System and method for detecting a glaze defect in a glass container by means of polarising filters

Abstract

The invention relates to a system for detecting a glaze defect in a glass container (200) arranged in an observation position, the system comprising: - a projector (100) emitting along an illumination axis (101); - a first polarising filter (F1) having a polarisation oriented at 45° with respect to a central axis (AC) of the container, and arranged so as to filter the light beam emitted by the projector; - an image sensor (300) configured to observe at least one observation portion of the container in the observation position, the image sensor having an observation axis (301); - a second polarising filter (F2) having a polarisation oriented at 45°, plus or minus 5°, with respect to the central axis of the container, and arranged between the container and the image sensor, wherein the illumination axis and the observation axis intersect at an angle (α) of between 10° and 150°.

Description

Description Title of the invention: System and method for detecting glaze-type defects in a glass container, using polarizing filters Technical Field [OOOlJThe present invention relates to the technical field of the inspection of empty glass containers, such as for example bottles, jars, flasks in order to detect possible glaze-type defects. Prior art

[0002] After manufacture, empty glass containers are subject to various checks for defects, including checks for the presence of glazes. It is well known that the presence of glazes in a glass container is generally a serious quality problem, as it almost always results in lower mechanical strength.

[0003] To detect glazes, a region of the container is illuminated at precise angles of incidence using projectors emitting directed (convergent or slightly divergent) light beams towards the region. The directed light beams reach the surface of the container at a precise angle of incidence so that part of the beam penetrates the glass wall and propagates in the glass. If a glaze is present in the path of light in the wall, then the glaze reflects the beam, which leaves in a modified direction to exit the wall at a precise exit angle, which is a function of the incident angle and the position and shape of the glaze.The illuminated region is observed, according to precise observation angles adapted to the exit angles of the beams reflected by the glazes, by means of light sensors, for example photodiodes as in patent application EP 0 053 151, photodiode arrays, or image sensors such as linear or matrix cameras as in patent applications EP 1 147 405 and EP 2 082 217. This observation is carried out at observation angles. precise such that the incident light reflected by a glaze-type defect is collected / observed by the light sensors, which will theoretically only receive light when a glaze passes during rotation of the container around its vertical axis. Indeed, known detections generally involve rotating the container to be inspected around a central axis, over at least one revolution.

[0004] Thus, the detection of glazes as described in the previous paragraph is implemented using the reflection of light by the glaze.

[0005] Conventionally, containers are conveyed on production lines, on belt or chain conveyors, at the most stable translation speed possible in order to limit all conveying accidents such as falls, collisions and jams caused by sudden accelerations and decelerations. Glaze detection solutions requiring rotation of each container around its vertical axis therefore have a certain number of disadvantages because these solutions require in particular to interrupt the translation of the containers. To carry out this rotational inspection, it is necessary to significantly slow down and stop the containers, remove them from the conveyor using handling systems and then put them back into translation on the conveyors. Furthermore, these handling systems (guides, star wheels, drive rollers, etc.) require heavy adaptations to changes in container format.In particular, format adaptations often involve disassembly and assembly operations, tooling specific to container models, as well as adjustment operations for these handling systems. Furthermore, these handling systems are poorly suited to handling containers with a non-round section. They are also limited in speed; typically, they halve the rate of inspection lines, which is not required by the in-line inspection systems that will be presented below.

[0006] Finally, complex handling operations are frequently the cause of breakages, blockages or line stoppages leading, through accumulation, to significant productivity losses. Contact between containers and guides, wheels stars, drive rollers, etc. are sources of unnecessary deterioration of containers and pose maintenance problems for wear parts, which are quite costly.

[0007] To overcome the disadvantages of detecting glazes by rotating the containers, there are devices that allow detection of certain glazes when the container is moving.

[0008] In particular, document FR 3 109 444 is known, which describes a station for detecting glaze-type defects in a slice of containers having a central axis and moving in a translation direction, without rotation around their central axis. The station uses a plurality of imagers with optical axes directed towards the interior of an inspection zone with chosen azimuths. Projectors are also used to form beams tangent to the container, with chosen azimuths. This document describes glaze detection for containers in translation, and this type of detection is called in-line detection.

[0009] US 4,293,219 proposes a camera-free solution. In this solution, the sensors each contain a single photosensitive element collecting all the reflected light perceived in a reception cone defined by the focal length of its lens and its aperture. It is impossible to distinguish the shape of the reflective objects observed, nor their precise location in the field of the sensors, so it is not possible to discriminate small objects, i.e. to differentiate between a small glaze and a small parasite.

[0010] The ARGOS machine, marketed by the applicant, is a translational glaze detection machine with cameras that does not require the container to rotate around its central axis. The cameras improve detection, since images are produced of each illuminated region. It is designed to detect glazes on the finish and on part of the shoulder of a container. It uses a lighting and observation head, in which the directed light emitters and the endoscope heads are organized according to the diameter of the container's finish. The lighting and observation head forms a tunnel through which the neck of the containers circulates during their translation through the installation for inspection. Endoscopes are used to bring back a number of images, acquired according to various observation directions, on a number of sensors reduced to two or three. For example, all the endoscopes intended for the detection of vertical glazes (by clockwise or counterclockwise tangential illumination), are connected to a single camera. In a first station, a single image acquisition is made per container for the detection of vertical glazes, and in a second separate station, a single image acquisition is made per container for the detection of horizontal glazes.In order to avoid interference between transmitters and receivers activated simultaneously in the first station, a separation of the transmitter / receiver pairs by color is used, in other words, there are red light transmitters which cooperate with endoscope heads equipped with red filters and green light transmitters which cooperate with endoscope heads equipped with green filters, which only allows a reduced number of image acquisition conditions in a station. [001 l]Patent EP 2 434 276 describes a machine that detects glazes on the neck of a container by combining two orthogonal translations, since a vertical translation is combined with the horizontal scrolling translation. A handling device is provided to allow vertical movement. Such a handling device is bulky and takes up space around the containers because the lifting elements that engage on opposite sides of the container to pick up the container, hide parts of the containers that cannot be inspected. These hidden parts of the containers represent a relatively large part at least in the case of low-height containers. In other words, the system is not suitable for small items such as cosmetic or pharmacy bottles.In addition, to inspect two parts of the containers with different edges such as the neck and the bottom of the containers, this machine requires the serial connection of two handling and inspection stations, leading to a costly and bulky installation.

