WO2014198847A1 - Decision device for deciding whether a surface is living tissue or not - Google Patents

Decision device for deciding whether a surface is living tissue or not Download PDF

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Publication number
WO2014198847A1
WO2014198847A1 PCT/EP2014/062277 EP2014062277W WO2014198847A1 WO 2014198847 A1 WO2014198847 A1 WO 2014198847A1 EP 2014062277 W EP2014062277 W EP 2014062277W WO 2014198847 A1 WO2014198847 A1 WO 2014198847A1
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WO
WIPO (PCT)
Prior art keywords
image
intensities
standard deviation
parallel
decision device
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PCT/EP2014/062277
Other languages
French (fr)
Inventor
Alain Thiebot
Andrey Tarasishin
Benjamin PEYRONNEAUD
Florence Guillemot
Aldo MAALOUF
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Morpho
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Publication of WO2014198847A1 publication Critical patent/WO2014198847A1/en

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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
    • G06V40/10—Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
    • G06V40/16—Human faces, e.g. facial parts, sketches or expressions
    • G06V40/172—Classification, e.g. identification
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V10/00—Arrangements for image or video recognition or understanding
    • G06V10/10—Image acquisition
    • G06V10/12—Details of acquisition arrangements; Constructional details thereof
    • G06V10/14—Optical characteristics of the device performing the acquisition or on the illumination arrangements
    • G06V10/143—Sensing or illuminating at different wavelengths
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V10/00—Arrangements for image or video recognition or understanding
    • G06V10/10—Image acquisition
    • G06V10/12—Details of acquisition arrangements; Constructional details thereof
    • G06V10/14—Optical characteristics of the device performing the acquisition or on the illumination arrangements
    • G06V10/145—Illumination specially adapted for pattern recognition, e.g. using gratings
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
    • G06V40/00—Recognition of biometric, human-related or animal-related patterns in image or video data
    • G06V40/40—Spoof detection, e.g. liveness detection
    • G06V40/45—Detection of the body part being alive

Definitions

  • Decision device provided for deciding whether a surface is living tissue or not
  • the present invention relates to a decision device provided for deciding whether a surface is a living tissue or not, and a decision process implemented by such a decision device.
  • the identification of a person by the biometric recognition of a face, the iris or a fingerprint or palmar, is used to secure facilities such as buildings or machines.
  • This technology eliminates access codes or cards that can be stolen or falsified.
  • the use of this technology enhances security as the probability of two people having two identical faces is very low.
  • the biometric recognition is based on comparing the image of a user's biometry with a set of reference images stored in a database. Although piracy of biometric recognition devices is difficult, it is not impossible.
  • lures such as a photo or a mask on which is reproduced the biometry to imitate.
  • the pirate can then place the decoy in front of the acquisition device of the biometric recognition device which is then deceived.
  • An object of the present invention is to provide a decision device for deciding whether a surface is a living tissue or not and that does not have the disadvantages of the prior art.
  • a decision device for deciding whether a surface is a living tissue or not, said decision device comprising:
  • lighting means emitting a coherent and polarized incident flux in a polarization direction having a coherence length greater than or equal to 1 cm and intended to illuminate said surface;
  • a capture means having a polarizing filter perpendicular and / or parallel to the direction of polarization and intended for acquiring at least one image of the illuminated surface presenting scab,
  • calculating means provided for calculating, from the perpendicular image and / or the parallel image, the value of at least one criterion representative of the scabs of said image (s),
  • a database containing for the or each criterion a range of reference values of said criterion which is representative of scabs of a living tissue, comparison means provided for comparing the or each value thus calculated with the corresponding reference value interval and for providing information representative of these comparisons, and
  • decision means provided for deciding whether the surface is a living tissue or not depending on the information delivered by the comparison means.
  • the representative criteria for scab are chosen from the standard deviation of the intensities of the perpendicular image, the standard deviation of the intensities of the parallel image, a logical and / or arithmetic combination between the standard deviation of the intensities of the parallel image and the standard deviation of the intensities of the perpendicular image, the standard deviation of the intensities of the perpendicular image on which a high pass type frequency filter is previously applied, the difference between type of the intensities of the parallel image on which a high-pass type frequency filter is previously applied, a logical and / or arithmetic combination between the standard deviation of the intensities of the parallel image on which a frequency filter is applied beforehand of the high-pass type and the standard deviation of the intensities of the perpendicular image on which a high pass type frequency filter is previously applied.
  • the criteria adopted are the standard deviation of the intensities of the perpendicular image, the standard deviation of the intensities of the parallel image, and the ratio between the standard deviation of the intensities of the parallel image and the standard deviation of the intensities of the perpendicular image.
  • the criteria used are the standard deviation of the intensities of the perpendicular image on which a highpass type frequency filter is previously applied, the standard deviation of the intensities of the parallel image on which a prior high-pass type frequency filter, and the ratio between the standard deviation of the intensities of the parallel image on which a high-pass type frequency filter is previously applied and the standard deviation of the intensities of the perpendicular image on which a high pass type frequency filter is applied beforehand.
  • the representative criteria for scab are characteristic dimensions of the scab observed and calculated by an autocorrelation calculation.
  • the representative criteria for scab is the standard deviation of the power spectral density.
  • the comparison means comprise the use of a learning mechanism of the ACP, SVM or neuron network type driven on the basis of real tissue and fraud.
  • the invention also proposes a decision method intended to decide whether a surface is a living tissue or not and implemented by a decision device according to one of the preceding variants, the decision method comprising:
  • a decision step during which the decision means decide whether the surface is a living tissue or not depending on the information delivered by the comparison means.
  • FIG. 1 represents a schematic view of a decision device according to the invention
  • FIG. 2 is an algorithm of a decision method according to the invention
  • FIG. 3 shows the application to a non-living tissue
  • FIG. 4 shows the application to living tissue
  • FIG. Figure 5 shows an example of test results.
  • Fig. 1 shows a decision device 100 for deciding whether a surface 50, here a face 50 of an individual is a living tissue or not.
  • the surface 50 is assimilated to a face, but the invention applies in the same way to all living tissues that can be obtained while respecting the integrity of the human body such as the skin of the face, the skin of a finger, the skin of a palm, or such as the iris or the retina.
  • the decision device 100 comprises lighting means 102 provided for illuminating the surface 50 with a coherent incident flux 104 having a linear polarization.
  • the lighting means 102 are chosen for their coherence length greater than or equal to 1 cm so that the latter is sufficient to generate scabs (or interference or speckles) on the illuminated surface 50.
  • monomode laser diodes having a coherence length well adapted to the application and widely available will be used.
  • all light sources characterized by a coherence length of the order of a few tens of micrometers (such as LEDs) or of the order of a few micrometers (such as white light) or generating no interference is proscribed for the implementation of the present invention.
  • the speckle is an interference due to the difference in step (phase shift) of the reflected beams of the coherent source scattered by an irregular reflecting surface (surface scattering).
  • the level of speckle is important for cases of fraud materials with a high surface diffusion (paper, plasters, resins, etc ...), and decreases in the case of the skin because the beams transmitted in the skin by diffusion of volume lose their coherence after multiple internal reflections and thus generate less interference, so a lower speckle level.
  • Some materials have a weak surface diffusion (low tinted silicone) and will have a lower speckle level than the skin.
  • Fig. 3 shows in the case of a fraud 301 that the speckle level is important when said fraud 301 is illuminated by an incident beam 302 due to a large surface scattering and represented by the beam 303 and a low volume diffusion represented by the beam 304.
  • Fig. 4 shows in the case of a living tissue 401 that the level of speckle is lower when the tissue 401 is illuminated by an incident beam 402 due to a reduced surface diffusion and represented by the beam 403 and a strong diffusion of volume represented by beam 404.
  • the principle of the invention is based on the fact that, depending on the absorption rate of a surface illuminated by the incident coherent flux 104, a level of scab ("speckles" in English) due to the roughness of the surface is generated.
  • the present invention does not seek to suppress the speckles contrary to prior art methods which aim to reconstruct either a faithful image of the object or a target extraction, but it relies on these speckles to characterize the nature of the surface to be studied.
  • the methods currently used for acquiring images with laser illumination seek to limit the generation of scabbing by favoring laser sources with short coherence lengths such as VCSEL lasers or by modulating the laser diodes.
  • the incident flux 104 may emit at a wavelength of between 550 and
  • the wavelength of 750 to 950 nm will be chosen to avoid dazzling the individual.
  • the wavelength chosen will be approximately 785 nm which is the optimal wavelength for the absorption of the skin of the face, iris or retina so as to obtain a minimum of speckle on the skin. living tissue and a maximum of speckle on other materials.
  • the object to be acquired is a part of the hand (one or more fingers, the palm ...)
  • the system does not light the eye of the user, the latter is not dazzled.
  • the decision device 100 also comprises one or two capture means 106 and 108 sensitive to the wavelength chosen according to the object to be illuminated, each being designed to capture a image of the surface 50 illuminated by the coherent stream 104 characterized by a coherence length of at least 1 cm generating scabs on the surface 50.
