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WO2001026049A1 - Etiquettes magnetiques - Google Patents

Etiquettes magnetiques Download PDF

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Publication number
WO2001026049A1
WO2001026049A1 PCT/GB2000/003752 GB0003752W WO0126049A1 WO 2001026049 A1 WO2001026049 A1 WO 2001026049A1 GB 0003752 W GB0003752 W GB 0003752W WO 0126049 A1 WO0126049 A1 WO 0126049A1
Authority
WO
WIPO (PCT)
Prior art keywords
elements
magnetic
data
tag according
magnetic tag
Prior art date
Application number
PCT/GB2000/003752
Other languages
English (en)
Inventor
Andrew Nicholas Dames
James Mark Carson England
Original Assignee
Btg International 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 Btg International Ltd filed Critical Btg International Ltd
Priority to EP00964454A priority Critical patent/EP1218852A1/fr
Priority to AU75389/00A priority patent/AU7538900A/en
Publication of WO2001026049A1 publication Critical patent/WO2001026049A1/fr

Links

Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/06187—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code with magnetically detectable marking

Definitions

  • This invention relates to the field of magnetic tags for storing data, particularly but not exclusively to tags in which data is stored by reference to a combination of magnetic element characteristics.
  • PCT publication number WO99/35610 describes tags and reader systems primarily intended for tags fabricated from magnetic material of low coercivity, with elements at different orientations, in which data is recorded primarily by means of the orientation of the elements with respect to each other.
  • the described system assumes that the coercivities of the tag elements are all the same, and are very small compared to the interrogation field.
  • a magnetic tag for storing data comprising at least one magnetic element configured such that the data is stored by reference to a combination of two or more characteristics associated with the or each element.
  • a first one of the characteristics can be used to identify or distinguish the elements from one another and a second one of the characteristics can be used to store data.
  • One or more further characteristics can be used to store additional data.
  • the characteristics can include one or more selected from element coercivity, element bias, element orientation, amplitude response of an element, response bandwidth, dependence of element switching field in response to the rate of change of an applied field, element switching speed, element location, maximum cross-field bias, permeability, Barkhausen response and resonant frequency.
  • the magnetic tag can comprise a plurality of magnetic elements, each of the magnetic elements being disposed in a different orientation by which it is distinguishable from the other elements and each having a magnetic bias member capable of assuming a plurality of states, wherein data is stored by the state assumed by the magnetic bias member. Further data can be stored by the orientation of each of the elements being selected from a set of possible orientations. Additional data can also be stored by arranging for one or more of the elements to exhibit a different coercivity and/or a different amplitude response from that of the other elements.
  • the magnetic tag can alternatively comprise a plurality of intersecting magnetic elements, each of the magnetic elements being disposed in a different orientation by which it is distinguishable from the other elements and each having a coercivity selected from a set of possible coercivities, whereby to store data.
  • the relative orientations of the elements can be used to identify the elements and to store data, and the coercivities of the elements can be used to store further data.
  • the magnetic tag can comprise a plurality of magnetic elements, each of the magnetic elements being disposed in a different orientation by which it is distinguishable from the other elements and each being located at one of a plurality of possible locations whereby to store data.
  • the magnetic tag can also comprise a plurality of magnetic elements, each of the magnetic elements being located at one of a plurality of possible locations and each having a coercivity which is selected from a set of possible coercivities, whereby to store data.
  • Figure 1 illustrates a 40-bit programmable thin-film data tag
  • Figure 2 illustrates a portion of a thin-film data tag in which data storage density is increased by varying the width of each element
  • Figure 3 illustrates a portion of a thin-film data tag in which data storage density is increased by varying the relative orientation of the elements;
  • Figure 4 shows a 7-element coercivity-angle-encoded data tag;
  • Figure 5 shows a 7-element location-angle-encoded data tag;
  • Figure 6 shows a 7-element coercivity-location-encoded data tag.
  • Passive magnetic data tags in accordance with the invention comprise one or more magnetically active dipole elements.
  • the primary constraints on data tag construction are:
  • More than one property varies between elements, for example selected from orientation, bias, response amplitude (i.e. saturated dipole moment), coercivity and location (or presence/absence) of an element. 2.
  • One parameter is used to distinguish the element, and one or more other parameters are used to store the data.
