Specifications:
| Substrates | Germanium | Diameter Range | Custom |
| Transmission | 10%, 20% or custom | Aperture BBAR Coating on back surface S2 | Optional |
| Dimension Tolerance | ±0.2mm | Clear Aperture | +/-0.2mm90% of outside dimension |
| Surface Quality | 80/50 S/D | Flatness | 2-4 waves per 25mm |
| Parallelism | 3-5 arc minutes | Mechanical | Unmounted |
Metallic-coated infrared neutral density filters (IR ND filters) obtain their optical density from a metal alloy coating on a substrate determined by the wavelength region of interest. Unlike the all-dielectric or absorption type, the metallic type ND filter employs a combination of absorption and reflection to reduce the intensity of light.
Infrared Neutral Density Filters are designed to attenuate radiation over a wide spectral range. These filters are coated on germanium substrates. The ND coating is optimized at 2.2 microns and can be used out to 15 microns.
Curves:
1. Transmission of IR ND filters (Germanium, T=10%, BBAR coating on back surface S2)
2. Transmission of IR ND filters (Germanium, T=10%, No BBAR coating on back surface S2)
