Inspection device and a method using color illumination

Abstract

Device for inspecting containers (10) for impurities (12) and three-dimensional container structures (36), comprising: - a radiation source (14), wherein the radiation source (14) is configured to emit radiation which passes through a container (10) to be examined, wherein the radiation source (14) has several spatially separated radiation zones (16), and wherein the radiation zones (16) of the radiation source (14) are configured to emit radiation of different wavelength ranges, - a detection device (20) which is designed to detect the radiation emitted by the radiation source (14) and which has passed through the container (10), and - an evaluation device which is configured to evaluate the radiation detected by the detection device (20) for contamination (12) and damage to the container (10), wherein the evaluation device is configured to determine local brightness contrasts in the detected radiation of the container (10) and to check in areas with local brightness contrasts whether local color contrasts are present in these areas.

Description

[0001] The invention relates to a device and a method for inspecting containers for contaminants and three-dimensional container structures. The device comprises a radiation source configured to emit radiation. The emitted radiation penetrates a container to be inspected. The device further comprises a detection unit configured to detect the radiation emitted by the radiation source and penetrating the container. The device also comprises an evaluation unit configured to evaluate the radiation detected by the detection unit for contamination and damage to the container.

[0002] The present invention is intended in particular for use in automated filling systems where containers are transported at high speeds. Specifically, the invention is intended for the inspection of empty containers. In automated filling systems, empty containers are inspected for possible contaminants or foreign bodies before filling. Conventionally, the containers are passed through an inspection device comprising a visible light source and a semiconductor camera. The containers are illuminated and inspected from different angles. During the inspection, differences in brightness are detected, and these differences are identified as contaminants or soiling of the container, which is then rejected. Containers rejected in this way can be sent to a cleaning system or recycled.

[0003] Containers, such as transparent glass containers, often feature decorative elements on their surface. These decorative elements are also known as embossing. When detecting contaminants, a problem arises because such decorative elements can create local variations in brightness that may be mistakenly identified as contaminants. This can lead to the incorrect rejection of containers.

[0004] It is therefore an object of the present invention to increase the reliability of a device and a method for inspecting containers for impurities and three-dimensional container structures, in particular to be able to reliably distinguish decorative elements from impurities and soiling.

[0005] According to the invention, a device for inspecting containers for impurities and three-dimensional container structures is proposed, comprising a radiation source. The radiation source is configured to emit radiation that penetrates the container under inspection. The device further comprises a detection unit configured to detect the radiation emitted by the radiation source and penetrating the container. The device also includes an evaluation unit configured to evaluate the radiation detected by the detection unit for contamination and damage to the container. The radiation source has several spatially separated radiation zones. The radiation zones of the radiation source are configured to emit radiation of different wavelength ranges.

[0006] To increase inspection accuracy, the device utilizes the effect that contaminants, impurities, or scuffing rings are typically light-absorbing. These light-absorbing contaminants attenuate the radiation passing through the container. In other words, the brightness of the radiation striking the contaminants is reduced, but the radiation zone from which the brightness originates remains unchanged. In contrast, decorative elements, due to their three-dimensional structure, collect or scatter radiation from different radiation zones.

[0007] If, conventionally, one or more light sources are used to inspect the container, emitting monochromatic light, i.e., light of a single wavelength range, it may not be possible to distinguish impurities from decorative elements. This is because the light scattering occurring at decorative elements can create a local brightness contrast similar to that caused by an impurity. The present invention enables the differentiation between impurities and decorative elements.

[0008] By using different wavelength ranges of radiation penetrating the container under investigation, local scattering effects occur at three-dimensional container structures, such as decorative elements, allowing the spatially separated radiation zones of the radiation source to be detected. This method exploits the fact that decorative elements have structures that lead to strong light scattering. Thus, multiple radiation zones are imaged in these intricate structures, whereas this is not the case in uniformly formed areas of the container or in the presence of impurities. Because the radiation zones emit radiation of different wavelength ranges, radiation of different wavelengths, i.e., originating from different radiation zones, can be detected within the three-dimensional container structures.The three-dimensional container structures map large areas of radiation zones onto small image areas in the detection device. Containers containing contamination can thus be reliably sorted out, while containers with decorative elements can be distinguished.

