EP1433114A1

EP1433114A1 - Method and arrangement for laser engraving a substrate surface

Info

Publication number: EP1433114A1
Application number: EP02779137A
Authority: EP
Inventors: Gerold Simke
Original assignee: Rodenstock GmbH; Laser 2000 GmbH
Current assignee: Rodenstock GmbH; Laser 2000 GmbH
Priority date: 2001-10-02
Filing date: 2002-10-02
Publication date: 2004-06-30
Also published as: US20050045605A1; WO2003032236A1; JP2005505837A

Abstract

The invention relates to a method and an arrangement for laser engraving a substrate surface, whereby during an engraving process a laser beam, produced by a laser generator, is shaped by means of beam-shaping diaphragms, focussed in a focussing unit and directed continuously or intermittently to the surface which is to be engraved. The aim of said invention is to permit an individual and freely programmable laser engraving of the substrate surface with reduced expenditures on production and maintenance. Said aim is achieved whereby, according to said method, the substrate is moved during the engraving process in a x-y plane, perpendicular to the beam direction and whereby, in said arrangement, the substrate support can be moved in a x-y plane, perpendicular to the laser beam direction.

Description

Method and arrangement for producing a laser engraving in a surface of a substrate

The invention relates to a method for producing a laser engraving into a surface of a substrate, in which a laser beam is directed at beam intervals or continuously onto the surface to be engraved during an engraving process, the substrate moving in an xy plane perpendicular to the beam direction during the engraving process is and the movements of the substrate movements of the laser beam in the x and y directions are superimposed.

US Pat. No. 6,121,574 describes a method of the type mentioned in the introduction in which the substrate is moved in an x-y plane perpendicular to the beam direction during the engraving process and movements of the laser beam in the x and y directions are superimposed on the movements of the substrate.

DE 198 40 926 AI describes an arrangement in which several laser beams are combined in one laser spot. It is possible to move the substrate in the vertical z-direction to compensate for different substrate heights and to keep the laser beam focused on the respective surface.

In EP 0 601 857 AI an arrangement is described which has a laser generator. Excimer lasers that work in the deep UV spectrum and have very good ablation properties are suitable for engraving transparent materials.

Beam shaping diaphragms are arranged in the beam path of the laser beam generated by the laser generator. On the one hand, these shield part of the laser beam in order to bring it into the form, for example of alphanumeric characters, which are to be applied to the surface of a substrate. On the other hand, the beam shaping shutters serve to to split the shaped laser beam into several partial beams, which then ensure that the character to be engraved consists of several points generated by the partial beams, which considerably improves readability.

A focusing unit is provided for imaging the beam shaped in this way. This focusing unit is used to focus the laser beam on the surface of the substrate lying on the substrate support and thus to sharply image the character embossed via the beam shaping diaphragm, which is then engraved into the surface by ablation.

During the engraving process, the laser beam is either constantly directed at the surface of the substrate or a so-called pulse laser is used, which irradiates the surface at beam intervals.

It has been shown that this known arrangement and the method implemented with it are not very flexible since each change of character also requires a change of the beam shaping diaphragms. In addition, a significant part of the laser energy is reflected at the beam shaping diaphragms or converted into heat.

One way of achieving a faster and more flexible change of characters is shown in US Pat. No. 4,194,814. This solution also provides for the use of beam shaping masks which are arranged on a rotatable mask drum. Depending on the desired character, the corresponding mask part that forms the character is rotated into the beam path of the laser beam.

In addition to the not inconsiderable mechanical effort, this solution requires the entire mask drum to be replaced when a mask part that bears, for example, the most frequently used symbol is worn, which results in a considerable amount of maintenance.

In the arrangement according to EP 0 601 857 AI already described a beam deflection unit in the form of a deflection mirror is also provided, which deflects the laser beam in order to bring it onto the surface of the substrate. This deflection takes place in the beam path before passing through the planfeid lens.

It is now known to use such a beam deflection unit for programmable and flexible laser engraving by arranging the deflecting mirror in a galvanometer head. With the help of the galvanometer head, the laser beam can be moved within the labeling field on the surface of the substrate. The shape of the character to be imaged can thus be influenced by a movement of the galvanometer head and no longer exclusively by a beam shaping diaphragm.

To achieve an image of the laser beam on the entire labeling field, a flat field lens is used.

Such an arrangement and a method implemented with it have the disadvantage, in particular in the case of the preferred laser spectrum, that such a flat field lens can be produced only with great effort and can only be used to achieve a short service life.

