Dissertations / Theses: 'Photonic imaging'

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Stumpf, Wolfgang. "High resolution imaging of photonic crystals." [S.l. : s.n.], 2004. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11051695.

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McCrindle, Iain James Hugh. "Structured photonic materials for multi-spectral imaging applications." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6446/.

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Structured photonic materials are typically composed of periodic subwavelength elements where the unit cell geometries can impact the overall optical characteristics of the bulk material. By using micro and nanofabrication technologies it is possible to engineer the electromagnetic properties of structured photonic materials for a given application and create a variety of optical components such as band pass filters and absorbers. Two structured photonic materials that have gained substantial interest in recent years are plasmonic filters and metamaterials which are well suited for optical and terahertz imaging applications, respectively. In addition to imaging applications within individual wavebands, structured photonic materials, such as plasmonic filters and metamaterials, could be hybridised and combined with suitable sensors to create a multi-spectral imaging system capable of imaging at optical and terahertz wavebands simultaneously. These new hybrid structured photonic materials are known as synthetic multi-spectral materials, and their development will be presented in this work. To design synthetic multi-spectral materials it was necessary to optimise the plasmonic filter and metamaterial components independently. This involved electromagnetic simulation studies using finite-difference time-domain techniques, fabrication of the structured materials and characterisation using suitable techniques for the relevant spectral band. It was also necessary to ensure that all structures used the same materials and similar fabrication processing techniques as a means of simplifying hybridisation of the two structures. Plasmonic filters exhibit extraordinary optical transmission due to coupling of light with surface plasmons at a metal-dielectric interface. A 16 colour plasmonic filter set, consisting of triangular hole arrays etched into an aluminium film, was optimised for imaging applications in the visible and near infrared spectral range. Initial work on the integration of synthetic multi-spectral materials with CMOS image sensors was undertaken by developing fabrication processes to integrate plasmonic colour filters with two different CMOS chips. Preliminary results from the characterisation of the optical filters fabricated on to the chips have been presented. The resonant wavelengths of the plasmonic colour filters were then scaled up to infrared wavelengths where it was necessary to consider the role of spoof surface plasmons on the extraordinary optical transmission phenomenon. This led to the fabrication of 8 short wave infrared plasmonic filters. Metamaterial band pass filters consist of a single metal film etched with a periodic complementary electric ring resonator unit cell structure. Metamaterial absorbers consist of an electric ring resonator, separated by a metallic ground layer by a dielectric spacer. In the course of this work, two metamaterial filters and four metamaterial absorbers were designed. The metamaterial structures exhibit resonant characteristics at terahertz frequencies. Three synthetic multi-spectral materials, each consisting of hybrid plasmonic filter and terahertz metamaterial structures, have been simulated, fabricated and characterised. The first synthetic multi-spectral material combines 16 plasmonic filters with a terahertz metamaterial filter and is capable of filtering 15 optical wavelengths and a single near infrared wavelength, whilst simultaneously filtering a single terahertz frequency. The multi-spectral filter demonstrates that it is possible to engineer the optical passband characteristics of a thin metal film over several decades of wavelength using a single electron beam lithography step. The second synthetic multi-spectral material consists of 16 plasmonic filters hybridised with a terahertz metamaterial absorber and can filter 15 optical wavelengths and a single near infrared wavelength whilst simultaneously absorbing a single terahertz frequency. Plasmonic filters and metamaterial absorbers are promising components for use in the development of new optical and terahertz imaging systems, respectively, and therefore the second synthetic multi-spectral material represents a significant step forward in the development of a visible and terahertz multi-spectral camera. The third synthetic multi-spectral material combines 7 plasmonic filters with a low metal fill factor metamaterial absorber, to increase the measured transmission of the plasmonic filter components. The third synthetic multi-spectral material is capable of filtering three optical wavelengths, a single near infrared wavelength, a single short wave infrared wavelength and two mid infrared wavelengths, whilst simultaneously absorbing a single terahertz frequency. Such a synthetic multi-spectral material could aid in the development of a visible, infrared and terahertz multi-spectral camera.

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Sriram, Paturi Atreya. "Image Contrast Enhancement using Biomolecular Photonic Contrast Agents and Polarimetric Imaging Principles." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1203118139.

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Paturi, Sriram Atreya. "Image Contrast Enhancement Using Biomolecular Photonic Contrast Agents and Polarimetric Imaging Principles." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1204225545.

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Lee, Seoungjun. "Super-resolution optical imaging using microsphere nanoscopy." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/superresolution-optical-imaging-using-microsphere-nanoscopy(c3b36c86-11b5-4c77-9a69-b966585b0509).html.

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Standard optical microscopes cannot resolve images below 200 nm within the visible wavelengths due to optical diffraction limit. This Thesis reports an investigation into super-resolution imaging beyond the optical diffraction limit by microsphere optical nano-scopy (MONS) and submerged microsphere optical nano-scopy (SMON). The effect of microsphere size, material and the liquid type as well as light illumination conditions and focal plane positions on imaging resolution and magnification have been studied for imaging both biological (viruses and cells) and non-biological (Blu-ray disk patterns and nano-pores of anodised aluminium oxide) samples. In particular, sub-surface imaging of nano-structures (data-recorded Blu-ray) that cannot even be seen by a scanning electron microscope (SEM) has been demonstrated using the SMON technique. Adenoviruses of 75 nm in size have been observed with white light optical microscopy for the first time. High refractive index microsphere materials such as BaTiO3 (refractive index n = 1.9) and TiO2-BaO-ZnO (refractive index n = 2.2) were investigated for the first time for the imaging. The super-resolution imaging of sub-diffraction-limited objects is strongly influenced by the relationship between the far-field propagating wave and the near-field evanescent waves. The diffraction limit free evanescent waves are the key to achieving super-resolution imaging. This work shows that the MONS and SMON techniques can generate super-resolution through converting evanescent waves into propagating wave. The optical interactions with the microspheres were simulated using special software (DSIMie) and finite different in time domain numerical analysis software (CST Microwave Studio). The optical field structures are observed in the near-field of a microsphere. The photonic nanojets waist and the distance between single dielectric microsphere and maximum intensity position were calculated. The theoretical modelling was calculated for comparisons with experimental measurements in order to develop and discover super-resolution potential.

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Wagner, Rebecca. "Local Structural and Optical Characterization of Photonic Crystals by Back Focal Plane Imaging and Spectroscopy." Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-164382.

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This thesis establishes methods to locally and effciently detect the fluorescence from photonic crystals (PCs) in dependence on wavelength and direction. These are applied to three dimensional (3D) PCs grown by vertical deposition of polystyrene beads. The experiments allow conclusions about the local 3D structure of a sample, about defects in its volume and about spatial structural variations. They thus provide more information than typical spectroscopy measurements that average over large areas and methods that only image the surface structure like scanning electron microscopy. A focused laser is used to excite emitters in the sample only locally. The fluorescence is then collected by a microscope objective. Every point in this objective’s back focal plane (BFP) corresponds to a certain direction. This property is utilized in two ways. When observing a small spectral range of the emission in the BFP, stop bands appear as intensity minima since they hinder the emission into the corresponding directions. Thus, back focal plane imaging (BFPI) allows to visualize stop bands of many directions at the same time. The detected patterns permit to find the in-plane and out-of-plane orientation of the PC lattice and to conclude on the presence of stacking faults. Spatial variations of the structure are observed on a length scale of a few micrometers. The depth of the stop band is reduced at sample positions, where structural changes occur. In back focal plane spectroscopy (BFPS), a slit selects light from certain points in the BFP, which is spectrally dispersed subsequently. This allows to record spectra from many directions simultaneously. From them, a lattice compression along the sample normal of about 4% is found. Small deformations are also observed for other directions. Scattering at defects redistributes the emission. This increases the detected intensity compared to homogeneous media at some stop band edges in a broad spectral range for samples thicker than the scattering mean free path. Thinner samples show a narrow enhancement due to an increase in the fractional density of optical states and thus in emission. BFPI and BFPS are also used to observe the growth of PCs from drying droplets. The experiments show that the beads initially form a non-close packed lattice. This causes stress as the lattice constant decreases, which is released by cracking of the PCs.

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Fu, Ling, and n/a. "Fibre-optic nonlinear optical microscopy and endoscopy." Swinburne University of Technology, 2007. http://adt.lib.swin.edu.au./public/adt-VSWT20070521.155004.

