Device for writing to and / or reading RFID tags

Abstract

The invention relates to a device for the parallel writing and / or reading of a plurality of RFID tags. For this purpose, the device comprises a read / write module (100) for each RFID tag, wherein each read / write module (100) comprises a shielding housing arrangement (120, 130) with an inner housing (120) and an outer housing (130), as well as an RFID antenna (110) which is arranged in the inner housing (120) and is configured to interact with the RFID tag. The inner housing (120) and the outer housing (130) are spaced apart from each other and are configured to prevent crosstalk to an adjacent read / write module (100) of the device.

Description

[0001] The present invention relates to a device for the parallel writing and / or reading of a plurality of RFID tags.

[0002] In production facilities, it is often necessary to read or write multiple Radio Frequency Identification Device (RFID) tags simultaneously, i.e., in parallel. This typically requires the use of several RFID readers, onto which the RFID tags are placed. The RFID readers operate, for example, at a frequency of 13.56 MHz and transmit energy to the RFID tags via a high-frequency electromagnetic field. The desired information can be transmitted by modulating this high-frequency field.

[0003] When multiple RFID readers in close proximity simultaneously read and / or write RFID tags, crosstalk can occur between the antennas of these readers. In this case, the modulated RF signal from one reader reaches a neighboring reader, preventing either the reader from correctly demodulating the signal from the attached RFID tag or vice versa. This crosstalk can lead to bit errors, where individual units of information are transmitted incorrectly. If these bit errors occur frequently, even an error correction code, commonly used to ensure data transmission, may be unable to correct them, potentially resulting in data transmission failure.

[0004] To avoid such effects, it is known, for example, from DE102013100981, to use a housing to shield the RF field between adjacent RFID readers, for which metallic materials such as aluminum, copper, iron, or ferrite are frequently used. Depending on the distance from the antenna and the type of material, however, such a housing can influence the field generated by an RFID reader. For example, when using an iron housing or shield, eddy currents are induced in the shield, which reduce the field strength. When using aluminum and copper shields, the resonant frequency and / or impedance of the RFID reader's antenna is often altered, resulting in the RFID reader's antenna no longer being optimally matched to the reader's electronics.While the use of additional ferrite foils can reduce such detuning of the antenna of a conventional RFID reader, it significantly increases the cost of the overall system.

[0005] US 2023 / 0177288A1 concerns devices, computer-implemented procedures, and computer program products for parallel wireless scanning.

[0006] US 11 514 766 B1 concerns the detection of interactions with storage units based on RFID signals and auxiliary signals.

[0007] DE 10 2013 100 981 A1 concerns a document buffer for accessing wirelessly readable circuits of electronically readable identification documents.

[0008] The object of the present invention is to provide an improved device for the parallel writing and / or reading of a plurality of RFID tags.

[0009] This problem is solved by the features of the independent claim. Advantageous embodiments are the subject of the dependent patent claims, the description, and the figures.

[0010] A device for the parallel writing and / or reading of a large number of RFID tags is provided. For this purpose, the device comprises a read / write module for each RFID tag, each module comprising a shielded housing assembly with an inner housing and an outer housing, as well as an RFID antenna located in the inner housing and configured to interact with the RFID tag. The inner housing and the outer housing are spaced apart and configured to prevent crosstalk with an adjacent read / write module of the device. Thus, a device for the parallel writing and / or reading of a large number of RFID tags is provided which, due to the shielded housing assembly with the inner housing and the spaced-apart outer housing, reduces crosstalk between the RFID antennas of adjacent read / write modules.Preferably, the outer housing is electrically decoupled from the inner housing by means of the distance. In other words, preferably the outer housing and the inner housing are not electrically connected to each other, which further reduces crosstalk between the RFID antennas of adjacent read / write modules.

[0011] According to a preferred embodiment, the inner housing can be made of aluminum, thus providing a lightweight and cost-effective component.

[0012] In a preferred embodiment, the inner housing can comprise side walls that define a frame surrounding the RFID antenna. Advantageously, by designing the inner housing as a horizontally surrounding frame, the propagation of the electromagnetic field generated by the RFID antenna can be focused vertically towards the RFID tag and a bottom wall of the outer housing. This, in turn, reduces the horizontal distance between the side walls of the inner housing and the side walls of the outer housing, thus requiring less installation space.

