BE1028021B1 - Optical device for marking transparent parts - Google Patents

Abstract

Optical device and system for the internal marking of transparent parts such as containers or transparent containers, which does not cause contamination and which is fast enough to be able to be integrated into a packaging line to allow marking thereof. The system comprising an optical device comprises separation means 30 for separating a pulsed laser beam 11 into a first 31 and a second 32 separate laser beams, deflection means 60 for directing the first 31 and said second 32 separate laser beams in the direction of the surface 3 of the part 2, and focusing means 70 configured to focus the first 31 and the second 32 laser beams separated below the surface 3 and inside the wall 4 of the transparent part 2.

Description

Optical device for marking transparent parts Technical area

[0001] According to a first aspect, the invention relates to an optical device for the marking of transparent parts. According to a second aspect, the invention relates to a system comprising said device. According to a third aspect, the invention relates to a method for internal marking of transparent parts. State of the art

The packaging of certain products often requires the implementation of means to ensure their traceability. Traceability is particularly important in a quality assurance process.

To ensure good traceability of packaged products, it is increasingly necessary to carry out individual marking thereof. An individual marking means that each product is identifiable thanks to unique means of identification. Unique means of identification are for example: a series of characters, a barcode, a QR-code, etc.

[0004] In the pharmaceutical field, when the packaged product is a liquid, it is preferred to have a transparent container, allowing the presence of the liquid to be verified by simple visual inspection. An individual marking of each transparent container is preferably carried out directly after its filling. This helps reduce the risk of errors that may occur in subsequent packaging steps as well as in the identification steps performed during quality control. When marking a container or receptacle, it is important that the method used does not damage or contaminate the product it contains. This is all the more critical in the field of the pharmaceutical industry.

Laser devices for carrying out selective ablation of the surface of a part are known, making it possible to mark said part. Unfortunately, such a surface marking is often poorly suited to transparent materials.

Summary of the invention

[0006] According to a first aspect, one of the aims of the present invention is to provide a device for the marking of transparent parts such as, for example, transparent containers or receptacles, which does not cause contamination and which allows sufficiently rapid marking for be able to be integrated into a packaging line.

[0007] To this end, the inventors propose an optical device for the internal marking of a transparent part delimited by a wall having an external surface, the optical device comprising: a pulsed laser source, configured to emit a pulse laser beam having a pulse duration of between 100 fs and 10 ps; - Separation means for separating the laser beam from the laser source into a first and a second separate laser beam; - Deflection means for directing the first and second separated laser beams towards the surface of the part; - focusing means for focusing the first and second laser beams separated inside the wall of the transparent part.

The optical device of the invention allows internal marking, thus avoiding any contamination. Thanks to the marking of several lines during the same scan of the surface of the transparent part by the separate laser beams, it is possible to significantly increase the marking speed of the part by reducing the number of scans required compared to devices using a single laser beam marking. Thanks to the great speed of the device of the invention for the internal marking of transparent parts, it becomes possible to mark moving transparent parts having a constant scrolling speed. Thus the device of the invention can easily be installed in a production line without requiring major integration work and without modifying the rate thereof.

The device of the invention makes it possible to create a modification of the refractive index of the transparent part at the focal points of the separate laser beams or in their periphery. When scanning these separate and focused laser beams below the workpiece surface, the refractive index of the transparent piece is observed to change along a line.

The device of the invention allows good resolution and good internal marking contrast through the use of laser beam separation means. Indeed, these separation means allow the marking of several lines simultaneously during a single scan of the surface of the part by the deflection means. As a result, the lines marked simultaneously are perfectly in phase, that is, they have identical dimensions and similar ends but offset by the interline distance.

In this way, the present invention solves the problems of internal marking of transparent parts, in a safe and reliable manner, by creating a change in refractive index. This results in high resolution markings with good contrast for fast and reliable reading of markings.

A transparent part preferably has a transmission coefficient (transmittance) of at least 10% in the visible and / or near infrared wavelengths, for example between 400 nm and 2 μm, more preferably at least 50%. For example a transparent part is a container, for example a syringe body, a vial, a vial. Transparent materials constituting the transparent part are, for example, glass, sandblasted glass, quartz, or even polymeric materials such as polystyrene (PS) or polymethyl methacrylate (PMMA). The transparent materials to be marked by changing the refractive index are preferably amorphous. Preferably, the transmission coefficient is greater than 25%, more preferably it is greater than 50%, even more preferably it is greater than 90% over the wavelength range 400 nm - 2 µm. Such a transmission coefficient is preferably defined according to the direction of the first or of the second separated laser beam. A transmission coefficient is a term known to those skilled in the art. Transparent materials according to the invention can also be opaque or semi-transparent (semi-reflective) materials. In the case of a transparent material, a transmission coefficient greater than 10% must allow the healthy human eye to be able to distinguish shapes or a light source through such a transparent part.

