Abstract:
To record an image of the mouth area (2) of a bottle (1), a luminous surface (3) is arranged below the mouth area to be recorded. The luminous surface (3) is lighted by means of a lighting device (4) and the image of the lighted mouth area (2) is sent to a camera by a mirror arrangement (5, 6, 11). With the luminous surface, it is possible to image the mouth area in transmitted light, which yields improved detection of defects and soiling in the mouth area and thus permits easier evaluation of the image recorded by the camera.

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     This invention relates to a device for inspecting bottles or the like, with a light source, an image recording element with a respective image analyzing device and a one-piece optical body made of a transparent material. Such a device is known from Unexamined European Patent No. 657,732. The device shown in various modifications in FIGS. 11 through 14 of this document has a ring-shaped optical body with an input and output surface for the optical beam paths. The internal and external ring surfaces of the body are mirrorized, so that an optical beam coming from the bottle is deflected in the direction of the image recording element by reflection after entering the optical body. The required coating of the body on the surfaces provided for reflection is not inexpensive. The optical body becomes useless if the coating is scratched during assembly or operation, and then it must be replaced. Another disadvantage of this inspection device is derived from the fact that the opposing reflective surfaces must be arranged at the same heights, thus requiring a relatively great distance between the imaging body and the side wall of the bottle mouth to be imaged. In addition, the side wall area of the mouth to be inspected can be detected only from an unfavorable angle, so the imaging quality is limited. Furthermore, all the light, even stray light, entering the optical imaging body is reflected. This device is also incapable of label inspection or the like, i.e., checking labels attached to the body of the bottle. 
     SUMMARY OF THE INVENTION 
     Consequently, the object of the present invention is to improve on an inspection device in this regard. 
     This object is achieved by the fact that the one-piece optical body made of a transparent material has a contour designed so that a full-range optical beam path coming from the lighted bottle to be imaged is deflected repeatedly by means of total reflection within the optical body on the path to the image recording element in its passage through the optical body. Because of the design of the body contour causing repeated total reflection of the optical beam, no opaque reflecting surfaces are necessary, so this reduces the manufacturing cost. According to one embodiment of the invention, the surfaces of the optical body causing the total reflection are arranged advantageously at offset heights to one another with at least triple total reflection so that the portions of a bottle to be inspected in the full circumference can be detected from a more advantageous angle. This embodiment is especially advantageous in inspection of a thread. 
     Since mirrorized surfaces are unnecessary, in contrast with the known related art, the peripheral areas of the bottle to be inspected are lighted from above through the optical body, with the advantage that problem-free ring lighting can be achieved, and secondly, undefined beams of light which are unwanted for the inspection are not reflected in the direction of the image recording element when the limiting angle which is definitive for the total reflection is exceeded, but instead such light can escape the optical body to the outside. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments are explained below on the basis of the figures, which show: 
     FIG. 1a is a vertical section through an optical body for the mouth side wall inspection of bottles, especially with a screw thread; 
     FIG. 1b is a second embodiment of an optical body with which it is also possible to inspect the inside wall, the bottom and the mouth sealing surfaces of transparent bottles; 
     FIGS. 1c through 1e is an optical body corresponding to FIG. 1a with a second concentric optical body in three different embodiments, and 
     FIGS. 2a through 2d is a vertical section through an optical body for imaging the side wall of a bottle. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The rotationally symmetrical body 4 shown in FIG. 1a is arranged coaxially below a CCD camera 2 pointing down. The image is recorded at the moment when an empty bottle 1 to be inspected with its vertical axis 1&#39; is briefly aligned essentially with the optical axis of the camera 2 and the axis of symmetry of body 4 during its continuous conveyance. The image is analyzed by using an electronic analyzer 2&#39; by means of which the bottles imaged are then classified as &#34;good&#34; or &#34;bad&#34; accordingly. 
     The empty bottle 1 which is open at the top and is made of a transparent material is lighted by a light source 3a, which is arranged beneath the bottom of the bottle, or by a light source 3c positioned at the side next to the bottle wall section to be inspected. Furthermore, the corresponding bottle wall section can be lighted at an oblique angle from top to bottom or vice versa, from bottom to top through light sources 3c and 3d placed above or below the mouth of the bottle. Since optical body 4 does not have any mirrorized surfaces, the light source 3d needed for lighting from above may also be arranged above the optical body, and, since it is outside the linear bottle conveyance path there, it is ideally designed in a ring shape in the manner of a toroidal body. Thus, a uniform lighting can be achieved over the entire circumference, especially the mouth area for inspection of the sealing surfaces. 
