WO2019180142A1

WO2019180142A1 - Method and device for processing a composite material by means of a laser, and composite material

Info

Publication number: WO2019180142A1
Application number: PCT/EP2019/057089
Authority: WO
Inventors: Jan Werschnik; Stefan Franz; Carolin MUENZBERG
Original assignee: Jenoptik Optical Systems Gmbh
Priority date: 2018-03-23
Filing date: 2019-03-21
Publication date: 2019-09-26
Also published as: DE102018106921A1

Abstract

The invention relates to a method for processing a composite material (102) having a first layer (118) and a second layer (120) by means of a laser beam (108), wherein material of the composite material (102) is removed when the laser beam (108) impinges on a processing region of the composite material (102). The method comprises a step of determining a change, in particular a frequency change and/or an intensity change, using a sensor signal (128) which represents a detection radiation emitted from the processing region (122), a step of illuminating the processing region with illumination radiation differing from the laser beam in order to identify the defined spectrum of the layer or a boundary surface, a step of comparing the change with a predetermined change which is expected during a transition of the processing region from the first layer (118) into a further layer (120), and a step of outputting at least one control signal (134, 138, 140) for controlling the processing as a function of a result of the comparison of the change with the predetermined change.

Description

Method and device for processing a composite material by means of laser and composite material

The present invention relates to a method and an apparatus for processing a composite material by means of a laser and to a corresponding one

Composite material.

A composite material can be processed for example by means of laser ablation, laser cutting or laser welding. The position of the laser focus can be determined, for example, by trial and error, to ensure that certain layers are not injured.

Against this background, the present invention provides an improved method of processing a composite material by laser, a corresponding apparatus and an improved composite material according to the main claims. advantageous

Embodiments emerge from the subclaims and the following description.

The invention relates to a method for processing a composite material comprising a first layer and a second layer by means of a laser beam, wherein material of the composite material is removed when the laser beam strikes a processing region of the composite material. The method comprises the following steps:

Determining a change using a sensor signal representing a detection radiation emitted from the processing area;

Illuminating the machining area with one of the laser beam

discriminating illumination radiation for identifying the defined spectrum of the layer or an interface to produce at least a portion of the detection radiation as a portion of the illumination radiation reflected from the processing region;

Comparing the change with a predetermined change expected in a transition of the processing area from the first layer to another layer; and

Outputting at least one control signal for controlling the processing depending on a result of comparing the change with the predetermined change. A composite material can be understood as meaning a layer composite composed of several layers of different material. For example, the composite material may be carbon or glass fiber reinforced plastic or a metal-containing composite. Also, the composite material may include anisotropic layers. The composite material may be a plurality

have contiguous to be processed and not to be processed layers. The processing region can be understood as meaning a portion of the composite material which, using the laser beam, has material of the

Composite material is removed. Also, under the processing area, a space adjacent to such a section can be understood. By doing

Processing region, at least a portion of the laser beam is reflected, for example, on the composite material or dissolved out of the composite material or plasma. Due to the material heating generated during processing, infrared radiation is also emitted from the processing area. Thus, the detection radiation may be radiation reflected or generated within the processing area. A change may, for example, be understood as a change of the detection radiation which is dependent on time, place and / or wavelength, which may be present for example in the form of an electrical signal or value. The change may, for example, relate to a change in the frequency or the intensity of the detection radiation. The frequency change may correspond to a color change. Accordingly, a predetermined change can be understood as at least one threshold value with respect to a parameter characterizing the change. For example, the predetermined change may be set prior to the start of processing or learned during processing in a learning process. The first and second layers can be directly adjacent. Alternatively, an interface between the first and second layers may be formed by an indicator layer disposed between the two layers. In this case, the first and the second layer can each adjoin the indicator layer. In the step of outputting, the control signal can be output, for example, in order to change a laser pulse parameter, a laser pulse sequence and / or a feed rate of the laser focus so that the second layer is not damaged by the laser. In particular, that can

Control signal can be used to prevent further transmission of the laser beam.

