Device for generating a defined laser line on a work surface

Abstract

The apparatus for generating a defined laser line (12) on a work surface (14) comprises a laser source (22) configured to generate a laser original beam (24) and an optical device (26) for receiving the laser original beam (24) and transforming it along an optical axis (46) into an illumination beam (28). The illumination beam (28) defines a beam direction (29) intersecting the work surface (14) and has a beam profile (18) in the region of the work surface (14), the beam profile (18) having a major axis with a major beam width perpendicular to the beam direction (29) and a minor axis with a minor beam width. The beam profile (18) is movable along a movement direction (20) relative to the work surface (14) for machining a workpiece (16) with the illumination beam (28). The beam profile (18) has a defined intensity profile across the minor beam width, the intensity profile having forward extending flank surfaces (48) in the direction of travel (20), rearward extending flank surfaces (50) in the direction of travel (20), and a plateau (52) between the forward extending flank surfaces (48) and the rearward extending flank surfaces (50). The plateau (52) has a different intensity level in the region of the forward extending flank surfaces (48) than in the region of the rearward extending flank surfaces (50). The optical arrangement (26) further comprises a beam transformer (30) configured to split the original laser beam (24) into multiple beam segments (36a, 36b) arranged one behind the other on the major axis. The optical arrangement (26) further comprises optical elements (56, 58) configured to selectively affect selected beam segments (36a, 36b).

Description

[Technical field]

[0001] The present invention relates to an apparatus for generating a defined laser line on a working surface, the apparatus comprising a laser source configured to generate a laser original beam and an optical device for receiving the laser original beam and converting it along an optical axis into an illumination beam, the illumination beam defining a beam direction intersecting the working surface, the illumination beam having a beam profile in the region of the working surface, the beam profile having a major axis with a major beam width perpendicular to the beam direction and a minor axis with a minor beam width, the beam profile being movable along a movement direction relative to the working surface in order to machine a workpiece with the illumination beam, the beam profile having a defined intensity profile over the minor beam width, the intensity profile having flank surfaces extending forward in the movement direction, flank surfaces extending backward in the movement direction and a plateau between the forward and rearward extending flank surfaces, the plateau having a different intensity level in the region of the forward extending flank surfaces than in the region of the rearward extending flank surfaces.

[0002] Such a device is known from US Patent Application Publication No. 2014 / 0027417(A1).

[0003] The known device generates a linearly shaped laser beam on a working surface for processing a workpiece, which in particular contains amorphous silicon and is arranged on a target plate. The amorphous silicon can be melted line by line using a laser line and transformed into polycrystalline silicon on cooling. The above type of application is in fact called Solid State Laser Annealing (SLA) or Excimer Laser Annealing (ELA).

[0004] For such applications, the laser line on the working surface is required to be as long as possible in one direction to cover the largest possible working surface, whereas it is required to be very short in another direction to provide the required energy density for the respective process. Accordingly, a long and thin laser line is desired parallel to the working surface. The direction in which the laser line extends is usually referred to as the major axis, and the line width is called the minor axis. Usually, the laser line shall have a defined intensity profile in both axes in the area of ​​the working surface. It is often desired that the laser line has an intensity profile as rectangular as possible in the major axis (i.e., a top-hat profile). Similarly in the minor axis, a top-hat profile is often desired for SLA / ELA applications, with a flank surface extending forward in the direction of travel, a flank surface extending backward in the direction of travel, and a plateau as flat as possible between the forward and backward flank surfaces.

[0005] DE 10 2018 115 126 (B4) discloses an apparatus for generating such a laser line, which comprises an optical device including a plate-shaped converter made of a material transparent to the laser beam. The converter has a front side and a parallel arranged rear side, each of which has a layer reflecting the laser beam. The area of ​​the front side serves as an optical coupling surface and thus provides an entrance opening through which the laser beam can be coupled into the converter. The combined laser beam is reflected many times between the front side and the rear side in the converter, and at each reflection on the rear side a part of the laser beam can exit the converter. The combined laser beam is thus emitted from the rear side in segments, the respective decoupled beam segments being arranged laterally offset from one another and having passed different path lengths in the converter. The combined laser beam is thereby expanded in a further beam path in a direction corresponding to the long axis.

[0006] US 2014 / 0027417 A1 describes that a modified, so to speak, two-stage top-hat profile is advantageous for SLA or ELA processes, since polycrystalline silicon is formed during the relative movement of the laser line in a number of steps that follow one another, and the optimal energy density for melting the material is reduced during the movement. The laser line is generated in pulses during its movement relative to the workpiece, each section of the workpiece being irradiated with about 20 laser pulses during the movement. By means of the laser pulses, the silicon is melted multiple times and its properties are changed. For this reason, US 2014 / 0027417 A1 proposes to generate the beam profile of the laser line using two laser original beams that overlap in the area of ​​the working surface. The optical device has a unique beam path for each of both laser original beams. Each of both beam paths generates an approximately top-hat shaped beam profile in the minor axis. Both top-hat beam profiles are positioned above the work surface offset from each other in the direction of the short axis, so that, overall, the beam profile results in a defined step that separates into two nearly flat plateau sections. The drawback of this solution is that, as a result of multiple laser pulses, there is only a two-step application of a fairly rough beam profile to the heating of the workpiece.

[0007] The subsequently published German patent application under application no. 10 2020 126 269.8 describes an apparatus of the type mentioned at the outset, in which the optical device is adjusted so that the plateau has an intensity level that falls continuously on average. This can be achieved, for example, by eccentrically irradiating the objective lens on the workpiece side with the transformed, expanded and homogenized laser original beam. However, the achievable plateau gradient is limited in this device and is rather small. For the main applications, a steeply falling plateau is desirable in order to make it possible to optimally adapt the irradiation intensity and fluence at the respective position of the workpiece in successive laser pulses.

[0008] In view of this, it is an object of the present invention to provide an apparatus of the type mentioned at the beginning, which makes it possible to generate a beam profile with a defined intensity profile over the minor axis which is derived from a top-hat profile in an alternative manner. In particular, it is an object of the present invention to provide an energy density adapted over time by means of a pulsed laser line during processing of a workpiece.

[0009] According to one aspect of the invention, in order to solve this problem, an apparatus of the type mentioned at the beginning is proposed, in which the optical device has a beam converter configured to split the original laser beam into a number of beam segments arranged one behind the other on the longitudinal axis, and the optical device further has an optical element configured to selectively influence selected beam segments.

[0010] The novel device accordingly has an optical element that allows individual beam segments from the multiplicity of beam segments to be appropriately changed at the exit of the beam converter, while other beam segments from the multiplicity of beam segments remain substantially unaffected. In particular, the optical element is configured to appropriately change the intensity of the individual beam segments. This change can reduce the intensity of the individual beam segments compared to their intensity without the optical element, in particular to the extent of blocking the individual beam segments. Alternatively or additionally, this change results in a changed intensity profile of the individual beam segments, for example a selective inversion / reversal of the intensity profile. In this case, it is advantageous that this change does not act on all beam segments at the exit of the beam converter in the same manner. Furthermore, the optical element is configured to change the individual beam segments at the exit of the beam converter in a different manner than the other beam segments at the exit of the beam converter. The optical element therefore acts to affect or change the ratio of the beam segments to one another at the exit of the beam converter. This has an effect on the intensity profile, which is caused by the per se known overlap of the subsequent beam segments in the beam path.

[0011] Similarly in the case of the device mentioned at the outset, the illumination beam is preferably generated in a pulsed manner in this case, in particular by the laser light source delivering the original laser beam in a pulsed manner. However, regardless of this, the novel device makes it possible to generate a beam profile in the short axis with an intensity profile that falls approximately linearly from a higher first level to a lower second level. In a preferred embodiment, the optical element is therefore configured such that the intensity profile of the beam profile in the region of the flank surface extending forward in the direction of movement has a higher intensity level than the flank surface extending backward, so that defined positions of the workpiece surface can be irradiated with temporally successive laser pulses during the relative movement, the intensity and fluence of the laser pulses decreasing. In principle, it is also possible with the novel device to realize an intensity profile in the short axis that rises from the forward to the backward flank surface by selectively changing the beam segment at the exit of the beam converter.

