Method and device for optically inspecting containers

Abstract

The invention relates to a method for optically inspecting containers (2), wherein the containers (2) are conveyed to an inspection unit having an illumination unit (3) and a camera (4), wherein the illumination unit (3) emits light from a planar luminous surface (30), wherein the light is transmitted or reflected by the container (2), wherein the camera (4) captures in at least one camera image (I) the corresponding at least one container (2) and the light transmitted or reflected by it, and wherein the at least one camera image (I) is analyzed by an image processing unit for intensity information in order to identify foreign bodies (8) and / or defects (7) in the container, wherein the light emitted from the luminous surface (30) is locally encoded based on polarization properties, intensity properties and / or phase properties and is captured by the camera (4) in such a way that different emission positions (31-42) on the luminous surface (30) can be distinguished from each other in the at least one camera image (I), and the image processing unit (6) analyzes the at least one camera image (I) for position information of the emission positions (31-42) in order to distinguish defects (7) from foreign bodies (8).

Description

Technical Field

[0001] The invention relates to a method and a device for optically inspecting containers, respectively having the features described herein. Background Art

[0002] Typically, such methods and devices are used to inspect containers for foreign bodies and / or defects. To this end, the container is conveyed to an inspection unit having an illumination unit and a camera so that the container can be inspected with transmitted or incident light. In the process, the illumination unit emits light from a planar luminous surface, wherein the light is transmitted or reflected by the container and is subsequently captured with the camera as at least one camera image. Subsequently, an image processing unit analyzes the at least one camera image for intensity information in order to identify foreign bodies and / or defects of the container.

[0003] Such methods and devices are used, for example, for side wall, bottom and / or fill level inspection of empty containers or containers already filled with product.

[0004] Here, containers are usually inspected with a diffusely illuminated surface to identify foreign objects, thereby suppressing, for example, glass marks or water drops in the camera image. Foreign objects can be, for example, contamination, product residues or label residues.

[0005] In contrast, for the detection of defects, a luminous surface that emits in a directed manner is used to amplify the resulting refraction of light in the camera image. For example, a defect can be damage to the container, such as a broken glass. It is also conceivable that these are defectively produced material points, such as local material protrusions, etc.

[0006] In order to be able to identify foreign objects and defects equally easily, therefore, two different inspection units are usually used with different emission characteristics of the illumination units.

[0007] The disadvantage here is that this requires corresponding effort and installation space for the optical inspection of the container.

[0008] A method for detecting defects in glass products and a device suitable for the method are known from US 2013 / 0215261 A1. In order to increase the contrast, an illumination with a plurality of light patterns offset relative to one another is proposed therein.

[0009] DE 10 2014 220 598 A1 discloses an inspection device for transmitted light inspection of containers, which has a device for dividing the luminous surface into at least two mainly horizontally separated partial areas, which can be selectively opened and closed for side wall inspection and / or closure head inspection of the container.

[0010] US 6,304,323 B1 discloses a method for detecting defects in bottles.

[0011] EP 0 472 881 A2 discloses a system and a method for optically inspecting the bottom surface of a transparent container.

[0012] US 2008 / 0310701 A1 discloses a method and a device for visually inspecting an object.

[0013] EP 0 926 486 B1 discloses a method for optically inspecting transparent containers using infrared and polarized visible light.

[0014] DE 10 2017 008 406 A1 discloses an inspection device with colored illumination for inspecting containers for foreign bodies and three-dimensional container structures. For this purpose, the radiation source comprises a plurality of spatially separated radiation bands which emit radiation of different wavelength ranges or different intensities. In the case of decorative elements, local color contrasts occur in this way, while in the case of foreign bodies, only local brightness contrasts occur, but not local color contrasts. However, in rare cases, defects may not be distinguishable from foreign bodies in colored containers. Summary of the invention

[0015] The object of the present invention is to provide a method and a device for optically inspecting containers, by means of which both foreign bodies and defects can be detected with little effort and requiring little installation space.

[0016] To achieve this object, the invention provides a method for optically inspecting a container having the features described herein. Advantageous embodiments of the invention are set out in the dependent claims.

[0017] During extensive investigations by the applicant, it was found that due to the local modification of the container surface associated with the defect, the light is refracted differently at the defect than at undamaged areas of the container. As a result, the light is deflected towards the camera via the defect from a different emission position of the light-emitting surface than at undamaged areas. In contrast, this is usually not the case or is less common for foreign matter, since, for example, contamination leads to a local absorption of light without substantially affecting the light path towards the camera in the process.

