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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Development Of The Depth-Fused Multi-Focal-Plane Display Technology

Hu, Xinda January 2014 (has links)
Conventional stereoscopic displays present a pair of stereoscopic images on a single and fixed image plane. In consequence, these displays lack the capability of correctly rendering focus cues (i.e. accommodation and retinal blur) and may induce the discrepancy between accommodation and convergence. A number of visual artifacts associated with incorrect focus cues in stereoscopic displays have been reported, limiting the applicability of these displays for demanding applications and daily usage. Depth-fused multi-focal-plane display was proposed to create a fixed-viewpoint volumetric display capable of rendering correct or nearly-correct focus cues in a stereoscopic display through a small number of discretely placed focal planes. It effectively addresses the negative effects of conventional stereoscopic displays on depth perception accuracy and visual fatigue. In this dissertation, the fundamental design methods and considerations of depth-fused displays were refined and extended based on previous works and a high-resolution optical see-through multi-focal-plane head-mounted display enabled by state-of-the-art freeform optics was developed. The prototype system is capable of rendering nearly-correct focus cues for a large volume of 3D space extending into a depth range from 0 to 3 diopters at flicker-free speed. By incorporating freeform optics, the prototype not only achieves high quality imagery across a large 3D volume for the virtual display path but it also maintains better than 0.5 arcminutes visual resolution of the see-through view. The optical design, implementation and experimental validation of the display are presented and discussed in detail.
92

Application of Fluidic Lens Technology to an Adaptive Holographic Optical Element See-Through Auto-Phoropter

Chancy, Carl Henri January 2014 (has links)
A device for performing an objective eye exam has been developed to automatically determine ophthalmic prescriptions. The closed loop fluidic auto-phoropter has been designed, modeled, fabricated and tested for the automatic measurement and correction of a patient's prescriptions. The adaptive phoropter is designed through the combination of a spherical-powered fluidic lens and two cylindrical fluidic lenses that are orientated 45° relative to each other. In addition, the system incorporates Shack-Hartmann wavefront sensing technology to identify the eye's wavefront error and corresponding prescription. Using the wavefront error information, the fluidic auto-phoropter nulls the eye's lower order wavefront error by applying the appropriate volumes to the fluidic lenses. The combination of the Shack-Hartmann wavefront sensor the fluidic auto-phoropter allows for the identification and control of spherical refractive error, as well as cylinder error and axis; thus, creating a truly automated refractometer and corrective system. The fluidic auto-phoropter is capable of correcting defocus error ranging from −20D to 20D and astigmatism from −10D to 10D. The transmissive see-through design allows for the observation of natural scenes through the system at varying object planes with no additional imaging optics in the patient's line of sight. In this research, two generations of the fluidic auto-phoropter are designed and tested; the first generation uses traditional glass optics for the measurement channel. The second generation of the fluidic auto-phoropter takes advantage of the progress in the development of holographic optical elements (HOEs) to replace all the traditional glass optics. The addition of the HOEs has enabled the development of a more compact, inexpensive and easily reproducible system without compromising its performance. Additionally, the fluidic lenses were tested during a National Aeronautics Space Administration (NASA) parabolic flight campaign, to determine the effect of varying gravitational acceleration on the performance and image quality of the fluidic lenses. Wavefront analysis has indicated that flight turbulence and the varying levels of gravitational acceleration ranging from zero-G (microgravity) to 2G (hypergravity) had minimal effect on the performance of the fluidic lenses, except for small changes in defocus; making them suitable for potential use in a portable space-based fluidic auto-phoropter.
93

