基于NI Vision的保偏光纤几何参数测量技术研究

近年来随着高精度光纤陀螺小型化的发展,细径保偏光纤的研制生产技术不断成熟,在研制和应用过程中急需对保偏光纤的几何参数进行准确测量。基于环形LED光源斜射照明的暗场成像技术,结合NI Vision视觉工具包提供的图像粒子分析处理算法,实现了保偏光纤各项几何参数的实时快速测量,且实验测量结果的重复性较好,能够很好地满足细径保偏光纤在研制生产和应用中的测量需求。     

用于光纤陀螺仪的保偏光纤

阐述了光纤陀螺仪对保偏光纤的基本性能要求,并介绍了一种新型直径为80 μm保偏光纤的主要性能参数和特征.     

一种全新结构的保偏光纤及其器件

本文在论述当代国外几种保偏光纤类型的基础上，着重讨论了我们自行发明的一种全新结构“类矩型”保偏光纤的特点，并介绍用“类矩型”保偏光纤研制的一系列保偏光纤器件的情况。     

保偏光纤拍长的测量

本文叙述了保偏光纤能够保证传输光波偏振特性的基本原理，介绍了测量保偏光纤拍长的基本方法。     

保偏光纤起偏器检测系统

本文介绍保偏光纤起偏器检测系统的原理，阐述了系统结构及关键技术问题的解决，给出了部分测试结果。     

数字图像法测量光纤端面几何参数

基于数字图像处理的方法对光纤端面的几何参数进行自动测量，具有处理速度快、测量精度高以及不过于依赖操作水平的优点。利用数字图像处理技术对各种光纤端面图像进行分析并进行必要的数字图像处理；针对不同光纤端面的特点，建立相应的数学物理模型，计算出各种待测光纤的几何参数；并用Matlab7．0软件设计出简单方便且功能完善的光纤端面几何参数测量软件系统。     

高双折射保偏光纤的温度和应变灵敏度测量

我们采用动态偏振法测量了三种常用的商品化高双折射保偏光纤（蝴蝶结型光纤，保偏光纤，吸收降低光纤和椭圆芯光纤）的应变和温度灵敏度。本文详细介绍了实验装置和测量程序，测量数据尽可能与已公布的数据作了比较，并获得良好的一致。     

保偏光纤器件的对轴角度分析与测量

理论推导了保偏光纤(PMF)对轴角度、起偏器起偏角与相干域检测信号的关系,仿真分析表明,对轴误差越大,引起的偏振耦合越大.根据白光干涉原理,采用Michelson干涉仪光程补偿的方法,实验研究了偏振耦合强度与对轴角度之间的关系,并根据测量的耦合强度数据计算出对轴角度.     

Development and investigation of real-time robust algorithms for estimating the parameters of geometric transformations of video-sequence frames

The problem of estimating the parameters of geometric transformations of the frames in a video sequence is considered. The solution to this problem is found through a combination of three basic approaches: the optical-flow feature-point methods and the direct correlation methods. A procedure for the detailed analysis of the behavior of the correlation function is used to ensure stable real-time operation of the proposed algorithms on modern (even unspecialized) computing systems for a wide range of shooting conditions.     

New algorithms for fixed and elastic geometric transformationmodels

This paper describes a new approach that leads to the discovery of substitutions or approximations for physical transformation by fixed and elastic geometric transformation models. These substitutions and approximations can simplify the solution of normalization and generation of shapes in signal processing, image processing, computer vision, computer graphics, and pattern recognition. In this paper, several new algorithms for fixed geometric transformation models such as bilinear, quadratic, bi-quadratic, cubic, and bi-cubic are presented based on the finite element theory. To tackle more general and more complicated problems, elastic geometric transformation models including Coons, harmonic, and general elastic models are discussed. Several useful algorithms are also presented in this paper. The performance of the proposed approach has been evaluated by a series of experiments with interesting results.     

圆柱工件几何参数的自动测量研究

针对圆柱工件在实际测量过程中测量速度慢、精度低的实际情况,本文介绍了一种利用几何位移光学精密测量完成圆柱工件几何参数测量的方法。该系统由机械系统、运动控制和数据采集系统、数据处理系统组成;利用激光位移传感器非接触测量的特点,对圆柱工件外表面几何信息进行采集;根据最小二乘法原理,计算机对测量数据进行处理,从而得到圆柱工件的外径、同轴度、高度等几何参数。该方法通过实验验证,目前已应用于生产中。     

基于几何特征的点云分割算法研究进展

点云是3维图像的一种特殊数据形式, 正逐渐成为3维图像信息处理的研究热点; 点云分割是点云数据处理的重要步骤, 对算法的结果有直接影响; 基于3维图像几何特征的点云分割算法结构简洁、运算结果稳定性强, 且易于调整, 在实际应用中占有主要地位。对最近几年涌现出来的基于几何特征的点云分割方法进行了梳理, 根据每种方法的理论基础和应用特点将算法归纳为基于边缘检测、表面特征和模型拟合的点云分割方法, 分析了各类算法的特点和存在的主要问题, 并进行了算法性能比较, 分析了影响点云分割算法效率的主要因素, 最后对未来的发展趋势进行了展望。     

