平顶高斯光束通过复杂光学系统的传输特性研究

为研究平顶高斯光束通过高斯光阑-透镜系统的传输特性,基于光学矩阵的方法和Collins公式导出了平顶高斯光束通过该复杂光学系统后的场分布的解析表达式和近轴光强分布值,进而分析了平顶高斯光束通过高斯光阑-透镜系统后的传输特性。研究结果表明,平顶高斯光束通过高斯光阑-透镜系统后,实际焦点位置和几何焦点位置并不重合,即发生焦移现象。焦移量的大小与高斯光阑宽度及光阑与透镜间的距离等因素有关,即在一定条件下,光阑宽度增大,相对焦移量变小,光阑与透镜之间的距离与焦距的比越小,相对焦移量就越小。     

单相压电电机驱动的高精度孔径光阑设计

为满足空间光学仪器小型化、轻量化、精密化需求,设计了一种单相压电电机驱动的孔径光阑。对压电光阑的整体结构进行设计,实现光阑结构与功能的一体化设计;以压电陶瓷和碳纤维为基体设计具有高强度和功率密度的压电定子;通过COMSOL有限元软件对复合压电定子动力学特性进行分析,以及进行模态频率一致性调节;最后对光阑动圈进行结构优化以及干扰模态分离设计。根据设计方案制作压电光阑样机,其质量仅为49 g,孔径可变范围为0.5~35 mm。实验结果显示：光阑完全放大与闭合时间分别为89 ms和92.4 ms,最小角分辨率为4×10-5 rad。该研究简化了光阑的组成和控制,使其在保证精度的同时,结构更紧凑,质量更小。     

受光阑约束的高斯光束变换的特性分析

对高斯光束通过光阑后产生的焦移，运用矩阵方法进行了分析，讨论了光阑不同大小对高斯光束变换的影响。     

光阑用螺纹式超声电机

研制了一种新型螺纹式空心超声电机,用于驱动光阑并控制和调节光束。由于光阑仅需有限角度转动,故采取螺纹方式连接超声电机定子和转子来施加轴向预压力和实现转子周向运动的耦合。电机仅由转子、定子和底座组成;其中转子与光阑定圈固定,实现了与光阑的一体化设计。运用有限元软件对定子进行了模态分析,选定工作频率为38.26kHz。受可加工螺纹螺距尺寸的限制,电机轴向运动使电机预压力变化较大,电机转动角度小,不能驱动光阑完成闭合或开启,故对转子进行了柔性化设计。仿真实验表明,在转动90°范围内,定、转子预压力变化在27%之内。试验研究表明:设计的电机定子振动特性良好,干扰模态距工作模态5kHz以上;阻抗值变化不超过10%。得到的结果验证了预压力变化对电机影响小;电机驱动光阑开启时间为5s,闭合时间为4.4s,开启、闭合直径与电机运行时间呈线性关系。该空心电机满足了光阑调节需求,具有结构简单、零部件少等特点。     

基于机器视觉的光纤连接插芯内径测量系统

为了实现针对光纤连接插芯内径参数的精密和快速测量,首先采用了机器视觉方案,通过显微镜把内孔图像成像在高分辨率的CCD上,并获取图像,然后通过图像处理方法,计算出了光纤连接插芯的内径大小和真圆度,最后通过合理设计相应的硬件和软件,实现了光纤连接插芯内径参数的快速非接触式自动测量;同时提出了一种确定图像边缘的新方法,消除了光强变化对阈值设定产生的干扰,并对所采用的参数检测算法进行了阐述。实验结果表明,整个自动测量系统的测量精度达到了亚微米级,且具备抗光强变化干扰的性能。     

一款新型可变光阑的设计

介绍在开发显微镜产品过程中所设计的一款新型可变光阑,采用两片式方形光阑结构,改变了传统多片光阑的结构,达到了传统结构所不能达到的最小光阑孔径,实现了显微镜在高倍物镜观察下的高衬度要求,更好地满足了实际应用的要求。     

双相编码系统对编码图像干扰的稳定性分析

本文考虑的是最新开发出的双相编码系统，并针对编码系统的干扰对解码图像产生的影响进行分析。由于在光学应用场合中解码图像的光强是在解码系统的输出端测量的，我们把解码图像光强上的信噪比(SNR)表达成复合编码图像SNR幅值的函数。我们指出，在两个SNR之间存在着简单的关系，且这种关系拟与编码图像干扰的性质无关。本文所阐明的结果可帮助描述光学解码系统元件的精确等级，这对于使解码图像达到预定的质量等级是必要的。     

烟气颗粒物浓度激光测量仪光电传感器运算处理电路设计

设计了一种烟气颗粒物激光检测仪的激光信号处理电路,检测系统应用激光Mie散射原理.信号处理电路采集散射光的光强信号,采用双光路结构消除干扰噪声,将微弱电流信号转换成便于测量或转换的0-10V电压信号,输出稳定,反应灵敏,能够对输入的变化快速反应产生可信输出.     

