AUTOMATIC CALIBRATION OF A LASER PROCESSING SYSTEM USING A NON-INTEGRATED TELECENTRIC OPTICAL DETECTOR WITH LIMITED DEGREES OF FREEDOM

Abstract

A laser calibration device includes a scanning surface, an optical detector for scanning a calibration substrate arranged on the scanning surface, and a processing unit. The optical detector is movable with respect to the scanning surface with not more than two, preferably not more than one, degree of freedom. The processing unit is configured for: generating pattern generation executable instructions to generate a calibration pattern on a calibration substrate by one or more laser processing devices of a laser processing apparatus; detecting a calibration pattern generated based on such pattern generation executable instructions; and based on a detected calibration pattern and on the corresponding pattern generation executable instructions, generating calibration executable instructions for calibrating the one or more laser processing devices of said laser processing apparatus.

Claims

1. A laser calibration device comprising: a scanning surface configured to receive a calibration substrate; an optical detector configured to scan the calibration substrate arranged on the scanning surface, wherein the optical detector is movable with respect to the scanning surface with not more than two degrees of freedom; and a processing unit coupled to the optical detector and configured for: generating pattern generation executable instructions which, when executed by a control unit of one or more laser processing devices of a laser processing apparatus, cause the one or more laser processing devices to generate a calibration pattern on the calibration substrate using one or more laser beams deflected by the one or more laser processing devices; detecting a calibration pattern generated based on the pattern generation executable instructions generated by the processing unit, the calibration pattern being comprised in the calibration substrate scanned by the optical detector; and based on the detected calibration pattern and on the corresponding pattern generation executable instructions, generating calibration executable instructions which, when executed by said control unit of the one or more laser processing devices of said laser processing apparatus, calibrate the one or more laser processing devices of said laser processing apparatus.

2. The laser calibration device of claim 1, wherein the laser calibration device is free of any laser source and/or any laser deflection unit.

3. The laser calibration device of claim 1, wherein the laser calibration device is structurally independent of the laser processing apparatus.

4. The laser calibration device of claim 1, wherein the optical detector comprises an illuminating device configured for illuminating the scanning surface and/or the calibration substrate arranged on the scanning surface.

5. The laser calibration device of claim 1, wherein the optical detector is movable with respect to the scanning surface with not more than one degree of freedom in one scanning direction, wherein the scanning direction is parallel to the scanning surface.

6. The laser calibration device of claim 1, wherein the optical detector extends in a detection direction parallel to the scanning surface, wherein the detection direction is perpendicular to a scanning direction in which the optical detector is movable.

7. The laser calibration device of claim 6, wherein an extension of the optical detector in the detection direction overlapping the scanning surface, is from 100 mm to 1500.

8. The laser calibration device of claim 6, wherein an extension of the optical detector in the detection direction corresponds at least to an extension of the scanning surface in the detection direction or a part thereof.

9. The laser calibration device according to claim 1, wherein the optical detector is movable with respect to the scanning surface with not more than one degree of freedom in one scanning direction, wherein the scanning direction is parallel to the scanning surface, wherein the optical detector extends in a detection direction parallel to the scanning surface, wherein the detection direction is perpendicular to a scanning direction in which the optical detector is movable, wherein the scanning direction corresponds to a direction in which the optical detector is movable with respect to the scanning surface and wherein the detection direction corresponds to a direction in which the optical detector is not movable with respect to the scanning surface.

10. The laser calibration device of claim 5, wherein the optical detector is movable in the scanning direction within a motion range corresponding at least to an extension of the scanning surface in the scanning direction or a part thereof.

11. The laser calibration device of claim 1, wherein a constant separation distance between the scanning surface and/or the calibration substrate arranged thereon and the optical detector is from 1 mm to 50 mm.

