Optical materials include optical glass, optical plastic and optical crystal. Optical glass is the earliest and most widely used optical material and the most widely used in imaging components. Optical glass is amorphous. Most glass is transparent in infrared wavelength ranging from visible to 2.5um. The crystals are solids with regular arrangement. The large size single crystal with symmetrical structure is often used because of its different transmissibility in different spectral regions, which plays an important role in the development of new technology. The main crystal we use are silicon, Germanium, Calcium Fluoride and Magnesium Fluoride.