1. An infrared Fourier transform spectrometer, comprising: an optical structure ( 22 , 25 ) configured to split received light into two paths; two mirrors ( 21 , 23 ) for reflecting the light in the two paths, wherein at least one mirror ( 23 ) is movable to perform a scan; the optical structure ( 22 , 25 ) being further configured to combine the light reflected by the mirrors ( 21 , 23 ), the optical structure having two outputs ( 26 , 28 ); and a first detector ( 32 ) at a first output ( 26 ), and a second detector ( 32 ) at a second output ( 28 ), for detecting the light flux at the first and second outputs respectively; each detector ( 32 ) having a plurality of pixels; two of the pixels being configured to obtain pixel samples alternately in time.