WO1999040472A2

WO1999040472A2 - Process and device for deflecting a laser beam

Info

Publication number: WO1999040472A2
Application number: PCT/DE1999/000235
Authority: WO
Inventors: Joachim Knappmeyer
Original assignee: Lpkf Laser & Electronics Ag
Priority date: 1998-02-04
Filing date: 1999-01-29
Publication date: 1999-08-12
Also published as: WO1999040472A3; DE19804305C1

Abstract

A process is disclosed for deflecting a laser beam around the circumference of a polar vector figure, in particular for trepanning purposes. The process is characterised in that the centre of laser beam focusing optics are moved along a path of displacement relative to the incident laser beam, the path of displacement being obtained by adding two vectors that are rotated. This process enables small structures to be accurately and quickly cut or machined, for example in thin metal flakes. Also disclosed is a device for carrying out the process, characterised in that a second rotary unit (3) is eccentrically secured on a first rotary unit (2), focusing optics (5) are in turn eccentrically secured on the second rotary unit (3), the first rotary unit (2) being rotated by a first drive (6) and the second unit (3) being rotated by a second drive (7).

Description

Method and device for deflecting a laser beam

The invention relates to a method and an apparatus for deflecting a laser beam along a circumference of a polar vector figure, such as. B. a circle or an ellipse, the method and the device are particularly suitable for trepanning.

It is known to use lasers according to the trepanning method for cutting or processing structures in certain objects, such as, for. B. thin metal sheets to use. With the help of the laser cutting systems used, small structures of up to 200 μm can be cut.

From DE 37 02 330 A1, for example, it is known to effect a beam of optical radiation by rotating prisms.

With the conventional technology of the above laser cutting systems, however, it is necessary to move the entire laser head or the object to be processed or to move the laser head and the object relative to one another. A disadvantage of moving the laser head is its relatively large mass of about 30 to 40 kg, which makes it difficult to achieve high precision with the desired structure. If the object is moved, it proves to be a disadvantage that the resolution of the measuring and control system must be designed depending on the processing area.

The invention is therefore based on the object of providing a method and a device for carrying out the method, with which structures of significantly less than 200 μm can be cut or processed, the resolution being independent of the drive of a positioning system for those to be processed Objects and a high throughput is possible

This object is achieved by the features of claim 1 and. Features of claim 8 solved.

The fact that the center of a focusing optics for the laser beam, which can consist, for example, of a focusing lens, is moved on a path of movement relative to the incident laser beam, which is created by adding two vectors that are rotated, so that only the focusing optics , and not the laser head itself or the object to be processed needs to be moved. Because of the much smaller mass of the focusing optics or the focusing lens compared to the laser head or because of the one always constant and, on the other hand, in comparison to the object to be processed often relatively small dimensions of the focusing optics, movement of the laser beam relative to the object is possible in a particularly simple and precise manner. The physical principle is exploited that a light beam striking a focusing lens parallel to the optical axis always runs through the focal point of the focusing lens. If the focusing lens is shifted perpendicular to its optical axis, its focal point also shifts accordingly. However, the laser beam that has remained stationary will continue to pass through the shifted focal point after the focusing lens has been shifted. The same applies to a focusing optic consisting of several components.

The addition of two vectors that move at the same angular velocity relative to a stationary coordinate system creates an overall vector that also rotates at this angular velocity and always has a constant amount and thus describes a circle, since the two added vectors are always the same relative to each other Maintain angle.

In particular, it can be provided that the two added vectors are rotated at different angular velocities. As a result, it is also possible to achieve movement paths of the total vector other than these circular paths, as will be explained in more detail below.

