METHOD AND DEVICE FOR PROCESSING IMAGES ON OR IN A PART

Description

FIELD OF INVENTION

[0001] The invention relates to the field of laser processing of materials, and in particular of glass, with a process and a processing system adapted to industrial rates, allowing for example the marking of products for traceability and anti-counterfeiting applications. STATE OF THE ART

[0002] In a rapidly expanding marking market, existing laser technologies have become widely established thanks to their ability to machine a broad range of materials. This allows them to address current industrial challenges while demonstrating significant potential for added value, depending on the parameters and operating processes. However, there are certain markets where laser technologies reach their limits, namely high-speed production, such as the food processing, pharmaceutical, security, and electronics sectors, which generally require the manufacture of small products in very large quantities.

[0003] Among existing technologies, some use a combination of a laser source, whose radiation properties vary (power, rate, energy, wavelength, pulse duration, etc.), coupled with a deflection head, or galvanometric scanner head. This head allows both the focusing of the laser beam, that is, its spatial concentration at a single point, and its controlled and automated movement within the space of the part to be marked, by analogy with the tip of a pen.

[0004] Application WO2016001335A1 describes a technology based on the use of a coherent light beam passing through a dynamic optical modulation device to generate a multibeam spatial profile on the surface of the material to be marked. A figure formed of several points can thus be machined or marked on the surface of the material.

[0005] With this technology, the number of achievable points in the figure is limited by the maximum light energy per pulse. This maximum energy can itself be limited by the damage threshold of the modulation device, that is, the light power passing through the device beyond which it is damaged. The maximum energy can also be limited by the maximum power emitted by commercially available lasers.

[0006] Furthermore, the size of the figures that can be created is also limited, so that it is sometimes difficult to create figures comprising more than 150 points and / or extending over an area greater than a few square millimeters.

[0007] US patent 2006 000 814 A1 discloses a pulsed laser engraving method for marking a part of an article. The marking is achieved by ablation of the material when a laser spot is applied to it. This laser spot is then moved to different locations within the part to create the marking pattern each time. However, US patent 2006 000 814 A1 does not specify that the pattern created by the laser spot includes at least two local maxima of contrast. Nor does US patent 2006 000 814 A1 disclose that two patterns created in the part during the process do not overlap.

[0008] Document WO 2009 / 114375 A2 discloses a method for creating a pattern on a surface or within a volume of a part. The pattern comprises a repetition of a motif, and the motif, for example, can be created by two laser impacts focused at two different depths within the part. Document WO 2009 / 114375 A2 does not disclose that the created pattern is located on a surface that is not parallel to a beam propagation direction. Document WO 2009 / 114375 A2 also does not disclose that two patterns created in the part during the method do not overlap.

[0009] There is therefore a need for a process to mark a figure on the surface of a material, and in particular glass, without being limited by the number of points or the size of the figure. DESCRIPTION OF THE INVENTION

[0010] One object of the invention is to provide a method for creating, by marking or micromachining, a figure on the surface or within the volume of a material, particularly glass, the dimensions and / or number of points of which are not limited, in particular, by the technical characteristics of the laser source used and the material of which the target is composed. This object is achieved within the scope of the present invention by means of a method for creating a figure on a surface or within the volume of a part, the figure comprising a repetition of a motif, the method comprising the following steps: realization of the pattern on the surface or in the volume of the part by shaping and focusing a coherent beam, the pattern comprising at least two local maxima of contrast; execution at least once of a cycle of the following steps: -- relative displacement of the beam and the part, and -- realization of the pattern on the surface or in the volume by shaping and focusing the beam, so that the patterns realized do not have any overlap.

[0011] The process comprises a cycle of steps, each iteration of which includes the emission of a light beam and its shaping to illuminate a laser pattern at a specific location on the workpiece. The illumination of the laser pattern marks the workpiece according to the pattern, which is not reduced to a single point. It should be noted here that the pattern is not necessarily identical to the laser pattern; this difference will be detailed later. From one iteration to the next, the location on the workpiece where the light beam strikes is modified, making it possible to create a figure larger than the pattern and containing more points. The cycle can be repeated indefinitely, so the dimensions of the final figure on the workpiece and the number of points it contains are not limited by the technical characteristics of the laser source used or the material of the target.

[0012] Such a process is advantageously complemented by the following various characteristics, taken alone or in combination: The pattern is formed from a plurality of spatially separated points; the coherent beam is pulsed, each realization of the pattern comprising the emission of a burst of at least one laser pulse, each burst comprising a number of laser pulses less than the number of points forming the pattern; each burst comprises a single laser pulse; the figure represents a one- or two-dimensional code composed of a set of empty cells and filled cells, the cells being located at predetermined positions; the filled cells comprise one or more repetitions of the pattern; the relative displacement of the beam and the part occurs over a length greater than one dimension of the pattern; the relative displacement of the beam and the part occurs over a length less than one dimension of the pattern;the figure includes a repetition of a second pattern, the second pattern comprising at least two local maxima of contrast, the process further comprising the execution of the following steps: realization of the second pattern on the surface or in the volume of the part by shaping and focusing a coherent beam; execution at least once of a cycle of the following steps: -- relative displacement of the beam and the part, and -- realization of the second pattern on the surface or in the volume by shaping and focusing the beam, so that the second patterns realized do not have an overlap;the figure includes an additional pattern formed of a plurality of points, the process further comprising the realization of the additional pattern on the surface or in the volume of the part by shaping and focusing a pulsed coherent beam, wherein the realization of the additional pattern on or in the part includes the emission of a train of pulses of the light beam, each train comprising a finite number of pulses strictly less than the number of points forming the additional pattern; the part is made of glass, metal, plastic or polymer; during the realization of the pattern the process includes an alteration by laser exposure of a first layer of material so as to reveal a second layer located below the first layer;The creation of the pattern on the surface or in the volume is carried out in a processing plane, the processing plane being separated from a laser beam focusing plane by a distance less than or equal to half the focal length of a focusing device, the focusing device defining the position of the focusing plane; a step of calculating a modulation instruction from an input instruction corresponding to the pattern, the modulation instruction being imposed on a modulation device to perform the beam shaping.

