| 摘要 |
PURPOSE:To secure a kick-back margin, by detecting the final sector of a data recording disk containing an index mark and suppressing a sector dividing signal that should be produced after a sector dividing signal of the final sector in a normal state. CONSTITUTION:An index detecting part 1 detects an index mark of an optical disk. A sector length counter 3 counts the pulses which are applied from an oscillator 2 and delivers sector pulses SP for each divided sector of a cylinder. A sector number counter 4 counts the pulses SP and delivers the sector number. The counter 4 is reset by the detecting output of the part 1. A decoder 5 discriminates that the counter 4 has counted the pulse SP which shows the last sector of the same cylinder track and delivers a control signal that suppresses the output of the next sector pulse. In such a way, it is facilitated to secure a margin for kick-back, and at the same time the sector length can be decided by a counter. Thus a change of revolution can be absorbed. |