[0018] By locally encoding the light emitted from the luminous surface based on polarization properties, intensity properties and / or phase properties and capturing the light by a camera, it is possible to determine for the image points of the camera image which emission position the corresponding light components each originate from, independently of the emission properties of the luminous surface. By analyzing at least one camera image with respect to the position information of the emission position by an image processing unit, defects can be distinguished from foreign matter, for example due to local modifications of the emission position. Conversely, the intensity information can also be analyzed so that the absorption of light by foreign matter can be particularly well identified using the preferred diffuse emission properties of the luminous surface. Therefore, using the method according to the invention, both foreign matter and defects can be identified equally well with a single inspection unit. By completing this processing with a single inspection unit, less installation space is required for this purpose.

[0019] The method for optically inspecting can be used in beverage processing plants. The method can be upstream or downstream of a container manufacturing process, a cleaning process, a filling and / or a closing process. The method can be used in full or empty bottle inspection machines. For example, the method can be used to inspect returned reusable containers.

[0020] A container can be provided to receive beverages, foods, hygiene products, pastes, chemicals, biological and / or pharmaceutical products. The container can be implemented as a bottle, in particular as a plastic bottle or a glass bottle. The plastic bottle can be specifically a PET, PEN, HD-PE or PP bottle. The container can also be a biodegradable container or bottle whose main component consists of renewable resources such as sugar cane, wheat or corn. The container can be provided with a lid, such as a crown lid, a screw lid or a tearable lid, etc. Likewise, the container can be empty, preferably without any lid.

[0021] It is conceivable that the method is used for the side wall, bottom, opening and / or content control of the container. Foreign matter may be contamination, product residue and / or label residue, etc. For example, the defect may be damage to the container, such as broken glass. It is also conceivable that the defect is a material point that is produced imperfectly, such as a local material bulge or taper.

[0022] The containers can be conveyed to the inspection unit as a container stream by means of a conveyor. The conveyor can comprise a carousel and / or a linear conveyor. For example, it is conceivable that the conveyor comprises a conveyor belt on which the containers are conveyed in an upright position to the area between the lighting unit and the camera. It is conceivable that a container (PUK) holds one or several containers during the conveyance. If, for example, the lighting transmits light through the container bottom and the camera examines the bottom through the container opening, the containers can also be held by a transverse belt for conveyance.

[0023] The lighting unit may generate light with at least one light source, such as a light bulb, a fluorescent tube or at least one LED. Preferably, the light may be generated with an LED matrix and emitted to the light-emitting surface. The light-emitting surface may be larger than the camera view of the container. It is also conceivable that the light-emitting surface illuminates only a portion of the camera view of the container. The light-emitting surface may emit light partially or completely diffusely. Preferably, the light-emitting surface may include a diffuse screen, through which light is diffusely scattered from the at least one light source to the camera plane. The emission position may here refer to a position point or a plane portion of the light-emitting surface. It is conceivable that the emission positions of the light-emitting surface continuously change with respect to each other, so that the polarization characteristics, intensity characteristics and / or phase characteristics continuously change on the light-emitting surface.

[0024] The camera can capture at least one of the containers and the light transmitted or reflected by the container with a lens and an image sensor. The image sensor can be, for example, a CMOS or CCD sensor. It is conceivable that the camera sends at least one camera image to the image processing unit using a data interface. It is conceivable that the light is generated by the lighting unit, then transmitted through the container, and then captured by the camera. For each image point of the at least one camera image, the camera can separate the polarization characteristics, intensity characteristics and / or phase characteristics of the captured transmitted or reflected light.

[0025] The image processing unit can process the at least one camera image with a signal processor and / or with a CPU and / or a GPU. For this purpose, it is also conceivable that the image processing unit comprises a storage unit, one or more data interfaces such as network interfaces, a display unit and / or an input unit. It is conceivable that the image processing unit analyzes the at least one camera image using an image processing algorithm present as a computer program product in the storage unit.

[0026] "Light emitted from a light emitting surface is locally encoded based on polarization characteristics, intensity characteristics and / or phase characteristics and captured by a camera such that in at least one camera image, different emission positions of the light emitting surface can be distinguished from one another" may mean here that light is emitted from a light emitting surface having polarization characteristics, intensity characteristics and / or phase characteristics in a locally varying manner such that different emission positions having polarization characteristics, intensity characteristics and / or phase characteristics are each encoded differently, wherein the camera captures the polarization characteristics, intensity characteristics and / or phase characteristics as position information in at least one camera image.

[0027] It is conceivable that the local coding of the emitted light is adapted to the task, in particular to the type of container, based on the polarization properties, intensity properties and / or phase properties. For example, for this purpose, the boundaries of the locally coded light can be adapted to the height and / or width of the container. In other words, the luminous surface area that varies with the polarization properties, intensity properties and / or phase properties can be variably enlarged or reduced.

