Laser beam irradiation

Abstract

The laser system (1) is configured to provide a laser line (L) in a working plane (WP) for line irradiation of an object (7). The laser line (L) extends to a significant extent in a first direction (x) and to a lesser extent in a second direction (y). The laser system (1) comprises a laser source (3) for providing a laser beam (3A) as a basis for an elongated input laser beam (13A) propagating along a propagation direction (z), and a homogenizing and focusing unit (60) for homogenizing the strip-shaped laser beam (13A) to form the laser line (L). The laser system (1) is particularly suitable for providing a laser line (L) that can be spliced ​​to another laser line (L') of a corresponding further laser system (1').

Description

Technical Field

[0001] The present disclosure relates generally to laser systems, and more particularly to laser systems for optically providing line-shaped illumination. Furthermore, the present disclosure relates generally to beam transformation and beam homogenization within line optical systems. Background Art

[0002] In certain applications, laser systems are used that provide a very uniform linear intensity distribution in a corresponding focal region. Such a focal region is also referred to herein as a laser line focus or simply a laser line. Exemplary applications using such a laser line focus include laser processing, such as recrystallization of silicon dioxide layers deposited on glass substrates, for example, for TFT displays, laser-based batching, for example, of solar cells, and laser lift-off processes, for example, for the production of microelectronic devices. For example, WO 2015 / 036427 A1 discloses an exemplary method for modifying metal nanoparticles using a laser line focus.

[0003] The corresponding laser system is intended to provide an intensity distribution with large to very large aspect ratio of the beam diameter in two orthogonal directions of the beam profile (i.e. orthogonal to the beam propagation direction) while ensuring a large depth of focus in the direction of smaller beam diameter.

[0004] EP 1 896 893 B1 discloses an exemplary optical configuration for generating a linear intensity distribution based on the transformation of light from, for example, an Nd-YAG laser source. Furthermore, EP 0 731 932 B1 discloses an exemplary optical configuration for beam shaping of a diode laser bar or beam restacking of light from a stack of diode laser bars, thereby providing an output beam having a uniform beam quality factor across the entire output beam. A similar light source combination for providing a pump laser beam is disclosed in WO 2012 / 166758 A1. Summary of the Invention

[0005] The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of existing systems. In particular, it is an object of the present invention to provide an optical system for providing a laser beam having a linear intensity distribution with a large aspect ratio and a large depth of focus along the direction of the smaller beam size. In addition, it is an object to achieve a large uniformity of the intensity distribution along the direction of the larger beam size, i.e., along the "line" formed by the linear intensity distribution. In some aspects, it is another object of the present invention to provide a laser system that enables the length of the line to be changed by arranging two or more laser lines having a linear intensity distribution, and in particular to provide a laser line with an adjustable line length.

[0006] In a first aspect, a beam transformation unit is disclosed for transforming an input laser beam into a transformed beam with reduced spatial and / or temporal coherence, such as that used for line irradiation of an object in a laser system. The beam transformation unit includes a transformation optical device made of a transparent, one-piece, plate-shaped optical element, the optical element having a front surface and a back surface extending substantially parallel to each other. The front surface includes an input surface region for receiving the input laser beam, the input surface region extending in a stripe-like manner along a pre-transformation direction adjacent to a front reflective surface region, and the back surface includes an output surface region for emitting an output laser beam, the output surface region extending in a stripe-like manner along a deformation direction adjacent to a back reflective surface region, the transformation direction being different from the pre-transformation direction. Furthermore, the beam transformation unit is configured such that the front reflective surface region and the back reflective surface region guide multiple input beam segments of the input laser beam through reflection in the transformation optical device, the input beam segments entering the transformation optical device through the input surface region and then emitting through the output surface region. Adjacent input beam segments are rearranged into output beam segments, each of which undergoes a different number of reflections, thereby providing the output beam segments with different optical path lengths within the beam transformation optical device.

[0007] In another aspect, a laser system is disclosed for providing a transformed light beam with reduced spatial and / or temporal coherence that can be used, for example, for line irradiation of an object with a laser line extending along a first direction. The laser system includes: a laser source for providing a laser beam as an input laser beam propagating along a propagation direction; and a beam transformation unit, which includes a transformation optical device made of a transparent, one-piece, plate-shaped optical element, the transformation optical device providing a front surface and a back surface extending substantially parallel to each other at a distance. The front surface includes an input (first) surface area for receiving the input laser beam, and the back surface includes an output (second) surface area for emitting an output laser beam, wherein the transformation unit is oriented relative to the propagation direction so that the input laser beam is incident on the input surface area at an inclination angle relative to the normal vector of the front surface. The inclination angle is selected so that the input laser beam enters the transformation optical device through the input surface area and is guided within the transformation optical device by reflection at the front reflective surface area of ​​the front surface and the back reflective surface area of ​​the back surface to be emitted through the output surface area. Furthermore, adjacent input beam segments are rearranged into output beam segments that undergo different numbers of reflections, thereby providing the output beam segments with different optical path lengths.

[0008] In another aspect, a homogenizing and focusing unit is disclosed for homogenizing a stripe-shaped laser beam to form a laser line extending in a first direction, such as for line illumination of an object in a laser system arrangement. The homogenizing and focusing unit includes a focusing unit comprising a short-axis focusing element that acts in a second direction, thereby defining a working plane of the laser line in the propagation direction of the laser beam at a focal plane of the short-axis focusing element. The homogenizing and focusing unit also includes a homogenizing unit configured to overlap a portion of the stripe-shaped laser beam arranged in the first direction along the stripe-shaped laser beam at the focal plane of the homogenizing unit. Furthermore, the position of the working plane in the propagation direction is selected to be different from the position of the focal plane of the homogenizing unit so that the intensity distribution of the laser line has a top-hat shape with a plateau bounded by slopes on each side. In particular, the plateau may extend over at most 95% of the full width at half maximum of the intensity distribution.

[0009] In another aspect, a laser system is disclosed for providing a laser line in a working plane for line irradiation of an object, the laser line extending a significant length in a first direction and a smaller extent in a second direction. The laser system includes a laser source for providing a laser beam based on an elongated input laser beam propagating along a propagation direction; and a homogenizing and focusing unit for homogenizing the stripe-shaped laser beam to form the laser line. The homogenizing and focusing unit includes a focusing unit comprising a short-axis focusing element that acts in the second direction, such that the position of the working plane of the laser line in the propagation direction of the laser beam is defined at a focal plane of the short-axis focusing element. The homogenizing and focusing unit also includes a homogenizing unit configured to overlap a portion of the stripe-shaped laser beam arranged along the first direction along the stripe-shaped laser beam at the focal plane of the homogenizing unit. The position of the working plane in the propagation direction is selected to be different from the position of the focal plane of the homogenizing unit so that the intensity distribution of the laser line has a top-hat shape with a plateau bounded by slopes on each side. In particular, the plateau can extend over at most 95% of the full width at half maximum of the intensity distribution.

