A band-pass filter is a series connection of a low-pass and a high-pass filter. Such a filter only allows the passing of signals within the frequency, respectively wave length range. This involves maximum roll-off. Band-pass filters are unavoidable for optical measuring devices that have strict fault tolerance requirements, so they are also used for our SmartRay laser scanner models. Typical everyday applications are, for example, in audio technology and photography, in research, like fluorescence microscopy, spectroscopy, but also in clinical chemistry. As they have multiple applications, band-pass filters are frequently used in industry as well as in everyday products and research.

From a technical point of view, band-pass filters belong to the group of so-called bell filters. The functioning of all band-pass filters is similar: They allow the desired part of the spectrum to pass and reflect all other wave lengths. The filters are available for the most diverse band widths. Laser line filters that are used for more demanding applications usually have smaller band widths, of only 2 to 5 nm. In order to be able to isolate the so-called excitation and emission wave lengths, you need band widths between 20 and 70 mm. Band-pass filters with a band width of 10 mm are ideal for applications in chemistry, environmental technology and elemental analysis. From the point of view of quality, there are hard-coated or simply vaporised models. The hard-coated band-pass filters distinguish themselves through a long life cycle and high stability. Band-pass filters are also switchable. You can choose between the manual and the automatic mode. The filter structure comprises several levels