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Cancer is a major health problem in the world today. Almost all cancers have a significantly better chance for therapy and recovery if detected at their early stage. The capability to perform disease diagnosis at an early stage requires high-resolution imaging that can visualise the physiological and morphological changes at a cellular level. However, resolving powers of current medical imaging systems are limited to sub-millimeter sizes. Furthermore, the majority of cancers are associated with morphological and functional alterations of cells in epithelial tissue, currently assessed by invasive and time-consuming biopsy. Optical imaging enables visualisations of tissue microstructures at the level of histology in non-invasive means. Optical imaging is suitable for detecting neoplastic changes with sub-cellular resolution in vivo without the need for biopsy. Nonlinear optical microscopy based on multi-photon absorption and higher harmonic generation has provided spectacular sights into visualisation of cellular events within live tissue due to advantages of an inherent sectioning ability, the relatively deep optical penetration, and the direct visualisation of intrinsic indicators. Two-photon excited uorescence (TPEF) from intrinsic cell components and second harmonic from asymmetric supermolecular structures can provide complementary information regarding functionalities and morphologies in tissue environments, thus enabling premalignant diagnosis by detecting the very earliest changes in cellular structures. During the past sixteen years, nonlinear optical microscopy has evolved from a photonic novelty to a well-established laboratory tool. At present, in vivo imaging and long-term bedside studies by use of nonlinear optical microscopy have been limited due to the fact that the lack of the compact nonlinear optical instrument/imaging technique forces the performance of nonlinear optical microscopy with bulk optics on the bench top. Rapid developments of fibre-optics components in terms of growing functionalities and decreasing sizes provide enormous opportunities for innovation in nonlinear optical microscopy. Fibre-based nonlinear optical endoscopy will be the soul instrumentation to permit the cellular imaging within hollow tissue tracts or solid organs that are inaccessible with a conventional optical microscope. Lots of efforts have been made for development of miniaturised nonlinear optical microscopy. However, there are major challenges remaining to create a nonlinear optical endoscope applicable within internal cavities of a body. First, an excitation laser beam with an ultrashort pulse width should be delivered eciently to a remote place where ecient collection of faint nonlinear optical signals from biological samples is required. Second, laser-scanning mechanisms adopted in such a miniaturised instrumentation should permit size reduction to a millimeter scale and enable fast scanning rates for monitoring biological processes. Finally, the design of a nonlinear optical endoscope based on micro-optics must maintain great exibility and compact size to be incorporated into endoscopes to image internal organs. Although there are obvious diculties, development of fibre-optic nonlinear optical microscopy/endoscopy would be indispensible to innovate conventional nonlinear optical microscopy, and therefore make a significant impact on medical diagnosis. The work conducted in this thesis demonstrates the new capability of nonlinear optical endoscopy based on a single-mode fibre (SMF) coupler or a double-clad photonic crystal fibre (PCF), a microelectromechanical system (MEMS) mirror, and a gradientindex (GRIN) lens. The feasibility of all-fibre nonlinear optical endoscopy is also demonstrated by the further integration of a double-clad PCF coupler. The thesis concentrates on the following key areas in order to exploit and understand the new imaging modality. It has been known from the previous studies that an SMF coupler is suitable for twoii photon excitation by transmitting near infrared illumination and collecting uorescence at visible wavelength as well. Although second harmonic generation (SHG) wavelength is farther away from the designed wavelength of the fibre coupler than that of normal TPEF, it is demonstrated in this thesis that both SHG and TPEF signals can be collected simultaneously and eciently through an SMF coupler with axial resolution of 1.8 um and 2.1 um, respectively. The fibre coupler shows a unique feature of linear polarisation preservation along the birefringent axis over the near infrared and the visible wavelength regions. Therefore, SHG polarisation anisotropy can be potentially extracted for probing the orientation of structural proteins in tissue. Furthermore, this thesis shows the characterisation of nonlinear optical microscopy based on the separation distance of an SMF coupler and a GRIN lens. Consequently, the collection of nonlinear signals has been optimised after the investigation of the intrinsic trade-off between signal level and axial resolution. These phenomena have been theoretically explored in this thesis through formalisation and numerical analysis of the three-dimensional (3D) coherent transfer function for a SHG microscope based on an SMF coupler. It has been discovered that a fibreoptic SHG microscope exhibits the same spatial frequency passband as that of a fibreoptic reection-mode non-uorescence microscope. When the numerical aperture of the fibre is much larger than the convergent angle of the illumination on the fibre aperture, the performance of fibre-optic SHG microscopy behaves as confocal SHG microscopy. Furthermore, it has been shown in both analysis and experiments that axial resolution in fibre-optic SHG microscopy is dependent on the normalised fibre spot size parameters. For a given illumination wavelength, axial resolution has an improvement of approximately 7% compared with TPEF microscopy using an SMF coupler. Although an SMF enables the delivery of a high quality laser beam and an enhanced sectioning capability, the low numerical aperture and the finite core size of an SMF give rise to a restricted sensitivity of a nonlinear optical microscope system. The key innovation demonstrated in this thesis is a significant signal enhancement of a nonlinear optical endoscope by use of a double-clad PCF. This thesis has characterised properties of our custom-designed double-clad PCF in order to construct a 3D nonlinear optical microscope. It has been shown that both the TPEF and SHG signal levels in a PCF-based system that has an optical sectioning property for 3D imaging can be significantly improved by two orders of magnitude in comparison with those in an SMF-based microscope. Furthermore, in contrast with the system using an SMF, simultaneous optimisations of axial resolution and signal level can be obtained by use of double-clad PCFs. More importantly, using a MEMS mirror as the scanning unit and a GRIN lens to produce a fast scanning focal spot, the concept of nonlinear optical endoscopy based on a double-clad PCF, a MEMS mirror and a GRIN lens has been experimentally demonstrated. The ability of the nonlinear optical endoscope to perform high-resolution 3D imaging in deep tissue has also been shown. A novel three-port double-clad PCF coupler has been developed in this thesis to achieve self-alignment and further replace bulk optics for an all-fibre endoscopic system. The double-clad PCF coupler exhibits the property of splitting the laser power as well as the separation of a near infrared single-mode beam from a visible multimode beam, showing advantages for compact nonlinear optical microscopy that cannot be achieved from an SMF coupler. A compact nonlinear optical microscope based on the doubleclad PCF coupler has been constructed in conjunction with a GRIN lens, demonstrating high-resolution 3D TPEF and SHG images with the axial resolution of approximately 10 m. Such a PCF coupler can be useful not only for a fibre-optic nonlinear optical probe but also for double-clad fibre lasers and amplifiers. The work presented in this thesis has led to the possibility of a new imaging device to complement current non-invasive imaging techniques and optical biopsy for cancer detection if an ultrashort-pulsed fibre laser is integrated and the commercialisation of the system is achieved. This technology will enable in vivo visualisations of functional and morphological changes of tissue at the microscopic level rather than direct observations with a traditional instrument at the macroscopic level. One can anticipate the progress in bre-optic nonlinear optical imaging that will propel imaging applications that require both miniaturisation and great functionality.

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Lombardini, Alberto. "Nonlinear optical endoscopy with micro-structured photonic crystal fibers." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4377.

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Dans cette thèse, nous proposons l'utilisation d'un nouveau type de fibre à cristal photonique, la fibre Kagomé à coeur creux, pour la livraison d'impulsions ultra-courtes en endoscopie non linéaire. Ces fibres permettent la livraison d'impulsions sans distorsion sur une large bande spectrale, avec un faible bruit de fond, grâce à la propagation dans le cœur creux. Nous avons résolu le problème de la résolution spatiale, à l'aide d'une microbille en silice, insérée dans le cœur de la fibre Kagomé. Nous avons développé un système d'imagerie compacte, qui utilise un tube piézo-électrique pour le balayage du faisceau, un système achromatiques de microlentilles et une fibre Kagomé double gaine, spécialement conçue pour l'endoscopie. Avec ce système, nous avons réussi à imager des tissus biologiques, à l'extrémité distale de la fibre (endoscopie), en utilisant des différentes techniques tels que TPEF, SHG et CARS, un résultat qui ne trouve pas d'égal dans la littérature actuelle. L'intégration dans une sonde portable (4,2 mm de diamètre) montre le potentiel de ce système pour de futures applications en endoscopie multimodale in-vivo In this thesis, we propose the use of a novel type of photonic crystal fiber, the Kagomé lattice hollow core fiber, for the delivery of ultra-short pulses in nonlinear endoscopy. These fibers allow undistorted pulse delivery, over a broad transmission window, with minimum background signal generated in the fiber, thanks to the propagation in a hollow-core. We solved the problem of spatial resolution, by means of a silica micro-bead inserted in the Kagomé fiber large core. We have developed a miniature imaging system, based on a piezo-electric tube scanner, an achromatic micro-lenses assembly and a specifically designed Kagomé double-clad fiber. With this system we were able to image biological tissues, in endoscope modality, activating different contrasts such as TPEF, SHG and CARS, at the distal end of the fiber, a result which finds no equal in current literature. The integration in a portable probe (4.2 mm in diameter) shows the potential of this system for future in-vivo multimodal endoscopy

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Schell, Andreas Wolfgang. "Photonic applications and hybrid integration of single nitrogen vacancy centres in nanodiamond." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17128.

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In dieser Arbeit wird das Stickstoff-Fehlstellenzentrum (NV Zentrum) in Diamant als ein solcher Einzelphotonenemitter untersucht. Durch Benutzung eines hybriden Ansatzes werden hier NV Zentren in Diamantnanopartikeln in photonische Strukturen integriert. Zuerst wird eine aufnehmen-und-ablegen-Nanomanipulationstechnik mittels eines Rasterkraftmikroskops verwendet um einzelne NV Zentren an eine photonische Kristallkavität und eine optische Faser zu koppeln. Durch Kopplung an die photonische Kristallkavität wird die Emission der Nullphononenlinie des NV Zentrums um den Faktor 12.1 erhöht und durch Kopplung an die optische Faser entsteht eine direkt gekoppelte Einzelphotonenquelle hoher effektiver numerischer Apertur. Durch Kopplung an plamonische Wellenleiter können einzelne Oberflächenplasmon-Polaritonen nachgewiesen werden. Zweitens wird ein anderer Ansatz, die Entwicklung eines hybriden Materials, verfolgt. Hier sind die Nanodiamanten, anstatt sie auf die Strukturen von Interesse zu legen, von Anfang in dem Material enthalten, aus dem die Strukturen hergestellt werden. Mittels direktem Zweiphotonen-Laserschreiben ist es dann möglich, Kombinationen aus chipintegrierten Wellenleitern, Resonatoren und Einzelphotonenemittern zu zeigen. Um mehr über die Dynamik von NV Zentren in Nanodiamant zu erfahren und Wege zu ihrer Verbesserung zu finden, wird die Dynamik der Nullphononenlinie des NV Zentrums mittels eines Photonenkorrelationsinterferometers untersucht. Zusätzlich zu Techniken zur Herstellung photonischer und plasmonischer Strukturen werden auch Methoden zu ihrer Charakterisierung benötigt. Hier für kann es ausgenutzt werden, dass das NV Zentrum weiter nicht nur ein Einzelphotonenemitters ist, sondern es ebenso als Sensor verwendet werden kann. Das NV Zentrum wird hier verwendet, um die lokale optische Zustandsdichte in einem Rastersondenverfahren zu messen, was die Technik der dreidimensionalen Quantenemitter Fluoreszenzlebensdauermikroskopie einführt. In this thesis, one of such single photon emitters, the nitrogen vacancy centre (NV centre) in diamond, will be examined. By using different hybrid approaches, NV centres in diamond nanoparticles are integrated into photonic structures. Firstly, using a pick-and-place nanomanipulation technique with an atomic force microscope, a single NV centre is coupled to a photonic crystal cavity and an optical fibre. Coupling to the photonic crystal cavity results in an enhancement of the NV centre''s zero phonon line by a factor of 12.1 and coupling to the fibre yields a directly coupled single photon source with an effective numerical aperture of 0.82. By coupling to plasmonic waveguides, the signature of single surface plasmon polaritons is found. Secondly, instead of placing the nanodiamonds on the structures of interest, a hybrid material where the emitters are incorporated is used. With two-photon direct laser writing, on-chip integration and combination of waveguides, resonators, and single photon emitters is demonstrated. In order to learn more on the dynamics of NV centre in nanodiamonds and find ways for improvements, the dynamics of the ultra-fast spectral diffusion of the NV centre''s zero phonon line are investigated using a photon correlation interferometer. In addition to techniques for the fabrication of photonic and plasmonic structures, also methods for their characterisation are needed.For this, it can be exploited that the NV centre also is not only a single photon emitter, but can also be employed as a sensor. Here, the NV centre is used to measure the local density of optical states in a scanning probe experiment, establishing the technique of three-dimensional quantum emitter fluorescence lifetime imaging.

