Patent ID: 7558178
Filing Date: 2009-07-07
Classification: G11B

Abstract:
1. An information recording/reproducing apparatus, comprising: an optical disk driver unit that holds and rotationally drives an optical disk; a laser source; a spherical aberration correction unit that adds the spherical aberration of a variable to a laser beam that is generated from the laser source; an objective lens that converges the laser beam added with the spherical aberration on the optical disk that is rotationally held by the optical disk driving section; a photodetector that receives the laser beam that is reflected by the optical disk; a focus error signal generator unit that generates a focus error signal from an output of the photodetector; a tracking error signal generator unit that generates a tracking error signal from the output of the photodetector; an actuator that drives the objective lens in a disk rotational axial direction; and a control unit that receives the focus error signal and the tracking error signal, and controls the amount of spherical aberration added by the spherical aberration correction unit and the amount of driving by the actuator, wherein the control unit controls the spherical aberration correction unit and the actuator so that the amplitude of the tracking error signal becomes maximum in a wide track pitch region having a track pitch TP that satisfies the following expression when it is assumed that a wavelength of the laser beam is λ and a numerical aperture of the objective lens is NA: