Linear scan computed tomography （LCT） is of great benefit to online industrial scanning and security inspection due to its characteristics of straight-line source trajectory and high scanning speed. However, in prac...Linear scan computed tomography （LCT） is of great benefit to online industrial scanning and security inspection due to its characteristics of straight-line source trajectory and high scanning speed. However, in practical applications of LCT, there are challenges to image reconstruction due to limited-angle and insufficient data. In this paper, a new reconstruction algorithm based on total-variation （TV） minimization is developed to reconstruct images from limited-angle and insufficient data in LCT. The main idea of our approach is to reformulate a TV problem as a linear equality constrained problem where the objective function is separable, and then minimize its augmented Lagrangian function by using alternating direction method （ADM） to solve subproblems. The proposed method is robust and efficient in the task of reconstruction by showing the convergence of ADM. The numerical simulations and real data reconstructions show that the proposed reconstruction method brings reasonable performance and outperforms some previous ones when applied to an LCT imaging problem.展开更多
In this paper an electron microscopic image of diameter 80 – 120 nm and of dimensions 180×220 pixels is used as a test object to fabricate Fresnel zone plate hologram. The author proposes a different set of pupi...In this paper an electron microscopic image of diameter 80 – 120 nm and of dimensions 180×220 pixels is used as a test object to fabricate Fresnel zone plate hologram. The author proposes a different set of pupils: one pupil still being a delta function and the other being a function of = sqrt(x2+y2). The obtained reconstructed images in case of scanning holography are investigated.展开更多
激光引信以体积小、分辨率高等优势,广泛应用于弹药领域,其动态探测能力决定毁伤效能。当前激光探测已经从单点探测转向线阵扫描开展,但仿真研究多限于单一场景,动态模拟能力和实时计算效率不足,为此提出动态扫描探测模型、多材质散射...激光引信以体积小、分辨率高等优势,广泛应用于弹药领域,其动态探测能力决定毁伤效能。当前激光探测已经从单点探测转向线阵扫描开展,但仿真研究多限于单一场景,动态模拟能力和实时计算效率不足,为此提出动态扫描探测模型、多材质散射模型与高效并行计算方法,并基于此设计全链路激光线阵成像仿真系统。通过建立激光线阵推扫模型和弹目交会模型,实现弹目动态交会场景下推扫成像;构建迷彩涂层、沙漠等多目标双向反射分布函数(Bidirectional Reflectance Distribution Function,BRDF)散射模型,基于实验数据标定关键参数,有效降低BRDF平均误差;为实现对动态弹目交会场景的高效仿真,在前述动态扫描探测模型与多材质散射模型的基础上设计并行计算架构,通过采用图形处理器和包围盒层次结构结合方法,优化光线与场景面元相交判断逻辑,提高面元场景的仿真效率。新方法在不同地面背景下的回波功率仿真结果与BRDF背景关系一致,体现了模型的准确性。展开更多
扫描电子显微镜(Scanning Electron Microscope, SEM)的图像质量高度依赖于扫描电路输出信号的精度与稳定性。而现有研究对扫描信号至图像质量的影响仍缺乏深入分析。基于此,首先建立了从扫描信号到图像质量的传递机制,分析了扫描信号...扫描电子显微镜(Scanning Electron Microscope, SEM)的图像质量高度依赖于扫描电路输出信号的精度与稳定性。而现有研究对扫描信号至图像质量的影响仍缺乏深入分析。基于此,首先建立了从扫描信号到图像质量的传递机制,分析了扫描信号性能指标对图像影响;然后,通过高精度数字万用表与示波器对实际扫描信号进行精准测量,并结合端点拟合法进行数据处理,从而量化了场扫描与行扫描信号在512×512像素模式下误差水平;进一步通过MATLAB仿真各类误差对标准网格图像的影响,并导入实测信号数据,评估其在实际成像中的表现。研究表明,扫描信号整体线性性能良好,中心区域平均误差为1.884像素,优于边缘区域的2.749像素。展开更多
It is difficult to develop image reconstruction algorithms for tomographic gamma scanning based on drummed radioactive residues or wastes.In this paper,a novel reconstruction algorithm of transmission image for tomogr...It is difficult to develop image reconstruction algorithms for tomographic gamma scanning based on drummed radioactive residues or wastes.In this paper,a novel reconstruction algorithm of transmission image for tomographic gamma scanning is proposed.It is based on the conventional transmission equation and equivalent gamma-ray track length modified by a Monte Carlo method.The algorithm is implemented by simulating the samples on the established platform.For the verification experiments of the algorithm,several cubic voxel samples were designed and manufactured.Experimental tests were conducted.The tomographic gamma scanning of transmission images is compared with the linear attenuation coefficients by the simulated values and experimental data with the algorithm and the reference values.The results show that the absolute relative errors of the reconstructed images are less than 5%.展开更多
