• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
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    • 专利摘要:
    A method and system for acquisition and fingerprint analysis with fraud detection, wherein: a fingerprint image of an object (100) is formed; the object is irradiated with the aid of an excitation beam (12); a fluorescence (13) emitted by the object in response to the excitation beam is analyzed; a validity criterion, established from the fluorescence analysis and making it possible to discriminate biological tissues with respect to other objects, is verified. According to the invention, a region of interest, capable of characterizing the biological tissues, is selected on the impression image, which region of interest defines by correspondence, on the object, a useful observation zone, and the validity criterion is established from fluorescence intensity measurements relative to the useful observation area only.
    公开号:FR3030834A1
    申请号:FR1463100
    申请日:2014-12-22
    公开日:2016-06-24
    发明作者:Jerome Boutet；Joel-Yann Fourre
    申请人:Commissariat a lEnergie Atomique CEA；Safran SA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
    IPC主号:
    专利说明:

    [0001] The invention relates to the technical field of biometry and more specifically to the acquisition and analysis of fingerprints or palmar. Throughout the description, for the sake of simplicity, the object whose fingerprint is to be analyzed is often likened to a finger, without this being limiting: it could be a set of several fingers, the palm with one hand, one hand, or any other similar object. Some optical fingerprint acquisition systems use the frustrated total reflection principle to produce very high contrast images. The finger (or other object to be analyzed) is then placed on a prism or a blade with an inclined face. The fingerprint acquisition system is further provided with a lighting means and an imaging system. Two arrangements are possible: light background and dark background. Other types of sensors have been developed: sensors with "opposite" imagery, such as the one disclosed by EP1789908; non-contact sensors such as those described in FR2927713 or WO201490750, flat contact sensors (TFT). Whatever the technique used, means of fraud have been developed, among which the use of finger moldings (or the object to be analyzed). These moldings can be made in various materials, generally accessible to all in DIY stores or creative hobbies, such as latex or silicone. It is also known, as a means of fraud, to use an impression of the imprint on a sheet of paper. The purpose of the acquisition of a fingerprint is to compare the acquired fingerprint with one or more images stored in a database and, in case of correspondence, to authenticate or identify the bearer. This is used in particular to give a right such as a right of access, a right of signature, or a right to use a system ... The detection of fraud allows, automatically, not to identify or authenticate a person who is luring the sensor. To achieve this function, several techniques are known. W02006 / 082550 proposes to use the acquisition of a fluorescence spectrum, or to verify the presence in the analyzed object of one or more endogenous fluorophores that is naturally present in the human body (collagen, trytophan ...) if it is only a question of eliminating the risk of being in the presence of a synthetic lure, or of checking the concordance between the acquired fluorescence spectrum and a reference fluorescence spectrum if it is is to authenticate a person whose identity is presupposed. The technique proposed by WO2006 / 082550 requires the implementation of a sufficiently energy-efficient spectrometer, which comes to burden the manufacturing cost of the fingerprint acquisition system. In addition, the spectrometric analysis increases the processing time of the imprint, which can generate an undesired queue. The use of endogenous fluorescence to detect a living finger in the context of imprint measurement is also disclosed in US20140037158, which discloses a system for measuring sweat fluorescence induced by an electromagnetic field. In this patent, the sensor passes an electric current in the finger to stimulate the production of sweat and locate the position of the pores by fluorescence. This patent assumes that the position of the pores, localized by fluorescence induced by an electromagnetic field, can be considered as a biometric data allowing to authenticate a subject to the presupposed identity. The invention disclosed by US20140037158 has the following disadvantages in particular: (pore imaging and their location require a high resolution sensor, which costs the cost of the final system; (the sweat induction process requires more than one second to operate, which is detrimental to the ergonomics of the device, as most fingerprint sensors must work in less than a second to avoid queues where they are installed. The invention aims at overcoming the aforementioned drawbacks by providing a system for acquisition and analysis of fingerprints including means for detecting fraud by discriminating biological tissues with respect to other objects, which are compatible with most known fingerprint sensors (total reflection sensor but also TFT flat sensor for example) .Integration of the fraud detection means 30 according to the invention in a system of FIG. acquisition and fingerprint analysis known should not require significant modifications of the latter. Another objective of the invention is to propose a new system for acquisition and analysis of fingerprints with fraud detection, which is less expensive, less congested, painless for the user, and able to analyze a fingerprint. and assess the risks of fraud in a processing time of the order of a second. To this end, the invention uses endogenous (non-labeled) fluorescence analysis of biological tissues as an indicator of living, but in a different and simplified way compared to WO2006 / 082550. More specifically, the invention provides a method for acquisition and analysis of fingerprints with fraud detection, comprising the following steps: (forming a fingerprint image of an object placed opposite a surface transparent reception (preferably, the object is placed on the transparent receiving surface), which impression image is representative of a micro-structuring of a surface of the object (said visible surface of the object) visible through the transparent receiving surface; (irradiation of the object by means of an excitation beam according to an excitation spectral band; (analysis of a fluorescence emitted by the object in response to the excitation beam, according to a fluorescence spectral band; (verification of a validity criterion for discriminating biological tissues with respect to other objects, which criterion of validity is established from the analysis of fluorescence.