Since the focusing optics or focusing lens is easy to move due to its small mass and small dimensions, it is possible to cut or process very small structures with a high throughput. The resolution of the measuring and control system can be designed independently of the area to be processed. In addition, the generation of the desired trajectory based on the addition of two vectors allows the object to be processed to be penetrated for the first time by the laser beam at a point which lies within the desired closed trajectory. It is thereby achieved that the circumference of the desired structure is only approached after the "piercing" of the laser beam. In this way, inaccuracies that may arise during the "piercing" of the laser beam can be shifted into an area of the object to be processed, which will be cut out after the cutting has been completed. The same procedure can also be followed when the desired cutting path is ended or when the laser beam is “taken out” in order to ensure that the system is again in its basic setting. Preferably, the angular velocities of the two added vectors are initially kept so differently, but kept constant or changed differently, that the path of movement of the center of the focusing optics from a starting point at which the focal point of the focusing optics lies within the polar vector figure to be cut, to the extent of the in the corresponding plane of the focusing optics or the lens plane lying vertical projection of the figure. For example, the two added vectors can initially have the same direction but opposite orientation. If the two vectors are moved at different angular velocities, the two vectors will move out of their antiparallel position and preferably maximally into the parallel position. The two vectors move relative to each other until the two angular velocities are equalized. From this point on, the two vectors form a fixed angle to each other, and the resulting total vector moves on a circular path. The two angular velocities can be kept constant from the point in time at which the focal point is located on the circumference of the polar vector figure to be cut, until the entire circumference of the polar vector figure is swept. In this way a circular cutting path is obtained.

In order to obtain polar vector figures other than a circle, the difference between the two rotation angles is also varied - i.e. H. the angular velocities are set differently - while the focal point is on the circumference of the polar vector figure to be cut. How the time course of the difference in the angles of rotation or the angular velocities should look depends of course on the shape of the polar vector figure, but on the other hand also on the length of the two added vectors.

For example, an ellipse, a rounded rectangular figure and a finger mask figure can be easily cut using this method. It is also possible to cut a rectangle.

After sweeping over the entire circumference of the polar vector figure, the angular velocities can again or still be kept different, but kept constant or changed differently, in such a way that the movement path of the center of the focusing optics reaches the starting point again. The center of the focusing optics or the focal point is thus again in its defined starting position, and a new cutting process can be started. The two vectors to be added preferably have the same length. The variety of polar vector figures that can be cut is particularly large. Furthermore, in this case the vectors can be rotated such that the total vector is the zero vector, that is to say the eccentricities cancel each other out, so that the laser beam runs through the center of the focusing optics. The polar vector figures can be created both from the standstill of the focusing optics and from their movement.

It can also be provided that the object to be processed is additionally moved. This is advantageous if, for example, figures are to be cut that are relatively large and - such as rectangular figures - can be easily cut by moving the object along two right-angled axes. It is advantageous if the system has been brought into its basic setting beforehand, as described above, in order to achieve the highest possible positioning accuracy when moving the object. The object can also be moved in order to cut several circles next to one another at a fixed radius or also by varying the radius, the laser beam being sealed off briefly after the end of a circle, while the object is being moved in order to subsequently cut another circle, to open the laser beam again for a few revolutions, for example.

The object is achieved in relation to the device by the features of claim 8. The device according to the invention has a first rotatable unit on which a second rotatable unit is attached eccentrically. A focusing optic is mounted eccentrically on the second rotatable unit. The focusing optics can consist, for example, of a focusing lens. Each unit is rotated by its own drive.

The two eccentricities mentioned represent the vectors to be added. It is therefore advantageous if the eccentricities are of the same amount.

The two rotatable units are preferably circular disks. The drive of the second rotatable unit can be mounted on the first rotatable unit. In this case, the drive only has to be switched on if the angular speeds of the two rotatable units are to be different; thus, the second rotatable unit is only set by its drive when a circular path is to be achieved. If, on the other hand, the drive of the second rotatable unit is not mounted on the first rotatable unit but externally, if a circle is to be cut, the drive of the second rotatable unit must drive it at the same angular velocity as the drive of the first rotatable unit drives. The two drives are preferably toothed belt drives. This has the advantage that, if the second drive is not mounted on the first rotatable unit, the toothed belt can be tensioned so that it is tensioned in any position of the eccentrically mounted second rotatable unit.