[0013] According to a preferred embodiment, the inner housing comprises a bent sheet metal part. In this preferred embodiment, the inner housing can be manufactured simply and cost-effectively.

[0014] In a preferred embodiment, to avoid eddy currents in the inner housing, an air gap can be formed in at least one side wall of the inner housing, thereby avoiding or at least reducing a negative influence on the radiation behavior of the RFID antenna by eddy currents in the inner housing.

[0015] According to a preferred embodiment, the air gap formed in at least one of the side walls of the inner housing can have a width between 0.1, 0.2, 0.3 or 0.4 and 0.6, 0.7, 0.8, 0.9 or 1 millimeter, in particular 0.5 millimeter.

[0016] In a preferred embodiment, the outer housing can comprise side walls and a bottom wall, which define a cup with a rectangular cross-section enclosing the inner housing with the RFID antenna mounted therein, thereby further reducing the crosstalk between the RFID antennas of adjacent read / write modules.

[0017] According to a preferred embodiment, each read / write module further comprises one or more spacers designed to maintain the inner housing, containing the RFID antenna, at a defined vertical distance from the bottom wall of the outer housing. Preferably, the spacers are electrically non-conductive. The spacers allow for the cost-effective creation of the desired vertical distance between the bottom wall of the outer housing and the inner housing with its RFID antenna, and also facilitate the attachment of the inner housing to the outer housing. The outer housing, in turn, can be attached to a machine body at its underside.

[0018] In a preferred embodiment, the defined vertical distance of the inner housing with the RFID antenna mounted therein is at least 5 centimeters from the bottom wall of the outer housing.

[0019] According to a preferred embodiment, the defined vertical distance of the inner housing with the RFID antenna mounted therein from the bottom wall of the outer housing is greater than a defined vertical distance between the RFID antenna and a bottom wall of the inner housing.

[0020] In a preferred embodiment, the one or more spacers are further configured to hold the inner housing with the RFID antenna mounted therein at a defined horizontal distance between at least one side wall of the inner housing and the corresponding side wall of the outer housing, wherein the defined horizontal distance between the at least one side wall of the inner housing and the corresponding side wall of the outer housing is at least 1 centimeter.

[0021] According to a preferred embodiment, the defined vertical distance of the inner housing with the RFID antenna mounted therein from the bottom wall of the outer housing is greater than the defined horizontal distance between at least one side wall of the inner housing and the corresponding side wall of the outer housing. In this embodiment, each read / write module has suitably optimized dimensions to reduce crosstalk between the RFID antennas of adjacent read / write modules and to avoid wasting installation space in the horizontal direction.

[0022] According to a preferred embodiment, the outer casing can comprise a bent sheet metal part. In this preferred embodiment, the outer casing can be manufactured simply and cost-effectively.

[0023] In a preferred embodiment, to avoid eddy currents in the outer housing, an air gap can be formed between at least one pair of adjacent side walls of the outer housing, thereby avoiding or at least reducing a negative influence on the radiation behavior of the RFID antenna by eddy currents in the outer housing.

[0024] According to a preferred embodiment, the air gap formed between at least one pair of adjacent side walls of the outer casing can have a width between 0.1, 0.2, 0.3 or 0.4 and 0.6, 0.7, 0.8, 0.9 or 1 millimeter, in particular 0.5 millimeter.

[0025] In contrast to conventional devices that use a single shielding layer, the device according to the invention provides double shielding through the inner and outer housings. The inner housing, i.e., the inner shielding, is located close to the RFID antenna and is designed in such a way that the resonant frequency and impedance of the RFID antenna are only minimally affected. The outer housing, i.e., the outer shielding, is located further away from the RFID antenna and, according to one embodiment, can completely shield the RFID antenna on five sides, namely the bottom wall and the four side walls of the outer housing, thereby significantly reducing crosstalk to adjacent read / write modules of the device.

[0026] Further examples are explained in more detail with reference to the accompanying figures. These show: Fig. 1a-c a perspective view and side views of a read / write module with a shielding housing arrangement for an RFID antenna, wherein the read / write module is part of a device for reading and / or writing a plurality of RFID tags according to an embodiment; Fig. 2a,b a schematic top view and a schematic side view of a device for reading and / or writing a plurality of RFID tags according to an embodiment with a plurality of read / write modules arranged as an array according to the Fig. 1a-c; Fig. 3a-d a perspective view, side views and a front view of an inner housing of the shielding housing arrangement of the read / write module of the Fig. 1a-c; and Fig. 4 A top view of a cut sheet metal for forming an outer housing of the shielding housing arrangement of the read / write module of the Fig. 1a-c.

