阅读说明：本技术 激光加工系统及用于激光加工系统的方法 (Laser processing system and method for laser processing system ) 是由 B·许尔曼 N·韦肯曼 于 2019-08-02 设计创作，主要内容包括：本公开涉及一种使用激光束加工工件、优选地利用激光束切割或焊接工件的激光加工系统。所述激光加工系统包括：具有壳体的加工头,所述壳体具有用于从所述加工头(101)发射所述激光束(10)的开口(212)；测量装置(120),其配置为能够引导光学测量光束(13)通过所述开口(212),以及用于使所述激光束(10)和所述光学测量光束(13)对准的光学单元,所述光学单元能够被设定以在开口(212)的区域内垂直于所述加工头(101)的光轴调整所述激光束(10)和所述光学测量光束(13)。测量装置(120)还配置为能够根据基于光学测量光束(13)对于光学单元的不同设定而言的反射的测量值来确定光学单元的与激光束(10)的居中对准相对应的设定。(The present disclosure relates to a laser processing system for processing a workpiece using a laser beam, preferably cutting or welding the workpiece with the laser beam. The laser processing system includes: a processing head having a housing with an opening (212) for emitting the laser beam (10) from the processing head (101); a measuring device (120) which is configured such that an optical measuring beam (13) can be guided through the opening (212), and an optical unit for aligning the laser beam (10) and the optical measuring beam (13), which can be set to adjust the laser beam (10) and the optical measuring beam (13) perpendicular to the optical axis of the processing head (101) in the region of the opening (212). The measuring device (120) is further configured to be able to determine a setting of the optical unit corresponding to the centered alignment of the laser beam (10) from measurements based on reflections of the optical measuring beam (13) for different settings of the optical unit.)

1. A laser machining system for machining a workpiece with a laser beam (10), the laser machining system comprising:

a processing head (101) having a housing (210), the housing (210) having an opening (212) for emitting the laser beam (10) from the processing head (101),

a measuring device (120) configured to be able to guide an optical measuring beam (13) through the opening (212), and

an optical unit for aligning the laser beam (10) and the optical measuring beam (13), which can be set to adjust the laser beam (10) and the optical measuring beam (13) perpendicular to the optical axis of the processing head (101) in the region of the opening (212);

wherein the measuring device (120) is configured to be able to determine a setting of the optical unit corresponding to a centered alignment of the laser beam (10) from measurements based on reflections of the optical measuring beam (13) for different settings of the optical unit.

2. The laser processing system of claim 1, wherein the optical unit comprises:

measuring optics (122, 124, 138, 222, 224, 238) for aligning the optical measuring beam (13), wherein the measuring optics (122, 124, 138; 224, 238) can be set to adjust the optical measuring beam (13) perpendicular to the optical axis of the processing head (101) in the region of the opening (212), and

laser optics (137, 124, 238, 222, 224) for aligning the laser beam (10), wherein the laser optics (137, 124; 238, 222, 224) can be set to adjust the laser beam (10) perpendicular to the optical axis of the processing head (101) in the region of the opening (212),

wherein the measuring device (120) is configured to be able to determine a setting of the laser optics corresponding to a centered alignment of the laser beam (10) based on reflections of the optical measuring beam (13) for different settings of the measuring optics.

3. The laser processing system of claim 1, wherein the optical unit comprises a common optical element (124, 222, 224, 238) arranged in a common beam path of the laser beam (10) and the optical measuring beam (13), the common optical element being configured to be able to shift a beam axis of the laser beam (10) and the optical measuring beam (13) after leaving the opening (212) by shifting the common optical element (124, 222, 224, 238) respectively in a plane perpendicular to the optical axis of the processing head (101).

4. The laser processing system of any of the preceding claims, wherein the measuring device (120) is further configured to be able to determine a distribution of measurement values based on the reflection of the optical measuring beam (13) for different settings of the optical unit, wherein the distribution of measurement values corresponds to the shape of the opening (212).

5. The laser processing system of claim 4, wherein the measuring device (120) is configured to be able to determine a setting of the optical unit corresponding to a center of the opening (212) and to determine a setting of the optical unit for centering the laser beam (10) based on the setting.

6. Laser machining system according to any of the preceding claims, wherein the measuring optics (124; 222; 224, 238) are configured to be able to scan the opening (212) in a plane perpendicular to the optical axis of the machining head (101) using the measuring beam (13).

7. The laser machining system of any one of the preceding claims, wherein the measuring device (120) comprises an optical coherence tomography.

8. The laser machining system of claim 1, wherein the optical unit is configured such that at least a first setting for not passing the measuring beam (13) through the opening (212) and a second setting for passing the measuring beam (13) through the opening (212) and reflecting on a surface (O) are settable along one direction (x, y).

9. The laser machining system of claim 8, wherein the measuring device (120) is configured to be able to detect a position (X4, Y4) of a burn-in (310) in the surface (O) based on reflection and to determine a setting of the optical unit corresponding to a centered alignment of the laser beam (10) based on the position (X4, Y4) of the burn-in (310).

10. The laser processing system according to any of the preceding claims, wherein the measuring device (120) is configured to be able to automatically determine a setting of the optical unit corresponding to a centered alignment of the laser beam (10).

11. The laser machining system of any one of the preceding claims, wherein the laser machining system further comprises at least one automated and/or motorized adjustment device for setting the optical unit.

12. Laser machining system according to any of the preceding claims, wherein the reflection of the optical measuring beam (13) comprises a reflection on a surface (O) outside the machining head (101) and/or within the machining head (101).

