Fluorescent brighteners in paper can emit visible blue lights or fluorescence after absorbing invisible
UV (ultraviolet) lights and the visible blue lights can increase the whiteness of the paper in the visual
effects. In this paper, we use the enhanced Clapper-Yule model to establish a new predicted reflectance
model for halftone image. The reflective law of halftone image on fluorescent supports is generalized
by utilizing the idea that the reflected light by fluorescent supports is divided into two parts: the
primary streams which consist of originally incident light and the fluorescent streams which are created
by absorption of the UV lights. Firstly, the spectral reflectance of the vacant fluorescent supports and
ink layer on fluorescent supports are analyzed. Secondly, the reflectance and transmittance of ink layer
on fluorescent supports are studied. Then the physical dot gain that results from the real extension of an
ink dot (i.e., ink spreading) is studied. Finally, we establish a reflection and transmission model for a
halftone image on paper with fluorescent additives. To prove the accuracy of the model, we make data
simulation with Matlab software and two reflectance curves (the reflectance of halftone image on paper
with and without fluorescent additives) were generated. From the results, we can make a conclusion
that the new model has a good accuracy to predict the reflectance of halftone image on fluorescent
supports.
In 1931, Kubelka and Munk introduced two-flux Kubelka-Munk model based on radiative transfer
theory[1]. But the model has lots of strict conditions. In 1942, Saunderson introduced revised method,
for there would occur multiple inside reflection in the interface of print, and it would induce density
increase in the ink layer, and influenced prediction precision. Dot gain is always the difficult problem
in print, it includes physics gain and optical gain. Kubelka-Munk model didn't consider dot gain's
effect, especially optical gain. There are many methods to calculate dot gain. Many of them are based
on point spread function principle[5]. Recently, Yang Li corrects the scattering coefficient S and
absorption coefficient K in the Kubelka-Munk model based on statistical physics theory[2][3][4]. This
makes the model has more widely applications. This article, taking into account of oil layer, oil
penetration layer and paper layer respectively, thinking over multiple reflection and optical dot gain,
builds a new halftone color prediction model.
It developped the Kubelka-Munk model and established a prediction model of fluorescence prints.Based on this,it
was developped to the halftone prints and we introduced the scattering probability function which was calculated by the
experience probability model. So we can establish an complete prediction model of halftone fluorescence prints.
Through the analysis of the light scattering within the ink and paper. we provide the fact of the total incident flux
that contains both the collimated flux and the diffuse flux which were caused by the specular reflection and diffuse
reflection on the air-ink interface in the process of color reproduction. Considering the phenomenon of the energy of
these two parts of the flux are changing constantly, the four-flux kubelka-munk model based on the radiative transfer
equation is given. Also, a new four-flux model for calculation of the reflectance of print with rough substrate is
established with the Beckmann-Spizzichino model which describe the reflectance of the incident flux with arbitrary
rough substrate.
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