高等别线纹尺中心线提取算法的研究

受制造技术、磨损以及污染等因素影响,对线纹尺大批量自动化检定技术的实现存在较大困难。在线纹尺特征的基础上,针对边缘对比度高但噪声严重的线纹尺,先边缘初定位将图像处理区域限制在线纹边缘区域,再边缘精定位,寻找边缘区域灰度变化最大的点,剔除不连续的边缘点后拟合边缘线,实现线纹中心线的提取。针对自身变形导致成像模糊的线纹尺,背景区域与线纹区域分别求取各列灰度均值,再利用最小二乘拟合直线求交点实现线纹中心线提取。对高等别三等标准线纹米尺多次检定,结果表明,同一刻线最大差值为1.4μm,标准差为0.66μm,提出的算法鲁棒性好,满足高等别线纹尺的检定要求。     

基于波数分辨的低相干干涉台阶高度测量系统的研究

提出一种基于波数分辨的低相干干涉台阶高度测量系统。由宽带光源发出的光通过光纤迈克耳孙干涉仪获取被测量信息,色散光栅将宽谱干涉光束色散成波长在空间连续分布的光片,由线阵CCD探测。将线阵CCD的各个像元探测到的各个波长干涉信号转换成对应的波数干涉信号。对于波数干涉信号,相邻两个干涉信号峰值之间的波数变化量与干涉仪光程差的绝对值呈正比。因此,利用此测量系统可实现对台阶高度等物理量的绝对测量。利用缩短测量系统中光纤迈克耳孙干涉仪的两个干涉臂的长度减小环境干扰对测量系统的影响,获得高测量精度。本测量系统的测量分辨率为6.03 nm。对一个高度为50μm的台阶重复10次测量,测量结果的标准差为6.8 nm。     

双频光栅纹影剪切干涉法对温度场的诊断

用双频光栅纹影剪切干涉法对无限热平板的自然对流温度场进行诊断。纹影系统光线从轴外入射造成的系统象散、彗差对剪切干涉图的系统误差可以通过减小入射角、增大纹影仪球反镜的曲率半径以及调节双频光栅的位置控制在给定精度范围内。     

衍射式光栅干涉测量系统发展现状及趋势

在车间条件下操作时,光栅干涉仪在测量精度方面优于He-Ne激光干涉仪.基于光栅干涉测量系统有一些特别的优点,导致其在高精密测量中用途不断增加.阐述了衍射式光栅干涉测量系统的工作原理和特点,同时详细总结了国际上生产和研究衍射光栅干涉测量系统的厂家和研究机构及他们的产品.并指出该系统的发展趋势和存在的问题,为衍射式光栅测量...     

测量托卡马克装置等离子体电子密度分布的远红外HCN激光干涉仪

本文介绍了用电磁波干涉的方法测量等离子体电子密度的原理、七道远红外HON激光干涉仪的结构及其在HT-6M托卡马克(TOKAMAK)装置上的测量结果.干涉仪的光源县一台腔长3.4m的连续辉光放电的HCN激光器,波长337μm;输出功率约100mW.干涉仪可以给出七道弦上的平均电子密度,最小可测相移为115条纹,时间分辨为0.1ms.也可以由七道弦上相移的线积分值通过非对称的Abel变换给出不同时刻的电子密度的空间分布或时-空分布的三维图形.     

激光干涉法测量硅高温环境下的线膨胀系数的实验研究

利用中国计量科学研究院自行设计的基于激光干涉法的材料线膨胀系数测量装置进行了材料线膨胀系数测量试验。该装置采用单频激光干涉，对称光路设计，其干涉仪分辨率小于1nm。实验过程中改进并完善了该装置，重新设计了加热炉，改进了实验方法，使该装置在800K以上的高温环境下能进行材料线膨胀系数的测量。在800K到1200K温度范围内，对单晶硅试样采用分段加热进行测量,并对样品变化过程及测量结果作了分析，得到了单晶硅线膨胀系数的曲线，实现了在1200K环境下采用激光干涉法材料线膨胀系数的纳米级测量。     

光栅干涉仪测量大偏差

光栅干涉仪测量大偏差包括有相位衍射光栅的干涉仪将光学精度引向高斜率的平面度测试。光栅将单光源输出分成两束光，在测试中又将两束光合并在一起。反射光产生的干涉图与具有实际光源尺寸１０倍波长的光源所产生的图形相同，从而提出系统“等效波长”概念。光栅干涉仪的...     

