阅读说明：本技术 用于容器的侧壁检查的透射光检查设备及透射光检查方法 (Transmission light inspection apparatus and transmission light inspection method for inspecting sidewall of container ) 是由 赖纳·克维兰特 于 2020-03-06 设计创作，主要内容包括：本发明涉及一种用于容器(2)的侧壁检查的透射光检查设备(1),其具有用于运输容器(2)的运输机(3),并具有附属于运输机(3)的至少一个检查站(4、5),其用于以偏振光(L)透视容器(2),其中,至少一个检查站(4、5)包括：具有光源(4.1)和下游的偏振器(4.2)的照射装置(4)；以及具有至少一个分析器(5.M、5.F1-5.F4、5.T1-5.T2)的摄像机系统(5),其中,摄像机系统(5)和至少一个分析器(5.M、5.F1-5.F4、5.T1-5.T2)被构造成用于同时检测至少四个不同的线性偏振方向。(The invention relates to a transmitted light inspection device (1) for inspecting the side walls of containers (2), having a conveyor (3) for transporting the containers (2) and having at least one inspection station (4, 5) attached to the conveyor (3) for viewing the containers (2) with polarized light (L), wherein the at least one inspection station (4, 5) comprises: an illumination device (4) having a light source (4.1) and a downstream polarizer (4.2); and a camera system (5) having at least one analyzer (5.M, 5.F1-5.F4, 5.T1-5.T2), wherein the camera system (5) and the at least one analyzer (5.M, 5.F1-5.F4, 5.T1-5.T2) are configured for detecting at least four different linear polarization directions simultaneously.)

1. A transmission light inspection device (1) for inspection of a side wall of a container (2) having

-a conveyor (3) for transporting the containers (2), and

-at least one inspection station (4, 5) attached to the conveyor (3) for transilluminating the containers (2) with polarized light (L),

wherein the at least one inspection station (4, 5) comprises: an illumination device (4) having a light source (4.1) and a downstream polarizer (4.2); and a camera system (5) having at least one analyzer (5.M, 5.F1-5.F4, 5.T1-5.T2),

it is characterized in that the preparation method is characterized in that,

the camera system (5) and the at least one analyzer (5.M, 5.F1-5.F4, 5.T1-5.T2) are configured for detecting at least four different linear polarization directions simultaneously.

2. The transmitted light inspection apparatus (1) according to claim 1, wherein the camera system (4) comprises an objective lens (5.3) and a matrix sensor (5.2), and wherein the at least one analyzer (5.M) is configured as an analyzer matrix arranged between the objective lens (5.3) and a front face of a photosensitive sensor element (5.21) of the matrix sensor (5.2) for simultaneously detecting the at least four different linear polarization directions with the matrix sensor (5.2).

3. The transmitted light inspection apparatus (1) according to claim 2, wherein the matrix sensor (5.2) comprises an analyzer (5.M) configured as an analyzer matrix as an element integrated in front of the photosensitive sensor element (5.21).

4. The transmission light inspection apparatus (1) according to claim 2 or 3, wherein the analyzer (5.M) configured as an analyzer matrix comprises a number of polarizer elements (5.M1-5.M4) arranged in a matrix, which are each associated with one of the photosensor elements (5.21), and which are preferably alternately oriented along the at least four different linear polarization directions.

5. The transmitted light inspection apparatus (1) of claim 4, wherein the polarizer elements (5.M1-5.M4) arranged in a matrix are grouped in such a way that four adjacently arranged polarizer elements (5.M1-5.M4) are respectively oriented along the at least four different linear polarization directions and form a group (G).

6. The transmitted light inspection apparatus (1) according to claim 1, wherein the camera system (5) comprises at least four cameras (5A-5D) with one analyzer (5.Fl-5.F4) each, an objective lens (5.3) and with a matrix sensor (5.2), and wherein the analyzers (5.Fl-5.F4) of the at least four cameras (5A-5D) are oriented in the at least four different linear polarization directions, so that the at least four different linear polarization directions are detected in a plurality of camera images.

7. The transmitted light inspection apparatus (1) according to claim 1, wherein the camera system (5) comprises at least four cameras (5A-5D) with objective lenses (5.3) and with matrix sensors (5.2), and wherein the at least one analyzer (5.T1-5.T2) comprises two polarization splitters in order to divide two of the at least four different linear polarization directions to two of the at least four cameras, respectively.

