Laser processing head and method for monitoring a processing operation on a workpiece

Abstract

The invention relates to a laser processing head for monitoring a processing operation on a workpiece, comprising at least one optical element and at least one optical sensor device. The optical element is designed to reflect process radiation emanating from the workpiece and irradiated into the laser processing head toward the optical sensor device. The optical element acts as a curved mirror for the process radiation. The optical sensor device is designed to measure the process radiation in order to monitor the processing operation on the workpiece.

Description

[0001] Precitec GmbH & Co. KG, Case: PR 979 WO

[0002] Laser processing head and method for monitoring the processing of a workpiece

[0003] The present disclosure relates to a laser processing head for monitoring the processing of a workpiece. The invention further relates to a method for monitoring the processing of a workpiece using a laser processing head.

[0004] background

[0005] To process a workpiece, a laser beam is directed onto its surface. The laser beam heats an area of ​​the workpiece so intensely that a portion of it melts and / or vaporizes. If the workpiece is to be cut, the laser beam is directed onto an area of ​​the workpiece until it penetrates the workpiece, i.e., until a hole has formed in the workpiece through which the laser beam can pass. The laser beam is then moved along a path on the workpiece to create a cut. During processing, particularly due to the heating of the workpiece, the workpiece emits process radiation. Additionally, laser radiation can be reflected or backscattered by the workpiece. The process radiation and the reflected or backscattered laser radiation can be referred to as process radiation.The laser processing process can be monitored based on the process radiation.

[0006] Especially with thicker workpieces, the beam path of the process radiation in and / or outside the laser processing head can be largely or completely superimposed on the beam path of the processing laser. It is known to arrange a beam splitter, which is transmissive for the processing laser and non-transmissive for at least wavelength ranges of the process radiation, in the laser processing head to couple out the process radiation located in the beam path of the processing laser and reflect it to a sensor. However, this requires the beam splitter to be arranged as an additional optical element in the beam path of the processing laser, which increases the design complexity and can alter the optical properties of the processing laser beam, since the processing laser beam must pass through the beam splitter to be directed onto the workpiece. Precitec GmbH & Co. KG, Case: PR 979 WO

[0007] Disclosure of the invention

[0008] One objective of the present disclosure is to provide monitoring of laser processing with minimal design effort, particularly when the process radiation in the laser processing head is at least partially or completely superimposed by the processing laser beam. A further objective of the present disclosure is to provide monitoring of laser processing with minimal interference with the processing laser beam, particularly when the process radiation in the laser processing head is at least partially or completely superimposed by the processing laser beam.

[0009] At least one of the problems is solved by the combination of features in the independent claims. Preferred embodiments are defined in the dependent claims and the description.

[0010] A laser processing head for monitoring the processing of a workpiece is disclosed. The laser processing head comprises at least one optical element and at least one optical sensor device. The optical element is configured to reflect process radiation emanating from the workpiece and / or directed into the laser processing head to the optical sensor device. The optical element acts as a curved mirror for the process radiation. The optical sensor device is configured to measure the process radiation in order to monitor the processing of the workpiece.

[0011] A method for monitoring the processing of a workpiece using a laser processing head is disclosed. The method comprises the following steps: shining a processing laser beam (hereinafter also referred to as "laser beam") from the laser processing head onto the workpiece, causing the workpiece to heat up and generate process radiation; shining the process radiation into the laser processing head; reflecting the process radiation by at least one optical element in the laser processing head to at least one optical sensor device, wherein the optical element acts as a curved mirror for the process radiation; and monitoring the laser processing based on a measurement of the process radiation using the optical sensor device. Precitec GmbH & Co. KG, Case: PR 979 WO

[0012] Each method disclosed herein can be carried out by each laser processing head disclosed herein. In particular, the laser processing head can include a control device configured to perform one or more of the process steps disclosed herein.

[0013] Each laser processing head disclosed herein can be used in each of the methods disclosed herein.

