Linear Variable Metallic Neutral Density Filters
  • Linear variable attenuator
  • Linear variable beamsplitter
  • Visible to NIR
  • Individual filters, or matched pairs to eliminate the density gradient over larger apertures
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DescriptionSpecifications Models Catalog PDF

These ND filters provide linearly varying attenuation or beamsplitting in the visible and near infrared region. The optical density varies linearly across the length. Attenuation is achieved by a thin film of aluminum protected with an overcoat. Variable beamsplitting is an added benefit due to the inherent reflectivity of aluminum. The rear surface is coated with a broadband antireflection coating for the visible region. The precision polished BK 7 or UV grade fused silica substrates have a slight wedge between the faces to eliminate unwanted fringe patterns and cavity feedback.

Linear variable filters can be used individually or in matched pairs. A matched pair will eliminate the density gradient over larger apertures when moved in opposing directions. Our Model 925B compensated attenuator utilizes a matched pair of these filters and the mechanics to move them precisely (see Compensated Attenuators).