A device for generating laser lines on a work surface

Abstract

The apparatus for generating a laser line (12) on a work surface (14) includes a first laser light source (16a) configured to generate a first raw laser beam (20a). The apparatus further includes a second laser light source (16b) configured to generate a second raw laser beam (20b). An optical device (22) having a first beam path (32a) receives the first raw laser beam (20a) and transforms it along a first optical axis (34a) into a first illumination beam (24a) having first caustics (38a) and a first beam profile (40a). The second beam path (32b) of the optical device (22) receives the second raw laser beam (20b) and transforms it along a second optical axis (34b) into a second illumination beam (24b) having second caustics (38b) and a second beam profile (40b). The first illumination beam (24a) and the second illumination beam (24b) are directed toward the work surface (14) in an overlapping manner, defining a common illumination direction (18). The first beam profile (40a) and the second beam profile (40b) each have a major axis with a predetermined major beam width and a minor axis with a predetermined minor beam width, perpendicular to the common illumination direction (18). The first beam profile (40a) and the second beam profile (40b) combine to form a laser line (12) on the work surface (14). According to one embodiment, the optical device (22) is configured to position the first caustic (38a) and the second caustic (38b) offset from each other in the illumination direction (18).

Description

[Technical field]

[0001] The present invention relates to an apparatus for generating a laser line on a work surface, the apparatus comprising a first laser source configured to generate a first raw laser beam, a second laser source configured to generate a second raw laser beam, and an optical device comprising a first beam path for receiving the first raw laser beam and transforming it along a first optical axis into a first irradiating beam having first caustics and a first beam profile, and a second beam path for receiving the second raw laser beam and transforming it along a second optical axis into a second irradiating beam having second caustics and a second beam profile, the first beam path being configured to generate ... the second beam path being configured to receive the second raw laser beam and transforming it along a second optical axis into a second irradiating beam having second caustics and a second beam profile, the first beam path being configured to generate a laser line on a work surface, the apparatus comprising a first laser source configured to generate a laser line on a work surface, the apparatus comprising a first laser source configured to generate a laser line on a work surface, the apparatus comprising a first laser source configured to generate a laser line on a work surface, the apparatus comprising a first laser source configured to generate a laser line on a work surface, the apparatus comprising a first laser source configured to generate a laser line on a work surface, the apparatus comprising a first laser source configured to generate a laser line on a work the first and second illumination beams are directed toward the work surface with overlapping beams to define a common beam direction, the first and second illumination beams are directed toward the work surface with overlapping beams to define a common illumination direction, the first and second beam profiles each have a major axis with a predetermined major beam width and a minor axis with a predetermined minor beam width perpendicular to the common illumination direction, and the first and second beam profiles combine to form a laser line on the work surface.

[0002] Such an apparatus is shown, for example, in US Patent Application Publication No. 2014 / 0027417.

[0003] The line-shaped laser radiation of such devices is typically used to process a workpiece. The workpiece can be, for example, a plastic material on a glass plate used 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 used for modern displays in smartphones, tablet PCs, television devices and other devices with screen displays. After the production of the electronic structure, the film needs to be peeled off from the glass support. This can be done by laser radiation in the form of a thin laser line, which is moved relative to the glass plate at a defined speed and penetrates the glass plate to peel off the fixed bond of the film. In practical operation, this type of application is often called LLO or Laser Lift Off.

[0004] Another possible application of irradiating a workpiece with a defined laser line is melting amorphous silicon on a carrier plate line by line. Again, the laser line is moved relative to the workpiece surface at a defined speed. By melting, the relatively low-cost amorphous silicon can be converted into expensive polycrystalline silicon. In practical operation, this type of application is often called Solid State Laser Annealing or SLA.

[0005] For this type of application, a laser line is required on the working surface, i.e., in one direction, the laser line is as long as possible in order to cover the working surface as wide as possible, and in the other direction, in contrast, it is significantly shorter in order to provide the required energy density for the respective process. Therefore, a device is desired that can generate a long and narrow laser line parallel to the working surface. The direction in which the laser line extends is generally called the so-called major axis of the beam profile, and the thickness of the line is called the minor axis. It is usually desirable for the laser line to have a respectively defined intensity profile in both axes. For example, it is desirable for the laser line to have a rectangular or possibly trapezoidal intensity profile in the major axis, the latter being advantageous if several such laser lines are to be joined together to form a longer overall line. In the minor axis, a rectangular intensity profile (so-called top hat profile), a Gaussian profile, or another intensity profile is desired depending on the application.