[0014] As the workpiece thickness increases, the proportion of process radiation entering the laser processing head and not being superimposed on the processing laser beam decreases drastically. This is due to the limited opening of, for example, a kerf and / or a through-hole. Through reflection of the process radiation by the optical element, which acts as a curved mirror for the process radiation, the process radiation can be "fanned out" or diverged. This allows it to pass through the sensor device after a relatively short distance, thus eliminating the need for a beam splitter in the processing laser beam path. As a result, the laser processing head design is more compact and less complex.Furthermore, an additional optical element in the beam path of the processing laser is avoided, which could interact with the processing laser and change the properties of the processing laser or reflect / absorb the processing laser.

[0015] Even with thinner workpieces, fanning out the process radiation can enable or improve the detection of the process radiation near the optical axis of the processing laser (especially the detection of process radiation incident coaxially into the head).

[0016] The processing of the workpiece using the laser beam can involve piercing, piercing, and / or cutting the workpiece. It can also involve welding or brazing. At least two workpieces can be welded or brazed together. Precitec GmbH & Co. KG, Case: PR 979 WO

[0017] The laser processing head can be a laser cutting head, a laser welding head, or a laser soldering head.

[0018] The workpiece can be a metallic workpiece, or consist of metal or comprise metal.

[0019] The process radiation can include process emissions and reflected or scattered laser radiation.

[0020] Process emission occurs when the workpiece is heated by the laser beam. This process emission can include radiation in the visible wavelength range, i.e., between 350 nm and 850 nm, or between 390 nm and 850 nm, or between 380 nm and 800 nm, for example, radiation from a plasma generated during processing. Process emission can also include radiation in the infrared wavelength range, particularly thermal radiation. Furthermore, the process emission can include a component that matches the wavelength of the laser radiation. This component of the process emission cannot be detected by the optical sensors if the optical sensors are insensitive to the wavelength of the processing laser beam. Preferably, the optical sensors are also sensitive to the wavelength of the processing laser beam.

[0021] Additionally, radiation from the laser beam can be backscattered or reflected by the workpiece and enter the laser processing head. This backscattered or reflected radiation cannot be detected by the optical sensors if the optical sensors are insensitive to the wavelength of the processing laser beam. Preferably, the optical sensors are (also) sensitive to the wavelength of the processing laser beam.

[0022] The process radiation can radiate from the workpiece towards the laser processing head. This allows the process radiation to enter the laser processing head, particularly through an exit or nozzle opening for the laser beam directed towards the workpiece. Precitec GmbH & Co. KG, Case: PR 979 WO

[0023] In the laser processing head, the process radiation can be at least partially, preferably at least 70%, at least 90%, or substantially completely, superimposed on the processing laser beam before the process radiation is reflected by the optical element. This superposition can be considered in the cross-section of the process radiation or the processing laser beam. That is, before the process radiation is reflected by the optical element, the beam path of the process radiation in the laser processing head can lie at least partially, preferably at least 70%, at least 90%, or substantially completely, within the beam path of the processing laser beam.

[0024] The process radiation is reflected within the laser processing head by means of the optical element. This reflection can alter the direction of propagation, resulting in a vector component parallel to the laser beam propagation direction and / or a vector component directed radially outward with respect to the laser beam axis. In particular, the process radiation can diverge towards the workpiece after reflection. Therefore, reflecting the process radiation via the optical element can modify its divergence property.

[0025] The optical element can function as a convex mirror or a concave mirror.

[0026] The optical element can have at least one curved surface from which the process radiation is reflected. The curved surface can be concave or convex with respect to the process radiation incident on the optical element or the curved surface.

[0027] The optical element can have at least one additional surface from which the process radiation can be reflected. The process radiation can be reflected by this additional surface to the optical sensor device. This additional surface can be curved or act as a curved mirror for the process radiation. The additional surface can be concave or convex with respect to the process radiation incident on the optical element or the additional surface. Precitec GmbH & Co. KG, Case: PR 979 WO

[0028] The machining of the workpiece is monitored based on the measurement of process radiation using the optical sensor device. The sensor device can be configured to detect a sensor signal. For example, the intensity of the process radiation at one or more wavelengths or across one or more wavelength ranges can be detected as the sensor signal. Depending on whether the sensor signal is above or below a threshold value, the machining of the workpiece can be evaluated as "OK" or "not OK".

