Laser machining head

Abstract

The invention relates to a laser machining head for machining a workpiece by means of a laser machining beam, said laser machining head comprising: a scanning device for directing the laser machining beam onto a plurality of positions on the workpiece; a machining beam optical system for adjusting a focus position of the laser machining beam and for focusing the laser machining beam, the machining beam optical system being arranged between an entry port for the laser machining beam and the scanning device; a sensor assembly for detecting process light using at least one sensor; a decoupling optical system for decoupling process light to the sensor assembly, the decoupling optical system being arranged between the machining beam optical system and the scanning device; and a process light optical system for adjusting a focus position of the process light with respect to the sensor, the process light optical system being arranged between the decoupling optical system and the sensor assembly and comprising a variable lens with an adjustable focal length.

Description

[0001] Precitec GmbH & Co. KG

[0002] Laser processing head

[0003] The present invention relates to a scanner laser processing head for processing a workpiece by means of a laser processing beam with a sensor arrangement for process observation or monitoring.

[0004] 5

[0005] background

[0006] With a laser processing head for material processing with lasers, in particular for processing a (metallic) workpiece using a laser processing beam, the laser processing beam emerging from a laser light source or one end of a laser guide fiber is focused onto the workpiece to be processed using processing beam optics. The processing can include, for example, laser cutting, soldering, ablation, cleaning, or welding. The laser processing head can be a laser cutting head or a laser welding head. 5

[0007] To ensure the quality of processing, it is desirable to continuously monitor a laser processing process by detecting process light using a sensor arrangement. The detection of process light can, for example, comprise detecting a portion of the laser processing beam that is scattered and / or reflected back from a surface of the workpiece and / or detecting process emissions using photodiodes. Process emissions include, for example, plasma radiation generated during processing, process emissions in the infrared range of light (e.g., thermal radiation), or process emissions in the visible range of light. The detection of process light can also comprise capturing an image of the workpiece surface to be processed or being processed using a camera.

[0008] When using such sensor arrangements for process monitoring on a scanner laser processing head, i.e. a laser processing head with a scanning device for directing the laser processing beam to a variety of positions on the workpiece, a problem arises in the dependence of the signals on the position in the scan field. While in a scanner laser processing head with an F-Theta lens this problem is partially compensated for by the process light emanating from the processing point (tool center point, TCP) being collimated again via the F-Theta lens5, this compensating effect is generally not present in so-called pre-focus systems. Scanner laser processing heads with a pre-focus system (pre-focus scanner laser processing heads), in which the focusing optics for the laser processing beam are arranged in front of the scanning device orin which the focusing of the laser processing beam is completed before the scanning device, are generally lighter, more compact, and less expensive, and therefore more flexible to handle. However, in a scanner laser processing head with a pre-focus system (pre-focus scanner laser processing head), the above-mentioned problem is exacerbated by the fact that the image of the process light fluctuates greatly depending on the deflection of the scanning device, i.e., depending on the scan field position, in particular due to the variation in the image plane distance. In other words, depending on the scan field position, the optical path length for the process light used for process monitoring can vary greatly, whereby the divergence of the process light leads to strong signal fluctuations within the scan field.

[0009] There are process monitoring systems for prefocus optics in which the process light is collimated using a converging lens with a fixed focal length. This approach has the disadvantage that the focal length remains constant across the entire scan field, meaning the process light is only actually collimated at specific scan field positions for the sensor array.

[0010] Especially for a scanner laser processing head with a so-called pre-focus system, it is therefore important to be able to adapt the collimation or focus position of the laser processing beam as well as the collimation or focus position of the process light to different processing planes, especially with uneven workpiece surfaces, and to different processing or scan field positions.

[0011] EP 3 532 238 B1 describes a scanner laser processing head with a prefocus system comprising a camera and an optical device arranged in front of the camera with a reciprocating lens for changing a focal length for the detection beams.

[0012] However, mechanically adjusting or shifting optical elements in the laser processing head is relatively slow, complex to construct, and costly. Mechanically adjusting optical elements also requires sufficient space within the laser processing head to accommodate the necessary components. Furthermore, with moving elements in the optical chamber of the laser processing head, wear caused by movement can become a problem.

