Inspection assembly for optically inspecting a component, and method for inspecting a component

Abstract

The invention relates to an inspection assembly (1) for optically inspecting a component (2), comprising: a camera device (3) for capturing images in a capturing region (9) of the camera device (3); preferably an actuating device (7) for shifting the capturing region (9) on the component (2); an adaptive optical unit (5) for shifting the object plane (11) of the camera device (3) in the capturing direction; a control device (10), the control device (10) being designed to control the inspection assembly (1) such that, for a capturing region (9) on the component (2), an image stack comprising images with different object planes (11) is captured; a combining device (12), the combining device (12) being designed to form a combination image from the image stack of a capturing region (9) on the basis of sharply imaged image regions of different images of the image stack; an evaluation device (14), the evaluation device (14) being designed to process the combination image in order to inspect the component (2).

Description

[0001] Description

[0002] Title to of a component and method for testing a component

[0003] State of the art

[0004] The invention relates to a test system for optically testing a component. The invention further relates to a method for testing a component or the component.

[0005] Often, 100% quality control is required for workpieces to reliably prevent failure during later, installed assembly. Optical methods are often used, especially for 100% quality control, as they are highly reliable and also enable non-destructive testing.

[0006] In camera-based testing procedures, the planning and implementation of quality control is particularly important, as constraints such as lighting, resolution, camera positioning, etc. are crucial for a meaningful inspection.

[0007] The publication DE 10 2021 208 648 A1, which represents the closest prior art, discloses a testing method for process quality control and a testing device. In the testing method, a joint is tested, wherein the component is first detected by at least one first detection sensor, wherein the detected joint is classified as inconspicuous or conspicuous by an evaluation unit, and wherein the joints classified as conspicuous are tested by at least one second detection sensor. Disclosure of the Invention

[0008] The invention relates to a test arrangement for the optical testing of a component having the features of claim 1 and to a method having the features of claim 11. Preferred or advantageous embodiments of the invention emerge from the subclaims, the following description and the attached figures.

[0009] The subject matter of the invention is a testing arrangement that is suitable and / or designed for the optical inspection of a component. In particular, the testing arrangement is designed for the optical inspection of a joint of the component. Specifically, the testing arrangement is suitable and / or designed for the optical inspection of a welded joint of the component. The component is designed, in particular, as a welded component, i.e., a component with at least one welded joint to be tested.

[0010] The test arrangement has a camera device for recording images in a recording area of ​​the camera device. The camera device is designed in particular as an area camera device for recording a two-dimensional image. In particular, the camera device is not realized as a line scan camera. The camera device can be designed as a grayscale camera or as a color camera. The camera device in particular has a chip for recording the image, wherein the chip can be designed, for example, as a CMOS chip or as a CCD chip. The chip can have a matrix of pixels and / or is realized as a matrix camera. In particular, the matrix has more than two columns and more than two rows. Particularly preferably, the matrix has at least 500 x 500, at least 1000 x 1000 or at least 5000 x 5000 pixels.The arrangement of the pixels is arbitrary; in addition to a matrix-like arrangement, they can also be arranged in a circle.

[0011] The camera device defines a recording area through beam guidance and / or beam shaping. The recording area refers in particular to the area that is recorded by the camera device and imaged in the respective image. The test setup preferably has an actuator device for displacing the recording area on the component. The actuator device can be designed to displace the recording area while simultaneously positioning the camera device stationary. Alternatively, the camera device is displaced, thereby displacing the recording area. A combination of these two options can also be implemented.

[0012] The test setup includes adaptive optics for shifting an object plane of the camera device in the recording direction of the camera device. The adaptive optics are arranged in the beam path between the camera device and the object plane. The adaptive optics are designed, in particular, as a beam-shaping element and / or a wavefront-modifying element. The adaptive optics can be designed as reflective adaptive optics or as transmissive adaptive optics. The object plane refers to the plane in which the component is sharply imaged by the camera device onto the image plane of the camera device. The adaptive optics can shift the object plane in the recording direction.The adaptive optics can be designed, for example, as a liquid lens with adjustable focal length, as a deformable mirror with adjustable focal length and / or wavefront, as a movable lens system or as a revolver optic with a lens exchange mechanism.

[0013] The test setup includes a control device, which is embodied, for example, as a digital data processing device. The control device is configured, in particular, in terms of programming and / or circuitry, to control the test setup, in particular the camera device, the actuator device, and the adaptive optics, such that an image stack with images of different object planes is acquired from a recording area on the component. For example, more than five images are acquired from the same or approximately the same recording area with different object planes.

[0014] The test arrangement comprises a combining device, which can be embodied as a digital data processing device. The combining device is designed to form a combined image from the image stack of a recording area. The combined image is formed by assembling sharp image regions, i.e., image regions that are sharply imaged onto the images and / or the image plane, from different images of the image stack. The combined image thus shows the entire recording area in a sharp image.