[0006] WO 2018 / 019374 discloses a suitable device, including many details regarding the optical elements of the optical device. The laser source generates an unprocessed laser beam, which is fanned out significantly in a first spatial direction by a so-called beam converter and then homogenized in order to obtain a major axis. In a second spatial direction, which is perpendicular to this, the laser beam is focused in order to obtain a minor axis. The first and second spatial directions are perpendicular to the beam direction in which the laser beam impinges on the working surface. In one embodiment, it is suggested that such multiple laser lines can be juxtaposed to one another in the direction of their respective major axes, thus forming a significantly long laser line. That is to say, two parallel irradiating beams, each forming a laser line on the working surface, are offset in the direction of the major axes in this embodiment.

[0007] The above-mentioned US Patent Application Publication No. 2014 / 0027417 discloses an apparatus of the type mentioned at the beginning, in which the first and second radiation beams are offset from one another in the direction of their respective short axes, whereby the first and second beam profiles combine to form a laser line with a stepped intensity profile, so that the energy delivered to the workpiece itself can be adapted to the changing material properties during the course of the laser processing process.

[0008] DE 102018200078 A1 discloses an optical device for generating a laser line by means of a telescope arrangement having an optical refractive power in relation to the short axis. The telescope arrangement comprises a first lens group and a second lens group which are movable relative to one another along the optical axis. A control unit controls the movement during the generation of the laser beam by the laser beam source with the aim of keeping the intensity of the laser line and its so-called full width at half maximum, i.e. the line width at 50% of the intensity (Full Width at Half Maximum, FWHM) as constant as possible in time. It turns out that the properties of the optical device can change during the generation of the laser beam. In particular, heating of the optical elements due to the laser beam can result in the formation of so-called thermal lenses which change the optical properties of the device. DE 102018200078 A1 proposes to compensate or at least reduce the resulting changes in the focal position by displacing the telescope lenses relative to one another.

[0009] A disadvantage of this solution is the mechanical effort required for adjusting the position of the telescope lens. This movement can cause wear and / or can lead to misalignment of the optical device. In view of this, the object of the present invention is to provide an apparatus of the type mentioned at the beginning, which serves to maintain the working surface in the working area of ​​the apparatus in an alternative way.

[0010] According to one aspect of the invention, in order to solve this problem, an apparatus of the type mentioned at the beginning is presented, in which the optical device is configured to position the first caustic and the second caustic offset from each other in the irradiation direction.

[0011] The caustics of the laser beam describe the progression of the beam diameter from the exit of the optical device to the so-called beam focus, i.e. to the location of the minimum beam diameter, and in the irradiation direction or beam propagation direction. Beam caustics are often also called beam waists, and therefore the caustics include the beam waists of the laser beam. In preferred embodiments, in particular the beam waists of the first and second irradiation beams are therefore offset relative to one another in the irradiation direction or beam propagation direction. The optical device is therefore configured in this embodiment to position the beam waists of the first irradiation beam (first beam waist) and the beam waists of the second irradiation beam (second beam waist) offset from one another in the irradiation direction. In preferred embodiments, the first and second caustics are offset from one another in the irradiation direction, in particular when the caustics are observed in the short axis, but are not offset from one another or at most only slightly offset from one another when the caustics are observed in the long axis.

[0012] The new arrangement makes it possible to dispense with mechanical adjustments of the optical devices or elements relative to one another that result in focusing of the beam profile in the short axis, since the displaced caustics in the short axis (and also in the long axis) overlap. As a result, the process window for processing the workpiece is enlarged. Even if focus drift occurs due to thermal lensing or other effects, the workpiece can be kept within the process window without mechanical tracking adjustments during laser operation.

[0013] Therefore, preferably, the optical elements having optical power with respect to the minor axis of the beam profile have a fixed distance relative to each other. In some preferred embodiments, the optical elements are stationary. This reduces mechanical wear and also reduces the risk of misalignment of the optical device due to mechanical movements.

