X8130型铣床相对振动相位特性研究

本文围绕机床相对振动相位特性的评价指标——相对振动放大因子,对X8130型万能工具铣床的相对振动相位特性进行了试验研究,并利用Lagrange方程建立了模拟该机床相对振动的动力学模型和数学模型,编制了计算机程序,进行了计算和评价,提出了改进机床的建议。     

Theory of paraxial lateral aberrations of electrostatic imaging electrostatic electron optics based on asymptotic solutions and its verification

In imaging electron optics, study of geometrical lateral aberrations of third order and paraxial lateral aberrations of second order has traditionally been paid more attention to, but the existence of paraxial chromatic aberrations of third order and paraxial chromatic aberrations of magnification of third order was almost ignored, and the general form of paraxial lateral aberration has not been studied theoretically.In the present paper, the paraxial lateral aberrations expressed in general form have been derived emphatically on the basis of asymptotic solutions of paraxial equation. The relationship between the coefficients of asymptotic solutions has been investigated, which proves that the coefficients of asymptotic solutions are related each other. Through a bi-electrode electrostatic spherical concentric system model, two special solutions expressed by asymptotic solutions and accurate solutions in a bi-electrode electrostatic spherical concentric system have been deduced, and the paraxial lateral aberrations have been verified and tested, in which the aberration coefficients are solved by asymptotic solutions of paraxial equation. Result completely proves that the approach based on asymptotic solutions to solve the paraxial lateral aberrations are practicable and accurate enough. The paraxial chromatic aberration of magnification of third order and the paraxial chromatic aberration of third order have been firstly derived, and the Recknagel-Artimovich formula of paraxial chromatic aberration of second order which possess an greatest part in the whole paraxial lateral aberrations has been deduced and confirmed. A simple and clear form for expressing paraxial lateral aberrations of imaging electron optics is suggested for practical use. Results of the present paper will have theoretical value for aberration theory of imaging electron optics and practical significance for the design of image tubes.     

A novel three-dimensional holographic display system based on LC-R2500 spatial light modulator

A novel holographic display system is proposed in this paper. The system takes LC-R2500, a kind of reflective liquid crystal spatial light modulator, (LC-SLM) as the core display unit, which can meet the requirement of real-time reconstruction of three-dimensional (3D) objects from holograms in free space. The relationship between hologram recording and image reconstruction is discussed, and the parameters associated with the magnification of reconstructed image over original object are determined. Experimental results of holographic display using the system are also given in the end.     

Scanning Electron Microscopy for Quantitative Small and Large Deformation Measurements Part I: SEM Imaging at Magnifications from 200 to 10,000

A series of baseline displacement measurements have been obtained using 2D Digital Image Correlation (2D-DIC) and images from Scanning Electron Microscopes (SEM). Direct correlation of subsets from a reference image to subsets in a series of uncorrected images is used to identify the presence of non-stationary step-changes in the measured displacements. Using image time integration and recently developed approaches to correct residual drift and spatial distortions in recorded images, results clearly indicate that the corrected SEM images can be used to extract deformations with displacement accuracy of ±0.02 pixels (1 nm at magnification of 10,000) and mean value strain measurements that are consistent with independent estimates and have point-to-point strain variability of ±1.5 × 10⁻⁴.

基于自由曲面的高倍率广角显微目镜设计

随着显微镜性能的不断提升,要求显微目镜具有更大的视场、放大倍率以及更好的成像质量.显微目镜由于孔径光阑外置,且焦距较短,其设计难点在于如何校正大视场带来的畸变与其他轴外像差,并在此基础上获得符合人眼观察要求的出瞳距离.本文分析了目镜光学系统存在的主要像差,特别是带有畸变的光学系统对成像所产生的影响.将自由曲面应用在显微目镜光学系统畸变校正中,设计出一款视场角达到60°(即±30°),放大倍率达到25×且全视场畸变小于5%的高倍率广角显微目镜.采用五片三组元式结构,其中自由曲面镜片采用塑料材料且关于XOZ与YOZ平面对称,实现了结构简单、易于加工且成本较低的高性能显微目镜设计.     

