EP1695112A1 - Device for detecting non-metallic objects located on a human subject - Google Patents

Device for detecting non-metallic objects located on a human subject

Info

Publication number
EP1695112A1
EP1695112A1 EP04821086A EP04821086A EP1695112A1 EP 1695112 A1 EP1695112 A1 EP 1695112A1 EP 04821086 A EP04821086 A EP 04821086A EP 04821086 A EP04821086 A EP 04821086A EP 1695112 A1 EP1695112 A1 EP 1695112A1
Authority
EP
European Patent Office
Prior art keywords
signal
horn
detection device
polarization
reception
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP04821086A
Other languages
German (de)
French (fr)
Inventor
M. Thales Intellectual Property RICHARD
J-C. Thales Intellectual Property LEHUREAU
G. Thales Intellectual Property CACHIER
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
Original Assignee
Thales SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thales SA filed Critical Thales SA
Publication of EP1695112A1 publication Critical patent/EP1695112A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/887—Radar or analogous systems specially adapted for specific applications for detection of concealed objects, e.g. contraband or weapons
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/04—Systems determining presence of a target
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/024—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using polarisation effects
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V8/00—Prospecting or detecting by optical means
    • G01V8/005—Prospecting or detecting by optical means operating with millimetre waves, e.g. measuring the black losey radiation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
    • G01S7/414—Discriminating targets with respect to background clutter

Definitions

  • the field of the invention is that of devices for detecting objects concealed on human subjects. These devices are more particularly dedicated to monitoring and securing airport areas and transport aircraft, but they can also be placed at the entrance to protected buildings, reserved access areas or other means of transport ( ships, trains, ...) to which you wish to secure access.
  • the dangerous objects or materials that we are trying to detect reflect waves very differently from that of the human body.
  • This imagery can be done either passively or actively.
  • the passive technique consists in making an image directly of the body without illuminating it with a particular millimeter source.
  • the active technique makes it possible to make an image by illuminating the body, for example with a known millimeter beam at a precise wavelength.
  • These techniques have several drawbacks. They are expensive and their systematic installation in an airport requires considerable investments.
  • the techniques of imaging the human body come up against an ethical problem. Indeed, the clothes being sparse and unstructured are transparent to millimeter radiation and therefore, the subject appears naked on the millimeter image.
  • the detection device overcomes the above drawbacks.
  • the proposed device does not make an image of the human body, the system simply measures physical characteristics on the surface of the human body and deduces therefrom the presence or absence of suspicious non-metallic objects.
  • the system is able to roughly locate the position of the suspect object placed on the body. An operator must then manually check the area indicated by the device.
  • This technique is simple to design, inexpensive and does not require high computing power and is very well suited to the objects to be detected. The complete measurement is extremely fast and does not require a sophisticated measuring device.
  • the subject of the invention is a device for detecting objects placed on a human subject, said device comprising at least • a source for generating a microwave signal; • a horn for transmitting said signal, said horn illuminating an area of the body of said human subject; • a horn for receiving the signal reflected by said zone; • a structure carrying at least the transmission horn and the reception horn; • means for analyzing said reflected signal; characterized in that • the signal generation source comprises means making it possible to generate the signal in a known state of polarization; • the analysis means include first means for determining the energy and polarimetric characteristics of the reflected signal, second means for determining from said characteristics the presence of objects placed on said human subject and third warning means of said presence.
  • FIG. 1 represents the reflection of an electromagnetic wave on an object substantially plane according to whether its initial polarization is linearly polarized in two directions called S or P;
  • FIG. 1 represents the reflection of an electromagnetic wave on an object substantially plane according to whether its initial polarization is linearly polarized in two directions called S or P;
  • FIG. 2 represents the reflection of an electromagnetic wave on a substantially planar object when its initial polarization is linearly polarized at 45 degrees from the previous polarizations;
  • Figure 3 shows the reflected polarizations of Figure 3 on the Poincaré sphere;
  • Figure 4 shows the polarizations reflected in a simplified representation mode;
  • Figures 5, 6, 7 and 8 show the variations of three main parameters of the reflected wave as a function of the frequency of the signal applied to different detected objects;
  • Figure 9 shows the arrangement of the signal transmission and reception horns to pick up the reflected signal;
  • Figures 10 and 11 show the sizes of the so-called Fresnel zones for two object geometries;
  • FIG. 1 shows the reflection of an electromagnetic wave on a substantially planar object when its initial polarization is linearly polarized at 45 degrees from the previous polarizations;
  • Figure 3 shows the reflected polarizations of Figure 3 on the Poincaré sphere;
  • Figure 4 shows the polarizations reflected in a
  • FIG. 12 is a graph giving for different frequencies and for different geometries of objects the size of the detection area; • Figure 13 shows a general view of the device according to the invention; • Figure 14 is a block diagram of a gantry comprising a device according to the invention; • Figure 15 shows a block diagram of a portable device according to the invention; • Figures 16, 17 and 18 show the steps for implementing said portable device.
  • the operating principle of the device according to the invention is based on the optical reflection properties of objects and living tissues lit by a polarized millimeter wave.
  • Two polarizations are preserved during the reflection on the plane 11. The first is located in the incidence plane 12, the second is perpendicular to the plane incidence 12.
  • These 2 polarizations are respectively named P and S. Any other polarization is transformed by reflection on this plane.
  • a PINC rectilinear polarization wave of any angle will be transformed into elliptical polarization P EF in the general case as shown in FIG. 2.
  • the elliptical polarization PREF is symbolized by a rotating arrow.
  • the polarization variation is representative of the optical characteristics of the body. Consequently, the analysis of the polarimetric “signature” of the body allows us to find its nature. Thus, if a microwave signal of known polarization is emitted, the analysis of the reflected signal makes it possible to determine the nature of the body on which the signal is reflected on the condition that the polarization of the signal is neither in the plane d 'incidence nor perpendicular to said plane of incidence.
  • Microwave waves emitting in the millimeter or centimeter wavelength range are particularly well suited to detection for two reasons: • clothing is almost transparent to this type of wave and the reflection of the waves is then done directly on the body human or concealed object; • In the microwave domain, the properties of the human body, which is essentially water, are very different from most other materials, thus facilitating detection.
  • the microwave range one can easily generate a linearly polarized wave in the desired direction. It suffices for this to orient the emission horn of the desired angle around the axis of propagation of the microwave wave.
  • the disadvantage of using a 45 ° rectilinear polarization is that it is possible that the object to be detected has its own polarization oriented along the axis of the incident polarization.
  • An elliptically polarized electromagnetic wave is defined by 5 parameters: • 3 parameters defining polarization: Orientation of the major axis of the ellipse - Ellipticity factor - Polarization rate; • the intensity of the wave; • and the frequency of the microwave wave
  • the reflection mainly retains the polarization rate and of course, the frequency of the wave is known. Your parameters are therefore representative of the polarimetric "signature" of the object. These are the two parameters governing the polarization and the intensity of the wave.
  • the two polarization parameters can be presented on a Poincaré sphere where: • the latitude L corresponds to the ellipticity of the polarization, the poles then represent the two circular polarizations right and left and the equator the linear polarizations and • the longitude I is twice the angle of orientation of the major axis of l 'ellipse.
  • FIG. 3 represents on said Poincaré sphere S P the polarization states P RE F of a reflected wave coming from an incident wave polarized at 45 ° for angles of incidence of 35 degrees and 55 degrees when the thickness of a dielectric body varies from 0 to infinity, the permittivity of this body being equal to 3.
  • the state of polarization follows an almost circular trace centered on the state of polarization incident as can be seen in figure 3.
  • the trace in solid lines represents the variations of PREF for the incidence of 55 degrees and the trace in dotted lines for the incidence of 35 degrees.
  • the polarization furthest from the equator is reached for a thickness multiple of ⁇ / 12.
  • the reflection on the skin remains almost linear even under strong incidence. It is therefore easy to detect small thicknesses of dielectric with centimeter waves.
  • FIGS. 5, 6, 7 and 8 represent the "signature" of a body through the variations in the amplitude of the reflected signal and the angles ⁇ and ⁇ , characteristics of the elliptical polarization as a function of the frequency F of the signal for a range of frequencies varying from a few gigaHertz to 70 gigahertz in 4 different cases.
  • the incident wave is linearly polarized at 45 degrees from the plane of incidence.
  • the signature is that of a human body.
  • the permittivity of the human body essentially made up of water is worth approximately 40.
  • the signature is almost independent of the frequency.
  • the signature is that of a material of low permittivity. It is worth approximately 2.
  • the thickness of the material is equal to 3 millimeters, which corresponds to the thickness of the objects to be detected. As seen in Figure 6, the variations in amplitude and ellipticity are significant.
  • the signature is that of a material also of low permittivity. It is worth approximately 3.
  • the thickness of the material is greater and equal to 5 millimeters. As can be seen in the figure, the variations in amplitude and ellipticity are much greater than in the previous case.
  • the signature is that of a material of higher permittivity. It is worth approximately 7.
  • the thickness of the material is 5 millimeters. As can be seen in the figure, the variations in amplitude and ellipticity are even greater than in the previous case. It is therefore possible by an analysis of "polarimetric signatures" to find the nature of the body and its thickness. This analysis can be carried out simply by applying different thresholds to the signals received. It is also possible to carry out a Fourier analysis of the components of the signal as a function of the frequency of the signal. Finally, it is also possible to correlate the signals when they are noisy so as to improve detection. Indeed, the signals representing 3 different aspects of the same signature are necessarily correlated with each other.
