| US 7,573,788 B2 | ||
| Method for correcting influence of thickness unevenness of recording medium, information recording/reproducing apparatus using the same method and optical head unit | ||
| Hideo Ando, Hino (Japan) | ||
| Assigned to Kabushiki Kaisha Toshiba, Tokyo (Japan) | ||
| Filed on Mar. 27, 2007, as Appl. No. 11/727,427. | ||
| Application 11/727427 is a division of application No. 11/299674, filed on Dec. 13, 2005, granted, now 7,274,628. | ||
| Application 11/299674 is a division of application No. 10/095007, filed on Mar. 12, 2002, granted, now 7,145,846. | ||
| Claims priority of application No. 2001-232633 (JP), filed on Jul. 31, 2001. | ||
| Prior Publication US 2007/0171780 A1, Jul. 26, 2007 | ||
| Int. Cl. G11B 7/095 (2006.01) | ||
| U.S. Cl. 369—44.26 [369/53.22] | 8 Claims |
| 1. An optical head unit comprising:
a light source that supplies light of a predetermined wavelength;
an objective lens that focuses the light from the light source to the recording layer of a recording medium;
an objective lens moving mechanism that moves the objective lens in the optical axis direction and in the direction intersecting
a signal mark string formed in the recording medium;
a defocus detecting system that detects a defocus in the objective lens;
a thickness unevenness detecting system that detects a thickness unevenness in a transparent resin layer of the recording
medium provided nearest the objective lens; and
a thickness unevenness correcting mechanism that changes a focusing characteristic of light impinging upon the objective lens
from the light source based on a change in the thickness of the transparent resin layer of the recording medium detected by
the thickness unevenness detecting system,
wherein a DC gain Gof of the objective lens moving mechanism is larger than a DC gain Got of the thickness unevenness correcting
mechanism.
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