[0027] Elements of the following embodiments described in detail, which correspond to one another, are identified with the same reference numerals as far as possible.

[0028] The Fig. Figures 1a-c show a perspective view and two side views of a read / write module 100 (also known as RFID reader 100) of a device 200 (which is schematically shown in the Fig. 2a and Fig. 2b) with a multitude of read / write modules 100 for the parallel reading and / or writing of a multitude of RFID tags 220. Such parallel reading and / or writing of a multitude of RFID tags 220 can be used, for example, in the production, in particular the personalization of the multitude of RFID tags 220.

[0029] The writing-reading module 100 in the Fig. 1a-c comprises an RFID antenna 110, which is arranged in a shielding housing assembly. As described in detail below, the shielding housing assembly comprises a preferably metallic inner housing 120 (also referred to as inner shield 120) and a preferably metallic outer housing 130 (also referred to as outer shield 130) in which the inner housing 120 is arranged. The inner housing 120 is frame-shaped and comprises four side walls 121a-d, which surround the RFID antenna 110. The outer housing 130 comprises four side walls 131a-d and a bottom wall 131e (see Figure 1). Fig. 4) The inner housing 120 with the RFID antenna 110 mounted therein is arranged in the cup-shaped outer housing 130 such that the respective side walls 121a-d of the inner housing 120 are spaced apart from the corresponding side walls 131a-d of the outer housing, and the bottom of the inner housing 120 is spaced apart from the bottom wall 131e of the outer housing 130. This is particularly evident from the Fig. 1b and Fig. As can be seen from Figure 1c, according to one embodiment, the read / write module 100 comprises spacers 140a,b, which are arranged (for example, screwed on) on the top of the bottom wall 131e of the outer housing 130 and are designed to position the inner housing 120 at a defined vertical distance Dz (in the Fig. 2b) to be held from the bottom wall 131e of the outer housing 130. According to one embodiment, the spacers 140a,b can be made of plastic. Preferably, the spacers are electrically non-conductive.

[0030] The RFID antenna 110, which is located in the Fig. The antenna board, as depicted in the embodiment shown in Figures 1a-c, is configured as a substantially planar antenna board and is arranged in the inner housing 120. It is designed to interact with an RFID tag 220 resting on the read / write module 100, in particular with an RFID antenna of the RFID tag 220, in order to write data to the RFID tag 220 and / or read data from the RFID tag 220. During the writing and / or reading of an RFID tag 220, the read / write module 100 can also be configured to verify the functionality of the RFID tag 220, for example, by determining the resonant frequency of an RFID antenna of the RFID tag 220.

[0031] The Fig. 2a and Fig. Figure 2b shows a schematic top view and a schematic side view of the device 200 for reading and / or writing a plurality of RFID tags 220 according to an embodiment with a plurality of read / write modules 100 arranged as an array. In the Fig. 2a and Fig. In the schematically illustrated embodiment 2b, four read / write modules 100 are arranged as a square 4x4 array, with which up to four RFID tags 220 can be read and / or written in parallel. However, those skilled in the art will recognize that the device 200 can be configured in further embodiments with any number of read / write modules 100 in the form of an array. As shown in Fig. As shown in Figure 2b, the device 200 can further comprise a support plate 210 which rests on the read / write modules 100 and defines a contact surface for the RFID tags 220. For example, the support plate 210 can be designed as a Plexiglas plate.

[0032] To avoid or reduce crosstalk between the adjacent read / write modules 100 of the device 200 during the parallel writing and / or reading of the multitude of RFID tags, as already mentioned above in connection with the Fig. As described in Figures 1a-c, each read / write module 100 comprises a shielding housing arrangement with an inner housing 120 and an outer housing 130, in which the inner housing 120 is arranged. As described in detail below, the inner housing 120 and the outer housing 130 of the read / write modules 100 of the device 200 provide double shielding between adjacent read / write modules 100. The RFID antenna 110 is located in and thus near the inner housing 120, which, according to one embodiment, is designed such that the resonant frequency and / or the impedance of the RFID antenna 110 is negligibly influenced by the inner housing 120.

