Marking apparatus with a plurality of lasers and a combining deflection device

Abstract

The invention relates to a marking apparatus (100) for marking an object with laser light, comprising a plurality of lasers (10), in particular gas lasers (10), and a control unit for individually activating each of the lasers (10) to emit a laser beam according to a sign to be marked. A deflection device (30) is provided by which at least two laser beams are combined on a common spot.

Claims

1. A marking apparatus for marking an object with laser light, the marking apparatus comprising: a plurality of lasers, wherein each laser is a gas laser and comprises resonator tubes, wherein the plurality of 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 lasers to emit a laser beam according to a sign to be marked; a deflection device by which at least two laser beams are combined on a common spot, the deflection device comprises a set of deflection means with at least one deflection means per laser beam, and each deflection means is at least one of: individually adjustable in its deflection direction or individually shiftable, for combining a laser beam with another or several other laser beams, the respective deflection means are accordingly adjustable, the set of deflection means allows for rearranging laser beams that are not combined on the common spot into a desired array of laser beams, for directing the laser beams that are combined by the deflection device into a desired direction, at least one scanning mirror device is provided, the scanning mirror device comprises a common mirror onto which all laser beams coming from the deflection device impinge, the control unit configured to pivot the scanning mirror device, wherein for stepwise scaling a laser beam power transferred onto the common spot, the control unit is configured to set the number of laser beams combined onto the common spot according to a desired power level or according to a user's input; and a set of telescopic means comprising at least one telescopic means per laser beam, each telescopic means being adjustable for individually setting a focal length of the respective laser beam, and for compensating for path length differences between the laser beams that are combined in the common spot, the control unit adapted to control the telescopic means such that the combined laser beams have a common focal length, wherein the set of telescopic means is located within the inner area.

2. The marking apparatus according to claim 1, wherein the at least one deflection means per laser beam is one of: at least one mapping mirror or one optical waveguide per laser beam, and each of the at least one mapping mirror or one optical waveguide is at least one of: individually adjustable in its deflection direction or individually shiftable.

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

4. The marking apparatus according to claim 2, wherein for forming a plurality of common spots, each laser is allocated into one of a plurality of groups, and the deflection means are arranged such that the laser beams of the lasers of each group are combined into a respective common spot.

5. The marking apparatus according to claim 2, 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, and the first set of mapping mirrors directs the laser beams onto the second set of mapping mirrors.

6. The marking apparatus according to claim 5, wherein the control unit is adapted for at least one of: shifting the deflection means or adjusting the deflection directions of the deflection means.

7. The marking apparatus according to claim 2, 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 set of deflection means.

8. The marking apparatus according to claim 1, wherein each deflection means comprises an optical waveguide, and the optical waveguides have the same length.

9. The marking apparatus according to claim 1, wherein the deflection means are adjusted such that a beam separation between the laser beams that are not combined in the common spot is reduced.

10. A marking system comprising the marking apparatus according to claim 1, wherein the marking apparatus is pivotably supported to be tiltable relative to an object movement direction of the object to be marked.

11. The marking apparatus according to claim 1, wherein the plurality of lasers are stacked on top of each other.

12. The marking apparatus according to claim 11, wherein the plurality of lasers includes at least two lasers stacked on top of each other.

13. The marking apparatus according to 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. 2 shows a first configuration of set of deflection means and a set of beam shaping means;

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

(6) FIG. 5 shows a marking system according to the invention and an object to be marked moving relative to the marking system.

DETAILED DESCRIPTION OF THE INVENTION

(7) FIG. 1 shows schematically a first embodiment of a marking apparatus 100 according to the invention. The marking apparatus 100 comprises a plurality of gas 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. Although the invention is described in the following with reference to a marking apparatus comprising gas lasers, other types of lasers may be employed instead.

(8) In the example shown, the plurality of gas lasers 10 consists of nine gas lasers 10a-10i. 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.

(9) 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.

(10) 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.

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

(12) 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 is 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 excited to generate laser light. Rather, the reservoir 19 is connected to the gas volumes of one or several resonator tubes 12.

(13) 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.

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

(15) 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.

(16) 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 a 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.

(17) In the inner area 5, optical means 30, 40, 45, 50 for shaping and deflecting the laser beams are provided. This arrangement leads to comparably low space requirements.

(18) 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 instead comprise at least two optical elements, e.g. mirrors or lenses, to form a telescopic means. Adjusting the focal lengths of the laser beams then may require only minor displacements of the optical elements of the telescopic means.

(19) After travelling through the beam shaping means 40, the laser beams impinge on a deflection device 30 which consists of a set 30 of deflection means. 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.

