5 results on '"Corey D. Packard"'
Search Results
2. Light Propagation in Clouds: From Digital Holography to Non-Exponential Extinction
- Author
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Susanne Glienke, Jeffrey L. Stith, Raymond A. Shaw, Will Cantrell, Corey D. Packard, Jacob P. Fugal, Michael L. Larsen, and Scott M. Spuler
- Subjects
Physics ,Field (physics) ,law ,Extinction (optical mineralogy) ,Fourier optics ,Phase (waves) ,Holography ,Radiative transfer ,Physics::Optics ,Digital holography ,Computational physics ,law.invention ,Exponential function - Abstract
Optical propagation is strongly influenced b y t he n umber concentration, size distribution, thermodynamic phase, and spatial distribution of particles in atmospheric clouds. These properties have been investigated in the field using an airborne digital holographic instrument. A laboratory facility has also been developed, in which optical propagation is being investigated in steady-state turbulent-cloud conditions.
- Published
- 2019
- Full Text
- View/download PDF
3. Measurement of optical blurring in a turbulent cloud chamber
- Author
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Will Cantrell, Michael C. Roggemann, David Ciochetto, Raymond A. Shaw, and Corey D. Packard
- Subjects
Physics ,Point spread function ,010504 meteorology & atmospheric sciences ,business.industry ,Scattering ,Turbulence ,01 natural sciences ,Computational physics ,law.invention ,Aerosol ,010309 optics ,Atmosphere ,Optics ,law ,0103 physical sciences ,Cloud chamber ,business ,Absorption (electromagnetic radiation) ,Physics::Atmospheric and Oceanic Physics ,Atmospheric optics ,0105 earth and related environmental sciences - Abstract
Earth’s atmosphere can significantly impact the propagation of electromagnetic radiation, degrading the performance of imaging systems. Deleterious effects of the atmosphere include turbulence, absorption and scattering by particulates. Turbulence leads to blurring, while absorption attenuates the energy that reaches imaging sensors. The optical properties of aerosols and clouds also impact radiation propagation via scattering, resulting in decorrelation from unscattered light. Models have been proposed for calculating a point spread function (PSF) for aerosol scattering, providing a method for simulating the contrast and spatial detail expected when imaging through atmospheres with significant aerosol optical depth. However, these synthetic images and their predicating theory would benefit from comparison with measurements in a controlled environment. Recently, Michigan Technological University (MTU) has designed a novel laboratory cloud chamber. This multiphase, turbulent “Pi Chamber” is capable of pressures down to 100 hPa and temperatures from -55 to +55°C. Additionally, humidity and aerosol concentrations are controllable. These boundary conditions can be combined to form and sustain clouds in an instrumented laboratory setting for measuring the impact of clouds on radiation propagation. This paper describes an experiment to generate mixing and expansion clouds in supersaturated conditions with salt aerosols, and an example of measured imagery viewed through the generated cloud is shown. Aerosol and cloud droplet distributions measured during the experiment are used to predict scattering PSF and MTF curves, and a methodology for validating existing theory is detailed. Measured atmospheric inputs will be used to simulate aerosol-induced image degradation for comparison with measured imagery taken through actual cloud conditions. The aerosol MTF will be experimentally calculated and compared to theoretical expressions. The key result of this study is the proposal of a closure experiment for verification of theoretical aerosol effects using actual clouds in a controlled laboratory setting.
- Published
- 2016
- Full Text
- View/download PDF
4. Measuring the detector-observed impact of optical blurring due to aerosols in a laboratory cloud chamber
- Author
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John R. Valenzuela, Corey D. Packard, Michael C. Roggemann, Will Cantrell, Raymond A. Shaw, and Greg Kinney
- Subjects
Number density ,Materials science ,010504 meteorology & atmospheric sciences ,Scattering ,business.industry ,Detector ,Atmospheric model ,01 natural sciences ,Light scattering ,law.invention ,Aerosol ,010309 optics ,Optics ,law ,0103 physical sciences ,General Earth and Planetary Sciences ,Cloud chamber ,Absorption (electromagnetic radiation) ,business ,Physics::Atmospheric and Oceanic Physics ,0105 earth and related environmental sciences - Abstract
Deleterious effects of the atmosphere on remotely acquired images includes absorption and scattering of light by aerosol particulates, which not only attenuates the signal but can potentially cause blurring due to forward-scattered light accepted by the imaging system. Proposed aerosol scattering models (e.g., Ishimaru) provide a method for simulating the contrast and spatial detail expected when imaging through atmospheres with significant aerosol optical depth. This work explores closure between modulation transfer functions (MTFs) obtained from directly measured images and MTFs calculated from theory using measured cloud properties. The closure experiments are performed in a laboratory cloud chamber in which cloud droplet number density and size distribution are directly measured. Images of a binary knife-edge target were taken with an optical detector on the other side of a water cloud generated through reduction of pressure in the humidified chamber. The key results of this closure experiment are: the theoretical expression for the aerosol MTF is likely overly simplistic and does not account for broad particle size distributions. The significance of optical blurring from light scattering by aerosol particles depends sensitively on the properties of both the particles and the imaging system.
- Published
- 2018
- Full Text
- View/download PDF
5. Simulation-based sensor modeling and at-range target detection characterization with MuSES
- Author
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Peter L. Rynes, Corey D. Packard, Allen Curran, and Nicholas E. Saur
- Subjects
Diffraction ,Pixel ,Computer science ,business.industry ,Thresholding ,Rendering (computer graphics) ,law.invention ,Lens (optics) ,Infrared signature ,law ,Radiative transfer ,Radiance ,Computer vision ,Specular reflection ,Artificial intelligence ,business - Abstract
Accurate infrared signature prediction of targets, such as humans or ground vehicles, depends primarily on the realistic prediction of physical temperatures. Thermal model development typically requires a geometric description of the target (i.e., a 3D surface mesh) along with material properties for characterizing the thermal response to simulated weather conditions. Once an accurate thermal solution has been obtained, signature predictions for an EO/IR spectral waveband can be generated. The image rendering algorithm should consider the radiative emissions, diffuse/specular reflections, and atmospheric effects to depict how an object in a natural scene would be perceived by an EO/IR sensor. The EO/IR rendering process within MuSES, developed by ThermoAnalytics, can be used to create a synthetic radiance image that predicts the energy detected by a specific sensor just prior to passing through its optics. For additional realism, blurring due to lens diffraction and noise due to variations in photon detection can also be included, via specification of sensor characteristics. Additionally, probability of detection can be obtained via the Targeting Task Performance (TTP) metric, making it possible to predict a target’s at-range detectability to a particular threat sensor. In this paper, we will investigate the at-range contrast and detectability of some example targets and examine the effect of various techniques such as sub-pixel sampling and target pixel thresholding.
- Published
- 2015
- Full Text
- View/download PDF
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