Fast mimo transmit antenna selection algorithms: a geometric approach

Motivated by matrix determinant properties, this letter develops a fast transmit antenna selection algorithm for MIMO systems: the G-circles method. This novel scheme is shown to achieve many advantages over other existing algorithms     

Coding of sources with two-sided geometric distributions andunknown parameters

Lossless compression is studied for a countably infinite alphabet source with an unknown, off-centered, two-sided geometric (TSG) distribution, which is a commonly used statistical model for image prediction residuals. We demonstrate that arithmetic coding based on a simple strategy of model adaptation, essentially attains the theoretical lower bound to the universal coding redundancy associated with this model. We then focus on more practical codes for the TSG model, that operate on a symbol-by-symbol basis, and study the problem of adaptively selecting a code from a given discrete family. By taking advantage of the structure of the optimum Huffman tree for a known TSG distribution, which enables simple calculation of the codeword of every given source symbol, an efficient adaptive strategy is derived     

Efficient burst scheduling algorithms in optical burst-switched networks using geometric techniques

Optical burst switching (OBS) is a promising paradigm for the next-generation Internet. In OBS, a key problem is to schedule bursts on wavelength channels, whose bandwidth may become fragmented with the so-called void (or idle) intervals, using both fast and bandwidth efficient algorithms so as to reduce burst loss. To date, two well-known scheduling algorithms, called Horizon and LAUC-VF, have been proposed in the literature, which trade off bandwidth efficiency for fast running time and vice versa, respectively. In this paper, we propose a set of novel burst scheduling algorithms for OBS networks with and without fiber delay lines (FDLs) utilizing the techniques from computational geometry. In networks without FDLs, our proposed minimum-starting-void (Min-SV) algorithm can schedule a burst in O(logm) time, where m is the total number of void intervals, as long as there is a suitable void interval. Simulation results suggest that our algorithm achieves a loss rate which is at least as low as LAUC-VF, but can run much faster. In fact, its speed can be almost the same as Horizon (which has a much higher loss rate). In networks with FDLs, our proposed batching FDL algorithm considers a batch of FDLs to find a suitable FDL to delay a burst which would otherwise be discarded due to contention, instead of considering the FDLs one by one. The average running time of this algorithm is therefore significantly reduced from that of the existing burst scheduling algorithms. Our algorithms can also be used as algorithmic tools to speed up the scheduling time of many other void-filling scheduling algorithms.     

Bridge measurement of tunnel-diode parameters

A specific bridge measurement technique is presented for measuring the important small-signal parameters of the tunnel diode at frequencies up to 100 Mc and at all significant operating levels. Particular attention is paid to the problem of biasing the tunnel diode to eliminate instability in the negative resistance region which would otherwise prevent significant measurements being made in this region. Requirements for stable bias circuits are analyzed in detail and specific criteria for stable operation given. A circle diagram method is presented which allows the significant parameters to be determined from a set of measurements made for a sequence of bias voltages, at a chosen frequency. From the results, curves of shunt capacitance and conductance as a function of bias voltage may be plotted. Measurements made using a Wayne Kerr Type B.801 VHF Admittance Bridge on a particular tunnel diode are presented. The experimentally determined capacitance vs voltage curve is found to agree closely with the theoretical curve of the normal junction diode, with no pecularities through the negative resistance region. Further results show that approximate parameter values may be obtained even when oscillatory or bistable behavior prevents satisfactory measurement in the negative resistance region.     

Calibration of geometric parameters and error compensation of non-geometric parameters for cable-driven parallel robots

Accuracy is an important performance indicator that affects the research and industrial application of cable-driven parallel robots (CDPRs). The error sources of CDPRs include geometric parameters (GPs) and non-geometric parameters (NGPs). Typically, GPs can be calibrated by external measurement devices whose position is dependent on coordinate system parameters. To improve the calibration accuracy and robustness, an iterative calibration method is proposed to calibrate the coordinate system parameters and GPs, and the asymptotic convergence is proven. Moreover, considering the tight coupling and non-linearity of NGPs, we design an artificial neural network to compensate for the residual position errors caused by NGPs. Based on the hierarchical genetic algorithm, a synchronization optimization algorithm is developed to improve the approximate accuracy and generalization to residual position errors of unknown trajectories. With theoretical initial parameters, experiments for the calibration of GPs and error compensation of NGPs were performed on a 3-DOFs CDPR. Finally, the average position error of the end-effector is reduced to 1.3 mm and the maximum error is 1.9 mm.