变线距全息光栅的在线检测

变线距平面光栅单色仪具有自动聚焦、消慧差、分辨率高以及装置简单等特点,在同步辐射装置、激光核聚变装置上有着广阔的应用前景。变线距平面光栅的全息制作越来越受到人们的关注,但变线距光栅的全息制作必需有高精度的密度检测技术,尤其是需要在线检测技术相配合。文中应用干涉云纹法和条纹图像处理技术,对全息光栅制作过程中的光栅线密度进行了在线检测,并给出了检测原理。讨论了变线距光栅线密度的表述,推导出了检测变线距光栅线密度的相关公式,介绍了变线距光栅线密度的在线检测原理以及干涉条纹图的处理方法。     

全息干涉条纹图的计算机自动处理与识别

本文应用数字图象处理与识别技术在IBM-PC/AT微处理计算机图象处理系统上对复杂的全息干涉条纹图进行了自动分析,文中采用二维灰度值检测的方法获取条纹的准峰或谷值二值图形,然后通过细化得到条纹中心,提出了用记忆跟踪算法自动去除毛刺和噪声线段.在用光标进行人机对话标定零级条纹后,可自动识别出其它整数条纹级数.分数级条纹级数可在整数级条纹数据之间进行线性或非线性插值得到.最后给出了全息条纹图分析的实例.     

高灵敏度,高温全息云纹光栅及其应用

本文简要介绍了高灵敏度，高温全息云纹光栅技术，主要包括旋转点光源激光全息干涉制栅系统，折射率介质超高频光栅制作技术，双镀层抗高温氧化制栅技术，耐高温光刻胶模板及转移技术，现场变形栅转移技术。在此基础上还给出了高灵敏度，高温全息云纹光栅的几个典型应用实例     

热毛细对流温度场全息干涉检测研究

本文采用Ｈｅｌｅ－Ｓｈａｗ盒体,在地面上模拟二维热毛细对流,应用全息干涉技术对热毛细对流温度场进行了测试研究,为了获得感兴趣的热毛细对流温度增量分布,文中提出了将背景温度分布条纹与热毛细对流温度增量分布条纹相分离的方法。     

超声速射流装置的流场特性研究

超声速射流装置能很好地模拟榴弹引信发电机飞行时大气环境的工况,已成为地面考核和验收必不可少的设备。本文结合双曝光全息干涉技术和数值模拟方法,对超声速射流装置有无模型的流场进行了研究,将实验干涉图与数值模拟结果进行了比较,从而辨识出实验干涉图中的条纹级数并计算了条纹位移量,由此得出实验干涉图的密度场,经适当的修正就可应用到实物飞行中,解决了过去引信电机选取当地参考密度难的问题。另外由实验结果也验证了数值模拟结果的可靠性。     

文献摘要

量测挠度的全息干涉图的数字化Gilbert,J.A.,Dudderar,T.D.,Mattys,DR.,Chern.J.H.,Digitization of HolograpicInterferograms for Deflection Measurement.Procedings of The SEM Spring Conferenceon Experimental Mechanios.294—301.本文讨论自动采集和分析全息干涉数据所需的载波条纹技术的基本原理.一个监视二维实时立即处理图片的实用方法.收集载波条纹的背景强度以及变形/载波条纹图,一个高分辨率的电视摄象机/电子组件使得所得的二维光强分布数字化和一个用来快速数据换算和整理的计算机.该系统明     

贴片云纹干涉法

将全息胶片粘贴到测试表面,利用全息干涉两次曝光法,获得高灵敏度二维云纹;曲于实现了制栅和测试过程的合一,胶片与试件分离后处理,本方法具有简易、省时、灵活,试验费用低,适用面广,可用于现场在位测试等优点。     

双参考光全息—散斑干涉术的原理和实验

本文用统计光学方法对双参考光全息——散斑干涉术进行了详尽的理论分析,给出了全息和散斑干涉场区域平均光强分布与光学系统主要参数及三维变形场各分量之间关系的解析表达式,进而讨论了离面位移和面内位移测量的上、下限,最后还给出了有关的实验结果。     

一种高灵敏度形状检测新技术

应用光的干涉和衍射理论，系统地阐述了一种高灵敏度形状检测技术的基本原理，并提出了一个新的测试方法，可以消除坐标影响项，从而得到纯等高线条纹图。文中应用该技术，实际测量了带有几种压痕的平板表面的深度分布，分析了测量灵敏度和精度，给出了部分实验结果。     

激光全息干涉法测三维位移的误差分析

激光全息干涉法测三维位移,通常采用多张全息图法和单张全息图法。本文推导了这两种方法的测量误差计算公式。并应用这些公式对全息条纹三维读数仪作了较为详尽的误差分析。     

试件栅刻蚀技术研究

本文研究和实现了在试件表面直接涂布光刻胶制得振幅型低频栅和位相型高频全息栅的基础上，分别利用湿法化学腐蚀和反应离子刻蚀技术蚀刻试件栅的工艺。在几种不同材料的试件表面刻蚀出了试件栅，这种技术的实现使云纹干涉法和精细网格法在高温高压环境下的广泛应用成为可能。     

Dual hologram shearing interference technique for wind tunnel flow fields testing