[0028] The light emitted from the light emitting surface can be emitted in the visible range and / or in the invisible range of the wavelength spectrum. For example, the light in the visible range can be perceptible to the human eye and / or in the wavelength range of 380nm-750nm. The invisible range can be imperceptible to the human eye and / or can be in the UV or IR wavelength range. It is also conceivable that the visible range is combined with the invisible range. For example, for a brown glass container, light can be emitted from the light emitting surface in red and infrared wavelengths.

[0029] Polarization characteristics here can mean that light is emitted from different emission positions of the light-emitting surface, and each emission position has a different polarization direction. For example, in the area of ​​the light-emitting surface, a polarization filter with a continuously changing polarization process, or a plurality of polarization filters with different orientations can be arranged so that the polarization of the emitted light changes locally. It is conceivable that the camera separates the polarization characteristics in at least one camera image. To this end, the camera can include, for example, a plurality of image sensors each having a polarization filter with a different orientation, or a single image sensor with a polarization filter matrix. In particular, the camera can include a Sony IMX250MZR sensor. Polarization characteristics here can mean linear polarization characteristics, elliptical polarization characteristics and / or circular polarization characteristics.

[0030] It is conceivable that the image processing unit analyzes at least one camera image to obtain position information of the emission position in order to additionally identify local material imprints such as embossing, glass imprints and pearls at the container and / or to distinguish local material imprints from foreign objects. Such material imprints can be used as decorative elements, for example. The image processing unit can analyze at least one camera image with respect to the intensity information and the position information of the emission position in order to identify a region with changed position information and changed intensity information as a container edge. Since at the container edge both blurring and particularly pronounced deflection of the light beam are affected, the container edge can be particularly easily identified. For example, the presence of a container edge can be concluded by the image processing unit analyzing at least one camera image of a third local region with deviating intensity information and deviating position information relative to the surrounding area.

[0031] It is also conceivable that, in addition to polarization properties, intensity properties and / or phase properties, the light emitted from the light emitting surface is locally encoded using wavelength properties. Thus, for example, the emitted light can be locally encoded both using wavelength and using polarization. The camera can then separate both the wavelength property and the polarization property in at least one camera image. For example, to this end, the camera can include a Sony IMX250MYR sensor.

[0032] The intensity characteristic here means that the light is emitted from different emission positions of the light-emitting surface, each emission position having a different intensity or intensity course. The phase characteristic of the emitted light here means that a periodic intensity course is modulated on the emitted light, in particular a sinusoidal intensity course is modulated on the emitted light, wherein the phase of the periodic intensity course is different for different emission positions.

[0033] The image processing unit can analyze at least one camera image for a first partial area with intensity information deviating from the surrounding area to draw conclusions about the presence of foreign matter. Defects that usually absorb light can be particularly easily identified in the at least one camera image via the deviating intensity information.

[0034] The image processing unit can analyze the at least one camera image for a second partial area having position information that deviates from the surrounding area in order to draw the conclusion that a defect is present. In this way, the defect can be particularly easily identified in the at least one camera image by the defect of the container deflecting the light in a different manner than the area surrounding the defect. For example, in the at least one camera image, the defect can have polarization information that differs from the polarization information of the surrounding area. From this, one can draw the conclusion that the refraction of light is different relative to the surrounding area and that a defect is therefore present.

[0035] By means of the image processing unit, at least one camera image can be divided into an intensity channel and a light property channel for polarization properties, intensity properties and / or phase properties, wherein the image processing unit identifies foreign objects based on the intensity channel and identifies defects based on the light property channel. Thus, foreign objects and defects can be analyzed separately in both channels particularly easily. The intensity channel here can mean a channel for relative brightness, absolute brightness or intensity.

[0036] It is conceivable that light is emitted from emission positions of the light-emitting surface, each of which has a different intensity course in time, so as to encode the different emission positions as intensity characteristics and / or phase characteristics. Therefore, containers with different color transparencies can be checked in a particularly reliable manner. It is conceivable that here, the phase characteristic includes a time offset of the intensity course that is different for each emission position in the different emission positions. "Time offset" can refer to an offset relative to a reference signal here. In other words, the intensity course can include an intensity sequence or a sinusoidal intensity course, and the time offset of the intensity course is selected differently at different emission positions relative to the reference signal. It is conceivable that the camera captures the propagation time difference of the light transmitted or reflected into the container to determine the phase characteristic. For example, it is known that the camera used for this captures the propagation time of the light of each image point, or the phase offset relative to the reference signal respectively.

