Method and apparatus for inspecting at least one outer surface of containers

Abstract

The invention relates to a method and a device for inspecting at least one outer surface of containers. According to the invention, the orientation of the container is detected, it is brought into a target orientation, and the outer surface and / or a decoration located on the outer surface is then inspected under defined conditions.

Description

[0001] The invention relates to a device for inspecting at least one outer surface of containers.

[0002] Furthermore, the invention relates to a method for inspecting at least one outer surface of containers.

[0003] Containers within the meaning of this document can be, for example, cans or bottles. In production, the containers are first manufactured as such and often subsequently decorated with a design that is printed on the outer surface of the container or applied as a label.

[0004] Defects can occur during both container production and subsequent container decoration, resulting in an undesirable appearance of the container's exterior surfaces. Therefore, it is already known to use inspection devices and procedures to identify and, if necessary, reject defective containers.

[0005] For example, during the production process of a food can, the can is transported upright on a conveyor belt to the next production process. To inspect the cans for decorative defects, photos are taken of the outside using several surrounding industrial cameras. The individual images captured by the industrial cameras are then combined in software, and the complete image of the decorative image is checked for defects.

[0006] Due to the arbitrary rotational positions of the cans, non-reproducible background noise (e.g., color and texture of the conveyor belt, subsequent cans, etc.), and the imperfect geometry and alignment of the can, configuring the software to correctly combine the individual images into an overall image is complex, computationally intensive, and error-prone. Small surface defects, for example, in the decoration of a can, cannot be detected with sufficient reliability. The inspection results achievable using conventional devices and methods are therefore generally unsatisfactory for market requirements.

[0007] It is therefore an object of the invention to provide a device for inspecting at least one outer surface of containers which solves at least some of the problems mentioned.

[0008] This object is achieved according to the invention by a device for inspecting at least one outer surface of containers according to patent claim 1.

[0009] It is a further object of the invention to provide a method for inspecting at least one outer surface of containers which solves at least some of the problems mentioned.

[0010] This object is achieved according to the invention by a method for inspecting at least one outer surface of containers according to patent claim 16.

[0011] The dependent patent claims claim advantageous developments of the invention.

[0012] The features of a device for inspecting at least one outer surface of containers and of a method for inspecting at least one outer surface of containers disclosed below are part of the invention in all executable combinations.

[0013] A device according to the invention for inspecting at least one outer surface of containers has at least one detection device for detecting the orientation of a container to be inspected, at least one alignment system for the defined orientation of a container to be inspected and at least one image detection device for detecting the at least one outer surface of the container to be inspected.

[0014] In embodiments of the invention, the detection device for detecting the orientation of a container to be inspected is designed to detect the container orientation based on the position determination of at least one container feature.

[0015] Preferably, the detection device for detecting the orientation of a container to be inspected has at least one camera.

[0016] In advantageous embodiments of the invention, the at least one camera is equipped with a wide-angle lens.

[0017] In embodiments of the invention, the at least one camera of the detection device for detecting the orientation of a container to be inspected is designed as a color matrix camera with a resolution of at least 1.3 MP.

[0018] Particularly preferably, the detection device for detecting the orientation of a container to be inspected has at least one lighting device.

[0019] In preferred embodiments of the invention, the at least one camera of the detection device for detecting the orientation of a container to be inspected is arranged above the container to be inspected and oriented such that the camera focus is directed from above onto and / or into the container. This is particularly advantageous with regard to containers to be inspected, such as cans or bottles, in which the outer surface to be inspected is completely or partially covered by the decoration or label.

[0020] In embodiments of the invention, the detection device is designed to detect the orientation of a container to be inspected in order to determine the position of at least one weld seam of the container.

[0021] Based on the determined position of the container feature and the comparison with the target position of the container feature in the defined orientation of the container, an alignment deviation can be determined automatically.

[0022] The alignment system is designed to align the container depending on the determined alignment deviation.

[0023] For this purpose, the alignment system preferably has at least one rotating element with which the container can be rotated from the determined alignment to the desired alignment.

[0024] In embodiments of the invention, the alignment system comprises two conveyor belts with their support surfaces opposite each other and aligned approximately parallel to each other, which are arranged at a distance from each other slightly smaller than the diameter of the container to be inspected. The conveyor belts are designed to contact the outer surface to be inspected with respect to a can of the outer surface in such a way that the container to be inspected can be rotated by means of different speeds of the two conveyor belts.

[0025] In embodiments of the invention, the distance between the conveyor belts corresponds to the diameter of the containers to be inspected less about 1 to 5 mm, particularly preferably less about 2 mm.

