Patent ID: 6219320
Filing Date: 2001-04-17
Classification: G11B

Abstract:
An information reproducing apparatus for reproducing a digital information signal recorded on an optical disk, said digital information signal being modulated with a run length limited code of a minimum run length d and a maximum run length k, said apparatus comprising:said optical disk being recorded with said digital information signal at a bit rate Fb which satisfies a relation Fb=K.multidot.d.multidot.Fm with a parameter K (wherein K>1 and is a coefficient relating to recording density on said optical disk), said Fm being defined as Fm=2.multidot.V.multidot.NA/.lambda., wherein said Fm is a cutoff frequency of a frequency response of said optical disk, .lambda. is a wavelength of a laser output, NA is a numerical aperture of an optical system, and V is a linear velocity of said optical disk; andan equalizer for equalizing said digital information signal reproduced from said optical disk, wherein said equalizer has characteristics for providing an overall frequency response characteristic H(f) as impulse response characteristics through an encoder for modulating said run length limited code for said optical disk, and said equalizer satisfies the relation of H(f)=cos((.pi./2).multidot.f/Fm) within a signal frequency range from said minimum run length d to said maximum run length k.