The approach described here is based on the finding that by observing a change in a detection radiation, the laser processing of a

Composite material is released, and a corresponding comparison of the

observe change with one or more known change profiles Layer transition to a layer not to be processed in the composite material can be detected reliably and precisely. This can be a quick and accurate

Processing of individual layers can be ensured. For example, this can stop the machining process in time so that certain layers are not damaged. Thus, the high demands on the process control, which in the laser processing of composite materials by the different

Absorption properties of the individual layers arise to be met already with relatively little effort, such as in the preparation of surfaces for bonding or repairs, cutting and drilling of structural and high performance plastics, especially CFRP and GRP, when joining thermoplastics and fiber reinforced composites or cutting and Drilling of plastics and fiber composites. In addition, such process control can be highly automated and continuously improved, for example, through machine learning.

According to one embodiment, in a step of lighting up the

Processing area with a different from the laser beam

Illuminating radiation to be illuminated. As a result, at least a portion of the detection radiation can be generated as a proportion of the illumination radiation reflected from the processing area. Thus, the detection radiation of reflected laser radiation and additionally or alternatively from reflected

Composed lighting radiation. The illumination radiation may be light having a spectrum defined depending on the given change. The lighting can be done, for example, using a color selective or

wavelength-selective, active illumination. By way of example, the light may be infrared radiation in the region of near, middle or far infrared. By this embodiment, a characteristic of the interface signal increase of the sensor signal can be achieved. As a result, the layers can be identified particularly reliably.

The method may include a step of emitting the laser beam into the

Include editing area. This allows the composite material to be processed. Furthermore, the method may comprise a step of detecting the sensor signal. At this time, the step of detecting may be performed at the same time as the sending step. Thereby, a so-called "closed loop" control can be realized, by which a very fast control of the processing of the composite material is made possible.Additionally or alternatively, the step of detecting can be carried out offset in time to the step of sending out "Control can be realized by the example of a low-cost sensors for Detection of the detection radiation can be used. In the step of

Send out the laser beam can be sent to material of the

Remove composite material. For this purpose, the laser beam may have a suitable intensity and / or focusing. During the step of detecting the

Laser beam can be emitted with an intensity or focus that is not suitable for removing the material or it can be sent out no laser beam and instead of the differs from the laser beam illumination radiation. Also, a so-called afterglow of the laser beam for generating the

Sensor signal can be used.

According to a further embodiment, the sensor signal may represent a spectrally resolved and / or integrated intensity of the detection radiation. A spectrally resolved intensity may, for example, be understood as an intensity resolved depending on a location, a time or a wavelength. An integrated intensity can, for example, be understood as an intensity that is partially integrated over a specific parameter such as time, spatial direction or wavelength. By this embodiment, the comparison of the change can be made particularly quickly and efficiently.

The method may include a step of determining the predetermined change or an adapted change using the sensor signal. In this way, a suitable value for the given change can be learned.

In particular, the step of determining may take place after the beginning of the processing, for example in a known time interval in which the first layer is processed. Thus, one can be learned for the given change during the processing of the first layer. For example, a method of machine learning can be used for this purpose. As a result, the reliability and accuracy of the process can be continuously increased.

The method may include a read-out step in which a value representing the predetermined change is read from a composite database. The composite database may be located in an internal memory of a composite material processing apparatus. Where the given

Change representing value may be a threshold.

According to another embodiment, in the step of outputting, the control signal may be output to stop the processing when the result of the

Comparing indicates that a value of the change reaches or exceeds a value of the predetermined change. For example, stopping by a Procedure of the laser focus relative to the composite material, a dimming of the laser beam or a shutdown of the laser source can be effected. This can be safely prevented that the second layer is injured by the laser.

At least a portion of the sensor signal may represent infrared radiation.

As a result, at least a portion of the detection radiation than from the

Processing area out reflected portion of the illumination radiation are generated. The infrared radiation may, for example, be an infrared radiation that exceeds a region of the near infrared, for example, medium or far infrared. As a result, individual layers of the composite material can be identified by means of thermography. In this way, the identification of the individual layers can be further improved.

The approach presented here also creates a composite material with the following

Characteristics: at least one first layer to be processed by means of at least one laser beam; at least one second layer which is not to be processed by means of the laser beam; and at least one indicator layer disposed between the first layer and the second layer and configured to contact one upon contact with the laser beam

To emit detection radiation in a spectrum characteristic of an interface between the first layer and the second layer.

