JP2009110074A - Rfid tag reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an RFID tag reading apparatus capable of reading a plurality of RFID tags at high speed. <P>SOLUTION: The RFID tag reading apparatus includes a reading device 100 which is connected with an antenna unit 200 for performing a reading process of the RFID tags 11, and a centralized control device 300 for controlling an operation of the reading device 100. The reading device 100 performs a reading process of the next time by using mask information which is used by the last reading process. The mask information used in the reading process is to be calculated based on a reading result from the reading device 100 by the centralized control device 300, or stored in the reading device 100. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an RFID tag reader that reads a unique identifier set in an RFID tag in a contactless manner from an RFID tag attached to a product or the like in the field of physical distribution or the like.

  In recent years, systems using RFID tags have become widespread in systems such as logistics management, entrance / exit management, and personal authentication. In this type of system, an RFID tag reader that reads information such as a unique identifier stored in the RFID tag is used. Wireless communication is performed between the RFID tag and the reader, and the RFID tag reader can read information from the RFID tag without contact.

  By the way, reading of the RFID tag may be performed by reading only one RFID tag or reading a plurality of RFID tags collectively according to the operation mode of the system. An example of the former is a personal authentication system. An example of the latter is a logistics management system. When reading a plurality of RFID tags together, it is essential to prevent collision of response signals of the RFID tags. This standard for preventing collision is defined in, for example, JISX6323-3.

  This collision prevention method employs a time slot method. Specifically, the response period for the response request command from the reader is divided into 16 slots. When the RFID tag receives the response request command from the reader, the RFID tag specifies the slot number by the lower 4 bits of its own unique identifier (UID) consisting of 64 bits. The RFID tag transmits a response signal including a unique identifier at a timing corresponding to the specified slot number. By such a method, the chance of occurrence of a collision is reduced.

However, when an RFID tag having the same lower 4 bits of the unique identifier exists in the readable area, a collision also occurs by the above method. Therefore, mask information including a mask value and a mask length can be set in the response request command. When a response request command includes mask information, the RFID tag applies a mask from the lower bit side to the unique identifier. When the lower bit of the unique identifier of the RFID tag matches the mask value, the RFID tag identifies the slot number by the lower 4 bits of the unmasked data, and identifies the unique identifier at the timing corresponding to the identified slot number. A response signal including is transmitted. By such a method, when the RFID tag reader detects the occurrence of a collision, it repeats the re-inquiry by setting an appropriate mask as a request command, and thereby all the existing in the readable area. RFID tags can be read. In general, the mask is set by adding the slot number in which the collision has occurred to the upper level of the mask value of the request command used at the time of the collision (the first time there is no normal mask).
IC card system utilization promotion council, etc., "IC card without external terminals-Neighborhood type-Part 3: Anti-collision and transmission protocol", JIS standard X6323-3, Date of establishment: September 20, 2001, latest Confirmation date: February 20, 2007 JP 2004-248310 A

  By the way, as a system for reading a plurality of RFID tags together, there is a shelf inventory management system using a product shelf called “smart shelf”. In this shelf inventory management system, RFID tags are attached to a large number of products displayed on a product shelf, and the shelf inventory is monitored in real time. In addition, the shelf inventory management system constantly monitors the RFID tag existing in the readable area, and determines that the product has been taken out by the user when the product is taken out from the product shelf and the RFID tag is removed from the readable area. . And it has additional functions, such as displaying the merchandise information regarding the taken-out merchandise as needed on a predetermined display.

  In such a shelf inventory management system, the reading speed of the RFID tag is extremely important. However, the conventional reading method has a problem that a sufficient reading speed cannot be obtained depending on the number of RFID tags existing in the readable area and the distribution of the unique identifiers.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an RFID tag reader capable of reading a plurality of RFID tags at high speed.

