Wireless tag communication device, image forming device, and program

Abstract

To perform stable communication with a plurality of wireless tags installed on one sheet.SOLUTION: A wireless tag communication device includes an antenna, a first maximum value acquisition unit, a second maximum value acquisition unit, a first minimum value acquisition unit, a second minimum value acquisition unit, and a polarization direction determination unit. The wireless tag communication device: acquires, for each wireless tag, a maximum value M1(k) of a received power intensity for each wireless tag when radio wave is outputted, from the antenna, to a sheet installed with the wireless tags in n-pieces, in a first polarization direction; acquires, for each wireless tag, a maximum value M2(k) of the received power intensity for each wireless tag when the radio wave is outputted from the antenna, in a second polarization direction different from the first polarization direction; and acquires a minimum value m1 of the M1(k). The second minimum value acquisition unit acquires a minimum value m2 of the M2(k), and determines the polarization direction in which either of the m1 or the m2, whichever is not smaller, is acquired, as the polarization direction of the radio wave to be outputted to the sheet.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a wireless tag communication device, an image forming device, and a program. [Background technology]

[0002] 2. Description of the Related Art There are wireless tag communication devices capable of communicating with sheets to which wireless tags using RFID (Radio Frequency Identifier) ​​technology are attached, and there are also image forming apparatuses equipped with wireless tag communication devices.

[0003] Some RFID tag communication devices can output radio waves of two types of polarization to a sheet. There are also sheets with multiple RFID tags. When outputting radio waves to a sheet with multiple RFID tags, stable communication can be achieved by outputting radio waves of the appropriate polarized wave out of the two types of polarization. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-290508 Summary of the Invention [Problem to be solved by the invention]

[0005] However, it is not always possible to determine which polarization is appropriate depending on the position on the sheet where the wireless tag is provided, and this can make it difficult to achieve stable communication.

[0006] The problem to be solved by the present invention is to provide a radio tag communication device, an image forming device, and a program that are capable of stable communication with multiple radio tags attached to a single sheet. [Means for solving the problem]

[0007] An RFID tag communication device according to an embodiment includes an antenna, a first maximum value acquisition unit, a second maximum value acquisition unit, a first minimum value acquisition unit, a second minimum value acquisition unit, and a polarization direction determination unit. The antenna is capable of switching the polarization direction of radio waves output to RFID tags. The first maximum value acquisition unit acquires, for each RFID tag, a maximum value M1(k) (k = 1 to n) of the received power intensity of each RFID tag when radio waves are output from the antenna in a first polarization direction for a sheet on which n (n is an integer equal to or greater than 2) RFID tags are provided. The second maximum value acquisition unit acquires, for each RFID tag, a maximum value M2(k) (k = 1 to n) of the received power intensity of each RFID tag when radio waves are output from the antenna in a second polarization direction different from the first polarization direction. The first minimum value acquisition unit acquires a minimum value m1 of M1(k) (k = 1 to n). The second minimum value acquisition unit acquires the minimum value m2 of M2(k) (k=1 to n). The polarization direction determination unit determines the polarization direction of the radio wave to be output to the sheet as the polarization direction of the radio wave that is acquired as the smaller of m1 and m2. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an external view showing an example of the overall configuration of an image forming apparatus according to an embodiment; [Figure 2] FIG. 1 is a block diagram showing a hardware configuration of an image forming apparatus according to an embodiment. [Figure 3] FIG. 2 is a diagram showing a specific example of the internal configuration of the image forming apparatus according to the embodiment. [Figure 4A] A diagram showing sheet A. [Figure 4B] A diagram showing sheet B. [Figure 4C] A diagram showing sheet C. [Figure 4D] A diagram showing sheet D. [Figure 5] Sheet and graph showing received power intensity. [Figure 6] Sheet and graph showing received power intensity. [Figure 7] Sheet and graph showing received power intensity. [Figure 8] Sheet and graph showing received power intensity. [Figure 9]Sheet and graph showing received power intensity. [Figure 10] Sheet and graph showing received power intensity. [Figure 11] 10 is a flowchart showing the flow of a proper polarization acquisition process. [Figure 12] 10 is a flowchart showing the flow of a proper polarization acquisition process. [Figure 13] 10 is a flowchart showing the flow of a proper polarization acquisition process. DETAILED DESCRIPTION OF THE INVENTION

[0009] The RFID tag communication device of the embodiment enables stable communication with multiple RFID tags attached to a single sheet. The RFID tag communication device of the embodiment and an image forming apparatus equipped with the RFID tag communication device will be described in detail below.

