Device and method for generating a defined laser illumination on a working plane

Abstract

Device for generating defined laser illumination on a working plane (50), comprising a laser light source (12) configured to generate a collimated raw laser beam (14) with a first angular spectrum (26), and an optical arrangement (64) that receives the collimated raw laser beam (14) and transforms it along an optical axis (20) into an illumination beam (48), wherein the illumination beam (48) defines a beam direction (52) that intersects the working plane (50), wherein the optical arrangement (64) comprises at least two microlens arrays (38, 40) arranged at a defined distance (42) from each other along the optical axis (20), and wherein the defined distance (42) is selected such that the illumination beam (48) in the region of the working plane (50) has an illumination beam profile (47) comprising a plurality of separate illumination spots (46).wherein the optical arrangement (64) further comprises a beam shaping element (24; 60) which is arranged along the optical axis (20) in front of the at least two microlens arrays (38, 40), wherein the beam shaping element (24; 60) generates a second angular spectrum (32) which is different from the first angular spectrum (26), characterized in that the optical arrangement (64) further comprises an adjustment mechanism (44) with which at least one microlens array (40) can be adjusted from the at least two microlens arrays (38, 40) along the optical axis (20) in order to selectively and variably adjust the distance between the at least two microlens arrays (38, 40).

Description

[0001] The present invention relates to a device for generating defined laser illumination on a working plane, comprising a laser light source configured to generate a collimated raw laser beam with a first angular spectrum, and comprising an optical arrangement that receives the collimated raw laser beam and transforms it along an optical axis into an illumination beam, wherein the illumination beam defines a beam direction that intersects the working plane, wherein the optical arrangement comprises at least two microlens arrays arranged at a defined distance from one another along the optical axis, and wherein the defined distance is selected such that the illumination beam in the region of the working plane has an illumination beam profile that includes a plurality of separate illumination spots, wherein the optical arrangement further comprises a beam-shaping element,which is arranged along the optical axis in front of the at least two microlens arrays, and wherein the beam-shaping element generates a second angular spectrum which is different from the first angular spectrum.,

[0002] Such a device is disclosed in DE 10 2011 101 585 A1.

[0003] Defined laser illumination on a work plane is often required to process workpieces. The workpiece can, for example, be a plastic material on a glass plate that serves as a carrier. The plastic material can, for example, be a film on which organic light-emitting diodes, so-called OLEDs, and / or thin-film transistors are manufactured. OLED films are increasingly being used for displays in smartphones, tablet PCs, televisions, and other devices with screen displays. After the electronic structures have been produced, the film must be detached from the glass carrier. This can advantageously be done with a laser illumination that is moved at a defined speed relative to the glass plate, thereby breaking the adhesive bond of the film through the glass plate. In some cases, the laser illumination can be a thin laser line. Such an application is often referred to in practice as LLO or.Laser Lift Off.

[0004] Another application in which a workpiece is illuminated with a defined laser line can be the line-by-line melting of amorphous silicon on a carrier plate. Here, too, the laser line is moved at a defined speed relative to the workpiece surface. Through melting, the comparatively inexpensive amorphous silicon can be converted into higher-quality polycrystalline silicon. In practice, this type of application is often referred to as excimer laser annealing, or ELA. In the ELA process, the amorphous silicon on the carrier plate is almost completely melted and crystallizes vertically upon cooling. The process is very energy-intensive, and the processing window for the silicon is very small, placing high demands on the homogeneity and power stability of the laser line.An alternative process for converting amorphous silicon on a carrier plate into higher-quality polycrystalline silicon is known from two publications by Ludolf Herbst, Frank Simon et al., namely "Advances in excimer laser annealing for LTPS manufacturing", 49-3 IMID 2009 DIGEST and "17-4: New Technology for Creation of LTPS with Excimer Laser Annealing", Asia Display / IMID 04 Proceedings. This alternative process is called sequential lateral solidification, or SLS, and uses a structured laser beam to selectively melt the amorphous silicon locally, with crystal formation starting laterally from the unmelted neighboring areas. A mask in the laser beam path is used to create a periodic structure on the processing surface.

