Device for detecting scattered radiation with a light-guiding channel

Abstract

The present invention relates to a device (1) for detecting scattered radiation (170) in the beam path of a laser system, having: an annular main body (5) which forms a light-guiding channel (14) in its interior; wherein the main body (5) has a first opening (6) and a second opening (7), which are spaced apart from one another in a wall of the main body (5), more particularly along an inner circumference of the main body (5), and each form a passage for the scattered radiation (170) into the light-guiding channel (14); and wherein the light-guiding channel (14) has a detection portion (3) in which a radiation intensity of the scattered radiation (170) received by the light-guiding channel (14) can be detected.

Description

[0001] Device for detecting scattered radiation with a light guide channel

[0002] Technical area

[0003] The present invention relates to a device for detecting scattered radiation in the beam path of a laser system.

[0004] State of the art

[0005] Laser systems, especially multi-axis laser systems, have become an indispensable technology in many industries in recent years. They offer high precision and flexibility, enabling efficient processing of workpieces, such as cutting, welding, and / or coating. Laser systems incorporate a variety of optical elements, such as lenses, mirrors, and protective glass. To enable efficient and process-compliant processing of the respective workpiece, it is essential that the optical elements are free of significant defects, for example, caused by excessive contamination.

[0006] European publication EP 3 978 179 A1 is known from the prior art. This discloses a processing head in which contamination appearing on a protective glass is detected by an optical sensor. For this purpose, the protective glass has an anti-reflection film on the surfaces orthogonal to the laser beam, while it has a reflective film on the surfaces running in the direction of the laser beam. In this way, a signal is fed to the optical sensor when contamination is present on the protective glass. This signal is usually reflected several times by the protective glass before reaching the optical sensor.

[0007] Description of the invention Starting from the known prior art, it is an object of the present invention to provide an improved device. In particular, the invention aims to detect scattered radiation in order to determine the condition of an optical interface, regardless of the position at the optical interface where a defect occurs. Further, in particular, the invention aims to provide a device that does not increase, or only slightly increases, the complexity of evaluating the detected signal. The invention can also aim to enable the device to be integrated into existing laser systems without relying on additional electronics. Further, in particular, the invention aims to enable the device to be reliably manufactured in large quantities.

[0008] The object is achieved by a device for detecting scattered radiation in the beam path of a laser system having the features of claim 1. Advantageous further developments emerge from the subclaims, the description, and the figures.

[0009] Accordingly, a device for detecting scattered radiation in the beam path of a laser system is proposed. The device can be referred to as a state detection device because it can be suitable for detecting a state of an optical interface of a substantially rotationally symmetrical optical element through which a laser beam is directed. The optical element can be a lens, a mirror and / or a protective glass. The optical interface can be smooth and in this respect differ from a diffractive optical element. The laser beam can strike the optical element substantially orthogonally, in particular if the optical element is a lens and / or a protective glass. The laser beam can also strike the optical element at an angle, in particular if the optical element is a mirror and / or a lens.The detected scattered radiation can provide information about whether there is a defect on the optical interface. For example, the degree of contamination of the optical interface can be detected. The device can communicate at least indirectly with a control unit in order to communicate the detected state of the optical interface to the control unit. If the detected state exceeds a limit value, for example, the control unit can communicate this to an operator of a laser system via a user interface so that the optical interface can be cleaned and / or replaced, for example. 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 a laser source via a fiber optic cable into a laser quill, from where it can enter a primary laser optics system via a movement unit. The beam path is determined by optical elements, particularly mirrors and lenses.

[0010] The device comprises an annular base body, which forms a light guide channel within its interior. The annular body can be designed to transmit the scattered radiation to a detection section, which is why it can also be referred to as a transmission element. The light guide channel is, in particular, formed entirely within the annular base body. The annular base body can define a hollow space within which the light guide channel runs.

