational and vibrational temperatures of each excited species for t=0.5-10 microseconds after laser irradiation. The rovibrational temperatures were found to vary with background gas for the CN Violet; however, only the vibrational temperature varied between He and the other background gases for C2 Swan. …

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Mult-Spectral Imaging Of Vegetation With A Diffractive Plenoptic Camera, Tristan R. Naranjo Mar 2020

Mult-Spectral Imaging Of Vegetation With A Diffractive Plenoptic Camera, Tristan R. Naranjo

Theses and Dissertations

Snapshot multi-spectral sensors allow for object detection based on its spectrum for remote sensing applications in air or space. By making these types of sensors more compact and lightweight, it allows drones to dwell longer on targets or the reduction of transport costs for satellites. To address this need, I designed and built a diffractive plenoptic camera (DPC) which utilized a Fresnel zone plate and a light field camera in order to detect vegetation via a normalized difference vegetation index (NDVI). This thesis derives design equations by relating DPC system parameters to its expected performance and evaluates its multi-spectral performance. …

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Validation Of Hts Optical Turbulence Profiling Via Sonic Anemometry, Alexander S. Boeckenstedt Mar 2020

Validation Of Hts Optical Turbulence Profiling Via Sonic Anemometry, Alexander S. Boeckenstedt

Theses and Dissertations

Previous turbulence measurements along a near-ground, 500 m, horizontal path using two helium-neon laser beacons and Hartmann Turbulence Sensor (HTS) yielded profiles of C2n by measuring local aberrated wavefront tilts. The HTS C2n estimates were consistent with integrated turbulence values collected along the same path by a BLS900 scintillometer. Further validation of the HTS profiling method is necessary to produce accurate optical turbulence profiles for wavefront correction and to eventually gain an improved understanding of turbulence in the lower atmosphere and its variation as a function of altitude. In order to add confidence to the HTS …

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Enhanced Brdf Modeling Using Directional Volume Scatter Terms, Michael W. Bishop Mar 2020

Enhanced Brdf Modeling Using Directional Volume Scatter Terms, Michael W. Bishop

Theses and Dissertations

Accurate Bidirectional Reflectance Distribution Function (BRDF) models provide critical scatter behavior for computer graphics and remote sensing performance. The popular microfacet class of BRDF models is geometric-based and computationally inexpensive compared to wave-optics models. Microfacet models commonly account for surface scatter and Lambertian volume scatter, but not directional volume scatter. This work proposes directional volume scatter modeling for enhanced performance over all observation regions. Five directional volume models are incorporated into the modified Cook-Torrance microfacet model. Additionally, a semi-empirical directional volume term is presented based on the Beckmann microfacet distribution and a modified Fresnel reflection term. High fidelity, low density …

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Analysis With Dynamic Bayesian Networks Compared To Simulation, Aaron J. Salazar Mar 2020

Analysis With Dynamic Bayesian Networks Compared To Simulation, Aaron J. Salazar

Theses and Dissertations

This research compares simulations to Dynamic Bayesian Networks in analyzing situations. The research applies models that have known output mean and variance. Queueing systems have theoretical values of the steady-state mean and variance for the number of entities in the system. Monte Carlo simulation development is broken down into two separate approaches: discrete-event simulation and time-oriented simulation. The discrete-event simulation uses pseudo-random numbers to schedule and trigger future events (i.e. customer arrivals and services) and is based on the generated objects.The time-oriented simulation utilizes fixed-width time intervals and updates the system state according to a stochastic process for the set …

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Global Gradient-Based Phase Unwrapping Algorithm For Increased Performance In Wavefront Sensing, Bryan R. Bartelt Mar 2020

Global Gradient-Based Phase Unwrapping Algorithm For Increased Performance In Wavefront Sensing, Bryan R. Bartelt

Theses and Dissertations

As the reliance on satellite data for military and commercial use increases, more effort must be exerted to protect our space-based assets. In order to help increase our space domain awareness (SDA), new approaches to ground-based space surveillance via wavefront sensing must be adopted. Improving phase-unwrapping algorithms in order to assist in phase retrieval methods is one way of increasing the performance in current adaptive optics (AO) systems. This thesis proposes a new phase-unwrapping algorithm that uses a global, gradient-based technique to more rapidly identify and correct for areas of phase wrapping during particular phase retrieval methods. This is beneficial …

