A sample which is exposed to excitation radiation scatters light to a separator filter. The scattered light includes a Raman spectrum. The separator filter reflects, a spectral band of the radiation which it receives and transmits, the remainder of the radiation which it receives. The reflected spectral band is centered on the excitation radiation. The spectral band is collected and guided to a band-eliminating filter in order to eliminate therefrom a spectral band which is narrower than the reflected spectral band, and which embraces the wavelength of the excitation radiation. The band-eliminating filter has a steep elimination slope. A signal corresponding to the reflected spectral band, from which the narrow band has been eliminated in this way, is combined with the radiation transmitted by the separator filter and the combined radiations are supplied to a detection and analysis unit.