[0011] The annular base body has a first opening and a second opening, which are arranged at a distance from one another in a wall of the base body, in particular along an inner circumference of the base body, and which each form a passage for the scattered radiation into the light guide channel. The first opening and the second opening can together be referred to as an opening unit. The opening unit is configured and provided to receive scattered radiation reflected from the optical interface. The reflected scattered radiation can be due to a defect on the optical interface. For example, the optical interface can be contaminated by metal dust or an oil mist, which causes Mie scattering in interaction with the laser beam. The contamination of the optical interface can be in the dimension of 0.5 pm to 10 pm, in which Mie scattering dominates.It can also have larger dimensions, in which classical scattering according to Snell's law of refraction dominates. The first opening and the second opening allow the reflected radiation to enter the ring-shaped base body and its light guide channel. The laser beam directed towards the optical interface can be reflected or diffracted by the defect in such a way that it deviates from the intended path of the laser radiation, i.e. the beam path, and thus reflects the scattered radiation. The intensity and direction of the scattered radiation depend on the dimension and internal properties of the defect. The larger the defect, the more intense the scattered radiation and the less intense the laser beam passed through the optical element.

[0012] The light guide channel of the device has a detection section in which a radiation intensity of the scattered radiation received by the light guide channel can be detected. The detection section can be adapted to accommodate a detector, which is why it can also be referred to as a detector receptacle. The detection section can be configured and provided to accommodate a detector, in particular in the manner of a photodiode, for detecting the scattered radiation. The detection section can have a shape such that the detector is received in the detection section in a form-fitting and / or force-fitting manner. The detection section can be machined into the device. The detector can be a photodiode. This is particularly suitable for laser beams that are in the form of infrared radiation.

[0013] The annular base body can be configured and provided to transmit the scattered radiation received by the opening unit, at least in sections along a circumferential direction of the optical element, to the detection section and in particular to the detector arranged therein. As a transmission element, the base body thus fulfills the function of transmitting the reflected scattered radiation received by the openings to the detection section. This transmission takes place, at least in sections, along the circumferential direction of the base body. The base body can be designed as a hollow channel within the device. The essentially rotationally symmetrical optical element has a circumferential direction around the axis of rotation.The fact that the captured scattered radiation extends at least partially along the circumferential direction ensures that the detection section and the openings define an angular range relative to the rotation axis. The reflected scattered radiation therefore does not reach the detection section via the shortest path, which prevents the detected signal from being distorted by the defect causing the reflected scattered radiation being in close proximity to the detection section. The scattered radiation captured by the openings can, for example, be transmitted to the detection section at 60°, 90°, 120°, and / or 180° along the circumferential direction of the base body.

[0014] In this way, defects can be reliably detected with a comparable signal level, regardless of their position relative to the detector and the detection section. The detected scattered radiation can be spatially homogenized and detected regardless of location. Reliable detection of smaller defects is also possible. The intensity with which the reflected scattered radiation hits the opening unit can be inversely proportional to the square of the radius relative to the center of the optical interface, and thus to the axis of rotation. The further the defect is from the center of the optical interface, the more the intensity of the reflected scattered radiation can distort the detected signal. In this respect, transmitting the recorded scattered radiation, at least in sections along the circumferential direction, provides a remedy. Exactly one detector can be accommodated in the detection section.This facilitates communication between the device and the control unit, as only one detector needs to be considered. Furthermore, the integration of the device into the processing head of the laser system is simplified because the single detector only requires one cable. Accordingly, the device helps detect scattered radiation in order to determine the condition of an optical interface, regardless of the position at the optical interface where a defect occurs. Furthermore, it helps to ensure that the complexity of evaluating the detected signal is not increased, or only slightly increased. Furthermore, it can be integrated into existing laser systems without the need for additional electronics. It can also be reliably manufactured in large quantities.

[0015] In one embodiment, the first opening and the second opening are spaced apart from one another along a circumferential direction of the annular base body, in particular by an angular span of at least 60°, in particular 120°, along the circumferential direction. Thus, the scattered radiation reflected by the optical interface can be received by the first opening and the second opening at two predetermined spaced-apart locations. This further contributes to the homogenization of the signal detected by the detection section and, consequently, to the detected state. The first opening and the second opening can each be arranged on an inner side of the annular base body. The angular span by which the first opening is spaced from the second opening can also be 180°.This ensures a maximum distance between the first opening and the second opening, whereby a defect that causes disproportionately reflected scattered radiation in the first opening causes underproportionately reflected scattered radiation in the second opening, so that the signal detected by the detector is balanced and free of distortions. The aperture angle of the first opening and the second opening is small compared to the circumference of the base body. This allows a sensor signal to be detected largely independently of the defect and the position of the contamination. Furthermore, particles with a wavelength similar to the laser light can be efficiently detected.