Preferably, said outer surface of the wall of the part is the surface through which the separated laser beams enter the part.

The deflection means are for example a scanner or a galvanometric head.

Preferably, the focusing means are an F-theta lens or an objective / telecentric lens.

[0016] Thus, the marking speeds obtained with the device according to the invention are fully compatible with the productivities required in industrial sectors. For example, the device of the invention makes it possible to burn 2D codes (QR code) of 16 lines x 16 columns readable by camera in less than 0.05 s. Thanks to the internal marking device of the invention, it is possible to carry out a marking with a 2D code (QR code) of 16 lines x 16 columns at a rate of 15 transparent pieces per second.

This rate is typical of the traceability needs with a view to monitoring production and monitoring the distribution channels of the pharmaceutical industry.

The inventors experimentally propose that the spatial distribution (X, Y directions) of refractive index consists of a superposition of sinus type profiles in the transverse direction X. They interpret it using theory simplified coupled waves due to Kogelnik. The latter supposes and is moreover valid only if the modulation of the index is constant in the direction Z. Moreover, this theory is strictly applicable in this case only to Bragg gratings with a density of lines greater than 500 lines / mm.

Diffractive function index modulations produced by the device according to the present invention are of variable amplitude in the Z direction corresponding to the direction of propagation of the marking laser beam in the transparent part.

This inhomogeneity can be explained by the self-focusing of the laser beam which modifies in a spatially nonlinear manner the index modulation in the focusing region. Such a modulation distribution

> BE2020 / 5490 of index does not constitute a Bragg grating and requires the use of rigorous coupled wave models for its description. These models also demonstrate diffractive behaviors that are very different from those obtained by Bragg gratings, such as multi-order diffraction. This is particularly true for low spatial frequency diffractive structures such as those produced by the device according to the present invention, that is to say with a line density between 25 and 200 lines / mm.

The invention can be used for: - the decoration industry: it is possible to reduce the glass processing time to a few seconds for large surfaces, which makes the productivity attractive for the perfume industries or drinks (wines, spirits,); - anti-fraud applications: it is possible to write individual codes reliably at more than 20 codes per second, or even at more than 50 codes per second and to read with the same reliability these invisible but highly contrasted signatures using a low-cost vision system both on production lines as with new hand-held readers and it is also possible to include "hidden" data in complex decorations associated with suitable reading devices; - normative marking: it is possible to write normative references which are independent of the quality of the lens and which can be interpreted visually or read by simple vision systems. In addition, it is possible to offer direct marking in the pharmaceutical, chemical and beverage industries, without modifying the mechanical properties, and therefore without microcracks, in order to maintain the integrity of the glass; - in the field of marking inside a glass substrate, more particularly in flasks, in perfume bottles, in automobile glazing, in tempered glass; - in the field of the identification of a data medium by the use of an identifier which can be inserted on the transparent part of the medium (center of the disc) or in the packaging in order to guarantee the originality of the medium, the identifier being able to be a mark, a code or the mixture of the two.

The device according to the invention allows the filling of the internal marking or of the identifier by a diffractive structure, which has the advantage that the paths of the light through the transparent object are modified but that the transparency of the object to be marked is not deleted, unlike a structure which would be diffusing.

A femtosecond laser source is a pulsed laser source, emitting very short pulses. Each pulse has a very short duration, typically of the order of 10 to a few hundred femtoseconds.

The use of such short pulses for the marking offers two main advantages: - due to the very short pulse duration, no thermal effect appears during the treatment, resulting in a high quality of the marking, without creation microcracks; and - due to the very high peak power of the pulses, the peak power being defined as being the ratio between the energy of a pulse and its duration, it is possible to achieve a marking inside the transparent part without damaging the surface thereof.

According to a preferred embodiment, the separation means are configured to separate the laser beam from the laser source into two to seven separate laser beams, more preferably into three separate laser beams.

According to a first embodiment, one of the aims of the present invention is to provide a device for an internal marking system making it possible to adapt the first and second separated laser beams in real time and independently of each other. According to this first embodiment, the inventors propose that the separation means are matrix modulation means, and, more preferably, matrix modulation means in reflection.

