Laser beam brilliance improvement, beam splitting for laser welding and laser brazing

Abstract

A laser processing head (50) for directing laser light onto a workpiece (WP), wherein the laser processing head (50) comprises the following: - a collimator (64) arranged in an optical axis of the laser light and configured to convert the laser light into collimated light; - a beam splitter (70) arranged in the optical axis between the collimator and a main output at an angle to the collimated light and having at least two sections arranged on a surface of the beam splitter (70), wherein the at least two sections comprise a peripheral antireflective section (72) configured to allow peripheral light of the collimated light at least partially to pass to the main output (55a), and an inner highly reflective section (74), wherein the peripheral region surrounds the inner region, and wherein the inner highly reflective section (74) has an oval shape such that the angled oval inner highly reflective section (74) reflects a secondary laser beam (SB) having a cylindrical shape towards a focusing lens 76 for a secondary fiber (40); - the main output (55a) which is arranged in optical connection with the beam splitter (70), wherein the main output (55a) is configured to direct at least the first light into a main laser beam onto the workpiece (WP); and - a secondary output (55b) arranged in optical connection with the beam splitter (70), wherein the secondary output (55b) is configured to direct at least the second section into a secondary laser beam alongside the main laser beam and comprises the following: - at least one focusing lens (68) arranged in optical connection with the beam splitter (70) and configured to focus any collimated light transmitted from the beam splitter (70) and falling onto the focusing lens (68); and - at least the secondary fiber (40) which has an input arranged in optical connection with the focusing lens (76) and which has an output arranged in optical connection with the workpiece (WP).

Description

Brief description of the state of the art

[0001] Certain joining processes can be used to connect different workpieces. For example, a laser brazing process joins different workpieces by melting a brazing material with a laser beam, allowing the molten brazing material to flow into a seam between the workpieces, and forming a joint. The brazing material can be a wire with a melting point lower than that of the workpiece materials. The brazing wire is positioned between the laser beam and the workpieces to be joined and moved along the seam during the brazing process to fill and create the joint. A similar joining process involves welding workpieces using a flux-cored wire made of the same material as at least one of the workpieces.

[0002] For successful joining (e.g., brazing or welding), the wire is moved along the seam while a constant force is applied to at least one of the workpieces. For this purpose, the wire or another element can be positioned against one or both workpieces to exert a force while the wire is melted by the laser beam.

[0003] In some implementations, a main laser beam is used to create a primary melting point for melting the wire for brazing, welding, etc., while a second laser beam is used to create one or more relatively small heating points upstream of the primary melting point. The heating point(s) can be used to preheat the workpiece(s) and / or to remove a coating from the workpiece(s).

[0004] To create the small heating point(s), a laser processing head can use an independent laser source separate from the main laser source. Alternatively, instead of using separate laser sources, a laser processing head can use a second laser beam derived from the main laser beam. Relatively small points are required for efficient heating during the joining process, so several solutions are available.

[0005] In one approach, the laser light used for preheating or coating removal is emitted from the same focusing lens used to focus the main laser beam. The laser light for preheating and / or coating removal is typically positioned very close to the wire and may touch it during movement (e.g., around a curve), resulting in unstable preheating and, consequently, an unstable joining process.

[0006] In a second solution, the main beam can be split so that a second fiber can transport a portion of the light to a second focusing unit, which creates the heating point(s). Unfortunately, with existing arrangements, the relatively smaller points may not be achievable due to the low brilliance of the light coupled into the second fiber.

[0007] A way is needed to deliver one or more heating points in front of a main brazing / welding point so that a workpiece can be preheated using (one) heating point(s) that is relatively small and does not interfere with the brazing / welding wire.

[0008] The published German patent application DE 27 08 039 A1 discloses a device for splitting a composite laser beam into two secondary beams, which then follow separate optical paths and have selected relative energy proportions.

[0009] Published patent US 6,992,965 B1 describes a method and apparatus for reading a three-dimensional information carrier. The three-dimensional information carrier consists of a plurality of spaced-apart data regions, each surrounded by surrounding regions. The data regions are made of a material capable of generating excited output radiation when interacting with a predetermined incident excitation radiation, while the surrounding regions are essentially optically transparent. The apparatus comprises an illumination unit, a light-guiding unit, and a detector unit. The illumination unit generates a scanning beam for the incident radiation. The light-guiding unit projects the incident radiation onto a scanning region located in an addressed plane within the carrier and collects the output radiation.The light steering unit is able to capture a predetermined portion of the collected output radiation in order to ensure spatial separation of the output radiation components generated by the data areas located in the addressed plane from the output radiation components generated by the data areas located at another location within the carrier.

[0010] The published German translation DE 601 31 935 T2 of European patent EP 1 179 382 B1 relates to a coaxial laser beam processing head and a laser beam processing device with this head. The head is small, poses no risk of damaging optical instruments, and is inexpensive. The head comprises a collimating lens arrangement, a first reflecting mirror for splitting the laser light into a first partial laser beam and a second partial laser beam, a second reflecting mirror for further reflecting the first partial laser beam to create a gap between the two partial laser beams, a focusing lens arrangement for focusing the two partial laser beams onto a part to be welded, and a GMA electrode arranged coaxially to the laser beams in the gap.or a collimating lens arrangement, comprising a first reflecting mirror for reflecting part of the laser light to form a spatial section in a body of the laser light, a second reflecting mirror for further reflecting the part of the laser light, a focusing lens arrangement for focusing the body of the laser light and the part of the laser light onto a section to be welded, and a GMA electrode arranged coaxially with the body of the laser light in the spatial section.

[0011] The published European patent application EP 2 402 107 A1 discloses a method and an apparatus for welding workpieces together by performing a laser beam welding process on a joint area containing a weld seam defined by and between the mating surfaces of the workpieces, and subsequently performing a hybrid laser arc welding process on the joint area. In laser beam welding, a first laser beam is guided along the joint area, penetrates the weld seam, and forms a weld. In the laser arc hybrid welding process, the weld seam is remelted by an overlapping electric arc and a second laser beam moving along the joint area, forming a weld pool within the weld seam. After cooling, a weld seam and its weld bead are formed in the joint area.

[0012] The published German patent application DE 10 2015 112 537 A1 relates to an optical device for shaping a laser beam propagating along a propagation axis, comprising at least one beam-shaping optical module for generating a focus geometry in a processing plane with a main laser spot and at least one secondary laser spot.

[0013] The published European patent application EP 3 486 019 A1 relates to a device for joining workpieces using a laser beam and a method for using the device for soldering sheet metal. The device for joining workpieces using a laser beam comprises a laser optic and a two-component fiber with a main fiber and a secondary fiber, wherein the main fiber is connected to a fiber coupling of the laser optic and the secondary fiber is arranged between a second laser beam source and a receptacle on a wire guide of the soldering element of the device.