    [0002] The method according to the invention is characterized in that: (it further comprises a step of selecting a region of interest on the impression image, which region of interest is able to characterize the biological tissues; this region of interest defines (i.e., corresponds to) an area on the visible surface of the object, hereinafter referred to as the useful observation area of the object, ^ (the validity criterion is established from fluorescence intensity measurements relative to the useful observation area of the object The invention also proposes a device for implementing the method according to the invention, and in particular an acquisition system and fingerprinting apparatus with fraud detection comprising: a transparent receiving surface; a detector for forming a fingerprint image of an object placed opposite the transparent receiving surface, which impression image is representative of a micro-structu ration of a visible surface of the object; it may be for example a photodetector or a capacitive sensor or a fluorescence imager; an excitation light source capable of producing an excitation beam in the direction of the object, according to an excitation spectral band, a fluorescence detector for the analysis of a fluorescence emitted by the object in response to the excitation beam, according to a fluorescence spectral band, ^ (a calculator for the verification of a validity criterion for discriminating biological tissue from other objects, which criterion of validity is set to The fingerprint acquisition and analysis system according to the invention is characterized in that the computer is configured to: (select a region of interest on the image impression region, which region of interest is capable of characterizing the biological tissues, the region of interest defining by correspondence, on the object, a zone called the useful observation zone, 15 ^ (establish the criterion of validity from of measurement fluorescence intensity relative to the useful observation area of the object. Unlike W02006 / 082550, the fluorescence analysis performed in the process according to the invention is not intended to determine the nature of the fluorophores and therefore of the material constituting the object to be analyzed, but simply whether or not it belongs to the whole biological tissues. The inventors have indeed established that fluorescence intensity measurements are sufficient for the establishment of such a validity criterion as soon as these intensity measurements are made in a useful observation area of the correctly selected object. using the impression image. Whereas in WO2006 / 082550 the fluorescence analysis relates to the entire visible surface of the object, in the invention the fluorescence analysis only concerns a reduced area (useful observation area of the object) which is really carrier of information. This useful observation area of the object is defined from the selection on the fingerprint image of a region of interest. Three main alternatives are proposed below for the selection of a region of interest. Moreover, only levels (or intensities) of fluorescence are measured in the process according to the invention whereas the method of WO2006 / 082550 requires the establishment of fluorescence spectra. It follows from all these differences that the response time of a system according to the invention is lower than that of WO2006 / 082550. It also follows that a simpler and less expensive fluorescence detector can be used in a system according to the invention. It is also easy to transform any known acquisition and fingerprint analysis system into a system according to the invention, the detector used for the formation of the imprinting image can be of any type, being specified that it is not advisable to use known acquisition and fingerprinting systems having a detector with spectral analysis means whose response times may be considered too long. In a first version of the invention: ^ (the region of interest (on the fingerprint image) is selected so that the corresponding useful observation area of the object is a peak area in contact In this first version, the object is thus placed on the transparent receiving surface In the corresponding capture and analysis system, the computer is configured to select such a region. of interest; ^ (and verification of the validity criterion includes the calculation of an average or sum of the fluorescence intensities measured for the useful observation area of the object and the comparison of this average or sum to a predetermined window of fluorescence intensities corresponding to biological tissues In the corresponding fingerprint acquisition and analysis system, the computer is configured to calculate an average or sum of intensities. fluorescence tees measured in the useful observation area of the object and compare this average or sum with a predetermined window of fluorescence intensities corresponding to biological tissues.
    [0003] It will be noted that only the fluorescence intensity measurements obtained for the useful observation area of the object are necessary to determine the criterion of validity according to the invention. However, in practice, it is simpler and probably faster to form a fluorescence image of the entire visible surface of the object and then to exploit only a part (called here region of interest on the fluorescence image) corresponding to the useful observation area of the object. The selection of the region of interest on the impression image may then be anterior to or subsequent to the acquisition of the fluorescence intensity measurements. By concentrating the fluorescence image analysis on portions of the finger actually in contact with the transparent surface, a more robust fluorescence signal is obtained and thus a more reliable response. In addition, the fluorescence signal can be normalized with respect to the useful viewing area of the object. A surface florescence intensity can then be obtained for the transparent receiving object / surface contact areas. The surface fluorescence intensity of the non-contact zones is not used by the invention, in this first version. The possibility, discovered by the inventors, of characterizing the biological tissues by fluorescence intensity measurements on a useful observation area of the object corresponding to a peak zone in contact with the transparent receiving surface is illustrated. in Figure 1 attached. The inventors' studies have furthermore made it possible to evaluate that the fluorescence signal could vary from one individual to another with a standard deviation of 30% maximum. This standard deviation corresponds to the range of fluorescence intensities 200 delimited by the dashed lines in FIG. 1 (ie approximately the range [800; 2000]). If one defines, as a window of validity, the referenced window 300 and corresponding to the intensities [500; 3000], the biological tissues of the entire population tested here are considered valid and the window thus selected makes it possible to reject the frauds by using decoys of white paper and modeling clay, the fluorescence intensity of which is greater at 3000, as well as frauds using candle lures, wood glue, aluminum foil, potato, PDMS, silicone and gelatin, whose fluorescence intensity is less than 500. Preferably, the window of validity is adjusted according to the population of users of the acquisition and fingerprinting system. The lower and upper bounds of the window of validity can indeed be learned by collecting measurements on a varied sample representative of the population of users of the system. The window of validity can also be adjusted according to the desired degree of security, according to whether one wishes to