[0010] 1 is an external view showing an example of the overall configuration of an image forming apparatus 100 according to an embodiment. The image forming apparatus 100 is, for example, a multifunction peripheral. The image forming apparatus 100 includes a display 110, a control panel 120, a printer unit 130, a sheet storage unit 140, and an image reading unit 200. The printer unit 130 of the image forming apparatus 100 may be an electrophotographic device that fixes a toner image, or may be an inkjet device.

[0011] The image forming apparatus 100 forms an image on a sheet using a developer such as toner. The sheet is, for example, paper or label paper. The sheet may be a sheet with a wireless tag attached. The sheet may be any material on whose surface the image forming apparatus 100 can form an image. Note that a sheet with a wireless tag attached may be a sheet in which the wireless tag is attached to the surface of the sheet, or a sheet in which the wireless tag is embedded inside the sheet. The wireless tag in this embodiment is a wireless tag that uses RFID (Radio Frequency IDentifier) ​​technology, and is also called an RF tag.

[0012] The display 110 is an image display device such as a liquid crystal display, an organic EL (Electro Luminescence) display, etc. The display 110 displays various information related to the image forming apparatus 100.

[0013] Control panel 120 has a plurality of buttons. Control panel 120 accepts operations from a user. Control panel 120 outputs a signal corresponding to the operation performed by the user to a control unit of image forming apparatus 100. Note that display 110 and control panel 120 may be configured as an integrated touch panel.

[0014] The printer unit 130 forms an image on a sheet based on image information generated by the image reading unit 200 or image information received via a communication path. The printer unit 130 forms an image by, for example, the following process: The printer unit 130 forms an electrostatic latent image on a photosensitive drum based on the image information. The printer unit 130 forms a visible image by attaching a developer to the electrostatic latent image. An example of the developer is toner. The printer unit 130 transfers the visible image onto the sheet. The printer unit 130 fixes the visible image on the sheet by applying heat and pressure to the sheet. The sheet on which the image is formed may be a sheet stored in the sheet storage unit 140 or a manually fed sheet. The sheet on which the image is formed is discharged to the paper discharge unit 210.

[0015] The sheet storage section 140 stores sheets to be used for image formation in the printer section 130. In this embodiment, the sheet storage section 140 is provided with four paper feed cassettes. The image reading unit 200 reads the image information of the object to be read as brightness and darkness of light. The image reading unit 200 records the read image information. The recorded image information may be transmitted to another information processing device via a network. The recorded image information may be formed into an image on a sheet by the printer unit 130.

[0016] 2 is a block diagram showing the hardware configuration of an image forming apparatus 100 according to an embodiment. The image forming apparatus 100 includes a display 110, a control panel 120, a printer unit 130, a paper feed unit 205, a storage device 151, a memory 152, a processor 153, a wireless tag communication device 154, an external interface 155, and an image reading unit 200. The display 110, the control panel 120, the printer unit 130, and the image reading unit 200 have been described above, and therefore further description thereof will be omitted. The paper feed unit 205 is a mechanism that feeds sheets placed in the sheet storage unit 140 and a manual feed tray (described later) to the printer unit 130. The storage device 151, the memory 152, the processor 153, the wireless tag communication device 154, and the external interface 155 will be described below. The functional units are connected to each other via a system bus 160 to enable data communication.

[0017] The storage device 151 is, for example, a hard disk or a solid state drive (SSD) and stores various data. The various data include print jobs received from an external communication device and software programs for controlling the operation of each functional unit of the image forming apparatus 100. The print job may be a job related to double-sided printing or a job related to printing multiple sheets. The print job may also include image information related to the image to be printed on the sheet.

[0018] The memory 152 temporarily stores data used by each functional unit of the image forming apparatus 100. The memory 152 is, for example, a RAM (Random Access Memory). The memory 152 may also store digital data generated by the image reading unit 200. The memory 152 may also temporarily store a print job being printed by the printer unit 130 and write information to be written to a wireless tag.

[0019] Processor 153 controls the operation of each functional unit of image forming apparatus 100. Processor 153 loads a software program stored in storage device 151 onto memory 152 and executes the software program to perform processing. Here, an example of specific processing by processor 153 will be described.

