Diaphragm is a kind of parallel plate, it is always used as protective window of electronic sensor and external environment detector. Diaphragm will not change the amplification factor, its basic material includes various crystal material such as optical glass, K9, Uv-fused quartz, infrared fused quartz, CaF2, MgF2, ZnSe, Ge and Si. it also provides various optical coating film like antireflection film, high-reflective film, beam splitting film and metal film. Wide antireflection film can be used in ultraviolet band, visible light band, near infrared band and intermediate infrared band.
Germanium single crystal is now the most popular and widely used infrared optical material in the world, its finished products are infrared germanium lens and germanium lens. The number of germanium lens is different according to their different use. Infrared germanium lens has high requirement on precision and technology, it always has more than six to ten germanium lens while germanium lens for civil use has lower requirement with two or three germanium lens. Germanium window always used for military equipment.