Laser-based device and method for determining the focus position and / or for contrast determination

Abstract

The present invention relates to a laser-based device (10) and to a method for determining the focus position of a process laser beam (22) in relation to a workpiece surface (100) and / or for contrast determination on a workpiece surface (100), optionally comprising or cooperating with a device (11) for providing the process laser beam (22), and optionally one or more optical devices (12, 13, 14) for shaping and / or deflecting the process laser beam (22). In order to determine the focus position of a process laser beam (22) in a simple and reliable manner, the device (10) comprises the following: a determination device (10a) which is configured as a device for determining the focus position of the process laser beam (22) in relation to the workpiece surface (100) and / or for determining the contrast on the workpiece surface (100). The determination device (10a) comprises a device (20) for providing a measuring laser beam (23) which is aligned in the beam direction in front of the focusing device (15) parallel to an optical axis (26) of the device (10a) and which is provided in an optical offset position (30 ) relative to the optical axis (29), a focusing device (15) for focusing the measuring laser beam (23) onto the workpiece surface (100) and a detector device (19) which is designed to receive the measuring laser beam (24) reflected back from the workpiece surface (100) and to generate a measuring signal (26) related to the focus position and / or the contrast.

Description

[0001] Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0002] Date: August 06, 2025

[0003] 1

[0004] Description

[0005] Laser-based device for determining the focus position and / or for contrast determination

[0006] The present invention initially relates to a laser-based device for determining the focus position of a process laser beam in relation to a workpiece surface and / or for contrast determination on a workpiece surface in accordance with the preamble of claim 1. Furthermore, the invention relates to a method for laser-based determination of the focus position of a process laser beam in relation to a workpiece surface and / or for contrast determination on a workpiece surface.

[0007] Laser-based devices and methods are characterized by the fact that they use laser beams for their operation. Such devices and methods are widely used in the prior art.

[0008] It is known, for example, that in a device for providing a process laser beam, a process laser beam is generated which is then used for machining a workpiece, for example a workpiece surface. The process laser beam is generated by means of a laser source and is then usually shaped and / or directed in one or more optical devices. The process laser beam is usually focused on the workpiece by means of a focusing device.

[0009] The workpiece can be processed in a wide variety of ways. For example, the process laser beam can be used to remove contamination or a coating from a workpiece surface, or the workpiece surface can be cleaned, or the workpiece can be analyzed, or the workpiece can be pretreated, it can be welded with laser radiation, and the like. The examples mentioned are purely illustrative and demonstrate the wide range of applications for laser-based processing.

[0010] Over time, it has become apparent that it is advantageous to provide additional light beams in addition to the actual process laser beam, which are incorporated into the machining process and generate and provide additional information about the machining process. Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0011] Date: August 06, 2025

[0012] 2

[0013] One example of this is color detection, which is performed during the decoating of workpieces. An example of this is described in EP 1 919651 B1. In this known solution, according to one partial aspect, a process laser beam is generated in the manner described above and is directed and focused onto the surface of the workpiece. This removes the coating from the surface. In addition, in a further partial aspect, an illumination light beam is provided and directed onto the processed area. The illumination light beam is reflected from the surface and is fed to a detector device. The measurement signal is evaluated and a conclusion is drawn about the color of the processed area. Based on the measurement results, a decision is then made as to whether the area needs to be reworked or whether the process can move on to another area.

[0014] In particular, it is important in such laser-based processes, that the surface of the workpiece to be processed lies in the focus of the process laser beam. Only in this case the laser-based process can deliver the desired results.

[0015] DE 10 2015 015651 B3 discloses a monitoring device for use in a laser-based machining process. According to this solution, an effective protection of the machining system against damage is ensured. To this end the actual path of the machining beam, at least between a processing beam optics and an impact area, is directly tracked by a coaxially parallel measuring beam. It is the purpose of this teaching to continuously monitoring the distance between the processing beam optics and the impact area. To make this possible, an essential feature of this known solution is that the measuring beam gets coupled into the processing beam and gets directed together with it toward the impact area.

[0016] JP2005088072A describes a laser processing device in which the focus position of a laser beam for the processing operation is controlled. Two laser devices are used for this purpose.

[0017] The present invention is based on the object of further developing a laser-based device and a laser-based method as described above in such a way that the focus position of a process laser beam and / or the contrast on a workpiece surface can be determined in a simple and reliable manner. Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0018] Date: August 06, 2025

[0019] 3

[0020] According to the invention, this object is solved by the device according to the independent claim 1 , which represents the first aspect of the invention, and by the method according to the independent claim 18, which represents the second aspect of the invention.

[0021] Further features and details of the invention become apparent from the dependent claims, from the description, and from the drawings. Features and details which are described in connection with one of the aspects of the invention are, of course, also fully applicable in connection with the other aspects of the invention, and vice versa. In particular, individual features of the method according to the invention are also described in connection with the device according to the invention, and vice versa, so that with regard to the disclosure of the individual categories, cross-reference is made between the individual aspects of the invention.

[0022] The present invention is based on the key idea that an optics is provided, which comprises a specific device that can perform several functions. According to one embodiment, the device is provided for determining the focus position of a process laser beam. According to another embodiment, the device is provided to make a statement about the contrast of the workpiece at the measuring point. The same components used to determine the focus position can also be used to measure the contrast at the measuring point, which can also be used for the machining process. According to one embodiment, the device is used either to determine the focus position or to determine the contrast. According to a preferred embodiment, the device is used both to measure the focus position and to measure the contrast. According to a preferred embodiment, the invention comprises a combined focus and contrast detection device.

[0023] According to the first aspect of the invention, a laser-based device is provided which comprises the features of independent claim 1.

