Method for securing access to a target area by persons with determination of the difficulty in obtaining biometric information

Abstract

Title: Method for securing access to a target area by persons with determination of the difficulty in obtaining biometric information Method for securing access to a target area (ZC) by persons, in which, for a person: - in a first area (Z1) located upstream of the target area, a tracking (S01) of the person is implemented when he or she moves in the first area in the direction of the target area, by means of a camera (400) which observes at least a portion of the first area, - biometric information is obtained (S02) from the person being tracked to verify (S03) whether this person corresponds to a pre-registered person, - a security indicator is determined (S04) indicating a level of difficulty in obtaining biometric information for the person being tracked and it is verified (S05) whether a security condition is verified from the indicator, - an alert signal is generated (S10). Figure for the abstract: Fig. 1.

Description

Title of the invention: Method for securing access to a target area by persons with determination of the difficulty in obtaining biometric information Technical field

[0001] The invention relates to the field of securing access to a target area towards which people are moving. The invention finds application in securing access to an airplane, a train, a boat, or even a building. Prior art

[0002] Access to areas with a certain level of security may be limited to only those persons who are authorized to enter them. For example, when boarding an aircraft, a check (by an operator) of the identity of the persons and their transport ticket is generally carried out before allowing the persons to advance towards access to an aircraft (typically an airport jetway).

[0003] The development of biometric-based solutions makes it possible to do without this control by an operator. In a context in which biometrics is used, people who want to have access to an aircraft pre-register for a flight with their biometric information (typically a facial image), and the recognition of the biometric information gives access to the aircraft without any operator intervention.

[0004] Solutions based on biometrics make it possible to no longer have a gate, as recognition is carried out as people pass through an area, for example towards the plane. Such an area could be a corridor observed by cameras which will monitor people and check their biometrics on the acquired images.

[0005] In the prior art, there are corridors in which several people can pass simultaneously (for example groups of less than 4 people) in an area observed by one or more cameras in which the biometric information of these people is obtained to verify that they are indeed pre-registered to access the aircraft.

[0006] This last solution is the least inconvenient for people who move around without any hindrance such as a gate, but it is also less secure than control by an operator. In fact, this solution is a solution in which the gates are open by default and can close if an unauthorized person is present.

[0007] There are few sufficiently secure solutions in which a group of people can pass (and not people one by one).

[0008] From the state of the prior art, the following documents are known: - US 20210358244, - ES 2860352, -US 11080955, - EP3494553, - KR20170111804, and -EP3179452.

[0009] The solutions described in these documents are not designed to allow several people to pass through or are not sufficiently secure or too inconvenient for people.

[0010] Object and summary of the invention

[0011] The present invention meets this need by proposing a method for securing access to a target area by persons, in which, for a person (for example one person among several persons who are moving towards the target area): - in a first zone located upstream of the target zone, tracking of the person is implemented as they move through the first zone in the direction of the target zone, by means of a camera which observes at least a portion of the first zone (several cameras can be used, with overlapping fields of observation, for example to cover the entire first zone), - biometric information (for example, information allowing facial recognition) is obtained from the person being tracked (and therefore by means of tracking which uses the camera) to check whether this person corresponds to a pre-registered person, - a security indicator is determined indicating a level of difficulty in obtaining biometric information for the person being tracked (and therefore by means of the tracking that uses the camera) and it is checked whether a security condition is verified from the indicator, - if the person corresponds to a pre-registered person and if the security condition relating to the indicator is not verified, then an alert signal is generated, and if the person does not correspond to a pre-registered person, then an alert signal is generated (for example the same alert signal as that generated if the security condition relating to the indicator is not verified, or a different alert signal).

[0012] Thus, the invention proposes to use an additional indicator and a verification of an additional security condition to generate or not an alert signal. In particular, this alert signal is generated even though the person has been recognized by his biometrics. In fact, the security indicator may indicate that too low a security level when obtaining the biometric information has been reached, since this has been difficult to obtain.

[0013] The security indicator actually indicates a level of cooperation of the person when moving towards the target area, this cooperation being measurable by the difficulty in obtaining the biometric information.

[0014] The alert signal, for example the one generated if the safety condition relating to the indicator is not verified, can be a visual signal, an audible signal, or a signal which triggers an actuator (for example to close an access). With this alert signal, an operator can be invited to implement a verification of the identity of the person. It is preferably restored in the vicinity of the exit of the first zone.

