| 摘要 |
<p>A method for measuring the difference between the center of a pre-pit pattern for control and the center of the groove formed between recording tracks of an optical disc of a sample-servo-tracking system. When the modulation factors of wobble pits are measured while continuously tracking the center (land part) of the groove, a difference is caused between the measured modulation factors, if the center of the wobble pits is displaced from the center of the groove. Also, when a tracking offset is so adjusted that the modulation factors of the wobble pits are made equal to each other by tracking the groove, the error signal of tracking the land part has an offset quantity (DC component). Therefore, by tracking the land part between the grooves and by scanning a light beam, the difference between the center of the groove and the pre-pit pattern is measured using the difference between the outputs reproduced from a pair of wobble pits. Alternatively, by so scanning the optical beam that the outputs reproduced from a pair of wobble pits are equal to each other, the difference between the center of the groove and the pre-pit pattern is measured, using the error signal of tracking the land part between the grooves.</p> |
