图像配准方法研究

图像配准是图像处理的基本任务之一,常常是作为图像处理应用的前期处理步骤使用,用于将不同时间、不同传感器、不同视角下获取的两幅或多幅图像进行匹配。本文在对图像配准的几种变换介绍的基础上总结了现有的几种配准方法,并分别分析了其存在的优缺点,在文章结尾对图像配准的发展趋势做了展望。     

于小波变换的等价图割SAR图像配准方法

为改进SAR图像匹配的稳健性和实时性,提出一种基于小波变换的等价图割SAR图像配准方法.该方法首先利用小波变换对图像进行分解,在低频子图像下构造等价图割,克服相干斑噪声干扰,避免NP困难,解决映射函数选取问题,从图像中分割出精确目标.其次利用尺度不变特征变换（SIFT）方法实现目标的特征匹配,降低搜索空间特征点描述,提高实时性.最后通过匹配关系找到变换参数,实现图像精确配准.实验结果表明,该方法能快速而精确地实现SAR图像配准.     

印刷电路板表观检测中光电图像的快速配准方法

印刷电路板(PCB)表观缺陷检测是机器视觉检测领域的一个重要问题,为了有效地利用参考法对印刷电路板光电图像进行检测,需要提高图像配准精度.本文提出了一种基于随机Hough变换(RHT)和空间数据坐标变换理论相结合的配准方法,该方法在寻找配准目标和完成配准效率方面均有很大提高.利用PCB光电图像进行实验,结果表明:在提高检测精度,降低内存空间,减少计算时间等方面,该配准算法的优势明显.     

基于相位相关的印刷全画面检测中图像定位的研究

结合印刷全画面检测系统的特点和对待检测图像的特定要求,使用相位相关法解决了印刷全画面检测系统中的图像定位问题。在实现过程中,运用四元数理论,充分利用了彩色图像中各通道的色度信息,在提高处理性能的同时,尽可能保留定位后彩色图像的忠实再现。经图像质量参数和印刷参数检测软件评价表明,该方法能够较好地运用到印刷全画面检测系统中。     

Multimodal Medical Image Registration and Fusion for Quality Enhancement

For the last two decades, physicians and clinical experts have used a single imaging modality to identify the normal and abnormal structure of the human body. However, most of the time, medical experts are unable to accurately analyze and examine the information from a single imaging modality due to the limited information. To overcome this problem, a multimodal approach is adopted to increase the qualitative and quantitative medical information which helps the doctors to easily diagnose diseases in their early stages. In the proposed method, a Multi-resolution Rigid Registration (MRR) technique is used for multimodal image registration while Discrete Wavelet Transform (DWT) along with Principal Component Averaging (PCAv) is utilized for image fusion. The proposed MRR method provides more accurate results as compared with Single Rigid Registration (SRR), while the proposed DWT-PCAv fusion process adds-on more constructive information with less computational time. The proposed method is tested on CT and MRI brain imaging modalities of the HARVARD dataset. The fusion results of the proposed method are compared with the existing fusion techniques. The quality assessment metrics such as Mutual Information (MI), Normalize Cross-correlation (NCC) and Feature Mutual Information (FMI) are computed for statistical comparison of the proposed method. The proposed methodology provides more accurate results, better image quality and valuable information for medical diagnoses.     

基于图像配准技术的二维平台位置参数视觉测量

提出一种基于图像配准技术测量移动平台二维平移、旋转等参数的视觉测量方法．固定基准图和镜头,使CCD随平台在基准图的像平面内移动或旋转,再由图像配准技术对当前CCD接收到的图像在整个像平面内的位置进行定位,从而可实现微位移平台位置参数的测量．对基准图进行分块设计,并且对每一分块进行二进制编码．如果保证至少有一分块落到CCD成像区域内．实验结果表明系统的位移测量精度可达到亚微米级．     

Formulation of Lucas–Kanade Digital Image Correlation Algorithms for Non‐contact Deformation Measurements: A Review

Digital image correlation (DIC) metrology has been increasingly used in a wide range of experimental mechanics research and applications. The DIC algorithm used so far is however limited mostly to the classic forward additive Lucas–Kanade type. In this paper, a survey is given about the formulation of other types of Lucas–Kanade DIC algorithms that have been appeared in computer vision, robotics, medical image analysis literature and so on. Concise notations consistent with the finite deformation kinematics analysis in continuum mechanics are used to describe all Lucas–Kanade DIC algorithms. An intermediate image is introduced as a frame of reference to clarify the so‐called compositional algorithms in a two‐frame DIC analysis. Explicit examples about the additive and compositional updating of deformation parameters are given for affine deformation mapping. Extensions of these algorithms to the so‐called consistent or symmetric types are also presented. The equivalency of final numerical solutions using additive, compositional and inverse compositional algorithms is shown analytically for the case of affine deformation mapping. In particular, the inverse compositional algorithm for affine image subset deformation is highlighted for its superior computational efficiency. While computationally less efficient, consistent and symmetric algorithms may be more robust and less biased and their potentials in experimental mechanics applications remain to be explored. The unified formulation of these Lucas–Kanade DIC algorithms collected all together in this paper can serve as a useful guide for researchers in experimental mechanics to further evaluate the merits as well as limitations of these non‐classic algorithms for image‐based precision displacement measurement applications.     

