Patent ID: 8441905

Claim:
A reproducing apparatus for reproducing an optical information recording medium, the reproducing apparatus irradiating, with reproducing light, an optical information recording medium including an information recording layer on which information is recorded as marks and spaces coded by RLL(1,7) modulation, each of the marks and spaces having one of a plurality of lengths, and 2T marks and 2T spaces of the marks and spaces being formed to be shorter than 0.12 μm, and reproducing a reproduction signal waveform obtained by the irradiation, said reproducing apparatus comprising: a means for irradiating said optical information recording medium with said reproducing light, having a power not less than 0.8 mW and having a wavelength of not less than 400 nm but not more than 410 nm, via an objective lens having a numerical aperture of not less than 0.84 but not more than 0.86; a means for real time updating, upon actual reproduction of the data region, a coefficient for attaining a waveform close to a target waveform in PRML decoding; and a means for generating a clock by use of a reproduction signal and decoding the obtained reproduction signal waveform in accordance with a PR(12221)ML decoding method.