[0013] Summary of the invention

[0014] It is therefore an object of the present invention to provide a scanner laser processing head, in particular a prefocus scanner laser processing head, with a sensor arrangement that can be used for various processing planes and positions. In particular, it is an object of the present invention to provide a scanner laser processing head, in particular a prefocus scanner laser processing head, with a sensor arrangement that can reduce or compensate for a variation in the image plane distance depending on a scan field position.

[0015] Furthermore, it is an object of the present invention to provide a scanner laser processing head, in particular a pre-focus scanner laser processing head, with a sensor arrangement, wherein a focus position or collimation of process light with respect to the sensor arrangement can be adjusted quickly and / or automatically.

[0016] A further object of the present invention is to provide a scanner laser processing head, in particular a pre-focus scanner laser processing head, with a sensor arrangement, wherein a collimation of the process light and / or a focusing or adjustment of the focus position of the process light for the entire scan field can be achieved.

[0017] Furthermore, it is an object of the present invention to provide a compact and cost-effective scanner laser processing head, in particular a prefocus scanner laser processing head, with a sensor arrangement for process monitoring.

[0018] At least one of these problems is solved by the subject matter of the independent claim.

[0019] The present disclosure is based on the idea of ​​replacing a fixed-focal-length process light collimation with a variable or adjustable focal length process light collimation. For this purpose, a variable lens with an adjustable focal length, such as a deformable lens or a liquid lens, is used in the process light optics. This allows the focal length to be adjusted very quickly depending on the scan field position, and a similarly good or even better signal can be obtained at the sensor array than when using an F-theta lens.

[0020] According to one aspect, a laser processing head for processing a workpiece by means of a laser processing beam comprises: a scanning device for directing the laser processing beam to a plurality of positions on the workpiece or to a plurality of scan field positions; processing beam optics for setting a focus position of the laser processing beam and for focusing the laser processing beam, wherein the processing beam optics are arranged between an entry port for the laser processing beam and the scanning device; a sensor arrangement for detecting process light with at least one sensor; output optics for outputting orGuide process light to the sensor assembly, wherein the output coupling optics are arranged between the processing beam optics and the scanning device; and process light optics for adjusting a focus position of the process light with respect to the sensor and / or for imaging the process light on the sensor, wherein the process light optics are arranged between the output coupling optics and the sensor assembly and comprise a variable lens with an adjustable focal length. The laser processing head can be referred to as a pre-focus scanner laser processing head, and the processing beam optics can be referred to as pre-focusing optics of the laser processing beam.

[0021] The present disclosure thus relates to a laser processing head with a device for process monitoring in scanner-based laser material processing, e.g., in laser processing beam welding, using so-called prefocus optics. Furthermore, the laser processing head according to the invention can also be used in other laser processing processes, such as laser processing beam cutting or additive processes such as SLS (selective laser processing beam melting). Furthermore, the invention can also be used in ablation processes such as laser vaporization and laser ablation.

[0022] The laser processing head according to an embodiment of the present disclosure can be configured for laser welding, laser soldering, laser cutting, and / or laser engraving, etc. The laser processing head can accordingly be a laser cutting head, a laser welding head, a laser soldering head, a laser engraving head, or the like. The workpiece can, for example, be or include a metallic workpiece. The workpiece can also be a mechanical and / or electrical component, for example, an electrode of a battery cell.

[0023] The scanning device is arranged in a common beam path of the laser processing beam and the sensor arrangement. Thus, the process light travels from the workpiece to the sensor arrangement via the scanning device and is subsequently coupled out to the sensor arrangement by the coupling-out optics. The scanning device is configured to direct the laser processing beam to many different positions (or scan field positions) on the workpiece, e.g., based on a control preset value, in particular a control preset value for a (scan field) position. The scanning device can comprise one or more movably mounted scanning elements, such as scanning mirrors. The scanning device can be configured to scan a workpiece surface. The scanning device can be a galvanometer scanner.

[0024] The processing beam optics are arranged between the entrance port of the laser processing head and the scanning device. The processing beam optics are thus arranged in the beam path of the laser processing beam and outside the beam path of the process light or the sensor arrangement, meaning that the process light does not pass through them. The laser processing beam can enter the laser processing head through the entrance port. The entrance port of the laser processing head can be, for example, a fiber coupler (particularly in the case of a fiber-guided laser processing beam) or an entrance opening.

