Abstract: An optical technique utilized during target detection for suppressing background radiation. This optical technique incorporates therein an optical mask interposed between the background radiation containing a target and an interferometer capable of performing double-beaming in Fourier spectroscopy. The optical mask divides the field-of-view of the interferometer into a plurality of subfields-of-view, the subfields-of-view being divided into first beams of light containing the background radiation alone and second beams of light containing both the background and target radiation, thereby enabling the output of the interferometer to be in the form of an interferogram having structure due only to the target radiation.