Optical disc playback apparatus and method of judging disc type

Details Optical disc playback apparatus and method of judging disc type Optical disc playback apparatus and method of judging disc type

2005-03-15

2005-03-15

To, Doris H. (Department: 2655)

Dynamic information storage or retrieval

Condition indicating, monitoring, or testing

Including radiation storage or retrieval

C369S053280, C369S044410, C369S053110, C369S053220, C369S059100

Reexamination Certificate

active

06868052

ABSTRACT:
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 circuit35in a tracking error detecting circuit7provides 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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