EP0800693A1 - Method and device for determining whether there are one or more magnetic anti-theft targets in a predetermined detection space - Google Patents

Method and device for determining whether there are one or more magnetic anti-theft targets in a predetermined detection space

Info

Publication number
EP0800693A1
EP0800693A1 EP95943554A EP95943554A EP0800693A1 EP 0800693 A1 EP0800693 A1 EP 0800693A1 EP 95943554 A EP95943554 A EP 95943554A EP 95943554 A EP95943554 A EP 95943554A EP 0800693 A1 EP0800693 A1 EP 0800693A1
Authority
EP
European Patent Office
Prior art keywords
targets
detection
field
volume
target
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Withdrawn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
EP95943554A
Other languages
German (de)
French (fr)
Inventor
Marc Schaefer
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.)
INTERNATIONALE DU LIBRE PAIEMENT SA
Original Assignee
INTERNATIONALE DU LIBRE PAIEMENT 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 INTERNATIONALE DU LIBRE PAIEMENT SA filed Critical INTERNATIONALE DU LIBRE PAIEMENT SA
Publication of EP0800693A1 publication Critical patent/EP0800693A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2405—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used
    • G08B13/2408—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used using ferromagnetic tags
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
    • G08B13/2468—Antenna in system and the related signal processing
    • G08B13/2471—Antenna signal processing by receiver or emitter
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2465—Aspects related to the EAS system, e.g. system components other than tags
    • G08B13/2468—Antenna in system and the related signal processing
    • G08B13/2477—Antenna or antenna activator circuit

Definitions

  • the present invention relates, in general, the locks type ma ⁇ gn government, that is to say comprising a label or filament matéri ⁇ the saturable magnetic secured to articles to be protected and, in par ⁇ ticular, a method for determining the uniqueness or the plurality of such anti-theft devices in a predetermined detection volume.
  • FR-A-763 681 is to produce in a detection volume 53dé ⁇ completed an alternating magnetic field, called "interrogation field" of given frequency. If there is in this volume an element made of saturable magnetic material (an element which will be designated generally in the following by the term "target"), and if the maximum magnetic field at l the location of the target is sufficient to bring the magnetic material to saturation, the repeated saturations and desaturations due to the alternating nature of the field will create secondary magnetic fields at harmonic frequencies of the frequency of the interrogation field.
  • target saturable magnetic material
  • the lock is disabled after payment section.
  • This neutralization generally results from a demagnetization of the target by application of an alternating magnetic field of any frequency and of decreasing intensity over time, in a manner well known in itself.
  • the neutralization is not done by demagnetization of the target, but by magnetization of the screen material, so that it comes to interfere with the response of the material of the actual target by preventing respond to the interrogation field as described above.
  • the invention is the particular problem that has not been addressed by the above document, an attempt demagnetization simulta ⁇ born of two or more articles, for example by superimposing two of these articles and passing them simultaneously in the demagnetization device.
  • Such attempted fraud may arise in particular in the case of automatic pay self-service, where the user places the jet ob ⁇ in a degaussing unit of the burglar ordered auto ⁇ matically after payment.
  • the utili- sateur it is plausible for the utili- sateur to place two or more items on each other, to present everything to the camera as if it were a single item (unit ana ⁇ lysing such as a bar code affixed Article most in-des ⁇ extra and requesting payment as if he s' was only a single item) and get simultaneous disabling of all articles.
  • the object of the invention is to remedy this type of fraud, by proposing a method and a device for determining whether, in a given detection volume, we are in the presence of a single magnetic target - in which case we can authorize payment and deactivation - or several of these targets - in which case the transaction will be interrupted and an anomaly will be reported, keeping or restoring the targets to their active state.
  • the method of the invention is of the general type known in which (a) is produced in the detection volume alter ⁇ native magnetic field frequency of interrogation data and intensity to saturate and desaturate repeatedly the target or targets; (b) detecting the harmonic disturbance of the alternating magnetic field produced by the target or targets in the detection volume due to repeated saturations and desaturations; and (c) in the event of detection of such a disturbance, it is considered that there is presence of a target or targets.
  • the invention further comprising: (d) after the detection of a perturba ⁇ tion, there is produced an inhibition magnetic field, essentially continuous and superimposed on the alternating magnetic interrogation field; this magnetic field inhibition being produced in a volume of predetermined inhi ⁇ bition, smaller than the detection volume, contained within it and whose extent is determined by the articles to be protected in such a way that only one article can be physically placed in the inhibition volume with its associated anti-theft target; and (e) again detecting a possible disturbance har ⁇ monic the alternating magnetic field produced by another target or other target within the sensing volume out of the volume of inhibi ⁇ tion, and (el) in case of detection again such a disturbance, it is considered that there is presence of a plurality of targets in the volume detection, and (e2) otherwise, it is considered that there is the presence of a single target in the detection volume.
  • the method of the invention can advantageously be applied to the case of anti-theft targets which each comprise two distinct magnetic materials saturable at different field levels so as to make the targets deactivatable and reactivable by magnetization and demagnetization, respectively, of the material magnetic saturable by the strongest field.
  • the target or targets are deactivated following the detection of the latter, and in step eJL the targets are reactivated after the detection of a plurality of targets.
  • step _ [ a resulting field is always produced which is lower than the deactivation or neutralization threshold of the anti-theft targets.
  • the invention also relates to a device suitable for implementing the steps of the above method.
  • Figure 1 illustrates the relationship between the magnetic field of inter ⁇ rogation and induction produced in the magnetic material of the target.
  • FIG. 2 shows the signal collected by the detection member in the situation of FIG. 1.
  • Figure 3 is similar to FIG 1, when it superimposes a DC magnetic field to the alternating interrogation field.
  • FIG. 4 is equivalent to FIG. 2, for the situation in FIG. 3.
  • FIG. 5 illustrates the spatial extent of the two detection and inhibition zones.
  • Figure 6 illustrates the gradient of the alternating magnetic field and the continuous magnetic field in these areas.
