Method for analyzing a workpiece surface for a laser machining process and analysis device for analyzing a workpiece surface

Abstract

The invention relates to a method for analyzing a workpiece surface for a laser machining process, comprising the following steps: emitting a light line of light of a first wavelength range onto a region of the workpiece surface and illuminating the region of the workpiece surface with light of at least one second wavelength range; taking an image of the region of the workpiece surface by means of a sensor device, the sensor device comprising an image sensor and optics for imaging light onto the image sensor, wherein the optics have different refractive indices for the first wavelength range and the second wavelength range, wherein a first plane defined by the light line and a light exit point of the light, the optics and the image sensor are arranged in a Scheimpflug arrangement; analyzing the image on the basis of a predetermined offset between the first plane and a second plane for analyzing a feature of the workpiece surface (22), for which the second wavelength range of light is sharply imaged by the optics (16) onto a sensor plane of the image sensor. The invention also relates to an analysis device which is provided for carrying out the method.

Description

Technical Field

[0001] This invention relates to a method for analyzing the surface of a workpiece used in a laser processing process, and an analytical apparatus for analyzing the workpiece surface. The invention also relates to a method for processing a workpiece using a laser beam, including this method, and a laser processing head equipped with such an analytical apparatus. Background Technology

[0002] In a laser processing system used to process workpieces using a laser beam, a laser beam emitted from one end of a laser source or laser guiding fiber is focused or concentrated onto the workpiece to be processed with the aid of beam guiding and focusing optics. Processing can include methods for joining workpieces, such as laser welding or laser brazing. The laser processing system can include laser processing equipment, such as a laser processing head, especially a laser welding head. To ensure quality and for adjustment, it is necessary to monitor the laser processing process.

[0003] Current solutions for monitoring laser processing include pre-processing, in-processing, and post-processing monitoring processes or systems. In joining, pre-processing monitoring is tasked with probing the joining area, particularly the joint gap, to guide the laser beam to the corresponding position or to determine the offset of the joining partner. In-processing and post-processing monitoring are typically used to monitor the laser processing and ensure the quality of the resulting joint. Post-processing monitoring, also known as post-processing inspection, is particularly important for quality control because it allows for the inspection of the resulting weld and measurement based on applicable standards (e.g., SEL100). The parameters or characteristics to be measured are typically edge offset, joint cross-section, and the concavity or convexity and under- or over-curved nature of the weld. The coatings on high-strength steel and the coatings that must be removed before welding necessitate additional coating measurements or removal measurements when monitoring the laser processing.

[0004] For these tasks, 3D methods are now used to monitor the three-dimensional height profile of a workpiece surface. Also known as "geometry". For this purpose, laser triangulation methods or laser optical sectioning (Laserlichtschnittverfahren) or devices, especially Scheimpflug sensors, are typically used. Here, a fan-shaped beam of light, i.e., a beam propagating in only one plane, is emitted onto the surface of the workpiece to produce light lines (Lichtlinie). An image is captured from the light lines using an image sensor at an angle to the emission direction. The captured image is then analyzed to detect the pose and / or shape of the light lines in the image. Based on this, the geometry of the workpiece surface can be inferred.

[0005] Furthermore, 2D methods are used, in which images of the workpiece surface are captured, particularly grayscale images, and surface analysis is performed using image processing. This improves the identification of welds and other features of the workpiece surface. For example, inhomogeneities and pinholes on the weld surface can be detected, and welds can be reliably distinguished from or separated from unprocessed workpiece surfaces. In practice, capturing images of the workpiece surface in parallel or simultaneously with laser cutting becomes difficult due to the following reasons.

[0006] On the one hand, using an image sensor oriented parallel to the workpiece surface to capture images (i.e., when imaging parallel to the workpiece surface) provides depth of field in the direction perpendicular to the workpiece surface. Very minor drawbacks. This results in high overhead during analysis and processing, as well as in the orientation of the image sensor, and requires, for example, a highly precise clamping device for parallel imaging with additional illumination.

[0007] On the other hand, as described in DE 10 2011 012 729 A1, grayscale images created by an image sensor used for laser cutting based on the intensity of laser lines reflected from the workpiece surface often only provide a low-contrast grayscale image of the workpiece surface, because the maximum intensity of the laser lines is typically within the saturation range of the image sensor. Similarly, obtaining grayscale images based on the scattered light from the laser lines has the disadvantage of achieving a small amount of contrast. Furthermore, the typical “spotting” effect of the laser lines results in uneven illumination of the workpiece surface. Additional illumination of the workpiece surface cannot eliminate this disadvantage, because the depth of field in the plane parallel to the workpiece surface is very small and is further limited by the presence of bright laser lines in this region. Therefore, even combining laser cutting with additional illumination and parallel imaging, as described in EP 1 448 334 A1, only results in a small depth of field. Summary of the Invention

[0008] One objective of this invention is to provide a method that can not only detect the three-dimensional height profile of a workpiece surface, but also capture two-dimensional images of the workpiece surface. Furthermore, another objective of this invention is to provide a method that can capture two-dimensional images, particularly grayscale images, of the workpiece surface in parallel or simultaneously with optical sectioning methods used for three-dimensional data detection, under large depth of field.

[0009] Furthermore, one objective of this invention is to provide a method for improving contrast and depth of field, particularly in parallel or simultaneously with optical sectioning, when capturing images of a workpiece surface. Additionally, another objective of this invention is to provide a method for achieving a high contour scanning rate when reading out an image sensor.

[0010] Finally, one objective of the present invention is to describe an apparatus configured to perform the method.

[0011] The aforementioned task is addressed by the subject matter of the independent claims. Advantageous configurations and extensions are the subject matter of the dependent claims.

[0012] This invention is based on the concept of using a sensor device with an image sensor and optics for three-dimensional inspection of a workpiece surface using optical sectioning or optical sectioning triangulation methods. The optics have different refractive indices for a first wavelength range and a second wavelength range. In this way, the optics have different focal planes for these two wavelength ranges, which are clearly imaged onto the sensor plane of the image sensor using a Scheimpflug arrangement. This characteristic of the optics allows for the simultaneous acquisition of clear images of light lines reflected from the workpiece surface for optical sectioning, and the acquisition of clear images of a portion of the workpiece surface spaced apart from the light lines. With this invention, the portion of the workpiece surface clearly imaged for the second wavelength range is spatially separated from the clearly imaged light lines for the first wavelength range on the sensor plane. Therefore, the sensor device does not need to include a color filter, and the same image sensor or the same sensor device can be used for detecting the height profile of the workpiece surface and for capturing a grayscale image of the workpiece surface. Furthermore, a height profile can be created from a first portion of the workpiece surface, and a grayscale image can be created simultaneously from a second portion of the workpiece surface. By repeatedly capturing images—that is, by sampling or scanning the workpiece surface—and taking into account known offsets, height profile data and grayscale image data can be merged accordingly to obtain a three-dimensional height profile and a two-dimensional grayscale image with a large depth of field from the same area of ​​the workpiece surface. Under red illumination, the depth of field of the resulting grayscale image can be increased from approximately ±0.5 mm to approximately ±5 mm, in the case of 1:1 imaging onto a 1-inch (Zoll) sensor, where a 10 mm x 10 mm image area approximately corresponds to the sensor size.

