Laser processing process using scanner optics

Abstract

The present invention relates to a laser processing head comprising a scanner unit arranged in a beam path of the laser processing head and having a scanner mirror tiltably mounted about two rotation axes. The scanner unit is arranged in the laser processing head so that a laser beam passing through the beam path is incident on the scanner mirror at an angle of incidence of at most 30°, preferably at most 22.5°, more preferably at most 15° relative to the surface normal of the scanner mirror. The present invention also relates to a scanner unit for such a laser processing head, a laser processing system comprising the laser processing head, and a laser cutting method.

Description

[Technical Field]

[0001] The present invention relates to the field of laser processing of workpieces, preferably laser cutting of metal workpieces. In particular, the present invention relates to a laser processing head having a scanner unit for deflecting a laser beam within the laser processing head. [Background technology]

[0002] Techniques for deflecting a laser beam in a laser processing head by means of a scanner device are known, for example, from WO2019145536A1. Furthermore, systems are known in which the laser beam is deflected in two spatial directions using only one movably mounted mirror. Examples of such single-mirror scanners are described in DE10027148A1 and EP4000789A2.

[0003] When using laser scanners for material machining, there are fundamental limitations regarding the speed of movement of the beam deflection optics (particularly the scanner mirrors) as well as regarding the process stability with increasing laser power, particularly due to the increased thermal load on the optics. The sensitivity of the scanner system to contamination also plays an important role in this regard.

[0004] The present invention is based on the object of improving the prior art. In particular, an increase in the deflection speed of the laser beam is made possible by a scanner device in a laser processing head, in particular in a laser cutting head. At the same time, the sensitivity of the sensitive scanner equipment to high laser powers in the kW and multi-kW range is reduced.

[0005] Summary of the Invention To achieve the underlying object of the present invention, according to a first aspect, a laser processing head is provided, the laser processing head comprising a scanner unit disposed in the beam path of the laser processing head and having a scanner mirror tiltably mounted about (at least) two rotation axes. The laser processing head is typically part of a laser processing system, and a laser beam is focused through the laser processing head and directed onto a workpiece to be processed. The tilting movement allows the laser beam incident on the scanner mirror to be deflected during operation of the laser processing head. The predefined tilt angles of the scanner mirror about each of the rotation axes can be at most ±2°, preferably at most ±0.3°, about a rest position.

[0006] The scanner unit is disposed in the laser processing head so that the laser beam passing through the beam path is incident on the scanner mirror at an angle of incidence of at most 30°, preferably at most 22.5°, and more preferably at most 15° relative to the surface normal of the scanner mirror. The predetermined angle of incidence of the laser beam on the scanner mirror may be relative to the rest position (i.e., zero position) of the scanner mirror. In other words, the angle of incidence of the laser beam on the scanner mirror during operation of the laser processing head may be at most 32°, preferably at most 24.5°, and more preferably at most 17°, when the maximum deflection of the scanner mirror relative to the rest position is 2°.

[0007] Because the angle of incidence of the laser beam on the scanner mirror is reduced, the projection of the laser beam on the scanner mirror can be kept small. Due to the relatively compact beam spot, the scanner mirror can be reduced in size compared to systems with larger angles of incidence, which also reduces its mass. The smaller the mass of the scanner mirror, the faster it can accelerate or decelerate, which increases the dynamics of the scanner unit and the potential deflection speed of the laser beam.

[0008] According to a preferred variant, the laser processing head further comprises a collimation unit designed to collimate the divergent laser beam entering the beam path. The collimation unit may preferably be a collimation lens, which is preferably arranged in the beam path of the laser processing head after the entrance of the divergent laser beam. Downstream of the collimation unit, the laser processing head may have a deflection unit designed to deflect the collimated laser beam onto the scanner mirror so that the collimated laser beam is incident on the scanner mirror at a predetermined angle of incidence. The deflection unit may preferably be a deflection mirror. The deflection mirror may preferably be arranged at a predetermined fixed angle in the beam path of the laser processing head. Downstream of the scanner unit, the laser processing head may also have a focusing unit, specifically a focusing lens, designed to receive the laser beam deflected by the scanner unit and focus it on a target object. In particular, the target object may be a plate-shaped or tubular, especially metallic, workpiece. For example, the laser beam may be focused on the surface of the workpiece. The beam entrance and exit of the beam path in the laser processing head are typically arranged parallel or perpendicular to each other. A deflection unit can be arranged in the beam path of the laser processing head to achieve a predetermined angle of incidence on the scanner mirror.

