Patent attributes
A reference-position learning unit measures a current of one rotation of a medium in a state in which the focus of an objective lens is pulled-in by a focus pull-in control unit at a predetermined point in the radial direction of the medium upon insertion of the medium, calculates a mean current value thereof, and stores the calculated mean current value in the memory as a reference current value for positioning the objective lens at a reference position at which focus pull-in control is started. In focus pull-in performed after a learning process, a reference-position control unit positions the objective lens at a reference position obtained through a learning process in accordance with the reference current, and then, causes the focus pull-in control unit to perform focus pull-in.
