Taking the head into account in the detection of unauthorized objects or materials in a protected access zone

Abstract

The present invention relates to a method (S) for inspecting an individual using a detector (1), the method comprising the following steps: S1: generating a magnetic field when an individual is in the passage and acquiring electrical signals representative of the magnetic field; S2: analyzing the electrical signals in order to detect the presence of a metal object; S3: producing an electronic image of the individual when the individual is in the passage, the electronic image comprising the head of the individual; S4: when a metal object is detected, determining the position of the head of the individual in the electronic image; S5: inferring the position of the metal object detected in step S2 relative to the head of the individual; and S6: when the position of the metal object is at the head of the individual, generating a specific alert; and S7: inspecting the head of the individual.

Description

[0001] DESCRIPTION

[0002] TITLE: Taking head tracking into account in the detection of unauthorized objects or materials in a restricted access area

[0003] TECHNICAL FIELD

[0004] This presentation concerns the field of detecting unauthorized objects or materials in a restricted access area.

[0005] STATE OF THE ART

[0006] It is now essential to reliably control attempts to introduce or remove prohibited goods, particularly weapons or explosives, into or from sensitive areas. This problem encompasses a wide range of situations, including but not limited to attempts to introduce prohibited goods into protected areas such as airports, stores, schools, train stations, or public and private organizations, or attempts to remove goods from a defined perimeter, for example, in the event of a theft from a business or protected site.

[0007] Various types of metal object detectors exist. For many years, continuous wave metal object detection portals have been available. These portals use an inductive field with waves of constant amplitude and frequency, typically in the 70 Hz to 50 kHz range. They consist of at least one transmitting coil and at least one receiving coil. The transmitting coil is powered by an alternating electric current. The receiving coil is designed to detect disturbances in the magnetic field generated by the transmitting coil caused by the presence of a metallic object. These detectors are very effective and can detect the presence of metallic objects throughout an individual's entire body, from head to toe, including inside shoes or body cavities.However, it is difficult to determine the exact position of metallic objects relative to the body solely from the electrical signals generated by the receiving coils. Current detectors display the height at which the metallic object(s) that triggered the alarm passed on screens positioned, at full scale, next to the probe's output. In this way, the displayed area can be easily referenced to the part of the person's body that must be searched by the screening personnel.

[0008] The use of body scanners has also been proposed. The oldest body scanners are X-ray scanners. More recent body scanners use millimeter wave (or microwave) technology. An example of a body scanner can be found in document EP 202 700.

[0009] For several years, body scanners have been developed to detect weapons, explosives, and other items concealed under the clothing of individuals entering a protected area. These scanners use technologies based on the detection of modulated radiation energies reflected or emitted by the bodies of the individuals being inspected. The radiation energies used include X-rays, microwaves, millimeter waves, infrared light, terahertz waves, and ultrasound.

[0010] Regardless of the type of radiant energy and imaging geometry used, these body scanners all operate on the principle of creating an electronic image of the individual in which their clothing is transparent. This image is then displayed on a screen and viewed by a security officer to determine if the individual is wearing a target item. However, some applications require users to cover all or part of their head with clothing of varying bulk, which could trigger an alert in a security scanner. To avoid false alarms, it is therefore standard practice not to use the body scanner to inspect the area corresponding to the individual's head.However, this involves either slowing down the flow of passengers in order to manually search, or with handheld detectors, individuals whose heads are covered, or risking allowing malicious individuals who have concealed target objects in such clothing to pass through.

[0011] Furthermore, body scanners are not currently certified to inspect the contents of shoes, particularly to detect threats placed between the foot and the ground, inside the sole. This is due to technical limitations in measurement and imaging, given the internal complexity of shoes and their components. Therefore, security authorities require individuals to remove their shoes. Individuals then pass through the body scanner without shoes, while their footwear is placed in a tray and inspected by X-ray scanners. This security procedure, however, significantly reduces passenger flow at the checkpoint due to the additional time required for shoe removal and handling.Furthermore, it poses hygiene problems, as shoes are placed in the same trays used for inspecting clothing and personal belongings. It also requires individuals to walk barefoot on the floor. Finally, people with reduced mobility (the elderly, pregnant women, etc.) may have difficulty removing and replacing their shoes, further slowing down the inspection process.