  • the capture means 106 and 108 here take the form of two cameras each provided with a interference filter for the wavelength of the coherent flux 104.
  • the perpendicular capture means 106 has a polarizing filter perpendicular to the polarization direction of the coherent stream 104 and the parallel capture means 108 has a polarizing filter parallel to the polarization direction of the coherent stream 104.
  • the image captured by the perpendicular capture means 106 is called the perpendicular image
  • the image captured by the parallel capture means 108 is called the parallel image.
  • the illumination means 102 and each capture means 106, 108 are oriented towards the surface 50 to be analyzed.
  • the scab intensity will be different.
  • the surface 50 is a living tissue, the latter diffuses in volume a significant part of the incident flux (at the wavelengths considered, the penetration of light into the skin is of the order of 1 mm), so the intensity scab is weak. If the surface 50 is a decoy, the material diffuses weakly in volume and strongly on the surface and the scab intensity is higher.
  • the principle of the invention is based on the quantification of speckles. This quantification can be done according to several image processing known to those skilled in the art such as for example: frequency analysis, variance, standard deviation.
  • intensity standard deviation analysis is used on all or part of the illuminated surface where living tissue is to be found.
  • the standard deviation of the intensities of the perpendicular image, and / or the standard deviation of the intensities of the parallel image, and / or the logical and / or arithmetic combination between the standard deviation of the intensities of the parallel image and the standard deviation of the intensities of the perpendicular image constitute different criteria which after analysis make it possible to decide on the veracity of the surface 50.
  • the logical and / or arithmetic combination of the standard deviations of the intensities makes it possible to confirm the coherence between the two standard deviations of the intensities.
  • the ratio of the standard deviation of the intensities of the parallel image to the standard deviation of the intensities of the perpendicular image must be greater than one.
  • the standard deviation of the intensities of the perpendicular image must be smaller than that of the parallel image because the specular reflection which does not lose its coherence is suppressed on the perpendicular image.
  • the standard deviation of the intensities of an image is calculated by the following operations: - identification of the zones to be analyzed (supposed presence of skin) by detection of the illuminated face on said image, and
  • the decision device 100 also comprises calculation means 112, 113 intended to carry out the preceding operations and thus to calculate the value or values of at least one criterion representative of the scabs of the perpendicular image and / or the filtered parallel image or no.
  • the decision device 100 includes a database containing for each of the criteria selected the range of reference values of said criterion which is representative of scabs of a living tissue.
  • the criteria used are the standard deviation of the intensities of the perpendicular image, the standard deviation of the intensities of the parallel image, and the relationship between the deviation type of the intensities of the parallel image and the standard deviation of the intensities of the perpendicular image.
  • the criteria used are the standard deviation of the intensities of the perpendicular image on which a high pass type frequency filter is previously applied, the standard deviation of the intensities of the parallel image on which a high-pass type frequency filter is previously applied, and the ratio between the standard deviation of the intensities of the parallel image on which a high-pass frequency the standard deviation of the intensities of the perpendicular image on which a highpass type frequency filter is previously applied.
  • the decision device 100 For each criterion selected for the analysis, the decision device 100 is subjected to a learning phase, during which real living tissues are presented and during which the value of said criterion is recorded.
  • This learning phase makes it possible to collect for each criterion selected, values of said criterion which are representative of a living tissue and thus to create an interval of reference values which, for said criterion, corresponds to a living tissue. It is also possible to present lures to refine the interval.
  • This learning phase is performed once at the start of the decision device 100.
  • the decision device 100 further comprises:
  • comparison means 114 provided for comparing the value of the or each criterion with the corresponding reference value interval and delivering representative information for each comparison
  • decision means 116 provided for deciding whether the surface 50 is a living tissue or not depending on the information delivered by the comparison means 114.
  • the decision device 100 comprises the perpendicular capture means 106 and the calculation means 112 are provided for calculating the standard deviation of the intensities of said image. perpendicular.
  • the decision device 100 comprises the parallel capture means 108 and the calculation means 113 are designed to calculate the standard deviation of the intensities of said image. parallel.
  • the decision device 100 comprises the perpendicular capture means 106 and the parallel capture means 108 and the calculation means are provided for calculating the standard deviation of the intensities of said perpendicular image, to calculate the standard deviation of the intensities of said parallel image, and calculating the logical and / or arithmetic combination between the standard deviation of the intensities of the perpendicular image and the standard deviation of the intensities of the parallel image.
  • the decision device 100 comprises the perpendicular capture means 106 and the calculation means 112 are provided for filtering the perpendicular image and calculating the difference -type of the intensities of said filtered perpendicular image.
  • the decision device 100 comprises the parallel capture means 108 and the calculation means 113 are provided for filtering the parallel image and calculating the difference -type of the intensities of said filtered parallel image.
  • the decision device 100 comprises the means of perpendicular capture 106 and the parallel capture means 108 and the computing means are provided for filtering the parallel and perpendicular images and calculating the standard deviation of the intensities of said filtered perpendicular image, for calculating the standard deviation of the intensities of said filtered parallel image, and calculating the logical and / or arithmetic combination between the standard deviation of the intensities of the filtered perpendicular image and the standard deviation of the intensities of the filtered parallel image.
  • the surface 50 is then considered as a living tissue and is not considered a living tissue if it is outside this range of values of reference.
  • Fig. 2 shows a flowchart of a decision method 300 implemented by the decision device 100 and provided to decide whether a surface 50 is a living tissue or not.
  • the decision process 300 comprises:
  • a capture step 304 during which the perpendicular capture means 106 captures a perpendicular image of the surface 50 thus illuminated and / or a capture step 306 in which the parallel capture means 108 captures a parallel image of the surface 50 thus illuminated
  • a calculation step 306 during which the calculation means 112 calculate the value of each of said criteria selected from each image thus captured and possibly previously filtered by a high-pass type frequency filter
  • comparison step 308 during which the comparison means 114 compare each value thus calculated with the corresponding reference value interval, and deliver information representative of this comparison
  • a decision step 310 during which the decision means 116 decide whether the surface 50 is a living tissue or not according to the information delivered by the comparison means 114.
  • the 300 comprises, prior to the lighting step 302, a learning step 312 which consists of a capture of live tissue images by each appropriate capture means 106, 108 according to the criterion (s) retained , a calculation of the value of each criterion retained by the computing means 112, 113 from the image or each image thus captured, and the definition for the or each criterion retained of an interval of the reference values for which the values of said criterion are considered representative of a living tissue.
  • the learning step 310 is performed only at the start of the decision device 100 and the decision step 310 then loop on the lighting step 302.
  • certain features of the speckle image are analyzed for living and non-living tissue. This method is based on a statistical approach.
  • the statistical criteria are defined based on the physical properties of the speckle that are measured based on the image processing.
  • the criteria are defined as follows:
  • 2nd order statistics describe relative light intensity variations at two points. As such, they give an indication of the grain size in the speckle figure and their distribution.
  • the most commonly used 2nd order statistical parameter in the speckle study is the autocorrelation function.
  • This shift varies from one tissue to another and makes it possible to distinguish between living and non-living tissues.
  • Wiener spectral power density or spectrum which describes the distribution of the spot sizes in the speckle figure. It is given by the Fourier transform of the autocorrelation function of the luminous intensity.
  • the second criterion is thus defined by the standard deviation of the spectral density.
  • Fig. 5 shows the performance of these two criteria.
  • the points to the left of the line 502 correspond to the non-living tissues while the points to the right of the line 502 correspond to the living tissues.
  • the abscissa corresponds to the Fourier score and therefore to the standard deviation of the spectral density
  • the ordinate corresponds to the speckle score and therefore to the autocorrelation score.
  • the final score for classifying tissues between living and non-living is obtained by conducting a principal component analysis to obtain the equation of line 502 that separates the two classes.
  • Any score above the threshold defined by the line corresponds to a living tissue.
  • All of the disclosed mechanisms include the use of an ACP, SVM or neural network-based learning mechanism driven on true tissue and fraud bases.

Abstract

The invention relates to a decision device (100) for deciding whether a surface (50) is a living tissue or not, said decision device (100) comprising: lighting means (102) which emit an incident coherent stream (104) that is polarized along a polarization direction, has a coherence length no lower than 1 cm and is intended to illuminate said surface (50); a sensing means (106, 108) having a polarizing filter perpendicular and/or parallel to the polarization direction and intended for acquiring at least one image of the illuminated surface (50) having stippling; calculation means (112, 113) for calculating, from the perpendicular image and/or from the parallel image, the value of at least one criterion representing the stippling of said image(s); a database containing, for the or each criterion, an range of reference values of said criterion which represents the stippling of a living tissue; comparison means (114) for comparing the or each value thus calculated to the corresponding range of reference values and for outputting information representing said comparisons; and decision means (116) for deciding whether the surface (50) is a living tissue or not, depending on the information output by the comparison means (114).

