Visualization of paper structure by optical coherence tomography: Monte Carlo simulations and experimental study

This paper analyzes the capability of an optical coherence tomography (OCT) setup to visualize paper structure by comparing experimental and Monte Carlo (MC) simulated OCT images. In the experiments, we used an OCT setup at 910 nm with the coherence length of an SLD source of 7.5 μm. Several different refractive index matching agents were applied to paper samples to enhance the visualization of their inner structure. The obtained OCT images show improved contrast in inner structure and enhanced visualization depth. A set of corresponding simulations were then performed using a previously developed MC code. A multilayer paper sheet model with non-planar fiber-air interfaces was developed to characterize the paper samples. MC simulations were carried out to study the effect of the setup parameters on the obtained OCT images. A comparison with the experimental data shows that the developed model provides a satisfactory correspondence between simulated and experimental images.