In both RMCS calibration and ACS calibration, the corresponding efficiency and robustness are tested by simulation and real experiments. In the real experiment of ACS calibration, the intrinsic and extrinsic parameters of the ACS are obtained simultaneously by our calibration procedure using the same image sequences, no extra data capturing step is required. The corresponding trajectory is recovered and illustrated using the calibration results of the ACS. Since the estimated translations of different cameras in an MCS may scaled by different scale factors, scale factor estimation algorithms are proposed for non-overlapping view RMCS calibration and ACS calibration respectively. To our knowledge, we are the first to study the calibration of ACS. / In this thesis, we focus on developing robust methods for the MCS calibration problems. In particular, we make two contributions. Firstly, we developed a novel extrinsic calibration method for the non-overlapping view Rigid Multiple Camera System (RMCS) using the kinematic information of the RMCS. The input are only the images captured when the non-overlapping RMCS is moved in an environment with enough static feature points. This assumption is true in many vision tasks such as SFM (Structure from Motion), SLAM (Simultaneous Localization and Map). The output is the extrinsic parameters of the cameras of the RMCS. / Multiple Camera Systems (MCS) have been widely applied in many vision applications and attracted much attention recently. Both intrinsic and extrinsic parameters of an MCS are needed to be calibrated before it is used. / Secondly, we proposed to solve the calibration of a particular model of non-rigid Multiple Camera System, namely, Articulated Camera System (ACS). In an ACS, the cameras are fixed on articulated arms with joints, the relative pose between them may change. Two ACS calibration methods are proposed. In the first approach, we assume the cameras have overlapping views. It uses the feature correspondences between the cameras in the ACS. In the second approach, we assume the cameras have no overlapping view. It requires only the ego-motion information of the cameras and can be used for the calibration of the non-overlapping view ACS. In both methods, the ACS is assumed to have performed general transformations in a static environment. / Chen, Junzhou. / Adviser: Kin Hong Wong. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3594. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 102-110). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

published_or_final_version / abstract / Computer Science / Doctoral / Doctor of Philosophy

The primary purpose of this investigation was to determine how magnification and perspective alter a person's judgements of pleasantness for images recorded in photographic prints. The magnification and perspective of four scenes were varied by recording each scene with each of six camera-lens focal lengths (28 mm, 35 mm, 50 mm, 70 mm, 85 mm, and 105 mm) from each of six distances. The distances revolved around a reference distance depending on scene content. The scenes were selected to be typical of the types of one person or multi-person scenes recorded most often by consumers of non-single-lens-reflex (non-SLR) 35 mm camera systems. The psychophysical scaling technique of magnitude estimation was used to assess each subjects' degree of pleasantness for each print in a single stimulus presentation format. The subjects were actual consumers of non-SLR camera systems. The results indicate that a wide variety of lens/distance combinations was found to produce pleasing images for each scene. Specifically, the combination of lens/distance which was representative of currently available non-SLR camera systems was almost always among the highest rated images for each scene. This result indicates that these consumers are quite pleased with the images they currently receive. These results are most easily explained using the theory of a compensation mechanism of picture perception. Suggestions for future research include the study of range effects, different methods of assessment, and attempts at understanding the emotional impact of photographs and how it relates to judgements of pleasantness. / Ph. D.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

The gas-liquid reaction between chlorodifluoromethane (R-22) and methanol, in the presence of sodium hydroxide, was investigated in an isothermal, stirred, semi-batch reactor. The objective of the study was to develop a model for the reaction and to identify the kinetic parameters. Reactor temperature was varied from 283 to 303 K, with inlet R-22 partial pressures between 40.5 and 60.8 kPa (absolute). Solutions containing sodium hydroxide concentrations of between 1.5 and 2.5 mol·dm-3 were charged into the reactor prior to each experiment. Preliminary investigations using the R-22-methanol system revealed that stainless steel was an inappropriate choice of material for the reactor as it displayed catalytic tendencies toward trimethyl orthoformate formation. Consequently, the reactor was constructed from glass and was equipped with an internal cooling coil, a single heating jacket and a temperature control unit. Liquid samples that were withdrawn from the reactor were degassed under vacuum to remove residual chlorodifluoromethane, and thereby inhibit further reaction. Spectrophotometry was used to analyze the liquid samples to determine the concentration of chloride ions in solution. The products obtained were difluorodimethyl ether (major product) and trimethyl orthoformate (by-product) as well as sodium chloride and sodium fluoride salts. Difluorodimethyl ether is a potential replacement for ozone depleting CFC refrigerants. A Box-Behnken experimental design was used to investigate the effect of reaction conditions on the product distribution. Variations in the reaction temperature, initial concentration of sodium hydroxide and inlet partial pressure of R-22 were considered. The modeling of the gas-liquid reactions was based on the -dehydrohalogenation mechanism. Since gas solubility in a liquid decreases in the presence of dissolved salts, the "salting-out" effect on mass transfer was included in the reactor model. Sechenov coefficients for sodium chloride and sodium fluoride were combined to give a salt Sechenov coefficient Ksalt . It was known from the literature that the presence of precipitated salts causes inefficient mixing and inhibits mass transfer, particularly in this system due to the relatively low salt solubilities in methanol. This mixing effect was also included in the appropriate mass transfer terms of the reactor model. The experimental data was fitted to a proposed kinetic scheme. Kinetic parameters for each of the proposed reactions, the Sechenov ‘salting out’ coefficients and the mixing parameter were obtained through the use of a non-linear, least-squares optimization algorithm. For the kinetic study, activation energies of 89.12 and 45.83 kJ·mol-1 were obtained for the difluorodimethyl ether and trimethyl orthoformate formation reactions, respectively, with a Sechenov salt coefficient of 0.712 and a mixing parameter of 22.43. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2013.