  • the object When the signature comes not from a single object but from an object and the human body placed underneath, for example in the case of small objects or elongated objects, then the object introduces a birefringence of form which disrupts the initial signature of the human body. In this case, the comparison of the disturbed signature and the initial signature makes it possible to detect the presence of the object.
  • the microwave wave is emitted by a point transmitter and the reflected wave is picked up by a non-directional receiver as shown in FIG. 9.
  • the illuminated bodies being perfectly reflective to millimeter waves, only the part of the illuminated body verifying the geometric laws of reflection and diffraction between the emitter and the receiver reflect radiation capable of being picked up by the receiver.
  • the average angle of the reflected ray is equal to the average angle of the incident ray.
  • this part is called the first Fresnel zone. It corresponds to an area within which the diffracted waves are not phase shifted by more than one wavelength ⁇ .
  • the Fresnel zone 13 is determined in the case
  • the Fresnel zone 13 is a circular zone whose radius RFRESNEL checks the following equation:
  • the Fresnel zone is determined in the case of an object having a local radius of curvature R, said object illuminated by a transmitter 1 located at a distance D from the object, said transmitter 1 emitting radiation 5 25 at the wavelength ⁇ .
  • the Fresnel zone is a circular zone whose radius RFRESNEL checks the following equation: TM £ - cos ⁇ aV ⁇ C 2 (+ R)
  • Figure 12 brings together a network of curves giving as a function 0 of the distance D emitter-surface of the object the variation of the Fresnel radius for two signal frequencies and 3 local radii of curvature R.
  • the curves in solid lines correspond to a frequency of 30 gigaHertz and the dashed lines correspond to a frequency of 70 gigahertz.
  • the low curve corresponds to a radius of curvature R of 15 cm
  • the central curve to a radius of curvature R of 20 cm
  • the high curve to a radius of curvature R of 50 cm.
  • These radii of curvature are representative of those that can be found on a human torso.
  • the emitter-surface distance from the body is limited to 60 centimeters, which corresponds to the current distances used in detection systems of the same type. Fresnel rays have sizes between 1 centimeter and 7 centimeters and correspond perfectly to the sizes of the objects to be detected.
  • the device according to the invention is shown in FIG. 13. it essentially comprises: • a source 3 for generating a microwave signal 5, said source for generating the signal comprising means making it possible to generate the signal in a known state of polarization; • an emission horn 1 of said signal, said horn illuminating an area 13 of the body of a human subject 14 capable of hiding an object; • a reception horn 2 for the signal reflected by said zone; • a structure 21 carrying at least the transmission horn 1 and the reception horn 2; • means of analysis 4 said reflected signal 5 comprising first means 41 making it possible to determine the energy and polarimetric characteristics of the reflected signal, second means 42 making it possible to determine from said characteristics the presence of objects placed on said human subject and third means 43 for warning of said presence symbolized by arrows in FIG. 13.
  • the source of generation 3 of the microwave signal comprises means making it possible to generate the signal at a variable frequency, said frequency being between a few gigaHertz and 70 gigaHertz.
  • the source 1 or the emission horn 2 comprises means making it possible to transmit said linearly polarized signal, the direction of polarization of the signal being able to be oriented at approximately 45 degrees from the plane of average incidence of the signal on the illuminated area of the body or to emit a circularly or elliptically polarized signal. This emission polarization can be kept constant or varied over time in a known manner.
  • the first means 41 for measuring the polarimetric characteristics of the reflected signal are of different types.
  • the means 41 are of the ellipsometric type, that is to say that they make it possible to measure the main orientation and the ellipticity of the polarization received. There are then different possible techniques for carrying out this measurement.
  • the analysis system is said to have a rotating analyzer. It consists of a rotating polarizer placed in front of an intensity detector and means for rotating said polarizer. For example, a microwave horn connected to a microwave guide constitutes a good polarizer, this guide is then connected to a rotating joint ensuring the pivoting connection between the guide and the coaxial connector connected to the intensity detector.
  • the guide and the horn are rotated by a DC motor and the absolute angular position of the horn is measured by an incremental encoder.
  • the motor can also be a stepping motor in the case where the measurement time is large compared to the desired rotation period, thus the orientation of the horn is fixed during the measurement. From the intensity measured as a function of the angular position of the receiver horn, we go back to the 3 parameters sought which are the received intensity and the two parameters of ellipticity of the polarization of the received signal.
  • the solution of the rotating analyzer has the advantage of being simple to implement for a low cost but this method has the disadvantage of involving moving parts.
  • the complex amplitude of two orthogonal polarizations which make up the polarization to be analyzed is measured.
  • the receiver horn is preferably a horn making it possible to receive a polarization oriented at 45 degrees from the reflection plane.
  • the analysis means can also include synchronous detection 44 symbolized by the dotted rectangle in FIG. 13. Synchronous detection makes it possible to filter the signal received in a narrow band. It is not necessary if the transmitted signal is strong enough.
  • the system according to the invention does not require precise detection in phase.
  • the analysis means make it possible to determine from the ellipsometric characteristics depending on the frequency the presence of objects placed on said human subject and warning means make it possible to warn an operator either by an audible alarm or by an optical signal of said presence.
  • the so-called Fresnel detection surface is of the order of a few centimeters. It is sufficient to allow detection, but of course insufficient to detect a suspicious object on the whole of a human body with only a fixed microwave detector and receiver.
  • the device includes means making it possible to transmit and receive on the same horn known as transmission / reception.
  • This arrangement makes it possible to reduce the number of transmission and reception sources required by a factor of two.
  • the first solution represented in FIG. 14 consists in placing a plurality of transmitters 1 and receivers 2 on a mechanical structure 21 in the form of a gantry of sufficient size under which passes the person 14 to be checked. The transmitters 1 successively transmit the polarized microwave signal 5.
  • each receiver 2 The signal seen by each receiver 2 is the sum of various specular reflections coming from different Fresnel zones 13. The angles of incidence are little different from each other for these different zones 13 as indicated in FIG. 14. In the absence of a dielectric on the body, these reflections are all linearly polarized and their sum has an amplitude strongly dependent on the frequency depending on whether they interfere constructively or destructively but their polarization is not very dependent on the frequency. The reflection on a dielectric, on the other hand, strongly acts on the polarization. It is on this last criterion that the detection of potentially dangerous objects will be made. Each transmitter thus covers one or more parts of the human body passing under the gantry. A judicious distribution of the transmitters makes it possible to cover most of the human body and thus to ensure effective detection.
  • the second solution represented in FIG. 15 consists in placing a reduced number of transmitters and receivers on a mechanical structure 21 in the form of a mobile support comprising a handle 22 connected to the source of emission of microwave waves and to the analysis means. by a cord 23.
  • the operator 15 then moves this support 21 along the body of the person 14 subjected to detection.
  • the structure comprises 4 transmission / reception horns denoted respectively 101, 102, 103 and 104 as indicated in FIG. 15. Said horns are arranged at the vertices of a parallelogram.
  • the operation is as follows: At a given instant, the mobile support 21 is held by the operator 15 near the body 14 to be checked.
  • the transmitting / receiving horns are then activated sequentially.
  • the polarized microwave wave 5 is emitted by the first horn 101 used in emission mode and illuminates a large surface of the body to be inspected.
  • Three areas of the body 131, 132 and 133 reflect the wave towards the second horn 102, the third horn 103 and the fourth horn 104 used in reception mode as indicated in FIG. 16.
  • the polarized microwave wave 5 is transmitted by the second horn 102 used in transmission mode and lights up the body to be inspected.
  • Two new areas of the body 134 and 135 different from the previous ones reflect the wave 5 towards the third horn 103 and the fourth horn 104 used in reception mode as indicated in FIG.
  • the polarized microwave wave 5 is emitted by the third horn 103 used in emission mode and illuminates the body to be inspected.
  • a new area of the body 136 different from the previous ones reflects the wave 5 towards the fourth horn 104 used in reception mode as indicated in FIG. 18.
  • This thus covers with the four transmitting / receiving horns six different areas of measurement in three stages .
  • the said three measurement steps take place in a time of approximately one hundredth of a second. During this brief period, we can consider that the operator and the human subject are immobile.
  • the device may also include means for measuring the temperature of the human body. Indeed, a false breast or abdominal prosthesis hiding dangerous objects may not be detectable by the device if this prosthesis is loaded with water on its surface. So to overcome this problem, we can add a temperature measurement to discriminate between hot skin where blood circulates, prostheses hiding dangerous objects, by nature cooler. It is indeed very difficult to correctly temper uniformly and at the same temperature as the rest of the body a false prosthesis.
  • the temperature measurement does not necessarily require an additional device and is carried out in about a hundredth of a second. Of course, the area to be analyzed by the thermal detector must correspond to the dimensions of the false prostheses to be detected. Indeed, false prostheses have surfaces generally close to 10 centimeters in diameter.
  • the detectors are placed close enough to the body that the analyzed area corresponds to these dimensions and the temperature detection does not require any special adaptation.
  • the detectors are placed on a gantry, they are placed at a greater distance from the body human.
