CONDUCTIVE-RING FERROMAGNETIC MARKER AND METHOD AND SYSTEM FOR USING SAME

• US 3,754,226 A
• Filed: 11/24/1971
• Issued: 08/21/1973
• Est. Priority Date: 03/22/1968
• Status: Expired due to Term

• Current Assignee: Edward R. Fearon
• Original Assignee: Edward R. Fearon
• Inventors: Fearon, Edward R.
• Primary Examiner(s): Trafton, David L.
• Application Number:
  US05/201,858
• Time in Patent Office: 636 Days
• Field of Search: 340/258R,258C,280,224 325/8,105 343/6.5SS,6.8,787,788 179/82
• US Class Current: 340/572.3
• CPC Class Codes: G01S 13/753 using frequency selective elements, e.g. resonator
• CPC Class Codes: G06K 7/10009 sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
• CPC Class Codes: G08B 13/2408 using ferromagnetic tags
• CPC Class Codes: G08B 13/2431 Tag circuit 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 13/2474 Antenna or antenna activator geometry, arrangement or layout loop antennae H01Q1/22

Abstract

A ferromagnetic marker is used in tagging objects to allow selective detection of the tagged objects within an interrogation zone having a magnetic field varying at a fundamental frequency. The marker comprises a ring-shaped electrical conductor for carrying a current induced by the varying magnetic field. An element which is non-linearly polarized in response to an electromagnetic field is disposed proximate the conductor to modulate the current flowing therethrough. A modulated electromagnetic signal is then generated and sensed to allow detection of a tagged object.

Claims

1. A marker for being secured to an object to enable detection of the object within an interrogation zone having an oscillating electromagnetic field, the marker comprising:

a generally ring-Shaped electrical conductor including a loop having a pair of ends which do not close for carrying a current induced by said electromagnetic field, and a ferromagnetic substance which is nonlinearly polarized in response to said electromagnetic field and is electrically connected to the ends of said conductor, wherein said marker radiates detectable electromagnetic radiation at a predetermined frequency when disposed within said interrogation zone.

2. A marker according to claim 1 wherein said substance comprises barium titanate.

3. A marker for being secured to an object to enable detection of the object within an interrogation zone having an oscillating electromagnetic field, the marker comprising:

a generally ring-shaped electrical conductor for carrying a current induced by said electromagnetic field, a substance which is nonlinearly polarized in response to said electromagnetic field and is electrically connected to said conductor, wherein said marker radiates detectable electromagnetic radiation at a predetermined frequency when disposed within said interrogation zone, and the conductivity of a segment of said ring-shaped conductor being degradable by a predetermined current flow therethrough to permit deactivation of said marker by inducing said predetermined current in said conductor.

4. A marker according to claim 3 wherein said segment comprises a substance of lower conductivity than the remainder of said conductor.

5. A marker according to claim 3 wherein said segment comprises a constriction in said conductor.

6. A system for detecting an object in an interrogation zone comprising:

means proximate the area for producing at least one oscillating electromagnetic field in the zone, a marker associated with each object to be detected for reflecting detectable electromagnetic radiation in response to energy received from said oscillating electromagnetic field, said marker including a ring-shaped electrical conductor for carrying a current induced by said electromagnetic field, and further including a substance which is nonlinearly polarized in response to an electromagnetic field and which is connected to said conductor, means for sensing reflected electromagnetic radiation from said marker in said interrogation zone, and means for deactivating said marker to permit an authorized passage of an object through the zone without detection.

7. A system according to claim 6 wherein said deactivating means comprises:

an electromagnetic energy source for producing electromagnetic energy corresponding with the frequency of mechanical resonance of said marker for fracturing said marker.

8. A system according to claim 6 wherein said marker includes a segment having a conductivity lower than the conductivity of the remainder of the conductor and wherein said deactivating means comprises means for inducing in said conductor enough current to destroy the electrical conductivity of said segment.

9. A method of detecting an object in an interrogation zone comprising the steps of:

providing each object to be detected with a marker comprising a ring-shaped electrical conductor for carrying a current induced by an electromagnetic field the lines of which link said conductor, and a substance connected to the conductor and which is nonlinearly polarized in response to an electromagnetic field, producing an oscillating electromagnetic field in the interrogation zone to induce a current in the conductor of a marker present in the zone to radiate detectable electromagnetic radiation, detecting in the interrogation zone said radiation, and selectively deactivating said marker when it is not desired to indicate the presence of an object in the interrogation zone.

10. A marker for being secured to an object to enable detection of the object within an interrogation zone having an oscillating electromagnetic field, the marker comprising:

a generally ring-shaped electrical conductor comprIsing a short-circuited loop for carrying a current induced by said electromagnetic field, and a ferromagnetic material of low coercive force formed about said conductor, said ferromagnetic material being nonlinearly polarized in response to said electromagnetic field wherein said marker radiates detectable electromagnetic radiation at a predetermined frequency when disposed within said interrogation zone.

11. A marker for being secured to an object to enable detection of the object within an interrogation zone having an oscillating electromagnetic field, the marker comprising:

an electrical conductor comprising a loop having a pair of spaced apart ends for carrying a current induced by said electromagnetic field, a nonlinearly polarized material electrically connecting the ends of said loop such that said marker radiates electromagnetic radiation when disposed within said interrogation zone, and ferromagnetic material disposed about the outer periphery of said loop to increase the inductance of said loop, wherein said marker radiates a resonance frequency when placed within said interrogation zone.

12. A marker for being secured to an object to enable detection of the object within an interrogation zone having an electromagnetic field, the marker comprising:

an electrical conductor for carrying a current induced by said electromagnetic field, a wire disposed around said conductor, and a nonlinearly polarized rectifier junction connected at each end to said wire wherein said marker radiates electromagnetic radiation when disposed within said interrogation zone.

13. A system for detecting an object in an interrogation zone comprising:

means proximate the area for producing at least one oscillating electromagnetic field in the zone, a marker associated with each object to be detected for reflecting detectable electromagnetic radiation in response to energy received from said oscillating electromagnetic field, said marker including a ring-shaped electrical conductor for carrying a current induced by said electromagnetic field, and further including barium titanate which is nonlinearly polarized in response to an electromagnetic field and which is connected to said conductor, and means for sensing reflected electromagnetic radiation from said marker in said interrogation zone.