[0014] Instead, the new arrangement is based on the idea of ​​intentionally widening the process window by at least two overlapping and offset caustics in the beam direction, also referred to below in part as the longitudinal direction. In a preferred embodiment, the new arrangement therefore intentionally tolerates focus drifts due to heating of the optical elements depending on the operating power and / or operating duration of the laser light source. However, the optical arrangement is intentionally designed to reduce the beam quality of the jointly formed beam profile, particularly in the short axis, so that the beam profile remains within the process window even in the event of a focus position drift. Instead of a mechanical tracking, the optical arrangement is intentionally designed for a greater depth of field by two offset caustics.

[0015] The new device therefore has an optical arrangement which favourably influences the ratio of depth of field to focus shift. The process window of the device is enlarged compared to the prior art devices. Mechanical tracking control and its attendant drawbacks are avoided. Thus, the above-mentioned problems are completely solved.

[0016] In one preferred embodiment, the optical device has a first beam converter in a first beam path and a second beam converter in a second beam path, the first beam converter modifies the first raw laser beam to generate a first beam profile, and the second beam converter modifies the second raw laser beam to generate a second beam profile, the first optical axis and the second optical axis define a common system axis, and the first beam converter and the second beam converter are arranged offset relative to each other along the common system axis.

[0017] In this embodiment, a "unique" beam converter is provided for each radiation beam, with the offset of the first caustic relative to the second caustic being achieved in such a way that the (at least) two beam converters are offset from one another along a common system axis. This embodiment has the advantage that the first and second beam paths can be implemented otherwise identically. In particular, the optical elements of the device that influence the two laser part beams and thus shape the (at least) two radiation beams can be positioned parallel to one another. This facilitates the manufacture and maintenance of new devices. Moreover, in this embodiment, the beam profile that is formed together in the major axis is hardly affected.

[0018] In a further embodiment, the optical device includes at least one beam converter that deforms the first raw laser beam and / or the second raw laser beam to generate a corresponding first beam profile and / or second beam profile, and the optical device further includes an optical element in the second beam path that shifts the second caustic relative to the first caustic.

[0019] In this embodiment, the offset of the first caustic relative to the second caustic is achieved in that the second beam path has at least one additional optical element compared to the first beam path. The first and second beam paths can thus be different. The additional optical element can be arranged upstream or downstream of the at least one beam transformer. Thus, an embodiment of this embodiment can essentially comprise a common beam transformer for the two illumination beams, such that the beam paths for the first illumination beam and the second illumination beam differ only downstream of the common beam transformer. In another embodiment of this embodiment, the optical device comprises one beam transformer each in the first beam path and in the second beam path. In some preferred embodiments of this embodiment, the additional optical element can be a telescope, which shifts the position of the second caustic compared to the position of the first caustic. The advantage of this embodiment is that the use of the additional optical element allows a relatively simple implementation of a new device based on an existing design.

[0020] In a further embodiment, the first caustic defines a process window having a predetermined process window length in the illumination direction, and the first caustic and the second caustic are offset in the illumination direction by a defined distance, which is shorter than 1.5 times the process window length and longer than 0.5 times the process window length, preferably shorter than 1.2 times the process window length and longer than 0.8 times the process window length, particularly preferably shorter than 1.1 times the process window length and longer than 0.9 times the process window length.

[0021] In this embodiment, the offset of the caustics relative to one another is in the order of the depth of field of the optical device. In this case, the depth of field can be defined in terms of the percentage deviation of the beam width FWHM in the minor axis along the irradiation direction. In particular, the depth of field can be defined as the distance between the points of the minor axis caustics, at which the minor axis beam width is wider than the minor axis beam width at the beam waist by 1% or by another percentage value between 1% and 10%. In a laborious analysis, this embodiment has been found to have a very advantageous dimension for the offset of the second caustic relative to the first caustic, since this dimension allows an associated widening of the process window with only a very slight effect on the major axis of the beam profile and thus on the quality of the laser line.

