载频调制大剪切电子散斑干涉系统

大剪切电子散斑干涉技术不需要引入参考光，具有条纹质量好等特点。提出将干涉场的载频调制技术引入到大剪切电子散斑干涉中，可形成具有载频调制功能的新的电子散斑干涉系统。该系统具有对测量环境的隔振振动要求低，能方便定量求解物体的变形场等优点。首先讨论大剪切载频的调制机理，然后利用中心加载、周边固定的圆盘进行典型实验，设计了可用计算机控制且可对参考物进行精确偏转的步进电机系统，进而实现了对电子散斑干涉场的自动控制调制。最后，利用傅里叶变换法对调制条纹进行解调，解调出变形场的相位，并通过相位与位移的转换计算，得到精确的物体变形场。实验结果证明，该系统能够调制电子散斑干涉场，求解物体的位移场。     

运动变形表面在相干光照明下的自由空间散斑位移分布

物体表面在一束相干光照明下的空间散斑位移场分布对于分析物体表面状态及位移、变形等信息具有重要意义。本文应用散斑场的相关方法与散斑相移技术得到了物体表面位移及变形参量与自由空间衍射场散斑位移的一般关系,给出了这种一般关系的简化与分离条件,并对物体平移、转动及热加载条件下的蜂窝结构进行了实验。     

大剪切电子散斑干涉的载频调制与位移场测量

将电子散斑干涉场的载波调制引入到大剪切电子散斑干涉中,通过对参考物的微小偏转引入载波条纹;利用傅里叶变换法,解调出了变形场的相位,从而实现了物体变形场的精确测量。讨论了大剪切载频的调制机理,理论分析表明,调制条纹的空间频率与参考面偏转的角度成正比;因此,控制参考面的偏转角度可实现不同位移量系统的调制。利用中心加载周边固定圆盘进行了典型实验,实验结果证明在大剪切电子散斑干涉技术中可以通过参考面的旋转高质量地实现电子散斑干涉条纹的调制,求解位移场。该系统具有系统简单,不需要专门引入参考光,条纹质量好等优点。该技术可扩展电子散斑干涉的应用范围,有一定的实际应用价值。     

旋转孔径锥镜剪切散斑照相法

本文提出利用旋转孔径和锥镜进行剪切散斑照相,研测动态问题.该法能在一张散斑图上记录下物体动态变形的全过程,在全场滤波时可得到任意时刻的瞬态位移偏导数场.     

一种可实现电子散斑干涉的新型大错位方棱镜

设计了一种可实现电子散斑干涉的大错位方棱镜.将普通方棱镜的一个面磨去一个楔角后变为斜面,该斜面和相邻的一个面镀反射膜,其他二个面镀增透膜.垂直入射的光线经过分光后变成二束光,分别经过平面反射和斜面反射,出射的二束光线就分开了.将该大错位方棱镜置于CCD镜头前,一个物体可以成二个错位的像;相邻的二个物体可叠加成像.错位量由楔角决定,错位量足够大,可实现大错位电子散斑干涉.根据试件大小和成像距离,楔角的大小可选择在1°到10°之间.对中心加载周边固定圆盘进行了电子散斑载频干涉实验,证明了大错位方棱镜能够高质量地实现电子散斑干涉,实现位移场测量.     

散斑位移量与照明激光束特性关系的实验研究

激光照射到粗糙物体的表面会形成激光散斑，散斑随物体的运动而运动，特别是物体在自身平面内运动时散斑的同步运动比较显著，因此可以用这一现象测物体的微小位移，散斑运动规律与照明光束的特性有关，本文通过实验研究了不同光束照明下散斑位移的规律，验证了散斑位移理论，并指出散斑位移测量中应注意的问题。     

二次波面干涉的剪切散斑干涉计量术

提出了一种新的剪切散斑干涉方法─—二次波面干涉的剪切散斑干涉计量术．这一方法将被测物体变形前后波面的第一次干涉信息分别储存在两张全息干板上，通过光学信息处理实现波面的第二次干涉．两次波面干涉分别消除了位移和位移的一阶导数场对波面位相的影响，得到仅反映位移二阶导数场的条纹图．     

双目视觉DIC测量系统的离面位移测量精度

采用离面位移测量精度达到10 nm~20 nm的电子散斑干涉测量系统验证了双目视觉数字散斑相关测量系统的离面位移测量精度。分别用电子散斑干涉测量系统和双目视觉数字散斑相关测量系统同时测量了平板离面位移,并对所测量的位移最大值进行了分析处理及比较。结果表明,双目视觉数字散斑相关测量系统的物体离面位移分布云图与电子散斑干涉测量系统的结果基本相同,且两者位移均方根相差为2.76 m~3.56 m,相对误差为4.59%~7.60%。因此,当被测量物体的离面位移大于4 m时,双目视觉Q400测量系统精度可达到电子散斑干涉测量系统的精度。     