[0029] Monitoring the machining of the workpiece can also involve comparing a sensor signal profile with a predefined sensor signal profile. For this purpose, the sensor signal profile can be recorded and / or used over a defined period.

[0030] Based on the measurement of process radiation, the processing can be controlled or regulated.

[0031] The optical element can be positioned in the optical path or beam path of the processing laser beam. The processing laser beam can pass through the optical element before exiting the laser processing head towards the workpiece. The optical path of the processing laser beam can be defined by optical elements, for example, at least by collimation optics and focusing optics for the processing laser beam.

[0032] The optical element can be an optical element that contributes to the beam shaping of the processing laser beam.

[0033] The optical element can be part of a collimation optic and / or a focusing optic. The optical element can include or be a collimation optic, a focusing optic, or a zoom lens. The optical element can be or include a lens. The collimation optic and / or the focusing optic can be or include a lens or a lens group. The optical element, the collimation optic, and / or the focusing optic can be movable or fixed within the laser processing head. Precitec GmbH & Co. KG, Case: PR 979 WO

[0034] If the optical element by which the process radiation is reflected towards the sensor device is an optical element that contributes to or is used to shape the processing laser beam, no additional optical element is necessary to reflect the process radiation to the sensor device.

[0035] The laser processing head can include at least one additional optical element. This additional optical element can be configured to reflect the process radiation to the optical sensor device.

[0036] The additional optical element can have a curved surface, for example, a concave or convex surface, from which the process radiation is reflected towards the sensor device. Alternatively, the additional optical element can have a flat or planar surface from which the process radiation is reflected towards the sensor device. Thus, the sensor device can detect process radiation that has been reflected by different or multiple optical elements. Multiple reflections of the process radiation from several optical elements before it reaches the sensor device are also possible.

[0037] The additional optical element can be a collimating optic, a focusing optic, and / or a protective glass. The protective glass can be positioned (in the direction of propagation of the processing laser beam in the laser processing head) in front of a collimating optic or after a focusing optic.

[0038] The workpiece can have a thickness of at least 20 mm, preferably at least 25 mm, preferably at least 30 mm. The thickness of the workpiece can be defined parallel to the direction of incidence of the processing laser beam on the workpiece, i.e., along the beam axis of the laser beam.

[0039] The sensor device can comprise a variety of optical sensors, for example, at least two, preferably at least five, preferably at least ten, preferably at least fifteen, preferably at least twenty, preferably at least thirty, preferably at least forty, preferably at least fifty. Precitec GmbH & Co. KG, Case: PR 979 WO

[0040] The optical sensors may include or be semiconductor optical sensors. At least 50%, at least 70%, at least 90%, or all of the optical sensors may be semiconductor optical sensors. A semiconductor optical sensor may include at least one semiconductor material or element used to detect radiation.

[0041] The optical sensors can be insensitive to the wavelength of the processing laser beam. "Insensitive" can mean that radiation with a wavelength to which an optical sensor is insensitive is not detected, or only barely detected, or that when this radiation strikes the optical sensor, no or only a weak measurement signal is generated. The weak measurement signal can be at least one order of magnitude (a factor of 10), preferably at least two orders of magnitude (a factor of 100), smaller than a measurement signal for radiation with a wavelength to which the sensor has the greatest sensitivity. In other words, a measurement signal from a sensor for radiation with an insensitive wavelength can be at most 0.1 or at most 0.01 of a measurement signal from the sensor for radiation with a wavelength to which the sensor has the greatest sensitivity.Thus, the optical sensors can have a measuring range that excludes the wavelength of the processing laser beam.

[0042] Preferably, the optical semiconductor sensors are compound semiconductor optical sensors. A compound semiconductor sensor can comprise at least one compound semiconductor material used to detect radiation. The compound semiconductor material can comprise at least two different elements or at least three different elements. The compound semiconductor material can be binary or ternary. The optical compound semiconductor optical sensors can be III-V compound semiconductor sensors or II-VI compound semiconductor sensors. The optical semiconductor optical sensors can be GaAsP sensors.