[0012] The intensity profile of the beam profile of the novel device resembles a shed roof in a preferred embodiment. A shed roof is a roof shape on a building that has only one sloping roof surface. Accordingly, the beam profile in this case preferably has a defined intensity profile of a shed roof shape in the minor axis. Preferably, the plateau is also stepless. It is clear to the skilled person that the intensity profile is then not really ideally straight / flat, but may have small waves and ripples in the plateau that is inclined with respect to the direction of travel. Small waves and ripples are unavoidable due to diffraction effects and manufacturing tolerances. However, in this case, the waves and ripples are small compared to the height of the plateau and may remain neglected in an idealized view. In a preferred embodiment, the waves and ripples are less than 10%, preferably less than 5%, relative to the intensity level of the plateau. Accordingly, the plateau falls continuously on average with respect to the direction of travel in a preferred embodiment of the novel device, especially when considering the regression line placed through the waves and ripples.

[0013] Unlike the case of the device described in the subsequently published German patent application no. 10 2020 126 269.8, the falling intensity profile is in this case realized at the exit of the beam converter by selective, and therefore non-uniform, influence of the beam segments. Such a beam converter is known, for example, from the above-mentioned German patent no. 10 2018 115 126 (B4), in which it is called a converter. The suitable non-uniform modification of the beam segments at the exit of the beam converter and the resulting modification of the beam profile in the region of the working surface is novel, the optical elements of the novel device making it possible to modify the irradiation intensity and fluence over the minor axis in a very wide setting range. In preferred embodiments, this is possible with very low or even soar without power losses. Advantageously, with the selective modification of the intensity of the beam segments it is possible to tilt the plateau of the beam profile in the region of the working surface with a steepness of more than 10% of the maximum fluence, in preferred embodiments up to 70%. Thus, the above mentioned problems are completely solved.

[0014] In a preferred embodiment of the invention, the optical element is configured to produce a plateau having an intensity level that, on average, decreases continuously with respect to the direction of movement.

[0015] This embodiment is very advantageous in its use due to the possibilities offered by the new device. The almost linear drop of the plateau inclined relative to the direction of movement results in a smaller fluence of the pulsed laser radiation with each further laser pulse, which in turn reduces the heat input into the workpiece by the laser pulse. Such an implementation is advantageous in order to avoid too strong local heating of the workpiece in the course of the processing process.

[0016] In a further embodiment, the optical element is displaceable transversely to the optical axis.

[0017] In some advantageous embodiments, the optical element is arranged in the beam path behind the beam converter and is displaceable in the direction of the major axis. In another embodiment, the optical element is arranged in the beam path in front of the beam converter and is preferably displaceable in the direction of the minor axis. In all embodiments of this embodiment, the optical element can be used appropriately to influence the individual beam segments at the exit of the beam converter, for example to completely or partially block or otherwise selectively modify them. The respective modified beam segments no longer provide a beam profile in the region of the working surface or provide it in a modified manner. Accordingly, this embodiment changes the intensity profile in the minor axis in a very simple and cost-effective manner. The displaceability then provides new flexibility and makes it possible to optimally set the beam profile for the desired processing.

[0018] In a further embodiment, the optical element is configured to flip a selected beam segment from the multiple beam segments about the major axis.

[0019] Inversion about the major axis means in this case the inversion of the selected beam segment about an axis extending parallel to the major axis, the inversion axis in the region of the beam transformer. This embodiment has the advantage that the change of the beam segment can be performed almost loss-free or even completely loss-free. The applicant's studies have shown that at the exit of the beam transformer, the beam segments often have an asymmetric segment-specific intensity profile along the minor axis. Inversion of the respective intensity profile of the selected beam segment about the major axis results in an inversion of the asymmetric segment-specific intensity profile, thereby resulting in a change of the beam profile in the region of the working surface in a very efficient manner.

[0020] In a further embodiment, the optical element comprises a prism, in particular a Dove prism.

[0021] The present embodiment allows an efficient and spatially compact implementation of the optical elements of the new device, so that it is well suited for retrofitting existing devices of the type mentioned in the introduction.

[0022] In a further embodiment, the optical element includes a lens set having an intermediate focus.

[0023] This embodiment makes it possible to influence the beam segments at the exit side of the beam transformer very individually and precisely.

[0024] In a further embodiment, the optical element comprises a mirror set.

[0025] This embodiment makes it possible to influence the beam segment at the exit side of the beam transformer in a very compact and precise manner.

[0026] In a further embodiment, the optical element includes a diaphragm.

[0027] This embodiment makes it possible to influence the beam segment at the exit side of the beam transformer very simply and cost-effectively, in addition to which the diaphragm can be easily retrofitted and can be displaced and / or opened simply and quickly.

[0028] In a further embodiment, the optical element is arranged in the beam direction downstream of the beam transformer.

