Method for comparing a laser processing system and method for monitoring a laser processing process and the laser processing system therefor

Abstract

The invention relates to a method for comparing a laser machining system, wherein the laser machining system comprises a laser machining head and a sensor module having at least one photodiode, the method comprising detecting radiation emitted by a light source by means of the photodiode and generating a corresponding intensity signal, wherein the radiation is guided from the light source to the photodiode by at least one optical element in the laser machining head and / or by at least one optical element of the sensor module; orienting the laser machining head and the light source relative to one another such that the intensity signal assumes a maximum value; and comparing the intensity signal with at least one predefined reference value. Furthermore, the invention relates to a method for monitoring a laser machining process and to a laser machining system therefor.

Description

Technical Field

[0001] The present invention relates to a method for comparing laser processing systems or components of one or more laser processing systems, as well as a method for monitoring a laser processing process and a laser processing system configured to perform the method. Background Technology

[0002] In a laser processing system, also known as laser processing equipment or simply equipment, a laser beam emitted from a laser beam source or the end of a laser transmission fiber is focused onto the workpiece to be processed using beam-guiding optics, thereby locally heating the workpiece to its melting temperature. Beam-guiding optics include, for example, focusing optics, beam splitters, and deflection units. Processing can include laser welding or laser cutting. A laser processing system can include a laser processing head, such as a laser welding head or a laser cutting head. The laser processing procedure can include both laser welding and laser cutting processes.

[0003] To ensure processing quality, monitoring the laser processing process is crucial. Monitoring is typically achieved by detecting and analyzing the process radiation generated during laser processing, also known as process light or process radiation (Prozessemissionen). Process radiation includes laser radiation scattered or reflected back by the workpiece, process radiation in the infrared wavelength range of light, such as temperature radiation, and process radiation in the visible light wavelength range, such as radiation from the plasma formed during processing.

[0004] Process radiation is typically detected using at least one sensor, such as a photodiode. The sensor senses the intensity of the process radiation at or within a pre-defined wavelength range and generates a corresponding intensity signal. For monitoring, the intensity signal is compared, for example, to a pre-defined envelope and / or threshold, and an error is output if the intensity signal is outside the envelope or exceeds or falls below the threshold.

[0005] Monitoring systems are commonly used in laser welding, utilizing the radiation reflected back from the process (process radiation) to provide qualitative information about weld quality. The proportion of radiation fed back to the monitoring system from the process depends heavily on the components involved and their quality. Manufacturing tolerances and quality variations in the optical and / or mechanical components of the laser processing system and / or monitoring system can lead to significant differences in the corresponding signal range. For example, optical elements such as lenses and mirrors in deflection units, scanners, or laser processing heads with identical or consistent structures may have different characteristics due to manufacturing tolerances. Manufacturing tolerances in photodiodes can also cause differences in the sensed process radiation. Therefore, the corresponding intensity signals may differ in laser processing systems with the same structure. For example, the average signal level of the intensity signal, also known as the signal potential, may differ.

[0006] These differences in intensity signals make comparisons between systems of the same type or structure difficult or impossible. Furthermore, identical monitoring parameters, such as envelopes or thresholds, cannot be used to monitor a given laser processing process on laser processing systems of the same type or structure. Error identification during laser processing is no longer guaranteed. Especially in industrial mass production, where multiple identical devices are often used, comparability plays an increasingly important role in the analysis and evaluation of intensity signals. Therefore, a convincing and stable comparison of the beam guiding characteristics of devices with the same structure is needed to achieve high-quality process monitoring. Summary of the Invention

[0007] The objective of this invention is to provide a method for comparing multiple laser processing systems of the same type or structure, particularly components of laser processing systems.

[0008] Another objective of the present invention is to provide a method by which multiple laser processing systems of the same structure, in particular the characteristics of the sensor modules and / or laser processing heads contained therein, especially the beam guiding and / or detection characteristics.

[0009] Furthermore, the objective of this invention is to provide a method by which the characteristics of a pre-given laser processing system, particularly beam guiding and / or detection characteristics, can be compared at different points in time.

[0010] Furthermore, the objective of this invention is to provide a method that enables the monitoring of identical laser processing projects using the same monitoring parameters, wherein the laser processing projects are executed by laser processing systems of the same type or structure with the same process parameters.

[0011] Furthermore, the objective of this invention is to provide a laser processing system configured to perform this method.

[0012] One or more of these tasks are addressed by the content of the independent claims. Favorable configurations and extensions are addressed by the content of the dependent claims.

[0013] This invention is based on the concept of detecting the radiation intensity emitted by a light source through a sensor module of a laser processing system, particularly through a photodiode-based sensor, and thereby generating an intensity signal. Here, the radiation is guided between the radiation source and the photodiode by at least one optical element of the laser processing head and / or sensor module. This guidance may include reflecting and / or transmitting the radiation via the optical element. The radiation intensity can be emitted by the light source in the infrared wavelength range, in the visible wavelength range, and / or at the wavelength of the processing laser beam of the laser processing system, and detected by the sensor. This at least one wavelength range preferably corresponds to the wavelength range of the process radiation sensed by a sensor module for error identification or process monitoring. Here, the laser processing system, i.e., the laser processing head and / or sensor module and the light source, is oriented relative to each other such that the sensed intensity signal exhibits a maximum value. The sensed intensity signal is then compared with at least one reference value.

[0014] By comparing the sensed intensity signal with at least one reference value, this method enables the comparison of multiple laser processing systems of the same type (i.e., structurally identical or consistent) based on the sensed intensity signal. By generating the intensity signal using the radiation of a light source, particularly a stable light source, the inspection of the laser processing system, i.e., the laser processing head and / or sensor module, can be performed independently, quickly, and simply, and the comparability of intensity signals from multiple laser processing systems of the same type used for monitoring the laser processing process can be guaranteed.

[0015] The scaling factor can also be determined based on the sensed intensity signal and a reference value. This scaling factor enables the monitoring of the same laser processing process performed by multiple laser processing systems of the same type with the same monitoring parameters or identical monitoring parameters. Here, the intensity signal or monitoring parameter sensed by each laser processing system can be scaled according to the scaling factor for that laser processing system.

[0016] Within the scope of this invention, laser processing systems of the same structure, identical or the same type mean multiple examples of a class of laser processing systems. These examples may be laser processing systems of the same commercially available type or model. Identical or identical laser processing processes refer to laser processing processes performed with the same process parameters.

[0017] According to a first aspect of the invention, a method is provided for comparing a laser processing system or at least one component of a laser processing system, wherein the laser processing system includes a laser processing head and a sensor module having at least one sensor, preferably a photodiode-based sensor or photodiode, for sensing process radiation. The method includes: detecting radiation emitted by a light source through the sensor and generating a corresponding intensity signal, wherein the radiation is guided from the light source to the sensor through at least one optical element in the laser processing head and / or at least one optical element in the sensor module; orienting the laser processing head and the light source relative to each other such that the intensity signal exhibits a maximum value; and comparing the intensity signal with a pre-given reference value.

[0018] Preferably, the sensor or photodiode-based sensor or photodiode is configured to detect process radiation during laser processing, particularly when the processing laser beam is irradiated onto at least one (to be processed) workpiece by a laser processing head. Preferably, the sensor or photodiode-based sensor or photodiode is configured to detect process radiation during laser processing within a predetermined wavelength range and / or within a predetermined wavelength. In particular, the sensor or photodiode-based sensor or photodiode may be configured to sense the intensity of the process radiation within the predetermined wavelength range and / or within a predetermined wavelength and generate a corresponding intensity signal (and output the intensity signal). Process radiation, particularly process radiation generated during the execution of the laser processing process. The laser processing head is preferably configured to irradiate at least one workpiece with the processing laser beam to perform one or more laser processing operations.

[0019] The beam path of radiation from the light source to the sensor may at least partially overlap with and / or be coaxial with the beam path of the processing laser beam in the laser processing head. The beam path of radiation from the light source to the sensor may at least partially extend within the laser processing head and / or the sensor module. Starting from the light source, the radiation may first extend outside the laser processing head, then enter and extend within the laser processing head, then enter and extend within the sensor module, and finally illuminate the sensor of at least one sensor module.

