JP4803755B2 - ID tag reader - Google Patents

Description

  The present invention relates to an antenna device, an antenna driving method, and an ID tag reading device, and communicates with an ID tag that is activated by obtaining operating power from an alternating magnetic field or a received radio wave, and reads information stored in the ID tag ( More particularly, the present invention relates to an antenna device, an antenna driving method, and an ID tag reader that can detect an ID with respect to a plurality of ID tags in an elongated space with higher accuracy.

  Conventionally, there is a known electromagnetic induction type ID tag standardized by the “ISO / IEC 15693” standard or the like. Various methods have been proposed as antennas and antenna devices for supplying power to and communicating with the ID tag. For example, as an antenna, there is an antenna device in which two loop antennas are arranged facing each other across a tag placement space and driven in the same phase to generate a uniform alternating magnetic field, and three sets of such antenna devices are used. A configuration has also been proposed in which the antenna device is arranged so that the axes of the antenna devices are orthogonal to each other around the tag.

Further, in the antenna driving system, the above-described three sets of antenna devices are switched in turn on and off for each axis in turn, a three-azimuth driving system, two-dimensional on a two-dimensional plane, or two-dimensional with a multi-axis cross antenna configuration A method of generating a rotating magnetic field on a plane has been proposed. For example, in the following patent document, a tag coil exciter that generates a rotating magnetic field on a two-dimensional plane with a multi-axis cross antenna configuration using a plurality of coil devices configured by facing a pair of excitation coils (antennas). Is disclosed. (However, the method of generating the rotating magnetic field is different from the present invention.)
Japanese Patent Laid-Open No. 10-200452

  A known ID tag operates with power supplied by an alternating magnetic field. However, when the ID tag antenna is tilted with respect to the magnetic flux, or when the resonance frequency of the ID tag is shifted due to a plurality of ID tags overlapping in the same direction, they are supplied to the ID tag. The power that is generated is reduced, making it difficult to detect. Therefore, the AC magnetic field needs to have a certain level of strength. However, if the magnetic field is too strong, the circuit in the ID tag is saturated and communication cannot be performed normally. In addition, there is a legal restriction, and an electric field strength exceeding a predetermined value cannot be generated.

  When such an ID tag is to be applied to a book shelf in a library or a bookstore, or a DVD or CD display shelf, there are the following problems. When an ID tag is attached to a book or DVD, the antenna surface of the tag is parallel to the surface of the book or DVD, and the position can be accommodated in an area within a substantially predetermined range near the center of the book or DVD. However, bookshelves and display shelves are oblong spaces, and there is a high possibility that many ID tags overlap, so even if loop antennas are placed at both ends of the shelves, the magnetic flux density decreases or resonates at the center of the shelves. There is a problem in that the frequency shift occurs, power is not supplied sufficiently, and the ID cannot be read.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an antenna device, an antenna driving method, and an ID tag reader that can solve the above-described problems of the prior art and can more reliably detect IDs for a plurality of ID tags near the center of an elongated space. And

  The antenna device according to the present invention includes antenna means in which two loop antennas are arranged facing each other on both sides of a predetermined space with their directional center axes aligned, and antenna driving means for driving the antenna means with a carrier signal of a predetermined frequency; And a resonance antenna circuit means including a loop antenna disposed in the predetermined space and constituting a resonance circuit that resonates at the predetermined frequency.

  The antenna device according to the present invention includes an antenna unit in which a plurality of loop antennas are arranged at predetermined first intervals inside a predetermined space of a rectangular parallelepiped so that the directional center axes thereof coincide with each other, and the plurality of loop antennas of the antenna unit Antenna driving means for simultaneously driving with a carrier signal of a predetermined frequency, and a resonance which is disposed at both ends of the plurality of loop antennas within the predetermined space with a predetermined second interval and resonates at the predetermined frequency. The main feature is that it includes resonant antenna circuit means including a loop antenna constituting the circuit. The antenna device described above is also characterized in that a magnetic plate is disposed on at least one of the bottom surface, both side surfaces, and the back surface of the predetermined space.

  In the antenna device described above, the antenna driving means includes an output power control means for controlling output power for driving the antenna, and an ID while controlling the output power control means so that the output power is increased or decreased stepwise. It is also characterized in that it has a control means for repeating the tag reading operation.

