光电编码器LED光源的准直

由于发光二极管(LED)光束的准直度对光电编码器性能影响很大,研究了LED光束的准直特性.分析了光源辐射角对光栅光通量的影响;运用图像旋转理论和频域分析方法,导出了莫尔条纹透光特性函数式,揭示了光源准直度参数对莫尔条纹函数特性的影响.获得了与光束准直度相关的不同透光缝宽度下的莫尔条纹仿真波形,分析了光源准直特性指标对莫尔条纹对比度以及光栅间隙的影响.理论计算结果表明,当透光缝宽度减小5 μm时,莫尔条纹图像的对比度下降17.66%,实验结果与理论仿真波形吻合,表明文中提出的莫尔条纹函数式可为高精度和高可靠性编码器没计和生产提供参考.     

光栅传感器的各部分几何参数对莫尔信号调制度的影响

本文以非相干照明的成像理论为依据,推导了计算莫尔光电信号调制度的理论公式。由公式可知,莫尔光电信号的调制度与光源的几何形状及尺寸、光栅的衍射效应、开口比、光栅副间隙、接收光栏的几何形状与尺寸等因素有关。讨论了非准直光照明时,光栅副间隙对莫尔条纹的周期和倾角的影响,比较了非准直光和准直光照明下莫尔光电信号调制度的变化情况。井以实验验证了理论公式。     

采用Matlab图形系统分析乘法倍频后莫尔条纹信号的波形

采用Ｍａｔｌａｂ图形系统对计量光栅输出的莫尔条纹原始信号进行了计算机仿真,并利用Ｍａｔｌａｂ函数计算、绘制出经乘法倍频后的莫尔条纹信号的波形。通过对仿真结果的探讨与分析,为提高倍频后莫尔条纹信号的质量提供了依据。     

非均匀采样莫尔条纹信号的分析与处理

为了动态、实时地测量光电编码器在变速转动情况下的细分误差,提出了一种莫尔条纹信号的非均匀采样分析与处理方法。利用傅里叶级数原理构造了实际情况下的莫尔条纹信号方程,根据编码器在不同转速下的实时采样,揭示了莫尔条纹信号的非均匀采样特征。鉴于信号采样的非均匀性,采用曲线拟合的最小二乘法重构莫尔条纹信号,利用离散傅里叶变换算法分析重构信号并求出波形参数。通过信号参数与细分误差的关系式,测量了编码器动态细分误差。采用该方法对21位绝对式光电编码器莫尔条纹信号进行了分析和处理,两次测试得到其动态细分极值误差为+3.21″、-4.69″和+3.45″、-4.81″。实验结果表明,该方法可以有效地分析和处理编码器在非匀速转动下产生的变频莫尔条纹信号,精确地测量编码器的动态细分误差,为工作现场编码器误差的实时检测与修正奠定了基础。     

一种新型纳米光栅传感器的理论研究

为了开发结构简单，抗干扰能力强的纳米测量精度光栅传感器，对基于二次莫尔条纹信号的纳米测量精度光栅传感器的测量原理进行了理论分析，通过仿真计算，其测量分辨力可达到5．40〉（10^10-10m，测量精度可达到纳米级。此外，对指示光栅和标尺光栅不平行时对二次莫尔条纹信号质量的影响进行了理论分析和仿真计算。     

空间精密位移信号软细分方法研究

为了解决高精度数控装备对位移传感器高分辨力反馈的需求,本文提出通过对空域信号特征的分析,从时空变换理论模型的角度去研究位移测量问题;利用光栅周期性栅线作为等空间位置触发位置采样建立空间序列模型;通过对光栅莫尔条纹信号自适应预测细分模型阶数与系数估计算法完成光栅莫尔条纹信号细分。实验结果证明此方法可以实现光栅莫尔条纹400倍细分,细分精度优于信号周期的±1%。此细分方法利用光栅刻划精度,信号细分精度与光栅信号波形质量无关,在不增加硬件的条件下实现光栅莫尔条纹精密细分,具有重要实际应用价值。     

