Página 1 dos resultados de 3358 itens digitais encontrados em 0.019 segundos

Estimação do fluxo multidirecional de pedestres em ambientes abertos e não restritos, pela análise de seqüências de imagens digitais; Pedestrians multi-directional flow estimation in opening and non-restricted environments by the analysis of digital images sequences

Gonçalves, Paulo Henrique
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/04/2005 PT
Relevância na Pesquisa
56.04%
O problema de contagem de pessoas em uma determinada região é de grande importância, e tem várias aplicações, tais como: planejamento dos serviços fornecidos por cinemas, shoppings centers, companhias de ônibus, assim como para o monitoramento do tráfego de pedestres em áreas urbanas. A necessidade de se conceber sistemas confiáveis capazes de contabilizar, em tempo real, o número de pessoas circulando em uma determinada região tem sido evidenciado por essas aplicações. Este trabalho apresenta um sistema de baixo custo para a estimação do fluxo multidirecional de pedestres, em ambientes abertos e não restritos, baseado na seqüência de imagens digitais, capturadas por uma única câmera vídeo tipo WEBCAM. A câmera é colocada na vertical do espaço a ser monitorado e conectada a um PC através da porta USB. A metodologia tem como base o trabalho desenvolvido por Pádua (2002) e utiliza o algoritmo proposto em Lucas e Kanade (1981) que computa o fluxo óptico das imagens capturadas pela câmera. Uma análise espaço-temporal desse fluxo é realizada para determinar o fluxo multidirecional dos pedestres.; The problem in counting people in restricted area is of great importance in planning the services offered by cinemas...

Co-projeto hardware/software para cálculo de fluxo ótico; Software/hardware co-desing for the optical flow calculation

Lobo, Tiago Mendonça
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 17/06/2013 PT
Relevância na Pesquisa
66.03%
O cálculo dos vetores de movimento é utilizado em vários processos na área de visão computacional. Problemas como estabelecer rotas de colisão e movimentação da câmera (egomotion) utilizam os vetores como entrada de algoritmos complexos e que demandam muitos recursos computacionais e consequentemente um consumo maior de energia. O fluxo ótico é uma aproximação do campo gerado pelos vetores de movimento. Porém, para aplicações móveis e de baixo consumo de energia se torna inviável o uso de computadores de uso geral. Um sistema embarcado é definido como um computador desenvolvido com um propósito específico referente à aplicação na qual está inserido. O objetivo principal deste trabalho foi elaborar um módulo em sistema embarcado que realiza o cálculo do fluxo ótico. Foi elaborado um co-projeto de hardware e software dedicado e implementados em FPGAs Cyclone II e Stratix IV para a prototipação do sistema. Desta forma, a implementação de um projeto que auxilia a detecção e medição do movimento é importante não só como aplicação isolada, mas para servir de base no desenvolvimento de outras aplicações como tracking, compressão de vídeos, predição de colisão, etc; The motion vectors calculation is used in many processes in the area of computer vision. Problems such as establishing collision routes and the movement of the camera (egomotion) use this vectors as input for complexes algorithms that require many computational and energy resources. The optical flow is an approximation of the field generated by the motion vectors. However...

Uso de fluxo óptico na odometria visual aplicada a robótica; Using the optical flow in the visual odometry applied robotics

Darla Caroline da Silva Araújo
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 16/01/2015 PT
Relevância na Pesquisa
66.06%
O presente trabalho descreve um método de odometria visual empregando a técnica de fluxo óptico, para estimar o movimento de um robô móvel, através de imagens digitais capturadas de duas câmeras estereoscópicas nele fixadas. Busca-se assim a construção de um mapa para a localização do Robô. Esta proposta, além de alternativa ao cálculo autônomo de movimento realizado por outros tipos de sensores como GPS, laser, sonares, utiliza uma técnica de processamento óptico de grande eficiência computacional. Foi construído um ambiente 3D para simulação do movimento do robô e captura das imagens necessárias para estimar sua trajetória e verificar a acurácia da técnica proposta. Utiliza-se a técnica de fluxo óptico de Lucas Kanade na identificação de características em imagens. Os resultados obtidos neste trabalho são de grande importância para os estudos de navegação robótica.; This work describes a method of visual odometry using the optical flow technique to estimate the motion of a mobile robot, through digital images captured from two stereoscopic cameras fixed on it, in order to obtain a map of location of the robot. This proposal is an alternative to the autonomous motion calculation performed by other types of sensors such as GPS...

