[go: up one dir, main page]

EP1096451A1 - Méthode de détection de dispositifs de sécurité mi-doux - Google Patents

Méthode de détection de dispositifs de sécurité mi-doux Download PDF

Info

Publication number
EP1096451A1
EP1096451A1 EP99203618A EP99203618A EP1096451A1 EP 1096451 A1 EP1096451 A1 EP 1096451A1 EP 99203618 A EP99203618 A EP 99203618A EP 99203618 A EP99203618 A EP 99203618A EP 1096451 A1 EP1096451 A1 EP 1096451A1
Authority
EP
European Patent Office
Prior art keywords
soft magnetic
magnetic
semi
article
security feature
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Withdrawn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
EP99203618A
Other languages
German (de)
English (en)
Inventor
Paul Robertson
John Fisher
Johannes Te Lintelo
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.)
Bekaert NV SA
PA Knowledge Ltd
Original Assignee
Bekaert NV SA
PA Knowledge Ltd
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 Bekaert NV SA, PA Knowledge Ltd filed Critical Bekaert NV SA
Priority to EP99203618A priority Critical patent/EP1096451A1/fr
Priority to PCT/EP2000/010722 priority patent/WO2001033525A1/fr
Priority to US10/111,482 priority patent/US6707295B1/en
Priority to AT00977446T priority patent/ATE248416T1/de
Priority to DE60004874T priority patent/DE60004874T2/de
Priority to EP00977446A priority patent/EP1226566B1/fr
Priority to AU15164/01A priority patent/AU1516401A/en
Priority to ES00977446T priority patent/ES2206323T3/es
Publication of EP1096451A1 publication Critical patent/EP1096451A1/fr
Withdrawn legal-status Critical Current

Links

Images

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
    • G08B13/2428—Tag details
    • G08B13/2437—Tag layered structure, processes for making layered tags
    • G08B13/2442—Tag materials and material properties thereof, e.g. magnetic material details
    • 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

