= Interference filter
{wiki}
An <interference filter> uses <wave interference> in a layered optical structure to transmit or reject selected <wavelengths>. The accumulated <optical path length> makes reflected contributions reinforce or cancel differently across the <optical spectrum>.
A narrow-band example can isolate emission before a <photodetector> or reject an excitation beam in <fluorescence microscopy>. Tilting the filter changes the propagation angles and optical paths inside its layers, shifting the transmitted band. A filter characterized in a collimated beam may therefore behave differently in a strongly converging beam; <temperature> and <polarization> can also affect transmission.
Back to article page
