Method for calibrating a measurement scanner on a laser processing optical device

Abstract

The invention relates to a method for calibrating a measurement scanner on a laser processing optics of a laser processing device, in which a measurement scan of a test body is created by means of a measurement beam, and the measurement scan is then compared with reference data of the test body, and in the case where the measurement scan data deviates from the reference data, the measurement scanner is corrected such that the measurement scan data is consistent with the reference data of the test body.

Description

Background Art

[0001] The calibration of the measuring scanner on the laser processing optics requires complex sensors for measuring the measuring beam at different positions of the measuring scanner. This calibration process is performed once before commissioning of the laser processing device. However, replacement of components of the laser processing device and / or collisions during workpiece processing may lead to erroneous factory calibration of the measuring scanner. Such erroneous measurement data may cause the laser beam to irradiate the workpiece to be processed at the wrong position, which leads to quality losses during laser processing of the workpiece.

[0002] Until now, users of laser processing devices have not been able to subsequently check the calibration and, if necessary, readjust the measuring scanner.

[0003] From DE 10 2016 106 648 B4 it is known to calibrate a measuring device on a laser processing optics by irradiating a known pattern into a sheet metal part with a processing laser beam and then scanning it with a measuring device. The actual data of the scanned sample are compared with the known target data of the sample and, if necessary, the calibration of the measuring device is readjusted.

[0004] However, this known method is relatively inaccurate. In addition, the result depends on the aspect ratio of the laser beam and the material of the sheet metal part.

[0005] Purpose of the Invention

[0006] The invention is based on the object of making it possible to carry out a calibration of a measuring scanner on laser processing optics fully automatically and with high accuracy. Summary of the invention

[0007] The object is achieved by means of a method for calibrating a measuring scanner on a laser processing optics, wherein a measuring scan of a test body is created using a measuring beam and the measuring scan is subsequently compared with reference data of the test body, wherein the measuring scanner is corrected in the event of deviations of the measuring scan data of the measuring scan from the reference data such that the measuring scan data and the reference data of the test body are consistent. The test body is arranged at a focus or in a focal plane or adjacent to the focus or the focal plane.

[0008] The test body used can be reused as many times as required. The result of the calibration does not depend on the quality of the laser optics or the process optics or on the material of the test body, as is the case with known methods in which reference samples are inserted into sheet metal parts. Calibration can therefore be performed with very high accuracy.

[0009] To carry out the method, a test body with known dimensions can be used, wherein the known dimensions are used as reference data for comparison with the measurement scan data from the measurement scanner of the laser processing device. The reference data can be stored as target data in the evaluation device, which reference data are compared with the measured actual data of the measurement scan.

[0010] However, alternatively, a test body with unknown dimensions can be used. In this alternative, the measuring beam is provided by laser processing optics, wherein the measuring beam is deflected by the laser processing optics to create a measuring scan of the test body, and the scan data of the measuring scan of the measuring beam of the laser processing optics are used as reference data, which are compared with the scan data of the measuring scan of the test body subsequently performed with the measuring beam of the measuring scanner. Thus, the test body is first scanned or swept over with the measuring beam from the laser processing optics, and then scanned or swept over with the measuring beam of the measuring scanner. In an alternative, in order to create the reference data, the measuring beam is not provided by the measuring scanner, but instead provided by the laser processing optics and deflected. In an alternative, the measuring scan is then created using the optics of the measuring scanner and compared with the reference data. In this method variant or alternative, different test bodies can be used, which also facilitates the verification of the calibration of the measuring scanner by the user of the laser processing device.

[0011] Preferably, after calibrating the measurement scanner, a new measurement scan of the test body is created and compared with the reference data to ensure that the corrective measures taken on the measurement scanner were successful.

[0012] The measuring scan can be used to create a three-dimensional model of the test body. In this way, the measuring scanner can be calibrated not only in the transverse direction but also in the axial direction of the processing laser beam. For example, in laser welding or laser cutting, precise adjustment of the focus of the processing laser beam on the workpiece to be processed is necessary for a good processing result. This standard can also be checked with the measuring scanner and, if necessary, the distance between the laser optics and the workpiece can be corrected.

[0013] Preferably, a circular test body or a test body with circular features or marks is used for calibration. In the measurement scan, the semi-axis of the circular mark or the semi-axis of the test body is measured in the x-direction and the y-direction. If the measurement scan deviates in the x-direction and / or the y-direction, the volume model of the test body or the circular mark in the volume model of the test body appears elliptical or oval instead of circular. The roundness of the body is relatively easy to check visually. If the measured semi-axis in the x-direction is, for example, x=r+a, where r is the radius of the test body or its circular mark, then the deflection of the measurement scanner in the x-direction is corrected by the factor x / (x+a). Similarly, the deviation of the semi-axis y=r+b in the y-direction can be compensated by correcting the measurement scanner in the y-direction by the factor y=y / (y+b).

