Abstract
A method for creating an image of a base of a container uses a matrix camera. The matrix camera captures a series of individual captures of regions of the base of the container which overlap in sections, while the base of the container is transilluminated by a light source arranged on the side opposite the matrix camera. A digital image of the base of the container is compiled from the individual captures. The invention is characterized in that the region of the base of the container captured in an individual capture is defined by an illumination structure, that the illumination structure is shifted relative to the base of the container between two individual captures, and that the container and the matrix camera remain rotationally invariant to one another during the capturing of the series of individual captures. The invention also relates to a device for carrying out the method.
Claims
1. Method for creating an image of a translucent or transparent base of a container, wherein a matrix camera with pixels arranged in a plurality of rows and a plurality of columns is provided, wherein a series of individual captures of regions of said base of said container is captured using said matrix camera, wherein adjacent individual captures overlap in sections, wherein during an individual capture, said base of said container is transilluminated by a light source located on the side of said base of said container opposite said matrix camera, and wherein a digital image of said base of said container is compiled from the series of individual captures, wherein said region of said base of said container captured in an individual capture is defined by an illumination structure, that said illumination structure is shifted relative to said base of said container between two individual captures, and that said container and said matrix camera remain rotationally invariant to one another during the capturing of the series of individual captures.
2. Method according to claim 1, wherein said illumination structure is shifted translationally and/or rotationally relative to said base of said container between two individual captures.
3. Method according to claim 1, wherein said illumination structure defines a rectangular, preferably square, or grid-shaped or stripe-shaped illumination region.
4. Method according to claim 3, wherein said illumination region is defined by one or more cut-outs in a mask arranged below said base.
5. Method according to claim 4, wherein said mask is shifted between two individual captures in a rotational, translational, arcuate, or combined motion.
6. Method according to claim 1, wherein said base of said container during the capturing of said individual captures is spaced from a support structure arranged below said base.
7. Method according to claim 1, wherein said individual captures captured by said matrix camera have a rectangular or square shape.
8. Method according to claim 1, wherein the series of individual captures is created while said container is being transported in a direction of transport relative to said illumination structure.
9. Device for creating an image of a translucent or transparent base of a container, comprising a matrix camera with pixels arranged in a plurality of rows and a plurality of columns, a light source for transilluminating said base of said container, and a mask for creating an illumination structure, wherein a memory is provided for storing a series of individual captures of regions of said base of said container captured by said matrix camera, and wherein said device comprises an evaluation unit configured to compile a digital image of said base of said container from the series of individual captures, wherein said device is configured to shift said illumination structure relative to said base of said container between two individual captures, and that said device comprises a holding structure configured to hold said container and said matrix camera in a manner rotationally invariant to one another when the series of individual captures is captured.
10. Device according to claim 9, wherein said illumination structure defines said region of said base of said container captured in an individual capture.
11. Device according to claim 9, wherein said device is configured for translational and/or rotational shifting of said illumination structure relative to said base of said container between two individual captures.
12. Device according to claim 9, wherein a support structure for supporting said container, wherein said support structure comprises or forms a mask.
13. Device according to claim 9, wherein said illumination structure defines a rectangular, preferably square, or grid-shaped illumination region.
14. Device according to claim 9, wherein said holding structure comprises a gripper for gripping or clamping said container.
15. Device according to claim 9, wherein it comprises an actuator configured to temporarily move said matrix camera or a camera optic system of said matrix camera synchronously with a motion of said container.
Description
BACKGROUND OF THE INVENTION
[0041] The invention shall be further explained hereafter on the basis of embodiments with reference to the figures.
[0042] FIG. 1 shows a schematic plan view of a device for inspecting containers.
[0043] FIG. 2 shows a schematic sectional view of a device for creating an image of the container base according to an embodiment, where the section is indicated by I-I in FIG. 1.
[0044] FIG. 3 shows a schematic representation of several individual captures of the base of the container.
[0045] FIG. 4 shows a schematic representation of a compiled image of the base of the container.
[0046] FIG. 5 shows a first embodiment of an illumination structure.
[0047] FIG. 6 shows a second embodiment of an illumination structure.
[0048] FIG. 7 shows a third embodiment of an illumination structure in plan view.