  In the antenna device of the present invention, a plurality of loop antenna means arranged for each of two opposing surfaces of the rectangular parallelepiped, and a magnetic flux having a component parallel to the two opposing surfaces in the central portion of the rectangular parallelepiped. The main feature is that it includes antenna driving means for driving at least some of the plurality of loop antenna means at the same or different desired phases. Further, the antenna device described above is characterized in that loop antenna means is provided on each of two opposing surfaces that are orthogonal to and opposite to the two surfaces of the rectangular parallelepiped.

  The ID tag reader of the present invention includes the antenna device described above, and further communicates with an ID tag that is activated by obtaining operating power from an AC magnetic field, and reads information stored in the ID tag, and an ID tag. And a position estimating means for estimating the position of the ID tag from the position of one or a plurality of antennas receiving the above signal and the transmission power value at that time.

  The antenna driving method of the present invention includes a step 1 for setting the antenna driving power to a minimum, and a step for simultaneously driving a plurality of loop antennas arranged in a predetermined space by supplying a carrier signal with the power set in step 1. 2. Communicate with the ID tag arranged in the predetermined space, read the ID information, step 3; determine whether the current driving power is greater than or equal to the preset maximum power; if the determination result is negative The main feature is that it includes a step 4 in which the driving power is increased by one step and then returned to the step 2.

  According to the antenna device of the present invention, the electromagnetic wave emitted from the facing antenna is amplified by the resonance of the resonant antenna, and sufficient power can be supplied to the ID tag even near the center of the shelf far from the antenna, so that the ID information can be more reliably obtained. There is an effect that it becomes detectable. In addition, since the response signal from the ID tag is also amplified by the resonant antenna, the reception accuracy of the weak response signal from the tag is improved. Therefore, there is an effect that ID tags densely packed in a wide reading space such as a bookshelf can be read collectively.

  According to the antenna device of the present invention, a plurality of loop antennas are provided for each of two opposing faces of the rectangular parallelepiped, and at least a part of the plurality of loop antennas is driven with the same or different desired phases. Accordingly, it is possible to generate a magnetic flux having a component parallel to the two opposing surfaces in the central portion of the rectangular parallelepiped. Therefore, for example, by arranging a plurality of antennas on the upper and lower surfaces of the horizontally long shelf, sufficient power can be supplied to the ID tag even near the center of the shelf without partitioning the horizontally long space. There is an effect that it is possible to collectively read ID tags densely in the reading space.

It is a block diagram which shows the structure of the whole system containing the ID tag reader of this invention. It is a block diagram which shows the structure of the resonant antenna circuit board 15 of this invention. It is a block diagram which shows the hardware constitutions of the Example of the ID tag reader 10 of this invention. 3 is a block diagram showing a configuration of an antenna drive circuit 41. FIG. It is a block diagram which shows the details of the modulator 62, the output amplifier 64, etc. FIG. 6 is an explanatory diagram illustrating a method for specifying a detection position of an ID tag in Embodiment 1. FIG. It is a block diagram which shows the structural example of a well-known ID tag. It is a flowchart which shows the content of the RFID tag reading process of this invention. It is the front view and side view which show the structure of the antenna of Example 2 of this invention. It is explanatory drawing which shows the drive pattern of the antenna in Example 2, and the magnetic field which generate | occur | produces. It is the perspective view and front view which show the structure of the shelf unit in Example 3. FIG. FIG. 10 is a block diagram illustrating a configuration of an ID tag reading device according to a third embodiment. 10 is a flowchart showing the contents of a book management process in Embodiment 3. 10 is a flowchart illustrating the contents of tag position search processing according to the third embodiment. It is a block diagram which shows the structure of the whole library management system in Example 3. FIG.

Explanation of symbols

10 ... ID tag reader 11 ... Host device (PC)
12 ... Bookshelf 13, 14 ... Loop antenna 15 ... Resonant antenna

Embodiments will be described below with reference to the drawings.

