Neutral Density & Transmitted Colour Filters
NPL offers a range of transmittance standards for use as calibration standards for spectrophotometers.
Neutral Density Filters
NPL can provide calibrated neutral density filters.The filters can be provided in a variety of sizes, typically mounted in frames for use in 10 mm path length cuvette holders. These cuvette-sized filters have a working aperture of 24 mm x 8 mm and are those that are typically used to certify spectrophotometers. Other sizes such as 50 mm square or 25 mm in diameter can also be provided.
Both glass and metal-on-silica filter types are available. The metal-on-silica filters consist of a silica substrate coated on one side with a nickel chromium alloy. The advantage of the metal-on-silica filters is that they can also be used in the UV.
A wide range of optical density values can be provided, with typical values shown below. Other optical density values are available on request.
Nominal optical density Nominal Transmittance 0.04 90
(T%)
0.22
0.5
1
1.5
2
2.5
3
4
5
60
30
10
3
1
0.3
0.1
0.01
0.001
Transmitted Colour Filters
NPL can also provide red, yellow and blue glass transmittance standards. For each colour, 9 transmittance levels are available, ranging from approximately 3% to 85%. The standards have a working aperture of are 19 x 9 mm and are compatible with 10 mm path length cuvette holders.
Transmittance data are usually supplied in 5 nm intervals from 380 nm to 780 nm. Colorimetric data such as, x, y, X, Y, Z, u', v', L*, a*, b* are calculated for CIE 2° and 10° Standard Observers and CIE Standard Illuminants A, C, and D65.
Contact
Customer Service tel: +44 20 8943 6151
E-mail: optical_enquiries@npl.co.uk