[0037] Additionally or alternatively, it is conceivable that the intensity characteristic comprises a light intensity time sequence of the intensity course which is different for different emission positions. For example, for different emission positions, a different intensity sequence of the emitted light can be selected in each case. An intensity sequence can here mean, for example, a sequence of several temporally consecutive time periods, wherein in each time period, the light is emitted brightly or darkly.

[0038] Furthermore, in order to achieve this object, the invention provides a device for optically inspecting containers, the device having the features described herein. Advantageous embodiments of the invention are stated in the dependent claims.

[0039] By implementing the lighting unit to emit light emitted from a light-emitting surface that is locally encoded based on polarization properties, intensity properties and / or phase properties, and by implementing the camera to capture the locally encoded light independently of the emission properties of the light-emitting surface, it is possible to determine for an image point of the camera image from which emission position the corresponding light components each originate. By implementing the image processing unit to analyze at least one camera image for position information of the emission position, it is possible to distinguish between defects and foreign bodies, for example due to local modifications of the emission position. Conversely, the intensity information can also be analyzed so that the absorption of light by foreign bodies can be particularly well identified using the preferably diffuse emission properties. Therefore, using the device according to the invention, foreign bodies and defects can be identified equally well using a single inspection unit. By completing this processing using a single inspection unit, less installation space is required for this.

[0040] The device for optically inspecting containers can be implemented to perform the above method. The device can similarly include the above features, in particular the features of the method.

[0041] The device for optical inspection can be arranged in a beverage processing plant. The beverage processing plant can include container processing machines, in particular container manufacturing machines, washing machines, fillers, closers, labelers, direct printers and / or packaging machines. It is conceivable that the device is associated with one of the container processing machines mentioned for inspection. Here, the device can be used for full or empty bottle inspection. It is conceivable, for example, that the device is used for inspecting recycled reusable containers.

[0042] The lighting unit can be implemented to emit light locally differently using polarization characteristics, intensity characteristics and / or phase characteristics. For example, in the area of ​​the light-emitting surface, a polarization filter with a continuously changing polarization process or a plurality of polarization filters with different orientations can be arranged to locally change the polarization of the emitted light.

[0043] It is conceivable that the lighting unit is embodied to emit light from emission positions of the luminous surface, the emission positions each having a temporally different intensity course, to encode different emission positions as intensity characteristics and / or phase characteristics. Containers of different colors can thus be inspected particularly reliably.

[0044] The camera can be implemented to capture polarization characteristics, intensity characteristics and / or phase characteristics in a spatially resolved manner. For example, as described above with respect to the method, this can be accomplished via a polarization filter, in particular via a polarization filter matrix. The camera can be implemented as a polarization camera and / or a propagation time camera. Therefore, it is possible to capture wavelength characteristics, polarization characteristics, intensity characteristics and / or phase characteristics in a spatially resolved manner with less effort. In particular, the camera can include a Sony IMX250MZR or IMX 250MYR sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Further features and advantages of the present invention will be illustrated in more detail below with reference to the exemplary embodiments shown in the accompanying drawings. In the drawings:

[0046] Figure 1 An exemplary embodiment of a method according to the invention for optically inspecting containers is shown in the form of a flow chart;

[0047] Figure 2 An exemplary embodiment of a device for optically inspecting containers according to the invention is shown in a perspective view;

[0048] Figure 3 Show Figure 2 a detailed view of a light emitting surface of a lighting unit;

[0049] Figure 4A-4B Shown during inspection for foreign matter and defects Figure 2 and Figure 3 A side view of the light emitting surface and the camera;

[0050] Figure 5A Show according to Figure 4A-4B Camera images during inspection for foreign matter and defects based on polarization properties;

[0051] Figure 5B-Figure 5C Show Figure 5A The intensity channel G and the light characteristic channel C of the camera image I; and

[0052] Figure 6A-6B Show Figure 2 Detailed view of a further embodiment of a lighting unit in which light is emitted from emission positions of a light-emitting surface each having a temporally different intensity course. DETAILED DESCRIPTION

[0053] exist Figure 1 In FIG. 1 , an exemplary embodiment of a method 100 for inspecting a container 2 according to the present invention is represented as a flow chart. Figure 2-6B The method 100 is illustrated in more detail:

[0054] exist Figure 2 In FIG. 1 , an exemplary embodiment of a device 1 for optically inspecting containers 2 according to the invention is shown as a perspective view. One can see an inspection unit 10 with an illumination unit 3 and a camera 4. Between the illumination unit 3 and the camera 4, a conveyor 5 is arranged, which is implemented here only as an example as a conveyor belt, on which the containers 2 are conveyed in the direction R between the illumination unit 3 and the camera 4 (step 101). As an example, only a single container 2 being inspected is shown. However, the containers 2 are conveyed as a container stream on the conveyor 5, and each container is optically inspected between the illumination unit 3 and the camera 4.