[0013] The invention also relates to a part comprising a figure produced by the process as just described.

[0014] The invention also relates to a system for creating a figure on a surface or within a volume of a room, the figure comprising a repetition of a motif, the system comprising: a device for producing the pattern on the surface or in the volume of the part by shaping and focusing a coherent beam, the pattern comprising at least two local maxima of contrast; and a device for relative displacement of the beam and the part.

[0015] Such a system is advantageously complemented by the following various characteristics, taken alone or in combination: the device for producing the pattern on the surface or in the volume of the part by shaping and focusing a coherent beam includes: a source of a coherent light beam; an optical modulation device including means for modulating the light beam in a modulation plane according to at least one phase modulation, in order to shape the light beam according to a laser pattern;a focusing device arranged to focus the light beam shaped by the modulation device into a focal plane, the focal plane being in Fourier or Fresnel configuration relative to the modulation plane of the modulation device, the system being adapted to receive the workpiece, so that the creation of the pattern on the surface or in the volume is carried out in a processing plane, the processing plane being separated from the focal plane by a distance less than or equal to half a focal length of the focusing device, the laser pattern being configured to produce a treatment of the workpiece according to the pattern in the processing plane; the laser beam is pulsed; the optical modulation device includes a fixed shaping optic; the optical modulation device and the focusing device are combined into a single apparatus;The relative displacement device includes a galvanometric scanner head; the relative displacement device includes at least one translation stage. DESCRIPTION OF THE FIGURES

[0016] We will now present several embodiments, by way of non-exhaustive list, with reference to the attached drawings on which: [ Fig. 1 ] there figure 1 is a schematic representation of a system to form a figure according to the different embodiments of the invention. Fig. 2 ] ] Fig. 3 ] THE figures 2 and 3 are schematic representations of two types of markings according respectively to a first and a second embodiment of the invention. Fig. 4A ] ] Fig. 4B ] THE Figures 4A and 4B represent two motifs according to the first embodiment of the invention. Fig. 5 ] There figure 5includes representations 5A, 5B, 5C, 5D and 5E of markings made on glass according to the first embodiment of the invention. Fig. 6 ] ] Fig. 7 ] THE figures 6 and 7 are representations of a secure QR code. Fig. 8 ] ] Fig. 9 ] THE figures 8 and 9 are examples of the realization of a secure QR code according to a third embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention relates to the processing of materials, that is to say the structural modification of materials on a small scale compared to the dimensions of the material, by laser.

[0018] A figure creation or processing is defined as a figure marking by laser, that is to say, a modification of the material by laser to generate: an optical contrast following the figure on the surface or in the volume of the part, or a micromachining of the figure by laser, that is to say a modification of the material by laser to generate a relief on the surface of the part, or a variation of density in the volume of the part (by ablation or addition of material) following the figure.

[0019] A specific case of micromachining for figures involves, when the material is composed of several layers of different composition, removing one of the layers to reveal the layer beneath. In other words, the process includes, during the creation of the figure, laser-exposing a first layer of material to expose a second layer located beneath the first.

[0020] This particular case is of interest when the optical appearance of the two layers (color, gloss, etc.) is significantly different. This case is not limited to the treatment of the outermost layers; for example, removing a layer of colored paint beneath a layer of varnish to reveal another colored layer of a different shade.

[0021] The figure is a spatial distribution of an optical contrast function. Once processed, the figure can be detected by an optical measurement method. The figure has a certain size and a certain resolution. Resolution can be defined as the minimum level of detail that can be detected in the figure. Resolution can differ in three dimensions; in particular, we speak of transverse resolution (i.e., in directions perpendicular to the direction of propagation of the laser beam) and depth resolution (i.e., in the direction of propagation of the laser beam).

[0022] Generally, the figure extends over a surface that is not necessarily flat and is not necessarily the same as the outer surface of the workpiece. The following description is given with regard to the specific example of surface marking, assuming that the figure extends over a flat working surface, but the invention is in no way limited to this particular example and covers the entire field of surface marking.

[0023] The figure to be created involves a repetition of a pattern without overlapping.

[0024] A pattern is a spatial distribution of an optical contrast function on the outer surface of the part, a distribution denoted C(x,y) depending on the spatial coordinates x, y. x and y correspond to transverse directions perpendicular to the direction of beam propagation. In this case, the pattern extends in a plane perpendicular to the direction of beam propagation.

[0025] The pattern can also extend in a plane inclined relative to a plane perpendicular to the beam propagation direction, but not parallel to the propagation direction. More generally, the pattern can extend over a surface that is not planar but not parallel to the propagation direction. It is then possible to define an equation for this planar or non-planar surface in the form z = S(x,y), which, for any point on the surface with spatial coordinates x, y, gives the z-coordinate of that point, the z-coordinate corresponding to the beam propagation direction. The distribution C(x,y) then gives the contrast C(x,y) for the point on the surface with coordinates (x, y, z = S(x,y)).

[0026] A pattern repetition is a spatial distribution obtained by summing several spatially shifted distributions C relative to each other: C(x+a 1 , y+b 1 )+ C(x+a 2 , y+b 2 )+...+C(x+an , y+bn ).

[0027] A pattern repetition is non-overlapping when no contrast zone of a first distribution overlaps any contrast zone of a second distribution. There is no overlap between contrast zones of two different distributions. A contrast zone of a distribution is a spatial region where the distribution takes values ​​significantly different from zero, so that it can be visually identified as a region distinct from where the distribution takes the value zero. In other words, a pattern repetition is non-overlapping if, at a point where one of the summed distributions C takes a non-zero value, then at that point all the other distributions take a value of zero.

