WO1996010777A1

WO1996010777A1 - Method and apparatus for performing several identical engravings by means of a laser beam

Info

Publication number: WO1996010777A1
Application number: PCT/SE1995/001124
Authority: WO
Inventors: Sven-Olov Roos; Ulf Sandström
Original assignee: Permanova Lasersystem AB
Current assignee: Permanova Lasersystem AB
Priority date: 1994-10-04
Filing date: 1995-10-03
Publication date: 1996-04-11
Anticipated expiration: 1997-04-04
Also published as: SE503496C2; SE9403349L; SE9403349D0

Abstract

The invention relates to a method and an apparatus for making a multiple of identical engravings by means of a laser beam (2) in which the power of the laser beam is concentrated on a small spot on an object surface and in which the laser beam is deflected in at least one, but preferably two, dimensions by means of at least one rotatable mirror (3) controlled by a predetermined pattern so that a script or any other graphic design is generated by the laser beam on the object on which the script is to be applied. The incident laser beam is divided into a number of individual sub beams (2a, 2b; 2c, 2d, 2e) before the deflection and the individual laser beams are arranged to impinge upon the rotatable mirror (3) under different angles of incidence so that the angular difference between the individual beams defines the distance between the individual engravings.

Description

Method and apparatus for performing several Identical engravings by means of a laser beam.

This invention relates to a method and an apparatus for making a multiple of identical engravings by means of a laser beam. The engravings may be a script or any other graphic design or indicia emplaced on articles, compo¬ nents, cinematic films or the like, specifically on such objects on which article numbers, texts, instructions, lo¬ gotypes or any other type of information is desired.

It is an advantage to create such engravings by means of a laser beam as the engravings can be made very sharp and clean due to the fact that the laser beam is concentrated on a small surface on the object on which the script is to be applied. Furthermore, the speed at which the engravings can be applied on the object is very high, even in case of extensive texts and other more complicated graphic de¬ signs.

A system for applying a script or other indicia on cinema¬ tic film by means of a laser beam is previously described in US-PS 4,854,696. In this system a UV pulse (excimer) laser beam 10 of adequate beam dimensions, modified by me¬ ans of lenses 2, passes through a mask 13 which contains the indicia to be printed on the film. When the beam has emerged from the mask it is projected by lenses 6 and 6a to concentrate the beam on a small spot on the actual film. In addition to the characters to be created on the film the mask also contains the information required to coordinate the system.

If more than one film is subtitled simultaneously the la¬ ser beam is divided into a number of separate beams by me¬ ans of rotatable mirrors as illustrated in figures 3 and 4. In the first case which is illustrated in figure 3, four rotatable mirrors 304 are placed in the path of the laser beam for continuously deflecting the incident laser beam to the four copies 307 of the film so that each of the film copies is provided with the same indicia. As an alternative, different indicia can be applied to each of the film copies, for instance different languages. In this case each film copy has its own mask as illustrated in fi- gure 4. Also in this case the laser beam is deflected by means of rotatable mirrors 404 into separate beams that goes to each film copy.

To prepare a specific mask for each individual text or graphic design is a complicated and expensive method, ho¬ wever. Therefore it is also previously known to apply the indicia by using a rotatable galvanometer mirror for de¬ flecting the laser beam according to a specific pattern before it passes a lens that is concentrating the beam energy on a small spot on the actual object surface. In practice the laser beam is deflected by means of two mir¬ rors in order to provide a desired deflection in two di¬ mensions, preferably one mirror for lateral, horizontal, deflections and one mirror for vertical deflections. When the mirrors are rotated the focused spot is moved on the surface. By controlling the movement of the mirrors in a predetermined way a specific text can be generated.

If a multiple of identical engravings are prepared by me- ans of such a galvanometer system, i. e. a system in which the engraved indicia are prepared by means of a controlled mirror deflection, it is a problem if the galvanometer mirrors are also controlled in order to continuously de¬ flect the laser beam to different engraving locations as illustrated in the above-mentioned US patent. Then two different patterns for controlling the mirrors would be required, i. e. one pattern for the generation of the text and one pattern for deflection of the beam into the diffe¬ rent engraving locations. It should be understood that this would be a complicated and expensive system.

It is an object of this invention to provide an engraving system for making a multiple of identical indicia without any extra control movements imparted onto the galvanometer mirrors.

It is another object of this invention to provide an engraving system comprising as few movable parts as possi¬ ble so that a high engraving speed can be maintained.

