The first two spread the radiation at specific angles and need to have detectors placed where each wavelength-dependent angle directs the radiation. Absorption filters pass only a limited range of radiation wavelengths, absorbing radiation outside this range. They may be either broad or narrow bandpass filters. Interference filters work by reflecting unwanted wavelengths and transmitting others in a specific interval. A common type of filter used in general optics and on many scanning spectroradiometers is the dichroic filter.
Absorption is nearly zero.
These can be either additive or subtractive color filters when operating in the visible range. The next step is to get the spectrally separated radiation to appropriate detectors. This can be done through lenses or by detector positioning or, in the case of the MSS and other sensors, by channeling radiation in specific ranges to fiber optics bundles that carry the focused radiation to an array of individual detectors. For the MSS, this involves 6 fiber optics leads for the six lines scanned simultaneously to 6 detectors for each of the four spectral bands, or a total of 24 detectors in all. Most detectors are made of solid-state semiconductor metals or alloys.