[0015] According to a particular mode of implementation, the alert signal designates the person.

[0016] For example, the alert signal can be reproduced by means of a display module on which the person is designated.

[0017] For example, if the display module includes augmented reality glasses (for example of the Hololens type (registered trademark)), a marker may appear in the vicinity of the person on these glasses, so that the operator wearing these glasses perceives the alert and the person concerned.

[0018] If the display module is a screen, this screen can show the images observed by the camera (or another camera) and display a marker in the vicinity of the person visible in these images.

[0019] According to a particular embodiment, the method comprises the generation of another alert signal designating another person for whom biometric information has been obtained for verification showing that this person corresponds to a pre-registered person (in other words, the verification based on biometrics shows that this other person is indeed a pre-registered person) and for which the security condition is verified.

[0020] In this particular embodiment, an alert designates a person who nevertheless corresponds to a pre-registered person, i.e. whose biometric identity is verified, and for whom the security condition was verified: this makes it possible to limit the impact of a bias in the use of the security indicator.

[0021] The other person is also a person who is traveling or has traveled through the first zone in the direction of the target zone.

[0022] According to a particular embodiment, the other person is chosen by means of random data.

[0023] In other words, the other person is chosen randomly, which further limits the impact of bias in determining the security indicator. In fact, this not only limits the impact of bias in determining the security indicator, but it also limits the impact of bias in obtaining biometric information and / or in biometric-based verification, or of bias in a operator if an operator also has the ability to generate alert signals.

[0024] Also, the choice of the other person can be implemented regularly, that is to say by repeating the choice of another person at a given time interval or given number of people having passed from the first zone to the fixed target zone, so as to limit the impact on the people who are moving towards the target zone. Advantageously, the occurrence of implementation of the choice can also be conditioned by the load of the operators.

[0025] According to a particular implementation mode, the security indicator is based on visibility of the person's face.

[0026] The visibility of a person's face can be affected by a viewing angle (a person turns their head away from a camera), by wearing an accessory (glasses, scarf, mask, etc.). A face that is not very visible makes it difficult to obtain biometric information, particularly if facial recognition technology is used.

[0027] For example, the security indicator may be based on one of the methods described in the document “Face Image Quality Assessment: A Literature Survey” (TORSTEN SCHLETT ET AL, ACM Computing Surveys, Volume 54 Issue January 10, 2022). Other methods may be used.

[0028] Face visibility can also be defined using ISO / IEC 39794-5, Part 5, Annex Dl (December 2019), and compliance with this standard can be assessed to determine face visibility.

[0029] According to a particular embodiment, the alert signal or, when the other alert signal exists, does not include any additional biometric information of the person or of the other person, additional biometric information being biometric information which differs from the obtained biometric information.

[0030] Additional biometric information may be information from a database, which may not be available in the environment where the present method is implemented (typically the environment may be an airport). The choice of additional biometric information is made depending on the environment.

[0031] For information purposes, in this embodiment, the alert signal or the other alert signal not comprising any additional biometric information may be an image of the person acquired for example during their passage through the first zone, and it may not contain any identity information (name, etc.) or fingerprint.

[0032] For example, the signal may be a marker visible in the vicinity of the person on augmented reality glasses. An operator will thus not have access to any sensitive data in terms of security but will be able to carry out an identity verification based on an identity document, if necessary.

[0033] According to a particular embodiment, the alert signal is intended to be produced in a second zone located between the first zone and the target zone, and possibly, the other signal is intended to be restored in a second zone located between the first zone and the target zone.

[0034] The first zone is the zone in which people circulate to enable their recognition based on biometrics. In the second zone, other people such as operators may be present. It is in this second zone that the alert signal is reproduced (for example, it is visible on a display module present in the second zone), or it is emitted so that it is audible in the second zone if it is an audible signal.

[0035] According to a particular embodiment, a third zone is separated from the first zone by means of a separation preventing people from passing from the first zone and possibly from the second zone to the third zone (when the second zone is provided, for example), the third zone being outside a field of tracking by the camera and a field of obtaining biometric information (typically in the first zone), and the third zone opens onto the target zone or the second zone, and comprising a control gate located before access to the target zone or the second zone.

