Transducers or Detectors:

The original Raman instrument which lead to the discovery of the Raman effect used eyes as the detector. Within initial versions of the spectrometers, photographic plates were used to detect the scattered radiation. This was followed through more sensitive photomultiplier tubes (PMTs) that permitted electronic data collection and manipulation. Therefore they had the drawback for they could count only one wavelength at a time. Presently most of the Raman spectrometers are FT instruments that use cooled germanium photoconductors as transducers. The multi channel dispersive instruments thus employ charge-coupled devices (CCDs) as transducers.

As the scattered radiation has a main component of the Rayleigh scattering, this is eliminated through using an appropriate filtering device like holographic grating or interference filters before the detector. Thus, the radiation reaching the transducer is primarily the Stokes component. You would have realized that this characteristic is specific to Raman spectrometers and is not needed in IR spectrometers.