[0029] This embodiment is easy to implement.

[0030] In a further embodiment, the optical element is arranged in the beam direction upstream of the beam converter.

[0031] This embodiment allows for cost-effective and compact integration of optical elements into the beam path of the novel device.

[0032] In a further embodiment, the laser source includes a pump solid state laser and a control unit for controlling the pump solid state laser in response to the optical element.

[0033] In this embodiment, the control unit is configured to optimally match the pulse repetition rate of the laser source to the set plateau slope in order to keep the workpiece surface within the desired process window with high precision.

[0034] It is to be understood that the features mentioned above and further described below can be used not only in the respective combinations presented, but also in other combinations or alone without departing from the scope of the present invention.

[0035] Exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. [Brief description of the drawings]

[0036] [Figure 1a] 1A-1C are simplified schematic diagrams of short axis beam paths in various embodiments of the novel apparatus. [Figure 1b] 1 is a simplified diagram of a beam profile in the region of a working surface according to an embodiment of the novel device. [Figure 1c] 1 is a simplified diagram of a beam transformer to illustrate an embodiment of the novel device. [Figure 2a] FIG. 13 illustrates the increase in heating of a workpiece with time during pulsed irradiation with locally overlapping laser pulses of the same fluence. [Figure 2b] FIG. 2b is an illustration of positionally overlapping laser pulses in the situation of FIG. 2a when the workpiece moves relative to the beam profile. [Figure 2c] FIG. 2b shows a situation similar to FIG. 2a, for pulsed irradiation with spatially overlapping laser pulses of decreasing fluence. [Figure 2d] FIG. 2c is an illustration of positionally overlapping laser pulses in an embodiment of the novel device in a situation corresponding to FIG. 2b. [Figure 3a]1 is a simplified diagram of the optical elements in an embodiment of the novel device. [Figure 3b] 13 is a simplified diagram of optical elements in a further embodiment of the novel device. [Figure 3c] 13 is a simplified diagram of optical elements in a further embodiment of the novel device. [Figure 4a] 13 is a simplified diagram of optical elements in a further embodiment of the novel device. [Figure 4b] 13 is a simplified diagram of optical elements in a further embodiment of the novel device. [Figure 4c] 13 is a simplified diagram of optical elements in a further embodiment of the novel device. [Figure 4d] 13 is a simplified diagram of optical elements in a further embodiment of the novel device. [Diagram 5] 13 is a simplified diagram of optical elements in a further embodiment of the novel device.

[0037] In Fig. 1a, an embodiment of the novel device is designated in its entirety with the reference number 10. The device 10 generates a laser line 12 in the region of a working surface 14 to process a workpiece 16 arranged in the region of the working surface 14. The laser line 12 extends in this case in the direction of the x-axis (Fig. 1b), the line width is observed in this case in the direction of the y-axis. Accordingly, in the following, the x-axis is referred to as the major axis of a beam profile 18 formed on the working surface 14, and the y-axis is referred to as the minor axis (Fig. 1b).

[0038] In a preferred embodiment, the workpiece 16 includes a layer of amorphous silicon that is melted and converted to polycrystalline silicon using the laser line 12. Figure 1a shows the apparatus 10 in a simplified schematic diagram of the minor axis beam path that forms the minor axis of the laser line. Accordingly, the laser line 12 appears only as a dot (along the x-axis) in the "side view" of Figure 1a. To process the workpiece 16, the laser line 12 can be moved in the direction of the arrow 20 relative to the workpiece 16.

[0039] The apparatus 10 includes a laser light source 22, which may be, for example, a solid-state laser, generating laser light in the infrared or UV range. For example, the laser light source 22 may include a Nd:YAG laser with a wavelength in the 1030 nm range. In further examples, the laser light source 22 may include a diode laser, an excimer laser, or a solid-state laser, generating laser light with a wavelength of 150 nm to 360 nm, 500 nm to 530 nm, or 900 nm to 1070 nm.

[0040] The laser source 22 emits a laser original beam 24, which can be coupled to the optical device 26, for example via an optical fiber. In principle, the device can have several laser sources 22, each generating one or more laser original beams 24 and coupled to the optical device 26. For simplicity's sake, only one laser original beam 24 will be mentioned below.

[0041] The original laser beam 24 is transformed by means of an optical device 26 into an illumination beam 28 that defines a beam direction 29. The beam direction 29 intersects with the work surface 14.