[0028] The pattern includes at least two local maxima of contrast, meaning that the spatial distribution of the contrast function has at least two local maxima. The spatial distribution of the contrast function reaches a local maximum at a point where the distribution takes a given value when, around this point, the contrast function takes values ​​less than or equal to this given value. In other words, the spatial distribution C(x,y) of the contrast function reaches a local maximum at a point (x0, y0) if there exists a neighborhood V of the point (x0, y0) such that for every element (x,y) of V, we have C(x,y) ≤ C(x0, y0).

[0029] The pattern includes at least two local maxima of contrast, the values ​​of these two local maxima of contrast being either equal or different.

[0030] The pattern can be discrete, meaning it is formed from a plurality of spatially separated points. In other words, the pattern consists of well-localized areas of contrast that are spatially separated from one another. The spatial distribution of the contrast function then exhibits separate peaks corresponding to each of these areas. Such a pattern appears optically as being formed from a plurality of points.

[0031] The pattern can be continuous, meaning it consists of one or more more spread-out contrast zones. The spatial distribution of the contrast function then exhibits high contrast plateaus corresponding to each of these spread-out contrast zones. Such a pattern appears optically as formed from a surface or a set of surfaces.

[0032] The pattern extends over a certain dimension which is strictly greater than the transverse resolution of the figure.

[0033] The process includes a first step of processing the pattern on a surface or in a volume of the part by conforming and focusing a coherent beam, possibly pulsed.

[0034] The first step involves emitting a coherent light beam and modifying its spatial energy distribution in a plane orthogonal to its direction of propagation. The spatial energy distribution of the light beam in the plane of the part to be marked then forms a laser pattern. Illuminating the part with this laser pattern creates a discrete or continuous design in which all contrasting areas are processed simultaneously on the surface or within the volume of the part to be marked. Coherent beam

[0035] We use a source that emits a spatially and temporally coherent beam of light, such as a laser beam. For example, we can use a standard laser source without any particular characteristics.

[0036] The light beam can be continuous or pulsed. A pulsed beam is temporally composed of a succession of pulses. Furthermore, the emission can be controlled so that the beam is emitted in the form of pulse trains, also called bursts or shots. A pulse train is formed from a finite number of pulses of the light beam.

[0037] The present system is compatible with the various firing modes currently in existence as presented in application WO2016001335A.

[0038] In the case of a pulsed beam, the duration of the pulses can be controlled to preferably be between 100 femtoseconds (fs) and 1 microsecond (µs).

[0039] The pulse duration range [100 fs - 10 picoseconds (ps)] is ideal for marking glass and, more generally, transparent materials. This makes it possible to limit defects or mechanical damage, commonly referred to as 'micro-cracks', which occur with longer pulse duration marking.

[0040] The pulse duration range [10ps - 1 µs] is compatible with most light sources, including lasers, which are widely used in industrial settings. These pulse durations are also compatible with high energy levels, which can be useful for marking certain materials with a pattern containing many points in a very small number of pulses.

[0041] The emission of the light beam is preferably controlled so that each pulse has a determined energy between 1 µJ and 100 mJ.

[0042] Preferably, the emission of the light beam is controlled so that the pulse train delivers an average power between 1 µW and 5000 W. Beam shaping by phase modulation

[0043] A modulator, or modulation device, is used to shape the laser beam. This device allows for the spatial modulation of the light beam, specifically controlling its shape—that is, its spatial distribution of optical energy—in order to create a laser pattern. When a laser strikes the workpiece in a marking plane corresponding to the marking plane on the material, this pattern will be discrete or continuous. The modulator is an optical element that enables the spatial modulation of the laser beam. The modulation used can affect the amplitude, phase, and / or polarization of the beam, independently or in combination. Preferably, at least phase modulation is always performed, which can optionally be complemented by amplitude or polarization modulation. Ideally, the modulator also allows for phase modulation of the light beam within the plane of the modulator.Depending on specific marking methods, pure phase modulation is preferred.

[0044] The modulation plane is defined as the modulator plane where the magnitude of the modulated laser beam (amplitude and / or phase and / or polarization) is controlled. This control within the modulation plane is performed sector by sector, or in other words, pixel by pixel.

[0045] The coherence of the light beam is maintained between the upstream and downstream sides of the modulator.

[0046] The modulation applied to the beam in the modulation plane generates sub-beams downstream.

[0047] The shaping plane is defined as the plane in Fourier configuration with the modulation plane.

[0048] The different sub-beams generated in the modulation plane appear according to the desired spatial distribution of optical energy in the shaping plane.

[0049] In other words, the modulation device introduces a modulation of a beam magnitude into the modulation plane, producing sub-beams in that plane. These sub-beams then produce the desired beam shape in the shaping plane, that is, the desired spatial distribution of optical energy. This energy distribution appears as the laser pattern on the plane of the workpiece being treated.

[0050] One type of modulator that can be used for this purpose consists of fixed-shaping optics, and in particular diffractive optical elements commonly referred to by the English acronym DOES (Diffractive Optical Elements). It should be noted that in this case, the beam focusing described below can be integrated into the DOES.

[0051] A second type of modulator is commonly referred to by the English acronym SLM (Spatial Light Modulator), regardless of the technology used to perform the modulation. This type of modulator, the underlying technologies, and the type of implementation configuration along the optical beam path (imaging configuration or Fourier configuration) are described in application WO2016001335A.

[0052] It is further noted here that SLM modulators are controllable, for example via software, so as to modify the modulation of the light beam passing through them. The characteristic time to switch from one modulation to another is typically between 1 millisecond (ms) and 100 ms, corresponding to a frequency between 10 Hz and 1000 Hz. Beam transport, adaptation and focusing

[0053] The optical path before and after the modulation device is composed of a set of optical elements as presented in application WO2016001335A.