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Cyber Risk Assessment And Scoring Model For Small Unmanned Aerial Vehicles, Dillon M. Pettit Mar 2020

Cyber Risk Assessment And Scoring Model For Small Unmanned Aerial Vehicles, Dillon M. Pettit

Theses and Dissertations

The commercial-off-the-shelf small Unmanned Aerial Vehicle (UAV) market is expanding rapidly in response to interest from hobbyists, commercial businesses, and military operators. The core commercial mission set directly relates to many current military requirements and strategies, with a priority on short range, low cost, real time aerial imaging, and limited modular payloads. These small vehicles present small radar cross sections, low heat signatures, and carry a variety of sensors and payloads. As with many new technologies, security seems secondary to the goal of reaching the market as soon as innovation is viable. Research indicates a growth in exploits and vulnerabilities …

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Quantum Transpiler Optimization: On The Development, Implementation, And Use Of A Quantum Research Testbed, Brandon K. Kamaka Mar 2020

Quantum Transpiler Optimization: On The Development, Implementation, And Use Of A Quantum Research Testbed, Brandon K. Kamaka

Theses and Dissertations

Quantum computing research is at the cusp of a paradigm shift. As the complexity of quantum systems increases, so does the complexity of research procedures for creating and testing layers of the quantum software stack. However, the tools used to perform these tasks have not experienced the increase in capability required to effectively handle the development burdens involved. This case is made particularly clear in the context of IBM QX Transpiler optimization algorithms and functions. IBM QX systems use the Qiskit library to create, transform, and execute quantum circuits. As coherence times and hardware qubit counts increase and qubit topologies …

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Characterizing Uncertainty In Correlated Response Variables For Pareto Front Optimization, Peter A. Calhoun Mar 2020

Characterizing Uncertainty In Correlated Response Variables For Pareto Front Optimization, Peter A. Calhoun

Theses and Dissertations

Current research provides a method to incorporate uncertainty into Pareto front optimization by simulating additional response surface model parameters according to a Multivariate Normal Distribution (MVN). This research shows that analogous to the univariate case, the MVN understates uncertainty, leading to overconfident conclusions when variance is not known and there are few observations (less than 25-30 per response). This research builds upon current methods using simulated response surface model parameters that are distributed according to an Multivariate t-Distribution (MVT), which can be shown to produce a more accurate inference when variance is not known. The MVT better addresses uncertainty in …

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Analysis And Forecasting Of The 360th Air Force Recruiting Group Goal Distribution, Tyler Spangler Mar 2020

Analysis And Forecasting Of The 360th Air Force Recruiting Group Goal Distribution, Tyler Spangler

Theses and Dissertations

This research utilizes monthly data from 2012-2017 to determine economic or demographic factors that significantly contribute to increased goaling and production potential in areas of the 360th Recruiting Groups. Using regression analysis, a model of recruiting goals and production is built to identify squadrons within the 360 RCGs zone that are capable of producing more or fewer recruits and the factors that contribute to this increased or decreased capability. This research identifies that a zones high school graduation rate, the number of recruiters, and the number of JROTC detachments in a zone are positively correlated with recruiting goals and that …

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Laser Shock Peening Pressure Impulse Determination Via Empirical Data-Matching With Optimization Software, Colin C. Engebretsen Mar 2020

Laser Shock Peening Pressure Impulse Determination Via Empirical Data-Matching With Optimization Software, Colin C. Engebretsen

Theses and Dissertations

Laser shock peening (LSP) is a form of work hardening by means of laser induced pressure impulse. LSP imparts compressive residual stresses which can improve fatigue life of metallic alloys for structural use. The finite element modeling (FEM) of LSP is typically done by applying an assumed pressure impulse, as useful experimental measurement of this pressure impulse has not been adequately accomplished. This shortfall in the field is a current limitation to the accuracy of FE modeling, and was addressed in the current work. A novel method was tested to determine the pressure impulse shape in time and space by …

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Characterizing Regime-Based Flow Uncertainty, John L. Fioretti Mar 2020

Characterizing Regime-Based Flow Uncertainty, John L. Fioretti

Theses and Dissertations

The goal of this work is to develop a regime-based quantification of horizontal wind field uncertainty utilizing a global ensemble numerical weather prediction model. In this case, the Global Ensemble Forecast System Reforecast (GEFSR) data is utilized. The machine learning algorithm that is employed is the mini-batch K-means clustering algorithm. 850 hPa Horizontal flow fields are clustered and the forecast uncertainty in these flow fields is calculated for different forecast times for regions across the globe. This provides end-users quantified flow-based forecast uncertainty.

