Rapid transfer alignment of laser SINS using quaternion based angular measurement

A novel rapid transfer alignment algorithm for laser strapdown inertial navigation system (SINS) is studied. Transfer alignment have typically relied on velocity measurements from the master SINS as the source of alignment information, but lever arm error must be compensated accurately while velocity information is utilized, all most every quaternion based error model is nonlinear, so nonlinear filtering algorithms are need, suffering from computational complex and large error. Aim at these problems, a novel improved rapid transfer alignment algorithm formulation is presented, applying quaternion to built the process and measurement models, the improvement employs a special manipulation of the measurement equation results in a linear pseudo-measurement equation, thus the classical linear Kalman filter is employed to estimate the state, need not lever arm error compensation, results in the reduce of computational burden. Observability analysis of this new transfer alignment algorithm has been done based on the piece-wise constant system (PWCS) method, results show that the presented algorithm can accomplish the initial alignment task perfectly. A transfer alignment simulation system is also developed for the evaluation and analysis of the presented algorithm, simulation results are confirmed with the theoretical conclusion, which can achieve the transfer alignment accuracy about 1 mrad within 10 s.     

基于空间二进制编码的3 D形貌测量方法

介绍了一种基于空间二进制编码的非接触３ Ｄ 形貌测量方法。它用一台ＬＣＤ 投影仪对被测物体表面进行空间编码,再用一台ＣＣＤ 摄像机获取物体编码信息,最后用三角法原理从摄像机图像中获取三维形貌数据。提出了基于三角法的空间二进制码的重要特性,描述了高效编码的构造方法。用这个构造方法构造出一个完全数字化的７ 位字长的二进制编码。基于这种编码的３ Ｄ 形貌测量方法在被测物体表面非常不连续和非构造的环境下取得了良好的测量结果。     

光电编码器单莫尔条纹测速方法

为了提高编码器的测速精度,研究了基于希尔伯特-黄变换的光电编码器单莫尔条纹测速方法。首先,利用AD采集编码器的单路莫尔条纹光电信号,并将信号序列通过EMD变换,滤除直流分量;然后,利用希尔伯特变换求出信号的相位变化,并通过差分运算求取信号的瞬时频率;最后,结合编码器的具体参数求取编码器的转速。实验结果表明:对某21位编码器进行测速实验,测速误差均方差由0.022 4 rad/s降低到0.013 4 rad/s。此方法测速稳定性高,抗干扰能力强,可用于速度精度要求较高的测速场合。     

基于原始波形测量的脉冲电场探测器

介绍了脉冲电场微分测量和原始波形测量的基本原理,设计研制了一系列不同灵敏度的脉冲电场原始波形测量系统,分析了脉冲电场探测器的理论修正模型。该测量系统主要包括天线模块、积分器模块、放大和驱动模块以及光电传输模块,利用同轴型TEM小室对测量系统进行了时域标定。结果表明:测量系统的前沿响应时间小于1.0 ns,系统输出脉冲平顶在10.0μs内下降不超过5%,测量系统输出幅度与电场强度在20 dB的动态范围内呈线性关系,该系列探测器可以用来测量最小10 V/m、最大100 kV/m的电场强度,满足高空电磁脉冲标准环境的测量要求。     

基于影像-位置序图的光学测姿方法

针对空中飞行目标姿态测量问题,提出一种新的光学测姿实现方法,对光学多站测姿实施复杂、单站测姿成像要求高等问题进行改进。该方法充分利用了目标飞行连续影像信息和相应的外弹道位置数据,首先通过目标位置数据确定目标轴线向量起点,根据轴线向量终点的约束方程确定向量终点;然后通过偏航角、俯仰角与轴线向量起点、终点的关系,解算目标姿态角;最后通过姿态连续变化的先验信息,确定解算结果的唯一值。仿真计算和精度分析表明,可实现测姿误差总体小于1,表明提出的方法兼顾了便捷性和测量精度,具有较高工程应用价值。     

基于傅里叶变换解相法的像增强管多参数测量

提出一种基于傅里叶变换解相法的像增强管成像质量多参数同时测量的新方法。将一正弦光栅图输入到像增强管,如果像增强管成像质量存在问题,将使图像输出发生改变,形成一变形条纹,采用傅里叶变换解相法对输出的变形条纹进行解相,可同时获得放大率、放大率不均匀度、枕形畸变、桶形畸变、蛇形畸变、剪切畸变等相关信息,对测量系统进行标定,即可实现对上述参数的同时测量。实验测得中心放大率与设定放大率的差值到了10-3量级,测得的畸变和畸变真值两者差异在0.4 pixel以内,结果证明了方法的有效性。     

