The optical properties of area detectors used in conjunction with Fabry–Pe´rot interferometers are analyzed. A system using a charge‐coupled device as a detector for Brillouin spectroscopy is described. With a 2 pass+2 pass tandem system the finesse ranges from 50 to 63. With a collection time of about 2.5 min, the intensity of the surface Rayleigh mode and the bulk acoustic modes of Si are comparable to those obtained by scanning for many hours. ©1996 American Institute of Physics.