[0033] The outer housing 130 is located further away from the RFID antenna 110 than the inner housing 120 and, according to one embodiment, is designed in the form of a cup with a rectangular cross-section in order to completely shield the RFID antenna 110 on five sides, thereby significantly reducing crosstalk to adjacent read / write modules 100. According to another embodiment, the outer housing 130 is designed and arranged relative to the inner housing 120 containing the RFID antenna 110 such that the outer housing 130 has a negligible influence on the resonant frequency and impedance of the RFID antenna 110 located in the inner housing 120.This has the particular advantage that the RFID antenna 110 no longer needs to be specially tuned in this new environment after assembly (together with the inner housing 120) in the outer housing 130, but a one-time tuning of the RFID antenna 110 after assembly in the inner housing 120 during the manufacture of the read / write module 100 is sufficient.

[0034] As further in the Fig. As shown in Figure 2b, according to one embodiment, the defined vertical distance Dz of the inner housing 120 with the RFID antenna 110 mounted therein from the bottom wall 131e of the outer housing 130 is greater than a defined vertical distance dz between the RFID antenna 110 and a bottom wall 121e of the inner housing 120. The defined vertical distance Dz of the inner housing 120 with the RFID antenna 110 mounted therein can be at least 5 centimeters from the bottom wall 131e of the outer housing 130.

[0035] In one embodiment, the one or more spacers 140a,b are further configured to hold the inner housing 120 with the RFID antenna 110 mounted therein at a defined horizontal distance Dx between at least one side wall 121a-d of the inner housing 120 and the corresponding side wall 131a-d of the outer housing 130. The defined horizontal distance Dx between the at least one side wall 121a-d of the inner housing 120 and the corresponding side wall 131a-d of the outer housing 130 can be at least 1 centimeter.

[0036] The defined vertical distance Dz of the inner housing 120 with the RFID antenna 110 mounted therein from the bottom wall 131e of the outer housing 130 can be greater than the defined horizontal distance Dx between at least one side wall 121a-d of the inner housing 120 and the corresponding side wall 131a-d of the outer housing 130.

[0037] A preferred embodiment according to the invention of the inner housing 120 and the outer housing 130 of a read / write module 100 of the device 200 is described in the Fig. 1a-c and the Fig. Figures 3a-d illustrate this. In the preferred embodiment shown, the inner housing 120, in which the RFID antenna 110 is mounted, is designed as a frame surrounding the RFID antenna 110. Designing the inner housing 120 as a surrounding frame has the advantage that the resonant frequency and impedance of the RFID antenna 110 are only minimally affected. Furthermore, according to one embodiment, the frame-designed inner housing 120 can be rigidly connected to the RFID antenna 110, so that the influence of the inner housing 120 on the resonant frequency and impedance of the RFID antenna 110 can be compensated for by suitable tuning of the RFID antenna 110, for example, during the manufacture of the device 200. According to one embodiment, the RFID antenna 110 can have a suitable capacitor for tuning the resonant frequency and impedance.For this purpose, the RFID antenna 110 can, for example, include one or more adjustable variable capacitors in an electrical matching network of the RFID antenna 110, which is attached to the output of an antenna coil of the RFID antenna 110. The electrical matching network of the RFID antenna 110 serves to match the impedance of the RFID antenna 110 to the impedance of the RFID electronics (usually 50 ohms). This ensures that the electrical power supplied by the RFID electronics is completely radiated via the RFID antenna 110.

[0038] How this manifests itself in particular in the Fig. 3a and Fig. As can be seen from Figure 3d, according to one embodiment, the frame-shaped inner housing 120 can consist of one or more segments which are insulated together via an air gap 123. Due to the segmentation of the frame-shaped inner housing 120 by the air gap 123, which is exemplified in the side wall 121d, it is possible to prevent the formation of annular eddy currents in the frame-shaped inner housing 120. In a [figure / model] shown in the Fig. In the embodiment shown in Figure 3d, the air gap 123 has a width b between 0.1, 0.2, 0.3, or 0.4 and 0.6, 0.7, 0.8, 0.9, or 1 millimeter, in particular 0.5 millimeters. According to one embodiment, the inner housing 120 is made of aluminum. According to another embodiment, the inner housing 120 can be designed as a suitably curved, circumferential sheet metal that surrounds the RFID antenna 110 in a frame-like manner. The two ends of the sheet metal (in the figures, the sections of the side wall 121d) can be fastened to each other with a plastic connector that is inserted into plug-in openings 127 in the side wall.

