Electronic speckle pattern interferometry based on spatial information using only two sheets of speckle patterns

Abstract

Speckle interferometry is an important deformation measurement method for an object with a rough surface. In this paper, a novel fringe analysis method is proposed that uses a new optical system, which uses a plane wave as the reference beam of the speckle interferometer. When the optical system is employed in fringe analysis, the deformation information and the bias components of the speckle patterns are clearly separated in the frequency domain. Therefore, the deformation information can be readily extracted using a Fourier transform, which gives a pair of real and imaginary components concerning the information. The specklegram is calculated using such a pair of components, and the phase map is obtained from the specklegram. Experimental results confirmed that the resolution power of this measurement method is higher than 1/261 of the wavelength of the light source of the optical system.     

Fringe analysis method for electronic speckle pattern interferometry using only speckle patterns before and after deformation

Electronic speckle pattern interferometry is employed in many industrial fields as a useful deformation measurement method. However, two speckle patterns obtained before and after the deformation are necessary for measurement. Furthermore, at least three speckle patterns are required for high resolution measurement using ordinary fringe scanning technologies. In this paper, a novel method that can measure high speed deformations using a limited number of speckle patterns without using high speed cameras is proposed. The method enables application to dynamic deformation analysis because the method involves analysis using only two speckle patterns obtained before and after the deformation. A novel optical system that can record some spatial information into each speckle is set up for the method. In experimental results, it is confirmed that the out-of-plane deformation measurement can be precisely performed by the method and that the resolution power is almost equivalent to that of the ordinary method.     

白光频闪散斑干涉术的研究

在利用白光对振动物体进行测量时,由于白光的相干性较差,难以得到质量较好的图像,为了克服这一缺点,本文提出了一种用白光光源照明进行振动测量的新方法-白光频闪散斑干涉术.阐述了白光频闪散斑干涉术的基本原理,分析了提高图象质量的主要原因,采用了相干性较好的白光光源和合理的光路,使系统的时间相干性和空间相干性得到提高,从而提高了图像的质量.实验结果表明,该方法用于振动的测量,能给出物体在任一瞬时的振动信息,得到清晰的、高对比度的全场干涉条纹图,图像的质量得到大大提高.     

Surface shape measurement of mirrors in the form of rotation figures by using point diffraction interferometer

The paper deals with the use of a point diffraction interferometer (PDI) to study the surface shape of rotation figures. The relations are given for the correspondence of the coordinates on the surfaces of an ellipsoid, a paraboloid and a hyperboloid as well as on an interferogram. Using PDI and Zygo white-light interferometer (WLI), we experimentally investigated the surface shape of the grazing incidence ellipsoid with the multilayer reflective coating on a wavelength of 0.154 nm with the following parameters: length is 55 mm, half-axis are 6 and 235 mm. The results coincided with an accuracy of 73 nm (RMS) without taking into account the PDI lateral resolution, and with an accuracy of 50 nm (RMS) with taking it into account, which ensures the local angles measurement accuracy of the ellipsoid-shaped reflecting surface at a level of 3 μrad. We think that this difference may be attributed to the limited lateral resolution of PDI and errors of frames stitching of WLI; nevertheless, we do believe that the PDI measurement accuracy is in the range of sub-μrad.     

Consideration of existence of phase information of object shape in zeroth-order diffraction beam using electromagnetic simulation with aperture in front of objective

ABSTRACT

It has been reported that the shape of a measured object can be determined by detecting the change in phase distribution generated by a lateral shift of the object using speckle interferometry. In speckle interferometry technique, it was also reported that the shape of the object beyond the diffraction limit can be measured. In this study, the principle of this method is discussed through experiments and electromagnetic analysis. Accordingly, the results of the experiments and electromagnetic analysis of phase change only under zeroth-order diffraction light through the lateral shift of the object are investigated by shutting out the higher harmonic diffraction lights using an aperture in front of the lens. The results indicate that even if the image of the object cannot be focused upon, three-dimensional shape measurement can be performed by analysing only the zeroth-order diffraction light from the object.     

Analysis of loaded mandible behaviour using speckle pattern interferometry

Orthognatic surgeons have a requirement for the measurement of stress distribution within the human lower jaw, in order to aid and improve surgical procedures. Validation of finite element modelling data describing mandible behaviour which has previously been attempted using holographic interferometry. Electronic speckle pattern interferometry (ESPI), a whole field non-contact optical technique has been applied to the study of a dry human mandible under load. This technique improves over previous methods by generating discrete quantitative displacement and strain components. The optical analysis of a dry mandible is described, with the results viewed in 'real time' as progressively greater forces were applied on the lower border of the chin, in the upwards (impact) direction with biting boundary conditions included in the experimental model. This has shown that the bone tissue holding the front teeth transmits the forces impacting on the chin, which are absorbed by the basal bone of the mandible.     

