Reference aperture for reflecting scattered radiation and method for adjusting a laser beam

Abstract

The invention relates to a reference aperture (8) for reflecting scattered radiation (51) of a laser beam (50) which passes through a laser optical unit (1), having: a reflection section (17) which is provided and configured to reflect the scattered radiation (51) to a device (9) arranged in the laser optical unit (1) for optically detecting the scattered radiation (51); and an alignment section (18) which is provided and configured to align the reference aperture (8) relative to a nozzle mouth (7) of the laser optical unit (1); wherein the alignment section (18) is provided and configured to come into contact with the nozzle mouth (7) during the alignment and to be released from the nozzle mouth (7) before stationary operation of the laser optical unit (1). The invention also relates to a method for adjusting a laser beam.

Description

[0001] Reference aperture for reflecting scattered radiation and method for adjusting a laser beam

[0002] Technical area

[0003] The present invention relates to a reference aperture for reflecting scattered radiation of a laser beam passing through a laser optics, and to a method for adjusting a laser beam along a beam path in a laser optics.

[0004] State of the art

[0005] Laser systems, especially multi-axis laser welding systems, have become an indispensable technology in many industries in recent years. They can offer high precision and flexibility and can enable efficient processing, especially welding, of a workpiece. Laser systems feature a processing head with laser optics that directs a high-intensity laser beam onto a workpiece.

[0006] The theoretical path of a laser beam within the processing head is known in advance. However, this theoretical path is subject to tolerances, which may be due, for example, to mechanical deficiencies within the laser optics, such as minimal manufacturing deviations, and / or to deviations in the production and / or assembly of optical components, and / or to contamination of the lenses involved. The actual path of the beam is therefore unknown.

[0007] To ensure precise laser processing, it is therefore desirable to compensate for the deviations in the beam path resulting from the tolerance by adjusting the laser beam accordingly. The focus position of the laser beam and the center of the nozzle are of particular importance during adjustment. For optimal processing of the workpiece, it may be desirable for the laser beam to hit the workpiece at least in the area of ​​the focus position, because this is where the energy density of the laser beam is greatest. The focus position therefore corresponds to the beam waist. Furthermore, it may be desirable for the laser beam to be concentric with a nozzle cross-section, i.e., centered within the nozzle, in order to avoid scattered radiation within the nozzle and / or to ensure optimal supply of the cutting gas to the process point.

[0008] A laser processing head with a focus position adjustment unit is known from published patent application DE 10 2009 042 529 A1. To adjust the position of a laser beam within the laser processing head, scattered radiation reflected by the nozzle itself is detected, and a beam trap capacitively coupled to the nozzle is used. These two input variables are evaluated to move a focusing unit in three spatial directions to adjust the position of the laser beam accordingly.

[0009] Description of the invention

[0010] The object of the present invention is to provide improved laser optics for aligning a laser beam onto a workpiece along a beam path, as well as an improved method for adjusting a laser beam along a beam path in a laser optics system. In particular, the invention aims to ensure high quality in laser processing. Furthermore, the invention may aim to contribute to the protection of optical components within the laser optics system and / or to minimize the calibration time before commissioning a laser system. Ultimately, the invention may aim to achieve scalable and reproducible adjustment of a laser optics system, which can be retrofitted, in particular, without increased effort. Operator-independent, automated adjustment of a laser optics system may also be desired.

[0011] The object is achieved by a reference aperture for reflecting scattered radiation from a laser beam passing through a laser optics, and by a method for adjusting a laser beam having the features of the independent claims. Advantageous further developments emerge from the subclaims, the description, and the figures.

[0012] The invention relates to a reference aperture for reflecting scattered radiation from a laser beam passing through a laser optics system. The reference aperture can be made of a reflective material, for example quartz glass or another optical glass, such as crown or flint glass, or of a metal.

[0013] The reference aperture can have a truncated cone shape in side view with a receiving volume for accommodating a nozzle mouth. The radial dimension of the reference aperture can exceed its axial dimension. The reference aperture can have a stepped through-opening to allow a beam path to pass through. It can have a conical inner surface, thus an inner contour that tapers conically towards a workpiece, which in particular has a coating to promote the reflection of scattered radiation. The reference aperture can be coupled to the nozzle mouth in such a way that the nozzle mouth protrudes at least partially into the reference aperture during commissioning. The reference aperture can be fixed to the nozzle mouth from the outside. It can also be stationary in a processing space so that the laser optics are moved to the reference aperture during commissioning.The reference aperture can be removed from the nozzle mouth without causing any damage. The reference aperture can have a conical inner surface whose smallest diameter corresponds in particular to the diameter of the laser beam in the focus position. The laser beam is provided by a laser source, from where it extends along a beam path through the laser system to be applied to a workpiece. The beam path can describe the path along which the laser beam is guided through the laser system and the components arranged therein. The beam path can vary depending on the process. The beam path can run from the laser source via a fiber optic cable into a laser quill, from where it can enter the processing head via a movement unit. The beam path is determined by optical elements, such as mirrors and lenses.