[0024] In the following, the laser-based device for determining, for example measuring, the focus position of a process laser beam in relation to a workpiece surface and / or for contrast determination, for example for contrast measurement, on a workpiece surface is also referred to as the determination device. The determination device comprises the components described below. Applicant: Clean Lasersysteme GmbH

[0025] Our reference: P8029PC00

[0026] Date: August 06, 2025

[0027] 4

[0028] According to one embodiment, a device for providing a process laser beam is provided. However, this device is an optional feature not necessarily part of the determination device. According to one embodiment, the determination device comprises such device for providing a process laser beam. In this case, the device for providing a process laser beam is part of the determination device. According to a different embodiment, the determination device cooperates with the device for generating the process laser beam. This means that the determination device and the device for generating the process laser beam act or work together. In the latter case, the device for generating the process laser beam is not part of the determination device. However, in the intended use of the determination device, the determination device collaborates or interacts with the device for generating a process laser beam. In this case the device for generating the process laser beam can be part of a laserbased device for machining a workpiece surface. In particular, a process laser beam, and therefore, a device for generating a process laser beam is applicable, if the determination device is used for determining, for example measuring, the focus position of a process laser beam in relation to a workpiece surface. If the determination device is used for contrast determination, for example for contrast measurement, on a workpiece surface, a process laser beam, and therefore a device for generating a process laser beam is not necessary at all.

[0029] Such a device for providing the process laser beam comprises at least one laser source or is designed as a laser source, by means of which the laser beam is generated. According to one embodiment, the device is arranged for providing a high-energy process laser beam. The laser radiation generated is preferably pulsed laser radiation. According to one embodiment, the device is provided for supplying a laser beam with a first wavelength and power. The first wavelength is selected such that it is suitable for the intended processing procedure. In this respect, the invention is not limited to specific wavelengths. According to an exemplary embodiment, the wavelength may be 1064 nm. According to an embodiment, the generated laser light is transported from the laser source via a fiber conductor.

[0030] The process laser beam is focused on the workpiece surface by means of a focusing device.

[0031] The focus is located in particular in the optical axis. The optical axis is in particular an imaginary line of symmetry in the measuring device. Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0032] Date: August 06, 2025

[0033] 5

[0034] The device according to the invention comprises a determination device. This determination device is configured as a device for determining the focus position of a process laser beam in relation to the workpiece surface and / or for determining the contrast on the workpiece surface. Various embodiments of the determination device are explained in more detail in the following description.

[0035] One component of the determination device according to the invention is a device for providing a measuring laser beam. This device comprises at least one laser source or is designed as a laser source, by means of which the measuring laser beam is generated. According to one embodiment, the device is arranged to provide a laser beam with a second wavelength. The second wavelength is selected such that it is suitable for the intended measurement. In this respect, the invention is not limited to specific wavelengths. According to an exemplary embodiment, the wavelength may be 980 nm. The device may, for example, be a laser diode or comprise a laser diode.

[0036] According to one embodiment, the wavelengths of the first and second laser beams, i.e. , the process laser beams, if used, and the measuring laser beams, differ from each other. This means that the first and second wavelengths are different from each other. The wavelength of the measuring laser beam differs from the wavelength of the process laser beam in particular in such a way that the two beams can be optically combined and separated.

[0037] Depending on the properties of the workpiece surface, suitable process wavelengths and measuring wavelengths can be used for contrast detection and workpiece machining.

[0038] According to one embodiment, the measuring laser beam is used to determine the focus position of a process laser beam in relation to the workpiece surface. The focus position is the position of the focus at which the beams of the process laser beam intersect. Normally, the focus of the process laser beam is on the workpiece surface when the process laser beam is properly focused via the focusing device for performing a machining process.

[0039] According to a different embodiment, alternatively, or additionally, the measuring laser beam can be used to measure the contrast on the workpiece surface. The contrast is basically the difference in brightness between light and dark areas of the workpiece surface. In contrast to the solution known from the prior art, the measuring laser beam is not used in the present Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0040] Date: August 06, 2025

[0041] 6 invention to determine the color of the workpiece surface or to trace the processing path of a process laser beam.

[0042] According to one embodiment, the laser-based device is set up in such a way that the process laser beam, if used, and the measuring laser beam are provided alternately or one after the other.

[0043] According to the invention, the measuring laser beam is focused on the workpiece surface by means of a focusing device. The focus is located in particular in the optical axis. If the determination device comprises a device for generating a process laser beam or co-operates therewith, the focusing device for the measuring laser beam and the focusing device for the process laser beam can be provided as one single optical component.

[0044] The measuring laser beam is aligned in the beam direction in front of a focusing device parallel to an optical axis of the measuring device and, optionally parallel to a process laser beam. This means that the measuring laser beam runs parallel to the optical axis and, optionally parallel to the process laser beam.

[0045] In addition, the measuring laser beam is provided in an optical offset position relative to the optical axis. This offset is therefore present before the measuring laser beam enters the focusing device. This means in particular that the measuring laser beam runs offset, i.e. spaced apart, from the optical axis and, optionally from the process laser beam. The measuring laser beam and the process laser beam thus run spatially separated from each other. The measuring laser beam is thus located and runs in particular in a position outside the optical axis, which is also referred to as the "Off-Axis” position."

[0046] The measuring laser beam is also guided through the focusing device. According to the invention, it is thus achieved that the measuring laser beam lies or runs parallel to the optical axis and, optionally the process laser beam before it enters the focusing device. However, it is additionally positioned at a certain distance from the optical axis. This means that the measuring laser beam runs in a position that deviates from the position of the optical axis.

[0047] According to one embodiment, the measuring laser beam can be positioned or run above the optical axis. According to another embodiment, the measuring laser beam can be positioned Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0048] Date: August 06, 2025

[0049] 7 or run below the optical axis. The distance between the measuring laser beam and the optical axis can be a few millimeters. According to one embodiment, the distance is less than or equal to 10 mm, preferably less than or equal to 5 mm, and in a preferred embodiment exactly 5 mm. Depending on the application and dimensions of the focusing device and / or a second optical device, which is described below, the distance can also be increased in particular.

[0050] Furthermore, the device comprises a detector device that is set up to receive the measuring laser beam reflected backward from the workpiece surface and to generate a measuring signal related to the focus position and / or the contrast. The backward reflected measuring laser beam is imaged in particular in the detector device. How this can be done in detail is illustrated below at hand of an example of embodiment.

[0051] According to one embodiment the laser-based device comprises a control device. This control device can, for example, be part of the detector device. According to another embodiment, the laser-based device comprises a control device that is connected to the detector device via a signal connection line. In both cases, the control device is part of the laser-based device.

