Image Evaluation and Analysis of Ink Jet Printing System (I): MTF Measurement and Analysis of Ink Jet Image

In this study, the modulation transfer functions of prints, which included both mechanical and optical dot gain effects were measured from samples printed by an ink jet printer on glossy-coated, matt-coated and uncoated papers. The MTF of prints were measured from sinusoidal patterns and Fourier transforms of line spread functions from one-pixel line and step images. The MTF of print from three measurement methods were analyzed and compared. The one-pixel line method was chosen to compare MTF of prints from different type of papers and printing directions. In addition, MTF of papers were also measured by contact sinusoidal pattern on papers. The point spread function of ink on each paper was estimated by using the measured point spread function of paper in the reflection image model. The results showed that glossy-coated ink jet paper had low MTF of paper but high MTF of print. Finally, printed densities of ink jet images were predicted using the estimated point spread function of ink and measured point spread function of paper. Because the spread function of ink was estimated as having a gaussian distribution, which is not correctly represented the real point spread function of ink jet printing, and therefore the predicted density did not fit well with the measured density.