[0022] In a further embodiment, the optical device comprises at least one lens having a predominant optical refractive power with respect to a minor axis of the first beam profile and the second beam profile, the lens having a predetermined effective diameter with respect to the minor axis, and further wherein the first illumination beam and / or the second illumination beam illuminates more than 50% of the effective diameter, preferably more than 70%, and more preferably more than 90%.

[0023] In this embodiment, the at least one lens is illuminated over a larger area than is typical in known devices. In other words, the at least one lens is illuminated up to its peripheral region. The large area of ​​illumination of the at least one lens by the laser beam to be focused has the consequence that the at least one lens is locally heated less strongly. This embodiment thus advantageously serves to reduce the formation of thermal lenses and focusing drift during operation of the device. Moreover, this embodiment allows a more compact design of the new device, since the offset of the caustics can advantageously be the size of the depth of field and can be selected correspondingly smaller in the case of a shallower depth of field. In this case, for example, the above-mentioned offset of the first beam converter relative to the second beam converter can also be selected small due to the imaging scale of the optical device. This embodiment is particularly advantageous for SLA applications, and more generally for applications in which the beam profile has a top-hat characteristic in the short axis.

[0024] In a further embodiment, the first beam path generates a first intermediate image and the second beam path generates a second intermediate image, the first optical axis and the second optical axis define a common system axis, and the first intermediate image and the second intermediate image are arranged offset relative to each other along the common system axis.

[0025] This embodiment is also particularly advantageous for applications in which the beam profile has a top-hat characteristic in the short axis. The relative offset of the caustics can in this case be easily achieved by a shift of the intermediate image. The process window or the waist position in the process window of each beam path defines a conjugate plane located upstream of the objective lens. This conjugate plane can be shifted by advantageous embodiments of the upstream arranged optical system. In some preferred embodiments, the optical device comprises a short-axis telescope in the second beam path, which is shifted along the common system axis compared to the corresponding short-axis telescope in the first beam path. Advantageously, this shift can be performed during installation and adjustment of the new device, which allows for an inexpensive implementation. Preferably, this shift is implemented while maintaining the telecentric condition. By this embodiment, separate image positions of the first caustic and the second caustic are generated.

[0026] In a further embodiment, the optical device has a first beam converter in the first beam path and a second beam converter in the second beam path, the second beam converter being rotated about a second optical axis relative to the first beam converter.

[0027] Preferably, the optical device in this embodiment includes a collimation optics with a plurality of lenses, which collimates the individual raw laser beams before they are incident on the individual beam converters. Advantageously, at least one of the lenses in the second beam path is shifted along the second optical axis relative to the corresponding lens in the first beam path, so that the collimation of the individual raw laser beams in the parallel beam paths is different from each other. This embodiment allows the relative shifting of the beam caustics in a highly efficient manner.

[0028] In a further embodiment, the optical device focuses the first beam profile and the second beam profile onto the working plane without having an explicit stop in the first beam path and in the second beam path.

[0029] This embodiment is particularly advantageous for LLO applications, as it allows for efficient transfer of the laser energy to the working surface with little loss by eliminating an explicit diaphragm, e.g. a slit diaphragm.

[0030] In a further embodiment, the optical device superimposes the first beam profile and the second beam profile in their respective major axes and their respective minor axes.

[0031] In this embodiment, the first and second beam profiles overlap each other to a large extent, in particular more than 90%, in both the major and minor axes. According to this embodiment, the laser lines are formed overlapping each other in both the major and minor axes. This embodiment advantageously serves to produce a highly uniform intensity distribution in the major axis and a defined intensity distribution in the minor axis.

[0032] As will be apparent, the features mentioned above and those to be described below can be applied not only in the combinations described, but also in other combinations or in separate forms without departing from the scope of the present invention.

