Pre-pit detecting apparatus

Abstract

On an optical disc, an information record track wobbled in accordance with a wobbling signal is formed and pre-pits are formed at an predetermined interval on a guide track adjacent to the information record track. A pre-pit signal based on the pre-pit is detected by a pre-pit detecting apparatus. The pre-pit detecting apparatus is provided with: a composite signal extracting device for extracting a composite signal, in which the pre-pit signal is superimposed on the wobbling signal, out of a reflection light from the optical disc; a relaying device for relaying the composite signal extracted by the composite signal extracting device; a pre-pit signal detecting device for detecting a component of the pre-pit signal from the composite signal relayed by the relaying device; a wobbling signal extracting device for extracting a component of the wobbling signal out of the composite signal relayed by the relaying device; a synchronization wobbling signal generating device for generating a synchronization wobbling signal, whose frequency and phase are respectively synchronous with a frequency and a phase of the wobbling signal extracted by the wobbling signal extracting device; and a defect detecting device for detecting a defect on the optical disc. The relaying device relays the synchronization wobbling signal instead of the composite signal, if the defect is detected by the defect detecting device.

Dependencies are inferred from the claim text.