The device of the invention makes it possible to provide a device for an internal marking system of transparent parts making it possible to offer great adaptability of the internal markings that can be inscribed. Thereby,

the invention allows great adaptability of the inscribed internal marking thanks to the separation of the pulsed laser beam by the matrix optical modulation means into a first and a second separate laser beam. Thus, it is possible to modulate in real time the dimensions and relative position of the first and second separated laser beams formed by the optical matrix modulation means. Such adaptability of the internal marking which can be inscribed in real time is implemented in a relatively simple manner since the invention allows the separation into a first and a second separate beams upstream of the beam deflection means.

According to a preferred embodiment of the first embodiment, the matrix optical modulation means is a spatial light modulator also known with the acronym SLM. Such an SLM can operate in reflection or transmission in order to interact with a source beam. An SLM makes it possible, for example, to spatially modify: the amplitude and / or the phase and / or the polarization of a beam having interacted with the optical matrix modulation means. For example, the optical matrix modulator is a matrix phase modulator of the liquid crystal on silicon (LCOS SLM) type. An SLM is preferably of the electrically addressed liquid crystal matrix type.

The first embodiment is particularly advantageous because it allows the use of matrix modulation means of relatively small area because illuminated with a fixed pulse laser beam. Thanks to the positioning of the matrix modulation means upstream of the deflection means, their programming is particularly easy because they are illuminated with a fixed beam. If the matrix modulation means were positioned downstream of the deflection means, the matrix modulation means would have to be modulated in real time in order to have beam separation for all deflection positions of the first and second beams thereon.

According to another preferred embodiment of the first embodiment, the matrix modulation means are matrix phase modulation means, more preferably matrix phase modulation means in reflection.

The matrix optical modulation means is an active optical element which makes it possible to spatially modulate laser radiation. Thus, the matrix modulation means makes it possible to modify the shape or the intensity of the beam by selectively modulating the interaction of the source laser beam with the matrix of pixels of the optical matrix modulation means. The display of a phase modulation map by the optical matrix modulation means makes it possible to separate by diffraction, a first and a second (a plurality of) beams from a single pulsed (collimated) laser beam. Preferably, the matrix optical modulation means allows modulation of the phase in reflection, and therefore the diffraction of the source beam into a first and a second (a plurality of) beams by reflection. An advantage of the first embodiment is to use a matrix optical modulation means which induces only a negligible divergence on the plurality of diffracted beams, which does not require the use of collimation / focusing means between the means. matrix optical modulation and the deflection means in order to be able to transport the first and second (the plurality of) beams to the workpiece.

According to another preferred embodiment of the first embodiment, the reflection matrix phase modulation means are an LCOS, in that they are capable of separating said linearly polarized pulse laser beam in first and second (in a plurality of) separate laser beams.

According to a second embodiment, the separation means comprise a fixed diffractive optical element for beam shaping. The shaping of the laser beam corresponds to a separation of the laser beam into a first and a second (in a plurality of) separate laser beams. A fixed diffractive optical element is for example a DOE, an acronym known to those skilled in the art.

[0034] According to a preferred embodiment of the second embodiment, the fixed diffractive optical element is a diffractive optical element in transmission.

According to another preferred embodiment of the second embodiment, the fixed diffractive optical element is a first diffractive optical element fixed in reflection.

According to another preferred embodiment of the second embodiment, the separation means further comprise a second

? BE2020 / 5490 fixed diffractive optical element in reflection so that the laser beam describes at least one reflection on each of the first and second diffractive optical elements in reflection, more preferably at least two reflections on each of the first and second diffractive optical elements in reflection.

[0037] At least two reflections of the pulsed laser beam on two diffractive optical elements allows better control of the separation of the pulsed laser beam into a first and a second (a plurality of) separate laser beams. Also, it allows for better control of the depth of field when the first and second (the plurality of) separate laser beams are then focused. When desired, this embodiment of the invention makes it possible to obtain a much greater depth of field in comparison with the depth of field obtained during a single interaction of the beam with a diffractive optical element.

Preferably, the deflection means comprise a scanner for moving the first and second laser beams separated in two orthogonal X and Y directions.

Even more preferably, the deflection means further comprise a motorized telescope positioned between said scanner and the focusing means so that it makes it possible to modify the position of the focusing points relative to said focusing means. The motorized telescope makes it possible to adjust the focusing of the laser beams separated in the wall in order to allow the internal marking of parts whose position relative to the focusing means may vary. The motorized telescope can also be used to change the depth of focus inside the room wall relative to the outside surface of the room. The motorized telescope makes it possible to adjust the position of the focal points relative to the surface of the room wall. This is particularly advantageous when it is desired to ensure an internal marking of a clean part, without the formation of debris or damage to a surface of the part wall.