8. The transmitted light inspection apparatus (1) according to any of the preceding claims, wherein the polarizer (4.2) of the illumination device (4) comprises a circular or elliptical polarizing filter.

9. The transmitted light inspection apparatus (1) according to any one of the preceding claims, wherein the camera system (5) is configured with filters for separately detecting different light wavelengths, in particular at least one bayer filter or at least one pixellated color filter, in order to detect different light wavelengths of the polarized light (L) in addition to different linear polarization directions.

10. Transmitted light inspection method for inspection of side walls of containers (2), wherein the containers (2) are transported with a conveyor (3) to at least one inspection station (4, 5) attached to the conveyor and are transilluminated with polarized light (L) with the at least one inspection station (4, 5), wherein the at least one inspection station (4, 5) comprises an illumination device (4) with a light source (4.1) and with a downstream polarizer (4.2), which emits the polarized light (L), and wherein the at least one inspection station (4, 5) comprises a camera system (5) with at least one analyzer (5.M, 5.F1-5.F4, 5.T1-5.T2), with which the transilluminated containers (2) are inspected,

it is characterized in that the preparation method is characterized in that,

the camera system (5) detects at least four different linear polarization directions simultaneously with the at least one analyzer (5.M, 5.F1-5.F4, 5.T1-5. T2).

11. The transmitted light inspection method according to claim 10, wherein the at least one analyzer (5.M) divides the four different linear polarization directions as an analyzer matrix after the objective (5.3) and before the photosensitive sensor elements (5.21) of the matrix sensor (5.2) in such a way that the four different linear polarization directions are detected in the camera image of the matrix sensor (5.2).

12. The transmitted light inspection method according to claim 10, wherein the four different linear polarization directions are detected by at least four cameras (5A-5D) with one analyzer (5.Fl-5.F4), one objective (5.3) each, and with a matrix sensor (5.2) each.

13. The transmitted light inspection method according to claim 10, wherein the four different linear polarization directions are detected by at least four cameras (5A-5D) with one objective lens (5.3) each and with one matrix sensor (5.2) each, and wherein the at least one analyzer (5.T1-5.T2) comprises two polarization splitters with which two of the at least four different linear polarization directions are divided to two of the at least four cameras (5A-5D) respectively.

14. The transmitted light inspection method according to any one of claims 10 to 13, wherein the different wavelengths of the polarized light are detected by means of the camera system (5) by means of optical filters.

Technical Field

The invention relates to a transmitted light inspection apparatus and a transmitted light inspection method for inspection of side walls of containers having the features of the preamble of claim 1 or 10.

Background

Typically, such transmitted light inspection apparatus and methods are used in beverage processing facilities to identify transparent foreign matter, such as film residue, in containers. The container may for example be a bottle into which the beverage is filled after inspection by transmission light.

A transmitted light inspection apparatus typically includes a conveyor for transporting containers and at least one inspection station attached to the conveyor for viewing the containers in polarized light. During inspection, the container is guided between the downstream illumination device with the polarizer and the upstream camera system with the analyzer and is therefore transilluminated by polarized light and detected by the camera system.

Since transparent foreign bodies tend to have stress birefringence and/or molecular induced birefringence, they can be better recognized when viewed through polarized light and imaged as darker areas in the camera image. They can then be identified in the camera image using image processing algorithms known per se.

The closest use of linear polarizing filters is avoided in practice, since all transparent foreign bodies having a stress optical principal axis parallel or perpendicular to the polarization direction of the linear polarizing filter are not darkened and therefore cannot be identified. Therefore, in order to keep the recognition as much as possible regardless of the orientation of the transparent foreign matter, a circular polarizing filter is generally used.

It has been found, however, that some foreign substances only act weakly as a polarizer and/or polarize in only a part of the spectrum. Therefore, it is particularly difficult to identify them with a unique circular analyzer.

For example, DE 202013100834 Ul discloses a device for detecting soiling on containers, in which a polarizer is designed to circularly or elliptically polarize the light emitted by an illumination device and the container is detected by two cameras, upstream of which analyzers with different directions of polarization rotation are connected, in order to identify soiling behind the label particularly well. However, this construction is complex and expensive.

Disclosure of Invention

It is therefore an object of the present invention to provide a transmitted light inspection device and a transmitted light inspection method, with which transparent foreign matter in a container can be more reliably detected in a container processing facility.

