Absorptive Neutral Density (ND) Filters
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.
Specifications
|
Material |
Float, B270, |
|
Dimension Tolerance |
+0.0/-0.1mm |
|
Thickness |
2.0±0.2mm |
|
Flatness |
2λ@632.8nm |
|
Surface Quality |
80/50 or better |
|
Parallelism |
<5 arc minutes |
|
Clear Aperture |
>90% |
|
Design Wavelength |
400-700nm |
|
Coating |
Metallic reflective coating |
|
OD Tolerance |
±5% of OD |
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