  First, an ID tag read by the ID tag reading device of the present invention will be described. FIG. 7 is a block diagram illustrating a configuration example of a known ID tag. The ID tag 50 includes a tag antenna 51 and an IC 52, and is also called an IC tag. The loop-shaped tag antenna 51 constitutes an LC circuit that resonates with the carrier frequency. Then, electric power is excited in the tag antenna 51 based on the change of the alternating magnetic flux penetrating the tag antenna 51. Therefore, the maximum power can be obtained when the loop plane of the tag antenna 51 is oriented in a direction perpendicular to the magnetic flux of the magnetic field, but no power can be obtained when they are parallel.

  The power supply circuit 53 generates a DC power supply from the power excited by the tag antenna 51 and supplies it to each circuit. When power is supplied from the power supply circuit 53, the control / arithmetic logic circuit 58 is reset by the power-on reset circuit, and based on the clock signal supplied from the clock extraction circuit 55 that extracts the clock from the received signal, Perform the action.

  The data demodulating circuit 56 receives and demodulates a signal transmitted from the ID tag reader and outputs it to the control / arithmetic logic circuit 58. For example, when a response instruction command is received from an ID tag reading device, the control / arithmetic logic circuit 58 receives 64-bit unique ID (identification) information stored in advance in the storage circuit 59 at a predetermined timing. The data is encoded and output to the data modulation circuit 57.

  The data modulation circuit 57 transmits a signal by changing the load of the tag antenna 51 based on the transmission data output from the control / arithmetic logic circuit 58. The configuration of this ID tag is an example, and the antenna driving method of the present invention can be applied to an ID tag having any known configuration as long as it is an electromagnetic induction method.

  Next, an example in which the present invention is applied to a bookshelf and the ID of an ID tag attached to a book is read will be described. FIG. 1 is a block diagram showing the configuration of the entire system including the ID tag reader of the present invention. Loop antennas 13 and 14 are arranged at both ends in the longitudinal direction of the horizontally long bookshelf 12, and are connected to the ID tag reader 10 according to the present invention. The ID tag reader 10 is further connected to a host device 11 such as a personal computer (PC).

  In the interior space of the bookshelf 12, a plurality (three in the figure) of resonant antenna circuit boards 15 are arranged at a predetermined interval. Each resonant antenna circuit board 15 is fixed to the bookshelf so that the surface of the resonant antenna circuit board 15 is parallel to the surfaces of the loop antennas 13 and 14 at both ends. The central axes should match.

  FIG. 2 is a block diagram showing the configuration of the resonant antenna circuit board 15 of the present invention. The resonant antenna circuit board 15 is a thin board provided with a loop antenna coil 30 and a capacitor 31 made of a copper wire or a copper plate. The inner space 32 of the loop antenna coil 30 is preferably as wide as possible and may be hollow.

  The loop antenna coil 30 and the capacitor 31 constitute a resonance circuit. When the dense ID tags are present in the vicinity of the resonant antenna circuit board 15, the resonant frequency of the resonant circuit is lowered. Considering this, the resonant frequency of the resonant circuit is slightly lower than the carrier frequency (for example, 13.56 MHz). It is good to set it higher.

  As a result of the experiment, the inventor arranges a resonant antenna circuit board 15 as shown in the figure as shown in FIG. 1 so that an ID tag that cannot be detected without the resonant antenna circuit board 15 can be detected. I found out that This is because by arranging the resonant antenna circuit board 15, the magnetic flux generated by the antennas 13 and 14 at both ends does not diffuse near the center of the shelf, and the magnetic flux density increases due to resonance of the resonant antenna. Presumed to be.

  FIG. 3 is a block diagram showing a hardware configuration of the embodiment of the ID tag reader 10 of the present invention. The ID tag reader 10 is roughly divided into an antenna device 40 and a control block 20, and power is supplied to each from a power supply unit (not shown).

  The antenna device 40 includes an antenna drive circuit 41 corresponding to each of the plurality of loop antennas 13 and 14. For example, the oscillator 42 generates a 13.56 MHz carrier signal (digital signal: rectangular wave, actually a clock signal that is an integral multiple of the carrier frequency) based on the above-mentioned standard.

  As will be described in detail later, the antenna drive circuit 41 generates a carrier signal having a plurality of phases from the carrier signal supplied from the oscillator 12, and controls each of the antennas 13 and 14 to have a desired phase and frequency based on the control of the control block 20. It is driven by a power carrier signal.

