Device and method for characterising a surface of a sample

Abstract

The invention relates to a device (100) for characterising a surface (102) of a sample (104), comprising: a laser (106) which is designed to irradiate the surface (102) of the sample (104) with an incident laser beam (118); a detector (108) which is designed to capture at least part of the laser beam (120) reflected by the surface (102) of the sample (104); and at least one common lens (112), wherein the incident laser beam (118) and the reflected laser beam (120) are each directed through the common lens (112) and the common lens (112) is designed to fan out the incident laser beam (118) and to focus the reflected laser beam (120) onto the detector (108).

Description

[0001]FRIESE GOEDEN Patentanwälte PartGmbB Widenmayerstraße 49 80538 Munich Our reference: 32000 PWO Applicant: Fraunhofer-Gesellschaft eV Device and method for characterizing a surface of a sample The application relates to a device for characterizing a surface of a sample. Furthermore, the present invention relates to a method for characterizing a surface of a sample. The characterization of sample surfaces serves to determine the surface properties, in particular the surface topography, also known as the surface texture or surface condition, because the surface topography significantly influences the mechanical and physical properties, such as friction, adhesion, oxidation, thermal and electrical conductivity. Such properties are particularly important for materials that are used in advanced technologies and devices (e.g.Advanced coatings, bearings, thermal, optical, and electronic / semiconductor devices are critical to performance: For example, increased surface roughness typically leads to increased friction between two contacting parts. A higher coefficient of friction, in turn, leads to accelerated wear and shortened lifetime. Small irregularities in semiconductor surfaces can cause charge localization and uneven electrical properties. The surface texture often differs from that of the core area due to oxidation, surface tension, impurities, or processing. Material preparation methods such as mechanical or chemical polishing or etching can also lead to surface defects and surface roughness.Against this background, metrological instruments and methods are required to evaluate surface morphology and determine its impact on component properties such as performance, reliability, and service life. The earlier surface defects are detected and surface topography controlled, the greater the benefit, particularly with regard to cost and energy savings for further processing of the defective products, which also benefits environmental protection and sustainable development. Various methods are known from the state of the art, such as scanning probe microscopy, scanning electron microscopy, white light interferometry, and confocal microscopy. One promising method is laser speckle photometry (LSP).This is a non-contact, non-invasive, and non-destructive monitoring technique that enables the characterization of surfaces through the detection and analysis of static or time-resolved dynamic speckle patterns. In laser speckle photometry, a surface is irradiated with an incident laser beam. Reflection from the surface creates interference patterns, known as speckles. These are recorded using a detector, such as a CMOS sensor or a CCD sensor. The surface topography can be determined from the speckles, allowing surface properties, such as roughness, to be determined. For example, DE 102014 224 852 A1 discloses a device for performing an LSP method in which the incident laser beam is shaped or directed by a first lens and thus directed onto the sample surface.At least a portion of the laser beam reflected from the surface of the sample is directed by a second lens onto a detector 3. The problem with this design is that at least two lenses are required to direct the incident laser beam and the reflected laser beam. These at least two lenses must also be focused and controlled independently of one another in order to, on the one hand, focus the incident laser beam on the surface of the sample and, on the other hand, focus at least a portion of the reflected laser beam onto the detector. The present invention is therefore based on the object of further developing a device of the type mentioned at the outset in such a way that its construction and / or operation are simplified. This object can be achieved by a device according to claim 1 and by a method according to claim 12.Possible advantageous developments of the invention can be found in the subclaims. According to a first aspect of the present invention, a device for characterizing a surface of a sample is described. The device has a laser and a detector, wherein the laser is configured to irradiate the surface of the sample with an incident laser beam, and wherein the detector is configured