[0014] A variant of the beam splitter, unlike the classic ring mirror, is known in the prior art and can be purchased from Thorlabs, Inc. (URL: https: / / www.thorlabs.com / newgrouppage9.cfm?objectgroup_id=13322#ad-image-0). These beam splitters have an inner section designed as a reflective surface and a peripheral section that is transmissive.

[0015] Published European patent application EP 3 219 832 A1 discloses a method for producing a directly bonded optical coating, comprising providing a growth substrate; providing an optical substrate; forming the optical coating on the growth substrate, wherein the optical coating has a top side facing away from the growth substrate; rotating the optical coating so that the top side of the optical coating faces the optical substrate; bonding the top side of the optical coating to the optical substrate; and separating the growth substrate from the optical coating, wherein the separation of the growth substrate from the coating is carried out either before or after bonding.

[0016] The subject of the present disclosure is aimed at overcoming one or more of the problems set out above, or at least at reducing their effects. Summary of Revelation

[0017] As disclosed herein, a laser processing head is used to direct laser light onto a workpiece. The laser processing head comprises a collimator, a beam splitter, a main output, and a secondary output. The collimator is arranged in an optical axis of the laser light and is configured to collimate the laser light into collimated light. The beam splitter is arranged in the collimated light and has at least two sections. The at least two sections comprise an antireflective section and a highly reflective section. The beam splitter is designed to split the collimated light into a first light from a first of the at least two sections and a second light from a second of the at least two sections.The main output is optically connected to the beam splitter and is configured to direct at least the first light into a main laser beam onto the workpiece. The secondary output is optically connected to the beam splitter and is configured to direct at least the second segment into a secondary laser beam adjacent to the main laser beam. It comprises at least one focusing lens, optically connected to the beam splitter and configured to focus any collimated light transmitted from the beam splitter and incident on the focusing lens; and at least one waveguide having an input optically connected to the focusing lens and an output optically connected to the workpiece.

[0018] As disclosed herein, a laser processing head is used to join workpieces using laser light and a wire. The laser processing head comprises a collimator, a beam splitter, a main output, a secondary output, and a cable. The collimator is positioned along the optical axis of the laser light and is configured to collimate the laser light into collimated light. The beam splitter is positioned along the optical axis between the collimator and the main output. The beam splitter has an antireflective section in a peripheral region and a highly reflective section in an inner region. The peripheral region surrounds the oval, inner region.The anti-reflective section is configured to allow at least some peripheral light from the collimated beam to pass through to the main output, and the highly reflective section is configured to reflect at least some internal light from the collimated beam. The main output is located on the optical axis and is configured to direct any collimated light that has passed through / exited the beam splitter into a main laser beam directed at the workpieces. The secondary output is optically connected to the beam splitter. The secondary output is configured to direct any collimated light reflected from the beam splitter into a secondary laser beam adjacent to the main laser beam. The cable is configured to feed the wire into the main laser beam.

[0019] The secondary output comprises a focusing lens and a waveguide. The focusing lens is optically connected to the beam splitter and configured to focus any collimated light transmitted from the beam splitter and incident upon the focusing lens. The waveguide has an input optically connected to the focusing lens and an output optically connected to the workpiece. The waveguide may comprise an optical fiber or a bundle of microfibers, and the waveguide output may comprise a microlens, an optical block, a beam shaping element, or a flat tip.

[0020] A method disclosed herein is used to direct laser light onto a workpiece. The method comprises: collimating the laser light into collimated light along an optical axis; splitting the collimated light into first light and second light using a beam splitter having at least two reflective sections, including an antireflective section and a highly reflective section; directing at least one section of the first light into a principal laser beam onto the workpiece, wherein at least one focusing lens arranged in optical communication with the beam splitter focuses any collimated light transmitted from the beam splitter (70) and falling onto the focusing lens; and at least one waveguide having an input arranged in optical communication with the focusing lens and an output arranged in optical communication with the workpiece;and directing at least one section of the second light into a secondary laser beam onto the workpiece.

[0021] The foregoing summary is not intended to cover every possible embodiment or aspect of the present disclosure. Brief description of the characters Fig. Figure 1A illustrates a laser delivery system according to the present disclosure. Fig. Figure 1B illustrates a perspective view of a laser processing head according to the present disclosure. Fig. Figure 2 illustrates a schematic view of a laser processing head having a secondary fiber according to a first embodiment of the present disclosure to emit a secondary beam onto a workpiece. Fig. Figure 3 illustrates a schematic view of a laser processing head having a secondary fiber according to a second embodiment of the present disclosure. Fig. Figure 4 illustrates a schematic view of a laser processing head having a secondary fiber according to a third embodiment of the present disclosure. Fig. Figure 5 illustrates a schematic view of a laser processing head having an alternative arrangement of the present disclosure. Fig. Figure 6 illustrates embodiments of an output end for the secondary fiber. Fig. Figure 7 illustrates an assembly that includes a secondary fiber mounted on a wire guide. Fig. Figures 8A-8E illustrate top views of beam splitters according to the present disclosure. Fig. Figures 9A-9B illustrate schematic views of a beam splitter whose lateral orientation is shifted to change the secondary output of the laser light. Detailed description of the revelation

[0022] Fig. Figure 1A illustrates a laser delivery system 10 according to the present disclosure. A laser source 12 generates laser light, which is guided via a fiber optic cable 14 to a laser processing head 50. The laser source 12 can be a multimode or a single-mode laser, depending on the desired quality of the laser beam. A single-mode laser provides a higher quality laser beam, but this high quality is not normally required for brazing or welding.

[0023] The laser processing head 50 can be moved relative to the workpiece(s) WP and / or can cause the workpiece(s) WP to move relative to it. For example, the laser processing head 50 can be moved by a gantry system, a robot arm, or other apparatus 16 used in the process. Internally, the laser processing head 50 incorporates optics to focus the laser energy in a laser beam LB onto the workpiece(s) WP to achieve brazing, soldering, welding, or another joining process.

[0024] A closer look reveals Fig. Figure 1B shows a perspective view of a laser processing head 50 for a laser processing device (not shown). Not all components of the laser processing head 50 are shown. In general, the laser processing head 50 includes a frame 52, a support body 54 coupled to the frame 52, and a focusing unit or focusing arm 56 coupled to the support body 54. In one configuration, the head 50 may be tactile, allowing the arm 56 to be moved laterally and used for tactile joining, where a lateral force on the wire W is used to follow a seam. In other configurations, the head 50 may not be tactile, so this element 56 may only be a focusing unit.

