Localisation pédestre : Synthèse bibliographique et illustration d'une approche par vision monoculaire embarquée

National audienceLocate our position is one of the tasks we naturally do with our view and our memory. However, ensuring this task in an artificial way is still a challenge for the whole community of computer vision. This paper presents a detailed literature review of pedestrian localization systems and their technologies. In the context of the visually impaired pedestrian navigation assistance, we also present an innovative solution based on the vision localization for both outdoor and indoor navigation. This new solution is established based on the independence of any collective equipment.Se localiser est une des tâches que nous faisons naturellement grâce à notre vue et notre mémoire. Cependant, l'assurer artificiellement demeure un défi pour toute la communauté de la vision par ordinateur. Cette communication présente une revue de la littérature détaillée des systèmes de localisation pédestre et de ses technologies. Dans le contexte de l'assistance à la navigation pédestre des déficients visuels, nous proposons aussi une solution innovante, pour un fonctionnement efficace aussi bien en extérieur qu'en intérieur, fondée sur l'indépendance vis-à-vis de l'équipement collectif

Smartphone-based Thermal Imaging System for Diabetic Foot Ulcer Assessment

International audienceThis research work is part of the STANDUP project http://www.standupproject.eu/ dedicated to improve diabetic foot ulcer prevention and treatment of the plantar foot surface using smartphone-embedded thermal imaging system. The aim of this preliminary work is to build an ulcer assessment tool based on a smartphone and an IR thermal camera. The proposed system represents a practical tool for accurate DFU healing assessment, combining color and thermal information in a single user-friendly system. To ensure robust tissue identification, an annotation software was developed based on SLIC superpixel segmentation algorithm. The tool thus developed allows clinicians to achieve objective and accurate tissue identification and annotation. The proposed system could serve as an intelligent telemedicine system to be deployed by clinicians at hospitals and healthcare centers for more accurate diagnosis of diabetic foot ulcers

Semi-automatic registration of 3D orthodontics models from photographs

International audienceIn orthodontics, a common practice used to diagnose and plan the treatment is the dental cast. After digitization by a CT-scan or a laser scanner, the obtained 3D surface models can feed orthodontics numerical tools for computer-aided diagnosis and treatment planning. One of the pre-processing critical steps is the 3D registration of dental arches to obtain the occlusion of these numerical models. For this task, we propose a vision based method to automatically compute the registration based on photos of patient mouth. From a set of matched singular points between two photos and the dental 3D models, the rigid transformation to apply to the mandible to be in contact with the maxillary may be computed by minimizing the reprojection errors. During a precedent study, we established the feasibility of this visual registration approach with a manual selection of singular points. This paper addresses the issue of automatic point detection. Based on a priori knowledge, histogram thresholding and edge detection are used to extract specific points in 2D images. Concurrently, curvatures information detects 3D corresponding points. To improve the quality of the final registration, we also introduce a combined optimization of the projection matrix with the 2D/3D point positions. These new developments are evaluated on real data by considering the reprojection errors and the deviation angles after registration in respect to the manual reference occlusion realized by a specialist. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Comparaison de méthodes de recalage visuel de modèles 3D pour l'orthodontie

National audienceIn this paper, we compare two vision registration methods of 3D models to develop a main tool for orthodontics based on the virtual occlusion of two dental casts. For that purpose, we process photos of the patient mouth and match points between pictures and dental geometrical models. From a set of 2D/3D matches of the two arcades, we calculate the projection matrix, and after we do the registration of the mandible under the maxillary through a rigid transformation. Two methods with or without the knowledge of camera intrinsic parameters are compared. Minimizing the reprojection errors, we perform the registration of the mandible. Tests are carried out on virtual data and real images. Using a virtual case, assumed as perfect, we evaluate the robustness against noise and the increase of performance using several views. Projection matrices and registration are evaluated, respectively, by reprojection errors and the recorded differences on the 6 parameters of rigid transformation compared with the reference pose.Dans cet article, nous comparons des méthodes de recalage de modèles 3D par vision pour développer un outil essentiel en orthodontie : la mise en occlusion virtuelle des deux moulages des mâchoires. Pour cela, on utilise des photos de la bouche du patient et des points mis en correspondance entre les images et les modèles dentaires surfaciques. A partir d'un ensemble de correspondances 2D/3D disponibles établies sur les deux arcades, on calcule la matrice de projection, puis on effectue le recalage de la mandibule sous le maxillaire en estimant une transformation rigide. Deux approches sont comparées selon que l'on dispose ou non de la connaissance des paramètres intrinsèques de la caméra. Le recalage de la mandibule est ensuite estimé en minimisant l'erreur de reprojection. Les tests sont effectués sur des données virtuelles puis des images réelles. A partir d'un cas virtuel " parfait ", nous évaluons la dégradation des performances avec l'ajout de bruit et l'intérêt de combiner plusieurs vues. Les matrices de projections estimées sont évaluées par les erreurs de reprojection et les recalages par les écarts constatés sur les 6 paramètres de la transformation rigide par rapport à un positionnement de référence

An optimized algorithm of image stitching in the case of a multi-modal probe for monitoring the evolution of scars

