Information reading device

Abstract

To provide a configuration capable of improving a reading performance without providing any movable parts and the like.SOLUTION: An article G to which a radio tag T is attached is housed in a housing space S formed so as to suppress leakage of electric waves by a casing 20, and reading processing for reading information from the radio tag T housed in the housing space S by utilizing antennas 31, 32 disposed in the housing space S is performed by a control part 40. The control part 40 includes: output frequency changing means for changing an output frequency of electric waves outputted from each of the antennas 31, 32; and phase difference changing means for changing a phase difference by changing phase of electric waves outputted from each of the antennas 31, 32.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an information reading device that reads information from a wireless tag attached to an article accommodated in an accommodation space.

Background Art

[0002] Conventionally, in order to acquire information regarding an article accommodated in an accommodation space such as a storage box, a wireless tag recording information regarding the article is attached to the article, and a technique of reading information from the wireless tag of the article via an antenna disposed in the storage box has been widely adopted. As a technique for reading information from the wireless tag of an article thus accommodated, for example, a reading device disclosed in Patent Document 1 below is known. This reading device includes a housing whose inner surface is formed of a radio wave reflecting material and an antenna accommodated inside the housing, and when reading information from an RFID tag attached to a document accommodated in the housing, by adjusting the distance between the upper surface and the lower surface constituting the inner surface of the housing, it is configured to suppress the influence of a region (null point) where the electric field strength extremely weakens due to interference of radio waves reflected in the housing and improve the reading performance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, since the null range changes depending on the accommodation state of the article etc., when there are many in-and-out operations of the article with respect to the accommodation space, in the configuration of suppressing the influence of null by adjusting the distance between the surface of the housing and the lower surface as described above, it is necessary to perform the above distance adjustment every time the article is taken in and out. For this reason, in the configuration provided with a movable part etc. for adjusting the distance as described above, there is a problem that not only the power consumption required for the distance adjustment increases, but also the manufacturing cost increases in order to ensure durability.

[0005] The present invention has been made to solve the above-described problems, and an object thereof is to provide a configuration capable of enhancing reading performance without providing a movable part or the like.

Means for Solving the Problems

[0006] To achieve the above object, the invention according to claim 1 of the claims is An information reading device (10) that reads information from a wireless tag (T) attached to an article (G) housed in a housing space (S), A housing body (21) in which an opening (21a) through which the article is inserted and removed is formed, and a lid body (22) that forms the housing space by closing the opening, and a housing (20) configured to suppress radio wave leakage from the housing space; A plurality of antennas (31, 32) disposed in the housing space; A control unit (40) that performs a reading process of reading information from the wireless tag housed in the housing space using the plurality of antennas; Comprising The control unit includes output frequency changing means for changing the output frequency of radio waves respectively output from the plurality of antennas, and phase difference changing means for changing the phase difference by changing the phases of the radio waves respectively output from the plurality of antennas. Based on the information obtained by the reading process intermittently performed on at least one wireless tag accommodated in the accommodation space as an opening / closing determination tag, a determination unit determines whether the lid is in an open / closed state such that the opening is closed again after being opened. Comprising The reading process is intermittently performed on the opening / closing determination tag until a positive determination is made by the determination unit, and in a predetermined period after the positive determination is made by the determination unit, the reading process is performed on all the wireless tags accommodated in the accommodation space. Characterized by Note that the reference numerals in each of the above parentheses indicate the correspondence with the specific means described in the embodiments described later.

Effects of the Invention

[0007] In the invention of claim 1, an article with a wireless tag attached thereto is accommodated in an accommodation space formed by a housing so as to suppress radio wave leakage, and a reading process for reading information from the wireless tag accommodated in the accommodation space is performed by a control unit using a plurality of antennas arranged in the accommodation space. The control unit is provided with an output frequency changing means for changing the output frequency of radio waves respectively output from the plurality of antennas, and a phase difference changing means for changing the phase difference by changing the phases of the radio waves respectively output from the plurality of antennas.

[0008] Accordingly, even if the null range changes each time an article is taken in or out, by collating the reading result obtained by the reading process each time the output frequency is changed or the reading result obtained by the reading process each time the phase difference is changed, it is possible to reduce the reading omission of the wireless tag due to the null range. Therefore, without providing a movable part or the like, it is possible to suppress the influence of the null and improve the reading performance.