According to the invention there is provided a system in which the received laser beam is divided into a multiple of separate beams which are incident on the galvanometer mirrors under different angles. If for example the imping¬ ing laser beam is divided into two separate beams each of these beams are incident on the galvanometer mirror under its own angle. This means that the two beams are focused on different located points on the object surface, which points are separated by a specific distance. If now also a controlled movement is imposed upon the mirrors, these points are also subject to a synchronous movement but still separated from each other by said distance.

The advantages of such a system is that no movement of the mirrors or any other component in the system, besides the text generating movement, is required. The mirrors can be made so small that a high engraving speed can be maintai- ned even for complicated patterns. The mirrors can be made small because the separated beams can be put together, or almost put together, on the mirror surface. The only re¬ quirement is that they are impinging the mirror surface under different incident angles.

According to one preferred embodiment of the invention the received laser beam is divided into separate beams by me¬ ans of semi-transparent mirrors and then the separated be¬ ams are brought together by another mirror.

According to another preferred embodiment of the invention the received laser beam is divided into separate beams by means of a chinoform in which the individual beams have the same power.

In common for both of these embodiments, however, is the fact that the individual beams are arranged to impinge upon the mirror suface under different angles of incidence which means that two individual beams will be focused on two separate points on the object surface.

In the following the invention will be described more in detail with reference to the accompanying schematic dra¬ wing which illustrates some preferred embodiments.

Figure 1 illustrates schematically a conventional engra¬ ving system using a laser beam,

Figure 2 illustrates schematically how text can be genera¬ ted in such an engraving system,

Figure 3 illustrates schematically how a multiple of iden- tical engravings can be generated according to the inven¬ tion,

Figure 4 illustrates a first embodiment of the invention for dividing the incident laser beam into separate beams, and

Figure 5 illustrates a second embodiment of the invention for separating the incident laser beam.

Figure I schematically illustrates a conventional engra¬ ving system in which the engravings are generated by means of a laser beam which is focused on a support surface 1 on which the engravings in the form of a script or any other type of graphic design or indicia are to be applied on an article, component, cinematic film or the like. Specifi¬ cally, the script or indicia might be in the form of arti¬ cle numbers, texts, instructions, logotypes or the like. It is not described in detail here how the laser beam it¬ self is generated as such technique is known per se. For instance, a UV pulse (excimer) laser beam 2 can be used, which beam is first deflected by a galvanometer mirror 3 and then arranged to pass a lens 4 that concentrates the beam power on a small spot on the support surface.

In order to generate a text or a specific graphic design on the support surface the focused beam spot 5 has to be moved relative to the support surface. This is usually do¬ ne as illustrated in figure 2, i.e. by making the mirror 3 rotatable about an axis 6. If the mirror is rotated a certain angle a, the focused spot 5 on the base surface will move a distance 2*a*f where f is the focal distance of the lens 4. In practise the deflection of the laser be¬ am is accomplished by means of two mirrors in order to de¬ flect the beam in two coordinates. In the figures, howe¬ ver, only one of these two mirrors is illustrated. By con¬ trolling the angular movement of the two mirrors it is un- derstood that a desired text can be generated on the sup¬ port surface 1.

Figure 3 illustrates two different laser beams that im¬ pinges on the mirror 3, one beam 2a indicated by a conrin- uous line and one beam 2b indicated by dashed lines. There is a specific angle b between these two beams so that they are impinging on the mirror surface under different angles of incidence. This means that the two beams will be focu¬ sed on different points on the base surface which points are separated by a specific distance b*f, where f is the focal distance of the focusing lens. If now an angular mo¬ vement is applied on the mirror 3, both of the points will be moved synchronously on the base surface and maintained separated by said distance b*f.

In the following two different ways to make the laser be¬ ams to impinge upon the mirror surface under different angles of incidence will be described. In the first exam- pie, which is illustrated in figure 4, the laser beam emerging from the laser source is divided into two separa¬ te laser beams 2a and 2b by means of a semi-transparent mirror 6. As both of the beams should impinge upon the sa- me galvanometer mirror 3 the beams must be brought toget¬ her, which is accomplished by an additional mirror 7. in order to maintain a high engraving speed the mirrors should be made as small as possible. Therefore it is an advantage that the two laser beams are brought together, or at least almost brought together, i.e. the beams are impinging upon the mirror surface under different angles of incidence on substantially the same place on the mirror surface. In figure 4 the mirror 7 is placed in the path of the laser beam 2a for deflecting the laser beam so that the two separated laser beams meet on substantially the same area of the rotatable mirror surface 3. Instead of using semi-transparent mirrors 6 as illustrated in the fi¬ gure it is also possible to use mirrors which are only partially put into the path of the laser beam for provi- ding separated laser beams. Still another way to provide separated laser beams is to use polarizing components.

