白光数字散斑照像术

本文提出一种新的数字散斑计量术——白光数字散斑照像术.它以两维数字偏心滤波技术实现全场信息的表征,而以数字相关技术实现点信息的表征.文中给出了计量方法、理论分析及实验结果.     

A study on spatially extended phase objects using speckle photography

We present an application of an improved speckle photography technique for spatially extended phase objects. A contour mapping of a thin lens displaying its phase variation is presented. A theoretical analysis is investigated followed by the experimental presentation. Reasonable interference fringes are obtained and compared with the fringes obtained for hot air. The phase information of the object is extracted using the point-by-point technique.     

部分相干光离焦像面散斑照相法研究

本文研究了部分相干光离焦像面散斑的运动规律.激光离焦散斑是其特例.讨论了制约离焦量的因素,并对其实验技术进行了探讨和验证.     

The application of high speed photography and white light speckle to the study of dynamic fracture

A white light speckle technique is combined with high speed photography to study the dynamic fracture of a sample of PMMA. A series of single exposure speckle patterns are photographically recorded at the rate of 2 × 10⁵ frames s^-1 during fracture of the sample. The displacement field around the tip of the propagating crack may then be determined by superimposing pairs of individual frames to form a ‘double-exposure’ speckle pattern. It is shown that the method gives values for the stress intensity factor K which are consistent with those obtained from other techniques.     

Measurement of 3-D displacement of cambered mirror of cryogenic optical system using white light speckle method

We report a method measuring 3-D displacement of cambered mirror for cryogenic optical system using white light speckle photography with double light sources and double cameras. Data acquiring and processing based on a digital image processing system is described. The 3-D displacement and displacement vector distributions in two low-temperature ranges are measured.     

一种用于自动分析散斑摄影条纹图的数字图像复原技术——衍射晕影响的消除

本文提出了一种消除衍射晕非均匀照度影响、提高计算机自动测量散斑摄影条纹图精度的数字图像复原算法.简单介绍了散斑摄影条纹的自动分析过程.在VAX-11/785计算机上对模拟的无噪声白光散斑条纹进行验证,结果表明,本算法和程序是可靠的.     

Digital speckle photography and speckle tomography in heat transfer studies

The line-of-sight speckle photography of transparent media is used for quantitative measurements of the instantaneous temperature fields in 3D unsteady flows. Both electronic and photographic methods are employed for specklegram recording. The subsequent specklegram treatment uses the Young's fringes method as well as cross-correlation analysis of small interrogation areas of the recordings. Experimental data for three different heat transfer configurations are obtained and discussed. The first one is natural convection over extended vertical heated plates with forward facing steps, the second is unsteady 3D convective flow around a suddenly heated vertical thin wire, and the third one is a convective plume above a multi-jet flame. Both local and global Nusselt numbers are determined via measuring local surface temperature gradients for these convective flows. The results are compared with Ostrach's theory for a single vertical plate and with the data obtained by Mach–Zehnder interferometry. The 3D temperature fields are reconstructed for axisymmetric convective flows around a suddenly heated vertical wire using quasi-double projection measurement and the Radon inversion. 3D temperature distributions above the combustion zone are reconstructed using multi-projection speckle photography measurements and computerised tomography.     

高温下数字图像相关散斑最优成像探究

为了测量材料在高温甚至超高温下的力学性能,采用数字图像相关方法,并研究其在高温下的最优成像。采取不同的散斑制作方法,同时加入不同颜色的高温漆,在不同的温度节点,外加不同光源及相应的滤波片,采集并观察图像是否具有良好的对比度。普通的单色光源在800℃以后会逐渐失效,无法获取图像,而紫外光在1 200℃时依然可以获取较好的图像,且直接利用试件本身颜色作为底色效果更佳。采用紫外光照明可以实现DIC在高温环境下的测量。同时利用黑色或者蓝色散斑直接喷涂在试件上有着最佳的对比度,要优于常规的散斑制作方法。     