  • Figure 7 is a schematic illustration of the device for implementation of the invention.
  • the hysteresis cycle 1 of the magnetic material of the target is represented (induction B as a function of the applied magnetic field H) and in 2 the shape of the interrogation magnetic field H, which is a sinusoidal field of given frequency, presenting the lowest possible harmonic distortion and whose amplitude is chosen so that, at any point of the detection volume, the instantaneous maximum value of the field exceeds the value of the saturation field, as this is illustrated by the dashed recall lines on FIG. 1.
  • the target material will be saturated and desaturated repeatedly, at the rate of the interrogation field, and this phenomenon will produce, well known manner, harmonic disturbances of the magnetic field, the rank and the relative amplitude of the different harmonics depending on the nature of the material and the geometry of the target.
  • Figure 2 shows the appearance of the signal collected by an induction coil placed in the detection zone: in addition to the sinusoidal part 3 at the fundamental frequency, due to the coupling between the transmission coil and the reception coil, we observe 4 peaks resulting from the harmonic disturbance peaks that are especially narrow and so recognizable that the hysteresis loop of the material is 1 square. It then suffices to carry out a high-pass filtering to eliminate the fundamental frequency and to keep only the harmonics to control a device signaling the presence of a target in the detection volume.
  • the invention is based on the finding that, if it is superimposed on the alternating magnetic interrogation field a continuous field H Q to the location of the target in spite of the variation of the field is demeu- will be in the saturated zone 5 of the hysteresis cycle of the material, as illustrated in FIG. 3; it will remain saturated and the hysteresis loop will not be described, so it will happen no harmonic disturbance and that can not detect any peak corresponding to the if- gnal detection, as shown in Figure 4.
  • the basic idea of the invention consists, taking into account what precedes, first radiating an alternating field alone in the detection volume. In the event of positive detection (situation in FIGS. 1 and 2), a continuous field is then superimposed on the alternating field (situation in FIGS. 3 and 4) but of shorter range, therefore in a volume (which will be called hereinafter "volume inhibition") smaller than the detection volume.
  • the detection becomes negative, this means that the target is located in the volume of inhibition near the detected tor, and that it does not target exists in the rest of the sensing volume. If the device has been configured so that the inhibition volume corresponds to the minimum thickness of an object, it can then be said that the device was presented with only one anti-theft device and therefore a single object.
  • FIG. 5 shows the geometry of detection volume 6 and vo ⁇ lume of inhibition 7, which is contained within the sensing volume 6, but of smaller size.
  • the intensity of the magnetic field, alternating H or continuous H_ is shown as a function of the distance z.
  • the H_ alternating field has a lower short-range intensity that continuous field H_, but a decay gradient less as steep as that of the latter.
  • two zones are thus defined: a close zone where the continuous field H_ is predominant (well understood when this field is applied), and a distant zone where the alternating field H_ is predominant.
  • the limit between these two zones defines the border of the inhibition volume 7. In practice, it can be seen that this border is fairly clear and independent of the sensitivity of the targets, which makes it possible to define the volume of inhibition with a border zone d very low uncertainty.
  • FIG. 7 illustrates schematically a device for implementing the teachings of the invention.
  • This device firstly comprises a receptacle 10 intended to receive an article 11, in principle a single article.
  • This article carries an anti-theft label (target) 12, located near the surface of the recepta ⁇ key 10.
  • the magnetic interrogation field is produced, in itself conventional, by coils 13 supplied by a circuit including a generator 14, a low-pass filter 15 (allowing a fundamental as pure as possible) and a power amplifier 16.
  • the assembly produces the alternating magnetic field of interrogation H_ mentioned more high in a detection volume 6, defined by the geometry and configuration of the coils 13.
  • the detection is carried out by coils 17 collecting a signal applied to a bandpass filter 18 (analog or digital) to eliminate the fundamental and to keep only the harmonic or the useful harmonics, for example only the harmonic 5, an amplifier 19, a detector 20 and a threshold circuit 21.
  • the threshold circuit delivers a signal to a control block 22 controlling the progress of the analysis procedure in particular, and of the transaction in general if the device of the invention is integrated with a complete payment system, such as a payment system for self-service.
  • the geometry and configuration of the receiving coils 17 is determined so that the detection takes place in the volume 6 covered by the alternating interrogation field.
  • a plurality of coils 23 supplied by a circuit 24 are controlled near the surface of the receptacle 11. block 22, and making it possible to produce the continuous magnetic field H_ of short range in an inhibition volume 7 as defined previously.
  • the coils 23 can be short coils (for example wound on cores in the form of studs) supplied by a relatively weak current, or with a plurality of coils on each core.
  • Geometry, configuration and the supply of the coils 23 are chosen so that the zone of inhibition 7 does not exceed the Constant ⁇ sor of an article 11, which is for instance easy to provide in the case of discs compact, packaged in a box of standard dimensions.
  • the block 22 controls the generator 24 so as to superimpose the continuous field H_ on the alternating field H_ in the volume d inhibition 7. Under these conditions, the response of the target 12 will be inhibited, in accordance with the principle set out in FIG. 3. Two cases can then arise:
  • the transaction can then continue and s completing a neu ⁇ tralisation of the target 12 or by degaussing (applying an alternating field of decreasing amplitude) by soapacti- vation, it is a deactivable and reactivable label; in in either case, the neutralization field can be advantageously produced by the coils 23, which are then supplied temporarily alternately by the generator 24, still under the control of block 22.
  • the neutralization field can be advantageously produced by the coils 23, which are then supplied temporarily alternately by the generator 24, still under the control of block 22.
  • a target which means that there are targets (such as the target 12 ′) outside the inhibition volume 7. This situation is abnormal; it reveals the presence of a plurality of articles on the device (or, as said above, of a single anti-theft device, but in a position too far apart).
  • any subsequent neutralization of the targets is prevented or, if the targets are deactivable and reactivable already deactivated, these targets are reactivated.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Signal Processing (AREA)
  • Automation & Control Theory (AREA)
  • Computer Security & Cryptography (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Burglar Alarm Systems (AREA)

