激光共焦显微光束的偏转扫描

为了提高激光共聚焦系统的扫描速度,本文提出一种逐场扫描的场同步扫描方法。构建了激光共焦显微系统,将美国THORLABS公司的GVS002型二维检流计振镜应用于该系统,根据光学系统参数以及扫描范围要求计算振镜的整场扫描波形。借助NI公司的PCIe6353多功能数据采集卡,输出行同步的扫描波形,同时,对共焦显微系统共焦位置上针孔处的光强信号进行采集,先后扫描一幅256×256和512×512的图像,记录扫描图像和成像时间;然后,在相同的硬件结构下,以场同步的方式输出扫描波形,记录扫描图像和成像时间。实验结果表明:场同步方式扫描256×256图像的速度可提高10倍,扫描512×512图像的速度可提高5倍,且满足共焦显微成像的清晰、抗干扰能力强等要求。与行同步扫描方法相比,场同步扫描方法可以消除行与行之间转换的停留时间,在不改变硬件的情况下大幅提高扫描速度。     

用平面CCD摄像机测量激光束轮廓的系统

本文研究了实时测量连续激光束轮廓的实验装置，介绍了用于同屏监测激光束轮廓、显示实时图像、处理图象的软件，并给出了程序流程图和具体的功能。利用此系统，我们监测了高功率ＹＡＧ激光束的不同空间模式，给出了它们的三维强度图和低阶混合模的一些重要参数。     

基于全相位谱分析的傅里叶望远镜外场实验数据处理

为了提高傅里叶望远镜(FT)的成像质量,实现对运动目标的高分辨率成像,研究了能抑制由声光移频器移频误差、光学器件偏差及信号采样截断等产生的频谱泄漏且能实时计算信号频率的数据处理方法。首先,采用全相位预处理技术对外场静态目标的采样信号进行处理;通过搜索算法得到每束干涉光的整点频率最大值。然后,基于apFFT谱分析时移相位差校正法计算每束干涉光的真实频率。最后,对非整点频率解调,采用5点最小二乘拟合方法,得到目标的傅里叶分量信息。实验结果表明:与传统方法相比,本文提出的数据处理方法得到的重构图像的斯托里尔比(Strehl)相应提高了3%。另外,本文方法对频谱泄漏的抑制能力更强;对静态目标实验数据进行处理后,重构图像质量有一定的提升;该方法也为运动目标的成像数据处理提供了参考。     

基于旁瓣光束衍射反演的强激光远场焦斑测量方法

针对大型激光装置使用纹影法无法实现旁瓣光束弱信号区域光强分布精确测量的问题,提出了基于旁瓣光束衍射反演的纹影法强激光远场焦斑测量方法.采用逆向推演间接测量的研究方法,沿光路传播逆方向推导,以旁瓣光束衍射光强图像和相位图像作为输入,通过计算获得未遮挡前旁瓣光束远场焦斑分布.相比传统基于纹影的远场焦斑测量方法,本文的主要改...     

Optimum condition of convergent beam illumination for observation of local structure by high resolution transmission electron microscopy

We propose the convergent beam illumination as a technique for the local structural analysis by high resolution transmission electron microscopy. The image contrast is lower in the convergent beam illumination than in the parallel beam illumination because of the lower coherency. However the intensity oscillation around an atom image, which appears due to interference effect, is much reduced with the convergent beam illumination, and pseudo-images do not appear at termination of crystal periodicity. The convergent beam illumination, rather than parallel beam illumination, precisely reveals non-periodic local structures, such as interfaces, surfaces and fine particles, which are even embedded in a crystal. From theoretical analysis the optimum condition is derived as divergence of q(s )* = 0.44 and focus of delta(z)* = 1.35 in generalized coordinates. Using the convergent beam illumination the point resolution is improved by 20% compared to conventional parallel beam illumination.     

SAR光学处理器中的电子控制与显示系统

本文讨论SAR光学处理器电子控制与显示系统.这套系统中含有将张力误差控制在±10g以内的胶片张力控制,它是带有AGC的位置控制系统.确保数据输片机和图像输片机跟踪精度优于0.5%的胶片速度控制,它是由一台精密脉冲信号发生器控制的两套具有复合控制功能的锁相速度控制系统.线阵CCD成像器件与图像存贮器的有效组合,使SAR光学处理器具有快速图像显示能力.采用声光调制器(AOM)的光强稳定系统,可将激光器输出强度稳定在±2%以内.还有位置伺服式电动调焦以及附加信息的译码显示与记录等.     