Generalized Pupil Aberrations Of Optical Imaging Systems

Elazhary, Tamer Mohamed Tawfik Ahmed Mohamed January 2014 (has links)
In this dissertation fully general conditions are presented to correct linear and quadratic field dependent aberrations that do not use any symmetry. They accurately predict the change in imaging aberrations in the presence of lower order field dependent aberrations. The definitions of the image, object, and coordinate system are completely arbitrary. These conditions are derived using a differential operator on the scalar wavefront function. The relationships are verified using ray trace simulations of a number of systems with varying degrees of complexity. The math is shown to be extendable to provide full expansion of the scalar aberration function about field. These conditions are used to guide the design of imaging systems starting with only paraxial surface patches, then growing freeform surfaces that maintain the analytic conditions satisfied for each point in the pupil. Two methods are proposed for the design of axisymmetric and plane symmetric optical imaging systems. Design examples are presented as a proof of the concept.
94

Polarimetric Road Ice Detection

Drummond, Krista January 2014 (has links)
Ever since automobiles became affordable for the average American, with the introduction of the Ford Model T in 1908, making driving safer has been a priority. While driver intoxication and distraction are the leading causes of automotive fatalities, poor road conditions increase the frequency and deadliness of these incidents. Monitoring road conditions for thousands of miles of road is a huge undertaking, one too large for human surveillance. Automated systems capable of detecting and reacting to dangerous road conditions would be life-saving. These systems could be mounted to the sides of road and notify an operator of conditions in real-time. Drivers could be warned, action taken, and many lives saved. This thesis investigated the science behind polarimetric road ice detection systems. Laboratory Mueller matrix measurements of a simulated road under differing surface conditions were collected searching for a discriminatory polarization property. These Mueller matrices were decomposed into depolarization, diattenuation, and retardance. Individual sample surface polarization properties were then calculated from these three unique matrices and compared. Simulated road samples were measured under many wavelengths and angles, which gave us a larger data library from which to observe trends. Specular and off-specular reflection responses of each sample were also collected. Four polarization properties stood out for having high separation between dry and iced measurements: Depolarization Index, Linear Diattenuation, Linear Polarizance, and Linear Retardance. Through our investigation polarimetric ice detection is possible. Continued research of the polarization properties of road ice can result in the development of a road ice detection system. Proposed deployment methods of such a system have been outlined following the analysis of the data collected in this experiment. Not only is polarimetric ice detection an exciting and novel use of polarization, it has the potential to improve road safety through real-time ice response measures.
95

Asphercial Metrology for Non-Specular Surfaces with the Scanning Long-Wave Optical Test System

Su, Tianquan January 2014 (has links)
Aspherical optics are increasingly used these days. The application of aspherical surfaces on large, astronomical telescope mirrors brings challenge to the fabrication. Since the surface radius of curvature varies across the surface, the grinding/polishing tool needs to change its shape when working on different parts of the surface, making surface error more easily embedded into the surface. Therefore, a tighter test-fab loop is needed to guide the fabrication process. To maximize the accuracy during the grinding of the surface and to minimize the working time in the polishing stage, a better metrology device that can measure rough surface is needed to guide the grinding process. Scanning long-wave optical test system (SLOTS) is designed to meet this demand by providing accurate, fast, large dynamic range, and high spatial resolution measurements on rough optical surfaces (surface rms roughness<1.7 µm).SLOTS is a slope measuring deflectometry system that works like a reversed wire test. It measures the reflection of the infrared light off the test surface, and calculates the local slope of the test surface. The surface sag/height is obtained through integration. During the test, a heated metal ribbon radiates long-wave infrared light that is reflected by the test surface. A thermal imaging camera records the reflected light. The ribbon is scanned in two orthogonal directions. From the variation of the irradiance recorded by the camera, slope maps of the test surface can be retrieved in the two orthogonal directions. SLOTS is a combination of tradition slope measurement and modern technology, processing advantages from both parts. It measures surface slope, so there is no need for null optics. It uses an uncooled thermal imaging camera that is made with high resolution and high sensitivity. The linear stage used to scan the hot ribbon has long travel, small resolution, and high accuracy. Both the camera and stage enable SLOTS a large dynamic range and high sensitivity. SLOTS has successfully guided the grinding process of the primary mirror of Daniel K. Inouye Solar Telescope. This mirror is a 4-meter diameter off-axis parabola (OAP). Its largest aspherical departure is 8 mm. SLOTS is able to measure it without any null optics. Under the guidance of SLOTS, the surface shape was controlled to be 1 µm rms within designed shape (with astigmatism removed) at 0.7 µm rms surface roughness (12 µm loose abrasive grits).
96

