Method and device for optical inspection of hollow glass articles

Abstract

Method and device for the optical inspection of hollow glass articles. The invention relates to a method for the optical inspection of configurational and material defects such as inclusions, cracks, and stress zones in hollow glass articles (1). The hollow glass article (1) is located on an optical path between a camera (3) and a light source (2), and also between two controllable optical modules (5, 6). At least one of the optical modules (5) contains a liquid lens that allows, through electrical control, a modification of the focal length and, therefore, a shift in the image plane. Thus, a clear reproduction of different areas to be inspected on the hollow glass article (1) is achievable.Another possibility for controllable optical modules (5, 6) lies in neutral polarization filters, whose polarization plane can be modified by electrical control, for the purpose of transferring from a bright-field reproduction to a dark-field reproduction, and vice versa. Figure for the abstract: Fig. 1.

Description

Title of the invention: Method and device for optical inspection of hollow glass articles

[0001] The present invention relates to a method for the optical inspection of hollow glass articles. It further relates to a device for implementing this method.

[0002] Hollow glass articles, as products of a glass-forming process, require inspection of various properties, including, for example, adherence to product dimensions, surface damage, shape characteristics in or on the surface, inclusions in the glass (including bubbles), and areas of stress within the glass material. Inspection is systematically based on tolerance ranges, with the understanding that if these ranges are not met, the hollow glass article must be discarded.

[0003] A clear, high-contrast reproduction of the area to be checked on the container is a prerequisite for accurately carrying out the inspection of containers such as hollow glass articles.

[0004] In this context, optical inspection methods in the form of transparency or reflection methods are known, in which the article is placed on an optical path and light reflected from cracks and inclusions within the glass material or from surface structures is received by means of a camera and directed to an evaluation system, which has the function of examining the type of said defects more precisely. In addition to features active by reflection, it is possible in this case to identify features forming shadow zones.

[0005] In this context, optical testing methods in the form of a set of transparency constraints are also known, it being understood that the article is located on an optical path between two polarization filters, whose polarization planes extend relative to each other at an angle of jt / 2. This set is intended to identify stress zones within the glass material, it being understood that the optical path, in the absence of any stress zone, is not permeable to light and that permeability to light is only present in the presence of stress zones after the polarization plane has been rotated by them relative to its initial position. Local stress zones within the glass can impair its mechanical stability, so defective articles must also be rejected in this respect.

[0006] Both variants of the process result, by means of using at least one camera, in the creation of at least one image, regularly however from sequences images, which reproduce a part of the periphery or any other location of the hollow glass article to be inspected, which forms the basis of a subsequent evaluation process.

[0007] The components required for the technical representation of said two processes can be arranged in the form of control modules along a glass-shaping production line, it being understood that each control module is designed for a specific control task of the apparatus. These control tasks also include, among others, batch control. This is a form of production line operation in which hollow glass articles of different heights, or different circumferences, or with any other characteristic configuration, follow one another at irregular intervals.

[0008] This results from a trend towards broadening control criteria with the aim of improving quality assurance, the need for devices in accordance with extended control procedures, and, consequently, an increasing number of control modules, it being understood that, however, limits are often imposed for reasons of space. Simply simplifying the control modules to be used does not address this problem, even in terms of the associated costs.

[0009] In this context, the invention aims to configure a process of the type mentioned in the introduction at lower costs and in particular with a reduced space footprint by aiming at the development of other control functions.This objective is achieved in an optical inspection method for hollow glass articles, concerning compliance with structures and dimensions as well as the presence of material defects, in which the hollow glass articles are guided through an inspection area, in which at least areas of the hollow glass article are illuminated by means of at least one light source and are reproduced by means of a camera, and in which the evaluation of the images thus obtained is carried out in an image processing unit, characterized in that the reproduction is carried out using at least one optical module whose focal length can be controlled and which is arranged on the optical path between the light source and the camera.