  • a temperature detector having a Teflon lens makes it possible to measure the temperature on a surface of approximately 10 centimeters in diameter at several tens of centimeters in distance.

Abstract

The invention concerns devices for detecting objects concealed on human subjects. These devices are particularly dedicated to the surveillance and security of airport areas and transport aircraft. Currently, existing devices rely either on detection using X-rays or on microwave imaging. In the first case, the system can prove to be dangerous to human beings and in the second case, the device poses ethical problems. The invention provides a device whose operation relies on the polarized microwave reflective properties of suspicious objects to be detected. This device can be portable or installed on security portals. This technique has a simple design, is inexpensive, does not require a high computing power and is very well adapted to objets to be detected. The complete measurement is extremely fast and does not require a sophisticated measuring instrument.

Description

DISPOSITIF DE DETECTION D'OBJETS NON METALLIQUES DISPOSES SUR UN SUJET HUMAIN. DEVICE FOR DETECTING NON-METALLIC OBJECTS ARRANGED ON A HUMAN SUBJECT.
Le domaine de l'invention est celui des dispositifs de détection d'objets dissimulés sur des sujets humains. Ces dispositifs sont plus particulièrement dédiés à la surveillance et à la sécurisation des zones aéroportuaires et des avions de transport, mais ils peuvent également être disposés à l'entrée de bâtiments protégés, de zones d'accès réservé ou d'autres moyens de transport (navires, trains, ...) dont on souhaite sécuriser l'accès.The field of the invention is that of devices for detecting objects concealed on human subjects. These devices are more particularly dedicated to monitoring and securing airport areas and transport aircraft, but they can also be placed at the entrance to protected buildings, reserved access areas or other means of transport ( ships, trains, ...) to which you wish to secure access.
Pour assurer la sécurité des passagers dans les avions, les valises de soute et les bagages à main sont contrôlés par des systèmes d'imagerie à rayons X. Le passager lui-même ne passe que par un portique détecteur de métaux. Or, il est nécessaire de détecter sur le passager les objets non métalliques présentant un réel danger comme des explosifs ou des armes en céramique. Pour combler, cette faille de sécurité, certains aéroports comme celui d'Orlando ont mis en place à titre expérimental des scanners à rayons X pour les passagers eux-mêmes. Toutefois l'utilisation de rayons X dans un but non médical est interdite dans un grand nombre de pays et en particulier dans la plupart des états européens . En effet, cette technique comporte un réel danger pour l'être humain en cas d'utilisation régulière. Afin de pallier les inconvénients de l'utilisation des rayons X, il est possible de réaliser une image du corps humain dans le domaine des ondes électromagnétiques millimétriques. En effet, les objets ou les matières dangereuses que l'on cherche à détecter réfléchissent les ondes de manière très différente de celle du corps humain. On peut ainsi facilement les détecter. Cette imagerie peut se faire soit de façon passive, soit de façon active. La technique passive consiste à réaliser une image directement du corps sans l'éclairer avec une source millimétrique particulière. A l'opposé, la technique active permet de faire une image en illuminant le corps, par exemple avec un faisceau millimétrique connu à une longueur d'onde précise. Ces techniques ont plusieurs inconvénients. Elles sont coûteuses et leur mise en place systématique dans un aéroport nécessite des investissements considérables. D'autre part, les techniques consistant à faire de l'imagerie du corps humain se heurtent à un problème d'éthique. En effet, les vêtements étant peu denses et déstructurés sont transparents au rayonnement millimétrique et par conséquent, le sujet apparaît nu sur l'image millimétrique. Or, le passager n'accepte pas d'être analysé à nu par un opérateur. Le dispositif de détection selon l'invention permet de résoudre les inconvénients précédents. Le dispositif proposé ne fait pas d'image du corps humain, le système mesure simplement des caractéristiques physiques sur la surface du corps humain et en déduit la présence ou l'absence d'objets suspects non métalliques. Toutefois, le système est capable de localiser grossièrement la position de l'objet suspect placé sur le corps. Un opérateur doit alors vérifier manuellement la zone indiquée par le dispositif. Cette technique est simple de conception, peu coûteuse et ne demande pas de puissance de calcul élevée et est très bien adaptée aux objets à détecter. La mesure complète est extrêmement rapide et ne nécessite pas d'appareil de mesure sophistiqué.To ensure passenger safety on airplanes, hold cases and hand luggage are checked by X-ray imaging systems. The passenger himself only goes through a metal detector gantry. However, it is necessary to detect on the passenger non-metallic objects presenting a real danger such as explosives or ceramic weapons. To fill this security gap, some airports such as Orlando have set up X-ray scanners on an experimental basis for the passengers themselves. However, the use of X-rays for non-medical purposes is prohibited in a large number of countries and in particular in most European states. Indeed, this technique involves a real danger for the human being in case of regular use. In order to overcome the drawbacks of using X-rays, it is possible to make an image of the human body in the field of millimeter electromagnetic waves. In fact, the dangerous objects or materials that we are trying to detect reflect waves very differently from that of the human body. We can easily detect them. This imagery can be done either passively or actively. The passive technique consists in making an image directly of the body without illuminating it with a particular millimeter source. In contrast, the active technique makes it possible to make an image by illuminating the body, for example with a known millimeter beam at a precise wavelength. These techniques have several drawbacks. They are expensive and their systematic installation in an airport requires considerable investments. On the other hand, the techniques of imaging the human body come up against an ethical problem. Indeed, the clothes being sparse and unstructured are transparent to millimeter radiation and therefore, the subject appears naked on the millimeter image. However, the passenger does not agree to be analyzed naked by an operator. The detection device according to the invention overcomes the above drawbacks. The proposed device does not make an image of the human body, the system simply measures physical characteristics on the surface of the human body and deduces therefrom the presence or absence of suspicious non-metallic objects. However, the system is able to roughly locate the position of the suspect object placed on the body. An operator must then manually check the area indicated by the device. This technique is simple to design, inexpensive and does not require high computing power and is very well suited to the objects to be detected. The complete measurement is extremely fast and does not require a sophisticated measuring device.
Plus précisément, l'invention a pour objet un dispositif de détection d'objets placés sur un sujet humain, ledit dispositif comportant au moins • une source de génération d'un signal hyperfréquence ; • un cornet d'émission dudit signal, ledit cornet éclairant une zone du corps dudit sujet humain ; • un cornet de réception du signal réfléchi par ladite zone ; • une structure portant au moins le cornet d'émission et le cornet de réception ; • des moyens d'analyse dudit signal réfléchi ; caractérisé en ce que • la source de génération du signal comporte des moyens permettant de générer le signal dans un état de polarisation connu ; • les moyens d'analyse comportent des premiers moyens permettant de déterminer les caractéristiques énergétiques et polarimétriques du signal réfléchi, des seconds moyens permettant de déterminer à partir desdites caractéristiques la présence d'objets placés sur ledit sujet humain et des troisièmes moyens d'avertissement de ladite présence.More specifically, the subject of the invention is a device for detecting objects placed on a human subject, said device comprising at least • a source for generating a microwave signal; • a horn for transmitting said signal, said horn illuminating an area of the body of said human subject; • a horn for receiving the signal reflected by said zone; • a structure carrying at least the transmission horn and the reception horn; • means for analyzing said reflected signal; characterized in that • the signal generation source comprises means making it possible to generate the signal in a known state of polarization; • the analysis means include first means for determining the energy and polarimetric characteristics of the reflected signal, second means for determining from said characteristics the presence of objects placed on said human subject and third warning means of said presence.
L'invention sera mieux comprise et d'autres avantages apparaîtront à la lecture de la description qui va suivre donnée à titre non limitatif et grâce aux figures annexées parmi lesquelles : • la figure 1 représente la réflexion d'une onde électromagnétique sur un objet sensiblement plan selon que sa polarisation initiale est polarisée linéairement selon deux directions dites S ou P; • la figure 2 représente la réflexion d'une onde électromagnétique sur un objet sensiblement plan lorsque sa polarisation initiale est polarisée linéairement à 45 degrés des polarisations précédentes ; • la figure 3 représente les polarisations réfléchies de la figure 3 sur la sphère de Poincaré ; • la figure 4 représente les polarisations réfléchies dans un mode de représentation simplifiée ; • les figures 5, 6, 7 et 8 représentent les variations de trois paramètres principaux de l'onde réfléchie en fonction de la fréquence du signal appliqué pour différents objets détectés ; • la figure 9 représente la disposition des cornets d'émission et de réception du signal pour capter le signal réfléchi ; • les figures 10 et 11 représentent les tailles des zones de détection dites zones de Fresnel pour deux géométries d'objets ; • la figure 12 est un graphique donnant pour différentes fréquences et pour différentes géométries d'objets la taille de la zone de détection ; • La figure 13 représente une vue générale du dispositif selon l'invention ; • la figure 14 est un schéma de principe d'un portique comportant un dispositif selon l'invention ; • la figure 15 représente un schéma de principe d'un dispositif portable selon l'invention ; • les figures 16, 17 et 18 représentent les étapes de mise en œuvre dudit dispositif portable.The invention will be better understood and other advantages will appear on reading the description which follows given without limitation and thanks to the appended figures among which: • FIG. 1 represents the reflection of an electromagnetic wave on an object substantially plane according to whether its initial polarization is linearly polarized in two directions called S or P; FIG. 2 represents the reflection of an electromagnetic wave on a substantially planar object when its initial polarization is linearly polarized at 45 degrees from the previous polarizations; • Figure 3 shows the reflected polarizations of Figure 3 on the Poincaré sphere; • Figure 4 shows the polarizations reflected in a simplified representation mode; • Figures 5, 6, 7 and 8 show the variations of three main parameters of the reflected wave as a function of the frequency of the signal applied to different detected objects; • Figure 9 shows the arrangement of the signal transmission and reception horns to pick up the reflected signal; • Figures 10 and 11 show the sizes of the so-called Fresnel zones for two object geometries; FIG. 12 is a graph giving for different frequencies and for different geometries of objects the size of the detection area; • Figure 13 shows a general view of the device according to the invention; • Figure 14 is a block diagram of a gantry comprising a device according to the invention; • Figure 15 shows a block diagram of a portable device according to the invention; • Figures 16, 17 and 18 show the steps for implementing said portable device.
