基于散斑干涉光谱分布变化量探测瞬态高温的研究

为了提高瞬态高温检测的精度,利用快速傅里叶变换(FFT)对散斑干涉条纹进行光谱分析,提出了通过光谱分布的偏移及幅值变化反演温度的方法。当激光照射应变材料时,瞬态高温使材料发生形变从而使散斑干涉条纹改变,被测表面形变前后获得的干涉条纹由面阵CCD采集。由于其对应的光谱密度分布函数也会发生相应的改变,即中心波长位置偏移及振幅变化,通过其改变反演材料的瞬态温度。在分析推导了瞬态温度变化、材料应变及干涉条纹变化之间的函数关系后,仿真分析得到了瞬态温度正比于压强系数、反比于温度系数。实验采用660 nm半导体激光器,SI6600型面阵CCD探测器,从获得的光谱分布函数中提取中心波长的偏移量,经计算和标定所得数据与传统的干涉测温方法进行对比,探测精度可达0.3%。相比传统的直接检测干涉条纹的变化量,由被测面形变量推导温度的方法精度提高近3倍。     

单幅对称变形相位图分离二维变形分量的相移电子散斑干涉技术

提出了利用相移电子散斑干涉测量物体二维变形分量的方法.单光束照明的传统电子散斑干涉技术,测量得到的是一幅物体变形的混合相位场.当物体具有对称变形时,可由这一幅相位图求得二维变形分量.方法是将该相位图镜像翻转得到第二幅相位图,通过二幅相位图的叠加、复位和分离运算,获得物体的二维变形场的分量值.利用三点加载的简支梁进行了实验,给出了实验结果,并与对称光照明实验结果进行了对比,验证了该方法的正确性.     

Speckle interferometry for measurement of continuous deformations

Improvements of a method for measurement of continuous displacements and deformations with digital phase shifting speckle pattern interferometry are presented. The method is based on an algorithm that, with the knowledge of the initial phase, only needs one image at a time to evaluate continuos phase changes due to object deformations. In the improved method, the initial random phase of the speckle pattern is evaluated using a number of phase-shifted images before the deformation under study. This is used for increasing the accuracy of the initial phase estimation and reducing influences from image noise and other measurement disturbances. The phase-shifted speckle patterns are used as references for comparison with the speckle patterns of the deformed object, thereby increasing the reliability and accuracy of the phase estimations of the deformed patterns. The technique can be used for measuring deformations such as transients and other dynamic events, heat expansion as well as other phenomena where it is difficult to accomplish phase shifting during deformation.     

High Accuracy Phase Measurement in Phase-Shifting Speckle Interferometry

A method for accurately measuring information about the deformation of a rough surface object using a phase-shifting speckle interferometer with a television camera and a computer is considered. In this case, the intensity change of the speckle by phase-shifting varies randomly in space because of the statistical property of the speckle. Then, at points with small intensity change, the accuracy of the phase measurement is affected significantly by the quantization error of an analog to digital converter for data recording. To improve the accuracy, the statistical property of the interference speckle must be clarified. This is done theoretically and experimentally, and the experimental results show that higher measurement accuracy can be attained by selecting large amplitude points.Presented at 1996 International Workshop on Interferometry (IWI ‘96), August 27–29, Saitama, Japan.     

一种新的多通道散斑照相术及其应用

提出了一种新的多通道散斑照相术，通过旋转光楔实现多通道散斑图记录。该方法不仅能在一张记录介质上记录物体动有一些状态的多通道散斑图，且用全场滤波分析时，能方便地同时给出所有通道的物变形信息，得到清晰高衬比的干涉条纹图。     

Speckle evolution of diffusive and localized waves

We show that while the statistics of static speckle patterns are generic, fluctuations in the change within speckle patterns are greatly enhanced in the localization transition. The probability distributions of the displacement of phase singularities and the standard deviations of the changes of phase and intensity with frequency shift of incident microwave radiation are given in terms of the same expression which describes the probability distribution of total transmission. This function depends only upon a single parameter, the variance of the corresponding variable. The changing statistics in the localization transition reflects the number of underlying electromagnetic modes with which the incident wave interacts.     