Preferably, the optical device of the invention comprises beam size management means positioned between the source and the separation means.

According to a second aspect, one of the aims of the present invention is to provide a system for the internal marking of transparent parts.

To this end, the inventors propose a system comprising: an optical device according to the first aspect; - the transparent part to be marked.

The different variants and advantages described for the optical device according to the first aspect of the invention apply to the system according to the second aspect, mutatis mutandis.

Preferably, - the separation means are configured to separate the laser beam from the laser source into three separate laser beams; the deflection and focusing means are configured and the part is positioned so that the first, second and third separate laser beams are aligned when they interact with the outer surface of the part. Aligned means that the impacts of the first, second and third beams on the surface of the part form a straight line.

Preferably, - the separation means are configured to separate the laser beam from the laser source into three separate laser beams; - the deflection and focusing means are configured and the part is positioned so that the first, second and third separate laser beams are focused in the wall of the part with a distance between the focal points of the separate laser beams between 5 µm and 40 µm, preferably 10 µm and 25 µm, for example equal to 15 µm.

Preferably, the focusing means are configured to focus the laser beams separated in the room, at a distance from the surface of between 50 μm and 200 μm, for example 100 μm.

Preferably, the system further comprises: - means for detecting a position in depth of the external surface of the part;

- A motorized telescope to adjust the depth of the focal points of the laser beams separated in the wall with respect to the external surface of the part, according to the position in depth, - control means for controlling the motorized telescope from information received from the means for detecting a position in depth of the external surface of the part. A depth position is a direction along the Z direction.

Preferably, the system further comprises: - viewing means for analyzing an internal marking of a transparent part; - sorting means for directing a transparent part towards: o a first direction, a transparent part when it is judged compliant by the viewing means, o a second direction, a transparent part when it is judged non-compliant by means of vision.

Preferably, the viewing means further comprise: - room lighting means configured to emit an inspection light beam, - a camera configured to detect when the part passes through the light beam d inspection, a light signal from the internal marking of the transparent part.

Preferably, the system further comprises: - means for conveying the transparent part.

According to a third aspect, the inventors propose a method for the internal marking of a transparent part comprising the following steps: a. providing a transparent part to be marked delimited by a wall having an external surface; b. providing an optical device according to the first aspect or a system according to the second aspect; vs. activate the optical device so as to direct and focus the first and second separate laser beams within the wall of the transparent part;

d. scan the surface of the part with the first and second separate laser beams by actuating the deflection means so as to mark the transparent part in a plurality of lines, by selectively modifying inside the wall of the transparent part, its index refraction.

The different variants and advantages described for the optical device according to the first aspect of the invention and for the system according to the second aspect apply to the method according to the third aspect, mutatis mutandis.

Preferably, the deflection means are configured to mark the transparent part with a plurality of lines essentially parallel to each other with a pitch between them which is essentially constant and between 5 μm and 40 μm.

Preferably the separated laser beams are focused within the wall having a thickness d, the separated laser beams are focused at a distance below the surface substantially equal to half of said thickness d.

Brief description of the figures

These aspects as well as other aspects of the invention will be clarified in the detailed description of particular embodiments of the invention, reference being made to the drawings of the figures, in which: - Fig.1 shows one embodiment realization of the device according to the invention; - Fig.2 shows a preferred embodiment of the device according to the invention; - Fig.3 shows an embodiment of the system according to the invention; - Fig.4 shows a preferred embodiment of the system according to the invention; - Fig.5 shows a preferred embodiment of the viewing means according to the invention; - Fig.6A shows a cross section of the wall of a part that has been marked internally;

- Fig. 6B shows a top view of a part that has been marked internally, the location of the cut in Fig. 6A being indicated therein. - Figs. 7, 8A, 8B, 9A, 9B show embodiments of the separation means included in the device.

The drawings of the figures are not to scale. Generally, like elements are denoted by like references in the figures. The presence of reference numbers in the drawings cannot be considered as limiting, including when these numbers are indicated in the claims. Detailed description of certain embodiments of the invention

Figures 1, 2, 3, 4, 5, 6A, 6B are defined according to Cartesian coordinates in space. These Cartesian coordinates in space are defined by three non-coplanar vectors X ÿ, Z which we will call here directions X, Y, Z respectively. The directions X, Y, Z are all orthogonal to each other.