基于窗口傅里叶变换的线性相位误差抑制

在窗口傅里叶变换(WFT)相位提取技术中,抑制线性相位误差和背景光强干扰对窗口尺寸的需求条件存在矛盾,无法对二者进行同时抑制,故提出一种通过改变输入信号频谱成分的线性相位误差抑制技术,该技术利用傅里叶空频分析法将输入信号进行背景光强滤除并保留基频成分,使测量结果不受背景光强影响;考虑到线性相位误差同样受到窗口尺寸选取的影响,通过仿真分析确定最优窗口尺寸判定依据;采用该方法重构抛物面形并以相移干涉技术所获面形结果为基准进行对比分析,结果表明,本文提出方法可实现线性相位误差与背景光强干扰的综合抑制效果并提高了传统WFT相位提取精度。     

采用调制光强测量浊度

为避免背景光的干扰 ,本文提出了采用调制光强测量浊度的新方法。讨论了对光信号转变为电信号时的非线性转换作线性化处理的问题。对测量过程在计算机上用MATLAB进行了仿真     

The near-field power density distribution characteristics for different types of optical fiber probes

When the mechanism of near-field photolithography is analyzed, the most important work is the near-zone field analysis of the optical fiber probe. In this paper, the electromagnetic theory for near-field radiation using the magnetic current and electric current as sources is adopted as the model of the near-field optics. By applying this theorem, the near-field distribution characteristics of the uncoated probe and metal-coated probe are explored. Furthermore, the simulations of the near-field for different light source, such as parallel beam of light (plane wave) and Gaussian-distributed light passing through the optical fiber probe are also discussed. Based upon the model of this research, the time-average Poynting vector distribution of the radiation field, and the relationship between the power density and near-field distance for the optical fiber probe can be estimated. According to the results, when the near-field distance between the metal-coated probe and sampling is maintained at 0.3ρ₀≤Z≤0.6ρ₀, the process is proved to be more adequate for the near-field photolithography. Meanwhile, from the analysis of the near-field power density distribution, it provides an evaluation of concentration of photo active compound (PAC) in the photoresist after exposure and contour after development. The relationship between the power density and near-field distance can be used as a rule of tip-sampling distance modulation when controlling the magnitude of exposure energy. This near-field photolithography engineering perplexity encountered can therefore be solved.     

Temperature field simulation of laser homogenizing equipment

The laser homogenizing equipment was devised using the ring scanning principle. Its working principle is explained. A laser scanning ring facula is obtained when the laser beam goes through the equipment’s optical system rotating with high-frequency. The scanning ring facula’s mathematic model is established based on the temperature field’s superposing principle. The ring facula’s light intensity distribution and temperature distribution characteristics are achieved by simulating its temperature field. By studying the effect of parameters on the temperature field, the best parameters can be found. Results show that favorable temperature distribution characteristics can be attained by choosing appropriate parameters, and even the thermal effect can be realized by utilizing the circumference power compensating for the heat exchange lost in the horizontal direction. The uniform hardness layer and better process quality can be attained using the ring facula optimized for metal laser heat treatment.     

A computer vision system for the inspection of light emitting diodes

This paper outlines the development of a computer vision system to enhance classification criteria for the inspection of infrared light emitting diodes (LEDs). Infrared LEDs used for fibre optics and optical switches are presently classified solely on the basis of power output. This test is performed by focusing the light beam from the LED through a circular aperture onto a solar cell. The output current from the solar cell is translated into a power output reading for the LED. The approach is limited in that it provides no information about other characteristics such as the misalignment of the beam from the mechanical centre or the intensity distribution of the beam. Improved classification criteria and testing methods based on emitted light intensity distribution can be utilised in engineering revision, setting specifications, monitoring manufacturing problems and classification for different applications.     

The effect of radar on cardiac pacemakers.

The susceptibility of 16 noncompetitive cardiac pacemakers to radiation from a powerful radar system was investigated in the laboratory and in the vicinity of its prototype. From comparative in vitro tests in air, fat, water, and saline it was concluded that only tests in fat or air represent the worst case condition after implantation. In air all pacemakers showed signs of interference at pulse power densities between 0.025 mW/cm2 and 62.5 mW/CM2. Three of six implanted pacemakers were triggered or inhibited depending on their mode of operation when tested at a location 1.2 km away from the radar station by the radar beam occurring every 5.5 sec. Because interfering radiation can enter the pacemaker circuitry directly along the electrode, acting as an antenna, metal encapsulation of the pulse generator does not provide sufficient shielding against microwave radiation. However, pacemakers modified by metal encapsulation and a low-pass filter at the electrode remained undistrubed at pulse power densities of greater than 10 W/cm2 when tested under worst case condition in air.     

