Tesi: "Digital holography"

1

Williams, Logan Andrew. "Digital Holography for Three Dimensional Tomographic and Topographic Measurements". University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1398436841.

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2

Hjartarson, Örn. "Separation of lobes in Multispectral Digital Holography". Thesis, Umeå universitet, Institutionen för fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-64314.

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Through a holographic recording a property from the third dimension, the depth, is obtained in the form of a phase map of the incident light. One wavelength holography will have a unique phase for the depth range corresponding to the wavelength of the light and outside this range the real depth can not be resolved. By introducing more wavelengths to the measurement the unique phase combination of the waves will have a wider range and larger objects can be resolved. Up to six wavelengths can be simultaneous recorded by making them occupy different spatial frequencies. A set of spatial frequencies together describing a property of the wave is referred to as a lobe. For more than 6 wavelengths and a larger depth range produced by a more seldom repeated unique phase combination the individual waves will occupy the same frequencies, i.e. the lobes overlap. The separation of overlapping lobes is essential in order to make precise and time independent measurements of large and/or moving objects. To separate the lobes the complex fields, i.e. the phases together with the amplitudes, were simulated to propagate a distance and again recorded. The propagation leads to a phase shift of the spatial frequencies which reveals the complex fields in the case of two overlapping wavelengths. For three overlapping wavelengths the resolution, i.e spatial frequencies describing the object, has to be reduced in order to determine the individual complex fields. Since the propagation is a linear transformation for the frequencies that do not overlap, only the overlapping elements whose propagation is nonlinear produce new information. The new information gained is therefore independent of the number of wavelengths used which limits the exact determination of the fields to two wavelengths. Through the holographic recording another property of the complex field is obtained which is the superimposed individual intensities. This bounds the complex fields to certain values, i.e. restricts the possible amplitude of the waves. The recording in the two planes produces two intensity distributions which both must be satisfied by the complex fields. The optimization model for this was formulated and a simple optimization algorithm was implemented. Instead of an equality constraint of the intensities the inequality constraint was implemented, mainly due to that the optimization process was out of the scope of the thesis and the inequality constraint resulted in a simple implementation. The result pointed out important properties even though the optimization could not separate the fields satisfactorily for more than three wavelengths. The inequality constraint contains enough information to solve the case of three overlapping wavelengths.

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3

Tapsell, John Peter. "Direct-Write Digital Holography". Thesis, University of Sussex, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487902.

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Chapter 1 gives a brief history of the field of holography along with an overview of this thesis. A more detailed description of holography is provided in Chapter 2 along with a discussion of digital holography. Chapter 3 examines the design of a one-step monochromatic hologram printer capable producing white-light viewable transmission holograms created with the aid of an LCOS display system and printed in a dot-matrix sequence. The lens system employed includes a microlens array and an afocal relay telescope which are both quantitatively examined in order to maximise the contrast, diffraction efficiency and depth of view of the final hologram image. A brief overview of speckle reduction techniques and their applicability to pulsed digital holography is presented along with experimental results of the use of a microlens array to reduce speckle effects. Chapter 4 presents an analysis of the unwanted side effects of the angular intensity distribution of a hologram pixel, using a case study for analysis. Chapter 5 examines methods for increasing both the printing speed and resolution of the hologram printer. Chapter 6 describes the analysis and design of a temperature-energy feedback system to correct for pulsed laser instabilities arising from mode beating due to temperature variations. Chapter 7 provides a conclusion to the work and discusses possible future developments.

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Lopez, Marcio André Prieto Aparicio. "Microscopia holográfica digital aplicada na análise de tecidos biológicos". Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-23032013-124944/.

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Este trabalho teve como objetivo a aplicação do Microscópio Holográfico Digital para análise de amostras biológicas, por meio de imagens de parâmetros físicos e informação quantitativa de uma amostra, gerados através de hologramas digitais, o que não ocorre na holografia clássica. O processamento e análise dos hologramas digitais foi efetuada por um programa escrito por meio do software MatLab, empregando o método de Dupla Propagação. São explicados outros métodos para tratamento de hologramas digitais, presentes no programa. O método de Dupla Propagação foi discutido, destacando suas vantagens frente aos outros métodos. Foi aplicado o método de Volkov para a retirada de ambiguidade de fase. O processo de montagem do Microscópio Holográfico Digital foi descrito, por apresentar modificações em relação ao protótipo inicial adotado. Sete amostras foram analisadas no Microscópio Holográfico Digital, três de calibração e quatro para análise - sangue e solução concentrada de proteína denominada Beta2 Glicoproteína tipo I, ou Beta2-GPI. Para calibração, foram realizados testes de formação de imagem, realizando comparação em quatro microscópios descritos e explicados em funcionamento e princípio envolvidos na formação de imagens, utilizando a mesma amostra; e verificação das dimensões de uma amostra, por meio de medição usando ferramentas disponíveis no programa. Uma amostra de sangue de um indivíduo heterozigoto para Hemoglobina S (anemia falciforme) e uma amostra de sangue de um indivíduo homozigoto para hemoglobina A1 (controle normal) foram empregadas na forma de filmes líquidos secos sobre lâminas de vidro (extensão sanguínea). O uso de fixação foi avaliado com a amostra controle. Foram geradas imagens em duas e três dimensões para as amostras biológicas, reproduzindo as estruturas morfológicas de cada. Para a proteína Beta2-GPI, a análise envolveu somente imagens, sem extração de valores; apesar disso, os resultados mostraram possibilidades de aplicações em estudos futuros. Grandezas físicas foram calculadas para dois dos componentes sanguíneos (Plasma e Eritrócito), mostrando valores próximos daqueles conhecidos anteriormente. Entretanto, alguns valores foram considerados estimativas novas, por não se conhecer, até o momento, nenhum cálculo efetuado anteriormente. A análise comprovou a formação de imagens e a capacidade de mensuração oferecida pelo aparelho. Devido ao parâmetro da fase, foi possível extrair informações em três dimensões.
This work aimed the implementation of the Digital Holographic Microscope for the analysis of biological samples, using physical parameters images and quantitative data from a sample, both generated through digital holograms, which does not occur in Classical holography. Processing and analysis of holograms were performed by a program written using the MatLab software, applying the Double Propagation method. Other methods for the treatment of digital holograms were explained. The Double Propagation method was discussed, highlighting their advantages over other methods. The method of Volkov was applied for removing phase ambiguity. The Digital Holographic Microscope assembly process was described, because of the modifications made to the initial prototype adopted. Seven samples were analyzed in the digital holographic microscope, three of them for calibration and the other to the analysis - blood and a concentrated solution of a protein called type I Beta2 Glycoprotein, or Beta2-GPI. Calibration tests were made by observing and comparing four image microscopes, described and explained in operation and principles involved in the formation of images, using the same testing sample; and checking the dimensions of another sample through measurement, using digital tools available in the program. Hb S heterozygous (Sickle Cell disease) and Hb A1 homozygous (Control) blood samples were prepared in microscope slide glasses. Images were acquired in two and three dimensions for biological samples, reproducing their morphological structures. For Beta2-GPI, the analysis involved only images, and no values were extracted; nevertheless, the results showed potential applications in future studies. Physical quantities were calculated for two blood components (Plasma and Erythrocyte), showing values closer to those previously known. However, some values were considered new estimates, because there is no knowledge of any calculation made previously, until now, using Digital Holographic Microscopy. The analysis proved the formation of images and the measurement capacity offered by the apparatus. Due to the phase parameter, we were able to extract information in three dimensions.

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5

Li, Yan. "Digital holography and optical contouring". Thesis, Liverpool John Moores University, 2009. http://researchonline.ljmu.ac.uk/4539/.

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Digital holography is a technique for the recording of holograms via CCD/CMOS devices and enables their subsequent numerical reconstruction within computers, thus avoiding the photographic processes that are used in optical holography. This thesis investigates the various techniques which have been developed for digital holography. It develops and successfully demonstrates a number of refinements and additions in order to enhance the performance of the method and extend its applicability. The thesis contributes to both the experimental and numerical analysis aspects of digital holography. Regarding experimental work: the thesis includes a comprehensive review and critique of the experimental arrangements used by other workers and actually implements and investigates a number of these in order to compare performance. Enhancements to these existing methods are proposed, and new methods developed, aimed at addressing some of the perceived short-comings of the method. Regarding the experimental aspects, the thesis specifically develops:• Super-resolution methods, introduced in order to restore the spatial frequencies that are lost or degraded during the hologram recording process, a problem which is caused by the limited resolution of CCD/CMOS devices.• Arrangements for combating problems in digital holography such as: dominance of the zero order term, the twin image problem and excessive speckle noise.• Fibre-based systems linked to tunable lasers, including a comprehensive analysis of the effects of: signal attenuation, noise and laser instability within such systems.• Two-source arrangements for contouring, including investigating the limitations on achievable accuracy with such systems. Regarding the numerical processing, the thesis focuses on three main areas. Firstly, the numerical calculation of the Fresnel-Kirchhoff integral, which is of vital importance in performing the numerical reconstruction of digital holograms. The Fresnel approximation and the convolution approach are the two most common methods used to perform numerical reconstruction. The results produced by these two methods for both simulated holograms and real holograms, created using our experimental systems, are presented and discussed. Secondly, the problems of the zero order term, twin image and speckle noise are tackled from a numerical processing point of view, complementing the experimental attack on these problems. A digital filtering method is proposed for use with reflective macroscopic objects, in order to suppress both the zero-order term and the twin image. Thirdly, for the two-source contouring technique, the following issues have been discussed and thoroughly analysed: the effects of the linear factor, the use of noise reduction filters, different phase unwrapping algorithms, the application of the super-resolution method, and errors in the illumination angle. Practical 3D measurement of a real object, of known geometry, is used as a benchmark for the accuracy improvements achievable via the use of these digital signal processing techniques within the numerical reconstruction stage. The thesis closes by seeking to draw practical conclusions from both the experimental and numerical aspects of the investigation, which it is hoped will be of value to those aiming to use digital holography as a metrology tool.

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6

Mann, Christopher J. "Quantiative biological micrsocopy by digital holography". [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001709.

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7

Mann, Christopher J. "Quantiative biological microsocopy by digital holography". Scholar Commons, 2006. http://scholarcommons.usf.edu/etd/2614.

