Ultrafast laser marking of 2d matrix codes

Abstract

A method and system for laser marking a 2D matrix code (MC) onto a target surface (T). A laser spot (Ls) is moved over the target surface (T) according to a scan sequence (S). The laser spot is active for writing pixels (P) in the grid (G), and inactive for leaving empty spaces (E) in the grid (G). For a first set of pixels (Px), the laser spot (Ls) is kept active while writing a first line (Lx) overlapping each of the first set of pixels (Px). For a second set of pixels (Py), the laser spot (Ls) is kept active while writing a second line (Ly) overlapping each of the second set of pixels (Px). The second line (Ly) is perpendicular to the first line (Lx). Advantageously, the 2D matrix code (MC) may be applied relatively quickly.

Description

[0001] Title: ULTRAFAST LASER MARKING OF 2D MATRIX CODES

[0002] TECHNICAL FIELD AND BACKGROUND

[0003] The present invention relates to the field of laser marking technologies and, more specifically, to methods and systems for laser marking various surfaces with machine readable codes, in particular two- dimensional (2D) matrix codes such as Quick Response (QR) codes.

[0004] Two-dimensional (2D) matrix codes such as QR codes find ubiquitous application due to their ability to store significant amounts of data in a compact, two-dimensional format. They are widely used in various industries for product identification, tracking, marketing, and security purposes. Traditional methods of printing 2D matrix codes, such as inkjet and thermal transfer printing, may face limitations in terms of durability, resolution, and environmental impact. These methods can be prone to wear, fading, and damage, especially in harsh environments. Laser marking technology offers a promising alternative due to its precision, permanence, and versatility. Laser marking involves using a focused beam of light to create high-resolution marks on a substrate. This process can be precisely controlled to produce detailed and durable marks that withstand challenging conditions. Advantageously, laser marking has the ability to apply the mark directly onto the product, eliminating the need for separate labels. This is particularly beneficial for containers such as cans and bottles (including bottle caps), or other products where labels are undesirable, such as fruit. Direct marking enhances product aesthetics, reduces waste, and ensures that the mark remains intact and readable throughout the product's lifecycle. Current technologies for laser marking of 2D matrix codes may still face challenges related to speed, efficiency, and accuracy of the marking process, especially in high volume product manufacturing and processing.

[0005] The present invention aims to address challenges of current laser marking techniques, and in particular 2D matrix codes, while maintaining at least some of the current advantages. SUMMARY

[0006] According to a first aspect of the invention, a method is provided for laser marking a 2D matrix code onto a target surface. A laser spot is moved over the target surface according to a scan sequence. The scan sequence corresponds to a two-dimensional path through a sequence of respective coordinates of modules arranged in a grid of the 2D matrix code. During this movement, the laser spot is intermittently active and inactive on the target surface. The laser spot is active for writing respective pixels in the grid and inactive for leaving respective empty spaces in the grid. By allowing the laser spot to stay continuously active while marking contiguous sets of pixels, the number of on-off transitions of the laser may be reduced, enhancing efficiency and speed of the marking process. By writing such lines in two different directions (e.g. both horizontally and vertically), the marking speed and efficiency may be increased, allowing for faster coverage of the grid area and reducing overall marking time. Moreover, by marking continuous lines of contiguous pixels more accurately than individual pixels, the precision of the marked 2D matrix code may be improved, leading to higher quality and more reliable data encoding and retrieval.

[0007] According to a second aspect of the invention, a system is provided for laser marking a 2D matrix code onto a target surface. Focusing optics are configured to produce a focusing beam. A beam steering device is configured to receive the focusing beam from the focusing optics and to controllably redirect the focusing beam as a moveable laser spot onto the target surface. A light modulator is configured to controllably activate and deactivate the laser spot as it moves along the target surface. A controller is configured to control the beam steering device and / or light modulator to perform the method according to the first aspect. By having all focusing optics before the beam steering device (e.g. one or more controllable mirrors), further advantages may be achieved. For example, this configuration may ensure that the beam remains properly focused throughout its entire path, leading to more precise and consistent marking. Advantageously, the beam may be focused at a relatively large distance from the focusing optics, so the mirror(s) in the beam steering device only need to make very small movements to apply the laser marking. This may result in quicker response times and higher marking speeds. It also enhances the reliability and durability of the system by minimizing the mechanical strain on the beam steering components. Moreover, the absence of an f-theta lens may allow for a wider range of marking with similar angular mirror movements.

