共查询到20条相似文献,搜索用时 890 毫秒
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与普通电子显微像的分辨率不同,电子全息图的分辨率并不仅仅由电子干涉条纹间距本身决定,而是取决于样品相对全息图的放大倍数,即全息图的实际空间分辨率等于干涉条纹间距除以样品相对全息图的放大倍数。因此电子全息图的分辨率可以通过两种方式而改变,(1)改变电子显微镜的成像模式,不同成像模式间的转换可以改变样品相对于全息图的放大数倍。(2)改变电子全息附件在电子光路中的位置,样品相对于全息图的放大倍数与它们的相对位置有关。将电子全息附件安装在样品前面时,样品相对于全息图并没有被放大,反而是全息图在物镜的物面处被放大了,出现在全息图中的样品多,尽管电子全息图分辨率低,但全息图具有分析样品区域大的优点。电子全息附件放在样品之后,样品相对于全息图被放大了,出现在全息图中的样品少了,尽管提高了电子全息图的分辨率,但是减小了可分析样品区域。 相似文献
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《光学精密工程》2020,(8)
为了同时满足较大的视场和较高分辨率的需求,开发了一套全息无透镜显微成像系统和配套算法,实现对微米级样品的无透镜显微成像。搭建了一套由LED光源、针孔、被测样品与CMOS图像传感器组成的全息无透镜显微成像系统,并对针孔直径、成像面尺寸、光源到样品的距离,以及样品面到CMOS图像传感器的距离进行了优化。其次,开发了从系统采集的全息图中恢复样品图像的角谱法算法。最后,使用该成像系统和配套算法,分别对具有微米级结构分辨率测试靶,和肺癌细胞悬浮液进行了显微成像。该全息无透镜显微成像系统的分辨率为4.4μm,成像视场尺寸为5.7 mm×4.3 mm,实现了微米级结构和肺癌细胞较清晰的显微成像。全息无透镜显微成像系统结构简单、无像差干扰,可以实现大视场下较高分辨率的显微成像。 相似文献
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在分析显微观察技术的基础上,提出了将数码相机与显微镜通过转接镜头连接进行显微观察的方法。深入地讨论了转接镜头的光学性能要求,并进行了光学设计。 相似文献
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A. TONOMURA 《Journal of microscopy》1995,179(2):105-111
Electron holography, originally devised for improving the resolution of electron microscopes, progressed significantly with the advent of the ‘coherent’ field-emission electron beam. This permitted high-resolution microscopy (Lichte, 1986), and opened up such new fields as high-precision electron interferomentry. This paper briefly describes the developments in electron holography. 相似文献
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基于加密傅里叶变换全息印刷防伪技术研究 总被引:1,自引:3,他引:1
在研究双随机相位数据加密技术的基础上,结合印刷技术和全息技术的特点,提出了一种基于傅里叶变换印刷全息标识防伪方法。该方法将二值认证图像经过输入面和频谱面上双随机相位加密模板调制生成的物光,与参考光叠加生成加密的傅里叶变换全息图,该全息图可生成印刷全息防伪标识。通过打印和扫描实验验证了加密的傅里叶变换全息标识,可以通过数字印刷技术印制在证件等印刷品上作为防伪标识,具有重要的实用意义。 相似文献
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正交球面波Patch近场声全息 总被引:1,自引:0,他引:1
常规近场声全息(Near-field acoustic holography,NAH)中,为减小算法误差对结果的影响,要求全息测量孔径必须大于声源面积。由于要求的全息孔径较大,导致该技术测量工作异常繁琐以及在大尺寸结构上应用困难。为解决此问题,以全息声压近场外推为基础的Patch近场声全息技术(Patchnear-field acoustic holography,PNAH)发展起来。根据声场的球面波近似原理,提出正交球面波Patch近场声全息方法,该方法将振动体产生的声场等效近似为一系列不同阶次的正交球面波源产生的声场的线性叠加,通过这些正交球面波源的声辐射过程来实现全息面声压的近场外推,然后利用近场外推所得声压数据采用计算简便的快速傅里叶变换(Fast Fourier transform,FFT)方法实现全息重建。数值仿真结果表明,该方法在小全息孔径条件下取得良好效果,显著减小对全息孔径大小的要求,从而方便工程运用。 相似文献
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The genesis, theoretical basis and practical application of the new electron holographic dark-field technique for mapping strain in nanostructures are presented. The development places geometric phase within a unified theoretical framework for phase measurements by electron holography. The total phase of the transmitted and diffracted beams is described as a sum of four contributions: crystalline, electrostatic, magnetic and geometric. Each contribution is outlined briefly and leads to the proposal to measure geometric phase by dark-field electron holography (DFEH). The experimental conditions, phase reconstruction and analysis are detailed for off-axis electron holography using examples from the field of semiconductors. A method for correcting for thickness variations will be proposed and demonstrated using the phase from the corresponding bright-field electron hologram. 相似文献
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介绍了一种新的3-D成像技术—光学外差扫描全息术的基本原理,以及基于光学外差扫描全息术基本原理的环形光栅光学扫描全息术,描述了其与传统的光学外差扫描全息术相比具有的优势。最后,以光学外差扫描全息术在三维空间滤波、遥感和三维混浊液体中成像应用为例,阐述了这一新技术的应用前景。 相似文献
