纳米磁流体动态散斑干涉场的奇异场分布

通过对由纳米磁流体运动引起的双扫描激光散斑干涉光场及其变化做拉盖尔-高斯滤波下的傅里叶变换,获得动态散斑干涉图对应的光学涡旋分布及变化特征。分析认为,光学涡旋分布及变化对应着由纳米磁微粒及其团族的运动所引起的动态散斑变化。当纳米磁微粒聚集到分散的过程中,动态激光散斑光场的奇异场分布发生相应变化,说明了磁流体运动过程对应涡旋密度有先大后小,再由小变大的两个变化;并且光学涡旋密度高,对应较小颗粒的散斑场,磁流体处于稳态的状况;光学涡旋密度低,对应较大颗粒的散斑场,对应着磁流体激烈的运动。研究结果体现了奇异场分布变化和纳米磁流体动后趋稳的过程存在对应关系。     

基于灰度共生矩阵的表面粗糙度研究

介绍了激光散斑的形成及其统计性质,拍摄大量不同加工工艺、不同表面粗糙度标准样块的散斑图像,基于激光散斑图像的灰度共生矩阵及惯性矩、角二阶矩、熵、相关性4个参量,对图像进行了纹理分析.分别绘制了不同加工工艺、不同表面粗糙度标准样块的4个参量与表面粗糙度关系的特性曲线.最后将实验结果和未知表面粗糙度工件的实验数据进行比对,准确估算出了工件的表面粗糙度.     

基于灰度共生矩阵的非平面表面粗糙度的图像纹理研究

采用灰度共生矩阵对不同加工工艺形成的非平面工件表面粗糙度进行了研究。讨论了灰度共生矩阵中二阶矩、对比度、相关值，熵等与图像纹理特性的关系，构建了实验装置，并利用Matlab软件对采集的激光散斑图像进行了处理，得到了共生矩阵的4个特征参数随表面粗糙度的变化曲线。为研究非平面工件的粗糙度，提供了一种新的技术途径。     

激光散斑在大学物理实验教学中的应用

介绍了激光散斑在大学物理实验中的几个具体应用.从激光散斑的特征公式出发,分析了利用激光散斑测量透镜焦距的原理和方法;介绍了应用双曝光散斑图测量物体面内位移的原理和方法;利用激光散斑的统计特性,提出了一种测量高斯光束特性参数的新方法.这些方法光路设计简便易行,且具有实用价值,引入到大学物理实验中是可取的,也是可行的.     

激光散斑漂移现象的理论模型与成像实验

基于傅里叶光学原理,建立了数值计算客观及主观激光散斑图样的方法.利用几何光学成像原理,推导了主观散斑现象中散斑及光斑漂移速率的表达式.搭建了成像实验装置,观察主客观散斑及其漂移现象.结合相关函数、快速傅里叶变换算法以及卷积定理,建立了基于图像处理定量计算散斑及光斑漂移量的方法.实验结果、数值计算结果、几何光学理论均互相符合,表明了数值方法与几何光学理论的正确性,为激光散斑漂移现象提供了系统性的研究方法和直观的理解.     

成像型任意反射面速度干涉仪的散斑抑制

成像型任意反射面速度干涉仪(VISAR)是激光驱动聚变实验中诊断冲击波速度的重要设备。由于采用了激光照明靶面的方式,所获得的速度条纹图中不可避免有激光散斑的干扰,严重影响动态条纹的质量。介绍了该系统的激光散斑形成原因和散斑对速度分析的影响,提出了一种频谱面滤波的方式去除高频散斑噪声的方法,并通过搭建散斑光路、合理设置滤波孔位置和大小,对该方法进行了验证。结果表明,该方法对影响条纹图的高频散斑噪声具有抑制作用,适合应用于成像型VISAR系统。     

利用激光散斑获取深度图

相对于普通灰度和彩色二维图像,深度图像可以得到物体的三维信息,使视觉识别和人机交互更加智能。国内外目前还没有低成本、公开的实时获取高质量深度图的方法。本文在对散斑图获取深度图原理研究的基础上,采取激光散斑的方式,运用块匹配的方法给出了一种大范围深度图的获取方法。首先,从原理上验证了块匹配方法的可行性;然后,分别从理论和实验两个方面对深度图的计算公式进行了推导和验证;再次,对深度图恢复过程进行了详细叙述,包括散斑图像的预处理和块匹配的过程;最后,给出了运用该块匹配方法得到的实验数据。实验结果表明,本文方法在物体距离相机50 cm左右时精度可以达到5 mm,200 cm时精度可以达到5 cm,可以满足室内大部分对象的识别要求。     

