Sheet characterization of crepe paper
The current method relates to an on-line characterization of paper or paper products, such as tissue or other crepe paper products. The method uses an imaging source wherein one or more images are obtained of the sheets surface or topographical area or region, or the image is of an edge of a formed sheet. The one or more images are enhanced and analyzed using various techniques and metrics for characterizing the structure of the formed sheet. The information provides for real time adjustments on the machine.
1. A method of characterizing creped sheet structure comprising:
providing an imaging system comprising one or more imaging or photographic sensors or devices;
generating one or more signals defining one or more images of a region of the creped sheet structure; and
evaluating the generated image taken of the creped sheet structure with a two-dimensional spectral analysis tool using at least one metric to determine crepe ridge characteristics, crepe trough characteristics, characterization of an imposed three dimensional structure, sheet bulk, sheet internal disruptions, and/or free fiber ends of the creped sheet structure.
2. The method according to claim 1 , wherein the creped sheet structure is an imposed three-dimensional structure.
3. The method according to claim 1 , wherein the imaging or photographic sensors or devices comprise one or more cameras configured to render an image of the region of the creped sheet structure being evaluated.
4. The method according to claim 1 , wherein the creped sheet structure has opposite upper and lower surfaces and terminates at an edge, and wherein the region of the creped sheet structure that is imaged is the edge of the creped sheet structure, and/or the upper and/or lower surface of the creped sheet structure.
5. The method according to claim 1 , wherein the method comprises using the two-dimensional spectral analysis tool to determine the frequency of structure in the imaged region of the creped sheet structure.
6. The method according to claim 1 , wherein the method comprises using imaging process techniques to highlight the crepe structure and to draw closed contours around the crepe ridge regions.
7. The method according to claim 1 , wherein the imaged region of the creped sheet structure is evaluated in a machine direction and a cross direction.
8. The method according to claim 1 , wherein the machine direction and cross direction of the creped sheet structure is evaluated using one or more of the metrics selected from the group consisting of region area; region perimeter; aspect ratio as defined by largest dimension/smallest dimension perpendicular to the largest dimension, average length/average width; closed contour perimeter/length; region boundary/width; region area/length; region area/width; elongation shape factor defined as F elongation =(I CD /I MD ) 1/2 , where I CD and I MD are the second moment of inertia in the MD and CD and the second moment of inertia is defined as I x =∫∫x 2 dx dy; compactness shape factor defined as F compactness =Area/[2π(I MD 2 +I CD 2 ) 1/2 ]; radius of gyration defined as R gyration-CD =[I CD /Area] 1/2 and R gyration-MD =[I MD /Area] 1/2 ; convex factor defined as P convex =portion of region perimeter that is convex/total region perimeter; isoperimetric quotient defined as Q=4π region area/region perimeter 2 ; roundness of regions are defined as the variation from a circle, light intensity in regions, light intensity between regions, number of regions in image that is then converted to a frequency number, minimum and maximum heights, vertical distribution of regions by size and shape, frequency of occurrence of long vertical regions, frequency of occurrence of short regions.
9. The method according to claim 1 , wherein crepe ridges and/or around regions in the imposed three-dimensional structure of a creped structured sheet are evaluated within the region of the creped sheet structure being imaged.
10. The method according to claim 1 , wherein the method comprises using the image to determine sheet bulk, sheet internal disruptions, free fiber ends, crepe structure and/or the imposed three-dimensional structure of a creped structured sheet.
11. The method according to claim 1 , wherein the region of the creped sheet structure that is imaged is a machine direction edge of the creped sheet structure.
12. The method according to claim 11 , wherein the method comprises using a two-dimensional spectral analysis tool to determine the frequency of structure in the imaged region of the creped sheet structure.
13. The method according to claim 11 , wherein the method comprises using imaging process techniques to highlight the crepe structure and to draw closed contours around the crepe ridge regions.
14. The method according to claim 11 , wherein the edge region of the creped sheet structure is evaluated using the at least one metric selected from the group consisting of region area; region perimeter; aspect ratio as defined by largest dimension/smallest dimension perpendicular to it, and ii) average length/average width; region boundary/length; region boundary/width; region area/length; region area/width; elongation shape factor defined as F elongation =(I CD /I MD ) 1/2 , where I CD and I MD are the second moment of inertia in the MD and CD and the second moment of inertia defined as I x =∫∫x 2 dx dy; compactness shape factor defined as F compactness =Area/[2π(I MD 2 +I CD 2 ) 1/2 ]; radius of gyration defined as R gyration-CD =[I CD /Area] 1/2 and R gyration-MD =[I MD /Area] 1/2 ; convex factor defined as P convex =portion of region perimeter that is convex/total region perimeter; isoperimetric quotient defined as Q=4π region area/region perimeter 2 ; roundness of regions defined as the variation from a circle, light intensity in regions, light intensity between regions, number of regions in image that is then converted to a frequency number, minimum and maximum heights, vertical distribution of regions by size and shape, frequency of occurrence of long vertical regions, frequency of occurrence of short regions.
15. The method according to claim 11 , wherein crepe ridges are evaluated within the region of the creped sheet structure being imaged.
16. The method according to claim 11 , wherein the method comprises using the image to determine sheet bulk, sheet internal disruptions, free fiber ends, crepe structure and/or the imposed three-dimensional structure of a creped structured sheet.