Color Zone Map in Peripheral Vision at Various Illuminance Levels

We measured the entire region of mesopic and photopic vision to determine the color zone covering the visual field with unique red, yellow, green, and blue hue components. Eight kinds of test stimuli in the natural color system (NCS) color notation system were used. These stimuli were presented at horizontal and vertical meridians, and at meridians inclined at 45° angles. The illuminance level was set at six levels: 0.01 lx-1000 lx. The evaluation method measured chromatic, white, and black components as well as the hue component of the stimuli. Results show that the color zone of the retina extended further into the periphery with increasing illuminance; the response of opponent colors y-b was shown to be greater than that of the opponent colors r-g.     

The Brain Adaptation to the Color of Illumination and not the Retinal Adaptation to the Color of Objects that Determines the Color Appearance of an Object in the Space

Color appearance was measured for a test patch which was placed in a test room illuminated by the daylight type of illumination and was looked at from the subject room illuminated by one of the four colored illuminations, red, yellow, green, and blue, through a window of three different sizes. When the window was the smallest so that only the test patch was seen within the window the color of the test patch appeared almost opponent to the illumination color, but as soon as something is seen within the window of larger size the color returned to the original color of the test patch to indicate the color constancy. To recognize the test room as a space was essential to perceive the real color of the test patch. This returning to the original colors was not influenced by green color of objects densely placed in the test room or by red color of objects again densely placed in the test room. The results imply that the color appearance of the test patch is not determined by the retinal chromatic adaptation, but by the brain adaptation to color of the illumination in the space.     

Chromatic Spatial Summation at Equiluminance

The effect of spatial summation on chromatic detection at suprathreshold levels for the red-green and yellow-blue chromatic opponent mechanisms has been studied using simple reaction time (RT) as a measurement of the response. We varied the target size in the experiments from 8 min of arc in diameter to 10 deg, and the hue-substitution paradigm was adopted to generate only chromatic changes in the cone input. Equiluminant stimuli were distributed along three tritan and three red-green confusion lines. Three reference stimuli were chosen as both reference and adapting stimuli, in this case to determine whether the chromatic adaptation affected the spatial summation. The results showed that the mean value of RT at a constant cone-input variation, either of the L #x2212; 2M channel or of the S #x2212; (L #x002B; M) channel, against the target size decreased until a stimulus size was reached, the RT being constant for greater sizes. The spatial summation was fulfilled for a maximum target size which was less for the L #x2212; 2M channel than for the S #x2212; (L #x002B; M) channel, this size decreasing as the cone-input variation rose. Furthermore, there was no spatial summation for high-enough variations in the cone input. In addition, the chromatic mechanisms appear to organize their spatial integration with the adapting level.     

Reverse correlation analysis of chromatic contrast perception based on chromatic mechanism models

We applied the classification image (CI) method to examine the effects of heterochromatic noise on color perception. Moreover, rather than the typical CI analysis procedure, we analyzed the CI data based on chromatic mechanism models. The stimulus was a superposition image of two uniformly colored squares (signal images) and a multicolored texture (a noise image), whose colors were chosen from an isoluminant plane of the Derrington-Krauskopf-Lennie color space. The observers judged the relative chromatic contrasts of the two signal squares on the different noise textures. The CI showed strong color modulations, whose color directions differed from the signal. Additionally, the model analysis demonstrated that the model with four mechanisms and the cardinal mechanisms model were not inferior to the model with more mechanisms with regard to explaining our experiment data; the cardinal model’s fit with the observer’s behaviors was improved by simply adjusting the relative sensitivities of the four mechanisms.     

Computerized Simulation and Chromatic Adaptation Experiments Based on a Model of Aged Human Lens

Color appearance seen by old people does not significantly differ from that seen by young subjects even though their ocular lens has become more yellow with age. We calculated the age-related change of lights reflected from Munsell color chips onto the retina, and derived results that show that the chromaticity values of all the color chips shifted to the yellow region of the xy-chromaticity diagram. However, a replot on the CIELAB diagram and the estimation by means of the von Kries adaptation model suggests that old people may compensate their color vision using a general chromatic adaptation process. To test this hypothesis, we conducted two experiments: a chromatic adaptation experiment and a color matching experiment to simulate D65-lights as seen by older people but using young subjects. The results indicate that chromatic adaptation does not provide a complete explanation for color compensation by older people, suggesting that an age-related change of the yellow-blue opponent color mechanism may contribute to this compensation.     