[0009] Containers can be correctly aligned in a subsequent process step. This is because, if necessary, the containers need to assume a specific orientation with respect to the decorative elements for applying labels. By detecting the decorative elements, the containers can be aligned in this specific orientation using a rotary device.

[0010] Preferably, different wavelength ranges of visible light are used. For example, radiation zones can be provided that exhibit the colors red, green, and blue, or other clearly distinguishable colors. In this case, a decorative element appears as a structure where several colors are closely spaced, whereas this is not the case with impurities. Thus, a local color contrast is created for decorative elements, while impurities only produce a local brightness contrast and no local color contrast. The radiation zones, in this case, create color-coded illumination, and decorative elements change the locally predominant hue.

[0011] For a given type of container under investigation, normalization can be performed according to container type. Different container types, for example, exhibit different colors and translucencies. To account for color distortion and brightness reduction caused by the container properties, normalization is therefore carried out. During normalization, at least one container is thoroughly cleaned, and the detection device captures an image of the container. The captured image is then normalized to the original signal, i.e., to the originally used colors and brightness.

[0012] The container under investigation can be placed between the radiation source and the detection device. With this bright-field illumination, the image detected by the device is created by light absorption and scattering within and around the container. Alternatively, the container can be positioned off-center with respect to the axis between the radiation source and the detection device. In the latter case, dark-field illumination is used, and the image detected by the device is created solely by light scattering within and around the container.

[0013] A combination of bright-field and dark-field illumination is also conceivable. Preferably, the container to be examined is placed in the optical path between a first light source and the detection device. The first light source is preferably a light source designed to determine brightness contrasts. The first light source can be a monochromatic light source with relatively high brightness. Additionally, one or more second light sources can be arranged offset, thereby creating dark-field illumination with respect to the second light source. Preferably, the second light source is designed as a light source with multiple radiation zones to enable the detection of a color contrast image. For example, second light sources can be placed above and below the container to be examined.In this way, combined bright-field and dark-field illumination can be achieved, whereby the bright-field illumination can be used essentially to generate the brightness contrast image, and the dark-field illumination can be used essentially to generate the color contrast image.

[0014] The term "wavelength ranges" refers to the wavelengths emitted by a radiation zone. This is a narrow wavelength spectrum. Preferably, the individual radiation zones emit radiation primarily within a single wavelength, allowing for a clear contrast to be detected on decorative elements.

[0015] In addition to decorative elements, other three-dimensional container structures can also be distinguished from contaminants. For example, water droplets or, in the case of glass containers, glass chips can be differentiated from contaminants. Generally, all structures that cause local light scattering can be distinguished from contaminants that merely produce a local difference in the brightness of transmitted radiation.

[0016] The radiation source can be a flat light source that emits essentially monochromatic, for example, white visible light. A colored filter can be placed between the radiation source and the containers being examined. The colored filter creates the individual radiation zones. Accordingly, the colored filter has several colored areas, e.g., in the seven colors of the rainbow: red, orange, yellow, green, light blue, indigo, and violet, thus defining the individual radiation zones.

[0017] Alternatively, the radiation source can have several light sources configured to emit radiation of different wavelength ranges. These light sources can preferably be LEDs, LCDs, or OLEDs of different colors. In this case, the individual light sources can be controlled, possibly depending on the shape of the container, to create desired radiation zones. To create radiation zones with homogeneous radiation, a diffuser can be positioned between the multiple light sources and the containers under investigation.

