荧光纸基的双面彩色半色调印刷品Clapper-Yule正面反射率模型

目的研究荧光纸基对双面彩色半色调印刷品反射率的影响。方法假设油墨与纸张的折射率相似,考虑到荧光部分可以吸收光线中不可见的紫外光,经过能量转换散发出可见光从而影响总反射率,将这部分影响等效于正、反面油墨的透射率,以及纸张内部向正、反面反射率的改变;考虑光学网点扩大因子,利用Clapper-Yule分程理论进行分析;通过数值模拟,对新、旧模型进行比较,验证新模型的合理性和准确性。结果建立了荧光纸基的双面彩色半色调印刷品Clapper-Yule正面反射率模型。结论色彩预测Clapper-Yule反射率模型必须考虑荧光纸基的影响。     

一种基于散射理论的光学网点扩大算法

目的研究一种基于纸基光散射理论的网目调光学网点扩大算法。方法应用点扩散函数和概率方法,分析网目调印刷品中光的散射和渗透效应,推导出印刷品上空白部分、网点部分反射率和网目调印刷品反射率的精确表达式,在此基础上,分析了网点光学扩大与印刷品网点面积率、墨层光谱透射率以及纸基光谱反射率的依赖关系,建立了一种新的光学网点扩大算法模型。将经典的光谱Murray-Davis模型与该算法修正后的光谱Murray-Davis模型分别预测的光谱反射率,与印刷品实际测量的光谱反射率作对比验证实验。结果提出算法修正后的光谱Murray-Davis模型与实测光谱反射率更加接近,色差ΔE2000最高为1.53、最低为0.89,而人眼对ΔE20002的颜色在视觉上近似相等。结论采用提出的模型修正经典的Murray-Davis公式,进而预测光谱反射率,达到了很好的效果,具有更高的精度。     

基于油墨不同叠印的二阶调频网物理网点扩大的研究

建立了二阶调频网点构成的半色调图像光谱预测模型。考虑油墨在不同叠印条件下由于油墨铺展引起的物理网点扩大,采用Yule-Nielsen修正的光谱聂格伯尔模型对打印的二阶调频网点图像的光谱进行预测,然后计算色度值,并与测量值进行比较。实验结果表明,考虑油墨在不同叠印条件下的铺展的EYNSN模型预测的平均和最大色差分别为2.64和6.21,与未考虑油墨铺展的预测结果相比,预测精度有所提高。     

基于Yule-Nielsen的半色调印刷品的光谱预测模型

介绍了Yule-Nielsen修正光谱Neugebauer方程的色彩预测模型.通过分析有效网点面积率、油墨铺展在不同叠印条件下,光谱反射率的预测模型,说明了物理网点扩大对方程的影响,然后又通过分析纸张的点传递函数PSF和概率模型,指出了光学网点扩大对方程的影响,更优化了模型,最后对Yule-Nielsen方程参数n值,具体做了解释并用迭代法求得最佳的n值.     

基于颜色并列与叠加模型的专色油墨光谱反射率预测算法

专色油墨的光谱预测一直以来都是色彩研究领域中的难题,分别采用颜色并列与叠加模型处理Clap-per-Yule模型,简化专色油墨光谱反射率预测模型,通过实验验证了该简化方式具有一定的实际应用价值,并且对于一般性印刷品的专色颜色预测,完全可以达到要求,最主要的是该简化极大地减小了计算难度。此外,还比较了颜色并列模型与叠加模型简化专色油墨光谱预测模型的精确性,结果表明,颜色叠加模型在简化专色油墨光谱预测模型时精确性较高。     

光学变色防伪油墨的颜色预测模型

为更好地研究光学变色油墨的显色性能,加大其在半色调印刷品防伪领域的应用,在分析光学变色油墨变色原理的基础上,着重分析了光变油墨中的薄膜理论,由此建立了一个统一的光学油墨半色调印刷品的光谱反射率预测模型。模型能够很好地预测防伪印刷品和油墨的颜色变化,从而为光变油墨的光谱分析提供了很好的理论依据,能更好地控制防伪油墨的颜色变化。     

可变墨滴喷墨打印印刷品的光谱预测模型

在喷墨打印机喷出墨滴大小可变时,以Clapper-Yule模型为基础,研究了可变墨滴喷墨打印印刷品的反射率预测模型。首先引入了墨滴大小变化和Clapper-Yule模型的调频加网形式;然后,用墨滴变化引起的墨层厚度变化和调频网点大小的变化扩展Clapper-Yule模型;最后,建立了墨滴大小扩展的Clapper-Yule模型,并通过模拟实验验证了模型的优越性。     

具有打底油墨的半色调印刷品的Clapper-Yule模型

通过经典的Clapper-Yule模型的应用,对已有的点对点的半色调印刷品进行扩展,在忽略油墨渗透的条件下,建立起能具有打底油墨的半色调印刷品的呈色规律的理论模型.在假定油墨是非散射介质以及油墨的折射率与纸张的折射率近似相等的近似下,利用光在油墨与纸张中散射迁移路径长短不同的分程理论,建立了具有打底油墨的半色调图像的分程Clapper-Yule光谱反射率模型.     