基于CRT的非对称视觉匹配实验中对立色的显示方法研究

对立色是颜色科学研究中的一类特殊颜色现象,通过对其特殊匹配现象的研究,可以揭示人眼彩色视觉信息传递的规律。针对基于CRT的非对称视觉匹配实验的要求,提出了一种色调均匀分布、强度成线性变化的对立色的定义和显示方法,实现了人眼锥体细胞响应LMS与计算机彩色量化值RGB之间的高精度转换和真彩色再现。     

Chromatic-Spatial Vision of the Aging Eye

The human visual system undergoes continuous anatomical, physiological and functional changes throughout the life span. There is also continuous change in the spectral distribution and intensity of light reaching the retina from infancy through senescence, primarily due to changes in the absorption of short-wave light by the lens. Despite these changes in the retinal stimulus and the signals leaving the retina for perceptual analysis, color appearance is relatively stable during aging as measured by broadband reflective or self-luminous samples, the wavelengths of unique blue and yellow, and the achromatic locus. Measures of ocular media density for younger and older observers show, indeed, that color appearance is independent of ocular media density. This may be explained by a renormalization process that was demonstrated by measuring the chromaticity of the achromatic point before and after cataract surgery. There was a shift following cataract surgery (removal of a brunescent lens) that was initially toward yellow in color space, but over the course of months, drifted back in the direction of the achromatic point before surgery. The spatial characteristics of color mechanisms were quantified for younger and older observers in terms of chromatic perceptive fields and the chromatic contrast sensitivity functions. Younger and older observers differed with small spots or with chromatic spatial gratings near threshold, but there were no significant differences with larger spots or suprathreshold spatial gratings.     

Optical Implementation of Precise Color Classification Using Computer Controlled Set of Light Emitting Diodes

Accurate color classification by vector subspace method was implemented by simple optical system including computer controlled set of light-emitting diodes and a photo-receiver operating in the integration regime. The technique is capable for fast and precise classification of color distribution within two-dimensional frame with high spatial resolution. The feasibility of the proposed system is shown by a test of four metameric colors, which were correctly distinguished.     

Color Discrimination Characteristics Depending on the Background Color in the (<Emphasis Type="Italic">L</Emphasis>, <Emphasis Type="Italic">M</Emphasis>) Plane of a Cone Space

We investigated color discriminability on the background color. The measurement was carried out at over 21 background colors in (L, M) plane of a cone space by four observers. We used low temporal stimulus frequency (1 Hz) so that threshold was determined by the red-green opponent mechanism. Results showed that color discriminability depends on the background colors. Threshold was higher with a more saturated background color. This suggests that the sensitivity of the red-green opponent mechanism is high when the mechanism’s output is small and increases with the output levels of the mechanism. To confirm this relationship between the red-green mechanism and color discriminability, color appearance depending the background color was also evaluated. There was a strong correlation between the sensitivity and the perceived whiteness. Both sensitivity and whiteness value were highest at around the equal energy white point and decreased with increase in the difference between background color and equal energy white. This suggests that the adaptation state of the red-green opponent color controls color discrimination.     

Color Appearance Determined by Recognition of Space

The color appearance was measured for a test patch which was placed in a test room illuminated by daylight lamps and was looked at from a subject room illuminated by one of four colored illuminations, red, yellow, green and blue, through windows of various sizes. When the window was small so that only the test patch was seen within the window the color of the test patch appeared almost opponent to the illumination color, but as soon as something was seen within the window of a larger size the color returned to the original color of the test patch. To recognize the test room as a space was essential to perceive the real color of the test patch. The results were explained by the concept of the recognized visual space of illumination.     