A method is known from DE 37 28 622 Cl and DE 196 12 406 C2 in which information that is macroscopically, ie essentially visible to the naked eye, is superimposed or embedded with information that is not visible macroscopically. This information can consist of a machine-readable form, such as a barcode, or simply by omitting burn-in points or by realizing small and large burn-in points. This either produces machine-readable information, which, however, cannot be produced with justifiable effort using laser technology, or the information width is very limited if pixels are omitted.

The object of the invention is now to create an individual and freely programmable laser engraving in the surface. nes substrate together with an invisible information with an approximately the same manufacturing time compared to conventional laser engraving.

On the process side, this object is achieved in that the laser engraving consists of a macroscopic structure which is composed of a pattern of microscopic engraving elements, the information encoded in the structure being impressed by macroscopically invisible deviations of the pattern from a desired pattern by the Structure by means of the x and y movements of the substrate and the deviations are generated by means of the x and y movements of the laser beam.

The shape of the character can therefore be set via the movement of the substrate. This makes it possible to create a wide variety of characters with a simple change in the movement program. This allows the production of so-called micro-engravings, in which the characters consist of engraving points within a matrix. Information is encrypted behind the presence or absence of engraving points within this matrix.

The simple change of the pattern to be engraved by the method according to the invention allows even substrate-specific patterns to be engraved and, furthermore, substrate-specific coded information to be engraved by means of micro-engraving and thus stored.

By superimposing the movements of the substrate with movements of the laser beam in the x and y directions, it becomes possible to minimize the required precision of the movement of the substrate, since the fine adjustment can be carried out by the movement of the laser beam. On the other hand, this has the advantage that additional movements can be applied by the laser beam during engraving. This makes it possible, for example, to broaden the engraving lines by circling the beam. Because the laser engraving consists of a macroscopic structure, which is composed of a pattern of microscopic engraving elements, information encoded on the structure is imprinted by macroscopically invisible deviations of the pattern from a target pattern. This creates the possibility of accommodating non-visible information in a normally visible structure, which in turn can convey visible information. This invisible information can then be read out again by appropriately enlarging the structure and by comparing the pattern, ie the actual pattern, with the target pattern.

The information is introduced with two movements, in that the structure is generated by means of the x and y movements of the substrate and the deviations are generated by means of the x and y movements of the laser beam. Since the deviations only require very small geometric changes in the position of the laser beam on the substrate surface, which, however, have to be carried out with some precision, it is advisable not to use the relatively slow movement of the substrate for this, but to move the massless laser beam, which can be done with higher speed and greater precision.

In a favorable embodiment of the invention it is provided that the substrate is moved in a z-direction parallel to the beam direction during the engraving process.

This configuration makes it possible to take into account different surface structures and / or different material thicknesses of the substrates.

It is particularly expedient here that the movement in the z direction is dependent on the structure of the surface. This is done in such a way that the focus of the laser beam is always on the surface at different positions of the substrate in the xy plane. To implement the z movement, a known surface structure of the substrates to be engraved one after the other can be taken into account in a control program, the surface structure can be programmed as it were. This then controls the z movement depending on the substrate position in the xy plane.

Another way of controlling the z movement is to regulate the focusing. Here, it is measured to what extent the laser beam is sharply imaged on the surface of the substrate and the z movement is accordingly initiated until the focus of the laser beam is imaged on the surface.

In another embodiment of the method, the beam is shaped via beam shaping diaphragms and the shape of the beam shaping diaphragms is sharply imaged on the surface as an engraving point. This makes it possible to use different beam shaping apertures to generate engraving points with a special shape, which are particularly suitable, for example, for automatic detection.

In a further embodiment of the method it is provided that the movements of the substrate take place discontinuously. This enables a point-by-point engraving in such a way that the substrate remains in a first position, is then moved to the next position, remains there again, etc.

A further embodiment of the discontinuous movement consists in the fact that when beam intervals are used, the movements take place in time intervals between the beam intervals. A step-by-step operation is thus realized: a laser pulse with relatively high energy generates the point-like engraving during a pulse interval. After the laser pulse and before the next one, the position of the substrate is changed. This offers the advantage that it is possible to work with relatively high radiation energy and that the engraving points are imaged very precisely, since ablation occurs the surface of the substrate is avoided during the process.

It is also possible that the laser engraving consists of a large number of macroscopic structures. In this way, for example, visible points can be lined up. The individual structures can in turn serve to group information.

