AN ALGORITHM FOR THE TRANSFORMATION OF XRF IMAGES INTO MINERAL-DISTRIBUTION MAPS
AN ALGORITHM FOR THE TRANSFORMATION OF XRF IMAGES INTO MINERAL-DISTRIBUTION MAPS
复制标题
将 XRF 图像转换为矿物分布图的算法
DOI：
10.2113/gscanmin.38.5.1283
复制
发表时间：
2000
影响因子：
0.9
通讯作者：
K. Michibayashi
中科院分区：
文献类型：
--
作者：
Shoji Togami;M. Takano;M. Kumazawa;K. Michibayashi
开发了一种新的数值方法，利用x射线荧光（XRF）图像的像素强度来生成矿物分布图像或地图。使用扫描x射线分析显微镜（SXAM）获得XRF图像；所得的矿物分布图可用于研究岩石或矿石的岩石学特征。作为测试案例，我们将该方法应用于石英、黑云母、斜长石和钾长石为主的花岗岩。用SXAM获得了Al、Si、K、Ca和Fe等主要元素的图。XRF强度记录在256 - 256像素的地图上的每个元素。为了将这些元素分布图转换为矿物分布图，我们采用高斯分布的最大似然方法，即最小二乘法。XRF强度与所需矿物比例之间的系数是根据几百个像素的平均值确定的，这些像素记录了隔离状态下所需矿物的XRF强度。如果一个像素记录了不止一种矿物的XRF强度，则假定其强度与像素中包含的矿物组成呈线性关系。所提出的最小二乘法是纯图像分析操作（如图像增强、侵蚀、膨胀和图像布尔运算）的替代技术。花岗岩样品的实验表明，如果XRF图的采集时间足够长，例如花岗岩的采集时间为48小时，则最小二乘法可以得到合适的矿物分布图。矿物比例计算误差的来源与x射线强度的波动和每种矿物化学成分的变化有关。提出了一种估计这些误差的方法。
A new numerical method has been developed that uses the pixel-intensities from X-ray fluorescence (XRF) images to produce mineral-distribution images or maps. The XRF images are obtained using a scanning X-ray analytical microscope (SXAM); the derived mineral-distribution maps can be applied to study the petrographic characterization of a rock or ores. As a test ca se, we applied this method to a granite consisting dominantly of quartz, biotite, plagioclase and K-feldspar. Maps of the major elements, including Al, Si, K, Ca and Fe, were obtained with the SXAM. XRF intensity is recorded for each element on a 256 � 256 pixel map. To transform these element-distribution maps into mineral-distribution maps, we employed the maximum likelihood method for a Gaussian distribution, i.e., a least-squares method. The coefficient between XRF intensity and the proportion of a desired mineral was determined from the average value in a few hundred pixels that record the XRF intensity of the desired mineral in isolation. Where one pixel recorded XRF intensity for more than one mineral, its intensity was assumed to have a lin ear relationship with the composition of the minerals included in the pixel. The proposed least-squares method is an alternative technique to methods using purely image-analysis operations, such as image enhancements, erosions, dilations and image Boolean operations. Experiments with the granite sample showed that the least-squares method gives appropriate mineral-distribution maps if the acquisition time for the XRF maps is sufficiently long, e.g., 48 hours for the granite. The sources of errors in the calculated proportions of the minerals are related to fluctuations of X-ray intensities and variations of chemical composition in each mineral. A method is also proposed to estimate these errors.