[0008] According to a third aspect of the invention, a method is provided for generating a scan sequence for laser marking a 2D matrix code onto a target surface. Input information to be encoded in the 2D matrix code may be received and converted into a grid of pixels with respective empty spaces between the pixels, based on an encoding standard of the 2D matrix code. A set of writing lines is determined based on respective sets of contiguously arranged pixels in the grid, with each line in the set of writing lines arranged to overlap one of the respective sets of contiguously arranged pixels. A path of the scan sequence is determined, sequentially traversing each of the set of writing lines as well as any isolated or single pixels in the grid that do not form part of any writing line, with respective writing lines and isolated pixels interconnected by respective non-writing lines. The respective coordinates of the respective parts of the path for sequentially traversing the scan sequence while writing the 2D matrix code may be stored, e.g. in a control file for performing the method according to the first aspect. The set of writing lines comprises at least a first line overlapping a first set of pixels contiguously arranged along a first coordinate of the grid, and at least a second line overlapping a second set of pixels contiguously arranged along a second coordinate of the grid, wherein the second line is arranged perpendicular to the first fine. By organizing the scan sequence in this manner, the efficiency and speed of the marking process may be enhanced. For example, the scan sequence may be used in the method according to the first aspect and / or used in the system according to the second aspect.

[0009] According to a fourth aspect of the invention, at least one or more writing lines may be stored with an extended length that extends beyond the length of the respective sets of contiguously arranged pixels. This extended length may be designed to account for the laser's ramp up and ramp down times, ensuring optimal marking quality and consistency. For example, the extended length may be arranged in the writing direction before the first writing fine to accommodate the laser's ramp up time. This may allow the laser to reach the appropriate marking power before reaching the actual set of contiguously arranged pixels. Alternatively, or additionally, the extended length may be arranged in the writing direction after the first writing line to account for the laser's ramp down time. By incorporating these extended lengths, the system may immediately start moving the mirror while turning on the laser, instead of introducing waiting times at the start of a line for the laser to reach full power before moving the mirror. This may significantly enhance the speed of the marking process, leading to more efficient and high-quality laser marking results.

[0010] According to a fifth aspect of the invention, a non-transitory computer-readable medium is provided, storing instructions that, when executed by a laser marking system for laser marking a 2D matrix code onto a target surface and / or a controller for generating a scan sequence for laser marking a 2D matrix code, cause the system and / or controller to perform the methods described herein. This aspect ensures that the laser marking process can be accurately and efficiently controlled by software, enabling precise execution of the laser marking method. The stored instructions facilitate the management of the scan sequence, activation and deactivation of the laser spot, and the movement of the laser spot over the target surface BRIEF DESCRIPTION OF DRAWINGS

[0011] 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:

[0012] FIGs 1A and IB illustrate photos of 2D matrix codes applied by laser marking onto respective target surfaces;

[0013] FIGs 2 A and 2B illustrate a raster scan path for applying a 2D matrix code line by line;

[0014] FIGs 3 A and 3B illustrate an optimized scan path for applying a 2D matrix code

[0015] FIG 4 illustrates a system and method for laser marking a 2D matrix code onto a target surface, with a top side view of the 2D matrix code on the target surface.

[0016] DESCRIPTION OF EMBODIMENTS

[0017] 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.

[0018] As described herein, a two-dimensional (2D) matrix code is a type of machine-readable marking that encodes information in a specific pattern applied to a surface. The smallest element (dark or light square) of the 2D matrix code is typically referred to as a “module”. The dark of filled in squares may also be referred to as “pixels”, while the light squares or empty positions, may be referred to as “spaces”. Advantageously, the 2D matrix code may stores data in both vertical and horizontal dimensions, allowing it to hold significantly more information than linear barcodes. The grid of pixels in a 2D matrix code may be at specific coordinates, with each pixel 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.