In order to solve the stated object, the invention provides a transmitted light inspection apparatus having the features of claim 1. Advantageous embodiments are listed in the dependent claims.

The applicant has found, in extensive studies, that transparent foreign matter can be best identified when at least four different linear polarization directions, for example, 0 °, 45 °, 90 ° and 135 °, are detected by means of at least one analyzer. Since the camera system and the at least one analyzer are designed to recognize four different linear polarization directions simultaneously, the transmitted light inspection can be carried out with little effort even in the case of high-throughput container processing installations. In addition, weakly polarized foreign bodies can be detected particularly reliably.

The transmitted light inspection apparatus may be disposed in a container processing facility. Likewise, the transmitted light inspection apparatus may also be arranged in a facility for manufacturing containers. The transmission light inspection device may be arranged behind the fork in order to sort out containers in which one or more transparent foreign bodies are identified by the at least one inspection station. The sorted containers may be cleaned or recycled. Furthermore, the diverter may be configured to deliver containers free of transparent foreign matter to a container handler, such as a filling machine.

The containers can be in particular glass bottles, but plastic bottles are also conceivable. Preferably, the container may be arranged to contain beverages, hygiene articles, pastes, chemical products, biological products and/or medical products. In general, the container can be provided for any flowable or pourable medium. The container may be an empty container or a container filled with a product.

The transparent foreign matter may include, for example, a film residue, a plastic part, and the like.

The conveyor can preferably be configured as a linear conveyor, wherein the illumination device with the polarizer is arranged at one side and the camera system with the at least one analyzer is arranged at the opposite side. It is also conceivable for the transport machine to be designed as a turret, with which the containers are transported between the illumination device with the polarizer and the camera system with the at least one analyzer.

The illumination means may comprise a light source, a lens, a diffuser and/or a shutter. The light source may comprise incandescent lamps, gas discharge lamps, fluorescent tubes and/or LEDs as light emitting devices. Preferably, the light source is formed by at least one circuit board having a matrix arrangement of LEDs.

The light source may emit in the visible spectrum and/or in the infrared spectrum. The wavelength range of the visible spectrum may be in the range of 380nm to 780nm, preferably 440nm to 650nm, and/or the wavelength range of the infrared spectrum may be in the range of 780nm to 3 μm, preferably 800nm-1 μm. It is likewise conceivable that the visible spectrum and/or the infrared spectrum are each only monochromatic spectra.

The polarizer may be arranged inside the illumination device or in the region of the light exit opening of the illumination device. The polarizer and/or the analyzer may be of disc-like or film-like design at least in sections. For example, the polarizer and/or analyzer may be a polarizing film.

The polarizer and/or analyzer may comprise a circular polarizing filter, independently of each other. The film can thus be identified in all rotational positions. For practical reasons, the use of 4 illumination devices with linear polarization filters of different orientations can thus be avoided. Therefore, preferably, the illumination device is equipped with a circular polarizing filter as a polarizer so as to emit circular light in the direction of the container and the camera.

The camera system may include a camera and an objective lens. The camera may comprise a line sensor or a matrix sensor, for example a CCD sensor or a CMOS sensor. The camera system can be connected to an image processing unit via a data line in order to evaluate the camera image of the container to be viewed in the light of transparent foreign bodies. However, it is also conceivable that the image processing unit is integrated into the camera system.

The linear polarization directions detected with the at least one analyzer and camera system may include 0 °, 45 °, 90 ° and 135 °. In other words, four different linear polarization directions may be twisted 45 ° with respect to each other. The at least one analyzer may be at least one linear polarizing filter. In other words, the at least one analyzer may be configured as at least one linear polarizer.

It is conceivable to connect a mirror cabinet upstream of the camera system, so that a plurality of container sides of the container are detected side by side as image sectors of the camera image.

The transmitted light inspection apparatus may comprise control means for controlling the illumination means and/or the camera system. Furthermore, the control device may comprise an image processing unit for receiving camera images of the camera system and for evaluating for transparent foreign bodies. Furthermore, the control device may be configured for controlling the conveyor and/or detecting the transport position of the container. It is conceivable that the control device includes a digital processor (CPU), a memory unit, an interface unit, an input unit, and/or an output unit.

