Inventory system and method for arranging two-dimensional code

Abstract

To provide a method of reading a two-dimensional code arranged on an article installed inside a mesh-shaped door, partition, or the like, thereby automatically detecting its location.SOLUTION: When the wire diameter of a line forming a mesh 31 is W, the period of the line in a first direction is L1, and the period of the line in an orthogonal second direction is L2, a two-dimensional code 34 has a length of less than (L1 / 2-W) in the first direction and a length of less than (L2 / 2-W) in the second direction. Regarding sets consisting of the two-dimensional codes 34, one or more two-dimensional codes 34 are arranged in the first direction at the period of L1, respectively, a second set is arranged with the phase shifted by L1 / 2 in the first direction and by L2 / 2 in the second direction for a first set arranged in an article, respectively, a third set is arranged with the phase shifted by L1 / 2 in the first direction, and a fourth set is arranged with the phase shifted by L2 / 2 in the second direction.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a technique for inventorying a large number of items, and in particular to a technique that is effective when applied to an inventory system that reads two-dimensional codes placed on target items and automatically performs inventory. [Background technology]

[0002] Data centers house a large number of servers and network devices. Autonomous and automatic systems are widely used to monitor and inspect whether these devices are operating normally.

[0003] On the other hand, tasks such as grasping, checking and inspecting the locations of these devices in the machine room, such as which server rack and which level they are stored in, are difficult to do automatically and have mainly been done by manual visual inspection. In such cases, the efficiency of the checking work can be improved by reading barcodes or other items that indicate the identification information placed or affixed to each device.

[0004] As a related technology, for example, JP 5-208716 A (Patent Document 1) describes an inventory function in an automated storage shelf, in which an actuator is provided on the hand fork section of a transfer robot and a barcode reader is attached to the actuator, eliminating the need for the transfer robot to remove a box and then read the barcode, and enabling inventory data to be restored without removing the box.

[0005] Furthermore, Japanese Patent Application Laid-Open No. 52-60026 (Patent Document 2) describes a barcode sign having a continuously scannable range of any size by arranging multiple identical barcodes closely spaced apart at an angle of 2α0 or less relative to each other, with the allowable scanning angle being ±α0 relative to the center line of the barcode. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 5-208716 [Patent Document 2] Japanese Patent Application Publication No. 52-60026 Summary of the Invention [Problem to be solved by the invention]

[0007] By combining conventional technologies, it is possible to automatically determine the location of each device (inventory), for example, by reading the barcodes placed on each device stored in a server rack with a barcode reader attached to a mechanism such as an actuator on a mobile robot, etc.

[0008] However, server racks in data centers usually house multiple devices and are often protected by lockable doors, so it is often impossible to bring a barcode reader close to the barcodes on each device from outside the door. Also, even if you try to read a barcode with a digital camera from outside the door, the door is usually made of mesh to allow cool air to be taken in from the aisle to cool the devices, and the mesh overlaps with the barcode, making it difficult to read the barcode correctly.

[0009] In addition, as in the technology described in Patent Document 1, it would be ideal if a mobile robot could reliably travel along a predetermined route such as a rail and position itself, but providing such a structure in the passageways of a machine room in a data center is not realistic. Even if a robot that moves autonomously along the passageway while detecting obstacles is used, the positioning precision of the stopping position of such a robot is insufficient, and it is difficult to accurately control the position and attitude of the camera every time so that the barcode can be read correctly.

[0010] Therefore, an object of the present invention is to provide an inventory system and a two-dimensional code placement method that can read two-dimensional codes placed on items installed behind mesh doors or partitions, such as equipment stored in a server rack, and automatically determine (inventory) the location.

[0011] The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0012] Among the inventions disclosed in this application, a brief summary of representative inventions is as follows.

[0013] An inventory system that is a representative embodiment of the present invention is an inventory system that grasps and records information regarding the location of an item based on the contents read by photographing a set of one or more two-dimensional codes placed on an item placed inside a mesh partition using a camera outside the mesh, and has the following features.

[0014] That is, when the wire diameter of the wires constituting the mesh is W, the period of the wires in a first direction is L1, and the period of the wires in a second direction perpendicular to the first direction is L2, the length of the two-dimensional code in the first direction is less than (L1 / 2-W) and the length of the second direction is less than (L2 / 2-W), and the set has one or more two-dimensional codes arranged in the first direction with a period of L1, and relative to a first set arranged on the item, a second set is arranged with a phase shift of L1 / 2 in the first direction and a phase shift of L2 / 2 in the second direction, a third set is arranged with a phase shift of L1 / 2 in the first direction, and a fourth set is arranged with a phase shift of L2 / 2 in the second direction.