[0020] The light source can be a stable and / or adjustable and / or controllable light source. The light source can be or include at least one of the following: electric light source, halogen lamp, light-emitting diode, super light-emitting diode and broadband light source, especially a light source having an emission spectrum between 350 nm and 2000 nm.

[0021] A stable light source can be defined as a light source with constant emission characteristics or intensity. Therefore, a stable light source can be defined as a light source with predetermined emission characteristics that remain constant or stable. Adjustment circuitry can be incorporated for this purpose. A stable light source can therefore be an adjustable light source. Emission characteristics can be defined as the intensity of radiation emitted by the light source at and / or within a predetermined wavelength range and / or the emission characteristics of the light source. By monitoring and adjusting the emission characteristics of the light source, it can be ensured that the emission characteristics do not change undesirably due to environmental conditions such as air humidity or temperature, or due to light source aging. This, in turn, ensures that the emission characteristics of the light source do not affect the analysis and evaluation of the beam guiding and detection characteristics of the laser processing system. A stable light source can be specifically constructed as an adjustable LED or an adjustable halogen lamp.

[0022] Radiation detection can include detecting the intensity of radiation within a predetermined wavelength range or wavelength. A corresponding intensity signal can be generated based on the detected radiation intensity. The light source can be configured to emit radiation within a predetermined wavelength range or wavelength.

[0023] Radiation detection may include detecting the radiation intensity within and / or within multiple pre-defined wavelength ranges using appropriate photodiodes. Based on this, a corresponding intensity signal can be generated. This intensity signal can then be compared with a corresponding reference value.

[0024] The predetermined wavelength range may be or include at least one of the following wavelength ranges: visible wavelength range, near-infrared (NIR) wavelength range, infrared wavelength range, thermal radiation wavelength range, plasma radiation wavelength range, wavelengths between 350 nm and 780 nm, wavelengths between 780 nm and 3 µm, and wavelengths greater than 1 µm. The predetermined wavelength may be or include at least one of the following wavelengths: the wavelength of the laser source of the laser processing head, wavelengths in the range of 1030 nm to 1070 nm, preferably 1064 nm, wavelengths in the visible green spectrum range, particularly in the range of 500 nm to 570 nm, preferably 515 nm, wavelengths in the visible blue spectrum range, particularly in the range of 400 nm to 500 nm, and wavelengths in the range of 440 nm to 460 nm, preferably 450 nm.

[0025] For example, the radiation intensity can be detected by a first photodiode in the visible wavelength range, for example, between 350 nm and 780 nm, and a first intensity signal can be generated; and / or the radiation intensity can be detected by a second photodiode in the wavelength of the processing laser beam of the laser processing system, for example, in the wavelength range between 1030 nm and 1070 nm, preferably 1064 nm, and a second intensity signal can be generated; and / or the radiation intensity can be detected by a third photodiode in the infrared wavelength range, for example, between 780 nm and 3 µm, and a third intensity signal can be generated. The first and third intensity signals can be compared with first and third reference values ​​accordingly. The visible wavelength range can correspond to the spectral range of plasma radiation generated during laser processing. The infrared wavelength range can correspond to the spectral range of thermal radiation generated during laser processing. The laser processing head and the light source are oriented relative to each other such that at least one of the first and third intensity signals has a maximum value.

[0026] Radiation emitted by the light source can be guided by at least one optical element of the laser processing head or sensor module and transmitted or reflected by at least one optical element. The optical element can be or includes at least one of the following: a transmission element, a reflection element, a protective glass, a beam splitter, a mirror, a lens, a lens group, a lens set, a focusing lens (group), a collimating lens (group), and an optical device.

[0027] Preferably, all the above steps are performed using at least two laser processing heads with the same structure, the same sensor module, and the same light source. This allows for comparison of the beam guiding characteristics of multiple laser processing heads with the same structure.

[0028] Alternatively or additionally, all the above steps are performed using the same laser processing head and the same light source, and utilizing at least two sensor modules with the same structure. This allows for comparison of the detection and beam guiding characteristics of multiple sensor modules with the same structure. For example, the method can be performed using the first and second sensor modules on the laser processing head, with the first sensor module replaced by a second sensor module of the same structure. This allows for comparison of the beam guiding and detection characteristics of the first and second sensor modules, and ensures that the sensed intensity signals are comparable.

[0029] Alternatively or additionally, all the above steps are repeated at predetermined time intervals using the same laser processing head, the same sensor module, and the same light source. This allows for comparison of the characteristics of the laser processing system at different points in time, particularly its beam guiding and / or detection characteristics. Aging and / or contamination of optical components, such as protective glass and / or sensors, can thus be identified. For example, the method can be re-executed on the same laser processing system during commissioning and / or maintenance, or after a certain period of time. The method can also be performed during commissioning and / or maintenance of the laser processing system, or after replacing at least one component of the laser processing system. At least one component of the laser processing system can be, for example, a laser source, a sensor module, a sensor of the sensor module, an optical element of the laser processing head, or an optical element of the sensor module.

[0030] Preferably, the sensor module and the laser processing head are arranged fixedly and / or statically relative to each other. For example, the sensor module and the laser processing head are fastened to each other. The sensor module can be mounted on the housing of the laser processing head. Particularly preferably, the distance and orientation between the sensor module and the laser processing head are fixed.

[0031] The orientation of the laser processing head and the light source relative to each other can be particularly performed such that the center point of the light source is located on the optical axis of the laser processing head, especially on the optical axis of the focusing optics, and / or the central axis of the laser processing head coincides with the optical axes of the laser processing head and / or the focusing optics. The central axis of the light source preferably refers to the central axis or central axis of the emitting cone of the light source. The orientation of the laser processing head and the light source relative to each other can particularly be performed such that the center point of the light source is located at the focal point of the focusing optics. The orientation of the laser processing head and the light source relative to each other may also include adjustment of the focal point of the focusing optics.

[0032] Therefore, the orientation of the laser processing head and the light source relative to each other may include at least one of the following steps: adjusting the distance between the laser processing head and the light source; adjusting the orientation of the laser processing head and the light source relative to each other; tilting the laser processing head and the light source relative to each other; moving the laser processing head relative to the light source; moving the light source relative to the laser processing head; moving the laser processing head in a plane perpendicular to the optical axis of the laser processing head; and moving the laser processing head parallel to the optical axis of the laser processing head. The optical axis of the laser processing head may be the optical axis of the focusing optics of the laser processing head or a corresponding optical axis.

[0033] The method may further include the step of orienting the sensor module relative to the laser processing head. Preferably, the sensor module is oriented such that its optical axis coincides with, or is coaxial with, the optical axis of the light output end of the laser processing head. The optical axis of the sensor module preferably refers to the optical axis of the light input end of the sensor module, through which radiation decoupled from the laser processing head enters the sensor module. The optical axis of the sensor module may be the optical axis of the focusing optics of the sensor module or a corresponding optical axis. The optical axis of the light output end of the laser processing head preferably refers to the optical axis of the light output end, through which radiation from the laser processing head to the sensor module is decoupled. The orientation of the sensor module may include movement of the sensor module relative to the optical axis of the light output end of the laser processing head, particularly tilting about the optical axis of the light output end and / or moving in a plane perpendicular to the optical axis of the light output end of the laser processing head.

[0034] The method may further include a step of orienting at least one photodiode in the sensor module. The orientation of the at least one photodiode can be achieved by moving the photodiode relative to the optical axis of the sensor module. The at least one photodiode can be oriented such that the sensed intensity is maximized.

[0035] The method may further include providing a light source outside the laser processing head. Providing the light source may include positioning the light source at a predetermined location, such as on a holding device or on a workpiece. The predetermined location may correspond to a processing position on the workpiece. This processing position may correspond to a predetermined position where the processing laser beam irradiates during laser processing. The light source may be fixedly mounted or can be fixedly mounted. In this case, the orientation of the laser processing head and the light source relative to each other can only be achieved by the movement of the laser processing head.