[0049] FIG. 8 shows a further embodiment of a grid-shaped or stripe-shaped illumination structure in plan view.
[0050] FIG. 9 shows an embodiment of the device with a grid-shaped illumination structure in a vertical sectional view.
[0051] FIG. 10 schematically shows a further embodiment of the device in a side view.
[0052] FIG. 11 schematically shows a further embodiment of the device in a side view.
DETAILED DESCRIPTION
[0053] FIG. 1 shows a schematic plan view of a device 1 for inspecting containers 3. As shown in FIG. 2, containers 3 are, for example, plastic or glass bottles with a base 5 and a side wall 7. Alternatively, containers 3 can be other types of jars or bottles, e.g., jam or preserving jars.
[0054] As shown in FIG. 1, device 1 comprises a transport device 9 for transporting containers 3 along a direction of transport 11. In the embodiment illustrated, transport device 9 comprises a star wheel 13 which transports containers 3 along a circular path. Star wheel 13 comprises holding elements 15 arranged one behind the other along a circumferential direction of star wheel 13. Containers 3 are transferred from a transfer station 17 to star wheel 13 by being placed between adjacent holding elements 15 of star wheel 13. By rotating star wheel 13, containers 3 are conveyed along direction of transport 11. During conveyance, containers 3 are pushed over a transport surface 19 of transport device 9 by holding elements 15 of star wheel 13. The transportation of containers 3 along direction of transport 11 is carried out in a clocked manner. Once containers 3 have been inspected in device 1, they are removed from transport device 9 by a removal station 21 located with reference to direction of transport 11 downstream of transfer station 17.
[0055] An inspection station 23 is provided with reference to direction of transport 11 between transfer station 17 and removal station 21 at which base 5 of container 3 that is respectively present in inspection station 23 is examined for imperfections or defects. During the inspection of a container 3 by inspection station 23, star wheel 13 is preferably at a standstill. During this time, container 3 is therefore preferably not transported along direction of transport 11.
[0056] During the inspection of a container 3 in inspection station 23, container 3 is in an inspection position. In the inspection position, container 3 is at rest relative to star wheel 13. If star wheel 13 itself is at a standstill during the inspection, container 3 is at rest overall during the inspection, i.e., also relative to the surroundings of transport device 9, e.g., a factory hall.
[0057] FIG. 2 shows a sectional view in the region of inspection station 23 along the section indicated by I-I in FIG. 1. A device 24 according to the invention for creating an image of base 5 of container 3 is arranged at inspection station 23. Device 24 and the most important components of this device, respectively, are shown in FIG. 2.
[0058] Container 3 shown in FIG. 2 is in the inspection position. In the inspection position, container 3 stands with its base 5 upon a support structure 30. In the embodiment illustrated, support structure 30 is inserted into a receptacle of transport surface 19. According to embodiments, support structure 30 can be inserted to be exchangeable into transport surface 19. Alternatively, support structure 30 can be formed integrally with transport surface 19. Transport surface 19 and support structure 30 can have upper surfaces that are flush with each other so that bottle 3 can be pushed from transport surface 19 onto support device 30 by star wheel 13.
[0059] As shall be explained below, support structure 30 can define an illumination structure 50 in the context of the invention. FIG. 2 shows various options for how support structure 30, and thereby the illumination structure, can be shifted between two individual captures. For example, support structure 30 (optionally together with transport surface 19) can be shifted between two individual captures in a translational motion B1, in an arcuate motion B2, in a substantially U-shaped motion B3 composed of several sections, and/or by a rotatory motion B4 about an axis 27 of container 3. To effect this shifting, various measures are again conceivable. For example, device 24 can comprise a single drive A1 or several drives A1, A2, e.g., servomotors. If multiple drives A1, A2 are present, each can be responsible for its own direction of motion or motion component, resulting overall in, for example, an arcuate or U-shaped shifting B2, B3. For this purpose, each drive A1, A2 is connected to support structure 30 and/or transport surface 19 by way of a suitable operative connection a1, a2. A specific embodiment of such an operative connection a2 can comprise a lever mechanism which is schematically shown in FIG. 2 in two different pivoting positions. The pivoting of such a lever mechanism a2 connected to support structure 30 can cause an arcuate motion b2. If multiple drives A1, A2 are provided, a controller (not shown), e.g., a computer or a microcontroller, can ensure suitable synchronization of the various drives A1, A2.
