Abstract: A lens pull-in method is used in a near-field optical accessing system. When a lens is in a far-field range, the lens is driven to approach a surface of an optical disc in an open loop control state. If the lens enters a near-field range, a first GES level is inputted as a set value and the lens is driven in a close loop control state. When the gap error signal decreases to the first GES level, the set value is changed to a second GES level, which is higher than the first GES level. When the gap error signal increases to the first GES level, the set value is changed to a target GES level, so that the gap error signal is maintained at the target gap error signal.

Abstract: A lens pull-in method is used in a near-field optical accessing system. When a lens is in a far-field range, the lens is driven to approach a surface of an optical disc in an open loop control state. If the lens enters a near-field range, a first GES level is inputted as a set value and the lens is driven in a close loop control state. When the gap error signal decreases to the first GES level, the set value is changed to a second GES level, which is higher than the first GES level. When the gap error signal increases to the first GES level, the set value is changed to a target GES level, so that the gap error signal is maintained at the target gap error signal.

Abstract: A CD drive has a pick-up head for reading data of an optical disc, and a motor for rotating the optical disc. The method first adjusts the rotary speed of the motor so that the vibration frequency of the CD drive is approximately the resonance frequency of a coil of the pick-up head. Then, when the vibration frequency of the CD drive is approximately the resonance frequency of the coil of the pick-up head, the method detects if the voltage of a central error (CE) signal of the CD drive is greater than a threshold voltage. Finally, the method determines if the optical disc is an unbalanced disc according to the comparison result.