[0010] The use of at least one controllable optical module in a control module associated with a glass-shaping machine, which allows the focal length and, consequently, the position of an image plane for a single shot to be electrically modified, is essential to this invention. Depending on the switching speed of the optical module, this opens the possibility of grouping several shots, which reproduce different areas of the hollow glass article to be inspected, within a control module, particularly within a camera.

[0011] The controllable optical module is used in accordance with the respective hollow glass article to reproduce different areas of the article, including the positions These are of particular interest for material control, risk assessment, and product shape control. This functional grouping of several control tasks within a single camera extends the scope of control on existing glass processing machines without requiring additional space for other control modules.

[0012] According to another feature, the polarization state of the optical path used for reproduction can be adjusted via controllable optical modules. This adjustment can be made in addition to the aforementioned focal length modification and allows for monitoring the presence of tension zones in the glass material at arbitrarily chosen locations within the article.

[0013] During inspection, the hollow glass article passes through a control zone at a speed defined by the machine speed of the glass shaping process. The control zone can be considered as the area corresponding to the camera's detection zone. Depending on the switching speed of the controllable optical modules, it is possible to record images from different viewing angles so that as complete a detection of the hollow glass article as possible can be represented for inspection purposes.

[0014] Furthermore, the present invention aims to design a device for implementing the method as described above, which allows, in a compact manner, an extension of the control functions of devices used for inspecting hollow glass articles. The device must be designed for integration into the glass shaping process. This objective is achieved in the case of such a device characterized by a camera, at least one light source, means for guiding a hollow glass article to be inspected through the optical path defining the inspection zone between the light source and the camera, and at least one controllable optical module located on said optical path.

[0015] In accordance with the foregoing, the use of an optical module that can be controlled within an optical path defined by a camera and a light source, intended for reproducing at least some areas of the hollow glass article to be inspected, is crucial to the invention. The optical module must be electrically controllable, for example, with regard to its focal length, the polarization state of the optical path, etc., and must thus be able to be rapidly adapted to changing inspection tasks, in particular to different areas to be reproduced on the hollow glass article, as well as to verifying the presence of voltage zones.

[0016] The optical module can advantageously be designed to adjust the focal length and can incorporate a liquid lens for this purpose. This lens, thanks to electrical control, allows for very rapid changes in focal length, given that the switching times of commercially available liquid lenses are on the order of 1 ms. These switching times readily allow for application to moving hollow glass articles.

[0017] Advantageously, optical modules can be designed to modify the polarization state of the optical path used for reproduction purposes. Thus, voltage states within the glass structure can be identified. An optical module can also contain a controllable neutral density filter to correct for lighting conditions.

[0018] In an advantageous configuration, the controllable optical modules can be developed both to modify the focal length and to modify the polarization state.

[0019] The light sources, optical modules, and camera are advantageously connected to a control system. Its operation is thus integrated into the glass forming process. The operation of the light sources can, for example, be configured to be timed and synchronized with the camera. This makes it possible to counteract the disruptive influence of external light.

[0020] The operation of the light sources can also be adapted to emit different wavelengths of light. This feature can be used to adapt the glass material to different colors.

[0021] The control is advantageously connected to an image processing unit. This is equipped in a manner known per se for the purpose of evaluating the determined images, it being understood that in accordance with the result of said evaluation, various hollow glass articles deemed to be defective may be rejected.

[0022] The control unit may advantageously be connected to, or contain, a data memory of this type, in which essential data or parameters of the manufactured hollow glass articles are stored and can be taken into account during inspection for the purpose of comparison with the hollow glass articles. It is advantageous to use such a data memory in batch operation, in which hollow glass articles of different configurations must be inspected in rapid succession.

[0023] The present invention is explained in more detail below with reference to the accompanying schematic figures, which show:

[0024] [Fig. 1] a representation of a first embodiment used to carry out the process according to the invention;

[0025] [Fig.2] a representation of a second embodiment used to carry out the process according to the invention;

[0026] [Fig.3] a representation of an embodiment, developed for the purpose of series control, of the process according to the invention;

[0027] [Fig.4] a representation of an embodiment intended for the control of outside diameters of mouth and of mouth threads of the process according to the invention;

[0028] [Fig.5] a representation of an embodiment intended for the control of mouths and clear inscriptions of the process according to the invention.