[0010] In another aspect, a combined laser system for laser processing an object using a combination of stitched laser lines comprises a plurality of substantially identical laser systems as described herein, wherein adjacent laser systems are shifted in a first direction by a distance corresponding at least to the width of a slope, thereby allowing overlapping of adjacent slopes in respective transition regions and forming an extended laser line having a flat overall intensity in the first direction.

[0011] In another aspect, a method for splicing laser lines to form a spliced ​​laser line extending along a first direction includes the following steps: for at least two strip-shaped laser beams, using a long-axis focusing element to overlap a portion of the corresponding strip-shaped laser beams arranged along the first direction on a focal plane; and using a short-axis focusing element to focus each strip-shaped laser beam in a second direction, thereby defining a common working plane within a corresponding focal region in the second direction in the propagation direction, wherein the position of the working plane in the propagation direction is selected to be different from the position of the focal plane; and aligning the at least two strip-shaped laser beams side by side in the first direction to form a spliced ​​laser line with a total intensity in the common working plane.

[0012] In another aspect, a homogenizing and focusing unit is disclosed for adjusting the length of a laser line formed by a stripe-shaped laser beam, the laser line extending along a first direction. The homogenizing and focusing unit includes a homogenizing unit configured to overlap portions of the stripe-shaped laser beam arranged along the first direction at a focal plane of the homogenizing unit, and a focusing unit including a short-axis focusing element that acts in a second direction, thereby defining a working plane of the laser line at a position in a propagation direction of the laser beam at the focal plane of the short-axis focusing element. Furthermore, the laser beam diverges along the first direction between the homogenizing unit and the focusing unit.

[0013] In some embodiments, a laser system includes a laser source configured to provide a multimode laser beam having a substantially symmetric beam parameter product.

[0014] In some embodiments, the laser system further comprises a beam transformation unit for transforming the multimode laser beam emitted by the laser source. The beam transformation can be based on a rearrangement of the beam segments of the beam cross section, also referred to herein as mode transformation. Due to the beam transformation, the beam parameter product, in particular M 2 The value increases along a first direction (x-direction) orthogonal to the beam propagation direction and decreases along a second direction (y-direction) orthogonal to the beam propagation direction and the first direction. Mode transformation can reduce the beam quality in one direction while improving the beam quality in another orthogonal direction. The beam transformation proposed in this application can particularly reduce the spatial and / or temporal correlation of the radiation output by the beam transformation unit. This output radiation is referred to herein as a radiation beam, as transformed radiation, or, for simplicity, as a laser beam. Therefore, beam transformation can reduce interference when more modes contribute to further beam homogenization steps.

[0015] In some embodiments of the beam transformation unit, the two reflective surfaces are arranged relative to the incident laser beam such that the beam segments of the laser beam are rearranged due to reflection of the laser beam at the reflective surfaces. In some embodiments, the reflective surfaces can be formed using the surface of a transparent, in particular, one-piece, plate-shaped optical element. The thickness of the plate-shaped optical element is selected such that, for a specific angular orientation (defining the optical path of the corresponding beam segment within the optical element), the difference in the optical path lengths experienced by the individual beam segments exiting the optical element is greater than the coherence length of the incident laser beam.

[0016] In this configuration, the resulting optical path length difference further contributes to output beam uniformity by reducing the temporal coherence of the laser beam, in addition to the spatial coherence caused by mode conversion. Individual beam segments travel for different time periods within the conversion unit, reducing temporal coherence. Because the phase relationship between the beam segments is at least partially lost, coherent interference is less likely to occur when the beam segments overlap in the focal region.

[0017] The output radiation of the beam transformation unit has reduced spatial and temporal coherence along the long axis of the linear beam and is suitable for input into a beam homogenization unit. In the beam homogenization unit, homogenization is achieved by a Fourier lens (long axis focusing element) so that the beam segments overlap in the Fourier plane. Any coherence of the overlapping beam parts can lead to irregularities in the intensity distribution of the resulting laser line, such as the generation of intensity peaks. The degree of interference ("interference contrast") depends significantly on any spatial and temporal coherence of the interfering radiation. The degree of interference decreases with an increasing number of overlapping modes that contribute to homogenizing the radiation, for example, with a decreasing spatial coherence of the radiation. Furthermore, the degree of interference decreases with a decreasing temporal coherence (coherence length) of the radiation, since phase relationships between the radiation parts are eliminated. Therefore, the beam transformation unit proposed here can be used in particular for generating a homogenous laser line.

[0018] The advantages of the concept of the optomechanical (simple) setup disclosed in this article include flexibility in the radiation intensity range due to the macroscopic size of the beam transformation unit, the absence of any intermediate focusing of the beam, and the improvement of the beam quality is basically limited by diffraction at the exit aperture of the beam transformation unit.

[0019] The concepts disclosed herein relate particularly to high-throughput laser processing with high-power / high-energy laser beams, and in particular to laser processing applications including annealing / recrystallization of thin films deposited on glass, annealing of semiconductors, and cladding. The laser sources used can provide coherent radiation in a wavelength range extending from the (near) ultraviolet to the (near) infrared, which can be generated using, for example, Yb-based solid-state lasers, excimer lasers, and diode lasers. For example, the laser sources can be operated in continuous mode or in pulsed mode.

[0020] Other features and aspects of the present disclosure will be apparent from the following description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. In the drawings:

[0022] Figure 1 is a schematic diagram of a laser system for generating a laser line for laser processing;

[0023] Figure 2 It shows that you can Figure 1 A perspective view of an exemplary optical embodiment of a collimation unit, a transformation unit, and a homogenization unit used in a laser system;

[0024] Figures 3A to 3C It is particularly applicable to Figure 2 A schematic diagram of an embodiment and principle of a collimating unit related to collimated light;

[0025] Figures 4A to 4H It is particularly applicable to Figure 2 A schematic diagram of an embodiment and principle of a transformation unit related to light beam transformation;

[0026] Figure 5A and 5B It is particularly applicable to Figure 2 A schematic diagram of an embodiment and principle of a homogenizing unit related to light beam homogenization;

[0027] Figures 6A to 6D is a schematic diagram of an embodiment related to a laser system that arranges a plurality of lasers in parallel and uses a non-focal averaging principle;

[0028] Figure 7 is a perspective view of a first embodiment of a short-axis focusing element that enables splicing of laser lines;

[0029] Figures 8A to 8C is a schematic diagram of a second embodiment of a short-axis focusing element that enables splicing of laser lines; and

[0030] Figure 9 is a schematic diagram of two laser systems positioned side by side for forming a combined (stitched) laser line. DETAILED DESCRIPTION

[0031] The following is a detailed description of exemplary embodiments of the present disclosure. The exemplary embodiments described herein and illustrated in the accompanying drawings are intended to teach the principles of the present disclosure and enable persons of ordinary skill in the art to implement and use the present disclosure in many different environments and for many different applications. Therefore, the exemplary embodiments are not intended to be, and should not be construed as, limiting the scope of patent protection.

