彩色叠焦显微颜色空间聚焦评价算法

聚焦评价是叠焦扩展显微景深的关键,为了准确快速地获取叠焦图像序列像素点聚焦位置,生成高质量全聚焦图像,提出了一种基于颜色向量空间的聚焦评价算法。该算法直接在RGB向量空间中计算彩色图像梯度,充分利用了颜色通道间的相关性,避免了传统聚焦评价算法将彩色图转化为灰度图时造成的信息损失,且相较于彩色分量梯度的简单叠加具有更高的准确度;将中心像素与邻域像素在RGB空间的曼哈顿距离均值作为聚焦评价权值,可增强聚焦部分的敏感度,降低离焦部分的评价值,使聚焦评价曲线特性趋向理想化。选取空域、频域和统计学中7种聚焦评价算法与所提算法进行性能对比实验,结果表明:所提算法在仿真图像和真实显微图像中,具有更好的灵敏度、聚焦分辨力和抗噪声能力,曲线特性提升显著,应用于显微镜景深扩展可进一步提升叠焦大景深成像的质量。

叠焦三维显微视觉测量聚焦评价算法研究

为了精确、快速提取叠焦三维显微视觉测量的叠焦图像序列像素点聚焦位置,提出了基于最大梯度的聚焦评价算法。设计了2个带通掩膜算子和4个高通掩膜算子,在带通信号和高通信号中提取每个像素点对于相邻像素点强度变化的最大值来表示该点的聚焦程度,以提高聚焦评价函数提取梯度信息的能力。采用自适应梯度阈值分割算法提高了聚焦评价的灵敏度,降低了聚焦评价曲线的波动及次峰的影响。开展实验对算法的实际性能进行验证,结果表明:相较经典的空间域聚焦评价算法,基于最大梯度的聚焦评价算法的鲁棒性、灵敏度、无偏性和单峰性均显著提高,且具有很好的实用性,能够有效满足复杂轮廓微纳米级三维显微测量聚焦评价要求。

叠焦大景深成像中的聚焦评价算子性能评估方法

聚焦评价算法是叠焦大景深成像的核心,针对聚焦评价算子性能评估方面的实验需求,提出了一种基于图像序列采样点聚焦评价散点图高斯拟合的聚焦评价算子性能评估方法,对已有的聚焦评价算子进行了性能评估实验。将传统的图像清晰程度指标加以改造,提出了一种梯度加权图像锐度算子,并采用实采图像和模拟图像分别对比了所提算子与现有算子的性能差异。研究结果对于实施叠焦测量有一定参考意义。

Carbonate metasomatism in the lithospheric mantle: Implications for cratonic destruction in North China

The activity of melts and fluids may have played a key role in inducing the destruction of the eastern North China Craton in the early Cretaceous. Carbonate melts are important agents in mantle metasomatism and can significantly modify the physical and chemical properties of the subcontinental lithospheric mantle. Carbonate metasomatism can be identified by specific geochemical indices in clinopyroxene, such as high Ca/Al and low Ti/Eu ratios. This study presents the spatial and temporal variations of carbonate metasomatism in the lithospheric mantle beneath the eastern North China Craton. Three types of carbonate metasomatism are classified based on the geochemical compositions of clinopyroxene in mantle peridotites. Clinopyroxene formed by Type 1 carbonate metasomatism is characterized by very high Ca/Al ratios(15–70) and^(87)Sr/^(86)Sr ratios(0.706–0.713). Clinopyroxene derived from Type 2 carbonate metasomatism shows relatively high Ca/Al ratios(5–18) and^(87)Sr/^(86)Sr ratios(0.703–0.706). However, clinopyroxene resulting from Type 3 carbonate metasomatism has low Ca/Al ratios(5–9) and^(87)Sr/^(86)Sr ratios(0.702–0.704). Deep(garnet-bearing) and shallow(spinel-bearing) lithospheric mantle beneath the Sulu orogen and surrounding areas in the eastern North China Craton were affected by intense Type 1 carbonate metasomatism before the late Triassic. The deep subduction of the South China Block with its accompanying carbonate sediments was the trigger for Type 1 carbonate metasomatism, which reduced strength of the lithospheric mantle and provided a prerequisite for the destruction of the eastern North China Craton in the early Cretaceous. After the destruction of the eastern North China Craton, the ancient relict lithospheric mantle, represented by spinel harzburgite xenoliths hosted in the late Cretaceous to Cenozoic basalts,only recorded Type 2 carbonate metasomatism. This implies that the lithospheric mantle experienced the intense Type 1 carbonate metasomatism was completely destroyed and not preserved during decratonization. Spinel lherzolite xenoliths hosted in the late Cretaceous to Cenozoic basalts represent the young, fertile lithospheric mantle formed after the cratonic destruction and only a few samples record Type 2 and 3 carbonate metasomatisms. We suggest that carbonate melts derived from the subduction-modified asthenospheric mantle with variable proportions of recycled crustal material was responsible for the Type 2 and 3 carbonate metasomatisms. The carbonate metasomatism of the lithospheric mantle beneath the Jiaodong Peninsula and surrounding areas is very pervasive and is spatially consistent with the remarkable thinning of lithospheric mantle and giant gold deposits in this region. Therefore, we conclude that carbonate metasomatism in the lithospheric mantle played a crucial part in the modification, destruction and gold deposits in the eastern North China Craton.