Interference band-pass filters These Interference Band pass Filters are used to isolate and transmit a narrow wavelength that is required and block all other wavelengths through reflection. This range of Interference Band pass Filters consist of an all-dielectric coating along with other coatings for additional blocking and cemented together to form a stack. The individual filters are mounted in nested rings, providing a labyrinth epoxy edge seal for greatly extended life. Although these are mounted, unmounted type can be supplied at special request. These Interference Band pass Filters are all typically 3-7 cavity. Uses include line selection, laser signal selection, colorimetry and fluorimetry. They can also be used for imaging. When using high powers the reflective side must be towards the incoming light.
Knight Optical > Filters > Interference band-pass filters > Standard IR range (10-18nm bandwidth) 12.5 diameter (mm) This is the section containing 12.5 diameter (mm). 25 diameter (mm) This is the section containing 25 diameter (mm). Only UK and EU customers are charged VAT at 17.5%, customers outside the EU and EU customers based outside the UK who have a valid EU VAT number will not be charged VAT Bulk Discounts! Where (B) appears next to a price below, bulk prices are available, click the (B) button to view! Knight Optical > Filters > Interference band-pass filters > Standard IR range (10-18nm bandwidth)
Dimensions   Diameter: +0,-0.3mm Thickness: 5-6mm Clear aperture:   12.5mm dia. 8.6mm 25mm dia. 19mm 50mm dia. 44mm   Specification
Range Fin FIB (<1100nm) FIB (=1100nm) FIJ FIR FIW CWL tolerance (nm) +0.7,-0.4 ±2 ±3 ±2 ±5 ±7 HBW tolerance (nm) +0.7 ±2 ±3 ±2 ±5 ±8 Bandwidth ratios*             10%BW/HBW 1.74 1.35 1.74 1.35 1.13 1.05 1%BW/HBW 3.21 1.99 3.21 1.99 1.30 1.18 0.1%BW/HBW 6.09 2.92 6.09 2.92 1.60 1.36 0.01%BW/HBW 12.68 4.41 12.68 4.41 2.04 1.69 Blocking type and specification Induced transmittance filter10?? absolute, 200-3500+ Dielectric stacks:10?? ave,10?³ abs, x-ray to 1150nm No of cavities (min) 2 3 2 3 5 7
Interference filter glossary Bandwidth (HBW, FWHM): Width of the passband; specifically, the difference between the two wavelengths at which the transmittance is half the peak value. Similarly, 10% bandwidth (10%BW) is measured between points where T=10% of peak, etc. Blocking: Rejection of any energy outside the passband. Absolute blocking is the transmittance level not exceeded at any point in the specified wavelength range. Average blocking is a value averaged over a range. Cavity: The basic element from which a filter is constructed, consisting of two reflective coating stacks with a spacer layer in between. Our standard range is based on a series of three cavities and therefore a squarer shape of passband. Centre wavelength (CWL): The wavelength midway between the half-power points which define bandwidth (se above) Transmittance (T): The guaranteed minimum value of peak transmittance of the filter (not necessarily occurring at the centre wavelength) Technical Notes To estimate the transmittance near the passband, use the bandwidth ratios given in "specifications" e.g. 340FIB12 has HBW-10; for FIB range 1%BW/HBW=1.99,so 1%BW-19.9; .e transmittance ill be 1% of pea (about 0.3% absolute) at 340nm ±(19.9/2), i.e. about 30nm and 350nm. For light incident at an angle the centre wavelength ?o (1-k sin²?) where k is approximately 0.24 for FIW filters and 0.11 for all others. The CWL shifts towards the longer wavelengths with increasing temperature at about 0.1nm/K.