  In order to achieve the above object, in the present application, in an RFID tag reader that reads a unique identifier of each RFID tag from a plurality of RFID tags within a readable range, a request command is transmitted to the RFID tag and the request command is transmitted to the RFID tag. A reading processing unit that receives a response including a unique identifier from the corresponding RFID tag, and the reading processing unit sets a request command in the next reading processing based on the collision prevention mask information used in the previous reading processing. We propose a feature that sets information.

  As described above, in a field of use such as a smart shelf, the fluctuation of the RFID tag in the readable range is extremely small compared to the frequency of the reading process. That is, there is a high probability that the RFID tag read last time will be read next time. Therefore, in the present invention, the next reading process is performed based on the mask information used in the previous reading process. As a result, the mask setting can be performed efficiently, so that the number of request command transmissions is reduced. Therefore, the reading process can be speeded up.

  An RFID tag reading apparatus according to an example of a specific aspect of the present invention includes a storage unit that stores collision prevention mask information used in reading processing. The reading processing means transmits a request command with no mask setting at the time of the initial reading processing, and when a collision of response signals is detected, at least one or both of the mask value and the mask length are changed and the request command is changed. The retransmitted mask information is stored in the storage means, and the retransmission process and the mask information storing process are repeated until no response signal collision is detected. In the subsequent reading process, the reading processing unit extracts the mask information stored in the storage unit in the previous reading process, and (a) transmits a request command in which the extracted mask information is set and transmits the set mask information. (B) When a collision of response signals is detected, the request command is retransmitted by changing at least one of the mask value and the mask length, and the set mask information is stored in the storage unit. (C) The retransmission process and the mask information storage process are repeated until no response signal collision is detected, and the processes (a) to (c) are repeated until the mask information stored in the storage means is exhausted.

  According to this reading apparatus, the request command is transmitted during the reading process, the mask information set in the request command is stored in the storage means, and the reading process is performed using the mask information stored in the storage means during the next reading process. The mask setting can be performed efficiently.

  An RFID tag reader according to an example of a specific aspect of the present invention includes a control unit that controls reading processing in the reading processing unit. When the reading processing unit receives a reading instruction from the control unit, the reading processing unit starts reading processing, and at the start of reading, sets a mask value and a mask length in a request command in order to prevent collision of response signals from the RFID tag, If a response signal collision is detected, at least one or both of the mask value and the mask length is changed and the request command is retransmitted. The retransmission process is repeated until no response signal collision is detected, and can be read. When reading of each RFID tag in the area is completed, the unique identifier read from each RFID tag is transmitted to the control means. On the other hand, the control unit calculates mask information used by the reading processing unit based on the reading result received from the reading processing unit, and when the reading processing unit is instructed to start reading, the mask value and the mask length are initialized. Specify a value.

  In this reading apparatus, the control means calculates what mask setting is performed in the reading process by the reading means, and adds the calculated mask information to the reading start instruction to the reading means. Further, the reading process can be performed with the mask value and the mask length specified in the reading start instruction as initial values. As a result, the reading means can be implemented without changing the algorithm of the conventional reading apparatus as it is or with a very slight modification.

  As described above, according to the present invention, since the next reading process is performed based on the mask information used in the previous reading process, the mask setting can be performed efficiently. As a result, the number of times of sending the request command is reduced, so that the reading process can be speeded up.

(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings. In this embodiment, a system that reads a unique identifier from an RFID tag of a product displayed on a product shelf will be described. FIG. 1 is an overall configuration diagram of the RFID tag reader, and FIG. 2 is a detailed configuration diagram of the RFID tag reader.

  As shown in FIG. 1, the RFID tag reader according to the present embodiment is used for reading a unique number of an RFID tag 11 from an RFID tag 11 attached to a product 10 displayed in a showcase 1. Shall be used. The showcase 1 includes a plurality of product shelves 2 for displaying the products 10 and a cooling mechanism (not shown) for cooling the products 10. Since the cooling mechanism is the same as that conventionally known, the description thereof is omitted here. On the upper surface of each product shelf 2, an antenna unit 200 for communicating with the RFID tag 11 of the displayed product 10 is provided. The antenna unit 200 includes a loop antenna and a matching circuit (both are not shown), and a plurality (two in FIG. 1) are arranged side by side on the upper surface of each product shelf 2. In addition, the showcase 1 includes a reading processing device 100 provided for each commodity shelf 2 and a centralized control device 300 that centrally controls each reading processing device 100. In the present embodiment, the RFID tag 11 and the RFID tag reader are assumed to conform to JIS standard X6323-1.