[0009] In the invention of claim 2, the output frequency changing means changes the timing of changing the output frequency according to the number of wireless tags accommodated in the accommodation space.

[0010] As the number of wireless tags accommodated in the accommodation space increases, it takes more time to read all the wireless tags in the accommodation space. Therefore, if the output frequency is changed at regular intervals, when the number of wireless tags is large, reading omission of the wireless tags is likely to occur during the above-mentioned regular intervals. On the other hand, if the above-mentioned regular interval is lengthened, when the number of wireless tags is small, wasted time occurs after the reading is completed, resulting in a longer reading time. For this reason, by changing the timing of changing the output frequency according to the number of wireless tags accommodated in the accommodation space, it is possible to shorten the reading time while suppressing reading omission and the like.

[0011] In the invention of claim 3, the phase difference changing means changes the timing of changing the phase difference according to the number of wireless tags accommodated in the accommodation space.

[0012] When the phase difference is changed at regular intervals, if there are a large number of wireless tags, reading omissions of the wireless tags are likely to occur during the above regular intervals. When the above regular interval is lengthened, if there are a small number of wireless tags, wasted time occurs after the reading is completed, resulting in a longer reading time. Therefore, by changing the timing of changing the phase difference according to the number of wireless tags accommodated in the accommodation space, it is possible to shorten the reading time while suppressing reading omissions and the like.

[0013] Claim 1 In the invention of claim, based on information obtained by intermittently performing a reading process on at least one wireless tag accommodated in the accommodation space as an opening / closing determination tag, it is determined by a determination unit whether or not the lid is in a state of being opened and closed so as to be closed again after the opening is opened. Then, the reading process is intermittently performed on the opening / closing determination tag until a positive determination is made by the determination unit, and in a predetermined period after a positive determination is made by the determination unit, a reading process is performed on all the wireless tags accommodated in the accommodation space.

[0014] The reading process for reading the wireless tags in the accommodation space is preferably performed not regularly but at the timing when the accommodated wireless tags are replaced, that is, at the timing when the lid is opened and closed, from the viewpoint of reducing power consumption. And in the open state where the opening is open, compared with the closed state where the opening is closed, radio waves leak out of the accommodation space. Therefore, even when reading the same wireless tag, the information obtained by the reading process such as the received signal strength changes. For this reason, based on the information (such as the received signal strength) obtained by intermittently performing the reading process on the opening / closing determination tag, it is possible to determine whether or not the lid is in a state of being opened and closed so as to be closed again after the opening is opened. Thereby, it is possible to determine whether or not the lid is in a state of being opened and closed without using an opening / closing sensor or the like, and by performing a reading process on all the wireless tags accommodated in the accommodation space in a predetermined period after a positive determination is made, it is possible to improve the reading performance and reduce the power consumption regarding the reading process.

[0015] Claim4 In the invention, further, based on information obtained by intermittently performing reading processing on a second opening / closing determination tag provided outside the accommodation space, it is determined by a determination unit whether or not the lid is in an open / closed state such that the opening is closed again after being opened. In this way, by considering the received signal strengths and the like of both the opening / closing determination tag in the accommodation space and the second opening / closing determination tag outside the accommodation space, the determination accuracy regarding the opening / closing determination of the lid can be improved.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0017] [First Embodiment] Hereinafter, a first embodiment embodying the information reading device of the present invention will be described with reference to the drawings. The information reading device 10 according to this embodiment is configured as a housing device that reads information about an article G housed in a housing space S provided in a housing 20 from a wireless tag (for example, an RFID tag) T attached to the article. As the article G, for example, a key that requires individual management is assumed, and information about the article is recordable in a readable manner on the wireless tag T attached to each article G. Therefore, by collectively reading the wireless tags T in the housing space S, the information of the articles G housed in the housing space S can be acquired. In FIG. 1 and the like, for convenience, one of the plurality of articles G housed in the housing space S is illustrated together with the wireless tag T.

[0018] As shown in FIG. 1, the housing 20 has a housing main body 21 in which an opening 21a through which the article G is inserted and removed is formed, and a lid body 22 that forms the housing space S by closing the opening 21a. The housing main body 21 and the lid body 22 are formed of a material (for example, aluminum) that blocks radio waves or attenuates radio wave intensity, thereby suppressing radio wave leakage from the housing space S.