FIG. 1 shows an exemplary embodiment of the device 1 according to the invention. The device 1 is configured to mark a part 2 comprising a wall 4 delimited by an external surface 3. The device 1 makes it possible to mark the part inside the transparent wall 4 of the part 2. The wall portion 4 to be marked inside is oriented in the X, Y directions. The definition of the orientation of the wall according to a plane does not mean that only essentially straight walls can be marked by the device 1 of the invention. For example, parts with walls 4 delimited by a curved surface 3, having a radius of curvature can be marked by the device 1 according to the invention.

The device 1 of Figure 1 shows a laser source 10 configured to emit a laser beam 11. The separation means 30 are configured to separate (in the Y direction) the laser beam 11 into a first 31 and a second 32 separate laser beam. These first 31 and second 32 separate laser beams are then directed towards the outer surface 3 of the part 2 by deflection means 60. The deflection means 60 shown in Figure 1 are configured to modify the directions of propagation of the first 31. and second 32 laser beams separated in the X and Y directions. Focusing means 70 are positioned between the deflection means 60 and the part 2 in order to allow focusing of the first 31 and second 32 laser beams separated inside the chamber. transparent part 2. In order to carry out the marking inside the wall 4, the first 31 and second 32 separate laser beams are focused below the surface 3, that is to say inside the wall 4. According to a preferred embodiment, the deflection means of FIG. 1 comprise a scanner 61 for moving said first 31 and second 32 laser beams separated in two orthogonal X and Y directions.

Figure 2 shows another embodiment of the device 1 of the invention similar to the embodiment of Figure 1. In the embodiment of Figure 2, the deflection means 60 include: - a scanner 61 for moving said first 31 and second 32 separated laser beams in two orthogonal X and Y directions; a motorized telescope 62 positioned between the scanner 61 and the focusing means 70 so that it makes it possible to modify the position of the focusing points relative to said focusing means 70. The embodiment of FIG. 2 allows adjustment of the marking depth inside the wall 4 of the part 2, thanks to the adjustment of the distance (depth) of focusing of the first 31 and second 32 laser beams separated from the outer surface 3 of the part 2. This embodiment is particularly advantageous because it makes it possible to maintain a fixed distance between the focusing means 70 and the external surface 3 of the part 2.

FIG. 3 shows an embodiment of the system 100 according to the second aspect of the invention. The system 100 of the invention comprises, in addition to the optical device 1, means 50 for conveying the transparent part 2 to allow the movement of the transparent part 2 so that it is exposed to the first 31 and second 32 separate laser beams. . The system 100 of the invention shown in FIG. 3 comprises means 80 for detecting a position in depth (in the Z direction) of the external surface 3 of the part 2. These detection means 80 are connected to means of control 85 to control said motorized telescope in order to be able to adjust the depth of the focal points of the separated laser beams 31, 32 in said wall 4 with respect to the external surface 3 of the part 2, as a function of said depth position. The detection means are for example a camera making it possible to define a position of an object in the Z direction, in particular the position of the external surface 3 of the part 2. Thus, the conveying means 50 make it possible to transport a part 2. at the level of the detection means 80, then at the level of the optical device 1 so that the part is marked on the inside by an internal marking 5. The position of the internal marking 5 can easily be adjusted thanks to the control of the permitted depth of focus by the information received from the detection means 80. FIG. 3 shows a first part 2 at the level of the detection means 80, a second part 2 at the level of the device 1 then a third part 2 having been marked inside the wall 4 by the device 1. The first, second and third parts are conveyed by the conveying means 50. FIG. 3 illustrates a movement of the parts 2 by the conveying means in the direction Y.

The embodiment of Figure 4, comprises in addition to the embodiment of Figure 3, viewing means 90 for analyzing an internal marking 5 of a transparent part 2 having been marked by the optical device 1. The embodiment of FIG. 4 further comprises sorting means 110 for selectively moving a transparent part 2 towards a first direction 111, when the latter is judged to be compliant by said viewing means 90, or towards a second direction. 112 when the latter is deemed to be non-compliant by said viewing means 90. The viewing means 90 for example comprise means for reading a QR code. The viewing means 90 shown in FIG. 4 comprise lighting means 93 of the part 2 configured to emit an inspection light beam 94, a camera 96 configured to detect during the passage of the part 2 in the light beam of inspection 94, a light signal 95 from the internal marking 5 of the transparent part 2. Depending on the light signal 95 detected by the camera 96 and transmitted to the sorting means 110, the sorting means 110 make it possible to direct the parts 2 towards the first 111 or towards the second direction 112.

