Method for calibrating one or more optical sensors of a laser machining head, laser machining head and laser machining system

Abstract

This invention relates to a method for calibrating at least one optical sensor (200, 300, 400) of a laser processing head (800) for machining workpieces by means of a processing laser beam (L). The laser processing head (800) includes a first optical sensor (200, 300, 400), a deflection device (500), and a focusing device (600). The beam path of the first optical sensor (200, 300, 400) passes through the deflection device (500) and the focusing device (600). The method includes the following steps: deflecting the beam path of a first optical sensor (200, 300, 400) to a first position on a first reference (R, R1, R2, R3, R4) by a deflection device (500); generating a first optical measurement signal based on the measurement light (210, 410) received by the first optical sensor (200, 300, 400) from the first position on the first reference (R, R1, R2, R3, R4); and determining a correction value for calibrating the first optical sensor (200, 300, 400) based on the first optical measurement signal and according to the deviation between the first position on the first reference (R, R1, R2, R3, R4) and a first nominal position, wherein the position of the first nominal position relative to the processing laser beam (L) is predetermined.

Description

Technical Field

[0001] This disclosure relates to a method for calibrating at least one optical sensor for a laser processing head. Furthermore, this disclosure also relates to a laser processing head and a laser processing system. Background Technology

[0002] A laser processing head can include a deflection device and a focusing device. The deflection device can deflect the laser beam incident on the processing head to different positions on the workpiece for processing. The laser beam can also be called a processing laser beam. The focusing device can focus the laser beam onto the workpiece. Processing can include laser welding, laser cutting, laser engraving, or laser hardening.

[0003] To monitor the processing, a laser processing head may include at least one optical sensor. The beam path of the optical sensor may extend partially coaxially with the beam path of the laser beam and pass through the same focusing device. In the case of multiple optical sensors, different spectral sensitivities are typically applied, meaning each optical sensor operates at a different wavelength or a different wavelength range. Thus, the beam paths of multiple or all optical sensors can be coaxially superimposed. In the case of a laser processing head with a deflection device, the beam path of the optical sensor may extend through the deflection device of the laser processing head to measure the workpiece surface at a predetermined position with respect to the incident point of the laser beam. To obtain reliable monitoring results, the optical sensor must typically be calibrated. Summary of the Invention

[0004] The objective of this disclosure is to provide methods and systems that enable cost-effective monitoring of improved laser processing procedures. Another objective is to provide methods and systems that enable cost-effective high-quality laser processing. Yet another objective is to provide methods and systems that cost-effectively improve the measurement accuracy of optical sensors used for monitoring laser processing procedures. In particular, the objective of this disclosure is to provide methods and systems that allow for more accurate setting of the desired measurement positions of optical sensors used for monitoring laser processing procedures.

[0005] One or more of these tasks are solved by preferred embodiments of the invention. Advantageous design options and improvements are given in alternative embodiments.

[0006] This invention is based on the concept that, in a scanner-based laser processing system with a focusing device or focusing optics, the beam path of an optical sensor is directed to a position in the scanning area different from the nominal position, particularly relative to the laser beam, by means of chromatic aberration. A focusing device or focusing optics can be disposed behind the scanner. Typically, the laser processing system and its components, particularly the scanner and / or focusing device or focusing optics, are designed according to the wavelength of the processing laser beam. In other words, the processing laser beam or its beam path and the beam path of the optical sensor can be deflected differently by the scanner (also called a deflection device), i.e., the measurement position of the optical sensor and the processing position of the processing laser beam move differently on the workpiece by the deflection device. Because the deflection device is driven by the wavelength of the processing laser beam, a deviation will occur between the desired measurement position (nominal position, e.g., predetermined position relative to the (theoretical) position of the processing laser) and the actual measurement position. This deviation can be related to the wavelength and the scanning or deflection angle. In particular, the deviation can be zero when perpendicular to the focusing device and increases with increasing deflection angle or deflection. Therefore, measurements by the optical sensor can occur at positions other than those expected. Therefore, according to this disclosure, at least one optical sensor of the laser processing head should be calibrated such that its beam path or its measurement position is aligned with the desired position.

[0007] According to one aspect of this disclosure, a method is provided for calibrating at least one optical sensor of a laser processing head used for machining a workpiece by means of a processing laser beam. The laser processing head includes a first optical sensor, a deflection device (also referred to as a scanner), and a focusing device. The beam path of the first optical sensor passes through or extends through the deflection device and the focusing device. The method includes the steps of: deflecting the beam path or measurement position of the first optical sensor to a first position on a first reference by means of the deflection device; generating a first optical measurement signal based on measurement light received by the first optical sensor from the first position on the first reference; and determining a correction value for calibrating the first optical sensor based on the first optical measurement signal and according to the deviation between the first position on the first reference and a first nominal position—which can be selectively predetermined relative to the (theoretical or virtual) position of the processing laser beam. Lateral calibration of the optical sensor can thus be achieved.

[0008] This method can be implemented at multiple locations on a reference, and a correction value can be determined for each location. The correction values ​​and corresponding locations can be stored in a table. Alternatively, or additionally, a correction function can be created based on the correction values ​​and corresponding locations.

[0009] According to another aspect, a method for process monitoring of a laser processing process is proposed. This method includes a calibration method according to an embodiment of this disclosure, and the steps of: deflecting the beam path or measurement position of a first optical sensor to a predetermined monitoring position via a deflection device; and receiving measurement light from the monitoring position via the first optical sensor for process monitoring, wherein the drive signal of the deflection device for deflecting the beam path or measurement position of the first optical sensor to the predetermined monitoring position is adjusted based on a determined correction value. The method for process monitoring of a laser processing process can be implemented, particularly before and / or after the laser processing process (pre-process and / or post-process). In particular, the method for process monitoring of a laser processing process can be implemented when the processing laser beam is turned off.

[0010] According to another aspect, a method for process monitoring of a laser processing process is proposed. This method includes a calibration method according to an embodiment of this disclosure, and the steps of: deflecting the processing laser beam and the beam path or measurement position of a first optical sensor to a predetermined processing position via a deflection device; processing a workpiece at that processing position using the processing laser beam; and generating a monitoring signal based on measurement light received from the processing position for process monitoring (during the process) via the first optical sensor, wherein the monitoring signal for process monitoring is adjusted based on the determined correction value. The method for process monitoring of a laser processing process can be implemented, in particular, during the laser processing process.

[0011] During laser processing, a processing laser beam is directed onto a position on the workpiece to be processed. To monitor the laser processing process, the beam path of the optical sensor—that is, the measurement position relative to the position of the processing laser beam on the workpiece—also known as the processing position—can be aligned to a location, such as the following position on the workpiece, spaced apart from a (predefined) position of the processing laser beam, to monitor the laser processing process. The position of the processing laser beam, in the case of a switched-off processing laser beam, can also be referred to as the virtual or theoretical position of the processing laser beam or the position of the beam path of the processing laser beam. If, for example, the beam path of the processing laser beam and the beam path of the optical sensor pass through a deflection device and a focusing device, a deviation can be induced on the workpiece between the position of the optical sensor's beam path and the position of the processing laser beam. This deviation can be related to the degree of deflection of the optical sensor's beam path and the wavelength that the optical sensor is sensitive to. The wavelength (wavelength range) that the optical sensor is sensitive to can differ from the wavelength of the applied processing laser beam, resulting in different refraction of light by the focusing device. This can cause a deviation between the measurement position of the optical sensor on the workpiece and the (theoretical or virtual) position of the processing laser beam on the workpiece, thus resulting in inaccuracies in the measurements by the optical sensor. The optical sensor can be used, in particular, as a sensor for monitoring the laser processing process through the processing laser beam, for example, for pre-process and / or post-process and / or in-process monitoring. For pre-process and / or post-process monitoring, the processing laser beam can be shut off. For example, the first optical sensor can be sensitive to the infrared wavelength range and / or the visible wavelength range.

[0012] The first position of the beam path of the first optical sensor can be the first measurement position of the first optical sensor. The first measurement position can be located on a first reference. The first measurement position can be, in particular, on the first reference, a position from which the first optical sensor receives the measurement light.

[0013] The measuring light can be light received by a first optical sensor from a first position on a first reference, the beam path of which is deflected to that first position. Based on the intensity of the measuring light, particularly based on detection, a first optical measurement signal can be generated, for example, by the first optical sensor. The first optical measurement signal can be an intensity signal. The first optical sensor can be a first intensity sensor.

[0014] Based on the first optical measurement signal, the deviation between the first position on the beam path or the measurement position of the first optical sensor and the first nominal position on the first reference can be determined, and correspondingly, the lateral deviation, i.e., the x / y deviation, of the measurement position of the optical sensor can be determined. The first nominal position of the first optical sensor can be a position on the reference where the beam path of the first optical sensor is deflected to or should be deflected to, or where the measurement position of the first optical sensor should exist.

[0015] The rated position of the first optical sensor or at least one of the optical sensors in the laser processing head can be located at the position of the processing laser beam (also known as the processing position), or at the position of the beam path of the processing laser beam, or at the theoretical or virtual position of the processing laser beam. Therefore, the beam path of the first optical sensor can be set to deflect to or toward the theoretical or virtual position of the processing laser beam.

