Our circular variable neutral density filters are designed to simplify attenuation and beamsplitting in the visible to near IR. The optical density gradient varies from 0.051.0 or 2.0 around a 270° circle for convenient attenuation adjustment by simply rotating the filter. Attenuation is achieved by a thin, reflective aluminum film, allowing these attenuators to withstand moderate laser energy as well as act as variable beamsplitters. A broadband, visible antireflection coating on the back side allows the optic to be left in the beam path at all times with minimal losses or ghost images.Circular variable ND filters are available with BK 7 substrates for general laboratory use, or UV fused silica substrates for maximum thermal stability. Although the coatings are optimized for 450700 nm, they will operate from 4001100 nm with only minor losses. Our circular variable attenuators are ideally mounted with our 941 and 946 mounts.
These graphs model performance of the front surface coating only.