Transparent container wall with machine readable marking

Abstract

A method and system for applying a machine readable marking (10) to a container (20). An inverted arrangement (10i) of the machine readable marking (10) is determined. The inverted arrangement (10i) is applied to a transparent wall (21) of the container (20), preferably using a laser marking system. The elements (11L) of the inverted arrangement (10i), as applied to the transparent wall (21), have a color (L) forming the background of the machine readable marking (10). Respective transparent areas (21T) of the transparent wall (21) are arranged in between the applied elements (11L) in accordance with an arrangement of elements (11D) forming the machine readable marking (10). The container (20) may be filled by contents (C) which has a color (D) appearing through the transparent areas (21T). The color (D) of the contents (C) may contrast pattern with the color (L) of the applied elements (11D).

Description

[0001] Title: TRANSPARENT CONTAINER WALL WITH

[0002] MACHINE READABLE MARKING

[0003] TECHNICAL FIELD AND BACKGROUND

[0004] The present disclosure relates to methods and systems for applying a machine readable marking to a transparent container wall, computer programs for applying such markings, and containers having a transparent wall with a machine readable marking.

[0005] Machine-readable (MR) markings may be used in various applications, including inventory management, product tracking, product information, et cetera. Some products may be held inside a container, and the MR marking may be applied to a surface of the container to encode corresponding information. For example, beverages and food articles are typically sold in containers such as bottles and other packages. MR markings such as linear barcodes and two dimensional matrix codes (e.g. QR code), may be imaged by a camera or scanner, and the information may be decoded using image processing. Typically, the MR marking may be printed at the same time as other graphics adorning the container, e.g. together with other (human-readable) product information, images, text, et cetera. Alternatively, the MR marking may be printed on a separate label or wrapper, which may be applied onto an existing container. The MR marking may also applied directly onto a container. However, it may be difficult to apply MR markings on surfaces of plastic and glass containers. For example, such materials may not be easily printed on and if the surface is transparent, this may require multiple ink patterns to form contrasting black and white colors of a typical MR marking.

[0006] There is yet a need for further improvement in the application of machine readable markings to transparent container walls such as plastic and glass containers. SUMMARY

[0007] According to some aspects of the present disclosure, methods and systems are provided for applying a machine readable marking to a transparent container wall. The machine readable marking is defined by an arrangement of first elements on a contrasting background. An inverted arrangement of the machine readable marking is determined. The inverted arrangement is defined by an arrangement of second elements exclusively forming the background of the machine readable marking, which is complementary to the arrangement of first elements. The inverted arrangement is applied to a transparent wall of the container. The second elements of the inverted arrangement, as applied to the transparent wall, thus form the background of the machine readable marking while respective transparent areas of the transparent wall are arranged in between the second elements in accordance with the arrangement of first elements.

[0008] As will be appreciated, marked areas of the transparent wall may generally become relatively less transparent, e.g. more reflective, scattering, or opaque, compared to unmarked areas. When imaging the surface of the container, a contrast between the transparent and opaque areas of the first elements and second elements, respectively, may appear as contrasting elements of the machine readable marking may appear. This may be especially the case when the opaque areas scatter more light in the direction of the imaging device thus appearing as relatively white areas. Contrast may be further enhanced by arranging an object or substance having a contrasting color behind the transparent wall. By filling the container with contents having a colour, which contrasts with the color of the applied markings, the first elements of the machine readable marking may be formed by the colour of the contents appearing through the respective transparent areas of the transparent wall in between the second elements of the inverted arrangement applied to the transparent wall. By creating a frame or background margin around the elements that form the machine readable marking, e.g. around the bars or modules of a barcode, machine readability may be improved. For example, this may facilitate a conventional imaging device or scanner to determining a background color of the machine readable marking and / or facilitate definition of transparent elements at the edges of the machine readable marking.

[0009] According to other or further aspects of the present disclosure, a system is configured to receive information to be encoded, convert the information into an inverted arrangement of a machine readable marking that encodes the information, and apply the inverted arrangement to a transparent wall of a container. Preferably, a laser system is used wherein the inverted arrangement is applied by a laser beam to the transparent wall, which is most preferably made of transparent plastic such as PET. By applying the inverted arrangement, i.e. second elements, using a laser system, laser marked of the transparent wall forming the second elements may have decreased transparency compared to the unmarked areas of the transparent wall. For example, the decreased transparency may be caused at least in part by the second elements having increased scattering characteristics compared to the unmarked areas of the transparent wall. Accordingly, the second elements may appear with a relatively scattering white color when imaging the machine readable marking whereas the first elements may have a relatively dark or absorbing color, e.g. caused by the contents of the container having a darker color. By forming the transparent wall is of a transparent plastic material, such as polyethylene terephthalate (PET), the transparency of the wall can be easily and quickly modified by a laser beam

[0010] Other or further aspects of the present disclosure may be embodied as a (non-transitory) computer-readable medium storing instructions that, when executed by a controller of a system, preferably a laser marking system, causes the system to perform operational acts as described herein, such as receiving information to be encoded, converting the information into an inverted arrangement of a machine readable marking that encodes the information, and applying the inverted arrangement to a transparent wall, preferably using a laser beam.