[0015] The present invention can also be applied to a two-dimensional code arrangement method for arranging two-dimensional identification codes on items that are the subject of inventory. Effect of the Invention

[0016] The effects obtained by the representative inventions disclosed in this application can be briefly explained as follows.

[0017] In other words, according to a representative embodiment of the present invention, it is possible to read two-dimensional codes placed on items installed behind mesh doors or partitions, such as equipment stored in a server rack, and automatically determine (inventory) the location. [Brief description of the drawings]

[0018] [Figure 1] 1 is a diagram showing an overview of a configuration example of an inventory system according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a diagram outlining an example of an image captured by a camera when a typical barcode is placed on a device housed in a server rack. [Diagram 3] 1A and 1B are diagrams showing an outline of an example of an image obtained when an AR marker in one embodiment of the present invention is photographed by a camera through a mesh. [Figure 4] 1 is a diagram showing an overview of an example of an image obtained when a set of multiple AR markers is photographed through a mesh by a camera in one embodiment of the present invention. FIG. [Diagram 5] 1A and 1B are diagrams outlining an example of a concept for a method of arranging AR codes in an embodiment of the present invention. [Figure 6] 1 is a diagram illustrating an overview of a method for calculating the length of one side and the phase d of an AR marker in an embodiment of the present invention. FIG. [Figure 7] 1A and 1B are diagrams illustrating an example of arranging a set of AR markers according to an embodiment of the present invention. [Figure 8]FIG. 13 is a diagram outlining another example of an image obtained when a set of multiple AR markers is photographed through a mesh by a camera in an embodiment of the present invention. [Figure 9] FIG. 1 is a diagram illustrating an example of a sheet on which AR markers are printed integrally according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In all the drawings for explaining the embodiment, the same parts are generally given the same reference numerals, and the repeated explanations will be omitted. On the other hand, a part that has been described with a reference numeral in a certain drawing may be referred to with the same reference numeral in the explanation of another drawing, although it will not be shown again.

[0020] <System configuration> Fig. 1 is a diagram showing an overview of an example of the configuration of an inventory system according to an embodiment of the present invention. The inventory system 1 of this embodiment is a system that performs an inventory to grasp the locations of server devices and network devices stored in a large number of server racks 3 installed in a data center as an example. Each server rack 3 is provided with a door, but the door is meshed so that cold air can be taken in from the aisle to cool the stored devices.

[0021] In this embodiment, two-dimensional codes that are placed or affixed to each device stored in server rack 3 and indicate information for identifying the device and location information (for example, which level of server rack 3 the device is installed on) are photographed through a door by camera 41 mounted on self-propelled robot 4 that moves on an aisle, and information read from the image of the two-dimensional code is sent to management server 2 by wireless communication. Image data of the two-dimensional code may be sent to management server 2 and the information may be read by management server 2, or the image data may be sent to an image analysis server (not shown) separate from management server 2, and the read information may be sent to management server 2. Details of the placement and reading of the two-dimensional code will be described later.

[0022] The location of the server rack 3 can be determined not only by reading the two-dimensional code placed on the aisle side of the server rack 3 itself, but also by combining this information with the location of each piece of equipment.

[0023] Management server 2 has, for example, a master database (DB) 21 that holds master data for each device, and performs an inventory by recording information on the location of each device in association with this master data in inventory DB 22. Management server 2 may control the running and movement of self-propelled robot 4, the height and attitude of camera 41, shooting conditions, etc.

[0024] Self-propelled robot 4 is a self-propelled robot equipped with camera 41, capable of traveling along a predetermined route in an aisle in which server racks 3 are installed, and autonomously moving by recognizing obstacles. It has a function of controlling its own stopping position, the height, posture, magnification, focus, aperture, etc. of camera 41 according to instructions from management server 2, and automatically sequentially photographing and reading two-dimensional codes arranged on each device in server rack 3. Camera 41 can be configured, for example, by using a general digital camera or USB camera as appropriate. Note that in this embodiment, self-propelled robot 4 is configured to perform an inventory automatically by photographing sequentially while moving autonomously, but it may also be configured that a person holds camera 41 and photographs sequentially manually.