[0012] PRESENTATION One aim of the presentation is to propose a detection method and an associated detector using radiant energy for the detection of target objects which overcomes the aforementioned disadvantages.

[0013] In particular, one aim of the presentation is to propose an inspection method and an associated detector to improve passenger flow at the control point, while also improving the detection of target objects, particularly at the head level and, where appropriate, shoes.

[0014] To this end, a method for inspecting an individual using a detector is proposed, according to a first aspect, comprising the following steps:

[0015] 51: generation of a magnetic field when an individual is in the passage and acquisition of electrical signals representative of the magnetic field;

[0016] 52: analysis of electrical signals to detect the presence of a metallic object;

[0017] 53: creation of an electronic image of the individual when the individual is in the passage, the electronic image including the head of the individual;

[0018] 54: when a metallic object is detected, determination of a position of the individual's head in the electronic image;

[0019] 55: deduction of the position of the metallic object detected in step S2 relative to the individual's head; and

[0020] 56: when the metallic object is positioned at the level of the individual's head, a specific alert is generated; and

[0021] 57: Inspection of the individual's head.

[0022] Some preferred but not limiting characteristics of the inspection process according to the first aspect are the following, taken individually or in combination:

[0023] - Step S4 includes a search for a geometric pattern in the electronic image, for example a top of the head, a lower area of ​​the individual's face and / or a base of the individual's neck;

[0024] - The electronic image is produced by microwave antennas and the search for a geometric pattern includes the following sub-steps:

[0025] - determine the intensity of a background signal;

[0026] - determine an average intensity of the signal generated by each antenna or each in the electronic image, preferably by scanning along a height of the detector;

[0027] - when a difference between the average signal intensity of a given microwave antenna and the background signal intensity exceeds a predefined single value, determine a position for the given microwave antenna; and

[0028] - deduce the position of the top of the individual's head;

[0029] - the detector includes several coils distributed along a height of the detector and in which step S5 includes a step of determining the coils located at the level of the individual's head, the specific alert being generated when the coils located at the level of the individual's head correspond to the coils which generated the electrical signals corresponding to the detection of the presence of the metallic object;

[0030] - the inspection process further includes a step of processing the electrical signals and the electronic image so as to obtain a combined electronic image including the metallic object detected by the central unit, and where appropriate a step of displaying the combined electronic image;

[0031] - when the position of the metallic object is not at the level of the individual's head, a different alert from the specific alert is generated;

[0032] - The inspection process also includes the following steps:

[0033] S9: when a metallic object is detected in step S2, determination of the position of the metallic object relative to a lower area of ​​the individual's body;

[0034] 510: when the metallic object is located in a lower area of ​​the individual's body, an additional alert is generated; and

[0035] 511: inspection of the lower area of ​​the individual's body;

[0036] - the inspection process further includes a step S8 of determining a position of the lower area of ​​the individual's body from the electronic image obtained in step S3, the determination of the position of the metallic object in step S9 being deduced from the position of the lower area of ​​the body;

[0037] - step S8 is carried out by searching for a geometric pattern in the electronic image;

[0038] - the detector comprises several windings distributed along a height of the detector and, during step S8, the detector determines if the windings that generated the electrical signals correspond to the windings located in the lower part of the panels; and / or

[0039] - Step S10 is performed by an additional detector independent of the detector.

[0040] According to a second aspect, a detector is proposed comprising:

[0041] - two fixed, opposing side panels, fixed to each other and together defining a passage;

[0042] - inductive type detection means comprising at least one transmitter coil configured to generate a magnetic field and at least one receiver coil configured to acquire electrical signals representative of a disturbance of the magnetic field by a metallic object;

[0043] - means of detection using radiant energy, for example microwave antennas, housed in at least one of the side panels;

[0044] - a central unit configured to implement the steps of the inspection process according to the first aspect; and

[0045] - an alarm configured to generate a specific alert.

