基于空间二进制编码的3 D形貌测量方法

介绍了一种基于空间二进制编码的非接触３ Ｄ 形貌测量方法。它用一台ＬＣＤ 投影仪对被测物体表面进行空间编码,再用一台ＣＣＤ 摄像机获取物体编码信息,最后用三角法原理从摄像机图像中获取三维形貌数据。提出了基于三角法的空间二进制码的重要特性,描述了高效编码的构造方法。用这个构造方法构造出一个完全数字化的７ 位字长的二进制编码。基于这种编码的３ Ｄ 形貌测量方法在被测物体表面非常不连续和非构造的环境下取得了良好的测量结果。     

与象电荷有关的能量和互作用力问题

指出与象电荷有关的系统的互能、互作用力和真实电荷系统的互能、互作用力分别相等,自能、有一般分别不等。     

数字图像处理在塞曼效应实验中的应用

利用计算机对塞曼效应实验进行了数字图像处理,使实验精度有很大提高,实验时间缩短,该方法对拓宽学生知识面,开发计算机的应用起到了一定作用,值得在其它实验中推广。     

几种光学图象相位加密方法的比较

本文分析比较了多种实现光学图象相位加密的方法,发现不同方法获得的加密图象有不同类型的噪音分布.无论加密相位是随机相位模板、浑沌序列的相位列阵,还是用相位重构迭代算法计算的结果,它们都能起到加密图象的功能.解密图象的质量或被相关识别的能力与解密过程中所使用正确解密相位的不同部分以及高低频分量多少有关,且其依赖程度是由不同的加密方法自身决定.     

Digital image correlation in experimental mechanics and image registration in computer vision: Similarities,differences and complements

Digital image correlation and image registration or matching are among the most widely used techniques in the fields of experimental mechanics and computer vision, respectively. Despite their applications in separate fields, both techniques primarily involve detecting the same physical points in two or more images. In this paper, a brief technical comparison of the two techniques is reviewed, and their similarities and differences as well as complements are presented. It is shown that some concepts from the image registration or matching technique can be applied to the digital image correlation technique to substantially enhance its performance, which can help broaden the applications of digital image correlation in scientific research and engineering practice.     

Development of microscale pattern for digital image correlation up to 1400 °C

Speckle patterns to be used for digital image correlation (DIC) at the micrometer level up to 1400 °C were fabricated by several methods. The quality of the patterns before and after heating was evaluated in terms of the mean intensity gradient (MIG) and the speckle size distribution. The displacement accuracy in simulative translation of images showed that the MIG alone was not enough to evaluate the pattern properties; a large MIG, an even speckle size distribution, and a wide speckle size range pattern were required for a good DIC. The reaction between the patterning material and substrate, the cracking of speckles, and the plastic flow of patterning material may cause changes in the pattern morphology at high temperature. Two patterning methods, spraying a mixture of ceramics powder and binder by a fine-nozzle air brush and abrading a polished surface, yielded a small pattern with high MIG values and even size distributions that was stable at 1400 °C. The potential of the fabricated patterns was shown by measuring the coefficient of thermal expansion of polycrystalline Al₂O₃ from 800 °C to 1400 °C.     

Local zone wise elastic and plastic properties of electron beam welded Ti–6Al–4V alloy using digital image correlation technique: A comparative study between uniform stress and virtual fields method

Joining of materials using welding results in the formation of material zones with varying microstructure across the weld. Extraction of the mechanical properties of those individual heterogeneous zones are important in designing components and structures comprised of welds. In this study, the zone wise local extraction of the elastic and plastic properties of an electron beam welded Ti–6Al–4V titanium alloy has been carried out using both the uniform stress method (USM) and the virtual fields method (VFM) involving digital image correlation (DIC) technique. The surface strain field obtained using DIC technique from a transverse weld specimen tensile testing is used for extracting the zone wise strain evolution. Initially, using uniform stress assumption, zone wise full range stress–strain curves are extracted. In USM methodology, the elastic and plastic material models are fitted to the zone wise stress–strain curves and required parameters are extracted from it. But inherent disadvantage is lot of images need to be processed for the parameter extraction. Recently, VFM is gaining lot of popularity in characterization domain as it is robust, accurate and faster. VFM is based on the principle of virtual work where, the weak form of local equilibrium equations and kinematically admissible virtual displacement fields are utilized for parameter extraction. Hollomon׳s power law is used here as the hardening rule. Young׳s modulus, Poisson׳s ratio, yield stress, strength coefficient and strain hardening exponent are the parameters extracted zone wise using both USM and VFM. A Vicker׳s microhardness measurement is also conducted across the weld zone towards mapping the strength behavior. Fusion zone has reported higher yield strength, strength coefficient and Poisson׳s ratio. Young׳s modulus value is found decreasing from base metal towards the fusion zone. The trend observed in parameter variation across the weld zone obtained by both USM and VFM compares very well. Due to various advantages associated with VFM technique it is generally recommended for parameter extraction.     

光纤倒像器的透过率

本文论述光纤倒像器中扭转光学纤维和尺寸及其特别的传光性能。用定性和定量的方法,分析影响光纤倒像器透过率的若干因素,给出透过率随径向位置和孔径角的变化关系。提出在制造、应用和测试这种光学元件时应该注意的有关问题。     

空间编码与灰度投影相结合实现高效3-D形貌测量的研究

介绍了一种结合空间编码与灰度投影来实现高效三维形貌测量的方法。用空间编码完成对被测空间的粗略编码,用灰度投影完成精确编码,将它们结合起来得到被测物体表面丰富的编码信息,作为一种基于三角法的三维形貌测量方法,能够在物体表面非常不连续和外部光照造成的背景光强分布不确定的情况下工作良好。同时,与传统的空间编码方法相比,它大大提高了空间编码的效率。实验表明,该方法用５ 幅图像取得了与灰度码１０幅图像相当的测量结果。     

小波分析在层析图像重构中的应用研究

小波分析作为一种非平稳信号分析方法,具有良好的时（ 空）、频局部化特性和多分辨率特性。介绍了小波分析的基本原理和应用,引入小波分析进行图像重构,利用小波分解后得到的多分辨率的稀疏矩阵表示,设计了一迭代重构算法。通过计算机仿真试验,验证了小波分析在计算层析（ＣＴ） 成像光谱技术中能够应用于图像重构,并证实了小波分析的迭代重构算法是稳定、多分辨率和快速收敛的。