炮体表面瞬态温度分布的散斑干涉测试研究

为了可以实现对炮体表面瞬态温度分布变化的实时监测,同时克服传统瞬态高温测试仪器单点探测以及热惯性大等局限性,设计了基于散斑干涉与光谱频域分析相结合的瞬态温度分布测试系统。系统采用散斑干涉技术将炮体瞬态温度变化引发的微小形变转换成散斑干涉条纹,再由傅氏变换完成干涉条纹形变到光谱分布的函数转换,从而通过光谱分布函数反演任意采样时刻上的温度分布。实验采用ZX-FB1型光纤测温仪测试单点位置上瞬态温度作为标准值,再由555 nm激光器与面阵CCD采集散斑干涉条纹,分别使用图像识别法与傅氏变换法完成干涉条纹与瞬态温度的算法匹配,从而反演瞬态温度。实验结果显示,两种方法均能实现瞬态温度检测,但基于傅氏变换频谱分析的散斑干涉法精度更高,并且可以有效地克服由表面瑕疵、漆面磨损等问题造成的粗大误差。     

剪切散斑干涉术的无损检测研究

剪切散斑干涉术用于复合材料的光学无损检测具有较宽的加载范围,便于实现缺陷的全场记录,防止漏检。本文从理论上推导了剪切散斑干涉条纹(等应变条纹)的强度分布,并证明随着加载量的增大,条纹变密的程度较全息干涉条纹(等位移条纹)缓慢。加之,剪切散斑干涉条纹灵敏度具有可调性,加载范围大为加宽。实验观察与理论分析一致。     

数字散斑干涉术物体形变测量

基于数字散斑干涉术测量物体形变的原理,研究了物体面内位移及变形的测试技术.采用电荷耦合器件记录变形前后的两幅散斑图,取代传统散斑干涉术中的记录干板,省去传统方法中干板显影、定影的繁琐的化学湿处理过程.分别用菲涅尔散斑和像面散斑方法获得散斑干涉图,用相减技术得到含有物体形变信息的散斑干涉条纹.设计高斯低通滤波器,对干涉条纹进行处理,提高了干涉条纹的对比度.提出扫描条纹中心行方法,由条纹中心行一维位相分布获得一维物面变形,实现了散斑干涉条纹的自动判读.试验表明,该方法简洁且实用.     

基于莫尔干涉的激光中心波长精确检测的研究

为了提高激光中心波长检测的精确度,提出了基于正交干涉原理的静态干涉系统,由两个相互垂直的棱镜组成产生二维平面上的光程差分布,以面阵CCD取代线阵CCD,对平面上的正交干涉条纹数据进行采集.在计算分析莫尔干涉仪的光程差分布的基础上,计算干涉图像中干涉条纹的拼接及傅氏变换等,最终得到光谱分辨率.由MATLAB仿真软件分析结果可知,静态莫尔干涉系统可以产生的光程差最大为234μm,比等尺寸的傅里叶干涉体高约一个数量级.实验标定用的光谱仪选用LAB SPAKR 750A型光谱仪,针对中心波长为635 nm的半导体激光器进行测量,结果显示中心波长位置基本一致,但在中心波长附近的光谱细节上莫尔干涉优于传统干涉具.     

基于傅里叶变换的激光数字散斑测量平板玻璃的楔角

采用基于傅里叶变换的激光数字散斑测量了平板玻璃的微小楔角.通过在光路中借助毛玻璃的散射特性,采用高分辨率CCD直接记录激光散斑图像,对散斑图像进行快速傅里叶变换获得散斑结构的高信噪比的杨氏双缝干涉条纹,分析干涉条纹获得光强分布曲线,采用移动平均法消除光强曲线噪声后计算出干涉条纹间距,从而计算出平板玻璃的微小楔角.     

基于干涉条纹图像对比法测量微位移

研究了基于迈克尔逊干涉条纹对比法测量微位移的实验。用He-Ne激光器、反射镜和分束镜组成的干涉光路,其中一个反射镜固定在被测物体上,通过被测物体的移动带动反射镜移动使干涉光路发生变化,从而导致干涉条纹的改变。在形成干涉条纹的位置利用线阵CCD采集干涉条纹图像,用序列图像对比的方法对图像进行处理和计算,得出被测物体的微位移。实验表明利用序列图像对比的方法测量微位移,方法切实可行、测量准确度高、测量的精度能够达到微米量级。     