[0054] It should be noted that downstream of the modulation, a set of elements can be chosen for: The modulator's characteristics are "virtually" adapted, and the laser beam is focused onto a focal plane. The focusing device is generally defined industrially by a focal length, a working distance, and an associated focal plane, given for specific optical conditions (wavelength, imaging at infinity, diffraction index, and diopter curvature). In this description, the focal plane is understood to be the plane of smallest area of ​​a light beam, that is, the plane where the light energy is most concentrated.

[0055] The processing plane, or working plane, is defined as the plane where the pattern to be created extends and where the processing of that pattern is performed. It should be noted that the processing plane can vary from one pattern to another. This is particularly true when the pattern extends over a non-planar surface. The processing plane may or may not coincide with the shaping plane and may or may not coincide with the focal plane.

[0056] When the focal plane corresponds to the shaping plane, the configuration is called a Fourier configuration. When these planes are different, the configuration is called a Fresnel configuration.

[0057] The distribution of light energy in the treatment plane is called the laser pattern.

[0058] The laser pattern's impact on the workpiece in the processing plane produces a treatment based on the pattern. The pattern is not necessarily identical to the laser pattern, which itself is not necessarily identical to the spatial energy distribution created by the modulator in the forming plane. On the workpiece, material is treated only at locations within the laser pattern where the incident light intensity exceeds a certain treatment threshold.

[0059] The resolution of the problem being addressed depends on the following elements: the beam power, beam size, energy distribution according to the laser pattern, material properties, and the technique and configuration (lighting, optics) used for capturing the contrast pattern. Displacement and processing cycle

[0060] Once the first pattern processing step is completed, the process continues by executing at least one cycle of subsequent steps: -- relative displacement of the beam and the part, and -- processing of the pattern on the surface or in the volume by conforming and focusing the beam.

[0061] The process is adapted so that all the patterns produced during the process do not overlap. In other words, the repetition of the pattern is non-overlapping; that is to say, as previously seen, no contrast area of ​​a first distribution overlaps any contrast area of ​​a second distribution.

[0062] It is thus possible to create a figure which includes a repetition of a pattern without overlapping. Relative displacement of the beam and the target

[0063] The system for forming a figure may include a device for the relative movement of the beam and the part so as to control and automate the position of the impact of the light beam on the part to be marked.

[0064] Such a displacement device can be a galvanometric scanner head device. This technology is based on the mechanical displacement of optics (mirrors, prisms, disks, polygons...).

[0065] Such a movement device can be a motorized mechanical translation stage or a set of several stages. The workpiece can be supported by, or at least rigidly attached to, this stage or these stages. In this way, a moving stage carries the workpiece along with it.

[0066] The use of these mechanical devices imposes a limit on the execution time of the relative beam and workpiece movement step. The movement is difficult to achieve in less than 500 microseconds (µs), or requires a very expensive installation.

[0067] The 2 kHz frequency, combined with this minimum travel time, impacts the rate at which patterns are created in the figure formation process. Therefore, the fewer pulses produced by a pulsed light source ensure the pattern is marked, the less advantageous it becomes to use a source emitting pulse trains at frequencies much higher than 2 kHz to accelerate the process.

[0068] In particular, there is an advantage to using a process where a figure is created by performing a pattern processing cycle and relative displacement when it is faster to mark a pattern with a laser pattern and a pulse burst than to mark the pattern point by point with a relative movement between two point markings.

[0069] Performing multiple cycles of movement and processing allows for the creation of as many patterns as needed on the part. These patterns are spatially distributed according to the relative movements. The process can be stopped when all the patterns contained in the figure are marked on the part. Number of pulses per pattern

[0070] Each step of processing the pattern on a surface or in a volume of the part by conforming and focusing a pulsed coherent beam corresponds to the emission of a pulse train (or pulse burst or pulse firing) comprising one or more pulses of the beam which come to strike the material.

[0071] The duration of this step can be limited by using a single pulse per treatment. This assumes that processing the pattern formed from a single pulse allows the desired result to be achieved (marking contrast, ablation depth, etc.).

[0072] The result of processing the pattern from a burst comprising a single pulse depends in particular on the material forming the part, the amount of energy contained in the pulse and the size of the pattern to be made and the wavelength of the laser.

[0073] For example, if the processing is marking, the contrast is generally greater when the amount of energy contained in the pulse is high. If we consider a constant energy input to the modulation device, then the contrast is greater when the number of points in the pattern is low and the extent of the surface or surfaces forming the pattern is small.

[0074] More generally, when the marking of a pattern is produced by a burst comprising several pulses, the contrast is all the more important as the amount of energy contained per pulse is large and the number of pulses in a burst is large.

[0075] For a given amount of energy per pulse at the input of the modulation device, it may then be advantageous to decrease the number of points composing the pattern, the extent of the surface or surfaces forming the pattern, so that a single pulse produces the pattern with sufficient contrast. Type of figures

[0076] The figure to be created includes a repetition of a pattern which can be discrete or continuous.

[0077] In cases where the pattern is discrete, each treatment is a simultaneous treatment of several points, that is, several well-localized areas of contrast. Such a treatment can be referred to as "multi-point processing" and can be performed by dividing the laser beam into several sub-beams, each allowing one of the pattern's points to be marked.

[0078] The figure to be created includes a repetition of a pattern, according to a plurality of predetermined offsets.

[0079] At each relative displacement step, the part is moved relative to the beam according to one of the offsets from the plurality of predetermined offsets.

[0080] The figure can be made up exactly of the repetition of the pattern.

[0081] In this case, when the pattern is repeated n times in the figure, the repetition of n pattern processing steps and (n-1) relative displacements allows us to obtain the final figure.

