Theoretical model for the transverse interference pattern of GRIN optical fiber using a laser sheet of light

A new technique (El-Ghandoor et al., Opt. Laser Technol. 31(7) (1999) 481–488) has been applied to study the shape of transverse interference fringes, instead of multiple beam Fizeau fringes (Marhic, Stein, Appl. Phys. Lett. 35 (1975) 1678–1682), from a GRIN optical fiber. In this technique, a laser light sheet is used to illuminate and pass directly through the optical fiber. Theoretical expressions are derived for the optical path differences of three groups of interference beams. The first one passes through the cladding, the core, and then the cladding once again; the second passes through the cladding only, and the third passes through the surrounding air. Theoretical expressions for the shape of transverse interference fringes formed across isotropic non-absorbing optical fibers are also calculated.     

Electron-holographic interference microscopy

Recent developments in electron interference microscopy are introduced based on holography principles. This technique has been given a major boost due to the development of a coherent field-emission electron beam. This has facilitated the measurement of the phase distribution of an electron beam transmitted through or reflected from an object to within 1/100 of the electron wavelength. Phase distribution can be displayed as a phase contour map in an electron micrograph. There the contour fringes directly and quantitatively indicate the thickness contours of a uniform sample, magnetic lines of force of a magnetic sample and equipotential lines of an electrostatic sample. Microscopic objects or fields have made their appearance in amplified interference micrographs through the use of this technique. Specific examples are the static and even dynamic observation of magnetic fluxons penetrating a superconductor and the quantitative measurement of specimen thickness or topography in atomic dimensions.     

Measurement of vibration with Young's fringe modulated speckle patterns in a photorefractive correlator

A technique has been proposed to analyze small in-plane component of vibrations by measuring the fringe shift, and analysing the correlation output of captured vibrating Young's fringes with a photorefractive correlator. Fringes are formed due to interference between the reconstructed speckled beam recorded for stationary object beam, and vibrated speckled beam transmitting through a BaTiO₃ crystal after introducing a small shift in the diffuser position. The correlation peak intensity is affected due to mismatch of vibrations between two piezo-mirrors in the object beam. High correlation output gives an indication of the frequency matching of known reference and unknown vibrations, thus giving information on the frequency of vibration. Vibration amplitudes of the order of a wavelength of light have been measured by counting the number of fringes passing past a line in the observation plane.     

Position magnifying sensor

This paper describes the application of multiple beam shearing interferometry to a position magnifying sensor. A multiple beam shearing interferometer (MBSI) with a shear plate wedged in the vertical direction produces sharp multiple beam fringes. When the lateral displacement of a point source (which gives rise to the input beam of the MBSI) or its image occurs in the horizontal direction, these fringes move vertically in a magnified manner. This characteristic was used in a position magnifying sensor to detect the displacement of a point image. The advantages of the sensor include a large displacement magnification (more than a hundred times) and a large working distance.     

An alternative technique for extraction of in-plane displacement from an image plane hologram

The combination of image plane holography and speckle photography for measurement of 3-D displacements has been reported earlier. It has been observed that when we interrogate such a hologram by an unexpanded laser beam, in addition to the formation of Young's fringes in the direct diffracted beam, very bright side lobes are also generated. If the specimen has undergone any in-plane displacement, high contrast fringes appear in the side lobes. We have demonstrated that these fringes can be used to obtain a precise quantitative in-plane displacement of the object.     

多光束等倾干涉圆环的实验研究

根据多光束干涉理论,推导出等倾干涉圆环直径的计算公式,进一步得出相邻两等倾干涉圆环的直径的平方差是常数,结果与实验相符合。用Ｆａｂｒｙ Ｐｅｒｏｔ 干涉仪观察钠双线的等倾干涉圆环,操作比较复杂,难度较大,提出一种简捷的调节方法,所测的钠双线波长差值与标准值的误差很小。     

高斯光束照射下的等倾双光束干涉

根据等倾干涉原理,对高斯光束经薄膜反射后的光强、可见度、条纹分布进行了理论分析,讨论了入射角对光强、可见度分布的影响,相位角对条纹可见度的影响.数值模拟计算表明：沿着垂直于光传播方向的平面,反射光束叠加区域为一圆斑,随着入射角的增大,可见度逐渐减小,光强分布偏离了高斯分布,光斑变大,峰值减小.干涉条纹在空间的分布类似于平面波的薄膜等倾干涉,主要由入射角及薄膜厚度决定.     

