数码彩扩机色域匹配模型研究

色域匹配是数码彩扩机实现图像颜色较好再现的关键.首先,采用一种较为实用的方法对CRT显示器进行了标定,运用Beer色料理论预测了彩色相纸的色域.在此基础上,运用非线性压缩算法实现从CRT到彩色相纸的色域匹配,同时提出了虚拟色域的概念,并加以分析研究.结果表明,非线性压缩色域匹配模型对于建立数码彩扩机的颜色管理系统具有重要实用价值.采用这种方法在国家高新技术激光数码彩扩机中取得了高质量的扩印效果.     

基于Zernike多项式表示色域边界的色域映射

在彩色图像的跨媒体复制中,由于不同媒体有不同的色域,所以在大多数情况下色域映射是不可避免的。不论采用何种映射算法,色域映射的第一步是确定有关媒体的色域边界。目前大多数的色域边界都是用一组测量的或用其它方法得到的离散数据来表示的。然而,由于这种表示方式是利用一组离散数据来实施色域映射的两个基本处理(即确定任一指定的等色调面平面中色域的边缘线以及确定色域边界与一条映射线的交点),比较复杂和费时,因此希望找到一种色域边界的解析表达式来解决这一问题。简述了不久前提出的一种解析函数色域边界表示方法,并用实例说明了如何利用这种解析表示(Zernike多项式)来实现上述的边缘线确定和交点确定。最后给出了几种映射算法的色域映射完整过程及其结果。     

普通LCD显示器色域边界的准确计算

目前针对普通LCD显示器色域边界计算的研究较少,本文耦合迭代求解法和反向特征化计算方法提出一种准确快速计算普通LCD显示屏色域边界点的方法。其中的反向特征化计算方法是:利用GOG模型初步计算已知颜色点的近似输入值,然后利用正向特征化模型、原色的主刺激值与设备输入值的函数关系,采用逐步逼近法计算颜色点对应的输入值RGB。计算步骤为:首先确定迭代计算初始值,迭代计算任意色相面上任意仰角上的颜色的XYZ;然后计算XYZ值对应的输入值RGB;最后,以RGB来判断颜色点是否在色域边界上。实验结果表明,与SMGBD相比,本算法无需插值计算,需要的样本少,其计算结果比SMGBD更能满足实际需求。     

数字全息波前重建中的像平面滤波技术研究

基于数字全息图的频谱平面滤波及像平面滤波技术,最近出现两种可变放大率的物光波前重建方法.为适应数字全息精细检测的要求,对两种滤波方法进行了研究,导出让局部重建图像布满重建平面的表达式.研究结果表明,像平面滤波技术优于频谱平面滤波技术,基于像平面滤波技术的重建方法能够按照需要的放大率高质量地重建局部物光场.给出彩色数字全...     

液晶显示器广色域技术的研究

针对当前液晶显示器存在色彩表现不佳的缺点, 从原理上研究了影响液晶显示器色域的主要因素。通过实验, 分别验证了彩色滤光片厚度、LED光源光谱以及量子点材料对液晶显示器色域的影响。通过增加液晶面板的彩色滤光片厚度, 将色域增加了8%;通过更改LED光源光谱, 将色域提升到85%NTSC以上;通过采用量子点材料, 实现了100%NTSC以上色域。     

彩色数字全息的非插值波面重建算法研究

彩色数字全息及多波长照明的数字全息检测研究中,避免插值误差的可变放大率波面重建是一个重要的研究内容.由于Fresnel衍射积分可以表示成Fourier变换及卷积两种形式,对应地存在两种波面重建算法：其一,将重建距离分为两段的衍射“接力”算法;其二,用球面波为重建波的卷积算法.文中对这两种算法进行理论分析及实验研究,讨论让重建计算满足取样定理的条件.结果表明,卷积算法较容易满足取样定理,能够获得较好的重建物光场.     