  The antennas 13 and 14 are loop antennas that are arranged facing each other with the directional center axes thereof facing each other across the bookshelf 12 that is a tag placement space, and generate a uniform magnetic field in the space by being driven in the same phase. Each antenna 13 and 14 is, for example, a copper plate or copper pipe wound in a ring shape.

  The control block 20 includes a CPU 21, a ROM 22, a RAM 23, a data interface (I / F) circuit 24 for inputting / outputting transmission / reception data with the ID tag, a control interface (I / F) circuit 25 for controlling the antenna device 40, and a host An external interface (I / F) circuit 26 for communication with the apparatus 11 and a bus for connecting internal circuits are provided. The CPU 21 executes processing to be described later based on the control program stored in the ROM 22.

  FIG. 4 is a block diagram showing the configuration of the antenna drive circuit 41. The antenna drive circuit 41 includes a phase converter 60, a phase switch 61, a modulator 62, a D / A converter 63, an output amplifier 64, a reception amplifier 65, and a demodulator 66. Based on a clock signal that is an integral multiple of, for example, a 13.56 MHz carrier signal input from the oscillator 42, the phase converter 60 generates a carrier signal (digital signal: rectangular wave) having a plurality of phases, for example, a phase of 0 degrees or 180 degrees. Output.

  The internal configuration of the phase converter 60 may be such that, for example, a carrier signal is input to a serial input of a shift register that is shifted by a clock signal that is an integral multiple of the carrier, and an output of a predetermined stage of the shift register is extracted as an output. Alternatively, the waveform information of each phase may be read from the ROM according to the value of the address counter that is incremented by the clock signal.

  The phase switch 61 consists of a gate group, and selects a carrier signal to be supplied to the antenna 13 (14) from among a plurality of types of carrier signals output from the phase converter 60 according to the phase control information from the control block 20. To do. In the first embodiment, the antennas 13 and 14 may be driven in the same phase, so that the phase converter 60 and the phase switch 61 may be omitted.

  Based on the modulation data from the control block 20, the modulator 62 amplitude modulates the carrier signal with a modulation degree of 10% to 100%. The D / A converter 63 converts the modulated carrier signal into an analog signal, and the output amplifier 64 amplifies the signal output from the D / A converter 63 to a desired power, and drives the antenna 13 (14). To do.

  The connection lines of the antennas 13 and 14 are also connected to reception amplifiers 65 corresponding to the respective antennas 13 and 14. The demodulator 66 performs reception, demodulation, and collision detection of a signal from the ID tag, and outputs received data or a collision detection signal.

  FIG. 5 is a block diagram showing details of the modulator 62, the output amplifier 64, and the like. The modulator 62 calculates the logical product of the digital carrier signal input by the AND gate 73 and the digital modulation data output from the control block 20, and outputs a 4-bit carrier signal. The D / A converter 63 D / A converts the 4-bit carrier signal and outputs a rectangular wave carrier signal having a desired amplitude. The BPF 70 is a band-pass filter that passes only the fundamental frequency of the carrier. By passing the BPF 70, a sine wave carrier signal is obtained.

  The output amplifier 64 includes a phase adjuster 71 and a power amplifier 72. The phase adjuster 71 is used to accurately align the phases of a pair of antennas facing each other, but is not an essential circuit for implementing the present invention. The power amplifier 72 drives the antenna 13 with desired power based on the output control signal from the control block 20.

  Next, a reading operation in the ID tag reader will be described. FIG. 8 is a flowchart showing the contents of the ID tag reading process of the present invention. This process is executed by the CPU 21 periodically, for example. In step S10, the phase switch 61 is controlled so that a carrier signal having a desired phase is generated, and the power amplifier 72 is controlled so that the driving power is minimized. In the first embodiment, the two antennas 13 and 14 are driven in the same phase.

  In S11, a command for reading the ID from the ID tag is sent based on a known protocol. The command is encoded and input to the modulator 62 via the data I / F 24, and the carrier is modulated. For example, when each ID tag receives a response instruction command, it transmits ID information at a predetermined timing.

