NL1009359C2 - Laser marking metal, glass or crystal surfaces, by introducing reflection surface matrix into the laser beam in an optical arrangement and selectively removing parts of this surface from the beam to form the pattern - Google Patents

Abstract

A reflection surface matrix is introduced into the optical arrangement and parts of it are selectively removed from or added to the beam in order to create the pattern. A method for applying a chosen pattern containing information characters in a material surface (6') uses a laser source (1) to generate a beam (2) which is directed against the surface using an optical arrangement (3-5). The beam is passed through the optical arrangement whilst the pattern is introduced into it. A reflection surface is used to reflect the beam passing through the optical arrangement and the pattern is created by introducing and/or removing selected parts of the reflection surface with respect to the beam. An Independent claim is also included for the pattern forming device, containing a reflective surface formed by a matrix comprising m x n adjacent sub-surfaces.

Description

Title: Method and device for applying a pattern of information features in a material surface using a laser beam.

The invention relates to a method for applying a pattern of information features in a material surface with the aid of a laser beam, which laser beam is generated in a laser source and guided through an optical system to the material surface and wherein during the beam path the pattern of information features is provided by the optical system in the laser beam.

The invention also relates to a device for applying a pattern of information features in a material surface by means of a laser beam, comprising a laser source, an optical system for guiding the laser beam from the laser source to the material surface, as well as one of the optical system part forming controllable pattern generating unit for generating the pattern of information features in the laser beam.

It is generally known that all kinds of markings can be made in the surface of all kinds of materials by means of laser sources. A method and apparatus described above is known, for example, from Hitachi Ltd., U.S. Patent No. 4,818,835. from Japan. In the device according to US-A-4,818,835, a character is applied to the surface of an object with the aid of the laser beam from a laser source. In order to include the character to be applied as an information characteristic in the laser beam, the laser beam is passed through a controllable liquid crystal panel, the liquid crystal segments of the panel being jointly controlled to form the character.

The above-mentioned method and device have the drawback, however, that such a liquid crystal panel limits the application possibilities for applying information characteristics with a laser beam. In order to prevent damage to the vulnerable liquid crystal panel from the incident 1009359 2 laser beam, concessions must be made to the beam properties (wavelength, energy, etc.). As a result, it is not possible with the current laser beams in combination with such a liquid crystal panel to apply patterns of information features of very small dimensions to a surface while retaining sharpness, image quality and resolution.

Although such patterns of information features generated by the device according to US-A-4,818,835 can be read both mechanically and visually, because of their large dimensions they can only be applied to flat surfaces. In order to maintain the functionality of the liquid crystal panel, a laser beam with "softer" beam properties must be used or the pattern of information features must be pulse-wise applied to the surface. However, these liquid crystal panel protection measures also limit the sharpness, resolution, and image quality of the information pattern ultimately disposed in the surface 20.

The object of the invention is to meet the aforementioned drawbacks and to provide a method and an apparatus with which, regardless of the composition and shape of the surface, patterns of information features of arbitrary dimensions and with an improved sharpness, resolution and image quality in a material surface can be applied without making concessions to the bundling properties.

The method according to the invention is therefore characterized in that the laser beam is reflected by the optical system during a beam path through a composite reflection surface and in that the pattern of information characteristics in the laser beam is obtained by one or more parts of the composite reflection. -35 bring surface into and / or out of the common plane of reflection. The incident of a laser beam on a composite reflection surface, parts of which can be brought into or out of the common plane of a reflection 1009359 3 and not as in the known methods through a radiation-sensitive liquid crystal panel, makes the use of "harder" laser beams possible. After all, no concessions have to be made to the beam properties of the laser beam used, so that sharper and qualitatively better information patterns with an improved resolution are applied in the surface to be processed. The information pattern can also be applied to the surface in one step, which not only benefits the image quality of the applied information pattern, but also the speed and efficiency of the method.

In addition, the method according to the invention can be characterized for this purpose in that after reflection through the composite reflection surface the laser beam is directed onto the material surface via a converging lens. It is hereby possible to provide patterns of information features with very small dimensions in the surface while retaining sharpness, resolution and image quality, which surface as an additional advantage can consequently be not flat, but possibly also curved. From a security point of view, it is also possible to apply patterns of information features with very small dimensions in places that are not obvious.

According to another feature, the method according to the invention is characterized in that a pattern of information features in the form of an m x n matrix is obtained through the composite reflection surface. Partly because the patterns of information features to be applied do not necessarily have to be visually readable, a random pointillic pattern of information features can be created with the composite reflection surface, which can then be read again by machine.

