Surface inspection system

Abstract

The present invention discloses a surface inspection system for capturing surface defects of a surface to be inspected, comprising a camera system, an illumination system comprising one or more light sources, and an evaluation system, wherein the evaluation system evaluates the brightness and / or color distribution of the surface to be inspected in at least one image captured by the camera system, and captures the surface defect of the surface to be inspected as a local deviation in brightness and / or color. In this case, it is provided that the evaluation system evaluates the local deviation in brightness and / or color as a surface defect if the local deviation in brightness and / or color appears brighter than a surface area surrounding the local deviation in at least one first sub-area and appears darker than the surface area in at least one second sub-area, and / or if different colors predominate in different sub-areas.

Description

Technical Field

[0001] The invention relates to a surface inspection system for capturing surface defects of a surface to be inspected, comprising a camera system and an illumination system, wherein the illumination system generates a brightness distribution and reflection and scattering properties of the surface to be inspected, in which brightness distribution surface defects become visible as local deviations in brightness, said distribution being detected by the camera system. Background Art

[0002] Industrial quality control often faces the task of inspecting the surfaces of finished or intermediate products for surface defects. Within the meaning of the present invention, surface defects are deviations from the expected shape of the surface of the object being measured. Such surface defects include, for example, localized, small-scale deviations from the expected surface shape, such as scratches, indentations, or dents in stamped sheet metal products, or surface contaminants such as adhesive residues or weld beads. In particular, such surface defects can be localized, small-scale shape deviations in areas of a component that are otherwise essentially flat or without contour elements.

[0003] The goal of surface inspection is to detect these defects. Inspection results can be qualitative, such as the presence of a defect, the extent or degree of deviation from the desired surface, or they can contain quantitative information, such as the depth of an indentation. To be detectable, surface defects must stand out in some way from the rest of the surface; that is, there must be contrast.

[0004] For optical surface inspection, the following properties of surface defects can typically be exploited to generate detectable contrast, for example: a localized severe deviation from the surface normal (the surface normal at any point P of the surface is given by a unit vector perpendicular to the tangent plane at point P), or a change in the reflective and scattering properties of the surface. This contrast can then be detectable, for example, as a brightness difference during surface inspection.

[0005] However, according to one aspect of the present invention, surface defects are local deviations from the desired surface shape, which are to be distinguished from local deviations in the reflective and scattering properties of the surface (e.g., due to local variations in the microscopic surface structure), and only the former are to be understood as surface defects within the meaning of the present invention. This presents a particular challenge for surface inspection systems.

[0006] In the following, reference to a surface to be tested refers to the surface of one or more objects, or a subregion of such a surface, that is intended to be captured by a surface inspection system. The inspection field is the spatial region within the optical field of view of the surface inspection system within which it can capture the surface to be inspected and detect surface defects. Depending on the size of the surface to be inspected, the inspection field can capture the surface completely or partially. In the latter case, displacement and further recording of the surface inspection system are necessary to capture the entire surface.

[0007] Optical surface inspection systems detect defects without contact using light (i.e., electromagnetic radiation). In most cases, an illumination system and a detection system are used. The illumination system consists of one or more light sources, while the detection system consists of one or more light detectors. If the inspection system consists of one or more cameras, it is called a camera system.

[0008] The light here can include one or more wavelengths, or one or more wavelength ranges. Different wavelengths or wavelength ranges are referred to as colors. The wavelength range in which an optical surface inspection system operates is generally determined by the sensitivity range of the light detector used. Photodiodes or photodiode arrays are commonly used as light detectors. The latter are used, for example, in monochrome cameras or color cameras. A single photodetector is referred to as a pixel. Color cameras typically have three different types of pixels, each with sensitivity to different wavelength ranges; typically, these are the blue, green, and red spectral ranges of the visible light spectrum. These sensitivity ranges are referred to as the camera's color channels.

[0009] For example, light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), lasers or gas discharge lamps are used as light sources in lighting systems. Based on the spatial extent and arrangement of the light-emitting area, light sources or lighting systems can be divided into point-type, linear, rod-shaped and ring-shaped. Point light sources are, for example, lasers or LEDs with very small emission surfaces. Rod-shaped light sources are, for example, gas discharge tubes. Linear, ring-shaped and rod-shaped light sources can also be realized, for example, by corresponding LED arrangements. In addition, light sources or lighting systems can be distinguished by their emission characteristics. For example, lasers usually emit directionally within a narrow angular range, while gas discharge lamps or LEDs emit non-directionally within a wider angular range. The emission characteristics of the light source may be influenced by reflectors, lenses, Fresnel lenses, diffusers and waveguides in the lighting system.

[0010] First of all, the scattering and reflection properties of the surface are very important for optical surface inspection. Different types of surfaces are distinguished based on their scattering and reflection properties:

[0011] An optically smooth surface is one whose surface roughness is less than the wavelength of observation. Examples include polished metal or glass surfaces, and painted surfaces. According to the law of reflection, light that strikes a surface at an angle relative to the surface normal is fully or partially reflected. According to the law of reflection, light is reflected in only a discrete direction. In this case, the absolute values ​​of the angle of incidence and the angle of reflection relative to the surface normal are equal, and the direction of incidence, the direction of reflection, and the surface normal lie in the same plane.

[0012] Optically rough surfaces have a surface roughness greater than the observation wavelength. They exhibit diffuse scattering behavior (e.g. chalk, etc.). The ideal case is a Lambertian scatterer. Here, the scattering intensity does not depend on the observation direction, but only on the cosine of the angle between the incident direction and the surface normal.

[0013] Optically glossy surfaces occur in the transition region from an optically rough surface with diffuse reflection behavior to an optically smooth, specularly reflecting surface. The surface roughness is within the wavelength range of the observing light. Light is preferentially reflected or scattered in the "reflection direction." However, unlike reflection on optically smooth surfaces, the scattering lobe has a finite width. However, the scattering is still highly directional, and the scattering intensity decreases relatively rapidly at larger and smaller angles.

[0014] So-called directional reflections occur. Glossy surfaces are a product of many material processing and shaping methods, such as pressing, grinding, and machining.

[0015] Deflectometry, photometric stereometry, and color deflectometry are methods for the optical detection of surface defects: essentially normal measurement methods that facilitate surface inspection. These methods directly determine the orientation of the surface normal or its deviation from the surroundings, either qualitatively or quantitatively. Local shape deviations in the surface are directly visible without the influence of measurement errors and error propagation, such as those that occur when determining the surface normal from surface data using mathematical gradient generation methods. These measurement methods are explained below:

[0016] In deflectometry, the image of a structured light source on the surface to be inspected is observed by a camera. If the surface normal of the inspected surface deviates locally, the image representation of the structured light source is distorted. This method is only suitable for optically smooth surfaces that reflect light according to the law of reflection. If scattering also occurs on the surface, light emitted from one point of the structured light source can strike different camera pixels via different points on the surface (the image representation of the structured light source becomes blurred). A unique assignment of a point of the structured light source to a camera pixel is no longer possible, so only inaccurate or undetectable surface defects are possible.

