Method of interrogating a package bearing an RFID tag

ES 2 344 741 T3

DESCRIPTION

RFID reader.

Incorporation by reference

This patent application claims priority from US patent application serial number 09 / 134,686, filed August 14, 1998 under the same title, and US patent application serial number 09 / 134,686. No. 09 / 344,758, filed June 25, 1999 with the same title, both assigned to the assignee of the present invention, and the contents of which are incorporated by reference to the present specification.

Technical field

The invention relates to applications of radio frequency identification (RFID) systems and particularly to the use of such systems in libraries.

Background of the invention

Electronic article surveillance ("EAS") systems detect the presence of small electronic devices placed on or in an article or carried by a person of interest and are often used in retail or library environments to prevent theft or unauthorized removal of items. These devices, which are commonly known as labels or markers, previously only contained information regarding the presence of an item. This information could be obtained by electronically interrogating the tag, intermittently or continuously. Over time, at least four different types of EAS systems have been developed based on how this interrogation is carried out: magnetic, magnetomechanical, radio frequency (RF) and microwave. Among these four systems, magnetic systems have provided the highest level of security in most applications. Magnetic labels are easily hidden in or on an object, are difficult to detect (because they are less susceptible to shielding, bending or pressing) and are easily deactivated and reactivated, thus providing a high degree of security and some information regarding the state of the tagged item.

Many EAS system users want to know more than just the presence of a tagged object. They also want to know what object it is, for example. Detailed information regarding the characteristics of the objects, such as their date of manufacture, their inventory status and their owner, has generally been communicated via an optical bar code to automated handling and control systems. Although the optical bar code system is cheap and effective, it nevertheless has certain limitations. Bar codes must be visible, which limits the positions in which they can be placed, and they can be easily, accidentally or intentionally covered up. Also, the distance at which a detector can detect the barcode is relatively small. The barcode also has to be appropriately positioned for detection. Also, since barcodes are often exposed to allow detection, the barcode is susceptible to deterioration, which can lead to detection failure. Finally, when there are multiple items they must be processed one by one. These limitations of barcode systems make them undesirable or inefficient in some applications, such as marking of library media.

Electronic identification techniques (also known as radio frequency identification or RFID) have been developed for some time to address the limitations of optical bar codes. RFID systems have been successful in identifying and tracking objects, but they are poor in terms of object safety because most RFID systems operate in frequency ranges (~ 1 MHz and above) in the that the tag easily fails. The security deficiency of radio frequency labels is because they can be “shielded”, for example by covering the label with one hand or aluminum foil, or even by placing the label on a book. Even battery powered RF tags can be blocked, although their range is longer and blocking would be more difficult. Consequently, objects tagged with an RFID tag may inadvertently or intentionally escape detection. This greatly reduces their effectiveness as security devices. RFID markers are also related to "smart cards." Both contact and contactless smart cards have appeared in commercial applications. Smart cards tend to be associated with a specific person, rather than a tagged object. Issues related to security and tracking of the smart card (or the person carrying it) are similar to those discussed above for RFID markers.

The security issues related to RFID markers are similar to those known to one of ordinary skill in the art of radio frequency or microwave based EAS tags. Substantial efforts have been made to try to remedy the shortcomings of microwave or radio frequency based EAS tags. However, none of them have substantially improved their effectiveness as security labels. US Pat. No. 5,517,195 (Narlow et al.), entitled "Dual Frequency EAS Tag with Deactivation Coil" - "Dual Frequency EAS Tag with Deactivation Coil", describes a dual frequency microwave EAS tag that includes a antenna circuit, which has a diode, and a disable circuit. The deactivation circuit responds to a low energy alternating magnetic field by inducing a voltage in the diode of the antenna circuit that disables the diode and antenna, thereby deactivating the tag. Although useful in some

In applications, the capacitor-based tag, described by Narlow et al., Can lose electrical charge over time, which could cause the tag to inadvertently activate.

EAS radio frequency tags of the type described in US Patent No. 4,745,401 (Montean et al.) Include a magnetic element. The magnetic element alters the tuning of the tag when properly magnetized by an accessory device and thus blocks the radio frequency response of the tag. Although these tags have some utility, however, they do not improve security issues and improved identification.

Radio frequency identification technology has been developed by various companies, including Motorola / Indala (see US Patent No.^you 5,378,880 and 5,565,846), Texas Instruments (see US Patent Nos.^you 5,347,280 and 5,541,604), Mikron / Philips Semiconductors, Single Chip Systems (see US Patent Nos.^you 4,442,507; 4,796,074; 5,095,362; 5,296,722 and 5,407,851), CSIR (see European documents no.^you 0 494 114 A2; 0 585 132 A1; 0 598 624 A1; and 0 615 285 A2), IBM (see US Patent Nos.^you 5,528,222; 5,550,547, 5,521,601, and 5,682,143) and Sensormatic Electronics (see US Patent No. 5,625,341). All of these tags attempt to provide remote identification without the need for a battery. These tags operate at frequencies in the 125 kHz to 2.45 GHz range. Lower frequency tags (~ 125 kHz) are moderately resistant to shielding, but have only limited radio frequency functionality due to bandwidth restrictions. In particular, systems based on these markers generally work reliably only when there is only one tag at a time in the interrogation zone. Furthermore, they tend to be relatively bulky and expensive to manufacture. At higher frequencies (typically 13.56 MHz, 915 MHz, and 2.45 GHz) the added bandwidth available has enabled the development of systems that can reliably process multiple tags in the interrogation zone over a short period of time. This is highly desirable in many product applications. Furthermore, some of the label designs promise to be relatively cheap to manufacture and therefore more attractive to a customer. However, these higher frequency devices have varying degrees of susceptibility to shielding in common, as discussed above. Therefore, these devices cannot provide the high level of security required in certain applications, such as a library.

