| 摘要 |
PURPOSE:To accurately control track jump, by detecting the central value, and the level of constant width over and under the central value of a track error signal, and varying an accelerating time and a decelerating time under execution of track jump. CONSTITUTION:The accelerating time and the decelerating time of an objective lens 2 are controlled by detecting the central value and the threshold value of constant width from the central value of the track error signal obtained at time of performing the track jump. In other words, when the accelerating time Ta required at a time when a second threshold value from the start of acceleration is detected, is smaller than a first reference accelerating time T1a, the accelerating time is set by the time to detect the second threshold value, and it is set by the time when the next threshold value is detected when the time Ta is larger than a second reference accelerating time T2a, and it is set by the time when the central value is detected when it is T1a< Ta<T2a. Also, the decelerating time is set by the time when the next threshold value is detected, in a case where the decelerating time Td required by a detecting time is set at Td>T2d for a first and a second decelerating time T1d and T2d, and it is set by the time when the next threshold value is detected in the case where it is Td<T1, and it is set by the time when a second central value is detected in the case where it is T1d<Td<T2d.
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