| 摘要 |
<p>In an optical head (20) including an optical unit (13) comprising a light source (1) and photosensor (9), and a main focus servo means (14) to allow an objective lens (5) to focus a light beam emitted from the light source (1), and further an auxiliary focus servo means (15) provided between the optical unit (13) and objective lens (5) to detect a position of the objective lens (5), the objective lens (5) staying outside a range in which the main focus servo means (14) provides a significant signal output, is moved into that range based on a detection signal from the auxiliary focus servo means (15). <IMAGE></p> |