采用光栅自成像技术的小型绝对式矩阵编码器

采用光栅自成像技术，可获得高质量的莫尔条纹信号，本文介绍了一种采用光栅自成像技术的小型绝对式矩阵编码器。     

光栅发讯器莫尔条纹光强分布及位移——光强关系

<正> 光栅发讯器莫尔条纹光强分布及位移—光强关系,在很大程度上决定了光电转换器件输出信号的幅度,波形及信号调制度等重要性质。本文推导了莫尔条纹光强分布及位移—光强关系的普遍表达式,并分别对光闸式,游标式及横向莫尔条纹进行了讨论。从光强表达式引出的莫尔条纹几何参数与文献(1)完全一致,从而把莫尔光强分布与几何计算统一起来。本文只讨论振幅光栅,光栅具有较长的空间周期与不变的空间频率,由平行的均匀的非相干光垂直入射,光栅组间无间隙或具有小间隙,光电器件直接接收从光栏出射的莫尔光强。     

光栅莫尔条纹细分技术的研究

光栅是一种精密测量装置 ,测量原理是以光栅移动形成的莫尔条纹为基础。介绍输出正弦信号和方波信号的光栅在位移测量中脉冲细分的常用方法 ,分析其中两种方法的电路与波形并对其进行实验 ,验证细分原理的正确性     

成象式莫尔条纹系统中条纹宽度的研究

分析了成象式莫尔条纹系统中光栅轴向调整精度和栅线夹角调整精度对莫尔条纹宽度的影响，探讨了该系统结构参数的选择与设计．     

The use of moiré patterns to determine the source and degree of adistortion in scanning electron microscopes

Scanning electron microscope images are subject to an appreciable amount of non-linear distortion which must be allowed for when quantitative analyses are made. A method is described for measuring the distortion by the use of moiré patterns. These greatly magnify any non-linearities and it is possible to measure distortions as small as 0?1%. In addition, the use of moiré patterns permits a separation of the distortion produced in the cathode-ray display tube from that occurring in the microscope itself.     

Radial grating master making

Automatic measuring systems, based on the formation of moiré interference fringers between two gratings, are used for the incremental control of linear and rotary movements in machine tools and instruments. Photoetched chrome-on-glass radial grating masters and photocopies of high quality can be made on a cnc rotaty table using positive photoresists, a continuous ultra-violet light source, and proximity printing in yellow safe-light illumination     

子区域拼接数字莫尔条纹非球面检测的理论分析

利用moire 条纹测量三维物体表面,由于这种方法具有非接触性、自动化程度高、速度快等特点。并且不需要补偿器、辅助镜、全息图等辅助组件就可以实现非球面检测,使其得到广泛的应用。但在测量大口径、高陡度非球面以至离轴非球面时,受到光栅面积、CCD相机分辨能力等因素的限制;存在着一些困难,就此问题,本文提出了利用数字莫尔条纹（结合数字相移技术）进行子区域拼接的非球面检测方法,给出了这种方法的基本原理,阐述了方法的数学实现过程,结果显示子区域拼接数字莫尔条纹法可以作为补偿检验以外的另一种非球面检测方式     

基于莫尔条纹测量扭转变形角的方案研究

为了精确检测大型光电测量设备之间的三维变形,提出了基于双光栅干涉产生莫尔条纹测量的一种高精度光学测角方法。采用平行光管模拟设备,通过微调机械结构调节平行光管的扭转角来模拟三维物体的扭转变形,在独立的地基平台上进行测量实验。通过实验比较不同的设计方案,采用使CCD靶面在平行光管内像面处安装固定的实验方案;并采用滤波细化等图像处理方法对采集的莫尔条纹进行处理得到条纹宽度,进而根据条纹宽度变化通过数学模型计算出扭转变形量。实验结果表明,当微调机构使平行光管在±7'的视场范围内旋转时,该方案可以得到较为清晰的莫尔条纹图像,经过算法处理后,当莫尔条纹宽度在1615~1712 范围内时,扭转角的测量精度为4.3"(3 )。该方法满足了设备间扭转角高精度测量的要求,为提高光电测量设备的测量精度奠定了基础。     

Modified color CCD moiré method and its application in optical distortion correction

The characterization and correction of lens distortion is an important part of optical measurement. This work analyzes the formation mechanism of color fringes and multiplication moiré, and discusses modification of the color CCD moiré method for correcting lens distortion. A demosaicing algorithm was used to simulate the color fringes in a CCD moiré pattern. We then performed a detailed analysis of the carrier field, and adopted a universal polynomial distortion model to characterize lens distortion, which increased the accuracy of distortion correction. Comparison experiments verified the feasibility of the modified method and the correctness of the formation mechanism for color CCD moiré. The modified method was then applied to lens distortion correction in the DIC measurement process, effectively reducing errors in displacement measurement.     

