SCHOTT NG Absorptive Neutral Density (ND) Filters consist of NG4, NG9, or NG11 SCHOTT glass types and provide even light attenuation through absorption in the visible spectrum. These filters are manufactured to achieve a specified optical density, ranging from 0.15 to 5.0, to simplify integration into optical systems. SCHOTT NG Absorptive Neutral Density (ND) Filters are available in a standard 50 x 50mm size and multiple filters can be stacked to achieve custom optical densities. Custom sizes from 5 to 160mm as well as custom optical densities or transmission values for specific wavelengths are available on request; for more information, visit our Colored Glass Filter Manufacturing capabilities webpage. SCHOTT NG Gray Glass Filters are also available.
Each filter lot is measured and thickness is adjusted to meet the specified transmission value at 546nm. Each filter is then polished with a ±0.05mm thickness tolerance to guarantee consistent performance. Variations in filter lot performance can result in variations in nominal thickness; however, the transmission variations between lots will be minimal.
Click here to download SCHOTT’s colored glass filter calculation program which can be used to calculate the internal transmittance and external transmission of each SCHOTT glass type. The program can simulate the performance of individual filters with user specified thickness or of stacked filters with varying glass types and thicknesses.