彩色数字全息的非插值波面重建算法研究

彩色数字全息及多波长照明的数字全息检测研究中,避免插值误差的可变放大率波面重建是一个重要的研究内容.由于Fresnel衍射积分可以表示成Fourier变换及卷积两种形式,对应地存在两种波面重建算法：其一,将重建距离分为两段的衍射“接力”算法;其二,用球面波为重建波的卷积算法.文中对这两种算法进行理论分析及实验研究,讨论让重建计算满足取样定理的条件.结果表明,卷积算法较容易满足取样定理,能够获得较好的重建物光场. 关键词： 彩色数字全息 波面重建 衍射计算     

重建彩色数字全息图时不同色光物光场的准确重叠研究

将数字全息检测物体表面视为散射面,球面波为参考波,使用角谱重建算法对不同波长照明情况下物平面光波场重建位置进行研究.结果表明,不考虑图像的物理意义时,衍射的一次傅里叶变换重建像中心与物光场频谱的中心相对应,以一次傅里叶变换重建像为参考,可以较好地确定物光场频谱位置,按照可变放大率的角谱重建算法实现不同色光重建场的准确重叠.     

重建彩色数字全息图时不同色光物光场的准确重叠研究

将数字全息检测物体表面视为散射面,球面波为参考波,使用角谱重建算法对不同波长照明情况下物平面光波场重建位置进行研究.结果表明,不考虑图像的物理意义时,衍射的一次傅里叶变换重建像中心与物光场频谱的中心相对应,以一次傅里叶变换重建像为参考,可以较好地确定物光场频谱位置,按照可变放大率的角谱重建算法实现不同色光重建场的准确重叠.     

基于数字电感的压电换能器动态匹配的研究

本文用实验的方法叙述了压电换能器的静态夹持电容随温度变化的特性,以及引起匹配质量下降的问题。提出了一种关于匹配的新概念－数字电感动态匹配,使匹配电感跟随静态电容的变化,从而提高匹配质量,实验结果表明,这种动态匹配方法是行之有效的。     

Color space conversion of digital photofinishing by neural network

A practical neural network model was designed to realize the color space conversion of digital photofinishing. The sampling, network structure and training process were introduced respectively. But in actual training, the networks fall into local minimum in all probability. To solve this problem, evolutionary programming (EP) algorithm was applied and the learning rate was adaptively adjusted. In the experiment, the performance of network was compared with pre-optimizing. Then the color space conversion was evaluated by the simulation error of samples from the point of color difference.     

CRT与LCD显示器色域特性研究

 显示器的色域（Color Gamut）决定了显示器能够显示的颜色范围。由于CRT和LCD的显色原理不同,同样的RGB值在不同的显示器上将表现出不同的颜色。通过实验的方法,对不同显示器进行大量不同颜色样块的测量,研究比较LCD和CRT的显色特性和色域。结果表明：LCD的显示色域比CRT要小,并且基本上被完全包围,也就是在CRT上能表现出的图像颜色无法在LCD上表现出来;另外从颜色视觉的感知属性来看,它们所表现出来的颜色明度、彩度和色调范围也有很大的差别。     

Color Conversion Method for Multiprimary Display Using Matrix Switching

The range of reproducible color, i.e., color gamut, of conventional three-primary display devices is sometimes insufficient for reproducing the natural color of an object through color imaging systems. A multiprimary display is being developed for the purpose of reproducing an expanded color gamut using more than three primary colors. In this paper, a color conversion method is proposed to reproduce the natural color by additive mixture of multiprimary colors. The multiprimary color signal in this conversion method is calculated from the three-dimensional color coordinates CIE-XYZ, considering the dynamic range of each primary color. Divided into some linear elements from the polyhedral color solid of the multiprimary display, the conversion considering the constraint of the dynamic range can be performed by simple calculation without iterative calculation or a huge three-dimensional look up table. A fast computation method with a two-dimensional look-up-table is also presented. Using the proposed method, the result of the color reproduction is experimentally demonstrated by a six-primary projection display.     

