光学显微镜中使用可见光或紫外线为光源,其波长为7500A或2000A,因此,应用光学显微镜观察0.2μm以下的微小物体就比较困难,即光学显微镜的分辨本领有一定的局限性。这样,人们开始利用波长短的电子束做为光源来观察分析物体的精细结构。早在一九○○年就用电子束为光源得到了电子放大的图象,到一九二六年人们对电子透镜有了初步的了解。后来人们根据电子波动理论,开始做电子透镜的实验。到一九 Optical microscope using visible or ultraviolet light source, the wavelength of 7500A or 2000A, therefore, the use of optical microscopy 0.2μm below the smaller objects is more difficult, that is, the resolution of light microscope has some limitations. In this way, people began to use the short wavelength electron beam as a light source to observe the fine structure of the analytic object. As early as 1910, electron-amplified images were obtained using electron beams as light sources. By 1926, people had a preliminary understanding of electronic lenses. Later, according to the theory of electronic fluctuations, people began to do electron lens experiments. To nine