[0019] In the housing main body 21, two antennas 31 and 32 for reading the wireless tag T in the housing space S are provided at positions inside the housing space S. The antenna 31 and the antenna 32 are arranged such that the transmission directions of their transmission waves are substantially orthogonal to each other. In addition, in the housing main body 21, a housing case or the like made of a material that does not attenuate radio wave intensity can be provided so that each article G housed in the housing space S does not come into contact with the antennas 31 and 32, covering the inner surface of the housing main body 21 except for the opening 21a.

[0020] The information reading device 10 also includes a control unit 40 that controls the whole, and a first communication unit 41 and a second communication unit 42. The first communication unit 41 is configured to perform wireless communication processing for reading the wireless tag T in the housing space S using the antenna 31 under the control of the control unit 40. The second communication unit 42 is configured to perform wireless communication processing for reading the wireless tag T in the housing space S using the antenna 32 under the control of the control unit 40.

[0021] The control unit 40 is configured to perform a reading process of reading information from the wireless tag T accommodated in the accommodation space S using the antennas 31 and 32. More specifically, when performing the reading process of reading the wireless tag T in the accommodation space S, the control unit 40 may adopt either the reading result read using the first communication unit 41 and the antenna 31 or the reading result read using the second communication unit 42 and the antenna 32, or may adopt the result of collating both reading results in order to improve the reading accuracy.

[0022] In particular, in the present embodiment, the first communication unit 41 is configured to be able to change the output frequency of the radio wave output from the antenna 31 under the control of the control unit 40. Further, the second communication unit 42 is configured to be able to change the output frequency of the radio wave output from the antenna 32 under the control of the control unit 40.

[0023] And in the present embodiment, the first communication unit 41 is configured to be able to change the phase of the radio wave output from the antenna 31 under the control of the control unit 40. Further, the second communication unit 42 is configured to be able to change the phase of the radio wave output from the antenna 32 under the control of the control unit 40. For this reason, the phase difference between the phase of the radio wave output from the antenna 31 and the phase of the radio wave output from the antenna 32 can be changed by the control by the control unit 40.

[0024] Note that the function of the control unit 40 for changing the output frequency of the radio wave as described above corresponds to an example of "output frequency changing means", and the function of the control unit 40 for changing the phase difference of the radio wave as described above may correspond to an example of "phase difference changing means". For this reason, the control unit 40 is configured to include an output frequency changing means for changing the output frequency of the radio wave output from each of the antennas 31 and 32, and a phase difference changing means for changing the phase difference by changing the phase of the radio wave output from each of the antennas 31 and 32.

[0025] In the information reading device 10 configured as described above, regarding the reading process performed by the control unit 40, in order to reduce the reading omission of the wireless tag due to the null range, a first reading mode for changing the output frequency of the radio wave and a second reading mode for changing the phase difference are adopted.

[0026] In the reading process of the first reading mode, when the output frequency of the radio wave output from the antenna 31 is sequentially changed, the result of collating the information obtained from each wireless tag T via the antenna 31 is collated with the result of collating the information obtained from each wireless tag T via the antenna 32 when the output frequency of the radio wave output from the antenna 32 is sequentially changed, and thus the reading result is obtained.

[0027] In the reading process of the second reading mode, when the phase difference between the phase of the radio wave output from the antenna 31 and the phase of the radio wave output from the antenna 32 is changed from the phase difference at the time of the previous reading process, the result of collating the information obtained from each wireless tag T via both antennas 31 and 32 is collated with the previously obtained collation result, and thus the reading result is obtained.

[0028] And based on the reading result in the first reading mode or the reading result in the second reading mode, the article G (wireless tag T) accommodated in the accommodation space S can be specified. In order to realize more accurate reading of the wireless tag T, by further collating the reading result in the first reading mode and the reading result in the second reading mode, the article G (wireless tag T) accommodated in the accommodation space S can also be specified.

[0029] In this way, even if the null range changes every time the article G is taken in and out, by collating the reading result obtained by the reading process every time the output frequency is changed and the reading result obtained by the reading process every time the phase difference is changed, the reading omission of the wireless tag T due to the null range can be reduced. Therefore, without providing a movable part or the like, the influence of the null can be suppressed and the reading performance can be improved.