From the foregoing argument it should be apparent that there are various RFID tag applications in various environments where the identity of the tagged item is important. For example, PCT Publication WO 99/05660, published February 4, 1999 and assigned to Checkpoint Systems, Inc., describes an inventory system using RFID tagged items. The preferred embodiment described therein considers the use of RFID tags on library materials, the compliance of which they meet all delivery requirements can then be verified automatically by interrogating the RFID tag to determine the identity of the material. However, various important or desirable functions in a library or inventory are neither described nor suggested in the '660 publication.

European patent EP301127 describes a portable RFID reader according to the preamble of claim 1.

Summary of the invention

The present invention relates to RFID devices, including handheld RFID devices, and applications for such devices. The devices and applications can be used in relation to articles that are associated with an RFID tag and optionally a magnetic security element. The devices and applications are described with particular reference to library materials, such as books, periodicals, and optical and magnetic media. Other applications of the present invention are also envisioned.

Brief description of the figures

The present invention is described in greater detail with reference to the accompanying Figures, in which like reference numerals represent like structures in the various views, and in which:

Figures 1A and 1B are schematic illustrations of radio frequency identification tags;

Figure 2 is a schematic illustration of a second embodiment of a radio frequency identification tag;

Figure 3 is a schematic top view of a combined tag;

Figure 4 is a block diagram of an RFID interrogation system that interacts with an RFID tag;

Figures 5, 6, 7 and 8 are illustrations of combined labels in accordance with the present invention; and Figures 9, 10, 11, 12, 13 and 14 are illustrations of various embodiments of the present invention.

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Detailed description of the invention

The embodiments of the present invention described herein make use of RFID tags and preferably combined RFID / magnetic security tags. Labels of this type were described in US patent application Ser. with serial number 09 / 093.120, filed on June 8, 1998 and entitled "Identification Tag With Enhanced Security", which was assigned to the assignee of the present invention and incorporated by reference in the US application from which the present application claims priority. A detailed description of magnetic tags, RFID tags, and combination tags used in conjunction with embodiments of the present invention is included in Section I below, and embodiments of the present invention are discussed in detail in Section II below.

I. Labels and Elements for Use with Embodiments of the Present Invention

A tag used with the embodiments of the invention described in Section II below, can incorporate both the identification of the object and its effective security in a single device. Preferably they include an element responsive to a magnetic interrogation signal and an element responsive to a radio frequency interrogation signal. In one embodiment, the magnetically responsive element also provides the antenna for the radio frequency responsive element. In the context of the present invention the term "sensitive" means that the element provides intelligible information when subjected to an appropriate interrogation field. The individual items are described first, followed by a description of a combined tag. As will be apparent, the embodiments of the present invention described in Section II below may include a single RFID element or a combination of an RFID element and a magnetic security element.

A. The Magnetically Sensitive Element

The magnetically sensitive element is preferably made of a ferromagnetic material of low coercive force and high permeability, such as the material used in the strips sold by Minnesota Mining and Manufacturing Company, of St. Paul, Minnesota, (3M), under the designation strips. from the brand “TATTLE-TAPE ™”. These marker strips, or sets, are described in various patents assigned to 3M including US Patent Nos.^you 5,331,313 (Koning) and 3,747,086 (Peterson), the contents of which are incorporated by reference herein. Examples of high permeability, low coercive force ferromagnetic materials include permalloy (iron nickel alloy) and high quality amorphous metals, such as those available from AlliedSignal Company of Morristown, NY, under the designations Metglas 2705M and Metglas 2714A.

The magnetically responsive element can be single-state or dual-state, depending on the nature of the article with which the element is associated. For example, certain library reference works are not to be removed from the library and therefore a single state marker (not deactivatable) would always indicate whether a work of this class passed within a question mark zone. Other items, such as common library materials or commercial items, may require a dual status marker assembly, so that when the article has been properly processed the marker can be properly deactivated to avoid detection by the source of interrogation. Dual state functionality is generally provided by adding sections of higher coercivity magnetic material in the vicinity of the low coercivity magnetic material, as described below and in the Peterson patent, referenced above.

Certain magnetically sensitive elements have the ability to rapidly change their magnetic orientation when passing through a low frequency alternating magnetic field (50 Hz to 100 kHz, for example) and produce a predetermined characteristic response that can be detected by the receiving coils of a detector. The change function of the marker assembly is controlled by the state of magnetization of the high coercive force elements, or "security elements". When these security elements are magnetized, the ability of the marker to magnetically shift in one direction or the other within the alternating magnetic field of the interrogation zone is impaired and the marker is typically not detected. When the security features are degaussed, the marker can perform the switching function again, allowing the interrogation source to detect the presence of the marker. Security features can be arranged in various ways, as is known in the art.

The marker assembly may also include an adhesive, on one or both sides of the marker, that allows the marker to be attached to a book or other item. The adhesive layer or layers may be covered by a removable protective coating, to prevent adhesion of the marker on an unwanted surface, before its application on the desired surface. These and other characteristics of the marker assembly are described in US Pat. Nos. 3,790,945 (Fearon), 5,083,112 (Piotrowski), and 5,331,313 (Koning), all incorporated by reference above.

Since low frequency magnetic elements of this type are difficult to shield against detection, they can be used effectively on a wide variety of items when their safety is important. Furthermore, they can be deactivated and reactivated more conveniently, completely and repeatedly than markers employing other EAS technologies, making them more suitable for use in certain applications (such as libraries) where this feature is highly desirable.

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B. The Radiofrequency Sensitive Element

RFID tags can be active or passive. An active tag incorporates an additional source of power, such as a battery, into the tag structure. This energy source enables RFID tags to be activated to create and transmit strong response signals, even in areas where the radio frequency interrogation field is weak, and consequently the active RFID tag can be detected at a greater distance. However, the relatively short battery life limits the life of the label. In addition, the battery increases the size and cost of the label. A passive tag obtains the energy necessary for the tag to function from the radio frequency interrogation field and uses that energy to transmit response codes by modulating the impedance presented by the antenna to the interrogation field, thus modulating the retroreflected signal towards the reading antenna. Consequently, its scope is more limited. Since passive tags are preferred in many applications, the rest of the discussion will focus on this kind of tag. However, those skilled in the art will recognize that these two types of labels have many characteristics in common and that both can be used with this invention.