[0016] In one embodiment, the base body has a third opening that is spaced apart from the first opening and the second opening along the circumferential direction, in particular by an angular span of at least 60° each, in particular 120° each, along the circumferential direction. The third opening further contributes to the homogenization of the signal detected by the detector and consequently to the detected state. The first opening, the second opening, and the third opening can be arranged evenly distributed along the circumferential direction, i.e. offset from one another by 120° each. This further counteracts the unwanted emphasis of a defect due to its position in the immediate vicinity of an opening. The third opening can be arranged on the inside of the base body. The first opening, the second opening, and the third opening can each have a chamfered opening slope that enables efficient detection of the reflected scattered radiation.For example, the openings can be chamfered at an angle of at least 30° relative to the plane in which the optical interface runs. These angles have proven advantageous when the reflected scattered radiation is scattered radiation reflected by oil mist or metal dust. This is because these are reflected according to Mie scattering and, in this case, have an angle of 15° to 30° relative to the plane in which the optical interface runs. The first opening, the second opening, and the third opening can be arranged such that the scattered radiation absorbed by the opening unit is transmitted from the base body and its light guide channel, thus the transmission element, completely along the circumferential direction to the detection section. This further contributes to the homogenization of the signal detected by the detection section and, consequently, to the detected state.

[0017] In one embodiment, the first opening is the opening furthest away from the detection section, in particular it is arranged diametrically opposite the detection section, and it defines a larger opening angle than the second opening and in particular than the second opening and the third opening. Because the furthest away opening defines the largest opening angle, any attenuation loss of the absorbed scattered radiation within the base body is counteracted. The larger opening angle causes the first opening to absorb more reflected scattered radiation than the second opening and in particular than the second opening and the third opening. This compensates for the unavoidable attenuation that the scattered radiation experiences in the light guide channel on the path from the first opening along the circumferential direction to the detection section. In particular, the larger opening angle is adapted to the position of the first opening.Because the second opening, and in particular the second opening and the third opening, are closer to the detection section than the first opening, the scattered radiation they absorb is less attenuated. Therefore, the aperture angle of the second opening and the third opening is smaller than that of the first opening without this affecting the detected signal. The larger aperture angle of the first opening ensures that the signal absorbed by the first opening is weighted according to its intensity to form a composite signal, which is then picked up by the detection section and subsequently by the detector. There can be a linear relationship between the aperture angle of each opening and the distance of the aperture angle from the detection section.In principle, it can be provided that an opening cross-section and / or an opening angle of the openings increases with the distance of the respective opening from the detection section in the circumferential direction of the base body.

[0018] In a configuration in which only two openings (i.e. the first opening and the second opening) are provided in the base body, it may be preferred that the openings lie opposite one another in the circumferential direction of the base body, i.e. are spaced 180° apart, and that both openings are the same distance from the detection section, as well as having the same opening cross-section and the same opening angle. In one embodiment, the light guide channel has a reflective surface, which is in particular made of a non-ferrous metal, a precious metal and / or an alloy. The light guide channel, also called annular channel, can extend from the detection section by essentially 360° around the axis of rotation. It can have a constant radius. The reflective surface can be selected such that a sufficiently high reflection is ensured at the wavelength of the laser beam.Sufficiently high reflection is characterized by the fact that it transmits the scattered radiation absorbed by the openings to the detection section with comparable intensity. For example, more than 90%, particularly more than 95%, of the scattered radiation absorbed by the openings can be transmitted to the detection section. During transmission, the absorbed scattered radiation can be scattered multiple times. Attenuation of the scattering can be achieved by a factor of T with a reflectivity T of the surface of the fiber optic channel and a number of scatterings n. nbe dampened. In particular, copper can be selected as the non-ferrous metal. Copper can be machined by diamond milling. Consequently, with a base body made of copper, the light guide channel can be efficiently machined. Brass can be selected as the alloy, which can also be machined. Consequently, with a base body made of brass, the light guide channel can be efficiently machined. Furthermore, in particular, not only the surface of the light guide channel can be made of a non-ferrous metal, a precious metal and / or an alloy, but the entire base body or the entire device. This increases the efficiency in the production of the device.

[0019] In one embodiment, the reflective surface is an applied coating. This allows the device to be made of a material that does not require attention to its reflective properties. Only the surface of the light guide channel needs to be coated accordingly to ensure a sufficiently high transmission rate from the opening unit to the detection section. In one embodiment, the light guide channel has a circular cross-section. The circular shape has a positive effect on the reflective properties of the light guide channel, which can also be referred to as an annular channel, as a transmission element. Furthermore, the circular shape ensures efficient machining of the light guide channel. The circular cross-section of the light guide channel can have a constant diameter.Alternatively, the diameter of the circular cross-section may be larger in the area of ​​the respective openings than in the remaining area.

