Wireless tag reader

Abstract

To provide a configuration capable of efficiently reading a tag by switching a modulation system of a wireless communication unit according to the estimated number of unread tags.SOLUTION: During a first modulation system of a wireless tag processing unit 30, when the number of wireless tags T read by the wireless tag processing unit 30 in a predetermined unit time is brought into a predetermined decreasing state, the system is controlled to be switched to a second modulation system. During the second modulation system, when the number of unread tags in the predetermined unit time is estimated to be in a predetermined increasing state, the system is controlled to be switched to the first modulation system.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a radio tag reader that reads data stored in a plurality of radio tags. [Background technology]

[0002] Conventionally, in order to improve the efficiency of inventory work, etc., wireless tags such as RF tags are attached to each managed object, and the results of reading these wireless tags collectively are used in management work, etc. In such applications, it is necessary to read many wireless tags in a short time, and as a technology for this purpose, for example, a tag reading device disclosed in the following Patent Document 1 is known. When many tags are present in a readable area and the IDs of the tags collide with each other, causing many collisions, this tag reading device is configured to first reduce the output power to narrow the readable area to suppress the occurrence of collisions, and when the number of unread tags present in the narrowed area decreases, increase the output power to expand the readable area and read the remaining tags. In this way, the output power is controlled according to the reception state of the response signal from the tag, thereby suppressing the occurrence of collisions, while suppressing an unnecessary increase in output power, thereby reducing the power consumption of the device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2007 / 034543 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when there are a large number of wireless tags to be read, wireless communication may not be possible due to poor reception sensitivity of some of the wireless tags due to the arrangement of the wireless tags, interference between the wireless tags, etc. With the method of increasing and decreasing the output power as in the above-mentioned tag reading device, it is difficult to efficiently read wireless tags with poor reception sensitivity.

[0005] Therefore, instead of increasing or decreasing the output power, by changing the modulation method during wireless communication with the wireless tag, it is possible to efficiently read many wireless tags, including those with poor reception sensitivity.Specifically, for example, after reading many wireless tags with relatively good reception sensitivity using a modulation method for reading at high speed communication (a modulation method that prioritizes communication speed over reading accuracy), the remaining wireless tags with relatively poor reception sensitivity can be read by switching to a modulation method for reading at low speed communication (a modulation method that prioritizes reading accuracy over communication speed), thereby making it possible to efficiently read more wireless tags.

[0006] However, in a configuration in which the modulation method is switched to one that emphasizes read accuracy in order to read wireless tags with relatively poor reception sensitivity as described above, if the number of unread wireless tags (hereinafter also referred to as unread tags) in the readable range increases after the change, the processing time required for reading may become longer, which may hinder efficient reading, unless an operation is performed to return to the modulation method that emphasizes communication speed.For example, when a reader that has switched to a modulation method that emphasizes read accuracy after performing a reading operation in a certain work area is carried to the next work area, there is a problem that efficient reading is hindered because many wireless tags with relatively good reception sensitivity are read with the modulation method that emphasizes read accuracy.

[0007] The present invention has been made to solve the above-mentioned problems, and its object is to provide a configuration that can perform reading efficiently by switching the modulation method of the wireless communication unit depending on the estimated number of unread tags. [Means for solving the problem]

[0008] In order to achieve the above object, the invention described in claim 1 of the claims is as follows: A radio tag reader (10) for reading data stored in a plurality of radio tags (T), a wireless communication unit (30) for wirelessly communicating with the plurality of wireless tags in a predetermined modulation method; A control unit (21) for controlling a modulation method of the wireless communication unit; an estimation unit (21) that estimates, as an unread tag number, the number of unread wireless tags that can be read by the wireless communication unit from the current location within a predetermined unit time; Equipped with A modulation method that prioritizes communication speed over reading accuracy is defined as a first modulation method, and a modulation method that prioritizes reading accuracy over communication speed in comparison with the first modulation method is defined as a second modulation method, The control unit is When the number of wireless tags read by the wireless communication unit during the specified unit time is in a predetermined decreasing state while the modulation method of the wireless communication unit is set to the first modulation method, control is performed to switch to the second modulation method, and when the number of unread tags is estimated to be in a predetermined increasing state from the estimation result of the estimation unit during the specified unit time while the modulation method of the wireless communication unit is set to the second modulation method, control is performed to switch to the first modulation method. stomach, The estimation unit is a collision number counting unit for counting the number of collisions of reply waves from two or more wireless tags during the predetermined unit time in which a plurality of time slots are set, Based on the number of collisions of the reply waves counted by the collision number counting unit, it is estimated whether the number of unread tags is in the predetermined increasing state. It is characterized by: The symbols in parentheses above indicate the corresponding relationship with the specific means described in the embodiments described later. Effect of the Invention