Multiple-surface interference fringes analysis basing on wavelength-modulated phase shifting interferometry

Phase-shifting interferometry is widely used for high-precision surface measurements, but has difficulty in dealing with parallel optical plates. In this paper, an advanced method is proposed to simultaneously measure surface distributions of parallel optical plates from multiple surface interference fringes. The basic theory behind the technique is by applying wavelength-modulated phase shifting interferometry (WMPSI) to get enough frames of multiple surface interference fringes. In the procession of wavelength-modulated phase shifting, the phase variation for one point of the surface is traced and is processed by Fourier transform, and then the frequency spectrum of every surface can be separated from each other. Therefore, it allows extraction of front surface, back surface and thickness variation from multiple surface interference fringes with high precision.     

Dynamic gratings in KDP induced by piezoelectric vibrations at optical frequencies

Optical interference fringes were observed in the beam spot of the He-Ne laser transmitted through KDP. The interference fringes originate from the dynamic gratings induced by the electromagnetic field of the incident light. Diffraction fringes appear only in certain propagation directions of light through KDP. This observation is different from that monitored in α-quartz.     

Compensation of beam walk-off in hollow metal waveguides

Hollow metal waveguides feature well collimated beams and small losses across air gaps. This enables introduction of multiple optical beam splitters, or taps, along the waveguide to multicast signals from a source to multiple receivers. The splitters need to be of sufficient thickness to provide mechanical integrity and ease of handling. As a result, passing through the thickness leads to a beam walk-off. Walk-off dependence on the splitter thickness and its effect on the system optical efficiency are investigated. Two methods to compensate the walk-off are described: by offsetting the outgoing waveguide, and by introducing an additional symmetric optical element to shift the beam back to the original optical path. Both methods have been shown to effectively mitigate the walk-off effects.     

Dependence of X-ray diffraction patterns on the parameters of primary incident beam

X-ray diffraction patterns obtained from a plane-parallel crystalline plate with a spherical cavity and from a wedge-shaped crystal have been investigated depending on the collimation of the primary incident beam. It is shown that in the case of ribbon-like incident beam the sectional topograms, obtained from the wedge-shaped crystal, have the form of V-shaped or straight fringes depending on the orientation of reflecting planes relative to the surface of the X-ray ribbon-like beam. In the case of a wide parallel beam or an asymmetrically reflected wide monochromatic beam the parallel fringes are obtained from the wedge-shaped crystals, and the circular fringes are obtained from the plane-parallel crystalline plates with a spherical cavity. For the primary ribbon-like beam the V-shaped patterns acquire the form of circular fringes as a result of scanning the crystal with a spherical cavity and the X-ray film.     

偏振光的杨氏干涉

在基础光学框架内,通过杨氏双孔干涉实验中线偏振光的干涉及线偏振光经过两任意厚度晶片的干涉等几个实例,说明了基于矢量波叠加概念的电磁干涉的基本思想、基本分析方法和基本现象.偏振光干涉时,观测平面上可以出现或不出现光强的周期性空间调制,但一般都产生光场偏振态的周期调制.它表明了光的矢量性对干涉的重要影响,并可揭示只分析强度条纹时被掩盖的一些物理效应.     

一种新的数字散斑振动定量分析系统

在数字散斑干涉(DSPI)测量方法中，数字散斑时间平均法测量振动时得到的是贝塞尔条纹，其定量分析比较困难。该文采用贝塞尔条纹准相移技术进行数字散斑振动定量分析，即在参考光路中引入和物体同频率的偏置参考振动,当参考振动的相位改变时,振动条纹会产生移动,这相当于静态余弦条纹的相移,可以采用相移算法对数字散斑振动测量的贝塞尔条纹进行定量分析。文中开发了一种新的数字散斑振动定量分析系统，研制了一种低压光学相移器和测量控制电路，给出了圆周固定圆片和四周固定方铜板的振动测量结果。实验结果表明：采用本系统可以方便地定量测出物体的振动模态。     