相位调制数字散斑干涉术

提出一种可绕Ｚ轴转动的粗糙平板（参考物体）实现相位调制，该方法在不改变电子散斑干涉术（ＥＳＰＩ）或数字散干涉术（ＤＳＰＩ）系统装置的情况下，可用于微小离而位移场（例如最大离面位移为λ）的测量，以及复杂形变的离面位移场的自动测量。     

双功能数字散斑干涉位移及空间梯度同时测量

为了满足无损检测中复合材料在复杂载荷下多参数变量评估的需求,提出了一种基于光路复用的双功能数字散斑干涉系统,能够同时实现数字散斑干涉和数字剪切散斑干涉测量功能.通过控制其中一个反射镜-波片组合,当该组合离位时,构成数字散斑干涉测量光路,实现离面位移测量;当该组合在位时,构成数字剪切散斑干涉测量光路,实现离面位移空间梯度的测量.测量过程中只需简单切换该组合的位置就可以实现单次加载下被测物体表面离面位移及其空间梯度的同时测量.该系统光路结构简单、切换效率高,能够同时获得高质量的位移及空间梯度测量结果.实验证明,双功能数字散斑干涉系统既具备高抗干扰能力,又具备高灵敏度测试能力,适合复合材料无损检测现场使用.     

单幅对称变形相位图分离二维变形分量的相移电子散斑干涉技术

提出了利用相移电子散斑干涉测量物体二维变形分量的方法.单光束照明的传统电子散斑干涉技术,测量得到的是一幅物体变形的混合相位场.当物体具有对称变形时,可由这一幅相位图求得二维变形分量.方法是将该相位图镜像翻转得到第二幅相位图,通过二幅相位图的叠加、复位和分离运算,获得物体的二维变形场的分量值.利用三点加载的简支梁进行了实验,给出了实验结果,并与对称光照明实验结果进行了对比,验证了该方法的正确性.     

EPSI validation for cylindrical gears

Shape deviations of spur gears obtained by using Electronic Speckle Pattern Interferometry are compared with the results of numerical simulation. The dual illumination method produces a speckle pattern by simultaneous illumination of a sample by two laser waves symmetrically in the direction of observation. Two images obtained, respectively, before and after deformation are subtracted to obtain the field of displacement. Furthermore, a study of meshing stiffness was performed for different types of setting for an internal gear.     

散斑面内形变场检测系统设计

数字散斑测量是一种非接触、全场测量的高精度光测方法。该系统由散斑生成装置、数据采集装置和数据处理装置三部分组成。散斑生成装置将扩散的激光束投射到待测物体上,用接收屏接收物体散射生成的散斑图像。数据采集装置主要由CCD和数字采集卡组成,CCD拍摄散斑图像,并将其传输给数字采集卡,经采集卡转换成数字图像,以矩阵形式输入到数据处理装置。数据处理装置根据光学相关识别技术设计的检测程序对采集到的数字图像进行相关运算,通过对相关峰的准确定位来获取物体的形变信息。     

基于光学涡旋相移技术的离面位移测量

设计了基于光学涡旋相移技术的离面位移测量实验方案,实现了电子散斑干涉中相移的数字控制.该方法利用输入液晶空间光调制器中的叉形光栅产生涡旋光束,通过涡旋光束绕轴的旋转产生相移;同时,产生的涡旋光束又作为参考光与物光干涉.实验中,在物体发生离面位移前后依次输入四幅叉形光栅,产生相移步长为π/2的涡旋光束,利用CCD获得涡旋光与物光的干涉光场,从而获得离面位移场的包裹相位;再通过解包裹,获得物体离面变形的相位变化.光学涡旋相移法可应用于离面位移测量.     

Micro- and macro deformation measurement by extension of correlation technique

In this work, we present the implementation of Electronic Speckle Pattern Interferometry (ESPI), Digital Speckle Photography (DSP) and Digital Image Correlation (DIC) as complementary techniques to measure in-plane micro and macro displacement. The main advantage of ESPI is its great sensitivity to small displacements (smaller than the size of the speckle). However, the contrast of fringes in this technique is severely affected by de-correlation effects when the in-plane displacement exceeds the size of the speckle. To eliminate the de-correlation effects, we use the DSP technique. It is possible to generate artificial speckles, usually bigger than those generated by means of illumination of the sample with laser light. By combining DSP and DIC the displacement field can be obtained when the ESPI method cannot be applied due to image de-correlation. The experimental results show that the combination of these techniques is useful to analyze deformations over a wider range.     

