Laser processing apparatus having optical device having beam splitter

Abstract

To provide a laser processing apparatus having the following device.SOLUTION: An optical device has an inlet for receiving a laser beam, the optical device has a beam splitter for dividing the laser beam into at least two partial beams, the optical device collects the partial beams into one laser spot again so as to produce an interference pattern in a laser spot, a first state of the laser beam at the inlet produces a first interference pattern, a second state of the laser beam produces a second interference pattern, in the first state and the second state, at least one of (i) the position of the laser beam at the inlet and (ii) an incident angle of the laser beam to the inlet is different, and the optical device is configured so that the second interference pattern continues the first interference pattern in the same phase.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The subject matter disclosed herein relates to the field of laser processing devices. [Background technology]

[0002] Processing of surfaces and components with laser radiation has a variety of applications, for example structuring of surfaces. For example, WO 2018 / 197555 discloses a method and an apparatus for producing riblets (i.e. ribs), which are introduced into a surface, in particular into an already painted and hardened surface, by laser interference structuring (DLIP - Direct Laser Interference Patterning). Components with riblets produced in this manner allow aircraft, ships and wind power plants to operate with relatively low flow resistance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 197555 Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the above situation, there is a need for techniques that allow the structuring of surfaces with improved properties. [Means for solving the problem]

[0005] This need is taken into account by the subject matter of the independent claims. Preferred embodiments are set forth in the dependent claims.

[0006] According to a first aspect of the subject matter disclosed herein, an apparatus, particularly a laser processing apparatus, is disclosed.

[0007] According to an embodiment of a first aspect, a laser processing apparatus is disclosed, the laser processing apparatus comprising an optical device having an inlet for receiving a laser beam, the optical device having a beam splitter for splitting the laser beam into at least two partial beams, the optical device combining the partial beams again into a laser spot to generate an interference pattern in the laser spot, wherein a change in the position of the laser beam at the inlet and / or a change in the angle of incidence of the laser beam with respect to the inlet causes at least one of the following: (i) a spacing change DP of a spacing between a center of the laser spot and a nearest interference maximum in a predetermined direction of the interference pattern, (ii) a position change DS of a position of the center of the laser spot, the optical device being configured to satisfy the condition |DS|+|DP|=n*L (Equation 1) is configured to apply to a continuous position change DS, n being a natural number, L being the spacing between two adjacent interference maxima of the interference pattern in a predetermined direction with a tolerance of ±5%, and a spacing change DP being defined by the difference between a first spacing and a second spacing, each of the first spacing and the second spacing being defined in the predetermined direction.

[0008] According to a second aspect of the presently disclosed subject matter, a method is disclosed.

[0009] According to an embodiment of a second aspect, a method for interference structuring a surface is disclosed, the method comprising the steps of generating a first interference pattern on the surface and generating a second interference pattern on the surface, the generation of the first interference pattern and the generation of the second interference pattern being performed by a single optical device having an inlet, the first interference pattern and the second interference pattern being generated by varying a position of a laser beam at the inlet and / or an angle of incidence of the laser beam with respect to the inlet, thereby causing (i) a spacing change DP of a spacing between a center of the laser spot and a nearest interference maximum in a predetermined direction of the interference pattern, and / or (ii) a position change DS of a position of the center of the laser spot, the optical device being configured to change the position of the first interference pattern and the second interference pattern by varying the position of the first interference pattern and the second interference pattern by varying the position of the second interference pattern and / or the angle of incidence of the laser beam with respect to the inlet, the optical device being configured to change ... second interference pattern with respect to the inlet, the optical device being configured to change the position of the second interference pattern and / or the condition |DS|+|DP|=n*L (Equation 1) is configured to be satisfied for a continuous position change DS, n being a natural number, L being the spacing between two adjacent interference maxima of the first interference pattern with a tolerance of ±5%, and a spacing change DP being defined by the difference between the first spacing and the second spacing, each of the first spacing and the second spacing being defined in a predetermined direction.

[0010] According to an embodiment of a third aspect, an application is disclosed.

[0011] According to an embodiment of the third aspect, the use of an optical device for generating a first interference pattern and a second interference pattern by changing the position of a laser beam at an inlet and / or changing the angle of incidence of the laser beam with respect to the inlet, thereby causing at least one of (i) a spacing change DP of the spacing between the center of the laser spot and the nearest interference maximum in a predetermined direction of the interference pattern, (ii) a position change DS of the position of the center of the laser spot, the optical device being configured to satisfy the condition |DS|+|DP|=n*L (Equation 1) applies to a continuous position change DS, n being a natural number, L being the spacing between two adjacent interference maxima of the interference pattern with a tolerance of ±5%, and a spacing change DP being defined by the difference between a first spacing and a second spacing, each of the first spacing and the second spacing being defined in a predetermined direction.

[0012] According to a fourth aspect of the presently disclosed subject matter, a laser processing apparatus is disclosed.

[0013] According to an embodiment of a fourth aspect, a laser processing apparatus is disclosed, the laser processing apparatus comprising an optical device having an entrance for receiving a laser beam, the optical device having a beam splitter for splitting the laser beam into at least two partial beams, the optical device combining the partial beams again into a laser spot to generate an interference pattern within the laser spot, a first state of the laser beam at the entrance generating a first interference pattern and a second state of the laser beam generating a second interference pattern, the first and second states differing in at least one of (i) a position of the laser beam at the entrance and (ii) an angle of incidence of the laser beam with respect to the entrance, the optical device being configured such that the second interference pattern continues in phase with the first interference pattern.

[0014] According to a fifth aspect of the presently disclosed subject matter, a method is disclosed.

[0015] According to an embodiment of the fifth aspect, a method is disclosed, the method comprising the steps of: providing an optical device having a beam splitter for splitting a laser beam into at least two partial beams; and directing the laser beam to an entrance of the optical device, the optical device recombining the partial beams into a laser spot, a first state of the laser beam at the entrance generating a laser spot at a first position P1, the laser spot having a first interference pattern, a second state of the laser beam at the entrance generating a laser spot at a second position P2, the laser spot having a first interference pattern, The spot has a second interference pattern, the first and second states differing in at least one of (i) the position of the laser beam at the inlet and (ii) the angle of incidence of the laser beam relative to the inlet, and the optical device provides a difference DI_AB=DI_A-DI_B between the first optical path length difference DI_A and the second optical path length difference DI_B due to a position change DS=P1-P2, which difference causes a spacing change DP between the center of the laser spot and the nearest interference maximum in a predetermined direction of the interference pattern, so that the second interference pattern continues in phase with the first interference pattern.

[0016] According to a sixth aspect of the presently disclosed subject matter, a laser processing apparatus is disclosed.

[0017] According to an embodiment of a sixth aspect, a laser processing apparatus is disclosed comprising an optical device having an entrance for receiving a laser beam, the optical device having a beam splitter for splitting the laser beam into at least two partial beams, the optical device recombining the partial beams into a laser spot to generate an interference pattern in the laser spot, a first state of the laser beam at the entrance generating a first interference pattern and a second state of the laser beam generating a second interference pattern, the first state and the second state being dependent on: (i) a position of the laser beam at the entrance; (ii) at least one of the angles of incidence of the laser beam with respect to the entrance is different, the centre of the first interference pattern and the centre of the second interference pattern have a separation corresponding to at least one diameter of the laser spot, in particular at least five times the diameter of the laser spot, more in particular at least ten times the diameter of the laser spot, and more in particular at least twenty times the diameter of the laser spot, and a change in path length of the radiation path of each of the partial beams upon a state change from the first state to the second state is less than ±5%, in particular less than ±1%, and more in particular less than ±0.5% of the total path length of the radiation path from the beam splitter to the laser spot.

[0018] According to a seventh aspect of the presently disclosed subject matter, an object is disclosed.

[0019] According to an embodiment of the seventh aspect, an object is disclosed having a surface with a periodic surface structure, the surface structure being bounded by a perimeter line, the perimeter line having a shape that periodically repeats a basic element at least in each section of the perimeter line, and the periodicity of the surface structure is different from the periodicity of the perimeter line section.

[0020] According to an eighth aspect of the presently disclosed subject matter, an object is disclosed.

[0021] According to an embodiment of an eighth aspect, an object is disclosed comprising a surface having a surface structure, the surface structure having a maximum depth elongation relative to the surface, a depth elongation of the surface structure from a first position to a second position at an edge of the surface structure increases to 80% of the maximum depth elongation, and a spacing between the first position and the second position is at least 100 μm.

[0022] Different aspects and embodiments of the subject matter disclosed herein are based on the idea that the interference pattern of one laser spot continues in phase beyond the laser spot. This can be done, for example, by a suitable adjustment of the phase, for example by providing a suitable difference DI_AB between the optical path length difference in the first state and the optical path length difference in the second state. Furthermore, the inventors have found that, contrary to the views of the relevant skilled group, at least for certain optical devices, an "automatic" coherent continuation of the interference pattern beyond the spatial extent of the laser spot is possible, simply due to the structure of the optical device. In any case, the coherent continuation allows the laser processing apparatus to be constructed extremely efficiently in applications where processing of large areas with periodic patterns is advantageous.

[0023] According to an embodiment of the first aspect, the laser processing apparatus is configured to provide the functionality of one or several of the embodiments disclosed herein and / or to provide the functionality required for one or several of the embodiments disclosed herein, in particular the embodiments of the first, second, third, fourth, fifth, sixth, seventh and / or eighth aspects.

[0024] According to an embodiment of the second aspect, the method is configured to provide the functionality of one or several of the embodiments disclosed herein and / or to provide the functionality required for one or several of the embodiments disclosed herein, in particular the embodiments of the first, second, third, fourth, fifth, sixth, seventh and / or eighth aspects.