[0009] The collimation device may preferably have a collimation focal length f≦100 mm, preferably f≈70 mm.

[0010] Preferably, the collimation unit can be arranged in the laser processing head so as to be displaceable longitudinally and / or transversely relative to the beam path. Alternatively or additionally, the deflection unit can be rotatably or pivotably mounted in the laser processing head. The laser beam can be fed to the optical arrangement by an optical fiber cable. The interface between the optical fiber cable and the optical arrangement, which can be specifically designed as a plug socket, can be arranged so as to be displaceable. Due to the adjustable configuration of the input interface, the collimation unit, and / or the deflection unit, the laser beam, specifically the beam focus of the laser beam, can be precisely aligned with the center of the scanner mirror. This corresponds to a narrow-tolerance aperture design of the scanner mirror, which also favorably affects the size and therefore the mass of the scanner mirror. Specifically, the input interface and / or the collimation unit of the laser beam can be displaceable longitudinally or transversely relative to the beam path, and / or the deflection unit can be rotatably mounted. The scanner unit can preferably be arranged in the laser processing head so as to be fixed, specifically on an axis defined by the beam exit opening of the laser processing head (specifically the cutting nozzle). Alternatively, the scanner unit may be arranged to be displaceably and / or rotatably mounted within the laser processing head.

[0011] In addition to the variants described above, the laser processing head can preferably further comprise a diverging unit or beam diverging unit, in particular a diverging lens. The diverging lens is preferably designed as a negative lens. The diverging unit can be arranged between the scanner unit and the focusing unit. The diverging unit preferably comprises: The focal length may be between f = -40 mm and f = -200 mm, specifically f = ≈ -50 mm. Such a configuration with a diverging unit or beam diverging unit can be advantageous for setting a predetermined imaging ratio while maintaining a relatively small beam diameter before the beam diverging unit. A small beam diameter, in turn, favors the design of a small scanner mirror aperture. For example, if the laser processing head is designed as a laser cutting head for laser flame cutting or laser melt cutting, it may be desirable for the entire optical assembly to have an imaging ratio of 1.5. When using a collimation unit with a relatively short focal length (e.g., f = 70 mm), this can lead to some design conflicts when using a conventional focusing lens with an equally short focal length (e.g., f = 105 mm). Therefore, the workpiece-side cutting width of the focusing lens assembly, including the diverging unit and the subsequent focusing unit, can preferably be designed so that the last optical element has a sufficiently large design distance from the cutting nozzle of the laser cutting head.

[0012] The diverging unit can be arranged in the laser processing head so that it can be displaced longitudinally relative to the beam path, preferably via a motorized displacement. This facilitates changing the focal position of the laser beam. The transmission ratio between the displacements of the diverging unit, designed as a negative lens, can be selected so that, for example, a longitudinal displacement of the negative lens of ±5 mm results in a focal position displacement of +10 mm to -30 mm.

[0013] The scanner unit can be preferably arranged suspended within the laser processing head. In other words, the reflective surface of the scanner mirror can be at least partially facing downward (in the direction of gravity) in the preferred processing position during operation of the laser processing head. This suspended configuration of the scanner unit within the laser processing head can reduce the scanner unit's susceptibility to dirt.

[0014] The collimation unit can preferably be designed as a collimation lens. The collimation lens can preferably be arranged upright in the laser processing head. This specification is understood to refer to the preferred orientation of the laser processing head during operation of the laser processing head. The "upright" or vertical configuration of the collimation lens is generally less susceptible to contamination than a horizontal configuration.