13. The laser machining system of any preceding claim, wherein the optical unit comprises at least one of: focusing optics (124, 224) for focusing the laser beam (10) and/or the measuring beam (13), collimator optics (112, 122, 222) for collimating the laser beam (10) and/or the measuring beam (13), a fiber end (137, 138, 238) for introducing the laser beam (10) and/or the measuring beam (13) into the processing head (101), and/or mirrors.

14. A method of centering a laser beam (10) in a processing head (101) of a laser processing system for processing a workpiece (1) with the laser beam (10), wherein the method comprises:

providing (410) the processing head (101) with a housing (210), the housing (210) having an opening (212) for emitting the laser beam (10) from the processing head (101);

-directing (420) an optical measuring beam (13) onto an optical unit for aligning the laser beam (10) and the optical measuring beam (13);

-adjusting (430), by means of the optical unit, the optical measuring beam (13) in at least one direction (x, y) perpendicular to the optical axis of the processing head (101) in the region of the opening (212);

determining (440) a setting of the optical unit in the at least one direction (x, y) corresponding to a centered alignment of the laser beam (10) from measurements based on reflections of the optical measuring beam (13) for different settings of the optical unit in the at least one direction (x, y).

15. The method as recited in claim 14, wherein determining (440) a setting of the optical unit corresponding to a centered alignment of the laser beam (10) includes:

determining (431, 432) a distribution of measurement values for different settings of the optical unit, the distribution corresponding to a shape of the opening (212); and

determining (441, 442) a setting of the optical unit corresponding to a center of the opening (212) in the at least one direction (x, y) based on the distribution,

wherein determining (440) a setting of the optical unit for centering the laser beam (10) in the direction (x, y) is performed based on the setting corresponding to the center of the opening (212).

16. The method of claim 14 or 15, wherein the method further comprises:

-burning in a burn-in (310) on said surface (O) to form a structure; and

determining from the measured values the position (X4, Y4) of the burn-in (310) on the surface (O);

wherein determining (440) a setting of the optical unit corresponding to a centered alignment of the laser beam (10) in the at least one direction (X, Y) is performed based on the position (X4, Y4) of the burn-in (310).

17. The method according to any one of claims 14-16, wherein the method further comprises:

the optical unit is set in correspondence with a centered alignment of the laser beam (10) in the x and/or y direction.

18. The method according to any one of claims 14-17, wherein the measured values correspond to the distances to the reflecting surfaces of the optical measuring beam (13) from which the respective reflections occur, respectively.

Technical Field

The present disclosure relates to a laser processing system configured to be able to process a workpiece using a laser beam and a method for the laser processing system. In particular, the present disclosure relates to a laser processing head having an optical coherence tomography imager for measuring a distance to a workpiece, for example a laser processing head for laser welding or laser cutting.

Background

In devices using laser processing materials, for example in laser processing heads for laser welding or laser cutting, a laser beam emitted from a laser light source or one end of a laser fiber is focused or collimated by means of beam guiding and focusing optics onto a workpiece to be processed.

For laser machining of materials, in particular for laser cutting or laser welding, a laser beam must be emitted centrally from the laser machining head. In particular, the laser beam must be centered or centered relative to the opening of the laser processing head through which the laser beam exits the processing head, in order to avoid undesired reflections of the laser beam within the processing head and to ensure an optimized processing. The opening may be formed in a nozzle or a cutting nozzle, for example. This centering of the laser beam must be performed each time a certain component of the laser processing head is changed, for example when changing a nozzle, optics in the beam path of the laser beam, a laser source, etc. Centering the laser beam is typically a tedious manual procedure, such as repeating the following steps: adhering the glue strip to the opening, burning in the laser beam and the position of the opening, and manually moving the focusing optics and thus the position of the laser beam perpendicular to the beam axis until the centered position of the laser beam relative to the opening is determined. For this purpose, a nozzle with a relatively large opening must be used, which can then be replaced by a nozzle with a smaller opening in order to improve the centering accuracy.

Disclosure of Invention

An object of the present disclosure is to provide a laser processing system for processing a workpiece using a laser beam and a method of processing a workpiece using a laser beam, thereby enabling the laser beam to be accurately and conveniently centered.

This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are specified in the dependent claims.

According to an aspect of the present disclosure, there is provided a laser machining system for machining a workpiece using a laser beam, preferably for cutting or welding a workpiece using a laser beam, the laser machining system comprising: a processing head having a housing with an opening for emitting the laser beam from the processing head; a measuring device configured to be able to direct an optical measuring beam through the opening. The laser machining system further comprises an optical unit for aligning the laser beam and the optical measuring beam, wherein the optical unit is settable to adjust the laser beam and the optical measuring beam perpendicular to the optical axis of the machining head in the region of the opening. The measuring device is further configured to be able to determine a setting of the optical unit corresponding to the centered alignment of the laser beam from measurements based on reflections of the optical measuring beam with different settings of the optical unit. The optical unit may comprise measuring optics for aligning the optical measuring beam, wherein the measuring optics may be set such that the optical measuring beam may be adjusted perpendicular to the optical axis of the processing head in the region of the opening. Furthermore, the optical unit may comprise laser optics for aligning the laser beam, wherein the laser optics may be set such that the laser beam may be adjusted perpendicular to the optical axis of the processing head in the opening region. The measuring device can thus be configured to be able to determine a setting of the laser optics corresponding to the centered alignment of the laser beam from measurements of reflections, for example on the surface of the substrate or within the processing head, based on different settings of the optical measuring beam for the measuring optics. The measurement optics may comprise at least one optical element which is arranged in the beam path of the measurement beam and is displaceable or adjustable in at least one direction x and/or y perpendicular to its optical axis and/or perpendicular to the beam axis of the measurement beam. Similarly, the laser optics may comprise at least one optical element which is arranged in the beam path of the laser beam and is displaceable or adjustable in at least one direction x and/or y perpendicular to its optical axis and/or perpendicular to the beam axis of the laser beam. The different settings of the measuring optics or the laser optics may comprise different positions of the measuring optics or the laser optics in at least one direction x and/or y perpendicular to the optical axis of the processing head. In other words, the measurement optics or the laser optics may be displaceable or adjustable in this direction. However, different settings of the measuring optics or the laser optics may also include a pivoting or tilting of the measuring optics or the laser optics about an axis perpendicular to the optical axis of the processing head. The measuring device may also be configured to enable a determined setting of the laser optics, i.e. a centering alignment of the laser beam in the direction x and/or y is set accordingly.