[0005] Further applications for defined laser illumination include so-called laser-induced forward transfer (LIFT), i.e., the transfer of previously detached semiconductor components to another substrate, such as the transfer of detached and separated micro-LEDs (µLEDs) to a future display, as well as laser cutting or laser punching processes. Depending on the workpiece and application, individually defined laser illumination is required on a working plane.

[0006] WO 2018 / 019374 A1 discloses a device for generating a defined laser line on a working plane. The device includes a collimator that collimates a raw laser beam, as well as a beam transformer, a homogenizer, and a focusing stage. The beam transformer receives the collimated raw laser beam and expands it in a direction perpendicular to the beam direction. In principle, the beam transformer can also receive multiple raw laser beams from multiple laser sources and combine them into an expanded laser beam with higher power. The homogenizer can have one or more multi-lens arrays with which the expanded laser beam is homogenized in the long direction, so that it achieves a rectangular (tophat-shaped) intensity profile along the long axis. The focusing stage focuses the reshaped laser beam to a defined position in the area of ​​the working plane.The known device is generally suitable for LLO and SLA applications. However, it is not optimal for some specific LLO applications, such as the dissolving of µLEDs. In such a case, it would be desirable to provide a plurality of separate, top-hat-shaped intensity profiles. For example, an arrangement may be desired in which a plurality of separate top-hat-shaped intensity profiles are arranged equidistantly next to one another along a line. The device of WO 2018 / 019374 A1 does not provide such laser illumination.

[0007] The aforementioned DE 10 2011 101 585 A1 discloses a device of the aforementioned type for producing light-emitting diodes or photovoltaic elements, wherein depressions are formed on at least one surface of a substrate made of a polymer material. A microlens array splits the laser beam into a plurality of individual laser beams. In some embodiments, the microlens array can include point-generating microlenses with crossed cylindrical microlenses, with hexagonal or square lens arrangements, or square microlens arrays. In all of these embodiments, the at least two microlens arrays are firmly connected to one another.

[0008] DE 10 2018 211 972 B4 discloses an optical arrangement for generating a beam profile with a plurality of separate illumination spots distributed along a line or over a surface. The arrangement includes a plurality of microlens arrays with microlenses arranged next to one another, each having a uniform aperture a, as well as a subsequent Fourier lens arrangement. Furthermore, the optical arrangement has an adjustment mechanism with which a mutual distance of at least some of the microlens arrays can be adjusted. As a result, the effective focal length of the entire microlens arrays can be adjusted. The adjustment mechanism has a plurality of selectable adjustment positions at which the ratio a2λ⋅fML,i is at least approximately a natural number, where a is the uniform aperture of the individual microlenses, λ is the mean wavelength of the laser beam and f ML,ithe effective focal length f set by the adjustment position i ML the entirety of the microlens arrays.

[0009] This known arrangement makes it possible to vary the number of illumination spots generated from a laser beam, while maintaining a uniform intensity distribution. However, the respective intensity profile of the laser illumination on the working plane at the separate illumination spots cannot be further varied. In view of this, there is a desire to further develop a device to enable even greater flexibility in the processing of workpieces. In particular, it is desirable to be able to vary not only the number but also the size of the individual illumination spots. Accordingly, it is an object of the present invention to provide a device of the type mentioned above with which the generation of even more variable multi-spot illumination is possible in an efficient manner.

[0010] According to one aspect of the present invention, a device of the type mentioned at the outset is proposed, in which the optical arrangement further comprises an adjustment mechanism with which at least one microlens array of the at least two microlens arrays can be adjusted along the optical axis.

