平行光管的调整方法

平行光管是一种能发射平行光束的精密光学仪器,也是调整光学仪器时的重要工具。为了正确使用平行光管和确保平行光管射出光束严格平行,在使用前必须对平行光管进行调整。使分划板严格处于物镜的焦平面上,并使它的中心与平行光管的光轴重合。一般使用自准直法调节,即在物镜焦平面上     

利用坐标变换分析塔差对编码器测角精度测试的影响

为了实现编码器测角精度的高精度测量,介绍了应用多面棱体和自准直仪组合测量编码器测角精度的原理和方法,建立了多面棱体坐标系和自准直仪测量坐标系,利用坐标变换的方法推导了塔差对测角精度测试结果影响的精确模型。结果表明,编码器转轴的倾斜角度和倾斜方向会影响编码器测角精度的测量结果。测量误差随编码器的倾斜角度的增大而增大,且近似成平方关系。测量误差随随编码器的倾斜方向改变,倾斜方向角为0°或180°时,测量误差最小;倾斜方向角为90°或270°时,测量误差最大。当倾斜角度为5′时,引入的测量误差为0.11″~0.48″,这对于Ⅰ~Ⅲ级编码器的测试是不能忽略的。根据被测编码器的精度等级将塔差控制在恰当的范围内,给出了不同精度等级编码器测试时塔差的控制要求。     

高精度共焦自准直中心偏测量装置

研制了一种基于共焦轴向层析定焦、自准直横向定焦的共焦自准直中心偏测量装置。利用共焦探测模块对被测球面镜的球心和顶点位置进行定焦,从而测得被测球面镜的曲率半径;利用光路自准直方法探测被测镜旋转过程中反射光在探测面上的路径获得被测镜的偏心量,结合偏心量和曲率半径计算得出中心偏。与传统中心偏测量装置相比,所提测量装置可以同时测得曲率半径和中心偏,避免了重复装卡引入的测量误差,有效地提高了测量精度、简化了测量过程、降低了测量成本。实验结果表明测量装置的中心偏重复测量不确定度可达0.065″。     

激光测距机三轴平行性智能检测校正方法研究

提出了一种激光测距机三轴平行性智能的检测校正方法。建立了光轴平行性偏差与偏心环(框)旋转角度之间的数学模型,利用传感器得到激光发射轴与瞄准轴之间的平行性偏差,根据所建立的数学模型计算出偏心环(框)需要调整的角度值,利用步进电机使偏心环(框)转动相应的角度,从而物镜产生径向移动,实现激光测距机光轴的校正。此方法在检测激光测距机光轴平行性的同时实现了光轴的自动校正,也适用于其它具有双偏心结构的光学仪器。     

码盘偏心对叠栅条纹信号相位影响的理论分析

增量式光学编码器根据径向辐射光栅产生的叠栅条纹进行角度测量，两光栅码盘轴之间及其与系统转动轴之间的偏心和晃动，影响着编码器读头输出的叠栅条纹信号的相位，这给角度测量带来了一定的系统误差。根据光栅码盘产生叠栅条纹的基本理论，在改进计量光栅码盘理论模型的基础上，推导出码盘偏心情况下码盘读头输出的叠栅条纹信号相位的理论公式，对码盘偏心给叠栅条纹信号相位带来的偏差、增量式光学编码器光学设计原理及消除此由此带来的系统误差的技术原理进行了分析与讨论。     

光杠杆放大法测量的误差分析及改进方法

分析了利用光杠杆放大法测量微小长度变化量的实验中,光杠杆镜面与望远镜光轴不垂直时,对测量结果所产生的误差。改进了实验装置,安装了两个量角器,可方便调节光杠杆平面镜与光学望远镜的角度,使光杠杆镜面与望远镜光轴能达到严格垂直的效果,从而减小因光杠杆镜面法线与望远镜光轴存在偏转角度而引起的测量误差。     

静态角标校装置的温度稳定性分析

静态角标校装置是由若干个平行光管组成测角场,形成角度基准,用于检验大型光电经纬仪静态测角精度。由于大型光电经纬仪对静态测角精度指标要求很高,因此对作为检验基准的静态角标校装置提出很高的精度要求,要求在24 小时内角度基准的稳定精度不大于2（rms）。针对这一要求,讨论了实验室环境温度变化对角度基准的影响,影响角度基准稳定精度的因素是平行光管光轴指向,通过试验说明实验室环境温度在一定范围的变化不会影响静态角标校装置中使用的卡塞格林反射式平行光管的光轴指向。当实验室温度变化超过规定的范围时,光轴指向会发生变化,静态角标校装置的精度将不能满足要求。为实验室建设提出环境保障的明确要求,确保测量的准确性。同时通过光学设计分析软件计算结果说明:光管制造材料的不均匀性及装配间隙、应力等因素是影响光轴指向变化的主要原因。因此在光管设计时应充分考虑这些因素的影响,合理分配公差,减小装配应力,使环境温度变化对光管光轴指向的影响最小化。     

大视场电视经纬仪摄像系统的标定研究

利用电视经纬仪的跟踪测量功能，以平行光管作为目标，实现了对摄像系统重要参量的精密测量.结合高准确度轴角编码器，可以对焦距进行标定.通过方位和俯仰方向的角位移，利用镜头畸变的轴对称性，可以确定光轴的位置.对整个视场进行抽样采点，得到一个畸变的网格场，通过拟合得到畸变系数，可以进行高准确度畸变修正.     

光电系统多光轴平行性校准方法的研究

 比较了目前常用的几种多光轴平行性测试方法。在大口径平行光管法的基础上,结合CCD技术提出了新的光轴平行性校准方法。该方法采用ZYGO干涉仪精确定焦,通过比较目标靶在CCD上共轭像的中心坐标和被测系统激光光斑中心坐标之间的差异,即可计算出红外或者可见光轴与激光轴的平行性误差。分析了该方法中大口径离轴抛物面镜焦面的确定与激光光斑中心定位等问题。讨论了该方法的测量不确定度,得到测量不确定度小于5″。     

光电校靶中捷联惯导轴线的表征校准方法

光电校靶采用捷联惯导系统,需将惯导轴线用光电自准直系统表征捷联,用于对设备轴线的测量。光电自准直系统所表征的轴线与惯导轴线的一致性是影响校靶精度的重要因素,为提高光电校靶系统测量精度和效率,提出了一种惯导轴线的光电表征和校准方法。该方法是在分析测量结果偏差与一致性关系的基础上,采用实验数据拟合的方式得到自准直系统光轴与惯导轴之间的角度偏差值,用于系统修正,从而实现高精度校准。通过试验,将传统光机校正法和光电校准法结合使用,可大幅度提高系统校正效率,同时得到惯导与光轴一致性精度在15″以内。试验结果表明,与传统光学平晶引出的光机校正法相比,该方法的表征准确度和校准精度更高,适用于高精度惯性测量系统。     

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.     

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.     

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.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.