  As shown in FIG. 2, the reading processing apparatus 100 is connected to an antenna unit provided in each corresponding product shelf 2, and each antenna unit 200 is used to uniquely set the tag from the RFID tag 11 to the tag. Read the identifier (UID). Each reading processing device 100 includes an RF circuit unit 110 for communicating with the RFID tag 11 within the communication range of each connected antenna 200, a reading processing unit 120 for reading a unique identifier from each RFID tag 11, and a concentration. And a communication interface 130 for connecting to the control device 300. The operation of the reading processing unit 120 will be described later.

  As shown in FIG. 2, the central control apparatus 300 includes an inventory management unit 310 that manages the shelf inventory of products for each product shelf based on the unique identifier of the RFID tag 11 received from each reading processing device 100, and the inventory management unit 310 includes a storage unit 320 used in the unique identifier counting process, a communication interface 330 for connecting to the reading processing apparatus 100, and a communication interface 340 for connecting to a LAN in the store. The operation of the inventory management unit 310 will be described later.

  Next, RFID tag reading processing in the inventory management unit 310 of the centralized control device 300 and the reading processing unit 120 of the reading processing device 100 will be described with reference to FIGS. 3 and 4. FIG. 3 is a sequence chart for explaining the reading process, and FIG. 4 is a flowchart of the reading processing apparatus.

  As shown in FIG. 3, the inventory management unit 310 of the centralized control device 300 sends a reading start instruction to the reading processing device 100 (step SA1). Here, mask information used as an initial value in the reading processing apparatus 100 at the start of reading is included. This mask information consists of a set of one or more mask values and mask lengths. The mask information is obtained based on the mask information used in the previous reading process as will be described later. Therefore, the mask information is set to null information (null) at the time of initial processing such as when power is turned on. When receiving the reading start instruction, the reading processing unit 120 of the reading processing apparatus 100 starts the reading process (step SB10). Details of the reading processing in the reading processing unit 120 will be described later.

  After the reading start instruction in step SA1, the inventory management unit 310 sends a reading end confirmation to the reading processing unit 120 at predetermined time intervals (steps SA21 and SA31). When the reading processing unit 120 receives a reading completion confirmation during the reading process in step SB10, the reading processing unit 120 responds that reading has not been completed (step SB22). On the other hand, when the reading processing unit 120 receives a reading completion confirmation after the reading process of step SB10 is completed, the reading processing unit 120 returns a list of unique identifiers of the read RFID tags 11 (step SB32). As described above, communication from the central control device 300 to the reading processing device 100 is performed asynchronously with the reading processing in the reading processing device 100. In addition, the inventory management unit 310 stores the reading result in the storage unit 320.

  The inventory management unit 310 of the centralized control device 300 determines mask information to be used for the next reading start instruction based on the reading result received from the reading processing unit 120 of the reading processing device 100 (step SA50). A method for determining mask information will be described later.

  Through the above processing, the inventory management unit 310 of the centralized control apparatus 300 holds the list of unique identifiers read from the RFID tag 11 of each product 10 placed on the product shelf 2 in the storage unit 320. If there is a difference between the reading result read last time and the reading result read this time, the inventory management unit 310 transmits the difference information to the store computer 500. In addition, the inventory management unit 310 returns the reading result stored in the storage unit 320 to the store computer 500 in response to a request from the store computer 500.