[0009] Claim 1 ,2In the invention, when a modulation method that prioritizes communication speed over reading accuracy is defined as a first modulation method and a modulation method that prioritizes reading accuracy over communication speed compared to the first modulation method is defined as a second modulation method, when the modulation method of the wireless communication unit is set to the first modulation method and the number of wireless tags read by the wireless communication unit within a specified unit time reaches a specified decreasing state, control is performed to switch to the second modulation method, and when the modulation method is set to the second modulation method and it is estimated from the estimation result of the estimation unit that the number of unread tags is within a specified unit time, control is performed to switch to the first modulation method.

[0010] As a result, when a wireless tag reader that has switched to the second modulation method (a slow modulation method that prioritizes reading accuracy over communication speed) by performing a reading operation in a certain work area is carried to the next work area, the estimation unit estimates that the number of unread tags is in a predetermined increasing state, and the modulation method is switched to the first modulation method (a fast modulation method that prioritizes communication speed over reading accuracy). In this way, by switching the modulation method of the wireless communication unit according to the estimated number of unread tags, reading can be performed efficiently even if the number of wireless tags within the readable range changes.

[0011] Claim 1 In the invention, the estimation section estimates whether the number of unread tags is in the above-mentioned predetermined increasing state based on the number of collisions of the reply waves counted by the collision number counting section.

[0012] Even if there are many unread tags, if the number of collisions of reply waves from each unread tag is large, the number of read wireless tags will be small. In other words, even if the number of read wireless tags is small, if the number of collisions of reply waves is large, it can be estimated that there are many unread tags, so it can be estimated whether the number of unread tags is in the above-mentioned specified increased state based on the number of collisions of reply waves.

[0013] Claim 2In the invention, the estimation unit estimates whether the number of unread tags is in the above-mentioned specified increasing state based on the comparison result between the number of collisions of response waves counted by the collision number counting unit and the number of no-responses counted by the no-response number counting unit.

[0014] Even when there are many unread tags, if the number of collisions of response waves from each unread tag is large, the number of read wireless tags will be small. On the other hand, even when there are few unread tags, the fewer the number of time slots set, the greater the number of collisions. In other words, it can be estimated that the greater the number of collisions of response waves relative to the number of no responses, the greater the number of unread tags. Therefore, based on the comparison result between the number of collisions of response waves and the number of no responses, it can be estimated whether the number of unread tags is in the above-mentioned specified increased state. In particular, since the number of unread tags is estimated taking into account both the number of collisions of response waves and the number of no responses, the accuracy of estimating the number of unread tags can be improved compared to the case where only the number of collisions of response waves is considered.

[0017] Claim 3 In the invention, when a modulation method that emphasizes reading accuracy over communication speed is set as the third modulation method, when the modulation method of the wireless communication unit is set to the second modulation method and the number of wireless tags read by the wireless communication unit during a specified unit time is in a second decreasing state, control is performed to switch to the third modulation method, and when the number of unread tags during a specified unit time is estimated to be in a second increasing state from the estimation result of the estimation unit while set to the third modulation method, control is performed to switch to the second modulation method.

[0018] This allows the modulation method to be switched in finer increments, so that the modulation method can be switched to better follow environmental changes, enabling more efficient reading. [Brief description of the drawings]