[0017] In color deflectometry, the different points of a surface or line light source are not or not only coded by brightness differences, but also by different colors or color distributions. In DE 102010001715A1 ("Method and device for surface inspection", Bosch), a rotationally symmetrical component with a smooth surface is illuminated by a line light source with a defined color distribution. A color linear array camera captures the color-coded image data. Based on the color distribution on the camera's linear array, the orientation of the surface normal can be reconstructed in a narrow strip of the object's surface. Capturing the entire surface requires a progressive recording of the rotating object. By means of color modulation in two directions or a combination of brightness and color modulation, this method also makes it possible to capture and inspect relatively large areas of the surface to be inspected with a single recording.

[0018] Photometric stereometry is used to inspect optically rough surfaces. Here, each point on the object's surface is illuminated from at least three different, linearly independent directions, and the surface is observed using a camera. The scattering properties of the surface to be measured must be such that the scattering intensity depends solely on the angle of incidence of the light relative to the surface normal, and not on the viewing direction. This is ideal for Lambertian scatterers. The direction of the surface normal at each point on the inspected surface can then be determined based on the ratio of the scattering intensities from at least three illumination directions. This method can also be used to inspect textured surfaces, where the reflectivity or scattering amplitude varies from surface to surface. A disadvantage is that surface inspection always requires multiple recordings. Therefore, this method is only applicable under static conditions, where there is no relative motion between the surface inspection system and the inspected surface. Another key drawback of this method is its limitation to optically rough surfaces with defined scattering behavior. In particular, it cannot inspect optically glossy surfaces, which occur in many industrial manufacturing processes and commonly used materials.

[0019] To date, few methods for examining glossy surfaces have been published. WO 2004 051186 A1 ("Method and device for optical form measurement and / or evaluation," SAC) describes a method that allows the scattering properties of a surface to be examined relatively independently. This method is applicable to optically smooth, rough, and glossy surfaces. For this purpose, a combination of deflectometry and photometric stereometry is used. Figure 13 The device is schematically depicted. A preferably hemispherical scatterer (S1) illuminated by multiple light sources illuminates the surface to be inspected in the region of a test field (M) so that at every point (P) on the surface, for every possible orientation of the surface normal (N), there is a light beam (L) that is directionally scattered or reflected (R) into a camera (K). The specific brightness distribution at each location on the scatterer allows the corresponding orientation of the surface normal to be determined by area coding. Reconstructing the shape of the object requires recordings from three cameras, or recordings of the three color channels red, green, and blue, a color camera, and a monochrome object.

[0020] In addition to illuminating an object by means of a spherical scatterer, a planar lighting device is also possible, as described in DE 10 2015 21 2 910 ("Device for illuminating an object", SAC). Figure 14 As shown. Here, at least two illumination distributions are generated on the planar emitting surface (L) in order to perform area coding on each position on the emitting surface. However, in all these embodiments, the following condition must always be met: a directional reflection (R) entering the camera is generated by each point of the surface to be inspected. In order to ensure that there is a light beam reflected into the camera for each possible orientation of the surface normal, each point of the object must be illuminated from a corresponding number of different directions. This inevitably leads to the following situation: the area enclosed by the lighting device must always be significantly larger than the area of ​​the surface to be measured, and therefore the area range (BM) of the lighting device must always be significantly larger than the size of the inspection field (B). This leads to obvious disadvantages in practice. In the following, the term surface inspection system, lighting system or range of the surface to be inspected is always used as area range.

[0021] Inspecting the surface of an object using the devices and methods described in the prior art requires an illumination device whose range significantly exceeds the size of the object to be inspected. This has profound disadvantages in practical applications, including:

[0022] Using a surface inspection system with a given range, it is only possible to inspect large objects to be inspected, such as pressed parts in the automotive industry, by progressively measuring many relatively small sub-areas.

[0023] Due to the large size of the surface inspection system, there must be a relatively large free space in front of the object to be inspected to avoid collisions. In particular, the shape of the object, the object's installation, and the object's surroundings must be adapted to the size of the surface inspection system.

[0024] Due to the large size of the lighting system, the surface inspection system is significantly heavier. This makes it more difficult to operate.

[0025] Especially in automated robotic applications, the large weight and mass distribution far from the recording point restrict maneuverability and measurement speed due to the large forces and moments.

[0026] In some methods, a predetermined, usually very small, distance relative to the object to be inspected is also required in order to meet the angular conditions of the lighting. In some of the methods described above, in order to detect surface defects, it is necessary to record multiple images continuously in time for different brightness distributions generated progressively by the lighting system. During the recording process, no relative movement of the object to be inspected and the surface inspection system is allowed, or only very small relative movement is allowed. In particular, in automated applications, the sensor must be stopped before measuring each sub-area of ​​the object to be inspected. This significantly increases the time required to detect relatively large objects that cannot be captured in one measurement. In-line inspection systems integrated in manufacturing processes may not be able to keep up with the production cycle. This is a serious disadvantage for automated robot-assisted inspection applications, which are often used for in-line inspection during the manufacturing process of large objects, such as in production lines in the automotive industry.

[0027] Furthermore, in prior art methods, the evaluation of the recordings is often very complex and generates a large amount of information that is unnecessary or inappropriate for capturing surface defects. Furthermore, it is often difficult to distinguish surface defects from local variations in the scattering and reflection properties. Summary of the Invention

[0028] An object of the present invention is to provide an improved device for optically inspecting surfaces which overcomes at least some of the above-mentioned problems. In particular, the object of the present invention is to provide a simple device for optically inspecting surfaces, the range of which does not exceed or does not significantly exceed the range of the surface to be inspected, thereby offering significant advantages over the prior art in practical applications, and / or the operation of which is substantially independent of the scattering and reflection properties of the surface or is suitable for glossy surfaces, and / or the device allows simple but reliable detection of surface defects.

[0029] This object is achieved in a first aspect by a surface inspection system having the features of claim 1 and in a second aspect by a surface inspection system having the features of claim 3 .

[0030] The dependent claims relate to preferred configurations of the invention.

[0031] In a first independent aspect, the present invention comprises a surface inspection system for capturing surface defects of a surface to be inspected, comprising a camera system, an illumination system, and an evaluation system, wherein the evaluation system evaluates the brightness and / or color distribution of the surface to be inspected in at least one image captured by the camera system and captures the surface defect of the surface to be inspected as a local deviation in brightness and / or color. In this case, it is provided that the evaluation system evaluates the local deviation in brightness and / or color as a surface defect if the local deviation in brightness and / or color appears brighter in at least one first sub-region than a surface region surrounding the local deviation and darker in at least one second sub-region than the surface region, and / or if different colors predominate in different sub-regions.

[0032] A first aspect of the present invention is based on the recognition that two opposing sides of a surface defect can, under different circumstances, reflect more or less light from a source than their surroundings, depending on the orientation of the side, regardless of the angle between the light source and the camera. Alternatively or additionally, by using spatially separated light sources or spatially separated light source regions of different colors, one color or the other will dominate, i.e., one color will stand out more than the other, depending on the orientation of the side. Surface defects can thus be distinguished from localized variations in scattering or reflection properties, which typically result in a brighter or darker overall appearance and / or affect all colors equally.