[0025] <Placement and reading of 2D codes> 2 is a diagram outlining an example of an image captured by camera 41 when a general barcode is placed on equipment stored in server rack 3. In the diagram, the surface of mesh 31 constituting the door of server rack 3 is set as the xy plane, the depth direction of the diagram is set as the z axis, and an example of an image is shown diagrammatically when a general barcode 33 placed on equipment (not shown) on the other side of mesh 31 (the negative side of the z axis) is captured by camera 41 through mesh 31 from the front side of mesh 31 (the positive side of the Z axis).

[0026] The mesh 31 used in the door of the server rack 3 has, for example, a wire diameter of several mm and has openings 32 of about 1 cm square that are too large for a human finger to pass through, whereas a typical two-dimensional barcode 33 has a width and height of about several cm. Therefore, when the barcode 33 is photographed through the mesh 31, since the barcode 33 is larger than the openings 32, the barcode 33 overlaps with the mesh 31 as shown in the figure, and part of it is hidden, resulting in a state in which the entire barcode cannot be read correctly.

[0027] In this embodiment, a plurality of images of AR (Augmented Reality) markers, each of which has a small amount of information per piece but can be made small in size, are used as a two-dimensional code that has the same amount of information (about 10 digits) as a general barcode 33 and can be read in its entirety through the mesh 32 without being hidden by the mesh 31 even when photographed through the mesh 31. In this embodiment, the ArUco marker, which is one of the two-dimensional codes in the open source library, is used, but is not limited to this. The ArUco marker is a square two-dimensional code, and each code has an amount of information of about three digits. Therefore, in this embodiment, three of these are used to express the same amount of information as a general barcode 33, but the number is not limited to this and can be changed appropriately depending on the number of items to be inventoryed.

[0028] 3 is a diagram outlining an example of an image obtained when an AR marker in one embodiment of the present invention is photographed by a camera 41 through a mesh 31. FIG. 3(a) shows an example in which three AR markers 34 such as ArUco markers are arranged in the x-axis direction and photographed through the mesh 31, and since the AR markers 34 are smaller than the mesh openings 32 of the mesh 31, each of the three AR markers 34 is not hidden by the mesh 31 and can be read in its entirety through the mesh openings 32. Note that, although the three AR markers 34 are arranged in the x-axis direction in this embodiment, it goes without saying that they may be arranged in the y-axis direction.

[0029] However, in this embodiment, AR marker 34 is photographed by camera 41 attached to self-propelled robot 4, and there is a limit to the precision with which self-propelled robot 4 can move and position. In addition, the condition of the passageway leading to server rack 3 may not be flat, with objects placed thereon or gratings, making it difficult to position camera 41 to capture images with high precision every time.

[0030] 3(b) shows an example of a case where the camera 41 captures an image with its shooting position shifted, for example, in the x-axis and / or y-axis directions. Even if the meshes 32 are larger than the AR markers 34, at least some of the three AR markers 34 (the left and center AR markers 34 in the figure) may be hidden by the mesh 31 depending on the shooting position, and the entire AR markers 34 may not be readable through the meshes 32.

[0031] Therefore, in this embodiment, multiple sets of three AR markers 34 are arranged, shifted a predetermined distance, so that even if the shooting position of the camera 41 is shifted in the x-axis and / or y-axis directions (or in the z-axis direction), at least one set of three AR markers 34 is not hidden by the mesh 31 and can be read entirely through the openings 32.

[0032] 4 is a diagram outlining an example of an image obtained when a set of a plurality of AR markers 34 in one embodiment of the present invention is photographed by a camera 41 through a mesh 31. The example of Fig. 4 shows a state in which a set of three AR markers 34 arranged in the x-axis direction is shifted in the x-axis direction and another set is arranged, and the set of AR markers 34 arranged on the upper side of the figure (negative side of the y-axis) is partially hidden by the mesh 31, but the set arranged on the lower side (positive side of the y-axis) is not hidden by the mesh 31 and can be read entirely through the mesh openings 32.

[0033] In the following, we will consider how large the AR markers 34 can be made (the larger they are, the easier they are to recognize when photographed by the camera 41) and how many and where they should be placed so that at least one set of AR markers 34 is not hidden by the mesh 31 and can be read in its entirety, as shown in the example of Figure 4, regardless of the photographing position of the camera 41.