法布里-珀罗干涉仪测平板玻璃折射率的方法研究

根据光线在法布里-珀罗干涉仪中的传播特点,提出了测量平板玻璃折射率的方法 .首先对法布里-珀罗干涉仪中插入平板玻璃前、后所产生的相邻等倾干涉亮纹直径平方的差值和法布里-珀罗干涉仪内、外介质的折射率之间的关系分别进行了理论分析;然后搭建实验光路,使用移测显微镜对干涉亮纹直径进行观察和测量,在平板玻璃厚度已知的前提下,即可得出平板玻璃的折射率,且实验中观察到的现象和测量结果与理论分析相吻合.     

同时测量温度和曲率的光纤传感器

提出了一种基于光纤布拉格光栅和马赫-曾德干涉仪相结合的同时测量曲率和温度的光纤传感器.该光纤传感器在马赫-曾德干涉仪中熔接一段布拉格光纤光栅,其中马赫-曾德干涉仪由两个花生形结构单模光纤熔接而成.实验结果表明,马赫-曾德干涉仪的透射谱中干涉峰和光纤布拉格光栅透射谱中谐振峰对曲率和温度有不同的响应灵敏度,因此可以利用矩阵实现对曲率和温度的同时测量.实验中测得马赫-曾德干涉仪曲率灵敏度为-27.58nm/m-1,光纤布拉格光栅在一定的测量范围内对曲率的变化不敏感,马赫-曾德干涉仪和光纤布拉格光栅的温度灵敏度分别为0.038 69nm/℃和0.012 17nm/℃.该系统采用全光纤结构,光纤布拉格光栅嵌入到马赫-曾德干涉仪中,因而结构紧凑和简单,且易于实现.     

用CMOS线阵图像传感器测量透明材料的折射率

将衍射光栅干涉和CMOS线阵图像传感器技术相结合,提出了自动测量透明材料折射率的方法.介绍了用CMOS线阵图像传感器来实现透明材料折射率测量的基本原理和数据采集方法.采用曲线拟合计算条纹移动距离,提高了对干涉条纹移动量测量的准确性,折射率精度可提高到10-5数量级.     

楔块调整式Talbot干涉仪改变写入Bragg波长的调谐误差

在楔块调整式Talbot干涉仪中,光纤Bragg光栅的写入区为直接由相位模板衍射的±1级衍射光束形成的干涉条纹的近场干涉区,和由±1级衍射光束经两平面镜反射后形成的可调谐写入Bragg波长的干涉条纹的远场干涉区。在改变写入光纤光栅Bragg波长的过程中,光纤光栅的Bragg波长是由平面镜的交叉角决定的,而且,影响调谐精度的三种主要因素被控制在光纤光栅生产允许的范围内,即推动机构的位移误差系数Cd为～-0.08nm/μm,楔块的倾斜误差系数Cα为-0.15～0.23nm/(′),和转动机构的传动角误差系数Cβ为～-0.08nm/(′)。     

The use of circular optical grating for measuring angular rotation of mirrors

This paper explores the feasible use of circular optical grating for measuring the rotation of mirrors that are commonly found in micro-systems. Both theoretical and experimental results show that distortion of the circular grating that is projected onto the mirror surface is a simple function of the angular rotation of the mirror. The circular grating may readily be generated using a standard Michelson interferometer or an LCD projector. Through manipulating the distance between the interferometer and the mirror surface, the diameter of the optical grating may be varied. Furthermore, the additional use of a converging lens enables a significant reduction in the size of the grating: with simple laboratory facility, small circular grating of about 400 μm is achieved for use on micro-systems. With the use of more sophisticated optical elements, the angular rotation of even smaller micro-mirrors may be measured.     

Grating Interferometer Using ± 1st Order Beams for Step-Profile Altitude Difference Measurement

We propose a grating interferometer for step-profile altitude difference measurement. There are two main characteristics in this interferometer. The first is that the intensity distribution of the interference pattern is independent of the wavelength of the laser-diode used. No change of the intensity distribution occurs when the wavelength fluctuates. The second is that the measuring range is much larger than the wavelength of the light source because the spatial period of the grating is much larger than the wavelength. Sinusoidal phase modulating interferometry is easily applied to detect the phase variation of the interference pattern by vibrating the grating sinusoidally. The thickness of a 3.5-inch disk is measured with an accuracy of less than 0.5 μm.     