[0020] The processor 153 controls printing on sheets with wireless tags attached based on print jobs received via an external communication device or the control panel 120. When the processor 153 receives a print job for sheets with wireless tags attached, it acquires the writing information specified in the print job and the image information associated with the writing information from, for example, a writing information server (not shown). The image information associated with the writing information is information about the image to be formed on the sheet. Note that the image information does not necessarily have to be associated with the writing information. In this case, it is sufficient that the image information is included in the print job. The processor 153 controls the paper feed unit 205. The paper feed unit 205 feeds sheets with wireless tags attached.

[0021] The processor 153 controls the printer unit 130. The printer unit 130 forms an image indicated by the image information on a sheet. The sheet on which the image has been formed is discharged to the paper discharge unit 210. The processor 153 communicates with the wireless tag communication device 154. For example, the processor 153 notifies the wireless tag communication device 154 that sheet transport has started.

[0022] The wireless tag communication device 154 includes a processing unit 501, a storage device 502, a communication device 503, and an antenna 504. The processing unit 501 is, for example, a central processing unit (CPU), an application specific integrated circuit (ASIC), etc. The storage device 502 is, for example, a read only memory (ROM), a random access memory (RAM), etc. The storage device 502 stores the received power intensity (RSSI) of the wireless tag, the time when the received power intensity was acquired, or identification information for identifying the wireless tag (for example, a unique identifier (UID)).

[0023] The communication device 503 outputs radio waves in two different polarization directions (first polarization direction and second polarization direction). The communication device 503 acquires information from the radio tag and writes information to the radio tag using an antenna 504 that can switch the polarization direction of the radio waves output to the radio tag. The radio tag communication device 154 writes information to the radio tag attached to the sheet. The radio tag communication device 154 also reads the above-mentioned identification information and the like from the radio tag attached to the sheet. In the following description, the radio waves in the first polarization direction may be simply referred to as the "first polarization." Similarly, the radio waves in the second polarization direction may be simply referred to as the "second polarization."

[0024] The external interface 155 transmits and receives data to and from other devices. Here, the other devices are, for example, information processing devices such as personal computers, tablet computers, or smart devices. The external interface 155 operates as an input interface and receives data or instructions transmitted from other devices. The instructions transmitted from other devices are print jobs, etc. The data transmitted from other devices are writing information and image information associated with the writing information, etc. The external interface 155 also operates as an output interface and transmits data to other devices.

[0025] Fig. 3 is a diagram showing the internal configuration of image forming apparatus 100. A manual feed tray 220 is newly shown in Fig. 3. A sheet is transported from sheet storage unit 140 or feed tray 220 along a transport path 250, an image is formed on the sheet in printer unit 130, and the sheet is discharged to paper discharge unit 210 by paper discharge rollers 156. A wireless tag communication device 154 communicates with a wireless tag while the sheet is being transported along transport path 250.

[0026] Next, an example of a sheet on which multiple wireless tags are provided will be described. As described above, the wireless tag communication device 154 is capable of outputting first and second polarized waves. However, it is often difficult to determine which radio wave is most suitable for a sheet, depending on factors such as the position on the sheet on which the wireless tag is provided. Therefore, manufacturers of the wireless tag communication device 154 and image forming apparatuses 100 equipped with the wireless tag communication device 154 may preset recommended polarizations for various sheets. To determine the polarization direction, a suitable polarization acquisition method, which will be described later, is performed.

[0027] 4A, 4B, 4C, and 4D are diagrams showing four types of sheet examples each having a plurality of wireless tags attached thereto. The conveyance direction of each sheet is the upward direction in the diagram. That is, the sheet is conveyed facing upward in the diagram. In addition, in FIGS. 4A, 4B, 4C, and 4D, reference numerals 400-1, 400-2, and 400-3 indicate wireless tags. FIG. 4A is a diagram showing an example of a sheet each having two wireless tags 400-1 and 400-2 attached thereto. In the sheet shown in FIG. 4A, wireless tag 400-1 is attached parallel to the conveyance direction, and wireless tag 400-2 is attached perpendicular to the conveyance direction. The type of sheet shown in FIG. 4A may be referred to as "sheet A" in the following description.

[0028] Fig. 4B is a diagram showing an example of a sheet on which three wireless tags 400-1, 400-2, and 400-3 are provided. In the sheet shown in Fig. 4B, the wireless tags 400-1, 400-2, and 400-3 are provided at equal intervals and perpendicular to the conveyance direction. In the following description, the type of sheet shown in Fig. 4B may be referred to as "sheet B."

