Eric Fauvet

Wavelets transform in artificial vision inspection of threading

We present an application of multiresolution analysis with orthonormal wavelets of 1D signal to quality control by artificial vision. The purpose of the control is to check the thread of a polyethylene bottle stopper. Using a section picture of the stopper provided by a linear CCD camera, we calculate the wavelet coefficients of the first three levels of resolution. The energy densities of these coefficients calculated on a given area, provide three discriminant parameters which permit to distinguish correctly between the two classes (defectless, defective) according to a classifying method which can run without supervision after a period of training.<<ETX>>

Detection of QRS complex in ECG signal based on classification approach

Electrocardiogram (ECG) signals are used to analyze the cardiovascular activity in the human body and have a primary role in the diagnosis of several heart diseases. The QRS complex is the most important and distinguishable component in the ECG because of its spiked nature and high amplitude. Automatic detection and delineation of the QRS complex in ECG is of extreme importance for computer aided diagnosis of cardiac disorder. Therefore, the accurate detection of this component is crucial to the performance of subsequent machine learning algorithms for cardiac disease classification. The aim of the present work is to detect the QRS wave from electrocardiogram (ECG) signals. Initially the baseline drift has been removed from the signal followed by the decomposition using continuous wavelet transform. Modulus maxima approach proposed by Mallat has been used to compute the Lipschitz exponent of the components. By using the property of R peak, having highest and prominent amplitude and Lipschitz exponents, we have applied the K means clustering technique to classify QRS complex. In order to evaluate the algorithm, the analysis has been done on MIT-BIH Arrhythmia database.

Study of a photosite for snapshot video

In this paper, we propose the architecture of the sensor of a snapshot video which allows to store the set of images from a sequence of snapshots. We describe the elementary cell which associates the photosensitive element to the memory zones. We present the circuit with which we are characterize the photoelements, and we present the charge transfer study circuit.

Human movement analysis with image processing in real time

In the field of the human sciences, a lot of applications needs to know the kinematic characteristics of the human movements Psycology is associating the characteristics with the control mechanism, sport and biomechariics are associating them with the performance of the sportman or of the patient. So the trainers or the doctors can correct the gesture of the subject to obtain a better performance if he knows the motion properties. Rohertons studies show the children motion evolution2 . Several investigations methods are able to measure the human movement But now most of the studies are based on image processing. Often the systems are working at the T.V. standard (50 frame per secund ). they permit only to study very slow gesture. A human operator analyses the digitizing sequence of the film manually giving a very expensive, especially long and unprecise operation. On these different grounds many human movement analysis systems were implemented. They consist of: - markers which are fixed to the anatomical interesting points on the subject in motion, - Image compression which is the art to coding picture data. Generally the compression Is limited to the centroid coordinates calculation tor each marker. These systems differ from one other in image acquisition and markers detection.

Geometrical characterization of 3D defects by artificial vision

In this article, the authors propose a real-time method for the geometrical characterization of defects located on the surface of a 3D object. The algorithm is built from information contained on a 3D grid of the object to be controlled. The efficiency of the characterization method is judging experimentally.

3D puzzle reconstruction for archeological fragments

The reconstruction of broken artifacts is a common task in archeology domain; it can be supported now by 3D data acquisition device and computer processing. Many works have been dedicated in the past to reconstructing 2D puzzles but very few propose a true 3D approach. We present here a complete solution including a dedicated transportable 3D acquisition set-up and a virtual tool with a graphic interface allowing the archeologists to manipulate the fragments and to, interactively, reconstruct the puzzle. The whole lateral part is acquired by rotating the fragment around an axis chosen within a light sheet thanks to a step-motor synchronized with the camera frame clock. Another camera provides a top view of the fragment under scanning. A scanning accuracy of 100μm is attained. The iterative automatic processing algorithm is based on segmentation into facets of the lateral part of the fragments followed by a 3D matching providing the user with a ranked short list of possible assemblies. The device has been applied to the reconstruction of a set of 1200 fragments from broken tablets supporting a Latin inscription dating from the first century AD.