[0012] Whether glaze inspection is performed in translation or rotation, it is necessary, in prior art techniques, to use projectors that project narrow light beams with precise contours, in order to limit parasitic reflections caused by multiple reflections. This constraint is particularly critical for articles with small diameter necks or openings. Also, the use of a narrow beam does not overcome the difficulties encountered in centering containers (and their necks or openings). Indeed, handling tolerances on the one hand and verticality tolerances of the containers on the other hand prevent high-precision centering from being achieved.

[0013] Furthermore, when the inspection system is intended for in-line inspection, a large number of light projectors directed tangentially to the part of the container to be inspected for the detection of vertical glazes is required. The inspection of containers of different diameters also multiplies the number of projectors required, these projectors being configured to project beams tangent to the containers. There is therefore a need for glaze detection that accepts wide beams.

[0014] The detection of a glaze at the level of the ring of a container, using a wide beam, is visible in Figure 1 which is a photograph of the ring of a container observed using prior art techniques. The ring of the container in Figure 1 has a vertical glaze DF which appears as a narrow line reflecting light. It is recalled that a glaze results from a particular thermal expansion which produces stresses inside the material, these stresses leading to a rupture which is called a glaze. At the level of the glaze, we can therefore have a glass / air interface, which explains why the glaze reflects light like that visible in Figure 1.

[0015] However, not all the parts that reflect light in the image of Figure 1 are glazes. The acquisition of the image of the ring in Figure 1 was implemented using a wide light beam, for example covering the ring over its entire width visible in the figure. As a result, several light areas can be seen in the image of Figure 1, which are PR stray reflections. As can be understood, the presence of these PR stray reflections makes it difficult (especially when using automated image processing) to identify the DR glaze defect which may appear drowned in the stray reflections.

[0016] Figure 2 shows schematically and in top view a configuration used to observe glazes by means of a system according to the prior art to obtain an image such as that of Figure 1. In other words, it is a configuration which produces wide beams which cover the entire width of the ring of the container visible in the figure. For this purpose, a projector 10 is used, directed towards a container 20 (and more precisely towards the ring of the container which is visible in the figure), and an image sensor 30 also directed towards the container 20.

[0017] A first ray shown in the figure is the ray RI, emitted by the projector 10 and which reaches the surface of the ring of the container so that it is totally reflected by the external surface 21 of the ring of the container 20, in the direction of the image sensor 30, the direction of propagation of the light being represented by an arrow arranged above the ray in the figure.

[0018] A second ray shown in the figure is ray R2, which encounters the outer wall 21 of the container ring so that it is fully transmitted inside the wall of the container ring, emerges when it encounters the inner wall 22, and reaches the glaze defect DF which leads to a reflection of ray R2 towards the image sensor 30. It is this ray R2 that we wish to observe, in isolation, on the images acquired by the image sensor 30. , the direction of propagation of the light being represented by an arrow arranged above the ray in the figure.

[0019] A third ray shown in the figure is ray R3, which encounters the outer wall 21 of the container ring so that it is fully transmitted to the inside of the container ring wall, emerges when it encounters the inner wall 22, and reaches from the inside of the container the inner wall 22 at another point, from where it is reflected towards the image sensor 30 (having passed through the container ring wall a second time), the direction of propagation of light being represented by an arrow arranged above the ray in the figure.

[0020] A fourth ray shown in the figure is ray R4, which encounters the outer wall 21 of the container ring so that it propagates inside the wall of the container ring which has a waveguide behavior for a certain distance, before ray R4 exits the wall to reach the image sensor 30, the direction of propagation of the light being represented by an arrow arranged above the ray in the figure.

[0021] There is therefore a need to obtain images in which only rays such as ray R2 reach the image sensor 30, even when a wide beam is used to illuminate the container.

[0022] The present invention aims to overcome the drawbacks of the prior art by proposing a defect detection system with a higher tolerance in terms of beam width, and therefore in terms of positioning and centering of the containers, and in terms of the variety of container diameters for which detection is possible. Statement of the invention

[0023] The present disclosure relates to a system for detecting a glaze-type defect in a glass container arranged at an observation position, comprising: - a projector emitting a light beam along an illumination axis, - a first polarizing filter having a polarization oriented at 45° at plus or minus 5° relative to a central axis of the container, and arranged to filter the light beam emitted by the projector, the filtered beam covering at least an illuminated portion of the container in the observation position, - an image sensor configured to observe at least an observation portion of the container in the observation position, the image sensor having an observation axis, the observation portion being further configured such that the illuminated portion is at least partly visible in an image obtained by the image sensor (the illuminated portion may be visible directly or indirectly (for example by transmission through the wall of the container)), and - a second polarizing filter having a polarization oriented in the same direction as the first polarizing filter at 45° to plus or minus 5° relative to the central axis of the container, and arranged between the container and the image sensor to filter the radiation observed by the image sensor, in which the illumination axis and the observation axis are configured so that their projections in a plane orthogonal to the central axis of the container intersect at an angle of between 10° and 150°, the first filter and the second filter forming angles oriented at 45° to plus or minus 5° relative to the central axis of the container in the same direction relative to the central axis of the container,when observed in the direction of propagation of the light from the projector to the illuminated portion and then from the observed portion to the image sensor, the system being configured so that the detection of a glaze-type defect uses the light reflected towards the image sensor by the glaze receiving the light beam from the projector.,