to detect at least a portion of the laser beam reflected from the surface of the sample. In some embodiments, the device can further comprise at least one common lens, wherein the incident laser beam and the reflected laser beam are each directed through the at least one common lens. Furthermore, the common lens is configured to fan out the incident laser beam 32000 PWO CP / GO - 4 / 27 - 17.04.2025 and to focus the reflected laser beam onto the detector.According to a second aspect of the invention, a method for characterizing a surface of a sample is described. The method comprises the following steps: a1) irradiating the surface of the sample with an incident laser beam; b) detecting at least a portion of a laser beam reflected from the surface of the sample with a detector, wherein at least one common lens is configured to fan out the incident laser beam through the lens and to focus the reflected laser beam through the lens onto the detector. In some embodiments of the invention, the laser and the detector can lie in a plane in which the focal point of the lens lies.In some embodiments of the invention, the common lens can have a first region and a second region, wherein the first region is configured to fan out and / or scatter and / or defocus the incident laser beam onto the surface of the sample, and the second region is configured to image the surface of the sample onto the detector. In some embodiments of the invention, the focal length of the first region and the focal length of the second region can be adjustable separately from one another. In some embodiments of the invention, at least one common lens or at least one common objective or at least one lens system can be present, through which both the incident laser radiation and the reflected laser radiation are transmitted or focused. In contrast to the prior art, two separate lenses are therefore not required for the respective 32000 PWO CP / GO - 5 / 27 - 17.04.2025 focusing orDefocusing or widening of the incident and reflected laser radiation is not required, but only at least one common lens that directs both beams and focuses or defocuses them on the surface of the sample or on the detector. In other words, the invention provides for the use of confocal optics to direct both the incident laser radiation and the laser radiation reflected from the surface of the sample. As a result, the construction, operation, and maintenance of the device for carrying out surface characterization, in particular by LSP, are simplified thanks to the presence of the common lens. In some embodiments of the invention, an optical system formed by at least one further lens group in combination with the common lens can widen the laser beam.At the same time, the optical system can focus the camera onto the sample surface so that the speckle pattern (2D image) created by the laser beam irradiation is clearly recorded. Furthermore, in some embodiments, the size of the camera's field of view can be increased or decreased by adjusting the optical system (e.g., by changing the distance between the lens groups), while the working distance of the common lens remains substantially unchanged. Simultaneously with the change in the size of the camera's field of view, the size of the patterns formed on the surface by the laser beam changes accordingly, so that the relative size of the speckle pattern within the camera's field of view is approximately constant. The common lens, which forms part of the confocal optics, can, for example, be part of a more complex optical system, such as a stereomicroscope system.For example, the device can have a stereomicroscope system with a first eyepiece channel and a second eyepiece channel, wherein the laser is coupled to the first eyepiece channel and the detector is coupled to the second eyepiece channel, wherein the at least one common lens is arranged on the side of the first eyepiece channel facing away from the laser and on the side of the second eyepiece channel facing away from the detector. Accordingly, the incident laser beam passes through the first eyepiece channel and the reflected laser beam passes through the second eyepiece channel. The first and second eyepiece channels can have further lenses, which are configured, for example, to focus the incident laser beam and / or the reflected laser beam. The second eyepiece channel can also have further lenses, wherein these further lenses are configured for the purpose of magnification.This makes it possible to use known devices, such as a stereomicroscope system, to characterize the surface of the sample simply and efficiently. The focus of this embodiment lies in the combination of the LSP with a stereomicroscope, i.e. in connecting the two eyepiece channels of the stereomicroscope system to the laser and to the detector, whereby the optical paths of the optical components of the stereomicroscope are used to generate and capture