It is expedient to select the target pattern as a matrix of set or not set engraving elements. The deviations are then formed by omitting or adding or by engraving elements. This matrix is visible as a small dot or small square. It is possible to achieve a high information density on the smallest geometrical area. Due to the small geometrical extent of the matrix, the information can also be stored on curved surfaces, since the small geometrical extent results in only an insignificant spatial extension of the structure even with a strong curvature. This makes both writing and reading the information considerably easier.

It is possible that the matrix is provided with a matrix frame made of engraving elements. In the macroscopic area, the matrix always appears as a geometric structure, regardless of the number of engraving elements inserted or missing. Such a matrix frame also precisely defines the boundaries of the matrix.

In a further embodiment of the method, it is provided that the target pattern is selected as engraving elements lying on a line and the deviations are formed by a macroscopically invisible offset of the engraving elements from the line. Such a line appears straight to the viewer because he does not perceive the offset, even though further information is not visibly stored in the line itself. In a variant of this, it is provided that the target pattern is chosen as engraving elements lying one behind the other on a double line, the line spacing of which lies in the microscopic range. The engraving elements lie on the one line of the double line in the representation of a logical 0 in the coded information and on the other line of the double line in the case of the representation of a logical 1. This results in an exact assignment of the lateral offset and thus an increase in the detection accuracy.

By omitting engraving elements on one or the other line, the information can even be encoded twice in binary.

The invention will be explained in more detail below on the basis of an exemplary embodiment. In the accompanying drawings

1 is a perspective view of an arrangement according to the invention with a simple steel deflection unit,

2 is a perspective view of an arrangement according to the invention with a galvanometer head,

3 shows a representation of a micro-engraving produced by the method according to the invention in the form of a matrix and

4 shows a macroscopic structure with a microscopic pattern containing information.

The arrangement shown in FIG. 1 has a laser generator 1 that generates a laser beam 2. This laser beam 2 passes through a beam shaping diaphragm 3, which is designed as a pinhole. One of the laser beams is serstrahl 2 shaped with a sharply defined circular cross section. It can be reproduced in good quality later.

The laser beam 2 undergoes another shape correction in a correction diaphragm 4.

In the further beam path, the laser beam passes through a beam deflection unit 5, in which a deflection mirror 6 is arranged, which deflects the laser beam 2 perpendicular to its previous direction.

This deflected laser beam 2 is focused in a focusing unit 7, which consists of a simple focusing lens, which is connected to the beam deflection unit 5.

Under the focus 8, a substrate support 9 is provided, which is connected to an x-y cross table 10. This x-y cross table 10 can be moved in an x-y plane which is determined by the directions of movement x and y and which is perpendicular to the direction of the deflected laser beam 2.

In addition, a z drive 1 is provided under the x-y cross table 10, through which the x-y cross table 10 and thus the substrate support 9 can be moved in a z direction lying parallel to the laser beam 2.

This arrangement allows a so-called micro-engraving, as shown in FIG. 3, to be produced on a substrate 12 which rests on the substrate support 9 and is fixed there in a manner not shown in any more detail. This micro engraving consists of engraving elements, which in this example are designed as engraving points 13. However, these engraving elements can also have other shapes, and the choice of shape can also already contain information.

The engraving points 13 are arranged within a matrix 14. Behind the presence or absence of engraving points 13- Within this matrix 14, information, for example about the substrate 12, is encrypted in that the pattern which is generated with the engraving points 13 within the matrix 14 is of a desired pattern which, in the case of the completely filled matrix 14, would correspond , deviates. For exact definition, the matrix 14 is provided with a matrix frame 15. The engraving points 13 in the matrix frame 15 are not available for coding the information.

At the locations within the matrix 14 at which an engraving point 13 is to be created, the x-y cross table 10 moves the substrate 12 below the focus 8, so that the focus 8 lies on the engraving point 13 to be generated. Since the substrate 12 is not flat, the focus 8 is precisely adjusted by means of the z drive 11.

The substrate 12 remains in this position until the engraving point 13 is created. The same procedure is then followed at the next engraving point 13 to be generated in the matrix 14.

As can be seen from the method, the positioning of the focus 8 on the substrate 12 requires a high degree of accuracy, which must be realized by the x-y cross table 10. This requires a high manufacturing effort and also involves longer positioning times.