[0025] The sensor arrangement is configured to detect process light and for this purpose comprises at least one sensor, e.g. a photodiode, a multispectral sensor, a spectrometer, an optical sensor (in particular a photodiode sensor) for infrared radiation, an optical sensor (in particular a photodiode sensor) for UV radiation, an optical sensor (in particular a photodiode sensor) for radiation in the visible wavelength range, a photodiode array, a CCD sensor, a camera, and / or a CMOS camera. The sensor can be configured to detect an intensity of the process light. In this case, the sensor arrangement can be configured to generate a sensor signal proportional to the intensity of the detected process light and, if necessary, to forward it to a controller.

[0026] Electromagnetic radiation is detected as process light. For example, electromagnetic radiation that emanates from the workpiece, in particular from a processing position on the workpiece, enters the laser processing head and is guided to the sensor arrangement is detected as process light. The process light can include process emissions, i.e. radiation caused or generated by the laser processing process, e.g. thermal radiation, infrared radiation, UV radiation, radiation in the visible wavelength range, plasma radiation, back reflections or scattered components of the laser processing beam, etc. The process light can also generally include light from the workpiece surface, e.g. in order to capture an image of the workpiece or of the workpiece surface.

[0027] The decoupling optics serve to guide the process light to the sensor arrangement or to decouple it from the beam path of the laser processing beam. The decoupling optics are arranged between the scanning device and the processing beam optics and / or between the scanning device and the process light optics. The decoupling optics are thus arranged in the beam path of the laser processing beam (and / or the sensor arrangement). The decoupling optics can be configured to coaxially couple a beam path of the sensor arrangement with a beam path of the laser processing beam or to separate the beam path of the laser processing beam and the beam path of the sensor arrangement. The decoupling optics can be a beam splitter or a dichroic mirror.The output coupling optics can either be transparent for a wavelength of the laser processing beam and reflective for a wavelength of the process light to be detected by the sensor arrangement, or conversely reflective for the wavelength of the laser processing beam and transparent for the wavelength of the process light.

[0028] A common beam path of the laser processing beam and the sensor arrangement can run between the output optics and the workpiece (in particular the processing position on the workpiece). The common beam path is part of both the beam path of the laser processing beam and the beam path of the sensor arrangement. In the common beam path, the beam path of the laser processing beam and the beam path of the sensor arrangement run coaxially. In the region of the common beam path, the laser processing beam can be or run in a focused manner, i.e. the common beam path can be arranged in an area through which the laser processing beam passes (already completely or fully) in a focused manner. Preferably, no refractive and / or beam-shaping optics (with the exception of the scanning device) are arranged in the region of the common beam path.In particular, preferably no lens and / or no focusing optics are arranged in the area of ​​the common beam path.

[0029] The process light optics are configured to adjust the focus position of the process light relative to the sensor and / or to image the process light onto the sensor. The process light optics are located between the output optics and the sensor assembly, i.e., outside the beam path of the laser processing beam. Since the process light optics are not traversed by the laser processing beam (and thus also not by the variable lens), there are no restrictions on the power of the laser processing beam or the material of the variable lens.

[0030] The process light optics comprise the variable lens, i.e. a lens with a variable or adjustable focal length, for adjusting the focus position of the process light with respect to the sensor. The process light optics can be controllable to adjust the focus position of the process light according to a control preset value, in particular a control preset value for the focus position of the process light. The process light optics can comprise a (second) focusing optic for focusing the process light and / or a (second) collimating optic for collimating the process light. The variable lens can be a / the (second) focusing optic for focusing the process light or a part thereof, and / or it can be a / the (second) collimating optic for collimating the process light or a part thereof. The variable lens can be arranged as a (second) collimating optic between the output optic and the (second) focusing optic.The variable lens can be arranged as a (second) focusing optic between the sensor assembly and the (second) collimating optic. The process light optic can consist of the variable lens or the variable lens and a focusing lens.

