Optical disk having information pits of different lengths and shapes

摘要

An optical disk includes: an information recording surface on which a laser light is irradiated; and information pits arranged on the information recording surface and including a plurality of shapes each corresponding to information to be recorded, each of the shapes having different lengths in at least one of a radial direction of the disk and a circumferential direction of the disk and a depth d substantially satisfying the following relationship with a wavelength lambda of the laser light:d=(2n+1)x lambda /4 (n: integer).