Abstract:
A reusable security tag is provided which is reversibly operable in a first magnetic condition to trigger a detector when the tag is within communication range of the detector, and a second magnetic condition in which the detector is not triggered when the tag is within communication range of the detector. The tag includes a visual indicator which has a first visual characteristic when the tag is in the first magnetic condition, and a second visual characteristic when the tag is in the second magnetic condition.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates to methods and apparatus for theft deterrence. More particularly, the invention relates to article surveillance techniques and systems.  
         BACKGROUND OF THE INVENTION  
         [0002]    Article surveillance systems are known in the art. Theft from retail establishments is a major problem, and article surveillance systems attempt to address this problem. To control theft, tags are secured to merchandise, and these tags must be removed or deactivated prior to removal of merchandise from a store or controlled area. If a tag is not removed or deactivated before merchandise is removed, detection equipment or a sensor near an exit will detect the tag and trigger an alarm and/or cause doors past the sensor to become locked.  
           [0003]    Various designs of article surveillance systems are known in the art. The tag may include, for example, an electrical circuit which is designed to be resonant at a particular frequency, and the detection equipment may include, for example, two antennas. One of the antennas radiates electrical signals in a band of frequencies that includes the resonant frequency of the tag. The other antenna is tuned to receive signals. Antenna pairs (also known as pedestals) can be positioned to bracket a path or exit such that the only way for a person to exit out of a store or leave a secured area requires passing in between the two antennas. One such antenna pair is described in greater detail in U.S. Pat. No. 6,061,552 to Cerasini et al., which is incorporated herein by reference.  
           [0004]    Some tags are permanently deactivatable by applying excessive energy to a resonant circuitry. The excess energy causes a resonant circuit to become deactivated by, for example, causing normally non-conductive material to become conductive. See, for example, U.S. Pat. No. 5,006,856 to Benge et al., which is incorporated herein by reference. Various designs for devices for deactivating tags are described in the following U.S. patents which are incorporated herein by reference: U.S. Pat. No. 5,949,318 to Copeland et al.; U.S. Pat. No. 5,990,794 to Alicot et al.; U.S. Pat. No. 6,011,474 to Coffey et al.; U.S. Pat. No. 6,061,552 to Cerasini et al.; and U.S. Pat. No. 6,281,796 to Canipe et al.  
           [0005]    Some tags are capable of being reactivated after being deactivated (e.g., they are reusable). These designs typically involve use of magnetic principles. Attention is directed to the following U.S. patents which relate generally to anti-theft tags, deactivation devices, and pedestals and which are incorporated herein by reference: U.S. Pat. No. 3,895,368 to Gordon et al.; U.S. Pat. No. 3,995,900 to Humble et al.; U.S. Pat. No. 4,063,229 to Welsh et al.; U.S. Pat. No. 4,510,489 to Anderson et al.; U.S. Pat. No. 4,660,025 to Humphrey; U.S. Pat. No. 4,686,516 to Humphrey; U.S. Pat. No. 5,313,192 to Ho et al.; U.S. Pat. No. 5,495,230 to Lian; U.S. Pat. No. 5,729,200 to Copeland et al.; U.S. Pat. No. 5,942,978 to Shafer; U.S. Pat. No. 5,955,951 to Wischerop et al.; U.S. Pat. No. 5,963,173 to Lian et al.; U.S. Pat. No. 6,307,474 to Lian et al.; U.S. Pat. No. 6,320,507 to Strzelec et al.; U.S. Pat. No. 6,339,378 to Seidel; U.S. Pat. No. 6,351,216 to Frederick et al.; and U.S. Pat. No. 6,352,606 to DiMarco et al.  
