Abstract: A method includes, using at least one processing device, obtaining an image of a web of creped tissue paper and identifying a caliper measurement of the web using the image. The caliper measurement is based on a dominant frequency of the web and a standard deviation of diffusely-reflected light from the web. The dominant frequency of the web can be based on a number of crepe folds having a dominant crepe fold size that fit within a specified unit distance of the web in the image. The dominant crepe fold size can be determined using a discrete auto-covariance function of the image or a second image of the web. The standard deviation can be based on a variation of reflected light from larger crepe structures in the web.

Abstract: A method includes, using at least one processing device, obtaining an image of a surface having a texture and identifying a dominant size of the texture using a discrete auto-covariance function of the image. A first positive local maximum of the discrete auto-covariance function could be identified. The discrete auto-covariance function could include points associated with positive numbers of whole pixels, and the first positive local maximum of the discrete auto-covariance function could be identified at one of the points. Sub-pixel estimation could also be performed using the point associated with the first positive local maximum and one or more neighboring points. Performing the sub-pixel estimation could include fitting a polynomial curve to the point associated with the first positive local maximum and the one or more neighboring points and identifying a number of whole and fractional pixels associated with a maximum of the polynomial curve.

Abstract: A method includes receiving multiple biased measurements associated with a property of a sheet of material, where the biased measurements correspond to multiple known sheet geometries. The method also includes determining an unbiased measurement associated with the property of the sheet using the biased measurements, where the unbiased measurement corresponds to a nominal sheet geometry. The method further includes storing and/or outputting the unbiased measurement. Determining the unbiased measurement could include performing regression using the biased measurements and their corresponding sheet geometries to identify an estimated value of the property of the sheet at the nominal sheet geometry. The biased measurements can be generated using one or more sensors, and the sheet may not be stabilized during the biased measurement generation. Additional sheet geometries can also be created, such as by varying a tilt angle, a curvature, and/or a position of the sheet.

Abstract: A method includes, using at least one processing device, obtaining an image of a surface having a texture and identifying a dominant size of the texture using a discrete auto-covariance function of the image. A first positive local maximum of the discrete auto-covariance function could be identified. The discrete auto-covariance function could include points associated with positive numbers of whole pixels, and the first positive local maximum of the discrete auto-covariance function could be identified at one of the points. Sub-pixel estimation could also be performed using the point associated with the first positive local maximum and one or more neighboring points. Performing the sub-pixel estimation could include fitting a polynomial curve to the point associated with the first positive local maximum and the one or more neighboring points and identifying a number of whole and fractional pixels associated with a maximum of the polynomial curve.

Abstract: A method includes, using at least one processing device, obtaining an image of a web of creped tissue paper and identifying a caliper measurement of the web using the image. The caliper measurement is based on a dominant frequency of the web and a standard deviation of diffusely-reflected light from the web. The dominant frequency of the web can be based on a number of crepe folds having a dominant crepe fold size that fit within a specified unit distance of the web in the image. The dominant crepe fold size can be determined using a discrete auto-covariance function of the image or a second image of the web. The standard deviation can be based on a variation of reflected light from larger crepe structures in the web.

Abstract: A method for fluidisation of a pulp flow in the headbox of a paper machine or such. The characteristics of the pulp flow are affected in the headbox's fluidiser (14) in one step only, whereby the height (h1) of the step is at least equal to the average fibre length, and after the fluidiser (14) the biggest permissible step expression in the flow channel in direction z is smaller than the average fibre length.

Abstract: A headbox (10) has a stock inlet header, a tube bank, a tubulence generator and a slice channel. Measurement targets (PA, PB, PC, P, PE) are provided with means for making measurements of the fiber mobility of the fiber suspension, then controlling the flow state of the suspension. Sensors on the width of the headbox (10) or traversing sensors are positioned on different width points of the headbox (10) and arranged to measure the fiber mobility profile, with means for changing the flow state on the basis of the measurements. Apparatus for diluting the thick stock into headbox consistency and units for cleaning the stock to be fed into the headbox may be provided. Sensors may be disposed in the short circulation pipes or cleaning units arranged to measure the fiber mobility of the fiber suspension with means for changing the flow state on the basis of the measurement data.