  • the number of bits of data per magnetic element is greatest. The embodiments described below do not represent the ultimate data capacity of the tag. The data capacity can be maximised by using more elements, by varying more properties, and by increasing the resolution of the reading system to distinguish between more states, for example, closer orientations or similar amplitude. In general terms, the more complex the tag becomes, the less robust the reading system becomes.
  • a first example of the invention is described with reference to Figure 1.
  • a plurality of magnetic elements 1-21 are arranged on a substrate 22, each at a different orientation, and each with a different bias field.
  • the orientation is used to identify and distinguish the elements, and the bias state of each element is used to store data.
  • Each element occupies a different position on the tag. In the simplest implementation, no information is stored in the position, coercivity or amplitude or by reference to any other properties.
  • Each element ' consists of a 9x9mm 2 square of soft magnetic material, for example, AtalanteTM thin film material (manufactured by 1ST of Zulte, Belgium, part number SPR97017A).
  • This material has an "easy" axis of magnetisation, which provides a nominal orientation or direction for the element, or, in other words, the material exhibits a directional response to an applied magnetic field.
  • a layer of a hard magnetic material for example, ferric oxide recording tape, with a coercivity of 24 kA/m, and a film thickness of lO ⁇ m.
  • This magnetic material is anisotropic, and the axis of magnetisation is aligned with that of the soft material.
  • the elements 1-21 are arranged on a square grid with a pitch of 10mm. Each element 1-21 is rotated to a different angle, as shown in the following table.
  • the magnetic recording film can be in one of four states: unmagnetised; magnetised parallel to the nominal direction of the element; magnetised at 180° to the nominal direction of the element; or magnetised with an AC waveform to produce a magnetisation pattern at a pitch of, for example, 1.8mm.
  • This final state has the effect of turning the element "off", i.e. preventing it from generating any response in the interrogation field.
  • Each element therefore has four states, and can store 2 bits of data.
  • the angular gaps between the last two elements 20, 21, and between the last element 21 and the first element 1 are 12 and 16 degrees respectively. All the other elements are at 8 degrees with respect to their neighbours. In a reader system for the tag, the two larger gaps provide a reference mark, so that the elements can be correctly ordered.
  • the total amount of useful data that can be stored is slightly less: one bit of data is lost because there is an ambiguity whereby all the elements are magnetised the other way around.
  • a number of states are not allowed. These are states in which all the elements are turned off (the extreme case), and more generally states in which the first and final two elements 1, 20, 21 are turned off, as this prevents correct identification of the elements.
  • a conservative figure for the total amount of useful data that can be stored is 40 bits.
  • the tag is read, in the simplest case, using a rotating magnetic field of around 2.5 kA/m. At this interrogation field, magnetising the film moves the position of the transitions by about 1°.
  • the tag can be made more compact by placing the lower two rows (elements 1 -10) on top of the upper two rows (elements 12-21). This is because the elements above each other are orthogonal.
  • a gapped "recording head” similar to those used for standard magnetic tape, is used to magnetise the tape; 2.
  • a small permanent magnet is used to magnetise the recording film in either direction.
  • AC magnetisation can be achieved using a magnet with alternate north-south magnetisation; 3.
  • the tag is manufactured initially without recording film. Pre-magnetised film is then stuck onto each element as required; and
  • each element is magnetised by a separate ferrite element, with separate coil connections. This permits all four states of all 21 elements to be defined.
  • the tag stores information by the magnetisation of the bias element above the soft magnetic material. No information is stored in the soft element orientation, amplitude response or coercivity. To increase the data density, one or more of these parameters is varied for each element.
  • Our co-pending application PCT/GB00/03092 describes how these parameters can be read independently, for each soft element.
  • the same data density can be achieved using fewer magnetic elements. This has many practical advantages.
  • the materials costs of the tag are lower, the tag can be smaller, and the reader system is able to distinguish more tags in the same volume.
  • each element can be made narrower than 9mm (perpendicular to the easy axis).
  • two widths are allowed - 9mm and 5mm and first, eighth and ninth elements 1,8,9 are shown with the reduced width.
  • This scheme codes approximately an extra 1 bit for each element.
  • the magnetic bias layer can be used to alter the dipole's effective width and length, by recording AC patterns on part of the film. Mechanical damage of the magnetic material can also be used to alter its effective geometry.
  • the gaps in the examples above are all 8°. By allowing these to be (for example) 7° or 9°, as shown in Figure 3, an extra 1 bit may be encoded for each element.
  • An upper limit of different states is for example around 4 states - e.g. 6.5°, 7.5°, 8.5° and 9.5°.