[0011] Other or further aspects of the present disclosure may be embodied as a container having a transparent wall, wherein an inverted arrangement of a machine readable marking is applied to the transparent wall, preferably using laser marking, wherein the machine readable marking is defined by an arrangement of first elements on a contrasting background, wherein the inverted arrangement is defined by an arrangement of second elements exclusively forming the background of the machine readable marking, which is complementary to the arrangement of first elements, wherein the second elements of the inverted arrangement, as applied to the transparent wall, have a second color forming the background of the machine readable marking, wherein respective transparent areas of the transparent wall are arranged in between the second elements in accordance with the arrangement of first elements, and wherein preferably the container is filled by contents having a first color (e.g. black or dark) that contrast with the second color (e.g. white).

[0012] BRIEF DESCRIPTION OF DRAWINGS

[0013] These and other features, aspects, and advantages of the apparatus, systems and methods of the present disclosure will become better understood from the following description, appended claims, and accompanying drawing wherein:

[0014] FIGs 1A - 10 illustrate application of a machine readable marking on a transparent container wall;

[0015] FIG 2 illustrates details of a machine readable marking applied to a transparent wall by laser marking;

[0016] FIG 3 illustrates a system for applying a machine readable marking according to an inverted arrangement; FIGs 4A and 4B illustrate photographs of a machine readable marking applied by a laser marking system to a PET bottle which may be filled by dark liquid.

[0017] DESCRIPTION OF EMBODIMENTS

[0018] Terminology used for describing particular embodiments is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "and / or" includes any and all combinations of one or more of the associated listed items. It will be understood that the terms "comprises" and / or "comprising" specify the presence of stated features but do not preclude the presence or addition of one or more other features. It will be further understood that when a particular step of a method is referred to as subsequent to another step, it can directly follow said other step or one or more intermediate steps may be carried out before carrying out the particular step, unless specified otherwise. Likewise it will be understood that when a connection between structures or components is described, this connection may be established directly or through intermediate structures or components unless specified otherwise.

[0019] As described herein, a machine-readable marking can be used to encode (useful) information in a specific pattern applied to a surface, which is intended for readout by a machine, typically including an imaging device. The marking is typically defined by a contrasting pattern of dark and light areas, most commonly black and white, so that elements of the pattern can be distinguished by the imaging device. In a linear barcode pattern, the dark elements are typically referred to as “bars”, while the light elements are typically referred to as “spaces”. The smallest dark or light elements (e.g. pixels) in the pattern forming a two dimensional (2D) matrix code is typically referred to as a “module”. Advantageously, a 2D matrix code may store data in both vertical and horizontal dimensions, allowing it to hold significantly more information than linear barcodes. The grid of dark and light modules in a 2D matrix code may be arranged at specific coordinates, with each module corresponding to a distinct coordinate pair defined by its horizontal (X) and vertical (Y) positions. The standardized structure of the grid may dedicate specific sections to encoding different types of information, such as data bits and error correction codes, ensuring the code remains readable even if partially damaged. Also other arrangements or coordinates may be used, e.g. radial. It will be understood that these are encompassed by the term “2D matrix code”.

[0020] In principle, the encoded data may include alphanumeric characters, binary data, and other forms of information. The arrangement of bars or modules typically follows a precise encoding algorithm specific to the type of marking. The encoding process typically involves converting input data into a binary format and mapping these values to the appropriate coordinates along the bar and / or within the grid. Error correction algorithms may add redundancy to enhance the code's resilience. The marking may thus be a precisely arranged pattern that can be scanned to retrieve the encoded information.