In addition, the method according to the invention is characterized in that a pulsed gas-discharged laser beam with a wavelength of less than 400 nm is used for applying the pattern of information features in the material surface. By the use of a composite 1009359 4 reflection surface, it is now possible to use laser sources with such "harder" beam properties, whereby, in terms of sharpness, resolution and image quality, greatly improved patterns of information features can be applied in the surface 5. to be.

The device according to the invention is characterized in that the controllable pattern generating unit comprises a composite reflection surface, consisting of a matrix of mxn adjoining partial surfaces and that for applying a pattern of information features one or more of the mxn partial surfaces in and / or can be brought out of the common reflection plane.

The reflecting surface is composed of m x n partial prisms. By the use of a composite reflection surface, of which partial surfaces can be brought into or out of the common reflection plane, and the pattern of information features is reflected by means of reflection and not as in the known device by means of absorption in the laser beam. no concessions have to be made to the bundling properties. On the contrary, with the invention such a "harder" laser beam can be used, whereby improved patterns of information features can be applied in surfaces in terms of sharpness, resolution and image quality.

According to an embodiment, the device is characterized in that the edges of the reflection surface of each sub-prism are non-reflective, for example by blackening or matting. This considerably improves the distinctiveness between the sub-prisms, so that a pattern of information features with improved sharpness, resolution and image quality can be applied.

According to another feature, the device according to the invention can be characterized in that the composite reflection surface is arranged at an angle α of 45 ° relative to the beam path of the laser beam. In addition, the device according to the invention can be characterized, 1009359, in that the laser beam, after reflection through the composite reflection surface, hits the material to be marked via a converging lens. Due to this converging effect on the laser beam, it is possible to apply the pattern of 5 information features with very small dimensions and while retaining sharpness, resolution and image quality in the material surface to be produced. This makes the device extremely suitable, irrespective of the shape of the surface, for applying patterns of information features with very small dimensions in places that are not obvious.

In addition, the device according to the invention is characterized in that the laser source is a pulsed gas-discharge laser source, the laser beam has a wavelength less than 400 nm and is incident on the surface of precious metals, in particular jewelry.

In addition, the device according to the invention can be characterized in that the device also comprises a reading unit for reading the pattern of information features arranged in the material surface 20. In addition, the display unit can comprise opto-electronic display equipment, for example a TV camera and an image processing unit.

The invention will now be further elucidated with reference to a drawing, which drawing successively shows: figure 1 a schematic representation of an embodiment of the device according to the invention; figure 2 shows an enlargement of an embodiment of the device according to the invention according to figure 1; figures 3a, 3b and 3c specific embodiments of a part of the device according to figures 1 and 2.

Figure 1 shows an embodiment of a device 35 according to the invention. The device comprises a laser source 1, which generates and emits a laser beam 2. Before incident on the surface 6 'of an object 6 to be processed, the laser beam 2 is guided via an optical system (3, 4, 5) 1 009359 6. The reference numeral 3 denotes a lens which forms part of the optical system 3, 4, 5 and which serves to convert the laser beam 2 into a parallel laser beam. The parallel laser beam 2 'is incident on a cartridge generating unit 4, the construction and function of which will be explained later in the description. The pattern generating unit 4 has a reflection surface 9, on which the laser beam 2 is reflected in the direction of the lens 5. The pattern generating unit 4 10 applies a random pattern of information features in the laser beam 2 in a manner described below, which pattern is the surface 6 'of the object 6, for example a metal surface, is applied. The object 6 is preferably a piece of jewelery made of precious metal, which can be provided with a unique code by this device.

After the laser beam 2 'has been reflected by the reflection surface 9 of the pattern generating unit 4, it is now passed through a lens 5, now provided with the pattern of information features. The lens 5 is preferably a converging lens, which focuses the laser beam 2 on the surface 6 'of the object 6.

In figure 2 the optical system 3, 4, 5 of the device of figure 1 is shown in more detail. The optical system shows the lens 3, which converts the laser beam 2 generated by the laser source 1 into a parallel laser beam 2 '. This laser beam 2 'is incident on the reflection surface 9 of the pattern generating unit 4, and is composed of an arbitrary number of sub-prisms placed against each other, here indicated by 7a-7e. The end surfaces of the partial prisms 7a - 7e are faceted such that they form a common reflection surface 9. The laser beam 2 'is incident at an angle to the composite reflection surface 9.

