Scanning electron microscopy and metallographic microscopy "go together but in different ways"
Scanning electron microscopes and metallographic microscopes are both optical instruments. Many people like to use a metallographic microscope as a scanning electron microscope, but there are big differences between them. Wrong use will only put more burden on the equipment and accelerate the consumption of the metallographic microscope.
1. First of all, the principles are different: the metallographic microscope uses the principle of geometric optical imaging to perform imaging, while the scanning electron microscope uses various physical signals excited by finely focused electron beams when scanning the sample surface to modulate imaging. The surface of the sample is bombarded with high-energy electron beams, and various physical signals are excited on the surface of the sample. Different signal detectors are used to receive the physical signals and then convert them into image information.
2. Secondly, the light sources are different: the metallographic microscope uses visible light as the light source for imaging, while the scanning electron microscope uses electron beams as the light source for imaging.
3. Different resolutions: Metallurgical microscopes are subject to interference and diffraction of visible light, and the resolution can only be limited to 0.2-0.5um. Since the scanning electron microscope uses electron beams as the light source, its resolution can reach between 1-3nm. Therefore, the tissue observation under the metallographic microscope is a micron-level analysis, while the tissue observation under the scanning electron microscope is a nano-level analysis. The sample information obtained by the scanning electron microscope is richer. .
4. Different depths of field: Generally, the depth of field of a metallographic microscope is between 2-3um, so it has extremely high requirements for the surface smoothness of the sample, so the sample preparation process is relatively complicated. The depth of field of a scanning electron microscope is hundreds of times that of a metallographic microscope. However, due to the limitations of its imaging principle, the sample surface must be conductive, so the sample surface must be conductive.
Compared with metallographic microscopes, scanning electron microscopes have a wide adjustable magnification range, high image resolution, large depth of field, rich three-dimensional images, and can obtain richer sample information. Their applications are deeper and more extensive than metallographic microscopes.