[0033] The drawings show exemplary embodiments of the invention and are explained in more detail in the following description. [Brief description of the drawings]

[0034] [Figure 1a] FIG. 1 shows a simplified diagram of a first embodiment of the new device. [Figure 1b] FIG. 1 shows a simplified diagram of a first embodiment of the new device. [Diagram 2]FIG. 2 is a simplified diagram showing a beam profile for explaining a first embodiment and a further embodiment. [Diagram 3] FIG. 1 shows a simplified diagram of two beam waists according to some embodiments of the new device, positioned offset from one another in the irradiation direction. [Figure 4a] FIG. 2 shows a schematic diagram of a second embodiment of the novel device. [Figure 4b] FIG. 2 shows a schematic diagram of a second embodiment of the novel device. [Diagram 5] FIG. 1 is a highly simplified diagram illustrating a further embodiment of the novel device. [Figure 6a] FIG. 13 shows a schematic diagram of a further embodiment of the novel device. [Figure 6b] FIG. 13 shows a schematic diagram of a further embodiment of the novel device.

[0035] In Fig. 1a and Fig. 1b, a first embodiment of the new device is shown in its entirety with the reference number 10. In Fig. 1a, the device 10 is shown in a simplified view from above on a laser line 12, which is arranged here in the region of a working surface 14. The device 10 comprises a first laser light source 16a and a second laser light source 16b, which can be, for example, a solid-state laser, respectively, generating laser light in the infrared or UV range. For example, the laser light sources 16a, 16b can each comprise a Nd:YAG laser with a wavelength in the range of 1030 nm. In further embodiments, the laser light sources 16a, 16b can comprise a diode laser, an excimer laser or a solid-state laser, respectively, generating laser light with a wavelength of 150 nm to 350 nm, 500 nm to 530 nm or 900 nm to 1070 nm. Further embodiments of the new device may include a Nd:YAG laser, a diode laser, an excimer laser or a solid-state laser, the raw laser beam of which is split into two partial beams, for example by a splitter mirror (not shown here), thus providing the two raw laser beams as input beams for the optical device described below. Thus, the first laser source 16a and the second laser source 16b may represent only one laser source followed by a beam splitter element in some embodiments not shown here. Further embodiments of the new device may include more than only two laser sources.

[0036] In Fig. 1b the device 10 is shown from the side, i.e. in the view towards the minor axis of the laser line 12. In the following, the irradiation direction 18 towards the working surface 14 is designated by the coordinate axis z. The laser line 12 extends in the direction of the x-axis, the line width is observed in the direction of the y-axis. In the following the x-axis therefore designates the major axis and the y-axis the minor axis of the beam profile formed on the working surface (Fig. 2).

[0037] The laser light sources 16a, 16b here generate one raw laser beam 20a, 20b respectively. The two raw laser beams 20a, 20b are transformed into radiation beams 24a, 24b by an optical device 22. The optical device 22 here comprises a first beam converter 26a for expanding the first raw laser beam 20a in the x-direction (corresponding to the longitudinal axis) and a second beam converter 26b for expanding the second raw laser beam 20b in the x-direction. In a preferred embodiment, the beam converters 26a, 26b respectively can be implemented as described in detail for the beam converters in the initially mentioned WO 2018 / 019374. Thus, the beam converters 26a, 26b respectively can comprise a transparent monolithic plate-like element with a front surface and a rear surface lying substantially parallel to each other. The plate-like element can be arranged at an acute angle (see FIG. 1b) to the respective raw laser beams 20a, 20b. The front and back surfaces may each have a reflective coating, such that each raw laser beam 20a, 20b is incident at an angle into the plate-like member at each front surface, is reflected multiple times within the plate-like member, and then fan-out and exits at the back surface of the plate-like member.

[0038] The optical device 22 further includes a longitudinal optics 28 with a number of optical elements 28a, 28b (shown here only in simplified form) that further shape the modified first raw laser beam 20a and the modified second raw laser beam 20b in the longitudinal axis. In particular, the longitudinal optics 28 may each include one or more microlens arrays (not shown here) and one or more lenses having a positive optical power primarily in the longitudinal axis for each of the raw laser beams 20a, 20b. In particular, the microlens arrays and the one or more lenses may each include a cylindrical lens that extends along the y-axis and has an optical power primarily in the longitudinal axis. The microlens array and the one or more lenses can in particular form an imaging homogenizer that homogenizes the raw laser beams 20a, 20b, respectively, in the long axis in order to obtain an advantageous top-hat intensity profile in the long axis in each of the two illumination beams 24a, 24b.

