Test device for checking component surfaces and method therefor

Description

[0001] The invention relates to a testing device for optically testing surfaces of a test specimen.

[0002] Surface inspection of components plays a particularly important role in the series production of high-quality formed metal parts. In the automotive industry, for example, surface inspection is performed on the housings of window lift motors. A forming press can produce 60 to 120 parts per minute, and the manufacturer requires 100% surface inspection, both for cosmetic reasons and to detect material defects that appear on the surface after the forming process.

[0003] Typical features that should be detected during a surface inspection are scratches, cracks, so-called doubling (arch-shaped material defects) and zinc flaking on coated surfaces.

[0004] Surface inspection can be performed by human visual inspection. The inspector picks up the part to be inspected and swings or rotates it in the light to find characteristic surface features.

[0005] Alternatively, a camera system can be used in which the parts to be inspected are separated and fed into an image processing system consisting of one or more stations.

[0006] Visual inspection by humans is fraught with highly variable results depending on individual assessment. Furthermore, the examiner's concentration may wane.

[0007] A camera system, on the other hand, requires a high level of mechanical effort and is inflexible because it is limited to the previously defined types.

[0008] US 2015 / 373319 A1 discloses a testing device for capturing 3D outlines of spatial bodies. The device comprises two half-shells, inside which a frame structure divided into two parts is housed. Plates on which camera and light units are arranged are held in recesses in the frame structure. Using the camera and light units, the bodies to be captured can be exposed to different lighting situations.

[0009] US 7 075 565 B1 describes an optical inspection system with several cameras and several lighting devices.

[0010] EP 2 251 639 A1 discloses a device for optically inspecting an object, comprising a rotatable support element on which a number of light sources are arranged. An image recording unit is used to record a number of images of the object.

[0011] CN 110 823 902 A describes an example of the use of artificial intelligence in the optical evaluation of images.

[0012] The invention is based on the object of providing a testing device for the (partially) automated optical testing of surfaces of a test object, with which existing camera systems can be improved.

[0013] The object is achieved according to the invention by a testing device having the features of claim 1. Advantageous embodiments are specified in the dependent claims.

[0014] A testing device for optically testing surfaces of a test object is specified, comprising a plurality of image capture devices, a plurality of illumination devices, and a test location at which a test object to be tested can be positioned in order to carry out a test procedure, wherein the image capture devices and the illumination devices are arranged in a dome-shaped manner around the test location, wherein at least one of the image capture devices and at least one of the illumination devices can be activated in such a way that the illumination device illuminates the test object at the test location and the image capture device captures an image of the test object at the test location, wherein a specific illumination situation can be defined by assigning one of the image capture devices and one of the illumination devices and their relative position to the test object at the test location,and wherein at least one or successively several or all of the image capture devices and at least one or successively several or all of the illumination devices can be activated in such a way that a plurality of images of the test object in different illumination situations can be captured by the image capture devices.

[0015] Suitable image capture devices include appropriate digital cameras, particularly high-resolution cameras, which are well suited to capturing the surface structure of the component to be inspected (the test piece).

[0016] The illumination devices may comprise LEDs or OLEDs. In particular, the illumination devices may be suitable for radiating a uniform, flat light onto the test specimen.

[0017] Depending on the application, the light generated by the lighting devices can last for a longer or shorter period of time. For example, it is possible to generate the light continuously for one second. However, it is also possible to generate the light only in flashes, with a flash duration in the range of thousandths of a second.

[0018] The exposure time can, for example, be in the range between 0.2 and 5 ms per lighting scenario.

[0019] The number of images per test object (component) can, for example, be at least equal to the number of image capture devices. However, depending on the lighting concept, this value can also be higher, e.g., by a factor of n.

[0020] The number of lighting fixtures can be chosen sensibly. It has been shown that, for example, 9 to 15, and especially 12, lighting fixtures can be used to accurately simulate the motion typically performed by humans of the test object in the light of a single light source. However, more or fewer lighting fixtures can be used as needed.

[0021] The image capture devices and the illumination devices must be aligned to capture the test location in order to produce images of the illuminated test specimens.

[0022] The test specimens themselves are, of course, not the subject of the test device. Rather, the test device is provided to inspect the surface of test specimens (components) according to a specified test plan or specified test specifications. Each test specimen is located at the test location at the time the test is performed.