[0055] The lighting unit emits light from the planar light emitting surface 30 to transmit the light through the container 2 (step 102). The emitted light is transmitted via the container 2 to the camera 4 (step 104). It is also conceivable that by arranging the lighting unit 3 opposite the camera 4, the light is reflected via the container 2. The camera 4 is arranged at the inspection unit 10 so that the camera captures the container 2 and the light transmitted via the container 2 in at least one camera image (step 105).

[0056] The lighting unit 3 may include, for example, an LED matrix, which emits light onto the light emitting surface 30. For example, the light emitting surface 30 may be implemented as a diffusion screen to preferably emit the light of the LED in a diffuse manner. In addition, the lighting unit 3 emits light from the light emitting surface 30 in a locally coded manner based on polarization characteristics, intensity characteristics and / or phase characteristics (step 103). This will be referred to below. Figure 3 and Figure 6A-6B Accordingly, the camera 4 is implemented to capture locally coded light, so that in at least one camera image, different emission positions of the light emitting surface 30 can be distinguished from each other (step 106).

[0057] Furthermore, an image processing unit 6 can be observed, by which at least one camera image is analyzed for intensity information in order to identify foreign objects and / or defects of the container (step 107). This can be done, for example, by image processing algorithms known per se for identifying local changes in at least one camera image.

[0058] Furthermore, the image processing unit 6 analyses the at least one camera image with respect to the position information of the emission location in order to distinguish defects from foreign objects (step 108 ).

[0059] The following will refer to Figure 3-6B The method 100 and the apparatus 1 are illustrated in more detail.

[0060] exist Figure 3 In, it is expressed Figure 2 Detailed view of the light emitting surface 30 of FIG. In detail, different emission positions 31 to 42 of the light emitting surface 30 can be seen which are locally encoded based on polarization properties, intensity properties and / or phase properties.

[0061] For example, it is the polarization property that causes different emission positions 31 to 42 to emit light having different polarization directions. For example, it is conceivable that emission position 31 emits light having a polarization direction of 0°, emission position 34 emits light having a polarization direction of 45°, emission position 37 emits light having a polarization direction of 90°, and emission position 40 emits light having a polarization direction of 135°. Accordingly, the polarization directions of emission positions 23, 33, 35, 36, 38, and 39 are interpolated between these polarization directions, or the polarization directions of emission positions 41 to 42 are extrapolated from these polarization directions. The distribution of polarization directions on the illuminated surface is exemplary. The polarization direction may also be embodied as discontinuous, meaning a sudden change in the polarization direction or a repetitive pattern of the polarization direction.

[0062] In this exemplary embodiment, the camera 4 is implemented as a polarization camera with a Sony IMX250MZR image sensor in order to capture the different emission positions 31 to 42 and store them as position information in at least one camera image.

[0063] exist Figure 4A-4B In the figure, the time during the inspection of foreign matter 8 and defect 7 is shown. Figure 2 and 3 A side view of the light emitting surface 30 and the camera 4. Figure 4B In the Figure 4A Details of D.

[0064] One can see a planar emitting luminous surface 30 with different emission positions 31 to 42 in lateral profile. From here, light is emitted planarly toward the camera 4 and is thus transmitted through the container 2. The container 2 consists here, for example, of a transparent glass material, so that light is transmitted through the container 2.

[0065] The camera 4 comprises an image sensor 41 and a lens 42 to capture the container 2 in at least one camera image. It is conceivable that the camera 4 is implemented as a polarization camera and / or a transit time camera.

[0066] It can also be seen that the light beam S1 passes through the container 2 starting from the emission position 39. This light beam strikes the foreign body 8, which absorbs part of the energy of the light beam. As a result, the foreign body 8 appears in at least one camera image of the camera 4 with a reduced intensity compared to the immediate surrounding area. As a result of the foreign body not deflecting the light beam S1, the foreign body appears in at least one camera image with the same polarization properties, intensity properties and / or phase properties as the immediate surrounding area of ​​the emission position 39.