基于一阶及二阶灰度梯度的散斑图质量评价方法

散斑图质量对数字图像相关(DIC)方法的测量精度具有重要的影响。以平均灰度梯度这一传统的散斑图质量评价参数作为基础,提出了一种新的评价参数——平均一阶及二阶灰度梯度商,该参数同时考虑了一阶和二阶灰度梯度。从整体上来说,一阶灰度梯度的曲面比较光滑,而一阶及二阶灰度梯度商的曲面比较粗糙。采用Zhou等人提出的方法制作了80张模拟散斑图,对这些模拟散斑图的传统参数和提出参数进行了计算。结果表明:当散斑半径相同时,随着散斑数量的增加,两种参数均先增加,后减小;当散斑数量一定时,二者均有一个峰值;散斑半径越大,提出参数的峰值越大,而传统参数的峰值越小。对提出参数的峰值所对应的4张散斑图进行了多次连续平动,并使用DIC方法测量了测点的水平位移。结果表明,在提出参数越大的散斑图上测点的水平位移误差越小,在一定程度上验证了提出参数的正确性。     

光盘信息符散斑图的统计特性研究

提出了一种用激光散斑测量光盘信息符统计特性的方法.利用散斑统计理论中衍射散斑场的平均对比度与散射屏表面粗糙度近似成线性关系,把光盘等效为弱散射屏,对未刻录、刻录及存在缺陷的CD-R光盘不同区域形成的衍射散斑图进行了对比研究.实验结果表明,该方法具有可量化、全场测量的优点,能够表征光盘信息符的某些统计特性,这为测量光盘刻录质量提供了一种新的方法和途径.     

像面散斑平均尺寸对激光散斑成像的影响

以激光散斑衬比分析为基础的激光散斑成像技术,是一种无需扫描的全场光学成像方法,在监测生理及病理状态下组织血流动态变化中的应用日益广泛.在实际应用中,像面散斑平均尺寸等多种因素影响散斑衬比值,使得该技术在反映血流变化的准确性方面受到影响.采用一种成像散斑计算机模拟方法研究了像面散斑平均尺寸对成像散斑统计特性的影响,分析了成像参数与像面散斑尺寸的定量关系,并通过物理模型实验对模拟结果进行了验证.研究结果确认了合理的像面散斑平均尺寸计算公式,证实了散斑衬比值随像面散斑平均尺寸增大而减小的现象,并为确定合理的成像参数提供了依据.     

Evaluation of activity through dynamic laser speckle using the absolute value of the differences

When a material is illuminated with a laser beam, it is possible to verify a phenomenon known as dynamic speckle or biospeckle. It exhibits an interference image that contains lots of information about the process being analyzed, and one of its most important applications is determining the activity quantity from the materials under study. The numerical analysis of the dynamic speckle images can be carried out by means of a co-occurrence matrix (COM) that assembles the intensity distributions of a speckle pattern with regard to time. An operational method that is widely used on the biospeckle COMs is the inertia moment (IM). Some studies demonstrate that IM is more sensitive on analyzing processes that involve high activities or high frequencies if considering the spectral analysis of the phenomena. However, when this variation is not so intense, this method is less efficient. For low variations on the activity or low frequencies, qualitative methods such as wavelet based entropy and cross-spectrum analysis have presented better results; however, processes that are in the intermediate range of activity are not well covered for any of these techniques mentioned earlier. The contribution of this research is to present an alternative approach, based on the absolute value of the differences (AVD) when handling the biospeckle COM. By using AVD on the seed-drying process, was found that it is efficient on verifying the behavior of the intermediate frequencies. Accumulated sum test (Coates and Diggle) showed that AVD and IM are generated from the same stochastic process. Thus, AVD is useful as an alternative method in some cases or even as a complementary tool for analyzing the dynamic speckle, mainly when the information of the activity is not present on high frequencies.     

