Optics: measuring and testing – Inspection of flaws or impurities – Transparent or translucent material
Reexamination Certificate
1999-11-30
2001-10-16
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
Inspection of flaws or impurities
Transparent or translucent material
C356S240100, C356S239600, C250S22300B
Reexamination Certificate
active
06304323
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for detecting a defect in a bottle based on an imaging technology, and more particularly to a method for detecting a refractive defect in a barrel portion of the bottle.
2. Description of the Related Art
Defects in a barrel portion of a glass bottle are classified into shading defects which block applied light to prevent the light from passing therethrough and refractive defects which refract applied light. The applicant of the present application has proposed a method of detecting both shading defects and refractive defects as disclosed in Japanese patent publication No. 6-90150. According to the disclosed method, a light shield plate (referred to as an obliquely slit plate in the specification) having a plurality of oblique slits is positioned between a source of diffused light and a bottle under test. Diffused light from the source passes through the light shield plate and the barrel portion of the bottle, producing an image of a striped pattern. The image of the striped pattern is scanned to compare the levels of brightness at three closely positioned spots in the image for flaw detection.
If the bottle suffers large wall thickness variations, then the striped pattern tends to be so irregular that it is difficult to detect defects in the barrel portion of the bottle. The inventors of the present invention have made efforts to develop a method of processing images of irregular striped patterns particularly for the detection of thin blisters among different types of blisters which are one kind of refractive defects. The thin blister refers to a blister in the form of a thin lens on a surface of the glass bottle or in the glass bottle.
Further, the inventors of the present invention have made efforts to develop a method of processing images of irregular striped patterns particularly for the detection of longitudinal streaks. The longitudinal streak refers to a linear recess that appears partly in the longitudinal direction of the bottle.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide a method for detecting a defect, which is referred to as a thin blister, in a barrel portion of a bottle.
It is a second object of the present invention to provide a method for detecting a defect, which is referred to as a longitudinal streak, in a barrel portion of a bottle.
In order to accomplish the first object, according to a first aspect of the present invention, there is provided a method for detecting defect in bottle, comprising: imaging a barrel portion of a bottle with a CCD camera based on light which has passed through a light shield plate having a plurality of oblique slits and the barrel portion; generating a binary image having a striped pattern of bright and dark areas within a window having a certain area from an image of the barrel portion generated by the CCD camera; scanning the binary image in a longitudinal direction of the barrel portion to generate a labeled image in which labels are assigned to the bright and dark areas of the striped pattern, respectively; and scanning the labeled image in a longitudinal direction of the barrel portion to determine a defect in the barrel portion if there is a label which is not in contact with any one of sides of the window or if one label appears more than a preset number of times along a scanning line.
With the above method, the barrel portion of the bottle is imaged by the CCD camera, and a generated image of a striped pattern is processed into a binary image having a striped pattern of bright and dark areas. In the binary image, a defect in the form of a thin blister is represented by an image of branched stripes or an isolated stripe. Then, a labeled image in which labels are assigned to the bright and dark areas of the striped pattern is produced from the binary image. Thereafter, the labeled image is scanned to determine an image of branched stripes or an isolated stripe for thereby detecting a thin blister if there is a label which is not in contact with any one of sides of the window or if one label appears more than a preset number of times along a scanning line.
In order to accomplish the second object, according to a second aspect of the present invention, there is provided a method for detecting defect in bottle, comprising: imaging a barrel portion of a bottle with a CCD camera based on light which has passed through a light shield plate having a plurality of oblique slits and the barrel portion; generating a binary image having a striped pattern of bright and dark areas within a window having a certain area from an image of the barrel portion generated by the CCD camera; scanning the binary image in a longitudinal direction of the barrel portion to determine the number of successive bright or dark pixels along a first scanning line; determining the number of area-changing points where a bright area changes to a dark area or a dark area changes to a bright area between a start point and an end point of pixels which are equal to the successive pixels whose number has exceeded the first preset number along the first scanning line, along a second scanning line which precedes the first scanning line by a second preset number, if the determined number of successive bright or dark pixels exceeds a first preset number; and determining the presence of a defect if the determined number of area-changing points is equal to or greater than a third preset number.
With the above method, the barrel portion of the bottle is imaged by the CCD camera, and a generated image of a striped pattern is processed into a binary image having a striped pattern of bright and dark areas. In the binary image, a defect in the form of a longitudinal streak is represented by a longitudinal succession of bright or dark pixels. The number of successive bright or dark pixels along a first scanning line (L) is determined from the binary image. If the determined number of successive bright or dark pixels exceeds a first preset number (K
1
), then the number of area-changing points where a bright area changes to a dark area or a dark area changes to a bright area is determined between a start point and an end point of pixels which are equal to the successive pixels whose number has exceeded the first preset number (K
1
) along the first scanning line (L), along a second scanning line (L′) which precedes the first scanning line (L) by a second preset number (K
2
). If the determined number of area-changing points is equal to or greater than a third preset number (K
3
), then the distance between adjacent stripes along the second scanning line (L′) is normal, and a defect in the form of a longitudinal streak is present along the first scanning line (L). If the determined number of area-changing points is smaller than the third preset number (K
3
), then the distance between adjacent stripes along the first and second scanning lines (L and L′) is normal, and a defect in the form of a longitudinal streak is not present along the first and second scanning lines (L and L′).
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate a preferred embodiment of the present invention by way of example.
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patent: 4701612 (1987-10-01), Sturgill
patent: 4831250 (1989-05-01), Fukuchi et al.
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patent: 5004909 (1991-04-01), Fukuchi
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patent: 5471297 (1995-11-01), Tani
patent: 0 344 617 (1989-12-01), None
patent: 0 491 555 (1992-06-01), None
Fukuchi Hiroyuki
Ishikura Tohru
Miwa Yasuo
Kirin Techno-System Corporation
Nguyen Sang H.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Rosenberger Richard A.
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