| 摘要 |
PURPOSE:To execute the operation of track servo even for the optical recording medium of a continuous servo system, and to obtain a small-sized and simple device by providing a means to detect independently the light outputs of three semiconductor lasers. CONSTITUTION:When a first light spot 11 advances on a track in the direction of an arrow mark in a figure, difference between quantity of light of reflected light in a second light spot 12 and the quantity of light of the reflected light in a third light spot 13 is caused accordingly to a deviation from the center of the track. Each reflected light is fed back to a second and a third semiconductor lasers, and the change of the quantity of light of the reflected light is detected as the change of the light output of the semiconductor laser. Accordingly, a track error signal can be obtained from the difference between the light output of the second semiconductor laser and the light output of the third semiconductor laser. Thus, the operation of track servo can be executed not only for the optical recording medium of a sample servo system but also for the optical recording medium of the continuous servo system, and the small-sized and simple device can be obtained. |
