Semiautomated analytical image correlation

Machine vision refers to computer programs consisting of a collection of pattern recognition and digital image processing algorithms (Fabel, G. Motion Control 2000, 53-54). A version of machine vision has been applied to correlating digital images generated by optical microscopy and secondary ion mass spectrometry (SIMS). By suitable application of image processing algorithms, semiautomated correlation between optical and secondary ion images is possible. For correlation of minor constituents evident in secondary ion images but invisible in optical images, correlation is performed by reference to the relative position of minor to major constituents. Precise coordinates of features apparent in one analytical image can be translated into the corresponding coordinates of an analytical image obtained by a different method. In principle, this capability yields a semiautomated system to combine complementary features of disparate imaging methods, such as secondary ion and optical microscopy.     

Nanoscale deformation measurement of microscale interconnection assemblies by a digital image correlation technique

The continuous miniaturization of microelectronic devices and interconnections demand more and more experimental strain/stress analysis of micro-?and nanoscale components for material characterization and structure reliability analysis. The digital image correlation (DIC) technique, with the aid of scanning probe microscopes, has become a very promising tool to meet this demand. In this study, an atomic force microscope (AFM) was used to scan and digitally image micro-interconnection assemblies in a micro-thermoelectric cooler. AFM images of the scan region of interest were obtained separately when the microelectronic device was operated before and after the cooling and heating stages. The AFM images were then used to obtain the in-plane deformation fields in the observed region of the micro-assembly. AFM image correlation is performed for nanoscale deformation analysis using the authors' AFM-DIC program. The results show that the observed region was subjected to cyclic strains when the device worked between its cooling and heating stages, and cyclic strain in the vertical direction was found to be a significant deformation mode. The thermally induced deformation behavior of the micro-assembly device was modeled by finite element analysis (FEA). Both thermal-electric analysis and thermal stress analysis were conducted on a 3D finite element model of the device. It is shown that the experimental results were able to validate the finite element analysis results.     

新型大扫描范围原子力显微镜的研究

研制了一种大扫描范围原子力显微镜(AFM)。设计了新的扫描驱动电路,使单幅图像的扫描范围大幅度提高;用步进电机和扫描器配合扫描,得到序列图像,序列图像拼接后获得大范围样品图像。实验结果表明,采用这一方法,在±150V 的电压驱动下,AFM 的扫描范围可增大到10 ìm?1 mm 的量级,同时保持 1 nm 量级的测试分辨力。     

数字图像相关技术在复合材料加筋曲板压缩试验中的应用

对复合材料自动铺丝和手工铺丝两种T型加筋曲板进行了单轴压缩试验，采用基于数字图像相关技术(Digital image correlation, DIC)的三维光学测量方法对该型加筋曲板的局部屈曲及后屈曲波形进行实时监测，并与传统应变、位移测量结果进行了对比分析。试验结果表明:DIC能够准确捕捉整个试验过程中的位移场，使用DIC设备观测到的屈曲模态与应变片数据反映的波形具有良好的一致性；不同于传统测量方法，DIC能够准确捕捉蒙皮在后屈曲阶段的屈曲模态转换的全过程；利用DIC技术能够对试验不同时间节点(即不同载荷水平)的屈曲模态进行清晰、直观的观测，因而能够较准确地获得结构的屈曲载荷，该载荷与由应变-载荷曲线确定的屈曲载荷相比，误差小于5%。采用ABAQUS有限元软件对试验过程进行了数值仿真分析，并通过与试验结果的对比表明了计算结果、DIC测量结果与传统方法测量结果三者具有良好的一致性。      

Fast image scanning method in liquid-AFM without image distortion

High speed imaging by atomic force microscopy (AFM) allows one to directly observe the dynamic behavior of a sample surface immersed in liquid media; thus, it has been considered to be an indispensable tool for nanobiotechnology and is used in many research fields, including molecular biology and surface science. For real-time observation of a certain behavior, the high speed imaging technique should be accompanied with a high resolution imaging technique to identify target materials. To improve the image quality at a high scanning rate, we developed a variable-controlled fast scanning method, which originated from the modified squeeze-drag superposition model in liquid media. A collection of non-distorted images was accomplished after proper modification of the operating conditions in a viscous fluid, via the simple handling of loading force and cantilever length. Consequently, a speeded-up AFM imaging process was achieved in the liquid environment at up to 200?μm?s(-1), without attachment of additional devices. The reliability of the proposed method was verified by the characterization of a grating sample immersed in three types of liquid media. In addition, the results were visualized for elastic biomolecules submerged in a liquid with high kinematic viscosity.     