[0020] In one embodiment, the device comprises an upper part and a lower part, which form the first opening, the second opening, optionally the third opening, the detection section and the light guide channel and which are in particular substantially identical in construction to one another. The upper part and the lower part can be designed such that, when joined together, they form the openings, the detection section and the light guide channel as cavities. This allows the device to be manufactured efficiently. Furthermore, the upper and lower parts can be identical in construction to one another, which further promotes manufacturing efficiency. For example, the cavities that form the openings, the detection section and the light guide channel can be machined into the upper part and the lower part.

[0021] In one embodiment, the base body of the device further comprises a light guide cable, in particular in the form of an optical quartz fiber, which extends in the light guide channel. The light guide cable can have light entry sections on its radially inwardly facing inner side, each of which is arranged at the location of one of the openings in the base body. For example, a surface of an optical quartz fiber can be removed to form a light entry section.

[0022] The disclosure further relates to a condition detection system. This comprises a device according to the above disclosure. Furthermore, the condition detection system includes a detector that is accommodated within the detection section and is intended to detect the reflected scattered radiation. The disclosure of the detector with respect to the device applies accordingly to the condition detection system. The detector of the condition detection system is configured to record the transmitted scattered radiation as a sum signal. The sum signal is formed from the scattered radiation recorded by the openings and transmitted via the light guide channel. For example, a first signal of the sum signal can be recorded from the first opening, a second signal of the sum signal from the second opening, and / or a third signal of the sum signal from the third opening.The sum signal can be weighted by the corresponding opening angle of the respective openings. In this way, the condition detected by the condition detection system is independent of the position of the respective defect at the optical interface. By forming the sum signal, the arrangement of multiple sensors is no longer necessary. This facilitates the design of the condition detection system and, on the other hand, its integration into an existing laser system. The condition detection system thus helps to detect scattered radiation in order to determine the condition of an optical interface regardless of the position at the optical interface where a defect occurs. Furthermore, it helps to ensure that the complexity of evaluating the detected signal is not increased, or only increased insignificantly. Furthermore, it can be integrated into existing laser systems without the need for additional electronics. It can also be reliably manufactured in large quantities.

[0023] In one embodiment, the condition detection system has an aperture unit designed to regulate the scattered radiation arriving at the detector. The aperture unit can ensure that the scattered radiation transmitted to the detector by the base body as a transmission element only hits the detector from a predetermined direction. This facilitates objective evaluation of the detector because laterally arriving signals that could corrupt the composite signal are regulated accordingly. The aperture unit can be adjustable so that the regulation it produces is adapted to the optical interface being monitored. For example, the regulation for detecting the condition of a mirror can differ from the regulation for detecting the condition of a lens.

[0024] In one embodiment, the aperture unit comprises two tubular elements arranged circumferentially on either side of the detector. This ensures that the detector only detects scattered radiation that impinges on it orthogonally. The tubular elements can be structurally identical to one another. They can be held in corresponding recesses of the device with a force-fitting and / or positive fit.

[0025] In one embodiment, the condition detection system further comprises an optical element through which a laser beam can be directed, in particular the lens, the mirror, the protective glass, wherein the device and the optical element extend in planes that are plane-parallel to one another, wherein a distance between the planes is selected such that the scattered radiation reflected at an optical interface of the optical element strikes the opening unit at an angle of 15° to 30°. The range of the angle can result from the fact that the exact position of the respective defect that causes the scattered radiation varies. Because the defect can be of a size that corresponds to the wavelength of the laser beam, Mie scattering can emanate from the defect.For particles with dimensions between 0.5 pm and 10 pm, an infrared laser beam can exhibit reflected scattered radiation that deviates by 15° to 30° from the plane of the optical interface. Therefore, the condition detection system is optimized for defects that cause Mie scattering.

