共查询到19条相似文献,搜索用时 125 毫秒
1.
2.
为完善极少声波飞行时间测量数据下温度场的实时在线监测,提出将重建精度高的指数SVD法应用于圆形区域,着重研究了更多区域划分块数对重建温度场精度的影响。首先按一定方式将待测温度场划分成若干区域,逐渐增加分块数目至545块(继续增加将影响监测实时性)。然后分别对单峰、双峰温度场模型采用指数SVD法实现温度场重建,利用均方根误差评价重建精度。重建结果表明,某些条件一定时,分块数目逐渐增加,重建精度有所提高。 相似文献
3.
4.
5.
6.
7.
针对投影数据受噪声影响严重、被检测工件体积大获取投影数据不完全等导致重建质量差的问题,提出一种自适应反锐化掩模算法对某发动机模拟件投影数据均匀抽取60个角度投影进行预处理,根据其边缘信息设定阈值进行自适应去噪并对高频信息乘以自适应增益增强,采用TV最小化约束的代数重建(ART)算法重建.将改进算法与经典ART、经典反锐化掩模技术处理投影以及投影未处理的POCS-TVM算法进行对比分析,实验结果表明,该方法能够平滑噪声,提高对比度,进而提升不完全投影重建图像质量.重建同样大小的图像,相对于全角度投影迭代一次时间100 s, 60个角度投影迭代一次18.7 s,时间缩短近6倍,大量节省重建时间. 相似文献
8.
9.
立体视觉定位算法的运动估计通常在3D欧式空间中进行,但由于特征点3D坐标的噪声各向异性且分布不均匀,3D重建在深度方向上比另两个方向上的准确性差,从而导致3D欧式空间运动估计精确不高.本文提出了一种新的基于视差空间运动估计的高精度立体视觉定位算法.算法首先采用视差空间4点闭环线性解法和RANSAC算法得到初始鲁棒运动估计和匹配内点.接着,利用新的视差空间再投影误差函数提出了基于LM算法的视差空间运动参数非线性优化方法,对初始运动参数进一步优化.视差空间噪声分布均匀且各向同性,本文的初始运动参数线性估计和非线性优化都在视差空间中进行且能达到全局最小.仿真实验和真实实验结果表明,本文算法能得到高精度的立体视觉定位结果,优于传统的3D欧式空间运动估计方法. 相似文献
10.
为了改善在主动噪声控制(Active Noise Control,ANC)中由不平稳脉冲噪声引起的经典仿射投影算法稳态误差高的缺陷,利用鲁棒类M估计器代价函数对误差信号的饱和特性,将其与权重向量的L2范数约束相结合,提出类M估计器函数仿射投影算法。该算法的收敛精度相较于经典符号仿射投影算法提升3.2 dB。为了进一步提升收敛速度,将组合步长技术引入上述算法来自适应调节权重约束中的步长参数,调节收敛速度与稳态误差之间的矛盾。仿真结果表明,最终提出的算法突破固定步长的限制,可实现更快的收敛速率和更低的稳态误差,相较于已有仿射投影算法,在收敛速度方面提升2倍,在收敛精度方面提高10 d B。该算法可为之后仿射投影算法的研究提供理论指导和实验依据。 相似文献
11.
12.
Three-dimensional optical tomography techniques were developed to reconstruct three-dimensional objects using a set of two-dimensional projection images. Five basis functions, such as cubic B-spline, o-Moms, keys, and cosine functions and Gaussian basis functions, were used to calculate the weighting coefficients for a projection matrix. Two different forms of a multiplicative algebraic reconstruction technique were also used to solve inverse problems. The reconstruction algorithm was examined by using several phantoms, which included droplet behaviors and random distributions of particles in a volume. The three-dimensional volume comprised of particles was reconstructed from four projection angles, which were positioned at an offset angle of 45° between each other. Then, three-dimensional velocity fields were obtained from the reconstructed particle volume by three-dimensional cross correlation. The velocity field of the synthetic vortex flow was reconstructed to analyze the three-dimensional tomography algorithm. 相似文献
13.
Orthographic double-beam holographic interferometry for limited-view optical tomography 总被引:2,自引:0,他引:2
A simultaneous algebraic reconstruction technique (SART) that was first applied to limited-view optical tomography reconstruction of a three-dimensional asymmetric refractive-index field or a temperature distribution is presented and numerically simulated. Within two orthographic-view directions and limited view ranges, the reconstruction speed and accuracy of the SART are adequate. A new orthographic double-beam holographic-interferometric system from which multidirectional interferometric data can be obtained is first built. An asymmetric heat air-flow field is experimentally investigated by the use of orthographic double-beam holographic interferometry with double exposures. The temperatures reconstructed with the SART are consistent with those measured with a thermocouple. 相似文献
14.
