Line Optics

Abstract

The present invention relates to a line optical system (10) for generating a predetermined laser line (24) on a work surface (26), the line optical system (10) comprising at least one laser source (12) for generating at least one laser beam (20), an optical assembly (14) configured to generate an illumination beam (22) from the at least one laser beam (20) along a beam path, the illumination beam (22) defining a beam direction intersecting the work surface (26) and forming the predetermined laser line (24) in the region of the work surface (26), the optical assembly (14) comprising a focusing lens (28) for focusing the illumination beam (22) in the beam path. a camera system (36) configured to observe the illumination beam (22) at at least three defined positions downstream of the beam of the focusing lens (28), the illumination beam (22) having a focus state at each of the at least three defined positions, and a control device (44) configured to determine a focus position of the focus of the focusing lens (28) based on the focus states at the at least three defined positions and to adjust the position of the focusing lens (28) parallel to the beam direction such that the focus position is located within the work surface (26).

Description

[Technical field]

[0001] The present invention relates to a line optic for producing a predetermined laser line on a work surface. [Background technology]

[0002] Such a line optical system is basically known from US Pat. No. 5,399,633.

[0003] Laser radiation in the form of a line of such line optics can be advantageously used for the thermal processing of workpieces. The workpiece can be, for example, a plastic material on a glass plate acting as a support material. The plastic material can in particular be a film on which organic light-emitting diodes, so-called OLEDs, and / or thin-film transistors are produced. OLED films are increasingly used for displays in smartphones, tablet PCs, televisions and other devices with screen displays. After the production of the electronic structure, the film has to be peeled off from the glass substrate. This is done by laser radiation in the form of a thin laser line, which moves at a defined speed relative to the glass plate, and in so doing can release the adhesive bond of the film through the glass plate. This type of application is often called LLO or laser lift-off in practice.

[0004] A further, frequently used application for sequential irradiation of a workpiece with a given laser line can be the line-by-line melting of amorphous silicon on a support plate. In this case too, the laser line moves at a given speed relative to the workpiece surface. By melting and subsequent cooling, the relatively cheap amorphous silicon can be converted into higher quality polycrystalline silicon. In practice, this kind of application is often called solid-state laser annealing (SLA), sequential lateral solidification (SLS) or excimer laser annealing (ELA).

[0005] For this type of application, the laser line on the working surface must be as long as possible in one direction in order to cover as large a processing surface as possible, and in comparison, must be very short in the other direction in order to provide the necessary energy density for the respective processing. Long and thin laser lines are therefore desirable, with a very large aspect ratio of line length to line width. In typical applications, line lengths of 100 mm or more are desirable, with line widths in the order of 20 μm. The direction in which the laser line extends is usually referred to as the so-called major axis (LA) of the beam profile, and the line width is called the minor axis (SA, short axis). Usually, the laser line has a defined intensity curve in both axes. It is often desirable for the laser line in the major axis to have an intensity profile that is as rectangular or trapezoidal as possible, the latter being advantageous when several laser lines are combined to form a long overall line. In some applications, a rectangular intensity profile (so-called top hat profile) or a Gaussian profile is often desired in the minor axis direction.

[0006] US Pat. No. 5,399,633 discloses an apparatus for generating such a laser line, with numerous details regarding the elements of the optical assembly. The optical assembly of that document includes a collimator for collimating the raw laser beam, as well as a beam converter, a homogenizer, and a focusing stage. The beam converter receives the collimated raw beam and expands it in the longitudinal direction. In principle, the beam converter can also receive multiple raw laser beams from multiple laser sources and combine them into one expanded laser beam of higher power. The homogenizer generates the desired beam profile in the longitudinal direction. The focusing stage focuses the converted laser beam at a defined position in the area of ​​the working surface. The known apparatus is suitable for LLO and SLA applications and can be implemented with laser radiation of wavelengths from the infrared (IR) to the ultraviolet (UV) range.

[0007] High laser powers can lead to changes in the optical properties of the line focus system, for example due to thermal lensing of the optics or mechanical expansion due to temperature changes, which can cause the focal position of the laser line to shift.

[0008] This problem is known in cutting optics and line focus systems. To compensate for this, the focusing optics of the line focus system have traditionally been adjusted on the basis of a characteristic curve, which indicates the position of the focusing optics as a function of time. The characteristic curve is predetermined, for example in a calibration process, and can be used, for example in the form of control data for the control unit of the line optics, to adjust the focusing optics during operation.

[0009] For example, Patent Document 3 presents an optical system for generating an illumination line. The optical system comprises a laser beam source for generating a laser beam along an optical axis. The optical system further comprises a beam shaping device configured to shape the laser beam such that the beam profile of the laser beam has a major axis and a minor axis, and an imaging device (e.g., a focusing lens) arranged after the beam shaping device in the beam path of the laser beam and configured to image the laser beam thus shaped as an illumination line. The beam shaping device comprises at least one telescope assembly including a first lens group and a second lens group, where the first lens group and the second lens group have optical refractive power at least with respect to the minor axis. The optical system comprises a first moving device for moving at least one of the first lens group and the second lens group along the optical axis. The optical system comprises a second moving means for moving the imaging device along the optical axis. The optical system further comprises a control unit configured to control the first and second movement devices such that at least one of the first and second lens groups and the imaging device are moved while the laser beam source generates the laser beam. Control data is stored in a memory of the control unit for controlling the first and second movement devices.

[0010] However, known line optics still leave room for improvement, especially with regard to the adjustment of the focusing optics. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] US Patent Application Publication No. 2006 / 182155A1 [Patent Document 2] International Publication No. 2018 / 019374A1 Brochure [Patent Document 3] German Patent Application Publication No. 102018200078A1 Summary of the Invention [Problem to be solved by the invention]

[0012] SUMMARY OF THE PRESENT EMBODIMENTS Against this background, it is an object of the present invention to provide a line optic having improved adjustment of the focusing optics. [Means for solving the problem]

[0013] According to one aspect, the problem is solved by a line optics for generating a predetermined laser line on a work surface. The line optics comprises at least one laser light source for generating at least one laser beam, an optical assembly, a camera system, and a control device. The optical assembly is configured to generate an illumination beam along a beam path from the at least one laser beam, where the illumination beam defines a beam direction intersecting the work surface and forms a predetermined laser line in the area of ​​the work surface, and the optical assembly has a focusing unit in the beam path with a focusing lens for focusing the illumination beam, the focusing lens being movable parallel to the beam direction. The camera system is configured to observe the illumination beam at at least three defined positions beam-downstream of the focusing lens, where the illumination beam has a focus state at each of the at least three defined positions. The control device is configured to determine a focus position of the focus of the focusing lens based on the focus states at the at least three defined positions, and to adjust the position of the focusing lens parallel to the beam direction such that the focus position is located in the work surface.