[0036] The third zone is an alternative zone to the first (and possibly the second). For people who have not previously shared their biometric information, passing through the third zone allows access to the target zone but by passing through a control gate that does not require pre-registration. For example, an operator may be present at the control gate.

[0037] For information purposes, the method may comprise the generation of another alert signal designating a person who has traveled through the third zone.

[0038] According to a particular embodiment, access blocking gates are controlled in a blocked state based on the result of the step of verifying the security condition (typically, if several security conditions are not verified) and / or on the result of the step of verifying the biometric correspondence (typically, if several people do not correspond to a pre-registered person) of a plurality of people.

[0039] These access blocking gates may be located between the first zone and the target zone, in particular between the second zone and the target zone.

[0040] In this embodiment, it is considered that the verification of the security condition and the verification of the biometric correspondence of the person are problematic for a plurality of people and the access to the target area is completely blocked by controlling the access blocking gates. For example, the blocking gates can be controlled in a blocked state if, during a given period of time, a number of people above a given threshold (for example equal to a number of operators capable of carrying out checks) led to the generation of alert signals (security condition not verified or failure of biometric matching).

[0041] According to a particular mode of implementation, for several people: - in the first zone located upstream of the target zone, monitoring of several people is implemented as they move through the first zone in the direction of the target zone, by means of the camera, - biometric information is obtained from each person followed among the several people to check whether each person corresponds to a pre-registered person, - the security indicator is determined for each person being tracked and it is checked whether a security condition is met from the indicator for each person being tracked, - for each person monitored, if the person corresponds to a pre-registered person and if the security condition relating to the indicator is not verified, then an alert signal is generated, and for each person who does not correspond to a pre-registered person, then an alert signal is generated (for example the same alert signal as that generated if the security condition relating to the indicator is not verified, or a different alert signal).

[0042] Thus, several people are monitored and as soon as the security condition is not verified for a pre-registered person, an alert is issued.

[0043] This alert can designate the person among several people.

[0044] According to one embodiment, the access blocking gates are controlled in a blocked state based on the verification of the security condition and on the verification of the biometric correspondence of the several persons.

[0045] For example, by "based on", it can be understood that a value based on the indicators of several people and the verification of correspondence of the several people is compared to a given threshold. For example, beyond a given number of people with an unverified security condition and beyond a given number of non-pre-registered people, access to the target area can be completely blocked.

[0046] According to a particular embodiment, the target area is an access to an airplane or an access to a train or an access to a boat or an access to a building.

[0047] The invention is particularly well suited to these accesses.

[0048] The invention also proposes a device for securing access to a target area by people, comprising: a module for obtaining a stream of images from a camera which observes at least a part of a first area in which a person moves in the direction of the target area, a module for tracking the person by means of the camera, a module for obtaining biometric information of the tracked person configured to check whether this person corresponds to a pre-registered person, a module for determining a security indicator for the person configured to check whether a security condition relating to the indicator is verified, a module configured to generate an alert signal if the person corresponds to a pre-registered person and if the security condition relating to the indicator is not verified, and to generate an alert signal if the person does not correspond to a pre-registered person.

[0049] This device can be configured to implement all the modes of implementation of the method as described above.

[0050] For example, this method may have a computer system structure, and the modules may be implemented using computer program instructions stored in non-volatile memory of the computer system which, when executed by a processor of the computer system, perform the steps of the method as described above.

[0051] The invention also proposes a system comprising the security device defined above and said camera (possibly a plurality of cameras).

[0052] In this system, the camera and the device are in communication.

[0053] The invention also relates to an installation comprising the system as defined above and the first zone.

[0054] System comprising a security device as defined above and said camera.

[0055] According to a particular embodiment, the system further comprises a module for restoring the alert signal generated if the person corresponds to a pre-registered person and if the safety condition relating to the indicator is not verified, and / or if the person does not correspond to a pre-registered person, the module for restoring the alert signal comprising augmented reality glasses (for example Hololens glasses (registered trademark)) or a tablet (a tablet with a screen) or an alert portal equipped with a signaling device (for example in the form of a portal such as is found at the exit of a store, or in the form of a viewing terminal).

[0056] Installation comprising the system as defined above and the first zone.

[0057] The installation therefore includes both the system and this zone which can be a zone of a building.

[0058] The installation may comprise the second zone and / or the third zone defined above- Before.