[0013] According to a first aspect of the invention, a method for analyzing the surface of a workpiece used in a laser processing process is described. The method includes the steps of: emitting a light ray of light in a first wavelength range onto a region of the workpiece surface and illuminating the region of the workpiece surface with light in at least one second wavelength range; capturing an image of the region of the workpiece surface using a sensor device comprising an image sensor and optics for imaging light onto the image sensor, wherein the optics have different refractive indices for the first wavelength range and the second wavelength range, wherein the image sensor (or a sensor plane of the image sensor), the optics, and a first plane defined by the light ray and the light emission point of the first wavelength range are arranged in a Scheimpflug arrangement; and analyzing the image based on a predetermined offset between the first plane and the second plane for analyzing features of the workpiece surface, wherein, for the second plane, the light in the second wavelength range is imaged sharply or focusedly onto the image sensor (or the sensor plane of the image sensor) by the optics.

[0014] In other words, the method according to the first aspect includes the following steps: emitting a fan-shaped beam of light in a plane of a first wavelength range to generate light lines in a region of a workpiece surface, and illuminating that region of the workpiece surface with light in a second wavelength range; capturing an image of that region of the workpiece surface using a sensor device, the sensor device including an image sensor and optics for imaging light onto the image sensor, wherein the optics have different refractive indices for the first wavelength range and the second wavelength range, wherein the first plane defined by the plane of the fan-shaped beam, the optics, and the image sensor are arranged in a Scheimpflug arrangement; and analyzing the image based on a predetermined offset on the workpiece surface between the first plane and the second plane to analyze features of the workpiece surface, wherein, for the second plane, light in the second wavelength range is imaged onto the image sensor by the optics.

[0015] The first plane, the optics, and the image sensor, or the sensor plane of the image sensor, are arranged in a Scheimpflug arrangement and thus satisfy the Scheimpflug condition. In other words, the first plane, the plane passing through the optics perpendicular to the optical axis, and the sensor plane of the image sensor have a common intersecting line. Accordingly, the second plane, the optics, and the sensor plane of the image sensor can also be arranged in a Scheimpflug arrangement.

[0016] The first wavelength range and the second wavelength range are preferably different from each other and / or spaced apart. Preferably, the two wavelength ranges are so different that sufficient offset can be ensured. The first wavelength range and the second wavelength range can be relatively narrow wavelength ranges, for example, the wavelength ranges can be less than 50 or even less than 30 nanometers wide. The distance between the first wavelength range and the second wavelength range can be 100 nanometers or more. The light in the first wavelength range can include or be blue light, preferably light with a wavelength in the range of 400 to 500 nanometers, especially light with a wavelength of 450 nanometers. The light in the second wavelength range can include or be red light, preferably light with a wavelength in the range of 600 to 700 nanometers, especially light with a wavelength of 660 nanometers. The image sensor is preferably sensitive to both wavelength ranges.

[0017] A light ray emitting light in a first wavelength range may include emitting a planar fan-shaped beam of light to generate a light ray on the surface of a workpiece. The first planar plane may correspond to a plane of the fan-shaped beam. In other words, the first planar plane may be defined by the light ray and the light exit point of the first wavelength range (especially the light exit point from the irradiation unit). The first planar plane may correspond to the focal plane of an optics for the first wavelength range or to a plane for which the light in the first wavelength range is (sharply or focusedly) imaged onto an image sensor or the sensor plane of an image sensor by an optics. The first planar plane is preferably arranged perpendicular to the workpiece surface. The first planar plane may include a light ray used for optical sectioning or triangulation methods. Therefore, the first planar plane may also be referred to as a "triangulation plane." A second planar plane may correspond to the focal plane of an optics for a second wavelength range.

[0018] The first plane and / or the second plane may intersect the workpiece surface. The first plane may intersect the workpiece surface at a first intersection line. The second plane may intersect the workpiece surface at a second intersection line. The first and second intersection lines are spaced apart from each other. The distance between the two intersection lines may also be referred to as the offset.

[0019] Furthermore, there exists a certain depth of field range within which points are sufficiently clearly imaged onto the image sensor by the optics for light in either a first wavelength range or a second wavelength range, for subsequent image analysis processing. Therefore, a first partial region of the workpiece surface (enclosing the intersection line of the first plane and the workpiece surface) and a second partial region of the workpiece surface (enclosing the intersection line of the second plane and the workpiece surface) are clearly imaged onto the image sensor. The first partial region may include or correspond to the depth of field range of the optics for light of the first wavelength. The second partial region may include or correspond to the described depth of field range of the optics for light of the second wavelength. The region of the workpiece surface surrounding the first intersection line may also be referred to as the first sharpness region or the first partial region. Correspondingly, the region of the workpiece surface surrounding the second intersection line may also be referred to as the second sharpness region or the second partial region. The offset is preferably chosen such that the two partial regions are spaced apart from each other. Based on the offset and the predetermined or known depth of field of the optics for light of the first wavelength range or light of the second wavelength range, the distance between the first and second partial regions of the workpiece surface can be determined. Therefore, light lines in the first wavelength range will not be located in the second region where light in the second wavelength range is clearly imaged. Since these light lines, such as laser lines, are not located in the second region, the image of the workpiece surface in that region will not be interfered with by the bright light lines. In this way, the contrast of the image captured in the second region will not be affected by the intensity of the light lines. Therefore, the contrast in the captured image for the second region of the workpiece surface can be increased. Thus, the present invention enables image capture by utilizing the large measurement range of the Scheimpflug arrangement.

[0020] The predetermined offset can be a pre-determined or known offset. This offset may depend on the optics, particularly on the respective refractive indices of the optics for a first wavelength range and a second wavelength range, and / or on the arrangement of the optics relative to the workpiece surface. The arrangement of the optics can describe the distance and / or orientation of the optics relative to the workpiece surface. The offset can be modeled, calculated, or determined by calibration measurements. The offset can be described with respect to the workpiece surface (e.g., as the distance between the first and second intersection lines) or along the optical axis of the optics.

