Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1994-10-03
1996-01-30
Evans, F. L.
Optics: measuring and testing
By polarized light examination
With light attenuation
356371, 25055922, G01B 1130, G01B 1124
Patent
active
054884780
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of determining the shape of objects and to apparatus for use therewith. More especially, the invention concerns methods of and apparatus for determining the manifest flatness of sheets and strips of metallic material, e.g. steel.
Steel strip and sheet (hereinafter referred to collectively as "steel strip") is conventionally produced by hot or cold rolling a semi-finished product (eg a bar) in a multi-stand rolling mill. The flatness of steel strip so produced is, of course, potentially of importance to the end user. The measurement of strip flatness is, however, hindered by the high operational speeds of conventional rolling mills. There is, consequently, a need for a method of and apparatus for rapidly measuring the flatness of the strip leaving a rolling mill.
One technique which has been commonly employed is that of illuminating the strip with a laser generated light beam and observing the position of the beam on the strip with a television area camera. The computing power required to analyse a television picture rapidly is, however, considerable and costly. Also, with less rapid computing power, the interval between measurements is likely to be much longer than is desirable to provide a true indication of flatness.
It is an object of the present invention to provide a method of and apparatus for rapidly measuring the shape of an object, especially the manifest flatness of a strip of steel or other material.
According to a first aspect of the present invention there is provided apparatus for measuring the shape of a surface of an object, the apparatus being characterised by laser means operable to direct onto a surface of an object moving relative to the laser means a plurality of light beams spaced one from another in the direction of movement of the object to produce on the object surface a plurality of light patterns which extend across the object in a direction generally normal to the direction of movement of the object, scanning means for scanning the laser-generated light beams continuously across the object surface in a direction generally normal to the direction of movement of the object, and an array of line-scan cameras positioned to view and record the said light patterns and to process in parallel the recorded data to provide a measure of the shape of the object surface. Scanning may be effected by rotating or oscillating mirror assemblies. These assemblies may comprise mirror galvanometers.
The images recorded by the individual line-scan cameras of the array may be processed in parallel each to provide a measure of the height of that part of each light pattern viewed by that camera above a reference plane.
In another aspect there is provided apparatus for for measuring the shape of a surface of a metal object moving over a support surface, the apparatus being characterised by laser means operable to direct onto the surface of the moving object a plurality of light beams, means operable to produce from these laser-generated light beams a plurality of light patterns each of which extends across the width of the object and is spaced from the other light patterns in the direction of object movement, scanning means for scanning the laser-generated light beams continuously across the object surface in a direction generally normal to the direction of movement of the object, an array of line-scan cameras extending across the width of the object and positioned to view and record the said light patterns, and to process in parallel the recorded data to provide a measure of shape of the object surface.
In a further aspect, there is provided a method of measuring the shape of a surface of an object moving over a support surface, the method being characterised by the steps of directing onto a surface of an object a plurality of laser-generated light beams to produce on that surface a plurality of light patterns which extend across the object surface in a direction generally normal to the direction of movement of the object, scanning the laser-generated light beams conti
REFERENCES:
patent: 4846576 (1989-07-01), Maruyama et al.
patent: 4929846 (1990-05-01), Mansour
patent: 5056922 (1991-10-01), Cielo et al.
patent: 5251010 (1993-10-01), Maltby, Jr.
Bullock John D.
Williams Norman W.
British Steel PLC
Evans F. L.
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