a high-resolution laser speckle pattern on the surface of the sample under investigation. According to one embodiment, the device further comprises a data processing unit which is configured to process the reflected laser beam captured by the detector in such a way that an image is generated.This allows images with speckle patterns to be generated from the portion of the reflected laser beam detected by the detector to characterize the surface. Speckle patterns are a spatial structure with randomly distributed intensity minima and maxima and carry information about the 2D and 3D nature of the surface. Speckle patterns allow for a wide range of applications with regard to materials and their properties. These applications are known to those skilled in the art. In particular, the laser can be configured to irradiate the surface of the sample with a pulsed incident laser beam. For the purposes of this description, "pulsed" means that the laser emits laser beams with a frequency of approximately 0.1 Hz to approximately 100 kHz.In other embodiments of the invention, the laser can emit laser beams with a frequency of approximately 1 Hz to approximately 10 kHz. In yet other embodiments of the invention, the laser can emit laser beams with a frequency of approximately 10 Hz to approximately 1 kHz. In yet other embodiments of the invention, the laser can emit laser beams with a frequency of approximately 100 Hz to approximately 500 Hz. Preferably, the device further comprises an image analysis unit which is configured to analyze the images generated by the data processing unit. As a result, time-resolved speckle patterns can be detected by the detector. These serve to generate time-resolved images of a sample surface. These images can be stored in a storage unit provided for this purpose. The image analysis unit can perform various analyses on one or more images.For example, time-resolved changes in a speckle pattern on the surface of the sample can be recorded, allowing correlation with material parameters through appropriate evaluation. To determine these parameters, a correlation model is created based on reference values, process boundary conditions, and material parameters, the algorithms of which represent process-describing parameters. This allows the image analysis unit to be used for real-time monitoring and has high sensitivity for both out-of-plane and in-plane deformations, as the LSP can measure the spatial-temporal dynamics of the speckle caused by the change in intensity of the reflected laser beams detected by the detector. The image analysis unit can be configured to process the images generated by the data processing unit using conventional image processing methods, such asThresholding methods, edge detection methods, blob analysis methods, and template matching methods are evaluated. The choice of an algorithm or combination of algorithms is made based on the conditions of the surfaces under investigation. Furthermore, the image analysis unit can use object detection models such as YOLO, Faster R-CNN, Mask R-CNN, and Cascade R-CNN to detect foreign objects on the surface under investigation. For example, in an image generated by the data processing unit, the image analysis unit can calculate the speckle size using the half-width of the normalized autocorrelation function according to equation (1). where: AC is the autocorrelation; I is the intensity of a pixel; i,j are the coordinates of the pixel in the image; is the time shift; FT is the Fourier transform; and * is the conjugation. The autocorrelation of a signal is defined as the Fourier transform of the signal's power density. This allows the power spectrum of the speckle image and the inverse power spectrum to be calculated to subsequently obtain the autocorrelation. Furthermore, the image analysis unit can also evaluate the entropy of the histogram of one of the images generated by the data processing unit according to equation (2). (2) where: h(i) is the frequency; and g is the gray value. Furthermore, the images can also be evaluated using the so-called gray level transition matrix (such as the gray level co-occurrence matrix (GLCM)). The grayscale transition matrix is ​​an image processing method for texture analysis.Typical parameters of this evaluation are:. Energie correlation homogeneity contrast where: is the row and column number of the GLCM is the entry of the GLCM; 32000 PWO CP / GO - 10 / 27 - 04 / 17 / 2025 The Energy E ngy provides the sum of the squared elements in the GLCM, also known as the second angular moment. The correlation Cr measures the joint probability of occurrence of the specified pixel pairs. The homogeneity H m measures the proximity of the distribution of elements in the GLCM to the GLCM diagonal, and the contrast C t measures the local variations in the GLCM. Furthermore, the image analysis unit can also be configured to calculate the standard deviation D of the