Consideration of footwear in the detection of unauthorized objects or materials in a restricted access area

Abstract

The present invention relates to a method for inspecting an individual using a radiant energy detector (1) comprising the following steps: S1: placing the individual within a passage delimited between lateral panels (2) of the detector (1) such that a lateral face of the shoe is substantially parallel to the lateral panels (2); S2: acquiring an electronic image of the individual, the electronic image including the shoe; S3: identifying, in the electronic image, the position of an underside (10) of the individual's foot; S4: estimating, from the position of the underside (10) of the foot in step S3, a volume of interest of the sole (10); and S5: generating an alert when the volume of interest of the sole (10) is greater than or equal to the threshold volume. Figure for the abstract: Fig. 7

Description

Title of the invention: Taking shoes into account in the detection of unauthorized objects or materials in a restricted access area. FIELD OF THE INVENTION

[0001] The present invention relates to the field of detection of unauthorized objects or materials in a protected access area. STATE OF THE ART

[0002] It now appears necessary to reliably control attempts to introduce or remove prohibited goods, particularly weapons or explosives, into or from a sensitive area. The problem thus posed covers a very wide range of situations, including, but not limited to, attempts to introduce prohibited goods into a protected area, such as an airport, a store, a school, a train station, a public or private organization, or attempts to remove goods from a defined perimeter, for example, in the event of a theft from a company or a protected site.

[0003] Various types of metal object detectors exist. In particular, continuous wave metal object detection portals have been proposed for many years. These portals use an inductive field whose waves have constant amplitude and frequency in frequency ranges typically between 70 Hz and 50 kHz. They comprise at least one transmitter coil and at least one receiver coil. The transmitter coil is powered by an alternating electric current. The receiver coil is designed to detect disturbances in the magnetic field generated by the transmitter coil due to the presence of a metallic object, for example, the attenuation of the magnetic field amplitude, or even the phase change of the signal, due, for example, to eddy currents generated on the metallic object.These detectors are very effective and are capable of detecting the presence of metallic objects throughout the entire volume of the individual, that is, from head to toe, including in shoes or body cavities.

[0004] It has also been proposed to use body scanners. The oldest body scanners are X-ray body scanners. More recent body scanners use so-called millimeter wave (or microwave) technology. An example of a body scanner can be found in document EP 202 700.

[0005] For several years, body scanners (generally referred to by their Anglo-Saxon terminology "body scanner") have been developed to detect weapons, explosives, etc., hidden 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.

[0006] Regardless of the type of radiant energy and imaging geometry, these body scanners all operate on the principle of creating an electronic image of the individual in which the individual's 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 object. However, it turns out that, to date, body scanners are not certified to inspect the contents of shoes, particularly to detect threats placed between the person's 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.

[0007] This is why security authorities require individuals to remove their shoes. Individuals then pass, barefoot, through the body scanner, while their shoes are 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 removing and handling the shoes. It also poses hygiene problems, as the shoes are placed in the same trays used for inspecting clothing and personal belongings. Furthermore, it requires individuals to walk barefoot on the ground. Finally, people with reduced mobility (the elderly, pregnant women, etc.) may have difficulty removing and putting on their shoes, which further slows down the inspection process.

[0008] To solve this problem, WO 2020 / 157139, submitted on behalf of the Applicant, proposes an integrated security scanner comprising a microwave field imaging body scanner and inductive field detection means. In this way, any type of metallic object (knives, firearms, metallic improvised explosive devices) is identified, regardless of its location. However, the need to detect explosives inside the sole of the shoe remains. In this case, the materials are dielectric, non-metallic, and non-conductive, and cannot be detected by inductive field detection means.

[0009] It has already been proposed to inspect shoes using millimeter-wave imaging systems placed beneath the surface of a platform on which the individual stands. Reference may be made, for example, to US patent 11,520,069, which describes a such a system. However, this system has limitations insofar as it requires the ability to distinguish the shape of the explosive from the rest of the sole, which is not necessarily easy when the explosive is distributed in a constant thickness across the surface of the sole and / or when the sole material is impermeable to radio waves.

[0010] Independent inspection systems configured to analyze an individual's leg and shoes have also been proposed in documents FR3050283, FR3050285, FR3050284, FR3072467, and FR3072470 on behalf of the Applicant. These systems comprise both an inductive magnetic field detection system for intercepting metallic threats—knives, pistols, metallic improvised explosive devices—and a millimeter-wave radio frequency field for detecting non-conductive materials, such as explosives.The radio frequency system measures the properties of dielectric materials (such as explosives) by either reflection or absorption. This specific system does not require removing shoes and is usually installed next to the body scanner. After the body scanner screening, the passenger is guided by a security officer to place their foot, shoe-on, into the shoe analysis system. The analysis takes only a few seconds per leg.