[0036] In one embodiment, the sensor module or at least one photodiode can first be oriented relative to the laser processing head. This can be accomplished, for example, by means of a leader laser that visualizes the focal position of the laser beam. The distance to the laser processing head, or the focal position or focus of the processing laser beam or the leader laser, can then be adjusted onto the light source. For this purpose, the ideal working distance of a pre-defined laser optics device for the laser processing head can be known, for example. The orientation of the laser processing head is then preferably performed in an XY plane perpendicular to the propagation direction of the processing laser beam with respect to the light source. For this purpose, the orientation of the laser processing head in the XY plane can be varied until a maximum signal is obtained through the sensor module or at least one photodiode.

[0037] At least one reference value may include an upper reference value and a lower reference value, i.e., a reference interval. Comparing the intensity signal with the reference values ​​may include: comparing the average value of the intensity signal with the reference values ​​and / or determining whether the average value of the intensity signal is within the reference interval. Alternatively, the maximum value of the intensity signal may also be used for the average value.

[0038] Comparing the average value of the intensity signal with a reference value can include determining the average value of the intensity signal. The average value of the intensity signal can be determined as the average value of the intensity signal over time. This average value can be an arithmetic mean or a geometric mean. Within the scope of this invention, the average value can also be defined as the median. Determining the average value can include: removing outliers from the intensity signal, i.e., removing minimum values ​​and / or maximum values, and determining the average value of the intensity signal based on the remaining values ​​of the intensity signal.

[0039] For a given laser processing head and a given sensor and / or a given sensor module, the average value of the intensity signal can be determined. A scaling factor for the given laser processing head and the given sensor can be determined based on this determined average value and a reference value. Alternatively, the maximum value of the intensity signal can also be used instead of the average value.

[0040] Determining the scaling factor can include finding the quotient between the average or maximum value of the intensity signal and a reference value. Alternatively, it can involve dividing the average or maximum value of the intensity signal by the reference value. Therefore, the scaling factor can be dimensionless.

[0041] Preferably, the reference value is the average or maximum value of the intensity signal, which has been determined through the detection of the radiation radiated in the above steps and the orientation of the laser processing head towards the reference laser processing system. The reference laser processing system may be structurally identical to the laser processing system under consideration.

[0042] Scaling factors can be stored for this laser processing head and this sensor. Storage can be achieved through the control unit.

[0043] The intensity signal can be a one-dimensional, time-varying signal. It can be a digital signal. An intensity signal can include multiple signal values, each associated with a specific time point. The signal value can correspond to the intensity of radiation sensed within a predetermined wavelength range or at its corresponding time point within a predetermined wavelength. A photodiode can output an analog signal as an intensity signal, such as a current or voltage signal. The analog intensity signal can be converted into a digital signal by a sensor module or control unit.

[0044] According to another aspect of the invention, a method for monitoring a laser processing process is provided, the method comprising: performing a laser processing process for processing at least one workpiece by irradiating a processing laser beam onto at least one workpiece through a laser beam processing head; detecting the process radiation of the laser processing process within a predetermined wavelength range by a sensor of a sensor module, preferably a photodiode, and generating a corresponding intensity signal; scaling the intensity signal using a scaling factor determined for the laser beam processing head and the sensor, and monitoring the laser processing process based on the scaled intensity signal and at least one monitoring parameter predetermined for the intensity signal, or scaling at least one monitoring parameter predetermined for the intensity signal using a scaling factor determined for the laser beam processing head and the sensor, and monitoring the laser processing process based on the intensity signal and at least one scaled monitoring parameter. The scaling factor may have been determined as described above.

[0045] Scaling an intensity signal can include dividing the intensity signal by a scaling factor. Scaling a monitoring parameter can include multiplying the monitoring parameter by a scaling factor.

[0046] Laser processing can include processing at least one workpiece by irradiating a pre-defined processing area on the workpiece with a processing laser beam, for example, along a predetermined processing path. Laser processing can include laser welding, also known as a laser welding process. In this case, a weld seam can be formed by irradiating the workpiece with a processing laser beam along the processing path. Alternatively or additionally, laser processing can include laser cutting, also known as a laser cutting process. In this case, a cutting edge can be formed by irradiating the workpiece with a processing laser beam along the processing path. Laser processing can also include an insertion process that penetrates into at least one workpiece. In this case, at least one processing area may correspond to an insertion hole. In this case, an insertion hole can be formed by irradiating the processing area with a processing laser beam.

[0047] The process radiation generated during laser processing can include at least one of the following: thermal radiation in the infrared wavelength range, plasma radiation in the visible wavelength range, and laser radiation reflected from the workpiece. The reflected laser radiation can be located in the infrared wavelength range or the visible wavelength range.

[0048] Laser processing can define one or more process parameters to perform processing as specified. Process parameters may include at least one predefined processing area, focal position, laser power, feed rate, laser beam diameter, and / or the distance and / or orientation of the laser processing head to the workpiece. Process parameters such as focal position, feed rate, laser power, and / or laser beam diameter can be predefined for each predefined processing area and can be variable or constant.

[0049] At least one monitoring parameter for the intensity signal can be selected from the following group: upper envelope, lower envelope, upper threshold, lower threshold, reference curve, and average value. An error will be output if the intensity signal is outside the envelope or exceeds or falls below the threshold.

[0050] By scaling the intensity signal and / or at least one corresponding monitoring parameter, the intensity signals generated when performing a laser processing procedure through multiple identical laser processing systems can be compared among these laser processing systems. Therefore, differences in intensity signals generated between laser processing systems with identical structures can be taken into account and compensated for.

[0051] Furthermore, to monitor the same laser processing process, the same monitoring parameters or methods or procedures can be used on all laser processing systems with the same structure. In particular, the laser processing process can be monitored based on monitoring parameters already determined for another laser processing system structurally identical to the one under consideration, or for a reference laser processing system with the same structure. Monitoring of the laser processing process is particularly performed based on monitoring parameters determined for a reference laser processing system.

[0052] According to another aspect of the present invention, a laser processing system is provided, comprising: a laser processing head configured to irradiate at least one workpiece with a processing laser beam to perform a laser processing process; a sensor module having at least one sensor, preferably a photodiode-based sensor or photodiode, for sensing the intensity of process radiation within a predetermined wavelength range and / or at a predetermined wavelength; and a control unit configured to perform a method for comparing laser processing systems according to an embodiment of the present invention and a method for monitoring laser processing processes according to an embodiment of the present invention. The control unit may be configured to control the laser processing head, the sensor module, the laser source, and / or the light source.

[0053] The laser processing system can be configured to perform a method for comparing laser processing systems and / or a method for monitoring the laser processing process according to embodiments of the present invention.

[0054] A laser processing system may include a laser source for generating a processing laser beam. The laser processing system may also include the aforementioned light source.

[0055] The laser processing head can be a laser welding head or a laser cutting head. The sensor module can be mounted or arranged on the housing of the laser processing head.

[0056] At least one sensor may have spectral sensitivity within and / or at a predetermined wavelength range in order to detect radiation intensity within and / or at the predetermined wavelength range. At least one sensor may be sensitive only within or at a predetermined wavelength range. Alternatively, at least one sensor may also be sensitive within multiple predetermined wavelength ranges or at multiple predetermined wavelengths.

[0057] Furthermore, the sensor can also be configured to output an intensity signal according to an embodiment of the present invention based on sensed process radiation or sensed light source radiation. The control unit can be configured to receive intensity signals from at least one sensor or from a sensor module.

[0058] Preferably, the sensor module includes a first photodiode configured to generate a first intensity signal based on radiation intensity sensed in the visible wavelength range, and / or includes a second photodiode configured to generate a second intensity signal based on radiation intensity sensed in the wavelength of the processing laser beam of the laser source, and / or includes a third photodiode configured to generate a third intensity signal based on radiation intensity sensed in the near-infrared or infrared wavelength range.