[0011] Contrary to previous assumptions, it has been shown that beam shaping upstream of the microlens arrays can be used very advantageously to further vary the beam profile in the area of ​​the working plane. Beam shaping upstream of the microlens arrays is cost-effective and efficient because it has a "central" effect on the laser beam before it is split into several partial beams using the microlens arrays. "Upstream of the microlens arrays" here means that the beam shaping element is arranged along the optical axis between the laser light source and the at least two microlens arrays used to generate the separate illumination spots. The beam shaping element is therefore located upstream of the at least two microlens arrays. It has been shown that each of the illumination spots generated using the microlens arrays represents the angular spectrum of the microlens illumination.Therefore, far-field beam shaping can advantageously be performed early in the beam path, i.e., before the microlens arrays. The laser beam with a desired second angular spectrum is efficiently split using the microlens arrays, and the desired second angular spectrum is multiplied into several separate illumination spots.

[0012] With the help of the adjustment mechanism, the distance between the at least two microlens arrays can be selectively and variably adjusted. This design thus enables a variable adjustment of the number of separate illumination spots on the work plane. The new device therefore has an additional degree of freedom with regard to generating a large number of illumination spots. The beam shaping in front of the microlens arrays allows the angular spectrum of the illumination spots to be adjusted. This makes it possible, in particular, to vary or adjust the respective extent and shape of the illumination spots on the work plane. The above-mentioned problem is fully solved.

[0013] In a preferred embodiment, the second angular spectrum has a tophat-shaped intensity profile.

[0014] A top-hat-shaped intensity profile is advantageous for many applications because it sharply defines a processing location on the work plane. It enables intricate processing and / or the creation of fine structures and is particularly suitable for simultaneous surface processing in a confined space, such as local melting or local cutting processes at multiple processing locations. Central beam shaping in front of the microlens arrays is advantageously used here to generate a uniform top-hat-shaped intensity profile for a large number of illumination spots.

[0015] In a further embodiment, the first angular spectrum has a first footprint in a plane perpendicular to the optical axis and the second angular spectrum has a second footprint in a further plane perpendicular to the optical axis, which is different from the first footprint.

[0016] The footprint represents the outline of an illumination spot generated with the laser beam. It therefore represents, in particular, the geometric shape of the illumination spot on a plane perpendicular to the beam direction or perpendicular to the optical axis. It also represents the surface area of ​​the generated illumination spot on the plane. In preferred embodiments, the first footprint and the second footprint can therefore differ from one another with respect to their respective geometric shape and / or surface area. This configuration makes it possible to efficiently adjust the extent and shape of the illumination spots on the working plane.

[0017] In a further embodiment, the second footprint is polygonal, in particular rectangular, pentagonal, hexagonal, or octagonal. In some preferred embodiments, the second footprint has an aspect ratio (maximum length to maximum width) that lies in the range of 1, in particular in the interval between 0.9 and 1.1, inclusive. Accordingly, in some preferred embodiments, the second footprint can be square. This design enables precise and efficient machining of a workpiece in numerous applications and particularly benefits from the new degree of freedom that the new device efficiently offers.

[0018] In a further embodiment, the optical arrangement comprises a Fourier lens arrangement arranged along the optical axis after the microlens arrays.

[0019] Preferably, the adjustment mechanism has several selectable adjustment positions at which the ratio a2λ⋅fML,i is at least approximately a natural number, where a is the uniform aperture of the individual microlenses of the microlens arrays, λ is the mean wavelength of the raw laser beam and f ML,i the effective focal length f set by the respective adjustment position i ML of the total of the microlens arrays. At least approximately, this means that the ratio in an interval of 0.8 N i up to 1.2 N i , including, where N i is the respective natural number. The embodiment makes advantageous use of the flexible possibilities offered by the optical arrangement from the aforementioned DE 10 2018 211 972 B4. DE 10 2018 211 972 B4 is therefore incorporated herein by reference with regard to the possible implementations of the embodiment.

[0020] In a further embodiment, the beam-shaping element includes a beam transformer that expands the raw laser beam in a direction transverse to the optical axis. In some embodiments, the beam transformer may include a Powell lens. Alternatively or additionally, the beam transformer may include a glass body with a mirror coating on opposing surfaces, so that an obliquely entering laser beam is reflected back and forth several times in the glass body and thereby expanded in one direction.