[0046] Optionally, the detector may include several coils distributed along its height, with the central unit configured to identify, using radiant energy detection methods, the coils located at the height of the individual's head; and / or

[0047] According to a third aspect, a detection system is proposed comprising a detector according to the second aspect and an additional detector independent of the detector, the additional detector being configured to inspect a lower area of ​​an individual's body.

[0048] DESCRIPTION OF THE FIGURES

[0049] Other features, purposes, and advantages will become apparent from the following description, which is purely illustrative and not exhaustive, and should be read in conjunction with the attached drawings on which:

[0050] Figure 1 schematically illustrates an example of an embodiment of a detector conforming to an embodiment.

[0051] Figure 2 is a flowchart of steps of an example implementation of an inspection process conforming to an embodiment, in which optional steps have been outlined in dashed lines.

[0052] Figure 3a is an example of implementing a specific alert when an object is detected at the level of an individual's head.

[0053] Figure 3b is an example of how an alert can be triggered when an object is detected on an individual's body.

[0054] Figure 3c is an example of implementing a specific alert when an object is detected at the feet of an individual.

[0055] Across all figures, similar elements bear identical references.

[0056] DETAILED DESCRIPTION

[0057] A detector 1 comprises two opposing side panels 2 which are fixed and together define a passage forming a transit channel for a person to be inspected. The transit channel thus comprises an entrance and an exit, positioned at opposite ends of the side panels 2.

[0058] The side panels 2 are substantially symmetrical with respect to a central plane (imaginary plane of symmetry). In one embodiment, the side panels 2 are connected at their upper edge by a ceiling and / or at their lower edge by a platform 4 so as to be monolithic. Alternatively, the side panels 2 can be separate and distinct, i.e., not connected by a ceiling or a platform 4.

[0059] Each side panel 2 has an internal face 3, oriented towards the passageway. More precisely, the internal face 3 of the first side panel 2 faces the internal face 3 of the second side panel 2 so as to laterally delimit the passageway. The internal faces 3 may be flat or curved along all or part of their length.

[0060] Detector 1 includes continuous wave inductive detection means, radiant energy detection means 5 and a central unit 6.

[0061] The inductive field detection means include at least one transmitter coil 7a located in one of the side panels 2 and at least one receiver coil 7b located in the other of the side panels 2. The transmitter coil 7a is supplied with an alternating electric current of controlled frequency, preferably within a defined and controlled frequency range, to generate a magnetic field, typically between 100 Hz and 50 kHz. The receiver coil 7b is designed to acquire electrical signals representative of the magnetic field generated by the receiver coil 7b. The central unit 6 is configured to analyze the electrical signals and detect disturbances in this magnetic field due to the presence of a metallic object in the passage and the movement of this metallic object within the passage.

[0062] In practice, each of the transmitter 7a and receiver 7b coils is preferably formed from a plurality of 7a, 7b coils or elementary turns, covering a respective portion of the gantry's height, to allow discrimination of the position of detected metal targets and thus localize their vertical position. Each of the 7a, 7b coils can alternately act as a transmitter and receiver.

[0063] In one embodiment, the detector 1 comprises several transmitting coils 7a, 7b and receiving coils 7a and 7b distributed along the height of the side panels 2 so as to determine the position of the metallic object. The detector 1 specifically includes transmitting coils 7a, 7b and receiving coils 7b in the lower part of the side panels 2, in the immediate vicinity of the platform 4, so as to detect the presence of a metallic object concealed in the shoes, as well as transmitting coils 7a, 7b and receiving coils 7b in the upper part of the side panels 2, opposite the platform 4, so as to detect the presence of a metallic object concealed at the level of the individual's head.Identifying the receiver coils 7a and 7b that have detected the magnetic field disturbance allows the central unit 6 to determine the volume containing the metallic object and generate an alert when the presence of a metallic object near platform 4 is detected. The generation of the magnetic field and the acquisition of electrical signals by the coils 7a and 7b can be continuous. Alternatively, the generation and acquisition of signals can be triggered by the passage detection means.

[0064] The central unit 6 may include a processor, microprocessor, microcontroller, etc. type computer configured to execute code instructions to analyze the electrical signals of the windings 7a, 7b to detect disturbances in the magnetic field due to the presence of a metallic object in the passage.