[0019] [Figure 1] 1A and 1B are explanatory diagrams showing an outline of the configuration of a wireless tag reading device according to a first embodiment, with FIG. 1A showing a plan view and FIG. 1B showing a side view. [Diagram 2] 2(A) is a block diagram illustrating the electrical configuration of the wireless tag reading device of FIG. 1, FIG. 2(B) is a block diagram illustrating a schematic example of the wireless tag processing unit of FIG. 2(A), and FIG. 2(C) is a block diagram illustrating a schematic example of the information code reading unit of FIG. 2(A). [Diagram 3] 4 is a flowchart illustrating the flow of a modulation method switching process performed by a control unit in the first embodiment. [Figure 4] 10 is a flowchart illustrating the flow of a modulation method switching process performed by a control unit in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] [First embodiment] Hereinafter, a first embodiment of a wireless tag reading device according to the present invention will be described with reference to the drawings. The wireless tag reading device 10 of this embodiment is configured as a portable information reading terminal that is carried by a user and used in various places, and in addition to the function of reading and writing information stored in a wireless tag T such as an RF tag using radio waves transmitted and received via an antenna as a medium, it also has the function of an information code reader that reads information codes such as barcodes and two-dimensional codes, and is configured to be able to read in two ways.

[0021] 1(A) and (B), the exterior of the wireless tag reader 10 is formed by a longitudinal housing 11 that is configured by assembling an upper case 11a and a lower case 11b that are made of a synthetic resin material such as ABS resin. The upper case 11a is provided with a key operation section 25 such as function keys and a numeric keypad that are operated when inputting predetermined information, a display section 24 for displaying predetermined information, and the like. The lower case 11b is provided with a reading port 12 that opens downward.

[0022] 2(A), a control unit 21 that controls the entire radio tag reading device 10 is provided inside the housing 11 of the radio tag reading device 10. The control unit 21 is mainly configured with a microcomputer and has a CPU, a system bus, an input / output interface, etc., and configures an information processing device together with a memory 22. The memory 22 stores in advance predetermined programs and the like for executing a modulation method switching process and a radio tag reading process, which will be described later, so that the programs can be executed by the control unit 21.

[0023] The control unit 21 is connected to the LED 23, the display unit 24, the key operation unit 25, the vibrator 26, the buzzer 27, the external interface 28, and the like. The key operation unit 25 is configured to give an operation signal to the control unit 21, and the control unit 21 performs an operation according to the contents of the operation signal upon receiving the operation signal. The LED 23, the display unit 24, the vibrator 26, and the buzzer 27 are configured to be controlled by the control unit 21, and each of them operates upon receiving an instruction from the control unit 21. The external interface 28 is configured as an interface for performing data communication with an external device such as a server via a predetermined network, and is configured to perform communication processing in cooperation with the control unit 21. A power supply unit 29 is provided in the housing 11, and power is supplied to the control unit 21 and various electric components by the power supply unit 29 and a battery 29a.

[0024] Further, the control unit 21 is connected to a wireless tag processing unit 30 and an information code reading unit 40 . First, the wireless tag processor 30 will be described with reference to FIG. The RF tag processing unit 30 functions as a wireless communication unit that wirelessly communicates with multiple RF tags T in a predetermined modulation method controlled by the control unit 21, and cooperates with an antenna 34 and the control unit 21 to communicate with the RF tags T by electromagnetic waves, reading data stored in the RF tags T, or writing data to the RF tags T. This RF tag processing unit 30 is configured as a circuit that transmits using a known radio wave method, and has a transmitting circuit 31, a receiving circuit 32, a matching circuit 33, etc., as shown roughly in Fig. 2(B).

[0025] The transmission circuit 31 is composed of a carrier oscillator, an encoding unit, an amplifier, a transmission filter, a modulation unit, and the like, and is configured such that a carrier (carrier wave) of a predetermined frequency is output from the carrier oscillator. The encoding unit is connected to the control unit 21, and encodes the transmission data output from the control unit 21 and outputs the encoded data to the modulation unit. The modulation unit is a part to which the carrier (carrier wave) from the carrier oscillator and the transmission data from the encoding unit are input, and generates a modulated signal modulated by the encoded transmission code (modulation signal) output from the encoding unit when transmitting a command to a communication target, for the carrier (carrier wave) output from the carrier oscillator, and outputs the modulated signal to the amplifier. The amplifier amplifies the input signal (the modulated signal modulated by the modulation unit) with a predetermined gain and outputs the amplified signal to the transmission filter, and the transmission filter outputs a transmission signal obtained by filtering the amplified signal from the amplifier to the antenna 34 via the matching circuit 33. When the transmission signal is output to the antenna 34 in this manner, the transmission signal is radiated to the outside from the antenna 34 as a transmission radio wave.