[0042] The optical device 26 comprises a beam converter 30, which expands the laser source beam 24 in the x-direction (corresponding to the long axis). In a preferred embodiment, the beam converter 30 can be realized like the beam converters which are also described in detail in the initially mentioned DE 10 2018 115 126 B4 or WO 2018 / 019374 A1. Accordingly, DE 10 2018 115 126 B4 and WO 2018 / 019374 A1 are incorporated by reference in this case with regard to the beam converter and also with regard to further details of the optical device, in particular with regard to the long axis beam shaping, which is shown in this case only in a simplified manner.

[0043] Corresponding to DE 10 2018 115 126 (B4) and WO 2018 / 019374 (A1), the beam converter 30 in this case has a preferably monolithic, plate-shaped element transparent to the laser original beam 24, with a front side 32 and a rear side 34 that are substantially parallel to one another. The plate-shaped element can be arranged at an acute angle to the laser original beam 24, so that the laser original beam is coupled obliquely into the plate-shaped element. The front side 32 and the rear side 34 in this case each have a reflective coating, so that the laser original beam 24 that is coupled obliquely into the plate-shaped element at the front side 32 undergoes multiple reflections in the plate-shaped element. At the rear side 34, a partial segment of the laser original beam 24 is then decoupled after each reflection. The respective decoupled partial segments exit laterally offset to one another at the rear side 34 of the beam converter, as is shown diagrammatically in FIG. 1c. In that case, in Fig. 1c, four parallel laser source beams 24 are exemplarily shown as being combined at the front side 32 of the beam converter. At the rear side 34, a number of beam segments 36a, 36b emerge from the beam converter laterally offset from one another in the direction of the long axis. Overall, the laser source beam 24 combined at the front side 32 is therefore split into beam segments 36a, 36b laterally offset from one another in the direction of the long axis.

[0044] The optical arrangement 26 includes longitudinal optics, not shown in detail in this case, which form the original laser beam 24 in the longitudinal axis, which is split into beam segments 36a, 36b. In particular, the longitudinal optics includes one or more microlens arrays 38, 40 extending in the x-direction, which in a preferred embodiment form an imaging homogenizer together with a Fourier lens 42. The longitudinal optics 38, 40, 42 mix and overlap the beam segments 36a, 36b to advantageously produce a top-hat intensity profile in the longitudinal axis, as shown in simplified form in FIG. 1b.

[0045] The optical arrangement 26 further comprises a number of optical elements which form the expanded laser original beam in the short axis and focus it on the working surface 14. For example, the optical arrangement 26 comprises an objective lens 44 which focuses the illumination beam 28 on the working surface 14. The optical arrangement 26 may comprise further lens elements and / or mirror elements (not shown in this case), in particular implementing a telescope system and / or a mirror fold (not shown in this case). The optical arrangement 26 forms an optical axis 46 which can be folded in contrast to the simplified diagram of FIG. 1c. Typically, the optical elements of the long axis optics and the short axis optics are arranged along the optical axis 46.

[0046] As already outlined, the optical device 26 is configured to generate an illumination beam 28 having a defined beam profile 18 in the region of the working surface 14. FIG. 1b illustrates an idealized version of the advantageous beam profile 18. The beam profile 18 depicts the intensity I of the laser beam on the working surface 14 as a function of the respective position along the x-axis and the y-axis. As shown, the beam profile 18 forms a laser line having a major axis with a major laser width in the x-direction and a minor axis with a minor laser width in the y-direction. The minor beam width may be defined, for example, as the full width at half maximum (FWHM) or as the width between the 90% intensity values ​​(FW@90%). The beam profile 18 has, in this case, in the minor axis, a first flank surface 48, a second flank surface 50 and a plateau 52 which, in this case, drops continuously from the first flank surface 48 to the second flank surface 50. In preferred embodiments, the plateau 52 decreases approximately linearly from the first flank surface 48 to the second flank surface 50 by a value corresponding to a fluence reduction of between 5% and 70%, and in some preferred embodiments, the fluence reduction is at least 10%.