基于BP网络的打印机色彩控制技术

报道了一种基于ＢＰ网络的打印机色彩控制技术。作为控制器模型的ＢＰ网络通过学习打印机的输入／输出特性,实现颜色数据从ＣＩＥＬＡＢ到打印机色空间的转换。实验结果表明,利用ＢＰ网络可以控制打印机实际输出与希望输出颜色之间的平均色差为４－２３ΔＥ＊ａｂ 。     

基于色彩恒常性的敦煌典型色彩光谱样本集构建方法

该研究目的为提出一种面向我国各类文物体系的典型色彩光谱样本集构建方法。以具有1700多年历史的世界级佛教艺术文化遗产敦煌莫高窟壁画彩绘为典型研究对象,以保证文物色彩传递过程中的色彩恒常性为主要创新,最终从视觉感知角度提出基于色彩恒常性的敦煌典型色彩光谱样本集构建方法。在具体实施过程中,在敦煌研究院美术所及保护所工作人员的配合与指导下,结合现有敦煌学研究成果,研究选取了48类敦煌典型颜料并设计制备了240个代表性色彩样本。利用分光光度计获取其在360～750 nm范围内反射光谱信息,通过聚类分析法对原始色彩光谱样本集进行分类,以6类典型光源场景条件下色彩易变性指数(color inconstancy index)的综合量值为依据,结合Wilcoxon符号秩检验,确定分类数量及各子类的代表性样本,初步构建光谱样本集。随后,从色域完整性角度对初步建立的样本集进行补充,最终构建由100个样本组成的全色域光谱数据集。分析结果显示,该样本集在99%置信条件下的色彩易变性指数可低至3.28,且均匀分布于敦煌色彩体系的整个色域,因而可以为敦煌色彩再现过程中合理的选用具有高恒常性水平的色彩提供数据参考及方法依据。     

On the chromatic aberration of magnetic lenses with a field distribution in the form of an inverse power low (B(z) ∝ z)

The chromatic aberration of magnetic lenses with the field distribution in the forms of inverse law have been studied by analytical and digital methods. These aberrations can be expressed in terms of Bessel function of fraction order. Analytical expressions for chromatic aberration coefficients of the spherical field model, which is useful for the study of single-pole magnetic lenses, are given.     

彩色图像着色

讨论了彩色图像着色的数值计算方法,即根据场景中物体表面的反射光谱能量分布来计算视觉响应的三刺激值.首先用线性模型来逼近物体表面的反射光谱连续函数,然后用高斯积分法、黎曼求和法进行了数值计算,最后把计算出来的三刺激值转化为色品坐标,在色品图上与CCD相机拍摄的图像进行了匹配     

Luminance and Chromaticity Conditions of a Bichromatic Cross Pattern for Chromatically-Uniform Transparency

We can perceive a surface through another surface. This perception is called transparency. It is known that transparency can be perceived even if the stimulus conditions are not consistent with physical conditions for a real transparent surface. In this study, we measured the ranges of luminance and chromaticity of the overlapping area of two crossed layers at which a surface was perceived as chromatically-uniform transparent. As the results, the luminance range of the overlapping area existed around or near the luminance of the inducing area. The upper and lower limits of the luminance range were higher for the dark background than for the light background. Moreover, the chromatic range existed around the additive colormixture line between two chromaticities of the inducing areas for both dark and light backgrounds. This indicates that the perceptual transparency mechanism would divide the color of an additive color mixture into the original colors that exist in the inducing areas. We noticed that the perceptual appearance of the stimulus changed greatly depending on the luminances of the overlapping area and the background. These differences in perceptual appearance would be a factor explaining individual difference and deciding the luminance conditions for transparency.     

