An Infrared Neutral Density Filter is a neutral density filter that offers even attenuation to a selective portion of wavelengths in the IR spectrum. Unlike a complete dielectric or absorption filter, the metallic ND IR filter of North Optics utilizes a combination of absorption and reflection to reduce the intensities of light. Our ND IR filter consists of a metal alloy coating deposited on a substrate chosen according to the wavelength region of interest, and the optical densities of the metallic-coated ND infrared filters are determined by the metal alloy coatings. 

North Optics offers Custom Infrared Neutral Density Filters comprising metallic coatings deposited upon germanium substrates designed to attenuate radiation over a stunningly wide range in the IR region, the ND coatings are optimized at 2.2 microns and are capable of covering extensive wavelengths up to15 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)