Device for detecting process light during laser processing

Abstract

Laser system (10) for irradiating a workpiece (12) with a first laser beam (22) in a core region (26) and / or a second laser beam (24) in an annular region (28), wherein the laser system (10) has a sensor device (18) for detecting the process light (16) generated by the laser beam (22, 24), wherein the sensor device (18) has a first sensor arrangement (42) for detecting the process light (16) in a core region (26) and a second sensor arrangement (44) for detecting the process light (16) in an annular region (28), wherein the core region (26) is located within the annular region (28), wherein the sensor device (18) is arranged or formed coaxially to the first laser beam (22) and / or second laser beam (24), wherein the laser system (10) has a fiber optic cable (30) with an inner conductor (32) and a cross-sectionally annular outer conductor (34),wherein both the first laser beam (22) and / or second laser beam (24) can be guided through the optical fiber cable (30) and the radiation of the process lamp (16) can be guided to the sensor device (18), wherein the sensor device (18) has photodiodes, wherein the sensor device (18) has photodiodes on the lateral surface of the inner conductor (32) and / or the outer conductor (34).,

Description

Background of the invention

[0001] The invention relates to a laser system for irradiating a workpiece.

[0002] During laser processing, a process zone is formed within the workpiece, which is heated by laser radiation. Metallic materials initially form a molten phase, which then partially or completely evaporates upon further heating. The quality of the processed workpiece is largely determined by the ratio of melt to vapor in the process zone. Heating the workpiece creates a characteristic process glow from the melt or vapor. It is known that this process glow can be measured to better control and regulate the processing process.

[0003] DE 10 2010 015 023 A1 discloses a method and a device for laser processing a workpiece. In the method, the workpiece is heated in a thermal effective zone by a laser beam emerging from a processing head. For process control, a spatially resolved temperature profile of the effective zone is determined non-contact using a temperature measuring device that records the temperature of the workpiece or a parameter proportional to the temperature of the workpiece at several measuring points spaced apart within the effective zone. At the same time, a measuring distance to the surface and the emissivity of the surface of the workpiece in the area of the effective zone are determined at each measuring point using a non-contact measuring device. The determined values of the measuring distance and emissivity are used to calculate and / or correct the temperature value determined at each measuring point.

[0004] DE 197 24 986 A1 discloses a laser device for welding sheet metal. The device is designed to detect UV radiation at the weld point and IR radiation in the melt.

[0005] Devices and methods for laser welding are known from US 2020 / 0 306 878 A1 and US 2016 / 0 263 700 A1.

[0006] DE 10 2016 223 215 A1 describes an irradiation device for irradiating a processing field with a processing beam, in particular with a laser beam, for carrying out a welding process.

[0007] From L. Wang, et al., “Monitoring of keyhole entrance and molten pool with quality analysis during adjustable ring mode laser welding” IN: Applied Optics, Vol.59, No.6, pp.1576-1584, process monitoring during laser welding using visual monitoring and confocal sensors is known.

[0008] DE 11 2015 000 994 T5 discloses a system and method for multi-beam laser arrangements with a variable beam parameter product. Object of the invention

[0009] In contrast, it is the object of the invention to enable a significantly improved characterization of laser processing processes in a structurally simple manner. Description of the invention

[0010] This object is achieved according to the invention by a laser system according to patent claim 1. The subclaims reflect preferred developments.

[0011] The object of the invention is thus achieved by a laser system for irradiating a workpiece with a first, in particular point-shaped, laser beam that strikes the workpiece in a core region and / or a second laser beam that strikes the workpiece in an annular, in particular circular, region. The annular region is located around the core region. The laser beam(s) generate(s) a process glow of the workpiece, which is detected by a sensor device. The sensor device has a first sensor arrangement for detecting the process glow in the core region and a second sensor arrangement for detecting the process glow in the annular region. This makes it easy to determine both the condition of the workpiece in the core region and the condition of the workpiece in the annular region during laser processing.

[0012] To enable precise determination of the workpiece condition, the annular region is preferably radially spaced from the core region.

[0013] The first sensor arrangement can be configured to detect both visible radiation and infrared, particularly near-infrared, radiation from the process lighting. Visible radiation is present in particular as line radiation from steam generated during processing. Infrared radiation is present in particular as thermal radiation from the melt.

