Patent ID: 7778130
Filing Date: 2010-08-17
Classification: G11B

Abstract:
1. An optical disc apparatus comprising: an optical pickup for irradiating a laser beam onto an optical disc through an objective lens to record or read data on or from the optical disc; an address information reading unit for using the data read by the optical pickup to read address information in the data based on wobbled grooves and/or land pre-pits preformatted and recorded on the optical disc, and to detect signal levels of the address information; an RF signal reading unit for reading an RF signal corresponding to the data recorded on the optical disc; and a defocus control unit for controlling jitter of the RF signal read by the RF signal reading unit and for adjusting a defocus position of the objective lens based on a focus error signal to perform focus control, wherein the defocus control unit comprises: a reading determination unit which, at an initial reading of the optical disc, controls the address information reading unit to read the address information, and determines based on the reading of the address information reading unit whether the address information reading unit succeeds in reading the address information; a defocus position offset unit for offsetting the defocus position of the objective lens when the reading determination unit determines that the address information reading unit fails in reading the address information; an approximate level line calculating unit for calculating an approximate line of characteristics of the signal levels of the address information detected by the address information reading unit at defocus positions offset by the defocus position offset unit; and a defocus position adjusting unit for adjusting the defocus position of the objective lens at a position corresponding to a peak value of the approximate line calculated by the approximate level line calculating unit, and wherein after the defocus position adjusting unit adjusts the defocus position, the defocus control unit controls the address information reading unit to read the address information, thereby improving the signal level of the address information to be read.