Method for calibrating a laser processing system

Abstract

The invention relates to a method for calibrating a laser processing system having a scanner device for deflecting a laser beam into a plurality of positions on a surface, and having an observation device, the observation beam path of which extends coaxially to the laser beam path through the scanner device, the invention relates to a method for processing a workpiece by means of a laser beam, comprising the calibration of a scanner device and the calibration of an observation device, and to a laser processing system for processing a workpiece by means of a laser beam, comprising a control device which is designed to carry out the method.

Description

Technical Field

[0001] The present disclosure relates to a method for calibrating a laser processing system, the laser processing system having a scanner device and an observation device, the scanner device being used to deflect a laser beam to a plurality of positions on a surface, the observation beam path of the observation device extending through the scanner device coaxially with the laser beam path, the method comprising calibration of the scanner device and calibration of the observation device, and to a laser processing system for processing a workpiece by means of a laser beam, the laser processing system comprising a control device which is configured to perform the method. Background Art

[0002] In systems for material processing by means of lasers, i.e. in laser processing systems, a laser beam emerging from a laser light source or the end of a laser conducting fiber is focused or bunched onto the workpiece to be processed by means of beam guiding optics and focusing optics. As a standard, a laser processing head with collimator optics and focusing optics is used, wherein the laser is supplied via an optical fiber. The laser beam, i.e. the processing laser beam, can be directed to different positions on the workpiece by means of a scanner device. Usually, the scanner device comprises at least one scanning element, for example at least one scanning mirror, which can be pivoted about one or two axes in order to deflect the laser beam. In order to observe the process and / or to monitor the process, a coaxial observation device, for example a camera, is also usually used, the optical path of which extends at least partially coaxially or together with the optical path of the laser beam through the scanner device.

[0003] In conventional laser processing systems with a scanner device, for example an xy galvanometer scanner device with two scanning elements, the focus position is determined by the scanner setting, i.e. by the angle of the scanning element. In this case, the focus position generally shows a nonlinear dependence on the angle of the scanning element. This is mainly due to at least one of the following reasons: 1) The spacing between the two scanning elements can lead to geometric, pillow-shaped 2) Focusing optics, such as F-Theta lenses or F-Theta lenses, can cause barrel distortion. Optical distortion. 3) Mechanical misalignment between the laser beam and the axis of rotation of the scanning elements, for example when the laser beam impinges on one or both scanning elements outside the axis of rotation of the scanning elements, and / or angular deviations of the scanning elements can also contribute to nonlinearities in the dependence of the focus position on the scanner settings. 4) In laser processing systems without encoder feedback, nonlinear correlations between the angle of the scanning elements and the voltage applied to the galvanometer can lead to systematic offsets. In laser processing systems with encoder feedback, systematic errors of the encoder can also lead to distortions. 5) Furthermore, thermal effects can lead to position drifts.

[0004] For applications with low precision, the geometrical and optical distortions according to 1) and 2) can be simulated with the aid of software for beam tracing ("ray tracing") in order to determine the assignment between the position in the world coordinate system and the galvanometer angle or the scanner setting required to deflect the laser beam to this position, i.e. between the world coordinate system and the scanner coordinate system. In reality, however, there are differences of approximately 500 μm or more between the simulation and the actual result with positioning errors, so that this solution is not suitable for precise applications.

[0005] In addition, the same problems as those in the case of positioning the laser beam also occur in the case of a coaxial viewing device, which has an optical path that is at least partially identical to that of the laser beam. As is known, due to the different wavelengths of the viewing illumination and the laser beam, i.e. due to chromatic aberrations, both systems, namely the scanner device and the viewing device, need to be calibrated separately. In addition, in the case of the viewing device, perspective distortions also occur if the scanning area is viewed at different angles by the scanning element and / or lens distortions caused by the lenses of the optical system of the viewing device. Therefore, in order to measure positions on the workpiece, such as the focal position of the laser beam or the laser position, by means of a coaxial viewing device, it is necessary to establish a nonlinear relationship between a pixel coordinate system (also called an image coordinate system or a camera coordinate system) and a world coordinate system (also called a reference coordinate system or a calibration coordinate system). In other words, it is necessary to determine which pixel coordinates in the image of the viewing device (or which pixel of the camera) correspond to the position x, y in the world coordinate system for a given scanner setting (e.g. galvanometer angles α and β).

[0006] Finally, the following question remains: what is the world coordinate system in the first place, how can the observation system, in particular the observation device, and the laser system, in particular the scanner device, be calibrated to the same world coordinate system in order to synchronize the two systems with each other. Unfortunately, there are many approaches to solving this coordination problem, which hinders the comparison or evaluation of different solutions. For this reason, the task is defined as follows in the present disclosure: 1) determine the assignment or function between the (reference) world coordinate system and the galvanometer angle for the laser beam (i.e. the scanner setting or scanner coordinate system) or between the (reference) world coordinate system and the scanner coordinate system, and 2) determine the assignment or function between the (reference) world coordinate system and the pixel coordinate system. As a result, the problem of observation coordinates and scanner coordinates is divided into two separate sub-problems in order to evaluate the results independently of each other, in that the actual position of the laser beam or the measured position in the image is compared with a reference object.

[0007] US 5,430,666 relates to an automated method and device for calibrating laser scanning in a laser sintering system. EP 3 046 747 relates to a system and method for calibrating a laser scanning system. In both documents, the so-called "mark and measure" method is used, in which a calibration plate or calibration sheet is marked by means of a laser beam and then measured by means of a scanner device or an external camera.

[0008] In a scanner laser processing system with a coaxial observation device, it is necessary to calibrate not only the scanner device but also the observation device, in which the observation device is used, for example, to position the laser beam. First, if the scanner device is calibrated with the aid of an external instrument, it is necessary to calibrate the observation device with the aid of a reference object, such as a calibration plate, which is the same as the reference object used to calibrate the scanner device. To this end, the calibration plate needs to be perfectly oriented to the axis of the scanner device and the working distance needs to be accurately adjusted, which is difficult in practice. Slight deviations in the length reference or in the pattern recognition algorithm can already lead to systematic errors. Another difficulty is that during the operation of the laser processing system, not only the scanner device but also the observation device is calibrated at the customer's place. Usually, due to the high time consumption or also due to the lack of suitable instruments, calibration with the aid of a flatbed scanner device is impossible. Summary of the invention

[0009] The object of the present invention is to provide a method for calibrating a scanner device, in particular an xy galvanometer scanner device, for a laser processing system, which does not require any external instruments and which comprises the scanner device and is configured to carry out the method.

[0010] The object of the present invention is in particular to provide a method for calibrating a scanner device for a laser processing system, in particular an xy galvanometer scanner device, and a laser processing system, which includes a scanner device and is set up to carry out the method, wherein, in particular when the scanner device has not been calibrated or has not been calibrated with sufficient accuracy by the manufacturer, a connection is established between a nonlinear scanner coordinate system or a nonlinear behavior of a scanner setting for deflecting the laser beam and a linear reference coordinate system or world coordinate system.

[0011] Another object of the present invention is to provide a method for calibrating a scanner device, in particular an xy galvanometer scanner device, and for calibrating a coaxial observation device for a laser processing system, and a laser processing system, which includes a scanner device and a coaxial observation device and is configured to perform the method.

[0012] The object of the present invention is in particular to propose a method for calibrating a scanner device, in particular an xy galvanometer scanner device, and for calibrating a coaxial observation device for a laser processing system, and a laser processing system, which comprises a scanner device and a coaxial observation device and is configured to carry out the method, wherein an observation coordinate system and a scanner coordinate system or scanner settings for deflecting the laser beam are accurately synchronized or coordinated with each other.

[0013] At least one of these tasks is achieved by the subject matter according to the invention.

[0014] The invention is based on the idea of ​​determining the relationship between the world coordinate system and the scanner settings (e.g. the angle of the galvanometer mirror) when using a coaxial viewing device included in the laser processing system. Thus, the use of external measuring devices is omitted. In addition, the coaxial viewing device and the scanner device can be calibrated to the same reference or relative to the same calibration plate, so that the same length reference is used for both calibrations. In addition, the same pattern recognition algorithm can be used for both calibrations.

[0015] According to one aspect of the present invention, a method for calibrating a laser processing system having a scanner device and having an observation device includes calibration of the scanner device, which is used to deflect a laser beam to multiple positions on a surface (for example, a workpiece and / or a calibration plate), and the observation beam path of the observation device extends through the scanner device coaxially with the laser beam path, and the calibration has the following steps: generating laser marks on the calibration plate with multiple predetermined scanner settings; recording images of the calibration plate and a calibration pattern by the observation device, respectively, the calibration pattern having periodically arranged pattern units, and determining in each image (especially relative to the pattern unit containing the corresponding laser mark) the mark position of at least one of the laser marks on the calibration plate relative to the calibration pattern; based on the determined mark position, determining scanner calibration data for each predetermined scanner setting in the predetermined scanner settings, so as to assign a position to the predetermined scanner settings in the world coordinate system, especially the position of the laser beam in the corresponding scanner setting.

[0016] According to one aspect of the present invention, a method for calibrating a laser processing system having a scanner device and an observation device includes calibration of the scanner device, which is used to deflect a laser beam to multiple positions on a surface (for example, a workpiece and / or a calibration plate), and the observation beam path of the observation device extends through the scanner device coaxially with the laser beam path, and the calibration has the following steps: generating laser marks on the calibration plate with multiple pre-given scanner settings, wherein the calibration plate has a calibration pattern, and the calibration pattern has periodically arranged pattern units; recording an image of the calibration plate with each pre-given scanner setting in the pre-given scanner settings by the observation device, and determining in each image (especially relative to the pattern unit containing the corresponding laser mark) a mark position of the corresponding laser mark on the calibration plate relative to the calibration pattern; based on the determined mark position, determining scanner calibration data for each pre-given scanner setting in the pre-given scanner settings, so as to assign a position to the pre-given scanner settings in the world coordinate system, especially the position of the laser beam in the case of the corresponding scanner setting.

[0017] That is, according to the present disclosure, calibration of the scanner device of the laser processing system is performed by means of the coaxial observation device of the laser processing system and the calibration plate having the calibration pattern without the need for an external measuring instrument.

[0018] According to another aspect of the present disclosure, a laser processing system for processing a workpiece by means of a laser beam comprises: a scanner device for deflecting the laser beam to a plurality of positions on a surface; an observation device, an observation beam path of the observation device extending through the scanner device coaxially with the laser beam path; and a control device configured to execute a method for calibrating a laser processing system according to one of the aspects and / or embodiments described in the present disclosure.

[0019] A method for calibrating a laser processing system and / or a laser processing system according to one of these aspects may include at least one or more of the following features:

[0020] The scanner device can be an xy galvanometer scanner device, which has at least one deflectable scanning element (e.g., a scanning mirror), in particular, two deflectable scanning elements. At least the angular setting of the scanning element can also be referred to as a scanner setting. The scanner setting for a certain deflection of the laser beam can be two-dimensional, that is, it can include two values, for example, a first value for setting a first scanning element and a second value for setting a second scanning element. In other words, the scanner device can be set up to deflect the laser beam in two different directions (i.e., forming an angle with each other). The scanner setting can specify the deflection of the laser beam and / or the position of the laser beam on the surface (laser position). The scanner device can be set up to deflect the laser beam in a predetermined scanning area. That is, the following area is called a scanning area: the laser beam can be directed into this area with the help of the scanner device. The scanning area can have a size of ≥100 mm x ≥100 mm or ≥200 mm x ≥200 mm or ≥250 mm x ≥250 mm. The scanning area is not necessarily square.

[0021] According to the method according to the invention, a position in world coordinates can be assigned to each of the predefined scanner settings. The position in world coordinates can be the position of the laser beam on the surface and / or on the calibration plate in the case of the corresponding scanner settings. In particular, the position in world coordinates can be the position of the laser beam, which the laser beam assumes on the surface and / or on the calibration plate at a predefined (working) distance, i.e., a distance from the surface or the calibration plate, with the corresponding scanner settings.

[0022] The world coordinate system may be defined relative to the calibration plate and / or relative to the laser processing system (or a component of the laser processing system).The calibration pattern may define the world coordinate system.

[0023] The observation device can be a camera, a CCD camera, a grayscale image camera or the like. The observation device can be set up to record a two-dimensional image of a calibration plate, in particular a calibration pattern. The observation device can have an image area that is smaller than or equal to the scanning area of ​​the scanner device. In the present disclosure, the following observation device is also referred to as a coaxial observation device: the observation beam path of the observation device extends coaxially with the laser beam path of the laser processing system at least in sections. For example, the observation beam path of the observation device is coupled into the beam path of the laser beam in front of the scanner device (i.e., in front of the scanner device in the propagation direction of the laser beam) through a beam splitter. Therefore, the observation beam path of the observation device extends through / through the scanner device.

[0024] The calibration plate may be or may comprise a metal plate or a thermal paper. The calibration plate may have a calibration pattern, i.e. the calibration pattern may be applied, marked, imprinted on the calibration plate or the like. The laser marking may be produced on the calibration plate with the calibration pattern. Alternatively, after producing the laser marking, a transparent film may be placed on the calibration plate, which has the calibration pattern. For example, the calibration pattern may be printed on the film. The calibration plate and / or the calibration pattern may cover the entire scanning area. The laser marking may be an optically visible mark by means of a laser beam, such as a weld penetration or the like.

[0025] The calibration pattern has a plurality of periodically arranged pattern units. The pattern unit may have a square, triangular or quadrilateral profile. The individual pattern units may be identical to each other. The world coordinate system may be defined by the calibration pattern. The calibration pattern may include a grid pattern or a checkerboard pattern. That is, the pattern unit may form a grid pattern or a checkerboard pattern. On the one hand, the checkerboard pattern has the following advantages: laser markings may be produced on black pattern units and / or on white pattern units for optimizing contrast. On the other hand, the checkerboard pattern may be easily identified with high accuracy and reliability. In the case of a checkerboard pattern, the pattern unit may be defined so that the pattern unit includes two black areas arranged diagonally to each other and two white areas arranged diagonally.

