Combined detector for detecting metal and magnetized targets

Abstract

The present invention relates to a combined detector (1), comprising: an active metal detection system (10), which comprises: ■ at least two vertical pillars (12) that jointly define a transition channel, and ■ windings (14, 15) distributed in the two vertical pillars (12), the windings being configured to emit an alternating magnetic field and being suitable for generating a signal representing the magnetic field disturbance caused when an individual passes between the two vertical pillars (12), and at least one passive metal detection system (20), which comprises at least one static magneto sensor (22), the static magneto sensor being configured to generate a signal indicating the strength of the static magnetic field, the passive metal detection system (20) being accommodated in one of the vertical pillars (12).

Description

Technical Field

[0001] The present invention relates to the field of target object detection. Background Art

[0002] Recently, various small phones and smartphones have appeared on the market that have proven to be undetectable by conventional walk-through metal detectors. In fact, the amount of metal contained in these devices has been reduced to a minimum due to the use of metallized plastics (e.g. RF shielding) or due to solutions molded in conductive plastics.

[0003] Of course, as long as these mobile phones always contain more or less metal, a walk-through metal detector will be able to detect such mobile phones if its sensitivity is high enough. However, this sensitivity is not suitable for all situations where inspection is required. Therefore, a choice must be made between adjusting the sensitivity of the walk-through metal detector to a level high enough to allow it to detect any metal element (including small phones) (which means that as long as the inspected person carries metal, the walk-through detector will generate a large number of unnecessary alarms), or adjusting the sensitivity to a moderate level (which allows the walk-through metal detector to detect large metal objects (such as weapons) without detecting small metal objects in daily life (watches, belts, etc.), thus avoiding the generation of false alarms). However, when the sensitivity is moderate, the walk-through metal detector will no longer be able to detect small objects such as small phones.

[0004] Alternatively, detection of mobile phones can also be performed using a single portable barrier comprising a static magneto sensor. Such a barrier generally comprises a column fixed to a base and equipped with at least one static magneto sensor, for example three static magneto sensors distributed over the height of the column. Each sensor is configured to generate a signal (voltage) indicating a change in the strength of the detected magnetic field.

[0005] Document EP 1 750 149 describes an example of a walk-through metal detector comprising coils distributed in the vertical supports of the walk-through detector, the coils being configured to emit an alternating magnetic field and being adapted to generate a signal representative of the disturbance of the magnetic field caused when an individual passes between the two vertical supports. However, this example of a walk-through detector does not allow the simultaneous detection of small target objects of the small mobile phone type and large metal objects, such as weapons.

[0006] The document "WI CODE: 11443 PRODUCT DATA SHEET WG Portable Walk-By mobile" by Westminster International Ltd. describes a detector including a detection system. However, the operation of the detector is not described in detail.

[0007] The article "Design of an electromagnetic imaging system for weapon detection based on GMR sensor arrays" by GUI UEN TIAN et al., published in SENSORS AND ACTUATORS A: PHYSICAL, ELSEVIER BV, NL, describes a detector that includes a conventional active metal detection system and an additional system that includes GMR (Giant Magneto-Resistance) sensors. GMR sensors measure the distortion of the alternating magnetic field generated when a metal object passes through the detector to obtain an image of the object. Again, the detector in this article does not allow for the simultaneous detection of large and small target objects. Summary of the invention

[0008] The object of the present invention is therefore to propose a novel detection device capable of improving the detection of target objects that may be carried by an individual, whether small target objects such as small mobile phones or large metal objects such as weapons, and regardless of the environment in which the detection is performed.

[0009] To this end, the present invention proposes a combined detector, comprising:

[0010] - An active metal detection system (10) comprising:

[0011] ■ at least two vertical supports defining a transition passage therebetween, and

[0012] ■ coils distributed in the two vertical supports, the coils being configured to emit an alternating magnetic field and suitable for generating a signal representative of the disturbance of the magnetic field caused by an individual passing between the two vertical supports,

[0013] - at least one passive metal detection system comprising at least one magnetostatic sensor configured to generate a signal indicative of a strength of a static magnetic field, said passive metal detection system being housed in one of said vertical supports.

[0014] Some preferred but non-limiting features of the above combined detector are as follows, which features can be used alone or in combination:

[0015] - The combined detector further comprises at least one conductive shield associated with the at least one magnetostatic sensor and configured to short-circuit surface currents.

[0016] - Each magnetostatic sensor is surrounded by a conductive shield.

[0017] - Each magnetostatic sensor has a determined height, and the height of the conductive shield is greater than the determined height of the associated magnetostatic sensor, preferably the height of the conductive shield is at least equal to 1.5 times the determined height of the associated magnetostatic sensor.

[0018] - said at least one magnetostatic sensor is centered in height relative to said associated conductive shield.

[0019] - The passive metal detection system comprises: at least two static magneto sensors distributed at the height of the passive metal detection system, each static magneto sensor being surrounded by a conductive shield, and a separation sleeve made of an electrically insulating material, the separation sleeve being placed between the two conductive shields to separate the conductive shields.

[0020] - The conductive shield is connected to a fixed potential, such as ground.

