Monitoring/measurement of out-of-plane vibrations using shearing interferometry and interferometric grating

In this paper, an application of shear plate interferometry combined with moiré readout to monitor/measure out-of-plane vibrations is presented. Moiré fringes are produced between the fringe pattern from the shear plate and interferometric grating recorded by photographing the interference pattern generated from the shear plate. It is demonstrated that the method can be used to study periodic and non-periodic vibrations.     

Application of digital phase-shift shadow Moiré to micro deformation measurements of curved surfaces

The shortcomings of conventional shadow Moiré topography have in the past been improved by means of the phase-shift method which enhances the sensitivity and allows to process the fringe patterns automatically. This paper presents a digital implementation of the phase-shifting process, which requires only one image to be taken. The grating lines, projected onto the deformed object surface, are captured directly with a digital camera. Next the reference grating is superimposed numerically onto the projected grating lines. Then a number of phase-shifts are performed taking into account the non-linearities in the expression for the height-dependent intensity field. Experimental results prove that these non-linearities can considerably affect the micro deformation measurements of curved surfaces. The proposed method is very efficient and eliminates all causes of erroneous measurements due to the miscalibration of phase-stepping devices.     

Electron moiré method and its application to micro-deformation measurement

In this paper, the single and two deposited metal layers method were proposed to produce the model grating for electron moiré method. The measurement principle of electron moiré method and the techniques for manufacturing model grid are expounded in detail. The accuracy of measuring strain using this method is discussed. The gratings with single deposited layer and two deposited layers with high frequency up to 5000 lines/mm were produced on different substrates. From the experimental results, both single deposited metal layer and two deposited metal layers gratings showed their heat resistance ability. Using the gratings produced and a replicated model grid, the electron moiré method was applied to measure the deformation of the strain around holes in a polyimide resin substrate, thermal strain of electronic packaging component and tensile creep around grain boundary in a pure copper specimen.     

Phase shifting nano-moiré method with scanning tunneling microscope

In this paper, a new nano-moiré method using scanning tunneling microscope (STM) is proposed. This method is capable of measuring nanoscopic deformation of matter. The formation mechanism of the STM moiré fringe and the phase shifting technique used in STM moiré fringes are explained in details. Typical experiments are conducted with the crystal lattices of freshly cleaved highly oriented pyrolytic graphite, are used as specimen grating, to generate STM moiré fringe patterns. Phase shifting is realized in four steps from 0 to 2π by controlling the PZT in the STM system to shift the specimen in the vertical direction. This method provides a new way for disposal of moiré fringes pattern in the nano-moiré measurement.     

Contribution to analysis of the reflection grating method

The reflection grating method is a special case of the well-known reflection moiré principle. Whereas this moiré effect is suitable for measurement of the slope and curvature of deformed object surfaces by superposition of at least two grating images, the same results can be determined using only one reflected grating image without moiré lines.Some fundamental relationships between grating lines, optical setup and the desired deformation are developed and compared with the simplifications that are known from the moiré principle. The theory is tested using a circular plate, uniformly loaded and clamped at the circumference.     

Optical alignment using Fourier imaging phenomenon and Moire technique

Optical alignment operations and Fourier imaging phenomena have the common property that both occur in space along a straight line. The self-imaging property of a circular grating is applied to centring-error detection and to alignment in space. Moiré fringes due to the interaction of Fourier (or Fresnel) images with a detecting grating provide an indicator of the alignment state. The merit of this approach is that it is easy and comfortable to make visual observations. Various applications of the method depending on the choice of the reference points used are discussed and some experimental data are presented.     

扫描离子束云纹法

提出了一种在微米尺度下测量物体面内位移的新型扫描离子束云纹法。对该方法的测量原理以及变形测量的精度进行了阐述。以平行云纹和转角云纹为典型实验对该方法的测量精度进行了检验。该方法成功地应用于微电子系统结构在去除SiO2牺牲层后的残余变形测量。实验结果证实了该方法的可行性。     

Realization of high sensitivity displacement field from moiré interferometer with rough phase shifting mechanism and pattern matching technique

In this study, phase shifting method is used to modify moiré system into micro moiré interferometer which can measure displacement field with highly improved sensitivity. Apart from existing micro moiré technique, a low cost and less precise translation stage with rough resolution (10 μm resolution) is adapted for the phase shifter. Least square algorithm is applied to estimate the arbitrary phase shifted amount and to minimize the errors induced by lowering the cost. Moreover, specimen grating is phase shifted instead of reference grating which enables simple construction from given moiré system. To compensate for rigid body in-plane translation of specimen that may occur during phase shifting, pattern matching algorithm is put into practice to ensure pixel correspondence for each phase shifted images. To verify the newly constructed micro moiré technique, local displacement fields of Fine pitch Ball Grid Array package and Wafer Level Chip Size Package with elevated sensitivity up to 26 nm per fringe was acquired.     

Phase shifting SEM moiré method

A new phase shifting scanning electron microscope (SEM) moiré method is proposed in this paper. The phase shifting technique is realized in four steps from 0 to 2π by shifting electron beam in the y-axis direction controlled by the SEM system. It is successfully applied to determine the residual strain of a deformed holographic grating with a frequency of 1200 lines/mm in an electronic package. As a further application, it is used to measure the virtual strain of a MEMS structure with a 5000-line/mm grating and to determine the phase distribution of a SEM moiré formed with a 6000-line/mm grating fabricated by electron beam lithography. The experiments show the feasibility of this method. It provides a new way for disposal of fringes pattern in sub-micro moiré method.     