[0021] In addition to using light of the second wavelength range to generate a second partial region on the workpiece surface, the method can be extended as follows: irradiation with at least one additional, i.e., a third wavelength range, the imaging of which causes a focus shift within the depth of field of the second wavelength range. Therefore, the surface that is clearly imaged can be magnified. Preferably, at least one additional irradiation unit is provided, configured to irradiate the workpiece surface with light of the third wavelength range. Alternatively, the irradiation unit can be configured to irradiate the workpiece surface with light of both the second and third wavelength ranges. The center wavelengths of the second and third wavelength ranges are preferably spaced apart from or offset from each other. Preferably, the wavelength ranges used for irradiation (i.e., especially the second and third wavelength ranges) do not overlap, but are adjacent to or spaced apart from each other. By irradiating with light of the third wavelength range, a third plane can be formed, for which the light of the third wavelength range is imaged onto an image sensor by an optics device, or a third partial region is generated on the workpiece surface, the third partial region surrounding the intersection line of the third plane and the workpiece surface. For each of the wavelength ranges used for irradiation, i.e., especially the second and third wavelength ranges, the optics preferably have a different refractive index. When analyzing and processing the image, a predetermined offset on the workpiece surface between the first and third planes can additionally be taken into account. Image analysis and processing can also include analyzing and processing intensity data of light in a third wavelength range in the region of the image corresponding to the third partial region to obtain a grayscale image of the third partial region. This can be applied to any number of wavelength ranges used for illumination. In particular, the multiple wavelength ranges used for illumination can be selected such that corresponding partial regions on the workpiece surface are adjacent to each other. In other words, the multiple wavelength ranges used for illumination can be selected such that, in the case of clear imaging, the focal length shift corresponds to the depth of field range of the image. Then, workpiece surfaces with clear imaging at different wavelengths are adjacent to each other. Preferably, the illumination unit has a continuous spectrum from which the first wavelength range has been removed, for example, by a filter. When using the continuous spectrum of the illumination unit, the illumination unit can achieve clear imaging of a continuous region of the surface by means of an implementation filter, such as an edge filter or a Notch filter, to cut off the first wavelength range. This region is limited by the depth of field of the optics, but is independent of color imaging errors.

[0022] Therefore, within the depth of field, regardless of the workpiece's depth, the area surrounding the laser line can be clearly imaged. Due to color errors in the optics, a plane produced by illumination with wavelengths offset from each other and offset from the laser line wavelength (i.e., from the first wavelength range) can also be clearly imaged. Thus, a clearly imaged workpiece surface can be magnified.

[0023] The sensor plane of an image sensor may include the sensor surface of the image sensor, onto which light is emitted to capture an image.

[0024] The image can be captured based on light reflected from the surface of the workpiece. The captured image can be, or may include, color images, brightness images, and / or intensity images.

[0025] The analysis and processing of the captured images may include analyzing the light intensity within a first wavelength range, for example, through triangulation or optical sectioning, to generate a (preferably three-dimensional) height profile of the workpiece surface, and / or analyzing the light intensity within a second wavelength range, for example, through image analysis or image processing, to generate a two-dimensional grayscale image. The image analysis and processing may include row-by-row and / or column-by-column analysis of the image.

[0026] Image analysis may include analyzing the brightness or intensity information contained in the image regarding light within a first wavelength range reflected from the workpiece surface. Image analysis may also include detecting the position and pose (Lage) of light lines imaged in the image. Based on this, triangulation or optical sectioning may be performed to detect features of the workpiece surface (e.g., joint edges, joint gaps, or welds) such as position, pose, height, and / or extension dimensions.

[0027] Image analysis may include analyzing brightness or intensity information contained in the image regarding light in a second wavelength range, the second wavelength range being reflected by the area of ​​the workpiece surface surrounding the second intersection line, which is also the second sharpness area or the second partial area.

[0028] The offset, i.e., the distance between the intersection lines of the first plane and the workpiece surface and the second plane and the workpiece surface, is predetermined or known. Therefore, it is also known where and in what pose the second portion of the workpiece surface is imaged in the image. Thus, the captured image can be analyzed with respect to the second portion. In other words, the brightness information of light in a second wavelength range can be read from the imaged second portion. Based on this, a (clear) grayscale image of the second portion can be obtained. Therefore, the analysis of the first portion based on light lines (e.g., based on the shape of the captured light lines) and the analysis of the second portion based on the intensity distribution captured in the second portion can be performed independently or separately.

[0029] The analysis and processing of the captured images are used to analyze the features of the workpiece surface. The features to be analyzed on the workpiece surface may include at least one of the following: geometry, height profile, roughness, color, reflectivity of the workpiece surface, joint edges, edge offset or joint gap between two workpieces, workpiece steps, welds, and cut edges. For example, particularly in laser welding, the weld can be analyzed, especially in terms of its position or pose on the workpiece surface, reflectivity of the weld, height and / or width of the weld, joint cross-section between welded workpieces, concavity or convexity of the weld, and under-curvature and over-curvature of the weld. For example, in laser cutting, the cut edges can be analyzed, especially in terms of their position or pose on the workpiece surface, roughness or bevel of the cut edges.

[0030] The method for analyzing the surface of a workpiece used in a laser processing process may further include the following steps: moving the workpiece relative to a sensor device and repeating the aforementioned steps, namely, emitting a light beam of light in a first wavelength range onto a region of the workpiece surface, illuminating that region of the workpiece surface with light in a second wavelength range, capturing an image of that region of the workpiece surface, and analyzing and processing the image. In other words, multiple images of the workpiece surface can be captured. In this way, a grayscale image or height profile of a large area of ​​the workpiece surface can be obtained. The workpiece is preferably moved in a plane parallel to the workpiece surface and / or perpendicular to the optical axis or the center line of the emitted light in the first wavelength range.

[0031] The optical axis of the optics and / or the optical axis of the sensor device may form an acute angle with the first plane. The optical axis of the sensor device and / or the optics may lie in a plane that extends perpendicular to the workpiece surface and parallel to a feature (e.g., a weld or joint edge) on the workpiece surface. Preferably, the optical axis of the sensor device and / or the optics intersects with this feature.

[0032] Optical devices can have a wavelength-dependent refractive index. In particular, the optical device can be an uncorrected optical device regarding color error. The optical device may include at least one optical element, such as a lens, which has such a longitudinal color error. The optical device may have chromatic aberration with respect to a first color and / or a second color, i.e., a longitudinal color error. Therefore, the optical device has different refractive indices for two wavelength ranges. The optical device may include lenses, lens groups, focusing lenses, focusing lens groups, lenses, and / or zoom lenses.