[0014] The at least one laser light source may be an ultraviolet laser light source for generating an ultraviolet laser beam or an infrared laser light source for generating an infrared laser beam. The at least one laser light source may be configured to generate a plurality of laser beams. In particular, a plurality of laser light sources may be provided, where each laser light source may be configured to generate a respective one laser beam.

[0015] The optical assembly is configured to generate an illumination beam along a beam path from the at least one laser beam. The illumination beam has a line-shaped beam profile in the region of the working surface. Thereby, the illumination beam generates a predetermined laser line in the working surface. In other words, the illumination beam has a beam profile in the region of the working surface, perpendicular to the beam direction, with a major axis having a major beam width and a minor axis having a minor beam width. To generate the illumination beam from the at least one laser beam, the optical assembly may have a series of beam-guiding and beam-shaping optics along the beam path. The optical assembly may further be movable relative to the working surface along a movement direction, preferably parallel to the working surface, in order to process the workpiece with the illumination beam.

[0016] The optical assembly comprises a focusing unit, which is configured to focus the illumination beam. In particular, the focusing unit can focus the illumination beam in a minor axis direction. In other words, the focusing unit is used for focusing the minor axis of the laser beam. The focusing unit is preferably arranged in the beam path downstream of the beam guide and of the beam shaping optics.

[0017] For focusing the illumination beam, the focusing unit has a focusing lens. The focusing lens can have one or more optical systems. The focus of the focusing lens is located at a downstream focus position of the focusing lens. In other words, the focus position of the focus of the focusing lens is the downstream position of the focusing lens at which the focusing lens focuses the illumination beam. The focus position thereby defines the downstream distance from the focusing lens at which the focus of the focusing lens is located. The term "downstream" should be understood in relation to the beam path and beam direction of the illumination beam and means that something is located downstream in the beam path or beam direction. In other words, the focus position of the focus of the focusing lens is located behind the focusing lens in the beam path or beam direction of the illumination beam.

[0018] The focusing lens is furthermore movable parallel to the beam direction. In other words, the focusing lens is mounted so as to be movable parallel to the beam direction. For the movement of the focusing lens, the focusing unit can for example have a movement device. By the movement of the focusing lens, the focal position of the focusing lens can be adjusted.

[0019] The line optics may also comprise other optics downstream of the focusing unit, such as, for example, protective lenses, deflection mirrors, etc. The other optics preferably do not have a beam shaping or focusing function.

[0020] The camera system is configured to observe the illumination beam at at least three defined positions on the beam downstream side of the focusing lens. Observation means that the camera system takes one or more images of the illumination beam, in which one or more images, for example, the illumination beam is imaged at the respective defined positions. The at least three positions are arranged downstream of the focusing lens in the beam direction of the illumination beam. In one embodiment, the camera system can be configured to observe the illumination beam at three defined positions on the beam downstream side of the focusing lens. In another embodiment, the camera system can be configured to observe the illumination beam at three or more defined positions on the beam downstream side of the focusing lens, in particular four, five or six defined positions. The plurality of defined positions is different. The plurality of defined positions can preferably be arranged consecutively at equal intervals in the beam direction.

[0021] The focusing lens has a different distance to each defined position in the beam direction. Depending on the distance to the focusing lens, the focus state of the illumination beam also changes. The focus state describes the focusing at a particular position relative to the focusing lens. In particular, the focus state describes how strongly the illumination beam is focused at the respective position. In other words, the focus state describes the degree of focusing at the respective position. At the focus position, i.e. at the focus of the focusing lens, the focusing is maximum. The further away parallel to the beam direction from the focus position, the lower the focusing becomes. Thus, each defined position is assigned a specific focus state of the illumination beam.

[0022] The control device is configured to determine a focal position of the focus of the focusing lens based on the focus state of at least three of the defined positions, and adjust the position of the focusing lens parallel to the beam direction so that the focal position is located on the work surface. The control device preferably analyzes the focus state observed by the camera system at the defined positions and determines the focal position based thereon. Based on the determined focal position, the control device can appropriately adjust the position of the focusing lens. In particular, the position of the focusing lens is adjusted so that the focal position is displaced to the work surface. In this way, the short axis of the laser line is focused in the work surface.

[0023] The control device may therefore in particular have an adjustment unit and a data processing unit. The data processing unit may for example carry out a calculation step for determining the focal position. The adjustment unit may for example generate control instructions which are used to adjust the position of the focusing lens. For example, said control instructions may control a movement device arranged to move the focusing lens.

[0024] The line optics according to the invention are designed so that the focal position can be determined online, i.e. during operation, and tracked, i.e. adjusted accordingly. In this case, several positions along the beam direction are observed by a camera system. For example, several positions can be imaged on the camera using suitable optics. Images of the illumination beam at these positions can then be processed using an algorithm to determine the exact focal position. The position of the focusing lens can be adjusted accordingly.

[0025] Thereby, the line optics according to the invention makes it possible to determine and correspondingly adjust the focal position of the focusing lens during operation, so that the illumination beam, in particular the laser line, is focused in the working plane.

[0026] This completely solves the problem that was initially set.

[0027] In a first embodiment of the line optics, the camera system is positioned downstream of the beam at the work surface.

[0028] The illumination beam is therefore observed in the beam path behind the work surface, so that the illumination beam can be observed after passing through the work surface or after being reflected at the work surface.

[0029] In particular, the camera system can be arranged to observe a reflected beam of the illumination beam on the working surface, which reflected beam is a return reflection of the illumination beam on the working surface. In particular, during operation, the illumination beam can be reflected on the surface of a workpiece that is arranged on the working surface and is processed by the laser line. This reflection can be observed by the camera system. In this way, in addition to the focal displacement, the variations of the working surface can also be compensated.

[0030] Alternatively, the camera system can be arranged behind the work surface, which is then located between the camera system and the focusing unit, whereby the camera system can observe the illuminating beam passing through the work surface. This arrangement of the camera system allows the focal position to be determined and adjusted when no workpiece is arranged in the work surface or when the workpiece is completely cut by the laser line, so that the laser line can pass through the work surface and reach the camera system.

