| 摘要 |
PROBLEM TO BE SOLVED: To quickly focus jump to an original recording layer prior to the occurrence of the out of focusing condition when an out of focusing occurred during a reproducing/recording of a multilayer optical disk having plural recording layers, to provide proper focusing and to restart reproducing/recording of the original recording layer. SOLUTION: An RF comparator 2 compares the levels of the envelope voltage of RF reproducing signals and a voltage value (a reference voltage VC) corresponding to the lower limit in the vicinity of a focused condition. A jump control section 3 computes the number of jumping over layers of the recording layers based on the frequencies, in which the voltage level of a focus error signal (an FE signal) exceeds the voltage value equivalent to the upper limit of the focused condition, and the frequencies in which the voltage level of the FE signal exceeds the voltage value equivalent to the lower limit of the focused condition. Then, based on the tilt of the waveforms of the FE signal when discrimination is made and determined that it is in the vicinity of a focused condition by the comparator 2, the direction of the out of focusing is detected and the focus jump is controlled based on the jumping layer number of the recording layers and the out of focusing direction.
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