基于环形合成孔径系统的图像复原技术

针对环形合成孔径成像系统在成像过程中产生噪声和图像模糊的问题,设计了一种基于Laplacian算子和参数维纳滤波的图像复原技术.针对环形合成孔径的成像退化特点,先对退化图像进行锐化处理,再使用参数维纳滤波对处理后的图像进行复原,同时对比传统的维纳滤波复原算法,以环形合成孔径系统为基本结构,分析和比较单个孔径与不同填充因...     

模具监视系统中的图像快速配准算法

注塑机的振动及模具归位不准等原因容易造成目标图像与样本图像间的偏移,从而引起模具监视系统产生误检和误报.为此,提出一种基于尺度不变特征变换描述子的实时图像配准算法.该算法采用一种快速角点检测算法提取图像关键点,围绕关键点构建128维描述子,依据最近邻匹配法得到特征匹配对,最后通过随机采样一致性(RANSAC)和最小二乘法剔除误配点并拟合变换参数.最后,用实验证明了该算法的有效性.     

冷冻电镜三维重构技术对生物大分子的研究意义与应用展望

冷冻电子显微镜是当今生物及医学研究的重要工具,其可以在不破坏生物样本的情况下拍摄分辨率极高的二维图像。而为了更好地研究生物大分子的结构如蛋白质这种对结构非常复杂的物质,科学家们通常需要三维的图像。在这之间,三维重构(3D Reconstruction)技术充当了二维图像与三位图像之间转换的桥梁。科学家们通过重构算法,将不同特征的样品二维图像转化为三维图像。通过阅读整理总结大量文献,本文主要介绍冷冻电子显微镜的优势,冷冻电子显微镜三维重构技术的原理与应用展望。     

点云数据的配准方法研究

利用三维扫描技术获取的点云数据在三维物体的恢复与重建中有重要的应用。本文首先论述了点云数据配准算法的研究进展,然后对点云数据配准方法中比较有代表性的ICP方法及其改进算法重点进行总结和分析,最后对ICP算法未来的研究重点进行总结。     

图像分割方法综述

图像分割是图像处理中的经典问题,也是计算机视觉领域的基本技术。图像分割质量的好坏,直接影响后续图像处理的效果。实践中,基于不同的分割标准,可以将图像分割算法分为:基于阈值的图像分割、基于聚类的图像分割、基于区域生长的图像分割以及基于深度学习的图像分割等。目前,在图像分割领域,多种方法技术成熟,每种分割方法适用于特定的分割对象。本文研究了近年来常用的图像分割算法,并对这些算法进行了归纳、总结及分析。     

基于微分算子的数字遥感图像边缘增强研究

针对遥感图像中的水系分布,研究了微分算子对二维遥感图像的边缘增强作用。算法仿真表明一阶Isotropic Sobel算子模板的边缘增强效果最优;所有四类一阶微分算子其垂直方向模板的边缘增强效果均好于水平和±45°方向模板;二阶微分算子由于有较高的敏感性,在提取边缘的同时,严重放大了遥感图像中各地物的细微边缘而形成了条纹状噪声。本文所得结果可为地物遥感特征提取提供依据。     

关于三维扫描技术在装配式施工过程中可实施方向的探讨

三维激光扫描技术又称“实景复制技术”,也称“激光雷达取景技术”。三维扫描仪,采用激光技术只需数分钟即可产生详细三维实体图像,通过数百万彩色点的点云,来实现对现实环境的数字化再现。三维激光扫描技术是相对于正向建模的技术应用,俗称逆向建模,也就是针对实体或者实景进行扫描,建立三维模型。其作业流程为点云数据采集、点云数据处理、三维模型建立、应用数据分析。     

陶瓷砖长、宽尺寸视觉检测系统研究

重点介绍了一种应用机器视觉技术进行陶瓷砖尺寸在线自动检测系统,采用面阵CCD或CMOS摄象机作为测量工具。提出了完整的图像预处理和尺寸测量算法,梯度算子和亚像素细分算法,实现了目标边缘的精确定位。综合应用哈夫变换和最小二乘法等算法实现了陶瓷砖边长尺寸的精确测量。     

基于一致性约束的图像匹配算法

采用Sift算法和一致性约束的特性,利用特征点附近的灰度信(?)相关联信息,建立图像局部匹配的准则,将图像特征点划分为多对多匹配对;利用对称性计算匹配特点邻域内其它特征点对该匹配特征点的支持强度,根据支持强度的不同建立精确的一对一匹配关系。(?)算法有效避免了Sift算法对大角度偏转图像误匹配的问题。     