[0065] The radiant energy sensing means comprise a plurality of radiant energy emitter / receiver transducers 5 arranged on the inner face 3 of at least one of the side panels 2, preferably of each side panel 2. Each transducer can successively form an emitter configured to generate radiant energy and a receiver configured to receive radiant energy.

[0066] In one embodiment, each transducer includes an antenna 5 configured to generate radiant energy of the millimeter wave (also called microwave wave), X-ray, terahertz wave, etc. type. The central unit 6 is further configured to receive signals representative of the radiant energy reflected and measured by the transducers 5 and to deduce an electronic image from them.

[0067] In what follows, the invention will be described more particularly in the case where the transducers 5 comprise microwave antennas 5, that is, antennas 5 configured to generate waves with wavelengths from 3 mm to 20 mm inclusive (i.e., a frequency range from approximately 15 GHz to 100 GHz), without this being limiting. Microwaves are indeed suitable for detecting metallic and non-metallic objects, such as ceramic objects. Furthermore, air and other materials, such as those used for clothing, are transparent to these radiations. It follows that microwaves can be used to detect objects concealed under clothing and to determine the exact silhouette of an individual. In order to detect target objects, the microwave antennas 5, as transmitters, generate pulses or a frequency sweep of microwaves.The reflected energy from each part of the individual is then measured by the microwave antennas 5, acting as receivers, which transmit a signal representing this reflected energy to the central processing unit 6. The central processing unit analyzes this signal to generate an electronic image of the inspected individual, in which their clothing is essentially transparent. If necessary, the detector 1 further includes a network interface configured to receive the signals representing the reflected energy and transmit them to the central processing unit 6. The computer in the central processing unit 6 is further configured to execute code instructions to process the signals representing the reflected radiant energy measured by the antennas 5 and to derive an electronic image from them.

[0068] Reference can be made to document WO 2020 / 157139 for further details on the operation of a detector 1 comprising both microwave field imaging and inductive field type detection means.

[0069] Optionally, detector 1 further includes presence detection means, for example, an optical barrier placed at the entrance of detector 1, each comprising a pair of transmitter / receivers arranged respectively in the two side panels 2. If necessary, the presence detection means may include several optical barriers distributed longitudinally along the path of movement in the channel, for example, three optical barriers. Alternatively, the passage detection means include a camera configured to detect the passage of a person.

[0070] Where appropriate, detector 1 further includes a signal that can be placed at the entrance of detector 1 and synchronized with the presence detection means, in order to indicate to the individual being inspected whether he or she can enter detector 1. The signal can, for example, be of the green / red light type.

[0071] To improve the inspection of an individual by a detector, an inspection procedure is proposed comprising the following steps:

[0072] 51: generation of a magnetic field when an individual is in the passage and acquisition of electrical signals representative of the magnetic field;

[0073] 52: analysis of electrical signals to detect the presence of a metallic object;

[0074] 53: creation of an electronic image of the individual when the individual is in the passage, the electronic image including the head of the individual;

[0075] 54: when a metallic object is detected, determination of a position of the individual's head in the electronic image;

[0076] 55: deduction of the position of the metallic object detected in step S2 relative to the individual's head; and

[0077] 56: when the metallic object is positioned at the level of the individual's head, an alert is generated; and

[0078] 57: Inspection of the individual's head.

[0079] More specifically, during step S1, the individual enters detector 1 and positions themselves between the two panels of the detector, at the level of the microwave antennas 5. The generation of the magnetic field and the acquisition of electrical signals can be carried out while the individual is stationary in the passage or in transit, that is to say in motion between the entrance and the exit of the detector.

[0080] In one embodiment, the coils 7a, 7b are placed at the input of detector 1, and the radiating energy antennas 5 are distributed along the inner face 3 of the side panels 2 downstream of the coils 7a, 7b, i.e., between the coils 7a, 7b and the exit of the passage. The individual therefore passes in front of the inductive field detection means 7a, 7b before positioning themselves in front of the microwave antennas 5. In this embodiment, step S1 is thus performed while the individual is moving in order to position themselves between the side panels 2 of the detector for the acquisition of the electronic image (step S3). Alternatively, the central unit 6 can process the electrical signals generated by the coils 7a, 7b and the signals representing the radiating energy reflected and measured by the antennas 5 simultaneously.As we will see below, this embodiment allows the signals from the 7a, 7b windings to be processed before or during the acquisition of the electronic image, which reduces the total time of the inspection.