[0026] The pattern units are arranged in the calibration pattern periodically, i.e., with a predetermined period. In other words, the pattern units are repeated periodically in the calibration pattern. The pattern units can be arranged in the calibration pattern with a predetermined first period (or x period) in a first direction (x direction) and / or with a predetermined second period (or y period) in a second direction (y direction). Preferably, on the one hand, the period of the calibration pattern and / or the size of the pattern units are large enough so that the laser marking can also be produced with the aid of an uncalibrated scanner device and / or in a case where the calibration plate has an orientation error for the entire scanning area, respectively, in one pattern unit. On the other hand, preferably, the size of the pattern units is small enough so that local nonlinearity and / or optical distortion of the image area of ​​the observation device can be detected during calibration, and / or multiple periods of the calibration pattern are present in the image area. For example, the size of each pattern unit can be 5 mm2.

[0027] The laser markings can be produced row by row. In each pattern unit, a laser marking can be produced. The laser markings can be produced at regular intervals. For example, the laser markings can be produced at intervals of 10 mm, for example in the case of a checkerboard pattern, in the black areas of the pattern units. The laser markings can be produced at regular intervals in the first and / or in the second direction, wherein the first and second directions can be perpendicular to each other.

[0028] A pattern element which corresponds to the position of the laser beam given certain scanner settings or in which a laser marking would be produced given certain scanner settings may also be referred to as a target pattern element.

[0029] The pattern units corresponding to the predetermined scanner settings, the so-called target pattern units, can be evenly distributed over the entire scanning area. In this way, it can be ensured that the entire scanning area is covered or that a calibration is performed for the entire scanning area. The laser marking can be produced in each pattern unit in the scanning area with the predetermined scanner settings. In other words, the predetermined scanner settings can correspond to all pattern units in the scanning area. In this case, the calibration can be performed with particularly high resolution or accuracy.

[0030] The predefined scanner settings can be selected such that each of the predefined scanner settings corresponds to a different pattern unit. In other words, the predefined scanner settings can be selected such that a laser mark is produced in a different pattern unit with each of the predefined scanner settings.

[0031] When calibrating the scanner device, the laser markings and the images for determining the marking positions of the laser markings are preferably generated with the same scanner settings. In other words, an image of the calibration plate is recorded by the viewing device in each of the predetermined scanner settings, i.e., in each scanner setting for generating the laser markings. Alternatively, however, the marking positions of a plurality of laser markings can also be determined simultaneously, for example when the plurality of laser markings can be seen simultaneously in one recorded image.

[0032] The marking position of the corresponding laser mark on the calibration plate can be determined relative to the pattern unit where the corresponding laser mark is located, in particular relative to the pattern features of the pattern unit, for example relative to at least one corner, at least one edge and / or the center point of the pattern unit. In order to determine the marking position in the image, the pixel position of the laser mark can be compared with the pixel position of at least one pattern feature of the pattern unit where the laser mark is located, so as to calculate the marking position in the world coordinates and / or the relative displacement of the marking position relative to the target position for the corresponding scanner setting. The at least one pattern feature of the pattern unit for determining the marking position can include at least one edge, at least one corner and / or the center point of the pattern unit.

[0033] The scanner calibration data can be based on the determined mark position and the corresponding scanner settings. The scanner calibration data can include a correction table or a lookup table, in which the position in the world coordinates or the position of the laser beam in the world coordinates and the assigned scanner settings are listed. In other words, the scanner calibration data can include a list of the mark positions in the world coordinates and the corresponding scanner settings. The scanner calibration data can include a correction file, which consists of parameters of a mathematical model that describes the relationship between the position in the world coordinate system and the corresponding scanner settings. The position of the laser beam in the world coordinates can be determined for a certain scanner setting through the scanner calibration data. Additionally or alternatively, the scanner calibration data can include a list of offset vectors in the world coordinates and the corresponding scanner settings, wherein the offset vectors respectively describe the offset between the determined mark position and the theoretical position of the laser mark corresponding to the corresponding scanner setting.

[0034] When calibrating the scanner device, in a first step, laser markings can be generated with all predefined scanner settings, and in a second step, all images can be recorded with all predefined scanner settings. The scanner settings for generating the laser markings and the scanner settings for recording the images for determining the marking positions are preferably identical. Alternatively, in a first step, laser markings can be generated with each of the predefined scanner settings and images can be recorded in a second step, and these two steps can be repeated for all predefined scanner settings. In other words, laser markings can be generated and images recorded with one of the predefined scanner settings, and subsequently, further laser markings can be generated and further images recorded with another of the predefined scanner settings, until laser markings have been generated and images recorded for all predefined scanner settings.

[0035] The calibration of the scanner device may further include the verification of the scanner calibration data. The verification of the scanner calibration data may include the following steps: generating a verification laser mark on the calibration plate with a scanner setting corrected based on the scanner calibration data, the corrected scanner setting corresponding to a predetermined position in the target pattern unit (e.g. in world coordinates and / or relative to the target pattern unit); recording an image of the calibration plate with the corrected scanner setting by an observation device, and determining the marking position of the verification laser mark on the calibration plate (e.g. in world coordinates and / or relative to the target pattern unit); comparing the determined marking position with the predetermined position. For example, the predetermined position in the target pattern unit may be the center point of the target pattern unit. In the recorded image, it can be checked whether the marking position of the verification laser mark corresponds to the center point of the target pattern unit. The steps for verifying the scanner calibration data may be performed for a plurality of target pattern units respectively. Here, the target pattern unit may represent the following pattern unit of the calibration pattern: the predetermined position is in the pattern unit. In other words, in order to verify the scanner calibration, a position may be predetermined for one of the plurality of target pattern units in the form of world coordinates. Based on the scanner calibration data, a calibrated scanner setting can be determined for each of these positions so that a verification laser mark can be generated on the calibration plate with the calibrated scanner setting. Next, an image can be recorded with each of these calibrated scanner settings by means of an observation device, and the mark position of the verification laser mark in the world coordinates and / or relative to the target pattern unit can be determined. The determined mark position of the verification laser mark can be compared with a predetermined position. If the two positions are consistent, the scanner calibration data can be regarded as verified. Here, the verification laser mark can also be generated with the same calibrated scanner setting and the image recorded for determining the mark position. The predetermined position in the target pattern unit can correspond to a feature of the target pattern unit, such as a center point, an angle, etc. For each target pattern unit, the predetermined position can be the same.