An optical flow-based sensing system for reactive mobile robot navigation

Caldeira,Eliete Maria de Oliveira; Schneebeli,Hans Jörg Andreas; Sarcinelli-Filho,Mário
Fonte: Sociedade Brasileira de Automática Publicador: Sociedade Brasileira de Automática
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2007 EN
Relevância na Pesquisa
66.08%
This work discusses the use of optical flow to generate the sensorial information a mobile robot needs to react to the presence of obstacles when navigating in a non-structured environment. A sensing system based on optical flow and time-to-collision calculation is here proposed and experimented, which accomplishes two important paradigms. The first one is that all computations are performed onboard the robot, in spite of the limited computational capability available. The second one is that the algorithms for optical flow and time-to-collision calculations are fast enough to give the mobile robot the capability of reacting to any environmental change in real-time. Results of real experiments in which the sensing system here proposed is used as the only source of sensorial data to guide a mobile robot to avoid obstacles while wandering around are presented, and the analysis of such results allows validating the proposed sensing system.

Motion Field and Optical Flow: Qualitative Properties

Verri, Alessandro; Poggio, Tomaso
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Formato: 32 p.; 3417509 bytes; 1316771 bytes; application/postscript; application/pdf
EN_US
Relevância na Pesquisa
66.15%
In this paper we show that the optical flow, a 2D field that can be associated with the variation of the image brightness pattern, and the 2D motion field, the projection on the image plane of the 3D velocity field of a moving scene, are in general different, unless very special conditions are satisfied. The optical flow, therefore, is ill-suited for computing structure from motion and for reconstructing the 3D velocity field, problems that require an accurate estimate of the 2D motion field. We then suggest a different use of the optical flow. We argue that stable qualitative properties of the 2D motion field give useful information about the 3D velocity field and the 3D structure of the scene, and that they can usually be obtained from the optical flow. To support this approach we show how the (smoothed) optical flow and 2D motion field, interpreted as vector fields tangent to flows of planar dynamical systems, may have the same qualitative properties from the point of view of the theory of structural stability of dynamical systems.

Exploring the Practical Limits of Optical Flow

Barnum, Peter ; Hu, Bo ; Brown, Christopher M. (1945 - )
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Relatório
ENG
Relevância na Pesquisa
66.17%
This report documents our experience with different optical flow estimation methods and our attempt to use optical flow both qualitatively and quantitatively. Special attention is devoted to improving the Lucas-Kanade method to obtain dense flow. We use a simple clustering technique to find looming objects. This method has the potential of supporting obstacle avoidance using optical flow. Experiments using real images demonstrate that this simple clustering is effective for certain scenes. We also point out when this technique will fail. We try to use optical flow quantitatively to recover the structure of a piecewise planar environment. First, we use the widely-known 8-parameter planar flow equations to locate individual planes in the scene. Second, in lieu of full flow, we try to use normal flow to compute both the ego-motion and the structure. Both trials fail ungracefully, mostly due to noisy flow data. We describe the mathematics ofboth methods and our experimental results.

Perception of Rigid Motion from Spatio-Temporal Derivatives of Optical Flow

Bandyopadhyay, Amit ; Aloimonos, John
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Relatório
ENG
Relevância na Pesquisa
66.02%
The perception of rigid motion from the optical flow generated on the retina is considered. In general, the problem does not have a unique answer. In addition, the equation that constrains the motion parameters based on flow information is nonlinear. We show here that by using either the temporal or the spatial derivatives of the retinal flow, linear equations in the motion parameters can be derived, which can then be used to compute the motion parameters uniquely.

