RU2777705C1 - Mobile detection system containing magnetostatic sensors - Google Patents

Abstract

FIELD: sensing equipment.

SUBSTANCE: invention relates to a system for detecting a target object containing magnetized or ferromagnetic components. Essence: the system contains the first detector (10), which contains at least the first magnetic sensor (5) and at least one emitter (8), the second detector (20), containing at least one second magnetic sensor (5) and at least one emitter (8), at least at least one processing unit (6) capable of receiving signals characterizing the intensity of the magnetic field and detected by the first magnetic sensor (5) and the second magnetic sensor (5), and a communication interface (7) capable of transmitting a signal, generated by the first and/or second magnetic sensor (5), into the processing unit (6). The processing unit (6) is designed to determine the value calculated on the basis of signals characterizing the intensity of the magnetic field detected by the first magnetic sensor (5) and the second magnetic sensor (5). The processing unit (6) it is also made with the possibility of transmitting instructions for generating an alarm signal to at least one emitter (8) when the specified calculated value exceeds the specified threshold value.

EFFECT: the ability to reliably detect small objects containing magnetic components with small dimensions.

19 cl, 8 dwg

Description

The technical field to which the invention belongs

The invention relates to the field of detection of target objects, in particular to the detection of objects containing magnetized or ferromagnetic components.

State of the art

The current environment, which is driven by various malicious activities in public places, has created a need to detect weapons such as automatic assault rifles (machine gun) at the entrance of public buildings such as stadiums, concert halls, department stores, and the like.

Currently, such detection is usually performed by security personnel equipped with hand-held portable detectors, which are passed along the body and around the property of persons who wish to enter the various public places in question. However, such control is lengthy and inconvenient, and the number of people who want to enter the protected area is often too large to carry out the control in a satisfactory manner.

There have also been proposals to create stationary walkways at the entrances to various public institutions. Such passages are a suitable solution in cases where a fixed installation is required. However, such an installation requires a significant amount of installation work, which makes it unsuitable for public facilities such as stadiums, concert halls and department stores. At the same time, it is necessary to be able to free up space in public places in order to allow an unobstructed emergency exit, which makes the use of mobile systems desirable.

There have also been proposals to use movable individual fences containing magnetostatic sensors. Such enclosures typically comprise a post attached to a base and equipped with at least one magnetostatic sensor, such as three magnetostatic sensors distributed along the height of the post. Each sensor is configured to generate a signal (voltage) that characterizes the intensity of the detected electromagnetic field. Such fences, in particular, are used in prisons to inspect prisoners for the smuggling of metal objects, in particular mobile phones. Such detection requires the sensitivity of the magnetic sensors to be very high, as prisoners are generally prohibited from carrying any metallic or magnetic materials.

In order to increase the sensitivity of such barriers, it has been proposed to use them in pairs, so as to create a passage. Characteristically, the sensitivity of the sensors decreases exponentially with distance. Fences of this type have the advantage that they are mobile and do not require any installation work. In addition, since modern automata are made of ferromagnetic material and are large in size, the disturbance they create in the Earth's electromagnetic field is significant enough to be detected by these sensors.

However, unlike inmates in prisons, people often wear or carry metal objects that may contain magnetized or ferromagnetic parts, and in most cases smartphones whose chips are magnetized. At the same time, the own magnetic field of smartphones is almost comparable to the disturbance of the Earth's magnetic field, which is created when the machine moves. Therefore, the passage of such people will systematically trigger the alarm of the fence, even in the absence of a machine gun. Therefore, it is necessary to be able to distinguish between smartphones and machine guns in order to guarantee the ability of fences to detect such weapons.

Therefore, in WO 2017/141022, it was proposed to add a stop to each of the fences to guide the person being examined and force him/her to pass through the middle of the passage formed by the fences, where the sensitivity in the passage formed by the pair of fences is more uniform. More precisely, since the sensitivity of magnetostatic sensors is inversely proportional to distance, the sensors are more sensitive near the fences than in the middle. At the same time, an excess of sensitivity near fences is the cause of almost all cases of false alarms. The presence of the restraints makes it possible to avoid that the persons being examined come too close to the barriers and to ensure that they remain in the middle of the aisle where the sensitivity is lower and more uniform.

However, such an increase in the distance between the fences is associated with the risk that the passage becomes somewhat sensitive to external interference, since the signal at such a distance from the fences is lower, and therefore more similar to the signals generated by the surrounding elements. In addition, the barriers obtained in this way are more difficult to carry, since they are much heavier and more bulky than the original barriers. Moreover, in cases where a plurality of aisles need to be organized, in particular in the case of stadiums or large concert halls, the complex formed by each pair of fences is very cumbersome, and thus limits the number of aisles that can be created.

US 2018/012465 discloses a detection system according to the preamble of claim 1. In particular, this document discloses a detection system comprising detectors, each of which includes at least one magnetic sensor configured to generate a signal indicative of the intensity of the detected magnetic field, and, for each detector, a processing unit configured to receive signals indicative of the intensity of the magnetic field detected by the sensors. Because the magnetic field produced at the location of the detector is inversely proportional to the third power of the radius r of the detector's sensitivity, the two detectors of the system discussed in this document are separated by a distance equal to half their sensitivity radius. Thus, the detectors are independent and their sensitivity can be reduced.

US 2006/197523 discloses a system for detecting an object, including multiple detectors, each containing multiple gradiometers, and a processor capable of collecting signals generated by the gradiometers. The processor calculates the average of the collected signals in order to measure the background noise. This average value is then subtracted from the signals generated by the gradiometers to eliminate noise.

Disclosure of invention

Therefore, the object of the present invention is to provide a detection system that can be quickly assembled and dismantled, for example at the entrance to public places, i.e. has a small size and, in appropriate cases, the ability to reliably distinguish small objects containing magnetic components, such as smartphones, as well as detect automatic assault rifles.

To do this, the invention proposes a system for detecting a target object, including:

- the first detector containing at least one first magnetic sensor configured to generate a signal characterizing the intensity of the detected magnetic field, and at least one emitter,

- a second detector, separate from the first detector, containing at least a second magnetic sensor configured to generate a signal characterizing the intensity of the detected magnetic field, and at least one emitter,

- at least one processing unit configured to receive signals indicative of the intensity of the magnetic field detected by the first magnetic sensor and/or the second magnetic sensor,

- a communication interface configured to transmit the signal generated by the first and/or second magnetic sensor to the processing unit.

In addition, at least one processing unit is configured to send instructions for generating an alarm signal to the emitter of the first detector and/or the second detector.

The following certain preferred, but non-limiting, aspects of the detection system described above may be implemented individually or in combination with each other:

- the processing unit is located in the first detector and is configured to transmit instructions for generating an alarm signal to the second detector via a communication interface,

- the communication interface is a wireless communication interface,

- the first and second detectors are mobile,

- the detection system further comprises a third detector, the third detector comprising at least one third magnetic sensor configured to detect the magnetic field and generate a signal characterizing the intensity of the detected magnetic field, the first detector and the second detector forming the first passage, and the second detector and the third detector together form the second passage.

- a processing unit is located in each of the first and second detectors, while the processing unit, located in the second detector, is configured to transmit instructions for generating an alarm signal to the second detector and to the third detector.

According to a second aspect of the invention, a method for detecting a target object using the detection system described above is provided, comprising the following steps:

S1: generating, by means of the first and/or second magnetic sensor, a signal indicative of the intensity of the magnetic field;

S2: processing, by means of a processing unit, the signals generated by the first and second magnetic pickups so as to obtain a processed value; and

S4: comparing said processed value with a given threshold value; wherein

S5: when the processed value exceeds the predetermined threshold, transmitting instructions for generating an alarm signal to the first detector and/or to the second detector.