gray values ​​of the acquired speckle patterns as a static parameter according to Equation 11: N is the total number of pixels of the acquired speckle pattern and is the average gray value of all pixels. The parameters calculated from the static speckle pattern described above can be correlated with the topological properties (e.g., roughness) of the sample to be examined. According to one embodiment, the device further comprises an image display unit configured to display the image. This allows the generated images to be visualized so that the recorded patterns can be evaluated by a user of the device. According to one embodiment, the device can further comprise a light source configured to irradiate the surface of the sample with incoherent light. This allows, on the one hand, reference images of the surface of the sample to be recorded, and, on the other hand, the light source can be used to focus the laser and / or the detector.The light source can therefore be used to support the measurement and / or for additional characterization of the surface by the device. According to one embodiment, the device further comprises a control unit configured to alternately switch on the laser and the light source. This makes it possible to automate the adjustment of the focus for the laser or for the detector and / or the recording of reference images. According to one embodiment, the control unit can be configured to alternately switch on the laser and the light source for between approximately 1 µs and approximately 1 s each. According to another embodiment, the control unit can be configured to alternately switch on the laser and the light source for between approximately 1 µs and approximately 1 ms each.According to yet another embodiment, the control unit can be configured to switch on the laser and the light source alternately for approximately 1 ms and approximately 1 s respectively. A shorter switch-on time between 1 µs and 1 ms can be advantageous, for example, in the case of an inline inspection. An inline inspection is an inspection carried out on products that are continuously conveyed to the device by a conveyor belt. In this case, short switch-on times are advantageous in order to enable high conveying rates. According to one embodiment, the control unit can be configured to switch on the laser and the light source alternately for approximately 10 µs and approximately 100 µs respectively. According to one embodiment, the control unit can be configured to switch on the laser and the light source alternately for approximately 20 µs and approximately 90 µs respectively.According to one embodiment, the control unit can be configured to switch on the laser and the light source alternately for approximately 30 µs and approximately 80 µs, respectively. According to one embodiment, the 32000 PWO CP / GO - 12 / 27 - April 17, 2025 control unit can be configured to switch on the laser and the light source alternately for approximately 40 µs and approximately 70 µs, respectively. According to one embodiment, the control unit can be configured to switch on the laser and the light source alternately for approximately 45 µs and approximately 55 µs, respectively. A longer switch-on time between 1 ms and 1 s can be advantageous, for example, for an offline inspection. An offline inspection is an inspection performed by a user of the device on individual products without them being transported by a conveyor belt. In this case, longer switch-on times are advantageous to enable longer exposure times and, thus, more detailed speckle patterns.According to one embodiment, the control unit can be configured to switch on the laser and the light source alternately for approximately 10 ms and approximately 100 ms, respectively. According to one embodiment, the control unit can be configured to switch on the laser and the light source alternately for approximately 20 ms and approximately 90 ms, respectively. According to one embodiment, the control unit can be configured to switch on the laser and the light source alternately for approximately 30 ms and approximately 80 ms, respectively. According to one embodiment, the control unit can be configured to switch on the laser and the light source alternately for approximately 40 ms and approximately 70 ms, respectively. According to one embodiment, the control unit can be configured to switch on the laser and the light source alternately for approximately 45 ms and approximately 55 ms, respectively.According to one embodiment, the control unit can be configured to alternately switch on the laser and the light source for approximately 0.1 ms and approximately 100 ms, respectively. According to one embodiment, the control unit can be configured to alternately switch on the laser and the light source for approximately 0.2 ms and approximately 50 ms, respectively. According to one embodiment, the control unit can be configured to alternately