[0029] Fig. 4C is a diagram showing an example of a sheet on which two wireless tags 400-1 and 400-2 are provided. In the sheet shown in Fig. 4C, the wireless tags 400-1 and 400-2 are spaced closer together than in Fig. 4B, and both are provided perpendicular to the conveying direction. The type of sheet shown in Fig. 4C may be referred to as "sheet C" in the following description.

[0030] Fig. 4D is a diagram showing an example of a sheet on which two wireless tags 400-1 and 400-2 are provided. In the sheet shown in Fig. 4D, the wireless tags 400-1 and 400-2 are provided on the left side as viewed from the front, parallel to the conveyance direction. The type of sheet shown in Fig. 4D may be referred to as "sheet D" in the following description.

[0031] The following Figures 5 to 10 explain the relationship between one of the four types of sheets, Sheets A to D, and the received power intensity. Figures 5 to 10 show graphs of the results of measuring the received power intensity using the appropriate polarization acquisition method described below. Note that Sheet A is used in Figures 5, 7, and 8, but the received power intensity is different in each figure. This is because Sheet A is reused for the sake of simplicity, and is explained as a sheet with different properties in Figures 5, 7, and 8.

[0032] The following describes a method for obtaining the appropriate polarization. In the following description, if there is no response from a wireless tag, the received power strength of that wireless tag is set to 0.

[0033] First, the radio tag communication device 154 acquires, for each radio tag, the maximum value M1(k) (k=1 to n) of the received power intensity of each radio tag when radio waves are output from the antenna 504 in the first polarization direction for a sheet on which n (n is an integer greater than or equal to 2) radio tags are provided.

[0034] Next, the RFID tag communication device 154 acquires, for each RFID tag, the maximum value M2(k) (k=1 to n) of the received power intensity of each RFID tag when the antenna 504 outputs radio waves in the second polarization direction.

[0035] The wireless tag communication device 154 acquires the minimum value m1 of M1(k) (k=1 to n), acquires the minimum value m2 of M2(k) (k=1 to n), and determines the polarization direction of the acquired m1 or m2, whichever is not the smaller, as the polarization direction of the radio waves to be output to the sheet.

[0036] 5 to 10, which will be described below, are graphs for n=2 or n=3, with the vertical axis representing the received power intensity of each wireless tag attached to the sheet and the horizontal axis representing time. Then, while the wireless tag communication device 154 is outputting the first polarized wave, a sheet of any type is conveyed, and the wireless tag communication device 154 measures the received power intensity. Next, while the wireless tag communication device 154 is outputting the second polarized wave, a sheet of the same type as the first sheet conveyed is conveyed again, and the wireless tag communication device 154 measures the received power intensity. The first sheet may be conveyed again, or a sheet of the same type but different from the first sheet may be conveyed.

[0037] As described above, the RFID tag communication device 154 outputs the first polarized wave and then the second polarized wave, and therefore the horizontal axis representing time indicates that the first polarized wave and then the second polarized wave are output in that order. Also, in Figures 5 to 10, the received power intensity of tag 400-1 provided on each sheet is indicated by a solid line, and the received power intensity of tag 400-2 is indicated by a dashed line. In Figure 6, the received power intensity of tag 400-3 is indicated by a dashed line.

[0038] Furthermore, when the first polarized wave is output from antenna 504 of wireless tag communication device 154, the maximum value of the received power intensity of tag 400-1 is set to M1(1), the maximum value of the received power intensity of tag 400-2 is set to M1(2), and the maximum value of the received power intensity of tag 400-3 is set to M1(3).When the second polarized wave is output from antenna 504 of wireless tag communication device 154, the maximum value of the received power intensity of tag 400-1 is set to M2(1), the maximum value of the received power intensity of tag 400-2 is set to M2(2), and the maximum value of the received power intensity of tag 400-3 is set to M2(3).

[0039] Furthermore, m1 indicates the minimum value of M1(1) and M1(2), or the minimum value of M1(1), M1(2), and M1(3). m2 indicates the minimum value of M2(1) and M2(2), or the minimum value of M2(1), M2(2), and M2(3). The polarization direction obtained by obtaining the non-smaller of m1 and m2 is determined as the polarization direction of the radio wave to be output to the sheet. Note that, as indicated by the symbols M1 and m2, the number (1 or 2) following M or m corresponds to the polarization direction. That is, M1 and m1 are values ​​relating to the first polarization direction, and M2 and m2 are values ​​relating to the second polarization direction. Based on the above, the following explanation will be given with reference to FIGS. 5 to 10.

