Patent ID: 6452879
Filing Date: 2002-09-17
Classification: G11B

Abstract:
An optical storage apparatus comprising:an actuator capable of positioning an objective lens for irradiating a medium with a light beam from a light source to a target position on the medium; a servo error signal generating circuit which generates a servo error signal indicative of a deviation from a target position of the objective lens on the basis of reflected light from the medium; an offset correcting circuit which corrects an offset by adding an arbitrary correction amount to the servo error signal outputted from said servo error signal generating circuit; a filter which eliminates an unnecessary frequency component from the servo error signal outputted from said offset correcting circuit; a servo control unit which positions said objective lens to a target position on the medium on the basis of the servo error signal outputted from said filter; an offset measuring unit which receives the servo error signal which does not pass through said filter and measures an offset amount in the servo error signal, caused by a change in an amount of reflection light; and a correction amount calculating unit which calculates a correction signal to cancel out said offset amount and outputs the correction signal to perform correction to said offset correcting circuit for an offset generating period.