DE102022205760A1 - Camera system for optical inspection and inspection procedures - Google Patents

Abstract

The invention relates to a camera system (10) for optically inspecting the surface (11) of an element (12) of an energy cell, in particular a battery, with at least one image capture device (13), which is set up to detect a surface section (14) of a cell relative to the image capture device (13) funded element (12). At least two light sources (15, 16, 17) are provided, the light of which strikes the surface section (14) of the conveyed element (12) from different lighting directions (18, 19, 20). The surface section (14) can be captured by the at least one image capture device (13) with at least two different images (21, 22), each of which is assigned to different lighting directions (18, 19, 20). A data processing unit (24) is provided, which is set up to process the captured, different images (21, 22) into a combination image (23) and to output the combination image (23). The invention further relates to a corresponding inspection method.

Description

The present invention relates to a camera system for optically inspecting the surface of an element of an energy cell, in particular a battery, according to the preamble of claim 1 and a corresponding inspection method for optically inspecting the surface of an element of an energy cell, in particular a battery, with such a camera system according to Preamble of claim 10.

Energy cells or energy storage devices within the meaning of the invention are used, for example, in motor vehicles, other land vehicles, ships, aircraft or in stationary storage systems in the form of battery cells or fuel cells, in which very large amounts of energy have to be stored over long periods of time.

In order to provide a sufficient amount of energy cells, especially battery cells, mass-produced manufacturing technologies with high production speeds are required. The high production speeds and the use of continuous production processes, together with high quality requirements, represent a challenge for inline inspection of intermediate products of energy cells. For high quality of the end product, it is advantageous, among other things, to check the surfaces of an intermediate product, for example an anode or cathode sheet, before stacking , folding or rolling an energy cell, especially a battery cell, to check for errors. Such surface defects can be particles or cracks. Furthermore, such errors can affect general edge quality on a conductor foil, particularly in the case of an active material, an energy cell or battery, i.e. in the case of anode or cathode material. The undesirable particles on the surface of an intermediate product or element of an energy cell can primarily be particles made of material of which the surface also consists, which prevents the particles from being distinguished from the surface on the basis of color. Furthermore, typical anode and cathode materials, e.g. NMC, LFP or graphite, have very dark colors, so that there is only a low brightness contrast of the particles on the surface. The inspection of the surface for particles larger than 50 µm, usually with a resolution of 10 µm to 15 µm, in combination with high conveying speeds, together with the optical properties of the materials, places very high demands on a camera system for the optical inspection of the surface an element of an energy cell, in particular a Li-ion battery.

Against this background, the invention is based on the object of specifying a camera system for the optical inspection of the surface of an element of an energy cell, in particular a battery, and a corresponding inspection method which can achieve the requirements mentioned.

The invention solves this problem with the features of the independent claims. Further preferred embodiments of the invention can be found in the subclaims and the associated descriptions and drawings.

To solve the problem, a camera system for optically inspecting the surface of an element of an energy cell, in particular a battery, is proposed with at least one image capture device, which is set up to capture a surface section of an element conveyed relative to the image capture device. At least two light sources are provided, the light of which strikes the surface section of the conveyed element from different lighting directions. The surface section can be captured by the at least one image capture device with at least two different images, each of which is assigned to different, preferably one of the, illumination directions. A data processing unit is provided, which is set up to process the captured, different images into a combination image and to output the combination image.

With such a camera system, a type of three-dimensional information about the surface defects, in particular particles on the surface to be inspected, can be recorded in the combination image. In particular, sensitivity can be achieved with respect to parts of the particle surface that are at a favorable reflection angle, for example the slope, of the respective light source to the image capture device. By combining several images of the same surface section and thus preferably also the surface defects, for example of the same particles on this surface section, with different exposure directions, such defects or particles can be recognized in the combined image and their size can be estimated. In the combination image, the particles are therefore not always completely reproduced; rather, it can be a representation of several partial areas of the particles, which, however, allow sufficient detection of particles. Particles can therefore form on the typical, extremely dark materials with the short possible exposure time due to the high conveying speeds in the Kombina tion image can be made comprehensible. In advantageous exemplary embodiments, the detection can take place through automated image evaluation of the combination image.

In the combination image, the at least two different images, which are each assigned to one of the lighting directions, are preferably offset against one another, more preferably offset against one another with pixel precision. Pixel-precise calculation or processing can be achieved in particular with a camera system that captures the at least two different images, each with one of the illumination directions of the same surface section, with the same sensor or sensor chip.