[0015] As mentioned above, the laser processing head can be provided with a connecting socket for the entrance of the laser beam into the beam path of the laser processing head. The connecting socket can preferably be arranged horizontally on the laser processing head or can be oriented downward. Here, too, the positional description refers to the orientation of the laser processing head in a preferred operating state. The horizontal orientation of the connecting socket has proven to be less susceptible to dirt in practice, and is therefore particularly preferred in this sense. In addition, the horizontal orientation of the connecting socket is advantageous for the upright arrangement of the collimation lens. Therefore, it may be preferable for the scanner unit to be integrated into the laser processing head as a whole in a so-called "delta convolution." In this regard, the connecting socket is arranged perpendicular to the exit opening of the laser beam from the laser processing head. After entering through the connecting socket, the laser beam is collimated and then deflected twice via a deflection unit (e.g., 60°) and a scanner unit (e.g., 30°).

[0016] As mentioned above, the laser processing head can preferably be designed as a laser cutting head. As a laser cutting head, the laser processing head includes at least one cutting nozzle and a process gas supply. A laser beam is directed through the cutting nozzle together with the process gas onto the workpiece to be processed, specifically a plate-shaped or tubular, preferably metallic workpiece. The laser beam is movable through the exit opening of the cutting nozzle through a scanner unit. The movement distance of the laser beam within the exit opening of the cutting nozzle can be up to 3 mm, preferably up to 2.5 mm, transverse to the nozzle's longitudinal axis. Such small beam deflections can be achieved by very small movements of the scanner mirror. Small mirror movements also limit the elliptical expansion of the beam projection on the mirror surface. This, in turn, allows the mirror dimensions, and therefore the mirror mass, to be kept small, increasing the dynamics and speed of the mirror movement.

[0017] To achieve the object underlying the present invention, according to a second aspect, there is provided a scanner unit for a laser processing head according to one of the variants described above. The scanner unit comprises a scanner mirror. The scanner mirror may preferably have a circular or approximately circular cross section. The scanner unit also comprises a drive unit for tilting the scanner mirror about (at least) two rotation axes. The rotation axes may preferably be arranged orthogonal to each other.

[0018] The scanner unit further comprises an aperture disposed on the reflective side of the scanner mirror facing the laser beam during operation of the scanner unit, the aperture having a funnel-shaped inner wall, the inclination angle of which is at most 30°, preferably at most 22.5°, and more preferably at most 15° relative to the surface normal of the scanner mirror. The design of the aperture functions, for example, to block scattered radiation and limit the projection of the incoming laser beam onto the scanner mirror. Furthermore, the drive unit is shielded from the incoming laser beam and thereby protected. Overall, this creates the conditions for keeping the cross section of the scanner mirror small, thereby reducing its mass and increasing the speed of mirror movement.

[0019] The scanner mirror together with the frame and drive unit can be designed, for example, as described in EP 4000 789 A2, the magnet pairs of the scanner drive being preferably arranged on the mirror frame.

[0020] The aperture is preferably made of a material with good heat conduction properties, such as a metal or metal alloy. In particular, the aperture can be made of steel. In this way, the aperture can also be used to remove heat that enters the system, for example, by scattered radiation. The frame of the scanner mirror and the scanner drive unit can thereby be protected from overheating.

[0021] The aperture of the scanner mirror is preferably 1.2 to 1.8 times, preferably 1.5 times, larger than the projection surface of the laser beam on the reflecting surface. For example, the second moment method can be used to determine the projection surface. In this case, the aperture of the scanner mirror is specifically determined by the inner diameter of the mirror frame. The preferred minimum size of the aperture of the scanner mirror compared to the projection surface of the laser beam can prevent diffraction effects and heating of the mirror frame due to the edge area.

[0022] To ensure freedom of movement of the scanner mirror, the aperture is spaced apart from the surface (reflective surface) of the scanner mirror by a gap. The gap should preferably be kept as small as possible, for example, <10 mm, preferably ≦1.5 mm, in the neutral or rest position of the scanner mirror. By minimizing the gap, the shielding effect of the aperture can be maximized.