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In this dissertation, improved techniques in digital holography, that have produced high-resolution, high-fidelity images, are discussed. In particular, the angular spectrum method of calculating holographic optical field is noted to have several advantages over the more commonly used Fresnel transformation or Huygens convolution method. It is observed that spurious noise and interference components can be tightly controlled through the analysis and filtering of the angular spectrum. In the angular spectrum method, the reconstruction distance does not have a lower limit, and the off-axis angle between the object and reference waves can be lower than that of the Fresnel requirement, while still allowing the zero-order background to be cleanly separated. Holographic phase images are largely immune from the coherent noise commonly found in amplitude images. With the use of a miniature pulsed laser, the resulting images have 0.5um diffraction-limited lateral resolution and the phase profile is accurate to about several nanometers of optical path length. Samples such as ovarian cancer cells (SKOV-3) and mouse-embryo fibroblast cells have been imaged. These images display intra-cellular and intra-nuclear organelles with clarity and quantitative accuracy. This technique clearly exceeds currently available methods in phase-contrast opticalmicroscopy in both resolution and detail and provides a new modality for imaging morphology of cellular and intracellular structures that is not currently available. Furthermore, we also demonstrate that phase imaging digital holographic movies provide a novel method of non-invasive quantitative viewing of living cells and other objects. This technique is shown to have significant advantages over conventional microscopy.

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8

Dong, Hongpai. "Applications and developments of digital holography". Thesis, University of Aberdeen, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.430382.

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Digital holography is a new technology emerged in 1994. Because of developments of Laser, personal computer, and CCD sensor, digital holography is finding a remarkably wide range for applications. The reconstruction algorithm is the corner stone of digital holography. It simulates and models the optical reconstruction process with numerical algorithms. A number of reconstruction algorithms have been developed for digital holography in recent years, for instance, the digital implementations of the Fresnel transform, the Fraunhofer transform, and Wavelet transform. We examined all above reconstruction algorithms and developed our own variants of Angular Spectrum and Wavelet/Chirplet reconstruction algorithms. Further to these reconstruction algorithms, we developed miscellaneous algorithms to make digital holography more sophisticated. To detect the focus of an individual hologram, auto-focusing algorithms are developed. To break the resolution limitation introduced by the CCD sensor we present digital in-line holography illuminated by divergent light and corresponding reconstruction algorithms. To expand digital holography in a wider range of common applications, digital video holography is exploited. The holographic video can be reconstructed in both z and time axes. We integrated all the algorithms into software for holographic recording and processing electronically. We also applied the digital holography in a real biological application, sediment erosion study.

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9

Khodadad, Davood. "Multiplexed Digital Holography incorporating Speckle Correlation". Doctoral thesis, Luleå University of Technology, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-55810.

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In manufacturing industry there is a high demand for on line quality control to minimize therisk of incorrectly produced objects. Conventional contact measurement methods are usuallyslow and invasive, meaning that they cannot be used for soft materials and for complexshapes without influencing the controlled parts. In contrast, interferometry and digitalholography in combination with computers become faster, more reliable and highly accurateas an alternative non-contact technique for industrial shape evaluation. For example in digitalholography, access to the complex wave field and the possibility to numerically reconstructholograms in different planes introduce a new degree of flexibility to optical metrology. Withdigital holography high resolution and precise three dimensional (3D) images of themanufactured parts can be generated. This technique can also be used to capture data in asingle exposure, which is important when doing measurements in a disturbed environment. The aim of this thesis is devoted to the theoretical and experimental development of shapeand deformation measurements. To perform online process control of free-formmanufactured objects, the measured shape is compared with the CAD-model to obtaindeviations. To do this, a new technique to measure surface gradients and shape based onsingle-shot multiplexed dual-wavelength digital holography and image correlation of speckledisplacements is demonstrated. Based on an analytical relation between phase gradients andspeckle displacements it is shown that an object is retrieved uniquely to shape, position anddeformation without the unwrapping problems that usually appear in dual-wavelengthholography. The method is first demonstrated using continues-wave laser light from twotemperature controlled laser diodes operating at 640 nm. Then a specially designed dual corediode pumped fiber laser that produces pulsed light with wavelengths close to 1030 nm isused. In addition, a Nd:YAG laser with the wavelength of 532 nm is used for 3D deformationmeasurements. One significant problem when using the dual-wavelength single-shot approach is that phaseambiguities are built in to the system that needs to be corrected. An automatic calibrationscheme is therefore required. The intrinsic flexibility of digital holography gives a possibilityto compensate these aberrations and to remove errors, fully numerically without mechanicalmovements. In this thesis I present a calibration method which allows multiplexed singleshotonline shape evaluation in a disturbed environment. It is shown that phase maps andspeckle displacements can be recovered free of chromatic aberrations. This is the first time that a multiplexed single-shot dual-wavelength calibration is reported by defining a criteria tomake an automatic procedure. Further, Digital Speckle Photography (DSP) is used for the full field measurement of 3Ddeformations. In order to do 3D deformation measurement, usually multi-cameras andintricate set-up are required. In this thesis I demonstrate the use of only one single camera torecord four sets of speckle patterns recorded by illuminating the object from four differentdirections. In this manner, meanwhile 3D speckle displacement is calculated and used for themeasurement of the 3D deformations, wrapping problems are also avoided. Further, the samescale of speckle images of the surface for all four images is guaranteed. Furthermore, a needfor calibration of the 3D deformation measurement that occurs in the multi-camera methods,is removed. By the results of the presented work, it is experimentally verified that the multiplexed singleshotdual wavelength digital holography and numerically generated speckle images can beused together with digital speckle correlation to retrieve and evaluate the object shape. Usingmultidirectional illumination, the 3D deformation measurements can also be obtained. Theproposed method is robust to large phase gradients and large movements within the intensitypatterns. The advantage of the approach is that, using speckle displacements, shape anddeformation measurements can be performed even though the synthetic wavelength is out ofthe dynamic range of the object deformation and/or height variation.

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Suck, Sarah Yasmine. "Digital heterodyne holography for plasmonic nanostructures". Paris 6, 2011. http://www.theses.fr/2011PA066681.

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Dans cette thèse, nous étudions les caractéristiques de diffusion de nanostructures plasmoniques tout en adaptant et améliorant l'holographie hétérodyne numérique, qui est une technique d'imagerie plein champ pour mesurer en trois dimensions le diagramme de rayonnement. En outre, nous avons effectué de nombreuses mesures spectroscopiques pour enregistrer les spectres de diffusion de nanoobjets uniques. Afin d'obtenir une compréhension plus profonde des caractéristiques du champ diffusé que nous mesurons, nous avons développé un modèle numérique basé sur la méthode des éléments finis. Ce modèle nous a permis de simuler le champ proche et le champ lointain d'une nanostructure avec une onde incidente en réflexion ou en transmission. Nous obtenons un excellent accord entre nos résultats expérimentaux et calculés. Dans cette thèse, nous avons étudié de nombreux nanostructures d'or fabriquées sur du verre par lithographie électronique. Des structures simples nous ont permis de valider la technique. Des objets plus sophistiques nous ont ensuite permis de constater que leur diagramme de diffusion est extrêmement sensible aux facteurs externes et internes, tels que la polarisation et la longueur d'onde de la lumière incidente ou la géométrie de la structure et sa longueur d'onde de résonance. En outre, nous montrons que la technique de l'holographie hétérodyne photothermique mesure directement l'augmentation de la température, et ainsi, se présente comme une nouvelle méthode pour étudier la distribution de la chaleur dans des nanostructures plasmoniques.

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Talukdar, Sumanta. "Microstereolithography implemented via visible light digital holography". Thesis, University of Sussex, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404209.

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The amalgamation of the technologies of Microfabrication and Rapid Prototyping and Manufacturing is a field that has witnessed a surge of research activity in recent years. This thesis demonstrates the development of a novel microfabrication system characterised by the use of Computer Generated Holograms (CGHs) as part of a StereoLithographic rapid prototyping system in cohesion with applied microfabrication techniques. CGHs are reconstructed using a laser diode operating at a visible wavelength (407nm) and subsequently implemented in the fabrication of a microstructure. The hologram encoding method utilized two-pixel macropixels implemented on a smectic, analogue ferroelectric liquid crystal (AFLC) spatial light modulator (SLM). This, in conjunction with the bipolar nature of the modulating device, allows for full complex optical modulation. A commercial photopolymer is chosen as the target material. The underlying chemical processes comprising its photochemical behaviour in its native state, as well as in the presence of sensitizers or visible light photoinitiators, are described and the suitability of each to the StereoLithographic processes evaluated. Experimental determination of the effect of such holograms on the target material is undertaken, which include nondegenerate four wave mixing to investigate optical characteristics and cure depth measurement techniques to evaluate photochemical response. The beneficial effects of using a visible light source with respect to the final physical properties of the component are determined. Final product microstructures displaying a variety of topologies are experimentally realised, accompanied by descriptions of their respective fabrication techniques and formulation requirements

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Claus, Daniel. "Resolution improvement methods applied to digital holography". Thesis, University of Warwick, 2010. http://wrap.warwick.ac.uk/47211/.

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This thesis discusses the creation, acquisition and processing of digital holograms. Several techniques to improve the optical resolution have been investigated and developed. The optical resolution of numerically reconstructed digital holograms is restricted by both the sampling frequency and the overall sensor-size of the digital camera chip used. This thesis explores the limitations on the optical resolution of the holograms obtained. A typical sensor-size and sampling frequency for digital holograms is 10 mm and 100 lp/mm, respectively, whereas holographic plates used for optical holography can be more than a meter in size and have a sampling frequency of 3000 lp/mm. In order to take full advantage of the benefits digital holography offers, such as fast image acquisition and direct phase accessibility, the problem of reduced resolution needs to be overcome. Three resolution improvement methods have been developed in the scope of this PhD thesis. Prior to implementing the resolution improvement methods, different holographic setups have been analyzed, using the Space-bandwidth product (SBP) to calculate the information distribution both in the recording and reconstruction process. The first resolution improvement method is based on the synthetic aperture method. In this manner an increased sensor area can be obtained resulting in a larger numerical aperture (NA). A larger NA enables a more detailed reconstruction. The problem encountered in doing this is that an increased optical resolution results in a smaller depth of field. This has been overcome in this thesis by applying the extended depth of field method. As a result a high resolution in focus reconstruction of all longitudinal object regions is obtained. Moreover, the extended depth of field method allows a topological mapping of the object. The second resolution improvement method is based on sampling the interference pattern with sub-pixel accuracy. This was carried out on a CMOS-sensor and implemented by moving the light sensitive pixel-area into the dead zone in a 4x4 grid to cover whole the pixel-area. As a result the sensor's sampling frequency is doubled. The increased sampling frequency permits a reduction of the recording distance which results in an increased optical resolution of the reconstructed hologram. The third and novel approach described in this thesis has been to increase the optical resolution stored in a digital hologram by the combination of the synthetic aperture and the sub-pixel sampling methodBy analogy with the Fresnel-. The resolution improvement methods have been demonstrated both for lens-less digital holography and digital holographic microscopy.