[0025] The laser processing head 50 can be used to join workpieces WP1 and WP2 by emitting a laser beam LB to braze, solder, weld, or otherwise join the workpieces WP1 and WP2 together. In the present example, brazing is referred to as the laser process, but the teachings of this disclosure can equally well be applied to other joining processes, such as soldering, welding, and the like.

[0026] A laser cable (not shown) is connected to the support body 54 to provide laser light, which is guided through the head 50 to direct a laser beam LB onto the workpieces WP1, WP2. A receiver 61 for the laser cable is located in Fig. 1B shown schematically only.

[0027] A wire feeder 20 is mounted on the frame 52 and feeds a consumable wire made of brazing material for the brazing process through a wire feed cable 22. The wire feeder 20 transports the brazing wire forward during the brazing process, and the wire feed cable 22 feeds the brazing wire at a shallow angle to a wire outlet 24, which is connected to one end 58 of the arm 56 of the head.

[0028] The head 50 is shown relative to the exemplary workpieces WP1 and WP2 to be joined. The laser brazing head 50 includes, among other things, the frame 52 and the support body 54 connected to the frame 52. The support body 54 can be movable relative to the frame 52 to assist in guiding the laser processing head 50 along a seam between the workpieces WP1 and WP2. However, the support body 54 can also be fixed relative to the frame 52.

[0029] The arm 56 is coupled to the support body 54, and a motor (not shown) on the support body 54 can move the arm 56 relative to the support body 54 to facilitate the correct positioning of one end 58 of the arm 56 relative to the workpieces WP1, WP2. The wire feed 20 is coupled to the frame 52 and feeds the consumable brazing wire through the wire feed cable 22. The wire extends from the wire outlet 24 of the wire feed cable 22 at the end 58 of the arm 56 and is positioned in the path of the main laser beam LB.

[0030] During operation, the laser beam LB melts the wire, allowing the wire material to flow between the workpieces WP1 and WP2 and join them. During typical operations, only the wire touches the workpieces WP1 and WP2 and is used to guide them along the seam. However, in some implementations, the wire is too soft for this purpose. Consequently, although in Fig. 1B not visible, additional support from a fixed element may be required, such as a guide finger, a needle, or another extension extending from the end 58 of the arm 56 to run along the seam. In any case, the process can automatically control the force between the fixed element and at least one of the workpieces WP1, WP2.

[0031] As in Fig. As shown in Figure 1B, the laser brazing head 50 includes a force sensor 30 positioned at the end 58 of the arm 56. The force sensor 30 can measure the forces at the end 58 of the arm 56. The measured forces can be used to control the brazing process and the guidance of the end 58 of the arm 56 along a seam between the workpieces WP1 and WP2.

[0032] To braze workpieces WP1 and WP2 together, a secondary laser beam SB is derived or split from the main laser beam inside the head 50. The main laser beam LB is used to melt the brazing material of the consumable wire supplied from the output 24, while the secondary laser beam SB is used to preheat the workpieces WP1 and WP2 to be joined. As shown, a secondary fiber 40 can direct the secondary laser beam SB from the head 50 to the end 58 of the arm 56 of the head.

[0033] In addition to preheating workpieces WP1 and WP2, the secondary laser beam SB can be used to remove sections of a surface coating from the workpiece(s) WP1 and WP2. The workpieces WP1 and WP2 to be joined may already have a corrosion protection coating or other type of surface coating at the joint, including unwanted surface contaminants. The surface coating can adversely affect the brazing process because, for example, the coating may exhibit different properties when heated than the workpiece material (WP1, WP2). This can lead to the formation of blisters or inclusions in the coating at the joint. These effects can impair the quality of the joining process.Accordingly, the secondary fiber 40 emits a separate, power-scalable laser beam SB, directed at one or both workpieces WP1, WP2 to pretreat the workpiece(s) WP1, WP2 by: (i) preheating the workpiece(s) WP1, WP2 and / or (ii) vaporizing the surface coating on the workpiece(s) WP1, WP2. This arrangement can be advantageous if the workpieces WP1, WP2 have a surface coating that makes it difficult to wet them with brazing material or the like.

[0034] Fig. Figure 2 illustrates a schematic view of a laser processing head 50, which has a first arrangement for emitting a secondary beam SB onto the workpiece(s) WP. The laser processing head 50 includes a housing 60, which has internal optics 62. The housing 60 may include a support body, an arm, and other features discussed above. A receiver 61 at one end of the housing 60 may be coupled to a laser cable 14, which directs high-power laser light into the interior of the housing.

[0035] During operation, the internal optics 62 collimates and focuses the high-power laser light emitted into the housing 60. For example, the internal optics 62 can include a collimator 64 and a focusing lens 68. The collimator 64 in the housing 60 is arranged in the optical axis A of the laser light in the housing 60. The collimator 64 is configured to collimate the laser light into collimated light CB.

[0036] A beam splitter 70 is also arranged in the optical axis A. The beam splitter 70 has sections, coatings, or the like arranged on areas of the beam splitter 70. The sections include an antireflective section 72 and a highly reflective section 74.

[0037] The regions comprising these antireflective and highly reflective sections 72, 74 may include a peripheral region and a central or inner region. The central or inner region is generally located on or near the optical axis A (although the position of the inner region can be adjusted as described herein). The peripheral region, in turn, surrounds the inner region. The beam splitter 70 is configured to split the collimated light CB into central or inner light from the inner region and peripheral light from the peripheral region of the beam splitter 70. (In the following discussion, the inner region and inner light are generally referred to as the central region and central light. However, this does not mean that the region is located at the center of the beam splitter or that the light is located at the center of the optical axis. Other arrangements are possible, as discussed below.)

[0038] The term "antireflective" generally means that the antireflective section 72 tends not to reflect the laser light at the relevant wavelength(s) or in the relevant range. Similarly, the term "highly reflective" means that the highly reflective section 74 tends to reflect the laser light at the relevant wavelength(s) or in the relevant range. The values ​​for non-reflectivity and reflectivity may vary depending on the implementation. Generally, the highly reflective section 74 may be configured to reflect 50% or more of the incident light, but other reflectivity values ​​may also be used. In fact, the surface area of ​​the highly reflective section 74 may be increased to reflect the laser light even when the section 74 has a lower reflectivity value, which may be advantageous in some applications.A reflectivity of 50% would require a larger central or inner highly reflective section 74, which in turn would require a larger diameter for the fiber 40. Such a solution is only suitable if the proportion of light required for preheating is small (e.g., less than 10%). Instead, a much higher reflectivity than 50% may be preferred for the highly reflective section 74 in most implementations. For example, the overall reflectivity of the highly reflective section 74 may be above 99.5%, and the reflectivity of the antireflective section 72 may be below 0.5%.

