Bandpass Filters transmit a selective range of light while blocking light outside of the desired range.
Bandpass Filters typically are characterized by their Center Wavelength (CWL) and Bandwidth which is specified by the Full Width at Half Maximum (FWHM). As Bandpass Filters are designed to transmit a range of light, the CWL indicates the wavelength and the center of the range. The FWHM is the 50% point at the cut-on slope and 50% point at the cut-off slope, with the distance in between being the designated bandwidth.
They are commonly used to isolate an illumination source such as LEDs, lasers or fluorescence to help eliminate the variability or overpowering effects of light outside of the application's interest. They are also useful in creating contrast between colors in monochromatic applications and help increase resolution by eliminating chromatic aberrations.
POSS offers Bandpass Filters ranging from the ultraviolet, visible, to infrared portions of the spectrum.