Secure biometric device

A device for capturing biometric characteristics, the device having an optical sensor with a field of view covering a detection zone for detecting optical characteristics, and an electronic control unit that is connected to the sensor in order to control it, the control unit being placed at least in part in the field of view of the sensor and includes a memory containing at least one signature resulting from at least one reference optical characteristic of the control unit as seen by the sensor, and a comparator module for comparing the signature with at least one corresponding signature that results from at least one optical characteristic of the control unit as supplied by the sensor.

The present invention relates to a device for capturing an image of a fingerprint, of an iris of an eye, of a face, or of some other body part, e.g. for purposes of identifying or authenticating a person having the body part that appears in the image.

BACKGROUND OF THE INVENTION

In general, an optical biometric capture device comprises an optical sensor such as a camera and an electronic control unit connected to the sensor in order to control it. The control unit is arranged to control image capture by the sensor, image processing, and extracting characteristics concerning the captured body part for the purposes of:comparing them with characteristics stored in the device or imported via secure external communication; orexporting them to a comparator device via secure communication.

The comparison serves to identify the person to whom said body part belongs or to verify that the characteristics of the body part appearing in the image do or do not belong to one of the people authorized to access a premises or a service. A dishonest person may attempt to act on the control unit to access its comparison algorithms or its encoding algorithms used for enciphering the characteristics prior to exporting them, or more generally to access operating parameters of the control unit. The control unit is therefore one of its central components of the device, and it needs to be made secure in order to prevent any action being taken thereon by a non-authorized person seeking to falsify identification or authentication.

It is known for the control unit to have incorporated therein a passive protection element such as a resin, or an active protection element such as a resistive film or mesh (see for example documents FR-A-2 805 074 and FR-A-2 824 697) so that any unauthorized physical alteration or manipulation on the control unit leads to an alteration of the protection element that reveals the intervention. Nevertheless, that solution is not practical, for example because it introduces constraints on the design of the device (overall size, position), of compatibility with light rays, and of passages for cables or electrical harnesses, that require discontinuities in the protection element and thus potentially provide access to the protected elements.

OBJECT OF THE INVENTION

An object of the invention is to propose a capture device that is protected against unauthorized interventions thereon.

SUMMARY OF THE INVENTION

To this end, the invention provides a device for capturing biometric characteristics, the device comprising an optical sensor having a field of view covering a detection zone for detecting biometric characteristics, and an electronic control unit that is connected to the sensor in order to control it. The control unit is placed at least in part in the field of view of the sensor and includes a memory containing at least one signature resulting from at least one reference optical characteristic of the control unit as seen by the sensor, and a comparator module for comparing the signature with at least one corresponding signature that results from at least one optical characteristic of the control unit as supplied by the sensor.

Thus, the sensor can detect optical characteristics of the control unit that themselves form a signature or from which it is possible to generate a signature. Comparing a stored signature with a signature that results from optical characteristics that are detected subsequently thus makes it possible to reveal an alteration in said optical characteristics. In the event of an intervention on the control unit, the signature that results from the optical characteristics provided by the sensor is different from the stored signature, such that comparing signatures reveals the intervention. Using the biometric characteristics sensor makes it possible to avoid any need to add a sensor that is dedicated to detecting the intervention, thereby making the structure of the device simpler, more compact, and less expensive.

Preferably, the comparator module is also arranged to compare biometric characteristics extracted from images provided by the sensor with stored biometric characteristics.

Thus, the comparator module serves simultaneously to check biometric characteristics and to verify the integrity of the control unit. As a result there is no dedicated comparator module, thereby simplifying the structure of the device and making it compact and relatively inexpensive.

In a preferred embodiment, the device includes a mirror placed between the sensor, the control unit, and the detection zone, and arranged to enable the control unit and the detection zone to be viewed, one in reflection and the other in transmission, the mirror preferably being a semi-reflecting mirror.

The use of the mirror gives greater freedom in positioning the control unit relative to the sensor.

Advantageously, the device includes a reflecting member surrounding at least part of the control unit, the reflecting member preferably comprising a plurality of reflecting facets forming angles between one another so as to provide the sensor with different angles of view of the control unit.

The reflecting member enables the sensor to detect the optical characteristics of the control unit simultaneously with different viewing angles.

Also advantageously, the control unit is covered in a protective layer having optical characteristics that are detectable by the sensor. Preferably, the protective layer is made of a non-opaque material incorporating optically detectable elements comprising reflecting flakes, at least one element for illuminating the control unit, more preferably being embedded in the protective layer, and still preferably, the material of the protective layer being viscous.

The protective layer serves to amplify visually any traces that a non-authorized intervention might leave on the control unit. The term “optically-detectable element” is used to mean any element capable of emitting, re-emitting, or reflecting a light flux, in particular when illuminated by an external source or that is itself an emitter of light flux.

