Image analysis – Applications – Manufacturing or product inspection
Reexamination Certificate
1998-06-24
2001-08-14
Mancus, Joseph (Department: 2623)
Image analysis
Applications
Manufacturing or product inspection
C250S22300B
Reexamination Certificate
active
06275603
ABSTRACT:
The present invention relates to a method as for example disclosed in U.S. Pat. No. 3,777,169, and an apparatus for detecting glass particles in glass bottles filled with a beverage such as beer.
Various methods for detecting foreign particles in a fluid contained in a transparant container have already been proposed. An important category of such methods uses at least one camera to obtain an image from the container and its contents, and an image processing technique is used to process the image obtained by the camera in order to determine whether or not foreign (i.e. unwanted) particles are present in the fluid. In order for the image processing facilities to be able to distinguish between an image obtained from the container on the one hand, and an image obtained from a particle in the fluid, a specific spin/stop technique has been proposed. Herein, the container is firstly made to rotate about its longitudinal axis with a rotation speed and for a time sufficient to cause the fluid in the container to rotate with the container (referred to as “spin”). Secondly, the rotation of the container is abrubtly stopped; the fluid, however, continues to rotate. Subsequently, two images of the container and its contents are obtained, and these two images are subtracted from each other. Since the rotation of the container has stopped, the details in the images which originate from the container will be identical in both images, and will cancel each other by subtraction. On the other hand, the details in the images which originate from the fluid, or from foreign particles in the fluid, will be displaced with respect to each other in both images, such that they will remain visible after subtraction.
For obtaining an image of the container and its contents, various setups have been proposed.
Some of these techniques, as for example disclosed in WO-A-92/14142, can be considered as “transmission mode”: herein, light from a light source travels through the container under investigation, and the camera is disposed opposite to the source, such that the axis of the camera makes an angle of 180° with the axis of the light source. Other techniques can be considered as “reflection back mode”: herein, light from a light source is reflected back by the container and its contents to a camera which is disposed adjacent to the light source, such that the axis of the camera makes a small angle, usually in the range of 0° to 30°, with the axis of the light source.
A variant of these latter techniques can be considered as “reflection sideways mode”: herein, light from a light source is reflected sideways back by the container and its contents to a camera which is disposed such that the axis of the camera makes an angle of substantially 90° with the axis of the light source. Such a setup also is disclosed in U.S. Pat. No. 3,777,169 or in U.S. Pat. No. 4,172,524.
Methods of the above indicated types have been utilized with varying degrees of success in a number of fields, such as the pharmaceutical industry. The present invention is directed to the field of beverages in bottles, and more particular bottles filled with beer. Hereinafter, the invention will be explained with reference to beer, but it is to be kept in mind that the same problems and the same solutions are applicable to other beverages, such that the scope of the invention also extends to such beverages.
An important aspect in the quality control when producing bottles filled with beer is detecting the presence of glass particles. It will be evident that the presence of glass particles in a beverage intended for human consumption is unacceptable, and a bottle containing such particles is to be considered as waste. Even though quality control has been a matter of constant attention in this field, none of the methods of the types described above have proved to be successful in a sufficient degree in the detection of small glass particles in beer. Especially very small particles, in the order of 0.2 mm, have proved to be very difficult to detect: known methods and apparatus and in particular those disclosed in U.S. Pat. No. 3,777,169 and WO-A-92/14142 do not detect these particles with a satisfying degree of certainty and reliability.
The cause of the unsatisfying performance of the methods and apparatus as available today can be attributed to a number of problems which are specifically involved with bottles of beer.
A first category of problems relates to the shape of the bottles. The bottom of a beer bottle, as seen from the inside of the bottle, is not flat or concave, such as in ampules as used in the pharmaceutical or medical field, but is convex. In other words, when the bottle stands upright, its bottom surface has the shape of a hill centered in the bottle. Because of this shape, glass particles tend to collect near the edge of the bottom, i.e. in the corner defined between the foot of said hill and the side wall of the bottle. In this position, glass particles are very difficult to detect in view of the optical characteristics of this portion of the bottle. On the one hand, the glass is curved relatively sharply in this area. On the other hand, the outside bottom is provided with a specific profile near the circumference, referred to as “knurling”, and the bottle shows scuff marks in the lower part of the outside sidewall, often to such extent that this portion of the wall may ultimately be rendered untransparent for the purposes of imaging. This may be further exacerbated by the presence of mould marks from the bottle forming process.
A second category of problems relates to the nature of the fluid in the bottle. Beverages such as beer contain a certain amount of dissolved gas, usually CO
2
, which causes bubbles to be generated when the fluid is disturbed. These bubbles tend to interfere with the optical detection methods. It will be evident that the detection methods should be able to discriminate between unwanted glass particles and CO
2
bubbles, or otherwise too many “correct” bottles will be rejected due to perfectly harmless objects, such as for instance CO
2
bubbles or other dissolved gases.
It is a general object of the invention to provide improved method and apparatus with an improved detection efficiency and reliability for glass particles in bottles filled with a beverage such as beer, in which the above-mentioned problems are overcome.
More particularly, it is an object of the invention to provide such detection method and apparatus suitable for detecting glass particles as small as 0.2 mm. Preferably, the method and apparatus should be able to detect glass particles in the range of 0.2 mm to 10 mm (or larger). In this respect it is observed that the upper limit of the size of the particles which can be expected to be present in bottles at all, is determined by the diameter of the mouth of the bottle.
Yet more particularly, it is an object of the invention to provide such detection method and apparatus capable of meeting the above demends, also suitable for implementation in a production line for producing filled bottles in a product plant without affecting the production speed in a negative way.
It is a further object of the invention to fulfill the above requirements in a cost-efficient way.
The above objectives are obtained by a method of detecting the presence of glass particles in a bottle filled with a beverage such as beer, the bottle (
1
) having a bottom (
4
) with a central, inwardly directed convex portion (
6
); the method comprising the steps of:
a) causing the beverage (
10
) in the bottle (
1
) to rotate with respect to the bottle (
1
);
b) holding the bottle (
1
) stationary with respect to a camera (
40
);
c) illuminating the bottle (
1
) with a light bundle (
31
) impinging on the bottom (
4
) of the bottle (
1
), the direction (
32
) of the bundle (
31
) being substantially aligned with the direction of the central axis (
13
) of the bottle (
1
);
d) directing the camera (
40
), preferably a CCD-camera, such that an optical axis (
41
) of the camera (
40
) makes an angle &agr; in the range of 120°-150°,
Cronshaw Anthony James
Hodges Christopher James
Humphries Mark Robson
Landman Bernardus Cornelis Johannes
Livingstone David
Bali Vikkram
Heineken Technical Services B.V.
Mancus Joseph
Pearne & Gordon LLP
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