[0059] According to a particular embodiment, the target area is an access to an airplane or an access to a train or an access to a boat or an access to a building. Brief description of the drawings

[0060] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an example free from any limiting characteristics.

[0061] In the figures:

[0062] [Fig-1] [Fig.l] schematically shows the steps of a method according to a example.

[0063] [Fig.2] [Fig.2] shows another example in which several people are being followed.

[0064] [Fig.3] [Fig.3] shows a device and a system according to an example.

[0065] [Fig.4] [Fig.4] shows an airport-type installation.

[0066] [Fig.5] [Fig.5] shows a railway station type installation.

[0067] Detailed description of an embodiment

[0068] We will now describe a method and a system for securing access to a target area by people.

[0069] This method and this system are particularly suitable for target areas such as access to an aircraft (typically an airport platform) or access to a train (a platform) or access to a boat or access to a building.

[0070] Also, the method and the system target the movement of people allowing the verification of their identity based on biometrics, in an area in which people circulate without hindrance and in the direction of the target area, to allow the verification of their identity. The method and the system therefore find application in secure accesses for which it is not necessary to systematically manually verify the identity of people. In English, these accesses can be called "free flow" accesses.

[0071] In [Fig.l], the steps of a method for securing access to a target area by persons are shown schematically and in the form of a flowchart, these steps relating to a person, for example one of several persons who are moving towards the target area (PI method). By moving, we mean moving on foot or by means of a device assisting mobility such as a wheelchair, etc.

[0072] The PI method is implemented using one or more observation cameras which each observe a first zone. The first zone can be a corridor in which several people can move simultaneously and even side by side.

[0073] In a first SOI step, tracking of the person is implemented, for example by using image processing algorithms which identify people and perform tracking. The person skilled in the art will know how to choose an algorithm which can be used for this purpose, which makes it possible to locate on a video stream where the same person is located. The video stream may comprise images from several cameras, for example with overlapping fields of observation and signals from the cameras merged, so that the tracking of the people can be consolidated.

[0074] It can be noted that the tracking of a person can be a tracking of his entire body and / or only of his face.

[0075] In a second step S02, biometric information is obtained from the person being tracked. This makes it possible to carry out, in step S03, a verification of the pre-recorded character of the person.

[0076] For example, to carry out step S02, any known facial recognition algorithm can be used, in particular on the basis of the images acquired during the tracking of people during step SOI by the camera 400. For example, an algorithm can be used which delivers a signature, in particular a biometric signature, used to verify in step S03 whether the person is pre-registered in a database, this pre-registration also using biometrics.

[0077] If the person is not pre-registered, the alert step S10 is implemented.

[0078] It may be noted that step S10 may only be implemented if the person has crossed the first zone to reach either the target zone or the second zone if it is present, as is the case in the examples described with reference to figures 4 and 5. This mode of implementation being advantageous for a first so-called “open” zone such as a station hall.

[0079] The alert may be a global alert, which does not designate the person among several people who are moving towards the target zone. For example, the alert signal may be restored by means of an alert portal located at the exit of the first zone, for example between the first zone and a second zone, this alert portal being equipped with a signaling device which flashes / sounds when the alert signal is generated (these alert portals being similar to those located at the exit of a store). Several alert portals may be used. The alert signal may also be restored on a display module such as a tablet screen or augmented reality glasses (for example of the Hololens type (registered trademark). Several of these alert restoration methods may be combined.

[0080] Preferably, the alert designates the person. For example, the alert signal can be reproduced by means of a display module on which the person is designated.

[0081] For example, if the display module includes augmented reality glasses (e.g., Hololens (registered trademark)), a marker may appear in the vicinity of the person on these glasses, so that the operator wearing these glasses perceives the alert. If the display module is a screen, this screen may show the images observed by the camera (or another camera) and display a marker in the vicinity of the person visible in these images.

[0082] For an alert that designates a person, one or more alert gates can also be used, configured so that the alert is returned when the person passes through (it will be noted that the width of the alert gates is advantageously chosen so that several people at the same time pass through an alert gate, in particular leaving sufficient space for the passage of a person with reduced mobility).

[0083] The alert that designates a person can be configured so that an operator is prompted to perform an identity check on the unregistered person, and for this purpose it is returned so that an operator can perceive it.