[0052] According to another embodiment, the laser-based device comprises an interface from the detector device to a control device. In this case, the control device can be a component external to the laser-based device that communicates with the laser-based device as required.

[0053] According to a further aspect of the invention a laser-based device for machining a workpiece surface is provided. This device will be referred to as "the machining device" in the following. The machining device initially comprises a device for providing a process laser beam. Furthermore, the machining device comprises a laser-based device according to the first aspect of the invention. To avoid repetition, reference is therefore made here to the disclosure of the first aspect of the invention in its entirety. This laser-based device is used to determine the focus position, for example by measurement, of the process laser beam on the surface of the workpiece to be processed and / or a contrast determination is performed on the workpiece surface. The resulting measurement signals are then used for the machining Applicant: Clean Lasersysteme GmbH

[0054] Our reference: P8029PC00

[0055] Date: August 06, 2025

[0056] 8 process of the workpieceis. Which is carried out in the machining device. In the case of such a machining device, the control device may also be part of the machining device.

[0057] The control device is, in particular, the entirety of all elements that influence the laser-based device. The control device can be designed in the form of hardware components or software components, or as a combination thereof. In particular, the control device comprises a processor device in which at least parts of the method according to the invention are carried out.

[0058] According to one embodiment, the control device also comprises a storage device for storing data, for example reference data, and / or an input device for entering information and commands, and / or a display device for displaying information, in particular a display. The control device is connected to the components of the device to be controlled via suitable signal connections. Examples of how the control device works are described below.

[0059] According to one embodiment, the focusing device is set up so that the measuring laser beam is deflected to the same point as the process laser beam. According to one embodiment, this point of the process laser beam, which ideally also represents the focal point, is located in the optical axis. According to one embodiment, the focusing device is designed in the form of a lens or in the form of a lens arrangement consisting of two or more lenses. While the beam path of the measuring laser beam and the process laser beam runs parallel in front of the focusing device, the beam path of the measuring laser beam in the beam direction behind the focusing device, i.e. between the focusing device and the workpiece surface, is tilted, in particular slightly, compared to the beam path of the process laser beam. After the measuring laser beam has passed through the focusing device, it is deflected to the same point as the process laser beam. If an object, in this case the workpiece surface, is located in the focal plane, the process laser beam and the measuring laser beam meet at the same point, the focal point, on the optical axis. If the object is located outside the focal plane, the point of impact of the measuring laser beam is not in the optical axis and therefore not at the point of the process laser beam.

[0060] If the wavelengths of the process laser beam and the measuring laser beam are close together, a focusing device optimized for the process laser beam can be used. If the two Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0061] Date: August 06, 2025

[0062] 9 wavelengths are far apart, the focusing device is preferably designed as an achromatic optics according to one embodiment.

[0063] According to one embodiment, the focusing device is provided for collecting the measuring laser beam reflected back from the workpiece surface. This means that the measuring laser beam reflected back from the workpiece surface is directed into the focusing device and passes through it again, this time in the opposite direction.

[0064] According to one embodiment, the focusing device is an autofocus device. In this case the measurement signal relating to the determination of the focus position is used to automatically adjust the focusing device.

[0065] According to one embodiment, the laser-based device comprises one or more optical devices for shaping and / or directing the process laser beam. The invention is not limited to specific types of optical devices. In the following, some embodiments are described, which are numbered for the purpose of differentiation. These can be implemented individually or in any combination in the device.

[0066] According to one embodiment, a first optical device is provided in the form of a collimating optics. A collimating optics is basically used to bring divergent beams into a parallel direction.

[0067] According to one embodiment, a second optical device is provided in the form of a beam combining device and / or a beam splitting device. This device can, for example, be designed or constructed in such a way that it is reflective for the process laser beam, and transparent for the measuring laser beam.

[0068] According to one embodiment, a third optical device in the form of a scanner device is provided. The scanner device serves in particular to deflect the process laser beam and / or the measuring laser beam in a desired manner. The scanner device can, for example, be designed in the form of a rotatable mirror or comprise such a mirror.

[0069] According to one embodiment, a fourth optical device in the form of a deflection device for the reflected measuring laser beam is connected upstream of the detector device in the beam direction of the reflected measuring laser beam. According to one embodiment, the Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0070] Date: August 06, 2025

[0071] 10 deflection device is positioned on the optical axis. The deflection device may be, for example, a deflection mirror. According to one embodiment, the deflection device is arranged between the device for providing the measuring laser beam and the focusing device in such a way that the deflection device does not obstruct the measuring laser beam passing in the offset position. The reflected measuring laser beam is collected, for example by the focusing device, and imaged into the detector device via the deflection device.

[0072] According to one embodiment, the detector device is configured to generate an electrical signal. The electrical signal is generated from the measuring laser beam reflected back from the workpiece surface. In this respect, invention is not limited to specific embodiments of the detector device.

[0073] According to one embodiment, the detector device comprises a photodiode device. In this case, the photodiode device is only part of the detector device. According to another embodiment, the detector device is designed as a photodiode device. The photodiode device converts light into electrical energy. When the light from the reflected measuring laser beam hits the photodiode device, charge carriers are generated which cause an electric current to flow through the photodiode device. The strength of the current depends directly on the intensity of the incident light. Such a photodiode device is therefore particularly suitable both for contrast determination and for focus determination.

[0074] According to one embodiment, the photodiode device is designed as a segmented photodiode device, for example as a photodiode device with two segments. The invention is not limited to a specific number of segments. This means that the photodiode device consists of several photodiodes, for example two photodiodes or four photodiodes, which are arranged in relation to each other, for example side by side (in the case of two photodiodes) or in a square (in the case of four photodiodes). The sensitive surfaces of the individual segments, each formed by a photodiode, are located close to each other so that, at maximum, there is only a narrow gap between them. The measuring laser beam is directed onto the photodiodes and the current of the photodiodes is compared. The ratio of the currents of the individual photodiodes allows a statement to be made about the area occupancy of each individual photodiode. This is illustrated by a few embodiments. Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0075] Date: August 06, 2025

[0076] 11

[0077] According to one embodiment, the detector device or the control device comprises an evaluation device which is provided for evaluating the measuring laser beam reflected back from the workpiece surface, in particular for evaluating a measurement signal generated from the measuring laser beam reflected back from the workpiece surfacemeasuring signal, for example an electrical signal.