[0034] FIG. 5 is a diagram for schematically explaining an example of the concept of the arrangement method of the AR code 34 in one embodiment of the present invention. Here, focusing on any one of the AR codes 34 in a set of three AR codes 34, when two of them are arranged, if one AR code 34a is hidden by the lines 35 (line 35a, line 35b) in the vertical direction (y-axis direction) constituting the mesh 31, it is considered how much to shift in the positive direction of the x-axis so that the other AR code 34b is not hidden.

[0035] FIG. 5(a) shows an example where the left end (negative direction of the x-axis) of the AR code 34a is just hidden by the vertical line 35a constituting the mesh 31. In the figure, the width (wire diameter) of the lines 35a and 35b constituting the mesh 31 is W, the period of the lines 35a and 35b is L, the length of one side of the AR marker 34 is l, and the phase (shift width) of the AR marker 34b with respect to the AR marker 34a is d. For convenience of explanation, the lines 35a and 35b are shown as white-out figures assuming they are transparent so that the part of the AR marker 34 hidden by them can be seen (the same applies to FIG. 5(b)).

[0036] In the example of FIG. 5(a), for the AR marker 34b not to be hidden by the line 35b adjacent to the line 35a where the AR marker 34a is hidden in the positive direction of the x-axis, the AR marker 34b needs to be on the left side (negative direction of the x-axis) of the line 35b, that is, arranged in the aperture 32 formed by the lines 35a and 35b. The relationship is d + l < L - W (Equation 1) which is represented by the formula. The left side is the distance from the left end of the AR marker 34a to the right end of the AR marker 34b, and the right side is the width (length in the x-axis direction) of the aperture 32.

[0037] On the other hand, FIG. 5(b) shows the case where the right end (positive direction of the x-axis) of the AR code 34a is just hidden by the line 35 constituting the mesh 31. In the example of FIG. 5(b), for the AR marker 34b not to be hidden by the line 35, the AR marker 34b needs to be on the right side (positive direction of the x-axis) of the line 35. The relationship is dl>W (Equation 2) The left side of the equation is the distance from the right end of the AR marker 34a to the left end of the AR marker 34b.

[0038] In the above inequalities of Equations 1 and 2, L and W are constants determined by the specifications of the mesh 31, and therefore these simultaneous inequalities are reduced to a domain problem of finding the maximum l and d that satisfy the conditions.

[0039] FIG. 6 is a diagram showing an outline of a method for obtaining the length of one side and the phase d of the AR marker 34 in an embodiment of the present invention. Here, the above formulas (1) and (2) are shown on a graph with d and l as the two axes, and the region satisfying the condition is shown shaded. The maximum l that satisfies the condition is (L / 2-W), and d at this time is L / 2. That is, by making the length of one side of the AR marker 34 (AR marker 34a, AR marker 34b) less than (L / 2-W) and disposing the AR marker 34b with a phase shift of L / 2 in the x-axis direction with respect to the AR marker 34a, at least one of the AR markers 34 can be read entirely without being hidden by the mesh 31 in the x-axis direction. In this embodiment, since the shape of the openings 32 of the mesh 31 and the shape of the AR marker 34 are both square, the same result is obtained in the y-axis direction.

[0040] In other words, by arranging the AR markers 34 in two patterns, one with no phase shift in the x-axis direction and one with a phase shift of d = L / 2 in the x-axis direction, and two patterns with no phase shift in the y-axis direction and one with a phase shift of d = L / 2 in the y-axis direction, a total of 2 × 2 = 4 patterns, it is possible to make at least one of the four AR markers 34 unobscured by the mesh 31 and entirely readable in the xy plane.

[0041] In this embodiment, the shape of the openings 32 of the mesh 31 is assumed to be a square, and the values ​​of d and l are set to be the same in the x-axis direction and the y-axis direction. However, even if the shape of the openings 32 of the mesh 31 is rectangular rather than square, this can be accommodated by calculating d and l individually for the x-axis direction and the y-axis direction using the above method.

[0042] 6, L and W represent the distance on the xy plane corresponding to the mesh 31, while l and d represent the distance on the xy plane corresponding to the surface of the equipment stored in the server rack 3. Since there is a depth (distance in the z-axis direction) from the mesh 31 to the equipment surface, if the distance (in the z-axis direction) between the camera 41 and the mesh 31 is close and not sufficiently long compared to the depth, the size of the mesh openings 32 on the mesh 31 projected onto the equipment surface may be larger than the actual size of the mesh openings 32 on the mesh 31. In this embodiment, however, the camera 41 takes an image from a distance (in the z-axis direction) that allows both the mesh 31 and the equipment surface to be focused, and no correction is made to the values ​​of L and W taking into account that they are projected onto the equipment surface.