Finite element formulation for a digital image correlation method

A finite element formulation for a digital image correlation method is presented that will determine directly the complete, two-dimensional displacement field during the image correlation process on digital images. The entire interested image area is discretized into finite elements that are involved in the common image correlation process by use of our algorithms. This image correlation method with finite element formulation has an advantage over subset-based image correlation methods because it satisfies the requirements of displacement continuity and derivative continuity among elements on images. Numerical studies and a real experiment are used to verify the proposed formulation. Results have shown that the image correlation with the finite element formulation is computationally efficient, accurate, and robust.     

A dual domain decomposition method for finite element digital image correlation

The computational burden associated to finite element based digital image correlation methods is mostly due to the inversion of finite element systems and to image interpolations. A non‐overlapping dual domain decomposition method is here proposed to rationalise the computational cost of high resolution finite element digital image correlation measurements when dealing with large images. It consists in splitting the global mesh into submeshes and the reference and deformed states images into subset images. Classic finite element digital image correlation formulations are first written in each subdomain independently. The displacement continuity at the interfaces is enforced by introducing a set of Lagrange multipliers. The problem is then condensed on the interface and solved by a conjugate gradient algorithm. Three different preconditioners are proposed to accelerate its convergence. The proposed domain decomposition method is here exemplified with real high resolution images. It is shown to combine the metrological performances of finite element based digital image correlation and the parallelisation ability of subset based methods. Copyright © 2015 John Wiley & Sons, Ltd.     

On mapping subangstrom electron clouds with force microscopy

In 2004 Hembacher et al. (Science 2004, 305, 380-383) reported simultaneous higher-harmonics atomic force mocroscopy (AFM)/scanning tunneling microscopy (STM) images acquired while scanning a graphite surface with a tungsten tip. They interpreted the observed subatomic features in the AFM images as the signature of lobes of increased electron density at the tungsten tip apex. Although these intriguing images have stirred controversy, an in-depth theoretical feasibility study has not yet been produced. Here we report on the development of a method for simulating higher harmonics AFM images and its application to the same system. Our calculations suggest that four lobes of increased electron density are expected to be present at a W(001) tip apex atom and that the corresponding higher harmonics AFM images of graphite can exhibit 4-fold symmetry features. Despite these promising results, open questions remain since the calculated amplitudes of the higher harmonics generated by the short-range forces are on the order of hundredths of picometers, leading to very small corrugations in the theoretical images. Additionally, the complex, intermittent nature of the tip-sample interaction, which causes constant readjustment of the tip and sample orbitals as the tip approaches and retracts from the surface, prevents a direct quantitative connection between the electron density and the AFM image features.     

Particle image velocimetry: image labeling by use of adaptive optics to modify the point-spread function

A simple method of labeling the first- and second-exposure images of a particle-image-velocimetry recording is discussed. One achieves this method by changing the transfer characteristics of the recording optics between exposures by inserting a rotating optic into the iris plane of the camera objective. Spatial filtering can then be used to address the images recorded by each exposure independently, permitting cross-correlation analysis to be implemented. Two practical systems using either an aperture plate or a phase plate are demonstrated, and we show that the phase plate is significantly more light efficient. Finally, the feasibility of image labeling high-speed flows using electro-optic devices is discussed.     

