数字散斑相关测量方法的研究与改进

通过对数字散斑相关测量方法的研究,提出一种新的数字散斑相关搜索方法.采用该方法可大大节省数字散斑相关测量中数据处理的时间.实验表明,本文所提出的方法是一种实用的快速、高精度位移和变形的测量方法.     

数字散斑技术在混凝土单轴压缩试验中的应用

数字散斑技术作为一种新兴的测量方法,它具有非接触、全场量测、精度高、操作简单等特点,随着计算机技术的迅猛发展,数字散斑技术得到了广泛的应用与研究。针对混凝土在外荷载作用下具有明显的非均匀变化的特征,借助传统的测量方法很难得到混凝土表面的全场变形结果的问题,结合数字散斑相关方法测量技术,开展了混凝土单轴压缩试验,拍摄了混凝土表面在单轴压缩过程中的位移与应变矢量场,为分析混凝土试件的损伤区域奠定了基础;与电测法测量结果进行了对比,其测量结果表明,这两种测量方法误差相对较小,且数字散斑技术能更早的发现混凝土表面的破坏,验证了数字散斑相关方法的准确性和可靠性。借助数字散斑技术可以更加方便准确的得到材料表面的变形场,这也将在一定程度上促进土木工程领域的发展,具有广阔的应用前景。     

白光数字散斑照像术

本文提出一种新的数字散斑计量术——白光数字散斑照像术.它以两维数字偏心滤波技术实现全场信息的表征,而以数字相关技术实现点信息的表征.文中给出了计量方法、理论分析及实验结果.     

频率域数字散斑相关方法的研究

提出一种利用二维快速傅里叶变换（ＦＦＴ）经频率域匹配滤波实现数字相关运算以提取散斑图携带位移信息的频率域数字散斑相关方法。该方法因采取快速傅里叶变换、散斑限幅、滤波器优化等措施而减弱了空间域相关方法中不利因素对相关波峰的影响,提出了相关点定位的时效性和精确性。     

数字散斑相关方法及应用进展

数字散斑相关方法（DSCM）是一种可以测量变形和应变的光学非接触测量方法,其通过对变形前后物体表面的图像进行灰度信息相关计算来获取被测物的力学性能。本文叙述了数字散斑相关方法近年来在国内外的发展动态和应用现状,详细论述了基于自适应遗传算法、智能神经网络方法、小波变换法的一系列新型相关搜索方法。文章指出,近年来,数字散斑相关技术已发展到相对成熟,目前的研究重点是提高测试精度和图像处理速度,而提高散斑图像质量和研究高效的算法是需要努力的方向。     

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。     

基于卷积神经网络的散斑图像位移场测量方法

提出了一种基于卷积神经网络(CNN)的数字散斑图像位移场测量方法.采用给定多种变形模式的精确位移场系列数字散斑图像构建数据集,提出了一种数字散斑图像位移场识别CNN模型.模拟散斑图像的验证实验表明,所提方法对随机变形、轴向均匀变形、剪切变形等模式具有良好的计算效率和测试精度.硅胶单轴拉伸验证实验表明,所提方法也可以精确测试真实实验散斑图像位移场并具有较高的计算效率.所提深度CNN能够高效、精确地测试数字散斑图像位移场,在材料变形测试中具有良好的应用前景.     

斜光轴面内位移测量的数字散斑相关法研究

以工程环境中远距离位移和位移场的光学测量为研究课题,分析了远距离斜光轴成像时,像模糊和成像位置变化对白光数字散斑相关方法产生的影响,给出了这两种影响的误差理论计算公式。提出使用参考测量技术克服斜光轴成像位置变化带来影响,给出一种新的远距离斜光轴高精度测量面内位移的方法,在2～50m处作静载挠度测量,其最大相对误差小于1％,测量精度在实验室环境和工程测量环境中都得到了验证。该方法无需共轴光路的测量环境要求,特别适用于桥梁、高速公路立交桥的静载挠度测量等工程应用。使用高速图像采集卡,该方法可应用于斜光轴动态位移测量,拓展了数字散斑相关方法的应用范围。     

频域数字散斑相关法对双材料界面裂纹的研究

本文将数字散斑相关方法与显微放大技术相结合,对铜、钢双材料界面裂纹试作进行了研究,提出了频率城数字散斑相关法,该方法在频率域中利用物体变形前后散斑图对应子区域的相关搜索来测量物体的变形位移,该方法与常用的空间域数字相关法相比,避免了相关识别中的反复搜索,极大地提高了信息提取速度,并且具有更高的定位精度和测量精度。文章最后给出了实验结果。     