[0011] However, since the shoe analysis system is separate from the body scanner, it still slows down the flow of passengers at the security checkpoint. In practice, it turns out that it is not necessary to analyze all passengers' shoes. The sole of the shoe must have sufficient volume to contain and conceal an explosive. Therefore, some security authorities choose to instruct security officers to visually inspect shoes and only examine those with soles thick enough to contain an explosive.

[0012] However, the variety of shapes and sizes of current shoes is such that a visual inspection can be misleading. For example, there are platform shoes whose heel is concealed within the upper of the sole: the sole of these shoes therefore appears thin when viewed from the outside, whereas in reality the wearer's heel is raised, thus creating a cavity that could contain an explosive. Description of the invention

[0013] An object of the invention is to propose an inspection method and an associated radiant energy detector for the detection of target objects which overcomes the aforementioned disadvantages.

[0014] In particular, an object of the invention is to provide an inspection method and an associated radiant energy detector that improves passenger flow at control post, while improving the detection of target objects, especially in shoes.

[0015] To this end, according to a first aspect of the invention, a method for inspecting an individual using a radiant energy detector is proposed, in which the individual wears a shoe having a sole, a toe, a heel, and two lateral faces connecting the toe and the heel. The inspection method comprises the following steps: SI: placement of the individual within a delimited passage between side panels of the detector so that one side face of the shoe is substantially parallel to the side panels; S2: creation of an electronic image of the individual, the electronic image including the shoe; S3: identification in the electronic image of a position of the underside of the individual's foot; S4: estimation, based on the position of the underside of the foot at step S3, of a volume of interest for the sole; and S5: generates an alert when the volume of interest of the sole is greater than or equal to the threshold volume.

[0016] Certain preferred but non-limiting features of the inspection process according to the first aspect are the following, taken individually or in combination: - the inspection process further comprises the following steps, prior to step S7: SI': placement of the individual within the passage so that one lateral face of the shoe is substantially perpendicular to the side panels; S2': creation of an additional electronic image of the individual, the additional electronic image including the shoe; and S3': determination in the supplementary electronic image, of a position of the underside of the individual's foot; the S4 stage of estimating the volume of interest being further based on the positions determined in the S3 stage; - steps SI and S2 are carried out entirely before or after steps SI' and S2', the process may also include a step of sending instructions to the individual to change position between steps S2 and SI' or between steps S2' and SI; - Step S4 for estimating the volume of interest is based on an estimated value of the width of the shoe; - The inspection process further includes a step of estimating the shoe length in the electronic image, and the estimated value of the shoe width. being a function of the shoe length estimated in the electronic image, for example equal to 0.25 times the shoe length; - the volume of interest includes an estimate of the total volume of the sole or an estimate of the volume of a rear portion of the sole, the rear portion extending from the heel of the shoe over a distance of between two-thirds and three-quarters of a foot length; - the inspection process further includes a step of inspecting the individual's shoe when the alert is generated; - during the SI step, the individual's shoe is placed at a predetermined distance from the side panels; - the inspection procedure also includes, prior to step S6, the following inductive field inspection steps: - generation of a magnetic field when the individual is present in the passage; - acquisition of electrical signals representative of the magnetic field; - analysis of electrical signals to detect the presence of a metallic object; - when a metallic object is detected, determination of the position of the metallic object relative to the individual's body; and - when the metallic object is positioned between the individual's shoe and knee, an alert is triggered; and / or - the signals representing radiant energy and electrical signals are combined in such a way as to generate a unique electronic image of the individual.

[0017] According to a second aspect, a detector is proposed comprising: - two fixed, opposing side panels, fixed to each other and together defining a passage; - radiant energy transducers, for example microwave antennas, housed in at least one of the side panels; and - a central unit configured to implement an inspection process according to the first aspect.

[0018] Certain preferred but non-limiting features of the detector according to the second aspect are as follows, taken individually or in combination: - the detector further comprises inductive detection means including 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, the central unit being configured to analyze the electrical signals and detect a disturbance of the magnetic field due to the presence of a metallic object in the passage; and / or - The central unit is configured to determine the position of the metallic object relative to the detector and generate the alert when the presence of a metallic object is detected in the lower part of the detector. DESCRIPTION OF THE FIGURES

[0019] Other features, objectives and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0020] Fig. 1 schematically illustrates an example of an embodiment of a detector. In this figure, an individual to be inspected is placed so that the lateral face of his shoes is substantially parallel to the side panels, and the surfaces of the individual likely to be explored by radiation transducers have been schematically represented.

