21 research outputs found
Une nouvelle classe d'opérateurs de Teager-Kaiser multidimensionnels basée sur les dérivées directionnelles d'ordre supérieur
This work aims at introducing some energy operators linked to Teager-Kaiser energy operator and its associated higher order versions and expand them to multidimensional signals. These operators are very useful for analyzing oscillatory signals with time-varying amplitude and frequency (AM-FM). We prove that gradient tensors combined with Kronecker powers allow to express these operators by directional derivatives along any n-D vector. In particular, we show that the construction of a large class of non linear operators for AM-FM multidimensional signal demodulation is possible. Also, a new scalar function using the directional derivative along a vector giving the âsignâ of the frequency components is introduced. An application of this model to local n-D AM-FM signal is presented and related demodulation error rates estimates. To show the effectiveness and the robustness of our method in term of envelope and frequency components extraction, results obtained on synthetic and real data are compared to multi-dimensional energy separation algorithm and to our recently introduced n-D operator
Estimation de l'enveloppe et de la fréquence locales par les opérateurs de Teager-Kaiser en interférométrie en lumiÚre blanche.
In this work, a new method for surface extraction in white light scanning interferometry (WLSI) is introduced. The proposed extraction scheme is based on the Teager-Kaiser energy operator and its extended versions. This non-linear class of operators is helpful to extract the local instantaneous envelope and frequency of any narrow band AM-FM signal. Namely, the combination of the envelope and frequency information, allows effective surface extraction by an iterative re-estimation of the phase in association with a new correlation technique, based on a recent TK crossenergy operator. Through the experiments, it is shown that the proposed method produces substantially effective results in term of surface extraction compared to the peak fringe scanning technique, the five step phase shifting algorithm and the continuous wavelet transform based method. In addition, the results obtained show the robustness of the proposed method to noise and to the fluctuations of the carrier frequency
Hidden fuzzy Markov chain model with K discrete classes
International audienceThis paper deals with a new unsupervised fuzzy Bayesian segmentation method based on the hidden Markov chain model, in order to separate continuous from discrete components in the hidden data. We present a new F-HMC (fuzzy hidden Markov chain) related to three hard classes, based on a general extension of the previously algorithms proposed. For a given observation, the hidden variable owns a density according to a measure containing Dirac and Lebesgue components. We have performed our approach in the multispectral context. The hyper-parameters are estimated using a Stochastic Expectation Maximization (SEM) algorithm. We present synthetic simulations and also segmentation results related to real multi-band data
Segmentation d'images multispectrales par arbre de Markov caché flou
Nous définissons un nouvel outil de segmentation statistique non supervisée, basé sur un modÚle d'arbre de Markov caché flou. Notre modÚle flou combine l'incertitude probabiliste des données observées avec les classes thématiques discrÚtes et continues qui représentent l'imprécision des données cachées. La technique de segmentation bayésienne mise en oeuvre correspond au critÚre MPM (Mode of Posterior Marginals). Notre approche permet d'une part le traitement d'objets contenant des structures diffuses comme c'est le cas en imagerie astronomique et d'autre part la prise en compte de données multi-bandes observées à différents niveaux de résolution et issues de capteurs corrélés. Nous validons notre modÚle sur des images de synthÚse et des images réelles multispectrales
Dempster-Shafer's Basic Probability Assignment Based on Fuzzy Membership Functions
In this paper, an image segmentation method based on Dempster-Shafer evidence theory is proposed. Basic probability assignment (bpa) is estimated in unsupervised way using pixels fuzzy membership degrees derived from image histogram. No assumption is made about the images data distribution. bpa is estimated at pixel level. The effectiveness of the method is demonstrated on synthetic and real images
Hidden fuzzy Markov chain model with K discrete classes