International audienceWe propose a new system that makes possible to monitor the evolution of scars after the excision of a tumorous dermatosis. The hardware part of this system is composed of a new optical innovative probe with which two types of images can be acquired simultaneously: an anatomic image acquired under a white light and a functional one based on autofluorescence from the protoporphyrin within the cancer cells. For technical reasons related to the maximum size of the area covered by the probe, acquired images are too small to cover the whole scar. That is why a sequence of overlapping images is taken in order to cover the required area. The main goal of this paper is to describe the creation of two panoramic images (anatomic and functional). Fluorescence images do not have enough salient information for matching the images; stitching algorithms are applied over each couple of successive white light images to produce an anatomic panorama of the entire scar. The same transformations obtained from this step are used to register and stitch the functional images. Several experiments have been implemented using different stitching algorithms (SIFT, ASIFT and SURF), with various transformation parameters (angles of rotation, projection, scaling, etc...) and different types of skin images. We present the results of these experiments that propose the best solution. Thus, clinician has two panoramic images superimposed and usable for diagnostic support. A collaborative layer is added to the system to allow sharing panoramas among several practitioners over different places

Modèle harmonique de surface déformable périodiquement application à l'échocardiographie

L'étude décrit une technique de reconstruction spatio-temporelle d'un objet périodiquement déformable à partir d'un ensemble de coupes planes. L'échantillonnage de la surface de l'objet est représentée par un ensemble de surfaces périodiques discrètes. Lorsque le capteur est en mouvement, les données sont localisées sur des droites particulières de ces surfaces. L'analyse harmonique conjointe des données 1D et des surfaces 2D a conduit à l'élaboration d'un modèle spatio-temporel (MHSDP). Les paramètres du modèle sont calculés de façon analytique et permettent la restitution complète des surfaces. Cette approche est notamment appliquée à la restitution du ventricule gauche (VG) du coeur en échocardiographie

Contributions à la localisation de personnes par vision monoculaire embarquée

Une des techniques alternatives au GPS pour le développement d un système d assistance à la navigationpédestre en milieux urbains est la vision embarquée. La localisation du porteur de la caméra s appuie alorssur l estimation de la pose à partir des images acquises au cours du cheminement. En s inspirant destravaux antérieurs sur la navigation autonome de robots, cette thèse explore deux approches dans le cadrespécifique de la localisation pédestre. La première méthode de localisation s appuie sur des appariementsde primitives images avec une cartographie 3D pré-estimée de l environnement. Elle permet une estimationprécise de la pose complète de la caméra (6 ddl), mais les expérimentations montrent des limitationscritiques de robustesse et temps de calcul liées à l étape de mise en correspondance. Une solutionalternative est proposée en utilisant les points de fuite. L orientation de la caméra (3ddl) est estimée defaçon robuste et rapide par le suivi de 3 points de fuites orthogonaux dans une séquence vidéo. L algorithmedéveloppé permet une localisation pédestre indoor en deux étapes : une phase d apprentissage hors lignedéfinit un itinéraire de référence en sélectionnant des images clef au long du parcours, puis, en phase delocalisation, une position approximative mais réaliste du porteur est estimée en temps réel en comparant lesorientations de la caméra dans l image courante et celle de référence.One of the alternative techniques to GPS for the development of pedestrian navigation assistive systems inurban environments is embedded vision. The walker localization is, then, based on the camera poseestimation from images acquired during the path. Inspired by previous work on autonomous navigation ofmobile robots, this thesis explores two approaches in the specific context of pedestrian localization. The firstlocalization method is based on image primitive matching with a pre-estimated 3D map of the environment. Itallows an accurate estimate of the complete pose of the camera (6 dof), but experiments show criticallimitations of robustness and computation time related to the matching step. An alternative solution isproposed using vanishing points. Robust and fast camera orientation (3 dof) is estimated by tracking threeorthogonal vanishing points in a video sequence. The developed algorithm allows indoor pedestrianlocalization in two steps: an off-line learning step defines a reference path by selecting key frames along theway, then, in localization step, an approximate but realistic position of the walker is estimated in real time bycomparing the orientation of the camera in the current image and that of reference.ORLEANS-SCD-Bib. electronique (452349901) / SudocSudocFranceF

Outdoor/Indoor Vision Based Localization for Blind Pedestrian Navigation Assistance

International audienceThe most challenging issue of the navigation assistive systems for the visually impaired is the instantaneous and accurate spatial localization of the user. Most of the previous proposed systems are based on GPS sensors. But, low cost versions have clearly insufficient accuracy for pedestrian use. Furthermore, they are confined to outdoor navigation with severe failing in urban area. This paper presents a new approach for localizing a person by using a single body mounted camera and computer vision techniques. Instantaneous accurate localization and heading estimates of the person are computed from images as the trip progresses along a memorised path. A first portable prototype has been tested for outdoor as well as indoor pedestrian trips. Experimental results demonstrate the effectiveness of the vision based localization: the accuracy around twenty centimetres, allows guiding and keeping the blind in a navigation corridor along the intended path. In combination with a suitable guiding interface, such a localization system will propose a convenient assistive navigation for the visually impaired

Hyperspectral interventional imaging for enhanced tissue visualization and discrimination combining band selection methods

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Combined Machine Learning with Multi-view Modeling for Robust Wound Tissue Assessment

International audienceFrom colour images acquired with a hand held digital camera, an innovative tool for assessing chronic wounds has been developed. It combines both types of assessment, colour analysis and dimensional measurement of injured tissues in a user-friendly system. Colour and texture descriptors have been extracted and selected from a sample database of wound tissues, before the learning stage of a support vector machine classifier with perceptron kernel on four categories of tissues. Relying on a triangulated 3D model captured using uncalibrated vision techniques applied on a stereoscopic image pair, a fusion algorithm elaborates new tissue labels on each model triangle from each view. The results of 2D classification are merged and directly mapped on the mesh surface of the 3D wound model. The result is a significative improvement in the robustness of the classification. Real tissue areas can be computed by retro projection of identified regions on the 3D model