[0031] In a further embodiment, the line optical system has a further optical system arranged beam downstream of the focusing unit, whereby the further optical system is configured to split the illumination beam, whereby a part of the illumination beam runs in the direction of the work surface and a further part of the illumination beam runs in the direction of the camera system.

[0032] As mentioned above, further optics, such as for example a deflection mirror or a protective glass, can be arranged along the beam after the focusing unit, through which the illumination beam reaches the direction of the working surface. The further optics can for example split the illumination beam into two parts. In particular, the further optics can be formed to reflect a part of the illumination beam and transmit another part of the illumination beam. Either the transmitted part or the reflected part runs in the direction of the working surface, while the corresponding other part runs in the direction of the camera system and is observed by the camera system. The reflected part of the illumination beam can be referred to as a back reflection of the illumination beam in the further optics.

[0033] In particular, the camera system can be configured to observe the return reflection of the illumination beam on the further optical system, which is particularly advantageous if the further optical system comprises a protective glass through which the illumination beam passes in the direction of the working surface, whereby the return reflection on the protective glass is observed by the camera system.

[0034] Alternatively, the camera system can also be configured to observe the transmitted part of the illumination beam. For this purpose, the further optical system can, for example, comprise a partially transparent, in particular semi-transparent, deflection mirror, which can deflect, i.e. reflect, the illumination beam in the direction of the working surface, so that the transmitted part of the illumination beam transmitted by the deflection mirror can be observed by the camera system.

[0035] In a further embodiment of the line optical system, the camera system comprises at least one camera for taking at least one image, the at least one image comprising an imaging of the illumination beam at at least three defined positions.

[0036] In other words, the at least one image has one image per defined position. Each of these images thus depicts the illumination beam at the respective defined position in a respective focus state. The illumination beam is thus depicted differently focused in the images. Based on these images, the control device can determine the corresponding focus state at the corresponding defined position.

[0037] In particular, the camera system can have a camera for taking an image, where the image has images of the illumination beam at at least three defined positions. These images are preferably depicted in the image at a distance from each other. This means that the images do not overlap in the image. In particular, the images in the image are displaced or offset from each other in the direction of the short axis. In this way, all focus states at at least three defined positions can be depicted in one image.

[0038] Alternatively, the camera system can have multiple cameras, each of which takes one image. Each image has an image of the illumination beam in one of at least three defined positions. In other words, the multiple cameras take corresponding images for each defined position. The number of cameras and the number of images then correspond to the number of defined positions, with each image depicting the illumination beam in a corresponding focus state.

[0039] In a further embodiment of the line optical system, the camera system has a beam splitter configured to split the illumination beam into partial beams, and at least one camera is configured to image the partial beams into at least one image, the imaging of the partial beams corresponding to the imaging of the illumination beam at at least three defined positions.

[0040] The number of partial beams corresponds to the number of defined positions. In particular, the partial beams are arranged apart from one another. This means that the partial beams run next to one another, in particular parallel to one another, and do not overlap in the image. The partial beams can be offset from one another in the direction of the short axis. In an embodiment in which the camera system has one camera, the partial beams are captured by this camera. In this way, the partial beams can be depicted together, preferably side by side, in one image. In an alternative embodiment in which the camera system has several cameras, each partial beam can be captured by one camera in each case. In particular, the number of partial beams then corresponds to the number of cameras and the number of captured images. In this way, each partial beam can be depicted in a separate image. The imaging of the partial beams corresponds to the imaging of the illumination beam at the defined positions. In other words, each partial beam is used for imaging of the illumination beam at a respective one of at least three defined positions. Preferably, the travel path or travel time of the partial beams to the camera at which the partial beams are captured is different. Due to the different lengths of the travel path, the imaging is obtained at different defined positions. The imaging of the partial beams images the illumination beam at different distances to the focusing lens and thus also images the illumination beam in different focus states. For example, the beam splitter can be formed such that the partial beams pass through it in paths of travel of different lengths. This can be realized in particular by one or more deflection mirrors in the beam splitter. In particular, the beam splitter can be configured to extend the paths of travel of the partial beams such that at least three defined positions are arranged successively at equal intervals in the beam direction. The use of the beam splitter thus facilitates the observation of the illumination beam at at least three defined positions with the aid of a camera system.

[0041] In a further embodiment of the line optical system, the control device is configured to determine focus values ​​for each focus state at at least three positions based on at least one image, whereby a focus position of the focus of the focusing lens is determined based on the determined focus values.

[0042] The focus value is a measure of the focusing at a defined position of the illumination beam in the beam direction, i.e. a measure of the sharpness of the image. The focus value has a global extreme value at the focus position of the focus of the focusing lens. In particular, the progression of the focus value in the beam direction can be modeled as a parabolic progression, with the positions of the extreme values ​​corresponding to the focus positions. By determining the focus value at at least three positions in the beam direction, the parabolic progression and thus the positions of the extreme values ​​can be determined. If the focus value is determined at three or more defined positions, an overdetermined system of equations is obtained, which can be solved, for example, by a smoothing calculation, in particular by the least squares method, in order to determine the positions of the extreme values. Alternatively, another function with a global extreme value, in particular a Gaussian function or an even function polynomial of degree 4 or higher, can also be used to model the focus value progression. Preferably, the number of defined positions observed using the camera system is equal to or greater than the degree of the polynomial function plus one.

[0043] In a further embodiment of the line optical system, for each imaging of the illumination beam in at least one image, the beam profile of the illumination beam is determined in the short axis direction, whereby each focus value is determined based on the beam profile of the corresponding imaging.

[0044] The beam profile is an intensity profile which represents the intensity curve of the illumination beam in the direction of the minor axis at each defined position. The respective beam profile can in particular be determined on the basis of a projection of the pixels of the corresponding image in at least one image in the direction of the minor axis along the major axis. The beam profile can preferably be a rectangular intensity profile (so-called top-hat profile) or a Gaussian profile. The focus value can for example be the steepness (also called side steepness) of the beam profile. The steepness represents the steepness in the edge region of the beam profile, i.e. in the sides of the beam profile. The smaller the steepness value, the steeper the sides. The focus value can for example also be the inverse of the steepness. In this case, the steeper the sides, the smaller the focus value. Alternatively, the focus value can also be the width of the beam profile. In particular, the width of the beam profile is determined on the basis of the intensity value 1 / e of the maximum value of the beam profile. 2 , 50% or 90% or more. At the focal position, the steepness of the beam profile is maximum and the inverse of the steepness and the width of the beam profile are minimum. To determine the focal position, it is therefore necessary to determine the position in the beam direction at which the steepness of the beam profile of the illumination beam in the minor axis direction is minimum. Alternatively, it is also possible to determine the position in the beam direction at which the inverse of the steepness of the beam profile of the illumination beam in the minor axis direction or its width is minimum. In particular, the steepness and the width describe a parabolic curve in the beam direction, with the positions of its extrema, in particular the positions of the minimum or maximum, corresponding to the focal position of the focus of the focusing lens. By determining the steepness or the width at three positions in the beam direction, the parabolic curve and thereby also the positions of the extrema can be determined.