Description

Dispositif de décision prévu pour décider si une surface est un tissu vivant ou non  Decision device provided for deciding whether a surface is living tissue or not
La présente invention concerne un dispositif de décision prévu pour décider si une surface est un tissu vivant ou non, ainsi qu'un procédé de décision mis en œuvre par un tel dispositif de décision. The present invention relates to a decision device provided for deciding whether a surface is a living tissue or not, and a decision process implemented by such a decision device.
Elle trouve application dans le domaine de la reconnaissance biométrique et en particulier dans le domaine de l'identification par reconnaissance d'un tissu vivant tel qu'un iris, une rétine, la peau d'un visage ou d'une main.  It finds application in the field of biometric recognition and in particular in the field of identification by recognition of a living tissue such as an iris, a retina, the skin of a face or a hand.
L'identification d'une personne par la reconnaissance biométrique d'un visage, de l'iris ou d'une empreinte digitale ou palmaire, est utilisée pour sécuriser des installations comme par exemple des bâtiments ou des machines. Cette technologie permet de s'affranchir de codes d'accès ou de cartes qui peuvent être volés ou falsifiés. L'utilisation de cette technologie permet de renforcer la sécurité dans la mesure où la probabilité que deux personnes aient deux visages identiques est très faible.  The identification of a person by the biometric recognition of a face, the iris or a fingerprint or palmar, is used to secure facilities such as buildings or machines. This technology eliminates access codes or cards that can be stolen or falsified. The use of this technology enhances security as the probability of two people having two identical faces is very low.
La reconnaissance biométrique est basée sur la comparaison de l'image d'une biométrie de l'utilisateur avec un ensemble d'images de référence stockées dans une base de données. Bien que le piratage des dispositifs de reconnaissance biométrique soit difficile, il n'est pas impossible. The biometric recognition is based on comparing the image of a user's biometry with a set of reference images stored in a database. Although piracy of biometric recognition devices is difficult, it is not impossible.
En effet, certains pirates réalisent des leurres, comme par exemple une photo ou un masque sur lequel est reproduite la biométrie à imiter. Le pirate peut alors placer le leurre devant le dispositif d'acquisition du dispositif de reconnaissance biométrique qui est alors trompé.  Indeed, some pirates realize lures, such as a photo or a mask on which is reproduced the biometry to imitate. The pirate can then place the decoy in front of the acquisition device of the biometric recognition device which is then deceived.
De nombreux dispositifs et procédés ont été mis en œuvre pour limiter les risques de piratage.  Numerous devices and processes have been implemented to limit the risks of piracy.
Pour différencier une vraie biométrie d'une fausse, les documents US 2008/0025579, WO 2008/108871 et US2008/0219522 proposent d'analyser des images multispectrales obtenues en captant la réflexion spéculaire d'un flux lumineux homogène sur la surface de la peau ou du matériau- leurre.  To differentiate a true biometry from a false, the documents US 2008/0025579, WO 2008/108871 and US2008 / 0219522 propose to analyze multispectral images obtained by capturing the specular reflection of a homogeneous light flux on the surface of the skin. or decoy material.
Le document US 2011/0163163 propose d'analyser des images multispectrales obtenues en captant la diffusion d'un flux lumineux homogène sur la surface de la peau ou du matériau- leurre.  Document US 2011/0163163 proposes to analyze multispectral images obtained by capturing the diffusion of a homogeneous light flux on the surface of the skin or of the decoy material.
Ces solutions présentent l'inconvénient de multiplier le nombre d'images à acquérir et à traiter.  These solutions have the disadvantage of multiplying the number of images to be acquired and processed.
Un objet de la présente invention est de proposer un dispositif de décision permettant de décider si une surface est un tissu vivant ou non et qui ne présente pas les inconvénients de l'art antérieur.  An object of the present invention is to provide a decision device for deciding whether a surface is a living tissue or not and that does not have the disadvantages of the prior art.
A cet effet, est proposé un dispositif de décision prévu pour décider si une surface est un tissu vivant ou non, ledit dispositif de décision comportant :  For this purpose, a decision device is provided for deciding whether a surface is a living tissue or not, said decision device comprising:
- des moyens d'éclairage émettant un flux incident cohérent et polarisé selon une direction de polarisation doté d'une longueur de cohérence supérieure ou égale à 1cm et destiné à éclairer ladite surface,  lighting means emitting a coherent and polarized incident flux in a polarization direction having a coherence length greater than or equal to 1 cm and intended to illuminate said surface;
- un moyen de capture présentant un filtre polarisant perpendiculaire et/ou parallèle à la direction de polarisation et destiné à l'acquisition d'au moins une image de la surface éclairée présentant des tavelures,  a capture means having a polarizing filter perpendicular and / or parallel to the direction of polarization and intended for acquiring at least one image of the illuminated surface presenting scab,
- des moyens de calcul prévus pour calculer, à partir de l'image perpendiculaire et/ou de l'image parallèle, la valeur d'au moins un critère représentatif des tavelures de ladite/ desdites image(s),  calculating means provided for calculating, from the perpendicular image and / or the parallel image, the value of at least one criterion representative of the scabs of said image (s),
- une base de données contenant pour le ou chaque critère un intervalle de valeurs de référence dudit critère qui soit représentatif de tavelures d'un tissu vivant, - des moyens de comparaison prévus pour comparer la ou chaque valeur ainsi calculée à l'intervalle de valeurs de référence correspondant et pour délivrer une information représentative de ces comparaisons, et a database containing for the or each criterion a range of reference values of said criterion which is representative of scabs of a living tissue, comparison means provided for comparing the or each value thus calculated with the corresponding reference value interval and for providing information representative of these comparisons, and
- des moyens de décision prévus pour décider si la surface est un tissu vivant ou non en fonction de l'information délivrée par les moyens de comparaison.  decision means provided for deciding whether the surface is a living tissue or not depending on the information delivered by the comparison means.
Avantageusement, les critères représentatifs des tavelures sont choisis parmi l'écart-type des intensités de l'image perpendiculaire, l'écart-type des intensités de l'image parallèle, une combinaison logique et/ou arithmétique entre l'écart-type des intensités de l'image parallèle et l'écart-type des intensités de l'image perpendiculaire, l'écart-type des intensités de l'image perpendiculaire sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut, l'écart-type des intensités de l'image parallèle sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut, une combinaison logique et/ou arithmétique entre l'écart-type des intensités de l'image parallèle sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut et l'écart-type des intensités de l'image perpendiculaire sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut.  Advantageously, the representative criteria for scab are chosen from the standard deviation of the intensities of the perpendicular image, the standard deviation of the intensities of the parallel image, a logical and / or arithmetic combination between the standard deviation of the intensities of the parallel image and the standard deviation of the intensities of the perpendicular image, the standard deviation of the intensities of the perpendicular image on which a high pass type frequency filter is previously applied, the difference between type of the intensities of the parallel image on which a high-pass type frequency filter is previously applied, a logical and / or arithmetic combination between the standard deviation of the intensities of the parallel image on which a frequency filter is applied beforehand of the high-pass type and the standard deviation of the intensities of the perpendicular image on which a high pass type frequency filter is previously applied.
Avantageusement, les critères retenus sont l'écart-type des intensités de l'image perpendiculaire, l'écart-type des intensités de l'image parallèle, et le rapport entre l'écart-type des intensités de l'image parallèle et l'écart-type des intensités de l'image perpendiculaire.  Advantageously, the criteria adopted are the standard deviation of the intensities of the perpendicular image, the standard deviation of the intensities of the parallel image, and the ratio between the standard deviation of the intensities of the parallel image and the standard deviation of the intensities of the perpendicular image.
Avantageusement, les critères retenus sont l'écart-type des intensités de l'image perpendiculaire sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut, l'écart-type des intensités de l'image parallèle sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut, et le rapport entre l'écart-type des intensités de l'image parallèle sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut et l'écart-type des intensités de l'image perpendiculaire sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut.  Advantageously, the criteria used are the standard deviation of the intensities of the perpendicular image on which a highpass type frequency filter is previously applied, the standard deviation of the intensities of the parallel image on which a prior high-pass type frequency filter, and the ratio between the standard deviation of the intensities of the parallel image on which a high-pass type frequency filter is previously applied and the standard deviation of the intensities of the perpendicular image on which a high pass type frequency filter is applied beforehand.
Avantageusement, les critères représentatifs des tavelures sont des dimensions caractéristiques des tavelures observées et calculées par un calcul d'auto-corrélation.  Advantageously, the representative criteria for scab are characteristic dimensions of the scab observed and calculated by an autocorrelation calculation.
Avantageusement, les critères représentatifs des tavelures est l'écart type de la densité spectrale de puissance.  Advantageously, the representative criteria for scab is the standard deviation of the power spectral density.