[0030] As a first modification example of the present embodiment, not only is the output frequency changed at regular intervals, but for example, depending on the number of wireless tags T accommodated in the accommodation space S, the timing for changing the output frequency may be changed. That is, the interval of the above-mentioned single reading process corresponding to a fixed interval may be changed according to the number of wireless tags T accommodated in the accommodation space S.

[0031] As the number of wireless tags T accommodated in the accommodation space S increases, it takes more time to read all the wireless tags T in the accommodation space S. Therefore, if the output frequency is changed at regular intervals, when the number of wireless tags T is large, reading omission of the wireless tags T during the above-mentioned fixed interval is likely to occur. On the other hand, if the above-mentioned fixed interval is lengthened, when the number of wireless tags T is small, wasted time occurs after the reading is completed, resulting in a longer reading time. For this reason, for example, by changing the timing for changing the output frequency according to the number of wireless tags T accommodated in the accommodation space S, such as lengthening the interval at which the output frequency is changed as the number of wireless tags T increases, it is possible to shorten the reading time while suppressing reading omission and the like.

[0032] Similarly, not only is the phase difference changed at regular intervals, but for example, depending on the number of wireless tags T accommodated in the accommodation space S, the timing for changing the phase difference may be changed.

[0033] When the phase difference is changed at regular intervals, when the number of wireless tags T is large, reading omission of the wireless tags T during the above-mentioned fixed interval is likely to occur. If the above-mentioned fixed interval is lengthened, when the number of wireless tags T is small, wasted time occurs after the reading is completed, resulting in a longer reading time. For this reason, by changing the timing for changing the phase difference according to the number of wireless tags T accommodated in the accommodation space S, it is possible to shorten the reading time while suppressing reading omission and the like.

[0034] Note that, as the antenna for reading the wireless tag T in the accommodation space S, the antennas 31 and 32 whose transmission directions of the transmission waves are substantially orthogonal to each other are not limited to being adopted. For example, two antennas whose transmission directions of the transmission waves are opposite to each other or two antennas whose transmission directions of the transmission waves are parallel to each other may be adopted, or three or more antennas may be adopted.

[0035] [Second Embodiment] Next, the information reading device according to the second embodiment of the present invention will be described with reference to the drawings. In this second embodiment, the main difference from the first embodiment is that the power consumption of the reading process is reduced by using the determination result regarding the open / closed state of the housing 20. Therefore, the same reference numerals are given to the substantially same components as those in the first embodiment, and the description thereof is omitted.

[0036] From the viewpoint of reducing power consumption, the reading process for reading a plurality of wireless tags T in the accommodation space S is preferably performed at the timing when the accommodated wireless tag T is replaced, that is, at the timing when the lid 22 of the housing 20 is opened and closed. For this reason, although an open / close sensor or the like that can detect the open / closed state of the housing 20 can be adopted, there is a problem that not only the manufacturing cost increases due to an increase in the number of parts, but also the device itself becomes larger depending on the constraints such as the installation position of the open / close sensor.

[0037] Therefore, in this embodiment, as shown in FIG. 2, a wireless tag (hereinafter referred to as an open / close determination tag Tj) separately provided for open / close determination is arranged in the accommodation space S. And in the reading process performed by the control unit 40 in this embodiment, based on the received signal strength (RSSI) from the open / close determination tag Tj, it is determined whether the lid 22 is in the open / closed state (hereinafter also referred to as the open / closed state of the housing 20) such that the opening 21a is closed again after being opened.

[0038] In the open state where the opening 21a is open, compared to the closed state where the opening 21a is blocked by the lid 22, radio waves leak out of the accommodation space S. Therefore, even when reading the same wireless tag T, the received signal strength becomes smaller. Note that the function of the control unit 40 that performs a process of determining whether or not the housing 20 is in an open / closed state based on the received signal strength (reading result) when intermittently reading the opening / closing determination tag Tj can correspond to an example of a "determination unit".

[0039] Also, in the present embodiment, a tag reading mode (continuous operation mode) for reading a plurality of wireless tags T in the accommodation space S and a low power consumption mode (intermittent operation mode) for intermittently reading only the opening / closing determination tag Tj are prepared. Then, in the reading process performed by the control unit 40 in the present embodiment, when it is determined (positive determination) that the housing 20 is in an open / closed state based on the received signal strength from the opening / closing determination tag Tj in the low power consumption mode, the mode is switched from the low power consumption mode to the tag reading mode. Thereby, power consumption can be reduced as compared with the case where the reading process is always performed in the above-described tag reading mode.