12. The laser calibration device of claim 1, wherein the optical detector is or comprises a contact image sensor.

13. A laser processing system comprising: one or more laser processing apparatuses comprising one or more respective laser processing devices configured to laser-process a work material; and a laser calibration device comprising: a scanning surface configured to receive a calibration substrate thereon; an optical detector configured to scan the calibration substrate on the scanning surface, wherein the optical detector is movable with respect to the scanning surface with not more than two degrees of freedom; and a processing unit coupled to the optical detector, wherein the processing unit of the laser calibration device is operatively connected to each of the one or more laser processing apparatuses and is configured for: generating pattern generation executable instructions such that, when executed by a control unit of the one or more laser processing devices of a given one of the one or more laser processing apparatuses, the pattern generation executable instructions cause the one or more laser processing devices of said given one of the one or more laser processing apparatuses to generate a calibration pattern on the calibration substrate, providing said pattern generation executable instructions to said control unit of the one or more laser processing devices of said given one of the one or more laser processing apparatuses; detecting the calibration pattern generated by the one or more laser processing devices of said given one of the one or more laser processing apparatuses based on said pattern generation executable instructions, the calibration pattern being comprised in the calibration substrate scanned by the optical detector of the laser calibration device; and based on the detected calibration pattern and on said pattern generation executable instructions provided to the control unit of the one or more laser processing devices of said given one of the one or more laser processing apparatuses, generating calibration executable instructions which, when executed by the control unit of the one or more laser processing devices of said given one of the one or more laser processing apparatuses, calibrate the one or more laser processing devices of said given one of the one or more laser processing apparatuses, and providing said calibration executable instructions to the control unit of the one or more laser processing devices of said given one of the one or more laser processing apparatuses.

14. The laser processing system of claim 13, wherein a control unit of the one or more laser processing devices of each of the one or more laser processing apparatuses is configured for calibrating the corresponding one or more laser processing devices based on calibration executable instructions generated by and/or received from the laser calibration device.

15. The laser processing system of claim 13, wherein each of the one or more laser processing apparatuses comprises a plurality of laser processing devices configured for laser-processing a work material on a common work field.

16. The laser processing system of claim 15, wherein the plurality of laser processing devices of each of the one or more laser processing apparatuses are configured for simultaneously laser-processing the work material on the common work field.

17. A method of calibrating one or more laser processing devices of one or more laser processing apparatuses using a laser calibration device, the laser calibration device comprising: a scanning surface configured to receive a calibration substrate thereon; and an optical detector configured to scan the calibration substrate arranged on the scanning surface, wherein the optical detector is movable with respect to the scanning surface with not more than two degrees of freedom, wherein the method comprises: generating, by the laser calibration device, pattern generation executable instructions and providing said pattern generation executable instructions to the one or more laser processing devices of each one of the one or more laser processing apparatuses, generating, by the one or more laser processing devices of each of the one or more laser processing apparatuses, a respective calibration pattern on the calibration substrate based on the respective pattern generation executable instructions provided by the laser calibration device; for each of the one or more laser processing apparatuses, scanning the corresponding calibration pattern using the laser calibration device, and generating calibration executable instructions based on the scanned calibration pattern and on the corresponding pattern generation executable instructions and providing the generated calibration executable instructions to a corresponding one of the one or more laser processing apparatuses; and calibrating the one or more laser processing devices of each of the one or more laser processing apparatuses based on the respective calibration executable instructions received from the laser calibration device.

18. The method of claim 17, wherein generating said respective calibration pattern on the corresponding calibration substrate based on the respective pattern generation executable instructions provided by the laser calibration device comprises including in the calibration pattern an identification marking identifying a laser processing apparatus used for generating said respective calibration pattern and/or the respective pattern generation executable instructions used for generating said respective calibration pattern.

19. The method of claim 17, wherein generating said respective calibration pattern on the corresponding calibration substrate based on the respective pattern generation executable instructions provided by the laser calibration device comprises including in the calibration pattern a plurality of substrate orientation markings identifying an orientation of the calibration substrate with respect to the laser processing apparatus used for generating said respective calibration pattern.

20. The method of claim 17, further comprising performing a basic calibration before the step of scanning the corresponding calibration pattern for each of the one or more laser processing apparatuses, wherein the basic calibration comprises scanning a basic calibration pattern one or more times and calibrating the laser calibration device based on the basic calibration pattern.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0091] FIG. 1 shows a schematic view of a laser processing system according to the invention.

[0092] FIG. 2 shows a schematic side view of a laser calibration device according to the invention, which can be included in the laser processing system of FIG. 1.

[0093] FIG. 3 shows a schematic front view of a calibration substrate, which can correspond to the calibration substrate of FIG. 2.

[0094] FIG. 4 shows a schematic top view of the laser calibration device of FIG. 2.

[0095] FIG. 5 shows a flow diagram of a method according to the invention of calibrating one or more laser processing devices of one or more laser processing apparatuses using a laser calibration device, which can correspond to the laser calibration device of FIG. 2.

DETAILED DESCRIPTION

[0096] For the purposes of promoting an understanding of the principles of the invention, reference will now be made to specific preferred embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated apparatus and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur now or in the future to someone skilled in the art to which the invention relates within the scope defined by the claims.