[0021] An imaging device, such as a scanner or camera, may read the marking, and / or the captured image can be processed to extract the encoded information. This process may involve error correction algorithms to ensure accurate interpretation of the code, even if parts are damaged or obscured. The colors of the bars, modules, or spaces of the marking may vary depending on the lighting and sensing conditions of the imaging device used for reading the code. The marking typically has contrasting colors, e.g. dark and light, in the visible wavelength range or other ranges such as infrared, with differing absorption and reflection coefficients suitable for the readout device. Various types of 2D matrix codes exist, each offering specific advantages for different applications. For example, QR codes are highly versatile and can store a significant amount of data, including alphanumeric characters, binary data, and URLs, making them popular in marketing, product tracking, and information dissemination. Micro QR codes are a smaller variant suitable for small products and components. Data Matrix codes are known for their high data density and robust error correction capabilities, making them ideal for small items like electronic components and pharmaceuticals. PDF417 codes are stacked linear barcodes that encode large volumes of text and binary data, often used in transportation and inventory management. Aztec codes feature a central finder pattern and can be read even if partially damaged, useful in high-reliability applications like transportation tickets and vehicle registration. MaxiCode, with its fixed-size hexagonal grid, is designed for fast and reliable scanning in logistics and shipping industries. Code One can encode both text and numeric data and is often used in document management. Han Xin Code supports the encoding of Chinese characters along with other data, primarily used in logistics and retail within China. Each type of 2D matrix code is tailored to meet specific industrial and commercial needs, ensuring efficient and accurate data encoding and retrieval.

[0022] Different types of codes may have different characteristics. For example, QR codes typically have specific structural elements such as the three distinctive corner squares, known as position detection patterns. These position detection patterns are located at three corners of the QR code, defining a square grid, and can be used for determining the orientation, size, and angle of the QR code during scanning. Further elements of the QR code, including alignment patterns, timing patterns, and data cells, may be positioned and sized relative to these position detection patterns, ensuring accurate and efficient decoding of the encoded information. For example, ISO / IEC 18004:2015 defines the current requirements for the symbology known as QR Code. It specifies the QR Code symbology characteristics, data character encoding methods, symbol formats, dimensional characteristics, error correction rules, reference decoding algorithm, production quality requirements, and user-selectable application parameters. In the meantime, also new standards are developed, such as ISO / IEC PRF 18004 may replace the current standard.

[0023] In general, it will be understood that the present teachings are directed to a specific way of applying a machine readable marking, in particular to a transparent container wall, and are not limited to any specific type of marking and / or any specific encoding standard. In principle, an inverted machine readable marking as described herein may be applied to a transparent surface in various ways. However, the present methods and systems most preferably involve the use of a laser beam, e.g. as laser part of a laser marking system, to apply the marking directly to the transparent surface. Advantageously, a laser marking system may use laser induced alteration of the transparent material itself to create a contrasting pattern and may not require any further materials, such as ink, to be applied.

[0024] Without being bound by theory, various mechanisms may contribute to laser-marked regions of an initially transparent surface changing appearance. The change in appearance may include one or more of the marked surface becoming less transparent, becoming more opaque, becoming more reflective, becoming more scattering, changing color and / or obtaining a color, e.g. getting becoming more white in appearance. For example, the laser may contribute to roughening of the surface, e.g. through controlled ablation or localized melting and rapid cooling, creating microstructures that diffusely scatter light. For example, the laser's intense heat may induce the formation of microbubbles, foam, and / or microcracks within the material, causing light scattering that results in a white appearance. For example, the laser's heat may promote crystallization of an initially amorphous structure, altering the microstructure and scattering light differently to produce a white appearance. For example, changes in the refractive index due to laser exposure may disrupt the uniform transmission of light, contributing to a white and / or less transparent appearance. Optionally, the transparent material of the wall and / or coating on the wall may include additives or chemicals that react to laser radiation by changing their physical state, resulting in a white appearance and / or obtaining any other color depending on the additives or chemicals.

[0025] As will be appreciated, various transparent materials may be marked by a laser to change their transparency characteristic. Most notably, plastics such as polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene (PE), and polyamide (PA or Nylon) can undergo a change in appearance from transparent to white or scattering. Additionally, glass materials, including soda-lime glass, borosilicate glass, quartz glass (fused silica), and aluminosilicate glass, can also be marked in this manner. Specialty coatings and films, such as transparent films with embedded additives and coated glass or plastic surfaces designed for laser marking, may exhibit similar changes. Polymers with additives, such as those doped with foaming agents, laser-sensitive additives, or embedded microbubbles, can also transition to a white appearance. Furthermore, other transparent polymers, including thermoplastic polyurethane (TPU) and cyclic olefin copolymer (COC), as well as certain transparent ceramics, can be affected by laser marking.

[0026] The invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. In the drawings, the absolute and relative sizes of systems, components, layers, and regions may be exaggerated for clarity. Embodiments may be described with reference to schematic and / or crosssection illustrations of possibly idealized embodiments and intermediate structures of the invention. In the description and drawings, like numbers refer to like elements throughout. Relative terms as well as derivatives thereof should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the system be constructed or operated in a particular orientation unless stated otherwise.

[0027] FIGs 1A - 1C illustrate application of a machine readable marking 10 on a transparent container wall.

