THE COHERENCE COEFFICIENT MAP AND RESIDUE GUIDED LEAST SQUARE PHASE UNWRAPPING ALGORITHM

The generation of high-resolution DEM from interferometric SAR has resulted in the need for accurate and efficient methods of 2-dimensional phase unwrapping. In this paper, we give a brief description of the mathematical base of phase unwrapping, and a detailed description of the unweighted and weighted least square phase unwrapping algorithm.Then our algorithm combining with the weighted least square phase unwrapping guided by the branch-cuts derived from Goldstein’ s algorithm and coherence coefficient map derived from the INSAR data is provided. In our experiment we write subroutines of the Goldstein’s branch-cut algorithm,unweighted and weighted least square phase unwrapping algorithm as well as our algorithm,and construct a small experiment system to resolve the phase unwrapping problem. Finally we test our algorithm on some INSAR data. The result shows that our approach can obtain unwrapped phase correctly and efficiently.

Phase noise filtering and phase unwrapping method based on unscented Kalman filter

This paper presents a new phase unwrapping algorithm based on the unscented Kalman filter(UKF) for synthetic aperture radar(SAR) interferometry.This method is the result of combining an UKF with path-following strategy and an omni-directional local phase slope estimator.This technique performs simultaneously noise filtering and phase unwrapping along the high-quality region to the low-quality region,which is also able to avoid going directly through the noisy regions.In addition,phase slope is estimated directly from the sample frequency spectrum of the complex interferogram,by which the underestimation of phase slope is overcome.Simulation and real data processing results validate the effectiveness of the proposed method,and show a significant improvement with respect to the extended Kalman filtering(EKF) algorithm and some conventional phase unwrapping algorithms in some situations.

Enhanced multi-baseline unscented Kalman filtering phase unwrapping algorithm

This paper presents an enhanced multi-baseline phase unwrapping algorithm by combining an unscented Kalman filter with an enhanced joint phase gradient estimator based on the amended matrix pencil model, and an optimal path-following strategy based on phase quality estimate function. The enhanced joint phase gradient estimator can accurately and effectively extract the phase gradient information of wrapped pixels from noisy interferograms, which greatly increases the performances of the proposed method. The optimal path-following strategy ensures that the proposed algorithm simultaneously performs noise suppression and phase unwrapping along the pixels with high-reliance to the pixels with low-reliance. Accordingly, the proposed algorithm can be predicted to obtain better results, with respect to some other algorithms, as will be demonstrated by the results obtained from synthetic data.

Quality Guided Phase Unwrapping for Fringe Projection Profilometry

Fringe projection technique is a non-contact, full field 3-D shape measurement method. The object depth information is recorded in one or several deformed fringe patterns. The phase-shifting algorithm or the Fourier transform method can be used to extract the wrapped phase data. A phase unwrapping process is then applied to retrieve a continuous phase distribution, which represents the surface profile of the test object. In this paper, a quality-guided phase unwrapping approach is incorporated and two novel phase quality evaluation methods are proposed to facilitate the phase unwrapping process.

Multi-baseline extended particle filtering phase unwrapping algorithm based on amended matrix pencil model and quantized path-following strategy

This paper proposes a new multi-baseline extended particle filtering phase unwrapping algorithm which combines an extended particle filter with an amended matrix pencil model and a quantized path-following strategy. The contributions to multibaseline synthetic aperture radar(SAR) interferometry are as follows: a new recursive multi-baseline phase unwrapping model based on an extended particle filter is built, and the amended matrix pencil model is used to acquire phase gradient information with a higher precision and lower computational cost, and the quantized path-following strategy is introduced to guide the proposed phase unwrapping procedure to efficiently unwrap wrapped phase image along the paths routed by a phase derivative variance map.

Investigation on Three Types of Residues in Phase-unwrapping

In phase unwrapping, how to control the residues and cut lines is critical to unwrap ill-state wrapped phase map successfully. Some new concepts in phase unwrapping field are proposed. Firstly, the residues in three types, i.e., singular residues, normal residues and virtual residues, are classified, which leads to some rational unwrapping paths. Secondly, some differences between cut-line and curved line are analyzed. And finally, experiment is carried out to compare our new enhanced Goldstein algorithm with the original Goldstein algorithm.