[0059] The sensor module can be mounted or arranged on the housing of the laser processing head. The laser processing head may have decoupling elements, such as a beam splitter, for decoupling process radiation or radiation emitted by the light source from the beam path of the processing laser beam. The laser processing head may include an optical output end for decoupling radiation, especially process radiation or radiation emitted by the light source, and the sensor module may include an optical input end for coupling radiation decoupled from the laser processing head. The sensor module is preferably mounted in the laser processing head such that the optical input end of the sensor module and the optical output end of the laser processing head are (optically) connected to each other. The position of the decoupling element in the laser processing head preferably corresponds to the position of the optical output end of the laser processing head for decoupling radiation from the laser processing head. The radiation, especially process radiation or radiation emitted by the light source, can therefore extend at least partially within the laser processing head and / or overlap with the processing laser beam between the workpiece or light source and at least one sensor.

[0060] Laser processing heads can be configured as so-called fixed-optics laser processing heads or so-called scanner laser processing heads. Scanner laser processing heads can have a deflection unit for deflecting the processing laser beam and the excitation beam onto the workpiece. This deflection unit can include scanner optics, a scanner system, a scanner mirror, and / or a galvanometer scanner. In a fixed-optics laser processing head, the processing laser beam can move relative to the workpiece through the movement of the laser processing head itself, or the workpiece can move relative to the laser processing head.

[0061] The processing laser beam generated by the laser source can have a wavelength in the infrared spectrum, particularly in the range of 1030 nm to 1070 nm, preferably 1064 nm, or in the visible green spectrum, particularly in the range of 500 nm to 570 nm, preferably 515 nm, or in the visible blue spectrum, particularly in the range of 400 nm to 500 nm, or in the range of 440 nm to 460 nm, preferably 450 nm. Attached Figure Description

[0062] The present invention will now be described in detail with reference to the accompanying drawings.

[0063] Figure 1 A schematic diagram of a laser processing system for performing a laser processing process according to an embodiment is shown;

[0064] Figure 2 The graph shows the time curve of the intensity signal for a pre-defined laser welding process, along with the corresponding upper and lower envelopes.

[0065] Figure 3 A schematic diagram of a light source according to an embodiment of the present invention is shown;

[0066] Figure 4 A flowchart illustrating a method for comparing laser processing systems according to an embodiment is shown;

[0067] Figure 5 The diagram shows an intensity signal generated by means of a method for comparing laser processing systems according to an embodiment of the present invention.

[0068] Unless otherwise stated, the same reference numerals are used for the same and same functions of the elements in the following figures. Detailed Implementation

[0069] Figure 1 A schematic diagram of a laser processing system for performing a laser processing process, according to an embodiment, is shown.

[0070] The laser processing system 10 includes a laser processing head 12, a sensor module 32, and a control unit (not shown). An embodiment is described below, wherein the laser processing head 12 is configured as a welding head, and the laser processing system 10 is configured to perform a laser welding process. However, the invention is not limited thereto. The laser processing head 12 may also be configured as a cutting head, for example, and the laser processing system 10 may be configured to perform laser cutting. The laser processing system 10 may also be simply referred to as an apparatus.

[0071] As shown, the laser processing head 12 is modularly constructed. The laser processing head 12 has a main module 16 with a housing 17. The laser processing head 12 also has a coupling module 18 for coupling a laser beam (not shown) into the laser processing head 12. However, the invention is not limited thereto.

[0072] The laser processing head 12 may have additional modules not shown. For example, the laser processing head 12 may have a camera module between the coupling module 18 and the sensor module 32 to capture images of the surface of the workpiece 24.

[0073] The laser processing system 10 may also include a laser source (not shown) for generating a laser beam, also referred to as a processing laser beam or simply a processing beam. The laser source may generate a laser beam, for example, with a wavelength of 1064 nm. This laser beam may be guided from the laser source to the laser processing head 12 via an optical fiber 14.

[0074] The end 15 of the optical fiber 14 is connected, for example, to the coupling module 18 of the laser processing head 12 via an optical fiber coupler to couple a laser beam into the coupling module 18. The laser beam coupled into the coupling module 18 then extends from the coupling module 18 into the main module 16 and exits from the main module 16 via the exit 19 of the laser processing head 12 for alignment with the workpiece 24. The main module 16 may also have a nozzle (not shown) at the exit 19.

[0075] According to a further embodiment not shown, the coupling module 18 may also be arranged on top of the main module 16 or may be omitted. In this example, the laser beam is coupled directly from the laser source or the end 15 of the optical fiber 14 into the main module 16.

[0076] exist Figure 1 The (theoretical) beam path of the laser beam is shown by reference numeral 22 in the figure. Within the laser processing head 12, the laser beam extends from the end 15 of the light source or optical fiber to the exit 19 of the laser processing head 12, and then irradiates the workpiece 24 to perform a laser processing process, such as a laser welding process.

[0077] The laser processing head 12 has at least one optical element for guiding the laser beam. This optical element can also be referred to as a beam guiding optics. For example, a focusing optics 30 is provided to focus the laser beam onto the workpiece 24, and a collimating optics (not shown) is provided to collimate the laser beam. Furthermore, the laser processing head 12 has a deflection unit 28 for deflecting the laser beam onto the workpiece 24 and a decoupling element 26, such as a beam splitter. The decoupling element 26 is described below with reference to an example of a beam splitter, but is not limited to a beam splitter. Figure 1In the example shown, the decoupling element 26 is arranged between the light output end 38 of the laser processing head and the deflection unit 28, but is not limited to this location. The decoupling element 26 may also be arranged between the focusing optics 30 and the deflection unit 28. The decoupling element or beam splitter 26 is used to decouple light or radiation entering the laser processing head 12 via the exit 19 from the beam path of the processing laser beam, such as process radiation (not shown) generated during laser processing and / or radiation emitted from the light source 42 for inspection. The beam splitter 26 may be configured, for example, as a dichroic mirror.

[0078] A light source 42 is provided for inspecting the laser processing system, particularly the laser processing head 12 and / or the sensor module 32, and is described in detail below. The laser processing head 12 may have other optical elements for beam guidance. For example, the laser processing head 12 preferably has a protective glass 31 at its exit 19 to protect the interior of the laser processing head 12 from contaminants, fumes, splashes, etc., generated during laser processing.

[0079] The laser processing head 12 can be configured as a so-called fixed optics laser processing head or a so-called scanner laser processing head. Figure 1 In this design, the laser processing head 12 is configured as a scanner laser processing head. The scanner laser processing head has a movable deflection unit 28 for deflecting the laser beam relative to the workpiece 24 and for irradiating the workpiece 24 along the processing path. The deflection unit 28 may include scanner optics, a scanner system, a scanner mirror, and / or a galvanometer scanner. In a fixed-optics laser processing head, the laser beam can be moved relative to the workpiece 24, or the workpiece 24 can be moved relative to the laser processing head 12, by the movement of the laser processing head 12 itself.

[0080] When a processing laser beam irradiates a workpiece 24 to perform a laser processing process, process radiation (not shown) is generated. This process radiation is emitted from the workpiece 24 and enters the laser processing head. The process radiation includes radiation in the visible wavelength range, particularly emitted plasma radiation; radiation in the infrared wavelength range, particularly emitted infrared or thermal radiation; and laser radiation reflected by the irradiated processing laser beam from the workpiece 24. After entering the laser processing head 12 or sensor module 32 and before irradiating the sensor 34, the process radiation may have a similar characteristic to that of the light source 42. Figure 1 The radiation 44 shown has essentially the same beam path. However, the invention is not limited thereto.

[0081] exist Figure 1In the illustrated embodiment, a portion of the radiation 44 from the light source 42 enters the laser processing head 12 via exit 19 and overlaps with the (theoretical) beam path of the processing laser beam within the laser processing head 12. The radiation 44 from the processing laser beam is decoupled by the beam splitter 26 so that it enters the sensor module 32 and illuminates the sensor 34. The laser processing head 12 has an optical output terminal 38 for decoupling the process radiation or the radiation 44 emitted by the light source 42, and the sensor module 32 has an optical input terminal 40 for coupling the radiation decoupled from the laser processing head 12. Therefore, the radiation 44 emitted by the light source 42 extends at least sectionally within the laser processing head 12 between the workpiece 24 and the sensor 34 and / or overlaps with the (theoretical) beam path of the processing laser beam.