[0033] The sensor device may include a Scheimpflug sensor or a Scheimpflug sensor. The image sensor may include at least one of the following: a matrix image sensor, a two-dimensional optical sensor, a camera sensor, a CCD sensor, a CMOS sensor, or a photodiode array. The sensor device may be a CMOS camera or include a CMOS camera.

[0034] The area of ​​the workpiece surface illuminated by light in the second wavelength range can be large and / or non-directional. The illuminating unit may include colored LEDs or LEDs that emit light in the second wavelength range. The illuminating unit may have a broadband light source and a color filter that allows light in the second wavelength range to pass through.

[0035] A light line unit can provide or generate continuous, straight light lines. In other words, a light line unit can provide a fan-shaped beam of light. The beam can be emitted perpendicularly onto the workpiece surface. In this case, the first plane can be perpendicular to the workpiece surface. The light line unit for emitting the light line can be a laser device, or can include a laser device. Alternatively, the light line unit can include a light conductor for emitting the light line. The beam can be a laser beam, or the light line can be a laser light line.

[0036] According to a second aspect of the present invention, an analytical apparatus for analyzing the surface of a workpiece is described, the apparatus being configured to perform the aforementioned method. The analytical apparatus includes: a sensor device having an image sensor for capturing an image and an optical device for imaging light onto the image sensor, wherein the optical device has different refractive indices for a first wavelength range and a second wavelength range; a light line unit for generating light lines in the first wavelength range; and an illumination unit for generating light in the second wavelength range. The analytical apparatus may further include an analysis processing unit for analyzing and processing the image captured by the image sensor.

[0037] According to a third aspect of the invention, a method for machining a workpiece by means of a laser beam, particularly laser welding or laser cutting, is described, wherein the method comprises: emitting a laser beam onto a point on the surface of the workpiece along a machining path, and the aforementioned method for analyzing the workpiece surface in a Vorlauf and / or a Nachlauf run along the point of the machining path.

[0038] According to a fourth aspect of the invention, a laser processing head for processing workpieces is described, particularly a laser welding head or laser cutting head using a laser beam, which includes the aforementioned analysis device. Attached Figure Description

[0039] The present invention will now be described in detail with reference to the accompanying drawings.

[0040] Figure 1 and Figure 2 A schematic diagram of an analytical apparatus for analyzing the surface of a workpiece is shown.

[0041] Figure 3 This illustration demonstrates, illustratively and exemplary, the method according to Figure 1 and Figure 2 Images captured by analytical equipment;

[0042] Figure 4 A schematic diagram of an image sensor and optical components is shown to explain the basic concept of the invention;

[0043] Figure 5A A schematic diagram of an analytical apparatus for analyzing the surface of a workpiece according to an embodiment of the present invention is shown;

[0044] Figure 5B A schematic diagram of an analytical apparatus for analyzing the surface of a workpiece according to an embodiment of the present invention is shown;

[0045] Figure 6 An image captured by an analysis device according to the present invention is illustrated schematically and exemplarily.

[0046] Figure 7 A block diagram of a method for analyzing the surface of a workpiece during a laser processing procedure, according to an embodiment of the present invention, is shown.

[0047] Figure 8 A schematic diagram of a method for processing a workpiece using a laser beam is shown, the method including a method for analyzing the workpiece surface according to an embodiment;

[0048] Figure 9 A schematic diagram of an exemplary grayscale image is shown, which is obtained by a method for analyzing the surface of a workpiece for a laser processing process according to an embodiment of the present invention. Detailed Implementation

[0049] In the following text, unless otherwise stated, the same reference numerals are used for the same and same elements.

[0050] Figure 1 and 2 A schematic diagram of an analytical apparatus for analyzing the surface 22' of a workpiece is shown to better understand the invention. Figure 1 A side view of the analysis device is shown. Figure 2A perspective view of the analytical apparatus is shown. A blue-line laser (typically 450 nm) is used for triangulation to generate an object plane (laser triangulation plane) in which the laser line reflected by the component lies. This plane is imaged using a Scheimpflug arrangement. The measurement range is defined according to the imaging location of the optics.

[0051] The analysis device 10' is configured to perform optical sectioning or optical sectioning triangulation to detect the three-dimensional height profile of the workpiece surface 22'. This allows, for example, the identification of mating edges or steps 23' on the workpiece surface 22'. The analysis device 10' may also be referred to as a triangulation sensor.

[0052] The analysis device 10' includes a sensor device 12' having an image sensor 14' for capturing images and an optics device 16' for imaging light onto the image sensor 14'. The analysis device 10' also includes a light line unit 18' for generating light lines 20' on the workpiece surface 22' and detecting the image of the light lines 20'. The light line unit 18' is configured to emit a fan-shaped light beam 24', i.e., propagating in only one plane, onto the workpiece surface 22' to generate light lines 20' on the workpiece surface 22'. The plane 26' opened by the fan-shaped light beam 24', the optics device 16', and the sensor plane of the image sensor 14' are arranged in a Scheimpflug arrangement or satisfy the Scheimpflug condition. Thus, the plane 26' is clearly imaged onto the image sensor 14' by the optics device 16'. In other words, all points on the plane 26' are clearly imaged on the image sensor 14'. Since plane 26' also includes light ray 20', the light ray 20' reflected from workpiece surface 22' is also clearly imaged on image sensor 14'. Plane 26' is typically arranged perpendicular to and intersects workpiece surface 22'. Due to the Scheimpflug arrangement, the intersection line 44' of plane 26' and workpiece surface 22' corresponds to or coincides with light ray 20'.

[0053] In the direction of the optical axis 17' of the optics 16', there exists a certain depth of field in front of and behind the plane 26'. Within this depth of field, points are sufficiently clearly imaged onto the image sensor 14' by the optics 16'. In other words, the depth of field surrounds the first plane 26'. Since the plane 26' intersects the workpiece surface 22', all points on the plane intersecting the plane 26' within the depth of field are clearly imaged onto the image. Therefore, a portion 28' of the line 44' where the plane 26' surrounds the workpiece surface 22' intersects the workpiece surface 22' in the direction of the optical axis 17' is clearly imaged onto the image sensor 14'. This portion 28' is located in front of and behind the line 44' in the direction of the optical axis of the optics 16'. This portion 28' can also be referred to as the "resolution region" because this region of the workpiece surface 22' is sufficiently clearly imaged in the captured image for image analysis and processing.