The following are certain preferred, but non-limiting, features of the detection method described above may be implemented individually or in combination with each other:

- the first detector comprises a processing unit and a communication interface, and the second detector comprises a communication interface, the method further comprising the step of transmitting a signal generated by the second magnetic sensor to the processing unit via the communication interface,

- the processing step contains one of the following sub-steps:

• calculation, on the basis of the signals generated by the first and second magnetic sensors, of the average value of these signals,

• calculating, on the basis of the signals generated by the first and second magnetic pickups, the average value of said signals and correcting the average value so as to obtain a corrected average value by applying an attenuation factor to the average value,

• correcting the signals generated by the first and second magnetic pickups so as to obtain corrected values by applying an attenuation factor to the signals, and calculating an average value based on said corrected signals,

• correcting the signals generated by the first and second magnetic pickups so as to obtain corrected values by applying an attenuation factor to the signals and calculating the sum of the corrected values,

• correcting the signals generated by the first and second magnetic pickups so as to obtain corrected values by applying an attenuation factor to the signals, and calculating the maximum value of the corrected signals,

• determining, on the basis of the signals generated by the first and second magnetic sensors, the sum of the signals, and correcting this sum by applying an attenuation factor to the sum,

• determining, based on the signals generated by the first and second magnetic sensors, the maximum value of the signals, and correcting the maximum value by applying an attenuation factor to the maximum value,

- the attenuation factor is calculated according to the following sub-steps:

S31: determining the maximum value of the signal generated by the first magnetic sensor and the second magnetic sensor,

S32: determining the minimum value of the signal generated by the first magnetic sensor and the second magnetic sensor,

S33: calculating the ratio of the found maximum value to the found minimum value,

S34: comparing said ratio with a first threshold and a second threshold, wherein the second threshold is higher than the first threshold, and

S35: obtaining an attenuation coefficient, wherein the attenuation coefficient is: a first value when the specified ratio is less than the first threshold, a second value different from the first value when the specified ratio is greater than the second threshold, and a value between the first value and the second value when the specified ratio lies between the first threshold and the second threshold.

- the attenuation coefficient is a linear function depending on the specified ratio, when the specified ratio lies between the first threshold and the second threshold,

- the first value is 1, the second value is 0.1, and the attenuation coefficient is determined from the following expression when the specified ratio lies between the first threshold and the second threshold:

-0.03*R+1.9

where R is the value of the ratio.

- the first detector contains at least two first magnetic sensors, and the second detector contains at least two second magnetic sensors, each first magnetic sensor is associated with a certain second magnetic sensor, so that a pair is formed, with each pair applying steps S1- S4.

- the detection system further comprises a third detector comprising at least one third magnetic sensor configured to detect a magnetic field and generate a signal indicative of the intensity of the detected magnetic field, the method further comprising, before the alarm signal generation step S5, a signal processing step, generated by the second and third magnetic pickups so as to obtain a processed value.

the detection method further includes, after the step of calculating the processed value of the signals generated by the second and third magnetic sensors, the step of determining, based on the processed value of the signals generated by the first and second magnetic sensors and the processed value of the signals generated by the second and third magnetic sensors, the passage or passages formed by the first detector and the second detector on the one hand, and the second detector and the third detector on the other hand, in which the magnetic field has been detected.

- the stage of determining the passage or passages includes the following sub-stages:

• multiplying the processed value calculated on the basis of the signals of the second and third sensors by a safety factor,

• comparison of the processed value calculated on the basis of the signals generated by the first and second sensors with the processed value calculated on the basis of the signals of the second and third sensors and multiplied by the safety factor,

• multiplying the processed value calculated on the basis of the signals of the first and second sensors by a safety factor,

• comparing the processed value calculated on the basis of the signals generated by the second and third sensors with the processed value calculated on the basis of the signals of the first and second sensors and multiplied by the safety factor.

- step S5 is only carried out in accordance with the first and second detectors, if the processed value calculated on the basis of the signals generated by the first and second sensors is greater than the processed value calculated on the basis of the signals of the second and third sensors and multiplied by the safety factor,

step S5 is only carried out in accordance with the second and third detectors if the processed value calculated on the basis of the signals generated by the second and third sensors is greater than the processed value calculated on the basis of the signals of the second and third sensors and multiplied by the safety factor.

- the first detector and the second detector each contain a processing unit, wherein:

• the step of calculating the processed value of the signals generated by the second and third magnetic sensors is performed by the processing unit of the second detector,

• the step of calculating the processed value of the signals generated by the first and second magnetic sensors is performed by the processing unit of the first detector, and

• the step of determining the pair or pairs of detectors that have detected the magnetic field is performed by the processing unit of the second detector and by the processing unit of the first detector.

- the detection system further comprises a fourth detector comprising at least one fourth magnetic sensor configured to detect a magnetic field and generate a signal indicative of the intensity of the detected magnetic field, the detection method further comprising the following sub-steps:

• calculation of the processed value of the signals generated by the third and fourth magnetic sensors,

• multiplying the processed value of the signals generated by the third and fourth magnetic sensors by a safety factor,

• comparison of the processed value of the signals generated by the second and third magnetic sensors with the processed value of the signals generated by the third and fourth magnetic sensors and multiplied by the safety factor,

• comparison of the processed value of the signals generated by the third and fourth magnetic sensors with the processed value of the signals,

generated by the second and third magnetic sensors and multiplied by the safety factor,

• identification of a pair or pairs of detectors among the first, second, third and fourth detectors in which the magnetic field was detected.

step S5 is only carried out in accordance with the second and third detectors if the processed value of the signals generated by the second and third sensors is greater than the processed value of the signals generated by the third and fourth magnetic sensors multiplied by the safety factor, and

step S5 is only carried out in accordance with the third and fourth detectors if the processed value of the signals generated by the third and fourth sensors is greater than the processed value of the signals generated by the second and third sensors and multiplied by the safety factor.

Brief description of the drawings

Other features, objects and advantages of the present invention will be better understood by reference to the following detailed description thereof with reference to the accompanying drawings, which are given by way of non-limiting examples.

Fig. 1 is a general diagram of an example of a detector that can be used in a detection system according to the present invention.

Fig. 2 illustrates an exemplary implementation of a detection system in accordance with the present invention and comprising two detectors.

Fig. 3 illustrates an exemplary embodiment of a detection system in accordance with the present invention, comprising three detectors forming two aisles together, and a person being examined in one of the aisles.

Fig. 4 illustrates an exemplary implementation of a detection system in accordance with the present invention and comprising m detectors, together forming m-1 passages.

Fig. 5 is a flowchart illustrating the main steps of an implementation example of a detection method according to the present invention.

Fig. 6 is a flowchart illustrating the main sub-steps of signal value correction.

7 is a flowchart illustrating the steps of an exemplary implementation of the detection method according to the present invention in the case where the detection system comprises at least four detectors (n-2, n-1, n and n+1).

Fig. 8a illustrates the signal intensity in a state of the art detection system containing two detectors spaced 130 cm apart.

Fig. 8b illustrates the signal intensity in a detection system according to an embodiment of the present invention and comprising two detectors separated by 130 cm, as well as a processing unit configured to calculate the average of the signals generated by the sensors of said two detectors.

Fig. 8c illustrates the signal strength in a detection system 1 according to an embodiment of the present invention, and comprising two detectors separated by 130 cm, and a processing unit configured to calculate the average value of the signals generated by the sensors of said two detectors.

