Marking apparatus with a plurality of lasers and individually adjustable sets of deflection means

Abstract

The invention relates to a marking apparatus for marking an object with laser light, comprising a plurality of lasers and a control unit for individually activating each of the lasers to emit a laser beam (90) according to a sign to be marked. A set of deflection means (30) for rearranging the laser beams (90) into a desired array of laser beams (90) is provided, the set of deflection means (30) comprises at least two deflection means (33a-i, 34a-i) per laser beam (90), in particular at least two mapping mirrors (33a-i, 34a-i) or at least one optical waveguide and one lens per laser beam (90a-i), and each deflection means (33a-i, 34a-i) is individually adjustable in its deflection direction and/or individually shiftable.

Claims

1. A marking apparatus for marking an object with laser light, the marking apparatus comprising: a plurality of distinct lasers, wherein each distinct laser is a gas laser and comprises resonator tubes, wherein the plurality of distinct lasers are arranged in the shape of a ring that at least partially surrounds an inner area; a control unit configured to individually activate each of the distinct lasers in the plurality of distinct lasers to emit a laser beam according to a sign to be marked, wherein: a set of deflection means for flexibly rearranging the laser beams into any desired array of laser beams is provided, the set of deflection means comprises at least two deflection means per laser beam, each deflection means is at least one of: individually adjustable in its deflection direction or individually shiftable, the control unit is adapted for at least one of: shifting the deflection means or adjusting the deflection directions of the deflection means, at least one scanning mirror device is provided which comprises a common mirror onto which all laser beams coming from the set of deflection means impinge, and the control unit is adapted for pivoting the at least one scanning mirror device; and a telescopic device with at least two lenses for global adjustment of the focal lengths of the laser beams, wherein the telescopic device is located within the inner area.

2. The marking apparatus according to claim 1, wherein the at least two deflection means per laser beam are at least two mapping mirrors or at least one optical waveguide and one lens per laser beam.

3. The marking apparatus according to claim 1, wherein the deflection means are adjusted such that a beam separation between the laser beams is reduced.

4. The marking apparatus according to claim 1, wherein the control unit is adapted for at least one of: shifting the deflection means or adjusting the deflection directions of the deflection means via gimbal mounts.

5. The marking apparatus according to claim 1, wherein the control unit is adapted for at least one of: shifting the deflection means or adjusting the deflection directions of the deflection means during a marking process to perform a scanning motion of the laser beams.

6. The marking apparatus according to claim 1, wherein the control unit is adapted for pivoting the scanning mirror device via a galvanometer.

7. The marking apparatus according to claim 1, wherein for marking the object while it is moving relative to the marking apparatus, the control unit is adapted to adjust at least one of: the deflection means or the at least one scanning mirror device based upon information on a movement of the object.

8. The marking apparatus according to claim 4, wherein the set of deflection means comprises a first and a second set of mapping mirrors, each set of mapping mirrors comprises at least one mapping mirror per laser beam, the first set of mapping mirrors directs the laser beams onto the second set of mapping mirrors, the first and the second set of mapping mirrors are each arranged in a linear array; and each mapping mirror is tiltable.

9. The marking apparatus according to claim 8, wherein at least one of a motor or actuator is provided for adjusting the position of at least one of the linear arrays of mapping mirrors.

10. The marking apparatus according to claim 1, wherein the control unit is adapted for controlling the deflection means to set a degree of convergence or divergence of the laser beams emanating from the deflection means.

11. The marking apparatus according to claim 1, wherein the control unit is adapted to adjust the deflection means such that a linear arrangement of laser beams impinging on the deflection means is rotated by 90 about an axis parallel to the direction of travel of the impinging laser beams.

12. The marking apparatus according to claim 1, wherein the control unit is adapted to set the telescopic device such that the focal lengths of the laser beams correspond to a distance to the object to be marked.

13. The marking apparatus according to claim 1, wherein the control unit is adapted to delay the activation of each laser individually such that, in response to an object moving relative to the marking apparatus in an object movement direction, at least two laser beams impinge on the object at the same position in the object movement direction.

14. The marking apparatus according to claim 1, wherein for each laser beam the deflection means comprise at least one optical waveguide and one lens, and the optical waveguides associated with different laser beams have the same length.

15. The marking apparatus according to claim 1, wherein a set of beam shaping means is provided for individually shaping each laser beam.

16. A marking system comprising: a marking apparatus according to claim 1; and a motor or actuator for tilting the marking apparatus relative to an object movement direction of the object to be marked.