[0047] As shown in FIG. 1a, the beam profile 18 is moved relative to the work surface 14 parallel to the y-axis to machine the workpiece 16. In a preferred embodiment, the workpiece 16 is placed on a table that can be advanced in the y-direction. Accordingly, the first flank surface 48 extends forward in the direction of travel 20 and the second flank surface 50 extends backward in the direction of travel 20 (FIG. 1b). The plateau 52 is inclined relative to the direction of travel 20 and has a shed-roof shape when viewed parallel to the x-axis. It should be noted that the minor axis beam profile 18 is shown in FIG. 1a at a very large magnification for illustrative purposes. In a preferred embodiment, the minor axis beam width FWHM is in the range of 50 μm to 150 μm. The major axis beam width can be in the range of 20 mm to 1200 mm in the preferred embodiment.

[0048] During operation, the apparatus 10 generates a beam profile 18 in a pulsed manner in the region of the work surface 14 by the controller 54 correspondingly controlling the laser light source in a pulsed manner. The pulsed generated beam profile 18 of the apparatus 10 can be achieved by the effects illustrated in Figures 2a-2d.

[0049] As shown in Fig. 2b and Fig. 2d, when the beam profile 18 is moved in the direction of the short axis relative to the workpiece, the laser pulses of the device 10 overlap spatially along the y-axis. Fig. 2a and Fig. 2b show the case of a top hat with a flat, non-inclined plateau 52. For each laser pulse, the beam profile 18 is offset by δy along the direction of movement. That is, in this case, every position on the workpiece is irradiated with N>1 laser pulses. Fig. 2a shows a continuous temperature increase over successive laser pulses. In the top hat profile according to Fig. 2b, the fluence with which the workpiece is irradiated successively in time in the respective laser pulses remains approximately the same. The workpiece temperature increases more and more, since the later laser pulse hits an already preheated workpiece and the time between successive laser pulses is not enough to allow the workpiece position to cool down to the ambient temperature. This can lead to undesirable crystallization processes and generally unfavorable workpiece quality.

[0050] 2c and 2d show strategies for reducing the temperature input over N>1 pulses. An example is shown in which the beam profile over the short axis has a plateau 52 that drops steeply relative to the direction of movement. As a result, the fluence irradiating the workpiece drops with each laser pulse. The temperature input, in this case the maximum temperature, remains approximately constant. Advantageously, the respective process can be optimized via appropriate settings of the plateau steepness δE, the line offset δy and the laser pulse repetition rate.

[0051] 3a-3c show an embodiment of an optical element 56 that can be arranged downstream of the beam converter 30 of the device 10 (FIG. 1a) in the beam path in order to influence the beam segments 36a, 36b at the exit of the beam converter 30 and thus change them relative to each other. In the embodiment according to FIG. 3a, the optical element 56a is a prism, in particular a Dove prism. A Dove prism can be understood as an isosceles right-angle prism with its optically inactive areas cut out. Accordingly, in a side view, a Dove prism has a trapezoidal face with side faces inclined at 45°. When a beam segment extending along the long axis of the prism strikes one of the inclined entrance faces, the beam segment is first refracted into the prism and directed towards the longest side of the prism. There, the beam segment is totally reflected and refracted again at the inclined exit face. The incoming and outgoing beam segments are aligned with each other, but are inverted about a line transverse to the beam direction due to the reflection in the prism. The same effect can also be achieved using an uncut triangular prism, which acts like a Dove prism and is accordingly considered in this case to be a Dove prism. In some preferred embodiments, the prism 56a is displaceable relative to the optical axis 46, as shown by the arrow in FIG. 1a. In preferred embodiments, the prism 56a is displaceable parallel to the long axis (x-axis), so that selected beam segments 36a, 36b can be selectively inverted relative to the long axis using the prism 56a. In this way, the asymmetric intensity profile of the selected beam segment can be changed.

[0052] In Fig. 3b, optical element 56b includes a lens set having lens elements 60a, 60b capable of flipping a selected beam segment, and in Fig. 3c, optical element 56c includes a mirror set having mirror elements 62a, 62b, 62c to flip and thus affect a selected beam segment relative to the long axis.

[0053] 4a-4c show further examples of an optical element 56 which can be arranged in the beam path downstream of the beam converter 30 of the device 10 (FIG. 1a) and / or an optical element 58 which can be arranged in the beam path upstream of the beam converter 30 of the device 10 (FIG. 1a). In principle, a combination of several optical elements 56, 58 of the kind shown here is also possible in order to vary the beam segments 36a, 36b. In a preferred embodiment in which the optical element 56 is arranged in the beam path downstream of the beam converter 30 of the device 10, the optical element 56 is advantageously arranged between the beam converter 30 and a homogenizer which in the device according to FIG. 1a comprises microlens arrays 38, 40.