[0045] In a further embodiment of the line optical system, the position of the work plane is predetermined downstream in the beam of the focusing lens, and the control device is configured to adjust the position of the focusing lens parallel to the beam direction such that the focal position of the focus of the focusing lens moves from the determined focal position to a predetermined position of the work plane.

[0046] The position of the working surface is therefore the target position of the focal position, and the focal position determined by the control device is the actual position of the focal position. The position of the focusing lens parallel to the beam direction is therefore adjusted such that the focal position is displaced from the actual position to the target position. For example, a displacement vector can be formed from the difference between the target position and the actual position, and the focusing lens is moved accordingly. The position of the working surface can for example be predefined, in particular by a user. In a preferred embodiment, the camera system is arranged such that one of the defined positions corresponds to the target position of the focal position. For this purpose, the illumination beam can be observed, for example, via the further optical system described above. The control device can then adjust the position of the focusing lens such that the focal position is displaced to the corresponding defined position.

[0047] In a further embodiment, the line optics comprises a moving device for moving the focusing lens parallel to the beam direction, wherein the control device is configured to control the moving device to adjust the position of the focusing lens.

[0048] For example, the control device can send control commands to the displacement device, whereby the displacement device displaces the focusing lens according to these control commands. The displacement device can for example have a linear guide, along which the focusing lens can be displaced parallel to the beam direction. The linear guide provides a guide for the focusing lens parallel to the beam direction. The displacement device can also have a drive device, in particular capable of displacing the focusing lens parallel to the beam direction, in particular along the linear guide. In particular, the control device can control the drive device.

[0049] In a further embodiment of the line optics system, the optical assembly further comprises beam guiding and beam shaping optics configured to generate an illumination beam from the at least one laser beam.

[0050] The optical assembly preferably comprises a series of beam-guiding and beam-shaping optics along the beam path, by which the illumination beam is generated. These optics are preferably arranged upstream of the focusing unit in the beam path. The illumination beam generated by the beam-guiding and beam-shaping optics is focused in the working plane by the focusing unit. The optical assembly may comprise, for example, a beam converter, a homogenizer and a large optical system as the beam-guiding and beam-shaping optics. The beam converter may be arranged downstream of the laser light source in the beam path. The beam converter is configured to expand the at least one laser beam transversely to the beam direction, in particular in the longitudinal direction. In particular, the beam converter serves to further optimize and / or efficiently optimize the aspect ratio of the illumination beam with respect to the desired laser line. The homogenizer may be arranged downstream of the beam converter in the beam path. The homogenizer is configured to distribute the at least one, preferably expanded, laser beam uniformly in the longitudinal direction. The homogenizer is thus used to achieve a uniform intensity distribution of the illumination beam along the longitudinal axis. The large optical system is preferably arranged downstream of the homogenizer in the beam path. The large optical system is used for forming the beam profile in the working surface. The large optical system can, for example, have one or more optical elements (e.g., Fourier lenses) along the beam path, which optical elements generate a line-shaped beam profile in the region of the working surface.

[0051] It is understood that the features mentioned above and those to be described below can be used not only in the respective indicated combinations, but also in other combinations or alone, without going beyond the scope of the invention.

[0052] Exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. [Brief description of the drawings]

[0053] [Figure 1]FIG. 1 is a schematic diagram showing one embodiment of a novel line optical system. [Diagram 2] FIG. 2 illustrates imaging of an illumination beam by a focusing lens and different beam profiles of the illumination beam. [Diagram 3] 2A to 2C are two diagrams showing the movement of the focal position of a focusing lens. [Figure 4] 4A-4D show four diagrams illustrating different arrangements of the camera system in the beam path of the line optics. [Diagram 5] 2A-2C show two different embodiments of a camera system; [Figure 6] 1 shows three graphs illustrating focus value distributions at three different focus positions. [Figure 7] 4 is a diagram of a further embodiment of a camera system for taking an image and a graph of the intensity profile of the image; [Figure 8] 11 is a plurality of graphs showing beam profiles and focus value distributions at different focus positions; [Figure 9] 13 shows two graphs illustrating a beam profile and a focus value distribution at a particular focus position. [Figure 10] 1 is a graph showing focus shift over time and corresponding realignment of the focusing lens; [Figure 11] 4 shows a further embodiment of a camera system for capturing an image and a graph showing the intensity profile of the image and the corresponding focus value distribution; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] In FIG. 1, an embodiment of the novel line optics is indicated as a whole by the reference number 10. The line optics 10 generates a laser line 24 in the area of ​​a working surface 26 for processing a workpiece (not shown here) placed in the area of ​​the working surface 26. The laser line 24 runs in a direction called the x-axis in the following. The laser line has a line width observed in the direction of a y-axis, which in this embodiment is perpendicular to the x-axis. In the following, the x-axis therefore corresponds to the major axis of the beam profile formed on the working surface 26, and the y-axis corresponds to the minor axis. In other words, the beam profile has a major axis with a major beam width in the x-direction and a minor axis with a minor beam width in the y-direction. The respective beam width can be defined, for example, as the width of the intensity profile I(x,y) at 50% of the maximum intensity (FWHM, Full Width at Half Maximum) or, for example, as the width between the 90% intensity values ​​(Full Width at 90% Maximum, FW@90%) or in another way.

[0055] In some embodiments, the workpiece may include a surface layer of amorphous silicon that is converted to polycrystalline silicon using the laser line 24. For processing, the laser line 24 may then be moved in a moving direction relative to the work surface 26. In other embodiments, the workpiece may be a transparent support plate from which a deposited film, for example an OLED film, is to be peeled off.

[0056] The line optics 10 includes at least one laser light source 12. In a preferred embodiment, the laser light source 12 may be a solid-state laser. The laser light source 12 generates at least one laser beam 20. In a preferred embodiment, the laser light source 12 may generate multiple laser beams. In an alternative embodiment, the line optics 10 includes multiple laser light sources 12, each generating at least one laser beam 20.