[0026] On the other hand, the response signal received by the antenna 34 is input to the receiving circuit 32 via the matching circuit 33. This receiving circuit 32 is composed of a receiving filter, an amplifier, a demodulation section, a binarization processing section, a decoding section, etc., and the response signal received via the antenna 34 is filtered by the receiving filter, amplified by the amplifier, and the amplified signal is demodulated by the demodulation section. Then, the demodulated signal waveform is binarized by the binarization processing section and decoded by the decoding section, and the decoded signal is output to the control section 21 as received data.

[0027] In particular, in this embodiment, the control unit 21 controls the wireless tag processing unit 30 in response to an estimation result of the number (number of unread tags) of wireless tags (unread tags) that are within a readable range from the current position and that have not yet been read, thereby switching the modulation method during wireless communication with the wireless tag T. Specific details of this modulation method switching process will be described later.

[0028] Next, the information code reading unit 40 will be described with reference to FIG. The information code reading unit 40 functions to optically read information codes, and as shown in FIG. 2(C), is configured with a light receiving sensor 43 consisting of a CCD area sensor, an imaging lens 42, and an illumination unit 41 consisting of multiple LEDs, lenses, etc., and functions in cooperation with the control unit 21 to read the information code C (barcode or two-dimensional code) attached to the reading object R.

[0029] When reading is performed by the information code reading unit 40, first, illumination light Lf is emitted from the illumination unit 41 in response to a command from the control unit 21, and this illumination light Lf is irradiated onto the reading target R through the reading port 12. Then, reflected light Lr, which is the illumination light Lf reflected by the information code C, is taken into the device through the reading port 12 and is received by the light receiving sensor 43 through the imaging lens 42. The imaging lens 42, which is disposed between the reading port 12 and the light receiving sensor 43, is configured to form an image of the information code C on the light receiving sensor 43, and the light receiving sensor 43 outputs a light receiving signal corresponding to the image of the information code C. The light receiving signal output from the light receiving sensor 43 is stored as image data in the memory 22 (FIG. 2(A)) and is used for a decoding process for acquiring information contained in the information code C. The information code reading unit 40 is provided with an amplifier circuit that amplifies the signal from the light receiving sensor 43, an AD conversion circuit that converts the amplified signal into a digital signal, and the like, but these circuits are omitted from the illustration.

[0030] Next, a detailed description will be given of a characteristic configuration of this embodiment in which the modulation method used by the RF tag processor 30 in wireless communication with the RF tags T is switched depending on the result of estimating the number of unread tags. In this embodiment, a first modulation method that prioritizes communication speed over reading accuracy and a second modulation method that prioritizes reading accuracy over communication speed are adopted as modulation methods that can be switched during wireless communication using the wireless tag processing unit 30. Specifically, for example, in the GS1 Gen2 standard, a modulation method that operates with Tari=12.5 μs, BLF=400 kHz, and FM0 baseband is adopted as the first modulation method, and a modulation method that operates with Tari=25.0 μs, BLF=250 kHz, and mirror subcarrier (M=4) is adopted as the second modulation method. Note that the first modulation method and the second modulation method are not limited to the above-mentioned modulation methods, and other modulation methods may be adopted as long as they are a modulation method that prioritizes communication speed over reading accuracy and a modulation method that prioritizes reading accuracy over communication speed.

[0031] The first modulation method can read many RF tags T with relatively good reception sensitivity in a short time, and the second modulation method can carefully read even RF tags T with relatively poor reception sensitivity. Therefore, after most of the RF tags T that are easy to read are first read in a short time by the first modulation method, the remaining few RF tags T that are difficult to read can be reliably read by the second modulation method, and many RF tags T can be read efficiently.

[0032] However, for example, when a reader that has switched to the second modulation method after performing a reading operation in a certain work area is carried to the next work area, efficient reading may be hindered because many RF tags T with relatively good reception sensitivity are read with the second modulation method. Specifically, for example, a case is assumed in which the reader switches to the second modulation method to read RF tags T that are difficult to read on a first shelf, and after finishing reading all the RF tags T on the first shelf, the reader moves to the next second shelf to continue the reading operation. When moving to the second shelf in this way, even if there are many unread RF tags T that are easy to read (unread RF tags T with relatively good reception sensitivity) on the second shelf, the reading is performed with the second modulation method, which increases the reading time and hinders efficient reading.