[0021] A Powell lens is a lens that can generate a linear beam profile with a largely homogeneous intensity distribution along the line from a rotationally symmetric Gaussian intensity distribution. Perpendicular to this, the Gaussian intensity distribution is maintained. The beam transformer can further be a beam transformer as described in the aforementioned WO 2018 / 019374 A1, which is incorporated herein by reference. The beam-shaping element of this embodiment enables a plurality of separate illumination spots along a defined line. In some embodiments, the line can be arranged obliquely, but not orthogonally, to the optical axis in order to generate a linear beam profile on the working plane that is oblique to the beam direction of the illumination beam.

[0022] In a further embodiment, the beam-shaping element includes a diffractive optical element (DOE).

[0023] A diffractive optical element is a beam-shaping element based on the principle of light diffraction. It typically has a glass substrate on or around which diffraction structures are arranged. These diffraction structures cause interference. A diffractive optical element can generate a desired second angular spectrum with a wide variety of variations and high quality. Furthermore, the beam energy is largely used to illuminate the work plane. For this reason, a diffractive optical element enables particularly efficient implementation.

[0024] In a further embodiment, the beam-shaping element includes a spatial filter.

[0025] A spatial filter typically consists of a lens and an aperture located behind the lens in the beam path. The aperture can be used to generate a desired second angular spectrum in a variety of ways. The lens ensures that the aperture is efficiently illuminated. Therefore, a spatial filter in front of the microlens arrays enables a very diverse and cost-effective beam shaping.

[0026] In a further embodiment, the beam-shaping element can be optionally inserted into the optical axis.

[0027] This embodiment offers particularly great flexibility in generating the defined laser illumination. The beam-shaping element is coupled here to an adjustment mechanism that makes it possible to selectively insert the beam-shaping element entirely or partially into the beam path of the optical arrangement or to remove it from it. The illumination beam profile can thus be selectively and specifically varied. In some embodiments, the device has a plurality of beam-shaping elements, each of which is configured to generate a second angular spectrum, wherein the second angular spectra differ from one another. In these embodiments, one of a plurality of beam-shaping elements can be selectively inserted into the beam path of the optical arrangement. For example, the (respective) beam-shaping element of this embodiment can be inserted and / or pivoted into the beam path of the optical arrangement.

[0028] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0029] Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. They show: Fig. 1 a simplified and schematic representation of a first embodiment of the new device, Fig. 2 a simplified and schematic representation of another embodiment of the new device, Fig. 3 a simplified and schematic representation of another embodiment of the new device, and Fig. 4 shows an advantageous trajectory of laser illumination during the melting of polycrystalline silicon.

[0030] In Fig. 1, an embodiment of the novel device is designated in its entirety by reference numeral 10. The device 10 includes a laser light source 12 that generates a raw laser beam 14. The laser light source 12 may include a collimator (not shown here) so that the raw laser beam 14 is a collimated raw laser beam.

[0031] The raw laser beam 14 illuminates a first lens 16 and a subsequent second lens 18, which are arranged along an optical axis 20. An aperture 22 is arranged between the lenses 16, 18 along the optical axis 20. The aperture 22, together with the lenses 16, 18, forms a spatial filter 24. The raw laser beam 14 has a first angular spectrum, indicated by reference numeral 26 and depicted as a Gaussian intensity profile. In an (imaginary) plane 28 perpendicular to the optical axis 20, the raw laser beam 14 with the first angular spectrum 26 generates, for example, a circular footprint 30.

[0032] Due to the spatial filter 24, the laser beam after the lens 18 has a modified second angular spectrum 32, which is illustrated here by way of example with a tophat-shaped intensity profile in a plane 34. In some preferred embodiments, the device 10 may have a 2f structure. The plane 34 may be located at a different location in these embodiments than in Fig. 1 for the sake of simplicity. The laser beam with the modified second angular spectrum 32 generates a second footprint 36 behind the lens 18, which is shown here as a square, for example.

