Patent ID: 8089841
Filing Date: 2012-01-03
Classification: G11B

Abstract:
1. A reproducing signal measurement method for a multilayer optical recording medium having at least three recording layers, a signal being recorded with a first frequency in a first recording area located on an nth recording layer when counted from an opposite side from a light incidence side used when the multilayer optical recording medium is irradiated with light, a signal being recorded with a second frequency different from the first frequency in a second recording area located on an (n+2)nd recording layer when counted from the opposite side from the light incidence side used when the multilayer optical recording medium is irradiated with light, the first recording area and the second recording area overlapping in a plane, the reproducing signal measurement method comprising the steps of: reproducing the signal recorded in the first recording area on the nth recording layer; separating signals recorded respectively with the first frequency and the second frequency from the reproduced signal; discriminating amplitude of the signal of the first frequency and a maximum value in amplitude of the signal of the second frequency; and calculating a signal amplitude ratio between the maximum value of the amplitude of the signal of the second frequency and the amplitude of the signal of the first frequency.