Bandpass Filters
Bandpass Filters
A bandpass filter transmits a well-defined range of wavelengths of light while blocking all others. The width of the transmitted band can be as narrow as less than 1 nm or as wide as a few hundred nanometers. The wavelengths range that the filter transmits depends on the choice of substrate and coatings used, which determine the specific wavelengths of light that are isolated and transmitted. This defines whether the filter works best for ultraviolet (UV), visible (VIS), or infrared (IR) applications.
Applications
Bandpass filters are essential wherever it’s desirable to transmit only a specific band of light, rather than the full spectrum. Common applications include clinical chemistry instrumentation, immunoassays, fluorescence, color separation, flame photometry, elemental and laser line separation, spectral radiometry and environmental testing.
Understanding bandpass filters
A band pass filter may be as simple as a combination of a high-pass filter and a low-pass filter. A high-pass filter transmits light with a wavelength greater than a certain cutoff (point a), and a low-pass filter transmits light below another cutoff (point b). Together, they create a filter that allows light with wavelengths greater than A but less than B, establishing a frequency range for the transmitted light.