Method and device for analysing surface structure in paper or board
First Claim
1. A method for analysing in real-time in a paper machine or board machine the surface structure of a web produced in a paper machine or a board machine, which method comprises:
- that an imaging system is arranged above or below the web and is directed towards a pre-determined area of the web, that an illumination system is arranged above or below the web in order to illuminate the area from a pre-determined direction with obliquely incident light, and that an image analysis system is arranged in association with the imaging system, wherein the method further comprises;
an image capture step in which the imaging system is caused to take several digital images of the web under the said oblique incident illumination and during a pre-determined period, when the web passes in front of the imaging system, which images form an image sequence that images a series of surface sections along a band in the web, and an evaluation step that is carried out by the image analysis system and which comprises an image analysis step, that comprises a first analysis operation in which the variance of the pixel values in each pixel row in each image in the image sequence is determined within a pre-determined wavelength band, and a second analysis operation in which the mean value of the variances of all pixel rows of all images in the image sequence is calculated.
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Abstract
A method for analysing in real-time in a paper machine or board machine the surface structure of a web (1) of paper or board which method comprises the direction of an imaging system towards a pre-determined area (3) of the web (1), the arrangement of an illumination system to illuminate the region from a pre-determined direction with obliquely incident light, and the arrangement of an image analysis system in association with the imaging system. Furthermore, the method comprises, according to the invention, an image capture step (7) in which the imaging system is caused to take several digital images of the web under the said oblique incident illumination and during a pre-determined period, which images form an image sequence that images a series of surface sections (4, 4′, 4″) along a band (8) in the web (1), and an evaluation step (9) that is carried out by the image analysis system and which comprises an image analysis step (11), which in turn comprises a first analysis operation (16) in which the variance of the pixel values in each pixel row in each image in the image sequence is determined within a pre-determined wavelength band, and a second analysis operation (17) in which the mean value of the variances of all pixel rows of all images in the image sequence is calculated. The invention also concerns a device for the execution of the method.
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Citations
9 Claims
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1. A method for analysing in real-time in a paper machine or board machine the surface structure of a web produced in a paper machine or a board machine, which method comprises:
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that an imaging system is arranged above or below the web and is directed towards a pre-determined area of the web, that an illumination system is arranged above or below the web in order to illuminate the area from a pre-determined direction with obliquely incident light, and that an image analysis system is arranged in association with the imaging system, wherein the method further comprises;
an image capture step in which the imaging system is caused to take several digital images of the web under the said oblique incident illumination and during a pre-determined period, when the web passes in front of the imaging system, which images form an image sequence that images a series of surface sections along a band in the web, and an evaluation step that is carried out by the image analysis system and which comprises an image analysis step, that comprises a first analysis operation in which the variance of the pixel values in each pixel row in each image in the image sequence is determined within a pre-determined wavelength band, and a second analysis operation in which the mean value of the variances of all pixel rows of all images in the image sequence is calculated. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A device for the real-time analysis in a paper machine or a board machine of the surface structure of a web of paper or board produced in a paper machine or a board machine, which device comprises:
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an imaging system that is arranged above or below the web and is directed towards a pre-determined area of the web, an illumination system that is arranged above or below the web in order to illuminate from a pre-determined direction the area with obliquely incident light, and an image analysis system that is arranged to be in communication with the imaging system, wherein the imaging system is arranged to take under said illumination and during a pre-determined period several digital images of the web when the web passes in front of the imaging system, which images form a series of surface sections along a band in the web, and the image analysis system is arranged to calculate the variance in the pixel values in each pixel row in each image in the image sequence, and to calculate the mean value of the variances of all pixel rows of all images in the image sequence.
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Specification