[0078] According to one embodiment, the evaluation device is provided in such a way, that it is capable of comparing the electrical signals of the individual segments of the photodiode device with one another. This procedure is used in particular when the focus position is to be determined.

[0079] The reflected measuring laser beam hits the photodiode device. There, an electrical signal is generated based on the reflected measuring laser beam. If the photodiode device is designed as a two-segment photodiode device, it comprises an impact surface formed by a first segment and a second segment. The reflected measuring laser beam is imaged on the impact surface of the photodiode device in the form of an image. Depending on the position of the workpiece surface, the reflected measuring laser beam hits the impact surface at different points on the impact surface, for example on the segments.

[0080] Depending on the focus position of the workpiece surface, the image is thus located at different points on the segments of the photodiode device. In the photodiode device, an electrical signal is generated from the signal of the reflected measuring laser beam. A separate electrical signal is generated in each of the segments. Depending on how large the proportion of the image is in one of the segments, an electrical signal of different magnitude is generated in the segments. The electrical signals of the segments are correlated with each other, in particular compared with each other. The comparison values are then used to determine, whether the workpiece surface is in focus or out of focus. If necessary, a control signal can then be generated in the control device.

[0081] If the photodiode device is a two-segment photodiode device, the following scenarios are possible. If the reflected measuring laser beam is centered, i.e., the image of the measuring laser beam is equally divided between the two segments, the workpiece surface is in focus. An electrical signal of equal magnitude is generated in both segments based on the image of the measuring laser beam. Electrical signals of equal magnitude in both segments mean that Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0082] Date: August 06, 2025

[0083] 12 the workpiece surface is in focus. This means that the measuring laser beam directed at the workpiece surface is in the same focus as the process laser beam. If the image of the measuring laser beam is more on one segment than the other, the electrical signals of the individual segments are of different sizes. Electrical signals of different sizes mean that the workpiece surface is out of focus.

[0084] According to one embodiment, the evaluation device comprises a comparator device. The comparator device is provided in such a way that it is capable to compare the measurement signals which are generated from the measuring laser beam reflected back from the the workpiece surface, for example electrical signals, with reference values. These reference values can be stored in a storage device. If the photodiode device comprises several segments, the entire electrical signal, which is composed of the partial signals of the segments and, in particular, the sum thereof, is compared with the reference value. This procedure is used in particular when the contrast is to be determined.

[0085] The entire measurement signal generated by the detector device from the reflected measurement laser beam, for example an electrical signal, can be thus also used to determine the contrast on the workpiece surface. The electrical signal is, for example, an electrical signal generated by the photodiode device. If the photodiode device is designed as a segmented photodiode device, the electrical signal corresponds to the sum of the electrical signals from the segments. The magnitude of the electrical signal depends on the degree of reflection of the measuring laser beam on the workpiece surface. The value of the electrical signal generated from the reflected measuring laser beam can, for example, be compared with a reference value, which is performed in particular in the control device, for example in the comparator device of the evaluation device. If the generated electrical signal is within the limit of the threshold value, this means that the workpiece surface has sufficient contrast. If the generated electrical signal is outside the limit of the threshold value, this means, for example, that the contrast is insufficient. A corresponding control signal is then generated in the control device, which can influence the device for supplying the process laser beam, for example.

[0086] The detection device generates measurement signals, which are then forwarded to the control device. There, control signals are generated based on the measurement signals, which can be used to control individual components. If the measurement of the focus position Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0087] Date: August 06, 2025

[0088] 13 shows that the workpiece surface or the process laser beam is not in focus, the measurement signals can be used to generate a control signal that readjusts the focus position and / or, in the case of a hand-guided optical system, signals to the operator that the focus distance has been deviated from or reached.

[0089] Similarly, the reflected measuring laser beam in the detector device can generate a measurement signal that provides information about the contrast on the workpiece surface.

[0090] According to the second aspect of the invention, a method for laser-based determination of the focus position of a process laser beam in relation to a workpiece surface and / or for contrast determination on a workpiece surface is provided, which comprises the features of independent claim 18. The method is also referred to as "the measuring method."

[0091] The measuring method is carried out in particular using a laser-based device according to the first aspect of the invention. To avoid repetition and to explain the sequence of the measuring method, reference is therefore made to the explanations of the first aspect of the invention in their entirety. The measuring method is characterized by the following steps:

[0092] Via a device for providing a measuring laser beam, which is part of a determination device configured as a device for determining the focus position of a process laser beam in relation to the workpiece surface and / or for determining the contrast on the workpiece surface, a measuring laser beam is generated which, in the beam direction, runs in front of the focusing device parallel to the optical axis and, optionally parallel to a process laser beam, and in an optical offset position relative to the optical axis.

[0093] In a focusing device, which is also provided along the optical axis, the measuring laser beam is focused onto the workpiece surface. In the focusing device, the measuring laser beam is influenced in such a way that the measuring laser beam is deflected onto the workpiece surface after the focusing device, optionally to the same focus as a process laser beam.

[0094] Compared to the optical axis, the measuring laser beam runs tilted behind the focusing device, namely in the direction of the optical axis.

[0095] The measuring laser beam is reflected, at least partially, on the workpiece surface and is received in a detector device, wherein, according to one embodiment, the measuring laser Applicant: Clean Lasersysteme GmbH

[0096] Our reference: P8029PC00

[0097] Date: August 06, 2025

[0098] 14 beam reflected back from the workpiece surface is collected in the focusing device and then imaged in the detector device.

[0099] In the detector device, a measurement signal relating to the focus position and / or the contrast is generated on the basis of the reflected measurement laser beam. For this purpose, according to one embodiment, the reflected measuring laser beam is converted into at least one electrical signal in the detector device. This is described in more detail in connection with the first aspect of the invention, so that reference is made here to the corresponding explanations above in their entirety.

[0100] According to one embodiment, the measurement signal is transmitted to a control device. In the control device, a control signal is generated based on the measurement signal.

