Rocky Mountain Instrument Co.

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Dichroic Filters » Infrared

Dichroic Filter coatings are designed to transmit one spectral region (passband) and reflect another (rejection band).

The filter is a Short Wave Pass (SWP) if the passband is to the left of the transition slope, and a Long Wave Pass (LWP) 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. 


RMI Standard Specifications
Angle of Incidence: 0º or 45º
Passband: T = 50% + 5% at λ0
Tavg > 90% at 0º 
Tavg > 85% at 45º
Rejection Band: Ravg > 99% at 0º 
Ravg > 98% at 45º