Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Patent
1994-03-14
1995-10-17
Westin, Edward R.
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
25055948, 356239, 356430, G01N 2189
Patent
active
054593301
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
Process and device for the inspection of glass
The invention relates to the field of automatic industrial inspection and more particularly concerns a process, and the corresponding device, for the inspection of glass.
2. Discussion of Background
In a general way, the purpose of the inspection of glass is the detection and the locating of defects, called "inclusions", which are generated in the course of the manufacturing phase in pieces of glass. The effect of these defects on the quality of the glass produced depends on their number, their shape and the standards imposed on the glassmakers according to the application aimed at. These defects are of two types: the material in the molten state; constituents involving the formation of a particle visible within the glass.
The size of these inclusions is in general less than 1 millimeter and the measuring thereof must be carried out with a high precision, at least for certain applications, the precision required possibly ranging from 1/10 to 1/100 of a millimeter.
The automatic detection of these defects is of great importance to glassmakers: a solution to this problem permits both an enhancement of the quality of the glass manufactured (improved compliance with the quality standards) and the availability of reliable statistics on the number and the size of the defects in order to modify, in consequence, the various production parameters of the glass.
The processes of inspection of glass which are currently known are restricted to the visual examination of the glass by a human observer. In fact, attempts to use artificial vision for the inspection of glass have not, up to the present time, given any results since these solutions effect a two-dimensional processing of the information. Accordingly, the corresponding processes do not permit the effective discrimination of the surface defects, dust and scratches, etc. . . . , which are eliminated by a single polishing of the glass, from the inclusions which are concealed in the mass of the glass.
SUMMARY OF THE INVENTION
The subject of the invention is a process for the inspection of glass, and the corresponding device, which permits the avoidance of the disadvantages of the conventional methods by permitting both the locating of the defects at the surface as within the thickness of the glass and an approximate knowledge of their positions within the thickness of the glass; this permits a very good discrimination between surface defects and inclusions.
According to the invention, the inspection process utilizes a three-dimensional processing and for that purpose effects a localized illumination of the glass by a laser beam, and an adapted detection which permits the separate viewing of the upper face of the glass and its lower face and, between the two, its thickness.
According to the invention, a process for the inspection of a glass by illumination by means of a light source external to the illumination surface, characterized in that it consists in illuminating the illumination surface by a laser beam applied in a direction almost perpendicular to the illumination face to form a light curtain in the form of a plane traversing the glass in its thickness, in order to detect by a camera the reflected radiation emerging from the piece of glass in an observation direction which is oblique in relation to the direction of the plane formed by the light curtain when inclusions are present in the glass at the location of the light curtain, and to view, via the camera, the image of the inclusions which is thus obtained, between two lines representing respectively the light beams slightly reflected by the entrance surface and the exit surface of the light beam in the course of its passage within the thickness of the glass.
The subject of the invention is also the inspection device intended to carry out the process as described hereinabove.
BRIEF DESCRIPTION OF DRAWINGS
The invention will be better understood and further features will become evident with the aid of
REFERENCES:
patent: 3652863 (1972-03-01), Gaskell et al.
patent: 4182575 (1980-01-01), Clark et al.
patent: 4568984 (1986-02-01), Juergensen et al.
patent: 4597665 (1986-07-01), Galbraith et al.
patent: 4697082 (1987-09-01), Bartelsen
Le Roy Philippe
Mischler Denis
Venaille Christophe
"Thomson-CSF"
Lee John R.
Westin Edward R.
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