  In S12, it is determined whether or not there is a response from the ID tag 50. If the determination result is negative, the process proceeds to S16, but if the determination is affirmative, the process proceeds to S13. In S13, it is determined whether or not there is a collision of responses from a plurality of ID tags. If the determination result is negative, the process proceeds to S15, but if the determination is affirmative, the process proceeds to S14.

  The ID tag transmits unique ID information as a response. However, since the Manchester code is used, if there are responses from a plurality of ID tags, the logical values 0 and 1 in the data overlap. When a code other than 0 or 1 is received, the demodulator 66 can detect a collision.

  In S14, a command for limiting the ID tag to respond based on the bit position where the collision is detected, for example, a command instructing to respond only to the ID tag whose logical value of the collision bit position is 1, is sent to S11. Return. In S15, the received ID information is saved, a command for stopping the response is sent to the corresponding ID tag, and the process returns to S11.

  In S16, it is determined whether or not the antenna drive power has reached a predetermined maximum value. If the determination result is negative, the process proceeds to S17, but if the determination is affirmative, the process proceeds to S18. In S17, the power amplifier 72 is controlled so that the antenna driving power is increased by one step, and the process proceeds to S11.

  In S19, duplicate data is excluded from all detected ID information. In S20, the ID information is output to the host device. All ID information is read by the above processing.

  As described above, first, ID is read with low power, the response of the read ID tag is stopped, and the power is increased stepwise, so that the ID tag near the antenna becomes unable to communicate with high power. The problem is solved. Note that reading may be started at the maximum power first, and the power may be lowered stepwise.

  FIG. 6 is an explanatory diagram illustrating a method for specifying the ID tag detection position in the first embodiment. FIG. 6C shows an example in which the material constituting the shelf is neither a magnetic body nor a conductor (shown by a dotted line in the figure). Two antennas 84 and two resonant antenna circuit boards 81 are arranged on the shelf, and each antenna 84 is shared by the left and right shelves. In this case, the ID tag in the vicinity of the antenna 84 may be detected in any direction, up, down, left, or right. Therefore, it is only found that the position of the ID tag is in the vicinity of the detected antenna.

  FIG. 6B is an example of a case where a horizontally arranged shelf board is made of a magnetic material such as an iron plate and a conductor (shown by a solid line in the figure) among the materials constituting the shelf. In this case, the ID tag in the vicinity of the antenna 84 may be detected only in the left or right direction. Therefore, it is found that the position of the ID tag is in the vicinity of the detected antenna on the shelf having the same height as the detected antenna.

  FIG. 6A shows a case where, among the materials constituting the shelf, the shelf plate arranged horizontally and the support column arranged vertically are made of a magnetic material such as an iron plate and a conductor (shown by a solid line in the figure). In this case, only the ID tag in the same shelf as the antenna 84 may be detected. Therefore, the position of the ID tag is found to be in the same shelf as the detected antenna. However, in this case, it is necessary to provide two antennas 80 for each shelf.

  In Example 1, although the example which arrange | positions the resonance antenna circuit board 15 in the reading area was disclosed, in order to arrange | position the resonance antenna circuit board 15, there exists a subject that the front surface of a shelf or at least a shelf will be partitioned off. The second embodiment solves this problem. Nothing is arranged inside the shelf, and a plurality of antenna devices arranged on the wall surface of the shelf are simultaneously driven at a desired phase, so that the desired inside of the shelf is achieved. The magnetic field is generated.

  FIG. 9 is a front view and a side view showing the configuration of the antenna according to the second embodiment of the present invention. 9A is a top view, FIG. 9B is a front view, and FIG. 9C is a side view. In the second embodiment, in addition to the antennas 90 and 91 corresponding to the antennas 13 and 14 of the first embodiment arranged at both ends in the longitudinal direction of the shelf, four antennas 92 to 95 are provided on the upper surface of the shelf and four are provided on the lower surface. Antennas 96 to 99 and four antennas 100 to 103 on the back.

  The four upper and lower antennas 92 and 96, 93 and 97, 94 and 98, and 95 and 99 face each other. In addition, you may arrange | position an antenna along the edge of the front of a shelf. The rear antennas 100 to 103 can be omitted. Furthermore, the antennas 92, 95, 96, and 99 may be omitted, and the antenna may be disposed only in the center portion. The antenna drive circuit may be provided with an antenna drive circuit 41 similar to that of the first embodiment corresponding to each antenna.

