| 摘要 |
PROBLEM TO BE SOLVED: To provide a focus control device and a focus control method which are capable of performing speedy and accurate layer jumping to a multi-layer type optical medium. SOLUTION: An FE signal comparator circuit outputs H as a comparison signal when an FE signal is larger than (+α) or less than (-β), and outputs L when the FE signal is from (-β) to (+α). A counter circuit counts the rise and fall of this comparison signal. A driving signal generation circuit outputs a kick signal to a pickup 12 when the count values are 0 and 1, outputs a uniform signal when the count value is 2, and outputs a brake signal when the count value is 3, and the focus control is carried out by locking on the focus servo to follow the FE signal when the count values are 4, 8, and 12. Moreover, when the count values are 6 and 10, a negative and a positive hold signal are outputted to converge an overshoot, respectively. COPYRIGHT: (C)2005,JPO&NCIPI
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