Abstract
A new approach to the evaluation of formation of paper sheet was performed by image analysis on digital image of mass distribution in the sheet.
To estimate the characteristics of variation in local mass density, the mass co-occurrence matrix was calculated from the digital image of mass density transformed from a soft x-ray image of the paper sheet. The matrix describes joint probability density distribution of mass density (local basis weight) of neighboring two points in the sheet (Fig. 1). The distribution patterns of joint probability density were classified into three types. These were dispersion in radial direction (type A), dispersion parallel to primary diagonal (type B), and dispersion perpendicular to primary diagonal (type C) in the matrix (Fig. 2). The parameters which describe the degrees of dispersion of types A-C quantitatively were also derived from the matrix (Table 1).
For handsheets and a commercial paper, coarseness and contrast of texture were expressed by the degree of type A dispersion. The amount of large flocks was expressed by the degree of type B dispersion, and contrast of fine texture and the amount of small flocks were expressed by the degree of type C dispersion (Fig. 3).