[0033] The laser beam with the second angular spectrum 32 illuminates an arrangement with at least two microlens arrays 38, 40, which are arranged at a defined distance 42 from one another along the optical axis 20. Each microlens array 38, 40 has a plurality of microlenses, which preferably each have the same aperture a. Furthermore, the optical arrangement has an adjustment mechanism 44, with which the relative distance 42 between the at least two microlens arrays 38, 40 along the optical axis 20 can be changed. In the preferred embodiments, the adjustment mechanism has several predefined adjustment positions, with each of which a distance 42 is set, at which the ratio a2λ⋅fML,i is at least approximately a natural number, where a is the uniform aperture of the individual microlenses of the microlens arrays 38, 40, λ is the mean wavelength of the raw laser beam 14 and f ML,ithe effective focal length f set by the respective adjustment position i ML of the total of the microlens arrays. At least approximately, this means that the ratio in an interval of 0.8 N i up to 1.2 N i , including, where N i is the respective natural number.

[0034] By varying the distance 42, the effective focal length f MLof the entirety of the microlens arrays 38, 40 is changed. By suitably adjusting the distance according to the above-mentioned ratio, the number of illumination spots 46 in the multi-spot beam profile 47 of the illumination beam 48 on the working plane 50 can be adjusted. The working plane 50 is arranged perpendicular to the beam direction 52 of the illumination beam 48. However, it could also be oblique to the beam direction 52. Preferably, the device 10 uses microlens arrays 38, 40 in one of the arrangements disclosed in DE 10 2018 211 972 B4, which is incorporated herein by reference. The illumination spots 46 are arranged side by side along a line that runs transversely to the beam direction 52 (referred to here as the x-axis).In some advantageous applications of the device 10, the multi-spot beam profile 47 can be moved transversely to the line of illumination spots 46 and transversely to the beam direction 52 relative to the work plane 50, as described below with reference to FIG. Fig. 4 is explained in more detail.

[0035] Fig. 2 shows a further embodiment of the novel device, which is now designated by reference numeral 10'. Otherwise, the same reference numerals designate the same elements as before. The device 10 has a beam transformer 54, which expands the raw laser beam in a direction transverse to the optical axis 20. In some embodiments, the beam transformer can include a Powell lens. Alternatively or additionally, the beam transformer can include a glass body with a front side 56 and a rear side 58, each of which is mirrored, so that the raw laser beam 14 is reflected back and forth several times in the glass body and thereby expanded transversely to the optical axis 20. Such a beam transformer is described in the aforementioned WO 2018 / 019374 A1, which is incorporated herein by reference. Alternatively or additionally, the beam transformer can include a Powell lens.In any case, the raw laser beam 14 is expanded in a direction perpendicular to the optical axis 20, and in this case perpendicular to the viewing plane, so that the beam profile on the working plane 50 has linear structures perpendicular to the viewing plane. The microlenses of the microlens arrays 38, 40 can be cylindrical lenses in this case. Alternatively, the microlenses of the microlens arrays 38, 40 can each be rotationally symmetric lenses in a 2-dimensional lens array. Such an arrangement makes it possible to generate an illumination beam profile with a plurality of illumination spots in a 2-dimensional arrangement.

[0036] Reference numeral 60 denotes a diffractive optical element that can be selectively inserted into the beam path of the (expanded) raw laser beam 14, i.e., at a position along the optical axis 20. Reference numeral 60' denotes an alternative diffractive optical element that can be selectively inserted into the beam path instead of or in addition to element 60. For this purpose, the diffractive optical elements 60, 60' are coupled to an adjustment mechanism 62, 62'.