[0039] The optical device 22 further includes a short-axis optics 30 with a number of optical elements 30a, 30b (shown here in a highly simplified manner), which further shape the modified first raw laser beam 20a and the modified second raw laser beam 20b in the short axis. As can be seen in FIG. 1b, the first beam converter 26a, the optical elements of the long-axis optics 28a and the optical elements of the short-axis optics 30a form a first beam path 32a with a first optical axis 34a. The second beam converter 26b, the optical elements of the long-axis optics 28b and the optical elements of the short-axis optics 30b form a first beam path 32b with a second optical axis 34b. In some preferred embodiments, the optical axes 34a, 34b extend parallel to one another. In principle, however, it is also possible that the optical axes 34a, 34b extend obliquely to one another. The optical axes 34a, 34b define a common system axis 36 which, in the embodiment shown, extends parallel to and centrally between the optical axes 34a, 34b. Typically, the common system axis 36 coincides with the illumination direction 18. This axis may form an axis of symmetry of the device 10 and / or the optical device 22.

[0040] As shown in Figures 1a and 1b, the first beam converter 26a and the second beam converter 26b are arranged in this example offset from one another (with respect to a common system axis 36) by a distance 38. As a result, a beam caustic 38a, 38b is generated by the beam paths 32a, 32b, respectively, with the beam caustics 38a, 38b being offset from one another in the projection direction (at least with respect to the short axis), as shown in Figure 1b. However, the beam caustics 38a, 38b overlap in the region of the working surface and therefore form a common beam profile.

[0041] In Fig. 2, such a beam profile 40 is shown in a simplified diagram. The beam profile 40 represents the intensity I of the laser radiation on the working surface 14 as a function of the respective positions along the x- and y-axes. As shown, the beam profile 40 of the device 10 has a major axis 42 with a given major beam width in the x-direction and a minor axis 44 with a given minor beam width in the y-direction. The minor beam width 33 can be defined, for example, as the full width at half maximum (FWHM) or as the width between 90% intensity values ​​(Full Width at 90% Maximum, FW@90%). Apart from the trapezoidal intensity profile in the minor axis shown here in a simplified manner, the beam profile 40 can be a Gaussian or top-hat profile (the latter of course in practice has a finite side slope). Ideally, the radiation beams 24a, 24b overlap congruently in the region of the working surface, so that the beam profile 40 is formed from two substantially identical beam profiles 40a, 40b of the corresponding radiation beams 24a, 24b. To process a workpiece (not shown here), the beam profile 40 is typically moved relative to the working surface 14, in particular in the y direction, transverse to the x direction.

[0042] In Fig. 3, the overlap of two mutually offset beam caustics 38a, 38b is shown in a simplified diagram. Each of the two beam caustics 38a, 38b includes a beam waist 42a or 42b at which the respective illumination beam 24a, 24b has a minimum beam diameter. Moreover, each of the two mutually offset beam caustics 38a, 38b has a depth of field that can be defined, for example, based on the Rayleigh length. In some embodiments, the depth of field is defined in terms of a percentage deviation of the beam width FWHM or FW@90%Maximum in the minor axis along the illumination direction 18. In particular, the depth of field can be defined as the distance between the points of the minor axis caustics 38a, 38b at which the respective minor axis beam width is wider than the minor axis beam width at the respective beam waist 42a, 42b by 1% or by some other percentage value between 1% and 10%. The depth of field defines a process window for each respective illumination beam 24a, 24b, having a process window length 46a, 46b, respectively.

[0043] 3, the optical arrangement 22 is configured in some embodiments to offset the first beam caustic 38a and the second beam caustic 38b by a distance 48 that is approximately on the order of the depth of field 46a, 46b. Due to the overlap of the beam caustics 38a, 38b offset in the illumination direction 18, the apparatus 10 has an enlarged process window 50.