High resolution speckle interferometry using virtual speckle pattern produced by information of deformation process

A high resolution new fringe analysis method for ESPI with only one camera is proposed by using features of speckle interferometry in a deformation process of a measured object. The profile of intensity of each speckle of the speckle patterns in the deformation process is analyzed by the Hilbert transform. A virtual speckle pattern for creating a carrier fringe image is produced artificially by using the information of profiles of intensities of speckles. The deformation map of the measured object can be detected by the virtual speckle pattern in an operation based on the spatial fringe analysis method. Experimental results show that the difference between the results by the new and the ordinary methods is 0.1 rad as standard deviation. From the results, it is confirmed that the high resolution measurement can be performed by this method the same as compared to the ordinary measurement method which needs to employ three speckle patterns.     

基于数字散斑的大型机翼弹性形变测量技术

飞机机翼在飞行过程中受气动力影响会发生弹性形变,导致机翼外载荷大小与分布变化,危及飞行安全.该文针对民用飞机在飞行过程中机翼弹性形变测量的需求,分析大型飞机的结构负荷,采用多组摄像机组合标定、机载摄像机位姿修正、大倾角散斑图像解算等视觉测量技术,开展多摄像机组合的大翼展数字散斑形变测量方法研究,设计适用于C919飞机飞...     

Absolute measurement of the generated aberrations from liquid crystal spatial light modulator using a common-path interferometry

A compact common-path interferometry is proposed to measure the wavefront aberration generated from liquid crystal spatial light modulator (LC-SLM). The LC-SLM is encoded with an aberration pattern and illuminated with a linearly polarized light oriented at ±45° with respect to the fast axis of liquid crystal, which is vertically oriented. The horizontal polarization component of the incident beam is not affected by the driving signal, while the vertical polarization component is modulated to the aberration loaded to the LC-SLM. By imposing a quarter-wave plate and a rotating analyzer, these two waves create four frames of phase-stepped interferograms. The aberration to be measured can be retrieved, and the result does not include any systematic error such as the substrate error of LC-SLM. Therefore, this method can implement absolute measurement, and help us to evaluate perfectly the fitting accuracy of the LC-SLM.     

数字散斑相关方法在木材科学中的应用及展望

随着现代光电子和计算机技术的发展以及数字图像处理理论的深入，数字散斑相关方法（DSCM）迅速成为实验力学领域一种重要的测试方法。文章介绍了DSCM的基本原理，并对其在木材科学领域的应用进行了综述，包括在木材常规力学测试和木材断裂、微观力学以及复合材料力学测试等方面的应用及一些新的成果。最后根据木材材料的特点, 对DSCM在木材科学上的进一步应用提出了几点建议。     

不透明薄膜厚度的光干涉法测量以及台阶的影响

提出使用数字CCD拍摄光干涉条纹,使用图像处理软件进行灰度值扫描分析光干涉条纹的方法,对不透明薄膜进行光干涉法测厚.数字CCD和图像处理软件的结合使用能够最大限度的降低目测带来的误差,并且也避免了使用复杂的干涉条纹提取算法,可以方便、准确地对不透明薄膜进行光干涉法测厚.同时我们使用光干涉法和轮廓仪法对不同高度遮挡物形成的台阶进行了对比测量,分析了不同台阶边缘斜坡对于光干涉法测量结果的影响,指出在制备台阶时遮挡物的高度必须满足一定的条件,并且根据这个条件推导出在我们的磁控溅射设备中,遮挡物高度小于50 μm可以得到满足光干涉法测厚条件的台阶.     

Non-contact strain measurement using metal foil gauges with the application of the laser speckle method

This paper presents a new method to measure cyclic strain with no contact using metal foil gauges assisted by the laser speckle method. When aluminium foil is pasted on a specimen and the specimen is loaded cyclically, slip bands are produced on the foil surface. There is a fixed relation between density of the slip bands and the strain amplitude or loading cycles depending on the foil material. Thus the fatigue strain of the base metal can be estimated by observing the surface change of the metal foil by the slip bands at a constant number of loading cycles. The method presented in this paper is intended to make a non-contacting strain measurement by the application of the laser speckle technique for the detection of the surface change. This method is based on observation of the changes in a laser speckle pattern depending on the surface roughness and surface property changes of the foil caused by fatigue. The laser speckle pattern can be analysed automatically and quantitatively using an image processing system.     

