Patent ID: 6754162
Filing Date: 2004-06-22
Classification: G11B

Abstract:
An optical pickup method for accessing an optical recording medium, the medium including a transparent substrate and a recording surface on the substrate, the optical pickup method comprising the steps of:passing a light beam, emitted by a light source, through a grating unit to separate the emitted light beam into a 0th order diffracted beam and 1st order diffracted beams; passing the diffracted beams, sent from the grating unit, through an objective lens to focus the beams onto the recording surface of the medium through the substrate, so that a main spot is formed on the recording surface by the 0th order diffracted beam and sub-spots, interposing the main spot therebetween, are formed on the recording surface by the 1st order diffracted beams; receiving respective reflection beams from the main spot and the sub-spots of the medium to generate detection signals from the received reflection beams; changing a pattern of the beams incident to the objective lens to correct a spherical aberration due to a deviation of a thickness of the substrate of the medium; and moving the grating unit relative to the light source along an optical axis to cancel shifting of sub-spot positions on the recording surface due to the spherical aberration correction, in order to generate a proper tracking error signal.