[0023] The aperture preferably has an aperture opening smaller than the aperture of the scanner mirror. In this way, shielding of the mirror frame and the drive unit can be ensured even in the case of an offset laser beam incidence. Preferably, the aperture of the scanner mirror and the aperture opening can each have a circular outline, and the aperture of the scanner mirror is larger than the smallest inner diameter of the aperture opening. The aperture of the scanner mirror can be specifically determined by the inner diameter of the mirror frame in which the scanner mirror is mounted.

[0024] The scanner mirror may preferably have a mirror substrate made of a transparent material, specifically quartz glass. Residual transmission of the laser radiation through the scanner mirror, which is unavoidable when the laser beam is incident on a reflective surface, can be targeted and directed to the rear side of the scanner mirror. This prevents lateral heat dissipation in the direction of the mirror frame and drive unit. The mirror substrate preferably has a thickness-to-diameter ratio of at most 1:10. This ensures the necessary rigidity of the scanner mirror. For example, the scanner mirror may have a diameter of 25 mm and a thickness of 2.5 mm.

[0025] The scanner mirrors may also have an oxide interference coating.

[0026] The scanner unit can further include a heat dissipation element disposed on the rear side of the scanner mirror, the heat dissipation element being spaced from the rear side of the scanner mirror or away from the frame mechanism by a gap just large enough to ensure that the scanner mirror can freely tilt together with the frame mechanism about its axis of rotation. The gap between the heat dissipation elements, which may also be referred to as heat sinks or cooling elements, is preferably 3 mm or less, more preferably 1 mm or less, e.g., approximately 0.8 mm. In this way, on the one hand, the freedom of movement of the scanner mirror is not impaired, and on the other hand, heat dissipation from the scanner mirror via the heat dissipation element is possible by free or forced convection. The heat dissipation element preferably has a conical portion adjacent to a cylindrical portion, the cylindrical portion being disposed in a recess formed by the rear side of the scanner mirror and the mirror frame to which the scanner mirror is attached or fixed. The lateral distance between the heat dissipation element and the mirror frame can preferably be at most 3 mm, more preferably at most 1 mm, e.g., approximately 0.8 mm. The heat dissipation element is preferably made of a material with good thermal conductivity, specifically a metal or metal alloy. The heat dissipation element is preferably made of steel and serves to efficiently dissipate heat from the scanner mirror, and in particular to protect the filigree mirror frame and drive unit (see EP 4000 789 A2) from damage due to thermal overload.

[0027] According to another preferred variant, the aperture and / or the heat dissipation element can be actively cooled. For example, the aperture and / or the heat sink can each have one or more cooling channels, through which a cooling fluid can flow. Active cooling allows the heat input to the scanner unit due to undesired radiation, such as scattered light in the beam path, directional reflections from optical interfaces, or process feedback, to be dissipated even more efficiently.

[0028] Additionally, to further improve cooling of the components, a cooling gas can be circulated in the gap between the heat dissipation element and the unit consisting of the scanner mirror and mirror frame.

[0029] To monitor its operating state, the scanner unit can be monitored contactlessly using a thermal sensor such as a thermopile. The thermopile can be used, for example, to monitor thermal changes in the rear side of the scanner mirror, the frame mechanism, or the scanner mirror suspension. For monitoring the frame mechanism, the area to be observed can preferably be blackened to increase and define the radiation emission at this point. Alternatively or additionally, to monitor the operating state of the scanner unit, a scattering light diode can be placed in the beam path of the incident laser beam, which monitors the beam path and can very quickly detect the occurrence of contamination on the surface of the scanner mirror. If particle burn-in occurs, the measurement level of the scattering light diode rises significantly and suddenly. The scattering light diode can preferably be aligned perpendicular or essentially perpendicular to the reflective surface of the scanner mirror.