[0014] The reference aperture has a reflection section designed and configured to reflect the scattered radiation to a device arranged in the laser optics for optically detecting the scattered radiation. Along the beam path, the reflection section can be located at the end of the reference aperture facing away from the nozzle orifice. The reflection section can have a coating that promotes reflection. An inner diameter of the reflection section can vary along the beam path. The smallest inner diameter of the reflection section can correspond to the diameter of the laser beam. The largest inner diameter of the reflection section can be smaller than the smallest inner diameter of an alignment section.

[0015] The reference aperture further includes an alignment section designed and configured to align the reference aperture relative to a nozzle orifice of the laser optics. The alignment section can form a receiving volume in the manner of a truncated cone. The receiving volume can be complementary to the geometry of the nozzle orifice in order to accommodate it with a precise fit. The reference aperture can be coupled to a machining floor of a machining chamber via a spring element to enable centering of the reference aperture relative to the nozzle orifice.

[0016] The alignment section is provided and configured to contact the nozzle mouth during alignment and to be released from the nozzle mouth before stationary operation of the laser optics. The contact enables alignment of the reference aperture relative to the nozzle mouth in order to enable adjustment of the nozzle centerline and / or the focus position. Release before stationary operation consists in the reference aperture and the laser optics being spatially separated from one another. This can be done by releasing the reference aperture from the nozzle mouth or by moving the laser optics out of the reference aperture. Stationary operation can be the operation in which the laser beam is applied to a workpiece at a nominal power in order to process it. Before stationary operation, a commissioning operation takes place in which the laser beam is aligned to a workpiece table at a power lower than the nominal power.The commissioning operation aims to adjust the beam path within the laser optics in accordance with the process.

[0017] The reference aperture is configured to reflect the scattered radiation to the device for optically detecting the scattered radiation. The reference aperture is further configured to be detached from the nozzle mouth prior to stationary operation of the laser optics. The reference aperture can be configured to be solely responsible for reflecting the scattered radiation, so that no reflection emanates from the nozzle mouth. Commissioning occurs prior to stationary operation of the laser optics. During commissioning, a beam position unit of a laser optics is adjusted such that the beam path does not generate any scattered radiation at its end in the area of ​​the nozzle unit. Consequently, the reference aperture is no longer required at the end of commissioning.It can be detrimental to the steady-state operation of the laser optics because it restricts the inner diameter of the nozzle unit, which can impede the alignment of the process gas to the workpiece. Consequently, the reference aperture is removed from the nozzle orifice before the laser optics can be operated in a steady-state manner.

[0018] The scattered radiation reflected by the reference aperture is thus detected by the device for optically detecting the scattered radiation. This provides information about whether the beam path is adjusted correctly for the process. The less scattered radiation the device for optically detecting the scattered radiation detects, the better the adjustment. If little or no scattered radiation is reflected by the reference aperture, this means that a maximum amount of laser radiation is decoupled from the laser optics so that it can be used for workpiece processing. Because the reference aperture can be removed after commissioning, laser processing is not affected by the geometry of the reference aperture. This enables precise determination of the focus position and / or nozzle centerline.The signals output by the device for optically detecting scattered radiation can be used to adjust the beam positioning unit so that the beam path through the nozzle unit does not generate any scattered radiation. This allows the laser optics to ensure high quality laser processing because the beam path can be reliably adjusted. Furthermore, the reference aperture helps protect the optical components within the laser optics by minimizing scattered radiation. The nozzle nozzle of the laser optics is also protected because the scattered radiation emanates from the reference aperture. The calibration time prior to commissioning the laser system is minimized by the reference aperture because the beam positioning unit can be controlled efficiently, scalably, and reproducibly. Furthermore, the provision of the external reference aperture enables automated calibration of the laser system.

[0019] In one embodiment, the alignment section forms a receiving volume in the form of a truncated cone, which is designed and configured to receive the nozzle orifice during alignment. The receiving volume can contact the nozzle orifice from at least two points, in particular in the form of a linear contact, to enable efficient alignment of the nozzle orifice to the reference aperture. The dimensions of the reference aperture can be adapted to the respective dimensions of the nozzle orifice. This further contributes to minimizing the calibration time before commissioning the laser system and facilitating automation.