[0097] FIG. 1 shows a schematic view of a laser processing system 100 according to an embodiment of the invention. The laser processing system 100 may be arranged in a climatized room under controlled temperature conditions. The laser processing system 100 comprises a plurality of laser processing apparatuses 102-1, . . . , 102-6. Although six laser processing apparatuses are exemplary shown and described for the laser processing system 100, the number of laser processing apparatuses may be greater or smaller in other related laser processing systems according to the invention. For example, a laser processing system similar to laser processing system 100 can comprise one single laser processing apparatus, two laser processing apparatuses, or ten laser processing apparatuses in other related embodiments.

[0098] Each of the laser processing apparatuses 102-1, . . . , 102-6 is operatively connected to an independent laser calibration device 10 via a connection 110. The connection 110 can for example be a wireless connection, such as a WLAN connection, or a wired connection, such as a LAN or Ethernet connection.

[0099] Each of the laser processing apparatuses 102-1, . . . , 102-6 comprises one or more respective laser processing devices (not shown) configured for laser processing a work material on a corresponding work field. The one or more laser processing devices of each given laser processing apparatus can be configured for simultaneously laser processing a work material on a common work field. Each of the one or more laser processing devices can for example be or comprise a deflection unit as described in EP 390 4946 A1 and/or as described in WO 2018/078137 A1, both of which are incorporated by reference herein. Each of the laser processing apparatuses 102-1, . . . , 102-6 can be or comprise an additive manufacturing apparatus.

[0100] FIG. 2 shows a schematic side view of the laser calibration device 10 shown in FIG. 1. The laser calibration device 10 comprises a flat and transparent scanning surface 12 configured for arranging thereon a calibration substrate 20. In the exemplary embodiment shown in FIG. 2, the calibration substrate 20 is a calibration plate comprising a laser sensitive layer arranged on a substrate layer. FIG. 3 shows a schematic top view of the calibration plate 20.

[0101] The laser calibration device 10 further comprises an optical detector 14 configured for scanning the calibration substrate 20 arranged on the scanning surface 12. The optical detector 14, which is configured as a CIS detector, is movable with respect to the scanning surface 12 with limited degrees of freedom. In the exemplary embodiment shown in FIG. 2, the optical detector 14 is movable with respect to the scanning surface 12 in one dimension only, e.g. with only one degree of freedom. In particular, the optical detector 14 is movable in the Y-direction with respect to the scanning surface 12 along a pair of opposite guiding rails 17, while a position of the optical detector 14 is fixed in the Z-direction and in the X-direction. Notably, in related embodiments, the optical detector 14 may be movable in the Y-direction with respect to the scanning surface 12 along one single guiding rail, for example a guiding rail extending along a central axis of the laser calibration device, while a position of the optical detector 14 is fixed in the Z-direction and in the X-direction. Thus, the laser calibration device 10 is configured as a flatbed scanner.

[0102] As shown in FIG. 2, the laser calibration device 10 comprises a housing 11 that includes a top part 11t and a bottom part 11b. The top part 11t is movable, in particular pivotable, with respect to the bottom part 11b to cover and uncover the calibration substrate 20 and/or the scanning surface 12. The top part 11t of the housing 11 can be lifted to arrange the calibration substrate 20 on the scanning surface 12 and for removing the calibration substrate 20 from the scanning surface 12 and can be closed to cover the scanning surface 12 and the calibration substrate 20 during the operation of the optical detector 14.

[0103] FIG. 4 shows a schematic top view of the laser calibration device 10 of FIG. 2, wherein the calibration substrate 20, which is separately shown in FIG. 3, has been removed for illustration purposes. As seen in FIG. 4, the scanning surface 12 has a quadrangular shape with an extension L.sub.X in the X direction and an extension L.sub.Y in the Y direction. For example, the scanning surface 12 can be a square surface having dimensions L.sub.X=L.sub.Y=300 mm, L.sub.X=L.sub.Y=600 mm or L.sub.X=L.sub.Y=900 mm. As a further example, the scanning surface 12 can be a rectangular surface having dimensions L.sub.X=300 mm and L.sub.Y=400 mm, L.sub.X=600 mm and L.sub.Y=800 mm or L.sub.X=800 mm and L.sub.Y=950 mm. The optical detector 14 extends in the detection direction X over the entire extension L.sub.X of the scanning surface 12 and is movable in the scanning direction Y over the entire extension L.sub.Y of the scanning surface 12 or over a part thereof. Therefore, the optical detector 14 can completely scan the scanning surface 12 by sweeping once in the scanning direction Y over the scanning surface 12. Having L.sub.Y>L.sub.X can ease the task of arranging the calibration substrate 20 on the scanning surface 12.