[0054] 4a and 4b, the optical element 56 comprises one or more apertures 56d, which can be selectively slid from one side and / or the other in a transverse direction to the optical axis 46 in front of selected beam segments. Preferably, the one or more apertures 56d are displaceable parallel to the longitudinal axis in order to completely or partially block selected beam segments 36a, 36b.

[0055] 4c and 4d, the optical element 58 comprises one or more apertures 58a, which can be selectively slid from one side and / or the other in a transverse direction relative to the optical axis 46 in order to completely or partially block one or more original laser beams 24 coupled into the beam converter 30. Preferably, the one or more apertures 58a are displaceable parallel to the minor axis in order to completely or partially change the selected beam segments 36a, 36b.

[0056] Fig. 5 shows an embodiment with an optical element 58b, which changes the laser original beam 24, so that the beam segments are also selectively changed at the exit of the beam converter 30. In the embodiment according to Fig. 5, the laser original beam initially has a Gaussian beam profile in the short axis, as indicated by reference number 64. Using the optical element 58b, the laser original beam 24 is transformed, so that the laser original beam 24 obtains an asymmetric beam profile in the short axis, corresponding to reference number 66. The asymmetric beam profile 66 of the laser original beam 24 coupled to the beam converter 30 results in changed beam segments 36a, 36b at the exit of the beam converter 30. In a preferred embodiment, the optical element 58b includes a combination of one or more aspherical lenses and one or more spherical lenses.

Claims

1. An apparatus for generating a defined laser line (12) on a working surface (14), comprising: a laser source (22) configured to generate a laser original beam (24); and an optical device (26) for receiving the laser original beam (24) and transforming it into an illumination beam (28) along an optical axis (46), the illumination beam (28) defining a beam direction (29) intersecting the working surface (14), the illumination beam (28) having a beam profile (18) in the area of ​​the working surface (14), the beam profile (18) having a major axis with a major beam width perpendicular to the beam direction (29) and a minor axis with a minor beam width, the beam profile (18) being movable along a movement direction (20) relative to the working surface (14) for machining a workpiece (16) with the illumination beam (28), ...

1. An apparatus for irradiating a laser beam having a defined intensity profile according to a direction of travel (20), the intensity profile comprising forward-extending flank surfaces (48) in a direction of travel (20), rearward-extending flank surfaces (50) in a direction of travel (20), and a plateau (52) between the forward-extending flank surfaces (48) and the rearward-extending flank surfaces (50), the plateau (52) having a different intensity level in the region of the forward-extending flank surfaces (48) than in the region of the rearward-extending flank surfaces (50), characterized in that the optical device (26) comprises a beam converter (30) configured to split the original laser beam (24) into a number of beam segments (36 a, 36 b) arranged one behind the other on the longitudinal axis, and the optical device (26) further comprises optical elements (56, 58) configured to selectively influence selected beam segments (36 a, 36 b).

2. 2. The apparatus of claim 1, wherein the optical elements (56, 58) are configured to generate the plateau (52) with a continuously decreasing intensity level on average relative to the direction of movement (20).

3. 3. Apparatus according to claim 1 or 2, characterized in that the optical elements (56, 58) are displaceable transversely to the optical axis (46).

4. 4. The apparatus of claim 1, wherein the optical element (56a, 56b, 56c) is configured to invert a selected beam segment from the multiple beam segments (36a, 36b) about the major axis.

5. 5. Apparatus according to any one of claims 1 to 4, characterized in that the optical element (56a) comprises a prism, in particular a Dove prism.

6. 6. The apparatus according to claim 1, wherein the optical element (56b) comprises a lens set having an intermediate focus.

7. 7. Apparatus according to any one of claims 1 to 6, characterized in that the optical element (56c) comprises a mirror set.

8. 8. Apparatus according to claim 1, characterized in that the optical element (56d) comprises a diaphragm.

9. 9. The device according to claim 1, wherein the optical element (56) is arranged downstream in the beam direction of the beam converter (30).

10. 10. The device according to claim 1, wherein the optical element (58) is arranged upstream in the beam direction of the beam converter (30).

11. 11. The apparatus according to claim 1, wherein the laser light source (22) comprises a pump solid-state laser and a control unit (54) for controlling the pump solid-state laser in response to the optical element.

Images