These filters possess level spectral transmittance characteristics in the visible region and attenuate light by absorption with minimal reflection. Typically, neutrality and density of absorptive filters are a function of the material and the thickness.
Specifications
Material
Absorptive Glass
Dimension Tolerance
+0.0/-0.1mm
Flatness
2λ@632.8nm
Surface Quality
80/50 or better
Parallelism
<5 arc minutes
Clear Aperture
>90%
Design Wavelength
400-700nm
OD Tolerance
±5% of OD, OD=Lg(1/T)
Reflective Neutral Density (ND) Filters
These filters have constant density values across the surface. The transmission to reflection ratio varies with density selection. ND filters are used primarily for the attenuation of light over a wide spectral range. They are often used in laser and photometer applications.
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