[0082] A portion of the process radiation, or radiation 44 emitted by light source 42, entering the laser processing head 12 is also used for guiding the beam-guiding optics of the processing laser beam as it passes through the laser processing head 12. This can include reflection or transmission of the radiation. For example, the radiation can be used to shape the focusing optics 36 of the processing laser beam and reflected or deflected by the deflection unit 26. Furthermore, the radiation passes through beam splitter 26 before entering sensor module 32. In sensor module 32, the radiation is focused by focusing optics 36 and then illuminates sensor 34. Figure 1 In the process, the radiation passes through beam splitter 26. However, beam splitter 26 can also be designed such that the radiation is reflected on beam splitter 26. In this case, the end position of fiber 14 is interchanged with the position of sensor module 32.

[0083] exist Figure 1 In this process, the processing laser beam is reflected or deflected on the beam splitter 26, and the process radiation or radiation 44 emitted by the light source 42 is transmitted through the beam splitter 26. However, the invention is not limited thereto.

[0084] Sensor module 32 has at least one sensor 34 configured to detect or measure the intensity of process radiation within a predetermined wavelength range or at a predetermined wavelength, and to generate and output an intensity signal based thereon. Therefore, at least one sensor 34 has spectral sensitivity within or at a predetermined wavelength range. At least one sensor 34 may be constructed as a photodiode or a pixel array. The intensity signal is a time-varying one-dimensional signal. The signal at a predetermined time point corresponds to the radiation intensity detected at that time point.

[0085] The intensity signal output by sensor 34 can be an analog signal, and the control unit can be configured to convert the analog signal into a digital signal.

[0086] According to one embodiment (not shown), the sensor module includes a first sensor for detecting radiation intensity in the visible wavelength range corresponding to plasma radiation, a second sensor for detecting radiation intensity in the wavelength of a processing laser beam corresponding to reflected laser radiation, and a third sensor for detecting radiation intensity in the infrared wavelength range corresponding to thermal radiation, wherein the three sensors generate and output corresponding first to third intensity signals. To redirect the process radiation entering the sensor module to the first to third sensors, the sensor module may have multiple beam splitters.

[0087] The control unit is connected to the sensor module 32 and receives intensity signals from at least one sensor 34. The control unit may be configured to record the intensity signals. The control unit 16 is configured to control the laser processing system 10, particularly the sensor module 32, at least one sensor 34, the light source 42, and / or the laser processing head 12, to perform methods for comparing laser processing systems and for monitoring the laser processing process according to embodiments of the present invention. The control unit is particularly configured to monitor and adjust the laser processing process based on the intensity signals from at least one sensor 34.

[0088] The laser welding process is described below as an example of a laser processing procedure. However, the invention is not limited thereto. The laser processing procedure can also be a laser cutting process.

[0089] When monitoring the laser welding process, according to embodiments of the present invention, the magnitude and shape of the generated intensity signal are typically analyzed and evaluated. Here, during the laser processing, the radiation intensity of the process radiation is detected by at least one sensor 34 of the sensor module 32 within a predetermined wavelength range or at a predetermined wavelength, and a corresponding intensity signal is generated.

[0090] The laser processing is monitored based on the intensity signal and at least one associated monitoring parameter. Monitoring parameters may include, for example, an upper envelope, a lower envelope, an upper threshold, a lower threshold, a reference curve, etc. For instance, the intensity signal is compared to a pre-defined envelope and / or threshold; if the intensity signal is outside the envelope or exceeds or falls below the threshold, an error is output. This error comparison and output can, for example, be performed by a control unit. In laser welding, the analysis and evaluation of process radiation can provide a qualitative description of the weld quality.

[0091] As described above, according to one embodiment, a first intensity signal is generated based on the radiation intensity detected by the process radiation in the visible wavelength range for detecting plasma radiation; a second intensity signal is generated based on the radiation intensity detected by the process radiation in the wavelength of the processing laser beam for detecting reflected laser radiation; and a third intensity signal is generated based on the radiation intensity detected by the process radiation in its infrared wavelength range for detecting thermal radiation.

[0092] Figure 2 The diagram shows the time curves of the intensity signals of the process radiation used in a pre-defined laser welding process, along with corresponding reference curves. The upper example shows the plasma radiation intensity signal during stainless steel welding onto stainless steel. The lower example shows the reflected intensity signal during pulsed welding of stainless steel to stainless steel. For monitoring the laser welding process, such as for monitoring the welding of workpieces, the deviation of the intensity signal from the reference curve is evaluated.

[0093] exist Figure 2 The upper part shows the intensity signal I1 generated by the laser processing system during the laser welding process. Additionally, the upper envelope H1o and lower envelope H1u are plotted as reference curves. In the case of intensity signal I1, the signal level of intensity signal I1 is compared with the signal levels of the upper envelope H1o and lower envelope H1u. If the signal level of intensity signal I1 is lower than or falls below the lower envelope H1u, or if the signal level of intensity signal I1 is higher than or rises above the upper envelope H1o, an error is output. The last case... Figure 2 The intensity signal I1' is used to illustrate this visually. To compare signal levels, for example, the time average of the intensity signal I1 can be compared with the time averages of the envelopes H1o and H1u.

[0094] exist Figure 2 The lower part shows another intensity signal I2 generated by the laser processing system during the same laser welding process. Furthermore, the upper envelope H2o and lower envelope H2u are plotted as reference curves. In the case of intensity signal I2, the signal shape of intensity signal I2 is compared with the signal levels of the upper envelope H2o and lower envelope H2u. If the signal shape of intensity signal I2 is significantly different from the pre-defined signal shape through the upper envelope H2o and lower envelope H2u, an error is output. This situation occurs in… Figure 2 The intensity signal I2' is used to illustrate this intuitively.

[0095] A reference parameter can be used to compare signal shapes. One possible reference parameter is the integral of the signal curve. If the integral of the reference curve deviates from the integral of the currently recorded signal curve, an error is output. Another example of a reference parameter is the "area error," which depends on the area formed between the currently recorded signal curve and the reference curve. Therefore, it is a measure of the position and distance of the currently recorded signal curve from the reference curve.

[0096] The inventors have recognized that the spectral distribution of the detected radiation intensity of the process radiation detected by sensor 34 depends to a large extent on the beam guiding characteristics of the beam guiding optics of the laser processing head 12 and sensor module 32 guiding the process radiation, as well as the detection characteristics of sensor 34.

[0097] Beamguide optics are subject to manufacturing tolerances or quality fluctuations. Furthermore, beamguide optics age and become contaminated over time. The sensor also experiences manufacturing tolerances, aging effects, and contamination. Therefore, even among components with identical structures, the reflection or transmission spectra of beamguide optics and the spectral sensitivity of sensors can differ and vary over time. Consequently, the radiation intensity of process radiation detected at or within a predetermined wavelength range, and thus the corresponding intensity signal level, may differ between laser processing systems of the same structure or between different points in time within the same laser processing system. Here, even small differences in two beamguide optics or sensors of identical structure can lead to significant changes in signal level and shape.

[0098] These effects of beam-guiding optics and sensors lead to significant differences in the generated intensity signals. In particular, the signal levels and shapes of the generated intensity signals can differ and vary over time. This makes it difficult to compare intensity signals between devices. Furthermore, it is no longer possible to guarantee the identification of errors during monitored laser processing. This is especially true in industrial mass production, where multiple devices with identical structures are often used. Therefore, the comparability of devices with the same structure is particularly important here.