Definitions

  • the present invention relates to a method for detecting the presence of a semi-soft magnetic security feature in a substrate of a security article.
  • Soft magnetic security features are well known in the art of electronic article surveillance systems (EAS) and are often called anti-pilferage tags.
  • the EAS systems make use of the non-linear magnetic properties of the B-H loop of the soft magnetic material. Small activating fields typically drive the soft magnetic material into saturation. Sensitivity to small fields is required here because it is difficult to generate a large magnetic field at a distance from a source, and typical EAS systems need to interrogate as large a volume as possible, e.g. the public access routes in and out of shops.
  • the security features used here are therefore commonly based upon very soft magnetic materials such as the amorphous Metglas® or Vitrovac® or thin films such as made of a Co a Fe b Ni c Mo d Si e B f alloy, where a to f are atomic percentages and a ranges between 35 % and 70 %, b between 0 % and 8 %, c between 0 % and 40 %, d between 0 % and 4 %, e between 0 % and 30 %, f between 0 % and 30 %, with at least one element of each of the groups (b, c, d) and (e, f) being non zero.
  • CoFeNiMoSiB composition Such a Co a Fe b Ni c Mo d Si e B f composition is hereinafter referred to as a CoFeNiMoSiB composition.
  • CoFeNiMoSiB films are marketed under the name of Atalante®.
  • the term “thin” here refers to a film having a thickness, which is smaller than 10 micrometer. These materials have a very low coercivity and a high magnetic permeability.
  • soft magnetic typically refers to materials having a low coercive force, e.g. a coercive force ranging between 3 A/m and 100 A/m (measured at 1 kHz).
  • Patent applications WO-A-98/26378 and WO-A-98/26377 disclose how to solve the above problem.
  • the security element used comprises small, elongated magnetic particles which require a magnetic field greater than 100 A/m, and preferably greater than 300 A/m, to saturate. This property is chosen to ensure that the magnetic hardness of the particles is sufficiently high that they will not be driven into saturation at the field strengths commonly used in EAS gates. The security feature used here will therefore not set-off the alarm of the EAS gates.
  • spin-soft magnetic material refers to magnetic materials typically having a magnetic saturation field ranging from 100 A/m to 3000 A/m, e.g. from 200 A/m to 3000 A/m, preferably from 300 A/m to 3000 A/m (measured at 1 kHz).
  • soft magnetic materials and semi-soft magnetic materials Another problem with soft magnetic materials and semi-soft magnetic materials is that soft magnetic materials may be looked as semi-soft magnetic materials at a great distance between the drive coil and the material. Moreover the drive field at which the security element will saturate, will vary with the orientation of the security element in the field. These problems can be solved by making the authentication method a contact one or by ensuring that the spatial orientation of the drive coil and material are fixed. However, for hand-held applications it is most convenient to validate the security element with a non-contact reading where the spatial orientation between drive coil and material is not fixed.
  • Still another problem is that there may be a magnetic field, external to the field generated by the drive coil, which could bias the total field.
  • the magnetic security feature is preferably a semi-soft magnetic security feature with a magnetic saturation field ranging from 100 A/m to 1000 A/m. The method comprises following steps :
  • the time or relative phase delay between a reference point of the drive signal and a point at which the peaks occur give, together with the height of the peaks, an indication of the magnetic softness of the article.
  • the detection method can be a non-contact method, and more particularly a hand-held method.
  • the electromagnetic detection signal is proportional to the rate of change of magnetic flux in the article (dB(t)/dt).
  • the electromagnetic detection signal is proportional to an integral of the rate of change of magnetic flux in the article (B(t)).
  • the detection method further comprises a step of measuring the width of the peaks of the detection signal at one or more levels in order to discriminate semi-soft magnetic security features from Ferro-magnetic materials such as iron.
  • the semi-soft magnetic security feature can take many forms.
  • the semi-soft magnetic security feature comprises a number of fibres such as disclosed in the above-mentioned patent applications WO-A-98/26378 and WO-A-98/26377.
  • the semi-soft magnetic security feature comprises a thin semi-soft magnetic film.
  • the demagnetisation factor N of the fibres or the thin films is very low.
  • the demagnetisation factor N ranges from 10 -5 to 10 -4 .
  • Such a low demagnetisation factor N means that the dynamic magnetic permeability ⁇ r ' is not reduced very much in comparison with the bulk permeability ⁇ r and remains very high.
  • the semi-soft magnetic security feature comprises two or more types of magnetic material with different magnetic coercivity values, e.g. two or more different thin semi-soft magnetic films.
  • two or more different magnetic coercivity values e.g. two or more different thin semi-soft magnetic films.
  • one or more coils the drive coils, are driven with an alternating current to drive the security elements into saturation for both positive and negative magnetic fields.
  • One or more coils, the detection coils are used to detect the returned signal which is proportional to the rate of change of flux with time (dB(t)/dt).
  • Signal processing electronics is then used to process and analyse the signals and to provide an indicator signal which may be visual or auditive, when materials having the correct magnetic properties are situated in the drive field.
  • FIGURE 1 shows time plots 10 and 20 of typical dB(t)/dt signals received from two magnetic materials with different magnetic properties. It can be seen that the two materials have both different shapes and that they occur at different distances along the time axis, which is referenced to the drive current in the drive coils. In this plot the peaks of the signal correspond with the maximum slope of the B-H loop.
  • the material corresponding to plot 10 is a soft magnetic material; the material corresponding to plot 20 is a semi-soft magnetic material.
  • FIGURE 2 shows a time plot 20 of a typical dB(t)/dt signal received from a semi-soft magnetic material and of a square wave 30.
  • Square wave 30 is derived from the sinusoidal drive current to the drive coils. This square wave 30 is used to provide a reference to start measuring the A-value and the B-value. Both the A-value and the B-value are time or relative phase delays between reference points of the drive signal and a point at which the peaks in the dB(t)/dt occur. In terms of signal processing it has been found practical to sum the A-value and the B-value to obtain an indication on the magnetic hardness of the material under detection. The height C of the peaks of the dB(t)/dt signal is also measured.
  • the height C provides information the distance or the orientation of the magnetic material. Due to the fact that an indication is given about the distance or orientation of the material, the detection method can be a hand-held method. Alternatively, if increased precision of measurement is needed, it may be used in a configuration in which the distance and orientation of the material from the signal drive and detection means is known.
  • the measurement of the magnetic hardness can then reliably based on the sum of the above-mentioned A- and B-values. Using this approach it has been found to be possible to minimise the effect of external fields and to give reliable discrimination between materials of different hardness. This reliability can be explained as follows.
  • the A-value is the time interval between a reference and a positive peak and the B-value is the time interval between a reference and a negative peak. Any extraneous magnetic fields are compensated in this way.
  • a parameter based on the shape of the positive and / or negative pulses of the dB(t)/dt signal can give a further improvement in the ability to discriminate materials.
  • This parameter is the width D of the peak at one or more levels of the dB(t)/dt signal. Measurement of D is a good way to determine if the returned signal is from a large object of common Ferro-magnetic materials such as iron. Magnetically hard materials such as iron will not be saturated by the detector field but they will return a large sinusoidal signal.
  • the shape of dB(t)/dt signals returned from iron is much more rounded than the signals from soft magnetic and semi-soft magnetic materials as shown in Figures 1 and 2.
  • To improve the consistency of the width measurement for different magnitudes of the returned signal it is beneficial to use a circuit which tracks the peak value and then measures the width at one or more fixed fractions of the peak value.
  • the security feature is constructed from several materials with different magnetic properties, and particularly if this property is the magnetic field required to drive them into saturation, then the returned signal will show changes in shape as each material goes into saturation. In fact, a double or a triple superimposed B-H hysteresis curve is obtained, because of the different magnetic properties. Ferromagnetic coupling between the various magnetic materials also effects this curve, which means that the coercivity values of the various materials taken in isolation, will be changed due to the combination of the materials. In the case of thin films, this ferromagnetic coupling is largely dependent upon the thickness of the layers so that a wide variety of security features can be obtained.
  • the relative positions of the shape changes of the B-H curve can be used in the same way as for the single materials to determine parameters proportional to the hardness of the materials.
  • An example of such a security element is a combination of a thin CoFeNiMoSiB film with a thin film of an amorphous Co x Zr Y Nb z alloy.
  • the magnetic properties of the materials can be strongly affected by the shape factor (the ratio of length to cross-section area).
  • shape factor the ratio of length to cross-section area
  • the security feature is in the form of magnetic fibres of high permeability material
  • the field at which they will saturate can be controlled by altering the length to diameter ratio.
  • altering the orientation of the fibres relative to the magnetic field will also change the field at which they will saturate and so this needs to be taken into account in interpreting the signals from the reading apparatus.
  • An alternative would be to orient the fibres so that they can be aligned with the interrogating magnetic field.
  • the security feature is made up from a combination of materials showing a significant anisotropy between the saturation field in the hard and soft directions, and these materials are arranged with their soft axes at a range of discrete angles, then the signal from a relative rotation between the detector and material will show peaks as the drive field aligns with each soft axis direction.
  • This approach can be used to provide a coded signal.
  • the reference point for the coded signal could be one layer with a greater thickness or permeability, which would always give a greater signal than the other layers, or it could be via an optical security feature and associated sensor system.
  • An alternative would be to use the shape anisotropy of magnetic fibres, which could then be aligned at a series of discrete angles in the substrate to give the same effect as, described above.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Computer Security & Cryptography (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Signal Processing (AREA)
  • Burglar Alarm Systems (AREA)
  • Geophysics And Detection Of Objects (AREA)
EP99203618A 1999-11-01 1999-11-01 Méthode de détection de dispositifs de sécurité mi-doux Withdrawn EP1096451A1 (fr)