[0082] When the coherent beam is pulsed, a particular implementation of the process involves each treatment of the pattern comprising the emission of a burst of at least one laser pulse, each burst containing fewer laser pulses than the number of points forming the pattern. Preferably, each burst comprises a single laser pulse.

[0083] In this way, the treatment is completed more quickly than with a conventional point-by-point treatment with the same laser rate. 1D or 2D codes

[0084] The figure is made up exactly of the repetition of the pattern in the case where the figure represents a one-dimensional code (barcode) or a two-dimensional code (2D code). A 2D code is composed of a set of cells located at predetermined positions, some cells being empty and others being filled.

[0085] Here, we distinguish between the term 'two-dimensional coding' (2D coding), which refers to the organization of a set of cells, each of which must be either empty or filled, and the term '2D code', which is a particular implementation or realization of a 2D coding. A 2D code is thus a specific choice of empty and filled cells according to the organization of the 2D coding, and which translates the content of the code.

[0086] Some 2D encodings are based on a Cartesian organization, where the set of cells forms a square or rectangular matrix with cells arranged in rows and columns. This is the case, for example, with the Data Matrix or the QR code.

[0087] Other 2D encodings exist in which the cells are organized on a "honeycomb" basis (as in dot-code or maxicode) or on a polar basis (as in shotcode or spotcode). The entire set of cells may, for example, exhibit central symmetry.

[0088] For all 2D encodings, each cell of a 2D code is either empty or filled.

[0089] The process can be adapted so that the pattern corresponds to the content of a filled cell. The filled cells are then filled with only the pattern. Each processing step corresponds to the creation of one filled cell.

[0090] In this case, between each of the processing steps, the relative displacement occurs at least over the minimum distance separating two neighboring cells in the set of cells of the 2D coding.

[0091] Since these cells do not overlap, each relative displacement of the beam and the piece occurs over a length greater than one total dimension of the pattern. Brush marking » or « Pixel stamp »

[0092] More generally, the methods of forming the figure in which the relative displacement always takes place over a length greater than a total dimension of the pattern can be designated under the term "brush" marking (i.e. brush marking or brush in French) or under the equivalent term "Pixel stamp" (i.e. pixel stamp marking in French) which is a first embodiment of the invention.

[0093] The principle of brush marking or pixel stamp marking is the decomposition of the image into a juxtaposition of several identical patterns. The image is then created by a succession of laser bursts, each burst being composed of one or more laser pulses and preferably composed of a single laser pulse, each burst marking one pattern.

[0094] There figure 2 schematically represents a brush marking or Pixel stamp marking.

[0095] The SM1 pattern consists of a square of four points aligned in two rows and two columns.

[0096] The set of relative displacements to be made is represented by the matrix D1, each cross in the matrix representing a position of a pattern to be made.

[0097] The figure M to be produced is obtained by replacing each cross of the matrix D1 with the pattern SM1.

[0098] It should be noted that any relative displacement, i.e. any distance between two crosses in the matrix D1, is of a length greater than the size of the pattern SM1.

[0099] One advantage of using brush marking or pixel stamp marking lies in the ability to mark different 2D codes within the same 2D code. Since the pattern remains the same regardless of the 2D codes, it is not necessary to modify the brush configuration from one 2D code to another. In particular, if different parts are being marked, each part having its own specific 2D code, for example, associated with a serial number, there is no need to change the brush configuration from one part to another. Given the relative slowness introduced by modifying the configuration, this allows for faster individual marking of a large number of parts. Individual marking refers to marking where each part is marked with a unique 2D code.

[0100] Furthermore, creating a pattern that is reduced to a cell fill in a 2D encoding requires relatively low energy. Marking such a pattern can therefore be achieved relatively easily with a single pulse of the light beam. Moreover, a wide variety of light sources are suitable for this type of marking.

[0101] It is therefore possible to achieve relatively short marking times, typically less than one second.

[0102] Finally, the size of the figure is not limited by the size of the pattern, and figures with a typical size of 100 mm x 100 mm can be made. Creating datamatrix codes on glass

[0103] This article presents an example of marking a 2D code on glass bottles (borosilicate and soda-lime) at room temperature using the "brush" or "pixel stamp" marking method, the conditions of which are listed below. These bottles may sometimes have additional surface or internal treatments, such as a varnish or paint coating applied prior to the marking process.

[0104] In this example, the objective is the marking of a 2D datamatrix code with variable content and variable size but typically in a range within the order of magnitude 100µm - 10cm.

[0105] In this application case, the resulting pattern represents either a square composed of four points aligned along two rows and two columns, or a square of nine points aligned along three rows and three columns.

[0106] The marking is carried out by conforming, with the aid of the modulator, the incident coherent beam so as to define in the treatment plane respectively four or nine points, in other words four or nine well localized contrast zones.

[0107] There figure 4A represents an elementary pattern of a brush marking or Pixel stamp marking according to a square composed of 2x2 = 4 points, in other words four well localized contrast zones.

[0108] There figure 4B represents an elementary pattern of a brush marking or Pixel stamp marking according to a square composed of 3x3 = 9 points, in other words nine well-localized contrast zones.

[0109] In these figures, the distance between points in the shaping plane can take different values ​​in the range of orders of magnitude from 1 µm to 100 µm.

[0110] The laser source used has the following characteristics: a pulse duration of between 150 fs and 10 ps, ​​preferably between 1 ps and 10 ps, ​​a near IR (Infrared) wavelength of 1030nm, an energy level per pulse of: ∘ 200 µJ-300 µJ for the 2x2 pattern, and ∘ 500 µJ-700 uJ for the elementary 3x3 pattern; each pattern is marked using between 1 and 10 laser pulses.