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Solving Combinatorial Optimization Problems Using The Quantum Approximation Optimization Algorithm, Nicholas J. Guerrero Mar 2020

Solving Combinatorial Optimization Problems Using The Quantum Approximation Optimization Algorithm, Nicholas J. Guerrero

Theses and Dissertations

The Quantum Approximation Optimization Algorithm (QAOA) is one of the most promising applications for noisy intermediate-scale quantum machines due to the low number of qubits required as well as the relatively low gate count. Much work has been done on QAOA regarding algorithm implementation and development; less has been done checking how these algorithms actually perform on a real quantum computer. Using the IBM Q Network, several instances of combinatorial optimization problems (the max cut problem and dominating set problem) were implemented into QAOA and analyzed. It was found that only the smallest toy max cut algorithms performed adequately: those …

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Localized Effects Of Hurricane Michael (2018) On Total Electron Content, Joanna E.S. Williams Mar 2020

Localized Effects Of Hurricane Michael (2018) On Total Electron Content, Joanna E.S. Williams

Theses and Dissertations

Understanding the connection between terrestrial and space environments is an emerging field of study that can significantly improve operational weather forecasting. In particular, it is well known that tropical cyclones (TCs) and thunderstorms can initiate gravity waves that generate fluctuations in the total electron content (TEC) of the ionosphere. These perturbations can deteriorate and delay the transmission of high-frequency (HF) communications, such as emergency services, amateur radio, and aviation. This study investigates changes in TEC according to the number of lightning ashes and the rainfall rates associated with Hurricane Michael (2018). A composite analysis will be performed using the GOES …

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Detection Of Reconnection Signatures In Solar Flares, Taylor R. Whitney Mar 2020

Detection Of Reconnection Signatures In Solar Flares, Taylor R. Whitney

Theses and Dissertations

Solar flare forecasting is limited by the current understanding of mechanisms that govern magnetic reconnection, the main physical phenomenon associated with these events. As a result, forecasting relies mainly on climatological correlations to historical events rather than the underlying physics principles. Solar physics models place the neutral point of the reconnection event in the solar corona. Correspondingly, studies of photospheric magnetic fields indicate changes during solar flares -- particularly in relation to the field helicity -- on the solar surface as a result of the associated magnetic reconnection. This study utilizes data from the Solar Dynamics Observatory (SDO) Helioseismic and …

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Simulation Of Sporadic-E Parameters Using Phase Screen Method, Daniel W. Stambovsky Mar 2020

Simulation Of Sporadic-E Parameters Using Phase Screen Method, Daniel W. Stambovsky

Theses and Dissertations

A phase screen simulation experiment is designed and implemented to model radio occultation through sporadic-E ionospheric disturbances between a GPS transmitter operating at the L1 frequency and a second receiving satellite in low earth orbit (LEO). Simulations were made to test the linear relationship between plasma intensity and scintillation S4 index both posited (Arras and Wickert, 2018) and contended (Gooch et al., 2020) in previous literature. Results brought into question both the linear relationship and the use of S4 as a whole and an alternate metric was sought.

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Modulation Of Lightning Occurrence By The Solar Wind, Adam L. Baxter Mar 2020

Modulation Of Lightning Occurrence By The Solar Wind, Adam L. Baxter

Theses and Dissertations

Lightning affects military and civilian operations. Characterization of the distribution of global lightning strikes of two detection networks based on solar wind events is analyzed. the median analysis by latitude gave different results for the two network datasets. The KLD pulled out some common features such as the seasonal dependence and a general increase in lightning at the equator. Comparisons between different datasets must be handled carefully. the KLD method may be a way to capture common features, or assess how similar the datasets are. A detailed analysis of the differences between the tow networks detection algorithms and investigating other …

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Conduction Mapping For Quality Control Of Laser Powder Bed Fusion Additive Manufacturing, Chance M. Baxter Mar 2020

Conduction Mapping For Quality Control Of Laser Powder Bed Fusion Additive Manufacturing, Chance M. Baxter