[0021] Fig. 2 schematically illustrates the lateral face of a first example of a shoe comprising a prohibited dielectric material worn by an individual and a graph representing the height h, which corresponds to the distance in the electronic image between the platform and the underside of the foot wearing this shoe, as a function of the distance 1 between the end of the heel and the end of the toes of the individual.

[0022] Fig. 3 schematically illustrates the lateral face of a second example of a shoe comprising a prohibited dielectric material worn by an individual and a graph representing the height h, which corresponds to the distance in the electronic image between the platform and the underside of the foot wearing this shoe, as a function of the distance 1 between the end of the heel and the end of the toes of the individual.

[0023] Fig. 4 schematically illustrates the detector of Fig. 1, in which an individual to be inspected is placed so that the lateral face of his shoes is substantially perpendicular to the side panels.

[0024] Fig. 5 schematically illustrates the front face of the first shoe example.

[0025] Fig. 6 schematically illustrates the front face of the second shoe example.

[0026] Fig. 7 is a flowchart of steps of an example implementation of an inspection process, in which the optional steps have been boxed in dashed lines.

[0027] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

[0028] A detector 1 comprises two opposing side panels 2 which are fixed and together delimit a passage forming a transit channel for a person to inspect. The transit channel thus includes an inlet and an outlet, positioned at opposite ends of the side panels 2.

[0029] The side panels 2 are substantially symmetrical with respect to a central plane (fictitious 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 may be separate and distinct, i.e., not connected via a ceiling or a platform 4.

[0030] 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.

[0031] The detector 1 includes radiant energy detection means formed of a series of radiant energy emitter / receiver transducers 5 and a central unit 6 configured to receive signals representative of the radiant energy reflected and measured by the transducers 5 and to deduce an electronic image.

[0032] The transducers 5 are arranged at 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.

[0033] 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.

[0034] In what follows, the invention will be described more particularly in the case where the transducers 5 comprise microwave antennas 5, that is to say, antennas 5 configured to generate waves with a wavelength between 3 mm and 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, for example, 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 for detecting objects concealed under clothing and make it possible 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, as receivers, which then transmit to the central unit 6 a signal representative of this reflected energy which analyzes it to generate an electronic image of the individual. inspected, on which his clothes are essentially transparent. Where applicable, detector 1 further includes a network interface configured to receive signals representative of reflected energy and transmit them to central unit 6.

[0035] The central unit 6 may in particular include a computer of the type processor, microprocessor, microcontroller, etc., configured to execute code instructions in order to process the signals representative of the radiant energy reflected and measured by the transducers 5 and to deduce an electronic image.

[0036] Optionally, detector 1 further includes presence detection means, for example, an optical barrier placed at the entrance of detector 1 and each comprising a pair of transmitter / receivers arranged respectively in the two side panels 2. Where appropriate, 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 an individual.

[0037] 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 inspected individual whether it can enter detector 1. The signal can, for example, be of the green light / red light type (see [Fig.5]).

[0038] This disclosure is based on the principle that the reflectivity of millimeter waves on skin is very strong, while clothing and footwear are made of wave-permeable materials. It is therefore possible to determine, in an electronic image, the position and shape of an individual's foot with precision, regardless of the type of footwear worn. This information can then be used to determine whether the individual's footwear requires specific inspection or whether inspection using detector 1 is sufficient.

[0039] For this purpose, an inspection method is proposed comprising the following steps: SI: placement of the individual within the passage delimited between the side panels 2 of the detector 1 so that a lateral face of the shoe is substantially parallel to the side panels 2; S2: creation of an electronic image of the individual, the electronic image including the shoe; S3: determination in the electronic image, of a position of an inferior face 10 of the individual's foot; S4: estimation, based on the position of the underside 10 of the foot at step S3, of a volume of interest for the sole 11; and S5: generates an alert when the volume of interest of sole 11 is greater than or equal to the threshold volume.

[0040] More specifically, during the SI step, the individual enters the detector 1 and is placed between the side panels 2, in a predetermined position called lateral (see [Fig.1]).

[0041] In this lateral position, the lateral face of at least one of the individual's shoes is parallel to the side panels 2, so that the electronic image represents the entire shoe, from toe to heel. The person is therefore facing the exit of the passage, with their sides positioned facing the side walls.