[0026] In embodiments of the invention, the conveyor belts can be controlled or driven in opposite directions such that the container can be rotated into the desired orientation to correct the alignment deviation.

[0027] In advantageous embodiments of the invention, the conveyor belts are rubberized.

[0028] The at least one image capture device for capturing the at least one outer surface of the container to be inspected has at least one imaging capture device, preferably at least one camera, for capturing the outer surface of the container to be inspected.

[0029] Depending on the shape of the container to be inspected and which areas of the outer surface of the container are to be inspected, the image capture device has more than one imaging capture device.

[0030] For the circumferential detection of the entire outer surface of a conventional cylindrical can or a conventionally shaped bottle, the image capture device preferably has at least three imaging detection devices, which are particularly preferably arranged at equal angular intervals, in the case of three imaging detection devices at an angle rotated by 120° to one another.

[0031] In other embodiments of the invention, the image capture device is divided into at least two stations, wherein at least one, preferably at least two imaging capture devices are arranged in each station.

[0032] In preferred embodiments of the invention, the imaging detection devices are arranged opposite one another in the stations of the image detection device.

[0033] An alignment system is preferably arranged between each station of the image capture device, with which the container to be inspected can be rotated into the respective desired alignment for the following station of the image capture device.

[0034] In particularly preferred embodiments of the invention, the device for inspecting at least one outer surface of containers has three stations of the image capture device arranged one behind the other, wherein an alignment system is arranged in front of each of the stations of the image capture device.

[0035] The image capture device preferably has at least one illumination device, preferably at least one illumination device for each imaging capture device.

[0036] Particularly preferably, the image capture device has at least two illumination devices per imaging capture device, each of which is directed laterally toward the container to be inspected when the container is in the focus of the respective imaging capture device.

[0037] Most preferably, the at least two illumination devices assigned to each imaging detection device are arranged such that the containers to be inspected can be illuminated synchronously in reverse in the focus of the respective imaging detection device.

[0038] In advantageous embodiments of the invention, the imaging detection devices are arranged in at least one detection chamber through which the container to be inspected can be transported. The use of detection chambers enables the reduction of external influences on the captured images of the containers to be inspected, thus enabling a more reliable inspection.

[0039] In embodiments of the invention with multiple stations of the image capture device, one capture chamber is preferably provided per station.

[0040] In order to create optimal conditions for an optical inspection of the container to be inspected using the imaging detection devices, the image detection device in advantageous embodiments of the invention preferably has at least one wall element for forming a defined homogeneous background, arranged opposite the at least one imaging detection device.

[0041] Preferably, the background is designed in terms of color and / or brightness so that it has a high contrast to the container to be inspected.

[0042] The background is particularly preferably matte.

[0043] The inventive use of wall elements to generate defined homogeneous backgrounds for the optical inspection of the containers minimizes background disturbances that have a negative impact on the image processing and evaluation required for the inspection.

[0044] In advantageous embodiments of the invention, the device for inspecting at least one outer surface of containers has at least one evaluation unit for automatically evaluating the recorded images and for automatically comparing the recorded images with reference images.

[0045] In the event of deviations between the recorded images and the reference images, a faulty container can be automatically identified with the aid of the evaluation unit, so that faulty containers can be automatically sorted out in embodiments of the invention and / or a corresponding output can be generated for the personnel.

[0046] In preferred embodiments, the device according to the invention for inspecting at least one outer surface of containers comprises at least one transport device for transporting the containers to be inspected between and / or in the detection device for detecting the orientation of a container to be inspected, the alignment system for the defined orientation of a container to be inspected and the image capture device for detecting the at least one outer surface of the container to be inspected.

[0047] In embodiments of the invention, the transport device is realized by at least one conveyor belt.

[0048] In embodiments of the invention in which the containers to be inspected are transported through the image capture device using a transport device, the imaging capture devices are preferably arranged and aligned such that the transport device is outside the capture range of the imaging capture devices. This at least significantly reduces the influence of, for example, the conveyor belt, which may be inhomogeneous due to wear and / or contamination, on the image to be inspected.

[0049] A method according to the invention for inspecting at least one outer surface of containers comprises at least the following method steps: - Detection of the orientation of a container to be inspected with respect to a rotation axis, - Automatic determination of the deviation of the detected alignment from a specified target alignment of the container to be inspected, - Automatic alignment of the container to be inspected into the desired orientation, - Inspection of at least one external surface of the container to be inspected using at least one image capture device by automatically capturing images of the external surface to be inspected and automatically comparing the captured images with stored reference images.

