Search results for "Computer Vision"
showing 10 items of 2353 documents
Magnetic resonance image segmentation and heart motion tracking with an active mesh based system
2002
International audience; Abstract: The work presented here relates to a method fir motion tracking in sequences of medical images. The purpose is to. quantify the general motions and the local deformations of a beating heart during a cardiac cycle. In order to achieve this goal, we first tessellate the,first image of the sequence into triangular patches. A Delaunay triangulation is applied to find the optimal set of triangles describing this image, giving a mesh covering the organs. One imposes the contours of the organs to correspond to edges of triangles so that each part of the heart (left ventricle, right ventricle, myocardium) can he described as a different set of triai izles, each set…
Silhouette encoding and synthesis using elliptic Fourier descriptors, and applications to videoconferencing
2004
Abstract This paper investigates the use of elliptic Fourier descriptors as a shape descriptor for encoding the silhouette of a person. Shape descriptors are here used for predicting the shape of silhouettes in missing frames within a sequence. This prediction scheme is applied to the case of generating in-between images in a low frame rate videoconferencing system, where the reconstructed silhouette is used as a binary mask for reducing the computational time for the frame reconstruction.
Quantifying the complexity of short-term heart period variability through K nearest neighbor local linear prediction
2008
The complexity of short-term heart period (HP) variability was quantified exploiting the paradigm that associates the degree of unpredictability of a time series to its dynamical complexity. Complexity was assessed through k-nearest neighbor local linear prediction. A proper selection of the parameter k allowed us to perform either linear or nonlinear prediction, and the comparison of the two approaches to infer the presence of nonlinear dynamics. The method was validated on simulations reproducing linear and nonlinear time series with varying levels of predictability. It was then applied to HP variability series measured from healthy subjects during head-up tilt test, showing that short-te…
Experimental approach for testing the uncoupling between cardiovascular variability series
2002
In cardiovascular variability analysis, the significance of the coupling between two series is commonly assessed by defining a zero level on the magnitude-squared coherence (MSC). Although the use of the conventional value of 0.5 does not consider the dependence of MSC estimates on the analysis parameters, a theoretical threshold Tt is available only for the weighted covariance (WC) estimator. In this study, an experimental threshold for zero coherence Te was derived by a statistical test from the sampling distribution of MSC estimated on completely uncoupled time series. MSC was estimated by the WC method (Parzen window, spectral bandwidth B = 0.015, 0.02, 0.025, 0.03 Hz) and by the parame…
Low Dose-Rate, High Total Dose Set-Up for Rad-Hard CMOS I/O Circuits Testing
2017
In this paper, the planning of low dose-rate, high total dose testing campaign for I/O circuits is reported. In particular, the paper describes all development steps, starting from the rad-hard I/O circuits design and the implementation of the test-chip, which is meant to allow comparative testing between rad-hard and standard devices. The designed experimental setup permits in situ measurements, therefore the circuits behavior can be remotely monitored for very long periods. This feature enables low dose-rate testing up to very high dose.
Algorithms for transforming an integral photography into a plenoptic picture
2013
We report a simple algorithm for transforming the set of elemental images captured with an integral-photography set up, into the set of micro-images ready to be projected into an integral-imaging monitor. The method is based in the transposing relation between an integral photography and a plenoptic picture. The reported technique permits to adapt the integral images to the resolution and size of the monitor.
3D Reconstruction of rough terrain for USARSim using a height-map method
2008
In this paper, a process for a simplified reconstruction of rough terrains from point clouds acquired using laser scanners is presented. The main idea of this work is to build height-maps which are level gray-scale images representing the ground elevation. These height-maps are generated from step-fields which can be represented by a set of side-by-side pillars. Although height-maps are a practical means for rough terrain reconstruction, it is not possible to represent two different elevations for a given location with one height-map. This is an important drawback as terrain point clouds can show different zones representing surfaces above other surfaces.In this paper, a methodology to crea…
Fully programmable display parameters in integral imaging by smart pseudoscopic-to-orthoscopic conversion
2011
Previously, we reported a digital technique for formation of real, non-distorted, orthoscopic integral images by direct pickup. However the technique was constrained to the case of symmetric image capture and display systems. Here, we report a more general algorithm which allows the pseudoscopic to orthoscopic transformation with full control over the display parameters so that one can generates a set of synthetic elemental images that suits the characteristics of the Integral-Imaging monitor and permits control over the depth and size of the reconstructed 3D scene.
Volumetric Reconstruction of Unorganized Set of Points with Implicit Surfaces
2005
Many solutions exist to rebuild a three-dimensional object represented by a set of points. The purpose of our work is to provide an automatic reconstruction from an unorganized cloud, describing an unknown shape, in the aim to compute its volume. The approach employed in this paper consists in filling the object's interior with isosurfaces of potential fields and to use their fusion property in order to find the full volume and the continuous shape of the sampled object. Thus, the first step of our reconstruction is to search a correct interior for the object described by the set of points. Then, comes the positioning of implicit primitives into the cloud, deep inside of it and close to the…
Detection and Isolation of Switches in Point Clouds of the German Railway Network
2015
In order to obtain an automated system of railway management, it is necessary to automatically detect, isolate and identify all switches in a point cloud which represents the railway. To realize this automated system of detection, a set of pre-processing steps is applied. The system begins by detecting and isolating tracks through application of a mask on each section of the point cloud. Then, it does a denoising through mathematical morphology and a compression in replacing a group of points by their centroid. Finally, it closes tracks holes through extrapolation. After that, the system does a low-level processing to search for all intersections between tracks, and records information on t…