METHOD FOR DISCRIMINATING THE NUMBER OF LAYERS FROM MULTI-LAYER DISK AND APPARATUS FOR RECORDING OR REPRODUCING DATA ON/FROM DISK

摘要

A method for discriminating the number of layers of a multilayered disk and an apparatus for recording or reproducing data in/from the disk are provided to set positions of a spherical aberration correction unit differently in up and down sweeping operations so as to extend the detection range of the recording layer. A method for discriminating the number of layers of a multilayered disk comprises the steps of: setting a spherical aberration correction unit at a first position(S10); up-sweeping an objective lens for a disk(S13); acquiring the number and positions of recording layers from a first focus error signal(S15); setting the spherical aberration correction unit at a second position(S23); down sweeping the objective lens for the disk(S25); acquiring the number and positions of recording layers from a second focus error signal(S30); and calculating the pulse number and time from the first and second focus error signals to distinguish the recording layer(S37).