Magnetic marker or tag

• US 6,329,916 B1
• Filed: 10/10/2000
• Issued: 12/11/2001
• Est. Priority Date: 04/04/1995
• Status: Expired due to Fees

• Current Assignee: Digital Magnetic Technologies, LLC
• Original Assignee: Flying Null, Ltd.
• Inventors: Dames, Andrew Nicholas
• Primary Examiner(s): MULLEN, THOMAS J
• Application Number:
  US09/685,248
• Time in Patent Office: 427 Days
• Field of Search: 340/572.6, 148/100, 148/304, 235/493, 428/611
• US Class Current: 340/572.6
• CPC Class Codes: G01V 15/00 Tags attached to, or associated with, an object, in order to enable detection of the object record carriers for use with machines having a detectable tag or marker G06K19/00
• CPC Class Codes: G06Q 10/0875 Itemisation or classification of parts, supplies or services, e.g. bill of materials
• CPC Class Codes: G08B 13/2417 having a radio frequency identification chip
• CPC Class Codes: G08B 13/2434 Tag housing and attachment details
• CPC Class Codes: G08B 13/2437 Tag layered structure, processes for making layered tags
• CPC Class Codes: G08B 13/2442 Tag materials and material properties thereof, e.g. magnetic material details
• CPC Class Codes: G08B 13/246 Check out systems combined with EAS, e.g. price information stored on EAS tag anti-theft systems in point of sale systems G07G3/003
• CPC Class Codes: G08B 13/2462 Asset location systems combined with EAS inventory, tracking, logistic G06Q10/00; entrance control systems G07C9/00
• CPC Class Codes: G08B 13/2471 Antenna signal processing by receiver or emitter
• CPC Class Codes: G08B 13/2474 Antenna or antenna activator geometry, arrangement or layout loop antennae H01Q1/22
• CPC Class Codes: G08B 13/2477 Antenna or antenna activator circuit
• CPC Class Codes: G08B 13/2485 Simultaneous detection of multiple EAS tags
• CPC Class Codes: Y10T 428/12465 having magnetic properties, or preformed fiber orientation coordinate with shape

Abstract

Magnetic tags or markers are disclosed, together with a variety of techniques by means of which such tags may be interrogated. In one aspect, the magnetic marker or tag which is characterised by carrying a plurality of discrete magnetically active regions in a linear array. In another aspect, the invention provides a method of interrogating a magnetic tag or marker within a predetermined interrogation zone, the tag compromising a high permeability magnetic material, for example to read data stored magnetically in the tag or to use the response of the tag to detect its presence and/or to determine its position within the interrogation zone, characterized in that the interrogation process includes the step of subjecting the tag sequentially to: (1) a magnetic field sufficient in field strength to saturate the high permeability magnetic material, and (2) a magnetic null as herein defined. Applications of such techniques are described, inter alia, in relation to (a) identifying articled to which tags are attached; (b) accurate determination of position, as in the location of surgical probes; (c) totalisation of purchases, where each item carries a tag coded with data representing its nature and its price.

Claims

1. A magnetic marker or tag which is characterized by a substrate carrying a plurality of discrete magnetically active regions disposed in one or more linear arrays, the magnetically active regions being formed of a thin film or spin-melt material having a preferential axis of magnetization, and the preferential axes of magnetization being aligned within the (or each) linear array.

2. A tag as claimed in claim 1, characterized in that either the magnetically active regions, or the spaces between said magnetically active regions, or both, is or are non-uniform.

3. A tag as claimed in claim 1, characterized in that said discrete magnetically active regions are formed from a continuous area of magnetisable material discrete regions of which are magnetized so as to generate space(s) between said magnetically active regions.

4. A tag as claimed in claim 1, characterized in that the tag has two linear arrays disposed orthogonally.

5. A tag as claimed in any one of claims 1, 2, 3 or 4, characterized in that it is in the form of a relatively long, thin strip having a preferential axis of magnetization along its length.

6. A tag as claimed in claim 1 or 2, characterized in that the preferential axes of magnetization are generated by longitudinal annealing of a spin-melt material.

7. A tag as claimed in claim 2, characterized in that the spacing between each of the magnetically active regions is non-uniform.

8. A tag as claimed in claim 1, characterized in that each of the magnetically active regions is of substantially the same shape and size.

9. A tag as claimed in claim 1, characterized in that the spacing between each of the magnetically active regions is uniform.