[0060] A matrix camera 39 with a vertically downward viewing direction is arranged above support structure 30. Container 3 is centered with its axis 27 substantially in the viewing direction of matrix camera 39 which is directed from above through an opening 7a of container 7 onto its base 5. Matrix camera 39 is characterized in that its image points (pixels) 40, as shown in FIG. 3, are arranged as a plurality of rows Z and a plurality of columns S, i.e., on an area (instead of just in a single row). Device 24 comprises a fixation device or holding structure 25, respectively, which is configured to hold container 3 and matrix camera 39 in a manner rotationally invariant to one another when the series of individual captures E is captured. Holding structure 25 can comprise a gripper 25a which is configured to grip container 3 and hold it at rest during the inspection. Alternatively, support structure 25 can be configured such that container 3 is clamped between support structure 25 and star wheel 15 in that a clamping element 25a presses laterally against container 3.
[0061] A light source 37 is arranged on the side of support structure 30 opposite matrix camera 39, i.e., in the embodiment illustrated, below support structure 30. Light source 37 is used to transilluminate base 5 of the container. For this purpose, support structure 30 can comprise, for example, a translucent placement surface 31 so that the light emitted by light source 37 can pass through base 5 of container 3. One or more recesses 31a through which light can pass can be present in support structure 30 or translucent placement surface 31. Light source 37 can be a pulsed light source, for example, a stroboscopic light source. In this case, the emission of its light pulses can be synchronized with the operation of matrix camera 39, for example by a controller (not shown) of device 24.
[0062] On the camera side, an optics system with an integrated beam splitter and two attached cameras 39 can be employed. One of cameras 39 is arranged axially, as shown in FIG. 2, while the other is mounted laterally at a 90 angle to the optic system. Light source 37 is provided with a linear polarizing filter 55 and the camera optic system with a linearly polarizing beam splitter. One camera 39 then sees a bright image, while other camera 39 normally sees nothing because the polarizing filters are arranged in a crossed manner. However, if there is a stress-bearing inclusion (imperfection) in bottle base 5, then the polarization plane is rotated and second camera 39 sees the stress source as a bright spot. Two cameras 39 are therefore used for normal base examination and stress examination. The use of a station 23 with only one camera without polarization evaluation is alternatively also conceivable. The use of image sensors with an upstream polarizing filter is also possible.
[0063] FIG. 3 shows a schematic representation of several individual captures E being captured by matrix camera 39. Due to the orientation of matrix camera 39 and the arrangement of its pixels 40 in several rows Z and columns S, each individual capture E consists of a stripe-shaped region B of base 5 of container 3preferably a square region B. In FIG. 3, captured region B of base 5 is the intersection between circular base 5 of container 3 and the total area of individual capture E. As mentioned at the outset, base 5 or the cross-section of container 3 do not have to be circular, but can have any shape, e.g., rectangular, square (in general: polygonal). Each individual capture E covers a specific length L and a specific width b. In one variant, length L and width b are equal in size (or approximately equal in size) and each is approximately 5 to 10% smaller than the diameter (21) of container 3.
[0064] While a series of individual captures E of base 5 of a container 3 is created, a shift of the illumination structure relative to base 5 of the container occurs between different individual captures E, e.g., a shift and/or a relative rotation. The relative rotation between two individual captures E can occur by an angle of, for example, 10 to 15, preferably by an angle of 2 to 12.
[0065] Device 24 comprises an evaluation unit 41 which can be integrated into matrix camera 39 or connected to matrix camera 39. Evaluation unit 41 comprises a memory 42 for storing a series of individual captures E as well as a computer 43 on which a computer program product 44 is installed. Evaluation unit 41, or specifically computer program product 44 installed therein, is configured to compile a digital image of base 5 from a series of individual captures E of a base 5 of container 3. FIG. 3 indicates in what manner this can be done:
[0066] There is a plurality of special spots 45 in base 5 of container 3. Special spots 45 can be indentations 45a selectively introduced into base 5, e.g., circumferential indentations 45a, or an undesired imperfection 45b, e.g., a bubble or a crack. An image recognition module of computer program product 44 is configured to recognize such special spots 45 in individual captures E. Evaluation unit 41 is then configured to manipulate individual captures E in such a way that an optimal superimposition of special spots 45 in respective individual captures E is obtained. The manipulation can comprise a rotation of respective individual captures E (e.g., but not necessarily, about axis 27 of container 3), a translation of individual captures E in their longitudinal and/or transverse direction and/or stretching or compressing respective individual captures E.