[0019] In principle, the encoded data may include alphanumeric characters, binary data, and other forms of information. The arrangement of these modules and spaces within the grid typically may follow a precise encoding algorithm specific to the type of 2D matrix code, ensuring high- density information storage and reliable data retrieval. The encoding process typically involves converting input data into a binary format and mapping these values to the appropriate coordinates within the grid. Error correction algorithms may add redundancy to enhance the code's resilience. The final 2D matrix code may thus be a precisely arranged pattern that can be scanned to retrieve the encoded information.

[0020] An imaging device, such as a scanner or camera, may read the 2D matrix code, 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 modules and spaces of the 2D matrix code may vary depending on the lighting and sensing conditions of the imaging device used for reading the code. The 2D matrix code can use contrasting colors in the visible wavelength range or other ranges such as infrared, with differing absorption and reflection coefficients suitable for the readout device.

[0021] 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 very 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] Of course, it will be understood that the present teachings are not limited to any specific type of 2D matrix code and / or any specific encoding standard.

[0024] 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.

[0025] FIGs 1A and IB illustrate photos of 2D matrix codes M applied by laser marking onto respective target surfaces T. Using the methods and systems described herein, FIG 1A illustrates a QR code (25 x 25 dot) applied within 20 ms, which is four time faster than using a standard raster scan. FIG IB illustrates a 2D matrix code (14 x 14 dot), as well as two hnes of text being applied within 30 ms, is three times faster than the standard. It will thus be understood that, the scan sequence as described herein may include, in addition to the 2D matrix code, a sequence of lines for drawing other parts, such as human readable text, drawing et cetara.

[0026] FIGs 2 A and 2B illustrate a laser scan path for applying a 2D matrix code MO line by line.

[0027] In some embodiments, a method for laser marking a 2D matrix code MO onto a target surface T comprises moving a laser spot Ls over the target surface T according to a scan sequence S. The scan sequence S corresponds to a two-dimensional path through a sequence of respective coordinates X,Y of modules M arranged in a grid G of the 2D matrix code MO. Typically the laser spot Ls, while moving, is intermittently active and inactive on the target surface T, wherein the laser spot is active for writing respective pixels P in the grid G, and the laser spot is inactive for leaving respective empty spaces E in the grid G.

[0028] Preferably, a spot size Ss of the laser spot Ls corresponds to a respective pixel size mx,my of the pixels P. For example, the laser spot is dimensioned to substantially fill the intended pixel area when marking the target surface, without requiring multiple passes or producing excessive overlap beyond pixel boundaries. By matching the laser spot size to the pixel size, the present methods and systems may enable complete marking of each pixel with a single pass of the laser spot, eliminating the need for multiple overlapping passes to fill a single pixel. For example, this may avoid having to turn around and pass over the same pixels repeatedly. Accordingly, this may also remove constraints related to turning radius or speed limitations that would otherwise be necessary when marking pixels with smaller spots in multiple passes. It will be particularly appreciated that the single-pass approach for each pixel, combined with the ability to write contiguous lines of pixels in different directions (both horizontally and vertically), may contribute to the overall efficiency and speed of the marking process while maintaining high precision and quality of the resulting 2D matrix code.

[0029] In a raster scan method, as shown in FIGs 2A and 2B, the 2D matrix code is written onto a target surface by moving a laser spot across the target surface in a predetermined scan sequence S, covering the entire area of the 2D matrix code through a series of horizontal lines, all in the same direction (here X). For example, the process begins by positioning the laser spot at the starting point Ss of the first row of the 2D matrix code grid. The laser spot moves horizontally across the target surface along the X-axis, alternating between active and inactive states based on the pattern of the 2D matrix code. When the laser spot encounters a module position that needs to be marked, it is activated to create the module, which could, e.g., be a dark or light square (module) depending on the marking process. For positions that do not require marking, the laser remains inactive and / or the light is temporarily interrupted. Once the laser spot reaches the end of the current row, it is moved to the starting position of the next row, typically by shifting it vertically one row along the Y-axis. The transition can occur in a zigzag manner, where the laser reverses direction at the end of each row, or by resetting to the start of the next row in the same horizontal direction. The laser spot may repeat the horizontal scanning process for each subsequent row, continuing this pattern until all rows of the 2D matrix code grid have been processed. The raster scan may ensure that every module position in the grid is addressed in a methodical manner. The process continues until the entire 2D matrix code has been written onto the target surface, resulting in a representation of the code with the desired pattern of dark and light modules. FIGs 3 A and 3B illustrate an optimized laser scan path for applying a 2D matrix code MC. In the embodiment shown, for a first set of pixels Px contiguously arranged along a first coordinate X of the grid G, the laser spot Ls is kept active while writing a first line Lx overlapping each of the first set of pixels Px. For a second set of pixels Py contiguously arranged along a second coordinate Y of the grid G, the laser spot Ls is kept active while writing a second line Ly overlapping each of the second set of pixels Px. For example, each set of pixels is formed by at least two, three, four, or more, pixels which are directly adjacent in the grid of pixels, without empty spaces E there between. In a preferred embodiment, the second line Ly may be arranged transverse, e.g. perpendicular, to the first line Lx. For example, the scan sequence S may include lines in both X (e.g. horizontal) and Y (e.g. vertical) directions.