As shown in Figure 1, a passive RF sensitive element 10 typically includes two components: an integrated circuit (IC) 12 and an antenna 14. The integrated circuit provides the primary identification function. The integrated circuit includes software and circuitry to permanently archive tag identification and other desirable information, interpret and process commands received from interrogation hardware, respond to interrogator requests for information, and assist hardware in resolving. conflicts resulting from the simultaneous responses of multiple labels to the interrogation. Optionally, the integrated circuit can update the information stored in its memory (read / write), instead of only reading the information (read-only). ICs suitable for use in RFID markers include those available from Texas Instruments (in their TIRIS or Tag-it product line), Philips (in their I-Code, Mifare, and Hitag product line), Motorola / Indala, and Single Chip Systems, among others.

The geometry and properties of the antenna depend on the desired frequency of operation of the RFID portion of the tag. For example, 2.45 GHz (or similar) RFID tags would typically include a dipole antenna, such as the linear dipole antennas 4a shown in Figure 1A or the folded dipole antennas 14a shown next to the RF sensitive element 10a. in Figure 1B. A 13.56 MHz RFID tag (or similar) would use a coil or coil antenna 14b, as shown next to the RF sensitive element 10b in Figure 2. In either case, the antenna 14 intercepts the radiated RF energy. by an interrogation source. This signal energy transmits both energy and commands to the tag. The antenna allows the RF sensitive element to absorb enough energy to drive the IC chip and thus provide the response to be detected. Therefore, the characteristics of the antenna must correspond to those of the system in which it is incorporated. For labels operating in the high MHz to GHz range, the most important characteristic is the length of the antenna. Typically, the effective length of a dipole antenna is selected to be close to half a wavelength or a multiple of a half wavelength of the interrogation signal. In the case of tags operating in the low to medium MHz zone (13.56 MHz, for example), where a half wavelength antenna is impractical due to size limitations, the important characteristics are the inductance of the antenna and the number of turns of the antenna coil. Both types of antenna require good electrical conductivity. Typically metals such as copper or aluminum would be used, but other conductors, including magnetic metals such as permalloy, are also acceptable and are in fact preferred for the purposes of this invention. It is also important that the input impedance of the selected IC chip corresponds to the maximum power transfer antenna impedance. Additional information regarding antennas is known to those skilled in the art, for example from reference texts such as JD Kraus, Antennas (2^to ed. 1988, McGraw-Hill, Inc., New York).

A capacitor 16 is typically included to increase the effectiveness of the marker, as shown in Figure 2. Capacitor 16, when present, tunes the operating frequency of the tag to a particular value. This is desirable to obtain the maximum range of operation and to ensure compliance with legal requirements. The capacitor can be a single component or integrated into the antenna, as described below. In some label designs, particularly in labels designed to operate at very high frequencies, such as 2.45 GHz, no tuning capacitor is required. The capacitor is selected so that when coupled to the inductance provided by the antenna, the resonant frequency of the composite structure, given by:

where

C = capacity (in Farads)

L = inductance (in Henries)

ES 2 344 741 T3 corresponds approximately to the desired frequency of operation of the RFID system. The capacitor can also be a distributed capacitor, such as that described in US Patent Nos.^you 4,598,276 (Tait et al.) And 4,578,654 (Tait et al.), Which are assigned to 3M. Distributed capacity is desirable to reduce the size of the label, particularly its thickness, and to minimize manual assembly.

In operation, as shown in Figure 4, the RF sensitive tag 110 is interrogated by an EAS security system 100, which is typically located near the point where the tags are to be monitored. An interrogation zone can be established by placing spaced detection panels across the exits of the room in which the tagged items are located, near a conveyor belt transporting the items to be monitored, or the like. Manual detection devices can also be used. An interrogation source 102 (typically including a drive oscillator and amplifier) ​​is coupled to an antenna 104 (sometimes described as a field coil) to transmit an alternating radio frequency field, or interrogation signal, in the interrogation zone. The system 100 also includes an antenna for receiving a signal (shown as an antenna 104 and sometimes described as a receiver coil) and a detector 106 for processing the signals produced by labels in the interrogation zone.

The interrogation source 102 transmits an interrogation signal 200, which can be selected within certain known frequency bands, which are preferred because they do not interfere with other applications and because they comply with applicable legal standards. When the RF sensitive element receives an interrogation signal, it transmits its own coded response signal 202 which is received by antenna 104 and transmitted to detector 106. The detector decodes the response, identifies the tag (typically based on information stored in a computer or other memory device 108), and acts based on the detected code signal. Various modifications of the illustrated system are known to those skilled in the art including, for example, using separate antennas for interrogation source 102 and detector 106, rather than a single antenna 104 as illustrated.

Modern RFID tags also provide a significant amount of user accessible memory, sometimes in the form of read-only memory or once-writable memory, but more preferably offer the user the ability to repeatedly update the memory by rewriting its contents from certain distance. The amount of memory provided can vary and influences the size and cost of the integrated circuit portion of an RFID tag. Typically, between 128 bits and 512 bits of total memory can be economically provided. For example, an RFID tag available from Texas Instruments of Dallas, Texas, under the designation "Tagit", provides 256 bits of user programmable memory, in addition to 128 bits of memory reserved for items such as the unique serial number of the label, version and manufacturing information, and the like. Similarly, an RFID tag available from Philips Semiconductors of Eindhoven, the Netherlands, under the designation "I-Code", provides 384 bits of user memory, along with an additional 128 bits reserved for the types of information mentioned above.