[0020] In one embodiment, the reference orifice has a spring element, for example in the form of an elastic element made of rubber or plastic or in the form of a solid-state joint with a corresponding restoring force, which is intended and configured to be connected to a machining floor of a machining chamber, wherein the spring element enables centering of the reference orifice relative to the nozzle orifice. The spring element can enable movement of the reference orifice in three spatial directions and thus ensure that the reference orifice is aligned to the desired extent with the nozzle orifice. This enables the compensation of tolerances when controlling the position of the nozzle orifice relative to the reference orifice.

[0021] In one embodiment, the reflection section is conically tapered in the direction away from the nozzle orifice to promote reflection. The smallest diameter of the reflection section can correspond to the diameter of the laser beam in the plane of the beam waist.

[0022] In one embodiment, the alignment section has an outer contour that enables reversible coupling to the nozzle orifice, in particular by means of a plug-in connection or a screw connection. In this way, the reference aperture can be inserted, in particular clamped or screwed, into or onto the nozzle orifice from outside the laser optics.

[0023] This allows the reference aperture to be manually or mechanically placed on the nozzle orifice without having to disassemble the laser optics. This further helps minimize calibration time before commissioning the laser system.

[0024] The disclosure further relates to laser optics for aligning a laser beam onto a workpiece along a beam path. The laser optics can be part of a processing head of a laser system. It can be used for laser welding, laser cutting, and / or laser cladding. The laser beam is provided by a laser source, from where it extends along the beam path through the laser system to be applied to a workpiece.

[0025] The laser optics has a beam positioning unit for adjusting the beam path, with an adjusting lens, a deflecting mirror, and focusing optics. The beam positioning unit can contain additional optical elements. Those elements that influence the course of the beam path can be assigned to the beam positioning unit. The beam positioning unit can be a functional system boundary. The beam path can be adjusted by controlling and / or positioning optical components that influence the beam path. The adjusting lens can be a lens whose surfaces are curved in such a way that its axial displacement causes an axial displacement of the focus position. The focus position is the position at which the laser beam has a beam waist.The deflection mirror can be a mirror that deflects incoming beams according to their angle of incidence, so that its tilt causes the laser beam to wander, which is aimed at determining the nozzle center. Nozzle center is the position at which a cross-section of the laser beam is concentric with a nozzle opening. The focusing optics can be a lens that focuses a beam bundle in a process-oriented manner. The beam positioning unit enables alignment of the laser beam in all three spatial directions.

[0026] The laser optics further comprises a nozzle unit with a nozzle opening, at which the beam path through the laser optics ends during stationary operation, and a reference aperture for reflecting scattered radiation from the beam path, the reference aperture being reversibly fixed to the nozzle opening. In one embodiment, the nozzle opening and the reference aperture can be configured as an integral component. Alternatively, the reference aperture is configured separately from the nozzle opening. The nozzle opening can be the component of the laser optics facing the workpiece, from which the laser beam emerges. The nozzle opening can have an inner diameter that exceeds the diameter of the laser beam in order to enable the guidance of a process gas in addition to guiding the laser beam. The laser optics further comprises a device for optically detecting the scattered radiation.The detected scattered radiation can provide information about how the beam path should be adjusted to achieve maximum coupling of laser light from the laser optics. The device can communicate at least indirectly with a control unit to transmit the state detected from the scattered radiation to the control unit. The device for optically detecting the scattered radiation can serve as a detector to monitor the state of the laser optics.

[0027] In one embodiment, the focusing optics are arranged in a fixed position within the laser optics. This means that the focusing optics do not move relative to the laser optics. To adjust the beam path, other components of the beam positioning unit are used. This simplifies the construction of the laser optics because the focusing optics cannot be adjusted. In particular, the distance between the focusing optics and the optical detection device is constant, which facilitates optical detection. In this respect, the fixed focusing optics contributes to the ease of retrofitting existing laser systems because no mechanism for controlling the focusing optics is required.

[0028] In one embodiment, the laser optics has an adjustment motor configured to move the adjustment lens axially along the beam path to adjust the focus position of the laser beam. The focus position can be efficiently changed by moving the adjustment lens. Because the reference aperture generates scattered radiation depending on the respective focus position, the actual focus position can be determined from the values ​​recorded by the device for optically detecting the scattered radiation, without requiring additional components. This facilitates commissioning of the laser system.

[0029] In one embodiment, the laser optics has a deflection motor configured to tilt the deflection mirror to adjust the lateral position of a laser beam spot within the nozzle orifice. Tilting the deflection mirror allows the lateral position of the laser beam to be efficiently changed until the nozzle center is reached. Because the reference aperture generates scattered radiation depending on the respective lateral position, the nozzle center can be determined from the values ​​acquired by the device for optically detecting the scattered radiation, without requiring additional components. This further facilitates commissioning of the laser system.

[0030] In one embodiment, the deflection mirror can be tilted about a first axis and a second axis to adjust the position of the laser beam along two spatial directions and align the beam spot concentrically with the nozzle orifice. A beam spot of the laser beam can thus be variably moved in the plane perpendicular to the laser beam. This enables precise adjustment of the beam path to achieve nozzle centering.