[0026] In one embodiment, the condition detection system further comprises a control unit to which the detector transmits the recorded sum signal, wherein the control unit determines a degree of contamination of the optical interface from the recorded sum signal. For this purpose, a limit value can be stored in the control unit for each optical interface, above which the control unit classifies the degree of contamination as critical. As soon as the degree of contamination of an optical interface is classified as critical, the control unit can send a corresponding alarm signal to a user interface, so that an operator of the system is informed of the corresponding contamination of the optical interface. A lookup table can be stored in the control unit, in which a critical degree of contamination is listed for each optical interface. The lookup table can have predetermined values ​​or can be modifiable by an operator.

[0027] The disclosure further relates to a laser system, thus a laser processing device, for aligning a laser beam onto a workpiece. The laser system comprises a state detection system according to the above disclosure and a processing head that aligns a laser beam onto a workpiece.

[0028] Short description of the characters

[0029] Preferred further embodiments of the invention are explained in more detail in the following description of the figures. In the figures:

[0030] Figure 1 is a schematic view of a laser system;

[0031] Figure 2 is a schematic sectional view of a condition detection system comprising a device, a detector and an optical element;

[0032] Figure 3 is a schematic plan view of a device with a detector;

[0033] Figure 4 is a schematic perspective view of a device comprising a diaphragm unit and a detector connected to a control unit by a cable;

[0034] Figure 5 is a schematic plan view of a device with an opening unit having three openings; and Figure 6 is a diagram in which reflected scattered radiation transmitted to a detector is normalized to the actually reflected scattered radiation.

[0035] Detailed description of preferred embodiments

[0036] 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 to avoid redundancies.

[0037] Figure 1 shows a laser system 100 having a processing head 110 that directs a laser beam 120 onto a workpiece 130. The laser system 100 has a plurality of optical elements 140 that are essentially rotationally symmetrical. The optical elements 140 can be a lens, a mirror, and / or a protective glass. The at least one lens is provided to focus the laser beam 120. The at least one mirror is provided to redirect the laser beam 120. The at least one protective glass is provided to protect the processing head 110 and the laser optics arranged therein from external interference factors, such as reflected laser light. The respective optical elements 140 can be arranged in the processing head 110 and / or in a laser sleeve 150.The laser beam 120 is provided by a laser source (not shown), such as a disk laser, a diode laser, or a fiber laser. The laser source can guide the laser beam 120 via a fiber optic cable to the laser sleeve 150, within which the laser beam 120 is collimated using lenses, in particular collimating lenses. From the laser sleeve 150, the laser beam 120 is guided into the processing head 110, in which the laser optics are arranged. The processing head 110 is controlled in a process-appropriate manner and ensures appropriate alignment of the laser beam 120 onto the workpiece 130. The laser system 110 can be a system for laser cutting, laser welding, and / or laser deposition welding. The individual optical elements 140 each have at least one optical interface 160 that forms a substantially smooth surface.If the optical interface 160 has a defect, for example due to contamination of the optical interface 160, a reflected scattered radiation 170 emanates from each defect (see Figure 2).

[0038] Figure 2 shows a device 1, also called a state detection device 1, for detecting a state of at least one optical interface 160 in a sectional view along a diameter of the state detection device 1. The state detection device 1 has an opening unit 2, thus a first opening 6 and a second opening 7, which receives scattered radiation 170 reflected by the optical interface 160. The state detection device 1 further has a detection section 3, in which a detector 4, in particular in the manner of a photodiode, is accommodated in order to detect and process the scattered radiation 170. The state detection device 1 further has a base body 5, which can also be referred to as a transmission element 5, which transmits the scattered radiation 170 received by the opening unit 2 along a circumferential direction U of the optical element 140 to the detector 4.

[0039] The laser beam 120 extends essentially orthogonally to the optical interface 160. The optical element 140 with the optical interface 160 is arranged upstream of the condition detection device 1. The laser beam 120 passes through the optical element 140, which is transparent to the laser beam 120. A defect 180 is present on the optical interface 160 of the optical element 140 facing the condition detection device 1. This defect can result, for example, from contamination of the optical element 140. The defect 180 disrupts the laser radiation 120 and causes the reflected scattered radiation 170. The larger the defect 180, the larger the reflected scattered radiation 170 and the lower the laser radiation 120 that is guided along the intended beam path through the laser system 100.

[0040] The reflected scattered radiation 170 is received by the first opening 6 and the second opening 7 of the opening unit 2 of the condition detection device 1. The first opening 6 and the second opening 7 are arranged on an inner side of the condition detection device 1.