[0101] According to one optional feature, a process laser beam is generated in a device for providing a process laser beam. The determination device according to the invention either comprises such a device for generating a process laser beam, or it co-operates therewith. In the further course of the beam, according to one embodiment, the process laser beam is shaped and / or deflected in one or more optical devices in particular. The optical devices are provided in particular along the optical axis. In a focusing device, which is also provided along the optical axis, the process laser beam is focused onto the workpiece surface, preferably at the same focus as the measuring laser beam.

[0102] According to a further aspect of the invention, a method for laser-based machining of a workpiece surface is provided. The method is also referred to as "the machining method." The machining method is carried out in particular using a machining device described above. The machining method is characterized by the following steps:

[0103] By making use of a device for generating a process laser beam, a process laser beam is generated.

[0104] Using a measuring method according to the second aspect of the invention, the focus position of a process laser beam in relation to a workpiece surface and / or the contrast on a workpiece surface is determined, for example measured. To avoid repetition and to explain Applicant: Clean Lasersysteme GmbH

[0105] Our reference: P8029PC00

[0106] Date: August 06, 2025

[0107] 15 the sequence of the measuring method, reference is therefore made in full to the explanations relating to the second aspect of the invention.

[0108] The measurement signals generated in the detector device of the measuring device are transmitted to a control device. In the control device, control signals are generated on the basis of the received measurement signals, by means of which individual components of the laser-based device can be controlled in accordance with the first aspect of the invention or the processing device. For example, a control signal can be generated on the basis of the measurement signals, which readjusts and / or indicates the focus position of the process laser beam. Similarly, the reflected measurement laser beam can generate a measurement signal in the detector device, which provides information about the contrast on the workpiece surface. A control signal generated from this can, for example, influence the device for providing the process laser beam or the parameters of the process laser beam, or individual optical devices such as the scanner device. This is also described in more detail in connection with the first aspect of the invention, so that reference is made here to the corresponding explanations above in their entirety.

[0109] According to one embodiment of the invention, the evaluation of measurement laser beam and the provision of the process laser beam is performed alternately. The evaluation of the measurement laser beam and the provision of the process laser beam is provided alternately. The process laser beam is provided depending on the results of the measurement laser beam, in particular the contrast measurement.

[0110] According to one embodiment, the measurement signal generated from the measuring laser beam reflected back from the workpiece surface, for example an electrical signal, is evaluated in an evaluation device.

[0111] According to one embodiment, the detector device comprises a photodiode device, in particular a photodiode device with two segments. In the evaluation device, the electrical signals from the photodiode device are compared with other values. According to one embodiment, if the photodiode device is designed as a segmented photodiode device, the electrical signals of the individual segments of the photodiode device are compared with each other. Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0112] Date: August 06, 2025

[0113] 16

[0114] According to one embodiment, the evaluation device comprises a comparator device. The measurement signals generated from the measurement laser beam reflected back from the workpiece surface, for example electrical signals, are compared with reference values in the comparator device.

[0115] The aforementioned embodiments are also described in more detail in connection with the first aspect of the invention, so that here reference is made to the corresponding descriptions above in their entirety.

[0116] The present invention, according to its various aspects, has the particular advantage of allowing determination and / or processing "on the fly," i.e. , during operation.

[0117] The invention will now be explained in more detail with reference to an embodiment and the accompanying drawings. Shown is in

[0118] Figures 1 and 2 different views of a laser-based device according to the present invention; and

[0119] Figures 3 and 4 two views illustrating the concept of combined focus and contrast detection.

[0120] Figures 1 and 2 show a laser-based device 10b (machining device) for processing a workpiece surface 100, which comprises a laser-based device 10 for determining the focus position and / or for contrast determination. An essential component of the laser-based device 10 is a determination device 10a for determining the focus position and / or for contrast determination. Figures 2 and 3 show the determination device 10a in greater detail. Identical components are each provided with identical reference numerals.

[0121] The laser-based device 10b comprises a device 11 for providing a process laser beam 22, which may, for example, have a first wavelength of 1064 nm. According to this embodiment, the device 11 is not part of the device 10. But co-operates therewith. According to a different embodiment, the device 11 can be a part of device 10. The process laser beam 22 passes through a first optical device 12 in the form of a collimating optic and is deflected in a second optical device 13 in the form of a beam combining / beam splitting optic. The process laser beam 22 is then fed to a third optical device 14 in the form of a scanner device before it is Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0122] Date: August 06, 2025

[0123] 17 focused by a focusing device 15 as a focused process laser beam 16 at the focus 16a onto the workpiece surface 100. The irradiation area 17 can be a few centimeters, for example 4 to 6 centimeters.

[0124] In addition, the laser-based device 10 comprises further components that enable combined focus / contrast detection. One of these components is a device 20 for providing a measuring laser beam 23, which is designed as a laser diode and provides a measuring laser beam 23 with a second wavelength of, for example, 980 nm. The second wavelength of the measuring laser beam differs from the first wavelength of the process laser beam in such a way that the two beams can be optically combined and separated.

[0125] If the process laser beam 22 and the measuring laser beam 23 are close together, a focusing device 15 optimized for the process laser beam 22 can be used. If the two wavelengths are far apart, the focusing device 15 is preferably designed as an achromatic optic. Depending on the properties of the workpiece surface 100, process wavelengths and measuring wavelengths suitable for contrast detection and workpiece machining can be used.

[0126] The measuring laser beam 23 passes a fourth optical device 18 outside the optical axis 29 and does not touch the fourth optical device 18, for example the deflection device, such as a deflection mirror, located in the optical axis 29, and then passes through the second optical device 13. The second optical device 13 is characterized in that it is reflective for the process laser beam 22 but transmissive for the measuring laser beam 23.

