| 摘要 |
<p>The intensity of an ultraviolet laser beam emitted from a UV laser beam source (1) is modulated based on additional information by an optical modulator (2), and directed to a mirror (14) through lenses (3, 4), a phase diffraction grating (5) and a half mirror (14). The laser beam is reflected from the mirror (14), focused by an objective lens (6) and then made to fall on an optical disc (8). Alternatively, an ultraviolet laser beam from a UV laser beam source (1) enters a phase diffraction grating through an optical modulator (2) and lenses (3, 4) and is divided into three beams by the phase diffraction grating (5). The three beams are applied to the optical disc (8) through a half mirror (11), a mirror (14) and an objective lens (6). Reflected light of visible laser beam from the optical disc (8) enters a half mirror (11), and is then reflected therefrom to enter an optical detector (13) through a cylindrical lens (12). The focusing control and tracking control are carried out on the basis of the output signal from this optical detector (13), whereby it is possible to form a spot of the ultraviolet laser beam in an accurate position in an additional information recording region and record the additional information thereon accurately.</p> |
