【作者】 孟卿君；

【导师】 李志健；

【作者基本信息】 陕西科技大学 ， 制浆造纸工程， 2014， 博士

【摘要】 纸张白度做为纸质印刷品品质的一项重要指标而备受印刷业及造纸业的关注。印品的质量要求及一些消费者的喜好，导致印刷企业对纸张的白度要求较高，造纸企业为迎合消费市场而不断地努力提高纸张白度。长期以来，纸张高白度所带来的负面影响被忽视了，如高白度纸张生产势必导致高化学品消耗、高能耗、高环境污染；同时高白度纸张的使用可能引起人眼的光刺激负荷加重、产生视疲劳等问题。为了解高白度纸张对人眼视力造成的影响状况，从而合理控制纸张白度，本文将采用仪器实证及人体实证相结合的方法揭示纸张与人眼视疲劳关系；并采用相关性分析法客观地评价纸张白度与印品质量参数间的相关性，从而判断纸张白度对印品质量的影响；根据白度对印品质量影响结果，有针对性的提出一种合适的印品质量评价方法；研究纸张结构与印品色差间的关系规律，并对输入图像进行色彩补偿，试图为改善印品质量开辟新途径，从而控制纸张印品质量。具体研究方法及结论如下所述：通过仪器实证及人体实证两种方法揭示纸张白度与视疲劳的关系。用色光匹配法合成匹配于纸张白度的光源照射人眼，采集人眼瞳孔动态变化特征值。根据瞳孔变化特征值判断人眼对强、弱光刺激的生理反应状况，预测人眼面对相应白度纸张产生的视疲劳情况。以观察、询问并记录受试者在相同阅读环境下阅读不同白度纸质文稿时出现的视疲劳反应情况分析纸张白度与视疲劳关系。结果表明：纸张白度越高，受试者瞳孔反应幅度越大，反应潜伏期越短，副交感神经的兴奋性增加，视疲劳的发生率增大；对于纸质阅读文稿，白度越高，受试者阅读时视疲劳状况增多且有视疲劳现象的人数增多。故随着纸张白度的增加，人眼视疲劳越易发生，所以以阅读为主要目的的纸质印刷品应选择使用中低白度纸张。采用Kendall相关系数及Spearman相关系数来判断样本数据间的相关性。以纸张白度值及能体现印品质量的实地密度、网点扩大值、叠印率、色差等参数指标为变量，用SPSS软件进行数据关联性判断。结果表明：纸张白度值对实地密度、网点扩大值、叠印率的影响没有规律，但纸张白度值对色差值影响较大。相关系数分析结果及其验证参数的验证结果，表明纸张白度与色差呈显著负相关关系。所以中低白度纸张会影响印刷色彩再现，要想广泛应用中低白度纸张，首先需要解决印品色差问题。人脑具有将独立的视觉机制聚集在一起的能力，而各种视觉机制仅对频率域的某一部分敏感。因此，可以用滤波器组来模拟人的视觉特性。用人眼对比度敏感函数为卷积核对图像进行滤波处理，以模拟视觉系统的工作原理，再用CIELAB色差模型进行色差分析，从而获得色差结果。并以人眼的真实感知来验证评价方法与人眼感知的贴合度。结果表明：基于人眼视觉特性的色差评价方法基本符合人眼感知色差结果，此方法使用方便、可重复性强，评价结果较准确，该方法可以有效评价印品色差。采用X射线衍射仪、原子力显微镜、扫描电镜表征纸张X射线衍射法结晶度，表面粗糙度，孔隙结构等纸张结构，并从物质光学现象分析纸张结构与印刷色差间的关系。研究结果表明：结晶度较大的纸张，纸张印刷色差较小；纸张粗糙度越低，纸张印刷色差越小；填料较多的纸张，增加了填料空气及填料纤维这两种光学界面，从而改变了非光学接触面积，所以纸张光散射系数及纸张内反射因数会相应发生变化，纸张的印刷色差也有相应变化。所以可根据纸张结构与印品色差的关系规律，来指导造纸企业优化工艺，调整纸张结构，最后达到改善印品色差的目的。将输入图像转换成R、G、B三通道，分别在三通道对图像进行直方图均衡化处理；将图像转换到YCrCb色彩空间，采用Sobel算法提取Y通道边沿，在边沿区域内以理想白度标准寻找合适的参考白度区域；待找到参考白度区域后，根据Von Kries模型对图像进行色彩补偿。结果表明：补偿后的输入图像输出到较低白度纸张上，经基于人眼视觉特性的色差评价方法评价发现色差明显减小。所以此方法有利于改善较低白度纸张印品的色差问题。综上所述，本文通过仪器实证及人体实证，揭示了纸张白度对人眼视力健康带来的影响，建议印刷企业使用中低白度纸张印刷以阅读为目的的纸质印刷品，并针对中低白度纸张造成印品色差的问题，提出了改善途径。研究结果有益于引导人们正确认识纸张白度，利于视力保护，并为中低白度的纸张能够得到广泛应用提供理论参考支持，该研究结果对于促进造纸与印刷工业节约资源，实现低碳经济、可持续发展具有现实和积极的意义。更多还原