Avantageusement, les moyens de comparaison comprennent l'utilisation d'un mécanisme d'apprentissage de type ACP, SVM ou réseau de neurones entraîné sur des bases de vrais tissus et de fraudes. L'invention propose également un procédé de décision prévu pour décider si une surface est un tissu vivant ou non et mis en œuvre par un dispositif de décision selon l'une des variantes précédentes, le procédé de décision comportant: Advantageously, the comparison means comprise the use of a learning mechanism of the ACP, SVM or neuron network type driven on the basis of real tissue and fraud. The invention also proposes a decision method intended to decide whether a surface is a living tissue or not and implemented by a decision device according to one of the preceding variants, the decision method comprising:
- une étape d'éclairage au cours de laquelle les moyens d'éclairage éclairent la surface à analyser,  a lighting step during which the lighting means illuminate the surface to be analyzed,
- une étape de capture au cours de laquelle le moyen de capture perpendiculaire capture une image perpendiculaire de la surface ainsi éclairée et/ou une étape de capture au cours de laquelle le moyen de capture parallèle capture une image parallèle de la surface ainsi éclairée,  a capture step during which the perpendicular capture means captures a perpendicular image of the illuminated surface and / or a capture step during which the parallel capture means captures a parallel image of the illuminated surface,
- une étape de calcul au cours de laquelle les moyens de calcul calculent la valeur de chacun desdits critères retenus à partir de chaque image ainsi capturée,  a calculation step during which the calculation means calculate the value of each of said criteria selected from each captured image,
- une étape de comparaison au cours de laquelle les moyens de comparaison comparent chaque valeur ainsi calculée à l'intervalle des valeurs de référence correspondant et délivrent une information représentative de cette comparaison,  a comparison step during which the comparison means compare each value thus calculated with the corresponding reference value interval and deliver information representative of this comparison,
- une étape de décision au cours de laquelle les moyens de décision décident si la surface est un tissu vivant ou non en fonction de l'information délivrée par les moyens de comparaison.  a decision step during which the decision means decide whether the surface is a living tissue or not depending on the information delivered by the comparison means.
Les caractéristiques de l'invention mentionnées ci-dessus, ainsi que d'autres, apparaîtront plus clairement à la lecture de la description suivante d'un exemple de réalisation, ladite description étant faite en relation avec les dessins joints, parmi lesquels :  The characteristics of the invention mentioned above, as well as others, will appear more clearly on reading the following description of an exemplary embodiment, said description being given in relation to the attached drawings, among which:
la Fig. 1 représente une vue schématique d'un dispositif de décision selon l'invention,  FIG. 1 represents a schematic view of a decision device according to the invention,
la Fig. 2 est un algorithme d'un procédé de décision selon l'invention, la Fig. 3 montre l'application à un tissu non vivant,  FIG. 2 is an algorithm of a decision method according to the invention, FIG. 3 shows the application to a non-living tissue,
la Fig. 4 montre l'application à un tissu vivant, et  FIG. 4 shows the application to living tissue, and
la Fig. 5 montre un exemple de résultats de tests.  FIG. Figure 5 shows an example of test results.
La Fig. 1 montre un dispositif de décision 100 destiné à décider si une surface 50, ici un visage 50 d'un individu est un tissu vivant ou non. Dans la suite de la description, la surface 50 est assimilée à un visage, mais l'invention s'applique de la même manière à tous tissus vivants pouvant être obtenus tout en respectant l'intégrité du corps humain tel que la peau du visage, la peau d'un doigt, la peau d'une paume, ou encore tel que l'iris ou la rétine. Le dispositif de décision 100 comprend des moyens d'éclairage 102 prévus pour éclairer la surface 50 avec un flux incident cohérent 104 ayant une polarisation rectiligne. Les moyens d'éclairage 102 sont choisis pour leur longueur de cohérence supérieure ou égale à 1 cm de sorte que cette dernière est suffisante pour générer des tavelures (ou interférences ou speckles) sur la surface éclairée 50. Fig. 1 shows a decision device 100 for deciding whether a surface 50, here a face 50 of an individual is a living tissue or not. In the remainder of the description, the surface 50 is assimilated to a face, but the invention applies in the same way to all living tissues that can be obtained while respecting the integrity of the human body such as the skin of the face, the skin of a finger, the skin of a palm, or such as the iris or the retina. The decision device 100 comprises lighting means 102 provided for illuminating the surface 50 with a coherent incident flux 104 having a linear polarization. The lighting means 102 are chosen for their coherence length greater than or equal to 1 cm so that the latter is sufficient to generate scabs (or interference or speckles) on the illuminated surface 50.
On utilisera préférentiellement des diodes laser monomodes présentant une longueur de cohérence bien adaptée à l'application et largement disponibles. En revanche, toutes sources lumineuses caractérisées par une longueur de cohérence de l'ordre de quelques dizaines de micro-mètres (tel que les LED) ou de l'ordre de quelques micromètres (telle que la lumière blanche) ou ne générant aucune interférence est proscrite pour la mise en œuvre de la présente invention.  Preferably, monomode laser diodes having a coherence length well adapted to the application and widely available will be used. On the other hand, all light sources characterized by a coherence length of the order of a few tens of micrometers (such as LEDs) or of the order of a few micrometers (such as white light) or generating no interference is proscribed for the implementation of the present invention.
Le speckle est une interférence due à la différence de marche (déphasage) des faisceaux réfléchis de la source cohérente diffusés par une surface réfléchissante irrégulière (diffusion de surface). Le niveau de speckle est important pour les cas de matériaux de fraude présentant une forte diffusion de surface (papier, plâtres, résines, etc...,), et diminue dans le cas de la peau car les faisceaux transmis dans la peau par diffusion de volume perdent leur cohérence après de multiples réflexions internes et donc génèrent moins d'interférence, donc un niveau de speckle moindre. Certains matériaux présentent une diffusion de surface faible (silicone faiblement teinté dans la masse) et présenteront un niveau de speckle encore plus faible que la peau.  The speckle is an interference due to the difference in step (phase shift) of the reflected beams of the coherent source scattered by an irregular reflecting surface (surface scattering). The level of speckle is important for cases of fraud materials with a high surface diffusion (paper, plasters, resins, etc ...), and decreases in the case of the skin because the beams transmitted in the skin by diffusion of volume lose their coherence after multiple internal reflections and thus generate less interference, so a lower speckle level. Some materials have a weak surface diffusion (low tinted silicone) and will have a lower speckle level than the skin.
La Fig. 3 montre dans le cas d'une fraude 301 que le niveau de speckle est important lorsque ladite fraude 301 est éclairée par un faisceaux incident 302 du fait d'une diffusion de surface importante et représentée par le faisceau 303 et une faible diffusion de volume représenté par le faisceau 304.  Fig. 3 shows in the case of a fraud 301 that the speckle level is important when said fraud 301 is illuminated by an incident beam 302 due to a large surface scattering and represented by the beam 303 and a low volume diffusion represented by the beam 304.
La Fig. 4 montre dans le cas d'un tissu vivant 401 que le niveau de speckle est plus faible lorsque le tissu 401 est éclairé par un faisceau incident 402 du fait d'une diffusion de surface réduite et représentée par le faisceau 403 et une forte diffusion de volume représenté par le faisceau 404.  Fig. 4 shows in the case of a living tissue 401 that the level of speckle is lower when the tissue 401 is illuminated by an incident beam 402 due to a reduced surface diffusion and represented by the beam 403 and a strong diffusion of volume represented by beam 404.
Le principe de l'invention repose sur le fait qu'en fonction du taux d'absorption d'une surface éclairée par le flux cohérent incident 104, un niveau de tavelures ("speckles" en anglais) dues à la rugosité de la surface est généré.  The principle of the invention is based on the fact that, depending on the absorption rate of a surface illuminated by the incident coherent flux 104, a level of scab ("speckles" in English) due to the roughness of the surface is generated.
La présente invention ne cherche pas à supprimer les speckles contrairement aux procédés de l'état de la technique qui visent à reconstituer soit une image fidèle de l'objet ou une extraction de mire, mais elle s'appuie sur ces speckles pour caractériser la nature de la surface à étudier. The present invention does not seek to suppress the speckles contrary to prior art methods which aim to reconstruct either a faithful image of the object or a target extraction, but it relies on these speckles to characterize the nature of the surface to be studied.
En particulier, les procédés actuellement mis en œuvre pour l'acquisition d'images avec un éclairage laser cherchent à limiter la génération des tavelures en privilégiant des sources laser à faibles longueurs de cohérence telles que les lasers VCSEL ou en modulant les diodes laser.  In particular, the methods currently used for acquiring images with laser illumination seek to limit the generation of scabbing by favoring laser sources with short coherence lengths such as VCSEL lasers or by modulating the laser diodes.
Les documents http://www.princetonoptronics.com/pdfs/7952-15.pdf et http ://www.princetonoptronics.corn/technology/technology.php#l 02 décrivent que sous certaines conditions, des lasers permettent d'éclairer sans générer de speckles.  The documents http://www.princetonoptronics.com/pdfs/7952-15.pdf and http: //www.princetonoptronics.corn/technology/technology.php#l 02 describe that under certain conditions, lasers can illuminate without generating speckles.
