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Conference on computer vision and Pattern Recognition (CVPR)

作者： A. Bosch X. Munoz A. Oliver J. Marti Computer Vision and Robotics Group University of Girona Girona Spain

We present a new approach to model and classify breast parenchymal tissue. Given a mammogram, first, we will discover the distribution of the different tissue densities in an unsupervised manner, and second, we will use this tissue distribution to perform the classification. We achieve this using a classifier based on local descriptors and probabilistic Latent Semantic Analysis (pLSA), a generative model from the statistical text literature. We studied the influence of different descriptors like texture and SIFT features at the classification stage showing that textons outperform SIFT in all cases. Moreover we demonstrate that pLSA automatically extracts meaningful latent aspects generating a compact tissue representation based on their densities, useful for discriminating on mammogram classification. We show the results of tissue classification over the MIAS and DDSM datasets. We compare our method with approaches that classified these same datasets showing a better performance of our proposal.

关键词： Breast tissue Breast cancer computer vision Mammography Medical diagnostic imaging Dictionaries Layout Robot vision systems Delta-sigma modulation Proposals

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INCLUDING THE VIRTUAL LABORATORY CONCEPT IN AN ON-LINE COLLABORATIVE ENVIRONMENT

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IFAC Proceedings Volumes 2006年第6期39卷 571-576页

作者： F.A. Candelas F. Torres P. Gil S. Puente J. Pomares Robotics and Computer Vision Group Physics Systems Engineering and Signal Theory Department University of Alicante (Spain)

With the aim of combining the main advantages of the virtual laboratories and the collaborative learning environments, a new on-line collaborative environment is proposed in this paper. This environment includes, in addition to other common tools, simulation applets in the user interface. To make possible the collaborative learning, the simulations work in a synchronized way for the users of a same group. The main features of the first prototype of the environment and its architecture are described. This prototype has been developed as a module for the popular CMS Moodle.

关键词： Education learning group work virtual user interfaces on-line laboratory

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PRIM an Open Mobile Robot Platform. Motivation, Present and Future Trends

PRIM an Open Mobile Robot Platform. Motivation, Present and ...

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IEEE International Conference on Automation, Quality and Testing, robotics, AQTR

作者： Lluis Pacheco Joan Batlle Xavier Cuff Roger Arbuse Computer Vision and Robotics Group Technical School University of Girona Girona Spain Computer Vision and Robotics Group Technical School Girona Spain Tech. Sch. Girona Univ.

This paper is focused on the robot mobile platform PRIM (platform robot information multimedia). This robot has been made in order to cover two main needs of our group, on one hand the need for a full open mobile robotic platform that is very useful in fulfilling the teaching and research activity of our school community, and on the other hand with the idea of introducing an ethical product which would be useful as mobile multimedia information point as a service tool. This paper introduces exactly how the system is made up and explains just what the philosophy is behind this work. The navigation strategies and sensor fusion, where machine vision system is the most important one, are oriented towards goal achievement and are the key to the behaviour of the robot

关键词： Mobile robots Educational robots Education Educational institutions Multimedia systems Navigation Sensor fusion Machine vision Robot sensing systems Robot vision systems

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Improving Clustering Algorithms for Image Segmentation using Contour and Region Information

Improving Clustering Algorithms for Image Segmentation using...

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IEEE International Conference on Automation, Quality and Testing, robotics, AQTR

作者： Arnau Oliver Xavier Munoz Joan Batlle Lluis Pacheco Jordi Freixenet Computer Vision and Robotics Group Institute of Informatics and Applications University of Girona Girona Spain

In image segmentation, clustering algorithms are very popular because they are intuitive and, some of them, easy to implement. For instance, the k-means is one of the most used in the literature, and many authors successfully compare their new proposal with the results achieved by the k-means. However, it is well known that clustering image segmentation has many problems. For instance, the number of regions of the image has to be known a priori, as well as different initial seed placement (initial clusters) could produce different segmentation results. Most of these algorithms could be slightly improved by considering the coordinates of the image as features in the clustering process (to take spatial region information into account). In this paper we propose a significant improvement of clustering algorithms for image segmentation. The method is qualitatively and quantitative evaluated over a set of synthetic and real images, and compared with classical clustering approaches. Results demonstrate the validity of this new approach