[0015] The test setup further includes an evaluation device configured to process the combined image to test the component. The test is performed, for example, based on digital image recognition, pattern recognition, etc.

[0016] The invention recognizes that optical inspection of a component always presents the problem of capturing a sharp image of the component in the respective image. In principle, such a sharp image could be achieved by precisely measuring the component, with the camera positioned to ensure a sharp image. However, this would require additional work and thus be time-consuming.

[0017] Particularly in the case of components that are subjected to thermal processing, for example joining processes, especially welding processes, the processing often leads to distortion of the component, so that the position of a surface of the component is no longer precisely defined. If one also takes into account that with a sufficiently high resolution for optical inspection of components, a depth of field of less than 1 mm, in particular less than 0.5 mm and especially less than 0.1 mm is sometimes available, it is understandable that a sharp image of the component for optical inspection is not easy to implement. The invention now proposes designing the inspection arrangement in such a way that for each recording area, the inspection arrangement is controlled such that an image stack with images with different object planes is recorded.The image areas that are in focus are extracted from the respective images, and these image areas are combined to form the combined image. This makes it possible, with reasonable effort, to obtain a combined image that sharply depicts the component in the captured area, making subsequent optical inspection of the component easy to implement.

[0018] In a preferred embodiment of the invention, the test arrangement comprises a lighting device, wherein the lighting device can implement different lighting scenarios for the component. The lighting scenarios differ, for example, in the irradiation directions or directional distributions on the component, in different lighting colors, and / or in different lighting intensities.

[0019] The control device is designed to control the inspection arrangement, and in this case, in particular, the lighting device, in such a way that multiple lighting scenarios are implemented for the different object planes in the image stack. The combining device is designed to create a combination image for each lighting scenario. This development is based on the consideration that different lighting scenarios are required for some inspection tasks, for example, to exclude reflections, mirroring, shadows, etc. In addition to the images in the different object planes, different lighting scenarios are also implemented in the object planes. This allows combination images of the same recording area with different lighting scenarios to be created.

[0020] In one possible embodiment of the invention, the evaluation device is designed to independently examine the combined images from different recording areas. In this embodiment, it is preferred to detect local defects on the component. Such an inspection strategy is advantageous, for example, when the quality of a joint, in particular a weld seam, is to be assessed with regard to the weld seam quality.

[0021] In an alternative or supplement to the invention, the evaluation device is designed to correctly combine combined images from different recording areas into an overall image and to examine the overall image. In this embodiment, geometric defects in the joint, such as an incorrect seam, etc., can be detected.

[0022] It is particularly preferable to correct the perspective of the combined images before stitching them together and / or the overall image. Knowing the positions of the image areas allows for a simple perspective correction. The combined images can then be stitched together with pixel precision, position, and perspective.

[0023] It is particularly preferred that the evaluation device is designed to generate a separate overall image for each lighting scenario. In this way, the overall images can be visually inspected separately for each lighting scenario.

[0024] In a particularly preferred implementation, the adaptive optics are designed as a liquid lens with an adjustable focal length. Such a liquid lens has a very high travel speed, allowing the image stack to be acquired in a short inspection time. Furthermore, the optical quality of the liquid lens is good, so that optical distortions caused by the adaptive optics are minimal.

[0025] Alternatively or additionally, the actuator device is designed as a scanner mirror. Such a scanner mirror can move the recording area with virtually no mass, so that the displacement of the recording area can occur very quickly and / or with high dynamics. In this embodiment, the camera device is preferably arranged stationary, so that the displacement of the recording area occurs with no or low mass.

[0026] It is particularly preferred that the adaptive optics be designed as the liquid lens and the actuator device as the scanner mirror, since this creates a highly dynamic beam guide so that the travel times when recording the image stack at the various recording areas are negligible in the overall inspection time, thus making the inspection method suitable for in-line use, for example. It is particularly preferred that the evaluation device be designed to inspect a weld seam on the component. In a possible development of the invention, the inspection arrangement comprises the component, wherein the component is designed as a bipolar plate for a fuel cell. Such bipolar plates must be welded gas-tight, so that precise inspection of the weld seam is particularly important.

[0027] Another object of the invention relates to a method for testing a component using the test setup as described above. The method comprises the following steps:

[0028] - Recording of an image stack with images of a recording area on the component, whereby different object distances are set when recording the images of the image stack;

[0029] - Combining the images of the image stack to form a combination image, whereby sharp image areas from the images of the image stack are transferred into the combination image to form the combination image.

[0030] - Process the combination image to inspect the component.