Analysis of period and visibility of dual phase grating interferometer

Dual phase grating interferometer may simultaneously achieve large field of view and high x-ray dose efficiency. Here, we develop a simple theoretical method to better understand the imaging process of the dual phase grating interferometer. The derivation process of fringe period and the optimal visibility conditions of the dual phase grating interferometer are given in detail. Then, we theoretically prove that the fringe period and optimal visibility conditions of the dual phase grating interferometer include that of the Talbot interferometer. By comparing our experimental results with those of other researchers, we find that when the positions of phase gratings are far away from the positions where the fringe visibility is optimal, the fringe period of the dual π -phase grating interferometer is twice the theoretical results under the illumination of polychromatic x-ray. This conclusion may explain the contradictory research results of dual phase grating interferometer among different researchers.     

High sensitivity HCN laser interferometer for plasma electron density measurements

This paper describes a high sensitivity 337 μm HCN laser interferometer for plasma electron density measurements. The plasma phase shift is transferred to a low frequency signal obtained by slightly shifting the frequency of the 337 μm radiation in the reference beam of the interferometer. The frequency shift is produced by diffracting the radiation of a cylindrical rotating blazed grating. A phase shift is deduced from the time variation of the zero crossings of the low frequency signal, giving a result which is independent of amplitude fluctuations. Using pyroelectric detectors, the interferometer has a time resolution of 100 μsec and a sensitivity of 10^-2 fringe.     

Analysis of nonlinearity in a high-resolution grating interferometer

Metrological feasibilities of a high-resolution grating interferometer (GI) based on a transverse Zeeman laser are investigated. When the grating pitch equals 20 μm, a resolution of 0.7 nm is obtained by means of a heterodyne signal processing method. The comparison of two approaches for determining the residual nonlinearity is presented. One is to evaluate the maximum residual error by determining the amplitude modulation degree of the measurement signal. The other is to do a high precision calibration with a differential dual-frequency interferometer that has a higher precision. The experimental results show that the nonlinearity is no more than 25 nm which fits well with the estimating result. Analysis of the depolarization effect of the grating indicates that it has little influence on the measurement accuracy.     

Absolute metrology by phase and frequency modulation for multiwavelength interferometry

A fiber interferometer for absolute distance measurements is presented whereby wavelength variation is achieved via a sinusoidal strain modulation of a fiber Bragg grating to generate a series of beat wavelengths. The interferometer employs fiber laser sources where the design is based on the use of narrow-bandwidth fiber Bragg gratings. The accuracy of the beat wavelengths is improved compared to the use of multiple wavelengths measured with conventional optical spectrum analyzers or available wavemeters. Initial measurements are presented for beat wavelengths of 254.74 mm and 27.4 m over an optical path difference of 200 mm and 3.8 m, respectively. Combined with a two (or three) wavelength interferometer, this technique has the potential for ultrahigh dynamic range metrology ranging over several meters while preserving subfringe resolution and a low system complexity.     

Optical transfer function analysis of Lau-Type grating atom interferometer

A grating interferometer composed of two transmission gratings in tandem irradiated incoherently was studied for an atom interferometer. Determination of its interference effect was made with consideration of the optical transfer function. An atom beam had a velocity distribution, which made the influence on the interference phenomenon. The calculated results show that the fringe (grating image) with relatively high contrast is obtained under a certain grating arrangement even if the interferometer is irradiated by a spatially incoherent polychromatic atom beam.     

Diffraction grating interferometers for mechanical characterisations of advanced fabric laminates

It is demonstrated that two grating interferometers with high spatial resolutions can successfully be applied for the mechanical characterisation of the advanced fabric composite materials. Based on these two techniques, the mechanical properties of two kinds of fabric laminates are obtained without assumption of uniform strain fields to be used in the characterisation approaches using the local strain sensors. The degree of the yarn crimp effects of the two laminates is compared in terms of the out-of-plane displacement derivatives. Especially, it is shown that the grating shearing interferometer is appropriate for the crimped fabric structure requiring a three-dimensional analysis. The modification from moiré interferometer to grating shearing interferometer is performed by introducing a Michelson interferometer modified for image shearing.