reinforce the security, even if it is necessary to reject some authentic fingers, or to favor the ergonomics of the system and to accept all the authentic fingers, even if let some fraud pass. In a second version of the invention: (the excitation beam has a spectral band centered on a wavelength located in the ultraviolet and forms a pattern (for example a point or a disc, a line, a square , or several of these forms ...), here called excitation pattern, on the visible surface of the object, the term "ultraviolet" in an abusive manner designates, throughout the application, all the lengths of wavelength between 100 nm and 450 nm (it therefore also includes the range [380; 450] generally classified in the visible range -violet-), preferably the central wavelength of the excitation spectral band is also greater at 280nm, that is, outside the UV-C range (so it is between 280nm and 450nm); ^ (the region of interest is selected so that the useful observation area ( of the corresponding object) does not intersect with this excitation pattern and is located at a predetermined distance terminating the excitation pattern as low as possible and sufficient so that the fluorescence measurements of this zone are not disturbed by a backscattering of the excitation beam. In the corresponding system, the excitation light source has a spectral band centered on a wavelength of less than 450 nm (that is to say in the ultraviolet in the sense of the present application) and is configured from so that the excitation beam forms an excitation pattern on the visible surface of the object, and the computer is configured to select, as a region of interest, a region corresponding (on the object) to a zone of useful observation having no intersection with this excitation pattern and located at a predetermined distance from the excitation pattern both as small as possible and sufficient so that the fluorescence measurements of this zone are not disturbed by a backscattering of the excitation beam; (and verification of the validity criterion includes comparing an average of the fluorescence intensity measurements obtained for the useful viewing area with a predetermined validity window corresponding to biological tissues.) In a possible variant of this second version of the invention: (again, the excitation beam has a spectral band in the ultraviolet (is centered on a wavelength less than 450 nm) and forms an excitation pattern on the visible surface of the object; 30 ^ (the region of interest is selected so as to correspond to at least two useful observation areas on the object having no intersection with this excitation pattern, namely a first zone of useful observation located at a first predetermined distance from the excitation pattern, which first distance is both the lowest possible and sufficient for the fluorescence measurements obtained for this first zone. e of useful observation are not disturbed by a backscattering of the excitation beam, and a second useful observation zone located at a second predetermined distance from the excitation pattern, the second distance being greater than the first distance; it should be noted that the first useful observation zone and the second useful observation zone are not necessarily located on the same side, or in the same alignment, of the excitation pattern; (verification of the validity criterion includes the establishment of a fluorescence decay profile as a function of distance from the excitation pattern, using the fluorescence intensities measured for the first and second useful viewing areas (which are located at different distances from the excitation pattern), and comparing a slope of this decay profile with a predetermined window of slopes of fluorescence decay profile corresponding to biological tissues. The fluorescence analyzed then combines a fluorescence intensity information and an absorption / scattering information.An analysis of the decay profile can more or less separate these two pieces of information, and thus allow a greater relevance of the discrimination. can be combined with the previously described variant of the second version of the invention, as follows: ection of at least two useful observation areas at different distances; comparing the measured fluorescence intensity for the first useful observation area with a first predetermined validity window (intensity window); comparing a slope of the fluorescence decay profile obtained from the two useful observation areas with a second predetermined validity window (slope window). The combination makes it possible to further refine the discrimination. In this second version, it is analyzed, beyond the intensity of the fluorescence signal, the attenuation of this signal in the finger as one moves away from the excitation pattern. The inventors have shown that this attenuation 30 could constitute a signature of the material constituting the analyzed finger. The remarks made about the validity window defined in the first version of the invention (possibility of adjusting the window depending on the degree desired security or according to the target user population) likewise apply to the various windows of validity defined above in the second version of the invention. In a third version of the invention applicable to a fingerprint acquisition and analysis system, the detector for the formation of the fingerprint image is a TFT sensor (for which radiation from the zones of valleys is sensed by the detector, as explained later), the region of interest (on the fingerprint image) is selected so that the corresponding useful observation area of the object is an area of valleys ( such a zone of valleys is not in contact with the transparent receiving surface). Like the first version of the invention, a validity window is defined beforehand, by measuring the fluorescence emitted by an equivalent zone of various lures and real fingers, and the verification of the validity criterion consists in comparing the fluorescence measured for the useful observation area of the object to be analyzed with this validity window, which window can be adjusted as previously explained. The use of a valleys zone as a useful viewing area in the case of a TFT sensor has the advantage that the fluorescence measurements are less dependent on the optical coupling between the skin and the transparent receiving surface and therefore are not degraded for dry fingers. In fact, for fingers that are too dry, it should be noted that there are few contact points between the finger and the transparent receiving surface, so a useful observation area limited to a contact zone is not very representative. because not enough extended. In both the first and second versions of the invention, the imprinted image can be formed from measurements of radiation reflected and / or backscattered by the object. In the third version, it is essentially backscattered since the use of a TFT sensor is required. In this case, the formation of the imprint image comprises irradiating the object through the transparent receiving surface with the aid of a lighting beam, according to a spectral band of illumination, and the measurement of a reflected beam or a beam transmitted by the object. The corresponding system comprises a light source emitting a light beam irradiating the object through the transparent receiving surface, along a spectral illumination band, and the detector for the formation of the imprint image is selected from: a total reflection sensor, with a dark background or with a light background, configured to measure a beam reflected by the object; a TFT sensor. In the second version of the invention, it is also possible to use a non-contact sensor as a detector for the formation of the impression image.