视觉测量中亚像元图像特征定位算法

提出一种利用Facet模型进行图像特征高精度定位的新方法。通过构造一组二维的正交多项式基底,能快速拟合Facet模型的曲面参数方程来表示图像灰度分布,再沿曲面上最大梯度方向的二阶导数的零交叉高精度定位图像角点和边缘特征。该方法采用拟合方法代替插值方法,能减少对噪声的敏感,可提高曲面小片构成的灵活性与边缘检测的精度及计算效率。通过对多幅不同真实图像进行试验验证,结果证明该方法稳定可靠、精度较高,能在视觉测量中有效地提高测量精度。     

A microcomputer-based system for rapid on-line stereological analysis in the SEM

A microcomputer-based image analysis system for the SEM is described. Through two digital-to-analog convertors it controls the position of the electron beam on the specimen inside the microscope. A raster of 128 × 128 pixels is created. At each pixel the signal from the BSE detector is sampled an operator-defined number of times and the median values of the resulting data streams are stored temporarily in the memory of the computer. Stored images may be redisplayed on the visual and record CRTs of the SEM or saved onto a diskette for subsequent recall and analysis. The 256 grey level image is reduced to one having only 64 grey levels and the distribution of the number of counts falling into any of these bins is displayed on the computer monitor, or output to a plotter or printer. The number of counts in each bin represents stereologically the area (and hence volume) fraction of the sample with that grey level. Three levels of threshold may be applied to give four slices in the image. Area (and hence volume) fractions are then calculated, as is the intercept value between slices. This data is output to a printer. An abbreviated program has also been written to permit greater automation of the analysis of samples of bone. Included is a further reduction in the number of grey levels to 16, and the provision of control for an automatic stage. Although presently being applied to the study of samples of mineralised biological tissues this system could be used for any investigation requiring rapid and simple stereological analysis of specimens in the SEM.     

采用特殊镀膜分束器的OCT系统性能分析

基于共焦模式的OCT蒙特卡罗仿真模型,研究了在OCT系统中高散射生物组织背向散射光的反射率。仿真结果:表明对OCT成像有贡献的背向散射光强是样品臂入射光强的10^-8~10^-10,这样微弱的有用信号限制OCT系统的成像速度、探测灵敏度、信噪比和图像对比度等系统的性能。为此设计了一种带有特殊镀膜分束器的OCT系统。采用这种结构的分束器,第一,在保证入射光对生物组织无热损伤的情况下,可以尽量提高光源的输出功率,改进之后的干涉仪可以使参考光衰减4个量级,因此不会使光电探测器的输出轻易达到饱和状态。第二,大幅度减小了参考光与信号光之间的能量差距,图像干涉对比度大约提高2个数量级,即使在高速成像的情况下,仍然能够使OCT系统具备较高的成像质量。第三,这种特殊结构的干涉仪可以使样品臂的入射光最强,并将背向散射信号光因分束器反射的损失减少到最低程度,从而使系统的信噪比提高了6 dB,并通过对样品的测试可以测得系统的探测灵敏度可以提高到43 dB。     

Real-time contactless measurement of robot pose in six degrees of freedom

For dynamically measuring position in three degrees of freedom laser tracking systems are well known. Up to now no possibility to measure also orientation using the same laser beam has been known. We present a technique to incorporate orientation measurement into a laser tracking system that requires only minor changes in the existing hardware. The method is based on the analysis of an image of the reflected laser beam intensity distribution. In this image the edges of a slightly modified retroreflector represent a function of the orientation of the end-effector holding the retroreflector. It is shown that from this image the orientation can be determined uniquely and in real time.

A laser tracking system including position and orientation measurement constitutes an instrument to accurately determine robot performance as well as to acquire hints on how to improve robot models and control algorithms.     

Computer experiments for tilted beam dark-field imaging.

Simulated high resolution tilted beam dark-field electron micrographs for the conventional transmission microscope were obtained by performing wave optical calculations with a high speed computer. Various organometallic molecules and point defects in crystals were studied to assess whether the image structures resembled the orginal object in terms of atom positions and atom correlations for a variety of microscope conditions. For the organometallic molecules close agreement was found between actual experimental micrographs and calculated images for specific combinations of microscope parameters. The images of point defects indicate that it should be possible to identify these structures based upon image size and intensity which in turn are highly dependent on the strain field surrounding the defect.     