Figure 5 shows a detailed view of the viewing means 90. The viewing means 90 allow reading of an internal marking 5 of a portion 4 of the part 2 when the latter has diffractive optical properties and / or refractive. Thanks to the properties of the internal marking 5, it is possible to read the internal marking 5 with a very high contrast, which allows a very reliable reading of the latter. This is possible by illuminating the internal marking with an inspection light beam 94, the direction of which describes an angle with the external surface 3 of the part greater than 10 °, or even greater than 20 °. Thanks to the refractive and / or diffractive properties of the internal marking 5, the latter selectively modifies the direction of propagation of the inspection light beam 94. The portion of the inspection light beam 94 whose direction is modified by the internal marking 5 becomes a 95 light signal from the internal marking

5. This light signal 95 is then directed towards the camera 96 (for example a CCD sensor). The angle of the inspection light beam 94 with the external surface 3 of the workpiece should be chosen depending on the refractive and / or diffractive properties of the desired internal marking 5. Preferably, the angle of the inspection light beam 94 with the external surface 3 is defined in a plane along the ZY directions.

[0063] Figure 6A shows a cross section of a part 2 in the ZY directions. This cross section is a cross section of the internal marking 5 shown in Figure 6B. The internal marking portions 5 shown in Figure 6A show that the device 1 and the system 100 according to the invention allow the formation of three-dimensional volumes inside the wall having different structural properties. For example, the portions of transparent materials modified by the internal marking 5 are in an amorphous phase different from the amorphous phase of the material of the part located all around. The internal marking portions obtained often have a shape - ovoid. Such internal marking portions have for example dimensions: - width 6, in an X or Y direction, minimum dimension corresponds to the smallest portion of an internal marking 5; the width is then between 10 and 20 µm; - depth 7, in a direction Z, dimension corresponds to the depth of the internal marking portions 5, this dimension is relatively constant for all the portions of an internal marking 5. This dimension is preferably less than 150 μm, more preferably less than 100 µm.

The internal marking portions 5 can be centered according to the thickness d of the part. The thickness d of the part is defined in the Z direction. For example, in order not to damage the surfaces of a portion 4 of a 1 mm thick part, it is often chosen to carry out the internal marking 5 in a zone of portion 4 located at least 200 µm from an outer surface 3 of part portion 4, more preferably at least 300 µm. Thus the risk of debris formation during the formation of the internal marking 5 is very greatly reduced.

FIG. 6B shows an internal marking 5 seen from the external surface 3 of the part 2. FIG. 6B represents the formation of an internal marking of the QR code type with the inscription of a row (of a column ) of pixels during a scan by the deflection means 60 on the surface 3 of the first 31 and second 32 separate laser beams. These lines (column) are thus selectively marked as a function of the information that it is desired to contain the internal marking 5. Thus in FIG. 6B, the scanning of the first 31 and second 32 separate laser beams has been carried out in the direction Y to create a row (column). A first row (column) has been entered comprising three marked pixels (represented by thin lines) separated by unmarked pixels. Each marked pixel has been marked by the first 31 and second 32 separate laser beams, which is represented by the thick lines. After moving the first 31 and second 32 laser beams separated in the X direction, a second line was then written comprising four adjacent marked pixels, two non-marked pixels then one marked pixel. After a subsequent displacement of the first 31 and second 32 laser beams separated in the X direction, a third line was then written comprising an unmarked pixel, a marked pixel, an unmarked pixel and then four adjacent marked pixels. A step 8 defines the spacing in the X direction between the barycenter of the marked pixels or lines. Such a pitch 8 is for example between 25 μm and 80 μm, preferably between 30 μm and 60 μm.

Figure 7 shows separation means 30 comprising a first reflective diffractive optical element 37 and a second reflective diffractive optical element 38. The first 37 and the second 38 reflective diffractive optical elements each comprise a diffraction grating for diffract a laser beam in reflection. The pulsed laser beam 11 is directed towards the diffraction grating of the first diffractive optical element 37 in reflection, the diffracted and reflected beam is then directed towards the second optical element in reflection 38 where it is again diffracted and reflected in a first 31 and a second 32 separate laser beams. In another embodiment of the separation means of FIG. 7, the pulse laser beam 11 is reflected and diffracted at least twice on each of the first 37 and second 38 reflective diffractive optical elements so that a first 31 and a second 32 separate laser beams are generated by the separation means 30 At least two reflections of the pulsed beam 11 allow better control of the separation of the first 31 and second 32 separate laser beams, and, in particular, better control of the depth of field when the first 31 and second 32 separate laser beams are then focused by the focusing means 70 inside the portion 4 of the part 2.

