有机和无机国画颜料漫反射光谱和吸收光谱特征研究

国画颜料解混一直是古画颜料研究的重要内容，其中光纤反射光谱（FORS）是无损化探测颜料类别的常用手段。通过CCD光纤光谱系统，从光谱线型对国画颜料进行了分类，分别探测了两种有机植物颜料藤黄和胭脂在不同比例混合下的漫反射光谱与吸收光谱，并获取了不同色系无机矿物质颜料混合后的漫反射光谱。分析了单一颜料和混合颜料的光谱特征峰值，运用多元线性回归（MLR）以及一阶导数光谱法（FDS），通过全波段线性解混获得了各组分颜料的比例。经过实验与理论分析，藤黄与胭脂的漫反射光谱为S型，混合颜料一阶导数光谱中两特征峰的位置分别为536和649 nm，在漫反射光谱中多元线性回归基本适用于该混合颜料的解混并显示出一定的线性规律，但无法精确地解混。而混合颜料的吸收光谱与单色光谱之间存在较好的线性关系，解混误差在5%左右。无机矿物质颜料中的漫反射光谱有S型（石黄和赭石）和钟型（石青和石绿）两种。首先，对于S型（石黄）与S型（赭石）混合颜料漫反射光谱，赭石的一阶导数光谱出现明显的“三峰”现象，并且混合颜料一阶导数光谱在534 nm处出现新的特征峰。多元线性回归理论虽适用于该混合颜料的解混，但由于不同颜料解混的权重因子不同，无法形成较为精准的线性模型。其次，对于S型（赭石）与钟型（石绿）混合颜料的反射光谱需要多元线性回归与导数光谱法共同判断混合比例的基本趋势，该光谱在400～800 nm范围内仅有一个交叉点。最后，利用钟型（石青）与钟型（石绿）混合颜料反射光谱的特征峰位置，即可判断出颜料混合比例的特征，随着混合比例的变化，反射光谱特征峰在457～524 nm出现了明显的横向移动，并且混合颜料光谱的峰值强度有明显的减弱。

Study on Diffuse Reflection and Absorption Spectra of Organic and Inorganic Chinese Painting Pigments

The unmixing of traditional Chinese painting pigments has always been an essential content in the study of ancient painting pigments, and the fiber optics reflectance spectra (FORS) is a standard method for nondestructive detection of pigment category. In this paper, through the CCD (charge-coupled device) optical fiber spectroscopy system, the classification of traditional Chinese painting pigments in terms of spectral lines was discussed. The diffuse reflectance and absorption spectra of two kinds of organic plant pigments gamboge and rouge in different mass ratios were detected, and the diffuse reflectance spectra of inorganic mineral pigments in different color series were obtained. The characteristic spectral peaks of a single pigment and different mixed pigments were analyzed, and the mass ratio of each pigment was obtained by the linear unmixing method of the whole band using multiple linear regression (MLR) and first derivative spectroscopy (FDS). Through experimental and theoretical analysis, the diffuse reflection spectra of gamboge and rouge are all S-type. The first derivative spectra of the mixed pigment have two characteristic peaks at 536 and 649 nm. MLR is suitable for unmixing the mixed pigment diffuse reflectance spectrum and shows a certain linear rule, but it cannot be precisely dis mixed. However, the absorption spectrum of the mixed pigment has a utterly linear relationship with the monochromatic spectrum, and the unmixing error is about 5%. The diffuse reflectance spectra of inorganic mineral pigments are S-type (mineral yellow and ochre) and bell-type (malachite and azurite). Firstly, for the diffuse reflection spectrum of S-type (mineral yellow) and S-type (ochre), the first derivative spectrum of ochre presents an obvious phenomenon of “triple-peak”. Meanwhile, the first derivative spectrum of mixed pigments presents a new characteristic peak at 534 nm. However, it cannot form a more accurate linear model due to the different weight factors of unmixing of different pigments. Secondly, for the mixed spectrum of S-type (ochre) and bell-type (malachite), it is necessary to use multiple linear regression and derivative spectroscopy to determine the basic trend of their mixing ratio jointly. Because of different lines, the reflection spectrum of mixed pigments has only one crossing point in the range of 400~800 nm. Finally, through the characteristic the peak positions of bell-type (malachite) and bell-type (azurite) pigment mixing spectra, the characteristics of pigment mixing ratio can be acquired. With the change of the mixing ratio, the characteristic peak position of the reflection spectrum showed a significant lateral movement at 457~524 nm, and the peak intensity of the mixed pigment spectrum decreased significantly.