基于电子散斑干涉与数字剪切散斑干涉法的悬臂薄板振动分析

基于激光光路的光波随机相位扰动,分析了电子散斑干涉实时图像相减时模态条纹图的形成机理,提出了一种振幅涨落测量法。搭建了用于离面振动分析的电子散斑干涉和数字剪切散斑干涉测量系统,并对完整和含狭缝的悬臂铝板的振动特性进行了实验研究。实验结果表明,实时图像相减模式获得的模态条纹图对比度明显优于其他方法,得到的前10阶模态条纹图与有限元法计算结果具有良好的一致性。相比于电子散斑干涉法,数字剪切散斑干涉法对试样局部的刚度变化和缺陷更敏感。     

Analysis of a synthetic Tadoma system as a multidimensional tactile display

The Tadoma method is a means of speech reception based on tactile monitoring of the articulatory process. A "synthetic" Tadoma system, involving an artificial face with six facial actions, has been developed as a first-order approximation to the natural Tadoma system. Experiments were conducted to explore the information-transmission characteristics of the synthetic Tadoma system in terms of the four facial movements it incorporates: upper lip in-out, lower lip in-out, lower lip up-down, and jaw up-down movements. Discrimination experiments showed that the just-noticeable difference associated with each movement is about 9% of the reference displacement. One-dimensional (1-D) absolute identification experiments produced, on the average, 1.6 bits of information transfer. Four dimensional (4-D) identification experiments produced information transfers in the range of 3-4 bits. Of the four dimensions considered, performance on the lower lip up-down movement was most affected, and performance on the jaw up-down movement was least affected, by simultaneous roving movements on the other dimensions. As a result of the interaction among the movement channels, the sum of the 1-D information transfers exceeds the 4-D information transfer. However, the sum of the 1-D information transfers obtained from tests with roving parameters is approximately equal to the 4-D information transfer (possibly exemplifying a "generalized information-transfer additivity law"). In general, both the discrimination and identification results appear unexceptional and, hence, the reception of facial movement information by itself does not appear to account for the extraordinary success of the Tadoma method.     

Displacement measurement method based on laser self-mixing interference in the presence of speckle

In order to achieve the accurate measurement of displacement, this Letter presents a self-mixing interference displacement measurement method suitable for the speckle effect. Because of the speckle effect, the amplitude of the self-mixing interference signal fluctuates greatly, which will affect the measurement accuracy of displacement. The ensemble empirical mode decomposition is used to process the interference signal, which can filter out high-frequency noise and low-frequency noise at the same time. The envelope of the self-mixing interference signal is extracted by Hilbert transform, and it is used to realize the normalization of the signal. Through a series of signal processing, the influence of speckle can be effectively reduced, and the self-mixing interference signal can be transformed into standard form. The displacement can be reconstructed by fringe counting and the interpolation method. The experimental results show that the method is successfully applied to the displacement measurement in the presence of speckle, which verifies the effectiveness and feasibility of the method.     

Articulatory movement characteristics of labial consonant productions by children and adults

One purpose of the present investigation was to attempt to better understand articulatory movement characteristics of children's speech, particularly as they might relate to the question of why acoustic measures of children's segment durations are often longer than those of adults. In order to address this issue and to consider other general characteristics of children's speech production development, a variety of data was obtained from three groups of children and from a group of adults using strain gauge instrumentation to monitor superior-inferior lip and jaw displacement and peak velocity. Results indicate that the children's peak velocity and articulatory displacement measures were in many respects quite similar to those of the adults, although certain differences were observed. For a number of measures, there were also few peak velocity or displacement differences observed among the three age groups of children, despite the fact that they spanned about a six-year age range. In general, it appears that even when children and adults produce consonant sounds that are perceptually "correct," articulatory differences can be observed among their productions.     

用Zernike多项式实现光机分析的技术方法

由于光学软件不能直接利用有限元分析的结果，而Zernike多项式的各项与光学像差有对应关系，因此常用Zernike多项式作为光机接口。针对目前常用轴向位移作为拟合量描述拟合面形的不足，给出了几种常用的表面位移校正方法并说明了其优缺点。用具体实例比较各校正位移，并对其进行Zernike多项式拟合，从拟合系数的差异可以看出,曲率比较大的表面必须采用校正位移进行拟合。最后指出：在不知道初始表面方程的情况下，轴向和法向校正位移均采用从初始表面出发的方法，如果已知初始表面方程，则轴向校正位移采用从变形表面出发的方法，法向校正位移仍采用从初始表面点出发进行计算。     

