Diffusion of the Laser Radiation to Characterise the Paper Fibre Orientation and the Paper Sheet Formation

This work concerns the determination of fiber orientation in the paper sheet and possibly the mass density distribution. Both parameters strongly influence the quality of the paper for end uses in printing and converting. The measurement of such parameters is done using different approaches, most commonly indirectly from the determination of the paper's physical properties. The measurement and analysis of the microscopic features of the paper sheet structure, using optical methods based on the laser radiation retro-diffusion and transmission, are the main aims of this work. The proposed method only uses laser light scattered by retro-diffusion from the paper surfaces for surface analysis and the laser light transmitted through the paper for analysis in the bulk. The system can analyze through a scanning procedure point-by-point, one paper sheet to produce a map of both paper surfaces with the selected results