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 39 for “"Axial resolution"”.
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Methods for optical microscopy beyond conventional limits
… are at odds with the fact that increased resolution necessarily entails a larger light dose. This thesis proposes methods for increasing the resolution of fluorescence microscopy beyond that of the widely employed confocal microscopy while reducing photodamage and phototoxicity. …
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Validation of a Confocal Light Sheet Microscope using Push Broom Translation for Biomedical Applications
… the deep chamber of the R-MHD device, an epitaxial light sheet confocal microscope (e-LSCM) was used to improve axial resolution. The linear sensor, having small pixels, blocked out-of-plane light while eliminating the need for a mechanical aperture which is used for traditional point-scanning …
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Deep structure ultrasound imaging using fundamental and third harmonic coded excitation techniques
… fundamental and third harmonic 1, 3 chirps with resolution enhancement compression (REC) and frequency compounding, increases the axial resolution, lateral resolution, penetration depth and the contrast-to-noise ratio (CNR) for an ultrasonic imaging system. The thickness mode of piezoelectric …
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STED-4Pi Microscopy
… depletion (STED) has been shown to break Abbe's resolution limit in fluorescence microscopy. This technique suppresses fluorescence at the focal rim by use of a depleting laser pulse. In this thesis, theoretical and experimental examinations show that the combination with another technique, …
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Submicron-resolution Photoacoustic Microscopy of Endogenous Light-absorbing Biomolecules
… modalities of photoacoustic imaging, optical-resolution photoacoustic microscopy (OR-PAM) can achieve high spatial resolution, on the order of optical wavelength, at <1 mm depth in biological tissue (the optical ballistic regime). OR-PAM has been applied successfully to structural and …
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Improving ultrasound display by retrieving high-frequency sonographic information
… at a certain depth in tissue is denoted as the axial resolution of the system, which is an important factor in image quality. The axial resolution of ultrasonic B-mode images has been studied by Wagner et al. (1983) and shown to be on the order of the pulse bandwidth. However, a broad pulse …
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Enhanced visualization of retinal pathologies with ultrahigh resolution optical coherence tomography
… than sound waves. OCT can achieve a much higher resolution than ultrasound in measuring the underlying tissue microstructures. Another advantage of OCT is that it can achieve imaging in a non-contact and non-invasive manner. With typical axial resolution of 10 [mu]m, OCT already provides …
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DEVELOPMENT OF NON-CONTACT MICROSPHERE CONFOCAL SCANNING MICROSCOPE
… three-dimensional (3D) imaging. However, the resolution of the confocal laser scanning microscope in the visible spectrum is restricted to be ~180 nm and ~500 nm in the lateral and axial direction respectively due to the optical diffraction. In this thesis, a novel technique, called the …
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Ultrahigh-Resolution Endoscopic Optical Coherence Tomography for In Vivo Mouse Colonoscopy
… deep in tissue. In this work, factors limiting resolution in OCT were examined and devices were created and applied to mouse colon imaging that extended the state-of-the-art in endoscopic ultrahigh-resolution OCT. First, axial chromatic aberration of the objective optics acts as a spectral …
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Improving ultrasonic imaging using novel coded excitation techniques
In ultrasound imaging, the axial resolution depends on the source bandwidth. Recently, a novel coded excitation and pulse compression technique, known as Resolution Enhancement Compression (REC), was developed. REC enhances the -6 dB bandwidth of an ultrasonic imaging system. In this dissertation, …
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System Design And Optimization Of Optical Coherence Tomography
… of the imaging system from two main standpoints: axial point spread function (PSF) and practical steps towards compact low-cost solutions. Up to recently, the criteria for the quality of a system was based on speed of imaging, sensitivity, and particularly axial resolution estimated solely from …
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Swept source optical coherence microscopy for pathological assessment of cancerous tissues
… of biological specimens with cellular resolution. OCM offers a suitable alternative to confocal imaging by providing enhanced contrast due to the additional coherence gate to the inherent confocal gate, increasing the field of view and imaging depth, and eliminating the need of external …
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Non-invasive assessment of biofilm growth in the middle ear using a portable low-coherence interferometry system
… at 940 nm with a bandwidth of 60 nm and the axial resolution of ~ 4.5 um in tissue. Axial scans are acquired in vivo at the rate of 2 kHz and using a custom automated algorithm classified according to microstructural features to provide statistical determination for OM status. Preliminary …
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Ultrahigh-resolution, deep-penetration spectral-domain optical coherence tomography
… structures in samples. With a typical resolution of 10-15 [mu]m and a penetration of up to a few mm, OCT is widely used for medical diagnoses in fields such as ophthalmology and cardiology. However, the more common diagnostic tool in the microscopic regime of medical imaging is …
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Improvements to the acoustic pulse reflectometry technique for measuring duct dimensions
… is shown to lead to bore reconstructions of high axial resolution, allowing rapid changes in cross-sectional area to be more accurately reproduced. Finally, limitations of the acoustic pulse reflectometry technique (particularly those brought about by the bandwidth improvements) are discussed and …
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Advanced functional and intraoperative ophthalmic optical coherence tomography imaging
… uses optical interferometry to generate high-resolution, depth-resolved images of tissue in vivo. Ophthalmologists now use commercial OCT systems as a standard diagnostic instrument for imaging the retina to detect or monitor pathologies. However, prototype OCT research instruments exceed …
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Three-Dimensional Microscopy by Laser Scanning and Multi-Wavelength Digital Holography
… a simple, low-cost method of achieving the resolution on the order of a micron. A further gain in terms of resolution and the depth of focus by using Bessel rather than Gaussian beams is discussed. Then, a phase-imaging technique to quantitatively study the three-dimensional structure of …
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Adaptive multiscale biological signal processing
… quality assessment, contrast gain estimation and resolution gain quantification as well as visual inspection highlighted very good results featured by the proposed ultrasound image deconvolution and restoring algorithms: axial resolution up to 5 times better than algorithms in literature are …
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High-speed Fourier domain Optical Coherence Tomography for structural and functional imaging of the retina
… tissue with high sensitivity and micron-scale resolution. In conventional OCT, the reference arm path length in a Michelson interferometer is scanned in time to generate a profile of backscattering versus depth from the sample arm. In conventional OCT, a broadband, low coherence light source is …
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