Implementation of the invention

System 1 for detecting a target object, and in particular an object containing large volume ferromagnetic material, such as an automatic rifle (machine gun), comprises:

- at least one first and second detector 10, 20, together forming a passage,

- at least one processing unit 6,

- at least one communication interface 7.

Each detector 10, 20 includes at least one magnetic sensor 5. It should be understood that in this context, the term "magnetic" (or magnetostatic) means a passive sensor capable of detecting the magnetic field that naturally surrounds objects containing iron or any ferromagnetic elements, unlike, for example, an induction coil.

More specifically, the first detector 10 comprises at least one first magnetic sensor 5, preferably at least two sensors, such as three first magnetic sensors 5, while the second detector 20 comprises at least one second magnetic sensor 5. Preferably, the second detector 20 and the first detector 10 contain the same number of sensors 5.

Each magnetic sensor 5 is configured to detect a magnetic field and generate a signal indicative of the intensity of the detected magnetic field. According to one embodiment, the signal is a voltage whose magnitude is proportional to the intensity of the detected magnetic field.

According to one embodiment, each magnetic sensor 5 is configured to detect the intensity of the magnetic field along three orthogonal axes.

Each detector 10, 20 further comprises a stand 3 capable of being placed on the surface of the earth, for example by means of a base 4. Preferably, the height of the stand 3 is substantially equal to the average height of the person 2, for example, about 1.7-2.0 m.

The unit formed by the column 3 and the base 4 is movable, i.e. it is not permanently attached to the ground and can be moved by the operator. If necessary, each detector 10, 20 can be equipped with a handle to facilitate said movement. The handle can be attached, in particular, to the base 4.

The magnetic sensors 5 are distributed along the height of the column 3 in order to ensure the detection of targets in the gap between the feet and the head of the persons being examined 2. For example, each column 3 may be equipped with three magnetic sensors 5 distributed between the base 4 and the free end of the column 3.

Finally, within the same detection system 1, the magnetic sensors of the detectors 10, 20 are arranged in pairs at the same height so as to obtain pairs of sensors 5 facing each other.

The system 1 additionally comprises at least one processing unit 6 configured to receive signals characterizing the intensity of the magnetic field generated by the first magnetic sensor 5 and/or the second magnetic sensor 5.

More precisely, and as will be seen below, the system 1 may comprise either a processing unit 6 configured to receive signals indicative of the intensity of the magnetic field detected by the first magnetic sensor 5 and/or the second magnetic sensor 5, or a processing unit 6 configured to receiving signals characterizing the intensity of the magnetic field detected by the first magnetic sensor 5, and a processing unit 6 configured to receive signals characterizing the intensity of the magnetic field detected by the second magnetic sensor 5

The communication interface 7 is configured to transmit the signal generated by the second magnetic sensor 5 to a processing unit 6 receiving signals indicative of the intensity of the magnetic field detected by the first magnetic sensor 5. This processing unit 6 is configured to determine a value calculated based on the signals indicative of the intensity of the magnetic field detected by the first magnetic sensor 5 and the second magnetic sensor 5. This calculated value may in particular be an average value and/or a corrected value of the signals generated by the magnetic sensors 5 of the first and second detectors 10, 20. Here, when said calculated value exceeds a predetermined threshold value, the processing unit 6 sends instructions to generate an alarm signal.

According to one embodiment, the processing unit 6 determines the arithmetic mean of the signals, which corresponds to the sum of the signal values divided by the number of signals.

Alternatively, the processing unit 6 determines the geometric mean of the signals, which corresponds to the square root of the product of the signals.

According to another variant, the processing unit 6 determines the corrected value of the signals generated by each of the magnetic pickups 5 by applying an attenuation factor to said signals.

According to one embodiment, the processing unit(s) 6 may be built into one of the detectors, the first detector 10 or the second detector 20. Preferably, each detector 10, 20 includes an embedded processing unit 6. It is to be understood that the term "embedded" means that the processing unit 6 is part of the detector 10, 20 and not a separate component to which the system 1 is connected.

In this embodiment, the processing unit 6 can be, for example, attached to the stand 3 of the corresponding detector, or alternatively to the base 4.

As a variant of this embodiment, the processing unit 6 may be located at a distance from the first and second detectors 10, 20. The detectors 10, 20 then transmit to the processing unit 6 the signals generated by the respective magnetic sensors 5 in order to process them along the route of their communication interface 7 .

According to one embodiment, processing unit 6 may comprise:

- analog-to-digital converter ADC (eng. A/D, Analog/Digital), configured to convert the analog signal (voltage) generated by the magnetic sensor 5 into a digital signal;

- digital signal processor DSP (eng. DSP, Digital Signal Processor), made with the ability to generate a converted digital signal; and

- a system management microcomputer (SMM, System Management Microcomputer), configured to receive a digital signal generated by a DSP and compare it with a predetermined threshold value.

The SMM is connected to at least one emitter 8 configured to generate an alarm signal, for example, to an acoustic emitter 8 configured to generate an acoustic signal and/or to a light emitter 8 configured to generate an optical signal (LED, flashing emitter, etc.). The emitter 8 can be located in the detector 10, 20, or alternatively, it can be worn by the operator (earphone, etc.). In this case, the processing unit 6 sends instructions for generating an alarm signal to the remote emitter 8 via the communication interface 7 of the corresponding detector 10, 20.

In addition, the SMM is connected to an asynchronous UART interface to allow the processing unit 6 to be connected to a computer (or equivalent device) and to allow various actions to be performed, including control of the detection program, diagnostics of one or more detectors, downloading updates, etc. .

Finally, the SMM is connected to the Human Machine Interface (HMI).

Each detector 10, 20 of the detection system 1 additionally contains a communication interface 7 designed to allow one of the detectors 10, 20 of the system 1 to communicate with another of the detectors 20, 10 of the system 1 and transmit to the latter a signal generated by its own magnetic sensor or sensors 5 For each detector 10, 20, the communication interface 7 may be connected to either a DSP (as shown in FIG. 1) of the processing unit 6 of the detector 10, 20, or to its SMM and its alarm emitters 8.

The communication interface 7 is preferably a wireless communication interface for facilitating the installation of the detection system 1, for example an interface of the Wi-Fi or Bluetooth type for exchanging data via an optical signal, a radio signal, an infrared signal, or alternatively an inductive coupling. Alternatively, the communication interface 7 may be wired.

In appropriate cases, the detection system 1 may contain more detectors in order to organize a plurality of passages, with each passage being formed by two adjacent detectors. Preferably, the detectors of one detection system 1 are essentially identical pairs.

For example, the detection system 1 may include a third detector 30 comprising at least one third magnetic sensor 5 configured to detect a magnetic field and generate a signal indicative of the strength of the detected magnetic field.

Similarly, as well as the first and second detectors 10, 20, the third detector 30 may include a stand 3 attached to the base 4 and equipped with a third magnetic sensor or sensors 5, as well as a communication interface 7, and, if necessary, a processing unit 6 .

In order to organize multiple passages, the present invention proposes to place the first detector 10, the second detector 20 and the third detector 30 next to each other so as to obtain two passages. More precisely, the first pass is formed by the first detector 10 and the second detector 20, while the second pass is formed by the second detector 20 and the third detector 30. Therefore, in the system, one detector (in this case, the second detector 20) is used to form two separate passes, which allows significantly reduce the scope of the detection system 1 compared to, for example, the system proposed in international application 2017/141022. In addition, the system according to the present invention is easier to install.