17. The marking apparatus of claim 2, wherein each of the at least two deflection means is individually adjustable or individually shiftable independent of the other deflection means.

18. The marking apparatus of claim 1, wherein the at least one scanning mirror device is distinct from the set of deflection means.

19. The marking apparatus of claim 1, wherein the ring has a substantially rectangular shape.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A better understanding of the invention and various other features and advantages of the present invention will become readily apparent by the following description in connection with the drawings, which are shown by way of example only, and not limitation, wherein like reference numerals refer to substantially alike components:

(2) FIG. 1 shows a schematic diagram of a first embodiment of an inventive marking apparatus;

(3) FIG. 2A to 2C show different views of a first configuration of a set of beam shaping means and a set of deflection means;

(4) FIG. 3A to 3C show different views of a second configuration of a set of beam shaping means and a set of deflection means;

(5) FIGS. 4A and 4B show different views of a third configuration of a set of beam shaping means and a set of deflection means;

(6) FIG. 5 shows still another configuration of a set of deflection means;

(7) FIG. 6 shows a configuration of mapping mirrors of a set of deflection means for rearranging the laser beams into a two-dimensional array:

(8) FIG. 7 shows a marking system according to the invention and an object to be marked moving relative to the marking system; and

(9) FIG. 8A to 8D schematically show an arrangement of laser beams exiting the inventive marking apparatus relative to an object movement direction, and markings produced by the laser beams.

DETAILED DESCRIPTION OF THE INVENTION

(10) FIG. 1 shows schematically a first embodiment of a marking apparatus 100 according to the invention. The marking apparatus 100 comprises a plurality of lasers 10, each emitting a laser beam that is used to produce a marking on an object (not depicted). For forming and directing the laser beams, the apparatus 100 further comprises optical means 30, 40, 45, 50.

(11) In the example shown, the plurality of lasers 10 consists of nine gas lasers 10a-10i. Other laser types than gas lasers may be employed instead. In general, a large number of gas lasers 10 is desirable, e.g., at least four or six lasers. Each gas laser 10 comprises resonator tubes 12 that are in fluidic connection to each other. That means, the resonator tubes 12 of one gas laser form a common resonator volume. It is also possible that the resonator tubes 12 of different lasers 10 are in fluidic connection.

(12) In the depicted embodiment, the gas lasers are CO.sub.2 lasers and the laser gas accordingly comprises, amongst others, CO.sub.2, N.sub.2 and He.

(13) The resonator tubes 12 are arranged in the shape of a ring surrounding an inner area or free central space 5 between them. The ring is formed with connecting elements 16 for connecting adjacent resonator tubes 12 belonging to the same laser. The connecting elements 16 are arranged in the corners of the stacked lasers and house mirrors for reflecting laser light from one of the adjacent tubes 12 to the other. All mirrors may be selected dependent on the laser gas used. In the present case, the mirrors comprise a material reflective in the wavelength region of a CO2 laser, i.e. medium-IR radiation, primarily at 10.6 ITI. For example, a copper mirror and/or a substrate with a coating for increasing reflectivity and/or preventing tarnishing in air may be provided.

(14) In the depicted example, the resonator tubes 12 form a sealed ring in the shape of a rectangle. In general, any other shape that at least partially encloses the inner area 5 may be chosen, such as a triangular, a square or a U-pattern.

(15) The resonator tubes 12 of each gas laser 10a-10i constitute a sealed volume. The volumes of the lasers may be separated from each other or interconnected to form a common sealed volume. In sealed lasers, it may be generally desired that the laser gas composition stays constant over a long period. To this end, the total gas volume is increased with an additional gas reservoir 19. The gas in the reservoir is not exited to generate laser light. Rather, the reservoir 19 is connected to the gas volumes of one or several resonator tubes 12.

(16) The marking apparatus 100 further comprises excitation means (not depicted) at each resonator tube 12 and cooling blocks (not depicted) attached to the resonator tubes 12. There may be one cooling block per side of the cubic arrangement of resonator tubes 12. Thus, each cooling block does not merely cool a single resonator tube, but a plurality of resonator tubes 12 of different lasers 10a-10i. The cooling blocks may have a plurality of channels through which a cooling fluid can circulate.

(17) The resonator tubes 12 of each laser 10 are arranged in individual, separate flat lay-ers. The lasers 10 are substantially identical and are stacked on top of each other in a parallel manner.

