An optical characterisation system is described for characterising optical material. The system typically comprises a diffractive element (104), a detector (106) and an optical element (102). The optical element (102) thereby typically is adapted for receiving an illumination beam, which may be an illumination response of the material. The optical element (102) typically has a refractive surface for refractively collimating the illumination beam on the diffractive element (104) and a reflective surface for reflecting the diffracted illumination beam on the detector (106). The optical element (102) furthermore is adapted for cooperating with the diffractive element (104) and the detector (106) being positioned at a same side of the optical element (102) opposite to the receiving side for receiving the illumination beam.