Abstract

A device including means (13-16) for generating an alternating magnetic detection field in a detection space in order to repeatedly saturate and desaturate one or more targets (12), and means (17-21) for sensing the resulting harmonic disturbance of the alternating magnetic field. The device further includes means (22, 23, 24) for generating an essentially continuous magnetic inhibition field on top of the alternating magnetic detection field, said magnetic inhibition field being generated in an inhibition space (7) which is smaller than the detection space (6) and sized depending on the articles to be protected so that it is physically impossible to place more than one article (11) combined with an anti-theft target in the inhibition space; as well as discriminating means (13-16, 22) for sensing any harmonic disturbance of the alternating magnetic field as a result of one or more other targets being placed in the detection space outside the inhibition space.

Description

Procédé et dispositif pour déterminer l'unicité ou la pluralité de cibles magnétiques antivol magnétiques dans un volume de détection prédéterminé Method and device for determining the uniqueness or the plurality of magnetic anti-theft magnetic targets in a predetermined detection volume
δ L'invention concerne, de façon générale, les antivols de type ma¬ gnétique, c'est-à-dire comprenant une étiquette ou filament en matéri¬ au magnétique saturable solidarisé à des articles à protéger et, en par¬ ticulier, un procédé pour déterminer l'unicité ou la pluralité de tels antivols dans un volume de détection prédéterminé.δ The present invention relates, in general, the locks type ma¬ gnétique, that is to say comprising a label or filament matéri¬ the saturable magnetic secured to articles to be protected and, in par¬ ticular, a method for determining the uniqueness or the plurality of such anti-theft devices in a predetermined detection volume.
10 Le principe de ces antivols, qui est connu depuis le brevet Picard10 The principle of these anti-theft devices, which has been known since the Picard patent
FR-A-763 681 , consiste à produire dans un volume de détection prédé¬ terminé un champ magnétique alternatif, dit "champ d'interrogation " de fréquence donnée. S'il se trouve dans ce volume un élément en ma¬ tériau magnétique saturable (élément que l'on désignera de façon géné- l δ raie dans la suite par le terme de "cible "), et si le champ magnétique maximal à l'endroit de la cible est suffisant pour amener le matériau magnétique à saturation, les saturations et désaturations répétées du fait du caractère alternatif du champ vont créer des champs magné¬ tiques secondaires à des fréquences harmoniques de la fréquence du champ d'interrogation. Il suffit alors de placer une bobine d'induction réceptrice dans le volume de détection et de filtrer le courant collecté reçu de manière à en éliminer la fréquence fondamentale pour détermi¬ ner, par la présence ou l'absence d'harmoniques, la présence ou l'absen- ce corrélative d'une cible dans le volume de détection.FR-A-763 681, is to produce in a detection volume prédé¬ completed an alternating magnetic field, called "interrogation field" of given frequency. If there is in this volume an element made of saturable magnetic material (an element which will be designated generally in the following by the term "target"), and if the maximum magnetic field at l the location of the target is sufficient to bring the magnetic material to saturation, the repeated saturations and desaturations due to the alternating nature of the field will create secondary magnetic fields at harmonic frequencies of the frequency of the interrogation field. It then suffices to place a receiver induction coil in the sensing volume and filtering the collected current received so as to remove the fundamental frequency for détermi¬ ner, by the presence or absence of harmonics, the presence or up the lack correlative of a target in the sensing volume.
Des systèmes de ce type ont été décrits dans de nombreux docu¬ ments ultérieurs, parmi lesquels on peut citer à titre d'exemple les US- A-3 790 945, EP-A-0 446 910 ou EP-A-0 545 422, auxquels on pourra se référer pour de plus amples détails sur cette technique et sur les per- fectionnements qui y ont été apportés : par exemple la discrimination entre des cibles de plusieurs types ou susceptibles de présenter plusi¬ eurs états distincts, l'utilisation de cibles désactivables et réactivables de manière à masquer à volonté la réponse du matériau magnétique à détecter, l'amélioration de la détection par analyse harmonique sélec- tive du signal reçu, etc.Systems of this type have been described in numerous subsequent documents, among which there may be mentioned, by way of example, US-A-3 790 945, EP-A-0 446 910 or EP-A-0 545 422 , to which one can refer for further details on this technique and the per- fectionnements that were made there: such as discrimination between target of several types or likely to plusi¬ owers separate statements, the use of target deactivatable and reactivatable so as to mask the response of the magnetic material will be detected, improving detection by harmonic analysis tive selectivity of the received signal, etc.
Lorsque le client passe à la caisse, l'antivol est neutralisé après paiement de l'article. Cette neutralisation résulte généralement d'une démagnétisation de la cible par application d'un champ magnétique alternatif de fréquence quelconque et d'intensité décroissante dans le temps, d'une manière bien connue en elle-même. En revanche, dans le cas particulier des étiquettes désactivables et réactivables, la neutrali¬ sation ne se fait pas par démagnétisation de la cible, mais par magnéti¬ sation du matériau écran, de manière que celui-ci vienne interférer avec la réponse du matériau de la cible proprement dite en l'empêchant de répondre au champ d'interrogation de la manière décrite plus haut. L'invention vise le problème particulier, qui n'a pas été abordé par les documents ci-dessus, d'une tentative de démagnétisation simulta¬ née de deux ou plusieurs articles, par exemple en superposant deux de ces articles et en les passant simultanément dans le dispositif de déma- gnétisation.When the customer goes to the checkout, the lock is disabled after payment section. This neutralization generally results from a demagnetization of the target by application of an alternating magnetic field of any frequency and of decreasing intensity over time, in a manner well known in itself. On the other hand, in the particular case of labels which can be deactivated and reactivated, the neutralization is not done by demagnetization of the target, but by magnetization of the screen material, so that it comes to interfere with the response of the material of the actual target by preventing respond to the interrogation field as described above. The invention is the particular problem that has not been addressed by the above document, an attempt demagnetization simulta¬ born of two or more articles, for example by superimposing two of these articles and passing them simultaneously in the demagnetization device.
Une telle tentative de fraude peut notamment se présenter dans le cas de caisses automatiques en libre-service, où l'utilisateur place l'ob¬ jet dans un appareil de démagnétisation de l'antivol commandé auto¬ matiquement après paiement. En particulier, dans le cas d'objets plats tels que des disques, des livres ou des revues, il est tentant pour l'utili- sateur de placer deux ou plusieurs articles l'un sur l'autre, de présenter le tout à l'appareil comme s'il s'agissait d'un seul article (l'appareil ana¬ lysant par exemple un code à barres apposé sur l'article le plus au-des¬ sus et demandant le paiement comme s'il ne s'agissait que d'un article unique) puis d'obtenir la désactivation simultanée de l'ensemble des articles.Such attempted fraud may arise in particular in the case of automatic pay self-service, where the user places the jet ob¬ in a degaussing unit of the burglar ordered auto¬ matically after payment. In particular, in the case of flat objects such as disks, books or magazines, it is tempting for the utili- sateur to place two or more items on each other, to present everything to the camera as if it were a single item (unit ana¬ lysing such as a bar code affixed Article most in-des¬ extra and requesting payment as if he s' was only a single item) and get simultaneous disabling of all articles.