[0025] According to an embodiment of the third aspect, the use is configured to provide the functionality of one or several of the embodiments disclosed herein and / or to provide the functionality required for one or several of the embodiments disclosed herein, in particular the embodiments of the first, second, third, fourth, fifth, sixth, seventh and / or eighth aspects.

[0026] According to an embodiment of the fourth aspect, the laser processing apparatus is configured to provide the functionality of one or several of the embodiments disclosed herein and / or to provide the functionality required for one or several of the embodiments disclosed herein, in particular the embodiments of the first, second, third, fourth, fifth, sixth, seventh and / or eighth aspects.

[0027] According to an embodiment of the fifth aspect, the method is configured to provide the functionality of one or several of the embodiments disclosed herein and / or to provide the functionality required for one or several of the embodiments disclosed herein, in particular the embodiments of the first, second, third, fourth, fifth, sixth, seventh and / or eighth aspects.

[0028] According to an embodiment of the sixth aspect, the laser processing apparatus is configured to provide the functionality of one or several of the embodiments disclosed herein and / or to provide the functionality required for one or several of the embodiments disclosed herein, in particular the embodiments of the first, second, third, fourth, fifth, sixth, seventh and / or eighth aspects.

[0029] According to an embodiment of the seventh aspect, the object is configured to provide the functionality of one or several of the embodiments disclosed herein and / or to provide the functionality required for one or several of the embodiments disclosed herein, in particular for one or several of the embodiments of the first, second, third, fourth, fifth, sixth, seventh and / or eighth aspects.

[0030] According to an embodiment of the eighth aspect, the object is configured to provide the functionality of one or several of the embodiments disclosed herein and / or to provide the functionality required for one or several of the embodiments disclosed herein, in particular the embodiments of the first, second, third, fourth, fifth, sixth, seventh and / or eighth aspects.

[0031] Further advantages and features of the subject matter disclosed herein will become apparent from the following illustrative description of a presently preferred embodiment, to which the disclosure is not limited. The individual figures of the drawings of this application are presented only diagrammatically and are not necessarily drawn to scale. [Brief description of the drawings]

[0032] [Figure 1] 1 illustrates a schematic diagram of the functional principle of an optical device according to an embodiment of the subject matter disclosed herein; [Diagram 2] 1 illustrates a laser processing apparatus according to an embodiment of the subject matter disclosed herein. [Diagram 3] 1 illustrates a portion of a laser processing apparatus according to an embodiment of the subject matter disclosed herein. [Figure 4] 1 illustrates a portion of a laser processing apparatus according to an embodiment of the subject matter disclosed herein. [Diagram 5] 3 shows a first interference pattern and a second interference pattern that can be generated by a laser processing apparatus according to embodiments of the subject matter disclosed herein. [Figure 6] 1 illustrates a cross-sectional view of a portion of an optical device of a laser processing apparatus according to an embodiment of the subject matter disclosed herein. [Figure 7] 1 illustrates a portion of an object according to an embodiment of the subject matter disclosed herein. [Figure 8] 1 illustrates a portion of an object according to an embodiment of the subject matter disclosed herein. [Figure 9] 1 illustrates a portion of an object according to an embodiment of the subject matter disclosed herein. [Figure 10]10 shows a cross-sectional view of a portion of the surface structure from FIG. 9 along section line XX in FIG. [Figure 11] 1 shows a plan view of a portion of a surface structure according to an embodiment of the subject matter disclosed herein. [Figure 12] 12 shows a cross-sectional view of the surface structure from FIG. 11 along section line XII-XII in FIG. [Figure 13] 13 shows a cross-sectional view of the surface structure from FIG. 11 along the section line XIII-XIII in FIG. [Figure 14] 1 illustrates a laser processing apparatus according to an embodiment of the subject matter disclosed herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] In the following, exemplary embodiments of the subject matter disclosed herein are described, for example, with reference to laser processing devices, methods, uses and articles. Of course, it should be emphasized that each combination of the features of the various aspects, embodiments and examples is possible. In particular, some embodiments are described with reference to a method or use, and other embodiments are described with reference to an apparatus, in particular a laser processing device or an article. However, a person skilled in the art will infer from the above and below description, claims and drawings that, unless otherwise specified, the features of the different aspects, embodiments and examples can be combined, and such combinations of features are considered to be disclosed by the present application. For example, even features related to a method or use can be combined with features related to an apparatus (e.g., a laser processing device or an article) and vice versa. Furthermore, features of an embodiment related to an apparatus can be combined with corresponding features related to a method or use. Furthermore, the disclosure of a method, an embodiment or a function of the method is considered to disclose the functionality of one or several actuators and a control device formed for the implementation of the method or function, which interacts with the actuators. Furthermore, the disclosure of a function of an apparatus is considered to disclose a corresponding method that specifies the function without the features of the apparatus. Furthermore, the features of the interference pattern define similar features of the surface structure or machining spot (the surface area machined by the laser spot with the interference pattern).

[0034] The method may be implemented as computer readable instruction code using any suitable programming language such as, for example, JAVA, C#, etc., and may be stored on a computer readable medium (removable disk, volatile or non-volatile memory, embedded memory / processor, etc.). The instruction code is operable to perform an intended function by programming a computer or any other programmable processor device. The instruction code may be available from a network, for example, the World Wide Web, from which it can be downloaded.

[0035] The subject matter disclosed herein can be realized by program elements or software. However, the subject matter disclosed herein can also be realized by one or several specialized electronic circuits or hardware. Moreover, the subject matter disclosed herein can also be realized in a hybrid form, i.e. a combination of software and hardware modules.

[0036] Unless otherwise specified, numerical values ​​should be understood to include an expansion range of ±5%, i.e. for example, a length indication of 10 mm includes lengths between the interval (10 mm ±5%)=[9.95 mm, 10.05 mm] according to one embodiment, and a percentage of 50% includes percentages between the interval 50% ±5%=[47.5%, 52.5%] according to one embodiment. According to another embodiment, numerical values ​​should be understood to include an expansion range of ±10%.

[0037] According to one embodiment, an apparatus is disclosed. According to another embodiment, the apparatus is a laser processing apparatus. According to another embodiment, the apparatus comprises an optical device, the optical device having an inlet for receiving the laser beam. According to another embodiment, the optical device has a beam splitter for splitting the laser beam into two or more partial beams, which the optical device recombine into a laser spot to generate an interference pattern in the laser spot. According to another embodiment, a change in the position of the laser beam at the inlet and / or a change in the incidence angle of the laser beam with respect to the inlet causes at least one of the following: (i) a spacing change DP of the spacing between the center of the laser spot and the nearest interference maximum in a predetermined direction of the interference pattern; and (ii) a position change DS of the position of the center of the laser spot. According to one embodiment, the optical device satisfies the condition in Equation 1 below: |DS|+|DP|=n*L (Equation 1) is configured to apply to a continuous position change DS, n being a natural number. L is the distance between two adjacent interference maxima of the interference pattern in the predetermined direction, including a tolerance of ±5%. In other words, this condition does not have to be met exactly according to an embodiment, and deviations of the order of ±5% from the exact value n*L are equally acceptable, i.e. this condition is considered to be met for deviations within the tolerance range. In general, according to another embodiment, the tolerance range is ±3%, or according to yet another embodiment, ±1%. According to yet another embodiment, equation 1 is met exactly (tolerance 0%). Furthermore, the distance change DP is defined by the difference between the first and second distances, each of which is defined in the predetermined direction. The first and second distances thus denote the distance between the center of the associated laser spot and the nearest interference maxima in the predetermined direction of the interference pattern of the associated laser spot. || here is the known absolute value function, ie, |x|=x for x≧0, and |x|=−x for x<0.

[0038] Accordingly, according to an embodiment, the method has one or several of the following embodiments: According to an embodiment, the method for interference structuring a surface has one or several of the following features: generating a first interference pattern on the surface, generating a second interference pattern on the surface, the generating of the first interference pattern and the generating of the second interference pattern being performed by a single optical device having an inlet. According to an embodiment, the first interference pattern and the second interference pattern are generated by the optical device by changing the position of the laser beam at the inlet and / or the angle of incidence of the laser beam with respect to the inlet, whereby (i) a spacing change DP of the spacing between the center of the laser spot and the nearest interference maximum in a predetermined direction of the interference pattern and / or (ii) a position change DS of the position of the center of the laser spot.

[0039] According to another embodiment, the method has one or several of the following features: providing an optical device having a beam splitter for splitting a laser beam into at least two partial beams, where the optical device recombines the partial beams into a laser spot; directing the laser beam to an entrance of the optical device, where a first state of the laser beam at the entrance generates a laser spot at a first position P1, the laser spot having a first interference pattern; and a second state of the laser beam at the entrance generates a laser spot at a second position P2, the laser spot having having a second interference pattern, the first and second states differing in at least one of (i) the position of the laser beam at the inlet and (ii) the angle of incidence of the laser beam relative to the inlet, and the optical device (or, according to another embodiment, the method) provides a difference DI_AB=DI_A-DI_B between the first optical path length difference DI_A and the second optical path length difference DI_B due to a position change DS=P1-P2, which difference causes a spacing change DP between the center of the laser spot and the nearest interference maximum in a predetermined direction of the interference pattern, so that the second interference pattern continues in phase with the first interference pattern.

[0040] According to one embodiment, the optical device is configured such that the condition according to equation 1 is satisfied for continuous position changes DS.