The camera system may comprise an objective lens and a matrix sensor, wherein the at least one analyzer is configured as an analyzer matrix which is arranged between the objective lens and a photosensitive sensor element of the matrix sensor for simultaneously detecting at least four different linear polarization directions with the matrix sensor. The camera system can thus be constructed in a particularly simple manner, since the four different linear polarization directions are detected by exactly one matrix sensor, rather than by a plurality of matrix sensors. "wherein the at least one analyzer is configured as an analyzer matrix which is arranged between the objective and the light-sensitive sensor element of the matrix sensor" may here mean that the analyzer matrix is arranged directly in front of the bayer filter and/or the light-sensitive sensor element of the matrix sensor. The matrix sensor may comprise an analyzer configured as an analyzer matrix as an element integrated in front of the light sensitive sensor elements. This makes the construction of the camera system more compact and simpler. It is conceivable that the analyzer constructed as an analyzer matrix is arranged between the microlens array and the photosensitive sensor elements of the matrix sensor. This enables a particularly large number of objective lens types to be used without impairing the imaging quality. However, it is also conceivable for the analyzers constructed as analyzer matrices to be arranged directly in front of the microlens array of the matrix sensor.

The analyzer, which is designed as an analyzer matrix, may comprise a plurality of polarizer elements arranged in a matrix, which are each associated with one of the light-sensitive sensor elements and are preferably alternately oriented in at least four different linear polarization directions. In this way, each light-sensitive sensor element of the matrix sensor is assigned a different polarizer element of the analyzer, so that in this way, a particularly high-resolution imaging of the container can be achieved, taking into account the polarization of each pixel. Each light-sensitive sensor element may correspond to a pixel of the camera image output from the matrix sensor, in particular wherein each light-sensitive sensor element is assigned a polarizer element of the analyzer. The polarizer elements arranged in a matrix can each be designed as a polarization filter, wherein the polarization filters are arranged in a matrix twisted with respect to one another in such a way that they detect four different linear polarization directions. For example, the linear polarization directions are 0 °, 45 °, 90 °, and 135 °.

The polarizer elements arranged in a matrix may be grouped in such a way that four adjacently arranged polarizer elements are oriented in at least four different linear polarization directions and form a group. In this way, different linear polarization directions are alternately detected by the light-sensitive sensor elements of the matrix sensor, as a result of which a higher spatial resolution is obtained in the camera image, taking into account the polarization. It is conceivable for the groups themselves to be arranged in a matrix on the matrix sensor. Thereby, different linear polarization directions are alternately detected along the two axes of the matrix sensor.

For example, the matrix sensor may be an image sensor of the sony IMX250MZR or IMX250MYR type, in particular wherein an analyzer configured as an analyzer matrix is arranged between the microlens array and the pixel array of the matrix sensor. However, it is also conceivable for the analyzer, which is designed as an analyzer matrix, to be arranged directly in front of the microlens array of the matrix sensor in the beam path of the camera system.

Alternatively, it is also conceivable that the camera system comprises at least four cameras with one analyzer, one objective and one matrix sensor each, wherein the analyzers of the at least four cameras are oriented in at least four different linear polarization directions in order to detect them in a plurality of camera images. Thus, although a plurality of cameras are required, the detection of the containers is spatially resolved to a higher degree. It is conceivable that the analyzers each include a linear polarization filter. The linear polarization filters may be twisted with respect to each other in such a manner that the linear polarization directions 0 °, 45 °, 90 °, and 135 ° can be detected.

In a further alternative, it is also conceivable that the camera system comprises at least four cameras with objective lenses and with matrix sensors, wherein the at least one analyzer comprises two polarization splitters in order to divide two of the at least four different linear polarization directions into two of the at least four cameras, respectively. This allows the image fields to be superimposed by two cameras, so that the image perspectives in the respective camera images are similar or even identical. This makes it possible to support the assignment of the image regions on the containers in the camera image during the evaluation. The polarizing beam splitter may be an optical element that transmits a first linear polarization direction but reflects a second linear polarization direction that is rotated by 90 ° with respect to the first linear polarization direction.

Preferably, the polarizer of the illumination device may comprise a circular or elliptical polarizing filter. Extensive studies by the applicant have found that this, in combination with the measures of four different linear polarization directions, leads to a particularly reliable detection of transparent foreign bodies. However, in principle it is also conceivable to use a linear polarizing filter as polarizer of the illumination device.