  FIG. 10 is an explanatory diagram illustrating an antenna drive pattern and a generated magnetic field in the second embodiment. In addition, this figure is the figure which looked at the shelf from the front, and the antennas 100 to 103 on the back are omitted. In the shelf of the first embodiment, the place where the magnetic flux density is the weakest is the central portion P of the shelf. Therefore, as shown in FIG. 10A, for example, the antenna 93 on the upper surface is driven at a phase of 0 degrees with respect to the reference phase as indicated by the solid arrow, and the antenna 98 on the lower surface not facing this is also used as the reference. Drive with the same phase of 0 degree to the phase.

  Then, at the point P, a magnetic field in an oblique direction as indicated by a dotted arrow is generated. Since this magnetic field also has a component in the longitudinal (left and right) direction, power can be supplied to the ID tag. At this time, the magnetic field at the point P is further strengthened by driving the antennas 90 and 91 at both ends in the same phase (0 degree).

  FIG. 10B shows a magnetic field generated when the antennas 93 and 98 are driven at a phase of 0 degrees and the antennas 94 and 97 are driven at a phase of 180 degrees. In this case, a horizontal magnetic field is generated at the point P. To do. At this time, the magnetic field at the point P is further increased by driving the antennas 90 and 91 at both ends with the same phase of 0 degrees. In order to generate a horizontal magnetic field in the central portion of the shelf, it is preferable to arrange the upper and lower antennas point-symmetrically with respect to the center of the shelf. Therefore, it is preferable that the number of antennas arranged on the upper surface and the lower surface is an even number (4 in the embodiment).

  FIG. 10C shows a case where the antennas 90 and 91 at both ends are driven in the same phase, and the antennas 92 to 95 are all driven at a phase of 0 degrees, the antennas 96 to 99 are all driven at a phase of 180 degrees, and all are driven with weak power. In this case, the magnetic flux generated by the antennas 90 and 91 at both ends can be prevented from spreading, as in the first embodiment. In FIG. 10C, the antennas 94 and 95 may be driven with a phase of 180 degrees and the antennas 98 and 99 may be driven with a phase of 0 degrees.

  In the second embodiment, since the vertical magnetic field can be easily generated by providing the antennas opposed to the top and bottom of the shelf, for example, a book placed horizontally on the bookshelf can be easily detected. Further, the configuration of the second embodiment and the resonant antenna circuit board 15 of the first embodiment may be combined.

  Example 3 is an example in which a wider range is simultaneously read by simultaneously driving three or more antennas. For example, a library in which books to be recognized are arranged on a bookshelf composed of a number of shelves, a library, This system can be applied to bookstores, CD / DVD shops, and the like.

  FIG. 11 is a perspective view and a front view showing the configuration of the shelf unit in the third embodiment. The shelf unit is a unit having a plurality of loop antennas, for example, having a size that can be stored in one shelf of a wooden bookshelf 410. The shelf unit includes a bottom plate 402 made of a magnetic material such as an iron plate, a back plate 403, and side plates 401 on both sides.

  These iron plates greatly reduce the possibility of reading the ID of the tag of another shelf unit when the antenna of this shelf unit is driven. Further, when there is an iron plate, even if the ID of the tag of another unit is read, the transmission power increases, so it is possible to easily determine in which unit the tag exists. In addition, when any one of the bottom surface, the side surface, and the back surface is made of a magnetic material such as an iron plate, such as an iron shelf or cabinet, the iron plate having a surface parallel to the surface may be omitted.

  In the unit, four loop antennas 405 are arranged at equal intervals (L2), and two resonant antennas 406 are arranged on both sides thereof at intervals (L1) narrower than the intervals of the loop antennas. In Embodiment 3, the loop antennas are not arranged at both ends, and the resonant antenna 406 is used, thereby reducing the possibility of reading the tag on the adjacent shelf and reducing the number of antennas. Note that the number of loop antennas 405 can be increased or decreased as desired. Further, a resonance antenna 406 may be added between the loop antennas 405.

