Patent ID: 7706244

Claim:
An information recording medium having pits with a size less than or equal to an optical resolution, for causing an amplitude of a playback signal to become a limited value upon irradiation of laser light with a prespecified level of power, wherein by letting Ph be the prespecified power, letting RF(Ph,Lsr) be the amplitude of a playback signal obtained by said prespecified power Ph from a pit and a space both having a length Lsr, letting P 1 be a power which is less than said power Ph and which causes a playback signal from a pit having said size to have its amplitude which is almost zero (0), and letting RF(Pl,Lnr) be the amplitude of a playback signal obtained from a pit and a space both having a length Lnr, the following equations are defined: RF ′( Lsr )= RF ( Ph,Lsr )/ Ph, NR ( Lsr )= RF ( P 1 ,Lsr )/ P 1, NR ( Lnr )= RF ( P 1 ,Lnr )/ P 1, and SR ( Lsr )= RF ′( Lsr )− NR ( Lsr ), and wherein when said length Lnr is greater in size than said optical resolution, a value of NR(Lnr) divided by SR(Lsr) is less than or equal to one (1).