Simple real-time 3-D displacement measurement by fringe analysis using a photorefractive interferometer

A simple 3-D displacement measurement method using a photorefractive interferometer is proposed and experimentally demonstrated. A photorefractive crystal attached to the sample under test is used to record an original spherical wave that provides a shifted reconstructed wave after displacement. The shifted wave interferes with direct wave to form an interferogram. By analyzing the fringe pattern the in-place and out-of-place displacements can be determined at the same time. This method works in real-time and is easy to operate with adequate accuracy comparable with or even better than that of other techniques.     

3-D Phase Object Reconstruction Using Beam-Deflection Iterative Tomography

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Fourier transform moiré tomography for high-sensitivity mapping asymmetric 3-D temperature field

Fourier transform evaluation for moiré deflectogram is proposed to automatically map the temperature field. The moiré deflectogram is generated by conventional deflectometer and is analyzed by means of Fourier transform algorithm. The convolution backprojection algorithm is used for the optical tomography. Asymmetric 3-D gas temperature distribution for a given layer is reconstructed.     

Microscopic 3-D displacement field measurements using digital speckle photography

A technique to measure object shape and 3-D displacement fields in micro-scale is offered by microscopic stereo digital speckle photography. The displacement of the random features that are often present on many engineering surfaces when viewed in a microscope is measured with the system, using image correlation. In this paper the equipment, physical model and calibration routines are described. The technique can be applied for sub-mm sized objects of arbitrary shape for small deformation fields. As a verifying experiment, an in-plane rotation of a flat calibration plate is presented. The expected in-plane errors are shown to be less than 0.1 μm and the corresponding out-of-plane errors about three times larger. As a pilot experiment, micro-structural paper expansion is studied, when exposed to humidity. The scaling properties of the microscope as well as the sampling criteria and reliability of the system are discussed in detail.     

台阶状面形的投影栅线法测量技术

采用光栅投影式三维轮廓术测量物体三维形貌时，当物体是台阶状物体时，物体表面的光栅条纹有阴影，导致后面的叠相还原过程无法进行。为了解决这一问题，将被测物体放在精密的旋转平台上。通过2次成像后，对2幅图像进行图像拼接，得到清晰的被光栅调制的物体图像。在图像拼接时，引入区域黑白对比度概念，区域的黑白对比度最大位置就是黑白区域的分界线。从而精确确定中间块2个边界的位置,然后进行图像拼接。最后采用双频光栅的傅里叶变换轮廓术来实现物体的三维形貌重建。结果表明：本方法简单、精度高，可以成功解决投影时具有阴影物体的三维形貌重建问题。     

Simultaneous measurement of flow velocity and Doppler angle by the use of Doppler optical coherence tomography

Monitoring blood flow velocity could have great value for biomedical research and clinical diagnostics. One of current restrictions to determine flow velocity by the use of Doppler optical coherence tomography (Doppler OCT) is that the Doppler angle should be predefined. However, from a practical point of view, it is not easy to predetermine Doppler angle for a flow beneath the tissue surface. In this work, a novel method for measuring both flow velocity and Doppler angle simultaneously by the use of Doppler OCT is proposed and demonstrated. Based on Doppler spectrum analysis, this technique measures both longitudinal and transverse components of flow velocity by detecting its Doppler shift and Doppler bandwidth to determine velocity and Doppler angle simultaneously. Such a technique extends flow velocity measurement into a broadening practical use of Doppler OCT where Doppler angle would not need to be predefined, for example, blood flow beneath the tissue surface. Therefore, with this technique, Doppler OCT could be applied to more practical diagnoses of microcirculation.     

三维物体360°面形自动测量方法

提出一种三维物体360°面形自动测量方法.简要介绍了方法原理,系统结构,信息获取与处理方案,并给出对圆锥-圆台金属模块和人头石膏模型360°面形测量结果.     