switch on the laser and the light source for approximately 0.3 ms and approximately 25 ms, respectively. According to one embodiment, the detector is a CCD or a CMOS sensor. This allows conventional detectors to be used to detect the reflected laser beams. According to one embodiment, the detector has a recording rate of approximately 0.001 Hz to approximately 100 kHz. In another embodiment, the detector has a recording rate of approximately 0.01 Hz to approximately 10 kHz.In yet another embodiment, the detector has a recording rate of approximately 0.1 Hz to approximately 1 kHz. In yet another embodiment, the detector has a recording rate of approximately 10 Hz to approximately 100 Hz. According to one embodiment, the detector is a two-dimensional sensor. This allows two-dimensional images or patterns to be captured with little effort. According to one embodiment, the device further comprises a sample holder. This allows the sample whose surface is being characterized to be securely picked up and held. According to one embodiment, the sample holder is configured to remove the sample from a conveyor system and / or to analyze the sample on a conveyor system.As a result, the device can be used in an in-line process in which the characterization of the surface is integrated into the production process, or in an offline process in which the surface is characterized as a maintenance measure. 32000 PWO CP / GO - 14 / 27 - April 17, 2025 According to one embodiment, the laser beam has a wavelength between approximately 261 nm and approximately 1700 nm. In another embodiment, the laser beam has a wavelength between approximately 261 nm and approximately 500 nm. In yet another embodiment, the laser beam has a wavelength between approximately 500 nm and approximately 750 nm. In yet another embodiment, the laser beam has a wavelength between approximately 750 nm and approximately 1000 nm. In yet another embodiment, the laser beam has a wavelength between approximately 100 nm and approximately 1700 nm.In some embodiments, the laser may be a UV laser with a wavelength between approximately 261 nm and approximately 355 nm, or a visible laser with a wavelength between approximately 500 nm and approximately 520 nm, or a visible laser with a wavelength between approximately 380 nm and approximately 780 nm, or an IR laser with a wavelength between approximately 780 nm and approximately 1000 nm. According to one embodiment, the light source for incoherent light is an LED, a superluminescent diode, or a fluorescent lamp. In some embodiments of the invention, the light source for incoherent light may be a ring light that surrounds the at least one common lens in a ring shape. According to one embodiment, the method comprises the following further steps: c2) processing the reflected laser beam detected by the detector into a data set; d) creating an image based on the data set.According to one embodiment, the method comprises the following further step: a2) Illuminating the surface of the sample with an incoherent light beam. 32000 PWO CP / GO - 15 / 27 - April 17, 2025 According to one embodiment, the irradiation of the surface with the incident laser beam and the illumination of the surface with the incoherent light beam take place alternately. According to one embodiment, the surface of the sample can be illuminated or irradiated only with the incoherent light beam. According to one embodiment, the surface of the sample can be illuminated or irradiated with both the incident laser beam and the incoherent light beam. This can take place simultaneously or alternately. In the present invention, all structural features can also be part of a method claim, and all procedural features can be part of a subject-matter claim.The invention will now be explained in more detail with reference to the accompanying drawings, without limiting the general inventive concept. Figure 1 shows a device according to one embodiment of the present invention. Figure 2 shows a flow chart of a method according to one embodiment of the invention. Figure 3 shows a calibration measurement of a sample showing a correlation between the surface roughness of the sample surface and the entropy of the histogram of the speckle pattern of the sample surface. Figure 4 shows speckle patterns generated on two sample surfaces with different degrees of polishing. 