           [0006]    Attention is also directed to an article titled “Antishoplifting Labels,” by Joseph Ryan, Jr., appearing in the Working Knowledge column of  Scientific American  magazine, May 1997 issue, page 120. This article describes an antishoplifting system that includes a pedestal that brackets a store entrance or checkout aisle and contains a unit that transmits low radio frequency pulses; e.g., 58 kHz. The system further includes a product label including a resonator configured to vibrate at a frequency identical to the transmitted frequency; e.g., 58 kHz, when passed through the pedestal. The product label includes a magnetized strip adjacent to the resonator to ensure that the oscillations of the resonator remain precisely at the transmitted frequency; e.g., 58 kHz. A deactivation device can turn off a label when merchandise is paid for by demagnetizing the strip or altering its magnetic properties such that the resonator either will not vibrate or will do so at a frequency different from the transmitted frequency. A receiver inside one of the pedestal arms turns on between each transmitted pulse (e.g., during an 11 millisecond interval between each transmitted pulse) so that it can pick up the identical signal emitted by the label. If it receives a signal at least four times, an alarm is triggered.  
           [0007]    Surveillance tags bearing coded indicia such as bar codes are known in the art. See, for example, U.S. Pat. No. 5,979,758 to Swartz et al., which is incorporated herein by reference.  
         SUMMARY OF THE INVENTION  
         [0008]    The invention provides a reusable security tag, which is reversibly operable in a first magnetic condition, to trigger a detector when the tag is within communication range of the detector, and a second magnetic condition, in which the detector is not triggered when the tag is within communication range of the detector. The tag includes a visual indicator which has a first visual characteristic when the tag is in the first magnetic condition, and a second visual characteristic when the tag is in the second magnetic condition.  
           [0009]    One aspect of the invention includes a surveillance system comprising a tag selectively switchable between an active state and an inactive state, the tag including a visual indicator configured to provide a visual indication of whether the tag is in the active state or the inactive state; a first antenna; a second antenna; a transmitter coupled to the first antenna and configured to transmit energy having a predetermined characteristic in an area between the first and second antennas, the tag providing a predetermined detectable output in response to the energy from the transmitter if the tag is in the active state; and a receiver coupled to the second antenna and configured to provide an alarm signal in response to detecting the detectable output of the tag in the area. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a perspective view of an article surveillance system embodying various aspects of the invention, including a tag shown partly broken away and showing an alarm in block diagram form.  
         [0011]    [0011]FIG. 2A is a simplified side view of the tag of FIG. 1, illustrating a magnetized state.  
         [0012]    [0012]FIG. 2B is a simplified side view of the tag of FIG. 1, illustrating an unmagnetized state.  
         [0013]    [0013]FIG. 3 is a plot of intensity versus frequency and illustrates a shift in frequency that occurs when the tag of FIG. 1 is in the magnetized state versus the unmagnetized state.  
         [0014]    [0014]FIG. 4A is a simplified top view of a tag that provides a visual indication of change of state between amorphous and crystalline states, and illustrates the amorphous state.  
         [0015]    [0015]FIG. 4B is a simplified top view of the tag of FIG. 4A, and illustrates the crystalline state.  
         [0016]    [0016]FIG. 5A is a simplified side view of the tag of FIGS. 4A and 4B, illustrating the amorphous state.  
         [0017]    [0017]FIG. 5B is a simplified side view of the tag of FIGS. 4A and 4B, illustrating the crystalline state. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    [0018]FIG. 1 shows a security system  10  embodying various aspects of the invention. The system includes two antennas  12  and  14  which, in one embodiment, are arranged in respective housings to define a pedestal  16  of the type that can be placed so as to bracket a store entrance or placed proximate a checkout aisle. The system includes a transmitter  18  coupled to one of the antennas  12  and  14  and a receiver  20  coupled to the other of the antennas  12  and  14 . The antenna  12  coupled to the transmitter  18  transmits pulses at a predetermined frequency.  
         [0019]    The system  10  further includes a product label or tag  22  (FIGS. 2A and 2B). The tag  22  includes a resonator  24  which is configured to vibrate at a frequency identical to the transmitted frequency when passed between the antennas  12  and  14 . The product label includes a magnetic strip  26  adjacent to the resonator  24  to keep the oscillations of the resonator  24  at the transmitted frequency.  
