Neutural Density Filter

Neutural Density Filter


Neutral density (ND) filters reduce light intensity in the visible region of 400nm to 700nm wavelength range.
Neutral density glass characteristics may vary with melting conditions but the filter performance can be compensated by changing the filter glass thickness.

Applications:

-Exposure control in color photography
-Calibration filters
-Light control in various instruments

 

There are two types of ND filters: absorptive and  reflective.

Absorptive Neutural Density Filter

Absorptive Neutural Density 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.

Capability

Common Specification
Material Optical Neutral Density Glass
Dimension tolerance ± 0.20 mm
Diameter tolerance +0/-0.2mm
Thickness tolerance ± 0.20 mm
Clear Aperture >85%
Parallelism <3 arc minutes
Flatness 2 Lambda per 1inch
Surface quality  S/D 80-50 
Bevel 0.2mmx45°
Optical Density Tolerance ±10%
Formula Optical Density: D
Transmittance: T
D=Log(1/T)
Part Number Diameter (mm) Ref. Thickness (mm) Optical Density Transmission
NDG-D25-OD0.04 25 2.00 0.04 92.00%
NDG-D25-OD0.1 25 1.35 0.10 79.40%
NDG-D25-OD0.2 25 3.44 0.20 63.10%
NDG-D25-OD0.3 25 2.40 0.30 50.10%
NDG-D25-OD0.4 25 3.31 0.40 39.80%
NDG-D25-OD0.5 25 1.84 0.50 31.60%
NDG-D25-OD0.8 25 3.03 0.80 15.80%
NDG-D25-OD1.0 25 2.05 1.00 10.00%
NDG-D25-OD2.0 25 4.19 2.00 1.00%
NDG-D25-OD3.0 25 1.50 3.00 0.10%
NDG-D25-OD4.0 25 2.05 4.00 0.01%
Part Number Dimension (mm) Ref. Thickness (mm) Optical Density Transmission
NDG-50-50-OD0.04 50x50 2.00 0.04 92.00%
NDG-50-50-OD0.1 50x50 1.35 0.10 79.40%
NDG-50-50-OD0.2 50x50 3.44 0.20 63.10%
NDG-50-50-OD0.3 50x50 2.40 0.30 50.10%
NDG-50-50-OD0.4 50x50 3.31 0.40 39.80%
NDG-50-50-OD0.5 50x50 1.84 0.50 31.60%
NDG-50-50-OD0.8 50x50 3.03 0.80 15.80%
NDG-50-50-OD1.0 50x50 2.05 1.00 10.00%
NDG-50-50-OD2.0 50x50 4.19 2.00 1.00%
NDG-50-50-OD3.0 50x50 1.50 3.00 0.10%
NDG-50-50-OD4.0 50x50 2.05 4.00 0.01%

Reflective Neutural Density Filter

Reflective ND filters consist of thin film optical coatings, typically metallic, that have been applied to a glass substrate. The coating can be optimized for specific wavelength ranges such as UV-VIS or NIR. The thin film coating primarily reflects light back toward the source.

Capability

Common Specification
Material BK7, Fused Silica
Dimension tolerance ± 0.20 mm
Diameter tolerance +0/-0.2mm
Thickness tolerance ± 0.20 mm
Clear Aperture >85%
Parallelism <3 arc minutes
Flatness 2 Lambda per Dia.1" area
Surface quality  S/D 80-50 
Bevel 0.2mmx45°
Optical Density Tolerance ±10%
Coating Vacuum-deposited metallic alloy
Part Number Material Diameter (mm) Thickness (mm) Optical Density Transmission
NMC-BK7-D25-2.0T-OD0.1 BK7 25 2.0 0.10 79.40%
NMC-BK7-D25-2.0T-OD0.2 BK7 25 2.0 0.20 63.10%
NMC-BK7-D25-2.0T-OD0.3 BK7 25 2.0 0.30 50.10%
NMC-BK7-D25-2.0T-OD0.5 BK7 25 2.0 0.50 31.60%
NMC-BK7-D25-2.0T-OD0.8 BK7 25 2.0 0.80 15.80%
NMC-BK7-D25-2.0T-OD1.0 BK7 25 2.0 1.00 10.00%
NMC-BK7-D25-2.0T-OD2.0 BK7 25 2.0 2.00 1.00%
NMC-BK7-D25-2.0T-OD3.0 BK7 25 2.0 3.00 0.10%
NMC-BK7-D25-2.0T-OD4.0 BK7 25 2.0 4.00 0.01%
Part Number Material Dimension (mm) Thickness (mm) Optical Density Transmission
NMC-BK7-50-50-2.0T-OD0.1 BK7 50x50 2.0 0.10 79.40%
NMC-BK7-50-50-2.0T-OD0.2 BK7 50x50 2.0 0.20 63.10%
NMC-BK7-50-50-2.0T-OD0.3 BK7 50x50 2.0 0.30 50.10%
NMC-BK7-50-50-2.0T-OD0.5 BK7 50x50 2.0 0.50 31.60%
NMC-BK7-50-50-2.0T-OD0.8 BK7 50x50 2.0 0.80 15.80%
NMC-BK7-50-50-2.0T-OD1.0 BK7 50x50 2.0 1.00 10.00%
NMC-BK7-50-50-2.0T-OD2.0 BK7 50x50 2.0 2.00 1.00%
NMC-BK7-50-50-2.0T-OD3.0 BK7 50x50 2.0 3.00 0.10%
NMC-BK7-50-50-2.0T-OD4.0 BK7 50x50 2.0 4.00 0.01%
Part Number Material Diameter (mm) Thickness (mm) Optical Density Transmission
NMC-JGS1-D25-2.0T-OD0.1 Fused Silica 25 2.0 0.10 79.40%
NMC-JGS1-D25-2.0T-OD0.2 Fused Silica 25 2.0 0.20 63.10%
NMC-JGS1-D25-2.0T-OD0.3 Fused Silica 25 2.0 0.30 50.10%
NMC-JGS1-D25-2.0T-OD0.5 Fused Silica 25 2.0 0.50 31.60%
NMC-JGS1-D25-2.0T-OD0.8 Fused Silica 25 2.0 0.80 15.80%
NMC-JGS1-D25-2.0T-OD1.0 Fused Silica 25 2.0 1.00 10.00%
NMC-JGS1-D25-2.0T-OD2.0 Fused Silica 25 2.0 2.00 1.00%
NMC-JGS1-D25-2.0T-OD3.0 Fused Silica 25 2.0 3.00 0.10%
NMC-JGS1-D25-2.0T-OD4.0 Fused Silica 25 2.0 4.00 0.01%