This user-accessible memory can be leveraged to improve the efficiency of an item identification system used, for example, in a library environment. Currently libraries identify items by scanning an optical barcode. The unique identifier contained in this barcode is used to access a circulation database that includes software provided by library automation vendors (LAV software), in which more extensive information on the item is permanently maintained. Although this system is highly developed and works very well in many applications, it can have two disadvantages. First, to access the information, a connection must be established with the circulation database. This limits the availability of information when an item is in a location remote from a connection to this database. Second, retrieving existing information in the circulation database can sometimes be time consuming, particularly during periods of extensive use. By storing certain critical information elements on the RFID tag, both limitations can be overcome.

An example of information that could improve the effectiveness of a library identification system would be a library identification number, if present on the RFID tag itself. Then, without accessing any databases, an article's "native" library could be quickly and conveniently determined simply by scanning the RFID tag. Another example of information preferably present on an RFID tag would be a code indicating whether the item is a book, videotape, audiotape, CD, or some other item. This code could comprise, for example, the media type code specified in the 3M Standard Interchange Protocol, which is obtainable from the assignee of the present invention. By knowing the media type directly, library materials management systems could ensure that an article is processed properly without incurring the delay and inconvenience of consulting a remote circulation database. Other examples of information suitable for incorporation into the RFID tag will be apparent to those skilled in the art.

Another area in which RFID systems offer an advantage over barcode-based systems is the identification of multiple items. Using sophisticated software algorithms, RFID readers and markers cooperate to ensure that all items in the reader's interrogation zone are successfully identified, without operator intervention. This capability enables the development of numerous useful applications in the areas of inventory control, item tracking, and sorting that would be difficult or impossible to implement with barcode-based identification systems.

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C. The Combined Label

As shown in Figures 3 and 5 through 8, the combo tag 20 combines a magnetically sensitive element with an RF sensitive element to provide the advantages of both. Consequently, the two elements can be applied at the same time in an article of interest, thus reducing the cost. The combination label may be provided with a pressure sensitive adhesive covered by a removable liner, which allows the combination label to adhere to a surface of the article when the liner has been removed. In another embodiment the tag uses the magnetically sensitive element as an antenna for the radio frequency sensitive element. The magnetically sensitive element, when used as an antenna, is electrically coupled to the radio frequency sensitive element and can also be physically coupled to the radio frequency sensitive element.

The combined tag manufactured according to the present invention can be interrogated in two ways. First, the RFID interrogation source would use radio frequency signals to request and receive codes to and from the integrated circuit. This information would indicate, for example, the identification of the item with which the tag is associated and whether the item has been properly processed. Second, an interrogation magnetic field would interrogate the tag to determine if the magnetic part of the marker assembly is active. If the marker set is active, the query source would produce a response, such as a notification that the marked item has not been processed properly. Since magnetic interrogation is more resistant to shielding than radio frequency interrogation, the magnetic part of the combined tag would provide greater security. Consequently, the characteristics of both magnetic and RFID tags are combined into a single combined tag.

In a preferred embodiment, the combo tag includes a magnetically responsive element that also functions as an antenna for the radio frequency responsive element circuitry. To serve both functions, the antenna material must have low magnetic coercivity and very high magnetic permeability (to serve as an efficient security element) and moderate to high electrical conductivity (to function as an efficient antenna). In addition, the geometry of the antenna must be compatible with the two functions. In this embodiment, the antenna could, for example, be made of an iron nickel alloy.

In one embodiment, a 3M brand "Tattle-Tape ™" security strip, or other equivalent magnetic element, can be used as a linear dipole antenna operating at 2.45 GHz or other similar high frequency. The length, width and thickness of this strip are selected to correspond to the particular frequency of operation and other characteristics of the RFID chip used. Typically, the strip would be made of permalloy (available from various sources including Carpenter Specialty Alloys, Reading, PA, under the trade designation "HyMu80") or an amorphous alloy such as available from AlliedSignal Company of Morristown, NY, under the designation 2705M, and its length would be between 6.35 and 16.5 cm (2.5 and 6.5 inches). The terminals of the integrated circuit would be physically connected to the ends of the security strip. Electrical impedance and power gain measurements have established that such a magnetic strip provides the same fundamental electrical characteristics as copper or aluminum dipole antennas normally used with such a chip and is therefore expected to perform both functions satisfactorily. .

When the magnetically sensitive element is used as at least part of the antenna of the radio frequency sensitive element, the two are electrically coupled to each other. Electrical coupling can be accomplished by a physical connection between multiple elements (as shown in Figure 5) or, in the absence of physical connection, with a non-contact electromagnetic coupling (as shown in Figures 6, 7 and 8). Non-contact coupling may include eddy current coupling, capacitive coupling, or inductive coupling and use such antenna components as passive antenna elements, reflector and director antennas, Yagi-Uda antennas, or other suitable antenna configurations.

The combination tag shown in Figure 3 includes coil turns made of magnetic material. The tag could be, for example, a 13.56 MHz tag having an antenna structure such as 14c in which flux collectors are arranged at the corners to enhance the magnetic function of the tag. Other types of flow collectors can be provided.

The combination tag 20 shown in Figure 5 includes a physical connection between the antenna 22, which is made of magnetically sensitive material, and the integrated circuit 12. One or more security elements of the type described above can also be applied to the magnetically sensitive material, so that they can be selectively turned on and off to provide a dual status tag. However, the antenna 22a shown in Figure 6 is not physically connected to the integrated circuit 12 or the dipole antenna 23, but is electrically coupled to the dipole antenna by eddy current dipole coupling to provide a combined tag 20a. The dipole antenna 23 can comprise magnetically sensitive material or non-magnetically sensitive material.

Figures 7 and 8 illustrate embodiments in which more than one antenna 22 is arranged to provide electrical coupling with antennas 23b and 23c, respectively. In the combination tag 20b shown in Figure 7, the integrated circuit 12 includes a dipole antenna 23b, which is eddy-coupled to the antennas 22b. The antennas 22b are made of magnetically sensitive material and the antenna (s) 23b can be made of magnetically sensitive material. In the combination tag 20c shown in Figure 8, a radio frequency sensitive element of the type shown in Figure 2 is electrically and eddy coupled to antennas 22c.