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Wagner, Rebecca [Verfasser], Frank [Akademischer Betreuer] Cichos, Frank [Gutachter] Cichos, and Cefe [Gutachter] Lopez. "Local Structural and Optical Characterization of Photonic Crystals by Back Focal Plane Imaging and Spectroscopy / Rebecca Wagner ; Gutachter: Frank Cichos, Cefe Lopez ; Betreuer: Frank Cichos." Leipzig : Universitätsbibliothek Leipzig, 2015. http://d-nb.info/1239565186/34.

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Zhang, Zihao. "Investigating the far- and near-field thermal radiation in carbon-based nanomaterials." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54433.

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Two classes of carbon nanomaterials—carbon nanotubes and graphene—have promoted the advancement of nanoelectronics, quantum computing, chemical sensing and storage, thermal management, and optoelectronic components. Studies of the thermal radiative properties of carbon nanotube thin film arrays and simple graphene hybrid structures reveal some of the most exciting characteristic electromagnetic interactions of an unusual sort of material, called hyperbolic metamaterials. The features and results on these materials in the context of both far-field and near-field radiation are presented in this dissertation. Due to the optically dark nature of pyrolytic carbon in the wavelength range from visible to infrared, it has been suggested vertically aligned carbon nanotube (VACNT) coatings may serve as effective radiative absorbers. The spectral optical constants of VACNT are modeled using the effective medium theory (EMT), which is based on the anisotropic permittivity components of graphite. The effects of other EMT parameters such as volume filling ratio and local filament alignment factor are explored. Low reflectance and high absorptance are observed up to the far-infrared and wide range of oblique incidence angles. The radiative properties of tilt-aligned carbon nanotube (TACNT) thin films are illustrated. Energy streamlines by tracing the Poynting vectors are used to show a self-collimation effect within the TACNT thin films, meaning infrared light can be transmitted along the axes of CNT filaments. Graphene, a single layer sheet of carbon atoms, produces variable conductance in the terahertz frequency regime by tailoring the applied voltage gating or doping. Periodically embedding between dielectric spacers, the substitution of graphene provides low radiative attenuation compared to traditional metal-dielectric multilayers. The hyperbolic nature, namely negative angle of refraction, is tested on the graphene-dielectric multilayers imposed with varying levels of doping. EMT should be valid for graphene-dielectric multilayers due to the nanometers-thick layers compared to the characteristic wavelength of infrared light. For metal- or semiconductor-dielectric multilayers with thicker or lossier layers, EMT may not hold. The validity of EMT for these multilayers is better understood by comparing against the radiative properties determined by layered medium optics. When bodies of different temperatures are separated by a nanometers-size vacuum gap, thermal radiation is enhanced several-fold over that of blackbodies. This phenomenon can be used to develop more efficient thermophotovoltaic devices. Due to their hyperbolic nature, VACNT and graphite are demonstrated to further increase evanescent wave tunneling. The heat flux between these materials separated by vacuum gaps smaller than a micron is vastly improved over traditional semiconductor materials. A hybrid structure composed of VACNT substrates covered by doped graphene is analyzed and is shown to further improve the heat flux, due to the surface plasmon polariton coupling between the graphene sheets.

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Smith, Brett. "Coherent Anti-Stokes Raman Scattering Miniaturized Microscope." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24281.

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Microscopy techniques have been developed and refined over multiple decades, but innovation around single photon modalities has slowed. The advancement of the utility of information acquired, and minimum resolution available is seemingly reaching an asymptote. The fusion of light microscopy and well-studied nonlinear processes has broken through this barrier and enabled the collection of vast amounts of additional information beyond the topographical information relayed by traditional microscopes. Through nonlinear imaging modalities, chemical information can also be extracted from tissue. Nonlinear microscopy also can beat the resolution limit caused by diffraction, and offers up three-dimensional capabilities. The power of nonlinear imaging has been demonstrated by countless research groups, solidifying it as a major player in biomedical imaging. The value of a nonlinear imaging system could be enhanced if a reduction in size would permit the insertion into bodily cavities, as has been demonstrated by linear imaging endoscopes. The miniaturization of single photon imaging devices has led to significant advancements in diagnostics and treatment in the medical field. Much more information can be extracted from a patient if the tissue can be imaged in vivo, a capability that traditional, bulky, table top microscopes cannot offer. The development of new technologies in optics has enabled the miniaturization of many critical components of standard microscopes. It is possible to combine nonlinear techniques with these miniaturized elements into a portable, hand held microscope that can be applied to various facets of the biomedical field. The research demonstrated in this thesis is based on the selection, testing and assembly of several miniaturized optical components for use as a nonlinear imaging device. This thesis is the first demonstration of a fibre delivered, microelectromechanical systems mirror with miniaturized optics housed in a portable, hand held package. Specifically, it is designed for coherent anti-Stokes Raman scattering, second harmonic generation, and two-photon excitation fluorescence imaging. Depending on the modality being exploited, different chemical information can be extracted from the sample being imaged. This miniaturized microscope can be applied to diagnostics and treatments of spinal cord diseases and injuries, atherosclerosis research, cancer tumour identification and a plethora of other biomedical applications. The device that will be revealed in the upcoming text is validated by demonstrating all designed-for nonlinear modalities, and later will be used to perform serialized imaging of myelin of a single specimen over time.

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Toullec, Alexis. "Dispositif d’aiguille fibrée pour la spectroscopie de fluorescence endogène de lésions mammaires et pulmonaires ex vivo et in vivo ; vers le développement d'une méthode d’ histopathologie in situ." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS154/document.

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Le troisième Plan Cancer lancé en 2013 désigne la précocité du diagnostic comme l'un des enjeux majeurs pour l'amélioration de la prise en charge des patients. Malgré l’essor des modalités et des performances de l’imagerie médicale, il reste des défis à relever pour l’aide au diagnostic et optimiser le recourt à la biopsie.L’imagerie photonique et spécialement la fluorescence résolue spectralement a déjà été éprouvée pour la caractérisation ex vivo des tumeurs mammaires et pulmonaires, sans agent de contraste ou traitement des échantillons. Notre objectif est de caractériser les capacités d'un dispositif médical innovant, développé au laboratoire, utilisant une aiguille fibrée de faible calibre pour l’analyse spectrale de la fluorescence endogène de ces lésions in situ. Nos premiers travaux dans le cadre d’études précliniques et cliniques ont montré des différences significatives de signatures spectrales entre tumeurs bénignes et malignes ex vivo et in vivo. Nos résultats ont également mis en évidence les limites d’utilisation du dispositif, en termes de spécificité, pour certains types de lésions.Une étude secondaire a été entreprise sur des tumeurs mammaires afin d'identifier les entités tissulaires majeures à l'origine des signatures spectrales obtenues avec notre dispositif fibré. L'imagerie spectrale en microscopie confocale et seconde harmonique (SHG), en multiphoton, ont été mises en œuvre afin d’établir une cartographie de biomarqueurs endogènes des tissus mammaires. Nous avons confronter ses résultats aux données obtenues avec le dispositif d'aiguille fibrée afin de pouvoir le positionner non seulement comme une aide au diagnostic mais aussi comme une méthode prometteuse pour l’histopathologie in situ The third Cancer Plan, launched in 2013, identifies early diagnosis as one of the major challenges for improving patient care. Despite the growth in medical imaging modalities and performance, challenges remain in diagnosis aid and optimizing the use of biopsy.Photonic imaging and especially spectrally resolved fluorescence has already been tested for the ex vivo characterization of breast and lung tumors, without contrast agent or sample processing. Our goal is to characterize the capabilities of an innovative medical device, developed in the laboratory, using a low-caliber fibered needle for the spectral analysis of the endogenous fluorescence of these lesions in situ. Our early work in preclinical and clinical studies showed significant differences in spectral signatures between benign and malignant tumors ex vivo and in vivo. Our results also highlighted the limits the device, in terms of specificity, for certain types of lesions.Another study was conducted on mammary tumors in order to identify the major tissue entities at the origin of the spectral signatures obtained with our fibered device. Spectral imaging in confocal and second harmonic microscopy (SHG), in multiphoton, has been implemented in order to establish a mapping of endogenous biomarkers of mammary tissues. We compare its results with the data obtained with the fibered needle device in order to position it not only as an aid to diagnosis but also as a promising method for in situ histopathology

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Steuwe, Christian. "Nonlinear photonics in biomedical imaging and plasmonics." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708016.

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Jollivet, Clemence. "Specialty Fiber Lasers and Novel Fiber Devices." Doctoral diss., University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6295.

