Outils logiciels temps réel pour l'assistance à la production stéréoscopique 3D

L'histoire du cinéma 3D est presque aussi longue que celle du cinéma 2D. Toutefois, ce n'est qu'avec l'utilisation des médias numériques que la commercialisation du contenu stéréoscopique 3D s'est concrétisée. Puisque la production stéréoscopique 3D nécessite l'utilisation de deux caméras, il est nécessaire de correctement ajuster celles-ci afin de produire du contenu pouvant être visualisé sans inconfort, tout en reproduisant adéquatement les caractéristiques du système visuel humain permettant la perception en profondeur. Les outils d'assistance à l'ajustement des caméras stéréoscopiques étant coûteux, la production de contenu stéréoscopique est généralement réservée aux utilisateurs expérimentés ou ayant des moyens financiers suffisants. Afin de rendre disponible l'utilisation et l'amélioration de cette technologie, il serait pertinent de fournir des outils gratuits et libres de droit. Puisqu'il existe des bibliothèques logicielles libres pour le traitement d'images stéréoscopiques appliqué au domaine de la reconstruction 3D, ce projet cherche à évaluer la possibilité d'adapter ces algorithmes pour le développement d'outils logiciels temps réel d'assistance à la production de contenu stéréoscopique. Pour ce faire, la détection et la correspondance de points caractéristiques sont utilisés afin de déterminer l'alignement relatif des caméras par l'estimation de la géométrie épipolaire. Les problèmes d'alignement sont par la suite corrigés par la rectification numérique des images. Afin d'obtenir une rectification stable en temps réel, les résultats montrent que des améliorations doivent être apportées aux algorithmes d'alignement et de rectification des images: 1) l'utilisation d'un détecteur de points caractéristiques alternatif non-propriétaire permettrait une meilleure performance; 2) l'utilisation d'un algorithme alternatif pour l'estimation robuste de l'alignement des caméras permettrait une estimation sans avoir à déterminer de paramètres de façon empirique; 3) l'utilisation d'un filtre de Kalman serait nécessaire pour une rectification stable des images lors d'une séquence vidéo. Le projet vise à l'intégration des techniques et de leurs améliorations dans une bibliothèque logicielle à code source ouvert, OpenS3D. Les fonctionnalités intégrées dans OpenS3D sont la visualisation de contenu stéréoscopique, les calculs pour l'assistance à l'alignement des caméras, la rectification numérique des images, l'analyse des profondeurs perçues pour une scène capturée. Toutes les fonctionnalités sont disponibles en temps réel à partir de l'interface utilisateur d'OpenS3D. Puisque les améliorations apportées aux techniques de calcul d'alignement des caméras permettent d'obtenir une estimation stable et cohérente au niveau temporel, cette estimation pourrait être directement utilisée afin de corriger les erreurs d’alignement de façon automatique. Une automatisation des paramètres des caméras permettrait par exemple de filmer des scènes 3D à partir de robots mobiles. De plus, des techniques supplémentaires pourraient être ajoutées au logiciel telles que l'analyse de rivalités rétiniennes pour les différences de couleur, de luminosité ou de reflets lumineux

Solid state electro-optic color filter and iris

A pair of solid state electro-optic filters (SSEF) in a binocular holder were designed and fabricated for evaluation of field sequential stereo TV applications. The electronic circuitry for use with the stereo goggles was designed and fabricated, requiring only an external video input. A polarizing screen suitable for attachment to various size TV monitors for use in conjunction with the stereo goggles was designed and fabricated. An improved engineering model 2 filter was fabricated using the bonded holder technique developed previously and integrated to a GCTA color TV camera. An engineering model color filter was fabricated and assembled using PLZT control elements. In addition, a ruggedized holder assembly was designed, fabricated and tested. This assembly provides electrical contacts, high voltage protection, and support for the fragile PLZT disk, and also permits mounting and optical alignment of the associated polarizers