光谱Neugebauer模型的抗差最小二乘优化

Yule-Nielsen修正光谱Neugebauer模型是一种用来预测彩色网目调印刷品颜色的重要光谱预测模型。为了提高Neugebauer模型预测精度,在分析光谱Neugebauer模型和抗差估计理论的基础上,提出了将抗差最小二乘法用于计算模型参数网点面积率和基色光谱反射率。常用的抗差估计方案有:Huber估计和IGG估计。实验表明,当存在粗差的情况下,与传统的最小二乘法相比,抗差最小二乘法的光谱Neugebauer模型的预测精度更高且更为稳定。     

油墨渗透下荧光半色调印刷品的预测模型

旨在普通油墨渗透条件下,建立能预测不同浓度的均匀荧光油墨半色调印刷品的呈色规律的理论模型;在假定油墨是非散射介质以及油墨的折射率与纸张的折射率近似相等的近似下,利用光在油墨与纸张中散射迁移路径长短不同的分程理论,建立了油墨渗透下荧光油墨半色调图像的分程Clapper-Yule光谱反射率模型.     

荧光油墨印刷品的预测模型

荧光油墨半色调印刷品的显色预测规律是彩色成像领域内十分关键的课题.详细介绍了荧光油墨印刷品的经典Clapper-yule预测模型以及其改善的模型分程Clapper-yule预测模型,并且介绍了基于点扩散的Clapper-yule预测模型.同时分析了各个模型的特点,最后进行前景展望.     

商标印刷色彩预测 Clapper-Yule 模型

把油墨与纸张等价为吸收薄膜,考虑光在纸基油墨间多重内反射和横向传播,运用吸收膜理论,建立了半色调商标印刷品的Clapper-Yule 色彩预测膜层模型。通过数值计算并与实验值比较,证明了新模型的预测精度明显高于之前的Murray-Davies 模型,而且改进了经典Clapper-Yule 模型预测偏暗的问题。     

Reflectance and transmittance model for recto-verso halftone prints

We propose a spectral prediction model for predicting the reflectance and transmittance of recto-verso halftone prints. A recto-verso halftone print is modeled as a diffusing substrate surrounded by two inked interfaces in contact with air (or with another medium). The interaction of light with the print comprises three components: (a) the attenuation of the incident light penetrating the print across the inked interface, (b) the internal reflectance and internal transmittance that accounts for the substrate's intrinsic reflectance and transmittance and for the multiple Fresnel internal reflections at the inked interfaces, and (c) the attenuation of light exiting the print across the inked interfaces. Both the classical Williams-Clapper and Clapper-Yule spectral prediction models are special cases of the proposed recto-verso reflectance and transmittance model. We also extend the Kubelka-Munk model to predict the reflectance and transmittance of recto-verso halftone prints. The extended Kubelka-Munk model is compatible with the proposed recto-verso reflectance and transmittance model. In the case of a homogeneous substrate, the recto-verso model's internal reflectance and transmittance can be expressed as a function Kubelka-Munk's scattering and absorption parameters, or the Kubelka-Munk's scattering and absorption parameters can be inferred from the recto-verso model's internal reflectance and transmittance, deduced from spectral measurements. The proposed model offers new perspectives both for spectral transmission and reflection predictions and for characterizing the properties of printed diffuse substrates.     

Spectral model of a fluorescent ink halftone

A model is presented of a fluorescent ink halftone. Unlike a nonfluorescent ink, which only absorbs, a fluorescent ink absorbs higher-energy photons and emits lower-energy photons. The amount of fluorescent light produced depends on the percent absorption of the incident light. For fluorescent ink printed on paper, both photon scattering within the paper substrate and multiple internal reflections between the ink layer and the paper substrate significantly increase the percent absorption, so a realistic model must include these effects. The model presented here utilizes the generalized Clapper-Yule theory, which accounts for photon diffusion that is due to both scatter and internal reflection. It is shown that while multiple internal reflections alone only marginally increase the percent absorption, when there are both scattering and internal reflection, the percent absorption is increased significantly. The current study is a theoretical model and does not present experimental results.     

Extending the Clapper-Yule model to rough printing supports

The Clapper-Yule model is the only classical spectral reflection model for halftone prints that takes explicitly into account both the multiple internal reflections between the print-air interface and the paper substrate and the lateral propagation of light within the paper bulk. However, the Clapper-Yule model assumes a planar interface and does not take into account the roughness of the print surface. In order to extend the Clapper-Yule model to rough printing supports (e.g., matte coated papers or calendered papers), we model the print surface as a set of randomly oriented microfacets. The influence of the shadowing effect is evaluated and incorporated into the model. By integrating over all incident angles and facet orientations, we are able to express the internal reflectance of the rough interface as a function of the rms facet slope. By considering also the rough interface transmittances both for the incident light and for the emerging light, we obtain a generalization of the Clapper-Yule model for rough interfaces. The comparison between the classical Clapper-Yule model and the model extended to rough surfaces shows that the influence of the surface roughness on the predicted reflectance factor is small. For high-quality papers such as coated and calendered papers, as well as for low-quality papers such as newsprint or copy papers, the influence of surface roughness is negligible, and the classical Clapper-Yule model can be used to predict the halftone-print reflectance factors. The influence of roughness becomes significant only for very rough and thick nondiffusing coatings.     

Clapper-Yule光谱预测模型

详细介绍了经典的Clapper-Yule模型以及其改善的模型--分程Clapper-Yule模型和点扩散Clapper-Yule模型,并在此基础上介绍了Clapper-Yule模型的扩展应用:将Clapper-Yule模型扩展到粗糙承基质和荧光半色调印品上,同时分析了各个模型的特点,最后进行前景展望.