According to two particular aspects of the invention:the device includes a plurality of lighting elements for lighting the control unit and controlled by the comparator module to take on different configurations, each corresponding to at least one stored signature; andthe memory contains a plurality of signatures resulting from a plurality of reference optical characteristics, and the comparator module is arranged to select a stored signature, to isolate the corresponding optical characteristics from amongst those detected by the sensor, and to compare at least one signature resulting from the optical characteristics detected by the sensor with the selected stored signature.

Thus, the comparison applies to a selected one of the signatures, possibly a randomly selected signature, in such a manner that it is possible to have a large number of signatures in memory with a reasonable comparison duration, so that a fraudulent person cannot determine which optical characteristics of the control unit are to be used for the signature that is to be compared with the selected memorized signature. This makes it more difficult to carry out a non-authorized intervention on the control unit without that being detected.

Other features and advantages of the invention appear on reading the following description of a particular and non-limiting embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIGS. 1 and 2, the capture device constituting the first embodiment of the invention is shown arranged to perform identification by recognizing fingerprints.

The device comprises a casing1having a prism2mounted thereon in known manner, the prism having a top surface that serves as a surface against which a candidate for identification presses a finger. The top surface of the prism2is thus the fingerprint detection zone3.

A light source4is located under the prism2for illuminating the detection zone3.

The capture device includes a sensor5, in this example forming part of a camera (not shown), that is located so that the sensor5has a field of view covering the detection zone3.

A semi-reflecting mirror6is placed between the sensor5and the prism2, in the field of view of the sensor5, so as to define a light path between the sensor5and the detection zone3so that the detection zone3lies within the field of view of the sensor5after reflection on the mirror6. The mirror6is arranged to reflect light rays at wavelengths lying within a first range of values, and to transmit light rays having wavelengths lying in a second range of values.

The positioning of the prism2, the sensor5, and the mirror6is itself known. An optical focusing element16is disposed between the sensor5and the mirror6to focus the image of the detection zone3on the sensor5.

The capture device also includes an electronic control unit7that is connected to the sensor5and to the light source4.

The control unit7is disposed on the side of the mirror6opposite from the sensor5so that the control unit7lies in the field of view of the sensor5for light that is transmitted through the mirror6.

The control unit7is placed in a cavity in a reflecting member8having reflecting facets9arranged as a truncated pyramid on a polygonal base. The cavity is closed by a lens10arranged to focus the image of the control unit7on the sensor5. The cavity of the reflecting member8is filled with a resin in which the control unit7is embedded, thereby forming a protective layer11around it. The resin in this example is viscous, transparent, and incorporates optically detectable elements, specifically reflecting flakes that are dispersed randomly in the resin. The protective layer11thus possesses characteristics that are optically detectable by the sensor5. Light-emitting diodes (LEDs)12are disposed in the cavity and they are embedded in the resin of the protective layer11. In this example, some of the diodes12are mounted directly on the control unit7while others are placed at a distance from the control unit7(however all of them could be mounted on the control unit7or all of them could be at a distance therefrom). The LEDs12are elements for illuminating the control unit7and they are connected to the control unit7.

The control unit7has a memory13containing a database associating fingerprint characteristics with the identities of their proprietors, and a processor module14, specifically a processor that is arranged and programmed:to control the capture of an image of the fingerprint by controlling the light source4and the sensor5;to extract characteristics from the image of the fingerprint and to encode them; andto compare the characteristics as encoded in this way with the characteristics stored in the memory13.

The control unit7also includes a memory15containing signatures that result from reference optical characteristics of the control unit7. The reference optical characteristics are captured by the sensor5during a step of initializing the device. Each signature corresponds to a configuration for lighting the LEDs12. The various lighting configurations depend on the light intensities, the wavelengths, and the distribution of the LEDs12that are switched on. By way of example, each signature is constituted:by the set of optical characteristics detected by the sensor for the lighting configuration concerned;by a selection of optical characteristics, e.g. as a function of the zones of the sensor where they were detected;by numerical information extracted from the optical characteristics (e.g. a mean contrast ratio, a frequency, an intensity, . . . ) or calculated, e.g. as a function of a geographical distribution of brightness levels; . . . .

The processor module14is arranged to form a comparator module for comparing:a signature that results from the optical characteristics of the control unit7as captured by the sensor5with one of the predetermined lighting configurations for the diodes12; andstored visual reference characteristics corresponding to the lighting configuration.

The control unit7, the sensor5, and the light source4are connected to an electrical power supply that is not shown in the figures.

When the capture device is started, and/or periodically, the processor module14controls the sensor5and the diodes12to obtain the optical characteristics of the control unit with a predetermined lighting configuration. Preferably, the same lighting configuration is not used twice in succession.

The processor module14extracts the signature of the detected optical characteristics and compares it with the signature stored for the same lighting configuration.

If the result of the comparison is positive, then the capture device continues to operate normally.

If the result of the comparison is negative, then the processor module14causes operation of the capture device to be stopped.