[0014] Preferably, an OCT (Optical Coherence Tomography) scanner of optical coherence tomography can be used as a measuring scanner. In such an OCT scanner, the object is illuminated with light of a low coherence length and the reflected and / or scattered light is compared with a reference beam using an interferometer. The test body is scanned at specific points with an OCT scanner, which is also called an OCT measuring scanner, and its contour is recorded with a very high resolution. OCT scanners are characterized by high accuracy or high sensitivity and high measuring speed.

[0015] Preferred embodiments of the method according to the present invention are described in more detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 shows a schematic representation of a laser processing device with laser processing optics and a measuring scanner;

[0017] Figure 2 shows a plan view of a test body with circular markings;

[0018] Figure 3 The xy coordinate system of the target state and the actual state of the measurement scan is shown. DETAILED DESCRIPTION

[0019] Figure 1The exemplary schematic side view of the laser processing device 10 shown in FIG. 1 has a laser processing optical device 11, which receives a processing laser beam 12 from a laser source (not shown) via an optical fiber cable 13 or an optical waveguide and comprises at least one optical device 14, through which the processing laser beam 12 passes. The optical device 14 is designed as a collimating lens for collimating the incident processing laser beam 12. The laser processing device 10 can be designed for different processing of workpieces by means of laser radiation, for example for welding or cutting workpieces. A first mirror 15 and a second mirror 16 are arranged in the laser processing optical device 11, each of which deflects the processing laser beam 12 by 90°, wherein the lens optical device (not shown here) focuses the processing laser beam 12 onto a test body 17. Further optical elements can be included in the laser processing optical device 11. The method described here refers to a calibration process; in this method, the processing laser beam 12 for processing the workpiece is not used.

[0020] A measuring scanner 20 is also coupled to the laser processing device 10, which measuring scanner can preferably be arranged in an exchangeable manner and is designed as an OCT scanner. Figure 1 In the embodiment of the present invention, a measuring scanner 20 is arranged on the left side of the laser processing optics 11. The measuring scanner 20 receives the measuring laser beam or measuring beam 21 via an optical waveguide 22. The measuring beam 21 is guided via a first mirror 23 and a second mirror 24 of the measuring scanner 20, which usually deflect the measuring beam 21 two-dimensionally, to a third mirror 25, which couples the measuring beam 21 coaxially into the processing laser beam 12 via a first mirror 15 of the laser processing optics 11, which is transparent for the measuring beam 21. The measuring beam 21 is then focused together with the processing laser beam 12 onto the test body 17 via a second mirror 16 of the laser processing optics 11.

[0021] The laser processing device 10 is also equipped with a camera 30 and an illumination device 31. The camera 30 receives light 33 reflected back from the test body 17, which is guided to the camera 30 from the mirror 16 and the mirror 32 in the laser processing optical device 11.

[0022] Figure 2 A schematic detailed representation of a test body 17 is shown, which has a circular marking 18 .

[0023] In a first method variant, a test body 17 with known dimensions, in particular with a known radius r of a marking 18, is placed in the focus of the machining laser beam 12. Subsequently, with the machining laser beam 12 switched off, the test body 17 is scanned point by point in the x- and y-directions by means of the first mirror 15 and the second mirror 16 of the laser machining optics 11 by means of the measuring beam 21 of the measuring scanner 20, and a three-dimensional measurement scan of the test body 17 is created. Figure 3 The xy coordinate system in indicates the target coordinate system, while the x'-y' coordinate system is the coordinate system actually measured by the measuring scanner 20. The data of the dimensions of the test body 17 in the measuring scan are compared with the stored target data of a known test body 17 in the evaluation device (not shown here). In particular, it is checked whether the mark 18 is also circular in the measuring scan and has a known radius r. If it is found that the radius of the measuring scan in the x direction deviates from the known radius r by a distance a, where a can have positive or negative values, the calibration of the measuring scanner 20 in the x direction is corrected by the factor x / (x+a). In the same way, if the radius of the mark 18 in the measuring scan deviates by an amount b, the calibration of the measuring scanner 20 in the y direction can be corrected. The correction factor is then y / (y+b).