Priority Applications (8)

Application Number Priority Date Filing Date Title
EP99203618A EP1096451A1 (fr) 1999-11-01 1999-11-01 Méthode de détection de dispositifs de sécurité mi-doux
PCT/EP2000/010722 WO2001033525A1 (fr) 1999-11-01 2000-10-23 Procede de distinction entre un materiau a aimantation temporaire et mi-doux
US10/111,482 US6707295B1 (en) 1999-11-01 2000-10-23 Method for distinguishing between semi-soft and soft magnetic material
AT00977446T ATE248416T1 (de) 1999-11-01 2000-10-23 Verfahren zum unterscheiden zwischen halbweichem und weichem magnetischem material
DE60004874T DE60004874T2 (de) 1999-11-01 2000-10-23 Verfahren zum unterscheiden zwischen halbweichem und weichem magnetischem material
EP00977446A EP1226566B1 (fr) 1999-11-01 2000-10-23 Procede de distinction entre un materiau a aimantation temporaire et mi-doux
AU15164/01A AU1516401A (en) 1999-11-01 2000-10-23 Method for distinguishing between semi-soft and soft magnetic material
ES00977446T ES2206323T3 (es) 1999-11-01 2000-10-23 Metodo para distinguir entre material magnetico semi-blando y blando.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP99203618A EP1096451A1 (fr) 1999-11-01 1999-11-01 Méthode de détection de dispositifs de sécurité mi-doux

