Monitoring device for a laser beam system and laser beam system

Abstract

The invention relates to a monitoring device (10) for a laser beam system (12), in particular a laser beam welding system, comprising a camera (14), wherein the camera (14) is arranged to detect at least a section of a joining region (30) of a workpiece (28) using sensor technology, wherein the monitoring device (10) comprises a dynamic vision sensor (16), wherein the dynamic vision sensor (16) is arranged to simultaneously detect the section of the joining region (30) detected by the camera (14). Furthermore, the invention relates to a laser beam system (12), in particular a laser beam welding system for laser beam welding, comprising a laser (22) for generating a processing laser beam (24), wherein the laser beam system (12) comprises a monitoring device (10).

Description

Prior ArtThe invention relates to a monitoring device for a laser beam system and a laser beam system.DE 10 2006 015 383 A1 discloses a device for laser welding a first workpiece to a second workpiece, wherein the device comprises a sensor for process monitoring of the welding process in addition to a laser source, wherein the sensor can be a camera.Disclosure of the InventionAdvantages of the InventionThe monitoring device according to the invention for a laser beam system, in particular a laser beam welding system, having a camera, wherein the camera is arranged to detect at least a portion of a joining region of a workpiece by sensor technology, wherein the monitoring device comprises a dynamic vision sensor, wherein the dynamic vision sensor is arranged to detect the portion of the joining region detected by the camera by sensor technology at the same time, has the advantage, in contrast, that errors during the processing of the workpiece by the laser, in particular welding errors during the laser beam welding of the workpiece, can be detected quickly and reliably. By using a camera, in particular a high-speed camera, and a dynamic vision sensor simultaneously, at least two known defect images can be clearly detected: the so-called false freund and the contamination of the component, which can lead to splashing and burns. By evaluating simple image features on an FPGA (field programmable gate array), the images of the camera can be evaluated in real time and the wrong friend can be detected. For the occurring soiling of the workpiece, the dynamic vision sensor offers the decisive advantage of producing larger quantities of data only when a soiling is present.A monitoring device is advantageous in which the camera generates image data of the captured section of the joining region and the dynamic vision sensor generates event data of the captured section of the joining region.A monitoring device is particularly advantageous in which the monitoring device comprises an evaluation unit, wherein the evaluation unit is designed to detect welding defects in the joining region by evaluating the image data and / or evaluating the event data. It is advantageous here that the evaluation unit is designed to detect as welding errors a lack of weld that is hidden and / or a gap and / or a reduced welding depth between two joining partners as a function of the image data of the camera and preferably to detect as welding errors spatter and / or burns as a function of the event data of the dynamic vision sensor. The evaluation unit is preferably designed to determine the welding error of the hidden missing weld (false freund) and / or the detection of a gap and / or a missing welding depth by means of brightness and shape of the capillary from the image data of the camera. The evaluation unit is preferably designed to determine the detection of a contamination of the workpiece on the basis of the event rate, in particular events per second and / or the number of sprays and / or burns per travel and / or time unit. The monitoring device allows two of the most important defects to be detected during a laser machining process even during the process, in particular during the welding process, and can thus save downstream test capacities. In particular, the two stated errors are very difficult to detect in many products, for example by destructive testing or failure in the functional testing. A simple visual inspection cannot usually identify the welding defect, referred to as false friend, of the hidden missing weld.Furthermore, a monitoring device is advantageous, which comprises at least one beam splitter, wherein the beam splitter is designed to deflect process radiation of the section of the joining region for detection by the camera and at the same time for detection by the dynamic vision sensor. It is particularly advantageous that the beam splitter is a chromatically dividing beam splitter and / or an intensity-dividing beam splitter.Preferably, the camera of the monitoring device is a high-speed camera.The invention further comprises a laser beam system, in particular a laser beam welding system for laser beam welding, with a laser for generating a machining laser beam, wherein the laser beam system comprises a monitoring device described above. Preferably, the camera and / or the dynamic vision sensor are arranged coaxially in a beam path of the processing laser beam. In particular, the laser beam system comprises a wavelength-dividing mirror, wherein the wavelength-dividing mirror is arranged to reflect the processing laser beam and to transmit process radiation of the section of the joining region through the camera and the dynamic vision sensor for detection. The laser beam installation is preferably designed to weld at least two joining partners, in particular at least two metal sheets, in an overlapping joint.The advantages mentioned for the monitoring device also apply accordingly to a laser beam system with this monitoring device.Further advantages result from the following description of exemplary embodiments with reference to the figure and from the dependent claims.Brief Description of the DrawingsExemplary embodiments of the invention are illustrated in the drawing with reference to FIG. 1 and are explained in more detail in the following description.It shows: FIG. 1 shows a laser beam system with a monitoring device.DESCRIPTION OF EMBODIMENTSA monitoring device for a laser beam system is described below, in particular a laser beam welding system, having a camera, wherein the camera is arranged to detect at least a portion of a joining region of a workpiece by sensor technology, wherein the monitoring device comprises a dynamic vision sensor, wherein the dynamic vision sensor is arranged to detect the portion of the joining region detected by the camera by sensor technology at the same time. Furthermore, a laser beam system is described, in particular a laser beam welding system for laser beam welding, with a laser for generating a machining laser beam, wherein the laser beam welding system comprises the described monitoring device.By using a camera, in particular a high-speed camera, and a dynamic vision sensor (event-based camera), it is possible to detect at least two defect images during laser beam welding, in particular two sheets in the overlap joint. The opening of the capillary of the welding bath, visible from above, is observed by means of the camera and its brightness and geometric properties are recorded. This geometry of the capillary opening changes, for example, when passing over a gap between the two metal sheets. In this case, the capillary opening becomes, for example, a horseshoe-shaped object from an initially circular object and / or then changes into an elliptical shape. Since the capillary radiates very brightly, it is not possible with the camera that substantially less bright effects are observed. Thus, for example, splashing and luminous phenomena cannot be ensured due to burns, for example due to the soiling on the surface, since the contrast is too low, so that these remain "in the dark". These effects can be observed by means of the dynamic vision sensor, since this reacts in particular to very rapid changes in brightness, as is caused, for example, by a sprayer. Both the camera and the dynamic vision sensor are introduced coaxially into the beam path of the processing laser. Preferably, a wavelength-splitting mirror is used for splitting, which reflects the laser wavelength to 99.99%, but transmits other selected wavelengths. It is essential to the invention here that the simultaneous operation of the two camera systems, the camera and the dynamic vision sensor, is carried out on a further beam splitter which is either chromatically dividing, for example <800 nm for the camera and >800 nm for the dynamic vision sensor, and / or intensity-dividing, for example 90% for the camera and 10% for the dynamic vision sensor, so that both camera systems can see the same location and time of the process.FIG. 1 shows a laser beam system 12 having a monitoring device 10. the monitoring device 10 comprises a camera 14 and a dynamic vision sensor 16. The high-speed camera is preferably designed to record more than 1000 images per second, in particular more than 10,000 images per second, for example more than 20,000 images per second or more than 100,000 images per second. The camera 14 is arranged in the monitoring device 10 in such a way that the camera 14 detects at least a portion of a joining region 30 of a workpiece 28 by sensor technology. The dynamic vision sensor 16 is also referred to in particular as event camera, event-based camera, neuromorphic camera and / or silicon retina. The dynamic vision sensor 16 has a plurality of pixels and is designed in particular to detect and / or output a brightness change in the respective pixel for the individual pixels independently and / or asynchronously of the other pixels, wherein pixels for which no brightness change can be detected remain muted and / or output no signal. It is a consideration of the dynamic vision sensor 16 for pixels to independently output an output signal and / or reaction based on brightness change, so that in particular only changes are detected and output, wherein for a static scene or pixel without brightness change these remain silent without outputting an output signal. In particular, the dynamic vision sensor 16 is designed to detect a change in brightness from a predefined and / or adjustable threshold value as such. The dynamic vision sensor 16 is preferably designed to determine and / or indicate additional information for outputting a pixel, for example a pixel address, a time stamp, a polarity and / or an increase / decrease behavior of the change in brightness. The dynamic vision sensor 16 preferably has a time resolution better than one microsecond and / or a dynamic better than 120 dB. The dynamic vision sensor 16 is arranged in the monitoring device 10 in such a way that the dynamic vision sensor 16 simultaneously detects the section of the joining region 30 detected by the camera 14 by means of sensor technology. The monitoring device 10 is configured such that the camera 14 and the dynamic vision sensor 16 simultaneously record the same process radiation 32 from the same section of the joining region 30. For this purpose, the monitoring device 10 comprises at least one beam splitter 20, wherein the beam splitter 20 is designed to deflect the section of the joining region 30 for detection by the camera 14 and at the same time for detection by the dynamic vision sensor 16. The beam splitter 20 is preferably a chromatically dividing beam splitter and / or an intensity-dividing beam splitter. Optionally, the monitoring device 10 additionally comprises one or more further sensors 18, for example a photodiode array, and at least one further beam splitter 20. Furthermore, the event data 40 generated by the dynamic vision sensor 16 are transmitted to the evaluation unit 34. The optional sensor 18 transmits sensor data 42 to the evaluation unit 34. the evaluation unit 34 is configured to detect welding defects 44 in the joining region 30 by evaluating the image data 38 and / or evaluating the event data 40 and / or evaluating the sensor data 42. The evaluation unit 34 is preferably designed to detect, as a function of the image data 38 of the camera 14, as a welding defect 44, a lack of a seal that is hidden and / or a gap and / or a reduced welding depth between two joining partners. The evaluation unit 34 is preferably designed to detect spatter and / or burns as a function of the event data 40 of the dynamic vision sensor 16 as welding fault 44. The evaluation unit 34 is designed to output the detected welding defects 44 from output data. The laser beam system 12 comprises the described monitoring device 10 and a laser 22 for generating a processing laser beam 24. The laser beam system 12 is configured to process a workpiece 28, in particular to weld at least two joining partners, in particular at least two metal sheets, in an overlap joint. The laser beam system 12 further comprises a wavelength-dividing mirror 36, wherein the wavelength-dividing mirror 36 is arranged to reflect the processing laser beam 24 and to transmit process radiation 32 of the portion of the joining region 30 for detection by the camera 14 and the dynamic vision sensor 16. Optionally, in the preferred exemplary embodiment, the laser beam system 12 comprises a deflection mirror 26. The processing laser beam 24 generated by the laser 22 is directed via the wavelength-dividing mirror 36 and the deflection mirror 26 onto the workpiece 28 to be processed. The process radiation 32 generated in the effective range of the processing laser beam 24 on the workpiece 28 is directed via the deflection mirror 26 onto the wavelength-dividing mirror 36, which transmits the process radiation 32 without reflection. The process radiation 32 is then supplied via the beam splitters 20 to the camera 14, to the dynamic vision sensor 16 and optionally to one or more further sensors 18.The use of the invention is readily apparent on a production machine.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2006 015 383 A1