[0040] Figure 5 is a graph showing sheet A and received power intensity. Since sheet A has two wireless tags, n=2. As shown in Figure 5, m1 is M1(2) and m2 is M2(1). The smaller of m1 and m2 is M2(1). The polarization direction in which M2(1) is obtained is the second polarization direction, so the second polarization direction is determined to be the appropriate polarization direction for sheet A. As a result, the wireless tag communication device 154 determines the second polarization direction as the polarization direction of the radio waves to be output to sheet A.

[0041] FIG. 6 is a graph showing sheet B and received power intensity. Since three wireless tags are provided on sheet B, n=3. As shown in FIG. 6, m1 is M1(3) and m2 is M2(1). The smaller of m1 and m2 is M1(3). Since the polarization direction in which M1(3) is obtained is the first polarization direction, the first polarization direction is determined to be the appropriate polarization direction for sheet A. As a result, the wireless tag communication device 154 determines the first polarization direction as the polarization direction of the radio waves to be output to sheet B.

[0042] 7, a case will be described in which neither m1 nor m2 is 0 and there is no significant difference between m1 and m2. When there is no significant difference between m1 and m2, the appropriate polarization direction may be either the first polarization direction or the second polarization direction, but the following may also be used.

[0043] The RFID tag communication device 154 sorts M1(k) in ascending order to obtain m1(k), and sorts M2(k) in ascending order to obtain m2(k). The RFID tag communication device 154 then increments k from 1 and acquires the k where |m1(k) - m2(k)| is equal to or greater than the threshold m for the first time. That is, the RFID tag communication device 154 finds the k with the largest difference (a difference equal to or greater than the threshold) in ascending order of maximum value. The RFID tag communication device 154 then determines the polarization direction of the acquired value, whichever is not the smaller of m1(k) and m2(k), as the polarization direction of the radio wave to be output to the sheet.

[0044] When |m1(k)-m2(k)| is less than m even when k is the maximum value, i.e., k=n, the RFID tag communication device 154 acquires the polarization direction acquired as the appropriate polarization direction, whichever of m1(1) and m2(1) is not the smaller. This is because it is preferable that the minimum received power intensity (m1(1), m2(1)) is not small.

[0045] Since there is no significant difference between m1(j) and m2(j) for j < k, for these, an appropriate polarization direction may be either the first polarization direction or the second polarization direction. On the other hand, since there is a significant difference between m1(k) and m2(k), it is better to determine the polarization direction of the radio wave output to the sheet as the polarization direction in which the larger of m1 and m2 described above was obtained. By doing so, more stable communication can be achieved. Note that the "significant difference", that is, the threshold value m, is appropriately determined according to the performance of the wireless tag communication device 154 and the wireless tag, or design considerations, etc. Based on the above, FIG. 7 will be described.

[0046] FIG. 7 is a graph showing the sheet A and the received power intensity. Since two wireless tags are provided on the sheet A, it corresponds to n = 2. As shown in FIG. 7, when m1(k) is the sorted result of M1(k) in ascending order, m1(1) = M1(2) and m1(2) = M1(1). When m2(k) is the sorted result of M2(k) in ascending order, m2(1) = M2(2) and m2(2) = M2(2).

[0047] In FIG. 7, let |m1(1) - m2(1)| < m and |m1(2) - m2(2)| ≥ m. In this case, as described above, the wireless tag communication device 154 obtains the polarization direction of the larger of m1(2) and m2(2) as the polarization direction of the radio wave output to the sheet. The larger of m1(2)(=M1(1)) and m2(2)(=M2(2)) is M2(2). Since the polarization direction in which M2(2) was obtained is the second polarization direction, the second polarization direction is set as the appropriate polarization direction for the sheet A. Thereby, the wireless tag communication device 154 determines the second polarization direction as the polarization direction of the radio wave output to the sheet A.