[0030] To achieve the underlying object of the present invention, according to a third aspect, a laser processing system, specifically a laser cutting system, is provided. The laser processing system comprises at least a laser beam source for providing a laser beam and a laser processing head according to one of the variations described above. The laser beam has a power of at least 0.3 kW, specifically several kW (e.g., at least 4 kW or 10 kW or more). Furthermore, the beam parameter product of the laser beam (when entering the laser processing head) is at most 4 mm*mrad, preferably at most 2.5 mm*mrad.

[0031] By using the proposed laser processing head with the proposed scanner unit, the laser processing system according to the invention is particularly suitable for deflecting high-intensity laser beams in the high-power range.

[0032] Preferably, a solid-state laser, in particular a disk laser or a fiber laser, is used as the laser beam source, but CO2 lasers or diode lasers can also be used.

[0033] The beam quality of the laser beam and the collimation focal length of the collimation unit can be preferably selected such that the diameter of the collimated laser beam, and therefore also the diameter of the beam projection on the surface of the scanner mirror, is kept small. For example, the beam parameter product can be about 2.5 mm*mrad with a collimation focal length of f≈70 mm.

[0034] In order to achieve the underlying object of the present invention, according to a fourth aspect, there is provided a laser beam cutting method, in which a laser processing beam is directed to a surface of a workpiece to be processed through a cutting nozzle of a laser cutting head together with a process gas, a secondary motion of the laser beam in the cutting nozzle is superimposed on a primary forward motion of the laser cutting head, and the laser beam for generating the secondary motion in the laser cutting head is directed to a scanner mirror that is tiltable about (at least) two rotation axes such that the angle of incidence of the laser beam on the scanner mirror is at most 30°, preferably at most 22.5°, more preferably at most 15° relative to a surface normal of the scanner mirror.

[0035] In summary, the present invention, particularly for laser cutting, offers advantages in terms of dynamics, contour accuracy, repeatability, ease of contamination, compactness, and thermal resistance regarding the deflection of the laser beam in the cutting nozzle compared to previously known systems from the prior art, particularly compared to previous single mirror scanners.

[0036] MODE FOR CARRYING OUT THE INVENTION The following description of preferred exemplary embodiments, taken in conjunction with the drawings, serves to explain the invention in more detail. [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 shows a schematic perspective view of a laser cutting system for laser beam cutting. [Figure 2a] 1 shows a schematic view of a laser cutting head according to the invention according to a first variant; [Figure 2b] 3 shows a schematic view of a laser cutting head according to the invention according to a second variant. [Figure 3a] 1 shows a cross-sectional view of a scanner unit according to the present invention; [Figure 3b] 3b shows a further cross-sectional view of the scanner unit shown in FIG. 3a;

[0038] FIG. 1 shows a laser processing system in the form of a laser cutting system 10. The laser cutting system 10 comprises a laser beam source 12. The laser beam source 12 can be a CO laser, a solid-state laser, or a diode laser. Even though the present figure shows a CO laser configuration in which the generated laser beam L is guided via a deflection mirror to a laser processing head, in this case, a laser cutting head 20, a solid-state laser, specifically a disk laser or a fiber laser, can in principle also be considered a preferred beam source. In a solid-state laser, the laser beam 20 is typically conveyed to the laser cutting head 20 by an optical fiber (not shown in FIG. 1) and fed to the laser cutting head 20 via a connecting socket.

[0039] The laser cutting system 10 further comprises a cutting gas supply 14, here in the form of a gas cylinder 14, via which cutting gas, typically containing nitrogen and / or oxygen, is conveyed via a line to the laser processing head 20 and directed together with the laser beam L through a cutting nozzle under a predetermined pressure onto the workpiece 30 to be processed, in this case a plate-shaped workpiece. The workpiece 30 is mounted on the workpiece support 20 for processing with the processing beam consisting of the laser beam L and the cutting gas jet. The workpiece 30, preferably a metal workpiece 30, is locally melted by relative motion between the workpiece 30 and the laser cutting head 20, and the resulting melt is discharged downwards so that a kerf 32 is formed in the workpiece 30. The laser cutting system 10 further comprises a control device that is programmed to move the cutting head 20 relative to the workpiece 30 according to the cutting contour.