Fresnel reflection in optical components and detectors for the terahertz frequency band

Plane-parallel dielectric and semiconductor windows, beam splitters and radiation absorbers, as well as reflecting metal surfaces, are important components used in experiments with monochromatic terahertz radiation. The wavelengths of this radiation are longer than the wavelengths of visible light; therefore, multibeam interference becomes important in relatively transparent components with a thickness of the order of 1 mm, which is typical for optical systems. This interference causes the characteristics of optical components and detectors to be dependent on the wavelength. It has been found that bolometric power meters with a crystal used as an absorber of terahertz radiation and pyroelectric detectors with a germanium entrance window demonstrate individual periodic variations in sensitivity under variations in the wavelength. Basic characteristics of the windows and beam splitters manufactured from germanium, polypropylene, and Dacron (the materials that are of the greatest interest for terahertz-band spectroscopy) are calculated in the wave band 30–300 μm. The phase shift of s- and p-polarized terahertz waves reflected from metal surfaces are calculated as functions of the wavelength and the angle of incidence. Using the Fresenel formulas for processing experimental data on the reflection coefficient of terahertz radiation incident onto a K8 glass specimen, it is shown that, in the terahertz frequency band, this coefficient is equal to 16% at normal incidence and the absorption coefficient is equal to 860 cm⁻¹. Original Russian Text ? V.V. Gerasimov, B.A. Knyazev, P.D. Rudych, V.S. Cherkassky, 2007, published in Pribory i Tekhnika Eksperimenta, 2007, No. 4, pp. 103–108.     

金属粉末激光烧结温度场的三维有限元模拟

综合考虑热传导、热辐射和热对流及变热物性参数,基于ANSYS平台建立了连续移动的三维瞬态金属粉末直接激光烧结温度场的有限元模型;利用APDL参数化设计语言实现热源移动,利用焓处理相变潜热的影响,对水雾化铁粉的烧结成型温度场进行了模拟,系统分析了激光熔池的加热和冷却规律及温度场随时间的变化规律。模拟结果表明:随着时间的增加,由于热积累效应使得激光熔池的温度越来越高;彗星状温度云图的最高温度并不在激光光斑中心而是稍微滞后;模拟结果显示烧结过程中将产生液相,这与先前的实验结果吻合较好。     

Important aspects of investigating optical excitations in semiconductors using a scanning transmission electron microscope

Since semiconductor structures are becoming smaller and smaller, the examination methods must also take this development into account. Optical methods have long reached their limits here, but small dimensions are also a challenge for electron beam techniques, especially when it comes to determining optical properties. In this paper, electron microscopic methods of investigating optical properties are discussed. Special attention is given to the physical limits and how to deal with them. We will cover electron energy loss spectrometry as well as cathodoluminescence spectrometry. We pay special attention to inelastic delocalisation, radiation damage, the Čerenkov effect, interference effects of optical excitations and higher diffraction orders on a grating analyser for the cathodoluminescence signal.     

基于拉盖尔-高斯光束的螺旋干涉模式研究

为提高粒子操控的灵活性和精度,一种基于拉盖尔-高斯光束的可控螺旋干涉模式被提出。通过理论分析两束拉盖尔-高斯光束同轴叠加光场,给出了不同参数的变化对干涉光场强度分布的影响。通过仿真模拟,研究参数变化对场强结构的调控作用。结果表明,通过改变两束拉盖尔-高斯光束的拓扑电荷数可以实现干涉模式光场强度极大值的数量和分布的动态调整,增加了对粒子操控的灵活性和可控性,为提高光束微粒操控的精度的提升提供了可能。     

Pulsed magnetic field excitation sensitivity of match-type electric blasting caps

This paper presents a study on energy deposition and electromagnetic compatibility of match-type electroexplosive devices (EEDs), which recently have found more usage in pulsed power environments with high electromagnetic interference (EMI) background. The sensitivity of these devices makes them dangerous to intended and unintended radiation produced by devices commonly used in pulsed power environments. Match-type EEDs have been found to be susceptible to such low levels of energy (7-8 mJ) that safe operation of these EEDs is vital when in use near devices that produce high levels of pulsed EMI. The scope of this paper is to provide an investigation that incorporates results of similar studies to provide detonation characteristics of these EEDs. The three topics included in this study are sensitivity testing, modeling of the thermodynamic heat propagation, and electromagnetic compatibility from pulsed electromagnetic radiation. The thermodynamic joule heating of the primary explosive has been modeled by a solution to the 1D heat equation. A simple pulsed generator, Marx generator with an inductive load, was used for the electromagnetic compatibility assessment of the coupled field between the pulse generator and shorted EED. The results of the electromagnetic compatibility assessment relate the resistive, inductive, and capacitive components of the pulse generator to the area of the shorted EED.     

全光纤激光器光束质量的优化

基于激光器的结构,实验研究了影响光束质量的因素。搭建了百瓦级全光纤激光器,在最大泵浦功率为436 W的条件下,在1 080 nm处获得的激光输出为300 W,光-光转换效率为69%,光束质量M²为1.13。实验研究了谐振腔出射的激光光束在传能光纤中传输时径向功率分布的变化,结果显示：随着光束在光纤中传输距离的增加,光纤中的包层光功率呈现出先增加后保持不变的趋势,因而在传输距离上选择不同的长度对包层光进行剥除,可以获得不同的光束质量。实验还显示,在相同的泵浦条件下,与包层光剥离器设置在腔外相比,其设置在谐振腔内可获得更高的激光输出功率,但是光束质量较差。最后,采用在腔内腔外各加一个包层光剥离器的方法获得了更好的光束质量,此时M²为1.07。