  Next, details of the reading process in step SB10 in the reading processing unit 120 will be described with reference to FIG. The reading processing unit 120 sets the mask value and the mask length in the inventory command using the mask information included in the reading start instruction received in Step SA1. Specifically, first, a set of one or more mask values and mask lengths included in the reading start instruction is put into a FIFO queue (hereinafter referred to as a mask storage queue) (step SB101). Then, the mask value and the mask length extracted from the mask storage queue are set in the inventory command (step SB102). This inventory command is a command for requesting a response to the RFID tag 11 existing in the readable area. However, the RFID tag 11 that returns a response is only a tag whose lower order of its own 64-bit unique identifier matches the mask. Further, the RFID tag 11 applies a mask to the unique identifier, and uses the lower 4 bits excluding the mask part as the slot number. When the time slot matches its own slot number, a response including its own unique identifier is returned.

  The reading processing unit 120 sends an inventory command (step SB103), and waits for a response from the RFID tag 11 while switching the time slot from 0 to 15 (steps SB104 to S110). Specifically, first, the time slot is set to 0 (step SB104), and a time slot switching signal is transmitted (step SB105). When there is no response from the RFID tag 11 within a predetermined time in the time slot, that is, when a time-out occurs, the process proceeds to the next time slot (steps SB106 and SB110). On the other hand, when there is a response from the RFID tag 11 and no collision has occurred (steps SB106 and SB107), the reading processing unit 120 assigns a unique identifier included in the response to a predetermined storage unit (hereinafter referred to as a UID storage unit). (Step SB108). On the other hand, when there is a response from the RFID tag 11 but a collision occurs in the response (steps SB106 and SB107), a mask to be used in the next inventory command is determined, and the mask information is stored in a predetermined storage unit (FIFO queue) ( (Hereinafter referred to as a mask storage queue) (step SB109). The next mask is determined as follows. The next mask length is assumed to be the mask length used this time +4. The next mask value is obtained by the logical sum of the current time slot shifted left by the mask length used this time and the mask value used this time.

  Thus, the process related to one inventory command is completed. The reading processing unit 120 sends a squiet command to the RFID tag 11 read by the inventory command so as not to respond to the next inventory command (step SB111). Next, when the mask information is stored in the mask storage queue (step SB112), the reading processing unit 120 extracts the mask information, sets the mask with the extracted mask information (step SB102), and executes the next inventory command. (Step SB103). With such a process, the reading process is executed with the mask setting changed for the time slot in which the collision has occurred. When mask information is not stored in the mask storage queue (step SB112), the reading processing unit 120 performs a process of confirming whether there is a reading omission (step SB113). Specifically, the inventory command is sent again with no mask setting. Since all RFID tags 11 that have already been read are in the stay state in step SB111, no response is made to the inventory command. Therefore, in this confirmation process, it is only necessary to confirm that there is no response to the inventory command (timeout occurs).

  Next, a method for determining mask information used by the inventory management unit 310 at the next reading instruction will be described with reference to FIGS. 5 and 6 are flowcharts illustrating a method for determining mask information.

  The inventory management unit 310 determines mask information used in the next reading process based on the reading result received from the reading processing unit 120, that is, the list of unique identifiers. More specifically, the inventory management unit 310 calculates mask information used in the reading processing unit 120 by using an algorithm of the reading processing in the reading processing unit 120 and the reading result. Hereinafter, processing in the inventory management unit 310 will be described in detail.

  As shown in FIG. 5, the inventory management unit 310 stores mask information when the mask length at the start of reading is 0 bits (that is, no mask) in a FIFO-type queue (hereinafter referred to as a mask storage queue) (step). SA101). Specifically, (mask length: 0, mask value: 0) is stored in the mask storage queue. Then, a pseudo reading process described later is executed (step SA102).

  Similarly, the inventory management unit 310 stores the mask information when the mask length at the start of reading is 1 bit in the mask storage queue (step SA103). Specifically, (mask length: 1, mask value: 0) and (mask length: 1, mask value: 1) are stored in the mask storage queue. Then, a pseudo reading process described later is executed (step SA104).

