| 摘要 |
<P>PROBLEM TO BE SOLVED: To realize proper data reproduction from a recording medium which is subject to high-density recording due to a narrow track pitch of an optical cutoff or less. <P>SOLUTION: In a recording medium, regarding information recording tracks, there is formed a track group in which a plurality of tracks are adjacent to each other with a track pitch Tp1 which is shorter than a track pitch corresponding to an optical cutoff defined from a wavelength of irradiated laser light and a NA of an irradiation optical system. A track group pitch TpG is set to be longer than the track pitch corresponding to the optical cutoff. A servo laser spot, which provides astigmatism which makes an angle of about 45 degrees with respect to a tangential direction of the tracks, and one or more reproduction laser spots are irradiated via an objective lens. A tangential push-pull signal obtained by reflected light information of the servo laser spot is set to be a tracking error signal. By tracking servo control, the reproduction laser spots are set to be on-track on any of the information recording tracks, and data is reproduced from the reflected light information thereof. <P>COPYRIGHT: (C)2013,JPO&INPIT |