[0031] The variable lens can be a deformable lens whose focal length can be adjusted depending on the deformation, e.g. a liquid lens. The focal length should approximately correspond to an optical path length from a processing position to the variable lens, i.e. from a position of the laser processing beam on the workpiece to the variable lens. In particular, the focal length of the variable lens can be adjustable according to an optical path length from a processing position to the variable lens, e.g. by a controller. The focal length of the variable lens can therefore be adjustable within a focal length range that corresponds to a range of optical path lengths from processing positions that can be adjusted by means of the scanning device to the variable lens. The focal length of the variable lens can be adjustable within a focal length range of 1000 ± 500 mm, in particular of 800 ± 100 mm.

[0032] The sensor arrangement can have at least two sensors. In this case, the process light optics can comprise at least one beam deflector, in particular at least one beam splitter, to direct the process light to the at least two sensors of the sensor arrangement. In particular, the process light optics can have a beam deflector for each sensor. Alternatively, the laser processing head can comprise multiple process light optics, in particular corresponding to a number of sensors of the sensor arrangement. The process light optics or their variable lenses can be individually controllable. The process light optics can each comprise a beam deflector to direct a portion of the process light to the respective sensor of the sensor arrangement. The beam deflector can be configured to split the process light depending on the wavelength, in particular according to a spectral range of the respective sensor. The beam deflector can therefore be a beam splitter.Preferably, several beam deflectors are arranged on an optical axis, whereby all beam deflectors (possibly with the exception of the last beam deflector) are designed as beam splitters.

[0033] In the laser processing head of the present invention, a (first) focusing optics for the laser processing beam and a (second) focusing optics for the process light can be provided separately or separately from one another. In other words, focusing and / or collimating the laser processing beam can be performed by (completely) different optical elements than focusing and / or collimating the process light. All lenses of the laser processing head are preferably arranged outside the common beam path. All lenses of the laser processing head are preferably either (exclusively) part of the processing beam optics or (exclusively) part of the process light optics. The processing beam optics and the process light optics therefore preferably do not have any common optical elements. All optical elements for focusing the laser processing beam can be arranged outside the beam path of the sensor arrangement.

[0034] The processing beam optics can comprise a first optic for adjusting the focus position of the laser processing beam. The processing beam optics and / or the first optic can be controllable to adjust the focus position of the laser processing beam according to a control preset value, in particular a control preset value for the focus position of the laser processing beam. The first optic can be a variable lens with an adjustable focal length, such as a liquid lens. Alternatively, the first optic can be arranged so as to be axially displaceable in the beam path of the laser processing beam, e.g., motorized and / or automated. The processing beam optics can comprise a (first) focusing optic for focusing the laser processing beam and / or a (first) collimating optic for collimating the laser processing beam.The (first) focusing optics for focusing the laser processing beam can be arranged between the (first) collimating optics for collimating the laser processing beam and the output coupling optics, and / or the (first) collimating optics for collimating the laser processing beam can be arranged between the entrance port and the (first) focusing optics for focusing the laser processing beam. The first optics can be a / the (first) focusing optics for focusing the laser processing beam or a part thereof, and / or it can be a / the (first) collimating optics for collimating the laser processing beam or a part thereof. The processing beam optics can consist of a focusing lens and an axially displaceable collimating lens.

[0035] The term "optics" in this disclosure may refer to a transparent optical element, a reflective optical element, a transmissive optical element, a beam-shaping optical element, a beam-splitting optical element, a lens, a lens group, etc. The term "focusing optics" or "collimating optics" may refer to an optical element for focusing or collimating.

[0036] The laser processing head can comprise a controller that is configured to: control the scanning device to adjust a scan field position or a position of the laser processing beam on the workpiece; and / or control the processing beam optics (in particular the first optics) to adjust the focus position of the laser processing beam; and / or control the process light optics (in particular the variable lens) to adjust the focus position of the process light. The controller can be configured to adjust the focal length of the variable lens to adjust the focus position of the process light. The controller can be configured to control the scanning device according to a control default value for the scan field position. The controller can be configured to control the processing beam optics according to a control default value for the focus position of the laser processing beam.The controller may be configured to adjust the focal length of the variable lens based on a / the control default value for the focus position of the laser processing beam and / or based on a / the control default value for the scan field position.