[0024] An observation of the filter in the direction of light propagation is made from upstream to downstream relative to the direction of light propagation. Here, the light is emitted by the projector in the direction of the illuminated portion, an observation of the first filter in the direction of propagation is made for example by observing this first filter from the projector, where we can see an orientation of 45° to plus or minus 5° in one direction (to the left or to the right) relative to the central axis of the container (if the central axis of the container is vertical, we will have 45° to plus or minus 5° relative to the vertical to the left or to the right).

[0025] Light is reflected from the observed portion (possibly but not necessarily after having partly passed through the wall of the container by transmission) towards the image sensor, an observation of the second filter in the direction of propagation is made for example by observing this second filter from the observation portion, where one can see an orientation of 45° at more or minus 5° in a direction which is the same as that of the first filter (towards the left if the first filter is at 45° plus or minus 5° or to the right otherwise) relative to the central axis of the container (if the central axis of the container is vertical, we will have 45° plus or minus 5° relative to the vertical towards the left or towards the right).

[0026] In this method, the reflection of light by the glaze is used. In fact, the light beam is reflected by the glaze towards the image sensor when a glaze is present. A projector and image sensor arrangement is chosen to operate in reflection, making it possible to illuminate the illuminated portion and to observe the observation portion so that a glaze which receives light from the projector can reflect this light towards the image sensor.

[0027] It has been observed that the use of two polarizing filters, oriented at around 45°, and with an angle between the image sensor and the projector, makes it possible to filter a large part of the parasitic reflections visible in Figure 1. For example, the polarizing filters can be arranged to be orthogonal or at least substantially orthogonal to the illumination and observation axes respectively.

[0028] In fact, the inventors of the present invention first observed that glazes, which have a structure in which on either side of the break (at the glass / air / glass interface), the glass presents mechanical stresses and has a birefringent effect on the light. Also, it was observed that the polarization of the incident light, which is a linear polarization according to the angle of the first polarizing filter, is modified in a specific way when it is reflected by the glaze. In fact, it can be said that the glaze in addition to being reflective, is birefringent, that is to say, it modifies the state of polarization of the light with a retardation blade behavior with a fast axis in the vicinity of 90° and a slow axis in the vicinity of 0° relative to the axis of the container, or vice versa.With a first filter oriented at 45° to the container axis (observed in the direction of light propagation), the light reflected by the glaze has an elliptical polarization. In fact, with the fast axis and the slow axis oriented at 0° and 90°, or vice versa, it is by using 45° filters (observed in the direction of. the propagation of light) that the transmission of the two components of the electric vector of the light wave is optimized and that the elliptically polarized light reflected by the glaze is transmitted while that reflected by the container elsewhere is blocked.

[0029] The light reflected by the glaze, having an elliptical polarization, is transmitted by passing through the second filter, also oriented at 45° (observed in the direction of propagation of the light, and in the same direction as the first filter), which gives it a linear polarization after passing through the second filter.

[0030] On the other hand, the light reflected by the container elsewhere than by passing through the glaze, has a linear polarization which is oriented at 135° due to the reflection, this polarization being observed in the direction of propagation of the light and in the same direction as the orientation of the filters. This light is therefore well filtered by the second filter at 45°, that is to say blocked. Only the reflection of the light by the glaze leads to light radiation which reaches the image sensor, which facilitates the visibility of the glaze and its detection. [003 l]Since the stray light is filtered, on the one hand detection is easier. On the other hand, the incident beam can be widened without causing stray reflections. This tolerance on the width of the projector beam also has an impact on the tolerance on the centering and positioning of the containers. Therefore, the invention makes it possible to obtain a simpler and less expensive, and / or faster, system, while presenting a good level of detection of the glazes. It is also possible to detect glazes within containers of different diameters with a single system.

[0032] The glazes referred to here are mainly so-called vertical glazes, that is to say, glazes which extend substantially in the same direction as the central axis of the containers. In fact, the invention is well suited to making these vertical glazes visible. The invention is nevertheless not limited to glazes which extend substantially in the same direction as the central axis of the containers but also applies to glazes inclined relative to this axis or even to horizontal glazes. [0033JAs an indication, it can be noted that substantially vertical glazes (i.e. in the same direction as the central axis of the containers) are glazes which can have an inclination of more or less 30° relative to the central axis of the containers. Furthermore, vertical glazes are generally not strictly flat and furthermore their penetration from the external or internal surface of the wall is not strictly radial. The term vertical glazes therefore encompasses the different glazes of varied shapes, more or less inclined.

[0034] The person skilled in the art will be able to identify the central axis of a container. For example, this axis may be an axis of symmetry of the containers, or even an axis of symmetry of revolution. For a container whose opening is located at the top when the container is placed (for example a bottle or a jar), the central axis passes through the center of the opening of the container, and it extends in the main direction of the containers (vertically for bottles and jars).

[0035] The illumination axis is preferably considered from the point of view of the container, it is the axis of the light beam FL incident on the container. The illumination axis may correspond to the optical axis of the projector, it extends in the main direction of the beam emitted by the projector, for example passing through a center of the projector and / or an optical center of the projector.