Thesis (MSc)--Stellenbosch University, 2015. / English abstract: We introduce a method for determining the position of a camera with accuracy beyond that which is obtainable through conventional methods, using a single image of a specially constructed calibration object. This is achieved by analysing the moiré pattern that emerges when two high spatial frequency patterns are superimposed, such that one pattern on a plane is observed through another pattern on a second, semi-transparent parallel plane, with the geometry of both the patterns and the planes known. Such an object can be created by suspending printed glass over printed paper or by suspending printed glass over a high resolution video display such as an OLED display or LCD. We show how the camera’s coordinate along the axis perpendicular to the planes can be estimated directly from frequency analysis of the moiré pattern relative to a set of guide points in one of the planes. This method does not require any prior camera knowledge. We further show how the choice of the patterns allows, within limits, arbitrary accuracy of this coordinate estimate at the cost of a stricter limit on the span along that coordinate for which the technique is usable. This improved accuracy is illustrated in simulation. With a sufficiently accurate estimate of the camera’s full set of 3D coordinates, obtained by conventional methods, we show how phase analysis of the moiré pattern in relation to the guides allows calculation of a new estimate of position in the two axes parallel to the planes. This new estimate is shown in simulation to offer significant improvement in accuracy. / Afrikaanse opsoming: Ons stel ’n metode bekend om die posisie van ’n kamera te bepaal met akkuuraatheid bo dit wat verkrygbaar is uit konvensionele metodes, deur gebruik te maak van ’n spesiaal gekonstrueerde kalibrasievoorwerp. Die metode berus op analise van moiré patrone wat onstaan waneer twee hoë ruimtelike frekwensie patrone oor mekaar neergelê word deurdat een patroon op ’n plat vlak waargeneem word deur ’n tweede patroon op ’n parallelle, gedeeltelik deursigtige vlak, met die geometrie van beide patrone en vlakke bekend. So ’n voorwerp kan geskep word deur ’n spesiaal gedrukte glas vlak te monteer oor gedrukte papier of oor ’n hoë resolusie skerm, soos ’n OLED skermof LCD. Onswys hoe die kamera se koördinaat langs die as loodreg op die vlakke direk uit frekwensie analise van die moiré patroon relatief tot ’n stel gidspunte in een van die vlakke bepaal kan word. Hierdie metode vereis geen vooraf kennis oor die kamera nie. Ons wys verder hoe die keuse van patrone, binne perke, arbitrêre akkuuraatheid in die bepaling van hierdie koördinaat kan verkry ten koste van ’n nouer bruikbare verstek in hierdie koördinaat. Die verbeterde akkuuraatheid is geïllustreer in simulasie. Indien ’n benadering van die kamera se volle stel 3D koördinate met voldoende akkuuraatheid ook beskikbaar is, wys ons ook hoe fase analise van die moiré patroon relatief tot die gidspunte ons in staat stel om’n nuwe benadering te kanmaak vir die koördinate in die twee asse parallel aan die vlakke. Daar word in simulasie getoon hoe hierdie nuwe benadering beduidend beter akkuuraatheid kan bied in vergelyking met konvensionele metodes van benadering.

The Large Format Camera is a high resolution wide-angle mapping camera. It will be carried into orbit as a payload in the Shuttle Orbiter vehicle's cargo bay. A mapping camera must be calibrated to determine precise values for its elements of interior orientation. The Large Format Camera was calibrated by the stellar method of camera calibration. Descriptions of the procedure used by the National Ocean Service to calibrate the Large Format Camera are included. / Master of Engineering

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

High capacity wireless and xed-line broadband services have a relatively small footprint over South Africa's vast expanse. This results in many rural areas, as well as military communication when deployed, relying on low-bandwidth communication networks instead, making live video communication over these links impractical. Traditional and advanced data compression methods cannot produce the payload reduction required for video use over these bandwidths. Instead, a model-based vision system is used to address this problem. This is not video compression but rather image understanding and representation in the context of prior models of the observed object. Markerless human tracking and pose recovery are the specific interests of this research. Markerless human pose tracking is a relatively new and growing field of image processing. It has many potential areas of application apart from low-bandwidth video communication, including the medical field, sporting arena, security and surveillance and human-machine interaction. As multimedia technologies continue to grow and improve, pose tracking systems have the potential to be used more and more. While a few markerless tracking devices are beginning to emerge, many currently available commercial motion capture systems require the use of a special suit and markers or sensors. This makes them very impractical for easy everyday, anywhere use. Current research in computer vision and image processing incorporates a significant focus on the development of markerless approaches to human motion capture. This dissertation looks at a complete markerless human pose tracking system which can be split into four distinct but interlinking stages: the image capture, image processing, body model and optimisation stages. After video data from multiple camera views is captured, the processing stage extracts image cues such as silhouettes, 2-D edges and 3-D colour volumetric reconstruction. Following the basic principle of a model-based approach, a 24 degree-of-freedom superellipsoid body model is fitted to the observed image cue data. An objective function is used to measure the closeness of this match. A number of different optimisation approaches are examined for use in refining and finding the best fitting body pose for each image frame. These approaches are all based around Stochastic Meta Descent (SMD) optimisation with SMD by itself, SMD in a hierarchical approach, SMD with pose prediction and Smart Particle Filtering, SMD inside a particle filter framework, all explored. The performance of the system with the various optimisation approaches is tested using the HumanEvaII datasets. These datasets contain a number of different subjects performing a variety of actions while wearing ordinary clothes. They contain markerbased ground-truth data obtained using a ViconPeak motion capture system. This allows a relative error measurement of the predicted poses to be calculated. With its robustness to clutter and occlusion, the Smart Particle Filter approach is shown to give the best results. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.