According to another aspect, a method of centering a laser beam in a processing head of a laser processing system for processing a workpiece with the laser beam is provided, wherein the method comprises the following steps: providing the process head with a housing having an opening for emitting the laser beam from the process head; directing an optical measuring beam onto an optical unit for aligning the laser beam and the optical measuring beam; adjusting the optical measuring beam in at least one direction perpendicular to the optical axis of the machining head within the opening region by means of the optical unit; determining a setting of the optical unit for aligning the laser beam in the at least one direction corresponding to a centered alignment of the laser beam in dependence on measurements based on reflections of the optical measuring beam for different settings of the optical unit in the at least one direction. In one embodiment, the method comprises: providing the process head with a housing having an opening for emitting the laser beam from the process head; directing the optical measuring beam onto an optical unit for aligning the optical measuring beam; adjusting the optical measuring beam in at least one direction perpendicular to the optical axis of the processing head within the opening region by means of measuring optics; determining a setting of laser optics for aligning the laser beam in the at least one direction corresponding to a centered alignment of the laser beam from measurements based on reflections of the optical measurement beam for different settings of measurement optics in the at least one direction. Adjusting the optical measurement beam may comprise displacing the measurement optics in a respective at least one direction x and/or y perpendicular to the optical axis of the measurement optics and/or the beam axis of the measurement beam. In other words, different settings of the measurement optics may correspond to different positions of the measurement optics in the at least one direction x and/or y.

The method may further comprise setting the centered alignment of the laser beam, e.g. in the x and/or y direction. The method may further comprise at least one of the following steps: determining a distribution of distances between the processing head and the workpiece for different settings of the measurement optics in at least one direction x and/or y, the distribution corresponding to the shape of the opening; determining a setting or position of the measurement optics corresponding to the center of the opening in the at least one direction x and/or y based on the distribution; and determining a setting of the laser optics for centering the laser beam in said direction x and/or y based on the setting or position. For at least one corresponding setting of the measuring optics, an optical measuring beam can be directed through the opening onto the surface, for example onto the workpiece or substrate, and the distance between the processing head and the surface can be determined on the basis of the reflection of the optical measuring beam from the surface. For this purpose, the measurement optics may be first displaced in a first direction x and then in a second direction y, or in both directions simultaneously. The at least one direction may include a first direction x and a second direction y perpendicular thereto. The method may further comprise: burning-in portions (Einbrands) to create a spatial structure, and determining the location of the burning-in portions based on the measurements. The position of the burn-in can be determined relative to the center of the measurement value distribution in at least one direction. Determining a setting of the laser optics corresponding to the centered alignment of the laser beam may be based on the position of the burn-in. Furthermore, the processing head may be configured to be able to perform a method according to the present disclosure.

The method and/or laser processing system according to aspects of the present disclosure may include one or more of the following preferred features:

the measuring optics are preferably arranged in the beam path of the measuring beam. The measurement optics may also be configured to be able to displace the beam axis of the measurement beam within the opening region in dependence on an adjustment of the measurement optics.

The beam paths of the measuring beam and the laser beam may be formed separately in one area. In this case, the determined setting may comprise a position of the laser optics in a beam path of the laser beam. The laser optics may be displaceable or adjustable in at least one direction X and/or y perpendicular to its optical axis. The laser optics may also be configured to be able to displace a beam axis of the laser beam in the opening area in accordance with the adjustment of the laser optics. Thus, for setting the centered alignment of the laser beam, the laser optics may be displaced or adjusted by the adjusting device, for example, according to the determined setting.

The optical unit may comprise a common optical element arranged in a common beam path of the laser beam and the measuring beam. This means that the measurement optics and the laser optics may be realized by at least one common optical element arranged in the common beam path of the laser beam and the measurement beam, or the common optical element may be or comprise the measurement optics and the laser optics. Both the laser beam and the measuring beam may be directed through a common optical element. Here, the determined setting of the optical unit may comprise a setting or a position of the common optical element in the at least one direction. The common optical element may be configured to be able to shift the beam axes of the laser beam and the measurement beam according to a setting of the common optical element. Thus, for setting the centered alignment of the laser beam, the common optical element may be displaced or adjusted by the adjusting device, for example, according to the determined setting.

The common optical element and/or the measuring optics and/or the laser optics may be part of or may comprise a machining optical element of the machining head. For example, the common optical element and/or the measurement optics and/or the laser optics may comprise one or more of the following elements: focusing optics for focusing the laser beam and/or the measuring beam, collimator optics for collimating the laser beam and/or the measuring beam, the end of the optical fiber from which the laser beam and/or the measuring beam is emitted, and mirrors, etc.

