US 6,144,300 AGranted

Spatial magnetic interrogation

AssigneeFlying Null Limited

InventorAndrew Nicholas Dames

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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 characterized 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 comprising 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 sacurate the high permeability magnetic material, and (2) a magnetic null as herein defined. Applications of such techniques are describer, inter alia, in relation to (a) identifying articles to which tags are attached; (b) accurate determination of position, as in the location of surgical probes; and (c) totalisation of purchases, where cash item carries a tag coded with data representing its nature and its price.

Claims21

Dependent claims

A method of determining the position of a magnetic element, or the relative positions of two or more magnetic elements on a tag, the magnetic element(s) having non-linear magnetic properties and a preferential axis of magnetisation, the method comprising the steps of:

(a) applying a magnetic field to an interrogation zone where the magnetic element(s) is or are located, or is or are expected to be located, said magnetic field being:
(i) generated by magnetic field generating means positioned independently of said magnetic element(s);
(ii) such that there exists within said interrogation zone a first region at which the component of the magnetic field resolved in a first direction is zero, and where in regions contiguous with said first region the component of the magnetic field resolved in said first direction is sufficient to saturate the, or a part of the, magnetic element(s);
and
(iii) such that said first direction is or can be aligned with the preferential axis of magnetisation of the or each magnetic element;
(b) causing relative movement between said magnetic field and said magnetic element(s) in the direction of the preferential axis of magnetisation of the magnetic element(s) such that at least a portion of the magnetic element, or of each of the magnetic elements in turn, become magnetically saturated and then enters said first region;
(c) detecting the magnetic response of the or each magnetic element during said relative movement;
and
(d) determining the position of the magnetic element, or the relative positions of the magnetic elements, from the time(s) of occurrence of the or each magnetic response.

6 more elements

A method of determining the location of an object, which comprises the steps of:

(a) securing to the object at least one magnetic element in the form of a small piece of a magnetic material having non-linear magnetic properties and a preferential axis of magnetisation,
(b) applying a magnetic field to an interrogation zone where the magnetic element(s) is or are located, or is or are expected to be located, said magnetic field being:
(i) generated by magnetic field generating means positioned independently of said magnetic element(s);
(ii) such that there exists within said interrogation zone a first region at which the component of the magnetic field resolved in a first direction is zero, and wherein in regions contiguous with said first region the component of the magnetic field resolve din said first direction is sufficient to saturate the, or part of the, magnetic element(s);
and
(iii) such that said first direction is or can be aligned with the preferential axis of magnetisation of the or each magnetic element;
(c) causing relative movement between said magnetic field and said magnetic element(s) in the direction of the preferential axis of magnetisation of the magnetic element(s) such that at least a portion of said magnetic element(s) becomes magnetically saturated and then enters said first region;
(d) detecting the response of the magnetic element(s);
and
(e) calculating the position of the object from a consideration of said magnetic response and from the known parameters relating to said applied field and to the properties of the said magnetic material.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/930,228Filed 12 Jan 1998
Priority: GB 95069092 Apr 1995
Granted: 7 Nov 2000
Term ends: Not estimatedThe source records don’t support an estimate.

Classification17 codes

G08B 13/246
Specific applications combined with EAS: check out systems combined with EAS, e.g. price information stored on EAS tag
G01V 15/00
Tags attached to, or associated with, an object, in order to enable
G06Q 10/0875
Inventory or stock management, e.g. order filling, procurement or balancing against orders: itemisation or classification of parts, supplies or…
G08B 13/2417
Using inductive tags: having a radio frequency identification chip