  • the design retains the feature of at least one large gap, for example a gap between the last and first elements, larger than any other gap, referred to herein as the "big gap" feature, so that the elements are always read in order. This also means that certain combinations of states (e.g.
  • All the elements in the examples described above have the same coercivity (near zero to about 10 A/m).
  • a coercivity selected from a set for example a set of two or a set of four
  • additional information can be encoded by each element.
  • About 2 bits of additional data can be stored in this way. In practice, the maximum number of elements used is reduced.
  • the gain in data capacity is less than the maximum number of states added, because certain states are indistinguishable - for example, those in which elements are turned off by the bias field, but have different amplitude, orientation or coercivity.
  • certain states are indistinguishable - for example, those in which elements are turned off by the bias field, but have different amplitude, orientation or coercivity.
  • most of these alterations lead to reduced number of elements in practice. It will be understood by the skilled person that the various arrangements described above can be combined to provide tags in which data is stored by any two or more properties, for example, a tag in which elements differ in amplitude response, coercivity, orientation and bias.
  • a particularly favourable class of tags can be made from elements selected from a range of available coercivities, and arranged at different angles to each other. Data is stored primarily by the coercivity of the wire, and by the angles between the wires.
  • each element is a glass-coated amorphous metal wire, 29mm long, with a metal core diameter of around 10 ⁇ m, and an overall diameter of around 25 ⁇ m, made, for example, by the Taylor-Ulitovsky method. See for example M. Vazquez, A. P. Zhukov : "Magnetic properties of glass-coated amorphous and nanocrystalline microwires” : J. Magn. Mat. 160(1996) 223-228, and J. Gonzalez, N. Murillo, V. Larin, J.M. Barandiaran, M. Vazquez, A.
  • Hernando Magnetic bistability of glass- covered Fe-rich amorphous microwire: influence of heating treatments and applied tensile stress
  • This material is magnetically bistable, with nearly rectangular B-H characteristics and rapid switching characteristics.
  • the elements can be constructed from other forms of wire, ribbon or film, such as cold-drawn amorphous metal wire, for example type 5T, a Barkhausen wire manufactured by Unitaka, Japan.
  • Suitable materials are available from a number of other manufacturers (e.g. Vacuumschmelze, Germany, Allied Signal, Four Winds Inc., USA). In general terms, suitable materials exhibit rapid switching transients in fields changing at more than 100,000 A/m/s, the field level at which these switching transients occur (“coercivity”) depends on the material type and a number of different coercivities of material are available.
  • the elements are chosen from a set of 7 different coercivities in the range, for example, 20-300 A/m. These coercivities are denoted A-G in the following description, with, for convenience, A as the lowest and G as the highest coercivity.
  • the 7 elements are disposed on a substrate 30, at different angles to each other. In the preferred configuration, the elements do not bisect. This is to avoid effects where the tag elements are deformed by all crossing at the same point. The preferred configuration also minimises element-element interactions, and keeps the thickness of the tag to a minimum.
  • the tag data is stored by a combination of angle and coercivity. For the 7-element embodiment described, the angular separations are used to identify the elements, and to store four decimal digits of data, which form the four least significant decimal digits of the data.
  • One gap between elements is required to be bigger than any of the other gaps, referred to herein as the big gap. This can exceed 35 degrees, and is used to provide a datum.
  • the six remaining gaps are split into two halves - three gaps clockwise from the big gap, and three gaps anticlockwise. Not all combinations of gaps are allowed (e.g. all gaps equal to 35 degrees), because the sum of all the gaps in the tag must equal 180 degrees.
  • all combinations of three consecutive gaps are sorted by the total angular space required. A lookup table is generated to convert between the three gaps and position in this sorted list. Combinations of three gaps involving two or more of the smallest gaps are, for example, omitted, as these can be more difficult to decode in a reader system.
  • Both of the three-gap sequences are converted into positions (numbers) in the sorted look-up table.
  • the coding scheme directs that one of these two resulting numbers is required to be larger than the other (equal numbers are not allowed).
  • the tag is read starting from the big gap, and working through the smaller numbers initially.
  • the tag elements can be unambiguously identified simply by finding the largest gap, and working out which way round to read the tag - i.e. starting with the smaller of the three gap sequences.
  • the combination of wires ABCDEFG would correspond to the base-7 number 0123456, i.e. 22875 decimal.
  • this number is multiplied by 10,000 and added to the value from the angular arrangement. There are about 33 bits of data in this arrangement.
  • the data storage capacity of the coercivity/angle tag described above can be increased in a number of ways.