压缩传感用于极弱光计数成像

为解决灵敏度达到单光子水平的面阵探测器件其单位像素上灵敏度有限和测量数多等问题,研制了具有极高灵敏度的成像系统来实现欠采样的极弱光成像探测。该成像系统基于光子计数成像技术和压缩感知理论,利用数字微镜器件(DMD)完成随机空间光调制,通过单光子点探测器收集光子,以计数形式记录下光强值。然后,利用算法重建出极弱光照明下的图像。文中设计了相关实验,研究了测量数、光强极弱程度和测量时间对成像质量的影响。最后,引入了图像质量评价标准和系统信噪比,分析对比了实验数据。结果表明,当测量数高于信号总维度的19.5%时,系统能完美成像,信噪比可低至2.843 8dB,DMD单位像素上的平均光子数可低于1.106count/s,成像的关键在于信号的波动大于噪声的波动。该成像系统基本满足了极弱光成像探测在光强、灵敏度和采样数等方面的要求。     

Computer-aided integrating microdensitometry and specimen imaging with the Vickers M85A

A Vickers M85A flying-spot microdensitometer has been linked to a standard BBC model B microcomputer with a commercially available interface, and programs developed in which the computer controls step-wise scanning of the specimen. At each image point thirty-two absorbance readings are made and the average value is stored in the computer memory at 8-bit resolution; a complete 48×48 raster takes less than 5 s. An image of the specimen displayed on the monitor uses eight different pseudo-grey-level characters, and the manner in which the 256 possible absorbance values are represented on the screen can be altered by the user. A mask of arbitrary shape and size, drawn on the screen under key-board control, makes it possible to measure the integrated absorbance of even small, irregular and closely packed specimens such as individual bands in Drosophila polytene chromosomes. The coefficient of variation of repeated measurements of a Feulgen-stained frog nucleus is typically better than 1%. Displayed images can be printed on a dot-matrix printer, and data stored on disc for subsequent analysis. The techniques can readily be modified and adapted for other purposes, some of which are briefly discussed.     

基于应力场强法的缺口构件场强值算法

工程上缺口构件疲劳寿命预测是结构设计过程中不可缺少的内容,基于这一现状通过修正后的场强法来更为有效地解决此类问题非常重要。针对传统应力场强法存在的问题,在考虑其原始假设的基础上,提出一种可以在不同结构尺寸及载荷环境下计算缺口构件场强值的方法。相比于原场强法中疲劳破坏区内各点对峰值点疲劳破坏的贡献作用,新方法认为破坏区内各点对峰值处的疲劳破坏具有“阻碍作用”,并将其做了定量分析。新方法还对模型所用参数、权函数的作用形式以及疲劳破坏区的界定准则做了适当修正,弱化了场径取值对场强求解的影响,克服了传统场强法中场径定义的难题,使场强值具有了一个客观存在的精确解。另外,综合考虑缺口形貌及其附近应力的分布特征,优化了原场强法的积分形式,大大简化了场强值的求解过程。最后还应用修正后的场强法对缺口试样疲劳数据进行了计算,分析结果表明,新模型的寿命预测误差系数可保持在0.24以内,充分满足工程需求。提出的修正模型能保持高预测精度,计算过程很简洁,有很高的推广价值。     

A pixel‐based likelihood framework for analysis of fluorescence recovery after photobleaching data

A new framework for the estimation of diffusion coefficients from data on fluorescence recovery after photobleaching (FRAP) with confocal laser scanning microscopy (CLSM) is presented. It is a pixel‐based statistical methodology that efficiently utilizes all information about the diffusion process in the available set of images. The likelihood function for a series of images is maximized which gives both an estimate of the diffusion coefficient and a corresponding error. This framework opens up possibilities (1) to obtain localized diffusion coefficient estimates in both homogeneous and heterogeneous materials, (2) to account for time differences between the registrations at the pixels within each image, and (3) to plan experiments optimized with respect to the number of replications, the number of bleached regions for each replicate, pixel size, the number of pixels, the number of images in each series etc. To demonstrate the use of the new framework, we have applied it to a simple system with polyethylene glycol (PEG) and water where we find good agreement with diffusion coefficient estimates from NMR diffusometry. In this experiment, it is also shown that the effect of the point spread function is negligible, and we find fluorochrome‐concentration levels that give a linear response function for the fluorescence intensity.     