Comparison between instantaneous and integral intensities in dynamic speckle pattern interferometry

A new speckle measurement technique called temporal speckle pattern interferometry or time sequential speckle pattern interferometry has been developed recently. Its principle is that by capturing the temporal speckle patterns related to the object deformation or displacement, the whole-field displacement, the amplitude of the vibrating object and the shape of the tested object can be calculated through speckle intensity fluctuation scanning technique or Fourier-transforming method. In this paper, we combine the analytical and numerical methods to simulate the properties of the time demodulation in temporal speckle patterns interferometry techniques. The performance of three kinds of temporal phase sequences, power, exponential and harmonic phase sequences, are studied with the parameters of temporal speckle intensity fluctuation, the value of the spatial phase term, optical integral time of the recording camera and the initial phase of the temporal speckle intensities. The results indicate that the normalized value and period change of the instantaneous intensity are nearly coincident with that of the integral intensity for the harmonic temporal phase sequences and are different for the power and exponential temporal phase sequences.     

数字散斑条纹图的滤波方法

在现代数字散斑测量方法中，一般采用减模式来产生数字散斑条纹图，它是进一步图像处理的信息载体，同时不可避免地附带有大量的乘性噪声。为了保证测量精度，在进一步图像处理前必须对其进行降噪，选择合适的滤波方法显得尤为重要。在多年实际经验及阅读了大量文献的基础上，该文对国内外常用的数字散斑干涉条纹图滤波方法进行了分类阐述，选择了一些有代表性的方法予以实现，给出实验结果，并进行了对比分析。最后对数字散斑干涉条纹图滤波方法的发展方向给出了自己的看法。     

Application of improved Speckle contouring technique to surface roughness measurements

One of the well known drawbacks in Electronic Speckle Pattern Interferometry (ESPI) is the poor fringe density due to electronic and speckle noise and decreasing fringe visibility with increasing speckle decorrelation. As recently reported we suggested improving the fringe density and enlarging the measurement range by the incremental addition of phase images. The technique has already been successfully applied to in-plane and out-of-plane displacement field measurements of carbon-fibre reinforced composites. This paper demonstrates how the technique can be used to improve the sensitivity and to extend the measurement range for speckle contouring applications. The angular correlation of the speckle phase images is used to get the desired 3D information of the investigated object surface. It is demonstrated how the angular speckle contouring techinque can easily be automated with respect, for example, to possible industrial applications. Roughness measurements are carried out on milled Rugo test surfaces. All measurements are performed without the usual vibration isolation, and of course, without the treatment of the surface with fine, white powder for contrast enhancement, which would falsify the results.     

Speckle interferometry methods for displacement and strain measurements using photorefractive crystal

Photorefractive crystals offer several attractive features such as high resolution and in situ processing. As the images are erasable, these crystals are suitable for read–write applications and hence find potential use in speckle photography, image processing and holography. The barium titanate (BaTiO₃) crystal as recording medium has been extensively used as a novelty filter for real-time in-plane displacement measurements employing two-beam coupling configuration. This paper presents new optical configurations in speckle shear photography to measure in-plan displacement and the strain in real time using BaTiO₃ crystal as recording medium. Speckle photography studies are made using a simple two-beam coupling configuration. In speckle shear photography, a diffused object illuminated with two parallel narrow laser beams is imaged inside the crystal, and a pump beam is added at this plane. The speckle patterns due to each beam and the pump beam produce index gratings. When the object is deformed, the speckle patterns shift consequently. We now have four speckle fields: two generated from the interaction of pump beam with the index gratings and two pertaining to deformed states directly transmitted through the crystal. Thus, the fields from respective points on the object interfere after passage through the crystal and produce the Young's fringe patterns. Due to strain, the fringes in each pattern are of different width and orientation, resulting in the generation of a Moiré pattern. The strain is obtained from the width and orientation of the fringes in the Moiré pattern. The experiments are conducted on a specimen with a notch, which is subjected to tensile loading. The in-plane displacement is measured separately in another experiment. The above studies are carried out at Nd–Yag laser.     

双散斑场相移数字干涉计量

本文介绍了一种检测散射表面变形的自动测量系统。将相移和数字图像处理技术应用于数字散斑干涉计量中,毋须中间记录过程,在计算机控制下采集数据和计算相位,产生相位条纹而非相关条纹。用图像处理技术消除散斑随机性引起的噪声。文中给出了面内、离面变形的测量结果。