[0081] Alternatively, the coils 7a, 7b can be placed at the output of detector 1, downstream of the radiating energy antennas 5. The individual thus positions themselves first in front of the microwave antennas 5, allowing the central unit 6 to acquire the electronic image, before passing in front of the inductive field detection means 7a, 7b. In this variant, step S1 is therefore performed while the individual is moving towards exiting the detector. This alternative embodiment requires processing the signals from the coils 7a, 7b after the electronic image has been acquired.

[0082] In what follows, the configuration in which the coils 7a, 7b are placed upstream of the microwave antennas 5 will be described in more detail, although this is not limiting.

[0083] In this configuration, the individual passes in front of the coils 7a, 7b of the inductive field type detection means before positioning themselves in front of the microwave antennas 5. Preferably, the individual only passes in front of the coils 7a, 7b before positioning themselves at the microwave antennas 5. Steps S1 and S2 can therefore be carried out or at least initiated before step S3.

[0084] When an individual passes in front of the inductive field detection devices, the transmitting coils 7a and 7b generate a magnetic field, and the receiving coils 7a and 7b detect the magnetic field generated by the transmitting coils 7a and 7b. When the individual is wearing a metallic object, the presence of this metallic object disturbs the magnetic field generated by the transmitting coils 7a and 7b. These disturbances may include, in particular, an attenuation of the magnetic field amplitude and / or a phase change in the electrical signal, due, for example, to eddy currents generated on the metallic object. These disturbances are translated into electrical signals generated by the receiving coils 7a and 7b, which are transmitted to the central processing unit 6.

[0085] During step S2, the central unit 6 analyzes the electrical signals (amplitude attenuation / phase change) of the windings 7a, 7b to detect these disturbances and deduce the presence of a metallic object.

[0086] During step S3, the individual positions themselves in the passage between the side panels 2, at the level of the microwave antennas 5, and an electronic image of the individual is acquired by the microwave antennas 5. The individual may position themselves facing the side panels 2, i.e., with their feet perpendicular to the panels, as described in document WO 2020 / 157139 on behalf of the Applicant, and / or to the side of the side panels 2, i.e., with their feet parallel to the panels, as described in detail in document WO 2021 / 209505 on behalf of the Applicant. To facilitate the individual's positioning relative to the side panels 2, the detector 1 may include visual indicators 8 configured to show the individual where to position their shoes during the inspection.Visual indicators may include markings on platform 4 and / or an image projected onto an area of ​​platform 4 (or, where appropriate, the ground in the absence of platform 4).

[0087] During step S3, the microwave antennas 5 create an electronic image that includes the individual's head. To do this, all or some of the microwave antennas 5 housed in the first side panel 2 and / or the second side panel 2 generate and emit pulses or trains of microwave waves towards the passageway. These microwave waves interact with the surface they face, and in particular the upper surface of the individual's body and any objects that may be concealed by the individual, as well as the inner surface 3 of the side panel 2 they face. These interactions modulate the energy of the microwave waves, which, once reflected, return to the antenna(s) 5, which act as receivers. The energy reflected from each part of the person being inspected is measured by the antennas 5, acting as receivers.Each antenna 5 then transmits to the central unit 6 a signal representing this reflected energy for processing and creation of the individual's electronic image. If necessary, this transmission can be carried out via a network interface.

[0088] To enable the detector to determine the position of the individual's head, the detector includes microwave antennas 5 in a portion of the side panels 2 extending at least in front of the upper part of the individual's body. Preferably, to ensure that the individual's head is included in the electronic image regardless of its size, the side panels 2 include microwave antennas 5 along their entire height. This also makes it possible to obtain an electronic image that includes the entire body of the individual, from their feet to the top of their head.