By an indicator layer, for example, a comparatively thin layer of a low-cost indicator material can be understood. For example, the indicator material may be a fluorescently enriched or highly reflective material. Such a composite material can be provided inexpensively and also offers the advantage of a particularly fast, inexpensive and low-error machinability of the composite material.

A device for processing a composite material comprising a first layer and a second layer by means of a laser beam is configured to correspondingly implement the steps of a variant of a method presented here

To implement, control or implement facilities. Also through this

Embodiment of the invention in the form of a device, the object underlying the invention can be solved quickly and efficiently. advantageously, For example, the corresponding devices or units may be integrated in a housing.

The device may comprise a beam splitter, a laser source for emitting the laser beam and an optical sensor for detecting the sensor signal. In this case, the optical sensor in a transmission channel and the laser source in a

Reflection channel of the beam splitter can be arranged. This arrangement is particularly suitable for machining with high laser power. Alternatively, the optical sensor can be arranged in the reflection channel and the laser source in the transmission channel of the beam splitter. The laser beam can be guided from the beam splitter through a lens to the workpiece to be machined.

The invention will be described by way of example with reference to the accompanying drawings. Show it:

Figure 1 is a schematic representation of a device according to a

Embodiment;

Figure 2 is a schematic representation of a beam path through a device according to an embodiment;

Figure 3 is a schematic representation of a composite material according to a

Embodiment;

FIG. 4 shows a flowchart of a method according to an exemplary embodiment;

Figure 5 is a schematic representation of a device according to a

Embodiment;

FIG. 6 shows a schematic representation of an exemplary beam path through a device according to an exemplary embodiment;

FIG. 7 shows a schematic representation of an exemplary beam path through a device according to an exemplary embodiment;

Figure 8 is a schematic representation of a target material and a sample of

Target material according to an embodiment; and

9 is a schematic representation of a composite material according to a

Embodiment.

In the following description of preferred embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and similarly acting, wherein a repeated description of these elements is omitted. FIG. 1 shows a schematic representation of a device 100 according to a

Embodiment. The apparatus 100 for processing a composite material 102 by means of laser comprises according to this embodiment, a transmission channel 104 with a laser source 106 for generating a laser beam 108, for example via a beam splitter 1 10, a scanner 1 12, such as a galvanometer scanner, and an objective. 1 14, such as an F-theta objective, is steerable on a workpiece of the composite material 102 to process it in a particular laser processing method such as laser ablation, laser cutting or laser welding. The lens 1 14 is color corrected according to one embodiment, so that processing and observation wavelength are in the same focus. This is especially important for versions with a galvo scanner, otherwise

different focus positions arise over the image field. According to one

Embodiment, however, one for the detection wavelength (s) mitoptimiertes lens 1 14 is used. Likewise, the mirrors are optimized for both wavelength ranges. Advantageous materials are depending on the wavelength, for example

Aluminum, silver or gold. The laser beam 108 is indicated by a thick arrow

characterized. For better clarity, the composite material 102 according to FIG. 1 is shown only with a first layer 1 18 to be processed and a second layer 120 that is not to be processed. In reality, the composite material 102 may include a plurality of such layers 1 18, 120. The two layers 1 18, 120 have a common interface, which is indicated by a dashed line.

A detection radiation 122 emanating from the workpiece, which is reflected, for example, by the composite material 102 upon contact with the laser beam 108 or by a plasma generated by the laser beam 108, reaches the beam splitter 110 and, for example, via the objective 1 14 and the scanner 1 12 becomes from this in a direction deviating from a direction of the transmission channel 104 in a direction

Reflection channel 124 steered. The detection radiation 122 is marked with several thin arrows. An optical sensor 126 arranged in the reflection channel 124, for example an optionally high-resolution camera or one or more photodiodes, is designed to detect the detection radiation 122 and to provide a corresponding sensor signal 128. The sensor signal 128 represents, for example, a spectrally resolved or (partially) integrated intensity of the detection radiation 122.