Hyperspectral video restoration using optical flow and sparse coding

Mian, Ajmal; Hartley, Richard
Fonte: Optical Society of America Publicador: Optical Society of America
Tipo: Artigo de Revista Científica Formato: 12 pages
Relevância na Pesquisa
76.1%
Hyperspectral video acquisition is a trade-off between spectral and temporal resolution. We present an algorithm for recovering dense hyperspectral video of dynamic scenes from a few measured multispectral bands per frame using optical flow and sparse coding. Different set of bands are measured in each video frame and optical flow is used to register them. Optical flow errors are corrected by exploiting sparsity in the spectra and the spatial correlation between images of a scene at different wavelengths. A redundant dictionary of atoms is learned that can sparsely approximate training spectra. The restoration of correct spectra is formulated as an ℓ1 convex optimization problem that minimizes a Mahalanobis-like weighted distance between the restored and corrupt signals as well as the restored signal and the median of the eight connected neighbours of the corrupt signal such that the restored signal is a sparse linear combination of the dictionary atoms. Spectral restoration is followed by spatial restoration using a guided dictionary approach where one dictionary is learned for measured bands and another for a band that is to be spatially restored. By constraining the sparse coding coefficients of both dictionaries to be the same...

Optical flow estimation in the presence of fast or discontinuous motion.

Niu, Yan
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2010
Relevância na Pesquisa
66.14%
This thesis focuses on the computation of optical flow, i.e., the motion perceived from a sequence of gradually changing images, as an estimate for the 2D velocity of the scene. Due to the large variety and high complexity of the motion types existing in practice, motion recovery requires the estimation process to be highly adaptive. This thesis investigates how to select and combine the reasoning rules, namely the optical flow constraints, according to the type of motion information detected. Moreover, the thesis extends optical flow computation to fast rotation, an important, frequent and challenging motion type, which has not been addressed much in the literature. The thesis starts by proposing various measures, based on theory as well as heuristics, for motion inconsistency detection. This facilitates selecting only the optical flow constraints that are valid for each pixel. While this selection benefits pixels affected by inconsistent motion, the combination of different constraints also enhances flow recovery for pixels that have consistent motion. Two frameworks are designed for the combination of flow constraints. One utilizes motion segmentation; and the other is close in spirit to Expectation-Maximization. Within these frameworks...

Locally oriented optical flow computation

Niu, Y.; Dick, A.; Brooks, M.
Fonte: IEEE-Inst Electrical Electronics Engineers Inc Publicador: IEEE-Inst Electrical Electronics Engineers Inc
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
66%
This paper proposes the use of an adaptive locally oriented coordinate frame when calculating an optical flow field. The coordinate frame is aligned with the least curvature direction in a local window about each pixel. This has advantages to both fitting the flow field to the image data and in imposing smoothness constraints between neighboring pixels. In terms of fitting, robustness is obtained to a wider variety of image motions due to the extra invariance provided by the coordinate frame. Smoothness constraints are naturally propagated along image boundaries which often correspond to motion boundaries. In addition, moving objects can be efficiently segmented in the least curvature direction. We show experimentally the benefits of the method and demonstrate robustness to fast rotational motion, such as what often occurs in human motion.; Yan Niu, Anthony Dick and Michael Brooks

Optical flow in a smart sensor based on hybrid analog-digital architecture

Guzm??n, Pablo; D??az, Javier; Ag??s, Rodrigo; Ros, Eduardo
Fonte: MDPI AG Publicador: MDPI AG
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.12%
The purpose of this study is to develop a motion sensor (delivering optical flow estimations) using a platform that includes the sensor itself, focal plane processing resources, and co-processing resources on a general purpose embedded processor. All this is implemented on a single device as a SoC (System-on-a-Chip). Optical flow is the 2-D projection into the camera plane of the 3-D motion information presented at the world scenario. This motion representation is widespread well-known and applied in the science community to solve a wide variety of problems. Most applications based on motion estimation require work in real-time; hence, this restriction must be taken into account. In this paper, we show an efficient approach to estimate the motion velocity vectors with an architecture based on a focal plane processor combined on-chip with a 32 bits NIOS II processor. Our approach relies on the simplification of the original optical flow model and its efficient implementation in a platform that combines an analog (focal-plane) and digital (NIOS II) processor. The system is fully functional and is organized in different stages where the early processing (focal plane) stage is mainly focus to pre-process the input image stream to reduce the computational cost in the post-processing (NIOS II) stage. We present the employed co-design techniques and analyze this novel architecture. We evaluate the system???s performance and accuracy with respect to the different proposed approaches described in the literature. We also discuss the advantages of the proposed approach as well as the degree of efficiency which can be obtained from the focal plane processing capabilities of the system. The final outcome is a low cost smart sensor for optical flow computation with real-time performance and reduced power consumption that can be used for very diverse application domains.