[0037] The controller can be configured to adjust the focal length of the variable lens based on a measured value, for example, a measured value of an optical path length to the (set or current) scan field position on the workpiece. The laser processing head can comprise an optical measuring device for measuring the optical path length, e.g., an OCT device, whose beam path extends over the scanning device.

[0038] The controller can be configured to control the processing beam optics (i.e., in particular, the first optics) for adjusting the focus position of the laser processing beam and the process light optics (i.e., in particular, the variable lens) for adjusting the focus position of the process light synchronously and / or proportionally to one another and / or correspondingly to one another. The controller can be configured to adjust the focal length of the variable lens and the focus position of the laser processing beam synchronously and / or proportionally to one another and / or correspondingly to one another. The controller can be configured to adjust the focus position of the process light and the focus position of the laser processing beam synchronously and / or proportionally to one another and / or correspondingly to one another.

[0039] In one embodiment, the controller is configured to synchronize the control of the variable lens with the control of the processing beam optics, in particular the first optics of the processing beam optics. Since, in pre-focus systems, the position of the collimating optics of the laser processing beam must be adjusted to the corresponding position in the scan field or on the workpiece anyway, the control of the variable lens can be synchronized with the control of the processing beam optics or can be implemented analogously. The focal length of the variable lens can, for example, be set so that it corresponds to the distance between the processing point or the TCP (tool center point) and a main plane of the variable lens.

[0040] The controller can be configured to adjust the focal length of the variable lens according to a position on the workpiece and / or a scan field position and / or a setting of the scanning device. Scan field position-dependent control of the variable lens enables a significant improvement in signal quality for process monitoring in prefocus scanner laser processing heads compared to previously available solutions.

[0041] The controller can be configured to adjust the focal length of the variable lens depending on a (current or set) scan field position such that the process light is defocused on the sensor. In other words, the controller can be configured to adjust the focal length of the variable lens depending on a (current or set) scan field position such that a focal position of the process light is spaced from a sensor plane of the sensor. In this way, saturation of the sensor can be avoided. This is particularly advantageous when the sensor is a photodiode. Here, the scan field-dependent control of the variable lens for the collimation of the process light enables a significant improvement in signal quality for photodiode-based process monitoring on pre-focus scanner systems compared to previously available solutions.

[0042] Brief description of the drawings

[0043] Fig. 1 is a schematic diagram of a laser processing head according to an embodiment;

[0044] Fig. 2 is a schematic representation of a laser processing head according to another embodiment; and

[0045] Fig. 3 is a schematic representation of a laser processing head according to yet another embodiment.

[0046] Detailed description of the drawings

[0047] Unless otherwise stated, the same reference numerals are used below for identical and identically functioning elements. A redundant description of recurring features and, where appropriate, a redundant use of recurring reference numerals is avoided wherever possible. The various embodiments and features of the figures described below are expressly combinable and should not be understood as complete versions.

[0048] Fig. 1 is a schematic representation of a laser processing head 1 for processing a workpiece 3, in particular a workpiece surface, using a laser processing beam 4 according to one embodiment. During the laser processing process, the laser processing head 1 can be guided over the workpiece 3 at a speed (arrow in Figures 2 and 3) in order to guide the laser processing beam 4 along a processing path on the workpiece 3.

[0049] The laser processing head 1 comprises a processing beam optics 10 for guiding the laser processing beam 4, in particular for setting a focus position and / or for focusing the laser processing beam 4, a scanning device 20 for directing the laser processing beam 4 to various scan field positions or processing positions on the workpiece 3, a sensor arrangement 50 for detecting process light for process monitoring, and a process light optics 40 for guiding the process light 5 to the sensor arrangement 50, in particular for setting a focus position of the process light with respect to at least one sensor 55 of the sensor arrangement 50. These components of the laser processing head 1 can be arranged in or on a housing (not shown).In particular, the optical elements that define a beam path of the laser processing beam 4 (solid line in Figure 1) and / or a beam path of the sensor arrangement (dashed line in Figure 1) can run in the housing of the laser processing head 1.