[0016] The first rated position of the first optical sensor, or at least one of the optical sensors in the laser processing head, can be spaced apart from the position of the processing laser beam—i.e., the processing position—or from the position of the beam path of the processing laser beam, or the theoretical or virtual position of the processing laser beam. The position of the beam path of the first optical sensor relative to the beam path of the processing laser beam can be set to have a (predefined) distance or (predefined) deviation. This distance can be a distance in a plane defined by a first reference. In particular, the first rated position can include a position in a pre-process and / or subsequent process with respect to the processing laser beam and processing direction. Accordingly, the first optical sensor can be a sensor used to monitor the laser processing process in pre-process and / or post-process steps.

[0017] The correction value can be an absolute or relative value. For example, the correction value is a distance or path. The correction value can correspond to the distance or path between a first position and a first rated position on the beam path of the first optical sensor. The correction value can be a factor.

[0018] The correction value can be associated with the position, orientation, or attitude of the deflection device.

[0019] The deviation between a first position on a first reference—from which measuring light is received by a first optical sensor—and a first nominal position can be caused by color difference. In particular, color difference can be caused by the focusing device of the laser processing head.

[0020] The first optical sensor can be spectrally sensitive to wavelengths other than the wavelength of the processing laser beam. The wavelength or wavelength range that the first optical sensor is sensitive to can be different from the wavelength of the processing laser beam.

[0021] The reference can be planar. Preferably, the reference is plate-shaped. The reference can be a calibration plate. A plane, such as the xy plane, can be defined or defined by the reference. Alternatively or additionally, the reference and / or the laser processing head can be oriented such that the surface of the reference is in a plane perpendicular to the propagation direction of the processing laser beam, i.e., in the zero position or when the processing laser beam is not deflected.

[0022] The deviation of the first position (measurement position) on the first datum from the nominal position can be a deviation in the plane defined by the datum or in a plane parallel to the datum. The deviation can be a lateral deviation on the datum. The deviation can be a deviation along the x-direction and / or along the y-direction in the xy-plane of the datum.

[0023] The beam path of the processing laser beam can also pass through or through deflection and / or focusing devices. The beam path of the first sensor can extend at least partially parallel to or coaxial with the beam path of the processing laser beam. During calibration, it is not necessary to incident the processing laser beam onto the reference; that is, the processing laser beam can be kept off.

[0024] Typically, a laser processing head can be a laser beam welding head, a laser beam brazing head, a laser beam cutting head, a laser beam engraving head, or a laser beam hardening head. The laser processing procedure can be laser beam welding, laser beam brazing, laser beam cutting, laser beam engraving, or laser beam hardening.

[0025] The deflection device can be configured to deflect the beam path of the first optical sensor on a reference and / or on the workpiece within the scanning area of ​​the deflection device. In other words, the deflection device can be configured to adjust the measurement position of the first optical sensor on a reference and / or on the workpiece within the scanning area of ​​the deflection device. Alternatively or additionally, the deflection device can be configured to deflect the beam path or processing position of the processing laser beam on a reference and / or on the workpiece within the scanning area of ​​the deflection device, or to adjust the processing position on a reference and / or on the workpiece within the scanning area of ​​the deflection device.

[0026] The focusing device may include a focusing optics device for focusing the measuring light of the first optical sensor and / or for focusing the processing laser beam. The focusing device may include one, two, or more lenses or lens groups. The focusing device may include one, two, or more lenses or lens groups whose spacing is at least partially variable to adjust or change the focusing position. Alternatively, lenses with a variable focal length (“liquid lens”) may be used.

[0027] A laser processing head can include multiple different optical sensors. These optical sensors can be configured to detect data for process monitoring during and after the laser processing process.

[0028] The laser processing head may include, in particular, a second optical sensor. The beam path of the second optical sensor may pass through a deflection device and a focusing device. The method may further include the steps of: deflecting the beam path of the second optical sensor to a first position on a second reference by the deflection device; generating a second optical measurement signal based on measurement light received by the second optical sensor from the first position on the second reference; and determining a correction value for calibrating the second optical sensor based on the second optical measurement signal and according to the deviation between the first position on the second reference and a second nominal position, the second nominal position optionally being predetermined relative to the beam path of the processing laser beam.

[0029] The laser processing head may further include a third optical sensor. The beam path of the third optical sensor may pass through a deflection device and a focusing device. The method may further include the steps of: deflecting the beam path of the third optical sensor to a first position on a third reference by the deflection device; generating a third optical measurement signal based on the measurement light received by the third optical sensor from the first position on the third reference; and determining a correction value for calibrating the third optical sensor based on the third optical measurement signal and according to the deviation between the first position on the third reference and a third nominal position, the third nominal position being predetermined relative to the beam path of the processing laser beam.

[0030] The laser processing head may include two, three, four or more optical sensors. The optical sensors may be selected from: at least one camera, an optical coherence tomography (OCT) scanner, at least one photodiode, a photodiode sensitive in the infrared wavelength range, a photodiode sensitive in the visible wavelength range, a photodiode sensitive in the ultraviolet wavelength range, and a photodiode sensitive to the wavelength of the processing laser beam or to the back reflection of the laser.

[0031] At least two of the first, second, and third reference datums may be different reference datums. Each reference datum may be distinguished by its shape, size, or by different reference datum markings. Preferably, the first, second, and third reference datums (all of them) are different reference datums.

[0032] At least two of the first, second, and third optical sensors may be different optical sensors. Each optical sensor can be distinguished by its spectral sensitivity, its signal detection method, or its intensity sensitivity. Preferably, the first, second, and third optical sensors (all of them) are different optical sensors.

[0033] The first beam path of the first optical sensor, the second beam path of the second optical sensor, and the third beam path of the third optical sensor can pass through a deflection device and a focusing device.

[0034] The generation of the first, second, and third optical measurement signals used for calibrating the first, second, and third optical sensors can be performed sequentially or asynchronously. The generation of the first, second, and third optical measurement signals can be performed at time intervals. Calibration of multiple optical sensors, particularly at least two of the first, second, and third optical sensors, can be performed sequentially or at time intervals. A different reference can be applied for each calibration.

[0035] The disclosure for the first optical sensor is applicable to the second optical sensor and / or the third optical sensor.

[0036] The beam path of at least one optical sensor, particularly the first, second and / or third optical sensor, can be deflected by a deflection device to a corresponding reference, i.e., multiple positions on the first, second and / or third reference, in order to generate corresponding optical measurement signals, i.e., the first, second and / or third optical measurement signals.

[0037] The beam path or measurement position of at least one optical sensor, particularly the first, second, and / or third optical sensor, can be scanned by a deflection device onto a corresponding reference, i.e., a surface on the first, second, and / or third reference, to generate a corresponding optical measurement signal, i.e., a first, second, and / or third optical measurement signal. For example, the surface of the corresponding reference can be implemented along a predetermined scanning path, for example, in the form of an intersection with a midpoint at the zero position. Alternatively, the entire surface of the corresponding reference can be scanned or moved over by the beam path of the corresponding optical sensor.

[0038] The beam path of the corresponding optical sensor can be deflected to multiple different positions, preferably at least two, more preferably at least five, more preferably at least nine or more different positions. In other words, the measurement position of the corresponding optical sensor can be oriented towards multiple different positions, preferably at least two, more preferably at least five, more preferably at least nine or more different positions. For example, a lookup table or correction function f(x,y) can be created based on correction values ​​for different measurement positions so that the measurement position can be corrected accordingly in future measurements, such as in monitoring of laser processing, or the measurement signal can be configured to the corresponding actual or corrected measurement position. Measurement signals can be generated when the position of the beam path or the measurement position on the reference changes. Especially if calibration is automated and not periodically related, then a great many positions can be shifted to improve accuracy. Preferably, a correction table can be created, and interpolation can be performed between each value at each position. In one example, an OCT scan of the entire line can be used. Thus, thousands of measurement points can be obtained at clock frequencies in the kilohertz range.

[0039] Multiple or numerous locations may be spaced apart from each other in a plane defined by a corresponding reference, along a first direction and / or along a second direction, wherein the second direction is not parallel to, and in particular perpendicular to, the first direction.

[0040] The beam path of the corresponding sensor can be offset or deflected within the scanning area by a deflection device. The scanning area can be located in a plane defined by a corresponding reference. The corresponding scanning area can be scanned by offsetting or deflecting the beam path of the corresponding sensor. Preferably, the scanning area has a width in the plane defined by the reference. At least 50%, preferably at least 70%, more preferably at least 90% of the width of the scanning area can be scanned by offsetting or deflecting the beam path of the corresponding sensor. In particular, the entire width of the scanning area is scanned by offsetting or deflecting the beam path of the corresponding sensor.

[0041] Preferably, the beam path of each optical sensor is deflected by a deflection device to at least two, preferably at least three, more preferably at least five or more positions on the corresponding reference, and a corresponding optical measurement signal is generated based on the measurement light received by the optical sensor from the corresponding position.

[0042] Each reference may include or have at least one reference mark. The deviation between the position of the first optical measurement signal and the (theoretical or virtual) orientation or position of the processing laser beam can be determined based on the reference mark.

