Patent ID: 7839752

Claim:
An optical disc drive for recording information to and/or reproducing information from three types of optical discs including a first optical disc having a highest recording density, a second optical disc having a second highest recording density and a third optical disc having a lowest recording density by selectively using one of three types of light beams including first, second and third light beams, the optical disc drive comprising an objective lens, at least one of surfaces of the objective lens comprising a step structure which has a plurality of concentric refractive surface zones and gives an optical path length difference to an incident beam at each step formed between adjacent refractive surface zones, wherein when the third laser beam passes through the objective lens, the objective lens produces normal diffraction order light converging to a recording surface of the third optical disc and undesired diffraction order light converging to a point deviating from the recording surface of the third optical disc, wherein a distance from a point to which the normal diffraction order light converges to a point to which the undesired diffraction order light converges is larger than or equal to twice a pull-in range of a focus error signal obtained when a recording operation or a reproducing operation for the third optical disc is performed.