[0050] In preferred embodiments of the method according to the invention, the outer wall of the container to be inspected is captured in succession in at least two stations of the image capture device, wherein the container to be inspected is brought into a predetermined target orientation before each station of the image capture device.

[0051] In particularly preferred embodiments of the invention, the outer wall of the container to be inspected is scanned consecutively at three stations of the image capture device, with the container to be inspected being moved into a predetermined target orientation before each station of the image capture device. The container to be inspected is rotated by 60° in the same direction after the first and second stations of the image capture device.

[0052] At the stations of the image capture system, images of the outer surface to be inspected are captured, preferably by opposing imaging devices, such as cameras, between which the container to be inspected is passed centrally. If an angular range of 60° is defined as the image area to be evaluated, a complete circumferential (360°) image of the outer surface to be inspected is obtained by capturing images of the container to be inspected from a total of six views, each with an angular range of 60° to be evaluated.

[0053] In embodiments of the method according to the invention, the images of the individual views of the container to be inspected are directly compared with reference images of the same view. This eliminates the need to combine the individual views into an overall view and enables simpler and more reliable image analysis for container inspection.

[0054] In preferred embodiments of the method, the containers are transported continuously in the conveying direction without stopping. This allows integration into systems with high production speeds without being affected by the inspection.

[0055] In a preferred embodiment of a method according to the invention, a device according to the invention is used for inspecting the outer surfaces of containers.

[0056] In embodiments of the invention, small decorative defects in the order of about 1 mm can be eliminated by means of the device according to the invention and / or the method according to the invention. 2 can be detected safely and with little parameterization effort.

[0057] The following figures illustrate an exemplary embodiment of the invention. They show: Fig. 1: A plan view of a horizontal section through a device according to the invention for inspecting at least one outer surface of containers and Fig. 2: A side view of the device for inspecting the outer surfaces of containers according to Fig. 1.

[0058] In Fig. Figure 1 shows a top view of a section through a device (1) according to the invention for inspecting at least one outer surface of containers (20). The inspection device (1) comprises a detection device (2) for detecting the orientation of a container (20) to be inspected based on a container feature (21), an alignment system (3), and an image capture device (4) comprising three stations (6). Furthermore, the device (1) has a transport device (13) designed as a conveyor belt.

[0059] An alignment system (3) is arranged in the conveying direction in front of each of the stations (6) of the image capture device (4) in order to bring the container (20) to be inspected into the predetermined target alignment for the respective image capture.

[0060] The alignment system (3) comprises two rotating elements (5) designed as conveyor belts, with which a container (20) can be rotated about a vertical axis of rotation while being transported on the transport device (13). For this purpose, the conveyor belts are aligned with a conveying direction parallel to the transport device (13) but positioned vertically, so that the conveyor belts contact the side wall of the container (20) being transported upright.

[0061] Each of the stations (6) of the image capture device (4) has a capture chamber (7) that is delimited externally by a housing. In each capture chamber (7), imaging capture devices (8) designed as cameras are arranged on opposite sides next to the conveyor belt, as well as two associated illumination devices (9) for each imaging capture device (8).

[0062] In the illustrated embodiment of the invention, the imaging capture devices (8) are integrated into wall elements (10) or arranged behind them. The wall elements (10) are shaped like tubular segments and serve to create a homogeneous background for image capture.

[0063] The lighting devices (9) are arranged in the area of ​​the ends of the wall elements (10) facing the transport device (13) and are directed towards the container (20) to be inspected, which is located in the focus of the imaging detection devices (8).

[0064] The imaging detection devices (8) each have a defined evaluable angular range (12) of 60°.

[0065] A beam splitter (11) is arranged in the area of ​​each imaging detection device (8).

[0066] In this construction, the beam splitter (11) prevents the imaging detection device (8), for example a camera, from “seeing” itself, but rather a homogeneous background generated by the beam splitter (11) itself, which is the same as the rest of the background.

[0067] The opposing illumination devices (9) create a homogeneous background for the imaging device (8). In advantageous embodiments of the invention, the distance between the illumination devices (9) is determined by the viewing angle of the imaging device (8) and the observed curvature of the test object. The goal is to prevent the illumination devices (9), the imaging device (8), and other interference variables from appearing in the mirror image of the test object.

[0068] Fig. Figure 2 shows the same embodiment of the device (1) according to the invention for inspecting outer surfaces of containers in a side view, wherein the sectional plane AA for the Fig. The view shown in Figure 1 is shown.

[0069] The previously described elements of the device (1) are arranged on a frame construction (14).

