Specialist in the supply of infra-red filters and coatings, LASER COMPONENTS, has announced that its 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 six percent 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 4.3µ for CO2.