[0043] The optical sensors can be configured to generate a common sensor signal. Based on this signal, the workpiece machining process can be monitored. Based on this signal, the workpiece machining process can be controlled or regulated. Precitec GmbH & Co. KG, Case: PR 979 WO

[0044] The optical element can be configured to reflect the process radiation directly to the optical sensor device. This means that no further reflection of the process radiation can occur between the optical element and the sensor device. The process radiation reflected by the optical element can then be detected by the sensor device.

[0045] The sensor device can be arranged in a ring shape around the optical path of the processing laser beam.

[0046] The optical sensors can be arranged on a ring surface of the sensor device. The ring surface can be flat. The optical sensors can be evenly or regularly distributed along or on the ring surface, or irregularly distributed. The sensor device can be rotationally symmetrical. The sensor device can be arranged coaxially with the optical axis of the focusing optics.

[0047] The sensor device may have a recess. The recess may be formed essentially in the center of the sensor device. The recess may be (completely) surrounded by the annular surface of the sensor device. The sensor device may be arranged in the laser processing head such that the processing laser beam passes through the recess during processing of the workpiece. The sensor device may at least partially, and in particular completely, surround the optical path of the laser beam.

[0048] In general, a recess here can be described as a cutout, hole, opening or passage.

[0049] The sensor device can have an inner diameter of at least 5 mm, preferably at least 10 mm, preferably at least 20 mm, preferably at least 25 mm. The inner diameter of the sensor device can be at most 150 mm, preferably at most 100 mm, preferably at most 50 mm, preferably at most 40 mm, preferably at most 35 mm. The inner diameter of the sensor device can correspond to the diameter of the recess. Precitec GmbH & Co. KG, Case: PR 979 WO

[0050] The sensor device can have a radiation-sensitive surface. The radiation-sensitive surface of the sensor device can correspond to radiation-sensitive surfaces of the optical sensors. That is, the radiation-sensitive surfaces of the optical sensors can (together) form the radiation-sensitive surface of the sensor device.

[0051] The radiation-sensitive surface of the sensor device can face the optical element. In particular, the radiation-sensitive surface of the sensor device can face the collimation optics. The radiation-sensitive surface of the sensor device and the optical element or the collimation optics can be opposite each other. The radiation-sensitive surface of the sensor device can face or be opposite an entry point of the processing laser into the laser processing head. The radiation-sensitive surface of the sensor device can face away from or not be opposite an exit point of the processing laser from the laser processing head.

[0052] The radiation-sensitive surface of the sensor device can be facing away from or not opposite the focusing optics.

[0053] The laser processing head can include several sensor devices, for example, at least two or at least three sensor devices. The sensor devices can be ring-shaped. The sensor devices can be arranged concentrically around the optical path of the processing laser.

[0054] The optical element can be configured to reflect the process radiation to the optical sensor device via at least one or exactly one mirror surface. This means the process radiation cannot be reflected directly from the optical element to the optical sensor device. The optical element can reflect the process radiation to the mirror surface, and the mirror surface can then reflect the process radiation further to the sensor device.

[0055] The mirror surface can be annular. The mirror surface can have a recess. The recess can be located essentially in the center of the mirror surface (Precitec GmbH & Co. KG, Case: PR 979 WO). The recess can be (completely) surrounded by the annular surface of the mirror surface. The mirror surface can be arranged in the laser processing head such that the processing laser beam passes through the recess during processing of the workpiece. The mirror surface can at least partially, and in particular completely, surround the optical path of the laser beam.

[0056] The mirror surface can have an inner diameter of at least 5 mm, preferably at least 10 mm, preferably at least 20 mm, preferably at least 25 mm. The inner diameter of the mirror surface can be at most 150 mm, preferably at most 100 mm, preferably at most 50 mm, preferably at most 40 mm, preferably at most 35 mm. The inner diameter of the mirror surface can correspond to the diameter of the recess.