L'invention a pour objet de remédier à ce type de fraude, en propo¬ sant un procédé et un dispositif pour déterminer si, dans un volume de détection donné, on se trouve en présence d'une seule cible magnétique — auquel cas on pourra autoriser le paiement et la désactivation — ou de plusieurs de ces cibles — auquel cas on interrompra la transaction et on signalera une anomalie, en maintenant ou restaurant bien enten¬ du les cibles dans leur état actif.The object of the invention is to remedy this type of fraud, by proposing a method and a device for determining whether, in a given detection volume, we are in the presence of a single magnetic target - in which case we can authorize payment and deactivation - or several of these targets - in which case the transaction will be interrupted and an anomaly will be reported, keeping or restoring the targets to their active state.
Le procédé de l'invention est du type général connu dans lequel : (a) on produit dans le volume de détection un champ magnétique alter¬ natif d'interrogation de fréquence donnée et d'intensité permettant de saturer et de désaturer de façon répétée la cible ou les cibles ; (b) on détecte la perturbation harmonique du champ magnétique alternatif produite par la cible ou les cibles dans le volume de détection du fait des saturations et désaturations répétées ; et (c) en cas de détection d'une telle perturbation, on considère qu'il y a présence d'une cible ou de cibles.The method of the invention is of the general type known in which (a) is produced in the detection volume alter¬ native magnetic field frequency of interrogation data and intensity to saturate and desaturate repeatedly the target or targets; (b) detecting the harmonic disturbance of the alternating magnetic field produced by the target or targets in the detection volume due to repeated saturations and desaturations; and (c) in the event of detection of such a disturbance, it is considered that there is presence of a target or targets.
Selon l'invention, en outre : (d) après la détection d'une perturba¬ tion, on produit un champ magnétique d'inhibition, essentiellement continu et superposé au champ magnétique alternatif d'interrogation ; ce champ magnétique d'inhibition étant produit dans un volume d'inhi¬ bition prédéterminé, plus réduit que le volume de détection, contenu à l'intérieur de ce dernier et dont l'étendue est déterminée en fonction des articles à protéger de telle sorte qu'il ne puisse être matériellement placé dans le volume d'inhibition qu'un seul article avec sa cible antivol associée ; et (e) on détecte à nouveau un éventuelle perturbation har¬ monique du champ magnétique alternatif produite par une autre cible ou d'autres cibles dans le volume de détection hors du volume d'inhibi¬ tion, et (el ) en cas de détection à nouveau d'une telle perturbation, on considère qu'il y a présence d'une pluralité de cibles dans le volume de détection, et (e2) dans le cas contraire, on considère qu'il y a présence d'une cible unique dans le volume de détection.According to the invention, further comprising: (d) after the detection of a perturba¬ tion, there is produced an inhibition magnetic field, essentially continuous and superimposed on the alternating magnetic interrogation field; this magnetic field inhibition being produced in a volume of predetermined inhi¬ bition, smaller than the detection volume, contained within it and whose extent is determined by the articles to be protected in such a way that only one article can be physically placed in the inhibition volume with its associated anti-theft target; and (e) again detecting a possible disturbance har¬ monic the alternating magnetic field produced by another target or other target within the sensing volume out of the volume of inhibi¬ tion, and (el) in case of detection again such a disturbance, it is considered that there is presence of a plurality of targets in the volume detection, and (e2) otherwise, it is considered that there is the presence of a single target in the detection volume.
Le procédé de l'invention peut avantageusement s'appliquer au cas des cibles antivol qui comprennent chacune deux matériaux magnéti- ques distincts saturables à des niveaux de champ différents de manière à rendre les cibles désactivables et réactivables par magnétisation et démagnétisation, respectivement, du matériau magnétique saturable par le champ le plus fort. Dans ce cas, à l'étape £ on désactive la cible ou les cibles suite à la détection de celle(s)-ci et à l'étape eJL on réactive les cibles suite à la détection d'une pluralité de cibles.The method of the invention can advantageously be applied to the case of anti-theft targets which each comprise two distinct magnetic materials saturable at different field levels so as to make the targets deactivatable and reactivable by magnetization and demagnetization, respectively, of the material magnetic saturable by the strongest field. In this case, in step £ the target or targets are deactivated following the detection of the latter, and in step eJL the targets are reactivated after the detection of a plurality of targets.
En outre, de préférence, à l'étape _[, on produit un champ résultant toujours inférieur au seuil de désactivation ou de neutralisation des cibles antivol.In addition, preferably, in step _ [, a resulting field is always produced which is lower than the deactivation or neutralization threshold of the anti-theft targets.
L'invention porte également sur un dispositif propre à mettre en œuvre les étapes du procédé ci-dessus.The invention also relates to a device suitable for implementing the steps of the above method.
D'autres caractéristiques et avantages de l'invention apparaîtront à la lecture de la description ci-dessous d'un exemple de mise en œuvre, faite en référence aux dessins annexés.Other characteristics and advantages of the invention will appear on reading the description below of an exemplary implementation, made with reference to the accompanying drawings.
La figure 1 illustre la relation entre le champ magnétique d'inter¬ rogation et l'induction produite dans le matériau magnétique de la cible. La figure 2 montre le signal recueilli par l'organe de détection dans la situation de la figure 1.Figure 1 illustrates the relationship between the magnetic field of inter¬ rogation and induction produced in the magnetic material of the target. FIG. 2 shows the signal collected by the detection member in the situation of FIG. 1.
La figure 3 est homologue de la figure 1 , lorsque l'on superpose un champ magnétique continu au champ alternatif d'interrogation.Figure 3 is similar to FIG 1, when it superimposes a DC magnetic field to the alternating interrogation field.
La figure 4 est homologue de la figure 2, pour la situation de la fi- gure 3.FIG. 4 is equivalent to FIG. 2, for the situation in FIG. 3.
La figure 5 illustre l'étendue dans l'espace des deux zones de détec¬ tion et d'inhibition.FIG. 5 illustrates the spatial extent of the two detection and inhibition zones.
La figure 6 illustre le gradient du champ magnétique alternatif et du champ magnétique continu dans ces zones. La figure 7 est une illustration schématique du dispositif pour la mise en œuvre de l'invention.Figure 6 illustrates the gradient of the alternating magnetic field and the continuous magnetic field in these areas. Figure 7 is a schematic illustration of the device for implementation of the invention.
Sur la figure 1 , on a représenté le cycle d'hystérésis 1 du matériau magnétique de la cible (induction B en fonction du champ magnétique appliqué H) et en 2 l'allure du champ magnétique d'interrogation H, qui est un champ sinusoïdal de fréquence donnée, présentant la distor¬ sion harmonique la plus faible possible et dont l'amplitude est choisie de manière que, en tout point du volume de détection, la valeur maxi¬ male instantanée du champ dépasse la valeur du champ de saturation, comme cela est illustré par les lignes de rappel en tiretés sur la figu¬ re 1. De la sorte, le matériau de la cible va être saturé et désaturé de façon répétée, au rythme du champ d'interrogation, et ce phénomène va produire, de manière bien connue, des perturbations harmoniques du champ magnétique, le rang et l'amplitude relative des différents har¬ moniques dépendant de la nature du matériau et de la géométrie de la cible.In FIG. 1, the hysteresis cycle 1 of the magnetic material of the target is represented (induction B as a function of the applied magnetic field H) and in 2 the shape of the interrogation magnetic field H, which is a sinusoidal field of given frequency, presenting the lowest possible harmonic distortion and whose amplitude is chosen so that, at any point of the detection volume, the instantaneous maximum value of the field exceeds the value of the saturation field, as this is illustrated by the dashed recall lines on FIG. 1. In this way, the target material will be saturated and desaturated repeatedly, at the rate of the interrogation field, and this phenomenon will produce, well known manner, harmonic disturbances of the magnetic field, the rank and the relative amplitude of the different harmonics depending on the nature of the material and the geometry of the target.