[0054] As the measurement range of the analysis device 10', a plane 26' and a depth range of the optics 16' can be defined. Due to the Scheimpflug arrangement, all points on the plane are clearly imaged on the image sensor 14'. The depth range surrounds the first plane 26' along the optical axis of the optics 16'. This measurement range can also be referred to as the "object field." The first plane 26' can also be referred to as the "object plane" of the sensor device 12'. If the workpiece surface 22' intersects the plane 26', the light reflected from the light ray 20' is also clearly imaged on the image sensor 14'. The region of the workpiece surface 22' located within the object field, i.e., a portion 28', is also sufficiently clearly imaged on the image sensor 14'.

[0055] Figure 3 An image captured by an analysis device is illustrated schematically. The image comprises a plurality of pixels (not shown) arranged in a matrix, with the pixels arranged in columns along a first direction x and in rows along a second direction y. Figure 3 As shown, light lines 20' are imaged on an image captured by image sensor 14'. Furthermore, a portion 28' of the workpiece surface 22' is marked, and this portion is clearly imaged in the image.

[0056] Due to color errors in the optics, the image width, i.e., the measurement range or the pose of the object plane, depends on the wavelength. This means that, for the case of optics 16' with color errors, the imaging plane 26' will be imaged differently for different wavelengths. For example, for light in the first wavelength range, such as blue light with a wavelength of approximately 450 nanometers, plane 26' will be clearly imaged on image sensor 14' by optics 16'. However, due to the color error of optics 16', for light in the second wavelength range, such as red light with a wavelength of approximately 660 nanometers, plane 26' will not be clearly imaged on image sensor 14' because the image width of optics 16' changes in the case of red light. The object width, i.e., the distance from optics 16' to plane 26', must be changed in order to obtain a clear image. In other words, for each wavelength range, the image plane will be located at a different distance from the main plane of the uncorrected optics 16'.

[0057] According to the present invention, the color error of the optical device is utilized to separate the sharp range of the workpiece surface for two-dimensional imaging, especially for grayscale images, from the imaging of light lines for laser triangulation. Thus, according to the present invention, for three-dimensional inspection of the workpiece surface by means of optical sectioning, a sensor device with an image sensor and an optical device having different refractive indices for light in a first wavelength range and a second wavelength range is used. In parallel with capturing a sharp image of the light lines reflected from the workpiece surface, a sharp image of another region of the workpiece surface spaced apart from the light lines can be captured. By means of the present invention, the workpiece surface region clearly imaged for light in the second wavelength range is spatially separated from the clearly imaged light lines in the first wavelength range, thereby combining the advantages of Scheimpflug imaging with grayscale image representation having a large depth of field. In this way, the depth of field, which has greatly limited the range of analysis and processing in grayscale images, can be extended to the measurement range of Scheimpflug imaging.

[0058] Figure 4 A schematic diagram of the image sensor and optical device of the present invention is shown.

[0059] Within the scope of this disclosure, optical devices having color errors, particularly longitudinal color errors or (longitudinal) chromatic aberration, and thus different refractive indices for different wavelengths or wavelength ranges of light, are also referred to as "uncorrected optical devices." Such optical devices may have at least one optical element with this color error, such as a lens. Uncorrected optical devices have different object planes for different wavelengths or wavelength ranges of light. In other words, the optical elements have different planes for different wavelength ranges of light, and these planes are clearly imaged onto a predetermined image plane by the optical elements, such as the sensor plane of an image sensor. Thus, for each wavelength range, there exists a corresponding object plane or focal plane onto which the light for that wavelength range is clearly imaged by the optical device.

[0060] Figure 4 The illustration schematically shows a workpiece surface 22, an optical device 16, and an image sensor 14 with a sensor plane 34. (As shown in...) Figure 4 As shown, there is a first plane 26 and a second plane 30. For the first plane, the optics 16 clearly images light 36 of a first wavelength range onto the sensor plane 34. For the second plane, the optics 16 clearly images light 38 of a second wavelength range onto the sensor plane 34. The optics 16, the sensor plane 34, and the first plane 26 for the light 36 of the first wavelength range or the second plane 30 for the light 38 of the second wavelength range satisfy the Scheimpflug condition. This means that the first plane 26, the second plane 30, the main plane 40 of the optics 14, and the sensor plane 34 of the image sensor 14 intersect on a line of intersection.

[0061] Figure 5A A schematic diagram of an analytical apparatus for analyzing the surface of a workpiece according to an embodiment of the present invention is shown.

[0062] The analysis device 10 is configured to perform a method for analyzing the surface of a workpiece used in a laser processing process according to an embodiment of the present invention.

[0063] The analysis device 10 is configured to capture a two-dimensional image of the workpiece surface 22 and analyze and process the captured image to identify features of the workpiece surface. In particular, the analysis device 10 is configured to perform optical sectioning or optical triangulation to detect the three-dimensional height profile of the workpiece surface 22. The analysis device 10 can, for example, identify joint edges, steps 23, or welds on the workpiece surface 22.

[0064] The analysis device 10 includes a sensor device 12 having an image sensor 14 for capturing images and an optics device 16 for imaging light onto the image sensor 14, and may include an analysis processing unit (not shown) for analyzing and processing the images captured by the image sensor 14. The image sensor 14 is a planar or two-dimensional optical sensor, such as a CMOS sensor or a CCD sensor. The optics device 16 may be configured as a lens or a lens assembly, but the invention is not limited thereto.

[0065] The analysis apparatus 10 also includes a light line unit 18 for generating light lines 20 of a first wavelength range on the workpiece surface 22. The light line unit 18 is configured to emit a fan-shaped beam 24 onto a region of the workpiece surface 22 to generate light lines 20 on the workpiece surface 22. The light lines 20 may be oriented, in particular, perpendicular to the transition process of the joint edge or step 23. The light line unit 18 may be configured as a line laser. Thus, the beam 24 may be a laser beam, and the light lines 20 may be laser lines, but the invention is not limited thereto. According to an embodiment, the light line unit 18 is configured to generate a blue laser beam having a wavelength of approximately 400 to 500 nanometers. According to an embodiment, the light line unit 18 is arranged such that it can emit the beam 24 perpendicularly onto the workpiece surface 22.

[0066] The analysis device 10 also includes an illumination unit 42, which is configured to generate light in a second wavelength range and emit it onto an area of ​​the workpiece surface 22. According to an embodiment, the illumination unit 42 is constructed as a red LED illumination device and configured to generate red light, for example, with a wavelength of approximately 620 nm to 720 nm. Illumination of the area of ​​the workpiece surface 22 with light in the second wavelength range can be performed over a large area and / or in a non-directional manner. The arrangement or orientation of the illumination unit 42 can be arbitrary as long as an area of ​​the workpiece surface 22 is illuminated. The image sensor 14 is sensitive to both wavelength ranges.

