Abstract:
A device for detecting elevations and/or depressions on bottles, in particular in a labeling machine, the device comprising a lighting unit with a light screen for generating a light reflection on a bottle to be examined and at least one camera for detecting the light reflection. By areas of varying luminance being formed on the light screen, molding seams can be reliably detected over a large area of the bottle wall and embossings can be located in various rotational positions of the bottle. The invention also relates to a method for applying the device.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit of priority of German Application No. 102009020919.0, filed May 12, 2009. The entire text of the priority application is incorporated herein by reference in its entirety. 
     FIELD OF THE DISCLOSURE 
     The disclosure relates to a device for detecting elevations and/or depressions on bottles as well as a method for using this device. 
     BACKGROUND 
     Elevations and/or depressions on bottle surfaces can occur e.g. at molding seams and relief-like impressions at the bottle body, the so-called embossings. 
     Bottles with a molding seam, such as bottles for beverages, must be preferably labeled such that the molding seam is not covered by the label. Furthermore, the label is possibly to be oriented with respect to an embossing. To detect the position of a molding seam or an embossing and permit later rotation of the bottle to a desired position, it is known to examine a lamp reflection formed on the bottle body for irregularities in various rotational positions of the bottle. In the process, normally only a portion of the molding seam or the embossing, respectively, can be detected by the lamp reflection. 
     DE 10 2004 040 164 A1, for example, describes a semicircular, uniformly illuminated lamp shade arranged coaxially around the axis of symmetry of a bottle to be examined and comprising an aperture through which the surface of the bottle is examined for irregular reflections by means of a camera. In case of profiled bottle surfaces, however, the edges of the light reflections can have an irregular shape and be difficult to detect exactly in a low-contrast representation. Furthermore, the molding seam might only be represented in a small area at the edge of the light reflection. With the known technique, the molding seam is therefore not always reliably detected. 
     Embossings are preferably arranged in the area of the shoulder of the bottle. In the usual horizontal viewing direction of the camera, the embossing is then often located outside of the lamp reflection. Therefore, comparably low-contrast, irregular reflections are formed at the embossing the shape of which changes while the bottle is rotated. 
     Due to these problems, a check measurement with an additional fine adjustment of the bottle is required. This requires an additional inspection device and much space in the labeling machine which is not desired. 
     SUMMARY OF THE DISCLOSURE 
     It is therefore an aspect of the disclosure to reliably detect molding seams over a maximum area of the bottle wall and to locate embossings in various rotational positions of the bottle as reliably as possible. 
     This is achieved by areas of varying luminance being formed on the light screen of the lighting unit. These superimpose the structures to be detected in the reflection and cause reflection zones of varying brightness, in particular with bright lines on a dark background and dark lines on a bright background. This facilitates the detection of molding seams and embossings. 
     Preferably, the areas of varying luminance are arranged in a stripe pattern. Thereby, a regular pattern enhancing the image contrast is provided in the reflection. 
     In one embodiment, the stripe pattern comprises two to four dark stripes. This improves the representation in essentially cylindrical bottle shapes which image vertical structures with a sharper definition and more compactly than horizontal structures. 
     Preferably, the areas of varying luminance alternate in the horizontal direction. This improves the detection of vertically running molding seams which mainly cause reflection disturbances in the horizontal direction. 
     Preferably, the transition of the luminance between the areas of varying luminance is gradual. This supports the evaluation of the camera images filtered with band-pass filters. 
     In one preferred embodiment, the areas of varying luminance are embodied as areas of varying light transmissions. Thereby, dark screen areas can be easily realized. 
     Preferably, the light screen comprises a foil on or in which the areas of varying luminance are formed. This permits an inexpensive and flexible realization of areas of varying luminance, e.g. by printing the foil, as well as an easy change between various illumination patterns. 
     In one preferred embodiment, the lighting unit furthermore comprises a light source and the light screen furthermore comprises a diffusion screen, the foil being disposed between the light source and the diffusion screen. In this manner, undesired print artifacts of the foil can be smoothened, such as e.g. superimposed patterns and stripes. 