[0048] Next, a case where m1 = m2 = 0 will be described using FIG. 8. FIG. 8 is a graph showing sheet A and received power intensity. Since two wireless tags are provided on sheet A, n = 2 applies. As shown in FIG. 8, M1(1) ≠ 0 and M1(2) = 0. Furthermore, M2(1) = 0 and M2(2) ≠ 0. Therefore, m1 = m2 = 0. In such a case, if only the first polarization or only the second polarization is acquired as the appropriate polarization direction, the wireless tag communication device 154 cannot communicate with either of the wireless tags. Therefore, both the first polarization direction and the second polarization direction are determined to be appropriate polarization directions for sheet A. As a result, the wireless tag communication device 154 determines both the first polarization direction and the second polarization direction as the polarization direction of the radio waves to be output to sheet A.

[0049] In addition, when using both the first polarization direction and the second polarization direction, the method of writing data to a wireless tag is to output the first polarization, and once writing to the wireless tag is complete, immediately output the second polarization and complete writing to the wireless tag.

[0050] To distinguish between the method of determining the polarization direction based on the non-smaller of m1 and m2 as shown in Figures 5 and 6 and the method of using a significant difference as shown in Figure 7, the former is referred to as the "simple minimum value acquisition method."

[0051] Next, a case where either m1 or m2 is 0 will be described using Figures 9 and 10. Figure 9 is a graph showing sheet C and received power intensity. Since two wireless tags are provided on sheet C, n=2 applies. As shown in Figure 9, M1(1)≠0 and M1(2)≠0. Also, M2(1)=0 and M2(2)=0. Therefore, m1≠0 and m2=0. In such a case, the first polarization direction is determined to be the appropriate polarization direction for sheet C. As a result, the wireless tag communication device 154 determines the first polarization direction as the polarization direction of the radio waves to be output to sheet C.

[0052] FIG. 10 is a graph showing sheet D and received power intensity. Since two wireless tags are provided on sheet D, n=2 applies. As shown in FIG. 10, M1(1)=0 and M1(2)=0. Furthermore, M2(1)≠0 and M2(2)≠0. Therefore, m1=0 and m2≠0. In such a case, the second polarization direction is determined to be the appropriate polarization direction for sheet D. As a result, the wireless tag communication device 154 determines the second polarization direction as the polarization direction of the radio waves to be output to sheet D.

[0053] Next, the method for obtaining the appropriate polarization will be described using a flowchart. Fig. 11 is a flowchart showing the flow of the appropriate polarization obtaining process. In the process described below, for ease of understanding, UIDs for identifying n wireless tags attached to a sheet to be conveyed are assumed to be 1 to n. For example, the UID of wireless tag 400-1 is assumed to be 1, and the UID of wireless tag 400-2 is assumed to be 2.

[0054] 11, the wireless tag communication device 154 receives a conveyance start signal indicating the start of sheet conveyance from the processor 153 that controls the paper feed unit 205 (ACT101). The wireless tag communication device 154 outputs a first polarized wave (ACT102). The wireless tag communication device 154 acquires the received power intensity from each wireless tag (ACT103), and stores the acquired received power intensity and a UID that identifies the wireless tag from which the received power intensity was acquired in the storage device 502 (ACT104). For example, the wireless tag communication device 154 stores the information so that the correspondence between the polarization, the wireless tag, and the received power intensity can be determined, such as (first polarized wave, UID, received power intensity).

[0055] By doing this, multiple (first polarization, UID, received power intensity) values ​​are obtained for each UID. For example, multiple received power intensities are obtained for each UID, such as (first polarization, 1, r1), (first polarization, 1, r2), ..., (first polarization, 1, rs). Note that s is an integer greater than or equal to 0, and is a different value for each UID depending on factors such as the state of communication with the wireless tag corresponding to the UID.

[0056] The wireless tag communication device 154 determines whether or not a conveyance end signal indicating that conveyance of the sheet has been completed has been received from the processor 153 (ACT105). If a conveyance end signal has not been received (ACT105: NO), the process returns to ACT103. Therefore, the wireless tag communication device 154 intermittently stores the combinations (first polarization, UID, received power intensity) while the sheet is being conveyed.

[0057] When the end of transportation is received (ACT105: YES) and the start of a second transportation is received (ACT106), the wireless tag communication device 154 outputs the second polarized wave (ACT107). The wireless tag communication device 154 acquires the received power intensity from each wireless tag (ACT108) and stores the acquired received power intensity and the UID that identifies the wireless tag from which the power intensity was acquired in the storage device 502 (ACT109). For example, the wireless tag communication device 154 stores the information so that the correspondence between the polarization, the wireless tag, and the received power intensity can be determined, such as (second polarized wave, UID, received power intensity).