纳米级正弦振动幅相特性测量技术的研究

概述外差激光干涉测量技术的基本原理和特点，针对马赫-泽德外差式激光干涉仪在绝对法振动校准技术中的应用，介绍测量系统的构架以及完成数据采集和信号处理的虚拟仪器技术。详细介绍了测量系统频移变换部分和数字信号处理部分的组成原理和技术实现，论述了其中数据采集、数字解调、曲线拟合等技术难点。本文描述的这种振动测量技术运用正弦逼近的信号处理方法，可以对线性正弦振动量进行幅值和相位的纳米级精确测量。     

A method of measuring the deviations of the shape of a shell of revolution

A method of measuring the deviations of the shape of large shells of revolution that makes it possible to control the shape of the shell on all stages of manufacturing, repair, and use is considered. The method is based on measurements of the variations of the curvature at points situated uniformly or nonuniformly along the perimeter of transverse control sections. __________ Translated from Izmeritel’naya Tekhnika, No. 3, pp. 33–35, March, 2007.     

A selective diffraction order based lens plane grating shearing interferometer for the study of bent plates

A simple, elegant and flexible technique for the determination of partial slope, curvature and twist contours of bent plates is proposed. A single frequency cross-grating (SFCG) placed just ahead of the field lens collects the light reflected by the smooth plate model. From the resultant diffraction pattern formed at the Fourier transform (FT) plane, based on the desired contours, only a few orders are permitted selectively to pass through to the recording plane. This manner of real time in-situ filtering of the diffraction orders is new. While slope contours require double exposures, curvature and twist contours are obtained from single exposures.     

Study of rectangular waveguides with grooves of irregular shape using the finite element method

Electromagnetic wave propagation through grooved waveguides is studied using the finite element method (FEM). The effect of grooves of irregular shape on TE₁₀, TE₂₀ mode frequencies and passband is studied. The variation in cutoff frequencies for TE₁₀, TE₂₀ mode and passband is observed.     

Construction of shape functions for the h- and p-versions of the FEM using tensorial product

This paper presents an uniform and unified approach to construct h- and p-shape functions for quadrilaterals, triangles, hexahedral and tetrahedral based on the tensorial product of one-dimensional Lagrange and Jacobi polynomials. The approach uses indices to denote the one-dimensional polynomials in each tensorization direction. The appropriate manipulation of the indices allows to obtain hierarchical or non-hierarchical and inter-element C⁰ continuous or non-continuous bases. For the one-dimensional elements, quadrilaterals, triangles and hexahedral, the optimal weights of the Jacobi polynomials are determined, the sparsity profiles of the local mass and stiffness matrices plotted and the condition numbers calculated. A brief discussion of the use of sum factorization and computational implementation is considered. Copyright © 2006 John Wiley & Sons, Ltd.     

微带法测试薄膜0.5～5G磁导率

提出了可以在0.5～5GHz频带扫频测量磁性薄膜复磁导率μr的微带线法,推导出了由倒置短路微带线单端口网络的反射系数R(S11)表示μr的理论公式.对微带线夹具进行了设计,并结合虚拟仪器技术,以LabVIEW为软件平台建立了一套测量薄膜微波复磁导率的自动测量系统.给出了FeCo基磁性纳米颗粒膜的磁导率测试曲线,表明微带法具有准确性较高、既适宜于面内各向异性薄膜又适合于各向同性薄膜的测量和容易操作等优点.     

Thermal deformation measurement of the solder joints in electronic packages using electron moiré method

In this paper, electron moiré method is used to measure the thermal deformation of electronic packages. In order to observe the electron moiré fringe, a holographic grid was replicated on the cross section of the BGA type package at 150°C. This grid was fabricated on a glass plate using a moving point holographic system, and was replicated to measured area at high temperature. Under SEM, the holographic grid(specimen grid) and a programmed electron beam scan(master grid) interfere and form electron moiré patterns. The shear strain measurement technique using electron moiré method is described. Using the electron moiré method, the shear strains in the different solder joints were measured and analysed. Some useful results were obtained.     

Improvement of numerical modeling in the solution of static and transient dynamic problems using finite element method based on spherical Hankel shape functions

In this paper, finite element method is reformulated using new shape functions to approximate the state variables (ie, displacement field and its derivatives) and inhomogeneous term (ie, inertia term) of Navier's differential equation. These shape functions and corresponding elements are called spherical Hankel hereafter. It is possible for these elements to satisfy the polynomial and the first and second kind of Bessel function fields simultaneously, while the classic Lagrange elements can only satisfy polynomial ones. These shape functions are so robust that with least degrees of freedom, much better results can be achieved in comparison with classic Lagrange ones. It is interesting that no Runge phenomenon exists in the interpolation of proposed shape functions when going to higher degrees of freedom, while it may occur in classic Lagrange ones. Moreover, the spherical Hankel shape functions have a significant robustness in the approximation of folded surfaces. Five numerical examples related to the usage of suggested shape functions in finite element method in solving problems are studied, and their results are compared with those obtained from classic Lagrange shape functions and analytical solutions (if available) to show the efficiency and accuracy of the present method.