[0031] In one embodiment, the reference aperture has an inner contour that tapers conically towards a workpiece, such that at a distal end of the laser optics there is a smallest inner diameter that essentially corresponds to the diameter of the laser beam in the focus position. The conical inner surface of the reference aperture provides a defined beam area for the scattered radiation. It can be made of a resilient material and / or be coated accordingly. Because the smallest inner diameter essentially corresponds to the diameter of the laser beam in the focus position, the focus position can be determined by axially moving the adjusting lens. The smallest inner diameter can be slightly larger than the diameter of the laser beam in the focus position in order to compensate for any skew of the laser beam relative to the laser optics resulting from the tilting of the deflection mirror.

[0032] In one embodiment, the device for optically detecting scattered radiation has an annular base body that forms a light channel within its interior. The light channel can have a reflective surface, which in particular consists of a non-ferrous metal, a precious metal, and / or an alloy. The reflective surface can be an applied coating. The light channel can have a circular cross-section to promote reflection of the light channel and thus achieve the smallest possible measurement error of the device for optically detecting scattered radiation.

[0033] In one embodiment, the device for optically detecting the scattered radiation is arranged completely downstream of the focusing lens along the beam path. In other words, the focusing lens is located farther away from the nozzle orifice than the device for optically detecting the scattered radiation. This protects the focusing lens because at least the majority of the scattered radiation emanating from the reference aperture is absorbed by the device. This further contributes to the protection of the optical components within the laser optics.

[0034] In one embodiment, the laser optics comprises a water-cooled absorber to compensate for the heat introduced by the scattered radiation. The water-cooled absorber can be arranged in the region of the device for optically detecting the scattered radiation. In this way, the scattered radiation reflected by the reference aperture can be efficiently removed from the laser optics. Because the absorber is water-cooled, the optical components are further protected during the laser beam adjustment according to the disclosure.

[0035] In one embodiment, the smallest inner diameter of the reference aperture essentially corresponds to a diameter of a focal position of the laser beam. The smallest diameter "essentially" corresponding to the diameter of the laser beam in the focal position includes, in particular, the smallest diameter being somewhat larger in order to compensate for any possible skew of the laser beam due to tilting by the deflection mirror.

[0036] The disclosure further relates to a laser system comprising a motion unit, a control unit, and laser optics according to this disclosure. The control unit controls the laser optics to adjust the focus position and nozzle centering. After adjustment, the reference aperture can be removed from the nozzle orifice. The motion unit can move the laser optics, for example, around five axes to ensure high flexibility in the processing of workpieces. The processing can involve laser cutting, laser welding, and / or laser cladding.

[0037] The disclosure further relates to a method for adjusting a laser beam along a beam path in a laser optics system, wherein the laser optics are configured in particular according to this disclosure. Adjusting the laser beam comprises determining a focus position and a nozzle center. The focus position is the position at which the laser beam has a beam waist. The nozzle center is the position at which a cross-section of the laser beam is concentric with an opening of the nozzle mouth.

[0038] The method comprises the step of moving the laser optics to a reference aperture fixed in a processing space. The reference aperture can form a cassette together with other reference apertures, with the laser optics being moved to the reference aperture matching the respective nozzle orifice.

[0039] The method further comprises the step of centering a nozzle orifice of the laser optics, at which the beam path through the laser optics ends, relative to the reference aperture. Centering can be performed mechanically. Centering can, for example, involve aligning the reference aperture to the nozzle orifice, with the alignment being facilitated by a spring element of the reference aperture. After commissioning, the reference aperture and the nozzle orifice are separated again, so that the reference aperture is detached from the nozzle orifice during stationary operation of the laser optics.

[0040] The method further comprises the step of igniting the laser beam at a first laser power, which is in particular less than 200 W. The first laser power is preferably less than a nominal laser power. Thus, if the beam path is such that it impinges on sensitive components within the laser optics, these components will not be damaged. This ensures that adjusting the laser beam along the beam path does not cause damage to the optical components of the laser optics. This increases the safety of the method.

[0041] The method further comprises the step of measuring scattered radiation emanating from the reference aperture, in particular using a device for optically detecting the scattered radiation. The measurement of the scattered radiation can begin simultaneously with the ignition of the laser beam. Thus, the device for optically detecting the scattered radiation can detect whether and how scattered radiation occurs within the laser optics.

[0042] The method further comprises the step of changing a lateral position of a beam spot of the laser beam within the nozzle orifice using a tiltable deflection mirror. In particular, the deflection mirror can be tilted about a first axis and a second axis, whereby the laser beam travels through the laser optics in each case and generates scattered radiation at the reference aperture, which is detected by the device for optically detecting the scattered radiation. In this way, the position at which the reference aperture generates a minimum of scattered radiation can be determined, which position corresponds to the center of the nozzle.

