Abstract:
An apparatus for detecting blisters in a container wall includes a light source for directing light energy onto a container wall in such a way that portions of the light energy are reflected from surfaces of the container wall, including surfaces of blisters in the container wall. A light sensor is disposed to receive light energy reflected from the container wall, and an information processor is coupled to the sensor to detect a blister in the container wall as a bright image against a darker background. Light energy reflected from the inner and outer surfaces of the container wall preferably establish the darker background, and light energy reflected from surfaces of blisters within the container wall establish the bright image.

Description:
[0001]     The present invention is directed to inspection of containers for commercial variations that affect optical properties of the containers, and more particularly to an apparatus and method for detecting blisters and/or embossments in the sidewalls of glass containers.  
       BACKGROUND AND OBJECTS OF THE INVENTION  
       [0002]     In the manufacture of containers such as glass bottles and jars, various types of anomalies can occur in the sidewalls, heels, bottoms, shoulders, necks and/or finishes of the containers. These anomalies, termed “commercial variations” in the art, can affect commercial acceptability of the containers. It has been proposed to employ electro-optical inspection techniques for detecting commercial variations that affect the optical properties of the containers. The basic principle is that a light source is positioned to direct light energy onto the container, and a light sensor is positioned to receive an image of a portion of the container illuminated by the light source. An information processor is coupled to the sensor to detect commercial variations in the container as a function of the light energy received at the sensor.  
         [0003]     Blisters can be envisioned as air pockets in a container wall, which can arise for various reasons during the container manufacturing process. It has been proposed to detect blisters in container walls by transmitting light through the container walls and detecting the blisters as a function of refraction of the light at the edges of the blisters. See U.S. Pat. Nos. 5,233,186 and 5,243,400. However, this technique can be problematic for large flat blisters, in which the edges are relatively small. It is a general object of the present invention to provide an apparatus and method for enhanced detection of blisters and/or embossments in a container wall.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention involves a number of aspects, which can be implemented separately from or more preferably in combination with each other.  
         [0005]     An apparatus for detecting blisters in a container wall, in accordance with one aspect of a presently preferred embodiment of the invention, includes a light source for directing light energy onto a container wall in such a way that portions of the light energy are reflected from surfaces of the container wall, including surfaces of blisters in the container wall. A light sensor is disposed to receive light energy reflected from the container wall, and an information processor is coupled to the sensor to detect a blister in the container wall as a bright image against a darker background. Light energy reflected from the inner and outer surfaces of the container wall preferably establish the darker background, and light energy reflected from surfaces of blisters within the container wall establish the bright image. The container preferably is rotated around an axis, and the information processor preferably scans the light sensor at increments of container rotation. The light sensor preferably is a linear array light sensor having an axis parallel to the axis of rotation of the container, and the light source preferably is a diffuse light source. The linear array sensor preferably is disposed to receive light energy from a central portion of the diffuse light source reflected from interior and exterior surfaces of the container.  
         [0006]     An apparatus for detecting embossments on a container wall, in accordance with another aspect of the presently preferred embodiment of the invention, includes a light source for directing light energy onto a container wall in such a way that portions of the light energy are reflected from surfaces of the container wall, including surfaces of embossments on the container wall. A light sensor is disposed to receive light energy reflected from the container wall, and an information processor is coupled to the sensor to detect an embossment on the container wall as a dark image against a brighter background. Light energy reflected from the inner and outer surfaces of the container wall preferably establish the brighter background, and light energy reflected from surfaces of embossments on the container wall establish the dark image.  