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At the Dawn of the 21st century, the field of specialty optical fibers experienced a scientific revolution with the introduction of the stack-and-draw technique, a multi-steps and advanced fiber fabrication method, which enabled the creation of well-controlled micro-structured designs. Since then, an extremely wide variety of finely tuned fiber structures have been demonstrated including novel materials and novel designs. As the complexity of the fiber design increased, highly-controlled fabrication processes became critical. To determine the ability of a novel fiber design to deliver light with properties tailored according to a specific application, several mode analysis techniques were reported, addressing the recurring needs for in-depth fiber characterization. The first part of this dissertation details a novel experiment that was demonstrated to achieve modal decomposition with extended capabilities, reaching beyond the limits set by the existing mode analysis techniques. As a result, individual transverse modes carrying between ~0.01% and ~30% of the total light were resolved with unmatched accuracy. Furthermore, this approach was employed to decompose the light guided in Large-Mode Area (LMA) fiber, Photonic Crystal Fiber (PCF) and Leakage Channel Fiber (LCF). The single-mode performances were evaluated and compared. As a result, the suitability of each specialty fiber design to be implemented for power-scaling applications of fiber laser systems was experimentally determined. The second part of this dissertation is dedicated to novel specialty fiber laser systems. First, challenges related to the monolithic integration of novel and complex specialty fiber designs in all-fiber systems were addressed. The poor design and size compatibility between specialty fibers and conventional fiber-based components limits their monolithic integration due to high coupling loss and unstable performances. Here, novel all-fiber Mode-Field Adapter (MFA) devices made of selected segments of Graded Index Multimode Fiber (GIMF) were implemented to mitigate the coupling losses between a LMA PCF and a conventional Single-Mode Fiber (SMF), presenting an initial 18-fold mode-field area mismatch. It was experimentally demonstrated that the overall transmission in the mode-matched fiber chain was increased by more than 11 dB (the MFA was a 250 ?m piece of 50 ?m core diameter GIMF). This approach was further employed to assemble monolithic fiber laser cavities combining an active LMA PCF and fiber Bragg gratings (FBG) in conventional SMF. It was demonstrated that intra-cavity mode-matching results in an efficient (60%) and narrow-linewidth (200 pm) laser emission at the FBG wavelength. In the last section of this dissertation, monolithic Multi-Core Fiber (MCF) laser cavities were reported for the first time. Compared to existing MCF lasers, renown for high-brightness beam delivery after selection of the in-phase supermode, the present new generation of 7-coupled-cores Yb-doped fiber laser uses the gain from several supermodes simultaneously. In order to uncover mode competition mechanisms during amplification and the complex dynamics of multi-supermode lasing, novel diagnostic approaches were demonstrated. After characterizing the laser behavior, the first observations of self-mode-locking in linear MCF laser cavities were discovered. Ph.D. Doctorate Optics and Photonics Optics and Photonics Optics and Photonics

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Ruan, Zhichao. "Dispersion Engineering : Negative Refraction and Designed Surface Plasmons in Periodic Structures." Doctoral thesis, Stockholm : Informations- och kommunikationsteknik, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4542.

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Allen, Kenneth Wayne Jr. "Waveguide, photodetector, and imaging applications of microspherical photonics." Thesis, The University of North Carolina at Charlotte, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3685782.

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Dielectric microspheres with diameters (D) on the order of several wavelengths of light have attracted increasing attention from the photonics community due to their ability to produce extraordinarily tightly focused beams termed "photonic nanojets," to be used as microlenses for achieving optical super-resolution or to develop sensors based on whispering gallery mode resonances. In this dissertation, we study the optical properties of more complicated structures formed by multiple spheres which can be assembled as linear chains, clusters or arrays, integrated with waveguides or embedded inside other materials to achieve new optical properties or device functionalities. For linear chains of polystyrene microspheres (n=1.59), we observed a transition from the regime of geometrical optics (at D>20 times the wavelength ) to the regime of wave optics (at D<20 times the wavelength ). We showed that this transition is accompanied by a dramatic change of focusing and optical transport properties of microsphere-chain waveguides. The results are found to be in qualitative agreement with numerical modeling. We developed, designed, and tested a single-mode microprobe device based on spheres integrated with a waveguide for ultraprecise laser surgery. Our design is optimized using a hollow-core microstructured fiber as a delivery system with a single-mode Er:YAG laser operating at an illuminating wavelength of 2.94 micron. Using a high-index (n&sim;1.7-1.9) microsphere as the focusing element we demonstrate experimentally a beam waist of &sim;4 times the wavelength, which is sufficiently small for achieving ultraprecise surgery. For embedded microspherical arrays, we developed a technology to incorporate high-index (n&sim;1.9-2.1) spheres inside thin-films made from polydimethylsiloxane (PDMS). We showed that by using liquid lubrication, such thin-films can be translated along the surface to investigate structures and align different spheres with various objects. Rigorous resolution treatment was implemented and we demonstrated a resolution of &sim;1/7 of the wavlength of illumination, which can be obtained by such thin-films. We experimentally demonstrated that microspheres integrated with mid-IR photodetectors produce up to 100 times photocurrent enhancement over a broad range of wavelengths from 2 to 5 microns. This effect is explained by an increased power density produced by the photonic jet coupled to the active device layers through the photodetector mesas. The photocurrent gain provided by photonic jets is found to be in good agreement with the numerical modeling.

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Palmer, Max John. "New developments for imaging energetic photons." Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243171.

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Emre, Eylem. "Scanning Imaging With High Energy Photons." Master's thesis, Ankara : METU, 2003. http://etd.lib.metu.edu.tr/upload/1206614/index.pdf.

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Gach, Jean-Luc. "Imageurs à amplification." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0317.

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La quête du détecteur parfait, sans bruit, capable de détecter des photons uniques dans le visible et l’infrarouge, et ultimement de déterminer leur énergie est le graal de la détection. Pour arriver à ce but, de nombreux scientifiques ont développé des dispositifs depuis plusieurs dizaines d’années, et les astronomes ont toujours été à la pointe en ce domaine. En ce sens les imageurs à amplification semblent être la voie la plus rapide et la plus prometteuse pour atteindre ce but ultime. Ainsi après un bref historique de l’état de l’art sont exposés les systèmes à comptage de photons (IPCS) développés au LAM, qui ont été utilisés sur les télescopes ESO 3m60, OHP 1m93 ou encore WHT 4m20. Sont ensuite abordés les dispositifs imageurs intégrés à amplification comme les EMCCD (Electron multiplying charge coupled devices) dans le visible, avec quelques exemples de leur utilisation en astronomie. C’est la technologie qui, appliquée aux senseurs de front d’onde, aura permis conjointement à d’autres développements l’avènement des optiques adaptatives extrêmes comme celle de l’instrument VLT-SPHERE ou encore de SUBARU-SCExAO. Pour finir les e-APD (electron initiated avalanche photodiode) dans l’infrarouge seront abordés. Les e-APD ont cette propriété très intéressante d’être des amplificateurs quasi parfaits, et ont une capacité à détecter l’énergie des photons, des propriétés qui seront développées et analysées. Nous finirons par les perspectives et les progrès que nous sommes en droit d’attendre dans les prochaines années The quest for the perfect, noiseless detector, capable of detecting unique photons in the visible and infrared, and ultimately determining their energy is the grail of detection. To achieve this goal, many scientists have developed devices for several decades, and astronomers have always been at the forefront in this area. In this sense amplification imagers seem to be the fastest and most promising way to achieve this ultimate goal. Thus, after a brief history of the state of the art are exposed the photon counting systems (IPCS) developed at LAM, which were used on ESO telescopes 3m60, OHP 1m93 or WHT 4m20. Imaging integrated imaging devices such as Electron Multiplying Charge Coupled Devices (EMCCDs) are then discussed in the visible, with some examples of their use in astronomy. It is the technology that, applied to the wavefront sensors, has jointly enabled other developments the advent of extreme adaptive optics such as the VLT-SPHERE or SUBARU-SCExAO. To finish the e-APD (electron-induced avalanche photodiode) in the infrared will be discussed. E-APDs have this very interesting property of being almost perfect amplifiers, and have an ability to detect photon energy, properties that will be developed and analyzed. We will end up with the prospects and the progress that we are entitled to expect in the coming years

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Monfort, Tual Remy. "Non linear photonics : developments & applications in biomedical imaging." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/422862/.

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Nonlinear polarization is explored in a biological and a technological contexts. Experimental set-ups are developed and built for interrogating nonlinear polarization in biological environment. Most notably, a Coherent Anti-Stokes Raman Scattering (CARS) and Second Harmonic Generation (SHG) microscopes are implemented in the Institute for Life Sciences (IfLS) at Southampton University. CARS and SHG are nonlinear effects based on different contrasts but both are label-free−and as a consequence truly in vivo; without perturbation of the biological mechanisms in opposition to fluorescence techniques (gold standard)− and enable fast imaging of living tissues, organisms and cells at 450 nm lateral spatial resolution. In collaboration with the mass-spectroscopy group at the General Hospital at Southampton and MedImmune, the capabilities of CARS & SHG are assessed for characterization of Pulmonary Alveoli Proteinosis (PAP) disease and drug impact on this phenotype and compared to its healthy version by tracking lipid droplets and collagen fibres. In an other collaboration with the clinical neuroanatomy and experimental neuropathology group at the University of Southampton, age related cerebrovascular and neurodegenerative diseases are linked to maternal obesity thanks to CARS thanks to its ability to track lipid droplets. In a second whole new project, multiplex CARS & SHG modalities are implemented and adapted to large area 4 mm2. Its methodology is developed. This last implementation allows microscopic and label-free characterization of large section of tissues which are compared to H&E (gold standard) valued by histological studies and proposed as a promising alternative. This ability leads to the development of a novel feature: texture analysis. The results obtained display novel insights and ability to characterize and localized healthy, pre-malignant and cancerous areas in tissues by a robust and unsupervised manner. Moreover, cancerous types could be further identified by this method. These results open up and bring the use of CARS & SHG for endoscopy/operative intervention for cancer/dysplasic localization at μm scale without prior labeling to an unprecedented level of specificity. To finish, a novel spectral CARS architecture is theoriticalized displaying unprecedented breadth and sensitivity; and enables the detection of many−usually too weak−biological Raman features.

