Filter optics are used to select the required radiation band, whether it is the transmittance of the filter, the accuracy of product parameters, surface finish, reflectivity and cut-off depth have high requirements, as an optical device It is an indispensable part of the development of the optical industry.

Optical industry OD is usually cut-off, OD=-log(T), according to OD1-OD6, the band pass transmittance of the filter is from 0.1 to 0.000001. The cut-off depth of the filter means that the transmittance is lower than 10 to the minus 4th power. The greater the depth, the smaller the transmittance, the lower the noise, and the more accurate the use accuracy. Generally, the larger the OD value, the cleaner the cut-off of the product, the greater the reflection of the product, the higher the quality of the product, and the more accurate.