         [0007]     An apparatus for detecting blisters and embossments in a container wall, in accordance with a further aspect of the presently preferred embodiment of the invention, includes a light source for directing light energy onto the container wall in such a way that a portion of the light energy is reflected from surfaces of the container wall, including surfaces of blisters in the container wall and surfaces of embossments on the container wall. A light sensor is disposed to receive light energy reflected from the container wall. An information processor is coupled to the light sensor to detect a blister as a bright image and an embossment as a dark image against an otherwise gray background of reflections from the container wall. In the preferred embodiment in accordance with this aspect of the invention, the gray background is established by light energy reflected from the inner and outer surfaces of the container wall. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The invention, together with additional objects, features, advantages and aspects thereof, will best be understood from the following description, the appended claims and the accompanying drawings, in which:  
         [0009]      FIG. 1  is an electro-optical schematic diagram in side elevation that illustrates an apparatus for detecting blisters and/or embossments in a container sidewall in accordance with one presently preferred embodiment of the invention;  
         [0010]      FIG. 2  is an electro-optical top plan schematic diagram of the optical portion of the apparatus in  FIG. 1 ;  
         [0011]      FIG. 3  is an enlargement of a portion of the apparatus as illustrated in  FIG. 2 ;  
         [0012]      FIGS. 4, 5  and  6 A to  6 C are fragmentary schematic illustrations of portions of  FIG. 3  for explaining operation of the invention;  
         [0013]      FIGS. 7A-7D  are graphic illustrations useful for explaining operation of the invention;  
         [0014]      FIG. 8  is a fragmentary side elevational view of an exemplary container wall that can be inspected in accordance with the present invention;  
         [0015]      FIG. 9  is a fragmentary view of a display of blisters and embossments on the container sidewall of  FIG. 8  as detected by the apparatus of  FIGS. 1-3 ; and  
         [0016]      FIG. 10  is a fragmentary electro-optical schematic diagram of a modification to the embodiment of  FIGS. 1-3 . 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0017]      FIGS. 1-3  illustrate an apparatus  20  for inspecting the sidewall of a container  22  in accordance with one presently preferred embodiment of the invention. Containers  22  preferably are brought to an inspection station, at which apparatus  20  is located, by means of a suitable conveyor  23  that presents the containers  22  in sequence for inspection. Suitable conveyors are disclosed in U.S. Pat. Nos. 4,378,493 and 6,581,751. Containers are presented in sequence for inspection, and are coupled to a suitable device  24  for rotating each container  22  around an axis of rotation, which preferably is coincident with the central axis of the container. Suitable drive roller devices  24  are disclosed in the U.S. Patents noted immediately above. A diffuse light source  26  is positioned to direct light energy onto the exterior surface of container  22 . Light energy reflected from the surfaces on and within the container sidewall is received at a camera  28 . Camera  28  includes an entrance lens system  30 , through which the reflected light energy is directed through an entrance pupil onto a light sensor  32 . Light sensor  32  preferably comprises a linear array light sensor having a long dimension or axis parallel to the axis of rotation of container  22 . Thus, the axis or long dimension of linear array sensor  32  extends from top to bottom in  FIG. 1 , and into the page in  FIG. 2 . An area array sensor could be used in place of a linear array sensor, from which a selected column of sensor elements would be employed for detection of blisters and/or embossments.  
         [0018]     An information processor  34  is coupled to camera  32  for scanning information from sensor  32 . Information processor  34  is also coupled to container rotation device  24  for controlling rotation of container  22  at the inspection station, and for scanning sensor  32  at increments of container rotation. Such increments of container rotation may comprise equal angular increments of container rotation, or equal time increments during which container  22  is rotated at constant velocity. Information processor  34  is coupled to a display  36  for displaying inspection data to an operator ( FIGS. 7A-7C  and  9 ), and to a suitable reject mechanism for removing containers  22  that do not pass inspection.  
         [0019]      FIG. 3  illustrates interaction between diffuse light source  26  and container  22  in greater detail. Light energy from source  26  is incident on the outer surface of container  22  over an angular portion of the container surface, and at an angle such that a bundle of light rays is reflected from surfaces of the container sidewall, including the surfaces of blisters within and embossments on the container sidewall. A chief reflection ray  40  is illustrated in  FIG. 3  (and  FIGS. 1-2 ). The term “chief ray” has its usual meaning in the art, and refers to the ray directed toward the center of the entrance pupil of lens  30  at camera  28  ( FIGS. 1 and 2 ). It will be understood that each chief ray  40  is surrounded by a cone of rays that will be accepted through the entrance pupil of the camera lens and focused onto light sensor  32 . However, the present invention is illustrated in the drawings and discussed hereinafter in connection with the chief reflection rays for purposes of simplification. It will be noted in  FIG. 3  that the chief ray  40  preferably is generated by reflections of light energy emanating from the central portion of diffuse light source  26 .  