[0037] Fig. Figure 3 shows a further preferred embodiment of the new device, which is designated here by the reference numeral 10". Otherwise, the same reference numerals designate the same elements as before. In the upper part, Fig. 3 shows the beam shaping for the multispot beam profile 47 in the long axis, which is referred to here as the x-axis. The lower part shows Fig. 3 shows the beam shaping in the short axis, which is referred to here as the y-axis. The device 10" has a spatial filter 24 according to the embodiment in Fig. 1. Alternatively or in addition to the spatial filter 24, the device 10" could be a DOE according to the embodiment in Fig. 2 to modify the angular spectrum of the raw laser beam 14. The raw laser beam with the modified angular spectrum impinges on a beam transformer 54, which expands the raw laser beam along the long axis. The laser beam expanded along the x-axis illuminates the microlens arrays 38, 40 arranged one behind the other in the beam direction, which are preferably also arranged here with a variably adjustable spacing 42 along the optical axis. Furthermore, the device 10" here has a first lens or lens group 66 for far-field imaging, which influences the beam profile predominantly along the long axis, and a second lens or lens group 68, which influences the beam profile predominantly along the short axis.

[0038] The beam-shaping element 24 modifies the angular spectrum with which the first microlens array 38 is illuminated. By reducing the angular spectrum in front of the microlens array 38, the width of the illumination spots 46 in the x-axis direction can be reduced. The length of the individual illumination spots 46 in the y-axis direction can be adjusted either by an intermediate image aperture and / or with the aid of the beam transformer 54. By imaging and reducing / enlarging the angular spectrum with the lenses or lens groups 66, 68, which are arranged downstream of the microlens arrays 38, 40 in the beam direction, the lateral distance between the individual illumination spots 46 can be scaled along the x-axis. In addition, the position of all illumination spots 46 on the working plane can also be adjusted by aligning (pointing) the laser beam upstream and / or downstream of the microlens arrays 38, 40.

[0039] Fig. Figure 4 shows a preferred and advantageous use of a device 10, 10' or 10" in a process for converting amorphous silicon on a carrier plate into higher-quality polycrystalline silicon. The preferred use is based on the SLS process mentioned above. In contrast to the device proposed by Ludolf Herbst, Frank Simon et al., the structured laser illumination is achieved here with the aid of microlens arrays 38, 40, which, due to the selected spacing 42, enable a multi-spot beam profile 47 on the working plane. Fig. 4, the multi-spot beam profile 47 with the illumination spots 46 spaced apart from one another in the long axis is moved in the direction of arrow 70 relative to the working plane 50. In the working plane 50, amorphous silicon 72 can advantageously be arranged on a carrier plate. The amorphous silicon 72 is locally selectively melted with the aid of the illumination spots 46 and can crystallize laterally during cooling, i.e. essentially parallel to the working plane 50. In the direction of movement 70 behind the multi-spot beam profile 47, polycrystalline silicon 74 with a plurality of crystallization cells 76 is thus formed. The multi-spot beam profile 47 is advantageously guided in the direction of movement 70 on a zigzag path which Fig. 4 is indicated by the reference numeral 78. In a particularly preferred embodiment, the transverse movement of the multi-spot beam profile 47 on the zigzag path 78 corresponds to the lateral distance 80 between two adjacent illumination spots 46 along the x-axis or along the extension direction of the multi-spot beam profile 47. In other embodiments, the multi-spot beam profile 47 can be moved in the direction of movement 70 with an alternating transverse component that is greater or smaller than the lateral distance 80 between two adjacent illumination spots 46.

[0040] In summary, embodiments of the novel device thus have an optical arrangement 64 with a beam-shaping element, such as the spatial filter 24 or the diffractive optical element 60, which is arranged in the beam path of a raw laser beam 14 in front of an arrangement with at least two microlens arrays 38, 40, the distance from each other being adjustable via an adjustment mechanism. Alternatively or in addition to the above-mentioned beam-shaping elements, the beam-shaping element could include an axicon or a freeform lens in front of the arrangement with at least the two microlens arrays 38, 40. Further optical elements can follow the microlens arrays 38, 40, in particular one or more Fourier lenses (not shown here) as well as the Fig.3. The beam-shaping element modifies the angular spectrum 26 of the raw laser beam 14 such that the arrangement with the at least two microlens arrays 38, 40 is illuminated with a modified angular spectrum 32. The at least two microlens arrays 38, 40 are arranged at a distance 42 along the optical axis 20, which is selected such that a plurality of separate illumination spots 46 are generated transversely to the beam direction 52 on a working plane 50. Each of the illumination spots 46 has the modified angular spectrum 32.