As will be seen below, the possibility of such a construction is provided by the fact that the processing unit 6 of the second detector 20, which is located between the first detector 10 and the second detector 20, can be configured to both process the signals generated by the magnetic sensor or sensors 5 of the third detector 30 , and for communication with the first detector 10 so that the detection system 1 can determine the passage within which the target object is detected, despite the fact that the magnetic sensors 5 perform scalar rather than vector detection.

More precisely, the processing unit 6 of the second detector 20 is configured to:

(i) calculating the average value (if necessary corrected) or the corrected value of the signals generated by the second and third magnetic sensors 5;

(ii) when said calculated value exceeds a given threshold value, transmitting to the processing unit 6 of the first detector 10 through the communication interface 7 a signal characterizing the intensity of the magnetic field detected by the second magnetic sensor or sensors 5, as well as the calculated value.

Naturally, the operator can also use four detectors according to the invention to make two passes, without having to share the second detector 20 to detect targets.

Each detector 10, 20 may further comprise identification means and a memory to enable collaboration and communication with other detectors of the detection system 1, as well as implementation of the detection method S. For example, each detector 10, 20, 30 may be assigned an address, which may be set when the detector 10, 20, 30 is manufactured, or programmed when the detectors 10, 20, 30 forming the detection system 1 are paired. According to an embodiment of the invention, the address of each detector 10, 20, 30 is fixed, ie. not amenable to modification in order to limit the errors that occur when the detection system 1 is manipulated and to simplify after-sales service.

For example, the address may contain a string of characters, which in particular may be formed by a given number of hexadecimal pairs, for example, eight.

When the detectors 10, 20, 30 of the detection system 1 are paired, the address of the detectors with which the given detector forms a passage is stored in the memory of said given detector. For example, when setting parameters for detection system 1, if system 1 contains a first detector 10, a second detector 20, and a third detector 30:

- the address of the second detector 20 is stored in the memory of the third detector 30;

- the address of the first detector 10 and the third detector 30 when setting the parameters of the system 1 is stored in the memory of the second detector 20; and

- the address of the second detector 20 is stored in the memory of the first detector 10. Next, the detection method S will be discussed, which uses

detection system 1 according to the invention and comprising two detectors 10, 20.

To simplify the reading of the description, the detection system 1 includes a first detector 10 and a second detector 20 containing, respectively, two first magnetic sensors 5 and two second magnetic sensors 5. The first and second magnetic sensors 5 form two pairs of magnetic sensors 5, each pair containing a first sensor 5 and a second sensor 5. Preferably, the pair comprises a first magnetic sensor 5 and a second magnetic sensor 5, each located near the free end of the column 3 of the first detector 10 and the second detector 20, while the other pair comprises the first a magnetic sensor 5 and a second magnetic sensor 5, each of which is located near the base 4.

Both detectors are identical to each other, and each contains a processing unit 6 and a communication interface 7.

Naturally, the invention is modified in the case where the detectors contain a different number of magnetic sensors 5. In particular, the detectors could contain only one magnetic sensor 5 or more than two magnetic sensors 5 (for example, three magnetic sensors 5). In addition, the second detector 20 could not contain the processing unit 6, or alternatively, the processing unit 6 could be located at a distance from the detectors instead of being located in the first detector 10

In a preliminary step, the first and second detectors 10, 20 are paired to make them work together, and configured to assign a function to each in the detection method S. For example, the first detector 10 may be configured as a master detector, while the second detector 20 may be configured as a slave detector. The term "master detector" of a given pass means a detector whose processing unit 6 is configured to calculate the average value and/or corrected signal value, while the term "slave detector" means another detector in the given pass.

In the first step S1, at least one of the magnetic sensors 5 - the first or the second - generates a signal characterizing the intensity of the magnetic field.

In practice, when a magnetic field is detected by one of the magnetic sensors 5 of the detection system 1, all the magnetic sensors 5 of said system generate a signal characterizing the intensity of the detected magnetic field, only the power of the signals from each sensor 5 will be different.

The signals generated by the first and second magnetic sensors 5 are transmitted to the processing unit 6, if necessary, through the communication interfaces 7 of the first detector 10 and/or the second detector 20. In this example, the first detector 10 is the master and contains the processing unit 6, while the signals of the second magnetic sensors 5 are transmitted to the first detector 10 via the communication interface 7 of the second detector 20, while the signals of the first magnetic sensors 5 can be transmitted there directly via the first magnetic sensors 5.

In step S2, the master detector processing unit 6 calculates an average of the signals generated by each pair of magnetic sensors 5. Thus, the processing unit 6 calculates a first average value corresponding to the first of the pairs of first and second magnetic sensors 5 and a second average corresponding to the second of steam.

Naturally, when each detector contains only one sensor 5, the processing unit 6 in step S2 calculates only one average of the signals of said two magnetic sensors 5.

As mentioned above, the processing unit 6 may calculate the arithmetic mean of the signals or, alternatively, the geometric mean.

Alternatively, instead of calculating the average value of the signals of each pair of magnetic pickups 5, the processing unit 6 may implement step S3 of correcting the signals generated by each of the magnetic pickups 5 by applying an attenuation factor to said signals.

This correction step S3 thus makes it possible to attenuate the signals generated by the magnetic sensors 5 of the detection system 1 by applying a correction factor to said signals depending on the value of the signals. More specifically, the purpose of the correction is to attenuate the signal when the target is close to one of the detectors 10, 20 where the sensitivity is higher, in order to reduce the "weight" of the signal upon detection.

For this, during sub-steps S31 and S32, for each pair of magnetic sensors 5, the processing unit 6 determines the maximum value and the minimum value among the signals generated by the first magnetic sensor 5 and the second magnetic sensor 5 at a given time.

During the third sub-step S33, the processing unit 6 calculates the ratio of the found maximum value to the found minimum value, and then, during the fourth sub-step S34, compares said ratio with the given thresholds, and on the basis of this obtains the value of the attenuation factor to be applied to the value of the signals.

For example, the processing unit 6 can in particular compare said ratio with a first threshold and with a second threshold which is higher than the first threshold, and obtain an attenuation factor based on this. Thus, the attenuation coefficient can be equal to:

- the first value, when the specified ratio is less than the first threshold,

- a second value less than the first value when said ratio is greater than the second threshold, and

- a value between the first value and the second value, when said ratio lies between the first threshold and the second threshold. In particular, the attenuation coefficient may be a linear function depending on the ratio when said ratio lies between the first threshold and the second threshold.

Using the situation where said ratio lies between the maximum value and the minimum value makes it possible to determine whether the target object, which creates a magnetic field or perturbs the Earth's electromagnetic field, is close to one of the detectors. In this case, the ratio value is greater than the second threshold, and the applied attenuation factor is equal to the second value, which is less than the first value. On the contrary, when the target is in the middle between two detectors, the sensitivity of the passage in this zone is lower. This is manifested in the fact that the ratio of the maximum value to the minimum value is also lower. Therefore, the attenuation factor may be higher and the resulting attenuation factor lower.

Thus, the relative actual similarity of the two detectors is achieved.

By way of (non-limiting) example, the first threshold may be 30, the second threshold may be 60, the first value may be 1, the second value may be 0.1, and the attenuation factor may be obtained from the following formula when the specified ratio lies between the first and second threshold:

-0.03*R+1.9

where R is the value of the ratio.

In other words, the attenuation factor may be 1 when said ratio is less than 30, 0.1 when said ratio is greater than 60, and -0.03*R+1.9 when said ratio is between 30 and 60.

According to another variant, the processing unit 6 calculates the average value of the signals for each pair of magnetic pickups 5 (step S2) and performs the step of correcting said signals (step S3).

For this, after calculating the average value of the signals for each pair of magnetic pickups 5 (step S2), the processing unit 6 may apply an attenuation factor to the found average values (step S3).