[0036] The observation axis is preferably considered from the point of view of the container, being the axis of propagation of the radiation from the container to the image sensor. The observation axis may correspond to the optical axis of the image sensor, it extends in a direction normal to the plane of the sensor of the image sensor, and passes through its center. It can be noted that the term image sensor refers to the device comprising a sensor (for example a matrix of photosites), and the optical elements which project an image onto the sensor.

[0037] The illumination and observation axes intersect in the vicinity of the container, or even within the container. The illuminated portion can be observed at least in part by the observation portion. This is not, however, obligatory, as a glaze can be illuminated after transmission through the wall of the container, and this glaze can be observed within a portion that is not directly illuminated. Preferably, the illuminated portion and the portion observation are located at the same level of the container, a level being a part of the container delimited in the direction of the central axis of the container. For example, for a container with a vertical central axis, the same level of the container corresponds to a part of a given height of the container. Preferably, the illuminated portion is the external surface of the container on which the illumination beam is incident, and the observation portion is the external surface of the container from which the radiation observed by the image sensor originates. Thus, preferably, the illuminated portion and the observation portion overlap at least partially, and more preferably at least 20% of the observation portion corresponds to the illumination portion.

[0038] According to a particular embodiment, the illumination axis and the observation axis are configured so that their projections in a plane orthogonal to the central axis of the container intersect, forming an angle preferably greater than 30°, preferably less than 100°, and more preferably between 30° and 90°.

[0039] This configuration was observed to further facilitate the detection of glazes.

[0040] According to one embodiment, the projector and the image sensor are arranged on either side of a plane orthogonal to the central axis of the container and passing through the container.

[0041] For example, for a container with a vertical central axis, this orthogonal plane can be a horizontal plane. For a horizontal plane, we either have the image sensor above this plane and the projector below, or we have a configuration in which the image sensor is below this plane and the projector above.

[0042] This particular method makes the glazes clearly visible.

[0043] According to a particular embodiment, the projector and the sensor are arranged on the same side of a plane orthogonal to the central axis of the container and passing through the container.

[0044] This particular embodiment has been observed as suitable for making visible glazes more or less inclined relative to the central axis of the container.

[0045] According to one embodiment, the illuminated portion of the container comprises at least a portion of the ring of the container.

[0046] The observed portion may also include a portion of the container ring (optionally, the entire container ring is observed).

[0047] The ring is a part that can be affected by glazes, and within which glazes can be difficult to detect. They are particularly difficult to detect for rings with threads, the presence of which causes stray reflections.

[0048] According to a particular embodiment, the filtered light beam overlaps only a slice of the container ring or overlaps the container ring over its entire width, to obtain the illuminated portion.

[0049] In this particular embodiment, according to a first alternative, only a slice of the ring is illuminated, which is advantageous for limiting parasitic reflections. According to a second alternative, the entire ring is illuminated, which is a more favorable configuration in terms of beam width tolerance, centering and positioning of the container.

[0050] According to a particular embodiment, the edge of the container is included in the observation portion, and, observed from the projector, the edge extends from an external vertical edge of the ring of the container towards the interior of the container (this illumination is observable on an image obtained by the image sensor).

[0051] Glazes are more easily observed with a tangential beam, which corresponds to illumination that extends from one edge towards the interior of the container.

[0052] According to one embodiment, the slice of the container observed from the projector comprises, from the external vertical edge of the ring of the container, a first portion extending between the external vertical edge of the ring of the container and the inner vertical wall of the container ring, the first portion having a width equal to the width of the wall of the container ring, and a second portion extending from the inner vertical wall of the container ring, the second portion having a width between 0% and 60% of the inner diameter of the container ring, or between 18% and 60% of the inner diameter of the container ring.

[0053] This particular embodiment makes it possible to both limit parasitic reflections and obtain good tolerance on the beam width and / or on the positioning and centering of the container.

[0054] According to a particular embodiment, the illumination axis and the observation axis are configured so that their projections in the plane orthogonal to the central axis of the container intersect at an angle of between 10° and 150° at a first external vertical edge of the ring of the container, the system further comprising: - an additional projector emitting a light beam along an illumination axis, - a first additional polarizing filter having a polarization oriented at 45° at plus or minus 5° relative to the central axis of the container, and arranged to filter the light beam emitted by the additional projector, the filtered beam covering at least one additional illuminated portion of the container in the observation position, - an additional image sensor configured to observe at least one additional observation portion of the container in the observation position, the additional image sensor having an observation axis, - a second additional polarizing filter having a polarization oriented in the same direction as the first polarizing filter at 45° at plus or minus 5° relative to the central axis of the container, and arranged between the container and the additional image sensor to filter the radiation observed by the additional image sensor, - detecting a glaze-type defect using light reflected back to the image sensor by the glaze-type defect receiving the light beam from the projector, in which the illumination axis of the additional projector and the observation axis of the additional image sensor are configured so that their projections in the plane orthogonal to the central axis of the container intersect at an angle of between 10° and 150°, at a second external vertical edge of the ring of the container, the second edge being diametrically opposite the first edge, the first additional filter and the second additional filter forming angles oriented at 45° to plus or minus 5° relative to the central axis of the container in the same direction relative to the central axis of the container, when they are observed in the direction of propagation of the light from the additional projector to the illuminated portion then from the observed portion to the additional image sensor.

[0055] In fact, in this particular embodiment, two opposite edges of the container ring are observed. This makes it easier to detect all the glazes.

[0056] According to a particular embodiment, the system is configured to rotate the container in the observation position around the central axis of the container.

[0057] According to a particular embodiment, the system is configured to drive the container in horizontal translation to the observation position.

[0058] For example, the system may include a container conveyor track.