[0089] During step S4, the position of the individual's head is detected in the electronic image when a metallic object is detected by the inductive field detection means 7a, 7b. Indeed, the inductive field detection means 7a, 7b enable the central unit 6 to detect the presence of metallic objects, regardless of their position relative to the individual's body (at the head, along the body, or in the shoes) or their shape. In particular, thanks to the coils 7a, 7b, the central unit 6 is able to detect the presence of a small metallic object, such as a thin blade, which could be concealed, for example, in the hair or in bulky clothing on the individual's head. Such a thin metallic object would, conversely, likely not be detected by the microwave antennas 5, especially when placed at the head or feet.However, as discussed above, the central unit 6 is not capable, from only the electrical signals generated by the windings 7a, 7b, of determining the precise position of the metallic objects in relation to the body of the individual.

[0090] It is therefore proposed to leverage the electronic image acquired in step S3 using microwave antennas 5 to determine the position of all parts of the individual's body within the passage, and in particular the position of the individual's head. To this end, during step S4, the central processing unit 6 can search for a geometric pattern in the electronic image to identify the area above the shoulders, typically by searching for the geometric pattern corresponding to the lower boundary of the face (end of the chin and beginning of the neck).

[0091] In one example implementation, the search for geometric patterns in the electronic image can be carried out by image processing.

[0092] In another embodiment, the central unit 6 can determine the position of the passenger's head during the screening using microwave antennas 5 by scanning signals along the height of detector 1. This scanning can be achieved, in particular, by each individual antenna, acting as a transmitter, transmitting a microwave signal, with these individual microwave signals being received by individual antennas, acting as receivers. In this embodiment, the microwave signals are preferably transmitted by the transmitters towards a transmitter located at the same height on the opposite panel, i.e., in the same horizontal plane.

[0093] Microwave signal scanning is performed along the height of the detector, preferably starting with the antennas located at the top of detector 1, for example near the upper edge of the panels (or, if applicable, near the ceiling), and then proceeding progressively downwards towards the lower edge of the panels (or, if applicable, down to platform 4). The transmitters can generate signals one after the other, or alternatively, by groups of antennas or by lines of antennas (the lines being substantially parallel to the ground or to platform 4).

[0094] The receivers receive the signals as the system scans from top to bottom, and the central processing unit 6 processes them sequentially. The central processing unit 6 also determines a background signal intensity, corresponding to the average intensity of a signal received by the receivers in the absence of an individual in detector 1. When the average intensity of the signals received by the antennas 5 exceeds the background signal intensity by a certain predefined threshold, for example, 10%, the central processing unit 6 deduces that the top of the passenger's head is located at the level of the receiving antennas that received the signal corresponding to this average intensity, and thus calculates the position of the top of the head. The accuracy with which the position of the top of the passenger's head can be estimated is on the order of millimeters.From determining the position of the top of the head and average human proportions, it is then possible to estimate the height of the head and deduce the position of the base of the neck or the bottom of the face (and any other anthropometric measurement). Average human proportions can, for example, correspond to those described in the manual "Measuring Men and Women: Human Factors in Design" by Henry Dreyfuss, published in 1959, which specifies, for example, that the height of the head (distance between the chin and the top of the head) is, on average, equal to 15% of the person's height.

[0095] In a variation of this embodiment, the emitters can emit pulses or trains of microwave waves, so that all or part of the surface of the panels emits microwave waves simultaneously rather than scanning the volume of the passage along its height. The position of the top of the head is then determined by the central unit 6 from the signals received by the receiving antennas, whose position relative to the panels is known.

[0096] Once the head's position is identified in the electronic image, the central unit 6 can determine whether the metallic object, detected by the inductive field detection means, is concealed at the level of the individual's head, or elsewhere. Knowing the head's position in the electronic image allows the determination of the head's position (and in particular its height) relative to the side panels 2, and therefore relative to the coils 7a, 7b.

