| 摘要 |
PROBLEM TO BE SOLVED: To decrease a crosstalks at the time of disk reproduction and to improve the recording density by forming prepit rows which are made narrower in the width of central parts than ends and manufacturing an optical disk by using this stamper. SOLUTION: An input signal 101 formed by modulation of only the central part of the prepit 104 by a high-frequency pulse is inputted to an acousto-optic modulator which modulates a laser beam. The high-frequency pulse is turned on and off at the period sufficiently finer than the diameter of the spot of a laser beam for recording, and is thereby equivalently acted as a pulse width modulation. The central part is eventually irradiated with the equivalent power 102 of the laser beam proportional to a high-frequency pulse duty ratio. The energy density is thus made lower than the equivalent power 103 of the laser beam at the end and the prepit 104 is formed to a shape narrower in the width in the central part than in the end. The optical disk injection-molded by using such stamper is suppressed in the crosstalks with the adjacent track parts in the central part and can be made narrower in pitch. |