[0059] According to a particular embodiment, the system comprises a device for processing the images obtained by the image sensor, configured to automatically detect glaze-type defects by processing the images.

[0060] Any type of image processing can be used to automatically detect glazes. For example, models obtained through machine learning, typically artificial neural networks, possibly convolutional neural networks, can be used.

[0061] The invention also provides a method for detecting a glaze-type defect in a glass container arranged in an observation position, comprising: - emit a light beam along an illumination axis, - filtering by means of a polarizing filter having a polarization oriented at 45° at plus or minus 5° relative to a central axis of the container, the light beam emitted by the projector, the filtered beam covering at least an illuminated portion of the container in the observation position, - observing by means of an image sensor configured to observe at least an observation portion of the container in the observation position, the image sensor having an observation axis, the observation portion being further configured so that the illuminated portion is at least partly visible on an image obtained by the image sensor, - filtering by means of a second polarizing filter having a polarization oriented at 45° at plus or minus 5% relative to the central axis of the container, and arranged between the container and the image sensor, the radiation observed by the image sensor, in which the illumination axis and the observation axis are configured so that their projections in the plane orthogonal to the central axis of the container intersect at an angle of between 30° and 90°, the first filter and the second filter forming angles oriented at 45° at plus or minus 5° relative to the central axis of the container in the same direction relative to the central axis of the container, when they are observed in the direction of propagation of the light from the projector to the illuminated portion then from the observed portion to the image sensor.

[0062] This method may be implemented by any of the embodiments of the system as described above.

[0063] The above-mentioned features and advantages, as well as others, will become apparent from the following detailed description of examples of embodiments of the system. This detailed description refers to the attached drawings. Brief description of the drawings

[0064] The attached drawings are schematic and are intended primarily to illustrate the principles of the presentation.

[0065] In these drawings, from one figure to another, identical elements (or parts of elements) are identified by the same reference signs.

[0066] [Fig. 1] Figure 1, already described, is a photograph of a container ring showing stray reflections.

[0067] [Fig. 2] Figure 2 is a schematic representation showing the ray path leading to spurious reflections.

[0068] [Fig. 3] Figure 3 is a top view of a container with a detection system according to an example.

[0069] [Fig. 4] Figure 4 shows the illumination of a container slice, according to an example.

[0070] [Fig. 5] Figure 5 is a perspective view of a container and system according to an example, with a conveyor track.

[0071] [Fig. 6A] Figure 6A is a side view of a container and system according to an example, with a support configured to rotate the container, and also a top view of this arrangement.

[0072] [Fig. 6B] Figure 6B is a side view of a container and system according to another example, with a support configured to rotate the container, and also a top view of this arrangement.

[0073] [Fig. 7] Figure 7 shows schematically the use of two projectors

[0074] [Fig. 8A] Figure 8A is an image of a container ring containing stray reflections.

[0075] [Fig. 8B] Figure 8B is an image of the container ring of Figure 8A, obtained by a system according to an example.

[0076] [Fig. 9A] Figure 9A is a photograph of a container ring including a vertical glaze.

[0077] [Fig. 9B] Figure 9B is an image obtained by a system according to an example in which the vertical glaze is visible.

[0078] [Fig. 10] Figure 10 shows the observation of the filter orientations. Description of the embodiments

[0079] We will now describe a system for detecting glaze defects affecting glass containers. We will also describe a method for detecting these defects, which can be implemented by this system.

[0080] In the present description, the main focus is on glazes present within the rings of containers (the part of a container comprising an opening, for example the part configured to receive a closing device (stopper, capsule, etc.)). The invention is nevertheless in no way limited to these glazes alone and also finds application in the detection of glazes present in the bodies of containers.

[0081] Figure 3 is a schematic representation of a system according to an example, usable for detecting glaze defects DF, present within a container 200. This container 200 is provided with a ring B. The container is here a container having a vertical central axis AC passing through the center of the ring B. In fact, the container is a bottle-type container. It has a symmetry of revolution around the central axis AC.

[0082] In Figure 3, the container is in an observation position. To reach this observation position, the container can be conveyed by a conveyor track, or even rotated. The observation position therefore corresponds to a position in the container's space, and to an orientation.

[0083] The system used here comprises a 100 projector and a 300 image sensor.

[0084] The projector 100 is directed towards a part of the container 200, and here, more precisely towards the ring B of the container. The projector is here a light-emitting diode projector which emits a light beam FL, which is directed around an illumination axis 101 (which is the center of the beam). The axis illumination axis 101 is here oriented so that it meets the ring B of the container, and it passes through the wall of the ring B at two points. In other words, the observation axis 101 is not exactly tangential to the ring B of the container 200. There is in fact a tolerance on the beam width and the orientation of the illumination axis 100, which allows this non-exactly tangential arrangement.

[0085] Before reaching the ring B of the container, the light beam FL is filtered by a first polarizing filter Fl so that a filtered light beam FLF is obtained at the output of the filter to reach the ring B of the container. As can be seen in the figure, the filtered light beam FLF has a width that covers an illuminated portion PI of the ring B. The illuminated portion PI does not only include the edge of the container ring as a narrow beam, but it also extends towards the inside of the container due to the shape of the filtered light beam FLF.

[0086] The first polarizing filter Fl has an orientation relative to the central axis, i.e. relative to the vertical, of 45° to plus or minus 5° (to the right or to the left when observing the filter in the direction of propagation of the light, represented by an arrow arranged above the ray in the figure). The light of the filtered light beam FLF is therefore polarized with a linear polarization oriented at 45° relative to the vertical direction observed from the projector.