32000 PWO CP / GO - 16 / 27 - 04 / 17 / 2025 Figure 5a shows speckle patterns of a sample consisting of a thin copper foil (approximately 20 µm), one half of which is coated with a resin layer. Figure 5b shows the results of calculating the speckle parameters for several samples according to Figure 5a, with and without a resin layer.Figure 1 shows a device 100 for characterizing a surface 102 of a sample 104 according to an embodiment of the present invention. The device 100 has at least one laser 106, at least one detector 108, and a stereomicroscope system 110 with at least one common lens 112. The laser 106, which can be, for example, a UV laser, a visible laser, or an IR laser, is connected to a first eyepiece channel 114 of the stereomicroscope system 110. The detector 108 is connected to a second eyepiece channel 115. The first eyepiece channel 114 and the second eyepiece channel 115 are arranged on an optical system 116 formed from a lens group, for example, a body of the stereomicroscope system 110. The at least one common lens 112 is arranged on the side of the optical system 116 opposite the first eyepiece channel 114.The optical system 116 can, for example, comprise one or more lenses for directing and / or focusing an incident or reflected laser beam. The laser 106 emits an incident laser beam 118, which is directed through the first eyepiece channel 114, through the optical system 116, and the common lens 112 such that the incident laser beam 118 irradiates or illuminates at least a partial area of ​​the surface 102. 32000 PWO CP / GO - 17 / 27 - 17.04.2025 The incident laser beam 118 is scattered by the rough surface 102 of the sample 104, creating an interference pattern (speckle pattern). This is directed as a reflected laser beam 120 through the common lens 112, the optical system 116, and the second eyepiece channel 115 to the detector 108. The detector 108 detects the reflected laser beam 120. The detector 108 may be or include a CMOS sensor or a CCD sensor.Furthermore, the detector 108 can be a two-dimensional sensor or a one-dimensional sensor (line scan sensor). The optical path of the incident laser beam 118 and the optical path of the reflected laser beam 120 through the optical system 116 can have further common lenses. The common lens 112 can be configured to spread the incident laser beam, which is directed by the common lens. Furthermore, the common lens 112 can be configured to focus the reflected laser beam, which is directed by the common lens, onto the detector. In some embodiments of the invention, an optical system 116 containing a further lens group, in combination with the common lens 112, can expand the laser beam.At the same time, the optical system can focus the camera on the sample surface so that the speckle pattern (2D image) created by the laser beam irradiation is clearly recorded. Furthermore, in some embodiments, the size of the camera's field of view can be increased or decreased by adjusting the optical system 116 (e.g., by changing the distance between the lens groups), while the working distance of the common lens 112 remains unchanged. 32000 PWO CP / GO - 18 / 27 - 17.04.2025 Regardless of the change in the size of the camera's field of view, the size of the patterns formed on the surface by the laser beam changes accordingly, so that the relative size of the speckle pattern within the camera's field of view is approximately constant.Furthermore, the device 100 has a sample holder 122, which is configured to hold the sample 104 during the characterization of the surface 102 and, if necessary, to remove the sample 104 from a conveyor system not shown in detail here. In some embodiments, the sample holder 122 can be part of a conveyor system of a production plant, so that measurement is possible during ongoing production. This enables both in-line and offline characterization of the surface 102, for example, to determine a change in the surface condition of the surface 102. Before measuring the speckle image by switching on the laser and detecting the reflected laser beam 120, the focus can be adjusted by adjusting the distance between the at least one common lens 112 and the surface of the sample.Due to the confocal design with at least one common lens 112, adjusting the focus position is significantly simplified because the focus of the incident laser beam and the focus of the detector are influenced simultaneously. The device 100 further comprises a computer 124 with a data processing unit 126, a storage unit 128, an image analysis unit 130, and a control unit 132. The data processing unit 126 can be configured to generate data sets from the reflected laser beam 120 detected by the detector 108 and to store these data sets as an image in the storage unit 128. 