Fourier transform spectroscopy by varying the path length difference between the paths in each of a plurality of pairs of optical paths

摘要

A Fourier-transform spectrometer includes a plurality of detectors (118-1 through 118-L), each of which receives light from a pair of optical paths of different optical path lengths. A movable mirror (116) varies the difference between the path lengths of each pair. Analog-to- digital converters (124-1 through 124-L) sample the resultant outputs at regular distance-difference intervals so as to generate sequences of sample values. The distance-difference ranges for the pairs of paths associated with different detectors are different, and the sequences together make up a synthetic interferogram that covers a range of distance differences 2L times the range of motion of the movable mirror (116). A Fourier transformation circuit (126) computes the Fourier transform of the synthetic interferogram, thereby determining the power spectrum of the incoming light, and operates a display (128) to indicate the result.