Matrix Structure for Information-Driven Polarimeter Design

Alenin, Andrey S. January 2015 (has links)
Estimating the polarization of light has been shown to have merit in a wide variety of applications between UV and LWIR wavelengths. These tasks include target identification, estimation of atmospheric aerosol properties, biomedical and other applications. In all of these applications, polarization sensing has been shown to assist in discrimination ability; however, due to the nature of many phenomena, it is difficult to add polarization sensing everywhere. The goal of this dissertation is to decrease the associated penalties of using polarimetry, and thereby broaden its applicability to other areas. First, the class of channeled polarimeter systems is generalized to relate the Fourier domains of applied modulations to the resulting information channels. The quality of reconstruction is maximized by virtue of using linear system manipulations rather than arithmetic derived by hand, while revealing system properties that allow for immediate performance estimation. Besides identifying optimal systems in terms of equally weighted variance (EWV), a way to redistribute the error between all the information channels is presented. The result of this development often leads to superficial changes that can improve signal-to-noise-ration (SNR) by up to a factor of three compared to existing designs in the literature. Second, the class of partial Mueller matrix polarimeters (pMMPs) is inspected in regards to their capacity to match the level of discrimination performance achieved by full systems. The concepts of structured decomposition and the reconstructables matrix are developed to provide insight into Mueller subspace coverage of pMMPs, while yielding a pMMP basis that allows the formation of ten classes of pMMP systems. A method for evaluating such systems while considering a multi-objective optimization of noise resilience and space coverage is provided. An example is presented for which the number of measurements was reduced to half. Third, the novel developments intended for channeled and partial systems are combined to form a previously undiscussed class of channeled partial Mueller matrix polarimeters (c-pMMPs). These systems leverage the gained understanding in manipulating the structure of the measurement to design modulations such that the desired pieces of information are mapped into channels with favorable reconstruction characteristics.
97

Design of Confocal Microendscopy for Fallopian Tube Imaging and Detection of Esophageal Cancer

Wu, Tzu-Yu January 2015 (has links)
This work presents several major developments related to a fluorescence confocal microendoscope technology that can provide instantaneous cellular level images from selected depths of tissue inside the human body. The confocal microendoscope systems discussed employ fiber-optic based imaging catheters coupled to custom built slit-scan confocal microscopes. One major new development involves the design, development, and testing of a new flexible confocal microgastroscope (CMG) system for imaging the esophagus. This new system has the potential to aid in the early detection of esophageal cancer. It consists of a new optical scan unit mounted on an endoscopy cart and a new flexible catheter that can be inserted through the instrument channel of a commercial gastroscope. The CMG system has higher spatial resolution and larger field of view than the previous generation clinical confocal microendoscopes in our lab. In addition, the new CMG system can be operated over a greater wavelength range than its predecessor. Central to the CMG system is the design, construction, and testing of a new distal miniature objective that enables high-quality microendoscopy. The miniature objective, built with all glass spherical surfaces, achieves diffraction-limited performance over a 486 to 1000 nm spectral range. The wide achromatic range of this lens allows the CMG system to be used with a variety of contrast agents including agents in the NIR region. In addition, the new miniature objective can be mounted on existing confocal microendoscopes in our lab such as the ovarian clinical confocal microlaparoscope and our laboratory based experimental system. Finally, a new confocal microlaparoscope with an articulating catheter capable of imaging inside the distal portion of fallopian tubes is presented. This instrument is intended to allow the detection of early stage ovarian cancer originating inside the fallopian tube. The new microlaparoscope is compatible with 5 mm trocars and includes a thin 2.2 mm diameter articulating distal tip consisting of a bare fiber bundle and an automated dye delivery system. The distal tip of this new endoscope can be articulated through simple wrist movements and locked in place at a given angle if desired. The thin distal tip and the ability to control the angle of the tip provide the size and flexibility needed to image inside the curved and delicate structures of the fallopian tube. Preliminary imaging results from the new CMG system, the achromatized miniature objective, and the new articulating confocal microlaparoscope are presented to demonstrate the performance and the potential of each system towards the overall goal of in vivo imaging and disease diagnosis.
98