[0111] The relative displacement between the laser and the target was achieved using translation stages placed under the glass vial. The laser impact point is therefore fixed in space.

[0112] Examples of markings produced, in particular varying the number of pulses in each laser burst (from 1 to 10 pulses), are visible in figures 5A to 5E of the figure 5 . Representation 5A corresponds to one pulse, representation 5B to two pulses, representation 5C to three pulses, representation 5D to five pulses and representation 5E to ten pulses.

[0113] It should be noted that the contrast of the marking increases when: the number of pulses per burst increases; the amount of energy contained in each subbeam increases; and the pattern extends over a smaller area.

[0114] The tolerance for positioning the part to be marked along the optical axis is close to 1 mm. In other words, the marked pattern exhibits satisfactory shape and contrast, even if the part is moved forward or backward by 0.5 mm relative to the shaping plane. In other words, if the distance between the work surface and the shaping plane is less than 0.5 mm, the shape and contrast of the marked pattern are satisfactory. This 1 mm tolerance is significantly greater than known glass marking solutions.

[0115] Furthermore, the area of ​​the surface of the part surrounding the laser impact points does not show any mechanical damage, such as micro-cracks, which are usually present during laser processing of glass. "Wobbling" marking

[0116] Figure formation processes in which the relative displacement always occurs over a length less than a total dimension of the pattern can be designated under the term "wobbling" marking (i.e., oscillating marking in French).

[0117] In this second embodiment of the invention, each motif extends over a certain encompassing surface and there is overlap between encompassing surfaces of two successively created motifs.

[0118] The bounding surface over which a pattern extends can be understood, for example, as the minimal continuous surface covering all the points of the pattern, whether the points are distributed discretely or continuously. In other words, the bounding surface over which a pattern extends can be the minimal continuous surface covering either all the points forming the pattern, or the continuous surface(s) forming the pattern.

[0119] The overlap of encompassing pattern surfaces does not imply repetition of the pattern with overlap. The corresponding patterns do not necessarily overlap. For example, the pattern is a spatial distribution of a contrast function that can consist of well-localized contrast zones, that is, a plurality of separate points. The points are spatially separated from each other by at least a minimum separation distance. The minimum separation distance is less than a total dimension, length or width, of the pattern. It can be less than half, a quarter, or even 1 / 10 or 1 / 20 of this total dimension. If a second pattern is created, formed by a second plurality of points, offset from the first pattern by a length less than the minimum separation distance, then: There is no overlap of points between the first and second plurality of points, and there is an overlap of the surfaces on which the first and second patterns respectively extend.

[0120] There figure 3 schematically represents a wobbling marking.

[0121] The SM2 pattern is composed of a plurality of discrete points distributed over a square, the surface of which is very close to that of the figure.

[0122] The set of relative movements to be performed is represented by matrix D2, where each cross in the matrix represents a position of a pattern to be executed. Matrix D2 comprises four crosses arranged in two rows and two columns.

[0123] The figure M to be produced is obtained by replacing each cross of the matrix D2 with the pattern SM2.

[0124] It should be noted that any relative displacement, that is, any distance between two crosses in the matrix D2, is of a length less than the size of the pattern SM2 and of a length less than the minimum distance that separates two points in the pattern M2.

[0125] Wobbling marking is suitable for cases where the figure, and therefore the pattern, is relatively large, i.e., when the number of points forming the pattern is significant, or when the surface area or areas forming the pattern are large. Wobbling marking can accommodate larger pattern sizes than brush or pixel stamp marking, and in this case, can make the figure formation process faster. Indeed, depending on the size of the figure and the laser's frequency, the time required to emit a laser pulse can be shorter than the time required for a relative movement, so the total marking time is shorter when the number of relative movements is low. On the other hand, a higher energy per pulse is generally required to achieve the same contrast because the pattern then has more points to mark.It should be noted that it is also theoretically possible to increase the number of pulses per processing burst without significantly increasing manufacturing time. The terms 'significantly lower' or 'significantly lower' can be understood here as 10 times higher or 10 times lower, respectively.

[0126] One advantage of using this type of marking lies in the ability to mark the same 2D code on different parts.

[0127] From the 2D code forming the figure, the positions of the filled cells are identified. The content of a filled cell is divided according to a repetition of the same fragment, so that the cell's filling consists solely of repetitions of that fragment.

[0128] The pattern is chosen as the repetition of the fragment at the different identified positions. In this way, at each processing step, a fragment from each filled cell of the pattern is marked on the part. The relative movements between two micromachining steps then occur over a distance that allows passage from one fragment to another, that is, over a distance smaller than the dimension of the pattern, and even smaller than the dimension of a cell. At each new processing step, a new fragment is created in each cell. When the number of processing steps performed equals the number of repeated fragments in a filled cell, the pattern is complete.

[0129] The number of processing steps required to obtain the figure is therefore equal to the number of repetitions of the fragment in the filling of a cell. This number of repetitions can easily be adjusted.

[0130] Between two parts to be marked with the same 2D code, it is not necessary, although possible, to modify the conformation of the modulator, the pattern being the same for each of these parts.

[0131] Furthermore, creating such a smaller pattern, or one with fewer points (in the case of figures composed of a plurality of points), requires less energy than marking the final figure without pattern decomposition (in a proportion roughly equal to the number of repeated fragments in a filled cell). Marking such a pattern can be achieved with a single pulse of the light beam. Moreover, a wide variety of light sources are suitable for this type of marking.

[0132] It is therefore possible to achieve relatively short marking times, typically less than one second.

[0133] Finally, the size of the final figure is not limited by the size of the pattern. Repetition of a second pattern

[0134] The figure may include, in addition to the repetition of a first motif, the repetition of a second motif.

[0135] This second pattern also includes at least two local maxima of contrast, and can be discrete or continuous.

