Color Prediction Model For Prints

With the fast development of modern society, an increasing number of prints need to recto-verso printing, such as books, newspapers, magazines and so on, so the quality detect and control of recto-verso prints become more serious. So in the color reproduction process, accurately predicting the color of recto-verso prints and establishing a spectral reflectance model for halftones prints are the great concern project of printing quality control field.In the process of print quality detection and control, the reflecting, absorbing and scattering of light within paper substrate, the spreading and penetration of ink are the key factors, which affect the color prediction of prints. In order to predict the spectral reflectance of recto-verso halftone images, we considered the scattering of light within paper and the ink penetration in the substrate and proposed the color spectral reflectance precise prediction model for recto-verso halftone prints. The paper based on the assumption that the colorant is non-scattering medium, the paper is strong scattering. By the multiple internal reflection of light between the paper substrate and the print-air interface, and the light along oblique path of the Williams-Clapper model, we proposed the color spectral reflectance precise prediction model of recto-verso halftone prints. The model take into account the multiple reflections and the lateral propagation of light within the paper substrate and the spreading of the inks according to their overprint conditions with one or several solid inks. The model includes nominal-to-effective dot area coverage functions for each of the different ink overprint conditions by the least square curve fitting method, so the functions for physical dot gain of various overprint halftones are given.Finally, we design an experimental method to measure the parameters of our model. In the experiment, we tested the model with offset printer on coated paper, with 501 samples on the verso of the paper and 22 samples on the recto. The result show that the average and maximum color difference between measured and predicted reflectance spectra is 0.92 dE and 3.1dE, respectively. It turned out that the modeled and the measured colors agree very well, confirming the validity of the used model. The model provide a theoretical foundation and a product manufacturing instruction for color prediction analysis of recto-verso halftone images and the development of prints quality detection system.