[0067] Furthermore, a light beam S2 can be seen, which, starting from position 36, passes through container 2 in the area surrounding defect 7. Here, depending on the material of container 2, the light is only slightly absorbed, so that the corresponding image point in at least one camera image appears with high intensity and polarization, intensity and / or phase characteristics of emission position 36. Furthermore, from Figure 4B , it can also be seen that the light beam S2 passes through the container 2 at a point where the container inner wall 22 and the container outer wall 21 extend in a plane-parallel manner relative to each other. Therefore, depending on the angle of impact, the light beam S2 undergoes only a slight deviation, but the direction does not change. Therefore, the corresponding image point appears in at least one camera image with high intensity and polarization characteristics, intensity characteristics and / or phase characteristics of the emission position 36.

[0068] In contrast, Figure 4B As can be seen in the figure, the defect 7 comprises local notched surfaces 71, 72 at the outer wall 21 of the container. This may be a notch caused by a fracture, for example. Therefore, the light beams S3, S4 are deflected at the local notched surfaces 71, 72 by refraction of light. More precisely, the light beam S3 is emitted from the emission position 38 and, during its passage through the container 2, is deflected towards the camera 4 at the first notched surface 71 by refraction of light. In contrast, the light beam S4 passes through the container 2 starting from the emission position 33 and is deflected towards the camera 4 at the second notched surface 72 by refraction of light. Therefore, due to the local refraction of light, in at least one camera image, the defect 7 appears at the notched surfaces 71, 72 having different polarization characteristics, intensity characteristics and / or phase characteristics than the surrounding area.

[0069] Figure 5A 1 is a camera image I showing in more detail the inspection of foreign matter 8 and defect 7 based on polarization characteristics.

[0070] It can be seen that the container 2 appears in front of the luminous surface 30 in the camera image I. It can also be seen that the foreign body 8 is imaged as a blurred first local area 8'. In contrast, the defect 7 is imaged as a second local area 7' with an intensity similar to that of the immediate surrounding area, however, because Figure 4AThe light beam is shown to be locally deflected by the defect 7 , so that the second partial region appears as an upper region with position information 33 ′ of the emission position 33 and as a lower region with position information 38 ′ of the emission position 38 .

[0071] exist Figure 5B-Figure 5C In, it is expressed Figure 5A The intensity channel G and the light characteristic channel C of the camera image I. The light characteristic channel C is provided for polarization characteristics, intensity characteristics and / or phase characteristics light characteristics.

[0072] Figure 2 The image processing unit 6 shown in FIG. Figure 5A The camera image I shown in FIG. 1 is divided into an intensity channel G and a light property channel C. Since in this embodiment the light emitting surface emits light based on polarization properties and the camera 4 captures the polarization direction as position information, the light property channel C is a polarization channel.

[0073] The image processing unit 6 then analyses the intensity channel G of the camera image I for the first partial area 8' using the intensity information deviating from the surrounding area U1 to conclude the presence of a foreign body 8. This is done, for example, by means of a filter for detecting brightness changes.

[0074] In addition, the image processing unit 6 uses the position information deviating from the surrounding area U2 to analyze the light characteristic channel C of the camera image I with polarization for the second local area 7'. Figure 5C As shown, the local area 7' of the defect 7 appears as an upper area with position information 33' and a lower area with position information 38'. In contrast, the immediate surrounding area U2 includes position information 36' of the emission position 36. Therefore, since the second local area 7' has different position information 33', 38' from its surrounding area U2, the defect 7 can be distinguished from the foreign matter 8.

[0075] After identifying foreign bodies 8 and / or defects 7, the image processing unit 6 generates a signal that the container 2 comprises foreign bodies 8 or defects 7, respectively. Based on this signal, a switch can be controlled to discharge the corresponding container 2, for example after inspection, for re-cleaning or recycling.

[0076] exist Figure 6A-6B In the Figure 2 Detailed view of a further embodiment of a lighting unit 3 in which light is emitted from emission positions 31 to 42 of a light-emitting surface 30 each having a different intensity course over time.

[0077] exist Fig. 6AIn the figure, it can be seen that the emission position 33 emits light with a sinusoidal intensity course 50, which includes a time offset P1=0 relative to the time reference or reference signal. In contrast, the intensity course of the emission position 39 also extends sinusoidally, however, it has a different time offset P2 compared to the time reference or reference signal. The intensity courses of the two emission positions 33, 39 are shown here only as an example. However, all other emission positions 31, 32, 34 to 38, 40 to 42 also have sinusoidal intensity courses, each with a different time offset. This corresponds to respectively different phases of the sinusoidal time variation, so that the light emitted from the light-emitting surface 30 is locally encoded based on the phase characteristic.

[0078] In order to capture the different phases or time shifts of the different emission positions 31 to 42 in the camera image, the camera 4 shows the propagation time differences of the light transmitted through the container 2 in order to determine the phase characteristics of the individual image points of the camera image. In other words, the camera 4 is embodied here as a propagation time camera. It is conceivable that the camera captures the respective time shift relative to a time reference or reference signal for the image points. This time shift then corresponds to position information, which is then analyzed by the image processing unit 6 as described above in order to distinguish defects 7 from foreign bodies 8.