The reflection of the optical measuring beam can be a reflection at a surface outside the machining head and/or within the machining head, for example within a nozzle of the machining head.

The measuring device may also be configured to be able to determine, based on the reflection of the optical measuring beam, a distribution of measured values or measuring signals for different settings or positions of the measuring optics in at least one direction x and/or y. The measured value distribution can be a distribution of distances, for example a distribution of distances to the workpiece or a distribution of distances between the processing head or a nozzle of the processing head and the workpiece. The measurement value distribution may correspond to the shape of the opening or show the shape of the opening. The measurement device may also be configured to be able to determine a setting or position of the laser optics based on a measurement value distribution corresponding to the centered alignment of the laser beam. For example, the measuring device may be configured to be able to determine a setting or position of the measuring optics corresponding to the center of the opening in at least one direction x and/or y, and to determine a setting or position of the laser optics for centering the laser beam in the direction x and/or y based on the setting or position of the measuring optics.

The measuring device can be configured to be able to direct an optical measuring beam onto the workpiece through the opening with at least one respective setting of the measuring optics or at least one respective position of the measuring optics and to be able to determine the distance to the workpiece or the distance between the processing head and the workpiece from the reflection of the optical measuring beam. The measuring device may comprise an optical coherence tomography. The optical coherence tomography can include a reference arm and a measurement arm, and can be configured to be capable of directing optical measurement light from the measurement arm through the opening to determine a distance to the workpiece based on reflections from the workpiece and back reflections from the reference beam.

The machining head or a housing of the machining head may comprise a nozzle comprising an opening. The diameter of the opening may be known. The measuring device may also be configured to be able to determine a setting of the laser optics corresponding to the centered alignment of the laser beam from the diameter of the opening and the reflection of the optical measuring beam.

The measurement value distribution may show the shape of the opening. That is, the distribution may include information about the edges of the opening. To this end, the profile may comprise a set value of the measurement optics for passing the measurement beam through the opening and a set value of the measurement optics for not passing the measurement beam through the opening. For example, the displacement path or the adjustment path of the measuring optics for at least one direction x and/or y can be selected such that at least the following settings can be set for this direction: a first setting or position of the measuring optics such that the measuring beam does not pass through the opening and/or such that the measuring beam remains or is reflected within the processing head; and a second setting or position of the measurement optics for passing the measurement beam through the opening and reflecting it on the surface. This causes a sharp increase in the distribution of measurement values or a sharp increase in the distance distribution based on the reflection of the optical measurement beam to a value which may correspond to the (optionally known) distance to the workpiece. If the diameter of the opening is known, the setting or position of the measuring optics corresponding to the center of the opening in this direction can be determined from the position at which the sharp increase in the measured value distribution occurs. Alternatively or additionally, the third position or setting of the measuring optics may be settable, the measuring beam also not passing through the opening and/or remaining or reflecting within the processing head when the measuring optics is in the third position or setting. The third position or setting may be arranged in the adjustment or displacement direction such that the second position or setting is between the first position or setting and the third position or setting. In other words, the third position of the measurement optics may be opposite to the first position with respect to the opening in the displacement direction. Thus, a sharp increase in the measured value distribution, for example to a value of the distance to the surface or to the workpiece, corresponding to the first edge region of the opening, occurs upon adjustment of the measuring optics from the first setting to the second setting, whereas a sharp decrease in the measured value distribution, for example from a value of the distance to the workpiece, corresponding to the second edge region of the opening, occurs upon adjustment of the measuring optics from the second setting to the third setting. The setting of the measurement optics corresponding to the center between the abrupt change values in the measurement value distribution may be determined as the setting corresponding to the center of the opening in that direction. For alignment in both x and y directions, the measurement optics may be shifted first in the first direction x and then in the second direction y, or in both directions simultaneously. The at least one direction may include a first direction x and a second direction y perpendicular thereto. In an exemplary embodiment, the measuring device is configured to be able to plot the measured values when the measuring optics are displaced in the first direction and/or the measured values when the measuring optics are displaced in the second direction with respect to the respective set or adjusted position of the measuring optics in the first and/or second direction.

In an exemplary embodiment, the optical measuring beam passes through the measuring optics and/or through the opening substantially parallel to the laser beam. The measuring beam and the laser beam can be coupled together into the laser processing head, for example, by a common optical fiber. Alternatively, the measuring beam and the laser beam can be coupled separately into the laser processing head, for example at different locations of the laser processing head. If the measuring beam and the laser beam pass coaxially through the common optical element, the position of the common optical element corresponding to the center of the opening in at least one direction x and/or y may correspond to the position of the common optical element for centering the laser beam, i.e. the positions may be identical. If the measuring beam and the laser beam are offset by a predetermined distance with respect to each other, the predetermined distance can be taken into account as an offset for determining a setting for centering the laser beam, for example the position of the common optical element or the laser optics. Alternatively or additionally, the measuring device may be configured to be able to take into account the offset and/or the setting for centering the laser beam from the position of the burn-in on the surface, for example the position of a common optical element or laser optics for centering the laser beam.

The optical measuring beam may be a continuous or pulsed measuring beam, for example having a circular or elliptical diameter. Alternatively, the optical measuring beam may comprise two or more partial beams.

