HROIC FILTER : SHORT WAVE PASS (SWP) & LONG WAVE PASS (LWP) Dichroic Filter coatings are designed to transmit one spectral region (passband) and reflect another (rejection 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 arc: 1) the rejection band is reflected rether 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. |