【Abstract】 Paper whiteness was one of important influencing factors of theprinting quality which was paid more and more attention by printingand paper industry. The high quality requirements and preferences ofconsumers demanded higher paper whiteness for printing enterprises.Thus, in order to cater to consumer market, the papermaking enterpriseshad to keep improving the paper whiteness.For a long time, Negative impact brought by the paper with highwhiteness had been ignored, for instance, high whiteness paperproduction lead to high loading, high chemicals consumption, highenergy consumption and heavy environmental pollution. Meanwhile, theutilization of high whiteness papers would inevitably cause theproblems such as serious sense of high light stimulation and visualfatigue. To explore the effects of high paper whiteness on our vision, itcould provide a basison controlling the whiteness reasonably. In thispaper, it was used the methods of instruments test and human feelingexperiments toreveal the relationship between the whiteness with visualfatigue of humans. The correlation analysis method was employed toevaluate the correlation between whiteness with the quality parameterof printing product and it could judge the effect of whiteness on productquality. According to this, a suitable method for evaluating the qualityof printing product was proposed targeted. Moreover, it was studied theregularity between paper structure with color difference which lookedforward to open up a new way for improving the quality of printingproduct. The specific researches and results were as follow:The relationship between the whiteness with visual fatigue ofhumans was detected by the methods of instruments test and humanfeeling experiments. Instrumentstest was to gather the pupil dynamics characteristic values of human when the synthesis of the light sourcewas illuminate and that value was to judge the eyes physiologicalreaction conditions with the change of radiation source which wasmatch to the corresponding paper whiteness, to predict the condition ofhuman eye fatigue when facing the different whiteness of paper. Humanfeeling experiments were implemented by observing, inquiring andrecording the visual fatigue reaction situation when the subjects werereading different whiteness paper manuscripts in the same readingenvironment. Research results show that the higher the paper whitenesswas, the greater the pupil response amplitude of subjects were and theshorter the response latency was, so with the paper whiteness increased,the parasympathetic nerve excitability increased, and the incidence ofvisual fatigue increased. The higher the whiteness of reading literarybackground was, the more the number of subjects with visual fatiguewere, and the more visual fatigue phenomenon was. Therefore, with theincrease of paper whiteness, the human eye fatigue more easily tohappen, it should choose lower whiteness of papers when the mainpurpose on printing product was read.According to the characteristics of the experimental data, thecorrelation between sample data would adopt the Kendall correlationcoefficient and Spearman rank correlation coefficient to determine.Paper whiteness value, the field density, dot enlargement value,overprint rate, and color difference value were choose to be variables,and using SPSS software judged data correlation mining. The resultsshow that there was no regularity existing between paper whitenessvalue with field density, dot enlargement and overprint rate, while theluctuation of the color difference was obvious. The result of correlationcoefficient analysis and validate parameter verified that the paperwhiteness and color difference has significant negative correlationrelationship. As a consequence, low whiteness paper will affect theprinting color reproduction. If the lower whiteness paper would bewidely used, the printing mills should solve the problem of print colordifference firstly. There was a special ability in human brains that could put thevisual mechanisms together in dependently. However, this mechanismswere sensitive only for a certain part of frequency domain. Hence, thefilter was applied to simulate visual characteristics of human. Firstly, Itwas used the contrast sensitivity function as the convolution kernel tofilter for the images which simulated the working principle of visualsystem. Secondly, the CIELAB color difference model was introducedby color difference analysis and obtained the results. Lastly, it wasverified the evaluate method and eyes perception fit by the feelingexperiments of eyes. It was showed that the color difference evaluationmodel based on human visual features largely in line with the humaneye perception color difference’s result, this method was easy to use,had strong repeatability, and the evaluation results were more accurate.It can effectively evaluate color difference of printed product.Paper X ray diffraction crystallinity, surface roughness, andporosity structure were characterized by the X ray diffraction, atomicforce microscopy, and scanning electron microscopy and therelationships between structure and printed product were researchedfrom the angle of the optical function of paper. It was described that thelarger the crystallinity was, the smaller the paper printing colordifference was; the smaller the roughness was, the smaller the paperprinting color difference was; For the paper with more filling, therewere two optical interfaces (packing air and packing fiber opticalinterface), which changed the optical contact area, so the paper andpaper internal reflection light and scattering coefficient factor wouldchange accordingly, paper printing color difference also havecorresponding change. Forth is reason, paper enterprises could use therelationship of paper structure and the color difference to guide tooptimize process, adjust the paper structure, finally printing qualitycolor difference would achieve the goal.The input image was converted into three channels(R, G, B), theimage was managed with histogram equalization processing algorithmrespectively in the three channel. Then image was converted to YCrCb color space, the Y channel edge was extracted by using the Sobelalgorithm, suitable reference whiteness area was found in the edge area.After reference white area was found, color image was corrected withVon Kries color correction model. The research results showed that theinput image is histogram equalization in three channel, color differencewas improved, and image after color correction according to Von Kriescolor correction model was closer to nature. After the input image wascorrected by digital printer output to the lower degree white paper, anevaluation method based on human visual characteristics was evaluatedwith the original color, the color difference obviously decreased. Thismethod was helpful for improving the color difference of the lowerdegree whiteness paper.To sum up, this research demonstrated that the paper whitenessreally threatened to the human eye vision. It was suggested for theprinting enterprises to use the low whiteness of paper to produce theprinting products which were only for reading. And put forward thesolution of the low whiteness paper printing color difference problem.The results were beneficial to lead people understand the paperwhiteness correctly which would be good for eyesight protection. It hadprovided a theoretical reference for the wide use of the low whitenesspaper. Furthermore, there was also a realistic and positive significancefor promoting the paper and printing industry to save resources,achieving a low carbon economy as well as sustainable development.更多还原