材料分析測試技術(shù)chapter5透射電鏡的結(jié)構(gòu)-wenkub
2023-04-28 22:35:22 本頁面
【正文】 he object of vision and not in the eye. Because of his extensive research on vision, he has been considered by many as the father of modern optics. 15th century on Studies done with glass magnifiers to study objects in detail mostly as a curiosity by nonscientists Antonie van Leeuwenhoek (linen draper) described three shapes of bacterial cells using his simple, single lens microscope (glass bead in metal holder). By mid19th century, became evident that theoretical limits of light were reached. Above magnification of 1500, resolution lost. Image was larger, but blurred (empty magnification). In 1870, Ernst Abbe derived mathematical expression for resolution of microscope: Resolution is limited to approx. 1/2 the wavelength of illuminating source. Wavelength distance between peaks of the waveform Blue light has a wavelength of um Resolution max um (200 nm) Cannot go beyond this even with better optics. Solution? Use illumination of shorter wavelength Antone de Broglie (1924) Theory of wave nature of electrons Hermann Busch (1924) axial magic fields refract electrons Electron optics ?1935 Max Knoll demonstrates the theory of the scanning electron microscope Knoll and Ruska 1986 Nobel Prize winners von Ardenne 1939 Ruska and von Borries, working for Siemens produce the first mercially available EM 1938 First scanning electron microscope produced by von Ardenne ?1939 First EM built in North America by James Hillier and Albert Prebus at the University of Toronto Dr. Prebus Dr. Ladd Light vs Electron Microscope 光學(xué)顯微鏡的分辨率 ? 由于光波的波動性，使得由透鏡各部分折射到像平面上的像點(diǎn)及其周圍區(qū)域的光波發(fā)生相互干涉作用，產(chǎn)生衍射效應(yīng)。人類認(rèn)識微觀世界的能力從此有了長足的發(fā)展。第五章 透射電鏡的結(jié)構(gòu) 光學(xué)顯微鏡的發(fā)明為人類認(rèn)識微觀世界提供了重要的工具。 Definitions Microscope A device with a lens or series of lenses that enlarge (magnify) the appearance of an object. Does not apply to SEM. Lens A lens is an optical ponent which is used to focus beams of radiation. Lenses for light are usually made of a glassy material, whereas nonuniform electromagic fields are used as lens for electrons. Image Perception of an object using your eyes (vision). One can sense an object without vision (touch, etc..). Requires visible light. Lenses Curved glass or mirror for Visible light Concave surface of metal (. satellite dish) Radio waves Concave mirror or Fresnel lens Heat Solenoid (electromagic fields that can be varied) Subatomic particles (electrons, protons, positrons) concave convex Resolution The point at which two or more objects can be distinguished as separate. Magnification The ratio between image size to the object size. Can be varied by changing the distance between the object and the final lens (of the eye) or by inserti
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