[0021] - Each passive metal detection system of the combined detector comprises at least two magnetostatic sensors, the at least two magnetostatic sensors of each passive metal detection system being connected to a fixed potential in a star configuration.

[0022] - The combined detector also comprises a central processing unit and a processing unit, the central processing unit being connected on the one hand to the coil and on the other hand to at least one magnetostatic sensor and being configured to simultaneously receive and process a signal representative of a disturbance in the alternating magnetic field and a signal indicative of the strength of the static magnetic field.

[0023] - The central processing unit is further configured to temporally and / or spatially correlate the signal representing a disturbance in the alternating magnetic field with the signal indicative of the strength of the static magnetic field.

[0024] - The combined detector further comprises a transmitter, the central processing unit being configured to send an alarm generating instruction to the transmitter when the signal representing a disturbance in the alternating magnetic field is greater than a first predetermined threshold and / or when the signal indicating the strength of the static magnetic field is greater than a second predetermined threshold.

[0025] - The combined detector comprises at least two passive metal detection systems, each of which comprises at least one static magneto sensor, the static magneto sensors of each passive metal detection system being positioned in pairs at the same height relative to the ground to form a pair of opposing sensors, each passive metal detection system being housed in an associated vertical support and connected to the central processing unit, the central processing unit being configured to calculate a value based on the signals generated by the static magneto sensors of the two passive metal detection systems, the calculated value comprising one of the following values: an average value of the signals generated by the static magneto sensors in each pair of static magneto sensors; an average value, a sum or a maximum value of the correction values ​​of the signals generated by the static magneto sensors obtained by applying an attenuation coefficient to the signals generated by each pair of sensors; a sum of the values ​​of the signals generated by each pair of static magneto sensors; a maximum value among the values ​​of the signals generated by each pair of static magneto sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other characteristics, objects and advantages of the invention will become more apparent on reading the following detailed description and with reference to the accompanying drawings, given by way of non-limiting examples, in which:

[0027] Figure 1 is a schematic diagram of a combined detector according to an embodiment of the present invention.

[0028] Figure 2 is a perspective view of an example of a combined pole detector according to an embodiment of the present invention, which is shown in a transparent manner and schematically represents the transmitter and receiver coils of an active metal detection system with an alternating magnetic field, and two passive metal detection systems housed in corresponding panels of the combined detector.

[0029] Figure 3 1 is a perspective view of an example of a combined panel detector according to an embodiment of the present invention, in which the upper portion of one of the columns is omitted in order to partially show the upper portion of the passive metal detection system.

[0030] Figure 4 yes Figure 3 Detailed exploded view of the upper portion of a passive metal detection system.

[0031] Figure 5 A signal representing, as a function of time, on the one hand, a disturbance in the alternating magnetic field generated by the coil of an exemplary embodiment of an active metal detection system when a small telephone having a size of approximately 2.5 cm×7 cm passes by, and on the other hand, a signal indicating the static magnetic field detected by an exemplary embodiment of a passive metal detection system.

[0032] Figure 6The representation of one aspect as a function of time when an elbow-shaped element made of a non-magnetic metal (here aluminum) passes by is given by Figure 5 An exemplary embodiment of an active metal detection system wherein the coil generates a signal indicating a disturbance in the alternating magnetic field, and on the other hand an indication of the Figure 5 An exemplary embodiment of a passive metal detection system detects a signal of a static magnetic field.

[0033] Figure 7 The representation of one aspect as a function of time when a regular phone (here a Samsung Galaxy Note 5) passes by is given by Figure 5 An exemplary embodiment of an active metal detection system wherein the coil generates a signal indicating a disturbance in the alternating magnetic field, and on the other hand an indication of the Figure 5 An exemplary embodiment of a passive metal detection system detects a signal of a static magnetic field.

[0034] Figure 8 is a flow chart showing an example of the steps by which the central processing unit of the combined detector infers the category of the detected object based on the magnetic moment of the received signal. DETAILED DESCRIPTION

[0035] The combined detector 1 according to the present invention comprises:

[0036] - an active metal detection system 10 comprising at least two vertical supports 12 and coils 14, 15 distributed in the two vertical supports 12, and

[0037] at least one passive metal detection system 20 housed in one of the vertical supports 12 and comprising at least one magnetostatic sensor 22 .

[0038] In fact, the applicant has noticed that phones that contain a small amount of metal and are therefore difficult to detect by active metal detection systems designed to detect them (e.g. small phones) have a significant magnetic strength (moment), while phones that contain a large amount of metal (e.g. smartphones sold by the current major mobile phone brands) have a smaller magnetic moment. Therefore, using this combined detector 1, it is possible to detect both small phones (with the help of the passive metal detection system 20) and current smartphones (with the help of the active metal detection system 10) in a simple and space-saving manner.

[0039] More specifically, the active metal detection system 10 comprises in a manner known per se a U-shaped structure comprising two vertical supports 12 connected at the top by a horizontal beam 16. The horizontal beam 16 may be equipped with any visualization device and / or any conventional control element, where appropriate.

[0040] Thus, the vertical supports 12 define a passage or transition passage through which the person being examined must pass.

[0041] In a variant not shown in the figures, the active metal detection system 10 does not comprise the horizontal beam 16, so that the vertical supports 12 are separated from each other.