CeO2/TiO2 composite nanoparticles with different Ce/Ti molar ratios have been successfully synthesized via sol-gel method. It was found that the band gap of the nanocomposite is tunable by varying Ce/Ti content. The n...CeO2/TiO2 composite nanoparticles with different Ce/Ti molar ratios have been successfully synthesized via sol-gel method. It was found that the band gap of the nanocomposite is tunable by varying Ce/Ti content. The nonlinear response of the sample was studied by using the nanosecond laser pulses from a Q switched Nd：Yag laser employing the Z-scan method. Open aperture Z-scan experiment revealed that with the increase in the CeO2 amount in the nanocomposite, the non-linearity of the composite increases, and it was assumed that this could be due to the modification of TiO2 dipole symmetry by the addition of CeO2. Closed aperture Z-scan experiment showed that when the CeO2 amount increases, positive nonlinear refraction decreases, and this could be attributed to the increase in the two photon absorption which subsequently suppresses the nonlinear refraction.展开更多
明暗恢复形状(shape from shading,SFS)算法是三维重建中不可缺少的关键技术。该方法通过单幅图像中物体的灰度的亮度信息,求出每个点的相对高度和表面法向量,现有的SFS线性化算法利用泰勒级数进行展开忽略了高阶部分的影响,导致三维重...明暗恢复形状(shape from shading,SFS)算法是三维重建中不可缺少的关键技术。该方法通过单幅图像中物体的灰度的亮度信息,求出每个点的相对高度和表面法向量,现有的SFS线性化算法利用泰勒级数进行展开忽略了高阶部分的影响,导致三维重建的图像不够精确等问题。为解决三维重建精度问题,本文提出一种基于SFS算法改进的高精度快速水下图像三维重建方法,在提高三维重建精度的前提下,解决了对本轮数据利用率不够、迭代速度慢等问题。将其应用在真实图像和虚拟图像上进行实验评估以及三维重建的量化分析,验证了相比于经典SFS线性化算法和SFS最小化算法,本文提出的SFS算法改进的高精度快速水下图像三维重建方法,取得了令人满意的信噪比和图像信息熵值。展开更多
基金the National High Technology Research and Development Program of China(Grant No.2012AA011603)
文摘Linear scan computed tomography （LCT） is of great benefit to online industrial scanning and security inspection due to its characteristics of straight-line source trajectory and high scanning speed. However, in practical applications of LCT, there are challenges to image reconstruction due to limited-angle and insufficient data. In this paper, a new reconstruction algorithm based on total-variation （TV） minimization is developed to reconstruct images from limited-angle and insufficient data in LCT. The main idea of our approach is to reformulate a TV problem as a linear equality constrained problem where the objective function is separable, and then minimize its augmented Lagrangian function by using alternating direction method （ADM） to solve subproblems. The proposed method is robust and efficient in the task of reconstruction by showing the convergence of ADM. The numerical simulations and real data reconstructions show that the proposed reconstruction method brings reasonable performance and outperforms some previous ones when applied to an LCT imaging problem.
文摘In this paper an electron microscopic image of diameter 80 – 120 nm and of dimensions 180×220 pixels is used as a test object to fabricate Fresnel zone plate hologram. The author proposes a different set of pupils: one pupil still being a delta function and the other being a function of = sqrt(x2+y2). The obtained reconstructed images in case of scanning holography are investigated.
