Inspection system

Abstract

The invention relates to an inspection system for visually inspecting an object, in particular the surface of an object, during the conveyance of the object along a conveying path, comprising a free space which allows the object to pass through the inspection system and comprises an inspection area in which the object is visually inspected, an illumination device which illuminates at least the peripheral surface of the object within the inspection area, and a plurality of camera / sensor devices, each of which is configured to take an image of a surface section of the peripheral surface in a respective field of view of the camera / sensor device by receiving light which propagates along a respective optical path from the illuminated object to the camera / sensor device, the fields of view of the camera / sensor devices combining to provide full circumferential coverage of the inspection area over 360° azimuth, wherein the length of at least one optical path is greater than the spatial distance between the ends of the optical path.

Description

Technical Field

[0001] This invention relates to an inspection system for visually inspecting an object, particularly its surface, during transport along a conveying path. The system includes a free space allowing the object to pass through, the free space comprising an inspection area in which the object is visually inspected. The system also includes an illumination device for illuminating at least a circumferential surface of the object in the inspection area, and a plurality of camera / sensor devices. Each camera / sensor device is configured to capture an image of a surface segment of the circumferential surface located within a corresponding field of view of the camera / sensor device by receiving light propagating along a corresponding optical path from the illuminated object to the camera / sensor device. The combined field of view of the camera / sensor devices provides complete circumferential coverage of the inspection area at a 360° azimuth angle. Background Technology

[0002] Such inspection systems are well known in the art. The reason for providing 360° coverage is that, in a production line, particularly cylindrical objects, may arrive at the inspection system in an unoriented manner, making it insufficient to inspect only one or two lateral sides of the object by camera systems arranged on the left and right sides of the transport path. This is because defining parts of the surface (e.g., barcodes or other codes or alphanumeric strings on product labels) may be outside the field of view of the lateral camera systems. Although known systems include additional workbenches with two lateral camera systems and provide 90° object rotation between the two workbenches / inspection areas, this does not provide 360° circumferential coverage of the inspection area. Systems exist where more than two cameras are used for 360° circumferential coverage of the same inspection area. Such a system is disclosed, for example, in DE 10 2012 100 987 B3.

[0003] The system disclosed in the aforementioned document includes four cameras spaced 90° apart in the azimuth direction and positioned at 45° relative to the transport path. By incorporating optical elements in the optical path of each camera that can switch between a transparent and an opaque state, the system can be used to inspect labels on bottles passing through the system, for example, when the optical elements are in a transparent state, and to perform translucent inspection of the bottles by using the optical elements in an opaque state as illumination for the cameras located on the other side of the transport path.

[0004] Other systems struggle to provide full circumferential coverage of the inspection area. These systems typically use only one camera on each side of the transport path, splitting the camera's optical path into three separate paths. The container being inspected rotates 90° after passing through the system and then passes through an identical system. Such a system is disclosed in EP 2 924 419 A2.

[0005] In addition, Cognex has developed an inspection system called Omniview, which is optimized for label inspection. Label inspection is becoming increasingly important, not only for verifying correct product identification but also for checking the expiration date and other visually readable information on the label to ensure its accuracy, thus removing incorrectly labeled products from the transport path. This system features a camera arrangement similar to that in DE 10 2012 100 987 B3. Four cameras are independently mounted on a distance holder at a certain distance relative to the transport path and are all connected to a central image analysis and evaluation device (typically a PC console / electrical cabinet). In the central image analysis and evaluation device, a seamless image composed of the images captured by the cameras is generated.

[0006] Such systems, as well as systems according to the present invention, can be used in the food industry, but can also be used in other industries, such as the consumer goods (cosmetics) industry or the pharmaceutical industry, in which some type of final control through visual inspection is necessary or beneficial, for example, not only to control product identification, but also, for example, to control the expiration date of pharmaceuticals.

[0007] Each of the systems described above or known in the art has its advantages and disadvantages and is designed to optimize visual inspection for the intended application area. Summary of the Invention

[0008] The purpose of this invention is to provide an inspection system that is improved for a wide range of applications, particularly in the food industry and / or, for example, the cosmetics or pharmaceutical industries, by balancing ease of use and reasonable reliability of label reading.

[0009] This objective is achieved by further improving the inspection system mentioned above, the main feature of which is that at least one of the optical paths is longer than the spatial distance to the end of the inspection system. This makes the system very compact, while still having a satisfactory depth of focus for improved image recognition reliability in the analysis and evaluation of product images captured in the inspection area, and covering the entire label with 360-degree azimuth coverage regardless of the object's orientation relative to the transport direction, thus making the system widely applicable.

