一种菲涅尔全息图的快速算法

通过分析菲涅尔全息图计算模型,发现大量的平方运算和三角函数运算是计算速度的瓶颈,提出了一种菲涅尔全息图的快速计算方法.根据菲涅尔全息图的数学模型,利用三角函数的和差化积公式,将全息图的数学模型变换为由仅与水平或垂直方向有关的独立分量,通过四则运算来表示.在菲涅尔全息图的计算中,用少量的三角函数、平方运算和大量的四则运算代替原来大量的三角函数和平方运算,减少了全息图的运算量.实验表明,采用该算法后全息图的计算速度提高了9倍以上.     

一种新的三维计算全息图的计算方法

介绍了一种制作真实三维物体计算全息图的新方法。用摄像机记录三维物体在非相干光照明条件下两个正交方向上不同视角的一系列投影像，将这些投影像导入计算机，在MATLAB中对其作快速傅里叶变换。对这一系列二维投影像的傅里叶变换图进行抽样，得到三维物体在透镜后焦平面上的光场分布，进而制成一张计算全息图。结果证明该方法可以实现对真实物体三维全息图的合成，并且在算法实现上更加简单，提高了程序的运行速度，有利于改善全息图再现像的质量。为解决真实物体相干全息记录中光源功率和相干长度对全息记录可行性的限制指出了一个新的方向。     

单波长编码计算机制彩色彩虹全息图的研究

提出计算机制三维物体彩色全息图的新方法.通过理论分析表明,在满足一定的条件下,三个不同原色的点光源所产生的全息图光栅结构和距全息图不同距离的三个同色物点的光产生的全息图光栅结构是等价的.根据这一原理并参照彩虹全息技术,研究了物体三原色信息光分布的编码方法和全息图的算法,用单波长计算实现彩色全息图的制作,同时,较为完满地解决了全息图叠加和色串扰问题.实验结果证明了该方法的可行性及有效性.     

二值干涉型计算全息图

本文研究二值干涉型计算全息图,这种全息图最适于综合位相型波前,因此本文的讨论也只限于位相型波前的情况,对物光和参考光的选择以及全息图的抽样进行了分析,并得出相应的结论。     

迂回位相型计算全息图和修正离轴参考光计算全息图的对比讨论

使用Matlab语言得到了迂回位相全息图和博奇型全息图,由傅里叶逆变换得到再现像。阐述了两种计算全息图各自的特点,对再现像的质量、数量、大小、程序运行速度作出对比讨论。迂回位相计算全息图有便于记录、方便传递的特点。利用博奇编码得到的修正离轴参考光计算全息图有高质量的再现像,而且计算速度也比较快,对于复杂的二维图像,可以考虑利用这种编码方法进行计算全息。     

一种非旋转对称"花瓣形"相位板的检测系统设计

提出了利用计算全息图检测非旋转对称的"花瓣"形位相板.分析并推导了光线经过"花瓣"形相位板传播中的高阶像差的理论公式,并以此为指导进行了"花瓣形"相位板的检测系统的设计,给出了设计的结果.讨论了计算全息图衍射级次的分离以及计算全息图的二元化,给出了振幅型的计算全息图的图样.计算全息图的刻线最小间隔是20 μm,计算全息图的制作精度对检测结果的波前误差的影响仅仅为0.005λ.对检测系统作了详细的公差分析,结果表明所有调整公差对整个检测系统的影响和方根值为103.187 nm.     

计算机制彩虹全息图的新算法

提出利用查表方法进行数字彩虹全息的计算方法.根据彩虹全息的基元全息图为线全息图的特点,找出物点与其线全息图的一一对应关系,建立空间点阵物点的线全息物光分布数据表.在对实际物体进行计算时,根据物点的位置,在数据表中找到与之对应的物光分布,并将这些分布进行叠加,从而形成实际物体被狭缝限制的物光分布,最后引入参考光计算其彩虹全息图.本方法充分利用了线全息图的性质,使得计算量大大减小,同时提高了计算速度.     

大视角计算机制彩虹全息图的研究

提出大视角计算机制彩虹全息图制作的新方法-计算机与光学相结合的两步法.采用这种方法,计算机制彩虹全息图的视角可以方便地做到适合显示需要的大小,并且全息图的计算时间比采用一般方法计算短,解决了目前计算机制全息用于显示实用化存在的难点:庞大的计算量,大视角全息图制作困难.     

基于Matlab的计算全息图的制作与数字再现的研究

 应用Matlab语言,结合博奇型计算全息的编码方法,利用计算机分别绘制了菲涅耳全息图和傅里叶变换全息图,实现了计算全息图的快速制作,讨论了制作计算全息图的原理、方法和步骤。利用CGH技术和数字全息技术所生成的全息图再现出原始图像,完成了全息图的数字重现,实现了整个全息记录和再现过程的计算机模拟。与传统的编程语言和绘图方法相比较,该算法在实现上更加简单和快捷,并且带有一系列提高计算全息图质量的措施,有效地消除了零级像和孪生像的影响,获得了清晰的数字再现图像。     

复数滤波器在数字全息图处理中的应用

数字全息图在微电路检测、粒度分析、透明场测量等小孔径、小视场对象测量和细胞观测等显微测量方面有着广泛的应用前景。根据离轴数字全息图的频谱特点,提出采用复数滤波器,利用计算机及相关算法对离轴数字全息图进行滤波,消除其零级及共轭像,同时可以得到全息图的相位分布。讨论了复数滤波器的设计方法,给出了实验结果。为数字全息图的压缩、再现和相息图制作提供了方便。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.