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Barton, Jennifer K., Babak Amirsolaimani, Photini Rice, Kenneth Hatch, and Khanh Kieu. "Three-photon imaging of ovarian cancer." SPIE-INT SOC OPTICAL ENGINEERING, 2016. http://hdl.handle.net/10150/621253.

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Optical imaging methods have the potential to detect ovarian cancer at an early, curable stage. Optical imaging has the disadvantage that high resolution techniques require access to the tissue of interest, but miniature endoscopes that traverse the natural orifice of the reproductive tract, or access the ovaries and fallopian tubes through a small incision in the vagina wall, can provide a minimally-invasive solution. We have imaged both rodent and human ovaries and fallopian tubes with a variety of endoscope-compatible modalities. The recent development of fiber-coupled femtosecond lasers will enable endoscopic multiphoton microscopy (MPM). We demonstrated two-and three-photon excited fluorescence (2PEF, 3PEF), and second-and third-harmonic generation microscopy (SHG, THG) in human ovarian and fallopian tube tissue. A study was undertaken to understand the mechanisms of contrast in these images. Six patients (normal, cystadenoma, and ovarian adenocarcinoma) provided ovarian and fallopian tube biopsies. The tissue was imaged with three-dimensional optical coherence tomography, multiphoton microscopy, and frozen for histological sectioning. Tissue sections were stained with hematoxylin and eosin, Masson's trichrome, and Sudan black. Approximately 1 mu m resolution images were obtained with an excitation source at 1550 nm. 2PEF signal was absent. SHG signal was mainly from collagen. 3PEF and THG signal came from a variety of sources, including a strong signal from fatty connective tissue and red blood cells. Adenocarcinoma was characterized by loss of SHG signal, whereas cystic abnormalities showed strong SHG. There was limited overlap of two-and three-photon signals, suggesting that three-photon imaging can provide additional information for early diagnosis of ovarian cancer.

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Cheng, Wu. "Optimal Denoising for Photon-limited Imaging." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1446401290.

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Shin, Dongeek. "Computational imaging with small numbers of photons." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103743.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016. Cataloged from PDF version of thesis. Includes bibliographical references (pages 189-202). The ability of an active imaging system to accurately reconstruct scene properties in low light-level conditions has wide-ranging applications, spanning biological imaging of delicate samples to long-range remote sensing. Conventionally, even with timeresolved detectors that are sensitive to individual photons, obtaining accurate images requires hundreds of photon detections at each pixel to mitigate the shot noise inherent in photon-counting optical sensors. In this thesis, we develop computational imaging frameworks that allow accurate reconstruction of scene properties using small numbers of photons. These frameworks first model the statistics of individual photon detections, which are observations of an inhomogeneous Poisson process, and express a priori scene constraints for the specific imaging problem. Each yields an inverse problem that can be accurately solved using novel variations on sparse signal pursuit methods and regularized convex optimization techniques. We demonstrate our frameworks' photon efficiencies in six imaging scenarios that have been well-studied in the classical settings with large numbers of photon detections: single-depth imaging, multi-depth imaging, array-based timeresolved imaging, super-resolution imaging, single-pixel imaging, and fluorescence imaging. Using simulations and experimental datasets, we show that our frameworks outperform conventional imagers that use more naive observation models based on high light-level assumptions. For example, when imaging depth, reflectivity, or fluorescence lifetime, our implementation gives accurate reconstruction results even when the average number of detected signal photons at a pixel is less than 1, in the presence of extraneous background light. by Dongeek Shin. Ph. D.

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Schøler, Mikkel. "Improving imaging performance in planar superlenses." Thesis, University of Canterbury. Department of Electrical and Computer Engineering, 2011. http://hdl.handle.net/10092/5804.

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The aim of this project was to improve the imaging performance of planar superlenses for evanescent near-field lithography. An experimental investigation of the performance of superlenses with reduced surface roughness was proposed. Such an investigation poses significant requirements in regards to process control in thin film deposition of silver onto dielectric substrates. Thin film deposition of silver films, onto silicon dioxide substrates, achieved films with root mean square surface roughness as low as 0.8 nm. While these experiments provided good understanding of the deposition process, significant variability of the surface roughness parameter remained an issue. The diffculty of achieving consistent control of surface roughness led to a finite element method simulation study where this parameter could be readily controlled. An improved understanding of how surface roughness affects superlens imaging performance was obtained from the results of this investigation. Furthermore, it was shown that in order to conduct an experimental investigation to verify the simulation results, it would be necessary to improve the imaging capability of super-resolution lithography protocols to achieve 3σ line edge roughness (LER) of <20 nm. Resist-scheme optimisation was identied as an important factor in this regard. Thus, a novel calixarene-based photoresist was formulated and characterised. The resist demonstrated superior imaging capabilities through interference lithography and evanescent near-field optical lithography, capable of resolving 250-nm period half-pitch line gratings with 3σ LER below 10 nm. The development of this novel photoresist will enable future lithographical investigations to be conducted with improved resolution and imaging fidelity.

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Beckett, Martin Gregory. "High resolution infrared imaging." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388828.

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Jang, Yuseong. "High resolution time-resolved imaging system in the vacuum ultraviolet region." Master's thesis, University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6293.

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High-power debris-free vacuum ultraviolet (VUV) light sources have applications in several scientific and engineering areas, such as high volume manufacturing lithography and inspection tools in the semiconductor industry, as well as other applications in material processing and photochemistry. For the past decades, the semiconductor industry has been driven by what is called "Moore's Law". The entire semiconductor industry relies on this rule, which requires chip makers to pack transistors more tightly with every new generation of chips, shrinking the size of transistors. The ability to solve roadmap challenges is, at least partly, proportional to our ability to measure them. The focus of this thesis is on imaging transient VUV laser plasma sources with specialized reflective imaging optics for metrology applications. The plasma dynamics in novel laser-based Zinc and Tin plasma sources will be discussed. The Schwarzschild optical system was installed to investigate the time evolution of the plasma size in the VUV region at wavelengths of 172 nm and 194 nm. The outcomes are valuable for interpreting the dynamics of low-temperature plasma and to optimize laser-based VUV light sources. M.S. Masters Optics and Photonics Optics and Photonics Optics and Photonics

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Ngo, Ndimba Alphonsine L. "Photoactive molecular assemblies for optical limiting and bio-imaging." Thesis, Rennes 1, 2020. http://www.theses.fr/2020REN1S103.

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Dans cette thèse, nous ciblons de nouveaux absorbeurs biphotoniques pour la bio-imagerie et la limitation optique. Nous nous sommes intéressés plus précisément à des octupôles, structures connues pour posséder des propriétés intéressantes en optique non-linéaire et plus particulièrement en absorption à deux photons. Ainsi, les cœurs isocyanurate et 1,3,5-triazine, connus comme étant des accepteurs, mènent à des octupôles bidimensionnels lorsqu’ils sont substitués de façon symétrique. Pour lors, les isocyanurates ont été peu étudiés pour l’optique non linéaire tandis que les triazines ont déjà été étudiées dans ce cadre et sont connues pour avoir de bonnes propriétés en absorption à deux photons. Dans un premier temps, nous nous sommes intéressés à la synthèse d’isocyanurates organiques et à l’étude de leurs propriétés optiques. Nous avons plus particulièrement étudié l’effet de la planarisation et de l’extension du système conjugué. Dans un deuxième temps, nous nous sommes intéressés à la synthèse et à l’étude des propriétés optiques des tristyryltriazines afin de comparer celles-ci à leurs analogues tristyrylisocyanurates et d’étudier l’influence du cœur sur les propriétés en sachant que la triazine est un cœur plus électroattracteur que l’isocyanurate. Puis, nous nous sommes intéressés à la synthèse de complexes ruthénium-alkynyl trinucléaires à cœurs isocyanurates et triazines, car le ruthénium est un métal d6 connu pour améliorer les propriétés en optique non linéaire. Enfin, nous avons synthétisé des dérivés hydrosolubles de composés organiques qui présentaient les propriétés optiques les plus prometteuses pour la bio-imagerie. En collaboration avec le Dr. Gary-Bobo, nous avons pu confirmer le potentiel de ces molécules pour de telles applications In this work, new biphotonic absorbers were targeted for applications in bio-imaging and optical limiting. We have investigated the synthesis of octupoles since these multipolar structures were often shown to lead to interesting optical properties, especially two-photon absorption. The structures studied were isocyanurate- or 1,3,5-triazine-cored star-shaped derivatives. Both cores are known to be electron-accepting units and to give rise to two-dimensional octupoles when symmetrically substituted. So far, isocyanurates have not often been studied in nonlinear optics, whereas triazines have already been screened and were shown to have good two-photon absorption properties. We first focused on the synthesis of organic isocyanurates and on the study of their optical properties. We started by studying the planarization effect of the extension of the peripheral arms on the optical properties. We then focused on the synthesis and study tristyryltriazines analogous to the previous tristyrylisocyanurates. New structure/property relationships were thus established since the triazine is more electron-attracting than the isocyanurate core. We next synthesized ruthenium-alkynyl trinuclear complexes with isocyanurate and triazine cores, since ruthenium is a d6 metal known to enhance the nonlinear optical properties. We finally studied water-soluble derivatives for bio-imaging. In collaboration with Dr. Gary-Bobo we confirmed their potential for such applications

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Lentz, Joshua K. "Perceptual image quality of launch vehicle imaging telescopes." Doctoral diss., University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4963.