(20) 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.

(21) In the depicted embodiment, the set of deflection means 30 comprises one deflection means 33a-33i per laser beam. These deflection means 33a-33i may also be referred to as a first set of mapping means or mirrors 33. In general, the deflection means may be any means that change the propagation direction of a laser beam, including optical fibers. The mapping mirrors 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.

(22) 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.

(23) At least two of the mapping mirrors 33a, 33b are adjusted such that the respective laser beams cross each other at one, or at least one, spot which may be referred to as common spot. This common spot or first common spot may be outside the apparatus 100 such that the object to be marked can be easily positioned at said spot.

(24) The remaining mapping mirrors 33c-33i may either be adjusted such that their laser beams form at least one other common spot, or such that their laser beams impinge on separate spots at the object to be marked.

(25) The control unit is adapted to adjust any of the remaining mapping mirrors 33c-33i such that its respective laser beam impinges on the first common spot formed by the two mapping mirrors 33a, 33b. Any desired laser beam intensity hitting the first common spot, up to the combined intensity of all laser beams, can thus be set.

(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 light beam, means for changing a polarisation of the light beams, in particular for achieving a common polarisation over the whole cross section of a light beam, or for depolarising the light 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.

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

(30) The laser beams 90a-90i coming from the right side in FIG. 2 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. As the second set of mapping mirrors 34 is depicted from above, the individual mirrors, in the present case nine mirrors, are not distinguishable in FIG. 2. The mapping mirrors of the first set 33 and those of the second set 34 are each arranged in a linear array 35, 36.

(31) 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. Whereas the laser beams 90a-90i impinging on the first set of mapping mirrors 33 may run in parallel, after redirection with the second set of mapping mirrors 34 at least some of the laser beams 90a-90i do not run in parallel but converge. As a consequence, they overlap at a common spot at which the object to be marked can be placed.

(32) The configuration shown can thus also be referred to as a horizontal to vertical pixel mapper. The first and second sets of mapping mirrors 33, 34 are arranged in one plane and perpendicular to one another.

(33) Behind the set of deflection means 30 a set of beam shaping means 40 for beam shaping and collimating the laser beams 90a-90i is provided. The set of beam shaping means 40 comprises a plurality of beam shaping means, each having at least two lenses. For adjusting the focus of each laser beam 90a-90i and thus a spot size on an object to be marked, the lenses can be offset in the propagating direction of the laser beams 90a-90i. The beam shaping means therefore constitute telescopic means. As there is one telescopic means for each laser beam 90a-90i, the beams can also be adjusted for path length differences. This may be important as those laser beams that overlap in the common spot exhibit, in general, different path lengths.

(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) FIGS. 3A and 3B show from different perspectives another configuration of the set of deflection means 30 and the set of beam shaping means 40.

(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 configuration of the mapping mirrors 33, 34. Here, the laser beams come from the left side and thus pass the beam shaping means 40 prior to impinging on the set of deflection means 30. 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 all reflected laser beams 90a-90i overlap and form a common spot at a desired distance from the apparatus. By setting a degree of convergence of the laser beams 90a-90i, the distance at which the common spot is located can be varied.

(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. 2 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 present. 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. 2 to 4B, a control unit may be provided.

(41) FIG. 5 shows schematically a marking system 120 and an object 1 to be marked.

(42) The object 1 is moved in an object movement direction 2 and is depicted at 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.

(43) 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. 5, 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.

(44) The marking apparatus 100 emits a plurality of combined laser beams, three of which 90a, 90b, 90c are shown in FIG. 5. As the object 1 moves, the combined laser beams 90a, 90b, 90c are correspondingly redirected. Each of the combined laser beams 90a, 90b, 90c consists of individual laser beams, or in other words, is produced by several gas lasers. In the depicted example, each beam 90a, 90b, 90c is formed by three gas lasers. In contrast to the afore described examples, those individual laser beams that form one common spot do not merely overlap at the common spot, but have partially identical paths. A movement of the object 1, e.g. an undesired vibration, may not affect whether the individual laser beams form a common spot on the object's surface.

(45) 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 of the combined laser beams 90a, 90b, 90c. Still, the spot sizes of the combined 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.

(46) The described marking apparatus provides for a flexible deployment of a plurality of lasers. A particularly high laser beam intensity can be achieved by combining the laser beams of any number of the lasers in a common spot. In case the required laser beam intensity is lower than that of all lasers combined, a plurality of common spots can be formed, each being made up by a plurality of laser beams. A compact design allowing for high beam intensities and a very flexible use of laser beams is thus provided.