Hong Shangguan Yi Liu Xueying Cui Yunjiao Bai Quan Zhang Zhiguo Gui 《International journal of imaging systems and technology》2016,26(1):3-14
It is a significant challenge to accurately reconstruct medical computed tomography (CT) images with important details and features. Reconstructed images always suffer from noise and artifact pollution because the acquired projection data may be insufficient or undersampled. In reality, some “isolated noise points” (similar to impulse noise) always exist in low‐dose CT projection measurements. Statistical iterative reconstruction (SIR) methods have shown greater potential to significantly reduce quantum noise but still maintain the image quality of reconstructions than the conventional filtered back‐projection (FBP) reconstruction algorithm. Although the typical total variation‐based SIR algorithms can obtain reconstructed images of relatively good quality, noticeable patchy artifacts are still unavoidable. To address such problems as impulse‐noise pollution and patchy‐artifact pollution, this work, for the first time, proposes a joint regularization constrained SIR algorithm for sparse‐view CT image reconstruction, named “SIR‐JR” for simplicity. The new joint regularization consists of two components: total generalized variation, which could process images with many directional features and yield high‐order smoothness, and the neighborhood median prior, which is a powerful filtering tool for impulse noise. Subsequently, a new alternating iterative algorithm is utilized to solve the objective function. Experiments on different head phantoms show that the obtained reconstruction images are of superior quality and that the presented method is feasible and effective. 相似文献
15.
用 3 个仿射图的投射方向构成 1 个仿射坐标系,同时也构成 1 个三棱锥,在此仿射坐标系中用球面三角重新研究由两个仿射图求第 3 个仿射图的投影作图理论 ——平行线束法。进一步还给出了由两个仿射图得到正投影的条件、由两个正投影得到第 3 个正投影的条件、以及由 V,H 两投影得到指定方向上的正投影的条件,简化了研究过程,得到了更简单的公式。 相似文献
16.
What is believed to be a new analysis algorithm to carry out profile measurement with low computational complexity and less noise sensitivity is presented. First, a discrete cosine transform (DCT)-based representation method is introduced to express the height distribution of a 3D surface. Then a novel shift estimation algorithm, called the DCT-based shift estimation (DCT-SE), is presented to reconstruct 3D object surfaces by using the proposed expression and the generalized analysis model. The advantage of DCT-SE is that without loss of measurement precision it provides lower computational complexity to implement 3D reconstruction from nonlinearly distorted fringe patterns and, at the same time, survives the random noise. Simulations and experiments show that the proposed DCT-SE is a fast, accurate, and efficient reconstruction algorithm for digital projection- based fringe pattern profilometry techniques. 相似文献
17.
波尔克定理的计算机化 总被引:2,自引:0,他引:2
计算机图学中轴测变换的典型算法是旋转加投影。方法可行,但有旋转角与轴测效果关系不够简明和正、斜轴测得分开讨论的两点不足。本文用图解法推出波尔克定理及轴测投射方向的表达式,使计算机图学中的轴测变换及自动消隐获得一种直观、简洁的算法,并给出本算法的BASIC子程序。 相似文献
18.
In the study of optical testing, the computed tomogaphy technique has been widely adopted to reconstruct three-dimensional distributions of physical parameters of various kinds of fluid fields, such as flame, plasma, etc. In most cases, projection data are often stained by noise due to environmental disturbance, instrumental inaccuracy, and other random interruptions. To improve the reconstruction performance in noisy cases, an algorithm that combines a self-adaptive prefiltering denoising approach (SPDA) with a multicriterion iterative reconstruction (MCIR) is proposed and studied. First, the level of noise is approximately estimated with a frequency domain statistical method. Then the cutoff frequency of a Butterworth low-pass filter was established based on the evaluated noise energy. After the SPDA processing, the MCIR algorithm was adopted for limited-view optical computed tomography reconstruction. Simulated reconstruction of two test phantoms and a flame emission spectral tomography experiment were employed to evaluate the performance of SPDA-MCIR in noisy cases. Comparison with some traditional methods and experiment results showed that the SPDA-MCIR combination had obvious improvement in the case of noisy data reconstructions. 相似文献
19.
针对语音信号压缩感知问题,在研究语音离散余弦变换(Discrete Cosine Transform,DCT)系数和小波包变换(Wavelet Packet Transform,WPT)特性的基础上构造了离散余弦小波包变换(Discrete Cosine Wavelet Packet Transform,DCWPT)。DCWPT首先获取语音信号的DCT域系数,结合语音频谱特性选取部分DCT系数进行WPT变换,从而得到比DCT系数更加稀疏的DCWPT系数。为将此变换直接用于压缩感知,构造了DCWPT的正交稀疏分解矩阵并分析了其稀疏表示性能。结合稀疏表示基优化了正交匹配追踪重构算法,提出了基于DCWPT的语音信号压缩感知框架。通过压缩重构对照实验,采用主客观评价指标,得出该方法优于传统基于DCT的语音压缩感知方法的结论。 相似文献