[0087] When the filtered FLF light beam reaches the DF glaze defect, the glaze acts as a retardation plate and reflects light rays with a linear polarization at about 45° into rays with an elliptical polarization. Light rays reflected by the container elsewhere than at the glaze level are reflected with a linear polarization, modified and oriented at about 135°.

[0088] To observe these rays reflected by the glaze defect DF, a camera-type image sensor 300 is used. The image sensor 300 has an observation axis 301 oriented towards the container. Preferably, the observation axis and the illumination axis intersect at a point I in the vicinity of the wall of the container 200 and its ring B.

[0089] Also, in Figure 3, being in top view, we observe a plane which is orthogonal to the central axis AC of the container 200. In the plane shown in the figure, we therefore observe the projections of the illumination axis and the observation axis, which intersect at an angle between 10° and 150°, or preferably between 30° and 90°. In the figure, this angle is noted a.

[0090] To filter out the stray radiation reflected by the glass of the container ring and not by the glaze DF, a second polarizing filter F2 is used, having an orientation relative to the central axis of the container AC which forms an angle of 45° (towards the same side as the first filter when this second filter is observed from the observed portion, i.e. in the direction of propagation of the light, the direction of propagation of the light being represented by an arrow arranged above the ray in the figure).

[0091] Thus, the images obtained by the image sensor 300 make it even easier to observe the DF glaze defect.

[0092] In fact, it is worth noting that glazes have a structure in which on both sides of the fracture (at the glass / air / glass interface), the glass exhibits mechanical stresses and has a birefringent effect on light. Also, it has been observed that the incident polarization of the light, i.e. the angle of the first polarizing filter, has an impact on the polarization of the light reflected by the glaze. In fact, the glaze has a retardation blade behavior with a fast axis at 90° and a slow axis at 0°.

[0093] With the first filter Fl oriented at 45° to the AC axis of the container, the light reflected by the glaze has an elliptical polarization. This behavior can be observed by polarimetric cameras.

[0094] Since the light reflected by the glaze has elliptical polarization, when passing through the second filter, also oriented at 45°, it has linear polarization after passing through the second filter. This behavior can be observed by polarimetric cameras.

[0095] On the other hand, light reflected by the container elsewhere than by passing through the glaze has a linear polarization which is oriented at 135° due to the reflection. This light is therefore well filtered by the second filter F2, i.e. blocked. Only the reflection of light by the glaze leads to radiation light that reaches the 300 image sensor, making it easier to see the glaze and detect it.

[0096] In this sense, we obtain the possibility of using a wide beam, and we relax the tolerances on the positioning and centering of the containers in the observation position.

[0097] It should be noted that the behavior described above can be confirmed by an analysis based on Stokes vectors, for example by changing the polarization angles of the filters F1 and F2 (typically by testing the angles 0°, 45°, 90°, and 135°) and by not using filters.

[0098] It can be noted that the image sensor 300 preferably has a field of observation which covers the ring B over its entire width. Also, the second filter F2 is sized so that all the radiation which arrives at the image sensor 300 is filtered. In the figure, an observed portion PO of the ring of the container B is shown, which is visible on the images obtained by the image sensor 300.

[0099] Also, the observation portion is further configured so that the illuminated portion is at least partly visible on an image obtained by the image sensor. For this purpose, the observation axis and the illumination axis may have projections in a plane comprising the central axis AC which intersect at the wall of the container, or inside the container, or at a short distance from the container (for example a few millimeters).

[0100] Figure 4 shows the covering of a part of the ring B of a container by the filtered light beam FLF. For reasons of simplification, the figure does not show the first polarizing filter arranged between the projector and the container and its ring B. This configuration is suitable for further limiting parasitic reflections. [OlOljThe projector 100 is configured so that only one slice of the container ring is illuminated (another slice of the container ring is not illuminated).

[0102] This slice is included in the observation portion, which is not shown in the figure, as are the image sensor and the second filter for reasons of simplicity.

[0103] When the ring is observed from the projector, it is seen that from an edge 203 (this edge being the one seen from a position corresponding to the projector), the edge of the container comprises, from this edge 203, a first portion PI which extends between the external vertical edge 201 of the ring of the container and the internal vertical wall 202 of the container. In fact, the first portion has a width equal to the width of the wall of the ring B of the container, when observed from the projector.

[0104] The slice also comprises a second portion P2 which extends from the internal vertical wall 202 of the container and which has a width between 0% and 60% of the internal diameter DI of the ring B, or between 18% (which corresponds to the width L1 in the figure) and 60% (which corresponds to the width L2 in the figure).

[0105] The width L1 can be chosen to improve the tolerance, for example, on the centering of the container. It has been observed that from 18% there is a good improvement in this tolerance.

[0106] The width L2 is chosen as representing a maximum beam width, which allows for good adaptation to positioning and centering errors of the containers, while partially limiting parasitic reflections.

[0107] The invention makes it possible to expand the illuminated area, without additional interference limiting the detection performance, and thus to increase the tolerance on the centering of the containers in the inspection station at the time of image acquisition by the image sensor.

[0108] Figure 5 is a perspective view of the system of Figure 3, in which the container 200 is shown in its entirety as it travels along a conveyor track, 400 from left to right in the figure. At the conveying instant shown in Figure 5, the container is in the observation position. For a system like that of Figure 5, a pair of a sensor can be used image and a projector, but several of these pairs configured to inspect different parts of the container can advantageously be used while the container is moving in translation due to the conveyor track 400.

[0109] The configuration shown in Figure 5 is a configuration in which the projector is arranged lower than the ring B of the container 200, and in which the projector is arranged above the ring B of the container. This configuration of Figure 5 is well suited for observing glazes, and particularly vertical glazes.