[0043] Each reference may include or have at least two, preferably at least five, more preferably at least nine or more reference marks. The corresponding deviation between the position of the optical measurement signal and the (theoretical or virtual) orientation or position of the processing laser beam can be determined based on the corresponding reference marks.

[0044] In particular, the beam path of at least one optical sensor can be oriented toward a corresponding reference by a deflection device parallel to or coaxial with the optical axis of the focusing device, so as to generate a corresponding optical measurement signal at the zero position.

[0045] At the zero position, the beam path of the optical sensor or processing laser beam may not be deflected. At the zero position, the beam path may be oriented perpendicular to the plane defined by the reference. Preferably, at the zero position, the distance between the plane defined by the reference and the focusing device is minimized. If the beam path is deflected from the zero position, then the distance between the plane defined by the reference and the focusing device may be increased compared to the distance at the zero position.

[0046] At the zero position, there may be no lateral chromatic aberration (at the zero position in a plane defined by a reference or in a plane perpendicular to the propagation direction of the processing laser beam) for beams of different wavelengths.

[0047] Zero position can be used to check the measurement position of the corresponding sensor, that is, the position of the beam path of the corresponding optical sensor, relative to the machining position or relative to the beam path of the machining laser beam on a reference.

[0048] A laser processing head may include multiple different optical sensors. Each of the optical sensors may be sensitive to a different wavelength range. The spectral sensitivity of the optical sensors may vary. Each of the optical sensors can be calibrated using the methods disclosed herein.

[0049] The corresponding beam paths of at least two, preferably all, of the optical sensors can pass through deflection and focusing devices.

[0050] The first, second, and / or third optical measurement signals can be based on measurement light of different wavelengths or different wavelength ranges.

[0051] A laser processing head may include multiple different optical sensors, each calibrated using its own distinct reference. A reference may be applied to each of the optical sensors, and these references are different. Each of the optical sensors may be calibrated using the methods disclosed herein.

[0052] The at least one optical sensor may include a device for measuring optical spacing, a conical device, a time-of-flight measuring device, an optical interferometer, an optical coherence tomography scanner, an image sensor, a camera, a spectrometer, a spectrometer, and / or a photodiode sensor having one or more photodiodes.

[0053] The optical sensors of the laser processing head can be various optical sensors. Each of the optical sensors may include a device for measuring optical spacing, a conical device, a time-of-flight measurement device, an optical interferometer, an optical coherence tomography scanner, an image sensor, a camera, a spectrometer, a spectrometer, and / or a photodiode sensor having one or more photodiodes.

[0054] Preferably, the first optical sensor includes an image sensor, particularly a camera. The second optical sensor may include a spectrometer, a photodiode sensor with one or more photodiodes. The third optical sensor may include an interferometer, particularly an optical coherence tomography (OCT) scanner.

[0055] An image of a reference can be detected using an image sensor. The image may include an area of ​​at least 25 square millimeters, preferably at least 100 square millimeters, more preferably at least 400 square millimeters, preferably 1000 square millimeters or larger, particularly the area on the reference.

[0056] Process emissions can be detected using photodiode sensors. For this purpose, photodiode sensors can be configured to detect process emissions. Process emissions can include plasma emission, thermal emission, and / or reflected laser emission, particularly from the processing area.

[0057] A photodiode sensor may include multiple photodiodes. These photodiodes may have different spectral sensitivities. Photodiodes may be sensitive to the visible wavelength range, particularly in the 350 nm to 780 nm range. Photodiodes may be sensitive to the infrared wavelength range, particularly in the 780 nm to 2200 nm range. Photodiodes may be sensitive to the wavelength range of processing laser beams, particularly in the 900 nm to 1080 nm or 500 nm to 550 nm range.

[0058] The at least one optical sensor may include an optical interferometer or an optical coherence tomography (OCT). The reference may be a calibration plate with multiple recesses at predetermined locations. The recesses may be reference markings. The recesses in the reference can be detected by a sensor with an optical interferometer, particularly by an OCT.

[0059] An optical measurement beam can be incident on a reference. A portion of the optical measurement beam can be reflected from the reference as measurement light to the optical sensor. The direction of the optical measurement beam can correspond to the beam path of the optical sensor, i.e., an optical interferometer or an optical coherence tomography scanner.

[0060] The measurement light used to generate the optical measurement signal can be the portion reflected from the incident optical measurement beam and detected by an optical sensor, particularly by an optical interferometer or optical coherence tomography scanner.

[0061] A method for calibrating an optical sensor, particularly an optical interferometer or an optical coherence tomography scanner, may include: orienting the beam path of a processing laser beam or the zero position of an optical measurement beam of an optical sensor to a predetermined zero position on a reference, particularly a calibration plate; incident and deflecting the optical measurement beam onto the reference, particularly the calibration plate, at least one position different from the zero position using a deflection device; generating a measurement signal for said at least one position or for each position; and determining a correction value based on the deviation of the position from the corresponding predetermined nominal position, or based on the corresponding deviation of each position from the corresponding predetermined nominal position.

[0062] A method for calibrating an optical sensor, particularly an optical interferometer or an optical coherence tomography scanner, may include: orienting a calibration plate such that a predetermined zero position on the calibration plate corresponds to the zero position of an optical measurement beam of the optical sensor; scanning the surface of the calibration plate with the optical measurement beam through a deflection device and generating a corresponding measurement signal; determining the position of each recess on the calibration plate based on the measurement signal; and determining a correction value based on the deviation between the determined position of the recess and a predetermined reference position.

[0063] A reference position can be a reference mark, such as the location of a recess or optical feature. A reference position can involve a zero position and / or another reference mark. For example, the zero position and the interval between it and the reference mark at the reference position can be known. Furthermore, the interval between the two reference marks can be known.

[0064] The zero position of the beam path of the optical sensor (or the optical measurement beam of the optical sensor) can be the same as or separated from the zero position of the beam path of the processing laser beam by a predetermined distance. At the zero position, the beam may not deflect, and in particular, it may be parallel or coaxial with the optical axis of the focusing device.

[0065] A method for calibrating optical sensors, particularly optical interferometers or optical coherence tomography scanners, may include: orienting a calibration plate such that a predetermined zero position on the calibration plate corresponds to the zero position of the optical measurement beam of the optical sensor; determining a working interval between a laser processing head and the calibration plate; scanning the surface of the calibration plate with the optical measurement beam through a deflection device, generating a corresponding measurement signal; determining the interval between the laser processing head and the calibration plate based on the measurement signal; and determining a correction value based on the deviation between the working interval and the determined interval. Axial calibration, i.e., along the beam propagation direction of the processing laser beam or the optical measurement beam, can be achieved in this way. The working interval can be the shortest interval between the laser processing head and the calibration plate, particularly at the zero position. Typically, the interval can be the displacement length of the optical measurement beam.

[0066] The at least one optical sensor may include a spectrometer, a spectrometer, and / or a photodiode sensor with one or more photodiodes for detecting process emissions. The reference may be a test workpiece. The test processing can be performed on the test workpiece by deflecting the processing laser beam to at least one predetermined reference position using a deflection device.

[0067] By testing the machining process, datum marks can be created on a datum, especially on the test workpiece. The location of the datum mark or the testing machining process can be the datum position.

[0068] The testing process can involve welding, cutting, drilling, or piercing using a processing laser beam with predetermined parameters. The testing process can be performed at different locations on a reference (test workpiece). The predetermined parameters for the testing process at different locations on the reference can be the same or identical.

[0069] The measurement light used to generate the optical measurement signal can correspond to process emission, which is emitted at one or more locations during the testing process. Process emission can include a processing laser beam reflected from a reference, plasma emission, and / or temperature radiation.

[0070] Preferably, the optical sensor includes at least three photodiodes. The first photodiode is sensitive to the infrared wavelength range. The second photodiode is sensitive to the wavelength range visible (to a person). The third photodiode is sensitive to the wavelength of the processing laser beam.

[0071] A method for calibrating optical sensors, particularly spectrometers, spectrometers, and / or photodiode sensors, may include: aligning a processing laser beam with a zero position on a test workpiece; performing a test processing procedure and detecting the process emission emitted therefrom by an optical sensor; deflecting the processing laser beam to a reference position; performing the test processing procedure at the reference position and detecting the process emission emitted therefrom by an optical sensor; and determining a correction value based on the deviation between the intensity of the process emission detected at the reference position and the intensity of the process emission detected at the zero position. When the processing laser beam is aligned with the zero position on the test workpiece, it is preferable that the processing laser is not deflected and that the processing laser reaches the test workpiece coaxially with the optical axis of the focusing device. The intensity of the process emission detected at the reference position may be a signal level or a signal strength. The correction value may correspond to or be the difference between the intensity of the process emission detected at the reference position and the intensity of the process emission detected at the zero position. The correction value may also correspond to a coefficient between the intensity of the process emission detected at the reference position and the intensity of the process emission detected at the zero position.

[0072] The method may include multiple test processes at corresponding reference positions. The optical measurement signal may be adjusted based on correction values ​​for the corresponding or most recent reference position, or quality standards, such as reference curves or envelopes, may be adjusted.

[0073] The at least one optical sensor may include an image sensor or a camera, or both. The reference may be a calibration plate with multiple optical features at a predetermined reference position. In this case, the position of the beam path or the measurement position of the sensor may relate to the midpoint of the sensor's field of view.