[0041] The change in the position of the laser beam at the inlet and / or the angle of incidence of the laser beam with respect to the inlet can also generally be described as the state of the laser beam at the inlet. According to an embodiment, the inlet of the optical device is formed by a beam splitter. This does not, of course, exclude that optical elements are arranged in front of the beam splitter, which in this sense of course do not belong to the optical device.

[0042] In this sense, according to one embodiment, a first state of the laser beam at the inlet generates a first interference pattern within the laser spot (within the first laser spot, in this case the first laser spot has its center at a first position P1) and a second state of the laser beam at the inlet generates a second interference pattern within the laser spot (within the second laser spot, in this case the second laser spot has its center at a second position P2), the first and second states differing in at least one of (i) the position of the laser beam at the inlet and (ii) the angle of incidence of the laser beam relative to the inlet.

[0043] Consistent with the above-mentioned aspects, one embodiment comprises the use of an optical device to generate a first interference pattern and a second interference pattern by changing the position of the laser beam at the inlet and / or changing the angle of incidence of the laser beam with respect to the inlet, thereby causing at least one of (i) a spacing change DP in the spacing between the center of the laser spot and the nearest interference maximum in a predetermined direction of the interference pattern, and (ii) a position change DS in the position of the center of the laser spot, wherein the optical device is configured to satisfy the condition according to Equation 1.

[0044] According to yet another embodiment, a laser processing apparatus has one or more of the following features of an optical device having an entrance for receiving a laser beam, the optical device having a beam splitter for splitting the laser beam into at least two partial beams, the optical device combining the partial beams again into a laser spot to generate an interference pattern in the laser spot, a first state of the laser beam at the entrance generating a first interference pattern and a second state of the laser beam at the entrance generating a second interference pattern, the first and second states differing in at least one of (i) a position of the laser beam at the entrance and (ii) an angle of incidence of the laser beam with respect to the entrance, the optical device being configured such that the second interference pattern is an in-phase continuation of the first interference pattern.

[0045] The change in the state of the laser beam at the inlet, in particular the change in the position of the laser beam at the inlet and / or the change in the angle of incidence of the laser beam with respect to the inlet, does not exclude the movement of the optical device and the surface relative to each other in order to structure a relatively large surface area. For example, in the case of two-beam interference (which gives rise to an interference pattern with a large number of parallel lines), the optical device can be moved in the direction of the longitudinal spread of the lines in order to achieve a large-area surface structuring, which is desirable, for example, in applications where the surface structure generated by the interference pattern forms so-called flow elements, for example riblets on aircraft parts.

[0046] According to one embodiment, the optical device is configured such that the second interference pattern is an in-phase continuation of the first interference pattern.

[0047] For example, according to an embodiment, the corresponding configuration of the optical device can be active, for example, by adjusting the distance change DP by a suitable actuator device acting, for example, on a mirror device or an optical medium. For example, a wedge-shaped optical element can be used for this purpose, which can further be inserted or removed from the partial beam, so that the path length of the partial beam in the wedge-shaped optical element can be increased or decreased, and thus the phase state (and thus the DP) can be changed. The control signal for the actuator device can be generated, for example, by using a look-up table from a study of the state of the laser beam, or also, for example, by a suitably trained artificial intelligence.

[0048] Furthermore, according to an embodiment, the configuration of the optical device for the in-phase continuation of the first interference pattern may have a passive structure, for example if the individual elements of the optical device as well as the interaction of the individual optical elements are constructed such that the coherent continuation of the first interference pattern occurs solely on the basis of the (static) construction of the optical device, at any rate within a given effective range, for example within an effective range for the state of the laser beam (for example within a given effective range for the position of the laser beam at the inlet and / or for the angle of incidence of the laser beam relative to the inlet) or within an effective range for the position change DS. In general, according to an embodiment, equation 1 is fulfilled at least within the effective range.

[0049] According to one embodiment, a first state of the laser beam at the inlet defines a first position P1 of the center of the laser spot and a first interference pattern, a second state of the laser beam at the inlet defines a second position P2 of the center of the laser spot and a second interference pattern, partial beam pairs of at least two partial beams in the first state have a first optical path length difference DI_A and partial beam pairs in the second state have a second optical path length difference DI_B, and for a position change DS=P1-P2 the optical device provides a difference DI_AB=DI_A-DI_B between the first optical path length difference DI_A and the second optical path length difference DI_B, which difference causes a spacing change DP, so that the second interference pattern continues in phase with the first interference pattern.

[0050] According to an embodiment, the predetermined direction, which defines both the first and second intervals, is a direction pointing from the center of the laser spot to the nearest interference maximum in this direction (e.g., an interference maximum of the first interference pattern, i.e., according to an embodiment, the first interference pattern defines the first direction). For example, insofar as the interference pattern has a number of parallel interference lines (e.g., the parallel interference lines are caused, for example, by two-beam interference), according to an embodiment, the predetermined direction is a direction perpendicular to the interference lines. For example, in this case, the predetermined direction may be defined as a direction pointing from the center of the laser spot to the right, perpendicular to the interference lines.

[0051] As known to those skilled in the art, in the case of interference of three or more partial beams, for example in the case of three partial beams (three-beam interference), the interference pattern is, for example, a dot pattern. According to one embodiment, there are two mutually linearly independent predetermined directions along which the interference pattern can continue in phase, which is advantageous in particular in the case of three-beam interference.

[0052] Although in some embodiments reference is made to different individual intervals, e.g., a first interval and a second interval, it is understood that the relevant embodiments apply to all intervals as long as the conditions set forth in Equation 1 are satisfied.

[0053] According to one embodiment, the condition shown in Equation 1 is true for a predetermined coverage area (e.g. coverage area defined by an optical device). According to one embodiment, the condition in Equation 1 is true at least up to a position change value equal to the diameter of the laser spot. According to another embodiment, the condition in Equation 1 is true for a continuous position change DS from a start position (position change equal to zero) up to a position change value. According to another embodiment, the position change value is equal to twice the diameter of the laser spot, according to yet another embodiment, five times, ten times or twenty times.

[0054] According to one embodiment, the inlet includes a first region and a second region, and the laser processing apparatus has an actuator device for positioning the laser beam within the first region and subsequently within the second region.

[0055] For example, according to one embodiment, the actuator device is a laser scanner actuator device, by means of which the laser beam can be scanned over the inlet, in particular over a first area and over a second area of ​​the inlet, in such a way that a continuous and coherent continuation of the interference pattern of the laser spots is possible.

[0056] In the sense of the above-mentioned embodiments, for example, the first state can correspond to a laser beam incident on a first region, and the second state can correspond to a laser beam incident on a second region.

[0057] According to an embodiment, the first and second interference patterns overlap. For example, according to an embodiment, the first and second interference patterns have a number of intensity maxima and minima arranged successively in the longitudinal direction. According to an embodiment, the second interference pattern is displaced longitudinally (or parallel to the longitudinal direction) with respect to the first interference pattern. Moreover, according to an embodiment, the longitudinal direction corresponds to a predetermined direction.

[0058] When there are at least two linearly independent longitudinal directions (e.g., in one embodiment, in the case of three-beam interference), the predetermined direction in which the first and second intervals are defined is parallel to at least one of the longitudinal directions.

[0059] According to an embodiment, the optical device has at least one optical element operating in transmission (in other words, this at least one optical element is a transmissive optical element). According to an embodiment, the path length portion of the radiation path of each of the partial beams (i.e. each of the partial beams whose radiation path extends through the transmissive optical element) in the transmissive optical element changes by less than ±5%, in particular less than ±1%, more in particular less than ±0.5%, the change in the path length portion being caused by a change in the state of the laser beam at the inlet. According to an embodiment (i.e. optional but not essential), all partial beams of the at least two partial beams (generated by the beam splitter from the laser beam) pass through the transmissive optical element.

[0060] According to one embodiment, the above-mentioned embodiments regarding the transmissive optical elements apply to each transmissive optical element of the optical device.

[0061] According to one embodiment, of the respective transmissive optical elements of the optical device behind the beam splitter, each transmitted plane pair present in the radiation path of at least one of the partial beams makes an angle of at most 10 degrees, in particular at most 5 degrees. In experiments, it has been found that a relatively small angle can promote the in-phase continuation of the interference patterns.

[0062] According to one embodiment, the optical device for at least one partial beam of the at least two partial beams defines a radiation path, in which the radiation path defines a first path difference between the optical path length of the radiation path and the geometrical path length of the radiation path for a first position of the laser spot, and the radiation path defines a second path difference between the optical path length of the radiation path and the geometrical path length of the radiation path for a second position of the laser spot, and within the validity range of the conditions, at least one of the following applies: (i) the difference between the first path difference and the second path difference is small enough that this condition is fulfilled, (ii) the difference between the first path difference and the second path difference is smaller than twenty times the wavelength of the laser beam, in particular smaller than ten times, and (iii) both the first path difference and the second path difference are smaller than 10 mm, in particular smaller than 5 mm.

[0063] According to one embodiment, the optical device after the beam splitter does not include a prism.

[0064] Without wishing to be limited to theory in this discussion, it is the inventor's current understanding that significant differences in path length difference between the optical path of the radiation path and the geometric path of the radiation path may adversely affect the effective range or even prevent the laser spot interference pattern from continuing in phase upon changes in the laser beam conditions or changes in the position of the laser spot.

[0065] In the above sense, according to one embodiment, the difference between the first path length difference and the second path length difference is sufficiently small if this difference is less than 10% of the wavelength of the laser beam or if this difference causes a deviation of the interference pattern from the ideal phase by less than 5% of the spacing L in the expected direction of two adjacent interference maxima.

