一种非接触测量光学零件厚度的方法

为了实现光学零件厚度的非接触测量,设计了一种基于电光扫描的非接触测量方法。采用电扫描技术控制光开关,形成半径依次减小的环状光束,经过锥透镜后在光轴上形成连续移动的光点,当光点瞄准待测光学零件表面时,反射能量出现峰值,即定位了待测零件的表面,进而获得光学零件的几何厚度。建立了测量平板零件厚度和透镜中心厚度的数学模型;从理论上探讨了该方法的测量范围和测量精度。结果表明:设定锥面镜口径为100mm,材料折射率为1.52,当锥面镜的锥角从1°变化到40°时,测量动态范围可以从5507mm变化到26mm;当测量范围为26mm时,测量精度可以达到2.5μm。该方法可基本满足目前光学零件中心厚度的测量需求。     

Wide measurement range scanning heterodyne interferometer utilizing astigmatic position sensing scheme

A scanning heterodyne I/Q-interferometer scheme is proposed to overcome phase ambiguity caused by the periodic nature of its phase-dependent signal. A position sensing scheme using an astigmatic method in the confocal arrangement has been interfaced to the interferometer to retrieve the real phase value during a scanning process. The experimental results show that the vertical measurement range can be expanded up to 16 μm. The potential of this interferometer on the scanning microscopy of a rough surface is discussed.     

Real space scanning — a new scanning principle

A new scanning principle based upon the impulse-echo technique has been developed. The basic principle is that a reflection of the sound impulse is shown as a light point (imaginary) placed exactly where the reflector is placed inside the body. This is called real space indication of reflecting structures.Based upon this principle, a real time scanner has been built. The clinical tests have confirmed that the real time real space scanner creates real time pictures with a very close correlation between the pictures and the actual size and orientation of the organs.It has been proved that modulated light emitting diodes can be used to create a real time picture with eight grey levels and a satisfactory resolution.     

一种基于机械式拼接的结构光扫描测量方法

测量大尺寸零部件一般需要较大的测量范围,而高精密扫描传感器往往视野较小。为了解决该矛盾,提出了一种基于机械式拼接的结构光扫描测量方法,通过结构光扫描仪获取局部高精点云,并利用高精十字平移台实现数据拼接。分析了测量系统的组成和测量原理,提出了一种基于加权非线性优化的外参标定方法,求解出结构光扫描仪和十字平移台之间非实物坐标系的变换关系。在实验中验证了系统在300 mm的测量范围内球心距的均方根误差（root-mean-square error,RMSE）优于45 μm;同时对实物进行了测量,检验了测量系统的实用性。     

大尺度阻隔空间姿态组合测量方法研究北大核心CSCD

针对大尺度空间姿态测量中因空间阻隔导致目标特征点遮挡的问题,提出了一种基于多传感器组合的姿态测量方法。通过数字水准仪与姿态探针实现被测特征点的单坐标基准测量,由特征点的水平高差和已知几何约束关系解算得到目标初始姿态值。在此基础上标定高精度倾角传感器与被测目标之间的姿态旋转矩阵,基于坐标变换理论可由传感器输出实时解算目标姿态。实验结果表明:在10 m范围内,姿态测量相对精度优于0.0015°,重复性测量误差小于0.0004°,适用于大尺度阻隔空间姿态的精密实时测量。     

Phase measurement for accurate mapping of chemical bonds in acentric space groups

Although the electron density is fundamental to the study of chemical bonding and density-functional theory, it cannot be accurately mapped experimentally for the important class of crystals lacking inversion symmetry, since structure factor phase information is normally inaccessible. We report the combination of x-ray and electron diffraction experiments for the determination of the electron density in acentric AlN, using multiple-scattering effects in convergent-beam electron diffraction to obtain sensitivity to structure factor phases, and describe a new error metric and weighting scheme for multipole refinement using combined measurements of structure factor magnitudes and phases.     