图像处理在自动焊接中的应用和展望

图像处理技术在自动焊接领域的应用已引起国内外学者的广泛重视。通过图像传感技术获取焊接熔池直观丰富的图像信息，使用高效的图像处理算法，提取焊接熔池的特征信息，用以实现自动焊接过程质量实时传感与控制。本文综合论述了图像处理技术在自动焊接中的应用原理、数字图像的采集方法、数字图像的特征信息定义、广义数字图像处理技术及其对自动化焊接理论研究和实践应用的推动作用。通过总结图像处理技术的研究和应用现状，综合分析了图像处理技术在现代焊接技术中发展和应用的前景。     

A Novel Non-Invasive Method for Extraction of Geometrical and Texture Features of Wood

Non invasive feature detection in wood based application requires exact discrimination between geometrical edges and texture. It has been found that traditional edge detection algorithms are highly sensitive to noise and texture and produces inferior results with wood. The present work encompasses a micro level reconstruction of Palash and Rosewood by using micro X-rays CT scanner. It also encompasses a new edge detection algorithm using newly constructed Chebyshev polynomial based fractional order differentiator. Transform based method has been used for reconstruction purpose. Newly designed fractional order filter has been applied on these reconstructed images. Chebyshev polynomial based fractional order differentiator has been used for filtering operation. Quadrature Mirror Filter (QMF) concept has been used for design of high pass filter and low pass filter. Preprocessing has been performed by using this filter. Canny edge detection algorithm has been used on this preprocessed image. The algorithm has been tested on two different test cases of wood images a) Palash and b) Rosewood. The effect of relaxation coefficient has also been presented and discussed.     

In Situ Nanoscale In-Plane Deformation Studies of Ultrathin Polymeric Films During Tensile Deformation Using Atomic Force Microscopy and Digital Image Correlation Techniques

The local, nanoscale deformation behavior of ultrathin polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) films used as substrates in magnetic tapes was studied by atomic force microscopy (AFM) and digital image correlation (DIC) techniques. A custom-designed tensile stage was integrated with the AFM to perform uniaxial tension tests on the polymeric films in situ where the film surfaces were imaged simultaneously by AFM. The surface features on the PET and PEN films were used as reference patterns for the DIC processing. To improve the accuracy of the AFM imaging system for the application of the DIC method, a simple, cost-effective experimental procedure was established. Axial and transverse strain fields and Poisson's ratio maps with a spatial resolution of 78.13 nm were constructed via processing the AFM images of unstretched and stretched samples with the DIC software. Results from the AFM studies indicate that the deformation in both PET and PEN is nonuniform at the nanoscale. The nanoscale deformation mechanisms are discussed in conjunction with the structure of the PET and PEN films     

Hybrid retinal image registration using phase correlation

Abstract

This paper deals with registration of retinal images, which were taken by high-resolution digital colour fundus cameras. The proposed method describes successful application of phase correlation method. It combines several basic steps — global correction of shift, rotation and scaling, detection of landmarks, their correspondences and finally image registration using second-order polynomial model. The method is tested on two sets of images. The first set contains images from the diabetic patients where many retinal pathologies can disturb the registration process. The second set contains images from healthy subjects, which were acquired by different illumination conditions. The method was evaluated using four different criteria - tree objective and one subjective. These criteria are also compared. The achieved registration accuracy of the landmarks position error is 1·13 and 0·93 pixels for respective image sets. Finally, the simple scheme for retinal pathology visualisation of registered fundus pairs is presented.     

Estimation of AFM tip shape and status in linewidth and profile measurement

An atomic force microscopy image is a dilation of the specimen surface with the probe tip. Tips wear or are damaged as they are used. And AFM tip shape and position status make AFM images distorted. So it is necessary to characterize AFM tip shape and position parameters so as to reconstruct AFM images. A geometric model-based approach is presented to estimate AFM tip shape and position status by AFM images of test specimens and scanning electron microscope (SEM) images of AFM tip. In this model, the AFM tip is characterized by using a dynamic cone model. The geometric relationship between AFM tip and the sample structure is revealed in linewidth and profile measurement. The method can easily calculate the tip parameters including half-cone angle, installation angle, scanning tilting angle and curvature radius, and easily estimate the position status of AFM tip when AFM tip moves on the specimen. The results of linewidth and profile measurement are amended accurately through this approach.     

