| 摘要 |
PROBLEM TO BE SOLVED: To prevent the focus servo from being released while suppressing the power consumption and heat generation by changing the gain of the focus servo in accordance with the progress degree at the time of moving an optical head to the objective position of the optical disk. SOLUTION: When the optical head 3 is moved to the objective position on the optical disk 2, the gain of the focus servo is changed in accordance with the progress degree of the movement. When the command to execute the access is received by a control means 9, the gain of the focus servo is increased first, that is, set to the 2nd gain (>1st gain) and increased by the specified value from the 1st gain. Next, the acceleration of the optical head 3 is started by impressing the driving voltage on a thread motor keeping to wait for the specific period. After this specific period is elapsed, the moving speed of the optical head 3 is converged to almost the prescribed value (becomes the constant speed). By means of comparatively increasing the gain of the focus servo at the time of acceleration (acceleration range) of the optical head 3, the focus servo is prevented from releasing.
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