Information recording medium, information supply system, and optical information device

Abstract

An optical disk compliant with both a conventional optical disk such as a BD, HD DVD, and the like and a next-generation high-density optical disk according to a near-field light recording system and the like is provided. An information recording medium includes a first information recording layer and a second information recording layer, to/from which information is recorded or reproduced using laser beam. The first information recording layer is formed at a laser beam entrance surface, and is configured so that information can be recorded thereupon and/or reproduced therefrom using a first objective lens having a first numerical aperture NA 1 and laser beam of a first wavelength λ 1 . The second information recording layer is formed so as to have a distance to the laser beam entrance surface is 0.05 mm to 1.2 mm and is configured so that information can be recorded thereupon and/or reproduced therefrom using a second objective lens having a second numerical aperture NA 2 and laser beam of a second wavelength λ 2 . When a diffraction limit δ 2, determined by the numerical aperture NA 2 and the second wavelength λ 2 , is taken as δ 2 =0.61×λ 2 /NA 2 , a track pitch Tp 1 of a track formed on the first information recording layer is Tp 1<δ2.

1 . An information recording medium onto which information is to be recorded and/or from which information is to be reproduced using laser beam, the information recording medium comprising:
 a first information recording layer formed at a laser beam entrance surface and configured so that information can be recorded thereupon and/or reproduced therefrom using a first objective lens having a first numerical aperture NA 1  and laser beam of a first wavelength λA; and   a second information recording layer formed so as to have a distance to the laser beam entrance surface is 0.05 mm to 1.2 mm and configured so that information can be recorded thereupon and/or reproduced therefrom using a second objective lens having a second numerical aperture NA 2  and laser beam of a second wavelength λ 2 ,   wherein when a diffraction limit δ 2 , determined by the numerical aperture NA 2  and the second wavelength λ 2 , is taken as δ 2 =0.61×λ 2 /NA 2 , a track pitch Tp 1  of a track formed on the first information recording layer is Tp 1 <δ 2 ,   wherein the content of the information recorded onto the first information recording layer is the same as the content of the information recorded onto the second information recording layer; and   the rate of compression of the information recorded onto the second information recording layer is greater than the rate of compression of the information recorded onto the first information recording layer.   
     
     
         2 . The information recording medium according to  claim 1 ,
 wherein the first information recording layer has a configuration capable of recording and/or reproducing information using near-field light.   
     
     
         3 . The information recording medium according to  claim 2 ,
 wherein the laser beam of the second wavelength λ 2  is reflected exclusively by the first information recording layer and the second information recording layer.   
     
     
         4 . The information recording medium according to  claim 1 ,
 wherein a recording capacity of the first information recording layer is greater than 50 Gbyte.   
     
     
         5 . An information supply system, being operable to record and supply information having identical content to the first information recording layer and the second information recording layer of the information recording medium according to  claim 1 .