Theses and Dissertations

A process was developed to identify potential defects in previous layers of Selective Laser Melting (SLM) Powder Bed Fusion (PBF) 3D printed metal parts using a mid-IR thermal camera to track infrared 3.8-4 m band emission over time as the part cooled to ambient temperature. Efforts focused on identifying anomalies in thermal conduction. To simplify the approach and reduce the need for significant computation, no attempts were made to calibrate measured intensity, extract surface temperature, apply machine learning, or compare measured cool-down behavior to computer model predictions. Raw intensity cool-down curves were fit to a simplified functional form designed to …

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Mobile Data Analysis Using Dynamic Binary Instrumentation And Static Analysis, Christopher Dukarm Mar 2020

Mobile Data Analysis Using Dynamic Binary Instrumentation And Static Analysis, Christopher Dukarm

Theses and Dissertations

Mobile classified data leakage poses a threat to the DoD programs and missions. Security experts must know the format of application data, in order to properly classify mobile applications. This research presents the DBIMAFIA methodology to identify stored data formats. DBIMAFIA uses DBI and static analysis to uncover the structure of mobile application data and validate the results with traditional reverse engineering methods. DBIMAFIA was applied to fifteen popular Android applications and revealed the format of stored data. Notably, user PII leakage is identified in the Rago Games application. The application's messaging service exposes the full name, birthday, and city …

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Interoperable Ads-B Confidentiality, Brandon C. Burfeind Mar 2020

Interoperable Ads-B Confidentiality, Brandon C. Burfeind

Theses and Dissertations

The worldwide air traffic infrastructure is in the late stages of transition from legacy transponder systems to Automatic Dependent Surveillance - Broadcast (ADS-B) based systems. ADS-B relies on position information from GNSS and requires aircraft to transmit their identification, state, and position. ADS-B promises the availability of high-fidelity air traffic information; however, position and identification data are not secured via authentication or encryption. This lack of security for ADS-B allows non-participants to observe and collect data on both government and private flight activity. This is a proposal for a lightweight, interoperable ADS-B confidentiality protocol which uses existing format preserving encryption …

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Pedestrian Navigation Using Artificial Neural Networks And Classical Filtering Techniques, David J. Ellis Mar 2020

Pedestrian Navigation Using Artificial Neural Networks And Classical Filtering Techniques, David J. Ellis

Theses and Dissertations

The objective of this thesis is to explore the improvements achieved through using classical filtering methods with Artificial Neural Network (ANN) for pedestrian navigation techniques. ANN have been improving dramatically in their ability to approximate various functions. These neural network solutions have been able to surpass many classical navigation techniques. However, research using ANN to solve problems appears to be solely focused on the ability of neural networks alone. The combination of ANN with classical filtering methods has the potential to bring beneficial aspects of both techniques to increase accuracy in many different applications. Pedestrian navigation is used as a …

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Quantitative Analysis Of Evaluation Criteria For Generative Models, Marvin W. Newlin Mar 2020

Quantitative Analysis Of Evaluation Criteria For Generative Models, Marvin W. Newlin

Theses and Dissertations

Machine Learning (ML) is rapidly becoming integrated in critical aspects of cybersecurity today, particularly in the area of network intrusion/anomaly detection. However, ML techniques require large volumes of data to be effective. The available data is a critical aspect of the ML process for training, classification, and testing purposes. One solution to the problem is to generate synthetic data that is realistic. With the application of ML to this area, one promising application is the use of ML to perform the data generation. With the ability to generate synthetic data comes the need to evaluate the “realness” of the generated …

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Meta Learning Recommendation System For Classification, Clarence O. Williams Iii Mar 2020

Meta Learning Recommendation System For Classification, Clarence O. Williams Iii

Theses and Dissertations

A data driven approach is an emerging paradigm for the handling of analytic problems. In this paradigm the mantra is to let the data speak freely. However, when using machine learning algorithms, the data does not naturally reveal the best or even a good approach for algorithm choice. One method to let the algorithm reveal itself is through the use of Meta Learning, which uses the features of a dataset to determine a useful model to represent the entire dataset. This research proposes an improvement on the meta-model recommendation system by adding classification problems to the candidate problem space with …

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Determining Virtual Practicality From Physical Stereo Vision Images And Gps, Bradley S. French Mar 2020

Determining Virtual Practicality From Physical Stereo Vision Images And Gps, Bradley S. French