Non-contact blood flow determination using a laser speckle method

An electro-optical device is described which allows the non-contact determination of the skin blood flow and its temporal course. As the laser light penetrates the skin, it is not only scattered from the epidermis but also from the moving red blood cells in the capillaries. The scattered light is time dependent and can be described in terms of the dynamic laser speckle effect. Measurements at the skin demonstrate that there is a so-called ‘involuntary body movement’ which must be taken into account when the measurement of the blood flow is determined. Theoretical considerations show a way to reduce the influence of this movement. Some measurements demonstrate the response of the device to blood flow variations.     

基于复合胞化空间的图胞映射方法

为了提高计算的准确性和效率,通过引入复合胞化空间概念,构建了一种迭代的图胞映射方法.该方法能够对任意感兴趣的空间区域进行细化处理,细化过程采用代数运算完成不会额外增加计算机内存且能保持细化前后图动力系统性质不变.为了便于计算机实施,也给出了相应的有效算法.通过对典型例子Henon映射的应用分析,证实了该方法的有效性. 关键词： 图胞映射方法 迭代方法 Henon映射     

Reciprocal space mapping

This review covers the recent advances in reciprocal space mapping. The experimental techniques as well as the theoretical and conceptual developments are discussed. The advantages of reciprocal space mapping over the conventional single scan X-ray scattering methods become clear from the examples presented. Extracting the additional information from mapping in reciprocal space maps has led to a deeper understanding of materials. Imperfect materials benefit enormously from these methods. Near perfect materials also indicate weak diffuse scattering that can now be interpreted in terms of defects, etc., whereas with single scans the influence is difficult to observe and separate from other features. Reciprocal space maps can be collected with both high and low angular resolution diffractometers, depending on the application, although a combination of resolutions may be necessary. It is also growing in importance in the analysis of materials using specular reflectometry. High-resolution reciprocal space mapping is not restricted to good crystalline quality. Examples of reciprocal space mapping are given for semiconductors, metals, ceramics and biological samples. For semiconductor materials, reciprocal space mapping has now become almost routine in the study of lattice relaxation in thin layers and in the assessment of the “quality” of materials. Combinations of mapping with topography and precision lattice parameter determination are also discussed. The latter part of this review discusses the advantages of three-dimensional reciprocal space mapping, which takes the analysis further. With this method the full three-dimensional shapes in reciprocal space can be studied.     

光电扫描植物根形状几何测量方法

植物根形状几何测量在植物生长研究方面起着重要的作用。但植物根的形状很不规则，对其形状的几何测量对植物研究工作者来说，一直是一件十分困难的工作，特别是根吸收表面积的测量。本文采用通用光电扫描仪，将植物根的形状转化成数字图像，应用数字图像处理技术对数字化的植物根图像进行分析，提出一种边缘点去除与内点保留相结合的“三步细化方法”，在细化基础上采用链码法进行长度测量；采用圆柱逼近模型对植物根的表面积进行测量；用对比法对测量方法的结果作了比较。本文的方法具有应用价值。除植物根外，本文方法也适用于类似根形状物体的几何测量。     

Non-contact acoustic method for the simultaneous measurement of thickness and acoustic properties of biological tissues

The frequency dependence of the magnitude and phase shift of reflected waves from a thin tissue specimen has been found to yield characteristics patterns as a function of the specimen thickness. By analysis of those characteristic patterns, the specimen thickness can be determined so that the attenuation constant and the sound speed can be obtained by a non-contact procedure. The method is demonstrated in the frequency range 100 MHz to 200 MHz, using a scanning acoustic microscope and approximately 10 μm thick myocardial tissue samples of human origin, one paraffin embedded.     