[0057] At least one mirror surface can be arranged to reflect or focus the process radiation onto a point or area, in particular on the sensor device.

[0058] At least one mirror surface can face the optical element. In particular, the mirror surface faces the collimation optics. The mirror surface and the optical element or collimation optics can be opposite each other. The mirror surface can face or be opposite an entry point of the processing laser into the laser processing head. The mirror surface can face away from or not be opposite an exit point of the processing laser from the laser processing head.

[0059] At least one mirror surface can be turned away from or not opposite the focusing optics.

[0060] At least one mirror surface can be positioned (in the direction of propagation of the processing laser beam) between the collimation optics and the focusing optics. Precitec GmbH & Co. KG, Case: PR 979 WO

[0061] The radiation-sensitive surface of the sensor device can face the mirror surface and / or face away from the optical element. In particular, the radiation-sensitive surface of the sensor device can face away from the collimation optics. The radiation-sensitive surface of the sensor device and the optical element or the collimation optics cannot be opposite each other. The radiation-sensitive surface of the sensor device can face away from, or not be opposite, the entry point of the processing laser into the laser processing head. The radiation-sensitive surface of the sensor device can face or be opposite an exit point of the processing laser from the laser processing head.

[0062] The radiation-sensitive surface of the sensor device can be facing or opposite the focusing optics.

[0063] The sensor device can be arranged between a collimation optic and a focusing optic with respect to the propagation direction of the processing laser beam.

[0064] No optical element can be placed in the beam path of the processing laser between the collimation optics and the focusing optics, where the process radiation is reflected.

[0065] Brief description of the drawings

[0066] The invention is described in detail below with reference to figures.

[0067] Fig. 1 shows a laser processing head 100 according to the state of the art;

[0068] Fig. 2 shows a laser processing head 1 according to one embodiment; and Fig. 3 shows a laser processing head 1 according to one embodiment.

[0069] Detailed description of the drawings

[0070] Fig. 1 shows a state-of-the-art laser processing head 100. A processing laser beam 5 is directed onto a workpiece 3 by the laser processing head 100. Precitec GmbH & Co. KG, Case: PR 979 WO

[0071] The workpiece 3 has a relatively large thickness t, for example a thickness t of over 20 mm or over 25 mm.

[0072] When the processing laser beam 5 is directed onto the workpiece 3, it heats up and emits process radiation. A portion of the processing laser beam 5 can also be reflected or backscattered by the workpiece 3. The process radiation and the reflected or backscattered processing laser radiation can be referred to as process radiation 7. The process radiation 7 enters the laser processing head 100. Due to the relatively large thickness t of the workpiece 3, the process radiation 7 exits the interior of the workpiece 3 at a relatively small angle. As a result, the process radiation is (practically) completely superimposed on the processing laser beam 5.

[0073] The laser processing head 100 includes a beam splitter 23, which is arranged in the beam path of the processing laser beam 5 within the laser processing head 100 and is transmissive to the processing laser beam 5. The process radiation 7 is reflected by the beam splitter 23 towards a radiation-sensitive surface 25S of a sensor 25 of a sensor device 20. That is, the process radiation 7 is to be coupled out of the beam path of the processing laser beam 5.

[0074] The beam splitter 23 makes the laser processing head 100 structurally complex and complicates a compact design. Furthermore, an additional optical element is present in the beam path of the processing laser beam 5, which can undesirably alter the properties of the processing laser beam 5 and reflect / absorb a (small) portion of the processing laser beam 5.

[0075] Fig. 2 shows a laser processing head 1 according to one embodiment of the invention. The laser processing head 1 can comprise a collimation optic 12 and a focusing optic 14. The laser processing head 1 comprises at least one optical sensor device 21.

[0076] A laser beam 5 (also referred to as a processing laser beam) can be coupled into the laser processing head 1 from a laser source (not shown). Precitec GmbH & Co. KG, Case: PR 979 WO

[0077] The laser source can be designed as a single-mode laser, a solid-state laser, or a fiber laser.