[0042] Each vertical support 12 houses one or more coils 14, 15 connected to a central processing unit, which can be housed in a horizontal beam, in one of the vertical supports 12, or placed at a distance from said vertical supports 12, and to the processing unit 2. Some of the coils 14, 15 form transmitters of alternating magnetic fields, and some of the coils 14, 15 form receivers. Furthermore, the same coils 14, 15 can alternately form transmitter coils 14 and receiver coils 15.

[0043] Several variants of such coils 14, 15 and the associated central processing unit 2 are known to those skilled in the art and will not be described in detail below.

[0044] Figure 1 A set of transmitter coils 14 (here eight transmitter coils 14 ) and a set of receiver coils 15 (here twelve receiver coils 15 ) are schematically shown, for example, forming several channels.

[0045] The central processing unit 2 has the function of analyzing the signals acquired from each receiver coil 15 in order to detect the presence of metal that affects the alternating magnetic and / or electromagnetic fields generated by the transmitter coil 14, and thus detect the coupling between the transmitter coil 14 and the receiver coil 15. Where appropriate, depending on the construction of the coils 14, 15 and the nature of the processing performed by the central processing unit 2, the central processing unit 2 may also be configured to determine the geometry of the detected objects, their density, their mass, etc. Therefore, the construction of the coils 14, 15, the signals and the nature of the processing performed by the central processing unit 2 enable a detailed analysis of the objects worn by the person being inspected passing through the active metal detection system 10.

[0046] exist Figure 3 In the first embodiment shown, the vertical support 12 consists of a panel and for this purpose has a substantially planar shape, that is to say a smaller thickness transversely to the direction of passage and a greater width parallel to this direction. Figure 2 In the second embodiment shown, the vertical support 12 consists of a column and for this purpose has a substantially circular shape of revolution or of an ellipse.

[0047] The vertical supports 12 have a sufficient height to allow the inspected person to pass through. To this end, each vertical support 12 has a height at least equal to 2.10 m.

[0048] Each passive metal detection system 20 includes one or more magnetostatic sensors 22 .

[0049] More specifically, each passive metal detection system 20 comprises at least one static magneto sensor 22, preferably at least two, for example three static magneto sensors 22, which are distributed over the height of the vertical support 12 that accommodates them. The height is here understood as the dimension between the base 18 and the horizontal beam 16 of the active metal detection system 10 along a direction perpendicular to the floor.

[0050] For example, the passive metal detection system 20 may include a first static magnetic sensor 22 located near the floor so as to detect target objects worn on the feet of the inspected person; a second static magnetic sensor 22 located at an intermediate height (e.g., between approximately 1.00 m and 1.2 cm from the ground) so as to detect target objects worn on the hips; and a third static magnetic sensor 22 located at shoulder height (e.g., approximately 1.70 m from the ground).

[0051] The sensor 22 in the passive metal detection system 20 can be fixed to the column 21 (the column 21 is added and fixed in the associated vertical support 12 of the active metal detection system 10), or it can be directly fixed to a one-piece structure belonging to the active metal detection system 10 (for example, it can be obtained by molding it together with the associated vertical support 12).

[0052] The height of the structure (pillar 21 or one-piece structure) carrying the sensors of the passive metal detection system 20 is less than or equal to the height of the vertical support 12 so as to be hidden in said support 12. For example, the height of the structure may be between 1.70 m and 2.00 m.

[0053] Each static magneto sensor 22 is configured to detect a static magnetic field generated by a magnetized element when the ferromagnetic element passes through a transition channel, or a static magnetic field caused by changes in the earth's magnetic field. To this end, each static magneto sensor 22 includes a magnetic field sensitive element (such as a Hall cell, a magnetic resistance or a flux gate, etc.), which is fixed on the electronic board 23 to generate a signal indicating the strength of the detected static magnetic field. In one embodiment, the signal generated by the static magneto sensor 22 is a voltage, and the value of the voltage is proportional to the strength of the detected static magnetic field.

[0054] In order to improve the detection efficiency of the passive metal detection system 20, all or part of the static magnetic sensor 22 is configured to detect the strength of the static magnetic field along three orthogonal axes.

[0055] The magnetostatic sensor 22 of the passive metal detection system 20 is connected to the central processing unit 2 in a daisy chain or directly on a separate line. Therefore, the central processing unit 2 is configured to simultaneously receive a signal indicating a disturbance in the alternating magnetic field from the coils 14, 15 of the active metal detection system 10, and a signal indicating the static magnetic field detected by the magnetostatic sensor 22 of the passive metal detection system 20.

[0056] Therefore, sharing the central processing unit 2 for the active metal detection system 10 and the passive metal detection system 20 allows the space requirement of the combined detector 1 to be reduced.

[0057] The central processing unit 2 can be accommodated in the horizontal beam 16 , for example.

[0058] As a variant, as described above, the central processing unit 2 may be located remotely and connected to the static magnetic sensor 22 of the passive metal detection system 20 and the coils 14, 15 of the active metal detection system 10 via a communication interface. The communication interface preferably comprises a wired interface, the combined detector 1 being typically permanently fixed. Alternatively, in the case where the combined detector 1 must be movable to facilitate its installation, the communication interface may comprise a wireless interface, such as an interface of the Wi-Fi or Bluetooth type or an interface for optical, radio, infrared or inductive communication, and the like.