     Preferably, the light screen has the shape of a funnel opened towards the bottle. In this manner, a sheet-like expanded reflection can be generated on the cylindrical bottle section as well as on the shoulder of the bottle. 
     In one preferred embodiment, the camera is inclined towards the bottom of the bottle, its optical axis including an angle of maximally 80° with the main axis of the bottle. Thus, not only large areas of the molding seam can be imaged, but the lamp reflection also permits a particularly advantageous representation of the shoulder region of the bottle. 
     Preferably, the device further comprises a transport means for the bottle for passing through an image recording region of the camera and a rotating support arranged on the transport means for retaining the bottle. With these, a continuous stream of bottles in various rotational positions can be inspected. 
     Another embodiment comprises a calculation unit for evaluating the detected reflection, for locating the elevations and/or depressions and for determining an actual rotational position of the bottle. Thereby, the bottle can be subsequently moved to a desired rotational position. 
     The one aspect of the invention is moreover achieved by a method for applying the device according to the disclosure, wherein the bottle is illuminated with the light screen, so that the light reflection at least temporarily overlaps the elevations and/or depressions to be detected, and the reflection is imaged with a camera. The superimposition of the structures to be detected with the areas of varying brightness of the light screen causes reflection zones of varying brightness, in particular bright lines on a dark background and dark lines on a bright background. This facilitates the detection of molding seams and embossings. 
     Preferably, the bottle is in the process moved through an image-recording area of the camera while it is rotated about its longitudinal axis, so that the reflection is imaged in various rotational positions of the bottle. Thereby, a continuous stream of bottles in various rotational positions can be inspected. 
     In one preferred embodiment, a calculation unit evaluates the camera images, detects the position of the elevations and/or depressions and determines from these an actual rotational position of the bottle. Thereby, the bottles can be subsequently moved to a desired rotational position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments are represented in the drawing and will be illustrated below. In the drawings: 
         FIG. 1  shows a schematic plan view onto a first embodiment, seen through the cutting plane C-C of  FIG. 2 ; 
         FIG. 2  shows a schematic side view of the first embodiment, seen through the cutting plane A-A of  FIG. 1 ; 
         FIG. 3  shows a schematic front view of the first embodiment, seen through the cutting plane B-B of  FIG. 1 ; 
         FIG. 4  shows a schematic representation of a camera image with a light reflection for detecting elevations or depressions, respectively, on a bottle to be examined; 
         FIG. 5  shows a schematic plan view onto a second embodiment, seen through the cutting plane E-E of  FIG. 6 ; and 
         FIG. 6  shows a schematic side view of the second embodiment, seen through the cutting plane D-D of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As can be seen in  FIGS. 1 and 2 , the inspection device  1  according to the disclosure comprises three cameras  3 , each having an image area  3   a  indicated by a dashed line, for imaging a bottle  7  passing the cameras  3  on a rotating transport means  5  (see arrow G). The cameras  3  are integrated in a lighting unit  9  with a funnel-shaped light screen  11 , several lamps  13  and a safety screen  14 . The bottle  7  is held upright and centered with respect to the main axis  7   a  of the bottle  7  by a rotating support  6 , such as a motor-driven rotary table with a lowerable centering device. Supports  6  for further bottles  7  for examining a continuous stream of bottles are indicated in a dotted line. The drive of the supports  6  is not represented and is symbolized by arrow F. 
     The light screen  11  comprises a diffusion screen  15 , such as an opal glass screen or a translucent plastic screen, on its side facing the bottle  7 , and a foil  17  printed with a colorant  19  in sections of varying intensities on its side facing the lamps  13 . The layer thickness of the colorant  19  is represented in the figures in a highly exaggerated way for a better understanding, where areas of a great layer thickness correspond to areas of low luminance and vice-versa. The light transmission of the colorant  19  repeatedly varies in the horizontal direction along the light screen  11 , so that on the light screen  11 , dark areas  21   a  with a low level of luminance alternate with bright areas  21   b  with a high level of luminance in the horizontal direction. The transition of the luminance from the dark areas  21   a  to the bright areas  21   b  and vice-versa is gradual. It becomes clear in particular from the parallel perspective of  FIG. 3  that the areas  21   a,b  of varying luminance form an essentially vertically oriented stripe pattern  21  on the light screen  11 . 