[0127] The measuring laser beam 23 continues to pass through the third optical device 14 to the focusing device 15 and through the focusing device 15. The process laser beam 22 and the measuring laser beam 23 run parallel in front of the focusing device 15. However, the measuring laser beam 23 is in an optical offset position 30 relative to the optical axis 29, i.e. , in an Off-Axis position relative to the optical axis 29. This means that the measuring laser beam 23 runs slightly offset, for example by a few millimeters, relative to the optical axis 29, for example above or below it, or next to it. The fourth optical device 14 is arranged so that it does not obstruct the beam path of the measuring laser beam 23 coming from the device 20 and deflects it in the same way as the process laser beam 22. Applicant: Clean Lasersysteme GmbH

[0128] Our reference: P8029PC00

[0129] Date: August 06, 2025

[0130] 18

[0131] The measuring laser beam 23 hits the workpiece surface 100 after passing through the focusing device 15 and is at least partially reflected from there. This is described in more detail in connection with Figures 3 and 4. The reflected measuring laser beam 24 is collected in the focusing device 15, passes through the third and second optical devices 14, 13 again, whereby passing through the second optical device 13, and is then deflected in the fourth optical device 18 and imaged in a detector device 19. The detector device 19 is another component of the invention and is designed as a segmented photodiode device 19a with two segments.

[0132] In the detector device 19, 19a, a measurement signal 26 is generated from the reflected measurement laser beam 24, which is transmitted via a signal connection 25 to a control device 21. In the control device 21, control signals 27 are generated on the basis of the measurement signals 26, which can then be used to control individual components of the device 10, 10a or 10b. For example, based on the measurement signals 26, a control signal 27 can be generated that readjusts the focus position. Similarly, the back-reflected measurement laser beam 24 in the detector device 19, 19a can generate a measurement signal 26 that provides information about the contrast on the workpiece surface 100. A control signal 27 generated from this can, for example, influence the device 11 for providing the process laser beam 22 or the parameters of the process laser beam 22.

[0133] The evaluation of the reflected measuring laser beam 24 and the provision of the process laser beam 22 take place alternately while the position of the measuring beam 23 passes through the irradiation area 17. The process laser beam 22 is provided depending on the results of the evaluated measuring laser beam 24, in particular the contrast measurement.

[0134] The processing of the measurement signals 26, generated by the detector device 19, is performed in the control device 21 , which for this purpose is connected with the detector device 19 via signal connection 25. For this purpose, the control device 21 comprises an evaluation device 21a. In addition, the control device 21 , in particular the evaluation device 21a, comprises a comparator device 21b. The comparator device 21b contains for example, reference values 28, which are stored in a storage device. The storage device with the reference values 28 can, of course, also be provided at another location within the control device 21. The storage device can also be a component external to the control device 21, Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0135] Date: August 06, 2025

[0136] 19 which the control device 21, in particular the evaluation device 21a and / or the comparator device 21b, accesses as required.

[0137] Figures 3 and 4 now illustrate the concept of combined focus / contrast detection. Figures 3 and 4 show only some of the components of the determination device 10a. In particular, only the measuring laser beam 23 and the components required for this are shown. The measuring laser beam 23 generated in the device 20 is directed into the focusing device 15. Before the measuring laser beam 23 enters the focusing device 15, it runs parallel to the optical axis 29 and to the process laser beam 22, which is not shown. In addition, the measuring laser beam 23 is located at a distance, the optical offset position 30, from the optical axis 29, for example above or below or next to the optical axis 29. The distance is a few millimeters. However, it can also be increased, depending on the application and the dimensions of the focusing device 15 and the second optical device 13.

[0138] After the measuring laser beam 23 has passed through the focusing device 15, it is deflected to the same focus as the process laser beam 22. This means that the path of the measuring laser beam 23 behind the focusing device 15 is slightly tilted in the direction of the optical axis 29. If the workpiece surface 100 is in the focal plane, the focal points of both beams, both the measuring laser beam 23 and the process laser beam 22, lie at the same point of impact 31a. The workpiece surface is therefore in focus 32a. If the workpiece surface 100 is outside the focal plane, the point of impact 31b, 31c of the measuring laser beam 23 on the workpiece surface 100 is not in the optical axis 29. The workpiece surface 100 is therefore outside the focus. For example, the workpiece surface is too far away 31b, 32c from the focusing device 15, or too close 31c, 32c.

[0139] The measuring laser beam is reflected by the workpiece surface 100 and collected as a back- reflected measuring laser beam 24 in the focusing device 15 and then imaged via the deflection device 18 in the detector device 19. The detector device 19 is designed as a two- segment photodiode device 19a with a first segment S1 and a second segment S2. Depending on the position of the workpiece surface 100 in relation to the focusing device 15, the reflected measuring laser beam 24a, 24b, 24c hits the segments S1 and S2 of the detector device 19, 19a at different points. Applicant: Clean Lasersysteme GmbH

[0140] Our reference: P8029PC00

[0141] Date: August 06, 2025

[0142] 20

[0143] This is illustrated in Figure 4. The measuring laser beam 24 reflected back from the workpiece surface 100 is detected by the detector device 19 in the form of the two-segment photodiode device 19a and imaged in the form of an image 33 on the segments S1 and S2. Depending on the focus position of the workpiece surface 100, the image 33 is located at different positions on the segments S1 and S2. In the photodiode device 19a, an electrical signal 26a, 26b is generated from the signal of the back-reflected measuring laser beam 24. In each of the segments S1 and S2, a separate electrical signal 26a, 26b is generated. Depending on how large the portion of the image 33 is in one of the segments S1, S2, an electrical signal 26a, 26b of different magnitude is generated in the segments S1, S2. The electrical signals 26a, 26b of segments S1 and S2 are correlated with each other, in particular compared with each other. This can still be done in the detector device 19, 19a or in the control device 21. The comparison values can then be used to determine whether the workpiece surface 100 is in focus or out of focus. If necessary, a control signal 27 can then be generated in the control device 21.

[0144] The middle of Figure 4 shows the situation in which the workpiece surface 100 is located in focus 32a. This means that the image 33 of the back-reflected measuring laser beam 24 is located centrally between segments S1 and S2. The partial-areas of image 33 that are to be assigned to segment S1 and segment S2, i.e. , that cover segments S1 and S2, are therefore of equal size. This means that the two segments S1 and S2 generate electrical signals 26a, 26b of equal magnitude. If both electrical signals 26a, 26b are of equal magnitude, this means that the workpiece surface 100 is in focus. From the equation, electrical signal (S1) = electrical signal (S2), it can therefore be seen that the workpiece surface 100 is in focus. This is the basic requirement for a process laser beam 22 to be generated.