Le principe de fonctionnement du dispositif selon l'invention repose sur les propriétés optiques de réflexion des objets et des tissus vivants éclairés par une onde millimétrique polarisée.The operating principle of the device according to the invention is based on the optical reflection properties of objects and living tissues lit by a polarized millimeter wave.
Soit un corps 10 tel que représenté en figure 1 , délimité par un plan 11 éclairé sous un angle d'incidence θ non nul par une onde 5 polarisée symbolisé par la flèche brisée. On note 12 le plan d'incidence contenant l'onde 5 et perpendiculaire au plan 11. Deux polarisations sont conservées lors de la réflexion sur le plan 11. La première est située dans le plan d'incidence 12, la seconde est perpendiculaire au plan d'incidence 12. Ces 2 polarisations sont respectivement nommées P et S. Toute autre polarisation est transformée par la réflexion sur ce plan. Par exemple, une onde de polarisation rectiligne PINC d'angle quelconque sera transformée en polarisation elliptique P EF dans le cas général comme indiqué sur la figure 2. La polarisation elliptique PREF est symbolisée par une flèche tournante. La variation de polarisation est représentative des caractéristiques optiques du corps. Par conséquent, l'analyse de la « signature » polarimétrique du corps permet de retrouver sa nature. Ainsi, si l'on émet un signal hyperfréquence de polarisation connue, l'analyse du signal réfléchi permet de déterminer la nature du corps sur lequel s'est réfléchi le signal à la condition que la polarisation du signal ne soit ni dans le plan d'incidence ni perpendiculaire audit plan d'incidence. Les ondes hyperfréquences émettant dans la gamme des longueurs d'onde millimétriques ou centimétriques sont particulièrement bien adaptées à la détection pour deux raisons : • les vêtements sont quasiment transparents à ce type d'onde et la réflexion des ondes se fait alors directement sur le corps humain ou l'objet dissimulé ; • Dans le domaine des hyperfréquences, les propriétés du corps humain composé essentiellement d'eau sont très différentes de la plupart des autres matériaux, facilitant ainsi la détection. Techniquement, dans la gamme des hyperfréquences, on peut facilement générer une onde polarisée linéairement dans la direction souhaitée. Il suffit pour cela d'orienter le cornet d'émission de l'angle souhaité autour de l'axe de propagation de l'onde hyperfréquence. L'inconvénient d'utiliser une polarisation rectiligne à 45° est qu'il est possible que l'objet à détecter présente une polarisation propre orientée selon l'axe de la polarisation incidente. L'utilisation d'une onde polarisée circulairement permet de résoudre ce problème. En effet, il est nettement plus difficile de fabriquer et de cacher sous des vêtements un objet qui présente une polarisation propre circulaire. Seuls des milieux optiquement actifs ou des milieux à biréfringence circulaire induit par effet Faraday peuvent avoir une polarisation propre circulaire de ce type. De façon plus générale, on peut utiliser une polarisation elliptique qui présente les mêmes avantages que la polarisation circulaire mais qui est plus simple à générer, surtout si on utilise une grande plage d'ondes hyperfréquences.Or a body 10 as shown in FIG. 1, delimited by a plane 11 lit at an angle of incidence θ not zero by a polarized wave 5 symbolized by the broken arrow. We note 12 the incidence plane containing wave 5 and perpendicular to the plane 11. Two polarizations are preserved during the reflection on the plane 11. The first is located in the incidence plane 12, the second is perpendicular to the plane incidence 12. These 2 polarizations are respectively named P and S. Any other polarization is transformed by reflection on this plane. For example, a PINC rectilinear polarization wave of any angle will be transformed into elliptical polarization P EF in the general case as shown in FIG. 2. The elliptical polarization PREF is symbolized by a rotating arrow. The polarization variation is representative of the optical characteristics of the body. Consequently, the analysis of the polarimetric “signature” of the body allows us to find its nature. Thus, if a microwave signal of known polarization is emitted, the analysis of the reflected signal makes it possible to determine the nature of the body on which the signal is reflected on the condition that the polarization of the signal is neither in the plane d 'incidence nor perpendicular to said plane of incidence. Microwave waves emitting in the millimeter or centimeter wavelength range are particularly well suited to detection for two reasons: • clothing is almost transparent to this type of wave and the reflection of the waves is then done directly on the body human or concealed object; • In the microwave domain, the properties of the human body, which is essentially water, are very different from most other materials, thus facilitating detection. Technically, in the microwave range, one can easily generate a linearly polarized wave in the desired direction. It suffices for this to orient the emission horn of the desired angle around the axis of propagation of the microwave wave. The disadvantage of using a 45 ° rectilinear polarization is that it is possible that the object to be detected has its own polarization oriented along the axis of the incident polarization. The use of a circularly polarized wave solves this problem. Indeed, it is much more difficult to manufacture and hide under clothing an object which has its own circular polarization. Only optically active media or media with circular birefringence induced by Faraday effect can have a circular own polarization of this type. More generally, an elliptical polarization can be used which has the same advantages as circular polarization but which is simpler to generate, especially if a large range of microwave waves is used.
Une onde électromagnétique polarisée elliptiquement est définie par 5 paramètres : • 3 paramètres définissant la polarisation : Orientation du grand axe de l'ellipse - Facteur d'ellipticité - Taux de polarisation ; • l'intensité de l'onde ; • et la fréquence de l'onde hyperfréquenceAn elliptically polarized electromagnetic wave is defined by 5 parameters: • 3 parameters defining polarization: Orientation of the major axis of the ellipse - Ellipticity factor - Polarization rate; • the intensity of the wave; • and the frequency of the microwave wave
La réflexion conserve majoritairement le taux de polarisation et bien entendu, la fréquence de l'onde est connue. Tois paramètres sont donc représentatifs de la « signature » polarimétrique de l'objet. Ce sont les deux paramètres régissant la polarisation et l'intensité de l'onde.The reflection mainly retains the polarization rate and of course, the frequency of the wave is known. Your parameters are therefore representative of the polarimetric "signature" of the object. These are the two parameters governing the polarization and the intensity of the wave.