     As can be further seen in  FIG. 1 , the lighting unit  9  comprises lateral mirrors  22  which are preferably embodied as mirror foils attached to a transparent mirror body  22   a . These reflect light  28  emitted from the light screen  11  towards the bottle  7 . 
     According to  FIG. 2 , the cameras  3  are inclined towards the bottom of the bottle  7   b , its optical axis  3   b  including an angle α of maximally 80° with the main axis  7   a  of the bottle. Here, the camera  3  views through a camera port  23  in the light screen  11  diagonally downwards onto the transitional area of the shoulder of the bottle  7   c  with the cylindrical section  7   d  of the bottle  7 . Thus, with the camera  3 , one obtains the camera image  25  with the light reflection  27  schematically represented in  FIG. 4 , which is a reflected image of the light screen  11  distorted by the bottle  7 . The dark or bright stripes  27   a,b  of the light reflection  27  here essentially correspond to the areas  21   a,b  of the stripe pattern  21 . 
     The reflection  27  contains additional dark and bright stripes  27   a ′ and  27   b ′, respectively, which correspond to the areas  21   a,b  reflected at the mirrors  22 . This proportion of the reflection  27  reflected at the mirrors  22  is schematically indicated by the ray of light  28  in  FIG. 1 . The number of reflected stripes  27   a ′ and  27   b ′ in the reflection  27  depends on the dimensioning of the lighting unit  9  and the distance between the light screen  11  and the bottle  7 . If this distance would be successively increased in the example, the lateral edges of the reflection  27  would migrate inwards, and first the outer stripes  27   b ′, then the adjacent stripes  27   a ′ would be “cut out” of the reflection  27 . 
     In  FIG. 4 , a molding seam  7   e  and an embossing  7   f  are moreover shown which are embodied like a relief and/or as a depression on the bottle  7 . Camera images  25  taken in various rotational positions φ, e.g. at distances of 30° each, are evaluated in a (non-depicted) calculation unit  29  to locate the molding seam  7   e  and/or the embossing  7   f , and in this manner determine an actual rotational position φ I  of the bottle  7 . Normally, the bottle surface  7   c ,  7   d  is completely laid out in front of the cameras  3  for doing so. 
     In the camera image  25 , the contours of the molding seam  7   e  and the embossing  7   f  appear sharply defined, e.g. as bright lines on the dark stripes  27   a,a ′ or as dark lines on the bright stripes  27   b,b ′. In contrast, the transitions between the stripes  27   a,a′,b,b ′ are gradual like the transitions between the areas  21   a,b  of the stripe pattern  21 . This supports band-pass filtering in the evaluation of the camera image  25  for distinguishing between the contours of the molding seam  7   e  or the embossing  7   f  and the stripes  27   a,a′,b,b ′. The stripes  27   a,a′,b,b ′ of the reflection  27  are perspectively distorted with respect to the areas  21   a,b  of the light screen and appear to be compressed due to the essentially cylindrical shape of the bottle  7  in the horizontal direction. 
     The number of dark stripes  27   a,a ′ in the reflection  27  is preferably three to eight. Thereby, the molding seams  7   c  and embossings  7   d  can be equally well detected. Depending on the number of dark areas  21   a  reflected at the mirrors  22  and utilizable in the reflection  27 , the number of the areas  21   a  of the light screen  11  is preferably one to eight, in a particularly advantageous further development of the disclosure two to four. However, the device is not restricted to the respective above mentioned number of dark stripes  27   a,a ′ or  21   a.    
     To be able to detect the molding seam  7   e  as reliably as possible, the stripes  27   a,a′,b,b ′ are oriented essentially in parallel to the molding seam  7   e . However, it is also possible to orient the stripes  27   a,a′,b,b ′ diagonally with respect to the molding seam  7   e , e.g. at an angle of up to 10°. This improves the molding seam detection in the center of the camera image  25 . In such a case, the areas  21   a,b  must be correspondingly disposed obliquely on the light screen  11 , e.g. at angles of up to 10° with respect to the vertical. 