Phase Unwrapping in Magnetic Resonance Elastography

Phase Unwrapping (PU) is an ill-posed problem in Magnetic Resonance Elastography (MRE). The phase information is not usable until the phases are retrieved by using PU algorithms. In this present study, we attempt to determine the ideal PU method for MRE using both phantom and volunteer psoas major (PM) muscle images. All the MRE experiments were carried out in Philips MRI (Achieva 3.0 T, Best, The Netherlands). A multi-echo gradient-echo MRE pulse sequence was employed and the four PU methods were considered based on their easy user platform. They are namely, Minimum Discontinuity (MD), Laplacian-Based Estimate (LBE), Region Growing (RG) and Dilate-Erode (DE) Propagate. Phantom images were successfully unwrapped by all four methods, whereas MD and LBE could only unwrap PM muscle images properly. RG and DE failed to unwrap the PM muscle images.

基于GPU的并行相位解卷绕算法

针对大量数据串行相位解卷绕实时性较差的问题,设计了基于GPU的并行相位解卷绕算法。首先分析了典型的串行解卷绕算法在GPU平台实现的可行性,之后设计了适合于GPU加速的并行解卷绕算法。最后对基于GPU的并行相位解卷绕算法进行了仿真验证,多次测试结果表明:在保证解卷绕正确性的基础上,基于GPU的并行相位解卷绕算法相比传统CPU串行解卷绕算法约有3.5倍的加速比,基于GPU的并行相位解卷绕算法相比GPU串行解卷绕算法有63倍的加速比。

MCJ-UNet:一种双/多通道联合InSAR相位解缠网络

干涉合成孔径雷达(InSAR)可实现地表高程的高效获取,在地形测绘中应用广泛。双/多通道InSAR技术可借助不同通道(基线、频点)的高程模糊度差异,解决相位欠采样问题,完成高程陡变区域的干涉相位解缠,实现InSAR技术在测绘困难区域的有效应用。该文即面向高效高精度相位解缠需求,利用深度学习这一有力工具,结合不同通道的相位特征及相互约束关系,提出了一种双/多通道联合干涉相位解缠网络:Multi-Channel-Joint-UNet(MCJ-UNet)。该网络的构建以双通道(双频、双基线)InSAR为基本观测构型,并可实现向多通道构型的扩展,其构建的核心思路主要包括3点:首先,将干涉相位解缠中的模糊数估计问题转化为语义分割问题,并采用UNet网络完成分割处理;其次,引入挤压激励模块(SE)动态调整信息权重,以增强网络不同通道对其所需信息的感知能力;最后,利用多通道联合约束下的相位残差优化损失函数,实现网络调谐。此外,为避免语义分割结果的边缘细节误差对解缠效果的影响,该文还提出了一种基于多通道联合约束的解缠误差自修正方法,以保证解缠质量。模拟地形仿真数据、真实地形仿真数据以及TerraSAR-X实测数据验证了所提方法的有效性。

InSAR相位解缠最大流/最小割权值改进算法

InSAR已经在高精度DEM反演中得到了广泛应用,相位解缠技术是影响DEM获取精度的关键步骤之一,然而大梯度变化区域一直是影响解缠结果精度的核心问题。针对该问题,本文提出一种基于势函数改进权值的最大流/最小割相位解缠算法。首先,针对PUMA模型权值设置不合理的问题进行研究,利用外部已有DEM获取相位梯度变化的先验信息,将窗口最大绝对相位梯度值代入相应的势函数公式中获取权值;然后,通过对势函数权值的设置进行阈值调节,解决由于势函数权值设置不合理导致PUMA势函数无法发挥作用引起的解缠错误问题,进而提高大梯度变化区域相位解缠精度;最后,通过仿真数据和真实TanDEM-X InSAR数据对本文算法进行验证,并与已有方法进行对比。结果表明,仿真数据中本文算法可以提高至少44.93%的解缠精度,真实数据中在大梯度变化区域,本文算法较已有算法可以获得更大范围的有效解缠结果。