    [0004] Alternatively, the imprint image is a fluorescence image, and the formation of the imprint image and the acquisition of the fluorescence measurements constitute a single operation performed using a fluorescence imager . This variant is compatible with the first two versions of the invention. The corresponding system comprises a fluorescence imager which serves both as a detector for the formation of the impression image, which is then a fluorescence image, and as a fluorescence detector for the analysis of a fluorescence emitted by the object. This variant has the advantage of using only one sensor for the formation of the fingerprint image and the detection of fraud by fluorescence measurement. This embodiment is therefore particularly simple, compact and inexpensive. It should be noted that all versions, variants, etc., of the invention can be made with a single sensor, for the sake of economy, simplicity and compactness. This is precisely one of the interests of the invention. The embodiment with fluorescence imager requires, in addition, less computing power. It is particularly fast since a single acquisition operation is sufficient to perform all functions. In a possible embodiment of the invention, the excitation spectral band (for fluorescence) is entirely below 500 nm. This allows for higher fluorescence intensities, better differentiation between biological tissues and other materials. This also allows, as explained in the next paragraph, to use a lower performance (and therefore less expensive) equipment for equivalent results. In a conventional manner, the fluorescence detector is associated with a filter, which will be referred to herein as a fluorescence detection filter, configured to exclude the spectral band of excitation of the rays transmitted to the detector material, in order to prevent the detector from fluorescence is blinded by the excitation beam backscattered by the object. However, the quantum efficiency of detection of known fluorescence detectors is low in the ultraviolet. By using an ultraviolet excitation spectral band, we take advantage of the fact that the detector is not very sensitive to the excitation wavelength (UV) and that it is much more sensitive to the length fluorescence wave. 0 thus lowers the level of requirement required for the florescence detection filter: an optical density filter of 3 or even 2 is sufficient; it is not necessary to use a filter whose optical density reaches 5 or 6, much more expensive. In a possible embodiment of the invention, the fluorescence analysis and validity criterion verification steps are repeated with different excitation beams whose excitation spectral bands are centered on different wavelengths. for example 375 nm, 405 nm and 450 nm. In this example, the three excitation wavelengths chosen are all less than 500 nm for the reasons mentioned above. But this does not exclude the possibility of using at least one excitation beam centered on a wavelength greater than 500 nm. The corresponding fingerprint acquisition and analysis system 10 then comprises a plurality of excitation sources, more precisely as many excitation sources as desired excitation beams. In a possible embodiment of the invention, a bottom measurement step is performed, in which fluorescence intensity measurements, henceforth referred to as fluorescence measurements without specific excitation, are carried out, according to the spectral band of fluorescence but in the absence of excitation beam. The fluorescence measurements without specific excitation obtained for the useful observation area of the object are then subtracted from the fluorescence intensity measurements obtained for this zone in response to the excitation beam. This additional step makes it possible in particular to render the system robust to the ambient light transmitted through the object and thus to improve the signal-to-noise ratio. In a possible embodiment of the invention, an additional discrimination step is performed, this step using fluorescence intensity measurements emitted in blue by the useful observation area of the object in response to the beam of light. 'excitation. This additional discrimination step may comprise: (a comparison of an average or sum of these fluorescence intensity measurements in blue with a maximum fluorescence threshold in blue.) The inventors have indeed established that the biological tissues had a low fluorescence emission in the blue, a characteristic that are not present in the materials usually used to create decoys, as shown in FIG. 6 in the case of an excitation beam centered on 405 nm (a narrow valley around 430 nm in the emission spectrum of true fingers). ^ (and / or a comparison, with a previously determined maximum ratio, of a ratio between the mean intensity of fluorescence in blue and the intensity mean of the fluorescence in another spectral band, for example in the green, emitted by the useful observation area, for example using a color camera to analyze the t blue in the fluorescence signal. Using the usual color filters of this type of sensor, a three-band decomposition (red, green and blue) of the fluorescence signal is obtained. The ratios between the answers on these three bands (which corresponds to the color in the usual sense of the term and can therefore extend to any other representation of the color such a, b in the space L, a, b or even Cr, Cb, in the Y, Cr, Cb space) are representative of the fluorophores of the object and can be used for an additional discrimination step. The low emission in the blue of the fluorophores of the biological tissues can thus be controlled to eliminate certain frauds which could have escaped the control carried out by verification of the criterion of validity according to the invention. Objects whose fluorescence intensity measured in blue is greater than the maximum fluorescence threshold in the blue defined above and / or whose blue / other spectral band ratio is greater than the above-mentioned maximum ratio, are considered as invalid and are rejected. The invention extends to a method and system for acquisition and analysis of fingerprints with fraud detection, characterized in combination by all or part of the features mentioned above and hereinafter. Other details and advantages of the present invention will appear on reading the following description, which refers to the attached schematic drawings and relates to preferred embodiments, provided as non-limiting examples. In these drawings: FIG. 1 is a graph showing the fluorescence level (number of photons detected, on the ordinate) of several objects (on the abscissa) among which are real fingers and decoys (FIGS. are diagrammatic elevational views of a first embodiment of an acquisition and analysis system of fingerprints according to the invention, with a total reflection sensor on a dark background, FIG. according to the invention, while FIG. 3 illustrates a second part of this process. FIG. 4 is a diagrammatic elevational view of a second embodiment of a data acquisition and analysis system. imprints according to the invention, with a total reflection sensor on a light background. FIG. 5 is a diagrammatic elevational view of a third embodiment of an acquisition and analysis system for fingerprints according to FIG. invention, with TFT flat sensor and used according to the second version of the invention. Fig. 6 is a graph showing fluorescence spectra for various objects including real fingers and decoys. Fig. 7 is a schematic view of the beams received by the TFT sensor of Fig. 5. Figs. 3 represent a first embodiment of the invention, described as acquisition system and analysis of total reflection impressions on a dark background.This system comprises a transparent prism 1 having a transparent upper surface 2 on which a finger 100 The prism 1 further has a first inclined lateral surface 8 provided with a black screen and a second inclined lateral surface 9 opposite the first lateral surface 8. A camera 5, or other photosensitive image sensor for forming an imprint image of the finger 100 placed on the transparent receiving surface 2, is arranged e opposite the second inclined lateral surface 9. A fluorescence detection filter 6 is interposed between the second inclined lateral surface 9 and the camera 5. The system finally comprises a first light-emitting diode 3 (light source) and a second light-emitting diode 7 (excitation source), both arranged under the prism 1 so as to respectively emit a light beam 10 (FIG. 2) and an excitation beam 12 (FIG. 3) through the prism 1 in the direction The light-emitting diode 3 is centered on 525 nm. The light-emitting diode 7 is centered on 405 nm. The filter 6 is a bandpass filter transmitting 525 nm, that is to say transmitting the spectral band lighting (spectral band of the beam emitted by the light emitting diode 3).