(18) The rectangular shape of the lasers 10 may be open at one corner. In the depicted embodiment this is the top left corner at which an integrated output flange 17 is provided. At this corner, the laser volume is terminated by a rear mirror 18 for reflecting laser light back inside the tubes 12. The rear mirror 18 may be connected to an end tube 12 which is supported by the integrated output flange 17, or the rear mirror 18 may be attached to the integrated output flange 17.

(19) The other end of the laser volume is terminated at the same corner by an output coupler 13. The output coupler 13 couples out a laser beam and may again be connected to either an end tube 12 or the integrated output flange 17. The output coupler 13 may be a partially reflecting mirror 13 and may also be referred to as partially reflecting output coupler. The emitted laser beams are then directed into the inner area 5 with beam delivery means 14. In the embodiment shown, the beam delivery means 14 comprise at least one mirror 14 arranged at the integrated output flange 17. The laser beams reflected from the beam delivery means 14 enter the inner area 5 through a hole in the integrated output flange 17. Generally it is possible that a common integrated output flange 17 for all lasers 10 is provided. In the depicted embodiment, however, there is one integrated output flange 17 per laser 10 and each integrated output flange 17 exhibits one beam delivery means 14 and one hole through which a respective laser beam can pass.

(20) In the inner area 5, optical means 30, 40, 45, 50 for shaping and deflecting the laser beams are provided. This arrangement may lead to comparably low space requirements. Simultaneously, opposing resonator tubes 12 of one laser are separated by the inner area 5 which facilitates cooling of the tubes 12.

(21) The laser beams coming from the beam delivery means 14 impinge on a set of beam shaping means 40 for refocusing the laser beams. The set of beam shaping means comprises one beam shaping means 40a-40i for each laser beam. Thus, the focuses of the laser beams can be set independently from each other. Depicted is one lens per beam shaping means 40a-40i. However, each beam shaping means may comprise at least two optical elements, e.g. mirrors or lenses, which form a telescopic means. Adjusting the focal lengths of the laser beams may then require only minor displacements of the optical elements of the telescopic means.

(22) The laser beams then impinge on a set of deflection means 30. In the example shown, the laser beams previously travel through the beam shaping means 40. However, this order may be changed or the single elements of both sets may alternate, i.e. one element of the beam shaping means 40 may be arranged between two elements of the deflection means 30.

(23) It is generally also possible that the beam delivery means 14 form part of the telescopic means 40 or part of the deflection means 30. In the latter case the beam delivery means 14 may constitute the first set of mapping mirrors. The number of required optical elements is then advantageously reduced.

(24) In the depicted embodiment, the set of deflection means 30 comprises two deflection means per laser beam, of which one deflection means 33a-33i per laser beam is depicted. These deflection means 33a-33i may also be referred to as a first set of mapping means 33. In general, the deflection means may be any means that change the propagation direction of a laser beam. In the shown example, the deflection means are mirrors. The mirrors of the set can be positioned independently from one another. Consequently, the arrangement of the laser beams impinging on the deflection means 30 can be altered by adjusting the position of the individual mirrors 33a-33i. The latter can thus be referred to as mapping mirrors 33a-33i.

(25) The mapping mirrors 33a-33i are tiltable and displaceable, that is translationally movable. For tilting the mirrors, each mapping mirror 33a-33i is gimbal mounted. A control unit (not depicted) may be adapted to set a desired position of each mapping mirror 33a-33i via the gimbals.

(26) After leaving the deflection means 30, the laser beams impinge on a number of common optical elements, i.e. optical elements onto which all laser beams impinge. These may comprise a telescopic device 45 for global adjustment of the focuses of the laser beams. In contrast to the set of telescopic means 40 described above, the telescopic device 45 affects all laser beams equally.

(27) The optical elements in the beam path may further comprise means for altering or homogenizing the intensity profile of a laser beam, means for changing a polarisation of the laser beams, in particular for achieving a common polarisation over the whole cross section of a laser beam, or for depolarising the laser beams.

(28) Finally, the laser beams are directed out of the apparatus 100 by a scanning mirror device 50. This device 50 may comprise two galvanometer scanners 50, each having a rotatable common mirror 50a onto which all laser beams impinge. With two galvanometer scanners 50, any direction of travel can be readily set for the laser beams.

(29) A first arrangement of the set of deflection means 30 and the set of beam shaping means 40 is shown in FIG. 2A to 2C from different perspectives.