     An “essentially vertically oriented” stripe pattern  21  means that on an upright bottle  7 , the stripe pattern  21  generates a reflection  27  with stripes  27   a,a′,b,b ′ oriented essentially in parallel to the molding seam  7   e  or the main axis  7   a  of the bottle  7 . In a deviating examination position, the orientation of the stripe pattern  21  on the light screen  11  would have to be adapted correspondingly. 
     In general, it is possible to provide other brightness distributions on the light screen  11 , e.g. essentially horizontally oriented stripe patterns or ring patterns, to be able to particularly reliably detect specially shaped elevations and/or depressions on the bottle  7 . 
     The cameras  3  are inclined such that not only large areas of the molding seam  7   e  can be observed in a camera image  25 . Moreover, the reflection  27  is then particularly suited for detecting embossings  7   f  in the shoulder area  7   c  of the bottle. Depending on the bottle shape, the angle α can be, for example, 30 to 80, but also 80 to 90, if required. The reflection  27  preferably completely includes the embossing  7   f  in the vertical direction, so that it can be reliably detected in various rotational positions of the bottle  7 . 
     For an uncomplicated adjustment of the inspection device  1  to different bottle types and/or structures  7   e,f  to be detected, in particular for the height adjustment of the reflection  27 , the lighting unit  9  is preferably embodied to be height adjustable. 
     The device  1  according to the disclosure can be equipped with several cameras  3 , of which the image-recording areas  3   a  overlap laterally, so that the bottle  7  passing the cameras  3  is imaged in various, predetermined rotational positions φ across its complete periphery while it is simultaneously rotated on the support  6 . The number of cameras  3  is not restricted to the shown example. Preferably, the distance between the cameras  3  is minimal to ensure as standardized imaging conditions as possible. 
     The light screen  11  is funnel-shaped and its surface is as large as possible to receive a reflection  27  as large as possible which smoothly passes from the cylindrical part  7   d  of the bottle  7  to the shoulder of the bottle  7 . Thereby, the number of camera images  25  required for a reliable inspection of the bottle  7  can be minimized. 
     The light screen  11  and the foil  17  consist of several, preferably flat segments. This permits an easy integration of the printed foils  17  into the light screen  11 . However, the light screen  11  could also be formed in one piece and/or comprise curved surfaces, such as ellipsoid segments. 
     The gradual transition of the luminance from the areas  21   a  to the areas  21   b  and vice-versa preferably corresponds to a waved pattern, for example a sinusoid. 
     The colorant  19  can be printed on any side of the foil  17 , or else on both sides of the foil  17 . It is also possible to incorporate the colorant into the foil  17 . It is also conceivable to apply the colorant  19  directly onto the side of the diffusion screen  15  facing the lamp  13 . The use of a foil  17 , however, is advantageous in that one can easily change between various stripe patterns  21  to adapt the device to certain bottle shapes and/or structures on the bottle surface. 
     Advantageously, the colorant  19  primarily has an optical absorption effect to form the areas  21   a  with a low level of luminance. However, it would also be possible to form the areas  21   b  with a high level of luminance by means of a fluorescent colorant  19 . The areas  21   a,b  could also be formed by a combination of absorbing and/or fluorescent colorants  19 . 
     The light sources  13  are e.g. LED background lamps. However, other types of lamps can also be used. The arrangement of the light sources  13  is not restricted to the example in  FIGS. 1 and 2 . It is also possible to only use one light source  13  in the lighting unit  9 . 
     As an alternative, the dark and bright areas  21   a,b  could be generated by an illumination of the light screen  11  of varying brightness in sections. To this end, the light sources  13  could be embodied as LED matrix of which the LED elements emit light at different levels of brightness. Depending on the number and size of the elements, these would have to be arranged at a suited distance to the diffusion screen  15 , so that a smoothed illumination pattern  21  with gradual brightness transitions is formed. With this variant, different patterns  21  could also be generated without any modifications. 