         [0020]      FIG. 4  illustrates reflections of light energy from a container sidewall without blisters or embossments. Each ray  42 ,  44  from light source  26  is incident on the outer surface of the container sidewall, and is partially reflected from and partially refracted into the container sidewall. The light energy that enters the container sidewall is incident on the inside surface of the sidewall, and is partially reflected from and partially refracted through the inside surface. In the specific situation illustrated in  FIG. 4 , the portion of ray  42  reflected from the inside surface of the container sidewall is refracted at and emerges from the outside surface of the container sidewall at the point of incidence of ray  44  onto the outside surface of the container sidewall. Thus, reflected chief ray path  40  directed toward sensor  32  includes the portion of ray  44  reflected from the outer surface of the container sidewall, and the portion of ray  42  refracted into the container sidewall, reflected from the inside surface of the container sidewall, and refracted at the outside surface of the container sidewall. (Not all reflections and refractions are shown in  FIG. 4 , or in  FIGS. 5-6C , for purposes of simplicity.)  
         [0021]      FIG. 5  illustrates refractions and reflections for detecting a blister  54  within the container sidewall. Four rays  46 - 52  are shown incident on the container sidewall from light source  26 . Blister  54  has air/glass surfaces at which reflections and refractions occur. As in  FIG. 4 , a portion of each light ray will be reflected from each surface of the blister and a portion (depending upon the angle of incidence and the index of refraction of the glass) will be refracted at each surface of the blister. A portion of light ray  46  illustrated in  FIG. 5  is refracted at the outer surface of the container sidewall, refracted again at the outer surface of blister  54 , refracted a third time at the inner surface of blister  54  and then reflected from the inside surface of the container sidewall. This reflected portion of light ray  46  is again refracted at the inner surface of blister  54 , at the outer surface of blister  54  and at the outer surface of the sidewall to form a portion of light ray  40  directed toward sensor  32 . The portion of light ray  48  that forms part of ray  40  is refracted at the outer surface of the container sidewall and at the outer surface of blister  54 , reflected from the inner surface of blister  54 , refracted at the outer surface of blister  54  and at the outer surface of the container sidewall, and emerges from the container sidewall. Likewise, the portion of ray  50  that forms part of ray  40  is refracted at the outer surface of the container sidewall, reflected from the outer surface of blister  54  and refracted at the outer surface of the container sidewall. The portion of ray  52  that forms part of ray  40  is reflected at the outer surface of the container sidewall. (Directional words such as “inner,” “outer,” “inside” and “outside” are employed by way of description and not limitation with respect to the axis of container  22 . Directional words such as “upper” and “lower” are employed by way of description and not limitation with respect to the upright orientation of the container illustrated in  FIG. 1 .) Thus, the presence of blister  54  ( FIG. 5 ) in the container sidewall, as compared with the absence of such a blister ( FIG. 4 ), means that additional light energy will be reflected from the container sidewall as part of chief ray  40  directed to the sensor. Thus, as a general proposition, the presence of a blister  54  in the container sidewall increases the amount of energy directed onto the sensor.  
         [0022]      FIGS. 6A-6C  illustrate operation in connection with an embossment  56  on the outside surface of the container sidewall.  FIGS. 6A-6C  show reflections along the path of chief ray  40  from three different points on an embossed surface feature  56  as the bottle rotates slightly in the direction  58  between views  6 A and  6 B, and again between the views of  FIGS. 6B and 6C . Whether the sensor  32  ( FIGS. 1 and 2 ) receives one or more reflected rays depends upon where on the embossed feature the light sensor is focused and upon the angular extent or size of the light source. For example, in the container position of  FIG. 6A , chief reflection ray  40  would include a portion of incident ray  60 , but not ray  62  unless the diffuse light source  26  ( FIGS. 1-3 ) is very wide. In  FIG. 6B , chief ray  40  directed to sensor  32  would include a portion of ray  60  and a portion of ray  64  reflected from the outside surface of the embossment  56 . In  FIG. 6C , the chief reflected ray  40  would include a portion of ray  66 , but would only include a portion of ray  68  if the diffuse light source were very wide. Thus, as a general proposition, the presence of an embossment  56  on the surface of the container  22  tends to diffuse or scatter the incident light energy from the light source. Light energy directed onto the sensor typically is either the same as or less than the light energy directed onto the sensor in the absence of an embossment or a blister ( FIG. 4 ).  