The device preferably has a movable positioning table that receives the object to be processed, so that the object to be processed can also be moved relative to the laser beam.

The method according to the invention and the device according to the invention for carrying out the method are explained in more detail below using an exemplary embodiment. Reference is made to the drawings. Show it:

Figure 1 is a schematic plan view of a device according to the invention;

FIG. 2 shows an enlarged schematic illustration of a partial unit of the device of FIG. 1;

Figure 3 is an enlarged schematic representation of a further sub-unit of the device of Figure 1;

Figure 4 is a schematic diagram of the addition and the movement of two vectors describing the eccentricities;

FIG. 5 shows a schematic illustration of a movement path of the center of the focusing lens provided for cutting a circle;

Figure 6 is a schematic diagram showing the difference in the angles of rotation of the two eccentricity vectors as a function of the angle of rotation of the total vector.

The device 1 shown in FIG. 1 for carrying out the method according to the invention has a first rotatable unit in the form of a circular disk 2. A second rotatable unit in the form of a further circular disk 3 is fastened on the disk 2. The disk 3 is mounted eccentrically on the disk 2, ie its center is in the current position shown in FIG. 1 against the x-direction of the fixed coordinate system 4 shown with respect to the center point M _{0 of} the disk 2, which lies at the origin of the coordinate system 4.

A focusing lens 5 is attached to the disk 3. The focusing lens 5 is arranged eccentrically with respect to the disk 3, specifically the center of the focusing lens 5 in the position shown in FIG. 1 is displaced in the direction of the x-axis with respect to the center of the disk 3.

The pulley 2 is rotated by a first toothed belt drive 6 around its center M ₀ . The pulley 3 is also rotated about its center by a second toothed belt drive 7.

In Figure 2, the disc 2 and the disc 3 are shown in more detail. The disc 2 has the radius η. The disk 3 has the center point Mi and has the radius r ₂ . A coordinate system with axes x and y 'related to disk 3 is designated by reference numeral 8. The eccentricity of the disk 3 with respect to the disk 2 is represented by the vector. In Figure 3, the disc 3 and the focusing lens 5 are shown in more detail. The focusing lens 5 has the center M ₂ and has the radius r ₃ . The eccentricity of the focusing lens 5 with respect to the disk 3 is represented by the vector a ₂ , which in turn is related to the coordinate system 4.

FIG. 4 shows the addition of the vectors a and a ₂ to the total vector c. The vector a is rotated at the angular velocity α ^, so that the vector assumes the angle of rotation φ ₁ to the x-axis. The vector εζ is rotated at the angular velocity ω ₂ and takes up the rotation angle φ ₂ with the x-axis. The lengths of the vectors i and a are the same. Thus, in the basic setting, in which the difference Δφ defined in FIG. 4, the angle of rotation is equal to zero, the two vectors cancel each other out or result in the total vector ^" c being the zero vector. Only when Δφ becomes different from zero by rotation of the disk 3 does tension occur a total vector c that differs from zero. The angle of rotation difference .DELTA..phi. is preferably a maximum of 180.degree. If the angle of rotation difference .DELTA..phi. is constant, as shown in FIG. 4, a disc results as a polar vector figure by rotating disc 2. The radius of this circle is the same the length c of the total vector ^' c.

FIG. 5 shows the basic course of the movement path of the center of the focusing lens 5. Starting from a starting point S, the lens center first moves on the section 9 up to the circumference 10 of the vertical projection of the polar vector figure to be cut, which is in this case a Circle is. The lens center then sweeps the entire circumference of circle 10. Then the lens center returns back to the starting point S by moving the lens center along the section 11. The angles of rotation of the vectors al and εζ and the total vector c, which describes the position of the lens center, cover an angle of more than 2 π.

