共查询到20条相似文献,搜索用时 31 毫秒
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Quantitative interferometric microscopy is an important method for observing biological samples such as cells and tissues. As a key step in phase recovery, a fast phase unwrapping algorithm is proposed. By shifting mod 2π wrapped phase map for one pixel, then multiplying the original phase map and the shifted one, the phase discontinuities could be easily determined with high speed and efficiency. The method aims at enhancing phase retrieving efficiency without any background knowledge. We test our algorithm with both numerical simulation and experiments, by focusing our attentions on wrapped quantitative phase maps of cells. The results indicate that this algorithm features fast, precise and reliable. 相似文献
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减少条纹投影轮廓术的条纹图数量一直是本领域的研究热点。传统的时间相位解包裹算法,一般需要额外的条纹信息来确定条纹级次,导致条纹图数量过多。提出一种用于三维测量的快速相位解包裹算法,只需要N步标准相移正弦条纹图,就可以完成绝对相位的计算。首先,利用标准相移算法计算包裹相位和消除背景的掩膜;然后,直接利用包裹相位和掩膜,根据连通域标记算法计算条纹级次,进而求得绝对相位。该方法最少只需3幅条纹图,就可以完成三维测量,数据处理速度快。计算机仿真和实验结果验证了该方法的有效性和鲁棒性。 相似文献
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A novel algorithm for branch cut phase unwrapping 总被引:1,自引:0,他引:1
Dongliang ZhengFeipeng Da 《Optics and Lasers in Engineering》2011,49(5):609-617
Branch cut method is a powerful noise-immune algorithm for correct phase unwrapping of noisy phase maps. The shortest branch cut length promises the optimal unwrapping result of the wrapped phase maps. A new algorithm is proposed to search for the shortest branch cut length by simple exchange operation. Although the algorithm is on the basis of stochastic search techniques, it has a high probability of finding the shortest branch cut length or an approximation of it. Compared with the traditional algorithms, the algorithm is fast and competitive. 相似文献
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Photoelastic stress analysis is a full-field optical technique for experimental stress analysis whose automation has received considerable research attention over the last 15 years. The latest developments have been made possible largely due to the availability of powerful calculators with large memory capacity and colour, high resolution, cameras. A further stimulus is provided by the photoelastic resins now used for rapid prototyping. However, one critical aspect which still deserves attention is phase unwrapping. The algorithms most commonly used for this purpose have been developed in other scientific areas (classical interferometry, profilometry, moiré, etc.) for solving different problems. In this article a new algorithm is proposed for temporal phase unwrapping, which offers several advantages over those used today. 相似文献
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A generalized temporal phase unwrapping algorithm for three-dimensional profilometry 总被引:1,自引:0,他引:1
A generalized temporal phase unwrapping algorithm is proposed for absolute phase measurement of object surfaces with complex topography. We first make comments on error analysis of various temporal phase unwrapping (TPU) algorithms and point out problems existing in these techniques. We present a generalized TPU algorithm (GTPU), which eliminates some limitations imposed on the fringe sequence for the classical TPU algorithms. So the desired number of fringes can be determined according to practical situation, leading to a flexible method for phase reconstruction. In addition, compared with the classical TPU algorithms, GTPU has better noise immunity and less computational complexity. Theoretical analysis and experiment results are presented to show the validity of the proposed algorithm. 相似文献
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Automatic phase unwrapping algorithm for reconstruction of three-dimensional objects 总被引:1,自引:0,他引:1
Phase unwrapping plays a very important role in noncontact optical profilometries and interforometric techniques. This phase unwrapping process is often hindered by the presence of noise, spots of low-intensity modulation, and the instability of the solutions. We present a systematic approach to the problem by formulating the phase solving and unwrapping as an ill-posed problem. By using the regularization method and taking intensity modulation into consideration, we will be able to provide a unified view to address various challenges in the problem. A new fully automated algorithm for phase unwrapping based on this approach is also presented. 相似文献
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A newly developed phase-unwrapping algorithm, which is termed Tapestry Cellular Automata, are presented. Fundamental restrictions of traditional path-dependent phase unwrapping algorithms such as noise propagation and inconsistent data reconstruction are discussed first. The advantages and drawbacks of a path-independent algorithm, Cellular Automata, are then examined. The parallel and distributed processing nature of Tapestry Cellular Automata is shown to be able to keep the merits of traditional Cellular Automata algorithm while taking advantage of the rapid advancement of personal computers such as distributed computing over internet or intranet and multi-tasks operating environment. Both numerical simulation and experiments used to examine the effectiveness of this newly developed algorithm are presented in detail as well. 相似文献
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最小二乘相位解包络方法 总被引:4,自引:0,他引:4
介绍一种最小二乘解相位包络的方法 ,该法的优点在于把图像作为一个整体处理 ,图像上每一个像素点的值由方程唯一确定 ,而且解得的相位图与原包裹的相位图偏差平方加权最小 ,具有局部解相法所不具有的优点。实验证明 ,它能够处理局部处理方法难以解决的相位图 ,并给出几幅实际相位图的处理结果 相似文献
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After discussing Schofield's fast Fourier transform (FFT) algorithm, a (weighted) discrete-cosine-transform-based (DCT-based) phase-unwrapping (PU) algorithm is described. The algorithm could unwrap some high-phase-variation map which the FFT algorithm could not solve. Although the DCT algorithm is derived from Schofield's FFT PU algorithm, unlike FFT, it avoids the mirroring operation in implementing the boundary conditions so that it has higher efficiency in PU. Furthermore, in order to improve the reliability and noise robustness, we introduce the phase derivative variance (PDV) quality weight extracted from quality map into the DCT algorithm. The unwrapped results of both the computer-simulated and interferometric synthetic aperture radar (IFSAR) data demonstrate that the (weighted) DCT PU algorithm is generally effective, especially in dealing with the high-phase-variation and/or irregular-phase-distribution maps. 相似文献