  Spacers 404 made of foam or the like are filled in order to leave a gap between the two resonant antennas 406 and the iron plates 401 at both ends. If the resonance antenna 406 is brought too close to the iron plate 401, the effect of the resonance antenna is reduced. In order to prevent this, a gap by the spacer 404 is provided.

  FIG. 12 is a block diagram illustrating the configuration of the ID tag reader according to the third embodiment. In the third embodiment, an example in which four shelf units shown in FIG. 11 are controlled by one ID tag reader 200 will be described, but the number of shelf units to be controlled is arbitrary. A plurality of coaxial cables 201 connected to each antenna of each shelf unit of the bookshelf 410 are connected to a switch 215 that is a coaxial relay in the ID tag reader 200.

  The ID tag reader 200 includes, for example, the same number (four) of antenna drive circuits 41 as the number of antennas in the shelf unit. The switches 215 are all switched by the same control signal, and the four antennas in the shelf unit are simultaneously connected to the antenna driving device 41 and driven in the same phase to read the ID tag. The power may be the same, but the power may be changed for each antenna. The configurations of the antenna drive circuit 41 and the oscillator 42 are the same as those in the first embodiment.

  Although the configuration of the control block 20 is the same as that of the first embodiment, the ID is detected together with the read ID information (only the difference) for the DB server 300 connected via the LAN 303 in order to perform the process described later. The information on the shelf number or the antenna number and the information on the transmission power value at that time are also transmitted.

  FIG. 15 is a block diagram illustrating a configuration of the entire library management system according to the third embodiment. A plurality of ID tag reading devices 200 each controlling a predetermined number (for example, four) of shelf units 400 are connected to the LAN 303. The controller 304 corresponds to the control block 20, the antenna drive circuit 41, and the oscillator 42 in FIG.

  Connected to the LAN 303 are a DB server 300 including the DB 301 and a PC terminal 302 that requests processing from the DB server 300 based on user operations. The ID tag reading device 200 and the DB server 300 perform processing described later. Do.

  FIG. 13 is a flowchart illustrating the contents of the book management process according to the third embodiment. This process is always executed in the DB server 300. In S30, it is determined whether or not ID update data has been received from any of the ID tag reading devices 200 via the LAN. If the determination result is negative, the process proceeds to S32. Migrate to

  In S31, the ID position information in the DB 301 is updated based on the received ID update information. That is, for the newly detected ID information, data such as the latest time, shelf number, and transmission power detected in the ID information is added, and the ID information that was detected last time and not detected this time is detected. Add lost time, shelf number, etc.

  When a plurality of ID tag readers 200 scan the bookshelf, the tags near the boundary may be read by the two ID tag readers 200 and transmitted to the DB server 300. Therefore, when updating the ID position information, it is checked whether it is detected in other shelf units. If it is detected in duplicate, the data with the larger transmission power is deleted and the data with the smaller transmission power is deleted. Leave only the data.

  In S32, it is determined whether or not there is a search request from any of the client PC terminals 302. If the determination result is negative, the process proceeds to S36, but if the determination result is affirmative, the process proceeds to S33. In S33, the book DB is searched based on a search key such as a book name input by the user to obtain pre-registered ID information.

  In S34, the position information corresponding to the ID acquired from the DB 301, that is, the shelf number is acquired. In S35, the search result is output to the requesting PC terminal. In the PC terminal 302, for example, a diagram of the entire bookcase is displayed on the screen of the display device, and the estimated tag position is displayed in a square area with a changed color.

  In S36, it is determined whether or not there is a request for statistical information from any of the client PC terminals 302. If the determination result is negative, the process proceeds to S30, but if the determination is affirmative, the process proceeds to S37. In S37, for example, the recorded data in the DB is statistically processed to calculate an inventory list, a misplaced list, a list being taken out, a book operation rate (how many times or how many hours have been taken from the bookshelf within a predetermined period), The output statistical process is executed. In S38, the statistical processing result is output to the requesting PC terminal.

  FIG. 14 is a flowchart illustrating the contents of the tag position search process according to the third embodiment. This process is always executed in each ID tag reader 200. In S41, it is determined whether or not a fixed time (for example, 0 to several tens of seconds) has passed since the previous scan. If the determination result is negative, the process returns to S41, but if the determination is affirmative, the process proceeds to S42.

