Patent ID: 8717858

Claim:
An information storage medium comprising: a substrate formed in a disk shape; and a recording layer which is formed on or above the substrate, the recording layer comprising a spiral track having a pre-groove configured to reproduce a push-pull signal, a track pitch of the spiral track being 500 nm or less, the pre-groove being wobbling to provide wobble detection signals, and at least a part of the pre-groove being modulated with Frequency Shift Keying, wherein the pre-groove is configured to generate a difference signal and an adding signal, wherein the push-pull signal is indicative of a first ratio of the difference signal to the adding signal, the first ratio being not less than 0.1 and not more than 0.8, wherein the information storage medium comprises a Low to High characteristic and is configured to record a mark regarding a minimum inversion length of 2T, wherein a second ratio of a first signal amount to a second signal amount is more than 0.2, where the first signal amount represents a reproduction signal amplitude relating to an inversion length of 3T, and the second signal amount represents another reproduction signal amplitude relating to a mark regarding a maximum inversion length, and wherein a value-of Wppmax/Wppmin is 3 or less, where Wppmax and Wppmin are the maximum and minimum amplitude values of the wobble detection signals, respectively.