The reflecting facets9of the reflector member8form angles between one another so as to provide the sensor5with simultaneous views of the control unit7at different viewing angles. The optical characteristics detected by the sensor5are thus not constituted by a true image of the control unit7, but rather by an image made up of partial images with different viewing angles.

Elements that are identical or analogous to those described above are given the same numerical references in the description below of variant embodiments shown inFIGS. 3 to 5.

In a first variant as shown inFIG. 3, the sensors5, the optical focusing element16, and the mirror6are placed in succession facing a side face of the prism so that the sensor5has a field of view covering both the detection zone3of the prism2and the top surface of the control unit7that is placed under the prism2. The light source4is placed facing the other side of the prism2in order to eliminate the detection zone3. The various components of the device are placed in such a manner that the detection zone3and the top surface of the control unit7coincide with the surface of the sensor5via the optical focusing element16.

This embodiment variant is particularly simple.

In a second embodiment variant shown inFIG. 4, the sensor5and the optical focusing element16are disposed in succession facing one of the side faces of the prism2so that the detection zone3is covered by the field of view of the sensor5. A mirror17that presents optical power is placed facing the opposite side face of the prism2so as to reflect the top surface of the control unit7placed under the prism2onto the sensor5via the optical element16and the prism2.

In a third embodiment variant, as shown inFIG. 5, the detection zone3of the prism2is surrounded by a reflecting surface18lying in the field of view of the sensor5, which, together with an optical focusing element16, is placed facing a side face of the prism2. The control unit7and an optical focusing element19are disposed in succession facing the bottom face of the prism2so that portions of the control unit7are reflected in focus in the reflecting border18.

Thus, the sensor5detects simultaneously (or in a variant sequentially) optical characteristics of the fingerprint appearing in the detection zone3and optical characteristics of portions of the control unit7reflected in the reflecting border18.

In the description below of a second embodiment, elements that are identical or analogous to those described above are given the same references.

With reference toFIG. 6, the device constituting the second embodiment is arranged to provide identification by iris recognition.

The device comprises a casing1, a sensor5, and a control unit7. An optical focusing element20is mounted on the casing1facing the sensor5in such a manner that a sharp image of an iris of a candidate for identification is formed on the sensor5.

A focusing mirror21is also placed in the field of view of the sensor5to reflect at least a portion of the control unit7towards the sensor5.

Thus, the field of view of the sensor5includes: the detection zone (zone where the iris is situated behind the optical focusing element20); and a portion of the control unit7reflected by the focusing mirror21. The operation of the device is identical to that of the first embodiment.

In a first variant (seeFIG. 7), a semi-reflecting plate or mirror22is placed between the sensor5and a porthole23mounted in the casing1between the sensor5and the detection zone. The mirror22is analogous to the mirror6and is placed so as to reflect at least a portion of the control unit7to the sensor5. The optical focusing element24in this example is mounted between the mirror22and the control unit7so as to enable a sharp image to be formed on the sensor5. The optical focusing element24is optional. The porthole23may be replaced by an optical focusing element20.

In a second variant shown inFIG. 8, the porthole23that is mounted on the casing1between the sensor5and the detection zone is surrounded by a reflecting zone25shaped to reflect an image of the control unit7to the sensor5, which control unit in this example is mounted in the vicinity of the sensor5, in the focal plane of the reflecting zone25.

Naturally, the invention is not limited to the embodiments described but covers any variant coming within the ambit of the invention as defined by the claims.

In particular, the control unit may be placed in the immediate vicinity of the fingerprint detection zone. It is possible to replace the control unit in the field of view of the sensor after reflection on a peripheral portion of the prism.

The reflecting member may be omitted or may be in the form of a kaleidoscope, or may have a shape that is curved, or a semi-enclosing shape that may be open or closed, or any other shape, in particular presenting two reflecting portions of identical or different shapes that form an angle between each other so as to form two viewing angles, . . . . The lens may have special optical properties making it possible to emphasize, enlarge, or mask portions of the control unit. The lens is likewise optional.

The protective layer may be omitted or it may be of some other composition, and for example it may be: solid or include a viscous phase and a solid phase, it may be opaque, it may incorporate phosphorescent elements, . . . .

The memory containing the reference optical characteristics or signatures may either be connected permanently to the control unit or else it may be associated therewith temporarily (the reference optical characteristics or signatures may be stored in a magnetic card or an integrated circuit card, an electronic key, . . . ), or it may be remote from the control unit and connected thereto via a wired or wireless connection.

The module for comparing visual characteristics may be independent of the comparison module used for identification by fingerprint recognition, and may for example be constituted by the integrated circuit of an integrated circuit card.

The device need have only one element for illuminating the control unit. The LEDs12may be placed on the surface of the control unit7.

The invention can be used with “print” capture devices in the general meaning of this term, i.e. fingerprints, iris prints (iris recognition), face prints (face recognition), . . . .

The positions of the prism2and the control unit7may be interchanged.