[0044] In Fig. 1b, the effective diameter of the lens 30a, which is preferably cylindrical, is indicated with the reference number 52 with respect to the minor axis. In some preferred embodiments, the laser beam to be deformed illuminates the lens 30a and the corresponding further lenses of the optical device 22, such as the lens 30b, up to the peripheral area, i.e. for example more than 70% or even 90% of the effective diameter 52. As a result, the depth of field of the illumination beams 24a, 24b is reduced, which is advantageous for minimizing the offset 38 of the beam transformer. For example, the distance 38 can be in the region of about 250 mm in some embodiments in order to obtain a distance 48 of the beam caustics 38a, 38b of about 100 μm. Because the distance 48 is determined by the offset 38 and the diffraction order M 2 The diffraction order represents the divergence angle of a real laser beam compared to the divergence angle of an ideal Gaussian beam with the same diameter at the beam waist.

[0045] 4a and 4b show a further embodiment of the new device, here with the reference number 10'. The same reference numbers refer to the same elements as before. In the embodiment according to fig. 4a and 4b, the offset of the beam caustics 38a, 38b is achieved by means of an additional optical element 54 arranged in the second beam path 32b. In some embodiments, the additional optical element 54 can be arranged downstream of the beam converter 26b in the second beam path 32b, as shown in fig. 4b. In other embodiments, the additional optical element 54 can be arranged upstream of the beam converter 26b in the second beam path 32b. In some preferred embodiments, the additional optical element 54 can be a telescope arrangement with a first additional optical element 54a and a second additional optical element 54b. The additional optical elements 54a, 54b can in particular be lens elements or mirror elements. Thanks to the additional optical element 54, the beam transformers 26a, 26b can be arranged "at the same height" with respect to the system axis 36, i.e. without a relative offset 38. As shown in Fig. 4b, the additional optical element 54 has an optical power that affects, among other things, the minor axis of the beam profile 40.

[0046] In FIG. 5, a further embodiment of the new device is shown in a simplified drawing of the beam path 32b with respect to the short axis. Here, the optical elements for beam shaping in the long axis are not shown for simplicity. Otherwise, the same reference numbers refer to the same elements as before. In this embodiment, the beam path 32b comprises a short-axis telescope with lens elements 56, 58, which generates an intermediate image 60 of the beam converter 26b along the beam path 32b. The intermediate image 60 is imaged onto the working surface 14 by means of a further lens element 62. Such an embodiment is particularly advantageous when the beam profile in the region of the working surface 14 should be a top-hat profile in the short axis, as is desired in particular in SLA applications. The offset of the beam caustics 38b can here be achieved via an offset of the beam converter 26b and / or by a shift of the intermediate image 60, as explained above with reference to FIGS. 1a and 1b, which can be achieved by suitable adjustment and / or dimensioning of the short-axis telescope by the lens elements 56, 58.

[0047] In Fig. 6a and Fig. 6b, a further embodiment of the new device is shown. The same reference numbers refer to the same elements as before. In the embodiment according to Fig. 6a and Fig. 6b, the beam converter 26b in the second beam path 32b is rotated about the z-axis compared to the beam converter 26a in the first beam path 32a, as indicated by the arrow 66 in Fig. 6b, so that a relative offset of the beam caustics 38a, 38b is achieved. The rotation 66 about the z-axis results in a vertical offset of the beam packets at the exit side, which affects the side slope of the short-axis beam profile at the working surface 14. Further details on this can be found in DE 102018115126 A1 as well as in the applicant's same-priority WO 2019 / 243042, which are hereby incorporated by reference. In this embodiment, the device also has a collimation optics 68a, 68b upstream of each individual beam converter 26a, 26b, respectively. The individual collimation optics 68a, 68b collimate the individual raw laser beams 20a, 20b before they enter the individual beam converters 26a, 26b. In one preferred variant of this embodiment, the individual collimation optics 68a, 68b include a number of lenses 70a, 72a or 70b, 72b. Advantageously, at least one of the lenses in the second beam path 32b, for example the lens 70b, is shifted relative to the corresponding lens 70a in the z-direction, so that the collimation of the individual raw laser beams 20a, 20b in the parallel beam paths 32a, 32b differs from one another. The variant of collimation by shifting the lens 70b results in a significantly advantageous shift of the caustics 38b in cooperation with the rotation 66 of the beam converter 26b. In some embodiments, the lenses 70a, 72a or 70b, 72b can each form a telescope device. The altered collimation can also be virtually located upstream of each individual beam transformer 26b.