[0050] The laser processing beam 4 enters the laser processing head 1 through an entrance port 11, e.g., a fiber coupler, and passes through the processing beam optics 10, where it is focused before reaching the scanning device 20. The processing beam optics 10 can therefore also be referred to as pre-focusing optics. The focused laser processing beam 4 is then deflected at an output optics 30, e.g., a beam splitter or dichroic mirror, to a scanning device 20, which directs the laser processing beam 4 to various positions on the workpiece 3 for processing. The scanning device 20 can comprise a scanning mirror pivotable about two different axes (see Fig. 2) or two scanning mirrors pivotable about one axis each (see Fig. 1) in order to deflect the laser processing beam 4 in two mutually perpendicular directions on the workpiece 3.

[0051] In order to adjust the focus position of the laser processing beam 4, the processing beam optics 10 can have a first optics 15. The focus position of the laser processing beam 4 can be achieved, for example, by a motorized adjustment of the first optics 15. The first optics 15 can be an axially displaceable lens (see arrow in Figure 1). Alternatively, the first optics 15 can be a variable lens with an adjustable focal length, for example a liquid lens. The processing beam optics 10 can further comprise a second optics 18. In the embodiment shown in Figure 1, the first optics 15 are arranged for collimating the laser processing beam 4 and the second optics 18 are arranged for focusing the laser processing beam 4. Accordingly, in this case, the first optics 15 can be referred to as the first collimating optics and the second optics 18 as the first focusing optics.

[0052] The laser processing head 1 further comprises a sensor arrangement 50 with at least one sensor 55, which is designed to detect process light 5 emanating from the workpiece 3 for process monitoring. Between the sensor arrangement 50 and the output optics 30 there is arranged the process light optics 40, which comprises a variable lens 45 with an adjustable focal length for adjusting a focus position of the process light 5 with respect to the sensor 55. The process light optics 40 can further comprise a further optic or a further lens, e.g. a focusing optic 48. In the embodiment shown in Fig. 1, the variable lens 45 is arranged for collimating the process light 5 and the focusing optics 48 is arranged for focusing the process light 5. In this case, the variable lens 45 can be referred to as a second collimating optic and the focusing optics 48 as a second focusing optic. However, the order of the variable lens 45 with an adjustable focal length and the further optics orthe focusing optics 48 may also be swapped.

[0053] The variable lens 45 (and possibly also the first optics 15) can be a liquid lens. The focal length of the variable lens 45 can be adjustable within a range of 1000 ± 500 mm, in particular 800 ± 100 mm.

[0054] The sensor arrangement 50 can be configured to detect an intensity of the process light, in particular at a predetermined wavelength or in a predetermined wavelength range. The process light can comprise process emissions, such as thermal radiation or IR radiation, UV radiation, reflected and / or scattered components of the laser processing beam 4, etc. For example, the sensor 55 can be a photodiode, a photodiode array, a multi-spectral sensor, or a spectrometer. However, the process light can also comprise scattered ambient or illumination light. In this case, the sensor 55 can be a camera to capture a (two-dimensional) image of the workpiece surface. The process light can originate from the workpiece 3, pass over the scanning device 2, and be guided through the output optics 30 and the process light optics 40 to the sensor arrangement 50.Thus, the intensity of the detected process light will strongly depend on the set scan field position.

[0055] The area of ​​the laser processing head 1 between the output optics 30 and the workpiece 3 or an exit opening of the laser processing head 1 can be referred to as the common beam path of the laser processing beam 4 and the process light 5 or the sensor arrangement 50. The output optics 30 can separate the beam path of the laser processing beam 4 and the beam path of the sensor arrangement 50 or coaxially superimpose them. In the figures, the output optics 30 is reflective for the laser processing beam 4 and transmissive for the process light 5. However, it can also be the other way around.

[0056] The laser processing head 1 can also include a controller 80. The controller 80 can be integrated into the laser processing head 1 or connected to it wirelessly via a cable or a communication interface. The controller 80 can be configured to control at least one of the components comprising the scanning device 20, the processing optics 10, and the process light optics 40 (in particular the variable lens 45). In particular, the controller 80 can control the process light optics 40 to adjust the focal length of the variable lens 45 based on a control default value and / or a measured value. The controller 80 can be configured to control the process light optics 40 and / or the processing beam optics 10 based on a current scan field position or on a control default value for the scan field position.For example, the controller 80 can be configured to control the process light optics 40 and the processing beam optics 10 synchronously (e.g., via a real-time protocol) and / or analogously. In a scanner laser processing head with pre-focusing optics, the focus position of the laser processing beam 4 must be adjusted according to a current scan field position or a current (processing) position on the workpiece 3 due to the different optical path lengths at different scan field positions, so that the process light optics 40 can be adjusted simultaneously and / or accordingly.