[0041] The annular base body 5 has a light guide channel 14 having a reflective surface 8. The reflective surface 8 guides the scattered radiation 170 received by the first opening 6 and the second opening 7 along the circumferential direction U of the optical element 140 to the detection section 3, in which the detector 4 is arranged. The reflective surface 8 can be part of the light guide channel 14 with a circular cross-section. The detector 4 detects the scattered radiation 170 received by the first opening 6 and the scattered radiation 170 received by the second opening 7 as a combined signal and transmits the combined signal via a cable 9 to a control unit (not shown). The first opening 6 is further away from the detector 4 than the second opening 7. Accordingly, the scattered radiation 170 received by the first opening 6 has a longer path to travel than the scattered radiation 170 received by the second opening 7.Because the path from the first opening 6 is longer, the attenuation of the scattered radiation 170 received by the first opening 6 is greater than the attenuation of the scattered radiation 170 received by the second opening 7. To compensate for this effect of increased attenuation with the increased distance from the detector 4, the first opening 6 can have a larger opening area than the second opening 7, so that the first opening 6 receives relatively more scattered radiation 170. Accordingly, the sum signal detected by the detector 4 is weighted in correlation with the respective distance of the openings 6, 7. In the present case, the defect 180 is eccentric on the optical interface 160. In particular, because the opening unit 2 has the first opening 6 and the second opening 7, the position of the defect 180 does not affect the result detected by the detector 4.

[0042] The laser source can, for example, generate laser beams, in particular infrared laser beams, with wavelengths of 0.4 pm and 1.5 pm, in particular of approximately 450 nm, of approximately 515 nm, between approximately 800 nm and approximately 1000 nm, or of approximately 1030 nm, 1060 nm, or 1070 nm. The defect 180 can be in the order of magnitude of 0.5 pm to 10 pm. Accordingly, the laser beam 120 can scatter elastically at the defect 180 in the manner of Mie scattering. For a particle size between 0.5 pm and 10 pm, the Mie scattering causes a scattering angle W between 15° and 30°. Accordingly, the distance between the state device 1 and the optical interface 160 is selected such that, with a corresponding positioning of the defect 180 on the optical interface 160, the reflected scattered radiation is detected by the opening unit 2.

[0043] Figure 3 shows the condition detection device 1 in a plan view. The first opening 6 is arranged diametrically opposite the detection section 3. The second opening 7 is provided along the circumferential direction U at a distance of 120° from the first opening 6. Starting from the first opening 6, along the direction away from the second opening 7 along the circumferential direction U, a third opening 10 is provided at a distance of 120° from the first opening 6. The second opening 7 and the third opening 10 are each offset from the detection section 3 by 60°, while the first opening 6 is offset from the detection section 3 by 180°. Accordingly, the first opening is the furthest opening because it is arranged opposite the detection section 3. The first opening 6 therefore defines a larger opening area than the second opening 7 and the third opening 10.The first opening 6, the second opening 7 and the third opening 10 form the opening unit 2. The third opening 10 can be arranged analogously to the first opening 6 and the second opening 7 on the inside of the condition detection device 1.

[0044] The defect 180 is located on the optical interface 160 eccentrically from a rotation axis R. The scattered radiation 170 reflected by the defect 180 is received by the opening unit 2, i.e., the first opening 6, the second opening 7, and the third opening 10, and is then transmitted by the base body 5 along the circumferential direction to the detector 4. The detector 4 thus receives three signals of reflected scattered radiation 170 and can determine, in particular from the intensity of the respectively detected signal and the time at which it receives the respectively detected signal, how severe the impairment of the optical interface 160 caused by the defect 180 is. From the first opening 6, the reflected scattered radiation 170 is transmitted to the detector 4 along a first scattered radiation path 171 and along a second scattered radiation path 172.In addition, the reflected scattered radiation is transmitted from the second opening 7 along a third scattered radiation path 173 and from the third opening 10 along a fourth scattered radiation path 174 to the detector 4. The first scattered radiation path 171 extends from the first opening 6 by 180° along the circumferential direction U of the optical element 140 to the detector 4. The second scattered radiation path 172 also extends from the first opening 6 by 180° along the circumferential direction U of the optical element 140 to the detector 4, but in the opposite direction to the first scattered radiation path 171. The third scattered radiation path 173 extends from the second opening 7 by 60° along the circumferential direction U of the optical element 140 to the detector 4, and the fourth scattered radiation path 174 extends from the third opening 10 by 60° along the circumferential direction U of the optical element 140 to the detector 4.Detector 4 receives the signals received according to the respective scattered radiation paths 171, 172, 173, 174 as a combined signal and forwards them to a control unit. The control unit can detect a state of the optical interface 160 from the received combined signal.

