基于Radon变换的横向剪切干涉图的自动检测技术

在分析测试原理的基础上,指出了现有方法的横向剪切量获得的不足,根据剪切图和Radon变换在边缘处具有突变的特点,提出了一种基于Radon变换的横向剪切干涉图的剪切量的自动检测方法,首先根据二维图像的Radon变换结果,得到剪切图的横向移动方向,对图形进行方向校正。然后利用干涉图形的特点对图形在X和Y方向上进行Radon变换,得到剪切量。利用MATLAB进行编程,实验结果表明该方法具有很好的性能和较高的实用价值。     

Real-time measurement of glucose concentration and average refractive index using a laser interferometer

This study presents a non-destructive, highly precise optical metrology system for measuring the average refractive index of a liquid solution such that its glucose concentration can be derived. The metrology system is employed to measure the average refractive indices of samples with known glucose concentrations ranging from 0 to 200 g/l. By applying a regressional analysis technique to the experimental results, an analytical expression is derived to describe the relationship between the refractive index and the glucose concentration. An excellent agreement is observed between the experimentally determined values of the glucose concentration and the analytically derived results. For an assumed laser interferometer resolution of 1 nm, the measurement resolution of the proposed metrology system is found to be at least F=0.05 g/l, which is significantly better than that of F=2 g/l obtained using the polarimetric glucose sensor presented by Lo and Yu [A polarimetric glucose sensor using a liquid-crystal polarization modulator driven by a sinusoidal signal. Opt Commun, 2006; 259: 40–8].     

In situ surface topography measurement method of granite base in scanning wafer stage with laser interferometer

Topography of a granite surface has an effect on the vertical positioning of a wafer stage in a lithographic tool, when the wafer stage moves on the granite. The inaccurate measurement of the topography results in a bad leveling and focusing performance. In this paper, an in situ method to measure the topography of a granite surface with high accuracy is present. In this method, a high-order polynomial is set up to express the topography of the granite surface. Two double-frequency laser interferometers are used to measure the tilts of the wafer stage in the X- and Y-directions. From the sampling tilts information, the coefficients of the high-order polynomial can be obtained by a special algorithm. Experiment results shows that the measurement reproducibility of the method is better than 10 nm.     

A vision measurement model of laser displacement sensor and its calibration method

Laser displacement sensors (LDSs) use a triangulation measurement model in general. However, the non-linearity of the triangulation measurement model influences the measurement accuracy of the LDS, and the geometric parameters calibration process of the components of the LDS is tedious. In this paper, we present a vision measurement model of the LDS based on the perspective projection principle. Furthermore, a corresponding calibration method is proposed. A planar target with featured lines is moved by a 2D moving platform to some preset known positions. At each position, the world coordinates of calibration points are obtained by the cross ratio invariance principle and the linear array camera of the LDS is used for collecting target images. The simulations verify the effectiveness of the proposed model and the feasibility of the calibration method. The experimental results indicate that the calibration method achieves a calibration accuracy of 0.026 mm. Compared with the traditional measurement model, the vision measurement model of the LDS is more comprehensive and avoids a linear approximation procedure, and the corresponding calibration method is easily complemented.     

总装调对心干涉仪的设计与测量精度分析

为了满足大口径光学系统各分立元件的高精度对心要求 ,设计制造了总装调对心干涉仪。介绍了仪器的工作原理及关键结构工艺 ,并对影响偏心测量的因素进行了讨论。仪器的测量精度同被测镜的曲率半径及两测量点的间距有关。当被测镜的曲率半径小于 1.5 m、两测量点的间距为 5 0 0 mm时 ,其偏心测量精度小于 1μm,仪器的测量偏心角度的最小格值达 0 .12     

Study of high precise measurement of large diameters by a dual frequency laser interferometer

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A sinusoidal phase-modulating fiber-optic interferometer insensitive to the intensity change of the light source

In a conventional laser-diode sinusoidal phase-modulating (LD-SPM) interferometer, the wavelength of the LD is modulated by varying its injection current. The intensity modulation concurrent with the wavelength modulation leads to measurement errors. A photothermal-modulation method has been proposed to decrease the intensity change of the LD; however, this method cannot be used to measure vibration with a high frequency, and the beam diameter is too large to be used to measure minute objects. In this paper, we propose LD-SPM fiber-optic interferometer, in which the effect of the intensity change of the light source on measurement is eliminated. The diameter of the light beam is less than 0.5 mm. Using this interferometer, we measured displacements of a mirror driven by a piezoelectric transducer. The measurement repeatability is less than 1 nm.     