[0104] The optical detector 14 comprises a plurality of optical detection units 13 that are arranged linearly along the detection direction X in a row. The number of optical detection units in the optical detector is reduced in FIG. 4 for illustration purposes, but can be greater in embodiments of the invention. For example, the optical detector can comprise 14.592 optical detection units linearly arranged in the X direction, with each optical detection unit comprising a corresponding optical detection sensor (pixel) covering a distance long the X direction of 42 μm for a detection resolution of 600 dpi. Each of the optical detection units comprises one or more focusing lenses or lens arrays, for example a focusing rod lens, for focusing detection light upon the corresponding optical detection sensor. Further, the optical detector 14 comprises an illumination device 15 configured for illuminating the scanning surface 12 with visible light during the operation of the optical detector 14 for detecting a calibration pattern comprised in a calibration substrate 20 arranged on the scanning surface 12. The illumination device 15 can for example comprise a plurality of illumination LEDs aligned along the direction X. A vertical distance D between the optical detector 14 and the calibration substrate 20 can for example be 12 mm, as indicated in FIG. 2. In related embodiments, the optical detector 14 can however have higher resolution, for example a resolution of 2400 dpi.

[0105] The laser calibration device 10 further comprises a processing unit 16. In the embodiment shown in FIG. 2, the processing unit 16 is an integrated processing unit 16 received within the housing 11. However, in other related embodiments, the processing unit 16 may be a non-integrated processing unit that can be partly or totally arranged outside of the housing 11, for example installed in an external CPU (e.g. laptop or PC), and functionally connected with the optical detector 14 by a corresponding connection.

[0106] The processing unit 16 is configured for carrying out a method 200 of calibrating the laser processing devices 102-1, . . . , 102-6 of the laser processing system 100 of FIG. 1 using the laser calibration device 10. The method 200 is schematically illustrated in the flow diagram of FIG. 5.

[0107] In step 202, the processing unit 16 generates pattern generation executable instructions and sends them to a control unit of each of the laser processing apparatuses 102-1 to 102-6, which is configured for controlling the corresponding laser processing devices. The pattern generation executable instructions contain laser settings and optical settings that instruct the laser processing devices of the laser processing apparatuses 102-12 100 to-6 to perform laser operations on the corresponding work field in order to generate a corresponding calibration pattern.

[0108] In step 204, the laser processing devices of each of the laser processing apparatuses 102-1 to 102-6 generate a respective calibration pattern on a respective calibration substrate arranged in the corresponding work field based on the pattern generation executable instructions received from the laser calibration device 10. This can for example comprise laser-marking a plurality of reference markings 22 on the calibration substrate 20, like the reference markings 22 shown in FIG. 3, and possibly also an identification marking 26 and a plurality of substrate orientation markings 24.

[0109] In the exemplary calibration plate 20 shown in FIG. 3, the calibration pattern comprises a regular square grid of 5×5 reference markings, three substrate orientation markings 24 arranged at first to third respective corners of the calibration plate 20 and an identification marking 26, which is configured as a QR code in the exemplary embodiment shown in FIG. 3, arranged on a fourth corner of the calibration plate 20, with the three substrate orientation markings 24 and the identification marking 26 surrounding the plurality of reference markings 22. In other related embodiments, the number of reference markings may be different, in particular greater. For example, the calibration plate 20 can comprise 49×49 reference markings arranged in a regular grid.

[0110] In other examples, if one laser processing apparatus comprises a plurality of laser processing devices, the calibration pattern generated on the calibration substrate 20 can comprise a corresponding plurality interleaved groups of reference markings forming respective regular grids, with each group of reference markings corresponding to one of the laser processing devices. For example, if a laser processing apparatus comprises two laser processing devices configured for laser processing a common work field, the calibration pattern for the two laser processing apparatuses may comprise two interleaved regular square grids of reference markings, each grid corresponding to one of the laser processing devices. The increased calibration accuracy achieved according to the present invention makes it possible to simultaneously calibrate a plurality of laser processing devices with partly or totally overlapping working fields (multi-field calibration).

[0111] After step 204, the calibration substrate 20 is removed from the corresponding laser processing apparatus 102-1, . . . , 102-6 and arranged on the scanning surface 12 of the laser calibration device 10 with a surface of the calibration substrate 20 on which the calibration pattern is formed facing the scanning surface 12.

[0112] Then, in step 206, possibly upon receiving a “start measurement” instruction by a user, the optical detector 14 scans the calibration pattern comprised in the calibration substrate 20 (e.g. the reference markings 22, the substrate orientation markings 24 and the identification marking 26) through the transparent scanning surface 12. Step 206 may comprise storing the scanned calibration pattern, for example in a memory device connected to the processing unit 16. Thanks to the substrate orientation markings 24, the calibration pattern can be scanned and the calibration executable instructions generated even irrespectively of an arrangement of the calibration substrate 20 on the scanning surface 12.