[0057] The line optical system 10 further comprises an optical assembly 14. The optical assembly 14 is configured to generate an illumination beam 22 from the at least one laser beam 20 along a beam path. The illumination beam 22 defines a beam direction intersecting a working surface 26. In the region of the working surface 26, the illumination beam 22 has a beam profile with a major axis having a major beam width and a minor axis having a minor beam width perpendicular to the beam direction. In other words, the illumination beam 22 has a line-shaped beam profile in the region of the working surface 26. The illumination beam 22 thereby generates a laser line 24 on the working surface 26.

[0058] The optical assembly comprises along the beam path a series of beam guiding and beam shaping optics 16 and a focusing unit 18. The focusing unit 18 is disposed downstream of the beam guiding and beam shaping optics 16.

[0059] The beam guiding and beam shaping optics 16 are configured to generate an illumination beam 22 from the at least one laser beam 20. As the beam guiding and beam shaping optics 16, the optical assembly may comprise, for example, a beam converter, a homogenizer, and a large optical system. The focusing unit 18 is configured to focus the illumination beam 22. In particular, the focusing unit 18 focuses the illumination beam 22 in the minor axis direction.

[0060] The focusing unit 18 comprises a focusing lens 28 for focusing the illumination beam 22. The focusing lens 28 may comprise one or more optical systems. The focusing lens 28 can be moved parallel to the beam direction. The focusing unit 18 comprises a movement device 30 configured to move the focusing lens 28 parallel to the beam direction. The movement device 30 comprises a linear guide 32 and a drive device 34. The linear guide 32 provides a guide for moving the focusing lens 28 parallel to the beam direction. Along the linear guide 32 the focusing lens 28 is movable. The drive device 34 is configured to move the focusing lens 28 parallel to the beam direction, in particular along the linear guide 32.

[0061] The line optical system 10 further comprises a camera system 36. The camera system 36 is configured to observe the illumination beam 22 at a defined position downstream of the focusing lens 28. In particular, the camera system 36 is configured to observe the illumination beam 22 at a defined position downstream of the focusing lens 28. The illumination beam 22 has a specific focus state at this defined position. The camera system 36 comprises an imaging system 38 and a camera 40. The imaging system 38 images the illumination beam 22 on the camera 40. The camera 40 is configured to take an image of the illumination beam 22. In particular, the camera 40 is arranged to take an image of the illumination beam 22 at a defined position downstream of the focusing lens 28. Thereby, the image comprises an image of the illumination beam 22 at the defined position.

[0062] In particular, the camera system 36 is configured to observe the illumination beam 22 in at least three defined positions downstream of the focusing lens 28, whereby the illumination beam 22 has a specific focus state in each defined position. To that end, the camera system 36 has at least one camera 40, which takes at least one image comprising an image of the illumination beam 22 in at least three defined positions. In a preferred embodiment, the camera system 36 has only one camera 40 for taking one image, whereby the image comprises an image of the illumination beam 22 in at least three defined positions. In an alternative embodiment, the camera system 36 can have several cameras 40, whereby each camera 40 takes one image, whereby each image comprises an image of the illumination beam 22 in one defined position.

[0063] The camera system 36 may have a beam splitter 42. The beam splitter 42 may be arranged in the beam path between the imaging system 38 and the camera 40. The beam splitter 42 is configured to split the illumination beam 22 to be observed into partial beams. At least one camera 40 is configured to image the partial beams in at least one image, whereby the imaging of the partial beams corresponds to the imaging of the illumination beam 22 in at least three defined positions. In particular, the beam splitter 42 is formed such that the partial beams pass through the beam splitter 42 by travel paths of different lengths. Several partial beams can be captured by one camera 40 and depicted together, preferably side-by-side, in one image. Alternatively, the partial beams can also be captured by several cameras 40 and depicted in separate images.

[0064] The line optical system 10 further comprises a control device 44. The control device 44 is configured to adjust the position of the focusing lens 28 parallel to the beam direction. For this purpose, the control device 44 can, for example, send a corresponding control command to the moving device 30. In this case, the moving device 30 can move the focusing lens 28 along the linear guide 32 by the drive device 34 according to the control command. The control device 44 can also receive data from the camera system 36. The data can comprise one or more captured images. The control device 44 adjusts the position of the focusing lens based on the data from the camera system 36.

[0065] For the adjustment of the position of the focusing lens 28, the control device 44 can, for example, have various subunits, which respectively perform the control of the components of the line optics 10 and / or the processing of data. To that end, the control device 44 can, for example, have an adjustment unit and a data processing unit. The adjustment unit can, for example, generate control commands for adjusting the position of the focusing lens. The data processing unit can, for example, perform a calculation step for analyzing data received from the camera system 36. Based on this analysis, the position of the focusing lens 28 is appropriately adjusted and, in particular, corresponding control commands are generated.

[0066] The controller 44 may be connected to or may include a non-volatile data memory in which a computer program is stored. In some embodiments, the controller 44 is a general-purpose computer, such as a commercially available personal computer running Windows, Linux, or MacOS, and the computer program from the memory includes program code configured and configured for the implementation of the adjustment of the focusing lens 28. In an alternative embodiment, the controller 44 is a logic circuit, such as a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a microcontroller, or any other suitable programmable electrical circuit, in which the adjustment of the focusing lens 28, in particular the control and decision steps, can be implemented using logic circuitry, so that the logic circuitry can be configured and configured for the implementation of the adjustment of the focusing lens 28. For the implementation of the adjustment of the focusing lens 28 in the logic circuitry, any suitable programming language or hardware description language, such as C, VHDL, may be used.

[0067] The control device 44 is configured to determine a focal position of the focal point of the focusing lens 28 based on the focal states at at least three defined positions, and adjust the position of the focusing lens 28 parallel to the beam direction such that the focal position is located within the work surface 26. For example, the control device 44 can analyze the focal states observed at the defined positions by the camera system 36 and determine the focal position based thereon. Based on the determined focal position, the control device 44 can adjust the position of the focusing lens 28 accordingly. In particular, the position of the focusing lens 28 is adjusted such that the focal position is shifted within the work surface 26.

[0068] Fig. 2A exemplarily shows a focusing lens 28 which focuses the illumination beam at a focal position 46. Fig. 2B and Fig. 2C show two beam profiles in the minor axis direction of the illumination beam 22. Fig. 2B shows a Gaussian profile. Fig. 2C shows a rectangular beam profile, a so-called top-hat profile.