[0032] The present disclosure is based in part on the recognition that in order to provide a uniform laser line, the spatial and temporal coherence within the laser beam should be reduced.

[0033] The present disclosure is also based in part on the recognition that the combination of laser lines for generating an extended laser line can be achieved by appropriate selection of working planes associated with the individual laser lines being combined.

[0034] refer to Figure 1 and 2 , a laser system 1 for generating a laser line, for example to be used in a laser machining process, comprises a laser source 3 for generating a laser beam 3A and an optical system 5. The optical system 5 receives the laser beam 3A and outputs a radiation beam 5A, which enables a laser line L to be formed in an associated focal zone. The intensity distribution on the radiation beam 5A in the focal zone is such that the laser line L extends mainly straight in, for example, the x-direction to a desired extent, while the width of the laser line L in the y-direction is greatly reduced. Here, the x-direction and the y-direction extend orthogonally with respect to each other and with respect to the beam propagation direction (assuming that the beam propagation direction extends in the z-direction), as shown in FIG. Figure 1 As shown schematically in FIG.

[0035] The laser line L is focused, for example, on an object 7 of a specific material, such as glass or semiconductor material. The object 7 is supported by a mount 9, and generally, the laser line L and the object 7 can be moved relative to each other so that a desired area is illuminated by the laser line L. Figure 1 As further shown in , a plurality of laser systems 1 may be provided adjacent to each other to together form an extended laser line consisting of a series of laser lines L, L'.

[0036] The laser source 3 may be a source for generating coherent radiation, for example a laser beam, in a wavelength range extending from the (near) ultraviolet to the (near) infrared, for example in particular in the range of 300 nm to 350 nm, 500 nm to 530 nm, or 900 nm to 1070 nm, which can be generated using, for example, Yb-based solid-state lasers, excimer lasers, and diode lasers. The coherent radiation is characterized by its beam quality, for example by the M in the x-direction and the y-direction, respectively. 2 The beam quality can be symmetrical, i.e., have substantially the same M in the x-direction and the y-direction. 2 Values, or those M 2The values ​​may be substantially the same or different to some extent. In the embodiments disclosed herein, it is assumed that the difference, if any, gives a better beam quality in the y direction than in the x direction (e.g., M 2 x =a·M 2 y).

[0037] The laser beam 3A can be provided to the optical system 5 using fiber transmission or free space transmission. The laser source 3 can be, for example, a fiber-coupled diode laser or a multimode solid-state laser, both of which can provide a laser beam having a beam parameter product that is substantially symmetrical about the propagation direction. The laser source 3 can be, for example, a multimode disk laser having a central wavelength of 1030 nanometers. A 200 micron optical fiber with a numerical aperture (NA) of 0.11 can enable the generation of a laser beam 3A having a beam parameter product BPP of 10 mm mrad. The coherence length of the laser beam can be determined based on the wavelength of the laser beam. c =λ2 / Δ λ, where Δλ is the spectral width of the solid-state laser. The coherence length l of the disk laser mentioned above is c About 0.5 mm.

[0038] With reference to the preliminary discussion on the effect of temporal coherence on the uniformity of the intensity distribution in the focal region, the use of optical plates with thicknesses in the millimeter range in the optical system 5 can produce optical path length differences between the beam segments that are sufficient to reduce the temporal coherence to the desired extent, as will be discussed below in conjunction with Figures 4A to 4H As explained.

[0039] like Figure 1 As shown in a separate box in FIG, the optical system 5 includes a collimating unit 11 (optional), a beam transformation unit 13, a homogenizing unit 15 and a focusing unit 17 (optional, provided separately, or integrated in an optical element such as the homogenizing unit 15, thereby forming a homogenizing and focusing unit 60).

[0040] The optical configuration of these units is designed to be able to generate a radiation beam 5A with a linear intensity distribution having a high aspect ratio (e.g. in the range of 10 to 100, such as 60 for a single beam or 30 for a dual beam configuration) from the laser beam 3A, while having a large depth of focus in the direction of a smaller beam diameter in the focal region.

[0041] To simplify and improve the transformation, the collimation unit 11 can be configured to provide an elliptical beam shape with corresponding divergences in the x- and y-directions as an input beam shape for the beam transformation unit 13. The beam transformation unit 13 is configured to rearrange beam segments of the input beam cross section arranged along the y-direction into beam segments arranged along the x-direction to form an output beam shape of the beam transformation unit 13. The output beam is thereby advantageously designed to enable, for example, the homogenization unit 15 to operate efficiently.

[0042] refer to Figure 2 and 3A 3C, an exemplary collimating unit 11 comprises folding anamorphic optics comprising a plurality of lenses 21 (cylindrical and spherical lenses) and a folding mirror 23. Laser beam 3A exiting, for example, an optical fiber (not shown) is shaped into a collimated laser beam 11A having an elliptical shaped intensity distribution.

[0043] Figure 3A and 3B The general beam shaping and collimation in the yz plane and the xy plane are shown respectively. For example, the collimation focal length F in the y direction c,y is indicated as being significantly larger than the collimation focal length F in the x-direction c,x For laser beam 11A, Figure 3C An elliptical beam profile 25 is shown, wherein the major axis of the ellipse extends in the y-direction and the minor axis of the ellipse extends in the x-direction. Due to the elliptical shape, the divergence characteristics of the laser beam 11A are such that the divergence in the x-direction and the y-direction have opposite ratios relative to the corresponding beam diameters along the x-direction and the y-direction.

[0044] Typically, laser beam 11A is designed to allow for an advantageous and compact size of beam transformation unit 13. For example, the beam waist in the x-direction and / or the beam waist in the y-direction of laser beam 11A can be positioned near or within beam transformation unit 13. For example, at least the beam waist in the x-direction can be located at the entrance aperture of beam transformation unit 13. For the sake of completeness, it should be noted that the elliptical shape of laser beam 11A may be less sensitive to beam alignment and position sensitivity than a circular shape of the beam, and therefore, fewer measures may be required with respect to beam alignment and stabilization.

[0045] like Figure 2 As further shown by the dashed lines in , two or more laser beams can be combined as input to the beam transformation unit 13 to allow for greater beam intensity.

[0046] refer to Figure 2 and 4A To 4H, the beam transformation unit 13 uses a specific reflective structure for rearranging the (input) beam segment 27 of the collimated laser beam 11A.

[0047] Figure 4A and 4B FIG. 2 shows the function of beam transformation in the case where two laser beams 11A and 11A′ are input to the beam transformation unit 13. Figure 4A As shown, the first input beam segment 271 corresponds to the lowest portion (in the y direction) of the laser beam 11A, while the nth input beam segment 27 n corresponds to the highest part (in the y-direction) of the laser beam 11A.

