一种相对距离导向的相位展开算法

提出了一种相对距离导向的相位展开算法,根据相邻像素相位数据的特点,在复数平面上定义一个像素间的相对距离,构成相对距离树,用来标识相位展开路径的可靠性,由距离树导向进行相位展开.给出了距离树的物理意义和算法设计,以相位测量轮廓术为例给出了新算法的应用实例.实验结果表明,算法是合理的和有效的.相位展开的路径总是沿着具有最小距离值的路径到较高距离值的路径方向进行,所以在最坏的情况下误差也被限制在局部最小区域.     

仿视觉过程的相位展开方法

在所有基于条纹分析的光学测量中,相位展开问题是难以避免的问题。所有传统的相位展开方法的共同点都是在相主值图中通过邻域内相主值差和寻找无噪声的相位展开路径来完成的。如果不利用整幅图像像素间的联系,则误差会沿展开路径传播。根据人眼识别栅线图周期的过程提出了一种与以往完全不同的相位展开方法。经过初步提取周期分界线、修补分界线和根据分界线确定周期三个步骤即可完成相位展开过程。该算法的原理简单明了,实现起来相对简单,只需单幅条纹图像即可得到周期,因而可用于动态测量。实验结果验证了该算法的可行性。     

基于边缘检测的最小不连续相位展开算法

为克服Fylnn最小不连续相位展开算法效率较低的缺陷,以快速高效地展开包裹相位图,提出了一种基于边缘检测的最小不连续相位展开新算法.先对孤立噪声点预处理并将其排除在增长环搜寻扫描区域外,然后利用边缘检测技术检测出相位不连续区域,并把其作为扫描区域.由于利用边缘检测使增长环搜寻所需的扫描范围在很大程度上缩小,最小不连续相位展开算法的效率得到了很大提高.详细描述了新算法的原理和实现步骤,并用计算机模拟和实际的包裹相位图来验证其有效性.相位展开结果表明,新算法能正确展开这些包裹相位图,且较最小不连续算法有更高的效率.     

单幅圆条纹相位展开光刻对准研究

针对光刻对准中产生的单幅封闭干涉条纹经相位解析后获得的包裹相位,提出在极坐标系对其进行相位展开进而获得对准偏移量的方法.该方法首先将对准过程中两圆光栅相对移动产生条纹的相位分布从直角坐标系转换到极坐标系;其次分析在极坐标系下对准偏移量与相位参量的关系;最后通过取不同径向半径获得初始相位振幅与相位延迟进而求取对准偏移量.数值模拟与实验验证该方法的可行性并与传统的最小二乘与路径跟踪相位展开方法进行了对比分析.结果表明该方法对包裹相位进行展开进而达到几十纳米量级的高准确度对准,具有很强的适应性.     

采用小波脊系数幅值导数方差质量图的相位展开法

针对小波变换轮廓术中相位无法快速准确展开的问题,提出了一种能有效抑制噪音的相位展开算法.首先,分析了小波脊系数幅值质量图和相位导数方差质量图的特征;然后依据相位值与其数学期望的偏差程度,利用小波脊系数幅值矩阵和导数方差思想构造了"小波脊系数幅值导数方差"质量图;最后分别进行软件仿真和真实模型实验,并将利用新质量图引导的相位展开效果与传统相位展开质量图法和改进的质量图法进行对比.实验结果表明,本文算法提高了相位展开精确度,相位展开误差率降低了2.61%.所提质量图易于构造,在引导相位展开时不仅能得到较准确的绝对相位值,还能有效抑制噪音的影响,从而重建出精确度高的物体三维模型.     

数字全息显微术中三种相位展开算法的比较研究

为了解决数字全息显微术相位重建中的欠采样问题,引用一种基于横向剪切干涉术的改进型最小二乘法相位展开算法,并与基于离散余弦变换的原始最小二乘法算法以及质量图导向路径算法进行比较。采用欠采样高斯函数进行计算机模拟,并进行了实验验证,结果表明了横向剪切干涉术方法的有效性。上述改进型最小二乘法相位展开算法在解决包裹相位图中的欠采样问题更有效,从而能够更精准地重建物体的相位信息。     

基于图切割的相位展开

剪切散斑干涉术中,普遍采取相移法提取相位,只可得到被包裹的相位信息,进一步量化计算之前,必须展开相位,但是大量的散斑噪音使相位展开变得非常困难.本文提出基于图切割理论的相位展开算法,将相位展开等价于整数的最优估计问题,通过最小化能量函数展开相位,无需对散斑包裹相位图进行滤波,就可以从包含大量散斑噪音的包裹相位图中准确地提取出真实相位,极大程度地保留了相位包裹图中的细节信息.对于同一幅模拟的散斑包裹相位图,传统的质量导向枝切法和最小二乘法的均方根误差分别为11.7076和4.9775,新算法的均方根误差则为0.9459,数值模拟与实验结果均验证了新算法优良的抗噪性能.     

