FILTER COATINGS VISIBLE / NEAR IR
DICHROIC FILTER : SHORT WAVE PASS (SWP) & LONG WAVE PASS (LWP)
Dichroic Filter coatings are designed to transmit one spectral region (passband) and reflectanother (refection band). The filter is a Short Wave Pass if the passband is to the left of the transition slope, and a Long Wave Pass if the passband is to the right of the slope. The advantages of dichroic filters over colored glass filters are: 1) the rejection band is reflected rather than absorbed; 2) steeper transition slope between the passband and the rejection band; i.e. sharper cut-on or cut-off; 3) coatings can be custom designed for specific center wavelengths.
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