Method for the machining of workpieces by means of several laser beams

• US 20030155336A1
• Filed: 02/04/2003
• Published: 08/21/2003
• Est. Priority Date: 02/15/2000
• Status: Active Grant

• Current Assignee: Entrust Datacard Corporation (Entrust Corp.)
• Original Assignee: Datacard Corp. (Entrust Corp.)
• Inventors: Bielesch, Ulrich, Kreuter, R?uuml;diger
• Granted Patent: US 6,838,639 B2
• Time in Patent Office: Days
• US Class Current: 219/121.76
• CPC Class Codes: B23K 26/0604 by a combination of beams
• CPC Class Codes: B23K 26/0613 having a common axis B23K26/0619 takes precedence

Abstract

In material machining by means of laser beams, in particular when engraving for example metal or when blackening and marking on plastic material, there is to be provided a process in which in spite of a high frequency of machining pulses the required minimum energy per pulse is achieved. For that purpose a plurality of laser beams are brought together by way of a beam-combining means and passed by way of a common beam-guide means on to the workpiece and in particular operated in time-displaced relationship.

Claims

1. A process for machining workpieces (4) by means of a machining laser beam (3, 3′

, 3″

),

characterised in that

at least two laser beams (2a, 2b) are brought together by way of a beam-combining means (5) and

are passed by way of a common beam-guide means on to the workpiece (4).

2. A process according to claim 1 characterised in that the at least two laser beams (2a, 2b) are guided on to the same target point.

3. A process according to claim 1 or claim 2 characterised in that the two laser beams (2a, 2b) are guided within the common beam-guide means not only parallel but in congruent relationship.

4. A process according to one of the preceding claims characterised in that the laser beams (2a, 2b) are discontinuous laser beams and in particular originate from different laser sources (1a, 1b) which discontinuously output the light and the light pulses arrive in the beam-combining means simultaneously and impinge on the workpiece (4) simultaneously.

5. A process according to claim 1 characterised in that the laser beams (2a, 2b) are discontinuous laser beams and in particular originate from different laser sources (1a, 1b) which discontinuously output the light and the light pulses of the two laser sources (1a, 1b) arrive in the beam-combining means (5) and impinge on one and the same workpiece (4) in mutually time-displaced relationship.

6. A process according to claim 1 characterised in that the laser sources (1a, 1b) are quality-switched lasers, so-called Q-switch lasers, whose energy per light flash decreases overproportionally with increasing frequency.

7. A process according to one of the preceding claims characterised in that the laser beams (2a, 2b) are linearly polarised laser beams, in particular with a polarisation plane turned through 90°

relative to each other.

8. A process according to one of the preceding claims characterised in that at least three laser beams (2a, 2b, 2c) are brought together and jointly form the machining laser beam (3) by a procedure whereby in succession possibly a multiple of times:

a first in particular discontinuous laser beam (2a) and a second in particular discontinuous laser beam (2b) are brought together in a beam-combining means in mutually time-displaced relationship,

the partial machining beam (3′

) obtained in that way is passed through an active optical component (6) which can alter the in particular linear polarisation of the partial machining beam (3′

) and which is activated whenever the one laser beam (for example 2b) impinges on the active optical component (6) and thereby alters its polarisation to the polarisation of the other laser beam (for example 2a), but is deactivated when the other laser beam (for example 2a) impinges on the component (6),

the altered partial machining beam (3′

) which is obtained in that way and which now has linear polarisation corresponding to the one laser beam (2a) is brought together in a further beam-combining means (5b) with a further laser beam (2c) whose in particular linear polarisation differs in particular from that of the partial machining beam (3′

), and

the machining laser beam is passed by way of a beam-guide means on to the workpiece (4).

9. A process according to claim 8 characterised in that the partial machining beam (3″

) obtained in that way is passed through a further active optical component which is capable of altering the in particular linear polarisation of the one arriving beam, for example the further laser beam (2c), to the in particular linear polarisation of the partial machining beam (3′

), whereby a machining laser beam (3″

) with the linear polarisation of the for example first laser beam (2a) is produced, and so forth.

10. A process according to one of the preceding claims characterised in that the active optical element (6) is a Pockel cell.

11. A process according to one of the preceding claims characterised in that the active optical element (6) is a Kerr cell.

12. A process according to one of the preceding claims characterised in that the active optical element (6) is a magneto-optical modulator which operates for example on the basis of the Faraday effect or an acousto-optical modulator which changes the polarisation by the action of a sound wave field.

13. A process according to one of the preceding claims characterised in that the active optical element (6) utilises the birefringence which is produced in certain materials by mechanical loading, for example pressure, and in particular the material is a uniaxial transparent crystal such as for example an NaCl- or LiF-crystal, or acrylic resin.

14. A process according to one of the preceding claims characterised in that during the machining operation the laser pulses of the individual laser beams (2a, b . . . ) can be changed over in their time succession relative to each other from synchronous to time-displaced and vice-versa.

15. A process according to one of the preceding claims characterised in that after the last bringing-together of a partial machining beam (3′

) and a last original laser beam (for example 2b), they no longer pass through any further active optical element which alters linear polarisation.

16. A process according to one of the preceding claims characterised in that the laser sources (1a, 1b, . . . ) emit laser beams (2a, 2b, . . . ) of the same wavelength.

17. A process according to one of the preceding claims characterised in that the laser sources (1a, 1b, . . . ) are laser sources of the same kind.

18. A process according to one of the preceding claims characterised in that the laser beams (2a, 2b, . . . ) have impressed thereon a polarisation of the same type, in particular linear polarisation.

19. Apparatus for machining workpieces (4) by means of a machining laser beam (3, 3′

, 3″

),

characterised by

at least two laser beams (1a, 1b),

at least one beam-combining means (5), and

at least one common beam-guide means arranged downstream of the beam-combining means (5) for the laser beams (2a, 2b) of the laser sources (1a, 1b) in a direction towards the workpiece (4).

20. Apparatus according to claim 19 characterised in that the laser sources (12a, 1b) are arranged in a mutually parallel position.

21. Apparatus according to one of the preceding apparatus claims characterised in that the optical path length from the laser sources (1a, 1b) to the coupling point in the beam-combining means (5) is equal.

22. Apparatus according to one of the preceding apparatus claims characterised in that an adjustable direction-changing mirror (7, 7′

) is arranged in the beam path of at least one of the laser beams (2a, 2b).

23. Apparatus according to one of the preceding apparatus claims characterised in that the beam-combining means (5a, 5b) is pivotable about an axis parallel to an axis parallel to the direction of the laser beam (2a) just passing therethrough.

24. Apparatus according to one of the preceding apparatus claims characterised in that the beam-combining means (5a, 5b) is pivotable about an axis parallel to an axis perpendicular to the direction of the laser beam (2a) just passing therethrough.

25. Apparatus according to one of the preceding apparatus claims characterised in that at least one pivotable mirror (8) is arranged in the beam path downstream of the last beam-combining means (5).

26. Apparatus according to one of the preceding apparatus claims characterised in that a beam shaping unit is arranged in the beam path downstream of the last beam-combining means (5b) and upstream of the last mirror (8).

27. Apparatus according to one of the preceding apparatus claims characterised in that the lens arranged downstream of the last mirror (8) is arranged stationarily and is of such a large diameter that the laser beams pass through the lens even upon maximum deflection of the mirror (8).