Le flux incident 104 pourra émettre à une longueur d'onde comprise entre 550 à The incident flux 104 may emit at a wavelength of between 550 and
950 nm lorsque le flux incident 104 éclaire les tissus d'un individu. 950 nm when the incident flux 104 illuminates the tissues of an individual.
Avantageusement, quand l'objet à éclairer est le visage, la longueur d'onde de 750 à 950 nm sera choisie afin d'éviter l'éblouissement de l'individu. Préférentiellement, la longueur d'onde choisie sera d'environ 785 nm qui est la longueur d'onde optimale pour l'absorption de la peau du visage, de l'iris ou de la rétine de sorte à obtenir un minimum de speckle sur le tissu vivant et un maximum de speckle sur les autres matériaux.  Advantageously, when the object to be illuminated is the face, the wavelength of 750 to 950 nm will be chosen to avoid dazzling the individual. Preferably, the wavelength chosen will be approximately 785 nm which is the optimal wavelength for the absorption of the skin of the face, iris or retina so as to obtain a minimum of speckle on the skin. living tissue and a maximum of speckle on other materials.
Selon un autre mode de réalisation, quand l'objet à acquérir est une partie de la main (un ou plusieurs doigts, la paume...), on pourra aussi utiliser un laser rouge émettant entre 635 et 650 nm. Dans ce cas, le système n'éclairant pas l'œil de l'utilisateur, ce dernier n'est pas ébloui.  According to another embodiment, when the object to be acquired is a part of the hand (one or more fingers, the palm ...), we can also use a red laser emitting between 635 and 650 nm. In this case, the system does not light the eye of the user, the latter is not dazzled.
Comme cela est expliqué ci-après, selon le critère retenu, le dispositif de décision 100 comprend également un ou deux moyens de capture 106 et 108 sensibles à la longueur d'onde choisie selon l'objet à éclairer, chacun étant prévu pour capturer une image de la surface 50 éclairée par le flux cohérent 104 caractérisé par une longueur de cohérence d'au moins 1 cm générant des tavelures sur la surface 50. Les moyens de capture 106 et 108 prennent ici la forme de deux caméras munies chacune d'un filtre interférentiel pour la longueur d'onde du flux cohérent 104.  As explained below, according to the criterion chosen, the decision device 100 also comprises one or two capture means 106 and 108 sensitive to the wavelength chosen according to the object to be illuminated, each being designed to capture a image of the surface 50 illuminated by the coherent stream 104 characterized by a coherence length of at least 1 cm generating scabs on the surface 50. The capture means 106 and 108 here take the form of two cameras each provided with a interference filter for the wavelength of the coherent flux 104.
Le moyen de capture perpendiculaire 106 présente un filtre polarisant perpendiculaire à la direction de polarisation du flux cohérent 104 et le moyen de capture parallèle 108 présente un filtre polarisant parallèle à la direction de polarisation du flux cohérent 104. L'image capturée par le moyen de capture perpendiculaire 106 est appelée l'image perpendiculaire, et l'image capturée par le moyen de capture parallèle 108 est appelée l'image parallèle. The perpendicular capture means 106 has a polarizing filter perpendicular to the polarization direction of the coherent stream 104 and the parallel capture means 108 has a polarizing filter parallel to the polarization direction of the coherent stream 104. The image captured by the perpendicular capture means 106 is called the perpendicular image, and the image captured by the parallel capture means 108 is called the parallel image.
Les moyens d'éclairage 102 et chaque moyen de capture 106, 108 sont orientés vers la surface 50 à analyser.  The illumination means 102 and each capture means 106, 108 are oriented towards the surface 50 to be analyzed.
Selon que la surface 50 est un tissu vivant ou un leurre, l'intensité des tavelures sera différente.  Depending on whether the surface 50 is a living tissue or a decoy, the scab intensity will be different.
Si la surface 50 est un tissu vivant, celui-ci diffuse en volume une partie importante du flux incident (aux longueurs d'onde considérées, la pénétration de la lumière dans la peau est de l'ordre de 1mm), donc l'intensité des tavelures est faible. Si la surface 50 est un leurre, le matériau diffuse faiblement en volume et fortement en surface et l'intensité des tavelures est plus élevée.  If the surface 50 is a living tissue, the latter diffuses in volume a significant part of the incident flux (at the wavelengths considered, the penetration of light into the skin is of the order of 1 mm), so the intensity scab is weak. If the surface 50 is a decoy, the material diffuses weakly in volume and strongly on the surface and the scab intensity is higher.
Le principe de l'invention est basé sur la quantification des speckles. Cette quantification peut se faire selon plusieurs traitements d'image connus de l'homme du métier comme par exemple : analyse fréquentielle, variance, écart-type.  The principle of the invention is based on the quantification of speckles. This quantification can be done according to several image processing known to those skilled in the art such as for example: frequency analysis, variance, standard deviation.
Dans un mode de réalisation préférentiel, on utilise l'analyse de l'écart-type des intensités sur l'ensemble ou une partie de la surface 50 éclairée où est censée se trouver du tissu vivant.  In a preferred embodiment, intensity standard deviation analysis is used on all or part of the illuminated surface where living tissue is to be found.
L'écart-type des intensités de l'image perpendiculaire, et/ou l'écart-type des intensités de l'image parallèle, et/ou la combinaison logique et/ou arithmétique entre l'écart-type des intensités de l'image parallèle et l'écart-type des intensités de l'image perpendiculaire constituent différents critères qui après analyse permettent de décider de la véracité de la surface 50.  The standard deviation of the intensities of the perpendicular image, and / or the standard deviation of the intensities of the parallel image, and / or the logical and / or arithmetic combination between the standard deviation of the intensities of the parallel image and the standard deviation of the intensities of the perpendicular image constitute different criteria which after analysis make it possible to decide on the veracity of the surface 50.
Il est également possible d'utiliser l'écart-type des intensités de l'image perpendiculaire sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut, et/ou l'écart-type des intensités de l'image parallèle sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut, et/ou la combinaison logique et/ou arithmétique entre l'écart-type des intensités de l'image parallèle sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut et l'écart- type des intensités de l'image perpendiculaire sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut.  It is also possible to use the standard deviation of the intensities of the perpendicular image on which a high pass type frequency filter is previously applied, and / or the standard deviation of the intensities of the parallel image on which a high pass type frequency filter is used beforehand, and / or the logical and / or arithmetic combination between the standard deviation of the intensities of the parallel image on which a highpass type frequency filter is first applied and the standard deviation of the intensities of the perpendicular image on which a high pass type frequency filter is previously applied.
Il est ainsi possible en analysant l'un de ces critères par rapport à un intervalle des valeurs de référence admissibles pour un tissu vivant de décider si la surface 50 est un tissu vivant ou non. Par exemple, si l'écart-type des intensités de l'image perpendiculaire ou parallèle est en dehors de l'intervalle attendu, cela détecte une fraude trop réfléchissante par rapport à un tissu vivant. It is thus possible by analyzing one of these criteria against a range of permissible reference values for living tissue to decide whether the surface 50 is living tissue or not. For example, if the standard deviation of the intensities of the perpendicular or parallel image is outside the expected range, this detects a too reflective fraud with respect to a living tissue.
De plus, si les deux écart-types des intensités sont dans les intervalles de valeurs de référence, la combinaison logique et/ou arithmétique des écart-types des intensités permet de confirmer la cohérence entre les deux écart-types des intensités.  Moreover, if the two standard deviations of the intensities are in the reference value ranges, the logical and / or arithmetic combination of the standard deviations of the intensities makes it possible to confirm the coherence between the two standard deviations of the intensities.
Dans un mode de réalisation particulier, le rapport de l'écart-type des intensités de l'image parallèle sur l'écart-type des intensités de l'image perpendiculaire doit être supérieur à un. En effet, l'écart-type des intensités de l'image perpendiculaire doit être inférieur à celui de de T'image parallèle car la réflexion spéculaire qui ne perd pas sa cohérence est supprimée sur l'image perpendiculaire.  In a particular embodiment, the ratio of the standard deviation of the intensities of the parallel image to the standard deviation of the intensities of the perpendicular image must be greater than one. In fact, the standard deviation of the intensities of the perpendicular image must be smaller than that of the parallel image because the specular reflection which does not lose its coherence is suppressed on the perpendicular image.
Pour augmenter la fiabilité du dispositif de décision 100, il est possible d'effectuer une analyse de deux ou plus de ces critères.  To increase the reliability of the decision device 100, it is possible to perform an analysis of two or more of these criteria.
L'écart-type des intensités d'une image est calculé par les opérations suivantes : - repérage des zones à analyser (présence supposée de peau) par détection du visage éclairé sur ladite image, et  The standard deviation of the intensities of an image is calculated by the following operations: - identification of the zones to be analyzed (supposed presence of skin) by detection of the illuminated face on said image, and
- calcul de l'écart-type des intensités dans chaque zone.  - calculation of the standard deviation of the intensities in each zone.