In Figure 6, the difference Δφ is the angle of rotation of the vectors a ^ or A ₂ as a function of the rotation angle φ ₃ of the resultant from the addition of the two vectors total vector c for the case of the movement path of Figure 5 shown. At the beginning, the difference in the angles of rotation is varied until an angle of rotation φ ₃ of approximately π / 4 is reached. After that, both angular velocities are the same and the difference in the angles of rotation is constant. When an angle of rotation φ ₃ of approximately 2 1/4 π is reached, the angular velocities are kept constant differently or changed differently. In the present example, the difference in the angle of rotation is brought back to zero. This value is reached at an angle of rotation φ ₃ of 5/2 π. In general, however, the angles of rotation of the two vectors can also be different in the start and in the end position. The difference between the angles of rotation φi and φ ₂ is therefore not constant between the φ ₃ values 0 and π / 4 or 2 1/4 π and 5/2 π. These are the ranges of the angles of rotation of the two added vectors, in which the lens center is not on the circumference of the vertical projection of the circle 10 to be cut, but on the subsections 9 or ^ H.

The movement of the lens center on the section 9 serves to guide the laser beam from a "piercing position" to the circumference of the polar vector figure to be cut in order to

"Plunge" to naturally shift inaccuracies that arise into the cut-out area. The movement of the lens center on the section 11 serves to

Completion of cutting the intended polar vector figure back into focus

Starting position attributed.

Very fine structures can be cut or processed with the method according to the invention or the device according to the invention.

Claims

claims

1. A method of deflecting a laser beam along a circumference of a polar vector figure, such as. B. a circle or an ellipse, in particular for trepanning, characterized in that the center of a focusing optics for the laser beam is moved on a path of movement relative to the incident laser beam, the path of movement being formed by adding two vectors which are rotated.

2. The method according to claim 1, characterized in that the vectors are rotated at different angular velocities.

3. The method according to claim 2, characterized in that the two angular velocities are initially so different that the path of movement of the center of the focusing optics from a starting point at which the focal point of the focusing optics lies within the polar vector figure to be cut, to the extent of the vertical projection of the polar vector figure lying on the corresponding plane of the focusing optics.

4. The method according to claim 3, characterized in that from the time at which the focal point is on the circumference of the polar vector figure, the two angular velocities are kept the same until the entire circumference of the polar vector figure is swept.

5. The method according to claim 3, characterized in that from the time at which the focal point is on the circumference of the polar vector figure to be cut, the two angular velocities are so different that the polar vector figure to be cut is obtained.

6. The method according to one or more of the preceding claims, characterized in that after sweeping over the circumference of the polar vector figure, the two angular velocities are so different that the trajectory reaches the starting point again.

7. The method according to one or more of the preceding claims, characterized in that the vectors have the same length.

8. The method according to one or more of the preceding claims, characterized in that in addition the object to be processed is moved.

9. Device for performing the method according to one of the preceding claims, characterized in that on a first rotatable unit (2) a second rotatable unit (3) is eccentrically fastened, on which in turn a focusing optics (5) is eccentrically fastened, wherein the first rotatable unit (2) is rotated by a first drive (6) and the second unit (3) is rotated by a second drive (7).

10. The device according to claim 9, characterized in that the focusing optics consists of a focusing lens.

11. The device according to claim 9 or 10, characterized in that the two rotatable units are circular discs (2, 3).

12. The device according to one or more of claims 9 to 11, characterized in that the eccentricities are equal in amount.

13. The device according to one or more of claims 9 to 12, characterized in that the second drive (7) is located on the first rotatable unit (2).

14. The device according to one or more of claims 9 to 13, characterized in that the two drives are toothed belt drives (6, 7).

15. The device according to one or more of claims 9 to 14, characterized in that the device has a movable positioning table for the object to be processed.