Patent ID: 8289828

Claim:
An optical data recording/reproduction apparatus comprising: a laser light source; an objective lens for focusing a light beam emitted from the laser light source on a data recording surface of a data recording medium; a spherical aberration correcting unit located in a light path between the laser light source and the objective lens; an optical pickup with a driving unit for tilting the objective lens; and a controller for the optical pickup, wherein: where SCD denotes coma aberration which occurs at a focused light spot on the data recording surface when the data recording medium is tilted by unit angle and SCO denotes coma aberration which occurs at a focused light spot on the data recording surface when the objective lens is tilted by unit angle, a relation between a cover layer thickness of the data recording surface and ratio Î± of SCO to SCD (SCO/SCD) is previously calculated and stored in a storage unit; where alpha 1 denotes the ratio alpha for a data recording surface corresponding to a smallest cover layer thickness, tilting angle Î¸ 1 of the objective lens is determined based on the Î± 1 and a tilt adjustment of the objective lens is made; and where Î± 2 denotes the ratio Î± for a target data recording surface, tilting angle Î¸ 2 of the objective lens is estimated based on a ratio of Î± 2 to Î± 1 and a tilt correction of the objective lens is made.