[0042] Preferably, the individual's two shoes are parallel to the side panels 2.

[0043] To facilitate the positioning of the individual 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. The visual indicators may include markings on the platform 4 and / or an image projected onto an area of ​​the platform 4 (or, where applicable, onto the floor in the absence of a platform 4).

[0044] When the inner face 3 of the side walls is curved, the person is positioned so that the shoe is substantially parallel to the general extension direction X of the walls 2.

[0045] During step S2, all or part 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 in the direction of the passageway. These microwave waves interact with the facing surface, and in particular the lateral surface of the individual's foot, the lateral surface of the shoe covering their foot, and any object possibly concealed by that person, as well as the inner surface 3 of the facing side panel 2. These interactions modulate the energy of the microwave waves which, once reflected, return to the antenna(s) 5, which act as a receiver.

[0046] The reflected energy from each part of the person to be inspected is measured by the antennas 5, acting as receivers. Each antenna 5 then transmits a signal representing this reflected energy to the central unit 6 for processing and creation of the electronic image of the individual. If necessary, this transmission can be carried out via a network interface.

[0047] During step S3, the position of the lower face 10 of the individual's foot is determined in the electronic image by the central unit 6.

[0048] To this end, the electronic image is processed to identify the boundary of the lower face 10 of the foot. This boundary is determined by image processing. In one embodiment, the boundary of the lower face is determined by image segmentation using a neural network. Image segmentation is an end-to-end image analysis process that consists of dividing a digital image into several segments and classifying the information contained in each region. For Image segmentation assigns a label to each pixel in the image to define the outlines and shape of the different objects and regions within the image. They are then classified according to various criteria: color, contrast, position in the image, etc.

[0049] Preferably, the boundary of the lower face is determined by semantic segmentation. Semantic segmentation is a type of image segmentation that relies on a deep learning algorithm to classify each pixel by assigning it a label. Semantic segmentation identifies sets of pixels and classifies them according to different characteristics.

[0050] Thus, the central unit 6 assigns the same label to the pixels of the electronic image corresponding to the foot, and a different label to the pixels in the background.

[0051] In one embodiment, the semantic segmentation method used is the thresholding method. This method is based on a clipping level (or threshold value) to transform the grayscale electronic image into a binary image. The key to this method is selecting the threshold value (or values ​​when several levels are selected). The intensity of each pixel in the source electronic image is multiplied by a weighting coefficient and then added to a shift value. This process is repeated, cascading, for a certain number of cycles, typically from 4 to 8 cycles. The output value of the last cycle is then compared with a threshold value, set, for example, to 0.5 on a scale of 0 to 1. If the input value is greater than 0.5, the comparator output will be 1; conversely, if the comparator input value is less than 0.5, the comparator output will be 0.A value of 1 corresponds to an activated pixel, a value of 0 to a deactivated pixel. In this way, the central processing unit 6 goes from the initial electronic image to an output image where the foot is clearly identified, for example by a white area, while the background and, in particular, the area between the sole of the foot and the ground, is identified by a black area.

[0052] The multiplication and compensation coefficients of the neural network can in particular be determined through training carried out on more than a thousand feet with different types of shoes, typically summer or winter shoes, open or closed, etc.

[0053] Optionally, once the boundary of the lower face 10 of the foot is detected in the electronic image, the central unit 6 corrects the boundary to take into account the curved shape of the lower face. Indeed, microwave imaging techniques exhibit a lack of reflection from the bottom of the foot for a thickness of approximately one centimeter between the foot itself and the ground. This lack of reflection is caused by the curvature of the distal part of the sole of the foot. It can therefore be taken into account when calculating the effective distance between the foot and the ground. For this purpose, the boundary is shifted (lowered) by a predetermined distance in the direction of platform 4, for example by 1 cm.

[0054] During step S4, a volume of interest of the footing 11 is estimated by the central unit 6. In a first embodiment, the volume of interest of the footing 11 corresponds to the volume of the space extending between the lower limit 10 (corrected or not) of the foot and the surface of the platform 4 (or even of the ground in the absence of a platform 4).

[0055] To this end, the central unit 6 determines the area in the electronic image between the lower limit (corrected or uncorrected) determined in step S3 and the platform 4 (or, where applicable, the ground in the absence of a platform 4). The position of the platform 4 in the electronic image can be predetermined, the position of the platform 4 and the microwave antennas 5 being known and fixed. Alternatively, the central unit 6 can determine the position of the platform 4 in the electronic image.