International audienceThis paper deals with a new unsupervised fuzzy Bayesian segmentation method based on the hidden Markov chain model, in order to separate continuous from discrete components in the hidden data. We present a new F-HMC (fuzzy hidden Markov chain) related to three hard classes, based on a general extension of the previously algorithms proposed. For a given observation, the hidden variable owns a density according to a measure containing Dirac and Lebesgue components. We have performed our approach in the multispectral context. The hyper-parameters are estimated using a Stochastic Expectation Maximization (SEM) algorithm. We present synthetic simulations and also segmentation results related to real multi-band data
Un arbre de Markov sélectif en fréquence pour la détection de signaux transitoires à faible rapport signal à bruit
Nous nous intĂ©ressons dans cet article Ă lâextraction de comportements statistiques
multirésolutions pour la caractérisation et la segmentation de signaux transitoires dans un
contexte fortement bruité. Ces signaux de courte durée possÚdent des composantes fréquentielles
trÚs localisées et fortement variables. Le choix du compromis temps/fréquence pour
lâĂ©tude de ces signaux est donc crucial. Nous nous plaçons de ce fait dans le domaine transformĂ©
en paquets dâondelettes, permettant une analyse fine des variations frĂ©quentielles du
signal. Nous proposons un modĂšle dâarbre de Markov original adaptĂ© Ă la dĂ©composition en
paquets dâondelettes afin dâintĂ©grer lâinformation multirĂ©solution dâĂ©chelle en Ă©chelle dans un
objectif de segmentation. Nous validons lâapproche sur des signaux synthĂ©tiques, puis nous
illustrons son intĂ©rĂȘt applicatif dans un contexte biomĂ©dical liĂ©e Ă la dĂ©tection de signaux
transitoires dans les signaux pulmonaires.We deal in this paper with the extraction of multiresolution statistical signatures for
the characterization of transient signals in strongly noisy contexts. These short-time signals
have sharp and highly variable frequency components. The Time-Frequency analysis window
to adopt is then a major issue. Thus we have chosen the wavelet packet domain due to its natural
ability to provide multiple time-frequency resolutions. We propose a new oriented Markov
model dedicated to the wavelet packet transform, which offers sharp analysis of frequency
variations in a signal, locally in time and at several resolutions. We show its efficiency on synthetic
signals and we then illustrate its applicative relevance in a biomedical context related
to the detection of transient signals in pulmonary sounds
Exact smoothing in triplet switching Markov trees
Dans le problĂšme de lissage Ă saut considĂ©rĂ© on considĂšre trois processus X, R, Y, avec X, Y Ă valeurs continues et R Ă valeurs discrĂštes. Y modĂ©lise le signal observĂ©, X le signal cachĂ© que l'on cherche Ă estimer, et R les « changements de regime », ou des « sauts » du systĂšme. Dans le cas des processus mono-dimensionnels, oĂč les processus en prĂ©sence sont des chaĂźnes, les modĂšles classiques sont des systĂšmes linĂ©aires Ă sauts markoviens: R est une chaĂźne de Markov et la loi du couple (X, Y) conditionnellement Ă R est celle d'un systĂšme linaire Gaussien prĂ©sentant des facilitĂ©s de calcul. Cependant, lorsque R n'est pas connu, les calculs ne peuvent plus ĂȘtre faits avec une complexitĂ© raisonnable et on doit faire appel Ă des approximations. Des modĂšles diffĂ©rents ont Ă©tĂ© proposes rĂ©cemment, autorisant le lissage avec une complexitĂ© linĂ©aire en temps. L'objet du prĂ©sent article est d'Ă©tendre ces modeles aux arbres de Markov triplets. Abstract - The problem of smoothing in switching linear systems dealt with in the paper consists of considering three stochastic processes X, R, Y, with X, Y continuous and R finite. Y models the observed signal, X models the hidden searched signal, and R models the "changes of regime", or « switches », of the system. In the mono-dimensional case, where the three processes are random chains, the classical models consists of taking a Markov distribution for R, and a linear Gaussian system distribution for the distribution of (X, Y) conditional on R. Then, when R is known, smoothing can be performed with a' reasonable complexity. However, when R is not known, such models do not allow the smoothing with reasonable complexity. Different models allowing such computation have been proposed recently. ' The aim of this paper is to extend them to the triplet Markov trees