Fluorescence filters were formerly almost exclusively made of colored glass or colored gelatin sandwiched between glass. These filters are designed to pass or reject wavelengths of light with great selectivity and high transmission. Dichromatic beam splitters are specialized interference filters. Today, most exciter filters are of the interference type. Numbers associated with these filters may refer to the wavelength of maximum transmission for band pass exciter filters.
Some manufacturers label their interference filters with the designation IF .
Narrow interference band pass filters are especially helpful if the Stokes' shift is small. Interactive Java Tutorial Fluorescence Filter Spectra Examine how changes in fluorescence filter bandwidths interact to pass specific wavelengths. Modern barrier filters are generally the interference type, many of which are band pass with sharp cut-offs at both the left and right sides of the transmission curve, as illustrated below in Figure 3. All of these terms should be considered interchangeable. These filters are always the interference type.