Design, Simulation, and Optimization of an RGB Polarization Independent Transmission Volume Hologram

Mahamat, Adoum Hassan January 2016 (has links)
Volume phase holographic (VPH) gratings have been designed for use in many areas of science and technology such as optical communication, medical imaging, spectroscopy and astronomy. The goal of this dissertation is to design a volume phase holographic grating that provides diffraction efficiencies of at least 70% for the entire visible wavelengths and higher than 90% for red, green, and blue light when the incident light is unpolarized. First, the complete design, simulation and optimization of the volume hologram are presented. The optimization is done using a Monte Carlo analysis to solve for the index modulation needed to provide higher diffraction efficiencies. The solutions are determined by solving the diffraction efficiency equations determined by Kogelnik's two wave coupled-wave theory. The hologram is further optimized using the rigorous coupled-wave analysis to correct for effects of absorption omitted by Kogelnik's method. Second, the fabrication or recording process of the volume hologram is described in detail. The active region of the volume hologram is created by interference of two coherent beams within the thin film. Third, the experimental set up and measurement of some properties including the diffraction efficiencies of the volume hologram, and the thickness of the active region are conducted. Fourth, the polarimetric response of the volume hologram is investigated. The polarization study is developed to provide insight into the effect of the refractive index modulation onto the polarization state and diffraction efficiency of incident light.
99

Time and Frequency Resolved Pump Probe Spectroscopy and Growth of Near Surface Quantum Confined Semiconductors Coupled to Metallic Nanostructures

Olitzky, Joshua D. January 2016 (has links)
Metallic nano-structures provide for new and exciting domains to investigate light-matter interactions. The coupling of these metallic nano-structures to semiconductor emitters allows for the observation of cavity QED effects including Purcell enhancement and Vacuum Rabi splitting. The focus of this dissertation will be to present an introduction and background to semiconductor optics, and metallic metamaterial systems. This will be followed by the presentation of the spectroscopy systems designed and constructed during my tenure as graduate student and the experimental data obtained with these systems. Some of the results have been published, while some of the presented material is still actively being pursued for publication. More specifically, the dissertation will cover the research at hand, experimental techniques, and results.
100

Characterization Techniques for Photonic Materials

Neelamraju, Bharati January 2016 (has links)
The advancement of photonics technologies depends on synthesis of novel materials and processes for device fabrication. The characterization techniques of the optical, electrical and magnetic properties of the synthesized materials and devices, by non-contact, non-invasive and nondestructive methods plays a significant role in development of new photonics technologies. The research reported in this thesis focuses on two such aspects of photonic materials characterization: Magneto-Optic characterization and Spectroscopic Ellipsometry. The theoretical and experimental basis of these two techniques, and experimental data analysis are presented in two parts. In Part 1, the changes in magneto-optic parameters of FePT PS-P2VP block copolymer nanocomposites with increasing concentrations of FePt nanoparticles in the block copolymer are analyzed. We present the results of change in MO anisotropy factor with the wt% of FePt and try to analyze these changes with further experimentation. Part 2 presents the results of spectroscopic ellipsometry of group III-IV multilayered thin film materials to give their precise thicknesses and optical constants. Both these techniques are unique ways to understand novel material characteristics for future use in device development.

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