[0039] According to one embodiment, the side walls 121a and 121c of the inner housing 120 can have a plurality of parallel receiving slots 124, which are formed in pairs at different heights of the side walls 121a and 121c of the inner housing 120, in order to receive projections or lugs 111 on the side edges of the RFID antenna for mounting the RFID antenna 110 in the inner housing 120. Due to the plurality of receiving slots 124 at different heights of the side walls 121a and 121c, the height of the RFID antenna 110 within the inner housing 120 can be suitably selected.

[0040] As in the Fig. 1c and Fig. As shown in 3c, for example, an opening 125 for supply and / or signal cables for the RFID antenna 110 can be formed in the side wall 121c of the inner housing 120.

[0041] As described above, the outer housing 130, with its side walls 131a-d and bottom wall 131e, is designed in the shape of a cup with a rectangular cross-section, i.e., as an outer housing 130 closed on five sides, into which the RFID antenna 110, together with the inner housing 120, can be inserted from above. To limit the influence of the outer housing 130 on the resonant frequency and the impedance of the (already tuned) RFID antenna 110 as much as possible, the outer housing 130 is built tall, so that the electromagnetic field generated by the RFID antenna 110 can also extend below the RFID antenna 110, i.e., between the underside of the RFID antenna 110 and the bottom wall 131e of the outer housing 130. According to one embodiment, the vertical distance Dz between the bottom wall 131e of the outer housing 130 and the inner housing 120 or the RFID antenna 110 mounted therein is at least 5 cm, preferably at least 7 cm.As shown in the figures, the respective horizontal distance Dx between the side walls 121a-d of the inner housing 120 and the corresponding side walls 131a-d of the outer housing 130 can be smaller than the vertical distance Dz between the bottom wall 131e of the outer housing 130 and the inner housing 120 or the RFID antenna 110 mounted therein.

[0042] As in the Fig. As shown in 1a-c, for example, one or more openings 135a,b for supply and / or signal cables for the RFID antenna 110 can be formed in the side walls 131a and / or 131c of the outer housing 130.

[0043] According to one embodiment, the outer casing 130 with the side walls 131a-d and the bottom wall 131e is made of aluminium. Fig. Figure 4 shows a top view of a cut sheet metal part with exemplary dimensions for forming the outer housing 130 of a read / write module 100 of the device 200 according to one embodiment. As can be seen Fig. As can be seen from section 4, the side walls 131a-d of the outer housing 130 can be formed by the side parts of the in Fig. The sheet metal shown in section 4 is bent upwards. According to one embodiment, the edges of the side parts of the sheet metal shown in the Fig. The sheet metal shown in Figure 4 is designed such that the side walls 131a-d of the outer housing 130 do not touch, but rather an air gap 133a-d is formed between each adjacent side wall 131a-d. In one embodiment, each air gap 133a-d has a width between 0.1, 0.2, 0.3, or 0.4 and 0.6, 0.7, 0.8, 0.9, or 1 millimeter, in particular 0.5 millimeters. The segmentation of the outer housing 130 by the air gaps 133a-d serves to prevent the formation of annular eddy currents in the outer housing that could weaken the electromagnetic field generated by the RFID antenna 110.

[0044] As in the Fig.As further shown in Figure 4, the bottom wall 131e of the outer housing 130 can comprise a plurality of fastening holes 137 for fastening the spacers 140a,b and / or for fastening the corresponding read / write module 100 to a base body of the device 200. REFERENCE MARK LIST 100 read / write modules or RFID readers 110 RFID antenna 111 noses of the RFID antenna 120 inner housings 121a-d Side walls of the inner housing 121e Bottom wall of the inner housing 123 Air gap in one of the side walls of the inner housing 124 slots for mounting the antenna noses 125 Opening in a side wall of the inner housing 127 plug-in openings for closing the inner housing 130 outdoor enclosures 131a-d Side walls of the outer casing 131e Bottom wall of the outer casing 133a-d Air gap between the side walls of the outer casing 135a,b Openings in side walls of the outer casing 137 mounting holes 140a,b Spacers between inner housing and outer housing 200 Device for parallel writing and / or reading of a large number of RFID tags 210 support plate 220 RFID tags b Width of the air gap in one of the side walls of the inner housing Dx horizontal distance between the side walls of the inner and outer housing dz vertical distance between the RFID antenna and the bottom wall of the inner housing Dz vertical distance between the bottom walls of inner and outer housing

