Application of Turbid Medium Theory to Paper Spread Function Measurements

It is becoming increasingly important in printing systems to expand the accuracy of imaging models; e.g. Neugebauer and structured dot. More complex models must ultimately include the spread of light within the paper structure (paper optical spread function). Paper makers have successfully used Kubelka-Munk (K-M) turbid medium theory for defining the tradeoffs of paper properties such as opacity and reflectivity. A theoretical analysis and a series of measurements are described that relates the scattering and absorbing coefficients, K and S, from the K-M theory to paper spread functions and their Fourier Transforms, the paper MTF. The results show that the paper MTFs of coated papers, not conforming to the assumptions of K-M theory, are poorly described by the theoretical MTF. So called plain papers, such as newsprint, copying and typewriter bond, are well described by the K-M MTF at low spatial frequencies.