[0058] By doing this, similar to the case of the first polarization, multiple (second polarization, UID, received power intensity) values ​​are obtained for each UID. For example, multiple received power intensities are obtained for each UID, such as (second polarization, 1, r1), (second polarization, 1, r2), ..., (second polarization, 1, rs). Note that s is an integer greater than or equal to 0, and is a different value for each UID depending on factors such as the state of communication with the wireless tag corresponding to the UID.

[0059] The wireless tag communication device 154 determines whether or not a conveyance end signal indicating that conveyance of the sheet has been completed has been received from the processor 153 (ACT110). If a conveyance end signal has not been received (ACT110: NO), the process returns to ACT108. Therefore, the wireless tag communication device 154 intermittently stores the combinations (second polarization, UID, received power intensity) while the sheet is being conveyed. The following description will be continued with reference to FIG. 12.

[0060] 12, the radio tag communication device 154 acquires M1(k) (k=1 to n) (ACT201). When s is 1 or more, the radio tag communication device 154 sets the maximum rq among (first polarization, k, rq) (1≦q≦s) to M1(k). When s is 0, M1(k)=0. Similarly, the radio tag communication device 154 acquires M2(k) (k=1 to n) (ACT201). When s is 1 or more, the radio tag communication device 154 sets the maximum rq among (second polarization, k, rq) (1≦q≦s) to M2(k). When s is 0, M2(k)=0.

[0061] Next, the RFID tag communication device 154 determines whether or not to acquire the proper polarization by the simple minimum value acquisition method described with reference to Figures 5 and 6 (ACT203). Here, the RFID tag communication device 154 may store, for example, a settable flag indicating whether or not to acquire the proper polarization by the simple minimum value acquisition method, and may make the determination using this flag. Alternatively, the RFID tag communication device 154 may display an inquiry screen on the control panel 120 and make the determination based on the content entered in response to the inquiry.

[0062] When the appropriate polarization is acquired using the simple minimum value acquisition method (ACT203: YES), the wireless tag communication device 154 assigns the minimum value of M1(k) to m1 (ACT213), assigns the minimum value of M2(k) to m2 (ACT214), and proceeds to ACT301 in Figure 13.

[0063] If the appropriate polarization is not acquired using the simple minimum value acquisition method (ACT203: NO), the method described in Fig. 7 is used. The RFID tag communication device 154 sorts M1(k) in ascending order as described in Fig. 7, and acquires m1(k) (ACT204). Similarly, the RFID tag communication device 154 sorts M2(k) in ascending order as described in Fig. 7, and acquires m2(k) (ACT205). The RFID tag communication device 154 assigns 1 to k (step S206).

[0064] The wireless tag communication device 154 determines whether |m1(1) - m2(1)| ≥ m (ACT207). If |m1(1) - m2(1)| ≥ m (ACT207: YES), since there is a significant difference, the wireless tag communication device 154 substitutes m1(k) into m1 (ACT211), substitutes m2(k) into m2 (ACT212), and proceeds to ACT301 in FIG. 13.

[0065] If |m1(1) - m2(1)| < m (ACT207: NO), since there is no significant difference, the wireless tag communication device 154 increments k by 1 (ACT208) and determines whether k > n (ACT209). That is, it determines whether k has exceeded the upper limit. If k ≤ n (ACT209: NO), the wireless tag communication device 154 determines again whether |m1(1) - m2(1)| ≥ m (ACT207). If k > n (ACT209: YES), the wireless tag communication device 154 substitutes 1 into k (step S210) and proceeds to ACT211 described above. The following continues to be described using FIG. 13.

[0066] In FIG. 13, the wireless tag communication device 154 determines whether m1 = m2 = 0 (ACT301). If m1 = m2 = 0 (ACT301: YES), the wireless tag communication device 154 determines the polarization directions of the radio waves output to the sheet A in both the first polarization direction and the second polarization direction (ACT302) and ends the process.

[0067] If m1 = m2 = 0 is not satisfied (ACT301: NO), the wireless tag communication device 154 determines whether m1 ≥ m2 (ACT303). If m1 ≥ m2 (ACT303: YES), the wireless tag communication device 154 determines the polarization direction of the radio wave output to the sheet as the first polarization direction (ACT304) and ends the process. If m1 < m2 (ACT3: NO), the wireless tag communication device 154 determines the polarization direction of the radio wave output to the sheet as the second polarization direction (ACT305) and ends the process.

