Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 22 for “"Fresnel zone"”.
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Image grating metrology using a Fresnel zone plate
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003.
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Multipath "Fresnel Zone" Routing for Wireless Ad Hoc Networks
… In this work, we propose the multipath “Fresnel zone” routing (FZR) algorithm for wireless ad hoc networks. FZR constructs multiple parallel paths from source to destination based on the concept of “Fresnel zones” in a wireless network. The zone construction method assigns intermediate …
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Theory and design of integrated optical isolators and broadband couplers using Fresnel zone plates
… vertical coupler. The structure utilizes a Fresnel lens, or more advanced integrated optics, placed above a short, ridge and deep etched, vertical coupler in a Si waveguide. This optics is placed in order to match the radiating fields to the fiber mode. We use semivectorial simulations with …
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Resolving Small Objects Using Seismic Traveltime Tomography
It is often claimed that the first Fresnel zone associated with the dominant frequency represents the spatial resolution limit of traveltime tomography. We show, however, that the relevant Fresnel limit for tomographic resolution is the maximum, not the dominant frequency in the data. For …
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Twin-image problems in optical scanning holography
… beam can be a time-dependent Gaussian apodized Fresnel zone pattern. We derive the resolution achievable with such a scanning beam. We then discuss the use of a larger and a smaller Fresnel zone pattern for holographic recording to investigate twin-image noise which results in the unwanted image …
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Characteristics of different focusing antennas in the near field region
… such as array antennas, reflector antennas and Fresnel zone plate (FZP) antennas have been used for these applications. Here, first, a new scheme in designing focused array antennas with desired sidelobe levels (SLLs) in the near field region is presented. The performance of the large focused …
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Femtosecond laser micro-machining and consequent self-assembled nano-structures in transparent materials
… directly written diffractive optic devices (Fresnel zone plates) embedded in a silica substrate. Both the focusing properties and efficiencies of the devices compared well with the theoretical values.
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Integrated diffractive optical elements for terahertz beam shaping and polarization control /
… the research introduces hybrid multi-phase Fresnel zone plate (H-MPZP) lenses with reduced structural complexity and enhanced focusing performance, high contrast grating (HCG) waveplates with sinusoidal surface modulation for broadband polarization manipulation, and free-standing …
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Detection and identification of converted modes and source independent converted phase imaging : Groningen, The Netherlands
… is shown to correlate well with the estimated Fresnel Zone dimension for the interface depth and data frequency. By using a kinematic version of the Source Independent Converted Phase Imaging Condition, we can map those interfaces. The positions of the interfaces are shown to correlate well …
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Investigations of Horizontal-Parallax-Only Optical Scanning Holography (HPO-OSH) through MATLAB Simulations
… The holograms are simulated by convolving the Fresnel zone plates (FZP) with the object. The simulations focus on generating HPO holograms using 1-D FZPs modeled as 1-D Gaussian chirp beams of varying waists. An optical reconstruction scheme by cylindrical lens was proposed and simulated. …
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Performance and Analysis of a Deployable Diffractive Optical Element for Small Satellite Missions
… contrasts geometric and wave-optical models for Fresnel zone plates and multilevel diffractive lenses, leading to quantitative predictions of diffraction efficiency and PSF quality under non-idealities. A key contribution is the analytical and numerical analysis of how uniform thickness errors, …
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Micro-optic elements for a compact opto-electronic integrated neural coprocessor
… an optical element based on the concept of the Fresnel Zone Plate was developed and experimentally tested. The zone plate based elements offer an easily scalable method for fabricating the COIN optical interconnects using standard lithographic processes and appear to be the best choice for the …
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Three-Dimensional Fluorescence Microscopy by Optical Scanning Holography
… heterodyned laser field consisting of a Fresnel zone pattern. A unique acousto-optic modulator configuration is employed to generate a suitable heterodyne frequency for excitation of the fluorescent object. The optical response of a solution containing a high concentration of 15 um …
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Microelectromechanical handheld laser-scanning confocal microscope: application to breast cancer imaging
… dimensions, employing reflective binary-phase Fresnel zone plates monolithically integrated on the surface of the micromirror is presented.
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Characterization of liquid crystal on silicon SLMs for in-situ Raman imaging for quality control of processed lunar regolith
… for Raman spectroscopy is possible by using Fresnel zone plates (FZP) superimposed by phase gradients mapped on the LCoS, which is an analytically computable and well understood method. In the presented work, a characterization and modelling of a LCoS is carried out with respect to the …
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Acoustic scattering of spherical directional waves by smooth and statistically rough solid elastic cylinders
… they insonify a target over a finite number of Fresnel zones and span a continuum of oblique incident angles, even when the center of the beam is at normal incidence. These effects strongly influence both the overall scattered pressure levels and resonances. For example, because of the spreading …
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Femtosekunden-Spektroskopie biologischer Systeme mittels kohärenter Kontrolle
… and theory. The novel phenomenon of a Fresnel zone plate in the time domain is first developed in theory and then successfully realised in experiment.
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Acoustic scattering of spherical directional waves by smooth and statistically rough solid elastic cylinders
… they insonify a target over a finite number of Fresnel zones and span a continuum of oblique incident angles, even when the center of the beam is at normal incidence. These effects strongly influence both the overall scattered pressure levels and resonances. For example, because of the spreading …
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Photogating Effect and Diffractive Optics in Low-Dimensional Structures
… transistors (GFETs) as well as multi-level Fresnel zone plates (MLFZPs) are provided in detail. The photogating effect, understood as the ability of charge carriers to generate photocurrent when excited by an incident photon within a material, is crucial to the device physics of GFETs. We …
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