[0066] According to an embodiment, all optical elements of the optical device operate in reflection, in particular according to an embodiment, all optical elements of the optical device operate exclusively in reflection, in other words all optical elements of the optical device are reflective elements, except for the beam splitter according to another embodiment.

[0067] In the present application, according to one embodiment, the concept "operating in reflection" means that the optical element concerned has an optical function based on the reflection of incident electromagnetic radiation and contributes with this optical function to the overall function of the optical device. In this sense, semi-transparent mirrors also operate in reflection.

[0068] According to one embodiment, the beam splitter is a semi-transparent mirror. According to one embodiment, the semi-transparent mirror is a light-transmitting medium with a flat surface, on one of which (the entrance side) at least one layer, in particular a dielectric stack, is applied, so that a certain part of the incident laser intensity is (intentionally) reflected and another part is (intentionally) transmitted. The reflected part of the incident laser intensity is referred to herein as the reflected laser beam. The transmitted part of the incident laser intensity is referred to herein as the transmitted laser beam. The incident laser intensity is also referred to herein as the intensity of the laser beam. On the exit side of the light-transmitting medium, optionally according to one embodiment, a dielectric stack is also applied, which has an anti-reflection effect, so that the intensity that penetrates into the medium can be released again with little loss. According to one embodiment, the transmitted and reflected beams have a similar (or even the same) beam shape and / or a similar (or even the same) beam profile. Furthermore, according to one embodiment, the transmitted and reflected beams have the same polarization. This has the advantage that the polarization does not have to be adapted again later on in one of the beams: in order to obtain good interference, both partial beams require according to one embodiment the same polarization.

[0069] According to one embodiment, the semi-transmissive mirror is configured to reflect a significant portion (greater than 10%) of the incident laser intensity and transmit a significant portion (greater than 10%) of the incident laser intensity. Preferably, the optically transmissive medium has negligible absorption for the laser beam.

[0070] According to one embodiment, the beam splitter is configured such that the intensity of the reflected laser radiation is equal to the intensity of the transmitted laser radiation. This type of beam splitter is referred to as a 50:50 beam splitter. According to another embodiment, the beam splitter is a non-polarizing 50:50 beam splitter.

[0071] According to an embodiment, the beam splitter is configured and arranged to generate a first intensity distribution under the at least two partial beams when the laser beam is incident on the first region (of the inlet) and to generate a second intensity distribution under the at least two partial beams when the laser beam is incident on the second region (of the inlet). According to an embodiment, the first and second intensity distributions differ from each other by less than 10%. In other words, according to an embodiment, the intensity distribution in the at least two partial beams is within a tolerance of 10%, regardless of the state of the laser beam.

[0072] According to one embodiment, processing of an object using a laser processing apparatus as described herein or using a method as described herein is performed to impart to the object a surface structure according to an embodiment of the subject matter disclosed herein.

[0073] According to one embodiment, the object has a surface with a periodic surface structure, the surface structure defining a perimeter line that is an envelope of the surface structure, the perimeter line having a shape that periodically repeats a basic element at least piecewise in a portion of the perimeter line, and the periodicity of the surface structure differs from the periodicity of the portion of the perimeter line.

[0074] In particular, the edge region of the surface structure may reflect the cross-sectional shape of the laser spot (or the processing spot produced by the laser spot).

[0075] According to one embodiment, the surface structure has at least one of the following characteristics: (i) the surface structure has a number of parallel grooves; (ii) the basic element has at least one arcuate portion (e.g., only one or two or more arcuate portions); (iii) the perimeter line portion is a first perimeter line portion, the basic element is a first basic element, the perimeter line has a second perimeter line portion, the second perimeter line portion is opposite the first perimeter line portion, and is a periodic repetition of the second basic element, and the periodicity of the surface structure is different from the periodicity of the second perimeter line portion.

[0076] According to another embodiment, the object comprises a surface having a surface structure, the surface structure having a maximum depth extension relative to the surface, the depth extension of the surface structure increases from a first position to a second position at the edge of the surface structure to 80% of the maximum depth extension, and the distance between the first and second positions is 100 μm. In other words, the depth extension of the surface structure increases from a first position to a second position at the edge of the surface structure to a maximum of 80% of the maximum depth, and the distance between the first and second positions is 100 μm.

[0077] A slow increase in the depth extension of the surface structure starting from the edge of the surface structure (80% of the maximum depth extension is only achieved at 100 μm or more) may be advantageous in terms of flow engineering, especially when the surface structure is a riblet structure, especially a riblet structure as described herein. According to one embodiment, the slow increase in the depth extension as described herein is performed at least in a direction parallel to the flow direction, for example to flow through the surface structure. EXAMPLES

[0078] In the following, exemplary embodiments of the subject matter disclosed herein are described with reference to the drawings. It should be noted that in different figures, similar or identical elements or components are partially labeled with the same reference numerals or with reference numerals that differ only in the first digit. Features or components that are the same or at least functionally the same as corresponding features or components in another figure are described in detail only when they first appear in the following text, and this description is not repeated when these features and components (or corresponding reference numerals) appear later. The above provisions also apply to the following embodiments according to one embodiment, and vice versa. Moreover, the features and embodiments described above can be combined with the features and embodiments described below.

[0079] FIG. 1 illustrates diagrammatically the functional principle of an optical device 100 according to an embodiment of the subject matter disclosed herein.

[0080] According to an embodiment, the optical device 100 has an inlet 101 for receiving the laser beam 102. According to an embodiment, the optical device 100 is configured to split the laser beam 102 into at least two (e.g. two) partial beams 104, 204 and to combine the partial beams 104, 204 again into a laser spot 106 in order to generate an interference pattern in the laser spot 106. According to an embodiment, the radiation paths of the partial beams are the same or approximately the same length, for example within a tolerance of ±5%. In the case of a real structure with a finite beam diameter, interference occurs in particular due to the angle between the partial beams.

[0081] According to an embodiment, the first partial beam 104 of both partial beams has a first optical path length I1 and the second partial beam 204 of the partial beams has a second optical path length I2. This results in a path length difference DI=I2-I1 of the partial beams. A change in this path length difference DI causes a spacing change DP as described herein. According to an embodiment, the laser spot 106 is directed towards the surface 107.

[0082] FIG. 2 illustrates a laser processing apparatus 108 according to an embodiment of the presently disclosed subject matter.

[0083] According to an embodiment, the laser processing apparatus 108 comprises an optical device 200. According to an embodiment, the optical device 200 comprises a beam splitter 110 for splitting the laser beam 102 into two partial beams 104, 204. According to an embodiment, the beam splitter 110 is a semi-transparent mirror, for example as shown in FIG. 2. According to an embodiment, the entrance 101 of the optical device 200 is formed by the beam splitter 110. According to another embodiment, the optical device 200 defines one radiation path 112, 212 for each of the partial beams 104, 204. According to an embodiment, the at least two radiation paths comprise a first radiation path 112 and a second radiation path 212. According to another embodiment, at least one of the radiation paths (for example each radiation path 112, 212) comprises at least one optical element, for example at least one mirror 114, 214. According to an embodiment, three mirrors 114, 214 may be provided, for example as shown in FIG. 2. According to an embodiment, at least one mirror 114, 214 defines the course of the associated radiation path 112, 212 through the optical device 200. According to an embodiment, the optical device 200 is configured to converge the partial beams 112, 212 (e.g. by the positioning and / or orientation of at least one optical element) into one laser spot 106. According to an embodiment, the convergence of the partial beams is performed by suitable optical elements, e.g. mirror 214, as shown, for example, in FIG.

[0084] According to an embodiment, the optical device 200 is positioned relative to the surface 107 of the object, so that the laser spot 106 and an interference pattern are generated on the surface 107 for processing the surface 107 by means of an interference pattern, for example structuring the surface 107 by means of an interference pattern, also referred to as direct interference structuring.

[0085] According to one embodiment, the laser processing apparatus includes a laser source 116 for generating the laser beam 102. According to another embodiment, the laser source 116 is located external to the laser processing apparatus and is connectable to the laser processing apparatus.

[0086] According to one embodiment, the laser beam is a CO2 laser beam, in particular a CO2 laser beam with a power of at least 800 W (800 Watts). Correspondingly, according to one embodiment, the laser source is a CO2 laser source. According to one embodiment, the CO2 laser source is configured to be operated in continuous wave or with a pulse time of <1 ms (less than 1 millisecond).

[0087] According to one embodiment, the laser processing device is provided for structuring a paint surface, in particular a cured paint surface.

[0088] According to another embodiment, the laser processing apparatus comprises at least one movable mirror 314 and an actuator device 118 for controlling the at least one movable mirror 314. According to an embodiment, the at least one movable mirror 314 is arranged to change the state of the laser beam at the inlet 101, for example to change the position of the laser beam at the inlet 101 and / or the angle of incidence of the laser beam 102 with respect to the inlet 101. For example, by pivoting the at least one movable mirror 314, the position of the laser beam 102 and the angle of incidence with respect to the inlet may be changed, for example as shown in FIG. 2 by a first state of the laser beam at the inlet (solid line at 102) and a second state of the laser beam at the inlet (dashed line at 102). In this case, in the first state, the laser beam 102 is positioned in a first area 119 of the semi-transparent mirror 110 (which semi-transparent mirror is considered as the inlet of the optical device according to an embodiment) and in the second state, the laser beam 102 is positioned in a second area 121 of the semi-transparent mirror 110.

