Narrow bandpass filters are designed to isolate a narrow region of the infrared spectrum. This is accomplished using a complex process of constructive and destructive interference.
Narrow band pass filters have bandwidths (measured at half-peak transmittance levels) less than 6% of the center of wavelength value. When ordering, the bandwidth can be expressed as a percentage of the center wavelength, or can be given in microns.
The filters exhibit high peak transmission (typically greater than 60%) combined with high attenuation levels outside the passband (typically less than 0.1%).
Typical Characteristics of Narrow Band Pass Filters
|Available wavelength range||~1 to 20um|
|Tolerance on CWL||
To customers requirements, but standard tolerances are typically +/-0.3% for a 1% bandwidth filter to +/-1% for a 6% bandwidth filter
|Peak transmittance||Typically >60% (depending on wavelength and bandwidth)|
|Available bandwidths||Typically 0.9% to 6%|
|Blocking (attenuation)||Typically <0.1 % from 0.3 micron to far infrared|
Northumbria Optical Coatings Ltd (NOC) was established in 1995, specializing in the design and manufacture of Infrared Optical Filters and Coatings, covering the spectral range 1.5μm -20.0μm. Before 1995 NOC operated as a business unit for Rolls Royce International Research & Development based in Newcastle upon Tyne. NOC offers competitively priced standard and non-standard filters which are used in many applications including environmental monitoring, analysis and control of gaseous effluent, analysis of vehicle exhaust gases, ozone layer monitoring, night vision systems and space applications. Contact EOC for more information.