Theses and Dissertations

Current research efforts for Automated Aerial Refueling (AAR) at The Air Force Institute of Technology (AFIT) utilize Stereo Computer Vision to compute a relative pose between a tanker and receiver aircraft. Due to costs, time, and availability, it can be onerous to test these algorithms using actual Air Force (AF) aircraft. Our solution to this problem consists of using a 3D Graphics Engine to simulate AAR endeavors. However, the question then arises, “Does the virtual world accurately represent the physical world?” This can be explored by comparing a set of truth data to a similar set of virtual data. First, …

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Comparison Of The Accuracy Of Rayleigh-Rice Polarization Factors To Improve Microfacet Brdf Models, Rachel L. Wolfgang Mar 2020

Comparison Of The Accuracy Of Rayleigh-Rice Polarization Factors To Improve Microfacet Brdf Models, Rachel L. Wolfgang

Theses and Dissertations

Microfacet BRDF models assume that a surface has many small microfacets making up the roughness of the surface. Despite their computational simplicity in applications in remote sensing and scene generation, microfacet models lack the physical accuracy of wave optics models. In a previous work, Butler proposed to replace the Fresnel reflectance term of microfacet models with the Rayleigh-Rice polarization factor, Q, to create a more accurate model. This work examines the novel model that combines microfacet and wave optics terms for its accuracy in the pp and ss polarized cases individually. The model is fitted to the polarized data in …

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Neutron Energy Effects On Asteroid Deflection, Lansing S. Horan Iv Mar 2020

Neutron Energy Effects On Asteroid Deflection, Lansing S. Horan Iv

Theses and Dissertations

In the future, a hazardous asteroid will find itself on a collision course with Earth. It is an inevitability; the question is not if, but when. For asteroids of moderate size or larger, a nuclear device is one of humanity's only technologies capable of mitigating this threat via deflection on a timescale of less than a decade. This work examined how changing the output neutron energy from a nuclear device detonation affects asteroid deflection. The notional asteroid target was 300 meters in diameter and composed of silicon dioxide at a bulk density of 1.855 g/cm3. To calculate the …

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Algorithm Selection Framework For Cyber Attack Detection, Marc W. Chalé, Nathaniel D. Bastian, Jeffery D. Weir Mar 2020

Algorithm Selection Framework For Cyber Attack Detection, Marc W. Chalé, Nathaniel D. Bastian, Jeffery D. Weir

Faculty Publications

The number of cyber threats against both wired and wireless computer systems and other components of the Internet of Things continues to increase annually. In this work, an algorithm selection framework is employed on the NSL-KDD data set and a novel paradigm of machine learning taxonomy is presented. The framework uses a combination of user input and meta-features to select the best algorithm to detect cyber attacks on a network. Performance is compared between a rule-of-thumb strategy and a meta-learning strategy. The framework removes the conjecture of the common trial-and-error algorithm selection method. The framework recommends five algorithms from the …

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Optimizing The Environmental And Economic Sustainability Of Remote Community Infrastructure, Jamie E. Filer, Justin D. Delorit, Andrew J. Hoisington, Steven J. Schuldt Mar 2020

Optimizing The Environmental And Economic Sustainability Of Remote Community Infrastructure, Jamie E. Filer, Justin D. Delorit, Andrew J. Hoisington, Steven J. Schuldt

Faculty Publications

Remote communities such as rural villages, post-disaster housing camps, and military forward operating bases are often located in remote and hostile areas with limited or no access to established infrastructure grids. Operating these communities with conventional assets requires constant resupply, which yields a significant logistical burden, creates negative environmental impacts, and increases costs. For example, a 2000-member isolated village in northern Canada relying on diesel generators required 8.6 million USD of fuel per year and emitted 8500 tons of carbon dioxide. Remote community planners can mitigate these negative impacts by selecting sustainable technologies that minimize resource consumption and emissions. However, …

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Non-Linear Statistical Photocalibration Of Photodetectors Without Calibrated Light Sources, Stephen C. Cain Mar 2020

Non-Linear Statistical Photocalibration Of Photodetectors Without Calibrated Light Sources, Stephen C. Cain

Faculty Publications

Calibration of CCD arrays is commonly conducted using dark frames. Non-absolute calibration techniques only measure the relative response of the detectors. For absolute calibration to be achieved, a second calibration is sometimes utilized by looking at sources with known radiances. A process like this can be used to calibrate photodetectors if a calibration source is available and sensor time can be spared to perform the operation. A previous attempt at creating a procedure for calibrating a photodetector using the underlying Poisson nature of the photodetection statistics relied on a linear model. This effort produced the statistically applied non-uniformity calibration algorithm, …

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