Stereo vision is a means of obtaining three-dimensional information by considering the same scene from two different positions. Stereo correspondence has long been and will continue to be the active research topic in computer vision. The requirement of dense disparity map output is great demand motivated by modern applications of stereo such as three-dimensional high-resolution object reconstruction and view synthesis, which require disparity estimates in all image regions. Stereo correspondence algorithms usually require significant computation. The challenges are computational economy, accuracy and robustness. While a large number of algorithms for stereo matching have been developed, there still leaves the space for improvement especially when a new mathematical tool such as wavelet analysis becomes mature. The aim of the thesis is to investigate the stereo matching approach using wavelet transform with a view to producing efficient and dense disparity map outputs. After the shift invariance property of various wavelet transforms is identified, the main contributions of the thesis are made in developing and evaluating two wavelet approaches (the dyadic wavelet transform and complex wavelet transform) for solving the standard correspondence problem. This comprises an analysis of the applicability of dyadic wavelet transform to disparity map computation, the definition of a waveletbased similarity measure for matching, the combination of matching results from different scales based on the detectable minimum disparity at each scale and the application of complex wavelet transform to stereo matching. The matching method using the dyadic wavelet transform is through SSD correlation comparison and is in particular detailed. A new measure using wavelet coefficients is defined for similarity comparison. The approach applying a dual tree of complex wavelet transform to stereo matching is formulated through phase information. A multiscale matching scheme is applied for both the matching methods. Imaging testing has been made with various synthesised and real image pairs. Experimental results with a variety of stereo image pairs exhibit a good agreement with ground truth data, where available, and are qualitatively similar to published results for other stereo matching approaches. Comparative results show that the dyadic wavelet transform-based matching method is superior in most cases to the other approaches considered.

Orientadores: Rafael Santos Mendes, Jonatas Manzolli / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-10T02:37:04Z (GMT). No. of bitstreams: 1 Luvizotto_AndreLuiz_M.pdf: 5323411 bytes, checksum: 87b1961bd111c6cc93b0d048c33bd164 (MD5) Previous issue date: 2007 / Resumo: Neste trabalho, as transformadas wavelet são utilizadas para recodificar e explorar sinais musicais. A idéia central do trabalho é mostrar que a reordenação adequada dos coeficientes provenientes das análises possibilita não somente recodificar de modo econômico o sinal como também transitar por sonoridades distintas. Ou seja, relaciona-se o posicionamento dos coeficientes wavelets, dentro de cada nível de multiresolução, com a geração de diferentes timbres. Uma vez definido o ordenamento dos coeficientes, duas formas de determinação de seus valores são exploradas. Na primeira forma, essas curvas ascendentes de coeficientes são aproximadas por uma função polinomial de grau p, levando a representações econômicas do sinal musical. Já no segundo modelo, os coeficientes de um sinal distinto (chamado sinal de base) são ordenados de forma ascendente. São então reordenados através das posições equivalentes do sinal original, também chamado de alvo, permitindo a sua reobtenção e também o trânsito entre as duas sonoridades envolvidas. Os resultados deste trabalho destacam a grande importância que o posicionamento dos coeficientes exercem na sonoridade com relação aos seus valores. Com os experimentos realizados, foi possível constatar que valores aproximados de coeficientes, corretamente dispostos no tempo, geram timbres alvos diversos de forma satisfatória. As análises dos resultados são feitas por metodologias diversas e pela audição dos arquivos de áudio gerados, que acompanham o texto em cd. Por fim, uma discussão sobre os resultados obtidos é realizada e uma proposta de continuação da pesquisa é sugerida, baseada em grupos de permutações como forma de síntese / Abstract: Musical signals are encoded and represented using wavelet transforms. Starting upon wavelet analysis, the main research idea is to show how an adequate re-ordination of wavelet coefticients makes possible to decode the signal economically and also to obtain different sonorities. Moreover, we relate a specific set of wavelet coeflicients from °each multi-resolution leveI to generate new timbres. Given re-ordination procedures, two forms to determine their values are explored. First one, coeflicient curves in ascendent order are approximated by a polynomial function of degree p that leads to an economic representation of musical signals. In the second approach, coeflicients from another signal (named "base"signal) are ordinated in ascendent order also. After they are re-ordinate across the positions ofthe original signal, called "target"signal. The results ofthis research highlight the great importance of the wavelet coeflicient's order to manipulate timbre. Experiments presented . here showed that coeflicients with approximated values and correct1y disposed in time, can be used to generate target timbres in a satisfactory way. The analysis of the results were done by different methodologies and by listening to the sound examples from the CD attached to this dissertation. Finally, a discussion of research aims is presented and a proposal for further work based on Mathematical Group of Permutation is projected as a way to develop a new synthesis method / Mestrado / Engenharia de Computação / Mestre em Engenharia Elétrica

A new technique that couples modal analysis and wavelet transforms for detection of multiple damage in structures is introduced. Structural damage may cause local changes in one or more of the following parameters; stiffness, mass and damping that affect the dynamic behavior of the structure. For example, a crack reduces the stiffness of the structure in a localized sense, and thus reducing its natural frequency, and causes changes in both modal damping and mode shapes. In this research, two different structures have been analyzed: beams and plates. First, uniform beams with a single damage (notch) of different sizes at different locations were considered. Then, a beam with multiple damages was analyzed. Secondly, a uniform plate with a single square damage was considered. For all structures considered, the responses were obtained experimentally (using experimental modal analysis) and numerically (using finite element analysis), then wavelet transform was used to detect and characterize these defects. Most vibration-based methods require knowledge of the undamaged state of the structure, which is unavailable in most cases. However, using wavelet transformation has the advantage of not requiring knowledge of the undamaged state. In addition, wavelet transform has the characteristics that make the visualization of the signal discontinuities clear. Here it has been found that some wavelets were able to detect the damage location for all cases. Also it was observed that the magnitude of the wavelet coefficient increased linearly with the increase in the amount of damage.

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Dissertation (PhD)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: See full text for abstract / AFRIKAANSE OPSOMMING: Sien volteks vir opsomming

published_or_final_version / abstract / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy