Reflective Neutral Density Filters

These neutral density filters consist of a thin Inconel alloy film applied to a BK7 or UV fused silica substrate.  Inconel has a broad neutral transmittance. The filters using BK7 glass substrates work well across the visible and near infra-red spectrum. For use below 400nm choose the UV fused silica filters which transmit down to about 200nm wavelength.

These filters are available in a range of optical densities, specified at 546nm (or 250nm in the case of the UV type) as follows:

Optical Density = 0.04, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.3, 1.5, 2.0, 2.5, 3.0, 4.0

Sizes are normally, 12.7 or 25.4mm diameter or 50.8mm square.  Thickness is adjusted between 1 and 3 mm to meet the optical density specification.

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