Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
1999-08-24
2001-10-23
Lee, Benjamin C. (Department: 2736)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S572200, C340S572400, C340S010100, C340S541000, C340S525000, C342S114000
Reexamination Certificate
active
06307473
ABSTRACT:
CROSS REFERENCES TO RELATED APPLICATIONS
N/A
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
N/A
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electronic article surveillance (EAS) systems, and more particularly to controlling the output power of an EAS transmitter using target range in an EAS interrogation zone.
2. Description of the Related Art
EAS systems are well known and are primarily used as a theft deterrent in retail establishments. U.S. Pat. No. 4,510,489 discloses one example of an EAS system that utilizes a marker adapted to resonate at a particular frequency provided by an incident magnetic field applied in an interrogation zone. One or more interrogation coils or antennas transmit the magnetic field, which defines the interrogation zone. Typically, antennas will be positioned at a store's exits to provide an interrogation zone through which customers must pass to exit the store. An active marker resonating in an interrogation zone is detected by EAS receive antennas and electronics, which can then trigger an alarm and/or result in other appropriate action. EAS systems detect the presence of an active marker anywhere in the interrogation zone. It would be advantageous, especially in applications involving very wide exits of 6 feet or wider, to determine where in the interrogation zone an active marker is located. The location of an active marker can aide in the identification of a potential shoplifter.
Presently, EAS interrogation antennas transmit at full power at all times to determine the presence of a marker. When an EAS marker is close to an antenna, full power is not necessary for detection, and needlessly causes excess power consumption. Constant operation at full power can also serve to reduce the long-term reliability of system components, causing increased service calls and failure rates. A marker placed outside, but close to the interrogation zone can, in certain circumstances, cause unintended alarms. An unintended alarm is an alarm that is due to the unintended detection of an active marker. Store personnel often display merchandise, with EAS markers attached, near store exits in the fringes of the intended interrogation zone that can sometimes cause unintended detection of the attached markers. The proximity of the EAS markers to the intended interrogation zone may cause an increased incidence of unintended alarms. Unintended alarms can result in an increased number of service calls, which unnecessarily increases the overall system operating expense. Detection of an active marker combined with detection of a target in the interrogation zone could eliminate the incidence of unintended alarms caused by markers being detected in areas adjacent to the intended interrogation zone. “Target” as used herein refers to people or other moving objects such as shopping carts capable of transporting an EAS marker into an interrogation zone.
In an attempt to solve some of the above mentioned problems, infrared beams and passive infrared (PIR) motion detectors have been used to detect people or other moving targets in the interrogation zone. In operation, if a marker is detected and there was no motion in the interrogation zone, then the detection was probably unintended. However, PIR detection zones often extended beyond the interrogation zone and result in detected motion when no one was actually in the interrogation zone. To try and control the PIR detection zone, freznel lenses were utilized that were difficult to set and control resulting in an expensive and less than ideal solution. Infrared detection of targets does not provide the capability, other than on/off control, of controlling transmitter power levels because only the presence or lack of presence of a target is detected. When transmitted, the interrogation electromagnetic field of present EAS systems is transmitted at full power.
What is needed is a solution to the problems discussed hereinabove, which includes transmitter power level control resulting in reduced incidence of unintended alarms, improved reliability, and reduced system operating and service costs.
BRIEF SUMMARY OF THE INVENTION
The present invention provides an electronic article surveillance system responsive to the distance to a target within an interrogation zone. The interrogation zone is defined by an electromagnetic field generated with a known output level and transmitted by at least one antenna. A target within the interrogation zone can be any object, such as a person or shopping cart, within the interrogation zone. The target may include an EAS marker securable to an article for passage through the interrogation zone. The EAS marker is adapted to be detectable at a selected frequency when in the interrogation electromagnetic field. The marker is detected by EAS detection equipment at the selected frequency, as known in the art. The target within the interrogation zone is detected, and the distance from the antenna to the target is measured. The output level of the electromagnetic field is controlled according to the distance to the target within the interrogation zone. The output level is adjusted to be proportional to the distance to the target. If the target is near to the antenna, the output level will be adjusted relatively low, and if the target is far from the antenna, the output level will be adjusted relatively high.
To measure the distance between the EAS antenna and the target within the interrogation zone, an ultrasonic ranging system can be utilized. Ultrasonic ranging equipment includes an ultrasonic transducer and associated ultrasonic ranging electronics. The ultrasonic transducer is mounted on or near the EAS antenna. The ultrasonic system measures distance by transmitting a burst of energy at ultrasonic frequencies from the ultrasonic transducer. The transmitted ultrasonic energy impinges upon the target and is reflected back to the transducer. The distance from the transducer to the target is derived from the round trip travel time of the ultrasonic energy.
Alternately, a microwave radar motion sensor can be utilized to determine the distance between the EAS antenna and the target within the interrogation zone. With microwave radar motion sensors, range is determined from the amplitude of a microwave transmission reflected back from the target. A microwave transducer is mounted on or near the EAS antenna in similar manner to the ultrasonic transducer described above.
In addition to ultrasonic and radar ranging systems, other ranging systems can be utilized such as laser ranging. Laser ranging requires the use of a scanning mirror, lens assembly, or other beam-spreading device to be implemented because of the narrow beam of the laser. Therefore, ultrasonic and radar ranging systems are preferred.
An LAS system often includes multiple antennas. The resultant interrogation zone will be defined by the combination of each electromagnetic field associated with each antenna. A transducer from a selected ranging system (ultrasonic, radar, or other suitable ranging system) is mounted on or near each antenna to measure the distance from that antenna to a target within the interrogation zone. The output level of each electromagnetic field transmitted by each antenna can be individually controlled according to the distance from that antenna to the target. Alternately, a ranging transducer is mounted on or near each opposing end of the interrogation zone to measure the distance to a target within the interrogation zone. The measured distance from the ranging transducers to the target can be utilized to detect multiple targets within the interrogation zone. The power output level of each electromagnetic field is controlled accordingly.
Accordingly, it is an object of the present invention to provide an EAS interrogation electromagnetic field with the output level selected according to the distance to a target within the EAS interrogation zone.
It is a further object of the present invention to provide power consumption savings for operation of an EAS system by contro
Taylor John W.
Zampini Michael A.
Comoglio Rick F.
Kashimba Paul T.
Lee Benjamin C.
Sensormatic Electronics Corporation
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