Très classiquement, les deux paramètres de polarisation peuvent être présentés sur une sphère de Poincaré où : • la latitude L correspond à l'ellipticité de la polarisation, les pôles représentent alors les deux polarisations circulaires droite et gauche et l'équateur les polarisations linéaires et • la longitude I vaut deux fois l'angle d'orientation du grand axe de l'ellipse. La figure 3 représente sur ladite sphère de Poincaré SP les états de polarisation PREF d'une onde réfléchie issu d'une onde incidente polarisée à 45° pour des angles d'incidence de 35 degrés et de 55 degrés lorsque l'épaisseur d'un corps diélectrique varie de 0 à l'infini, la permittivité de ce corps étant égal à 3. En faisant varier la longueur d'onde λ, l'état de polarisation suit une trace quasi circulaire centrée sur l'état de polarisation incident comme on peut le voir sur la figure 3. La trace en traits pleins représente les variations de PREF pour l'incidence de 55 degrés et la trace en traits pointillés pour l'incidence de 35 degrés. On démontre que la polarisation la plus éloignée de l'équateur est atteinte pour une épaisseur multiple de λ/12 . Au contraire, la réflexion sur la peau reste quasiment linéaire même sous incidence forte. On peut donc facilement détecter des épaisseurs faibles de diélectrique avec des ondes centimétriques. Il est également possible de représenter les paramètres définissant la polarisation elliptique PREF par deux angles δ et Ψ comme on peut le voir sur la figure 4 dans le cas où la polarisation initiale PINC est une polarisation linéaire inclinée para rapport au plan d'incidence 12. On appelle alors δ l'angle que fait le grand axe de l'ellipse avec la direction de la polarisation initiale et Ψ l'angle vérifiant la relation suivante : Tg(Ψ)= A/B avec A dimension du petit axe de l'ellipse et B dimension du grand axe de l'ellipse. Un objet a une signature ellipsométrique périodique en fonction de la fréquence du signal. Ces périodes sont plus grandes si l'objet est de faible épaisseur optique, l'épaisseur optique étant le produit de l'épaisseur géométrique par l'indice optique du matériau qui est égal à la racine carré de la permittivité du matériau. Il est donc fondamental d'analyser le signal en fonction de la fréquence et sur une large bande de fréquences pour obtenir une signature représentative de l'objet. Les figures 5, 6, 7 et 8 représentent la « signature » d'un corps à travers les variations de l'amplitude du signal réfléchi et des angles δ et Ψ, caractéristiques de la polarisation elliptique en fonction de la fréquence F du signal pour une gamme de fréquences variant de quelques gigaHertz à 70 gigahertz dans 4 cas différents. Dans les 4 cas, l'onde incidente est polarisée linéairement à 45 degrés du plan d'incidence. Dans le premier cas de la figure 5, la signature est celle d'un corps humain. La permittivité du corps humain essentiellement constituée d'eau vaut environ 40. Comme on le voit, la signature est quasiment indépendante de la fréquence. Dans le second cas de la figure 6, la signature est celle d'un matériau de faible permittivité. Elle vaut environ 2. L'épaisseur du matériau est égale à 3 millimètres, ce qui correspond à l'épaisseur des objets à détecter. Comme on le voit sur la figure 6, les variations de l'amplitude et de l'ellipticité sont importantes. Dans le troisième cas de la figure 7, la signature est celle d'un matériau également de faible permittivité. Elle vaut environ 3. L'épaisseur du matériau est plus importante et égale à 5 millimètres. Comme on le voit sur la figure, les variations de l'amplitude et de l'ellipticité sont nettement plus importantes que dans le cas précédent. Dans le quatrième cas de la figure 8, la signature est celle d'un matériau de permittivité plus élevée. Elle vaut environ 7. Elle correspond par exemple à celle du verre. L'épaisseur du matériau est égale à 5 millimètres. Comme on le voit sur la figure, les variations de l'amplitude et de l'ellipticité sont encore plus importantes que dans le cas précédent. Il est donc possible par une analyse des « signatures polarimétriques » de retrouver la nature du corps et son épaisseur. Cette analyse peut être réalisée simplement en appliquant différents seuils sur les signaux reçus. On peut également réaliser une analyse de Fourier des composantes du signal en fonction de la fréquence du signal. Enfin, il est également possible de corréler les signaux lorsque ceux-ci sont bruités de façon à améliorer la détection. En effet, les signaux représentant 3 aspects différents d'une même signature sont nécessairement corrélés entre eux. Lorsque la signature provient non pas d'un objet unique mais d'un objet et du corps humain placé dessous, par exemple dans le cas d'objets de petites dimension ou d'objets longiformes, alors l'objet introduit une biréfringence de forme qui perturbe la signature initiale du corps humain. Dans ce cas, la comparaison de la signature perturbée et de la signature initiale permet de détecter la présence de l'objet.Very conventionally, the two polarization parameters can be presented on a Poincaré sphere where: • the latitude L corresponds to the ellipticity of the polarization, the poles then represent the two circular polarizations right and left and the equator the linear polarizations and • the longitude I is twice the angle of orientation of the major axis of l 'ellipse. FIG. 3 represents on said Poincaré sphere S P the polarization states P RE F of a reflected wave coming from an incident wave polarized at 45 ° for angles of incidence of 35 degrees and 55 degrees when the thickness of a dielectric body varies from 0 to infinity, the permittivity of this body being equal to 3. By varying the wavelength λ, the state of polarization follows an almost circular trace centered on the state of polarization incident as can be seen in figure 3. The trace in solid lines represents the variations of PREF for the incidence of 55 degrees and the trace in dotted lines for the incidence of 35 degrees. We show that the polarization furthest from the equator is reached for a thickness multiple of λ / 12. On the contrary, the reflection on the skin remains almost linear even under strong incidence. It is therefore easy to detect small thicknesses of dielectric with centimeter waves. It is also possible to represent the parameters defining the elliptical polarization PREF by two angles δ and Ψ as can be seen in FIG. 4 in the case where the initial polarization PINC is a linear polarization inclined relative to the plane of incidence 12. We then call δ the angle made by the major axis of the ellipse with the direction of the initial polarization and Ψ the angle verifying the following relationship: Tg (Ψ) = A / B with A dimension of the minor axis of the ellipse and B dimension of the major axis of the ellipse. An object has a periodic ellipsometric signature as a function of the frequency of the signal. These periods are greater if the object is of low optical thickness, the optical thickness being the product of the geometric thickness by the optical index of the material which is equal to the square root of the permittivity of the material. It is therefore fundamental to analyze the signal as a function of frequency and over a wide frequency band to obtain a signature representative of the object. FIGS. 5, 6, 7 and 8 represent the "signature" of a body through the variations in the amplitude of the reflected signal and the angles δ and Ψ, characteristics of the elliptical polarization as a function of the frequency F of the signal for a range of frequencies varying from a few gigaHertz to 70 gigahertz in 4 different cases. In all 4 cases, the incident wave is linearly polarized at 45 degrees from the plane of incidence. In the first case of Figure 5, the signature is that of a human body. The permittivity of the human body essentially made up of water is worth approximately 40. As we can see, the signature is almost independent of the frequency. In the second case of FIG. 6, the signature is that of a material of low permittivity. It is worth approximately 2. The thickness of the material is equal to 3 millimeters, which corresponds to the thickness of the objects to be detected. As seen in Figure 6, the variations in amplitude and ellipticity are significant. In the third case of FIG. 7, the signature is that of a material also of low permittivity. It is worth approximately 3. The thickness of the material is greater and equal to 5 millimeters. As can be seen in the figure, the variations in amplitude and ellipticity are much greater than in the previous case. In the fourth case of FIG. 8, the signature is that of a material of higher permittivity. It is worth approximately 7. It corresponds for example to that of glass. The thickness of the material is 5 millimeters. As can be seen in the figure, the variations in amplitude and ellipticity are even greater than in the previous case. It is therefore possible by an analysis of "polarimetric signatures" to find the nature of the body and its thickness. This analysis can be carried out simply by applying different thresholds to the signals received. It is also possible to carry out a Fourier analysis of the components of the signal as a function of the frequency of the signal. Finally, it is also possible to correlate the signals when they are noisy so as to improve detection. Indeed, the signals representing 3 different aspects of the same signature are necessarily correlated with each other. When the signature comes not from a single object but from an object and the human body placed underneath, for example in the case of small objects or elongated objects, then the object introduces a birefringence of form which disrupts the initial signature of the human body. In this case, the comparison of the disturbed signature and the initial signature makes it possible to detect the presence of the object.
L'onde hyperfréquence est émise par un émetteur ponctuel et 5 l'onde réfléchie est captée par un récepteur non directif comme indiqué sur la figure 9. Cependant, les corps éclairés étant parfaitement réfléchissants aux ondes millimétriques, seule la partie du corps éclairée vérifiant les lois géométriques de la réflexion et de la diffraction entre l'émetteur et le récepteur réfléchit un rayonnement susceptible d'être capté par le récepteur.The microwave wave is emitted by a point transmitter and the reflected wave is picked up by a non-directional receiver as shown in FIG. 9. However, the illuminated bodies being perfectly reflective to millimeter waves, only the part of the illuminated body verifying the geometric laws of reflection and diffraction between the emitter and the receiver reflect radiation capable of being picked up by the receiver.
10 En particulier, l'angle moyen du rayon réfléchi est égal à l'angle moyen du rayon incident. Classiquement, on appelle cette partie première zone de Fresnel. Elle correspond à une zone à l'intérieur de laquelle les ondes diffractées ne sont pas déphasées de plus d'une longueur d'onde λ. En figure 10, la zone de Fresnel 13 est déterminée dans le casIn particular, the average angle of the reflected ray is equal to the average angle of the incident ray. Conventionally, this part is called the first Fresnel zone. It corresponds to an area within which the diffracted waves are not phase shifted by more than one wavelength λ. In FIG. 10, the Fresnel zone 13 is determined in the case
15 d'un objet plan éclairé par un émetteur 1 situé à une distance D de l'objet, ledit émetteur 1 émettant un rayonnement 5 à la longueur d'onde λ. Dans une direction inclinée d'un angle θ par rapport à la normale à l'objet, la zone de Fresnel 13 est une zone circulaire dont le rayon RFRESNEL vérifie l'équation suivante : 15 of a planar object illuminated by a transmitter 1 located at a distance D from the object, said transmitter 1 emitting radiation 5 at the wavelength λ. In a direction inclined by an angle θ with respect to the normal to the object, the Fresnel zone 13 is a circular zone whose radius RFRESNEL checks the following equation:
En figure 11 , la zone de Fresnel est déterminée dans le cas d'un objet ayant un rayon de courbure local R, ledit objet éclairé par un émetteur 1 situé à une distance D de l'objet, ledit émetteur 1 émettant un rayonnement 5 25 à la longueur d'onde λ. Dans une direction inclinée d'un angle θ par rapport à la normale à l'objet, la zone de Fresnel est une zone circulaire dont le rayon RFRESNEL vérifie l'équation suivante : ™£ - cosθ aVΘC 2( + R) La figure 12 regroupe un réseau de courbes donnant en fonction 0 de la distance D émetteur-surface de l'objet la variation du rayon de Fresnel pour deux fréquences de signal et 3 rayons de courbure locaux R. Les courbes en traits pleins correspondent à une fréquence de 30 gigaHertz et les courbes en traits pointillés correspondent à une fréquence de 70 gigaHertz. Pour chaque fréquence, la courbe basse correspond à un rayon de courbure R de 15 centimètres, la courbe centrale à un rayon de courbure R de 20 centimètres et la courbe haute à un rayon de courbure R de 50 centimètres. Ces rayons de courbure sont représentatifs de ceux que l'on peut trouver sur un torse humain. De la même façon, la distance émetteur- surface du corps est limitée à 60 centimètres, ce qui correspond aux distances courantes utilisées dans des systèmes de détection du même type. Les rayons de Fresnel ont des tailles comprises entre 1 centimètre et 7 centimètres et correspondent parfaitement aux tailles des objets à détecter.In FIG. 11, the Fresnel zone is determined in the case of an object having a local radius of curvature R, said object illuminated by a transmitter 1 located at a distance D from the object, said transmitter 1 emitting radiation 5 25 at the wavelength λ. In a direction inclined by an angle θ with respect to the normal to the object, the Fresnel zone is a circular zone whose radius RFRESNEL checks the following equation: ™ £ - cosθ aVΘC 2 (+ R) Figure 12 brings together a network of curves giving as a function 0 of the distance D emitter-surface of the object the variation of the Fresnel radius for two signal frequencies and 3 local radii of curvature R. The curves in solid lines correspond to a frequency of 30 gigaHertz and the dashed lines correspond to a frequency of 70 gigahertz. For each frequency, the low curve corresponds to a radius of curvature R of 15 cm, the central curve to a radius of curvature R of 20 cm and the high curve to a radius of curvature R of 50 cm. These radii of curvature are representative of those that can be found on a human torso. Likewise, the emitter-surface distance from the body is limited to 60 centimeters, which corresponds to the current distances used in detection systems of the same type. Fresnel rays have sizes between 1 centimeter and 7 centimeters and correspond perfectly to the sizes of the objects to be detected.