基于图像的树木测量方法

树木是城市绿化、美化的一个重要的组成部分,具有重要的科学、历史和观赏价值。传统的树木生长信息采集方式,利用人工使用卷尺或不易操作、低效率和复杂麻烦的大型测量仪器等,费时、费力、准确度又不高。结合计算机视觉、数学几何模型等技术,设计了一种新式的树木高度、胸径和冠幅测量模型,提出了基于图像的树木测量方法和实现了树木信息采集软件系统;为了得到更精确的测量结果,使用摄像头标定技术和坐标校正方法对图像进行畸变矫正;并且利用正交试验分析法分析本设计使用的最佳拍摄环境,最终相对误差控制在4%左右。本方法具有携带方便、操作简单、适用面广、准确度高的优势。     

空间编码与灰度投影相结合实现高效3-D形貌测量的研究

介绍了一种结合空间编码与灰度投影来实现高效三维形貌测量的方法。用空间编码完成对被测空间的粗略编码,用灰度投影完成精确编码,将它们结合起来得到被测物体表面丰富的编码信息,作为一种基于三角法的三维形貌测量方法,能够在物体表面非常不连续和外部光照造成的背景光强分布不确定的情况下工作良好。同时,与传统的空间编码方法相比,它大大提高了空间编码的效率。实验表明,该方法用５ 幅图像取得了与灰度码１０幅图像相当的测量结果。     

CCD立靶光源适用性的图像判定技术

针对CCD立靶在室外自然环境下和配有主动光源的工程应用,提出一种基于背景图像分析的光源适用性判定方法。在图像采集与实际测试状态一致的条件下,采集无目标背景图像,通过数字图像处理,确定采集视场内各个位置处图像的灰度变化范围f及灰度均值fmean,若背景图像中各个像元的fmean2f,即认为CCD立靶可以对目标图像进行可靠识别。实验室及外场CCD立靶应用实验结果验证了该判据的有效性和可靠性。     

Low-coherence interferometry based roughness measurement on turbine blade surfaces using wavelet analysis

In this paper, a non-contact optical system, a low-coherence interferometer (LCI), is introduced for the purpose of measuring the surface roughness of turbine blades. The designed system not only possesses a high vertical resolution and is able to acquire the roughness topography, but also it has a large vertical scanning range compared to other commonly used optical systems. The latter characteristic allows us to measure turbine blades surfaces with large curvature without collisions between the lens and the measurement object. After obtaining the surface topography, wavelet analysis is applied to decompose the original surface into multiple bandwidths to conduct a multiscale analysis. The results show that the developed LCI system proofs a good performance not only in obtaining the surface topography in the roughness scale but also in being able to measure surfaces of objects that possess a complex geometry in a large vertical range. Furthermore, the applied biorthogonal wavelet in this study has performed good amplitude and phase properties in extracting the roughness microstructures from the whole surface. Finally, the traditional roughness parameters, such as the mean surface roughness S_a and the Root Mean Square (RMS) roughness S_q, are evaluated in each decomposed subband and their correlations with the scale of each subband are analyzed.     

基于线阵CCD空间滤波效应的航空相机像移速度测量方法

基于空间滤波测速原理,提出了利用线阵CCD空间滤波效应进行航空相机像移速度测量的新方法。对线阵CCD输出图像进行隔行采样,模拟了多狭缝的空间滤波特性,实现了对航空相机像移速度的光学非接触测量。通过研究空间滤波器的功率谱密度函数,对影响线阵CCD空间滤波特性的关键因素进行了特性分析,并在实验上验证了利用线阵CCD推扫图像模拟多狭缝空间滤波器测量像移速度的可行性。结果表明,对于5～53.2 mm/s范围内的像移速度,测量误差导致的像移量误差不大于1/3 pixel,能够满足航空相机像移补偿精度的要求。     

Fiber chromatic dispersion measurement based on wavelength-to-time mapping using a femtosecond pulse laser and an optical comb filter

A novel method for the measurement of chromatic dispersion of an optical fiber based on wavelength-to-time mapping using a femtosecond pulse laser (FSPL) and an optical comb filter is proposed and experimentally evaluated. In the proposed approach, the spectrum of an ultrashort optical pulse generated by an FSPL is sliced by an optical comb filter. The spectrum-sliced optical pulse is then coupled into the optical fiber under test. Thanks to the chromatic-dispersion-induced wavelength-to-time mapping in the optical fiber under test, a time-domain waveform similar to the sliced spectrum is generated at the output of the optical fiber, with different frequency components having different time delays. The time delay vs. frequency data are then recorded for the estimation of the chromatic dispersion by using least square fitting. Chromatic dispersions of two types of optical fibers with different lengths are tested. The measured dispersion values agree well with those measured by the conventional modulation phase shift (MPS) method.     