[0040] Hereinafter, the reading process performed by the control unit 40 so as to switch between the low power consumption mode and the tag reading mode will be described in detail with reference to the timing chart shown in FIG. 3. Note that in FIG. 3, the relationship between the switching between the tag reading mode and the low power consumption mode, the open / closed state (closed state or open state) of the housing 20, and the received signal strength of the response wave from the opening / closing determination tag Tj is illustrated in the timing chart.

[0041] At the start of the reading process (when the opening 21a is in the closed state blocked by the lid 22), the mode is switched to the low power consumption mode, and the opening / closing determination tag Tj is intermittently read. Since the process of intermittently reading only the opening / closing determination tag Tj is performed as the reading target, power saving is achieved as compared with the process of continuously reading a plurality of wireless tags T. In the reading process in this low power consumption mode, as shown in FIG. 3, when the closed state is maintained, the received signal strength of the opening / closing determination tag Tj becomes a constant value.

[0042] Then, based on the received signal strength of the opening / closing determination tag Tj, it is determined whether the housing 20 is in an open or closed state. When the received signal strength of the opening / closing determination tag Tj has hardly changed from the above-mentioned fixed value, it is determined that the housing 20 is not in an open / closed state, and the low power consumption mode is maintained.

[0043] During this low power consumption mode, when the lid 22 is opened by a user putting in and taking out the article G and the opening 21a is opened (see time t1 in FIG. 3), radio waves leak outside the storage space S, so the received signal strength of the opening / closing determination tag Tj received thereafter becomes smaller (see time t2 in FIG. 3). Then, when the lid 22 is closed by the user who has finished putting in and taking out the article G and the opening 21a is closed (see time t3 in FIG. 3), the leakage of radio waves outside the storage space S is suppressed, so the received signal strength of the opening / closing determination tag Tj received thereafter increases to the above-mentioned fixed value (see time t4 in FIG. 3).

[0044] In this way, when the received signal strength of the opening / closing determination tag Tj once becomes smaller and then returns to the original value, it is determined (positive determination) that the housing 20 is in an open / closed state, and it is assumed that the putting in and taking out of the article G is completed, and the tag reading mode is switched (see time t5 in FIG. 3). Thereby, processing for continuously reading a plurality of wireless tags T in the storage space S as reading targets is performed.

[0045] Then, when the tag reading mode continues for a predetermined period and the reading of the wireless tag T in the storage space S is completed (see time t6 in FIG. 3), it is switched back to the low power consumption mode, and only the opening / closing determination tag Tj is intermittently read until the received signal strength of the opening / closing determination tag Tj changes as described above.

[0046] As described above, in the information reading device 10 according to the present embodiment, based on the received signal strength obtained by intermittently performing the reading process on the opening / closing determination tag Tj accommodated in the accommodation space S, it is determined whether the housing 20 in which the lid 22 is opened and closed such that the opening 21a is closed again after being opened. Then, the reading process is intermittently performed on the opening / closing determination tag Tj until an affirmative determination is made, and in a predetermined period after the affirmative determination is made, the reading process is performed on all the wireless tags T accommodated in the accommodation space S.

[0047] In this way, based on the received signal strength and the like obtained by intermittently performing the reading process on the opening / closing determination tag Tj, it is possible to determine whether the housing 20 in which the lid 22 is opened and closed such that the opening 21a is closed again after being opened. Thereby, it is possible to determine whether the lid 22 of the housing 20 is in an opened or closed state without using an opening / closing sensor or the like, and by performing the reading process on all the wireless tags T accommodated in the accommodation space S in a predetermined period after an affirmative determination is made, it is possible to improve the reading performance and reduce the power consumption regarding the reading process.

[0048] Note that the opening / closing determination tag Tj may be arranged, for example, by being attached to the inside of the lid 22 so that the change in the received signal strength obtained when the lid 22 is opened and closed becomes large. Further, the opening / closing determination tag Tj is not limited to being provided separately from the wireless tag T attached to the article G to be managed, and may be configured to use one of the wireless tags T attached to any one of the articles G accommodated in the accommodation space S as the management target for each opening / closing state of the housing 20.