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基于数字全息技术的变形测量 总被引:2,自引:10,他引:2
全息技术在测量、防伪中有大量应用.数字全息技术采用数字记录和计算机处理,实现测量的方法上有其特点.本文重点对数字全息技术实现变形测量的方法和具体算法开展了研究.论文首先总结了数字全息技术应用中的基本问题,包括数字全息算法问题和噪声抑制问题等.叙述了基于数字全息技术的变形测量基本思想,及相位恢复算法,同时分析了几种变形测量的实现方法,并提出了"2+2"步变形测量方法.该方法相对于"1+1"步变形测量方法,提高了测量精度,同时比"4+4"步变形测量法提高了动态性.本文建立了实验系统,获得了硬币的数字全息图,实现了常用的"1+1"步变形测量方法、相移算法的变形测量方法以及"2+2"步变形测量方法,给出了"2+2"变形测量的实验结果.实验结果表明在数字全息技术中结合相移技术进行测量,可以提高物波再现精度,进而提高变形等的测量精度. 相似文献
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Electron holography is a very powerful technique for mapping static electric and magnetic potentials down to atomic resolution. While electron holography is commonly considered synonymous with its off-axis variant in the high energy electron microscopy community, inline electron holography is widely applied in low-energy electron microscopy, where the realization of the off-axis setup is still an experimental challenge. This paper demonstrates that both inline and off-axis holography may be used to recover amplitude and phase shift of the very same object, in our example latex spheres of 90 and 200 nm in diameter, producing very similar results, provided the object does not charge under the electron beam. 相似文献
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The need to determine the electrical properties of semiconductor junctions with high spatial resolution is as pressing now as ever. One technique that offers the possibility of quantitative high-resolution mapping of two- and three-dimensional electrostatic potential distributions is off-axis electron holography. In this study, we review some of the issues associated with interpreting phase shifts measured using off-axis electron holography, and we describe how a quantitative determination of the dopant-related electrostatic potential can be achieved for device structures. Issues that include the presence of surface "dead" layers, external electrostatic fringing fields, variations in specimen thickness and dynamical diffraction are discussed, and their impact on the quantification of results obtained using off-axis electron holography is examined. 相似文献
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LDER M. SEBESTA M. GUSTAFSSON L. GISSELSON A. GJ
RLOFF WINGREN K. ALM 《Journal of microscopy》2008,232(2):240-247
Manual cell counting is time consuming and requires a high degree of skill on behalf of the person performing the count. Here we use a technique that utilizes digital holography, allowing label‐free and completely non‐invasive cell counting directly in cell culture vessels with adherent viable cells. The images produced can provide both quantitative and qualitative phase information from a single hologram. The recently constructed microscope Holomonitor™ (Phase Holographic Imaging AB, Lund, Sweden) combines the commonly used phase contrast microscope with digital holography, the latter giving us the possibility of achieving quantitative information on cellular shape, area, confluence and optical thickness. This project aimed at determining the accuracy and repeatability of cell counting measurements using digital holography compared to the conventional manual cell counting method using a haemocytometer. The collected data were also used to determine cell size and cellular optical thickness. The results show that digital holography can be used for non‐invasive automatic cell counting as precisely as conventional manual cell counting 相似文献