| 摘要 |
<p>Two-side storage medium (1) formed of a first substrate (2) and a second substrate (3), each having embedded data-carrying layers for optical reading, e.g. by means of a laser beam (7, 8), from either side of the storage medium (1), where the density of the first data-carrying layer (5) of the storage medium (1) differs from the density of the second data-carrying layer (6) of the storage medium (1). The thickness of the first substrate (2) ranges between 1.1 and 1.3 mm, while the thickness of the second substrate (3) ranges between 0.5 and 0.7 mm. As a result a storage medium which can be read by the most common devices adapted for reading storage media in one or more of the standard type formats corresponding to the format of the data layers, the thickness of the first substrate corresponding to the thickness of conventional storage media with only one layer. No adjustment of the read head, which effects reading from below, is thus needed. A superjacent layer does not impede the said reading. Consequently, the problems with correctly focussing the scanning laser beams on the data-carrying layer in the first substrate are no longer present.</p> |