In possible embodiments, the illumination directions can be a combination of several directions and/or sources, as long as different illumination scenarios are achieved, each with different illumination directions overall, which can be assigned to different images of the same surface section.

The element of an energy cell, in particular a battery cell, is preferably a flat preliminary or intermediate product of such a cell. The element can be, for example, a conductor foil coated with anode material, for example graphite, a conductor foil coated with cathode material, for example NMC (lithium-nickel-manganese-cobalt oxides), or a separator foil. Furthermore, the element can be a track, for example an electrode track, in particular an anode or cathode track, or a separator track. Preferably the element is an endless sheet material. Alternatively, the element can be, for example, an isolated electrode sheet which is not conveyed as web material. The element is preferably conveyed continuously.

Furthermore, the camera system is preferably set up for inspecting a surface section on one side of a flat element. In possible exemplary embodiments, the camera system is set up for a double-sided inspection, so that surface sections on both sides of the flat element of an energy or battery cell can be inspected.

The camera system is set up to preferably inspect the entire surface of an active material of an element. A large number of surface sections can therefore be inspected or checked in a time sequence corresponding to the, in particular continuous, conveyance of the element relative to the camera system and the image capture device. The captured surface sections preferably border one another so that optimal efficiency of the camera system can be achieved. In possible alternative embodiments, the detected surface sections overlap.

An image with an assigned illumination direction can also correspond to a partial image of a partial area of a sensor or a partial image of an image recording (frame).

According to a further development, it is proposed that the at least two light sources each have different light colors.

Different light colors of the respective light sources, which throw light onto the surface section with different lighting directions, enable a technically simple assignment of an image to a corresponding lighting direction. Different light colors result from different emission spectra of the light sources. A light source with one illumination direction can, for example, also consist of an arrangement of several light-emitting diodes. Such an assignment can be achieved, for example, via the spectral sensitivity of the image capture device or parts thereof. A corresponding spectral sensitivity, which enables detection and assignment of only one direction of illumination from a light source, can be achieved, for example, via color filters and a corresponding design of a sensor in the image capture device.

According to a further development, it is proposed that the at least two different images of the surface section can be captured at different measuring positions relative to the camera system.

The different measuring positions can result, for example, from the conveyance of the element relative to the camera system, so that, for example, two images, which are assigned to two different lighting directions, are recorded from the same surface section at different times. The resulting time difference preferably corresponds to the distance between the measuring positions due to the relative conveying speed of the element. In possible embodiments, these two or more different images can be captured by the camera system using an image capture device, whereby the respective surface section can be positioned, for example, at a different position in the image capture. Accordingly, two or more images of different surface sections can be created. In this case, several surface sections, for example two or more, can preferably be captured in parallel with an image capture device in an image recording. The parts of the image recording that show a respective surface section can thus form an image of a surface section with an assigned illumination direction. In a further possible embodiment, the two or more different images can be recorded using two or more different image capture devices.

In an advantageous embodiment, the light sources are switched alternately. In this way, it can be achieved that only one light source with one illumination direction is incident on a surface section of an element at the same time. In this way, a clear assignment of images to a lighting direction can be achieved.

In alternative embodiments, the light sources can be arranged spatially separately, so that a clear assignment of lighting directions to images is possible, preferably with the appropriate number of image capture devices.

According to a further development, it is proposed that the image capture device comprises a color line time delay and integration line camera (multi-field TDI line camera).

A time delay and integration line scan camera, also known as a TDI line scan camera, where TDI stands for Time Delay and Integration, includes a sensor that has multiple levels of illumination. The lighting levels each preferably capture the same section corresponding to the movement of the conveyed element or the surface section, with the charges also preferably being moved or copied from lighting level to lighting level, so that integration can be achieved over the corresponding number of lighting levels used.

A color line time delay and integration line camera (multi-field TDI line camera) also has, for example, three different areas with different spectral sensitivity, so that three different images can be captured with such a camera. In combination with different lighting directions, each with different light colors, which are each adapted to the three different areas, the camera system can capture at least two, in particular three, corresponding images, which can be processed by the data processing device into a combination image. The combination image is preferably processed from several images that are grayscale images, which can also be carried out with color image recording.

Such an image capture device enables sufficient exposure and a sufficient signal-to-noise ratio on the surface of an element to be inspected, even at high conveying speeds and dark materials. In addition, the different color lines can be used to easily assign different lighting directions, provided that the different lighting directions each have different light colors. In particular, with a color line time delay and integration line camera, for example, three different images with different exposure directions can be captured and easily processed into a combination image, since in particular pixel-precise calculation of the different images is possible due to the images being recorded on a common chip.