[0036] The method for calibrating a laser processing system may further comprise calibration of an observation device, the calibration comprising the following steps: determining, for each of a plurality of first and second scanner settings, a position (e.g., in pixel coordinates) of a feature of a first target pattern unit in a first image of a calibration plate recorded with a first scanner setting corresponding to the first target pattern unit, and determining a position (e.g., in pixel coordinates) of a (preferably corresponding) feature of a second target pattern unit in a second image of the calibration plate recorded with a second scanner setting corresponding to the second target pattern unit, the second scanner setting being shifted relative to the first scanner setting; determining, for each of a plurality of first and second scanner settings, a feature shift (e.g., in pixel coordinates) by comparing a position of a feature of the first target pattern unit in the first image with a position of a (preferably corresponding) feature of the second target pattern unit in the second image, taking into account a shift between the first and second scanner settings and a period of the calibration pattern; and determining image calibration data based on the determined feature shift for correcting chromatic aberration for each of the first scanner settings.

[0037] In this way, it can be ensured that the observation device and the scanner device can be calibrated relative to the same reference system, that is, relative to the world coordinate system of the calibration plate. In addition, when calibrating the observation device, the same calibration plate and / or pattern recognition algorithm as used when calibrating the scanner device can be used to identify the characteristics of the calibration pattern, that is, the characteristics of the pattern unit. After correcting the chromatic aberration, the target pattern unit should be in the center point of the corresponding image (that is, the image recorded under the scanner settings corresponding to the target pattern unit). Due to chromatic aberration, the displacement of the pattern unit in the pixel coordinates can occur in a manner related to the scanner settings. It should be pointed out here that the optical elements of the laser processing system are usually optimized according to the wavelength of the laser beam, so that optical errors occur for visible light.

[0038] In other words, in the image, the positions in world coordinates may be shifted in a manner related to the scanner settings when recording the image. Therefore, it may be necessary to calibrate the viewing device to correct for chromatic aberrations in order to assign positions in pixel coordinates (i.e. positions in the image) to positions in world coordinates (i.e. positions on a calibration plate or on a surface). Positions in pixel coordinates may also be referred to as pixel positions.

[0039] This means that the observation device can be calibrated without the laser beam being radiated. When calibrating the observation device, two images recorded by the observation device with different scanner settings can be compared.

[0040] In contrast, a scanner setting corresponding to a target pattern unit can represent a scanner setting in which the laser beam is located in the pattern unit. The first or second target pattern unit can be characterized by pattern features and / or laser markings, in particular verification laser markings, in the target pattern unit, such as edges, corners, center points of the first or second target pattern unit. The features of the first target pattern unit can correspond to the features of the second target pattern unit, i.e. the features can be specific corners or center points of the target pattern unit, respectively.

[0041] Determining the position of the feature of the target pattern unit in the image can result in the position in pixel coordinates. Similarly, the feature shift in pixel coordinates can be described. If the features of the first and second target pattern units correspond to each other and the shift between the first and second scanner settings corresponds to an integer multiple of the period of the calibration pattern, the position of the feature in the first and second images should be the same, i.e. there should be no feature shift or the feature shift should be zero.

[0042] The second scanner setting may be shifted relative to the first scanner setting by at least one period of the calibration pattern. In other words, the shift between the first and second scanner settings may correspond to at least one period of the calibration pattern. Preferably, the first target pattern unit and the second target pattern unit are continuous pattern units of the calibration pattern. That is, the first target pattern unit and the second target pattern unit may be adjacent to or directly adjacent to each other.

[0043] The first scanner setting and the second scanner setting or the first target pattern unit and the second target pattern unit or the first image and the second image can be referred to as a comparison pair of scanner settings or a comparison pair of target pattern units or a comparison pair of images, respectively, for determining the characteristic shift. The determination of the characteristic shift can be performed for multiple comparison pairs. A first scanner setting of the multiple first scanner settings can, for example, shift from one target pattern unit to the next target pattern unit line by line.

[0044] The first scanner setting and the second scanner setting can be included in the predetermined scanner setting for calibrating the scanner device. In this case, the first image and the second image can be images that are recorded for calibrating the scanner device, in particular for determining the marking position of the laser marking. The first image and the second image can also be images that are recorded for verifying the scanner calibration data. Here, then, preferably, the center point of the target pattern unit can be used as a feature of the first and second target pattern unit. The feature shift can be defined by means of a shift vector in pixel coordinates. The feature shift can be defined as a deviation of the position of the feature of the second target pattern unit in the second image from a theoretical position of the feature of the second target pattern unit, which theoretical position can be expected based on the shift between the first and second scanner setting and the period of the calibration pattern.

[0045] Based on the characteristic shifts determined for a plurality of first and second scanner settings (or for a plurality of comparison pairs of scanner settings), image calibration data can be determined for correcting chromatic aberrations for each scanner setting in the first and / or second scanner settings. The image calibration data can be based on the determined characteristic shifts and the corresponding scanner settings. That is, the image calibration data can indicate a corresponding pixel position for each scanner setting, which corresponds to the position of the laser beam and / or the position of a feature (e.g., a center point) of a target pattern unit in the image under the scanner setting. The image calibration data can include a list of scanner settings and corresponding pixel positions. The image calibration data can include a correction table or a lookup table, wherein, for a corresponding scanner setting, a position in world coordinates or a position of the laser beam in world coordinates is assigned to a corresponding pixel position in the image recorded under the corresponding scanner setting. For a certain scanner setting, the position of the laser beam in the image, i.e., the position of the laser beam in pixel coordinates, can be assigned to the position of the laser beam in world coordinates by means of the image calibration data. As a result, error-free process observation and / or process guidance becomes possible.

[0046] The image calibration data for correcting chromatic aberrations can include a list of positions in world coordinates corresponding to the scanner setting and characteristic shifts in pixel coordinates ascertained for the first scanner setting.

[0047] Image calibration data for correcting chromatic aberrations may include a list of shift vectors in pixel coordinates and corresponding positions in world coordinates corresponding to scanner settings. The shift vectors may respectively describe deviations of positions of features of the second target pattern element in the second image from theoretical positions of the features of the second target pattern element that can be expected based on the shift between the first and second scanner settings and the period of the calibration pattern.

[0048] The features used to determine the marking position when calibrating the scanner device can be identical to or different from the features used to determine the feature displacement when calibrating the viewing device.

[0049] For a plurality of first and second scanner settings, the calibration of the observation device can respectively include: recording a first image of the calibration plate with a first scanner setting corresponding to the first target pattern unit and recording a second image of the calibration plate with a second scanner setting corresponding to the second target pattern unit, the second scanner setting being shifted relative to the first scanner setting, wherein the first and second scanner settings are corrected based on scanner calibration data. Alternatively, the plurality of first and second scanner settings can be contained in a plurality of predefined scanner settings for calibrating the scanner device, and / or the first and second images can respectively be images recorded with the corresponding scanner settings for calibrating the scanner device. The scanner calibration data can then be additionally taken into account when determining the feature shift.

[0050] The calibration of the observation device can further include image distortion correction. For some or all of the first and / or second images, the following steps can be performed respectively: correct the image based on image calibration data corresponding to the scanner settings when recording the image for correcting chromatic aberrations; determine the pixel position of at least one feature of a plurality of (or all) pattern units in the corrected image; create a model for image distortion correction for the corresponding scanner settings when recording the image based on a comparison of the determined pixel spacings between the pixel positions with the corresponding spacings of the corresponding features on the calibration plate in world coordinates. For example, in the case of a checkerboard pattern as a calibration pattern, the pixel positions of all corners in the image can be determined, and a model for image distortion correction can be created on this basis and based on the known angular spacings in the world coordinate system (i.e. on the calibration plate).