[0059] Preferably, in order to improve the detection of ferromagnetic objects and / or objects comprising magnetized elements, the combined detector 1 comprises at least two passive metal detection systems 20 , each passive metal detection system 20 being housed in an associated vertical support 12 of the active metal detection system 10 .

[0060] In this case, the magnetostatic sensors 22 of each passive metal detection system 20 are positioned two by two at the same height relative to the floor to form pairs of opposing sensors.

[0061] As shown below, the central processing unit 2 is then configured to calculate a value based on the signals generated by the static magnetic sensors 22 of the two passive metal detection systems. The calculated value may then include one of the following values: the average value of the signals generated by the sensors in each pair of sensors; the average value, sum or maximum value of the corrected values ​​of the signals generated by the sensors obtained by applying the attenuation coefficient to the signals generated by each pair of sensors; the sum of the values ​​of the signals generated by each pair of sensors; the maximum value of the values ​​of the signals generated by each pair of sensors.

[0062] The combination of coils 14, 15 and magnetostatic sensor 22 in the same detector will produce significant parasitic signals and major coupling problems for two reasons:

[0063] - the transmitter coil 14 of the active metal detection system 10 generates an alternating magnetic field which interferes with the magnetostatic sensor 22 of the passive metal detection system 20, and

[0064] The magnetostatic sensor 22 of the passive metal detection system 20 generates a voltage which interferes with the receiver coil 15 of the active metal detection system 10 .

[0065] Therefore, in order to allow reliable detection and avoid interference caused by interfering signals and capacitive coupling, each magnetostatic sensor 22 of the combined detector 1 is at least partially surrounded by a conductive shield 24. For example, the shield 24 can be made of a non-magnetic metal material (i.e. a metal material that does not acquire transient or permanent magnetic properties when placed in a magnetic field or subjected to a magnetization treatment), typically one of the materials in the following list: aluminum, copper and / or brass.

[0066] In this way, the shield 24 short-circuits the alternating magnetic field generated by the transmitter coil 14 by inducing a current on its outer surface, which prevents the penetration of said magnetic field and any disturbance in the magnetostatic sensor 22 .

[0067] In one embodiment, each shield 24 is also connected to a fixed potential source, such as ground, to form a capacitive barrier and avoid capacitive coupling between the enclosed magnetostatic sensor 22 and the receiver coil 15. To this end, the wires 25 may be connected, for example, to metal rods or screws fixed to the shield 24 and the fixed potential source 26' (usually the floor).

[0068] In the case where the combined detector 1 comprises several magnetostatic sensors 22 and therefore several shields 24, each shield 24 is configured, for example, in a star shape (see Figure 1 ) is connected to a fixed potential 26 ′ (eg ground), or is individually connected to a fixed potential 26 ′ (eg ground) according to individual lines.

[0069] Preferably, the shape and size of the conductive shield 24 are chosen so that the maximum surface of the enclosed magnetostatic sensor 22 is covered by the shield 24, thereby minimizing the risk of coupling and parasitic signals. For example, only the upper end (horizontal beam side 16) and the lower end (floor side) may remain open.

[0070] For example, the conductive shield 24 may include a hollow sleeve having a generally cylindrical shape in which the magnetostatic sensor 22 is housed. The size and shape of the conductive shield 24 are selected so that the conductive shield 24 is adjusted around the magnetostatic sensor 22, thereby improving its efficiency. For example, the conductive shield 24 may have a cylindrical shape, generally a rotational shape, with a square cross-section, a polygonal cross-section, etc. Where appropriate, a blind window may be formed on the inner surface of the conductive shield 24 facing the sensor to avoid any contact between the magnetostatic sensor 22 and the conductive shield 24. Optionally, an insulating layer may also be applied next to the window, which is located between the magnetostatic sensor 22 and the bottom of the window.

[0071] In one embodiment, the height H of each conductive shield 24 is at least equal to the height h of the magnetostatic sensor 22 it surrounds to cover its entire surface. Where appropriate, the magnetostatic sensor 22 may be centered (in height) relative to the conductive shield 24. For example, the height H of each conductive shield 24 may be greater than or equal to 1.5 times the height h of the magnetostatic sensor 22 it covers to reduce the risk of coupling. Then, in this exemplary embodiment, the upper and lower ends of the conductive shield 24 remain open.

[0072] When the passive metal detection system 20 includes several static magneto-sensors 22 distributed over its height, a separation sleeve 26 made of an insulating material (e.g., non-conductive plastic) can be placed between the shielding covers 24 to separate the shielding covers. Similar to the sleeve forming the shielding cover 24, the separation sleeve 26 can also have a cylindrical shape.

[0073] The breakaway sleeve 26 may form an integral part of the structure carrying the sensor, whether that structure is a column 21 or an integral structure with the active metal detection system 10 .

