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Neutral Density Filter

Product Description

Neutral Density Filters are the reflective type of ND filters, which are used to control the light intensity. Coated chromel layer attenuates the light by mainly reflecting and partially absorbing. Our ND filters are designed to keep spectrally even performance especially in VIS range without altering the relative spectral distribution of the energy. Still they are available from UV through IR because the substrate material is fused silica.

Shapeoptics ND filters uniformly attenuate the intensity of light over a broad spectral range. Attenuation is accomplished by either absorption using light absorbing glass or by a combination of absorption and reflection using a thin-film metal coating.  Our ND filters can attenuate spectral regions selected from 250 to 2500nm. The level of attenuation can be specified from optical density (OD) 0.04 to 4.0 where OD is defined as -log10 (T).

Overall attenuation may be increased by stacking neutral density filters serially in the light path. For example, a 0.5 (OD 0.5) neutral density filter placed in series with a 0.3 (OD 0.3) neutral density filter will produce total attenuation of OD 0.8 (10-0.8) or 16% transmission. A six-filter set of 0.1, 0.3, 0.5, 1.0, 2.0, and 3.0 optical densities can achieve a graduated range of spectrally neutral attenuation from OD 0.1 to 6.9.

Optical Density Definition:

Optical Density—the level of neutral transmission across the wavelength region;

Optical Density—OD = -log10 (T).

Our ND filter General Specifications

Tolerances (at 550nm):
   For OD <1.0 ±0.05 OD from nominal
   For OD 1.0–3.0 ±0.1 OD from nominal
   For OD >3.0 ±0.2 OD from nominal
Neutrality Tolerance The variation in optical density from 400 to 700nm
will be less than 10% of the OD measured at 550nm
Outer Dimension Tolerance +0, -0.25mm (+0, -0.01”)
Clear Aperture 4mm less than nominal outside dimension
Maximum Thickness 4mm
Substrate Material Optical quality glass or UV-grade quartz
Surface Quality 80/50 scratch/dig per Mil-O-13830A
Operating Temperature Range -60°C to +80°C
Coating Vacuum-deposited metallic alloy, if not absorption glass type
Construction Either (a) exposed, front-surface metalic coating,
(b) metallic coating laminated and protected in a
moisture-resistant assembly, or (c) absorption glass

Our Standard ND Filter Products

Description Transmission (%) Item#
25mm dia. 50x50mm
ND Filter / 1% 1 XND0001 ZND0001
 ND Filter / 3% 3 XND0003 ZND0003
 ND Filter / 6% 6 XND0006 ZND0006
Neutral-Density Filter / 12% 12 XND0012 ZND0012
Neutral-Density Filter / 25% 25 XND0025 ZND0025
Neutral-Density Filter / 50% 50 XND0050 ZND0050

Custom filters are available for both large manufacturing needs and in prototype volumes. Contact us for more information or to arrange a quote.

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