Measurement of three-dimensional rigid body motion by multiple exposure speckle photography: use of uncollimated beam illumination in free space geometry

A theoretical and experimental analysis is carried out showing the effect of multiple exposures on fringes in the case of three-dimensional motion of a diffuse object illuminated by a diverging beam from a laser point source. Experimental conditions are such that the speckle patterns remain fully correlated in spite of the object moving in three-dimensional space in a direction that makes an angle with the optical axis. Owing to the in-plane component of the three-dimensional displacement the point of null-speckle displacement shifts either in the direction of the in-plane component of the motion or in the opposite direction depending upon the direction of the out-of-plane displacement component. This modifies the fringe profile as compared with the case of pure out-of-plane motion. The intensity distribution at the Fresnel plane of a specklegram is investigated after filtering by a converging beam for double exposure and multiple exposures. Good agreement is found between the theoretical and experimental results.     

TiO2微粒对远程荧光粉膜及白光发光二极管器件光色性能的影响

利用热压法将TiO₂微粒掺入至YAG:Ce荧光粉和硅树脂中制备出远程荧光粉膜并封装成白光发光二极管(LED)器件, 通过荧光粉相对亮度仪、双积分球测试系统和可见光光谱分析系统对样品的光色性能及机理进行了研究. 结果表明: TiO₂的散射效应能够显著提高蓝光的利用率和黄光的透射强度, 白光LED器件的光通量在TiO₂浓度为0.966 g/cm³ 时达到最高值415.28 lm(@300 mA, 9.3 V), 提高了8.15%, 相关色温从冷白6900 K逐渐变化至暖白3832 K. TiO₂的掺入不仅提高了远程荧光粉膜的发射强度和白光LED器件的光通量, 同时能调控其相关色温.     

The design of a non-cube beam-splitter used for electronic speckle pattern interferometry

A non-cube beam-splitter (NCBS) is proposed, by which an incident beam can be separated largely in a direction and then the lights from the test object and the lights from a reference surface placed adjacently to the test object can be combined to construct a simple electronic speckle pattern interferometry (ESPI) system. Two mainly useful quantitative ways, to calculate the phase change of the test object, the phase-shift and the fringe carrier method with Fourier transform, can be achieved in the ESPI system with the NCBS. Experiments with phase-shifting and fringe carrier method are completed. The experimental results show that the monolithic design of the proposed NCBS is effective in ESPI measurement and immunity to vibrations.     

Separation of 3-D displacement components in the white light speckle method

Measurement of in-plane and out-of-plane displacement components using the white light speckle method is considered for three different cases. The first is applicable when in-plane components are small and stresses are directly related to the second differential of the out-of-plane component. The other cases involve components of the same order of magnitude but require recording of either one or two specklegrams. Evidence of experimental demonstration of each case is given.     

Influence of out-of-plane deformation and its elimination in white light speckle photography

The aim of this paper is to present the white light speckle method as a practical tool in metrology and to search for the optimum conditions for its application. In particular, the study provides evidence that the white light speckle technique is not exclusively sensitive to the in-plane components of displacement. Consequently, the interpretation of the Young's fringes as pure in-plane fringes is prone to inaccurate measurements. The errors so introduced are systematically analysed for various optical parameters. Some practical considerations are then pointed out to aid in the design of an error-tolerance limited white light displacement measurement system to suit a particular need. two complementary techniques are next proposed which promise to eliminate the influence of the out-of-plane movements on the measurement of the lateral components of displacement. The proposed methods not only allow an increase in the accuracy of in-plane measurements, but also permit mapping of the out-of-plane movements undergone by the object surface. The techniques presented, apply equally to coherent speckle photography where the same problems are manifest, and should pave the way for the application of these methods to concrete engineering problems.     