La figure 2 montre l'allure du signal recueilli par une bobine d'in- duction placée dans la zone de détection : outre la partie sinusoïdale 3 à la fréquence fondamentale, due au couplage entre bobine d'émission et bobine de réception, on observe des pics 4 résultant de la perturbation harmonique, pics qui sont d'autant plus étroits et donc reconnaissables que le cycle d'hystérésis 1 du matériau est carré. Il suffit alors de pro- céder à un filtrage passe-haut pour éliminer la fréquence fondamentale et ne conserver que les harmoniques pour commander un dispositif si¬ gnalant la présence d'une cible dans le volume de détection. Divers per¬ fectionnements peuvent être apportés à ce niveau, notamment en ce qui concerne le filtrage, pour éliminer l'incidence des perturbations ex- térieures et facteurs parasites et abaisser ainsi le taux de fausse alar¬ me, mais ces perfectionnements ne font pas l'objet du brevet et ne seront donc pas décrits en détail.Figure 2 shows the appearance of the signal collected by an induction coil placed in the detection zone: in addition to the sinusoidal part 3 at the fundamental frequency, due to the coupling between the transmission coil and the reception coil, we observe 4 peaks resulting from the harmonic disturbance peaks that are especially narrow and so recognizable that the hysteresis loop of the material is 1 square. It then suffices to carry out a high-pass filtering to eliminate the fundamental frequency and to keep only the harmonics to control a device signaling the presence of a target in the detection volume. Various per¬ fectionnements can be made at this level, especially with regard to filtering, to eliminate the impact of disturbances and former térieures confounders and thus lower the false rate alar¬ me, but these improvements are not the subject of the patent and will therefore not be described in detail.
L'invention est basée sur la constatation que, si l'on superpose au champ magnétique alternatif d'interrogation un champ continu HQ à l'endroit où se trouve la cible, malgré la variation du champ on demeu- rera dans la zone saturée 5 du cycle d'hystérésis du matériau, comme illustré figure 3 ; ce dernier restera donc saturé et le cycle d'hystérésis ne sera pas décrit, de sorte qu'il ne se produira aucune perturbation harmonique et que l'on ne détectera aucun pic correspondant sur le si- gnal de détection, comme illustré figure 4.The invention is based on the finding that, if it is superimposed on the alternating magnetic interrogation field a continuous field H Q to the location of the target in spite of the variation of the field is demeu- will be in the saturated zone 5 of the hysteresis cycle of the material, as illustrated in FIG. 3; it will remain saturated and the hysteresis loop will not be described, so it will happen no harmonic disturbance and that can not detect any peak corresponding to the if- gnal detection, as shown in Figure 4.
L'idée de base de l'invention consiste, compte tenu de ce qui pré¬ cède, à rayonner tout d'abord un champ alternatif seul dans le volume de détection. En cas de détection positive (situation des figures 1 et 2), on superpose alors au champ alternatif un champ continu (situation des figures 3 et 4) mais de portée plus courte, donc dans un volume (que l'on appellera par la suite "volume d'inhibition") plus réduit que le volume de détection.The basic idea of the invention consists, taking into account what precedes, first radiating an alternating field alone in the detection volume. In the event of positive detection (situation in FIGS. 1 and 2), a continuous field is then superimposed on the alternating field (situation in FIGS. 3 and 4) but of shorter range, therefore in a volume (which will be called hereinafter "volume inhibition") smaller than the detection volume.
Si, dans ces conditions, la détection devient négative, ceci signifie que la cible est située dans le volume d'inhibition, à proximité du détec- teur, et qu'il n'existe pas de cible dans le reste du volume de détection. Si l'on a configuré l'appareil pour que le volume d'inhibition corres¬ ponde à l'épaisseur minimale d'un objet, on peut alors dire qu'il n'a été présenté au dispositif qu'un seul antivol et donc un seul objet.If, under these conditions, the detection becomes negative, this means that the target is located in the volume of inhibition near the detected tor, and that it does not target exists in the rest of the sensing volume. If the device has been configured so that the inhibition volume corresponds to the minimum thickness of an object, it can then be said that the device was presented with only one anti-theft device and therefore a single object.
Si en revanche, malgré la superposition du champ continu à courte portée la détection est encore positive, ceci révèle (i) soit la présence, outre l'antivol situé dans le volume d'inhibition, d'un ou plusieurs autres antivols dans le reste du volume de détection, (ii) soit la pré¬ sence d'un seul antivol, mais en une position trop éloignée. Dans l'un ou l'autre cas, cette situation est anormale et la procédure ou transac- tion en cours est alors interrompue ou suspendue automatiquement par l'appareil.If, however, despite the superposition of the constant field short-range detection is still positive, this indicates (i) the presence, in addition to the lock located in the volume of inhibition of one or more other anti-theft devices in the rest of the detection volume, (ii) either the presence of a single anti-theft device, but in a position that is too far away. In one or the other case, this situation is abnormal and the procedure or transac- tion current is then interrupted or suspended automatically by the camera.
La figure 5 montre la géométrie du volume de détection 6 et du vo¬ lume d'inhibition 7, qui est contenu à l'intérieur du volume de détection 6 mais qui de taille plus réduite. Sur la figure 6, on a représenté l'intensité du champ magnétique, alternatif H ou continu H_ en fonction de l'éloignement z.5 shows the geometry of detection volume 6 and vo¬ lume of inhibition 7, which is contained within the sensing volume 6, but of smaller size. In FIG. 6, the intensity of the magnetic field, alternating H or continuous H_ is shown as a function of the distance z.
Par un choix approprié des paramètres géométriques, électriques et magnétiques des différentes bobines de l'appareil, on fait en sorte que le champ alternatif H_ ait une intensité à courte portée plus faible que le champ continu H_, mais un gradient de décroissance moins abrupt que celui de ce dernier. De la sorte, on définit ainsi deux zones : une zone proche où le champ continu H_ est prédominant (bien enten¬ du lorsque ce champ est appliqué), et une zone lointaine où le champ alternatif H_est prédominant. La limite entre ces deux zones définit la frontière du volume d'inhibition 7. En pratique, on constate que cette frontière est assez nette et indépendante de la sensibilité des cibles, ce qui permet de définir le volume d'inhibition avec une zone frontière d'incertitude très réduite.By appropriate choice of the geometric parameters, the different electric and magnetic coils of the apparatus, it is ensured that the H_ alternating field has a lower short-range intensity that continuous field H_, but a decay gradient less as steep as that of the latter. In this way, two zones are thus defined: a close zone where the continuous field H_ is predominant (well understood when this field is applied), and a distant zone where the alternating field H_ is predominant. The limit between these two zones defines the border of the inhibition volume 7. In practice, it can be seen that this border is fairly clear and independent of the sensitivity of the targets, which makes it possible to define the volume of inhibition with a border zone d very low uncertainty.
La figure 7 illustre de façon schématique un dispositif permettant de mettre en œuvre les enseignements de l'invention.7 illustrates schematically a device for implementing the teachings of the invention.
