Real-time holography using an active optical heterodyne scanning technique for recording and electron beam addressed spatial light modulator-based reconstruction has recently been studied and demonstrated. Advances in this area are presented in this thesis. For the first time, holograms of two dimensional objects have been recorded and two-dimensional images have been reconstructed using this system. The ability to digitally store holograms recorded by this method has been added to the system. This capability increases the robustness of the overall system and allows for digital processing of the holograms for improved reconstruction. Nonlinear digital processing for fringe contrast enhancement is demonstrated. The use of an intermediate display process has previously been identified as a major drawback in the real-time optical scanning holographic system. A digital frame memory is introduced into the system, eliminating the need for the intermediate display process, and thus improving the system. The two systems are compared. / Master of Science

Throughout the decades, different techniques have been proposed to improve the depth-of-focus in optical microscopy. Common techniques like optical sectioning microscopy and scanning confocal microscopy have innate problems. By simply modifying the pupil function in microscope imaging system, we can also extend the depth-of-focus. The scanning system with a thin annular pupil has a high depth-of-focus and can scan the whole object, but the output light is too dim to be detected well by a photodetector. In this thesis, we propose a scanning technique employing an optical heterodyne scanning system using a difference-of-Gaussians (DoG) pupil. The object is illuminated by the combined beam which consists of two Gaussian beams with different waists, frequencies, and amplitudes. This system does not block most light like the annular pupil system and can obtain high depth-of-focus. The main objective of the thesis is to extend the depth-of-focus using the proposed system. The depth-of-focus characteristics of the DoG pupil function are examined and compared with those of well-known functions such as the circular, annular, and Gaussian pupils. / Master of Science

The objective of this thesis is to demonstrate the feasibility of developing holograms in the cladding region of an optical fiber. The cladding is first stripped and replaced with dichromated gelatin ( DCG ) which is a highly efficient holographic storage medium. The evanescent field of the fiber is used as the reference beam to form an interference pattern with an object wave. The interference of the two fields is recorded in the DCG and forms the hologram. The holograms recorded have a grating type structure and can be utilized for guiding light selectively in and out of the fiber. / Master of Science

This work contains two key contributions to the development of 3D displays. First a successful exploratory human trial research study. By comparing multiple real displays in human trials, the factors of ease of use, time, and accuracy were able to be examined in a general setting, instead of isolated to only a specific type of 3D display. These human tests showed that 3D displays in general offer better ease of use and accuracy compared to 2D displays when showing 3D media. This differs from previous studies where only a single display was examined or theoretical papers discussing factors on paper. After proving the validity and merit of 3D displays, the scope is narrowed to a single display - the volumetric display. The second bulk of work resulted in improvements to volumetric displays through iterative design and testing of 3D display apparatus. Testing reveals better materials to be use in image creation in terms of reliability, and leads to a more cost effective and smaller display. The creation of both large and small scale test apparatuses leads to further improvements in reliability through mass testing.

State-of-the art Fourier transform holography (FTH) techniques use x-ray magnetic circular dichroism (XMCD) as a contrast mechanism for element-specfi c imaging of magnetic domains. With the soft x-ray Nanoscience beamline at Diamond Light Source in the UK, and the Dragon beamline at the European Synchrotron Radiation Facility (ESRF) in France, the possibility of new methods to study nanostructured magnetic systems has been demonstrated. The ability to record images without the use of lenses, in varying magnetic fi elds and with high spatial resolution down to 30 nm has been used to study in-plane magnetism of 50 nm thin permalloy (NiFe alloy) nanoelements. The holographic technique used extended reference objects rather than conventional pinhole references, which allowed a high flexibility on the direction of magnetisation that is probed. The element specific nature of the imaging, with the additional choice in the directions of magnetisation that are probed has been used to study dipolar interactions in a hard/Ta/soft [Co/Pt]30/Ta/Py multi-layered system. Images of the out-of-plane magnetised domains of [Co/Pt]30 were found to bare strong spatial resemblance to the in-plane domains of the permalloy. The domain structure is thought to be magnetostatically imprinted into permalloy during the growth stage of the lm, where stray elds generated by the adjacent Co/Pt multilayer influence the formation of domains in the permalloy. Strong resemblance between the two layers could be found at remanence within a pristine sample, however the similarities disappear after the sample was exposed to a saturating magnetic field. This disagreed with micromagnetic simulations performed in The Object Oriented MicroMagnetic Framework (OOMMF) program, and an explanation for the observations has been sought in the growth process of the multi-layered fi lm, with conditions that are diffi cult to recreate in the model. Optical holography has been used for preliminary insight into implementing a method of FTH in a reflective geometry at soft x-rays wavelength. With scattering chambers at BESSY II in Germany and at the Stanford Synchrotron Radiation Lightsource (SSRL) in California the possibility of reducing scattered noise in a hologram recorded in a reflective geometry has been investigated. Studies into specular and dif use reflections have been performed optically however the use of extended references alone may alleviate the current problem at x-ray wavelengths which lie in the weak signal given by a reflective point-like reference source.

Optical Confocal Holography is a combination of two well known concepts: confocal microscopy and optical (laser) holography. Confocal microscopy places an aperture at a conjugate focus to the specimen focus. This filters any rays that are not on the focus plane, allowing a 3-dimensional image of the specimen to be built up over a set of planes. Holography is the measurement of both the amplitude and phase characteristics of light. Typically most methods only measure the amplitude of the image. The phenomenon of interference allows the determination of the phase shift for a coherent source as well. The phase information is directly related to the index of refraction of a material, which in turn is a function of the temperature and composition. As a technique, confocal holography holds promise to better characterize many physical processes in materials science, such as combustion and convection. It also may contribute to the biological sciences by imaging low-contrast, weak-phase objects. Thanks to the ongoing, continued improvement in computer processing speed, it has recently become practical to interpret data from confocal holography microscopy with a computer. The objective of the microscope is to non-invasively measure the three-dimensional, internal temperatures and compositions (e.g. solute/solvent gradient) of a specimen. My contributions over the course of two years to the project were: generation and optimization of an optical design with a software package known as Zemax; sourcing and purchasing all components; formation of a CAD model of the microscope; experiments to characterize building vibrations and air currents; and the development of software in Visual Basic to simulate holograms and execute reconstruction algorithms for the specific application of confocal holography.