[0023] The test location can be a defined, fixed position and be located inside or outside the dome (in the latter case, however, in close proximity, particularly within line of sight, to the interior of the dome). It is also possible to extend the test location over a larger area (test space), so that the part to be tested (the test specimen) is exposed to different lighting situations while moving, in order to generate images with varied illumination. Accordingly, it is not mandatory for the test specimen to remain stationary during image acquisition. Image acquisition is also possible with a moving test specimen.

[0024] To accommodate different lighting situations, new assignments can be made between one of the lighting devices and one of the image capture devices. Thus, new pairings are continually created.

[0025] A suitable control device may be provided for controlling and thus activating the image capture devices and the illumination devices.

[0026] Particularly suitable lighting situations are those in which backlight or obliquely incident backlight (e.g. grazing light) or incident light is generated in order to be able to assess the quality or structure of the test specimen surface and its properties.

[0027] By means of the appropriate (backlight) lighting situation, the visual inspection can be simulated by people who hold the test specimen against light incident obliquely from the opposite side (especially grazing light) or swivel it in the oblique backlight in order to be able to better assess the surface quality.

[0028] Incident light or grazing light are particularly suitable for surface analysis.

[0029] Using the test fixture, many images can be generated by many image capture devices under varied illumination.

[0030] A connecting axis between the active illumination device and the test location, on the one hand, and a connecting axis between the active image capture device and the test location, on the other, can be at an obtuse angle to each other. The angle can, for example, be in a range between 120° and less than 180°. In this way, the desired backlight or grazing light effect can be achieved.

[0031] In principle, the angle can be set arbitrarily, allowing for any combination of illumination device and image capture device. Accordingly, the angle can also range between 0° and 180°.

[0032] The dome-shaped arrangement of the image capture devices and the illumination devices can have the shape of a partial spherical shell, for example, the shape of a hemispherical shell. However, this shape is not strictly limited to a hemisphere; it can also extend to a sphere, with at least one opening for introducing and removing the test specimen to or from the test location located inside the dome or sphere. The image capture devices and the illumination devices can be arranged on the inside of the spherical shell.

[0033] The respective different lighting situations can be achieved by positioning the respectively activated image capture device and the respectively activated lighting device at least partially at different angles to a test object provided at the test location. In this way, respective pairings with different angles and thus different lighting situations are possible.

[0034] A support structure is provided on which the image capture devices and the lighting devices are supported in the dome-shaped arrangement. The support structure can, in particular, be designed as a frame to support the components. With the aid of the support structure, it is particularly possible to construct and support the image capture devices and the lighting devices as a dome.

[0035] The approximate diameter of the dome (e.g., a sphere diameter) depends on the size of the parts to be tested. In practice, a test specimen size of no more than 200 mm has proven effective. In this case, the sphere diameter (dome diameter) can be approximately 800 mm, allowing an interior diameter of, for example, 600 mm.

[0036] However, other dome sizes are also possible if larger or smaller parts are to be tested.

[0037] Accordingly, an inspection device for optically inspecting the surface of a test object can be specified, comprising a plurality of image capture devices, a plurality of illumination devices and a test location at which a test object to be inspected can be positioned in order to carry out an inspection, wherein the image capture devices and the illumination devices are arranged in a dome shape around the test location, wherein one of the image capture devices and one of the illumination devices can be activated in such a way that the illumination device illuminates the test object at the test location and the image capture device captures an image of the test object at the test location, and wherein a support structure is provided on which the image capture devices and the illumination devices are carried in the dome-shaped arrangement.

[0038] The support structure has recesses into which optical units can be inserted, each of which has an image capture device and / or an illumination device.

[0039] The optical units can be constructed similarly to tiles as compact structural units in which all required components are housed. The optical units can each have correspondingly designed housings, whereby all optical unit housings in the test fixture can be identical, allowing for a high number of common parts. In this way, for example, an image capture device and an illumination device can be combined into one optical unit.

[0040] The optical units can be inserted into the corresponding recesses in the support structure. The support structure must therefore have a sufficient number of recesses to accommodate the desired number of optical units.

