Neutral Density Filter

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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