Publications (1)

Publication Number Publication Date
EP1096451A1 true EP1096451A1 (fr) 2001-05-02

Family

ID=8240815

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99203618A Withdrawn EP1096451A1 (fr) 1999-11-01 1999-11-01 Méthode de détection de dispositifs de sécurité mi-doux

Country Status (1)

Country Link
EP (1) EP1096451A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100545881C (zh) * 2005-03-24 2009-09-30 郡是株式会社 标签检测装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0295028A1 (fr) * 1987-06-08 1988-12-14 Esselte Meto International GmbH Dispositifs magnétiques
EP0295085A1 (fr) * 1987-06-08 1988-12-14 Esselte Meto International GmbH Détection et/ou identification d'articles utilisant des dispositifs magnétiques
EP0366335A2 (fr) * 1988-10-25 1990-05-02 THORN EMI plc Identificateur magnétique
US5204526A (en) * 1988-02-08 1993-04-20 Fuji Electric Co., Ltd. Magnetic marker and reading and identifying apparatus therefor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0295028A1 (fr) * 1987-06-08 1988-12-14 Esselte Meto International GmbH Dispositifs magnétiques
EP0295085A1 (fr) * 1987-06-08 1988-12-14 Esselte Meto International GmbH Détection et/ou identification d'articles utilisant des dispositifs magnétiques
US5204526A (en) * 1988-02-08 1993-04-20 Fuji Electric Co., Ltd. Magnetic marker and reading and identifying apparatus therefor
EP0366335A2 (fr) * 1988-10-25 1990-05-02 THORN EMI plc Identificateur magnétique

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100545881C (zh) * 2005-03-24 2009-09-30 郡是株式会社 标签检测装置

Similar Documents

Publication Publication Date Title
US5576693A (en) Method and device for remote sensing of objects
EP0632398B1 (fr) Méthode et dispositif de contrÔle d'authenticité d'objet
EP0839330B1 (fr) Perfectionnement relatifs a des marqueurs ou etiquettes magnetiques
US4940966A (en) Article detection and/or recognition using magnetic devices
CN101501532B (zh) 适用于识别和跟踪埋设在地下或嵌入市政工程中的埋设管或其他物体的探测系统
JP3153697B2 (ja) 物品検出方法及びシステム
Wernsdorfer et al. High sensitivity magnetization measurements of nanoscale cobalt clusters
US6257488B1 (en) Magnetic detector for security document
PL181016B1 (pl) Sposób i urządzenie do określania położenia elementu magnetycznego
JPH11503875A (ja) 機械的共振マーカー監視システム用金属ガラス合金
JPH11505353A (ja) 磁気セキュリティ・スレッド用の検査装置
US4791412A (en) Magnetic article surveillance system and method
EP0804773A1 (fr) Procede d'excitation et de detection d'elements magnetiques
EP0897569B1 (fr) Particules magnetique, substrat contenant de telles particules, document securise et procede pour detecter de telles particules.
US6577237B1 (en) Uni-directional magnetic tag
US4622542A (en) Magnetic article surveillance system, method and coded marker
EP1226566B1 (fr) Procede de distinction entre un materiau a aimantation temporaire et mi-doux
EP0434089A1 (fr) Procédé et dispositif pour detection et protection contre statique electromagnetiques champ en transducteur magnéto-elastique
US5353010A (en) Device and a method for detecting a magnetizable marker element
EP1096451A1 (fr) Méthode de détection de dispositifs de sécurité mi-doux
KR100990989B1 (ko) 코딩된 전자 물품 식별 시스템용 마커
US6937011B2 (en) Detector for magnetizable material using amplitude and phase discrimination
US20070114786A1 (en) Magnetic tag and method for reading information store therein
JPH09512362A (ja) 電子的ラベルの符号化方法及び装置
KR100368299B1 (ko) 비선형성 자기 센서의 제조방법

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

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE

AX Request for extension of the european patent

Free format text: AL;LT;LV;MK;RO;SI

AKX Designation fees paid
REG Reference to a national code

Ref country code: DE

Ref legal event code: 8566

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

18D Application deemed to be withdrawn

Effective date: 20011103