    [0005] On the other hand, the filter 6 is a blocking bandpass filter 405nm, that is to say blocking the excitation spectral band (spectral band of the beam emitted by the light-emitting diode 7). Note that a bandpass filter 4 transmitting 405 nm can be interposed between the light emitting diode 7 and the prism 1 to limit the excitation spectral band.
    [0006] The fingerprint acquisition and analysis system illustrated in FIGS. 2 and 3 functions as follows in the context of a biometric identification process for giving access to a right. In a first step (see FIG. 2), the camera 5 and the electroluminescent diode 3 are used to form an imprint image of the visible surface of the finger 100. The light-emitting diode 3 is on; it then illuminates the visible surface of the finger 100 through the transparent prism 1, with an angle less than the limit angle of total reflection of the glass / air interface. The spectral band of illumination of the light-emitting diode 3 is in the transmission zone of the filter 6 situated in front of the camera 5. At the places where the finger 100 is in contact with the transparent receiving surface 2 of the prism, that is ie in the crest areas of the visible surface of the finger, the light is backscattered by the finger, in all directions, because the index of refraction of the tissue of the finger is close to the refractive index of the glass. Part of this light is captured by the camera 5. At the places where there is no contact between the finger 100 and the transparent receiving surface 2, that is to say in the valley areas of the surface visible finger 100, the difference in air / glass index is an obstacle to the backscattering of light in an angle captured by the camera 5. In the valley areas, so the image of the black screen that , by total reflection at the surface 2 of the prism is seen by the camera 5. Thus the image of the impression formed by the camera 5 comprises intense pixels, that is to say bright (clear), corresponding to the peaks the visible surface of the finger, and dark pixels corresponding to the valleys (or hollow) of the visible surface of the finger. We obtain a very contrasted image. In a second step (see FIG. 3), the camera 5 and the light-emitting diode 7 are used for a fraud detection operation, more precisely to check whether the constituent material of the finger 100 placed on the transparent reception surface 2 belongs to good at the class of biological tissues. The light-emitting diode 3 is off and the light-emitting diode 7 is lit. The light emitted by the latter, called the excitation beam 12, may optionally be filtered by the filter 4 before being directed into the prism to illuminate the visible surface of the finger. The fluorescence beam 13 generated by the tissues of the finger passes through the filter 6 and reaches the camera 5, which filter 6 also blocks the direct light of the light-emitting diode 7 and especially the excitation beam reflected by the visible surface of the finger. The imprint image formed in the first part of the method is used to select a region of interest formed by a set of intense pixels of the imprint image, i.e., a set of pixels corresponding to a useful viewing area of the finger consisting essentially of one or more peak areas in contact with the transparent receiving surface 2. Preferably, the selected region of interest is the combination of several subregions, each of which regions corresponding to a useful observation area on the finger of very small dimensions, from 1 to 20 mm 2, for example of the order of 9 mm 2. The interest of selecting a region of interest thus divided (discontinuous) is to obtain a system robust to juxtaposition frauds, the expression "juxtaposition fraud" denoting a situation in which the object comprises a dummy part and a part authentic. The level of fluorescence captured by the camera during the second part of the process is summed over the region of the fluorescence image corresponding to the useful observation area (which includes points of contact with the transparent receiving surface 2). that is, corresponding in turn to the previously selected region of interest on the fingerprint image. Summing the level of fluorescence over the set of pixels of the region of interest only makes it possible to reduce the influence of the noise and to define a parameter that is truly representative of the biological tissues. If the measured fluorescence level is within a predetermined validity window corresponding to the class of biological tissues (the level of fluorescence summed over a region of the same dimension in contact with the transparent receiving surface, in response to the same excitation beam 12, was previously measured for a certain number of materials and especially for a certain number of real fingers representative of the target population, in order to determine this window of validity of which we can observe an example 300 in FIG. The fingerprint formed in the first part of the process is analyzed: it is compared to an imprint image bank if it is to identify the person; it is compared to a specific fingerprint image corresponding to the person previously identified, if it is to authenticate this person. Conversely, if the level of fluorescence measured in the region of interest is outside the validity window, the finger 100 is considered a decoy and the right to which access to the biometric identification is denied. FIG. 4 represents a second embodiment known as a total-reflection acquisition and analysis system on a light background. The reference numerals identical to those of FIG. 3 designate the same elements, namely: a prism 1 with a transparent receiving surface 2, a first inclined lateral surface 8, a second inclined lateral surface 9; a light-emitting diode 3 emitting a lighting beam 10 through the prism 1 in the direction of a finger 100 placed on the transparent receiving surface 2; a light-emitting diode 7 emitting an excitation beam 12 through the prism 1 towards the finger 100; reflected radiation 11, reflected by the finger when the light-emitting diode 3 is on; a fluorescence radiation 13 emitted by the finger when the light-emitting diode 7 is on; a camera 5 for forming a cavity image by capturing the reflected radiation 11 and for measuring a fluorescence intensity level by capture of the fluorescence radiation 13; a filter 6 associated with the camera 5 capable of transmitting the spectral band of illumination (and thus the reflected radiation 11, for the formation of the impression image) as well as the spectral band of fluorescence emitted by the finger in response to the excitation beam 12 and able to block the excitation spectral band; an optional filter 4 for limiting the excitation beam 12 in terms of excitation spectral band. However, this embodiment with total light-field reflection (FIG. 4) differs from the dark-field total-reflection embodiment (FIGS. 2 and 3) described above in particular in that: (The first inclined lateral surface 8 is devoid of black screen, it is therefore transparent. (the light-emitting diode 3 emitting the illumination beam 10 is arranged facing this first inclined lateral surface 8 transparent.) As previously explained for the