Noise Estimation From Digital Step-Model Signal

This paper addresses the noise estimation in the digital domain and proposes a noise estimator based on the step signal model. It is efficient for any distribution of noise because it does not rely only on the smallest amplitudes in the signal or image. The proposed approach uses polarized/directional derivatives and a nonlinear combination of these derivatives to estimate the noise distribution (e.g., Gaussian, Poisson, speckle, etc.). The moments of this measured distribution can be computed and are also calculated theoretically on the basis of noise distribution models. The 1D performances are detailed, and as this paper is mostly dedicated to image processing, a 2D extension is proposed. The 2D performances for several noise distributions and noise models are presented and are compared with selected other methods.

Empirical modal decomposition applied to cardiac signals analysis

In this article, we present the method of empirical modal decomposition (EMD) applied to the electrocardiograms and phonocardiograms signals analysis and denoising. The objective of this work is to detect automatically cardiac anomalies of a patient. As these anomalies are localized in time, therefore the localization of all the events should be preserved precisely. The methods based on the Fourier Transform (TFD) lose the localization property [13] and in the case of Wavelet Transform (WT) which makes possible to overcome the problem of localization, but the interpretation remains still difficult to characterize the signal precisely. In this work we propose to apply the EMD (Empirical Modal Decomposition) which have very significant properties on pseudo periodic signals. The second section describes the algorithm of EMD. In the third part we present the result obtained on Phonocardiograms (PCG) and on Electrocardiograms (ECG) test signals. The analysis and the interpretation of these signals are given in this same section. Finally, we introduce an adaptation of the EMD algorithm which seems to be very efficient for denoising.

Machine vision prototype for defect detection on metallic tubes

Metallurgy Industry which mainly changes the steel or its derivative products into products with either better surface properties (thanks to the surface transformations....), or into different shape products (lamination...), involves some processing tools which can generate flaws (cracks, grooves...) within the process. Prior to this study the laminated tubes, recipient for the uranium inside the nuclear reactor, where visually inspected after the lamination process. According to the quality estimation of the tube, subjectively done by the operator (between 1 and 4), the process was possibly stopped (grade 4). In order to have a more objective control of the tube, a machine vision set-up was developed. The primary goal of this prototype is to provide a view of the whole surface of the tube to the operator. Various lighting systems where tested so as to reveal the maximum number of defect (tool marks, scratches, ..). The tube surface being not even (rough), we found that an homogenous lighting of the scene enabled a clear inspection of the tube surface and reveal most of the defects. Unfortunately a structured lighting system was also required for the tool-marks to be visible. Then, different image processing tools have been applied to the images. At this point, all the defects are detected. Further experiments are currently being done to classify the defects.

Toward a virtual reconstruction of an antique three-dimensional marble puzzle

The reconstruction of broken objects is an important field of research for many applications, such as art restoration, surgery, forensics, and solving puzzles. In archaeology, the reconstruction of broken artifacts is a very time-consuming task due to the handling of fractured objects, which are generally fragile. However, it can now be supported by three-dimensional (3-D) data acquisition devices and computer processing. Those techniques are very useful in this domain because they allow the remote handling of very accurate models of fragile parts, they permit the extensive testing of reconstruction solutions, and they provide access to the parts for the entire research community. An interesting problem has recently been proposed by archaeologists in the form of a huge puzzle composed of a thousand fragments of Pentelic marble of different sizes found in Autun (France), and all attempts to reconstruct the puzzle during the last two centuries have failed. Archaeologists are sure that some fragments are missing and that some of the ones we have come from different slabs. We propose an inexpensive transportable system for 3-D acquisition setup and a 3-D reconstruction method that is applied to this Roman inscription but is also relevant to other applications.