[0010] For the purposes of this invention, the following conventions regarding direction are provided. The conveying direction T is the direction of the conveying path (more specifically, when considering curved conveying paths, the conveying direction is the tangential direction of the conveying path), while the lateral or width directions orthogonal to the left and right of the conveying direction, together with the conveying direction, define an area referred to as the "reference plane," which in several preferred applications is a horizontal plane. When the inspection area is used to completely cover the field of view of multiple cameras / sensors at a 360° azimuth angle, objects not oriented in the reference plane—that is, objects with arbitrary rotational positions relative to the object's axis of rotation (e.g., the axis of symmetry of a cylindrical product)—can still be visually inspected across their entire circumferential surface in the inspection area, wherein the azimuth angle lies within the reference plane (see description of the accompanying drawings). Figure 5 ).

[0011] Furthermore, regarding the optical path, in a geometric description, it refers to the central ray of the camera's field of view.

[0012] In a preferred embodiment, for light propagating from a segment of the illuminated surface of an object to one or each camera / sensor device, there exists only one optical path, which is not divided into several separate portions that propagate in different ways.

[0013] In a preferred embodiment, at least one optical path has a first portion and a second portion, wherein the main path direction component of the first portion lies within a reference plane, while the main path component of the second portion extends along a reference axis perpendicular to the reference plane. That is, for example, in applications where the reference plane is predominantly horizontal, the main path direction lies within the horizontal plane, meaning that the vertical component of the path direction of the first portion is lower than its horizontal component. Preferably, this vertical component is even lower than 50% of the horizontal component. Preferably, the image region is centered within the surface curvature of the object so that the image center and image boundary have substantially the same distance relative to the focal point.

[0014] In another preferred embodiment, the path direction of the first portion lies entirely within the reference plane and, in particular, is entirely radial relative to the center of the inspection area. The main path component of the second portion is exactly the opposite. Here, the main path component is along a reference axis perpendicular to the reference plane, which for primary applications is along a vertical axis or height axis. In a preferred embodiment, the component other than the vertical component is less than half the vertical component; preferably, the main path component of the second portion is along the reference axis perpendicular to the reference plane.

[0015] This balances the installation space by shifting the installation space from the width direction to the height direction to maintain an acceptable depth of focus.

[0016] In another preferred embodiment, the path length of one of the first and second portions is less than twice the path length of the other portion, preferably less than 1.2 times, and particularly less than 0.6 times. This provides an advantage in terms of installation space for the deflection device used to change the optical path direction.

[0017] The targets of visual inspection are, in particular, label reading, especially reading of unoriented 2D data matrices, barcode reading, security detection / pattern matching of alphanumeric strings (including, for example, shelf-life data and LOT control), or product identification control (correct packaging, correct product, RPRP requirements), and 360° circumferential coverage is provided. Furthermore, in a preferred embodiment, the fields of view overlap along the circumferential direction at intervals of one adjacent camera / sensor device. This overlap, given at the peripheral surface of the inspected object, allows for easy capture of the entire pattern with a larger circumference using only one of the camera / sensor devices. That is, for objects arbitrarily oriented in rotation passing through the inspection system, 360° coverage of barcodes, for example, located outside the intersection of the fields of view of directly adjacent camera / sensor devices, can be achieved, but this requires combined evaluation of two images captured by the two adjacent camera / sensor devices. However, in the preferred embodiment, the entire barcode can be read using only one camera / sensor device.

[0018] In a preferred embodiment, the first viewing angle α in the reference plane of the camera / sensor device h The second viewing angle α of the camera / sensor device's reference axis is less than 30°, preferably less than 26°, more preferably less than 22°, especially less than 18°, and / or less than 30°. v The angle is less than 40°, preferably less than 36°, more preferably less than 32°, and particularly less than 28°. This improves the depth of focus, taking into account subsequent imaging. It also compensates for the fact that the inspection light originates from a curved surface, for example, objects with rounded contours or slightly conical shapes, which are the primary applications of the inspection system, given the difficulty in rotating and orienting such objects on a production line. In another preferred embodiment, particularly in conjunction with the features discussed above, the optical path length is 20 cm or more, preferably 28 cm or more, particularly 32 cm or more, and preferably less than 72 cm, preferably less than 54 cm, and particularly less than 48 cm. This allows for space savings and also increases the flexibility of using the inspection system in existing equipment that may already have multiple fixed production lines for conveying objects.