[0043] 7 is a diagram outlining an example of arranging a set of AR markers 34 in one embodiment of the present invention. Here, an example is shown in which a set of three AR markers 34 arranged horizontally (in the x-axis direction) as shown in FIG. 3 and the like is arranged in the above four patterns. When arranging three AR markers 34 horizontally (in the x-axis direction), the period of each marker should be the same as the period L (any multiple of) of the lines constituting the mesh 31.

[0044] 7(a), the first set of AR markers 34 from the top (starting from the side with the smaller y-axis) shows an arrangement in a pattern with no phase shift in either the x-axis or y-axis directions, the second set shows an arrangement in a pattern with a phase shift of d=L / 2 in both the x-axis and y-axis directions from the first set, the third set shows an arrangement in a pattern with a phase shift of d=L / 2 only in the x-axis direction from the first set (the y-axis direction is shifted by period L, so there is no phase shift), and the fourth set shows an arrangement in a pattern with a phase shift of d=L / 2 only in the y-axis direction from the first set (shifted by period L and then).

[0045] In this way, when displaying information using a set of three AR markers 34, 3 markers x 4 patterns = 12 AR markers 34 are required. Note that, with respect to the first set, the second, third, and fourth sets can be shifted by any multiple of the period L in the x-axis and y-axis directions within a range where they do not overlap, as long as the phase of each set is not changed from the above pattern.

[0046] FIG. 7(b) is a diagram showing an outline of an example of an image obtained when the sets of AR markers 34 arranged in the four patterns shown in FIG. 7(a) are photographed by the camera 41 through the mesh 31. In this example, the first, third, and fourth sets from the top are partially hidden by the mesh 31 and cannot be read as a whole, whereas the second set (the set surrounded by the dotted line in the figure) is not hidden by the mesh 31 and can be read as a whole through the openings 32. Even if the photographing position of the camera 41 shifts from this state and the second set is hidden by the mesh 31 and cannot be read as a whole, any of the other sets will not be hidden, and at least one set will always be not hidden by the mesh 31 and can be read as a whole.

[0047] When arranging the AR markers 34 on the equipment in the server rack 3 as shown in Figure 7(a), for example, each AR marker 34 may be printed on paper, stickers, etc. and arranged individually, or a sheet (paper, sticker, etc.) on which each AR marker 34 is printed as a whole with the AR markers 34 arranged in advance as shown in Figure 7(a) may be arranged.

[0048] Furthermore, in this embodiment, mesh 31 is configured such that a horizontal line (x-axis direction) intersects with a vertical line (y-axis direction) perpendicular to the horizontal line relative to the floor surface of the data center, etc.; however, this is not limited to this, and the lines constituting mesh 31 may be oblique to the floor surface of the data center, etc. (mesh 31 may be rotated around the z-axis).

[0049] 8 is a diagram outlining another example of an image obtained when a set of a plurality of AR markers 34 in one embodiment of the present invention is photographed by the camera 41 through the mesh 31. Here, an example is shown in which the mesh 31 is rotated by an angle α around the z-axis. In this case, it is assumed that the mesh 31 is not rotated around the z-axis, and each AR marker 34 is virtually arranged by finding d and l for each of the x-axis and y-axis by the above-mentioned method, and then each AR marker 34 is rotated by the angle α around the z-axis and arranged, so that each line of the mesh 31 and the corresponding side of the AR marker 34 can be arranged parallel to each other as shown in the figure.

[0050] Instead of rotating each AR marker 34 (or a sheet on which they are printed as one unit) by the angle α around the z axis, for example, a sheet on which each AR marker 34 is printed rotated by the angle α around the z axis may be arranged in a state where it is not rotated around the z axis (parallel or perpendicular to the floor surface of the data center, etc.). FIG. 9 is a diagram showing an overview of an example of a sheet on which each AR marker 34 is printed as one unit in one embodiment of the present invention. For an operator who places the AR marker 34 on a device, it is more efficient to place the sheet 36 as shown in the figure parallel to the floor surface of the data center, etc., than to place the AR marker 34 at an angle α.

