Patent ID: 7116609

Claim:
An optical storage system having a carriage actuator for moving an objective lens, which is for irradiating a medium with an optical beam, in the direction across tracks of the medium, a lens actuator for moving the objective lens in the direction toward the medium, a focus error signal generation circuit for generating a focus error signal indicating deviation between the focal point of the optical beam and a recording layer of the medium in accordance with received output of the light returned from the medium, and a focus pull-in control unit for closing a focus servo loop at a point where the focus error signal crosses zero while slowly moving the objective lens in the direction getting away from the medium after the objective lens is moved in the direction toward the medium by a predetermined distance in a state in which the medium is being rotated, the optical storage system comprising: a reference-position learning unit for measuring a current of one rotation of the medium in a state in which the focus of the objective lens is pulled-in by the focus pull-in control unit at a predetermined point in the radial direction of the medium upon insertion of the medium, calculating a mean current value thereof, and storing the calculated mean current value in a memory as a reference current value for positioning the objective lens at a reference position at which focus pull-in control is started; and a reference-position control unit for causing the focus pull-in control unit to perform focus pull-in after positioning the objective lens in accordance with the reference current when focus pull-in is performed after the learning process.