油墨红外光谱相似度与计算机配色精度的关系研究

为了获得高精度的配色样品,提出了一种配色方法-成分分析配色法。该方法将化学分析法与计算机配色相结合,其核心是选取与目标色成分最接近的油墨进行配色,从而实现高精度的色彩匹配,为计算机配色发展提供新的思路。与目标色成分相近的油墨配色效果验证：使用某种油墨印制目标色,并用相同的油墨进行配色,以实现目标色成分与配色色样成分的一致性。使用三个不同品牌的油墨对目标色进行配色,比较配色精度及效率。使用泗联牌三种颜色油墨以任意比例通过印刷适性仪IGT-CI(荷兰)印制目标色,这些目标色包括间色和复色,各3个色样;使用配色软件X-Rite color master(美国)建立泗联、东洋、牡丹三个品牌油墨的配色基础数据库,并对不同目标色进行配色。结果表明使用与目标色相同的泗联油墨的配色精度远高于东洋、牡丹两个品牌的油墨,配色色差整体都很小,校正1～2次就能得到小于1.0的色差,最小达到0.36,几乎实现了目标色的同色同谱匹配。实验验证了成分分析配色法的核心“选取与目标色成分最接近的油墨进行配色,可以实现高精度色彩匹配”的可行性。判别目标色与配色油墨在成分上区别的化学分析工具探讨：为了判别目标色色料与配色油墨在成分上有区别,尝试使用“红外光谱相似度”作为判别的分析工具。使用红外光谱仪Thermo Nicolet 6700(美国)测出泗联、东洋、牡丹三个品牌的三种颜色油墨的红外光谱图,使用OMNIC软件中的相关性算法得到它们与目标色油墨的红外光谱相似度,并计算出平均相似度;将各品牌油墨的红外光谱相似度与其配色实验的精度进行对比分析,评价红外光谱相似度作为化学分析判别工具的有效性。结果表明泗联牌油墨与目标色的平均红外光谱相似度为100%,东洋的为86.53%,牡丹的为64.63%。当校正次数相同时,泗联油墨配色色差最小,配色精度最高;东洋次之,是泗联油墨配色色差的2倍左右;牡丹最差,是泗联油墨配色色差的3倍以上。配色结果与其红外光谱相似度的规律是一致的,目标色油墨与配色油墨之间的红外光谱相似度越高,越容易得到高精度的配色样品。实验证明了用成分分析配色法获得高精度的色彩匹配是可行的,使用红外光谱相似度作为目标色与配色油墨在成分上的分析工具对判别配色精度是有效的。今后的工作将探讨红外光谱相似度与配色精度间的相关性数值关系,以及进一步寻求更为有效的化学分析方法来判断目标色色料与配色油墨之间的成分关系。     

线性色散设计的光谱共焦测量技术

研制了高精度的光谱共焦位移测量系统并完成相关测试。基于色差理论和材料优化选择设计一种色差与波长成线性关系的色散物镜,有助于平衡系统在全测量范围的灵敏度。理论分析了系统参数对系统的影响规律,计算了针孔尺寸与系统的分辨率和信噪比的关系,给出了参数优化结果。利用设计的线性色散物镜和参数优化结果,构建了光谱共焦测量系统,完成了系统的校准、测试和应用研究。结果表明,系统的轴向测量范围达到1 mm,分辨力优于0.5μm,全程测量误差小于2μm,符合设计要求。     

High color rendering index and chromatic stability of top‐emitting white organic light‐emitting diodes capped with a supplementary green color conversion layer

We have demonstrated high color rendering index (CRI) and chromatic stability of top‐emitting white organic light‐emitting diodes (TEWOLEDs) by capping a supplementary green color conversion layer (CCL) on the cathode of single blue emitter based TEWOLEDs. By employing CCLs, blue photon energy is absorbed and converted to green emission efficiently, resulting in an improvement of CRI from 72 to 86. We attribute the increased high CRI to the broadening of the out‐coupled spectrum and an appropriate intensity match among the three primary colors. Meanwhile, the TEWOLEDs show extremely high chromatic stability. The results indicate that this method provides a new avenue to improve the CRI of TEWOLEDs.

     

A Color Appearance Model Applicable in Mesopic Vision

We propose a color vision model that can be used to predict color appearance in mesopic vision as well as photopic and scotopic vision. It is based on a two-stage model which consists of the cone and opponent stages and it assumes rod intrusion at the opponent stage. The model has the following features to describe the color appearance in mesopic vision. First, it includes a gradual and nonlinear shift in spectral luminous efficiency from V (LD) to V (LD) to cope with the spectral sensitivity difference between photopic and scotopic vision and the nonlinearity of rod influence on the luminance channel. Second, the model assumes decrease of the chromatic component with decreasing illuminance to explain the reduction of saturation at low illuminance levels. Third, it assumes that red/green and yellow/blue components change with illuminance levels independently, thus explaining hue shifts with decreasing illuminance. We applied the model for color appearance simulation of natural scenes in a mesopic visual environment.     

Evaluation of small suprathreshold color differences under different background colors

A psychophysical experiment under constant stimuli is conducted on a CRT display to measure the visual suprathreshold color differences for five color centers recommended by CIE under the same five background colors.The performances of four CIELAB-based,three CIECAM02-based,and two OSA-UCS-based formulas are tested.Detailed analysis results indicate the existence of chromatic crispening effect.CIEDE2000 performs best for the gray center and gray background,whereas CAM02-LCD and CAM02-UCS have the best performance for non-neutral backgrounds.CAM02-LCD significantly outperforms all other formulas for all color centers under all background colors.