It is also proposed that the light sources can be operated in a pulsed manner. For example, together with the proposed color line time delay and integration line camera, this enables a sufficient signal-to-noise ratio. Furthermore, the energy requirement can be minimized in this way compared to continuous operation.

According to a further development, it is proposed that the image capture device comprises a matrix camera. With a matrix camera, at least two different images with different illumination directions of the same surface section at different measuring positions and separated in time can be captured in a simple manner using at least two temporally successive image recordings (frames). The direction of illumination preferably changes between the image recordings (frames), so that two different images of a surface section, which can each be a partial image of the image recording, can be captured with different lighting directions. Furthermore, there is the advantageous possibility of using a color matrix camera and different light colors for the different lighting directions to capture different images with continuous lighting.

In an advantageous embodiment, it is proposed that the image capture device comprises a plurality of matrix cameras, which are positioned side by side and transversely to the conveying direction of the conveyed Elements are arranged. The arrangement of several matrix cameras next to each other simplifies the scalability of the camera system in relation to the width of the element to be inspected, which is promoted transversely to the width relative to the camera system. The images from the matrix cameras are preferably evaluated individually, but they can alternatively also be evaluated together in a composite image. An overlap area is preferably provided at the transition between the detection area of two matrix cameras. A matrix camera usually has an area sensor; this can be, for example, square or in a 4:3 format or a comparable format and therefore differs from a line camera.

The camera system is preferably set up to capture a surface section of an element conveyed on a drum relative to the image capture device. A drum enables the continuous conveying of individual elements of an energy or battery cell, for example electrode sheets, which can be continuously conveyed on the drum relative to the camera system. Preferably, a color line time delay and integration line camera can be used as an image capture device when conveying on a drum, since the depth of field with the typical curvature of the element conveyed on a drum is not a problem with this image capture device. When using a matrix camera as an image capture device, the recording area on the drum in the conveying direction of the captured images is preferably limited in order to avoid a disadvantageous depth of field due to the curvature of the element on the drum.

• - Beleuchten eines Oberflächenabschnitts eines relativ zur Bilderfassungsvorrichtung geförderten Elements mit wenigstens zwei Lichtquellen, deren Licht aus unterschiedlichen Beleuchtungsrichtungen auf den Oberflächenabschnitt des geförderten Elements einfällt;
• - Erfassen des Oberflächenabschnitts mit mindestens einer Bilderfassungsvorrichtung mit wenigstens zwei unterschiedlichen Bildern, welche jeweils unterschiedlichen, vorzugsweise jeweils einer der, Beleuchtungsrichtungen zugeordnet sind;
• - Verarbeiten der erfassten, unterschiedlichen Bilder zu einem Kombinationsbild in einer Datenverarbeitungseinheit;
• - Ausgeben des Kombinationsbilds.

Furthermore, to solve the problem, an inspection method for optically inspecting the surface of an element of an energy cell, in particular a battery, with a camera system according to one of claims 1 to 9 is proposed with the following steps:

• - Illuminating a surface section of an element conveyed relative to the image capture device with at least two light sources, the light of which is incident on the surface section of the conveyed element from different illumination directions;
• - Detecting the surface section with at least one image capture device with at least two different images, each of which is assigned to different, preferably one of the, illumination directions;
• - Processing the captured, different images into a combination image in a data processing unit;
• - Outputting the combination image.

The combination image allows detection of surface defects, such as particles larger than 50 µm on the surface, despite very dark materials on the surface with a very high degree of optical absorption and a very high conveying speed, for example larger than 60 m/min.

According to a further development, it is proposed that the processing into a combination image takes place by forming the difference between the at least two images with different illumination directions. Difference formation of the different images with different illumination directions of the same surface section is a particularly advantageous method for achieving a combined image that contains corresponding advantageous indirect 3D information.

It is further proposed that digital filtering of the combination image takes place in the data processing unit before output. For example, digital filtering of the combined image can remove noise.

According to a further development, it is proposed that the combination image is binarized in the data processing unit before output. This allows the contrast between surface defects and intact areas of the surface to be further increased. A binarization of the combination image preferably takes place after digital filtering of a difference image.

Furthermore, an opening is preferably carried out in digital image processing before the combination image is output, in particular after binarization. This opening serves to remove very small disturbances or errors, for example smaller than 50 µm.