[0099] On the other hand, pre-defined process parameters of the laser processing procedure, such as laser power and other laser parameters, or system parameters—that is, the parameters of the mechanical components of the laser processing system or equipment, such as the robotic arm that guides the laser processing head—also significantly influence the detected radiation power and thus the generated intensity signal. For example, differences in the positioning or size of these components can cause the signal intensity (i.e., the value of the intensity signal) to vary from system to system, as this affects the backscattered radiation power of the laser. Therefore, it is important to distinguish the aforementioned influences of the beam guiding and detection characteristics of the laser processing system from the influences of the process parameters.

[0100] Overall, the comparability of the generated intensity signals plays a crucial role in the comparability between devices with the same structure and in the quality of process monitoring (i.e., in the analysis and evaluation of intensity signals). Therefore, it is necessary to be able to analyze, evaluate, and compare the beam guiding and detection characteristics of laser processing systems.

[0101] Therefore, according to the present invention, the light source 42 is used for inspection (see...) Figure 1The light source 42 may be part of the laser processing system 10.

[0102] The light source 42 is disposed outside the laser processing head 12, for example, on the workpiece 24 or holding device at a predetermined position corresponding to a predetermined laser processing procedure or processing area. However, the invention is not limited thereto. The light source 42 is preferably fixedly mounted. More preferably, the light source 42 emits a spectrum having or including the process radiation corresponding to the laser processing procedure. The light source 42 preferably emits light in the visible wavelength range corresponding to plasma radiation, in the infrared wavelength range corresponding to thermal radiation, and in the wavelength of the processing laser beam.

[0103] The light source 42 is constructed, for example, as a broadband LED or halogen lamp and is preferably a stable or adjustable light source. Adjustment can be performed via the control unit of the laser processing system 10 or via a separate control unit. Adjustment includes monitoring the emission characteristics of the light source 42, such as its emission spectrum and radiation characteristics, and adjusting the light source 42 so that its emission characteristics remain constant and thus stable. This ensures that the emission characteristics do not change undesirably due to environmental conditions such as temperature or due to light source aging. This also ensures that the emission characteristics of the light source 42 do not affect the analysis and evaluation of the beam guiding and detection characteristics of the laser processing system 10. Emission characteristics particularly include the emission spectrum, i.e., the spectral distribution of the emitted radiation intensity, and the radiation characteristics, i.e., the angular distribution of the emitted radiation.

[0104] To ensure that the emission characteristics of the light source 42 are constant throughout its lifespan and unaffected by temperature variations, and thus, in particular, that the emitted radiation intensity is constant, an adjustment circuit can be provided, which can be implemented by a control unit. The adjustment circuit can be configured to increase the drive current of the light source 42 when the efficiency of the light source 42 decreases, so as to maintain the emitted radiation intensity at a constant potential. For example, an LED is used as the light source 42, and the adjustment circuit includes a photodiode for detecting the radiation intensity emitted by the LED. The photodiode is connected to an amplifier circuit of the adjustment circuit. The drive current of the LED is adjusted according to the detected radiation intensity. If the detected radiation intensity decreases, the drive current of the LED is increased. To detect the radiation intensity of the LED via the photodiode, the adjustment circuit also includes a partially transparent mirror through which a portion of the radiation intensity emitted by the LED is deflected onto the photodiode. The photodiode can output a current based on the detected radiation intensity. An operational amplifier of the amplifier circuit can be connected to the photodiode and act as a voltage converter. The operational amplifier and the photodiode can be constructed as a single component.

[0105] Figure 3 A light source according to an embodiment of the present invention is shown.

[0106] The light source 42 includes a halogen lamp 46 arranged between a first aperture 48 and a second aperture 50. The first aperture 48 may be located above the halogen lamp 46, and the second aperture 50 may be located below the halogen lamp 46, but the invention is not limited thereto.

[0107] The filter 52 is preferably arranged on the side of the second aperture 50 opposite to the light-emitting diode 42. The filter 52 has a transmittance of 50% for the radiation emitted by the halogen lamp 46. However, the invention is not limited thereto. The filter 52 may have a different transmittance or may be omitted. Furthermore, the light source 42 includes a photodiode 54 with an operational amplifier, which is arranged on the side of the second aperture 50 opposite to the light-emitting diode 42 or on the side of the filter 52 opposite to the second aperture 50. The second aperture 50 limits the proportion of emitted radiation 56 reaching the photodiode 54 from the light source 42.

[0108] Laser processing head 12 (see) Figure 1 The first aperture 48 is positioned on the side opposite to the light-emitting diode 42. The first aperture 48 limits the proportion of emitted radiation 44 that reaches and is detected by the sensor 34 from the light source 42 toward the laser processing head 12.

[0109] By providing light source 42, it is unnecessary to perform a laser processing procedure to generate process radiation for analyzing and evaluating beam guiding and detection characteristics. Furthermore, the (stable) light source 42 offers the advantage of providing a baseline or constant compensation for comparing the laser processing system 10. The comparison is independent of the aforementioned influencing factors such as the process parameters of the laser source or the laser parameters.

[0110] Figure 4 A flowchart is shown for comparing a laser processing system according to an embodiment. This method can be described by reference to... Figure 1 The laser processing system 10 described herein is used to perform this process.

[0111] The method for comparing laser processing systems includes, as a first step (S1), detecting radiation 44 emitted by light source 42 within a predetermined wavelength range or in a predetermined wavelength range by sensor 34, and generating a corresponding intensity signal.

[0112] Radiation 44 extends from the light source 42 through the laser processing head 12 and the sensor module 32 to the sensor 34.

[0113] As radiation 44 extends through laser processing head 12 or sensor module 32, the radiation 44 emitted by light source 42 is guided by at least one beam guiding system of laser processing head 12, such as deflection unit 28, beam splitter 26, or focusing optics 30, just like process radiation, and by at least one beam guiding optics of sensor module 32, such as focusing optics 36. As discussed previously regarding process radiation, the spectral distribution of the intensity of the detected radiation 44 is also influenced by the beam guiding characteristics of the laser processing head 12 and the beam guiding optics of sensor module 32, and by sensor 34 of sensor module 32.

[0114] The method further includes orienting the laser processing head 12 and the light source 42 relative to each other such that the radiation intensity detected by the sensor 34 and the corresponding intensity signal reach their maximum values ​​(S2).

[0115] Furthermore, the sensor module 34 and the laser processing head 12 can initially be oriented relative to each other. For example, the optical axis of the sensor module 34 can be aligned with the optical axis of the light output end 38 of the laser processing head 12. In particular, the optical axis of the light input end 40 of the sensor module 32 can be aligned with the optical axis of the light output end 38 of the laser processing head 12, such that the optical axis of the light input end 40 of the sensor module 32 coincides with the optical axis of the light output end 38 of the laser processing head 12.

[0116] Subsequently, the laser processing head 12 and the light source 42 can be oriented relative to each other to detect the maximum value of the intensity signal. For this purpose, the laser processing head 12 and the light source 42 can be oriented relative to each other such that the center point of the light source 42 is located on the optical axis of the laser processing head 12. In particular, the center point of the light source 42 can be located on the optical axis of the focusing optics 30. Furthermore, it can be oriented such that the central axis of the light source 42 coincides with the optical axis of the laser processing head, and especially with the optical axis of the focusing optics 30.

[0117] Alternatively, orientation can be achieved by positioning the center point of the light source 42 at the focal point of the focusing optics 30 of the laser processing head 12 or the focusing optics 36 of the sensor module 32.

[0118] Therefore, for example, the laser processing head 12 and / or the light source 42 can move not only in a plane perpendicular to the optical axis of the focusing optics 30, but also along the optical axis of the focusing optics 30. Furthermore, the distance between the laser processing head 12 and the light source 42, and their orientation, can be adjusted. For example, the laser processing head 12 and the light source 42 can be tilted relative to each other. These adjustment possibilities are... Figure 1 It is shown by double arrow 58 in the middle.

[0119] Furthermore, the sensor 34 of the sensor module 32 can be oriented such that the radiation 44 coupled to the sensor module 32 and focused onto the sensor 34 is substantially completely detected by the sensor 34. For this purpose, the sensor 34 can be oriented such that its center point lies on the optical axis of the focusing optics 36, and the central axis of the sensor 34 coincides with the optical axis 36 of the focusing optics. Therefore, the sensor 34 can move in a plane that is not only perpendicular to but also along the optical axis of the focusing optics 36. This... Figure 1 The number 60 is indicated by a double arrow.