[0078] The laser beam 5 generated by the laser source can be transmitted from the laser source to the laser processing head 1 via an optical fiber. The laser beam 5 can be coupled into the laser processing head 1 via a fiber connector. The beam can enter the laser processing head 1 divergently via a fiber end 4.

[0079] The collimation optics 12 can be arranged and designed in the laser processing head 1 such that the laser beam 5 entering the laser processing head 1 at a divergent angle is collimated.

[0080] The collimation optics 12 can comprise at least one lens or two or more lenses. The distance between the two or more lenses can be adjustable, in particular by an electric motor 13. The collimation optics 12 can define an optical axis 2.

[0081] The focusing optics 14 can be arranged and designed in the laser processing head 1 such that the collimated laser beam 5 is focused.

[0082] The focusing optics 14 can comprise at least one lens or two or more lenses. The distance between the two or more lenses can be adjustable, in particular by an electric motor. An optical axis 2 can be defined by the focusing optics 14. In particular, the optical axis 2 is defined by the collimating optics 12 and the focusing optics 14. The focusing optics 14 can be an F-theta lens.

[0083] The laser processing head 1 can comprise at least one protective glass 10, 11. Preferably, the laser processing head 1 comprises at least one protective glass 10, which is arranged (in the propagation direction of the laser beam 5) in front of the collimation optics 12, and one protective glass 11, which is arranged (in the propagation direction of the laser beam 5) after the focusing optics 14.

[0084] The focused laser beam 5 can be emitted from the laser processing head 1 via an exit aperture and directed onto a workpiece 3 to process the workpiece. Precitec GmbH & Co. KG, Case: PR 979 WO

[0085] 3. Workpiece 3 can be a workpiece with a relatively large thickness t. The thickness t can be at least 20 mm or at least 25 mm.

[0086] For example, workpiece 3 can be cut. The laser beam 5 can be directed onto a surface of workpiece 3 until a section of it melts. The laser beam 5 can be directed onto this section of workpiece 3 until it penetrates the workpiece (so-called piercing). This creates a hole in workpiece 3 through which the laser beam 5 can pass. The laser beam can then be moved along a machining path to create a cut in workpiece 3. Similarly, workpiece 3 can be welded or soldered. In particular, two workpieces 3 can be welded or soldered together.

[0087] When the workpiece 3 is pierced, a kerf is formed. The kerf can have a top surface 31 and a bottom surface 32. The top surface 31 can be closer to the laser processing head 1 than the bottom surface 32.

[0088] The laser processing head 1 can be a laser beam cutting head, a laser beam welding head or a laser beam soldering head.

[0089] The process radiation 7 can originate from the workpiece 3. The process radiation 7 can comprise radiation in various wavelength ranges, e.g., in the visible wavelength range, the infrared wavelength range, the ultraviolet wavelength range, and the wavelength range of laser radiation. The process radiation 7 can radiate from the workpiece 3 into the laser processing head 1, particularly via the exit aperture. Radiation from the laser beam 5 that is backscattered or reflected from the workpiece 3 and may be part of the process radiation 7 is not emitted by the workpiece 3. However, the workpiece 3 can also emit radiation with the wavelength of the laser beam 5.

[0090] When thick workpieces 3 are processed, a large part of the process radiation 7 can be superimposed on the laser beam 5. This means that a large part of the beam path of the process radiation is obstructed. Precitec GmbH & Co. KG, Case: PR 979 WO

[0091] 7 or the entire beam path of the process radiation 7 can be located in the beam path of the processing laser 5. This is particularly true in the laser processing head 1.

[0092] The process radiation 7 is reflected by at least one optical element, for example, the collimation optics 12 and / or the focusing optics 14. The optical element acts as a curved mirror. The optical element can have at least one curved surface, so that it acts as a curved mirror.

[0093] The reflection of the process radiation 7 causes its path to spread out. The spreading of the process radiation 7 per unit path length can differ after reflection compared to before reflection. In particular, the spreading of the process radiation per unit path length is greater after reflection than before reflection. In the figures, the process radiation after reflection is labeled with the reference symbol 8.