[0033] Therefore, in this embodiment, after switching from the first modulation method that prioritizes communication speed to the second modulation method that prioritizes reading accuracy as the number of wireless tags T read during a unit time (per inventory: one reading cycle) decreases, the number of unread tags during the unit time is estimated, and if it is estimated from this estimation result that the number of unread tags is in a predetermined increasing state, a process of switching from the second modulation method to the first modulation method is performed. As described above, a case in which it is estimated that the number of unread tags is in a predetermined increasing state may be assumed, for example, when the number of unread tags exceeds a preset threshold value.

[0034] Specifically, in this embodiment, the reading of the wireless tag T is performed by anti-collision using a time slot method, and it is estimated whether the number of unread tags is in the above-mentioned predetermined increase state based on the number of collisions of the response waves in a unit time obtained for the estimation result of the number of unread tags. Even if there are many unread tags, if the number of collisions of the response waves from each unread tag is large, the number of read wireless tags T will be small. That is, even if the number of read wireless tags T is small, if the number of collisions of the response waves is large, it can be estimated that there are many unread tags, so it can be estimated whether the number of unread tags is in the above-mentioned predetermined increase state based on the number of collisions of the response waves. Note that the control unit 21 that performs the collision number counting process of counting the collision number of the response waves for the estimation result of the number of unread tags corresponds to an example of the "collision number counting unit", and the control unit 21 that performs the estimation process of estimating the number of unread tags as described above can correspond to an example of the "estimation unit".

[0035] The modulation method switching process in which the RFID tag processing unit 30 switches the modulation method during wireless communication with the RFID tag T depending on the estimation result of the number of unread tags will be described below with reference to the flowchart shown in Fig. 3. It should be noted that when the modulation method switching process starts, the modulation method during wireless communication is set to the first modulation method.

[0036] When the control unit 21 starts a wireless tag reading process to read many wireless tags T in an inventory operation or the like, the control unit 21 starts a modulation method switching process in parallel. In this modulation method switching process, first, in a determination process shown in step S101 of Fig. 3, it is determined whether or not the number of wireless tags T read in the wireless tag reading process during the unit time (hereinafter also referred to as the tag response number) is in a predetermined decreasing state. Here, since it is immediately after the start of the operation, many wireless tags T with relatively good reception sensitivity are read one after another, so the number of tag responses increases, and if it is determined that the number of tag responses is not in the predetermined decreasing state, the result is No in step S101.

[0037] On the other hand, if the number of tag responses gradually decreases as the reading operation progresses and it is determined that the number of tag responses is in a predetermined decreasing state (Yes in S101), and if the modulation method for wireless communication is not set to the second modulation method (if it is set to the first modulation method) (No in S103), the modulation method for wireless communication is switched to the second modulation method (S105). This switches from the first modulation method that prioritizes communication speed to the second modulation method that prioritizes reading accuracy, making it possible to read even wireless tags T with relatively poor reception sensitivity.

[0038] As described above, if the modulation method during wireless communication is switched to the second modulation method (S105), and if it is not determined that the number of tag responses is not in a predetermined decreasing state (No in S101), it is determined in the determination process of step S107 whether the number of unread tags is in a predetermined increasing state. As described above, if it is determined that the number of unread tags is not in the predetermined increasing state based on the number of collisions of response waves (No in S107), and if the wireless tag reading process is not completed (No in S113), the process from the determination process of step S101 is repeated.

[0039] On the other hand, when it is determined that the number of unread tags is in the above-mentioned predetermined increased state based on the number of collisions of the response waves (Yes in S107), if the modulation method during wireless communication is not set to the above-mentioned first modulation method (if it is set to the above-mentioned second modulation method) (No in S109), the modulation method during wireless communication is switched to the above-mentioned first modulation method (S111). As a result, when moving to a work area where many unread wireless tags T that are easy to read are present, by switching from the second modulation method that prioritizes reading accuracy to the first modulation method that prioritizes communication speed, it is possible to read many unread wireless tags T that are easy to read in a short period of time.

[0040] Thereafter, as the reading operation progresses at the destination, the number of tag responses gradually decreases, and when it is determined that the number of tag responses is at a predetermined decreased state (Yes in S101), the modulation method during wireless communication is switched to the above-mentioned second modulation method (S105), so that the remaining wireless tags T with relatively poor reception sensitivity can be read efficiently.

