Optical disk device and method for controlling the same
View Patent ↗In an optical disk device, a technique for AC tilt correction with stability and following capability is provided in which, during an operation of a tracking servo mechanism, a lens shift amount obtained from a tracking control signal or a lens position error signal is measured for each of predetermined angles of rotation of an optical disk, and the measured values are averaged in a radial direction of the optical disk, and a tilt controller corrects an AC tilt based on the resulting average value.
1. An optical disk device comprising:
an optical pickup including an objective lens configured to focus laser light onto an optical disk;
a tilt actuator configured to drive and tilt the objective lens in a radial direction of the optical disk;
a tilt driver configured to drive the tilt actuator;
a lens shift amount extractor configured to extract, as a lens shift amount, a displacement amount of the objective lens from a normal position in the optical pickup in the radial direction of the optical disk; and
a tilt controller configured to average the lens shift amounts for a predetermined angle of rotation of the optical disk in the radial direction of the optical disk to calculate a lens shift amount average value for the predetermined angle of rotation of the optical disk, and control the tilt driver based on a lens shift amount average value for each of the predetermined angles of rotation of the optical disk,
wherein the tilt controller has a memory area configured to store a lens shift amount average value for each of the predetermined angles of rotation of the optical disk, calculates an updated lens shift amount average value based on a lens shift amount average value read from the memory area based on a current angle of rotation of the optical disk, and a lens shift amount extracted by the lens shift amount extractor, and writes the updated lens shift amount average value to the memory area.
2. The optical disk device of claim 1 , wherein the lens shift amount extractor extracts the lens shift amount based on a lens position error signal indicating the displacement amount of the objective lens in the optical pickup in the radial direction of the optical disk with reference to a center position of the optical pickup including the objective lens.
3. The optical disk device of claim 1 , further comprising:
a tracking actuator configured to drive and translate the optical pickup in the radial direction of the optical disk;
a tracking driver configured to drive the tracking actuator; and
a tracking controller configured to control the tracking driver,
wherein the lens shift amount extractor extracts the lens shift amount based on a tracking control signal which is supplied from the tracking controller to the tracking driver.
4. The optical disk device of claim 3 , wherein the lens shift amount extractor extracts the lens shift amount based on a signal selected to improve an index of a reproduced signal, the selected signal being selected from a lens position error signal indicating the displacement amount of the objective lens in the optical pickup in the radial direction of the optical disk with reference to a center position of the optical pickup including the objective lens, and the tracking control signal which is supplied from the tracking controller to the tracking driver.
5. The optical disk device of claim 1 , further comprising:
a tracking actuator configured to drive and translate the optical pickup in the radial direction of the optical disk;
a tracking driver configured to drive the tracking actuator; and
a tracking controller configured to control the tracking driver,
wherein the tilt controller, during at least one of recording and reproduction of information to and from the optical disk, reads and writes the memory area to update a lens shift amount average value for each of the predetermined angles of rotation of the optical disk which is stored in the memory area, simultaneously with an operation of a tracking servo mechanism including the tracking actuator, the tracking driver, and the tracking controller.
6. The optical disk device of claim 1 , wherein the tilt controller controls the tilt driver based on a lens shift amount average value read from a memory position different from memory positions which are used when the memory area is read and written to update a lens shift amount average value for each of the predetermined angles of rotation of the optical disk which is stored in the memory area, to correct a phase delay which occurs due to the averaging of the lens shift amounts.
7. The optical disk device of claim 1 , further comprising:
a tracking actuator configured to drive and translate the optical pickup in the radial direction of the optical disk;
a tracking driver configured to drive the tracking actuator; and
a tracking controller configured to control the tracking driver,
wherein the tilt controller, when a tracking servo mechanism including the tracking actuator, the tracking driver, and the tracking controller is inactive, does not update a lens shift amount average value for each of the predetermined angles of rotation of the optical disk which is stored in the memory area.
8. The optical disk device of claim 1 , further comprising:
a focus actuator configured to drive and move the objective lens in an optical axis direction of the optical pickup;
a focus driver configured to drive the focus actuator; and
a focus controller configured to control the focus driver,
wherein the tilt controller, when a focus servo mechanism including the focus actuator, the focus driver, and the focus controller is inactive, does not update a lens shift amount average value for each of the predetermined angles of rotation of the optical disk which is stored in the memory area.
9. A method for controlling an optical disk device including an optical pickup including an objective lens configured to focus laser light onto an optical disk , the method comprising:
a lens shift amount extracting step of extracting, as a lens shift amount, a displacement amount of the objective lens from a normal position in the optical pickup in a radial direction of the optical disk; and
a tilt control step of averaging the lens shift amounts for a predetermined angle of rotation of the optical disk in the radial direction of the optical disk to calculate a lens shift amount average value for the predetermined angle of rotation of the optical disk, and controlling tilting and driving of the objective lens in the radial direction of the optical disk based on a lens shift amount average value for each of the predetermined angles of rotation of the optical disk,
wherein a lens shift amount average value for each of the predetermined angles of rotation of the optical disk is stored in a memory, an updated lens shift amount average value is calculated based on a lens shift amount average value read from the memory based on a current angle of rotation of the optical disk, and a lens shift amount extracted by the lens shift amount extracting step, and the updated lens shift amount average value is written to the memory.