Optics: measuring and testing – By inspection with agitation or rotation – Of containers
Reexamination Certificate
1999-09-29
2001-02-06
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By inspection with agitation or rotation
Of containers
C356S240100
Reexamination Certificate
active
06184988
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to devices for monitoring the quality of silk-screen printing on plastic or glass bottles of any shape.
In the known art this monitoring is effected by video cameras arranged to photograph individual images of the object to be inspected in successive positions, and compare them with a like number of reference images to determine any discrepancies.
In particular, the known devices for monitoring print quality on bottles of circular cross-section comprise a number of successive inspection stations, in each of which a video camera photographs the image of the bottle to be inspected in a determined position.
If the device comprises two stations the bottle is rotated through 180° prior to the second station, so that by placing the two acquired images side by side an image of the entire bottle surface is reconstructed, this then being compared with the reference image.
If there are three image inspection stations, the bottle has to be rotated through 120° prior to each station following the first.
It is also known that the photographic image of a circular or otherwise non-flat object presents distortions commencing from the centre plane. These distortions are greater the smaller the radius of curvature of the object surface, and the larger the lens opening angle, for equal distances between the object centre and the lens. Consequently the known devices have the drawback of lack of photographic accuracy in proximity to the lateral portions of the image.
In the known art this drawback is reduced by providing at least four inspection stations each comprising its own video camera, and means for rotating the object through 90° between one station and the next, but this in addition to being complicated is also of high cost.
SUMMARY OF THE INVENTION
The object of the present invention is to overcome the stated drawbacks within the framework of a flexible, rational and low-cost solution.
This object is attained according to the invention by a device for determining the quality of silk-screen printing on objects which comprises only one image inspection station provided with a single video camera and, upstream of the inspection station, an initial positioning station for the bottle to be inspected.
Specifically, the invention uses a single video camera arranged to acquire at least two successive images of the bottle while this is rotated at constant speed by suitable means within the single inspection station.
Said images are acquired by known means, each image being acquired after each rotation of the bottle through an angle equal to 360° divided by the total number of images to be acquired.
The invention also comprises upstream of the inspection station a positioning station in which the bottle is positioned with the desired orientation relative to a fixed angular reference device. This is achieved by suitable means for sensing a fixed reference device positioned on the bottle and arranged to interact with it to position the bottle with the required orientation.
The acquired images are then compared with a reference image to evaluate any print imperfections. The invention is also provided with selector means arranged to separate those bottles presenting imperfections from those judged perfect during inspection.
REFERENCES:
patent: 0516968 (1992-12-01), None
patent: 0802054 (1997-10-01), None
Birch & Stewart Kolasch & Birch, LLP
Font Frank G.
O.M.S.O. S.p.A.
Punnoose Roy M.
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