[0030] In some embodiments, the scan sequence S is based on a vector sequence. Each vector in the vector sequence may determine a respective part of the two-dimensional path traversed along the target surface T. In one embodiment, a first subset of vectors Vx,Vy in the vector sequence correspond to parts of the two-dimensional path where the laser spot Ls is active for writing respective lines Lx,Ly of pixels of the 2D matrix code MC. In another or further embodiment, a second set of vectors Vi in the vector sequence correspond to parts of the of the two-dimensional path where the laser spot Ls is inactive for traveling between the respective vectors in the first set of vectors Vx,Vy without writing and / or leaving respective empty spaces E in the grid G.

[0031] In a preferred embodiment, the vector sequence is optimized to minimize a total path length of the two-dimensional path traversed along the target surface T. Advantageously, the optimized vector sequence may have a total path length that is less than a path traversed by a raster scan method of scanning each line of the grid G. So application of the 2D matrix code MC based on the optimized vector sequence may be faster than if this was based on a raster scan.

[0032] This optimization process may comprise various steps to achieve maximum efficiency. For example, the system may determine all possible contiguous sets of pixels along both the first coordinate (X) and the second coordinate (Y), then compare a first path length using only horizontal vectors to a second path length using a combination of horizontal and vertical vectors, ultimately selecting the path with the shorter total length. The optimization may further involve calculating multiple possible travel paths between writing lines, determining the shortest non-writing vectors (Vi) to interconnect the writing lines, and arranging the writing lines in a sequence that minimizes the total path length including both writing and non-writing vectors.

[0033] In some embodiments, the system may analyze the 2D matrix code (MC) to be marked to determine a ratio of horizontal writing lines to vertical writing lines, and select a scan strategy based on said ratio to minimize the total marking time. This adaptive approach may ensure that each specific 2D matrix code is marked using an optimal strategy tailored to its particular pattern of pixels. Accordingly, such optimization can result in marking times that are faster than conventional raster scanning methods. Furthermore, the optimized vector sequence may enable the laser spot to move at a substantially higher velocity compared to a raster scan method, as the optimization reduces the total number of direction changes and eliminates redundant movements across empty spaces in the grid.

[0034] In some embodiments, the first set of vectors Vx,Vy comprises a first subset of vectors Vx arranged along the first coordinate X of the grid G, and a second subset of vectors Vy arranged along the second coordinate Y of the grid G, wherein a direction of the second coordinate Y is transverse, e.g. perpendicular, to a direction of the first coordinate X. Preferably, vectors in the first subset of vectors Vx that are interconnected with respective vectors in the second subset of vectors Vy, or vice versa, are connected via respective vectors in the second set of vectors Vi. In other words, the laser spot Ls is preferably inactive when transitioning between writing horizontal lines and writing vertical lines, as the laser travels along non-writing vectors Vi during these transitions.

[0035] Most preferably all vectors in the first subset of vectors Vx are interconnected with respective vectors in the second subset of vectors Vy exclusively via respective vectors in the second set of vectors Vi. In this way, the laser spot Ls is always deactivated when changing direction from horizontal to vertical writing or vice versa.

[0036] By deactivating the laser during directional transitions, the present methods and systems may advantageously achieve the efficiency of drawing contiguous pixels in different directions without constraining the writing speed. For example, without the need to keep the laser active during direction changes, the beam steering device can operate at optimal speeds along straight vectors without being limited by a minimum turning radius. For example, the system can execute direction changes rapidly when the laser is inactive, avoiding any curved transitions in the writing pattern that would otherwise slow the process. So, this combination of contiguous pixel marking and unconstrained direction changes may achieve both higher marking precision and reduced total marking time.

