Multi-layered recording disk and recording/reproducing system using the same

摘要

A multi-layered disk which can improve a data recording density and also can record signals and allow reading and reproduction of the recorded signals in good conditions and a recording system as well as a reproducing system using the same and a multi-layered recording disk in which a plurality of data recording surfaces are laminated. In a band wherein, against an MTF level obtained when a read light is on-focus to one of the data recording surfaces, an MTF level obtained when the read light is defocusing to other data recording surfaces is 1/N (N is a real number larger than 1), data signals are recorded in each of the data recording surfaces. A distance t between each data recording surface, numerical aperture NA of an objective lens guiding a read light to any of the data recording surfaces, a wavelength lambda of the read light, an equivalent refractive index n between each data recording surface, and a number i of laminated data recording surfaces satisfy the following relation: 1.4 n lambda /(NA)2>/=t>/=7.5 n3 lambda /{(n2-1)(NA)4(i-1)}.