| 摘要 |
PURPOSE:To improve the reliability of tracking by changing groove widths within the same medium. CONSTITUTION:The surface of the medium is irradiated with two sub-beams 2 and one main beam 1 and tracking servo is executed by a difference in the reflected light quantity of the two sub-beams from the grooves 4 formed on the optical recording medium 4 as a tracking error signal. Information is reproduced with this optical recording medium by the main beam 1. The widths of the grooves 4 are changed within the same medium in correspondence to the shapes or/and optical properties of the recorded information. The specified tracking error signal level is thereby obtd. within the medium. Setting of the tracking error signal at a sufficiently high level is consequently possible even if the tracking error signal is dropped by the contamination of the optical head and the surface of the disk substrate, etc., owing to the long term use and, therefore, the reliability of the tracking is improved. |