[0037] In some embodiments, a scan sequence S for laser marking a 2D matrix code MC onto a target surface T is generated. For example, the scan sequence S may be used in the method and systems described herein. In one embodiment, input information Ic to be encoded in the 2D matrix code MC is received. In another or further embodiment, the input information Ic is converted, e.g. based on an encoding standard of the 2D matrix code MC, into a grid G of pixels P with respective empty spaces E between the pixels P. In another or further embodiment, a set of writing lines Lx,Ly, is determined, based on respective sets of contiguously arranged pixels Px,Py in the grid of pixels P. For example, each line in the set of writing lines is arranged to overlap one of the respective sets of contiguously arranged pixels. In another or further embodiment, a path of the scan sequence S is determined based on the set of writing lines Lx,Ly. The path of the scan sequence S sequentially traverses each of the set of writing lines as well as any isolated or single pixels Ps in the grid G of pixels, not forming part of any writing line. Typically respective writing lines and / or isolated pixels are interconnected by respective non-writing lines (where the laser spot Ls is inactive).

[0038] The resulting scan sequence S may be stored, e.g. in a scan file that can be used by a laser marking system as described herein. Alternatively, or additionally, the scan sequence S may be stored in memory for direct use and / or sent to the laser marking system. In some embodiments, respective coordinates of respective parts of the path are stored for sequentially traversing the scan sequence S while writing the 2D matrix code MC.

[0039] In some embodiments, the set of writing lines comprises at least a first line Lx overlapping a first set of pixels Px contiguously arranged along a first coordinate X of the grid G. In some embodiments, the set of writing lines comprises at least a second line Ly overlapping a second set of pixels Px contiguously arranged along a second coordinate Y of the grid G. In some preferred embodiments, the second line Ly may be arranged transverse, e.g. perpendicular, to the first line Lx.

[0040] In some embodiments, at least one writing line VI in the set of writing lines is stored having an extended length Le extending beyond a length LI of the respective sets of contiguously arranged pixels. For example, the length of the writing line VI, between a point where the laser is instructed to enable and a point where the laser is instructed to disable, may be larger than the length LI of the actual pixels to be written, by a certain offset Le. The offset or extended length Le may be based on a distance that the spot moves between a point that the laser is enabled, and a point where the laser spot has sufficient power, e.g. above a predetermined threshold sufficient to substantially start the laser marking. Alternatively, or in addition, the offset or extended length Le may be related to a (rotational) velocity of the mirror and / or powerup or ramp up time of the laser.

[0041] Advantageously, this extended length approach may allow the laser to “hit the ground running” when marking the pixels. For example, the moving part of the writing device, e.g. rotational mirror, does not need to wait in place while the laser ramps up or down; instead, it can start or keep moving at maximum velocity throughout the marking process. This may eliminate idle waiting time that would otherwise be required at the beginning of each line for the laser to reach full power before the mirror begins moving. For example, the spot may continuously move while powering up and writing the line preferably with constant velocity, or with variable velocity.

[0042] In one embodiment, the extended length Le is arranged, in a writing direction, before the first writing line VI in accordance with a laser ramp up time. This pre-pixel extension may allow the laser to reach its intended marking power while the beam steering device is already in motion, maximizing throughput by eliminating stationary waiting periods. In another or further embodiment, the extended length Le is arranged, in the writing direction, after the first writing line VI in accordance with a laser ramp down time. This may enable the mirror to immediately begin moving toward the next writing position while the laser is still powering down.

[0043] In other or further embodiments, the extended length Le extends beyond an edge Ge of the grid G at least for an initial writing line which initiates the scan sequence S. This feature may represents a rather unique signature of the present methods; normally there are no write lines outside the intended marking area. For example, this deliberate extension beyond the grid boundary can be particularly important when writing lines at the edge of the pattern. For example, the first line when the device first starts speeding up may extend beyond the grid boundary to ensure the system reaches optimal marking conditions precisely when it encounters the first actual pixel to be marked. Similarly, for the last line in the sequence, the extended length may continue beyond the grid edge while the laser is powering down, allowing the system to maintain maximum efficiency until the very end of the marking process.