[0074] For example, in the case where the passive metal detection system 20 includes a column 21 and at least two static magneto sensors 22, each static magneto sensor 22 can be fixed on the upper edge and the lower edge of the separation sleeve 26. To this end, a slot 27 can be formed in one end of the separation sleeve 26 to receive one of the edges of the electronic board 23 of the static magneto sensor 22 (see, for example, Figure 4 ) and hold it in a fixed position in the column 21, the shielding cover 24 is then added and fixed on these separation sleeves 26 to enclose the static magnetoelectric sensor 22 and cover its entire height. Preferably, the shielding cover 24 overlaps the separation sleeves 26 because its height H is greater than the height H of the static magnetoelectric sensor 22. Generally, the shielding cover 24 can overlap each separation sleeve 26 by a certain distance, which is equal to about 25% of the height of the shielding cover.

[0075] Where appropriate, each release sleeve 26 may be locally thinned to form a shoulder 28 configured to receive an adjusted shield 24 .

[0076] Usually, in Figure 4 In the exemplary embodiment shown, the passive metal detection system 20 comprises a static magnetoelectric sensor 22, which is located in the upper part surrounded by a shield 24, which comprises a sleeve with a polygonal cross section formed by several metal plates assembled along its longitudinal edges. The shield 24 is fixed to the upper and lower parts of the separation sleeve 26. One end of each separation sleeve 26 includes a slot 27 for fixing the electronic board 23 of the static magnetoelectric sensor 22. The cross section of this end is also polygonal so as to engage with the adjusted inner surface of the sleeve.

[0077] As a variant, a separating sleeve 26 may be added and fixed to the structure carrying the magnetostatic sensor 22 .

[0078] The combined detector 1 also comprises, in a manner known per se, a power supply module 3 and a human-machine interface 4 (HMI), both connected to the central processing unit and the processing unit 2 , and one or more transmitters 5 , 6 , 7 connected to the human-machine interface HMI or the central processing unit 2 .

[0079] Each transmitter 5, 6, 7 is configured to generate an alarm signal, such as an acoustic signal and / or an optical signal (LED, flashing light, etc.). The transmitter 5, 6, 7 may be included in the combined detector 1, or may be worn by the operator (head-mounted device, etc.), in which case the central processing unit 2 sends the alarm generation instruction to the remote transmitter 5, 6, 7 via a wireless communication interface (such as the above-mentioned communication interface).

[0080] Where appropriate, the combined detector 1 may include at least one transmitter 7 associated with an active metal detection system 10 and at least one transmitter 5, 6 associated with a passive metal detection system 20 to allow an operator to easily determine the origin of an alarm.

[0081] Optionally, the combined detector 1 may also include one or more pairs of photoelectric units 8a and as many reflectors 8b as possible, which are fixed two by two on the vertical supports 12 of the active metal detection system 10 so as to extend toward each other at the entrance and exit of the detector, thereby detecting the entrance and tracking the inspected person passing through the transition channel. Therefore, it can be determined whether the inspected person is actually detected when passing through the active metal detection system 10 between the two vertical supports 12, and if appropriate, it can be determined whether the inspected person is located at the entrance, the central part, or the exit.

[0082] To this end, the photoelectric unit 8a is connected to the central processing unit 2 and, when detected, transmits position information about the person being examined to the central processing unit 2. Where appropriate, the central processing unit 2 can temporally and / or spatially correlate the position information of the person being examined with the signals generated by the static magnetoelectric sensor 22 and the coils 14, 15.

[0083] An example of the operation of the combined detector 1 may then include the following steps.

[0084] During a first step, the operator uses the human-machine interface HMI to adjust the sensitivity of the combined detector 1 to a level adapted to the area in which said combined detector 1 is located.

[0085] Preferably, the operator inputs only one sensitivity level for both (active and passive) detection systems. This sensitivity level is then applied to both the active metal detection system 10 and the passive metal detection system 20 according to a predetermined distribution.

[0086] As a variation, the operator may adjust the sensitivity levels of the active metal detection system 10 and the passive metal detection system 20 individually.

[0087] In the second step, the person being inspected passes through a transition passage defined by the vertical supports 12 of the active metal detection system 10 .

[0088] If the person being checked carries a metal element (such as a weapon or a large smartphone), it will disturb the alternating magnetic field generated by the transmitter coil 14 when passing through the transition channel. Therefore, the receiver coil 15 will send a signal representing this magnetic field disturbance caused by the person being checked passing through to the central processing unit 2.

[0089] If the value of the signal is less than a first predetermined value (depending on the sensitivity level of the operator input), the central processing unit 2 does not send an alarm generation instruction to the transmitters 5 , 6 , 7 .

[0090] On the contrary, if the value of the signal is greater than or equal to the predetermined value, the central processing unit 2 sends an alarm generation instruction to at least one of the transmitters 5 , 6 , 7 .

[0091] In one embodiment, the transmitter 7 receiving the alarm generating command is a transmitter 7 associated with the active metal detection system 10 to allow an operator to determine that the passive metal detection system 20 has detected a target object and thereby infer the type of target object being sought.

[0092] If the person being examined carries a magnetized element such as a small phone, the static magnetic sensor 22 detects a static magnetic field generated by the magnetized element. Therefore, the static magnetic sensor 22 sends a signal indicating the magnetic field to the central processing unit 2.

[0093] Where appropriate, the central processing unit 2 calculates values ​​from the signals generated by the magnetostatic sensors 22 of the two passive metal detection systems.