The setting of the centered alignment of the laser beam, e.g. the position of the common optical element or laser optics, corresponding to the centered alignment of the laser beam in the at least one direction x and/or y, may be determined automatically. For this purpose, at least one automated and/or motorized adjustment device can be provided for displacing or adjusting at least one common optical element or measuring optics and/or laser optics. If a plurality of optical elements are displaced, respective adjustment means may be provided, respectively, or the adjustment means may be configured to be able to adjust a plurality of optical devices. The adjusting device and/or the control device of the adjusting device can be connected to the measuring device in order to transmit the position of the at least one common optical element, the measuring optics or the laser optics to the measuring device.

The optical measuring beam and the laser beam may have different wavelengths. In this way, the reflected portion of the laser beam can be distinguished from the reflection of the optical measuring beam.

Drawings

Embodiments of the present disclosure are illustrated in the drawings and will be described in greater detail below. In the drawings:

figure 1 illustrates a laser machining system having a machining head according to an embodiment of the present disclosure,

figure 2 shows a method of centered alignment of a measuring beam or laser beam,

figures 3A and 3B are schematic views of the opening and burn-in without or with superimposed optical measuring beams,

figures 4A and 4B show measured distance curves in the X and Y directions,

figure 5 shows a laser machining system with a machining head according to another embodiment of the present disclosure,

FIG. 6 shows a flow chart of a method of centered alignment of a laser beam, an

Fig. 7 shows a flow chart of further steps of a laser beam centering method according to an embodiment of the present disclosure.

Detailed Description

In the following, identical and equivalent elements will be provided with the same reference numerals, unless otherwise specified.

Fig. 1 shows a schematic diagram of a laser processing system 100 according to an embodiment of the present disclosure. The laser machining system 100 comprises a machining head 101, for example a laser cutting or laser welding head.

The laser machining system 100 comprises a laser device 110 for providing a laser beam 10 (also referred to as "laser beam" or "machining laser beam") and a measuring device for measuring a measured value, for example a distance between the workpiece 1 and the machining head 101 (for example a nozzle). The processing head or nozzle comprises an opening 212 through which the laser beam 10 is emitted from the processing head 101.

According to an embodiment, the laser processing system 100 or a component thereof, for example the processing head 101, may be movable along the processing direction 20. The machining direction 20 may be a cutting or welding direction and/or a movement direction of the laser machining system 100 (e.g. the machining head 101) relative to the workpiece 1. In particular, the machine direction 20 may be a horizontal direction. The machine direction 20 may also be referred to as the "feed direction".

The laser device 110 may comprise a fiber end 137 for coupling the laser beam 10 into the processing head and collimator optics 112 for collimating the laser beam 10. Within the processing head 101, the laser beam 10 is deflected or reflected by suitable optical elements or optics 103 by approximately 90 ° in the direction of the workpiece 1. The measuring device may have a fiber end 138 for coupling the optical measuring beam 13 into the processing head 101. The optical element 103, e.g. a semi-transparent mirror, may be configured to allow light, e.g. reflected back from the workpiece 1, to pass to the measurement device. The optical measuring beam and the laser beam may have different wavelengths, so that only the retro-reflected measuring light reaches the measuring device. Of course, the point of coupling of the laser beam 10 can be interchanged with the point of coupling of the measuring beam 13, so that the measuring beam is deflected by 90 ° towards the workpiece and the semitransparent mirror 103 reflects the measuring beam wavelength.

The measuring device may be configured to be able to determine the distance to the workpiece 1. Thereby, the distance between the processing head and the workpiece surface or the distance between a nozzle arranged at the end of the processing head and the workpiece surface can be kept constant. The more constant the distance can be kept during the machining, the more stable the machining process.

The measurement device may include the coherence tomography 120 or may be the coherence tomography 120. The coherence tomography instrument 120 may include an evaluation unit 130 with a broadband light source (e.g., superluminescent diode, SLD) that couples measurement light into an optical waveguide 132. In the beam splitter 134, which preferably comprises a fiber optic coupler, the measurement light is typically split into a reference arm 136 and a measurement arm which is introduced into the processing head 101 via a fiber end 138 of the optical waveguide. The coherence tomography instrument 120 may also include collimator optics 122, the collimator optics 122 configured to collimate the optical measurement beam 13. The collimator optics 122 may be integrated into the processing head 101 or mounted on the processing head 101. Furthermore, the collimator optics 112 or 122 can be used to align the optical axes of the measuring beam 13 and the laser beam 10 coaxially with respect to one another in the region of the focusing optics 124 (fig. 1) in a preliminary adjustment step, for example a manual adjustment. To this end, the collimator optics 112 or 122 can be designed to be displaceable in the x and y directions, i.e. perpendicular to the optical axis of the laser beam 10 and the measuring beam 13.

In the processing head 101, there is also provided a focusing optics 124 configured to be able to focus the laser beam 10 and/or the optical measuring beam 13 on the workpiece 1. The focusing optics 124 may be common focusing optics for the laser beam 10 and the measuring beam 13, e.g. a focusing lens.

In some embodiments, the laser beam 10 and the optical measuring beam 13 may be at least partially parallel or even coaxial, in particular may be at least partially coaxially superimposed. For example, the coherence tomography unit 120 may be configured to couple the optical measuring beam 13 into the beam path of the laser device 110. The combination of the optical measuring beam 13 and the laser beam 10 may take place downstream of the collimator optics 122 and upstream of the focusing optics 124. Alternatively, the beam path of the measuring beam 13 and the beam path of the laser beam 10 are directed substantially separately and are combined only downstream of the collimator optics 122 and upstream of the focusing optics 124 or only downstream of the focusing optics 124 and upstream of the opening of the laser processing head 101. The beam axis of the laser beam 10 and the beam axis of the measuring beam 13 may be parallel or even coaxial in the vicinity of the opening 212 and preferably perpendicular to the workpiece surface.

