Biometrics is a very complex technology.By optical scanning human facial bones and human eyes and other details and computer operation and identification.The function of optical filter is to effectively eliminate the influence of stray light from the outside world, keep the recognition background in the same state, and ensure that every recognition is 100% correct.Filters are also different depending on the infrared light source.Commonly used are 850nm infrared light source and 940nm infrared light source, which are relatively mature LED light source on the market at present.