Measuring the surface roughness of a moving sheet material
AssigneeDomtar Inc.
InventorsJohn M. Lucas, Serge Gracovetsky
Life of this patent
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Abstract
The invention is concerned with measuring "on-line" the surface roughness of a moving sheet material, e.g. a paper web. The method comprises illuminating the moving web, preferably at a low angle, suitably collecting the light reflected from the moving web and processing the light by means of a sensitive photo-electrical system. The electrical signals thus obtained are divided into an AC and a DC component, the components are separately measured and their ratio used as an index of roughness. An apparatus for carrying out roughness measurements on a moving paper web, e.g. on a paper machine, is described.
Claims12
An apparatus for the on-line measuring of the surface roughness of a moving web which comprises;
- illuminating means for projecting a beam of light obliquely onto the surface of said web;
- collector means disposed to collect scattered light reflected at a non-specular angle from a small area of said surface;
- a support structure adapted to be placed adjacent said surface, said illuminating means and said collector means being fixedly set in said support;
- means providing relative movement between said web and said support thereby to collect reflected light from a multiplicity of small areas sequentially appearing in front of said collector means;
- photoelectric means for converting the light collected from the said small areas into electrical signals;
- and analyzer means for converting said electrical signals into an index of roughness, said analyzer means comprising means for dividing said electrical signals into a direct component and on alternating component and for computing the ratio of said alternating to said direct component, said ratio providing said index of roughness.
A method of measuring the surface roughness of a moving web which comprises;
- projecting a beam of light obliquely onto said surface;
- collecting scattered light reflected at a non specular angle from a small area of said surface;
- continuously moving said web thereby to collect scattered reflected light from a continuous sequence of small areas of said surface;
- converting the collected light to electrical signals;
- analyzing said electrical signals into a direct component and an alternating components;
- computing the ratio of values of said direct and said alternating components said ratio providing an index of roughness.
Dependencies are inferred from the claim text.