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Czarske, Jürgen W., Nektarios Koukourakis, Bob Fregin, Jörg König e Lars Büttner. "Adaptive flow-field measurements using digital holography". SPIE, 2017. https://tud.qucosa.de/id/qucosa%3A35119.

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Variations of the optical detection path-length in image correlation based flow-field measurements result in strong errors in position allocation and thus lead to a strong enhancement of the measurement uncertainty of the velocity. In this contribution we use digital holography to measure the wavefront distortion induced by fluctuating phase boundary, employing spatially extended guide stars. The measured phase information is used to correct the influence of the phase boundary in the detection path employing a spatial light modulator. We analyze the potential of guide stars that are reflected by the phase boundary, i.e. the Fresnel reflex, and transmitted. Our results show, that the usage of wavefront shaping enables to strongly reduce the measurement uncertainty and to strongly improve the quality of image correlation based flow-field measurements. The approaches presented here are not limited to application in flow measurement, but could be useful for a variety of applications.

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Li, Peiyun. "Suppression of Moire Patterns in Digital Holography". University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1449273439.

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Amer, Eynas. "Pulsed laser ablation studied using digital holography". Doctoral thesis, Luleå tekniska universitet, Strömningslära och experimentell mekanik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18194.

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Pulsed digital holographic interferometry has been used to study the plume and the shock wave generated in the laser ablation process on different targets under atmospheric air pressure. A pulsed Nd-YAG laser system (pulse duration 12 ns) has been used both for ablating the material (wavelength 1064 nm) and for measurement (wavelength 532 nm). Digital holograms were recorded for different time delays using collimated laser light passed through the volume along the target. Numerical data of the integrated refractive index field were calculated and presented as phase maps. The Radon inversion has been used to estimate the 3D refractive index fields measured from the projections assuming rotational symmetry. Intensity maps have been calculated from the recorded digital holograms and used to calculate the attenuation of the probing laser beam by the ablated plume. Qualitative and quantitative information have been extracted from both the phase map and the intensity map to help describing the laser ablation process. Also 3D information about the induced plume has been obtained by numerical reconstruction of the digital holograms at different planes along the plume. The amount of released energy due to laser impact on a PCBM target has been estimated using the point explosion model. The released energy is normalized by the incident laser pulse energy and the energy conversion efficiency between the laser pulse and the target has been calculated and it seems to be constant around 80 %. The 3D refractive index fields have been used to calculate the shock wave front density and the electron number density distribution within the induced plasma. The electron number densities are found to be in the order of 1018 cm-3 and decay at a rate of 3x1015 electrons/cm3ns. The effect of the laser spot diameter on the shock wave generated in the ablation process of a Zn target has been studied. The induced shock wave has an ellipsoidal shape that approaches a sphere for decreasing spot diameter. A model was developed that approaches the density distribution that facilitates the derivation of the particle velocity field. The method provides quantitative results that are discussed; in particular a comparison with the point explosion theory. The effect of the physical properties of the target on the laser ablation process has been studied. The comparison of the laser ablation of Zn and Ti shows that different laser ablation mechanisms are observed for the same laser settings and surrounding gas. At a laser fluence of 5 J/cm2, phase explosion appears to be the ablation mechanism in case of Zn, while for Ti normal vaporisation seems to be the dominant mechanism. The results show that pulsed digital holographic interferometry is a promising technique to give a physical picture and increase the understanding of the laser ablation process in a time resolved manner.
Godkänd; 2009; 20091018 (eyname); DISPUTATION Ämnesområde: Experimentell mekanik/Experimental Mechanics Opponent: Reader in Laser Engineering Bill O’Neill, University of Cambridge, UK Ordförande: Professor Mikael Sjödahl, Luleå tekniska universitet Tid: Fredag den 20 november 2009, kl 10.00 Plats: E 231, Luleå tekniska universitet

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Amer, Mohamed Eynas. "Pulsed laser ablation studied using digital holography /". Luleå : Department of Applied Physics and Mechanical Engineering, Luleå University of Technology, 2009. http://pure.ltu.se/ws/fbspretrieve/3315450.

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Parshall, Daniel. "Phase imaging digital holography for biological microscopy". [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000285.

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18

Schockaert, Cédric. "Three dimensional object analysis and tracking by digital holography microscopy". Doctoral thesis, Universite Libre de Bruxelles, 2007. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210718.

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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.

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.

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.

Doctorat en sciences appliquées
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19

Okman, Osman Erman. "Quantization Index Modulation Based Watermarking Using Digital Holography". Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607506/index.pdf.

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The multimedia watermarking techniques are evolved very quickly in the last years with the increase in the use of internet. The evolution of the internet makes the copyright issues very important and many different approaches are appeared to protect the digital content. On the other hand, holography is the method to store the 3-D information of an object but it is very applicable to use as a watermark because of the nature of the holographic data. The 3-D object can be reconstructed from the hologram even if the hologram is cropped or occluded. However, watermarking of an image with a hologram is a very novel approach and there are only a few works in the literature which are not very robust against the attacks like filtering or compression. In this thesis, we propose to embed the phase of the hologram to an image using quantization index modulation (QIM). QIM is utilized to make the watermarking scheme blind and degrade the host image as low as possible. The robustness of the proposed technique is also tested against several attacks such as filtering, compression, etc. The evaluated performance of this system is compared with the existing methods in the literature which uses either holograms or logos as the secret mark. Furthermore, the characteristics of the holograms are investigated and the findings about the hologram compression are reported in this work.

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20

Pejchang, Darawan. "Measurement of nanoparticles by digital in-line holography". Rouen, 2015. http://www.theses.fr/2015ROUES052.

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Dans cette thèse, nous proposons une nouvelle méthode pour mesurer la taille et la forme de nanoparticules en utilisant l'holographie numérique dans l’axe en association un processus photo-thermique d’échauffement induit par laser. Une suspension de nanoparticules en très faible concentration et en milieu dilué dans une goutte d’eau, est chauffée par un laser impulsionnel. Une bulle de vapeur d’eau, stable, entourant la nanoparticule secondaire à l’échauffement est créée. La transposition de taille de l’échelle nanométrique à l’échelle micrométrique est alors obtenue. Ce processus photo-thermique est utilisé pour relier la taille de la bulle à la taille de la nanoparticule. On obtient les relations fonctionnelles entre le rapport d'aspect et le volume de la bulle et ceux de la nanoparticule. Ces fonctions dépendent des caractéristiques de l'impulsion laser, de la température initiale de la nanoparticule et l’indice optique de l'eau et sont également spécifiques à la matière et à la forme de la nanoparticule. Une nanoparticule sphérique de TiO2 est utilisée dans cette démonstration. Le diamètre mesuré expérimentalement est en bon accord avec le diamètre moyen de l'échantillon. Cela signifie que la mesure indirecte utilisant la bulle de vapeur d’eau obtenue par cavitation autour de la nanoparticule peut être considéré comme efficace pour obtenir la taille d'une nanoparticule
In this thesis we study and develop a new methodology to measure the size and shape of individual nanoparticles by using digital in-line holography (DIH) microscopy in association with a photothermal process. Due to the limited resolution of the direct DIH technique at the nanoscale, an indirect measurement is treated. Instead of recording the hologram of a nanoparticle directly, the nanoparticle suspension is suddenly heated by a powerful pulse laser. Then a vapor bubble cavitation surrounding the nanoparticle is formed in order to increase the object size from the DIH point of view. The photothermal process is used to link the size of the bubble to the size of the nanoparticle. We obtain the functional relations between the aspect ratio and volume of the bubble and those of the nanoparticle from this process. These functions are dependent on the characteristics of the laser pulse, the initial temperature of the nanoparticle and the water medium, and are also specific to the material and shape of the nanoparticle. A spherical nanoparticle of TiO2 is used in this demonstration. The measured diameter is in good agreement with the average diameter of the sample. This means that the indirect measurement employing the cavitation vapor bubble around the nanoparticle can be considered as efficient to obtain the size of a nanoparticle. This technique has the ability to take into account the shape (ellipticity) of the bubble

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21

El, Rhammad Anas. "Efficient compression for scalable transmission of digital holograms". Electronic Thesis or Diss., Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAT002.