[0028] In some embodiments, an inverted arrangement lOi of the machine readable marking 10 is determined. In one embodiment, the inverted arrangement lOi may be determined by inverting an image of the original machine readable marking 10. In another or further embodiment, the inverted arrangement lOi is determined by directly or indirectly calculating the inverted arrangement lOi from received information to be encoded. In another or further embodiment, the inverted arrangement lOi may be directly received from a pre-processor which may be integrated or separate from the system applying the marking.

[0029] Typically, the machine readable marking 10 is defined by an arrangement of first elements 1 ID on a contrasting background. As described herein, the inverted arrangement lOi is defined by an arrangement of second elements 1 IL which is complementary to the arrangement of first elements 11D. Accordingly, the second elements 11L applied to the transparent wall 21 may essentially form only the background of the original machine readable marking 10.

[0030] In some embodiments, the inverted arrangement lOi is applied to a transparent wall 21 of the container 20. In one embodiment, the second elements 11L of the inverted arrangement lOi, as applied to the transparent wall 21, have a second color “L” forming the background of the machine readable marking 10. In another or further embodiment, respective transparent areas 2 IT of the transparent wall 21 are arranged in between the second elements 1 IL in accordance with the arrangement of first elements 11D.

[0031] In some embodiments, the container 20 is filled by contents “C” having a first colour “D”, which contrasts with the second color “L”, wherein the first elements 11D of the machine readable marking 10 are formed by the first colour “D” of the contents “C” appearing through the respective transparent areas 2 IT of the transparent wall 21 in between the second elements 11L of the inverted arrangement applied to the transparent wall 21 having the second color.

[0032] In some embodiments, a frame 12 is applied around the machine readable marking 10. Preferably, the frame 12, as applied to the transparent wall 21, has the second color “L” forming a background margin around the machine readable marking 10. The inventors find that forming a frame or background margin around the elements forming the machine readable marking, e.g. around the bars or modules, may improve machine readability. For example, this may facilitate a conventional imaging device or scanner to determining a background color of the machine readable marking and / or facilitate definition of transparent elements at the edges of the machine readable marking.

[0033] In a preferred embodiment, the second elements 11L and / or margin 12L are applied by a laser marking system 100. In one embodiment, the laser marking system 100 is configured to cause that laser marked of the transparent wall 21 forming the second elements 11L have decreased transparency compared to the unmarked areas of the transparent wall 21 (including the transparent areas 2 IT forming the arrangements of first elements 11D in between the second elements 11L).

[0034] In some embodiments, a decreased transparency of the second elements 11L is caused at least in part by the second elements 11L having increased scattering characteristics compared to the unmarked areas of the transparent wall 21. In one embodiment, the increased scattering causes the second elements 11L to appear with a relatively light color when imaging the machine readable marking 10, e.g. using a camera. Most preferably, the (laser) marked second elements 11L have a general whitish appearance. In another or further embodiment, the container 20 is filled by contents “C” having a relatively dark color “D”. Accordingly, the relatively dark color “D” may appear through the respective transparent areas 2 IT of the transparent wall 21 so that the arrangements of first elements 11D appears to have a relatively dark color contrasting with the relatively light color of the second elements 11L, e.g. when imaging the machine readable marking 10.

[0035] In some embodiments, the second elements 11L have a higher reflection coefficient than the respective transparent areas 2 IT there between and / or higher reflection coefficient than contents “C” filling the container 20. For example, the second elements 11L are configured to reflect, e.g. scatter, at least 10% of light, preferably at least 20% of light, more preferably at least 50% of light, more preferably at least 75% of light, e.g. up to 90% or essentially all the light (fully reflective). For example, the respective transparent areas 2 IT are configured to transmit at least 10% of light, preferably at least 20% of light, more preferably at least 50% of light, more preferably at least 75% of light, e.g. up to 90% or essentially all the light (fully transparent). For example, the contents “C” are configured to absorb at least 10% of light, preferably at least 20% of light, more preferably at least 50% of light, more preferably at least 75% of light, e.g. up to 90% or essentially all the light (fully absorbing). Preferably, said characteristics may hold at least for visible light and / or infrared light.

[0036] In some embodiments, the transparent wall 21 is formed by a plastic material. The inventors find that transparent plastic materials may be relatively easily marked by a laser. In principle also other transparent materials may be used such as glass. Most preferably, the transparent wall 21 is made of polyethylene terephthalate (PET) or similar transparent plastic materials. Advantageously, PET has a relatively high transparency, as well as good strength and thermo-stabihty making it surprisingly suitable for the laser marking process as described herein. PET is also highly suitable to form various types of containers. For example, PET is used in the manufacturing of beverage bottles, food packaging, et cetera. In one embodiment, the present methods are applied in the manufacturing of PET bottles, e.g. bottles intended to hold a dark liquid such as cola. Of course also other types of containers and / or contents may be envisaged. For example, containers may also be made of any one or more of Polycarbonate (PC), Acrylic (PMMA), and Polypropylene (PP).