[0048] Figure 4B 1 shows rearranged (output) beam segments 29 associated with the transformed light beam 13A before passing through any further optical components. The first rearranged beam segment 291 corresponds to the first input beam segment 271 that has passed through the beam transformation unit without any reflection, i.e., its optical path in the beam transformation unit is the shortest with respect to the other rearranged beam segments. The sequence of input beam segments arranged adjacent to each other in the y-direction are rearranged side by side in the transformed light beam 13A along the x-direction until a segment corresponding to the n-th input beam segment 271 is formed at the opposite lateral end of the transformed light beam 13A. n The nth rearranged beam segment 29 n .

[0049] The transformation within the beam transformation unit 13 generally degrades the beam quality in the x-direction while improving the beam quality in the y-direction.

[0050] Figure 4C and 4D shows a beam transformation based on an exemplary transformation optical device 31, Figure 4E and 4F A side view of the transformation optics 31 and the applied coating is shown.

[0051] The transformation optical element 31 is a solid optically transmissive plate-like material having a thickness d. The transformation optical element 31 has a front face 31A and a back face 31B of substantially triangular shape with two, for example orthogonal, long sides originating from a common edge 32. Figures 4D to 4F The directions of the two long sides are indicated by x' and y'. In the mounted state, the transformation optical element 31 is tilted relative to the x and y directions. The front face 31A and the back face 31B are essentially parallel to each other. It should be noted that the triangular base shape shown by way of example is particularly compact because it only provides material where needed.

[0052] The first (input) surface area 33A of the front side 31A extends along one of the long sides, which extends in the y' direction (also referred to herein as the pre-transformation direction), for example slightly inclined relative to the y direction, and is intended to receive the laser beam 11A. The input surface area 33A forms an entrance aperture of the beam transformation unit 13 (see also Figure 4E ). The second (output) surface area 35A of the back side 31B extends along the other long side which extends substantially in the x' direction (also referred to herein as the transformation direction), for example slightly inclined relative to the x direction, and serves for emitting the laser beam 13A. The output surface area 35A forms the exit aperture of the beam transformation unit 13 (see also Figure 4F ).

[0053] The input and / or output surface regions 33A, 35A may have an antireflection coating 34 applied thereto and may be sized according to the input beam size and a desired output beam size, which substantially corresponds to the input beam size. In the exemplary embodiment shown in the figures, the input surface region 33A extends perpendicularly relative to the output surface region 35A in the plane of the plate-shaped transformation optical element 31. The input and output surface regions 33A, 35A overlap in the edge region 32A, so that an incident light beam passing through the edge region is transmitted through the transformation optical element 31 without reflection, even in an oblique orientation relative to the x- and y-directions.

[0054] Next to the entrance and exit apertures (input and output surface areas 33A, 35A), the front face 31A and back face 31B include respective third (front reflective) and fourth (back reflective) surface areas 33B, 35B. In an exemplary embodiment, those surface areas are coated with a high-reflectivity coating 36. The coating reflects the laser beam 11A—in the illustrated example, with the exception of the first input beam segment 271—at least once at the front face 31A and back face 31B. The number of reflections increases with the order of the beam segments 27 in the y-direction. To provide this multiple reflection within the transformation optic 31, the transformation optic 31 does not extend orthogonally relative to the beam propagation direction (z-direction), but is tilted such that the entrance aperture (input surface area 33A) is tilted relative to the y-direction and the exit aperture (output surface area 35A) is tilted relative to the x-direction. The common edge 32 can be considered a fixed point of tilt in both directions. The final orientation is determined by the angle α between the normal vector n of the front face 31A and the normal vector n of the front face 31A when oriented perpendicular to the propagation direction. eff representation.

[0055] exist Figure 4DIn FIG. 3 , three exemplary optical paths 37A, 37B, and 37C are shown for obliquely incidenting the input light beam 11A onto the reflective surface of the plate-shaped transformation optical device 31. While the optical path 37A does not include any reflection, the optical paths 37B and 37C reflect multiple times. eff , the transformation optical device 31 generates a signal corresponding to D=2d / cos(α eff ). In other words, for each additional pair of reflections, this path length difference D is added to the path of the beam segment within the beam transformation optics 31.

[0056] As the number of reflections increases (and thus as the order of the input / rearranged beam segments increases), the optical path length increases, so that the rearranged beam segments 291 to 29 n The beam cross section within is reduced in sharpness due to the divergence of the beam. n This can be done in Figure 4B as seen in the x- (and y-) direction.

[0057] In summary, the concept of multiple reflections of input beam portions within the transformation optics 31 rearranges the beam segments so that the transformed beam 13A has a greater divergence at the exit aperture in the direction of its larger diameter (in the x / x' direction in the drawing) than in the direction of its smaller diameter (in the y / y' direction in the drawing). Figure 4E and 4F In the embodiment shown, the multiple reflection concept is achieved by tilting the direction of the transformation optical element 31 relative to the incident laser beam 11A (11A') and by providing areas with a reflective coating (third and fourth surface areas 33B, 35B) or an anti-reflective coating (entry / exit aperture, i.e., first and second surface areas 33A, 35A).

[0058] The beam parameter product BPP of the beam 13A leaving the transformation optical device 31 is given in two directions x and y, i.e. along the long dimension and the short dimension of the transformed beam 13A, as

[0059] BPP x (Long dimension) = BPP fiber A and BPP y (Short size) = BPP fiber / A, where the parameter A corresponds to the segmentation parameter of the transformation unit 13 (i.e. the number of beam segments 29 associated with the transformation unit 13) and typically has a value in the range of 3 to 15 or even up to 20 or more. However, due to diffraction, for short dimensions the improvement of the beam parameter product may be limited to an M of about 2. 2 value.

[0060] refer to Figure 4E and 4F The transformation optic 31 comprises a low-absorption, high-transmission, and preferably low-thermal-expansion material, such as fused silica. The thickness d of the transformation optic 31 can, for example, be in the range of 3 mm to 20 mm. The flatness of the front face 31A and back face 31B, as well as their parallel orientation, can be in the range of λ / 10 or less. The antireflection coating can be a 99.9% transmissive coating, and the reflective coating can be a 99.98% reflective coating within the desired spectral range, thereby providing a transmission in the range of, for example, 99% to 99.8%.

[0061] In order to provide efficient coupling-in of the light beam despite the tilted configuration, the shape of the input surface area 33A can be adapted to the tilted orientation. For example, the width w of the input surface area 33A in the x' direction can be reduced in the y' direction, as shown in FIG. Figure 4E 33T. For example, the transformation optical device 31 includes an input surface region 33A in the shape of an acute trapezoid, wherein the acute trapezoid has two adjacent acute angles on its longer (and in the y' direction) base edge. In contrast, the transition in the y' direction (at Figure 4F The height h of the output surface area 35A, which is configured as a rectangle, is selected to be constant along the x' direction.