[0019] In another preferred embodiment, the inspection system includes a computing device for analyzing and evaluating images captured by the camera / sensor device, wherein at least a portion of the computing device is located locally at the location where the images to be analyzed and evaluated were captured. That is, in existing systems, the analysis and evaluation of the captured images are performed centrally on some PC or electrical cabinet, such as on an operator's workbench installed at the production line. In contrast to the prior art, at least a portion (particularly including the portion necessary to determine whether the inspected object meets preset conditions to be inspected) is performed locally at the measurement location. Specifically, preferably, the optical path length is less than 2.4 times, more preferably less than 2.0 times, and especially less than 1.6 times, the spatial distance between the camera / sensor device and the CPU location for analyzing and evaluating the images acquired from the camera / sensor device. This enhances the self-deployment capability of the inspection system, enabling it to be used as a modular component that can be plugged into a production line as a single unit.

[0020] In another preferred embodiment, the analysis and evaluation of images captured by different camera / sensor devices or by different subgroups of camera / sensor devices are performed independently and in parallel. This means that instead of a single computing device processing images captured by all camera / sensor devices, multiple computing devices are assigned to each camera / sensor device within each subgroup of camera / sensor devices. For example, in a preferred embodiment with six camera / sensor devices, each of the three CPUs is assigned to a pair (two) camera / sensor devices. This assignment includes local assignment such that the local spacing between the multiple CPUs and / or the spatial distance between the CPU assigned to a camera / sensor device and that camera / sensor device is less than the average distance from that CPU to all camera / sensor devices.

[0021] The aforementioned features can also be advantageously considered independently of the relationship between the length of the optical path and the spatial distance between the ends of the optical path, in relation to the analysis and evaluation of the captured image. Therefore, the present invention also independently and separately discloses an inspection system for visually inspecting an object, particularly its surface, during transport along a conveying path. The inspection system includes a free space that allows the object to pass through the system and includes an inspection area in which the object is visually inspected. The system also includes an illumination device for illuminating at least the outer peripheral surface of the object within the inspection area, and a plurality of camera / sensor devices, each configured to capture images of a segment of the outer peripheral surface in its respective field of view. The combined fields of view of the camera / sensor devices provide 360° circumferential coverage of the inspection area. The system further includes a computing device for analyzing and evaluating the images captured by the camera / sensor devices, wherein at least a portion of the computing device is located locally at the location where the images to be analyzed and evaluated were captured, and / or the analysis and evaluation of images captured by different camera / sensor devices or different subgroups of camera / sensor devices are performed independently and in parallel, and / or subunits of the computing device associated with a camera / sensor device or a subgroup of camera / sensor devices are locally separate from each other.

[0022] It should be understood that these inspection systems defined in the foregoing paragraphs are also disclosed in conjunction with the contextual description and one or more features of the claims.

[0023] Furthermore, preferably, a cable connection is provided between the camera / sensor device and the computing device, wherein the length and / or average cable length of a cable connecting the camera / sensor device to a portion of the computing device used for analyzing and evaluating images of the camera / sensor device is less than 400 mm, preferably less than 240 mm, and particularly less than 160 mm.

[0024] Furthermore, as described above, it is preferred that the computing device includes more than one locally separated sub-unit, and each sub-unit is associated with a camera / sensor device or a subgroup of camera / sensor devices, wherein, in particular, one of these sub-units is configured as a master unit, while the other units are configured as slave units.

[0025] This allows for hierarchical organization, particularly in computational organizations. Communication between units can be achieved, for example, via a bus system (CANopen bus system). In a preferred embodiment, each sub-unit / CPU has received information about a target pattern, the current settings of which are verified by the CPU. Once the verification is affirmatively confirmed by one of the camera / sensor devices using a CPU associated with that device, information that the standard is met is obtained, and thus there is no need to remove defective products from the production line; such removal can be done via subsequent sorting systems, pushers, etc. If any CPU cannot confirm this verification, a corresponding fault or rejection signal for the inspected product is generated and provided to a central control center, for example, using an inspection system.

[0026] In another preferred embodiment, the computing device is configured to capture an image upon receiving a trigger signal. That is, by knowing the progress and loading of the product to be inspected by the system, time information indicating when the product is in the inspection area can be obtained, thereby enabling time-synchronized image capture and, in the case of strobe lighting, ensuring that the lighting is also time-synchronized, as used by a technician.

[0027] In another preferred embodiment, the camera / sensor devices are arranged symmetrically, and the optical path lengths from the camera / sensor devices to the inspection area are the same. That is, at least in the case of inspecting cylindrical objects, the conditions for image analysis and evaluation are the same for all camera / sensor devices, and image recognition is simplified.

[0028] As already mentioned, the analysis and evaluation of the captured images includes pattern / image recognition, specifically configured with one or more capabilities such as barcode and / or QR code recognition and / or string recognition. This achieves the most important goal of the visual inspection described above. Additional specialized image software products can be used, for example, for checking label quality and label application quality, which is achieved, for example, by providing seamless images of the labels carried by the objects.