[0110] Figure 6A shows another configuration in which the projector 100 and the image sensor 300 are both above the container. Thus, the projector 100 and the image sensor 300 are both on the same side of a plane P which passes through the container (and even here through the ring) and which is orthogonal to the central axis AC of the container. Here, the plane P is fixed as comprising the surface of the ring of the container (this is the upper surface of the ring). [011 l]The upper part of Figure 6A is a top view of the arrangement, in which the angle α between the observation and illumination axes can be seen. The lower part of Figure 6A is a side view of the arrangement, in which the arrangement of the projector and the image sensor can be seen above the container and its ring.

[0112] Alternatively and not shown, the projector 100 and the image sensor 300 may both be below the container ring to observe the latter.

[0113] In Figure 6A, a device 500 configured to rotate the container is also shown, for example provided with an actuator. As can be seen, while the container is rotated, glaze defects can be detected along the entire periphery of the container ring due to the rotation. Thus, there is a continuity of observation positions which all differ by the orientation of the container around its central axis AC.

[0114] Figure 6B shows yet another configuration in which the projector 100 is located above the ring B of the container, and the image sensor 300 is located below the ring B of the container. This configuration is well suited for detecting vertical glazes. Also, in this configuration, there is a plane P orthogonal to the central axis AC of the container so that the projector 100 and the image sensor 300 are arranged on either side of this plane. The plane P is here arranged to include the base of the ring of the container.

[0115] The upper part of Figure 6B is a top view of the arrangement, in which the angle α between the observation and illumination axes can be seen. The lower part of Figure 6B is a side view of the arrangement, in which the arrangement of the projector and the image sensor can be seen on either side of said plane P.

[0116] It may be noted that another possible configuration is that of Figure 5 in which it is the projector 100 which is lower than the image sensor 300.

[0117] Figure 7 shows a schematic representation of another system, comprising two projectors referenced 100A and 100B, as well as two image sensors 300A and 300B, which both observe a ring B of a container 200. More precisely, the two projectors 100A and 100B respectively emit light beams along respective illumination axes 101A and 101B (in the figure, for reasons of simplicity, the filters have not been shown, but the beams which reach the container are filtered light beams, respectively FLFA and FLFB). The image sensor 300A and the projector 100A are configured so that the observation axis 301A has a projection in a plane orthogonal to the central axis AC of the container which intersects that of the illumination axis 10IA in the vicinity of an edge 203 of the ring B (by in the vicinity, we mean a few millimeters, or even around ten millimeters from the edge).The image sensor 300B and the projector 100B are configured so that the observation axis 301B has a projection in a plane orthogonal to the central axis AC of the container which intersects that of the illumination axis 101B in the vicinity of an edge 204 of the ring B. The edges 203 and 204 are diametrically opposed, e.g. example observed from one or other of the projectors. This configuration is particularly advantageous for detecting all of the glazes that may be present within a ring B, in particular when using a device such as the device 500 which rotates the container.

[0118] Figure 8A is a photograph of a threaded ring of a bottle, obtained by a projector and image sensor pair without the use of filters as illustrated above, for example, with reference to Figure 3. As can be seen in the figure, and as was the case in Figure 1, stray reflections prevent easy detection of an ice defect located on the right in the image.

[0119] Figure 8B is obtained by a system such as that described above with reference to Figure 3. The parasitic reflection located on the left in Figure 8A is eliminated in Figure 8B, and the glaze on the right of the figure is easily distinguished.

[0120] Thus, the use of automated image processing, implemented in FIG. 8B, makes it even easier to detect the glaze. For this purpose, any type of image processing can be used, for example image processing using models trained by machine learning for the detection of glazes in these images. The system can thus be configured to detect a glaze-type defect on the basis of the light reflected towards the image sensor by the glaze receiving the light beam from the projector, which appears in the image acquired by the image sensor without the appearance of certain parasitic reflections.

[0121] In Figure 9A, which is a photograph of the rim of a container, a vertical glaze can be seen. In fact, the person skilled in the art refers to glazes that extend substantially in the direction of the central axis of a container as vertical glazes, even if these glazes are not perfectly straight along this direction. In fact, one can have angles relative to the central axis of the container that are of the order of plus or minus 30° for the general direction of the glazes, while still considering them as vertical glazes.

[0122] In Figure 9B, an image of the container ring of Figure 9A is seen to be obtained using a detection system such as that described above with reference to Figure 3.

[0123] Figure 10 is an illustration of the orientation of the first filter F1 and the second filter F2, according to two possible variants.

[0124] In the upper part of the figure, we can see that the filter Fl is oriented at 45° to the left (relative to the central axis of the container here vertical) observed in the direction of propagation of the light, i.e. from the projector, and that the filter F2 is oriented at 45° to the left (relative to the central axis of the container here vertical) observed in the direction of propagation of the light, i.e. from the observation portion. On the other hand, the filter F2 seen from the sensor has an orientation at 45° to the right (relative to the central axis of the container here vertical).

[0125] In the lower part of the figure, we can see that the filter Fl is oriented at 45° to the right (relative to the central axis of the container here vertical) observed in the direction of propagation of the light, i.e. from the projector, and that the filter F2 is oriented at 45° to the right (relative to the central axis of the container here vertical) observed in the direction of propagation of the light, i.e. from the observation portion. On the other hand, the filter F2 seen from the sensor has an orientation at 45° to the left (relative to the central axis of the container here vertical).

[0126] In other words, the filters must filter the incident light with the same orientation.