[0041] At least some of the optical units can have an illumination device, wherein the illumination device can have a plurality of illumination elements arranged in a planar manner. For example, it is possible to arrange a plurality of illumination elements in the form of LEDs in a planar manner to form an illumination device. To even out the light, a diffuser element, for example, an opaque plate, can also be arranged in front of the illumination elements, in particular, for example, in front of the LEDs.

[0042] At least some of the optical units can have an image capture device in addition to the illumination device. The individual illumination elements of the illumination device can be arranged around the image capture device. The image capture device can thus be arranged centrally, for example, in the center of the diffuser element.

[0043] The optical units can have a contour on their inner surface in the form of a portion of a spherical surface. The inner surface can thus be spherical or partially spherical, depending on the desired dome shape.

[0044] At least some of the optical units have a triangular or prismatic basic shape.

[0045] The triangular basic shape can be achieved, in particular, by appropriately designing the housing of the optical units. Using the triangular basic shape, the desired spherical dome can be easily recreated.

[0046] The triangular or prism-shaped optical units can be easily suspended or secured from the outside of the support structure. Without modifying the support structure, the equipment of the test fixture can be adapted by attaching a corresponding number of compact optical units to the support structure. Areas of the support structure originally designed for the attachment of optical units can also remain free if optical units are not required there due to the respective test task or test configuration.

[0047] A transport device may be provided for transporting the test specimen to and from the test location. The transport device may thus be suitable for positioning the test specimen at the test location and also for holding it there for a short period of time, for example, according to a timing of the partial or test specimen transport.

[0048] The fixed positioning of the test object, i.e. the holding of the test object at the test location, should in particular take place for a period of time during which a pairing of a lighting device and an image capture device is activated in order to capture an image of the test object in a specific lighting situation.

[0049] The specimen can be transported horizontally or vertically. The specimen should only be stationary during image generation. In particular, no movement of the specimen in the light is required.

[0050] The transport device is particularly capable of moving the test specimen or the parts to be tested through the dome-shaped test fixture in any desired motion. Horizontal, vertical, or circular movements are particularly suitable. Vertical dropping of the test specimen and subsequent retrieval is also possible.

[0051] To enable the test specimens to be transported into the interior of the dome, at least one opening must be provided in the dome through which the transport device protrudes. This opening then serves both as an inlet and outlet opening. In one variant, the inlet and outlet openings can also be formed separately in the dome.

[0052] A method for optically testing surfaces of a test specimen by controlling a testing device of the above type is specified, comprising the steps a) illuminating a test specimen at the test location by activating at least one of the illumination devices; b) capturing an image of the test specimen at the test location with at least one of the image capture devices; and c) repeating steps a) "illuminating" and b) "capturing" several times with different combinations of illumination devices and image capture devices.

[0053] For this procedure, the test specimen can first be transported to the test location and stopped there. The illumination devices are activated and the images are captured using the image capture devices (or even just one image capture device). This makes it possible to capture images using one image capture device and different illumination devices, or multiple image capture devices and one (always the same) illumination device, or various combinations of different illumination devices and different image capture devices.

[0054] The images are captured alternately in quick succession, with the goal of capturing many images of the test specimen in a short period of time. The number of repetitions and the respective lighting conditions can be determined by the respective test specifications.

[0055] After capturing a sufficient number of images with a sufficient number of lighting situations, the test specimen can be transported away from the test site and a new test specimen can be brought to the test site.

[0056] After completing step c) and thus completing the multiple acquisition of images of the test object under different lighting conditions, the next step can be performed: evaluating the two-dimensional images acquired by merging them into a three-dimensional surface model of the test object. This allows the multitude of partial images with different lighting scenarios to be combined into an overall image or final image that can be applied to the outer surface of a virtual 3D part. By combining the individual images, the virtual 3D part can be "painted" with the final image.

[0057] A method for optically testing surfaces of a test specimen is specified, comprising the steps Providing a plurality of illumination devices and a plurality of image capture devices; illuminating the test object with one of the illumination devices and, in this illumination situation, capturing an image of the test object with one of the image capture devices; in this way, successively capturing a plurality of images with different illumination devices and image capture devices in different illumination situations; and merging the two-dimensional images of the test object captured in this way to form a virtual three-dimensional surface image of the test object.