双波长剪切散斑干涉法在复合材料缺陷检测中的应用

为使剪切散斑干涉能适用于物体大变形的测量,选用双波长激光照射和彩色相机,用傅里叶变换法对干涉图进行频谱分离,用红色波长相位减去绿色波长相位,得到合成波长相位,经频域滤波和相位解包裹,得到连续相位.理论计算表明合成波长相位条纹数是单波长相位条纹数的0.189倍.合成波长参与计算可以有效减小相位条纹密度,解决剪切散斑干涉在物体离面位移测量中由于变形条纹过于密集而导致欠采样的问题,同时降低对干涉条纹滤波和相位解包裹难度,增强图像处理可靠度,提高了测量准确度.给出了合成波长与单波长相位幅度的比较以及相同外力下二者相位条纹密度的对比,实验验证了所提方法的有效性、准确性和可靠性,实现了剪切散斑干涉对复合材料大变形的测量,扩展了剪切散斑干涉工程应用的范围,为新型剪切散斑干涉测量系统的设计提供了参考.     

基于物体像的干涉条纹图像中散斑噪声的识别方法

散斑噪声是激光干涉时的普遍现象,其覆盖被测表面对应区域的形状信息,造成测量误差。针对斜入式激光干涉测量中散斑噪声的特点,提出一种基于物体像的散斑噪声的识别方法。该方法通过统计物体像中有效测量区域和背景区域内灰度分布的特点,自动计算出判定散斑噪声的上下阈值。基于物体像与干涉条纹图像间微米级的映射关系,得到干涉条纹图像中散斑噪声的位置。设计了相关实验,对干涉条纹图像中识别出的散斑噪声区域进行修补,消除了包裹相位图中一个条纹周期内相邻像素点间大于π的相位突变。     

非接触散斑干涉法测量高温物体应变的研究

描述了散斑干涉高温物体应变测试实验装置工作原理及其实验结果，对钨和石墨的测量表明，该装置可实现高温状态下材料应变测试，测试精度达１μｍ，选择波长６３２．８ｎｍ，半宽２．４ｎｍ的窄带滤光片，配之预处理电路，对６３２．８ｎｍ辐射散射能力较强的材料（诸如钨带等）可实现２３００℃高温非接触应变测量，对６３２．８ｎｍ辐射散射能力较好的材料（诸如石墨等）可实现１５００℃高温接触应变测量。     

基于非扫描式干涉仪的光谱探测研究

探测视场的大小是激光预警性能好坏的一个重要指标。在采用非扫描式傅里叶变换干涉仪探测激光光谱的实验基础上,计算了在60°视场范围内激光以任意角度入射时关于入射角度与相干位置的光程差函数,推导了干涉条纹间距与入射角度及波长的方程组,提出了采用两个干涉仪在垂直角度下运算求解的方法。经仿真计算可知,随入射角度的变化而造成干涉条纹变密、亮带变细和波长偏移等结果。实验证明,干涉条纹计算和仿真结果与实验相符,在较宽的视场范围内可以有效探测激光光谱信息,求解激光入射方向的最高精度可达1°。     

Quantitative vibration amplitude measurement with time-averaged digital speckle pattern interferometry

A new method of using time-averaged digital speckle pattern interferometry for the quantitative measurement of vibration amplitude was developed. Signal processing techniques especially the Hilbert transformation for quantitative evaluation of the Bessel fringes obtained in time-averaged digital speckle pattern interferometry were explored. The quadrature signal after Hilbert transformation is equivalent to a 90° phase-shifted interferogram for a monotonically increasing or decreasing phase function. An algorithm was developed for Bessel fringe contrast enhancement and phase extraction. The techniques were tested numerically and experimentally. Sub-fringe quantification of the time-averaged vibration fringes is realised with the proposed method. Compared with the commonly used phase shift method which requires a minimum of two images for image processing, this method requires only one fringe pattern for data extraction.     

Measurement of dynamic crack tip displacement field by speckle photography and interferometry

Speckle interferometry has been used to measure the transient displacement field around a crack due to stress wave loading. Double exposure interferograms are recorded with a pulsed ruby laser, and correlation fringes formed by spatial filtering of the developed film. A new technique is presented for reducing the noise level in spatially filtered speckle interferograms. Independent fringe patterns, obtained from one interferogram but with the filtering aperture sampling different regions of the Fourier transform plane, are digitised by a CCD camera and combined numerically. It is demonstrated that accurate analysis of fringe patterns by the Fourier transform method can be carried out, even if no carrier fringes are present. The measurements are compared with those obtained by speckle photography. Least-squares fitting of the theoretical displacement field is used to calculate the stress intensity factor at the crack tip as a function of time.     