基于图切割的相位展开

剪切散斑干涉术中,普遍采取相移法提取相位,只可得到被包裹的相位信息,进一步量化计算之前,必须展开相位,但是大量的散斑噪音使相位展开变得非常困难.本文提出基于图切割理论的相位展开算法,将相位展开等价于整数的最优估计问题,通过最小化能量函数展开相位,无需对散斑包裹相位图进行滤波,就可以从包含大量散斑噪音的包裹相位图中准确地提取出真实相位,极大程度地保留了相位包裹图中的细节信息.对于同一幅模拟的散斑包裹相位图,传统的质量导向枝切法和最小二乘法的均方根误差分别为11.707 6和4.977 5,新算法的均方根误差则为0.945 9,数值模拟与实验结果均验证了新算法优良的抗噪性能.     

禁忌搜索在最小不连续相位展开算法中的应用

Flynn最小不连续相位展开算法能成功展开多种类型的包裹相位数据,但该算法在整个包裹相位图像中循环搜寻相位不连续区域,使整个图像的相位不连续最小,计算量大,效率较低.为了克服该缺点,将禁忌搜索的思想应用于最小不连续相位展开算法中,利用包裹相位图的质量图,按照质量从劣到优把所有节点划分到不同的等级,将高质最区域的节点暂时禁忌.这种禁忌搜索策略,优先在低质量区域搜索相位不连续,确保搜索区域从不连续概率最高的区域开始,因此最大可能地减少了无用的搜索过程,加快了算法的收敛速度,提高了相位展开算法的运行效率.     

基于取整最小二乘的全局相位展开新方法

基于取整操作和全局最小二乘,提出了一种快速简单的相位展开算法;不同与传统的相位展开方法,该算法通过一种非迭代的和健壮的方法来处理相位跳变部分的梯度;因此,降低了残差点的传播和平滑的影响;并用提出的算法与四种经典的相位展开算法:切枝法、最小费用流法(MCF)、质量图导向(QG)和快速傅里叶变换(FFT)进行对比;通过计算机模拟和实验结果表明:该算法仅仅需要与FFT方法相接近的较低的运算时间,就能达到比MCF方法更高的精度;而且,该算法运算速度快,非常简单,可以在干涉测量技术中得到实时的应用。     

光弹性测量中的位相展开

根据调制度排序，提出了一个新的用于模型全场光弹条纹级次测量的位相展开方法，并进行了实验验证。在位相展开区域的边界上，位相展开的路径由像素的强度调制决定。这个方法的优点是很明显的，即使在最坏情况下，其误差也限制在局部最小区域上。     

基于分支设置的质量导引相位展开算法

二维相位展开方法是近年来较为活跃、引起关注的一个研究课题,它在许多测量应用中有着重要的作用。尽管掩膜阻断算法在多个领域都有成功应用实例,该算法存在着固有的缺陷。为了克服掩膜阻断算法的缺陷,综合分支阻断方法和质量导引方法的优点,提出一种基于分支设置的质量导引相位展开新算法。它先以一个初始质量图来引导分支的设置,然后把分支对应的相位质量设置为最低,从而产生一个新的质量图,最后按新质量图来引导相位展开,并使用几个包裹相位图来验证此方法的有效性。计算机模拟相位图和实际相位图的相位展开结果表明,在存在复杂轮廓不连续和高噪声的情况下,该算法优于模板阻断算法,能得到较好的相位展开结果。     

Comparison of eight unwrapping algorithms applied to Fourier-transform profilometry

Phase unwrapping is a task common to many applications like interferometry imaging, medical magnetic resonance imaging, solid-state physics, etc. Fourier transform profilometry (FTP) values the height distribution of object, elaborating the interference between a plane reference grating and a deformed object grating. Since the height information is extracted from the phase of a complex function, the phase unwrapping is a critical step of the process. Several unwrapping algorithms are proposed in literature, but applied to measurement technologies different from FTP. The purpose of this paper is to define the performances of eight different unwrapping algorithms applied to FTP optical scan method and to define the best one. The algorithms chosen are: Goldstein's algorithm, quality guided path following method, Mask cut method, Flynn's method, multi-grid method, weighted multi-grid method, preconditioned conjugate gradient method and minimum L_p-norm method. The methods were tested on real images acquired by a FTP scanner developed and calibrated for these experiments. The objects used vary from simple geometries, like planes and cylinders, to complex shapes of common use objects. Algorithms were qualified considering the phase unwrapping errors, execution time and accuracy of the shape of objects obtained from the scan method in comparison with real ones. The results show that quality guided algorithm best fits in FTP application.     