         [0023]     Thus, as a general proposition, the presence of a blister in the container sidewall increases the amount of light energy directed onto a sensor  32 , whereas the presence of an embossment on the surface of the container sidewall reduces the amount of light energy directed onto the sensor. This is graphically illustrated in  FIGS. 7A-7D  and  9 . It will be appreciated that  FIGS. 4-6C  illustrate operation in only one plane and in association with only one reflected chief ray  40 . There will be an infinite number of chief rays  40  within the vertical field of view ( FIG. 1 ) of sensor  32 .  
         [0024]      FIGS. 7A-7D  are each a graphic illustration of reflected light intensity versus axial position along a container for one scan along the container and at a particular angular position of the container. In each illustration, the ordinate indicates light intensity while the abscissa indicates vertical axial position on the container.  FIG. 7A  illustrates the results of scanning a container at an angular position having no blisters or embossments. Light intensity  70  at sensor  32  is generally uniform as a function of vertical axial position on the container.  FIG. 7B  illustrates the additive effect of reflections  72 ,  74  from blisters in the container sidewall. In other words, reflections  72 ,  74  are superimposed on the generally uniform light energy  70  of  FIG. 7A .  FIG. 7C  illustrates the subtractive effect of embossments on the container surface, with reductions  76 ,  78  due to embossments as compared with the generally uniform level  70  of  FIG. 7A .  FIG. 7D  illustrates the cumulative effect of both blisters and embossments in the container sidewall.  
         [0025]      FIG. 8  is a fragmentary elevational view of a container  22   a  having sidewall blisters  54   a ,  54   b  and  54   c , and surface embossments  56   a ,  56   b  in the form of decorations or logos molded into the container sidewall.  
         [0026]      FIG. 9  is a graphic illustration of a display at  36  in  FIG. 1  from inspecting the container of  FIG. 8 . The graphic illustration of  FIG. 9  depicts two full rotations of container  22   a  ( FIG. 8 ). In the display of  FIG. 9 , which depicts nearly two full revolutions, and with the intensity level  70  ( FIGS. 7A-7D ) having no blisters or bubbles establishing a mid level or gray intensity background, blisters  54   a , 54   b , 54   c  appear as bright images against the gray background due to the additive reflection effect of the blisters previously discussed, while embossments  56   a ,  56   b  appear as dark images against the gray background due to the subtractive reflective effect of embossments previously discussed.  
         [0027]      FIG. 10  illustrates a modification to the embodiment of  FIGS. 1-3 , in which a vertical check detection light source  80  is positioned to direct light energy through the container sidewall onto the portion of the container illuminated by light source  26  from interiorly of the container. A vertical check  82  in the container sidewall, which is a minute vertically oriented crack in the container sidewall, functions as a mirror and reflects light energy along the path of chief ray  40 . Check detection light source  80  may be as disclosed in U.S. Pat. No. 4,584,469 or 5,637,864. Information processor  34  ( FIG. 1 ) can readily distinguish between vertical checks in the container sidewall and blisters in the container sidewall by the angular dimension of the reflection. In other words, in the unwrapped image of the container sidewall ( FIG. 9 ), a vertical check will have a relatively small horizontal (container rotation) dimension as compared with a blister.  
         [0028]     There thus have been disclosed a method and apparatus that fully satisfy all of the objects and aims previously set forth. The invention has been disclosed in conjunction with two presently preferred embodiments thereof, and a number of modifications and variations have been discussed. Other modifications and variations readily will suggest themselves to persons of ordinary skill in the art. The invention is intended to embrace all such modifications and variations as fall within the spirit and broad scope of the appended claims.