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.