Weighted robust Basis Function for phase unwrapping

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.     

A quasi-one-frame phase-unwrapping algorithm through zone-switching and zone-shifting hybrid implementation

This study presents a wrapped-data-switching model and a corresponding regional unwrapping algorithm for 2D phase fields retrieval. In contrast to earlier techniques, which only produce successive frames of transient unwrapping, the proposed method can produce correct unwrapping in quasi-one frames. The approach tolerates isolated phase inconsistencies, and thus is quite effective for unwrapping speckle-coded contour map with numerous discrete inconsistencies. Since the analysis is based on a wrapped-data-switching model, the proposed criterion is path independent and error-propagation free. Additionally, the criteria are simple, concise, efficient, and easily implemented. The criteria and characteristics of the algorithm are demonstrated by simulating ideal and problematic cases, as well as by conducting experiments.     

Phase unwrapping algorithms, respectively, based on path-following and discrete cosine transform

This paper describes a path-following phase unwrapping algorithm and a phase unwrapping algorithm based on discrete cosine transform (DCT) which accelerates the computation and suppresses the propagation of noise. Through analysis of fringe pattern with serious noises simulated in mathematic model, we make a contrast between path-following algorithm and DCT algorithm. The advantages and disadvantages of analytical fringe pattern are also given through comparison of two algorithms. Three-dimensional experimental results have been given to prove the validity of these algorithms. Despite DCT phase unwrapping technique robustness and speed in some cases, it cannot be unwrapping inconsistencies phase. The path-following algorithm can be used in automation analysis of fringe patterns with little influence of noise.     

Accuracy and sensitivity of a hole drilling and digital speckle pattern interferometry combined technique to measure residual stresses

This paper reports on the accuracy and sensitivity of digital speckle pattern interferometry (DSPI) when it is combined with the hole drilling technique for measuring residual stresses. The in-plane displacement field generated by the introduction of a small hole is determined using an automated data analysis approach. This method is based on the calculation of the optical phase distribution through a phase-shifting method and the application of a robust iterative phase unwrapping algorithm. It is experimentally demonstrated that residual stresses can be measured with a relative uncertainty of 7.5%. It is also shown that the minimum value of residual stress that can be determined with the DSPI and hole drilling combined technique is about 10% of the yield stress of the material.     

基于可靠性的相位去包裹算法

提出了一种新的基于可靠性的相位去包裹算法。采用了队列算法及去包裹可靠性的判别标准。与传统方法相比,能够自动避开噪声区域,解决了相位去包裹中的阴影遮挡以及空洞等问题,克服了传统去包裹方法中的误差传播效应,能准确快速地对全场进行相位去包裹。设计了一套基于此算法的三维形面测量系统。     

小波变换轮廓术中用小波脊系数幅值引导相位展开的研究

为了减少小波变换轮廓术中相位展开过程的误差传递,从小波变换的相关实质出发,提出了在小波变换轮廓术中利用以前被忽略的小波脊系数幅值作为可靠度判据指导相位展开的方法.该方法选择最大幅值的小波脊系数所在位置作为相位展开起始点,根据小波脊系数幅值的大小,确定一条由大幅值到小幅值的最优化的展开路径,最大限度减少了相位展开过程中的误差传递.由于充分利用了小波变换系数的幅值信息,最大限度减小了相位展开过程中的误差传递.计算机模拟和实验验证了基于小波脊系数幅值的相位展开方法的正确性.     

A fast,accurate phase unwrapping method for wavelet-transform profilometry

A novel phase unwrapping method used in wavelet-transform profilometry is presented to improve the accuracy and speed of the unwrapping process. The wrapped phase of the fringe image is extracted by using wavelet transform. How to establish quality map using scale factor at wavelet ridge is discussed firstly. The proposed method can reflect the reliability of the pixels in fringe image effectively. As the consuming time of traditional flood-fill phase unwrapping algorithm is too long, an improved quality-guided method is used in phase unwrapping process. We divide the wrapped phase map into two levels following the established quality map, and process these two levels using different algorithms. Compared with the traditional flood-fill algorithm, we can get the accurate result while the consuming time of the phase unwrapping process is much less by using the proposed method. Simulation and experiment results verify that the 3D information of the measured object can be obtained rapidly and accurately by using the proposed method. Also the dynamic object can be measured too.