On the other hand, the processing unit 6 may first apply an attenuation factor to the signals of each pair of magnetic pickups 5 (step S3), and then calculate the average of the corrected signals of each pair of magnetic pickups 5 (step S2, applied to the corrected signals and not to the signals generated magnetic sensors 5).

The attenuation factor may be identical to the factor described above (equal to the first value, the second value, or a ratio function according to the magnitude of the ratio).

During the fifth step S5, the processing unit 6 compares the calculated value with a predetermined threshold value.

The calculated value used by the processing unit 6 in the fifth step S5 may be either the average value of the signals generated by the pair of magnetic pickups 5 obtained in step S2 or the average value corrected by applying the attenuation factor after step S3. When the average value, and optionally the corrected average value, exceeds the predetermined threshold value, in the sixth step S6, the processing unit 6 sends instructions to at least one of the emitters 8 to generate an alarm signal (optical, audible, etc.). Preferably, the processing unit 6 sends instructions for generating an alarm signal to the emitters 8 of the first detector 10 and the second detector 20 (via communication interfaces 7) so that one or more alarm signals are given on both sides of the passage. Alternatively, only a specific emitter or emitters 8 of one of the detectors 10, 20 can receive signaling instructions from the processing unit 6.

Alternatively, when the processing unit 6 determines only the corrected value of the signals, without taking into account the average value, in step S5 the sum of the corrected signal values (and not their average) is compared with a predetermined threshold value. Naturally, the signals generated by the sensors 5 may first be summed before the correction step S3 is applied to them.

On the other hand, instead of calculating the sum of the corrected signal values, the processing unit 6 may determine the maximum value of the corrected signals and compare, in step S5, the found maximum value with a threshold value. Similar to what was discussed above, it is possible to first determine the maximum value of the signals generated by the sensors 5 and then apply a correction step S3 to this maximum value.

According to this variant, the processing unit 6 compares the sum of the corrected values (or correspondingly corrected maximum values) of the signals of the same pair of magnetic sensors 5 with a predetermined threshold value. When said sum (or correspondingly adjusted maximum value) exceeds a given threshold value, in the sixth step S6, the processing unit 6 sends instructions for generating an alarm signal (optical, audible, etc.) to at least one of the emitters 8. As mentioned above, the processing unit 6 may send instructions for generating an alarm signal to the emitters 8 of the first detector 10 and/or the second detector 20.

Fig. 8a, 8b and 8c illustrate the measured signal intensity for four detection systems as a function of the distance to the detector(s).

Fig. 8a illustrates the case of a state of the art detection system comprising two detectors separated by a distance of 130 cm. In this figure, the represented intensity corresponds to the maximum value of the signals generated by the sensors of the two detectors.

Fig. 8b illustrates a case of a detection system 1 according to an embodiment of the present invention comprising two detectors separated by a distance of 130 cm and a processing unit. In this figure, the presented intensity corresponds to the average value of the signals generated by the sensors of the two detectors.

Fig. 8c illustrates a case of a detection system 1 according to an embodiment of the present invention comprising two detectors separated by a distance of 130 cm and a processing unit. In this figure, the presented intensity corresponds to the corrected average of the signals generated by the sensors of the two detectors

From the presented curves it is clearly seen that the calculation of the average value, and if appropriate, the application of attenuation coefficients at the stage of correction of the average value, makes it possible to equalize the signal intensity between the two detectors of the detection system compared to the case of simply determining the maximum signal values (Fig.8a).

Example

Table 1 below provides an example of comparing detection of the same target by three detection system configurations, namely: (i) detection system 1 containing only one detector; (ii) a detection system 1 according to the first embodiment of the invention, comprising two detectors separated by 130 cm, calculating the average value of the signals; and (iii) a detection system 1 according to the second embodiment of the invention, comprising two detectors separated by 130 cm, calculating the average value of the signals and correcting said average value to determine whether an alarm should be triggered.

In this example, the SE sensitivity of the three detection system configurations was set to 85% (1400 mV equivalent). In other words, the sensitivity was set such that the set threshold was 1400 mV. The parameters of the systems were set so that at the specified sensitivity, passing a 75 mm sphere at a height of 1 m from the ground would not trigger any alarm when the sphere was passed at a distance of 65 cm from a single detector (first configuration (i)) or midway between two detectors. detectors (second and third configurations ((ii) (iii)). In other words, the diameter of 75 mm is the limiting diameter of detection by the systems under test. More precisely, the disturbance of the electromagnetic field by an iron sphere with a diameter of 75 mm practically corresponds to the disturbance that an automatic machine of the AK47 type creates in the middle of the passage .

In this table, "diameter limit [mm]" corresponds to the minimum diameter in millimeters from which the detection system 1 under test generates an alarm.

Tests show that in the case when the detection system 1 contains two detectors forming a passage (configurations (ii) and (iii)), and the processing unit 6 calculates the average value of the signals generated by the magnetic sensors 5 of these detectors, the system is able to distinguish between targets, magnetic field equivalent to that of an iron sphere approximately 62 mm in diameter from smaller objects such as smartphones, even if the target object is 50 cm away from one of the detectors (which in practice is already quite far from the middle of the passage; in the test, the detectors were separated by 130 cm apart).

In the case where the processing unit 6 of the detection system 1 further applies the correction step S2 to the average value of the signals (configuration (iii)), the detection system 1 is further capable of distinguishing targets with a magnetic field that is equivalent to that of an iron sphere with a diameter of approximately 64 mm, even if the target is 25 cm away from one of the detectors (i.e. very close to the detector since the detectors are 130 cm apart in this test).

Therefore, the detection systems of the present invention (configurations (ii) and (iii)) are capable of distinguishing small objects even if these objects contain magnetic components (e.g. smartphones) from large volume targets such as automatic rifles, even if the examined person 2 does not pass in the middle between the detectors.

The invention also relates to the case where the detection system 1 comprises a number of detectors, the number of which is three or more than three, so that a plurality of passages are formed, with two adjacent passages sharing the same detector. Next, an example of a target object detection method using such a detection system 1 will be described.

The detection system 1 includes three detectors, each of which contains two magnetic sensors 5 (figure 3). In other words, the detection system 1 includes first, second and third detectors 10, 20, 30 containing respectively two first, two second and two third magnetic sensors 5. The second detector 20 forms a first passage with the first detector 10 and a second passage with the third detector 30. Therefore, the second detector 20 is located between the first detector 10 and the third detector 30.

These three detectors are identical and therefore each contains a processing unit 6 and a communication interface 7. Naturally, the processing unit 6 could alternatively be located at a distance from the detectors rather than built into the detectors. In this case, the signals generated by the magnetic sensors 5 of this detector are transmitted to the remote processing unit 6 through the communication interfaces 7 of the detectors, so that the processing unit applies a detection algorithm to the signals, and then transmits any instructions for generating an alarm signal to the emitters 8 of the detectors through their detectors, through their respective communication interfaces 7.

Naturally, mutatis mutandis, the invention is applicable when the system comprises only two detectors that together form one pass, or more detectors (e.g., n detectors, where n is an integer) that together form (n-1) passes. In addition, the detectors could contain only one magnetic sensor 5 or more than two magnetic sensors 5 (for example, three magnetic sensors 5).