Between the optical sensor 126 and the beam splitter 1 10 is an optional

Bandpass filter 130 is arranged.

The device 100 comprises an evaluation device 132, which is designed to use the sensor signal 128 at least one control signal 134, 136, 138, 140th output that is suitable for influencing further processing of the composite material 102. According to one embodiment, the device 100 comprises a detection device, a comparison device and an output device. The determination device is designed to be a change, in particular a

Frequency change and / or a change in intensity, the detection radiation 122 using the sensor signal 128 to determine. For example, the

Detection device is designed to determine a change in the color of the detection radiation 122 as the change. The comparison device is designed to compare the change with a predetermined change. The predetermined change corresponds, for example, to an expected value, which is a change in the

Detection radiation 122 indicates, which is expected as soon as the currently hit by the laser beam 108 processing area reaches the interface between the first layer 1 18 and the second layer 120. The output device is designed to output the at least one control signal 134, 136, 138, 140.

For example, the output device is formed around the at least one

Control signal 134, 136, 138, 140 output to further processing the

To terminate composite material 102, in particular to prevent further removal of material in the processing area just processed when the last detected change in the detection radiation 122 reaches or exceeds the predetermined change.

The evaluation device 132, for example in the form of a controller, is in accordance with a

Embodiment is designed to perform a spectral analysis of the detection radiation 122 using the sensor signal 128. In this case, the evaluation device 132 determines a change and compares it with a predetermined change, for example with at least one known change, which indicates the presence of the interface between the first layer 1 18 and the second layer 120. The known change has been determined, for example, experimentally or in a method of machine learning.

According to an exemplary embodiment, the predetermined change is set prior to starting the processing of the composite material 102 by means of the device 100, for example in the form of one or more threshold values, for example written to a memory of the device 100. Additionally or alternatively, the predetermined change is learned or adjusted during processing of the composite material 102. For this purpose, for example, using a learning method, a threshold value representing the predetermined change that differs sufficiently from changes in the detection radiation 122 that occur during the processing of the first layer 18 can be determined. As a result of the comparison, the evaluation device 132 gives a first example

Control signal 134 for controlling a traversing device 136 for the method of

Workpiece with respect to a focus of the laser beam 108, a second control signal 138 for driving the scanner 1 12 and a third control signal 140 for driving the laser source 106 from. The control by means of the control signals 134, 138, 140 is carried out depending on a degree of agreement between the determined and the known change. In particular, the evaluation device 132 is designed to control the processing of the workpiece as a function of the change in the detection radiation 122 so that the second layer 120 is not illuminated by the laser beam 108

is damaged, for example, by the processing is stopped upon detection of the interface or continued in a direction away from the interface direction.

According to a particular embodiment, the device 100 comprises a

Lighting device 142, which is designed to illuminate the processing region, also referred to as a processing zone, in which the composite material 102 is processed by means of the laser beam 108, with an illumination radiation 144, for example, with light in a spectrum defined for the identification of the interface. The

Control of the illumination device 142 takes place for example by means of

Evaluation device 132 in response to the predetermined change profiles.

By such a color-selective or wavelength-selective, active illumination of the processing zone, an increase in signal for the unique and thus particularly reliable identification of the layers 1 18, 120 or the interface can be achieved. In this case, the optical sensor 126 or another sensor is designed to be as

Detection radiation 122 to detect a reflected portion of the illumination radiation 144.

For this purpose, a laser-induced plasma spectroscopy or Raman spectroscopy can be used, which are compared simultaneously with the data stored in the evaluation unit 132, identified and the process is controlled.

Using special real-time Raman spectrometers, the measurements can be used for fast data acquisition for real-time applications. Also suitable is the

Pump-probe technique as a measuring method of spectroscopy, in which short laser pulses for the measurement of ultrafast relaxation processes induce changes between the

Light pulses are determined. According to an exemplary embodiment, the optical sensor 126 or another sensor is designed to additionally or alternatively detect long-wave infrared light in the middle or far infrared range and thus to allow an even more accurate identification of the layers 1 18, 120 by means of thermography.