[0084] For a pre-registered person, it is possible to implement step S04 of determining a security indicator indicating a level of difficulty in obtaining biometric information for the person being tracked and it is verified whether a security condition is verified from the indicator.

[0085] In the present example, the indicator relates to a visibility of the person's face. By measuring this visibility, information is obtained on the level of cooperation of the person with the biometrics-based access system.

[0086] In fact, concealing the face with glasses, a hat, etc. can affect the obtaining of biometric information. This measurable information reflects the level of cooperation of the person.

[0087] As an indication, one of the methods described in the document “Face Image Quality Assessment: A Literature Survey” (TORSTEN SCHLETT ET AL, ACM Computing Surveys, Volume 54 Issue January 10, 2022) can be used.

[0088] In step S05, it is checked whether a safety condition is verified from the indicator. This step may include a comparison with a given threshold.

[0089] If the safety condition is not verified, step S10 of generating an alert signal described above is implemented.

[0090] In other words, the person is a pre-registered person but their cooperation is not at an expected level, and the alert signal is generated.

[0091] If the safety condition is verified, step S06 can be implemented in which, according to random data, it is decided whether or not to generate another alert signal.

[0092] If it is decided to generate a signal on the basis of the random data, step S10' of generating another alert signal is implemented.

[0093] Step S10' is analogous to step S10. Preferably, the signals generated by steps S10' and S10 are identical, so that it is not possible to distinguish an alert justified in view of checks S03 and S05 from an alert based on random data. These signals can be restored in the same way.

[0094] The use of random data makes it possible to avoid the impact that bias would have in the verification of biometric information or the determination of the security indicator.

[0095] If it is not decided to generate a signal based on the random data, the method ends at step SU.

[0096] In [Fig.2], an example is shown in which the PI method has been implemented for n people, the n people passing through the first zone in the direction of the target zone.

[0097] This corresponds to the implementation of a method in which, for n people: - in the first zone located upstream of the target zone, monitoring of several people is implemented when they move in the first zone in the direction of the target zone, by means of the camera, - biometric information is obtained from each person followed among the several people to check whether each person corresponds to a pre-registered person, - the said security indicator is determined for each person being tracked and it is checked whether a security condition is met from the indicator for each person being tracked, - for each person monitored, if the person corresponds to a pre-registered person and if the security condition relating to the indicator is not verified, then an alert signal is generated.

[0098] Subsequently, step S20 may be implemented in which access blocking gates are checked in a blocked state based on all the verifications of the safety condition and all the verifications of the correspondence of the n people.

[0099] These blocking gantries can be arranged between the first zone and the target zone, in particular between a second zone and the target zone as will be visible in Figures 4 and 5 described later.

[0100] For example, beyond a given threshold of persons for whom the safety condition was not verified, the blocking gates can be controlled in a blocked state. Beyond another given threshold of persons who do not correspond to pre-registered persons, the blocking gates can be controlled in a blocked state.

[0101] In the steps shown in Figures 1 and 2, when alert signals are generated, no biometric information of the persons may be transmitted. concerned with alerts. This ensures the security of biometric information while allowing operators to carry out checks on people with, for example, their identity documents. This can be achieved with an alert signal that indicates the position of a person designated by an alert (such as a marker). In fact, no information allowing the implementation of step S03 is transmitted.

[0102] In [Fig.3], a system 200 is shown comprising a device 100 configured for implementing the method steps described above.

[0103] The system 200 and the device are configured to secure access to the target zone ZC shown in the figure, from the first zone Zl.

[0104] For this purpose, the system comprises cameras 400 which observe the first zone, here each a portion.

[0105] The device 100 has a computer system structure and comprises a processor 101 and a non-volatile memory 102 which comprises computer program instructions.

[0106] The device 100 is in communication (for example by means of a communication network) with a biometric database 300 in which pre-registered biometric information of persons is stored. The biometric database may be centralized, for example managed by a state, or local and managed by the entity hosting the target area (typically the airport).

[0107] The system 200 also comprises a module 500 configured to restore the generated alerts, for example a display device (screen, augmented reality glasses).