embodiment of total reflection on a dark background , an impression image is first formed by irradiating the surface of the finger 100 visible through the transparent receiving surface 2, with the aid of the illumination beam 10 emitted by the light-emitting diode 3, which exhibits this angle of incidence greater than the limit angle of total reflection of the glass / air interface, in which case a smaller thickness of air between the glass and the e finger, that is to say in a valley area (or hollow), leads to a total reflection of the incident beam. Conversely, in the areas where the finger 100 is in contact with the transparent receiving surface 2, i.e. in a crest area of the surface of the finger, the light is not reflected because the The refractive index of the fabric is close to the refractive index of the glass. Thus, in contrast to the dark background embodiment, the bright (bright) pixels of the fingerprint image correspond to the valleys (troughs) of the finger surface and the dark pixels correspond to the peaks. One gets here also a very contrasted image. The rest of the process proceeds as explained for the dark-field total-reflection embodiment, except that the selected region of interest corresponds to dark pixels of the fingerprint image (again the Useful observation area is a peak area in contact with the transparent receiving surface 2). FIG. 5 represents a third embodiment of the invention described as a TFT sensor acquisition and analysis system, preferably with an optical TFT sensor (in addition to an optical sensor, it is possible to use a sensor Capacitive TFT, pyroelectric, or a combination of all three). Such a TFT sensor is known, for example from US20020054394 or US2002000915 incorporated herein by reference. It is an image sensor of similar design to a CMOS sensor, made using thin film transistor production technologies used mainly for the manufacture of screens. Photosensitive pixels (PIN diode, amorphous silicon phototransistor 20 or IGZO, etc.) and addressing transistors 251 are distributed in a regular matrix, with a step (between two successive photosensitive elements) ranging from 25 pm to 50 pm on the surface of a substrate 21 of glass or quartz or of plastic, provided that it is transparent. A transparent protection 22 is affixed to this matrix. This provides a transparent receiving surface 2 on which a finger 100 to be imaged can be placed. The protection 22 is thin, that is to say preferably less than the pitch of the photosensitive matrix, typically less than 50 μm. The matrix has a dimension usually between 200 and 3000 lines and 250 to 3500 columns depending on the size of the object to be imaged. A backlight 23 (for example a light-emitting diode backlight 30 (organic or non-organic) or an electroluminescent film) is provided under the glass substrate 21. It emits a light beam 231 upwards, that is to say in the direction of the light. finger 100 through the substrate 21 and the protection 22. The imaging principle with such a TFT sensor is based on the backscattering of light through the finger. At the 50 pm scale, backscattering of light is important for the entire visible spectrum. As the finger is illuminated through a matrix of steps of up to 50 pm, it can be considered that it re-emits light almost uniformly. The re-emitted radiation is captured by the photosensitive pixels 25.
    [0007] The TFT sensor embodiment has the advantage of being more compact and less expensive than the two previously described embodiments. In addition, the image is substantially independent of the lighting color because there is no optics forming the image and therefore no chromaticism problem. However, the contrast is more moderate than with a total reflection sensor with a dark background. Indeed, because of the proximity between the light source and the finger, the light passes through the transparent plate with a large number of angles of incidence, and the phenomenon of limit angle of total reflection is much less marked than with the previous embodiments. Some rays, including incident rays whose angle of incidence is close to normal with respect to the transparent receiving surface 2, then pass through the glass / air interface and reach the valleys of the surface of the finger. In other words, with such a TFT sensor, because of the angles of incidence of the rays, there is no total reflection (it is backscattering) so that the peaks appear in the clear while the valleys appear darker, resulting in a less contrasting image.
    [0008] In addition, it is possible, in particular for solutions using organic photosensitive elements (organic photodiodes for example) to control the spectral domain where the quantum efficiency is important. It will thus be possible to obtain a very low quantum efficiency in the ultraviolet or violet and a maximum of efficiency in green and / or red.
    [0009] The second part of the method, relating to the detection of fraud, can be integrated as previously described in relation to a total reflection sensor. It will be possible in the embodiment to integrate excitation sources in the backlight 23 or, alternatively, to pass the excitation light through the backlight 23 provided to use a backlight 23 devoid of reflective film on its back side. The region of interest is selected to correspond to: (i) intense pixels of the fingerprint image, i.e., a peak zone (s), in accordance with the first version of the invention, (ie to less intense or even dark pixels, that is to say to a valley zone (s), according to the third version of the invention, especially if the signal at the level of the peak areas is insufficient because the finger is dry.The fact of addressing dark pixels (or rather less intense), which correspond to valleys, has an advantage because we observe parts of the object that are not in contact with the transparent window, avoiding a possible bias related to the quality of the optical contact between the object and the transparent window, for example, when a finger is wet or greasy the optical contact is favored because moisture or grease ensures a On the other hand, when the finger is dry, the optical coupling be the finger and the window is not optimized. Thus, a zone in contact with the window may generate a different fluorescence signal at the ridges, depending on whether it is dry or wet. Conversely, the fluorescence signal corresponding to the valleys is more stable because it is not influenced by the surface state of the object (dry or wet). (either to a combination of both: the two subregions are then processed independently of one another, i.e. two comparisons with different validity windows are made successively. previously described can be used according to the following variant (second version of the invention), subject to adapting its excitation source.This version of the invention is illustrated in Figure 5, with a TFT sensor, being It is recalled that it can be applied to the other types of sensor A print image (first part of the process) is carried out as previously described, but the second part of the method differs from that described above in that the light excitation is projected on the finger in the form of a pattern, for example a point, a line