[0002]

Claims

Monitoring device (10) for a laser beam system (12), in particular a laser beam welding system, having a camera (14), wherein the camera (14) is arranged to detect at least a portion of a joining region (30) of a workpiece (28) by sensor technology, characterized in that the monitoring device (10) comprises a dynamic vision sensor (16), wherein the dynamic vision sensor (16) is arranged to detect at the same time the portion of the joining region (30) detected by the camera (14) by sensor technology.Monitoring device (10) according to Claim 1, characterized in that the camera (14) generates image data (38) of the captured section of the joining region (30), and the dynamic vision sensor (16) generates event data (40) of the captured section of the joining region (30).Monitoring device (10) according to one of the preceding claims, characterized in that the monitoring device (10) comprises an evaluation unit (34), wherein the evaluation unit (34) is designed to detect welding defects (44) in the joining region (30) by evaluating the image data (38) and / or evaluating the event data (40).Monitoring device (10) according to Claim 3, characterized in that the evaluation unit (34) is designed to detect, as a function of the image data (38) of the camera (14), as a welding defect (44), a lack of a seal which is concealed and / or a gap and / or a reduced welding depth between two joining partners.Monitoring device (10) according to Claim 3, characterized in that the evaluation unit (34) is designed to detect spatter and / or burns as a function of the event data (40) of the dynamic vision sensor (16) as welding fault (44).Monitoring device (10) according to one of the preceding claims, characterized in that the monitoring device (10) comprises at least one beam splitter (20), wherein the beam splitter (20) is designed to deflect process radiation (32) of the section of the joining region (30) for detection by the camera (14) and at the same time for detection by the dynamic vision sensor (16).Monitoring device (10) according to Claim 6, characterized in that the beam splitter (20) is a chromatically dividing beam splitter and / or an intensity-dividing beam splitter.Monitoring device (10) according to one of the preceding claims, characterized in that the camera (14) is a high-speed camera.Laser beam system (12), in particular a laser beam welding system for laser beam welding, having a laser (22) for generating a machining laser beam (24), characterized in that the laser beam system (12) comprises a monitoring device (10) according to one of the preceding claims.Laser beam system (12) according to Claim 9, characterized in that a detection region of the camera (14) and / or a detection region of the dynamic vision sensor (16) are arranged coaxially in a beam path of the processing laser beam (24).Laser beam system (12) according to either of Claims 9 and 10, characterized in that the laser beam system (12) comprises a wavelength-dividing mirror (36), wherein the wavelength-dividing mirror (36) is arranged to reflect the processing laser beam (24) and to transmit process radiation (32) of the section of the joining region (30) for detection by the camera (14) and the dynamic vision sensor (16).Laser beam system (12) according to one of Claims 9 to 11, characterized in that the laser beam system (12) is designed to weld at least two joining partners, in particular at least two metal sheets, in an overlap joint.

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