Digital Holography Microscopy (DHM) is a new 3D measurement technique that exists since Charge Coupled Devices (or CCD cameras) allow to record numerically high resolution images. That opens a new door to the theory of holography discovered in 1949 by Gabor: the door that masked the world of digital hologram processing. A hologram is a usual image but that contains the complex amplitude of the light coded into intensities recorded by the camera. The complex amplitude of the light can be seen as the combination of the energy information (squared amplitude modulus) with the information of the propagation angle of the light (phase of the amplitude) for each point of the image. When the hologram is digital, this dual information associated with a diffractive model of the light propagation permits to numerically investigate back and front planes to the recorded plane of the imaging system. We understand that 3D information can be recorded by a CCD camera and the acquisition rate of this volume information is only limited by the acquisition rate of the unique camera. For each digital hologram, the numerical investigation of front and back regions to the recorded plane is a tool to numerically refocus objects appearing unfocused in the original plane acquired by the CCD.<p>This thesis aims to develop general and robust algorithms that are devoted to automate the analysis process in the 3D space and in time of objects present in a volume studied by a specific imaging system that permits to record holograms. Indeed, the manual processing of a huge amount of holograms is not realistic and has to be automated by software implementing precise algorithms. In this thesis, the imaging system that records holograms is a Mach-Zehnder interferometer working in transmission and studied objects are either of biological nature (crystals, vesicles, cancer cells) or latex particles. We propose and test focus criteria, based on an identical focus metric, for both amplitude and phase objects. These criteria allow the determination of the best focus plane of an object when the numerical investigation is performed. The precision of the best focus plane is lower than the depth of field of the microscope. From this refocus theory, we develop object detection algorithms that build a synthetic image where objects are bright on a dark background. This detection map of objects is the first step to a fully automatic analysis of objects present in one hologram. The combination of the detection algorithm and the focus criteria allow the precise measurement of the 3D position of the objects, and of other relevant characteristics like the object surface in its focus plane, or its convexity or whatever. These extra relevant measures are carried out with a segmentation algorithm adapted to the studied objects of this thesis (opaque objects, and transparent objects in a uniform refractive index environment). The last algorithm investigated in this research work is the data association in time of objects from hologram to hologram in order to extract 3D trajectories by using the predictive Kalman filtering theory. <p>These algorithms are the abstract bricks of two software: DHM Object Detection and Analysis software, and Kalman Tracking software. The first software is designed for both opaque and transparent objects. The term object is not defined by one other characteristic in this work, and as a consequence, the developed algorithms are very general and can be applied on various objects studied in transmission by DHM. The tracking software is adapted to the dynamic applications of the thesis, which are flows of objects. Performance and results are exposed in a specific chapter. <p> / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

Near-field Acoustical Holography is a tool that is conventionally used to visualize sound fields through an inverse process in a three-dimensional space so that either sound field projections or sound source localization can be performed. The visualization is conducted by using sound pressure measurements taken in the near-field region close to the surface of the unknown sound source. Traditional Fourier-based Near-field Acoustical Holography requires a large number of measurement inputs to avoid spatial truncation effects. However, the use of a large number of measurements is usually not feasible since having a large number of microphones is costly, and usually the array is limited in size by the physical environment, thus limiting the practicality of this method. In the present work, because of the desire to reduce the number of microphones required to conduct acoustical holography, a method known as Statistically Optimized Near-field Acoustical Holography initially proposed by Steiner and Hald was analyzed. The main difference between the present work and the concept mentioned by Steiner and Hald is the cylindrical coordinate system employed here for the purpose of experimenting on a bladeless fan, which resembles a cylindrical structure and which could be assumed to be a cylindrical source. The algorithm was first verified <i>via</i> simulations and measurements, and was then applied to experimental data obtained <i>via</i> pressure measurements made with a cylindrical microphone array. Finally, suggestions for noise control strategies for the bladeless fan are described, based on the measurement results.<br>

In this thesis, we explain and illustrate on several examples how to derive supergravity solutions by computing observables in the corresponding dual, lower-dimensional field theory.<p>In particular, no a priori knowledge on the gravitational dual is assumed, including its dimensionality. The basic idea to construct the pre-geometric models is to consider the world-volume theory of probe D-branes in the presence of a large number N of higher-dimensional background branes. In the standard decoupling limit, the probes are moving only in the flat directions parallel to the background D-branes. We show however that the quantum effective action of the probe world-volume theory, obtained at large $N$ using standard vector model techniques, has the required field content to be interpreted as the action describing the probes in a higher-dimensional, curved and classical spacetime. The properties of the emerging supergravity solution are easily found by comparing the quantum effective action of the pre-geometric model with the non-abelian D-brane action. In all the examples we consider, this allows us to derive the metric, the dilaton and various form fields, overall performing exclusively field theoretic computations.<p><p>The first part of the thesis consists of introductory chapters, where we review vector models at large N, aspects of brane physics in supergravity and string theory and the gauge/gravity correspondence. The second part contains the original contributions of this thesis, consisting of various explicit emergent geometry examples.<p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

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