| 摘要 |
PURPOSE:To stabilize tracking control by recording an index signal to a common position of each tracking detection track and using three independent laser beams to trace both tracking tracks at both sides of the information recording track. CONSTITUTION:Tracking detection tracks 10, 11 are provided between information recording track regions 7, tracking detection signals f1, f2 are recorded alternately at each period and an index signal f3 is recorded to a position in common to each tracking detection track. Thus, a sub laser beam different from a main laser beam for information recording track region tracing is used to read independently the tracking detection track placed at both sides f the information track region. The tracking error signal immune to the effect of the warp of an optical memory disc is obtained by obtaining a difference between both read signals of the tracking detection track and stable tracking control is ensured in such a way. |