[0058] As explained above, the lighting devices and image capture devices are fixed in position. This allows images from multiple cameras (image capture devices) to be generated under varying illumination.

[0059] From the resulting two-dimensional images, a uniform three-dimensional surface image can be generated by projecting it onto a virtual 3D part. A real surface (texture) is "painted" onto the virtual 3D object, with the source of the real texture being the images from the numerous image capture devices under varying illumination.

[0060] The individual two-dimensional images or the virtual three-dimensional surface image can be processed by suitable image processing methods, for example by sharpening, blurring, increasing the contrast, in order to enhance disturbances or features of the surface image.

[0061] The following step can be provided: evaluating the three-dimensional surface image using a deterministic image evaluation method and / or an image evaluation method based on artificial intelligence. Known deterministic evaluation methods can be used, for example, exceeding a contrast threshold within a surface. For solutions based on artificial intelligence, the system can be trained on typical surface defects or features that are typically observed in corresponding test specimens.

[0062] In other words, the invention can be described as follows: The invention thus relates to a type of hemispherical shell, the interior of which is tiled with numerous cameras and numerous individual lighting devices or lighting elements. A large number of images are taken of the test specimen, which is briefly stationary, with the lighting devices being briefly activated one after the other in a suitable manner.

[0063] The result is a multitude of partial images with different lighting situations or scenarios. The individual partial images can be combined to "paint" a virtual 3D part with the resulting image. The resulting image can display the optimally enhanced features on its surface, thus enabling evaluation by suitable systems. The virtual 3D part thus bears the surface features documented in the form of the many individual images of the real test piece.

[0064] The virtual 3D part can be unwrapped at will into a resulting planar projection image. Appropriate defect detection algorithms can be applied to this image, which contains a mixture of the enhanced features and the normal manufacturing traces on the surface of the test piece.

[0065] When using an AI system based on deep learning, a two-stage process with deep neural networks can be used. This process first localizes the defects using a detector network and then classifies the object features found in this way. The two stages of "localization" and "classification" can also be implemented in an integrated structure.

[0066] These and other advantages and features of the invention are explained in more detail below using examples with the aid of the accompanying figures. They show: Fig. 1 a testing device according to the invention with a hemispherical dome in perspective view; Fig. 2 a variant of the test device from Fig. 1 ; Fig. 3 a test fixture with support structure and optical units; Fig. 4 the supporting structure of Fig. 3 without optical units; Fig. 5 an optical unit in perspective view; Fig. 6 the optical unit of Fig. 5 in another view in partial exploded view; Fig. 7 an application example for a testing device according to the invention; Fig. 8 a different structure for a test device; Fig. 9 another variant of a testing device; and Fig. 10 again another variant for a testing device.

[0067] Fig. 1 shows a dome-like testing device in perspective view.

[0068] The test device is constructed in the form of a hemispherical dome 1 (dome-shaped arrangement) and has a supporting structure 2 with many interconnected struts. The supporting structure 2 will be described later, in particular with reference to the Fig. 3 and 4 explained in more detail.

[0069] Individual optical units 3 are suspended between the struts of the support structure 2 and secured to the support structure 2 by holding elements 4. As in Fig. 1 As can be clearly seen, the hemispherical structure of the dome 1 is created by the construction of the supporting structure 2, optical units 3 and holding elements 4.

[0070] The holding elements 4 are plate-like and can be screwed to the supporting structure.

[0071] The respective optical units 3 each have on their inner side a camera 5 serving as an image capture device and an illumination surface 6 serving as an illumination device.

[0072] The optical units 3 are essentially triangular in design, with the camera 5 being arranged in the middle of the triangle, approximately near the center of gravity of the triangular surface, as in Fig. 1 The illumination area 6 surrounds the camera 5.

[0073] In the Fig. 1 Of the optical units 3 shown, each optical unit 3 has a camera 5 and an illumination surface 6. In variants not shown, there are also optical units 3 that have only one camera 5 or only one illumination surface 6, i.e., not a camera 5 and an illumination surface 6 in combination. The specification regarding the equipment of the optical units 3 depends on the respective testing tasks and scenarios.

