Image-plane speckle in partially coherent illumination

Expressions are derived for the first and second order statistical properties of speckle formed in the image of a diffuse object when the illumination is both temporally and spatially partially coherent. Sunlight falls into this illumination category, and we are therefore able to deduce conditions under which sunlight speckle will show best contrast.     

光源编码的白光散斑剪切干涉计量术

本文提出了一种用非相干光源照明进行剪切干涉计量的方法—光源编码的白光散斑剪切干涉计量术.它采用光栅对光源进行编码以提高空间相干性,使物体的两个剪切像的波面部分相干叠加,以实现剪切干涉.     

频闪剪切散斑干涉术的研究

提出了一种用于振动研究的方法——频闪剪切散斑干涉照相法。该方法由于采用了剪切镜,能得到较为精确的散斑剪切图,提高了测量的精度,是一种用于振动研究较为理想的散斑照相的新方法。讨论了频闪剪切散斑干涉术的基本原理,给出了频闪剪切散斑图的全场分析的平均光强分析的解析式,并给出了实验结果。理论和实验都表明频闪剪切散斑干涉照相法要优于时间平均剪切散斑干涉照相法。该方法在全场滤波分析时,能给出任一瞬时物体振动信息,得到清晰的、高衬比的全场干涉条纹图,是一种实用可行的方法。     

用于多参数同时测量的散斑干涉仪

本文描述了一种新的散斑干涉仪,它可以同时对表面应变物体的面内位移、离面位移、位移梯度和莫尔曲率进行测量;由于利用了取向滤波方法,在滤波系统输出平面同时得到了与这些参数对应的散斑条纹.还利用散斑空间运动规律较好地解释了散斑干涉与散斑剪切干涉之间的关系.     

Phase shifting speckle shearing polarization interferometer using a birefringent wedge

A digital speckle pattern shearing interferometer is presented which utilizes a single birefringent wedge. Two orthogonally polarized images of an object measured are sheared by the wedge, and the bias phase difference between two polarized images is shifted by translating the wedge. The phase shifting technique applied to speckle pattern shearing interferometry makes it possible to analyze a slope and surface strain numerically. The fringe formation in the present interferometer is analyzed with statistical theory. Experimental results are also presented in two cases: (1) measurement of a slope and normal displacement with a single illumination; (2) simultaneous and separate measurement of a slope and surface strain with two symmetrical illuminations.     

A speckle-shearing interferometer: A tool for measuring derivatives of surface displacements

A speckle-shearing interferometer is developed using a sheared Michelson interferometer. The tool, like speckle interferometry, utilizes the speckle effect of coherent light. However, while speckle interferometry measures surface displacements, the speckle-shearing interferometer determines the derivatives of the surface displacements. Hence, it eliminates the necessity of differentiating the measured displacements to obtain strain.     

Measurement of the wavefront curvature of small diameter laser beams using the Fourier imaging phenomenon

A simple and very fast method of determining the radius of curvature of small diameter laser beams is proposed and experimentally verified. It is based on the Fourier imaging phenomenon in spatially coherent illumination and is particularly recommended for measuring unexpanded Gaussian laser beams when optical flat shearing interferometry methods are not applicable.     

数字散斑法在局域剪切带三维变形研究中的应用

在适当的温度、应变率和预变形下,合金材料的拉伸试验中,将会出现伴随应力锯齿形跌落的雪崩式剪切变形带,即波特文-勒夏特利埃(Portevin-Le Chatelier,PLC)效应。利用高速数字摄像系统(分辨力1000 frames/s)并结合数字散斑干涉法(Digital speckle pattern interferometry,DSPI)和数字散斑相关法设计了一套光学变形测量系统,实现了拉伸试验中对试件表面三维变形的实时、精确测量。利用该光学系统对铝铜合金试件在拉伸试验中产生的跳跃传播的局域剪切带瞬态成核过程进行捕捉。通过结合数字散斑相关法得到的面内变形定量结果和数字散斑干涉法得到的表现离面变形的条纹图,再现了剪切变形带成核和传播瞬间的三维变形过程。     

Speckle interferometry for the strain field of geologic structure model

Based on imitative experiment of structure mechanics,four-aperture defocusedspeckle shearing interferometry is used to obtain the distribution of strain field of the geologicstructure model of the Jiulong mountain in Sichuan Basin.And through the analysis of the ex-perimental data,we can give some experdriental basis for recognizing the distribution of thegeologic fracture in the district of the Jiulong Mountain. Exploration practice shows that fracture distribution predicted by theory agrees with actu-al situation.     

High-dynamic-range measurement of the two-point field correlation function by carrier-encoded spatial shearing interferometry

We present a new technique for the direct measurement of the two-point field correlation function of a monochromatic light source based on carrier-encoded lateral shearing interferometry. The technique provides a higher dynamic range and a significant reduction of the amount of data compared with previously demonstrated methods. We demonstrate the measurement of coherent and partially coherent sources.     

Effect of surface roughness on the statistical distribution of image speckle intensity

An experimental investigation is made of the effect of surface roughness on the statistical distribution of image speckle intensity. A speckle pattern is formed by spatially coherent light at the image plane of an object having some surface roughness and its statistical properties are investigated. It is found that the contrast of the speckle is related to the surface roughness. By this relation, a new technique for the measurement of surface roughness is proposed.     

