Linear Variable Metallic ND Filter, N-BK7, 79.4 x 25.4 mm, 0.08-2 OD

The 31W00ML.1 Linear Variable Metallic ND Filter is a 79.4 x 25.4 mm linear variable metallic ND filter made of N-BK7 glass with an OD of 0.08-2, and surface flatness of ≤2λ. This ND filter provides linearly varying attenuation or beam splitting in the visible and NIR region. Attenuation is achieved by a thin film of aluminum protected with an overcoat, and variable beam splitting is an added benefit of the inherent reflectivity of aluminum. The N-BK7 substrate has a slight wedge between the faces to eliminate unwanted fringe patterns and cavity feedback, and the rear surface is also antireflection coated for the broadband visible range.