[0051] The control device of the laser processing system is configured to control the scanner device and / or the viewing device. The control device of the laser processing system is configured to perform an image analysis on the image recorded by the viewing device, for example by applying a pattern recognition algorithm.

[0052] Furthermore, the laser processing system can have focusing optics, in particular an F-Theta lens or an F-Theta lens, for focusing the laser beam. The focusing optics can be arranged behind the scanner device (with respect to the beam propagation direction of the laser beam).

[0053] The laser processing system may be a laser processing system for performing a process on a workpiece by means of a laser beam, in particular a laser processing system for laser cutting, laser welding, laser brazing, laser drilling or the like.

[0054] The workpiece can be a metal workpiece in particular. The laser processing system can be configured for processing metal workpieces. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Embodiments of the present disclosure are shown in the accompanying drawings and described in more detail below. The accompanying drawings show:

[0056] Figure 1 is a schematic diagram of a laser processing system for laser processing a workpiece by means of a laser beam according to an embodiment of the present invention;

[0057] Figure 2 A schematic diagram showing different coordinate systems of a laser processing system according to an embodiment of the present invention that can be synchronized with each other;

[0058] Figure 3A and 3B An example of a calibration pattern of a calibration plate according to an embodiment of the present invention is shown;

[0059] Figure 4A and 4B A flow chart showing a method for calibrating a scanner device according to an embodiment of the present invention;

[0060] Figure 5A and 5B A flow chart showing verification of calibration of a scanner device according to an embodiment of the present invention;

[0061] Figure 6 Flow chart showing a method for calibrating a coaxial viewing device to correct chromatic aberration according to an embodiment of the present invention

[0062] Figure 7 A flow chart showing a method for calibrating a coaxial observation device for image distortion correction according to an embodiment of the present invention;

[0063] Figure 8 A flow chart showing a method for calibrating a scanner device and for calibrating a coaxial viewing device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0064] Unless otherwise indicated, the same reference numerals are used below for identical and identically functioning elements.

[0065] Figure 1 A schematic diagram of a laser processing system 1 according to an embodiment of the present disclosure is shown.

[0066] The laser processing system 1 comprises a scanner device 80 having one or two scanning elements 81, which is used to deflect the laser beam 4 to a plurality of positions on a surface 2, for example, a surface of a workpiece to be processed, and an observation device 60, whose observation beam path 6 extends at least partially coaxially with the beam path of the laser beam 4. The observation device 60 can be or include a camera, in particular a grayscale image camera or a CCD camera. The laser beam 4 and the observation beam path 6 can be coupled by means of a beam coupling element 50, for example, by means of a beam combiner, a dichroic mirror, etc. The coupling of the two beam paths 4 and 6 takes place in front of the scanner device 80 (in the beam propagation direction of the laser beam 4) or between the scanner device 80 and the observation device 60. Therefore, not only the laser beam path 4 but also the observation beam path 6 extends through the scanner device 80. Therefore, depending on the scanner settings, that is, depending on the settings of the at least one scanning element 81, the image area of ​​the observation device 60 is oriented or deflected on the surface. The image field of the observation device 60 contains the impingement points of the laser beam 4 on the surface 2 .

[0067] Furthermore, the laser processing system 1 comprises a control device 70. The control device 70 can be configured to control a scanner device 80, in particular based on scanner settings for positioning the laser beam 4 for laser processing, and / or can be configured to control an observation device 60 for capturing or recording images. Furthermore, the control device 70 can be configured to receive an image of the surface 2 recorded by the observation device 60. The control device 70 can be configured to control a laser source for emitting the laser beam 4.

[0068] The scanner device 80 can be a 1D or 2D galvanometer scanner. The scanner device 80 can include exactly one scanning element 81, for example a scanning mirror, which can be rotated or pivoted about an axis in order to deflect the laser beam 4 on the surface 2. The scanning element can also be rotated or pivoted about two mutually different axes in order to deflect the laser beam 4 on the surface 2 in two different directions, for example in two orthogonal directions x and y. Even in Figure 1 Although not shown in the figure, the scanner device 80 preferably comprises two scanning elements 81 or scanning mirrors, which can each be rotated or pivoted about an axis in order to deflect the laser beam 4 in two different directions, for example in two orthogonal directions x and y, on the surface 2. The control device 70 can be configured to set the scanner device 80 according to a scanner setting, for example an angle pair (α, β). The scanner setting can be regarded as a position in the scanner coordinate system.

[0069] In addition, the laser processing system 1 may have a collimating optical device 10 for collimating the laser beam 4 that diverges into the laser processing system 1, and a focusing optical device 30, such as an F-Theta lens, for focusing the laser beam 4 relative to the surface 2. In particular, the laser beam 4 emitted from the end of the laser light source or the laser conducting fiber 5 can be focused or bundled on the surface of the workpiece 2 to be processed by means of the collimating optical device 10 and the focusing optical device 30, so as to perform processing or a processing process. The processing may include, for example, laser cutting, laser brazing, laser melting welding or laser drilling.

[0070] In the case of a laser processing system 1 having a scanner device 80 and a coaxially mounted observation device 60, the position of the laser beam 4 and the scanner settings are nonlinearly related to one another. Therefore, a calibration of the scanner device 80 or a synchronization of the scanner coordinate system 800 with the world coordinate system 200, i.e. with the spatial coordinates x, y, z of the processing area is necessary. Likewise, the pixel coordinate system of the observation device 60 and the world coordinate system of the surface 2 or of the processing area are nonlinearly related to one another. However, in order to also use the observation device 60 for positioning the laser beam 4, it is necessary not only to calibrate the scanner device 80 but also the observation device 60. Therefore, preferably, as Figure 2 As shown, the scanner coordinate system 800 and the pixel coordinate system 600 of the observation device 60 are synchronized with the world coordinate system 200, that is, the spatial coordinates x, y, z of the processing area.

[0071] According to the invention, a method is proposed for calibrating a scanner device 80 by means of a calibration plate 90 having a calibration pattern and a coaxial viewing device 60. Figure 3A and 3B An example of a calibration plate 90 having different calibration patterns is shown in FIG. The calibration pattern may be composed of periodically arranged pattern units 91 (in Figure 3A and 3B The calibration pattern may be defined relative to the world coordinate system 200 or may define the world coordinate system 200. For example, the calibration pattern may be as follows: Figure 3A The grid shown or Figure 3B In the case of a checkerboard pattern, the pattern elements 91 can consist of two diagonally arranged black and white areas. To optimize the image contrast, the laser markings 95 can be produced either on the black areas of the calibration pattern or on the white areas of the calibration pattern.

