大口径激光波前测量方法

采用大型透镜阵列对激光波前进行采样，实现了对宽光束的测量。大口径激光束经过大型透镜阵列进行采样形成光斑点阵，通过成像系统，获取点阵图像，得到激光束波前信息，根据激光传输理论和光学系统像差理论，已知激光束的波前函数和强度分布时，可以求出激光束会聚后在焦面处任意位置的光强，因此激光束的波前、发散角、近场分布、远场分布等参数能够通过测量求解得到。     

基于已知球面波前的Hartmann-Shack传感器结构参量标定

微透镜阵列到CCD的距离是影响Hartmann-Shack波前探测器精度的主要装配误差之一。对该平移装配误差的修正,能够有效减小波前探测误差。理论求解了球面波前通过微透镜引起的子孔径光斑质心移动量与波前探测器结构参数之间的关系,借助该关系能够求出微透镜到CCD之间的实际距离,以其改进波前斜率的计算。实验验证了理论推导的合理性,并对实际装配参数进行标定,得实际距离为24.2 mm。利用标定后的参数重建波前,其相对误差减小20.4%。实验表明该标定方法能够有效提高波前传感器测量准确性。     

飞机风挡玻璃光学角偏差测量的研究

介绍一种新的测量飞机风挡玻璃光学角偏差的方法和全自动测量装置。与现行的角偏差自动测量方法相比,这种方法的物理意义清晰、样件被测量位置明确、测量结果准确度高。标靶采用针孔而不是十字叉丝或“L”形。采用钨灯和投射透镜产生准直白光,用CCD探测器作为光斑位置传感器在成像透镜的后焦面测量光斑位置的变化,从而可得光学角偏差。测量系统通过标准样品可溯源到国家角度基准。分析表明：测量系统的测量不确定度达到7.3″(k=2)。     

组合式面形测量系统的优化设计

在明确线结构光三角测量法原理的基础上,针对目前面形测量系统测量功能的单一性,设计了一种集旋转测量和移动测量于一体的面形测量系统。在系统结构设计中,系统参数,包括激光器和CCD之间的基线距离L、工作距离D、测量角α、透镜焦距f和CCD自身的参数对系统测量分辨率和测量范围有直接影响。在分析了这些参数之间的关系的基础上,对系统进行了优化设计和工作参数的确定。     

微透镜阵列误差对半导体激光匀化性能的影响

为了减小微透镜阵列误差对匀化光斑的影响,深入研究微透镜阵列光束匀化系统中微透镜阵列相对位置误差对光束匀化性能的影响,设计了一种微透镜阵列光束匀化系统。依据相对位置误差类型的不同,将双列微透镜阵列间六个自由度变化导致的误差分为距离误差、偏移误差以及转动误差进行分析,并对每种误差对光束匀化性能的影响进行了研究。采用6板条半导体激光器堆栈对上述匀化系统进行实验验证,实现了均匀性为90.75%的光斑,并对系统影响光斑性能的原因进行了分析。     

五维自动调整差动共焦间隙测量方法

为精确、快速测量镜组内各透镜间的轴向间隙,提出一种基于五维自动调整的差动共焦间隙测量方法。该方法根据CCD探测器实时获取的光斑信号检测被测镜组光轴的平移偏差与倾斜偏差,依据偏差信息、通过五维自动调整技术实现镜组高精度调整,再利用差动共焦高精度层析定焦和镜组内部光线追迹实现轴向间隙高精度测量。分析和实验表明,本方法可以有效提高姿态调整效率3.4倍,透镜间隙重复测量精度可达到0.53μm。该方法为实现镜组间隙的快速高精度测量提供了有效途径,同时还为透镜的中心厚度、焦距、半径等多种参数快速高精度测量提供了有效方法。     

利用CCD准确测量激光远场发散角

 利用CCD面阵接收器,通过标定的方法,将其准确安置在长焦距透镜后焦面上,并找出CCD 象元数与原场发散角的对应关系,从而迅速确定远场发散角。同时用短焦距透镜对 光束限制光阑成像,测得近场光斑光强分布。以激光束振幅函数的傅里叶变换作为理想衍射 极限,将远场发散角与之比较,可以得到用几倍衍射极限的方法表示的实际光束质量。     

CCD大范围轴向位移量检测研究

基于CCD图像测量技术,设计了一种利用CCD成像系统检测火车轮对几何尺寸的非接触在线测量系统,并给出了系统的结构及原理.激光束垂直入射到火车车轮上,再用透镜将火车车轮上的激光光斑成像到CCD上,当火车车轮产生磨损时,CCD上激光光斑的像也将发生位移.通过对CCD上弥散斑中心位移的测量,就可精确计算出火车车轮的磨损量.     

方形LED阵列光斑发散特性的幂函数拟合

利用LED照度公式推导方形LED阵列的光斑半径和发散角公式,建立了研究方形LED阵列光斑发散特性的数值计算方法.通过拟合得到方形LED阵列的光斑半径和发散角随目标距离、m值及阵列边长变化的幂函数公式.结果表明,幂函数拟合方法与数值计算结果吻合,平均相对误差小于1%.该方法弥补了数值计算方法不能对方形LED阵列光斑发散特性解析研究的缺陷.     

基于双CCD的滚转角测量方法研究

提出了一种基于双CCD的滚转角测量方法。测量系统包括两部分:移动部分由通过连接杆连接的两个CCD组成,连接杆固接在被测物上;固定部分包括光源、光开关和两个光学准直器,可以得到两路分别以一定角度相交入射到两个CCD上的准直光束。被测物发生滚转变化时,两CCD也同步变化,通过投射在其上的两个光斑位置变化,可求解出滚转角变化。MATLAB仿真证明被测物的各平动变化对滚转角测量无影响,在200″范围内的俯仰和偏摆变化,引起的滚转角测量误差不超过1″。搭建了滚转角测量实验系统,并与HP5529A双频激光干涉仪测量结果进行比对。测量结果表明,在1000″的测量范围内,系统滚转角测量偏差最大不超过1.5″。     

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.     

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.     

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.     

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.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.