Load increment procedure for post‐buckling analysis of laminated plates under in‐plane loads by finite strip method

A load increment procedure has been presented to integrate with the finite strip method for the post‐buckling analysis of laminated plates when subjected to uniform end shortening. In‐plane loads are introduced to reflect the end shortening effect. The Newton–Raphson procedure is implemented to attend a solution that satisfies the equilibrium condition and at the same time meets the loading requirements. Error associated with loading condition is minimised by adjusting the load factor to preserve the rate of convergence. The enhanced capability can be easily incorporated into the context of both classical and shear deformation plate theories. A range of application has been described. Convergence test and numerical results are presented for isotropic plate and laminates with general lay‐up arrangement. Copyright © 2000 John Wiley & Sons, Ltd.     

Adaptive binary joint transform correlator for image recognition

Our research has shown that the autocorrelation peaks of a binary joint transform correlator are affected by input scenes' backgrounds. An adaptive method is proposed to overcome this problem. The image of interest is first extracted from the background based on the position of the highest correlation peak of the input and reference images. The extracted image is then correlated with the reference to obtain the final correlation peak. Numerical simulations showed that the final autocorrelation peak is the maximum constant for a specified reference image.     

A domain coupling method for finite element digital image correlation with mechanical regularization: Application to multiscale measurements and parallel computing

A general method is proposed to couple two subregions analyzed with finite element digital image correlation even when using a mechanical regularization (regularized digital image correlation). A Lagrange multiplier is introduced to stitch both displacements fields in order to recover continuity over the full region of interest. Another interface unknown is introduced to ensure, additionally, the equilibrium of the mechanical models used for regularization. As a first application, the method is used to perform a single measurement from images at two different resolutions. Secondly, the method is also extended to parallel computing in regularized digital image correlation. The problem is formulated at the interface and solved with a Krylov‐type algorithm. A dedicated preconditioner is proposed to significantly accelerate convergence. The resulting method is a good candidate for the analysis of large data sets. Copyright © 2016 John Wiley & Sons, Ltd.     

Neural-network method applied to the stereo image correspondence problem in three-component particle image velocimetry

The successful application of a recurrent neural network of the Hopfield type to the solution of the stereo image-pair reconciliation problem in stereoscopic particle image velocimetry (PIV) in the tracking mode is described. The results of applying the network to both virtual-flow and physical-flow PIV data sets are presented, and the usefulness of this novel approach to PIV stereo image analysis is demonstrated. A partner-particle image-pair density (PPID) parameter is defined as the average number of potential particle image-pair candidates in the search window in the second view corresponding to a single image pair in the first view. A quantitative assessment of the performance of the method is then made from groups of 100 synthetic flow images at various values of the PPID. The successful pairing of complementary image points is shown to vary from 100% at a PPID of 1 and to remain greater than 97% successful for PPID's up to 5. The application of the method to a hydraulic flow is also described, with in-line stereo images presented, and the application of the neural-matching method is demonstrated for a typical data set.     

基于条件生成式对抗网络的AFM图像盲重构方法

针对原子力显微镜(AFM)成像过程中针尖展宽效应引起的误差,提出一种基于条件生成式对抗网络(CGAN)的AFM图像盲重构方法.首先,以pix2pixHD模型为基础,通过全局生成网络对仿真样本数据进行对抗训练,引入AFM测量数据采用局部提升网络联合训练;最后,特征匹配损失函数以用于提升栅格边缘横向分辨力.实验结果表明:对...     

Contactless transfer of image via the gas phase in a thermoactivated process

The formation of hafnium oxide (HfO₂) layers in slit structures by pulsed metalorganic chemicalvapor deposition (MOCVD) method with discrete dosage of reactants has been studied. The MOCVD process employed hafnium tetrakisdipivaloylmethanate as a precursor and oxygen as a gaseous reactant. The slit structure was formed by a silicon plate and a glass substrate with a chromium-film pattern. The slit width was varied within 0.1–2.0 mm, so that the aspect ratio changed from 150 to 30. The deposited layers were studied by the scanning ellipsometry technique. The phenomenon of image transfer from the glass substrate to the opposite plate in the form of a nanosized HfO₂ film relief, which reproduces the chromium-film pattern, is discovered. The in-plane resolution of the obtained image in these experiments reached 0.025 mm. This effect can be used for nonlithographic formation of images of film structures.