         [0020]    The tag  22  includes (see FIGS. 2A and 2B) one or more pieces  28  of spongy or resilient material separating the strip  26  from the resonator  24 . The material could be, for example, foam, rubber, or other resilient material. The material could be only in the corners or dispersed more thoroughly between the resonator and the metal plate. Shallow bores or indents could be used to maintain the material in a desired location, such as in corners. The material could be defined by plastic or metal springs. Any appropriate material or location could be employed.  
         [0021]    At least portions of the insides (facing surfaces  30  and  32 ) of the strip  26  and resonator  24  are made to be at least partially reflecting. One of the strip  26  and resonator  24  has an opening or aperture  34 .  
         [0022]    The tag  22  further includes a housing or covering  36  (see FIG. 1) which may be, for example, made of plastic or other suitable material. The housing  36  may include a surface  37  which is intended to be affixed to or supported by products or inventory which is to be monitored. A double sided tape or an adhesive, such as a pressure sensitive adhesive, can be provided on this surface.  
         [0023]    The tag  22  further includes a partially-silvered (e.g., half-silvered), or one-way mirror  38  or similar device configured to split incoming light such that a portion is reflected in one direction and another portion is transmitted in a second direction different from the first direction. The mirror  38  is supported in or covers the opening or aperture  34  such that the partially-silvered surface faces the surface  32  (if the aperture  34  is in the strip  26 ) or the surface  30  (if the aperture  34  is in the resonator  24 ). A half-silvered mirror is one in which reflective molecules coat glass so sparsely that only about half the molecules needed to make the glass an opaque mirror are applied. Reflective molecules are speckled all over the glass in a generally even film, but only half of the glass is covered. The half-silvered surface will reflect about half the light that strikes its surface, while letting the other half go straight through.  
         [0024]    The overall size or size range can be the same as for existing tags. In one embodiment, the tags  22  are 1-2 cm long and a few mm wide.  
         [0025]    When the tag is magnetized (FIG. 2A), the plate  26  and resonator  24  have a slightly different spacing than when the tag is not magnetized (FIG. 2B). Light entering the hole  34  bounces between the plate  26  and the resonator  24 . Constructive and destructive interference results in light exiting the hole  34  at a particular set of wavelengths. The spectrum looks, for example, as shown in FIG. 3. When the spacing between the plates changes, the locations of the peaks  44 ,  46 , and  48  shift. For example, plot  40  illustrates intensity versus frequency when the tag is magnetized (FIG. 2A), and plot  42  illustrates intensity versus frequency when the tag is not magnetized (FIG. 2B). This is similar to what happens in Fabry-Perot interferometers used in physics and astronomy.  
         [0026]    In the illustrated embodiment, the magnetic force that controls the separation between the resonator  24  and magnetic strip  26  is sufficient to overcome the effects of gravity such that the tag will operate correctly at any orientation, as is the case with present tags.  
         [0027]    The shift in frequency between the magnetized and unmagnetized states results in a difference in the color of light that exits the hole  34 . This difference gives a visual indication as to the state of magnetization.  
         [0028]    The receiver  20  can be, for example, inside one of the pedestal arms or otherwise coupled to the antenna  14 . The receiver  20  turns on at least between each transmitted pulse (e.g., during an interval between each transmitted pulse) so that it can pick up the signal emitted by the tag  22  if the resonator is vibrating at the correct predetermined frequency (e.g., the frequency used by the transmitter  18 ). The resonator  24  will be vibrating at the correct frequency if the strip  26  is magnetized, but will not be vibrating at the correct frequency if the strip  26  is not magnetized.  
         [0029]    The system  10  further includes (see FIG. 1) a deactivation device  50  that can turn off the tag when removal of an item is authorized (e.g., after receipt of a payment or accounting procedures have been complied with), by demagnetizing the strip  26  or altering its magnetic properties such that the resonator  24  either will not vibrate or will do so at a frequency different from the transmitted frequency. The deactivation device  50  can be located, for example, proximate a point of sale terminal  52 .  