[0062] In this embodiment, if the upper boundary of the rectangular outlet aperture is oriented parallel to the xz plane and if the normal vector n of the front face 31A is at a corresponding angle α relative to the z direction eff Oriented obliquely, a virtual entrance aperture is then created, which has an effective front transition line (extending in the y-direction) relative to the reflection area provided by the front reflective surface area 33B. In addition, a virtual exit aperture is also created, which has an effective horizontal rear transition line (along the x-direction) relative to the reflection area provided by the rear reflective surface area 35B. Thus, the splitting of the incident light beam 11A into square beam segments 29 can be performed, as shown in FIG. Figure 4B As shown exemplarily in .

[0063] It should be noted that, although the exemplary embodiment shown shows that the (anti-reflection coating) regions 33A and 35A are provided on opposite sides, i.e. on the front side 31A and the back side 31B of the transformation optics 31, respectively, in some embodiments these regions may be provided on the same side. Figure 4G and 4H A corresponding embodiment of the beam transformation unit 31 ′ is shown in FIG.

[0064] like Figure 4GAs shown, the entrance and exit apertures are defined by the extent of the anti-reflection coating 34' provided at the same side (here referred to as the front side 31A') of the beam transforming unit 31' along the base (i.e. in the x' direction) and the sides (i.e. in the y' direction) of the triangular basic shape of the beam transforming unit 31'. The front side 31A' and the back side 31B' (as shown in FIG. Figure 4H The remaining portion (shown) is coated with a high reflectivity coating 36'. Therefore, the collimated laser beam 11A enters and exits the beam transformation unit 31' on the same side, i.e., through the front face 31A'. Thus, the system can be designed in a more compact manner.

[0065] The transformed beam 13A is homogenized in a homogenizing unit 15 to produce a top-hat shaped intensity distribution in the focal zone Z with high uniformity along the long dimension (x direction, long axis) of the laser line L. For a single laser line L, this homogenization will be combined with Figures 4A to 4H 5A, 5B briefly described, for example, may be based on a non-imaging or imaging homogenizer arrangement, such as that disclosed in the above-mentioned EP 1 896 893 B1.

[0066] In some embodiments, an arrangement of laser lines is performed, which requires a smooth transition between adjacent laser lines L, L'. This is referred to herein as "stitching" of laser lines. To improve and simplify stitching, a non-focal concept is disclosed herein that combines Figures 6A to 6D In addition, Figures 8A to 8C A reflective focusing arrangement for further improving and simplifying splicing is disclosed, wherein the reflective focusing arrangement enables the acceptance of the beam divergence required for splicing multiple units.

[0067] In some embodiments, homogenization unit 15 may include multiple lens elements and a focusing element active in the x-direction. Focusing in the y-direction may be further performed by an additional focusing unit 17, which includes a focusing element active only in the y-direction (defining the line thickness on the minor axis) and positions the working plane at its focus. Thus, in the resulting focal zone Z, an intensity distribution extending uniformly in the x-direction is obtained, with a large depth of focus in the y-direction.

[0068] With respect to the multi-lens element, for example, a single-step tangent integrator (non-imaging homogenizer) or a two-step tangent integrator (imaging homogenizer) can be used to form a top-hat shape. Generally, an imaging homogenizer can provide better uniformity. The integrator can be a microlens array of cylindrical lenses with sizes ranging from, for example, less than 0.5 mm to 5 mm or more than 5 mm, which are oriented to provide focusing in the x-direction. Thus, the spacing between the microlenses can be in the range of 0.5 mm to 5 mm, for example, in the range of 0.5 mm to 4 mm. For example, the numerical aperture NA of the homogenizer can be in the range of 0.05 to 0.15.

[0069] Regarding the long-axis focusing element acting in the x-direction, a Fourier lens can be used to overlap the individual beam segments in the x-direction in the working plane. The focusing element corresponds to a one-dimensional transformation from the near field to the far field, thereby overlapping the intensity distribution of each lens element in the focal plane—due to a substantially no interference of the beam segments or a reduced coherence reduction with reduced interference of the beam segments. The focal length of the long-axis focusing element acting in the x-direction (e.g., a Fourier lens) can be in the range of 0.5 microns to 10 microns. This enables the generation of laser lines up to 0.5 meters or more in length (along the long axis of the line).

[0070] In some embodiments, the focal length of the focusing element is selected to be smaller or larger than the distance relative to the working plane (e.g., smaller or larger by a factor of 1.x to 2). This allows for control of the slope at the sides (edges) of the laser line L and reduction of the diffraction peak, and avoids a corresponding broadening of the intensity distribution.

[0071] Figure 5A and 5B An embodiment of the averaging unit 15 is schematically shown, wherein the averaging unit 15 comprises two multi-lens elements 41A and 41B (each comprising a plurality of lens elements 42 ) and a Fourier lens 43 . Specifically, Figure 5A The optical elements acting in the x-direction are shown (i.e., without any focusing elements acting in the y-direction of the (short axis) focusing unit 17). Thus, the multi-lens elements 41A, 41B have, for example, a common focal length f, and the Fourier lens 43 has a focal length F in the x-direction (long axis of the line). Figure 5B Schematically shown is a top-hat shape of the intensity distribution 45 in the x-direction that can be achieved at the Fourier plane FP defined by the focal length F of the Fourier lens 43. In certain applications, the Fourier plane FP can be used as a working plane in which the object 7 is located.

[0072] It should be noted that the first of the multi-lens elements 41A, 41B is located at a distance from the exit aperture of the transformation optics 31 such that the transformed beam 13A will generally be widened in the x- and y-directions. Furthermore, each lens element 42 of the first multi-lens element 41A is smaller than the widened beam segment 29. For example, 40 lens elements 42 can cover 10 beam segments 29. To reduce any interference in the imaging homogenizer, the multi-lens elements 41A, 41B can be separated by a distance greater than their common focal length f. For example, the distance between the multi-lens elements 41A, 41B can be in the range of 1f to 1.3f. The Fourier lens 43 causes the images of the individual lens elements 42 to overlap in the focal region, particularly in the Fourier plane FP, as shown by the beam line 44.

[0073] Reference again Figure 5B In the top-hat shape of the intensity distribution 45 shown in FIG, the flanks 46 of the distribution (also referred to herein as slopes) that bound the top-hat shape are very steep, corresponding to a rapid drop in intensity in the x-direction, for example, a drop in intensity to approximately 10% over a range of less than 5 mm. This is acceptable if splicing of multiple laser lines is not performed, but such steep slopes may not be well suited for splicing adjacent laser lines. As will become apparent from considering the non-focal settings described below, steep slopes may be more difficult to locate when creating a smooth transition between adjacent flat-top shaped intensity distributions. Therefore, in embodiments particularly suitable for splicing, at least one of the slopes extends over at least about 5 mm and less than about 60 mm, for example, extending in the range of about 10 mm to about 40 mm.

[0074] Along the short dimension (in the y direction) of the transformed beam 13A, the beam can be focused by a corresponding cylindrical focusing element (combined with Figure 7 and 8A 8C (discussing exemplary configurations) achieve a quasi-Gaussian intensity distribution with a FWHM of, for example, 30 μm to 100 μm. The focusing element (lens or mirror) typically has a focal length of 80 mm to 200 mm and is therefore positioned shortly before the Fourier plane FP and extends substantially along the entire length of the laser line L.