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The antennas 22c are made of magnetically sensitive material and the antenna (s) 23c may be made of a magnetically sensitive material. Other variations of these embodiments are easily designed.

The total thickness of the combined label should be as small as possible so that the label can be inconspicuously placed on or on an item. For example, the label can be adhesively applied between the pages of a book and it is desirable to make the label thin enough to avoid being easily detected by looking at the book from the side. Conventional ICs can be about 0.5 mm (0.02 inches) thick and the total thickness of the label is preferably less than 0.635 mm (0.025 inches).

The combination labels of this invention can be arranged in roll form, to allow automated sequential application of individual labels to articles. This general system is described, for example, in PCT Publication No. WO 97/36270 (De Vale et al.). Individual combination labels, where one or more of their surfaces may be covered with an adhesive (such as a pressure sensitive adhesive), can be removed from the roll and applied between two pages of a book, near the spine. A page separator may be provided to facilitate insertion of the combined label and other options, such as sensors, may also be provided to sense the position of various components in the system.

The combined label is believed to have a particular, though not exclusive, use in the processing of library materials. Library materials with such an RFID tag could more easily be checked to see if they meet all return or delivery requirements, perhaps without human intervention. That is, it would automatically check if the materials meet all the delivery requirements to a particular user (who may have their own RFID tag associated with their library card) when the user passes through a suitable detection zone and becomes to automatically verify that all return requirements are met when the patron re-enters the library with the materials. The inventive tag can also facilitate inventory management and analysis, allowing library managers to instantly and continuously track materials. Of course, these and other features of the invention can be used for the purposes of other applications, such as materials management in stores, warehouses, and the like.

In another embodiment, the combined tag could provide dual status marker information, both by a magnetic response (indicating whether the tag's magnetic features have been turned on or off), and by a radio frequency response (indicating, using the appropriate software, if the database or memory of the RFID chip itself indicates that the item has been processed properly).

The following Examples will provide even more information regarding the labels used in the embodiments of the invention described in Section II below.

Example First

A combination label was made according to the present invention. A permalloy strip produced from an alloy available from Carpenter Technology Corporation of Reading, Pennsylvania, under the designation "HyMu80", was attached to a test fixture manufactured by Single Chip Systems (SCS) of San Diego, California. The strip was approximately 1.6mm (0.625 inches) wide, by 0.0254mm (0.001 inches) thick, and by 10.16cm (4 inches) long. The test fixture consisted of a standard 2.45 GHz SCS antenna connected to an LED diode. The device was designed so that upon exposure to a 2.45 GHz field, strong enough to power a typical RFID SCS tag, the LED would turn on providing immediate visible confirmation of proper function of the receiving device part. of energy. By exchanging the standard SCS antenna for the prototype permalloy antenna, the LED illuminated with approximately the same field strength, confirming the satisfactory operation of the prototype.

Second Example

Figure 3 illustrates another embodiment of an antenna believed to be useful with a 13.56 MHz RFID design. At this frequency a coil-type antenna geometry is preferred. The turns that comprise the coil are formed from a magnetic alloy, such as perma lloy, by etching (physical or chemical), punching, or deposition through a mask. In this design, the straight "arm" portions of the coil also serve as magnetically sensitive elements. However, in this geometry the reduced length of these metallic elements limits the effectiveness of the magnetic safety part of the device. In the embodiment shown in Figure 3 and to overcome this limitation, the flux collector elements arranged in the corners have been added to the antenna coil. The structure shown in Figure 3 would preferably include a capacitor, as previously described, to tune the antenna operating frequency to the required interrogation frequency.

The characteristics of the antenna described in this example were compared with the characteristics of known antennas intended for radio frequency integrated circuits, and since these characteristics were similar, it is believed that the antenna of this example would work well in such an application.

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The embodiments of the present invention described below may use a tag having only one RFID element or a combined tag, both described above.

II. Embodiments of the Present Invention

A. Magnetic Capable RFID Device

Since a library user may intentionally or unintentionally shield RFID tags, it is often important to have both magnetic and RFID security features on the library tagged material, preferably on the tag itself. When the magnetic safety element is dual state, meaning that it can be selectively turned on and off, its state is typically changed by applying a magnetic field to the element. Magnetizing operations of this type do not affect library materials such as books and magazines, but can have detrimental effects on magnetically recorded media. The inventive magnetic-capable RFID device solves such problems, preferably without involving library employees.

As can be seen in Figure 9, an RFID device is equipped to read information from an RFID tag on an item, such as a book, user card, or other material. Preferably, the information read from the RFID tag includes a designation of the media type (magnetic, printed, or optical, for example), which can be used to ensure proper subsequent processing of the item. The RFID device also has a device, such as the coil, designed to allow activation and deactivation of the security element portion of the item tag. After the RFID device reads the RFID tag, the device transmits the item identification information to a computer that has software provided by a library automation vendor (LAV). Among approximately 50 existing LAV software systems are “Dynix”, which is available from Ameritech Library Services, of Provo, Utah, “Carl ILS”, which is available from CARL Corporation, of Denver, Colorado, and “DRA”, which It is available from DRA, St. Louis, Missouri.

There are several ways to transmit the information obtained on an RFID tag to the LAV system. One way would be to use the commands implemented in the 3M Standard Interchange Protocol (SIP). Another way would involve using an electronic device known as a "wedge" to transmit the information as it originates from a conventional barcode scanner. These and other techniques are well known to those of skill in the art. In this way, the RFID component of the RFID device performs the functions previously performed by an optical barcode scanner, which can continue to be used with the device. As a result, libraries can continue to use their existing LAV software system interfaces and terminals, while enjoying the added functionality and features that RFID technology provides. The RFID device need not include a display if it cooperates with a display of the LAV software system to provide feedback to the operator. Optionally, a display, or other feedback mechanisms, can be included in the RFID device as an integrated package.

