According to the light reflection characteristics of different structure components on the surface of metal samples, optical study and qualitative and quantitative description of these structure components were carried out in the visible light range by metallographic microscope. It can show the characteristics of metal structure in 500-0.2m scale. As early as 1841, the Russian (п. п. Ансов) studied the patterns on the steel sword under the magnifying glass. By 1863, the British (H.C. Sorby) transplanted the petrographic methods, including sample preparation, polishing and etching, into the research of iron and steel, developed the metallographic technology, and later took a number of metallographic photos with low magnification and other structures. The scientific practice of soby and his contemporaries, A. Martens and F. Osmond, laid the foundation for modern optical metallography. At the beginning of the 20th century, optical metallographic microscope technology is becoming more and more perfect, and it is widely used in the micro analysis of metals and alloys.
Metallographic microscope is a kind of microscope using visible light as illumination source. They include three systems: optical amplification, lighting and machinery. It is mainly used in LCD, led, IC packaging and other industries.