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A large fleet (in the hundreds) of high quality telescopes are used for tracking and imaging of launch vehicles during ascent from Cape Canaveral Air Force Station and Kennedy Space Center. A maintenance tool has been development for use with these telescopes. The tool requires rankings of telescope condition in terms of the ability to generate useful imagery. It is thus a case of ranking telescope conditions on the basis of the perceptual image quality of their imagery. Perceptual image quality metrics that are well-correlated to observer opinions of image quality have been available for several decades. However, these are quite limited in their applications, not being designed to compare various optical systems. The perceptual correlation of the metrics implies that a constant image quality curve (such as the boundary between two qualitative categories labeled as excellent and good) would have a constant value of the metric. This is not the case if the optical system parameters (such as object distance or aperture diameter) are varied. No published data on such direct variation is available and this dissertation presents an investigation made into the perceptual metric responses as system parameters are varied. This investigation leads to some non-intuitive conclusions. The perceptual metrics are reviewed as well as more common metrics and their inability to perform in the necessary manner for the research of interest. Perceptual test methods are also reviewed, as is the human visual system. Image formation theory is presented in a non-traditional form, yielding the surprising result that perceptual image quality is invariant under changes in focal length if the final displayed image remains constant. Experimental results are presented of changes in perceived image quality as aperture diameter is varied. Results are analyzed and shortcomings in the process and metrics are discussed.; Using the test results, predictions are made about the form of the metric response to object distance variations, and subsequent testing was conducted to validate the predictions. The utility of the results, limitations of applicability, and the immediate ability to further generalize the results is presented. ID: 030423279; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2011.; Includes bibliographical references (p. 151-155). Ph.D. Doctorate Center for Research and Education in Optics and Lasers Optics and Photonics

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Rumbley, Sarah (Sarah E. ). "Photon-efficient computational imaging with single-photon avalanche diode (SPAD) arrays." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/106005.

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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015. This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. Cataloged from student-submitted PDF version of thesis. Includes bibliographical references (pages 77-78). Single-photon avalanche diodes (SPADs) are highly sensitive photodetectors that enable LIDAR imaging at extremely low photon flux levels. While conventional image formation methods require hundreds or thousands of photon detections per pixel to suppress noise, a recent computational approach achieves comparable results when forming reflectivity and depth images from on the order of 1 photon detection per pixel. This method uses the statistics underlying photon detections, along with the assumption that depth and reflectivity are spatially correlated in natural scenes, to perform noise censoring and regularized maximum-likelihood estimation. We expand on this research by adapting the method for use with SPAD arrays, accounting for the spatial non-uniformity of imaging parameters and the effects of crosstalk. We develop statistical models that incorporate these non-idealities, and present a statistical method for censoring crosstalk detections. We show results that demonstrate the performance of our method on simulated data with a range of imaging parameters. by Sarah Rumbley. M. Eng.

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Selig, Marco. "Information theory based high energy photon imaging." Diss., Ludwig-Maximilians-Universität München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:19-178899.

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Northcott, Malcolm John. "Photon limited imaging using the triple correlation." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47593.

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Maccarone, Aurora. "Single-photon detection techniques for underwater imaging." Thesis, Heriot-Watt University, 2016. http://hdl.handle.net/10399/3287.

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This Thesis investigates the potential of a single-photon depth profiling system for imaging in highly scattering underwater environments. This scanning system measured depth using the time-of-flight and the time-correlated single-photon counting (TCSPC) technique. The system comprised a pulsed laser source, a monostatic scanning transceiver, with a silicon single-photon avalanche diode (SPAD) used for detection of the returned optical signal. Spectral transmittance measurements were performed on a number of different water samples in order to characterize the water types used in the experiments. This identified an optimum operational wavelength for each environment selected, which was in the wavelength region of 525 - 690 nm. Then, depth profiles measurements were performed in different scattering conditions, demonstrating high-resolution image re-construction for targets placed at stand-off distances up to nine attenuation lengths, using average optical power in the sub-milliwatt range. Depth and spatial resolution were investigated in several environments, demonstrating a depth resolution in the range of 500 μm to a few millimetres depending on the attenuation level of the medium. The angular resolution of the system was approximately 60 μrad in water with different levels of attenuation, illustrating that the narrow field of view helped preserve spatial resolution in the presence of high levels of forward scattering. Bespoke algorithms were developed for image reconstruction in order to recover depth, intensity and reflectivity information, and to investigate shorter acquisition times, illustrating the practicality of the approach for rapid frame rates. In addition, advanced signal processing approaches were used to investigate the potential of multispectral single-photon depth imaging in target discrimination and recognition, in free-space and underwater environments. Finally, a LiDAR model was developed and validated using experimental data. The model was used to estimate the performance of the system under a variety of scattering conditions and system parameters.

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Hafian, Hilal. "IMAGERIE CELLULAIRE ET TISSULAIRE DE BIO-MARQUEURS TUMORAUX : EXCITATION MULTI-PHOTONIQUE DE QUANTUM DOTS CONJUGUES AVEC DES ANTICORPS DE DOMAINE SIMPLE." Thesis, Reims, 2016. http://www.theses.fr/2016REIMP201.

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Les conjugués QD-sdAbs sont des nano-sondes qui associent un quantum dot (QD) et des anticorps de domaine simple (sdAbs). Ces nano-sondes fluorescentes permettent des immunomarquages sur coupes tissulaires et sur cellules. L’objectif de ce travail est de montrer l’intérêt de l’excitation multi-photonique pour la détection et la localisation très spécifiques de biomarqueurs tumoraux.L’excitation multi-photonique des nano-sondes QD570-sdAb anti-CEA a été étudiée, sur coupes d’appendice et de carcinome du côlon humains pour optimiser le rapport signal/auto-fluorescence. L’utilisation du QD comme capteur d’énergie d’excitation dans un modéle de FRET QD-fluorophore organique a été démontré. Un modéle innovant pour une détéction ultra spécifique du CEA sur cellules MC38 CEA par double immunomarquage spécifique pour un transfert d’énergie résonnant entre QD et Alexa Fluor à été mis en oeuvre.Les résutats montrent l’intérêt de l’excitation multi-photonique par rapport à l’excitation à 458,9 nm pour la discrimination et l’optimisation du rapport signal/auto-fluorescence. Il est 40 fois supérieur en excitation à 800 nm qu’à 458,9 nm sur les coupes étudiées.L’utilisation des conjugués QD556-sdAb anti-CEA et d’un anticorps monoclonal permet un double immunomarquage du CEA membranaire sur cellules MC38 CEA. L’utilisation du QD comme nano-capteur d’énergie d’excitation multi-photonique permet une séléctivité d’excitation et un FRET entre QD et Alexa Fluor. Ce schéma permet une détéction spectrale aisée du FRET et une localisation très spécifique et sensible du CEA membranaire. Ceci est conforté par la diminution du temps de déclin du QD556 donneur d’énergie non radiative The QD-sdAbs conjugates are nano-sensors that combine a quantum dot (QD) and single domain antibodies (sdAbs). These fluorescent nanoprobes allow immunostaining on tissue sections and cells. The objective of this work is to show the interest of the multi-photon excitation for the detection and highly specific location of tumor biomarkers.Multi-photon excitation of anti CEA QD570-sdAb nanoprobes was investigated on human appendix and colon carcinoma slides for specifical detection and an optimization of the signal/auto-fluorescence emission ratio. The use of QD as excitation energy sensor for a QD-organic fluorophore FRET model has been shown. An innovative model for ultra-specific detection of CEA on MC38 CEA membrane cells by double immunostaining for a resonant energy transfer between QD and Alexa Fluor has been implemented.Our results shows the great interest of the multi-photon excitation compared to 458.9 nm excitation for discrimination and optimization of the signal / autofluorescence. It is 40 times higher at 800 nm two photon excitation has 458.9 nm one photon excitation on the studied sections.The use of conjugated QD556-sdAb anti-CEA and a conventional monoclonal antibody allows a double immunostaining on CEA on MC38 CEA membrane cells. The QD is use as multi-photon excitation energy nano-sensor enables an excitation selectivity and FRET between QD and Alexa Fluor. This configuration enables easy spectral detection of FRET and a very specific and sensitive location of membrane CEA. This is reinforced by the decrease in decay time of QD556 as donor of non radiative energy

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Jha, Abhinav K. "Retrieving Information from Scattered Photons in Medical Imaging." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/301705.

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In many medical imaging modalities, as photons travel from the emission source to the detector, they are scattered by the biological tissue. Often this scatter is viewed as a phenomenon that degrades image quality, and most research is focused on designing methods for either discarding the scattered photons or correcting for scatter. However, the scattered photons also carry information about the tissue that they pass through, which can perhaps be extracted. In this research, we investigate methods to retrieve information from the scattered photons in two specific medical imaging modalities: diffuse optical tomography (DOT) and single photon emission computed tomography (SPECT). To model the scattering of photons in biological tissue, we investigate using the Neumann-series form of the radiative transport equation (RTE). Since the scattering phenomenon are different in DOT and SPECT, the models are individually designed for each modality. In the DOT study, we use the developed photon-propagation model to investigate signal detectability in tissue. To study this detectability, we demonstrate the application of a surrogate figure of merit, based on Fisher information, which approximates the Bayesian ideal observer performance. In the SPECT study, our aim is to determine if only the SPECT emission data acquired in list-mode (LM) format, including the scattered-photon data, can be used to compute the tissue-attenuation map. We first propose a path-based formalism to process scattered photon data, and follow it with deriving expressions for the Fisher information that help determine the information content of LM data. We then derive a maximum-likelihood expectation-maximization algorithm that can jointly reconstruct the activity and attenuation map using LM SPECT emission data. While the DOT study can provide a boost in transition of DOT to clinical imaging, the SPECT study will provide insights on whether it is worth exposing the patient to extra X-ray radiation dose in order to obtain an attenuation map. Finally, although the RTE can be used to model light propagation in tissues, it is computationally intensive and therefore time consuming. To increase the speed of computation in the DOT study, we develop software to implement the RTE on parallel computing architectures, specifically the NVIDIA graphics processing units (GPUs).

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Yin, Tengfei. "Advanced ultrawideband imaging algorithms for breast cancer detection." Thesis, University of Sussex, 2015. http://sro.sussex.ac.uk/id/eprint/57367/.

