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 13 of 13 for “"Coherent Imaging"”.
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Stroboscopic Inline Coherent Imaging
Inline coherent imaging (ICI) is an in-situ monitoring technique, used in laser processing applications such as welding and additive manufacturing. Conventional ICI systems image with a continuous-wave broadband light source, which makes the system susceptible to an effect known as motion artifact. …
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Inline Coherent Imaging of Laser Additive Manufacturing
… In this thesis a low-coherence interferometric imaging technique, termed inline coherent imaging (ICI), is integrated into the selective laser melting process to monitor melt pool morphology changes and stability at 200 kHz with axial and transverse resolutions reaching 6 µm and 35 µm …
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Monitoring Material Modification using Inline Coherent Imaging
… in situ metrology is required. In this work, a coherent imaging technique analogous to spectral domain optical coherence tomography (SD-OCT) was applied inline with a machining laser in order to monitor the cut development of various materials for industrial and biomedical applications. Such …
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Homodyne High-harmonic Spectroscopy: Coherent Imaging of a Unimolecular Chemical Reaction
… based on charged particle detection, to a fully coherent one, based on light characterization. The main achievement presented in this thesis is to use high harmonic generation to probe femtosecond (femto=10^-15) chemical dynamics for the first time. Thanks to the coherence imposed by the strong …
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Ablation of Steel by Microsecond Pulse Trains
… changes to melt and vapour ejection. Inline coherent imaging (ICI), a broadband, spatially-coherent imaging technique, is used to monitor the ablation process. The pulse parameter space is explored and the key regimes are determined. Material removal is observed when the pulse delay is on the …
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Quantification and Reconstruction in Photoacoustic Tomography
… considered ubiquitous in all scattering-based coherent imaging technologies. As a coherent imaging modality based on optical absorption, photoacoustic: PA) tomography: PAT) is generally devoid of speckles. PAT suppresses speckles by building up prominent boundary signals, via a mechanism …
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Generating pictures from waves : aspects of image formation
… vision and graphics researchers analyze incoherent light using coarse geometric approximations from optics. On the other hand, array signal processing and acoustics researchers analyze coherent sound waves using stochastic estimation theory and diffraction formulas from physics. The ability …
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Techniques for Approximating Optimal Linear Estimators of Multidimensional Data
… the speckle noise that is characteristic of coherent imaging. Next, a blind estimator for fMRI data is constructed that significantly improves the ability to detect low CNR functional activation in small regions of activation without a compromise to the false detection rate. Finally, the …
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Scaling and Gating Attosecond Pulse Generation
… basis for attosecond light sources delivering coherent pulses in the extreme ultraviolet spectral region. Such light sources are employed for a variety of applications within imaging, attosecond spectroscopy, and high-precision frequency metrology. However, the rather low efficiency of the HHG …
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Highly Efficient Thermal Ablation of Silicon and Ablation in Other Materials
… cost. The work here shows that by combining an imaging technique frequently used in ophthalmology called optical coherence tomography (OCT) with a machining platform, in situ observation of ablation can be made. This combination, known as in-line coherent imaging (ICI), allows information to be …
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Studying Electronic Textures with Coherent Lensless Imaging
… years, research has exploded into the use of coherent x-ray light to improve the quality and resolution of x-ray microscopes. In many cases, using coherent light makes it possible to remove the objective lens in a microscope, replacing it with an algorithmic analysis of the direct scattering …
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High-resolution 3-D refractive index imaging and Its biological applications
This thesis presents a theory of 3-D imaging in partially coherent light under a non-paraxial condition. The transmission cross-coefficient (TCC) has been used to characterize partially coherent imaging in a 2- D and 3-D paraxial model. It is shown that the 3-D TCC under the non-paraxial condition …
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Computational optical coherence tomography for polarization-sensitive imaging, aberration correction, and wavefront measurement
… multiple longstanding challenges in optical imaging are solved by the development of new computational imaging methods, where computational imaging does not simply refer to simulation or modeling, but to the entirety of an imaging technology in which significant computation is required to …