[0069] Both beam profiles in Figures 2B and 2C have a steepness in the side or edge regions of the beam profile. This steepness imposes an intensity drop y on the side, i.e., in the edge region of the beam profile, over an interval x. The side is the edge region of the profile where the steepness is maximum. Thus, the steepness is defined by the quotient y / x. Correspondingly, the inverse of the steepness is defined as the quotient x / y.

[0070] 2B and 2C also have a width. In particular, the width of the beam profile is defined as the intensity value that is 1 / e of the maximum intensity value of the beam profile. 2 , 50%, or 90% or more of the region of the beam profile.

[0071] At the focal position 46, the beam profile of the illumination beam has a minimum width and a maximum steepness in the minor axis direction. As the beam moves away from the focal position 46 in the direction parallel to the beam direction, the steepness of the beam profile decreases, and the width of the beam profile and the inverse of the steepness increase.

[0072] Therefore, the steepness, inverse steepness, or width of the beam profile can be used to represent the focus state of the illumination beam at a particular position in the beam direction. In other words, the steepness, inverse steepness, or width of the beam profile can be the focus value of the focus state.

[0073] 3A shows an example of how the focal position 46 of the focusing lens 28 may be displaced during operation due to thermal effects, while the position of the focusing lens 28 does not change. The original focal position is labeled 46. The displaced focal position is labeled 46'.

[0074] Fig. 3B shows an example of how the focal position 46 of the focusing lens 28 can be adjusted. The focusing lens 28 can be moved along the linear guide 32. In Fig. 3B, the focusing lens is, for example, displaced in the direction of the focal position, the displaced focusing lens position being indicated by the reference sign 28''. Correspondingly, the displacement of the focusing lens 28 leads to a corresponding displacement of the focal position 46, the displaced focal position being indicated by the reference sign 46''.

[0075] FIG. 4 shows four exemplary positions of the camera system 36 in the beam path of the line optics 10 at which the camera system 36 can view the illumination beam 22.

[0076] 4A, the camera system 36 is positioned behind the work surface 26. In this position, the camera system 36 views the illumination beam 22 as it passes through the work surface.

[0077] 4B, a deflection mirror 48 is disposed in the beam path between the focusing lens 28 and the work surface 26, and deflects the illumination beam 22 toward the work surface 26. The deflection mirror 48 is partially transparent. The camera system 36 is positioned such that the portion of the illumination beam 22 that is transmitted through the deflection mirror 48 runs toward the camera system 36. In this position, the camera system 36 observes the portion of the illumination beam 22 that is transmitted through the deflection mirror 48.

[0078] 4C, the illumination beam 22 is reflected off the work surface 26. The camera system 36 is positioned such that the illumination beam reflected off the work surface 26 runs towards the camera system 36. In this position, the camera system 36 observes the illumination beam 22 reflected off the work surface.

[0079] 4D, a further optical system 50, e.g. a protective glass, is arranged in the beam path between the focusing lens 28 and the work surface 26, through which the illumination beam 22 passes in the direction of the work surface 26. A part of the illumination beam 22 is reflected by the further optical system 50. The camera system 36 is arranged such that the part of the illumination beam 22 reflected in the further optical system 50 runs in the direction of the camera system 36. In this arrangement, the camera system 36 observes the part of the illumination beam 22 reflected in the further optical system 50.

[0080] 5A shows an exemplary embodiment of a camera system 36 of the line optical system 10 of FIG. 1, by means of which the illumination beam 22 of the line optical system 10 can be observed at a defined position. In the camera system 36, the illumination beam 22, and in particular the work surface 26, is imaged by an imaging system 38 onto a camera 40. The image plane of the image of the illumination beam 22 on the camera is marked with the reference number 52. The camera system 36 and the camera 40 are preferably arranged such that the image plane 52 is located at the target position of the focal position 46. However, the image plane 52 can also be located anywhere in the beam direction.

[0081] 5B shows a further exemplary embodiment of a camera system 36 of the line optical system 10 of FIG. 1, in which the illumination beam 22 of the line optical system 10 can be observed in three defined positions. In the camera system 36, the illumination beam 22 is imaged by an imaging system 38 onto a camera 40. In this embodiment, the camera system 36 further comprises a beam splitter 42. The beam splitter 42 splits the illumination beam 22 into three partial beams, which run parallel to one another from the beam splitter 42 to the camera 40 and are imaged onto the camera 40, whereby the partial beams are spaced apart from one another and do not overlap. In the image captured by the camera 40, the partial beams are thereby depicted next to one another, i.e. at a distance from one another.

[0082] The partial beams have paths of travel of different lengths in the beam splitter 42. Due to the different paths of travel of the partial beams, the partial beams are imaged on different image planes 52, 52', 52'' in the camera. The first partial beam is imaged on plane 52', the second partial beam on plane 52 and the third partial beam on plane 52''. The paths of travel of the partial beams in the beam splitter 42 are such that the image planes 52, 52', 52'' are successive and offset from one another by the same distance. In particular, the image plane 52 is arranged between and at the same distance from the image planes 52' and 52''. By means of the beam splitter 42, the partial beams of the illumination beam 22 are imaged on the camera 40 at different defined positions downstream of the focusing lens 28 and therefore also in different focus states. The three images of the partial beams of the illumination beam 22 on the camera 40 are therefore three images of the illumination beam 22 at three defined positions z1, z2, z3 beamly downstream of the focusing lens 28. The first partial beam is imaged at position z1, the second partial beam at position z2 and the third partial beam at position z3.

[0083] The camera system 36 and the camera 40 are preferably arranged such that the image plane 52 of the second partial beam is located at the target position of the focal position 46. In Fig. 5B, the image plane 52 of the second partial beam is arranged at the focal position 46. Correspondingly, the image plane 52' is arranged in front of the focal position 46 and the image plane 52'' is arranged behind the focal position 46. In this case, the camera 40 captures the beam profile in front of the focal position 46 (imaging at position z1), at that position (imaging at position z2) and behind the focal position 46 (imaging at position z3).

[0084] The beam profile of the illumination beam 22 can be a Gaussian profile or a rectangular intensity profile, a so-called top-hat profile, as explained above with reference to Fig. 2B and 2C. The control device 44 can analyze the correspondingly imaged beam profile for each imaging of the partial beams, i.e. for each of the three defined positions z1, z2, z3, in order to determine the focus state at the respective position z1, z2, z3. For this purpose, for example, the steepness, the inverse of the steepness or the width of the beam profile can be determined as focus values ​​s1, s2, s3 of the focus state.