[0097] For example, the central unit 6 can create an avatar of the person and correlate the signals from the coils 7a, 7b with the avatar to determine the position of a detected object relative to the person's body and trigger the corresponding alerts accordingly. In particular, the central unit 6 can identify the coils 7a, 7b located at the height of the individual's head, regardless of their height: when the coils 7a, 7b located at the level of the individual's head correspond to the coils 7a, 7b that detected the disturbance in the magnetic field, the central unit 6 infers that the metallic object is concealed at head level and generates a specific alert (FIG. 3a) so that the individual's head can be inspected, for example by a security guard (step S7).Conversely, when the central unit 6 determines that the coils 7a, 7b that detected the magnetic field disturbance are different from those located at head height, the central unit 6 does not generate a specific alert for head inspection. However, an alert can be generated to inspect the individual's body (FIG. 3b).

[0098] The combined operation of the coils 7a, 7b and the microwave antennas 5 thus ensures a complete and efficient inspection of the individual, including their head.

[0099] If necessary, the central unit 6 can process the electrical signals and the electronic image to obtain a combined electronic image including the metallic object detected by the central unit 6 placed on the individual's body. The combined electronic image can then be displayed on a screen 11 for viewing by a security officer (see Figures 3a, 3b and 3c).

[0100] The specific alert for head inspection can, for example, be generated by an audible (loudspeaker) and / or visual (screen 11, light, etc.) alarm and include an audible and / or visual signal. The alarm can, for example, include a dedicated light-emitting diode (LED) mounted on the panel(s) of detector 1 and / or screen 11 configured to display a message to the security officer, such as a light bar prompting the officer to inspect the individual's lower body. For example, the central unit 6 can display an avatar of the individual on screen 11: the specific alert can then include highlighting the head in relation to the rest of the body (for example, by coloring only the head area red, as illustrated in Figure 3a). If the detector does not detect any object, the avatar can, for example, be colored green.

[0101] The same process can be applied to the inspection of the individual's shoes. In particular, when a metallic object is detected, the central unit 6 can determine the position of the lower part of the individual's body in the electronic image (typically, the area extending below their knees or shoes) by searching for a geometric pattern and deduce the position of the metallic object in relation to the lower part of the individual (where applicable, their shoes) (step S8).Alternatively (which can be combined with the search for geometric patterns), with the individual's shoes always close to the ground, regardless of the individual's height, and the vertical movement of the shoes limited when an individual walks, the central unit 6 can determine if the metallic object is concealed in the shoes (or generally under the knees) as soon as the coils 7a, 7b that detected the disturbance of the magnetic field correspond to the coils 7a, 7b in the lower part of the detector, i.e. located at a distance less than or equal to 50 cm from the platform.

[0102] When the central unit 6 determines that the metallic object is positioned on the lower part of the individual's body (step S9), a specific alert can be generated so that the lower area of ​​the individual's body (step S10 - FIG. 3c), typically their shoes (and, where applicable, the lower part of the legs, down to the knee), can be inspected. The inspection can be carried out manually by a security officer or using an independent inspection system configured to analyze an individual's leg and shoes, such as the systems described in documents FR3050283, FR3050285, FR3050284, FR3072467, and FR3072470 on behalf of the Applicant (step S11). Since the central unit 6 is unable to determine which side of the individual triggered the alert (right or left leg), the security officer preferably inspects both legs.

[0103] The specific alert for detecting a concealed metallic object in the lower body area of ​​an individual is preferably different from the specific alert for detecting a concealed metallic object at head level. For example, the specific alert for inspecting the lower body area of ​​an individual may include an audible and / or visual signal (different from the specific alerts for the head) which may include a dedicated LED mounted on the gate (where applicable, in a different location from the LED generating the specific alert for the head) and / or a message displayed on the security officer's screen, for example, a banner prompting the security officer to inspect the lower body area of ​​the individual.In the example embodiment in which central unit 6 displays an avatar on screen 11, the specific alert may include highlighting the feet of the avatar in relation to the rest of the body (for example by coloring only the part corresponding to the feet in red, as illustrated in Figure 3c).

[0104] The S inspection procedure thus assists security officers in selecting individuals whose heads and, where applicable, shoes require specific inspection. It is therefore no longer necessary to systematically inspect individuals who are covering all or part of their heads or their shoes, thereby avoiding unnecessary delays in passenger flow while ensuring that those who must be inspected are indeed inspected.

