受干扰光谱信息中矿物颜料粒径信息的获取

摘要

Accurate color matching of mineral pigments is a key to attaining high-quality restoration and high-fidelity reproduc-tion of the cultural heritage murals .The particle size of mineral pigments is an important factor affecting color information and spectral reflectance .Accurately obtaining the spectral reflectance of mineral pigments on the mural surface facilitates the identifi-cation of pigment particle size .However ,spectral information which is disturbed cannot match with the spectral database of min-eral pigment particle sizes accurately .Therefore ,determining the effective particle size from the spectral information is impossi-ble .The ratio derivative method is proposed to compensate for the disturbance .The spectral information is converted from spec-tral reflectance space to ratio derivative spectrum space ,which reduces disturbances and enhances the spectra information charac-teristics of mineral pigments .Spectral matching is then performed in the ratio derivative spectrum space .In the experiments ,Azurite and Malachite mineral pigments ,which are frequently used in murals ,were utilized as color samples disturbed by sub-strate and white pigments .The proposed method was used to analyze the experimental sample data .Results of spectral angle measurement and matching of the spectral curve in the ratio derivative space showed that matching accuracy can meet the require-ments ,verifying the validity of the method .The proposed method solves the problem of inaccurate matching of the disturbed spectral reflectance and provides accurate particle size reference information for color matching of mineral pigments during mural restoration .%矿物颜料的准确配色是实现文物壁画高品质修复,颜色高保真还原的关键技术.矿物颜料颗粒的粒径大小是影响矿物颜料颜色信息和光谱反射率信息的一个重要因素.准确获取壁画表面的矿物颜料光谱反射率信息,是实现颜料颗粒粒径信息识别的有效途径.但是,由于壁画表面矿物颜料部分采样点的光谱信息受到了干扰,无法与不同粒径的矿物颜料的光谱数据库准确匹配,因此也无法从采集的光谱信息中获取有效的粒径信息.针对受干扰的颜料光谱信息,提出利用比值导数法对其进行处理.把光谱信息从光谱反射率空间转换到比值导数光谱空间进行匹配,降低光谱中的干扰信息,增强矿物颜料颗粒本身的光谱特征信息.以壁画中常用的不同粒径的石青和石绿矿物颜料为实验对象,制成色块样本,以基底和白色颜料为主要影响因素,对文中提出的方法进行测试.光谱角度量的结果和光谱曲线图的匹配结果显示,在比值导数光谱空间,获得了满意的光谱匹配精度.验证了文中提出的分析方法可以解决实验中受干扰颜料光谱匹配不准确而无法获得粒径信息的问题,能够为壁画修复过程中矿物颜料的配色提供准确的粒径信息参考.