Claims

Claims 1. Glaze type defect detection system in a glass container (200) arranged in an observation position, comprising: - a projector (100) emitting a light beam (FL) along an illumination axis (101), - a first polarizing filter (Fl) having a polarization oriented at 45° at plus or minus 5° relative to a central axis (AC) of the container, and arranged to filter the light beam emitted by the projector, the filtered beam covering at least one illuminated portion (PI) of the container in the observation position, - an image sensor (300) configured to observe at least an observation portion of the container in the observation position, the image sensor having an observation axis (301), the observation portion being further configured such that the illuminated portion is at least partly visible on an image obtained by the image sensor, - a second polarizing filter (F2) having a polarization oriented in the same direction as the first polarizing filter at 45° at plus or minus 5° relative to the central axis of the container, and arranged between the container and the image sensor to filter the radiation observed by the image sensor, in which the illumination axis and the observation axis are configured so that their projections in a plane orthogonal to the central axis of the container intersect at an angle (a) of between 10° and 150°, the first filter and the second filter forming angles oriented at 45° at plus or minus 5° relative to the central axis of the container in the same direction relative to the central axis of the container, when they are observed in the direction of propagation of the light from the projector to the illuminated portion then from the observed portion to the image sensor,the system being configured so that the detection of a glaze-type defect uses the light reflected towards the image sensor by the glaze receiving the light beam from the projector., 2. System according to claim 1, in which the illumination axis and the observation axis are configured so that their projections in the plane orthogonal to the central axis of the container intersect at an angle (a) of between 30° and 90°.

3. System according to claim 1 or 2, in which the projector and the image sensor are arranged on either side of a plane orthogonal to the central axis (AC) of the container and passing through the container.

4. System according to claim 1 or 2, in which the projector and the sensor are arranged on the same side of a plane orthogonal to the central axis of the container and passing through the container.

5. System according to any one of claims 1 to 4, in which the illuminated portion of the container comprises at least a portion of the ring (B) of the container.

6. The system of claim 5, wherein the filtered light beam overlaps only a slice of the container ring or overlaps the container ring across its entire width, to obtain the illuminated portion.

7. The system of claim 6, wherein the edge of the container is included in the observation portion, and, observed from the projector, the edge extends from an external vertical edge of the ring of the container towards the interior of the container.

8. The system of claim 7, wherein the slice of the container observed from the projector comprises, from the outer vertical edge of the container ring, a first portion (PI) extending between the outer vertical edge of the container ring and the inner vertical wall of the container ring, the first portion having a width equal to the width of the wall of the container ring, and a second portion (P2) extending from the inner vertical wall of the container ring, the second portion having a width between 0% and 60% of the inner diameter of the container ring, or between 18% and 60% of the inner diameter of the container ring.

9. System according to any one of claims 1 to 8, in which the illumination axis (101A) and the observation axis (301A) are configured so that their projections in the plane orthogonal to the central axis of the container intersect at an angle of between 10° and 150°, or between 30° and 90°, at a first external vertical edge (203) of the ring of the container, the system further comprising: - an additional projector (100B) emitting a light beam along an illumination axis (101B), - a first additional polarizing filter having a polarization oriented at 45° at plus or minus 5° relative to the central axis of the container, and arranged to filter the light beam emitted by the additional projector, the filtered beam covering at least one additional illuminated portion of the container in the observation position, - an additional image sensor (300B) configured to observe at least one additional observation portion of the container in the observation position, the additional image sensor having an observation axis (301B), - a second additional polarizing filter having a polarization oriented at 45° at plus or minus 5° relative to the central axis of the container, and arranged between the container and the additional image sensor to filter the radiation observed by the additional image sensor, in which the illumination axis of the additional projector and the observation axis of the additional image sensor are configured so that their projections in the plane orthogonal to the central axis of the container intersect at an angle of between 10° and 150°, at a second external vertical edge (204) of the ring of the container, the second edge being diametrically opposite the first edge, the first additional filter and the second additional filter forming angles oriented at 45° at plus or minus 5° relative to the central axis of the container in the same direction relative to the central axis of the container,when observed in the direction of propagation of light from the additional projector to the illuminated portion and then from the observed portion to the additional image sensor., 10. System according to any one of claims 1 to 9, configured to rotate the container in the observation position around the central axis of the container.

11. System according to any one of claims 1 to 10, configured to drive the container in horizontal translation to the observation position.

12. System according to any one of claims 1 to 11, comprising a device for processing the images obtained by the image sensor, configured to automatically detect glaze-type defects by processing the images.

13. A method for detecting a glaze-type defect in a glass container (200) arranged in an observation position, comprising: - emit a light beam along an illumination axis (101), - filtering by means of a polarizing filter (Fl) having a polarization oriented at 45° at plus or minus 5° relative to a central axis (AC) of the container, the light beam emitted by the projector, the filtered beam covering at least one illuminated portion (PI) of the container in the observation position, - observing by means of an image sensor (300) configured to observe at least one observation portion (PO) of the container in the observation position, the image sensor having an observation axis, the observation portion being further configured so that the illuminated portion is at least partly visible on an image obtained by the image sensor, - filtering by means of a second polarizing filter (F2) having a polarization oriented in the same direction as the first polarizing filter at 45° at plus or minus 5% relative to the central axis of the container, and arranged between the container and the image sensor, the radiation observed by the image sensor, - detecting a glaze-type defect using light reflected towards the image sensor by the glaze-type defect receiving the light beam from the projector, in which the illumination axis and the observation axis are configured so that their projections in the plane orthogonal to the central axis of the container intersect at an angle (a) of between 30° and 90°, the first filter and the second filter forming angles oriented at 45° at plus or minus 5° relative to the central axis of the container in the same direction relative to the central axis of the container, when observed in the direction of propagation of the light from the projector to the illuminated portion then from the observed portion to the image sensor.

Images