[0041] As described above, in the wireless tag reading device 10 of this embodiment, when the modulation method of the wireless tag processing unit 30 is set to the first modulation method and the number of wireless tags T read by the wireless tag processing unit 30 during a specified unit time is in a specified decreasing state (No in S103, Yes in S101), control is performed to switch to the second modulation method (S105), and when the number of unread tags during a specified unit time is estimated to be in a specified increasing state (No in S109, Yes in S107) while set to the second modulation method, control is performed to switch to the first modulation method (S111).

[0042] As a result, when the RFID reader 10 that has switched to the second modulation method by performing a reading operation in a certain work area is carried to the next work area, the number of unread tags is estimated to be in a predetermined increasing state, and the modulation method is switched back to the first modulation method. In this way, by switching the modulation method of the RFID tag processor 30 according to the estimated number of unread tags, reading can be performed efficiently even if the number of RFID tags T within the readable range changes.

[0043] In particular, whether the number of unread tags is in the above-mentioned predetermined increasing state is estimated based on the number of collisions of reply waves counted by the collision number counting process. As described above, even if the number of read wireless tags T is small, if the number of collisions of reply waves is large, it can be estimated that there are many unread tags, so whether the number of unread tags is in the above-mentioned predetermined increasing state can be estimated based on the number of collisions of reply waves.

[0044] In addition, the determination as to whether the number of unread tags is in the above-mentioned specified increasing state may not only be made based on the number of response wave collisions as described above, but may also be made based on other factors that affect the number of unread tags, such as the number of no responses (the number of time slots in which neither response waves nor collisions are detected).

[0045] [Second embodiment] Next, a radio tag reading device according to a second embodiment of the present invention will be described with reference to the drawings. The second embodiment differs from the first embodiment in that it estimates whether the number of unread tags is in the above-mentioned predetermined increased state based on the result of comparing the number of collisions of response waves with the number of no responses, and increases or decreases the number of time slots depending on the number of time slots, but does not switch the modulation method. Therefore, the same reference numerals are used for the components that are substantially the same as those in the first embodiment, and their explanations are omitted.

[0046] Even if there are many unread tags, if the number of collisions of reply waves from each unread tag is large, the number of read RF tags T will be small. On the other hand, even if there are few unread tags, the number of collisions will be greater as the number of set time slots increases. In other words, it can be estimated that the greater the number of reply wave collisions relative to the number of no responses (the number of time slots in which neither reply waves nor collisions are detected), the greater the number of unread tags.

[0047] Therefore, in the modulation method switching process in this embodiment, the number of collisions of response waves and the number of no responses are counted, and based on the result of comparing the number of collisions of response waves and the number of no responses, it is estimated whether the number of unread tags is in the above-mentioned predetermined increase state. Specifically, when the number of collisions of response waves is greater than the number of no responses, it is estimated that the number of unread tags is in the above-mentioned predetermined increase state. Then, when it is estimated that the number of unread tags is in the above-mentioned predetermined increase state, a process of switching from the second modulation method to the first modulation method is performed. Note that, as described above, it is not limited to estimating that the number of unread tags is in the above-mentioned predetermined increase state when the number of collisions of response waves is greater than the number of no responses, but it may also be estimated that the number of unread tags is in the above-mentioned predetermined increase state when, for example, the ratio of the number of collisions of response waves to the number of no responses is equal to or greater than a predetermined value depending on the number of time slots to be set and the surrounding environment. Note that the control unit 21 that performs the no-response number counting process for counting the number of no responses as described above may correspond to one example of a "no-response number counting unit".

[0048] Furthermore, when the number of set time slots is small, the number of collisions of reply waves is likely to increase, and it is easy to estimate that the number of unread tags is in the above-mentioned specified increased state. On the other hand, even in such a case, if the number of collisions of reply waves can be effectively reduced by increasing the number of time slots by one step, it is possible to smoothly read unread RF tags T without switching the modulation method. Furthermore, the process of gradually increasing or decreasing the number of time slots takes less processing time than the process of switching the modulation method.