[0029] In another preferred embodiment, at least one camera / sensor device includes a mechanism for compensating for changes in object distance without moving the camera / sensor device itself. That is, in a very simple construction of the inspection system, the system can be specifically designed for objects with a predetermined lateral dimension / diameter; this simplification has some drawbacks in terms of flexibility in the system's application range. To also be able to inspect objects of different diameters, the length of the optical path is compensated in the prior art by repositioning the camera / sensor device relative to the inspection area, for example, by means of a shift driver (such as a servo motor).

[0030] In contrast, the present invention preferably uses a mechanism for compensating for varying object distances, preferably for all camera / sensor devices, without requiring the camera / sensor devices themselves to move, thereby again saving installation space and further simplifying the structure.

[0031] This aspect, independent of the length of the optical path and the spatial distance between its ends, is also considered advantageous. Therefore, the present invention provides and independently discloses an inspection system for visually inspecting an object, particularly its surface, during transport along a conveyor path. The inspection system includes a free space that allows the object to pass through and includes an inspection area in which the object is visually inspected. The system also includes an illumination device for illuminating at least the outer peripheral surface of the object in the inspection area, and a plurality of camera / sensor devices, each configured to capture an image of a segment of the outer peripheral surface within a corresponding field of view of the camera / sensor device. The combined field of view of the camera / sensor devices provides full circumferential coverage of the inspection area. At least one camera / sensor device includes a mechanism for compensating for varying object distances without moving the camera / sensor device itself. It should be understood that these inspection systems defined in the foregoing paragraphs are also disclosed in conjunction with one or more features of the preceding and following description and claims.

[0032] In a preferred embodiment, the compensation mechanism includes altering the lens system of the camera / sensor device, specifically by applying a voltage to the lens system. This allows for changing the focus of the lens system so that it is no longer necessary to move the camera / sensor device itself. A preferred application of such a lens system is a liquid lens system.

[0033] In a preferred embodiment, the compensation mechanism is controlled to adjust the focus to match predetermined dimensional characteristics (e.g., the diameter of the product to be inspected), information provided prior to inspection. This information can be provided as electronic setup information, or it can be considered to use sensors to measure desired parameters of the object and use these measurements to provide control over the compensation mechanism. Preferably, a temperature sensor is included in the compensation mechanism to provide precise focus adjustment through inverse compensation for temperature shifts in the lens system, wherein the sensor is preferably integrated into the camera / sensor device.

[0034] As previously stated, the inspection system according to the invention is designed for compact installation space and is adapted to be formed as a module in the form of a structural component for a device. To form such a module, the inspection system may be provided with a housing, the components of which are connected to the housing, preferably arranged within the housing, such that the installation of the housing into and / or removal from the device automatically results in the provision / removal of the components. Therefore, integrating the inspection system into a device in this modular form becomes quite easy.

[0035] Preferably, a first interface and / or a second interface are provided, the first interface for exchanging data with the inspection system and / or supplying power to the inspection system, and the second interface for mechanically coupling the module to the device. Regarding the second interface, a mechanical coupling unit is preferably provided, for example, for coupling the module to a support frame. Preferably, the module is configured to be laterally attached to the side of the housing, particularly only to one side of the housing.

[0036] In another preferred embodiment, the maximum dimension of the housing transverse to the transmission path is less than twice the length of the at least one optical path, preferably less than 5 / 3 of the length of the at least one optical path, more preferably less than 3 / 3 of the length of the at least one optical path, and particularly less than 7 / 5 of the length of the at least one optical path. This advantageously combines depth of focus with savings in module mounting space.

[0037] In another preferred embodiment, the module comprises at least IP65 (according to DIN EN 60529), has an outer surface made of stainless steel, and / or has a weight of less than 36 kg, preferably less than 28 kg, and particularly less than 24 kg. This enables wide applicability in the food industry on the one hand, and maintains good manageability for its modular application on the other.

[0038] Furthermore, the present invention provides an arrangement comprising a support frame and an inspection system according to any of the aspects described above, particularly modules according to any of the aspects described above, the modules being height-adjustable relative to the support frame. Again, it is preferred that the system be attached (only) laterally to the support frame. This allows for better integration with existing equipment with product lines.

[0039] Furthermore, the present invention provides an apparatus comprising a conveying system for conveying objects along a conveying path and including an inspection system, module, and / or arrangement structure according to any of the aspects described above.

[0040] As partially noted above, the inspection system preferably has six image sensors arranged 360° around the inspection area, where the upright product to be inspected stands. For symmetrical arrangement, the azimuth distance between two cameras / image sensors can be 60°. Preferably, two image sensors are connected to a single CPU board. The three CPU boards then analyze and evaluate the images from their respective image sensors in parallel. The visual inspection includes one or more of the following: reading barcodes / QR codes, reading the LCN string, verifying the graphic ID on the product label, and reading the expiration date and batch number.