Differential confocal measurement method of linear scanning based on dual linear array camera北大核心CSCD

针对目前微观三维表面形貌测量技术中存在检测效率和测量范围较小的问题,提出一种基于双线阵相机的线扫描差动共聚焦三维形貌测量方法。采用线扫描光源,利用线扫描拼接算法,分别合成焦前和焦后图像;再利用差动算法获得样本位于测量区域的差动图像,结合预先刻度的轴向响应曲线,完成样本的三维形貌还原,实现大范围高效测量。实验结果证明:基于双线阵相机的线扫描差动共聚焦三维形貌测量方法在相同时间内测量范围和测量效率分别是白光干涉仪的16.48倍和6.59倍,并且该方法在测量过程中不需要停顿,只需实现一次对焦,就可以对样品进行连续不间断的扫描检测。研究成果为满足智能制造中在线在位、实时高效、大范围测量的检测需求提供依据。     

An improved method for shape measurement using two-dimensional digital image correlation

Shape measurement is a significant application of digital image correlation (DIC). An improved method that combines a rotatable plane mirror is proposed to measure the shape of an immovable object. In this method, two images, one before and the other after rotating the plane mirror, are obtained and then in-plane translation which related to the shape of the detected object can be calculated by the use of two-dimensional digital image correlation (2D DIC). The relationship between the in-plane translation and the shape of the object is described. Experimental results show that the proposed method is feasible for shape and distance measurement with high accuracy.     

基于旋滤波的散斑干涉图预处理方法

介绍了旋滤波算法中窗口大小变化对滤波效果的影响,得出旋滤波的窗口应该取在约1/4条纹宽度的结论。处理了大散斑噪声的干涉图,发现窗口尺寸必须超过散斑尺寸才能得到比较好的滤波效果。确定了旋滤波算法应用的范围是大于散斑尺寸,且在1/4条纹宽度处比较合适。针对滤波后条纹对比度降低的问题,使用灰度拉伸的方法进行对比度增强。     

不同后处理方法对溶胶-凝胶SiO2膜层抗污染能力的影响

以正硅酸乙酯作为前驱体,利用碱催化方式制备了SiO2溶胶,采用提拉法在K9基片上镀制SiO2单层薄膜,分别用热处理、紫外辐射处理、氨水加六甲基二硅胺烷气氛处理和酸碱复合膜4种后处理法对膜层进行处理,采用分光光度计、红外光谱、扫描探针显微镜、静滴接触角测量仪、椭偏仪等分析了薄膜的特性,通过真空环境加速污染实验对处理前后的膜层进行抗污染能力对比,结果表明:在碱性SiO2膜层上加镀一层酸性SiO2膜的复合膜层整体透过率仍保持在99%以上,疏水角达到128°,膜层真空抗污染能力大大加强。     

A novel method for simultaneous measurement of current and voltage using one low-birefringence fiber

A novel method for simultaneous measurement of current and voltage employing a single monomode low-birefringence (Lo-Bi) fiber is described. This uses the Faraday effect for detection of current and the Kerr effect for detection of voltage. The waveform of the output light intensity due to the Kerr effect has been detected and the Kerr constant was measured as 5.4×10⁻¹⁶ m/V⁻² at 25°C. Theoretical analysis shows that the current component can be measured free from the influence of the voltage component and the two components can be easily separated.     

毫米级高分辨率的混沌激光分布式光纤测温技术

近年来,随着分布式光纤传感技术在各大基础设施健康监测领域的广泛应用,人们对能够实现毫米量级精准定位和监测技术的需求日益增长.本文提出了一种基于宽线宽混沌激光的高分辨率分布式光纤测温技术.实验通过改变光反馈混沌源的偏振匹配态和反馈强度等外部参数,产生了–3 dB线宽约为7.5 GHz的宽线宽混沌激光,并在300 m传感光纤实现了空间分辨率为7.05 mm的分布式温度测量.同时,为了抑制光源线宽增加造成的布里渊增益谱恶化,在泵浦路中引入了时间门控技术,其中经脉冲调制后的泵浦光峰值功率提高了约9.5 dB,同时脉冲调制使混沌互相关锁定于脉冲持续时间内,从而布里渊增益谱的信号背景噪声比由约2.28 dB提升为4.55 dB,最终实现了空间分辨率为3.12 mm的分布式温度测量.     

基于GoogLeNet和空间谱变换的高光谱图像超分辨率方法

为了提高高光谱图像的空间分辨率,提出了一种基于GoogLeNet和空间谱变换的高光谱图像超分辨率(SR)方法.设计出遥感图像的光谱SR框架,对图像中不同反射光谱进行提取;采用GoogLeNet的稀疏编码对粗像素光谱进行放大,并投影到高分辨率字典上,将潜在SR表示进行反转,以获得超分辨光谱;为了提高图像重构的保真度,利用...     

人眼光焦度客观式测量的图像采集处理研究

描述了人眼光焦度的测量原理。设计了一套光焦度测量采集处理系统。该系统是以一束红外脉冲光射入眼底 ,由CCD接受反射的眼底图像 ,将CCD图像进行数字化处理并存入SRAM。CPU采用重心法计算图像环中心坐标 ,以扫描法计算图像环的长、短轴 ,最后计算出人眼的光焦度值。研究结果表明 ,光焦度测量采集处理系统工作可靠、实用 ,能准确地测量人眼光焦度值