[0072] exist Figure 4A and 4B, a flowchart of a method S100 for calibrating a scanner device 80 according to an embodiment of the present invention is shown in FIG. According to the present invention, first, laser marks 95 are generated (S101) on a calibration plate 90 with a plurality of predetermined scanner settings. The predetermined scanner settings may correspond to some or all pattern units 91, so that a respective laser mark 95 is generated in some or all pattern units 91. Preferably, in the case of each of the predetermined scanner settings, an image of the calibration plate 90 is recorded (S102) by the observation device 60, and in the image, the marking position of the corresponding laser mark 95, i.e. the laser mark 95 generated with the scanner setting, on the calibration plate 90 relative to the calibration pattern is determined (S103). Alternatively, an image of the calibration plate 90 may also be recorded by the observation device 60 in order to determine the marking positions of a plurality of laser marks 95 on the calibration plate 90 relative to the calibration pattern. Based on the determined marking positions, scanner calibration data are determined for all predetermined scanner settings in the predetermined scanner settings, so that a position can be respectively assigned to the predetermined scanner settings in the world coordinate system 200. Optionally, verification of the scanner calibration data may be performed S110 , which is described below with reference to FIG. 5 .

[0073] Figure 4A The method and Figure 4B The method shown in differs only in that, in the case of the i-th scanner setting of the predefined scanner settings, not only is the laser mark generated ( S101 ) but also the image is recorded ( S102 ), and these steps are then repeated for the (i+1)-th scanner setting. Figure 4A As shown, if possible, before changing the scanner setting to the (i+1)th scanner setting, step S103 of determining the marking position of the laser mark produced under the i-th scanner setting and step S104 of determining the scanner calibration data for the i-th scanner setting are also performed. Alternatively, as Figure 4B As shown, first, all laser markings are generated (S101) in all the predetermined scanner settings in the predetermined scanner settings, so that images are subsequently recorded in each of the predetermined scanner settings (S102). That is, each of the predetermined scanner settings is performed twice.

[0074] When obtaining the mark position in S103, the pixel position of the laser mark in the corresponding image relative to the calibration pattern can be determined, and the image is recorded with the same scanner setting as the scanner setting used to generate the laser mark 95. In particular, the pixel position of the laser mark 95 can be compared with the pixel position of at least one pattern feature of the pattern unit 91 where the laser mark is located, so as to calculate the mark position in the world coordinates for the corresponding scanner setting. Here, the pixel position represents the position in the image recorded by the observation device 60, that is, the position in the pixel coordinate system. For example, the pattern feature can be at least one of the following features: the center point of the pattern unit 91, the upper left corner of the pattern unit 91, the lower left corner of the pattern unit 91, the upper right corner of the pattern unit 91, the lower right corner of the pattern unit 91, the left edge of the pattern unit 91, the right edge of the pattern unit 91, the upper edge of the pattern unit 91, and the lower edge of the pattern unit 91. For example, after the laser mark 95 is generated, the mark position can be determined by comparing the pixel position of the laser mark 95 with the pixel positions of the four corners surrounding the laser mark 95. Since the calibration pattern, in particular the size of the pattern unit 91 and / or the position of the pattern unit 91 in the world coordinate system 200 is known, the position of the marking in the world coordinate system 200 can be determined.

[0075] The scanner calibration data may include a list of marker positions in world coordinates and corresponding scanner settings. From this information, which may be pre-processed, a correction file may be created, which consists of a lookup table of positions in world coordinates and their corresponding scanner settings. Alternatively, the correction file may consist of parameters of a mathematical model that describes the association between positions in world coordinates and their corresponding scanner settings. For example, the correction file may be stored in the control device 70 in order to operate the scanner device 80.

[0076] exist Figure 5A and 5B, a process of verifying S110 the scanner calibration data according to an embodiment of the present invention is shown, which can be optionally performed after calibrating the scanner device 80 at S100. The verification S110 of the scanner calibration data can include the following steps: on the calibration plate 90, respectively generating (S111) verification laser marks in the case of a plurality of calibrated scanner settings. The calibrated scanner settings are scanner settings that are corrected based on the corresponding scanner calibration data. The calibrated scanner settings correspond to a predetermined position in the target pattern unit, for example, a predetermined position in the following pattern unit 91: in which the verification laser mark should be generated. For example, the calibrated scanner settings can respectively correspond to a center point in the target pattern unit. The predetermined position in the target pattern unit can be predetermined relative to at least one pattern feature of the target pattern unit. In addition, an image is recorded (S112) with each of the plurality of calibrated scanner settings by means of the observation device 60, and the mark position of the verification laser mark relative to the calibration pattern, in particular relative to the pattern feature of the target pattern unit, is determined (S113). Next, the pixel position of the verification laser mark in the corresponding image is compared with the predetermined position in the target pattern unit (S114). Thus, it can be checked based on the corresponding recorded image whether the verification laser mark is actually generated at the predetermined position with the calibrated scanner setting corresponding to the center point of the target pattern unit, for example.

[0077] exist Figure 5A In, according to Figure 4A The flow of verification is shown, wherein, in the case of each of the calibrated scanner settings, a verification laser mark is generated in a first step and an image is recorded in a second step, and these two steps are repeated for all calibrated scanner settings. However, in verification S110, as in Figure 5B Corresponding to Figure 4B As shown, it is also possible to generate the verification laser marking in a first step with all calibrated scanner settings and to record all images in a second step with all calibrated scanner settings.

[0078] Additionally, calibration of the viewing device 60 may be necessary, for example to enable image-based positioning of the laser beam 4. The same calibration plate 90 and / or the same image analysis algorithm or pattern recognition algorithm can be used to calibrate the viewing device 60 and to calibrate the scanner device 80. The workload can thus be kept very low. Figure 6, a process for calibrating the viewing device 60 according to an embodiment of the present invention is shown in order to correct chromatic aberrations according to the scanner settings. If the scanner device 80 is perfectly calibrated, the image of the calibration pattern must remain unchanged when the scanner device shifts exactly one period of the calibration pattern. However, due to chromatic aberrations, a slight image deviation occurs so that the calibration pattern between the two images is no longer coincident. When calibrating the viewing device 60 to correct chromatic aberrations, this deviation can be recorded for each scanner setting.

[0079] In order to calibrate the observation device 60, a plurality of scanner settings can be divided into K comparison pairs, each of which has a first and a second scanner setting. Here, the calibration of the scanner device 80 has been completed so that the first and second scanner devices are scanner settings corrected based on the scanner calibration data. For each comparison pair in the comparison pair of scanner settings, the position of a feature in a first target pattern unit corresponding to the first scanner setting of the comparison pair in a first image recorded with the first scanner setting of the comparison pair and the position of a feature in a second target pattern unit corresponding to the second scanner setting of the comparison pair in a second image recorded with the second scanner setting of the comparison pair can be obtained (S201). The first target pattern unit and the second target pattern unit can be adjacent pattern units in the calibration pattern. In other words, the first scanner setting can be shifted relative to the second scanner setting by a period of the calibration pattern. Next, for each comparison pair in the comparison pair of scanner settings, the feature shift from the first image to the second image can be obtained (S202). Here, the pixel position of the feature of the first target pattern unit in the first image can be compared with the pixel position of the feature of the second target pattern unit in the second image, taking into account the shift between the first and second scanner settings and the period of the calibration pattern. Based on the feature shift of the comparison pair for the scanner settings, image calibration data can be obtained (S203) for correcting chromatic aberrations for multiple scanner settings.