[0089] According to an embodiment, the optical device 200 is configured such that a first state generates a first interference pattern and a second state generates a second interference pattern, the second interference pattern being a continuation of the first interference pattern in phase. According to an embodiment, this in-phase continuation of the (first) interference pattern is performed even during a continuous change of state of the laser beam at the inlet 101, whereby a resulting interference pattern that is expanded in size can be effectively achieved while simultaneously achieving a defined phase relationship between the interference maxima and minima in the expanded interference pattern. Compared to the development of a single laser spot, a more homogeneous processing is achieved by the in-phase continuation of the interference pattern, since the single laser spot typically has a Gaussian beam profile. According to an embodiment, a homogeneous processing of the surface is achieved by a uniform integrated total intensity per unit area, and the generated intensity maxima are in phase.

[0090] The resulting interference pattern may be generated, for example, by pivoting the laser beam 102 on the inlet 101, that is, according to one embodiment, on the beam splitter 110.

[0091] According to an embodiment, the optical element 128, in particular the optical element for focusing the laser beam, is provided, for example, as part of an optical device or as part of a laser processing apparatus. According to an embodiment, the optical element for focusing the laser beam is a lens, for example a lens arranged between the at least one movable mirror 314 and the beam splitter 110, as shown in FIG. 2. According to another embodiment, the optical element 128 is a focus shifting device. According to another embodiment, an optical element 228, in particular an optical element for focusing the laser beam, as shown, for example, by two dashed lines, may be arranged between the laser source and the at least one movable mirror 314 (for example separately or additionally to the optical element 128).

[0092] According to another embodiment, the laser processing apparatus 108 includes a controller 120 for controlling the components of the laser processing apparatus (e.g., actuator device 118 and, if present, laser source 116) via control signals 122. According to one embodiment, the controller includes a computing device 124 and a memory device 126 for storing computer programming executable by the computing device 124 to implement the functionality of embodiments of the subject matter disclosed herein.

[0093] According to another embodiment, a further actuator device 130 is provided for positioning the optical device 200 and the surface 107 relative to each other. This can be advantageous, for example, in the case of large-area laser processing to move the resulting interference pattern on the surface 107. According to an embodiment, the further actuator device 130 may be controlled by the controller 120 of the laser processing apparatus via the control signal 122, or alternatively by an external controller (not shown in FIG. 2). It should be understood that the (further) actuator device 130 is shown in this figure only exemplarily, especially with regard to the position. For example, the optical device and possibly other components of the laser processing apparatus, such as at least one movable mirror 314, the actuator device 118, the optical system 128 or the optical system 228, may be intended to be slidable with respect to the laser source 116 and the surface 107. For example, the optical device 100 (and optionally the optical system 228) may be attached to a robot arm for positioning (and possibly moving) these components on the surface 107. The robot arm in this case forms the actuator device 130 or part of the actuator device 130 .

[0094] FIG. 3 illustrates a portion of a laser processing apparatus 208 according to an embodiment of the subject matter disclosed herein.

[0095] Laser processing apparatus 208 may include one or more of the features described in connection with laser processing apparatus 108 from FIG. 2 even though the features associated with FIG. 3 are not shown.

[0096] According to an embodiment, the laser processing apparatus 208 comprises an optical device 300. Unlike the optical device 200 described in connection with Fig. 2, the optical device 300 has two mirrors 114, 214 in each of the radiation paths 112, 212. Furthermore, according to an embodiment, the optical element 228 for focusing the laser beam 102 is arranged in front of the at least one movable mirror 314 in the beam direction. Furthermore, according to an embodiment, no optical element is arranged between the at least one movable mirror 314 and the beam splitter 110 (which may be realized, for example, by a semi-transparent mirror as shown in Fig. 3).

[0097] FIG. 4 illustrates a portion of a laser processing apparatus 308 according to an embodiment of the subject matter disclosed herein.

[0098] Laser processing apparatus 308 may include one or more of the features described in connection with laser processing apparatus 108 from FIG. 2, even though the features associated with FIG. 4 are not shown.

[0099] According to one embodiment, the laser processing apparatus 308 includes an optical device 400. According to one embodiment, the beam splitter 110 of the optical device is formed by a diffractive optical element (DOE) that splits the laser beam 102 into at least two partial beams 104, 204.

[0100] According to one embodiment, the diffractive optical element is configured such that at least two partial beams 104, 204 emerging from the diffractive optical element form an acute angle, as shown, for example, in FIG.

[0101] According to one embodiment, each of the radiation paths 112 , 212 of the at least two partial beams 104 , 204 comprises only one optical element, for example only one mirror 214 .

[0102] The optical devices 300, 400 described in relation to Figures 3 and 4 require only relatively few optical elements to be present in the radiation path 112, 212 due to the very shallow angle of incidence on the final mirror 214, which may result in distortion of the associated partial beams 104, 204.

[0103] FIG. 5 illustrates a first interference pattern 108 and a second interference pattern 208 that can be generated by a laser processing apparatus according to embodiments of the subject matter disclosed herein.

[0104] According to an embodiment, the first interference pattern 108 is generated by the laser spot 106, whose center 132 is at a first position 134, and the second interference pattern 208 is generated by the laser spot 106, whose center 132 is at a second position 136. The statement "the center 132 of the laser spot 106 is at a predetermined position (e.g., the first position 134)" is also abbreviated to the statement "the laser spot 106 is at a predetermined position" in this specification. Therefore, both expressions can be considered equivalent. According to an embodiment, the laser spot 106 at the first position 134 and the second position 136 are generated by the fact that for the first position 134, a first condition occurs for the laser beam at the entrance of the optical device (in one embodiment, with respect to the position and the incidence angle of the laser beam) and for the second position 136 of the laser spot 106, a second condition occurs for the laser beam at the entrance of the optical device.

[0105] Thus, a change in the state of the laser beam (eg, a change in position and angle of incidence) causes a position change 142 (also referred to herein as DS) of the position of the center 132 of the laser spot 106 .

[0106] According to one embodiment, the optical device generating the laser spot 106 is configured such that the second interference pattern 208 is an in-phase continuation of the first interference pattern 108, as shown, for example, in Fig. 5. The in-phase continuation of the interference patterns is also referred to as "beyond the boundaries of the individual laser spots" in the case of two-beam interference, for example at a constant spacing 138 (also referred to herein as L) between two adjacent interference maxima.

[0107] Thus, the phase position of the interference maximum 140 of the second interference pattern 208 coincides with the phase position of the interference maximum 140 of the first interference pattern 108. In other words, the optical device changes from a first spacing 141 between the center 132 of the laser spot 106 and the nearest interference maximum 240 in the predetermined direction 144 at the first position 134 to a second spacing 241 between the center 132 of the laser spot 106 and the nearest interference maximum 240 in the predetermined direction 144 at the second position 136. In this case, the difference between the first spacing 141 and the second spacing 241 corresponds to the spacing change DP.

[0108] According to an embodiment, the optical device ensures the continuation of the first interference pattern in phase for successive position changes (in any case within the effective range, e.g. within the effective range for position changes). In this manner, a continuous filling of the plane between the first interference pattern 108 and the second interference pattern 208 occurs during a continuous position change of the center 132 of the laser spot 106 from the first position 134 to the second position 136. Since the phase alignment is guaranteed at each position, an interference maximum 340 (shown by a dashed line in FIG. 5 ) occurs between the first position and the second position, which has the same phase relationship as the interference maximum 140 of the first interference pattern 108 and the interference maximum 140 of the second interference pattern 208. In other words, all interference maxima 140, 240, 340 resulting from a continuous position change between the first position 134 and the second position 136, as shown for example in FIG. 5 , are in phase.

[0109] FIG. 6 illustrates a cross-sectional view of a portion of an optical device 100 of a laser processing apparatus according to an embodiment of the subject matter disclosed herein.

[0110] According to one embodiment, the optical device 100 comprises at least one transmissive optical element 150, which is in the radiation path 112 of at least one of the partial beams, for example the partial beam 104 from FIG. 1. According to one embodiment, the transmissive optical element 150 comprises a transmitted plane pair comprising a first plane 154 and a second plane 156. According to another embodiment, the plane pair 154, 156 form an angle 158 of, according to one embodiment, at most 10 degrees.

[0111] FIG. 7 illustrates a portion of an object 160 according to an embodiment of the subject matter disclosed herein.

[0112] According to an embodiment, the object has a surface 107 with a periodic surface structure 162. According to an embodiment, the surface structure 162 has a number of parallel grooves, which are illustrated in FIG. 7 by a number of parallel lines 164. It is noted that the lines 164 do not represent the dimensions of the grooves of the surface structure 162, but merely illustrate the periodicity. Indeed, according to an embodiment, for example in a riblet application, the grooves are wider than the ribs that remain between the grooves. In this sense, according to an embodiment, the lines 164 may represent, for example, the center lines (or center lines) of the grooves. According to an embodiment, the surface structure is a riblet structure with a number of riblets as described in WO 2018 / 197555, i.e. a surface structure that reduces the flow resistance of the surface compared to a smooth surface. In particular, with regard to the use, function, shape, dimensions, properties, etc. of the riblets, explicit reference is made to WO 2018 / 197555, the entire disclosure of which, in particular the dimensions and use of the riblets, is hereby incorporated by reference.

[0113] As is usual for riblets, in one embodiment the grooves have respective walls. The adjacent walls of each two adjacent grooves thus form the two opposite sides of the rib between these two grooves. In other words, according to one embodiment, a large number of grooves produces a large number of ribs on the surface, which act as riblets (i.e. reduce the flow resistance on the surface) in the case of suitable dimensions, for example as described in the above-cited WO 2018 / 197555. According to one embodiment, the sides of the ribs are at an acute angle. In particular, the ribs are configured to be tapered according to one embodiment.

[0114] According to one embodiment, the ribs extend substantially parallel to one another and in particular parallel to the flow direction of the flow expected on the surface.

