Efficient and Accurate MTF Measurement for Spatially Non- uniform Paper

摘要

The conventional Koopipat's method was modified to measure the modulation transfer function (MTF) of spatially non-uniform paper. First, we analyzed and removed the non-uniform characteristic caused by the fiber structure of paper. Secondly, in order to calculate the paper MTF. the edge spread function (ESF) was analyzed using the edge part of a neutral density (ND) filter superposed on paper. A microscope which can illuminate paper from front or back side was used to measure the ESF. Gans' method was used to calculate the Fourier transform of ESF. MTFs were measured for three types of paper: uncoated paper, coated paper and glossy paper, whose graininess levels are high, normal and low, respectively. As a result of the experiment, regardless of graininess level, the MTFs were measured efficiently and accurately. The measured MTF was applied to predict reflectance distribution of monochrome inkjet images from transmittance distribution. We conclude that our method is effective to simulate inkjet printing since the RMSE and difference of average reflectance between the measured and predicted data were low.