[0033] In particular, the evaluation system thus determines areas where the brightness and / or color deviate locally, i.e., where the brightness and / or color of these areas deviate locally from the surroundings, which have uniform brightness and / or color. In this case, by using a color camera, the brightness deviation can be determined individually for multiple color channels or jointly for all color channels.

[0034] However, in a first variant, an area with local deviations in brightness and / or color is evaluated as a surface defect only if the local deviation appears brighter in at least one first subarea than the surface area surrounding the local deviation and darker in at least one second subarea than the surface area. In this case, using a color camera, such brightness deviations can be determined individually for multiple color channels or jointly for all color channels.

[0035] In a second variant, by using a color camera, areas with local deviations in brightness and / or color can be evaluated as surface defects even if different colors dominate in different subareas, i.e., if the first color channel appears brighter than the remaining color channels in at least one first subarea and the second color channel appears brighter than the remaining color channels in at least one second subarea.

[0036] In a second aspect, the present invention comprises a surface inspection system for capturing surface defects of a surface to be inspected, comprising a camera system, an illumination system comprising one or more light sources, and an evaluation system, wherein the evaluation system evaluates the brightness and / or color distribution of the surface to be inspected in at least one image captured by the camera system, and captures surface defects of the surface to be inspected as local deviations in brightness and / or color. This second aspect is characterized in that the camera system comprises at least two cameras, which fully or partially image the surface to be inspected, wherein the cameras and the one or more light sources of the illumination system are arranged relative to each other such that directional reflections of the one or more light sources for each camera occur at different locations of an inspection field of the surface inspection system.

[0037] According to a first aspect and according to a second aspect, the invention makes it possible to capture surface defects on optically rough and optically glossy surfaces, such as occur in many processing methods and materials used in industrial manufacturing.

[0038] The inventors of the present invention have recognized that the angular conditions between the light source and the camera are crucial for the reliable detection of surface defects. In particular, surface defects near the first region with directional reflections can be captured with particularly high reliability because deviations from the surface normal produce particularly large brightness variations, making one side of the surface defect appear brighter than its surroundings, while the other side appears darker.

[0039] The use of multiple cameras according to the second aspect means that the area where favorable conditions exist for capturing surface defects is correspondingly expanded. Conversely, the use of at least two cameras means that the size of the apparatus, in particular the size of the lighting system, can be reduced compared to the extent of the inspection field.

[0040] In one possible configuration of the present invention, for each camera, a second area of ​​the inspection field where no directional reflection of the light source occurs is reserved next to a first area of ​​the inspection field where directional reflection of the light source occurs.

[0041] Under these circumstances, the inventors have realized that surface defects in the second region, which is located adjacent to the region with directional reflection and therefore presents non-directional scattering, can be captured particularly reliably. This is because in the first region with directional reflection, surface defects appear only as darker areas and are therefore barely distinguishable from local variations in the reflectivity. Furthermore, they are easily masked by bright surroundings. In contrast, in the second region without directional reflection, conditions are more favorable, yet this second region is located adjacent to the region with directional reflection.

[0042] In contrast, the conditions are also less favorable in the third region where no directional reflection occurs, which is located away from the region with directional reflection, since surface defects here also usually appear only as darker areas and are therefore barely distinguishable from local changes in the reflection properties.

[0043] The second region within the meaning of the present invention preferably extends on both sides of the first region with directional reflection to a maximum extent of 10 cm and / or 20% of the working distance between the surface inspection system and the surface to be inspected, more preferably to 6 cm and / or 15% of the working distance between the surface inspection system and the surface to be inspected. Conversely, the further region preferably constitutes the third region within the meaning of the present invention.

[0044] Preferably, the second area of ​​each color channel and each camera covers at least 10%, preferably at least 15% of the area of ​​the inspection field.

[0045] Where multiple cameras are used, the second region of each colour channel preferably covers at least 40%, more preferably at least 60% of the area of ​​the inspection field for all cameras taken together.

[0046] Preferably, all color channels and the second area on the camera together cover the entire inspection field.

[0047] The use of areas without directional reflections can in turn reduce the size of the device, in particular the size of the illumination system, since the function of the surface inspection system no longer depends on the directional reflection of the illumination system for every area of ​​the inspection field.

[0048] Preferably, the camera system comprises at least four cameras, more preferably at least six cameras. This enables coverage of large inspection fields.

[0049] Preferably, the cameras are arranged along columns and rows. This allows particularly large inspection fields to be covered.

[0050] In one possible configuration of the present invention, at least two cameras arranged in the same row or column are arranged to be offset relative to each other in a direction perpendicular to the extent of the row or column. This expands the area where favorable measurement conditions exist for at least one camera.

[0051] With regard to the position of the directional reflection of the one or more light sources of the illumination system in the inspection field, it is mentioned in the context of the present invention that the inspection field is a plane extending in a measurement area that can be captured by the surface inspection system in a plane arranged centrally relative to the measurement depth, and preferably extending parallel to the plane defined by the position of the camera. However, in a preferred embodiment of the invention, the specified conditions apply to all measurement depths, i.e., to each measurement plane extending within the measurement area and parallel to the inspection field defined in this manner.

[0052] The first and second aspects are independent of each other and can be used independently of each other. In this regard, for example, the evaluation according to the first aspect can also be used in the case of a surface inspection system with only one camera. In this system, favorable conditions for capturing surface defects exist only in a small sub-area of ​​the inspection field. However, for example, the surface to be measured can be inspected in multiple steps, and in each case the surface inspection system has offset positions. Furthermore, a surface inspection system according to the second aspect using multiple cameras is also conceivable, with the evaluation performed in a different manner.

[0053] However, preferably, the first and second aspects of the present invention are combined with each other.

[0054] Preferred configurations of the present invention will be described in more detail below, which make it possible to develop a surface inspection system according to the first aspect, according to the second aspect and according to a combination of the first and second aspects.

[0055] According to one possible configuration, the range of the device does not exceed the range of the inspection field, or only slightly exceeds the range of the inspection field, i.e., it does not exceed 1.5 times the basic area of ​​the surface inspection system measured in a plane parallel to the inspection field, which provides significant advantages in practical applications. Due to the relatively small size (relative to the inspection field), the invention makes the operation of the surface inspection system simple. This is especially true when the available space in front of the object to be inspected is limited, which is the case in many industrial applications. In addition, in automated applications, the risk of collision between the surface inspection device and objects from the manufacturing or inspection environment is significantly reduced.

[0056] The small size also results in low weight and a favorable mass distribution with low moments. In automated applications, this allows high movement and measuring speeds with less force and greater precision.

[0057] Furthermore, the invention makes it possible to inspect a surface by simultaneous image recording of all cameras of a camera system. In particular, by using a suitably bright light source and short exposure times, surface inspection can be performed during relative motion of the surface to be inspected and the inspection system.

[0058] According to one possible configuration, it is provided that the camera system and the lighting system are arranged relative to each other so that, next to at least one first area of ​​the inspection field in which directional reflections of the light source of the lighting system occur, at least one second area in which directional reflections of the light source do not occur remains in the camera's recording, wherein the evaluation system evaluates the recording in the second area.

