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 “"depth-of-focus"”.
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Laser Scanning Imaging for Increased Depth-Of-Focus
… techniques have been proposed to improve the depth-of-focus in optical microscopy. Common techniques like optical sectioning microscopy and scanning confocal microscopy have innate problems. By simply modifying the pupil function in microscope imaging system, we can also extend the …
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Extending the depth of focus using digital image filtering
Two types of image processing methods capable of forming a composite image from a set of image slices which have in-focus as well as out-of-focus segments are discussed. The first type is based on space domain operations and has been discussed in the literature. The second type, to be introduced, …
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Extended Depth-of-focus in a Laser Scanning System Employing a Synthesized Difference-of-Gaussians Pupil
… used for microscopy, typically image objects of finite thickness. If the depth-of-focus of such systems is low, as is the case when a simple clear pupil is used, the object must be very thin or the image will be distorted. Several methods have been developed to deal with this problem. A …
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An optical/digital incoherent image processing system for an extended depth of field
A severely defocused incoherent system has isolated zeros in its optical transfer function(OTF); therefore, an exact inverse filtering cannot be performed. It has been established that, by using an annular aperture in an optical system, the depth of focus can be extended. Isolated zeros in the OTF …
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Assessment of Ocular Accommodation in Humans
Accommodation is the change in the dioptric power of the eye altering the focus from distance to near. Presbyopia is the loss of accommodative function that occurs with age. There are many techniques used to measure accommodation, however, there is little consensus as to how clinical data should be …
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Developmental tissue dynamics using non-diffracting light-sheet microscopy
The development of a new organism is one of the most complex processes in biology. Observing this process in vivo is a prerequisite for many quantitative studies, but requires imaging techniques with a high spatio-temporal resolution that do not affect the development of the sample. Light-sheet …
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Multi-contrast Photoacoustic Microscopy
… with high spatial resolution, moderate imaging depth, excellent imaging contrast and functional imaging capability. Taking full advantage of this powerful weapon, we have investigated different anatomical, functional, flow dynamic and metabolic parameter measurements using photoacoustic …
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Development of an immersion maskless lithography system
… its limits with current technologies, a host of new ideas is being proposed in hopes of pushing lithography to new levels of performance. The work presented in this thesis explores the use of an immersion scheme to improve the performance of a maskless lithographic technique known as …
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Interferometric Synthetic Aperture Microscopy (ISAM) Reconstruction and Characterization in a High Numerical Aperture System
… (OCM) is an imaging modality that is capable of visualizing structural features of biological samples at high resolution based on their scattering properties. Interferometric synthetic aperture microscopy (ISAM) is a newer technique that can overcome the typical dependence between lateral …
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IMAGING INTERFEROMETRIC MICROSCOPY TO THE LIMITS OF AVAILABLE FREQUENCY SPACE
… (IIM) is a synthetic aperture approach offering the potential of optical resolution to the linear systems limit of optics (~lambda/4n). IIM allows one to resolve structures not accessible in a conventional illumination setup, while using a low NA microscope objective and thus keeping the …
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The effect of the oxygen inhibition layer on interfacial bond strengths and stain resistance of dental resin composites
The free-radical polymerisation reactions of photoactive resins used in dentistry are inhibited by oxygen. There is a need to better understand the effects oxygen inhibition on critical properties of dental resins and resin composites which may compromise the success of dental resin composite …
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Development and translation of label-free functional microscopy based on optical coherence tomography
… endogenous functional contrasts. This thesis focuses on the development and translation of angiographic and polarization sensitive (PS) OCT techniques for clinical and preclinical applications. This goal includes four specific aims. The first aim is to develop a clinical imaging system to …
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Three-Dimensional Microscopy by Laser Scanning and Multi-Wavelength Digital Holography
This dissertation presents techniques of three-dimensional microscopy. First, an economical method of microscopic image formation that employs a raster-scanning laser beam focused on a sample, while non-imaging detector receives the scattered light is presented. The images produced by this method …
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Portal Imaging Using a CSI (TL) Scintillator Coupled to a Cooled CCD Camera
<p>The purpose of this research was to design a high performance digital portal imaging <br />system, using a transparent x-ray scintillator coupled to a cooled CCD camera. Theoretical <br />analysis using Monte Carlo simulation was performed to calculate the QDE, SNR and DQE of <br />the system. A …
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Development of Three-Dimensional Super-Resolution Imaging Using a Double-Helix Point Spread Function
… the diffraction limit. The intrinsic 3D nature of biology has motivated the development of 3D-SMLM with novel techniques, including the double-helix point spread function (DHPSF). A bespoke microscope platform employing the DHPSF transformation was built, achieving ~10 nm lateral and ~20 nm …
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Acoustic Radiation Force on a Fluid to Fluid Boundary by Phase Plate Focused Ultrasound
In this study, the physics and applications of the ultrasonic radiation force at the interface between two immiscible fluids were investigated. These studies were performed using low-profile discrete-stepped lenses to the modify the phase of the incident radiation generating multiple field …
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COHERENT DETECTION OF SCATTERED LIGHT BY SUBMICROMETER AEROSOLS.
… directly measured. COPS uses the coherent nature of light available in a laser beam to measure the phase shift in the scattered light, which is fundamentally different from previous intensity based techniques. The Van-Cittert-Zernike theorem shows that scattered light from small particles will be …
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Optimization of the holographic process for imaging and lithography
… have demonstrated to be important components of a variety of optical systems and their implementation in new fields and methods is expected to continue growing. Their ability to encode 3D optical fields on a 2D plane opened the possibility of novel applications for imaging and lithography. In …
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Fabrication and Dynamic Tuning of Periodic Structures From Holographic Lithography
… was generated due to microphase separation of the polymer chain segments in nonsolvents during rinsing, which could be tuned by crosslinking density of the polymer and choice of solvents. Such structure offers opportunities to realize superhydrophobicity, enhanced dye adsorption in addition …
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Magnetic mitigation of energetic ions for extreme ultraviolet lithography sources
… known as Moore’s Law by doubling the number of transistors that can fit on a given area every two years. Moore’s Law has been obeyed with remarkable reliability. Now, however, the future of Moore’s Law is in doubt, as current methods of semiconductor manufacturing have reached their limits. …
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