[0018] The radiation source is preferably an electromagnetic radiation source, e.g., a radiation source for visible light. Preferably, the radiation zones emit visible light that can be clearly distinguished from one another, e.g., red, green, and blue light. Other colors, such as yellow, are also conceivable. The radiation source can further be configured to emit UV or infrared light, or a combination thereof. Infrared radiation can advantageously be used with colored containers, particularly brown glass bottles.

[0019] The radiation source can be operated in pulsed mode and controlled so that the radiation pulses are only emitted when a container under investigation is in front of the radiation source. Alternatively, the radiation source can be operated continuously.

[0020] The present invention can be used for inspecting containers made of any transparent material. It is particularly advantageous for use with containers made of glass or transparent plastics such as PET. In particular, the invention is applicable to the inspection of glass bottles in the beverage industry.

[0021] The radiation zones of the radiation source can be designed to maximize contrast between impurities and three-dimensional glass structures, such as embossing. This requires at least two horizontal or at least two vertical radiation zones. Radiation zones can be linear or circular, curved, or polygonal. Essentially, the radiation zones can have any suitable shape that facilitates the differentiation between impurities and decorative elements.

[0022] The detection device is preferably a commercially available color camera, in particular a semiconductor camera. Infrared and UV cameras can also be used. To avoid or reduce motion blur, shutter cameras with short exposure times can be used. This is particularly advantageous when the radiation source is operated continuously.

[0023] Preferably, the detection device detects one image of each container under investigation. This ensures high speed. Alternatively, the detection device can detect multiple images of each container under investigation. The images can be detected with a time delay, for example, a delay of 100 µs to 1000 µs, preferably 500 µs. The time-delayed images are preferably detected depending on the transport speed of the containers under investigation. It is also conceivable to provide several detection devices, each designed to detect at least one image of the container under investigation. Preferably, the detection devices are arranged so that they can take images of the container under investigation from different directions.

[0024] If multiple images of the container to be detected are taken, the radiation source can be controlled between shots, modifying the radiation zones. This allows for the creation of an individual color pattern for each image. For example, the colors emitted by the radiation zones can be changed. Alternatively or additionally, the shape of the radiation zones can be varied. For instance, vertical, striped radiation zones could be used in the first image, while horizontal, striped radiation zones could be used in the second. This allows for the optimal highlighting of various three-dimensional structural elements, such as vertically or horizontally oriented portions of decorative elements.

[0025] The evaluation unit is advantageously designed to convert the image of the container under inspection detected by the detection unit into an image in the HSV color space. The image detected by the detection unit is preferably in the RGB color space. The HSV color space yields a hue image (H), a brightness image (V), and a saturation image (S). The brightness image corresponds to an image from a conventional inspection system using a monochromatic light source and allows for the determination of local brightness contrasts. These brightness contrasts can represent contaminants or three-dimensional decorative elements. The hue signal can be used for further evaluation. For example, local brightness contrasts can be verified by checking this local area for the presence of color contrasts.Suitable filtering and classification methods are used for the evaluation.

[0026] If a local brightness contrast is observed and no color contrast is present in this area, the evaluation unit detects the presence of contamination in this area. If a local brightness contrast coincides with a local color contrast, the evaluation unit detects the presence of a three-dimensional container structure, such as an embossing, in this area. Saturation can also be used to assess the significance of the color contrast signal.

[0027] The evaluation unit can also identify structures that cause essentially no or only a slight local brightness contrast but do cause local color contrast. For example, chips in glass or water droplets can cause such local color contrast, while translucent light can pass through these areas with virtually no loss of brightness.

[0028] The evaluation unit can control the rejection of containers depending on the evaluation of the detected signal. Preferably, containers are rejected when contamination is detected and it has been verified that this is not a three-dimensional container structure, such as a decorative element. Therefore, a container is preferably rejected when the evaluation unit detects a local brightness contrast but no local color contrast. Containers can also be rejected if there is no local brightness contrast but a local color contrast. In this case, it could be a chip in the glass. If the container under inspection has no embossing or other three-dimensional structures, it can also be rejected if both a local brightness contrast and a local color contrast are detected.