[0136] In this case, the process may also include the execution of the following steps: processing of the second pattern on a surface or in a volume of the part by shaping and focusing a pulsed coherent beam; execution of at least one cycle of the following steps: -- relative movement of the beam and the part, and -- processing of the second pattern on the surface or in the volume by shaping and focusing the beam.

[0137] The process used to repeat the first motif in the figure is implemented a second time and adapted to repeat the second motif this time.

[0138] In this situation, it is necessary to modify the conformation of the modulator, between the realization of the first pattern and the realization of the second pattern.

[0139] It should be noted that the process can be modified further, on the same basis, to perform other repetitions of one (or more) additional motif. Calculating a modulation setpoint

[0140] In prior art, the shaping of bundles according to pre-established, even fixed, bundle forms is mentioned. In other words, the motif that can be marked must be chosen from a limited number of possible motif shapes. The motifs that can be marked are therefore limited in their form, by extension limiting the possibilities of figures and / or the associated marking time.

[0141] Using an SLM modulator allows the shape of the pattern to be modified, even during the pattern formation process itself. This modification can be dynamic.

[0142] In particular, it is possible to integrate control software that processes in the background all the necessary mathematical concepts to transfer the user's desired pattern into a laser pattern through a focusing lens using the modulation device. The laser pattern located in the working plane, through its equivalent in the shaping plane—that is, the spatial distribution of light energy—can be defined so as to be composed of only a plurality of sub-beams, like a pixelated image (each pixel of this laser shape then represents a possible laser impact point or impact surface, which can be activated as desired by the operator). This approach facilitates, in particular, the control of laser-matter interaction, but also makes it easier for the end user to understand how to simply transform their single, standard beam into a plurality of sub-beams.

[0143] It is therefore possible to add to the figure formation process, as presented so far, a step of calculating a modulation command from an input command corresponding to a new desired pattern shape, for example, a second pattern repeated within the figure. The modulation command is imposed on the modulation device to perform the beam shaping. This shaping is a dynamic shaping of the light beam.

[0144] The input instruction sending step and / or the calculation step can be executed while the training process is in progress. Additional pattern not repeated

[0145] The figure may include, in addition to the repetition of the first motif, one or more additional motifs that do not appear repeatedly in the figure.

[0146] Each additional pattern can in particular be formed from a plurality of points. In this case, the process may further include the processing of the additional pattern on a surface or in a volume of the part by shaping and focusing a pulsed coherent beam; the formation of the additional pattern on the part includes the emission of a train of pulses from the light beam, each train comprising a finite number of pulses strictly less than the number of points forming the additional pattern.

[0147] This type of marking, which is not based on the repetition of a pattern, was described in detail in application WO2016001335A. It is referred to in the rest of the text as a "stamp" marking.

[0148] Such a method, which allows for marking both the repetition of a pattern and an additional pattern not repeated within the figure, can be used, in particular, in the creation of secure QR codes. This method constitutes a third embodiment of the invention. Creation of a secure QR code on a polymer

[0149] A secure QR code is a QR code within which one or more proprietary codes are integrated, for example secure proprietary markings described in application WO2010034897A1, in order to secure the entire QR code.

[0150] There figure 6 represents a QR code comprising three secure proprietary markings, and the figure 7 is a detailed view of one of these security markings.

[0151] This article presents an example of how to implement this QR code on a polymer part (POLYAMIDE 6 and Polycarbonate) at room temperature. The 2D QR code can contain variable content and is typically between 1 and 10 cm in size.

[0152] In this example, each secure proprietary marking is done using a mode close to buffer marking, and the rest of the figure is marked in brush marking or Pixel stamp marking mode.

[0153] Given the target time for complete marking (less than one second), the material's behavior under laser irradiation, and the limitations of currently available lasers, these secure proprietary markings cannot be applied with a single stamp. Therefore, in this example, each secure proprietary marking is itself divided into four subsets such that: Each point of the marking is marked using a laser sub-beam, and each point of the marking belongs to only one unique subset.

[0154] Each subassembly is thus marked by a stamp marking, preferably with a single laser pulse. The complete secure proprietary marking is therefore marked by an interlocking of four stamp markings.

[0155] The rest of the figure is obtained by brush marking or pixel stamp marking using a single pattern. This pattern spans a square and can be marked by a total of 16 x 16 = 256 subbeams. The distance in the shaping plane from one subbeam center to a neighboring subbeam center can take different values. In the optimized case, this distance is 25 µm.

[0156] There figure 8 represents a realization of the QR code shown in figure 6 , and the figure 9 an implementation of the secure proprietary marking represented in figure 7 .

[0157] In this example, the light source used is a laser source with the following characteristics: a pulse duration of 7 ns, a visible wavelength (532 nm), an energy per pulse of 5 mJ, and bursts comprising 1 to 2 laser pulses. System for forming a figure on a coin

[0158] A treatment system is also proposed, allowing materials to be treated according to the process described above.

[0159] Such a system is suitable for forming a figure on or in a piece, the figure comprising a repetition of a motif, the system comprising: a device for creating the pattern on the surface or within the volume of the part by shaping and focusing a coherent beam, the pattern comprising at least two local maxima of contrast; a device for the relative displacement of the beam and the part

[0160] There figure 1schematically represents one way in which such a system could be implemented. 1.

[0161] The relative beam and workpiece displacement device is referenced as 5 in figure 1 .

[0162] System 1 comprises the device for creating the pattern on the surface or within the volume of the part by shaping and focusing a coherent beam, which itself comprises: a source 2 of a coherent light beam 8A, such as a laser source, an optical modulation device 3 comprising means for modulating 4 in a modulation plane the light beam according to at least one phase modulation, in order to conform the light beam according to a laser pattern; a focusing device 7 arranged to focus the light beam formed by the modulation device into a focal plane, the focal plane being in Fourier or Fresnel configuration with respect to the modulation plane of the modulation device.