Study and design of exponential and Butterworth low-pass filters used for digital speckle interference fringe filtering

This paper studies the exponential and Butterworth low-pass filtering methods and proposes improved exponential and Butterworth low-pass filters. The improved low-pass filters proposed in the paper can be used effectively for filtering processing of digital speckle interference fringes obtained in digital speckle pattern interferometry. Both theoretical analysis and experimental results are presented in the paper.     

Measurement of curvature distribution using digital speckle three-shearing aperture interferometry

Digital speckle three-shearing-aperture interferometry used for the measurement of curvature distribution fields of a deformation object is proposed for the first time. In this method, pure curvature distribution fringes without containing slope distribution fringes can be obtained by using digital speckle three-shearing-aperture interferometry. Two specklegrams, one before and the other after object deformation, are recorded by a CCD camera and stored in a computer. A 2-D fast Fourier transform (FFT) and a 2-D inverse FFT (IFFT) are performed on the two specklegrams. The subtraction of the transformed specklegrams will produce curvature distribution fringes, and the speckle noises in curvature distribution fringes can be removed after these fringes pass through low-pass filtering. Results from theory and experiments are in good agreement.     

Digital holographic interferometry based on wavelength and angular multiplexing for measuring the ternary diffusion

We present a novel method for dynamical measurement of the ternary diffusion by using digital holographic interferometry based on wavelength and angular multiplexing techniques. Two laser beams with different wavelengths (λ1=532 nm and λ2=473 nm) are used for the ternary diffusion measurement, and they are adjusted to make corresponding interference fringes in orthogonal directions on the CCD target. The orthogonal splitting of the fringes enables the spatial frequencies of each wavelength to be filtered separately in the Fourier spectrum of the hologram. Finally, they are reconstructed to obtain the molar concentration. This method is also suitable for two-phase diffusion measurement.     

基于迈克尔逊干涉的傅里叶变换散斑形貌测量技术

提出了电子散斑干涉载频调制测量物体形貌的方法。采用典型的迈克尔逊干涉光路,将物体偏转一微小角度（等效为物面与参考面间形成空气楔）产生等厚干涉,可在物体的表面引入包含物体高度信息的载波干涉条纹。用CCD采集该载波条纹图,利用傅里叶变换法可解调出物体高度的位相信息,从而实现物体的形貌测量。介绍了电子散斑干涉载频调制测量物体形貌的原理,并进行了实物测量,给出了实验结果。由于该方法采用散斑干涉方法测量物体形貌,所以具有灵敏度高的优点。     

电子学全息干涉术用于温度场测量

探讨了用电子学全息干涉术（双称数字全息干涉术）测量温度场分布及其变化的可行性，利用所设计的全息干涉实验光路，对一电烙铁头部周围温度场分布进行了实时全息记录，进而利用一维快速傅里叶变换及数字滤波处理再现出了反映温度场分布的全息干涉条纹图样，实验结果表明，与传统的光学全息干涉术相比，电子学全息干涉术借助于高分辨率CCD记录及高速计算机数字处理技术，从而可实现光学全息图的数字化记录、存储和重现。同时，利用再现物场相位倍增原理还可实现对干涉条纹数目的倍增，或利用物场相位分布的直接计算精确获取任意两点间的相位差，从而提高测量精度。此外，由于能够在不改变光路的前提下以较高的重复频率完成光学全息图的记录，电子学全息干涉术可以用于记录三维物场的变化并接近实时地再现和测量三维物场的变化规律，因此是一种极有发展前途的新型实时全息干涉计量技术。     

A new formula for fringe localization in holographic interferometry

Holographic interferometry generally involves the interference of two or more speckle fields reflected from or transmitted through a diffused object. The visibility of the resulting fringes depends on the degree of coherence of the interfering speckle fields. Through a statistical analysis it is found that the degree of coherence of speckle fields is essentially a function of the relative speckle displacement and average speckle size. The analysis leads to a new physical model for holographic interferometry. With this model the problem of fringe formation and localization may be analyzed and formulated in terms of speckle movement. A new formula for ideal fringe localization is then derived from the analysis. Furthermore, a localization factor V_c, i.e. the visibility of the holographic fringes, is introduced to analyze the partial fringe localization in holographic interferometry, which is of practical interest to most researchers.