Spectral Flattening Filters

Spectral Flattening Filter mounted on a lens

Some light sources produce more light in one part of the spectrum than the other. In order to broaden the region of highest energy, the areas of higher energy need to be reduced relative to the lower energy areas. Spectral flattening filters may be used to reduce such dynamic range problems between different wavelengths that are caused by differences in the light source radiance or detector sensitivity. The filters generally lower the throughput to a greater degree in the middle of the wavelength ranges than towards the ends of the range, resulting in a “flattened” signal.

The signal-to-noise ratio can also be improved with the use of a spectral flattening filter. A filter is always used for a SWIR spectral camera, especially when a halogen light source provides the illumination. Halogen light sources produce greater light intensity towards the short wavelength side of the SWIR region. A filter is also highly recommended for use with VIS/VNIR spectral cameras for color measurement applications.


Spectral Flattening Filter Signal Graphs


Spectral Flattening Filters Ordering Information
Part numberDescriptionProduct Name
MRC-309-001-01 Spectral VNIR range flattening filter, 380-1000 nm, 14.5 x 17.5 mm SFVNIR/17
MRC-309-001-02 Spectral VNIR range flattening filter, 380-1000 nm, Ø 35 mm SFVNIR/35
MRC-309-001-03 Spectral VNIR range flattening filter, 380-1000 nm, Ø 40 mm, with holder SFVNIR/40
MRC-309-002-01 Spectral SWIR range flattening filter, 1000-2500 nm, Ø 40 mm, with holder SFSWIR/40

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