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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.
151

Waveguide-Based Spatial Light Modulators for Use in Holographic Video Displays

Qaderi, Kamran 01 March 2018 (has links)
Film display holograms typically diffract light over a wide enough view-angle to be viewed, directly, without intervening optics. However, all holographic video displays must use optics beyond the hologram surface to overcome the challenges of small display extent and low diffraction angle by using some form of demagnification and derotation. We report a leaky mode waveg- uide spatial light modulator (SLM) with sufficiently high angular diffraction to obviate the need for demagnification in scanned aperture systems. This was achieved by performing a number of experiments to determine the depth of the annealed, proton-exchanged waveguide which corresponded to a maximized diffracted angle. Diffraction sweeps were recorded in excess of 19.5<°> for 632.8 nm light which is above the 15<°> required for direct view display.Moreover, we present a paired set of waveguide SLMs capable of a maximum light deflection nearing 28<°> for red. This deflection, which is several times larger than the angular sweep of current, state-of-the-art modulators, is made possible by the unilateral, near-collinear waveguide nature of the leaky mode interaction. The ability to double angular output in this way, which is either not possible or not practical in other SLMs, is possible in leaky mode devices, thanks to the absence of zero-order light and the lack of high-order outputs. This combined structure has angu- lar deflection high enough to enable color holographic video monitors that do not require angular magnification. Furthermore, the low cost and high angular deflection of these devices may make it possible to make large arrays for flat-screen video holography.One improvement that could be made to the current setup would be to increase the device<&trade>s diffraction efficiency. One highly influential factor of diffraction efficiency for a Bragg-regime surface acoustic wave (SAW) grating is the length of the interaction between the light and the grating. In this work, we have shown that guided light in a reverse proton exchanged (RPE) waveguide experiences less loss. This enables us to create longer devices which eventually results in devices with higher diffraction efficiency.We have also researched on LCoS SLMs and used them for two different applications: (a) photophoretic-trap volumetric displays and (b) holographic video displays. In the first case, aberrations including spherical, astigmatism, and coma can make particles to trap tighter in the focal point of the beam. Also, a new approach for holographic computations is presented which uses the electromagnetic nature of light in Maxwell Equations to find a unique phase map for every specific 3D object in space.
152

Quantiative biological microsocopy by digital holography

Mann, Christopher J 01 June 2006 (has links)
In this dissertation, improved techniques in digital holography, that have produced high-resolution, high-fidelity images, are discussed. In particular, the angular spectrum method of calculating holographic optical field is noted to have several advantages over the more commonly used Fresnel transformation or Huygens convolution method. It is observed that spurious noise and interference components can be tightly controlled through the analysis and filtering of the angular spectrum. In the angular spectrum method, the reconstruction distance does not have a lower limit, and the off-axis angle between the object and reference waves can be lower than that of the Fresnel requirement, while still allowing the zero-order background to be cleanly separated. Holographic phase images are largely immune from the coherent noise commonly found in amplitude images. With the use of a miniature pulsed laser, the resulting images have 0.5um diffraction-limited lateral resolution and the phase profile is accurate to about several nanometers of optical path length. Samples such as ovarian cancer cells (SKOV-3) and mouse-embryo fibroblast cells have been imaged. These images display intra-cellular and intra-nuclear organelles with clarity and quantitative accuracy. This technique clearly exceeds currently available methods in phase-contrast opticalmicroscopy in both resolution and detail and provides a new modality for imaging morphology of cellular and intracellular structures that is not currently available. Furthermore, we also demonstrate that phase imaging digital holographic movies provide a novel method of non-invasive quantitative viewing of living cells and other objects. This technique is shown to have significant advantages over conventional microscopy.
153

Development of confocal optical holographic microscopy

McLeod, Robert A. 06 September 2006 (has links)
Optical Confocal Holography is a combination of two well known concepts: confocal microscopy and optical (laser) holography. Confocal microscopy places an aperture at a conjugate focus to the specimen focus. This filters any rays that are not on the focus plane, allowing a 3-dimensional image of the specimen to be built up over a set of planes. Holography is the measurement of both the amplitude and phase characteristics of light. Typically most methods only measure the amplitude of the image. The phenomenon of interference allows the determination of the phase shift for a coherent source as well. The phase information is directly related to the index of refraction of a material, which in turn is a function of the temperature and composition. As a technique, confocal holography holds promise to better characterize many physical processes in materials science, such as combustion and convection. It also may contribute to the biological sciences by imaging low-contrast, weak-phase objects. Thanks to the ongoing, continued improvement in computer processing speed, it has recently become practical to interpret data from confocal holography microscopy with a computer. The objective of the microscope is to non-invasively measure the three-dimensional, internal temperatures and compositions (e.g. solute/solvent gradient) of a specimen. My contributions over the course of two years to the project were: generation and optimization of an optical design with a software package known as Zemax; sourcing and purchasing all components; formation of a CAD model of the microscope; experiments to characterize building vibrations and air currents; and the development of software in Visual Basic to simulate holograms and execute reconstruction algorithms for the specific application of confocal holography.
154

