Patent ID: 6845068
Filing Date: 2005-01-18
Classification: G11B

Abstract:
1. An optical disk apparatus, comprising: a lens actuator for moving an objective lens toward a light axis direction of a light beam to be radiated to an optical disk; a focus error detection unit for detecting a position error from a just focus position of a recording surface of the optical disk; a feedback control unit for computing a control signal for moving said lens actuator so that a focus position error amount is controlled to zero or a predetermined value; a drive unit for driving said lens actuator based on said control signal; and a learning control unit for obtaining an unknown function for one disk rotation along with a periodic disturbance to memory which is comprised of N number of memory cells by a learning algorithm that is an approximate function which is approximated by a height allocated to each time block when the time required for one rotation of said disk is divided by N; wherein said learning control unit: samples a signal which follows a focus positional signal according to said learning algorithm at a sampling period which is less than the time obtained by dividing the time required for one rotation of said disk by N; updates one or more memory cells corresponding to a sampling time synchronizing with said sampling period according to a signal value; reads a value of at least one memory cell located at cell positions corresponding to an output time at an output period which is less than a time obtained by dividing the time required for one rotation of said disk by N; and outputs a feed-forward signal of a periodic disturbance compensation according to said read value.