| 摘要 |
PURPOSE:To attain correct focusing by containing a lens supporting mechanism, lens actuator and a positional error detector having plural multi-division photodetecting parts. CONSTITUTION:A laser beam emitted from a multibeam laser diode 1 is converged on the face of a recording medium 3 through a converging lens 2, the reflected light passes through the converging lens 2 oppositely again and its one part reaches a positional error detector 4. The lens actuator has the converging lens 2, a movable part 11, a supporting part 22 and first and second two focus actuators 23 and 24 as first and second focus driving parts. In this case, by impressing a current on the coil of the second focus actuator 24 in accordance with the output of a second two-division photodetecting part 42, the converging lens 2 executes an action which is the combination of translation and rotation so that two beam spots 25 and 26 are both correctly focused in accordance with the waviness of the face of the recording medium 3 and correct focus control can be executed. |