According to one embodiment, the change is observed via broadband optics and spectral analysis. As soon as a specific change is known, processing is stopped. The device 100 thus has the function to provide information about when the processing of the layer 1 18 is completed. The focus of the laser beam 108 is automatically determined by the device 100 in this sense.

The spectral changes of the detection radiation 122 are determined according to a

Embodiment classified in a method of machine learning.

According to one embodiment, the scanner 1 12, the lens 1 14, the

Evaluation device 132 and the reflection channel 124, which may also be referred to as a camera channel, integrated in a compact device. According to one exemplary embodiment, the device has a housing into which the scanner 1 12, the lens 1 14, the evaluation device 132 and the reflection channel 124 are integrated. The observation via the reflection channel 124 takes place, for example, coaxially. Of the

Reflection channel 124 can be replaced or supplemented, for example, by a spectrometer or an imaging spectrometer.

According to one embodiment, the observation of the processing zone takes place simultaneously with the processing. For this purpose, very fast image sensors or photodiodes are suitable as an optical sensor 126, since the scanning of the laser in the kHz range, ie. H. with residence times in the ps range, takes place. If, for example, the sensor signal 128 exceeds a specific threshold value, then the evaluation device 132 switches the laser immediately, that is to say the threshold value. H. in less than 1 ps, off. The repetition rates of the short-pulse lasers are also in the three-digit kHz range. Such a procedure can also be referred to as a closed loop.

Alternatively, the observation takes place after processing. Depending on the result of the observation, further processing is triggered. Such a procedure can also be referred to as open loop.

The evaluation of the change is generally by combination, ie by mathematical linkage, at least one sensor response of the optical sensor 126, such as a spectrally resolved intensity over (x, y, z, t, l) or a (partially) integrated intensity such as l (t), l (z) or I (l).

Thresholds For example, to evaluate the change are definable by an operator of the device 100. For example, if the functional f [l (t)] is greater than the threshold s ₀ , the laser is automatically shut off.

Optionally, the threshold s _{0 is} context-dependent: s ₀ = s ₀ [object property, x, y, z, t]. In addition to setting hard thresholds, the So threshold is optionally trained via a suitable algorithm.

According to one embodiment, an external or internal

Composite database 150 is provided. From the composite database 150, threshold values stored in the composite database 150 may be stored.

Machining recipes are retrieved. Demands, for example from unanswered queries, are stored in composite material database 150 according to one embodiment. External service providers can generate recipes or thresholds in the composite database 150. According to one exemplary embodiment, the evaluation device 132 is coupled to the composite material database 150 via an interface. By way of example, a threshold value can be understood as meaning an intensity value of the detection radiation 122. If such a threshold value is reached, for example, the processing of the composite material 102 can be terminated.

FIG. 2 shows a schematic representation of an exemplary beam path through a device 100 according to one exemplary embodiment. Shown is a beam of several laser beams 108 different wavelength ranges, which are focused on the lens 1 14 on the processed layer 1 18. As can be seen, the lens 1 14 is realized as a lens system. The lens system is inserted after a scan head of the scanner in the beam path of the device 100 and has the function to focus the laser beams 108 to a focal point and the

Focus during scanning to keep in a plane perpendicular to an optical axis of the lens 1 14 working plane. For example, the position of the focal point in the working plane approximately follows the F-theta condition, where a scan length or height is approximately proportional to a set scan angle. Deviations from this proportionality can be compensated by a corresponding control of mirrors of the scanner.

FIG. 3 shows a schematic representation of a composite material 102 according to one exemplary embodiment. The composite material 102 essentially corresponds to the Previously described with reference to Figure 1 composite material, with the difference that according to this embodiment, between the two layers 1 18, 120, a thin, possibly inexpensive indicator layer 300 is introduced. The

Indicator layer 300 is made, for example, of a material which is enriched or highly reflective with specially fluorescents and by means of which, upon contact with the laser beam generated by the device, a characteristic detection radiation is produced which indicates the reaching of the interface between the two layers 1, 18, 120. The indicator layer 300 thus makes it possible to generate a particularly strong signal for identifying the interface.

According to one embodiment, the composite material 102 includes a plurality of such indicator layers 300 each disposed between a layer to be processed and a layer of composite material 102 that is not to be processed.