[0059] According to one possible configuration, it is provided that the evaluation system evaluates a plurality of recordings of the surface to be inspected, which recordings differ in the position of the camera used to record them relative to the surface to be inspected.

[0060] According to one possible configuration, it is provided that the evaluation system evaluates local deviations in brightness and / or color contained in a plurality of recordings as surface defects if the local deviation in at least one recording appears brighter in at least one first sub-area and darker than the surface area surrounding the local deviation in at least one second sub-area, and / or if different sub-areas predominate with different colors.

[0061] In this context, the present invention takes into account the fact that, depending on the relative position between the camera and the surface defect, there may be more favorable or less favorable conditions for capturing the surface defect. If a local deviation thus has a structure typical of a surface defect in at least one image, then this local deviation is evaluated as a surface defect.

[0062] The multiple recordings of the surface to be inspected can be recorded by multiple cameras of a camera system, which are arranged offset relative to each other at the surface inspection system. Preferably, the cameras are controlled in such a way that multiple recordings are recorded simultaneously.

[0063] Alternatively or additionally, a plurality of recordings of the surface to be inspected may be recorded consecutively at different positions of the surface inspection system relative to the surface to be inspected, preferably a motion unit being provided which moves the surface inspection system accordingly. Preferably, the controller controls the motion unit along a predetermined trajectory.

[0064] According to one possible configuration, it is provided that, by means of the setting of the surface inspection system, the positions of the multiple cameras of the camera system for multiple recordings are offset relative to each other so that the inspection field and / or the surface to be inspected is completely covered by a second area in which no directional reflections of the light source occur.

[0065] According to one possible configuration, it is provided that, by means of control of a motion unit of the surface inspection system, the positions of the multiple recording cameras are shifted relative to one another so that the inspection field and / or the surface to be inspected is completely covered by a second area in which no directional reflections of the light source occur.

[0066] According to one possible configuration, it is provided that the lighting system comprises at least two spatially separated areas.

[0067] In one possible configuration, the two regions have different colors.

[0068] The use of different colored areas firstly allows areas of the inspected surface with favorable conditions to be magnified, since the different colors can be evaluated separately from one another and therefore do not interfere with one another. Furthermore, the different colors allow surface defects to be identified.

[0069] In one possible configuration, the areas are arranged on opposite sides of the surface inspection system.

[0070] According to one possible configuration, it is provided that the lighting system or its spatially separated areas are implemented in the form of points, lines, rods and rings, or in some other advantageous embodiments comprise one or more surface-emitting light sources or point light sources, which either emit directionally within a narrow angular range or emit non-directionally within a wider angular range.

[0071] According to a preferred configuration, however, the lighting system or its spatially separated regions are realized in a rod-shaped or ring-shaped manner and / or comprise one or more surface-emitting light sources that emit non-directionally within a large angular range.

[0072] According to one possible configuration, it is provided that the illumination system has at least two spatially separated areas of different colors, and that the camera system includes at least one color camera having at least two color channels.

[0073] According to one possible configuration, it is provided that the sensitivities of the color channels correspond to the different colors of the lighting system, and thus:

[0074] According to one possible configuration, it is provided that the brightness distributions generated by spatially separated, differently colored areas of the lighting device are recorded simultaneously and independently of one another on different color channels of a camera and / or evaluated by an evaluation system. In particular, in this case, it is possible to evaluate in each color channel whether a local deviation in brightness has a first area in which the deviation is brighter than the surrounding area of ​​the local deviation and a second area in which the deviation is darker than the surrounding area of ​​the local deviation.

[0075] According to one possible configuration, it is provided that the evaluation system evaluates a local deviation in brightness as a surface defect if the local deviation appears brighter or darker in at least one first sub-region of the first color channel and in at least one second sub-region of the second color channel than the surface area surrounding the local deviation.

[0076] According to one possible configuration, it is provided that the illumination system has at least three spatially separated regions of different colors, and that the camera system comprises at least one color camera having at least three color channels.

[0077] In one possible configuration, the spatially separated regions form a frame.

[0078] In one possible configuration, the frame has a first color on a first side and a different second color on an opposing second side.

[0079] In one possible configuration, areas also having the first or second color are provided on the third and / or fourth side of the frame, respectively, these areas being preferably arranged at a distance from the respective first or second side having the same color.

[0080] In one possible configuration, the remaining areas of the third and fourth sides have a third color. In particular, an area with the third color is provided between the first side and another area with the first color and between the second side and another area with the second color.

[0081] According to one possible configuration, provision is made for the simultaneous image recording of all cameras of the camera system to be sufficient for a comprehensive inspection of the inspection field.

[0082] According to one possible configuration, it is provided that, relative to the basic area of ​​the surface inspection system in a plane parallel to the inspection field, the area of ​​the surface inspection system is not greater than 1.5 times the area of ​​the inspection field.

[0083] According to one possible configuration, it is provided that a plurality of areas of the lighting system are arranged so as to be rotated by an angle relative to one another with respect to the test field.

[0084] According to one possible configuration, it is provided that the two regions of the illumination system are arranged rotated by 90° relative to one another with respect to the test field, wherein the regions of the illumination system preferably extend in a rod-like manner along the edge of the surface inspection system.

[0085] According to one possible configuration, it is provided that the cameras of the camera system are located within an area enclosed by the area of ​​the lighting system, wherein the area of ​​the lighting system preferably extends in a rod-shaped manner along the edge of the surface inspection system.

[0086] According to one possible configuration, it is provided that the surface inspection system comprises a movement unit which allows the surface inspection system to be moved relative to the surface to be inspected.

[0087] According to one possible configuration, provision is made for the movement unit to be controlled by a controller along a predetermined path. In particular, the surface inspection system can thus be guided over a surface to be inspected that is larger than the inspection field.

[0088] According to one possible configuration, provision is made for the inspection to be carried out during a relative movement of the surface inspection system relative to the surface to be inspected.

[0089] According to one possible configuration, it is provided that the surface inspection system forms a structural unit with a 3D measuring system, in particular with a fringe projection system.

[0090] According to one possible configuration, it is provided that the camera of the 3D measuring system is surrounded by the area of ​​the camera and / or the lighting system of the camera system of the surface inspection system.

[0091] The surface inspection system can be used to inspect components. Preferably, the surface inspection system is configured so that it performs the inspection of the components in an automated manner.

[0092] Surface inspection systems can be implemented in a way that automatically captures and outputs surface defects.

[0093] The surface inspection system is preferably implemented so that it can capture even relatively small surface defects extending over only a few pixels. In particular, the surface inspection system can be implemented so that it can capture surface defects extending over less than 100 pixels, preferably less than 50 pixels, more preferably less than 20 pixels.

[0094] The surface inspection system is preferably designed to detect only relatively small surface defects. In particular, the evaluation system can be configured so that areas with deviating brightness and / or color exceeding a predetermined size are not evaluated as surface defects. These areas are more likely to represent expected changes in surface shape rather than surface defects.