[0074] Optical features can be reference marks. Optical features can include circles, lines, intersecting lines, and / or grids.

[0075] In addition, lighting equipment can be installed. This lighting equipment can be aligned with the reference (calibration plate). The lighting equipment can produce white light or light of a specific wavelength (color). The optical measurement signal can correspond to a (two-dimensional) camera image or photograph.

[0076] Methods for calibrating optical sensors, particularly camera or image sensors, may include: orienting a calibration plate such that a predetermined zero position on the calibration plate corresponds to the zero position of the beam path of the optical sensor; deflecting a discontinuous segment of the beam path of the optical sensor, the processing laser beam being deflected by the discontinuous segment in order to align with the optical features of the calibration plate; and determining a correction value based on the position of the deflected beam path and the interval between the optical features.

[0077] The interval or correction value can be determined based on the position of an optical feature in a plane defined by a calibration plate (reference). The plane defined by the calibration plate can be an xy-plane, i.e., a plane perpendicular to the beam propagation direction of the processing laser beam toward the zero position or the undeflected position. This position can be an xy-position. The interval or correction value can be determined based on the orientation of the optical sensor with respect to the plane defined by the calibration plate (reference). The interval or correction value can also be determined based on the attitude, position, or orientation of the deflection device. The interval or spacing can also be referred to as lateral deviation or offset due to chromatic aberration.

[0078] The camera's coordinate system can be calibrated according to the deflection device's coordinate system, so that the position of the processing laser beam, identifiable in the camera image, can be adjusted via the deflection device. That is, the orientation of the optical sensor can be matched to the direction of the deflection device; in other words, the rotational orientation of the optical sensor can be oriented specifically relative to the orientation of the deflection device. The rotation of the image sensor or camera can be detected specifically based on calibration.

[0079] Furthermore, images from image sensors or cameras can be calibrated. Calibration between pixel size and true size can be performed based on optical characteristics. In other words, the pixel size of an image from an image sensor or camera can be determined based on optical characteristics.

[0080] The focusing device may include a flat-field focusing (F-Theta) objective. Alternatively or additionally, the focusing device may be positioned in the laser processing head after the deflection device with respect to the beam propagation direction of the processing laser beam.

[0081] The focusing device may include at least one lens, lens group, or optical device. The focusing device may be configured to focus a processing laser beam at a predetermined focusing position.

[0082] The deflection device may include at least one movable mirror, particularly two movable mirrors. For example, the deflection device may be a galvanometer-scanner. The beam path of the processing laser beam, optical measurement beam, and / or optical sensor can be deflected in the scanning area by the deflection device; that is, the scanning area can be defined as the maximum area achievable by a single beam or multiple beams passing through the deflection device. The scanning field of the deflection device may have a length and / or width of at least 50 mm. The beam path of the processing laser beam, optical measurement beam, and / or optical sensor can be deflected by the deflection device by an angle of at least 5°, preferably at least 10°, more preferably between 5° and 20°, and even more preferably between 10° and 20°.

[0083] The deflection device can be configured to deflect the beam path of the processing laser beam, optical measurement beam, and / or optical sensor along a first axis by at least a first deflection angle. Preferably, the deflection device is additionally configured to deflect the processing laser beam along a second axis by a second deflection angle, wherein the first and second axes are arranged at an angle, for example, oriented perpendicularly to each other. The maximum first deflection angle and / or the maximum second deflection angle of the deflection device can each be at least 5° or at least 10°, particularly 10° to 20°. The deflection angle corresponds to a mirror angle of at least + / -5°, particularly + / -10°, because the beam is deflected by twice the mirror angle.

[0084] The scanning area of ​​the deflection device can be defined as a region on a reference, particularly on a reference surface, and / or can be predetermined by the maximum first deflection angle and the maximum second deflection angle of the first deflection device. The length and / or width of the scanning area can be equal to or greater than 50 mm. The scanning area can, for example, have a size greater than 50 × 50 mm on the reference, particularly at least about 100 × 200 mm or 250 × 150 mm.

[0085] The deflection device can be a so-called large-area scanner. The deflection device can be configured to deflect the beam path of the processing laser beam, optical measurement beam, and / or optical sensor in at least two dimensions, i.e., along one direction in a plane defined by a reference and along a second direction in the same plane, wherein the first direction is not parallel to the second direction, and in particular, perpendicular to the second direction. The deflection of the deflection device can be implemented perpendicular to the optical axis of the focusing device. The axis of the deflection device can have an angle equal to 90° or between 25° and 80°.

[0086] This invention discloses a laser processing head for processing workpieces using a processing laser beam. The laser processing head may include a first optical sensor, a deflection device, a focusing device, and a computing device. The deflection device and the focusing device may be located in the beam path of the first optical sensor. The deflection device may be configured to deflect the beam path of the first optical sensor to a first position on a first reference. The first optical sensor may be configured to receive measurement light from the first position on the first reference and generate a first optical measurement signal based on the measurement light.

[0087] The laser processing head or computing device (also known as a controller) can be configured to execute each of the methods disclosed herein.

[0088] Furthermore, a laser processing system is also disclosed. The laser processing system includes a laser processing head for processing a workpiece by means of a processing laser beam and a computing device. The laser processing head may include a first optical sensor, a deflection device, and a focusing device. The deflection device and the focusing device may be located in the beam path of the first optical sensor. The deflection device may be configured to deflect the beam path of the first optical sensor to a first position on a first reference. The first optical sensor may be configured to receive measurement light from the first position on the first reference and generate a first optical measurement signal based on the measurement light. The computing device may be configured to determine a correction value for calibrating the first optical sensor based on the first optical measurement signal and according to a deviation between the first position on the first reference and a first nominal position, which may be predetermined relative to a (theoretical or virtual) position of the processing laser beam. The computing device may also be referred to as a controller and may be disposed on or in connection with the laser processing head or disposed separately from the laser processing head.

[0089] A laser processing system may include a laser source for generating a processing laser beam. Alternatively, the laser processing system may be configured to direct the processing laser beam from the laser source into a laser processing head, particularly via a fiber optic coupler.

[0090] The laser processing system or computing device (also known as a controller) can be configured to execute each of the methods disclosed herein.

[0091] According to this disclosure, one or more optical sensors of the laser processing head can be calibrated such that the optical sensors are oriented at a desired nominal position relative to the processing position, independent of the adjusted xy position in the scanning area or the adjusted deflection device. This ensures that measurement and processing are performed in the corresponding desired orientation and are not undesirably laterally misaligned. Attached Figure Description

[0092] This disclosure is described in detail below with reference to the accompanying drawings.

[0093] Figure 1A laser processing system 1000 with a laser processing head 800 is shown;

[0094] Figure 2 The different beam paths of the laser processing system 1000 are shown;

[0095] Figure 3 Reference R1 is shown;

[0096] Figure 4 The reference R2 is shown;

[0097] Figures 5a to 5c The axial alignment of the laser processing head 800 is schematically shown;

[0098] Figure 6a and 6b The diagram illustrates the identification of the tilt posture of the laser processing head 800;

[0099] Figure 7 Reference R3 is shown;

[0100] Figure 8 This shows an enlarged portion of the reference R3;

[0101] Figure 9 The measurements of the optical sensor are shown; and

[0102] Figure 10 The reference R4 is shown. Detailed Implementation

[0103] Figure 1 A laser processing system 1000 with a laser processing head 800 is schematically shown. The laser processing system 1000 may include a laser source and / or a computing device 700. The laser processing head 800 may include a first optical sensor 200, a second optical sensor 300, and a third optical sensor 400. Figure 1 The laser processing system 1000 is shown only for illustrative purposes. A laser processing head 800 having at least one optical sensor, such as a first optical sensor 200, a second optical sensor 300 and / or a third optical sensor 400, is also disclosed independently.

[0104] In addition, the laser processing head 800 includes a deflection device 500 and a focusing device 600.

[0105] A laser source can generate a processing laser beam L. The laser source can be configured as a single-mode laser, a solid-state laser, or a fiber laser.

[0106] The processing laser beam L generated by the laser source can be transmitted from the laser source to the laser processing head 800 via an optical fiber. The processing laser beam L can be coupled into the laser processing head 800 via an optical fiber coupler 100. For example, the processing laser beam L can be coupled into the laser processing head 800 via a beam splitter 105.

[0107] The laser processing head 800 may include a collimating optics device or a collimating optical device (not shown). The collimating optics device may be arranged and configured in the laser processing head 800 such that the processing laser beam L, which diverges into the laser processing head 800, is collimated. The collimating optics device may include at least one lens or two or more lenses. The spacing between the two or more lenses is adjustable, particularly by means of a motor, such as an electric motor.

[0108] In addition, the laser processing head 800 includes a laser beam L for deflecting the processing laser beam, and measuring beams 210 and 410 (see...). Figure 2 The deflection device 500 may include a first movable mirror 510, which is rotatable about a first rotation axis. Furthermore, the deflection device 500 may include a second movable mirror 520, which is rotatable about a second rotation axis. The first and second rotation axes may be angularly positioned relative to each other. This angle may be between 45° and 135°, particularly approximately 75° or approximately 90°. The first and / or second movable mirrors 510, 520 may be configured as a galvanometer-scanner, or simply a Galvo-scanner. The deflection device may be configured as a galvanometer- or Galvo-scanner.