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。     

Speckle pattern interferometer

We describe in this paper a speckle interferometer constituted by two partially diffusing plates. They are illuminated by a laser and the resulting intensity distribution is observed in the image plane of the source. Each speckle of this plane (Fourier plane) is modulated by a ring system whose interference order depends on its phase. Since the observation plane is a Fourier plane, a longitudinal or lateral shift of one of the diffusers results only into a change of the modulating fringes, the speckles themselves remaining unchanged. A photographic plate which records successively the intensity distribution lying in the Fourier plane before and after the considered shift, exhibits after processing a system of Moiré fringes, the shape of which depends on the nature of the translation given to the diffuser between the exposures.     

一种改进的载波电子散斑干涉处理方法

提出了一种新的载波电子散斑干涉的处理方法,该方法将载波所形成的直条纹和包含物体变形信息的弯曲条纹在频域直接比较, 避免了传统载波干涉方法中的载波频率计算和由此带来的误差. 因此在准确程度和方便性方面都有明显改进. 本文在给出理论分析的同时进行了实验验证.     

The distribution of plastic deformation during 21 kHz fatigue of copper samples

A new method of investigating the portion of plastic deformation during fatigue tests of copper samples has been developed. Until now plastic deformation could only be estimated as opposed to being directly measured. Cholesteric li-crystals were applied to the sample surfaces before the fatique test and the temperature distribution during deformation was measured by the change in colour of these crystals. This then allows the distribution of the plastic deformation along the sample to be calculated. Film recordings of the colour, and hence the temperature change showed that plastic deformation is spread along the sample in a manner similar to that predicted by theory; plastic deformation is not mainly concentrated in the middle of a specimen.     

平行式向列液晶实现相移剪切电子散斑干涉术的研究

研究了向列型液晶的相位调制特性，采用平行式向列液昌作为相移器建立了相移剪切电子散斑干涉计量系统。该方法将相移技术引入到剪切电子散斑干涉术中，提高了检测精度，采用了相关条纹法求解相位，简化了计算；相移方法简单，可靠。用该系统进行应变场的测量实验，取得了满意的效果。     

激光散斑图样的光流场分析研究

提出了一种基于动态图像处理的新的电子散斑计量方法－光流场分析法，从新的角度出发讨论了运用图像序列分析的概念秋解决散斑图样测量的可行性和简便性。并且解决了当散斑图像不满足进行光流场分析的约束条件时的测量问题，即通过多通道的图像处理方法来改变图像连续特性，从而扩大了测量范围。     

相位调制数字散斑干涉术

提出一种可绕Ｚ轴转动的粗糙平板（参考物体）实现相位调制，该方法在不改变电子散斑干涉术（ＥＳＰＩ）或数字散干涉术（ＤＳＰＩ）系统装置的情况下，可用于微小离而位移场（例如最大离面位移为λ）的测量，以及复杂形变的离面位移场的自动测量。     

Speckle correlation for the analysis of random processes at rough surfaces

The importance of technological processes like corrosion, ablation or deposition causes interest in the quantitative monitoring of changes at rough surfaces. Thus, there is a need for effective methods to measure the statistical parameters characterizing changes in the profile or the material composition of such objects. The speckle field scattered from the surface is used as information carrier and its change is measured by correlation. This is realized by sophisticated data acquisition and digital processing techniques. An important issue is the interpretation of the correlation output in terms of statistical parameters describing the surface change. For many random surfaces a geometrical relation between surface profile and optical phase proves satisfactory. This allows to determine the standard deviation of the profile change. For a verification, speckle decorrelation in model surfaces of known deviation is measured. The paper introduces the speckle correlation concept, outlines some history and current setups and describes methods for data evaluation. The reliability of the quantitative interpretation of the speckle decorrelation is demonstrated. The method is illustrated by studies of metal corrosion and material removal in the cleaning of historical objects by laser ablation.     

双模晶体相场研究形变诱导的多级微结构演化

本文采用双模晶体相场模型,计算了双模二维相图;模拟了形变诱导六角相向正方相转变过程的多级微结构演化,详细分析了位相差、形变方向对位错、晶界、晶体结构、新相形貌的影响规律.模拟结果表明:形变方向影响正方相晶核的形核位置和生长方向,拉伸时正方相优先在变形带上形核,垂直于形变方向长大,而压缩时正方相直接在位错和晶界的能量较高处形核,平行于形变方向长大;位相差对形变诱发晶界甄没过程有显著影响,体现在能量峰上为,小位相差晶界位错的攀滑移和甄没形成一个能量峰,大位相差晶界位错攀滑移和甄没因分阶段完成而不出现明显的能量峰;形变诱导相变过程中各种因素相互作用复杂,是相变与动态再结晶的复合转变.     