Low-temperature SEM studies of beam-induced voltage contrast in YBCO thin films

Beam-induced voltage contrast has been demonstrated in a superconducting thin film of YBa₂Cu₃O_7-x (YBCO) grown on MgO. Copper-rich inclusions in the material contribute to spatially varying resistive behaviour but do not account for all the observed details. A new method of scanning in which the beam was moved away from the sample between each data acquisition point was found to increase the resolution by limiting thermalisation, to allow imaging of resistive features as small as 0.5 μm. Direct comparisons of beam-induced contrast and micro-structure at 9000 times magnification were possible using simultaneous image acquisition via a purpose-built image store. Mounting a preamplifier within the scanning electron microscope chamber, to give a variable overall gain of 1000–100,000, was also found to significantly improve the signal-to-noise ratio.     

具有精细结构的圆对称爱里光束的传输特性研究

为了研究具有精细结构的圆对称爱里光束的传输特性,通过减小与光斑宽度相关的参数w,使初始光场具有与波长相近的精细结构。在此特定情况下,用瑞利-索末菲衍射理论对圆对称爱里光束的传输特性进行数值计算。研究结果表明:随着参数w的减小,圆对称爱里光束的精细结构增加,使得代表高频成分的离轴光场影响逐渐增大并参与聚焦行为,焦点光强峰值增大,焦点主光斑的半高全宽减小,突然自聚焦能力得到显著提升;当w减小到某一阈值后,由于持续增加的高频分量进入到倏逝波,焦点光强峰值减小,焦点主光斑的半高全宽增大,突然自聚焦性能下降。     

Maximum pixel spectrum: a new tool for detecting and recovering rare, unanticipated features from spectrum image data cubes

A new software tool, the maximum pixel spectrum, detects rare events within a spectrum image data cube, such as that generated with electron‐excited energy‐dispersive X‐ray spectrometry in a scanning electron microscope. The maximum pixel spectrum is a member of a class of ‘derived spectra’ that are constructed from the spectrum image data cube. Similar to a conventional spectrum, a derived spectrum is a linear array of intensity vs. channel index that corresponds to photon energy. A derived spectrum has the principal characteristics of a real spectrum so that X‐ray peaks can be recognized. A common example of a derived spectrum is the summation spectrum, which is a linear array in which the summation of all pixels within each energy plane gives the intensity value for that channel. The summation spectrum is sensitive to the dominant features of the data cube. The maximum pixel spectrum is constructed by selecting the maximum pixel value within each X‐ray energy plane, ignoring the remaining pixels. Peaks corresponding to highly localized trace constituents or foreign contaminants, even those that are confined to one pixel of the image, can be seen at a glance when the maximum pixel spectrum is compared with the summation spectrum.     

基于荧光成像的准分子激光系统多路光束自动准直

研究了基于准直光束成像的准分子激光主振荡功率放大(MOPA)系统的多路光束自动准直,实现了激光在放大器中的多程放大及高的靶面指向精度。采用352nm He-Cd激光作为准直光源,提出了多光束感光屏同步接收与可见光CCD荧光成像相结合的复合图像采集技术,解决了自动准直系统多路激光的近场、远场图像获取问题。利用图像区域分割处理方法编制了准直信息处理软件,实现了对多光束的自动准直闭环反馈控制。最后,结合准分子激光MOPA系统中的预放大器光学设计进行了自动准直验证实验。结果表明:准直成像光强可调谐倍数为300,成像系统在放大器窗口处固有误差占放大器口径比例小于设计值1.08%,3路激光的自动准直时间为40s,完全满足放大器的几何填充和能量提取要求。     

"Derived spectra" software tools for detecting spatial and spectral features in spectrum images

A spectrum image is recorded as an x-y array of beam locations at each of which a spectrum of radiation is recorded as stimulated by the beam. The large database or "datacube" that results from a single image presents a significant challenge to the analyst to recover information efficiently, especially in the case where a true unknown is examined. This paper describes a class of "derived spectra" software tools that can aid the analyst in recognizing both common and rare features within the datacube. A derived spectrum tool creates a spectrum-like display (intensity vs. channel number) in which the intensity (e.g., x-ray counts) at a particular channel (e.g., x-ray photon energy) is calculated from all of or a subset of the pixel intensities measured for that channel. Derived spectra tools considered include the SUM, MAXIMUM PIXEL, RUNNING SUM, and RUNNING MAXIMUM. The SUM-derived spectrum is useful for recognizing common features of the datacube, while the MAXIMUM PIXEL-and RUNNING MAXIMUM-derived spectra can locate rare, unanticipated features, which may occur as infrequently as being present at a single pixel in the original datacube.