Real-time analysis of 3-D axisymmetric refractive index field by photorefractive holographic interferometry

A real-time test method for determining the refractive index distributions of 3-D axisymmetric temperature field around a flame with the use of a photorefractive holographic interferometer is proposed. Some techniques in data processing for improving the quality of resultant interferogram are developed. Experimental results, which show the effectiveness of this method and agree with theoretical expectations, are also given.     

用条纹图形拼接法测量三维大物体面形

三维物体面形的测量在各个领域中有着广泛的应用，用莫尔法、调制光场分析法测量具有非接触性、高精度、快速的特点，但对于大物体的测量却存在着许多困难，诸如阴影噪声难以消除、条纹对比度低。考虑到图形的相关性，本文提出了一种基于多孔径拼接原理的测量三维大物体面形的方法：条纹图形拼接法，给出了数学模型、计算机模拟结果和实验结果。     

3D displacement field measurement with correlation based on the micro-geometrical surface texture

Image correlation methods are widely used in experimental mechanics to obtain displacement field measurements. Currently, these methods are applied using digital images of the initial and deformed surfaces sprayed with black or white paint. Speckle patterns are then captured and the correlation is performed with a high degree of accuracy to an order of 0.01 pixels. In 3D, however, stereo-correlation leads to a lower degree of accuracy. Correlation techniques are based on the search for a sub-image (or pattern) displacement field. The work presented in this paper introduces a new correlation-based approach for 3D displacement field measurement that uses an additional 3D laser scanner and a CMM (Coordinate Measurement Machine). Unlike most existing methods that require the presence of markers on the observed object (such as black speckle, grids or random patterns), this approach relies solely on micro-geometrical surface textures such as waviness, roughness and aperiodic random defects. The latter are assumed to remain sufficiently small thus providing an adequate estimate of the particle displacement. The proposed approach can be used in a wide range of applications such as sheet metal forming with large strains. The method proceeds by first obtaining cloud points using the 3D laser scanner mounted on a CMM. These points are used to create 2D maps that are then correlated. In this respect, various criteria have been investigated for creating maps consisting of patterns, which facilitate the correlation procedure. Once the maps are created, the correlation between both configurations (initial and moved) is carried out using traditional methods developed for field measurements. Measurement validation was conducted using experiments in 2D and 3D with good results for rigid displacements in 2D, 3D and 2D rotations.     

利用激光并采用热释电探测器的实时测温系统的灵敏度

在介绍一种利用 In Ga As/I半导体激光器并采用钽酸锂 ( L i Ta O3)热释电探测器实时测温系统的基础上 ,着重分析了在该系统测量中和在高温度时的极限灵敏度 ,并导出了该系统极限灵敏度的数学表达式。给合其温度的测量误差 ,分析了系统的工作波长、被测温度、放大器带宽以及光学系统的相对孔径对极限灵敏度的影响 ,并进行了计算机模拟 ,得到了一系列有意义的结论     

用于物体三维测量的光纤投影器的设计与数值模拟

新的光学三维传感和计量方法不断涌现,在这些测量方法中,结构光投影器的设计至关重要。将光纤引入其中,设计了多光纤空间编码面结构投影器,利用多光纤干涉可以在空间形成条形、方形、六角形等多种干涉图样,从而构成了多功能光纤干涉图像投影器,并对各种空间编码结构的投影图像给出了计算机仿真结果。讨论了投影器的空间编码结构参数对测量范围和测量精度的影响,以及与编码器结构相适应的测量方法。该研究对多光纤干涉图像投影器的设计制作与实际应用具有一定的参考意义。     

荧光余辉光纤测温中的数据处理

根据荧光光纤温度传感器的理论基础和现状,针对荧光余辉时间常数提出了两种数据处理方法,并对这两种数据处理方法进行了建模和分析,以便在不同情况下选用不同的方案。     

Simultaneous strain and temperature measurement of advanced 3-D braided composite materials using an improved EFPI/FBG system

