Information recording medium having substrate with microscopic pattern and reproducing apparatus therefor

Abstract

A recording medium includes a substrate having a microscopic pattern, which includes a shape of continuous substance of approximately parallel grooves formed with a convex shaped section and a concave shaped section alternating on a surface of the substrate. A recording layer is formed on the microscopic pattern and a light transmitting layer has a thickness of 0.05 mm to 0.12 mm formed on the recording layer. The microscopic pattern satisfies a relation of P≦λ/NA, wherein P is a pitch of the convex shaped section, λ is a wavelength of a reproducing light beam and NA is a numerical aperture of an objective lens. The microscopic pattern also includes modulated address information formed on both side walls of the convex shaped section viewed from the light transmitting layer as a wobble, both the side walls being parallel to each other, and furthermore wherein the address information is modulated by the phase-shift keying modulation system. A reproducing apparatus is particularly suited for the recording medium.

1 . An information recording medium comprising:
 a substrate having a microscopic pattern, which includes a shape of continuous substance of approximately parallel grooves formed with a convex shaped section and a concave shaped section alternating on a surface of the substrate;   a recording layer formed on the microscopic pattern; and   a light transmitting layer having thickness of 0.05 mm to 0.12 mm formed on the recording layer, wherein a fluctuation amount of thickness of the light transmitting layer in one surface is within ±0.003 mm,   the microscopic pattern satisfying a relation of P≦λ/NA, wherein P is a pitch of the convex shaped section, λ is a wavelength of a reproducing light beam and NA is a numerical aperture of an objective lens, and   further wherein the microscopic pattern includes a modulated address information formed on both side walls of the convex shaped section viewed from the light transmitting layer as a wobble, both the side walls being parallel to each other, and   furthermore wherein the wavelength λ is 405 nm and the numerical aperture NA is 0.85.   
   
   
       2 . A reproducing apparatus for reproducing an information recording medium comprising:
 a substrate having a microscopic pattern, which includes a shape of continuous substance of approximately parallel grooves formed with a convex shaped section and a concave shaped section alternating on a surface of the substrate;   a recording layer formed on the microscopic pattern; and   a light transmitting layer having thickness of 0.05 mm to 0.12 mm formed on the recording layer, wherein a fluctuation amount of thickness of the light transmitting layer in one surface is within ±0.003 mm,   the microscopic pattern satisfying a relation of P≦λ/NA, wherein P is a pitch of the convex shaped section, and   further wherein the microscopic pattern includes a modulated address information formed on both side walls of the convex shaped section viewed from the light transmitting layer as a wobble, both the side walls being parallel to each other,   the reproducing apparatus at least comprising:   a light emitting element configured to emit a reproducing light beam having a wavelength λ of 405 nm;   an objective lens having a numerical aperture NA of 0.85; and   a pick-up having a photodetector,   wherein the objective lens is arranged so as to confront with the light transmitting layer.