| 摘要 |
In a system using a pickup including a bifocal lens which is one lens having two focal points, mere judgment by the number of peaks of a focus error signal does not achieve a clear judgment of the type of an optical disc, especially whether it is a CD or a DVD. Therefore, it is required to perform a judgment based on a difference in recording density of the optical disc. According to the present invention, when detecting a tracking error by the phase difference method, a pulse width limit circuit 35 in a tracking error detecting circuit 7 provides such limitations that a pulse of a width larger than a predetermined pulse width should not appear in a pulse train of a phase error signal. Disc type judgment is then performed for discs having different recording densities, for instance, whether it is a CD or a DVD, based on the phase error signal after the pulse width limitation or that before and after the pulse width limitation.
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