Le dispositif selon l'invention est représenté en figure 13. il comprend essentiellement : • une source 3 de génération d'un signal hyperfréquence 5, ladite source de génération du signal comportant des moyens permettant de générer le signal dans un état de polarisation connu ; • un cornet d'émission 1 dudit signal, ledit cornet éclairant une zone 13 du corps d'un sujet humain 14 susceptible de cacher un objet ; • un cornet de réception 2 du signal réfléchi par ladite zone ; • une structure 21 portant au moins le cornet d'émission 1et le cornet de réception 2 ; • des moyens d'analyse 4dudit signal réfléchi 5 comportant des premiers moyens 41 permettant de déterminer les caractéristiques énergétiques et polarimétriques du signal réfléchi, des seconds moyens 42 permettant de déterminer à partir desdites caractéristiques la présence d'objets placés sur ledit sujet humain et des troisièmes moyens 43 d'avertissement de ladite présence symbolisé par des flèches sur la figure 13.The device according to the invention is shown in FIG. 13. it essentially comprises: • a source 3 for generating a microwave signal 5, said source for generating the signal comprising means making it possible to generate the signal in a known state of polarization; • an emission horn 1 of said signal, said horn illuminating an area 13 of the body of a human subject 14 capable of hiding an object; • a reception horn 2 for the signal reflected by said zone; • a structure 21 carrying at least the transmission horn 1 and the reception horn 2; • means of analysis 4 said reflected signal 5 comprising first means 41 making it possible to determine the energy and polarimetric characteristics of the reflected signal, second means 42 making it possible to determine from said characteristics the presence of objects placed on said human subject and third means 43 for warning of said presence symbolized by arrows in FIG. 13.
La source de génération 3 du signal hyperfréquence comporte des moyens permettant de générer le signal à une fréquence variable, ladite fréquence étant comprise entre quelques gigaHertz et 70 gigaHertz. La source 1 ou le cornet d 'émission 2 comporte des moyens permettant d'émettre ledit signal polarisé linéairement, la direction de polarisation du signal pouvant être orienté à environ 45 degrés du plan d'incidence moyen du signal sur la zone éclairée du corps ou d'émettre un signal polarisé circulairement ou elliptiquement. Cette polarisation d'émission peut être maintenue constante ou variée dans le temps de façon connue. Les premiers moyens 41 de mesure des caractéristiques polarimétriques du signal réfléchi sont de différents types. Lorsque la polarisation émise est maintenue constante, les moyens 41 sont de type ellipsométrique, c'est-à-dire qu'ils permettent de mesurer l'orientation principale et l'ellipticité de la polarisation reçue. Il existe alors différentes techniques possibles pour réaliser cette mesure. Dans un premier mode de réalisation, le système d'analyse est dit à analyseur tournant. Il est constitué d'un polariseur tournant placé devant un détecteur d'intensité et des moyens de mise en rotation dudit polariseur. Par exemple, un cornet hyperfréquence connecté à un guide hyperfréquence constitue un bon polariseur, ce guide est ensuite connecté à un joint tournant assurant la liaison pivotante entre le guide et le connecteur coaxial relié au détecteur d'intensité. Le guide et le cornet sont entraînés en rotation par un moteur à courant continu et la position angulaire absolue du cornet est mesurée par un codeur incrémental. Le moteur peut également être un moteur pas à pas dans le cas ou le temps de mesure est grand devant la période de rotation souhaitée, ainsi l'orientation du cornet est fixe pendant la mesure. A partir de l'intensité mesurée en fonction de la position angulaire du cornet récepteur, on remonte aux 3 paramètres recherchés qui sont l'intensité reçue et les deux paramètres d'éllipticité de la polarisation du signal reçu. La solution de l'analyseur tournant a l'avantage d'être simple à mettre en œuvre pour un bas coût mais cette méthode a l'inconvénient de faire intervenir des pièces mobiles. Dans un second mode de réalisation, on effectue la mesure de l'amplitude complexe de deux polarisations orthogonales qui composent la polarisation à analyser. Pour cela, on utilise un cornet dit orthomode qui donne sur 2 voies distinctes les 2 polarisations incidentes verticale et horizontale. Ayant ces 2 signaux, on mesure d'une part chaqueamplitude, puis le déphasage relatif entre ces 2 amplitudes. La mesure peut alors se faire à une fréquence de répétition de l'ordre du kilohertz. Lorsque la polarisation émise varie dans le temps, par exemple lorsque la source ou le cornet d'émission comporte des moyens permettant d'émettre différentes combinaisons de polarisations parallèle et perpendiculaire variant dans le temps, alors le cornet récepteur est préférentiellement un cornet permettant de recevoir une polarisation orientée à 45 degrés du plan de réflexion. L'analyse des variations de la polarisation permet de retrouver comme dans le cas précédent les caractéristiques ellipsométriques de la zone éclairée du corps par l'onde d'émission polarisée.The source of generation 3 of the microwave signal comprises means making it possible to generate the signal at a variable frequency, said frequency being between a few gigaHertz and 70 gigaHertz. The source 1 or the emission horn 2 comprises means making it possible to transmit said linearly polarized signal, the direction of polarization of the signal being able to be oriented at approximately 45 degrees from the plane of average incidence of the signal on the illuminated area of the body or to emit a circularly or elliptically polarized signal. This emission polarization can be kept constant or varied over time in a known manner. The first means 41 for measuring the polarimetric characteristics of the reflected signal are of different types. When the transmitted polarization is kept constant, the means 41 are of the ellipsometric type, that is to say that they make it possible to measure the main orientation and the ellipticity of the polarization received. There are then different possible techniques for carrying out this measurement. In a first embodiment, the analysis system is said to have a rotating analyzer. It consists of a rotating polarizer placed in front of an intensity detector and means for rotating said polarizer. For example, a microwave horn connected to a microwave guide constitutes a good polarizer, this guide is then connected to a rotating joint ensuring the pivoting connection between the guide and the coaxial connector connected to the intensity detector. The guide and the horn are rotated by a DC motor and the absolute angular position of the horn is measured by an incremental encoder. The motor can also be a stepping motor in the case where the measurement time is large compared to the desired rotation period, thus the orientation of the horn is fixed during the measurement. From the intensity measured as a function of the angular position of the receiver horn, we go back to the 3 parameters sought which are the received intensity and the two parameters of ellipticity of the polarization of the received signal. The solution of the rotating analyzer has the advantage of being simple to implement for a low cost but this method has the disadvantage of involving moving parts. In a second embodiment, the complex amplitude of two orthogonal polarizations which make up the polarization to be analyzed is measured. For this, we use a so-called orthomode horn which gives on 2 distinct channels the 2 incident vertical and horizontal polarizations. Having these 2 signals, we measure each amplitude, then the relative phase shift between these 2 amplitudes. The measurement can then be made at a repetition frequency of the order of a kilohertz. When the polarization transmitted varies over time, for example when the source or the transmission horn comprises means making it possible to transmit different combinations of parallel and perpendicular polarizations varying over time, then the receiver horn is preferably a horn making it possible to receive a polarization oriented at 45 degrees from the reflection plane. The analysis of the variations in polarization makes it possible to find, as in the previous case, the ellipsometric characteristics of the area illuminated by the body by the polarized emission wave.