! According to the invention this angle, represented here with the sign a, is preferably 45 °.

The desired pattern of information characteristics can continue! the pattern generating unit 4 is arranged in the laser beam 2 by moving one or more arbitrary subprisms in and / or out of the common reflection surface 9. For this purpose, the assembly of sub-prisms 7a-7e is coupled to a control 8, which, depending on the desired pattern of information features, brings the respective sub-prisms into or out of the common reflection plane 9. As Figure 2 shows, of the assembly of the sub-prisms 7a-7e, the sub-prisms 7b and 7d are displaced from the common reflection plane 9 (in the direction of the arrows) by the control 8.

The displacement in and / or out of the common reflection plane 9 of the different sub-prisms 7a-7e can for instance be performed in a (servo) mechanical manner by the control 8. However, the displacement of these partial prisms can also take place in an electromagnetic or other manner, for example.

The laser beam 2 'incident at the angle α on the common reflection plane 9 is reflected only by the faceted partial surfaces of those partial prisms 7a - 7e which lie in the common reflective plane 9. The laser beam 2 ', which in this example is incident on the partial surfaces 10 of the partial prisms 7b and 7d, is not reflected, but absorbed by the pattern generating unit 4. As a result, the reflected, coherent, parallel laser beam 2 '' has a pattern of reflected light and non-reflected portions. The portions of the laser beam 2 ', which are not reflected by the common reflection plane 9, are shown in hatching in the figure. The laser beam 2 '' is then converged through the lens 5 and is incident on the surface 6 'of the object 6.

Laser light has the characteristic property that, depending on the beam properties, it can locally attack the surface on which it falls. As a result, the reflected, non-hatched portions of the laser beam 35 2 will locally attack the surface 6 'in accordance with the pattern generated by the cartridge generating unit 4. This pattern in the surface 6 'is shown enlarged in Figure 2a.

Converging the laser beam 2 '' through the lens 5 1009359 8 serves a dual purpose. First of all, an image of small to very small dimensions is formed on the surface 6 'of the object 6. As a result, it is possible with the device according to the invention to apply a pattern of information features in the surface 6 'of, for example, jewelery 6 in places that are not visible, which are barely visible to the eye. The reduced pattern can also be applied regardless of the composition and shape of the surface 6, which considerably increases the application possibilities of the device.

Secondly, due to the convergence by the lens, possibly in combination with a "harder" laser beam, the pattern of information features can be applied in the surface in one step and no longer has to, in order to damage the vulnerable parts of the known prevent devices from being carried out in steps or pulses.

As a result, an information pattern with greatly improved sharpness, resolution and image quality is obtained, which makes it possible to read the information pattern in a more reliable and correct manner by opto-electronic equipment, for instance a T.V. camera.

Figure 2a shows the top view of the surface 6 ·, parts of which have been adapted or etched in accordance with the pattern 25 of information features arranged by the cartridge generating unit 4 in the laser beam 2 by the action of the laser beam. These parts correspond to the incident laser light of the laser beam 2, which is reflected by the facetted partial surfaces 10 of the partial prisms 7a, 7c and 7e, respectively. Since the laser beam incident on the partial surfaces 10 of the partial prisms 7b and 7d has not been reflected, the corresponding parts of the surface 6 'have not been exposed and are therefore not affected.

Figures 3a, 3b and 3c show specific embodiments of an assembly of partial prisms of the controllable pattern generating unit 4, which are designed as an m x n matrix.

In Figure 3a, the sub-prism assembly is constructed as a 1x5 matrix. As described above, the 5; 100935? 9 line prisms n-n5 placed against each other depending on the desired pattern of information features in or out of the common reflection plane 9. After reflection, convergence and incidence on the surface 6 'of the laser beam 52, an image is obtained, as shown in the associated circle. This image is composed of a number of dark c.g. affected areas and light or unaffected areas of the surface 6 '. The affected parts of the surface 6 'are obtained by the action of the laser beam reflected by the corresponding partial prism. The laser beam incident on the sub-prisms displaced from the common reflection plane (here n2 and n4) is not reflected, so that the surface 6 'is not exposed on site and is therefore not adapted. The pattern of dark and light strips forms a pattern of information features, with which the treated object 6 can be indicated and identified.

It will be clear, however, that this number (5) of sub-prisms limits the number of combinations of distinct patterns of information features according to this embodiment. Much more cartridge combinations and, consequently, a much wider range of application can be obtained with the sub-prism assembly, as shown in Figure 3b. In this embodiment, the partial prisms are also built up from a matrix of mxn (m = n = 5), each of which has a faceted end surface 10, which form a common reflection surface 9.