[0115] According to an embodiment, the periodic surface structure 162 is generated by irradiation with a laser spot, which is illustrated in Fig. 7 by a dashed line at 106 at a first position. According to an embodiment, the surface structure 162 is generated by generation of laser spots 106 at various positions on the surface 107. According to an embodiment, the laser spots have an interference pattern at each position, which interference pattern continues in phase with the interference pattern of the laser spot at the first position, as for example shown in Fig. 7. According to an embodiment, the surface 107 is machined by each interference pattern, which each interference pattern generates a machined spot 169 in the surface 107. By stitching together the interference patterns or machined spots 169 according to an embodiment, the surface structure 162 arises. If the laser source is a pulsed laser source, then as the laser beam moves continuously on the entrance of the optical device (not shown in FIG. 7), discontinuous machining spots 169 result, which overlap and are distinguishable from one another, for example as shown in FIG. 7, upon appropriate selection of, for example, the laser pulse frequency and the moving speed of the laser beam on the entrance of the optical device.

[0116] According to one embodiment, the processing spots 169 may be generated along a straight line, for example in one direction 167 on the surface 107 as shown in FIG.

[0117] As a result, the overlapping processing spots 169 define a perimeter 168, which is the envelope of the surface structure and according to an embodiment has the shape of a periodic repetition of basic elements, some of which are represented by reference 171 in FIG. 7, at least within a perimeter section, for example within a perimeter section 170 illustrated in FIG. 7. According to an embodiment, the basic elements are at least piecewise arc-shaped, for example circular arc-shaped as shown in FIG. 7. According to another embodiment, the basic elements may be segments of an ellipse or basic elements of other shapes. According to an embodiment, for example when the surface structure 162 is exposed to a flow, the arc-shaped basic elements or the arc-shaped parts of the basic elements can cause the flow not to occur along a straight line and therefore in a very narrow inlet area in the surface structure, but over the entire inlet area that is extended in the flow direction. This can be advantageous in terms of flow engineering.

[0118] According to an embodiment, the periodicity of the periodic surface structure 162 differs from the periodicity of the peripheral line portion 170, as shown for example in Fig. 7. According to an embodiment, the difference between the periodicity of the surface structure 162 and the periodicity of the peripheral line portion 170 is therefore based on the fact that the periodicity of the surface structure 162 is determined by the interference of at least two partial beams, whereas the periodicity of the peripheral line portion 170 is determined by the dimensions of the laser spot and the resulting overlap of the processing spots 169.

[0119] FIG. 8 illustrates a portion of another object 260 in accordance with an embodiment of the subject matter disclosed herein.

[0120] According to one embodiment, the surface 107 of the object 260 has a periodic surface structure 162 generated by the movement of the laser spot 106 in two mutually independent linear directions. For example, the laser processing apparatus may be configured such that the laser spot 106 moves along a meandering path 172, as shown, for example, in FIG. 8. The movement of the laser spot 106 in two mutually independent linear directions may be achieved, for example, by positioning the laser spot along a first path portion 174 parallel to the first direction 167 and by positioning the laser spot along a second path portion 176 extending at an angle (e.g., perpendicular) to the first path portion 174.

[0121] Furthermore, it may be provided that the laser spot 106 moves in two mutually linear and independent directions with two parallel path portions, for example with two parallel path portions 174, 178 as shown in FIG. 8. According to an embodiment, a movement in the opposite direction is performed on both parallel path portions, indicated by 182 in FIG. 8, whereby for example a meander-shaped path can be realized, for example as shown in FIG. 8. According to an embodiment, a movement in the same direction can always be performed on the parallel path portions of the laser spot (not shown in FIG. 8). Due to the overlap of the laser spot on the parallel path portions, a backward movement (along a second path portion, not shown in FIG. 8) is necessary, during which, according to an embodiment, the laser beam is switched off, so that no laser spot is generated during the backward movement. Furthermore, according to an embodiment, it may also be provided that the laser beam is switched off along the second path portion 176, so that no laser spot is generated along the second path portion. For example, it may be planned that the laser beam is switched on only at the end point of a path portion, e.g., the second path portion 176, so that a laser spot is generated at the end point, e.g., as shown in FIG. 8.

[0122] According to an embodiment, the positioning of the laser spot along the parallel path portions, for example along the parallel path portions 174, 178, is generated by a movement of the laser beam on the entrance of the optical device, while the movement inclined to the parallel path portions, for example along the path portions 176, 180, is performed by a movement of the surface 107 relative to the reference point 184. This has the advantage that large surfaces can be processed. The movement of the surface 107 relative to the optical device can for example be performed continuously, and according to an embodiment, for the realization of a predetermined path (for example a meandering path as shown in FIG. 8), the laser processing device is configured to perform a corrective movement by a movement of the optical device relative to the reference point 184, thereby positioning the laser spot along the predetermined path. According to another embodiment, instead of the movement of the surface 107 relative to the reference point 184, the laser processing device can also be configured so that a movement inclined to the parallel path portions (for example perpendicular to the parallel path portions) is also generated by a movement of the laser beam on the entrance of the optical device. In general, for example, the actuator device 118 and the at least one movable mirror 314 may be configured such that a movement of the laser beam 102 is possible in two mutually linear and independent directions. According to an embodiment, the actuator device 118 and the at least one movable mirror 314 may be formed by a galvanometer scanner known per se.

[0123] According to one embodiment, the surface structure 162 defines a first perimeter portion 170 of the perimeter to be introduced, which perimeter portion 170 has a shape that periodically repeats a basic element 171. According to another embodiment, the surface structure 162 has a second perimeter portion 172 that has a shape that periodically repeats a basic element 171, which second perimeter portion 172 faces the first perimeter portion 170, as shown for example in Fig. 8. According to one embodiment, the second perimeter portion 172 is a mirror image of the first perimeter portion 170, as shown for example in Fig. 8.

[0124] It is self-evident that under certain conditions the perimeter line portion will not have a shape that (recognizably) periodically repeats the basic element, for example if the laser beam is emitted continuously (without pulses) along the first path portion 174 during the positioning of the laser spot 106 or if the overlap of the interference patterns of the individual pulses is very high. However, in such a case the further perimeter line portion 185, 186 may have a shape that sufficiently periodically repeats the basic element, for example if the continuous laser beam is switched off when positioning in the direction 188 of this further perimeter line portion 185, 186.

[0125] FIG. 9 illustrates a portion of an object 360 according to an embodiment of the subject matter disclosed herein.

[0126] Similar to FIG. 8, FIG. 9 also shows an object 360 having a surface 107 with a periodic surface structure 162, which defines a perimeter 168 that is the envelope of the surface structure 162. According to one embodiment, the perimeter 168 comprises a first perimeter portion 170 and a second perimeter portion 172, which periodically repeat a primitive element 171, which according to one embodiment consists of only one arc-shaped portion, as shown for example in FIG. 9. According to another embodiment, the perimeter 168 comprises a third perimeter portion 185, which periodically repeats a primitive element 183, which consists of two arc-shaped portions, as shown for example in FIG. 9. According to another embodiment, the perimeter 168 comprises a fourth perimeter portion 186, which periodically repeats another primitive element 187, which consists of two arc-shaped portions, as shown for example in FIG. 9.

[0127] FIG. 10 shows a cross-sectional view of a portion of the surface structure 162 from FIG. 9 along section line XX in FIG.

[0128] According to an embodiment, the surface 107 is formed by a paint layer 109, which is formed on the body of the object 360 (this body is not shown in FIG. 10). According to an embodiment, the paint layer 109 is a hardened paint layer, for example an aircraft paint layer. According to an embodiment, the surface structure 162 comprises a number of grooves 189, one of which is exemplarily shown in cross section in FIG. 10. According to an embodiment, the surface structure, and thus at least one of the grooves 189, has a maximum depth extension (or depth) 190, which according to an embodiment is smaller than a thickness 191 of the paint layer 109.

[0129] According to one embodiment, the depth extension of the surface structure 162 from a first position 198 at the edge of the surface structure 162 to the nearest second position 199 increases to 80% of the maximum depth extension. "Nearest" in this sense means that if there are several second positions whose depth extension is 80% of the maximum depth extension, the one having the shortest distance to the first position 198 is selected. According to another embodiment, the distance 163 between the first position 198 and the second position 199 is at least 100 μm, for example at least 300 μm or at least 500 μm.

[0130] For example, according to one embodiment, the depth 190 decreases in the edge region 192 of the groove 189 and goes continuously to zero, i.e., to the level of the surface 107, as shown, for example, in FIG. 10. The aspect of the surface structure 162 in the edge region 192 is, according to one embodiment, due to the shooting behavior of the laser, whereby in the edge region 192 the removal by the laser spot is relatively small, since the laser spot typically has a smaller intensity in the edge region than in the center of the laser spot (average over the interference pattern of the laser spot). A shooting behavior with the characteristics described herein can be achieved, for example, by a surface formed by a paint layer and processed using a CO2 laser.

[0131] According to one embodiment, the paint surface is a paint surface as described in WO 2018 / 197555. In particular, the paint surface may be formed by a paint based on a polymer, in particular based on polyurethane or acrylic or epoxy. According to one embodiment, the paint is a clear coat or a top coat. According to one embodiment, the absorption spectrum of the paint has an overlap with the emission spectrum of the CO2 laser. According to one embodiment, the CO2 laser can operate at a wavelength in the range of 9 μm to 11 μm.

[0132] According to one embodiment, the paint contains a pigment that affects the coloring of the paint. Typically, topcoats contain such pigments. According to another embodiment, the pigment changes the absorption behavior of the paint with respect to the laser beam. According to one embodiment, the laser penetration behavior may be influenced by the type and concentration of the pigment.