[0068] According to the embodiment described above, by determining the radio wave with the polarization direction in which the minimum value of the maximum value of the received power intensity is not small, it is possible to perform stable communication with multiple wireless tags attached to a single sheet.

[0069] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0070] 100...image forming apparatus, 110...display, 120...control panel, 130...printer unit, 140...sheet storage unit, 151...storage device, 152...memory, 153...processor, 154...wireless tag communication device, 155...external interface, 156...paper discharge roller, 160...system bus, 200...image reading unit, 205...paper feed unit, 210...paper discharge unit, 220...manual feed tray, 250...conveyance path, 400-1, 400-2, 400-3...wireless tag, 501...arithmetic unit, 502...storage device, 503...communication device, 504...antenna

Claims

1. an antenna capable of switching the polarization direction of radio waves output to a wireless tag; a first maximum value acquiring unit that acquires, for each wireless tag, a maximum value M1(k) (k=1 to n) of the received power intensity of each wireless tag when radio waves are output from the antenna in a first polarization direction to a sheet on which n wireless tags (n is an integer equal to or greater than 2) are provided; a second maximum value acquiring unit that acquires, for each wireless tag, a maximum value M2(k) (k=1 to n) of the received power intensity of each wireless tag when radio waves are output from the antenna in a second polarization direction different from the first polarization direction; a first minimum value acquisition unit that acquires a minimum value m1 of M1(k) (k=1 to n); a second minimum value acquisition unit that acquires the minimum value m2 of M2(k) (k=1 to n); a polarization direction determination unit that determines the polarization direction obtained by determining which of m1 and m2 is not smaller as the polarization direction of the radio wave to be output to the sheet; A wireless tag communication device comprising:

2. an antenna capable of switching the polarization direction of radio waves output to a wireless tag; a first maximum value acquiring unit that acquires, for each wireless tag, a maximum value M1(k) (k=1 to n) of the received power intensity of each wireless tag when radio waves are output from the antenna in a first polarization direction to a sheet on which n wireless tags (n is an integer equal to or greater than 2) are provided; a second maximum value acquiring unit that acquires, for each wireless tag, a maximum value M2(k) (k=1 to n) of the received power intensity of each wireless tag when radio waves are output from the antenna in a second polarization direction different from the first polarization direction; a significant difference acquisition unit that sorts M1(k) in ascending order, defines m1(k), sorts M2(k) in ascending order, and increments k from 1 to acquire the k at which |m1(k)-m2(k)| is equal to or greater than a threshold m; a polarization direction determination unit that determines the polarization direction obtained by determining which of m1(k) and m2(k) is not the smaller as the polarization direction of the radio wave to be output to the sheet; A wireless tag communication device comprising:

3. The radio tag communication device according to claim 1, wherein the polarization direction determination unit determines both the first polarization direction and the second polarization direction as the polarization direction of the radio wave to be output to the sheet when m1 = m2 = 0.

4. The RFID tag communication device according to any one of claims 1 to 3, a conveying unit that conveys the sheet; an image forming unit that forms an image on the sheet; Equipped with The wireless tag communication device is an image forming apparatus that outputs radio waves to the sheet being transported by the transport unit.

5. A program that causes a computer to function as a radio tag communication device having an antenna that can switch the polarization direction of radio waves output to a radio tag, The computer a first maximum value acquiring unit that acquires, for each wireless tag, a maximum value M1(k) (k=1 to n) of the received power intensity of each wireless tag when radio waves are output from the antenna in a first polarization direction to a sheet on which n wireless tags (n is an integer equal to or greater than 2) are provided; a second maximum value acquiring unit that acquires, for each wireless tag, a maximum value M2(k) (k=1 to n) of the received power intensity of each wireless tag when radio waves are output from the antenna in a second polarization direction different from the first polarization direction; a first minimum value acquisition unit that acquires a minimum value m1 of M1(k) (k=1 to n); a second minimum value acquisition unit that acquires the minimum value m2 of M2(k) (k=1 to n); a polarization direction determination unit that determines the polarization direction obtained by determining which of m1 and m2 is not smaller as the polarization direction of the radio wave to be output to the sheet; A program to make it function as such.

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