Xiao Bian once knew very little about scanning electron microscope for a period of time, and made a joke about using metallographic microscope as scanning electron microscope. When colleagues in the laboratory mentioned it, it became a bridge, which made everyone happy. The editor of Chain Metallography has brought up this section with the aim of hoping that new friends like me will no longer make the same mistakes as me. Don't make any mistakes, metallographic microscopy should never be used as a scanning electron microscope.


In fact, there is a big difference between metallographic microscopy and scanning electron microscopy. I will summarize it for your reference!

    1、 The principle is different: the metallographic microscope uses the Geometrical optics imaging principle to image, while the scanning electron microscope uses various physical signals excited by the fine focused electron beam when scanning the sample surface to modulate the imaging. By bombarding the surface of the sample with high-energy electron beams, various physical signals are excited on the surface, and different signal detectors are used to receive the physical signals, which are then converted into image information.


2、 Different light sources: A metallographic microscope uses visible light as the light source for imaging, while a scanning electron microscope uses an electron beam as the light source for imaging.


3、 Different resolutions: Metallographic microscopes are subject to interference and diffraction of visible light, and their resolution can only be limited to 0.2-0.5um. Due to the use of an electron beam as the light source, scanning electron microscopy can achieve a resolution between 1-3nm. Therefore, the microstructure observation of metallographic microscopy belongs to microscale analysis, while the microstructure observation of scanning electron microscopy belongs to nanoscale analysis. The sample information obtained by scanning electron microscopy is more abundant.


4、 Different depth of field: Generally, the depth of field of a metallographic microscope is between 2-3um, so there is a high requirement for the surface smoothness of the sample, so the sample preparation process is relatively complex. The depth of field of a scanning electron microscope is several hundred times that of a metallographic microscope, but due to its imaging principle, the surface of the sample must be conductive, so conductive treatment must be performed on the surface of the sample.

    Through the above comparison, it can be clearly understood that a metallographic microscope is an optical microscope that uses incident illumination to observe the surface (metallographic structure) of a metal sample. The current metallographic microscopes are a perfect combination of optical microscopy technology, photoelectric conversion technology, and computer image processing technology. They can easily observe metallographic images on a computer and use software to measure, analyze, and grade metallographic patterns. You can also output, print, and store images. Metallographic microscopy has lower resolution and magnification compared to scanning electron microscopy. But metallographic microscopes are easier to operate, have a larger field of view, and are relatively cheaper.


The scanning electron microscope is a Electron optics instrument. Compared to metallographic microscopes, they have a wide adjustable magnification range, high image resolution, and large depth of field. The images are rich in three-dimensional sense, and the sample information obtained is more abundant. They are more in-depth and extensive in application than metallographic microscopes.