For Compactness and Ruggedness, Linear Variable Filters Fit the Bill
Spectroscopic optical applications have conventionally utilized dispersive elements such as diffraction gratings and, less commonly, prisms to separate light into its constituent wavelengths for spectral interrogation. Gratings have the advantage in that a wide range of dispersion levels is made available by adjusting the grating pitch, and they can be used in ways that are light-efficient. However, as they disperse the light as a function of angle, they intrinsically require a fairly complex
Photonics Spectra, September 2016