[0041] Preferably, focusing on different product diameters is integrated into the system without mechanical adjustment. The following components can be integrated into the housing: a camera / sensor device with an image sensor and optics, a lamp for illumination, and / or a CPU. In some preferred embodiments, the housing may be no more than 720 mm in length and / or width, preferably less than 640 mm, particularly less than 560 mm, and / or less than 600 mm in height, preferably less than 540 mm, particularly less than 480 mm. Housing dimensions smaller than 540 mm × 540 mm × 440 mm are even possible. The housing may be made of aluminum, but preferably has an outer surface made of stainless steel. Image processing can be performed via a smart camera. The module's interface can be, for example, set to Ethernet 100 / 1000 Mbit. Regarding sensor resolution (HxV), sensors with, for example, 2 to 3 megapixels can be used, or even higher resolution sensors, such as 1600 pixels × 1200 pixels or higher, can be used. For the lens system, a C-mount lens is preferred. However, other lenses are also conceivable.

[0042] The flow inspection rate can be 400 to 1000 parts per minute, preferably 480 parts per minute or more. To reduce the error probability, it is also envisioned that the rate should not exceed 800 parts per minute. Here, 600 parts per minute ± 10% is a good compromise.

[0043] Similar to the arrangement of the camera / sensor device, illumination is preferably provided from above the inspection area. Various configurations for the illumination device are considered, such as large-area LED illumination with a diffuser. However, it is preferred to use a ring-like form, preferably composed of LED dots, combined with optics that focus the light cone of each LED onto the object surface. The angle of the illumination path relative to the horizontal plane is preferably in the range of 45°–65°.

[0044] As already mentioned, in a preferred embodiment, image analysis and evaluation are performed partially or entirely within the module, and it is worth considering that an operator panel is not even required during the use of the inspection system. However, the operator panel can be attached to an interface or control system device and / or used to feed data about the charge of the object to be inspected to the control system.

[0045] Furthermore, as already partially noted, the main CPU can send the check results after obtaining the results from the CPU.

[0046] Furthermore, the inspection system can have an additional operating setting in which only one or two camera / sensor devices at the three o'clock and nine o'clock positions are active. This is advantageous when the inspection system is used for objects whose shape deviates from a cylindrical shape, such as objects that are easily oriented relative to the transport direction. Attached Figure Description

[0047] Other features, details, and advantages of the invention will become apparent from the following detailed description of the embodiments illustrated in the accompanying drawings, wherein:

[0048] Figure 1 It is a perspective view of the inspection system and supporting framework;

[0049] Figure 2 The camera arrangement of the inspection system is shown;

[0050] Figure 3 The optical path within the inspection system is shown;

[0051] Figure 4 The lighting device of the inspection system is shown;

[0052] Figure 5 The diagram schematically illustrates the 360° coverage provided by the inspection system; and

[0053] Figure 6 The local analysis and evaluation device for the inspection system is illustrated schematically. Detailed Implementation

[0054] Figure 1The inspection system, in the form of module 20, is shown in perspective and is mounted on support frame 40 in a height-adjustable manner. In this embodiment, support frame 40 includes two vertically arranged columns 42 located on legs 43, which are capable of leveling unevenness of the floor on which support frame 40 is placed. In the lower part of support frame 40, a base portion 44 is provided to impart stability by, in this embodiment, by having two additional short vertical columns 46 interconnected with each other at their lower parts by horizontal bars 48 and interconnected with vertical columns 42 at their bottom parts by connecting legs 50, and interconnected with inclined connecting arms 52 at their upper parts to improve the rigidity of the support frame. Connecting elements 54 stably connect the two vertical columns 52 to each other in an intermittent manner. In the upper part of vertical columns 42, a height-adjustable sliding device 56 is movable along the vertical column and can be fixed to the vertical column at a desired height by clamping device 58. It can be recognized that by using vertical columns 42 of different heights, module 20 can be arranged at the desired height, or even higher. Figure 1 The height shown.

[0055] In this embodiment, the height will be determined by the height of the conveyor belt 60, which is flush with the bottom of the module 20, wherein the conveyor belt is configured to transport objects through the module 20 along the conveying direction T.

[0056] exist Figure 1 In the illustrated embodiment, the inspection system is, for example, module 20, which has a housing 22 including left and right wall portions 24a, 24b, and a cover portion 26 releasably attached to the left and right wall portions. Inlet 28 and Figure 1 An outlet 29 (not shown) is provided to allow the product to be inspected to pass through the inspection system 20, i.e., through the internal space of the housing 22.

