Optical microscope is an ancient and young scientific tool. Since its birth, it has been used for 300 years. For example, in biology, chemistry, physics, astronomy and so on, it is inseparable from the microscope in some scientific research work.

According to different application purposes, microscopes can be roughly classified into four categories: biological microscope, metallographic microscope, stereoscopic microscope and polarizing microscope. As the name implies, biomicroscopes are mainly used in biomedicine, and the observation objects are mostly transparent or translucent micro-bodies; Metallographic microscope is mainly used to observe the surface of opaque objects, such as the metallographic structure and surface defects of materials; Stereo microscope enlarges and images micro-objects, at the same time, it also makes the orientation of objects and images consistent with human eyes, and has a sense of depth, which conforms to people's conventional visual habits; Polarizing microscope uses the transmission or reflection characteristics of different materials to distinguish different micro-components. In addition, it can be subdivided into some special types, such as inverted biological microscope or culture microscope, which is mainly used to observe culture through the bottom of culture vessels; Fluorescence microscope uses the characteristics that some substances absorb light with a specific shorter wavelength and emit light with a specific longer wavelength to find the existence of these substances and judge their content. A comparative microscope can form a parallel or overlapping image of two objects in the same field of view, so as to compare the similarities and differences between the two objects.