Abstract: An objective for an optical data storage read/write head focuses a laser beam at a spot on an optical recording surface protected by a transparent cover of an optical disc. The imaging is provided by a gradient index singlet lens having bending and an index gradient which is selected depending on the thickness of the lens and the thickness of the cover over the recording surface so as to provide aberration correction over a paraxial image height of the spot which tolerates tracking errors (displacements with respect to the track) on the recording surface. The objective desirably obtains its power exclusively from the curvature of its surfaces, with the index gradient providing for aberration correction. The gradient is preferably axial, decreasing from the vertex at the front surface (the surface on which the laser beam is incident) over a sag distance along the optical axis towards the back surface, which is opposite to the cover of the optical data storage device.