  • a further way of increasing data content is to select the wires from a wider range of material types. If there are more types of magnetic material to choose between, then more data can be stored per wire. For example, 8 different states stores 3 bits/wire; 16 states stores 4 bits/wire. It quickly becomes impractical to increase the number of coercivity states above about 20 states.
  • many other properties vary between different types of material. For example, certain types of wire show a dependence in switching field on the rate of change of the applied field dH/dt, depending on the conditions of manufacture. This dependence can differ strongly, even for wires of very similar coercivity. Similarly, material switching speeds and switching amplitudes can also vary independently from each other and the coercivity.
  • Switching speeds generally depend on the material construction (for example, glass-coated wire, cold-drawn wire, thin-film and so on), whereas amplitude can also be altered by changing the physical properties of the element, for example, its length, or for thin-film materials, its width.
  • material construction for example, glass-coated wire, cold-drawn wire, thin-film and so on
  • amplitude can also be altered by changing the physical properties of the element, for example, its length, or for thin-film materials, its width.
  • Coercivity 3 bits (8 coercivities) dH/dt 1 bit (e.g. little/large variation)
  • Amplitude 1 bit (e.g. high/low amplitude)
  • the material-encoded part of the tag data is constructed most easily as an n-digit base-w number. This is added to the angle-encoded part in a similar way to that described above.
  • Another particularly favourable arrangement is one in which data is stored by a combination of angle and location.
  • a simple tag consists of a 2D grid, for example, 5x5 locations, 31, as illustrated in Figure 5.
  • a limited number of magnetic elements are arranged on this grid, for example, 7.
  • the elements are disposed at angles relative to each other, in exactly the same way as the coercivity/angle embodiment described above. With 7 elements, about 10,000 different angular arrangements can be stored and each element uniquely identified.
  • the elements can be constructed from a wide range of magnetic wires, ribbons and films. The general requirement is that the element displays a relatively rapid and detectable switching transient in fields changing at more than 100,000 A/m/s.
  • a low-cost embodiment uses 9x9mm squares of soft magnetic material, for example, AtalanteTM thin film material (manufactured by 1ST of Zulte, Belgium, part number SPR97017A). Any of the materials described above in the coercivity/angle tag embodiment can also be used.
  • the first element, 32 generally occupies the same point in the grid, for example, the bottom left.
  • the remaining elements can be positioned at any of the remaining sites. For example, with a 5x5 grid and 7 elements, the remaining 24 sites are filled by the remaining 6 elements, giving 96909120 arrangements (about 26 bits). Thus the total tag data capacity is about 40 bits.
  • Data storage in the location/angle tag described above can be increased in a number of ways.
  • the data content can be increased by using more elements or locations.
  • the penalties of this are that the tag may be larger, or that the reader may require better position resolution to separate out the different location states.
  • Using more elements also increases the tag complexity.
  • Each tag element can also vary in coercivity, dH/dt dependence, switching speed, amplitude response and bias.
  • Coercivity 3 bits (8 coercivities) dH/dt 1 bit (e.g. little/large variation)
  • Amplitude 1 bit (e.g. high/low amplitude)
  • tags with amorphous wire elements where the elements are kept parallel, because this allows the wires to be incorporated into a moving web using standard available equipment. This can also facilitate the use of a simpler reader configuration.
  • Suitable magnetic materials are, for example, bistable glass-coated amorphous metal wires, as described above, or Barkhausen wires.
  • Figure 6 shows a tag 33, which appears similar to a bar code, constructed from a series of, (in this example) 7 different parallel wires, 34, 35, each 30 mm long, with a choice of, for example, 25 locations at spaced at 2mm intervals, giving a rectangular tag around 30x50mm.
  • the different wire types are used to identify the elements, and data is stored by the location of each element. Using 7 elements, about 26 bits of data can be stored, since one element 34 is assumed to be in a fixed location. Using 9 elements, about 34 bits of data can be stored. Again, data capacity can be increased by selecting the actual elements from a larger pool of available elements, which may differ in amplitude, switching speed or dH/dt variation, or any other measurable magnetic properties.
  • Combinations of different properties, numbers of allowable states, or numbers of elements are not limited to the embodiments described above. Many factors affect the exact choice of properties to combine in the tag, including the cost of the tag, the size, the required data capacity, the geometry of the reader, the available materials, and the reading environment.
  • Resonant frequency of magnetostrictive materials Any of the properties, individually or together with any of the other properties described in this disclosure, can be used to increase the number of states for each element, and hence the total data encoded by the tag.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Burglar Alarm Systems (AREA)