[0039] A main output 55a of the head 50 is optically connected to the beam splitter 70 and configured to direct at least the peripheral light into the main laser beam LB onto the workpiece(s) WP. Simultaneously, a secondary output 55b of the head 50 is optically connected to the beam splitter 70 and configured to direct at least a central section into a waveguide 40.

[0040] In the present example, the beam splitter 70 comprises the antireflective section 72 in the form of a coating or the like, which is arranged on the peripheral region of the beam splitter 70. The beam splitter 70 also comprises the highly reflective section 74 in the form of a coating or the like, which is arranged on the central region of the beam splitter 70.

[0041] The coatings for sections 72 and 74 are preferably arranged on the front surface of the beam splitter 70. At the same time, the back side of the beam splitter 70 is preferably coated with an AR coating 73. This coating 73 on the back side need not necessarily be a lithographic coating, and the entire back side can have the same AR coating 73. Since the coatings 72, 73, and 74 on the surfaces can induce a certain amount of stress in the beam splitter 70, providing coatings 72, 73, and 74 on both the front and back sides is preferred in order to counteract competing stresses.

[0042] The highly reflective coating 74 is configured to reflect at least some of the central light to the secondary output 55b. In contrast, the antireflective coating 72 is configured to transmit at least some of the peripheral light to the main output 55a. It is evident that any light passing through the HR coating 74 becomes part of the main laser beam LB, but the light reflected by the AR coating 72 may miss the lens 76 and be lost. Therefore, a preferred embodiment can use a low (< 0.5%) reflectivity for the AR coating 72.

[0043] In general, and as shown, the main output 55a includes the focusing lens 68, which is arranged in the optical axis A. The focusing lens 68 is configured to focus any collimated light CB incident on it into the main laser beam LB onto the workpiece(s) WP. Additionally, the main output 55a can also include at least one reflector 66a-b, which is arranged in the optical axis A between the beam splitter 70 and the focusing lens 68. The reflector 66a-b is configured to reflect any collimated light CB incident on it.

[0044] The secondary output 55b for the secondary beam SB comprises a focusing lens 76 and a waveguide 40. The focusing lens 76 is arranged in optical communication with the highly reflective coating 74 in a central region of the beam splitter 70 and is configured to focus the central light. The waveguide 40, which can be an optical fiber, has an input that is arranged in optical communication with the focusing lens 76 and a distal end 42 that is arranged in optical communication with the workpiece(s) WP.

[0045] As previously noted, the collimator 64 collimates the laser light from the laser cable 14 into the collimated beam CB. The collimator 64 can have one or more lenses (not shown) that collimate the laser light. As is evident and shown here, collimation can be achieved using a single lens for the collimator 64. In alternative arrangements, the collimator 64 can provide zoom collimation, for example, using two or more lenses.

[0046] The focusing lens 68 focuses the collimated beam CB into the main laser beam LB at a focal point, which is then directed onto the workpiece WP to achieve the purposes of the laser process, such as brazing, welding, soldering, etc. The outlet 69 of the housing 60 can include any suitable cover slide, nozzle, cross-jet, cooling system, etc. Other arrangements are possible. (References to a lens, lens element, lens group, etc., are interchangeable, and it is understood that each of the mentioned lenses or the like may consist of one or more lens optics—that is, a transmissive optic for focusing, dispersing, or collimating the laser light.)

[0047] Following the preceding examples related to brazing, the laser processing head 50 can be a brazing head for brazing components of the workpiece(s) WP together. In the context of brazing, the head 50 can, for example, be a component of a brazing system with fixed optics, in which the head 50 is mounted on an apparatus such as a robot or a gantry (16: Fig. 1) is attached and configured to move the head 50 relative to the workpiece(s) WP being joined. Alternatively, the workpiece(s) can be moved relative to the head 50.

[0048] The internal optics 62 can also include several other components, such as other lenses or mirrors, positioned between the receiver 61 and the output 69, where the laser beam LB leaves the internal optics 62. For example, the head 50 can use the reflectors or mirrors 66a-b to guide or otherwise manipulate the collimated beam CB.

[0049] The laser light leaves the receiver 61 as a beam cone or in a conical shape before entering the collimator 64. The laser light is collimated in the collimated beam CB that exits the collimator 64. The collimated beam CB is reflected by the mirrors 66a-b, which direct the collimated beam CB onto the focusing lens 68, which finally focuses the laser light as the main laser beam LB from the output 69 of the housing.

[0050] As previously mentioned, the beam splitter 70, located in the collimated beam CB of the collimator 64, incorporates the antireflective (AR) coating 72 around the circumference of the splitter's surface and the highly reflective (HR) coating 74 towards the center of the splitter's surface. The HR coating 74 can be oval-shaped, allowing the angled oval coating 74 to reflect the secondary laser beam SB, which has a cylindrical shape, towards the focusing optics 76 for the secondary fiber 40. The secondary fiber 40 then outputs the secondary beam SB to the output 42, which directs the secondary beam SB onto the workpiece(s) WP. This output 42 can incorporate any suitable optics, shutters, cross-jets, cooling devices, etc.

[0051] In the arrangement described above, the lens 76 can focus light onto the fiber 40 up to a maximum angle. Any light beyond this maximum angle is not guided through the fiber 40. If the diameter of the enclosed secondary beam SB, which is reflected to the lens 76, is large, the focal length of the lens 76 must be increased so that the maximum angle for the light is not exceeded. The longer focal length results in a larger focus of the lens 76, thus requiring a larger core of the optical fiber 40. This applies to all possible light beams across the entire range of power variation. For this reason, laterally (horizontally) shifting the beam splitter 70 is a preferred way to adjust the power for the secondary beam SB.

[0052] In one configuration, the coatings 72, 74 can be lithographically structured coatings and can exhibit micrometer-scale accuracy to provide high-performance beam splitting. Generally, the coatings 72, 74 can be dielectric coatings, metallic coatings, or metallic-dielectric coatings on a suitable substrate, which is preferably transparent to the transmission wavelength to reduce absorption and heating. The coatings 72, 74 can be applied by thermal electron beam evaporation, sputtering, magnetron sputtering, ion beam sputtering, lithography, a combination of structuring and coating, or another technique.

[0053] In general, lithography refers to a method of depositing two different layers close together onto a substrate. Lithography can include photolithography, optical lithography, shadow masking and deposition, and other processes. For example, in photolithography, a photoresist can be used to mask selected surface areas of the substrate during the various stages of coating application. Essentially, a photoresist can be applied to the substrate surface and shaped as desired to cover a specific area. One of the coating components (e.g., AR or HR) can be deposited onto the substrate to adhere to the exposed surface area. The photoresist can then be developed and removed, and the process can be repeated for another portion of the coating component (e.g., HR or AR).