or any shape.It is necessary that the visible surface of the finger has a portion not illuminated by the 25 excitation light, complementary to this pattern. A fluorescence image is produced. Note that the area on the finger illuminated by the excitation pattern may correspond to a brighter region on the fluorescence image because the excitation beam is backscattered by the finger, this backscattered excitation beam is, however, attenuated by the filter 6 before reaching the fluorescence detector. FIG. 7 illustrates the rays reaching the florescence detector, namely a backscattered excitation beam 131 by the finger and a fluorescence beam 132. It is then taken advantage of the fact that the excitation light chosen in the ultraviolet (centered at a wavelength of less than 450 nm) is absorbed by the tissue (it hardly extends beyond the point of impact of the excitation beam, the backscattered excitation beam 131 is thus limited to the pattern of excitation), while the fluorescence light, of higher wavelength, is transmitted (it is re-emitted, at least partially, outside the excitation pattern). The fluorescence beam 132 (FIG. 7) comprises radii 15 (see FIG. 5) which have traveled a small distance in the finger with respect to the point of impact of the excitation beam 231, that is to say relative to at the point where the fluorescence is generated, as well as rays 14 which have traveled a greater distance and are therefore attenuated. A region of interest that does not intersect with the excitation pattern and is located at a distance from the excitation pattern that is greater than a predetermined threshold is selected to prevent the corresponding region on the fluorescence image is disturbed by the backscattered excitation beam 131, for example at a distance greater than 0.5mm. The selected region of interest (on the imprint image) corresponds, on the fluorescence image, to one or more measurement regions such as the regions 133 that can be observed in FIG. 7. In this case, a comparison of the fluorescence level at a given distance from the excitation pattern or as a function of the distance with respect to the excitation pattern makes it possible to translate a fluorescence wavelength diffusion profile into the tissue, which 'proves to be an indicator characterizing the fabric. Finally, the first two embodiments described can be modified using, instead of the camera 5, a fluorescence imager. In this case, the impression image and the fluorescence image are combined. The process is however unchanged.
    [0010] The invention can be the subject of numerous variants with respect to the preferred embodiments previously described, provided that these variants remain within the scope delimited by the appended claims. For example, the prism of the full reflection embodiments illustrated in FIGS. 3 and 4 can be replaced by a thin blade. In this variant, which has the advantage of being more compact, the impression image is obtained after a series of total reflection in the glass slide. Another solution, also more compact, could be to use a glass tear, one side of which forms a succession of micro-prisms.
    权利要求:
    Claims (15)
    [0001]
    REVENDICATIONS1. A method for acquisition and fingerprint analysis with fraud detection, comprising the following steps: (forming a fingerprint image of an object (100) placed opposite a transparent receiving surface ( 2), which impression image is representative of a micro-patterning of a visible surface of the object, ^ (irradiation of the object (100) through the transparent receiving surface (2) to the using an excitation beam (12) according to an excitation spectral band, (analysis of a fluorescence emitted by the object in response to the excitation beam (12), according to a fluorescence spectral band , (verification of a validity criterion for discriminating biological tissue from other objects, which criterion of validity is established from the fluorescence analysis, the method is characterized in that: it further comprises a selection step on the imprint image of a suitable region of interest to characterize the biological tissues, which region of interest defines by correspondence, on the object, a useful observation area, ^ (the validity criterion is established from fluorescence intensity measurements relative to the area of useful observation of the object. 20
    [0002]
    Method according to claim 1, characterized in that: (the region of interest is selected so that the corresponding useful observation area of the object is a peak zone in contact with the receiving surface transparent (2); 25 ^ (and the verification of the validity criterion comprises calculating an average or a sum of the fluorescence intensities measured in the useful observation area and comparing this average or sum to a window predetermined amount of fluorescence intensities corresponding to biological tissues.
    [0003]
    3. Method according to claim 1, characterized in that: (the excitation beam has a spectral band centered at a wavelength of less than 450 nm and forms an excitation pattern on the visible surface of the object (The region of interest on the cavity image is selected so that the corresponding useful observation area does not intersect with this excitation pattern and is located at a distance from the pattern as small as possible and sufficient to ensure that the fluorescence measurements of this zone are not disturbed by a backscattering of the excitation beam; (and the verification of the criterion of validity comprises the comparison of an average fluorescence intensity measurements obtained for the useful observation area with a predetermined validity window corresponding to biological tissues.
    [0004]
    4. Method according to one of claims 1 or 3, characterized in that: ^ (the excitation beam has a spectral band centered on a wavelength less than 450nm and it forms an excitation pattern on the surface visible from the object; ^ (the region of interest is selected so as to correspond to at least two useful observation areas on the object having no intersection with this excitation pattern, namely a first useful observation area located at a first predetermined distance from the excitation pattern, which first distance is both the lowest possible and sufficient so that the fluorescence measurements of this first useful observation area are not disturbed by a backscattering the excitation beam, and a second useful viewing area located at a second predetermined distance from the excitation pattern, the second distance being greater than the first distance; The validity criterion includes establishing a fluorescence decay profile as a function of distance from the excitation pattern, using the fluorescence intensities measured for the first and second useful viewing areas, and comparing a slope of this decay profile with a window of predetermined validity slopes of fluorescence decay profile corresponding to biological tissues.
    [0005]
    5. Method according to one of claims 1 to 4, characterized in that the imprint image is a fluorescence image, and in that the formation of the imprint image and the acquisition of fluorescence measurements constitute one and the same operation.