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基于小波变换的最小二乘相位解缠算法 总被引:1,自引:2,他引:1
最小二乘法是求解二维相位解缠问题最稳健的方法之一,其本质是在最小二乘意义下使缠绕相位的离散偏导数与解缠相位的偏导数整体偏差最小,并等效为可求解一大型的稀疏线性方程系统。由于系统矩阵结构的稀疏性,在采用迭代法求解时收敛速度非常慢。为了改善收敛特性,提出一种基于多分辨率表示的离散小波变换相位解缠算法。利用小波变换将原线性系统转化成具有较好收敛条件的等价新系统。仿真实验表明,该方法能够很好的恢复真实相位,其解缠效果优于Gauss-Seidel松弛迭代和多重网格法。 相似文献
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Phase unwrapping is the process of determining the absolute phase given its principal value. In this paper, we show that morphological image processing techniques can be helpful for solving this problem. The proposed procedure consists of three independent modules. The first aims at extracting a region of interest corresponding to the areas where interferences occur. This is achieved by processing the input interferograms with a combination of morphological opening and closing operators. The second finds the high boundaries of the wrapped fringes by enhancing them with a morphological gradient by erosion. Gaps along the fringe boundaries which would lead to errors in the unwrapped phase map are filled in by a morphological region growing segmentation technique. The third module consists in integrating the wrapped phase while taking into account the segmented fringes. 相似文献
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Half-quadratic cost functions for phase unwrapping 总被引:2,自引:0,他引:2
We present a generic regularized formulation, based on robust half-quadratic regularization, for unwrapping noisy and discontinuous wrapped phase maps. Two cases are presented: the convex case and the nonconvex case. The unwrapped phase with the convex formulation is unique and robust to noise; however, the convex function solution deteriorates as a result of real discontinuities in phase maps. Therefore we also present a nonconvex formulation that, with a parameter continuation strategy, shows superior performance. 相似文献
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Weighted least-squares phase unwrapping algorithm based on derivative variance correlation map 总被引:1,自引:0,他引:1
Among different phase unwrapping approaches, the weighted least-squares minimization methods are gaining attention. In these algorithms, weighting coefficient is generated from a quality map. The intrinsic drawbacks of existing quality maps constrain the application of these algorithms. They often fail to handle wrapped phase data contains error sources, such as phase discontinuities, noise and undersampling. In order to deal with those intractable wrapped phase data, a new weighted least-squares phase unwrapping algorithm based on derivative variance correlation map is proposed. In the algorithm, derivative variance correlation map, a novel quality map, can truly reflect wrapped phase quality, ensuring a more reliable unwrapped result. The definition of the derivative variance correlation map and the principle of the proposed algorithm are present in detail. The performance of the new algorithm has been tested by use of a simulated spherical surface wrapped data and an experimental interferometric synthetic aperture radar (IFSAR) wrapped data. Computer simulation and experimental results have verified that the proposed algorithm can work effectively even when a wrapped phase map contains intractable error sources. 相似文献
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This work presents a robust algorithm for phase unwrapping. The proposed algorithm is based on the expansion of the estimated phase through a linear combination of a set of Basis Functions. We present a novel weighted robust functional which is minimised using a two step strategy. This model allows us to reduce the influence of noise and to remove inconsistent pixels in the estimation of the unwrapped phase. The proposed model assumes that the phase is smooth. Under this assumption, experiments demonstrate that if the phase is corrupted by high levels of noise, our model presents a better performance than state of the art algorithms. For low levels of noise, the results are comparable. 相似文献
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The intrinsic drawbacks of existing reliability-based algorithms, they often fail to handle wrapped phase data contains error sources, such as phase discontinuities, noise and undersampling. These algorithms often calculate the reliability only relying on the recorded pixel intensity or wrapped phase value, but the intensity of pixel always exist many noises. In this paper, we present a new method to define the reliability of pixel and path of phase unwrapping, the pixel's intensity and color are employed in fringe analysis simultaneously. The reliability function is calculated based on modulation, second difference of wrapped phase, and second difference of modulation, then we present the concept of smoothness of path, the reliability of path is calculated based on reliability of pixel and smoothness of path. Experiment results validate our proposed algorithm is more accurate than many previous algorithms. The proposed algorithm can be used to unwrap the complex phase map with discontinuous jump, and can be implemented with high efficiency without any manual interface. 相似文献
19.
A novel phase unwraping method has been presented and evaluated in this paper. This method works by first constructing a quality map based on the characteristic of the active triangulation system from the wrapped phase data. The quality map is then used to guide the unwrapping. In order to reduce the execution time of phase unwrapping, we tessellate the whole wrapped phase map into blocks. Blocks with higher confidence will be unwrapped first. Experiment shows that this method can unwrap the wrapped phase map derived from the digital moiré system successfully. In data integration stage, only data with higher confidence will be reserved and used to merge together to form a complete 3D model. 相似文献
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A novel phase unwraping method has been presented and evaluated in this paper. This method works by first constructing a quality map based on the characteristic of the active triangulation system from the wrapped phase data. The quality map is then used to guide the unwrapping. In order to reduce the execution time of phase unwrapping, we tessellate the whole wrapped phase map into blocks. Blocks with higher confidence will be unwrapped first. Experiment shows that this method can unwrap the wrapped phase map derived from the digital moiré system successfully. In data integration stage, only data with higher confidence will be reserved and used to merge together to form a complete 3D model. 相似文献