| 摘要 |
PURPOSE:To stably execute focusing control scarcely changing the outputs of focus error signals in a land part L and a group part G on the track of a medium by providing a sample and hold means to hold the level of the first signal in the preceding stage of a normalizing means. CONSTITUTION:Sample and hold can be executed to a first signal 5a based on the command of a CPU9 by a sample and hold circuit 7. For example, in a tracking state in the land part L on the track of a medium 1, the level of the first signal 5a is simultaneously held by the circuit 7 at a moment that a seek command is outputted from the CPU9. By using the held first signal 5a, a normalized focus error signal 8a is obtained through a normalizing circuit 8. By holding the level of the first signal 5a in such a way, the output of the focus error signal 8a can be kept almost constant. Thus, the level of the focus error signal is scarcely changed for a focus error signal 8aL in the land part L and a focus error signal 8aG in the group part G and focusing servo can be stably executed. |