(30) For beam shaping and collimating the laser beams 90a-90i, the set of beam shaping means 40 comprises a plurality of beam shaping means 40a-40i, each having at least two lenses 41 and 42. For adjusting the focus of each laser beam 90a-90i and thus a spot size on an object to be marked, the lenses 41 and 42 can be offset in the propagating direction of the laser beams 90a-90i. The beam shaping means 40a-40i therefore constitute telescopic means 40a-40i. As there is one telescopic means 40a-40i for each laser beam 90a-90i, the beams can also be adjusted for path length differences.

(31) After passing the telescopic means 40a-40i, the laser beams 90a-90i impinge on a set of deflection means 30 which comprises a first and a second set of mapping mirrors 33, 34. That is, each light beam 90a-90i is directed from a first mapping mirror 33a-33i to a second mapping mirror 34a-34i. The mapping mirrors of the first set 33 and those of the second set 34 are each arranged in a linear array 35, 36.

(32) In the example shown, the laser beams 90a-90i are mapped with the set of deflection means 30 such that a linear arrangement of laser beams is rotated, e.g. by 90. This configuration can thus also be referred to as a horizontal to vertical pixel mapper. The first and second set of mapping mirrors 33, 34 are arranged in one plane and perpendicular to one another.

(33) With the gimbal mounts, the mapping mirrors 33, 34 can be adjusted such that the outgoing laser beams 90a-90i run in parallel in the desired direction.

(34) A scanning motion of the laser beams 90a-90i for printing a sign on an object may be performed by the second set of mapping mirrors 34. Alternatively, the second set of mapping mirrors 34 may direct the laser beams 90a-90i to a scanning mirror device.

(35) FIG. 3A to 3C show different schematic views of another configuration of the set of beam shaping means 40 and the set of deflection means 30.

(36) This configuration differs from the previous one in the arrangement of the first and second set of mapping mirrors 33, 34. In the present case, the sets 33, 34 form linear arrays whichunlike the former configurationare not in one plane. Rather, the two linear arrays are at an angle, in this case 45, to reduce the space between the laser beams 90a-90i. At the same time, the linear arrangement of laser beams 90a-90i is rotated by 90.

(37) FIGS. 4A and 4B show still another advantageous configuration of the mapping mirrors 33, 34. As in the previous cases, the configuration depicted in FIGS. 4A and 4B exhibits mapping mirrors of a first and a second set 33, 34, each set being arranged in a linear array 35, 36. In the incident embodiment, however, the mapping mirrors of the second set 34 are tilted such that the reflected laser beams 90a-90i converge, that is the beam separation is further reduced depending on the desired separation at the desired distance from the apparatus for varying the resolution and dimensions of markings being produced.

(38) The mapping mirrors of the second set 34 may be tiltable via gimbal mounts by the control unit. The mapping mirrors of the first set 33 may either be fixed such that a displacement of these mirrors is not possible during a printing operation, or the mirrors may be gimballed as well.

(39) In the embodiments shown in FIGS. 1 to 4B, a scanning motion of the laser beams 90a-90i may be performed by tilting the mapping mirrors 34a-34i of the second set of mapping mirrors 34. Scanning devices such as galvanometer scanners with a common mirror for redirecting all laser beams 90a-90i are in this case not necessarily required. However, it may also be useful to provide such scanning devices.

(40) For setting the deflection means to any of the configurations shown in the FIGS. 1, 2A to 2C, 3A to 3C, and 4A and 4B, a control unit is preferably provided.

(41) FIG. 5 shows schematically another arrangement of mapping mirrors 33a-33i. Here, only a first set of mapping mirrors 33 of the set of deflection means 30 is shown. A linear array of laser beams 90a-90i passing through the telescopic means 40a-40i is reflected from the mapping mirrors 33a-33i such that the beam distance between the laser beams 90a-90i is reduced. The beam distance may be the same between any two neighbouring reflected laser beams 90a-90i. In the example shown, the line of laser beams 90a-90i is not rotated out of a plane formed by the mapping mirrors 33a-33i and the telescopic means 40a-40i. Tilting the mapping mirrors 33a-33i such that the reflected laser beams 90a-90i run out of said plane would result in a change of the beam distance or separation. Therefore, in this embodiment a scanning motion of the laser beams 90a-90i may either be performed with the second set of deflection means or with at least one scanning device as shown in FIG. 1.

(42) Reducing the beam separation allows the design of the stack of gas lasers to be optimized for thermal cooling and RF excitation without penalizing the resolution or character size of the print, i.e., a larger separation of the gas lasers can be compensated.

(43) FIG. 6 depicts a configuration of the mapping mirrors for rearranging the laser beams 90a-90i into a two-dimensional array of laser beams, e.g. a three by three square.