[0095] The surface inspection system may include an output unit on which the captured surface defects are displayed. For example, the location of the captured surface defects may be displayed on a representation of the component to be inspected. For this purpose, the output unit may include a screen.

[0096] The evaluation system and controller used in the context of the present invention preferably automatically capture surface defects in one or more runs. They preferably include a microprocessor and a non-volatile memory on which is stored a computer program having instructions executed on the microprocessor, thereby enabling the functions of the evaluation system and / or controller described in the context of the present application. Therefore, in particular, the evaluation system and controller are configured and programmed to perform these functions. The evaluation system and controller are connected to the camera system and the lighting system, and also to the motion unit (if present), in order to evaluate their data and / or control them.

[0097] The present invention also comprises a method for capturing surface defects of a surface to be inspected by means of a surface inspection system comprising a camera system and an illumination system, wherein the illumination system generates a brightness and / or color distribution and reflection and scattering properties of the surface to be inspected, wherein the surface defects become visible as local deviations in brightness and / or color, said distribution being detected by the camera system.

[0098] According to a first aspect, the method is characterized by the fact that a local deviation in brightness and / or color appears brighter in at least one first sub-region than a surface area surrounding the local deviation and darker in at least one second sub-region than the surface area, and / or if different colors predominate in different sub-regions, the local deviation is evaluated as a surface defect.

[0099] According to a first aspect, the method is characterized in that the surface to be inspected is in each case imaged completely or partially by at least two cameras, wherein the cameras and the light source or light sources of the illumination system are arranged relative to one another and relative to the surface to be inspected in such a way that a directional reflection of the light source of each camera occurs at a different location on the surface to be inspected.

[0100] These two aspects are initially independent of each other but can be combined.

[0101] The method is preferably performed in a manner such as has been described in more detail above with respect to the surface inspection system according to the invention.

[0102] In particular, the method is implemented using one of the surface inspection systems described above and in more detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0103] The present invention will now be explained in more detail based on exemplary embodiments and the accompanying drawings.

[0104] In the attached figure:

[0105] Figure 1 shows a schematic diagram of the dependence of the amount of reflected light on the angle between the camera, the light source and the position on the surface to be inspected, two resulting images of a surface defect, and a diagram of the surface course in the area of ​​the surface defect in the case of a first exemplary embodiment of the surface inspection system according to the invention,

[0106] Figure 2 shows a schematic diagram regarding the dependence on the amount of reflected light in the case of a second exemplary embodiment of a surface inspection system according to the present invention,

[0107] Figure 3 shows a schematic diagram regarding the dependence of the amount of reflected light in the case of a third exemplary embodiment of a surface inspection system according to the invention, in which two cameras are used according to the second aspect,

[0108] Figure 4 A schematic diagram showing the distribution of areas with directional reflections within the inspection field when only one camera is used is shown.

[0109] Figure 5shows a schematic diagram of the distribution of directional reflections within an inspection field in the case of an exemplary embodiment of a surface inspection system with multiple cameras according to the second aspect,

[0110] Figure 6 Shown in accordance with Figure 5 Side view of the beam path for the configuration case,

[0111] Figure 7a A schematic diagram showing the arrangement of two areas of the lighting system relative to the test field is shown,

[0112] Figure 7b shows a schematic diagram of the arrangement of four separate areas of the lighting system relative to the test field,

[0113] Figure 8 A schematic diagram of the distribution of directional reflections in the test field, perpendicular to the direction of the reflections, is shown when using additional areas of the illumination system. Figure 5 Those extensions in

[0114] Figure 9 A schematic diagram showing an exemplary moment in time of a lighting system with six cameras and four separation zones,

[0115] Figure 10 An exemplary embodiment in which each camera is partially offset is shown. Figure 9 Basic settings,

[0116] Figure 11 Shown Figure 10 The exemplary embodiment shown has a lighting system with multiple separate areas emitting three different colors.

[0117] Figure 12 shows a schematic diagram of an exemplary embodiment of a surface inspection system according to the present invention, which has been combined with a 3D measurement system,

[0118] Figure 13 A first embodiment of a surface inspection system according to the prior art is shown, and

[0119] Figure 14 A second embodiment of a surface inspection system according to the prior art is shown. DETAILED DESCRIPTION

[0120] Hereinafter, exemplary embodiments of the present invention will be described in more detail. Where clearly advantageous, this description will be illustrated by the accompanying drawings.

[0121] Figure 1A first exemplary embodiment of a surface inspection system according to the invention is shown in schematic form. The surface inspection system comprises a camera system including a camera K and an illumination system including a light source L1. The light source L1 illuminates the surface O to be inspected and generates a brightness distribution as well as reflection and scattering properties of the surface to be inspected, which is recorded by the camera system and evaluated by an evaluation system (not shown in greater detail).

[0122] Surface O has two surface defects D1 and D2, whose contours are Figure 1 This is shown in the bottommost cross-sectional view. In this case, the surface defects are, for example, small embossing defects, at which the surface has been recessed at a plurality of points so that the defects have opposite, relatively steep sides.

[0123] To explain the nature of this defect which is exploited according to the first aspect of the present invention, Figure 1 The corresponding light beams L emitted from the light source L1 and illuminating the first and second surface defects D1 and D2 respectively are shown. In addition, in the case where there is a flat surface in the area around the surface defect, for example, R represents the direction of the corresponding directional reflection of the light beam L. The brightness distribution in the direction deviating from the directional reflection direction R is also shown. It can be clearly seen that most of the light is radiated in the direction of directional reflection, while the light radiated in other angle ranges decreases rapidly as the angle increases. In addition, in addition to the brightness distribution of the reflection in the case of a flat surface, two brightness distributions of the reflection at the two sides of the surface defect are also shown. In addition, the three arrows R D The brightness of the light reflected from these three areas in the direction of the camera K is shown in each case.

[0124] In the case of the first surface defect D1 shown on the left, one side surface is arranged and oriented relative to light source L1 and camera K so that it reflects light from light source L1 almost directly toward the camera, making it appear significantly brighter than the surroundings of the surface defect. In contrast, light is reflected directionally from the opposite side surface at a significantly greater angle relative to the camera, making the light reflected toward the camera significantly darker than the surroundings. As a result, a first region, brighter than the surroundings, and a second region, darker than the surroundings, appear in the area of ​​the surface defect.

[0125] In contrast, in the case of the second surface defect D2 shown on the right, both side areas are darker than the area surrounding the surface defect due to the less favorable angular relationship. Furthermore, the overall brightness difference is significantly smaller. Therefore, in this view, the surface defect cannot be distinguished from locations with less reflection, for example due to increased roughness.

[0126] In contrast, since different areas are brighter than the surroundings in one case and darker in another case, the first surface defect D1 can be clearly identified as a defect with respect to the surface shape, since the brightness distribution represents the typical characteristics of a defect with two sides.

[0127] According to a first aspect of the invention, the evaluation system thus evaluates images from at least one camera K and classifies local deviations in brightness as surface defects, which have first areas that are brighter than their surroundings and second areas that are darker than their surroundings. In contrast, local deviations in brightness that are entirely darker or brighter than their surroundings are not classified as surface defects, as they may also be local deviations in reflective or scattering properties.