In a preliminary step, the first, second and third detectors 10, 20, 30 are paired to make them work together, and configured to assign a function to each in the detection method S. For example, for the first pass, the first detector 10 may be configured as the master detector while detector 20 is configured as the slave detector. For the second pass, detector 20 is configured as the master detector while detector 30 is configured as the slave detector. During pairing, the means of identifying each detector of the system (usually their address) is also entered and stored in the memory of each of the neighboring detectors. Thus, the identification means of the first detector 10 is inserted into the second detector 20, while the identification means of the second detector 20 is inserted into the first detector 10 to enable them to work in pairs. Similarly, second detector identification means 20 is inserted into third detector 30, while third detector identification means 30 is inserted into second detector 20.

At the first stage, at least one of the magnetic sensors 5 - the first, second or third - registers the magnetic field and generates a signal characterizing the intensity of the detected magnetic field.

In practice, all magnetic sensors 5 of one pass continuously or periodically generate a signal characterizing the intensity of the detected magnetic field, only the power of the signals from each sensor 5 will be different.

Next, to illustrate the steps of method S, an example will be considered in which a signal is generated by two second magnetic sensors 5 and two third magnetic sensors 5.

The signals generated by the magnetic sensors 5 are then transmitted to the processing unit 6 of the leading passage detector, if necessary via communication interfaces 7. In this example, the signal generated by the third magnetic sensors 5 is transmitted via the communication interface 7 of the third detector 30 to the processing unit 6 of the second detector 20 The signal generated by the second magnetic sensors 5 is itself transmitted directly to the processing unit 6 of the second detector 20 (remembering that this signal would be transmitted via the communication interface 7 if the processing unit 6 were external).

At the second stage, the processing unit 6 of the leading detector of the passage in question (in this case, the second detector 20) calculates the average value of the PGS[2,3] signals generated by each pair of magnetic sensors 5. Therefore, in this case, the processing unit 6 calculates a first average value corresponding to the first of the pairs of second and third magnetic sensors 5 and a second average value corresponding to the second of the pairs.

Naturally, when each detector contains only one sensor 5, the processing unit 6 calculates only one average value corresponding to the average value of the signals of said two magnetic sensors 5.

As mentioned above, the processing unit 6 may calculate the arithmetic mean of the signals or, alternatively, the geometric mean.

As an alternative implementation, instead of calculating the average value of the signals of each pair of magnetic sensors 5, the processing unit 6 may implement the step of correcting the signals generated by each of the magnetic sensors 5 by applying the attenuation factor of these signals, and then calculating the sum of the values of the corrected signals (or alternatively , determining the maximum value of the corrected signals for each pair of sensors 5. Since this correction step has already been described above with respect to sub-steps S31-S35, it will not be discussed in detail here.In another embodiment, the processing unit 6 can immediately calculate the average value of the signals for each a pair of magnetic pickups 5 and implement the signal correction step as described above so as to obtain a corrected average value.

Similarly to what was described above, the correction step S2 can be applied either to the signals generated by the sensors 5, or to the sum of the signals (or their maximum value), or to the average value of the signals.

In the third step, when one of the PGS[2,3] values calculated in the second step exceeds a predetermined threshold value, the processing unit 6 of the second detector 20 transmits to the processing unit 6 of the first detector 10 on the one hand the specified calculated value PGS[2, 3 ], and on the other hand, the signals generated by its second magnetic sensors 5.

In the fourth step, simultaneously with the third step, the processing unit 6 of the first detector 10 calculates the value of PGS[1, 2] based on the signals generated for each pair of magnetic sensors 5 of the first pass. The calculation of said value performed by the processing unit 6 of the first detector 10 is the same as the calculation performed by the processing unit 6 of the second detector 20. In other words, when one of the master detectors calculates the average values, or the maximum corrected value), the other master detectors perform the same calculation (respectively, the calculation of the average value, the corrected average value corresponding to the sum of the corrected values, or the maximum corrected value).

Here, the processing unit 6 of the first detector 10 calculates, for example, a first average corresponding to the first of the pairs of the first and second magnetic sensors 5 and a second average corresponding to the second pair, so as to obtain the average values of the signals.

When the value of PGS[1, 2] calculated by the first detector 10 is less than the predetermined threshold value, the processing unit 6 of the first detector 10 does not send any instructions to the emitters 8 of the first detector 10 or the second detector 20 to generate an alarm.

However, when the value of PGS[1, 2] calculated by the first detector 10 is larger than the predetermined threshold value, in the fifth step, the processing unit 6 of the first detector 10 as the master detector of the first pass determines whether the target object was detected in the first pass (which is formed the first and second detectors 10, 20) or in the second passage (which is formed by the second and third detectors 20, 30).

To do this, the processing unit 6 of the first detector 10 compares the PGS[2, 3] values (corrected or uncorrected average values, sum or corrected maximum value) calculated by the second detector 20 with the PGS[1, 2] values calculated by the first detector 10.

To this end, in the first sub-step, the processing unit 6 of the first detector 10 multiplies the PGS[2,3] value calculated on the basis of the signals generated by the second and third sensors 5 by a predetermined safety factor Ks: Ks*PGS[2,3]. The safety factor is greater than or equal to 1, such as 1.5 or 2.

In parallel, in the second sub-step, the processing unit 6 of the first detector 10 multiplies the PGS[1,2] value calculated on the basis of the signals generated by the first and second sensors 5 by a predetermined safety factor Ks: Ks*PGS[1,2]

In the third sub-step, the first detector 10 compares the PGS[1,2] value with the Ks*PGS[2,3] value that the detector has calculated based on the signals generated by the second and third sensors 5. If the PGS[1,2] value calculated on based on the signals generated by the first and second sensors 5 is less than the value Ks*PGS[2,3] obtained by multiplying the safety factor Ks by the value calculated based on the signals generated by the second and third sensors 5 (i.e., if PGS[ 1,2]<Ks*PGS[2,3]), the processing unit 6 of the first detector 10 cancels the instructions or does not transmit any instructions for generating an alarm signal by the emitters 8 of the first and second detectors 10, 20.

In parallel, in the fourth sub-step, the second detector 20 compares the value of PGS[2,3] with the value of Ks*PGS[1,2] obtained by multiplying Ks by the value of the signals generated by the first and second sensors 5. If the value of PGS[2,3 ] calculated based on the signals generated by the second and third sensors 5 is smaller than the value Ks*PGS[1,2] obtained by multiplying the safety factor Ks by the value calculated based on the signals generated by the first and second sensors 5 (i.e. , if PGS[2,3]<Ks*PGS[1,2]) the processing unit 6 of the second detector 20 cancels the instructions or does not transmit any instructions for generating an alarm signal by the emitters 8 of the second and third detectors 20, 30. Otherwise, if PGS[2,3]>Ks*PGS[1,2], the second detector 20 transmits instructions for transmitting an alarm signal to the emitters 8 of the second detector 20 and the third detector 30.

The operator can then easily determine the pass (in this case the second one) in which the target is detected.

It should be noted that the application of the safety factor Ks when comparing the values calculated by the detectors on either side of a given passage creates a headroom when detecting targets and reduces the risk of false alarms.

Thus, the transmission of the slave passage detector to the master passage detector of the calculated value (average value with or without correction, or the sum of the adjusted values) for the adjacent passage, for which the same detector is the master, allows to determine the location of the target object that was detected. It should be remembered that the result of object detection by the magnetic sensors 5 is a scalar value, and that the detector that is shared for two adjacent passes (in this case the second detector 20) is not able to determine which side the detected target object is located.

The detection method S can be generalized to cover any detection system 1 containing n detectors, where n is greater than or equal to 4, so as to form n-1 passes, and that two adjacent passes have the same common detector.

