| 摘要 |
PURPOSE:To prevent a circuit from malfunctioning by recording a clock signal which indicates a sector position as a diffracting means which performs optical reflection or transmission on radial lines of a sector groups arranged radially. CONSTITUTION:An optical disk 1 is provided with grooves 2 for track following, sector marks 3 which has track and address information on respective tracks, and sector indicators 5 where a diffraction grating is formed by arranging plural sector indicator grooves 4 which have heads and tails on prolongations of a sector mark group positioned on the medium radially in constant position relation with the sector mark group in a peripheral direction at constant pitch. Sector marks 3 recorded on the grooves 2 for track following are read with laser light converged by an optical disk device, but variation in the quantity of reflected light due to diffraction is obtained on a sector indicator 5 even with ordinary light which is not converged. Thus, the clock signal which indicates a recorded sector position is provided as a diffracting means, so a clock signal for controlling the recording and reproduction of the optical disk medium is obtained stably and easily. |