[0066] Figure 8A shows separation means 30 comprising a transmission diffractive optical element 36. A transmission diffractive element 36 comprises a diffraction grating on at least one of its surfaces. For example, a transmission diffractive element 36 is made of a material transparent to the pulsed laser beam 11. The transmission diffractive element 36 makes it possible to diffract the pulsed laser beam 11 into a first 31 and a second 32 separate laser beams.

FIG. 8B shows separation means 30 comprising a reflection diffractive optical element 37. A reflection diffractive element 37 comprises a diffraction grating on its reflecting surface. The reflective diffractive element 37 makes it possible to diffract the pulsed laser beam 11 into a first 31 and a second 32 separate laser beams.

FIG. 9A shows separation means 30 comprising transmission matrix modulation means 35. For example a liquid crystal filter. Matrix modulation means in transmission 35 comprise a matrix of pixels which can be traversed by the pulse laser beam 11. For example, the pixel matrix is configured to display a phase modulation map (a diffractive pattern) making it possible to diffract the beam. pulsed laser 11 during transmission thereof through the displayed phase modulation map, in a first 31 and a second 32 separate laser beam.

FIG. 9B shows separation means 30 comprising reflection matrix modulation means 39. For example a matrix of liquid crystals on silicon (LCOS). Reflection matrix modulation means 39 comprise a pixel matrix making it possible to reflect the pulsed laser beam 11. For example, the pixel matrix is configured to display a phase modulation map (a diffractive pattern) making it possible to diffract the laser beam. pulsed 11 during the reflection thereof on the displayed phase modulation map, in a first 31 and a second 32 separate laser beams.

The present invention has been described in relation to specific embodiments, which have a purely illustrative value and should not be considered as limiting. In general, the present invention is not limited to the examples illustrated and / or described above. The use of the verbs "to understand", "to include", "to include", or any other variant, as well as their conjugations, can in no way exclude the presence of elements other than those mentioned. The use of the indefinite article "a", "a", or of the definite article "the", "the" or "the", to introduce an element does not exclude the presence of a plurality of these elements. Reference numbers in the claims do not limit their scope.

In summary, the invention can also be described as follows. Optical device and system for the internal marking of transparent parts such as containers or transparent containers, which does not cause contamination and which is fast enough to be able to be integrated into a packaging line to allow marking thereof. The system comprising an optical device comprises separation means 30 for separating a pulsed laser beam 11 into a first 31 and a second 32 separate laser beams, deflection means 60 for directing the first 31 and said second 32 separate laser beams in the direction of the surface 3 of the part 2, and focusing means 70 configured to focus the first 31 and the second 32 laser beams separated below the surface 3 and inside the wall 4 of the transparent part 2.

Claims (23)