Research on the Application of Super Resolution Reconstruction Algorithm for Underwater Image

Underwater imaging is widely used in ocean, river and lake exploration, but it is affected by properties of water and the optics. In order to solve the lower-resolution underwater image formed by the influence of water and light, the image super-resolution reconstruction technique is applied to the underwater image processing. This paper addresses the problem of generating super-resolution underwater images by convolutional neural network framework technology. We research the degradation model of underwater images, and analyze the lower-resolution factors of underwater images in different situations, and compare different traditional super-resolution image reconstruction algorithms. We further show that the algorithm of super-resolution using deep convolution networks (SRCNN) which applied to super-resolution underwater images achieves good results.     

点特征提取在锂电池丝印图像配准的应用

目的 为了提高锂电池丝印图像配准精度,从而解决产品质量检测中的漏检和误报问题,研究点特征提取算法在锂电池丝印图像配准中的应用.方法 对基于点特征的锂电池丝印图像配准进行综述,首先概述点特征提取算法的发展历程,然后着重围绕Harris,SIFT,SURF,ORB和AKAZE等5种经典的点特征提取算法进行分析,并介绍近几年的提升算法,最后对锂电池丝印图像进行配准测试,利用几种测评技术对实验效果进行分析,总结不同点特征提取算法在锂电池丝印图像配准中的优缺点和适用性.结果 实验结果表明,AKAZE算法提取的特征点具有较高的重复率和匹配准确率,经过配准后的定位误差也都控制在1个像素以内,但是该算法的尺度不变性较差.结论 相较于前4种算法,AKAZE算法具有较高的可靠性和稳定性,能够满足锂电池丝印图像配准的实时性和高效性需求.     

图像配准在缓动弱小空间目标检测中的应用

在固定大视场光电探测系统图像中,远距离空间目标运动角速度慢、星像小,难以从众多恒星星像中有效检测到.针对上述问题,提出了一种基于恒星配准后差分相乘的缓动弱小空间目标检测算法,首先在空域上利用形态学Top-hat滤波抑制背景增强目标,然后在时域上将恒星配准后差分相乘增强缓动弱小空间目标,最后经自适应门限分割与航迹关联进行目标确认.实测结果表明,算法全面考虑了缓动弱小空间目标在时域及空域方面的特性,能有效地从复杂背景中检测到低信噪比缓动弱小目标,并满足实时性的要求.     

A Fourth-Order Compact Finite Difference Scheme for Higher-Order PDE-Based Image Registration

Image registration is an ill-posed problem that has been studied widely in recent years. The so-called curvature-based image registration method is one of the most effective and well-known approaches, as it produces smooth solutions and allows an automatic rigid alignment. An important outstanding issue is the accurate and efficient numerical solution of the Euler-Lagrange system of two coupled nonlinear biharmonic equations, addressed in this article. We propose a fourth-order compact (FOC) finite difference scheme using a splitting operator on a 9-point stencil, and discuss how the resulting nonlinear discrete system can be solved efficiently by a nonlinear multi-grid (NMG) method. Thus after measuring the h-ellipticity of the nonlinear discrete operator involved by a local Fourier analysis (LFA), we show that our FOC finite difference method is amenable to multi-grid (MG) methods and an appropriate point-wise smoothing procedure. A high potential point-wise smoother using an outer-inner iteration method is shown to be effective by the LFA and numerical experiments. Real medical images are used to compare the accuracy and efficiency of our approach and the standard second-order central (SSOC) finite difference scheme in the same NMG framework. As expected for a higher-order finite difference scheme, the images generated by our FOC finite difference scheme prove significantly more accurate than those computed using the SSOC finite difference scheme. Our numerical results are consistent with the LFA analysis, and also demonstrate that the NMG method converges within a few steps.     

弹性配准在冠状动脉三维运动分析中的应用

针对冠状动脉的运动分析问题,本文提出基于弹性配准的血管骨架三维运动估计方法.在对X射线冠脉造影图像序列进行三维血管骨架序列重建的基础上,寻找两个时刻同一血管分支上点之间的对应关系,得到各点的运动向量.通过使适当的目标函数最小化,运用动态规划算法,得到最优匹配.通过采用运动场已知的模拟数据对算法精度进行定量估计,并采用临床图像序列进行实验,结果表明,算法具有较高的精度和较快的运算速度.     

