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针对传统的层析方法中,投影方向多、系统复杂等特点,提出了基于三个投影方向的层析重建方法.论文选取适用于少投影方向的代数迭代重建算法,采用参量修正方法,能较好的提高重建准确度和抑制椒盐噪音.同时对影响重建图像质量和速度的迭代次数、不同原图像结构对重建图像质量的影响进行了分析,给出了相应分析模拟结果.结果表明,迭代300次后,重建结果基本稳定.同时对于具有轴对称结构物体,三个方向投影数据能够较好地实现三维层析重建.分析结果为后期开展的基于单幅层析全息图的三维层析重建实验研究提供了理论依据. 相似文献
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基于三投影方向的层析重建分析 总被引:2,自引:0,他引:2
针对传统的层析方法中,投影方向多、系统复杂等特点,提出了基于三个投影方向的层析重建方法.论文选取适用于少投影方向的代数迭代重建算法,采用参量修正方法,能较好的提高重建准确度和抑制椒盐噪音.同时对影响重建图像质量和速度的迭代次数、不同原图像结构对重建图像质量的影响进行了分析,给出了相应分析模拟结果.结果表明,迭代300次后,重建结果基本稳定.同时对于具有轴对称结构物体,三个方向投影数据能够较好地实现三维层析重建.分析结果为后期开展的基于单幅层析全息图的三维层析重建实验研究提供了理论依据. 相似文献
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提出了少量投影数字全息层析重建技术.以具有轴对称结构的光纤和非轴对称结构的石膏头像为实验样本,开展了基于单幅全息图和代数迭代重建算法的层析重建模拟分析及实验研究.模拟分析表明,代数迭代重建算法中的加权因子以及松弛因子对重建图像质量影响显著,因此对加权因子采用非线性加权计算方法,以及通过多次模拟重建结果的比较选择合适的松弛因子.层析重建实验结果表明,无论被测物体是轴对称结构或是非轴对称结构,少量投影数字全息层析重建是可行的,也是有效的.这为下一步针对生物样本内部多层折射率检测和基于单幅层析全息图实现三向实时数字全息层析重建技术研究提供了必要的基础. 相似文献
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本文主要针对计算机断层成像(computed tomography,CT)不完全投影数据重建中探测器全覆盖稀疏角度重建和探测器部分覆盖截断数据重建问题,综述了其在研究方法上国内外的进展.在探测器对被检测物体可以完全覆盖的情况下,针对稀疏均匀采样和视角受限采样,探讨了离散模型迭代重建算法和压缩感知采样重建算法.在探测器对被检测物体不能完全覆盖的情况下,探讨了锥束螺旋BPF重建算法、加型迭代重建算法和锥束FDK改进算法.论文可以为CT重建领域的研究工作者提供全面的方法梳理和总结,并指出了当前研究的重点和未来研究的方向. 相似文献
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用改进的共轭斜量迭代法重建三维折射率场 总被引:3,自引:0,他引:3
本文通过计算机模拟运算,结合折射率场(温度场)的先验知识,考查了改进的共轭斜量迭代法用于全息干涉计量三维折射率场的重建精度及视角范围和数据噪声的影响,并介绍了一种抑制较大噪声的算法.作为一个应用实例,计算了某一截面火焰温度场的分布,并与热电偶测量的值进行了比较. 相似文献
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用正交光路全息干涉CT技术重建电弧等离子体三维温度场 总被引:3,自引:3,他引:0
本文利用正交光路全息干涉技术和计算机有限角层析算法,借助电弧等离子体物理方程,对非对称电弧等离子体三维温度场的诊断进行了研究. 相似文献
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用快速傅里叶变换迭代法重建三维折射率场 总被引:6,自引:2,他引:4
本文通过计算机模拟运算,结合折射率场的先验知识,考查了以卷积法为基的快速傅里叶变换迭代法的重建精度以及误差数据和视角范围大小对其的影响.作为一个应用实例,计算了某一截面火焰温度场的分布,并与热电偶测量的值进行了比较. 相似文献
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For reconstructing based on incomplete projection data, an improved max-entropy reconstruction algorithm is presented in this paper. Both least-square and max-entropy are used in this algorithm, and the penalize-function method is used in iterative processing. The numerical simulation of three different tested fields has been done. Compared with conventional three-dimensional reconstruction algorithms, this novel algorithm has a higher reconstruction precision as well as a better astringency, particularly in the case of easy tested field. For the reconstruction of asymmetric complicated tested field, it also has a good result if suitable projective direction and iterative times can be choosen. Finally, the application of this novel algorithm to diagnose the temperature field of arc plasma is presented. 相似文献
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Reconstruction model for temperature and concentration profiles of soot and metal-oxide nanoparticles in a nanofluid fuel flame by using a CCD camera 下载免费PDF全文
This paper presents a numerical study on the simultaneous reconstruction of temperature and volume fraction fields of soot and metal-oxide nanoparticles in an axisymmetric nanofluid fuel sooting flame based on the radiative energy images captured by a charge-coupled device(CCD) camera. The least squares QR decomposition method was introduced to deal with the reconstruction inverse problem. The effects of ray numbers and measurement errors on the reconstruction accuracy were investigated. It was found that the reconstruction accuracies for volume fraction fields of soot and metaloxide nanoparticles were easily affected by the measurement errors for radiation intensity, whereas only the metal-oxide volume fraction field reconstruction was more sensitive to the measurement error for the volume fraction ratio of metaloxide nanoparticles to soot. The results show that the temperature, soot volume fraction, and metal-oxide nanoparticles volume fraction fields can be simultaneously and accurately retrieved for exact and noisy data using a single CCD camera. 相似文献
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声波在非均匀温度场中传播时会由于声波的折射而产生声线弯曲现象。为提高非均匀温度场声学CT (Computer Tomography)重建精度,提出一种考虑声线弯曲的重建算法。首先用最小二乘法获得一个不考虑声线弯曲的重建温度场,然后用打靶-插值法确定本征声线出射角,用三角形前向展开法追踪声线,获得此温度场中声波发射/接收器间的本征声线,建立本征声线上声波传播时间与温度分布间的关系,进而实现考虑声线弯曲的最小二乘法温度场重建。单峰、双峰温度场仿真重建结果表明:所采用的本征声线追踪法计算简单运行速度快;考虑声线弯曲后,可明显提高温度场重建精度。因此所提重建算法能更好地适应实际温度场重建需求。 相似文献
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Vecherin SN Ostashev VE Ziemann A Wilson DK Arnold K Barth M 《The Journal of the Acoustical Society of America》2007,122(3):1416
Acoustic travel-time tomography allows one to reconstruct temperature and wind velocity fields in the atmosphere. In a recently published paper [S. Vecherin et al., J. Acoust. Soc. Am. 119, 2579 (2006)], a time-dependent stochastic inversion (TDSI) was developed for the reconstruction of these fields from travel times of sound propagation between sources and receivers in a tomography array. TDSI accounts for the correlation of temperature and wind velocity fluctuations both in space and time and therefore yields more accurate reconstruction of these fields in comparison with algebraic techniques and regular stochastic inversion. To use TDSI, one needs to estimate spatial-temporal covariance functions of temperature and wind velocity fluctuations. In this paper, these spatial-temporal covariance functions are derived for locally frozen turbulence which is a more general concept than a widely used hypothesis of frozen turbulence. The developed theory is applied to reconstruction of temperature and wind velocity fields in the acoustic tomography experiment carried out by University of Leipzig, Germany. The reconstructed temperature and velocity fields are presented and errors in reconstruction of these fields are studied. 相似文献