[0029] Reference number 1 designates in [Fig.1] a hollow glass article to be inspected, for example a bottle, which is placed upright on a support not shown in the figure or is held by a transport strap and is uniformly illuminated from the underside by means of a surface-active light source 2.

[0030] The hollow glass article 1 can be stationary during the control, can rotate around its longitudinal axis or can perform another preferably linear movement.

[0031] Reference number 3 designates a camera above the hollow glass article, which is held stationarily in a frame not shown in the figures, and in such a way that the axis of its lens 4 extends coaxially with respect to the axis of the hollow glass article 1.

[0032] The optical path between the light source 2 and the lens 4 is characterized by a first optical module 5 that can be controlled above the hollow glass article 1 and a second optical module 6 that can be controlled below the hollow glass article 1, which are connected in the same way as the light source 2 to a control 7. The control 7 and also the camera 3 are connected to an image processing unit 8. The two optical modules 5, 6 are added as independent components to the assembly.

[0033] In accordance with the respective control task, the optical modules 5, 6 are liquid lenses, polarizing filters, diaphragms, and neutral density filters—in other words, modules whose optical properties can be electrically controlled. The focal length underlying the respective reproduction, and thus the spatial position of an image plane, can be modified by means of corresponding control of the liquid lenses. The polarization state of the reproduction radiation can be modified by means of corresponding control of a polarizing filter, for example, for the purpose of representing a bright-field or dark-field image. The amount of incident light in the lens, and thus the related reproduction parameters, can be modified by means of corresponding control of diaphragms and neutral density filters.

[0034] For example, the optical module 5 in the case of the assembly according to [Fig. 1] can be a liquid lens, which allows image planes to be positioned along the axis of the hollow glass article 1 in different positions. The optical module 6 can, for example, be a neutral density filter, which, depending on its adjustment, allows the representation of different lighting conditions.

[0035] For example, the optical modules 5, 6 can be alternatively controllable linear polarization filters, whose polarization planes can vary relative to each other between parallelism and right angles. Thus, a bright-field assembly and a dark-field assembly can be represented with the possibilities of a transparency assembly or a transparency constraint assembly.

[0036] In all cases, one or more images are taken of the hollow glass article 1 to be inspected, in particular of parts thereof. These images are transmitted via the camera 3 to the image processing unit 8 and evaluated there, in particular with the aim of detecting deviations in configuration characteristics compared to reference characteristics, or imperfections on the surface or within the glass material. The external dimensions of the hollow glass article 1, in particular its symmetry properties with respect to its axis, are also among the characteristics to be inspected.

[0037] It is identified that, depending on the specific adjustment of the optical modules 5 and 6, numerous control functions can be represented, which can be implemented in a single control module consisting of only a camera, two optical modules, and a light source. Such an assembly can be housed with minimal space requirements and, in particular, after the image planes of the optical recording system have been modified, allows for very simple adaptation to different positions of the recorded images and also to hollow glass objects of different configurations.

[0038] Functional elements, which coincide with those of [Fig.1], are given the same reference numbers in Figures 2 to 5 so that in this context it is unnecessary to repeat the description.

[0039] The embodiment according to [Fig.2] differs from that according to [Fig.1] only in that a controllable optical module 9 is integrated into the modular unit of the lens 10 of the camera 3. Alternatively, the optical module can also be designed as a component of the camera 3.

[0040] Regarding the technical embodiment of the optical module 9, the explanations relating to optical modules 5, 6 apply similarly.

[0041] The embodiment shown in [Fig. 3] is designed to control the type of batch operation. This means that the formats of the glass articles hollows to be controlled change over time, and in the extreme case at a speed that approaches the machine rate of the glass shaping process.