Study of drying process of paint by dynamic speckle with B/D pixel counting technique

The aim of the work is the assessment of drying process of latex paint by dynamic Laser speckle method. The basic concept of dynamic speckle technique is described. Laser light scattering by water borne sample is a time dependent surface activity. The variation of laser speckle intensity is due to the change of refractive index and the particle movements of the latex paint. A novel method, B/D counting technique to measure the dynamic activity of drying paint using co-occurrence matrix of Time History of Speckle Pattern (THSP) is presented. The result of drying process of latex paint by dynamic laser speckle method is compared with the gravimetric method and agreed well.     

Application of dynamic speckle method using in sedimentation process of silver chloride

The generation process of silver chloride was studied using dynamic speckle methods including speckle size measurement and speckle contrast measurement. The quantity and size changes of the sedimentation particles in the illuminating region were investigated and analyzed.     

Quantitative phase retrieval in dynamic laser speckle interferometry

The rapid progress of modern manufacturing and inspection technologies has posed stringent requirements on optical techniques for vibration characterization and dynamic testing. Due to its simplicity, accuracy and whole-field characters, laser speckle interferometry has served as one of the major techniques for dynamic measurement. In this paper, a two-step phase shifting method is developed for quantitative speckle phase measurement, which helps to eliminate the specklegrams needed for phase evaluation and facilitate dynamic measurement. Unlike previously reported two-step methods using fringe patterns with known phase shift of π/2, a small unknown phase shift is employed instead in the proposed method, which eliminates the need for phase shifting devices. Further investigation shows that small phase shifts are preferable over large phase shifts in this method. Shearographic experiments conducted have demonstrated the effectiveness of the proposed technique.     

电磁驱动大尺寸MEMS扫描镜的研究

基于微机电系统工艺,设计并制作了一种电磁驱动大尺寸的二维扫描振镜.分析了两种不同的电磁驱动方式产生的力的大小,选择驱动力较大的双极子方式作为驱动.运用有限元法模拟了器件的谐振频率静态及动态响应,仿真结果与实际测得的结果一致.描述了振镜的工艺流程及封装方式,并制备了振镜.实验测得振镜在120mA静态电流驱动下,慢轴和快轴分别能达到的最大转角为±4.5°及±5°,慢轴及快轴的谐振频率分别为348Hz及660Hz,并得到在此谐振频率下的李萨如图形.将器件用于激光成像系统之中,使得散斑对比度下降到4.2%,激光成像质量得到很大提升.     

Full-field laser metrology for fluid velocity measurement

This paper reviews the development of full-field laser metrology from its inception as a dynamic extension of scattered light speckle photography, a voherent optical technique originally developed to make full-field measurements of quasi-static displacements in transparent solids, to its present applications in fluid dynamic studies. The full-field laser velocimetry technique, including both double exposure and multiple exposure recording methods, is discussed in detail, and comparison is made of their advantages and disadvantages in applications to steady and unsteady flows. Both the coherent light speckle and the particle image modes of operation are defined and evaluated. Computer aided ‘point-wise’ (Young's fringe) and ‘global’ (Fourier filtering) methods of optically analyzing the specklegrams are also discussed. Finally, experiments in which full-field laser velocimetry has been applied to a study of convective flow in a liquid are described, thus illustrating the potential of this new, non-onvasive optical technique.     

牛乳β-乳球蛋白热稳定与免疫原性关系的光谱学研究

利用圆二色性光谱和荧光光谱对牛乳β-乳球蛋白的热变性过程进行光谱学分析,得到其热变性过程的光谱学特征;结合生物信息学方法,进一步分析了热变性过程中牛乳β-乳球蛋白构象变化的特点,探讨了热变性使牛乳β-乳球蛋白蛋白构象变化导致其免疫原性发生变化的关系,建立了一种研究过敏原蛋白热变性与免疫原性关系的光谱实验方法,为探讨热变...     

牛乳β-乳球蛋白热稳定与免疫原性关系的光谱学研究

利用圆二色性光谱和荧光光谱对牛乳β-乳球蛋白的热变性过程进行光谱学分析,得到其热变性过程的光谱学特征;结合生物信息学方法,进一步分析了热变性过程中牛乳β-乳球蛋白构象变化的特点,探讨了热变性使牛乳β-乳球蛋白蛋白构象变化导致其免疫原性发生变化的关系,建立了一种研究过敏原蛋白热变性与免疫原性关系的光谱实验方法,为探讨热变性改变食物中主要过敏原的免疫原性提供了理论依据。