[0128] If a lighting system with multiple, separate areas of different colors is used, then given the appropriate angular relationships, the various sides of a surface defect will reflect different colors to varying degrees in different situations. This aspect can also serve as a "tag" within the context of the second aspect, allowing the evaluation system to identify surface defects. If the local deviation thus has multiple areas, and different colors have different brightness within these areas, the presence of a surface defect can also be inferred from this.

[0129] In this case, instead of the evaluation according to the first described label, the last described process can be used, in which the different color channels are not evaluated separately, but the result images from the different color channels are compared with each other. However, it is preferred that this evaluation is supplemented.

[0130] It is also obvious from the comparison of the two defects D1 and D2 that for each of the two defects, Figure 1 A representation of the resulting image is inserted in Figure 1. Here, the captureability of the defect depends primarily on the angular relationship between the light source, the surface defect, and the camera. In this case, a particularly favorable possibility of capturing the surface defect exists in the second region of the surface, directly adjacent to the first region where the light source is reflected directionally into the camera. In contrast, if the defect is located in a third region, further away from the first region with the directionally reflected light, the captureability of the surface defect becomes significantly more difficult. The second region with favorable angular characteristics extends on both sides of the first region with the directionally reflected light. As the angular relationship becomes increasingly less favorable, the region with a maximum distance of 10 cm and / or 20% of the working distance between the surface inspection system and the surface to be inspected is preferably considered to be highly suitable for capturing surface defects, and more preferably, the region with a maximum distance of 6 cm and / or 15% of the working distance between the surface inspection system and the surface to be inspected is considered to be highly suitable for capturing surface defects. Thus, the further away region constitutes the third region with unfavorable angular characteristics.

[0131] Therefore, if only one camera and one light source are present, the measurement area in which surface defects can be captured is relatively small. However, one possibility for capturing surface defects over a larger area of ​​a surface using only one light source and one camera is to move the surface inspection system relative to the surface, thereby successively scanning the surface with areas favorable for capturing surface defects. This results in the generation of multiple recordings of the surface, which differ in the position of the camera relative to the surface and, accordingly, also have different angular relationships between the light source, the corresponding surface defect, and the camera.

[0132] In contrast, if one wants to zoom in on an area that is particularly suitable for capturing surface defects and that is provided by a stationary surface inspection system, e.g. Figure 2 As shown, in a first possibility, another light source L2 can be used, which illuminates the surface to be inspected and produces an area with directional reflection at a different position relative to the camera K. This results in an additional area with a favorable angular relationship between the light source, the surface area and the camera. Figure 2 In the embodiment of the present invention, the second surface defect D2 can also be well captured by the light source L2. In order to prevent the two light sources from interfering with each other, they preferably have different colors and / or are continuously controlled.

[0133] However, from Figure 2 It is also obvious that a very large distance is required between the light source L2 and the camera to produce a favorable angular characteristic for the second surface defect D2. Therefore, this configuration leads to a large size of the surface inspection system compared to the inspection field.

[0134] therefore, Figure 3 An exemplary embodiment of a surface inspection system according to the second aspect of the invention is shown, wherein the camera system has at least two cameras K1 and K2. In the exemplary embodiment, the cameras cooperate with two light sources L1 and L2. However, it is also conceivable to use only one light source L1. The second camera K2 generates at least one further area with favorable angular properties in which surface defects can be captured well. If a plurality of light sources are used in addition, even more favorable areas can be generated. Here, too, light sources with different colors or which are continuously controlled are preferably used to avoid mutual interference. In contrast to the use of light sources such as Figure 2 Compared to the other light source shown, the other camera requires significantly less space to provide a favorable angular relationship.

[0135] refer to Figure 4 and Figure 5 , again illustrating the effect of using multiple cameras on the area that is best captured. Here, Figure 4An exemplary embodiment is shown in which one camera and two light sources L1, L2 are arranged on opposite sides of a camera K. This creates two areas R1 and R2 with direct reflections of the light sources L1 and L2 into the camera. The areas that are advantageous for capturing surface defects are arranged adjacent to these areas with direct reflections and thus only cover a small portion of the inspection field M. In contrast, in Figure 5 In the case of the exemplary embodiment in FIG, with the same arrangement of the two light sources L1 and L2, the use of multiple cameras K1-K6 results in a much larger area of ​​the measurement field M with favorable measurement conditions, because the corresponding areas R1-R6 with directional reflections are distributed over the entire measurement field.

[0136] The following will refer to Figure 6 Explain the basic concept of the first aspect of the present invention again, Figure 6 Shown according to Figure 5 A side view of the configuration, which features only three cameras.

[0137] Figure 6 An exemplary embodiment of a surface inspection system according to the present invention is shown, comprising a camera system and an illumination system, the camera system including a plurality of cameras, for example, three cameras (K1, K2; K3). In this case, it is advantageous if the illumination system consists of a plurality of spatially separated areas or light sources (L1, L2). For each area of ​​the illumination system and each camera of the camera system, the geometric condition of directional reflection (angle of incidence relative to the surface normal = angle of reflection) is satisfied at different locations on the surface to be inspected. In the case of glossy surfaces, this results in a continuous brightness distribution for each possible combination of camera and illumination system areas, with a maximum at the location where the reflection condition is satisfied. If surface defects (e.g., local deviations from the surface normal or scattering properties) are located within this brightness distribution, this results in a local variation of the brightness distribution generated by the corresponding illumination system area in the corresponding camera. By appropriately arranging the camera and illumination system areas, subareas of the surface to be inspected can be distributed over the entire surface to be inspected, with the combination of camera and illumination area in each subarea allowing the detection of surface defects. In this case, in contrast to prior art methods, the range of the surface inspection system (BM) does not need to exceed the range of the surface to be inspected (B).

[0138] In an advantageous embodiment, the brightness distributions generated by different areas or parts of spatially separated areas of the lighting system are captured in the camera independently of one another. This eliminates the brightness distributions of different spatially separated areas of the lighting system from being superimposed on the camera, and local brightness deviations caused by surface defects have the highest contrast.

[0139] Independent capture can be achieved, for example, by temporally consecutive camera recordings, with only one of the spatially separated areas of the lighting system being active for each camera recording. Preferably, a corresponding controller is provided for this purpose, and the areas of the lighting system are controlled accordingly. However, it is advantageous to implement the spatially separated areas or parts thereof in different colors. If the camera of the lighting system is implemented as a color camera, and if the colors of the lighting system are selected based on the different sensitivities of their color channels, the brightness distributions generated by the differently colored areas of the lighting system can be captured simultaneously, and the entire surface to be inspected can be inspected with a single recording of the camera system.

[0140] Figure 7 shows another advantageous embodiment in which different areas of one or both lighting systems are arranged in a manner rotated 90° relative to the surface to be inspected. The figure shows a front view of the inspection field and the surface to be inspected (O) as seen from the viewing direction of the surface inspection system. Figure 7a This embodiment is explained based on an illumination system consisting of two rod-shaped areas (L1 and L2), which are located, for example, at two opposite edges of the test field. Figure 7b In the embodiment of , there is additionally at least one second illumination system ( L3 and L4 ) which is rotated by an angle W=90° relative to the test field about axis A. Here too, two rod-shaped areas ( L3 and L4 ) are provided, for example, at the two remaining opposite edges of the test field.