Simultaneous strain and temperature measurement for advanced 3-D braided composite materials using fibre-optic sensor technology is demonstrated, for the first time. These advanced 3-D braided composites can virtually eliminate the most serious problem of delamination for conventional composites. A tandem in-fibre Bragg-grating (FBG)/extrinsic Fabry–Perot interferometric sensor (EFPI) system with improved accuracy has been used to facilitate simultaneous temperature and strain measurement in this work. The non-symmetric distortion of the optical spectrum of the FBG, due to the combination of the FBG and the EFPI, is observed for the first time. Experimental and theoretical studies indicate that this type of distortion can affect the measurement accuracy seriously and it is mainly caused by the modulation of the periodic output of the EFPI. A simple method has been demonstrated to improve the accuracy for detection of the wavelength-shift of the FBG induced by temperature change. A strain accuracy of ±20μ and a temperature accuracy of ±1°C have been achieved, which can meet the requirements for practical applications of 3-D braided composites.     

数字图像处理技术在叠栅条纹测量中的应用

将数字图像处理技术应用于叠栅条纹测量物体三维形状,使用Inter公司的开源视觉库OpecCV,经过灰度化、锐化和去噪、叠加虚参考光栅对图像进行处理,简化测量过程,提高测量速度和精度.     

激光辐照下转动柱壳平均温度与破坏时间的工程估算

 推导了激光辐照下转动壳体平均温度沿壳体母线方向分布的解析公式。由于对高斯功率密度分布光束无法得到工程上实用的结果,对公式进行了解析拟合,仅由一个具有实际物理意义的拟合系数——分布因子确定了解析拟合公式的形式,明确了温度估算公式中各项的物理意义。解析拟合公式计算结果与数值模拟结果较为一致。作为温升估算方法的一个应用实例,推导了转动充压柱壳在激光辐照下破坏时间的解析公式,与数值计算结果吻合得较好。     

用改进的共轭斜量迭代法重建三维折射率场

本文通过计算机模拟运算,结合折射率场(温度场)的先验知识,考查了改进的共轭斜量迭代法用于全息干涉计量三维折射率场的重建精度及视角范围和数据噪声的影响,并介绍了一种抑制较大噪声的算法.作为一个应用实例,计算了某一截面火焰温度场的分布,并与热电偶测量的值进行了比较.     

CW激光辐照薄板热力响应全场测量

实验研究了CW激光辐照铝合金薄板的热力响应过程,利用三维数字图像相关技术（3D-DIC）结合红外测温系统对整个过程的变形场和温度场实现了全场实时测量。分析了入射激光功率对变形场和温度场的影响,发现变形和温度均随入射激光功率线性增长。建立了三维有限元模型对实验过程进行模拟,模拟结果与实验结果吻合较好,验证了有限元模型的可靠性。3D-DIC结合红外测温系统可以很好地对激光破坏试验中的靶体变形场和温度场进行实时测量,是一种很有效的实验测量手段。     

Recognition of a light line pattern by Hu moments for 3-D reconstruction of a rotated object

A simple technique of a light line projection for 3-D shape detection of rotated objects is presented. In this technique, an object is rotated around its symmetrical axis four times at an angle by using an electromechanical device and scanned by a light line. Four views of the object surface are extracted from each one of these rotations by processing a set of light line images. These views are connected using rotation angle and origin coordinates to obtain the complete 3-D shape. Angle and origin are calculated by recognition of a light line pattern. Light line pattern is recognized by Hu moments. In this manner, measurement errors on setup are avoided. It is an advantage over common methods, where these two parameters are measured directly on the setup to obtain the 3-D shape. Local profilometric method is based on the perturbation that the light line suffers when it is projected on the object surface. This perturbation is observed on an image plane due to the different direction between light line projector and viewer. These perturbations are measured by using Gaussian functions. In this technique the light line images are processed in very fast form. The technique and processing time are presented in detail. This technique is tested with objects, which have little information and its experimental results are also presented.