[0031] The idea is to create a fast, relatively cost-effective system that doesn't have the disadvantages of line-scan camera systems (insufficient depth of field, glare on the welds, slow operation). Specifically, the following components are used:

[0032] - Image capture with high-resolution matrix camera

[0033] - Scanning: Very fast scanning with a 2D scanning mirror (camera remains fixed)

[0034] - Focusing the image with a liquid lens (i.e. an optical lens whose focal length can be changed by an applied voltage)

[0035] - Depth scan: At each scan position, a stack of images (e.g., 10) is captured. To do this, the focus of the liquid lens is changed for each capture so that the depth of field of one image is adjacent to that of the previous image. By combining the sharp areas of the individual images, a single depth-of-field image is calculated. - Optional: Photometric stereo: At each image acquisition position of the image stack, several (e.g., four) images are taken. The lighting is changed so that the light comes from several (e.g., four) different directions. Four depth-of-field images are then calculated as combined images.

[0036] Further features, advantages, and effects of the invention will become apparent from the following description of a preferred embodiment of the invention and the accompanying figures. These show:

[0037] Figure 1 is a schematic block diagram of a test arrangement for optical testing of a component as an embodiment of the invention;

[0038] Figure 2 is a schematic representation of the method for generating a combination image in the test arrangement of Figure 1.

[0039] Figure 1 shows a highly schematic representation of a test arrangement for a component 2, wherein the test arrangement 1 is designed to carry out an optical test of the component 2.

[0040] The inspection system 1 comprises a camera device 3, wherein the camera device 3 is designed as an area-scan camera and comprises, for example, a chip, in particular a CCD chip or a CMOS chip. The chip, as an image sensor, has a plurality of pixels, wherein the pixels are arranged in a matrix.

[0041] The inspection arrangement 1 has an adaptive optics system 4, wherein the adaptive optics system 4 comprises a liquid lens 5. The liquid lens 5 can be controlled to change its optical focal length. The adaptive optics system 4 and / or the liquid lens 5 are arranged in the imaging path 6 of the camera device 3, so that, with a constant image plane, an object plane is changed by changing the focal length of the adaptive optics system 4, in particular of the liquid lens 5. Only the paraxial beam path of the imaging path 6 is indicated. Furthermore, the inspection arrangement 1 comprises an actuator device 7, wherein the actuator device 7 has a controllable scanner mirror 8. The scanner mirror 8 can be moved, for example, by an electric motor, magnetically, or galvanically. The actuator device 7 is arranged in the imaging path 6 such that a recording area 9 on the component 2 can be displaced by changing the angle of the scanner mirror 8.This is indicated on component 2 with different fields, each of which represents a receiving area 9.

[0042] The test setup 1 comprises a control device 10, which controls the camera device 3, the adaptive optics 4, and the actuator device 7 such that a stack of images is taken of the recording area 8, each image having a different object plane, which was adjusted via the adaptive optics 4.

[0043] Figure 2 shows a schematic cross-section through component 2, with the different object planes 11 schematically indicated. Component 2 has a height profile, with the object planes 11 arranged like different contour lines on the height profile.

[0044] The test arrangement 1 has a combining device 12, wherein the combining device 12 is designed to form a combination image from the image stack of a recording area 9 on the basis of sharply imaged image areas 13 of different images with different object planes 11 of the image stack.

[0045] This process is visualized in Figure 2: For each object plane 11, a certain depth of field in the vertical direction results from the depth of field. As long as the height profiling in the depth of field extends in the vertical direction around the respective object plane 11, this section of the height profiling is sharply imaged. The image area of ​​the image with the object plane 11 is thus formed as a sharply imaged image area 13. As soon as the height profiling of the component 2 leaves the depth of field of the current object plane 11, the sharply imaged image area 13 of the associated image is also terminated, and an adjacent, further sharply imaged image area 13 results in another image with a different object plane 11.

[0046] The combining device 12 collects all sharply imaged image areas 13 and creates the combined image from them. The combined image is transferred to an evaluation device 14, which further processes the combined image and optically inspects the component 2 based on the combined image.

[0047] Optionally, the inspection arrangement 1 comprises an illumination device 15, which can implement different illumination scenarios. In the illustrated embodiment, the illumination device 15 can, for example, illuminate the component 2 from two different sides to create two different illumination scenarios. The illumination device 15 is controlled by the control device 10, so that for each object plane 11 in the image stack, images with the different illumination scenarios are captured by the camera device 3. The combining device 12 is designed to generate combination images for the different illumination scenarios. The combination images with different illumination scenarios for the same respective recording area 9 can support the optical inspection of the component 2, since, for example, shadows, reflections, etc. can be taken into account.Another possibility is the implementation of “photometry stereo”, where additional information about the shape of the surface (in particular the inclination of the surface at each pixel) is obtained from at least three images, with each image being illuminated from a different direction, so that three illumination scenarios are formed.