[0029] The invention further relates to a method for inspecting containers for impurities and three-dimensional container structures. The method comprises the following steps: - Providing a radiation source, wherein the radiation source is configured to emit radiation that penetrates a container under investigation, wherein the radiation source has several spatially separated radiation zones, and wherein the radiation zones are configured to emit radiation of different wavelength ranges, - Providing a detection device designed to detect the radiation emitted by the radiation source and passing through the container, - Providing an evaluation unit that is designed to evaluate the radiation detected by the detection unit for contamination and damage to the container, - Emitting radiation of different wavelength ranges through the radiation zones of the radiation source, whereby the radiation passes through the container under investigation. - Detecting, by the detection device, the radiation, wherein the radiation was emitted from the radiation zones of the radiation source and passed through the container under investigation, and - Evaluating, by the evaluation device, the radiation detected by the detection device for contamination and damage to the container under investigation.

[0030] The present invention is described in more detail below with reference to the accompanying drawings. These show: Fig. 1 the inspection device according to the invention, Fig. 2 different designs of the radiation source and the radiation zones, Fig. 3 a container with a glass bead decoration, Fig. 4 a container with water droplets, Fig. 5 a container with a chip in the glass, Fig. 6 an illustrative representation of the detection of light-absorbing contaminants, and Fig. 7 an illustrative representation of the detection of a three-dimensional container structure.

[0031] In Fig. Figure 1 shows the inspection device according to the invention. In the inspection device, containers 10, such as glass bottles, are examined for impurities and contamination. At the same time, it is ensured that decorative elements, such as embossings, are not identified as impurities. The Fig. 1. Container 10 shown has a contamination 12.

[0032] A radiation source 14 is provided for the identification of the contaminant 12. The radiation source 14 has several radiation zones 16. The radiation source 14 can be designed as a planar, homogeneously radiating radiation source. In this case, a colored film is located between the radiation source 14 and the container 10. The radiation zones 16 are created by the colored film. For example, a red radiation zone 16.1, a green radiation zone 16.2, and a blue radiation zone 16.3 can be provided. Alternatively, the radiation source 14 has a multitude of controllable, differently colored LEDs, by which the radiation zones 16 can be created.

[0033] The radiation zones 16 emit radiation in the direction of the container 10 under investigation. The radiation is preferably visible light 18. The light 18 passes through the container 10 and is detected by a detection device 20. The detection device 20 is preferably a semiconductor camera.

[0034] Light 18 striking the contaminant 12 is attenuated. The detection device 20 thus detects an image of the container 10 with locally reduced brightness at the location of the contaminant 12, i.e., with a local brightness contrast.

[0035] The image of container 10 detected by the detection unit 20 is forwarded to an evaluation unit. The evaluation unit converts the image of container 10 into an image in the HSV color space. This results in a hue value, a saturation value, and a brightness value of the original image.

[0036] For evaluation, the evaluation unit determines whether the brightness measurement exhibits local brightness contrasts, i.e., areas with locally reduced brightness. If local brightness contrasts are present, either a contamination 12 or a three-dimensional container structure, such as a decorative element, is present. A three-dimensional container structure scatters the light 18 that travels from the radiation source 14 through the container 10 to the detection device 20.

[0037] If a brightness contrast is present, the evaluation unit compares the brightness measurement at the point of the brightness contrast with the color measurement at that point. If, in addition to the brightness contrast, a color contrast is also visible in the color measurement at this point, it is not a contamination, as contaminants only reduce brightness. In this case, it is therefore a three-dimensional container structure, such as a glass decoration, and container 10 is not rejected. However, if there is no local color contrast at the point of the local brightness contrast, a contamination 12 is detected, and container 10 is rejected.