(44) Once again, the set of deflection means 30 comprises a first and a second set of mapping mirrors 33, 34. In the example shown, the telescopic means 40a-40i are arranged between the first and the second set of mapping mirrors 33, 34. However, the telescopic means 40a-40i may instead be arranged prior to the first set 33 or after the second set 34 of mapping mirrors.

(45) Also shown in FIG. 6 are the beam delivery means which redirect the light beams 90a-90i coming from the lasers to the first set of mapping mirrors 33. The beam delivery means are formed by a set of mirrors 14a-14i. In other embodiments, this set may be substituted by one long mirror.

(46) The mapping mirrors 34a-34i of the second set are arranged in a two-dimensional array such that the reflected laser beams 90a-90i are mapped in a two-dimensional array. The distance between the laser beams 90a, 90i being most distant to one another may be greatly reduced, especially in comparison to any linear arrangement of the laser beams. The beams are more tightly packed and therefore go through the central portion of optical elements, such as focusing optics 45.

(47) As optical aberrations occur mainly in the outer regions of optical elements, the two dimensional arrangement has the benefit of improved focusing and beam quality of the laser beams. Especially the outer most laser beams suffer less distortion compared to a linear arrangement of the laser beams. Furthermore, the size of optical elements can be reduced, leading to lower overall costs.

(48) Although in the embodiments of the FIGS. 1 to 6 the deflections means are formed with mirrors, optical waveguides may be employed instead. At least one end of each optical waveguide, in some embodiments both ends, may be connected to positioning means controlled by the control unit for individually adjusting the deflection caused by the respective optical waveguide. When an end of the optical fiber is adjusted in its position, a lens for directing the laser light into the optical fiber or for collecting the laser light emanating from the optical fiber is adjusted correspondingly. This lens serves as a second deflection means.

(49) FIG. 7 shows schematically a marking system 120 and an object 1 to be marked.

(50) The object 1 is moved in an object movement direction 2 and is depicted in three different positions, that is at three different points in time. The marking system 120 comprises a marking apparatus 100 and pivoting means 110 for tilting the marking apparatus 100.

(51) The marking apparatus 100 may comprise any components as described above, e.g. deflection means constituted by two sets of mapping mirrors each arranged in a linear array. As shown in FIG. 7, a control unit 20 is also provided as well as positioning means 60. The latter serves for positioning the linear arrays of mapping mirrors. The individual mapping mirrors may be fixed within the respective array such that they cannot be displaced but tilted, e.g. with gimbal mounts.

(52) The marking apparatus 100 emits a plurality of laser beams, three of which 90a, 90b, 90c are shown in FIG. 7. As the object 1 moves, the laser beams 90a, 90b, 90c are correspondingly redirected.

(53) Depending on the shape and the position of the object 1, the distance between the apparatus 100 and the object 1 may change by as much as indicated with the reference sign d. Furthermore, at one point in time, the distance may be different for each laser beam 90a, 90b, 90c. Still, the spot sizes of the laser beams 90a, 90b, 90c on the object 1 are to be equal. To this end, beam shaping means as described above are provided and adjusted by the control unit 20.

(54) In the following, the function and benefit of the pivoting means 110 are explained with reference to FIGS. 8A to 8D, each of which shows schematically the arrangement of laser beams 90a-90i emitted by the apparatus 100 relative to an object movement direction 2.

(55) In FIG. 8A the linear arrangement of laser beams 90a-90i is parallel to the object movement direction. At least two of the laser beams 90a-90i impinge on the same spot 80 on the object 1 by individually delaying the firing of the gas lasers. The delay may be set to be equal to the separation between the laser beams 90a-90i divided by the speed of the object or the speed of the object in the direction of the linear arrangement of laser beams.

(56) In the FIG. 8B to 8D the linear arrangement of laser beams 90a-90i is angularly tilted to the direction of travel 2 of the object by an angle . This tilt angle may be set with the pivoting means 110. Together with a delay of the firing, the tilting leads to the printing of a line formed by dots 81-89. The dots 81-89 may overlap, as in FIG. 8B, or may be separated as in FIGS. 8C and 8D. The length of the line thus produced is determined by the tilt angle between the laser beams 90a-90i and the object movement direction 2. The size of each dot 81 to 89 and thus the width of the line can then be controlled with the beam shaping means.

(57) The described marking apparatus allows for changing the beam separation and the arrangement of a plurality of laser beams produced by lasers. Each laser beam can be individually adjusted by beam shaping means. Space requirements are minimized by arranging optical elements within an area surrounded by the lasers.