IR Filters and Coatings

10 Oct 2017

LASER COMPONENTS specialises in the supply of infra-red filters and coatings.

These optical components can be used in the analysis of vehicle exhaust emissions

using Non Dispersive Infrared spectroscopy (NDIR). The coatings used in narrow

band pass filters are made up of several layers which create a complicated process of

destructive and constructive interference, isolating a narrow region of the IR spectrum.

These filters have a high peak transmission at the chosen wavelength; typically greater

than 70% combined with high attenuation levels outside the passband, typically less

than 0.1%. The passband measured at the half peak transmittance levels is less than

6% of the centre wavelength value.

In NDIR gas is passed through a measurement cell where a broadband IR source is

used to emit light through the cell to a detector. The detector uses our IR optical filters

to filter light at the absorption wavelength of the target gas, say 4.3 microns for CO2.