激光数码冲印机颜色校正方法研究

建立了激光数码冲印设备中颜色校正的理论模型,通过集成的扫描密度计扫描测试照片的密度值,找到激光数码冲印设备中颜色的输入输出关系,在色域映射的基础上得出了由密度实现真实颜色再现的理论模型,完整地实现了激光数码冲印设备的颜色的真实再现.     

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.     

Suppression of Noise Effects in Color Correction by Spectral Sensitivities of Image Sensors

The accurate transformation of device responses to tristimulus values is important at an early stage in color management and this transformation is usually called color correction. In this paper it is shown that the influence of noise on color correction can be suppressed if the square of the singular values by the singular value decomposition (SVD) of a sensor matrix represented by surface reflectance, SLVA^1/2, is larger than the noise variance, where S is the M × N matrix of M channel spectral sensitivities, L is the N × N diagonal matrix for an recording illuminant, V is the N × N matrix which is composed of eigenvectors of an autocorrelation matrix for spectral reflectance of samples, A is the N × N diagonal matrix with eigenvalues of the autocorrelation matrix along the diagonal and N is the number of the dimension, respectively. A method to suppress the influence of noise on color correction by spectral sensitivities of sensors is presented for the first time.     

基于LCD显示器光谱特性的图像颜色一致性研究

为了解决环境光和显示器色温对LCD显示器图像颜色再现有较大影响的问题,提出一种基于LCD显示器光谱特性的图像颜色一致性方法。通过测量在不同环境光和色温下99个行业认可颜色的光谱,总结出不同环境光和色温对LCD显示器图像颜色再现的光谱规律。利用不同环境光下的光谱叠加性及不同色温下的光谱对应规律,实现了不同环境光和色温下的LCD显示器图像颜色一致性,一致性后的图像平均主观评价Z得分为0.50。研究结果表明,该方法能够很好地解决不同环境光和色温下的LCD显示器图像颜色的一致性问题。     

Total Colorimetric Evaluation of a Set of Color Sensors for a Variety of Illuminants and Objects

Recently, a new colorimetric evaluation model for a set of color sensors was proposed by the author (N. Shimano: J. Inst. Image Electron. Eng. Jpn. 29 (2000) 506 and 517.), and the quality was shown to be defined by the ratio of the statistical mean energy of color stimuli at the retina (SMECS) to the captured energy of the SMECS by the sensors. It was also shown that the quality depends on the illuminants and objects. The experimental results agreed quite well with the proposed model. However, an extension of the model is needed to evaluate the full colorimetric quality of an image acquisition device for a variety of illuminants and objects. In this paper the extended model called the total colorimetric quality model and experimental results for sensors under such a variety are presented.     

Color Modification of Pictures Requiring Same Color Impression as Real Scene

Color constancy is an important feature of the human visual system. Our visual system adapts almost instantly to new illumination and we can perceive the color of objects in a new space correctly whatever color the illumination may be. This feature is not solely that of a commercially available camera. The difference between the human visual system and a camera raises a problem in our observation of pictures. We cannot see the exact color that a photographer intended to show us through a picture. Some color modification must be made to the picture to resolve this. In the present paper, the degree of modification was determined for various color combinations of illumination for taking a picture, FL_L and observing the picture, FL_o. An entire experiment was carried out in an actual room based on the belief that color appearance of objects is determined in relation to the recognized visual space of illumination (RVSI). A subject observed the color of a room lit by FL_L and pictures of the room lit by various colors of FL_L were taken. The pictures were displayed in another room lit by FL_o and the subject chose the picture that gave him/her the same color impression as the room of FL_L. In the case of picture slide, the color of the picture must be modified as if it were taken with the illumination inbetween the color of FL_L and FL_o. In the case of picture print, a similar modification was needed for reddish FL_L and white FL_O, but it was not needed for white FL_L and reddish FL_o.