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Contrairement à la stéréoscopie, l'holographie permet une visualisation 3D la plus naturelle et confortable possible. En revanche, les hologrammes numériques contiennent une grande quantité de données avec peu de corrélations. Dans la première partie de ce travail, nous avons introduit deux méthodes de compression des hologrammes numériques. Tout d'abord, nous avons décomposé l'hologramme en faisceaux lumineux en utilisant les ondelettes de Gabor. Pour des fins de compression, nous avons compacté l'expansion obtenue en utilisant l'algorithme du guillemotleft Matching Pursuitguillemotright. Ensuite, nous avons conçu un schéma de codage spécifique aux coefficients et indices des atomes de Gabor. L'approche proposée a atteint une meilleure performance par rapport aux codeurs classiques.Deuxièmement, en exploitant la dualité entre les ondelettes de Gabor et les faisceaux lumineux émis par l'hologramme, nous avons développé un schéma de codage scalable en termes de point de vue et qualité. En effet, seuls les atomes de Gabor qui émettent la lumière dans la fenêtre de l'observateur considéré sont sélectionnés, triés et puis encodés. Le débit binaire a été considérablement réduit, sans dégrader la qualité de reconstruction par rapport à celle obtenue en encodant la totalité de l'hologramme.Dans la deuxième partie de ce travail, nous avons conçu deux architectures serveur-client pour une transmission progressive d'hologrammes en fonction de la position d'observateur à l'aide d'un codage scalable. Dans la première solution, un flux binaire scalable à grain fin est généré en ligne par le serveur, après chaque notification client concernant la position de l'utilisateur. Les résultats expérimentaux ont révélé que la méthode proposée permet une visualisation rapide en décodant les premiers atomes reçus en plus d'une augmentation progressive de la qualité.Enfin, pour réduire la latence causée par la charge de calcul au moment du codage, nous avons proposé une deuxième solution où l'intégralité de l'expansion de Gabor est encodée hors ligne par le serveur, puis décodée en ligne suivant la trajectoire de l'observateur. Pour permettre un codage scalable, nous avons regroupé les atomes de Gabor à la suite d'une décomposition par blocs du plan de l'observateur. Ensuite, les atomes de chaque bloc sont affectés à différents niveaux de qualité et codés par paquets. Les tests de simulation ont montré que l'architecture proposée permet une transmission à faible latence sans augmenter significativement le coût d'encodage
Contrary to conventional stereoscopy, holography provides the most natural and comfortable 3D visualization. However, digital holograms contain massive amount of data with very few correlations. In the first part of this work, we introduced two methods for digital holograms compression. First, we proposed a redundant light beams-based decomposition of holograms using the Gabor wavelets. For compression purposes, we sparsified the obtained expansion using the Matching Pursuit algorithm. Then, we designed a specific encoder framework for the coefficients and indexes of Gabor atoms. The proposed approach achieved better compression performance compared to the state of the art methods. Second, by exploiting the duality between Gabor wavelets and diffracted light beams, we developed a viewpoint-quality scalable coding scheme. Indeed, for a given observer's position, only the Gabor atoms that emit light into the viewer's window are selected, sorted and then encoded. The bit rate has been significantly reduced, without degrading the reconstruction quality obtained by encoding the whole hologram. In the second part of this work, we designed two server-client architectures for a view-dependent progressive transmission of holograms using scalable coding. In the first solution, a fine-grain scalable bitstream is generated online by the server, after each client notification about the user's position. Experimental results reveal that this method enables a rapid visualization by decoding the first received atoms in addition to a progressive increase of quality.Finally, to reduce the latency caused by the computational burden of encoding, we proposed a second solution where the whole Gabor expansion is encoded offline by the server, and then decoded online with respect to the viewer’s trajectory. To enable a scalable compression, we grouped the Gabor atoms following a block-based decomposition of the observer plane. Then, the atoms of each block are assigned to different quality levels and encoded in packets. Simulations tests show that the proposed architecture allows a low-latency transmission without significantly increasing the encoding rate

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22

Akin, Enver Turan. "Investigations of Horizontal-Parallax-Only Optical Scanning Holography (HPO-OSH) through MATLAB Simulations". Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/32430.

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The concept of generating horizontal-parallax-only (HPO) holograms by computer simulations is investigated. The simulations in this thesis are based on Optical Scanning Holography (OSH) aimed at acquiring HPO information electronically. The principles of OSH, a technique that allows the extraction of 3-D information by a 2-D optical scan of the object is first summarized. The HPO principles and simulation scenarios are then discussed. In order to illustrate the ideas, holograms were created and reconstructed using MATLAB simulations. The holograms are simulated by convolving the Fresnel zone plates (FZP) with the object. The simulations focus on generating HPO holograms using 1-D FZPs modeled as 1-D Gaussian chirp beams of varying waists. An optical reconstruction scheme by cylindrical lens was proposed and simulated. Three-dimensional imaging using HPO-holograms was also discussed. Several reconstruction scenarios were investigated by digitally convolving the complex HPO-hologram with the free space impulse response or the Gaussian chirp beam. Although many ideas of HPO-holography have been proposed and studied, to the best of our knowledge, this is the first proposed electronic technique to acquire HPO-holographic information. The simulations demonstrate that holographic information reduction techniques also help to alleviate the problems associated with the restricted field of view upon holographic reconstruction for 3-D display. The simulations show that horizontal-parallax-only holography is an excellent way to reduce holographic information. Suggested future work includes actual optical experimentation to verify the ideas presented in this thesis.
Master of Science

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23

Fernández, Meylí Valin. "Desenvolvimento da microscopia holográfica digital por reflexão para avaliação 3D de superfícies". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3151/tde-04012018-105154/.

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Dentre dos procedimentos geradores de perfil óptico encontra-se a microscopia holográfica digital. Esta ferramenta interferométrica surgiu da ideia inicial proposta por D. Gabor sobre holografia, a qual permite mediante o registro da interferência de campos ópticos coerentes, guardar e extrair informações de imagens. A microscopia holográfica digital permite a análise de objetos com resoluções transversais semelhantes às obtidas por microscopia óptica, e ainda, possui a vantagem pela natureza da holografia de permitir realizar análises através do acesso a valores quantitativos de fase. Apresentam-se neste trabalho os conceitos básicos da holografia digital e da microscopia holográfica digital, com o objetivo, de introduzir o desenvolvimento de uma metodologia para a implementação da microscopia holográfica digital por reflexão para o controle dimensional de objetos e determinação da rugosidade superficial de amostras de aço. Os hologramas são obtidos mediante uma instalação óptica, que consiste em um interferômetro de Michelson por reflexão com o uso de uma lente objetiva de microscópio e uma câmera CCD sem lente. Para a reconstrução das imagens de contraste de fase são utilizadas técnicas numéricas que capacitam à microscopia holográfica digital para a supressão do termo de ordem zero, controle da resolução de pixel, desmodulação da fase óptica, determinação dos mapas de intensidades e fase, filtragem e compensação de aberrações dos hologramas obtidos. As reconstruções numéricas dos feixes objeto e referência são realizadas utilizando o método de dupla propagação. Foi desenvolvido um algoritmo que apresenta a imagem de contraste de fase com base num critério de distância a partir de um único holograma. Desta forma o programa utilizado permite a realização de medições quantitativas das dimensões dos objetos e da rugosidade superficial de amostras de aço, assim como, a representação em 3D da imagem de fase reconstruída com resultados validados através de um perfilômetro óptico 3D sem contacto modelo CCI-MP.
Among the procedures generating optical profile is the digital holographic microscopy. This interferometric tool arose from the initial idea proposed by D. Gabor on holography, which allows by recording the interference of coherent optical fields, save and extract information from images. Digital holographic microscopy allows the analysis of objects with transversal resolutions similar to those obtained by optical microscopy, and also has the advantage of the nature of holography to allow to perform analyzes through the access to quantitative phase values. This paper presents the basic concepts of digital holography and digital holographic microscopy, with the objective of introducing the development of a methodology for the implementation of digital holographic microscopy by reflection for the dimensional control of objects and determination of surface roughness of samples of steel. The holograms are obtained by means of an optical installation consisting of a Michelson interferometer by reflection using an objective microscope lens and a lensless CCD camera. For the reconstruction of phase contrast images, numerical techniques are used that enable digital holographic microscopy to suppress the zero-order term, control pixel resolution, optical phase demodulation, determination of intensity and phase maps, filtering and compensation of aberrations of the obtained holograms. Numerical reconstructions of the object and reference beams are performed using the double propagation method. An algorithm has been developed that presents the phase contrast image based on a distance criterion from a single hologram. In this way the program used allows the realization of quantitative measurements of the object dimensions and the surface roughness of steel samples, as well as the 3D representation of the reconstructed phase image with results validated through a 3D contactless optical profilometer model CCI- MP.

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El, Mallahi Ahmed. "Automated 3D object analysis by digital holographic microscopy". Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209489.

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The main objective of this thesis is the development of new processing techniques for digital holograms. The present work is part of the HoloFlow project that intends to integrate the DHM technology for the monitoring of water quality. Different tools for an automated analysis of digital holograms have been developed to detect, refocus and classify particles in continuous fluid flows. A detailed study of the refocusing criterion permits to determine its dependencies and to quantify its robustness. An automated detection procedure has been developed to determine automatically the 3D positions of organisms flowing in the experiment volume. Two detection techniques are proposed: a usual method based on a global threshold and a new robust and generic method based on propagation matrices, allowing to considerably increase the amount of detected organisms (up to 95 %) and the reliability of the detection. To handle the case of aggregates of particles commonly encountered when working with large concentrations, a new separation procedure, based on a complete analysis of the evolution of the focus planes, has been proposed. This method allows the separation aggregates up to an overlapping area of around 80 %. These processing tools have been used to classify organisms where the use of the full interferometric information of species enables high classifier performances to be reached (higher than 93 %).
Doctorat en Sciences de l'ingénieur
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Czarske, Jürgen W., Daniel Haufe, Nektarios Koukourakis e Lars Büttner. "Perspectives of multimode fibers and digital holography for optogenetics". SPIE, 2016. https://tud.qucosa.de/id/qucosa%3A34836.

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Optogenetic approaches allow the activation or inhibition of genetically prescribed populations of neurons by light. In principle, optogenetics offers not only the ability to elucidate the functions of neural circuitry, but also new approaches to a treatment of neurodegenerative diseases and recovery of vision and auditory perception. Optogenetics already has revolutionized research in neuroscience. However, new methods for delivering light to three-dimensionally distributed structures e.g. in the brain are necessary. A major hurdle for focusing light through biological tissue is the occurring scattering and scrambling of the light. We demonstrate the correction of the scrambling in a multimode fiber by digital optical phase conjugation with a perspective for ptogenetics.

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26

Abeywickrema, Haburugala Vithanage Ujitha A. "Applications of Induced Gratings in Nonlinear Media". University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1429985534.

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27

Khmaladze, Alexander. "Three-dimensional microscopy by laser scanning and multi-wavelength digital holography". [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002638.

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28

Kaczorowski, Andrzej. "Adaptive aberration correction for holographic projectors". Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/270322.

