Method and apparatus for measuring the crepe of a moving sheet
First Claim
1. A computer implemented method for measuring crepe pattern features on a surface of a moving sheet that comprises the steps of:
- (a) illuminating an area on at least one side of the sheet with radiation and forming an optical image of the illuminated area using at least one lens with the proviso that no stabilizer to constrain the moving sheet to a narrow path is required;
(b) obtaining and recording at least one digital image of the optical image of the illuminated area by employing an image detector wherein the digital image comprises a plurality of pixels and a pixel in the digital image represents a dimension in the moving sheet that does not exceed one quarter the nominal crepe pitch of the moving sheet so that the crepe pattern features can be discerned; and
(c) calculating the crepe pattern features of the sheet by processing at least one digital image by evaluating at least one spectrum on a linear section through the digital image wherein the at least one spectrum represents physical spacing of the crepe pattern features that are discerned from the digital image wherein the crepe pattern features are characterized as at least one of;
(i) an average folding pitch, (ii) a distribution of folding pitches, (iii) an average folding length, (iv) a distribution of folding lengths, and (v) a distribution of folding angles.
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Abstract
An image-based measurement technique that directly measures the crepe pattern on a moving sheet employs a suitable arrangement of illumination, optical elements, and an imaging device to obtain digital images of the sheet surface. The image resolution is sufficient to represent tissue crepe folds at the scale of the crepe. A spectral analysis of some or of all the images reveals the crepe folding pitch. Further analysis of the image optionally reveals other crepe structural parameters, such as the distribution of crepe fold orientation angles and distribution of linear fold lengths. Corrective actions can be implemented in response to changes in the crepe structure. The pitch of creping is the primary parameter for describing the crepe pattern; in addition, analyzing the images with a gradient operator can yield information regarding the orientation of the crepe folds and distribution of angles of the crepe furrows on the hood side or equivalently of the crepe seams on the cylinder side.
69 Citations
37 Claims
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1. A computer implemented method for measuring crepe pattern features on a surface of a moving sheet that comprises the steps of:
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(a) illuminating an area on at least one side of the sheet with radiation and forming an optical image of the illuminated area using at least one lens with the proviso that no stabilizer to constrain the moving sheet to a narrow path is required; (b) obtaining and recording at least one digital image of the optical image of the illuminated area by employing an image detector wherein the digital image comprises a plurality of pixels and a pixel in the digital image represents a dimension in the moving sheet that does not exceed one quarter the nominal crepe pitch of the moving sheet so that the crepe pattern features can be discerned; and (c) calculating the crepe pattern features of the sheet by processing at least one digital image by evaluating at least one spectrum on a linear section through the digital image wherein the at least one spectrum represents physical spacing of the crepe pattern features that are discerned from the digital image wherein the crepe pattern features are characterized as at least one of;
(i) an average folding pitch, (ii) a distribution of folding pitches, (iii) an average folding length, (iv) a distribution of folding lengths, and (v) a distribution of folding angles. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A computer implemented method for measuring crepe pattern features on a surface of a moving sheet that comprises the steps of:
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(a) illuminating an area on at least one side of the sheet with radiation and forming an optical image of the illuminated area using at least one lens with the proviso that no stabilizer to constrain the moving sheet to a narrow path is required; (b) obtaining and recording at least one digital image of the optical image of the illuminated area by employing an image detector wherein the digital image comprises a plurality of pixels and a pixel in the digital image represents a dimension in the moving sheet that does not exceed one quarter the nominal crepe pitch of the moving sheet so that the crepe pattern features can be discerned; and (c) calculating crepe folding of the sheet by processing at least one digital image with a gradient operator that produces a gradient magnitude and direction for at least one of the pixels. - View Dependent Claims (25, 26)
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27. A system for measuring crepe pattern features on a surface of a moving sheet that comprises:
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means for forming an optical image of an illuminated area on the surface of the moving sheet that includes at least one lens with the proviso that no stabilizer to constrain the moving sheet to a narrow path is required; image obtaining means, that includes an image detector, for obtaining and recording at least one digital image of the optical image of the illuminated area on the moving sheet wherein the digital image comprises a plurality of pixels and a pixel in the digital image represents a dimension in the moving sheet that does not exceed one quarter the nominal crepe pitch of the moving sheet so that the crepe pattern features can be discerned; and control means for calculating the crepe pattern features of the sheet by processing the at least one digital image wherein the control means evaluates at least one spectrum on a linear section through the digital image wherein the at least one spectrum represents physical spacing of the crepe pattern features that are discerned from the digital image wherein the crepe pattern features are characterized as at least one of;
(i) an average folding pitch, (ii) a distribution of folding pitches, (iii) an average folding length, (iv) a distribution of folding lengths, and (v) a distribution of folding angles. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
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Specification