[0056] Since the shoe is substantially parallel to the side panels 2 and the distance between the shoe and the microwave antennas 5 is known at step S2, since the individual's shoe is placed in a determined position relative to the side panels 2 at step SI, the central unit 6 deduces the surface of interest which separates the lower limit of the foot and the platform 4 by applying a scale factor to the surface determined at step S3.

[0057] The area of ​​interest between the lower limit and the platform 4 thus determined then corresponds substantially to the actual area of ​​the lateral face of the sole 11.

[0058] For example, the upper part of [Fig. 2] illustrates an example of a sneaker-type shoe worn by an individual and comprising, in the sole 11, a material 12 whose dielectric properties are different from those of the sole 11. The height H corresponds to the distance in the electronic image between the platform 4, on which the shoe rests, and the lower face 10 of the foot at the level of the rear limit of the foot (which corresponds to the end of the heel) of the individual. The length L1 corresponds to the distance between the end of the heel and the tips of the toes of the individual in the electronic image and the length L2 corresponds to the distance between the heel and the end of the shoe. The lower part of [Fig.2] As for the other hand, it is a graph representing the height h, which corresponds to the distance in the electronic image between the platform 4 and the lower face 10 of the foot, as a function of the distance 1 between the end of the heel and the tips of the individual's toes. The area of ​​interest of the sole 11 of the shoe in [Fig.2] then corresponds to the integral of the curve h as a function of 1 (lower part of [Fig.2]).

[0059] Figure 3 similarly illustrates an example of heeled shoes including a concealed heel lift. In particular, the upper part of Figure 3 is a graph representing the height h as a function of the distance 1 in the image electronic corresponding to the shoe in [Fig.3], and the surface of interest of the sole 11 of this shoe corresponds to the integral of the curve h as a function of 1 (lower part of [Fig.3]).

[0060] The volume of interest of the footing 11 can then be determined by multiplying the actual surface of the footing 11 by the width of the footing 11. The width of the footing 11 can be a pre-recorded value, an estimated value or a measured value.

[0061] Thus, in a first embodiment, the central unit 6 multiplies the actual surface area by a value pre-recorded in memory. The pre-recorded value may, in particular, correspond to an average of the widths observed on shoes.

[0062] In a second embodiment, the central unit 6 determines the estimated width of the shoe based on the shoe's length. The shoe's length can, for example, be determined from the electronic image by measuring the distance between the toe and the heel of the shoe. The image processing implemented to determine the lower limit of the foot can, for example, be repeated to determine the shoe's length. The estimated width is then equal to a percentage of the length thus determined, the percentage being between 0.22 and 0.30 times the shoe's length, for example, 0.25 times. Indeed, by studying the anthropometric measurements of men and women, the Applicant observed that the ratio between the length and width of an adult's foot is always between 0.35 and 0.38 (regardless of age or gender).Since the length and width of a shoe are correlated with the length and width of a foot, the Applicant determined that selecting a width between 0.22 and 0.30 times the length of the shoe gave volumes of interest very close to the actual volume of the sole 11, with a width equal to 0.25 times the length giving even more precise results.

[0063] In a third embodiment, the central unit 6 estimates the width of the sole 11 in an electronic image. To do this, during a step SI', the individual is placed within the passage delimited between the side panels 2 of the detector 1 so that the lateral face of the shoe is substantially perpendicular to the side panels 2 (see [Fig. 4]). In other words, the person to be inspected pivots 90°, the objective being to position the person facing a side panel 2 so that the toe or heel of the shoe is facing the panel 2. To facilitate the positioning of the individual relative to the side panels 2, the detector 1 may include visual indicators 8 (marking and / or image projected onto the platform 4) configured to indicate to the individual where to position their shoes during step SI'. During a step S2', a new image is acquired by the microwave antennas 5.This electronic image includes the toe (or heel) of the shoe in order to allow central unit 6 to estimate the . shoe width. Preferably, the electronic image includes the toe of the shoe, as the toe is generally wider than the heel, thus increasing the volume determined. During step S3', the position of the underside 10 of the individual's foot is determined. The central processing unit 6 can apply the image processing described in step S3 to determine the lower limit of the foot, and optionally correct this lower limit to account for the curvature of the underside 10 of the foot. During step S4', the central processing unit 6 deduces the width of the foot W. The central processing unit 6 can then calculate the volume of interest of the sole 11 by multiplying the foot width W thus determined by the actual surface area. Alternatively, the central processing unit 6 can estimate the width of the sole 11 by multiplying the foot width determined in step S4' by a multiplier, for example, between 1.1 and 1.3.According to yet another variant, the central unit 6 can determine the area between the lower limit of the foot and the surface of the platform 4 (or where applicable the ground) and deduce the area of ​​interest of the end of the sole 11, and use this area of ​​interest to deduce by integration, from the actual area of ​​the lateral face of the sole 11, the volume of interest of the sole 11.