[0057] In this embodiment, when viewed vertically (in a reference plane), the housing 22 is approximately hexagonal in shape. On one side of the housing 22, a mounting portion 23 is provided at the cover portion 26 for attachment to the sliding device 56 of the support frame 40.

[0058] An interface 21 is provided near the (mechanical) mounting interface 23 to provide a connection for data transmission and power supply lines.

[0059] from Figure 1 It is understood that in order to install / remove the inspection system 20 in a device having a conveyor belt 60 and, for example, a support frame 40, it is only necessary to mechanically couple the mounting portion 23 to or decouple it from the support frame 40, without any separate installation / removal steps for individual components of the inspection system as described below (e.g., only the module needs to be removed along with the frame).

[0060] from Figure 2 As can be better seen, six cameras 10 (10a to 10f) are arranged within a horizontal frame 27 in the upper portion of the housing 22. The cameras 10 are arranged symmetrically about the center C of the module 20 with respect to a reference plane, which is also the center of the inspection area A in which objects / products passing through the module 20 are visually inspected. The reference plane is a horizontal plane defined by the transport direction T and the width direction W. The cameras 10a to 10f are equidistant from each other at 60° angles along the circumference. That is, when the transport direction is pointed to the 12 o'clock position, the cameras are positioned at 1 o'clock, 3 o'clock, 5 o'clock, 7 o'clock, 9 o'clock, and 11 o'clock. However, the objective lens of each camera does not point directly to the center C. Instead, it is positioned as if... Figure 3 As can be seen better in the following reference, the objective lens is pointing vertically. Figure 3 The description is in more detail.

[0061] Illumination of the inspection area A, or illumination of the surface 6 of the object 5 passing through the inspection area A, is provided by an illumination device 12, which consists of a plurality of individual illumination points 13 arranged in a circle around a center C in a reference plane to provide uniform illumination. Each point 13, in this case an LED point 13, has an optical element in front of it that focuses the light cone of the LED point onto the surface 6 of the object 5 being inspected. In an exemplary embodiment, the plurality of points 13, in this case four points, are grouped together for common mounting to a housing 22, which in this embodiment is commonly mounted within a cover portion 26 of the housing 22. The illumination device 12 is configured to allow flickering illumination.

[0062] Now for reference Figure 3 , Figure 3 One side of module 20 is shown in part in a cross-sectional view through camera 10a and in part in a perspective view for illustrating the lighting device 12. It can be understood that camera 10a is not directly pointed at object 5, in this case, the surface 6 of the bottle. Instead, light from surface 6 reaches camera 10a via optical path 3, which includes a first portion 1 extending in the W direction (for camera 10a), i.e., generally in a radial direction about the reference plane and center C, and a subsequent second portion 2 extending in the vertical or height direction H (it is understood that a central ray is used to characterize the optical path). For this purpose, mirror 8a is arranged at a 45° angle relative to the reference plane (horizontal plane) to deflect the beam 3. This arrangement applies symmetrically to all the other cameras 10b to 10f.

[0063] In the exemplary arrangement, the (vertical) viewing angle α vThe horizontal (first) angle is approximately 14°, and the angle is approximately 18° (not shown). Figure 5 Furthermore, the lengths of the first part 1 and the second part 2 of the optical path 3 are approximately within the same range (for an object 5 with a diameter approximately equal to the maximum diameter applicable to the inspection system 20). The cover 7 blocks unwanted incident light not originating from the optical path 3 from entering the optical path 3.

[0064] from Figure 3 As can be seen, the combined arrangement of the lighting device 12 and the camera 10 at approximately the same height, along with the use of the reflector 8, allows module 20 to have a compact design in both its lateral and height dimensions. In the exemplary embodiment, the ratio of the maximum lateral width of module 20 to the optical path length L is approximately 1.6, and the ratio of the height of module 20 to the optical path length L of optical path 3 is approximately 0.94. It is understood that the exemplary module designed for a maximum product diameter of approximately 10 cm to 11 cm can be scaled up to accommodate / inspect larger products. The total weight of module 20 is only approximately 20 kg, making module 20 easy to handle and eliminating the need for excessive strength and rigidity in the support frame 40 or any other support structure.

[0065] from Figure 5 As can be seen, the combined field of view of cameras 10a to 10f provides complete 360° coverage of the periphery or circumferential surface 6 of object / product 5. The illustrated exemplary module does not inspect the top and bottom surfaces of product 5. However, the following embodiments (not shown) are also conceivable: in these embodiments, an additional camera is centrally positioned above the inspection area to visually inspect the top surface of product 5, while additionally or alternatively, another camera may be used to inspect the bottom.

