| 摘要 |
PURPOSE:To prevent the erroneous detection of an on-track signal on the outside of reference tracks by setting the spacing between the adjacent reference tracks longer than the spacing between the reference tracks and the information part within the same information tracks adjacent to the respective reference tracks. CONSTITUTION:Reference parts C2 consist of the reference tracks Kt disposed on the center lines (a) of the respective tracks Ct. The tracks Kt are formed longer in the spacing A from the adjacent information tracks than the spacing B from a synchronizing part C1 and the spacing B' from a start part C3. Regions N which are separated to the right and left are connected in the case of setting the boundary (m) of 1/2 the spacing B from the respective bit edges of the synchronizing part C1 and the start part C3. The quantity of light in this part is nearly the same and the valley parts generated at both ends of the signal region S2 of the output signal of a line sensor 6 decrease to a negligible level; therefore, the differential signal settles down between reference levels VH and VL. The digital signal of an L level, i.e., off-track detection signal is thus obtd. |