[0064] For example, [Fig. 5] illustrates a front view of the shoe example from [Fig. 2] worn by an individual. The distance W1 corresponds to the corrected width in the electronic image between the lateral extremities of the lower face 10 of the foot, and the distance W2 corresponds to the width in the electronic image of the individual's shoe. The volume of interest of the sole 11 of the shoe in [Fig. 2] can then be estimated either as a function of the area of ​​interest corresponding to the integral of the curve h as a function of the distance w, or as a function of the distance W1.

[0065] The upper part of [Fig.6] illustrates front view of the example of heeled shoes of [Fig.2].

[0066] It should be noted here that steps SI and S2 can be carried out either before or after steps SI' and S2'. Step S3 (respectively S3') can also be carried out before, during or after steps SI' and S2' (respectively SI and S2).

[0067] In a second embodiment, the volume of interest of the sole 11 corresponds to the volume of a rear portion of the sole 11. Indeed, the Applicant has observed that it is extremely difficult to conceal prohibited dielectric materials in the front portion of the sole 11, which generally corresponds to the first quarter or even the first third of the sole 11 at the toe of the shoe. The volume of the sole 11 that is actually capable of housing a prohibited dielectric material then corresponds to the volume of the rear portion of the sole 11, i.e., three-quarters or even two-thirds of the shoe extending from the heel. In this embodiment, during step S3, the volume of interest that is determined includes only the volume of the rear portion of the sole 11. Taking this volume of interest into account makes it possible to refine the inspection of shoes, a shoe having a platform 4 in the front part may present a significant total volume while the volume actually usable to conceal a prohibited dielectric material may in practice be less than the authorized volume.

[0068] To this end, the central unit 6 determines the anterior and posterior limits of the lower face 10 of the foot in the electronic image, which correspond respectively to the limits of the individual's toes and heel, and deduces the length L1 of the foot. The same image processing can be used to determine the anterior and posterior limits of the foot as for determining the lower limit of the foot. Then, the central unit 6 identifies in the electronic image the posterior part of the foot, which extends from the heel over a distance of between 2 / 3 and 3 / 4 of the foot's length, and determines the volume of interest corresponding to the volume between the lower limit of the foot (possibly corrected) and the platform 4 (or even the ground, in the absence of a platform 4), along the posterior part of the foot.The determination of the rear portion's volume can be carried out in the same way as the determination of the total volume of the sole 11 (first variant), the only difference being that the determination of the actual surface area of ​​the lateral face of the sole 11 only takes into account the part of the image corresponding to the rear portion of the sole 11. Alternatively, the volume of the rear portion can be estimated from the total volume of the sole 11 and correspond to 2 / 3 or 3 / 4 of the total volume determined in step S3, depending on the definition chosen for the rear portion. For example, choosing a rear portion corresponding to 2 / 3 of the shoe's length allows a sufficient volume to be excluded from the front portion of the shoe and provides more precise information on the risk of material being concealed within the sole 11.

[0069] Optionally, the volume of interest (whether the total volume or the volume of the rear portion of the sole 11) is adjusted to account for the need for the shoe to maintain its fit and structural function. Indeed, when an individual conceals an object in the sole 11 of their shoe, they must maintain a certain thickness of sole 11 beneath the concealed object to ensure that the object remains confined within the shoe when moving through the protected access area. This thickness of sole 11 can therefore be subtracted from the volume of interest when comparing it with the predetermined volume, thus further refining the results obtained. For example, a volume corresponding to a sole thickness 11 of 5 mm (along the entire length of the sole 11 or along the rear portion of the sole 11, depending on the definition of the volume of interest) can be subtracted from the volume of interest.

[0070] Alternatively, the predetermined volume with which the volume of interest is compared in step S5 can be reduced to take into account the existence of this thickness of sole 11. This alternative is however less precise since the volume removed depends on the length and width of sole 11.

[0071] During step S5, the volume of interest determined for the sole 11 is compared to the predetermined volume.

[0072] Security authorities require that detectors generate an alert when an individual is carrying a mass exceeding a given threshold of prohibited dielectric material (such as material used to manufacture explosives). The predetermined volume is therefore set according to this given mass.