[0094] If the calculated value is less than a second predetermined value (depending on the sensitivity level input by the operator), the central processing unit 2 will not send an alarm generation instruction to the transmitter.

[0095] On the contrary, if the calculated value is greater than or equal to the second predetermined value, the central processing unit 2 sends an alarm generation instruction to at least one of the transmitters 5 , 6 , 7 .

[0096] In one embodiment, the transmitter 5, 6 receiving the alarm generating instruction is a transmitter 5, 6 associated with the passive metal detection system 20 to allow an operator to determine that the passive metal detection system 20 has detected a target object and thereby infer the type of target object to be sought.

[0097] If the person being inspected carries both a metal element and a magnetized element, the alternating magnetic field generated by the transmitter coil 14 is disturbed when the person passes by and causes the static magnetic sensor to generate a signal indicating a high magnetic field strength. Therefore, the receiver coil 15 sends a signal indicating the disturbance in the alternating magnetic field caused by the person being inspected passing by to the central processing unit 2, and at the same time, the static magnetic sensor 22 sends a signal indicating the strength of the static magnetic field generated by the magnetized element to the central processing unit 2.

[0098] If the value of the signal from the coils 14 , 15 is less than the first predetermined value and the value of the signal generated by the static magnetoelectric sensor 22 (or its calculated value) is less than the second predetermined value, the central processing unit 2 does not send an alarm generation instruction to the transmitters 5 , 6 , 7 .

[0099] On the other hand, if the signal from the coils 14, 15 is greater than or equal to the first predetermined value and / or if the value of the signal generated by the static magnetoelectric sensor 22 (or its calculated value) is greater than or equal to the second predetermined value, the central processing unit 2 sends an alarm generation instruction to the corresponding transmitter 5, 6 or 7.

[0100] In one embodiment, in order to improve the detection of target objects by the passive metal detection system 20, in particular to improve its ability to distinguish small target objects from large ferromagnetic objects, the system includes two passive metal detection systems 20, each barrier includes at least two opposing sensors, and each passive metal detection system 20 is located in a corresponding vertical support 12. In addition, the central processing unit 2 calculates a value based on the signals generated by each pair of sensors. Then, the central processing unit 2 compares the calculated value with the second detection threshold.

[0101] Reference is made in particular to any of the French patent applications FR 18 55900, FR 1855903 and FR 1855907 filed on 28 June 2018 in the name of the applicant, which relate for example to the calculation of values ​​from signals generated by pairs of sensors.

[0102] Specifically, in the first embodiment, the central processing unit 2 calculates the average value of the signals generated by each pair of static magneto-sensors 22. Of course, when the passive metal detection system 20 includes only one static magneto-sensor 22 respectively, the central processing unit 2 calculates only one average value corresponding to the average value of the signals from the two static magneto-sensors 22. The average value may be the arithmetic mean of the signals, which corresponds to the sum of the signal values ​​divided by the number of signals, or alternatively may be the geometric mean of the signals, which corresponds to the square root of the product of the signals.

[0103] In the second embodiment, instead of calculating the average value of the signals of each pair of static magneto-sensors 22, the central processing unit 2 can correct these signals by applying an attenuation coefficient to the signals of the pairs of static magneto-sensors 22. Thus, this correction step allows the signals generated by the static magneto-sensors 22 of the passive metal detection system 20 to be attenuated by applying a correction coefficient to the signals, which correction coefficient depends on the value of these signals. More specifically, the purpose of the correction is to attenuate the signal when the target object is closer to one of the passive metal detection systems 20 with higher sensitivity, so as to reduce the weight of this signal in the detection.

[0104] To this end, the central processing unit 2 determines, for each pair of magnetostatic sensors 22, the maximum and minimum values ​​in the signals generated at a given time by the first magnetostatic sensor 22 and the second magnetostatic sensor 22. The central processing unit 2 then calculates the ratio between the maximum and minimum values ​​thus determined and compares this ratio with the determined threshold value in order to infer therefrom the value of the attenuation coefficient to be applied to the signal value.

[0105] For example, the central processing unit 2 may specifically compare the ratio with a first threshold and a second threshold, wherein the second threshold is greater than the first threshold, and infer the attenuation coefficient. Therefore, the following conditions exist:

[0106] - when the ratio is less than a first threshold, the attenuation coefficient is equal to a first value;

[0107] - when the ratio is greater than a second threshold, the attenuation coefficient is equal to a second value that is smaller than the first value, and

[0108] - When the ratio is between the first threshold and the second threshold, the attenuation coefficient is equal to a value between the first value and the second value. In particular, when the ratio is between the first threshold and the second threshold, the attenuation coefficient may be a linear function depending on the ratio.

[0109] The ratio between the maximum and minimum values ​​can be used to determine whether a target object that generates a static magnetic field or interferes with the earth's electromagnetic field is placed near one of the passive metal detection systems 20. In this case, the value of the ratio is greater than the second threshold, and the applied attenuation coefficient is equal to the second value, which is less than the first value. In contrast, when the target object is centered between the two passive metal detection systems 20, the sensitivity of the horizontal beam in this area is lower. This causes the ratio between the maximum and minimum values ​​to be lower. Therefore, the attenuation coefficient can be higher, thereby reducing attenuation. In this way, relative virtual uniformity is obtained between the two passive metal detection systems 20. As a non-limiting example, the first threshold can be equal to 30, the second threshold can be equal to 60, the first value can be equal to 1, the second threshold can be equal to 0.1, and when the ratio is between the first threshold and the second threshold, the attenuation coefficient can be defined by the following function:

[0110] 0.03*R+1.9

[0111] Where R is the value of the ratio.