[0051] 8 and 9, the mesh 31 is rotated by the angle α around the z-axis, and therefore each AR marker 34 is also rotated by the angle α, and is arranged so that each line of the mesh 31 and the corresponding side of the AR marker 34 are parallel to each other, but this is not limited to this. As long as the AR marker 34 fits inside the openings 32 formed by each line of the mesh 31, the angle and shape of the AR marker 34 can be arbitrary (naturally, the size of the AR marker 34 will be small).

[0052] As described above, according to the inventory system 1 which is one embodiment of the present invention, two-dimensional codes (AR codes 34) such as ArUco markers placed on items installed inside mesh doors or partitions, such as equipment stored in a server rack 3, can be read by the camera 41 equipped on the self-propelled robot 4 through the mesh 31 regardless of deviation in the shooting position, and the location of the equipment can be automatically determined and inventoryed.

[0053] The invention made by the present inventor has been specifically described above based on the embodiment, but it goes without saying that the present invention is not limited to the above embodiment and can be modified in various ways without departing from the gist of the invention. Furthermore, the above embodiment has been described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all of the configurations described. Furthermore, it is possible to add, delete, or replace part of the configuration of the above embodiment with other configurations.

[0054] In addition, the above-mentioned configurations, functions, processing units, processing means, etc. may be realized in part or in whole by hardware, for example, by designing them as integrated circuits. In addition, the above-mentioned configurations, functions, etc. may be realized in software by a processor interpreting and executing a program that realizes each function. Information such as the program, table, file, etc. that realizes each function can be stored in a recording device such as a memory, a hard disk, or an SSD, or in a recording medium such as an IC card, an SD card, or a DVD.

[0055] In addition, in each of the above figures, the control lines and information lines are shown as those considered necessary for explanation, and do not necessarily show all the control lines and information lines in the actual implementation. In reality, it can be considered that almost all the components are connected to each other. [Industrial Applicability]

[0056] INDUSTRIAL APPLICABILITY The present invention can be used in an inventory system and a two-dimensional code arrangement method that reads two-dimensional codes arranged on target items and automatically performs inventory. [Explanation of symbols]

[0057] 1...Inventory system, 2...Management server, 3...Server rack, 4...Self-propelled robot, 21...Master DB, 22...Inventory DB, 31...mesh, 32...opening, 33...barcode, 34...AR marker, 35, 35a, 35b...line, 36...sheet

Claims

1. An inventory system that grasps and records information related to the location of an item based on a set of one or more two-dimensional codes placed on an item placed inside a partition made of a mesh and reading the contents of the set by a camera from outside the mesh, comprising: The wire diameter of the wire constituting the mesh is W, and the period of the wire in the first direction is L. １ , the period in a second direction perpendicular to the first direction is L ２ If The two-dimensional code has a length in the first direction (L １ / 2-W) and the length in the second direction is (L ２ / 2-W), The set includes one or more two-dimensional codes each having a period L in the first direction. １ are arranged in For a first set disposed on the article, The second set has a phase L in the first direction. １ / 2, the phase in the second direction is L ２ / 2, and The third set has a phase difference L in the first direction. １ / 2 offset, The fourth set shifts the phase in the second direction by L ２ / The inventory system is arranged with a shift of 2.

2. In the inventory system according to claim 1 , The camera is installed on a self-propelled robot, The self-propelled robot self-propels to a predetermined position outside the mesh and controls the camera to photograph and read the set of two-dimensional codes placed on the items, in an inventory system.

3. A two-dimensional code arrangement method for photographing and reading a set of one or more two-dimensional codes arranged on an item placed inside a partition made of a mesh by a camera from outside the mesh, comprising: The wire diameter of the wire constituting the mesh is W, and the period of the wire in the first direction is L. １ , the period in a second direction perpendicular to the first direction is L ２ If The two-dimensional code is formed such that the length in the first direction is (L １ / 2-W) and the length in the second direction is (L ２ / 2-W) or less, One or more of the two-dimensional codes are arranged in the first direction with a period L １ to form the set, For a first set disposed on the article, The second set is phase-shifted in the first direction. １ / 2, the phase in the second direction is L ２ / 2 each, and place them separately. The third set is arranged such that the phase is shifted to L in the first direction. １ / Shift it by 2 and place it. The fourth set is arranged such that the phase is shifted to L in the second direction. ２ A two-dimensional code placement method in which the code is shifted by 2.

Images