共查询到16条相似文献,搜索用时 125 毫秒
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针对光学计算机层析术(Optical Computerized Tomography,OCT)中有限角条件下的严重非完全数据重建问题,提出了正交投影采样,结合基于改进的代数重建术(ART)的先验知识算法,以在尽可能少的投影方向数下较好地重建含遮挡物的三维流场。通过计算机模拟,详细讨论了在有限角条件下含遮挡物的三维流场的非完全数据重建精度及误差分析。结果表明,在有限角及含遮挡物条件下,采用正交投影采样可以极大地减少严重非完全数据重建中的误差,提高重建精度,从而为将光学计算机层析术应用于非完全数据的实测中提供了参考。 相似文献
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一种新的叠栅层析迭代算法 总被引:4,自引:3,他引:1
利用叠栅层析具有的测量动态范围大,对震动环境不敏感的特点,从其偏折原理的本质出发,提出一种利用代数迭代法来重建三维流场的叠栅层析重建算法。在此基础上进行了双峰函数的模拟实验,分别进行了6方向,12方向以及叠加高斯噪声的12方向的数值重建,并在相同条件下与滤波反投影方法和对偏折投影数据积分的代数迭代算法这两种已有的叠栅层析重建算法进行了比较,同时用该新算法结合属性矩阵对包含遮挡物的模拟场进行重建。对比重建结果,本算法具有较强的抗噪声能力,并且对非完全数据下的层析重建也有较好的处理效果。 相似文献
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使用叠栅层析技术测量超音速风洞中的非对称复杂密度场 总被引:1,自引:1,他引:0
使用叠栅层析技术解决超音速风洞中复杂密度场的测量难题。应用高灵敏度叠栅偏折仪和间隔角度旋转模型的方法获取超音速风洞中流场的多方向叠栅条纹图。层析计算中使用一种新的偏折角修正迭代的叠栅层析算法,该方法可以实现对有限角采样和包含遮挡物的非完全数据重建,迭代过程中结合内边界平滑滤波提高重建精度。实验中获取了马赫数为2.52的超音速风洞中9幅不同采样角的条纹图,经过50次迭代计算后重建出膨胀波区非对称密度场的截面分布,并对测量结果和误差进行了分析和讨论。使用计算流体力学技术对该密度场进行建模和计算,验证了叠栅层析重建结果的正确性,证实了该技术在测量复杂流场领域的重要价值。 相似文献
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光学层析重建算法改进的研究 总被引:17,自引:8,他引:9
光学层析技术在温度、密度等流场的非接触测试中有着广泛的应用前景,然而光学层析的重建是非完全数据的投影重建,通常采用的代数迭代法不能很好地解决重建精度这一难题。为此提出了一种新的光学层析技术的代数迭代重建算法,在算法中引入了包含先验知识的属性矩阵,并摒弃了通常所采用的对超松弛系数人为的确定取法,采用了变超松弛系数。实验计算结果表明,引入属性矩阵和变超松弛系数的代数迭代法能够较好的重建非完全数据投影的待测场,极大地提高重建精度,较好地与实测结果吻合。 相似文献
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计算流动显示技术(CFI)在自然对流流场测量中的应用 总被引:1,自引:0,他引:1
计算流动显示(CFI)技术通过利用仿真光测实验中光束的运动规律与光学干涉测量方法的数学模型,并根据计算流体动力学(CFD)的结果,获得仿真的光学干涉图像。本文通过计算机模拟数字散斑干涉中激光光束的运动规律得到了封闭方腔中空气自然对流的CFI光学图像,并将此仿真光学图像与实验得到的图像进行对比,指导实验的进行和自然对流中测试参数的计算。 相似文献
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三维重建是层析粒子图像测速(PIV)中重要的一步,重建过程中的权重系数计算通常较为繁琐。基于此,提出一种层析PIV快速权重计算方法——正向投影面积(FPA)法,即将离散体素投影在相应像元上的面积作为权重系数计算的方法。首先,基于针孔相机模型构建三维空间内粒子多视角投影成像仿真程序,生成仿真图片用于方法分析与验证;其次,将FPA方法结合目前主流重建算法开展三维重建精度和耗时分析。结果表明,当用于本研究所述测量区域重建时,相比于传统后向方法与亚网格法权重系数计算方法,FPA法的权重矩阵元素个数分别降低了大约3个和1个数量级,计算时间分别减少了97%与85%,相应地降低了计算机的内存占用,且FPA法与传统后向方法所计算的权重矩阵的平均相似度高于0.9974。在常用实验粒子数分数(pppp=0.05)下,该方法结合目前主流重建算法的重建精度可达0.8以上。同时基于仿真图片分析了相机最佳采集角度以及实验相机噪声对重建结果的影响,结果表明,在实验噪声条件下重建结果仍然满足三维流场重建的要求。 相似文献
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使用计算流体动力学、传热学、固体弹性力学和光学的多物理场耦合集成仿真分析技术完成了红外热像仪中光机的热特性与热设计研究.采用有限单元法(Finite Element Method,FEM)和计算流体动力学(Computational Fluid Dynamics,CFD)得到了光机内部的温度场、应力变形分布及光学件面形... 相似文献
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An algorithm, termed the variable grid method (VGM), has been developed to provide enhanced reconstruction by interferometric tomography under the ill-posed problems of restricted angular scanning and incomplete projection that frequently arise in flow measurements. The algorithm is based on variable grid decomposition of a field. The performances of the two versions of the VGM are compared to investigate the effects of the redundancy criteria in generating variable grid elements. Performance comparison is also made with a conventional fixed grid method. The testing is conducted through computer simulation of experiments and reconstruction with a known three-dimensional field that has been produced