[0040] FIG. 2a shows a schematic diagram of a laser cutting head 20 according to the present invention, which has a so-called "Z-fold" beam path. The beam path is determined by the optical configuration within the laser cutting head 20. The laser beam L enters the laser cutting head 20 through an entrance opening 21. Preferably, the entrance opening 21 can be designed as a connection socket for a fiber optic cable, through which the laser beam L is transported from the laser beam source to the laser cutting head 20. The diverging laser beam L emerging from the fiber optic cable is collimated by a collimation lens 22. The collimated laser beam L is then deflected via a deflection mirror 23 so as to be directed at a predefined angle of incidence onto a scanner mirror 242 of a scanner unit 24, which is suspended and arranged within the laser cutting head 20. The scanner unit 24 is configured to tilt the scanner mirror 242 about two rotation axes with a relatively small movement interval of at most ±2°, preferably at most ±0.3°, relative to a rest position. The scanner unit 24 also includes an aperture 246, located in front of the scanner mirror 242, which shields the sensitive scanner mechanism from unwanted irradiation. The laser beam L is deflected by the scanner mirror 242 by an angle α of up to 60°, preferably up to 45°, and more preferably up to 30°, i.e., twice the angle of incidence according to the present invention, and directed toward the exit opening 28 of the laser cutting head 20. The deflection may vary slightly depending on the tilt position of the scanner mirror 242. On its way to the exit opening 28, which is preferably configured as a cutting nozzle, the laser beam L is first diverged by a negative lens 25 and then focused by a focusing lens 26 in the direction of the exit opening 28, through which the laser beam L leaves the laser cutting head 20 together with a cutting gas jet (not shown) and is directed as a cutting beam onto the workpiece to be processed.

[0041] By controlled tilting of the scanner mirror 242, the laser beam L can be deflected very quickly in a plane transverse to the exit direction (here the xy plane) at predetermined movement intervals within the exit opening 28, i.e., within the cutting nozzle. A relatively small and fast secondary movement of the laser beam can thus be superimposed on the primary forward movement of the cutting beam during the cutting process. This superimposed secondary oscillatory or scanner movement of the laser beam L can affect the cutting process in a targeted manner, for example, to widen the kerf in place or to change the cutting front slope.

[0042] The plug receptacle of the plug socket and / or the collimation lens 22 at the entrance opening 21 of the laser cutting head 20 may be displaceable transversely to the beam path (here in the X direction). Furthermore, the deflection mirror 23 may be rotationally mounted, thereby exhibiting tilt adjustment. This allows the laser light L to be accurately aligned with the center of the scanner mirror 242. The negative lens 25 may be mounted so as to be displaceable along the beam path (here in the Z direction). By displacing the negative lens 25 in the Z direction, the focal position L of the laser beam can be adjusted. f can be easily changed.

[0043] FIG. 2b shows a schematic diagram of a laser cutting head 20 according to the present invention, which differs from the laser cutting head 20 according to FIG. 2a by the arrangement of the optical elements and therefore by the course of the beam path. The beam path shown in FIG. 2b corresponds to a so-called "delta convolution." The main difference from the Z convolution according to FIG. 2a is that the orientation of the entrance opening 21 is orthogonal (not parallel) to the exit opening 28. A horizontal arrangement of the entrance opening 21 is generally less susceptible to contamination than a vertical arrangement. Due to the horizontal arrangement of the entrance opening 21, the collimation lens 22 is oriented upright in the laser cutting head 20. The upright arrangement of the collimation lens 22 is also less susceptible to contamination, since particles cannot easily accumulate on the lens surface.

