| 摘要 |
A detection signal is asserted when a surface of an optical disc or an information recording layer is detected. An asserting (masking) time interval of the detection signal is set such that the number of times of asserting the detection signal becomes at most two times when a focal position of the objective lens passes at least the surface of the optical disc. After the objective lens is moved for a prescribed section in a direction along which the objective lens comes closer to the optical disc, a kind of the optical disc is discriminated based on a time interval T1 from a first beginning of assertion to a second beginning of assertion, if the number of times of asserting the detection signal is two times, or based on a time interval which is a longer time interval between the time interval T1 from the first beginning of assertion to the second beginning of assertion and a time interval T2 from the second beginning of assertion to a third beginning of assertion if the number of times of asserting the detection signal is more than two times.
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