[0079] Relatively speaking, in Figure 6B , it can be seen that light is emitted from emission positions 31 to 42 of the luminous surface 30, each with a different intensity course 52, 53, wherein the intensity courses 52, 53 each have a different sequence of intensity levels I1 to I6 or I7 to I12, respectively. For example, the first intensity course 52 alternately has two bright and two dark intensity levels I1 to I6. In contrast, the second intensity course 53 alternately has one bright and one dark intensity level I7 to I12. The intensity courses 52, 53 of the emission positions 33 and 39 are indicated here only as examples. In other words, the different emission positions 31 to 42 each emit a time sequence of different intensity levels, so that the different emission positions are encoded based on the intensity characteristics.

[0080] The different intensity curves 52 , 53 are captured by the camera 4 in a camera image sequence and are evaluated by the image processing unit 6 as position information of the emission positions 31 to 42 in order to distinguish defects 7 from foreign bodies 8 .

[0081] Analogy Figure 5A-Figure 5C , after analysis, the second local area 7' has an intensity course (or a plurality of deviated intensity courses) corresponding to different position information that deviates from the surrounding area U2, and therefore it can be concluded that the defect 7 exists.

[0082] By Figure 1-6BThe illumination unit 3 in the exemplary embodiment of the embodiment of the invention is implemented to emit the light emitted from the luminous surface 30 in a locally coded manner based on polarization properties, intensity properties and / or phase properties, and by implementing the camera 4 to capture the locally coded light, it is possible to determine for an image point of the camera image which of the emission positions 31 to 42 the corresponding light component originates, independently of the emission properties of the luminous surface 30. By implementing the image processing unit 6 to analyze at least one camera image for local information of the emission positions 31 to 42, it is possible, for example, to distinguish between defects and foreign bodies due to local changes in the emission positions 33, 38. Conversely, the intensity information can also be analyzed in order to be able to particularly well identify the absorption of light by foreign bodies 7 with the preferably diffuse emission properties. Therefore, with the method 100 or the device 1 according to the invention, both foreign bodies 7 and defects 8 can be identified equally well with a single inspection unit 10. By completing this processing with a single inspection unit 10, less installation space is required for this purpose.

[0083] It will be understood that the features mentioned in the above exemplary embodiments are not limited to the combination of these features, but may also appear alone or in any other combination.

Claims

1. A method (100) for optically inspecting a container (2), wherein: The containers (2) are empty and are conveyed (101) to an inspection unit (10) having an illumination unit (3) and a camera (4), the illumination unit (3) emitting light from a planar luminous surface (30) having diffuse emission properties, the light being transmitted or reflected (104) by the containers (2), the camera (4) capturing (105) at least one of the containers (2) and the light transmitted or reflected by each of the containers in at least one camera image (I), and analyzing the at least one camera image (I) by an image processing unit (6) for intensity information in order to identify (107) foreign bodies (8) and / or defects (7) in the containers, Features: The light emitted from the light emitting surface (30) is locally encoded (103) based on polarization properties and / or phase properties and is captured by the camera (4) in such a way that different emission positions (31-42) of the light emitting surface (30) can be distinguished from each other (106) in the at least one camera image (I), and The image processing unit (6) analyzes the at least one camera image (I) based on the position information of the emission positions (31-42) to distinguish the defect (7) from the foreign matter (8) by determining, for an image point of the at least one camera image (I), from which of the emission positions (31-42) the corresponding light component originates, independently of the emission characteristics of the light-emitting surface (30) (108).

2. The method (100) according to claim 1, wherein: The light emitted from the light emitting surface (30) is also locally encoded based on an intensity characteristic.

3. The method (100) according to claim 1, wherein: The light is emitted from the light emitting surface (30) having the polarization property and / or the phase property in a locally varying manner, so that the different emission positions (31-42) having the polarization property and / or the phase property are each encoded differently, and the camera (4) captures the polarization property and / or the phase property as the position information in the at least one camera image (I).

4. The method (100) according to claim 2, wherein: The light is emitted from the light emitting surface (30) having the intensity characteristic in a locally varying manner so that the different emission positions (31-42) having the intensity characteristic are each encoded differently, and the camera (4) captures the intensity characteristic as the position information in the at least one camera image (I).

5. The method (100) according to any one of claims 1 to 4, wherein: The image processing unit (6) analyses the at least one camera image (I) for a first partial area (8') having intensity information which deviates from the surrounding area (U1) in order to draw a conclusion on the presence of a foreign body (8).