In devices that have both optical and RF barcode reading capabilities, the device should be able to handle library materials tagged with RF tags, barcode tags, or both. In operation, the device would process an item to verify that it meets all return requirements by scanning an RFID tag, or a barcode, or both, retrieving the item's identification code and preferably the type of item from one or both tags. medium, and passing this information to the LAV software system. When the device includes both an RFID system and an optical barcode scanning system, the device can also be used to create RFID labels for barcode-only media. The barcode would first be scanned and then the identifier (or an ID code associated with that identifier, depending on the system design) would be written (engraved) on (on) the RFID tag along with other data, such as the type of media and other selected information returned by LAV's software system regarding that media. The RFID tag could then be applied to the article.

The RFID device of the present invention preferably also performs "smart" resensitization and desensitization of magnetic security elements attached to library materials. When the device reads the RFID tag and transmits the identification information to the LAV software, the LAV software may be programmed to respond with an indication of the type of library material with which the RFID tag is associated. If the LAV software responds with an indication that the tagged material is one that requires a specialized magnetization operation (typically a magnetically etched medium), the device can activate only the system that performs that operation. For example, if the LAV software indicates that the RFID tag is associated with a current book and that the book satisfies all delivery requirements to the requesting user, then a magnetization system can be activated to deactivate the magnetic element associated with that book. . However, if the LAV software indicates that an RFID tag is associated with a videotape, for example, then a different magnetization system may be activated to deactivate the magnetic security element associated with that videotape. This different magnetization system could involve, for example, a weaker magnetic field or a confined field in the immediate area of ​​the security element, in order to avoid any deterioration of the magnetic medium itself, depending on the detailed characteristics of use of the labels. of security. Depending on the detailed design of the device, the procedure could include inhibiting automatic activation so as not to damage the magnetic medium.

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Preferably, enough information can be stored in the memory of the RFID tag itself so that the interrogation source does not need to transmit that information to the LAV software and can directly call the appropriate magnetization system. This embodiment would likely improve the efficiency of the system, since fewer steps are required to achieve the same result. At a minimum, the RFID tag should store one type of media in the memory of the RFID item, but, as noted above, could include additional information. This type of process, which is not retransmitted to a separate database from the RFID device, is referred to herein as occurring in "real time".

An advantage of an RFID device, such as the one described, is that it can accept and process items with less dependence on their orientation relative to the device. Accordingly, although a library material can be processed with an optical barcode scanner only when the barcode label is properly positioned and readable by the scanner, a book having an RFID tag or a combination tag can be placed with the front cover up or down and without needing to carefully align the label with the scanner. This advantage of RFID systems, over conventional optical and barcode systems, results in considerable time savings for users and library staff. The "read distance" may be different with different scanners, labels or other components, but it is believed that a read distance of approximately 15 centimeters (6 inches) would be satisfactory. However, to provide reliable RFID scanning, it may be desirable for the RFID tags of various articles to be positioned in the same fixed position relative to an edge of the article. For example, all RFID tags on library books could be placed 5 centimeters (2 inches) above the bottom of the book.

The benefits of the inventive RFID device are numerous and significant, and include: have only one station to identify, resensitize and desensitize library materials, elimination of operator training on and the efficiency of different magnetization operations, higher processing speed by reducing orientation restrictions present only in code systems bars, and less likelihood of operators suffering repeated fatigue injuries. Another benefit is that it is faster to scan RFID labels than to read a barcode, especially with codes located within the cover or box of the item, largely because the user does not need to position and align the barcode. Finally, the system is also inexpensive because RFID readers are expected to cost less than high-quality barcode scanners. These and other benefits and advantages will be apparent to one of ordinary skill in the art.

B. Using the RFID Device with Multiple Items

Another benefit of an RFID device is the ability to process multiple items at once, as shown in Figure 10. While conventional devices that only have optical barcode scanners can only process a single item presented at a time. barcode scanner, a group of items having RFID elements can be processed essentially simultaneously. This is accomplished by having multiple RFID interrogation sources (readers) mounted in or on the device, or by having a single high-speed RFID reader possessing multiple item identification algorithms. This ability greatly reduces the time required for library staff to process multiple items.

To prevent the device from performing a magnetizing operation that is inappropriate for one or more of the materials in a group of materials being processed, the device can be adapted to send a message to the user requesting that all materials be presented together of a certain type (books and magazines, for example) and then all other materials (videotapes and audio tapes, for example). The RFID reader can determine, from the information obtained in the individual RFID elements, if the user has separated the materials appropriately and if not can suggest the user to do so, as shown in Figure 12. In another In one embodiment, the device includes an area for processing media of one type (books and magazines, for example) and a separate area for processing media of another type (video and audio tapes, for example). In this way, the proper magnetization operation can be reliably performed for each material.

The device may also include a display to indicate the number of RFID tagged items that have been presented to the device for processing. That is, the RFID reader would retrieve information from each item presented to the device and update the display to indicate that, for example, five items had been presented. An optical or other detector could also be used to verify that that number of items had actually been presented, to alert the patron or library staff if an item without an RFID tag was inadvertently or intentionally included. in the group of other materials. Optical detectors of this type may include those described in US patent application Ser. with serial number 09 / 058,585 (Belka et al.), filed on April 10, 1998 and entitled “Apparatus and Method for the Optical Detection of Multiple Items on a Platform”. located on a Platform "), assigned to the assignee of the present invention, the content of which is incorporated by reference in the present invention. Other detectors may include weight-based detectors (in which the RFID reader can determine from the RFID tag or LAV software the weight of the detected items and compare it to the actual weight of the materials presented) or on the number of magnetic elements detected [as described in US Patent No. 5,260,690 (Mann et al.) the content of which is incorporated by reference into the present invention]. Comparing the number of articles detected by the RFID reader and the number detected by an optical or other detector ensures that magnetic security elements associated with articles without an RFID tag are not deactivated without loading the article to a specific user. The device can process the items after they have been presented

ES 2 344 741 T3 after a predetermined number of articles (five articles, for example) either after an operator instructs the device to process the articles or automatically without any operator intervention. A suitable display can advise the operator as to the status of the operation.