[0109] The laser processing head 800 includes a focusing device 600 for focusing a processing laser beam L, measuring lights 210, 410, and / or a measuring beam. The focusing device 600 may include at least one lens or two or more lenses. The spacing between the two or more lenses is adjustable, particularly by means of a motor, such as an electric motor. The focusing optics may be specifically configured to focus the processing laser beam L, measuring lights 210, 410, and / or the measuring beam onto a workpiece or reference R, particularly on the surface of the workpiece or reference R. The focusing optics may include a plan-field focusing objective 610 or be configured such a plan-field focusing objective. The plan-field focusing objective may be telecentrically configured. The focusing device 600 has an optical axis. To adjust or change the focusing position, the position of at least one element or lens or the spacing between two elements or lenses of the focusing device or collimating optics may be changed.

[0110] The processing laser beam L can exit from the laser processing head 800 and be incident on the workpiece for processing. The processing can be laser welding, laser cutting, laser engraving, or laser hardening.

[0111] The deflection device 500 can offset or deflect the processing laser beam L in the scanning area. It can also deflect the measurement lights 210, 410, and / or the measurement beam in the scanning area. The deflection can be achieved along a first direction perpendicular to the optical axis of the focusing device 600. Furthermore, the deflection can be achieved along a second direction perpendicular to the optical axis of the focusing device 600. The first and second directions may not be parallel, but rather perpendicular to each other. The first direction may be the x-axis. The second direction may be the y-axis. The deflection device 500 can be configured as a large-area scanner. For example, the maximum deflection angle along the first and / or second directions can be at least 10°.

[0112] The deflection device 500 can be configured to deflect the processing laser beam L, the measurement beams 210, 410, and / or the measurement beam along the x-axis (first direction) by a first deflection angle, and to deflect the processing laser beam L, the measurement beams 210, 410, and / or the measurement beam along the y-axis by a second deflection angle. The deflection device 500 can have a zero orientation about the x-axis and about the y-axis, for which the processing laser beam L, the measurement beams 210, 410, and / or the measurement beam occupy a zero position.

[0113] The zero position corresponds to the undeflected orientation of the processing laser beam L, measuring beams 210, 410, and / or the measuring beam, i.e., the (general) zero orientation. In the undeflected orientation, the processing laser beam L, measuring beams 210, 410, and / or the measuring beam can extend coaxially between the laser processing head 800 and the workpiece or reference R, and with the optical axis of the laser processing head 800 and / or the focusing device 600. In the zero position, the processing laser beam L, measuring beams 210, 410, and / or the measuring beam can have the shortest path or distance between the focusing device 600 and the workpiece or reference R.

[0114] The laser processing head 800 includes at least one optical sensor for monitoring the laser processing process. To monitor the laser processing process, the at least one optical sensor can be oriented at a position on the workpiece to be processed relative to the processing laser beam L, so as to receive measurement light 210, 410 from that position. The optical sensor can be configured to be oriented at the position on the workpiece to be processed relative to the processing laser beam L or at a predetermined distance from the position of the processing laser beam L.

[0115] In particular, the laser processing head 800 includes a first optical sensor 200. The first optical sensor 200 may include an image sensor, particularly a camera. The laser processing head 800 may include a second optical sensor 300. The second optical sensor 300 may include a spectrometer, a spectrometer, and / or a photodiode sensor having one or more photodiodes. The laser processing head 800 may include a third optical sensor 400. The third optical sensor 400 may include a device for measuring optical spacing, a conical device, particularly an optical interferometer, particularly an optical coherence tomography scanner.

[0116] Each of the optical sensors 200, 300, and 400 can receive measuring light 210 or 410 from the workpiece to be processed in order to monitor the laser processing process. Here, the measuring light 210 or 410 for the respective sensors 200, 300, and 400 can pass through a focusing device 600 and a deflection device 500. At the zero position, that is, if the beam path of the processing laser beam L and the beam paths of the respective optical sensors 200, 300, and 400 are not deflected, then the respective optical sensors 200, 300, and 400 are oriented towards a predetermined position relative to the processing laser beam L. For example, the beam path of the processing laser beam L and the beam paths of the respective optical sensors 200, 300, and 400 can be oriented towards the same position, that is, the same or overlapping.

[0117] At least two of the first, second, and third optical sensors 200, 300, and 400 may be sensitive to different wavelengths or different wavelength ranges.

[0118] exist Figure 2 The middle shows Figure 1 The laser processing system 1000 has a processing laser beam L that has been deflected. If the processing laser beam L has been deflected, then the processing laser beam L can have an angle (greater than 0) with the optical axis of the focusing device 600.

[0119] For example in Figure 2 The diagram schematically illustrates the beam path of the processing laser beam L, the beam path of the measuring light 210 for the first optical sensor 200, and the beam path of the measuring light 410 for the third optical sensor 400. By deflecting the processing laser beam L (via the deflection device 500), the processing laser beam L and the beam paths of the optical sensors 200, 300, and 400 are oriented towards a position different from the zero position.

[0120] The measuring lights 210 and 410 and the processing laser beam L are initially extended coaxially. However, due to different refractions of their different wavelengths in the focusing device 600, different angles are generated with respect to the surface, resulting in different points of arrival, i.e., different measuring positions. The different wavelengths of the measuring lights 210 and 410 and the processing laser beam L, when deflected by the focusing device 600, cause deviations on the workpiece to be processed or the reference R. This deviation can be caused by chromatic aberration. Due to this deviation, monitoring of the laser processing process can become inaccurate because the optical sensors 200, 300, and 400 receive the measuring lights 210 and 410 from positions different from the desired positions.

[0121] The measurement light 210 for the first optical sensor 200 can pass through the focusing device 600 and the deflection device 500. The measurement light 210 can be coupled into the first optical sensor 200 through the beam splitter 205. The measurement light for the second optical sensor 300 (in...) Figure 2 (Not shown) The light (not shown) can pass through the focusing device 600 and the deflection device 500. The measurement light can be coupled into the second optical sensor 300 through the beam splitter 305. The measurement light 410 for the third optical sensor 400 can pass through the focusing device 600 and the deflection device 500. The measurement light 410 can be coupled into the third optical sensor 400 through the beam splitter 405.

[0122] To improve the accuracy of process monitoring or to follow the desired measurement position, according to the present invention, at least one optical sensor of the laser processing head is calibrated using a reference R.

[0123] Figure 3 A reference R1 is shown, which can be used to calibrate an optical sensor, such as a third optical sensor 400, or a device for measuring optical spacing. The planar extension of the reference can define the xy plane. The Z direction can be oriented perpendicular to the xy plane.

[0124] Reference R1 can be a calibration plate. Reference R1 can have at least one reference mark R11. Reference mark R11 can be a recess, particularly a recess in the surface of reference R1. Reference mark R11 can be (completely) circular. Preferably, reference R1 has multiple reference marks R11.

[0125] In one embodiment, the datum R1 may have at least two, particularly at least three or five datum marks R11. Each datum mark R11 may be circular. Preferably, the datum marks R11 are arranged concentrically. A datum mark R11 may be a recess in the surface of the datum R1. The recess may be pointed, i.e., the transition from the surface of the datum R1 to the recess may be pointed or discontinuous. The datum marks R11 may be evenly spaced from each other, particularly evenly spaced from each other. The datum marks R11 may have the same size.

[0126] The size of one or more datum markers R11 can be known. The interval between datum markers R11 can be known.

[0127] exist Figure 4 Alternative embodiments of the reference R2 are shown. The reference R2 may be a calibration plate. The reference R2 may have at least one reference mark R21. The reference mark R21 may be a recess, particularly a recess in the surface of the reference R2. The reference mark R21 may be linear, particularly a straight line. Preferably, the reference R2 has multiple reference marks R21.

[0128] A datum R2 may have multiple datum markers R21, which are arranged radially from the center or in a straight line outwards. A datum R2 may have multiple rows of datum markers R21, where each row has multiple datum markers R21 arranged radially outwards from the center. Datum markers may not exist between rows of datum markers R21.

[0129] The position and / or size of the reference marks R11 and R21 can usually be predetermined.

[0130] For example, lateral calibration of the third optical sensor 400, such as an optical coherence tomography (OCT) scanner, can be achieved using references R1 or R2, which are designed as calibration plates with recesses. For calibration, references R1 and R2 can be positioned relative to the laser processing head 800 (see...). Figure 1 and 2 Furthermore, for calibration, the optical measurement beam can be incident on references R1 and R2. The optical measurement beam can be based on the third optical sensor 400, passing through the deflection device 500 and the focusing device 600 to reach the references R1 and R2.

[0131] Specifically, references R1 and R2 can be positioned or oriented relative to the laser processing head 800 such that a predetermined zero position on references R1 and R2 corresponds to the zero position of the optical measurement beam. The zero position on references R1 and R2 can be the center of references R1 and R2. Reference marks R11 and R21 can be provided at the zero position on references R1 and R2. If the optical measurement beam is not deflected, that is, for example, coaxial or parallel to the optical axis of the focusing device 600, then the zero position of the optical measurement beam can exist.