In an advantageous embodiment, the data processing device evaluates the combination image for surface defects, in particular particles, on the surface section. In alternative embodiments, the evaluation can also take place outside the camera system. The evaluation can be used, for example, to exclude the corresponding parts of the element, for example in the case of an electrode track, or the entire element, for example in the case of an electrode sheet, from further processing.

According to a further development, it is proposed that successive image recordings using a matrix camera as an image capture device with different lighting directions on the surface section.

The lighting direction can therefore change between the image recordings (frames), so that two different images of a surface section, which can each be a partial image of the image recording, can be captured with different lighting directions.

According to a further development, it is proposed that two successive image recordings using a matrix camera as an image capture device capture the same surface section on different sensor areas of the matrix camera. For example, a surface section can be captured in a first image recording in a first half of the lines (e.g. lines 1 to 500) of the image recording (frame) as a sensor area of the matrix camera, and the same surface section can be recorded in a second, subsequent image recording in the second half of the lines (e.g. Lines 501 to 1000) of the image recording (frame) are recorded as a sensor area.

In a possible embodiment, a light change, i.e. a different lighting direction, can be carried out within an image recording, so that, for example, the first 500 lines are captured with a first illumination direction and the second 500 lines with a second illumination direction.

In an advantageous embodiment, a matrix camera as an image capture device has an image capture rate that is matched to the conveying speed of the element conveyed relative to the image capture device such that a surface section of the conveyed element covers a maximum of half, preferably half, the sensor area of the matrix camera between two image captures. This means that the same surface section can be captured with two successive image recordings (frames) using the same image capture device.

• 1 eine schematische Darstellung eines Kamerasystems;
• 2 ein Bild eines Oberflächenabschnitts mit einer ersten Beleuchtungsrichtung;
• 3 ein Bild eines Oberflächenabschnitts mit einer zweiten Beleuchtungsrichtung;
• 4 ein Kombinationsbild eines Oberflächenabschnitts;
• 5 ein gefiltertes Kombinationsbild;
• 6 eine Binarisierung des gefilterten Kombinationsbildes;
• 7 eine Öffnung des binarisierten Kombinationsbildes.

The invention is explained below using preferred embodiments with reference to the attached figures. This shows

• 1 a schematic representation of a camera system;
• 2 an image of a surface section with a first illumination direction;
• 3 an image of a surface portion with a second illumination direction;
• 4 a combination image of a surface section;
• 5 a filtered combination image;
• 6 a binarization of the filtered combination image;
• 7 an opening of the binarized combination image.

In 1 an exemplary embodiment of a proposed camera system 10 for the optical inspection of the surface 11 of an element 12, for example a cathode track, is shown schematically as a preliminary product for a battery. The element 12 is promoted relative to the camera system 10, see symbolic arrow. The camera system 10 has an image capture device 13, which captures a surface section 14 of the element 12. In this exemplary embodiment, three light sources 15, 16, 17 are provided, each of which throws light from different illumination directions 18, 19, 20 onto the surface section 14. In this exemplary embodiment, the light sources 15, 16, 17 each have a different light color, so that light with different light colors, for example red, green, blue, hits the surface section 14 from the three lighting directions 18, 19, 20.

In this exemplary embodiment, the image capture device 13 is a color line time delay and integration line camera that captures the three colors of light from the different lighting directions separately from one another. Therefore there are three images 21, 22, see also 2 and 3 , each with different information about the surface 11 in the surface section 14.

The 2 until 7 show an example of the processing of image data of the surface 11 of an element 12 with the camera system 10. The 2 until 7 show the typical dark surface 1 of an electrode material, where the 2 until 7 are shown inverted for better illustration. In this advantageous exemplary embodiment, two different images 21, 22 of the same surface section 14 are captured, see 2 and 3 . In the data processing unit 24, the images 21, 22 are processed by forming the difference to form a combination image 23, see 4 . The combination image 23 thus has the combined information with indirect additional 3D information of the surface 11 based on the different lighting directions 18, 19, so that the combination image 23 enables an improved inspection of the surface section 14, for example with digital image evaluation. The combination image 23 obtained can, in possible embodiments, be output by the data processing unit 24 for further data processing, or alternatively be evaluated by the data processing unit 24 itself.