关键词： Clustering algorithms Image segmentation Partitioning algorithms Proposals Clustering methods computer vision Robot kinematics Robot vision systems Informatics Application software

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Autonomous Detection of Safe Landing Areas for an UAV from Monocular Images

Autonomous Detection of Safe Landing Areas for an UAV from M...

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2006 IEEE/RSJ International Conference on Intelligent Robots and Systems

作者： Sebastien Bosch Simon Lacroix Fernando Caballero LAAS CNRS Toulouse France Robotics Computer Vision and Intelligent Control Group University of Seville Spain

This paper presents an approach to detect safe landing areas for a flying robot, on the basis of a sequence of monocular images. The approach does not require precise position and attitude sensors: it exploits the relations between 2D image homographies and 3D planes. The combination of a robust homography estimation and of an adaptive thresholding of correlation scores between registered images yields the update of a stochastic grid, that exhibits the horizontal planar areas perceived. This grid allows the integration of data gathered at various altitudes. Results are presented

关键词： Unmanned aerial vehicles Layout Intelligent robots Transmission line matrix methods Image reconstruction Robot sensing systems Robot vision systems Image sensors Robustness Yield estimation

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Experimental Modeling and Control Strategies on an Open Mobile Robot Platform PRIM

Experimental Modeling and Control Strategies on an Open Mobi...

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IEEE International Conference on Automation, Quality and Testing, robotics, AQTR

作者： Lluis Pacheco Roger Arbuse Ningsu Luo Computer Vision and Robotics Group University of Girona Girona Spain Modal Interval and Control Engineering Group University of Girona Girona Spain

This research work deals with the problem of modeling and design of low level speed controller for the mobile robot PRIM. The main objective is to develop an effective educational tool. On one hand, the interests in using the open mobile platform PRIM consist in integrating several highly related subjects to the automatic control theory in an educational context, by embracing the subjects of communications, signal processing, sensor fusion and hardware design, amongst others. On the other hand, the idea is to implement useful navigation strategies such that the robot can be served as a mobile multimedia information point. It is in this context, when navigation strategies are oriented to goal achievement, that a local model predictive control is attained. Hence, such studies are presented as a very interesting control strategy in order to develop the future capabilities of the system

关键词： Mobile robots Automatic control Navigation Communication system control Context Mobile communication Signal processing Sensor fusion Hardware Signal design

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Viewpoint independent human motion analysis in man-made environments

Viewpoint independent human motion analysis in man-made envi...

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2006 17th British Machine vision Conference, BMVC 2006

作者： Rogez, G. Guerrero, J.J. Martínez, J. Orrite, C. Computer Vision Lab. I3A - University of Zaragoza Maria de Luna 1 50018 Zaragoza Spain Robotics Perception and Real Time Group I3A - University of Zaragoza Maria de Luna 1 50018 Zaragoza Spain

ISBN: (纸本)1904410146

This work addresses the problem of human motion analysis in video sequences of a scene observed by a single fixed camera with high perspective effect. The goal of this work is to make a 2D-Model (made of Shape and Stick figure) viewpoint-insensitive and preprocess the input image for removing the perspective effect. We focus our methodology on using the 3D principal directions of man-made environments and also the direction of motion to transform both 2D-Model and input images to a common frontal view (parallel or orthogonal to the direction of motion) before the fitting process. The inverse transformation is then performed on the resulting human features obtaining a segmented silhouette and a pose estimation in the original input image. Preliminary results are very promising since the proposed algorithm is able to locate head and feet with a better precision than previous one.

关键词： Motion analysis

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Attenuating stereo pixel-locking via affine window adaptation

Attenuating stereo pixel-locking via affine window adaptatio...