[0049] For this reason, in the modulation method switching process in this embodiment, if the number of collisions of reply waves can be effectively reduced by increasing the number of time slots, which was set to a small number, by one step, it is deemed necessary to increase the number of time slots without switching the modulation method, and by increasing the number of time slots by one step, it is possible to shorten the processing time for the wireless tag reading process. Note that the control unit 21, which performs the process of adjusting the number of time slots to increase or decrease in stages, can correspond to an example of a "slot adjustment unit".

[0050] Hereinafter, the modulation method switching process performed by the control unit 21 in this embodiment will be described with reference to the flowchart shown in FIG. The control unit 21 starts a modulation method switching process, and when it is determined in the determination process shown in step S101 of Fig. 4 that the number of tag responses is in a predetermined reduced state (Yes in S101), if the modulation method during wireless communication is not set to the second modulation method (set to the first modulation method) (No in S103), it is determined in the determination process of step S201 whether or not the number of slots needs to be reduced. Here, if the number of collisions of response waves is relatively small and the number of no-responses is relatively large compared to the number of time slots, it is determined that the number of slots needs to be reduced (Yes in S201), and a process for reducing the number of slots by one step is performed in step S203. By reducing the number of unnecessary slots in this way, the reading time can be shortened.

[0051] On the other hand, if it is not determined that the number of slots needs to be reduced (No in S201), the modulation method for wireless communication is switched to the second modulation method (S105).

[0052] As described above, when the modulation method during wireless communication is switched to the second modulation method (S105), when it is determined that the number of tag responses is not in a predetermined decreasing state (No in S101), or when the number of slots is decreased (S203), the judgment process of step S205 determines whether the number of unread tags is in a predetermined increasing state.

[0053] In this embodiment, as described above, based on the result of comparing the number of collisions of reply waves with the number of no responses, it is determined whether the number of unread tags is in the above-mentioned predetermined increased state. Here, if it is determined that the number of unread tags is in the above-mentioned predetermined increased state because the number of collisions of reply waves is greater than the number of no responses (Yes in S205), and if the modulation method during wireless communication is not set to the above-mentioned first modulation method (if it is set to the above-mentioned second modulation method) (No in S109), it is determined in the determination process of step S207 whether or not the number of slots needs to be increased.

[0054] Here, if the number of collisions of reply waves can be effectively reduced by increasing the number of time slots, which was set to be small, by one step, it is determined that the number of slots needs to be increased (Yes in S207), and a process for increasing the number of slots by one step is performed in step S209. On the other hand, if the number of time slots cannot be increased because it has already been increased close to the upper limit, it is determined that the number of slots does not need to be increased (No in S207), and the modulation method during wireless communication is switched to the first modulation method (S111). Note that the control unit 21 that performs the process of determining whether or not the number of time slots needs to be increased based on the number of time slots and the number of collisions of reply waves (the determination process in S207) may correspond to one example of a "determination unit".

[0055] As described above, in the wireless tag reading device 10 of this embodiment, based on the comparison result between the number of collisions of response waves counted by the collision number counting process and the number of non-responses counted by the non-response number counting process, it is estimated whether the number of unread tags is in the above-mentioned specified increasing state.

[0056] In this way, based on the comparison result between the number of collisions of reply waves and the number of no-responses, it is possible to estimate whether the number of unread tags is in the above-mentioned predetermined increasing state. In particular, since the number of unread tags is estimated taking into account both the number of collisions of reply waves and the number of no-responses, it is possible to improve the accuracy of estimating the number of unread tags compared to the case where only the number of collisions of reply waves is taken into account.

[0057] In particular, in this embodiment, when it is estimated that the number of unread tags is at a predetermined increasing state (Yes in S205), and it is determined that the number of time slots needs to be increased (Yes in S207), the number of time slots is increased (S209) and the modulation method is not switched.

[0058] In this way, when the number of collisions of response waves can be effectively reduced by increasing the number of time slots that was set to a small number, it is determined that the number of time slots needs to be increased, and the number of time slots is increased without switching the modulation method. If the remaining unread RF tags T can be read by increasing the number of time slots in this way, there is no need to switch the modulation method, which contributes to efficient reading.