[0108] In the non-volatile memory, instructions have been stored: - instructions 111 for obtaining a stream of images from a camera which observes at least part of the first zone Z1 in which a person is moving in the direction of the target zone ZC, forming an obtaining module when they are executed by the processor, - instructions 112 for tracking the person using the cameras 400 and determining their signature, in particular biometric, forming a person tracking module when they are executed by the processor, - instructions 113 for obtaining biometric information from the person being tracked and for verifying whether this person corresponds to a pre-registered person, in particular by comparing the determined signature with the base of pre-registered persons 300, forming a biometric matching module when they are executed by the processor, - instructions 114 for determining a security indicator indicating a level of difficulty in obtaining biometric information for the person, the instructions 114 further being instructions for checking whether a security condition relating to the indicator is verified, in particular by comparing the indicator to a threshold, forming a determination module when they are executed by the processor, - instructions 115 for generating an alert signal if the person corresponds to a pre-registered person and if the security condition relating to the indicator is not verified, and for generating an alert signal if the person does not correspond to a pre-registered person, forming a generation module when they are executed by the processor.

[0109] The non-volatile memory 102 also comprises instructions 116 which, when executed by the processor 101, implement the step S20 described above.

[0110] Furthermore, the non-volatile memory may include instructions for generating another alert signal for a randomly chosen person, for example to implement step S10' described above.

[0111] [Fig.4] shows a target area configuration which may be that for a airport (or a port).

[0112] For example, the target area may be an airport platform leading to an aircraft (not shown).

[0113] Two cameras 400 are shown for the first zone. For example, cameras arranged at a height of 2m can be used, preferably equally distributed so as to completely cover the volume / space of zone 1. For information purposes, and if several cameras are used, they can have overlapping fields of observation (this allows the data from the cameras to be merged), this being able to be achieved by choosing cameras with appropriate fields of observation (for example fish-eye / wide-angle / etc.). Preferably, the entire first zone is observed by the cameras.

[0114] Here, the first zone opens, in the direction of circulation which goes from bottom to top in the figure, onto a second zone Z2. The second zone Z2 is a zone in which the module 500 is arranged so that the alert is restored in this zone.

[0115] For example, one or more operators may be present in this area and, based on the alert, they may control persons designated by alerts.

[0116] The target zone ZC can be reached by means of an alternative path, here a third zone Z3. The third zone is separated from the first zone by means of a separation 610 preventing people from passing from the first zone and the second zone to the third zone.

[0117] The separation 610 may be opaque or not, so that the third zone Z3 is outside the field of observation of the cameras 400, i.e. outside the field of automated biometric monitoring and control. Thus, no biometric information is used. people moving around in the third zone Z3. This zone allows, for personal reasons, not to have to transmit information for pre-registration. On the other hand, a control gate 600 is arranged between the third zone Z3 and the second zone Z2, with for example an operator.

[0118] Optionally, a camera 410 has also been arranged observing the second zone, making it possible, for example, on the basis of the monitoring which has been carried out in the first zone, to continue this monitoring and to produce alerts which clearly designate the right people, which is particularly useful in the case of a large group of uncooperative people.

[0119] Between the second zone, and / or the third zone, on the one hand, and the target zone, on the other hand, access blocking gates 700 have been arranged which can be controlled during step S20.

[0120] These access blocking gantries 700 can, when they are open, allow easy access, typically with a width of the preferred order of at least 1.20 m, depending on the configuration of the location (train door, boarding door, etc.).

[0121] Alert gates 800 have been shown in the figure between the first zone Z1 and the second zone Z2. These alert gates 800 can restore an alert signal like the module 500 (which they can replace), for example with signaling device 801 which produces a light or sound signal (mounted here on the alert gates 800 but which can be placed elsewhere). The restitution of the alert signal can be triggered for example when a person designated by an alert passes through one of the alert gates 800, of a width narrower than the width of the zone 1 (here, for the whole of the zone 1, three alert gates have been shown). These alert gates 800 can, when they are open, allow easy access, typically with a width of the order of 1.20 m to 1.50 m. [Fig.5] shows another configuration, more suitable for access to a train, in which the third zone and the first zone open onto the second zone.Access blocking gates are arranged between the second zone and the target zone ZC.