On the optical flow model selection through metaheuristics

Pereira, Danillo R.; Delpiano, José; Papa, João P.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 1-10
ENG
Relevância na Pesquisa
66.03%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 2013/20387-7; Processo FAPESP: 2014/16250-9; Optical flow methods are accurate algorithms for estimating the displacement and velocity fields of objects in a wide variety of applications, being their performance dependent on the configuration of a set of parameters. Since there is a lack of research that aims to automatically tune such parameters, in this work, we have proposed an optimization-based framework for such task based on social-spider optimization, harmony search, particle swarm optimization, and Nelder-Mead algorithm. The proposed framework employed the well-known large displacement optical flow (LDOF) approach as a basis algorithm over the Middlebury and Sintel public datasets, with promising results considering the baseline proposed by the authors of LDOF.

Shack - Hartmann spot dislocation map determination using an optical flow method; Shack - Hartmann spot dislocation map determination using an optical flow method

Belenguer, Tom??s; Restrepo G??mez, Ren??; Vargas, Javier
Fonte: OSA; Escuela de Ciencias y Humanidades Publicador: OSA; Escuela de Ciencias y Humanidades
Tipo: article; Art??culo; publishedVersion
ENG
Relevância na Pesquisa
56.02%
We present a robust, dense, and accurate Shack-Hartmann spot dislocation map determination method based on a regularized optical flow algorithm that does not require obtaining the spot centroids. The method is capable to measure in presence of strong noise, background illumination and spot modulating signals, which are typical limiting factors of traditional centroid detection algorithms. Moreover, the proposed approach is able to face cases where some of the reference beam spots have not a corresponding one in the distorted Hartmann diagram, and it can expand the dynamic range of the Shack-Hartmann sensor unwrapping the obtained dense dislocation maps. We have tested the algorithm with both simulations and experimental data obtaining satisfactory results. A complete MATLAB package that can reproduce all the results can be downloaded from [http://goo.gl/XbZVOr].

Performance of optical flow techniques for motion analysis of fluorescent point signals in confocal microscopy

Ramírez, Omar A.; Ruiz del Solar, Javier; Jara, Jorge; Scheer, Jan; Härtel, Steffen; Delpiano Costabal, José
Fonte: Springer Publicador: Springer
Tipo: Artículo de revista
EN
Relevância na Pesquisa
66.12%
Artículo de publicación ISI; Optical flow approaches calculate vector fields which determine the apparent velocities of objects in timevarying image sequences. They have been analyzed extensively in computer science using both natural and synthetic video sequences. In life sciences, there is an increasing need to extract kinetic information from temporal image sequences which reveals the interplay between form and function of microscopic biological structures. In this work, we test different variational optical flow techniques to quantify the displacements of biological objects in 2D fluorescent image sequences. The accuracy of the vector fields is tested for defined displacements of fluorescent point sources in synthetic image series which mimic protein traffic in neuronal dendrites, and for GABABR1 receptor subunits in dendrites of hippocampal neurons. Our results reveal that optical flow fields predict the movement of fluorescent point sources within an error of 3% for a maximum displacement of 160 nm. Displacement of agglomerated GABABR1 receptor subunits can be predicted correctly for maximum displacements of 640 nm. Based on these results, we introduce a criteria to derive the optimum parameter combinations for the calculation of the optical flow fields in experimental images. From these results...