 A novel optical diagnostic technique, dual hologram shearing interferometry, for measuring density gradients of different phase objects is proposed and demonstrated. The lateral shearing is achieved by using a phase grating. A holographic interferometer has been developed and designed on the base of a single pass Z type conventional schlieren device. The interferometer’s scheme is insensitive to acoustical disturbances, similarly to the conventional schlieren layout, and is capable of recording holograms with a continuous wave laser during the wind tunnel run. The features of the technique make it tolerant to both the temporal coherence of the laser light source and to the relatively low, schlieren quality optical windows of the wind tunnel’s test section. The obtained reconstructed lateral shearing interferograms with a large region of overlap have high contrast and may have an arbitrary orientation and/or spacing of the background interference fringes. It is believed that the proposed approach will become a useful tool for visualization and accurate mapping of the density gradients of gas dynamic flow fields, in wind and shock tunnels, where acoustic noise problems may dramatically affect reference beam holographic schemes. Received: 9 January 1997 / Accepted: 12 April 1997     

Full-field surface-strain and displacement analysis of three-dimensional objects by speckle interferometry

A method of full-field measurement of displacements as well as strain on arbitrarily curved surfaces is introduced. The speckle effect of coherent light is utilized to produce fringes due to displacements. Unlike the fringes produced by holographic interferometry, these fringes have a unique interpretation in relating to displacements and they localize on the surface. Three measurements are required to determine the three components of displacement; and, knowing the geometry of the object, its surface strains can be deduced. Three ways of recording displacement fringes, namely, real time, double exposure and superposition, are described.     

The moiré method of zonal and line gratings

The theory of moiré fringes produced by zonal gratings interfering with line gratings of equal or slightly different pitch was developed. Differential equations relating the pitches of the two gratings to the interfringe spacing of the moiré pattern produced were established. It was shown that the moiré fringes produced belong to families of confocal ellipses, parabolas or hyperbolas in the cases where the zonal-grating pitch (p _m ) is greater than, equal to, or smaller than the line reference-grating pitch (p _r ). These patterns yielded all the displacement components of a two-dimensional strain field. Therefore, they are sufficient for the complete determination of the strain and stress distribution in any elastic or plastic plane-stress problem. As an illustration, the method has been applied to the determination of the lateral-contraction-ratio function of a polymeric substance (cold-setting pure epoxy resin) in creep at various steps of temperature.     

Application of refractive medium in optical micromechanics

The refractive medium is used in moire interferometry and holographic grating fabrication technique. The sensitivity of traditional interferometry and the frequency of grating are enhanced effectively. These two novel techniques extend the application scope of the moire interferometry and facilitate the realization of superlattice method in micromechanics study. The project supported by the National Natural Science Foundation of China     

Holographic sensor for measurement of wall velocity gradients

Time-resolved measurements of skin friction and boundary layer turbulence are important to the design of more fuel efficient aircraft. In this paper we describe the design and testing of a holographic fan fringe sensor that can non-intrusively measure time-resolved velocity gradients near an aerodynamic surface. The holographic sensor produces a set of optical interference fringes inside the viscous sub-layer that form a fan rather than a linear array. Particles scattering light in the sub-layer produce a Doppler frequency that is a direct measurement of the velocity gradient and is proportional to aerodynamic shear stress and skin friction. The holographic recording condenses the optics necessary to form the fringes into a small 3–5 mm package, eliminates the need for optical access from behind the model, and produces a compact and robust sensor.     

Grating holographic interferometry

A holographic interferometric technique, combining an image hologram with a grating approach, is proposed for three-dimensional deformation measurements on opaque planar object surfaces. In this technique, the holographic plate is brought close to the object surface, onto which a high-frequency crossed-line diffraction grating has been replicated. The grating surface produces multiple object waves rather than the usual diffusely reflected object waves. The double-exposed single holograms can be reconstructed at multiple off-axis angles. Four independent high-contrast fringe patterns are extracted simultaneously. Displacement vectors over the entire measurement area are separated in three orthogonal directions. The resultant displacements are presented as three-dimensional meshed plots and topographic contour maps. The optical system for both recording and reconstruction of the holograms has been simplified compared to conventional holographic interferometry. Experimental errors associated with fringe readout and system geometry are reduced because of the sharp images and the well-defined spatial orientation in the reconstruction system.     

Scanning moiré at high magnification using optical methods

Methods of employing scanning moiré at high magnification are developed and demonstrated. Modern lithographic techniques for producing custom moiré gratings with a frequency up to 250l/mm are described. On a probing station equipped with a video system, pseudo-color moiré fringes are produced using the scannning lines of the color charge-coupled-device (CCD) camera. Fringe multiplication from 1 to 5 is possible with correct combinations of magnification and grating pitch. An analysis is given to show that strain sensitivity depends only on the number of scanning lines used to record the image. The grating pitch and the magnification are important because they reduce the gage length of the strain measurement. The high-magnification scanning moiré was used to study plastic- strain fields in an aluminum tensile specimen. Local disturbances in the strain field were observed at 2 to 2.5 percent applied strain. These discontinuities became more significant at higher levels of applied strain.     

Differential interferometry with adjustable spatial carrier fringes for turbine blade cascade flow investigations

 Digital evaluated differential interferometry using adjustable spatial carrier fringes was applied to flow measurements in a transonic turbine blade cascade. The interferograms were evaluated using a two-dimensional Fourier Analysis. This evaluation provided density gradient maps of the flow field in a digital form. A specially designed interferometer was used allowing adjustment of sensitivity and superposition of carrier-fringe system separately. This type of interferometer is also highly insensitive to vibration noise. For a turbine blade cooling film a comparison of this type of differential interferometry with holographic interferometry and a Schlieren visualisation is also given. As a result differential interferometry using adjustable spatial carrier fringes and digital fringe analysis gave density-gradient maps similar to Schlieren recordings but of quantitative nature, thus enabling compensation of wave front distortions. Integration of these density gradient maps resulted in density maps which were then compared to recordings done with pulsed holographic interferometry. Received: 27 December 1996/Accepted: 30 April 1997