[0132] The surfaces of references R1 and R2 can be scanned or moved over by an optical measurement beam. In the case of scanning, the optical measurement beam can pass through at least one, preferably multiple, reference marks R11 and R21. Scanning can be achieved by deflecting the optical measurement beam by a deflection device 500.

[0133] The measuring beam can scan the surfaces of references R1 and R2 along at least one direction, preferably along two mutually orthogonal directions, such as the x and y directions. To verify or improve accuracy, additional scanning with angular time can also be performed. Depth can be measured during the scan, and the current x and y positions can be detected simultaneously. The measuring light, which is a reflected portion of the optical measuring beam, can be received by a third optical sensor 400. An optical measuring signal can be generated based on the received measuring light. Based on the optical measuring signal, the deviation between the position on references R1 and R2 and the nominal position can be determined. A correction value can be determined based on the deviation. Because the lateral deviation is zero due to chromatic aberration at x=0 and y=0, but increases with increasing deflection, this method allows for the determination and correction of deviations for multiple measurement positions. Multiple correction values ​​for different deflection positions or measurement positions can be determined and stored. The corresponding correction values ​​can be assigned to the corresponding deflection positions. The deflection position can be the attitude or position of the deflection device. Furthermore, the deflection position can also be a position in a coordinate system, such as in a coordinate system defined by references R1 and R2. The correction function can be obtained or a table can be consulted based on one or more correction values.

[0134] For example, references R1 and R2 can have two reference marks R11 and R21. The interval between reference marks R11 and R21 on the surfaces of references R1 and R2 can be known. When scanning the surfaces of references R1 and R2, the interval between reference marks R11 and R21 can be determined as the measurement interval value. The known (true) interval value is comparable to the measurement interval value. Based on the difference (deviation) between the values, a correction value for that measurement position can be obtained. The correction value is storable. For example, a lookup table or correction function f(x,y) can be created based on the correction values ​​for different measurement positions so that the measurement position can be corrected accordingly in future measurements, such as in monitoring the laser processing process, or the measurement signal can be configured to the corresponding actual measurement position. This can improve the accuracy of monitoring the laser processing process. In particular, the chromatic aberration caused by the focusing device can be adjusted by the correction value.

[0135] After calibration, a method for process monitoring of the laser processing can be implemented using optical sensors. This process monitoring method can be implemented before the laser processing process (pre-process) to, for example, detect the workpiece geometry or determine the processing position for the laser processing. It can also be implemented after the laser processing process (post-process) to, for example, measure the processing result, such as a weld. In this process monitoring method, the beam path of the measurement beam from the optical sensor or optical coherence tomography scanner can be directed towards a predetermined monitoring position via a deflection device to generate a measurement signal for that position. Here, the drive signal of the deflection device used to deflect the beam path of the optical sensor or the measurement position to the predetermined monitoring position can be adjusted based on a determined correction value. If the third sensor 400, such as an optical coherence tomography scanner, is used, for example, to measure the distance to the workpiece surface before the original laser processing process, particularly when the processing laser beam is turned off, then lateral deviations between the measurement position and the nominal position, such as the position in subsequent laser processing, can be reduced or even avoided. Therefore, even so, the positions of specific features such as ridges, recesses, steps, etc., can be accurately determined for subsequent laser processing.

[0136] Figures 5a to 5c The axial calibration of an optical sensor, such as a third optical sensor 400, is schematically shown here. Figure 5a A laser processing head 800 as disclosed herein is shown.

[0137] The reference datum R can be a calibration plate with a flat or planar surface. The reference datum R can be oriented parallel to the machining system and located at the working interval or focus position. The reference datum R may not have reference markings.

[0138] The measurement beam of the optical sensor 400 is incident on the reference R at the zero position, that is, without deflection or with x=0 and y=0. In the zero position, the measurement beam is not deflected by the deflection device 500, that is, the beam path of the measurement beam is coaxial or parallel to the optical axis of the focusing device 600 and is emitted from the laser processing head 800 from the focusing device 600 toward the reference R.

[0139] At the zero position, the shortest distance from the reference R can be determined by the optical sensor 400. This distance should correspond to the working interval and is defined as z = 0. Figure 5b In this context, the interval is represented by z at the zero position x0. real .

[0140] If the measurement beam of the optical sensor 400 is deflected by the deflection device 500, i.e., x and / or y are not equal to zero, then the measured interval between the reference R and the laser processing head 800 increases with the increase of the deflection. The deflection can be achieved along a certain direction, for example, along the x-direction. The measured interval can be referred to as z. mess (see Figure 5b ).

[0141] The correction value can be determined based on the interval measured at the zero position and the interval measured at different deflection or measurement positions. For example, the difference between the interval at the zero position and the interval measured at each deflection or measurement position can be calculated. Based on this difference, a corresponding correction value can be generated. The corresponding correction value can then be assigned to the corresponding deflection or measurement position.

[0142] In future measurements, the corresponding correction values ​​can be applied to the measurement results to correct them. This also allows for accurate spacing measurement based on increasing the optical displacement length by deflecting the beam path through the deflection device 500. For example, lookup tables or correction functions f(x,y) can be created based on correction values ​​for different measurement positions to adjust the measurement values ​​accordingly in future measurements, such as in monitoring the laser processing process.

[0143] exist Figure 5c The image shows the spacing measurement after axial correction. The corrected measurement spacing z mess The calibration remains constant along the x-direction for different deflection or measurement positions. Naturally, the same calibration can be performed along the y-direction. The axial calibration value can also be used in optical coherence tomography (OCT) scanners to adjust the measurement range accordingly using a dynamic reference arm.

[0144] The tilt of the laser processing head can also be identified within the axial calibration range of an optical coherence tomography (OCT) scanner. These values ​​can be used for manual or automatic orientation of the laser processing head perpendicular to the working plane or workpiece surface (e.g., in the case of a robotic arm). Figure 6a and 6b The diagram schematically illustrates the identification of the tilt posture of the laser processing head 800 relative to the reference R, which can be achieved in a manner similar to the axial calibration of the third optical sensor 400.

[0145] To identify tilt posture, the optical measurement beam of the third sensor 400 can be incident on the reference R at a zero position or zero posture. Furthermore, the measurement beam can be deflected along a certain direction, such as the x-direction, to different positions. At each of these different positions, the interval (measurement) between the laser processing head 800 and the reference R can be performed. These different positions can exist based on both a zero position or zero posture in the positive and negative directions. Based on the measured interval values, it can be determined whether a tilt posture of the laser processing head 800 relative to the reference R exists.

[0146] Specifically, it can identify whether the minimum value of the distance measurement is obtained at the zero position or zero attitude. If so, that is, if a smaller value of the distance measurement is obtained at the deflection position compared to the zero position, then it can be identified that a tilt attitude exists.

[0147] Here you can check whether the spacing measurement value is substantially equal (±5% or ±1%) to the spacing measurement value when deflecting in the positive direction and when deflecting in the negative direction. The deflection values ​​in the positive and negative directions can be the same. If the spacing measurements are different, then the tilt attitude can be identified.

[0148] A signal or message may be generated, requesting the user to eliminate the tilt posture of the laser processing head 800. Alternatively, the laser processing head 800 may be (automatically) positioned so that the tilt posture is absent, i.e., the tilt posture is corrected.

[0149] Figure 7 The reference R3 is shown, which can be used in particular to calibrate the first optical sensor 200, such as an image sensor or a camera; and Figure 8 This shows an enlarged view of the reference R3.

[0150] In the case of image sensors or cameras, where the image sensor or camera is coaxially incident on the beam path of the processing laser, lateral deviation does not initially have such a significant effect because the sensor signal typically detects a larger area (image region). However, if the image is used to determine the processing location of a feature to be identified, for example through automated image recognition or feature recognition, then lateral deviation has a greater impact. If lateral deviation is not calibrated, then although the feature can be identified, processing occurs at a different location. This can be particularly problematic with small components or small features to be welded. As an example, the contact of a battery, where the positive and negative electrodes are very close together, can lead to a short circuit and potentially cause the battery cell to explode. For this reason, it is necessary to calibrate the image sensor or camera as accurately as possible, both laterally and / or during rotation.

[0151] exist Figure 7 and 8 The reference R3 shown may be a calibration plate. Reference R3 may have at least one first reference mark R31. Reference R3 may have at least one second reference mark R32. The first reference mark R31 and the second reference mark R32 may be different or distinguishable reference marks. Preferably, reference R3 has at least two first reference marks R31 and at least two second reference marks R32. The reference marks of reference R3 may include optical features, such as colored marks, particularly black marks on a bright background.

[0152] The first reference mark R31 can be a circle, triangle, quadrilateral, particularly a rectangle, square, or n-sided polygon. The first reference mark R31 can be a geometric figure. Reference R3 can have at least five, preferably at least ten, and more preferably at least twenty first reference marks R31. The first reference marks R31 can be uniformly distributed on reference R3. Preferably, the first reference marks R31 are distributed on reference R3 in a (uniform) grid.