[0043] The method further comprises the step of changing an axial position of a focal position of the laser beam using a movable adjusting lens. In particular, the adjusting lens can be moved along the beam path, whereby the focal position moves axially and generates scattered radiation at the reference aperture, which is detected by the device for optically detecting the scattered radiation. In this way, the position at which the reference aperture generates a minimum of scattered radiation can be determined, which position corresponds to the focal position. The step of changing the lateral position and the step of changing the axial position can be interchanged in order. From both steps together, the nozzle center and the focal position can be determined, resulting in optimal adjustability of the laser optics.

[0044] This records the reflected scattered radiation. This provides information about whether the beam path is adjusted correctly for the process. The less scattered radiation that is recorded, the better the adjustment. If little or no scattered radiation is reflected, this means that a maximum amount of laser radiation is coupled out of the laser optics so that it can be used for workpiece processing. This enables precise determination of the focus position and / or nozzle centerline. The laser optics can thus ensure high quality in laser processing because the beam path can be reliably adjusted. Furthermore, the process helps to protect the optical components within the laser optics because scattered radiation is minimized. The calibration time before commissioning the laser system is minimized because the process is automatically reproducible.In one embodiment, changing the lateral position involves tilting the beam spot around a first axis and tilting the beam spot around a second axis to align the beam spot concentrically with the nozzle orifice. Tilting the beam spot around two axes enables a change in the lateral position in two spatial directions. In the plane perpendicular to the laser beam, a beam spot of the laser beam can thus be variably moved. This enables precise adjustment of the beam path to achieve nozzle centering.

[0045] In one embodiment, changing the axial position determines the focal position of the laser beam, which is then used for subsequent adjustment of the focal position outside the laser optics. The focal position can be achieved when the change in the axial position results in minimal scattered radiation. Typically, the beam path is adjusted so that the focal position is directly above the workpiece. Once the focal position is known, it can be adjusted accordingly.

[0046] In one embodiment, the method further comprises the step of igniting the laser beam at a second laser power corresponding to a nominal laser power, followed by repeating the steps of measuring the scattered radiation, changing the lateral position, and changing the axial position. This additional adjustment allows for the consideration of thermo-optical effects that only occur during operation at the nominal power.

[0047] In one embodiment, the lateral position and / or the axial position are changed depending on the scattered radiation measurement. Alternatively and / or additionally, the scattered radiation is measured continuously. This interaction between the change in the respective position and the measurement enables a precise determination of the focus position and / or the nozzle center. The continuous measurement further contributes to the precise determination of the focus position and / or the nozzle center.

[0048] Short description of the characters

[0049] Preferred further embodiments of the invention are explained in more detail in the following description of the figures. In the figures:

[0050] Figure 1 shows a laser optics with a beam positioning unit that defines a beam path;

[0051] Figure 2 is a schematic view of a reference aperture in a first embodiment;

[0052] Figure 3 is a schematic view of three different focus positions of a laser optic; Figure 4 is a schematic view of a nozzle center adjustment;

[0053] Figure 5 is a diagram in which a device for optically detecting scattered radiation has determined various values; and

[0054] Figure 6 is a schematic view of a reference aperture in a further embodiment.

[0055] Detailed description of preferred embodiments

[0056] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the different figures are provided with identical reference numerals, and a repeated description of these elements is partially omitted.

[0057] Figure 1 shows a laser optics system 1 for aligning a laser beam 50 onto a workpiece (not shown). The laser optics system 1 has a beam positioning unit 2, which has an adjusting lens 3, a deflecting mirror 4, and a focusing optics system 5. The laser optics system 1 further has a nozzle unit 6, which has a nozzle mouth 7 and a reference aperture 8. A device 9 for optically detecting scattered radiation 51 is also part of the laser optics system 1. The reference aperture 8 is configured to reflect the scattered radiation 51 onto the device 9. Optical sensors are arranged in the device 9. Furthermore, the reference aperture 8 is detached from the nozzle mouth 7 before the stationary operation of the laser optics system 1.