6. The method (100) according to any one of claims 1 to 4, wherein: The image processing unit (6) analyses the at least one camera image (I) for a second partial area (7') having position information deviating from the surrounding area (U2) in order to draw a conclusion on the presence of a defect (7).

7. The method (100) according to claim 1 or 3, wherein: The image processing unit (6) is used to divide the at least one camera image (I) into an intensity channel (G) and a light characteristic channel (C) according to the polarization characteristic and / or the phase characteristic, and the image processing unit (6) identifies the foreign matter (8) based on the intensity channel (G) and identifies the defect (7) based on the light characteristic channel (C).

8. The method (100) according to claim 2 or 4, wherein: The image processing unit (6) is used to divide the at least one camera image (I) into an intensity channel (G) and a light characteristic channel (C) according to the intensity characteristic, and the image processing unit (6) identifies the foreign matter (8) based on the intensity channel (G) and identifies the defect (7) based on the light characteristic channel (C).

9. The method (100) according to claim 1 or 3, wherein: The light is emitted from the emission positions (31-42) of the light emitting surface (30) each having a temporally different intensity course (50-53) to encode the different emission positions into the phase characteristic.

10. The method (100) according to claim 2 or 4, wherein: in, The light is emitted from the emission positions (31-42) of the light emitting surface (30) each having a temporally different intensity course (50-53) to encode the different emission positions into the intensity characteristic.

11. The method (100) according to claim 9, wherein: The phase characteristic comprises different time offsets (P1, P2) of the intensity course, the different time offsets (P1, P2) being respectively different for the different emission positions (31-42).

12. The method (100) according to claim 10, wherein: The intensity characteristic comprises different light intensity time series (I1-I12) of the intensity course (52, 53), the different light intensity time series (I1-I12) being different for each of the different emission positions (31-42).

13. The method (100) of claim 9, wherein: The camera (4) captures the difference in propagation time of light transmitted or reflected by the container (2) to determine the phase characteristic.

14. A device (1) for optically inspecting containers, for carrying out the method (100) according to any one of claims 1 to 13, the device (1) comprising: an inspection unit (10) having an illumination unit (3) and a camera (4), an image processing unit (6) for processing at least one camera image (I) of the camera, a conveyor (5) for conveying the container (2) in an empty state to the inspection unit (10), The lighting unit (3) is implemented to emit light using a planar light emitting surface (30) with diffuse emission characteristics to illuminate the container (2) and / or transmit light through the container (2), wherein the camera (4) is arranged at the inspection unit (10) in such a way that in each case the camera (4) captures at least one of the containers (2) and light transmitted or reflected by the container in the at least one camera image (I), wherein the image processing unit (6) is designed to analyze the at least one camera image (I) with respect to intensity information in order to detect foreign objects (8) and / or defects (7) of the container (2), Features: The lighting unit (3) is implemented to emit the light from the light emitting surface (30) in a locally coded manner based on polarization characteristics and / or phase characteristics, The camera (4) is implemented to capture locally coded light so that in the at least one camera image (I) different emission positions (31-42) of the light emitting surface (30) can be distinguished from one another, and The image processing unit (6) is implemented to analyze the at least one camera image (I) based on the position information of the emission position (31-42) by determining, for an image point of the at least one camera image (I), from which emission position of the emission positions (31-42) the corresponding light component originates, independently of the emission characteristics of the light-emitting surface (30), so as to distinguish the defect (7) from the foreign matter (8).

15. The device (1) according to claim 14, the lighting unit (3) being further implemented to emit the light from the light emitting surface (30) in a locally coded manner based on an intensity characteristic.

16. The device (1) according to claim 14, wherein: The camera (4) is implemented to capture the polarization property and / or the phase property in a spatially resolved manner.

17. The device (1) according to claim 15, wherein: The camera (4) is embodied to capture the intensity characteristics in a spatially resolved manner.

18. The device (1) according to claim 14 or 16, wherein: The lighting unit (3) is implemented to emit light from the emission positions (31-42) of the light emitting surface (30) each having a temporally different intensity course (50-53) in order to encode the different emission positions (31-42) into the phase characteristic.

19. The device (1) according to claim 15 or 17, wherein: The lighting unit (3) is implemented to emit light from the emission positions (31-42) of the light emitting surface (30) each having a temporally different intensity course (50-53) in order to encode the different emission positions (31-42) as the intensity characteristic.

20. The device (1) according to claim 14 or 16, wherein: The camera (4) is embodied as a polarization camera and / or a transit time camera.

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