| 摘要 |
PURPOSE:To optionally control the spot diameters of laser beams and to easily form signal recording parts having various width on the original disk of an optical disk by restricting the beam diameter of a laser beam by a shielding plate. CONSTITUTION:A shielding disk 1 is rotated synchronously with a signal for a track group part and an address signal for a prebit part. In the case of exposing the track group part, the disk 1 is rotated so that a laser beam 4 is passed through a narrow transmission part 2 to restrict the beam diameter. In the case of exposing the prebit part having address information, the disk 1 is rotated so that the laser beam 4 is passed through a wide transmission part 3 without restricting the beam diameter. Consequently, the signal recording parts such as the track group part and the prebit part having various width values are easily formed on the original disk of the optical disk by using the same optical system. |