[0145] The left-hand side of Figure 4 shows a situation in which the workpiece surface 100 is outside the focus 32b and is, for example, too far away. As can be seen, the image 33 of the back-reflected measuring laser beam 24 lies mainly in segment S1 and only to a small extent in segment S2. This means that the two segments S1 and S2 generate electrical signals 26a, 26b of different magnitudes. In the situation shown, segment S1 generates an electrical signal 26a, that is greater than the electrical signal 26b of segment S2. From the equation, electrical signal (S1) > electrical signal (S2), it can therefore be determined that the workpiece surface 100 is outside the focus and too far away. A change in distance and / or Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0146] Date: August 06, 2025

[0147] 21 readjustment of the focusing device 15 is corrected, for which a corresponding control signal 27 is generated in the control device 21 .

[0148] The right-hand side of Figure 4 shows a situation in which the workpiece surface 100 is outside the focus 32c and is, for example, too close. As can be seen, the image 33 of the back-reflected measuring laser beam 24 lies mainly in segment S2 and only to a small extent in segment S1 . This means that the two segments S1 and S2 generate electrical signals 26a, 26b of different magnitudes. In the situation shown, segment S2 generates an electrical signal 26b that is greater than the electrical signal 26a of segment S1. From the equation, electrical signal (S1) < electrical signal (S2), it is thus recognized that the workpiece surface 100 is outside the focus and is too close. A change in distance and / or readjustment of the focusing device 15 is therefore necessary, for which a corresponding control signal 27 is generated in the control device 21.

[0149] In the manner described above, the focus position of the workpiece surface 100 can thus be determined and, if necessary, readjusted.

[0150] However, the total electrical signal generated by the detector device 19, 19a from the back- reflected measuring laser beam 24, which corresponds to the sum of the two electrical signals 26a, 26b in the segments S1 and S2, can also be used to determine the contrast on the workpiece surface 100. The total magnitude of the electrical signal generated by the detector device 19, which corresponds, for example, to the sum of the two electrical signals 26a, 26b from the two segments S1 and S2, depends on the degree of reflection of the measuring laser beam 23 at the workpiece surface 100. The value of the electrical signal generated from the reflected measuring laser beam 24 can, for example, be compared with a reference value 28, which is preferably performed in the control device 21 , in particular in the comparator device 21 b. If the generated electrical signal lies within the range of the threshold value, for example, this means that the workpiece surface has sufficient contrast. If the generated electrical signal violates the threshold value, this means, for example, that the contrast is insufficient. A corresponding control signal 27 is then generated in the control device 21 in a manner that can influence, for example, the device 11 for providing the process laser beam 22. Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0151] Date: August 06, 2025

[0152] 22

[0153] List of reference numerals

[0154] 10 Laser-based device for determining the focus position and / or for contrast determination

[0155] 10a Determination device for determining the focus position and / or for contrast determination

[0156] 10b Laser-based device for machining a workpiece surface (machining device)

[0157] 11 Device for providing a process laser beam

[0158] 12 First optical device (collimation optics)

[0159] 13 Second optical device (beam combining / beam splitting device)

[0160] 14 Third optical device (scanner device)

[0161] 15 Focusing device

[0162] 16 Focused laser beam

[0163] 16a Focus on workpiece surface

[0164] 17 Irradiation area on workpiece surface

[0165] 18 Fourth optical device (deflection device)

[0166] 19 Detector device

[0167] 19a Photodiode device

[0168] 20 Device for providing a measuring laser beam

[0169] 21 Control device

[0170] 21a Evaluation device

[0171] 21b Comparator device

[0172] 22 Process laser beam

[0173] 23 Measuring laser beam

[0174] 24 Backward reflected measuring laser beam

[0175] 24a Backward reflected measuring laser beam

[0176] 24b Backward reflected measuring laser beam

[0177] 24c Backward reflected measuring laser beam

[0178] 25 Signal connection

[0179] 26 Measurement signal

[0180] 26a Electrical signal

[0181] 26b Electrical signal

[0182] 27 Control signal

[0183] 28 Reference value Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00

[0184] Date: August 06, 2025

[0185] 23

[0186] 29 Optical axis

[0187] 30 Optical offset position (Off-axis position)

[0188] 31a Point of impact

[0189] 31b Point of impact 31c Point of impact

[0190] 32a Workpiece surface in focus

[0191] 32b Workpiece surface outside focus

[0192] 32c Workpiece surface outside focus

[0193] 33 Image of the reflected measuring laser beam

[0194] 51 Segment of the photodiode device

[0195] 52 Segment of the photodiode device

[0196] 100 Workpiece surface

Claims

Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00Date: August 06, 202524Claims1. Laser-based device (10) for determining the focus position of a process laser beam (22) in relation to a workpiece surface (100) and / or for determining the contrast on a workpiece surface (100), comprising: a determination device (10a) which is configured as a device for determining the focus position of a process laser beam (22) in relation to the workpiece surface (100) and / or for determining the contrast on the workpiece surface (100), the determination device (10a) comprising: a device (20) for providing a measuring laser beam (23) which is aligned in the beam direction in front of the focusing device (15) parallel to an optical axis (29) of the device (10) and which is provided in an optical offset position (30) relative to the optical axis (29), a focusing device (15) for focusing the measuring laser beam (23) on the workpiece surface (100); and a detector device (19) which is designed to receive the measuring laser beam (24) reflected back from the workpiece surface (100) and to generate a measurement signal (26) related to the focus position and / or the contrast.

2. Laser-based device (10) according to claim 1, further comprising a control device (21), which is part of the detector device (19), or which is connected to the detector device (19) via a signal connection line (25), or comprising an interface from the detector device (19) to a control device (21).

3. Laser-based device (10) according to anyone of claims 1 or 2, characterized in that the focusing device (15) is designed as an achromatic optics.

4. Laser-based device (10) according to anyone of claims 1 to 3, characterized in that the focusing device (15) is provided for collecting the measuring laser beam (24) reflected back from the workpiece surface (100).