[0057] The sensor arrangement 50 can comprise one sensor 55 or several different sensors 55, 55', 55". For example, the sensor arrangement 50 can contain several photodiodes that detect an intensity of the process light in different wavelength ranges (see Figures 2 and 3). For example, the sensor arrangement 50 can comprise a photodiode for IR radiation, a photodiode for UV radiation, a photodiode for laser processing beam reflections, and / or a photodiode for the visible spectral range.

[0058] Figure 2 shows a laser processing head 1 in which the process light optics 40, in comparison to the process light optics 40 of Figure 1, further contains at least one beam deflector 43, in particular a beam splitter, in order to split the process light 5 and guide it to one of a plurality of sensors 55, 55', 55" of the sensor arrangement 50. In the example shown in Figure 2, the process light optics 40 contains three different sensors 55, 55', 55", for example three photodiodes that detect process light in different wavelength ranges, or a camera, a spectrometer and a photodiode, etc. By means of a plurality of beam deflectors 43, 43 43", the process light 5 is guided to the various sensors 55, 55', 55" of the sensor arrangement 50. Each sensor 55, 55', 55" can therefore be assigned a beam deflector 43, 43', 43", which decouples part of the process light and directs it to this sensor 55, 55', 55".In Figure 2, the beam deflectors 43, 43', with the exception of the last beam deflector 43", are beam splitters. The beam splitters can, for example, couple out a wavelength or wavelength range from the process light 5 that corresponds to the sensitivity of the respective sensor and forward the remaining part of the process light 5. Alternatively, the last sensor 55" can be arranged on the optical axis of the beam deflector 43', so that the process light optics 40 comprises only two beam deflectors 43, 43', which are designed as beam splitters.

[0059] Alternatively, as shown in Figure 3, each sensor 55, 55', 55" can be assigned a process light optic 40, 40', 40"'. The process light optics 40, 40', 40" can each comprise an individually adjustable variable lens 45 and a beam deflector 43, 43', 43". Optionally, each process light optic 40, 40', 40" can additionally contain a focusing optic 48. The process light optics 40, 40', 40" can thus be designed like the process light optic 40 in Figure 1, but additionally contain a beam deflector 43. As described above for Figure 2, the beam splitters 43 and 43' can be designed as beam splitters, i.e., they can spectrally split the process light 5 and guide it to the sensors 55, 55' or photodiodes with the corresponding spectral range. The last process light optics 40" can be arranged on the optical axis of the beam deflector 43' of the preceding process light optics 40'. In this case, the last process light optics 40" does not have a beam deflector 43'.

[0060] Through the inventive use of a variable lens with a variable focal length, a "sensor collimation" or a focus position of the process light relative to the sensor can be adjusted over a wide working range. This makes it possible to use the same setup for different scanning devices, different scan field positions, and different working distances, with the controller 80 adapting the control of the variable lens accordingly. Furthermore, by targeted "adjustment," i.e., targeted defocusing, of the variable lens, the signal at specific scan field positions can be attenuated so that no (over)saturation of the sensor or photodiode occurs. For example, this can be advantageous at the zero or center position, where the laser's back reflection is reflected back along the same optical path, thus delivering a very high intensity to the photodiode.

[0061] Laser processing head workpiece

[0062] Laser processing beam process light

[0063] Processing beam optics Entrance port First optics Second optics Scanning device Output optics Process light optics Beam deflector Variable lens Focusing optics Sensor arrangement Sensor control