     The different lighting variants mentioned above can be used not only as alternatives but also in suitable combinations, depending on the properties of the bottle (contour, etc.) and the areas to be inspected. If light cannot be shone through the bottles, light is directed in the incident lighting method is provided by light sources 3b through 3d, and then the bottom light source can be omitted. 
     The optical beam S shown in FIG. 1a is determined by the selected contour of optical body 4 which has three inclined sectional surfaces B, C, D such that an optical beam S coming from the mouth side wall of bottle 1, directed obliquely from bottom to top, entering body 4 made of glass or a plastic such as acrylic will be deflected a total of three times by total reflection on surfaces B, C, D, finally emerging from body 4 at the top and converging, then traveling on to camera 2. It is self-evident that the inclination of the three above-mentioned surfaces B, C, D with respect to the incident optical beam S is selected so that the angle does not drop below the limiting angle which depends on the material and is definitive for the total reflection. Especially useful images can be achieved when the angle of inclination of the middle axis of the optical beam section striking the mouth area is in a range of 15 to 30 degrees, based on the horizontal mouth area, especially 27 degrees. 
     Due to the fact that the first surface section B is arranged at a lower level than the second surface section C, which also lies on the outside surface, the lower edge of the rotationally symmetrical disk body 4, which is in the form of a hollow truncated cone, extends right up to the mouth of bottle 1 to be inspected, so it is possible to take a mostly side image of the mouth side wall area which has a screw thread, i.e., the optical beam 5, which diverges to the full extent from the mouth of the bottle, forms an acute angle with the horizontal. Owing to the inclination of the optical beam entry surface A, which is located in the lower area of body 4, and outside surface section B, the body 4 has a blade-shaped lower edge, as seen in cross section. 
     The inside surface labeled as A on the lower edge of the body is oriented at a right angle to the central axis of the optical beam S coming from the side wall of the mouth of the bottle, i.e., the plumb line of the entry surface A is aligned with the axis of the optical beam. This prevents refraction in the transition from the optically less dense medium to the optically denser medium. For the same reason, the outlet surface E which is on the top side of body 4 and faces camera 2 is also inclined so that it is passed perpendicularly upward in the direction of the camera by the emerging beam. 
     Furthermore, optical body 4 has two opposing, inclined, parallel surface sections G and F on its inside and outside contour; they are arranged with respect to the mouth of the bottle so that in the case of lighting of the mouth with a light source 3d arranged above body 4, a portion of the emitted light can pass through body 4 normal to surface sections G and F aligned in the direction of the mouth of the bottle, essentially without any refraction. 
     If a bottom light source 3a is used, but no bottom inspection of the bottle is necessary or is not to take place in conjunction with the inspection of the side wall of the mouth, an opaque disk 5 may be used in the hollow space of body 4 above the surface section G, so that the light coming vertically from the bottom of the bottle and passing upward through the inside cross section of the mouth will not reach the lens of the camera. 
     In this last point mentioned above, the variant of body 4 illustrated in FIG. 1b is different; in this variant, inspection of the inside wall, the bottom and the mouth sealing surface can take place simultaneously with inspection of the thread by means of bottom lighting, where recording of the image of the full extent of the mouth side wall takes way in the same manner as in the embodiment illustrated in FIG. 1a. In the variant according to FIG. 1b, there is no opaque disk at the center of the body, so that light bundle SZ coming out of the mouth of the bottle and the mouth sealing surface can pass vertically upward through body 4 to camera 2 unhindered. In contrast with the embodiment in FIG. 1a, body 4 according to FIG. 1b has two horizontal parallel surfaces H and I on the inside and outside of its upper central part through which the vertical beam of light SZ imaging the mouth and the bottom of the bottle can pass essentially without refraction. As shown in the figures, the surface sections A, B, C, D, F and G which have a circular curvature in the circumferential direction have straight surface lines. 
     The variants shown in FIGS. 1c through 1d differ from the embodiments in FIGS. 1a and 1b in an additional body 4&#39; attached concentrically in the interior of body 4, e.g., with adhesive. FIG. 1c shows light coming light source 3a upward out of the mouth of the bottle is reflected by body 4&#39; which is also made of an opaque material by being reflected twice on two conical body surfaces K and L so that it strikes the mouth sealing surface obliquely from above and lights it optimally. 