[0024] After correcting the calibration of the measurement scanner 20 , a new measurement scan is created and checked to see whether the deviations of the previously detected measurement scan from the target value have been corrected. Figure 3 It is shown how the measurement is performed: the test body 17 is scanned by the measuring beam 21 in increments δx in the x-direction and in increments δy in the y-direction. If the resolution in the x-direction and in the y-direction is correct, the measuring scan will produce a circular mark with a radius r. However, if the resolution in the x-direction and / or in the y-direction deviates, the measured values ​​deviate from the target values ​​of the test body 17 and the measuring scanner 20 is readjusted in a subsequent processing step. In addition to the deviations in the x-direction and in the y-direction, angular deviations are also measured and corrected if necessary. and

[0025] In a second method variant, a test body 17 with circular marks 18 or features of unknown size is used. In the second method variant, the test body 17 is first scanned by the laser processing optics 11, wherein the measuring beam 42 of the laser processing optics 11 is supplied from the fiber optic cable 13 or the optical waveguide via the laser processing optics 11. The low-power measuring beam 42 of the laser processing optics 11 passes through the laser processing optics 11 instead of the high-power processing laser beam 12; this measuring beam 42 is defined as the measuring beam 42 of the laser processing optics 11. Therefore, the laser source either generates the high-power processing laser beam 12 for processing the workpiece or generates the measuring beam 42 of the laser processing optics 11 for scanning the test body 17. The measuring beam 42 is deflected by the first mirror 15 and the second mirror 16 of the laser processing optics 11. The volume model of the test body 17 created in this way is then used as a reference model for subsequent measurement scans created by the measuring scanner 20 with the measuring beam 21 as described above. The measuring beam 21 supplied from the optical waveguide 22 to the measuring scanner 20 and passing through the measuring scanner 20 is defined as the measuring beam 21 of the measuring scanner 20, which scans or sweeps the test body 17 similarly to the measuring beam 42 of the laser processing optics 11. Here too, as in the first method variant, deviations of the recorded data of the measuring scan in the x-direction and the y-direction from the reference values ​​as well as angular deviations are detected and, if necessary, corrected by changing the calibration of the measuring scanner 20.

[0026] Reference numerals list

[0027] 10 Laser processing equipment

[0028] 11 Laser processing optical devices

[0029] 12 Processing laser beam

[0030] 13 Fiber Optic Cable

[0031] 14 Optical Devices

[0032] 15The first mirror of laser processing optical devices

[0033] 16 Second mirror of laser processing optics

[0034] 17 Test body

[0035] 18 Mark

[0036] 20 Measurement Scanner

[0037] 21 Measuring beam of the measuring scanner

[0038] 22 Optical waveguide

[0039] 23 Measuring the first mirror of the scanner

[0040] 24 Measuring the second mirror of the scanner

[0041] 25 The Third Mirror

[0042] 30 Cameras

[0043] 31 lighting fixtures

[0044] 32 Mirror

[0045] 33 Reflected Light

[0046] 42 Measurement beams for laser processing optics

Claims

1. A method for calibrating a measuring scanner (20) on a laser processing optical device (11) of a laser processing device (10), characterized in that: A measurement scan of a test body (17) is created using a measuring beam (21, 42), the measurement scan is subsequently compared with reference data of the test body (17), and a measurement scanner (20) is corrected if the measurement scan data of the measurement scan deviate from the reference data so that the measurement scan data is consistent with the reference data of the test body (17).

2. The method according to claim 1, characterized in that The measuring beam (21) is deflected by the measuring scanner (20), wherein a test body (17) with known dimensions is used and the known dimensions are used as reference data for comparison of the measuring scan data.

3. The method according to claim 1, characterized in that The measuring beam (42) is provided by the laser processing optics (11), wherein a test body (17) of unknown dimensions is used and the measuring beam (42) is deflected by the laser processing optics (11) to create a measuring scan of the test body (17), and scan data from the measuring scan of the measuring beam (42) of the laser processing optics (11) is used as reference data to be compared with scan data of a subsequently performed measuring scan of the test body (17) using the measuring beam (21) of the measuring scanner (20).

4. The method according to claim 3, characterized in that The measuring beam (42) supplied from the laser processing optics (11) to the test body (17) is supplied to the laser processing optics (11) via a fiber optic cable (13).

5. The method according to one of the preceding claims, characterized in that After calibration of the measurement scanner (20) has been performed, a measurement scan is recreated and the scan data of the measurement scan is compared with the reference data.

6. The method according to one of the preceding claims, characterized in that A three-dimensional model of the test body (17) is created using the measurement scan.

7. The method according to one of the preceding claims, characterized in that A circular test body (17) or a test body with circular markings (18) is used.

8. The method according to claim 4, characterized in that The semi-axis of the circular marking (18) or the semi-axis of the test body (17) is measured in the x-direction and the y-direction.

9. The method according to one of the preceding claims, characterized in that An OCT scanner is used as the measuring scanner (20), wherein the measuring beam (21) is an OCT measuring beam.

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