[0037] Some aspects of the present disclosure relate to a container 20 having a transparent wall 21, e.g. as illustrated in FIG IB or 1C. In the embodiment shown, an inverted arrangement lOi of a machine readable marking 10 is applied to the transparent wall 21. The machine readable marking 10 is defined by an arrangement of first elements 1 ID on a contrasting background, wherein the inverted arrangement lOi is defined by an arrangement of second elements 11L exclusively forming the background of the machine readable marking 10, which is complementary to the arrangement of first elements 11D. The second elements 11L of the inverted arrangement lOi, as applied to the transparent wall 21, have a second color “L” forming the background of the machine readable marking 10 whereas respective transparent areas 2 IT of the transparent wall 21 are arranged in between the second elements 1 IL in accordance with the arrangement of first elements 11D. In a preferred embodiment, e.g. as shown in FIG 1C, the container 20 is filled by contents “C” having a first colour “D” (preferably dark), which contrasts with the second color “L” (preferably light). Accordingly, the first elements 11D of the machine readable marking 10 are formed by the first colour “D” of the contents “C” appearing through the respective transparent areas 2 IT of the transparent wall 21 in between the second elements 11L of the inverted arrangement applied to the transparent wall 21 having the second color. Preferably, a frame 12 is applied around the machine readable marking 10, wherein the frame 12, as applied to the transparent wall 21, has the second color “L” forming a background margin around the machine readable marking 10. Most preferably, the second elements 11L and / or margin 12L are applied by a laser marking system 100, e.g. as described below.

[0038] FIG 2 illustrates details of a machine readable marking 10 applied to a transparent wall 21 by laser marking. In the embodiment shown, the machine readable marking 10 is formed by an arrangement of elements “E”. In the case of a QR code, these elements are typically referred to as “modules”. Also other arrangements of elements such as pixels and / or bars may be envisaged depending on the type of machine readable marking. As described herein, the dark elements form the arrangement of first elements 1 ID and the light elements form the arrangement of second elements 11L.

[0039] In some embodiments, a spot size of a laser beam impinging the transparent wall 21 is configured so that a linewidth Lw of a line drawn by the laser on the transparent wall 21 matches a respective size Ex,Ey of respective single element in the arrangement of elements E with a tolerance of less than 30% (e.g. 0.7*Ey<Lw<1.3*Ey and 0.7*Ex<Lw<1.3*Ex) , preferably less than 20%, more preferably less than 10%. Most preferably the linewidth Lw is essentially the same as the element size Ex,Ey. In this way a separation width Ls between the lines may be minimized and machine readout of the pattern may be facilitated. A period Lp between adjacent lines and or between adjacent elements preferably corresponds to the element size Ex,Ey. For a 2D matrix marking, as shown, preferably the element size Sx in one direction is the same or similar as the element size Sy in another direction. For a linear barcode not shown the element size in one direction is typically larger than in the other direction. Preferably, a margin size 12w of the aforementioned frame 12, applied around the elements E of the machine readable marking 10, is larger than a minimum size Sx,Sy of a single element E in the arrangement of elements (e.g. the arrangement of first elements 11D and / or second elements 11L). Preferably, the margin size 12w is larger the size of a single element by at least a factor two, more preferably at least a factor three, or at least a factor four (as shown here). The inventors find that such margin may be sufficient to be recognized as a surrounding background color for various of machine readout technology. Alternatively, or additionally, the margin size 12w may be determined relative to the size lOw of the machine readable marking 10 inside. For example, the margin size 12 w may be less than size lOw of the machine readable marking 10 by at least a factor two, preferably at least a factor three, up to a factor five, or more. By not unnecessarily increasing a size of the margin, the marking may be applied relatively quickly and / or may minimally impact an overall appearance of the container 20.

[0040] FIG 3 illustrates a system 100 for applying a machine readable marking 10 according to an inverted arrangement lOi. In some embodiments, the system 100 is configured to receive information IC to be encoded. In other or further embodiments, the system is configured to convert the information IC into an inverted arrangement lOi of a machine readable marking 10 that encodes the information IC. For example, in the embodiment shown, the information IC is received by an encoder 61 that encodes the information into an image of a machine readable marking 10. The image of the machine readable marking 10 may be inverted by an image inverter 62 to yield the inverted arrangement lOi. The inverted arrangement may include a frame around the inverted arrangement. Of course also other ways of determining the inverted arrangement lOi may be envisaged. For example, the encoder and image inverter may be integrated in a single component, i.e. the inverted arrangement lOi may be directly determined based on information IC to be encoded. The encoder and image inverter components may be integrated in the system 100, as shown, or embodied separately, e.g. as an add-on on an existing marking system.