Another embodiment of the device of the invention is the ability to verify the contents of a package or box containing multiple items, as shown in Figure 11. For example, a set of audio tapes can be packaged within a single box. To ensure that only those tapes, and all those tapes, are processed together, the RFID reader can identify the box, identify each of the tapes inside the box, and cross-check the identities before allowing the materials to be tested for compliance. all delivery requirements to a user. The RFID tag on the box can include the information regarding the contents of the box or that information can be stored in the LAV software and accessed using the identification information obtained from the RFID tag.

Devices that have the ability to process multiple materials further increase the speed with which materials can be verified to meet all the return or delivery requirements of a library. The device can be adapted to transmit a single signal to the LAV software system in order to process multiple items and receive a single signal from that software in response.

C. Portable RFID Devices

In various applications it is desirable to provide a portable RFID device, preferably handheld. The RFID handheld device is capable of searching through library shelves, drawers, stacks and carts. You can essentially search anywhere that you can get close enough to the items. It is able to identify multiple items that are within range of the device. These and other features make the portable RFID device of the invention a valuable library tool. For simplicity, portable RFID devices will be described first in terms of their components and operation, and second in terms of various useful functions or methods of using such devices. It is important to note that the functions and methods described herein are also applicable to non-portable RFID devices and that the functions and methods described above with reference to non-portable RFID devices are similarly applicable to portable RFID devices. . The various functions and methods have only been grouped with the type of RFID device most frequently used to perform that function or method.

1. Components and operation. The handheld RFID device of the present invention includes an RFID reader and writer, a memory, a power supply, and software that enables various functions of the types described herein. The RFID reader / writer could consist of an RFID reader, Commander 320 13.56 MHz, manufactured by Texas Instruments of Dallas, Texas. The memory, preferably in the form of a computer, can be provided, for example, by a "pocket" or handheld computer available from 3Com Company, Santa Clara, California, under the designation Palm Pilot. The laptop may include an operating system, a touch screen, various buttons for user-developed interfaces, a charging station, a docking station for transferring data between the device and another computer, one or more ports for connecting peripherals to the device. handheld (such as an RFID reader) and a battery power source. Some units may also include a built-in peripheral, such as a barcode scanner. It can also contain a variety of feedback systems, including lights, audio, and a display.

As described above, there are several options for transferring data between the handheld and another processing station. A docking station solution can be used to upload or download data, as shown in Figure 14. This method could be used, for example, to upload item identification information prior to performing a search for those specific items. Another example would be downloading data after collecting items that have been used within the library. The connection could be implemented in the form of: docking station (as illustrated); wireless or cable upload and / or download; real-time wired or wireless connection between the handheld and another processor, or in any other suitable way to transfer such data. An example of this class is a Spectrum24 wireless LAN system from Symbol Technologies of Holtsville, New York. Systems similar to the Spectrum24 allow mobile users to establish wireless communication between mobile devices and local area networks. To carry out this operation, the mobile unit will typically include a communication component that supports wireless communication, such as Symbol's LA 2400 Wireless LAN PC Card.

The user interface of the device is designed to communicate the status of the search and allow the user to enter data. Data entry may include switching the device between various search modes and entering specific data into a task (eg checking if all delivery requirements for an item are met or reserving an item). Feedback to the user is preferably provided by a combination of sound, lights, and a display. The display can be separate from or integrated into the unit. When it is a separate screen it can be designed in various ways, including as a "portable" screen that can be easily viewed by the user.

A particularly useful embodiment of the RFID handheld device is as follows. A handheld RFID device is provided in which the RFID reader, user interface, power source, antenna, processor and software are arranged in a single integrated unit, as shown in Figure 13. Using a computer hand,

ES 2 344 741 T3 such as the Palm Pilot described above, various real-time functions of the type described below can be performed, as opposed to systems in which the RFID device must interact with another computer, database, software and the like. The software may also provide a limited or full capability to support functions of the type described herein, as desired. The RFID handheld device preferably also includes an integral power source, although it can be connected to a larger power source of the type that can be placed around the wearer's waist. In the case of an integral power source, the source can power the processor and can be recharged when it is connected to the docking station. When using a handheld computer, it can include its own power source and can be recharged when connected to the docking station to upload and / or download information, as shown in Figure 14.

A handheld RFID device can interrogate and identify RFID tagged items, as long as it is activated within range of the items. Intermittent activation can be provided, for example, by a trigger associated with the device, so that the time interval in which the RFID device requires power is minimized. The reading distance is a function of many factors, but is expected to be between 6 and 18 inches (15 to 45 centimeters) given current technology and the likely frequencies the system would operate at. In some applications it may be desirable to restrict the range of operation of the device, so that only RFID tags associated with items located in a nearby area are interrogated. In other cases, the maximum available range of operation will be desired. In other applications it may be preferred to restrict the power output (and thus the read range) to allow longer continuous operation of the battery pack. The read range will also be influenced by the design of the antenna, as well as the orientation of the RFID tag relative to the antenna. It should be noted that the reading range, the weight of the batteries and the duration between recharging or replacing the batteries are often mutually dependent. A trade-off between these factors can be envisaged, based on the particular application of the device.

In operation, a particularly useful feature of a handheld device is to obtain real-time information regarding an item that has been scanned by the device. That is, the handheld device obtains information from the RFID tag and immediately displays that information or immediately displays information stored in the handheld that is related to the tagged item. This is in contrast to devices that must dock or communicate in some way with another database of information, before that information can be displayed to the user. The handheld device of the present invention may also be coupled or may otherwise communicate with a separate database, if such a feature is desired.

2. Functions, Methods and Applications. The RFID handheld device of the present invention can be used for various functions, methods, and applications, including the following.

