Patent ID: 8094532
Filing Date: 2012-01-10
Classification: G11B

Abstract:
1. An interlayer movement apparatus for moving a focal point of a laser light between layers of an optical disc in an optical disc apparatus which performs recording and reproduction of data with irradiating the laser light onto the optical disc which has a plurality of information layers with inter-layer distances between the respective information layers that are different due to the optical disc specifications, comprising: an objective lens which collects the laser light from an optical source; a focus actuator for moving the objective lens in its optical axis direction; a focus error detection means for detecting a focus error signal which indicates a convergent state of the laser light on the information layer of the optical disc; a focus control system for controlling the focus actuator so that the laser light on a predetermined information layer of the optical disc comes into a predetermined convergent state; and an interlayer movement control system operated to drive said focus actuator according to a relative speed between the information layer of the optical disc and the focal point which was calculated using the respective interlayer distances which are specified by the optical disc specifications and the time required for the focal point of the laser light passing through the respective layers which was measured on the basis of the focus error signal, thereby to perform one or both of a first interlayer movement that makes the focal point of the laser light interlayer-move to the information layer that is two or more layers apart and a second interlayer movement that makes the focal point of the laser light interlayer-move to an adjacent information layer, thereby to make the focal point of the laser light move to an objective information layer, wherein said interlayer movement control system is one which is operated, when moving the focal point of said laser light to the information layer of said optical disc that is most apart from said objective lens, after moving the focal point of said laser light to an information layer that is one prior to the objective information layer by said first interlayer movement, to once close the focus control by the focus control system, and thereafter, to make the focal point of the laser light move to the objective information layer.