合成孔径声呐时延估计误差校正改进算法

由相位解缠错误造成的时延估计误差会严重降低合成孔径声呐时延估计的精度。现有的时延估计误差校正算法采用二次函数作为时延的拟合模型,该模型在距离向近端和远端处不符合时延空变规律,拟合误差较大且无法估计载体的横荡和升沉运动。针对该问题,文章提出一种改进的时延估计误差校正算法,利用时延的距离空变函数代替二次函数作为拟合模型。数值仿真和实验结果表明,相较于参考算法,改进算法校正时延估计误差的效果更好、速度更快,同时还能准确地估计载体的横荡和升沉运动。运动补偿结果显示了改进算法能较好地提升成像质量。

基于空洞空间卷积网络的点衍射干涉图像相位解包技术

为满足点衍射干涉测量对解包算法高精度、高效以及抗干扰的检测需求。提出一种基于空洞空间卷积的相移点衍射干涉图像的相位解包方法,通过将自编码器结构和空洞空间卷积结合获得更高的相位解包精度,实现对包裹相位图像可控的多尺度特征提取。根据点衍射图像特点制作的大量多样化数据集对其进行训练和优化,从而实现准确识别包裹相位所在阶次,最终可以快速处理包裹图像得到高精度的解包结果。利用所提方法对实际点衍射干涉图像进行处理,并与ESDI专业干涉图像处理软件以及其他解包算法处理结果进行比对,结果表明:本文解包结果与软件枝切法解包处理结果均方根误差值为0.0222 rad,面形拟合结果与软件面形拟合结果峰谷差值仅为0.0121λ、均方根差值仅为0.0042λ;时间效率上,完成一幅图像的处理平均仅需0.035 s,而传统方法均大于1 s。与其他方法相比,所提方法在处理包裹相位方面具有快速、高精度的特性,为点衍射干涉图像处理的高精度相位解包提供了新的可行方案。

基于改进U-Net网络的相位解包裹技术研究

提出了一种结合深度学习的空间相位解包裹方法,采用基于改进U-Net网络的编码器-解码器架构,同时加入包含双向长短期记忆网络(BILSTM)的CBiLSTM模块,并且结合注意力机制,避免了典型卷积神经网络学习全局空间依赖关系的固有缺陷的同时增强了深度学习模型对相位解包裹任务中的关键信息的关注能力。通过大量的模拟数据,验证了文中方法在严重噪声(SNR=0)、不连续条件和混叠条件下的鲁棒性,在以上三种情况下,同其他深度学习网络模型进行对比,文中所提出的网络模型的归一化均方根误差(NRMSE)分别为0.75%、1.81%和1.68%;结构相似性指数(SSIM)分别为0.98、0.92和0.94;峰值信噪比(PSNR)分别为40.87、32.56、37.38;同时计算时间显著减少,适合应用到需要快速准确的空间相位解包裹任务中去。通过实际测量数据,验证了文中提出网络模型的可行性。该研究将双向长短期记忆网络(BILSTM)和注意力机制同时引入光学相位解包裹问题中,为解决复杂相位场的解包裹提供了新的思路和方案。

Tsallis相对熵引导的包裹相位修补

齿轮齿面形貌激光干涉测量中,由于容易受到多种噪声干扰,采集到的包裹相位图中会存在相位质量差的区域,解包路径经过这些区域会造成解包裹错误,降低测量精度。针对这一问题,根据干涉条纹图像的概率分布特点,本文提出一种基于Tsallis相对熵质量评价的包裹相位修补方法。该方法先利用高斯分布拟合阈值处理后的图像,再由Tsallis相对熵评价相位质量,最后修补质量较差的区域以提高相位解包裹质量。设计对比实验验证本方法的有效性,实验结果表明,该方法可以减少40%的相位残差点,并且有效提高了相位质量。该方法使用简单,准确率高,同样适用于其他移相光学领域。