32000 PWO CP / GO - 19 / 27 - 17.04.2025 These images can be shown to a user via an image display unit (not shown in detail here), such as a monitor.The image analysis unit 130 can be configured to analyze the images stored in the storage unit 128 and to extract information about the surface properties of the surface 102 from them. For example, the image analysis unit 130 can perform a calibration measurement of an LSP method for the surface 102 and thereby determine a correlation between the surface roughness of the surface 102 and the entropy E. nt of the histogram of the images. The entropy E nt of the histogram of the images is determined using equation (2). Such a calibration measurement with correlation between the surface roughness of the surface 102 and the entropy E ntThe histogram of the images is shown in Figure 3. The calibration measurement was performed on battery electrode samples (graphite on copper foil). The reference surface roughness of the surface 102 of the sample 104 was determined using infinite focus microscopy. The results show that the LSP parameters are monotonically correlated with the surface roughness. The control unit 132 can be configured to control the laser 106 and the detector 108. In particular, the control unit 132 can determine the recording rate of the detector 108. This can be between approximately 0.001 Hz and approximately 100 kHz. The device 100 also features a light source 134, which can be an LED, a superluminescent diode, or a fluorescent lamp, and which is configured to irradiate the surface 102 of the sample 104 with an incoherent light beam (not shown in detail here). 32000 PWO CP / GO - 20 / 27 - 17.04.2025 This serves, on the one hand, to record reference images of the surface 102 of the sample 104 using the detector 108 and, on the other hand, to be able to focus both the incident laser beam 118 on the surface 102 and the reflected laser beam 120 on the detector 108. For this purpose, the optical system 116 is monitored and controlled by the control unit 132. The control unit 132 can also be configured to switch on the laser 108 and the light source 134 alternately, in particular at time intervals between approximately 0.01 ms and approximately 1 ms and / or between approximately 0.05 ms and approximately 0.5 ms and / or between approximately 0.1 ms and approximately 0.3. According to one embodiment, control unit 132 generates trigger signals for the laser 106, the light source 134, the detector 108 and the optical system 116 in a predefined order when it receives an input signal.The input signal to the control unit 132 can be sent either by a user of the device 100 for an offline inspection or by a machine or an encoder for an inline inspection. Figure 2 shows a flowchart of a method according to an embodiment of the invention. The control unit 132 generates trigger signals for the laser 106, the light source 134, the detector 108, and the optical system 116 in a predefined order when it receives an input signal. The input signal to the control unit 132 can be sent either by the inspector for an offline inspection or by a machine or an encoder for an inline inspection. The measurement data recorded by the detector 108 as reflected laser beams is stored in the storage unit 128. 32000 PWO CP / GO - 21 / 27 - 17.04.2025 The measurement data are forwarded to various operation modules of the image analysis unit 130 for further evaluation.These modules may, for example, include a first module 136 for static evaluations using speckle parameters according to equations (1) to (11) and a second module 138 for image processing or AI evaluations. The first and second modules 136, 138 can run in parallel using a single measurement file. The results of both operation modules are sent to an LSP database 140 to consolidate all results obtained from the same measurement position. The final evaluation results in the form of images or patterns are transmitted to the image display unit 142 to display the results in real time. If necessary, a deep learning module can be integrated into the LSP database 140 to classify the quality of the tested samples and can also provide a feedback signal to the device 100 to optimize the process parameters for inline application.Figure 4 shows speckle patterns created on two sample surfaces with different degrees of polishing. By observing the speckle patterns, the degree of polishing can be qualitatively distinguished. The defects / inhomogeneities on the surfaces show contrast-enhancing features (more white or black), which are marked in the images. Figure 5a shows a speckle pattern of a sample consisting of a thin copper foil (approximately 20 µm), with one half of the sample coated with a resin layer. Figure 5b shows the results of calculating the speckle parameters for several samples according to Figure 5a, with and without a resin layer. The results show that, based on the speckle parameters, the sample area with a resin layer can be distinguished from the sample area without a resin layer. Figure 5b determines the standard deviation D of the gray values ​​for the acquired speckle patterns of several samples with and without a resin layer.Of course, the invention is not limited to the illustrated embodiments. The above description is therefore not to be considered restrictive, but rather explanatory. The following claims are to be understood in such a way that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Where the claims and the above description define "first" and "second" embodiments, this designation serves to distinguish between two similar embodiments without establishing a priority.