    [0006]
    An acquisition and fingerprint analysis system with fraud detection, comprising: a transparent receiving surface (2); a detector (5; 20) for forming a fingerprint image an object (100) placed opposite the transparent receiving surface, which impression image is representative of a micro structuring of a visible surface of the object; ) capable of producing an excitation beam (12) according to an excitation spectral band, 10 (a fluorescence detector (5; 25) for the analysis of a fluorescence emitted by the object in response to the beam of excitation, according to a fluorescence spectral band, (a calculator (50) for the verification of a validity criterion for discriminating biological tissue from other objects, which criterion of validity is established from the fluorescence analysis, characterized in that the computer (50) is configured from to: (select from the imprint image a region of interest suitable for characterizing the biological tissues, which region of interest defines by correspondence, on the object, a useful observation zone, 20 ^ (Establish the validity criterion from fluorescence intensity measurements relative to the useful observation area.
    [0007]
    7. System according to claim 6, characterized in that the excitation light source (7) has an excitation spectral band entirely below 500 nm.
    [0008]
    8. System according to one of claims 6 or 7, characterized in that it comprises a plurality of excitation beams (12) whose excitation spectral bands are centered on different wavelengths. 30
    [0009]
    9. System according to one of claims 6 to 8, characterized in that: (the system comprises a lighting source (3; 23) emitting a lighting beam (10) irradiating the object through the surface transparent receiver, according to a spectral band of illumination, and ^ (the detector for the formation of the impression image is chosen from a total reflection sensor (5), with a dark background or with a light background, configured to measure a beam reflected (11) by the object, a TFT sensor (25, 251).
    [0010]
    10. System according to one of claims 6 to 8, characterized in that it comprises a fluorescence imager which acts as both a detector for the formation of the imprint image, which is then a fluorescence image , and fluorescence detector for the analysis of a fluorescence emitted by the object.
    [0011]
    11. System according to one of claims 6 to 10, characterized in that the computer (50) is configured to: (select, as a region of interest, a region defining a useful observation area on the object corresponding to a peak area in contact with the transparent receiving surface, ^ (calculating an average or sum of the fluorescence intensities measured for the useful observation area and comparing this average or sum with a predetermined validity window delimiting fluorescence intensities corresponding to biological tissues.
    [0012]
    12. System according to one of claims 6 to 10, characterized in that the detector for the formation of a cavity image is a TFT sensor and in that the computer (50) is configured to: (select, as a region of interest, a region defining a useful observation area on the object corresponding to a valley area, ^ (calculating an average or a sum of the fluorescence intensities measured for the useful observation area and comparing this average or sum at a predetermined window of validity delimiting fluorescence intensities corresponding to biological tissues.
    [0013]
    13. System according to one of claims 6 to 10, characterized in that: ^ (the excitation light source (7) has a spectral band centered on a wavelength less than 450 nm and is configured so that the excitation beam (12) forms an excitation pattern on the visible surface of the object; ^ (the computer (50) is configured to select on the image of the fingerprint as a region of interest a region such that the useful observation area of the corresponding object does not intersect with the excitation pattern and is located at a predetermined distance from the excitation pattern which is both as low as possible and sufficient for that the fluorescence measurements of this zone are not disturbed by a backscattering of the excitation beam. (The computer (50) is configured to compare an average of the fluorescence intensity measurements obtained for the useful observation area with a pre validity window determined corresponding to biological tissues.
    [0014]
    14. System according to one of claims 6 to 10 or 13, characterized in that: ^ (the excitation light source (7) has a spectral band centered on a wavelength less than 450nm and is configured so the excitation beam (12) forms an excitation pattern on the visible surface of the object; (the computer (50) is configured to select on the fingerprint image as a region of interest , a region corresponding to at least two useful observation areas on the object having no intersection with this excitation pattern, namely a first useful observation area located at a first predetermined distance from the pattern of excitation, which first distance is both the lowest possible and sufficient for the fluorescence measurements of this first useful observation area are not disturbed by a backscattering of the excitation beam, and a second useful observation area located one x predetermined distance of the excitation pattern, the second distance being greater than the first distance; the calculator (50) is configured to establish a fluorescence decay profile as a function of distance from the excitation pattern, using the fluorescence intensities measured for the first and second useful viewing areas, and compare a slope of this fluorescence decay profile with a window of predetermined validity of fluorescence decay profile slopes corresponding to biological tissues.
    [0015]
    15. System according to one of claims 6 to 14, characterized in that the computer (50) is configured to perform an additional discrimination step using intensity measurements of the fluorescence emitted in the blue by the observation area. useful in response to the excitation beam.
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    同族专利:
    公开号 | 公开日
    US10664713B2|2020-05-26|
    WO2016102854A1|2016-06-30|
    FR3030834B1|2017-02-10|
    US20180032827A1|2018-02-01|
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    法律状态:
    2015-12-31| PLFP| Fee payment|Year of fee payment: 2 |
    2016-06-24| PLSC| Publication of the preliminary search report|Effective date: 20160624 |
    2016-12-29| PLFP| Fee payment|Year of fee payment: 3 |
    2018-01-02| PLFP| Fee payment|Year of fee payment: 4 |
    2019-11-20| PLFP| Fee payment|Year of fee payment: 6 |
    2020-11-20| PLFP| Fee payment|Year of fee payment: 7 |
    2021-11-18| PLFP| Fee payment|Year of fee payment: 8 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1463100A|FR3030834B1|2014-12-22|2014-12-22|METHOD AND SYSTEM FOR ACQUIRING AND ANALYZING IMPRESSIONS WITH DETECTION OF FRAUD|FR1463100A| FR3030834B1|2014-12-22|2014-12-22|METHOD AND SYSTEM FOR ACQUIRING AND ANALYZING IMPRESSIONS WITH DETECTION OF FRAUD|
    PCT/FR2015/053643| WO2016102854A1|2014-12-22|2015-12-18|Method and system for acquiring and analysing fingerprints with fraud detection|
    US15/538,425| US10664713B2|2014-12-22|2015-12-18|Method and system for acquiring and analysing fingerprints with fraud detection|
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