Abstract

Selon l'invention, une étiquette de données magnétique comprend plusieurs éléments magnétiques dans lesquels des données sont stockées en référence à une combinaison de caractéristiques choisies parmi un grand nombre de caractéristiques possibles. Une des caractéristiques, telle que l'orientation ou l'emplacement, est utilisée afin de distinguer des éléments les uns des autres, et une autre caractéristique, telle que la coercivité ou l'amplitude, est utilisée afin de stocker des bits multiples de données par élément. On utilise d'autres caractéristiques aux fins de stockage supplémentaire de données.
PCT/GB2000/003752 1999-10-01 2000-09-29 Etiquettes magnetiques WO2001026049A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP00964454A EP1218852A1 (fr) 1999-10-01 2000-09-29 Etiquettes magnetiques
AU75389/00A AU7538900A (en) 1999-10-01 2000-09-29 Magnetic tags

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9923199.5 1999-10-01
GBGB9923199.5A GB9923199D0 (en) 1999-10-01 1999-10-01 Magnetic data tags

Publications (1)

Publication Number Publication Date
WO2001026049A1 true WO2001026049A1 (fr) 2001-04-12

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EP (1) EP1218852A1 (fr)
AU (1) AU7538900A (fr)
GB (2) GB9923199D0 (fr)
WO (1) WO2001026049A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003015017A1 (fr) * 2001-08-06 2003-02-20 Btg International Limited Etiquette de donnees magnetique programmable
US10325439B2 (en) 2015-07-03 2019-06-18 Custom Security Industries, Inc. Article identification reader, marker element for article identification and method of article identification

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102015200666B4 (de) 2015-01-16 2024-10-10 Vacuumschmelze Gmbh & Co. Kg Magnetkern, Verfahren zur Herstellung eines solchen Magnetkerns und Verfahren zum Herstellen einer elektrischen oder elektronischen Baugruppe mit einem solchen Magnetkern
DE102021116855B3 (de) 2021-06-30 2022-04-21 Sick Ag Magnetcodierte Kennzeichnungsvorrichtung zum Anbringen an einem Objekt und magnetische Identifizierungsvorrichtung

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US4940966A (en) * 1987-06-08 1990-07-10 Scientific Generics Limited Article detection and/or recognition using magnetic devices
DE19535019A1 (de) * 1995-09-21 1997-03-27 Cardtec Entwicklungs Und Vertr Magnetisches Speichermedium mit verschlüsselten Rohdaten
WO1999028852A1 (fr) * 1997-12-02 1999-06-10 Technical Graphics Security Products, Llc Dispositif de securite comportant de multiples elements de securite et procede de fabrication correspondant

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Publication number Priority date Publication date Assignee Title
GB2322769B (en) * 1995-04-04 1999-11-10 Flying Null Ltd Magnetic coding of articles
US5834748A (en) * 1996-05-17 1998-11-10 Aveka, Inc. Transactional item with non-parallel magnetic elements
GB9619896D0 (en) * 1996-09-24 1996-11-06 Flying Null Ltd Improvements in or relating to magnetic sensors
GB9625561D0 (en) * 1996-12-09 1997-01-29 Flying Null Ltd Magnetic tags
GB9816969D0 (en) * 1998-08-04 1998-09-30 Flying Null Ltd Magnetic tags and readers therefor

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
US4940966A (en) * 1987-06-08 1990-07-10 Scientific Generics Limited Article detection and/or recognition using magnetic devices
DE19535019A1 (de) * 1995-09-21 1997-03-27 Cardtec Entwicklungs Und Vertr Magnetisches Speichermedium mit verschlüsselten Rohdaten
WO1999028852A1 (fr) * 1997-12-02 1999-06-10 Technical Graphics Security Products, Llc Dispositif de securite comportant de multiples elements de securite et procede de fabrication correspondant

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003015017A1 (fr) * 2001-08-06 2003-02-20 Btg International Limited Etiquette de donnees magnetique programmable
US10325439B2 (en) 2015-07-03 2019-06-18 Custom Security Industries, Inc. Article identification reader, marker element for article identification and method of article identification

Also Published As

Publication number Publication date
EP1218852A1 (fr) 2002-07-03
GB2359962B (en) 2002-06-12
GB2359962A (en) 2001-09-05
GB0023923D0 (en) 2000-11-15
GB9923199D0 (en) 1999-12-01
AU7538900A (en) 2001-05-10

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