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This work builds up on the greatest minds of Cambridge Holography: Adrian Cable, Edward Buckley, Jonathan Freeman, and Christoph Bay. Cable and Buckley, developed an OSPR algorithm which was the first to provide high-quality real-time hologram generation using general-purpose hardware while Freeman designed a method to correct arbitrary aberrations. As ingenious as the method was, the calculations were extensively lengthy. Addressing this issue, a variant of OSPR suited for correcting spatially-varying aberration is presented. The algorithm combines the approaches of Cable, Buckley and Freeman to provide real-time hologram generation while incorporating various corrections (aberration, distortion, and pixel shape envelope). A high-performance implementation on a mid-range GPU achieved hologram generation up to 12 fps. Following topic studied is an adaptive optical correction. This work attempts to construct a set of methods, forming an automated testbed for holographic projectors. Each model, after exiting the production line is placed on such testbed, having all of its imperfections characterized. Once calibrated, each model is able to display highest-quality image throughout its life-span. An application of this work to industry was carried in collaboration with Dr Phillip Hands (University of Edinburgh) and LumeJET. Three demonstrators are constructed intending for a cost-effective system for holographic lithography. They are characterized using the developed testbed. Using the supersampled Adaptive OSPR algorithm, the diffraction limit was surpassed 2.75 times allowing to increase the patterning area. This combines approaches of Cable, Buckley, Freeman and Bay to achieve a wide field-of-view and high pixel-count replay field using off-the-shelf components. This thesis is finished describing the work on 3D holography carried with Penteract28. It is shown that the 2D hologram in the presence of spatially-varying aberrations is mathematically equivalent to a 3D hologram. The same implementation of the algorithm can be used to provide real-time 3D hologram generation.

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Khodadad, Davood. "Combined Digital Holography and Speckle Correlation for Rapid Shape Evaluation". Licentiate thesis, Luleå University of Technology, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-55813.

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In manufacturing industry there is a high demand for on line quality control to minimize the risk of incorrectly produced objects. Conventional contact measurement methods are usually slow and invasive, meaning that they cannot be used for soft materials and for complex shapes without influencing thecontrolled parts. In contrast, interferometry and digital holography in combination with computers become faster, more reliable and highly accurate as an alternative non-contact technique for industrial shape evaluation. In digital holography, access to the complex wave field and the possibility tonumerically reconstruct holograms in different planes introduce a new degree of flexibility to optical metrology. With digital holography high resolution and precise three dimensional (3D) images of the manufactured parts can be generated. This technique can also be used to capture data in a single exposure,which is important when doing measurements in a disturbed environment.The aim of this thesis is to perform online process control of free-form manufactured objects by measuring the shape and compare it to the CAD-model. To do this, a new technique to measure surface gradients and shape based on single-shot dual wavelength digital holography and image correlation of speckle displacements is demonstrated. Based on an analytical relation between phase gradients and speckle displacements it is shown that an object is retrieved uniquely to shape and position without the unwrapping problems that usually appear in dual wavelength holography. The method is firstdemonstrated using continues wave laser light from two temperature controlled laser diodes operating at 640 nm. Further a specially designed dual core diode pumped fiber laser that produces pulsed light with wavelengths close to 1030 nm is used. One significant problem when using the dual wavelength single-shot approach is that phase ambiguities are built in to the system that needs to be corrected. An automatic calibration scheme is therefore required. The intrinsic flexibility of digital holography gives a possibility to compensate these aberrations and to remove errors, fully numerically without mechanical movements. In this thesis I present a calibration method which allows single-shot online shape evaluation in a disturbed environment. It is shown that phase maps and speckle displacements can be recovered free of chromatic aberrations. This is the first time that a single-shot dual wavelength calibration is reported by defining a criteria to make an automatic procedure.By the results of the presented work, it is experimentally verified that the single-shot dual wavelength digital holography and numerically generated speckle images can be used together with digital speckle correlation to retrieve and evaluate the object shape. The proposed method is also robust to large phasegradients and large movements within the intensity patterns. The advantage of the approach is that, using speckle displacements, the shape measurement can be done even though the synthetic wavelength is out of the dynamic range of the height variation of the object.

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30

Potcoava, Mariana Camelia. "Digital holography applications in ophthalmology, biometry, and optical trapping characterization". [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003037.

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31

Liu, Haipeng. "Evaluation of Digital Holographic Reconstruction Techniques for Use in One-shot Multi-angle Holographic Tomography". University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1406912572.

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32

Fung, Jerome. "Measuring the 3D Dynamics of Multiple Colloidal Particles with Digital Holographic Microscopy". Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11200.

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We discuss digital holographic microscopy (DHM), a 3D imaging technique capable of measuring the positions of micron-sized colloidal particles with nanometer precision and sub-millisecond temporal resolution. We use exact electromagnetic scattering solutions to model holograms of multiple colloidal spheres. While the Lorenz-Mie solution for scattering by isolated spheres has previously been used to model digital holograms, we apply for the first time an exact multisphere superposition scattering model that is capable of modeling holograms from spheres that are sufficiently close together to exhibit optical coupling.
Physics

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33

Wichitwong, Wisuttida. "Application of digital holography for metrology of inclusions in a droplet". Thesis, Rouen, INSA, 2015. http://www.theses.fr/2015ISAM0007/document.

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Dans cette thèse, l'holographie numérique dans l'axe (DIH) est la principale méthode optique utilisée pour analyser des inclusions dans une gouttelette. L'holographie numérique dans l'axe est utilisée pour caractériser des inclusions du point de vue de leur taille, leur position 3D et leur trajectoire à l'intérieur de la gouttelette. Comme les particules sont situées à l'intérieur d'une gouttelette, le front d'onde incident sur l'inclusion est modifié avant qu'il l'illumine. Le défi de ce travail est double : premièrement de prendre en compte la forme de la gouttelette dans le modèle d'holographie et deuxièmement d'étendre l'analyse aux inclusions transparentes (type objet de phase). Pour décrire l'hologramme enregistré par le capteur CCD, l'intégrale d'Huygens-Fresnel et le formalisme des matrices ABCD ont été utilisés. Dans ce modèle, nous introduisons les polynômes de Zernike pour décrire la fonction de transmission d'une particule. Pour l'analyse des hologrammes, l'outil mathématique de la transformation de Fourier fractionnaire 2D (2D-FRFT) est utilisé pour restituer l'image des inclusions et dans ce cas une mesure la taille de l'inclusion et de sa position 3D sont réalisées. Les trajectoires des inclusions dans la goutte est possible avec un long temps de pose de l'obturateur du capteur CCD. Nous avons également proposé un nouveau modèle pour décrire des objets de phases quelconque et des particules opaques. Pour ce nouveau modèle, les mêmes procédés ont été utilisés. Dans le cas d'inclusions filiformes à l'intérieur d'une géométrie cylindrique comme un canal, une méthode de simulation d'imagerie interférométrique multi-coeurs est proposée. Dans ce cas, une somme de distributions de Dirac, localisées le long d'une droite, introduite dans l'intégrale de Fresnel généralisée (c'est-à-dire le formalisme des matrices ABCD et l'intégrale de Fresnel) permet d'obtenir un bon degré de similitude entre l'expérience et la simulation
In this thesis, the digital in-line holography (DIH) is the main optical method used to analyze inclusions in a droplet. The digital in-line holography is used to characterize the inclusions in terms of of their size, their 3D position, and their trajectories inside the droplet. Since the particles are located within a droplet, the incident wavefront is changed before it illuminates the inclusions. The challenge of this work has two points : first to take into account the shape of the droplet in the holographic model and secondly to extend the analysis to the transparent inclusions (phase object). To describe the hologram recorded by the CCD sensor, the Huygens-Fresnel integral and the ABCD matrix formalism were used. In this model, we introduce the Zernike polynomials to describe the transmission function of a particle. For the analysis of holograms, the2D fractional Fourier transformation (2D-FRFT) is used to reconstruct the image of inclusions and in this case the size and their 3D position of the inclusions are performed.The trajectories of the inclusions in the drop are possible tracked with a long exposure shutter speed of the CCD. We also proposed a new simulation to describe objects of any phases and opaque particles. For this simulation, the same methods of reconstruction were used. In the case of micro-channel inclusions inside a cylindrical geometry such as a pipe, the interferometric imaging of multi-core pipe is proposed. In this case, summation of Dirac delta distribution, located along a line, introduced into the generalized Fresnel integral allows us to get a good agreement between the experiment and the simulation

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34

Rivet, Julie. "Non-iterative methods for image improvement in digital holography of the retina". Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS246.

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Avec l’augmentation du nombre de personnes souffrant de déficience visuelle modérée à sévère, la surveillance et le traitement des troubles de la vision sont devenus des enjeux majeurs de la médecine actuelle. Au centre hospitalier national d’ophtalmologie des Quinze-Vingts à Paris, deux bancs optiques ont été installés ces dernières années pour développer deux techniques d'holographie numérique en temps-réel pour l’imagerie de la rétine : la tomographie holographique par cohérence optique (OCT holographique) plein champ et l'holographie laser Doppler. La première reconstitue des images en trois dimensions, tandis que la seconde permet de visualiser le flux sanguin dans les vaisseaux. Outre les problèmes inhérents au système d'imagerie lui-même, les appareils optiques sont soumis à des perturbations externes, ce qui entraîne également des difficultés d'imagerie et une perte de résolution. Les principaux obstacles auxquels ces technologies sont confrontées sont le mouvement des yeux et les aberrations oculaires. Dans cette thèse, nous avons étudié plusieurs méthodes d'amélioration de la qualité des images en holographie numérique, et les avons validées expérimentalement. La résolution des images holographiques a été améliorée par des méthodes non itératives robustes : compensation des mouvements et mesure et compensation des aberrations optiques. Ce travail ouvre la voie à de nouvelles méthodes de traitement qui permettront une amélioration majeure de la résolution des images en holographie numérique de la rétine, et qui pourront fournir des informations très précieuses aux cliniciens, à terme
With the increase of the number of people with moderate to severe visual impairment, monitoring and treatment of vision disorders have become major issues in medicine today. At the Quinze-Vingts national ophthalmology hospital in Paris, two optical benches have been settled in recent years to develop two real-time digital holography techniques for the retina: holographic optical coherence tomography (OCT) and laser Doppler holography. The first reconstructs three-dimensional images, while the second allows visualization of blood flow in vessels. Besides problems inherent to the imaging system itself, optical devices are subject to external disturbance, bringing also difficulties in imaging and loss of accuracy. The main obstacles these technologies face are eye motion and eye aberrations.In this thesis, we have introduced several methods for image quality improvement in digital holography, and validated them experimentally. The resolution of holographic images has been improved by robust non-iterative methods: lateral and axial tracking and compensation of translation movements, and measurement and compensation of optical aberrations. This allows us to be optimistic that structures on holographic images of the retina will be more visible and sharper, which could ultimately provide very valuable information to clinicians

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35

Thiesing, Benjamin P. "High temperature measurements of surface changes in metal alloys using digital holography". Thesis, Northern Arizona University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1537812.