[0044] 3a and 3b each show a cross-sectional view of a scanner unit 24 according to the present invention. The scanner unit 24 comprises a scanner mirror 242 laterally mounted on a mirror frame 243. The unit consisting of the scanner mirror 242 and the mirror frame is movably mounted on the frame 241 via a mechanical suspension. For example, the mirror frame 243 can be suspended at four locations evenly distributed around its periphery by solid joints. The drive unit 244 (shown here as a dashed box) is designed to tilt the scanner mirror 242 and the mirror frame 243 at high frequency around at least two rotation axes, preferably oriented orthogonally to each other. The scanner mirror 242, together with the mirror frame 243 and the drive unit 244, can be designed, for example, as described in EP 4000 789 A2, and the magnet pairs of the scanner drive unit can preferably be arranged on the mirror frame 243.

[0045] The scanner unit 24 further includes an aperture 246 having a funnel-shaped inner wall 245, and the inclination angle of the inner wall 245 with respect to the surface normal of the scanner mirror 242 (when the scanner mirror 242 is in its rest position) is at most 30°, preferably at most 22.5°, and more preferably at most 15°. The minimum opening diameter of the aperture 246 on the side facing the scanner mirror 242 is smaller than the aperture of the scanner mirror 242. In this way, the mirror frame 243 and the scanner drive unit 244 can be effectively shielded by the aperture and protected from unnecessary irradiation. A heat dissipation portion 248 in the form of a heat sink 248 is disposed on the rear side of the scanner mirror 242. The aperture 246 and the heat sink 248 are connected by the side frame 241 of the scanner unit 24. An elastic sealing membrane 245 is disposed between the mirror frame 243 and the side frame 241 to protect the drive unit from contamination.

[0046] Aperture 246 and heat sink 248 are spaced apart from scanner mirror 242 and mirror frame 243 by a narrow gap to ensure freedom of movement during tilting. At the same time, the distance between aperture 242 and / or heat sink 248 and scanner mirror 242 and mirror frame 243 is kept as small as possible to ensure efficient heat dissipation. To improve heat dissipation from scanner mirror 242 and / or mirror frame 243, aperture 246 and heat sink 248 are preferably made of steel or another material with good thermal conductivity properties. Furthermore, aperture 246 and heat sink 248 can be actively cooled. The latter is advantageous for natural convection with small air gaps. For this purpose, they can each have one or more cooling channels 247. The cooling channels can be connected to a cooling circuit via cooling fluid connections 249, and liquid or gaseous cooling fluid flows through the cooling channels, thereby removing heat from aperture 246 and / or heat sink 248. [Explanation of symbols]

[0047] 10 Laser Cutting System 12 Laser beam source 14 Cutting gas supply unit 16 Workpiece support 20 Laser Cutting Head 21 Inlet opening 22 Collimation Lens 23 Deflecting mirror 24 Scanner Unit 241 frames 242 Scanner Mirror 243 Mirror Frame 244 Drive Unit 245 Sealing Film 246 Aperture 2462 Inner wall of aperture 247 Cooling Channel 248 Heat Dissipation Element 249 Cooling fluid connection 25 Negative lens 26 Focusing lens 28 Exit opening 30 workpieces 32 Calf L laser beam L f Laser beam focus α Deflection angle relative to the scanner mirror

Claims

1. A laser processing head (20), a scanner unit (24) disposed in a beam path of the laser processing head (20) and having a scanner mirror (242) tiltably mounted about two rotation axes; The scanner unit (24) is arranged in the laser processing head (20) so that the laser beam (L) passing through the beam path is incident on the scanner mirror (242) at an incident angle α of at most 30°, preferably at most 22.5°, and more preferably at most 15° relative to the surface normal of the scanner mirror (242).

2. a collimation unit (22), in particular a collimation lens (22), designed to collimate the divergent laser beam (L) entering said beam path; a deflection unit (23), specifically a deflection mirror (23), designed to deflect the collimated laser beam (L) onto the scanner mirror (242) so that the collimated laser beam (L) is incident on the scanner mirror (242) at the predetermined angle of incidence α; 2. The laser processing head (20) of claim 1, further comprising: a focusing unit (26), specifically a focusing lens (26), designed to receive the laser beam (L) deflected by the scanner unit (24) and focus it on a target object (30).

