Optical disc having information units comprising a plurality of separated pit pieces, and playback apparatus and recording and playback method therefor

摘要

An optical disc is provided with: a disc substrate having a disc shape; a recording surface formed on the disc substrate and having a spiral or coaxial track with a predetermined track pitch; a plurality of information units formed on the track, each of which has a predetermined unit length in a circumferential direction and a radial direction of the optical disc respectively; and a pit formed in each of the information units, for recording information by converting the information in a shape of the pit, the pit having one of a plurality of shapes comprising a combination of presence and absence of 4 pit pieces, each of the pit pieces being separated from each other and disposed outside of an area, which is approximately shaped in a X letter in the information unit and includes a unit center of the information unit.