The inventive handheld RFID device has particular utility in locating items. For example, the device could be programmed with specific information that identifies certain items that an operator wishes to locate. The unique identifier of each desired item would be stored in a reserved memory location on the handheld. As the identifiers, for example, of the items on a shelf were read by the RF reader, each of them would be compared, using standard software routines known to those of skill in the art, against the list of items stored in memory. When a match occurred the device would generate one or more visual, audio, tactile, or other signals indicating the presence of the item. One application of this feature includes locating items that are deemed lost. A library typically maintains a list of lost items - that is, items that are expected to be in the library, but cannot be found. By downloading the identifiers of those lost items to the handheld device, the operator can pass the device through items and get feedback when a lost item is found.

Another example is locating items that have not circulated or have not been used for a specified number of months. Again, the identifiers of those items could be downloaded to the handheld for searching. Alternatively, the circulation counts can be maintained directly in the memory of the RFID tag. In this case the handheld device does not need to download any data from another computer system. The handheld device only compares the RFID memory data against established criteria and provides feedback to the operator based on selected parameters.

Another example where data can be downloaded from a library database into the handheld device, or retrieved directly from the RFID tag, is locating library items that have not been verified to meet all return or return requirements. entrance. A list of items that have not been checked for meeting all return or entry requirements could be taken and downloaded to the handheld device, or the RFID tag could hold a memory location indicating the status of the check that is being checked. have satisfied all the return or entry requirements for an item. When the RFID tag memory indicates the status of the verification that all return or entry requirements have been satisfied, the handheld does not need any data from an external database to perform the search. A natural application of obtaining matching data directly from the RFID tag is to locate items that belong to different library buildings or different library systems. For this application, the proprietary library is preferably encoded on the RFID tag and the handheld device alerts the operator when an RFID tag with a different proprietary library code is encountered. The RFID handheld device could also be used to determine, like the RFID device described above, whether all members of a set of associated items are presented together, such as the case tapes of books that have an attached tape.

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The RFID device of the present invention could also be used to verify the order of materials placed on a shelf. In this mode, one or more rows of items are scanned with the device. The device reads each item and indicates to the operator which items are not placed on the shelves in the correct order. As input, the device accesses the shelving algorithm used by the library for the scanned section. Possible algorithms include: Dewey Decimal order, Library of Congress order, and Author / Title last name order. There are other classification methods, as determined by each library.

Another method of establishing shelf information is to associate each item with a location. Shelf locations can be as specific or as general as the library desires. For example, a general shelf location might include all "Adult Narrative titles." A more specific shelf location might be "Adult Narrative, Authors AA - AB". In the preferred embodiment, the shelf location of an item is encoded directly into the memory of that item's RFID tag. An indexing system can also be used to save memory, so that a short coded number is used to indicate a shelf location. For example, the number 1 could represent Adult Narrative, the number 2 could represent Youth Narrative, and so on. The amount of memory required to store all shelf locations depends on the number of locations in a library. Another embodiment is to obtain the desired shelf location from a library database and download those locations as part of the data transfer to the handheld device.

When items are associated with a shelf location, by any of the above methods, the operator can use the handheld device to locate items that are in the wrong location. Two processing methods can be used to determine the shelf location currently being processed to find items with mismatched locations. In one embodiment, the correct shelf location is obtained by reading multiple RFID tags and heuristically processing the data to derive a location. For example, if the RFID device reads a number of tags that are indexed in the Adult Narrative area, the device can be programmed to alert the user when non-Adult Narrative items are found. In another embodiment, the library puts "location tags" on shelves or other locations to search. These location tags are first read by the handheld to indicate that subsequent articles read should belong to that location and an alert is given when a mismatch occurs.

In another embodiment, the RFID handheld device can be used to enter data into the device relating to a specific item. That information can be transmitted immediately and directly to the LAV software, or it can be transmitted later when the handheld device is reconnected to a docking station and the information is downloaded into the LAV software. For example, when a user picks up a library material from their location, the user can enter the new status of the article into the RFID handheld device. Since this information must eventually be entered into the LAV software, operator time is saved by being able to indicate that status directly and immediately, rather than waiting until he or she can access a terminal in the LAV software system.

In yet another embodiment, the handheld device could be used to provide additional information about a specific item after the item has been obtained and its RFID tag scanned with the RFID device. For example, library staff can collect materials that have been used in the library and scan those materials either to obtain more information regarding that material (who last checked that it met all delivery requirements; frequency of use of the same) or to provide information to a database that generates statistical profiles of the use of library materials or for both. The operator simply reads the RFID tags on the items as they are collected from the various locations in the library where they were used. As the items are collected, the operator can also indicate where the items were collected by selecting it from a list of locations, entering a location code, or reading an "RFID Location Tag" that is associated with that location and is preferably displayed. would post at or near that location. In this way, library staff are able to obtain additional information about where such materials were used in the library. Alternatively, if the items used in the library are first put into a book cart, for example, the handheld could make a single pass through the items in the cart to register them. The functions described in this paragraph are referred to herein as "scanning."

The benefits of a handheld RFID device are numerous and include the ability to locate items more quickly and with greater security compared to reading each item signature or title, the ability to "zoom in" more quickly to a desired item, and then examine articles more closely to locate an article of interest, the ability to quickly identify articles that match a certain set of criteria (loss, without checking that all delivery requirements are met, conformance to specific circulation values, etc.), and the ability to identify items that are on the wrong shelf and direct the operator to the correct location of the items. This would include items not belonging to the collection being scanned. Other benefits include the ability to enter transactions directly on the handheld when items are located, the ability to identify an item without having to scan any barcodes or other markings on the item, such as author, title, and item. signature, and the ability to determine if a certain item is somewhere on a shelf, in a library cart, in a drawer, on a table, or even in a pile. These and other advantages will be apparent to those skilled in the art.

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In the claims appended hereto, those of ordinary skill will recognize that the items listed could be library materials (including books, periodicals, magnetic or optical media, and the like) or could be other unrelated complete materials, such as packages. , letters, pictures, electronic devices, animals, cars, bicycles or any other item of value.