3. at least the collimation unit (22) is arranged in the laser processing head (20) so as to be displaceable longitudinally and / or transversely with respect to the beam path; and / or 3. The laser processing head (20) according to claim 2, wherein the deflection unit (23) is rotatably mounted in the laser processing head (20).

4. 4. The laser processing head (20) according to claim 2 or 3, further comprising a diverging unit (25), in particular a negative lens (25), arranged between the scanner unit (24) and the focusing unit (26).

5. 5. The laser processing head (20) according to claim 4, wherein the diverging unit (25) is arranged in the laser processing head (20) so as to be longitudinally displaceable with respect to the beam path.

6. The laser processing head (20) according to any one of claims 1 to 5, wherein the scanner unit (24) is arranged suspended within the laser processing head (20).

7. The laser processing head (20) according to any one of claims 2 to 6, wherein the collimation lens (22) is arranged upright in the laser processing head (20).

8. a connection socket for the entrance of the laser beam (L) into the beam path of the laser processing head (20); The laser processing head (20) according to any one of claims 1 to 7, wherein the connection socket is arranged horizontally on the laser processing head (20) or is oriented downwards.

9. 9. The laser processing head (20) according to claim 1, wherein the laser processing head (20) is designed as a laser cutting head (20) and comprises at least one cutting nozzle and a process gas supply, the laser beam (L) being directed together with process gas through the cutting nozzle onto an object (30) to be processed, in particular a plate-shaped or tubular, preferably metallic workpiece (30), and the laser beam (L) being movable through the scanner unit (24) within an outlet opening (28) of the cutting nozzle.

10. A scanner unit (24) for a laser processing head (20) according to any one of claims 1 to 9, comprising: a scanner mirror (242); a drive unit (244) for tilting the scanner mirror about two rotation axes; and an aperture (246) arranged on the reflective side of the scanner mirror (242), wherein the aperture (246) has a funnel-shaped inner wall (2462) and the inclination angle of the inner wall (2462) is at most 30°, preferably at most 22.5°, and more preferably at most 15° with respect to the surface normal of the scanner mirror (242).

11. The scanner unit (24) of claim 10, wherein the aperture (246) has an aperture opening that is smaller than the aperture of the scanner mirror (242).

12. Scanner unit (24) according to claim 10 or 11, wherein the scanner mirror (242) comprises a mirror substrate made of a transparent material, in particular quartz glass.

13. A scanner unit (24) as described in any one of claims 10 to 12, further comprising a heat dissipation element (248) disposed on a rear side of the scanner mirror (242), the heat dissipation element (248) being spaced apart from the rear side of the scanner mirror (242) by a gap just large enough to ensure that the scanner mirror (242) can tilt freely about the rotation axis.

14. Scanner unit (24) according to any one of claims 10 to 13, wherein the aperture (246) and / or the heat dissipation element (248) can be actively cooled.

15. A laser processing system (10) comprising at least: a laser beam source (12) for providing a laser beam (L); The laser processing head (20) according to any one of claims 1 to 9, the laser beam (L) has a power of at least 0.3 kW; and A laser processing system (10) in which the beam parameter product of the laser beam (L) is at most 4 mm*mrad, preferably at most 2.5 mm*mrad.

16. A method for laser beam cutting, comprising: directing a laser processing beam (L) together with a process gas through a cutting nozzle of a laser cutting head (20) onto a surface of a workpiece (30) to be processed; a secondary motion of the laser processing beam (L) within the cutting nozzle is superimposed on a primary forward motion of the laser cutting head (20); and The laser processing beam (L) for generating the secondary motion within the laser cutting head (20) is directed onto a scanner mirror (242) that is tiltable about two rotation axes such that the angle of incidence of the laser processing beam (L) on the scanner mirror (242) is at most 30°, preferably at most 22.5°, and more preferably at most 15° with respect to a surface normal of the scanner mirror (242).

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