In-focus electron microscopy of frozen-hydrated biological samples with a Boersch phase plate

We report the implementation of an electrostatic Einzel lens (Boersch) phase plate in a prototype transmission electron microscope dedicated to aberration-corrected cryo-EM. The combination of phase plate, C_s corrector and Diffraction Magnification Unit (DMU) as a new electron-optical element ensures minimal information loss due to obstruction by the phase plate and enables in-focus phase contrast imaging of large macromolecular assemblies. As no defocussing is necessary and the spherical aberration is corrected, maximal, non-oscillating phase contrast transfer can be achieved up to the information limit of the instrument. A microchip produced by a scalable micro-fabrication process has 10 phase plates, which are positioned in a conjugate, magnified diffraction plane generated by the DMU. Phase plates remained fully functional for weeks or months. The large distance between phase plate and the cryo sample permits the use of an effective anti-contaminator, resulting in ice contamination rates of <0.6 nm/h at the specimen. Maximal in-focus phase contrast was obtained by applying voltages between 80 and 700 mV to the phase plate electrode. The phase plate allows for in-focus imaging of biological objects with a signal-to-noise of 5-10 at a resolution of 2-3 nm, as demonstrated for frozen-hydrated virus particles and purple membrane at liquid-nitrogen temperature.     

Image blur and energy broadening effects in XPEEM

We report image blurring and energy broadening effects in energy-filtered XPEEM when illuminating the specimen with soft X-rays at high flux densities. With a flux of 2×10¹³ photons/s, the lateral resolution in XPEEM imaging with either core level or secondary electrons is degraded to more than 50 nm. Fermi level broadening up to several hundred meV and spectral shift to higher kinetic energies are also systematically observed. Simple considerations suggest that these artifacts result from Boersch and Loeffler effects, and that the electron-electron interactions are strongest in the initial part of the microscope optical path. Implications for aberration corrected instruments are discussed.     

Caustic imaging of gallium droplets using mirror electron microscopy

We discuss a new interpretation of mirror electron microscopy (MEM) images, whereby electric field distortions caused by surface topography and/or potential variations are sufficiently large to create caustics in the image contrast. Using a ray-based trajectory method, we consider how a family of rays overlaps to create caustics in the vicinity of the imaging plane of the magnetic objective lens. Such image caustics contain useful information on the surface topography and/or potential, and can be directly related to surface features. Specifically we show how a through-focus series of MEM images can be used to extract the contact angle of a Ga droplet on a GaAs (001) surface.     

Improved phase performance for rotman lens

Rotman lenses are used to obtain multiple beams from a single array. Although the beams produced by the feed antennas at focal points have no path length errors, the beams produced by feed antennas at off focal points may have large path length errors. These path length errors cause deterioration in the multiple beams. In this article, two novel methods are introduced to obtain feed curves which reduce the path length errors of off focal feed points significantly, compared with the commonly used circular and elliptical feed curves. The first method obtains feed curve points based on having zero path length error at three chosen points of the radiating array for each beam direction. The second method uses the particle swarm optimization method for obtaining optimum feed points for each beam direction. The results show that there is a very significant drop in the level of the maximum path length errors (in the order of about 1:4). © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 634–638, 2013.     

基于热释电红外传感器的人防警报器防盗系统设计

目前我们所使用的防空警报器经常由于监管不严发生盗窃事故或被不法分子恶意操作发生警报器误响世故,严重扰乱了人民的正常工作、学习和生活,造成了十分严重的后果和影响。为此对现有的人防警报器设计了一个自动防盗、防破坏报警系统,该系统由菲涅尔透镜、热释电红外传感器、单片机、语音警示电路组成,响应速度快,抗干扰能力强,灵敏度高。当有人距离警报器低于1 m时,就会发出语音警示,同时向管理平台回传信息,达到了安全防护的目的。     

散景效果的真实感绘制

针对现有方法绘制的散景效果真实感较差的问题,提出一种基于几何光学理论的散景效果真实感绘制方法.该方法以光线传播的折射定律为基础,利用序列光线追踪方法对相机镜头的光学成像特性进行精确建模;对相机镜头的内部结构进行精确模拟,包括孔径光阑和渐晕光阑,以绘制出由孔径形状和渐晕共同作用的散景效果;利用几何光学理论和序列光线追踪方法精确计算出出射光瞳的位置和大小,以辅助光线采样,提高光线追踪效率.绘制结果表明,利用该方法能够绘制出较为逼真的散景效果,正确模拟了孔径形状和渐晕对散景效果的影响,并具有较高的光线追踪效率.     

景深效果绘制技术综述

景深效果能够增强计算机生成图像的真实感,因此关于这类效果的绘制已成为计算机图形学中的重要研究方向。针对景深效果的绘制问题,首先研究和分析各种相机镜头模型的光学成像原理,比较各类镜头模型的特点和模拟景深效果的能力;然后分类总结景深效果绘制的基本原理和典型算法,比较各类景深绘制方法的优缺点。最后指出景深效果绘制技术的应用价值,并展望未来的研究方向。     

基于IMS移动终端的即时通信联系人列表管理器

本文主要介绍基于IMS移动终端的即时通信联系人管理器,该管理器主要由XML搜索器、XML解析器、XML管理模块、XCAP通信模块构成。分析联系人列表中联系人的XML片段的定长特性,设计了XML搜索器,实现了节点的快速查找。在XML管理器模块中,以节点路径和消息片段的方式提交联系人修改,减少XML消息传输的字节数,从而提高了消息的传输速率。     

Full perimeter obstacle contact sensor based on flex sensors

This paper presents an obstacle contact sensor system that can detect both the contact state and the direction of contact parallel to the movement plane of a mobile system carrying the sensor. This sensor system is based on a regular- or irregular-shaped ring surrounding the mobile system’s perimeter, connected to the mobile system’s body by a set of soft springs and also coupled mechanically to a set of four flex sensors measuring the relative displacement and direction of the ring when contacting an obstacle. The set of flex sensors is connected to a low-cost electronic module that implements a data acquisition block and a fuzzy processing block, delivering a value representing the estimated contact zone of the ring. Some experiments show how this detection system effectively reduces the sensor count needed for full coverage of the mobile system’s perimeter. Despite the kind of output implemented in the experiments, the contact force can also be estimated.     

后期模拟制作相机镜头背景模糊效果

在摄影实践中,虚化背景是突出主体的常用手段。但是由于消费级DC镜头的实际焦距都很短,因此实现浅景深而虚化背景的难度较大。如果我们希望用消费级DC也能达到虚化背景突出主体的效果,那么,Photoshop后期处理可以派上用场。