Laser surface micro/nano patterning for improving aerodynamic performance

Otanocha, Omonigho January 2016 (has links)
The use of ultrafast lasers in material surface engineering has gained pre-eminence in recent years. This is due to optimal utility arising from their versatility, better process control, repeatability and high precision fabrication, without need for post processing. Reported in this thesis are experimental results on the use of picosecond laser to produce micro-patterns on cyclone components and their effects on flow characteristics. Results show that micro- dimples achieved reduction in dust accumulation within a multi-cyclone system considered, up to 78%. These micro-dimples when applied on the cyclone roof effected a 3% reduction in inlet velocity and 5% reduction on the dynamic pressure across the cyclone, without dust introduction. Results support the possibility for energy savings, without compromise on cyclone overall separation efficiency. Findings further demonstrated the effects of micro-riblets on cyclonic airflow at the wall boundary. Research outcomes supported the view that surface roughness of the cyclone roof could contribute on its dust separation capacity. Injection moulding was used to produce bumps on ABS plastic materials utilising picosecond laser machined micro-dimples on H13 tool steel. A statistical model detailing the interactions between the critical factors involved with picosecond laser interaction with H13 for micro-patterning was proposed. Critical factors identified were laser fluence, scanning speed and number of laser scans. In addition, results demonstrated the suitability of predicting depth of 40 - 100 µm for H13 tool steel, with 96% accuracy. The findings in this research could be explored to develop embedded micro/nano-wires within riblets through injection moulding, to effect electrically biased charging within the internal walls of a cyclone to aid dust separation processes.
155

Novos limites para o parâmetro deTsallis em um espaço de fases não comutativo, gravidade entrópica e equações de Friedmann não extensivas

Paula, Rodrigo Machado de 19 February 2016 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-12-21T14:32:11Z No. of bitstreams: 1 rodrigomachadodepaula.pdf: 916339 bytes, checksum: 430b9be0b67c1ae2c2713dc483ebcfc3 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-12-22T12:52:09Z (GMT) No. of bitstreams: 1 rodrigomachadodepaula.pdf: 916339 bytes, checksum: 430b9be0b67c1ae2c2713dc483ebcfc3 (MD5) / Made available in DSpace on 2016-12-22T12:52:09Z (GMT). No. of bitstreams: 1 rodrigomachadodepaula.pdf: 916339 bytes, checksum: 430b9be0b67c1ae2c2713dc483ebcfc3 (MD5) Previous issue date: 2016-02-19 / Este trabalho foi inspirado pelo artigo [1] “New bounds for Tsallis parameter in a noncommutativephase-spaceentropicgravityandnonextensiveFriedmannequations”. Inicialmente, é apresentada uma nova teoria que deriva a lei de gravitação de Newton, segunda lei e Relatividade Geral do ponto de vista termodinâmico. Além disso, é apresentada a teoria estatística não-extensiva de Tsallis onde sua principal característica é a inserção do parâmetro q que mede o grau de não-extensividade. Novos limites para este parâmetro são calculados, em um espaço de fases não-comutativo. As equações de Friedmann são derivadas a partir do princípio holográfico e uma generalização não-extensiva para estas equações também é apresentada. Ao final, é feita uma análise dos parâmetros cosmológicos incorporando-se propriedades não-extensivas. / This work was inspired by the article [1] “New bounds for Tsallis parameter in a noncommutative phase-space entropic gravity and nonextensive Friedmann equations”. First of all, it is presented a new theory that obtains Newton’s law for gravity, second law and General Relativity from termodynamics. Moreover, it is also presented the Tsallis’s nonextensive statistical theory where the principal feature is the insertion of q parameter which quantifies the degree of nonextensivity. New bounds are obtained for this parameter, in a noncommutative phase-space. The Friedmann equations are developed from holographic principles and a nonextensive generalization for this equations are also presented. Finally, it is made an analyses from cosmological parameters proposing nonextensivity properties.
156