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IEEE International Conference on robotics and Automation (ICRA)

作者： A.N. Stein A. Huertas L. Matthies Robotics Institute Carnegie Mellon University Pittsburgh PA USA Computer Vision Group Jet Propulsion Laboratory Pasadena CA USA

For real-time stereo vision systems, the standard method for estimating sub-pixel stereo disparity given an initial integer disparity map involves fitting parabolas to a matching cost function aggregated over rectangular windows. This results in a phenomenon known as pixel-locking, which produces artificially-peaked histograms of sub-pixel disparity. These peaks correspond to the introduction of erroneous ripples or waves in the 3D reconstruction of truly flat surfaces. Since stereo vision is a common input modality for autonomous vehicles, these inaccuracies can pose a problem for safe, reliable navigation. This paper proposes a new method for sub-pixel stereo disparity estimation, based on ideas from Lucas-Kanade tracking and optical flow, which substantially reduces the pixel-locking effect. In addition, it has the ability to correct much larger initial disparity errors than previous approaches and is more general as it applies not only to the ground plane. We demonstrate the method on synthetic imagery as well as real stereo data from an autonomous outdoor vehicle

关键词： Stereo vision Remotely operated vehicles Mobile robots Real time systems Cost function Histograms Image reconstruction Surface waves Optical surface waves Surface fitting

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A visual servoing approach for tracking features in urban areas using an autonomous helicopter

A visual servoing approach for tracking features in urban ar...

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IEEE International Conference on robotics and Automation (ICRA)

作者： L. Mejias P. Campoy S. Saripalli G.S. Sukhatme Computer Vision Group Universidad Politécnica de Madrid Madrid Spain Robotic Embedded Systems Laboratory Center for Robotics and Embedded Systems Department of Computer Science University of Southern California Los Angeles CA USA

The use of unmanned aerial vehicles (UAVs) in civilian and domestic applications is highly demanding, requiring a high-level of capability from the vehicles. This work addresses the design and implementation of a vision-based feature tracker for an autonomous helicopter. Using vision in the control loop allows estimating the position and velocity of a set of features with respect to the helicopter. The helicopter is then autonomously guided to track these features (in this case windows in an urban environment) in real time. The results obtained from flight trials in a real world scenario demonstrate that the algorithm for tracking features in an urban environment, used for visual servoing of an autonomous helicopter is reliable and robust

关键词： Visual servoing Urban areas Helicopters Aircraft navigation Machine vision Control systems Unmanned aerial vehicles Global Positioning System computer vision Robot vision systems

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Monocular-based 3-D seafloor reconstruction and ortho-mosaicing by piecewise planar representation

Monocular-based 3-D seafloor reconstruction and ortho-mosaic...

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MTS/IEEE OCEANS, 2005

作者： Nicosevici, Tudor Negahdaripour, Shahriar Garcia, Rafael Computer Vision and Robotics Group University of Girona Girona Spain Electrical and Computer Engineering Department University of Miami Miami FL United States

ISBN: (纸本)0933957343

Photo-mosaicing techniques have become popular for seafloor mapping in various marine science applications. However, the common methods cannot accurately map regions with high relief and topographical variations. Ortho-mosaicing borrowed from photogrammetry is an alternative technique that enables taking into account the 3-D shape of the terrain. A serious bottleneck is the volume of elevation information that needs to be estimated from the video data, fused, and processed for the generation of a composite ortho-photo that covers a relatively large seafloor area. We present a framework that combines the advantages of dense depth-map and 3-D feature estimation techniques based on visual motion cues. The main goal is to identify and reconstruct certain key terrain feature points that adequately represent the surface with minimal complexity in the form of piecewise planar patches. The proposed implementation utilizes local depth maps for feature selection, while tracking over several views enables 3-D reconstruction by bundle adjustment. Experimental results with synthetic and real data validate the effectiveness of the proposed approach.

关键词： Underwater imaging

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