Spectral Neugebauer-based color halftone prediction model accounting for paper fluorescence

Abstract

We present a spectral model for predicting the fluorescent emission and the total reflectance of color halftones printed on optically brightened paper. By relying on extended Neugebauer models, the proposed model accounts for the attenuation by the ink halftones of both the incident exciting light in the UV wavelength range and the emerging fluorescent emission in the visible wavelength range. The total reflectance is predicted by adding the predicted fluorescent emission relative to the incident light and the pure reflectance predicted with an ink-spreading enhanced Yule-Nielsen modified Neugebauer reflectance prediction model. The predicted fluorescent emission spectrum as a function of the amounts of cyan, magenta, and yellow inks is very accurate. It can be useful to paper and ink manufacturers who would like to study in detail the contribution of the fluorescent brighteners and the attenuation of the fluorescent emission by ink halftones.

A Texture-Hidden Anti-Counterfeiting QR Code and Authentication Method

“…Since the printing device can only print black and white, the continuous gray tone image must be processed into a binary halftone image in the printing process, and the unit coverage area of small black and white dots that human eyes cannot distinguish is used to simulate the gray level change of the image so that the binary image looks as close as possible to the original image. In this paper, the error diffusion method proposed by [ 33 ] is adopted for the halftone processing of texture images, that is, every pixel in the image and its neighboring pixels are processed, and the error (the difference between the actual output and the original image) generated on a pixel is dispersed to the surrounding pixels in a certain proportion. After the above operation, is obtained.…”

Theory, Modeling, and Simulation of Printing

“…Assuming opacity in the excitation wavelength band and introducing an equivalent scalar transmittance t 0 j of the Neugebauer primaries (NP) in the excitation band, Hersch (2014) derived an extension of the spectral Neugebauer model expressing the total reflectance factor R tot from measurement of the substrate and NPs in one illumination without excitation radiation and in one illumination with excitation radiation: where R tot s is the reflectance factor of the substrate in an illumination including the excitation wavelengths, R * s is the reflectance factor of the substrate in an Figure 19.6 Subdomain of a 3-colorant space. The incident light is first partly absorbed by the ink dots before it changes wavelength due to the fluorescence process and is finally partly absorbed at that longer wavelength by the ink dots.…”

“…However, for spectral reflectance prediction purposes in one defined illumination, applying the classical YNSN model calibrated with measurements including fluorescence excitation leads to similar accuracy (Hersch, 2014). The YuleeNielsen model is applied with a factor n to account for the lateral light propagation within the substrate (optical dot gain).…”

Spectral gamut mapping and ink separation with fluorescing substrates

“…Assuming opacity in the excitation wavelength band and introducing an equivalent scalar transmittance of the Neugebauer Primaries (NP) in the excitation band t j , Hersch [6] proposed an extension of the spectral Yule-Nielsen modified Neugebauer model [4] expressing the total reflectance factor from measurement of the substrate and NPs in one illumination without excitation radiation and in one illumination with excitation radiation:…”