[0041] In a preferred embodiment, e.g. as shown, the system 100 comprises a laser marking system. In one embodiment, e.g. as shown, the laser marking system is configured to apply the inverted arrangement lOi using a laser beam B to a transparent wall 21 of a container 20, e.g. according to the methods described herein. For example, the system comprises or accesses a a non-transitory computer-readable medium storing instructions that, when executed by a controller of a system 100, causes the system 100 to perform any of the methods described herein.

[0042] In some embodiments, focusing optics 40 are configured to produce a focusing beam B. For example, the focusing optics 40 comprise one or more focusing elements 41,42 such as lenses and / or curved mirrors. In a preferred embodiment, the set of focusing elements 41,42 comprise at least one spherical surface 4 Is, 42s configured to introduce a respective set of spherical aberrations into the focusing beam B, wherein the spherical aberrations are tuned to maximize a focal region length Lr along which a spot size of the laser spot Ls is smaller than or equal to a respective size of the light color modules 11L. Also conventional optics may be used.

[0043] In some embodiments, a beam steering device 30 is configured to receive the focusing beam B from the focusing optics 40 and controllably redirect the focusing beam B as a moveable laser spot Ls onto the transparent wall 21. In one embodiment, the beam steering device 30 comprises a steering controller 31. In another or further embodiment, the beam steering device 30 comprises at least one beam scanning mirror 32. Also other beam redirection means may be envisaged.

[0044] In some embodiments, a target distance At between the beam steering device 30, e.g. scanning mirror 32, and the transparent wall 21 is relatively large compared to a size of the inverted arrangement lOi, e.g. larger by at least a factor five, preferably at least a factor ten, at least a factor twenty, or even more than a factor forty. For example, the target distance At may more than ten centimeter, more than twenty centimeter, or even more than forty centimeter, up to one meter, or more, while the size of the inverted arrangement lOi may be less than two centimeter, less than one centimeter, down to five millimeter, or less. Accordingly, the angle 5 that the scanning mirror 32 needs to move to cover the entire inverted arrangement lOi may be relatively small. For example, the angle 5 may be less than ten degrees (plane angle), preferably less than five degrees, less than three degree, less than two degrees, or even less than one degree. The less the mirror has to move, the quicker it may react and / or the more linear may be the marking coordinates X,Y as function of angle. Advantageously, an f- theta lens, or a similar flat-field lens, may be omitted. For example, the target distance At is determined by the focal distance Af of the focusing optics 40, as shown.

[0045] In some embodiments, a light modulator 50 is configured to controllably activate and deactivate the laser spot Ls moving along the transparent wall 21. In one embodiment, the light modulator 50 comprises or forms part of a light source configured to generate laser light. In another or further embodiment, the light modulator 50 may receive laser light from an external light source. Preferably, the light source generates laser light in a wavelength range absorbed by the transparent wall 21. Because visible light essentially passes through the transparent wall 21, preferably the wavelength of the laser lights is selected to outside a visible wavelength range, e.g. infrared or UV light, preferably mid-infrared light in a wavelength range between 3 - 50 micrometer. For example, in the production of the images as shown in FIGs 4A and 4B, laser light having as wavelength of 9.3 micrometer was used. While the light modulator 50 is shown here as modulating the laser light before the focusing optics 40, the light modulator 50 can also be placed elsewhere in a path of the focusing beam B before reaching the transparent wall 21. In some embodiments (not shown), an inverter may be inserted to invert a control signal Ca, which is used by the light modulator to determine whether the laser beam should be on or off. In this way the inverted arrangement lOi may be written directly based on a (normal) machine readable marking 10, and the image inverter 62 may be omitted.

[0046] In some embodiments, a controller 60 is configured to generate a scan sequence and / or cause application of an inverted arrangement lOi of a machine readable code 10 as described herein. In one embodiment, the controller 60 is configured to control the beam steering device 30. In another or further embodiment, controller 60 is configured to control the light modulator 50. In other or further embodiments, the controller 60 may also be configured to control the focusing optics 40.

[0047] In some embodiments, the container 20 is provided on a platform 70. For example, the platform 70 is configured to place the container 20 with the transparent wall 21 at a designated target position and / or distance At from the laser marking system 100. In one embodiment, the platform 70 is part of a conveyor system, e.g. endless belt, configured to consecutively and / or simultaneously supply containers in range of the laser marking system 100.