5. Laser-based device (10) according to anyone of claims 1 to 4, characterized in that the laser-based device (10) comprises a device (11) for providing a process laser beam (22), or that the laser-based device (10) co-operates with a device (11) for providing a process laser beam (22).Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00Date: August 06, 2025256. Laser-based device (10) according to anyone of claims 1 to 5, characterized in that the focusing device (15) is designed such that the measuring laser beam (23) is deflected to the same focus (16a) as the process laser beam (22).

7. Laser-based device (10) according to claim 5 or 6, characterized in that the device (11) for providing the process laser beam (22) is provided for generating first laser beams, and / or that the device (20) for providing the measuring laser beam (23) is provided for generating second laser beams.

8. Laser-based device (10) according to claim 7, characterized in that the wavelengths of the first and second laser beams differ from each other.

9. Laser-based device according to anyone of claims 1 to 8, characterized by one or more optical devices (12, 13, 14) for shaping and / or directing the measuring laser beam (23) and / or the process laser beam (22).

10. Laser-based device (10) according to claim 9, characterized in that the optical device is selected from the group consisting of: a first optical device (12) in the form of a collimating optic; a second optical device (13) in the form of a beam combining device and / or a beam splitting device; a third optical device (14) in the form of a scanner device; or a combination thereof.

11. Laser-based device (10) according to anyone of claims 1 to 10, characterized in that the detector device (19) is preceded in the beam direction of the reflected measuring laser beam (24) by a - fourth - optical device (18) in the form of a deflection device for the back-reflected measuring laser beam (24).

12. Laser-based device (10) according to anyone of claims 1 to 11, characterized in that the detector device (19) is configured to generate an electrical signal (26a, 26b) from the measuring laser beam (24) reflected back from the workpiece surface (100).

13. Laser-based device (10) according to anyone of claims 1 to 12, characterized in that the detector device (19) comprises a photodiode device (19a).Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00Date: August 06, 20252614. Laser-based device (10) according to claim 13, characterized in that the photodiode device (19a) is designed as a segmented photodiode device, in particular a photodiode device (19a) with two segments (S1, S2).

15. Laser-based device (10) according to anyone of claims 1 to 14, characterized in that the detector device (19) or the control device (21) comprises an evaluation device (21a), which is provided for evaluating the measuring laser beam (24) reflected back from the workpiece surface (100), in particular for evaluating an electrical signal (26a, 26b) generated from the measuring laser beam (24) reflected back from the workpiece surface (100).

16. Laser-based device (10) according to claim 15, as far as referred back to claim 14, characterized in that the evaluation device (21a) is provided in such a way that it is capable of comparing the electrical signals (26a, 26b) of the individual segments (S1, S2) of the photodiode device (19a) with one another.

17. Laser-based device according to claim 15 or 16, characterized in that the evaluation device (21a) comprises a comparator device (21b), and that the comparator device (21b) is provided in such a way that it is capable of comparing the measurement signals (26) generated from the measurement laser beam (24) reflected back from the workpiece surface (100) with reference values (28).

18. Method for laser-based determination of the focus position of a process laser beam (22) in relation to a workpiece surface (100) and / or for contrast determination on a workpiece surface (100), in particular by using a device (10) according to anyone of claims 1 to 17, characterized by the following steps:Via a device (20) for providing a measuring laser beam, which is part of a determination device (10a) configured as a device for determining the focus position of a process laser beam (22) in relation to the workpiece surface (100) and / or for determining the contrast on the workpiece surface (100), generating a measuring laser beam (23) which, in the beam direction in front of the focusing device (15), runs parallel to an optical axis (29) and in an optical offset position (30) relative to the optical axis (29);In a focusing device (15), focusing the measuring laser beam (23) onto the workpiece surface (100);Applicant: Clean Lasersysteme GmbHOur reference: P8029PC00Date: August 06, 202527Deflecting the measuring laser beam (23) onto the workpiece surface (100) after the focusing device (15)Receiving the measuring laser beam (24) reflected back from the workpiece surface (100) in a detector device (19);In the detector device (19), generating a measurement signal (26) related to the focus position and / or the contrast on the basis of the back-reflected measuring laser beam (24).

19. Method according to claim 18, further comprising the following steps:In a device (11) for providing a process laser beam, generating a process laser beam (22);In the focusing device (15), focusing the process laser beam (22) onto the workpiece surface (100).

20. Method according to claim 19, characterized in that the measuring laser beam (23) is focused onto the workpiece surface (100) at the same focus (16a) as the process laser beam (22).

21. Method according to anyone of claims 18 to 20, characterized in that the measuring laser beam (24) reflected back from the workpiece surface (100) is collected in the focusing device (15) and then imaged in the detector device (19).

22. Method according to anyone of claims 18 to 21 , characterized in that in the detector device (19), the back-reflected measuring laser beam (24) is converted into at least one electrical signal (26a, 26b).

23. Method according to anyone of claims 18 to 22, further characterized by the following steps:Transmitting the measurement signal (26) to a control device (21);In the control device (21), generating a control signal (27) based on the measurement signal (26).

24. Method according to anyone of claims 18 to 23, characterized in that the measurement signal (26) generated from the measurement laser beam (24) reflected back from the workpiece surface (100) is evaluated in an evaluation device (21a).Applicant: Clean Lasersysteme GmbH Our reference: P8029PC00Date: August 06, 20252825. Method according to anyone of claims 18 to 24, characterized in that the evaluation of the measuring laser beam (24) and the provision of the process laser beam (22) are performed alternately.

26. Method according to claim 24 or 25, characterized in that the detector device (19) comprises a photodiode device (19a), in particular a photodiode device (19a) with two segments (S1, S2), and that in the evaluation device (21a) the electrical signals (26a, 26b) of the individual segments (S1 , S2) of the photodiode device (19a) are compared with each other.

27. Method according to anyone of claims 24 to 26, characterized in that the evaluation device (21a) comprises a comparator device (21b), and that the measurement signals (26 generated from the measurement laser beam (24) reflected back from the workpiece surface (100) are compared with reference values (28) in the comparator device (21b).

Images