[0113] Based on the scanned calibration pattern and on the pattern generation executable instructions that were used for generating the calibration pattern, the processing unit 16 generates calibration executable instructions, which are then sent to a laser processing apparatus 102-1, 102-2, 102-3, 102-4, 102-5 or 102-6 via the connection 110, possibly upon receiving a “proceed with calibration” instruction by a user. The processing unit 16 can know from the identification marking 26 from which one of the laser processing apparatus 102-1, 102-2, 102-3, 102-4, 102-5 or 102-6 the calibration pattern on the calibration substrate 20 originates and correspondingly sends the generated calibration executable instructions to said one of the laser processing apparatus 102-1, 102-2, 102-3, 102-4, 102-5 or 102-6.

[0114] Optionally, before the calibration executable instructions are then sent to a laser processing apparatus 102-1, 102-2, 102-3, 102-4, 102-5 or 102-6, the calibration executable instructions which may comprise correction data implementable by the respective control unit of the corresponding one of the laser processing apparatus 102-1, 102-2, 102-3, 102-4, 102-5 or 102-6 to correct/calibrate positional, orientational and/or focussing settings of each of the one or more respective laser processing devices, are displayed to a user of the laser calibration device 10, for example by being represented on a screen. This may for example comprise displaying on a screen a matrix of correction values corresponding to the calibration executable instructions. The user can then check the calibration executable instructions before sending the to the corresponding laser processing apparatus and using them for calibration.

[0115] The method 200 can comprise, before step 206, possibly before steps 202 and/or 204, an optional step of performing a basic calibration of the laser calibration device 10 by scanning a basic calibration pattern one or more times and by calibrating the laser calibration device 10 based on the basic calibration pattern. The basic calibration pattern can be formed on a high precision calibration glass substrate, on which a plurality of basic calibration marks are arranged with a positional precision between 1 μm and 2 μm. For increased calibration precision, the basic calibration can be carried out at a constant controlled ambient temperature of for example 20° C. During the basic calibration, the optical detector 14 of the laser calibration device 10 scans the basic calibration pattern. The basic calibration may allow detecting and compensating (calibrating away) possible inaccuracy sources due to inhomogeneities or fluctuations of the properties of the different optical detection units 13 of the optical detector 14.

[0116] In step 208, the corresponding laser processing apparatus 102-1, 102-2, 102-3, 102-4, 102-5 or 102-6 uses the corresponding calibration executable instructions provided by the laser processing apparatus 10 for calibrating the respective laser processing devices. This may comprise for example adjusting a focus position, a laser field position, a laser field orientation and/or a laser field size of the one or more laser processing devices of the corresponding laser processing apparatus, possibly by means of corresponding settings of optical and/or electronic components such as lenses, mirrors, galvanometers and the like. Additionally or alternatively, this may also comprise calibrating the laser processing devices of each of the laser processing apparatus is with respect to each other for improved coordination.

[0117] The calibration instructions can be based on a difference between the real calibration pattern detected by the optical detector 14 as laser-marked on the calibration substrate 20 and a virtual calibration pattern corresponding to the pattern generation executable instructions that were originally used for generating the calibration pattern. Such difference may for example comprise differences in the positions and/or orientations of the reference markings 22 as compared to virtual reference markings based on the corresponding pattern generation executable instructions.

[0118] The steps 202 to 208 can be carried out for each or all of the laser processing apparatuses sequentially. Thus, it is possible to first execute step 202 for all laser processing apparatuses 102-1, . . . , 102-6, then step 204 for all laser processing apparatuses 102-1, . . . , 102-6, then step 206 for all laser processing apparatuses 102-1, . . . , 102-6 and then step 208 for all laser processing apparatuses 102-1, . . . , 102-6. However, it is also possible to first execute steps 202 to 208 for laser processing apparatus 102-1, then for laser processing apparatus 102-2, and so on.

[0119] Thanks to the invention, it is possible to accurately and reliably calibrate each of the laser processing apparatuses 102-1, . . . , 102-6 in a reduced time, for example in 10 minutes or less.

[0120] Although preferred exemplary embodiments are shown and specified in detail in the drawings and the preceding specification, these should be viewed as purely exemplary and not as limiting the invention. It is noted in this regard that only the preferred exemplary embodiments are shown and specified, and all variations and modifications should be protected that presently or in the future lie within the scope of protection of the invention as defined in the claims.