[0153] The second datum mark R32 can be a line, specifically a straight line. At least two second datum marks R32 can each be a line. The lines can intersect. Figure 7 and 8 The reference R3 shown includes lines set in the grid and circles set at the intersections or points of the grid. The lateral position can be more accurately identified using the lines as a second reference marker R32. Additionally, the rotation of the first optical sensor 200, i.e., the rotation of its coordinate system about the coordinate system or axis of the deflection device 500, can be identified. Besides calibration along the x and y directions, reference 3 can therefore also be used for the orientation of the optical sensor's rotation. This is particularly important for deflection devices 500 that have Galvo mirrors not set at right angles.

[0154] One or more first reference markers R31 and one or more second reference markers R32 may at least partially overlap. For example, at least one second reference marker R32 may overlap one or more first reference markers R31. A first reference marker R31 may be formed by the overlap of at least two second reference markers R32. In particular, a first reference marker R31 may be located at the intersection of at least two second reference markers R32. The position or spacing of the first reference marker R31 and / or the second reference markers R32 on reference R3 is predetermined.

[0155] For calibration, reference R3 can be positioned relative to the laser processing head 800 (see...). Figure 1 and 2 Next, the first optical sensor 200 can record an image of the reference R3. The reference marks R31 and R32 can be identified by means of image processing, for example, by the first optical sensor itself or by a computing device.

[0156] The reference R3 can be positioned or oriented relative to the laser processing head 800 such that a predetermined zero position on the reference R3 corresponds to the zero position of the beam path of the first optical sensor 200. The zero position on the reference R3 can be the center of the reference R3. At least one reference mark R31, R32 can be provided at the zero position on the reference R3. Two reference marks R31, R32, and particularly two second reference marks R32, can intersect at the zero position. The zero position of the beam path can exist if the beam path is undeflected, i.e., coaxial with or parallel to the optical axis of the focusing device 600.

[0157] The beam path of the first optical sensor 200 can be deflected in the next step by a discontinuous segment, wherein the processing laser beam must be deflected towards reference marks R31 and R32. This discontinuous segment can be at least 1 mm, preferably at least 5 mm. Due to chromatic aberration, the deflection segment for the wavelength of the processing laser beam does not correspond to the observation wavelength for the first optical sensor. The road section. However, the difference is very small, so even so, the reference marks R31, R32 on reference 3 are included in the image area of ​​the first optical sensor 200 and can be automatically (e.g., by image processing) identified.

[0158] Next, the image is recorded by the first optical sensor 200, and reference marks R31 and R32 are detected. The interval or lateral deviation between the deflected beam path and the positions of reference marks R31 and R32 can be determined based on the measurement position or deflection position. A correction value can be determined based on the interval. The correction value can be stored for the corresponding deflection position or measurement position, for example, in a lookup table. Alternatively, a correction function f(x,y) can be obtained. In future measurements, such as in monitoring the laser processing process, the correction value can be used for the measured value to correct the measurement position accordingly or to assign the image point (i.e., its position in the image) to the corresponding actual position.

[0159] The reference marks R31, R32, and especially the first reference mark R31, may each have an indicator. Based on the indicator, the position of the corresponding reference mark R31, R32 relative to the zero position can be derived or determined.

[0160] The size and / or spacing of the reference marks R31 and R32 can be known. The optical sensor can be a camera. The pixel size of the camera image can be determined by the size or spacing of the reference marks R31 and R32. For example, it can be... Figure 7 In the example, calibration between the pixel size and the true size is achieved by the known circle diameter of the first reference mark R31 or the known spacing of the lines of the second reference mark R32, thereby allowing the spacing to be determined from the image. Furthermore, refocusing of the first optical sensor 200 can be performed after a discontinuous segment of the beam path deflection or before image recording to calibrate the first optical sensor 200.

[0161] Furthermore, the orientation of the optical sensor can be matched with the orientation of the deflection device 500, meaning the rotational position of the first optical sensor is oriented, particularly with respect to the orientation of the deflection device 500. Therefore, the x or y axis in the image can correspond to the x or y axis of the deflection device 500.

[0162] After calibration, a process monitoring method for the laser processing can be implemented using the first optical sensor 200. This process monitoring method can be implemented before (pre-process), during (process), or after the laser processing process to, for example, detect workpiece geometry, determine the processing position for the laser processing, or measure processing results such as weld seams. In the process monitoring method, the beam path of the first optical sensor 200 can be directed towards a predetermined monitoring position via a deflection device to generate a measurement signal for that position. Here, the drive signal of the deflection device 500 used to deflect the beam path or measurement position of the optical sensor to the predetermined monitoring position can be adjusted based on a determined correction value. Alternatively, the monitoring signal, i.e., the feature position determined from the image in the case of an image sensor, can be adjusted based on a determined correction value. If the first sensor 200, such as a camera, is used to determine the processing position on the workpiece surface before the original laser processing, particularly when the processing laser beam is turned off, then lateral deviations between the position determined in the image and the actual position, such as the nominal position for subsequent laser processing, can be reduced or even avoided. Therefore, even so, it is possible to accurately determine the actual location of specific features such as ridges, depressions, and steps in subsequent laser processing.

[0163] Figure 9 The measurement is shown using an optical sensor, particularly a second optical sensor 300, such as a photodiode sensor having one or more photodiodes. Figure 10 Reference R4 is shown, which can be used for the calibration of the second optical sensor 300.

[0164] The second optical sensor 300 may include three photodiodes. Each of the photodiodes may be sensitive to different wavelength ranges λ1, λ2, and λ3. For example, the first photodiode may be sensitive to the visible wavelength range λ1. The second photodiode may be sensitive to the infrared wavelength range λ2. The third photodiode may be sensitive to the wavelength range λ3 of the processing laser beam L.

[0165] The different spectral sensitivities of photodiodes generate different measurement positions for each photodiode due to color differences.

[0166] If an additional "series-connected" deflection device is provided for each photodiode, then lateral deviations caused by chromatic aberration can be compensated for during photodiode-based process monitoring during laser processing. However, the additional deflection device requires structural space, incurring additional costs, and is technically demanding in terms of control (synchronization of the two deflection devices). However, if lateral chromatic aberration is not corrected, then different intensities of the measurement light may be detected, resulting in different signal levels depending on the deflection or measurement position under nominally identical welding conditions (see...). Figure 9 Comparative measurements or process monitoring with previously recorded baseline values ​​are therefore no longer possible, or only have significantly reduced accuracy or false recognition rates.

[0167] To avoid this, calibration is proposed according to this disclosure using a reference R4. The reference R4 can be a test workpiece. The reference R4 can be planar and can have a flat or smooth surface.

[0168] For calibration, reference R4 can be positioned relative to the laser processing head 800 (see...). Figure 1 and 2 This allows the processing laser beam L to be directed at the reference R4, specifically the test workpiece, from a zero position, i.e., without deflection. The testing process can be performed from this zero position, and the emitted process emissions can be detected by the second optical sensor 300. Preferably, different photodiodes of the optical sensor detect process emissions in different wavelength ranges.

[0169] The first reference mark R41 can be formed on the reference R4 by testing the machining process.

[0170] The processing laser beam L is now deflected to a reference position, where another test processing procedure is performed. The emitted process emission is detected by a second optical sensor 300. Another reference mark 42 can be formed on the reference R4 through the other test processing procedure.

[0171] The deviation between the intensity of the process emission detected at the reference position and the intensity of the process emission detected at the zero position is determinable. A correction value can be determined based on this deviation. Preferably, such a correction value is determined for each of the photodiodes in the second optical sensor. The correction value can be a correction coefficient.

[0172] Preferably, at least three, more preferably at least five, and more preferably at least nine test processing steps are performed. Based on each test processing step, a correction value for the corresponding position can be determined. Because all test processing steps are performed nominally identically only at different reference positions, the same intensity should be measured for each photodiode at each position. Intensity or signal level may differ due to color difference.

[0173] exist Figure 9 The different intensities are indicated for different photodiodes. At reference positions 1 to 9, or for test processes 1 to 9, the upper curve corresponds to the measured intensity of the first photodiode; the middle curve corresponds to the measured intensity of the second photodiode; and the lower curve corresponds to the measured intensity of the third photodiode.

[0174] For example, at position 1 on reference R4—which can be understood as the zero position—the measured intensity for the first and second photodiodes is relatively high. The measured intensity for the third photodiode is relatively low at this position. At position 7, the measured intensity for the first photodiode is relatively high, the measured intensity for the second photodiode is relatively low, and the measured intensity for the third photodiode is between that of the first and second photodiodes.

[0175] At reference position 1, i.e., the zero position (x = 0, y = 0), the measured intensity or measurement signal for all photodiodes is considered ideal. At other reference positions (x and / or y not equal to zero), the measured intensity differs from the ideal intensity. This difference allows for the determination of a correction value or correction coefficient for each position relative to the corresponding reference position. The correction values ​​for different reference positions can be stored in a lookup table or used to determine the correction function. For measurement positions different from the zero position, a correction value corresponding to the reference position closest to the measurement position can be applied. Alternatively, interpolation of the correction values ​​from reference positions adjacent to the measurement position can be applied to determine the interpolated correction value for measurement positions different from the reference positions.

[0176] For future measurements at locations different from the zero position, the intensity or measurement signal of the corresponding photodiode can be adjusted based on the intensity or measurement signal at the zero position, particularly by a determined correction value. This adjustment can be implemented via hardware or software amplification. Alternatively, quality standards, such as reference curves or envelopes, can be adjusted based on the correction value.

