The range of spatial frequencies of the information areas in an optical record carrier ( 130 ) that can be read by conventional means can be increased substantially by providing the information layer ( 1134 ) with a birefringent diffraction grating ( 136 ) and using a read beam (b) that comprises two mutually perpendicular polarised components (b 1 , b 2 ) only one of which will be diffracted by the grating.