[0058] The adjustment lens 3 is connected to an adjustment motor 10. The adjustment motor 10 can move the adjustment lens 3 along the beam path. In this way, a focus position 52 (see Figure 3) of the laser beam 50 is moved. The focus position 52 describes the beam waist of the laser beam 50. The theoretical focus position of the laser beam is known in advance. However, since the actual focus position 52 is subject to tolerances, it must first be determined and the laser beam 50 then adjusted such that the focus position lies in the area of ​​the workpiece surface. In one embodiment, the focus position 52 is determined as follows: the reference aperture 8 is placed on the nozzle mouth 7. The reference aperture 8 can have a conical inner surface with a smallest diameter 11 (see Figure 2). The smallest diameter 11 can correspond to a diameter of the laser beam 50 in the focus position.When the laser beam now radiates along the beam path through the laser optics 1, the reference aperture 8 reflects the scattered radiation 51 to the device 9 until the focal position 52 of the laser beam 50 is at the position where the smallest diameter 11 of the reference aperture 8 is located. This position can be determined via the movement of the adjusting lens 3. As soon as the device 9 informs a control unit that it is no longer detecting any scattered radiation 51 from the reference aperture 8, the position of the focal position 52 is known. The focal position 52 is thus determined. It can then be moved in accordance with the process.

[0059] The deflection mirror 4 is connected to a deflection motor 12. The deflection motor 12 can tilt the deflection mirror 4 about a first axis 53 and / or a second axis 54. In this way, a nozzle center 55 (see Figure 4) of the laser beam is established. The nozzle center describes the position in which the laser beam 50 lies concentrically on a longitudinal axis of the nozzle orifice 7. The theoretical nozzle center is known in advance. However, since the actual nozzle center 55 is subject to tolerances, it must first be determined and the laser beam 50 then adjusted such that the nozzle center is ensured. In one embodiment, the nozzle center 55 is determined as follows: the reference aperture 8 is placed on the nozzle orifice 7. The deflection mirror 4 is tilted about the first axis 53 from a first extreme position to a second extreme position.At both the first extreme position and the second extreme position, the reference aperture 8 reflects scattered radiation to the device 9 for optically detecting the scattered radiation. The device 9 continuously detects the scattered radiation during the transition from the first extreme position to the second extreme position. The position at which the device 9 detects the least, preferably no, scattered radiation is stored as the position of the first axis 53 intended for the nozzle center 55. The deflecting mirror 4 is then tilted about the second axis 54 from a third extreme position to a fourth extreme position. In accordance with the tilt of the first axis 53, the position at which the device 9 detects the least, preferably no, scattered radiation is also determined when the second axis 54 is tilted. This position is stored as the position of the second axis 54 intended for the nozzle center 55.Thus, by changing a lateral position 56 (see Figure 4), the nozzle centering 55 is achieved. This tilting of the deflection mirror 4 can result in a beam path that is skewed to the longitudinal axis of the laser optics 1. According to the disclosure, this skew is accepted because the advantage of efficient detection offsets the disadvantage of the skew. Furthermore, because the workpiece is machined in close proximity to the nozzle orifice 7, the skew surprisingly has only a negligible effect on the process quality.

[0060] Figure 2 shows a reference aperture 8. This has the shape of a truncated cone. At a distal end 13, i.e. the end facing the workpiece, the reference aperture 8 has the smallest diameter 11. This can essentially correspond to the diameter of the laser beam 50 in the focus position 52. The fact that the smallest diameter 11 "essentially" corresponds to the diameter of the laser beam in the focus position 52 includes, in particular, that the smallest diameter 11 is somewhat larger in order to be able to compensate for possible skew due to tilting by the deflecting mirror 4. The reference aperture 8 has a conical inner surface 14, i.e., an inner contour that tapers conically towards a workpiece. An outer contour 15 can be matched to the nozzle mouth 7 in order to be able to realize, for example, a plug-in connection and / or a screw connection between the reference aperture 8 and the nozzle mouth 7.

[0061] Figure 3 schematically shows the process in which the focus position 52 is changed by the axial movement of the adjusting lens 3. After the determination of the focus position 52 as described above, it is adjusted according to the subsequent processing process. In the left-hand illustration, the focus position 52 is slightly below a workpiece 57. In the middle illustration, the focus position 52 is directly above the workpiece 57. In the right-hand illustration, the focus position 52 is directly at the exit of the nozzle mouth 7. The preferred focus position 52 depends on the subsequent laser processing process. During laser cutting, it is usually desirable to set the focus position 52 directly above the workpiece 57, as shown in the middle illustration. According to the disclosure, neither the position of the nozzle mouth 7 nor that of the focusing optics 5 changes during the movement of the focus position 52. Instead, the adjusting lens 3 is moved by means of the adjustment motor 10.

[0062] Figure 4 schematically shows the process in which the nozzle center 55 is achieved by tilting the deflection mirror 4. The nozzle unit 6 has a circular cross-section 16. This is, in particular, the smallest diameter 11 of the reference aperture 8. In the left-hand illustration, a beam spot 58 of the laser beam 50 is arranged eccentrically to the opening of the nozzle unit 6 with the circular cross-section 16. After the nozzle center 55 has been determined as described above, the beam spot 58 is changed in the lateral position 56 in order to achieve the nozzle center 55, as shown in the right-hand illustration. At the nozzle center 55, the beam spot 58 is concentric to the circular cross section 16 of the nozzle unit 6. By tilting the deflection mirror 4 about the first axis 53 and the second axis 54, it is possible for the change in the lateral position 56 to take place in two spatial directions.