[0067] When all individual captures E of a series have been processed by evaluation unit 41, it has created a digital image A of base 5 of container 3, as shown in FIG. 4. Digital image A is compiled from respective individual captures E, where individual captures E are arranged at an angle relative to one another. As a result, this does not produce an unwinding of base 5 with corresponding distortions, but rather a distortion-free image of base 5 of container 3.
[0068] To facilitate the evaluation and compilation of image A, evaluation unit 41 can take into account angle (see FIG. 3) as an input variable, by which the illumination structure is shifted, e.g., rotated, relative to container 3 between two individual captures E. This input variable makes it easier for evaluation unit 41 to compile digital image A, as the probability of the need to shift, move, or rotate individual captures E is reduced.
[0069] If device 1, inspection station 23, or device 24 has a display 46 (see FIG. 2), then digital image A can be displayed there. Alternatively, digital image A can be evaluated mechanically. If imperfections 45b are detected, respective container 3 can be discharged manually or in an automated manner.
[0070] FIG. 5 schematically shows a plan view of an illumination structure 50. In this comparatively simple embodiment, illumination structure 50 comprises a central bright illumination region 51 (i.e., a region of high light intensity) having a rectangular contour 52. Bright region 51 is surrounded by an annular dark region 53, i.e., a region of low light intensity. Illumination structure 50 can be created in that a mask 54 (e.g., one that can be inserted into or integrated into support structure 19) with a central recess 31a is provided. Central recess 31a defines illumination region 51, i.e., bright region 51 of illumination structure 50. Recess 31a can be free (i.e., formed as a hole) or formed by a transparent or translucent material, e.g., sapphire glass. The shifting of illumination structure 50 relative to base 5 of container 3 can be achieved in that mask 54 is shifted. The size of recess 31a can be selected such that it is smaller than a dimension of container 3 so that container 3 can stand on mask 54 during the capturing of individual captures E.
[0071] The use of a mask 54 has the advantage that the use of a large-region or even full-region light source 37 is enabled, as well as the optional use of a polarizing filter 55 between light source 37 and container 3 (see FIG. 2), and that neither light source 37 nor (if present) polarizing filter 55 need to be shifted relative to container 3 for shifting illumination structure 50 during inspection.
[0072] FIG. 6 shows a second embodiment of an illumination structure 50. It differs from the embodiment shown in FIG. 5 only in that illumination region 51, i.e., the bright region of illumination structure 50, is not shaped to be square, but cross-shaped. Various other shapes of illumination region 51 are conceivable, for example, a rectangular shape.
[0073] FIG. 7 shows a further embodiment of an illumination structure 50. This illumination structure 50 is grid-shaped, i.e., it comprises a regular two-dimensional arrangement of bright fields 51 between which dark regions or webs 53a are located. In the present embodiment, grid-shaped illumination structure 50 has a number of 1010 bright fields 51.
[0074] While FIG. 7 shows an illumination structure 50 in the shape of a two-dimensional grid, FIG. 8 shows an embodiment of an illumination structure 50 in a stripe-shaped or one-dimensional grid shape. In this embodiment, webs 53a are provided only in the y-direction. Stripe-shaped bright (i.e., illuminated) fields or stripes 51, respectively, extend between webs 53a. Embodiments of such a stripe-shaped illumination structure 50 are conceivable and advantageous in which the width of webs 53a in the x-direction is approximately 40 to 60 percent of the width of a bright region (stripe) 51 in the x-direction. In other words, in such an embodiment, each web 53a has approximately half the width of a bright region or stripe 51, respectively. Specifically, for example, each web 53a could have a width of 5 to 10 millimeters, while each bright region, slit, or stripe 51 could have an extension of 10 to 20 millimeters in the x direction. Variations of these proportions are, of course, conceivable.