[0048] The evaluation device 14 can examine the combined images independently of one another, for example, to detect local defects on the component 2. Alternatively, the combined images from different recording areas 9 can be combined to form an overall image, with the evaluation device 14 being configured to visually examine the overall image, for example, to detect geometric defects in the seam path of a weld seam or the like. Optionally, the evaluation device 14 can correct the perspective and / or correctly assemble the combined images before or after combining them to form the overall image.

[0049] In one embodiment, component 2 is designed as a bipolar plate, for example, for a fuel cell. The bipolar plate consists of two sheet metal parts that must be welded together in a gas-tight manner, forming a weld seam. The test setup 1 can be designed for this test task as follows:

[0050] Matrix camera e.g. chip, 7000 x 7000 pixels, 70 frames / sec as camera device 3;

[0051] - Switchable LED lighting (switching frequencies of several kHz)

[0052] - Patch size 37.5 mm x 37.5 mm as recording area

[0053] - 16 patches result in an image field of 150 mm x 150 mm

[0054] 40 images are taken per patch: 10 depth of field layers as image stacks, in each layer 4 images with different lighting scenarios;

[0055] - Makes a total of 640 pictures, takes less than 10 seconds at 70 frames per second (camera value)

[0056] Focus sweep by adaptive optics 4 and 2D scanner mirror 8; adjustment times are less than 100 ps and therefore not relevant

[0057] This allows an area of ​​150 mm x 150 mm to be imaged in 10 seconds. One side of a bipolar plate can therefore be completely imaged with three such imaging sets, covering the entire 450 mm area. In addition to the 3 x 10 seconds of pure image acquisition time, approximately 5 seconds of travel time are added. The total image acquisition time is thus 35 seconds.

[0058] With the liquid lens 5, a much larger depth range can be "traversed." The 10 images described here are due to the cycle time.

[0059] The same applies to very large cameras: Depending on the task, a smaller camera can also be used. Tasks are conceivable where images are captured using a camera with a small (and therefore significantly cheaper) chip (e.g., only 1000 x 1000 pixels), but more positions are scanned. A depth image stack can also be captured without photometric image acquisition.

Claims

Claims 1. Test arrangement (1) for the optical inspection of a component (2), comprising a camera device (3) for recording images in a recording area (9) of the camera device (3), an adaptive optics system (5) for shifting the object plane (11) of the camera device (3) in the recording direction, a control device (10), the control device (10) being designed to control the test arrangement (1) such that an image stack with images having different object planes (11) is recorded from the recording area (9) on the component (2), a combining device (12), the combining device (12) being designed to form a combination image from the image stack of the recording area (9) on the basis of sharply depicted image areas of different images of the image stack, an evaluation device (14), the evaluation device (14) being designed to process the combination image in order to test the component (2).

2. Test arrangement (1) according to claim 1, characterized in that it has an illumination device (15), wherein the illumination device (15) can implement different illumination scenarios, wherein the control device (10) is designed to control the test arrangement (1) such that a plurality of illumination scenarios are implemented for the object planes (11) in the image stack, wherein the combining device (12) is designed to form a combination image for each illumination scenario.

3. Test arrangement (1) according to one of the preceding claims, characterized in that the evaluation device (14) is designed to test the combination images from different recording areas (9) independently.

4. Test arrangement (1) according to one of claims 1 or 2, characterized in that the evaluation device (14) is designed to combine combination images from different recording areas (9) in the correct position to form an overall image and to test the overall image.

5. Test arrangement (1) according to claim 3, characterized in that the evaluation device (14) is designed to correct the combination images before joining and / or the overall image in perspective.

6. Test arrangement (1) according to one of the preceding claims 3 to 5, characterized in that the evaluation device (14) is designed to generate a separate overall image for each lighting scenario.

7. Test arrangement (1) according to one of the preceding claims, characterized in that the adaptive optics (4) is designed as a liquid lens (5).

8. Test arrangement (1) according to one of the preceding claims, characterized in that it has an actuator device (7) for displacing the receiving area (9) on the component (2), wherein the actuator device (7) is preferably designed as a scanner mirror (8).

9. Test arrangement (1) according to one of the preceding claims, characterized in that the evaluation device (14) is designed to test a weld seam on the component (2).

10. Test arrangement (1) according to one of the preceding claims, characterized by the component (2), wherein the component (2) is designed as a bipolar plate.

11. Method for testing a component (2) with the test arrangement (1) according to one of the preceding claims, comprising the steps: - Recording an image stack with images of a recording area (9) on the component (2), wherein different object distances (11) are set when recording the images of the image stack; - Combining the images of the image stack to form a combination image, wherein sharp image areas from the images of the image stack are transferred into the combination image to form the combination image. - Processing the combination image to inspect the component (2).

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