[0014] The first sensor arrangement can comprise a first sensor for detecting visible radiation and a second sensor for detecting infrared, in particular near-infrared, radiation. A first wavelength filter for visible radiation can be connected upstream of the first sensor. A wavelength filter for infrared, in particular near-infrared, radiation can be connected upstream of the second sensor. The first sensor arrangement can further comprise an optical element for splitting the radiation impinging on the first sensor arrangement in order to direct it to the first wavelength filter and the second wavelength filter.

[0015] The second sensor arrangement can be designed both for the detection of visible radiation and for the detection of infrared, in particular near-infrared, radiation of the process lighting.

[0016] The second sensor arrangement can have a first sensor for detecting visible radiation and a second sensor for detecting infrared, in particular near-infrared, radiation. A first wavelength filter for visible radiation can be connected upstream of the first sensor. A wavelength filter for infrared, in particular near-infrared, radiation can be connected upstream of the second sensor. The second sensor arrangement can further have an optical element for splitting the radiation impinging on the first sensor arrangement in order to direct it to the first wavelength filter and the second wavelength filter.

[0017] The laser system may comprise a first laser source for the first laser beam and a second laser source for the second laser beam or may comprise a beam splitter configured to split a primary laser beam into the first laser beam and the second laser beam.

[0018] The first laser source can be in the form of a first fiber laser, and the second laser source can be in the form of a second fiber laser. The beam splitter can be in the form of a pivotable wedge-shaped beam splitter.

[0019] A particularly simple laser system design is achieved if the sensor device is arranged or configured coaxially with the first laser beam and / or the second laser beam. In this case, the optical axis of the laser radiation directed onto the workpiece preferably corresponds to the optical axis of the returned process light.

[0020] The laser system comprises a fiber optic cable with an inner conductor, i.e., a core fiber, and an outer conductor with a ring-shaped cross-section, i.e., an outer fiber. The fiber optic cable serves both to guide the first and / or second laser beam and to return the process light. The fiber optic cable can be part of the sensor device.

[0021] Preferably, the intensity ratio between the first laser beam and the second laser beam is adjustable.

[0022] In a particularly preferred embodiment of the invention, the laser system comprises a control device. The control device can be configured to control, preferably regulate, the first laser beam and / or the second laser beam depending on the ratio of the process light in the annular region to the process light in the core region. The control device thus allows for processing optimization based on the currently measured states of the workpiece in the core region and in the annular region.

[0023] To detect the process light, the sensor device can be equipped with a color camera. This allows for a particularly simple design of the laser system.

[0024] The color camera can be mounted on a scanner optic (workpiece moves relative to the fixed optic) and / or on a flying optic (optics move relative to the fixed workpiece) of the laser system. The scanner optic can be designed as a programmable focusing optic. The flying optic can be designed as a processing optic.

[0025] The sensor device has photodiodes for detecting the process light. At least some photodiodes, in particular all photodiodes, can have a special VIS coating (coating for absorbing radiation in the visible wavelength range) or an IR coating (coating for absorbing radiation in the infrared wavelength range). The special IR coating can be designed as a special NIR coating for absorbing wavelengths in the near infrared range.

[0026] The photodiodes are provided in a space-saving manner on the outer surface of the inner conductor and / or the outer conductor of the previously described optical fiber cable.

[0027] The laser system is preferably designed in the form of a laser cutting system and / or in the form of a laser welding system.

[0028] The workpiece can be part of the laser system.

[0029] Further advantages of the invention will become apparent from the description and the drawings. Likewise, the above-mentioned and further-described features can be used individually or in combinations according to the invention. The embodiments shown and described are not intended to be exhaustive, but rather are exemplary in nature for describing the invention. Detailed description of the invention and drawing Fig. 1 schematically shows a first embodiment of a laser system during irradiation of a workpiece with laser radiation and measurement of the resulting process light. Fig. 2 shows a schematic view of the workpiece from Fig. 1. Fig. 3 schematically shows another embodiment of a laser system with a fiber optic cable. Fig. 4 schematically shows another embodiment of a fiber optic cable for a laser system.

[0030] Fig. 1 shows a laser system 10 for laser processing a workpiece 12. The laser system 10 has a processing head 14. The laser processing generates process light 16 emanating from the workpiece 12, which is detected by a sensor device 18. The sensor device 18 can have a color camera for this purpose. The laser system 10 has a control device 20 for controlling the laser system 10. The control device 20 is designed to perform the control based on the evaluation of the process light 16. In particular, the control device 20 is designed to adjust the laser power of the laser system 10 depending on the measured process light 16.