[0080] The feature of the first target pattern unit and the feature of the second target pattern unit can be the same, for example, the center point of the target pattern unit. The feature of the first target pattern unit and the feature of the second target pattern unit can be pattern features, or can also be a verification laser mark in the target pattern unit, if the verification laser mark is the same in the predetermined position in the corresponding target pattern unit when verifying the scanner calibration data. In one example, the pixel position of the center point of all target pattern units set by the scanner and its displacement relative to the scanner setting corresponding to the zero position (non-deflected laser beam) can be obtained. Image calibration data for correcting chromatic aberrations may include a list of feature displacements obtained for the scanner setting in the position corresponding to the scanner setting in the world coordinates and in the pixel coordinates. The list can be converted into a lookup table, which describes the exact position of the laser beam 4 for a given scanner setting with the pixel coordinates of the observation device 60. Alternatively, image calibration data for correcting chromatic aberrations may include a list of shift vectors in pixel coordinates and corresponding positions in world coordinates corresponding to scanner settings, and the shift vectors may respectively account for deviations of positions of features of a second target pattern unit in the second image from theoretical positions of features of the second target pattern unit that can be expected based on the shifts between the first and second scanner settings and the periodicity of the calibration pattern.

[0081] The calibration of the observation device 60 may include recording the first and second images of the comparison pair for the scanner setting. Alternatively, the first and second images of the comparison pair for the scanner setting may be images recorded for calibrating the scanner device 80. In this case, when determining S202 the characteristic shift, in addition to considering the shift between the first and second scanner settings and the period of the calibration pattern, the corresponding scanner calibration data may also be additionally considered.

[0082] In addition to chromatic aberrations, further optical errors may occur which lead to image distortions. Therefore, the calibration of the viewing device 60 may further include an image distortion correction S210 in order to correct, for example, effects related to the scanner settings, such as changes in imaging scale, rotation, shearing effects and radial lens distortion effects, for the entire scanning area.

[0083] Image distortion correction S210 can be performed on some or all of the first and / or second images for correcting chromatic aberration. Preferably, image distortion correction S210 is performed on images corresponding to a plurality of scanner settings distributed over the entire scanning area. First, each image is corrected (S211) based on image calibration data corresponding to the corresponding scanner settings used to record the image for correcting chromatic aberration. Next, the pixel position of at least one feature is obtained (S212) for each of the plurality of pattern units 91. For example, the pixel positions of all corners of all pattern units 91 in the image can be obtained. Based on the pixel positions of the features of the pattern units in the world coordinates and the known spacing, a model for image distortion correction can be created (S213) for the corresponding scanner settings used to record the image. In this way, based on the spacing of two pixel positions in an image, the relative positions of the two pixel positions in the world coordinate system 200 are determined with the aid of a model for image distortion correction.

[0084] exist Figure 8 An embodiment of a scanner device 80 and a coaxial observation device 60 for combined calibration S800 of a laser processing system 1 is shown. In step S801, a calibration plate 90 can be arranged in the scanning area of ​​the laser processing system 1 and oriented approximately relative to the axis of the scanner coordinate system 800. Preferably, the calibration plate is larger than the scanning area or completely covers the scanning area. Next, in step S802, a calibration of the scanner device can be performed, wherein laser marks 95 are generated on the calibration plate 80 and the position in the world coordinates is determined for each laser mark with the aid of the coaxial observation device 60 and the calibration pattern of the calibration plate 90. Next, a correction file with the scanner calibration data is generated, i.e., the correction file consists, for example, of a lookup table with world coordinate positions and corresponding scanner settings. As step S802, it is also possible to perform Figure 4A Or the method S100 for calibrating a scanner device 80 shown in FIG. 4B, which has steps S101 to S104. In step S803, a correction file or scanner calibration data is stored and loaded for operating the scanner device 80. In step S804, the calibration of the scanner device is verified by reproducing the laser marking on the same calibration plate 90. As step S804, a calibration process can also be performed in Figure 5AOr the process S110 for verifying the scanner calibration data shown in 5B. In step S805, the same calibration plate 80 and the same pattern recognition algorithm (e.g., corner recognition algorithm and / or edge recognition algorithm) are used to calibrate the observation device to correct chromatic aberration. For example, each scanner can be set to capture all corners of the target pattern unit in the scanning area, and the shift of the angular position can be used to obtain the offset of the chromatic aberration for each scanner setting. The offset of the chromatic aberration is used to generate a lookup table or function of the scanner setting relative to the pixel offset. As step S805, it is also possible to perform Figure 6 . In step S806, the coaxial viewing device is calibrated for image distortion correction. By knowing the angular position in pixel coordinates and the relative position in world coordinates, a model for image distortion correction can be found that converts the relative position in pixel coordinates to the relative position in world coordinates for a given scanner setting. As step S806, method S210 can be performed. In step S807, the calibration of the viewing device can be verified and stored.

[0085] According to the present disclosure, a scanner device of a laser processing system can be calibrated using a calibration plate with a calibration pattern and a coaxial observation device integrated in the laser processing system without the assistance of an external measuring instrument. As a result, the efficiency of calibration can be greatly improved and the cost for calibration can be greatly reduced. Verification of calibration can be easily and directly performed immediately following calibration.

[0086] In addition, the same settings can be used to calibrate a coaxial observation device to correct chromatic aberrations and / or for correcting image distortions. In general, it is more important to calibrate two systems or devices to the same reference object than to calibrate the same device to an absolute reference object. This results in lower requirements for the calibration plate and lower requirements for the orientation process when arranging the calibration plate. In particular, according to the present disclosure, a coaxial observation device can be calibrated to the same reference object as a scanner device, so that the two calibrations can use the same capture algorithm or pattern recognition algorithm and the same length reference object. Since the observation device and the scanner device are calibrated with the help of the same reference object, slight scaling errors in the calibration plate can be better tolerated than calibrating the two devices separately with different methods. In addition, the calibration of the scanner device and / or the observation device can be performed automatically, in addition to the one-time arrangement of the calibration plate.

[0087] Reference numerals list

[0088] 1Laser processing system

[0089] 2 surfaces (workpiece, calibration plate)

[0090] 4 laser beams

[0091] 5Laser transmission fiber

[0092] 6Observe the beam path

[0093] 10 Collimating optics

[0094] 50 Beam coupling element

[0095] 30 Focusing optics

[0096] 60 Observation equipment

[0097] 70 Control device

[0098] 80 Scanner devices

[0099] 81 Scanning element

[0100] 90 Calibration Plate

[0101] 91 pattern units

[0102] 95 Laser Marking

[0103] 200 World Coordinate System

[0104] 600 pixel coordinate system 800 scanner coordinate system

Claims

1. A method for calibrating a laser processing system (1), the laser processing system having a scanner device (80) for deflecting a laser beam (4) to a plurality of positions on a surface (2) and having an observation device (60), the observation device having an observation beam path (6) extending at least in sections coaxially with the laser beam path and extending through the scanner device (80), the method comprising calibrating the scanner device (80), the calibration having the following steps: Generating (S101) laser markings (95) on a calibration plate (90) with a plurality of predetermined scanner settings; Recording (S102) images of the calibration plate (90) and a calibration pattern on the calibration plate (90) respectively by means of the observation device (60), the calibration pattern having periodically arranged pattern units (91), and determining (S103) in each image the marking position of at least one of the laser markings (95) on the calibration plate (90) relative to the calibration pattern; Based on the determined marking positions, scanner calibration data are determined (S104) for each of the predetermined scanner settings in order to respectively assign a position in the world coordinate system (200) to the predetermined scanner settings.