[0141] With this arrangement, it is possible to detect directionally dependent surface defects with higher contrast. In this case, the lighting system or parts thereof can be implemented, for example, in different shapes (e.g., rings, ring segments, etc.) as described above and can be composed of different light sources (flashlights, LEDs, etc.). Preferably, the light source emits light in a non-directional manner.

[0142] Figure 8 Shown in Figure 5 The light distribution shown for a camera arrangement comprising six cameras K1-K6 occurs, for example, if only the light sources L3 and L4, each extending along a longitudinal side, are considered. The two-row camera arrangement generates four areas R7-R10 with directional reflections, which are also distributed over the measuring field M.

[0143] Preferably, the plurality of cameras K1-K6 are combined with a light source extending along the edge of the measurement field, such as Figure 9 Schematically shown again in FIG.

[0144] Figure 9An example of an advantageous embodiment is shown, in which the cameras (K1-K6) of the camera system are located within an area defined by the lighting system (L1 to L4). As a result, the range of the surface inspection system can be kept very small.

[0145] As mentioned above, unlike the prior art, the present invention allows the detection of surface defects within a test field whose range (O) corresponds at least to the range of the surface inspection device (BM). As mentioned above, this has important advantages in practical applications. Figure 9 , an arrangement comprising six cameras is shown by way of example.

[0146] Figure 10 Shown as Figure 9 The schematic diagram of an exemplary embodiment with six cameras in Figure 1 illustrates the precise positioning of the cameras. Specifically, the cameras are not arranged precisely one above the other or adjacent to one another in a grid of columns and rows, but are at least partially offset relative to the grid. As a result, the areas with directional reflections for the individual cameras are again offset relative to one another.

[0147] exist Figure 10 In the case of the exemplary embodiment shown with six cameras, the cameras K2 and K5 arranged centrally in rows of three are cameras offset by a distance v relative to a connecting line connecting the cameras K1, K3 and the cameras K4, K6 surrounding the cameras K1, K3 on both sides. Figure 8 Compared to the illustration of the area with directional reflection shown in , this results in better coverage of the measurement field, since the cameras, displaced relative to the grid, create additional areas with directional reflection. In the exemplary embodiment, cameras K2 and K5 are displaced relative to the grid toward each other. Alternatively or additionally, cameras K2 and K5 can also be displaced relative to their position in the direction of the connecting line.

[0148] In principle, all cameras can be moved by different vectors relative to their positions within the regular grid in different situations in order to further enhance this effect. However, at the same time, the cameras should cover the largest possible inspection field. Figure 10 In the exemplary embodiment shown, a configuration has been selected in which the corner cameras K1 , K3 , K4 and K6 are respectively arranged at the corners of a rectangle and only the two central cameras K2 and K5 are arranged displaced relative to the rectangle.

[0149] As mentioned above, different colors are used for the separate areas L1-L4 of the lighting system (also referred to as light sources in some cases within the context of this application) to avoid mutual interference during simultaneous recording. Alternatively, the light sources can also emit continuously, thus also allowing for separate evaluation. In contrast, the separate areas L1-L4 of the lighting system do not have patterns for measurement or evaluation within the corresponding areas. However, any production-related brightness fluctuations in these areas are not harmful.

[0150] In such Figure 10 In the case of the configuration shown with four separated areas L1 - L4, by using different colors, the optimal configuration will require four color channels. If the camera has four color channels, four different colors can be used.

[0151] However, commercial cameras usually have only three color channels. Figure 11 A configuration is shown that manages only three different colors, but substantially prevents separate areas of the lighting system from influencing each other.

[0152] In this case, in the exemplary embodiment, areas L3 and L4, which are arranged on opposite sides of the surface measurement system, have different colors. In this case, they each extend along the entire side. In the exemplary embodiment, these areas L3 and L4 are arranged on the longer side (along which the three cameras are arranged). Then, on the lateral side, area L2 is arranged, which has the same color as area L3, but is spaced apart from area L3 and adjacent to area L4. Conversely, area L2' is arranged, which has the same color as area L4, at a certain distance from area L4 and adjacent to area L3. The remaining areas L1 and L1' have a third color.

[0153] In this case, the exemplary embodiment provides two areas, L2 and L2', on opposite sides of the surface inspection device. Thus, areas L1 and L1', each having a third color, separate areas L3, L2 and L4, L2' of the same color from one another. Alternatively, it is conceivable to provide two areas, L2 and L2', adjacent to one another on one side, allowing the opposite side to always radiate with the third color.

[0154] The number of cameras used depends primarily on the measurement field to be obtained. Therefore, it goes without saying that configurations comprising fewer cameras (for example two, three or four cameras) or comprising more cameras (for example eight or nine cameras) are also conceivable.

[0155] Figure 12An exemplary embodiment of a surface inspection device according to the present invention is shown, which is already combined with a 3D measuring device and forms a structural unit therewith. In particular, in this case, the camera K0 of the 3D measuring device is arranged in the area of ​​the surface inspection device, and in particular is arranged within the camera system and / or lighting system of the surface inspection device. In the exemplary embodiment, a separate camera is used for the 3D measuring device, which is preferably a monochrome camera because monochrome cameras are much faster than color cameras. However, it is also conceivable to use one of the cameras of the surface inspection device for 3D measurement. Preferably, the 3D measuring device and the surface inspection device have the same inspection field. More preferably, these can be used to capture the surface simultaneously or intermittently.

[0156] exist Figure 12 In the case of the exemplary embodiment shown, the 3D measuring device is a measuring device which operates with a projector P arranged on a base T which in turn carries a surface inspection device on the opposite side. In particular, this concerns a fringe projection device.

[0157] An evaluation system (not shown in more detail) of the surface inspection device preferably automatically captures surface defects and preferably has an output unit for outputting said surface defects.

[0158] In this case, for example, the output device may graphically represent the location of a surface defect on the component.

[0159] In one possible configuration, the evaluation system of the surface inspection device captures surface defects based exclusively on their brightness distribution and using the aforementioned typical labels for such defects. In particular, no a priori knowledge of the shape of the surface to be measured is used for this capture. Furthermore, in this exemplary embodiment, the capture is achieved without any comparison of the captured brightness distribution with a predetermined brightness distribution.

[0160] However, the evaluation system can output the result of the 3D measurement in conjunction with the result of the surface inspection, which result is preferably compared with the CAD data of the component to be measured.

[0161] In this case, the surface inspection device complements the 3D capture and enables reliable capture of surface defects that are usually difficult to identify with 3D measurement systems.