[0075] refer to Figures 6A to 6D The concept of non-focal averaging is based on the recognition that the working plane is shifted from the focal plane of the long axis focusing element acting in the x direction (e.g. Figure 5AShifting the Fourier plane FP of the Fourier lens 43 in the image plane reduces the slope at the lateral ends of the individual laser lines L. Consequently, the tolerance for alignment of adjacent laser lines L and L' in the x-direction is increased. Furthermore, the less steep slope creates a wider stitching zone, resulting in less stringent positioning tolerances. Furthermore, positioning the final focusing lens away from the far field, for example, before the Fourier plane FP, reduces diffraction effects at the edges, resulting in a smoother overlap of adjacent laser lines.

[0076] Specifically, Figure 6A The intensity distribution of laser lines for joining a plurality of laser lines L1, L2, L3 generated by corresponding laser systems and extending in the x-direction is shown. Each laser line L1, L2, L3 corresponds essentially to a trapezoidal intensity distribution 51, wherein the top-hat shape is bounded on each side by a slope 53L, 53R, which results in an essentially linear drop in intensity to approximately 10% over, for example, 25 millimeters.

[0077] Figure 6B Schematically shows how to combine Figure 6C The explained top-hat shape of the intensity distribution 54 in the x-direction that can be achieved at a corresponding working plane that is offset relative to the focal zone of the focusing element.

[0078] In some embodiments, the concept of non-focal averaging is achieved by appropriately selecting the focal lengths of the optical elements and the distances between them so that the working plane is moved away from the focal region of the focusing elements so that the platform of the top-hat profile extends over a maximum of 95% of the full width at half maximum (FWHM) of the intensity distribution. L , 53 R It extends over at least 2.5% or more than 2.5%, for example 5% or more than 5%, for example 10%, of the FWHM of the intensity distribution. Thus, a desired insensitivity with respect to alignment in the x-direction is provided.

[0079] Since adjacent intensity distributions 51 have substantially the same slope 53 L , 53 R But in opposite directions, so that the overlap of the intensity distributions produces a substantially flat total intensity 55, as Figure 6A The modulation in the transition region 57 between adjacent intensity distributions 51 is related to the slope 53. L , 53 R The steepness of is related to the accuracy of the alignment of the laser lines L1 , L2 , L3 with respect to their position in the x-direction.

[0080] Regarding the exemplary non-focal settings implemented in the averaging and focusing unit 60, Figure 6C Those optical elements acting in the x-direction are shown, while Figure 6D Those optical elements that act in the y-direction are shown. By way of example, Figure 6C An optical setup using an imaging homogenizer is shown. However, it should be appreciated that non-imaging homogenizers can also apply the basic concept to improve the stitching of the laser lines L1 , L2, L3.

[0081] refer to Figure 6C The averaging and focusing unit 60 includes two microlens arrays 61A, 61B of cylindrical lenses as exemplary multi-lens elements and a long axis focusing element (e.g., Fourier lens 63) having a focal length F as a focusing element acting in the x direction. The microlens arrays 61A, 61B and the long axis focusing element 63 can be considered to constitute a similar Figure 5A Although the long-axis focusing element 63 is referred to as a Fourier lens here, in principle a reflective structure can also be implemented.

[0082] refer to Figure 6D , the homogenizing and focusing unit 60 further comprises a short axis focusing element 65 acting in the y direction.

[0083] The short axis focusing element 65 extends substantially across the magnified light beam provided by the microlens arrays 61A, 61B and the Fourier lens 63. The short axis focusing element 65 typically has a focal length f that is significantly smaller than the focal length F. y , for example 1% to 10% of the focal length F. For example, the focal length F may be approximately 2000 mm, while the focal length f y It may be in the range of 80 mm to 250 mm, for example approximately 150 mm.

[0084] The short axis focusing element 65 may comprise a (cylindrical) focusing lens and / or a (cylindrical) focusing mirror, which are arranged to act in the y direction (only in the y direction, i.e. essentially not act in the x direction, e.g. the cylinder axis is along the y direction) or a plurality of those optical elements.

[0085] exist Figure 7 In the exemplary embodiment shown, the short axis focusing element 65 is configured as a parabolic reflector 70. The parabolic reflector 70 has a highly reflective surface 71 having a parabolic shape in the yz plane to focus the laser beam at an angle of, for example, 90° along the strip shape of the laser beam in the short axis direction at intervals of focal length f. y Place.

[0086] The following will be combined Figures 8A to 8C Another embodiment of a short-axis focusing element 65 using reflective cylindrical optics is described.

[0087] Reference again Figure 6C and 6DIn order to reduce the slope of both sides of each top-hat intensity distribution, thereby allowing the specific splicing of laser lines as disclosed herein, the short axis focusing element 65 is arranged in parallel with the Fourier lens 63 (at Figure 6D The short-axis focusing element 65 is positioned at a non-focal distance 66 (indicated by the dashed line in FIG. ), wherein the non-focal distance 66 is within a range of 20% to 90% or 120% to 200% of the focal length F. That is, the position of the short-axis focusing element 65 deviates from the position of the short-axis focusing element 65 required to position the focal point of the Fourier lens 63 and the focal point of the short-axis focusing element 65 in the same plane. For example, the short-axis focusing element 65 is positioned 0.5F away from the Fourier lens 63. This position of the short-axis focusing element 65 results in the position of the working plane WP differing from the position of the Fourier plane FP of the Fourier lens 63 by approximately 55% of the focal length F. This difference in position is sufficient to reduce the side slope in a manner suitable for stitching the intensity distributions of two adjacent laser systems 1, 1'.

[0088] In other words, the distance of the working plane WP relative to the Fourier lens 63 is in the range of about 30% to 80% or 130% to 180% of the focal length F. Based on this and knowing the focal length f of the short axis focusing element 65 y For example, it can be determined that the position of the short-axis focusing element 65 relative to the Fourier lens 63 falls within the range given above.

[0089] As an example of the short axis focusing element 65, Figures 8A to 8C An optical focusing system 80 is shown which enables the incident laser light to be focused in the y-direction, thereby providing a line focus 81 with a line length 11 (in the x-direction in the drawing) at the working plane WP. Figure 6A , the line length 11 includes the full width at half maximum FWHM and two halves of the remaining transition region 57 on each side.

[0090] The optical focusing system 80 is specifically designed to provide a line length 11 that extends, at least at one end, beyond the lateral system width ws of the optical focusing system 80. The system width ws is typically given by the dimensions of a housing 83 surrounding the optical focusing system 80. Typically, the housing 83 has an exit window 85 through which the laser light exits onto an object 87 to be irradiated. The object 87 is positioned, for example, on top of a mount 89. The optical focusing system 80 and / or the mount 89 can be mounted to one or more multi-axis robots, such as a hexapod (not shown), to enable the correct orientation of the laser line on the object 87.