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Ultrawideband (UWB) technology has received considerable attention in recent years as it is regarded to be able to revolutionise a wide range of applications. UWB imaging for breast cancer detection is particularly promising due to its appealing capabilities and advantages over existing techniques, which can serve as an early-stage screening tool, thereby saving millions of lives. Although a lot of progress has been made, several challenges still need to be overcome before it can be applied in practice. These challenges include accurate signal propagation modelling and breast phantom construction, artefact resistant imaging algorithms in realistic breast models, and low-complexity implementations. Under this context, novel solutions are proposed in this thesis to address these key bottlenecks. The thesis first proposes a versatile electromagnetic computational engine (VECE) for simulating the interaction between UWB signals and breast tissues. VECE provides the first implementation of its kind combining auxiliary differential equations (ADE) and convolutional perfectly matched layer (CPML) for describing Debye dispersive medium, and truncating computational domain, respectively. High accuracy and improved computational and memory storage efficiency are offered by VECE, which are validated via extensive analysis and simulations. VECE integrates the state-of-the-art realistic breast phantoms, enabling the modelling of signal propagation and evaluation of imaging algorithms. To mitigate the severe interference of artefacts in UWB breast cancer imaging, a robust and artefact resistant (RAR) algorithm based on neighbourhood pairwise correlation is proposed. RAR is fully investigated and evaluated in a variety of scenarios, and compared with four well-known algorithms. It has been shown to achieve improved tumour detection and robust artefact resistance over its counterparts in most cases, while maintaining high computational efficiency. Simulated tumours in both homogeneous and heterogeneous breast phantoms with mild to moderate densities, combined with an entropy-based artefact removal algorithm, are successfully identified and localised. To further improve the performance of algorithms, diverse and dynamic correlation weighting factors are investigated. Two new algorithms, local coherence exploration (LCE) and dynamic neighbourhood pairwise correlation (DNPC), are presented, which offer improved clutter suppression and image resolution. Moreover, a multiple spatial diversity (MSD) algorithm, which explores and exploits the richness of signals among different transmitter and receiver pairs, is proposed. It is shown to achieve enhanced tumour detection even in severely dense breasts. Finally, two accelerated image reconstruction mechanisms referred to as redundancy elimination (RE) and annulus predication (AP) are proposed. RE removes a huge number of repetitive operations, whereas AP employs a novel annulus prediction to calculate millions of time delays in a highly efficient batch mode. Their efficacy is demonstrated by extensive analysis and simulations. Compared with the non-accelerated method, RE increases the computation speed by two-fold without any performance loss, whereas AP can be 45 times faster with negligible performance degradation.

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Richardson, Justin Andrew. "Time resolved single photon imaging in nanometer scale CMOS technology." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/7588.

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Time resolved imaging is concerned with the measurement of photon arrival time. It has a wealth of emerging applications including biomedical uses such as fluorescence lifetime microscopy and positron emission tomography, as well as laser ranging and imaging in three dimensions. The impact of time resolved imaging on human life is significant: it can be used to identify cancerous cells in-vivo, how well new drugs may perform, or to guide a robot around a factory or hospital. Two essential building blocks of a time resolved imaging system are a photon detector capable of sensing single photons, and fast time resolvers that can measure the time of flight of light to picosecond resolution. In order to address these emerging applications, miniaturised, single-chip, integrated arrays of photon detectors and time resolvers must be developed with state of the art performance and low cost. The goal of this research is therefore the design, layout and verification of arrays of low noise Single Photon Avalanche Diodes (SPADs) together with high resolution Time-Digital Converters (TDCs) using an advanced silicon fabrication process. The research reported in this Thesis was carried out as part of the E.U. funded Megaframe FP6 Project. A 32x32 pixel, one million frames per second, time correlated imaging device has been designed, simulated and fabricated using a 130nm CMOS Imaging process from ST Microelectronics. The imager array has been implemented together with required support cells in order to transmit data off chip at high speed as well as providing a means of device control, test and calibration. The fabricated imaging device successfully demonstrates the research objectives. The Thesis presents details of design, simulation and characterisation results of the elements of the Megaframe device which were the author’s own work. Highlights of the results include the smallest and lowest noise SPAD devices yet published for this class of fabrication process and an imaging array capable of recording single photon arrivals every microsecond, with a minimum time resolution of fifty picoseconds and single bit linearity.

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Neimert-Andersson, Thomas. "3D imaging using time-correlated single photon counting." Thesis, Uppsala University, Signals and Systems Group, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-121104.

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This project investigates a laser radar system. The system is based on the principles of time-correlated single photon counting, and by measuring the times-of-flight of reflected photons it can find range profiles and perform three-dimensional imaging of scenes. Because of the photon counting technique the resolution and precision that the system can achieve is very high compared to analog systems. These properties make the system interesting for many military applications. For example, the system can be used to interrogate non-cooperative targets at a safe distance in order to gather intelligence. However, signal processing is needed in order to extract the information from the data acquired by the system. This project focuses on the analysis of different signal processing methods.The Wiener filter and the Richardson-Lucy algorithm are used to deconvolve the data acquired by the photon counting system. In order to find the positions of potential targets different approaches of non-linear least squares methods are tested, as well as a more unconventional method called ESPRIT. The methods are evaluated based on their ability to resolve two targets separated by some known distance and the accuracy with which they calculate the position of a single target, as well as their robustness to noise and their computational burden.Results show that fitting a curve made of a linear combination of asymmetric super-Gaussians to the data by a method of non-linear least squares manages to accurately resolve targets separated by 1.75 cm, which is the best result of all the methods tested. The accuracy for finding the position of a single target is similar between the methods but ESPRIT has a much faster computation time.

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Kosmeier, Sebastian. "Optical eigenmodes for illumination & imaging." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3369.

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This thesis exploits so called “Optical Eigenmodes” (OEi) in the focal plane of an optical system. The concept of OEi is introduced and the OEi operator approach is outlined, for which quadratic measures of the light field are expressed as real eigenvalues of an Hermitian operator. As an example, the latter is employed to locally minimise the width of a focal spot. The limitations of implementing these spots with state of the art spatial beam shaping technique are explored and a selected spot with a by 40 % decreased core width is used to confocally scan an in focus pair of holes, delivering a two-point resolution enhanced by a factor of 1.3. As a second application, OEi are utilised for fullfield imaging. Therefore they are projected onto an object and for each mode a complex coupling coefficient describing the light-sample interaction is determined. The superposition of the OEi weighted with these coefficients delivers an image of the object. Compared to a point-by-point scan of the sample with the same number of probes, i.e. scanning points, the OEi image features higher spatial resolution and localisation of object features, rendering OEi imaging a compressive imaging modality. With respect to a raster scan a compression by a factor four is achieved. Compared to ghost imaging as another fullfield imaging method, 2-3 orders of magnitude less probes are required to obtain similar images. The application of OEi for imaging in transmission as well as for fluorescence and (surface enhanced) Raman spectroscopy is demonstrated. Finally, the applicability of the OEi concept for the coherent control of nanostructures is shown. For this, OEi are generated with respect to elements on a nanostructure, such as nanoantennas or nanopads. The OEi can be superimposed in order to generate an illumination of choice, for example to address one or multiple nanoelements with a defined intensity. It is shown that, compared to addressing such elements just with a focussed beam, the OEi concept reduces illumination crosstalk in addressing individual nanoelements by up to 70 %. Furthermore, a fullfield aberration correction is inherent to experimentally determined OEi, hence enabling addressing of nanoelements through turbid media.

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Finnemeyer, Valerie A. "Development of Liquid Crystal Infrared Imaging Sensors." Kent State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=kent1463139065.

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Noronha, e. Tavora Luis Miguel O. P. "Imaging applications and an extension of the EGS4 code system." Thesis, University of Surrey, 1998. http://epubs.surrey.ac.uk/843180/.

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This thesis investigates the use of Monte Carlo methods to study several imaging applications. Studies are based on the EGS4 code system, and some of these used a low energy electron expansion for this software package that was developed during this work. The code is firstly used to gain some insight into one-sided imaging techniques making use of megavoltage radiation. The method explored is based on induced positron annihilation. The dependence of annihilation yields on atomic number demonstrates that the technique is suitable for the inspection of high-Z inclusions in low-Z, less dense, matrices. Results obtained with the EGS4 code were found to be in good agreement with experimental data. Several applications have been considered via the simulation approach, showing that areas like civil engineering and nuclear material inspection can benefit from this novel inspection technique. The limited accuracy of EGS4 in the simulation of X-ray tubes operating at diagnostic energies led to an expansion of the code to be developed. The enhanced code incorporates a generalized oscillator strength (GOS) model for electron atom inelastic collisions, where atomic bound effects are considered. An enhanced version of this model has been developed so that K-shell ionisation events could be reproduced realistically. The accuracy of low energy bremsstrahlung emissions has also been assessed, and an improved scheme for the angular sampling of newly created photons suggested. The low energy electron expansion of EGS4 (the EGS4/GOS code) is described, and used to simulate photon spectra from diagnostic X-ray tubes. The results were compared with experimental data, showing an accuracy of the order of 15% near the Ka line. Some X-ray tube design studies were carried out using the EGS4/GOS code. The importance of the different physical interactions was analysed. The results show that better fluorescence-to-bremsstrahlung ratios can be obtained with thinner targets, but a factor 2 increase in this ratio is achieved at the expense of a decrease of 40 times in efficiency. The need for low-Z substrates in thin-target applications is also discussed.

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Watt, John. "A photon counting pixel detector for X-ray imaging." Thesis, University of Glasgow, 2001. http://theses.gla.ac.uk/1009/.