Optical Flow Estimation using Fourier Mellin Transform

Ho, Huy Tho; Goecke, Roland
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Relevância na Pesquisa
56%
In this paper, we propose a novel method of computing the optical flow using the Fourier Mellin Transform (FMT). Each image in a sequence is divided into a regular grid of patches and the optical flow is estimated by calculating the phase correlation of e

Real Time Biologically-Inspired Depth Maps from Spherical Flow

McCarthy , Christopher; Barnes, Nick; Srinivasan, Mandyam V
Fonte: OmniPress Publicador: OmniPress
Tipo: Conference paper
Relevância na Pesquisa
56.06%
We present a strategy for generating real-time relative depth maps of an environment from optical flow, under general motion. We achieve this using an insect-inspired hemispherical fish-eye sensor with 190 degree FOV, and a derotated optical flow field. T

A Robust Docking Strategy for a Mobile Robot Using Flow Field Divergence

McCarthy , Christopher; Barnes, Nick; Mahony, Robert
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.06%
We present a robust strategy for docking a mobile robot in close proximity with an upright surface using optical flow field divergence and proportional feedback control. Unlike previous approaches, we achieve this without the need for explicit segmentatio

A condence framework for the assessment of optical flow performance

Márquez Valle, Patricia
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis; info:eu-repo/semantics/publishedVersion
Publicado em //2015 ENG
Relevância na Pesquisa
66.22%
L'Optical Flow (OF) és l'input d'una gran varietat de Sistemes de Suport a Decisions (DSS) com ara assistència a la conducció, guia UAV o diagnosis mèdic. En aquestes situacions, l'absència de ground truth ens obliga a avaluar la qualitat de l'OF calculat mitjançant quantitats calculades a partir de les seqüències o bé a partir del mateix OF. Aquestes quantitats es coneixen generalment com a Mesures de Confiança (CM). Encara que tinguem una mesura de confiança, necessitem alguna eina per tal d'avaluar la seva capacitat per descartar píxels de la imatge que tenen tendència a tindre error. Els mètodes actuals només aporten una avaluació descriptiva del rendiment de les CM, el problema és que aquests mètodes no són capaços de comparar equitativament les diferents CM i OF. Així doncs, necessitem definir una metodologia que avalu¨ı el rendiment de les tècniques d'OF. Aquesta tesi aporta la definició d'una metodologia que ens permet decidir quines parelles "optical flow - mesura de confiança" (OF-CM) estan millor preparades per a definir una cota de l'error de l'OF donat un nivell de confiança per a un DSS. Per tal de definir aquesta metodologia, la tesis engloba els següents punts: • Marcadors qualificatius. Es presenten 3 gràfiques descriptives que avaluen de forma visual les capacitats de CM d'acotar l'error de l'OF. A més a més de les gràfiques descriptives...

Compass rose: A rotational robust signature for optical flow computation

Niu, Y.; Dick, A.; Brooks, M.
Fonte: IEEE Publicador: IEEE
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
Relevância na Pesquisa
66.08%
This paper proposes a new image signature, called Compass Rose, which is particularly suited to optical flow computation. It is differentiable, fast to compute, and robust to additive illumination changes, translation, and fast rotation. We design a sparse flow computation system based on the invariance of the Compass Rose signatures. This is then extended to dense motion estimation by the addition of an optional diffusion step. Quantitative testing on several benchmark sequences shows the Compass Rose attains higher accuracy than the traditional flow signatures under a range of conditions. Finally, we demonstrate its application to human motion estimation, which is challenging for optical flow methods due to fast limb rotation.; Yan Niu, Anthony Dick, and Michael Brooks

Periodicity-Based Computation of Optical Flow

Khachaturov,Georgii; González Brambila,Silvia Beatriz; González Trejo,Jesús Isidro
Fonte: Centro de Investigación en computación, IPN Publicador: Centro de Investigación en computación, IPN
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2014 EN
Relevância na Pesquisa
66.06%
The standard Brightness Constancy Equation states spatiotemporal shift invariance of the input data along a local velocity of optical flow. In its turn, the shift invariance leads to a periodic function of a real argument. This allows application of a known test for periodicity to computation of optical flow at random locations. The approach is valid also for higher dimensions: for example, it applies to a sequence of 3D tomography images. The proposed method has a reasonably high accuracy for continuous flow and is noise tolerant. Special attention is paid to weak signal input. It is shown that a drastic reduction in the signal strength worsens the accuracy of estimates insignificantly. For a possible application to tomography, this would lead to an unprecedented diminution of harmful radiation exposure.