[0031] Fig. 2 shows a top view of the workpiece 12 from Fig. 1. From Fig. 2 it can be seen that the laser system 10 (see Fig. 1) is designed to process the workpiece 12 with a first laser beam 22 and a second laser beam 24. The first laser beam 22 irradiates a core region 26. The second laser beam 24 irradiates an annular region 28, which here is particularly radially spaced from the core region 26. Radiation in the form of process lights 16 (see Fig. 1) and detected by the sensor device 18 (see Fig. 1) detected.

[0032] Fig. 3 shows part of a laser system 10 with a fiber optic cable 30. The fiber optic cable 30, shown here in longitudinal section, has an inner conductor 32, in particular circular in cross-section, and an outer conductor 34, in particular annular in cross-section. The inner conductor 32 preferably has a diameter d1 between 11 µm and 300 µm, in particular between 50 µm and 100 µm. The outer conductor 34 preferably has a diameter d2 between 50 µm and 1000 µm, in particular between 200 µm and 400 µm. The outer conductor 34 is coaxial with the inner conductor 32.

[0033] Through the inner conductor 32, both the first laser beam 22 can be directed onto the workpiece 12 (see Fig. 1) as well as the process lights 16 (see Fig. 1) from core area 26 (see Fig. 2) from the workpiece 12 (see Fig. 1). Through the outer conductor 34, both the second laser beam 24 can be directed onto the workpiece 12 (see Fig. 1) as well as the process lights 16 (see Fig. 1) from the annular area 28 (see Fig. 2) from the workpiece 12 (see Fig. 1) be redirected.

[0034] The division of a primary laser beam 36 into the first laser beam 22 and the second laser beam 24 can be carried out by a beam splitter 38, here in the form of a wedge switch. The beam splitter 38 is connected to the control device 20 according to an arrow 40 (see Fig. 1) in order to be able to adjust the proportions of the first laser beam 22 and the second laser beam 24 which are directed into the core area 26 (see Fig. 2) or the annular area 28 (see Fig. 2) be conducted.

[0035] The workpiece 12 (see Fig. 1) is detected by the sensor device 18. The sensor device 18 has a first sensor arrangement 42 for detecting the process light 16 in the core area 26 (see Fig. 2) and a second sensor arrangement 44 for detecting the process light 16 in the annular area 28 (see Fig. 2). The sensor arrangements 42, 44 each have first sensors 46a, 46b for detecting visible radiation and second sensors 48a, 48b for detecting infrared, in particular near-infrared, radiation. First wavelength filters 50a, 50b for visible radiation and second wavelength filters 52a, 52b for infrared, in particular near-infrared, radiation are connected upstream of the sensors 46a, b, 48a, b. Optical elements 54a, 54b split the radiation between the wavelength filters 50a, b, 52a, b. Further optical elements 56a, 56b, for example in the form of dichroic mirrors, direct the process light 16 to the optical elements 54a, b.

[0036] Fig. Figure 4 shows a variant of a laser system 10 with a fiber optic cable 30 in longitudinal section. The fiber optic cable 30 leads at one end (see arrow 58) directly or indirectly to the workpiece 12 (see Fig. 1). At the other end (see arrow 60), the fiber optic cable 30 leads directly or indirectly to a laser resonator (not shown). The fiber optic cable 30 can be part of the sensor device 18 according to Fig. 1.

[0037] A first sensor arrangement 42 and a second sensor arrangement 44 for detecting process lights 16 are arranged on the lateral surfaces of the inner conductor 32 and the outer conductor 34. The order of the sensor arrangement 42, 44 in the fiber optic cable 30 can be reversed to that in Fig.4. The sensor arrangements 42, 44 each comprise at least a first sensor 46a, b and a second sensor 48a, b for detecting visible or infrared, in particular near-infrared, radiation. The sensors 46a, b, 48a, b can have photodiodes. The sensors 46a, b can have a special VIS coating (coating for absorbing radiation in the visible wavelength range) and / or the sensors 48a, b can have a special IR coating (coating for absorbing radiation in the infrared wavelength range).