Claims

Patent claims 1. A laser processing head (1) for processing a workpiece (3) using a laser processing beam (4), comprising: a scanning device (20) for directing the laser processing beam (4) to a plurality of positions on the workpiece (3); processing beam optics (10) for adjusting a focus position of the laser processing beam (4) and for focusing the laser processing beam (4), wherein the processing beam optics (10) are arranged between an entrance port (11) for the laser processing beam (4) and the scanning device (20); a sensor arrangement (50) for detecting process light (5) with at least one sensor (55); output optics (30) for outputting process light (5) to the sensor arrangement (50), wherein the output optics (30) are arranged between the processing beam optics (10) and the scanning device (20);and a process light optics (40) for adjusting a focus position of the process light (5) with respect to the sensor (55), wherein the process light optics (40) is arranged between the output optics (30) and the sensor arrangement (50) and comprises a variable lens (45) with an adjustable focal length.; 2. Laser processing head (1) according to claim 1, wherein the variable lens (45) is a deformable lens whose focal length is adjustable depending on the deformation; and / or wherein the variable lens (45) is a liquid lens; and / or wherein the focal length of the variable lens (45) is adjustable within a focal length range of 1000 ± 500 mm or 800 ± 100 mm.

3. Laser processing head according to one of the preceding claims, wherein the coupling-out optics (30) are configured to coaxially couple a beam path of the sensor arrangement (50) with a beam path of the laser processing beam (4).

4. Laser processing head according to one of the preceding claims, wherein a common beam path of the laser processing beam (4) and the sensor arrangement (50) is arranged in a region of the focused laser processing beam (4).

5. Laser processing head according to one of the preceding claims, wherein the processing beam optics (10) is a pre-focusing optics of the laser processing beam (4); and / or wherein all optical elements for focusing the laser processing beam (4) are arranged outside the beam path of the sensor arrangement (50) or between the output optics (30) and the entrance port (11).

6. Laser processing head according to one of the preceding claims, wherein no focusing optics and / or no lens are arranged in a common beam path of the laser processing beam (4) and the sensor arrangement (50); and / or wherein all lenses of the laser processing head (1) are arranged outside a common beam path of the laser processing beam (4) and the sensor arrangement (50).

7. Laser processing head according to one of the preceding claims, wherein the processing beam optics (10) comprises a first optics (15) for adjusting the focus position of the laser processing beam (4), wherein the first optics (15) comprises a lens with an adjustable focal length or a lens which is arranged to be axially displaceable in the beam path of the laser processing beam.

8. Laser processing head according to claim 7, wherein the processing beam optics (10) comprises a second optics (18) and wherein one of the first and second optics (15, 18) serves to collimate the laser processing beam (4) and the other of the first and second optics (15, 18) serves to focus the laser processing beam (4).

9. Laser processing head according to one of the preceding claims, wherein the process light optics (40) comprises the variable lens (45) for collimating the process light (5) and a focusing optics (48) for focusing the process light (5).

10. Laser processing head according to one of the preceding claims, wherein the sensor arrangement (50) comprises at least one of the following sensors (55): a photodiode, a photodiode array, a camera, a spectrometer, a multi-spectral sensor, a sensor for detecting an intensity of the process light, an optical sensor for infrared radiation, an optical sensor for UV radiation, and a sensor for visible light.

11. Laser processing head (1) according to one of the preceding claims, further comprising a controller (80) which is configured to: adjust the focal length of the variable lens (45); and / or to control the scanning device (20) according to a control preset value for a scan field position; and / or to control the processing beam optics (10) for adjusting the focus position of the laser processing beam (4) according to a control default value for the focus position of the laser processing beam (4).

12. Laser processing head (1) according to claim 11, wherein the controller (80) is configured to adjust the focal length of the variable lens (45) based on the control default value for a scan field position and / or on the control default value for the focus position of the laser processing beam (4).

13. Laser processing head (1) according to claim 11 or 12, wherein the controller (80) is configured to control the variable lens (45) to adjust its focal length synchronously with and / or proportionally to a control of the processing beam optics (10) to adjust the focus position of the laser processing beam (4) and / or to a control of the scanning device (4).

14. Laser processing head (1) according to one of claims 11 to 13, wherein the controller (80) is configured to adjust the focal length of the variable lens (45) based on a measured value or a measured value of an optical path length to a current position of the laser processing beam (4) on the workpiece (3).

15. Laser processing head (1) according to one of claims 11 to 14, wherein the sensor arrangement (50) comprises a photodiode as a sensor (55) and the controller (80) is configured to adjust the focal length of the variable lens (45) as a function of a scan field position such that a targeted defocusing of the process light (5) on the sensor (55) occurs in order to avoid saturation of the photodiode.

Images