Patent ID: 6157599
Filing Date: 2000-12-05
Classification: G11B

Abstract:
An optical storage apparatus comprising:a lens actuator for moving an objective lens through which a beam of light falls on a medium, to the direction across tracks of said medium;a carriage actuator for moving a carriage on which said lens actuator is mounted, to the direction across said tracks of said medium;a tracking error signal generating circuit for generating a tracking error signal in response to a position of said beam of light in the direction across said tracks, on the basis of a photosensitive output of a return light from said medium; anda low speed seek control unit for moving at a low speed a beam of light up to a target track, through speed control of said actuator lens;said low speed seek control unit including:a zero-cross detection unit for detecting a track zero-crossing of said tracking error signal;an interval detection unit for detecting an interval of said track zero-crossing;a speed control unit which detects a speed of a beam of light on the basis of said track zero-cross interval, sets a target speed on the basis of the number of remaining tracks up to said target track in the seeking operation, detects a speed error between said target speed and a detected speed, and drives said lens actuator by a current obtained by multiplying said speed error by a predetermined gain, to allow the detection speed of said beam of light to follow said target speed;an error detection judging unit for judging an error detection by said zero-cross detection circuit in the seeking operation; anda speed prediction calculating unit which, when it is judged that a zero-cross error detection has occurred during the seeking operation, predictively calculates a correct speed on the basis of the last track zero-cross interval free from any error detection and supplies said predicted speed in place of said detected speed to said speed control unit for the execution of speed control.