文摘激光引信以体积小、分辨率高等优势,广泛应用于弹药领域,其动态探测能力决定毁伤效能。当前激光探测已经从单点探测转向线阵扫描开展,但仿真研究多限于单一场景,动态模拟能力和实时计算效率不足,为此提出动态扫描探测模型、多材质散射模型与高效并行计算方法,并基于此设计全链路激光线阵成像仿真系统。通过建立激光线阵推扫模型和弹目交会模型,实现弹目动态交会场景下推扫成像;构建迷彩涂层、沙漠等多目标双向反射分布函数(Bidirectional Reflectance Distribution Function,BRDF)散射模型,基于实验数据标定关键参数,有效降低BRDF平均误差;为实现对动态弹目交会场景的高效仿真,在前述动态扫描探测模型与多材质散射模型的基础上设计并行计算架构,通过采用图形处理器和包围盒层次结构结合方法,优化光线与场景面元相交判断逻辑,提高面元场景的仿真效率。新方法在不同地面背景下的回波功率仿真结果与BRDF背景关系一致,体现了模型的准确性。
文摘扫描电子显微镜(Scanning Electron Microscope, SEM)的图像质量高度依赖于扫描电路输出信号的精度与稳定性。而现有研究对扫描信号至图像质量的影响仍缺乏深入分析。基于此,首先建立了从扫描信号到图像质量的传递机制,分析了扫描信号性能指标对图像影响;然后,通过高精度数字万用表与示波器对实际扫描信号进行精准测量,并结合端点拟合法进行数据处理,从而量化了场扫描与行扫描信号在512×512像素模式下误差水平;进一步通过MATLAB仿真各类误差对标准网格图像的影响,并导入实测信号数据,评估其在实际成像中的表现。研究表明,扫描信号整体线性性能良好,中心区域平均误差为1.884像素,优于边缘区域的2.749像素。
基金Supported by the Foundation for Returned Oversea Chinese Scholars(No.33)
文摘It is difficult to develop image reconstruction algorithms for tomographic gamma scanning based on drummed radioactive residues or wastes.In this paper,a novel reconstruction algorithm of transmission image for tomographic gamma scanning is proposed.It is based on the conventional transmission equation and equivalent gamma-ray track length modified by a Monte Carlo method.The algorithm is implemented by simulating the samples on the established platform.For the verification experiments of the algorithm,several cubic voxel samples were designed and manufactured.Experimental tests were conducted.The tomographic gamma scanning of transmission images is compared with the linear attenuation coefficients by the simulated values and experimental data with the algorithm and the reference values.The results show that the absolute relative errors of the reconstructed images are less than 5%.
基金Project supported by the Department of Science and Technology(DST),Govt.of India
文摘CeO2/TiO2 composite nanoparticles with different Ce/Ti molar ratios have been successfully synthesized via sol-gel method. It was found that the band gap of the nanocomposite is tunable by varying Ce/Ti content. The nonlinear response of the sample was studied by using the nanosecond laser pulses from a Q switched Nd：Yag laser employing the Z-scan method. Open aperture Z-scan experiment revealed that with the increase in the CeO2 amount in the nanocomposite, the non-linearity of the composite increases, and it was assumed that this could be due to the modification of TiO2 dipole symmetry by the addition of CeO2. Closed aperture Z-scan experiment showed that when the CeO2 amount increases, positive nonlinear refraction decreases, and this could be attributed to the increase in the two photon absorption which subsequently suppresses the nonlinear refraction.
文摘明暗恢复形状(shape from shading,SFS)算法是三维重建中不可缺少的关键技术。该方法通过单幅图像中物体的灰度的亮度信息,求出每个点的相对高度和表面法向量,现有的SFS线性化算法利用泰勒级数进行展开忽略了高阶部分的影响,导致三维重建的图像不够精确等问题。为解决三维重建精度问题,本文提出一种基于SFS算法改进的高精度快速水下图像三维重建方法,在提高三维重建精度的前提下,解决了对本轮数据利用率不够、迭代速度慢等问题。将其应用在真实图像和虚拟图像上进行实验评估以及三维重建的量化分析,验证了相比于经典SFS线性化算法和SFS最小化算法,本文提出的SFS算法改进的高精度快速水下图像三维重建方法,取得了令人满意的信噪比和图像信息熵值。