5 shows the combination picture 23 of the 4 after digital filtering of the combination image 23 by the data processing unit 24, which can, for example, remove noise in the combination image 23. The combination image 23 can then be binarized so that preferably only the colors black and white with a corresponding maximum contrast are present in the image. Finally, an opening can be carried out by the data processing unit 24 on the binarized combination image 23, so that the smallest structures in irrelevant sizes can be filtered out.

The combination image 23 can in principle be used to optically inspect the surface 11 of an element 12 of an energy cell, in particular a battery cell, and, if necessary, in the event of surface defects, e.g. exceeding defined limit values of the size and/or number of particles on a surface section 14 Exclude part from further processing.

Reference symbol list

10

Camera system

11

surface

12

element

13

Image capture device

14

surface section

15, 16, 17

light source

18, 19, 20

Lighting directions

21, 22

Picture

23

Combination image

24

Data processing unit

Claims (17)

Camera system (10) for optically inspecting the surface (11) of an element (12) of an energy cell, in particular a battery, - with at least one image capture device (13), which is set up to detect a surface section (14) of an energy cell relative to the image capture device (13). conveyed element (12), characterized in that - at least two light sources (15, 16, 17) are provided, the light from different lighting directions (18, 19, 20) onto the surface section (14) of the conveyed element (12) occurs, wherein - the surface section (14) with at least two different images (21, 22), which are each assigned to different lighting directions (18, 19, 20), can be detected by the at least one image capture device (13), and - a data processing unit ( 24) is provided, which is set up to - process the captured, different images (21, 22) into a combination image (23), and - output the combination image (23). Camera system (10). Claim 1 , characterized in that - the at least two light sources (15, 16, 17) each have different light colors. Camera system (10). Claim 1 or 2 , characterized in that - the at least two different images (21, 22) of the surface section (14) can be captured at different measuring positions relative to the camera system (10). Camera system (10) according to one of the preceding claims, characterized in that the light sources (15, 16, 17) are switched alternately. Camera system (10) according to one of the preceding claims, characterized in that the image capture device (13) comprises a color line time delay and integration line camera. Camera system (10) according to one of the preceding claims, characterized in that the light sources (15, 16, 17) can be operated in a pulsed manner. Camera system (10) according to one of the preceding claims, characterized in that the image capture device (13) comprises a matrix camera. Camera system (10). Claim 7 , characterized in that the image capture device (13) comprises a plurality of matrix cameras, which are arranged next to one another and transversely to the conveying direction of the conveyed element (12). Camera system (10) according to one of the preceding claims, characterized in that the camera system (10) is set up to capture a surface section (14) of an element (12) conveyed on a drum relative to the image capture device (13). Inspection method for optically inspecting the surface (11) of an element (12) of an energy cell, in particular a battery, with a camera system (10) according to one of Claims 1 until 9 , characterized by the steps: - Illuminating a surface section (14) of an element (12) conveyed relative to the image capture device (13) with at least two light sources (15, 16, 17), the light of which shines on the surface section (14) from different lighting directions (18, 19, 20). promoted element (12) occurs; - Detecting the surface section (14) with at least one image capture device (13) with at least two different images (21, 22), each of which is assigned to different lighting directions (18, 19, 20); - Processing the captured, different images (21, 22) into a combination image in a data processing unit (24); - Output the combination image (23). inspection procedures Claim 10 , characterized in that the processing into a combination image (23) takes place by forming the difference between the at least two images (20, 21) with different lighting directions (18, 19, 20). inspection procedures Claim 10 and 11 , characterized in that the combination image (23) is digitally filtered in the data processing unit (24) before output. Inspection procedure according to one of the Claims 10 until 12 , characterized in that the combination image (23) is binarized in the data processing unit (24) before output. Inspection procedure according to one of the Claims 10 until 13 , characterized in that the data processing unit (24) evaluates the combination image (23) for particles on the surface section (14). Inspection procedure according to one of the Claims 10 until 14 , characterized in that successive image recordings are carried out using a matrix camera as an image capture device (13), each with different lighting directions (18, 19, 20) on the surface section (14). Inspection procedure according to one of the Claims 10 until 15 , characterized in that two successive image recordings using a matrix camera as an image capture device (13) capture the same surface section (14) on different sensor areas of the matrix camera. Inspection procedure according to one of the Claims 10 until 16 , characterized in that a matrix camera as an image capture device (13) has an image capture rate matched to the conveying speed of the element (12) conveyed relative to the image capture device (13) such that a surface section (14) of the conveyed element (12) has the maximum between two image captures half, preferably half, of the sensor area of the matrix camera.

Images