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Digital Holography (DH) is an emerging tool for use in the structural investigation of temperature dependent material processes. DH is able to reveal deformations and topological details at ultrahigh sensitivity (a few tens of nanometers) for particular details such as point-like objects and interfacial structures, allowing for the investigation of a range of processes. However, while DH is able to provide high precision data, the height measurement range is limited by the probe wavelength. Therefore a 'synthetic' wavelength created from the superposition of two or more individual wavelengths is often required in order to increase the measurement range to a suitable value dependent upon the object dimensions.

The use of multiple wavelengths attached to one system thus allows for surface height measurements over a relatively long range. In addition as the complex wave-front of each wavelength can be captured simultaneously in one digital image, real-time performance is achievable. In this thesis a number of materials processes were investigated at differing temperatures. The structural changes associated with the martensite to austenite phase transformation were measured using dual-wavelength digital holography during thermal cycling of nickel-aluminum-platinum (NiAlPt) and single-crystal Fe-15Cr-15Ni alloys. Real-time in-situ measurements reveal the formation of striations within the NiPtAl alloy at ∼70°C, and the FeCrNi alloy at ∼520°C. The results demonstrate that digital holography is an effective technique for acquiring non-contact, high precision information of the 3D surface evolution of alloys at high temperatures.

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Dobrev, Ivo Tsvetanov. "Full-field vibrometry by high-speed digital holography for middle-ear mechanics". Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-dissertations/328.

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"Hearing loss affects approximately 1 in 10 people in the world and this percentage is increasing every year. Some of the most common causes of hearing loss are disorders of the middle-ear. Early detection and diagnosis of hearing loss as well as research to understand the hearing processes depend on medical and research tools for quantification of hearing capabilities and the function of the middle-ear in the complex acousto-mechanical transformation of environmental sounds into vibrations of the middle-ear, particular of the human tympanic membrane (TM or eardrum). Current ear exams assess the state of a patient’s hearing capabilities mainly based on qualitative evaluation of the healthiness of the TM. Existing quantitative clinical methods for description of the motion of the TM are limited to either average acoustic estimates (admittance or reflectance) or single-point displacement measurements. Such methods could leave examiners and researchers blind to the complex spatio-temporal response of the nanometer scale displacements of the entire TM. Current state-of-the-art medical research tools provide full-field nanometer displacement measurements of the surface of the human TM excited by steady state (tonal) stimuli. However, to fully understand the mechanics of hearing, and the complex acousto-mechanical characteristics of TM in particular, new tools are needed for full-field high-speed characterization of the nanometer scale displacements of the human TM subjected to impulse (wideband) acoustic excitation. This Dissertation reports the development of a new high-speed holographic system (HHS) for full-field nanometer transient (i.e., > 10 kHz) displacement measurement of the human middle-ear and the tympanic membrane, in particular. The HHS allows spatial (i.e., >500k data points) and temporal (i.e., > 40 kHz) resolutions that enable the study of the acoustical and mechanical characteristics of the middle-ear at a level of detail that have never been reached before. The realization of the HHS includes the development and implementation of novel phase sampling and acquisition approaches that allow the use of state-of-the-art high-resolution (i.e., >5 MP) and high-speed (> 80,000 fps) cameras through modular and expandable control architectures. The development of novel acquisition approaches allows the use of conventional speed (i.e., <20 fps) cameras to realize high-temporal resolutions (i.e., <15 us) at equivalent sampling rates of > 50,000 fps with minimum hardware cost and modifications. The design and implementation of novel spatio-temporal phase sampling methods utilize the high temporal resolution (i.e., < 5 us exposure) and frame rate (i.e., >80,000 fps) of high-speed cameras without imposing constraints on their spatial resolution (i.e., >20 um pixel size). Additionally, the research and in-vivo applications capabilities of the HHS are extended through the development and implementation of a holographic otoscope head (OH) and a mechatronic otoscope positioner (MOP). The large (i.e., > 1 GB with > 8x10^9 parameters) spatio-temporal data sets of the HHS measurements are automatically processed by custom parallel data mining and interpretation (PDMI) methods, which allow automatic quantification of medically relevant motion parameters (MRMPs), such as modal frequencies, time constants, and acoustic delays. Such capabilities could allow inferring local material properties across the surface of the TM. The HHS is a new medical tool that enables otologists to improve the quality of diagnosis and treatments as well as provides researchers with spatio-temporal information of the hearing process at a level of detail never reached before. "

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Öhman, Johan. "3D localization in digital holography from scattered light from micrometer-sized particles". Licentiate thesis, Luleå tekniska universitet, Strömningslära och experimentell mekanik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-68374.

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When a particle is illuminated by a beam of light it will scatter and redistribute the light in all directions. How it scatters depends on the size, shape and refractive index of the particle. Additionally, it depends on the wavelength and polarization of the illuminating beam. The direction and distance to the observer relative the particle also needs to be considered. A digital holographic imaging system is used to collect parts of the scattered light from micrometer-sized particles. By utilizing digital holography a three-dimensional reconstruction of the imaged scene is possible. Traditionally, particles are localized based on the intensity in the holographic reconstructions. In this licentiate thesis, the phase response of the scattered light is investigated and utilized. An alternative method for locating spherical particles is presented. The method locate particles based on a simple feature of a propagating wave, namely the fact that the wavefront curvature changes from converging to diverging at the axial location of the particle. The wavefront curvature is estimated using two different methods. The first method estimates the lateral phase-gradients using a finite-difference method. The second method uses a three-dimensional parametric model based on a Chebyshev polynomial expansion. The methods are demonstrated using both simulations and experimental measurements. The simulations are based on the Lorenz-Mie scattering theory for spherical particles and are combined with an imaging system model. Experiments are performed using an off-axis polarization sensitive digital holographic system with a coherent Nd:YAG laser. Measurements of stationary particles are made to validate and evaluate the proposed method. It is found that these methods estimate the true axial position and does not have the offset that is associated with intensity-based methods. Additionally, it is possible to exclude noise that shows up as false particles since noise does not have the same phase response as a real particle. The second method, that uses a parametric model, also improves the standard deviation in the positioning.

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Flewellen, James Lewis. "Digital holographic microscopy for three-dimensional studies of bacteria". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:94ff344b-51ec-41c5-a5f8-c579e16dccd7.

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Holography has the ability to render three-dimensional information of a recorded scene by capturing both the amplitude and phase of light incident on the recording medium. The application of digital camera technology and high-speed computing means digital holograms can be analysed numerically and novel applications can be found for this technology. This thesis explores the potential for both inline and off-axis digital holographic microscopy to study the three-dimensional swimming behaviour of bacteria. A high-magnification (225x) digital holographic microscope was designed and constructed with the ability to switch easily between inline and off-axis imaging modalities. Hardware aspects, in particular the illumination source, the choice of camera and data transfer rates, were considered. Novel strategies for off-axis holography combining dark field microscopy were designed and implemented. The localisation accuracy of the inline imaging modality was assessed by studying samples of polystyrene microspheres. The microscope is sensitive to stage drift on the order of angstroms per second and can successfully localise microspheres in dilute suspensions at least 100μm from the objective specimen plane. As a simple test of the capabilities of the microscope, the diffusion coefficient of a 0.5μm microsphere was found to be isotropic and consistent with the theoretical value. Amplitude and phase image reconstructions from the off-axis modality are demonstrated. High-magnification dark field off-axis holographic microscopy is shown to be superior to inline microscopy in localising 100nm gold nanoparticles. An artifact from our method of dark-field imaging, however, restricts the depth range to 15μm. A lower-magnification (45x) configuration of the microscope was used to study the 3D swimming behaviour of wild type Escherichia coli as a qualitative demonstration of the potential for this instrument in microbiological applications.

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Burns, Nicholas. "Automated analysis system for the study of digital inline holograms of aquatic particles". Thesis, University of Aberdeen, 2011. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=166951.

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The work embodied in this thesis describes software techniques developed to analyse digital inline holograms of suspended particle fields, particularly in aquatic environ- ments. The primary motivation behind this work has been development of tech- niques to extract useable information from individual holograms within holovideos, producing focused silhouettes of recorded plankton and other particulates with min- imal user intervention. Two automated focusing algorithms are developed and presented in this work, both of which obtain comparable results for holograms of sparse plankton populations. The first approach is based on rectangular regions of interest (ROIs), which are aligned to (x, y) dimensions, and localise particles within the two-dimensional recon- structed planes obtained from holovideo frames. Due to poor immunity to particle merging when applied to denser particle fields, a second approach was developed using arbitrary polygons with which to localise particle positions in reconstructed planes. This new approach offers a greater immunity to the merging of particles lying in close proximity in the (x, y) dimensions of the hologram, and allows better particle localisation for high density particle holograms. Both ROI and polygon based particle localisation are explored to identify strengths and weaknesses, and complete automated scanning procedures developed in both cases. Examples are provided of typical output from automated scanning algorithms when applied to a number of sample holograms, and areas of weakness highlighted for future work.

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Hattay, Jamel. "Wavelet-based lifting structures and blind source separation : applications to digital in-line holography". Rouen, 2016. http://www.theses.fr/2016ROUES016.