[0163] The system is adapted to receive a part to be treated, so that the creation of the pattern on the surface or in the volume is carried out in a treatment plane, the treatment plane being separated from the focal plane by a distance less than or equal to half a focal length of the focusing device, the laser pattern being configured to produce a treatment of the part according to the pattern in the treatment plane.

[0164] The laser beam can be pulsed.

[0165] The optical modulation device can be a dynamic SLM or a fixed shaping optic.

[0166] The optical modulation device and the focusing device can be combined into a single device.

[0167] The relative displacement device can be a galvanometric scanner head device or a set of translation stages.

[0168] The displacement device can be placed in the beam path, as shown schematically in the figure 1 , or under the piece.

[0169] The Fourier configuration was described in request WO2016001335A1.

[0170] At the output of the modulation device 3, the light beam 8B is shaped according to the laser pattern to produce the pattern 11 in the processing plane where the pattern to be created on the surface or in the volume of the part 9 to be marked is located. This processing plane is situated in the vicinity of the focal plane of the laser beam, that is to say, the processing plane is separated from the focal plane by a distance less than or equal to half the focal length of the focusing device, the focusing device defining the position of the focal plane.

[0171] The system may also include electronic control of the modulation device and / or the light beam source and / or database management and / or a graphical interface for communication with the operator or other components of the processing installation. Pattern shapes may be stored in a database.

[0172] The system may also include a modulation setpoint calculator based on an input setpoint corresponding to a desired pattern shape.

Claims

1. A method for producing a figure on a surface or within the volume of a workpiece (9), the figure comprising a repetition of a pattern (11), the method comprising the following steps: - forming the pattern (11) on the surface or within the volume of the workpiece (9) by shaping and focusing a coherent beam (8A), the pattern being located on a surface not parallel to a direction of propagation of the beam , the pattern comprising at least two local maxima of contrast; - performing at least once a cycle of the following steps: -- relative movement of the beam and the workpiece, and -- forming the pattern (11) on the surface or within the volume by shaping and focusing the beam, such that the formed patterns do not overlap.

2. A method according to claim 1, wherein the pattern is formed of a plurality of spatially separated points.

3. A method according to claim 2, wherein the coherent beam is pulsed, each formation of the pattern comprising the emission of a burst of at least one laser pulse, each burst comprising a number of laser pulses less than the number of points forming the pattern, each burst preferably comprising a single laser pulse.

4. A method according to one of the preceding claims, wherein the figure represents a one- or two-dimensional code composed of a set of empty cells and filled cells, the cells being located at predetermined positions, the filled cells preferably comprising the pattern once or more times.

5. A method according to one of the preceding claims, wherein the relative movement of the beam and the workpiece takes place over a length greater than one dimension of the pattern, or the relative movement of the beam and the workpiece takes place over a length less than one dimension of the pattern.

6. A method according to one of the preceding claims, wherein the figure comprises a repetition of a second pattern, the second pattern comprising at least two local contrast maxima, the method further comprising performing the steps of claim 1 adapted to realise the repetition of the second pattern.

7. A method according to one of the preceding claims, wherein the figure comprises an additional pattern formed of a plurality of points, the method further comprising forming the additional pattern on the surface or within the volume of the workpiece by shaping and focusing a pulsed coherent beam, wherein forming the additional pattern on or within the workpiece comprises emitting a pulse train of the light beam, each train comprising a finite number of pulses strictly less than the number of dots forming the additional pattern.

8. A method according to one of the preceding claims, wherein the workpiece is made of glass, metal, plastic or polymer.

9. A method according to any one of claims 1 to 8, comprising, during the formation of the pattern, altering a first layer of material by laser exposure so as to expose a second layer located beneath the first layer.

10. A method according to one of the preceding claims, wherein the formation of the pattern on the surface or within the volume takes place in a processing plane, the processing plane being separated from a focal plane of the laser beam by a distance less than or equal to half the focal length of a focusing device, the focusing device defining the position of the focal plane.

11. A method according to one of the preceding claims, further comprising a step of calculating a modulation setpoint from an input setpoint corresponding to the pattern, the modulation setpoint being applied to a modulation device to shape the beam.

12. A system for forming a figure on a surface or within a volume of a workpiece, the figure comprising a repetition of a pattern, the system comprising: - a device for forming the pattern on the surface or within the volume of the workpiece by shaping and focusing a coherent beam, the pattern comprising at least two local maxima of contrast, the pattern being situated on a surface not parallel to a direction of propagation of the beam; and - a device for the relative movement of the beam and the workpiece.

13. A system according to claim 12, wherein the device for forming the pattern on the surface or within the volume of the workpiece by shaping and focusing a coherent beam comprises: - a source of a coherent light beam, the laser beam preferably being pulsed; - an optical modulation device comprising means for modulating the light beam in a modulation plane according to at least one phase modulation, in order to shape the light beam into a laser pattern; - a focusing device arranged to focus the light beam shaped by the modulation device in a focal plane, the focal plane being in a Fourier or Fresnel configuration relative to the modulation plane of the modulation device, the system being adapted to receive the workpiece, such that the pattern is formed on the surface or within the volume in a processing plane, the processing plane being separated from the focal plane by a distance less than or equal to half the focal length of the focusing device, the laser pattern being configured to produce processing of the workpiece according to the pattern in the processing plane.

14. A system according to one of claims 12 to 13, wherein the optical modulation device comprises a fixed shaping optical element, the optical modulation device and the focusing device preferably being combined into a single unit.

15. A system according to one of claims 12 to 14, wherein the relative displacement device comprises a galvanometric scanning head.

16. A system according to any one of claims 12 to 14, wherein the relative displacement device comprises at least one translation stage.

17. A workpiece comprising a pattern produced by the method according to one of claims 1 to 11.