The scanning electron microscope uses an electron beam as the illumination source, and irradiates the sample with a focused and fine electron beam in a raster scanning manner, generating various information related to the properties of the sample, which is collected and processed to obtain a magnified image of the microscopic morphology. Compared with an optical microscope or a transmission microscope, it has the advantages of high resolution, large depth of field, and a three-dimensional image.

The scanning electron microscope is mainly composed of an electron optical system, a signal collection and processing system, a vacuum system, an image processing display and recording system, a sample chamber and a sample stage, a power supply system, and a computer control system. The electron optical system is mainly composed of an electron gun, an electromagnetic condenser, an aperture, a scanning system, an stigmator, an objective lens, and various centering coils. It mainly provides the scanning electron microscope with a certain energy controllable and sufficient intensity, an adjustable beam spot size, a perfectly symmetrical shape, and a stable electron beam.