Measurement of spray characteristics using optical measurement methods

Diplomová práce se zabývá měřením charakteristik sprejů dvou tlakových vířivých trysek pro spalovací komoru malého turbínového motoru na zkušebním stavu za studena pomocí metod Particle Image Velocimetry (PIV) a fázové Dopplerovské anemometrie (PDA). Cílem měření bylo stanovit a porovnat charakteristiky sprejů obou trysek. Výsledky měření mají objasnit rozdílnost chování trysek za provozu a možný dopad na proces spalování. Úvodní teoretická část pojednává o základních fyzikálních principech atomizace kapalin, konstrukci a oblasti uplatnění tlakových vířivých trysek a o principech laserových diagnostických metod použitých při experimentálním měření. Nasledující část popisuje návrh a montáž zkušební trati a dalších zařízení navržených pro experimentální měření v této práci. Experimentální část se zabývá nastavením parametrů měřícího systému a zpracováním dat. Výsledky měření zahrnují vektorová rychlostní pole, axiální rychlostní profily a distribuce velikosti kapek pro různé provozní podmínky obou trysek.The present thesis deals with measurement of spray characteristics of two pressure–swirl atomizers for a combustion chamber of a small–sized jet engine investigated on a cold test bench by means of Particle Image Velocimetry (PIV) and Phase-Doppler Anemometry (PDA). The aim of these measurements is to investigate and compare the spray characteristics of these nozzles in order to elucidate the possible impacts of the design change on the nozzle operation in the combustion chamber. The theoretical part deals with fundamental concepts of liquid atomization, design and performance of pressure–swirl atomizers and description of principles of the used laser diagnostic techniques. Next part describes design and operation of the test bench. The experimental part is devoted to experimental set-up and digital image processing and post–processing techniques of the gathered data. Results contain velocity vector fields, axial velocity profiles and droplet size distributions for various operating conditions of both nozzles.

Doctor of Philosophy

dissertation3D reconstruction from image pairs relies on finding corresponding points between images and using the corresponding points to estimate a dense disparity map. Today's correspondence-finding algorithms primarily use image features or pixel intensities common between image pairs. Some 3D computer vision applications, however, don't produce the desired results using correspondences derived from image features or pixel intensities. Two examples are the multimodal camera rig and the center region of a coaxial camera rig. Additionally, traditional stereo correspondence-finding techniques which use image features or pixel intensities sometimes produce inaccurate results. This thesis presents a novel image correspondence-finding technique that aligns pairs of image sequences using the optical flow fields. The optical flow fields provide information about the structure and motion of the scene which is not available in still images, but which can be used to align images taken from different camera positions. The method applies to applications where there is inherent motion between the camera rig and the scene and where the scene has enough visual texture to produce optical flow. We apply the technique to a traditional binocular stereo rig consisting of an RGB/IR camera pair and to a coaxial camera rig. We present results for synthetic flow fields and for real images sequences with accuracy metrics and reconstructed depth maps

State of the art 3D technologies and MVV end to end system design

L’oggetto del presente lavoro di tesi è costituito dall’analisi e dalla recensione di tutte le tecnologie 3D: esistenti e in via di sviluppo per ambienti domestici; tenendo come punto di riferimento le tecnologie multiview video (MVV). Tutte le sezioni della catena dalla fase di cattura a quella di riproduzione sono analizzate. Lo scopo è di progettare una possibile architettura satellitare per un futuro sistema MVV televisivo, nell’ambito di due possibili scenari, broadcast o interattivo. L’analisi coprirà considerazioni tecniche, ma anche limitazioni commerciali

LDA and PIV characterization of the flow in a hydrocyclone without an air-core

The three-dimensional flow in a hydrocyclone especially developed for application in the petroleum industry has been investigated through the LDA and PIV techniques for one experimental condition. In the present physical simulation, the hydrocyclone is set to operate without an air-core. The tangential (Vθ) and axial (Vz) mean velocity profiles are analyzed through both measuring techniques. Radial (Vr) mean velocity profiles are only accounted for through PIV. The exponent n in the tangential velocity equation, Vθrn = C, was determined to be about 0.61. For the radial profile, Vrrm = − D, m was found to be 1.59. The rms-values of two-velocity components — tangential and axial — were evaluated via LDA. Turbulence in the axial direction is observed to be slightly higher than turbulence in the tangential direction. Approaching the axis of symmetry of the cyclone, however, this trend is reversed. The fluctuations in the tangential direction are found to be at least twice higher than the axial fluctuations.Indisponível

Development and applications of two and three component particle image velocimetry techniques for simultaneous measurement in multi-phase flows and automative fuel sprays