A nano-scale alignment method for imprint lithography

A novel nano-scale alignment technique based on moiré signal for room-temperature imprint lithography in the submicron realm is proposed. The moiré signals generated by two pairs of quadruple gratings on mold and wafer are optically projected onto two photo-detector arrays, then the detected moiré signals are used to estimate the alignment errors in the x and y directions. The experiment results indicate that complex differential moiré signal is sensitive to relative displacement of the mold and wafer, and the alignment accuracy obtained in the x and y directions and in ϑ are ±20 nm, ±25 nm and ±1 μrad (3σ), respectively. They can meet the requirements of alignment accuracy for submicron imprint lithography.     

基于CPLD的光电编码器测量系统

为了提高光电编码器的反馈精度和消除正交波形中的抖动,提出了一种基于复杂可编程逻辑器件且具有倍频鉴相和滤波功能的光电编码器测量系统。介绍了光电编码器测量原理,将系统划分为滤波鉴相、倍频、计数3个模块,并对这3个模块进行了电路设计和仿真。仿真结果表明,该设计方法能够满足高精度伺服电机正交编码的信号处理要求。     

Residual stress interference by two micro-Vickers indentations

An electron beam moiré method is employed to measure the residual strain produced by a Vickers indenter in a WC-4,7wt.% Co specimen. Line gratings 57μm wide by 45μm high, with a pitch of 87nm, are written by electron beam lithography. Two interior regions of the grating are loaded by the micro-Vickers indenter with 9.8N for 30s. The residual stress interference phenomena caused by two impressions of the Vickers indenter are estimated by using the displacement fringes recorded with the aid of an electron beam moiré (EBM) technique. The measured residual stresses are fitted to the theoretical values estimated by two available models such as Yoffe model and CME (Chiang-Marshall-Evans) model.     

Introduction to the computer image processing of electron micrographs of two-dimensionally ordered biological structures

Methods are described for the analysis of electron micrographs of regular biological objects. Fourier-based processing of one-dimensionally ordered arrays is described by way of introduction, before analysing two-dimensional crystals in projection with the aim of enhancing signal:noise ratio and thus of feint features that were initially obscured. This form of analysis is then extended to decomposing the moiré patterns formed when sheets overlap, thereby enabling the separation of interfering image patterns. Analogous forms of an analysis can also be applied to objects with rotational symmetry. Methods for treating the effect of the microscope imaging system and compensating for lattice disorder in crystalline specimens are also discussed.     

Micro-strain distribution around a crack tip by electron beam moiré methods

The microscopic deformation around a crack tip in a small tensile specimen of aluminum was measured by using electron beam moiré methods. The tensile test was carried out in a scanning electron microscope(SEM) by using specially designed small tensile testing apparatus for an SEM. A line grating with a pitch of 87 nm was written at the crack tip by electron beam lithography. SEM images of the grating contained(original) moiré fringes at certain magnifications without loadings on the specimen. The displacement and strain in the region 10 to 50 μ m from the crack tip were evaluated by analyzing the (mismatch) moiré fringes. Measured strains normal to loadings(longitudinal strains) near the crack tip were found to be comparable to those estimated using linear elastic fracture mechanics(LEFM), for the lowest load, and elastic-plastic fracture mechanics, at effective crack tip position located within the actual crack tip. The exponent of the strain singularity in the vicinity of the actual crack tip changed with applied stress, ranging between ?0.64 and ?1.0. The measured crack tip opening displacement(CTOD) values disagreed with CTODs based on the Hutchinson-Rice-Rosengren(HRR) field, the Dugdale model, and LEFM. The experimental plastic zones spread from the line of crack extension up to an angle of about 60°, as expected from LEFM theory.