It is also conceivable that the camera system is constructed with filters for separately detecting different wavelengths of light, in particular at least one bayer filter or at least one pixel-like color filter, in order to detect different wavelengths of light of the polarized light in addition to different linear polarization directions. This makes the identification particularly reliable, since the polarization effect of the transparent foreign body also depends on the wavelength of the light. This improves the identification of the colourless container. This may for example relate to a matrix sensor of the sony IMX250MYR type, which is capable of colour detection in addition to polarization.

The invention also provides a transmitted light inspection method for inspecting the side walls of containers, having the features of claim 10. Advantageous embodiments of the invention are set out in the dependent claims.

The applicant's extensive research has found that transparent foreign matter can be optimally identified when at least four different linear polarization directions are detected with at least one analyzer. Since the camera system with at least one analyzer detects four different linear polarization directions simultaneously, the transmitted light inspection can be reliably carried out with little effort even in the case of high-throughput container processing facilities. In addition, weakly polarized foreign bodies can be detected particularly reliably.

The transmitted light inspection method may comprise the features described above in relation to the transmitted light inspection apparatus, in particular the features according to any of claims 1-9, either individually or in any combination. It is conceivable that the transmitted light inspection method is performed with the above-described transmitted light inspection apparatus, particularly the transmitted light inspection apparatus according to any one of claims 1 to 9.

Preferably, the transmitted light inspection method can be used in empty bottle inspection, especially in bottom wall and/or side wall inspection. However, it is also conceivable that the transmitted light inspection method is used in full bottle inspection to identify floating plastic parts, especially in sidewall inspection.

The at least one analyzer can divide the four different linear polarization directions as an analyzer matrix behind the objective lens and in front of the light-sensitive sensor elements of the matrix sensor in such a way that the four different linear polarization directions are detected in the camera image of the matrix sensor. The camera system can thus be constructed particularly simply, since the four different linear polarization directions are detected with exactly one matrix sensor, rather than with a plurality of matrix sensors.

Alternatively, it is also conceivable that four different linear polarization directions are detected by at least four cameras with one analyzer, one objective each and with a matrix sensor each. Thus, the spatial resolution of the detection of the container is higher, although more cameras are required.

It is also conceivable that the different linear polarization directions are detected by at least four cameras having in each case one objective and one matrix sensor, wherein the at least one analyzer comprises two polarization splitters, with which two of the at least four different linear polarization directions are respectively divided into two of the at least four cameras. This allows the image fields to be superimposed by two cameras, so that the image perspectives in the respective camera images are similar or even identical.

This makes it possible to support the assignment of the image regions on the containers in the camera image during the evaluation.

It is also conceivable to detect different wavelengths of light of the polarized light by means of a camera system via a filter. This makes the identification particularly reliable, since the polarization effect of the transparent foreign body also depends on the wavelength of the light. This improves the identification of the colourless container.

Drawings

Further features and advantages of the invention will be explained in more detail below with reference to embodiments shown in the drawings. Wherein:

FIG. 1 shows an embodiment according to the invention of a transmission light inspection apparatus in a side view;

FIG. 2 shows a detailed view of a matrix sensor with analyzers configured as a matrix of analyzers in a front view;

fig. 3 shows a further exemplary embodiment of a transillumination inspection apparatus according to the invention in a side view, with four cameras, in front of which an analyzer is arranged in each case; and

fig. 4 shows a further embodiment according to the invention of a transmission-light inspection apparatus in a side view, with four cameras and two polarizing beam splitters.

Detailed Description

An embodiment according to the invention of a transmitted light inspection apparatus 1 is shown in a side view in fig. 1. A conveyor 3 and inspection stations 4, 5 attached to the conveyor for making a perspective of the side walls 2a of the containers 2 with polarized light L can be seen.

The conveyor 3 is designed here, for example, as a linear conveyor, in order to transport the containers 2 through between the illumination device 4 and the camera system 5. The containers 2 can preferably be transported continuously and continuously detected by the camera system 5.

The illumination means 4 comprises a light source 4.1 for emitting a visible and/or infrared spectrum. For example, the light source 4.1 is constructed with a plurality of LEDs emitting white light with a preferred wavelength range of 380nm to 780 nm. It is preferable to use an LED containing a plurality of chips for different colors. This enables the color of the lamp to be coordinated with the color of the container. It is also conceivable that the light source 4.1 is constructed with a plurality of LEDs emitting infrared light in the wavelength range, preferably from 780nm to 3 μm.