Compensation of output error due to the change of input intensity in an optical wavemeter based on a polarization interferometer

The optical wavemeter implemented with a polarization interferometer is simple and accurate. However, the wavemeter is very sensitive to the intensity of the input light. If the light is modulated or its intensity through the polarizer is varied due to a change of polarization state, the measurement error is increased and, in turn, the resolution and bandwidth are limited. In this study, the source of error, which is generated by a change of light intensity, is analyzed, compensated, and experimentally demonstrated. The measurement error due to fluctuated intensity can be reduced by compensating the output offset values of photo detectors. After compensation, the output errors are reduced to ±0.1 nm from ±1.85 nm at 1540 nm, ±0.12 nm from ±1.6 nm at 1550 nm, and ±0.31 nm from ±0.66 nm at 1570 nm.     

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介绍了用于保护HL-2A装置远红外激光干涉仪探测器的双色滤波器。根据双色滤波器理论优化设计了双色滤波器的外型和结构,并首次用于HL-2A远红外激光干涉仪密度测量系统。实验结果表明,当双色滤波器长度l=0.2mm,直径d=0.23mm,孔之间的间隔s=0.33mm时,双色滤波器能够很好地隔离68GHz的ECRH波带来的干扰,并对890GHz的HCN激光波有较好的透过率。     

双色滤波器在远红外激光干涉仪上的应用

介绍了用于保护HL-2A装置远红外激光干涉仪探测器的双色滤波器。根据双色滤波器理论优化设计了双色滤波器的外型和结构,并首次用于HL-2A远红外激光干涉仪密度测量系统。实验结果表明,当双色滤波器长度l=0.2mm,直径d=0.23mm,孔之间的间隔s=0.33mm时,双色滤波器能够很好地隔离68GHz的ECRH波带来的干扰,并对890GHz的HCN激光波有较好的透过率。     

EAST远红外激光干涉仪与密度爬升实验研究

利用EAST装置单道远红外HCN激光干涉仪测量了等离子体中心道(R=1.82m)线平均电子密度。通过充气加料连续提升主等离子体密度,首次在EAST装置上观察到偏滤器等离子体的三种不同状态：低再循环(偏滤器靶板处等离子体温度较高,密度较低),高再循环(偏滤器靶板处等离子体温度较低,密度较高)和脱靶(偏滤器靶板处等离子体温度和密度都很低)等离子体状态。分析了EAST偏滤器在这三种不同状态下的物理现象。     

Sinusoidal phase-modulating laser diode interferometer insensitive to the intensity modulation of the light source

In a conventional sinusoidal phase-modulating laser-diode (SPM-LD) interferometer, the wavelength of the LD is sinusoidally modulated by varying its injection current. However, the intensity modulation is associated with the wavelength modulation, which affects the measurement accuracy. We propose an SPM-LD interferometer insensitive to the intensity modulation of the light source, in which the influence of the intensity modulation is eliminated by choosing the appropriate sinusoidal phase modulation depth. Computer simulations and experiments are performed for real-time displacement measurement with the proposed SPM-LD interferometer. The measurement accuracy has been improved and the measurement repeatability is less than 1 nm. No additional components are required in our proposed method that leads to a simple system compared with the other previously proposed methods.     

微型石英敏感平板玻璃零件参数的激光视觉测量研究

高精度、快速非接触的平板玻璃零件的几何参数测量,已成为相关生产领域的主要问题,也是激光光谱学的一个重要应用方向。平板玻璃零件几何参数的准确检测不仅有助于加工工艺的改进和产品装配精度的提高,还可以实现按参数分档管理。为实现微型石英敏感平板玻璃零件参数的精密测量,提出了一种基于激光与视觉图像处理技术的多参数测量方法,设计了由自适应同轴视觉检测单元和激光视觉厚度测量单元构成的测试系统。为了保证其中的半导体激光器LD(laser diode)能提供稳定的光源,设计了一种恒功率驱动控制系统。在亚像素图像处理中给出了改进的亚像素边缘定位算法,实现了二次曲线特征边缘亚像素精确定位。利用检测出的曲线边缘点数据,通过定义一个新的误差函数并最小化,可以计算出微型石英敏感平板玻璃零件参数,从而实现图像特征参数的精确提取。在实验室条件下进行微型石英敏感平板玻璃零件几何参数的检测试验,测量结果的平均偏差优于2 μm。该方法稳定性好,测量精度高,满足微型石英敏感平板玻璃零件参数检测的精度要求。     