     Body 4&#39; in FIG. 1d is shaped so that light coming upward out of the mouth of the bottle and its sealing surface is reflected to the camera on three body surfaces K, L and M by total reflection in each case. FIG. 1e shows a body 4&#39; which serves to inspect a supporting ring 10 in the area below the mouth. The full-range optical beam ST formed by total reflection twice has an optimal angle of incidence for detecting cracks, chips or codes on the supporting ring. The optical beams can be deflected toward a camera at the side by a ring wheel shaped mirror 11, so that the bottle can be lighted from above, through the hole in the middle of the mirror. 
     FIG. 2a shows an optical body 14 whose geometry and inside and outside contours are designed so that the side wall of the bottle is imaged completely over its entire height. At the same time, as in the embodiment according to FIG. 1b, the bottom of the bottle and the mouth sealing surface can be inspected for damage or soiling by using appropriate lighting. To this end, a centrally oriented optical beam SZ running vertically is directed through the center of body 14 to the camera 2. As in the embodiment according to FIG. 1b, the optical body has a horizontal section in the center with parallel surfaces H and I for the optical beam SZ coming from the mouth of the bottle, so that it images the sealing surface of the mouth and the bottom of the bottle in camera 2. Here again, there is essentially no refraction in the passage of the optical beam through the parallel surfaces H and I. 
     As in the embodiments described above, the beam inlet and outlet surfaces A and E with the optical body 14 illustrated in FIG. 2a are arranged so that an optical beam S encompassing the side wall of the bottle passes through these surfaces perpendicularly, i.e., essentially without refraction. In passage through optical body 14, optical beam S is reflected twice by total reflection on an outside surface of the body and on an inside surface of the body (unmirrorized), where a beam S running obliquely upward from the outside wall of the bottle, after entering the optical body 14, is then reflected first radially inward by the outside surface C to the second inside surface D, where it is again reflected upward to a CCD camera 2. The bottle can be lighted from the bottom and/or the side. The two surfaces C and D have a circular curvature in the circumferential direction, but they have straight side lines. With body 14, the entire outside wall of the bottle can be projected to the full extent onto camera 2, where it is imaged as a circle. The image is then analyzed in the traditional manner to detect damage or soiling. 
     As an alternative, there is the possibility of designing the optical body 14 in the form of a truncated pyramid, so that the surfaces causing the total reflection consist of several flat component surfaces offset in the circumference. With such a contour or geometry, it is possible to minimize the imaging errors caused by distortion, which cannot otherwise be avoided entirely with curved surfaces. This design can also be applied to the optical body 4 illustrated in FIGS 1a and 1b. 
     FIG. 2b shows an especially advantageous application of body 14, where certain quality features on the cylindrical surface of the bottle, which may be at any location on the circumference, can be detected in a controlled manner with the least effort on the basis of the full-extent imaging of the cylindrical surface of the bottle, without having to align the bottle before recording the image, as has been the case in the past, e.g., for inspecting the closure of a clip-lock bottle (see European Patent 512,539 B1). Body 14 projects the entire shoulder surface of an opened clip-lock bottle onto camera 2, whose image analyzing device then determines first the position of the bottle closure 20 from the circular image and then checks for the presence of a rubber sealing ring 21. As already explained in conjunction with FIGS. 1a and 1b, the lighting can be provided by suitable lighting elements 3c, 3d from the side or from above. The bottles to be inspected can easily be conveyed continuously in any rotational position beneath the body 14 by a plate conveyor or the like. 
     Labels can also be inspected in the same way to detect misaligned, missing or defective labels, i.e., those with an inverted logo or bar code (FIG. 2c). Here again, the entire lateral surface is recorded here first to the full extent to determine the position of the labels from the circular image. For this task, the correct position, shape and alignment of the labels with regard to the vertical axis of the bottle, the loco and the bar code of the labels can be given to the image analyzing device as preset values. The light can in turn be provided by lighting bodies 3c, 3d, 3e, 3g from the side or from above. 
     According to FIG. 2d, with the help of body 14, with a filled bottle made of a transparent material, it is also possible to inspect the filling level 30, which appears as a circular line between two circular rings 31, 32 with a difference in brightness in the figure. This filling level inspection is also possible to advantage even when there is a label in the area of the filling level, covering the bottle only partially, where the circumferential area without a label is used for image analysis.