Furthermore, downstream of the light source 4.1 a polarizer 4.2 is connected, which is designed to circularly polarize the light spectrum emitted by the light source 4.1. The unpolarized light of the light source 4.1 is circularly polarized by the polarizer 4.2 and is therefore emitted as polarized light L. However, it is also conceivable that the polarizer is a linear or elliptical polarizer.

It can furthermore be seen that the camera system 5 comprises an objective 5.3, an analyzer 5.M and a matrix sensor 5.2, wherein the analyzer 5.M is constructed as an analyzer matrix which is arranged between the objective 5.3 and a photosensitive sensor element (5.21) of the matrix sensor 5.2. Four different polarization directions can thus be detected in the camera image of the matrix sensor 5.2. Furthermore, the analyzer 5.M, which is designed as an analyzer matrix, is designed as an integrated component of the matrix sensor 5.2. For example, the matrix sensor 5.2 and the analyzer 5.M constructed as an analyzer matrix may be a sony image sensor of the IMX250MZR (monochrome) or IMX250MYR (color) type. The structure of the matrix sensor 5.2 and the analyzer 5.M will be explained in more detail below with reference to fig. 2.

The container 2 is imaged with an objective 5.3 via an analyzer 5.M onto a matrix sensor 5.2 of a camera system 5. The side walls 2a of the containers 2 can thus be detected simultaneously with spatial resolution in four different polarization directions by means of the camera system 5.

It is also conceivable for a mirror cabinet, which is not shown in greater detail here, to be connected upstream of the camera system 5. It is thereby possible to image a plurality of container sides side by side as image sectors into the camera system 5. For example, with a mirror cabinet and an objective 5.3, at least two views of the container 2 from different perspectives can be imaged side by side onto the matrix sensor 5.2 and thus detected in the camera image.

Furthermore, a control device 6 is visible, with which the illumination device 4 and the camera system 5 can be controlled. It is conceivable that the control device 6 comprises image processing means for evaluating the camera images from the camera system 5. Furthermore, it is also conceivable that the control device 6 controls the illumination device 4, for example on the basis of signals from the light barrier, so that the illumination device emits light pulses when the container 2 is positioned in front of the illumination device 4 in the field of view of the camera system 5.

Fig. 2 shows a detail of a matrix sensor 5.2 with an analyzer 5.M in the form of an analyzer matrix in a front view. A matrix sensor 5.2 can be seen, which acts as an image sensor in the camera system shown in fig. 1.

The matrix sensor 5.2 corresponds to the usual structure of a CMOS or CCD image sensor, wherein the light-sensitive sensor elements 5.21 are arranged in a matrix-like grid in order to record a camera image. However, a hexagonal arrangement of the light-sensitive sensor elements 5.21 is also conceivable.

Furthermore, an analyzer 5.M, which is configured as an analyzer matrix, is arranged in front of the photosensitive sensor element 5.21, comprising a plurality of polarizer elements 5.Ml-5.M4 arranged in a matrix. The matrix of polarizer elements 5.Ml-5.M4 corresponds here to the positioning of the light-sensitive sensor elements 5.21 of the matrix sensor 5.2. The polarizer elements 5.Ml to 5.M4 each belong to one of the light-sensitive sensor elements 5.21, as can be seen in detail D, alternately oriented in four different linear polarization directions. For example, the polarizer elements 5.Ml-5.M4 are arranged along the polarization direction 0 °, towards 40 °, 90 ° and 135 °, respectively. It is conceivable that the analyzer 5.M, which is configured as an analyzer matrix, is arranged between the microlens array and the photosensitive sensor element 5.21 of the matrix sensor 5.2.

Furthermore, the polarizer elements 5.Ml-5.M4 arranged in a matrix are grouped in such a way that four adjacently arranged polarizer elements 5.Ml-5.M4 are respectively oriented in four different linear polarization directions and form a group G. Several groups G are also arranged in a matrix form.

It is also conceivable that the matrix sensor 5.2 comprises a bayer filter in order to separate colors in the camera image in addition to polarization and thus to separately detect different wavelengths of light. The transparent foreign matter F can thereby be identified more reliably based on the color information.

Thus, all four polarization directions can be detected in the camera image with the matrix sensor shown in fig. 2. The transmission-light inspection apparatus 1 shown in fig. 1 can therefore be constructed particularly easily with only one camera.