  Further, the inventory management unit 310 stores the mask information when the mask length at the start of reading is 2 bits in the mask storage queue (step SA105). Specifically, (mask length: 2, mask value: 0), (mask length: 2, mask value: 1), (mask length: 2, mask value: 2), (mask length: 2, mask value: 3) is stored in the mask storage queue. Then, a pseudo reading process to be described later is executed (step SA106).

  In each pseudo reading process (steps SA102, SA104, SA106), the number of pseudo inventory is calculated, and mask information used in the pseudo reading process is stored in a predetermined stack area. The inventory management unit 310 selects the process having the smallest number of pseudo inventory times among the three pseudo reading processes, and uses the mask information obtained by the process in the next actual reading process (step SA107).

  Next, the pseudo reading process in steps SA102, SA104, and SA106 will be described with reference to FIG. The algorithm of the pseudo reading process is the same as the algorithm in the reading processing apparatus 100 described above with reference to FIG. First, the inventory management unit 310 takes out mask information from the mask storage queue, and sets the current mask value and mask length (step SA201). Next, the inventory management unit 310 increases the pseudo inventory count (initial value is 0) by 1 and sets the normal response flag to FALSE (step SA202). Next, the inventory management unit 310 performs pseudo inventory processing using the mask information set in step SA201 (steps SA203 to SA208). Specifically, the inventory management unit 310 first sets the time slot to 0 (step SA203), and whether there is a tag that meets the conditions made up of each time slot and the current mask setting among the previously read tags. It is determined whether or not (step SA204). If there is one matching tag, the unique identifier of the tag can be read, so the normal response flag is set to TRUE (steps SA205 and SA206). On the other hand, if the number of matching tags is 2 or more, it means that a collision occurs, so the mask to be used in the next inventory command is determined and the mask information is stored in the mask storage queue (steps SA205 and SA207). The algorithm for determining the next mask is the same as the algorithm in the reading processing apparatus 100. The above processing is repeated until the time slot reaches 15 (steps SA203 and SA208).

  One pseudo inventory process is completed by the above process. When the normal response flag is TRUE, the inventory management unit 310 has pseudo-read one or more RFID tags in one pseudo inventory process, so the current mask information is stored in a predetermined stack. Store in the area (steps SA209 and SA210). The inventory management unit 310 repeats the above processing until the mask storage queue becomes empty (step SA211).

  Through such processing, one or more pieces of mask information are recorded in a predetermined stack area. Each mask information can always be read by one or more RFID tags under the assumption that the RFID tag arrangement state has not changed even during the next reading process. Moreover, all the RFID tags can be read by using all the mask information.

  As described above, in the RFID tag reader according to the present embodiment, the next mask information is set based on the mask information used in the previous reading process. As a result, in a situation where there is little variation with time in the distribution situation of the RFID tags 11 existing in the readable area, it is possible to perform an appropriate mask setting with a small number of inventory command transmissions. As a result, the number of times the inventory command is sent is reduced, so that the reading process can be speeded up. Further, in the RFID tag reading device according to the present embodiment, the reading processing algorithm in the reading processing unit 120 is the same as that of the conventional one. Can be implemented.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to the drawings. This embodiment is different from the first embodiment in the mask information acquisition method. That is, in the first embodiment, the central control device 300 different from the reading processing device 100 calculates the mask information used in the reading processing from the reading result from the reading processing device 100. In the present embodiment, the mask information is stored in the reading process in the reading processing apparatus 100. Hereinafter, RFID tag reading processing in the inventory management unit 310 of the central control device 300 and the reading processing unit 120 of the reading processing device 100 will be described with reference to FIGS. 7 and 8. FIG. 7 is a sequence chart for explaining the reading process, and FIG. 8 is a flowchart of the reading processing apparatus.

  As shown in FIG. 7, the inventory management unit 310 of the centralized control device 300 sends a reading start instruction to the reading processing device 100 (step SC1). This embodiment is different from the first embodiment in that mask information is not included in the reading start instruction. When receiving the reading start time, the reading processing unit 120 of the reading processing apparatus 100 starts the reading process (step SD10). Details of the reading processing in the reading processing unit 120 will be described later.

