| 摘要 |
<p>An optical recording and/or reproducing apparatus in which a main beam and two sub-beams are directed upon a disk. On the disk are arranged two sub-beam spots on the both sides of a main beam spot, peripheral side and central side, both spots being apart from the main beam spot by 1/4 track pitch. The reflected light of the main beam (Lm') and two sub-beams (Lp', Ln') from the disk are detected by first, second and third two-split light detecting elements (60, 62, 64) to produce first, second and third differential outputs (Sm, Sp, Sn) based on the detected outputs of the first, second and third two-split light detecting elements. The ratio of a first difference between the first and second differential outputs to a second difference between the first differential output and the sum of the second and third differential outputs are calculated by a divider to produce a tracking error signal (St). This makes it possible to obtain a tracking error signal having nearly a constant amplitude being unaffected by the depth of pits or height of bumps forming the recording tracks in a disk, the depth of guide grooves, the quantity of light of beams, and the reflection factor of the disk.</p> |