A displacement measurement system, utilizing a Wollaston interferometer

A dual interferometric displacement measurement system is presented where a Wollaston prism interferometer is employed in conjunction with a normal Michelson interferometer. The system operates without the use of external polarizers, apart from those associated with the Wollaston prism interferometer itself. It is shown that an optical path difference induced in the Michelson interferometer can be detected using the Wollaston prism in a normal interferometer arrangement. Further, the interference pattern produced by the Wollaston prism interferometer changes in a measurable, linear fashion as the optical path difference from the Michelson interferometer alters. A simple theoretical analysis of the system is presented and used to derive a computer model of the optical arrangement. Results from an experimental implementation of the system, using a Wollaston prism with a beam separation of 0.5 degrees and a superluminescent diode, of wavelength 825 nm, as a light source, are included and compared to the results from the computer model.     

Non-contact electrodynamic measurement on metallic vibrators at 20kHz

Measurement of vibration amplitude on metallic rods by a contactless electrodynamic method is described. The sensitivity of a typical pick-up is investigated     

像方扫描技术研究

基于显微摄影的成像原理,研究了像方扫描以扩大视场的途径,并建立了一个二次成像的设计模型,包括一个大视场的固定前置物镜组和一个运动轨迹为球面的中继透镜组。物镜组所成的一次像面优化了场曲,中继透镜组则根据该场曲进行运动,对一次像面不同区域成像,并采用光学被动消热差以保证不同温度的像质。该模型的相对孔径1∶3,波长3.7 m~4.8 m,焦距90 mm,瞬时凝视视场为4,扫描视场达24,采用7片透镜3个非球面,在全视场范围内具有接近衍射限的像质。     

正交狭缝扫描式激光光束质量测量方法研究

传统激光光束质量测量方法在CCD相机靶面前激光光路上加装可调衰减模块,对激光光束进行衰减。但该方法受限于CCD相机像元尺寸限制,难以进行高精度测量。为此该文提出了一种滚轮狭缝式激光光束质量评价方法,在测量时采用狭缝滚轮上的扫描狭缝直接扫描被测激光光束,使用InGaAs探测器配合聚焦透镜进行测量。经过与电机同轴的高精度增量式编码器确保采集位置与采集数据同步,扫描频率根据被测激光脉冲频率和光斑的直径范围可进行调整,该方法对光斑空间采样分辨率优于1 μm。实验结果表明,采用该方法测得的激光M2因子数值与被测激光器提供数值一致,测量不确定度小于10%。     

A new method of flame temperature measurement utilizing the acoustic emissions from laser-induced plasmas

The optical emissions from laser-induced plasmas have been successfully exploited for elemental composition measurements in flames; however, the information from the accompanying plasma-generated acoustic emissions has not been well utilized. In this study, we investigated the influence of flame temperature and composition on the acoustic emissions from laser-induced plasmas in an ethylene-air premixed flame. The acoustic emissions are sensitive to temperature, and a negative correlation can be established. The effect of composition on acoustic emissions was found to be second order compared to that of temperature. Based on these findings, we introduce acoustic-based laser-induced breakdown thermometry (LIBT). A statistical analysis was performed to mitigate the bias introduced by anomalous extreme values. The spatial and temporal resolution of LIBT were also analyzed to demonstrate its potential to perform simultaneous composition and temperature measurements when used along with laser induced breakdown spectroscopy (LIBS). Finally, the temperature distribution in an ethylene-air counter-flow diffusion flame was measured; and the results compared favorably with numerical results.     

基于平行平板的折射率高精度非接触测量

常用的测量折射率的方法如偏向角法、自准直法、临界角法、 V棱镜法等,这些方法通常需特制三棱镜与待测件。待测样品不一致且过程复杂,测试定标周期长,难于自动化。为了保证待测材料的完整及实现自动化测量,进行了基于平行平板的折射率非接触测量的尝试。运用该方法进行折射率的测量,不需特制三棱镜并且待测件与待测样品一致。分析表明,通过选择合适的测量角度,该方法旋转角度精度为a=0.003（即10）,导轨精度为L=0.000 8 mm,平行平板厚度测量精度为d=0.001 mm。