[0042] Figure 3 shows, by way of example, hollow glass articles 1, 1', 1”, and 1”', which have different sizes, in particular different heights, it being understood that compliance with their outside diameters of the mouth and their mouth threads must be checked. The hollow glass article 1 is shown here in two positions, namely a first position outside a control zone 12 and a second position inside the control zone 12. The hollow glass articles, placed upright on a first conveyor belt 11, are transferred into the control zone 12 and then guided out of the control zone by means of a second conveyor belt 13.The transfer from the first conveyor belt 11 into the control zone 12 and, similarly, the transfer out of the control zone 12 onto the second conveyor belt 13 with the assistance of the transport belt 14 are not shown in the figures, are implemented at the level of a higher-order lifting unit known in itself, which at the same time ensures the transport through the control zone 12.

[0043] The representation on the figures of a light source located under the control zone 12 is omitted.

[0044] For the purposes of implementing the control, in the case of [Fig.3], the focal length of the socket must be adjusted according to the different distances 15, 16 and 18 of the hollow glass articles 1, 1' and 1”, which can be easily represented, in particular without changing the speed of the scrolling of the hollow glass articles after the reaction time of commercially available liquid lenses is on the order of about 1 ms and focal length adjustments of several 10 mm can be achieved.

[0045] It is therefore possible to create shots following one another at very short intervals of a container to be controlled, for example at a distance of a few ms, it being understood that the properties of at least one of the optical modules 5, 6 are modified by an electrical signal, and this in order to reproduce clearly different areas of the container or to modify lighting conditions.

[0046] The embodiment shown in [Fig. 4] is based on checking the outside diameter of the mouth and the mouth thread of a hollow glass article 1. The figure illustrates the assembly in a top view. The representation of a light source in the figures is again omitted, it being understood that the hollow glass article 1 to be checked moves in a straight line in the direction of arrow 19.

[0047] Only by way of example, a view of the hollow glass article 1 is taken in a first position 20 - view in the direction of scrolling - and in a second position 21 after the first position 20, thus according to different angles of observation. To this end, the focal length for the first shot is set by the control of the optical module 5 in accordance with a distance 22, while the focal length for the second shot is set in accordance with the sum of the distances 22, 23 and 24, it being understood that the reference number 25 designates a plane mirror.

[0048] This operating method is not limited to two shots of the hollow glass article 1 to be checked; it is possible, as needed, to produce other shots, it being understood that the required focal lengths are adjusted accordingly according to the speed of movement of the hollow glass article via the control 7.

[0049] The shots are produced in the case of the assembly according to [Fig.4] laterally with respect to the hollow glass articles and are intended for checking the outside diameter of the mouthpiece.

[0050] The embodiment according to [Fig.5] is developed for the purpose of checking mouthpieces as well as for checking inscriptions in plain text on the bottom side of hollow glass articles 1, and this on the basis of shots created vertically, in other words parallel to the axis of the hollow glass article.

[0051] To this end, another light source 27 in the form of a ring light source is arranged, in addition to the light source 2 below the hollow glass article 1, above the article so as to surround it and in particular the mouth area. Using the photographs, the mouth area and, after the corresponding adjustment of the focal length of the optical module 5, a field of clear markings 28 on the back side, which bears, for example, the symbol "15", can be monitored.

[0052] The assemblies shown in Figures 3 to 5 can be expanded in a versatile manner. In particular, housing a second optical module 6 can enable the development of the prerequisites for implementing both a transparency assembly and a transparency constraint assembly. Specific effects can be achieved by timing the operation of the light sources 2, 27. These operational variants can be centrally adjusted via the respective control 7.

[0053] In another configuration of the assembly according to the invention, essential parts such as light sources 2, 27, the camera 3, and optical modules 5, 6, 9 are arranged so as to be able to slide horizontally and / or vertically relative to the hollow glass article 1 to be inspected. In the present case, movement by pivoting can also be provided, for example, with the aim of replacing a vertically oriented view with a horizontally oriented view. The movable arrangement of essential components makes it possible to further improve the adaptability to different shapes of the hollow glass article 1. Preferably, a such position adjustment is developed with electric drives via the control.