[0133] According to one embodiment, the coating is a first coating that is disposed on a second coating. The first coating layer is therefore also called a topcoat layer, and the second coating layer is therefore also called a basecoat layer. According to one embodiment, the topcoat layer is a clear coat layer or a topcoat layer, in particular based on polyurethane. According to another embodiment, the basecoat layer is formed by an epoxy system (e.g. cured epoxy resin) or generally by plastics.

[0134] FIG. 11 shows a plan view of a portion of a surface structure 162 according to an embodiment of the subject matter disclosed herein.

[0135] As already explained above, the surface structure 162 defines an envelope, also referred to herein as a perimeter 168. As in the figures already described above, the surface structure 162 is only indicated diagrammatically in Figure 11 by a number of parallel lines, each of which represents a groove 189 in the surface (not shown in Figure 11).

[0136] 12 and 13 show cross-sectional views of the surface structure 162 from Fig. 11 along the section lines XII-XII or XIII-XIII in Fig. 11. The allocation of corresponding section lines from Fig. 13 to Fig. 12 is further represented by arrows 193.

[0137] According to one embodiment, the parallel grooves 189 have a relatively shallow depth in edge regions 192 (shown by rays in FIG. 11), as can be seen, for example, in conjunction with FIGS. 11 and 12-13.

[0138] The increasing depth elongation from the edge of the surface structure is also evident in Figures 12 and 13. It should be understood that the second position 199 corresponding to 80% of the maximum depth elongation can also be determined by interpolation or extrapolation, as long as the surface structure does not have a recess at a percentage of 80% of the maximum depth elongation. According to one embodiment, for example, starting from the first position, it may be provided that the second position is determined in a direction along the maximum gradient of the depth elongation of the surface structure.

[0139] FIG. 14 illustrates a laser processing apparatus 408 according to an embodiment of the presently disclosed subject matter.

[0140] According to one embodiment, the laser processing apparatus 408 includes an optical device 500 formed according to one or more of the embodiments disclosed herein.

[0141] According to another embodiment, the laser processing apparatus 408 includes a scanning device 194, which may include, for example, an actuator device and at least one movable mirror according to an embodiment of the subject matter disclosed herein. According to one embodiment, the scanning device 194 is formed by a galvanometer scanner. According to one embodiment, the scanning device 194 is configured to direct the laser beam 102 to the entrance 101 of the optical device 500 and move the laser beam 102 over the entrance 101 of the optical device 500.

[0142] According to another embodiment, the laser processing apparatus 408 includes a laser inlet 195 that is connectable to the laser source 116. According to one embodiment, the laser inlet 195 is formed by a scanning device 194, as shown, for example, in FIG. 14. According to one embodiment, the laser source 116 is external to the laser processing apparatus 408. For example, if the laser processing apparatus 408 is mounted on a robot arm, the laser source 116 may be positioned on the floor next to the robot arm and optically connected to the laser inlet 195. According to another embodiment (not shown in FIG. 14), the laser source 116 is part of the laser processing apparatus 408.

[0143] According to one embodiment, the optical device generates at least two partial beams 112, 212 from the laser beam 102, which generate an interference pattern in the laser spot 106.

[0144] According to one embodiment, the object 160 is positioned relative to the optical device 500 such that the laser spot 106 is positioned on the surface 107 of the object 160 .

[0145] According to one embodiment, the laser processing apparatus is fitted with a further actuator device 130, by means of which the optical device 500 and the object 160 can be moved relative to each other, for example, to structure surface portions of the object 160 that cannot be covered solely by the movement of the laser beam 102 on the entrance 101 of the optical device 500.

[0146] According to an embodiment, the further actuator device 130 comprises at least one first actuator 196, by means of which the object 160 can be moved relative to the reference point 184. According to an embodiment, the further actuator device 130 further comprises at least one further actuator 197, by means of which the laser processing apparatus 408 can be moved relative to the reference point 184. According to an embodiment, the at least one second actuator 197 is formed by a robot arm.

[0147] It should be noted that the components (e.g., apparatus, features, method steps, controllers, actuator devices, optical devices, actuators, optical elements, etc.) disclosed herein are not limited to the critical components as illustrated in some embodiments. Rather, the subject matter disclosed herein can be implemented in a variety of ways while still providing the specific functionality disclosed.

[0148] In particular, the subject matter described herein may be provided in a variety of ways, at a variety of granularities at the device level, or at the method level, or at the software level, while still providing the indicated functionality. It should also be noted that, according to an embodiment, separate components may be provided for each of the functions disclosed herein. According to another embodiment, a single component may be constructed to provide two or more of the functions described herein. For example, the functionality of both mirrors 214 in FIG. 2 according to one embodiment may be realized by a single roof edge mirror. According to yet another embodiment, two or more components may be constructed to together provide a single function described herein.

[0149] It is pointed out that the embodiment in the drawings described in this specification is only a limited selection of possible implementation variations of the subject matter disclosed in this specification. Therefore, the features of the individual embodiments can be combined with each other in an appropriate manner, so that a person skilled in the art can consider that a large number of different embodiments are disclosed by the implementation variations explicitly stated in this specification. Furthermore, it should be mentioned that concepts such as "ein" or "eines" do not exclude a plurality. Concepts such as "enthaltend" or "having" do not exclude other features or method steps. The concepts "having" or "enthaltend" or "comprising" respectively include both the meanings of "comprising, inter alia" and "consisting of".

[0150] Furthermore, it should be noted that the illustrated subject matter and elements in the drawings (e.g., laser processing apparatus, optical devices, etc.) depict certain combinations of several embodiments of the subject matter disclosed in this specification, and that other combinations of each of the embodiments are likewise possible and are considered to be disclosed by this application.