[0091] Having a line length 11 extending beyond the system enables splicing of laser lines to produce a combined laser line 91 by simply positioning housings 83 of substantially identical optical focusing systems 80 side by side, as shown. Figure 9Adjusting the length ll and slope of each line (and the emission light intensity of each laser system) enables the formation of a laser beam having the following characteristics: Figure 6A A combined laser line 91 of uniform intensity is shown.

[0092] exist Figure 9 In FIG, the divergence of the beam forming the laser line (segment) in the x-direction is represented by angle δ. This beam divergence enables the positioning of laser systems side by side. Angle δ is defined by the minimum required distance dmin between housings 83 and the distance from exit window 85 to working plane WP (herein referred to as free working distance WD).

[0093] However, due to the required beam divergence, focusing with a cylindrical lens is not feasible because the incident angle of the beam at the outer end of the cylindrical lens is tilted, which will cause focusing aberrations.

[0094] on the contrary, Figures 8A to 8C The configuration of the optical focusing system 80 shown in is less sensitive to those focusing aberrations. The optical focusing system 80 comprises a set of two cylindrical mirrors for influencing the convergence of the light beam in the y direction, the cylindrical axis of the cylindrical mirrors extending in the x direction. In particular, downstream of the Fourier lens 63, a light beam 93 is formed, which is collimated in the y direction and diverges in the x direction. The diverging (convex) cylindrical mirror 95A (radius R1<0) causes the light beam 93 to leave the XZ plane at an angle β and be reflected onto the focusing (concave) cylindrical mirror 95B (radius R2>0), which is mounted at a distance l2 from the diverging (convex) cylindrical mirror 95A. The focusing powers of the two cylindrical mirrors are selected so that the working plane WP is at a distance l1 from the focusing (concave) cylindrical mirror 95B, so that the focusing (concave) cylindrical mirror 95B reflects the light beam 93 at an angle γ. According to the angle γ, the outgoing light beam 93A (corresponding to Figure 1 The radiation beam 5A) in can propagate at a certain angle relative to the xz plane.

[0095] The optical path length modification unit can provide further folding of the beam path. Typically, the laser system can be pre-positioned or freely positionable relative to the object 87 to ensure the desired angle of incidence ε. The angle of incidence ε is Figure 8C 8 is shown by way of example relative to a surface normal n of an object 87 extending, for example, in a plane.

[0096] Exemplary parameter values ​​include a range of from about 40° to about 60° for angle β and a range of from about 20° to about 30° for angle γ. The optical focusing system 80 can have a combined focusing power (fy) of the two cylindrical mirrors in the range of 90 mm to 300 mm, such that, for example, the distance l1 ranges from about 200 mm to about 1200 mm and the distance l2 ranges from about 70 mm to about 400 mm. These parameter ranges further correspond to a ratio β / γ in the range of about 1.7 to about 2.3 and an absolute value of the curvature ratio of the two cylindrical mirrors R1 / R2 in the range of about 1.6 to about 2.1 (e.g., for R1=410 mm and R2=230 mm, Figure 8C ( , which shows a curvature in the yz plane, while there is an essentially straight extension in the x direction). In particular, the parameters fy, l2 and β are independent parameters that can be selected depending on the specific application of the laser system.

[0097] like Figure 8C As shown, in particular, a diverging (convex) cylindrical mirror 95A is positioned adjacent to the working plane WP, such that the housing 83 will generally cover the mirror and provide an exit window 85 spaced approximately the same distance from the working plane 83, thereby defining a free working distance WD between the optical focusing system 80 and the object 87 / working plane WP. Exemplary values ​​for the free working distance WD range from, for example, about 10 mm to about 1000 mm.

[0098] The optical focusing system 80 provides diffraction-limited focusing in the y-direction using purely cylindrical components. This is cost-effective compared to parabolic reflectors. In addition, the reflective design has no or less coupled aberrations (compared to lens embodiments) and provides very high transmission of the light beam 93.

[0099] To splice laser lines, embodiments disclosed herein enable each line to have a specific beam divergence in the x-direction so that adjacent shells do not collide. The corresponding constraint for splicing can be determined as FWHM—the line length FWHM (in the working plane) is the same as or greater than the width ws of shell 83. The inventors recognized that due to line divergence in the x-direction, lens-based telecentric designs may have drawbacks that can be reduced or even avoided by using reflective focusing.

[0100] Therefore, the averaging and focusing unit, in particular the Fourier lens 63, is configured to provide the required minimum divergence. In general, the required beam divergence is related to the free working distance WD, the desired FWHM-line length FWHM, and the desired length of the transition region 57. For example, the angle δ can be approximated as being proportional to the ratio of the FWHM-line length FWHM to the free working distance WD.

[0101] The aforementioned need to adjust the line length 11 of the spliced ​​laser line can be addressed by an optical path length modification unit 100 configured to adjust the optical path length between Fourier lens 63 and optical focusing system 80. Within optical path length modification unit 100, the light beam is collimated, for example, in the y-direction, but diverges in the x-direction. Here, optical path length modification unit 100 includes, for example, a beam folding structure having a folding mirror 101 positioned on a translation stage (indicated by arrow 103). Therefore, when the folding mirror is moved, the light path within optical path length modification unit 100 can be lengthened, and the line length 11 will increase, and vice versa. Figure 8A The long optical path length setting in the optical path length modification unit 100 is shown with a solid line, and the short optical path length setting is shown with a dashed line.

[0102] It should be noted that at least some of the aspects disclosed herein, for example those related to homogenization (particularly splicing of laser lines), can also be implemented in known laser systems for line-shaped illumination, for example using transformation optics known in the art instead of as described herein in conjunction with Figures 4C to 4H The disclosed integrated plate-shaped optical element. In addition, Figures 8A to 8C The short-dimension focusing system shown in can also be implemented in known laser systems for line-shaped irradiation to provide specific tiled shapes and / or dimensions of the laser line.

[0103] In this respect, the homogenizing and focusing unit (for homogenizing the strip-shaped laser beam to form a laser line extending in a first direction, which is to be used, for example, for line-shaped illumination of an object in an arrangement of a laser system) may comprise:

[0104] a focusing unit comprising a short-axis focusing element acting in the second direction so as to define the position of the working plane of the laser line in the propagation direction of the laser beam at its focal plane; and

[0105] The homogenizing unit is configured to enable portions of the stripe-shaped laser beams arranged along a first direction to overlap along the stripe-shaped laser beams at a focal plane of the homogenizing unit, wherein the beams diverge along the first direction between the homogenizing unit and the focusing unit.

[0106] The diverging beam enables the splicing of laser lines generated by homogenizing and focusing units positioned side by side, since each laser line can extend in the working plane beyond any structural components of the respective homogenizing and focusing unit.