基于位相分布限制衍射光学元件的散斑抑制方法

根据散斑产生的机理,利用像素点之间干涉的概念,提出了通过限制光场的位相分布范围来抑制投影图像中散斑对比度的方法.在部分发展散斑的条件下,推导了位相均匀分布情况下的散斑对比度公式,揭示了当相位分布范围在0.6π~2π之间时,散斑对比度随相位分布范围的变化而震荡变化,当把相位分布范围限制在0.6π以下时,散斑对比度会随相位分布范围的减小而迅速下降.建立了理想仿真模型和实际仿真模型来验证该方法的正确性和可行性.在理想仿真模型中,当位相分布范围从2π变到0,所得散斑图样对比度从66.44%降到0;在实际仿真模型中,模拟了实际激光投影系统的光路结构,并运用了两片衍射光学元件,一片用于激光整形匀化,一片用于光场的位相分布范围限制,散斑图样对比度从92.78%降低到2.09%.该方法稳定性高、耗能低、使用元件尺寸小,为全息投影显示的散斑抑制提供了参考.     

Modeling and computation of two phase geometric biomembranes using surface finite elements

Biomembranes consisting of multiple lipids may involve phase separation phenomena leading to coexisting domains of different lipid compositions. The modeling of such biomembranes involves an elastic or bending energy together with a line energy associated with the phase interfaces. This leads to a free boundary problem for the phase interface on the unknown equilibrium surface which minimizes an energy functional subject to volume and area constraints. In this paper we propose a new computational tool for computing equilibria based on an L² relaxation flow for the total energy in which the line energy is approximated by a surface Ginzburg–Landau phase field functional. The relaxation dynamics couple a nonlinear fourth order geometric evolution equation of Willmore flow type for the membrane with a surface Allen–Cahn equation describing the lateral decomposition. A novel system is derived involving second order elliptic operators where the field variables are the positions of material points of the surface, the mean curvature vector and the surface phase field function. The resulting variational formulation uses H¹ spaces, and we employ triangulated surfaces and H¹ conforming quadratic surface finite elements for approximating solutions. Together with a semi-implicit time discretization of the evolution equations an iterative scheme is obtained essentially requiring linear solvers only. Numerical experiments are presented which exhibit convergence and the power of this new method for two component geometric biomembranes by computing equilibria such as dumbbells, discocytes and starfishes with lateral phase separation.     

Strongly deformed nuclei near the magic proton shell 82?

The sudden change of the isotope phase shift in the Hg isotopes is explained by studying the deformation energy with the Strutinsky shell correction method. It is shown that going from the spherical isotope ²⁰⁴Hg to the isotope ¹⁸⁴Hg a small negative deformation (up to β₂ = −0.19) is built up. Between the mass numbers 186 and 182 the deformation is shifted through the γ instability valley to larger positive deformations (β₂ ≈ 0.3). The experimentally observed anomaly can be explained with the theoretical isotope shift constant, if this change of ground state deformations is taken into account.     

Speckle averaging in deformation analysis using video speckle interferometry

We show that speckle averaging in deformation analysis using video speckle interferometry increases the signal to noise ratio and improves the resolution in the resulting image. Speckle averaging in deformation analysis normally demands a very high degree of stability and repeatibility. Averaging phase gradient maps reduces these demands considerably. Experimentally, deformation details down to 2 × 2 pixels in the averaged pictures have been resolved.     

数字散斑相位图去包裹新算法

提出了一种新的数字散斑相位图去包裹算法,主要针对检测对象为复杂非连续物体这一情况。物体在激光照明下,采用光学相位反相相减图像的方法来检测并标识出相位间断区,并利用改进了的行列去包裹算法。使去包裹过程只在相位有效区域进行,从而准确快速地实现全场有效区域的相位去包裹。与已提出的相位去包裹方法相比,该算法具有计算量小,速度快,并能有效地避开大面积的相位间断区的优点,该方法使数字散斑技术可以方便地应用于工程实际中如对复杂非连续构件的变形、振动等方面的定量分析。