[0074] Since the optical units 3 - as already from Fig. 1 As can be seen, they are very simply suspended from the outside of the support structure 2 and only need to be secured by the holding elements 4. It is also easy to exchange the optical units 3 to adapt the test fixture to other testing tasks. It is also possible to replace the optical units 3 with placeholders or "dummies," i.e., triangular plates that carry neither a camera 5 nor an illumination surface 6.

[0075] The dome 1 is open at its bottom, forming an opening 7 there. The opening 7 serves to guide a test specimen (not shown) into the interior of the dome 1 to a virtual test location, which can be located, for example, in the geometric center of the hemispherical dome 1 or above or below it.

[0076] The part to be tested (test specimen) can be transported into and out of the interior of the dome 1 or to the test location using a transport device which will be explained later.

[0077] When the test specimen is at the test location, the images explained later can be created with varied lighting.

[0078] Fig. 2 shows a variant of the test device from Fig. 1 , in which the dome 1 is essentially realized as a solid sphere.

[0079] However, in order to be able to move a test specimen into the interior of dome 1 to the test location, Fig. 2 There is an opening on the opposite side that is not shown.

[0080] Fig. 3 shows a variant of dome 1 of Fig. 2 , in which additional support legs 8 are provided on the support structure 2. Of course, the support legs 8 can also be designed in a different way in order to reliably hold the support structure 2 with the entire testing device.

[0081] When displaying Fig. 3 In addition, one of the optical units 3 has been removed from the supporting structure 2. The triangular basic structure of the optical units 3 is visible. Furthermore, a view into the interior of the dome 1 is possible at the point where the optical unit 3 was removed.

[0082] The opening created by the omission of one optical unit 3 can also be used as an opening 7 for introducing and removing test specimens into the interior of the dome 1.

[0083] Fig. 4 shows the complete supporting structure 2 with the support legs 8 as well as the corresponding many struts 9 and nodes 10.

[0084] The struts 9 can, for example, be made of straight aluminum profile parts. The nodes 10 have correspondingly angled connection openings to insert the struts 9 at an angle to the horizontal and thus to achieve the desired spherical structure of the dome 1 by assembling all struts 9 and all nodes 10.

[0085] Threaded holes are provided at the nodes 10 for screwing the holding elements 4. In this way, the optical units 3 can be securely held in the respective triangular recesses, formed by three struts 9 and three nodes 10.

[0086] Fig. 5 shows a perspective view of an optical unit 3 in an external view. The optical unit 3 has a housing 11 with triangular side walls 12. Respective connection surfaces 13 are provided in the corners of the triangular structure, on which the holding elements 4 rest to hold the optical unit 3 in the support structure 2.

[0087] In addition, bevelled holding surfaces 14 are provided on the rear or outer side of the optical unit 3, with which the optical units 3 can be inserted precisely into the triangular recesses of the support structure 2.

[0088] Fig. 6 shows the Fig. 5 shown optical unit 3 from the other side (inside) in a partial exploded view.

[0089] Part of the optical unit 3 is the camera 5 and the illumination surface 6, which is formed by a plurality of light-emitting diodes (LEDs) 15 arranged in a surface-like manner and serving as illumination elements.

[0090] To equalize the light generated by the LEDs 15, a triangular diffuser plate 16 is arranged above the LEDs 15, which has an opening 17 for the camera 5 in its center. Fig. 6 the diffuser plate 16 is shown separated from the rest of the optical unit 3 in order to better recognize the area of ​​the light-emitting diodes 15 otherwise covered by the diffuser plate 16.

[0091] As in the Fig. 5 und 6 As can be clearly seen, the diffuser plate 16 is spherically curved toward the inside of the dome 1. By assembling the optical units 3 in the support structure 2, a spherical inner contour can be created.

[0092] The optical unit 3 is thus capable of generating uniform light from one side via the illumination surface 6 with the numerous LEDs 15 and the diffuser plate 16, and thus illuminating a test specimen held inside the dome 1 at the test location. A corresponding image can be captured using the camera 5. Since a large number of optical units 3 are provided, new pairings of illumination surfaces 6 and cameras 5 can be repeatedly activated to generate images with different lighting situations. In this case, it can be particularly interesting to create lighting situations with a type of backlight or oblique backlight, or incident light or grazing light, in order to be able to recognize the surface features of the test specimen particularly well.