[0075] An advantage of a grid-shaped illumination structure 50 like in FIG. 8 or 9 is that webs 53a can ensure increased strength and therefore improved bearing strength of mask 54 for container 3. A further advantage becomes clear in the vertical sectional view shown in FIG. 9. The lower part of container 3 is indicated there which stands with its base 5 on mask 54 as part of support structure 19 during the inspection. The grid-shaped illumination structure 50 enables the compilation of a (digital) image A of any point on the container base 50 using a minimal number of just two individual captures E. For this purpose, only illumination structure 50 needs to be offset between two individual captures E in both the x-direction and the y-direction (see the coordinate system in FIG. 7) by a distance that does not correspond to an integer grid spacing. For example, shifting in the x-direction and in the y-direction can be achieved by, for example, 0.4 to 0.6 times the grid spacing, for example, 0.5 times the grid spacing. The shifting of illumination structure 50 can be achieved by moving mask 54. Various options are available for this. For example, mask 54 could be shifted in its plane by a solely translational motion B1. Alternatively, mask 54 could be shifted between two individual captures by an arcuate motion B2. Arcuate motion B2 has the advantage that, during the shifting of illumination structure 50, less or even no frictional forces act upon base 5 of container 3, which further increases the positional stability of container 3. This could be further improved by a U-shaped motion B3, in which the structure or mask 54, respectively, is first moved axially downwardly until there is no longer any contact with container 3, and only then is it moved translationally.
[0076] Depending on the technical configuration of the overall system and, above all, the number of images to be captured per container and the number of containers per unit of time, a fast to very fast camera can be used as matrix camera 39. For example, cameras with an interface of 1, 5, 10, or more gigabits per second are conceivable. The image region of camera 39 is preferably selected to be large enough to always capture the entire illumination region 51regardless of its orientation relative to the image. Synchronization between the captured image and the respective orientation of illumination structure 50 can be achieved either solely through image processing, for example, in that image recognition software independently searches for illuminated region 51 in respective individual capture E. Alternatively, to improve process stabilization, the selectively performed shifting of illumination structure 50 between individual captures E can be taken into account, for example, the size of the selectively performed shifting and/or rotation of the illumination structure.
[0077] It is conceivable that the total duration of capturing a series S of individual captures is completed in less than 100 milliseconds, preferably even within 75 milliseconds or less. This enables a very high throughput of the inspection device, i.e., a high number of containers inspected per unit of time.
[0078] FIG. 10 schematically shows a side view of a further embodiment of a device 24 according to the invention for creating an image A of base 5 of a container 3. In this embodiment, containers 3 are transported while their base 5 rests upon a support structure 30, for example, a translucent placement surface 31. Placement surface 31 is configured to define, for example, a stripe-shaped illumination structure 50 with alternating light and dark stripes. Placement surface 31 is illuminated from below by a light source 37.
[0079] The drinking containers 3 are transported in a direction of transport 11, for example, on a star wheel 13 (see FIG. 1). FIG. 10 schematically shows three different states: namely an initial state (with solid lines of the container), and the positions of container 3 at two later points in time with dashed lines. It would be conceivable for container 3 to be at a standstill in the middle one of the three positions (which enables particularly precise capturing), and for the other two positions to be shortly before and shortly after the standstill, for example, at distances of approximately 7 to 14 mm from the standstill position.
[0080] In this exemplary embodiment, matrix camera 39 is temporarily moved synchronously with the motion of container 3. This is ensured by an actuator 60, which temporarily couples the motion of matrix camera 39, for example, with the transport speed of container 3 on star wheel 13. In this exemplary embodiment, the series captured by matrix camera 39 could consist of, for example, three individual captures E. However, any other (in particular higher) number of individual captures E would also be conceivable.
[0081] FIG. 11 shows a modification of the embodiment from FIG. 10. In contrast to FIG. 10, actuator 60 there does not move matrix camera 39 with the container; instead, actuator 60 temporarily moves a camera optic system 61 synchronously with the motion of container 3 along direction of transport 11. Camera optic system 61 can be, for example, a mirror or mirror optic system.
[0082] Based on the embodiments illustrated and the appended claims, the invention can be modified in various ways. One possibility, for example, is to capture and inspect individual images E (visually or mechanically) before or even without a digital image A of base 5 of container 3 being compiled from several images.