[0073] When the volume of interest is greater than or equal to the predetermined volume, the central unit 6 sends instructions to generate an alert. The alert serves to warn the security officer that the individual is wearing shoes with a sole 11 that has a volume sufficient to conceal a prohibited dielectric material. The alert may, for example, include a message displayed on the screen 11 that shows the individual's electronic image, a visual alarm on the gate (such as an LED), an audible alarm, etc.

[0074] During an S6 step, when an alert is generated, the security officer proceeds to inspect the individual's shoes, either manually 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.

[0075] The inspection method thus assists security personnel in selecting individuals whose footwear requires specific inspection. It is therefore no longer necessary to systematically inspect footwear, thereby avoiding unnecessary delays to passenger flow, while ensuring that footwear with a sole 11 of sufficient volume to contain a prohibited dielectric material is identified.

[0076] Of course, the electronic image produced by the central unit 6 can also include the rest of the individual's body. Thus, during step S3 (and, where applicable, step S3'), the central unit 6 determines the presence of a target object (knives, firearms, improvised explosive device, etc.) on the surface of the individual's body. Furthermore, when a target is identified by the central unit 6, said target can be displayed in the electronic image and an alarm (audible and / or visual) can be generated by the detector 1.

[0077] In the case where an electronic image is taken in two different positions (steps SI to S3 and SI' to S3'), an inspection method in accordance with the disclosure of document WO 2021 / 209505 can be implemented in order to improve object detection.

[0078] In one embodiment, the detector 1 further comprises continuous wave inductive field detection means, including 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 a determined and controlled frequency range, to generate a magnetic field, typically between 100 Hz and 50 kHz. The receiver coil 6b is designed to acquire electrical signals representative of the magnetic field generated by the receiver coil 6b.The central unit 6 is also configured to analyze 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 in the passage, for example the attenuation of the amplitude of the magnetic field, or even the change in phase of the signal, due for example to eddy currents generated on the metallic object.

[0079] In practice, each of the transmitter 7a and receiver 7b coils is preferably formed of a plurality of elementary coils or turns, covering a respective portion of the gantry height, to allow discrimination of the position of the detected metal targets and thus localize the position of these targets vertically. Each of the coils 7a, 7b can alternately act as a transmitter and receiver.

[0080] In one embodiment, the detector 1 comprises several transmitter coils 7a and receiver coils 7b distributed along the height of the side panels 2 so as to determine the position of the metallic object. In particular, the detector 1 comprises transmitter coil(s) 7a and receiver coil(s) 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. The central unit 6 can thus determine the position of the metallic object and generate an alert when the presence of a metallic object near the platform 4 is detected.

[0081] The alert generated by the central unit 6 upon detection of a metallic object by the coils 7a, 7b can be identical to the alert generated by the central unit 6 upon detection of a volume of interest greater than or equal to the predetermined volume, the principle being to warn the security officer of the need for a specific inspection of the individual's shoes (and, where applicable, legs). 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.

[0082] The generation of the magnetic field and the acquisition of electrical signals by the windings 7a, 7b can be carried out continuously. Alternatively, the generation and Signal acquisition can be triggered by passage detection means.

[0083] Reference may 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.

[0084] In one embodiment, the coils 7a, 7b are placed at the input of the detector 1, upstream of the radiant energy detection means 5. The individual therefore passes in front of the inductive field type detection means 7a, 7b before positioning themselves in front of the radiant energy detection means 5. The generation of the magnetic field and the acquisition of electrical signals by the coils 7a, 7b (step S7 in [Fig. 7]) are thus carried out while the individual is in transit through the passage. The individual does not, in fact, need to remain stationary between the coils 7a, 7b. Thus, the signals are acquired while the individual is transiting through the passage towards the transducers 5 and can be processed by the central unit 6 while the individual is positioned within the panels (steps S1 / S1').Alternatively, the central unit 6 can process the electrical signals generated by the coils and the signals representing the radiant energy reflected and measured by the transducers 5 simultaneously. The fact that the individual is moving during detection does not prevent the determination of the position of any metallic objects, as the vertical displacement of the feet during walking is limited.