[0067] Optical device 16 has different refractive indices for light in the first wavelength range and light in the second wavelength range. Optical device 16 may be referred to as an uncorrected optical device. According to an embodiment, the optical axis 17 of optical device 16 may be located in a plane that is perpendicular to the workpiece surface 22 and extends parallel to (or through) the joint edge or step 23.

[0068] The first plane 26 is defined by the light emission point of light from the light ray unit 18 and the light ray 22 within a first wavelength range. In other words, the first plane 26 is opened by a planar fan-shaped beam 24. The first plane 26, the optics 16, and the sensor plane of the image sensor 14 are arranged in a Scheimpflug arrangement or satisfy the Scheimpflug condition. In this way, all points of the first plane 26 are clearly imaged onto the sensor plane of the image sensor 14 by the optics 16. The first plane 26 can also be referred to as the "triangulation plane". Since the first plane 26 also includes the light ray 20, the light of the light ray 20 reflected by the workpiece surface 22 is also clearly imaged onto the image sensor 14. The first plane 26 intersects the workpiece surface 22 at the first intersection line 44. In this way, all points of the workpiece surface 22 are clearly imaged on different planes that intersect with the first plane 26. The first intersection line 44 between the first plane 26 and the workpiece surface 22 corresponds to or coincides with the light ray 20.

[0069] Preferably, the first plane 26 is arranged substantially perpendicular to the workpiece surface 22. In other words, the optical axis of the light line unit 18 can extend substantially perpendicular to the workpiece surface 22. The optical axis 17 of the optical device 16 can intersect the first plane 26 at an acute angle.

[0070] As previously described, the workpiece surface 22 is also irradiated by the irradiation unit 42 with light in the second wavelength range. This second wavelength range light is clearly imaged by the optical device 16 onto the sensor plane 30 of the image sensor 14. This second plane 30 differs from the first plane 26, as shown in the reference... Figure 4 As explained, the second plane 30, the optical device 16, and the sensor plane of the image sensor 14 are also arranged in a Scheimpflug arrangement or satisfy the Scheimpflug condition for light in the second wavelength range. The second plane 30 intersects the workpiece surface 22 at the second intersection line 46. The second intersection line 46 and the first intersection line 44 are spaced apart from each other. The (shortest) distance between the two intersection lines 44 and 46 is called the offset 47.

[0071] Along the optical axis 17 of the optical device 16, there exist specific three-dimensional depth ranges in front of and behind the plane 26 and behind the second plane 30, respectively. Within these depth ranges, points are clearly imaged onto the image sensor 14 by the optical device 16. In other words, the first depth range surrounds the first plane 26, and the second depth range surrounds the second plane 30. Since the first plane 26 intersects the workpiece surface, within the first depth range, all points on the plane intersecting the first plane 26 are clearly imaged on the image for reflected light of the first wavelength range. Since the second plane 30 intersects the workpiece surface, within the second depth range, all points on the plane intersecting the second plane 30 are clearly imaged on the image for reflected light of the second wavelength range. Therefore, the first portion region 28 of the workpiece surface 22, surrounding the intersection line 44 of the first plane 26 and the workpiece surface 22, is clearly imaged onto the image sensor 14 for light of the first wavelength range, and the second portion region 32 of the workpiece surface 22, surrounding the intersection line 46 of the second plane 30 and the workpiece surface 22, is clearly imaged onto the image sensor 14 for light of the second wavelength range. The portion region 28 is located in front of and behind the intersection line 44 in the optical axis 17 direction of the optics 16. The portion region 32 is located in front of and behind the intersection line 46 in the optical axis 17 direction of the optics 16. According to the embodiment, the two portion regions 28 and 32 are spaced apart from each other and do not intersect or overlap. Therefore, the light line 20 of the first wavelength range will not be located in the second portion region 32, which is clearly imaged for light of the second wavelength range.

[0072] Of course, illumination can be performed using other, different, or spaced-apart center wavelengths. Here, the center wavelength refers to the wavelength located in the middle of a wavelength range. For this purpose, an illumination unit 42, 42' can be provided for each illumination wavelength. Additionally, an illumination unit 42 emitting light over a wide wavelength range (e.g., a broadband light source or a white light source) and one or more filters that allow multiple wavelengths or wavelength ranges spaced apart from each other can be provided. The filters are arranged in front of the image sensor 14, i.e., the filters can be arranged either at the illumination unit 42 or in front of or behind the optics 16. If illumination is performed with at least one other, third wavelength range of light, an additional, third plane 31 is generated, which creates a third partial region 33 on the workpiece surface that is offset parallel to the second partial region 32. A number of wavelengths—as they are generated by illumination units with a continuous spectrum—create a number of such cross-sectional planes that intersect the workpiece surface parallel to the second plane 30. Each wavelength creates a depth range or partial region on the workpiece surface that is offset parallel to the second partial region 32. Therefore, the overall area of ​​the surface that can be clearly imaged can be expanded. This is exemplary in... Figure 5BThe diagram illustrates illumination with light of a third wavelength range via an additional illumination unit 42', thereby creating a third plane 31 with a third phase line 45, around which a third partial region 33 is arranged. For example, the second wavelength range can be 660 ± 5 nm, and the third wavelength range can be 720 ± 5 nm. The first wavelength range can be 450 ± 5 nm. The center wavelengths of the second and third wavelength ranges used for illumination are preferably selected such that their respective depth ranges or partial regions are adjacent to each other.

[0073] Figure 6 An image captured by an analysis device according to the invention is illustrated schematically and exemplary. The image comprises a plurality of pixels (not shown) arranged in a matrix, the pixels arranged in columns along a first direction x and in rows along a second direction y. (As shown in...) Figure 6 As shown, the laser line 20 is imaged in an image captured by the image sensor 14. Furthermore, a first portion 28 and a second portion 32 of the workpiece surface 22 are marked, and these portions are clearly imaged in the image. In the image, the two portions 28 and 32 are also spaced apart from each other. Since the light line 20 is not located in the second portion 32, the image of the workpiece surface in the second portion 32 is not interfered with by the bright light line 20. In this way, the contrast for the second portion 32 is increased in the captured image. Furthermore, for light in the second wavelength range, the second portion 32 is clearly imaged on the image sensor 14.