Claims

Claims

1. Method for securing access to a target zone (ZC) by persons, in which, for a person: - in a first zone (Zl) located upstream of the target zone, a tracking (SOI) of the person is implemented when he or she moves in the first zone in the direction of the target zone, by means of a camera (400) which observes at least a portion of the first zone, - biometric information is obtained (S02) of the person being tracked to verify (S03) whether this person corresponds to a pre-registered person, - a security indicator is determined (S04) indicating a level of difficulty in obtaining biometric information for the person being tracked and it is verified (S05) whether a security condition is verified from the indicator, - if the person corresponds to a pre-registered person and if the security condition relating to the indicator is not verified, then an alert signal is generated (S 10),and if the person does not correspond to a pre-registered person, then an alert signal is generated, wherein the security indicator indicating a level of difficulty in obtaining biometric information for the tracked person is based on a visibility of the face of the tracked person, and wherein open access blocking gates (700) are controlled (S20) in a blocked state based on the verification of the security condition and on the verification of the biometric correspondence of a plurality of people, or the alert signal is restored by an open alert gate equipped with a signaling device.,

2. The method of claim 1, wherein the alert signal designates the person.

3. A method according to claim 2, comprising generating (S 10') another alert signal designating another person for whom biometric information has been obtained for verification showing that this person corresponds to another pre-registered person and for which the security condition is verified.

4. The method of claim 3, wherein the other person is chosen by means of random data.

5. A method according to any one of claims 1 to 4, wherein the alert signal or, when the method is taken in its connection with claim 3 or 4, the other alert signal, does not include any additional biometric information of the person or of the other person, additional biometric information being biometric information which differs from the obtained biometric information.

6. A method according to any one of claims 1 to 5, wherein the alert signal is intended to be produced in a second zone located between the first zone and the target zone, and when the method is taken in its attachment to at least claim 3, the other signal is intended to be restored in a second zone located between the first zone and the target zone.

7. A method according to any one of claims 1 to 5, wherein a third zone is separated from the first zone by means of a partition preventing people from passing from the first zone and possibly from the second zone to the third zone, the third zone being outside a field of tracking by the camera and a field of obtaining biometric information, and the third zone opens onto the target zone or the second zone, and comprising a control gate (600) located before access to the target zone or the second zone.

8. A method according to any one of claims 1 to 7, wherein access blocking gates (700) are controlled (S20) in a blocked state based on verification of the security condition and verification of the biometric match of a plurality of persons.

9. Method according to any one of the preceding claims, in which, for several people: - in the first zone located upstream of the target zone, a tracking of the several people is implemented as they move in the first zone in the direction of the target zone, by means of the camera, - biometric information is obtained from each person tracked among the several people to check whether each person corresponds to a pre-registered person, - said security indicator is determined for each person tracked and it is checked whether a security condition is verified from the indicator for each person tracked, - for each person tracked, if the person corresponds to a pre-registered person and if the security condition relating to the indicator is not not verified, then an alert signal is generated, and for each person who does not correspond to a pre-registered person, then an alert signal is generated (for example the same alert signal as that generated if the security condition relating to the indicator is not verified, or a different alert signal.

10. A method according to any one of claims 1 to 0, wherein the target area is an access to an aircraft or an access to a train or an access to a boat or an access to a building.

11. Device for securing access to a target area by people, comprising: a module (101, 111) for obtaining a stream of images from a camera which observes at least a portion of a first area in which a person is moving in the direction of the target area, a module (101, 112) for tracking the person by means of the camera, a module (101, 113) for obtaining biometric information of the person being tracked configured to check whether this person corresponds to a pre-registered person, a module (101, 114) for determining a security indicator indicating a level of difficulty in obtaining biometric information for the person configured to check whether a security condition relating to the indicator is verified, a module (101, 115) configured to generate an alert signal if the person corresponds to a pre-registered person and if the security condition relating to the indicator is not verified,and to generate an alert signal if the person does not match a pre-registered person, wherein the security indicator indicating a level of difficulty in obtaining biometric information for the tracked person is based on a visibility of the face of the tracked person, and wherein the device is configured to control open access blocking gates (700) in a blocked state based on verification of the security condition and verification of the biometric match of a plurality of people, or the device is configured so that the alert signal is restored by an open alert gate equipped with a signaling device.,

12. System comprising a security device according to claim 11 and said camera.

13. The system of claim 12, further comprising a module of restitution of the alert signal generated if the person corresponds to a pre-registered person and if the security condition relating to the indicator is not verified, and / or if the person does not correspond to a pre-registered person, the alert signal restitution module comprising augmented reality glasses (500) or a tablet (500) or said alert portal (800) equipped with a signaling device (801).

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