[0038] Fig. Figure 2 shows different embodiments of the radiation source 14 and the radiation zones 16. Fig. Figure 2A shows a flat light source 22 of the radiation source 14. A colored film 24 is arranged in front of the light source 22, between the radiation source 14 and the container 10. The colored film 24 has several colored areas that correspond to the radiation zones 16. Fig. Figure 2A shows radiation zones 16, which have a substantially horizontal extent. Alternatively, and in Fig. As shown in Figure 2B, the radiation zones 16 can also have a vertical extent. Fig. Figure 2C shows a further embodiment of the radiation source 14. According to this embodiment, the radiation source 14 has a plurality of LEDs 26, LCDs 26, or OLEDs 26. The LEDs 26 can be controlled and thereby generate desired radiation zones 16. For example, a plurality of red, green, and blue LEDs 26 is provided.

[0039] Preferably, the detection device 20 detects an image of the container 10, which is then evaluated by the evaluation device. Alternatively, several images of the container 10 can be taken. For these images, the radiation source 14 can be controlled such that different radiation zones 16 are formed for the images. For example, the Fig. The LEDs 26 shown in Figure 2C generate horizontal radiation zones 16 for a first image and vertical radiation zones 16 for a second image. This allows for optimal detection of contaminants and three-dimensional container elements such as embossings that have an essentially horizontal or vertical orientation.

[0040] Fig. Figure 3 shows a container 10 with a glass bead decoration. Fig. Figure 3 shows brightness contrasts in the area of ​​some decorative elements 28. These decorative elements 28 are not contaminants and should therefore not lead to the rejection of the containers 10. Due to the three-dimensional structure of the decorative elements 28, strong light scattering effects occur at their edges. When using different colored radiation zones 16, a color contrast can therefore be detected at the edges of the decorative elements 28 in the colorimetric analysis. Thus, despite the generated brightness contrast, a decorative element 28 can be distinguished from a contaminant and classified as a glass bead artifact.

[0041] Fig. Figure 4 shows a container 10 with water droplets 30. The water droplets 30 produce a low brightness contrast. However, in the lower part of the water droplets 30, they produce a color contrast. Water droplets 30 can therefore be distinguished from impurities 12 by using both brightness and color measurements. This allows for better filtering of disturbances caused by water droplets 30.

[0042] Fig. Figure 5 shows a container 10 with a glass chip 32. Similar to a water droplet 30, glass chips 32 often produce a low brightness contrast. However, large-area color contrasts can be observed in glass chips 32. Thus, glass chips 32 can also be distinguished from impurities 12 by using both brightness and color measurements.

[0043] In Fig. Figure 6 shows a container 10 containing a light-absorbing impurity 34. The light 18, emitted from a radiation zone 16.2 of the radiation source 14, passes through the light-absorbing impurity 34 and enters the detection device 20. Evaluation of the image from the detection device 20 reveals that the intensity of the light 18 has decreased due to the light-absorbing impurity 34, but no light scattering has occurred. The image from the detection device 20 therefore shows, in the Fig. In the case shown in Figure 6, a local brightness contrast is observed in the area of ​​the light-absorbing impurity 34. However, no local color contrast is observed in this area.

[0044] In Fig. Figure 7 shows the case where a three-dimensional container structure 36 is located in the optical path between the radiation source 14 and the detection device 20. The light 18 coming from the radiation zones 16.1, 16.2, 16.3 is scattered by the three-dimensional container structure 36. In the image of the detection device 20, light 18 from several radiation zones 16.1, 16.2, 16.3 can therefore be observed in the region of the three-dimensional container structure 36. In contrast to the light-absorbing impurity 34, as in Fig. As shown in Figure 6, a local color contrast is observed in the area of ​​the three-dimensional container structure 36, which is used to distinguish a light-absorbing impurity 34 from a three-dimensional container structure 36.