[0054] It is recognized that, due to the numerous adjustment possibilities of a control module equipped with an assembly as described above, many control functions can be grouped within the control module so that a control program more extensive than the prior art can be implemented. This grouping results in a considerable space saving, which makes it possible to meet the often limited spatial requirements during the operation of a glassworks.

[0055] All settings can be made centrally via the control associated with the control module, which thus makes it possible to contribute, in connection with a database, in which among other things the data of the hollow glass articles to be processed are stored, to a representation of an automated operation, which also includes a series operation.

[0056] List of reference numbers:

[0057] 1 Hollow glass article 1 ' Hollow glass item 1 ' ' Hollow glass item 1' ” Hollow glass item 2. Light source 3 Camera 4. Objective 5 Optical Module 6 Optical Module 7. Command 8 Image Processing Unit 9 Optical Module 10. Objective 11 Conveyor belt 12 Control Zone 13 Conveyor belt 14 Conveyor belt 15 Distance 16 Distance 18 Distance 19 Arrow 20th Position 21st Position 22 Distance 23 Distance 24 Distance 25 Mirror 26 Outer diameter of mouth 27 Light source used to illuminate the mouth 28 Plain text field

Claims

Demands

1. A method for optically inspecting hollow glass articles (1) for conformity to structure and dimensions and for the presence of material defects, wherein the hollow glass articles (1) are guided through an inspection zone (12), in an optical path between at least one light source (2, 27) and a camera (3), wherein at least areas of the hollow glass article (1) are illuminated by means of at least one light source (2, 27) and are reproduced by means of the camera (3), and wherein the evaluation of the images thus obtained is carried out in an image processing unit (8), the reproduction being carried out using at least one optical module (5, 6) whose focal length can be controlled and which is arranged on the optical path, characterized in that the optical path comprises two optical modules (5, 6, 9) respectively arranged above and below the inspection zone (12),connected to a control (7) and capable of being controlled with regard to focal length, polarization state, and of acting as a diaphragm or neutral density filter.

2. Method according to claim 1, characterized in that the polarization state of the optical path used for the purpose of reproduction is adapted for the purpose of reproduction by means of optical modules (5, 6).

3. A method according to any one of claims 1 or 2, characterized in that during the movement of a hollow glass article (1) through the control zone (12), at least two images of it are produced from different viewing angles.

4. A device for implementing the method according to any one of claims 1 to 3, characterized by a camera (3), at least one light source (2, 27), means for guiding a hollow glass article (1) to be inspected through an optical path defining the inspection zone (12) between the light source (2, 27) and the camera (3), and at least one controllable optical module (5, 6) located on said optical path; said device being characterized in that the optical path comprises two optical modules (5, 6, 9) respectively disposed above and below the inspection zone (12), connected to a control (7) and capable of being controlled with regard to the focal length, the state of polarization as well as to play the role of diaphragm or neutral filter.

5. Device according to claim 4, characterized in that at least one of the two optical modules (5, 6) is focused to adjust the focal length of the optical path.

6. Device according to claim 5, characterized in that at least one of the two optical modules (5, 6) contains a liquid lens.

7. Device according to claim 4, characterized in that at least one of the two optical modules (5, 6) contains a neutral filter.

8. Device according to claim 4, characterized in that the optical modules (5, 6) are designed to modify the polarization state of the optical path.

9. Device according to any one of claims 4 to 8, characterized in that the light sources (2, 27), and the camera (3) are connected to the control (7).

10. Device according to claim 9, characterized in that the light sources (2, 27) are focused to represent a light of a different color.

11. Device according to claim 9 or 10, characterized in that the control (7) is connected to the image processing unit (8).

12. Device according to any one of claims 9 to 11, characterized in that the control (7) is linked to a data memory, in which at least the data of the hollow glass articles (1) to be processed are stored.

Images