Claims

[1] Device (1) for inspecting at least one outer surface of containers (20), comprising at least one image capture device (4) for capturing the at least one outer surface of the container (20) to be inspected by means of at least one imaging capture device (8), characterized by that the device (1) has at least one detection device (2) for detecting the orientation of a container (20) to be inspected based on the position determination of at least one container feature and at least one alignment system (3) for the defined alignment of a container (20) to be inspected in a desired alignment. [2] Device (1) according to claim 1, characterized byin that the detection device (2) for detecting the orientation of a container (20) to be inspected has at least one camera which is arranged above the container (20) to be inspected and is aligned such that the camera focus is directed from above onto and / or into the container (20). [3] Device (1) according to one of claims 1 and 2, characterized by that the detection device (2) is designed to detect the orientation of a container (20) to be inspected based on the position determination of at least one weld seam as a container feature. [4] Device (1) according to one of claims 1 to 3, characterized by that an alignment deviation can be determined based on the determined position of the container feature and the comparison with the target position of the container feature in the target orientation of the container. [5] Device (1) according to claim 4, characterized bythat the alignment system (3) is designed for the defined alignment of the container (20) to be inspected depending on the determined alignment deviation. [6] Device (1) according to one of claims 1 to 5, characterized by that the alignment system (3) has at least one rotating element (5) with which the container (20) can be rotated from the determined alignment into the desired alignment. [7] Device (1) according to claim 6, characterized by in that the alignment system (3) has two conveyor belts which are aligned with their support surfaces opposite one another and approximately parallel to one another and which are arranged at a distance from one another which is slightly smaller than the diameter of the container (20) to be inspected, wherein the conveyor belts are designed to contact the outer surface of the container (20) to be inspected in such a way that the container (20) to be inspected can be rotated by means of a different speed of the two conveyor belts. [8] Device (1) according to one of claims 1 to 7, characterized by that the image capture device (4) is divided into at least two stations (6), wherein at least two imaging capture devices (8) are arranged in each station (6). [9] Device (1) according to claim 6, characterized by that an alignment system (3) is arranged in front of the first and between the remaining stations (6) of the image capture device (4), with which the container (20) to be inspected can be rotated into the respective desired alignment for the following station (6) of the image capture device (4). [10] Device (1) according to one of claims 1 to 9, characterized by that the at least one imaging detection device (8) is arranged in at least one detection chamber (7) through which the container (20) to be inspected can be transported. [11] Device (1) according to one of claims 1 to 10, characterized bythat the image capture device (4) arranged opposite the at least one imaging capture device (8) has at least one wall element (10) for forming a defined homogeneous background. [12] Device (1) according to one of claims 1 to 11, characterized by that the image capture device (4) has at least one associated illumination device (9) for each imaging capture device (8). [13] Device (1) according to one of claims 1 to 12, characterized by that it has at least one evaluation unit for the automatic evaluation of the recorded images and for the automatic comparison of the recorded images with reference images. [14] Device (1) according to one of claims 1 to 13, characterized bythat it has at least one transport device (13) for transporting the containers (20) to be inspected between and / or in the detection device (2), the alignment system (3) and the image detection device (4). [15] Device (1) according to claim 14, characterized by , the at least one imaging detection device (8) is arranged and aligned such that the transport device (13) lies outside the detection range of the imaging detection device (8). [16] Method for inspecting at least one outer surface of containers (20) comprising at least the steps: a. detecting the orientation of a container (20) to be inspected with respect to a rotation axis, b. -Automatic determination of the deviation of the detected alignment from a predetermined target alignment of the container to be inspected (20), c. Automatic alignment of the container (20) to be inspected into the desired orientation, d. Inspection of at least one outer surface of the container (20) to be inspected using at least one image capture device (4) by automatically capturing images of the outer surface to be inspected and automatically comparing the captured images with stored reference images. [17] Method according to claim 16, characterized by that the outer wall of the container (20) to be inspected is detected in succession in at least two stations (6) of the image capture device (4), wherein the container (20) to be inspected is brought into a predetermined desired orientation before each station (6) of the image capture device (4). [18] Method according to claim 17, characterized bythat the outer wall of the container (20) to be inspected is detected in three stations (6) of the image capture device (4) one after the other, wherein the container (20) to be inspected is brought into a predetermined desired orientation before each station of the image capture device (4) and wherein the container (20) to be inspected is rotated further by 60° in the same direction after the first and after the second station (6) of the image capture device (4). [19] Method according to one of claims 16 to 18, characterized by that a device (1) for inspecting at least one outer surface of containers (20) according to one of claims 1 to 15 is used.

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