Online measurement of quality variables in paper: formation and creping

In this paper, two novel techniques developed by the authors to measure certain quality variables in paper manufacturing are described. These methods are based on the new online image sensors for digital image processing of paper samples. The techniques use the two dimensional Fourier transform of the original images to estimate basically two variables: the floc size distribution in paper formation and creping of tissue paper. In the first case, a new method to estimate the floc size distribution in paper is presented. The method computes only a reduced portion of the spectrum to determine, in frequency, the floc sizes present. The technique to measure creping gives the degree of roughness that has been induced on the tissue paper by looking also at its power spectra distribution. This characteristic is essential in determining the smoothness of tissue paper.<>