[0120] According to the embodiment, the light source 42 is fixedly mounted. In this case, orientation is achieved solely through the movement of the laser processing head 12 and the sensor module 32 fastened thereto.

[0121] The mutual orientation of the laser processing head 12 and the light source 42 should ensure that the maximum radiation intensity of the emitted radiation enters the laser processing head 12 or the sensor module 32, so that the intensity signal presents the maximum value.

[0122] According to the above embodiment, first to third intensity signals are generated. In this case, the laser processing head 12 and the light source 42 can be oriented relative to each other such that at least one of the first to third intensity signals exhibits a maximum value.

[0123] According to the invention, the signal is recorded after the light source 42 is precisely oriented relative to the optical axis. Here, the center of the light source 42 is oriented relative to the optical axis in such a way that the maximum intensity signal is achieved under plasma radiation, thermal radiation, and reflected radiation conditions.

[0124] As a final step, the method includes comparing the intensity signal with a pre-given reference value (S3). For example, the time average of the generated intensity signal can be compared with the reference value. Alternatively or additionally, the maximum value of the intensity signal can be compared with the reference value. According to an embodiment, the reference value is the average or maximum value of the intensity signal determined for a reference laser processing system through the above steps S1 and S2, wherein the reference laser processing system has the same structure as the laser processing system under consideration.

[0125] By detecting radiation from the light source, maximizing the intensity signal by orienting the laser processing head relative to the light source, and comparing the intensity signal with a reference value, comparability of laser processing systems with the same structure can be achieved. No laser processing procedure is required in this process.

[0126] On one hand, steps S1-S3 can be performed for the first time using the first laser processing system, and on the other hand, steps S1-S3 can be performed using a second laser processing system with the same structure as the first laser processing system. Here, the corresponding intensity signal for each laser processing system with the same structure is compared with the same reference value. In this case, a laser processing system with the same structure means that the laser processing system has a laser processing head and a sensor module with the same structure. Based on the results obtained from the comparison, it can then be determined in a further step whether, for example, mechanical or optical changes are needed in the structure, such as replacing or repositioning at least one optical or mechanical component of the laser processing system, and / or whether the parameters in the control or monitoring software of the control unit need to be matched, for example, a small offset must be set to compensate for different signal levels of the intensity signal in order to ensure comparability between laser processing systems 10 with the same structure.

[0127] For example, steps S1-S3 can be performed using at least two laser processing heads with identical structures, identical sensor modules, and identical light sources. Here, the sensor modules can be sequentially mounted on at least two laser processing heads with identical structures. This allows for comparison of the beam guiding characteristics of the optical elements of multiple identically constructed laser processing heads. Here, the influence of the beam guiding and detection characteristics of different sensor modules on the detected radiation intensity and the resulting intensity signal is masked.

[0128] Alternatively or additionally, steps S1-S3 can be performed using the same laser processing head, the same light source, and at least two sensor modules of the same structure. This allows for comparison of the detection and beam steering characteristics of multiple sensor modules with identical structures. Here, the influence of the beam steering and detection characteristics of the sensor modules on the detected radiation intensity and the resulting intensity signal is eliminated by using a laser processing head with the same structure. This process can be meaningful, for example, when replacing the sensor modules on the laser processing head with sensor modules of the same structure, so as to enable comparison of the intensity signals generated between sensor modules of the same structure.

[0129] Alternatively or additionally, steps S1-S3 can be performed multiple times using the same laser processing head, the same sensor module, and the same light source, and / or can be repeated at predetermined time intervals. This allows for comparison of the characteristics of the laser processing system at different time points, particularly its beam guiding and / or detection characteristics. Thus, beam guiding optics, such as... Figure 1The protective glass 31 and / or sensor in the laser processing system are subject to aging and / or contamination. For example, this method can be performed during commissioning and / or maintenance of the laser processing system and / or after replacing at least one component of the laser processing system. At least one component of the laser processing system may be, for example, a laser source, a sensor module, a sensor of the sensor module, or a beam-guiding optics of the laser processing head, such as in... Figure 1 The focusing optics 30 or protective glass 31 shown, or the beam guiding optics of the sensor module, for example in Figure 1 The focusing optics 36 shown.

[0130] Furthermore, the calibration of the intensity signal on the laser processing system serves as a quality check before starting the laser processing process and thus beginning the detection of process radiation. This can, for example, identify larger damage or variations, such as contaminated protective eyewear. Based on the intensity signal generated during the commissioning of the laser processing system, it can be determined whether the maximum intensity signal can be reached while keeping the software / hardware configuration unchanged. During commissioning by technicians at the customer's site, any laser processing system operating in the visible to near-infrared wavelength range can be independently tested using the aforementioned method and light source process.

[0131] Figure 5 The diagram shows an intensity signal generated by means of a method according to an embodiment of the present invention and an intensity signal recorded while monitoring a laser processing process.

[0132] exist Figure 5 The left side shows first to third intensity signals ("light sources") based on radiation intensity sensed in the visible wavelength range corresponding to plasma radiation ("plasma"), radiation intensity sensed in the wavelength of the processing laser beam ("reflection"), and radiation intensity sensed in the infrared wavelength range corresponding to thermal radiation ("temperature"), which are obtained according to steps S1-S3 above.

[0133] Through the corresponding sensors of the sensor module for Figure 1 Two identical examples of the laser processing system 10 are used to record the first to third intensity signals. The two identical examples of the laser processing system are equipped with two identical beam splitters 26, “Mirror #1” and “Mirror #2”. However, as can be seen, the two beam splitters 26 have slightly different transmission spectra or curves (“wavelength”-“transmission”-curves). For example, beam splitter “Mirror #1” has a higher transmittance in the visible light wavelength range than beam splitter “Mirror #2”, while beam splitter “Mirror #2” has a higher transmittance in the infrared wavelength range than beam splitter “Mirror #1”.

[0134] Therefore, the signal level of the "plasma" intensity signal for the laser processing system with beam splitter "mirror #1" is greater than the signal level of the "plasma" intensity signal for the laser processing system with beam splitter "mirror #2". Conversely, the signal level of the "temperature" intensity signal for the laser processing system with beam splitter "mirror #2" is greater than the signal level of the "temperature" intensity signal for the laser processing system with beam splitter "mirror #1". Different transmission curves for other beam splitters with the same structure show significant variations in the signal level of the corresponding intensity signals.

[0135] These differences, recorded using a light source using this method, are also evident in typical laser welding processes, such as... Figure 5 As shown on the right (“Process”). Therefore, differences or tolerances in other beam splitters of the same structure also affect the radiation intensity sensed during the laser welding process and thus also affect the resulting intensity signal. If the differences in the intensity signals of two laser processing systems of the same structure are not considered or corrected, this may lead to errors in the monitoring of the laser welding process.

[0136] Furthermore, the above method also enables the subsequent determination of a scaling factor for a pre-defined sensor used in a pre-defined laser processing head and a pre-defined sensor module. This scaling factor can then be stored in monitoring software. The scaling factor allows the signal level of the intensity signal based on the detected radiation intensity during laser processing to be adjusted to a pre-defined value or a pre-defined signal level. If the method is repeated on the same laser processing system when changing sensors, it ensures that the signal levels of each sensor are comparable, thus eliminating the need for software parameterization or simplifying it.

[0137] The scaling factor can be determined by dividing the time average or maximum value of the intensity signal generated in steps S1-S3 by the corresponding reference value.

[0138] According to one embodiment, the laser processing system is configured to scale the intensity signal generated during monitoring of the laser processing process using a scaling factor determined in this manner, and to monitor the laser processing process based on the scaled intensity signal as described above. Scaling the intensity signal may include dividing the intensity signal by the scaling factor.

