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Method and device for analysing surface structure in paper or board

  • US 7,510,629 B2
  • Filed: 06/28/2004
  • Issued: 03/31/2009
  • Est. Priority Date: 07/08/2003
  • Status: Expired due to Fees
First Claim
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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:

  • 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, andthat 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, andan 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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