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Infrared Optical Interference Filters

Wide Bandpass Filters

Wide band pass filters are designed to isolate a very wide spectral band. They are classified by having bandwidths (measured at half peak transmittance levels) greater than 13%.

When ordering, it is necessary to specify the 5% cut on/cut off transmission points or the 50% cut on/cut off transmission points (the 5% points are measured as absolute values but the 50% points are measured as 50% of peak transmittance).

The filters exhibit high average transmission in the pass band (typically greater than 70%) and very low transmission levels outside the pass band (typically less than 0.1 %).

This type of filter is particularly useful for isolating the 3-5μm or 8-12μm atmospheric windows and finds widespread use in thermal imaging/human body sensor applications.

Typical Performance

Wide Band Pass Curve
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Typical Characteristics

Available wavelength range ~1 to 20um
Cut on / off tolerance  
To customers requirements, from +/-1%. Standard tolerances are typically +/-4% for a 3-5um or 8-12um wide bandwidth filter.
Average transmittance  Typically >70%
Blocking (attenuation) Typically <0.1 % from 0.3 micron to far infrared.

IR Filter - Wide Bandpass (WBP)

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.