Claims

DEMANDS 1. A method for inspecting (S) an individual using a detector (1) comprising the following steps: 51: generation of a magnetic field when an individual is in a passage of the detector and acquisition of electrical signals representative of the magnetic field; 52: analysis of electrical signals to detect the presence of a metallic object; 53: creation of an electronic image of the individual when the individual is in the passage, the electronic image including the head of the individual; 54: when a metallic object is detected, determination of a position of the individual's head in the electronic image; 55: deduction of the position of the metallic object detected in step S2 relative to the individual's head; and 56: when the metallic object is positioned at the level of the individual's head, a specific alert is generated; and 57: Inspection of the individual's head.

2. Inspection method (S) according to claim 1, wherein step S4 comprises a search for a geometric pattern in the electronic image, for example a top of the head, a lower area of ​​the individual's face and / or a base of the individual's neck.

3. Inspection method (S) according to any one of claims 1 and 2, wherein the electronic image is obtained by microwave antennas.

4. Inspection method (S) according to claim 2, wherein the electronic image is obtained by microwave antennas and the search for a geometric pattern comprises the following substeps: - determine the intensity of a background signal; - determine an average intensity of the signal generated by each antenna in the electronic image, preferably by scanning along a height of the detector; - when a difference between the average signal intensity of a given microwave antenna and the background signal intensity exceeds a predefined single value, determine a position for the given microwave antenna; and - to deduce the position of the top of the individual's head.

5. Inspection method (S) according to any one of claims 1 to 4, wherein the detector (1) comprises several windings (7a, 7b) distributed along a height of the detector (1) and in which step S5 includes a step of determining the coils (7a, 7b) located at the level of the individual's head, the specific alert being generated when the coils located at the level of the individual's head correspond to the coils (7a, 7b) which generated the electrical signals corresponding to the detection of the presence of the metallic object.

6. Detection inspection method (S) according to any one of claims 1 to 5, further comprising a step of processing electrical signals and the electronic image so as to obtain a combined electronic image comprising the metallic object detected by a central unit of the detector, and where appropriate a step of displaying the combined electronic image.

7. Inspection method (S) according to any one of claims 1 to 6, wherein when the position of the metallic object is not at the level of the individual's head, a different alert from the specific alert is generated.

8. Inspection method (S) according to any one of claims 1 to 7, further comprising the following steps: S9: when a metallic object is detected in step S2, determination of the position of the metallic object relative to a lower area of ​​the individual's body; 510: when the metallic object is located in a lower area of ​​the individual's body, an additional alert is generated; and 511: Inspection of the lower area of ​​the individual's body.

9. Inspection method (S) according to claim 8, further comprising a step S8 of determining a position of the lower area of ​​the individual's body from the electronic image obtained in step S3.

10. Inspection method (S) according to claim 9, wherein step S8 is carried out by searching for a geometric pattern in the electronic image.

11. Inspection method (S) according to any one of claims 8 to 10, wherein the detector (1) comprises several windings (7a, 7b) distributed along a height of the detector (1) and, during step S8, the detector (1) determines whether the windings (7a, 7b) which generated the electrical signals correspond to the windings located in the lower part of the panels.

12. Inspection method (S) according to any one of claims 8 to 11, wherein step S10 is carried out by an additional detector (1) independent of detector (1). 17 13. Detector (1) comprising: - two opposite side panels (2) fixed to each other and together delimiting a passage; - inductive type detection means comprising at least one transmitter coil (7a) configured to generate a magnetic field and at least one receiver coil (7b) configured to acquire electrical signals representative of a disturbance of the magnetic field by a metallic object; - radiant energy detection means (5), for example microwave antennas, housed in at least one of the side panels (2); - a central unit (6) configured to implement the steps of the inspection process (S) according to any one of claims 1 to 12; and - an alarm configured to generate a specific alert.

14. Detector (1) according to claim 13, comprising several coils distributed over a height of the detector (1), the central unit (6) being configured to identify, by means of radiant energy detection means (5), the coils (5a, 5b) located at the height of the individual's head.

15. Detection system comprising a detector (1) according to any one of claims 13 and 14 and an additional detector independent of detector (1), the additional detector (1) being configured to inspect a lower area of ​​an individual's body.

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