Claims

[1] Device for inspecting containers (10) for impurities (12) and three-dimensional container structures (36), comprising: - a radiation source (14), wherein the radiation source (14) is configured to emit radiation which passes through a container (10) to be examined, wherein the radiation source (14) has several spatially separated radiation zones (16), and wherein the radiation zones (16) of the radiation source (14) are configured to emit radiation of different wavelength ranges, - a detection device (20) which is designed to detect the radiation emitted by the radiation source (14) and which has passed through the container (10), and - an evaluation device which is configured to evaluate the radiation detected by the detection device (20) for contamination (12) and damage to the container (10), wherein the evaluation device is configured to determine local brightness contrasts in the detected radiation of the container (10) and to check in areas with local brightness contrasts whether local color contrasts are present in these areas. [2] Device according to claim 1, wherein the radiation zones (16) of the radiation source (14) are configured to emit visible light (18). [3] Device according to claim 2, wherein a first radiation zone (16.1) of the radiation source (14) is configured to emit visible red light, a second radiation zone (16.2) of the radiation source (14) is configured to emit visible green light and a third radiation zone (16.3) of the radiation source (14) is configured to emit visible blue light. [4] Device according to one of the preceding claims, wherein the radiation source (14) has a planar light source (22) which is configured to emit white visible light, and wherein the radiation source (14) further comprises a color film (24) which is arranged between the light source (22) and the container (10). [5] Device according to one of claims 1 to 3, wherein the radiation source (14) has several luminous elements which are configured to emit radiation of different wavelength ranges. [6] Device according to claim 5, wherein the container (10) to be examined is arranged in the optical path between a first radiation source (14) and the detection device (20), and the container (10) to be examined is not arranged in the optical path between a second radiation source (14) and the detection device (20), and wherein the second radiation source (14) has the spatially separated radiation zones (16). [7] Device according to one of the preceding claims, wherein the radiation source (14) is configured to emit infrared radiation and / or ultraviolet radiation, and wherein the detection device (20) is configured to detect infrared radiation and / or ultraviolet radiation. [8] Device according to one of the preceding claims, wherein the radiation source (14) has at least two horizontal radiation zones (16) or at least two vertical radiation zones (16). [9] Device according to one of the preceding claims, wherein the evaluation device is configured to convert the signal detected by the detection device (20) into a signal in the HSV color space. [10] Device according to one of the preceding claims, wherein the detection device (20) is configured to detect a recording from each container (10) to be examined. [11] Device according to any one of claims 1 to 9, wherein the detection device (20) is configured to detect multiple images of each container (10) to be examined. [12] Device according to claim 11, wherein the device has several detection devices (20). [13] Method for inspecting containers (10) for impurities (12) and three-dimensional container structures, the method comprising the following steps: - Providing a radiation source (14), wherein the radiation source (14) is configured to emit radiation which passes through a container (10) to be examined, wherein the radiation source (14) has several spatially separated radiation zones (16), and wherein the radiation zones (16) are configured to emit radiation of different wavelength ranges, - Providing a detection device (20) which is designed to detect the radiation emitted by the radiation source (14) and which has passed through the container (10), - Providing an evaluation device that is designed to evaluate the radiation detected by the detection device (20) for contamination (12) and damage to the container, - Emitting, through the radiation zones (16) of the radiation source (14), radiation of different wavelength ranges, wherein the radiation passes through the container (10) to be examined, - Detecting, by the detection device (20), the radiation, wherein the radiation was emitted from the radiation zones (16) of the radiation source (14) and passed through the container (10) to be examined, and - Evaluating, by the evaluation device, the radiation detected by the detection device (20) for contamination (12) and damage to the container (10) under investigation, and wherein the method in the process step of evaluating the radiation detected by the detection device (20) comprises the further process step of determining local brightness contrasts in the detected radiation of the container (10) by the evaluation device and checking, by the evaluation device, in the areas of the locally detected brightness contrasts whether local color contrasts are present in these areas.

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