Patent ID: 7606121

Claim:
An optical disk drive comprising: a light source for producing a light beam; an objective lens for converging the light beam; an actuator for moving the objective lens with respect to an optical disk; converging state detecting means for generating a focus error signal representing a converging state of the light beam on an information storage layer of the optical disk; a focus position changing means for changing information about a target focus position of the light beam when modes of operation are switched between a read mode and a write mode, the target focus position of the light beam being defined relative to the information storage layer of the optical disk; a circuit offset canceling section for adding a read mode offset signal onto the focus error signal so as to cancel a read mode electrical offset that is produced in the read mode, and adding a write mode offset signal onto the focus error signal so as to cancel a write mode electrical offset that is produced in the write mode; focus control means for controlling the operation of the actuator such that the focus position of the light beam matches its target focus position of the light beam as closely as possible in accordance with information about the target focus position and the focus error signal, the focus position of the light beam being defined relative to the information storage layer of the optical disk, wherein the target focus position of the light beam includes a first target focus position for the read mode and a second target focus position for the write mode, the first target focus position being different from the second target focus position, wherein the focus control means sets the focus position of the light beam to the first target focus position in the read mode and to the second target focus position in the write mode, respectively.