Digital Photography in Measuring the Inclination of the Object Surface with Formation of a Speckle Structure

Optical schemes for measuring surface inclination due to shift or deformation are considered. Speckle-interferometry methods are used. The distinguished features of these schemes are connected with using a digital photocamera and a forming speckle structure in nonmonochromatic light. Several technical solutions are proposed making it possibile to measure inclination with an accuracy up to tenths of degree using standard cheap equipment. To form the speckle structure, the pattern of a random binary structure with unit size of several millimeters is used in the base fixed plane. The digital camera was placed in the analyzed plane and turned together with the plane. It registered a reduced image of the pattern. The registration was done for two positions of the surface, the pattern being illuminated by the camera flash lamp. Measuring the width and orientation of the interference fringes formed for the two speckle structures allows one to determine the inclination and orientation of the rotation axis.     

Manipulation of speckle fringes for non-destructive testing of defects in composites

A digital speckle pattern interferometer with optical fibres is proposed for composite materials diagnostics in an operative environment. Detection of a variety of flaws, such as disbonds, delaminations and cracks in aircraft components, is reported. Additional fringes are introduced for linearizing the fringe pattern and obtaining quantitative deformation measurements by Fourier transform analysis.     

动态白光散斑法的灵敏度及其提高

本文用非相干成象系统频谱分析的概念,分析了动态白光散斑法的灵敏度问题。提出了提高灵敏度的方法,使之不仅能测量大的动态变形,而且也能测量小的动态变形,如果用光弹性材料作试件,能同时得到动态等差线,进行主应力分离。     

研测动态问题的旋转孔径散斑照相法Ⅱ:矩位、平四位、直三位孔径

本文提出了旋转孔径散斑照相法中三种新颖的基本孔径:矩位孔、平四位孔和直三位孔,进行了理论分析和实验证明。采用新孔径拍摄散斑照相,散斑信息利用率高,衍射晕能量分布合理,信噪比提高,因而散斑条纹清晰度得到改善,相应的实验误差减小。     

污染气体扫描成像红外被动遥测系统实时数据处理研究

使用红外被动遥测技术可实现污染气体的远程监控和预警. 该技术应用过程中, 获取背景辐射是进行定量解析的关键, 在已有的应用中, 多采用同条件测量法和上风口测量方法获取背景光谱和环境光谱, 但这些方法均需要提前或者同时测量无目标物的背景光谱, 难以在实际应用中满足快速响应的需求. 本文基于红外辐射传输模型分析, 通过研究在800–1200 cm^-1波段内的实测光谱中同时包含目标、背景和环境辐射的基本原理, 采用了一种不需要事先测量背景的目标特征的背景光谱实时提取算法, 通过将该方法应用于自主研制的污染气体扫描成像红外被动遥测系统, 以六氟化硫为示踪气体, 开展了遥测验证实验. 将获取的浓度数据与应用同条件测量法获取的数据进行了比较, 结果显示两者的相关系数平方值达到0.99, 表明该方法切实可行, 可有效提高系统的响应速度和适用范围. 关键词： 傅里叶变换红外光谱 被动遥测 实时光谱提取算法     

激光相干场成像散斑噪声复合去噪方法

噪声是影响激光相干场高分辨成像系统像质的重要因素,激光相干场成像系统既受背景光加性噪声影响,又受激光乘性散斑噪声影响.为解决激光相干场成像系统受激光乘性散斑噪声和背景光加性噪声叠加引起的成像像质退化效应问题,从噪声抑制角度提高激光相干场系统高分辨成像像质,研究建立了激光散斑乘性噪声和背景光加性噪声对大气下行链路激光回波场信号影响干扰模型,并基于该模型提出了一种基于同态滤波和稀疏基追踪级联复合去噪算法.首先基于同态滤波理论将激光乘性散斑噪声转化为加性噪声,再由高通滤波器滤除散斑噪声,最后采用基追踪稀疏理论方法抑制背景光等加性噪声对像质的影响.研究表明,较现有单一去噪方法,该级联复合去噪方法可一次性消除激光乘性散斑噪声和背景加性噪声两种不同性质的噪声,有效改善了激光相干场成像质量.