Ce dispositif comporte tout d'abord un réceptacle 10 destiné à rece¬ voir un article 11 , en principe un seul article. Cet article porte une éti¬ quette antivol (cible) 12, située à proximité de la surface du récepta¬ cle 10. Le champ magnétique d'interrogation est produit, de manière en elle-même classique, par des bobines 13 alimentées par un circuit com¬ prenant un générateur 14, un filtre passe-bas 15 (permettant d'avoir une fondamentale aussi pure que possible) et un amplificateur de puis¬ sance 16. L'ensemble produit le champ magnétique alternatif d'interro- gation H_ mentionné plus haut dans un volume de détection 6, défini par la géométrie et la configuration des bobines 13.This device firstly comprises a receptacle 10 intended to receive an article 11, in principle a single article. This article carries an anti-theft label (target) 12, located near the surface of the recepta¬ key 10. The magnetic interrogation field is produced, in itself conventional, by coils 13 supplied by a circuit including a generator 14, a low-pass filter 15 (allowing a fundamental as pure as possible) and a power amplifier 16. The assembly produces the alternating magnetic field of interrogation H_ mentioned more high in a detection volume 6, defined by the geometry and configuration of the coils 13.
La détection est opérée par des bobines 17 recueillant un signal ap¬ pliqué à un filtre passe-bande 18 (analogique ou numérique) pour éli¬ miner la fondamentale et ne conserver que l'harmonique ou les harmo- niques utiles, par exemple uniquement l'harmonique 5, un amplifica¬ teur 19, un détecteur 20 et un circuit à seuil 21. Le circuit à seuil déli¬ vre un signal à un bloc de commande 22 pilotant le déroulement de la procédure d'analyse en particulier, et de la transaction en général dans le cas où le dispositif de l'invention est intégré à un système de paie- ment complet, par exemple un système de paiement en libre- service.The detection is carried out by coils 17 collecting a signal applied to a bandpass filter 18 (analog or digital) to eliminate the fundamental and to keep only the harmonic or the useful harmonics, for example only the harmonic 5, an amplifier 19, a detector 20 and a threshold circuit 21. The threshold circuit delivers a signal to a control block 22 controlling the progress of the analysis procedure in particular, and of the transaction in general if the device of the invention is integrated with a complete payment system, such as a payment system for self-service.
La géométrie et la configuration des bobines réceptrices 17 est dé¬ terminée de manière que la détection se fasse dans le volume 6 couvert par le champ alternatif d'interrogation.The geometry and configuration of the receiving coils 17 is determined so that the detection takes place in the volume 6 covered by the alternating interrogation field.
On prévoit en outre, à proximité de la surface du réceptacle 11 , une pluralité de bobines 23 alimentées par un circuit 24 sous contrôle du bloc 22, et permettant de produire le champ magnétique continu H_ de courte portée dans un volume d'inhibition 7 tel que défini précédem¬ ment. Pour assurer cette courte portée, les bobines 23 peuvent être des bobines de faible longueur (par exemple bobinées sur des noyaux en forme de plots) alimentées par un courant relativement faible, ou avec une pluralité de bobines sur chaque noyau.In addition, a plurality of coils 23 supplied by a circuit 24 are controlled near the surface of the receptacle 11. block 22, and making it possible to produce the continuous magnetic field H_ of short range in an inhibition volume 7 as defined previously. To ensure this short range, the coils 23 can be short coils (for example wound on cores in the form of studs) supplied by a relatively weak current, or with a plurality of coils on each core.
La géométrie, la configuration et l'alimentation des bobines 23 sont choisies de manière que la zone d'inhibition 7 ne dépasse pas l'épais¬ seur d'un article 11, ce qui est par exemple aisé à prévoir dans le cas des disques compacts, conditionnés dans un boîtier de dimensions nor¬ malisées.Geometry, configuration and the supply of the coils 23 are chosen so that the zone of inhibition 7 does not exceed the épais¬ sor of an article 11, which is for instance easy to provide in the case of discs compact, packaged in a box of standard dimensions.
De la sorte, si, comme illustré, on superpose sur le premier article 11 placé dans le réceptacle 10 un second article 11' de même nature pourvu de son étiquette antivol 12', cette dernière se trouvera hors du champ d'inhibition 7 mais dans le champ de détection 6. C'est cette particularité que l'on va mettre à profit pour détecter la présence, non admise, de la seconde cible 12' et donc du second article 11'.In this way, if, as illustrated, a second article 11 'of the same type provided with its anti-theft label 12' is superimposed on the first article 11 placed in the receptacle 10, the latter will be outside the inhibition field 7 but in the detection field 6. It is this peculiarity that we will take advantage of to detect the presence, not admitted, of the second target 12 'and therefore of the second article 11'.
À cet effet, on commence par rayonner le champ alternatif H_ seul par les bobines 13 dans le volume de détection 6 ; ce champ alternatif est maintenu pendant toute la durée de l'opération.To this end, we start by radiating the alternating field H_ alone by the coils 13 in the detection volume 6; this alternating field is maintained throughout the duration of the operation.
Si l'on détecte, par les bobines 17, la présence d'une ou plusieurs cibles dans le volume de détection 6, le bloc 22 commande alors le générateur 24 de manière à superposer le champ continu H_ au champ alternatif H_ dans le volume d'inhibition 7. Dans ces conditions, la réponse de la cible 12 sera inhibée, confor¬ mément au principe exposé figure 3. Deux cas peuvent alors se présen¬ ter :If the presence of one or more targets in the detection volume 6 is detected by the coils 17, the block 22 then controls the generator 24 so as to superimpose the continuous field H_ on the alternating field H_ in the volume d inhibition 7. Under these conditions, the response of the target 12 will be inhibited, in accordance with the principle set out in FIG. 3. Two cases can then arise:
— Soit les bobines 17 ne détectent plus aucune cible, ce qui signifie qu'aucune autre cible ne se trouve en dehors du volume d'inhibi- tion 7, et donc qu'un seul article 11 a été placé dans le récepta¬ cle 10.- Let the coils 17 do not detect any target more, which means that no further target is outside the volume of inhibition tion 7, and thus only one section 11 has been placed in the key 10 récepta¬ .
La transaction peut alors se poursuivre et s'achever par une neu¬ tralisation de la cible 12, soit par démagnétisation (application d'un champ alternatif d'amplitude décroissante) soit par désacti- vation, s'il s'agit d'une étiquette désactivable et réactivable ; dans l'un et l'autre cas, le champ de neutralisation peut être avantageu¬ sement produit par les bobines 23, qui sont alors alimentées tem¬ porairement en alternatif par le générateur 24, toujours sous contrôle du bloc 22. Soit on continue à détecter une cible, ce qui signifie qu'il existe des cibles (telles que la cible 12') hors du volume d'inhibition 7. Cette situation est anormale ; elle révèle la présence d'une plura¬ lité d'articles sur le dispositif (ou bien, comme on l'a dit plus haut, d'un seul antivol, mais en une position trop éloignée). On signale alors l'anomalie (message visuel, sonore, etc.) et on interrompt ou on suspend la transaction en cours. En particulier, on empêche toute neutralisation consécutive des cibles ou, s'il s'agit de cibles désactivables et réactivables déjà désactivées, on réactive ces ci¬ bles. The transaction can then continue and s completing a neu¬ tralisation of the target 12 or by degaussing (applying an alternating field of decreasing amplitude) by désacti- vation, it is a deactivable and reactivable label; in in either case, the neutralization field can be advantageously produced by the coils 23, which are then supplied temporarily alternately by the generator 24, still under the control of block 22. Either we continue to detect a target, which means that there are targets (such as the target 12 ′) outside the inhibition volume 7. This situation is abnormal; it reveals the presence of a plurality of articles on the device (or, as said above, of a single anti-theft device, but in a position too far apart). It then signals the anomaly (visual message, sound, etc.) and it interrupts or suspends the current transaction. In particular, any subsequent neutralization of the targets is prevented or, if the targets are deactivable and reactivable already deactivated, these targets are reactivated.