[0112] In other words, when the ratio is less than 30, the attenuation coefficient is equal to 1; when the ratio is greater than 60, the attenuation coefficient is equal to 0.1; when the ratio is between 30 and 60, the attenuation coefficient is equal to 0.03*R+1.9.

[0113] Once the signal value is corrected, the central processing unit 2 calculates the average value of the corrected value of each pair of static magnetoelectric sensors 22 based on the corrected value of the signal. Then, the value of the corrected sum is compared with a second predetermined threshold value.

[0114] Alternatively, instead of calculating the average value of the correction signal, the central processing unit 2 may calculate the sum of the correction values ​​of the signal or the maximum value thereof and compare this value (the sum or the maximum value) with the second predetermined threshold value.

[0115] Of course, it will be appreciated that in the second embodiment the central processing unit 2 may first calculate the average value (respectively the sum or the maximum value) of the signal and then apply a correction step to the average value (respectively to the sum or to the maximum value).

[0116] Where appropriate, the central processing unit 2 may also temporally and / or spatially correlate the signal representing a disturbance in the alternating magnetic field with the signal indicative of the strength of the static magnetic field.

[0117] In practice, when the active metal detection system 10 comprises a plurality of transmitter coils 14 and receiver coils 15 forming a number of channels, and when the passive metal detection system 20 comprises several magnetostatic sensors 22, each channel of the coils 14, 15 and each magnetostatic sensor 22 or pair of magnetostatic sensors 22 has a peak sensitivity when the target object being detected is located in an associated predetermined spatial region. Thus, based on the signals generated by the various coils 14, 15 and magnetostatic sensors 22, the central processing unit 2 can determine the approximate location of the spatial region in which the magnetostatic sensors 22 and / or coils 14, 15 have detected the target object. Thus, the spatial correlation of the signals allows the central processing unit 2 to determine whether the signals transmitted by the coils 14, 15 and the signals generated by the magnetostatic sensors 22 are related to a target object that is spatially located in the same region as the active metal detection system 10, or to a separate target object that is located in a different region of the active metal detection system 10.

[0118] This spatial correlation of the signals can also be taken into account when sending the alarm generation command. For example, the combined detector 1 can include several optical emitters 5, 6 in each vertical support 12. These optical emitters are distributed between the upper and lower parts of the vertical supports. By determining the spatial area where the target object has been detected (which area may be confirmed by spatial correlation), the central processing unit 2 can send the alarm generation command only to the emitters located near this area, for example, the emitters located near the floor of one of the vertical supports 12.

[0119] Similarly, the central processing unit 2 can correlate the signals received from the static magnetoelectric sensor 22 and the coils 14, 15 over a period of time to determine whether the detection is performed substantially simultaneously or sequentially. In the case of substantially simultaneous detection, the same target object may have been detected, or in the case of sequential detection, the active metal detection system 10 and the passive metal detection system 20 may have detected different objects.

[0120] For example, Figure 8 As shown, in the same spatial area of ​​the walk-through detector and in the same time interval, the central processing unit 2 can determine, based on the strength of the signal sent to it and the spatial and temporal correlation of the signal, whether the detected object belongs to one of the following categories: small telephone, weapon or conventional telephone. Where appropriate, a specific transmitter can be associated with each category of detected object so that the combined detector automatically provides the operator with information about the type of object detected.

[0121] For example, in the same spatial region of the walk-through detector and in the same time interval, when the magnetostatic sensor generates a signal S1 indicating a high intensity of the static magnetic field, but a signal S2 indicating a disturbance in the alternating magnetic field is low or very low (see Figure 5 ), the central processing unit 2 deduces that the detected object includes a small amount of metal and a magnetized element. Therefore, the central processing unit 2 determines that the detected object belongs to the category of a small phone and sends an alarm generation instruction to the dedicated transmitter of the object category.

[0122] In another example, in the same spatial region of the walk-through detector and in the same time interval, when the magnetostatic sensor generates a signal S1 indicating a low or very low intensity of the static magnetic field, but a signal S2 indicating a disturbance in the alternating magnetic field is high (see Figure 6 ), the central processing unit 2 deduces from this that the detected object comprises metal and has little or no magnetized components. Therefore, the central processing unit 2 determines that the detected object belongs to the category of weapons and sends an alarm generation instruction to the dedicated transmitter of the object category.

[0123] In yet another example, in the same spatial region of the walk-through detector and in the same time interval, when the magnetostatic sensor generates a signal S1 indicating a high or medium strength of the static magnetic field, but the signal S2 indicating a disturbance in the alternating magnetic field is also high (see Figure 7 ), the central processing unit 2 deduces that the detected object includes metal and magnetized elements. Therefore, the central processing unit 2 determines that the detected object belongs to the category of conventional telephones and sends an alarm generation instruction to the dedicated transmitter of the object category.