Dans le cas d'un écart-type des intensités d'une image sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut, un filtrage de l'image est effectué entre le repérage et le calcul.  In the case of a standard deviation of the intensities of an image on which a high pass type frequency filter is previously applied, a filtering of the image is carried out between the registration and the calculation.
Le dispositif de décision 100 comporte également des moyens de calcul 112, 113 prévus pour effectuer les opérations précédentes et calculer ainsi la ou les valeurs d'au moins un critère représentatif des tavelures de l'image perpendiculaire et/ou l'image parallèle filtrée ou non.  The decision device 100 also comprises calculation means 112, 113 intended to carry out the preceding operations and thus to calculate the value or values of at least one criterion representative of the scabs of the perpendicular image and / or the filtered parallel image or no.
Le dispositif de décision 100 comporte une base de données contenant pour chacun des critères retenus l'intervalle des valeurs de référence dudit critère qui est représentatif de tavelures d'un tissu vivant.  The decision device 100 includes a database containing for each of the criteria selected the range of reference values of said criterion which is representative of scabs of a living tissue.
Selon un premier mode de réalisation préféré de l'invention, les critères retenus sont l'écart-type des intensités de l'image perpendiculaire, l'écart-type des intensités de l'image parallèle, et le rapport entre l'écart-type des intensités de l'image parallèle et l'écart-type des intensités de l'image perpendiculaire.  According to a first preferred embodiment of the invention, the criteria used are the standard deviation of the intensities of the perpendicular image, the standard deviation of the intensities of the parallel image, and the relationship between the deviation type of the intensities of the parallel image and the standard deviation of the intensities of the perpendicular image.
Selon un deuxième mode de réalisation préféré de l'invention, les critères retenus sont l'écart-type des intensités de l'image perpendiculaire sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut, l'écart-type des intensités de l'image parallèle sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut, et le rapport entre l'écart-type des intensités de l'image parallèle sur laquelle on applique préalablement un filtre fréquentiel de type passe- haut et l'écart-type des intensités de l'image perpendiculaire sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut. According to a second preferred embodiment of the invention, the criteria used are the standard deviation of the intensities of the perpendicular image on which a high pass type frequency filter is previously applied, the standard deviation of the intensities of the parallel image on which a high-pass type frequency filter is previously applied, and the ratio between the standard deviation of the intensities of the parallel image on which a high-pass frequency the standard deviation of the intensities of the perpendicular image on which a highpass type frequency filter is previously applied.
Il est possible de combiner les deux modes de réalisation préférés en analysant des écart-types des intensités des images originelles et des écart-types des intensités des images filtrées.  It is possible to combine the two preferred embodiments by analyzing standard deviations of the intensities of the original images and the standard deviations of the intensities of the filtered images.
Pour chaque critère retenu pour l'analyse, le dispositif de décision 100 est soumis à une phase d'apprentissage, au cours de laquelle de véritables tissus vivants sont présentés et au cours de laquelle la valeur dudit critère est relevée. Cette phase d'apprentissage permet de recueillir pour chaque critère retenu, des valeurs dudit critère qui sont représentatives d'un tissu vivant et ainsi de créer un intervalle des valeurs de référence qui, pour ledit critère, correspond à un tissu vivant. Il est également possible de présenter des leurres pour affiner l'intervalle. Cette phase d'apprentissage s'effectue une fois à la mise en route du dispositif de décision 100.  For each criterion selected for the analysis, the decision device 100 is subjected to a learning phase, during which real living tissues are presented and during which the value of said criterion is recorded. This learning phase makes it possible to collect for each criterion selected, values of said criterion which are representative of a living tissue and thus to create an interval of reference values which, for said criterion, corresponds to a living tissue. It is also possible to present lures to refine the interval. This learning phase is performed once at the start of the decision device 100.
Le dispositif de décision 100 comporte en outre:  The decision device 100 further comprises:
- des moyens de comparaison 114 prévus pour comparer la valeur du ou de chaque critère à l'intervalle des valeurs de référence correspondant et délivrer une information représentative pour chaque comparaison, et  comparison means 114 provided for comparing the value of the or each criterion with the corresponding reference value interval and delivering representative information for each comparison, and
- des moyens de décision 116 prévus pour décider si la surface 50 est un tissu vivant ou non en fonction de l'information délivrée par les moyens de comparaison 114.  decision means 116 provided for deciding whether the surface 50 is a living tissue or not depending on the information delivered by the comparison means 114.
Si le critère retenu est l'écart-type des intensités de l'image perpendiculaire, le dispositif de décision 100 comprend le moyen de capture perpendiculaire 106 et les moyens de calcul 112 sont prévus pour calculer l'écart-type des intensités de ladite image perpendiculaire.  If the criterion adopted is the standard deviation of the intensities of the perpendicular image, the decision device 100 comprises the perpendicular capture means 106 and the calculation means 112 are provided for calculating the standard deviation of the intensities of said image. perpendicular.
Si le critère retenu est l'écart-type des intensités de l'image parallèle, le dispositif de décision 100 comprend le moyen de capture parallèle 108 et les moyens de calcul 113 sont prévus pour calculer l'écart-type des intensités de ladite image parallèle.  If the criterion adopted is the standard deviation of the intensities of the parallel image, the decision device 100 comprises the parallel capture means 108 and the calculation means 113 are designed to calculate the standard deviation of the intensities of said image. parallel.
Si le critère retenu est une combinaison logique et/ou arithmétique entre l'écart- type des intensités de l'image perpendiculaire et l'écart-type des intensités de l'image parallèle, le dispositif de décision 100 comprend le moyen de capture perpendiculaire 106 et le moyen de capture parallèle 108 et les moyens de calcul sont prévus pour calculer l'écart-type des intensités de ladite image perpendiculaire, pour calculer l'écart-type des intensités de ladite image parallèle, et calculer la combinaison logique et/ou arithmétique entre l'écart-type des intensités de l'image perpendiculaire et l'écart- type des intensités de l'image parallèle. If the criterion adopted is a logical and / or arithmetic combination between the standard deviation of the intensities of the perpendicular image and the standard deviation of the intensities of the parallel image, the decision device 100 comprises the perpendicular capture means 106 and the parallel capture means 108 and the calculation means are provided for calculating the standard deviation of the intensities of said perpendicular image, to calculate the standard deviation of the intensities of said parallel image, and calculating the logical and / or arithmetic combination between the standard deviation of the intensities of the perpendicular image and the standard deviation of the intensities of the parallel image.
Si le critère retenu est l'écart-type des intensités de l'image perpendiculaire filtrée, le dispositif de décision 100 comprend le moyen de capture perpendiculaire 106 et les moyens de calcul 112 sont prévus pour filtrer l'image perpendiculaire et calculer l'écart-type des intensités de ladite image perpendiculaire filtrée.  If the criterion adopted is the standard deviation of the intensities of the filtered perpendicular image, the decision device 100 comprises the perpendicular capture means 106 and the calculation means 112 are provided for filtering the perpendicular image and calculating the difference -type of the intensities of said filtered perpendicular image.
Si le critère retenu est l'écart-type des intensités de l'image parallèle filtrée, le dispositif de décision 100 comprend le moyen de capture parallèle 108 et les moyens de calcul 113 sont prévus pour filtrer l'image parallèle et calculer l'écart-type des intensités de ladite image parallèle filtrée.  If the criterion adopted is the standard deviation of the intensities of the filtered parallel image, the decision device 100 comprises the parallel capture means 108 and the calculation means 113 are provided for filtering the parallel image and calculating the difference -type of the intensities of said filtered parallel image.
Si le critère retenu est une combinaison logique et/ou arithmétique entre l'écart- type des intensités de l'image perpendiculaire filtrée et l'écart-type des intensités de l'image parallèle filtrée, le dispositif de décision 100 comprend le moyen de capture perpendiculaire 106 et le moyen de capture parallèle 108 et les moyens de calcul sont prévus pour filtrer les images parallèle et perpendiculaire et calculer l'écart-type des intensités de ladite image perpendiculaire filtrée, pour calculer l'écart-type des intensités de ladite image parallèle filtrée, et calculer la combinaison logique et/ou arithmétique entre l'écart-type des intensités de l'image perpendiculaire filtrée et l'écart-type des intensités de l'image parallèle filtrée.  If the criterion adopted is a logical and / or arithmetical combination between the standard deviation of the intensities of the filtered perpendicular image and the standard deviation of the intensities of the filtered parallel image, the decision device 100 comprises the means of perpendicular capture 106 and the parallel capture means 108 and the computing means are provided for filtering the parallel and perpendicular images and calculating the standard deviation of the intensities of said filtered perpendicular image, for calculating the standard deviation of the intensities of said filtered parallel image, and calculating the logical and / or arithmetic combination between the standard deviation of the intensities of the filtered perpendicular image and the standard deviation of the intensities of the filtered parallel image.