[0093] Fig. 7 shows a conveyor belt serving as a transport device 18, which transports a component serving as a test piece 19 horizontally under the dome 1. In the Fig. 7 In the situation shown, the test specimen 19 is located approximately at the test location. In this situation, the images can be generated with alternately activated cameras 5 and illumination surfaces 6.

[0094] Fig. 8 shows a variant with a substantially spherical dome 1 having two openings 7, one of which serves as an inlet opening and one as an outlet opening. The transport device 18 is depicted as a continuous conveyor belt that guides the test specimen 19 horizontally through the dome 1 and thus also through the test location.

[0095] Fig. 9 shows a further variant with a circular transport device 18, which moves the test specimen 19 on a circular path through the interior of the dome 1 and a corresponding inlet opening and an outlet opening.

[0096] For all variants of the Fig. 7 bis 9 It is possible for the test object 19 to move in a timed manner, meaning that the test object 19 briefly stops at the test location to generate the desired number of images with different lighting situations. Alternatively, it is also possible to move the test object 19 continuously through the interior of the dome 1 and create the images in the process.

[0097] Fig. 10 shows a further variant in which the dome 1 has an opening 7 on its underside, into which the transport device 18, in the form of a pneumatically or hydraulically operated lifting platform, extends. The test specimen 19 (not shown) is guided by the transport device 18 from below into the interior of the dome 1 and held in the test location for the desired images to be taken. The transport device 18 then moves the test specimen back down, out of the dome 1.

[0098] In one variant, the test specimen 19 can also be removed above the dome 1, so that a further opening 7 must be provided on the top side of the dome 1.

Claims

1. Inspection device for optically checking surfaces of an inspection object (19), with - a plurality of image-capturing devices (5); - a plurality of illuminating devices (6); and with - an inspection location at which an inspection object (19) to be inspected can be positioned in order to carry out an inspection process; wherein - the image-capturing devices (5) and the illuminating devices (6) are arranged in a dome shape around the inspection location; - at least one of each of the image-capturing devices (5) and the illuminating devices (6) can be activated such that the illuminating device (6) illuminates the inspection object (19) at the inspection location and the image-capturing device (5) captures an image of the inspection object (5) at the inspection location; - a specific illumination situation is defined by assigning one of each of the image-capturing devices (5) and the illuminating devices (6) and their relative positions to the inspection object (19) at the inspection location; - consecutively a plurality or all of the image-capturing devices (5) and at least one or consecutively a plurality or all of the illuminating devices (6) can be activated such that overall a multiplicity of images of the inspection object can be captured by the image-capturing devices (5) in different illumination situations; - a support structure (2) is provided on which the image-capturing devices (5) and the illuminating devices (6) are supported in the dome-shaped arrangement (1); - the support structure (2) has triangular recesses into which the optical units (3) can be inserted from outside, each having an image-capturing device (5) and / or an illuminating device (6); - at least part of the optical units (3) has a triangular basic shape; and wherein - sloped holding surfaces (14) are provided on the outer side of each optical unit (3), with which holding surfaces the optical units (3) can be secured, perfectly fitting, in the triangular recesses of the support structure (2).

2. Inspection device according to claim 1, wherein a connecting axis between each active illuminating device (6) and the inspection location, and a connecting axis between each active image-capturing device (5) and the inspection location, are at acute angles to one another.

3. Inspection device according to one of the preceding claims, wherein the dome-shaped arrangement (1) has the shape of a partial ball socket.

4. Inspection device according to one of the preceding claims, wherein each of the different illumination situations is caused by each activated image-capturing device (5) and each activated illuminating device (6) being at least partially at different angles to an inspection object (19) provided at the inspection location.

5. Inspection device according to one of the preceding claims, wherein - at least part of the optical units (3) has an illuminating device (6); and wherein - the illuminating device (6) has a plurality of illuminating elements (15) which are arranged flat.

6. Inspection device according to one of the preceding claims, wherein at least part of the optical units (3) has an image-capturing device (5) in addition to the illuminating device (6).

7. Inspection device according to one of the preceding claims, wherein a transport device (18) is provided for transporting the inspection object (19) to the inspection location and away from the inspection location.