[0085] Advantageously, the inductive field means 7a, 7b enable the central unit 6 to detect the presence of a metallic object in the shoes, regardless of their shape. In particular, thanks to the inductive field means 7a, 7b, the central unit 6 is able to detect the presence of a small metallic object, such as a blade, which could be concealed in a small insole 11 (or even between the individual's foot and the insole 11). Conversely, a prohibited dielectric material must have a minimum mass (and therefore a minimum volume) to be likely to cause damage considered risky. The combination of the inductive field means 7a, 7b, for the detection of small metallic objects, with the detection of the volume of interest of the insoles 11, for the detection of prohibited dielectric materials, among other things, thus ensures a complete and efficient inspection of the individual, including their shoes.

[0086] The Applicant observed that the actual volume of passengers' soles in warm weather was on average comparable to the actual volume of soles in cold weather and that, on average, only 15% of shoes had a sole whose volume of interest (corresponding to the back part of the shoe (which extends over 2 / 3 of the shoe's length)) was greater than or equal to the predetermined volume (corresponding to current safety authority requirements). The possibility Identifying the actual volume of the soles of shoes allows for a significant increase in passenger flow, while ensuring the possibility of checking passengers' footwear for prohibited dielectric materials. It is indeed possible to inspect only about 15% of passengers' shoes, instead of all of them.

Claims

Demands

1. A method for inspecting an individual using a radiant energy detector (1), wherein the individual wears a shoe having a sole (10), a toe, a heel, and two lateral faces connecting the toe and the heel, the inspection method (S) comprising the following steps: S1: placing the individual within a passage delimited between lateral panels (2) of the detector (1) such that one lateral face of the shoe is substantially parallel to the lateral panels (2); S2: acquiring an electronic image of the individual, the electronic image including the shoe; S3: identifying, in the electronic image, a position of an underside (10) of the individual's foot; S4: estimating, from the position of the underside (10) of the foot in step S3, a volume of interest of the sole (10); and S5: generation of an alert when the volume of interest of the sole (10) is greater than or equal to a threshold volume.

2. An inspection method according to claim 1, further comprising the following steps, prior to step S4: S1': placing the individual within the passage so that a lateral face of the shoe is substantially perpendicular to the lateral panels (2); S2': acquiring an additional electronic image of the individual, the additional electronic image including the shoe; and S3': determining in the additional electronic image, a position of the lower face (10) of the individual's foot; step S4 of estimating the volume of interest being further based on the positions determined in step S3'.

3. Inspection method (S) according to claim 2, wherein steps S1 and S2 are carried out entirely before or after steps SI' and S2', the method may further include a step of sending instructions to the individual to change position between steps S2 and SI' or between steps S2' and SI.

4. Inspection method according to claim 1, wherein the step S4 of estimating the volume of interest is based on an estimated value of a shoe width.

5. An inspection method according to claim 4, further comprising a step of estimating the length of the shoe in the electronic image, the estimated value of the width of the shoe being a function of the shoe length estimated in the electronic image, for example equal to 0.25 times the length of the shoe.

6. An inspection method according to any one of claims 1 to 5, wherein the volume of interest comprises an estimate of the total volume of the sole (10) or an estimate of the volume of a rear portion of the sole (10), the rear portion extending from the heel of the shoe over a distance of between two-thirds and three-quarters of a foot length.

7. An inspection method according to any one of claims 1 to 6, further comprising a step of inspecting the individual's shoe when the alert is generated.

8. An inspection method according to any one of claims 1 to 7, wherein, during step SI, the individual's shoe is placed at a predetermined distance from the side panels (2).

9. An inspection method according to any one of claims 1 to 8, further comprising, prior to step S6, the following inductive field inspection steps (S7): - generation of a magnetic field when the individual is present in the passage; - acquisition of electrical signals representative of the magnetic field; - analysis of the electrical signals to detect the presence of a metallic object; - when a metallic object is detected, determination of a position of the metallic object relative to the body of the individual; and - when the position of the metallic object is between the shoe and the knee of the individual, generation of the alert (S6).

10. An inspection method according to claim 9, wherein the signals representing radiant energy and electrical signals are combined so as to generate a unique electronic image of the individual.

11. Detector (1) comprising: - two opposing side panels (2) fixed relative to each other and together delimiting a passage; - radiant energy transducers (5), for example microwave antennas, housed in at least one of the side panels (2); and - a central unit (6) configured to implement an inspection method (S) according to any one of claims 1 to 10.

12. Detector (1) according to claim 11 further comprising 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, the central unit (6) being configured to analyze the electrical signals and detect a disturbance of the magnetic field due to the presence of a metallic object in the passage.

13. Detector (1) according to claim 12, wherein the central unit (6) is configured to determine a position of the metallic object relative to the detector (1) and generate the alert when the presence of a metallic object in the lower part of the detector (1) is detected.

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