Ainsi, si la valeur de chaque critère retenu est dans l'intervalle des valeurs de référence, la surface 50 est alors considérée comme un tissu vivant et n'est pas considérée comme un tissu vivant si elle est en dehors de cet intervalle des valeurs de référence.  Thus, if the value of each criterion retained is in the range of the reference values, the surface 50 is then considered as a living tissue and is not considered a living tissue if it is outside this range of values of reference.
La Fig. 2 montre un organigramme d'un procédé de décision 300 mis en œuvre par le dispositif de décision 100 et prévu pour décider si une surface 50 est un tissu vivant ou non.  Fig. 2 shows a flowchart of a decision method 300 implemented by the decision device 100 and provided to decide whether a surface 50 is a living tissue or not.
Le procédé de décision 300 comprend :  The decision process 300 comprises:
- une étape d'éclairage 302 au cours de laquelle les moyens d'éclairage cohérent a lighting step 302 during which the coherent lighting means
102 éclairent la surface 50 à analyser, 102 illuminate the surface 50 to be analyzed,
selon le critère retenu,  according to the criterion chosen,
- une étape de capture 304 au cours de laquelle le moyen de capture perpendiculaire 106 capture une image perpendiculaire de la surface 50 ainsi éclairée et/ou une étape de capture 306 au cours de laquelle le moyen de capture parallèle 108 capture une image parallèle de la surface 50 ainsi éclairée, a capture step 304 during which the perpendicular capture means 106 captures a perpendicular image of the surface 50 thus illuminated and / or a capture step 306 in which the parallel capture means 108 captures a parallel image of the surface 50 thus illuminated,
- une étape de calcul 306 au cours de laquelle les moyens de calcul 112 calculent la valeur de chacun desdits critères retenus à partir de chaque image ainsi capturée et éventuellement préalablement filtrée par un filtre fréquentiel de type passe-haut,  a calculation step 306 during which the calculation means 112 calculate the value of each of said criteria selected from each image thus captured and possibly previously filtered by a high-pass type frequency filter,
- une étape de comparaison 308 au cours de laquelle les moyens de comparaison 114 comparent chaque valeur ainsi calculée à l'intervalle des valeurs de référence correspondant, et délivrent une information représentative de cette comparaison,  a comparison step 308 during which the comparison means 114 compare each value thus calculated with the corresponding reference value interval, and deliver information representative of this comparison,
- une étape de décision 310 au cours de laquelle les moyens de décision 116 décident si la surface 50 est un tissu vivant ou non en fonction de l'information délivrée par les moyens de comparaison 114.  a decision step 310 during which the decision means 116 decide whether the surface 50 is a living tissue or not according to the information delivered by the comparison means 114.
Selon un mode de réalisation particulier de l'invention, le procédé de décision According to a particular embodiment of the invention, the decision process
300 comprend préalablement à l'étape d'éclairage 302, une étape d'apprentissage 312 qui consiste en une capture d'images de tissus vivants par chaque moyen de capture 106, 108 approprié selon le/les critère(s) retenu(s), un calcul de la valeur de chaque critère retenu par les moyens de calcul 112, 113 à partir de l'image ou chaque image ainsi capturée, et la définition pour le ou chaque critère retenu d'un intervalle des valeurs de référence pour lequel les valeurs dudit critère sont considérées comme représentatives d'un tissu vivant. Comme mentionné ci-dessus, l'étape d'apprentissage 310 ne s'effectue qu'à la mise en route du dispositif de décision 100 et l'étape de décision 310 boucle alors sur l'étape d'éclairage 302. 300 comprises, prior to the lighting step 302, a learning step 312 which consists of a capture of live tissue images by each appropriate capture means 106, 108 according to the criterion (s) retained , a calculation of the value of each criterion retained by the computing means 112, 113 from the image or each image thus captured, and the definition for the or each criterion retained of an interval of the reference values for which the values of said criterion are considered representative of a living tissue. As mentioned above, the learning step 310 is performed only at the start of the decision device 100 and the decision step 310 then loop on the lighting step 302.
Dans un autre mode de réalisation, certaines caractéristiques de l'image de speckle sont analysées pour détecter les tissus vivants ou non. Cette méthode s'appuie sur une approche statistique.  In another embodiment, certain features of the speckle image are analyzed for living and non-living tissue. This method is based on a statistical approach.
Tout calcul statistique suppose que soit défini un ensemble d'événements (des critères) sur lequel sont basés les calculs. Ainsi, l'ensemble statistique correspond à l'ensemble des tirages possibles, supposé infini.  Any statistical calculation assumes that a set of events (criteria) on which the calculations are based is defined. Thus, the statistical set corresponds to the set of possible draws, supposed infinite.
Il est alors possible de calculer, par exemple, la probabilité de voir un élément particulier (un tissu vivant ou non-vivant) se produire dans cet ensemble.  It is then possible to calculate, for example, the probability of seeing a particular element (a living or non-living tissue) occurring in this set.
Deux critères statistiques sont ainsi définis pour définir un score final. Si ce score final est plus grand qu'un seuil, le tissu est considéré comme vivant. Sinon, le tissu est considéré comme non- vivant.  Two statistical criteria are thus defined to define a final score. If this final score is greater than a threshold, the tissue is considered alive. Otherwise, the tissue is considered non-alive.
Les critères statistiques sont définis en se basant sur les propriétés physiques du speckle qui sont mesurées en se basant sur le traitement d'images. Les critères sont définis comme suit : The statistical criteria are defined based on the physical properties of the speckle that are measured based on the image processing. The criteria are defined as follows:
Critère d'autocorrélation pour la caractérisation du speckle :  Autocorrelation criterion for speckle characterization:
Les statistiques du 2ème ordre décrivent les variations de l'intensité lumineuse relatives en deux points. De ce fait, elles donnent une indication sur la taille des grains dans la figure de speckle et leur distribution. Le paramètre statistique du 2ème ordre le plus couramment employé dans l'étude du speckle est la fonction d'autocorrélation.  2nd order statistics describe relative light intensity variations at two points. As such, they give an indication of the grain size in the speckle figure and their distribution. The most commonly used 2nd order statistical parameter in the speckle study is the autocorrelation function.
Le décalage pour lequel la fonction d'autocorrélation chute à une valeur définie The offset for which the autocorrelation function drops to a defined value
(1/2, 1/e ou 1/e2, ou encore passe par 0) peut être utilisé pour mesurer une dimension caractéristique du speckle observé, en particulier la taille moyenne des grains de speckles. (1/2, 1 / e or 1 / e 2 , or pass through 0) can be used to measure a characteristic dimension of the observed speckle, in particular the average size of speckles grains.
Ce décalage varie d'un tissu à un autre et permet de distinguer entre les tissus vivants et non- vivants.  This shift varies from one tissue to another and makes it possible to distinguish between living and non-living tissues.
Critère basé sur la transformée de Fourier:  Criterion based on the Fourier transform:
Un autre paramètre statistique du 2ème ordre employé est la densité spectrale de puissance ou spectre de Wiener qui décrit la distribution des tailles de taches dans la figure de speckle. Elle est donnée par la transformée de Fourier de la fonction d'autocorrélation de l'intensité lumineuse.  Another second-order statistical parameter employed is the Wiener spectral power density or spectrum which describes the distribution of the spot sizes in the speckle figure. It is given by the Fourier transform of the autocorrelation function of the luminous intensity.
Le deuxième critère est ainsi défini par l'écart type de la densité spectrale.  The second criterion is thus defined by the standard deviation of the spectral density.
La Fig. 5 montre les performances de ces deux critères. Les points à gauche de la droite 502 correspondent aux tissus non- vivants tandis que les points à droite de la droite 502 correspondent aux tissus vivants.  Fig. 5 shows the performance of these two criteria. The points to the left of the line 502 correspond to the non-living tissues while the points to the right of the line 502 correspond to the living tissues.
L'abscisse correspond au score Fourier et donc à l'écart type de la densité spectrale, l'ordonnée correspond au score speckle et donc au score d'autocorrélation.  The abscissa corresponds to the Fourier score and therefore to the standard deviation of the spectral density, the ordinate corresponds to the speckle score and therefore to the autocorrelation score.
Le score final qui permet de classifier les tissus entre vivants et non- vivants est obtenu en effectuant une analyse par composante principale pour obtenir l'équation de la droite 502 qui sépare les deux classes.  The final score for classifying tissues between living and non-living is obtained by conducting a principal component analysis to obtain the equation of line 502 that separates the two classes.
Tout score supérieur au seuil défini par la droite correspond à un tissu vivant. Any score above the threshold defined by the line corresponds to a living tissue.
Tous les mécanismes décrits comprennent l'utilisation d'un mécanisme d'apprentissage de type ACP, SVM ou réseau de neurones entraîné sur des bases de vrais tissus et de fraudes. All of the disclosed mechanisms include the use of an ACP, SVM or neural network-based learning mechanism driven on true tissue and fraud bases.
