| 摘要 |
PURPOSE:To eliminate a variation of a detecting output due to a fitting height error of a disk, a variation of a reflection factor or some uneven flaws, by adjusting so that a detecting output of a start end position mark is obtained by a prescribed number in a prescribed period. CONSTITUTION:An output of a microcomputer 12 obtains reference voltage VR2 corresponding to a data by setting a data latched by an OUT port 13 (flip- flop) to a D/A converter 11. An input signal (b) of a comparator 9 is waveform- shaped by the reference voltage VR2 of the comparator by the comparator and an output (c) is inputted to a counting circuit 14. The microcomputer 12 operates a timer of one rotation portion of an optical disk 5, reads the count number of the counting circuit 14 by an IC15 (IN port) constituted of three states, outputs a data to the OUT port 13 so that the count number becomes one, and varies the reference voltage VR2 of the comparator 9 to the potential for outputting only a rotation start end signal level, by which a desired rotation start end position signal (c) is obtained. |