  The inventory management unit 310 sends a reading end confirmation to the reading processing unit 120 at predetermined time intervals after the reading start instruction in step SC1 (steps SC21 and SC31). When the reading processing unit 120 receives a reading completion confirmation during the reading process in step SD10, the reading processing unit 120 responds that reading has not been completed (step SD22). On the other hand, when the reading processing unit 120 receives a reading completion confirmation after the reading processing in step SD10, the reading processing unit 120 returns a list of the unique identifiers of the read RFID tags 11 (step SD32). As described above, communication from the central control device 300 to the reading processing device 100 is performed asynchronously with the reading processing in the reading processing device 100. In addition, the inventory management unit 310 stores the reading result in the storage unit 320.

  Through the above processing, the inventory management unit 310 of the centralized control apparatus 300 holds the list of unique identifiers read from the RFID tag 11 of each product 10 placed on the product shelf 2 in the storage unit 320. If there is a difference between the reading result read last time and the reading result read this time, the inventory management unit 310 transmits the difference information to the store computer 500. In addition, the inventory management unit 310 returns the reading result stored in the storage unit 320 to the store computer 500 in response to a request from the store computer 500.

  Next, details of the reading process in step SD10 in the reading processing unit 120 will be described with reference to FIG. The reading processing unit 120 includes a FIFO queue (hereinafter referred to as a previous mask storage queue) for storing mask information used in the previous reading process. The initial value of the previous mask storage queue is null.

  Upon receiving the reading start instruction in step SC1, the reading processing unit 120 moves the contents of the previous mask storage queue to a predetermined FIFO type queue (hereinafter referred to as the current mask storage queue) (step SD101). The mask storage queue this time is a storage unit for temporarily storing mask information in the reading process for one reading start instruction. Next, the reading processing unit 120 extracts the mask information from the current mask storage queue, and sets the mask value and the mask length in the inventory command using the mask information (step SD102).

  Next, the reading processing unit 120 sends an inventory command (step SD103) and waits for a response from the RFID tag 11 while switching the time slot from 0 to 15 (steps SD104 to S110). Specifically, the time slot is first set to 0 (step SD104), and a time slot switching signal is transmitted (step SD105). When there is no response from the RFID tag 11 within a predetermined time in the time slot, that is, when a time-out occurs, the process proceeds to the next time slot (steps SD106 and SD110). On the other hand, when there is a response from the RFID tag 11 and no collision has occurred (steps SD106 and SD107), the reading processing unit 120 stores the unique identifier included in the response in a predetermined UID storage unit ( Step SD108). On the other hand, when there is a response from the RFID tag 11 but a collision occurs in the response (steps SD106 and SD107), a mask to be used in the next inventory command is determined, and the mask information is stored in the current mask storage queue (step SD109). The next mask determination method is the same as in the first embodiment.

  Thus, the process related to one inventory command is completed. When there is one or more RFID tags 11 read by this inventory command (step SD111), the reading processing unit 120 stores the mask value and mask length set in the inventory command in the previous mask storage queue (step SD112). . Further, the reading processing unit 120 sends a squeeze command to the read RFID tag 11 so as not to respond to the next inventory command (step SB113). Next, when the mask information is currently stored in the mask storage queue (step SB114), the reading processing unit 120 retrieves the mask information, sets a mask with the retrieved mask information (step SD102), and performs the next inventory command. (Step SD103). With such a process, the reading process is executed with the mask setting changed for the time slot in which the collision has occurred. If the mask information is not stored in the mask storage queue this time (step SD114), the reading processing unit 120 performs a process of confirming whether there is a reading omission (step SB115). Specifically, the inventory command is sent again with no mask setting. Since all the RFID tags 11 that have already been read are in the stay state in step SD113, no response is made to the inventory command. Therefore, in this confirmation process, it is only necessary to confirm that there is no response to the inventory command (timeout occurs).

