Edge Filter Coatings

Splitting Incident Light

Edge filters typically split a spectral band of interest into two narrower bands – one transmitted and one reflected (or absorbed).  The transition from one band to the other defines the ‘edge’ of the filter and is typically defined at either the 5% (absolute) or 50% (relative) transmission wavelength.  Edge filters used to transmit wavelengths shorter than the edge are typically called shortpass filters, while those transmitting wavelengths longer than the edge area called longpass filters.  Shortpass and longpass filters can be used as stand-alone filter solutions or in combination to filter a broader spectral band (two filters of same type) or to generate a passband within the selected spectral band (longpass and shortpass used in combination).