Claims

[1] Device (200) for parallel writing to and / or reading from a plurality of RFID tags (220), wherein the device (200) comprises a read / write module (100) for each RFID tag (220), wherein each read / write module (100) comprises a shielding housing arrangement (120, 130) with an inner housing (120) and an outer housing (130) and an RFID antenna (110) which is arranged in the inner housing (120) and is designed to interact with the RFID tag (220), wherein the inner housing (120) and the outer housing (130) are arranged at a distance from one another and are designed to prevent crosstalk to an adjacent read / write module (100). [2] The device (200) of claim 1, wherein the inner housing (120) is made of aluminum. [3] Device (200) according to claim 1 or 2, wherein the inner housing (120) comprises side walls (121a-d) which define a frame surrounding the RFID antenna (110). [4] The device (200) of claim 3, wherein the inner housing (120) comprises a bent sheet metal. [5] Device (200) according to claim 3 or 4, wherein an air gap (123) is formed in at least one side wall (121a-d) of the inner housing (120) to avoid eddy currents in the inner housing (120). [6] Device (200) according to claim 5, wherein the air gap (123) formed in at least one of the side walls (121a-d) of the inner housing (120) has a width (b) between 0.1, 0.2, 0.3 or 0.4 and 0.6, 0.7, 0.8, 0.9 or 1 millimeter, in particular of 0.5 millimeter. [7] Device (200) according to one of the preceding claims, wherein the outer housing (130) comprises side walls (131a-d) and a bottom wall (131e) which define a cup with a rectangular cross-section enclosing the inner housing (120) with the RFID antenna (110) mounted therein. [8] Device (200) according to claim 7, wherein each read / write module (100) further comprises one or more spacers (140a,b) which are designed to hold the inner housing (120) with the RFID antenna (110) mounted therein at a defined vertical distance (Dz) from the bottom wall (131e) of the outer housing (130). [9] Device (200) according to claim 8, wherein the defined vertical distance (Dz) of the inner housing (120) with the RFID antenna (110) mounted therein is at least 5 centimeters from the bottom wall (131e) of the outer housing (130). [10] Device (200) according to claim 8 or 9, wherein the defined vertical distance (Dz) of the inner housing (120) with the RFID antenna (110) mounted therein from the bottom wall (131e) of the outer housing (130) is greater than a defined vertical distance (dz) between the RFID antenna (110) and a bottom wall (121e) of the inner housing (120). [11] Device (200) according to one of claims 8 to 10, wherein the one or more spacers (140a,b) are further configured to hold the inner housing (120) with the RFID antenna (110) mounted therein at a defined horizontal distance (Dx) between at least one side wall (121a-d) of the inner housing (120) and the corresponding side wall (131a-d) of the outer housing (130), and wherein the defined horizontal distance (Dx) between the at least one side wall (121a-d) of the inner housing (120) and the corresponding side wall (131a-d) of the outer housing (130) is at least 1 centimeter. [12] Device (200) according to claim 11, wherein the defined vertical distance (Dz) of the inner housing (120) with the RFID antenna (110) mounted therein from the bottom wall (131e) of the outer housing (130) is greater than the defined horizontal distance (Dx) between the at least one side wall (121a-d) of the inner housing (120) and the corresponding side wall (131a-d) of the outer housing (130). [13] Device (200) according to one of claims 7 to 12, wherein the outer housing (130) comprises a bent sheet metal. [14] Device (200) according to one of claims 7 to 13, wherein an air gap (133a-d) is formed between at least one pair of adjacent side walls (131a-d) of the outer housing (130) to avoid eddy currents in the outer housing (130). [15] Device (200) according to claim 14, wherein the air gap (123) formed between at least one pair of adjacent side walls (131a-d) of the outer housing (130) has a width between 0.1, 0.2, 0.3 or 0.4 and 0.6, 0.7, 0.8, 0.9 or 1 millimeter, in particular 0.5 millimeter.

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