[0054] A coating section (AR or HR) can also be applied to an entire area. A photoresist can be applied, textured, developed, and then etched away to expose selected areas for further coating steps. In other examples, a shadow mask can be used on the substrate during the deposition of coating materials to create different areas for antireflective and highly reflective coatings. These and other processes can be used.

[0055] The coatings 72, 74 are preferred so that a sharp demarcation between the antireflective and highly reflective areas can be made on the surface of a monolithic substrate for the beam splitter. The beam splitter 70 may nevertheless have sections, segments, or the like that are assembled to form the antireflective and highly reflective areas.

[0056] In most cases, the most brilliant part of the laser light is located near the optical axis A. The beam splitter 70 with the HR coating 74 is used to couple this more brilliant part of the laser light into the secondary fiber 40. Generally, the surface area of ​​the HR coating 74 is much smaller than the surface area of ​​the AR coating 72 because the proportion of light required for preheating can be less than 50% of the total laser light, and because only the most intense part of the beam is used. Due to the much higher local brilliance, the focal length of the lens 76 can be chosen to be small, resulting in a small focus, and the secondary fiber 40 can have a core diameter of less than 0.2 mm.The smaller core diameter of the secondary fiber 40 can produce a much smaller heating point(s), enable better focus shaping of the point(s), and provide better beam shaping to realize various point geometries. As an additional advantage, a significantly smaller output coupler (e.g., lens 76) can be required when the central light from the optical axis A of the collimated beam CB is used.

[0057] The beam splitter 70 is positioned at an angle (e.g., 45 degrees) to the collimated beam CB from the collimator 64, such that a cylindrically shaped collimated secondary beam SB from the elliptically shaped or oval central area, which has the HR coating 74, strikes the secondary fiber 40. The optical power coupled into the secondary fiber 40 can be adjusted by moving, shifting, relocating, rotating, etc., the splitter 70 relative to the central axis A of the collimated primary beam CB. Moving the splitter 70 changes the amount of central light reflected from the HR coating 74 to the lens 76 and the fiber 40, since the intensity of the collimated beam CB typically decreases with distance from the optical axis A.The angular orientation of the beam splitter 70 can be adjusted relative to the collimated beam CB using one or more actuators 75, such as a motor, electromagnet, or the like. A change in the angular orientation of the beam splitter 70 would cause the light to be reflected away from the fixed lens 76. A lateral displacement of the beam splitter 70 relative to the central axis A using one or more actuators 75, such as a motor, electromagnet, or the like, as described below with reference to... Fig. As discussed in 9A-9B, it may be preferred that the reflected light always passes through the fixed lens 76.

[0058] As shown, the head 50 typically has two reflectors or mirrors 66a-b to guide the collimated beam CB into the housing 60. This arrangement is used because the reflector 66b allows for a rotation of the arm (56; Fig. 1B) allows the LB to remain focused on the feed wire. This arrangement is also used in part to allow a camera or other image sensor 32 to monitor the process based on the light reflected from the process and returned through the output 69 to the second reflector 66b. The image sensor 32 may include a separate lens to focus the light onto the detector surface. As an alternative arrangement, the collimated beam CB can be split using a beam splitter that replaces one of these reflectors 66a-b.

[0059] For example, it illustrates Fig. Figure 3 shows a schematic view of a laser processing head 50, which has a second arrangement for emitting a secondary beam SB onto the workpiece(s) WP. Here, one of the reflectors in the head 50 is replaced by a beam splitter 80 according to the present disclosure.

[0060] The beam splitter 80 includes a highly reflective (HR) coating 82 around its circumference and an antireflective (AR) coating 84 towards the center of the splitter 80. (Again, the coatings 82 and 84 are preferably arranged on the front surface of the beam splitter 80. At the same time, the rear surface of the beam splitter 80 preferably has an AR coating 83, at least on the portion of the surface through which light is transmitted. Likewise, if fitted, one or more actuators 85 can be used to move the beam splitter 80.)

[0061] The head 50 includes a main output 55a, which has a reflector 66b and a focusing lens 68 to direct a portion of the laser light in the main laser beam LB onto the workpiece(s) WP. The head 50 also includes a secondary output 55b to direct a portion of the laser light in a secondary laser beam SB onto the workpiece(s) WP. Here, the secondary output 55b includes a focusing lens 86 and a waveguide or optical fiber 40. The same focusing lens 86 can be used here as the focusing lens in Fig. 2 can be used, just as the same waveguide or optical fiber 40 can be used.

[0062] On the beam splitter 80, the AR coating 84 can have an elliptical or oval shape, so that the secondary laser beam SB, which has a cylindrical shape, is directed towards the focusing optics 86 for the secondary fiber 40. The coatings 82 and 84 can be arranged as before, but the coatings 82 and 84 are positioned with the AR coating 82 in the central region to transmit the more brilliant central light. The HR coating 84 is positioned in the peripheral region of the beam splitter 80 to reflect the less brilliant peripheral light for the main laser beam LB. As noted, the splitter 80 can be moved to regulate the power supplied for preheating. Moving the splitter 80 can be coupled with moving the lens 86 and the fiber 40 input. Alternatively, a coupled second mirror can be used.

[0063] Fig. Figure 4 illustrates a schematic view of a laser processing head 50, which has a third arrangement for emitting a secondary beam SB onto the workpiece(s) WP. This arrangement is similar to the one disclosed above, except that the beam splitter 80 replaces a reflector located towards the output end 69 of the laser processing head 50. (Here too, the coatings 82, 84 are preferably arranged on the front surface of the beam splitter 80. At the same time, the rear side of the beam splitter 80 preferably has an AR coating 83, at least on the portion of the surface through which light is transmitted. Likewise, if fitted, one or more actuators 85 can be used to move the beam splitter 80.)

[0064] The head 50 includes a main output 55a, which has a reflector 66a and a focusing lens 68 to direct a portion of the laser light in the main laser beam LB onto the workpiece(s) WP. In this arrangement, the reflector 66a is also part of the secondary beam path. The head 50 also includes a secondary output 55b to direct a portion of the laser light in a secondary laser beam SB onto the workpiece(s) WP. Here, the secondary output 55b includes a focusing lens 86 and a waveguide or optical fiber 40.

[0065] This arrangement, which includes the beam splitter 80 at the output end 69, may not be particularly advantageous, as an image sensor 32, such as a camera, can be used at this location to image the reflected light in order to monitor the process carried out by the laser beam LB. Including the beam splitter 80 in this path may complicate monitoring, as it alters how the light reflected from the process can reach the image sensor 32. Furthermore, moving the beam splitter 80 to regulate the preheating power may require moving the lens 86 and the fiber input 40.

