The Sunyaev-Zel'dovich effect in the millimetric region

We analyse the spectral shape and possible spurious distortions of the Sunyaev-Zel'dovich effect, arising from the interaction of the cosmic background radiation with hot gases of rich clusters, in the millimetric region. We show that one can measure this effect with high accuracy with present-day infrared detectors, obtaining a larger amount of information than by using radio systems. In particular, one can accurately measure the temperature of the cosmic background radiation without the usual absolute calibration of the detector.