Apparatus and process for measuring formation and roughness of a paper web

Apparatus for the on-line continuous detection of the formation of a moving paper web comprising:

• a formation light source disposed opposite one side of the plane of the moving paper web for illuminating an area of said paper web, said area including four adjacent portions;
• optical means disposed opposite the other surface of said paper web for directing illumination from said area onto a focal plane;
• illumination detector means in said focal plane for receiving said illumination and producing signals proportional to the intensity thereof, said illumination detector means comprising four adjacent sectors corresponding to said four adjacent portions in said illuminated area of said paper web, two spatially adjacent sectors corresponding to two spatially adjacent portions in said illuminated area of said paper web;
• signal processing means responsive to said illumination detector means for determining the root-mean-square of the quotient resulting from the difference in received illumination intensity from said two spatially adjacent portions in said illuminated area of said paper web in said focal plane and the sum of the received illumination intensity from said four adjacent portions in said illuminated area of said paper web in said focal plane;
• and
• display means connected to said signal processing means for providing a continuous indication of the formation of the paper web.

Apparatus for selectively determining the roughness of one surface of a moving paper web or the formation of the paper web comprising:

• a roughness light source directed at an oblique angle to said surface with respect to a plane through said surface of the moving paper web for illuminating an area including four adjacent portions;
• a formation light source substantially orthogonally disposed opposite the opposite surface of the moving paper web for illuminating said area including four adjacent portions when said roughness light source is not operating;
• optical means disposed opposite the side of said surface of the moving paper web illuminated by said roughness light source for directing illumination from said area onto a focal plane;
• an illumination detector means in said focal plane for receiving said illumination produced by either said roughness light source or said formation light source and producing signals proportional to the intensity thereof, said illumination detector means including four adjacent sectors, two spatially adjacent sectors corresponding to two spatially adjacent portions of said illuminated area of the moving paper web;
• signal processing means responsive to said illumination detector means for determining the root-mean-square of the quotient resulting from the difference in received illumination intensity from said two spatially adjacent portions of said illuminated area of the moving paper web in said focal plane and the sum of the received illumination intensity from said two spatially adjacent portions and two additional adjacent portions of said illuminated area of the moving paper web in said focal plane;
• and
• display means connected to said signal processing means for providing a continuous indication of either the surface roughness or the formation of the moving paper web.

Process for selectively detecting either the formation or the surface roughness of a moving paper web comprising:

• illuminating an area of the moving paper web at a location along its path of movement either by transmitted light from one side of and through the moving paper web or by reflected light at an oblique angle to the plane of the surface on the other side of the moving paper web;
• directing illumination from said area onto a focal plane;
• measuring said illumination in the focal plane and producing signals proportional to the intensity thereof;
• processing said signals to determine either the formation or the surface roughness of the moving paper web;
• and
• continuously displaying the resulting determination of either the formation or the surface roughness of the moving paper web.

Process for making and testing a web of paper to determine its formation comprising:

• preparing a continuous web of paper;
• conveying the web of paper past a light source for illuminating an area on one side of the paper web at a location along its path of movement;
• directing illumination transmitted through said area onto a focal plane on the other side of the paper web;
• measuring said illumination in the focal plane and producing signals proportional to the intensity thereof;
• processing said signals to determine the root-mean-square of the quotient resulting from the difference in received illumination intensity from two spatially adjacent illuminated portions of the web of paper in said focal plane and the sum of the received illumination in said focal plane from said two spatially adjusted illuminated portions of the web of paper and at least one additional illuminated portion adjacent said two spatially adjacent illuminated portions of the web of paper;
• and
• continuously displaying the resulting determination of the formation of the web of paper.