Broadband wide-angle antireflection infrared optical multilayer film

The invention discloses a structure of a broadband wide-angle antireflection infrared optical multilayer film. The structure comprises a substrate and a four-layer film structure, wherein the four-layer film structure comprises a fourth layer, wherein the fourth layer is a hard protective film to be used in an infrared wave band and achieves the function of protecting the window, the third layer is made of a low-refractive-index material, the second layer is made of a high-refractive-index material, the first layer is made of a medium-refractive-index material, and the film system structure ofthe multilayer reflecting film is Sub/x1M x2Hx3L x4A/Air, wherein the substrate Sub is silicon or germanium, H represents the high-refractive-index material, M represents the medium-refractive-indexmaterial, A represents another medium-refractive-index material, L represents the low-refractive-index material, x1 represents an optical thickness coefficient corresponding to a film made of the M material, x2 represents the