[0045] Figure 4 shows the condition detection device 1 in a perspective view. The first opening 6 has chamfered opening surfaces to optimally detect the scattered radiation 170 reflected by the optical interface 160. The chamfer angle can, for example, be at least 30° relative to the plane along which the optical element 140 runs. In this way, the Mie scattering reflected by a defect 170 is efficiently absorbed by the first opening 6. Likewise, the second opening 7 and the third opening 10 can have chamfered opening surfaces with a chamfer angle of at least 30°. An aperture unit 11 is arranged in the region of the detector 4. The aperture unit 11 regulates the scattered radiation 170 arriving at the detector 4. It can consist of two tubular elements arranged on either side of the detector 4. The tubular elements can each be embedded in a corresponding opening of the condition detection device 1.The scattered radiation 170 arriving at the detector 4 can be detected via the position and / or diameter of the tubular elements. The base body 5 has an upper part 12 and a lower part 13. The upper part 12 and the lower part 13 can be connected to one another in a force-fitting manner, in particular by screwing, and / or by a material bond. Together, they form the light-guiding channel 14 with the circular cross-section. The upper part 12 and the lower part 13 can be structurally identical to one another. This increases the efficiency in the manufacture of the condition detection device 1. The condition detection device 1 can be made of a non-ferrous metal, such as copper, into which the light-guiding channel 14 is diamond-milled. The condition device 1 can also be made of a precious metal. The condition device 1 can also be made of an alloy, such as brass, into which the light-guiding channel 14 is milled.Furthermore, the opening unit 2, thus the openings, as well as the detection section 3 can be machined into the state device 1.

[0046] Figure 5 shows a sectional view of the condition detection device 1 in plan view. The detection section 3 is arranged diametrically opposite the first opening 6. The first opening 6 extends along an opening angle α. The opening angle α results in a first opening area of ​​the first opening 6. The second opening 7 and the third opening 10 are arranged offset by 120° in both directions along the circumferential direction U, starting from the first opening 6. These each extend along an opening angle β. The opening angle β results in a second opening area of ​​the second opening 7 and an equally large third opening area of ​​the third opening 10.The first opening area is larger than the second opening area and than the third opening area because the first opening 6 is further away from the detection section 3 than the second opening 7 and the third opening 10, so that the scattered radiation 170 detected by the first opening area 6 is subject to greater attenuation than the scattered radiation 170 detected by the second opening 7 and the third opening 10. The first opening 6, the second opening 7 and the third opening 10 are connected to the detection section 4 via the light guide channel 14. This extends circularly around the rotation axis R, which forms the center of the optical interface 160.

[0047] Figure 6 schematically shows a diagram in which reflected scattered radiation 170 transmitted to detector 4 is normalized to the actual reflected scattered radiation 170. The individual points 190 represent measurement points. The dashed outer diameter in Figure 6 corresponds to the inner diameter of the annular base body 5. In the embodiment of Figure 6, the first opening 6, the second opening 7, and the third opening 10 are arranged according to the embodiment of Figure 5. In a central region 200, the design of the opening unit 2 enables the actually reflected scattered radiation 170 to be completely detected and transmitted to the detector 4. Even in an extended region 210, which extends between the central region 200 and the respective openings 6, 7, 10, the arrangement of the opening unit 2 according to this embodiment enables approximately 80% of the actually reflected scattered radiation 170 to be detected.In the area that is not covered by the central area 200 or the extended area 210, less than 80%, in particular less than 60%, of the actually reflected scattered radiation 170 is detected. This does not affect the state detected by the state detection device 1 insofar as defects 180 located outside the central area 200 and the machined area 210 have less of an impact on the laser beam 120 and cause less intense scattered radiation 170. Thus, the arrangement of the opening unit 2 in this exemplary embodiment results in an optimal compromise between state detection and the number of openings 6, 7, 10.Too large a number of openings, for example five or more openings, may be disadvantageous in certain configurations because this would result in increased reflection of scattered radiation out of the light guide channel 14 before the reflected scattered radiation 170 has reached the detector 4.

[0048] Where applicable, all individual features presented in the embodiments may be combined and / or exchanged without departing from the scope of the invention.