  In S42, it is determined whether or not the entire shelf scan is completed. If the determination result is negative, the process proceeds to S43, but if the determination is affirmative, the process proceeds to S49. In S43, the selector switch 215 is controlled to switch to an unread shelf. In S44, the transmission power of all antennas is set to the minimum level. In S45, a tag ID reading process is executed. That is, the processing from S11 to S15 in FIG.

  In S46, the read ID, transmission power, shelf number (and antenna number), time, etc. are recorded. In S47, it is determined whether or not the transmission power is a predetermined maximum value. If the determination result is negative, the process proceeds to S48, but if the determination is affirmative, the process proceeds to S42. In S48, the transmission power of all antennas is increased by one step, and the process proceeds to S45.

  In S49, data other than the one with the lowest transmission power is deleted from the data with duplicate IDs. This process and the duplication deletion process between the plurality of ID tag readers 200 are presumed that the tag exists on the shelf where the transmission power can be detected at the minimum, and the position estimation for estimating the position of the ID tag is performed. Corresponds to means.

In S50, all the data for which the ID is detected are stored. In S51, the difference from the ID detection data at the time of the previous scan, that is, the data not detected last time but detected this time, or the data detected last time but not detected this time is extracted. In S52, the difference data is transmitted to the DB server 300.
With the configuration and processing as described above, a large number of books in a library or the like can be managed with high accuracy in almost real time.

  Although the embodiments have been described above, the following modifications may be considered in the present invention. In Example 1, although the example which arrange | positions the resonant antenna circuit board 15 in parallel with an antenna was disclosed, the structure which arrange | positions the resonant antenna circuit board 15 in the bottom face is also considered. By doing so, it is possible to make it easy to read an ID tag that is orthogonal to the transmitting / receiving antenna and is difficult to read.

  In the second embodiment, the strength of the received signal may be detected for each antenna, and the position of the detected ID tag may be estimated together with the transmission power pattern at that time. In the second embodiment, an example of generating a magnetic field having a rectangular parallelepiped longitudinal component has been disclosed. For example, four antennas 93, 94, 97, and 98 arranged on two opposing surfaces shown in FIG. 10 are used. In addition, by driving the antennas 93 and 98 at a phase of 0 degree and the antennas 94 and 97 at a phase of 90 degrees, a rotating magnetic field can be generated in a plane including the axis of each antenna. Therefore, for example, when reading an ID tag on a belt conveyor, the ID can be read by arranging a plurality of antennas on both sides of the conveyor, for example, without installing antennas on a plane perpendicular to the moving direction of the conveyor. it can.

  In the second embodiment, in order to generate a longitudinal magnetic field between the antennas 93 and 97, the non-adjacent antennas 92 and 98 are driven at a phase of 0 degrees and the antennas 94 and 96 are driven at a phase of 180 degrees. do it.

In the third embodiment, for example, when a search for a book is requested, a reread check may be performed to determine whether or not the corresponding tag is on a shelf recorded in the DB. Further, data may be recorded up to the antenna number, and it may be displayed whether it is estimated to be in that part of the shelf.

Claims (1)

Antenna means having a plurality of loop antennas arranged at predetermined first intervals inside a predetermined space of a rectangular parallelepiped so that the directional center axes thereof coincide with each other;
A loop antenna that constitutes a resonance circuit that is disposed at both ends of the plurality of loop antennas within the predetermined space with a predetermined second interval narrower than the predetermined first interval and resonates at a predetermined frequency. A resonant antenna circuit means comprising:
A magnetic plate disposed outside the resonant antenna circuit means inside the predetermined space;
A spacer filled between the magnetic plate and the resonant antenna circuit means;
A plurality of loop antennas of the antenna means are driven with a carrier signal having an arbitrary output power at the predetermined frequency, communicate with an ID tag that starts by obtaining operating power from an AC magnetic field, and stored in the ID tag Antenna driving means for reading the information ,
Control means for controlling the antenna driving means and repeating the reading operation of the ID tag while controlling the output power so that the output power increases or decreases stepwise;
ID tag comprising the <br/> a position estimation means for estimating the location of the ID tags from the location and transmission power value at that time of the one or more antennas receiving a signal from the ID tag Reader .

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