Likewise, each of the m x n partial prisms can be brought into and / or out of the common reflection plane 9 to create a random reflection pattern of information features. Analogously to the foregoing, after reflection and convergence, the surface 6 'is exposed locally or not by the laser beam and, accordingly, affected or not.

In order to obtain a pattern of information features with a considerably improved image quality in terms of sharpness or resolution, as shown in figure 3c, the edges 10a of the faceted surface 10 of each sub-prism 7 can be non-reflective. This can be achieved, for example, by blackening or matting the edges 10a. In the pointillic image in the surface 6 'thus obtained, the non-reflective edges of the partial surfaces 10 make it easier to distinguish the affected parts of the surface 6' from one another. The pattern of information features thus arranged in the surface 6 'is made up of clear and sharply distinguished damaged parts.

Due to the greatly improved resolution and image sharpness, the applied pattern of information features can be read in a more reliable and correct manner with the aid of opto-electronic equipment, for instance a T.V. camera and an image processing unit. This makes the application of the device according to the invention and the random patterns of information features thus to be applied an extremely reliable and safe system for marking and identifying objects 6. The above-mentioned method and device is therefore particularly suitable. for the jewelery industry, for example, where such a safe, comprehensive and fraud-resistant system is highly desirable for jewelery and jewelery authentication.

In the pattern of information features arranged according to the invention, a price indication and / or information about the designer of the jewelery can thus be included in a simple manner. This has the advantage that physical price indications in the form of labels or stickers are superfluous, which provides an aesthetically improved display and facilitates the periodic maintenance and cleaning of the displayed jewelery.

Preferably, the laser source is a pulsed gas discharge laser source and the laser beam preferably has a wavelength less than 400 mn. Such a laser source is eminently suitable for applying patterns in the surface of precious metals by means of the method and device according to the invention.

It will be clear that the application of the method and device according to the invention is not limited to metal surfaces, but also to apply patterns of information features in the surface of other materials, for example glass and crystal. to be.

1009359

Claims (12)

A method for applying a random pattern of information features in a material surface 5 with the aid of a laser beam, which laser beam is generated in a laser source and is guided through an optical system to the material surface and wherein during the beam path through the optical system in the laser beam the pattern of information features is provided, with the feature. that the laser beam is reflected during the beam path through the optical system via a composite reflection surface and that the pattern of information features in the laser beam is obtained by one or more parts of the composite reflection surface in and / or from the common reflection plane. Method according to claim 1, characterized in that after reflection by the composite reflection surface, the laser beam is aimed at the material surface via a converging lens. Method according to any one of the preceding claims, characterized in that a pattern of information features in the form of an m x n matrix is obtained by the composite reflection surface. 4. A method according to any one of the preceding claims, characterized in that a pulsed gas-discharged laser beam with a wavelength of less than 400 nm is used for applying the pattern of information features in the material surface. 5. Device for applying a pattern of information features in a material surface by means of a laser beam according to one of the preceding methods, comprising a laser source, an optical system for guiding the laser beam from the laser source to the material surface, and one of the optical system part forming controllable pattern generating unit for generating the pattern of information features in the laser beam, characterized in that the controllable pattern generating unit comprises a composite reflection surface, consisting of a 1009353 matrix of mxn adjacent part surfaces and that for generating a pattern of information features, one or more of the mxn sub-surfaces can be brought into and / or out of the common plane of reflection. Device as claimed in claim 5, characterized in that the reflection surface is composed of m x n partial prisms. 7. Device as claimed in claim 5 or 6, characterized in that the edges of the reflection surface of each sub-prism are non-reflective, for instance by blackening or matting. 8. Device according to any one of claims 5 to 8, characterized in that the composite reflection surface is arranged at an angle α of 45 ° relative to the beam path of the laser beam. Device according to any one of claims 5 to 8, characterized in that the laser beam, after reflection through the composite reflection surface, hits the material to be marked via a converging lens. Device according to any one of claims 5 to 9, characterized in that the laser source is a pulsed gas discharge laser source, the laser beam has a wavelength of less than 400 nm and is incident on the surface of precious metals, in particular jewelery . A device according to any one of claims 5 to 10, characterized in that the device also comprises a display unit for reading the pattern of information features arranged in the material surface. Device according to claim 11, characterized in that the display unit comprises opto-electronic display equipment, for example a TV camera and an image processing unit. * Ί p n o c Λ