With the transmission light inspection apparatus 1 shown in fig. 1 and 2, a container 2 is transported by a conveyor 3 to inspection stations 4, 5 attached to the conveyor, and is transilluminated there with polarized light L. For this purpose, the initially unpolarized light from the light source 4.1 is polarized by the polarizer 4.2, for example circularly, and emitted as polarized light L. In the case of transillumination, the polarization of the light is influenced by the transparent foreign matter F, for example, by stress birefringence. The container 2, which is transparent in this way, is detected with a camera system 5, which comprises a matrix sensor 5.2 and an analyzer 5.M, which is configured as an analyzer matrix. Thereby, different linear polarization directions are detected simultaneously in the camera images of the camera system 5. Depending on the arrangement and the properties of the transparent foreign bodies F, these appear darker or lighter in the camera image than the remaining regions of the side wall 2a of the container 2 in the case of a specific linear polarization direction, so that they can be recognized by image processing methods known per se.

Fig. 3 shows a further exemplary embodiment of a transmission-light inspection device 1 according to the invention in a side view, with four cameras 5A-5D, in front of which an analyzer 5.Fl-5.F4 is arranged in each case. The exemplary embodiment shown in fig. 3 differs from the exemplary embodiment of fig. 1 only in the design of the camera system 5. Accordingly, the features of the illumination device 4 and the conveyor 3 in the embodiment in fig. 1 apply correspondingly to fig. 3 as well, or to fig. 4 below as well.

It can be seen that the objective lenses 5.3 of the cameras 5A-5D are respectively arranged with an analyzer 5.Fl-5.F4 in front. Here, they are, for example, linear polarization filters which are twisted into different rotational positions about the axis of the objective 5.3 in such a way that they respectively allow different linear polarization directions to pass through, for example 0 °, 45 °, 90 ° and 135 ° directions. Whereby one of the linear polarization directions can be detected by one of the cameras 5A-5D, respectively. Thus, although the construction is more complex, a higher spatial resolution in the camera image can still be achieved.

A further embodiment according to the invention of a transmission-light inspection apparatus 1 with four cameras 5A-5D and two polarizing beam splitters 5.T1-5.T2 is shown in side view in fig. 4. The embodiment in fig. 4 differs from that in fig. 3 only in the type of analyzer 5.T1-5. T2. The four different linear polarization directions are divided into the four cameras 5A to 5D not by polarization filters but by the illustrated polarization beam splitter 5.T1 to 5.T2, whereby the image fields of the cameras 5A, 5B or 5C, 5D can be superimposed so that the image perspectives in the respective camera images are similar or even identical. This makes it possible to support the assignment of the image region of the container 2 in the camera image during the evaluation.

With the transmission light inspection apparatus 1 shown in fig. 3 and 4, the container 2 is transported with the conveyor 3 to the inspection stations 4, 5 attached to the conveyor, and is transilluminated there with polarized light L. For this purpose, the initially unpolarized light from the light source 4.1 is polarized by the polarizer 4.2, for example circularly, and emitted as polarized light L. In the case of transillumination, the polarization of the light is influenced by the transparent foreign matter F, for example, by being rotated by stress birefringence or being absorbed in a specific direction. The container 2, which is viewed through in this way, is detected with four cameras 5A-5D in four different linear polarization directions. For this purpose, a polarizing filter 5.Fl-5.F4 or a polarizing beam splitter 5.T1-5.T2 is arranged in front of the cameras 5A-5B. In this way, different linear polarization directions are detected simultaneously in each of the four camera images of the camera system 5. Depending on the arrangement and the properties of the transparent foreign bodies F, these appear darker in the camera image in a particular linear polarization direction than in other regions of the side wall 2a of the container 2, so that they can be recognized by image processing methods which are conventional per se.

Since in the embodiment of fig. 1 to 4 the camera system 5 and the at least one analyzer 5.M, 5.Fl-5.F4 or 5.T1-5.T2 are configured for simultaneous recognition of four different linear polarization directions, a transmission inspection of the side wall 2a of the container 2 can be carried out with little effort even in the case of high-throughput container processing facilities. In addition, weakly polarized foreign bodies F can be detected particularly reliably.

It is to be understood that the features mentioned in the embodiments described above are not limited to this combination of features, but can also be combined individually or in any other way.