| 摘要 |
PURPOSE:To obtain an optical disc for recording with high density by forming pit arrays having main axes shifted 45 deg. each other at a data-holding surface, thereby narrowing a track pitch. CONSTITUTION:A pit array A having a main axis in a direction and a pit array B having a main axis shifted 45 deg. to the main axis of the pit array A are arranged on a data-holding surface. The pit arrays A, B are arranged sequentially to be adjacent to each other at right angles to a radial direction of the surface, whereby the optical disc is obtained. Since beam depths are so set that polarization main axes are different by 45 deg., it is possible to read a signal by detecting a difference of one pit array A (Al-A2), but not possible to read the signal from the other pit array (B1-B2). On the contrary, it is possible to read a signal from the pit array B (B1-B2), but impossible to read from tone pit array A (A1-A2). Therefore, if a distance of a pair of the pit arrays is kept the same as in a currently used optical disc, a track density becomes twice. |
