| 摘要 |
<p>An optical disk comprises a substrate, on one side of which a first recording layer and a second recording layer of different reflectivities are formed one on another, and a protective coating is provided on the first or second recording layer, which is farther from the substrate. For reproduction, a light beam is emitted from a single light source to the first or second recording layer through a single object lens. Based on whether the light beam is reflected from the first or second recording layer, the object lens is moved along its optical axis and focused on the recording layer to reproduce information.</p> |