[0124] Optionally, the passage of the person being examined is further detected by a photoelectric unit 8a and a reflector 8b, which transmits position information about the person being examined to the control unit. This position information can then also be associated in time and / or space with a signal representing a disturbance in the alternating magnetic field and a signal indicating the strength of the static magnetic field.

[0125] In particular, the photoelectric unit 8a can be synchronized with the alarm generation when the active metal detection system 10 and / or one or more passive metal detection systems 20 detect a target object. In fact, depending on the orientation and size of the target object, the distance between the target object and the coils 14, 15 corresponding to the peak of the signal generated by the active metal detection system 10 can be different from the distance between the target object and the static magnetic sensor 22 corresponding to the peak of the signal generated by the passive metal detection system 20. Similarly, depending on the configuration of the combined detector, the spatial positions of these coils 14, 15 and these static magnetic sensors 22 may also be different. Therefore, the central processing unit 30 can use the photoelectric unit 8a and the reflector 8b to detect the passage of the inspected person, so as not to compare the signals generated by these coils 14, 15 and these static magnetic sensors 22 with a predetermined threshold value only when the inspected person leaves the transition channel (that is, when the inspected person crosses the beam of a pair of photoelectric units 8a and reflectors 8b located at the lowermost end of the active metal detection system 10). In this way, the processing of the signal by the central processing unit (30) becomes easier and more accurate.

Claims

1. A combined detector (1), comprising: An active metal detection system (10) comprising: at least two vertical supports (12) defining a transition passage therebetween, and Coils (14, 15) housed in the two vertical supports (12) and configured to emit an alternating magnetic field, wherein the coils are configured to generate a first signal representative of a disturbance in the magnetic field caused by an individual passing between the two vertical supports (12), at least one passive metal detection system (20) comprising at least one static magneto sensor (22) configured to generate a second signal based on detection of a static magnetic field when an individual passes between the two vertical supports, wherein the second signal is proportional to the strength of the static magnetic field, the passive metal detection system (20) being housed in one of the vertical supports (12); and a central processing unit (30) connected to the coils (14, 15) and to the magnetostatic sensor (22), wherein the central processing unit is configured to receive and process the first signal and the second signal; When the first signal is greater than a first predetermined threshold or the second signal is greater than a second predetermined threshold, sending an alarm generating instruction to a transmitter; and At least one conductive shield (24) is associated with the at least one magnetostatic sensor (22) and is configured to short-circuit surface currents.

2. The combined detector (1) according to claim 1, wherein each magnetostatic sensor (22) is surrounded by a conductive shield (24).

3. The combined detector (1) according to claim 1, wherein the conductive shield (24) comprises a cylindrical sleeve made of a non-magnetic metal material.

4. The combined detector (1) according to any one of claims 1 to 3, wherein each magnetostatic sensor (22) has a determined height (h), and the height (H) of the conductive shield (24) is greater than the determined height (h) of the associated magnetostatic sensor (22).

5. The combined detector (1) according to claim 4, wherein: The height (H) of the conductive shield (24) is at least equal to 1.5 times the determined height (h) of the associated magnetostatic sensor (22).

6. The combined detector (1) according to claim 4, wherein the at least one magnetostatic sensor (22) is centered in height relative to the associated conductive shield (24).

7. The combined detector (1) according to claim 1, wherein the passive metal detection system (20) comprises: - at least two static magneto sensors (22) distributed over the height of the passive metal detection system (20), each static magneto sensor (22) being surrounded by a conductive shield (24), and - A separation sleeve made of a conductive insulating material, the separation sleeve being placed between the two conductive shielding covers (24) to separate the conductive shielding covers (24).

8. The combined detector (1) according to claim 1, wherein the conductive shield (24) is connected to a fixed potential.

9. The combined detector (1) according to claim 1, wherein each passive metal detection system (20) comprises at least two static magneto sensors (22), and the at least two static magneto sensors (22) of each passive metal detection system (20) are connected to a fixed potential in a star configuration.

10. The combined detector (1) according to claim 1, wherein the central processing unit (30) is further configured to temporally and / or spatially correlate the signal representing the disturbance in the alternating magnetic field with the signal indicating the strength of the static magnetic field.

11. The combined detector (1) according to claim 1, comprising at least two passive metal detection systems (20), each of the passive metal detection systems (20) comprising at least one static magnetic sensor (22), the static magnetic sensors (22) of each passive metal detection system (20) being positioned in pairs at the same height relative to the ground to form pairs of opposing sensors, Each passive metal detection system (20) is housed in an associated vertical support (12) and connected to said central processing unit (30), The central processing unit (30) is configured to calculate a value based on the signals generated by the static magnetic sensors (22) of the two passive metal detection systems (20), the calculated value comprising one of the following values: an average value of the signals generated by the static magnetic sensors (22) for each pair of static magnetic sensors (22); an average value, a sum or a maximum value of correction values ​​of the signals generated by the static magnetic sensors (22) obtained by applying an attenuation coefficient to the signals generated by each pair of sensors; a sum of the values ​​of the signals generated by each pair of static magnetic sensors (22); a maximum value among the values ​​of the signals generated by each pair of static magnetic sensors (22).

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