Patent ID: 7079470

Claim:
A device for reading and/or writing a record carrier, the device including a radiation source and means tbr converging a radiation beam from the radiation source on a written surface and/or a surface to be written of the record carrier, said means including polarization means and a diffraction grating of at least a birefringent material for focusing the radiation beam on one of two possible types of surfaces in dependence upon a direction of polarization of the radiation beam, a first surface of said two possible types of surfaces corresponding to a surface to be read and/or to be written of a first type of record carrier, and a second surface corresponding to a surface to be read and/or to be written of a second type of record carrier, characterized in that the diffraction grating is present in a central area of the radiation beam, and in that the diffraction grating forms substantially a first diffraction beam for a first direction of polarization of the radiation beam and substantially a second, higher-order diffraction beam for a second direction of polarization of the radiation beam, such that the radiation beam contains both the first and second diffraction beams and wherein the diffraction grating is divided into a plurality of zones with the zones becoming more narrow preceding from a center of the diffraction grating towards an edge of the diffraction grating in a direction perpendicular to to optical axis.