[0085] FIG. 6 shows how the focus values ​​s1, s2, s3 determined at three defined positions z1, z2, z3 change when the focus position 46 of the focus of the focusing lens 28 is displaced, in particular due to heating of the optical system. In FIG. 6, the inverse of the steepness is used as the focus value. In the graphs of FIG. 6(A) to (C), the focus value distributions 56, 56', 56'' for different positions of the focus position 46 are plotted in the beam direction (z direction). The focus value distributions 56, 56', 56'' have a parabolic shape, with the parabola's minimum being located at the focus position 46.

[0086] 6A shows the focus value distribution 56 when the focus position 46 is at position z2. Therefore, the focus value distribution 56 has a minimum at position z2.

[0087] Fig. 6B shows a focus value distribution 56', where the focus position 46 is displaced in the beam direction (z direction) compared to the diagram in Fig. 6A. The minimum of the focus value distribution 56' is near the position z3 on the downstream side of the beam of positions z1, z2, and z3. For comparison, the focus value distribution 56 is shown by a dashed line.

[0088] FIG. 6C shows a focus value distribution 56″, in which the focus position 46 is displaced further in the beam direction (z direction) compared to the diagrams of FIGS. 6A and 6B. The minimum of the focus value distribution 56″ is located further away from position z3, downstream of positions z1, z2, z3, compared to FIG. 6B. For comparison, the focus value distribution 56 is shown by a dashed line.

[0089] Instead of the steepness or the inverse of the steepness, the width of the respective beam profile at positions z1, z2, z3 can also be used as focus value, with the width at each position varying in the same way.

[0090] In Fig. 7A a further embodiment of the line-optical camera system 36 of Fig. 1 is shown. The camera system 36 has essentially the same structure as the camera system 36 of Fig. 5B. The imaging system 38 is formed as a telescope assembly. The telescope assembly magnifies the image of the illumination beam 22 by a factor k. This magnification therefore changes the scale.

[0091] The illumination beam 22 is reflected several times between two mirrors by the beam splitter 42. The mirrors are arranged parallel to one another and have a distance d between them. One of the mirrors is partially transparent, through which the partial beams are transmitted in the direction of the camera 40. Due to the different number of reflections between the mirrors, the partial beams have different path lengths. The path difference between two adjacent partial beams is 2d. The offset δz of the positions z1, z2, z3 in the beam direction results from the change in scale according to the formula δz=2d×g(k), where g(k) is a function of the magnification factor k. For a Gaussian beam, for example, g(k)=1 / k2 In other words, δz is the distance between the three image planes 52, 52', 52''.

[0092] In Fig. 7B the intensity profile of an image taken by the camera 40 of the camera system 36 in Fig. 7A is shown along the minor axis direction (Y direction). The illumination beam 22 has a rectangular beam profile. The intensity profile comprises an image of the beam profiles of three partial beams of the illumination beam 22. The beam profiles are in this case arranged next to one another in the intensity profile, i.e. at a distance from one another in the minor axis direction.

[0093] 8A to 8E show five measurements of the beam profile at positions z1, z2, and z3 and the corresponding distribution of focus values ​​at different focus positions. From FIG. 8A to FIG. 8E, the focus positions are all displaced by 250 μm. In FIG. 8C, the focus position is at approximately z2. If the focus position in FIG. 8C is 0 μm, the focus position in FIG. 8A is −500 μm, the focus position in FIG. 8B is −250 μm, the focus position in FIG. 8C is 0 μm, the focus position in FIG. 8D is 250 μm, and the focus position in FIG. 8E is 500 μm. In addition, the positions of the focus values ​​s1, s2, and s3 at the respective positions z1, z2, and z3 also change according to the displacement of the focus position.

[0094] An example of a method for determining the focal position of the focusing lens 28 based on the determined focus values ​​s1, s2, s3 at the positions z1, z2, z3 will now be described.

[0095] For this purpose, we first assume that the focus value distribution follows a parabola, for example as shown in Fig. 6. This is the case for a Gaussian beam, for example. As described above, the steepness, the inverse steepness, or the width of the beam profile at each position z1, z2, z3 can be determined as the focus value.

[0096] The progression of the parabola in the beam direction (z direction) can be expressed by the following equation: f(Z)=α(Z-Z') 2 +β Here, Z' denotes the location of the extreme point of the parabola.

[0097] The discrete derivative of this equation with respect to the locations z1, z2, and z3 is given by:

number

[0098] The discrete derivative of the left-hand side is given via: A=s3-s1

[0099] The second derivative is given by:

number

[0100] where B is given by: B=s3-2s2+s1

[0101] From this, the focal position during image capture can be determined by the following equation:

number

[0102] As stated above, δz is the distance between positions z1, z2, and z3.

[0103] The following describes an example of an adjustment process for adjusting the position of the focusing lens 28. Initially, the focusing lens 28 is at position P1.

[0104] In a first step, the camera system 36 performs a measurement at time t1. For the measurement, the camera system 36 observes the illumination beam 22 at at least three defined positions. In particular, the camera system 36 observes the illumination beam 22 at positions z1, z2, z3 using the camera 40, as described above.

[0105] In a further step, the control device 44 determines the focus value of the focus state at the corresponding defined position. For this purpose, the control device 44 analyzes the beam profile at each defined position in order to determine the focus value of the focus state at the corresponding defined position. In particular, focus values ​​s1, s2, s3 are determined at positions z1, z2, z3. This is exemplarily shown again in Fig. 9 (A) and (B). Fig. 9 (A) shows the beam profile at positions z1, z2, z3. Fig. 9 (B) shows the corresponding focus value distribution of focus values ​​s1, s2, s3. As focus value, for example, the steepness, the inverse of the steepness or the width of the beam profile can be determined.

[0106] In a further step, the control device 44 then determines the focus position on the basis of the determined focus values. For this purpose, in particular the above-described method can be used, in which the values ​​A and B are first determined, and the focus position can then be determined on the basis of the values ​​A and B.

[0107] In a further step, the control device 44 adjusts the position of the focusing lens 28 such that the focal position of the focal point of the focusing lens 28 is located in the work surface 26. The position of the work surface is predetermined and specifies a target position of the focal position. The focal position determined by the control device 44 is the actual position of the focal position. The control device 44 adjusts the position of the focusing lens 28 such that the focal position moves from the actual position to the target position with a predefined speed v0. In particular, the focusing lens 28 is then moved corresponding to a difference between the target position and the actual position, in particular a difference vector. The speed v0 can be predetermined, for example, in particular by a user.