Spectral anomalies and spectral switches of partially coherent and polychromatic light diffracted at an aperture

Inrecentyearsanewbranchofmodernphysicalopticscalledsingularoptics[1]hasbeendeveloped.In2002theworkinsingularopticswasextendedfrommonochromaticlighttospatiallyfullycoherentandpolychromaticlightbyGburetal.[2—4].Itwasfoundthat,whenaconverging,spatiallyfullycoherentandpolychromaticsphericalwaveisdiffractedatanaperture,anomalousspectralchangestakeplaceclosetozerosoftheintensityinthefarfield;i.e.thespectrumisredshiftedatsomepoints,blueshiftedatothers,andsplitintotwolineselsewhere.Thepredictionsofsp…     

Holography, speckle, and computers

Surveys are presented on automatic and quantitative deformation measurements using CCDs and computers in holographic interferometry and speckle metrology for diffusely reflecting surfaces. For delivering relationships between object deformation and observed quantities, we discuss formations of fringes and signals observed in these methods in terms of correlation functions of spatially randomly varying complex amplitude of light. Dependencies of the observed patterns on object deformation and optical systems are discussed. Physical meanings of the derived relationships are explained in terms of the dynamic behaviors of speckles resulting from surface deformation. Automatic measurements are described in chronological orders. They include analysis of fringe patterns resulting from photographic recording of specklegrams, video recording and analysis of speckle patterns used in electronic speckle pattern interferometry as well as direct digital correlation techniques, and digital holography that uses both digital recording and reconstruction of holograms.     

Iterative Fourier transform method for phase map recovery in electronic speckle-shearing pattern interferometry

Increasing phase values at the edges of objects under analysis in electronic speckle shearing interferometry (ESSPI) cause errors in the actual recovering methods to obtain the spatially integrated phase. An iterative least minimum squares method is proposed here to recover the phase map from the approximated ESSPI derivatives when the displacement phase is increasing near the object edges. It is based in an iterative Fourier transform method derived from a least-squares phase map recovery algorithm. Experimental results from a rotating cylindrical bar show the validity of our approach.     

Methods of strain measurement and their comparison

Three methods for strain measurement are described—speckle shearing interferometry (SSI), electrical strain gages and mechanical deflectometers; they were compared to the analytical method based on the theory of elasticity. The experimental methods were simultaneously applied on a simply supported uniformly loaded plate of a composite material. Good agreement was obtained between the measured and the calculated results, at the points of measurement within the range of loading.     

菲涅耳衍射区和夫琅和费衍射区的动态部分相干光散斑场特性

研究了菲涅耳衍射区和夫琅和费衍射区动态部分相干光散斑的特性.利用部分相干光互强度传播的理论，得出了在部分相干光照明时，由运动散射体产生的动态散斑光强时空交叉的自相关函数的一般形式，并由此得出了散斑沸腾和平移的一般规律.通过适当选择光源和调整光路参数，在实验上得到了菲涅耳和夫琅和费衍射区的部分相干光散斑，对夫琅和费面上的动态部分相干光散斑的平移和沸腾现象进行了定性研究；采用光子计数及数据自动采集的方法，对部分相干光散斑随时间的演化及动态部分相干光散斑的沸腾进行了定量测量.这些实验结果与理论结果相符合. 关键词： 部分相干光动态散斑 时空交叉相关函数 沸腾     

Synthesis of spatial coherence

The mutual intensity function plays a major role in characterizing quasi-monochromatic, partially coherent optical signals. We propose to use the mutual intensity as a carrier of information to avoid speckle noise in coherent illumination systems and to permit the use of complex functions that are prohibited spatially incoherent sources. To do this we require methods for encoding the information as a coherence function. An optical system for synthesizing a beam with a given mutual intensity function is proposed. The optical system permits the synthesis of any desired mutual intensity function. The illumination is supplied by a quasi-monochromatic, spatially incoherent source. Experimental results demonstrate the performance of this system for several cases.     

光纤全息散斑干涉计量

脉冲激光经光导纤维传输后，其偏振性变化为随机分布，相干性有所降低，但它用在全息干涉计量中却有突出的优点，对于涉条纹的形成和清晰度没有影响。经常使用的光纤散斑全息干涉系统有两种类型：一种是只用传光束形成物光，参考光，此种系统形成的全息象清晰度有所下降，但做全息干涉计量时对条纹的衬比度和清晰度没有任何影响．另一种类型是物光和参考光都是用光导纤维传输，然后用光纤传象束将物体的象进行传输，再用透镜将其成象在底片上，做双曝光全息干涉时则形成全息散斑干涉计量，用全息方法再现时干涉图类似“杨氏”条纹。本文对上述两种系统，结合实验结果、分三种情况进行了研究。文章共分为三个部分：（一）引言；（二）散斑全息干涉计量；（三）结论。     

Using Speckle Interferometry for Controlling the Units of Multi‐Mirror

Applications of speckle interferometry for measuring displacements of mirrors of multi‐mirror centimeter radiotelescopes are considered and analyzed in modeling experiments. The general principles of speckle photography, speckle interferometry, and the use of two-exposure speckle patterns for the analysis of displacements of rough surfaces (units of the radiotelescope mirrors) are worked out. Experiments are carried out for three possible displacements of the object surface: parallel shifts along the surface itself, rotations, and shifts in the perpendicular direction. The shape and structure of the displaced units do not change. The experiments prove that speckle interferometry is a rather effective and practical tool for measuring shifts and rotations of composite radiotelescope mirrors.     

Polarizing interferometer with constant radial and azimuthal shears

An interferometer is described in which a rotatable Wollaston prism is used to achieve constant radial and azimuthal shears in a converging beam. These displacements may have applications in speckle shearing interferometry for the deformation measurement of objects with axial symmetry.