Claims

REVENDICATIONS
1. Un procédé pour déterminer l'unicité ou la pluralité de cibles magnétiques dans un volume de détection (6) prédéterminé, ces cibles δ étant des cibles antivol (12) comprenant un matériau magnétique satu¬ rable et solidarisées à des articles (11 ) à protéger, procédé dans lequel : a) on produit dans le volume de détection un champ magnétique al¬ ternatif d'interrogation (H_) de fréquence donnée et d'intensité permettant de saturer et de désaturer de façon répétée la cible ou1. A method for determining the uniqueness or the plurality of magnetic targets in a predetermined detection volume (6), these targets δ being anti-theft targets (12) comprising a saturable magnetic material and secured to articles (11) to be protected, process in which: a) an alternating magnetic interrogation field (H_) of given frequency and intensity is produced in the detection volume making it possible to repeatedly saturate and desaturate the target or
10 les cibles, b) on détecte la perturbation harmonique du champ magnétique al¬ ternatif produite par la cible ou les cibles dans le volume de détec¬ tion du fait des saturations et désaturations répétées, et c) en cas de détection d'une telle perturbation, on considère qu'il y a l δ présence d'une cible ou de cibles, procédé caractérisé en ce que, en outre : d) après la détection d'une perturbation, on produit un champ magné¬ tique d'inhibition (H_), essentiellement continu et superposé au champ magnétique alternatif d'interrogation (H_),10 the targets, b) detecting the harmonic disturbance of the alternating magnetic field produced by the target or targets in the detection volume due to repeated saturations and desaturations, and c) in the event of detection of such a disturbance, it is considered that it is al δ presence of a target or targets, characterized in that, further comprising: d) after detection of a disturbance, producing a field magné¬ tick inhibition (H_ ), essentially continuous and superimposed on the alternating magnetic interrogation field (H_),
20 ce champ magnétique d'inhibition étant produit dans un volume d'inhibition (7) prédéterminé, plus réduit que le volume de détec¬ tion (6), contenu à l'intérieur de ce dernier et dont l'étendue est déterminée en fonction des articles à protéger de telle sorte qu'il ne puisse être matériellement placé dans le volume d'inhibition qu'un 5 seul article avec sa cible antivol associée, et e) on détecte à nouveau un éventuelle perturbation harmonique du champ magnétique alternatif produite par une autre cible ou d'au¬ tres cibles dans le volume de détection hors du volume d'inhibition, et 0 el ) en cas de détection à nouveau d'une telle perturbation, on con¬ sidère qu'il y a présence d'une pluralité de cibles dans le volu¬ me de détection, et e2) dans le cas contraire, on considère qu'il y a présence d'une ci¬ ble unique dans le volume de détection. 5 20 this magnetic muting field being produced in a predetermined muting volume (7), smaller than the detection volume (6), contained inside the latter and the extent of which is determined as a function of the articles to be protected so that it could be physically placed in the volume of inhibition that a 5 single item with its anti-theft target associated, and e) again detects a possible harmonic disturbance of the alternating magnetic field produced by another target or targets very au¬ in the sensing volume out of the volume of inhibition and 0 el) in case of detection again of such a disturbance, it con¬ amazes there presence of a plurality of targets in the detection volu¬ me, and e2) in the opposite case, it is considered that there is presence of a single cable ci¬ in the sensing volume. 5
2. Le procédé de la revendication 1, dans lequel, les cibles antivol comprenant chacune deux matériaux magnétiques distincts saturables à des niveaux de champ différents de manière à rendre les cibles désac¬ tivables et réactivables par magnétisation et démagnétisation, respec- δ tivement. du matériau magnétique saturable par le champ le plus fort :2. The method of claim 1, wherein the anti-theft targets each comprising two distinct magnetic materials saturable at different field levels so as to make the targets deactivatable and reactivable by magnetization and demagnetization, respectively. magnetic material saturable by the strongest field:
— à l'étape _., on désactive la cible ou les cibles suite à la détection de celle(s)-ci, et-. _ Step, the target is quenched or the target upon detection of one (s) -Cl, and
— à l'étape ___,, on réactive les cibles suite à la détection d'une plura¬ lité de cibles.- In step ___ ,, the targets are reactivated following the detection of a plurality of targets.
3. Le procédé de la revendication 1 , dans lequel, à l'étape i on pro¬ duit un champ résultant toujours inférieur au seuil de désactivation ou de neutralisation des cibles antivol.3. The process of claim 1, in which, in step i, a resulting field is always produced which is always lower than the deactivation or neutralization threshold of the anti-theft targets.
4. Un dispositif pour déterminer l'unicité ou la pluralité de cibles magnétiques dans un volume de détection (6) prédéterminé, ces cibles étant des cibles antivol (12) comprenant un matériau magnétique satu¬ rable et solidarisées à des articles (11 ) à protéger, dispositif compre¬ nant : — des moyens (13 à 16) pour produire dans le volume de détection un champ magnétique alternatif d'interrogation (H_) de fréquence donnée et d'intensité permettant de saturer et de désaturer de fa¬ çon répétée la cible ou les cibles, et4. A device for determining the uniqueness or the plurality of magnetic targets in a predetermined detection volume (6), these targets being anti-theft targets (12) comprising a saturable magnetic material and secured to articles (11) to protect, compre¬ device ing: - means (13 to 16) for generating in the detection volume an alternating magnetic interrogation field (H_) of given frequency and intensity to saturate and desaturate of fa¬ cON repeated the target (s), and
— des moyens (17 à 21 ) détecteurs de la perturbation harmonique du champ magnétique alternatif produite par la cible ou les cibles dans le volume de détection du fait des saturations et désatura¬ tions répétées, dispositif caractérisé en ce qu'il comprend en outre :- means (17 to 21) sensors of the harmonic disturbance of the alternating magnetic field produced by the target or targets in the detection volume due to the saturation and désatura¬ repeated tions, device characterized in that it further comprises:
— des moyens (22, 23, 24) pour produire, après détection d'une per- turbation. un champ magnétique d'inhibition (H_), essentiellement continu et superposé au champ magnétique alternatif d'interroga¬ tion (H ), ce champ magnétique d'inhibition étant produit dans un volume d'inhibition (7) prédéterminé, plus réduit que le volume de détection (6), contenu à l'intérieur de ce dernier et dont l'étendue est déterminée en fonction des articles à protéger de telle sorte qu'il ne puisse être matériellement placé dans le volume d'inhibi¬ tion qu'un seul article avec sa cible antivol associée, et — des moyens discriminateurs (13 à 16, 22), pour détecter à nouveau l'éventuelle perturbation harmonique du champ magnétique alter- 5 natif produite par une autre cible ou d'autres cibles dans le volume de détection hors du volume d'inhibition.- means (22, 23, 24) for generating, upon detection of a per- turbation. a magnetic field of inhibition (H_), substantially continuous and superimposed on the alternating magnetic field of interroga¬ tion (H), this inhibition magnetic field being generated in a volume inhibition (7) predetermined, smaller than the sensing volume (6) contained inside it and whose extent is determined by the articles to be protected in such a way it can not be physically placed in the volume of a single article inhibi¬ tion with its associated lock target, and - discriminating means (13-16, 22) to detect again the possible disturbance of the harmonic alternating magnetic field produced by another target or targets in the detection volume outside the inhibition volume.
5. Le dispositif de la revendication 4, dans lequel, les cibles antivol comprenant chacune deux matériaux magnétiques distincts saturables5. The device of claim 4, in which the anti-theft targets each comprising two distinct saturable magnetic materials
10 à des niveaux de champ différents de manière à rendre les cibles désac¬ tivables et réactivables par magnétisation et démagnétisation, respec¬ tivement, du matériau magnétique saturable par le champ le plus fort, il est prévu des moyens (22, 23, 24) désactivateurs et réactivateurs de cible, coopérant avec les moyens détecteurs de manière à désactiver la l δ cible ou les cibles suite à la détection de celle(s)-ci et coopérant avec les moyens discriminateurs de manière à réactiver les cibles suite à la détection d'une pluralité de cibles.10 at different field levels so as to make the targets deactivatable and reactivable by magnetization and demagnetization, respectively, of the magnetic material saturable by the strongest field, means are provided (22, 23, 24) target deactivators and reactivators, cooperating with the detecting means so as to deactivate the target (s) following the detection of the latter and cooperating with the discriminating means so as to reactivate the targets following the detection of 'a plurality of targets.
6. Le dispositif de la revendication 4, dans lequel les moyens (22, 20 23, 24) pour produire le champ magnétique d'inhibition superposé au champ magnétique d'interrogation produisent un champ résultant tou¬ jours inférieur au seuil de désactivation ou de neutralisation des cibles antivol.6. The device of claim 4, wherein the means (22, 20 23, 24) for generating the magnetic field for inhibiting superimposed on the magnetic interrogation field produce a resultant field tou¬ days less than the deactivation threshold or neutralization of anti-theft targets.
2525
3030
5 5
EP95943554A 1994-12-30 1995-12-29 Method and device for determining whether there are one or more magnetic anti-theft targets in a predetermined detection space Withdrawn EP0800693A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9415913A FR2728992B1 (en) 1994-12-30 1994-12-30 METHOD AND DEVICE FOR DETERMINING THE SINGLE OR PLURALITY OF MAGNETIC ANTI-THEFT MAGNETIC TARGETS IN A PREDETERMINED DETECTION VOLUME
FR9415913 1994-12-30
PCT/FR1995/001762 WO1996021207A1 (en) 1994-12-30 1995-12-29 Method and device for determining whether there are one or more magnetic anti-theft targets in a predetermined detection space