     The lighting unit  9  preferably comprises reflecting or highly backscattering inner walls  9   a , such as they are known, for example, from Ulbricht spheres, to increase light efficiency and/or ensure a uniform illumination of the light screen  11 . 
     This improves the quality of the camera images with short exposure times. For this purpose, the lighting unit can also be provided with additional mirrors and/or backscattering dividing walls (not shown). The screen  14  protects the lighting unit  9  from soiling, however, it is not imperative. 
     The transparent mirror body  22   a , in particular in cooperation with reflecting or backscattering inner walls  9   a , causes the light screen  11  to be illuminated from different directions, and thus with an optimally uniform brightness, even in the transitional area to the mirrors  22 . Thereby, dark, sharply defined lines are avoided at the transition from the light screen  11  to the mirror  22  and in the corresponding areas of the reflection  27 , respectively. 
     The transport means  5  is preferably a transport carousel as indicated in  FIGS. 1 and 2 . However, it could also be linear or curved. The senses of rotation F and G of the support  6  and of the transport means  5  are preferably identical, but they could also be contradirectional. 
     Hereinafter, a second embodiment will be described which essentially differs from the first embodiment by an alternative funnel shape of the light screen  11  and by no lateral mirrors  22  being provided. If nothing to the contrary is stated, the other features correspond to those of the first embodiment and are therefore not described again, and some of them are not provided with reference numerals in  FIGS. 5 and 6 . 
     As one can see in  FIG. 5 , the light screen  11  of the second embodiment has a funnel shape also in the plan view. It can be formed, for example, of five flat segments  11   a - e  which each face an examination position of the bottle  7  within the image-recording area  3   a . In the second embodiment, the areas  21   a,b  are not only embodied on the central segments  11   b,d,e , but also on the lateral segments  11   a,c . Therefore, the reflection  27  shown in  FIG. 4  also results when the bottle  7  is irradiated, wherein, however, the stripes  27   a′,b ′ of the first embodiment generated by reflection at the mirrors  22  are replaced in the second embodiment by further stripes  27   a,b  generated by means of direct irradiation of the bottle  7 . Correspondingly, the preferred number of dark areas  21   a  of the light screen  11  is three to eight in the second embodiment. 
     The dark and bright areas  21   a,b  can be inclined to varying degrees with respect to the vertical, depending on the design of the light screen  11 , so that essentially vertically oriented stripes  27   a,b  result in the reflection  27 . In the front view, the stripes  21   a  and/or  21   b  preferably include an angle of maximally 45° with the vertical or the main axis  7   a  of the bottle  7  in the parallel perspective. Suited stripe patterns  21  can be calculated e.g. by ray tracing for a predetermined funnel shape, so that a predetermined reflection  27  results on the bottle type to be examined in the simulation. 
     The features of the described embodiments can be combined. In particular, the design of the light screen  11  is not restricted to the shown examples. For example, the screens could be tilted orthogonally, so that their plan view becomes the side view and vice-versa. Equally, the areas  21   a,b  could be embodied on (non-depicted) bent sections of the light screen  11 . 
     One can work as follows with the inspection device according to the disclosure: 
     A bottle  7  fixed to the support  6  is moved along the transport path  5  into the recording area  3   a  of a camera  3 , while it is simultaneously rotated about its longitudinal axis  7   a . As long as the bottle  7  is within the image area  3   a  of the camera  3 , recordings  25  of the reflection  27  are taken in predetermined rotational positions φ of the bottle  7  or at predetermined intervals, respectively, and these recordings are further processed with an image evaluation in the calculation unit  29 . When the bottle  7  leaves the image area  3   a  of the camera  3  before the total periphery of the bottle  7  could be examined (depending on the transport or rotational speed of the transport means  5  or the support  6 , respectively), the image area  3   a  is followed by at least one further image area  3   a  of a further camera  3  so as to overlap until the total bottle periphery has been detected by the camera recordings  25 . By evaluating the recordings  25  in the calculation unit  29 , the position of a molding seam  7   e  and/or an embossing  7   f  is detected and an actual rotational position φ I  of the bottle  7  or the support  6  is determined, so that subsequently the bottle  7  can be moved to a desired rotational position φ S .