[0074] Therefore, the clearly imaged light lines 20 can be extracted and analyzed from the captured image to perform optical sectioning for detecting the three-dimensional height profile of the workpiece surface. Based on the aforementioned offset 47, the second portion region 32 for clearly imaged light in the second wavelength range can be read from the image in a manner offset from the light lines, so as to obtain a clear image, especially a grayscale image, of the second portion region 32 of the workpiece surface 22.

[0075] The readout of the image sensor or image is optimized such that the second region 32 is read out with an offset from or offset from the peak intensity of the light line 20, extracting the light line 20. In the image, the second region 32 is typically comprised of rows between 20 and 100, depending on the imaging performed by the optics and the image sensor used. The points of the light line can be directly converted into distance values ​​using calibration values.

[0076] According to one embodiment, the analysis device 10 is arranged on a laser processing head used to process workpieces by means of a laser beam. For example, the analysis device can be mounted on the housing of the laser processing head.

[0077] Figure 7A block diagram of a method for analyzing the surface of a workpiece during a laser processing procedure, according to an embodiment of the present invention, is shown. This method can be derived from previously referenced... Figure 5A , Figure 5B and Figure 6 The described analysis device 10 is used for execution.

[0078] The method includes the following steps: First, a light ray 20 of a first wavelength range is emitted onto a region of the workpiece surface 22, and the region of the workpiece surface 22 is illuminated with light of a second wavelength range (S1). Then, an image of the region of the workpiece surface 22 is captured using a sensor device 12 (S2). The sensor device 12 includes an image sensor 14 and an optical element 16 for imaging light onto the image sensor 14, wherein the optical element 16 has different refractive indices for the first and second wavelength ranges, and wherein a first plane 26 (defined by the light ray 20 and the light emission point of the first wavelength range), the optical element 16, and the image sensor 14 are arranged in a Scheimpflug configuration. Therefore, image capture is based on light of the first and second wavelength ranges reflected from the region of the workpiece surface 22 and imaged onto the image sensor 14 by the optical element 16. Next, the image is analyzed to analyze the features of the workpiece surface (S3).

[0079] The analysis is performed based on a predetermined offset between the first plane 26 and the second plane 30, whereby light in a second wavelength range is clearly imaged onto the sensor plane of the image sensor 14 by the optics 16 with respect to the second plane. The predetermined offset can be a pre-determined or known offset. This offset can be modeled, calculated, or determined by measurement. This offset can be described with respect to the workpiece surface or along the optical axis 17 of the optics 16 or the sensor device 12.

[0080] In the captured images, as referenced above... Figure 5A , Figure 5B and Figure 6The first region 28 is clearly imaged for light in a first wavelength range reflected from the workpiece surface 22, and the second region 32 is clearly imaged for light in a second wavelength range reflected from the workpiece surface. According to an embodiment, image analysis processing includes analysis processing of the first region 28. Specifically, this may include reading out the brightness information of the first wavelength range of light contained in the image for the imaged first region 28. Specifically, this may include determining the position or shape of the imaged light lines 22. Based on this, optical sectioning can be performed to, for example, determine the position and pose of features on the workpiece surface, such as joint edges, joint gaps, or welds. Image analysis processing may also include analysis processing of the second region 32 of the image. Specifically, this may include reading out the brightness information of the second wavelength range of light contained in the image for the imaged second region 32. Based on this, a clear grayscale image of the second region 32 can be obtained. Based on this grayscale image, additional features of the workpiece surface 22, especially weld features, such as roughness, color, and reflectivity, can be identified and analyzed. This analysis processing can be performed using known methods for image processing and image analysis. Image analysis and processing can include performing row-by-row and / or column-by-column analysis on the captured image. This analysis and processing can be performed using known machine learning methods.

[0081] The method according to the invention can be part of a method for processing workpieces using a laser beam, such as laser welding. Figure 8 As shown, according to an embodiment, a method for machining a workpiece using a laser beam includes emitting a laser beam 48 onto a point 50 on the workpiece surface 22 along a predetermined machining path 52. For pre-processing monitoring and / or post-processing monitoring, the method for machining the workpiece includes a method according to the invention for analyzing the workpiece surface 22. The method according to the invention can be performed in a pre-processing run 54 (pre-processing) and / or a post-processing run 56 (post-processing) about the machining direction 58 at point 50. In the pre-processing run 54, for example, edge misalignment, joint gaps, and joint edges can be identified or detected. In the post-processing run 56, welds can be identified or detected and analyzed, and additional features of the workpiece surface 22 or the weld can be detected.

[0082] According to an embodiment, the method for analyzing the surface of a workpiece used in a laser processing process may include moving the workpiece surface relative to a sensor device and repeating S1 to S3 as previously described. In other words, multiple images of the workpiece surface 22 may be captured sequentially. For this purpose, respective second-part regions 32 read from the multiple images may be combined to form a grayscale image of the workpiece surface 22. In this way, a clear grayscale image of a large area of ​​the workpiece surface 22 can be obtained.

[0083] exist Figure 9 An example of such a composite grayscale image is illustrated below. The composite grayscale image 60 is based on three second partial regions 32a, 32b, and 32c, which have been read from their respective captured images and combined to form the grayscale image 60. Since each of the second partial regions 32a, 32b, and 32c is clearly imaged on its respective image, the composite grayscale image clearly images a large portion of the workpiece surface 22. The grayscale image 60 also shows the weld 62. Combining the partial regions 32a, 32b, and 32c to form the grayscale image 60 may include image processing, particularly perspective or spatial transformations of the second partial regions 32a, 32b, and 32c.

[0084] Accordingly, the respective first portion regions 28 read from multiple images can be combined to form a three-dimensional height profile of a larger area of ​​the workpiece surface 22.

[0085] This invention is based on the concept that an optics device with color longitudinal error images the object plane differently for different wavelengths. In this case, the imaging plane is located at a different distance from the main plane of the optics for each wavelength. This characteristic can be utilized in laser processing to separate the area of ​​the workpiece surface clearly imaged on the image sensor by the optics from the imaging of the optical tangent used for optical sectioning. In this way, the advantages of the large measurement range in the Scheimpflug arrangement or Scheimpflug image can be combined with the advantages of the large depth of field in grayscale image representation. This means that the depth of field, which severely limits the range of analysis and processing in grayscale images, is extended to the measurement range of Scheimpflug imaging.