         [0030]    The system  10  further includes an alarm  54  coupled to the receiver  20 . If the receiver  20  receives the signal from a tag  22  at the correct predetermined frequency, (e.g. once, four times, or some other predetermined number of times), an alarm is triggered. In one embodiment, instead of or in addition to an alarm being triggered, an exit is locked.  
         [0031]    Because of the color change, visual examination of the half silvered mirror  38  shows the state of magnetization.  
         [0032]    An alternative embodiment, illustrated in FIGS. 4A, 4B,  5 A, and  5 B, makes use of a change between amorphous and crystalline states of a material to provide a visual indication of state of magnetization. In some tag designs, such as those described in incorporated U.S. Pat. Nos. 4,686,516 to Humphrey and 4,660,025 to Humphrey, the molecular organization of an active component of a tag is changed to activate or deactivate the tag. More particularly, the tag is deactivated by selectively changing a component made of amorphous material to crystalline form, such as by adjusting temperature. Temperature is adjusted in part by applying radiant energy and adjusted in part by conducting electric current through the component. A similar property, based on a change of state responsive to current flow, is used in LCD displays. A visual indicator is provided for tags of this or similar designs.  
         [0033]    [0033]FIGS. 4A and 4B show a top view of a tag  60  which make use of this principle. The tag  60  is deactivated by selectively changing a component  62  made of amorphous material to crystalline form, such as by adjusting temperature. Temperature is selectively adjusted either by applying radiant energy, by conducting electric current through the component, or a combination. The tag  60  includes a window  64  made of a polarizing material. The polarizing material in the window can be material of the type that is used in LCD displays, for example, or the type of material used in plastic sunglasses. When the tag material  62  is in its amorphous state (FIG. 4A and FIG. 5A), most of the light reflected from inside the tag  60  is unpolarized, and the window  64  looks white. When the tag material  62  is in the crystalline state (FIG. 4B and FIG. 5B), with the crystal aligned perpendicular to the polarizer in the window  64 , very little light escapes the tag  60  and the window  64  looks black.  
         [0034]    In another alternative embodiment, the window  64  is not necessarily made of a polarizing material, but is clear in one embodiment, but the material  62  is of a type that changes color or opacity between the amorphous and crystalline states. This material can be, for example, a phase-change chalcogenide alloy. A phase-change chalcogenide alloy changes from high resistance, nonreflective to low resistance reflective as its state changes from amorphous to crystalline. The inventor has recognized that such a material would advantageously change from high resistance, nonreflective, to low resistance, reflective, as its state changes from amorphous to crystalline. These two changes (reflective to nonreflective and amorphous to crystalline) together provide for both the visible indicator and the change in resonance. Another material that could possibly be used includes, for example, N,N′-bis(2-phenylethyl)perylene-3,4:9,10-bis(dicarb oximide) which is discussed in an article by J. Mizuguchi, proceedings of Third Japan-France Joint Forum-Organic Materials for Electronics and Photonics, Apr. 6-8, 1998, Tsukuba, Japan, published in the journal Molecular Crystals and Liquid Crystals. Another material that could possibly be used is an Nb/sub 2/O/sub 5/ or sol-gel niobium oxide which is discussed in an article by M. Schmitt, S. Heusing, M. A. Aegerter, A. Pawlicka, and C. Avellaneda in the journal Solar Energy Materials and Solar Cells, vol. 54, no.1-4, p. 9-17, August 1998. Other materials that could possibly be used include, for example, TbFe and GaTbFe; TbFeCo; TeSeSb; SeInSb; and alloys with various concentrations of Cu, Al, Ni and Zn such as discussed in an article titled Perspectives of reversible optical storage by F. Hoff, in the Czech journal Slaboproudy Obzor, vol. 48, no. 4, pp.197-8, published April 1987. Another material that could be used is an amorphous-crystalline transformation of basic copper carbonates such as is discussed in an article titled Nucleation and crystal proliferation kinetics: amorphous-crystalline transformation of basic copper carbonates by A.C.T. Hsu, A.C.T. in the AlChE Journal, vol. 17, no. 6, pp.1311-15, published November 1971. Yet another material that could be used is LaNiO3 such as is described in an article by H. Seim; H. Molsa; M. Nieminen; H. Fjellvag; and L. Niinisto in the JOURNAL OF MATERIALS CHEMISTRY, 1997, V7, N3 (MAR), P449-454.  