  According to such an RFID tag reader, when the reading processing unit 120 performs reading processing, the mask information actually used is stored in the previous mask storage queue. In the next reading process, the mask information stored in the previous mask storage queue is used. As a result, in a situation where there is little variation with time in the distribution situation of the RFID tags 11 existing in the readable area, it is possible to perform an appropriate mask setting with a small number of inventory command transmissions. As a result, the number of times the inventory command is sent is reduced, so that the reading process can be speeded up.

  As mentioned above, although embodiment of this invention was explained in full detail, this invention is not limited to this. For example, in the first embodiment, a plurality of pieces of mask information are collectively transmitted at the start of reading from the central control apparatus 300 to the reading processing apparatus 100, but may be transmitted one by one.

  In the first embodiment, the inventory management unit 310 of the central control device 300 calculates the mask information used in the reading process from the reading result from the reading processing device 100. However, the reading processing device 100 reads the mask information. Mask information may be transmitted to the inventory management unit 310 together with the result. With such a configuration, the pseudo reading process in the inventory management unit 310 can be omitted, so that the centralized control device can be simplified and speeded up.

  In the present embodiment, the system for managing the shelf inventory of the showcase in real time is exemplified as the usage application of the RFID tag reader. However, the present invention can be implemented even in other usages.

Overall configuration diagram of RFID tag reader Detailed configuration diagram of RFID tag reader Sequence chart for explaining a reading process according to the first embodiment A flowchart for explaining the operation of the reading processing apparatus according to the first embodiment. Flowchart for explaining a mask information determination method according to the first embodiment Flowchart for explaining a mask information determination method according to the first embodiment Sequence chart for explaining a reading process according to the second embodiment The flowchart explaining operation | movement of the reading processing apparatus which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Showcase, 2 ... Merchandise shelf, 100 ... Reading processing apparatus, 120 ... Reading processing part, 200 ... Antenna unit, 300 ... Centralized control apparatus, 310 ... Inventory management part, 500 ... Store computer

Claims (3)

In an RFID tag reader that reads a unique identifier of each RFID tag from a plurality of RFID tags in a readable area,
Read processing means for transmitting a request command to the RFID tag and receiving a response including a unique identifier from the RFID tag according to the request command,
The RFID tag reading apparatus, wherein the reading processing means sets mask information to be set in a request command in the next reading process based on the collision preventing mask information used in the previous reading process. Comprising storage means for storing anti-collision mask information used in the reading process;
The reading processing means transmits a request command with no mask setting at the time of the first reading processing, and retransmits the request command by changing at least one or both of the mask value and the mask length when a collision of response signals is detected. And storing the set mask information in the storage means, repeating the retransmission process and the mask information storage process until no response signal collision is detected,
In the subsequent reading process, the mask information stored in the storage unit in the previous reading process is extracted, (a) a request command in which the extracted mask information is set is transmitted, and the set mask information is stored in the storage unit. b) When a response signal collision is detected, at least one or both of the mask value and the mask length are changed, the request command is retransmitted, and the set mask information is stored in the storage means, and (c) the response signal 2. The retransmission process and the mask information storage process are repeated until no collision is detected, and the processes (a) to (c) are repeated until the mask information stored in the storage means is exhausted. The RFID tag reader according to claim. Control means for controlling the reading process in the reading processing means,
When the reading processing unit receives a reading instruction from the control unit, the reading processing unit starts reading processing, and at the start of reading, sets a mask value and a mask length in a request command in order to prevent collision of response signals from the RFID tag, If a response signal collision is detected, at least one or both of the mask value and the mask length is changed and the request command is retransmitted. The retransmission process is repeated until no response signal collision is detected, and can be read. When reading of each RFID tag in the area is completed, a unique identifier read from each RFID tag is transmitted to the control means,
The control unit calculates mask information used by the reading processing unit based on the reading result received from the reading processing unit, and sets an initial value of a mask value and a mask length when instructing the reading processing unit to start reading. The RFID tag reader according to claim 1, wherein the RFID tag reader is specified.

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