Claims

[1] A device for generating defined laser illumination on a working plane (50), comprising a laser light source (12) configured to generate a collimated raw laser beam (14) with a first angular spectrum (26), and comprising an optical arrangement (64) receiving the collimated raw laser beam (14) and transforming it along an optical axis (20) into an illumination beam (48), wherein the illumination beam (48) defines a beam direction (52) that intersects the working plane (50), wherein the optical arrangement (64) comprises at least two microlens arrays (38, 40) arranged at a defined distance (42) from one another along the optical axis (20), and wherein the defined distance (42) is selected such that the illumination beam (48) has an illumination beam profile (47) in the region of the working plane (50) that includes a plurality of separate illumination spots (46),wherein the optical arrangement (64) further comprises a beam-shaping element (24; 60) arranged along the optical axis (20) in front of the at least two microlens arrays (38, 40), wherein the beam-shaping element (24; 60) generates a second angular spectrum (32) which is different from the first angular spectrum (26), , characterized by in that the optical arrangement (64) further comprises an adjustment mechanism (44) with which at least one microlens array (40) of the at least two microlens arrays (38, 40) can be adjusted along the optical axis (20) in order to selectively and variably adjust the distance between the at least two microlens arrays (38, 40) from one another. [2] Device according to claim 1, characterized by that the second angular spectrum (32) has a tophat-shaped intensity profile. [3] Device according to claim 1 or 2, characterized bythat the first angular spectrum (26) has a first footprint (30) in a plane (28) perpendicular to the optical axis (20) and that the second angular spectrum (32) has a second footprint (36) in a further plane (34) perpendicular to the optical axis (20), which second footprint is different from the first footprint (30). [4] Device according to claim 3, characterized by that the second footprint (36) is polygonal. [5] Device according to one of claims 1 to 4 characterized by that the beam-shaping element includes a beam transformer (54) which expands the raw laser beam (14) in a direction perpendicular to the optical axis (20). [6] Device according to one of claims 1 to 5 characterized by that the beam-shaping element includes a diffractive optical element (60). [7] Device according to one of claims 1 to 6, characterized by that the beam-shaping element includes a spatial filter (24). [8] Device according to one of claims 1 to 7, characterized by that the beam-shaping element (24, 60) can be selectively introduced into a position along the optical axis. [9] Method for generating a defined laser illumination on a working plane (50) with a laser light source (12) that generates a collimated raw laser beam (14) with a first angular spectrum (26), wherein the collimated raw laser beam (14) is transformed into an illumination beam (48) with an optical arrangement (64) along an optical axis (20), wherein the illumination beam (48) defines a beam direction (52) that intersects the working plane (50), wherein the optical arrangement (64) has at least two microlens arrays (38, 40) that are positioned at a defined distance (42) from one another along the optical axis (20), and wherein the defined distance (42) is selected such that the illumination beam (48) in the region of the working plane (50) has an illumination beam profile (47) that includes a plurality of separate illumination spots (46), wherein the optical arrangement (64) further a beam-shaping element (24;60) arranged along the optical axis (20) in front of the at least two microlens arrays (38, 40), wherein the beam-shaping element (24; 60) generates a second angular spectrum (32) which is different from the first angular spectrum (26); characterized by in that the illumination beam profile (47) is moved along a zigzag path (78) relative to the working plane (50) in order to locally selectively melt amorphous silicon (72) with the aid of the illumination spots (46) and to form polycrystalline silicon (74) having a multiplicity of crystallization cells (76).

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