Patent ID: 8456628

Claim:
A spectroscopy system comprising: a light source for illuminating a sample such that scattering at wavenumbers shifted from an illumination wavenumber of the light source takes place at the sample; a detector; an optical path for collecting the scattered light and passing it to the detector; and a filter arrangement, comprising: a pair of filters in series in the optical path, arranged to reject light of the illumination wavenumber and accept light of the shifted wavenumbers, the pair of filters each being tilted with respect to the optical path at an angle of incidence such that each filter has a transmission characteristic for one of the first and second polarisation states having a cut-off edge closer to the illumination wavenumber than for the other of the first and second polarisation states, wherein the pair of filters are arranged so that, the cut-off edges for one of the pair of filters relative to the other of the pair of filters for the first and second polarisation states are reversed such that overall transmission characteristics for the first and second polarisation states for the pair of filters combined are closer together than for each of the pair of filters individually.