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|
|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
|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.