[0094] The figures show the reflection of the process radiation 7 only at the collimation optics 12. However, reflection can occur at other optical elements. In particular, reflections of the process radiation 7 can occur at more than one optical element. For example, the process radiation 7 can occur at at least one optical element acting as a curved mirror and at least one other optical element that does not act as a curved mirror. The process radiation 7 can also occur at multiple surfaces of the collimation optics 12 or another optical element. That is, the process radiation 7 can be reflected from more than one surface of an optical element to the sensor device. The surfaces can be curved.

[0095] The reflected process radiation 8 radiates towards the sensor device 21. The sensor device 21 can have at least one radiation-sensitive surface 21S. The reflected process radiation 8 can strike the radiation-sensitive surface 21S and be measured there. Precitec GmbH & Co. KG, Case: PR 979 WO

[0096] The radiation-sensitive area 21 S can be formed by radiation-sensitive areas of several optical sensors, for example at least five or at least ten optical sensors.

[0097] The radiation-sensitive surface 21S can be arranged (in the direction of propagation of the laser beam 5) between the collimation optics 12 and the focusing optics 14. The radiation-sensitive surface 21S can face the collimation optics 12. At least at the optical element that acts as a curved mirror, the reflection of the process radiation 7 can occur directly. That is, no further optical element can be arranged between the collimation optics 12 and the radiation-sensitive surface 21S at which the reflected process radiation 8 is (again) reflected.

[0098] The sensor device 21 can be ring-shaped. The ring-shaped sensor device 21 can be arranged around the optical path of the laser beam 5, in particular completely enclosing or surrounding it.

[0099] The sensor device 21 may have a recess. The laser beam 5 can pass through the recess when the workpiece 3 is being processed.

[0100] Preferably, the sensor device 21 is arranged closer to the focusing optics 14 than to the collimating optics 14. The distance between the sensor device 21 and the focusing optics 14 can be smaller than the distance between the sensor device 21 and the collimating optics 12.

[0101] Fig. 3 shows a laser processing head 1 according to one embodiment of the invention. The components and properties of the laser processing head 1 described with reference to Fig. 2 are also valid for the laser processing head 1 of Fig. 3 and are not repeated here.

[0102] In Fig. 3, the process radiation 7 in the laser processing head 1 can be reflected by the optical element, which acts as a curved mirror, to a mirror surface 25. The reflected process radiation 8 can be reflected by the mirror surface 25 to a radiation-sensitive surface 22S of the sensor device 22. The sensor device 22 can measure the reflected process radiation 8.

[0103] The mirror surface 25 can be ring-shaped. The ring-shaped mirror surface 25 can be arranged around the optical path of the laser beam 5, in particular completely enclosing or surrounding it.

[0104] The mirror surface 25 may have a recess. The laser beam 5 can pass through the recess when the workpiece 3 is being processed.

[0105] Preferably, the mirror surface 25 is arranged closer to the focusing optics 14 than to the collimating optics 14. The distance between the mirror surface 25 and the focusing optics 14 can be smaller than the distance between the mirror surface 25 and the collimating optics 12.

[0106] The sensor device 22 can be arranged (in the direction of propagation of the laser beam 5) between the collimation optics 12 and the focusing optics 14. The sensor device 22 is preferably arranged closer to the focusing optics 14 than to the collimation optics 12. The distance between the sensor device 22 and the focusing optics 14 can be smaller than the distance between the sensor device 22 and the collimation optics 12.

[0107] The mirror surface 25 can face the collimation optics 12. The mirror surface 25 can face away from the focusing optics 14. The radiation-sensitive surface 22S of the sensor device 22 can face away from the collimation optics 12. The radiation-sensitive surface 22S of the sensor device 22 can face away from the focusing optics 14.

[0108] The mirror surface 25 can reflect the reflected process radiation 8 onto a point or area of ​​the radiation-sensitive surface 22S.

[0109] By reflecting the process radiation 7 in the laser processing head 1 off an optical element acting as a curved mirror, it is possible to couple out process radiation that is located close to the optical axis of the laser beam 5. An additional optical element, e.g., a beam splitter, can be avoided. This makes the laser processing head compact and minimizes interference with the laser beam.