[0107] In some embodiments, the homogenizing and focusing unit further comprises an optical path length modification unit positioned between the homogenizing unit and the focusing unit, wherein the optical path length modification unit is configured to adjust the optical path length between the homogenizing unit and the focusing unit. Changing the optical path length affects the line length of the laser line on the working plane while maintaining the position of the working plane, as a beam diverging in a first direction will become more (or less) diffuse. In some embodiments, the optical path length modification unit comprises a beam folding structure comprising a folding mirror positioned on a translation stage. Moving the position of the folding mirror using the translation stage changes the optical path length within the optical path length modification unit, thereby changing the optical path length between the homogenizing unit and the focusing unit.

[0108] In the exemplary embodiments disclosed herein, reference is made to coordinates x, y, and z. A skilled artisan will appreciate that those coordinates may represent an orthogonal coordinate system related to the corresponding parts of the system and the direction of beam propagation, but may not align with a common orthogonal coordinate system due to the folding of the beam path. Generally, the x- and y-directions can be considered orthogonal to the actual propagation direction (z-direction) and to each other.

[0109] Although preferred embodiments of the present invention have been described herein, improvements and modifications may be incorporated without departing from the scope of the invention.

Claims

1. A laser system for providing a transformed laser beam (13A) with reduced spatial and / or temporal coherence capable of being used for line irradiation of an object (7) with a laser line (L) extending along a first direction (x), the laser system comprising: a laser source (3) for providing a laser beam (3A) as an input laser beam (11A) propagating along a propagation direction (z); as well as A beam transformation unit (13) comprising a transformation optical device (31) made of a transparent, one-piece, plate-shaped optical element, the transformation optical device providing a front surface (31A) and a back surface (31B) extending substantially parallel to each other at a distance (d), wherein the front surface (31A) comprises an input surface area (33A) for receiving an input laser beam (11A), the input surface area (33A) extending adjacent to a front reflection surface area (33B) in a strip-shaped manner along a front transformation direction (y'), and the back surface (31B) comprises an output surface area (35A) for emitting an output laser beam (11A), the output surface area (35A) extending adjacent to a rear reflection surface area (35B) in a strip-shaped manner along a transformation direction (x'), wherein The beam transformation unit (13) is oriented relative to the propagation direction (z) so that the input laser beam (11A) is tilted at an angle (α) relative to the normal vector (n) of the front face (31A). eff ) falls onto the input surface area (33A), wherein the tilt angle (α eff ) is selected so that: the input laser beam (11A) enters the transformation optical device (31) through the input surface area (33A), and is guided within the transformation optical device (31) by reflection at the front reflection surface area (33B) of the front surface (31A) and reflection at the back reflection surface area (35B) of the back surface (31B) to be emitted through the output surface area (35A) to become an elongated laser beam (13A) elongated along the first direction (x), and The beam transformation unit (13) is configured such that a front reflection surface area (33B) and a rear reflection surface area (35B) guide a plurality of input beam segments (27) of an input laser beam (11A) through reflection within a transformation optical device (31), the plurality of input beam segments (27) entering the transformation optical device (31) through the input surface area (33A) and then exiting through the output surface area (35A), wherein adjacent input beam segments (27) are rearranged into output beam segments (29), the output beam segments (29) undergoing different numbers of reflections, thereby providing the output beam segments (29) with different optical path lengths.

2. The laser system according to claim 1, wherein: The front surface (31A) and the back surface (31B) are arranged to be separated by a distance (d) of at least 0.5 mm.

3. The laser system according to claim 1 or 2, wherein: The input surface area (33A) and the output surface area (35A) are arranged so that when the input laser beam (11A) is inclined at an angle (α) relative to the normal vector (n) of the front surface (31A), eff ) falls on the input surface area (33A), the input beam segments (27) arranged substantially along the pre-transformation direction (y') are rearranged into output beam segments (29) arranged substantially along the transformation direction (x').

4. The laser system according to claim 1, wherein: The light beam transformation unit (13) further comprises: A reflective coating (36) is provided at the front reflective surface region (33B) and the rear reflective surface region (35B), thereby providing a reflective structure of the beam transforming unit (13) at the front reflective surface region (33B) and the rear reflective surface region (35B), and / or An anti-reflective coating is provided at the input surface region (33A) and / or the output surface region (35A).

5. The laser system according to claim 4, wherein: The anti-reflective coating is a dielectric coating.

6. The laser system according to claim 1, wherein: The pre-transformation direction (y') and the transformation direction (x') extend substantially orthogonally with respect to each other.

7. The laser system of claim 1 , wherein: The input surface area (33A) has a strip shape and extends along a straight front transition line (33T) between the input surface area (33A) and the front reflective surface area (33B), and The output surface area (35A) has a strip shape and extends along a straight rear transition line (35T) between the output surface area (35A) and the rear reflective surface area (35B), And the straight front transition line (33T) is at an angle of less than 90° relative to the straight rear transition line (35T).

8. The laser system according to claim 7, wherein: The strip shape is a rectangular shape, and the angle is adapted to the tilt angle (α eff ) angle orientation.

9. The laser system according to claim 7, wherein: The front reflective surface area (33B) and / or the rear reflective surface area (35B) has a triangular shape, and the straight front transition line (33T) and the straight rear transition line (35T) form short sides of the triangular shape.

10. The laser system of claim 1, wherein: The laser system further comprises: A deformable collimating unit (11) is used for shaping a laser beam (11A) of a laser source (3) to be elongated along a second direction (y) different from the first direction (x).

11. The laser system of claim 10, wherein: The second direction (y) is orthogonal to the first direction (x).

12. The laser system of claim 1, wherein: The laser source (3) is configured to generate laser radiation in a continuous mode and / or pulsed mode in a wavelength range extending from the ultraviolet to the infrared.

13. The laser system of claim 12, wherein: The wavelength range extends from the near ultraviolet to the near infrared.

14. The laser system of claim 1, wherein: The laser system further comprises: At least one further laser source provides at least one further laser beam to form the input laser beam (11A) together with the laser beam (3A).

15. The laser system of claim 1, wherein: The laser system further comprises a homogenizing and focusing unit (60) for homogenizing the strip-shaped laser beam (13A) to form a laser line (L) extending along a first direction (x), wherein the homogenizing and focusing unit (60) comprises: a focusing unit (17) comprising a short-axis focusing element (65) acting in the second direction (y) so as to define the position of the working plane (WP) of the laser line (L) in the propagation direction (z) of the laser beam (13A) to the focal plane of said short-axis focusing element (65); and A homogenizing unit (15) is configured to enable a portion of a stripe-shaped laser beam (13A) arranged along a first direction (x) to overlap along the stripe-shaped laser beam (13A) at a focal plane (FP) of the homogenizing unit (15), wherein The position of the working plane (WP) in the propagation direction (z) is chosen to be different from the position of the focal plane (FP) of the homogenization unit (15) so that the intensity distribution (51, 54) of the laser line (L) comprises a top-hat shape with a plateau bounded at each side by a slope (53L, 53R).

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