针对光在半透明涂层和粗糙基底构成的两层粗糙面的散射过程,采用表面生成法,考虑入射遮蔽以及多次散射效应,构建表面散射的蒙特卡罗模型,得到粗糙基底上半透明涂层的反射光的能量分布,研究涂层厚度、表面粗糙度、入射光波长等对双向反...针对光在半透明涂层和粗糙基底构成的两层粗糙面的散射过程,采用表面生成法,考虑入射遮蔽以及多次散射效应,构建表面散射的蒙特卡罗模型,得到粗糙基底上半透明涂层的反射光的能量分布,研究涂层厚度、表面粗糙度、入射光波长等对双向反射分布函数(Bidirectional Reflectance Distribution Function,BRDF)的影响.结果表明,BRDF受表面的粗糙程度影响较大,其峰值随表面均方根斜率的增加线性递减;半透明涂层厚度影响BRDF峰值的大小,厚度为十分之一波长时,BRDF达最小值;近红外光入射时镜反射方向附近BRDF的局部分布曲线相对于可见光入射时有展宽趋势,且方向半球反射率相对于可见光入射时更大.展开更多
Modeling of rough surfaces with given roughness parameters is studied,where surfaces with Gaussian height distribution and exponential auto-correlation function(ACF) are concerned.A large number of micro topography sa...Modeling of rough surfaces with given roughness parameters is studied,where surfaces with Gaussian height distribution and exponential auto-correlation function(ACF) are concerned.A large number of micro topography samples are randomly generated first using the rough surface simulation method with FFT.Then roughness parameters of the simulated roughness profiles are calculated according to parameter definition,and the relationship between roughness parameters and statistical distribution parameters is investigated.The effects of high-pass filtering with different cut-off lengths on the relationship are analyzed.Subsequently,computing formulae of roughness parameters based on standard deviation and correlation length are constructed with mathematical regression method.The constructed formulae are tested with measured data of actual topographies,and the influences of auto-correlation variations at different lag lengths on the change of roughness parameter are discussed.The constructed computing formulae provide an approach to active modeling of rough surfaces with given roughness parameters.展开更多
A novel method for multi-image matching by synthesizing image and object-space information is proposed. Firstly, four levels of image pyramids are generated according to the rule that the next pyramid level is generat...A novel method for multi-image matching by synthesizing image and object-space information is proposed. Firstly, four levels of image pyramids are generated according to the rule that the next pyramid level is generated from the previous level using the average gray values of the 3 by 3 pixels, and the first level of pyramid image is generated from the original image. The initial horizontal parallaxes between the reference image and each searching image are calculated at the highest level of the image pyramid. Secondly, corresponding image points are searched in each stereo image pair from the third level of image pyramid, and the matching results in all stereo pairs are integrated in the object space, by which the mismatched image points can be eliminated and more accurate spatial information can be obtained for the subsequent pyramid image matching. The matching method based on correlation coefficient with geometric constraints and global relaxation matching is introduced in the process of image matching. Finally, the feasibility of the method proposed in this paper is verified by the experiments using a set of digital frame aerial images with big overlap. Compared with the traditional image matching method with two images, the accuracy of the digital surface model (DSM) generated using the proposed method shows that the multiimage matching method can eliminate the mismatched points effectively and can improve the matching success rate significantly.展开更多
文摘针对光在半透明涂层和粗糙基底构成的两层粗糙面的散射过程,采用表面生成法,考虑入射遮蔽以及多次散射效应,构建表面散射的蒙特卡罗模型,得到粗糙基底上半透明涂层的反射光的能量分布,研究涂层厚度、表面粗糙度、入射光波长等对双向反射分布函数(Bidirectional Reflectance Distribution Function,BRDF)的影响.结果表明,BRDF受表面的粗糙程度影响较大,其峰值随表面均方根斜率的增加线性递减;半透明涂层厚度影响BRDF峰值的大小,厚度为十分之一波长时,BRDF达最小值;近红外光入射时镜反射方向附近BRDF的局部分布曲线相对于可见光入射时有展宽趋势,且方向半球反射率相对于可见光入射时更大.
基金Projects(51535012,U1604255)supported by the National Natural Science Foundation of ChinaProject(2016JC2001)supported by the Key Research and Development Project of Hunan Province,China
文摘Modeling of rough surfaces with given roughness parameters is studied,where surfaces with Gaussian height distribution and exponential auto-correlation function(ACF) are concerned.A large number of micro topography samples are randomly generated first using the rough surface simulation method with FFT.Then roughness parameters of the simulated roughness profiles are calculated according to parameter definition,and the relationship between roughness parameters and statistical distribution parameters is investigated.The effects of high-pass filtering with different cut-off lengths on the relationship are analyzed.Subsequently,computing formulae of roughness parameters based on standard deviation and correlation length are constructed with mathematical regression method.The constructed formulae are tested with measured data of actual topographies,and the influences of auto-correlation variations at different lag lengths on the change of roughness parameter are discussed.The constructed computing formulae provide an approach to active modeling of rough surfaces with given roughness parameters.
基金Supported by the National Natural Science Foundation of China (Nos. 40771176, 40721001)
文摘A novel method for multi-image matching by synthesizing image and object-space information is proposed. Firstly, four levels of image pyramids are generated according to the rule that the next pyramid level is generated from the previous level using the average gray values of the 3 by 3 pixels, and the first level of pyramid image is generated from the original image. The initial horizontal parallaxes between the reference image and each searching image are calculated at the highest level of the image pyramid. Secondly, corresponding image points are searched in each stereo image pair from the third level of image pyramid, and the matching results in all stereo pairs are integrated in the object space, by which the mismatched image points can be eliminated and more accurate spatial information can be obtained for the subsequent pyramid image matching. The matching method based on correlation coefficient with geometric constraints and global relaxation matching is introduced in the process of image matching. Finally, the feasibility of the method proposed in this paper is verified by the experiments using a set of digital frame aerial images with big overlap. Compared with the traditional image matching method with two images, the accuracy of the digital surface model (DSM) generated using the proposed method shows that the multiimage matching method can eliminate the mismatched points effectively and can improve the matching success rate significantly.