拼接干涉仪在控制装校面形中的应用

通过对比大口径光学元件夹持不当时全口径与局部口径之间的图像关系,研究局部面形控制的新方式。并与高精度的大口径干涉仪进行比对测试,验证拼接干涉仪的测试精度。实验表明,拼接干涉仪局部测试精度可达50 nm（PV值）,空间分辨力高达5 mm-1,可以实现中频段的装校监控。使用拼接干涉仪扫描测试全口径面形,测试不确定度小于100 nm,与600 mm的大口径干涉仪测试结果差别小于0.04（波长=632.8 nm）。     

Design and operation of a laser scanning system

Design and operation of a laser scanning system based on a synchronized scanning geometry is described. Results for scanning plane and cylindrical surfaces are reported. Deviations of the experimental results from that of the expected theoretical ones are presented. The described system offers a good reproducibility and results agree well with the theory. The results obtained from our system are satisfactory and show a promise in order to be used in the real applications. The reported approach can also be used in the design of a three-dimensional vision system.     

神光-III激光装置时标激光和任意反射面速度干涉仪探针光源产生技术

在惯性约束聚变研究中, 时标激光是对物理诊断数据进行分析的重要时间标尺, 而任意反射面速度干涉仪(VISAR)光源则是冲击波精密诊断必不可少的探针光源. 通过对物理需求的分析, 提出对时标激光与VISAR光源共用脉冲产生单元, 采用时分复用技术实现二者在同一台幅度调制器上的精密整形, 经1×2分束后再通过声光开关进行选择输出, 从而降低了系统造价, 便于集中控制. 采用了脉冲稳偏、高稳定空间放大、高精度温控谐波转换技术及可快速插拔精密复位的光纤耦合和传能技术, 实现了时标和VISAR光源脉冲的高稳定输出. 研制的时标激光系统可产生与主激光高精度同步的12路二倍频、4路三倍频时标信号, 为神光-III激光装置物理实验提供了重要的时间基准. 产生的VISAR光源脉冲在经过光纤系统和Nd: YAG棒状放大器后, 通过温控LBO晶体倍频, 然后经1 mm芯径的多模传能光纤传输至成像型VISAR系统, 为物理实验提供了单纵模、高亮度、可精密整形的脉冲激光. 系统已用于VISAR诊断物理实验, 获得了完整的冲击加载、减速的图像, 从而为冲击波调速及相关高压物理实验提供了可靠的技术手段.     

Application of laser speckle analysis for the assessment of cementitious surfaces subjected to laser cleaning

This paper focuses on the application of laser speckle technique for the assessment of the effectiveness of laser cleaning of cementitious surfaces. Laser speckle-based methods are non-contact, highly resolving techniques for the measurement of displacement, rotation, and strain of an illuminated area on a rough surface. Since the intensity of reflected light depends on the geometrical microstructure and colour of the samples, any alterations of the surface result in different speckle images. Analysis of speckle images presented here is based on the analysis of the distribution of intensity of reflected light obtained in a selected plane, and analysis of statistical parameters describing such distribution (skewness and kurtosis). A wide range of laser-cleaned mortar samples with different geometrical microstructure and moisture content has been subjected to the assessment by He-Ne laser. Laser speckle method has been successfully used to identify the effectiveness of the laser cleaning process with respect to different surface conditions. It appears that the changes in kurtosis and skewness should be mainly associated with the alterations of geometrical microstructure. Whereas, mean light intensity seemed to depend predominantly on the mortar's absorption characteristics (colour).     

用于冷原子干涉仪激光时序控制的DDS跳频系统设计与实现

为了满足冷原子干涉实验对时序控制的需求,设计并实现了一个基于LABVIEW软件的激光时序控制DDS系统,其工作过程为通过设计的LABVIEW上位机软件输入需要产生的频率和频率间隔时间,ARM芯片根据LABVIEW软件发送来的控制信息实现对射频信号芯片的控制,CPLD芯片用来控制射频信号之间的时间间隔,最后DDS芯片产生与控制信息相对应的射频信号。与目前同类装置相比,系统实现了跳频时间和频率更加精确和工作稳定性更好。经过系统的调试分析以及性能测试,DDS跳频系统能够满足原子干涉仪激光时序控制需求。通过测试DDS装置,DDS装置能够输出准确输出射频频率值,并且射频频率时间间隔能精确到微秒。DDS装置可以有效控制冷原子干涉仪的激光时序,在探询时间为120毫秒且重复率为2.2赫兹的情况下,冷原子重力仪的重力测量灵敏度达到 。