Optical disk apparatus and tracking method
AssigneesHitachi, Ltd., Hitachi-LG Data Storage, Inc.
InventorsMariko Umeda, Hiroyuki Minemura, Motoyuki Suzuki
Life of this patent
Estimating the term…
Abstract
A tracking offset is reduced. The effect of an SPP signal fluctuation is reduced by using a variable mixing ratio DPP method, and a residual tracking offset is minimized.
Claims10
An optical disk apparatus, comprising:
- an optical head including a light source, a beam splitter which splits a beam from the light source into a plurality of beams, an objective lens which converges the plurality of beams split by the beam splitter into a plurality of optical spots on an optical disk, a photo-detector which detects the plurality of optical spots reflected from the optical disk, and an actuator which drives the objective lens in a radial direction of the optical disk;
- a thread motor which drives the optical head in the radial direction of the optical disk;
- a unit which generates a plurality of tracking spot signals from detection signals generated by detecting the plurality of optical spots;
- a unit which generates a tracking control signal for driving the actuator by mixing the plurality of tracking spot signals;
- and
- a mixing ratio changing unit which changes a mixing ratio of the plurality of tracking spot signals;
- wherein the mixing ratio changing unit determines the mixing ratio based on a measured amount of fluctuation of each of the tracking spot signals and a measured amount of decentering of the optical disk.
A tracking method of an optical disk apparatus which irradiates an optical disk with a plurality of optical spots and generates a tracking signal from detection signals generated by detecting light reflected from the plurality of optical spots, the tracking method comprising the steps of:
- generating a tracking signal with a variable mixing ratio by adjusting outputs of a plurality of tracking error signals, which are generated from detection signals generated by detecting the light reflected from the plurality of optical spots, and by performing addition or subtraction using the plurality of adjusted tracking error signals;
- changing the mixing ratio according to an operating condition of the optical disk apparatus;
- and
- controlling positions in a disk radial direction of the plurality of optical spots by using the tracking signal with a variable mixing ratio;
- wherein the plurality of optical spots include a main spot and two sub-spots positioned, being shifted by half a track pitch each, on both sides of the main spot;
- and
- wherein the step of changing the mixing ratio according to an operating condition of the optical disk apparatus includes
- obtaining an amount of fluctuation of a second tracking error signal which is generated from detection signals generated by detecting the two sub-spots and an amount of shifting of an objective lens which converges the plurality of optical spots on the optical disk,
- obtaining, when the amount of fluctuation is greater than a predetermined threshold value, an amount of offset of the second tracking error signal resulting from the shifting of the objective lens, and
- obtaining the mixing ratio based on the amount of offset and the amount of fluctuation.
A tracking method of an optical disk apparatus which irradiates an optical disk with a plurality of optical spots and generates a tracking signal from detection signals generated by detecting light reflected from the plurality of optical spots, the tracking method comprising the steps of:
- generating a tracking signal with a variable mixing ratio by adjusting outputs of a plurality of tracking error signals, which are generated from detection signals generated by detecting the light reflected from the plurality of optical spots, and by performing addition or subtraction using the plurality of adjusted tracking error signals;
- changing the mixing ratio according to an operating condition of the optical disk apparatus;
- and
- controlling positions in a disk radial direction of the plurality of optical spots by using the tracking signal with a variable mixing ratio;
- wherein the mixing ratio is changed in steps.
Dependencies are inferred from the claim text.