The detection method S then comprises the same steps as those described above with respect to the detection system 1 with three detectors. However, in this case, when detector n-1 calculates the value PGS[n-1; n] greater than the predetermined threshold value AT, the detection method S comprises, in addition to the comparison steps, the values PGS[n-1; n] with the value calculated by the detector n-2 (PGS[n-2; n-1]), the step of comparing this value PGS[n-1; n] with the value computed by detector n (PGS[n; n+1]) to determine the pass in which the target was detected (see FIG. 7). If necessary, at the stage of comparison to the value of PGS[n; n+1] safety factor Ks (Ks>1) is applied.

For example, detector n-1 calculates the given value PGS[n-1; n], usually an average value (corrected if necessary) based on the signals generated by the magnetic sensors 5 of detectors n and n-1. Detector n-1 (as a slave detector) then sends this computed value PGS[n-1; n] to detector n-2 (as master detector), as well as the values of the signals generated by magnetic sensors 5. Detector n-2 then calculates PGS[n-2; n-1], in this case the average value (corrected if necessary) based on the signal values generated by the magnetic sensors 5 of the detectors n-2 and n-1. In the same way, detector n (as the slave detector of detector n-1) calculates and transmits the computed value PGS[n; n+1] to detector n-1, as well as the values of signals generated by magnetic sensors 5. If the value calculated by detector n-2 (as the master detector) is greater than the specified threshold value, then:

- detector n-2:

• multiplies the value of PGS[n-1; n] calculated and transmitted by the detector n-1 by the safety factor Ks and

• compares the value of PGS[n-2; n-1], which the detector calculated with the value Ks*PGS[n-1; n], which the detector obtained by multiplication. If the value of PGS[n-2; n-1] that the detector computed is less than the value computed by detector n-1 multiplied by the Ks factor (i.e., if PGS[n-2; n-1]<Ks*PGS[n-1; n] , detector n-2 concludes that no alarm signal should be generated from the passage that is formed by detectors n-2 and n-1.Therefore, detector n-2 does not send any instructions to generate an alarm signal by emitters of 8 detectors n-2 and n-1 (or cancels the instructions to trigger the alarm, if necessary).

- detector n-1 in parallel:

• multiplies the value of PGS[n-2; n-1], calculated and transmitted by the detector n-2, by the safety factor Ks and

• compares the value of PGS[n-1; n], which the detector calculated with the value Ks*PGS[n-2; n-1], which the detector received by multiplication.

If the value of PGS[n-1; n] that the detector computed is less than the value computed by detector n-2 multiplied by the Ks factor (i.e., if PGS[n-1; n]<Ks*PGS[n-2; n-1], the detector n-1 concludes that no alarm should be generated from the passage that is formed by detectors n-1 and n. Therefore, detector n-1 does not send any instructions to generate an alarm signal by emitters 8 of detectors n-1 and n (or cancels the instructions to trigger the alarm, if necessary).

• multiplies the value of PGS[n; n+1], calculated and transmitted by the detector n, by the safety factor Ks and

• compares the value of PGS[n-1; n], which the detector calculated with the value Ks*PGS[n; n+1], which the detector obtained by multiplication.

If the value of PGS[n-1; n] that detector computed is less than the value computed by detector n multiplied by the factor Ks (i.e., if PGS[n-1; n]<Ks*PGS[n; n+1], detector n-1 does the conclusion is that no alarm signal should be generated from the passage that is formed by detectors n-1 and n. Therefore, detector n-1 does not send any instructions to generate an alarm signal by emitters 8 of detectors n-1 and n (or, if necessary, cancels the instructions to trigger an alarm).

- detector n in parallel:

• multiplies the value of PGS[n-1; n] calculated and transmitted by the detector n-1 by the safety factor Ks and

• compares the value of PGS[n; n+1], which the detector calculated with the value Ks*PGS[n-1; n], which the detector obtained by multiplication.

If the value of PGS[n; n+1] that the detector computed is less than the value computed by detector n-1 multiplied by the Ks factor (i.e., if PGS[n; n+1]<Ks*PGS[n-1; n], the detector n concludes that no alarm signal should be generated from the passage that is formed by detectors n and n + 1. Therefore, detector n does not send any instructions to generate an alarm signal by the emitters 8 of detectors n and n + 1 (or cancel the instructions if necessary to trigger an alarm).It should be noted that when adjacent passages do not share the same detector, but each passage is formed by two separate detectors, detection within each passage is performed by pairs of detectors. Thus, the detectors of a given passage do not necessarily communicate This is because each pass can operate independently, since it is not necessary to determine the pass through which the target was passed.

Claims (77)

