| 摘要 |
<p>PURPOSE:To indirectly detect the rotating speed of a cylinder and to reduce the thickness of the cylinder by extracting a clock signal synchronized with a regenerative signal from the regenerative signal reproduced by a magnetic head and generating a signal corresponding to a frequency deviation between this clock signal and a reference clock signal as a speed error signal. CONSTITUTION:The regenerative signal reproduced by reproducing heads 3a and 3b is amplified, while the clock signal synchronized with the regenerative signal is extracted from the regenerative signal, and the signal corresponding to a frequency change between this clock signal and the reference clock signal is generated as the speed error signal. By this method, the rotating speed of the cylinder 2 can indirectly be detected, and it is not necessary to fix a detector for detecting the rotating speed of the cylinder 2, and then the thickness of the cylinder can be reduced.</p> |
