Smoothness of the surface and runnability are the most important parameters to describe paper quality in the print industry. The smoothness defines printability, while the runnability is defined by the tear strength that is needed for the winding of the paper. Variance of paper thickness, creases and inhomogeneous tear strength impair the runnability. The main reason for these problems is a non-homogeneous distribution of fibres and fillers inside the paper.

The rate of rejected paper could be drastically reduced by the use of an online measurement system for this distribution. Additionally, with better homogeneity the paper thickness could be reduced without reducing the tear strength, which results in a better mass efficiency.

The goal of my Ph.D. project is the development of an online measurement system based on Fourier-domain Optical Coherence Tomography (FD-OCT) that allows continuous surveillance of the paper’s internal structure during the production process. Closed loop control of production parameters based on the acquired information should then help to enhance efficiency and constant quality by regulating smoothness and runnability.