1. A system (1) for detecting a target containing magnetized or ferromagnetic components, comprising: - the first detector (10), containing at least one first magnetic sensor (5), configured to generate a signal characterizing the intensity of the detected magnetic field, and at least one emitter (8), - a second detector (20), separate from the first detector (10), containing at least a second magnetic sensor (5) configured to generate a signal characterizing the intensity of the detected magnetic field, - at least one emitter (8), - at least one processing unit (6), which is or a processing unit (6) configured to receive signals characterizing the intensity of the magnetic field detected by the first magnetic sensor (5) and the second magnetic sensor (5), or a processing unit (6) configured to receive signals characterizing the intensity of the magnetic field detected by the first magnetic sensor (5), and a processing unit (6) configured to receive signals characterizing the intensity of the magnetic field detected by the second magnetic sensor (5 ), - and at least one communication interface (7) configured to transmit the signal generated by the second magnetic sensor (5) to the processing unit (6) receiving signals characterizing the intensity of the magnetic field detected by the first magnetic sensor (5), wherein said processing unit (6) is configured to determine a value calculated on the basis of signals characterizing the intensity of the magnetic field detected by the first magnetic sensor (5) and the second magnetic sensor (5), and when said calculated value exceeds a predetermined threshold value, with the possibility of transmitting instructions for generating an alarm signal to the specified at least one emitter (8). 2. The detection system (1) according to claim 1, in which the calculated value is the average value of the signals generated by the first and second magnetic sensors, (5) and/or the value corrected by applying the attenuation coefficient to the signals generated by the first and second magnetic sensors (5), wherein said attenuation factor is calculated according to the following sub-steps: S31: determination of the maximum value of the signal generated by the first magnetic sensor (5) and the second magnetic sensor (5), S32: determination of the minimum value of the signal generated by the first magnetic sensor (5) and the second magnetic sensor (5), S33: calculation of the ratio of the found maximum value to the found minimum value, S34: comparing said ratio with a first threshold and a second threshold, the second threshold being higher than the first threshold, and S35: obtaining an attenuation factor, wherein the attenuation factor is: - the first value, when the specified ratio is less than the first threshold, - a second value different from the first value when said ratio is greater than the second threshold, - and a value between the first value and the second value, when said ratio lies between the first threshold and the second threshold. 3. System (1) detection according to any one of paragraphs. 1, 2, in which the processing unit (6) is located in the first detector (10) and is configured to transmit instructions for generating an alarm signal to the second detector (20) via a communication interface (7). 4. System (1) detection according to any one of paragraphs. 1-3, in which the communication interface (7) is a wireless communication interface (7), wherein the first and second detectors (10, 20) are movable. 5. System (1) detection according to any one of paragraphs. 1-4, additionally containing a third detector (30), wherein: - the third detector (30) contains at least a third magnetic sensor (5) configured to detect the magnetic field and generate a signal characterizing the intensity of the detected magnetic field, - the first detector (10) and the second detector (20) form the first passage, and the second detector (20) and the third detector (30) together form the second passage. 6. The detection system (1) according to claim 5, wherein: - processing unit (6) is located in each of the first and second detectors (10, 20), while - a processing unit (6) located in the second detector (20) is configured to transmit instructions for generating an alarm signal to the second detector (20) and to the third detector (30). 7. Method (S) for detecting a target containing magnetized or ferromagnetic components using the detection system (1) described in any one of paragraphs. 1-6, including the following steps: S1: generating, by means of the first and second magnetic sensors (5), a signal indicative of the intensity of the magnetic field; S2: processing by the processing unit (6) of the signals generated by the first and second magnetic sensors so as to obtain a processed value, S4: comparing said processed value with a given threshold value; and S5: when the processed value exceeds the predetermined threshold value, transmitting instructions for generating an alarm signal to the first detector (10) and/or the second detector (20) using the wireless communication interface (7). 8. The detection method (S) according to claim 7, wherein the first detector (10) comprises a processing unit (6) and a communication interface (7), and the second detector (20) comprises a communication interface (7), wherein the method further comprises the stage of transmitting the signal generated by the second magnetic sensor (5) to the processing unit (6) via communication interfaces (7). 9. The method (S) according to claim 7 or 8, wherein the processing step (S2) comprises one of the following sub-steps: - calculation based on the signals generated by the first and second magnetic sensors (5), the average value of these signals, - calculating, on the basis of the signals generated by the first and second magnetic pickups (5), the mean value of said signals and correcting (S3) the mean value so as to obtain a corrected mean value by applying an attenuation factor to the mean value, - correcting the signals generated by the first and second magnetic pickups (5) so as to obtain corrected values by applying an attenuation factor to said signals and calculating an average value based on the corrected signals, - correcting the signals generated by the first and second magnetic pickups (5) so as to obtain corrected values by applying an attenuation factor to said signals and calculating the sum of the corrected values, - correcting the signals generated by the first and second magnetic pickups (5) so as to obtain corrected values by applying an attenuation factor to said signals and determining the maximum value of said corrected values, - determining, on the basis of the signals generated by the first and second magnetic sensors (5), the sum of the signals, and correcting the said sum by applying an attenuation coefficient to the said sum, - determining, on the basis of the signals generated by the first and second magnetic sensors (5), the maximum value of the signals, and correcting said maximum value by applying an attenuation factor to said maximum value, wherein the attenuation coefficient is calculated according to the following sub-steps: S31: determination of the maximum value of the signal generated by the first magnetic sensor (5) and the second magnetic sensor (5), S32: determination of the minimum value of the signal generated by the first magnetic sensor (5) and the second magnetic sensor (5), S33: calculation of the ratio of the found maximum value to the found minimum value, S34: comparing said ratio with a first threshold and a second threshold, wherein the second threshold is higher than the first threshold, and S35: Obtain attenuation factor, where attenuation factor is: - the first value, when the specified ratio is less than the first threshold, - a second value different from the first value when said ratio is greater than the second threshold, - and a value between the first value and the second value, when said ratio lies between the first threshold and the second threshold. 10. The detection method (S) of claim 9, wherein the attenuation coefficient is a linear function of said ratio when said ratio lies between the first threshold and the second threshold. 11. The detection method (S) according to claim 9 or 10, wherein the first value is 1, the second value is 0.1, and the attenuation coefficient is determined from the following expression when said ratio lies between the first threshold and the second threshold: -0.03*R+1.9, where R is the value of the ratio. 12. Method (S) detection according to any one of paragraphs. 8-11, in which the first detector (10) contains at least two first magnetic sensors (5), and the second detector (20) contains at least two second magnetic sensors (5), each first magnetic sensor (5) is connected with a certain second magnetic sensor (5), so that a pair is formed, with each pair applying steps S1-S4. 13. Method (S) detection according to any one of paragraphs. 8-12, in which the detection system (1) further comprises a third detector (30) containing at least a third magnetic sensor (5) configured to detect a magnetic field and generate a signal characterizing the intensity of the detected magnetic field, while the method ( S) further includes, before the alarm generation step S5, the step of processing the signals generated by the second and third magnetic sensors (5) so as to obtain a processed value. 14. The detection method (S) according to claim 13, further comprising, after the step of calculating the processed value of the signals generated by the second and third magnetic sensors (5), the step of determining, based on the processed value of the signals generated by the first and second magnetic sensors (5), and the processed value of the signals generated by the second and third magnetic sensors (5), the passage or passages formed by the first detector (10) and the second detector (20), on the one hand, and the second detector (20) and the third detector (30), with the other side, in which a magnetic field was detected. 15. The detection method (S) of claim 14, wherein the step of determining a passage or passages includes the following sub-steps: - multiplying the processed value calculated on the basis of the signals of the second and third sensors (5) by the safety factor (Ks), - comparing the processed value calculated on the basis of the signals generated by the first and second sensors (5) with the processed value calculated on the basis of the signals of the second and third sensors (5) and multiplied by the safety factor (Ks), - multiplying the processed value calculated on the basis of the signals of the first and second sensors (5) by the safety factor (Ks), - comparing the processed value calculated on the basis of the signals of the second and third sensors (5) with the processed value calculated on the basis of the signals of the first and second sensors (5) and multiplied by the safety factor (Ks). 16. The detection method (S) of claim 15, wherein: - step S5 is only carried out in accordance with the first and second detectors (10, 20) if the processed value calculated on the basis of the signals generated by the first and second sensors (5) is greater than the processed value calculated on the basis of the signals of the second and third sensors (5 ) and multiplied by the safety factor (Ks), - step S5 is only carried out in accordance with the second and third detectors (20, 30) if the processed value calculated on the basis of the signals generated by the second and third sensors (5) is greater than the processed value calculated on the basis of the signals of the second and third sensors (5 ) and multiplied by the safety factor (Ks). 17. Method (S) detection according to any one of paragraphs. 14-16, in which the first detector (10) and the second detector (20) each contain a processing unit (6), wherein: - the step of calculating the processed value of the signals generated by the second and third magnetic sensors (5) is performed by means of the processing unit (6) of the second detector (20), - the step of calculating the processed value of the signals generated by the first and second magnetic sensors (5) is performed by means of the processing unit (6) of the first detector (10), - and the step of determining the pair or pairs of detectors (10, 20, 30) that have detected the magnetic field is performed by the processing unit (6) of the second detector (20) and by the processing unit (6) of the first detector (10). 18. The detection method (S) according to claim 15, wherein the detection system (1) further comprises a fourth detector (n+1) comprising at least one fourth magnetic sensor (5) configured to detect the magnetic field and generate a signal , characterizing the intensity of the detected magnetic field, while the detection method (S) further includes the following sub-steps: - calculation of the processed value of the signals generated by the third and fourth magnetic sensors (5), - multiplying the processed value of the signals generated by the third and fourth magnetic sensors (5) by the safety factor (Ks), - comparing the processed value of the signals generated by the second and third magnetic sensors with the processed value of the signals generated by the third and fourth magnetic sensors (5) and multiplied by the safety factor (Ks), - comparing the processed value of the signals generated by the third and fourth magnetic sensors with the processed value of the signals generated by the second and third magnetic sensors (5) and multiplied by the safety factor (Ks), - determining the pair or pairs of detectors among the first, second, third and the fourth detectors (10, 20, 30, n+1) in which the magnetic field was detected. 19. The detection method (S) of claim 18, wherein - step S5 is only carried out in accordance with the second and third detectors (20, 30) if the processed value of the signals generated by the second and third sensors (5) is greater than the processed value of the signals generated by the third and fourth magnetic sensors (5) and multiplied by coefficient (Ks) of safety, - and step S5 is only carried out in accordance with the third and fourth detectors (30, 20) if the processed value of the signals generated by the third and fourth sensors (5) is greater than the processed value of the signals generated by the second and third magnetic sensors (5), and multiplied on the coefficient (Ks) of safety.

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