[0063] Figure 5 shows an image of scattered radiation taken by the device 9 for optically detecting scattered radiation. The position of the beam spot 58 is plotted on the x-axis. This can be achieved by tilting the deflecting mirror 4. A measured value detected by the device 9, for example a current strength, is plotted on the y-axis. In the measuring process from Figure 5, the deflecting mirror 4 is tilted about the first axis 53. In a first extreme region 59, the device 9 detects a large amount of scattered radiation, as can be seen from the correspondingly detected measured values. In a central region 60, the device 9 detects no scattered radiation, as can be seen from the absence of detected values. In a second extreme region 61, the device 9 detects a large amount of scattered radiation, as can be seen from the correspondingly detected measured values. After tilting about the first axis 53, a corresponding tilting about the second axis 54 takes place.From the evaluation of both measurement curves, the nozzle center 55 can be determined by selecting the position of the deflection mirror 4 in such a way that no scattered radiation occurs.

[0064] Figure 6 shows a further embodiment of a reference aperture 8. The reference aperture 8 can be provided in a stationary manner in a processing space of a laser system. The reference aperture 8 can be made of metal or quartz glass, for example. The quartz glass can be provided with micro-bores. Before the stationary operation of the laser system, the laser optics 1 can be moved to the stationary reference aperture 8 in order to adjust the nozzle centering and / or focus position there via the scattered radiation 51 reflected by the reference aperture 8. The reference aperture 8 has a reflection section 17 that tapers conically in the direction away from the nozzle mouth 7 in order to promote reflection to the device 9 for optically detecting the scattered radiation 51. The reflection section 17 can also be cylindrical or, in the case of a cylindrical reference aperture, represent an edge or a line.The reference aperture 8 further has an alignment section 18 that forms a receiving volume 19 in the manner of a truncated cone. The nozzle orifice 7 can be moved into the receiving volume. The receiving volume 19 can be designed to complement the geometry of the nozzle orifice 7. The reference aperture 8 can be connected to a machining floor of the machining chamber by means of a spring element 20 to enable centering of the reference aperture 8 relative to the nozzle orifice 7. The spring element 20 can be arranged resiliently in two or three spatial directions to enable precise mechanical centering via a positive fit.

[0065] In order to provide different diameters of a nozzle mouth 7 in a laser system without operator intervention, a plurality of reference apertures 8 can be arranged in a processing space in the manner of a cassette, wherein the respective reference apertures 8 have different diameters of the reflection section 17 in order to be able to adapt to the respective focus diameters of the various laser beams. The cassette can, for example, be equipped as required. Screwing and changing a reference aperture 8 on the laser optics 1 is not necessary with this solution, which offers a completely automated, operator-independent solution. Where applicable, all individual features illustrated in the exemplary embodiments can be combined and / or exchanged with one another without departing from the scope of the invention.

[0066] List of reference symbols

[0067] 1 Laser optics 20 18 Alignment section

[0068] 2 beam position unit 19 recording volume

[0069] 3 Adjusting lens 20 Spring element 4 Deflecting mirror

[0070] 5 Focusing optics 50 Laser beam

[0071] 6 Nozzle unit 25 51 Scattered radiation

[0072] 7 Nozzle mouth 52 Focus position

[0073] 8 Reference aperture 53 first axis 9 Device for optical detection 54 second axis of scattered radiation

[0074] 55 Nozzle centering

[0075] 10 Adjustment motor

[0076] 30 56 Lateral position

[0077] 11 smallest diameter

[0078] 57 Workpiece

[0079] 12 Deflection motor

[0080] 58 Ray spot 13 distal end

[0081] 59 first extreme range

[0082] 14 conical inner surface

[0083] 60 central area

[0084] 15 Outer contour

[0085] 35 61 second extreme range

[0086] 16 circular cross-section

[0087] 17 Reflection section

Claims

Claims 1. A reference diaphragm (8) for reflecting scattered radiation (51) of a laser beam (50) passing through a laser optics system (1), comprising: a reflection section (17) provided and configured to reflect the scattered radiation (51) to a device (9) arranged in the laser optics (1) for optically detecting the scattered radiation (51); and an alignment section (18) provided and configured to align the reference diaphragm (8) relative to a nozzle mouth (7) of the laser optics (1); wherein the alignment section (18) is provided and configured to contact the nozzle mouth (7) during alignment and to be detached from the nozzle mouth (7) before stationary operation of the laser optics (1).