The distance measurement principle described herein is based on the principle of optical coherence tomography, using an interferometer to exploit the coherence properties of light. For distance measurement, an optical measuring beam 13 is directed onto the surface 2 of the workpiece 1. The measurement light reflected back from the surface is imaged by the focusing optics 124 onto the exit/entrance surface of the optical waveguide 138, superimposed in the fiber coupler 134 with the light reflected back from the reference arm 136 and then guided back to the evaluation unit 130. The superimposed light contains information about the path length difference between the reference arm 136 and the measurement arm. This information is evaluated in an evaluation unit 130, whereby the user obtains information about the distance between the workpiece surface and the processing head 101.

The measuring device may be configured for centered alignment of the laser beam relative to the opening. In order to position the laser beam 10 centrally in the opening 212, the measurement optics in the beam path of the measurement beam 13 can be displaced by the adjusting device in a plane perpendicular to the beam axis of the measurement beam 13. When displaced perpendicular to its optical axis, the measurement optics may be configured to be able to displace the measurement beam 13 accordingly. For example, the measurement optics may include at least one of fiber end 138, collimator optics 122, and focusing optics 124. Alternatively, the measuring optics can also be designed to be pivotable.

For example, the measurement optics are automatically displaced when the optical measurement beam 13 is directed through the measurement optics. Thereby, the measuring device can record a measuring signal or a measured value based on the reflection of the measuring beam 13. The measuring device may convert the measured value into a distance.

The respective measured values or distances for different positions of the measurement optics or for each position of the measurement optics may be plotted against the respective position of the measurement optics. This forms a local signal distribution, from which the center of the opening can be derived: if the measuring beam does not enter the opening 212, the optical measuring beam 13 may be reflected in the processing head. In contrast, if the measuring beam 13 is directed through the opening 212 onto a surface, for example onto the workpiece 1 or onto a centering body, and reflected, the measured value increases sharply. The distance determined from the measured values may correspond to the distance to the workpiece 1 or to the centering matrix. This method is particularly suitable for laser processing heads in which a laser beam and a measuring beam are coupled together, as will be described below with reference to fig. 5.

Thus, when the measuring optics are displaced in two directions x, y perpendicular to each other, a signal distribution corresponding to the shape or cross section of the opening 212 can be recorded, so that the position of the measuring optics corresponding to the center or the center of the signal distribution can be determined. The dimensions of the displacement path or adjustment path of the measurement optics in one or each of the two directions may be such that the following positions can be set in that direction: a first position of the measuring optics, in which the measuring beam does not exit from the opening 212 or the measuring beam is reflected in the processing head; and a second position of the measuring optics, in which the measuring beam is guided through the opening onto the surface, for example onto the workpiece or the centering body, and is reflected. Furthermore, a third position of the measuring optics may be settable, in which the measuring beam is also reflected in the processing head or does not emerge from the opening. The third position of the measurement optics may be opposite the first position relative to the opening 212 in the processing head. The first and second (and optionally third) positions may be sequentially passed in succession as the measurement optics are displaced in one direction. In any case, the displacement path of the measurement optics in the x and/or y direction may be configured such that the edge of the opening 212 may be represented in the measurement values at the time of the x and/or y displacement of the measurement optics, i.e. there are settings of the measurement optics in the x and/or y direction with measurement values corresponding to the distance to the surface and those without measurement values or with measurement values different from the distance to the surface.

The measurement optics may be a common optical element, i.e. the measurement optics may be arranged in a common beam path of the laser beam 10 and the measurement beam 13 and configured to be able to displace the laser beam 10 and the measurement beam 13 accordingly when displaced perpendicular to their optical axes. In this case, the measuring optics is also a laser optics, or the measuring optics and the laser optics are realized by a common optical element. Thus, based on the measurement values, the position of the common optical element corresponding to the centered alignment of the laser beam can be determined. For example, the common optical element may include or may be focusing optics, collimator optics, and/or an optical fiber end that emits a laser beam and a measurement beam. Alternatively, in the case of a split beam path of the laser beam 10 and the measuring beam 13, in addition to the measuring optics in the beam path of the measuring beam 13, laser optics in the beam path of the laser beam 10 can be provided to centrally position the laser beam 10 in the opening 212, which can be adjusted by the adjusting means in a plane perpendicular to the beam axis of the laser beam 10. The laser optics may include, for example, focusing optics, collimator optics, and/or an optical fiber end that emits a laser beam. The laser optics are configured to be able to displace the laser beam 10 by correspondingly displacing the laser optics perpendicularly to the optical axis of the laser beam 10. The position of the laser optics corresponding to the centered alignment of the laser beam can thus be determined from the measured values based on the displacement of the measuring optics in the beam path of the measuring beam. In this way, the laser beam 10 or the measuring beam 13 can be centered in the laser processing head in a simple and automated manner.