基于B样条自由形变三维医学图像非刚性配准研究

医学超声成像具有成本低、实时成像等优势,基于超声的多模态配准在临床诊断、病情监测、外科手术等应用上具有较大的意义。三维医学图像能够清晰地显示病变大小、形态,提供相对完整的人体组织的三维结构信息。本文采用基于B样条自由形变模型的非刚性配准方法对三维超声图像和计算机断层扫描图像(Computed Tomography,CT)进行配准,利用薄板样条能量约束项解决三维图像配准过程中的图像交叉与重叠问题。此外,使用仿体数据以及临床数据验证算法性能,通过感兴趣区域的相对重叠率,互信息值和程序运行时间这三个指标对算法精度和速度进行评价。其中Demons方法平均耗时1896s,本文改进算法平均耗时195s,运行效率提高8.7倍;算法改进前后的感兴趣区域重叠率分别是89.58%和91.35%,精度提高2.0%。实验结果表明此算法能够对超声和CT图像进行配准并获得较好的结果。     

Deep learning-based hybrid reconstruction algorithm for fibre instance segmentation from 3D x-ray tomographic images

3D x-ray tomography is a powerful scanning technique used for generating images of complex fibre structures. A novel machine-learning algorithm to identify and separate individual fibres using 3D images is proposed in this article. The developed four-step hybrid 3D fibre segmentation algorithm involves deep-learning aided semantic segmentation that slices 3D images to create 2D images for fibre extraction, elliptical contour estimation combined with the marker-controlled watershed algorithm for separating fibres from the background area, identifying individual fibres through 3D reconstruction, and, lastly, the 3D object refining approach based on outlier object detection and replacement. The proposed methodology is implemented on a real-time sample of nylon fibre bundle under compression and its 3D x-ray image volume to validate the performance. The results show its superior performance compared to off-the-shelf image processing algorithms in terms of precision, that is, with a validation accuracy greater than 90%, and efficiency, that is, preventing the need for a huge data set and reducing the complexity.     

Investigation of colour appearance models for illumination changes across media

The key to achieving successful cross‐media colour reproduction is a reliable colour appearance model, which is capable of predicting the colour appearance across a variety of imaging devices under different viewing conditions. The two most commonly used media, CRT displays (soft copy) and printed images (hard copy), were included in this study using four complex images. The original printed images were captured using a digital camera and processed using eight colour appearance models (CIELAB, RLAB, LLAB, ATD, Hunt96, Nayatani97, CIECAM97s, and CAM97s2) and two chromatic adaptation transforms (von Kries and CMCCAT97). Psychophysical experiments were carried out to assess colour model performance in terms of colour fidelity by comparing soft‐copy and hard‐copy images. By employing the memory‐matching method, observers categorized the reproductions displayed on a CRT and compared them to the original printed images viewed in a viewing cabinet. The experiment was divided into three phases according to the different colour temperatures between the CRT and light source, i.e., print (D50, A, and A) and CRT (D93, D93, and D50), respectively). It was found that the CIECAM97s‐type models performed better than the other models. In addition, input parameters for each model had a distinct impact on model performance. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 428–435, 2001     

光栅立体影像的技术进展

人类处于三维世界之中．用我们一双明亮的眼睛能够辨别周围物体所处的相对空间位置，感受这美妙的立体世界．但是，至今广泛采用的照相术，只能记录平面影像，缺乏真实感．立体影像是继平面影像的自然演进．大约30年前，东京大学教授大越孝敬在他1976年的著作《三次元画像工学》里提到“重建空间影像是人类的梦想”．其实，这个梦想早已开始，F．E．Ives^[1]于1903年已发表利用光栅的立体影像原理．光栅立体影像的应用发展始于1940年，至今已有60多年历史，但一直都未能普及化，一定有其中的原因．     

Stereo imaging of crystal growth

Significance A methodology that directly images the full three‐dimensional (3‐D) shape of crystals within a crystallizer is reported. It is based on the mathematical principle that if the two‐dimensional (2‐D) images of an object are obtained from two or more different angles, the full 3‐D crystal shape could be reconstructed. A prototype instrument is built and proof of concept study performed to demonstrate the potentials in using the system for 3‐D measurement of crystal shape and shape distribution. It is our belief that 3‐D measurement of crystal shape represents a significant step forward from existing work of 2‐D measurement of crystal morphology and is potentially of great significance to research toward closed‐loop control of crystal morphology. © 2015 American Institute of Chemical Engineers AIChE J, 62: 18–25, 2016     