2. The method according to claim 1, in, Producing the laser marking (95) on a calibration plate (90) having the calibration pattern; or After the laser mark (95) is produced (S101) on the calibration plate (90), a transparent film having the calibration pattern is placed on the calibration plate (90).

3. A method according to any one of the preceding claims, wherein: When calibrating the scanner device (80): For each of the predetermined scanner settings, an image of the calibration plate (90) is recorded (S102), and in each image, a marking position of a corresponding laser mark (95) generated with the scanner setting on the calibration plate (90) relative to the calibration pattern is determined (S103); and / or In a first step, the laser marking (95) is produced with all predefined scanner settings, and in a second step, all images are recorded with all predefined scanner settings, or With each of the predefined scanner settings, a laser marking (95) is produced in a first step and an image is recorded in a second step, and these two steps are repeated for all predefined scanner settings.

4. A method according to any one of the preceding claims, wherein: In order to determine the mark position in the image, the pixel position of the laser mark (95) is compared with the pixel position of at least one pattern feature of the pattern unit (91) where the laser mark (95) is located, so as to calculate the mark position in the world coordinate system (200) for the corresponding scanner setting.

5. The method according to claim 4, wherein: At least one pattern feature of the pattern element (91) for determining the marking position comprises at least one edge, at least one corner and / or a center point of the pattern element.

6. A method according to any one of the preceding claims, wherein: The scanner calibration data includes a list of marker locations in world coordinates and corresponding scanner settings; or wherein the scanner calibration data comprises a list of offset vectors and corresponding scanner settings in world coordinates, and the offset vectors respectively indicate an offset between a determined marking position and a theoretical position of the laser marking corresponding to the corresponding scanner settings; or The scanner calibration data comprises a correction file, which consists of parameters of a mathematical model, which describes the relationship between a position in the world coordinate system (200) and a corresponding scanner setting.

7. A method according to any one of the preceding claims, wherein: The calibration of the scanner device (80) further comprises verification of the scanner calibration data (S110), wherein the following steps are respectively performed for a plurality of target pattern units: Producing (S111) a verification laser mark on the calibration plate (90) with a scanner setting calibrated based on the scanner calibration data, the calibrated scanner setting corresponding to a predetermined position in a target pattern element; Recording (S112) the image of the calibration plate with the calibrated scanner setting by means of the observation device (60), and obtaining (S113) the marking position of the verification laser mark on the calibration plate (90) relative to the target pattern unit; The determined marking position of the verification laser marking is compared with the predetermined position ( S114 ).

8. The method according to any one of the preceding claims, further comprising a calibration (S200) of the viewing device (60), the calibration comprising the following steps: For each of a plurality of first and second scanner settings, determining (S201) a position of a feature of a first target pattern unit in a first image of the calibration plate recorded with a first scanner setting corresponding to the first target pattern unit, and determining a position of a feature of a second target pattern unit in a second image of the calibration plate recorded with a second scanner setting corresponding to the second target pattern unit, the second scanner setting being shifted relative to the first scanner setting; for each of the plurality of first and second scanner settings, determining (S202) a feature shift by comparing a position of a feature of the first target pattern unit in the first image with a position of a feature of the second target pattern unit in the second image, taking into account a shift between the first and second scanner settings and a period of the calibration pattern; Based on the obtained characteristic shift, image calibration data is obtained (S203) for setting correction chromatic aberration for the scanner.

9. The method according to claim 8, wherein: For calibrating the viewing device, the features of the target pattern element include at least one edge, at least one corner, a center point and / or a verification laser mark of the target pattern element.

10. The method according to claim 8 or 9, wherein: For each of the plurality of first and second scanner settings, the calibration of the viewing device (60) comprises: recording the first image with the first scanner setting and recording the second image with the second scanner setting, wherein the first and second scanner settings are calibrated based on the scanner calibration data; or Therein, the first images are images recorded with scanner settings corresponding to the corresponding first scanner settings in order to calibrate the scanner device, and the second images are images recorded with scanner settings corresponding to the corresponding second scanner settings in order to calibrate the scanner device, and when determining the feature shift, the corresponding scanner calibration data are additionally taken into account.

11. The method according to claim 8, 9 or 10, wherein: The image calibration data for correcting the chromatic aberrations comprise a list of positions in world coordinates corresponding to the scanner settings and characteristic shifts in pixel coordinates ascertained for the scanner settings; or Wherein, the image calibration data for correcting the chromatic aberration includes a list of shift vectors in pixel coordinates and corresponding positions in world coordinates corresponding to the scanner settings, and the shift vectors respectively describe the deviations of the positions of the features of the second target pattern unit in the second image from the theoretical positions of the features of the second target pattern unit, and the theoretical positions can be expected based on the shifts between the first and second scanner settings and the period of the calibration pattern.

12. The method according to any one of claims 8 to 11, wherein: The shift between the first and the second scanner setting corresponds to a shift by at least one period of the calibration pattern, in particular by an integer multiple of a period of the calibration pattern.

13. The method according to any one of claims 8 to 12, wherein: The first target pattern unit and the second target pattern unit are consecutive pattern units in the calibration pattern.

14. The method according to any one of claims 8 to 13, wherein: The calibration of the viewing device (60) furthermore comprises an image distortion correction, wherein for some or all of the first and / or second images the following steps are respectively performed: correcting (S211) the image based on image calibration data corresponding to scanner settings when recording the image for correcting the chromatic aberration; Determining (S212) the pixel position of at least one feature of each of a plurality of pattern units (91) in the corrected image; Based on a comparison of the determined pixel spacings between the pixel positions with the corresponding spacings of the corresponding features on the calibration plate in world coordinates, a model for the image distortion correction is created (S213) for the corresponding scanner settings when recording the image.

15. A method according to any one of the preceding claims, wherein: The calibration pattern comprises a grid pattern or a checkerboard pattern, and / or Wherein, the periodically arranged pattern units (91) are square, rectangular, quadrilateral or triangular.

16. A laser processing system (1) for processing a workpiece by means of a laser beam (4), the laser processing system comprising: a scanner device (80) for deflecting the laser beam (4) to a plurality of positions on the surface (2); an observation device (60), the observation beam path (6) of which extends coaxially with the laser beam path (4) through the scanner device (80); A control device (70) is configured to carry out the method for calibrating the laser processing system according to any one of the preceding claims.

Images