Claims

1. An apparatus for generating a laser line (12) on a work surface (14), comprising: The apparatus comprises a first laser source (16a) configured to generate a first raw laser beam (20a), a second laser source (16b) configured to generate a second raw laser beam (20b), and an optical device (22); The optical device (22) includes a first beam path (32a) for receiving the first raw laser beam (20a) and transforming it along a first optical axis (34a) into a first illumination beam (24a) having first caustics (38a) and a first beam profile (40a), and a second beam path (32a) for receiving the second raw laser beam (20b) and transforming it along a second optical axis (34b) into a first illumination beam (24a) having first caustics (38a) and a first beam profile (40a). a second beam path (32b) that transforms into a second illumination beam (24b) having second caustics (38b) and a second beam profile (40b); the first illumination beam (24a) and the second illumination beam (24b) are directed toward the work surface (14) in an overlapping manner to define a common illumination direction (18); the first beam profile (40a) and the second beam profile (40b) each have a major axis with a predetermined major beam width and a minor axis with a predetermined minor beam width perpendicular to the common irradiation direction (18); the first beam profile (40a) and the second beam profile (40b) combine to form the laser line (12) on the work surface (14); An apparatus for generating a laser line (12) on a work surface (14), comprising: the optical device (22) is configured to position the first caustics (38a) and the second caustics (38b) offset from one another in the illumination direction (18); the first caustic (38a) and the second caustic (38b) overlap at the minor axis and / or the major axis; An apparatus for producing a laser line (12) on a work surface (14).

2. the optical device comprises a first beam converter (26a) in the first beam path (32a) and a second beam converter (26b) in the second beam path (32b); the first beam transformer (26a) transforms the first raw laser beam (20a) to generate the first beam profile (40a); the second beam transformer (26b) transforms the second raw laser beam (20b) to produce the second beam profile (40b); the first optical axis (34a) and the second optical axis (34b) define a common system axis (36); the first beam converter (26a) and the second beam converter (26b) are arranged offset relative to one another along the common system axis (36); 2. The apparatus of claim 1.

3. the optical device (22) includes at least one beam converter (26a, 26b) for modifying the first unprocessed laser beam (20a) and / or the second unprocessed laser beam (20b) to generate the corresponding first beam profile (40a) and / or the corresponding second beam profile (40b); the optical device (22) has an optical element (54) in the second beam path (32b), the optical element (54) displacing the second caustic (38b) relative to the first caustic (38a); 3. The device according to claim 1 or 2.

4. the first caustics (38a) defining a process window (46a) having a process window length (46a) in an illumination direction (18); the first caustic (38a) and the second caustic (38b) are offset in the illumination direction (18) by a defined distance (48), the distance (48) being less than 1.5 times the process window length and greater than 0.5 times the process window length; 4. Apparatus according to any one of claims 1 to 3.

5. the optical device (22) comprises at least one lens (30a), the lens (30a) having a predominant optical power with respect to the minor axis of the first beam profile (40a) and the second beam profile (40b); the lens (30a) has a predetermined effective diameter (52) relative to the minor axis; the first illumination beam (24a) and / or the second illumination beam (24b) illuminate the lens over more than 50% of the effective diameter (52); 5. An apparatus according to any one of claims 1 to 4.

6. the first beam path (32a) produces a first intermediate image; the second beam path produces a second intermediate image (60); the first optical axis and the second optical axis define a common system axis (36), and the first intermediate image and the second intermediate image are disposed offset relative to one another along the common system axis (36).

6. An apparatus according to any one of claims 1 to 5.

7. the optical device comprises a first beam converter (26a) in the first beam path (32a) and a second beam converter (26b) in the second beam path (32b); the second beam converter (26b) is rotated (66) about the second optical axis (34b) relative to the first beam converter (26a); 7. An apparatus according to any one of claims 1 to 6.

8. the optical device (22) focuses the first beam profile (40a) and the second beam profile (40b) on the working surface (14) without any clear stop in the first beam path (32a) and the second beam path (32b).

8. Apparatus according to any one of claims 1 to 7.

9. 9. The apparatus according to claim 1, wherein the optical device (22) superimposes the first beam profile (40a) and the second beam profile (40b) in the respective major axis and in the respective minor axis.

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