MULTILAYER OPTICAL DISC HAVING PREGROOVE MODULATION.

摘要

A record carrier is for recording information by writing marks in a track. The record carrier has at least a first recording layer (40) and a second recording layer (41). Each layer has a pregroove (14) indicating the position of the track and exhibiting a wobble modulated for representing physical address information. In addition the pregroove has a pregroove modulation (13) consituted by variations of a physical parameter related to the shape of the pregroove for encoding axiliary control information. In a scanning device the pregroove modulation is detected in the main detector signal by variations of the reflected radiation.