转炉内壁蚀损趋势分析的红外系列图像配准

根据铜转炉内壁蚀损趋势分析的需要,提出了一种基于等温线轮廓特征的红外系列图像配准算法。使用了质心距离函数和傅里叶描述寻找相似度最高的等温线轮廓,在相似轮廓线对的点集合上建立对应关系,经匹配将图像配准问题转换为标准的参数矩阵最小二乘估计问题,由仿射变换建立图像的配准空间。测试结果表明,算法具有简单、运算速度快的特点,能满足分析精度要求。     

Non‐iterative reconstruction with a prior for undersampled radial MRI data

This paper develops an FBP‐MAP (filtered backprojection, maximum a posteriori) algorithm to reconstruct MRI images from undersampled data. An objective function is first set up for the MRI reconstruction problem with a data fidelity term and a Bayesian term. The Bayesian term is a constraint in the temporal dimension. This objective function is minimized using the calculus of variations. The proposed algorithm is non‐iterative. Undersampled dynamic myocardial perfusion MRI data were used to test the feasibility of the proposed technique. It is shown that the non‐iterative Fourier–Bayesian reconstruction method effectively incorporates the temporal constraint and significantly reduces the angular aliasing artifacts caused by undersampling. A significant advantage of the proposed non‐iterative Fourier–Bayesian technique over the iterative techniques is its fast computation time and its ability to reach the optimal solution. © 2013 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 23, 53–58, 2013.     

SAR图像配准的二元Rayleigh分布互信息方法

合成孔径雷达(Synthetic Aperture Radar,简称SAR)图像中乘性斑点噪声的存在,使得传统的互信息配准方法中的插值假象更为严重.本文把单视SAR幅值图像同质区域服从Rayleigh分布这一先验信息引入互信息配准方法中,对同源单视SAR幅值图像进行配准.以合成图像和真实图像的试验结果和分析证实了方法的...     

High Accuracy and Wide Temperature Measurement by Non‐Contact Speckle Extensometer

Abstract: A new extensometer that has been developed needs neither markings nor mechanical clips to be attached onto the specimen and is perfectly noncontacting to automatise tensile test. Separate laser beams are incident at the positions where the markings were attached in the conventional extensometer. The spots on the specimen are imaged on a separate charge‐coupled device (CCD) to produce a speckle pattern, the displacement of which is detected by real‐time digital speckle correlation. Each of the optical systems is installed in a separate movable probe head that is moved under feedback control to nullify the speckle displacement detected. For detecting a small amount of specimen displacement, less than a few millimetres, the optical head is fixed to output speckle displacement. A resolution of 1 μm was attained by comparison with a linear laser encoder. A larger displacement was detected from displacement of the probe head that cancels the detected speckle displacement by feedback control of the head movement. We also conducted tensile test in a temperature chamber controlled in a range between ?40 and 100°C, by placing the probe heads outside a window of the chamber.     

基于邻域重构模型的高分辨SAR图像精确配准

合成孔径雷达(SAR)的成像过程使其高分辨图像的几何形变呈现局部性.针对高分辨SAR图像精确配准问题,本文提出一种基于邻域重构模型的局部转换函数.邻域重构模型首先采用重构系数刻画参考图像中每个像素点的几何位置;接着给出了一种重构控制点的选择标准使每个像素的配准误差达到最小;最后根据重构系数及控制点坐标对输入图像进行再抽样以实现配准.与经典分片线性映射相比,该模型从理论上给出了一种区域剖分准则:对于每个像素选取能使配准误差能达到最小的控制点作为重构控制点.对模拟数据和真实SAR图像进行了试验,结果表明,该模型能有效地提高配准精度.     

A Novel Class of Strain Measures for Digital Image Correlation

We propose a novel class strain measures for use with digital image correlation (DIC). Whereas the traditional notion of compatibility (strain as the derivative of the displacement field) is problematic when the displacement field varies substantially because of either measurement noise or material irregularity, the proposed measure remains robust, well defined and invariant under rigid body motion. Moreover, when the displacement field is smooth, the classical and proposed strain measures are approximations of each other. We demonstrate, via several numerical examples, the potential of this new strain measure for problems with steep gradients. We also show how the non‐local strain provides an intrinsic mechanism for filtering high‐frequency content from the strain profile and so has a high signal to noise ratio. This is a convenient feature considering image noise and its impact on strain calculations.     

Strain Localisation and Damage Measurement by Full 3D Digital Image Correlation: Application to 15‐5PH Stainless Steel

Abstract: The objective of this paper is to propose a method for measuring damage in ductile materials, from its inception to rupture. In the first stage of damage, which occurs before localisation, the usual method for determining damage through the measurement of stiffness variation is used. A damageable elastic–plastic model of the modified Lemaitre/Chaboche type is identified from these tests. An original method is proposed for measuring damage following the initiation of strain localisation. This method is based on a full 3D image correlation analysis using four cameras. The principle of the method consists in identifying the damage through tensile experiments on thin, flat‐notched specimens subjected to tensile loading. Speckles are applied on both faces of each specimen in order to follow the strain fields on the two faces at the same time. These two strain fields are digitised simultaneously by two synchronised sets of two digital cameras. This paper shows how this method enables one to identify strain localisation and deduce the evolution of damage directly. Here, the method is developed for 15‐5 PH stainless steel.