Determination of ordinary and extraordinary refractive indices of nematic liquid crystals by using wedge cells

A new accurate and fast interference method for determining ordinary and extraordinary refractive indices of nematic liquid crystals is presented and discussed. The method relies on microscopic measurements of distances between interference fringes appearing in polarised parallel coherent monochromatic light beam transmitted normally to the surfaces through a wedge cell filled with a nematic. Both glass plates confining the cell are coated with a partly transparent thin film of metal which is deposited by evaporation in vacuum. Owing to the multiple reflections between the surfaces and a small edge angle, the interference fringes observed near the wedge apex edge are sharp and equidistant. To apply this method one needs only small amount of an investigated liquid crystal. Basic mathematical formulae and results of an experiment are briefly discussed.     

润滑油膜双色光干涉测量系统的特性研究

基于多光束干涉理论和摄像系统的光谱响应特性,建立了润滑油膜彩色光干涉测量的色度学模型,以红绿双色光干涉测量为例设计了计算机程序复现了油膜厚度测量的干涉图像。双色光干涉的理论计算和实验测量取得了很好的一致性。进一步的计算表明,润滑油膜双色光干涉图像的色彩主要受光源双色光的半峰全宽、析光膜厚度、垫层厚度及润滑介质特性的影响。在所设定的计算参数条件下,双色光的半峰全宽较窄,析光膜厚度为4～10nm和垫层厚度较薄时图像的对比度较高。     

全息干涉法在实验应力分析中的应用

通过对简支梁受力前后的双曝光全息图进行再现,利用透过全息图的条纹解释办法,分别用目测和数字图像处理办法测量物面上干涉条纹间距,从而得出简支梁的挠度;再利用最小二乘法求出被测物件的弹性模量。     

Propagation characteristics of zero field truncation of COS beam

The central spot of COS beam (CS-COS) can be obtained from COS beam by using the zero field truncation technique. The transversal intensity distributions of CS-COS through three different kinds of aperture functions are simulated numerically from the near field to the far field. It is shown that the CS-COS has the property of eliminating the diffraction fringes in the whole propagation process if a suitable aperture is introduced.     

弹流油膜彩色光干涉系统的特性研究

彩色光干涉技术是润滑油膜厚度测量的最有效的方法之一,但对其测量光学理论的研究并不十分透彻。以球-盘弹性流体动压润滑油膜测量装置为对象,建立了彩色光干涉的色度学计算模型,对该系统的干涉条纹和色彩进行了数值模拟与分析。分析结果与实验数据的一致性表明了所建立的模型和分析方法的正确。分析表明:铬膜厚度对图像的色彩和对比度有明显的影响,当其厚度为5～10nm时,能够获得对比度和色彩理想的图像;垫层厚度影响各颜色分量强度分布的初相变;LED光源可产生对比度较好的干涉条纹。     

Method for extracting Bessel-structured light fringes’ center lines in a triangulation measurement system

To accurately extract the center lines of the structured light fringes is of the utmost importance for an active vision measurement system based on the laser triangulation method. The characteristic of the ring-structured light fringe pattern in the triangulation measurement system by a Bessel beam has been analyzed. The normal directions of the fringes are determined by solving the directions in which the change of the gray distribution is the greatest. The positions of the light fringes’ center lines can be obtained in normal directions by using the 2D derivative-sign binary map. The experimental results show that the center lines of the ring-structured light fringes can be accurately extracted with the method and the extracted center lines have a good consistency with the original center lines.     

Zn1—xMnx／ZnSe应变超晶格分子束外延生长及光学特性研究

用分子束外延方法在ＧａＡｓ（１００）衬底上成功生长了高质量的Ｚｎ１－ｘＭｎｘＳｅ／ＺｎＳｅ（ｘ＝０．１６），超晶格结构，用Ｘ射线衍射和低温光致发光（ＰＬ）对其结构，应变分布以及光学性能进行了研究，结果表明，２Ｋ温度下，Ｚｎ１－ｘＭｎｘＳｅ／ＺｎＳｅ超晶格的光致发光中主发光峰对应于ＺｎＳｅ阱中基态电子和基态轻空穴之间的自由激子跃迁，而且其峰位相对于ＺｎＳｅ薄膜材料的自由激子峰有明显移动。其中，当超晶