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Ce projet de thèse expose des méthodes de traitement, dans le domaine des ondelettes, pour résoudre certains problèmes liés à la mise en oeuvre de l’holographie numérique dans l’axe. Ce developpement utilise des outils de la théorie de l’information et des divers moyens de traitement du signal tels que la séparation aveugle de sources (SAS). Cette technique est exploitée, ici, pour améliorer l’efficacité de l’holographie numérique, tels que la suppression de l’image jumelle, l’estimation de l’indice de réfraction, le codage et la transmission temps réel des hologrammes. Tout d’abord, nous donnons une brève introduction à la configuration dans l’axe de l’holographie numérique telle qu’elle est mise en oeuvre à l’UMR 6614 CORIA: l'explication de l’étape d’enregistrement ainsi que les différentes approches de restitution des hologrammes utilisés dans cette thèse. Ensuite, nous présentons un état de l’art des méthodes permettant de résoudre les deux principaux obstacles rencontrés dans la reconstruction des hologrammes numériques: l’étape de mise au point et la suppression de l’image jumelle. Ensuite, nous expliquons méticuleusement l’outil basé sur la transformée d’ondelettes, pour assurer une décomposition multi résolution de l’image, qui permet la séparation aveugle des images mélangées par un produit de convolution. Notre proposition consiste à utiliser la 2ème génération de la transformée en ondelettes d’une manière adaptative appelée aussi Schéma de lifting en quinconce Adaptif (SLQA). Cette décomposition est couplée à un algorithme de séparation appropriée pour former les trois étapes suivantes : les images d’entrées, mélangées par convolution, sont décomposées par SLQA pour former un arbre d’ondelettes. Ensuite, on applique l’algorithme de séparation sur le noeud le plus parcimonieux, généralement à la résolution la plus élevée, et enfin les images séparées sont reconstruites à l’aide de l’inverse de SLQA. Cet outil est appliqué pour résoudre plusieurs problèmes liés à des applications d’holographie numérique dans l’axe. Dans ce contexte, deux méthodes sont proposées. La première méthode, utilisant l’entropie globale, est développée pour rechercher de manière automatique le meilleur plan de mise au point des images holographiques. La deuxième méthode sert à supprimer l’image jumelle qui accompagne l’image restituée. Cette dernière se base sur la décomposition SLQA avec un algorithme de séparation statistique qui utilise la fameuse technique Analyse en Composantes Indépendantes (ACI). Vu que le formalisme d’un produit de convolution est retenu dans l’étape de formation de l’hologramme, l’outil SLQA et ACI assurent parfaitement la tâche de déconvolution. Les résultats expérimentaux confirment bien que nos deux méthodes proposées sont capables d’estimer le meilleur plan de mise au point et d’éliminer l’effet de l’image jumelle dans l’image restituée. Puis, nous proposons d’estimer l’épaisseur d’un anneau dans une image restituée d’un hologramme contenant la diffraction d’une bulle de vapeur stable dans une gouttelette d’un liquide. La dernière partie met en oeuvre le nouveau concept de Télé-Holographie. Il s’agit de mettre en place un échange de flux interactif entre la chambre d’enregistrement des hologrammes in-situ et un laboratoire distant au sein duquel s’effectue le traitement numérique de ces hologrammes. Pour atteindre cet objectif, nous proposons de réaliser une compression sans perte des hologrammes numériques par transformée en ondelettes. Pour la phase de la transmission progressive, selon la capacité du canal de transmission, nous proposons une manière efficace pour le codage de l’arbre des zéros des coefficients emboités obtenu par la transformée d’ondelette en quinconce (SLQA). Ce codeur nous permet une réduction considérable du débit binaire lors de la transmission des hologrammes. Les premiers tests effectués sur des hologrammes réels, enregistrés au sein du laboratoire CORIA, montrent une amélioration significative des taux de compression totale et de la taille de l’hologramme compressé
The present thesis is meant to develop specific processes, in the realm of wavelets domain, for certain digital holography applications. We mainly use the so-called blind source separation (BSS) techniques to solve numerous digital holography problems, namely, the twin image suppression, real time coding and transmission of holograms. Firstly, we give a brief introduction to in-line configuration of digital holography in flow measurements: the recording step explanation and the study of two reconstruction approaches that have been used during this thesis. Then, we emphasize the two well known obstacles of digital holograms reconstruction, namely, the determination of the best focus plane and the twin image removal. Secondly, we propose a meticulous scrutiny of the tool, based on the Blind Source Separation (BSS), enhanced by a multiscale decomposition algorithm, which enables the blind separation of convolutively mixed images. The suggested algorithm uses a wavelet-based transformer, called Adaptive Quincunx Lifting Scheme (AQLS), coupled with an appropriate unmixing algorithm. The resulting deconvolution process is made up of three steps. In the first step, the convolutively mixed images are decomposed by AQLS. Then, separation algorithm is applied to the most relevant component to unmix the transformed images. The unmixed images are, thereafter, reconstructed using the inverse of the AQLS transform. In a subsequent part, we adopt the blind source separation technique in the wavelet field domain to solve several problems related to digital holography. In this context, we present two main contributions for digital in-line hologram processing. The first contribution consists in an entropy-based method to retrieve the best focus plane, a crucial issue in digital hologram reconstruction. The second contribution consists in a new approach to remove a common unwanted artifact in holography called the twin image. The latter contribution is based on the blind source separation technique, and the resulting algorithm is made up of two steps: an Adaptive Quincunx Lifting Scheme (AQLS) based on the wavelet packet transform and a statistical unmixing algorithm based on Independent Component Analysis (ICA) tool. The role of the AQLS is to maximize the sparseness of the input holograms. Since the convolutive formalism is retained in digital in-line holography, BSS-based tool is extended and coupled with wavelet-based AQLS to fulfill the deconvolution task. Experimental results confirm that convolutive blind source separation is able to discard the unwanted twin image from digital in-line holograms. The last of this part consists in measuring the thickness of a ring. This ring is obtained from an improved reconstructed image of an hologram containing a vapor bubble created by thermal coupling between a laser pulse and nanoparticles in a droplet of a liquid. The last part introduces the Tele-Holography concept. Once the image of the object is perfectly reconstructed, the next objective is to code and transmit the reconstructed image for an interactive flow of exchange between a given laboratory, where the holograms are recorded, and a distant partner research. We propose the tele-holography process that involves the wavelet transform tool for lossless compression and transmission of digital holograms. The concept of tele-holography is motivated by the fact that the digital holograms are considered as a 2D image yielding the depth information of 3D objects. Besides, we propose a quincunx embedded zero-tree wavelet coder (QEZW) for scalable transmission. Owing to the transmission channel capacity, it reduces drastically the bit rate of the holography transmission flow. A flurry of experimental results carried out on real digital holograms show that the proposed lossless compression process yields a significant improvement in compression ratio and total compressed size. These experimentations reveal the capacities of the proposed coder in terms of real bitrate for progressive transmission

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Naidoo, Thegaran. "Digital holographic microscopy with automated detection of red blood cells". Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/61032.

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The digital in-line holographic configuration is motivated by the goal of developing a portable, cost effective sensor system for pre-screening patient blood samples. The theory of holography is explained from the foundational concepts in scalar diffraction theory all the way through to the implementation of reconstruction algorithms. Methods for the enhancement of holographic reconstructions are described. The algorithms that perform an automated count of the reconstructed objects are described and demonstrated. Simulated and experimental results are provided. Together, the lens-free holographic microscopy of micro-sized particles along with the application of image processing techniques for the automated detection and counting of objects of interest, provide a component towards realising a sensor system that can be used for pre-screening patient blood samples.
Dissertation (MSc)--University of Pretoria, 2017.
CSIR
Computer Science
MSc
Unrestricted

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Downham, Alexander David. "True 3D Digital Holographic Tomography for Virtual Reality Applications". University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1513204001924421.

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Brito, Isis Vasconcelos de. "Técnicas de microscopia holográfica digital aplicadas à análise de sistemas biológicos". Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-11012016-131143/.

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A Microscopia Holográfica Digital (MHD) é uma poderosa ferramenta para análise não destrutiva de superfícies e caracterização morfológica e estrutural de materiais. Várias técnicas microscópicas têm sido utilizadas com esses objetivos, mas, em todas elas, a visualização de campo completo não é permitida em uma única aquisição da informação do sistema analisado, além disso, a necessidade de uso de corantes, o processo de varredura, entre outros fatores, dificulta a aquisição das imagens. A Microscopia Holográfica Digital permite contornar essas dificuldades através de um método simples e rápido. Com uma modificação em seu arranjo original, é possível revelar as diferenças na absorção e nos índices de refração experimentados por um campo transmitido por um material anisotrópico. Este método, neste trabalho, foi nomeado como Microscopia Holográfica de Polarização, o qual permite medir as diferenças de fase e de intensidade relacionadas com a birrefringência e com o dicroísmo do material, respectivamente. Dessa forma, A MHD se mostra uma ferramenta promissora na análise de problemas em diversas áreas, pois possibilita, através de uma única captura, obter informações sobre as propriedades ópticas e estruturais dos sistemas de interesse. O objetivo desse trabalho foi, além do desenvolvimento instrumental, analisar variações nas propriedades ópticas e morfológicas de eritrócitos através da quantificação dos índices de refração e perfis topográficos destes quando submetidos aos principais agentes de fixação de amostras. Essas variações são determinantes na escolha do método de análise, já que estes podem alterar significativamente os resultados, assim como a sua interpretação. Também foi descrito um novo método, baseado na técnica holográfica, de análise do dicroísmo linear através de uma varredura executada sobre os padrões de difração das componentes ortogonais do campo transmitido pela amostra. A aplicação da MHD ao estudo de processos dinâmicos também foi realizada, utilizando células cardíacas vivas e proteínas em solução. Somados, estes resultados demonstraram a possibilidade de se utilizar as técnicas holográficas como métodos de estudo amplo de microssistemas biológicos.
The Digital Holographic Microscopy (DHM) is a powerful tool for nondestructive analysis of surfaces and for morphological and structural characterization of materials. Several microscopic techniques have been used with these purposes, but in all cases, the complete field reconstruction is not allowed in a single acquisition of information of the analyzed system, moreover, the requirements of staining and scanning procedures, among other factors, difficult the image acquisition. Digital Holographic Microscopy allows to overcome these difficulties through a simple and quick method. With a modification in its original setup, is possible to reveal the differences in absorption and refractive index experienced by a wavefield transmitted by an anisotropic material. This method, in this thesis, is named Polarization Holographic Microscopy, which allows to measure differences in phase and intensity related to the birefringence and the dichroism of the material, respectively. Thereby, the DHM is shown as a promising tool for the study of problems in several fields, because it allows, through a single capture, to obtain information related to optical and morphological properties of the systems of interest. The objective of this work was, besides instrumental development, to evaluate changes in optical and morphological properties of erythrocytes through quantification of their refractive index and topographic profiles when submitted to the main fixating agents. These changes are crucial once the method of analysis is chosen, as they can significantly alter the results, as well as their interpretation. A new method was also described based on the holographic technique, for analysis of linear dichroism, through scans performed on the diffraction patterns of the orthogonal components of the field transmitted by the sample. The application of the DHM to the study of dynamic processes was also performed, using live cardiac cells and proteins in solution. Together, these results demonstrate the possibility of using holographic techniques such as extensive methods for studying biological microsystems.

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Antier-Murgey, Marie. "Mesure interférométrique de phase et application à la combinaison cohérente d’un grand nombre de fibres amplificatrices". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112334/document.