With reference to fig. 2, a method for setting the centered alignment of the laser beam 10 and the measuring beam 13 with respect to the opening 212 of the housing 210 of the laser processing head 101 according to one embodiment is described in more detail. For this purpose, a laser processing system as shown in fig. 1 or 5 may be used. According to the present disclosure, a simplified method of centering alignment by measuring the reflection of the optical measuring beam 13 when the measuring optics are displaced is provided. The displacement or adjustment of the measuring optics can be performed automatically and/or motor-driven by an adjustment device (not shown). The setting of the central alignment of the laser beam 10 can then be carried out automatically and/or motor-driven by setting the position of the respective common optical element in the common beam path or by setting the laser optics in the beam path of the laser beam by means of an adjusting device (not shown). In the following, a laser machining system or a method of centering a laser beam will be exemplarily explained with reference to a common optical element in a common beam path of the laser beam and the measuring beam. However, the invention is not limited to this, but in the case of a split beam path, in addition to the measuring optics in the beam path of the measuring beam, laser optics for the central alignment of the laser beam can also be provided in the beam path of the laser beam.

In one example, the common optical element, in this case the focusing optics 124, is displaced in at least one of the two directions x and y in a plane perpendicular to the beam axis of the laser beam 10 or the measuring beam 13, whereby, as exemplarily shown in the upper part of fig. 2, for a displacement in the x-direction, the beam axis of the measuring beam 13 (different dashed lines) is also displaced in this direction. While the focusing optics 124 are displaced, a measured value for each position of the focusing optics 124 is determined on the basis of a reflection of the optical measuring beam 13, for example within the housing 210 of the processing head or on the workpiece surface 2. In one embodiment, the distance d1 to the workpiece 1 is determined here on the basis of the reflection of the optical measuring beam 13 from the workpiece surface 2 and the light back-reflected from the reference arm 136. If the optical measuring beam 13 does not pass through the opening 212 no measurement value, or at least no measurement value corresponding to the distance d1, is obtained. Here, the distance d1 to the workpiece 1 may be known. However, if the measuring beam 13 passes at least partially through the opening 212, a measured value corresponding to the distance d1 is derived for the respective position X of the focusing optics 124 (see middle of fig. 2). When the focusing optics 124 are displaced in the x and y directions perpendicular to the beam axis, the shape of the opening 212 can be mapped by the distribution of the measurement values, the center M of which corresponds to the position of the focusing optics 124 for centering the measurement beam 13 (see lower part of fig. 2). Thus, the position of the focusing optics 124 for centering the measuring beam 13 in the x-direction may be determined as the center of the x-shifted segment on which the distance signal is obtained. The same applies for the position for the centering alignment in the y direction.

Since the entire opening 212 can be reflected in the distribution of the measurement signal, an opening having any diameter can be selected. Therefore, the centering method can be performed regardless of which nozzle is selected for machining.

For the coaxial course of the laser beam 10 and the measuring beam 13, the determined position of the common optical element (in this case the focusing optics 124) for centered alignment of the measuring beam 13 also corresponds to the position of the common optical element for centered alignment of the laser beam 10. In particular, in the exemplary embodiment shown in fig. 5, the laser beam 10 and the measuring beam 13 are coupled coaxially into the processing head or the processing optics of the processing head via optical fibers, as is the case. Alternatively, the beam axis of the laser beam 10 may be offset in a known manner, for example with a known x and/or y offset, parallel to the beam axis of the measuring beam 13.

In the exemplary embodiment of the laser processing system according to fig. 1, however, the measuring beam 13 and the laser beam 10 are coupled into the processing head or processing optics at two different locations. Thus, the position of the laser beam 10 may not be automatically deduced from the geometric position of the measuring beam 13. In this case, for example, the burn-in 310 may be required so that the geometric position of the laser beam 10 relative to the opening 212 becomes visible or measurable. This will be explained by way of example with reference to fig. 3A and 3B.

In a first step the laser processing head is movable to a position x, y and z (relative to the machine coordinate system) at which beam centering is to be performed. This position may be on the surface O of a substrate, for example the workpiece 1 or a separate centering station. Here, the z-direction denotes a direction parallel to the laser beam axis in the region of the opening 212, and the x-and y-directions extend in a plane perpendicular thereto. In a second step, the laser beam 10 is ignited onto the surface O for a defined time with defined parameters. As shown in fig. 3A and 3B, a spatial structure, the so-called burn-in 310, is produced on the surface O, which burn-in is geometrically detectable at least in the x, y plane. During beam centering operations, the position of the laser processing head may remain unchanged at least in the x, y directions. The optical measuring beam 13 is then shifted, for example in a grid, in the x-y plane by a displacement of the measuring optics in order to scan the opening 212, the surface O and the burn-in 310 (topography measurement). Other forms of movement for scanning are also conceivable, such as circular, spiral, serpentine, zigzag, etc. Thus, at each x, y coordinate, a measurement, i.e., a distance value, is produced. In fig. 4A and 4B, measured value profiles measured in the x direction and the y direction, respectively, in the vicinity of the position of the burn-in portion 310 are schematically shown. The center X3, which is located at the very center of the sharp rise or fall of the signal, is derived from the points X1 and X2 corresponding to the sharp rise or fall of the signal. The position X4 of the burned-in portion 310 or the center of the burned-in portion can be determined as the extreme value of the measurement values between the positions X1 and X2, that is, the position of the minimum value or the maximum value. The distance between the center X3 and the position X4 of the burned-in portion forms an offset Δ X. The same calculation is performed for the Y direction. With the offsets Δ X and Δ Y, the laser beam 10 can now be centered in the center of the opening 212 by setting the respective positions of the laser optics.