[0066] Fig. Figure 5 illustrates a schematic view of a laser processing head 50, which has an alternative arrangement. Fig. 5. A beam splitter 70 similar to the one above can be used with reference to Fig. 2 discussed. (Here too, the coatings for sections 72, 74 are preferably arranged on the front surface of the beam splitter 70, and the rear surface of the beam splitter 70 is preferably coated with an AR coating 73. Optionally, one or more actuators 75 can also be used to move the beam splitter 70.) Here, the beam splitter 70 can be positioned in the collimated beam CB between the reflectors 66a-b. In some cases, the distance between the reflectors 66a-b is preferably short, so that the overall size of the housing 60 can be more compact, in which case a different arrangement may be preferred.

[0067] In Fig. 5. The light for heating comes from one side of the process and the feed wire comes from the other side of the process. In other words, the head 50 in Fig. In the figure, 5 can move to the left (direction D), and the wire feed W can be located on this side of the laser beam LB. Accordingly, the light from fiber 40 can provide post-heating for the joining process. Of course, fiber 40 can also be positioned on the other side to provide pre-heating. However, each of the arrangements disclosed herein can be configured for pre-heating, post-heating, or both.

[0068] In other alternatives, more than one beam splitter 70, 80 can divide more than one secondary beam SB onto more than one secondary fiber 40, or one beam splitter 70, 80 can divide several secondary beams SB onto several optical fibers 40. A corresponding retrofit of the laser processing head 50 is also the subject of this disclosure. For example, retrofit elements of a beam splitter 70 / 80, an optic 76 / 86, a fiber 40, and the like can be added to an existing head 50 to configure the head 50 to emit the secondary laser beam SB, as disclosed herein.

[0069] The outlet 42 of the secondary fiber 40 can have various configurations, depending on which heating point(s) are to be generated by the secondary beam SB. As already noted, the outlet 42 can incorporate any suitable optics, cover slide, cross-jet, cooling, etc. In general, the outlet 42 of the secondary fiber 40 can have a flat tip (i.e., a fiber tip without any form of beam-shaping element). In particular, the flat tip can be used to generate an acceptable spot size, which depends on the distance of the outlet 42 to the workpiece and the numerical aperture. For example, if the distance of the outlet 42 to the workpiece is 80 mm and the numerical aperture is only 20 mrads, then a spot of 3.2 mm can be formed without any imaging optics, such as a beam-shaping element, being required at all. Alternatively, a beam-shaping element can be positioned at the outlet 42 of the secondary fiber 40.The intensity profile of the secondary beam SB of the secondary fiber 40 can also be adjusted at output 42 to meet the requirements of a connection.

[0070] Possible embodiments of the output 42 for the secondary fiber 40 are shown in magnifications A, B and C of Fig. Figure 6 shows that in magnification A, a distal end of the secondary fiber 40a is positioned in front of a microlens 44a for the output 42. The lens 44a may be located in an end cap or housing connected to the end of the fiber 40a.

[0071] In magnification B, the secondary fiber 40b contains microfibers 44b that are exposed at the outlet 42. The microfibers 44b can scatter or otherwise direct the shape of the laser light for the heating spot(s). The microfibers 44b can also be distributed at the outlet 42 so that the microfibers 44ab, in combination with a focusing lens (not shown), can produce a desired preheating spot shape. At the input end of the fiber 40, the microfibers 44b can be bundled to form a packed input for the focus of the lens 76.

[0072] In magnification C, an optical block 44c is coupled to the end of fiber 40c. The optical block 44c can be configured to shape the secondary beam into a line or other shape. As shown, for example, the optical block 44c can be fanned out so that the secondary beam can be shaped into a beam line to vaporize coatings and / or heat the workpieces. Other configurations can be used. For example, a diffractive optical element can be used at the distal end of fiber 40.

[0073] As noted above, the secondary beam SB is emitted next to the main laser beam LB at a point near the wire that is fed into the processing area. Fig. Figure 7 illustrates an assembly comprising a secondary fiber 40 mounted on a guide 26 at the wire exit 24 at the end 58 of the housing arm 56. A mechanical fastener or clamp 90 secures the secondary fiber 40 to the guide 26. As shown, the guide 26 is connected to the cable 22, which delivers the wire W adjacent to the main laser beam LB. The guide 26 may include a mechanical guide finger 28 that engages the workpiece(s) to, for example, follow the seam and exert a force, as discussed herein.

[0074] Fig. Figures 8A-8E illustrate top views of beam splitters 100 according to the present disclosure. As noted above, the beam splitter 100 of the present disclosure may include at least two reflective sections, including an antireflective section and a highly reflective section. As also noted above, the at least two reflective sections may be located in at least two regions of the beam splitter 100, comprising an inner region and a peripheral region. As further noted, the shape of the regions may be round, elliptical, or oval. This configuration may be most suitable if the central section of the collimated beam can provide the highest brilliance and if the configuration is intended to distribute the highest brilliance to the secondary beam.Lateral movement of the beam splitter 100 can adjust how much of the highest brilliance (and thus the total power) is directed onto the secondary beam. However, as is evident from the present disclosure, other configurations are possible.

[0075] First, in some implementations it may not be desirable or necessary for the portion of the collimated light directed toward the secondary beam to include the central light (i.e., the light with the highest brilliance). Instead, depending on the implementation, the light directed toward the secondary beam by either the HR section or the AR section of the beam splitter 100 may be positioned elsewhere in the collimated beam, such as offset from the center of the beam splitter. For example, depending on the light, the brilliance of an offset section of the beam splitter 100 may be lower, but still sufficient for preheating, postheating, or other purposes disclosed herein. Furthermore, while the collimated beam may tend to have higher brilliance at its center, there may also be laser light with a flatter power distribution in the collimated beam.

[0076] With this understanding in mind, Fig. 8A the beam splitter 100, which has at least two sections 102, 104 (e.g., AR and HR sections) located in a peripheral region and an inner region, comparable to those described above. The section 104 in the inner region can be the HR section, and the section 102 in the peripheral region can be the AR section. A reverse arrangement is also possible. Since the beam splitter 100 is angled with respect to the optical axis of the collimated beam, the section 104 of the inner region can have an oval or elliptical shape, as already discussed. However, the size and shape of the sections 102, 104, and regions can be configured as required.