多层CT多平面重组及三维重建在齿状突骨折中的诊断价值

目的探讨多层螺旋CT多平面重组及三维重建在枢椎齿状突骨折中的诊断价值。方法回顾性分析12例枢椎齿状突骨折的CT横轴位图像、多平面重组(MPR)图像及三维重建(3D)图像。结果10例枢椎齿状突骨折运用CT横轴位图像结合MPR及3D重建首次即明确诊断。2例隐匿性骨折首次未做MPR、3D重建而漏诊,再加做MPR、3D重建后确诊。结论多层螺旋CT的MPR、3D重建对枢椎齿状突骨折,尤其是隐匿性骨折具有重要诊断价值。     

Viewing techniques for cross-media image comparisons

Several viewing techniques can be used to compare CRT images to printed images under different illuminants and luminance levels. This research examined five such viewing techniques including memory, successive-binocular, simultaneous-binocular, simultaneous-haploscopic, and successive-Ganzfeld-haploscopic viewing. The results showed that these techniques yielded different results when comparing printed originals to matching CRT reproductions, derived using various color-appearance models. Memory viewing was determined to be the most appropriate viewing technique for further study of cross-media color reproduction. © 1996 John Wiley & Sons, Inc.     

Tensile properties and corrosion resistance of PCL-based 3D printed composites

The practicality of implantable biomedical materials depends on the design of size and function to meet the needs of personal customization. This paper used fused deposition modeling 3D printing process to make composite materials, and studied the performance of 3D printed samples through different matrix molecular weights, print filling settings, additives, and their contents. Mechanical properties, thermal analysis, structural characterization, surface hydrophilicity, and functional verification of PCL-based 3D printed composites were discussed. We found that 80% print filling and 10% SA addition could greatly improve the work of fracture of the tensile sample. Furthermore, the efficacy and content of CS was also verified and analyzed. These resulting information are helpful for structural design and functional matching of medical composites.     

Errors implicit in digital particle characterisation

Factors affecting the accuracy of using digitised images of projected particles in order to determine particle properties such as shape, size and particle perimeter are defined. In particular, the inaccuracies in the representation of particles of known shapes as digitised particles under different resolutions due to loss of information at the particle boundary are quantified. The results are generalised for arbitrary shapes by the use of mathematical proof and implications are considered for relevant particle analysis techniques. An attempt is made to find relationships between resolution and accuracy, and between particle shape and accuracy. Accuracy here is defined as the deviation of the area of the digitised image from the actual area of the real particle. Implications for accuracy of 3D digitised representations of particles are highlighted and its relevance to predictions of 3D particle packing based on the digitised data.     

掺煤矸石的水泥性能与颗粒群分布的关系研究

将不同细度的煤矸石、纯硅酸盐水泥分别按30％和70％的比例混合，测其胶砂流动度、净浆标准稠度用水量和3d、28d胶砂抗压强度。以宏观性能指标为z轴，水泥与煤矸石的中位径D50之差为x轴，水泥与煤矸石混合样的中位径D50为y轴，进行三维区域图分析。给出各项性能指标发展趋势与水泥、煤矸石的相对位置以及混合体系总体细度的相互关系。     

熔融沉积3D打印机机械结构的设计

3D打印技术作为一种快速成型技术,其采用数字式模型文件作为基础,采取逐层打印的办法将可粘合性的塑料或者粉末金属用以构筑所预想的实体技术。由于3D打印技术可采用的耗材种类不同,故其存在着不同的3D打印技术用于构造不同类型的部件。3D打印耗材常有尼龙玻纤、铝合金、钛合金、石膏、镀金银以及橡胶等材料。为了拓宽3D打印机所使用的耗材范围,所以针对不同种类耗材需要开发不同类型的3D打印机。因此,本文针对特种工程材料,开发其配套的3D打印机,并设计其机械结构。设计完善其单喷嘴形制,x-y扫描机,z轴升降以及传动机构。文中对扫的方向、机械传动、打印精度、传动精密性等进行了计算。为使3D打印机的响应准确、快速,机械结构的简化,设计中采用了滚珠丝杆与线性步进机直接相连的方式。本文所设计的熔融沉积打印机结构,其运动合理,传动平稳,为其应用于实际生产做好基础工作。