Light to be analysed is introduced into a spatially dispersive Fourier Transform spectrometer (105). The resulting image which consists of interference fringes is then relayed into an analyser which superimposes the image onto a single or a plurality of spatial filters (112). The light passing through the spatial filter(s) is then detected. Such detection can be spatially discriminatory or can integrate over space. By comparison of the signal passing through the various filters the level of match to particular spectral characteristics can be ascertained and the properties of the light source, or of an analyte (103) through which the light has passed, can be inferred.