离散优化框架下的多基线InSAR相位解缠方法

多基线相位解缠技术通过扩展InSAR干涉相位的模糊度区间,突破了单基线解缠的相位连续性限制。然而,相位噪声始终困扰着多基线解缠,聚类分析算法能够在一定程度上抑制噪声,但聚类簇边界的相位连续性难以保障。针对该问题,本文提出了一种离散优化多基线InSAR抗噪相位解缠方法,该方法将经典的多基线解缠模型转化为离散优化问题,构建了多基线解缠解析框架。本文方法以双向遍历的形式求解相位模糊度,针对相位噪声引起的模糊度个数突变问题,采用分块聚类的策略予以校正,提高了算法的抗噪稳健性,解决了聚类簇边界跳变问题。本文基于模拟数据集及实测数据集验证了本文方法的有效性。结果表明,本文方法相对于传统聚类方法,均方根误差减少了约20%。

TBP-HNO_3萃取体系中U(Ⅳ)、Th(Ⅳ)和Pu(Ⅳ)第三相形成及计算机模拟研究进展

在PUREX或Thorex流程中,第三相的形成是一个实际问题,其形成不仅会影响U(Ⅳ)、Th(Ⅳ)和Pu(Ⅳ)的收率,还会影响工艺的正常运行。研究多集中在第三相的形成机理和影响因素上,发现四价锕系元素第三相的溶剂化物结构与正常溶剂化物结构并不相同;萃取剂结构与浓度、稀释剂结构与浓度、温度、平衡水相酸浓度和离子强度等为影响第三相形成的因素。在第三相基础数据的基础上建立了可以定量计算M(Ⅳ)形成三相的经验或半经验模型,模型大多使用萃取剂浓度、平衡水相酸度或平衡水相离子强度等关联得到,但尚未见到这些第三相数学模型在PUREX流程或Thorex流程模拟软件中应用,还需要进一步的研究。

PU微胶囊的合成、表征及降解性能研究

本文采用预聚-扩链-中和-分散溶解法，一步合成出聚氨酯（PU）水溶液，再用凝聚相分离法合成出Pu微胶囊。由傅立叶变换红外光谱（FT—IR）研究了PU微胶囊的化学结构；使用差示扫描量热仪（DSC），对PU微胶囊的玻璃化转变及微相分离结构进行了研究；通过扫描电子显微镜（SEM）的观测，对PU微胶囊的表面及剖面形态进行了研究，并测定出PU微胶囊直径约2．5mm，内腔直径50～600μm，膜孔直径为20～120nm；研究了PU微胶囊在磷酸缓冲液（PBS）中的降解行为，发现本实验合成的PU微胶囊基本上是不降解的。这种PU微胶囊有利于转基因CHO细胞的包覆，有利于临床应用中进行腹腔植入。

改进PConvUNet图像修补的解包裹方法

包裹相位图是描述相位信息分布的二维或三维图像,广泛应用于光学干涉和计算机视觉等领域。精密齿轮齿面由于自身形状特征、加工及使用等因素影响,在激光干涉测量中包裹相位图常出现区域分布异常的条纹,导致解包裹时出现错误,极大降低了齿面形貌的测量精度。针对此问题,提出一种包裹相位图修补的解包裹方法,在PConvUNet网络中添加了深度残差模块与CBAM注意力模块用于修补相位图中质量差的包裹相位区域。实验证明,修补后的相位图能在解包裹时有效消除相位跳变点,有效提高了干涉图像处理的精度。

一种基于非均匀线性麦克风阵列的窄带声源定向方法及系统

提出了一种基于窄带信号相位时延估计的信号定位方法,通过非均匀线性阵列的布放,解决增大阵元孔径带来的相位卷绕问题,提高定位精度。提出了非均匀线性布阵方式情况下,修正卷绕量计算延时量的估计算法,并给出了非均匀阵列间距需要满足的条件。此方法提高了定位可用基阵孔径,与一般均匀间隔线性阵列相比,大大减少了同孔径下所需的阵元个数,从而降低了对后续信号处理设备的需求。构建了定位系统并进行实际测试。实验表明,所提方法有效地提高了在开放空间中对窄带声源的定位精度。