FIG. 4 shows a flowchart of a method 400 according to FIG

Embodiment. The method 400 for processing a composite material by means of a laser can be carried out, for example, using the apparatus described above with reference to FIGS. 1 and 2. In this case, in a first step 410, the change in the detection radiation is determined using the sensor signal. In a further step 420, the determined change is compared with at least one predetermined change, which represents a characteristic spectral change of the detection radiation which occurs when the interface between the layer to be processed and the layer not to be processed is reached. Depending on the result of this comparison, in a further step 430 at least one control signal is output, by means of which the laser processing can be controlled in such a way that the layer not to be processed is not damaged.

For example, steps 410, 420, 430 are performed continuously to ensure continuous monitoring of the machining process.

FIG. 5 shows a schematic representation of a device 100 according to a

Embodiment. The device 100 for processing a composite material by means of a laser corresponds to the device described with reference to FIG. 1, with the difference that the arrangement of the laser source 106 and the optical sensor 126 with respect to the beam splitter 110 is interchanged. This exemplary embodiment is therefore particularly suitable for realizing a high power variant of the device 100, for example for a device 100 having a laser source 106 with a laser power of more than 100W. According to this embodiment, the transmission channel 104 leads from the

Beam splitter 1 10 via the optional filter 130 to the optical sensor 126. The reflection channel 124 leads from the beam splitter 1 10 to the laser source 106th

According to an embodiment, the workpiece to be processed using the laser beam 108 emitted from the laser source 106 comprises layers with high reflectivity. Such layers in reflection are realized, for example, precisely at wavelengths of 1030 nm-1080 nm with very high reflectivity. The resulting losses in the camera channel, here in the transmission channel 104, ie in transmission, are not critical. In the laser channel, however, such losses would lead to high heat losses and thus instabilities in the system.

FIG. 6 shows a schematic representation of an exemplary beam path through a device 100 according to one exemplary embodiment. This may be the device described with reference to FIG. In particular, the image channel to the optical sensor 126 is shown, which according to this exemplary embodiment comprises the transmission channel 104 through the beam splitter 110.

An objective 650 is arranged in the transmission channel 104 and images an object 652 into an intermediate image 654. Another objective 656, here by way of example a simple embodiment by means of two plano-lens lenses 658, 660, images the intermediate image 654 onto the sensor 126.

This embodiment has the advantage that it can be done vignettierunsgfrei, which is e.g. important for radiometric measures.

For example, if a so-called power sensor were used as the sensor 126, shadowing across the field would occur without the intermediate image 654, e.g. In the case of power measurements, errors are generated or complicated calibration is required.

In one embodiment, the objective 656 is realized by two plano-convex lenses 658, 660. According to an alternative embodiment, the

Implementation of the lens 656 complicated, for example, using 3 to 4 lenses, whereby the lens 656 becomes shorter. Depending on the version, the implementation is also color-corrected. This is advantageous, for example, if the

Lighting used several wavelengths. The beam splitter 1 10 allows further coupling and uncoupling. By way of example, a possible coupling of a laser beam over the reflection channel 124 is shown.

FIG. 7 shows a schematic representation of an exemplary beam path through a device 100 according to one exemplary embodiment. This may be the device described with reference to FIG. In particular, the laser beam 108 is shown running along the reflection channel 124 to the beam splitter 1 10 and from the beam splitter 1 10, for example via the lens 1 14 to the workpiece.

8 shows an exemplary schematic representation of a target material 802 and a sample 803 of the target material or a region that may be "sacrificed." The target material 802 is, for example, a material of a layer of the composite material to be processed.

FIG. 9 shows a schematic representation of an exemplary composite material 102 with three layers arranged one above the other. Laser beams 108 are in

different depths of the composite material 102 penetrated.

According to one exemplary embodiment, parameters are run through and measured for the analysis of the composite material 102, for example systematically. These

Parameter tests, so-called recipes, for example, are retrieved from a server, applied and evaluated by an algorithm. Threshold values resulting therefrom and / or processing recipes are, for example, shown in FIG

Composite database stored and can be retrieved later in the processing of a composite material 102 having workpiece.