Cost Optimized Non-Contacting Experimental Modal Analysis Using a Smartphone

The vibrations behavior analysis is an essential step in the mechanical design process. Several methods such as analytical modelling, numerical analysis and experimental measurements can be used for this purpose. However, the numerical or analytical models should be validated through experimental measurements, usually expensive. This paper introduces an inexpensive smartphone as an accurate, non-intrusive vibrations’ behavior measurement device. An experimental measurement procedure based on the video processing method is presented. This procedure allows the measurement of the natural frequencies and the mode shapes of a vibrating structure, simply by using a smartphone built-in camera. The experimental results are compared to those obtained using an accurate analytical model, where the natural frequencies error is less than 2.7% and the modal assurance criterion is higher than 0.89. In order to highlight the obtained results, a comparison has been done using a high quality and high frame per second (fps) camera-based measurement of material properties. Since the highest recovered natural frequency and its associated mode shape depend on the frame per second rate of the recorded video, this procedure has great potential in low frequencies problems such as for big structures like buildings and bridges. This validated technique re-introduces the personal smartphone as an accurate inexpensive non-contacting vibration measurement tool.     

一种基于小波变换的红外图像放大算法

图像放大技术的关键在于使放大后的图像尽可能地保持原始图像的清晰度。对于红外图像而言,传统的内插法存在着一定的缺陷。提出了一种基于小波变换的图像放大新算法,该算法对原始图像先进行小波变换获得高频系数,然后运用牛顿插值算法放大高频系数,以此作为放大图像的高频成份,而将原始图像作为低频成份,最后进行小波逆变换,重构出放大图像。实验证明该方法在图像细节方面具有很好的放大效果。     

Study on the radial vibration and acoustic field of an isotropic circular ring radiator

Based on the exact analytical theory, the radial vibration of an isotropic circular ring is studied and its electro-mechanical equivalent circuit is obtained. By means of the equivalent circuit model, the resonance frequency equation is derived; the relationship between the radial resonance frequency, the radial displacement amplitude magnification and the geometrical dimensions, the material property is analyzed. For comparison, numerical method is used to simulate the radial vibration of isotropic circular rings. The resonance frequency and the radial vibrational displacement distribution are obtained, and the radial radiation acoustic field of the circular ring in radial vibration is simulated. It is illustrated that the radial resonance frequencies from the analytical method and the numerical method are in good agreement when the height is much less than the radius. When the height becomes large relative to the radius, the frequency deviation from the two methods becomes large. The reason is that the exact analytical theory is limited to thin circular ring whose height must be much less than its radius.     

球面参考光预放大数字全息成像系统分辨力

为了提高数字全息成像系统的成像分辨力,对以球面波作为参考光波的预放大数字全息成像系统的记录和再现过程进行了理论推导,得出了该系统的脉冲响应表达式,并由此分析了决定该系统成像分辨力的因素。在CCD成像分辨力高于显微物镜分辨力的情况下,通过对分辨力测试板进行实验,讨论了系统分辨力与记录距离的关系。结果表明:再现像的分辨力对记录距离不敏感;但在记录距离为零,即像面数字全息系统下,再现像具有更高的分辨力。实验结果与理论分析一致。     

基于多路复用体全息光栅的角度放大器设计

为设计基于多路复用体全息光栅的角度放大器, 建立了多路复用角度放大器(MAM)模型, 从效率均衡性和角度分布均匀性两个方面归纳了其设计规则; 研究了光刻过程中的误差对MAM性能的影响; 分析了实际发散光束对MAM性能的影响. 研究表明:控制光栅空间频率和光栅倾斜角可以实现需要的MAM角度分布, 控制光栅厚度和折射率调制深度可以实现MAM最佳衍射效率; MAM最大复用路数不超过10路; 增大光栅倾角或者记录光与工作光波长之比有利于抑制参考光角度误差带来的MAM出射角分布误差, 减小光栅厚度有利于抑制厚度误差与折射率调制深度误差对衍射效率的影响; 当远场发散角大于光栅角半宽时, 最佳衍射效率下降到50%以下且角度选择曲线失去局部最小值; 增大空间频率或者光栅厚度可以减小所需的折射率调制深度, 增多MAM可复用路数, 但是不利于效率均衡性设计和抑制发散光束的影响.