Claims

Precitec GmbH & Co. KG, Case: PR 979 WO Patent claims 1. Laser processing head (1) for monitoring the processing of a workpiece (3), the laser processing head (1) comprising: - at least one optical element (12, 14); and - at least one optical sensor device (21, 22), wherein the optical element (12, 14) is configured to reflect process radiation (7, 8) entering the laser processing head (1) from the workpiece (3) to the optical sensor device (21, 22), wherein the optical element (12, 14) acts as a curved mirror for the process radiation (7, 8); and wherein the optical sensor device (21, 22) is configured to measure the process radiation (7, 8) in order to monitor the processing of the workpiece (3).

2. Laser processing head according to claim 1, wherein the optical element (12, 14) is arranged in an optical path of the processing laser beam (5) and / or wherein the optical element (12, 14) is transmissive for the processing laser beam (5).

3. Laser processing head according to one of the preceding claims, wherein the optical element (12, 14) is part of a collimation optic (12) and / or a focusing optic (14).

4. Laser processing head according to one of the preceding claims, wherein the laser processing head (1) comprises at least one further optical element (10, 11) which is configured to reflect the process radiation (7, 8) to the optical sensor device (21, 22).

5. Laser processing head according to one of the preceding claims, wherein the workpiece (3) has a thickness (t) of at least 20 mm, preferably at least 25 mm, preferably at least 30 mm.

6. Laser processing head according to one of the preceding claims, wherein the sensor device (21, 22) comprises at least two, preferably at least five, preferably at least ten, optical sensors, in particular optical semiconductor sensors. Precitec GmbH & Co. KG, Case: PR 979 WO 7. Laser processing head according to one of the preceding claims, wherein the optical element (12, 14) is configured to reflect the process radiation (7, 8) directly to the optical sensor device (21).

8. Laser processing head according to claim 7, wherein the sensor device (21) is arranged in a ring shape around the optical path of the processing laser beam (5).

9. Laser processing head according to claim 7 or 8, wherein a radiation-sensitive surface (21S) of the sensor device (21) faces the optical element (12, 14), in particular a collimation optic (12), and / or a radiation-sensitive surface (22S) of the sensor device (22) faces away from a focusing optic (14).

10. Laser processing head according to one of claims 1 to 6, wherein the optical element (12, 14) is configured to reflect the process radiation (7, 8) via at least one mirror surface (25), in particular at least one annular mirror surface (25), to the optical sensor device (22).

11. Laser processing head according to claim 10, wherein the at least one mirror surface (25) is arranged to reflect the process radiation (7, 8) onto a point or area.

12. Laser processing head according to claim 10 or 11, wherein the at least one mirror surface (25) faces the optical element (12, 14), in particular a collimation optic (12) and / or wherein the at least one mirror surface (25) faces away from a focusing optic (14).

13. Laser processing head according to one of claims 10 to 12, wherein a radiation-sensitive area (22S) of the sensor device (22) is facing away from the optical element (12, 14), in particular a collimation optic (12), and / or a radiation-sensitive area (22S) of the sensor device (22) is facing a focusing optic (14). Precitec GmbH & Co. KG, Case: PR 979 WO 14. Laser processing head according to one of the preceding claims, wherein the sensor device (21, 22) is arranged between a collimation optic (12) and a focusing optic (14) with respect to the propagation direction of the processing laser beam (5).

15. Method for monitoring the processing of a workpiece (3) using a laser processing head (1), the method comprising the steps: - Direction of a processing laser beam (5) from the laser processing head (1) onto the workpiece (3), so that the workpiece (3) is heated and process radiation (7, 8) occurs; - Projection of the process radiation (7, 8) into the laser processing head (1); - Reflecting the process radiation (7, 8) at at least one optical element (12, 14) in the laser processing head (1) to at least one optical sensor device (21, 22), wherein the optical element (12, 14) acts as a curved mirror for the process radiation (7, 8); and - Monitoring of the laser processing based on a measurement of the process radiation (7, 8) using the optical sensor device (21, 22).

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