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Hybrid semiconductor pixel detector technology is presented in this thesis as an alternative to current imaging systems in medical imaging and synchrotron radiation applications. The technology has been developed from research performed in High Energy Physics, in particular, for the ATLAS experiment at the LHC, planned for 2005. This thesis describes work done by the author on behalf of the MEDIPIX project, a collaboration between 13 international institutions for the development of hybrid pixel detectors for non-HEP applications. Chapter 1 describes the motivation for these detectors, the origin of the technology, and the current state of the art in imaging devices. A description of the requirements of medical imaging on X-ray sensors is described, and the properties of film and CCDs are discussed. The work of the RD19 collaboration is introduced to show the evolution of these devices. Chapter 2 presents the basic semiconductor theory required to understand the operation of these detectors, and a section on image theory introduces the fundamental parameters which are necessary to define the quality of an imaging device. Chapter 3 presents measurements made by the author on a photon counting detector (PCD1) comprising a PCC1 (MEDIPIX1) readout chip bumpbonded to silicon and gallium arsenide pixel detectors. Tests on the seperate readout chip and the bump-bonded assembly are shown with comparisons between the performance of the two materials. Measurements of signal-tonoise ratio, detection efficiency and noise performance are presented, along with an MTF measurement made by the Freiburg group. The X-ray tube energy spectrum was calibrated by REGAM. The performance of the PCD in a powder diffraction experiment using a synchrotron radiation source is described in chapter 4. This chapter reports the first use of a true 2-D hybrid pixel detector in a synchrotron application, and a comparison with the existing scintillator based technology is made. The measurements made by the author have been presented at the 1st International Workshop on Radiation Imaging Detectors at Sundsvall, Sweden, June 1999. The PCD1 operates in single photon counting mode, which attempts to overcome the limitations of charge integrating devices such as CCDs. The pros and cons of the two detection methods are discussed in chapter 5, and a comparison was made of the PCD1 performance with the performance of a commercial dental X-ray sensor. The two detectors are compared in terms of contrast and signal-to-noise ratio for identical X-ray fluences. The results were presented at the 2nd International Workshop on Radiation Imaging Detectors, Freiburg, Germany, 2nd-6th July 2000. The author was involved in the conversion of the LabWindows MRS software to a LabView platform, which was presented in an MSc- thesis in the University of Glasgow by F. Doherty. All image processing, data manipulation and analysis code was written by the author.

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Lapington, Jonathan Stephen. "New techniques for imaging photon counting and particle detectors." Thesis, University College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411261.

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Sjulson, Lucas L. "Two photon imaging of a genetically encodable voltage sensor /." Access full-text from WCMC, 2007. http://proquest.umi.com/pqdweb?did=1445034911&sid=23&Fmt=2&clientId=8424&RQT=309&VName=PQD.

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Shin, Dongeek. "Computational 3D and reflectivity imaging with high photon efficiency." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90142.

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Thesis: S.M. in Computer Science and Engineering, Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014. 45 Cataloged from PDF version of thesis. Includes bibliographical references (pages 77-81). Imaging the 3D structure and reflectivity of a scene can be done using photon-counting detectors. Traditional imagers of this type typically require hundreds of detected photons per pixel for accurate 3D and reflectivity imaging. Under low light-level conditions, in which the mean photon count is small, the inverse problem of forming 3D and reflectivity images is difficult due to the Poisson noise inherent in low-flux operation. In this thesis, we propose and study two computational imagers (one passive, one active) that can form accurate images at low light levels. We demonstrate the superior imaging quality of the proposed imagers by comparing them with the state-of-the-art optical imaging techniques. by Dongeek Shin. S.M. in Computer Science and Engineering

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Ren, Ximing. "Advanced photon counting techniques for long-range depth imaging." Thesis, Heriot-Watt University, 2015. http://hdl.handle.net/10399/2980.

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The Time-Correlated Single-Photon Counting (TCSPC) technique has emerged as a candidate approach for Light Detection and Ranging (LiDAR) and active depth imaging applications. The work of this Thesis concentrates on the development and investigation of functional TCSPC-based long-range scanning time-of-flight (TOF) depth imaging systems. Although these systems have several different configurations and functions, all can facilitate depth profiling of remote targets at low light levels and with good surface-to-surface depth resolution. Firstly, a Superconducting Nanowire Single-Photon Detector (SNSPD) and an InGaAs/InP Single-Photon Avalanche Diode (SPAD) module were employed for developing kilometre-range TOF depth imaging systems at wavelengths of ~1550 nm. Secondly, a TOF depth imaging system at a wavelength of 817 nm that incorporated a Complementary Metal-Oxide-Semiconductor (CMOS) 32×32 Si-SPAD detector array was developed. This system was used with structured illumination to examine the potential for covert, eye-safe and high-speed depth imaging. In order to improve the light coupling efficiency onto the detectors, the arrayed CMOS Si-SPAD detector chips were integrated with microlens arrays using flip-chip bonding technology. This approach led to the improvement in the fill factor by up to a factor of 15. Thirdly, a multispectral TCSPC-based full-waveform LiDAR system was developed using a tunable broadband pulsed supercontinuum laser source which can provide simultaneous multispectral illumination, at wavelengths of 531, 570, 670 and ~780 nm. The investigated multispectral reflectance data on a tree was used to provide the determination of physiological parameters as a function of the tree depth profile relating to biomass and foliage photosynthetic efficiency. Fourthly, depth images were estimated using spatial correlation techniques in order to reduce the aggregate number of photon required for depth reconstruction with low error. A depth imaging system was characterised and re-configured to reduce the effects of scintillation due to atmospheric turbulence. In addition, depth images were analysed in terms of spatial and depth resolution.

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Weir, Iain Stewart. "Statistical modelling and reconstructions in single photon emission computed tomography." Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335395.

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Kniffin, Gabriel Paul. "Physics-Based Imaging Methods for Terahertz Nondestructive Evaluation Applications." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/2945.

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Lying between the microwave and far infrared (IR) regions, the "terahertz gap" is a relatively unexplored frequency band in the electromagnetic spectrum that exhibits a unique combination of properties from its neighbors. Like in IR, many materials have characteristic absorption spectra in the terahertz (THz) band, facilitating the spectroscopic "fingerprinting" of compounds such as drugs and explosives. In addition, non-polar dielectric materials such as clothing, paper, and plastic are transparent to THz, just as they are to microwaves and millimeter waves. These factors, combined with sub-millimeter wavelengths and non-ionizing energy levels, makes sensing in the THz band uniquely suited for many NDE applications. In a typical nondestructive test, the objective is to detect a feature of interest within the object and provide an accurate estimate of some geometrical property of the feature. Notable examples include the thickness of a pharmaceutical tablet coating layer or the 3D location, size, and shape of a flaw or defect in an integrated circuit. While the material properties of the object under test are often tightly controlled and are generally known a priori, many objects of interest exhibit irregular surface topographies such as varying degrees of curvature over the extent of their surfaces. Common THz pulsed imaging (TPI) methods originally developed for objects with planar surfaces have been adapted for objects with curved surfaces through use of mechanical scanning procedures in which measurements are taken at normal incidence over the extent of the surface. While effective, these methods often require expensive robotic arm assemblies, the cost and complexity of which would likely be prohibitive should a large volume of tests be needed to be carried out on a production line. This work presents a robust and efficient physics-based image processing approach based on the mature field of parabolic equation methods, common to undersea acoustics, seismology, and other areas of science and engineering. The method allows the generation of accurate 3D THz tomographic images of objects with irregular, non-planar surfaces using a simple planar scan geometry, thereby facilitating the integration of 3D THz imaging into mainstream NDE use.

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Nagaraja, Chetan. "Implementation of 3D Imaging for Two-photon Laser Scanning Microscopy." Thesis, Uppsala University, Department of Information Technology, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-129479.

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Information exchange between neural systems occurs at the level of populations of neurons. Thus in order to understand how this information exchange occurs, it is indispensible to understand the role of underlying neuronal systems.Electrophysiological techniques have enhanced our understanding of the nervous system by enabling the study of properties of single ion channels to that of ensembles of neurons. While electrophysiological measurements offer excellent temporal resolution, they lack spatial resolution as this method provides a readout of the electrical signals from single or ensembles of neurons in the vicinity of the electrodes (Scanziani et al, 2009). Imaging techniques have gained a lot of prominence because they are non-invasive and provides excellent spatial resolution (Scanziani et al, 2009). The advent of fluorescent genetically encoded optical probes and other fluorescent synthetic indicators has enabled the study of network functions of neurons (Handel et al, 2008). There are various imaging techniques but the one most suited to study network activity is Multiphoton emission (MPE) microscopy because of its ability to image at greater depths in the tissue. In particular, the most popular and extensively used method in this class is the 2-Photon Microscopy. Imaging method suntil recently have employed 2D scanning at planes normal to the light axis. It is known that processing of information occurs at local ensembles of neurons, hence obtaining population activity in a volume of interest is of greater relevance. This has been possible with the technological advancements over the past couple of years (Gobel et al,2007).The aim of this thesis is to implement a fast 3D scanning algorithm using 2-photon microscopy to measure the activity patterns of neuronal ensembles. Further, this technique could be used in order to relate the activity of neurons with the behavioral output.

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Rogers, Sylvia Caren 1957. "Efficient sampling for dynamic single-photon emission computed tomographic imaging." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/278605.

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Our goal is to develop a single-photon emission computed tomography (SPECT) system for dynamic cardiac imaging so that heart disease may be more accurately evaluated. We have developed multiple, stationary, modular scintillation cameras that allow for dynamic imaging because of large detector area, large collection efficiency, high count-rate capability, and no motion of detector, collimator, or aperture. We make use of coded-aperture pinhole arrays because they increase photon-collection efficiency. The coded apertures allow for overlapping projections or multiplexing of an object onto the detector face. We have designed a novel collimation system that allows for an increased number of pinhole projections without substantial multiplexing. This new method is called "subslicing". We verified the subslice concept both in computer simulation and with our 16-module ring imaging system. Comparison of results with and without subslicing shows that the new approach substantially reduces artifacts in the image reconstruction. (Abstract shortened with permission of author.)

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Dissertations / Theses on the topic 'Photonic imaging'

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