[0048] In some embodiments, an imaging device 80, e.g. camera, is configured to determine an image of one or more of the container 20, the transparent wall 21, and the inverted arrangement lOi, as (being) applied to the transparent wall 21. In one embodiment, the imaging device 80 is used to determine the presence of the container 20 in a target zone of the laser marking system 100. In another or further embodiment, the imaging device 80 is used to determine a position of the container 20 and / or transparent wall 21 within a target range At of the laser marking system 100. For example, the laser marking system 100 may initiate the marking process based on detecting the presence and / or position of the container 20 and / or transparent wall 21. Also other or further types of devices could be used to determine the presence and / or position of the container 20 and / or transparent wall 21, e.g. a LIDAR device (not shown) may be advantageously used to detect the specific position of the transparent wall 21 and / or distance with respect to the laser marking system 100.

[0049] In other or further embodiments, the same imaging device 80, or another imaging device or scanner, is configured to capture an image 10c of the container 20 and / or transparent wall 21 including the machine readable marking 10 and / or inverted arrangement lOi applied thereto. In one embodiment, the captured image is received by an image decoder 81 configure to generate decoded information “DI”, e.g. based on a machinereadout algorithm of the captured image 10c. In another or further embodiment, the decoded information “DI” may be compared to the original information “IC” to be encoded. For example, a comparator program or circuit 63 may determine whether the decoded information “DI” matches the original information “IC” to be encoded in the inverted arrangement lOi of the machine readable marking 10. Based on determining that the information matches, an verification signal (“OK”) may be generated, as shown. In case the information does not match, the system may take further action, such as re-applying the machine readable marking 10 and / or discarding the container 20. For example, the platform 70 may be controlled to discard the container 20 in case the machine readable marking 10 has be incorrectly, or insufficiently applied. For completeness, it may be noted that in the embodiment shown, the container 20 is filled by (dark) contents which may improve the contrast of machine readout. However, this may not be necessary and / or contrast may be provided in other ways, e.g. by placing a dark surface in an imaging path behind the transparent wall 21, e.g. behind the container 20 (not shown). FIGs 4A and 4B illustrate photographs of a machine readable marking applied by a laser marking system to a PET bottle which in FIG 4B was filled by dark liquid, e.g. cola. It may be observed that the machine readable code in FIG 4A is still visible because a dark background was used behind the bottle. On the other hand, the machine readable code of FIG 4B may be especially visible because of the darker contents filling the container, which is visible through the transparent wall.

[0050] For the purpose of clarity and a concise description, features are described herein as part of the same or separate embodiments, however, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described. For example, various advantages may be achieved by applying an inverted arrangement of a machine readable marking using a laser marking system, also alternative ways may be envisaged by those skilled in the art having the benefit of the present disclosure. For example, the inverted arrangement of a machine readable marking could also be applied by other or further techniques such as printing, or using a sticker or label (e.g. having white and transparent areas). The various elements of the embodiments as discussed and shown offer certain advantages, such as quick and efficient application of machine readable markings with minimal material requirements (e.g. ink). Of course, it is to be appreciated that any one of the above embodiments or processes may be combined with one or more other embodiments or processes to provide even further improvements in finding and matching designs and advantages. It is appreciated that this disclosure offers particular advantages to laser marking of plastic containers, and in general can be applied for any application wherein a machine readable marking is to be applied to a container having a transparent wall. In interpreting the appended claims, it should be understood that the word "comprising" does not exclude the presence of other elements or acts than those listed in a given claim; the word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements; any reference signs in the claims do not limit their scope; several "means" may be represented by the same or different item(s) or implemented structure or function; any of the disclosed devices or portions thereof may be combined together or separated into further portions unless specifically stated otherwise. Where one claim refers to another claim, this may indicate synergetic advantage achieved by the combination of their respective features. But the mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot also be used to advantage. The present embodiments may thus include all working combinations of the claims wherein each claim can in principle refer to any preceding claim unless clearly excluded by context.

Claims

CLAIMS1. A method of applying a machine readable marking (10) to a container (20), the method comprising determining an inverted arrangement ( lOi) of the machine readable marking (10), wherein the machine readable marking (10) is defined by an arrangement of first elements (11D) on a contrasting background for encoding information (IC) in a machine readable format, wherein the inverted arrangement ( lOi) is defined by an arrangement of second elements (11L) exclusively forming the background of the machine readable marking (10), which is complementary to the arrangement of first elements (11D); applying the inverted arrangement (lOi) to a transparent wall (21) of the container (20), wherein the second elements (1 IL) of the inverted arrangement (lOi), as applied to the transparent wall (21), have a second color (L) for forming the background of the machine readable marking (10), wherein respective transparent areas (2 IT) of the transparent wall (21) are arranged in between the second elements (11L) in accordance with the arrangement of first elements (11D).

