| 摘要 |
A push-pull signal Spp fetched with tracking open is smoothed to a smoothing signal Spp to remove signal components generated wobbling due to radial runout, and the smoothing signal is binarized to compute an autocorrelation value in the autocorrelation computing circuit 210 . This computing is made by multiplying the binarized signal by a signal delayed by the half cycle and sign-negated to compute the integrated value, and the integrated value output signal Dint is generated. A maximum value of the integrated value output signal Dint within a predetermined period of time is computed by the maximum value holding circuit 220 to output a maximum value output signal Dout. Depending on the amplitude of the maximum value signal Dout, the CPU 105 determines whether the recording medium is a writable one or read only one. Wobble determination can be made keeping tracking open, and a type of a recording medium is carried out accurately.
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