[0077] In Fig. Figure 8B shows that the beam splitter 100 again has at least two reflective sections 102 and 106. A first "inner" section 106 is located within the second "peripheral" section 102, but the first section 106 is offset from the center of the beam splitter 100. The first section 106 can even be located towards the edge of the beam splitter 100, as also shown. The first section 106 can be the HR section, and the second section 102 can be the AR section. A reverse arrangement is also possible. Since the beam splitter 100 is angled with respect to the optical axis of the collimated beam, the inner section 106 can have an oval or elliptical shape, as already discussed. However, the size and shape of the sections and areas can be configured as needed.

[0078] The sections of the beam splitter 100 can be freely shaped areas, and the beam splitter 100 with the lithographic areas of the antireflective and highly reflective sections can shape the deflected beam. Fig. Figure 8C, for example, shows an inner section 108 that has a free-form shape, such as a crescent moon, as shown, but which could also have any other shape. A ring shape, a cross shape, or the like could also be used. A specific shape, such as the one used for one of the sections 108, can be more or less preserved in the light during transmission through the short fiber of the secondary output. In this way, the shaped light can generate a specific power distribution outside the near field of the laser spot.

[0079] Fig. Figure 8D shows how one of the sections (e.g., the inner section 110) can have a shape other than round or elliptical. Fig. Figure 8E shows how one of the sections (e.g., the inner section 112) can consist of several discrete sections that, in a specific shape and orientation, exhibit the same or different reflectivity. The shape of sections 102, 104, 106, 108, 110, and 112 can provide a specific power distribution in the secondary beam and provide a gradient or discrete steps of the emitted power based on a lateral position of the beam splitter 100. As these examples with sections 102, 104, 106, 108, 110, and 112 show, various configurations for the beam splitter 100 of the present disclosure can be used, and the shape of the sections can be symmetrical, asymmetrical, uniform, non-uniform, or the like.

[0080] As noted above, the orientation of the beam splitter of the present disclosure can be changed to alter the secondary output of the laser light. For example, changing the lateral orientation of the beam splitter can adjust the amount of light reflected from the HR coating to the lens for emission into the fiber.

[0081] Fig. Figures 9A-9B illustrate schematic views of a beam splitter 120 whose lateral orientation is moved to change the secondary output of the laser light. The optical power coupled into the secondary fiber 40 can be adjusted by moving the beam splitter 120 relative to the optical axis A of the collimated main beam CB. In this example, the beam splitter 120 has a peripheral section with an antireflective coating 122 and an inner or central section with a highly reflective coating 124.

[0082] In Fig. In 9A, the beam splitter 120 is set up in the lateral position x0, with the center of the splitter 120 aligned with the optical axis A. As shown, the beam splitter 120 can be set up at an angle (e.g., 45 degrees), which can be fixed or adjustable. A larger amount of the central light CL is reflected by the HR coating 124 to the lens 126 and the fiber 40. Fig.In 9B, the lateral orientation of the beam splitter 120 was adjusted to a different lateral position x1, so that the center of the splitter is not aligned with the optical axis A. As is evident, the HR coating 124 still has the same size, so the dimension of the secondary beam reflected from the HR coating 124 towards lens 126 remains the same. However, since the HR coating 124 is no longer centered with respect to the optical axis A, less of the central light CL is reflected from the HR coating 124. Therefore, the off-axis portion of the HR coating 124 produces a portion of the reflected beam that has lower power. The movement can be achieved using one or more actuators 125, such as a motor, electromagnet, or the like.This change in the lateral orientation of the beam splitter 120 adjusts the amount of central light CL that is reflected from the HR coating 124 to the lens 126 to be emitted into the fiber 40.