Claims

1. A surface inspection system for detecting surface defects of a surface to be inspected, comprising a camera system, an illumination system and an evaluation system, in, the illumination system having at least two spatially separated and differently colored areas, and the camera system comprising at least one color camera having a plurality of color channels, wherein the brightness distributions generated by the spatially separated and differently colored areas of the illumination system are recorded simultaneously and independently of one another on the plurality of color channels of the camera, wherein the evaluation system evaluates the color distribution of the surface to be inspected in at least one image captured by the camera system and determines surface defects of the surface to be inspected as local deviations in color, in, The evaluation system determines that the local deviation in color is a surface defect if a first color channel of the plurality of color channels of the camera system appears brighter than the remaining color channels of the plurality of color channels in at least one first subregion and a second color channel of the plurality of color channels of the camera system appears brighter than the remaining color channels in at least one second subregion, i.e., if different colors predominate in different subregions of the local deviation in color, and wherein the camera system comprises at least two cameras, which fully or partially image the surface to be inspected, wherein the at least two cameras are controlled to simultaneously image the surface to be inspected, wherein the cameras and one or more light sources of the lighting system are arranged relative to each other so that: directional reflections of one or more light sources for each camera occur at different positions of the inspection field of the surface inspection system, wherein the camera system and the lighting system are arranged relative to each other so that: next to at least one first area of ​​the inspection field where directional reflections of the light sources of the lighting system occur, at least one second area where directional reflections of the light sources do not occur remains in the recording of the camera, wherein the evaluation system evaluates the recording in the second area.

2. A surface inspection system for detecting surface defects on a surface to be inspected, comprising a camera system, an illumination system comprising one or more light sources, and an evaluation system, wherein: the evaluation system evaluates the brightness and / or color distribution of the surface to be inspected in at least one image captured by the camera system and determines surface defects of the surface to be inspected as local deviations in brightness and / or color, wherein the evaluation system determines that a local deviation in brightness and / or color is a surface defect if the local deviation appears brighter in at least one first sub-region than a surface region surrounding the local deviation and darker in at least one second sub-region than the surface region, and / or if different colors predominate in different sub-regions, and wherein the camera system comprises at least two cameras, which fully or partially image the surface to be inspected, wherein the at least two cameras are controlled to image the surface to be inspected simultaneously, wherein the cameras and the one or more light sources of the illumination system are arranged relative to each other such that directional reflections of the one or more light sources for each camera occur at different locations of the inspection field of the surface inspection system, In which, the camera system and the lighting system are arranged relative to each other so that: next to at least one first area of ​​the inspection field in which directional reflections of the light source of the lighting system occur, at least one second area in which directional reflections of the light source do not occur remains in the camera recording, wherein the evaluation system evaluates the recording in the second area.

3. The surface inspection system according to claim 1 or 2, wherein: For each camera in the camera system, a second area of ​​the test field in which no directional reflection of the light source occurs is retained next to a first area of ​​the test field in which directional reflections of the light source occur, wherein, for all cameras taken together, the second area constitutes at least 40% of the area of ​​the test field for each color channel and / or wherein the second area covers the entire test field over all color channels and cameras.

4. The surface inspection system according to claim 1 or 2, wherein: The evaluation system evaluates a plurality of recordings of the surface to be inspected, the plurality of recordings differing in the position of the cameras used to record them relative to the surface to be inspected, wherein the evaluation system evaluates a local deviation in brightness and / or color contained in the plurality of recordings as a surface defect if the local deviation in at least one recording appears brighter in at least one first sub-area and darker than the surface area surrounding the local deviation in at least one second sub-area, and / or if there are different sub-areas and different colors predominate in the different sub-areas.

5. The surface inspection system according to claim 1, wherein: The at least two spatially separated areas of the illumination system are arranged on opposite sides of the surface inspection system.

6. The surface inspection system according to claim 1 or 2, wherein: The illumination system or its spatially separated regions are realized in a rod-shaped or ring-shaped manner and / or comprise one or more surface-emitting light sources that emit non-directionally within a large angular range.

7. The surface inspection system according to claim 1, wherein: The evaluation system evaluates a local deviation in brightness as a surface defect if the local deviation appears brighter or darker in the at least one first subregion in the first color channel and in the at least one second subregion in the second color channel than a surface area surrounding the local deviation.

8. The surface inspection system according to claim 1 or 2, wherein: The simultaneous image recording of all cameras of the camera system is sufficient for a complete inspection of the inspection field, and / or wherein the range of the surface inspection system relative to a basic area of ​​the surface inspection system in a plane parallel to the inspection field is no greater than 1.5 times the range of the inspection field.

9. The surface inspection system according to claim 1 or 2, wherein: The plurality of areas of the lighting system are arranged in a manner rotated at an angle relative to the inspection field.

10. The surface inspection system according to claim 1 or 2, wherein: The cameras of the camera system are located within an area enclosed by the region of the illumination system, wherein the region of the illumination system extends in a rod-like manner along the edge of the surface inspection system.

11. The surface inspection system according to claim 1 or 2, comprising a motion unit allowing the surface inspection system to be movable relative to the surface to be inspected, wherein The motion unit is controlled by a controller along a defined path.

12. The surface inspection system according to claim 1 or 2, wherein: The inspection is achieved during the relative movement of the surface inspection system relative to the surface to be inspected.

13. The surface inspection system according to claim 1 or 2, wherein: The surface inspection system forms a structural unit with a 3D measuring system, which is a fringe projection system, wherein the camera of the 3D measuring system is surrounded by the area of ​​the camera of the camera system and / or the illumination system of the surface inspection system.

14. A method for detecting surface defects of a surface to be inspected by means of a surface inspection system, the surface inspection system comprising a camera system, an illumination system and an evaluation system, wherein: the illumination system generates a brightness and / or color distribution and reflection and scattering properties of the surface to be inspected, in which surface defects become visible as local deviations in brightness and / or color, and the distribution is detected by the camera system, wherein the illumination system has at least two spatially separated and differently colored areas, and the camera system comprises at least one color camera with a plurality of color channels, wherein the brightness distributions generated by the spatially separated and differently colored areas of the illumination system are recorded simultaneously and independently of one another on the plurality of different color channels of the camera, wherein a local deviation in brightness and / or color is determined as a surface defect if a first color channel of the plurality of color channels of the camera system appears brighter than the remaining color channels of the plurality of color channels in at least one first subarea and a second color channel of the plurality of color channels of the camera system appears brighter than the remaining color channels in at least one second subarea, i.e., if different colors predominate in different subareas, and / or wherein the evaluation system determines that a local deviation in brightness and / or color is a surface defect if the local deviation appears brighter in at least one first sub-area and darker in at least one second sub-area than the surface area surrounding the local deviation, and / or if different colors prevail in different sub-areas, wherein in each case the surface to be inspected is imaged completely or partially by at least two cameras, wherein the at least two cameras are controlled to image the surface to be inspected simultaneously, wherein the cameras and one or more light sources of the lighting system are arranged relative to each other and to the surface to be inspected such that: directional reflections of the light source for each camera occur at different positions on the surface to be inspected, wherein the camera system and the lighting system are arranged relative to each other such that: next to at least one first area of ​​the inspection field of the surface inspection system in which directional reflections of the light source of the lighting system occur, at least one second area in which directional reflections of the light source do not occur remains in the recording of the camera, wherein the evaluation system evaluates the recording in the second area.

Images