Quadrature demodulation technique for self-mixing interferometry displacement sensor

A new, to the best of our knowledge, signal processing method based on quadrature demodulation technique is presented for laser diode self-mixing interferometry(LDSMI) displacement sensor. Phase modulation of the laser beam is obtained by an electro-optic modulator (EOM) in the external cavity. Detection of the target's displacement can be easily achieved by sampling the interference signal at those times which satisfied certain conditions. The major advantage of the technique is that it does not involve any complicated calculation and insensitive to the sampling error. Experimental results show that the proposed method can effectively improve the displacement measurement resolution of the laser diode self-mixing displacement sensor to a few nanometers.     

Simultaneous measurement of whole in-plane displacement using phase-shifting ESPI

A novel method for simultaneously measuring whole field in-plane displacements by using optical fiber phase-shifting electronic speckle pattern interferometry (ESPI) is presented in this paper. A 1 × 4 single mode optical fiber beamsplitter is employed to split the laser beam into four beams of equal intensity. One pair of fibers is utilized to illuminate the diffuse target at equal angles in the horizontal plane so it is sensitive only to horizontal in-plane displacement. Another pair of optical fibers is set to be sensitive only to vertical in-plane displacement. The polarization directions of light emitted by fibers are the same for each pair, but are at a right angle between pairs. The optical fibers are equal in length for each pair, but are not equal between two pairs. In this case the speckles are interference between each pair of fibers, thus the horizontal and vertical displacement components can be obtained simultaneously. By means of a fiber phase shift technique we can obtain the quantitative data of whole field displacements. This method has made it possible to study the in-plane displacement of a thin metal plate, and the examples of the results are shown to demonstrate the novel method.     

Nanoscale deformation measurement by using the hybrid method of gray-level and holographic interferometry

This study extends the use of holographic interferometry to measure the nanoscale out-of-plane displacement with high surface resolution. It is noted that if the deformation is less than half of the optical wavelength, it is hard to find an obvious fringe pattern. Under such a situation, in general, the phase shift method is used. However, it needs to take more than 3 images for phase shifting and phase reconstruction In this paper, a more simple hybrid method of gray-level and holographic interferometry is used to extract fringe skeletons, in which it just needs to take one or two images for the normal deformation measurement directly, even if there exists no obvious fringe pattern. The displacement field with high surface resolution can also be obtained. The proposed method yielded a theoretical precision of 0.15 nm for out-of-plane displacement with a monochromatic CCD camera of 10-bit gray scale (1024 gray scales) sensitivity and microscale surface resolution for millimeter scale object with 640×480 pixels image resolution by an He–Ne LASER (632.8 nm wavelength) light source. The gray-level method is proposed to calculate the non-obvious interferometry fringe by traditional holographic interferometry hologram, and the result showed that this method works for this purpose.     

Study on Combined Method Based on 3-D ESPI

The finite element method (FEM),whether the calculation is accurate or not,depends closely on object boundary condition.If the three dimensional displacement of the object obtained in experiment is regarded as its boundary condition,a new method combining the results of experiment and calculation,called combined method (CM),is formed.The combined method possess advantages of experiment and calculation.It can correct calculation and improve the accuracy of FEM.Accordingly it has more practicability.In this paper,the three dimensional displacement fields of a typical beam loaded at three points are tested by using 3-D electric speckle pattern interferometry (ESPI).Using the experimental results as boundary condition the whole three-dimensional displacement fields can be calculated by FEM.The beam′s three-dimensional displacement fields obtained by FEM agree very well with those obtained by experiment.This proves that the combined method is effective and practicable.     

Study on Combined Method Based on 3-D ESPI

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A novel lip reading algorithm by using localized ACM and HMM: Tested for digit recognition

Lip contour tracking is an integral part of lip reading application. Fast and accurate lip tracking is an important step in lip reading. This paper uses a novel active contour model for lip tracking and proposes geometrical feature extraction approach for lip reading. Effect of individual features are compared and a joint feature model is obtained by combining weighted decision obtained by a feature vector of difference in inner area, height and width of lip. Ergodic hidden markov model (HMM) is used as a classifier. For each digit Markov Model is tested for 3 states and 5 states. Videos of English digit from 0 to 9 have been recorded for recognition test. Cuave database is used for comparison along with an in-house database. While doing computation of feature vectors, only significant frames are used to reduce the computation complexity. Results of experimentations on digit utterances are given to show that the maximum recognized digit can be used for important programming command of computerized numerical control machines.