2. The method according to the preceding claim, wherein a frame (12) is applied around the second elements (11L) forming the inverted arrangement ( lOi) of the machine readable marking (10), wherein the frame (12), as applied to the transparent wall (21), has the second color (L) for forming a background margin around the machine readable marking (10).

3. The method according to the preceding claim, wherein the second elements (11L) and margin (12L) are applied by a laser marking system (100).

4. The method according to the preceding claim, wherein the laser marking system (100) is configured to cause that laser marked of the transparent wall (21) forming the second elements (11L) have decreased transparency compared to the unmarked areas of the transparent wall (21) including the transparent areas (2 IT) forming the arrangement of first elements (11D) in between the second elements (11L).

5. The method according to the preceding claim, wherein the decreased transparency is caused at least in part by the second elements (11L) having increased scattering characteristics compared to the unmarked areas of the transparent wall (21), wherein the increased scattering causes the second elements (11L) to appear with a relatively light color when imaging the machine readable marking (10).

6. The method according to any of the preceding claims, wherein the container (20) is filled by contents (C) having a first colour (D), which contrasts with the second color (L), wherein the first elements (11D) of the machine readable marking (10) are formed by the first colour (D) of the contents (C) appearing through the respective transparent areas (2 IT) of the transparent wall (21) in between the second elements (11L) of the inverted arrangement applied to the transparent wall (21) having the second color.

7. The method according to the two preceding claims, wherein the container (20) is filled by contents (C) having a relatively dark color, wherein the relatively dark color appears through the respective transparent areas (2 IT) of the transparent wall (21) so that the arrangement of first elements (11D) appears to have a relatively dark color contrasting with the relatively light color of the second elements (11L).

8. The method according to the preceding claim, wherein the second elements (11L) have a higher reflection coefficient than the respective transparent areas (2 IT) there between and / or higher reflection coefficient than the contents (C) filling the container (20).

9. The method according to any of the preceding claims, wherein the transparent wall (21) is formed by a plastic material, preferably polyethylene terephthalate, PET.

10. The method according to claim 2, or any claim dependent thereon, wherein a margin size (12w) of the frame (12), applied around the machine readable marking (10) is larger than a minimum size (Sx,Sy) of a single element in the arrangement of first elements (11D) and / or second elements (11L) by at least a factor two; and the margin size (12w) is less than a size (lOw) of the combined arrangements of first elements (11D) and second elements (11L) by at least a factor two.

11. A system (100) configured to receive information (IC) to be encoded , convert the information (IC) into an inverted arrangement (lOi) of a machine readable marking (10) that encodes the information (IC) in a machine readable format, and apply the inverted arrangement (lOi) to a transparent wall (21) of a container (20) according to the method of any of the preceding claims.

12. The system (100) according to the preceding claim, comprising a laser marking system configured to apply the inverted arrangement (lOi) to the transparent wall (21)13. A non-transitory computer-readable medium storing instructions that, when executed by a controller of the system (100) of the preceding claim,causes the system (100) to perform the method according to any of the preceding claims.

14. A container (20) having a transparent wall (21), wherein an inverted arrangement ( lOi) of a machine readable marking (10) is applied to the transparent wall (21), wherein the machine readable marking (10) is defined by an arrangement of first elements (11D) on a contrasting background for encoding information (IC) in a machine readable format, wherein the inverted arrangement (lOi) is defined by an arrangement of second elements (11L) exclusively forming the background of the machine readable marking (10), which is complementary to the arrangement of first elements (11D), wherein the second elements (11L) of the inverted arrangement (lOi), as applied to the transparent wall (21), have a second color (L) for forming the background of the machine readable marking (10), wherein respective transparent areas (2 IT) of the transparent wall (21) are arranged in between the second elements (11L) in accordance with the arrangement of first elements (11D).

15. The container (20) according to the preceding claim, wherein a frame (12) is applied around the machine readable marking (10), wherein the frame (12), as applied to the transparent wall (21), has the second color (L) for forming a background margin around the machine readable marking (10), wherein the second elements (11L) and / or margin (12L) are applied by a laser marking system (100); wherein the container (20) is filled by contents (C) having a first colour (D), which contrasts with the second color (L), wherein the first elements (11D) of the machine readable marking (10) are formed by the first colour (D) of the contents (C) appearing through the respective transparent areas (2 IT) of the transparent wall (21) in between the second elements (11L) of the inverted arrangement applied to the transparent wall (21) having the second color.

Images