[0086] List of reference numerals

[0087] 10 Analytical Equipment

[0088] 12 Sensor Devices

[0089] 14 Image Sensor

[0090] 16 Optical Devices

[0091] 17 Optical axis of optical devices

[0092] 18 light line units

[0093] 20 light lines

[0094] 22. Workpiece surface

[0095] 23. Workpiece Step

[0096] 24 beams

[0097] 26 First plane

[0098] 28 Part One Area

[0099] 30 Second plane

[0100] 32 Part Two Area

[0101] 31 Third plane

[0102] 33. Third Part Area

[0103] 34 Sensor plane

[0104] 36. Light in the first wavelength range

[0105] 38 Light in the second wavelength range

[0106] 40 Main Plane

[0107] 42 Irradiation Units

[0108] 44 First Intersection Line

[0109] 46 Second intersection line

[0110] 45 Third Intersection Line

[0111] 47 Offset

[0112] 48 laser beams

[0113] 50 Points on the processing path

[0114] 52 Processing Path

[0115] Running before 54

[0116] Run after 56

[0117] 58. Processing Direction

[0118] 60 grayscale image

[0119] 62 Weld

Claims

1. A method for analyzing the surface of a workpiece used in a laser processing procedure, the method comprising the following steps: - A planar fan-shaped beam of light emitting light in a first wavelength range is used to generate light lines (20) on the surface (22) of the workpiece and to irradiate the surface (22) of the workpiece by means of light in at least one second wavelength range. - An image of the workpiece surface (22) is captured using a sensor device (12), the sensor device including an image sensor (14) and an optical device (16) for imaging light onto the image sensor (14). The optical device (16) has different refractive indices for the first wavelength range and the second wavelength range, wherein the first plane (26) defined by the plane of the fan-shaped beam, the optical device (16), and the image sensor (14) are arranged in a Scheimpflug configuration; and - The image is processed based on a predetermined offset on the workpiece surface between the first plane (26) and the second plane (30) to analyze the features of the workpiece surface (22), wherein the second plane is the plane on which light of the second wavelength range is imaged onto the image sensor (14) by the optical device (16). Wherein, the first plane intersects the workpiece surface at the first intersection line, the second plane intersects the workpiece surface at the second intersection line, and the distance between the first intersection line and the second intersection line is the predetermined offset.

2. The method according to claim 1, wherein, The first plane (26) is arranged perpendicular to the surface (22) of the workpiece, and / or wherein the optical axis (17) of the optical device (16) and / or the optical axis of the sensor device (12) form an acute angle with the first plane (26).

3. The method according to claim 1 or 2, wherein, The features of the workpiece surface (22) include weld seams or joint edges, and the optical axis of the sensor device (12) and / or the optical axis (17) of the optics (16) lie in a plane that is perpendicular to the workpiece surface (22) and extends parallel to the weld seam or the joint edge.

4. The method according to claim 1 or 2, wherein, The first wavelength range includes blue light, and / or the second wavelength range includes red light.

5. The method according to claim 4, wherein, The first wavelength range includes light with wavelengths from 400 nanometers to 500 nanometers.

6. The method according to claim 5, wherein, The first wavelength range includes light with a wavelength of 450 nanometers.

7. The method according to claim 4, wherein, The second wavelength range includes light with wavelengths from 620 nanometers to 720 nanometers.

8. The method according to claim 7, wherein, The second wavelength range includes light with a wavelength of 660 nanometers.

9. The method according to claim 1 or 2, wherein, The image analysis and processing includes: - Analyze and process the intensity data of light in the first wavelength range to generate the height profile of the workpiece surface.

10. The method according to claim 1 or 2, wherein, A portion (32) of the workpiece surface (22) surrounds the intersection line (44) of the second plane (30) and the workpiece surface (22), wherein the image analysis and processing includes: - Analyze and process the intensity data of the light in the second wavelength range in the region of the image corresponding to the partial region (32) in order to obtain a grayscale image of the partial region (32).

11. The method according to claim 1 or 2, wherein, The workpiece surface (22) is also illuminated by light of at least one third wavelength range, the optical device (16) having different refractive indices for the first wavelength range, the second wavelength range and the third wavelength range, wherein the image is also analyzed based on a predetermined offset on the workpiece surface between the first plane (26) and the third plane (31) for analyzing the features of the workpiece surface (22), the third plane being a plane from which light of the third wavelength range is imaged by the optical device (16) onto the image sensor (14).

12. The method according to claim 11, wherein, The third wavelength range includes light with a wavelength of 720 nanometers.

13. The method according to claim 1 or 2, wherein, The workpiece surface (22) is then moved relative to the sensor device (12), and the aforementioned steps are repeated.

14. A method for processing a workpiece using a laser beam, the method comprising: - The laser beam (48) is emitted to a point (50) along the machining path (52) on the workpiece surface (22); - The method according to any one of claims 1 to 12, wherein light rays are emitted onto the workpiece surface (22) in a pre-run (54) and / or a post-run (56) with respect to the point (50).

15. The method according to claim 14, wherein, The workpiece is processed by laser welding or laser cutting.

16. An analytical apparatus (10) for analyzing the surface of a workpiece, the analytical apparatus comprising: - A sensor device (12) having an image sensor (14) for capturing images and an optical device (16) for imaging light onto the image sensor (14), wherein the optical device (16) has a different refractive index for a first wavelength range and at least one second wavelength range; - A light line unit (18) for emitting light lines (20) in the first wavelength range and an illumination unit (42) for emitting light in at least one second wavelength range, and - An analysis and processing unit, which is used to analyze and process the images captured by the image sensor (14). The analysis device (10) is configured to perform a method for analyzing the surface (22) of the workpiece according to any one of claims 1 to 15.

17. The analytical apparatus (10) according to claim 16, wherein, The optical device (16) includes a lens, a lens group or a lens.

18. The analytical apparatus (10) according to claim 17, wherein, The lens is a focusing lens.

19. The analytical apparatus (10) according to claim 17, wherein, The lens group is a focusing lens group.

20. The analytical apparatus (10) according to claim 17, wherein, The lens in question is a zoom lens.

21. The analytical apparatus (10) according to any one of claims 16 to 20, wherein, The image sensor (14) includes a matrix image sensor, a two-dimensional optical sensor, a CCD sensor, a CMOS sensor, and / or a photodiode array.

22. The analytical apparatus (10) according to claim 21, wherein, The image sensor is configured as a camera sensor.

23. The analytical apparatus (10) according to any one of claims 16 to 20, wherein, The light line unit (18) includes LEDs or an LED array.

24. A laser processing head for processing workpieces by means of a laser beam, the laser processing head comprising an analysis device according to any one of claims 16 to 23.

25. The laser processing head according to claim 24, wherein, The laser processing head is configured to perform the method according to claim 14.

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