[0177] After calibration, a method for process monitoring of the laser processing can be implemented using the second optical sensor 300. This method can be implemented during the laser processing process to describe the process, for example, based on the intensity of detected process emissions. In the process monitoring method, the beam path of the second optical sensor 300 can be aligned with a predetermined monitoring position via a deflection device 500 to generate a monitoring signal for that position. Before analyzing and processing the monitoring signal for process monitoring, the monitoring signal can be adjusted based on a determined correction value.

[0178] According to this disclosure, all optical sensors of the laser processing head can be calibrated such that these optical sensors detect comparable signals independently of their deflection position or position in the scanning area, or accurately measure along the x, y, and z directions in which laser processing subsequently occurs or has occurred prior to laser processing. This simplifies the complexity of the system because multiple coordinate systems no longer need to be considered.

Claims

1. A method for calibrating at least one optical sensor (200, 300, 400) of a laser processing head (800) for processing a workpiece by means of a processing laser beam (L), wherein the laser processing head (800) includes a first optical sensor (200, 300, 400), a deflection device (500), and a focusing device (600), and the beam path of the first optical sensor (200, 300, 400) passes through the deflection device (500) and the focusing device (600), the method comprising the steps of: - The beam path of the first optical sensor (200, 300, 400) is deflected to a first position on the first reference (R, R1, R2, R3, R4) by the deflection device (500); -A first optical measurement signal is generated based on measurement light (210, 410) received from a first position on a first reference (R, R1, R2, R3, R4) via a first optical sensor (200, 300, 400); and - Based on the first optical measurement signal and according to the deviation between the first position and the first rated position on the first reference (R, R1, R2, R3, R4), a correction value for calibrating the first optical sensor (200, 300, 400) is determined.

2. The method according to claim 1, wherein, The laser processing head (800) includes a second optical sensor (200, 300, 400), the beam path of which passes through a deflection device (500) and a focusing device (600). The method further includes the following steps: - The beam path of the second optical sensor (200, 300, 400) is deflected to a first position on the second reference (R, R1, R2, R3, R4) by the deflection device (500); -A second optical measurement signal is generated based on the measurement light (210, 410) received from a first position on a second reference (R, R1, R2, R3, R4) via a second optical sensor (200, 300, 400); and - Based on the second optical measurement signal and according to the deviation between the first position and the second rated position on the second reference (R, R1, R2, R3, R4), the calibration value for calibrating the second optical sensor (200, 300, 400) is determined.

3. The method according to claim 1, wherein, The laser processing head (800) includes a third optical sensor (200, 300, 400), the beam path of which passes through a deflection device (500) and a focusing device (600). The method further includes the following steps: - The beam path of the third optical sensor (200, 300, 400) is deflected to a first position on the third reference (R, R1, R2, R3, R4) by the deflection device (500); -A third optical measurement signal is generated based on the measurement light (210, 410) received from the first position on the third reference (R, R1, R2, R3, R4) by the third optical sensor (200, 300, 400); as well as - Based on the third optical measurement signal and according to the deviation between the first position and the second rated position on the third reference (R, R1, R2, R3, R4), the correction value for calibrating the third optical sensor (200, 300, 400) is determined.

4. The method according to any one of claims 1 to 3, wherein, The beam path of at least one optical sensor (200, 300, 400) is deflected by a deflection device (500) to multiple positions on corresponding references (R, R1, R2, R3, R4) to generate corresponding optical measurement signals; and / or The beam path of the at least one optical sensor (200, 300, 400) scans the surface of the corresponding reference (R, R1, R2, R3, R4) through the deflection device (500) in order to generate the corresponding optical measurement signal.

5. The method according to any one of claims 1 to 3, wherein, The beam path of the at least one optical sensor (200, 300, 400) is directed toward the corresponding reference (R, R1, R2, R3, R4) by a deflection device (500) parallel to or coaxial with the optical axis of the focusing device (600) so as to generate the corresponding optical measurement signal at the zero position.

6. The method according to any one of claims 1 to 3, wherein, The laser processing head (800) includes multiple different optical sensors (200, 300, 400), which are sensitive to different wavelength ranges.

7. The method according to any one of claims 1 to 3, wherein, The laser processing head (800) includes multiple different optical sensors (200, 300, 400), which are calibrated using their respective references (R, R1, R2, R3, R4).

8. The method according to any one of claims 1 to 3, wherein, The at least one optical sensor (200, 300, 400) includes a device for measuring optical spacing, a conical device, a time-of-flight measuring device, an optical interferometer, an optical coherence tomography scanner, an image sensor, a camera, a spectrometer, a spectrometer, and / or a photodiode sensor having one or more photodiodes.

9. The method according to claim 8, wherein, The at least one optical sensor (200, 300, 400) includes an optical interferometer or an optical coherence tomography scanner, and the reference (R1, R2) is a calibration plate having a plurality of recesses at a predetermined position.

10. The method of claim 9, further comprising: - Orient the calibration plate so that a predetermined zero position on the calibration plate corresponds to the zero position of the optical measurement beam of the optical sensor (200, 300, 400); - An optical measurement beam scans the surface of the calibration plate through a deflection device (500) and generates a corresponding measurement signal; - Determine the position of the recess on the calibration plate based on the measurement signal; and - Determine the correction value based on the deviation between the obtained position of the concave part and the predetermined reference position.

11. The method according to claim 8, wherein, The at least one optical sensor (200, 300, 400) includes a spectrometer, a spectrometer and / or a photodiode sensor having one or more photodiodes for detecting process emission; and the reference (R4) is a test workpiece on which the processing laser beam (L) is deflected at at least one predetermined reference position by means of a deflection device (500), and the test processing process is carried out by means of the processing laser beam.

12. The method of claim 9, further comprising: - Align the processing laser beam (L) with the zero position on the test workpiece; Implement testing and processing procedures; And the emission process is detected by optical sensors (200, 300, 400); - Deflect the processing laser beam (L) to a reference position; perform a test processing at the reference position; and detect the process emission emitted thereby using optical sensors (200, 300, 400); and - The correction value is determined based on the deviation between the intensity of the process emission detected at the reference position and the intensity of the process emission detected at the zero position.

13. The method according to any one of claims 9 to 12, wherein, The at least one optical sensor includes an image sensor or a camera; and the reference is a calibration plate having multiple optical features at a predetermined reference position.

14. The method of claim 13, further comprising: - Orient the calibration plate so that a predetermined zero position on the calibration plate corresponds to the zero position of the beam path of the optical sensor (200, 300, 400); - The beam path of the optical sensors (200, 300, 400) is deflected in the following discontinuous segment: the processing laser beam (L) must be deflected in this discontinuous segment in order to align with the optical features of the calibration plate; as well as - The correction value is determined based on the distance between the position of the deflected beam path and the optical feature.

15. The method according to any one of claims 1 to 3, wherein, The focusing device (600) includes a flat focusing objective (610) and / or is positioned in the laser processing head (800) behind the deflection device (500) with respect to the beam propagation direction of the processing laser beam.

16. The method according to any one of claims 1 to 3, wherein, The scanning area of ​​the deflection device (500) has a length and / or width of at least 50 mm; and / or The processing laser beam (L) can be deflected by at least 5° by the deflection device (500).

17. The method according to claim 16, wherein, The processing laser beam (L) can be deflected by at least 10° by the deflection device (500).

18. The method according to claim 16, wherein, The processing laser beam (L) can be deflected by the deflection device (500) at an angle between 5° and 20°.

19. The method according to claim 18, wherein, The processing laser beam (L) can be deflected by the deflection device (500) at an angle between 10° and 20°.

20. A method for process monitoring of a laser processing procedure, the method comprising the calibration method according to any one of claims 1 to 19 and the following steps: - The beam path of the first optical sensor (200, 300, 400) is deflected to a predetermined monitoring position by a deflection device (500); and - Receive measurement light from the monitoring location via the first optical sensor (200, 300, 400) and generate a monitoring signal based on the measurement light received from the monitoring location for process monitoring; The drive signal of the deflection device (500) used to deflect the beam path of the first optical sensor (200, 300, 400) to the monitoring position is adjusted based on the determined correction value, or the monitoring signal used for process monitoring is adjusted based on the determined correction value.

21. A laser processing system (1000) comprising a laser processing head (800) for processing a workpiece by means of a processing laser beam (L) and a computing device (700), wherein, - The laser processing head (800) includes a first optical sensor (200, 300, 400), a deflection device (500), and a focusing device (600); - The deflection device (500) and the focusing device (600) are located in the beam path of the first optical sensor (200, 300, 400); - The deflection device (500) is configured to deflect the beam path of the first optical sensor (200, 300, 400) to a first position on the first reference (R, R1, R2, R3, R4); - A first optical sensor (200, 300, 400) is configured to receive measurement light (210, 410) at a first position on a first reference (R, R1, R2, R3, R4) and generate a first optical measurement signal based on the measurement light; and - The computing device (700) is configured to determine a calibration value for calibrating the first optical sensor (200, 300, 400) based on the first optical measurement signal and according to the deviation between the first position and the first rated position on the first reference (R, R1, R2, R3, R4).

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