[0038] Taking a synopsis of all the figures in the drawing, the invention relates in summary to a laser system 10 for processing a workpiece 12. The workpiece 12 can be irradiated by a first laser beam 22 in a, in particular point-shaped, core region 26. Alternatively or additionally, the workpiece 12 can be irradiated in an annular region 28 around the core region 26. The laser system 10 is designed, by means of a sensor device 18, both to detect process lights 16 from the core region 26 and to detect process lights 16 from the annular region 28. The sensor device 18 can be designed to detect visible process lights 16 and infrared process lights 16 separately from one another in both the core region 26 and the annular region 28.The laser system 10 can have a control device 20 configured to control and / or regulate the components of the first laser beam 22 and the second laser beam 24 as a function of the sensor device 18. The invention further relates to a method for laser processing in which process light 16 is measured from both the core region 26 and the annular region 28 and is used, in particular, to control and / or regulate the laser system 10. List of reference symbols 10 laser system 12 Workpiece 14 Machining head 16 process lights 18 Sensor device 20 Control device 22 first laser beam 24 second laser beam 26 Core area 28 annular area 30 fiber optic cables 32 inner conductors 34 outer conductors 36 primary laser beam 38 beam splitters 40 Arrow (direction of rotation of the beam splitter 38) 42 first sensor arrangement 44 second sensor arrangement 46a, b first sensor (VIS) 48a, b second sensor (IR) 50a, b first wavelength filter (VIS) 52a, b second wavelength filter (IR) 54a, b optical element 56a, b additional optical element 58 Arrow (to workpiece 12) 60 bearings (to the laser resonator) d1 Diameter of inner conductor d2 Diameter of outer conductor

Claims

[1] Laser system (10) for irradiating a workpiece (12) with a first laser beam (22) in a core region (26) and / or a second laser beam (24) in an annular region (28), wherein the laser system (10) has a sensor device (18) for detecting the process light (16) generated by the laser beam (22, 24), wherein the sensor device (18) has a first sensor arrangement (42) for detecting the process light (16) in a core region (26) and a second sensor arrangement (44) for detecting the process light (16) in an annular region (28), wherein the core region (26) is located within the annular region (28), wherein the sensor device (18) is arranged or formed coaxially to the first laser beam (22) and / or second laser beam (24), wherein the laser system (10) has a fiber optic cable (30) with an inner conductor (32) and a cross-sectionally annular outer conductor (34),wherein both the first laser beam (22) and / or second laser beam (24) can be guided through the optical fiber cable (30) and the radiation of the process lamp (16) can be guided to the sensor device (18), wherein the sensor device (18) has photodiodes, wherein the sensor device (18) has photodiodes on the lateral surface of the inner conductor (32) and / or the outer conductor (34)., [2] Laser system according to claim 1, wherein the annular region (28) is radially spaced from the core region (26). [3] Laser system according to claim 1 or 2, wherein the first sensor arrangement (42) is designed to detect visible and infrared radiation of the process lamp (16). [4] Laser system according to claim 3, wherein the first sensor arrangement (42) comprises: A first sensor (46a) for detecting visible radiation, wherein a first wavelength filter (50a) for visible radiation is connected upstream of the first sensor (46a); a second sensor (48a) for detecting infrared radiation, wherein a second wavelength filter (52a) for infrared radiation is connected upstream of the second sensor (48a); an optical element (54a) for splitting the radiation incident on the first sensor arrangement (42) between the first wavelength filter (50a) and the second wavelength filter (52a). [5] Laser system according to one of the preceding claims, in which the second sensor arrangement (44) is designed to detect visible and infrared radiation of the process lamp (16). [6] Laser system according to claim 5, wherein the second sensor arrangement (44) comprises: A first sensor (46b) for detecting visible radiation, wherein a first wavelength filter (50b) for visible radiation is connected upstream of the first sensor (46b); a second sensor (48b) for detecting infrared radiation, wherein a second wavelength filter (52b) for infrared radiation is connected upstream of the second sensor (48b); an optical element (54b) for splitting the radiation incident on the second sensor arrangement (44) between the first wavelength filter (50b) and the second wavelength filter (52b). [7] Laser system according to one of the preceding claims, in which the laser system (10) a) a first laser source for the first laser beam (22) and a second laser source for the second laser beam (24); or b) a beam splitter (38) for splitting a primary laser beam (36) into the first laser beam (22) and the second laser beam (24). [8] Laser system according to one of the preceding claims, in which the laser system (10) has a control device (20), wherein the control device (20) is designed to control or regulate the first laser beam (22) and / or second laser beam (24) as a function of the ratio of the process illumination (16) in the annular region (28) to the process illumination (16) in the core region (26). [9] Laser system according to one of the preceding claims, wherein the sensor device (18) comprises a color camera. [10] Laser system according to one of the preceding claims, in which the laser system (10) is designed in the form of a laser cutting system for cutting the workpiece (12) and / or in the form of a laser welding system for welding the workpiece (12).

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