The introduction of a new imaging approach for simultaneous multi-phase and multi-constituent velocity measurements is the main focus of this research. The proposed approach is based on the use of a single off-the-shelf colour camera which will enable simultaneous imaging of phases/constituents which are colourtagged using fluorescent droplets and multi-wavelength illumination. Highly efficient florescent tracers used to seed the constituents are presented and their visibility in full field imaging experiments is evaluated. A commonly found problem in experimental systems using laser illumination, known as flare, is discussed and the application of the developed fluorescent tracers for its reduction is presented. A strong focus of the imaging approach proposed is its flexibility and simplicity allowing its extension to stereoscopic imaging to obtain simultaneous multi-phase/constituent 3-component measurements with the addition of a second imaging camera. Proof of principle experiments with spatially separated and well mixed flows are presented for which successful phase discrimination is obtained and the uncertainty of the measurements is estimated. The imaging system developed is applied for simultaneous air and fuel velocimetry measurements in a Gasoline Direct Injection spray for which a more detailed understating of the interaction mechanisms is required to generate improved designs. The modified imaging system and experimental setup are presented and previously unavailable simultaneous air/fuel 2 and 3-component velocity fields are presented and analysed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

LASER Tech Briefs, September 1993

This edition of LASER Tech briefs contains a feature on photonics. The other topics include: Electronic Components and Circuits. Electronic Systems, Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Fabrication Technology, Mathematics and Information Sciences, Life Sciences and books and reports

Jet fuel spray characterisation using optical methods: an experimental study of high speed fuel injection systems in small rotary engines

This thesis was initiated by the need to develop a stable low vibration engine with a high power to weight ratio. A new rotary (Wankel) engine was chosen to meet these requirements. A further operating criterion was that the engine was required to use JP8 (aviation fuel). The difficulty created by the use of JP8 is that its combustion temperature is higher than other conventional fuels, and preheating is necessary, especially in the case of cold start. Thus, the question posed was, could a more appropriate and efficient method of fuel delivery be devised? This thesis presents the design and construction of a fluid spray visualisation system for investigating the macroscopic and microscopic characteristics of fuel sprays using low injection pressure up to 10 bar (1 MPa). Laser imaging techniques have been used for data acquisition. The thesis has been divided into several aspects. Firstly, a background study of fluid sprays and fuel injection strategies was carried out. This has centred on the relationship between droplet size and the combustion process. It further investigated what differentiated the fuel delivery approach to Wankle from that to other engines. Secondly, two families of fuel injector were tested and evaluated within the optical engineering laboratory using deionised water (DI) water for safety reasons. The first family involved conventional gasoline injectors with several nozzle arrangements. The second family involved medical nebulisers with several nozzle diameters. The evaluation of the fuel injectors required developing a fluid delivery circuit, and a specific ECU (Electronic Control Unit) for controlling pulse delivery and imaging instrument. The company associated with the project then set up a test cell for performing experiments on JP8 fuel. The initial global visualisation of the jet spray was made using a conventional digital camera. This gave a measurement of the spray angle and penetration length. However, as the study moved to the more precise determination of the fuel spray particulate size, a specialised Nd:YAG laser based diagnostic was created combined with a long range diffraction limited microscope. Microscopic characterisation of the fuel sprays was carried out using a backlight shadowgraph method. The microscopic shadowgraphy method was applied successfully to resolve droplets larger than 4 microns in diameter. The spray development process during an individual fuel injection cycle was investigated, presenting the frequency response effect of electronic fuel injectors (EFI) on the spray characteristics when operating at high injection frequencies (0.25 -­‐ 3.3 kHz). The velocity distribution during the different stages of an injection cycle was investigated using PIV. The influence of the injection pressure on the spray pattern and droplet size was also presented. Novel fluid atomisation systems were investigated for the capability of generating an optimum particulate distribution under low pressure. Finally, it was found that a new electronic medical nebuliser (micro-­‐dispenser) could be used to deliver the fuel supply with the relevant particle size distribution at low flow rate and high injection frequency. However, as yet it has not been possible to apply this approach to the engine; it is hoped that it will yield a more efficient method of cold starting the engine. The characteristics of this atomiser can be applied to provide a controllable fuel supply approach for all rotary engines to improve their fuel efficiency. The second part of this research discusses the droplets-­‐light interaction using Mie scattering for fluid droplets smaller than the microscope visualisation limit (4 microns). Mie scattering theory was implemented into Three-­‐Components Particle Image Velocimetry (3C-­‐ PIV) tests to address a number of problems associated with flow seeding using oil smoke. Mie curves were used to generate the scattering profile of the oil sub-­‐micron droplets, and therefore the scattering efficiency can be calculated at different angles of observation. The results were used in jet flow PIV system for the determination of the optimum position of the two cameras to generate balanced brightness between the images pairs. The brightness balance between images is important for improving the correlation quality in the PIV calculations. The scattering efficiency and the correlation quality were investigated for different seeding materials and using different interrogation window sizes