[0139] By scaling the intensity signal, the same monitoring parameters, methods, or procedures can be used on all laser processing systems with identical structures to monitor the same laser processing process. In particular, the laser processing process can be monitored based on monitoring parameters derived for another laser processing system with the same structure as the considered laser processing system, or for a reference laser processing system with the same structure. Specifically, monitoring of the laser processing process can be performed based on monitoring parameters determined for a reference laser processing system.

[0140] According to the above implementation, if the pre-given sensor module includes first to third sensors, three corresponding scaling factors can be determined. For example, a first scaling factor can be determined for the first sensor, a second scaling factor can be determined for the second sensor, and a third scaling factor can be determined for the third sensor.

[0141] This invention provides a method for machine quality inspection or for inspecting diode-based sensor systems, wherein, using a light source, preferably a stable light source, and a photodiode-based sensor module, the beam-guiding characteristics, particularly transmission and / or reflection characteristics, of a laser processing system, i.e., the laser processing head and / or sensor module, can be recorded and evaluated. Based on the principles disclosed herein, it can be determined and shown, in particular, whether the process radiation required for monitoring a laser processing process, such as a laser welding process, is within a considered wavelength range, and what proportion of the process radiation is within the corresponding wavelength range. Furthermore, it can be determined whether comparability with equipment of the same structure is guaranteed. The considered wavelength range can particularly include the following wavelength ranges associated with error identification: the visible wavelength range for detecting plasma radiation, the (near)infrared wavelength range for detecting thermal radiation, and the wavelength range including the processing laser beam wavelength for detecting laser radiation reflected by the workpiece.

Claims

1. A method for comparing laser processing systems (10), wherein, The laser processing system (10) includes a laser processing head (12) and a sensor module (32) having at least one photodiode (34) for sensing process radiation, the method comprising: - The photodiode (34) detects the radiation emitted by the light source (42) and generates a corresponding intensity signal, wherein the radiation is guided from the light source (42) to the photodiode (34) by at least one optical element (26, 28, 30) in the laser processing head (12) and / or by at least one optical element (36) of the sensor module (32). - Orient the laser processing head (12) and the light source (42) relative to each other so that the intensity signal reaches its maximum value; and - Compare the intensity signal scaled by the scaling factor with at least one monitoring parameter, or compare the intensity signal with at least one monitoring parameter scaled by the scaling factor; wherein the scaling factor for the given laser processing head (12) and the given photodiode (34) is determined based on the average value of the intensity signals for the given laser processing head (12) and the given photodiode (34) and based on a given reference value.

2. The method according to claim 1, wherein, The light source (42) is a stable or adjustable light source.

3. The method according to claim 1 or 2, wherein, The detected radiation beam path overlaps at least partially with the beam path of the processing laser beam in the laser processing head (12).

4. The method according to claim 1 or 2, wherein, The detected radiation beam path is at least partially coaxial with the beam path of the processing laser beam in the laser processing head (12).

5. The method according to claim 1 or 2, wherein, The light source (42) includes at least one of the following: halogen lamp, light-emitting diode.

6. The method according to claim 1 or 2, wherein, The light source (42) includes a broadband light source.

7. The method according to claim 1 or 2, wherein, The light source (42) is a light source having an emission spectrum between 350 nm and 2000 nm.

8. The method according to claim 1 or 2, wherein, The detection of the radiation includes detecting the intensity of the radiation within a predetermined wavelength range using at least one photodiode (34).

9. The method according to claim 8, wherein, The predefined wavelength range includes one of the following wavelength ranges: visible wavelength range, infrared wavelength range, thermal radiation wavelength range, and plasma radiation wavelength range.

10. The method according to claim 8, wherein, The predefined wavelength range includes one of the following wavelength ranges: wavelengths between 350 nm and 780 nm, wavelengths between 780 nm and 3 µm, and wavelengths greater than 1 µm.

11. The method according to claim 8, wherein, The pre-defined wavelength is the wavelength of the processing laser beam of the laser processing system.

12. The method according to claim 8, wherein, The predetermined wavelength is 1064nm.

13. The method according to any one of claims 1-2 and 9-12, wherein, The radiation intensity is detected in the visible wavelength range by a first photodiode and a first intensity signal is generated based on this detection, and / or, The radiation intensity is detected by a second photodiode within the wavelength of the processing laser beam in the laser processing system (10), and a second intensity signal is generated based on this detection, and / or, The radiation intensity is detected in the infrared wavelength range by a third photodiode, and a third intensity signal is generated based on this detection.

14. The method according to any one of claims 1-2 and 9-12, wherein, The optical elements (26, 28, 30, 36) include one of the following optical elements: a transmission element and a reflection element.

15. The method according to any one of claims 1-2 and 9-12, wherein, The optical elements (26, 28, 30, 36) include lenses.

16. The method according to any one of claims 1-2 and 9-12, wherein, The optical elements (26, 28, 30, 36) include one of the following optical elements: a lens group, a focusing lens, and a collimating lens.

17. The method according to any one of claims 1-2 and 9-12, wherein, The optical elements (26, 28, 30, 36) include one of the following optical elements: focusing optics (30, 36), collimating optics, and deflecting optics (28).

18. The method according to any one of claims 1-2 and 9-12, wherein, The optical elements (26, 28, 30, 36) include protective glass.

19. The method according to any one of claims 1-2 and 9-12, wherein, The optical elements (26, 28, 30, 36) include a beam splitter (26).

20. The method according to any one of claims 1-2 and 9-12, wherein, The optical elements (26, 28, 30, 36) include mirrors.

21. The method according to any one of claims 1-2 and 9-12, wherein, To compare the beam guiding characteristics of multiple laser processing heads (12) with the same structure, all steps are performed using at least two laser processing heads (12) with the same structure, the same sensor module (32), and the same light source (42), and / or In order to compare the detection characteristics of multiple sensor modules (32) with the same structure, all steps are performed using the same laser processing head (12), the same light source (42), and at least two sensor modules (32) with the same structure, and / or In order to compare the characteristics of the laser processing system (10) at different time points, all steps are repeated at a predetermined time interval using the same laser processing head (12), the same sensor module (32) and the same light source (42).

22. The method according to any one of claims 1-2 and 9-12, wherein, The light source (42) is fixedly installed, and / or, The orientation of the laser processing head (12) and the light source (42) relative to each other is achieved by the movement of the laser processing head (12).

23. A method for monitoring a laser processing process, the method comprising: - A laser processing procedure for processing the at least one workpiece (24) is performed by irradiating a processing laser beam onto at least one workpiece (24) using a laser processing head (12); - The photodiode (34) of the sensor module (32) detects the process radiation of the laser processing within a predetermined wavelength range and generates a corresponding intensity signal; and - The intensity signal is scaled using a scaling factor determined for the laser processing head (12) and the photodiode (34) performing the laser processing, and the laser processing is monitored based on the scaled intensity signal and at least one monitoring parameter pre-given for the intensity signal; or - The intensity signal is scaled using a scaling factor determined for the laser processing head (12) and the photodiode (34), and the laser processing process is monitored based on the intensity signal and the scaled intensity signal and the at least one monitoring parameter. Specifically, a scaling factor for the given laser processing head (12) and the given photodiode (34) is determined based on the average value of the intensity signals for the given laser processing head (12) and the given photodiode (34) and based on a given reference value; and the determination of the scaling factor includes determining the quotient between the average value of the intensity signal and the reference value; the scaling of the intensity signal includes dividing the intensity signal by the scaling factor; and the scaling of the monitoring parameter includes multiplying the monitoring parameter by the scaling factor.

24. The method according to claim 23, wherein, The at least one monitoring parameter for the intensity signal is selected from the group consisting of: upper envelope, lower envelope, upper threshold, lower threshold, reference curve, and / or average value.

25. A laser processing system (10), comprising: - A laser processing head (12) configured to direct a processing laser beam onto at least one workpiece (24) to perform a laser processing procedure. - A sensor module (32) having at least one photodiode (34) for sensing the intensity of process radiation within a pre-given wavelength range, and - A control unit configured to perform the method according to claim 23 or 24.

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