Claims

32000 PWO CP / GO - 23 / 27 - April 17, 2025 Claims 1. A device (100) for characterizing a surface (102) of a sample (104), comprising: a laser (106) configured to irradiate the surface (102) of the sample (104) with an incident laser beam (118); a detector (108) configured to detect at least a portion of the laser beam (120) reflected from the surface (102) of the sample (104); characterized in that the device (100) further comprises at least one common lens (112), wherein the incident laser beam (118) and the reflected laser beam (120) are each directed through the common lens (112), and the common lens (112) is configured to fan out the incident laser beam (118) and to focus the reflected laser beam (120) onto the detector (108).2.The device (100) of claim 1, further comprising a data processing unit (126) configured to process the reflected laser beam (120) detected by the detector (108) to generate an image.

3. The device (100) of claim 2, further comprising an image display unit (142) configured to display the image.

4. The device (100) of any one of claims 1 to 3, further comprising a light source (134) configured to do so. 32000 PWO CP / GO - 24 / 27 - 17.04.2025 is configured to irradiate the surface (102) of the sample (104) with an incoherent light beam.

5. The device (100) according to claim 4, further comprising a control device (132) configured to alternately switch the laser (106) and the light source (134).

6. Device (100) according to claim 5, characterized in that the control unit (132) is configured to switch on the laser (106) and the light source (134) alternately between 0.01 ms and 1 ms, or that the control unit (132) is configured to switch on the laser (106) and the light source (134) alternately between 0.05 ms and 0.5 ms, or that the control unit (132) is configured to switch on the laser (106) and the light source (134) alternately between 0.1 ms and 0.3 ms.7.Device (100) according to one of claims 1 to 6, characterized in that the detector (108) is a CCD or a CMOS sensor and / or that the detector (108) has a recording rate of approximately 0.01 Hz to approximately 10 kHz and / or that the detector (108) has a recording rate of approximately 0.1 Hz to approximately 1 kHz and / or that the detector (108) has a recording rate of approximately 10 Hz to approximately 100 Hz and / or that the detector (108) is a two-dimensional sensor.

8. Device (100) according to one of claims 1 to 7, further comprising a sample holder (122).

9. Device (100) according to claim 8, characterized in that the sample holder (122) is configured to. 32000 PWO CP / GO - 25 / 27 - 17.04.2025 is to remove the sample (104) from a conveyor system and / or that the sample holder (122) is designed to fix the sample (104) on a conveyor system and / or that the sample holder (122) is part of a conveyor system.

10. Device (100) according to one of claims 1 to 9, characterized in that the laser beam (106) has a wavelength between 261 nm and 1700 nm and / or that the laser beam (106) has a wavelength between 261 nm and 500 nm and / or that the laser beam (106) has a wavelength between 500 nm and 750 nm and / or that the laser beam (106) has a wavelength between 500 nm and 520 nm and / or that the laser beam (106) has a wavelength between 750 nm and 1000 nm.11.Device (100) according to one of claims 1 to 10, wherein the light source (134) is an LED or a superluminescent diode or a fluorescent lamp and / or wherein the light source (134) is a ring light.

12. Method for characterizing a surface (102) of a sample (104), the method comprising the following steps: a1) irradiating the surface (102) of the sample (104) with an incident laser beam (118); b) detecting at least a portion of a laser beam (120) reflected from the surface (102) of the sample (104) with a detector (108), characterized in that the incident laser beam (118) and the reflected laser beam. 32000 PWO CP / GO - 26 / 27 - 17.04.2025 Laser beam (120) is directed through at least one common lens (112), wherein the common lens (112) spreads out the incident laser beam (118) and the reflected laser beam (120) is focused onto the detector (108) by the common lens (112).

13. The method according to claim 12, wherein the method includes the following further steps: c2) processing the reflected laser beam (120) detected by the detector (108) into a data set; d) creating an image based on the data set.

14. Method according to claim 12 or 13, wherein the method includes the following further steps: a2) illuminating the surface (102) of the sample (104) with an incoherent light beam or a2) alternately irradiating and illuminating the surface (102) with the incident laser beam (118) and the incoherent light beam.15.Method according to one of claims 12 to 14, wherein, with an optical system (116) containing at least one further lens group in combination with the common lens (112), the size of the field of view of the camera and the size of the patterns formed by the laser beam (118) on the surface (102) are increased or reduced by adjusting the optical system (116), while the working distance of the common lens (112) remains approximately unchanged.

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