Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2001-11-15
2004-02-17
Lee, Benjamin C. (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S572300, C340S572600, C360S135000, C369S273000, C369S282000, C235S493000
Reexamination Certificate
active
06693542
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to magnetic markers for electronic surveillance of recorded media; and more particularly to the identification of pre-recorded or recordable disks, such as compact disks, digital video disks, laser disks and the like, as well as cartridges or cassettes and the like, by magnetic markers of electronic article surveillance systems, based on magnetic harmonic generation and detection.
2. Description of the Prior Art
Inventory control is a major consideration in wholesale and retail sales. Inventory control includes anti-theft and anti-pilferage considerations so to minimize lost profits. Various devices and various techniques are known to limit theft and recently amongst the most successful are the use of electronic article surveillance systems (“EAS”), which include a marker affixed to an item, and a sensor means that can detect the marker. Typically, such sensor means are devices which are strategically placed in suitable locations, often described as “interrogation zones” i.e., points of entry or exit where wholesale and retails sales may take place, or locations through which the transport of vendible articles may occur.
Currently there are two EAS systems in wide use that employ techniques based on magnetics. A first technique involves detecting higher harmonic signals generated by a magnetic marker excited at a given fundamental frequency. In this case higher harmonics are integral multiple of the fundamental frequency. There are, therefore, a number of different methods of operations that are conceivable depending on the needs and objectives for the envisaged types of surveillance. Advances in this class of technology have been made, including the development of markers whose performance is not affected when they are flexed or bent. Such are known, for example in U.S. Pat. No. 4,553,136. A second technique is based on the magneto-mechanical properties of magnetostrictive strips that are used as markers. Examples of this second technique are disclosed, for example, in U.S. Pat. No. 4,510,489 and 4,510,490.
The present invention relates to the former class of EAS systems, viz., those based on magnetic harmonics. In such systems, a magnetic marker comprising of one or more magnetically “soft” strips is excited in an interrogation zone by an external oscillating magnetic field at a fundamental frequency. Because of the non-linear magnetization behavior of the soft magnetic strip or strips in the marker, the magnetic response may be measured as an electrical signal that is detectable by the sensor means in the interrogation zone. The electrical signal detected by the sensor means in the interrogation zone contains both higher harmonic signals as well as a signal at the aforesaid fundamental frequency. According to this technique, by selecting a specific harmonic signal to track, the sensor means in the interrogation zone may identify the magnetic state of the magnetic marker, (i.e., ‘activated’, or ‘deactivated’). When such a magnetic marker is ‘activated’, the sensor means may sense such a condition and may in turn trigger an alarm when an unauthorized vendible article is placed in the interrogation zone. Such a magnetic marker is normally in an activated state and can be used repeatedly. When it is desired to permit a vendible article bearing a marker safe passage through the interrogation zone, the marker must be deactivated. Typically, when deactivation is needed, a magnetically semi-hard magnet or magnets are attached to, or placed in close proximity with the soft magnetic strip or strips. Deactivation is accomplished by simply magnetizing the semi-hard magnet or magnets, which magnetically saturate the soft magnetic strip or strips, resulting in essentially no higher harmonics in the detection signal. The presence or absence of higher harmonics in the detection signal, detectable by the sensor means, determines the nature of the article in the interrogation zone, thereby establishing a condition which can be used to determine if an alarm or other indicator should be activated or deactivated. Such a marker may be used many times as it is readily re-activated by demagnetization of the semi-hard magnetic piece or pieces which, in turn, will desaturate the magnetically soft strip or strips of the marker.
Markers which include only one or more magnetically soft strips without semi-hard magnets, as well as those which include semi-hard magnets in contact with, or in near physical proximity to one or more magnetically soft strips are known to the art.
Such EAS markers described above have been used for surveillance of many types of vendible articles. Typically they are conveniently provided as small tags, strips or casings which include the requisite one or more magnetically soft strips and optionally but very frequently also include one or more semi-hard magnets in contact with, or in near physical proximity to one or more magnetically soft strips. Such markers are very conveniently adhered to a vendible article or its packaging or can also be hidden within the interior of the same. Such markers are very cost effective and have found widespread use in inventory control of many classes of vendible goods.
However, the use of such markers has met with only limited success when used with pre-recorded or recordable media. By way of non-limiting example these include; disk media such as compact disks (“CD”, “CD-R”, “CD-RW”), digital video disks (“DVD”), larger formatted laser disks (“LD”) and the like, as well as cassette media which includes videocassettes (such as “VHS” full-size and micro cassettes) and recordable or prerecorded audio cassettes as well as DAT cassettes, and the like. Generally markers are placed on the packages containing these media, which however can be easily circumvented. For greatest effect in inventory control, markers are ideally attached directly to the recordable/recorded media. U.S. Pat. No. 5,699,047 discloses certain such markers, and recites that these markers can be used for disks which have one, or two optically recorded surfaces. Unfortunately, the magnetic strips placed on a disk with two optically recorded surfaces according to the teachings of U.S. Pat. No. 5,699,047, however, are not properly configured so that effective surveillance is difficult to achieve.
In certain embodiments described in U.S. Pat. No. 5,699,047, the marker strips are essentially magnetically closed, due to magnetic proximity of the two strips. Therefore, in such a configuration the marker strips do not emanate a sufficiently strong magnetic field outside the disk area in response to a sensor means in a typical interrogation zone. Detection of the presence of a marker at some distance from the sensor means becomes increasingly difficult as the distance increases. In a typical surveillance system, this distance between the marker and the detecting coil typically used in the sensor means is of the order of 1 to 2 meters. Where the excited magnetic field from the marker is insufficiently strong, as may be the case with the embodiments described in U.S. Pat. No. 5,699,047, the marker may pass through the interrogation zone undetected.
Accordingly there is a real and continuing need in the art for improved markers for electronic article surveillance systems which may be directly attached to recordable or recorded media. Especially needed are improved markers for electronic surveillance of optically recorded or recordable media such as compact disks, digital video disks, larger formatted laser disks, and the like.
There is also a real and continuing need in the art for improved inventory control techniques which employ electronic article surveillance systems, and improved markers which may be directly attached to recordable or recorded media.
There is also a real need in the art for improved media, either pre-recorded media, or recordable media, that comprises an improved marker capable of being sensed by electronic article surveillance systems.
There is a further need in the art for improved media, eit
Buff Ernest D.
Ernest D. Buff & Associates LLC
Fish Gordon E.
Lee Benjamin C.
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