A large number of optical properties in paper and print are determined by measuring the light reflected from an illuminated paper surface.
These measurements are interpreted through a model, and the one that has been in use in the paper industry since the 1930s is deficient in some respects.
“We discovered that this is because the light is reflected in different amounts in different directions in an unexpected way. Our new model can explain and cope with this,” says researcher Per Edström.
What made this new discovery possible is his research into numerical methods for effectively solving a class of integro-differential equations. This is a type of problem that has applications in such diverse spheres as the greenhouse effect, medical tomography, and light diffusion in diffuse media.
“The methods Per Edström has developed are not only original. They have also been shown to be robust, accurate, and extremely effective,” says Professor Mårten Gulliksson.
Developmental work has involved collaboration with several companies in the paper industry. There has been a great interest since increased knowledge in this field means greater competitiveness.
“We have already started to use the new model,” says Nils Pauler at M-Real’s Research Center in Örnsköldsvik in Sweden. “We hope it will help us understand different variations in the visual impression made by paper and print.”
“It should be pointed out that Per Edström’s dissertation involves a tremendously broad spectrum of subject areas. From an advanced formulation of the physical problem in mathematical form, which is extremely well rooted in applications, he develops a stable and effective software that can be directly put to use by the industry with great success. This is an impressive achievement that is seldom witnessed in the field of mathematics.”
These are the concluding remarks of Professor Mårten Gulliksson.
The dissertation is titled ”Mathematical Modeling and Numerical Tools for Simulation and Design of Light Scattering in Paper and Print.”