[0044] FIG 4 illustrates a system 100 for laser marking a 2D matrix code MC onto a target surface T, with a top side view of the 2D matrix code MC on the target surface T.

[0045] In some embodiments, focusing optics 10 are configured to produce a focusing beam B. For example, the focusing optics 10 comprise one or more focusing elements 11,12 such as lenses and / or curved mirrors. In a preferred embodiment, the set of focusing elements 11,12 comprise at least one spherical surface Ils, 12s 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 Ss of the laser spot Ls is smaller than or equal to a respective pixel size (mx,my) of the pixels P. Also conventional optics may be used.

[0046] In some embodiments, a beam steering device 20 is configured to receive the focusing beam B from the focusing optics 10 and controllably redirect the focusing beam B as a moveable laser spot Ls onto the target surface T. In one embodiment, the beam steering device 20 comprises a steering controller 21. In another or further embodiment, the beam steering device 20 comprises at least one beam scanning mirror 22. Also other beam redirection means may be envisaged. In some embodiments, a target distance At between the beam steering device 20, e.g. scanning mirror 22, and the target surface T is relatively large compared to a size DX and / or DY of the 2D matrix code MC, 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 2D matrix code MC may be less than two centimeter, less than one centimeter, down to five millimeter, or less Accordingly, the angle 5 that the scanning mirror 22 needs to move to cover the entire 2D matrix code MC 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 10, as shown.

[0047] In some embodiments, a light modulator 30 is configured to controllably activate and deactivate the laser spot Ls moving along the target surface T. In one embodiment, the light modulator 30 comprises or forms part of a light source configured to generate laser light. In another or further embodiment, the light modulator 30 may receive laser light from an external light source. While the light modulator 30 is shown here as modulating the laser light before the focusing optics 10, the light modulator 30 can also be placed elsewhere in a path of the focusing beam B before reaching the target surface T.

[0048] In some embodiments, a controller 40 is configured to generate a scan sequence S and / or laser mark a 2D matrix code MC as described herein. In one embodiment, the controller 40 is configured to control the beam steering device 20. In another or further embodiment, controller 40 is configured to control the light modulator 30. In other or further embodiments, the controller 40 may also be configured to control the focusing optics 10. 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.

Claims

CLAIMS1. A method for laser marking a 2D matrix code (MC) onto a target surface (T), the method comprising moving a laser spot (Ls) over the target surface (T) according to a scan sequence (S), wherein the scan sequence (S) corresponds to a two-dimensional path through a sequence of respective coordinates (X,Y) of modules (M) forming a matrix of pixels (P) and empty spaces (E) arranged in a grid (G) of the 2D matrix code (MC); wherein the laser spot (Ls), while moving, is intermittently active and inactive on the target surface (T), wherein the laser spot is active for writing respective pixels (P) in the grid (G), and the laser spot is inactive for leaving respective empty spaces (E) in the grid (G); wherein, for a first set of pixels (Px) contiguously arranged along a first coordinate (X) of the grid (G), the laser spot (Ls) is kept active while writing a first line (Lx) overlapping each of the first set of pixels (Px); wherein, for a second set of pixels (Py) contiguously arranged along a second coordinate (Y) of the grid (G), the laser spot (Ls) is kept active while writing a second line (Ly) overlapping each of the second set of pixels (Px); wherein the second line (Ly) is perpendicular to the first line (Lx).

2. A method for generating a scan sequence (S) for laser marking a 2D matrix code (MC) according to the preceding claim, the method comprising receiving input information (Ic) to be encoded in the 2D matrix code (MC); based on an encoding standard of the 2D matrix code (MC), converting the input information (Ic) into a grid (G) of pixels (P) with respective empty spaces (E) between the pixels (P);determining, based on respective sets of contiguously arranged pixels (Px,Py) in the grid of pixels (P), a set of writing lines (Lx,Ly), wherein each line in the set of writing lines is arranged to overlap one of the respective sets of contiguously arranged pixels; determining, based on the set of writing lines (Lx,Ly), a path of the scan sequence (S) which sequentially traverses each of the set of writing lines as well as any isolated pixels (Ps) in the grid (G) of pixels, not forming part of any writing line, wherein respective writing lines and / or isolated pixels are interconnected by respective non-writing lines (Vi); and storing respective coordinates of respective parts of the path for sequentially traversing the scan sequence (S) while writing the 2D matrix code (MC); wherein the set of writing lines comprises at least a first fine (Lx) overlapping a first set of pixels (Px) contiguously arranged along a first coordinate (X) of the grid (G); wherein the set of writing lines comprises at least a second line (Ly) overlapping a second set of pixels (Px) contiguously arranged along a second coordinate (Y) of the grid (G); wherein the second line (Ly) is perpendicular to the first line (Lx).