[0059] The present invention is not limited to the above-described embodiments, and may be embodied as follows, for example. (1) The modulation method of the wireless tag processor 30 switched by the modulation method switching process is not limited to the above-mentioned first modulation method and second modulation method, and may be three or more modulation methods. For example, when a modulation method that prioritizes reading accuracy over communication speed is set as a third modulation method, the modulation method of the wireless tag processor 30 may be controlled to be switched to the third modulation method when the number of wireless tags T read by the wireless tag processor 30 during a predetermined unit time in a state set to the second modulation method is in a second decreasing state, and may be controlled to be switched to the second modulation method when the number of unread tags during a predetermined unit time in a state set to the third modulation method is estimated to be in a second increasing state. This allows the modulation method to be switched in finer steps so as to more closely follow environmental changes, thereby making it possible to perform more efficient reading. [Explanation of symbols]

[0060] 10...Radio tag reader 21...Control unit (estimation unit, collision number counting unit, no-response number counting unit, judgment unit, slot adjustment unit) 30...Radio tag processing unit (wireless communication unit) T: Radio tag

Claims

1. A radio tag reader that reads data stored in a plurality of radio tags, comprising: a wireless communication unit that wirelessly communicates with the wireless tags using a predetermined modulation method; A control unit that controls a modulation method of the wireless communication unit; an estimation unit that estimates, as an unread tag number, the number of unread wireless tags that can be read by the wireless communication unit from the current location within a predetermined unit time; Equipped with A modulation method that prioritizes communication speed over reading accuracy is defined as a first modulation method, and a modulation method that prioritizes reading accuracy over communication speed in comparison with the first modulation method is defined as a second modulation method. The control unit is a control for switching the modulation method of the wireless communication unit to the second modulation method when the number of wireless tags read by the wireless communication unit during the specified unit time is in a predetermined decreasing state while the modulation method of the wireless communication unit is set to the first modulation method, and a control for switching the modulation method to the first modulation method when the number of unread tags is estimated to be in a predetermined increasing state from the estimation result of the estimation unit during the specified unit time while the modulation method of the wireless communication unit is set to the second modulation method; The estimation unit is a collision number counting unit for counting the number of collisions of reply waves from two or more wireless tags during the predetermined unit time in which a plurality of time slots are set, A radio tag reading device comprising: a collision number counter for counting the number of collisions of the response waves; a collision number counter for counting the number of collisions of the response waves;

2. A radio tag reader that reads data stored in a plurality of radio tags, comprising: a wireless communication unit that wirelessly communicates with the wireless tags using a predetermined modulation method; A control unit that controls a modulation method of the wireless communication unit; an estimation unit that estimates, as an unread tag number, the number of unread wireless tags that can be read by the wireless communication unit from the current location within a predetermined unit time; Equipped with A modulation method that prioritizes communication speed over reading accuracy is defined as a first modulation method, and a modulation method that prioritizes reading accuracy over communication speed in comparison with the first modulation method is defined as a second modulation method. The control unit is a control for switching the modulation method of the wireless communication unit to the second modulation method when the number of wireless tags read by the wireless communication unit during the specified unit time is in a predetermined decreasing state while the modulation method of the wireless communication unit is set to the first modulation method, and a control for switching the modulation method to the first modulation method when the number of unread tags is estimated to be in a predetermined increasing state from the estimation result of the estimation unit during the specified unit time while the modulation method of the wireless communication unit is set to the second modulation method; The estimation unit is a collision number counting unit for counting the number of collisions of reply waves from two or more wireless tags during the predetermined unit time in which a plurality of time slots are set; a no-response counting unit that counts the number of time slots during the unit time during which the wireless communication unit does not receive a response wave from a wireless tag as a no-response number, A radio tag reading device characterized in that it estimates whether the number of unread tags is in the specified increasing state based on a comparison result between the number of collisions of the response wave counted by the collision number counting unit and the number of no-responses counted by the no-response number counting unit.

3. When a modulation method that places more importance on reading accuracy than on communication speed compared to the second modulation method is set as a third modulation method, The control unit is The radio tag reading device according to claim 1 or 2, characterized in that when the modulation method of the wireless communication unit is set to the second modulation method and the number of wireless tags read by the wireless communication unit during the specified unit time is in a second decreasing state, control is performed to switch to the third modulation method, and when the number of unread tags is estimated to be in a second increasing state from the estimation result of the estimation unit during the specified unit time while set to the third modulation method, control is performed to switch to the second modulation method.

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