Bien entendu, la présente invention n'est pas limitée aux exemples et modes de réalisation décrits et représentés, mais elle est susceptible de nombreuses variantes accessibles à l'homme de l'art.  Of course, the present invention is not limited to the examples and embodiments described and shown, but it is capable of many variants accessible to those skilled in the art.

Claims

REVENDICATIONS
1) Dispositif de décision (100) prévu pour décider si une surface (50) est un tissu vivant ou non, ledit dispositif de décision (100) comportant : 1) Decision device (100) for deciding whether a surface (50) is a living tissue or not, said decision device (100) comprising:
- des moyens d'éclairage (102) émettant un flux incident (104) cohérent et polarisé selon une direction de polarisation doté d'une longueur de cohérence supérieure ou égale à 1cm et destiné à éclairer ladite surface (50),  lighting means (102) emitting a coherent and polarized incident flux (104) in a polarization direction with a coherence length greater than or equal to 1 cm and intended to illuminate said surface (50),
- un moyen de capture (106, 108) présentant un filtre polarisant perpendiculaire et/ou parallèle à la direction de polarisation et destiné à l'acquisition d'au moins une image de la surface (50) éclairée présentant des tavelures,  a capture means (106, 108) having a polarizing filter perpendicular to and / or parallel to the direction of polarization and intended for acquiring at least one image of the illuminated surface (50) presenting with scab,
- des moyens de calcul (112, 113) prévus pour calculer, à partir de l'image perpendiculaire et/ou de l'image parallèle, la valeur d'au moins un critère représentatif des tavelures de ladite/ desdites image(s),  calculating means (112, 113) for calculating, from the perpendicular image and / or the parallel image, the value of at least one criterion representative of the scabs of said image (s),
- une base de données contenant pour le ou chaque critère un intervalle de valeurs de référence dudit critère qui soit représentatif de tavelures d'un tissu vivant, a database containing for the or each criterion a range of reference values of said criterion which is representative of scabs of a living tissue,
- des moyens de comparaison (114) prévus pour comparer la ou chaque valeur ainsi calculée à l'intervalle de valeurs de référence correspondant et pour délivrer une information représentative de ces comparaisons, et comparison means (114) provided for comparing the or each value thus calculated with the corresponding reference value interval and for providing information representative of these comparisons, and
- des moyens de décision (116) prévus pour décider si la surface (50) est un tissu vivant ou non en fonction de l'information délivrée par les moyens de comparaison decision means (116) provided for deciding whether the surface (50) is a living tissue or not depending on the information delivered by the comparison means
(114). (114).
2) Dispositif de décision (100) selon la revendication 1, caractérisé en ce que les critères représentatifs des tavelures sont choisis parmi l'écart-type des intensités de l'image perpendiculaire, l'écart-type des intensités de l'image parallèle, une combinaison logique et/ou arithmétique entre l'écart-type des intensités de l'image parallèle et l'écart-type des intensités de l'image perpendiculaire, l'écart-type des intensités de l'image perpendiculaire sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut, l'écart-type des intensités de l'image parallèle sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut, une combinaison logique et/ou arithmétique entre l'écart-type des intensités de l'image parallèle sur laquelle on applique préalablement un filtre fréquentiel de type passe- haut et l'écart-type des intensités de l'image perpendiculaire sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut. 3) Dispositif de décision (100) selon la revendication 2, caractérisé en ce que les critères retenus sont l'écart-type des intensités de l'image perpendiculaire, l'écart-type des intensités de l'image parallèle, et le rapport entre l'écart-type des intensités de l'image parallèle et l'écart-type des intensités de l'image perpendiculaire. 4) Dispositif de décision (100) selon la revendication 2, caractérisé en ce que les critères retenus sont l'écart-type des intensités de l'image perpendiculaire sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut, l'écart-type des intensités de l'image parallèle sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut, et le rapport entre l'écart-type des intensités de l'image parallèle sur laquelle on applique préalablement un filtre fréquentiel de type passe- haut et l'écart-type des intensités de l'image perpendiculaire sur laquelle on applique préalablement un filtre fréquentiel de type passe-haut. 2) Decision device (100) according to claim 1, characterized in that the criteria representative of scab are selected from the standard deviation of the intensities of the perpendicular image, the standard deviation of the intensities of the parallel image , a logical and / or arithmetic combination between the standard deviation of the intensities of the parallel image and the standard deviation of the intensities of the perpendicular image, the standard deviation of the intensities of the perpendicular image on which one applies beforehand a high-pass type frequency filter, the standard deviation of the intensities of the parallel image on which a high-pass type frequency filter is previously applied, a logical and / or arithmetic combination between the standard deviation intensities of the parallel image on which a high pass type frequency filter is previously applied and the standard deviation of the intensities of the perpendicular image on which a frequency filter is applied beforehand el type high pass. 3) Decision device (100) according to claim 2, characterized in that the criteria selected are the standard deviation of the intensities of the perpendicular image, the standard deviation of the intensities of the parallel image, and the ratio between the standard deviation of the intensities of the parallel image and the standard deviation of the intensities of the perpendicular image. 4) Decision device (100) according to claim 2, characterized in that the criteria used are the standard deviation of the intensities of the perpendicular image on which a high-pass type frequency filter is applied beforehand, the difference -type of the intensities of the parallel image on which a high-pass type frequency filter is previously applied, and the ratio between the standard deviation of the intensities of the parallel image on which a pass-type frequency filter is applied beforehand high and the standard deviation of the intensities of the perpendicular image on which a high pass type frequency filter is applied beforehand.
5) Dispositif de décision (100) selon la revendication 1, caractérisé en ce que les critères représentatifs des tavelures sont des dimensions caractéristiques des tavelures observées et calculées par un calcul d'auto-corrélation. 5) Decision device (100) according to claim 1, characterized in that the representative criteria of scab are characteristic dimensions of the scab observed and calculated by an autocorrelation calculation.
6) Dispositif de décision (100) selon la revendication 1 ou 5, caractérisé en ce que les critères représentatifs des tavelures est l'écart type de la densité spectrale de puissance. 6) Decision device (100) according to claim 1 or 5, characterized in that the criteria representative of scab is the standard deviation of the power spectral density.
7) Dispositif de décision (100) selon une des revendications 1 à 6 caractérisé en ce que les moyens de comparaison comprennent l'utilisation d'un mécanisme d'apprentissage de type ACP, SVM ou réseau de neurones entraîné sur des bases de vrais tissus et de fraudes. 7) Decision device (100) according to one of claims 1 to 6 characterized in that the comparison means comprise the use of a learning mechanism of the ACP type, SVM or neuron network driven on bases of real tissue and fraud.
8) Procédé de décision (300) prévu pour décider si une surface (50) est un tissu vivant ou non et mis en œuvre par un dispositif de décision (100) selon l'une des revendications 1 à 4, le procédé de décision (300) comportant: 8) A decision method (300) provided for deciding whether a surface (50) is a living tissue or not and implemented by a decision device (100) according to one of claims 1 to 4, the decision process ( 300) comprising:
- une étape d'éclairage (302) au cours de laquelle les moyens d'éclairage (102) éclairent la surface (50) à analyser,  a lighting step (302) during which the lighting means (102) illuminate the surface (50) to be analyzed,
- une étape de capture (304) au cours de laquelle le moyen de capture perpendiculaire (106) capture une image perpendiculaire de la surface (50) ainsi éclairée et/ou une étape de capture (306) au cours de laquelle le moyen de capture parallèle (108) capture une image parallèle de la surface (50) ainsi éclairée, a capture step (304) in which the perpendicular capture means (106) captures a perpendicular image of the surface (50) and illuminated and / or a capture step (306) during which the parallel capture means (108) captures a parallel image of the illuminated surface (50),
- une étape de calcul (306) au cours de laquelle les moyens de calcul (112) calculent la valeur de chacun desdits critères retenus à partir de chaque image ainsi capturée,  a calculation step (306) during which the computing means (112) calculate the value of each of said criteria selected from each captured image,
- une étape de comparaison (308) au cours de laquelle les moyens de comparaison (1 14) comparent chaque valeur ainsi calculée à l'intervalle des valeurs de référence correspondant et délivrent une information représentative de cette comparaison,  a comparison step (308) during which the comparison means (1 14) compares each value thus calculated with the interval of the corresponding reference values and delivers information representative of this comparison,
- une étape de décision (310) au cours de laquelle les moyens de décision (116) décident si la surface (50) est un tissu vivant ou non en fonction de l'information délivrée par les moyens de comparaison (114).  - a decision step (310) in which the decision means (116) decide whether the surface (50) is a living tissue or not according to the information provided by the comparison means (114).
PCT/EP2014/062277 2013-06-12 2014-06-12 Decision device for deciding whether a surface is living tissue or not WO2014198847A1 (en)

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