3. The method according to the preceding claim, wherein the scan sequence (S) is based on a vector sequence, wherein each vector in the vector sequence determines a respective part of the two-dimensional path traversed along the target surface (T); wherein a first set of vectors (Vx,Vy) in the vector sequence correspond to parts of the two-dimensional path where the laser spot (Ls) is active for writing respective lines (Lx,Ly) of pixels of the 2D matrix code (MC);wherein a second set of vectors (Vi) in the vector sequence correspond to parts of the two-dimensional path where the laser spot (Ls) is inactive for traveling between the respective vectors in the first set of vectors (Vx,Vy) without writing.

4. The method according to the preceding claim, wherein the vector sequence is optimized to minimize a total path length of the two- dimensional path traversed along the target surface (T), wherein the optimized vector sequence has a total path length that is less than a path traversed by a raster scan method of scanning each line of the grid (G).

5. The method according to the two preceding claims, wherein the first set of vectors (Vx,Vy) comprises a first subset of vectors (Vx) arranged along the first coordinate (X) of the grid (G), and a second subset of vectors (Vy) arranged along the second coordinate (Y) of the grid (G), wherein the second coordinate (Y) is perpendicular to the first coordinate (X).

6. The method according to the preceding claim, wherein at least some vectors in the first subset of vectors (Vx) are interconnected with respective vectors in the second subset of vectors (Vy) via respective vectors in the second set of vectors (Vi).

7. The method according to any of the preceding claims, wherein at least one writing line (V 1) is stored having an extended length (Le) extending beyond a length (LI) of the respective sets of contiguously arranged pixels.

8. The method according to the preceding claim, wherein the extended length (Le) is arranged, in a writing direction, before the first writing line (VI) in accordance with a laser ramp up time.

9. The method according to any of the two preceding claims, wherein the extended length (Le) is arranged, in the writing direction, after the first writing line (VI) in accordance with a laser ramp down time.

10. The method according to any of the three preceding claims, wherein the extended length (Le) extends beyond an edge (Ge) of the grid (G) at least for an initial writing line which initiates the scan sequence (S).

11. The method according to any of the preceding claim, wherein a spot size (Ss) of the laser spot (Ls) corresponds to a respective pixel size (mx,my) of the pixels (P).

12. A system (100) for laser marking a 2D matrix code (MO) onto a target surface (T), the system (100) comprising focusing optics (10) comprising a set of focusing elements (11,12) configured to produce a focusing beam (B); a beam steering device (20) configured to receive the focusing beam (B) from the focusing optics (10) and controllably redirect the focusing beam (B) as a moveable laser spot (Ls) onto the target surface (T); a light modulator (30) configured to controllably activate and deactivate the laser spot (Ls) moving along the target surface (T); and a controller (40) configured to control the beam steering optics (20) and the light modulator (32) for performing the method according to any of the preceding claims.

13. The system according to the preceding claim, wherein the beam steering device (20) comprises a scanning mirror (22) which is arranged at a target distance (At) from a focal region coinciding with the target surface(T), as determined by a focal distance (Af) of the focusing optics (10), wherein the target distance (At) is larger than a size (DX,DY) of the 2D matrix code (MC) projected on the target surface (T), by at least a factor twenty.

14. The system according to the preceding claim, wherein no focusing optics are arranged between the scanning mirror (22) and the target surface (T).

15. A non-transitory computer-readable medium storing instructions that, when executed by a laser marking system (100) for laser marking a 2D matrix code (MC) onto a target surface (T) and / or a controller (40) for generating a scan sequence (S) for laser marking a 2D matrix code (MC), causes the system and / or controller to perform the method according to any of the preceding claims.

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