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Les propriétés intrinsèques des fibres amplificatrices telles que leur robustesse, leur efficacité, leur qualité de faisceau ou encore leur compacité ou leur bonne gestion thermique, en font un candidat idéal pour le développement de sources lasers de haute puissance, capables de rivaliser aujourd’hui avec les lasers solides. Les applications de ces sources avec de fortes puissances sont nombreuses : l’industrie (usinage, marquage), la défense (télémétrie, imagerie), la physique des particules. Dans ce dernier cas, des sources ultra-brèves et ultra-intenses permettent d’envisager de nouvelles applications telles que la proton-thérapie ou bien le remplacement des synchrotrons actuels par des architectures moins encombrantes et ayant un rendement plus important. Ce travail de thèse s’est déroulé dans le contexte du projet ICAN qui vise à étudier l’architecture de ces nouvelles sources.La combinaison cohérente de plusieurs amplificateurs fibrés en parallèle permet d’augmenter la puissance de ces sources. Pour atteindre les énergies visées dans le projet ICAN, la combinaison cohérente de 10 000 fibres doit être envisagée. L’objectif de cette thèse est de développer des techniques de contrôle de la phase compatibles avec un très grand nombre de fibres, pour leur application aux lasers ultra-intenses nécessaires à la physique des particules.Deux architectures de combinaison cohérente basées sur une mesure de phase interférométrique ont été réalisées dans cette thèse. La première, basé sur l’holographie numérique, permet un contrôle de la phase sans aucun calcul, collectif tant au niveau de la mesure que de la correction. La seconde architecture possède un contrôle actif de phase basé sur un algorithme de traitement d’images et elle a une bande passante compatible avec le spectre de bruit des amplificateurs. La combinaison cohérente de 16 fibres à 1kHz avec une erreur résiduelle de phase de λ/60mrs a été démontrée. La compatibilité de ces deux architectures avec 10 000 fibres a été étudiée et nous avons apporté quelques éléments pour la combinaison cohérente d’un très grand nombre de fibres
The intrinsic properties of optical fibers like robustness, efficiency, beam quality, compactness and good thermal management can now compete with solid state lasers to develop high power laser sources. The applications of such sources include industry (machining, marking), defense (telemetry, lidar), and fundamental research. In this case, high intensity lasers are compulsory to produce the next generation of particles accelerators more efficient and more compact, both for fundamental research and its direct applications such as proton therapy. This work was done in the context of the ICAN project, which studies the feasibility of such sources.To overcome the limitations in terms of power of a single amplified fiber, an idea is to use several fiber lasers and to combine them coherently. To reach the ultra-high peak power and high average power requirements for these applications, the coherent beam combining of 10,000 fiber amplifiers has to be envisaged. The goal of the work is to develop a scheme of phase control scalable to a high number of combined fibers.Two schemes based on an interferometric phase measurement are realized in this work. The fist scheme, based on digital holography, permits a collective phase measurement and correction without calculation. The second scheme is based on an active phase control with individual phase modulators. This control requires an image processing algorithm and has a bandwidth compatible with the phase spectral noise of the amplifiers. The coherent combining of 16 fibers at 1kHz with a residual phase shift error of λ/60rms is achieved in this case. We use this second scheme to evaluate its scalability. We show that the coherent combining of 10,000 fibers using off-the-shelf components is already possible

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Welsh, Thomas V. "Quantitative Analysis of 3D Images Formed Using Range Compressed Holography". University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1512317926568769.

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Philipp, Katrin, Florian Lemke, Matthias C. Wapler, Ulrike Wallrabe, Nektarios Koukourakis e Jürgen W. Czarske. "Spherical aberration correction of adaptive lenses". SPIE, 2017. https://tud.qucosa.de/id/qucosa%3A34878.

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Deformable mirrors are the standard adaptive optical elements for aberration correction in confocal microscopy. Their usage leads to increased contrast and resolution. However, these improvements are achieved at the cost of bulky optical setups. Since spherical aberrations are the dominating aberrations in confocal microscopy, it is not required to employ all degrees of freedom commonly offered by deformable mirrors. In this contribution, we present an alternative approach for aberration correction in confocal microscopy based on a novel adaptive lens with two degrees of freedom. These lenses enable both axial scanning and aberration correction, keeping the setup simple and compact. Using digital holography, we characterize the tuning range of the focal length and the spherical aberration correction ability of the adaptive lens. The operation at fixed trajectories in terms of focal length and spherical aberrations is demonstrated and investigated in terms of reproducibility. First results indicate that such adaptive lenses are a promising approach towards high-resolution, high-speed three-dimensional microscopy.

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McReynolds, Naomi. "Advanced multimodal methods in biomedicine : Raman spectroscopy and digital holographic microscopy". Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/12129.

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Moving towards label-free technologies is essential for many clinical and research applications. Raman spectroscopy is a powerful tool in the field of biomedicine for label-free cell characterisation and disease diagnosis, owing to its high chemical specificity. However, Raman scattering is a relatively weak process and can require long acquisition times, thus hampering its integration to clinical technologies. Multimodal analysis is currently pushing the boundaries in biomedicine, obtaining more information than would be possible using a single mode and overcoming any limitations specific to a single technique. Digital holographic microscopy (DHM) is a rapid and label-free quantitative phase imaging modality, providing complementary information to Raman spectroscopy, and is thus an ideal candidate for combination in a multimodal system. Firstly, this thesis explores the use of wavelength modulated Raman spectroscopy (WMRS), for the classification of immune cell subsets. Following this a multimodal approach, combining Raman spectroscopy and DHM, is demonstrated, where each technique is considered individually and in combination. The complementary modalities provide a wealth of information (both chemical and morphological) for cell characterisation, which is a step towards achieving a label-free technology for the identification of human immune cells. The suitability of WMRS to discriminate between closely related neuronal cell types is also explored. Furthermore optical spectroscopic techniques are useful for the analysis of food and beverages. The use of Raman and fluorescence spectroscopy to successfully discriminate between various whisky and extra-virgin olive oil brands is demonstrated, which may aid the detection of counterfeit or adulterated samples. The use of a compact Raman device is utilised, demonstrating the potential for in-field analysis. Finally, monodisperse and highly spherical nanoparticles are synthesised. A short study demonstrates the potential for these nanoparticles to benefit the techniques of surface enhanced Raman spectroscopy and optical trapping, by way of minimising variability.

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48

Grosse, Doris [Verfasser], Martin [Gutachter] Hofmann e Thomas [Gutachter] Mussenbrock. "Topographic measurements using digital holographic microscopy combined with photorefractive single-shot holography / Doris Grosse ; Gutachter: Martin Hofmann, Thomas Mussenbrock ; Fakultät für Elektrotechnik und Informationstechnik". Bochum : Ruhr-Universität Bochum, 2014. http://d-nb.info/1214440932/34.

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Kirchmann, Carl Christian, Elin Lundin e Jakob Andrén. "A Study of Digital In-Line Holographic Microscopy for Malaria Detection". Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-229840.

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The main purpose of the project was to create an initial lab set-up for a dig-ital in-line holographic microscope and a reconstruction algorithm. Different parameters including: light source, pin-hole size and distances pinhole-object and object-camera had to be optimized. The lab set-up is to be developed further by a master student at the University of Nairobi and then be used for malaria detection in blood samples. To acquire good enough resolution for malaria detection it has been found necessary to purchase a gray scale camera with smaller pixel size. Two dierent approaches, in this report called the on-sensor approach and the object-magnication approach, were investigated. A reconstruction algorithm anda phase recovery algorithm was implemented as well as a super resolution algorithm to improve resolution of the holograms. The on-sensor approach proved easier and cheaper to use with approximately the same results as the object-magnication method. Necessary further research and development of experimental set-up was thoroughly discussed.
Projketet har gått ut på att bygga en billigare och enklare metod för att identifiera malaria i blodprover. Malaria är ett stort problem i en mängd områden i världen. Flera av dessa är fattiga och kan i nuläget inte tillhandahålla den här tjänsten till sin befolkning. Förutom att dyr apparatur krävs måste även utbildad personal lägga ner mycket tid för att kolla en stor mängd blodprover för att statistiskt säkerställa om en person har malaria eller inte. Vårt mål var att bygga en labbuppställning för "Digital in line holographic microscopy" och en rekonstruktionsalgoritm som en masterstudent vid Nairobi universitet ska fortsätta utveckla. Vi kom också fram till vilken upplösning som krävdes för att kunna urskilja malaria i blodproverna. Digital in line holographic microscopy går till så att man har en ljuskälla som riktas genom ett pinnhål, ljuset som går genom pinnhålet ljuser upp det prov, blodproverna i vårt fall, man vill undersöka och det resulterande ljuset fångas på en kamera. Med kunskap om fourieroptik går det att rekonstruera den digitala bilden man fångat på kameran, innan rekonstruktion är den ett hologram vilken är svårtydd. Labbuppställningen byggdes delvis med en 3D printer. För att förbättra resultaten implementerades flera algoritmer vilka lade ihop en mängd förskjutna bilder till en bättre bild, så kallad super resolution. Vi lyckades inte komma till den upplösning som krävdes för att urskilja malaria men gjorde en grundlig förstudie och en utförlig beskrivning av det arbete som väntar den student som fortsätter med projektet. Framför allt beskrevs värden på parametrar och vilken typ av kamera som ska användas för att optimera uppställningen.

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Monnom, Olivier. "Méthodes algorithmiques de traitement d'images en holographie digitale". Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210840.

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Le présent travail traite de problèmes particuliers en traitement de signal soulevés par l'holographie digitale. Le premier chapitre présente l'holographie et l'holographie digitale. Le deuxième chapitre aborde le problème des artéfacts apparaissant sur le bord des hologrammes lorsque ceux-ci sont propagés numériquement. Le troisième chapitre propose une méthode automatique pour éliminer la phase de fond d'un hologramme. Le quatrième chapitre montre comment améliorer la visibilité des hologrammes en supprimant les objets diffractants. Le cinquième chapitre expose un logiciel d'aide à l'analyse des hologrammes enregistrés dans le temps. On montre la capacité du logiciel à effectuer du tracking d'objets en trois dimensions à posteriori. Le sixième chapitre traite de la reconnaissance de forme dans les hologrammes, le problème de la reconnaissance de particules micrométriques est abordé. Des conclusions et perspectives terminent le travail.
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

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