A further exemplary embodiment of a laser machining system 100 is shown in fig. 5, in which the laser beam 10 and the optical measuring beam 13 are coupled together and thus coaxially via a fiber end 238 of the common optical fiber 131 into the laser machining head 101 or into the machining optics. The laser beam 10 from the laser source and the measuring beam 13 of the measuring device may be introduced into the optical fiber 131, for example via a coupling unit 140, for example a fiber coupler. The laser beam 10 and the measuring beam 13 pass coaxially through optics of the processing head 101, such as collimator optics 222 and focusing optics 224. This has the advantage that no burn-in on the surface O is required in the beam pair, since the optical information of the measuring beam 13 enables the position of the laser beam 10 to be derived directly. The measurement optics and the laser optics are thus formed as a common optical element located in a common beam path. The common optical element can therefore also center the laser beam 10 by means of a corresponding positioning. Similarly as described above, the measuring beam 13 scans the internal geometry of the opening at least four locations in the x and y directions. For example, the deflection of the measuring beam 13 is performed by a displacement of the measuring optics or common optical element in the x and y directions (perpendicular to the optical axis). First, the measuring beam 13 is shifted in, for example, the + X direction and the-X direction (X1 and X2). Thereby, the center X3 is determined, and the measuring beam 13 is centered in this position in the X direction accordingly. Then, starting from point X3, the center in the y direction is similarly determined and the beam is centered at that position in the y direction. Now, both the measuring beam 13 and the laser beam 10 are positioned centrally with respect to the opening 121. In one example, the common focusing optic 124 may be displaced as a common optical element. Alternatively or additionally, however, the common collimator optics 122 and/or the fiber ends of the optical fibers 131 from which the laser beam and the measuring beam are emitted together can be displaced as a common optical element (see fig. 5).

Fig. 6 shows a flow chart of a method 400 for centering a laser beam in a machining head. The method 400 may be performed by a machining head or a laser machining system of the present disclosure. Further, the processing head may be configured to be able to perform the method 400 according to the present disclosure.

The method 400 includes, at block 410: a processing head 101 is provided having a housing 210, the housing 210 having an opening 212 for emitting a laser beam from the processing head 101. At block 420, the optical measuring beam 13 is directed onto measuring optics located in the beam path of the processing head 101. At the same time, at block 430, the measurement optics are adjusted in at least one direction x and/or y perpendicular to the optical axis of the measurement optics or perpendicular to the beam axis of the measurement beam 13. At block 440, a setting of the laser optics corresponding to a centered alignment of the laser beam 10 in the at least one direction x and/or y is determined from measurements based on reflections of the optical measuring beam 13 with different positions of the measuring optics in the at least one direction x and/or y. When the measurement optics and the laser optics are formed by a common optical element arranged in a common beam path of the laser beam and the measurement beam, and the common optical element is configured to be able to shift the beam axes of the measurement beam and the laser beam, the setting may comprise a position of the common optical element corresponding to a centered alignment of the laser beam 10 in the respective direction. At block 450, a setting of the laser optics corresponding to the centered alignment of the laser beam 10, i.e., for example, the position of the common optical element 124, is set.

Here, the method 400 may comprise the further steps of: for example, as shown in fig. 7, adjusting the measurement optics in block 430 may include steps 431 and/or 432, and determining the setting of the laser optics, e.g., the position of the common optical element, corresponding to the centered alignment of the laser beam 10 in block 440 includes steps 441 and/or 442. In step 431, the opening 212 is scanned by the optical measuring beam 13 in the x-direction, i.e. in a first direction perpendicular to the optical axis of the measuring optics or the beam axis of the measuring beam, by displacing the measuring optics (e.g. the focusing optics 124) located in the beam path of the measuring beam 13 only in the x-direction. To this end, for example, the measuring beam may be shifted first in the + x direction and then in the-x direction (with the center of the opening as the origin of coordinates). In step 441, a distribution center X3 is determined from the distribution of the measurement values in the X direction. In step 432, the opening 212 is scanned by the optical measuring beam 13 in the y-direction, i.e. in a second direction perpendicular to the optical axis of the measuring optics or the beam axis of the measuring beam, by displacing the measuring optics in the y-direction. To this end, for example, the measuring beam may be first shifted in the + y direction and shifted in the-y direction (with the center of the opening as the origin of coordinates). In step 442, the distribution center Y3 in the Y direction is determined from the measured value distribution. Alternatively, steps 421 and 422 can also be performed overlapping with respect to scanning sequentially in the x-direction and the y-direction, so that topography measurements are made by scanning the measuring beam in the x-and y-directions in parallel or simultaneously.

In the case of a measuring beam and a laser beam coupled coaxially into the processing head, as shown in fig. 5, the X position or the Y position of the distribution center X3 or Y3 may correspond to the centered alignment position of the laser beam in the X or Y direction. When the measuring beam 13 is coupled into the processing head independently of the laser beam 10, as shown, for example, in fig. 1, an offset, which is known or determined by the burn-in process, can additionally be taken into account as described above. To this end, the method 400 may include: a step of burning in burned-in portion 310 into surface O by means of laser beam 10 before block 420, and determining offsets Δ X and Δ Y in X and Y directions based on positions X4 and Y4 of burned-in portion 310, for example, in or before block 440 (see fig. 3B, 4A and 4B).

According to the present invention, a laser machining system and a method for a laser machining system are specified, wherein a simple and precise centering of the laser beam can be achieved by means of optical coherence tomography. In a preferred embodiment, the centered alignment of the laser beam is carried out in an automated process, wherein the measuring optics are displaced by a motor in a plane perpendicular to the optical axis of the measuring optics, in order to scan the outlet opening of the processing head with the measuring beam and thereby determine the position of the laser optics corresponding to the centered alignment. Thus, cumbersome and manual process of centering alignment can be avoided, and accuracy can be improved.