Publications (1)

Publication Number Publication Date
EP0800693A1 true EP0800693A1 (en) 1997-10-15

Family

ID=9470447

Family Applications (1)

Application Number Title Priority Date Filing Date
EP95943554A Withdrawn EP0800693A1 (en) 1994-12-30 1995-12-29 Method and device for determining whether there are one or more magnetic anti-theft targets in a predetermined detection space

Country Status (4)

Country Link
EP (1) EP0800693A1 (en)
AU (1) AU4489796A (en)
FR (1) FR2728992B1 (en)
WO (1) WO1996021207A1 (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2316230B (en) * 1996-08-08 1999-03-24 Automated Library Systems Limi Apparatus & method for magnetising security targets

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2073421C (en) * 1991-07-25 2003-09-23 Graeme R. Mann Article removal control system

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9621207A1 *

Also Published As

Publication number Publication date
FR2728992B1 (en) 1997-03-28
WO1996021207A1 (en) 1996-07-11
AU4489796A (en) 1996-07-24
FR2728992A1 (en) 1996-07-05

Similar Documents

Publication Publication Date Title
CA2058947C (en) Process and device for registering and checking items
FR2515362A1 (en) METHOD AND APPARATUS FOR DETECTING THE FLIGHT BY DETECTING THE ATTENUATION OF A RESONANT CIRCUIT
EP2517147B1 (en) Protection process in a wireless radio frequency communication
FR2559914A1 (en) SECURITY MARK DETECTION SYSTEM
FR2720519A1 (en) Metal detector integrated in combination with a transponder detector for access control.
FR2493531A1 (en) ELECTRONIC DEVICE FOR DETECTING THE FLIGHT OF OBJECTS MARKED, IN PARTICULAR FOR SUPERMARKETS
FR2774176A1 (en) Retrieving information from LC resonance tag to discriminate counterfeit articles
EP1794896B1 (en) Contactless privacy protection device
WO1996021207A1 (en) Method and device for determining whether there are one or more magnetic anti-theft targets in a predetermined detection space
EP3535737B1 (en) Trolley or other container including means for optimally determining in real-time the contents thereof
FR2814267A1 (en) IMPLEMENTATION METHOD AND MONITORING DEVICE FOR PREVENTING DURING AN INTRUSION INTO THE AREA IT IS MONITORING
AU769526B2 (en) Security systems for inhibiting theft of goods from retail stores
FR2553523A1 (en) Inductive anti-theft alarm working by detection of resonant circuits
EP3940614A1 (en) Autonomous shop for self-service retail sales
FR2726659A1 (en) DEVICE AND METHOD FOR MONITORING OBJECTS DEPOSITED IN A PREMISES
FR2828967A1 (en) METHOD FOR AUTHORIZING THE UNLOCKING AND / OR STARTING OF A MOTOR VEHICLE AND ASSOCIATED DEVICE
EP2068289A1 (en) Method for protecting against terminal theft, corresponding system, terminal and computer program product
FR3097657A1 (en) Open metal detector
WO1992012503A1 (en) DEVICE FOR PROTECTING OBJECTS, IN PARTICULAR $i(OBJETS D'ART)
EP0506164A1 (en) Remote control for auction-price display
FR2727549A1 (en) Security system for surveillance of goods in warehouse, shop etc.
FR2836581A1 (en) Detection of a transponder label signal, especially for use in shops, etc., using a detection panel with antennae whose operating frequencies are continuously modulated to enable detection of a wider frequency range
FR3122268A1 (en) Device and method for monitoring an installation for handling and packaging valuables
FR3112466A1 (en) Stand-alone self-service retail store
WO2020115378A1 (en) Personalisation system using near-field communication

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19970829

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE GB

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

17Q First examination report despatched

Effective date: 19980216

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

18D Application deemed to be withdrawn

Effective date: 19980627

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

R18D Application deemed to be withdrawn (corrected)

Effective date: 19981006