[0049]

[0050] 1 Device, condition detection device 140 optical element device 150 laser quill

[0051] 2 aperture unit 160 optical interface

[0052] 3 Detection section 25 170 scattered radiation

[0053] 4 Detector 171 first scattered radiation path

[0054] 5 Base body 172 second scattered radiation path

[0055] 6 first opening 173 third scattered radiation path

[0056] 7 second opening 174 fourth scattered radiation path

[0057] 8 reflective surface 30 180 defect

[0058] 9 cables 190 measuring points

[0059] 10 third opening 200 central area

[0060] 11 Aperture unit 210 extended range

[0061] 12 upper part

[0062] 13 lower part 35 U circumferential direction

[0063] 14 Light guide channel W scattering angle

[0064] R rotation axis

[0065] 100 laser system

[0066] 110 Machining head a first opening angle

[0067] 120 laser beam 40 ß second opening angle

[0068] 130 workpiece

Claims

Claims 1. A device (1) for detecting scattered radiation (170) in the beam path of a laser system, comprising: an annular base body (5) which forms a light-guiding channel (14) in its interior; wherein the base body (5) has a first opening (6) and a second opening (7) which are arranged at a distance from one another in a wall of the base body (5), in particular along an inner circumference of the base body (5), and which each form a passage for the scattered radiation (170) into the light-guiding channel (14); and wherein the light-guiding channel (14) has a detection section (3) in which a radiation intensity of the scattered radiation (170) received by the light-guiding channel (14) can be detected.

2. Device (1) according to claim 1, wherein the first opening (6) and the second opening (7) are spaced apart from one another along a circumferential direction (U) of the annular base body (5), in particular by an angular span of at least 60°, in particular 120°, along the circumferential direction (U).

3. Device (1) according to one of the preceding claims, wherein the base body (5) has a third opening (10) which is spaced from the first opening (6) and the second opening (7) along the circumferential direction (U), in particular by an angular span of at least 60° in each case, in particular 120° in each case, along the circumferential direction (U).

4. Device (1) according to one of the preceding claims, wherein the first opening (6) is the opening furthest away from the detection section (3), in particular is arranged diametrically opposite the detection section (3), and defines a larger opening angle (α) than the second opening (7) and in particular than the second opening (7) and the third opening (10).

5. Device (1) according to one of the preceding claims, wherein the light guide channel (14) has a reflective surface which is in particular made of a non-ferrous metal, a noble metal and / or an alloy.

6. Device (1) according to claim 5, wherein the reflective surface is an applied coating.

7. Device (1) according to one of the preceding claims, wherein the light guide channel (14) has a circular cross-section.

8. Device (1) according to one of the preceding claims, wherein the device (1) has an upper part (12) and a lower part (13) which form the first opening (6), the second opening (7), the detection section (3) and the light guide channel (14) and which are in particular substantially identical in construction to one another.

9. Device (1) according to one of the preceding claims, further comprising a light guide cable, in particular in the manner of an optical quartz fiber, which extends in the light guide channel (14).

10. A condition detection system comprising a device (1) according to any one of the preceding claims; and a detector (4) accommodated within the detection section (3) and provided to detect the reflected scattered radiation (170); wherein the detector (4) is configured to receive the transmitted scattered radiation (170) as a sum signal.

11. A condition detection system according to claim 10, further comprising a diaphragm unit (11) provided to regulate the scattered radiation (170) arriving at the detector (4).

12. A condition detection system according to claim 11, wherein the aperture unit (11) comprises two tubular elements arranged on both sides of the detector (4) in the circumferential direction (U).

13. A condition detection system according to any one of claims 10 to 12, further comprising an optical element (140) through which a laser beam (120) can be directed; wherein the device (1) and the optical element (140) extend in planes that are plane-parallel to one another, wherein a distance between the planes is selected such that the scattered radiation (170) reflected at an optical interface of the optical element (140) strikes the opening unit (2) at an angle of 15° to 30°.

14. Condition detection system according to one of claims 10 to 13, further comprising a control unit to which the detector (4) transmits the recorded sum signal, wherein the control unit determines a degree of contamination of the optical interface from the recorded sum signal.

15. A laser system (100) for directing a laser beam (120) onto a workpiece (130), comprising: the condition detection system according to any one of the preceding claims; and a processing head (110) directing a laser beam (120) onto a workpiece (130).

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