In figure 5 another example how to divide a laser beam in¬ to a number of separate sub beams is illustrated. In this case a chinoform 8 is used for the division of an incident laser beam into three separate beams 2e, 2f and 2g. Chino- forms are known per se and will not be described here.

The invention makes it possible to effectuate two or more identical engravings simultaneously as already described, i.e. by dividing the incident laser beam into a number of separate sub beams, which sub beams then are arranged to impinge upon the surface of the galvanometer mirror, or galvanometer mirrors in case of a two-dimensional system, under different angles of incidence. The articles on which the engravings are to be applied are disposed on a distan¬ ce b*f from each other in such a way that the individual beams are focused on each of the articles. The engravings are then effectuated synchronously by controlling the angular movement of the galvanic mirrors according to a specific pattern determined by the text in question.

The invention is not limited to the described examples but can be varied within the scope of the following claims. Specifically, it should be understood that instead of a rotatable galvanometer mirror 3 any other type of rotata¬ ble mirror surface could be used. Also, as to lens 4 and the additional mirror 7, equivalent optical components could be used.

Claims

C L A I M S

1. A method for making a multiple of identical engravings by means of a laser beam (2) in which the power of the la- ser beam is concentrated on a small spot on an object sur¬ face and the laser beam is deflected in at least one, but preferably two, dimensions by means of at least one rotat¬ able mirror (3) controlled by a predetermined pattern so that a script or any other graphic design is generated by the laser beam on the object surface on which the script is to be applied c h a r a c t e r i z e d i n that the incident laser beam (2) is divided into a number of indi¬ vidual sub beams (2a, 2b; 2c, 2d, 2e) before the deflec¬ tion and the individual sub beams are arranged to impinge upon the rotatable mirror (3) under different angles of incidence so that the angular difference between the indi¬ vidual sub beams defines the distance between the individ¬ ual engravings.

2. A method as claimed in claim 1 c h a r a c t e r i z ¬ e d i n that the incident laser beam (2) is divided by means of semi-transparent mirrors (6), or, as an alterna¬ tive, by means of polarizing components.

3. A method as claimed in claim 1 c h a r a c t e r i z ¬ e d i n that the incident laser beam (2) is divided by means of mirrors which are only partially put into th path of the laser beam.

4. A method as claimed in claim 1 c h a r a c t e r i z ¬ e d i n that the incident laser beam (2) is divided by means of a chinoform (8).

5. A method as claimed in claim 1 c h a r a c t e r i z - e d i n that the individual sub beams (2a, 2b) are brought together before the deflection so that they are substantially impinging upon the the same area of the mir¬ ror (3) .

6. An apparatus for making a multiple of identical engrav¬ ings by means of a laser beam (2) comprising at least a rotatable mirror (3) on which the incident laser beam is impinging, said mirror being controlled by a predetermined pattern so that a script or other graphic design is gener¬ ated by the deflected laser beam on an object surface on which the script is to be applied, and a lens (4) for con- centrating the laser beam on a small spot on the object surface c h a r a c t e r i z e d b y means (6, 8) for dividing the incident laser beam (2) into a number of in¬ dividual sub beams (2a, 2b; 2c, 2d, 2e) before the deflec¬ tion on the surface of the rotatable mirror (3), said sub beams being arranged to impinge upon the mirror (3) under different angles of incidence so that the angular differ¬ ences (b) between the individual sub beams define the dis¬ tance between the individual engravings.

7. An apparatus as claimed in claim 6 c h a r a c t e r ¬ i z e d by two rotatable mirrors (3) for deflecting the incident laser beam (2) in two dimensions, for instance a mirror for vertical deflection and a mirror for horizontal deflection.

8. An apparatus as claimed in claim 6 c h a r a c t e r ¬ i z e d in that said means for dividing the incident la¬ ser beam (2) into a number of individual sub beams com¬ prises at least one semi-transparent mirror (6), or, as an alternative, polarizing components.

9. An apparatus as claimed in claim 6 c h a r a c t e r ¬ i z e d in that said means for dividing the incident la¬ ser beam (2) into a number of individual sub beams com- prises mirrors which are only partially put into the path of the laser beam.

10. An apparatus as claimed in claim 6 c h a r a c t e r - i z e d in that said means for dividing the incident la¬ ser beam (2) into a number of individual sub beams com¬ prises a chinoform (8).

11. An apparatus as claimed in claim 6 c h a r a c t e r - i z e d by an additional mirror (7) placed between said means (6, 8) for dividing the incident laser beam and the rotatable mirror (3) in order to bring the individual sub beams (2a, 2b) together before the deflection on the ro¬ tatable mirror (3), thereby limiting the size of the mir¬ ror.