To avoid this, the arrangement is in Fig. 2 instead of

Beam deflection unit 5 in FIG. 1 is provided with a galvanometer head 16. The galvanometer head 16 includes a first one

Galvanometer mirror 17 and a second galvanometer mirror

18, The first galvanometer mirror 17 is about a first axis

19, which is perpendicular to the direction of the undeflected laser beam 2 and parallel to an x-y plane, pivotable. The second galvanometer mirror 18 is about a second axis

20, which is perpendicular to the direction of the undeflected laser beam 2 and perpendicular to the xy plane, is pivotable. The xy plane is an imaginary and not shown E- plane that expands in the x and y directions.

The galvanometer mirrors 17 and 18 are magnetically biased and deflected by an electric field. This makes it possible to carry out deflections of the focus 8 with high speed and high precision. With this arrangement, a movement of the focus 8 can be superimposed on the movement of the substrate 12. This makes it much easier to generate the only microscopically visible deviations of the pattern from engraving points 13. The electrical control of the galvanometer mirrors 17 and 18 also offers the possibility that the information can be written directly from a computing device.

As shown in FIG. 4, the laser engraving consists of a macroscopic structure 21, which is composed of a pattern of engraving points 13. Information coded to structure 21 has been impressed on it by macroscopically invisible deviations of the pattern from a target pattern.

As can be seen in the enlargement 22 of a section 23 of the structure 21, the pattern is designed as engraving points 13 lying one behind the other on a double line 24. The line spacing of the double line 24 is in the microscopic range. The engraving points 13 lie on the one line of the double line 24 in the representation of a logical 0 in the coded information and on the other line of the double line 24 in the case of a logical 1.

LIST OF REFERENCE NUMBERS

1 laser generator

2 laser beam 3 beam shaping aperture

4 correction aperture

5 steel deflection unit

6 deflecting mirror

7 focusing unit 8 focus

9 substrate support

10 x y cross table

11 sterndrive

12 substrate 13 engraving point

14 matrix

15 matrix frames

16 galvanometer head

17 first galvanometer mirror 18 second galvanometer mirror

19 first axis

20 second axis

21 structure

22 Magnification 23 Detail

24 double line x direction of movement y direction of movement z direction of movement

Claims

1. A method for producing a laser engraving into a surface of a substrate, in which a laser beam is directed at beam intervals or continuously onto the surface to be engraved during an engraving process, the substrate (12) during the engraving process in an xy plane perpendicular to the beam direction is moved and the movements of the substrate are superimposed on movements of the laser beam in the x and y directions, since you are characterized in that the laser engraving consists of a macroscopic structure (21) consisting of a pattern (14) of microscopic engraving elements (13) the structure (21) coded information is impressed by macroscopically invisible deviations of the pattern (14) from a target pattern by the structure (21) by means of the x and y movement of the substrate (12) and the deviations are generated by means of the x and y movements of the laser beam (2).

2. The method according to claim 1, so that the substrate (12) is moved during the engraving process in a z direction parallel to the beam direction.

3. The method according to claim 2, characterized in that the movement in the z-direction is dependent on the structure of the surface, such that the focus (8) of the laser beam (2) in different positions of the substrate (12) in the xy plane is always on the surface.

4. The method according to claim 2, characterized - zeic hn et that the beam is shaped using beam shaping shutters and the shape of the beam shaping shutters is sharply depicted as an engraving point on the surface.

5. The method according to any one of claims 1 to 4, so that the movements of the substrate (13) are discontinuous.

6. The method as claimed in claim 5, so that the use of beam intervals means that the movements take place in time intervals between the beam intervals when using beam intervals.

7. The method according to any one of claims 1 to 6, d a d u r c h g e k e nn z e i c hn e t that the laser engraving from a

Numerous macroscopic structures (21) exist.

8. The method according to any one of claims 1 to 6, characterized in that the target pattern is selected as the matrix (14) of set or not set engraving elements (13) and the deviations by omitting or adding or by engraving elements ( 13) can be formed.

9. The method according to claim 8, so that the matrix (14) is provided with a matrix frame (15) made of engraving elements (13).

10. The method according to any one of claims 1 to 6, so that the desired pattern is chosen as engraving elements (13) lying on a line and the deviations are formed by a macroscopically invisible offset of the engraving elements (13) from the line.

11. The method according to claim 10, characterized in that the target pattern as on a double line (24) one behind the other engraving elements (13) is selected, the line spacing of which is in the microscopic range, the engraving elements (13) when displaying a logical 0 in the coded information on one line of the double line (24) and when displaying a logical 1 on the other line of the double line (24 ) lie.