CA2347333A1

CA2347333A1 - Electromagnetic anti-shoplifting system

Info

Publication number: CA2347333A1
Application number: CA 2347333
Authority: CA
Inventors: Jean Courtot
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-05-11
Filing date: 2001-05-11
Publication date: 2002-11-11

Abstract

The present invention provides an antitheft system to detect the presence of an object which has a label affixed thereto when said object passes through a surveillance zone comprising an oscillatory electromagnetic interrogation field having three separate and distinct vector components produced by driving the transmitting coils located in housing on either side of said surveillance zone with an alternating power source repetitively in and out of phase with respect to one another so as to form magnetic lines of flux having one vector component in the out-of-phase mode. The signals generated by the label are received by coils in said housing and are processed by electronic circuitry adapted to distinguish said label signals from spurious signals with a high degree of accuracy. The label can be deactivated so as to pass through the surveillance zone without triggering a system response.

Description

ELECTROMAGNETIC ANTI-SHOPLIFTING SYSTEM
Background To Invention There are in existence several kinds of systems for detecting or preventing the theft of articles of value. One of these corresponds to U.S. Pat. No.
3,292,080 granted to E.M. Trikilis on December 13, 1966 which makes use of a magnetometer and utilizes a magnetized object which identifies the article unless check-out procedure has removed the magnetism from the object.
Another system involves radioactive material which emits nuclear radiation.
When the label containing the magnetic material is removed from the merchandise, the radiation is no longer emitted, and therefore radiation detectors situated in the doorway are not energized. On the other hand, if the radiation emitters remain on the merchandise, doorway sensors of nuclear radiation react, and security personnel are in a position to prevent the theft. However, there are severe health problems with this system involving danger to people from the nuclear radiation.
A further system involves the use of radio frequency generating device imbedded in a rubber pad. The radio frequency emitting device is fastened to articles and if not removed will energize radio frequency detecting antenna at the doorway. In the normal course of events, when the merchandise is sold, a special fastener is unlocked and radio frequency emitter is removed from the article at the time it is sold, permitting the buyer to pass through the doorway without attracting the attention of the store detectives.
The following United States patents illustrate a number of alternative proposals which will serve as background to the invention described and illustrated herein namely:

U.S. Pat. No. 3,631,442; U.S. Pat. No. 3,747,086; U.S. Pat. No. 3,754,228;
U.S.
Pat. No. 3,790,945; U.S. Pat. No. 3,820,103; U.S. Pat. No. 4,527,152; U.S.
Pat.
No. 4,888,579; U.S. Pat. No. 5,459,452; U.S. Pat. No. 5,602,556; U.S. Pad. No.
5,661,470.
Features Of The Invention It is feature of this invention to provide an apparatus for detecting the passage of an object through a surveillance zone comprising a transmitting coil for generating an oscillatory electromagnetic interrogation field within the surveillance zone, a label secured to an object, whereby said label is adapted to cut or link up with the electromagnetic field during its traversal through the electromagnetic interrogation field regardless of the label's special orientation, and thereby generating signals captured by a receiving coil including electronic circuitry adapted to set off an alarm.
More particularly, the electronic circuitry is adapted to minimize distortion of the generated signal by the label. The electronic circuitry is also adapted so as to differentiate label signals from other signals such as pop cans generating lower harmonics.
It is a further feature of this invention to provide people counting while passing through the interrogation zone.
It is another important feature, that the electronic circuitry has a memory to be able to store up to 256 alarms providing a detailed description of these events, including all main parameters of markers' signals as well as an exact day and a time of the events.
Brief Description Of Drawings These and other objects and features will become apparent in the following description to be read in conjunction with the sheets of drawings in which:
FIG.1 is a perspective view of the anti-shoplifting system.
FIG. 2 is a block diagram illustrating the various components of the electronic circuitry.

Claims

1. In a system for detecting the passage of an object through a surveillance zone, the combination includes: means for detecting a signal generated by said marker means in response to said generated oscillating magnetic lines of flux within said surveillance zone; said detection means include circuitry for time domain blanking and circuitry for signal recognition; said time domain blanking circuitry permits the entry to said signal recognition circuitry of said signal generated by said ferromagnetic marker and received by said detection means during a predetermined timed interval corresponding to said in-phase and out-of-phase mode switching and eliminates all other signals during all other time periods from entry to said signal recognition circuitry; said signal recognition circuitry includes pulse width detection circuitry for detecting the pulse width of said signal generated by said ferromagnetic marker.

2. In detection apparatus, circuitry means associated with said transmitting coil means for generating from said transmitting coil means an oscillating magnetic field having a predetermined fundamental frequency; receiving coil means mounted in said coil housing unit and adapted to receive signals generated by a ferromagnetic marker means in response to said generated oscillating magnetic field within said surveillance zone, whereby said receiving coil means is adapted to substantially eliminate said fundamental frequency and amplify said signals generated by said ferromagnetic marker means.

3. In a method for detecting the passage of an object through a surveillance zone, including the step of detecting a signal generated by said ferromagnetic marker in response to said generated oscillating magnetic lines of flux within said surveillance zone: said detection step is followed by the step of filtering and amplifying said signal generated from said ferromagnetic marker in said oscillating magnetic interrogation field; said filtering and amplifying step is followed by the step of distinguishing said signal generated from said ferromagnetic marker in said oscillating magnetic interrogation field from other signals by utilizing time domain blanking; said distinguishing step distinguishes the pulse width of signals generated from said ferromagnetic marker in said oscillating magnetic field from other signals; said distinguishing step includes the step of correlating said signals generated by said ferromagnetic marker in said oscillating magnetic field; said detection step averages said signal generated by said ferromagnetic marker in said oscillating magnetic field.