Rekonstrukční metody v holografické mikroskopii / Reconstruction methods in holographic microscopy

Findejsová, Anna January 2019 (has links)
This master’s thesis focuses on the image reconstruction from holographic microscope. The first part of the thesis summarizes problems of holography, describes its principle and application particularly in live cell biology. In the second part the description of several methods used for off-axis hologram reconstruction is provided. The last part describes the implementation of the basic step in holographic reconstruction – the elimination of autocorrelation and twin image – and then also the reconstruction of 3D information of the sample.
157

Příprava a charakterizace nanostruktur s funkčními vlastnostmi v oblasti plazmoniky / Fabrication and characterization of nanostructures with functional properties in the field of plasmonics

Babocký, Jiří January 2020 (has links)
Tato dizertční práce se zabývá výrbou a charakterizací plasmonických nanostruktur. Její první část začíná krátkým úvodem do plasmoniky s navazujícím přehledem metod, které jsou v dnešní době nejčastěji používány k výrobě a charakterizaci plasmonických nanostruktur. Druhá část se pak zaměřuje na samotný výzkum, který byl v rámci PhD studia realizován. Cílem prvních experimentů bylo prozkouat možnosti použití elektronové litografie za variabilního tlaku v procesní komoře pro výrobu plasmonických nanostruktur na nevodivých substrátech jako je např. sklo. Jelikož se jedná o materiály, které jsou velice často používány k přípravě plasmonických struktur pacujících v oblasti viditelného světla. Druhá sekce pak diskutuje některé specifické aspekty přípravy plasmonických mikrostruktur elektronovou litografií pro THz oblast. Poslední část se pak zaměřuje na funkční vlastnosti plasmonických nanostruktur, převážně pak na kvantitativní charakterizaci fáze dalekého pole indukovaného plasmonickými nanostrukturami a jejich aplikacemi v oblasti optických metapovrchů - uměle připravených povrchů, které mohou být použity jako planární optické komponenty. Práce demonstruje a diskutuje různé experimentální přístupy použití mimoosové holografické mikroskopie pro jejich charakterizaci.
158

Optimalizace parametrů optické soustavy digitálního holografického mikroskopu pro odražené světlo. / Optimization of parameters of the optical system of reflected-light digital holographic microscope.

Dostál, Zbyněk January 2009 (has links)
The diploma thesis deals with the construction design of reflective type of holographic microscope together with the proposal for the mechanical imposition of optical elements. Thesis contains parts where the illumination beam tracing through the optical system is calculated and discussed, followed up with the accuracy requirements for rectification mechanisms and their design. The three-dimensional model of modularly solved microscope is presented in conclusion of this thesis together with selected microscope sub-assemblies.
159

Automatizace metody měření povrchových struktur reflexním digitálním holografickým mikroskopem. / Automatization of method of surface structure measurement by means of reflection mode digital holographic microscope.

Vacula, Daniel January 2010 (has links)
Reflected-light digital holographic microscope developed at IPE FME BUT uses off-axis holography principle and low spatial and temporal coherence illumination. Microscope allows reconstruction of the image amplitude and the image phase, which can be handled in real time. The only limiting factors are imaging speed of the detector and computer performance when processing holograms. Reconstruction of image phase and amplitude allows high-resolution profilometric measurements in the vertical axis direction. This thesis deals with the automatization of profilometric measurement method proposed in [2]. Proposed method uses the combination of the image phase and the image amplitude for the measurement of specimens with surface structure the vertical size of which cause the uncertainty of the image phase by a factor of 2pí. Futher the thesis deals with the construction design of the illumination system of the microscope and its realization together with experimental verification of functionality of proposed method automatization.
160

Teoretický popis zobrazení digitálním holografickým mikroskopem / Theoretical description of imaging by a digital holographic microscope

Slabá, Michala January 2010 (has links)
The diploma thesis deals with theory of imaging in a transmitted-light digital holographic microscope using partially coherent illumination. The influence of spatial and temporal coherence state on optical sectioning property is solved. The coherent transfer function is calculated. From this function imaging characteristics for a two-dimensional scattering object are derived depending on its defocus. Two different designs of microscopes developed in the Laboratory of optical microscopy in IPE FME BUT are considered.

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