         [0035]    Several applications, in addition to anti-shoplifting applications, are possible. One application is in a warehouse. Items are scanned as they enter using a scanner that changes the magnetization of the tag  22 . If a scanned item is removed from the warehouse without authorization, an alarm or alarms are activated. If an item is not scanned as it enters the warehouse, the color of the tag  22  gives immediate feedback of the error. When an item is to be removed from the warehouse, a different scanner that reverses the magnetization is used. Again, the visible change of the color via the aperture  34  provides feedback. After this second scan, the tag  22  will not activate alarms.  
         [0036]    Another application is in a hospital. By some reports, a percentage of the supplies used are never charged to a patient while, at the same time, hospitals are sometimes accused of double charging. Each medical supply item (or selected medical supply items), such as an IV bag, can carry one of the tags  22  which is additionally marked with machine readable markings, such as a bar code or UPC  56 . A scanner  56  that reads this bar code is also configured to selectively demagnetize the tag  22  in a manner similar to that described, for example, in incorporated U.S. Pat. No. 5,979,758 to Swartz et al. This change in demagnetization is visible as a change in color in the light exiting the aperture  34 . A simple visual check will show if the item has been scanned by the scanner  56 . If the item is scanned in error, remagnetizing the tag  22  changes the color back. A scanner  56  can be provided particularly for use in returning items to inventory, and this scanner  56  is also capable of remagnetizing the tag  22 . In one embodiment, a pedestal  16  or antenna pair  12 ,  14 , is provided at the exit of a garbage collection area. If an unscanned item is discarded, an alarm will sound before the trash is removed from the site.  
         [0037]    Various alternatives will be apparent and are intended to be encompassed by the following claims. For example, in one embodiment, the tag  22  is configured with a stiffer elastic material to make the color change undetectable to the human eye, but still detectable by the scanner  56 . In this way, the scanner  56  can detect double scanning or the absence of an expected scan. It is also possible to provide special filters that make small color changes visible to the eye.  
         [0038]    In another alternative embodiment, an alternative separator piece  28  is used that comprises air or one or more air filled bags. For this embodiment, the bag has the metallic material on each side, and the window in one of the sides. The air pressure would be such that the change in magnetic state would be enough to change the spacing of the metal plates. Alternatively, a foam material could be employed if air-tightness is a problem, but the foam would have to be very compressible and transparent at the wavelengths of interest. Another alternative is to use rigid spacers at the end points. The change in magnetization will cause the metal plates to flex, changing the spacing at the location of the window.  
         [0039]    Conventional security tags, such as those that leave the store with the merchandise, provide no visible indication of their state. Hence, stores must manually check that the tags are properly set to activate alarms before attaching them to merchandise. This invention provides a visual indication of the state of the tag. This invention also provides for a resetting of the state that automatically changes the visible state of the device, which current tags do not do.  
         [0040]    One of the problems solved by this invention deals with knowing whether a security tag is set in a state that will trigger an alarm or not, knowing whether an item has been previously scanned, either by looking or by detecting a change in the spectral signature, and reversing the sense of the tag and providing visual feedback automatically.  
         [0041]    The protection sought is not to be limited to the disclosed embodiments, which are given by way of example only, but instead is to be limited only by the scope of the appended claims.