[0066] from Figure 5 It can be further seen that the fields of view of an adjacent camera, such as cameras 10a and 10c, overlap at the circumferential surface 6 of object 5 with an overlapping region 4. Therefore, (besides pattern recognition, barcode recognition can be achieved through 360° inspection regardless of the rotational orientation of object 5 in the reference plane), when any rotational orientation of object 5 is unfavorably centered within the camera positions, the barcode can be read using only one camera; otherwise, a combination of two adjacent cameras would be required. When the center of the barcode is located within the overlapping region 4, camera 10b should be able to read the barcode.

[0067] In an exemplary embodiment, cameras 10a to 10f are fixedly mounted to housing 22, i.e., immovably, to prevent possible movement of the cameras when their height relative to mirror 8 is changed during camera arrangement. Therefore, additional components acting as actuators (e.g., in the form of servo motors) are omitted to simplify the structure and reduce weight. However, the ability to set different focal points for objects 5 with different diameters is provided within the optical system of each camera 10. Specifically, this is achieved by applying voltage to change the internal structure of the optical / lens system. For the exemplary embodiment, a liquid lens is included in camera 10a. More specifically, in the exemplary embodiment, a C-mount objective lens with an integrated liquid lens is used, for example, a commercially available one. C-C39N0-250; however, similar systems can also be used. Furthermore, the inspection system 20 includes a temperature sensor to determine the actual temperature and compensate for temperature migration in the liquid lens system. The temperature sensor can also be integrated into the camera's own optical system. In particular, the objective lens composed of liquid lenses can be focused in the region from 120mm to infinity. Furthermore, in this embodiment, the camera sensor is a CMOS sensor; however, other sensor technologies, such as CCD sensors, can also be used.

[0068] As in Figure 6 As can be seen, the analysis and evaluation of images captured by camera 10 are performed at least partially locally on the measurement side. For this purpose, one or more computing units, CPU1 to CPU3, are arranged near housing 22 and / or, in the exemplary embodiment, within housing 22 and also near the sensor head 11 of camera 10. Furthermore, subgroups of cameras and their sensors can be grouped to connect to one of the CPUs respectively. In the exemplary embodiment, two cameras are grouped together to connect to a CPU that performs pattern recognition and image analysis and evaluation for both cameras / sensors (e.g., CPU2 for 10a, 11a and 10f, 11f). Preferably, the two sensor heads 11 of the two thus coupled cameras 10 are arranged so that their data output sides face each other. This allows for the use of short cables 15 to connect the sensor heads to the respective CPUs. Preferably, the length of such connecting cable is no more than 400 mm, more preferably no more than 300 mm, and especially no more than 200 mm; in the exemplary embodiment, the length of cable 15 is only about 160 mm.

[0069] In an exemplary embodiment, one of the CPUs is configured as a master CPU, while the other two are configured as slave CPUs. The master and slave CPUs can communicate via, for example, an open CAN bus system. To perform pattern reading such as barcode reading, QR code (matrix code) reading, or other image recognition, the CPUs preferably have a pre-prepared pattern prototype (code, etc.) of the charge to be inspected for inspection / verification. Once one of the CPUs detects that the inspected product appropriately possesses such a pattern matching the prototype, the object / product can be retained in the production line. If the presence of a pattern corresponding to the prototype is not verified by any camera / sensor or their image evaluation, a signal indicating the defect is generated, allowing the corresponding product to be removed from the production line.

[0070] More complex forms of image analysis and evaluation can be performed, such as generating a complete seamless image of the circumferential surface 6 of object 5 or a complete seamless image of one or more labels of object 5.

[0071] This invention is not limited to the embodiments described above. Rather, the features described above and the appended claims may be used individually or in combination in various aspects of this invention.

Claims

1. An inspection system for visually inspecting objects during their conveyance along a conveyance path, the inspection system comprising: a free space allowing objects to pass through the inspection system and comprising an inspection area (A) in which objects are visually inspected, an illumination device (12) illuminating at least a peripheral surface (6) of an object (5) within the inspection area, and a plurality of camera / sensor devices (10a-10f), each of which is configured to take an image of a surface section of the peripheral surface in a respective field of view of the camera / sensor device by receiving light propagating along a respective optical path (3) from the illuminated object to the camera / sensor device, the fields of view of the camera / sensor devices in combination providing a full circumferential coverage of the inspection area over 360° azimuth, a plurality of mirrors (8a-8f), each mirror being arranged with respect to a respective optical path (3) and configured to direct light propagating along the respective optical path (3) towards the respective camera / sensor device, wherein a length of at least one optical path (3) is greater than a spatial distance between the ends of the optical path, wherein the camera / sensor devices and the mirrors (8a) assigned to the respective camera / sensor devices (10a) are configured such that, in operation of the inspection system, a light ray from the surface (6) reaches the respective camera / sensor device by propagating along a first portion (1) of the respective optical path (3) having a main path direction component in a radial direction within a reference plane being a plane of azimuth and subsequently along a second portion having a main path component along a reference axis being perpendicular to the reference plane, wherein a path length of one of the first portion and the second portion is below twice a path length of the other one.