[0049] Further, as shown in FIG. 4, information such as the received signal strength obtained by intermittently performing a reading process on a second opening / closing determination tag Tj2 provided outside the accommodation space S may also be considered to determine whether or not the housing 20 is in an open / closed state. In this way, by considering the received signal strengths and the like of both the opening / closing determination tag Tj in the accommodation space S and the second opening / closing determination tag Tj2 outside the accommodation space S, the determination accuracy regarding the opening and closing of the lid 22 of the housing 20 can be improved.

[0050] As a modification of the present embodiment, the invention is not limited to adopting two antennas 31 and 32 as antennas for reading a plurality of wireless tags T and opening / closing determination tags Tj etc. in the accommodation space S. For example, one antenna may be adopted, and in this case, it is not necessary to be configured to be able to change the output frequency or phase of the radio wave output from the antenna.

[0051] The information reading device 10 according to the above modification can be defined as an invention as described below. An information reading device 10 that reads information from a wireless tag T attached to an article G accommodated in an accommodation space S, comprising a housing main body 21 in which an opening 21a through which the article is inserted and removed is formed, and a lid 22 that forms the accommodation space by closing the opening, the housing 20 being configured to suppress radio wave leakage from the accommodation space, an antenna disposed in the accommodation space, a control unit 40 that controls the antenna to perform a reading process for reading information from the wireless tag accommodated in the accommodation space, and the control unit comprises a determination unit that determines, based on a reading result when the reading process is intermittently performed on at least one wireless tag accommodated in the accommodation space as an opening / closing determination tag Tj, whether or not the lid is in an open / closed state such that it is closed again after the opening is opened. The reading process is intermittently performed on the opening / closing determination tag until a positive determination is made by the determination unit, and in a predetermined period after the positive determination is made by the determination unit, the reading process is performed on all the wireless tags accommodated in the accommodation space. An information reading device characterized by this.

[0052] Note that the present invention is not limited to the above-described embodiments and the like, and may be embodied as follows, for example. (1) The article G to be managed in the present invention is not limited to a key that requires individual management. For example, it may be a drug or a container containing a drug, or a product temporarily stored in the housing 20 before shipment from the factory.

[0053] (2) The housing 20 is not limited to being formed in a box shape so as to block radio waves or attenuate radio wave intensity by having a housing main body 21 and a lid body 22, and at least one of the upper side or the side may be configured to be openable and closable to form an accommodation space that blocks radio waves or attenuates radio wave intensity.

Explanation of Reference Numerals

[0054] 10... Information reading device 20... Housing 21... Housing main body 21a... Opening 22... Lid body 31, 32... Antenna 40... Control unit 41... First communication unit 42... Second communication unit G... Article S... Accommodation space T... Wireless tag Tj... Opening / closing determination tag Tj2... Second opening / closing determination tag

Claims

1. An information reading device that reads information from a wireless tag attached to an article housed in a housing space, having a housing body in which an opening through which the article is inserted and removed is formed, and a lid body that forms the housing space by closing the opening, the housing being configured to suppress radio wave leakage from the housing space, a plurality of antennas arranged in the housing space, a control unit that performs a reading process of reading information from the wireless tag housed in the housing space using the plurality of antennas, comprising: the control unit includes output frequency changing means for changing the output frequency of radio waves respectively output from the plurality of antennas, phase difference changing means for changing the phase difference by changing the phases of the radio waves respectively output from the plurality of antennas, and based on information obtained by the reading process intermittently performed on at least one wireless tag housed in the housing space as an opening / closing determination tag, a determination unit that determines whether or not the lid body is in a state of being opened and then closed again so as to close the opening; The information reading device is characterized in that the reading process is intermittently performed on the opening / closing determination tag until a positive determination is made by the determination unit, and in a predetermined period after the positive determination is made by the determination unit, the reading process is performed on all the wireless tags housed in the housing space.

2. The information reading device according to claim 1, wherein the output frequency changing means changes the timing of changing the output frequency according to the number of wireless tags housed in the housing space.

3. The information reading device according to claim 1 or 2, wherein the phase difference changing means changes the timing of changing the phase difference according to the number of wireless tags housed in the housing space.

4. The determination unit further determines whether or not the lid body is in a state of being opened and closed such that the opening is closed again after being opened, in consideration of information obtained by the reading process intermittently performed on a second opening / closing determination tag provided outside the accommodation space. The information reading device according to any one of claims 1 to 3, characterized in that.

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