An optical head (1) for scanning an optical record carrier (2) is provided with a compensator (16) for compensating the field curvature aberration of the objective system (18) caused by operation of the optical head at a different field angles. A surface of the compensator (16) comprises a phase structure in the form of annular areas (52, 53, 54, 55, 56), the areas forming a non-periodic pattern of optical paths of different lengths. The optical paths change as a function of field angle and form a field angle-dependent wavefront deviation that compensates field curvature of the optical head.