2. The inspection system of claim 1, wherein, a path length of one of the first portion and the second portion is below 1.2 times a path length of the other one.

3. The inspection system of claim 1, wherein, a path length of one of the first portion and the second portion is below 0.6 times a path length of the other one.

4. The inspection system according to any one of claims 1-3, characterized in that, fields of view of camera / sensor devices (10a, 10c) spaced one adjacent to the other overlap when viewed in a circumferential direction.

5. The inspection system according to any one of claims 1-3, characterized in that, a length of the optical path is 20 cm or more; and / or a length of the optical path is 72 cm or less.

6. The inspection system of claim 5, wherein, a length of the optical path is 28 cm or more.

7. The inspection system of claim 5, wherein, a length of the optical path is 32 cm or more.

8. The inspection system of claim 5, wherein, a length of the optical path is 54 cm or less.

9. The inspection system of claim 5, wherein, a length of the optical path is 48 cm or less.

10. The inspection system of claim 1, wherein, the inspection system comprises a computing device for analytically evaluating images taken by the camera / sensor devices, wherein at least a part of the computing device is located locally to a location where the images are taken for analytical evaluation.

11. The inspection system of claim 1, wherein, the inspection system comprises a computing device for analytically evaluating images taken by the camera / sensor devices, wherein the analytical evaluation of images taken by different camera / sensor devices or by different subgroups (10a, 10b; 10c, 10d; 10e, 10f) of camera / sensor devices is computed independently in parallel.

12. The inspection system of claim 10 or 11, characterized in that The computing device comprises more than one locally separated subunit, each of the subunits being assigned to one camera / sensor device or a subgroup of camera / sensor devices, respectively, at least one of the subunits being configured as master unit and the other units being configured as slave units.

13. The inspection system of any one of claims 1-3, 6-11, wherein, The camera / sensor devices are arranged symmetrically and the length of the optical paths of the camera / sensor devices to the inspection area are identical.

14. The inspection system of claim 10 or 11, wherein, The computing device is configured to provide an analytical evaluation of the taken images, the analytical evaluation comprising pattern / image recognition, and the computing device is configured with one or more than one of the following capabilities: bar code recognition, unoriented 2D data matrix recognition.

15. The inspection system of any one of claims 1-3, 6-11, wherein, At least one camera / sensor device comprises a compensation mechanism for compensating varying object distances without moving the camera / sensor device itself.

16. The inspection system of claim 15, wherein, The compensation mechanism comprises a modification of a lens system of the camera / sensor device.

17. The inspection system of claim 16, wherein, The compensation mechanism performs the modification by applying a voltage to the lens system.

18. An inspection module (20) in the form of a structural component for an inspection apparatus in which objects are conveyed and inspected during their conveyance, the inspection module comprising a housing (22) and an inspection system according to any one of claims 1-17, the components of the inspection system being connected with and arranged within the housing such that mounting and / or dismounting of the housing to / from the inspection apparatus automatically results in the provision / disprovision of the components.

19. The inspection module of claim 18, wherein, The maximum dimension of the housing transverse to the conveyance path is less than twice the length of the at least one optical path.

20. The inspection module of claim 18, wherein, The maximum dimension of the housing transverse to the conveyance path is less than 5 / 3 times the length of the at least one optical path.

21. The inspection module of claim 18, wherein, The maximum dimension of the housing transverse to the conveyance path is less than 3 / 2 times the length of the at least one optical path.

22. The inspection module of claim 18, wherein, The maximum dimension of the housing transverse to the conveyance path is less than 7 / 5 times the length of the at least one optical path.

23. The inspection module of any one of claims 18-22, wherein, The inspection module complies with at least IP65, has an outer surface made of stainless steel, and / or has a weight of less than 36 kg.

24. The inspection module of claim 23, wherein, The inspection module has a weight of less than 28 kg.

25. The inspection module of claim 23, wherein, The inspection module has a weight of less than 24 kg.

26. An inspection apparatus comprising a support frame (40) and an inspection module according to any one of claims 18-25, the inspection module being height adjustable relative to the support frame.

27. An inspection apparatus comprising a conveyance system (60) for conveying objects along a conveyance path, the inspection apparatus further comprising an inspection system according to any one of claims 1-17, an inspection module according to any one of claims 18-25, and / or an inspection apparatus according to claim 26.

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