[0108] In a preferred embodiment, the target position of the focal position may be position z2. In this case, the focusing lens 28 is moved to the following position with a velocity v0:

number

[0109] The adjustment steps can then be repeated at a later time t2, with focusing lens 28 moved further from position P2.

[0110] In particular, the above adjustment steps can be repeated at regular time intervals to periodically readjust the focal position of the focusing lens focal point during operation of the line optics.

[0111] Such periodic readjustment is exemplarily shown in Fig. 10. Fig. 10 shows a simulation result, in which the arrival behavior of the focal position is adjusted in time corresponding to the following equation:

number

[0112] The figure further shows the focal position determined by the above method and the corresponding correction δz comp The simulations show that the measurement principle and the proposed method are sufficient for tracking the focal spot during operation, i.e. for the so-called online tracking of the focal spot.

[0113] In Fig. 11(A) a further embodiment of a camera system for the capture of images is shown. This embodiment differs from the embodiment of Fig. 7(A) in that the beam splitter 42 is arranged to split the illumination beam 22 into three or more partial beams. In this way the camera system 36 can observe three or more defined positions downstream of the beam of the focusing lens 28. The number of observed positions corresponds to the number of partial beams. The number of observed defined positions can be, for example, between 4 and 20, preferably between 5 and 15, in particular 7 or 10. In this embodiment of Fig. 11 seven defined positions are observed. The defined positions are preferably arranged equidistant from one another in the beam direction (z-direction).

[0114] The camera 40 of the camera system 36 can capture an image in which the partial beams are focused. Fig. 11B shows the intensity profile of the image captured by the camera 40 along the minor axis direction (y direction). The beam profiles of the partial beams are arranged next to each other in the intensity profile.

[0115] Then, the control device 44 can determine a focus value for each of the defined positions based on this beam profile. The focus value progression of the determined focus values ​​is shown in FIG. 11C. Based on the determined focus values, the focus position can be determined by a correspondingly adjusted method.

[0116] When a parabola is employed for modeling the focus value course, when considering three or more defined positions, an over-determined system of equations is obtained, which can be solved, for example by smoothing calculations, in order to determine the focus position.

[0117] Alternatively, other functions with global extrema can also be used to model the focus value progression, in particular Gaussian functions or even polynomials of degree 4 or higher. Preferably, the number of defined positions observed using the camera system 36 is equal to or greater than the degree of the polynomial function plus one.

[0118] By observing three or more defined positions, the focus position can be calculated more accurately. Furthermore, direct access to parameters such as the depth of field is possible, which is possible in this measurement online. [Explanation of symbols]

[0119] 10 Line Optical System 12 Laser light source 14 Optical Assembly 16 Beam guiding and beam shaping optics 18 Focusing Unit 20 Laser Beam 22 Irradiation beam 24 Laser Line 26 Work Surface 28 Focusing Lens 30 Mobile Device 36 Camera System 40 Camera 42 Beam splitter 44 Control device 48 Deflection Mirror 50 Further Optical Systems

Claims

1. A line optic (10) for generating a predetermined laser line (24) on a work surface (26), comprising: at least one laser source (12) for generating at least one laser beam (20); an optical assembly (14) configured to generate an illumination beam (22) along a beam path from the at least one laser beam (20), the illumination beam (22) defining a beam direction intersecting the work surface (26) and forming the predetermined laser line (24) in the area of ​​the work surface (26), the optical assembly (14) comprising in the beam path a focusing unit (18) having a focusing lens (28) for focusing the illumination beam (22), the focusing lens (28) being movable parallel to the beam direction, a camera system (36) configured to observe the illumination beam (22) at at least three defined positions downstream of the focusing lens (28), wherein the illumination beam (22) has a focus state at each of the at least three defined positions; and a control device (44) configured to determine a focus position of the focal point of the focusing lens (28) based on the focus states at the at least three defined positions, and to adjust a position of the focusing lens (28) parallel to the beam direction so that the focus position is located within the work plane (26).

2. The line optics (10) of claim 1 , wherein the camera system (36) is positioned downstream of the beam of the work surface (26).

3. the line optical system (10) comprises further optical systems (48, 50) arranged downstream in the beam of the focusing unit (18); the further optical system (48, 50) being configured to split the illumination beam (22); 2. The line optical system (10) of claim 1, wherein a portion of the illumination beam (22) runs in the direction of the work surface (26) and a further portion of the illumination beam (22) runs in the direction of the camera system (36).

4. The camera system (36) comprises at least one camera (40) for taking at least one image, The line optical system (10) according to any one of claims 1 to 3, wherein the at least one image comprises an imaging of the illumination beam (22) at the at least three defined positions.

5. The camera system (36) comprises a beam splitter (42) configured to split the illumination beam (22) into partial beams; the at least one camera (40) is configured to image the partial beams into the at least one image; 5. The line optical system (10) according to claim 4, wherein the imaging of the partial beams corresponds to the imaging of the illumination beam (22) at the at least three defined positions.

6. the control device (44) is configured to determine a focus value for each focus state at the at least three positions based on the at least one image; 6. The line optical system (10) of claim 4 or 5, wherein the focus position of the focal point of the focusing lens (28) is determined based on the determined focus value.

7. For each image of the illumination beam (22) in the at least one image, a beam profile of the illumination beam (22) is determined in a minor axis direction; The line optical system (10) of claim 6, wherein each focus value is determined based on the beam profile of the corresponding image.

8. The position of the working surface (26) is predetermined downstream of the beam of the focusing lens; The line optical system (10) of any one of claims 1 to 7, wherein the control device (44) is configured to adjust the position of the focusing lens (28) parallel to the beam direction so that the focal position of the focal point of the focusing lens (28) moves from a determined focal position to a position of the work surface (26).

9. The line optical system (10) includes a moving device (30) for moving the focusing lens (28) parallel to the beam direction; The line optical system (10) of any one of claims 1 to 8, wherein the control device (44) is configured to control the moving device (30) to adjust the position of the focusing lens (28).

10. The line optical system (10) of any one of claims 1 to 9, wherein the optical assembly (14) further comprises a beam guiding and beam shaping optical system (16) configured to generate the illumination beam (22) from the at least one laser beam (20).

Images