[0151] Advantageous combinations of embodiments of the subject matter disclosed herein can be summarized as follows: The laser processing apparatus comprises an optical device having an entrance for receiving a laser beam, the optical device having a beam splitter for splitting the laser beam into at least two partial beams, the optical device combining the partial beams again into a laser spot to generate an interference pattern within the laser spot, a first state of the laser beam at the entrance generating a first interference pattern and a second state of the laser beam generating a second interference pattern, the first and second states differing in at least one of (i) a position of the laser beam at the entrance and (ii) an angle of incidence of the laser beam relative to the entrance, the optical device being configured such that the second interference pattern is an in-phase continuation of the first interference pattern. (Other possible items) [Item 1] In a laser processing apparatus (108, 208, 308, 408) including an optical device (100, 200, 300, 400, 500), The optical device (100, 200, 300, 400, 500) has an inlet (101) for receiving a laser beam (102); The optical device (100, 200, 300, 400, 500) comprises a beam splitter (110) for splitting the laser beam (102) into at least two partial beams (104, 204); the optical device (100, 200, 300, 400, 500) recombines the partial beams (104, 204) into a laser spot (106) to generate an interference pattern (108, 208) within the laser spot (106); The change in the position of the laser beam at the inlet (101) and / or the change in the angle of incidence of the laser beam (102) relative to the inlet (101) is (i) a spacing change DP of a spacing (141, 241) between a center (132) of the laser spot (106) and a nearest interference maximum (240) in a predetermined direction (144) of the interference pattern (108, 208); (ii) the position change DS of the position (134, 136) of the center (132) of the laser spot (106); causing at least one of the following: The optical device (100, 200, 300, 400, 500) is |DS|+|DP|=n*L is constructed to apply to continuous position changes DS, n is a natural number, L is the spacing between two adjacent interference maxima (140, 240, 340) of the interference pattern (108, 208) in the predetermined direction (144), including a tolerance of ±5%; the spacing change DP is defined by the difference between the first spacing (141) and the second spacing (241); Each of the first interval (141) and the second interval (241) is defined in the predetermined direction (144). Laser processing equipment (108, 208, 308, 408). [Item 2] a first state of the laser beam (102) at the entrance (101) defines a first position P1 (134) of the center (132) of the laser spot (106) and a first interference pattern (108); a second state of the laser beam (102) at the entrance (101) defines a second position P2 (136) of the center (132) of the laser spot (106) and a second interference pattern (208); a pair of partial beams (104, 204) of the at least two partial beams (104, 204) has a first optical path length difference DI_A in the first state; the pair of partial beams (104, 204) has a second optical path length difference DI_B in the second state; the optical device (100, 200, 300, 400, 500) provides a difference DI_AB=DI_A-DI_B between the first optical path length difference and the second optical path length difference due to the position change DS (DS=P1-P2), said difference causing a spacing change DP, so that the second interference pattern (208) continues in phase with the first interference pattern (108); Item 1. The laser processing apparatus (108, 208, 308, 408) according to item 1. [Item 3] said condition being true at least up to a position change value equal to the diameter of said laser spot (106); Item 3. The laser processing apparatus (108, 208, 308, 408) according to item 1 or 2. [Item 4] the inlet (101) includes a first region (119) and a second region (121); an actuator device (118) for positioning the laser beam (102) within the first region (119) and subsequently within the second region (121), A laser processing apparatus (108, 208, 308, 408) according to any one of items 1 to 3. [Item 5] the optical device (100, 200, 300, 400, 500) has at least one optical element (150) operating in transmission, in particular a path length portion (151) of the radiation path of each of the partial beams (104, 204) whose radiation path extends through the optical element varies within the optical element (150) by less than ±5%, in particular less than ±1%, more particularly less than ±0.5%, the variation of the path length portion (151) being caused by a change in the condition of the laser beam (102) at the inlet (101), A laser processing apparatus (108, 208, 308, 408) according to any one of items 1 to 4. [Item 6] A laser processing apparatus (108, 208, 308, 408) according to any one of items 1 to 4, wherein all optical elements of the optical device operate exclusively in reflection. [Item 7] 7. The laser processing apparatus (108, 208, 308, 408) of any one of items 1 to 6, wherein the beam splitter (110) is a semi-transparent mirror. [Item 8] A laser processing apparatus (108, 208, 308, 408) according to any one of items 1 to 5 and 7, wherein among the respective transmissive optical elements of the optical device behind the beam splitter (110), each transmitted plane pair (154, 156) present in at least one radiation path (112, 212) of the partial beam (104, 204) forms an angle (158) of at most 10 degrees, in particular an angle (158) of at most 5 degrees. [Item 9] 9. The laser processing apparatus (108, 208, 308, 408) of any one of claims 1 to 8, wherein the optical device (100, 200, 300, 400, 500) behind the beam splitter (110) does not have a prism. [Item 10] A laser processing apparatus (108, 208, 308, 408) according to any one of items 1 to 9, wherein the laser beam (102) is a CO2 laser beam, in particular a CO2 laser beam having an output of at least 800 W. [Item 11] 11. The laser processing apparatus (108, 208, 308, 408) according to any one of claims 1 to 10, wherein the laser processing apparatus (108, 208, 308, 408) is installed for structuring a paint surface. [Item 12] 1. A method for interference structuring a surface, the method comprising the steps of: generating a first interference pattern (108) on the surface; generating a second interference pattern (208) on the surface, wherein the generation of the first interference pattern (108) and the generation of the second interference pattern (208) are performed by a single optical device (100, 200, 300, 400, 500) having an inlet (101); The first interference pattern (108) and the second interference pattern (208) are generated by the optical device (100, 200, 300, 400, 500) by varying the position of the laser beam at the inlet (101) and / or the angle of incidence of the laser beam (102) with respect to the inlet (101), thereby (i) a change in the spacing DP of the spacing (141, 241) between the center (132) of the laser spot (106) and the nearest interference maximum (240) in a predetermined direction (144) of the first interference pattern and the second interference pattern (108, 208) is performed; and / or (ii) a position change DS of the center (132) of the laser spot (106) is performed; The optical device (100, 200, 300, 400, 500) is |DS|+|DP|=n*L is constructed to satisfy the continuous position change DS, n is a natural number, L is the spacing between two adjacent interference maxima (140, 240, 340) of the first interference pattern (108) in the predetermined direction (144), including a tolerance of ±5%; the spacing change DP is defined by the difference between the first spacing (141) and the second spacing (241); Each of the first interval (141) and the second interval (241) is defined in the predetermined direction (144). A method for interference structuring surfaces. [Item 13] generating a first interference pattern (108) and a second interference pattern (208) by varying the position of the laser beam at the inlet (101) and / or varying the angle of incidence of the laser beam (102) relative to said inlet (101), thereby (i) a change in spacing DP between the center (132) of the laser spot (106) and the nearest interference maximum (240) in a predetermined direction (144) of the first interference pattern and the second interference pattern (108, 208); (ii) the position change DS of the center (132) of the laser spot (106); Using an optical device to cause at least one of The optical device (100, 200, 300, 400, 500) is |DS|+|DP|=n*L is constructed to apply to continuous position changes DS, n is a natural number, L is the spacing between two adjacent interference maxima (140, 240, 340) of the first and second interference patterns (108, 208) in the predetermined direction (144), including a tolerance of ±5%; the spacing change DP is defined by the difference between the first spacing (141) and the second spacing (241); Each of the first interval (141) and the second interval (241) is defined in the predetermined direction (144). Use of optical devices. [Item 14] In a laser processing apparatus (108, 208, 308, 408) including an optical device (100, 200, 300, 400, 500), The optical device (100, 200, 300, 400, 500) has an inlet (101) for receiving a laser beam (102); The optical device (100, 200, 300, 400, 500) comprises a beam splitter (110) for splitting the laser beam (102) into at least two partial beams (104, 204); the optical device (100, 200, 300, 400, 500) recombines the partial beams (104, 204) into a laser spot (106) to generate an interference pattern (108, 208) within the laser spot (106); a first state of the laser beam (102) at the inlet (101) generates a first interference pattern and a second state of the laser beam (102) generates a second interference pattern; The first state and the second state differ in at least one of: (i) a position of the laser beam at the inlet (101); and (ii) an angle of incidence of the laser beam (102) with respect to the inlet (101); the optical device (100, 200, 300, 400, 500) is configured such that the second interference pattern is an in-phase continuation of the first interference pattern; Laser processing equipment (108, 208, 308, 408). [Item 15] In a laser processing apparatus (108, 208, 308, 408) including an optical device (100, 200, 300, 400, 500), The optical device (100, 200, 300, 400, 500) has an inlet (101) for receiving a laser beam (102); The optical device (100, 200, 300, 400, 500) comprises a beam splitter (110) for splitting the laser beam (102) into at least two partial beams (104, 204); the optical device (100, 200, 300, 400, 500) combines the partial beams (104, 204) again into a laser spot (106) to generate an interference pattern (108, 208) within the laser spot (106), a first state of the laser beam (102) at the inlet (101) generating a first interference pattern and a second state of the laser beam (102) generating a second interference pattern; The first state and the second state differ in at least one of: (i) a position of the laser beam at the inlet (101); and (ii) an angle of incidence of the laser beam (102) with respect to the inlet (101); the center (132) of the first interference pattern (108) and the center (132) of the second interference pattern (208) have a distance corresponding to at least one diameter of the laser spot (106), in particular at least five times the diameter of the laser spot (106), and more particularly at least ten times the diameter of the laser spot (106); a change in path length of the radiation path of each of the partial beams (104, 204) upon a state change from the first state to the second state is less than ±5%, in particular less than ±1%, and more in particular less than ±0.5% of the total path length of the radiation path from the beam splitter (110) to the laser spot (106); Laser processing equipment (108, 208, 308, 408). [Item 16] An object (160, 260, 360) having a surface (107) with a periodic surface structure (162), wherein the surface structure (162) defines a perimeter line (168) that is an envelope of the surface structure (162), the perimeter line (168) having a shape that periodically repeats basic elements (171, 183, 187) at least for each segment in a perimeter line portion (170, 172, 185, 186), and the periodicity of the surface structure (162) is different from the periodicity of the perimeter line portion (170, 172, 185, 186). [Item 17] The surface structure (162) has the following characteristics: - said surface structure (162) comprises a multiplicity of parallel grooves (189); - said basic element has at least one arcuate portion; and having at least one of the characteristics of the perimeter portion is a first perimeter portion (170, 185), the basic element is a first basic element (171, 183), and the perimeter (168) has a second perimeter portion (172, 186) opposite the first perimeter portion (170, 185); The object described in item 16 (160, 260, 360). [Item 18] The surface (107) has a surface structure (162); the surface structure (162) has a maximum depth extension (190) relative to the surface (107); a depth extension of the surface structure (162) increases by 80% of the maximum depth extension (190) from a first location (198) to a second location (199) at an edge of the surface structure (162); the spacing (163) between the first location (198) and the second location (199) is at least 100 μm; An object with a surface (160, 260, 360).

Claims

1. the surface has a surface structure; the surface structure has a maximum depth extension relative to the surface; the depth extension of the surface structure increases from a first location to a second location at an edge of the surface structure by 80% of the maximum depth extension; The spacing between the first location and the second location is at least 100 μm. An object with a surface.

2. The object of claim 1 , wherein the surface structure comprises a plurality of parallel grooves.

3. 3. The object of claim 1 or 2, wherein the walls of each two adjacent grooves form two opposite sides of a rib between said two adjacent grooves.

4. a surface having a periodic surface structure, the surface structure defining a perimeter that is an envelope of the surface structure, the perimeter having a shape that periodically repeats a basic element at least piecewise in a perimeter portion, the periodicity of the surface structure being different from the periodicity of the perimeter portion; The perimeter is defined by overlapping processing spots, the processing spots including a first processing spot and a second processing spot; The surface structure has a plurality of parallel grooves; the surface structure includes a first portion at the processing spot and a second portion at the second processing spot, the second portion of the surface structure being continuous in phase with the first portion of the surface structure; a first distance between a center of the first processing spot and a nearest groove in a predetermined direction is different from a second distance between a center of the second processing spot and a nearest groove in the predetermined direction; object.

5. The surface structure has the following characteristics: - said basic element has at least one arcuate portion; and having at least one of the characteristics of the perimeter portion is a first perimeter portion, the base element is a first base element, and the perimeter has a second perimeter portion opposite the first perimeter portion; 5. The object of claim 4.

6. 6. The object of claim 4 or 5, wherein the parallel grooves have a reduced depth in an edge region.

7. The peripheral line portion may be determined by switching off a continuous laser beam during positioning in the direction of the peripheral line portion.

6. An object according to claim 4 or 5, having said shape of a periodic repetition of a basic element.

8. 6. An object according to claim 4 or 5, wherein the surface structure extends from the surface into a depth of the object.

9. 9. The object according to claim 1, wherein the surface is a painted surface.

10. The object of claim 9 , wherein the surface is formed by a layer of paint formed on a body of the object.

11. The object of claim 10 , wherein the surface structure has a maximum depth extension that is less than a thickness of the paint layer.

12. 12. The object according to claim 9, wherein the painted surface is formed by a polymer-based paint.

13. 12. An object according to any one of claims 9 to 11, wherein the paint is based on polyurethane or acrylic or epoxy.

14. 14. The object according to any one of claims 9 to 13, wherein the paint is a clear coat or a top coat.

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