by computational fluid dynamics. The reconstruction through computer simulation demonstrates the superiority of the two VGMs to the conventional method. Both the maximum and average reconstruction errors are reduced appreciably. The VGM version with stricter parameter contro performs best. The technique can reflect spatial information contained in measured data. Thus, improvement is noticeable in the regions with dense scanning of probing rays. These regions are usually of interest in engineering applications. 相似文献
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In this paper, we propose a novel performance-enhanced computational integral imaging reconstruction (CIIR) scheme by additional use of an imaging lens. In the proposed scheme, elemental images can be obtained by using a simultaneous pickup scheme of far three-dimensional (3D) objects from the lenslet array in both real and virtual image fields. And additional imaging lens produces an image shift effect of 3D objects located far away from the lenslet array and improve the visual quality of reconstructed images in CIIR by overcoming limitation of pickup range in integral imaging. To show the usefulness of the proposed system, some experiments are carried out for real 3D objects and its results are presented. 相似文献
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Aiming at the effect of species composition distribution on flow field's temperature reconstruction from the experimentally measured refractive index, a temperature partition reconstruction method based on flow field's phase distribution is proposed. Moiré deflection tomography is chosen to obtain the refractive index of a flame with probe wavelength of 808 nm. Enlightened by the visual characteristic of optical computerized tomography (OCT) for flow field and the practical structure of the flame, it is divided into three regions in radial direction based on its phase distribution. The essence is that the temperature is reconstructed with adopting different species composition for different regions. Finally, the rationality of the method is analyzed. 相似文献
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Deflection tomography with limited angle projections was investigated to visualize a premixed flame. A projection sampling system for deflection tomography was used to obtain chronological deflectogram arrays at six view angles with only a pair of gratings. A new iterative reconstruction algorithm with deflection angle compressed-sensing revision was developed to improve reconstruction-distribution quality from incomplete projection data. Numerical simulation and error analysis provided a good indication of algorithm precision and convergence. In the experiment, 150 fringes were processed, and temperature distributions in 20 cross-sections were reconstructed from projection data in four instants. Four-dimensional flame structures and temperature distributions in the flame interior were visualized using the visualization toolkit. The experimental reconstruction was then compared with the result obtained from computational fluid dynamic analysis. 相似文献