Les moyens d'analyse peuvent également comporter une détection synchrone 44 symbolisée par le rectangle en pointillés de la figure 13. La détection synchrone permet de filtrer le signal reçu dans une bande étroite. Elle n'est pas nécessaire si le signal émis est suffisamment fort. Le système selon l'invention ne nécessite pas une détection précise en phase. Les moyens d'analyse permettent de déterminer à partir des caractéristiques ellipsométriques dépendant de la fréquence la présence d'objets placés sur ledit sujet humain et des moyens d'avertissement permettent d'avertir un opérateur soit par une alarme sonore soit par un signal optique de ladite présence. Comme on l'a vu, la surface de détection dite de Fresnel est de l'ordre de quelques centimètres. Elle est suffisante pour permettre la détection, mais bien entendu insuffisante pour détecter un objet suspect sur l'ensemble d'un corps humain avec uniquement un détecteur et un récepteur hyperfréquence fixes. Il faut, par conséquent disposer d'une pluralité de cornets d'émission et de réception, les moyens d'analyse pouvant être communs à ces différents cornets. Avantageusement, pour limiter le nombre de cornets d'émission et de réception, le dispositif comporte des moyens permettant d'émettre et de recevoir sur un même cornet dit d'émission/réception . Cette disposition permet de réduire d'un facteur deux le nombre de sources d'émission et de réception nécessaires. Pour assurer la détection sur la totalité du corps humain, plusieurs solutions sont possibles. La première solution représentée en figure 14 consiste à disposer une pluralité d'émetteurs 1 et de récepteurs 2 sur une structure mécanique 21 en forme de portique de taille suffisante sous lequel passe la personne 14 à contrôler. Les émetteurs 1 émettent successivement le signal hyperfréquence polarisé 5. Le signal vu par chaque récepteur 2 est la somme de diverses réflexions spéculaires provenant de différentes zones de Fresnel 13. Les angles d'incidences sont peu différents l'un de l'autre pour ces différentes zones 13 comme indiqué sur la figure 14. En l'absence de diélectrique sur le corps, ces réflexions sont toutes polarisées linéairement et leur somme a une amplitude fortement dépendante de la fréquence selon qu'elles interfèrent de façon constructive ou destructive mais leur polarisation est peu dépendante de la fréquence. La réflexion sur un diélectrique agit par contre fortement sur la polarisation. C'est sur ce dernier critère que se fera la détection d'objets potentiellement dangereux. Chaque émetteur couvre ainsi une ou plusieurs parties du corps humain passant sous le portique. Une répartition judicieuse des émetteurs permet de couvrir la majeure partie du corps humain et d'assurer ainsi une détection efficace. La seconde solution représentée en figure 15 consiste à disposer un nombre réduit d'émetteurs et de récepteurs sur une structure mécanique 21 en forme de support mobile comportant une poignée 22 reliée à la source d'émission d'ondes hyperfréquences et aux moyens d'analyse par un cordon 23. L'opérateur 15 déplace alors ce support 21 le long du corps de la personne 14 soumise à la détection. Dans un mode particulier de réalisation donné à titre d'exemple, la structure comporte 4 cornets d'émission/réception notés respectivement 101, 102, 103 et 104 comme indiqué sur la figure 15. Lesdits cornets sont disposés aux sommets d'un parallélogramme. A titre d'exemple, le fonctionnement est le suivant : A un instant donné, le support mobile 21 est tenu par l'opérateur 15 près du corps 14 à contrôler. Les cornets d'émission/réception sont alors activés de façon séquentielle. Dans une première étape représentée en figure 16, l'onde hyperfréquence polarisée 5 est émise par le premier cornet 101 utilisé en mode émission et éclaire une surface importante du corps à inspecter. Trois zones du corps 131 , 132 et 133 réfléchissent l'onde vers le second cornet 102, le troisième cornet 103 et le quatrième cornet 104 utilisés en mode réception comme indiqué sur la figure 16. Dans une seconde étape représentée en figure 17, l'onde hyperfréquence polarisée 5 est émise par le second cornet 102 utilisé en mode émission et éclaire le corps à inspecter. Deux nouvelles zones du corps 134 et 135 différentes des précédentes réfléchissent l'onde 5 vers le troisième cornet 103 et le quatrième cornet 104 utilisés en mode réception comme indiqué sur la figure 17. Enfin, dans une troisième étape représentée en figure 18, l'onde hyperfréquence polarisée 5 est émise par le troisième cornet 103 utilisé en mode émission et éclaire le corps à inspecter. Une nouvelle zone du corps 136 différente des précédentes réfléchit l'onde 5 vers le quatrième cornet 104 utilisé en mode réception comme indiqué sur la figure 18. On couvre ainsi avec les quatre cornets d'émission/réception six zones différentes de mesure en trois étapes. Lesdites trois étapes de mesure se font dans un temps d'environ un centième de seconde. Pendant cette brève période, on peut considérer que l'opérateur et le sujet humain sont immobiles.The analysis means can also include synchronous detection 44 symbolized by the dotted rectangle in FIG. 13. Synchronous detection makes it possible to filter the signal received in a narrow band. It is not necessary if the transmitted signal is strong enough. The system according to the invention does not require precise detection in phase. The analysis means make it possible to determine from the ellipsometric characteristics depending on the frequency the presence of objects placed on said human subject and warning means make it possible to warn an operator either by an audible alarm or by an optical signal of said presence. As we have seen, the so-called Fresnel detection surface is of the order of a few centimeters. It is sufficient to allow detection, but of course insufficient to detect a suspicious object on the whole of a human body with only a fixed microwave detector and receiver. It is therefore necessary to have a plurality of transmission and reception horns, the analysis means possibly being common to these different horns. Advantageously, in order to limit the number of transmission and reception horns, the device includes means making it possible to transmit and receive on the same horn known as transmission / reception. This arrangement makes it possible to reduce the number of transmission and reception sources required by a factor of two. To ensure detection on the entire human body, several solutions are possible. The first solution represented in FIG. 14 consists in placing a plurality of transmitters 1 and receivers 2 on a mechanical structure 21 in the form of a gantry of sufficient size under which passes the person 14 to be checked. The transmitters 1 successively transmit the polarized microwave signal 5. The signal seen by each receiver 2 is the sum of various specular reflections coming from different Fresnel zones 13. The angles of incidence are little different from each other for these different zones 13 as indicated in FIG. 14. In the absence of a dielectric on the body, these reflections are all linearly polarized and their sum has an amplitude strongly dependent on the frequency depending on whether they interfere constructively or destructively but their polarization is not very dependent on the frequency. The reflection on a dielectric, on the other hand, strongly acts on the polarization. It is on this last criterion that the detection of potentially dangerous objects will be made. Each transmitter thus covers one or more parts of the human body passing under the gantry. A judicious distribution of the transmitters makes it possible to cover most of the human body and thus to ensure effective detection. The second solution represented in FIG. 15 consists in placing a reduced number of transmitters and receivers on a mechanical structure 21 in the form of a mobile support comprising a handle 22 connected to the source of emission of microwave waves and to the analysis means. by a cord 23. The operator 15 then moves this support 21 along the body of the person 14 subjected to detection. In a particular embodiment given by way of example, the structure comprises 4 transmission / reception horns denoted respectively 101, 102, 103 and 104 as indicated in FIG. 15. Said horns are arranged at the vertices of a parallelogram. By way of example, the operation is as follows: At a given instant, the mobile support 21 is held by the operator 15 near the body 14 to be checked. The transmitting / receiving horns are then activated sequentially. In a first step shown in FIG. 16, the polarized microwave wave 5 is emitted by the first horn 101 used in emission mode and illuminates a large surface of the body to be inspected. Three areas of the body 131, 132 and 133 reflect the wave towards the second horn 102, the third horn 103 and the fourth horn 104 used in reception mode as indicated in FIG. 16. In a second step represented in FIG. 17, the polarized microwave wave 5 is transmitted by the second horn 102 used in transmission mode and lights up the body to be inspected. Two new areas of the body 134 and 135 different from the previous ones reflect the wave 5 towards the third horn 103 and the fourth horn 104 used in reception mode as indicated in FIG. 17. Finally, in a third step represented in FIG. 18, the polarized microwave wave 5 is emitted by the third horn 103 used in emission mode and illuminates the body to be inspected. A new area of the body 136 different from the previous ones reflects the wave 5 towards the fourth horn 104 used in reception mode as indicated in FIG. 18. This thus covers with the four transmitting / receiving horns six different areas of measurement in three stages . The said three measurement steps take place in a time of approximately one hundredth of a second. During this brief period, we can consider that the operator and the human subject are immobile.
