Optical disk device adapted for reliably detecting pre-pit...

Dynamic information storage or retrieval – Control of storage or retrieval operation by a control... – Control of information signal processing channel

Reexamination Certificate

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Details

C369S047170

Reexamination Certificate

active

07054246

ABSTRACT:
An optical disk device which performs data recording and reproduction with regard to an optical disk on which pre-pit information for specifying an address is formed. An optical disk is irradiated with a laser beam and return light from the optical disk is detected by two photodetectors which are disposed in the radial direction. After the levels of two signals from the photodetectors are limited, a difference between these signals is calculated. Due to the limitation of the levels, noise during the recording power period is removed so that pre-pit information during the reproducing power period, namely during the space period, is extracted. Further, by calculating a difference between the two signals from the photodetectors, pre-pit information during the recording power period is extracted. It is also possible for a laser beam to be split into a main laser beam and a sub laser beam, and the sub laser beam is irradiated onto a track on which a pre-pit is formed and the pre-pit information is extracted from a signal of return light from the sub laser beam.

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