Claims

[1] A laser processing head (50) for directing laser light onto a workpiece (WP), wherein the laser processing head (50) comprises: - a collimator (64) arranged in an optical axis of the laser light and configured to convert the laser light into collimated light; - a beam splitter (70) arranged in the optical axis between the collimator and a main output at an angle to the collimated light and having at least two sections arranged on a surface of the beam splitter (70), wherein the at least two sections comprise a peripheral antireflective section (72) configured to allow peripheral light of the collimated light at least partially to pass to the main output (55a), and an inner highly reflective section (74), wherein the peripheral region surrounds the inner region, and wherein the inner highly reflective section (74) has an oval shape such that the angled oval inner highly reflective section (74) reflects a secondary laser beam (SB) having a cylindrical shape towards a focusing lens 76 for a secondary fiber (40); - the main output (55a) which is arranged in optical connection with the beam splitter (70), wherein the main output (55a) is configured to direct at least the first light into a main laser beam onto the workpiece (WP); and - a secondary output (55b) arranged in optical connection with the beam splitter (70), wherein the secondary output (55b) is configured to direct at least the second section into a secondary laser beam alongside the main laser beam and comprises the following: - at least one focusing lens (68) arranged in optical connection with the beam splitter (70) and configured to focus any collimated light transmitted from the beam splitter (70) and falling onto the focusing lens (68); and - at least the secondary fiber (40) which has an input arranged in optical connection with the focusing lens (76) and which has an output arranged in optical connection with the workpiece (WP). [2] The laser processing head (50) according to claim 1, wherein the collimator (64) comprises one or more lenses. [3] The laser processing head (50) according to claim 1, wherein the beam splitter (70) comprises a substrate; wherein the highly reflective section (74) comprises a highly reflective coating which is lithographically structured on the substrate or on an antireflective coating. [4] The laser processing head (50) according to claim 1, wherein the beam splitter (70) is arranged at a lateral position relative to the optical axis of the collimated light, wherein the lateral position relative to the optical axis of the collimated light is adjustable, wherein the lateral position is configured to adjust an amount of the first light, the second light or the first and second light that are split by the beam splitter (70). [5] The laser processing head (50) according to claim 1, wherein the main output (55a) comprises a focusing lens (68) arranged on the optical axis and configured to focus any collimated light transmitted from the beam splitter (70) and falling on the focusing lens (68) into the main laser beam on the workpiece (WP). [6] The laser processing head (50) according to claim 1, wherein the waveguide (40) comprises an optical fiber or a bundle of microfibers (44b). [7] Laser processing head (50) according to claim 1, wherein the output (42) of the waveguide (40) comprises a microlens (44a), an optical block (44c), a beam shaping element or a flat tip. [8] The laser processing head (50) according to claim 1, - wherein the at least two sections are arranged on at least two areas of the beam splitter (70), wherein the at least two areas comprise a peripheral area and an inner area, wherein the peripheral area surrounds the inner area, wherein the beam splitter (70) is configured to split the collimated light into inner light from the inner area and into peripheral light from the peripheral area; - wherein the main output (55a) is configured to direct at least the peripheral light as the first light into the main laser beam onto the workpiece (WP); and - wherein the secondary output (55b) is configured to direct at least the inner light as the second light into the secondary laser beam alongside the main laser beam. [9] The laser processing head (50) according to claim 8, wherein the beam splitter (70) comprises the antireflective section at the peripheral region thereof and the highly reflective section (74) at the inner region thereof, wherein the highly reflective section (74) is configured to reflect the inner light at least partially to the secondary output (55b) and the antireflective section (72) is configured to allow the peripheral light to pass at least partially to the main output (55a). [10] The laser processing head (50) according to claim 9, wherein the main output (55a) comprises a focusing lens (68) arranged in the optical axis and configured to focus any collimated light incident thereon into the main laser beam on the workpiece (WP). [11] The laser processing head (50) according to claim 10, wherein the main output (55a) comprises at least one reflector (66a, 66b) arranged in the optical axis between the beam splitter (70) and the focusing lens (68) and configured to reflect any collimated light transmitted from the beam splitter (70) and falling onto the focusing lens (68). [12] The laser processing head (50) according to claim 9, wherein the secondary output (55b) comprises: - at least one focusing lens (68) arranged in optical connection with the beam splitter (70) and configured to focus any collimated light transmitted from the beam splitter (70) and falling onto the focusing lens (68); and - at least one waveguide (40) having an input arranged in optical connection with the focusing lens (68) and having an output arranged in optical connection with the workpiece (WP). [13] The laser processing head (50) according to claim 8, wherein the beam splitter (70) comprises the antireflective section (72) on the inner region thereof and the highly reflective section (74) on the peripheral region thereof, wherein the highly reflective section (74) is configured to reflect the peripheral light at least partially to the main output (55a), and the antireflective section (72) is configured to allow the inner light to pass at least partially to the secondary output (55b). [14] The laser processing head (50) according to claim 13, wherein the main output (55a) comprises a focusing lens (68) arranged in the optical axis and configured to focus any collimated light transmitted from the beam splitter (70) and falling on the focusing lens (68) into the main laser beam on the workpiece (WP). [15] The laser processing head (50) according to claim 14, wherein the main output (55a) comprises a reflector (66a) arranged in the optical axis between the beam splitter (70) and the focusing lens (68) or between the collimator (64) and the beam splitter (70), wherein the reflector (66a) is configured to reflect at least part of the collimated light incident on it. [16] The laser processing head (50) according to claim 14, wherein the main output (55a) comprises two reflectors (66a, 66b), wherein a first reflector (66b) is arranged in the optical axis between the beam splitter (70) and the focusing lens (68) and a second reflector (66a) is arranged between the collimator (64) and the beam splitter (70), wherein the reflectors (66a, 66b) are configured to reflect the collimated light incident on them. [17] The laser processing head (50) according to claim 14, wherein the secondary output (55b) comprises: - a focusing lens (68) arranged in optical connection with the beam splitter (70) and configured to focus any collimated light transmitted from the beam splitter and falling onto the focusing lens (68); and - a waveguide having an input arranged in optical connection with the focusing lens (68) and having an output arranged in optical connection with the workpiece (WP). [18] A laser processing head (50) for joining workpieces (WP1; WP2) using laser light and a wire, wherein the laser processing head (50) comprises: - a collimator (64) arranged in an optical axis of the laser light and configured to convert the laser light into collimated light; - a beam splitter (70) arranged in the optical axis between the collimator and a main output at an angle to the collimated light and having at least two sections arranged on a surface of the beam splitter (70), wherein the at least two sections comprise a peripheral antireflective section (72) configured to allow peripheral light of the collimated light at least partially to pass to the main output (55a), and an inner highly reflective section (74), wherein the peripheral region surrounds the inner region, and wherein the inner highly reflective section (74) has an oval shape such that the angled oval inner highly reflective section (74) reflects a secondary laser beam (SB) having a cylindrical shape towards a focusing lens 76 for a secondary fiber (40); - a main output (55a) arranged in optical connection with the beam splitter (70), wherein the main output (55a) is configured to direct at least the first light into a main laser beam onto the workpiece (WP); and - a secondary output (55b) arranged in optical connection with the beam splitter (70), wherein the secondary output (55b) is configured to direct at least the second section into a secondary laser beam alongside the main laser beam and comprises the following: - at least one focusing lens (68) arranged in optical connection with the beam splitter (70) and configured to focus any collimated light transmitted from the beam splitter (70) and falling onto the focusing lens (68); and - at least the secondary fiber (40) which has an input arranged in optical connection with the focusing lens (76) and which has an output arranged in optical connection with the workpiece (WP); and - a cable configured to feed the wire into the main laser beam. [19] The laser processing head (50) according to claim 1, wherein the inner section has several discrete sections. [20] The laser processing head (50) according to claim 1, wherein the inner section is arranged offset from the center of the beam splitter. [21] The laser processing head (50) according to claim 1, comprising an actuator for lateral displacement of the beam splitter (70). [22] A method for directing laser light onto a workpiece (WP), the method comprising: - Collimating the laser light into collimated light along an optical axis; - Splitting the collimated light into a first light and a second light using a beam splitter (70) arranged in the optical axis between the collimator and a main output at an angle to the collimated light and having at least two sections arranged on a surface of the beam splitter (70), wherein the at least two sections comprise a peripheral antireflective section (72) configured to allow peripheral light of the collimated light to pass at least partially to the main output (55a), and an inner highly reflective section (74), wherein the peripheral region surrounds the inner region, and wherein the inner highly reflective section (74) has an oval shape such that the angled oval inner highly reflective section (74) provides a secondary laser beam (SB) having a cylindrical shape,reflected towards a focusing lens 76 for a secondary fiber (40), - Directing at least one section of the first light into a main laser beam onto the workpiece (WP); and - Directing at least one section of the second light into a secondary laser beam onto the workpiece, wherein - at least one focusing lens (68) arranged in optical connection with the beam splitter (70), focusing any collimated light transmitted from the beam splitter (70) and falling onto the focusing lens (68); and - at least one waveguide (40) having an input arranged in optical connection with the focusing lens (68) and having an output arranged in optical connection with the workpiece (WP). [23] The method according to claim 22, further comprising feeding a wire to the main laser beam; and wherein directing at least the portion of the first light into the main laser beam onto the workpiece (WP) comprises melting the wire with the main laser beam. [24] The method according to claim 23, wherein directing at least the portion of the second light into the secondary laser beam onto the workpiece (WP) comprises: - Preheating the workpiece (WP) using the secondary laser beam before a connection is made; or - Heating the workpiece (WP) using the secondary laser beam after a connection has been established. [25] The method according to claim 22, further comprising adjusting an amount of the second light directed towards the secondary beam by moving the beam splitter (70) perpendicular to the optical axis of the collimated light.

Images