Claims 1. Optical device (1) for the internal marking of a transparent part (2) delimited by a wall (4) having an external surface (3), said optical device (1) comprising: - a pulsed laser source (10) , configured to emit a pulsed laser beam (11) having a pulse duration between 100 fs and 10 ps; - separation means (30) for separating said laser beam (11) from said laser source (10) into a first (31) and a second (32) separate laser beams; - deflection means (60) for directing said first (31) and said second (32) separated laser beams in the direction of said surface (3) of said part (2); - focusing means (70) for focusing said first (31) and said second (32) laser beams separated inside said wall (4) of said transparent part (2). 2. Optical device (1) according to the preceding claim characterized in that said separation means (30) are configured to separate said laser beam (11) from said laser source (10) into two (31, 32) with seven beams separate laser, preferably in three separate laser beams. 3. Device (1) according to any one of the preceding claims characterized in that said separation means (30) are matrix modulation means (35, 39), preferably matrix reflection modulation means (39). 4. Device (1) according to any one of the preceding claims characterized in that said matrix modulation means (35, 39) are matrix phase modulation means (35, 39), preferably phase modulation means. matrices in reflection (39). 5. Device (1) according to the preceding claim characterized in that said matrix phase modulation means in reflection (39) comprise a LCOS and in that they are configured to separate a linearly polarized source laser beam (101) into said plurality of separate laser beams (301). 6. Device (1) according to any one of claims 1 to 3 characterized in that said separating means (30) comprise a fixed diffractive optical element (36, 37, 38) for shaping beams. 7. Device (1) according to the preceding claim characterized in that the fixed diffractive optical element (36, 37, 38) is a diffractive optical element in transmission (36). 8. Device (1) according to claim 6 characterized in that the fixed diffractive optical element (36, 37, 38) is a first diffractive optical element fixed in reflection (37). 9. Device (1) according to the preceding claim characterized in that it further comprises a second diffractive optical element fixed in reflection (38) so that said laser beam (101) describes at least one reflection on each of the first (37 ) and second (38) reflective diffractive optical elements, preferably at least two reflections on each of the first (37) and second (38) diffractive reflective optical elements. 10. Optical device (1) according to any one of the preceding claims characterized in that said deflection means (60) comprise a scanner (61) for moving said first (31) and second (32) laser beams separated in two directions. X and Y orthogonal. 11. Optical device (1) according to the preceding claim characterized in that said deflection means (60) further comprise a motorized telescope (62) positioned between said scanner (61) and said focusing means (70) so that it makes it possible to modify the position of focusing points relative to said focusing means (70). 12. Optical device (1) according to any one of the preceding claims characterized in that it comprises beam size management means (20) positioned between said source (10) and said separation means (30). 13. System (100) comprising: - an optical device (1) according to any one of the preceding claims; - said transparent part (2) to be marked. 14. System (100) according to the preceding claim characterized in that: - said separation means (30) are configured to separate said laser beam (11) from said laser source (10) into three separate laser beams (31, 32 , 33); - the deflection (60) and focusing (70) means are configured and the part (2) is positioned so that said first (31), second (32) and third (33) separate laser beams are aligned when '' they interact with said outer surface (3) of said part (2). 15. System (100) according to any one of claims 13 to 14 characterized in that: - said separation means (30) are configured to separate said laser beam (11) from said laser source (10) into three beams separate lasers (31, 32, 33); - the deflection (60) and focusing (70) means are configured and the part (2) is positioned so that said first (31), second (32) and third (33) separate laser beams are focused in the wall (4) of said part (2) with a distance between the focal points of said separate laser beams (31, 32, 33) of between 5 µm and 40 µm, preferably 10 µm and 25 µm, for example equal to 15 µm . 16. System (100) according to any one of claims 13 to 15 characterized in that said focusing means (70) are configured to focus said separate laser beams (31, 32) in said part (2), at a distance from said surface of between 50 µm and 200 µm, for example 100 µm. 17. The system (100) of claim 16 further comprising: - detection means (80) of a position in depth of the outer surface (3) of the part (2); - a motorized telescope (62) for adjusting the depth of the focal points of the separate laser beams (31, 32) in said wall (4) relative to the outer surface (3) of the part (2), as a function of said depth position - control means (85) for controlling said motorized telescope (62) on the basis of information received from said means for detecting (80) a position in depth of the external surface (3) of the part ( 2). 18. System (100) according to any one of claims 13 to 17 characterized in that it further comprises: - viewing means (90) for analyzing an internal marking (5) of a transparent part (2) ; - sorting means (110) for directing a transparent part (2) towards: o a first direction (111), a transparent part (2) when the latter is judged to be compliant by said viewing means (90), o a second direction (112), a transparent part (2) when the latter is deemed non-compliant by said viewing means (90). 19. System (100) according to the preceding claim characterized in that said viewing means (90) further comprise: - lighting means (93) of said part (2) configured to emit an inspection light beam ( 94), - a camera configured to detect during the passage of the part (2) in the inspection light beam (94), a light signal (95) coming from said internal marking (5) of the transparent part (2). 20. System (100) according to any one of claims 13 to 19 characterized in that it further comprises: - conveying means (50) of said transparent part (2). 21. Internal marking process for a transparent part (2) comprising the following steps: a. providing a transparent part (2) to be marked delimited by a wall (4) having an external surface (3); b. providing an optical device (1) according to any one of claims 1 to 12 or a system (100) according to any one of claims 13 to 20; vs. activating said optical device (1) so as to direct and focus said first (31) and second (32) laser beams separated within said wall (4) of said transparent part (2); d. scanning said surface of said part (2) with said first (31) and second (32) separate laser beams by actuating said deflection means (60) so as to mark said transparent part (2) in a plurality of lines, modifying selectively inside said wall (4) of said transparent part (2), its refractive index. 22.Procédé according to the preceding claim characterized in that said deflection means (60) are configured to mark said transparent part (2) with a plurality of lines essentially parallel to each other with a pitch (8) between them essentially constant and between 5 µm and 40 µm. 23.Process according to the preceding claim characterized in that said separated laser beams are focused inside the wall (4) having a thickness d, said separated laser beams (31, 32) are focused at a distance below the surface ( 3) substantially equal to half of said thickness d.