Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a grid.

focus size越大，粗调，越小，细调。 一般 光阑的选择 ：一级聚光镜-----4（一般不动）；二级聚光镜----3（TEM）2（EDX/STEM）；物镜和选取光阑随时可调。 养成好习惯：CCD开启前，确定screen亮度、曝光时间等；CCD开启后，不要再调Intensity和Mag.，要先把CCD关闭再调两者。

Achieving correct focus of an image is important. When the beam cross-over point is slightly above the sample or slightly below the sample, the beam is not at focus. The presence of an artifact known as a Fresnel fringe can be used as a guide to help focus an image.

In order to understand the focusing action of a TEM objective lens, a simple imaging system (figure 1) is best considered. This system consists of an objective lens and a single projector. In operation, the projector is adjusted as required within the total imaging system to achieve a magnification, M2, on the screen.

In Light Microscopy, an image is formed after photons of illuminating light, pass through the sample, are focused by an optical lens. The final image is the result of absorption, reflection and refraction when light interacts with the sample. In Electron Microscopy, an electron beam illuminates and passes through the sample.

2012年4月1日 · High-resolution transmission electron microscopy (HRTEM) is one of the most powerful tools for structural characterization of crystals, especially for those of nanometer size and defects. However, its applications are hampered by various factors that make the direct interpretation of HRTEM images difficult.

In order to understand the focusing action of a TEM objective lens, a simple imaging system (figure 1) is best considered. This system consists of an objective lens and a single projector. In opera-tion, the projector is adjusted as required within the total imaging system to achieve a magnification, M2, on the screen.

2022年5月19日 · How does a Transmission Electron Microscope (TEM) work? The working principle of the Transmission Electron Microscope (TEM) is similar to the light microscope. The major difference is that light microscopes use light rays to focus and produce an image while the TEM uses a beam of electrons to focus on the specimen, to produce an image.

In TEM imaging, the conventional modes of high-resolution imaging are mainly determined by the objective lens defocus. There are four generally used defocus settings: i) “Standard” defocus. iv) Minimum phase-contrast defocus.

In TEM operation, before doing any adjustments and alignments on the microscope, the current of the objective lens should be set to its “Standard Focus” value for high resolution work. This standard focus value is defined by the microscope manufacturer.