Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1988-03-11
1990-02-06
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356387, G01N 2186
Patent
active
048990612
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a method and apparatus for determining a dimension of an article such as the width or thickness of a plate or slab produced in a steel mill.
SUMMARY OF THE INVENTION
The invention may be said to reside in a method of determining a dimension of an article, the method comprising the steps of viewing two points on the article with a sensing device, the two points being displaced by a known relationship, using the known relationship and the two viewed points to determine the location in space of one of the points, and using the absolute location in space of another point determining the dimension of the article between the one point and the another point.
The invention may also be said to reside in an apparatus for determining the dimension of an article, the apparatus comprising two sensing device each sensing one of two points on the article which are displaced by a known relationship, a processing device for resolving the location in space of one of the two points and for determining the distance between one point and another point to enable a dimension of the article to be determined.
The another point could be a known fixed point. However according to the preferred embodiments of the invention, the another point is determined by viewing a second pair of points including the another point, the second pair of points being displaced by a further known relationship and determining the location in space of the another point from the viewed second pair of points and the further known relationship.
Preferably two sensing device each view one of the first two points and a further two sensing device each view one of the second two points. However only two sensing device could be used with one sensing device viewing one of the first two points and one of the second two points and the other sensing device viewing the other of the first two points and the other of the second two points. In one embodiment of the invention the two pair of points, which are displaced by a known distance, can comprise points at the edges of a generally rectangular cross-sectioned article, and in a second embodiment, the pairs of points can be points on an arc of a circle of a curved portion of the article.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiment of the invention will be described with reference to the accompanying drawings in which:
FIG. 1 is a view of the first embodiment of the invention;
FIG. 2 is a view of a second embodiment of the invention;
FIG. 3 shows a third embodiment; and
FIG. 4 shows one preferred manner of making calculations according to the preferred embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to FIG. 1 a system is shown for determining the width W of a plate or slab of a generally rectangular cross-section. The system comprises a first sensor means comprising a first linescan camera 10 and a second linescan camera 12. Located at the other end of the plate or slab S is a second pair of linescan cameras (which are not shown). The linescan camera 10 views the point A at the top edge of the slab S and the linescan camera 12 views the point B at the bottom edge of the slab S. The slab S could be hot enough to provide illumination for the cameras 10 and 12 or a back light (not shown) could be utilized.
The points A and B are displaced by the known thickness T of the slab S and are assumed to be vertically displaced, one above the other. Since the thickness T of the slab S is known and the points A and B are vertically displaced, a computing apparatus 5 coupled to the linescan cameras 10 and 12 can resolve the location of point A in space from the images in the cameras. The other pair of linescan cameras (not shown) at the other end of the slab S resolve the location of a corresponding point A at the top edge of the slab in a similar manner. Since the location in space of two points at the edges of the slab S are known, the distance between the two points can be determined by simple geometry to enable the width W of the slab to be
REFERENCES:
patent: 4319270 (1982-03-01), Kimura et al.
patent: 4381152 (1983-04-01), Riech et al.
Van Hoek Hendrik C.
Williams Daryl N.
Nelms David C.
The Broken Hill Proprietary Company Limited
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