Large-deformation analysis in microscopic area using micro-moiré methods with a focused ion beam milling grating

In this study, the focused ion beam (FIB) milling method is applied to fabricate sub-micron grating on TiNi shape memory alloy materials. With self-made FIB milling gratings, scanning electron microscope (SEM) micro-moiré and digital moiré methods are successfully used to measure large deformation of porous TiNi shape memory alloys (SMA) in uni-axial compressive tests. The principles of the SEM micro-moiré method and digital moiré method are introduced, and applied to calculate large strain. The full field deformation around shear bands can be measured precisely. During the investigation, the phenomenon of furcated moiré fringes was found, and a corresponding explanation is given in this paper. The furcated fringes are generated in the locations of combined shear bands where sudden changes of strain occur. Successful results also verify that the FIB milling gratings are suitable for micro-moiré measurement and can generate high quality moiré fringes.     

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.     

Defects analysis of Al/Si artificial nanocluster with moiré fringes

In this paper, it is demonstrated the defects play a very important role in determining the quality of artificial nanoclusters grown. The surface strain (stress) distribution around defects in Al artificial nanocluster is analyzed by Moiré fringes pattern. The moiré fringes generated by scanning lines in monitor and nanocluster array can be used as a “magnifier” to study surface imperfections with scanning tunneling microscopy (STM). As moiré fringes’ exist in many ordered nanostructures and adsorbate systems, the method is expected to have wide applications.     

Analysis of moiré fringes for measuring the focal length of lenses

We describe a technique based on fast Fourier transform and least-squares fit for automated analysis of moiré fringe patterns for accurately measuring the focal length of lenses. An interference fringe pattern is produced by a reflective diffraction grating interferometer and illuminates the test lens. Moiré fringes are generated by digitally superimposing the magnified fringe pattern imaged by the lens on the interference fringe pattern without the test lens. We analyze two common ways to generate the digital moiré effect: multiplication and subtraction with successive rectification of the two digitally stored intensity distributions, and we show that in the latter case by means of the described technique it is possible to determine the moiré spatial frequency by a simple and fully automated procedure.     

Shadow Moiré method for the determination of the source position in three-dimensional shearography

Shearography is a full-field non-contact optical technique used for characterisation of surface strain. In a multi-component system, the displacement derivative components are measured using a number of illumination positions. These components are then transformed into a three-dimensional coordinate system, using a knowledge of the source positions. This process is highly sensitive to errors in the knowledge of the source position. Shadow Moiré, with either linear or circular gratings, can be used to measure angle of illumination, with the measurement sensitivity and accuracy variable by changing the grating pitch. Circular gratings have a measurement range determined by multiple fringe analysis and linear gratings have a different measurement range determined by sub-fringe analysis. In this paper vertical linear, horizontal linear and circular gratings are combined to extend the measurement range and the accuracy of the measurement of the source position in two directions. Using this method the source position was measured to an accuracy of ±3%.     

On the visualization of heterogeneous plastic strains by Moiré interferometry

Moiré interferometry is a valuable tool for investigations of the mechanics of materials. It is characterized by high-sensitivity and full-field capability. In this paper, the applicability of moiré interferometry and microscopic magnification to the visualization of the heterogeneous nature of the plastic strains in a polycrystalline material is considered. Plastic deformation of a coarse-grained aluminum is considered in detail.     

Whole-field analysis of uniaxial tensile tests by Moiré interferometry

Moiré interferometry—a high sensitivity whole-field optical technique—was used to follow the evolution of the deformation process of an aluminium sample subjected to a uniaxial tensile test. This technique allowed us to measure the two in-plane displacement components undergone by the sample, to evaluate the strain, stress and rotation fields, and to appreciate the trends in the deformation pattern that characterized the different stages of the test. Through a subtraction process between fields obtained at two different load levels, we were able to identify the area where strains began to localize and to observe the appearance of the diffuse neck.     

Moiré fringes in metrology

Moiré fringe phenomena have been exploited in a wide range of transducers, particularly in the field of engineering metrology. Paying particular attention to developments which have taken place during the last 15 years, the paper presents a cross-section of moiré techniques for the measurement of displacement, surface topography, deformation, vibration and refractive index gradient.     

The phase shift method applied to cross grating moiré measurements

The automatic evaluation of the grating deformation in a moiré image is greatly enhanced by the phase shift method. Based on three or more local grey values of a related number of phase shifted moiré patterns, the local displacement of a deformed grating against a reference grating, and hence the total displacement in one direction, is calculated. In this paper an extension to cross gratings is presented yielding a two- dimensional displacement field.     

Moiré gauging by projected interference fringes

The formation of Moiré patterns by doubly exposed photographs of projected interference fringes is analysed in detail. The possible applications of these patterns for the measurement of surface deformation and vibration, phase object visualization and height contouring are examined theoretically and experimentally.The described methods are closely related to holographic techniques, but they are usually simpler and applicable in unfavourable environments.     

纳米云纹法条纹倍增技术研究

提出了一种纳米云纹法的条纹倍增技术，可用于单晶材料纳米级变形测量.在测量中，单晶材料的晶格结构由透射电镜（TEM）采集并记录在感光胶片上作为试件栅，几何光栅作为参考栅.对纳米云纹条纹的形成原理，透射电镜放大倍数与试件栅的频率关系，条纹倍增技术，位移、应变测量方法等进行了详细讨论.该方法不仅能够测量连续力学参量，如应变和位移，而且能够表征纳观非连续参量，如位错、夹杂.