2. Reference aperture (8) according to claim 1, wherein the alignment section (18) forms a receiving volume (19) in the manner of a truncated cone, which is provided and configured to receive the nozzle mouth (7) during alignment.

3. Reference aperture (8) according to one of the preceding claims, further comprising a spring element (20) which is provided and configured to be connected to a processing floor of a processing space, wherein the spring element (20) enables centering of the reference aperture (8) relative to the nozzle mouth (7).

4. Reference aperture (8) according to one of the preceding claims, wherein the reflection section (17) is conically tapered in the direction away from the nozzle mouth (7) in order to promote reflection.

5. Reference aperture (8) according to claim 1, wherein the alignment section (18) has an outer contour (15) which enables a reversible coupling with the nozzle mouth (7), in particular by means of a plug connection or a screw connection.

6. Laser optics (1) for aligning a laser beam (50) onto a workpiece along a beam path, comprising a beam position unit (2) for adjusting the beam path, with an adjusting lens (3), a deflecting mirror (4) and a focusing optics (5); a nozzle unit (6) with a nozzle mouth (7) at which the beam path through the laser optics (1) ends in stationary operation, and the reference aperture (8) according to one of the preceding claims; and a device (9) for optically detecting the scattered radiation (51).

7. Laser optics (1) according to claim 6, wherein the focusing optics (5) is arranged in a fixed position in the laser optics (1).

8. Laser optics (1) according to one of claims 6 or 7, further comprising an adjustment motor (10) which is configured to move the adjustment lens (3) axially along the beam path in order to adjust a focus position (52) of the laser beam (50).

9. Laser optics (1) according to one of claims 6 to 8, further comprising a deflection motor (12) which is configured to tilt the deflection mirror (4) in order to adjust a lateral position of a beam spot (58) of the laser beam (50) within the nozzle mouth (8).

10. Laser optics (1) according to one of claims 6 to 9, wherein the deflecting mirror (4) is tiltable about a first axis (53) and about a second axis (54) in order to adjust the position of the laser beam (50) along two spatial directions in order to align the beam spot (58) concentrically with the nozzle mouth (8).

11. Laser optics (1) according to one of claims 6 to 10, wherein the reference aperture (8) has an inner contour which tapers conically towards a workpiece, so that at a distal end (13) of the laser optics there is a smallest inner diameter (11) which substantially corresponds to the diameter of the laser beam (50) in the focus position (52).

12. Laser optics (1) according to one of claims 6 to 11, wherein the device (9) for optically detecting the scattered radiation (51) has an annular base body which forms a light guide channel in its interior.

13. Laser optics (1) according to one of claims 6 to 12, wherein the device (9) for optically detecting the scattered radiation (51) along the beam path is arranged completely downstream of the focusing lens (5).

14. Laser optics (1) according to one of claims 6 to 13, further comprising a water-cooled absorber for compensating the heat introduced by the scattered radiation (51).

15. Laser system with a movement unit, a control unit and a laser optics (1) according to one of claims 6 to 14, wherein the control unit controls the laser optics (1) to adjust a focus position (52) and a nozzle center (55).

16. A method for adjusting a laser beam (50) along a beam path in a laser optics system (1), in particular according to one of the preceding claims, wherein the adjustment comprises determining a focus position and a nozzle center, comprising the steps of: a moving the laser optics (1) to a reference aperture (8) arranged in a stationary manner in a processing space, in particular according to one of claims 1 to 4, b centering a nozzle mouth (7) of the laser optics (1), at which the beam path through the laser optics (1) ends, relative to the reference aperture (8); c igniting the laser beam (50) at a first laser power, which is in particular less than 200 W; d measuring scattered radiation (51) emanating from the reference aperture (8), in particular by means of a device (9) for optically detecting the scattered radiation (51); e changing a lateral position (56) of a beam spot (58) of the laser beam (50) within the nozzle mouth (7) by means of a tiltable deflecting mirror (4);and f changing an axial position of a focus position (52) of the laser beam (50) by means of a movable adjusting lens (3); 17. The method according to claim 16, wherein the change in the lateral position according to step e includes a tilt about a first axis (53) and a tilt about a second axis (54) in order to align the beam spot concentrically with the nozzle mouth (7).

18. Method according to one of claims 16 or 17, wherein the change in the axial position according to step f results in the focus position (52) of the laser beam (50), which is used for a subsequent adjustment of the focus position (52) outside the laser optics (1).

19. A method according to any one of claims 16 to 18, which further comprises the following step after steps a to f: Igniting the laser beam (50) at a second laser power corresponding to a nominal power of the laser, and performing steps d to f again.

20. The method according to any one of claims 16 to 19, wherein the change according to step e and / or according to step f is carried out as a function of the measurement according to step d and / or wherein the measurement according to step d takes place continuously.

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