Patent ID: 6633523
Filing Date: 2003-10-14
Classification: G11B

Abstract:
Optical memory apparatus for conducting focus servo control to maintain constant relative positional relationship between a memory medium and an optical spot, comprising:a focus actuator for moving said optical spot relative to said memory medium; a driving unit for driving said focus actuator; a focus detecting unit for detecting a focus error signal indicating relative positional relationship between said memory medium and said optical spot; a focus servo control unit for driving said driving unit based on the focus error signal detected from said focus detecting unit in order to move said focus actuator; an offset inserting unit for inserting a predetermined offset to said focus error signal; and a focus servo pull-in determining unit for detecting level change of said focus error signal where said predetermined offset is inserted to said focus error signal when said focus servo control unit has conducted the focus servo pull-in, and determining success or failure of focus servo pull-in, wherein a successful focus servo pull-in is determined if the level change of said focus error signal is an expected value which corresponds to an amount of level change which occurs when such predetermined offset is inserted in said focus error signal.