In a parameter test, according to one exemplary embodiment, S (z (t), lambda) is first recorded. An algorithm then determines an optimal stop. A verification cycle - with and without release - tests the reproducibility. Then the procedure is applied and the recipe deposited, for example in the

Composite materials database.

Optionally, an additional sensor is placed under the material sample, which is not possible in later use, but which can be used during the parameter test and can provide feedback, a so-called feedback, that can be used to create the recipe. For example, the additional sensor can provide an indication of the remaining material thickness. If an exemplary embodiment comprises a "and / or" link between a first feature and a second feature, this can be read so that the embodiment according to one embodiment, both the first feature and the second feature and according to another embodiment, either only the first Feature or only the second feature.

Claims

claims

1 . Method (400) for processing a first layer (1 18) and a second layer

Layer (120) comprising composite material (102) by means of a laser beam (108), wherein upon impact of the laser beam (108) on a processing region of the composite material (102) material of the composite material (102) is removed, and wherein the method (400) following Steps includes:

Determining (410) a change, in particular a frequency change and / or a change in intensity, using a sensor signal (128) representing a detection radiation (122) emitted from the processing area;

Illuminating the processing area with illumination radiation (144) different from the laser beam (108) to produce at least a portion of the detection radiation (122) as a portion of the illumination radiation reflected from the processing area to identify the defined spectrum of the layer or interface;

Comparing (420) the change with a predetermined change expected in a transition of the processing area from the first layer (1 18) to another layer (120; 300); and

Outputting (430) at least one control signal (134, 138, 140) for controlling the processing depending on a result of comparing the change with the predetermined change.

The method (400) according to one of the preceding claims, comprising a step of emitting the laser beam (108) into the processing area and a step of detecting the sensor signal (128), wherein the step of detecting coincides with or coincides with the step of transmitting is performed.

3. The method (400) according to one of the preceding claims, wherein the

Sensor signal (128) represents a spectrally resolved and / or integrated intensity of the detection radiation (122).

A method (400) according to any one of the preceding claims, comprising a step of determining the predetermined change using the sensor signal (128).

The method (400) of any one of the preceding claims, comprising a step of reading out a value representing a predetermined change from a composite database (150).

The method (400) according to one of the preceding claims, wherein in the step of outputting (430), the control signal (134, 138, 140) is output to stop the processing when the result of the comparing (420) indicates that a value of the change reaches or exceeds a value of the predetermined change.

7. Method (400) according to one of the preceding claims, in which at least a portion of the sensor signal (128) represents an infrared radiation.

8. Method (400) according to one of the preceding claims, in which the

predetermined change, represents a characteristic change, which is expected in a transition of the processing area of the first layer (1 18) in an indicator layer (300) arranged between the first layer (1 18) and the second layer (120).

9. composite material (102) having the following features: at least one first layer (1 18) to be processed by means of at least one laser beam (108); at least one second layer (120) that is not to be processed by the laser beam (108); and at least one indicator layer (300) disposed between the first layer (1 18) and the second layer (120) and configured to emit a detection radiation (122) in a spectrum when in contact with the laser beam (108) Interface between the first layer (1 18) and the second

Layer (120) is characteristic.

10. Apparatus (100) for processing a composite material (102) having a first layer (1 18) and a second layer (120) by means of a laser beam (108), wherein the device comprises units (106, 110, 112, 14) , 126, 130, 132, 136, 142) configured to execute and / or drive the method (400) according to one of claims 1 to 8.

1 1. Device (100) according to claim 1 1, comprising a housing in which the

Units (106, 1 10, 1 12, 1 14, 126, 130, 132, 136, 142) are arranged integrated.

12. Device (100) according to claim 1 1 or 12, comprising a beam splitter (1 10), a laser source (106) for emitting the laser beam (108) and an optical sensor (126) for detecting the sensor signal (128), wherein the optical sensor (126) in a transmission channel (104) and the laser source (106) in one

Reflection channel (124) of the beam splitter (1 10) is arranged, or wherein the optical sensor (126) in the reflection channel (124) and the laser source (106) in the

Transmission channel (104) of the beam splitter (1 10) is arranged.