Le dispositif peut comporter également des moyens de mesure de la température du corps humain. En effet, une fausse prothèse mammaire ou abdominale cachant des objets dangereux peut ne pas être détectable par le dispositif si cette prothèse est chargée en eau sur sa surface. Ainsi pour pallier ce problème, on peut ajouter une mesure de température permettant de discriminer les peaux chaudes où le sang circule, des prothèses cachant des objets dangereux, par nature plus froides. Il est en effet très difficile de tempérer correctement de façon uniforme et à la même température que le reste du corps une fausse prothèse. La mesure de température ne nécessite pas nécessairement d'appareil supplémentaire et est effectuée en un centième de seconde environ. Il faut bien entendu que la zone à analyser par le détecteur thermique corresponde aux dimensions des fausses prothèses à détecter. En effet, les fausses prothèses ont des surfaces généralement voisines de 10 centimètres de diamètre. Dans le cas d'un détecteur mobile à main, les détecteurs sont placés suffisamment près du corps pour que la zone analysée corresponde à ces dimensions et la détection de température ne nécessite pas d'adaptation spéciale. Dans le cas ou les détecteurs sont placés sur un portique, ils sont placés à plus grande distance du corps humain. Dans ce cas, un détecteur de température possédant une lentille de téflon permet de faire la mesure de température sur une surface d'environ 10 centimètres de diamètre à plusieurs dizaines de centimètres de distance. The device may also include means for measuring the temperature of the human body. Indeed, a false breast or abdominal prosthesis hiding dangerous objects may not be detectable by the device if this prosthesis is loaded with water on its surface. So to overcome this problem, we can add a temperature measurement to discriminate between hot skin where blood circulates, prostheses hiding dangerous objects, by nature cooler. It is indeed very difficult to correctly temper uniformly and at the same temperature as the rest of the body a false prosthesis. The temperature measurement does not necessarily require an additional device and is carried out in about a hundredth of a second. Of course, the area to be analyzed by the thermal detector must correspond to the dimensions of the false prostheses to be detected. Indeed, false prostheses have surfaces generally close to 10 centimeters in diameter. In the case of a mobile hand-held detector, the detectors are placed close enough to the body that the analyzed area corresponds to these dimensions and the temperature detection does not require any special adaptation. In the case where the detectors are placed on a gantry, they are placed at a greater distance from the body human. In this case, a temperature detector having a Teflon lens makes it possible to measure the temperature on a surface of approximately 10 centimeters in diameter at several tens of centimeters in distance.

Claims

REVENDICATIONS
1. Dispositif de détection d'objets placés sur un sujet humain, ledit dispositif comportant au moins • une source de génération d'un signal hyperfréquence ; • un cornet d'émission dudit signal, ledit cornet éclairant une zone du corps dudit sujet humain ; • un cornet de réception du signal réfléchi par ladite zone ; • une structure portant au moins le cornet d'émission et le cornet de réception ; • des moyens d'analyse dudit signal réfléchi ; caractérisé en ce que • la source de génération du signal comporte des moyens permettant de générer le signal dans un état de polarisation connu, ledit signal éclairant ladite zone du corps sous un angle d'incidence non nul ; • les moyens d'analyse comportent des premiers moyens permettant de déterminer les caractéristiques énergétiques et polarimétriques du signal réfléchi, des seconds moyens permettant de déterminer à partir desdites caractéristiques la présence d'objets placés sur ledit sujet humain et des troisièmes moyens d'avertissement de ladite présence. 1. Device for detecting objects placed on a human subject, said device comprising at least • a source for generating a microwave signal; • a horn for transmitting said signal, said horn illuminating an area of the body of said human subject; • a horn for receiving the signal reflected by said zone; • a structure carrying at least the transmission horn and the reception horn; • means for analyzing said reflected signal; characterized in that • the signal generation source comprises means making it possible to generate the signal in a known state of polarization, said signal illuminating said area of the body at a non-zero angle of incidence; • the analysis means include first means for determining the energy and polarimetric characteristics of the reflected signal, second means for determining from said characteristics the presence of objects placed on said human subject and third warning means of said presence.
2. Dispositif de détection selon la revendication 1 , caractérisé en ce que le dispositif comporte des moyens permettant d'émettre ou de recevoir le signal sur un même cornet dit d'émission/réception.2. Detection device according to claim 1, characterized in that the device comprises means for transmitting or receiving the signal on the same horn called transmission / reception.
3. Dispositif de détection selon les revendications 1 ou 2, caractérisé en ce que le dispositif comporte également une détection synchrone reliant la source de génération du signal hyperfréquence et les moyens d'analyse.3. Detection device according to claims 1 or 2, characterized in that the device also comprises a synchronous detection connecting the source of generation of the microwave signal and the analysis means.
4. Dispositif de détection selon l'une des revendications 1 à 3, caractérisé en ce que la source comporte des moyens permettant de générer le signal à une fréquence variable, ladite fréquence étant comprise entre quelques gigaHertz et 70 gigaHertz.4. Detection device according to one of claims 1 to 3, characterized in that the source comprises means making it possible to generate the signal at a variable frequency, said frequency being between a few gigaHertz and 70 gigaHertz.
5. Dispositif de détection selon l'une des revendications 1 à 4, caractérisé en ce que la source ou le cornet d 'émission comporte des moyens permettant d'émettre un signal polarisé linéairement, la direction de polarisation dudit signal étant orienté à environ 45 degrés du plan d'incidence moyen du signal sur la zone éclairée du corps. 5. Detection device according to one of claims 1 to 4, characterized in that the source or the transmission horn comprises means making it possible to transmit a linearly polarized signal, the direction of polarization of said signal being oriented at approximately 45 degrees of the plane of average incidence of the signal on the illuminated area of the body.
6. Dispositif de détection selon l'une des revendications 1 à 4, caractérisé en ce que la source ou le cornet d 'émission comporte des moyens permettant d'émettre un signal polarisé circulairement ou elliptiquement. 6. Detection device according to one of claims 1 to 4, characterized in that the source or the transmission horn comprises means for transmitting a circularly or elliptically polarized signal.
7. Dispositif de détection selon l'une des revendications 1 à 4, caractérisé en ce que la source ou le cornet d 'émission comporte des moyens permettant d'émettre un signal polarisé comportant différentes combinaisons de polarisations parallèle et perpendiculaire variant dans le temps.7. Detection device according to one of claims 1 to 4, characterized in that the source or the emission horn comprises means making it possible to emit a polarized signal comprising different combinations of parallel and perpendicular polarizations varying in time.
8. Dispositif de détection selon l'une des revendications 5 ou 6, caractérisé en ce que les premiers moyens de mesure des caractéristiques polarimétriques du signal réfléchi sont de type ellipsométriques, c'est-à-dire qu'ils permettent de mesurer l'orientation principale et l'ellipticité de la polarisation reçue.8. Detection device according to one of claims 5 or 6, characterized in that the first means for measuring the polarimetric characteristics of the reflected signal are of ellipsometric type, that is to say that they make it possible to measure the main orientation and ellipticity of the received polarization.
9. Dispositif de détection selon la revendication 8, caractérisé en ce que les premiers moyens de mesure ellipsométriques comportent un polariseur hyperfréquence disposé devant un détecteur d'intensité et des moyens de mise en rotation dudit polariseur.9. Detection device according to claim 8, characterized in that the first ellipsometric measurement means comprise a microwave polarizer disposed in front of an intensity detector and means for rotating said polarizer.
10. Dispositif de détection selon la revendication 9, caractérisé en ce que les moyens de mise en rotation comportent soit un moteur à courant continu, soit un moteur pas à pas. 10. Detection device according to claim 9, characterized in that the means for rotating comprise either a DC motor or a stepping motor.
11. Dispositif de détection selon la revendication 8, caractérisé en ce que le cornet de réception est du type orthomode et que les premiers moyens de mesure comportent deux détecteurs placés en sortie dudit cornet de réception.11. Detection device according to claim 8, characterized in that the reception horn is of the orthomode type and that the first measurement means comprise two detectors placed at the output of said reception horn.
12. Dispositif de détection selon la revendication 7, caractérisé en ce que les premiers moyens de mesure des caractéristiques polarimétriques du signal réfléchi sont un cornet récepteur permettant de recevoir une polarisation orientée à 45 degrés du plan de réflexion de la zone éclairée du corps.12. Detection device according to claim 7, characterized in that the first means for measuring the polarimetric characteristics of the reflected signal are a receiver horn making it possible to receive a polarization oriented at 45 degrees from the reflection plane of the illuminated area of the body.
13. Dispositif de détection selon l'une des revendications précédentes, caractérisé en ce que la structure mécanique est un portique de sécurité de taille suffisante pour laisser passer le sujet humain.13. Detection device according to one of the preceding claims, characterized in that the mechanical structure is a security gantry of sufficient size to allow the human subject to pass.
14. Dispositif de détection selon l'une des revendications 1 à 12, caractérisé en ce que la structure mécanique est portable et comporte une partie mécanique sur laquelle sont disposés les cornets d'émission et ce réception et une poignée.14. Detection device according to one of claims 1 to 12, characterized in that the mechanical structure is portable and comprises a mechanical part on which are arranged the emission horns and this reception and a handle.
15. Dispositif de détection selon la revendication 14, caractérisé en ce que les cornets sont du type émission/réception.15. Detection device according to claim 14, characterized in that the horns are of the transmission / reception type.
16. Dispositif de détection selon les revendication 14 ou 15, caractérisé en ce que la structure comporte 4 cornets disposés aux sommets d'un parallélogramme.16. Detection device according to claim 14 or 15, characterized in that the structure comprises 4 horns arranged at the vertices of a parallelogram.
17. Dispositif de détection selon l'une des revendications précédentes, caractérisé en ce qu'il comporte également des moyens de mesure de la température du corps humain. 17. Detection device according to one of the preceding claims, characterized in that it also comprises means for measuring the temperature of the human body.
EP04821086A 2003-12-19 2004-12-08 Device for detecting non-metallic objects located on a human subject Withdrawn EP1695112A1 (en)

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FR0315033A FR2864307A1 (en) 2003-12-19 2003-12-19 Non metallic object detecting device for e.g. airport, has analyzing unit with one unit for detecting energetic and polarimetric characteristics of reflected signal, and another unit detecting presence of objects in human body
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